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: 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: 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: 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: 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: 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
Abstract: Due to the growing interconnectedness and complexity of in-vehicle networks, in addition to safety, security is becoming an increasingly important topic in the automotive domain. In this paper, we study techniques for detecting security infringements in automotive electrical and electronic (E/E) architectures. Toward this we propose in-vehicle network traffic monitoring to detect increased transmission rates of manipulated message streams. Attacks causing timing violations can disrupt safety-critical functions and have severe consequences. To reduce costs and prevent single points of failure, our approach enables an automatic distribution of detection tasks among selected E/E architecture components, such as a subset of electronic control units. First, we analyze a concrete E/E system architecture to determine the communication parameters and properties necessary for detecting security attacks. These are then used for a parametrization of the corresponding detection algorithms and the distribution of attack detection tasks. We use a lightweight message monitoring method and optimize the placement of detection tasks to ensure a full-coverage of the E/E system architecture and a timely detection of an attack.
Autors: Peter Waszecki;Philipp Mundhenk;Sebastian Steinhorst;Martin Lukasiewycz;Ramesh Karri;Samarjit Chakraborty;
Appeared in: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems
Abstract: We investigate the effect of a skewed permanent magnet (PM) with overhang on the axial unbalanced magnetic force (UMF) of a PM motor, especially in the presence of static and dynamic eccentricities of a rotor. We derive the mathematical equations of the axial UMF acting on PM motor due to the skewed PM with overhang and rotor eccentricities. We develop a 3-D finite-element model of the PM motor, not only to verify the frequency components of the proposed equations but also to determine the amplitude of the axial UMF. Further, we develop an experimental setup to measure the axial UMF caused by a skewed PM with overhang and rotor eccentricities. We confirm that the skewed PM with overhang generates an axial UMF with the harmonic of the least common multiple of pole and slot numbers. In addition, the static and dynamic eccentricities with the interaction of the skewed PM and overhang generate the axial UMF with the pole harmonics and slot harmonics, respectively.
Autors: Chi Ho Kang;Kyung Jin Kang;Jeong Yong Song;Young Jin Cho;Gun Hee Jang;
Abstract: This paper presents the results of a study, implemented for the equivalent circuit model (ECM), concerning the bandwidth in square-loop frequency-selective surfaces (FSSs). For the square-loop ECM, there is no formulation to quantify the effects of dielectric supporting layers, geometric features, and incident wave properties on the FSS bandwidth. Hence, it is not possible to control or evaluate the bandwidth of the FSS in the design from the knowledge of these parameters. In this paper, we addressed this issue using the ECM as an analysis method. In the first part of this study, we considered the square-loop FSS with thin dielectric supporting layers, where the bandwidth was expressed as a function of geometric parameters, incidence angle, and polarization of the incident wave as well as a factor that takes into account the effective permittivity of the dielectric support. Particle swarm optimization method was used to synthesize square-loop FSSs via the ECM with a specific resonant frequency and bandwidth requirements. In the second part, the behavior of bandwidth as a function of dielectric thickness was obtained by using a matrix cascading technique (MCT), implemented with ECM and a model for the dielectric effective permittivity. This approach takes into account the modifications on bandwidth due to multiple reflections on dielectric boundaries and allows calculating its value for any dielectric thickness and configuration. It is remarkable the low computational cost and acceptable accuracy obtained with the proposed approaches. All simulation results using ECM and MCT were compared with Ansys-HFSS commercial software simulations.
Autors: Mario A. Rodriguez Barrera;Walter Pereira Carpes;
Appeared in: IEEE Transactions on Antennas and Propagation
Abstract: The magnetic behaviors influenced by the hydrostatic pressure in the polycrystalline hexagonal Mn3Sn intermetallic compound are briefly reported. The crystalline structure of Mn3Sn is determined to be hexagonal with lattice parameters (6) Å and (6) Å by means of the powder X-ray diffraction and the subsequent Rietveld refinement. Two distinct transitions can be observed from the M(T) curves in the range of 150-450 K. During the cooling process, Mn3Sn sample first changes into a triangular antiferromagnetic (AFM) state with weak ferromagnetism at the Néel temperature of ~412 K, and then, it further transforms to a spiral AFM spin arrangement over a broad temperature range from 260 to 180 K at ambient pressure. With the application or the increase of hydrostatic pressures, this triangular to spiral AFM transition occurs at higher temperatures, while the magnetization of triangular AFM phase increases significantly. Such a phenomenon can be explained by the fact that the hydrostatic pressure compresses the sample and shortens the Mn–Mn separation, and thus, the moments of Mn will deviate from their ideal 120° configuration to their easy axis in the basal plane. The variations of transition temperature and maximum magnetization with applied hydrostatic pressure confirm the incremental instability of the triangular AFM arrangement under pressure.
Autors: K. Xu;Y. L. Zhang;Y. M. Cao;X. J. He;Z. Li;S. X. Wei;Y. R. Kang;C. Jing;
Abstract: Rate adaptation and scheduling are essential in ensuring that contemporary orthogonal frequency division multiplexing systems achieve high downlink spectral efficiencies. They depend upon reduced feedback schemes to efficiently feedback channel state information from the users to the base station (BS). In the popular threshold-based quantized feedback scheme, a user feeds back to the BS the quantized value of the signal-to-noise ratio for each subchannel. For this scheme, we derive a novel, throughput-optimal discrete rate adaptation (TORA) policy, which enables a system designer to reduce the feedback overhead. We present it in closed form for different multi-antenna diversity modes for the exponentially correlated subchannel gains model. We also develop a computationally simpler suboptimal variant of it. We derive an insightful lower bound for the fading- and user location-averaged throughput gain achieved by TORA over conventional rate adaptation for 1-bit feedback. We present extensive results to benchmark the system-level performance of TORA for different numbers of feedback bits and modulation and coding schemes available at the BS, and various schedulers, quantizers, and multi-antenna modes.
Autors: Vineeth Kumar;Neelesh B. Mehta;
Appeared in: IEEE Transactions on Wireless Communications
Abstract: Recently, there has been an increase in the demand for high-efficiency miniature electronic equipment such as personal computers. Therefore, using high drive frequencies and reducing copper loss have become important in meeting the demand. In this paper, we propose the use of magnetocoated wires (MCWs) for coil windings fabricated using the spray method. MCW coils reduce the resistance due to the proximity effect because a magnetic layer leads a magnetic field. As a result, the resistances of the copper wire (COW) and MCW coils at the frequency MHz are 668 and 447 , respectively, which show a reduction of 33% from resistance of COW to MCW. The resistances of the MCW coils at the frequency kHz and the current A decreased by 10% compared with the resistances of the COW. The temperature increment of the MCW coils decreased by 5 °C compared with that of COW. This was because MCWs decrease the ac resistance of coils. The magnetic saturation was examined in detail using the finite-element method from the measured value of complex permeability. From the calculated magnetic field and measured magnetization curve, we show the absence of magnetic saturation in coils of nine turns.
Abstract: We operated a Hall sensor using energy harvested from a magnetic wire. A batteryless sensor is expected to be a key device for the Internet of Things. Magnetization reversal in magnetic wires with bistable magnetization states induces a pulse voltage in a pickup coil. The amplitude of the voltage is independent of the applied field frequency, down to zero. This fast magnetization reversal is accompanied by a large Barkhausen jump, which has been known as the Wiegand effect. Electricity generation using this effect, obtained with twisted FeCoV magnetic wires, was studied. The energy obtained as a single pulse voltage was 600 nJ. The Hall sensor operated with this pulse voltage. The pulse power of 0.88 V/1.3 mA was applied to the Hall sensor. The Hall voltage was proportional to the sensing magnetic field of 50–300 mT.
Abstract: To deal with the increasing complexity of distribution networks that are experiencing important changes, due to the widespread installation of distributed generation and the expected penetration of new energy resources, modern control applications must rely on an accurate picture of the grid status, given by the distribution system state estimation (DSSE). The DSSE is required to integrate all the available information on loads and generators power exchanges (pseudomeasurements) with the real-time measurements available from the field. In most cases, the statistical behavior of the measured and pseudomeasured quantities cannot be approximated by a Gaussian distribution. For this reason, it is necessary to design estimators that are able to use measurements and forecast data on power flows that can show a non-Gaussian behavior. In this paper, a DSSE algorithm based on Bayes's rule, conceived to perfectly match the uncertainty description of the available input information, is presented. The method is able to correctly handle the measurement uncertainty of conventional and synchronized measurements and to include possible correlation existing between the pseudomeasurements. Its applicability to medium voltage distribution networks and its advantages, in terms of accuracy of both estimated quantities and uncertainty intervals, are demonstrated.
Autors: Paolo Attilio Pegoraro;Andrea Angioni;Marco Pau;Antonello Monti;Carlo Muscas;Ferdinanda Ponci;Sara Sulis;
Appeared in: IEEE Transactions on Instrumentation and Measurement
Abstract: The ionospheric propagation path delay is a major error source in synthetic aperture radar (SAR) interferograms and, therefore, has to be estimated and corrected. Various methods can be used to extract different kinds of information about the ionosphere from SAR images, with different accuracies. This paper presents a general technique, based on a Bayesian inverse problem, that combines various information sources in order to increase the estimation accuracy, and thus the correction. A physically realistic fractal modeling of the ionosphere turbulence and a data-based estimation of the model parameters allow the avoidance of arbitrary filtering windows and coefficients. To test the technique, the differential ionospheric phase screen was estimated by combining the split-spectrum method with the azimuth mutual shifts between interferometric pair images. This combination is convenient since it can benefit from the strengths of both sources: range and azimuth variations from the split-spectrum method and small-scale azimuth variations from more sensitive azimuth shifts. Therefore, the two methods can recover the long and short wavelength components of the ionospheric phase screen, respectively. A theoretical comparison between the Faraday rotation method and the split-spectrum method is also reported. For the use in the combination, precedence was then given to the split-spectrum method because of the comparable precision level, lower susceptibility to biases, and wider applicability. Finally, Advanced Land Observing Satellite Phased Array type L-band SAR L-band images are used to show how the combined result is more accurate than that obtained with the simple split-spectrum method.
Autors: Giorgio Gomba;Francesco De Zan;
Appeared in: IEEE Transactions on Geoscience and Remote Sensing
Abstract: Voltage dip state estimation (VDSE) tries to estimate the voltage dip characteristics at nonmonitored buses from measured voltage dip values at monitored buses. In this paper, the VDSE is addressed through the method based on Bayesian inference. A priori including the fault position among other grid conditions is used to estimate the residual voltage at each bus based on the measurement quantities, including their uncertainties. The dip duration is calculated with the time setting of protection system incorporating the uncertainties due to dip detection algorithm of the root mean square values. The proposed method has been applied to the IEEE 13-bus and IEEE 123-bus distribution test systems for multiple simulation scenarios, such as with or without distributed generation and different types of faults. The simulation results show good observability of the network.
Autors: Gu Ye;Yu Xiang;Michiel Nijhuis;Vladimir Cuk;J. F. G. Cobben;
Appeared in: IEEE Transactions on Instrumentation and Measurement
Abstract: In this communication, the beam properties of one-dimensional leaky-wave antennas (1-D LWAs) are explored when the LWA scanning approaches endfire. By increasing the phase constant beyond the ordinary endfire condition, smaller beamwidths can be produced at the expense of increased sidelobe level (SLL). This tradeoff is quantified here for the first time for endfire 1-D LWAs. Simple CAD formulas are also proposed that describe accurately the beamwidth and SLL for 1-D LWAs operating at endfire. This communication is conducted for different radiation efficiencies covering most practical ranges. A closed-form expression for the beamwdith of a 1-D LWA with an infinite aperture is also given, in which case there are no sidelobes. These results allow for a better understanding and efficient design of LWAs radiating at endfire.
Autors: Walter Fuscaldo;David R. Jackson;Alessandro Galli;
Appeared in: IEEE Transactions on Antennas and Propagation
Abstract: Cognitive radio is one of the enabling technologies considered for the next generation communication systems for many mission-critical applications. In cognitive radio systems, cooperative spectrum sensing is one of the key techniques that can improve reliability and agility. In this paper, a framework that integrates quickest detection and belief propagation is applied to the cooperative spectrum sensing, where the primary user activities are heterogeneous in the space and dynamic in the time. The performance of the proposed scheme is analyzed mathematically. Using numerical simulations, detection performance measured by false alarm rate and average detection delay is obtained for different setups. The results show that the proposed scheme achieves better receiver operational curves than traditional detection method.
Autors: Yifan Wang;Husheng Li;Lijun Qian;
Appeared in: IEEE Transactions on Wireless Communications
Abstract: Studies in machine learning have shown promising classification performance of ensemble methods employing "perturb and combine" strategies. In particular, the classical random forest algorithm performs the best among 179 classifiers on 121 UCI datasets from different domains. Motivated by this observation, we extend our previous work on oblique decision tree ensemble. We also propose an efficient co-trained kernel ridge regression method. In addition, a random vector functional link network ensemble is also introduced. Our experiments show that our two oblique decision tree ensemble variants and the co-trained kernel ridge regression ensemble are the top three ranked methods among the 183 classifiers. The proposed random vector functional link network ensemble also outperforms all neural network based methods used in the experiments.
Autors: Le Zhang;Ponnuthurai Nagaratnam Suganthan;
Appeared in: IEEE Computational Intelligence Magazine
Abstract: Optical connections support virtual links in MPLS-over-optical multilayer networks and therefore, errors in the optical layer impact on the quality of the services deployed on such networks. Monitoring the performance of the physical layer allows verifying the proper operation of optical connections, as well as detecting bit error rate (BER) degradations and anticipating connection disruption. In addition, failure identification facilitates localizing the cause of the failure by providing a short list of potential failed elements and enables self-decision making to keep committed service level. In this paper, we analyze several failure causes affecting the quality of optical connections and propose two different algorithms: one focused on detecting significant BER changes in optical connections, named as BANDO, and the other focused on identifying the most probable failure pattern, named as LUCIDA. BANDO runs inside the network nodes to accelerate degradation detection and sends a notification to the LUCIDA algorithm running on the centralized controller. Experimental measures were carried out on two different setups to obtain values for BER and received power and used to generate synthetic data used in subsequent simulations. Results show significant improvement anticipating maximum BER violation with small failure identification errors.
Autors: Alba P. Vela;Marc Ruiz;Francesco Fresi;Nicola Sambo;Filippo Cugini;Gianluca Meloni;Luca Potì;Luis Velasco;Piero Castoldi;
Abstract: This paper presents a bi-level model for distribution network and renewable energy expansion planning under a demand response (DR) framework. The role of DR has recently attracted an increasing interest in power systems. However, previous models have not been completely adapted in order to treat DR on an equal footing. The target of the distribution network and generation planner, modeled through the upper-level problem, is to minimize generation and network investment cost while meeting the demand. This upper-level problem is constrained by the lower-level problem, stressing the importance of integrating DR to time-varying prices into those investment models. The objective function considered for the lower level is the minimization of overall payment faced by the consumers. Using the Karush-Kuhn-Tucker complementarity constraints, the proposed bi-level model is recast as a mixed-integer linear programming problem, which is solvable using efficient off-the-shelf branch-and-cut solvers. Detailed results from an insular case study (La Graciosa, Canary Islands, Spain) are presented.
Autors: Miguel Asensio;Gregorio Muñoz-Delgado;Javier Contreras;
Abstract: A novel beyond-CMOS device concept, the Bilayer pseudoSpin Junction Transistor (BiSJT), is proposed. Like the previously proposed Bilayer pseudoSpin FET (BiSFET), the BiSJT is motivated by the possibility of interlayer electron–hole exciton condensation in bilayer 2-D material systems, and could provide switching energies of a few 10 s of zJ, orders of magnitude below even end-of-the-roadmap CMOS. The BiSJT is, however, current-controlled, and may allow for simpler device design, smaller device area, and more flexible gate design.
Autors: Xuehao Mou;Leonard F. Register;Allan H. MacDonald;Sanjay K. Banerjee;
Appeared in: IEEE Transactions on Electron Devices
Abstract: In the frame of this paper, the synthesis of self-assembled magnetic and biocompatible nanovehicles movable in aqueous solutions by a magnetic field gradient is presented. The systems consist of a mesoporous silicon template and encapsulated iron oxide nanostructures, both materials known to be biocompatible. Two routes are applied to produce iron oxide nanostructures embedded within porous silicon. First, readily synthesized superparamagnetic iron oxide nanoparticles (NPs) are infiltrated into the pores. The second attempt is the chemical deposition of iron oxide structures inside the PSi templates. Concerning the adjustability of the magnetic properties of the system the loading procedure of the PSi with iron oxide NPs will be elucidated in detail as well as the growth of iron oxide structures within the pores. An assessment of the iron oxide deposition dependent on the template and the chemical parameters as well as of the magnetic properties in dependence on the particle size and template morphology of the nanocomposite will be presented. A further approach is the transition from a magnetite to the stable hematite phase by heat treatment of the specimens. A sufficient filling leading to a magnetization high enough for the movement of the nanovehicles within aqueous surroundings (e.g., body fluid) by magnetic field gradients could be reached easily.
Autors: Petra Granitzer;Klemens Rumpf;Peter Poelt;Michael Reissner;
Abstract: Bioluminescence tomography (BLT) is a powerful non-invasive molecular imaging tool for in vivo studies of glioma in mice. However, because of the light scattering and resulted ill-posed problems, it is challenging to develop a sufficient reconstruction method, which can accurately locate the tumor and define the tumor morphology in three-dimension. In this paper, we proposed a novel Gaussian weighted Laplace prior (GWLP) regularization method. It considered the variance of the bioluminescence energy between any two voxels inside an organ had a non-linear inverse relationship with their Gaussian distance to solve the over-smoothed tumor morphology in BLT reconstruction. We compared the GWLP with conventional Tikhonov and Laplace regularization methods through various numerical simulations and in vivo orthotopic glioma mouse model experiments. The in vivo magnetic resonance imaging and ex vivo green fluorescent protein images and hematoxylin-eosin stained images of whole head cryoslicing specimens were utilized as gold standards. The results demonstrated that GWLP achieved the highest accuracy in tumor localization and tumor morphology preservation. To the best of our knowledge, this is the first study that achieved such accurate BLT morphological reconstruction of orthotopic glioma without using any segmented tumor structure from any other structural imaging modalities as the prior for reconstruction guidance. This enabled BLT more suitable and practical for in vivo imaging of orthotopic glioma mouse models.
Abstract: Spasticity is an important factor in designing wearable and lightweight exoskeleton neurorehabilitation robots. The proposed study evaluates biomechanical reactions of an exoskeleton robot to spasticity and establishes relevant guidelines for robot design. A two-axis exoskeleton robot is used to evaluate a group of 20 patients post-stroke with spastic elbow and/or wrist joints. All subjects are given isokinetic movements at various angular velocities within the capable range of motion for both joints. The resistance torque and corresponding angular position at each joint are recorded continuously. Maximal resistance torques caused by low (modified Ashworth scale (MAS) 0, 1), intermediate (MAS 1+), and high (MAS 2 and 3) grade spasticity were 3.68 ± 2.42, 5.94 ± 2.55, and 8.25 ± 3.35 Nm for the elbow flexor (, between each grades) and 4.23 ± 1.75, 5.68 ± 1.96, and 5.44 ± 2.02 Nm for the wrist flexor (, for low versus intermediate, low versus high grade spasticity). The angular velocity did not significantly influence maximal resistance torque in either joint. The catch occurred more quickly at higher velocities for low and intermediate elbow flexor spasticity (). Spasticity caused considerable resistance to the robots during mechanically actuated movements. The resistance range according to the degree of spasticity should be considered when designing practical neurorehabilitation robots.
Abstract: We analyzed the bistatic coherent scattering mechanism of a layered randomly corrugated snow surface, a typical rough surface, with radar polarimetry theory whose scattering matrix was obtained from a physical-based full wave numerical simulation by solving Maxwell's equations. The effects of top–bottom structure, layer thickness, frequency response, and angular dependence are illustrated by observing stokes vector, coherence matrix, and Kennaugh matrix. The results show that top–bottom structure and snow thickness change the state of polarization depending on frequency and bistatic configuration. Analyzing the bistatic polarimetric scattering mechanism based on numerical simulation and the polarimetry theory can be an efficacious source for configuring bistatic observation to detect and classify radar targets. For example, observation at a specular angle of 55° comparatively contains more information on surface structure, and wave entropy is more preferable over degree of polarization as a snow surface structure estimator. Moreover, parameters from Kennaugh decomposition can indicate top–bottom structure better than layer thickness. Last but not the least, we also found that the symmetry assumption commonly used in classical theory of polarization is generally not valid for bistatic observation, and the combination of some Huynen parameters can be reasonably good indicators of snow surface structural symmetry. We expect this paper to offer deeper understanding of the coherent imaging of snow surfaces and to help design a novel bistatic imaging system for layered snow surface.
Abstract: In super-Nyquist wavelength division multiplexed (WDM) systems with frequency spacing smaller than the signal baudrate, the maximum-likelihood (ML) decoder in the receiver is usually introduced to compensate for intersymbol interference due to tight spectral filtering, such as polybinary shaping. After the ML decoder, symbol errors tend to propagate, causing excess continuous errors. Considering that forward error correction (FEC) is commonly introduced, the excess continuous errors degrade bit-error ratio (BER) performance after FEC, so-called post-FEC BER. In order to suppress the performance degradation, we introduce iterative decoding between the first ML decoder for polybinary shaping and the second FEC decoder in the receiver. First, we calculate BER characteristics of polybinary-shaped super-Nyquist WDM quadrature phase-shift keying (QPSK) signals. The results show that iterative decoding is effective for improving post-FEC BER performance. A lager pre-FEC BER threshold for post-FEC BER <; 10-5 is obtained in super-Nyquist WDM case than in the Nyquist WDM case, although a higher signal-to-noise ratio (SNR) is required. Next, we measure the BER characteristics of three-channel duobinary-shaped super-Nyquist WDM 12.5-Gbaud dual-polarization QPSK signals. The iterative decoding reduces the optical SNR penalty by 0.8 dB. A larger pre-FEC BER threshold of 3.1 × 10-2 is obtained in the duobinary-shaped super-Nyquist WDM case, compared with the threshold of 2.2 × 10-2 in the Nyquist WDM case.
Abstract: In recent years, engineering education teachers have needed to incorporate technology-supported collaboration to enhance learning. Implementing these activities requires course redesign, which must be meticulous for their full potential to be reached. This can require a lot of work for first time users, which can be a barrier to implementation. Educational design patterns alleviate this burden by facilitating new course design with practices demonstrated to promote student engagement. This paper reports on the redesign of an introductory programming course and its experimental evaluation. The redesign was based on the community of inquiry learning framework (CoL), using design patterns from online Web communities and team-based learning (TBL). The evaluation included 562 students, 117 of them randomly assigned to two different experimental groups. One group used a CoL approach, and the other a blended TBL and CoL methodology. The remaining students were assigned to control groups. Results showed that students in the experimental groups outperformed those in the control group by the end of the semester, while the experimental CoL and TBL methodology helped students achieve a higher level of understanding in a shorter period of time due to increased participation rates. These data provide empirical evidence of the learning gains offered by online learning communities, and the way in which educational design patterns can facilitate course redesign.
Abstract: Creating realistic 3D face models is a challenging problem in computer graphics because humans are so sensitive to facial abnormalities. The authors propose a method to synthesize a 3D face model using weighted blending of multiscale details from different face models. Using multiscale continuous displacement maps (CDMs), they achieve full correspondences across multiple scales in the parameter space. Their results demonstrate detail transfer across faces with highly different proportions, such as between humans and nonhuman creatures. An artist evaluation also indicated the proposed approach is intuitive and easy to use.
Autors: Seung-Hyun Yoon;John Lewis;Taehyun Rhee;
Appeared in: IEEE Computer Graphics and Applications
Abstract: In this letter, we propose a pair of blind detectors for spatial modulation multiple-input multiple-output (MIMO) systems based on the clustering concept. Specifically, an improved K-means clustering (KMC) with lower-complexity detector is first proposed to avoid the error floor effects and to reduce the imposed complexity of the conventional KMC detector by employing an initial centroid optimizer. Furthermore, an affinity propagation (AP) detector is developed based on the belief propagation concept, where the number of clusters is not required in the clustering process by using the intelligence information exchanges. The results show that the proposed KMC detector can efficiently avoid the occurrence of error floor effects, while the proposed AP detector is capable of achieving better performance than that of the conventional KMC detector.
Abstract: Blind image quality assessment (BIQA) aims to estimate the subjective quality of a query image without access to the reference image. Existing learning-based methods typically train a regression function by minimizing the average error between subjective opinion scores and model predictions. However, minimizing average error does not necessarily lead to correct quality rank-orders between the test images, which is a highly desirable property of image quality models. In this paper, we propose a novel rank-order regularized regression model to address this problem. The key idea is to introduce a pairwise rank-order constraint into the maximum margin regression framework, aiming to better preserve the correct perceptual preference. To the best of our knowledge, this is the first attempt to incorporate rank-order constraints into margin-based quality regression model. By combing with a new local spatial structure feature, we achieve highly consistent quality prediction with human perception. Experimental results show that the proposed method outperforms many state-of-the-art BIQA metrics on popular publicly available IQA databases (i.e., LIVE-II, TID2013, VCL@FER, LIVEMD, and ChallengeDB).
Autors: Qingbo Wu;Hongliang Li;Zhou Wang;Fanman Meng;Bing Luo;Wei Li;King N. Ngan;
Abstract: Quality assessment of stereo images confronts more challenges than its 2D counterparts. Direct use of 2D assessment methods is not sufficient to deal with the challenges of 3D perception. In this paper, an efficient general-purpose no-reference stereo image quality assessment, based on unsupervised feature learning, is presented. The proposed method extracts features without any prior knowledge about the types and levels of distortions. This property enables our method to be adaptable for different applications. The perceived contrast and phase of the binocular combination of original stereo images are utilized to learn individual dictionaries. For each distorted stereo image, two feature vectors are pooled, in a hierarchical manner, over all sparse representation vectors of phase and contrast blocks by their corresponding dictionaries. Performance results of learning a regression model by the features acknowledge the superiority of the proposed method to state-of-the-art algorithms.
Autors: Maryam Karimi;Mansour Nejati;S. M. Reza Soroushmehr;Shadrokh Samavi;Nader Karimi;Kayvan Najarian;
Abstract: Predation refers to the strategic reduction of market price by a monopolist in order to eradicate its potential competitors. We investigate this strategy in a single service provider (SP) dominated cellular network for two different cases: 1) when a new contender attempts to enter into the network and 2) when the contender has already entered and is co-existing with the dominant SP. In both the cases, the sole objective of the predating SP is driving its opponent into losses, therefore discouraging its entry/stay in the market. In this letter, with the assumption that the government is sole provider of bandwidth and infrastructure, we establish the followings: 1) if the spectrum pricing is linear, then the pre-existing SP can always succeed in predation and 2) on the other hand, if government switches to quadratic spectrum pricing, then it is always possible to restrain the predatory behavior.
Abstract: The following books are reviewed: Microgrid-Advanced Control Methods and Renewable Energy System Integration by M. S. Mahmoud; Nanofabrication-Principles to Laboratory Practice by A. Sarangan; Protection of Substation Critical Equipment Against Intentional Electromagnetic Threats by V. Gurevich; Nitride Wide Bandgap Semiconductor Material and Electronic Devices by Y. Hao, J. F. Zhang, and J. C. Zhang; Principles of Lightning Physics by V. Mazur; Atom Probe Tomography-Put Theory into Practice by W. Lefebvre-Ulrikson, F. Vurpillot, and X. Sauvage
Abstract: We investigate the problem of base station (BS) on-off switching, user association, and power control in a heterogeneous network (HetNet) with massive multiple input multiple output (MIMO), aiming to turn off under-utilized BS’s and maximize the system energy efficiency. With a mixed integer programming problem formulation, we first develop a centralized scheme to derive the near optimal BS on-off switching, which is an iterative framework with proven convergence. We further propose two distributed schemes based on game theory, with a bidding game between users and BS’s, and a pricing game between wireless service provider and users. Both games are proven to achieve a Nash Equilibrium. Simulation studies demonstrate the efficacy of the proposed schemes.
Autors: Mingjie Feng;Shiwen Mao;Tao Jiang;
Appeared in: IEEE Transactions on Wireless Communications
Abstract: We show a direct relationship between the variance and the differential entropy for subclasses of symmetric and asymmetric unimodal distributions by providing an upper bound on variance in terms of entropy power. Combining this bound with the well-known entropy power lower bound on variance, we prove that the variance of the appropriate subclasses of unimodal distributions can be bounded below and above by the scaled entropy power. As the differential entropy decreases, the variance is sandwiched between two exponentially decreasing functions in the differential entropy. This establishes that for the subclasses of unimodal distributions, the differential entropy can be used as a surrogate for concentration of the distribution.
Autors: Hye Won Chung;Brian M. Sadler;Alfred O. Hero;
Appeared in: IEEE Transactions on Information Theory
Abstract: A new method is presented to obtain arbitrary coupling levels of the branch-line couplers through the simple modification of the 3-dB coupler. It is shown that the coupling of the conventional 3-dB branch-line coupler can be adjusted to arbitrary values by varying the electrical length of the branches without changing the impedances. A very wide range of coupling values can easily be obtained using the same line impedances as the conventional 3-dB couplers based on the proposed method.
Autors: Jaegook Lee;Jongchul Lee;Myun-Joo Park;
Appeared in: IEEE Microwave and Wireless Components Letters
Abstract: In this letter, a device structure of high-resistivity-cap-layer HEMT (HRCL-HEMT) is developed for normally-off p-GaN gate HEMT toward high breakdown voltage and low current collapse. It demonstrates that the breakdown capability and current collapse of the device were effectively improved due to the introduction of a thick HR-GaN cap layer. The fabricated HRCL-HEMT exhibits a high breakdown voltage of 1020 V at /mm with the substrate grounded. Meanwhile, the dynamic is only 2.4 times the static after off-state stress of 1000 V with the substrate grounded (the OFF to ON switching time interval is set to ).
Abstract: Broadband 0.03–1.1 THz signal generation and radiation are demonstrated based on an oscillator-free direct digital-to-impulse architecture with a 1.9-ps full width at half maximum and 130-GHz 3-dB bandwidth (BW) (200-GHz 10-dB BW) centered at 160 GHz. The radiated pulse achieves a peak pulse effective isotropic-radiated power of 19.2 dBm and peak pulse-radiated power of 2.6 mW. An ON/OFF impulse-shaping technique is introduced and implemented to suppress undesired ringing and to increase dc-to-radiated efficiency. The frequency-comb spectrum of the radiated pulse train with 5.2-GHz repetition rate is measured up to 1.1 THz. At a distance of 4 cm, the measured received SNR at 1 and 1.1 THz is 28 and 22 dB, respectively. A 1.1-THz tone is measured with a 10-dB spectral width of 2 Hz, demonstrating an extremely narrow spectral line width (two parts per trillion). Time-domain picosecond pulses are characterized using a custom femtosecond-laser-based terahertz time-domain spectroscopy system. Coherent spatial combining from two widely spaced chips is demonstrated. It is shown that the starting time of the radiated pulses is locked to the edge of the input digital trigger with a timing jitter of 270 fs. The chip is fabricated in a 130-nm SiGe BiCMOS process technology.
Abstract: Broadband permeability spectra of aligned ferromagnetic flakes embedded in a nonmagnetic polymer matrix have been measured using an APC-7 coaxial line within the frequency range 10 MHz–18 GHz. These spectra reveal two well-defined resonance lines. The low-frequency one (sub-GHz range) has previously been attributed to the fundamental vortex translation mode in a multidomain magnetic structure, whereas the high-frequency resonance (beyond 1 GHz) is assigned to the natural spin resonance. A two-level analytical model combining a spin dynamics description including these two contributions at the flake scale and a Maxwell–Garnett mixing rule at the composite scale has been developed and reproduces very satisfactorily the experimental spectra in terms of resonance frequencies, resonance linewidths, and resonance mode amplitudes.
Autors: Z. Raolison;Q. Clément;A.-L. Adenot-Engelvin;N. Malléjac;C. Lefevre;G. Pourroy;F. Boust;N. Vukadinovic;
Abstract: Objective: A critical point in any definition of entropy is the selection of the parameters employed to obtain an estimate in practice. We propose a new definition of entropy aiming to reduce the significance of this selection. Methods: We call the new definition Bubble Entropy. Bubble Entropy is based on permutation entropy, where the vectors in the embedding space are ranked. We use the bubble sort algorithm for the ordering procedure and count instead the number of swaps performed for each vector. Doing so, we create a more coarse-grained distribution and then compute the entropy of this distribution. Results: Experimental results with both real and synthetic HRV signals showed that bubble entropy presents remarkable stability and exhibits increased descriptive and discriminating power compared to all other definitions, including the most popular ones. Conclusion: The definition proposed is almost free of parameters. The most common ones are the scale factor r and the embedding dimension m . In our definition, the scale factor is totally eliminated and the importance of m is significantly reduced. The proposed method presents increased stability and discriminating power. Significance: After the extensive use of some entropy measures in physiological signals, typical values for their parameters have been suggested, or at least, widely used. However, the parameters are still there, application and dataset dependent, influencing the computed value and affecting the descriptive power. Reducing their significance or eliminating them alleviates the problem, decoupling the method from the data and the application, and eliminating subjective factors.
Autors: George Manis;Md Aktaruzzaman;Roberto Sassi;
Appeared in: IEEE Transactions on Biomedical Engineering
Abstract: In this paper, we propose a relay selection scheme for cooperative buffer-aided relay networks with specific information rates and delay bounds. The proposed scheme differs from most of the well-known schemes in the literature that assume the source is saturated with data and/or without delay constraints. The proposed scheme is designed to encompass the delay-sensitive applications that are subject to delay limits and have certain rates. The proposed scheme exploits the channel state information, buffer state information, and delay state information to minimize the outage probability and achieve higher throughput. To achieve that, it uses these information to compromise between the selections of relays for reception and transmission. The proposed scheme is analyzed in the independent and identically distributed and independent and nonidentically distributed Rayleigh fading channels. The analysis is in terms of outage probability, packet dropping probability of the source node, packet dropping probability of the entire system, and throughput. For systems with high delay constraints, simulation results show that the proposed scheme offers lower packet dropping probability and higher throughput as compared to the renowned relay selection schemes.
Autors: Ali Ahmed Mohamed Siddig;Mohd Fadzli Mohd Salleh;
Appeared in: IEEE Transactions on Vehicular Technology
Abstract: Buffer-layer dependences of dead-layer thickness, saturation magnetization (, and interface magnetic anisotropy ( were systematically investigated for Co2Fe0.4Mn0.6Si (CFMS) Heusler alloy ultrathin films with Pd, Ru, and Cr buffer layers. Perpendicular magnetization was only achieved in 0.6 and 0.8 nm-thick CFMS ultrathin films deposited on Pd buffer layer and annealed at 400 °C. At the optimum annealing temperature of 400 °C, of 1.2 erg/cm2 was obtained for the Pd buffer layer, which was 3–6 times larger than those for Ru and Cr buffer layers. The difference in probably originates from the interdiffusion and different crystallized compounds at the interface between Pd (Ru, Cr) and CFMS layers.