Abstract: This paper investigates an agile confidential transmission strategy combining big data driven cluster and opportunistic beamforming (OBF) in the scenario where the same huge content is downloaded simultaneously by many users from the same base station. Instead of a burden from the traditional perspective, big data can be viewed as a resource. With the help of big data, data driven cluster taking into account security issues can be formed. Due to some obvious advantages, physical layer security (PHY-security) techniques as an alternative to the traditional high complexity cryptography-based secrecy methods are employed to achieve confidential transmission. For the purpose of superior secrecy performance, the scheme combining big data driven cluster and OBF, each of which can configure limited communication resources agilely and effectively in a dynamically changing network environment, is proposed. As the number of authorized users increases in the system, not only the channel vectors of cluster heads can tend to match with beamforming vectors with a high probability, but also more authorized users can be added into clusters and attain confidential content. These advantages ensure the combination of these two techniques is an attractive approach to transmit confidential message at a high rate. Based on different demand cases, multiple versions of the scheme combining cluster and OBF are put forward. In order to validate our proposed schemes, numerical simulations are carried out and the results show that a significant performance gain over both the average secrecy sum-capacity and the average number of authorized users accessing the system is achieved.
Autors: Shuai Han;Sai Xu;Weixiao Meng;Cheng Li;
Appeared in: IEEE Transactions on Vehicular Technology
Abstract: Recently, micro electro-mechanical systems (MEMS) inertial sensors have found their way in various applications. These sensors are fairly low cost and easily available but their measurements are noisy and imprecise, which poses the necessity of calibration. In this paper, we present an approach to calibrate an inertial measurement unit (IMU) comprised of a low-cost tri-axial MEMS accelerometer and a gyroscope. As opposed to existing methods, our method is truly infield as it requires no external equipment and utilizes gravity signal as a stable reference. It only requires the sensor to be placed in approximate orientations, along with the application of simple rotations. This also offers easier and quicker calibration comparatively. We analyzed the method by performing experiments on two different IMUs: an in-house built IMU and a commercially calibrated IMU. We also calibrated the in-house built IMU using an aviation grade rate table for comparison. The results validate the calibration method as a useful low-cost IMU calibration scheme.
Abstract: An all-region short-channel MOSFET, model is developed for nanowire semiconductors with 1-D density of states. It is shown that in the quantum capacitance limit, the long-channel saturation current exhibits a (Vgs − Vt)3/2 dependence on gate voltage. With the velocity saturation effect implemented in the model, the Ids–Vgs characteristics of 1-D MOSFETs are compared to those of 2-D MOSFETs at 10-nm channel length. The above threshold model is joined with a subthreshold current model derived from short-channel solutions to form an I– V model continuous in all regions.
Abstract: Sparse sampling (SS) has shown a significant promise for the recovery of biomedical signals from noisy measurements. In practice, the premeasurement noise, i.e., the noise associated with the unprocessed signal is often ignored. At large compression, a small perturbation in the raw signal may degrade the signal-to-noise ratio by a significant amount due to the noise-folding effect. In this paper, a new antinoise-folding sparse recovery framework is proposed, which is blind-to-noise-statistics, and it does not require any prior warm-up step to select the starting point. The source signal is recovered from the noisy measurements by solving a nonconvex regularization-based constrained minimization problem followed by a data-adaptive Stein's unbiased risk estimate-based denoising process. The constrained problem is linearized by employing the method of majorization-minorization. Furthermore, the sparse recovery analysis of the new algorithm is established. The numerical test results obtained by employing noisy photoplethysmogram data and real-world fetal-electrocardiogram data show the superior performance of the proposed method as compared with various state-of-the-art SS methods.
Autors: Priya Ranjan Muduli;Atindra Kanti Mandal;Anirban Mukherjee;
Appeared in: IEEE Transactions on Instrumentation and Measurement
Abstract: Attitude jitter is a common problem for high-resolution earth-observation satellites and can diminish the geo-positioning and mapping performance of observed images. It is especially necessary to address this problem when high-performance attitude measurements are unavailable. Therefore, an attitude jitter correction method for multispectral parallax imagery that utilizes the compressive-sensing technology is proposed in this letter. In the proposed method, the attitude jitter is estimated from the parallax disparities of different band images, and then the image displacement caused by attitude jitter can be corrected. Using the normalized cross correlation method and compressive-sensing technology, the proposed method can deal with the condition of texture-feature deficiency in the partial image. The multispectral images of the Terra and ZY-3 satellites are used as experimental data to evaluate the proposed method. The registration errors of different bands are greatly reduced in both the cross- and along-track directions, and the experiment results indicate that the proposed method is effective for correcting the attitude jitter of both satellites.
Autors: Jun Chen;Jun-Gang Yang;Wei An;Zhi-Jie Chen;
Appeared in: IEEE Geoscience and Remote Sensing Letters
Abstract: The classical Preisach hysteresis model and its modifications are time consuming to implement due to the determination of the weight function. Another defect of the Preisach-based model is that it could only be an approximation in the absence of the congruency property. For such reasons, this paper proposes a hysteresis model identification method based on support vector regression which could be a promising alternative in practical applications. Support vector machine is attractive in regression analysis due to its strong generalization capability. A four-stage identification procedure is implemented and key techniques are introduced in detail. The penalty parameter and the kernel parameter are optimized using grid search and cross-validation method. The influences of data scaling and parameter optimization are analyzed. An identified hysteresis model of aluminum nickel cobalt alloy is evaluated and verified with the criteria of mean squared error and identified time.
Abstract: A facile, environmental friendly green approach was introduced in this study, which superparamagnetic magnetite nanoparticles (Fe3O4-NPs) have been satisfactorily synthesized. Seaweed Kappaphycus alvarezii (K. alvarezii) extract was employed in this synthesis process, which played a role as bio-stabilizer. The structure and morphology of the synthesized K. alvarezii/Fe3O 4-NPs were analyzed by X-ray diffraction (XRD) and transmission electron microscope. The spherical shape of K. alvarezii/Fe3O4-NPs with an average size of 19.4 nm showed high crystallinity and purity based on the characteristic XRD planes at (220), (311), (400), (422), (511), (440), and (533). The presence of Fe3O4-NPs was identified by Fourier transform infrared, Raman spectroscopy, and energy-dispersive X-ray spectroscopy. The magnetic properties of K. alvarezii /Fe3O4-NPs were studied using vibrating sample magnetometer, which gave a result of 24.85 emu/g. The K. alvarezii/Fe3O4-NPs were very stable, where zeta potential value showed −53.57 mV.
Autors: Yen Pin Yew;Kamyar Shameli;Mikio Miyake;Nurul Bahiyah Bt Ahmad Khairudin;Shaza Eva Bt Mohamad;Hirofumi Hara;Mariam Firdhaus Bt Mad Nordin;Kar Xin Lee;
Abstract: This paper provides a reformulation of the scenario-based two-stage unit commitment problem under uncertainty that allows finding unit-commitment plans that perform reasonably well both in expectation and for the worst case. The proposed reformulation is based on partitioning the sample space of the uncertain factors by clustering the scenarios that approximate their probability distributions. The degree of conservatism of the resulting unit-commitment plan (that is, how close it is to the one provided by a purely robust or stochastic unit-commitment formulation) is controlled by the number of partitions into which the said sample space is split. To efficiently solve the proposed reformulation of the unit-commitment problem under uncertainty, we develop two alternative parallelization and decomposition schemes that rely on a column-and-constraint generation procedure. Finally, we analyze the quality of the solutions provided by this reformulation for a case study based on the IEEE 14-node power system and test the effectiveness of the proposed parallelization and decomposition solution approaches on the larger IEEE 3-Area RTS-96 power system.
Abstract: This paper proposes an electromagnet-assisted ferrite magnet motor (EMaFM) with a double air-gap structure. To confirm the principle and validity of the proposed EMaFM, a prototype machine was designed and fabricated. Moreover, the electromagnetic performance of the prototype machine was simulated using a finite-element analysis (FEA) and was supported by experiments. The proposed EMaFM has field regulation capability while utilizing the ferrite magnets. From the FEA and experimental results, it was found that the torque can be controlled widely by the armature current or field current.
Abstract: Searching for associations between entities is needed in many domains like national security and bioinformatics. In recent years, it has been facilitated by the emergence of graph-structured semantic data on the Web, which offers structured semantic associations more explicit than those hiding in unstructured text for computers to discover. The increasing volume of semantic data often produces excessively many semantic associations, and requires ranking techniques to identify the more important ones for users. Despite the fruitful theoretical research on innovative ranking techniques, there is a lack of comprehensive empirical evaluation of these techniques. In this article, we carry out an extensive evaluation of eight techniques for ranking semantic associations, including two novel ones we propose. The practical effectiveness of these techniques is assessed based on 1,200 ground-truth rankings created by 30 human experts for real-life semantic associations and the explanations given by the experts. Our findings also suggest a number of directions in improving existing techniques and developing novel techniques for future work.
Autors: Gong Cheng;Fei Shao;Yuzhong Qu;
Appeared in: IEEE Transactions on Knowledge and Data Engineering
Abstract: In this paper, sea surface wind direction and speed are obtained from X-band nautical radar images. A data control strategy is proposed to distinguish rain-free and rain-contaminated radar data. The radar data are decomposed by an ensemble empirical mode decomposition method into several intrinsic mode functions (IMFs) and a residual. A normalization scheme is applied to the first IMF to obtain the amplitude modulation (AM) component. Wind direction is determined from the residual for the rain-free and high-wind-speed rain-contaminated data, and from the AM portion of the first IMF for the low-wind-speed rain-contaminated data, based on curve fitting a harmonic function. Wind speed is determined from a combination of the residual and the AM part of the first IMF for both rain-free and rain-contaminated data using a logarithmic relationship. Results employing ship-borne radar and anemometer data collected in a sea trial off the east coast of Canada are presented. The root-mean-square differences for wind direction and speed measurements are 11.5° and 1.31 m/s, respectively, compared with reference values from anemometers.
Autors: Weimin Huang;Xinlong Liu;Eric W. Gill;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Abstract: Telecommunications service industry provides services that transmit voice, data, text, sound, video, and other signals. In the Internet age, the telecommunications service industry has experienced tremendous growth to form an indispensable infrastructure platform for today's global networked economy. In this study, we examine the output performance of telecommunications service industries in 13 Organization of Economic Cooperation and Development countries from 2000 to 2011 using the Malmquist total factor productivity index (MTFPI) as the performance metric and data envelopment analysis as the measurement approach. We further decompose MTFPI into three factors: 1) technical change; 2) pure efficiency change; and 3) scale efficiency change, that represent innovation, catch-up, and demand fluctuation, respectively. The results show that these telecommunications service industries exhibit comparatively strong productivity growth. In addition, through our decomposition analysis, it is found that telecommunications service industry is an innovator skilled at adopting technological advances that turn out to be the key driving force for the observed productivity growth. By contrast, both pure efficiency change and scale efficiency change lead to negative impacts. Based on these findings, we draw and discuss implications for telecommunications service at the country and industry levels, and provide suggestions for practice and future research.
Autors: Benjamin B. M. Shao;Winston T. Lin;Juliana Y. Tsai;
Appeared in: IEEE Transactions on Engineering Management
Abstract: Image-based sequence recognition has been a long-standing research topic in computer vision. In this paper, we investigate the problem of scene text recognition, which is among the most important and challenging tasks in image-based sequence recognition. A novel neural network architecture, which integrates feature extraction, sequence modeling and transcription into a unified framework, is proposed. Compared with previous systems for scene text recognition, the proposed architecture possesses four distinctive properties: (1) It is end-to-end trainable, in contrast to most of the existing algorithms whose components are separately trained and tuned. (2) It naturally handles sequences in arbitrary lengths, involving no character segmentation or horizontal scale normalization. (3) It is not confined to any predefined lexicon and achieves remarkable performances in both lexicon-free and lexicon-based scene text recognition tasks. (4) It generates an effective yet much smaller model, which is more practical for real-world application scenarios. The experiments on standard benchmarks, including the IIIT-5K, Street View Text and ICDAR datasets, demonstrate the superiority of the proposed algorithm over the prior arts. Moreover, the proposed algorithm performs well in the task of image-based music score recognition, which evidently verifies the generality of it.
Autors: Baoguang Shi;Xiang Bai;Cong Yao;
Appeared in: IEEE Transactions on Pattern Analysis and Machine Intelligence
Abstract: A network with nodes contains possible links. Even for networks of modest size, it is often difficult to evaluate all pairwise possibilities for links in a meaningful way. Further, even though link prediction is closely related to missing value estimation problems, it is often difficult to use sophisticated models such as latent factor methods because of their computational complexity on large networks. Hence, most known link prediction methods are designed for evaluating the link propensity on a specified subset of links, rather than on the entire networks. In practice, however, it is essential to perform an exhaustive search over the entire networks. In this article, we propose an ensemble enabled approach to scaling up link prediction, by decomposing traditional link prediction problems into subproblems of smaller size. These subproblems are each solved with latent factor models, which can be effectively implemented on networks of modest size. By incorporating with the characteristics of link prediction, the ensemble approach further reduces the sizes of subproblems without sacrificing its prediction accuracy. The ensemble enabled approach has several advantages in terms of performance, and our experimental results demonstrate the effectiveness and scalability of our approach.
Abstract: This letter describes a new approach for fabricating quasi-vertical submillimeter-wave GaAs Schottky diodes heterogeneously integrated to high-resistivity silicon substrates. The new method is robust and eliminates previous processing steps that were prone to result in wafer fracture and delamination. Diodes fabricated with the new process and measured in the 325–500 GHz range using on-wafer RF probes exhibits low parasitic capacitance and series resistance, achieving device characteristics comparable to the prior state-of-the-art submillimeter-wave diodes.
Autors: Linli Xie;Souheil Nadri;Naser Alijabbari;Michael E. Cyberey;Matthew F. Bauwens;Arthur W. Lichtenberger;N. Scott Barker;Robert M. Weikle;
Abstract: Nonoverlapping multicamera visual object tracking typically consists of two steps: single-camera object tracking (SCT) and inter-camera object tracking (ICT). Most of tracking methods focus on SCT, which happens in the same scene, while for real surveillance scenes, ICT is needed and single-camera tracking methods cannot work effectively. In this paper, we try to improve the overall multicamera object tracking performance by a global graph model with an improved similarity metric. Our method treats the similarities of single-camera tracking and inter-camera tracking differently and obtains the optimization in a global graph model. The results show that our method can work better even in the condition of poor SCT.
Abstract: The increasing coupling between natural gas and electricity systems by gas-fired generation units brings new challenges to system analysis, such as pressure variations due to consumption perturbations of generation units. The emerging issues require revolutionary modeling and analysis techniques. This paper proposes a novel model to quantify gas pressure variations due to gas-fired power unit ramping and the impact of constraints from natural gas pressure change on ramp rates of gas-fired plants. By utilizing Laplace transform to resolve the governing equations of gas networks, the proposed model can significantly reduce modeling complexity and computational burden. The dynamic behaviors in time scale in s-domain and spatial partial differential equations are transformed into finite difference equations. By introducing the concept of transfer matrices, the relation between states at each node of gas systems can be expressed by transfer parameter matrices. Additionally, a simplified model is introduced to simply the analysis. The explicit expressions of nodal pressure variations in response to demand change are very convenient for analyzing system dynamic performance under disturbances, identifying the most influential factors. The new models are extensively demonstrated on three natural gas networks and benchmarked with traditional simulation approaches. Results illustrate that they produce very close results with the simulation approach, particularly when gas pipelines are long and enter steady states.
Abstract: Electrohydrodynamic motion and deformation of a sedimenting drop in the presence of a uniform alternating electric field is investigated experimentally. Application of an electric field causes a drop to deform to an ellipsoidal shape. As a result of this deformation, the terminal velocity of the drop is affected. In this study, a detailed experimental investigation of the effect of a horizontally directed uniform alternating electric field on the sedimentation velocity and deformation characteristics of deionized water drop and silicone oil drop falling in castor oil medium is presented. Both water and silicone oil drops are found to deform to a prolate shape on application of electric field, which retards the drop motion in the vertical direction. There is a marked decrease in drop velocity with increase in strength of the alternating electric field.
Autors: Rajorshi Paul;Guttapalli Naveen Kumar;Shubhadeep Mandal;N. K. Kishore;Saurav Pramanik;Suman Chakraborty;
Appeared in: IEEE Transactions on Industry Applications
Abstract: An external capacitor-less ultra low-dropout (LDO) regulator that can continue to provide high power-supply rejection (PSR) over a wide range of the load current is proposed. Using the loop-gain stabilizer (LGS) to fix the dc level of the output voltage of the error amplifier to the optimal value, the LDO can keep maximizing the unity-gain frequency, while the load current changes widely up to 200 mA. Despite the multiple poles in the regulating loop, the stability can easily be obtained due to an intrinsic left-half plane zero, generated by the auxiliary path of the LGS. The proposed LDO was fabricated in a 40-nm CMOS process, and it had an input voltage of 1.1 V. When the dropout voltage was 0.1 V and the load current was 200 mA, the measured PSRs were −60 and −35 dB at 1 and 10 MHz, respectively. Due to the LGS, the dc loop gain was maintained to be high, resulting in good load and line regulations of /mA and 0.75 mV/V, respectively. While the total current consumption of the LDO was , the LGS consumed only . The area was 0.008 mm2 with 4-pF on-chip capacitance for compensation.
Abstract: Class imbalance refers to the instance where the number of training samples for the majority classes is far more than that of the minority classes (relative imbalance), and the quality of training samples for the minority classes is inferior to that of the majority classes (absolute imbalance), which are further complicated by other imbalance factors, e.g., data overlapping. Video background subtraction aims to classify each pixel into two classes: foreground and background. This paper first reveals that background subtraction is a class imbalance problem, where the foreground and background are the minority and majority classes, respectively. By exploring spatial and temporal correlation inherent in video data, we present an imbalance compensation framework for background subtraction, which consists of two sequential modules, imbalance-compensated bilayer modeling, and imbalance-compensated Bayesian classification. In the first module, spatio-temporal oversampling (SOS) and selective downsampling (SDS) are proposed to compensate the imbalance at data level. SOS attempts to synthesize representative samples appended to the minority sample set, while SDS selectively deletes a number of majority samples in data overlapping areas. The rebalanced samples are then used to learn a bilayer model. In the second module, novel cost functions are proposed to compensate the effect of class imbalance at algorithm level. The cost functions are based on imbalance measurement, and used to construct the prior term in the Bayesian classification scheme. Experiments are conducted on public databases to demonstrate the effectiveness of the proposed method.
Abstract: This paper tackles the controllability problem of Boolean control networks (BCNs). By resorting to the semi-tensor product technique and the Warshall algorithm, several improved novel reachability and controllability criteria are obtained for the BCNs. Through constructing a sequence of rigorous Boolean matrices, controllability matrix of the considered BCNs is derived iteratively. It is worth pointing out that the proposed method has lower computational complexity, and thus facilitates the reachability and controllability analysis for BCNs. In addition, the issue concerning controllability of BCNs with undesirable interior states is investigated by checking a set of designated Boolean matrices. Finally, to test the effectiveness of the obtained theoretical results, a genetic network model known as the switch is used as an example for numerical simulation.
Autors: Jinling Liang;Hongwei Chen;James Lam;
Appeared in: IEEE Transactions on Automatic Control
Abstract: Permanent magnet synchronous linear motor (PMSLM) and PM synchronous planar motor are important motion devices in the modern precision industry. Their inherent periodic magnetic fields are highly related to motor position. Correspondingly, the magnetic fields can be utilized to determine their own displacement and replace expensive sensors. However, the measurement result of this strategy seriously depends on magnetic field model (MFM) preciseness. To improve measurement accuracy, a novel MFM with Fourier series is proposed in this paper. First, a high-order theoretical model from theoretical derivation is developed. And the analyses show that even harmonics exist in the magnetic field of motor, which are not included in the theoretical model. This model deviation obviously affects measurement accuracy. Hence, the new MFM is reconstructed based on a high-order theoretical model. Comparative experiments with the three different MFMs are carried out to measure the displacement of the PMSLM. In the experiments, a linear hall sensors array containing eight sensors is self-developed to detect motor magnetic field. The root mean square of displacement measurement errors using a reconstruction model, a high-order theoretical model, and a fundamental model is 4.84, 8.42, and 758 μm, respectively. The experimental results validate that the measurement result of the proposed reconstruction MFM is better than the other two MFMs.
Autors: Shengwu Du;Jinchun Hu;Yu Zhu;Ming Zhang;
Appeared in: IEEE Transactions on Instrumentation and Measurement
Abstract: In this paper, we propose an improved hybrid turbo equalizer (TEQ) for single-carrier transmission over multipath channels with symmetric alpha-stable noise. First, a nonlinear myriad filter is adopted for combating the effect of impulsive noise. The noise output of this nonlinear filter is analyzed by an asymptotic statistic method and shown to be asymptotically Gaussian. Then, a matched minimum mean square error based linear TEQ is proposed for further mitigating the effects of the residual impulsive noise and the intersymbol interference caused by multipath fading. In our proposed TEQ design procedure, the instantaneous estimation of the noise variance is exploited to obtain robust TEQ coefficients. Simulation results show that the proposed hybrid TEQ provides geometric signal-to-noise ratio improvements (of up to 4.5 dB) compared to conventional algorithms designed for Gaussian channels.
Autors: Ping Yang;Yong Liang Guan;Xiao Bei Liu;Zilong Liu;
Appeared in: IEEE Transactions on Vehicular Technology
Abstract: This paper presents an improved magnetic circuit (MC) model considering the leakage, cross coupling, and saturation effects for the performance analysis of an integrated 3 degrees of freedom magnetic bearing (3-DOF MB). Compared with the conventional MC model, this paper analyzes the permanent-magnet bias field, radial and axial control current fields together. By using this improved MC model, it reveals the cross-coupling effect between radial and axial directions in such an integrated 3-DOF MB. The stiffnesses of radial force are significantly influenced by the axial control current, while the stiffnesses of the axial force are independent of the radial control current. Its accuracy is verified by the 3-D finite-element method.
Abstract: Mobile data offloading can help the mobile network operator (MNO) cope with the explosive growth of cellular traffic, by delivering mobile traffic through third-party access points. However, the access point owners (APOs) would need proper incentives to participate in data offloading. In this paper, we consider a data offloading market that includes both price-taking and price-setting APOs. We formulate the interactions among the MNO and these two types of APOs as a three-stage Stackelberg game, and study the MNO’s profit maximization problem. Due to a non-convex strategy space, it is in general a non-convex game. Nevertheless, we transform the strategy space into a convex set and prove that a unique subgame perfect equilibrium exists. We further propose iterative algorithms for the MNO and price-setting APOs to obtain the equilibrium. Employing the proposed algorithms, the APOs do not need to obtain full information about the MNO and other APOs. Through numerical studies, we show that the MNO’s profit can increase up to three times comparing with the no-offloading case. Furthermore, our proposed incentive mechanism outperforms an existing algorithm by 18 percent in terms of the MNO’s profit. Results further show that price competition among price-setting APOs drives the equilibrium market prices down.
Abstract: Packing programming for extravehicular missions to the space station is the process of arranging a set of missions into multiple extravehicular activities. It is an interesting combinatorial optimization problem developed from the traditional bin-packing problem. This paper first formulates a practical mathematical model that considers both the constraints of the time window for each extravehicular mission and the spacewalk time per astronaut. An Ant Colony Optimization (ACO) algorithm with a self-adaptation strategy and a new pheromone matrix characterizing the relationship between any two extravehicular missions is then proposed. The simulation results on various independent experiments show that the proposed ACO algorithm is capable of producing optimal packing programming schemes with a success rate of over 90%, which is acceptable for application to real-world problems.
Abstract: Informal science learning aims to improve public understanding of STEM. Free-choice learners can be engaged in a wide range of experiences, ranging from watching entertaining educational videos to actively participating in hands-on projects. Efforts in informal science learning are often gauged by their ability to elicit interaction, to foster learning, and to influence perceptions of STEM fields. This paper presents the installation of a biomimetic robotic fish controlled by an iDevice application at an informal science learning exhibit. Visitors to the exhibit are offered a unique experience that spans engineering and science, in which they can steer the robotic fish, choosing from three modes of control. Visitor engagement is examined through the lens of the Selinda model of visitor learning, while their behavior is examined using an adapted model of Borun’s framework for behaviors indicative of learning. The evaluation of the efficacy of the exhibit is assessed through a post-experience survey questionnaire, an analysis of the application usage, and a behavior coding study. Data collected on visitor interactions with the exhibit indicate that free-choice learners value the importance of engineering research, and prefer interactive modes. Further, behavior coding results support the ability of the robotic fish platform to capture the visitors’ attention. Findings offer compelling evidence that the exhibit is both highly engaging to visitors and a suitable format for science inquiry.
Autors: Paul Phamduy;Mary Leou;Catherine Milne;Maurizio Porfiri;
Abstract: An interference-robust reconfigurable receiver in 65-nm CMOS is presented. The front end is split into a low-band (LB) RF path (0.1–1.5 GHz) and a high-band (HB) RF path (1–5 GHz). By utilizing a harmonic recombination technique, the LB path could reject the third /fifth-order harmonic interferences. A tunable narrowband dual-feedback common-gate low-noise amplifier (LNA) with resonant load provides second-order bandpass filtering to reject the harmonic interferences in the HB path. The RF high-Q bandpass filtering based on the voltage-mode passive mixer and the current-mode low-pass filter in the analog baseband improves the receiver’s resilience to out-of-band interferences. A novel power-detection-based automatic frequency calibration technique is proposed to calibrate the operating frequency of the LNA in the HB path and overcome the effects of process, voltage, and temperature variations. The presented receiver has been implemented in a 65-nm CMOS and consumes 20–76-mW power from 1.2-V power supplies, with a core die area of 5 mm2. The measured results show that the receiver can tolerate −5-dBm interference with 16-dB noise figure (NF) and achieve 95–105-dB maximum conversion gain and 1.7–8-dB NF over 0.1–5 GHz. It also achieves an average harmonic rejection (HR3)/HR5 of 61/68-dB, +7.1/+14.4 dBm in-band/out-of-band input third-order intercept point (OB-IIP3), +71.2-dBm OB-IIP2, and 58.1-dB-image rejection, after the digitally assisted calibrations. The system-level measurements show that the presented receiver achieves 2.1% error vector magnitude (EVM) for 850-MHz Global System for Mobile Communication signals and 5% EVM for band -
2 time division duplexing-local thermal equilibrium (LTE) signals, respectively.
Abstract: Surface cross-track clutter can corrupt both earth and planetary radar sounder (RS) observations preventing definitive interpretation of subsurface features, which are often of primary interest to geologists and planetary scientists. This clutter is usually identified either by manual or automatic techniques that require ancillary information about the topography of the surface, or by using multichannel RS systems with arrays of antennas. However, topographic information is not always available and multichannel systems are generally too massive and costly to mount on satellites for the planetary exploration. In this paper, we propose a novel approach to clutter discrimination that is independent of ancillary information and limits the hardware complexity of the RS system. This approach uses a two-channel RS and exploits cross-channel interferometric phase differences to discriminate the clutter. Our approach includes three main steps: 1) manual feature extraction and theoretical phase-difference estimation; 2) RS interferogram formation; and 3) comparison of theoretical and real phase difference distributions. The proposed method was validated on RS data acquired in Greenland and provides a proof of concept for the surface clutter discrimination using RS data.
Autors: Davide Castelletti;Dustin M. Schroeder;Scott Hensley;Cyril Grima;Gregory Ng;Duncan Young;Yonggyu Gim;Lorenzo Bruzzone;Alina Moussessian;Don D. Blankenship;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Abstract: This paper presents a linear-quadratic regulator (LQR) for damping of subsynchronous interaction (SSI) in doubly-fed induction generator (DFIG)-based wind farms. The proposed LQR controller employs a full-state observer to estimate all state variables. The output of the LQR is added to control signals of inner current control loops of DFIG converters as supplementary control signals. The supplementary control signals are dynamically limited to avoid saturating the converters and to provide the DFIG with the desired transient response against power system faults. The proposed SSI damping controller is designed for a realistic series compensated wind farm, and its performance is verified using electromagnetic transient (EMT) simulations. The EMT simulations are performed using a detailed DFIG model which includes all nonlinearities and all required transient functions to meet the grid code requirements corresponding to fault-ride-through (FRT). The results show that the proposed SSI controller is able to significantly mitigate the oscillations due to the SSI phenomenon, and to provide excellent transient response against systems faults.
Autors: Mohsen Ghafouri;Ulas Karaagac;Houshang Karimi;Simon Jensen;Jean Mahseredjian;Sherif O. Faried;
Abstract: There is a growing pressure on antenna designers to provide ever increasing operating bandwidth, efficiency, and flexibility. Emerging communications standards are requiring operation over wide frequency ranges, often with multiple, separated bands of operation. This communication proposes and demonstrates an optically tunable cavity backed slot antenna. Through the incorporation of four silicon bridging pieces and a fiber coupled laser, the operating frequency can be tuned between 4.2 and 6 GHz. Antenna efficiency has been measured and ranges between 36% and 62% depending upon the combination of frequency and tuning state, with the gain taking values between 4.3 and 6.9 dBi. An effective fabrication process for the incorporation of silicon into the antenna has been described, as well as methods for effectively simulating the optically generated conductivity. Simulations and measurements show good agreement, and several proposed improvements are proposed for this novel and flexible tuning technology.
Autors: M. A. Collett;C. D. Gamlath;M. Cryan;
Appeared in: IEEE Transactions on Antennas and Propagation
Abstract: This paper develops a novel framework to design an optimal robust excitation system controller considering the uncertainties in the parameters of the model of the excitation system. The uncertainties may cause the parameter values to vary from their nominal values within a specified upper and lower limit. These uncertainties can have a significant influence on the dynamic characteristics of the power system, that is, the variations in the parameters of the excitation controller model due to the uncertainties in the parameters can cause the system to change from being stable to unstable. It is, therefore, important to design a robust excitation system controller that can ensure that irrespective of the values of the parameters within the boundary of the uncertainties, the power system will not have any variation from its stability. The proposed framework decomposes the uncertainties in the parameters of the excitation system model into two components: matched and unmatched. To eliminate the uncertainties from both components, a linear quadratic regulator problem is constructed to deal with the matched component, while an augmented control is used to cope with the unmatched component. The robustness of the resulting controller is verified using time-domain dynamic stability simulations of a single-machine test system and the IEEE 39-bus New England system.
Autors: Hadi Lomei;Danny Sutanto;Kashem M. Muttaqi;Alireza Alfi;
Abstract: Air-coupled capacitive micromachined ultrasonic transducers (CMUTs) with annular cell geometry have recently been reported to have a promising transmit sensitivity. This paper reports three optimization schemes, which further improve the transmit sensitivity and also help achieve a reasonable comparison between the novel annular and conventional circular cells. Lumped element models of both cell types with laminate plate structures are presented. Based on these models, a design optimization flowchart was constructed to facilitate analytical optimization on the three schemes. Circular and annular CMUTs with a common 97-kHz natural resonance frequency were fabricated and characterized to verify the efficacy of the optimization principle. Using the optimization flowchart, annular and circular cells with frequencies ranging from 100 to 300 kHz were analytically optimized and then compared. The comparison results demonstrate that, given the same dc bias and ac excitation voltage, the output power density at the plate surface of the optimized annular cell is double that of the optimized circular cell. Additionally, when generating the same surface power density, an optimized annular cell requires either half the dc bias or half the ac excitation voltage of an optimized circular cell. This paper provides a practical optimization framework for CMUT cell design and demonstrates the superiority of annular cells for air-coupled applications.
Autors: Shuai Na;Zhenhao Li;Lawrence L. P. Wong;Albert I.-Hsiang Chen;Mirek Macecek;John T. W. Yeow;
Appeared in: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Abstract: We propose a localization refinement approach for candidate traffic signs. Previous traffic sign localization approaches, which place a bounding rectangle around the sign, do not always give a compact bounding box, making the subsequent classification task more difficult. We formulate localization as a segmentation problem, and incorporate prior knowledge concerning color and shape of traffic signs. To evaluate the effectiveness of our approach, we use it as an intermediate step between a standard traffic sign localizer and a classifier. Our experiments use the well-known German Traffic Sign Detection Benchmark (GTSDB) as well as our new Chinese Traffic Sign Detection Benchmark. This newly created benchmark is publicly available,1 and goes beyond previous benchmark data sets: it has over 5000 high-resolution images containing more than 14 000 traffic signs taken in realistic driving conditions. Experimental results show that our localization approach significantly improves bounding boxes when compared with a standard localizer, thereby allowing a standard traffic sign classifier to generate more accurate classification results.
Autors: Zhe Zhu;Jiaming Lu;Ralph R. Martin;Shimin Hu;
Appeared in: IEEE Transactions on Intelligent Transportation Systems
Abstract: Evolutionary process of a nanoscale FinFET channel during rapid hydrogen thermal treatment is modeled using a kinetic Monte Carlo simulation. In this paper, a novel model of nanoscale FinFET channel is proposed based on the surface diffusion theory of silicon fin structures. The evolution characteristics of fin surface morphology, including line edge roughness (LER), line width roughness, and the cross-correlation coefficient ρ, are investigated in the diffusion process of silicon fin structures at different temperatures and time. All the characteristic parameters can directly affect the carrier transport performance of FinFET. The LER of a silicon fin has been effectively reduced by at least 60%. The linewidth roughness and ρ was also investigated in the evolution of FinFET channel. The results indicate that an optimized nanoscale FinFET channel can be achieved by controlling the migration of surface silicon atoms in rapid hydrogen thermal treatment technology application, yielding atomically smooth sidewall surfaces. The present experimental results are coincided with the simulation results. Thus, such technology plays a crucial role in the application of nanoscale FinFET.
Autors: Gang Wang;Yu Wang;Junzhuan Wang;Lijia Pan;Linwei Yu;Youdou Zheng;Yi Shi;
Abstract: Cooperative regenerating codes are a kind of erasure codes, which are optimal in terms of minimizing the repair bandwidth. An -cooperative regenerating code has storage nodes, where arbitrary nodes are enough to reconstruct original data, and failed nodes can be repaired cooperatively with the help of arbitrary surviving nodes. In the regenerating-code framework, there exists a tradeoff between the storage capacity of each node and the repair bandwidth , but the problem of specifying the optimal storage-bandwidth tradeoff of the exact-repair cooperative regenerating codes remains open. A key contribution of this paper is that an outer bound on the storage-bandwidth tradeoff of exact-repair linear cooperative regenerating codes is proposed. This result can be regarded as a generalization of the outer bound proposed by Prakash et al., which specifies the optimal tradeoff of exact-repair regenerating codes for the case of . The proposed outer bound suggests the pairs that no exact-repair codes can achieve but only functional-repair codes can. By observing the size of the set of such pairs, the performance of the proposed outer bound is evalua-
ed under various parameter settings.
Autors: Hyuk Lee;Jungwoo Lee;
Appeared in: IEEE Transactions on Information Theory
Abstract: Computing on time-based data is a recent evolution of research in stochastic computing. As with stochastic computing, complex functions can be computed with remarkably low area cost. Unlike stochastic computing, the latency and energy efficiency are very favorable compared to computations on conventional binary radix. In this article, the authors review and evaluate the design and implementation of arithmetic operations on time-encoded signals, with a particular focus on low power. The advantages, challenges, and potential applications are discussed.
Autors: M. Hassan Najafi;Shiva Jamali-Zavareh;David J. Lilja;Marc D. Riedel;Kia Bazargan;Ramesh Harjani;
Abstract: This brief presents a wireline transmitter architecture, enabling multilevel signaling with feedforward equalization (FFE) in voltage-mode. A compact R2R-DAC-based front end is proposed and analyzed in terms of its speed, power consumption, and linearity. A voltage-mode PAM-4 transmitter with 2-tap FFE utilizing the proposed architecture is implemented in the 65-nm CMOS technology. It achieves a data rate of 34 Gb/s and an energy efficiency of 2.7 mW/Gb/s.
Autors: Boyu Hu;Yuan Du;Rulin Huang;Jeffrey Lee;Young-Kai Chen;Mau-Chung Frank Chang;
Appeared in: IEEE Transactions on Very Large Scale Integration Systems
Abstract: Analog transmission of correlated information over Gaussian broadcast channels (BCs) using analog joint source–channel coding (JSCC) is addressed. This communication strategy has attractive advantages, such as low complexity, minimal delay, graceful degradation, and adaptation to time-varying environments. In this paper, we focus on the optimization of parametric continuous mappings that satisfy individual quality of service requirements over Gaussian BCs. This optimization is based on the balancing of the user distortions to ensure the feasibility of the resulting optimization problems. An analysis of the overall distortion corresponding to the considered mappings is carried out to design algorithms that determine the optimal values for the mappings parameters. Results show that the proposed analog JSCC scheme provides near optimal performance and an adequate balancing of the individual distortions.
Autors: Pedro Suárez-Casal;Óscar Fresnedo;Luis Castedo;Javier García-Frías;
Abstract: This paper analyzes the large positive bias of sea surface temperature (SST) retrievals of selected remotely sensed algorithms recorded during the simultaneous occurrence of upwelling and atmospheric subsidence along the coastal waters of Rio de Janeiro, Brazil. The optimal estimator (OE) for retrieving SST and the multichannel (MCSST) and nonlinear (NLSST) estimators are compared using Advanced Very High Resolution Radiometer-3 data. The in situ SST (SSTbuoy) data set used to validate the remotely sensed SST retrievals was collected from five moored buoys (four in the open sea and one in coastal waters). The principal results of this paper are as follows. First, the sensitivity analyses show that OE is quite susceptible to the first-guess SST rather than to the humidity profiles. Second, the comparison between the SSTOE and 365 cloud-free SSTbuoy measurements in open sea waters presents an root mean squared error (RMSE), bias, and standard deviation (STD) with the intervals of [0.5, 0.6], [−0.51, 0.13], and [0.27, 0.48], respectively. Third, the MCSST, NLSST, and OE SST produce a positive bias that can reach 5 K during simultaneous upwelling and atmospheric subsidence in coastal waters. Such unexpected errors are due to low SST values and water vapor compression in the lower layer of the atmosphere related to a temperature inversion. Fourth, an alternative approach using SSTbuoy obtained on the previous day as a first guess instead of the climatological SST significantly improves the errors (SSTOE–SSTbuoy) by reducing RMSE, bias, and STD by 58% (from 3.30 to 1.39 K), 73% (from 3.00 to 0.80 K), and 19% (from 1.38 to 1.12 K), respectively.
Autors: Leonardo F. Peres;Gutemberg B. França;Rosa C. O. V. Paes;Rodrigo C. Sousa;Antônio N. Oliveira;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Abstract: A semi-analytical and efficient computational method is presented for the analysis of uniaxial-anisotropic tapered dielectric rod antennas (DRAs). This technique benefits of the local mode theory to predict the transverse distribution of polarization currents in the tapered dielectric rod. The method results in a formula for the radiation pattern that needs only simple integrations over the cross section of the antenna. Radiation patterns for DRAs of different length and radii are calculated. This technique is validated by the comparison with the data obtained from ANSYS Electronics Desktop full-wave simulator. Furthermore, it is demonstrated that the antenna gain and bandwidth increase over the isotropic DRAs. Also sinusoidal profiles have more gain compared to linear profiles. Moreover, the radiation patterns are calculated for different types of excitation to demonstrate that the method is applicable for any feed system.
Autors: Alireza Bostani;Homayoon Oraizi;
Appeared in: IEEE Transactions on Antennas and Propagation
Abstract: This paper presents the analysis and experimental of the effective normal force and power consumption in a maglev vehicle. A maglev vehicle employs the electromagnets as suspension and linear motors for propulsion. These components give the higher ride comfort but suffered from energy efficiency. Therefore, a vector control-based algorithm and various air gaps are employed to increase the propulsion efficiency and lower the system energy consumption. The effective levitation load according to the levitation gap and normal force of a linear induction motor is calculated by power consumption in a levitation system and compared with finite-element analysis results. The experiment is carried out with the full-scaled train in test line and the efficiency of a propulsion system is also presented.
Abstract: Field-circuit coupling method is increasingly drawing attention from researchers who engage in electric machine design. It is worth mentioning that no related field-circuit coupling methods have been presented to investigate the dynamic performance for slotted limited-angle torque motor (LATM). Hence, this paper presents a simplified field-circuit coupling method to evaluate the dynamic performance including position tracking ability and operating temperature for slotted LATM during its design optimization process. All magnetic saturation problems including nonlinear torque characteristic and inductance parameter variation with rotor position can be taken into account, which is completely consistent with the actual operation condition. The simplified field-circuit coupling method contains a thermal resistance network (TRN) module which can be applied to estimate the slotted LATM operating temperature in accordance with the accurate winding current and copper loss information. Therefore, whether the slotted LATMs meet design requirements should be evaluated before manufacturing prototypes. Related experiments for the slotted LATM are carried out to validate the field-circuit coupling method cooperating with TRN module.
Abstract: Self-mixing or optical feedback interferometry has been widely used for displacement and velocity measurement applications. For metric information retrieval with precision, various phase unwrapping methods have been proposed. However, these are computationally heavy and require large number of hardware resources, thereby hindering the development of real-time, embedded solutions for large bandwidth applications. In this regard, a simple and efficient feedback phase retrieval algorithm, called consecutive samples-based unwrapping (CSU) is presented. Detailed analysis of its error performance has been conducted as a function of key optical feedback parameters. A theoretical study has also been conducted to explain as to why such good error performance is obtained for such a simple algorithm by establishing a linear relation between the modulated laser power signal and the laser phase in the absence of optical feedback for specific ranges of key optical feedback parameters. We applied CSU on various simulated and experimentally acquired signals using SMI for the retrieval of harmonic and arbitrary displacements and found out that CSU retrieves target displacement with a precision of about while consuming much less time and hardware resources. The paper also presents FPGA based hardware design results of CSU and compares its performance with a traditional analytical phase unwrapping method in terms of maximum clock frequency, latency, and on-chip hardware resources. This hardware comparison strongly establishes the advantages of such a fast and computationally light algorithm, readily suitable for large bandwidth, embedded, and real-time sensing applications.
Autors: Ayesha Ehtesham;Usman Zabit;Olivier D. Bernal;Gulistan Raja;Thierry Bosch;
Abstract: This paper presents an analytical method based on the magnetic equivalent circuit to derive permanent magnet (PM) load-lines of two general types of a variable flux memory motor (VFMM), which are circumferentially embedded (CE)-type and radially embedded (RE)-type PM motors. The proposed PM load-line models are valid and suitable for investigating the PM magnetization characteristics of VFMMs. It is validated via visible comparison with the PM load-lines derived by the finite-element method. Furthermore, by making use of the proposed method, the magnetization characteristics of several CE and RE VFMMs, which have different geometry parameters, have been examined and compared. According to the analysis results, RE-type VFMMs require approximately ten times larger remagnetizing field than CE-type VFMMs, although RE VFMMs are further influenced by demagnetizing field than CE VFMMs.
Abstract: A series hybrid variable flux memory (VFM) machine employing two kinds of permanent magnets (PMs) on alternate rotor poles is investigated. This VFM machine features controllable PM flux and thus good flux-weakening capability, as well as improved torque density. However, it is found that the unipolar end leakage flux occurs if the two kinds of PMs are not balanced. According to the analyses of series connection between two PMs based on the fundamental magnetic circuit, the mechanism of the unbalanced rotor poles and the unipolar end leakage flux is revealed. Further, the rule of obtaining balanced poles is identified and the effects of operating conditions are presented. A series hybrid VFM machine prototype is fabricated and tested.
Autors: Z. Q. Zhu;Hao Hua;Adam Pride;Rajesh Deodhar;Toshinori Sasaki;
Abstract: Halbach array magnetic gearboxes have been discussed as being able to create high torque density. However, Halbach arrays are difficult to mechanically assemble, and often the effective air gap must be made larger to provide space for a retaining sleeve. This paper investigates the benefits of using an additional ferromagnetic retaining pole within the Halbach array structure. It is shown that utilizing this flux concentration ferromagnetic pole improves the torque density and can also help retain the magnets in place.
Autors: Debarupa Som;Kang Li;Joshua Kadel;Jason Wright;Sina Modaresahmadi;Jonathan Z. Bird;W. William;
Abstract: In this paper, a novel direct drive, bilateral planar switched reluctance generator (BPSRG) is developed for 2-D wave energy conversion with a mixed type of flux circulation. The proposed BPSRG has longitudinal flux type of the magnetic circuit on one direction and transverse flux-type magnetic circulation for the other perpendicular direction. The characteristics of the magnetic flux and static inductance are calculated for the BPSRG based on the 3-D finite-element method, in order to ensure negligible coupling effect between any phases. Theoretical model of the BPSRG is derived, and parameters that impact the open-loop operation performance of the power generation are analyzed, optimized, and supported by experimental results.
Abstract: The conventional transverse-flux permanent-magnet generator (TFPMG), preferred for wind power applications, has a few limitations, e.g., the flux distribution in a U-shaped stator core is uneven, and its inactive permanent magnet (PM) poles lead to high magnetic flux leakage. In this paper, a new fall-back transverse-flux permanent-magnet generator (FB-TFPMG), suitable for direct-drive applications, is proposed to reduce the magnetic flux leakage between the stator cores and the PMs. In the proposed configuration, half the number of PMs (i.e., only active PMs) are employed with the elliptical-shaped stator core and toroidal-shaped coil. This leads to immediate benefit of lower mass and better flux utilization. The performance of the new topology is analyzed, under no-load and loaded conditions, using a 3-D finite-element tool, and the results are presented in comparison with the conventional TFPMG. The results show improved outcome of the proposed topology in comparison to the conventional TFPMG.
Abstract: A novel linear doubly salient slot permanent magnet motor (LDSSPMM) is proposed in this paper. First, the topology and geometric parameters of the LDSSPMM with 12 slots (12s) are proposed and the basic operating principle is investigated. By analyzing the feasible slot/pole combinations and harmonic winding factors, 11 poles and 13 poles (11p/13p) are proved to have higher winding factor for working harmonic. In addition, the LDSSPMMs with 12s/11p and 12s/13p are optimized by global optimization with genetic algorithm. It is shown that 12s/13p is the optimal slot/pole combination. Finally, the electromagnetic performance of the 12s/13p LDSSPMM is investigated by 2-D finite-element analysis (FEA) and validated by 3-D FEA.
Abstract: A piezoelectric generator (PEG) under propagation of an elastic wave is studied. A PEG under an elastic wave shows a different phenomenon compared to a shock wave, especially in pulse rise time. With the shock wave, the rise time of the generated impulse waveform is the same as the wave propagation time in the piezoelectric material. But, the rise time of the impulse waveform due to an elastic wave is longer than the propagation time. To examine this phenomenon, a physical model is established, and the experiment data and the calculation results are compared to verify the model.
Abstract: Measurements of the ac susceptibility (ACS) as a function of frequency have been widely applied for the determination of structure parameters of magnetic nanoparticles (MNP). The analysis of spectra of real and imaginary parts measured on suspensions of MNP is generally based on the Debye model, extended by distributions of size parameters. Here, we compare different modifications of the Debye model with experimental data recorded on suspensions of single-core and multi-core iron-oxide nanoparticles. The applied models also depend on whether the nanoparticle’s magnetic moments are thermally blocked and whether both Brownian and Néel relaxation have to be taken into account. The obtained core and hydrodynamic size parameters are compared with those from transmission electron microscopy and dynamic light scattering. Whereas structure parameters can be reliably determined for single-core nanoparticles, the interpretation of ACS spectra measured on multi-core nanoparticles is more complicated, especially regarding the contribution of particles relaxing via the Néel mechanism. Depending on the packing density and thus the interaction between cores in a particle, the effective core parameters derived from the spectrum must be interpreted with care.
Autors: Frank Ludwig;Christoph Balceris;Christian Jonasson;Christer Johansson;
Abstract: The technology to send a magnetic field in a particular direction, known as energy beamforming, has been recently introduced as a magnetic field shaping technology in nonradiative wireless power transmission. In general, one of the most efficient conditions for energy beamforming is that the magnetic fields induced by each antenna should be synthesized to head the same direction. To synthesize the magnetic fields induced at each antenna, interference by mutual inductance that can occur between transmitting (TX) antennas should be minimized. In addition, energy should not be exchanged between the TXs, otherwise it lowers the transmission efficiencies of TX and receiving antenna. In this paper, we present an optimal antenna structure that minimizes the mutual inductance between two TX antennas. First, we have analyzed the mutual inductance between TX antennas that have asymmetric sizes with different antenna lengths and arrangement angles. The directivity of the magnetic field vector is also investigated through an experimental analysis of an antenna structure. Finally, it has been verified that the optimal TX antennas for energy beamforming should be symmetric, which means that all the length of antennas are same and disposed perpendicular to each other. The experimental results show that the deviations of magnetic field directivity for symmetric and asymmetric antennas are 0.045 and 0.355, respectively, which shows that the symmetric structure shows 8.2 times larger consistency over the asymmetric structure.
Autors: Yongseok Lim;Hyun-Seok Ahn;Jongsun Park;
Appeared in: IEEE Transactions on Antennas and Propagation
Abstract: Common solids (e.g., flour, sugar, etc.,) can be suspended and transported in air via pneumatic conveying systems. Finely divided solid substances dispersed into a dust cloud (e.g., into a silo) can form a potential explosive atmosphere, if in the right concentration with the oxidizing agent (e.g., air). In addition, it is known that the pneumatic handling of substance, which allows its transport at a certain velocity, can generate static charges; thus, a possible competent ignition source may be also created. In this paper, the causation of an actual dust explosion involving a flour silo being loaded from a tank truck through pneumatic conveying systems in an industrial plant is analyzed. The mechanisms of static discharge applicable to the case in question are discussed, in light of both actual empirical data collected at the incident site, and theory. To fully explain the events that led to the explosion, plausible hypotheses and alternative to static discharge were also evaluated.
Abstract: In this paper, the dark count mechanisms of 4H-SiC ultraviolet avalanche photodiodes (APDs) working in Geiger mode are studied by temperature-dependent characterizations. At temperatures above 260 K, the activation energy derived from the dark count characteristics is much less than half of the bandgap of 4H-SiC. Trap-assisted tunneling is determined as the dominant carrier transport mechanism in this temperature regime, which is supported by the observed capacitance frequency dispersion and low-temperature persistent photoconductivity effect. As temperature further decreases, the temperature dependence of dark count rate (DCR) becomes weaker, suggesting that band-to-band tunneling starts to play a role in the dark count generation process, which turns into the major mechanism below 120 K. As a consequence, one way to suppress dark counts for SiC APDs is to inhibit tunneling process, which can be realized by increasing the intrinsic layer thickness. In addition, it is found that when the single photon detection efficiency is in the range of 0%–30%, the DCR of the SiC APD can be reduced by an order of magnitude as temperature decreases from room temperature to 77 K, which is the first report of low-temperature performance of SiC APDs.
Abstract: This paper describes the analysis of the eddy current loss of a double-sided cored slotless-type permanent magnet linear synchronous generator considering tapped holes in mover magnets using the space harmonic method. To calculate the eddy current, an analytical solution was derived by applying the Maxwell’s equation, magnetic vector potential, and Faraday’s law in a 2-D Cartesian coordinate system. Based on the armature reaction field distribution produced by the armature winding current, we obtained an analytical solution for the eddy current density distribution. Then, an analytical solution for eddy current loss induced in a permanent magnet (PM) was derived using the equivalent electrical resistance calculated from the PM’s volume and eddy current density distribution solution. Finally, the resulting current was determined based on the analysis of eddy current loss. The analytical results produced by using this application of the space harmonic method were validated extensively through comparisons with finite-element method results.
Abstract: Microgrids are subjected to limits on system voltage and frequency deviations for transient and steady state operation. Similar to a conventional power system with rotating generators, inertia and damping of frequency are necessary for frequency profile and stability of an isolated microgrid. This work proposes an approach to analyze inertia and frequency damping coefficient for a system based on the fact that sources relatively close to each other observe similar transients in frequency within an isolated microgrid. This is validated through bode plots and simulation. The approach allows defining the system response to transients in frequency in terms of individual source response using standard frequency mode parameters such as damping and inertia. Further, to optimize the overall system response so that sources share the frequency regulation requirement, a novel strategy is proposed to design individual source inertia and damping coefficient based on the source capacity. An experimental setup consisting of a microgrid system having three inverter-based sources working as virtual synchronous generators operating in parallel has been set up to verify the analysis.
Autors: Nimish Soni;Suryanarayana Doolla;Mukul C. Chandorkar;
Appeared in: IEEE Transactions on Industry Applications
Abstract: The Poisson point process (PPP) has been widely employed to model wireless networks and analyze their performance. The PPP has the property that nodes are conditionally independent from each other. As such, it may not be a suitable model for many networks, where there exists repulsion among the nodes. In order to address this limitation, we adopt a Poisson hardcore process (PHCP), in which no two nodes can be closer than a repulsion radius from one another. We consider two-tier heterogeneous networks, where the spatial distributions of transmitters in the first-tier and the second-tier networks follow a PHCP and a PPP, respectively. To alleviate inter-tier interference, we consider a guard zone for the first-tier network and presume that the second-tier transmitters located in the zone are deactivated. Under this setup, the activated second-tier transmitters form a Poisson hard-core hole process. We first derive exact computable expressions of the coverage probability and introduce a method to efficiently evaluate the expressions. Then, we provide approximations of the coverage probability, which have lower computational complexities. In addition, as a special case, we investigate the coverage probability of single-tier networks by modeling the locations of transmitters as a PHCP.
Autors: Ian Flint;Han-Bae Kong;Nicolas Privault;Ping Wang;Dusit Niyato;
Appeared in: IEEE Transactions on Wireless Communications
Abstract: This paper introduces an alternative pathway to designing an efficient interior permanent magnet machine (IPMM) for direct–drive (D-D) wind energy applications. It analyzes the design optimization methodology in great detail, employing multiple experimental verifications to acutely pinpoint the most desirable and feasible format. The focal objectives of minimizing cogging torque, torque ripple, and maximizing efficiency were among the priority design goals and obtained through design optimization. It is demonstrated in the process that both the torque ripple and the cogging torque can be reduced to less than 5% by adjusting the slot and pole dimensions, without any other alterations in rotor pole shaping or skewing. This paper leads the way, pioneering experimental substantiation of theory, by varying existing geometrical parameters, winding, and pole design of a basic IPMM to come up with a highly efficient wind turbine generator with negligible cogging torque and torque ripple. The electromagnetic is at the heart of this paper’s design goals, as parameter optimization is essential for a wind turbine application. The winding layout is brought under scrutiny and both the distributed and concentrated wound IPMMs are compared to further adopt the design optimization. The superiority of the concentrated-wound design is demonstrated, and consequently a prototype machine is constructed based on the proposed design for experimental verification. The results from the experiment verify the feasibility of the proposed design for D-D wind turbine applications.
Abstract: Among key technologies that support areal density growth, shingled magnetic recording (SMR) can be applied with a conventional magnetic recording head and does not require significant head design or structure changes compared to heat-assisted magnetic recording and microwave-assisted magnetic recording. Shingled writing is also essential for 2-D magnetic recording. In the application of SMR with a conventional head which has a single reader and a symmetrical writer, one would expect equal performance between writing with the inner side and the outer side when the head is at 0° skew angle. However, it is found statistically, with a large quantity of samples, that there is a preference toward writing with either inner or outer side depending on whether the head is an up or down facing head in a drive. Two types of readers with opposite wafer level free layer (FL) and reference layer (RL) canting directions also show opposite preference for the data written by the same heads. Experiments performed suggest that the reader may induce some “skew” bias in SMR application on top of the writer contribution. A hypothesis combining reader FL direction and reader RL canting is proposed to explain the observed phenomena.
Abstract: Two equivalent models to sleeve dipole antennas fed by ferrite-loaded coaxial cables for a scaled-down cross-borehole radar are tested by employing the finite-difference time-domain method. Compared to the measured diffraction patterns of an air-filled circular cylinder in water, the simulated results based on the simplified perfect magnetic conductor model cannot provide sufficient attenuation not only in the single dip pattern at 2.6 GHz but also in double dip pattern at 2.8 GHz. It leads us to develop a more accurate one so-called distributed element model which is implemented by a finite sum of serial sections consisting of a resistor, a finite length of perfect electric conductor (PEC) cylinder, an inductor, and the same PEC cylinder. When the values of the distributed elements as well as the number of serial sections are adjusted properly, the simulated diffraction patterns closely approach to the experimentally measured data at both frequencies of 2.6 and 2.8 GHz.
Autors: Ji-Hyun Jung;Jae-Hyoung Cho;Se-Yun Kim;
Appeared in: IEEE Transactions on Antennas and Propagation
Abstract: The noise of electrical machines has drawn more attention in recent years due to their harm to people and the environment. Normal skewed slot has proven to be an effective method to reduce vibration and noise of squirrel-cage induction motor. Double skewed slot is superior to normal skewed slot on reducing vibration and noise. However, it is still difficult to meet the requirements of noise standards in some occasions. In this paper, based on double skewed slot, a new skewed slot type is proposed, which can offer a better effect on reducing vibration and noise. 2-D fast Fourier transform and 3-D finite-element method are adopted to analyze and compare the performance of the three types of skewed slots.
Abstract: This paper discusses a motor that was designed to satisfy the size constraints of system by using ferrite magnet and has the same performance as rare-earth magnet motor. In general, the size of the motor is increased in order to meet the same performance of motor using a ferrite magnet, because of its very low energy density compared to the rare-earth magnet. In order to compensate for these drawbacks, spoke structures capable of generating maximum magnetic flux at the same rotor size have been frequently studied. However, the spoke type motor structure has a drawback that demagnetization occurs in a magnet-specific portion. However, because it affects harmonics of the airgap flux density by demagnetization, it affects mechanical torque ripple and vibration. Therefore, in this paper, the changed air-gap flux density due to the demagnetization phenomenon and the changed mechanical vibration are analyzed by the finite-element method. In addition, we proposed an optimal rotor structure that can reduce the demagnetization phenomenon of magnets in spoke interior permanent magnet synchronous motor. Experiments were performed to evaluate the reliability of the optimized design.
Abstract: The plasma sheath surrounding a hypersonic vehicle will cause severe interference to the wireless communications and even interrupt the communications, threatening the flight safety. To better understand and mitigate the interference of the plasma sheath to electromagnetic (EM) wave propagation, the interaction mechanisms between them are studied in this paper. First, using the COMSOL multiphysics software, the flow field of the plasma sheath is simulated, from which the EM parameters are obtained. The plasma sheath is then separated into three zones with different behaviors of the electron density profile. Finally, combining the theory of the EM wave propagation in the plasma, ray tracing equations are solved numerically to observe the EM wave propagation characteristics in the plasma sheath. On this basis, some special propagation characteristics result, such as the directional characteristic of the wave propagation and the “waveguide” behavior of the plasma sheath, which are then explained using the geometrical optics theory. The results obtained in this paper are expected to be able to provide some new applications for wireless communications during hypersonic flight, and to further advance the research related to this subjects.
Abstract: Ion thruster is the most useful electronic propulsion system in deep space to control the orbit of a satellite due to its high exhaust velocity. Erosion of extraction grid is a critical parameter, which limits the life of an ion thruster. In this paper, an analytical model has been presented to estimate the rate of erosion of the extraction grid. The analytical results show that the rate of erosion can be reduced by about 66% using modified extraction grid as compared with conventional grid.
Autors: S. E. Rahaman;A. K. Singh;S. K. Shukla;R. K. Barik;
Abstract: We study magnetization oscillations in a uniformly magnetized nanomagnet driven by ac excitations (external fields and injected currents) when the frequency of excitation is close to ferromagnetic resonance frequency. By using separation of time scale and the averaging technique, we derive dynamical equations, which can be studied by the methods of dynamical systems theory. This leads to an analytical description of nonlinear frequency response and to the analysis of relevant bifurcation phenomena. The theoretical results are compared with numerical simulations.
Autors: M. d’Aquino;A. Quercia;V. Scalera;S. Perna;G. Bertotti;I. D. Mayergoyz;C. Serpico;
Abstract: Magnetization reversal in segmented Co/Ni nanowires with varying number of segments was studied using angular magnetoresistance (MR) measurements on isolated nanowires. The MR measurements offer an insight into the pinning of domain walls (DWs) within the nanowires. Angular MR measurements were performed on nanowires with two and multiple segments by varying the angle between the applied magnetic field and nanowire (). The angular MR measurements reveal that at lower values of , the switching fields are nearly identical for the multisegmented and two-segmented nanowires, whereas at higher values of , a decrease in the switching field is observed in the case of two-segmented nanowires. The two-segmented nanowires generally exhibit a single DW pinning event, whereas an increased number of pinning events are characteristic of the multisegmented nanowires at higher values of . In situ magnetic force microscopy substantiates reversal by DW nucleation and propagation in multisegmented nanowires.
Autors: H. Mohammed;H. Corte-León;Y. P. Ivanov;J. A. Moreno;O. Kazakova;J. Kosel;
Abstract: In this paper, the anisotropic consolidation behavior of isotropic Nd–Fe–B HDDR powders has been studied as a function of the strain, strain rate, and processing temperature. The compacts, produced by hot-pressing at 700 °C under 400 MPa in vacuum, were subjected to die-upsetting at 700 °C and 800 °C with different deformation conditions of strain rate 0.01–0.001 s−1 and strain 0.5–1.5. After die-upset, the coercivity and remanence decreased and increased with increasing strain, respectively, with the change of grain morphology from the sphere to platelet. And the high deformation temperature and slow deformation rate reduce the coercivity further. The coercivity of die-upset magnet, produced at 700 °C with a strain of 1.4 and a strain rate of 0.001 s−1, was largely increased about 2 kOe after post-annealing at 800 °C. The maximum coercivity, remanence, and (BH)max were 10.4 kOe, 12.4 kG, and 35.6 MGOe, respectively.
Abstract: In this paper, an analysis method and a measurement method for anisotropic magnetic shielding effectiveness (MSE) are discussed. Some magnetic sensors and memories require small magnetic shielded packages to decrease the influence of external magnetic noise. Whereas, the packages are applied for the external noise from various directions, sensitivity of the magnetic device in the package is affected by the direction and intensity of applied field noise. Influenced by the directions of external and internal magnetic fields, MSE of the shielded package varies several dozen decibels. Therefore, understanding the anisotropic MSE of the shielded package is indispensable for designing a shielded package that prevents malfunctions attributable to external magnetic noise. The MSE matrix and the directivity of MSE are introduced as evaluation indicators of the anisotropic MSE. The MSE matrix and the directivity of MSE revealed that the MSE of the fabricated package varied significantly, from 24 dB to more than 60 dB, according to the direction of external field and internal field.
Abstract: We have investigated the magnetic properties of evaporated Co thin films covalently functionalized with different organic thin films, namely, 1-(2-bisthienyl benzene) and nitrobenzene. The coating is realized thanks to a diazonium-based electro-reduction process. Brillouin light scattering experiments revealed that the magnetic properties are sensitive to the presence of the organic film. For 1-(2-bisthienyl benzene) thin films, the perpendicular magnetic anisotropy is increased as well as the magnetic damping. However, for nitrobenzene, only the perpendicular anisotropy is increased albeit less than for 1-(2-bisthienyl benzene). This change in magnetic properties might be attributed to the coupling with the organic molecules.
Autors: O. Rousseau;S. M. Chérif;Y. Roussigné;M. Belmeguenai;P. Martin;J-C. Lacroix;M. L. Della Rocca;P. Lafarge;C. Barraud;
Abstract: The electrical degradation of InAlN/GaN high-electron-mobility transistors for millimeter-wave applications has been examined under simultaneous high and high electrical stress. Besides a drain current decrease and a positive threshold voltage shift, the creation of an anomalous source-side gate leakage path has been identified. We attribute this to high electric-field induced trap generation in the AlN layer directly under the gate edge on the source side. The resulting increase in gate leakage further exacerbates the degradation of the gate diode. In addition, we postulate that high-power stress leads to significant device self-heating that causes gate sinking and leads to a permanent positive threshold voltage shift and drain current degradation.
Autors: Yufei Wu;W. A. Sasangka;Jesus A. del Alamo;
Appeared in: IEEE Transactions on Electron Devices
Abstract: Minimizing the ongoing impact of train delays has benefits to both the users of the railway system and the railway stakeholders. However, the efficient rescheduling of trains after a perturbation is a complex real-world problem. The complexity is compounded by the fact that the problem may be both dynamic and multi-objective. The aim of this research is to investigate the ability of ant colony optimization algorithms to solve a simulated dynamic multi-objective railway rescheduling problem and, in the process, to attempt to identify the features of the algorithms that enable them to cope with a multi-objective problem that is also dynamic. Results showed that, when the changes in the problem are large and frequent, retaining the archive of non-dominated solution between changes and updating the pheromones to reflect the new environment play an important role in enabling the algorithms to perform well on this dynamic multi-objective railway rescheduling problem.
Abstract: For phased arrays used in satellite communications and radio astronomy, high sensitivity is required, and minimizing antenna losses is critical. Losses for single antennas can be minimized using high conductivity materials. It is less well understood that loss for array antennas is also influenced by mutual coupling between array elements and the beamformer weights applied to the signal from each element. In this paper, we study the antenna loss and receiving efficiency for phased array antennas and focal plane phased array feeds. To better elucidate the physics of array antenna loss related to mutual coupling and beamformer weights, losses for a coupled array can be lumped into an array effective resistance similar to the loss resistance of an equivalent single antenna. Numerical results show that although the antenna loss for a single isolated array element is low, the array antenna loss can be significantly increased by mutual coupling, particularly for beams with a large scan angle.
Autors: Junming Diao;Karl F. Warnick;
Appeared in: IEEE Transactions on Antennas and Propagation
Abstract: This letter proposes an antenna tilt adaptation approach for multi-cell massive multiple-input multiple-output systems. The asymptotic spectral efficiency of the system with pilot contamination in the limit of the antennas is first derived. The analysis demonstrates that the spectral efficiency is a concave function of the tilts with some specific requirements being satisfied. As a result, a gradient descent-based method is proposed to approach the optimal tilt. Numerical results verify that the proposed approach performs better than a traditional low-complexity approach.
Abstract: Provisioning of hardware resources through virtual machines (VMs) has been widely used for supporting server consolidation and infrastructure-as-a-cloud computing. We propose NICBLE to support accurate CPU resource provisioning for application workload running on VMs. While CPU is essential for any application workload, not every workload requires the same level of CPU resource. The VM tenants may also have different expectations of application performance and preferences. NICBLE models the execution of an application workload and employs a simulation-based algorithm to predict the impact on application execution time for a hypothetical VM configuration change on the number of CPUs. One may use NICBLE to reason about whether changing the number of CPUs will significantly affect the application performance. We built the NICBLE prototype on top of the Xen hypervisor  . NICBLE does not require modification to the guest systems. The performance overhead on the guest system is negligible. Our evaluation indicates that NICBLE is able to provide accurate prediction with an average error rate of less than 15 percent for non-adaptive application workload.
Abstract: In systems with hydraulic predominance, the medium-term hydrothermal scheduling problem (MTHS) is usually modeled as a stochastic programming model where the objective is to obtain an optimal operation policy over a planning horizon. Inflows follow a stochastic process that is approximated by a multistage scenario tree and a multistage stochastic programming model is employed to compute the generation policy. The difficulty in solving the MTHS depends on the size of the scenario tree. To obtain a small but representative scenario tree, we employ the scenario reduction algorithm of Kovacevic and Pichler with quadratic process distances defined by appropriate metrics exploiting relevant features of the problem. Numerical assessments of the MTHS problem, using a reduced hydrothermal configuration extracted from the Brazilian system, show that reduced trees obtained by eliminating 80% scenarios provide approximate solutions to the problem with less than 1% accuracy errors and CPU time reduction of around 90%.
Autors: Felipe Beltrán;Welington de Oliveira;Erlon Cristian Finardi;
Abstract: In this literature, we have investigated the magnetic properties and Schottky device-based charge transport properties of hydrothermally derived Mn0.04Cu0.05Zn0.91O nanorod. The doping of 3-D transitional metals, Mn and Cu, within ZnO makes it potentially applicable in spin-based electronics, whereas its temperature-dependent conductivity (of the order of 10−3 in C.G.S.) makes it suitable for semiconductor-based devices. The observation of intrinsic ferromagnetism of the synthesized composite and its variation of magnetization with magnetic field and temperature exhibited the suitability of spin-based electronic application. To check the applicability in optoelectronic devices, metal–semiconductor (Al/Mn0.04Cu0.05Zn0.91O) junction was fabricated and analyzed. The current–voltage characteristic represented the rectifying behavior of the junction with on/off current ratio 4.3 at ±1 V in dark and potential barrier height 0.61 eV. The significant change in rectification due to the influence of incident radiation makes this material suitable for photosensing electronic device application.
Abstract: We analyze the performance of direct detection receivers with low-order bandpass filtering in terms of achievable rates. Such analysis is of interest in the context of millimeter-wave wireless systems as well as wired and wireless optical links, where low power and low cost are considered to be key requirements. By using a bandpass filter with asymmetric passband transfer function of low order ( roll-off rate) prior to the intensity detection device (a diode or photodiode), we show that the ideal Shannon data rate attainable with coherent receivers can still be asymptotically approached with simple filtering and direct detection. We also discuss practical aspects that partially limit this remarkable behavior, and show that gains are still possible compared with conventional direct detection.
Abstract: The computation of the achievable sum rate for integer-forcing (IF) linear receivers requires the search for the shortest set of linearly independent lattice vectors (SIVP). Since SIVP is considered an NP-hard problem, we propose two approximations to the IF achievable sum rate. The first approximation is suitable for systems with two antennas at both transmitter and receiver ( arrays) and is based on the analysis of the Gauss-Lagrange algorithm. The second approximation considers array systems and is based on Minkowski’s second theorem. Assuming a block-fading channel with Rayleigh distribution, we have derived the exact probability density function of both approximations. We have used these results to obtain the mean sum-rate, outage probability, and outage rate for uncorrelated fading channels. For the second approximation, the effect of channel correlation on these metrics was also analyzed. An exhaustive series of simulations have been conducted to assess the tightness and robustness of both solutions.
Autors: André Saito Guerreiro;Gustavo Fraidenraich;Santosh Kumar;
Abstract: Modern high-level synthesis (HLS) tools commonly employ pipelining to achieve efficient loop acceleration by overlapping the execution of successive loop iterations. While existing HLS pipelining techniques obtain good performance with low complexity for regular loop nests, they provide inadequate support for effectively synthesizing irregular loop nests. For loop nests with dynamic-bound inner loops, current pipelining techniques require unrolling of the inner loops, which is either very expensive in resource or even inapplicable due to dynamic loop bounds. To address this major limitation, this paper proposes ElasticFlow, a novel architecture capable of dynamically distributing inner loops to an array of processing units (LPUs) in an area-efficient manner. The proposed LPUs can be either specialized to execute an individual inner loop or shared among multiple inner loops to balance the tradeoff between performance and area. A customized banked memory architecture is proposed to coordinate memory accesses among different LPUs to maximize memory bandwidth without significantly increasing memory footprint. We evaluate ElasticFlow using a variety of real-life applications and demonstrate significant performance improvements over a state-of-the-art commercial HLS tool for Xilinx FPGAs.
Autors: Gai Liu;Mingxing Tan;Steve Dai;Ritchie Zhao;Zhiru Zhang;
Appeared in: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems
Abstract: Applying the recursive compensated simplified reformulated inversionless Berlekamp–Massey (rCS-RiBM) architecture, an improved Reed–Solomon (RS) decoder with the advantages of high speed and high area efficiency is proposed in this letter. The proposed architecture only includes a processing element and a compensation unit, resulting in low hardware complexity. In addition, to further increase the throughout, we adopt the technique of pipelining and new initialization. The RS (255, 239) decoder applying the rCS-RiBM architecture has been designed and synthesized with SMIC 0.18- CMOS technology library. The results illustrate that our decoder needs about 13k gates (excluding FIFO stacks) and operates at 640 MHz to achieve the throughout of 5.1 Gb/s, which can be applied in optical communication systems. Meanwhile, it is at least 11% more area-efficient compared with previously reported RS decoders.
Abstract: This letter focuses on the hard deadline constrained prioritized data multicasting scene, in which each user device (UD) that equips with dual wireless interfaces can receive data from the base station and transmit or receive data from near-by UDs simultaneously. In order to maximize the sum throughput, we aim to find the optimal and suboptimal solutions using the backward induction algorithm (BIA) and greedy algorithm (GA) based on full feedback. To decrease the large feedback resources caused by full feedback, we propose a limited feedback strategy, which requires very few channel occupation. We find that the optimal and suboptimal solutions under this limited feedback strategy can also be solved using BIA and GA, but with high complexity. Hence, a heuristic algorithm under this strategy is proposed, which has very low complexity and can keep considerable performance at the same time.
Abstract: Direct time-of-flight (d-ToF) estimation with high frame rate requires the incorporation of a time-to-digital converter (TDC) at pixel level. A feasible approach to a compact implementation of the TDC is to use the multiple phases of a voltage-controlled ring-oscillator (VCRO) for the finest bits. The VCRO becomes central in determining the performance parameters of a d-ToF image sensor. In this paper, we are covering the modeling, design, and measurement of a CMOS pseudo-differential VCRO. The oscillation frequency, the jitter due to mismatches and noise and the power consumption are analytically evaluated. This design has been incorporated into a -pixel array. It has been fabricated in a 0.18 standard CMOS technology. Occupation area is and power consumption is 1.17 mW at 850 MHz. The measured gain of the VCRO is of 477 MHz/V with a frequency tuning range of 53%. Moreover, it features a linearity of 99.4% over a wide range of control frequencies, namely, from 400 to 850 MHz. The phase noise is of -102 dBc/Hz at 2 MHz offset frequency from 850 MHz. The influence of these parameters in the performance of the TDC has been measured. The minimum time bin of the TDC is 147 ps with a rms DNL/ INL of 0.13/ 1.7LSB.
Autors: Ion Vornicu;Ricardo Carmona-Galán;Ángel Rodríguez-Vázquez;
Appeared in: IEEE Transactions on Circuits and Systems I: Regular Papers
Abstract: Artificial intelligence (AI) techniques, such as expert systems (ESs), fuzzy logic (FL), and artificial neural networks (ANNs or NNWs) have brought an advancing frontier in power electronics and power engineering. These techniques provide powerful tools for design, simulation, control, estimation, fault diagnostics, and fault-tolerant control in modern smart grid (SG) and renewable energy systems (RESs). The AI technology has gone through fast evolution during last several decades, and their applications have increased rapidly in modern industrial systems. This special issue will remain incomplete without some discussion on AI applications in SG and RESs. The paper will discuss some novel application examples of AI in these areas. These applications are automated design of modern wind generation system and its health monitoring in the operating condition, fault pattern identification of an SG subsystem, and control of SG based on real-time simulator. The concepts of these application examples can be expanded to formulate many other applications. In the beginning of the paper, the basic features of AI that are relevant to these applications have been briefly reviewed.
Abstract: This paper studies the artificial noise (AN) aided beamforming design in the multiple-input, single-output, and multiple-eavesdropper wiretap channel from the perspective of secrecy outage. Unlike many existing works, which directly adopted the traditional null-space AN scheme, we start with a general assumption on the structure of the transmit signal, and seek to find the optimal structure by solving a secrecy outage probability (SOP) constrained secrecy rate maximization problem. By generalizing several existing conclusions regarding a single-antenna eavesdropper, we prove that the null-space AN scheme is indeed optimal for an arbitrary number of the eavesdropper’s antennas from the perspective of secrecy outage. Furthermore, the optimal power allocation between the information-bearing signal and the AN is found under both general conditions and the conservative assumption that the eavesdropper can be arbitrarily close to the transmitter or his receiver noise power can be arbitrarily low. It is also found that the increase in the eavesdropper’s antenna number is equivalent to requiring a smaller SOP under the conservative assumption. The results in this paper can help generalize existing design solutions for single-antenna eavesdroppers to multi-antenna eavesdroppers.
Autors: Bo Wang;Pengcheng Mu;Zongze Li;
Appeared in: IEEE Transactions on Wireless Communications
Abstract: The current state-of-the-art method used for medium- and long-term planning studies of hydrothermal power system operation is the stochastic dual dynamic programming (SDDP) algorithm. The computational savings provided by this method notwithstanding, it still relies on major system simplifications to achieve acceptable performances in practical applications. In contrast with its actual implementation, simplifications in the planning stage may induce time-inconsistent policies, and consequently, a suboptimality gap. In this paper, we extend the concept of time inconsistency to measure the effects of modeling simplifications in the SDDP framework for hydrothermal operation planning. Case studies involving simplifications in transmission lines modeling and in security criteria indicate that these source of time inconsistency may result in unexpected reservoir depletion and spikes in energy market spot prices.
Autors: Arthur Brigatto;Alexandre Street;Davi M. Valladão;
Abstract: In the last decade, the transmission system operator (TSO) in Great Britain has seen an acute declining trend of reactive power demand during periods of minimum load. Reactive power traditionally being absorbed by distribution networks is now in many cases injected to transmission. This not only results in significant voltage regulation challenges to the TSO but may also trigger future requirements for distribution network operators (DNOs) to manage these reactive power exchanges. Nonetheless, for the TSO and DNOs to adopt suitable investment strategies, it is crucial to first quantify the extent of this decline in the near future. This study proposes a methodology to identify trends of reactive power demand using historical DNO monitoring and network data. Multiple scenarios are also considered to cater for potential changes in demand, generation, and networks. The methodology is demonstrated on real British distribution networks, from the transmission–distribution interface to primary substations. The assessment reveals the significant effect of demand trends in primary substations on the overall transmission–distribution exchanges. It was also found that the potential use of shunt reactors in distribution networks would require significant investment, highlighting the importance of understanding reactive demand trends in planning cost-effective solutions.
Autors: Christos G. Kaloudas;Luis F. Ochoa;Ben Marshall;Shanti Majithia;Ian Fletcher;
Abstract: The vast majority of power transformers have an insulation system consisting of both insulating mineral oil and Kraft paper. The principal oil degradation agents are oxygen and temperature, whereas the main mechanisms of insulating Kraft paper degradation are water and acids (acidic hydrolysis degradation), temperature (pyrolytic degradation), and oxygen (oxidative degradation).
Abstract: One may identify two independent sources of nonlinearities in digital-to-analog converters: (i) deviations at input sources and switches and (ii) nonidealities in the posterior summation circuit. The first are described by specific figures of merit, mainly integral nonlinearity and differential nonlinearity; the second, in terms of standard amplifier performance (e.g., total harmonic distortion, and so on). Performance is assessed without considering prior separation of the two, resulting in misleading characterization. We address the cross influence of (i) and (ii), and propose a novel figure of merit for bandpass response that separately addresses nonlinear deviations and memory effects attending to DACs inner structure.
Autors: José Luis Blanco-Murillo;Virginia Yagüe-Jiménez;Francisco Javier Casajús-Quirós;
Appeared in: IEEE Transactions on Instrumentation and Measurement
Abstract: Since the boom of smartphones and location-based services, spatio-temporal data (i.e., user locations with timestamps) have become increasingly essential in many real-life applications. To ensure these data are faithfully extracted from the underlying location tracking hardware and not altered by any malicious party or the user himself/herself, integrity assurance schemes such as digital signatures or message authentication codes (MAC) must be adopted. However, these conventional schemes disclose to the verifier the complete plaintext location and thus jeopardize users’ privacy. In this paper, we propose an integrity assurance scheme with minimum location disclosure. That is, the granule of the disclosed location is just small enough to prove the user is/has been to a certain place, and the verifier cannot learn anything beyond it. To this end, we propose a new MAC scheme called Prefix-verifiable MAC (PMAC), based on which we design indexes and protocols to authenticate both spatial and spatio-temporal predicates. Security analysis and experimental results show our scheme is both secure and efficient for practical use.
Abstract: We investigate the behavior of Linear Time-Varying (LTV) systems with randomly appearing, sub-stochastic system matrices. Motivated by dynamic fusion over mobile networks, we develop conditions on the system matrices that lead to asymptotic stability of the underlying LTV system. By partitioning the sequence of system matrices into slices, we obtain the stability conditions in terms of slice lengths and introduce the notion of unbounded connectivity , i.e., the time-intervals, over which the multi-agent network is connected, do not have to be bounded as long as they do not grow faster than a certain exponential rate. We further apply the above analysis to derive the asymptotic behavior of a dynamic leader-follower algorithm.
Autors: Sam Safavi;Usman A. Khan;
Appeared in: IEEE Transactions on Automatic Control
Abstract: In this paper, we study the problem of real-time optimal distributed partitioning for perimeter patrolling in the context of multicamera networks for surveillance, where each camera has limited mobility range and speed, and the communication is unreliable. The objective is to coordinate the cameras in order to minimize the time elapsed between two different visits of each point of the perimeter. We address this problem by casting it into a convex problem in which the perimeter is partitioned into nonoverlapping segments, each patrolled by a camera that sweeps back and forth at the maximum speed. We then propose an asynchronous distributed algorithm that guarantees that these segments cover the whole patrolling perimeter at any time and asymptotically converge to the optimal centralized solution under reliable communication. We finally modify the proposed algorithm in order to attain the same convergence and covering properties even in the more challenging scenario, where communication is lossy and there is no channel feedback, i.e., the transmitting camera is not aware whether a packet has been received or not by its neighbors.
Abstract: The authors would like to apologize for and correct a few errors about the references in our recently published paper ( of this reply), and make some comments:
References  (by T. Alfrey et al.) and  in our paper should be  (by R. M. Fuoss et al.) and  as listed in this reply, respectively.
We would also like to recognize the work of Paolucci et al. ( of this reply), in particular, their introduction of two transformation variables (Eq. (4)) to solve the nonlinear cylindrical 1-D Poisson’s Equation. We were not aware of their work at the time of our paper publication. Actually, the involved transformation variables/method were first reported by Fuoss et al., hereinafter referred to as Fuoss’ transformation variables/method. On the other hand, it should be pointed out that before the paper by Paolucci et al. was submitted for consideration of publication, we had been aware of the work of Fuoss et al. The related early work of our corresponding author (Chen) dates back to 2001 (e.g.,  in our paper). All the research reports of our students, including the cited thesis ( in our paper) of Jun Zhou (one of our authors), have been well documented in the database and library of our university. Jun Zhou’s first report on Fuoss’ transformation variables was submitted in November of 2014 (the evidence materi-
l has been submitted to the editor for a review). In his report, Jun Zhou used Fuoss’ transformation variables to prove that the cylindrical nonlinear Poisson’s equation can be transformed to the Cartesian form. His thesis proposal  was submitted in November of 2015 for an approval from his advisor and the thesis committee. The thesis was completed and officially signed (and documented in our university library) in May of 2016.
Autors: Chuyang Hong;Jun Zhou;Rui Wang;Jiasheng Huang;Wenlong Bai;James B. Kuo;Yijian Chen;
Abstract: Brain extraction or whole brain segmentation is an important first step in many of the neuroimage analysis pipelines. The accuracy and the robustness of brain extraction, therefore, are crucial for the accuracy of the entire brain analysis process. The state-of-the-art brain extraction techniques rely heavily on the accuracy of alignment or registration between brain atlases and query brain anatomy, and/or make assumptions about the image geometry, and therefore have limited success when these assumptions do not hold or image registration fails. With the aim of designing an accurate, learning-based, geometry-independent, and registration-free brain extraction tool, in this paper, we present a technique based on an auto-context convolutional neural network (CNN), in which intrinsic local and global image features are learned through 2-D patches of different window sizes. We consider two different architectures: 1) a voxelwise approach based on three parallel 2-D convolutional pathways for three different directions (axial, coronal, and sagittal) that implicitly learn 3-D image information without the need for computationally expensive 3-D convolutions and 2) a fully convolutional network based on the U-net architecture. Posterior probability maps generated by the networks are used iteratively as context information along with the original image patches to learn the local shape and connectedness of the brain to extract it from non-brain tissue. The brain extraction results we have obtained from our CNNs are superior to the recently reported results in the literature on two publicly available benchmark data sets, namely, LPBA40 and OASIS, in which we obtained the Dice overlap coefficients of 97.73% and 97.62%, respectively. Significant improvement was achieved via our auto-context algorithm. Furthermore, we evaluated the performance of our algorithm in the challenging problem of extracting arbitrarily oriented fetal brains in reco-
structed fetal brain magnetic resonance imaging (MRI) data sets. In this application, our voxelwise auto-context CNN performed much better than the other methods (Dice coefficient: 95.97%), where the other methods performed poorly due to the non-standard orientation and geometry of the fetal brain in MRI. Through training, our method can provide accurate brain extraction in challenging applications. This, in turn, may reduce the problems associated with image registration in segmentation tasks.
Abstract: We describe an automated methodology for the analysis of unregistered cranio-caudal (CC) and medio-lateral oblique (MLO) mammography views in order to estimate the patient’s risk of developing breast cancer. The main innovation behind this methodology lies in the use of deep learning models for the problem of jointly classifying unregistered mammogram views and respective segmentation maps of breast lesions (i.e., masses and micro-calcifications). This is a holistic methodology that can classify a whole mammographic exam, containing the CC and MLO views and the segmentation maps, as opposed to the classification of individual lesions, which is the dominant approach in the field. We also demonstrate that the proposed system is capable of using the segmentation maps generated by automated mass and micro-calcification detection systems, and still producing accurate results. The semi-automated approach (using manually defined mass and micro-calcification segmentation maps) is tested on two publicly available data sets (INbreast and DDSM), and results show that the volume under ROC surface (VUS) for a 3-class problem (normal tissue, benign, and malignant) is over 0.9, the area under ROC curve (AUC) for the 2-class “benign versus malignant” problem is over 0.9, and for the 2-class breast screening problem (malignancy versus normal/benign) is also over 0.9. For the fully automated approach, the VUS results on INbreast is over 0.7, and the AUC for the 2-class “benign versus malignant” problem is over 0.78, and the AUC for the 2-class breast screening is 0.86.
Autors: Gustavo Carneiro;Jacinto Nascimento;Andrew P. Bradley;
Abstract: Patient condition during rehabilitation has been traditionally assessed using clinical scales. These scales typically require the patient and/or the clinician to rate a number of condition-related items to obtain a final score. This is a time-consuming task, specially if a large number of patients are involved. Furthermore, during rehabilitation, user condition is expected to change steadily in time, so assessment may require to run these scales several times to each user. To save time, much effort has been focused on developing clinical scales that require little time to be completed. This is usually achieved by measuring a reduced set of features, i.e., focusing the scales on specific features of a defined target population (Parkinson’s disease, Stroke, and so on). However, these scales still require the therapist’s intervention and may be tiresome for patients who have to fill them repeatedly. This paper proposes a novel approach to automatically obtain balance scales from the onboard sensors of a robotic rollator. These sensors are used to extract spatiotemporal gait parameters from patients using the rollator for support. These parameters are derived from the user forces on the rollator handles and its odometry. Resulting parameters are used to predict the Tinetti mobility clinical scale on the fly, without therapist intervention. Our approach has been validated with 19 rollator volunteers with a variety of physical and neurological disabilities at Hospital Civil (Malaga) and Fondazione Santa Lucia (Rome). Clinicians provided traditionally obtained Tinetti scores and the proposed system was used to estimate them on the fly. Results show a small root mean squared prediction error. This method can be used for any rollator user anywhere in everyday walking conditions to obtain the Tinetti scores as often as desired and, hence evaluate their progress.
Autors: Joaquin Ballesteros;Cristina Urdiales;Antonio B. Martinez;Marina Tirado;
Appeared in: IEEE Transactions on Neural Systems and Rehabilitation Engineering
Abstract: The conventional automatic ball balancer (ABB) reduces the mass unbalance of a rotating body by locating balls to the opposite side, thereby suppressing the steady-state vibration. However, the transient vibration increases due to rotating balls in such a way that they increase the mass unbalance before moving to the opposite side of the mass unbalance. We propose an ABB using permanent magnets (APM) that reduces the vibration of a rotating system, not only in the steady state but also in the transient state. The proposed APM is composed of four balls and two permanent magnets attached to a conventional ABB system. We designed the permanent magnets of the APM by using the multi-physics finite-element software COMSOL. We investigated the behavior of the rotating balls and the vibration suppression due to the APM by using the multi-body dynamic program ADAMS to validate the effectiveness of the proposed APM.
Abstract: This paper proposes a new method for automatic co-registration of digital elevation models (DEMs) based on centroids of subwatersheds. Subwatersheds are stable physical features, making their centroids more reliable and accurate as control points (CPs) than the other features. In the present method, subwatersheds are delineated from DEMs using hydrological analysis procedures. Modified invariant moments are employed to measure the similarity of subwatersheds for determining the correspondences between the reference and input. Centroids of matched subwatersheds are then derived as CP candidates, where the root-mean-square error is applied to eliminate mismatches using a global consistency check method. The established CP pairs are used to estimate parameters of a 3-D conformal transformation model, which is employed to rectify the input DEM. The accuracy of CP detection was assessed using two DEM subsets of different terrains. The results of six tests showed that the maximum shift and rotation errors were about 2 m (1/45 pixel) and 0.006°. The developed approach was used to co-register the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global DEM to the Shuttle Radar Topography Mission DEM at three locations. The results revealed that both the mean absolute error and the standard deviation of the elevation differences were reduced for all the tests after co-registration, showing the good performance of the proposed method. Comparisons have also been made against previous works, which suggested that our results were consistent with the previous studies.
Autors: Hui Li;Qinglu Deng;Lunche Wang;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Abstract: This work presents a novel approach to automatic detection of long period events (LP) in continuous seismic records. Without any supervised learning, the proposal is based on a simple processing to search for the LP characteristic shape, duration, and band of activity. Continuous raw signals from the seismometer are first filtered into three frequency bands separating lower, central, and upper frequency components. These new signals are then processed in parallel to extract subband envelopes and create a characteristic function that enhances LP features. Experiments to test the proposal are presented using: 1) 2 h of continuous recordings of the Volcano of Deception Island, Antarctica, containing LP events artificially contaminated with seismic background noise to create low signal-to-noise ratio scenarios and 2) a set of earthquake-like computer generated signals, randomly produced and inserted in the continuous records to recreate a testing environment as challenging as possible. A receiver operating curve analysis of the results compared to those of a classical short/long time average approach, provides positive conclusions on the performance of the technique presented.
Autors: Luz García;Isaac Álvarez;Manuel Titos;Alejandro Díaz-Moreno;M. Carmen Benítez;Ángel de la Torre;
Appeared in: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
Abstract: Objective: Wrist joint space narrowing is a main radiographic outcome of rheumatoid arthritis (RA). Yet, automatic radiographic wrist joint space width (JSW) quantification for RA patients has not been widely investigated. The aim of this paper is to present an automatic method to quantify the JSW of three wrist joints that are least affected by bone overlapping and are frequently involved in RA. These joints are located around the scaphoid bone, viz. the multangular-navicular, capitate-navicular-lunate, and radiocarpal joints. Methods: The joint space around the scaphoid bone is detected by using consecutive searches of separate path segments, where each segment location aids in constraining the subsequent one. For joint margin delineation, first the boundary not affected by X-ray projection is extracted, followed by a backtrace process to obtain the actual joint margin. The accuracy of the quantified JSW is evaluated by comparison with the manually obtained ground truth. Results: Two of the 50 radiographs used for evaluation of the method did not yield a correct path through all three wrist joints. The delineated joint margins of the remaining 48 radiographs were used for JSW quantification. It was found that 90% of the joints had a JSW deviating less than 20% from the mean JSW of manual indications, with the mean JSW error less than 10%. Conclusion: The proposed method is able to automatically quantify the JSW of radiographic wrist joints reliably. Significance: The proposed method may aid clinical researchers to study the progression of wrist joint damage in RA studies.
Autors: Yinghe Huo;Koen L. Vincken;Désirée van der Heijde;Maria J. H. de Hair;Floris P. Lafeber;Max A. Viergever;
Appeared in: IEEE Transactions on Biomedical Engineering