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This paper presents a new transistor self-oscillating inverter suitable for high efficiency switch mode power supplies, which can operate directly from high voltages and is free from output transformer saturation problems due to transistor characteristic mismatch. It uses a half-bridge power circuit, consisting of two transistors in one limb and two capacitors in the other. Amongst several advantages of this configuration, the switching transistors need to withstand a minimum voltage equal to the dc supply only and not higher as in conventional circuits, while using only two transistors.

An alternative integration scheme for a half-bridge switch using 70 μm thin Si IGBTs and diodes is presented. This flat switch, which is designed for high-frequency application with high power density, exhibits high strength, high toughness, low parasitic inductance and high thermal conductivity. Such a novel assembly approach is suitable to optimize performance, reliability and availability of the power system in which it is used. The paper focuses on the thermal performance of this assembly at normal and extreme operating conditions, studied by means of FEM thermo-fluidynamic simulations of the module integrated with connectors and liquid cooler, and thermal measurement performed on an early prototype. Improved solutions are also investigated by the FE model.

Mode Group Diversity Multiplexing (MGDM) aims at creating independent and parallel communication channels over a single Multimode Fiber (MMF) by exciting several groups of modes. It can significantly improve the capacity of short-reach Multimode Fiber networks. One of the key techniques involves demultiplexing the mixed signals from the output. In this paper, we proposed a fast independent component analysis (FastICA) algorithm to demultiplex the output signals of a 2 × 2 MGDM system more efficiently. The performance of this algorithm is evaluated and compared with the zero-forcing method. Our results indicate that FastICA can demultiplex the mixed signals, improve the eye opening of the eye diagram and achieve the similar results as zero-forcing method.

In this paper, a new reference symbol (RS) mapping scheme for the Third-Generation Partnership Project (3GPP) long-term evolution (LTE) and LTE-Advanced (LTE-A) downlink is proposed to improve channel estimation performance in high-mobility communication scenarios. The proposed scheme employs null subcarriers to guard RSs, which helps mitigate the effect of intercarrier interference (ICI) on subcarriers carrying RSs. Additionally, the proposed scheme allows the ICI gain parameters to be estimated via a simple frequency-domain estimator. Modified Cramer-Rao bound (MCRB) expressions are derived for the proposed scheme, as well as for the conventional RS mapping scheme defined in the 3GPP LTE and LTE-A standards to compare their performance at high mobile user speeds. These bounds, together with mean square errors obtained from simulations, reveal superior performance achieved by the proposed scheme in high-mobility scenarios. Additionally, at high mobile user speeds, the proposed scheme offers significant bit-error-rate (BER) performance improvement over the standard RS mapping.

This paper focuses on methods of achieving direct field orientation (DFO) of induction machines based on closed-loop, stator, and rotor flux observers which are well suited to both zero and very high-speed operation. Both observer topologies are dominated by a current model at zero and low speeds, and a voltage model at high speeds. Application of such rotor and stator flux observers to both stator and rotor direct field orientation is presented, including experimental results for three different methods. The influence which flux regulation has on parameter sensitivity of the complete DFO system is analyzed. A rotor-flux-regulated and -oriented system is shown to be sensitive to leakage inductance under high slip (i.e., field weakened) operation. Both a stator-flux-regulated and -oriented system and a stator-flux-regulated, rotor-flux-oriented system are shown to have reduced parameter sensitivity at high speeds. Unlike stator flux orientation using simple voltage integration stator flux models, excellent zero and low-speed operation of an observer-based stator-flux-oriented system is demonstrated. >

The paper proposes a multidisciplinary design optimization (MDO) of permanent magnet synchronous generators (PMSG) for wind energy conversion systems (WECS). Such a MDO seeks the best compromise between the PMSG cost and the lifetime energy production of the WECS. So far, most of the papers in this field presented design methods using quite a few optimization variables and requiring a lot of assumptions. In the proposed MDO the specifications consist of geometrical, economical, magnetic, electrical and thermal constraints. Several analytic and semi-analytic sub-models where used to deal with these constraints, resulting in a large non-linear optimization problem that uses a sequential quadratic programming optimization algorithm. The paper considers the annual wind profile to estimate the lifetime wind turbine energy production. Moreover, the best possible solutions are presented in a Pareto front showing the trade-off between the generator cost and the wind turbine energy production. Among them, one optimal solution machine was chosen to be further investigated and its results were verified by finite element analysis.

This paper describes the development of a new type of tactile sensor which is designed to operate with a piezoelectric element employed as the sensor. Conventional tactile sensors, which consist of a strain gauge, conductive elastomer and piezoelectric polymer film, are confined solely to data acquisition relating to pressure or force. However, the new sensor proposed here is able to detect, very much like the human hand, the hardness and/or softness of an object. Several experiments have been carried out to investigate its possible applications in robotics and medicine. It is demonstrated that the visualization of tactile sensory performance using the new sensor is most useful in a robotics application; the sensor is also able to detect the hardness of an extraneous substance and that of skin.

Limiter-discriminator detection of continuous phase modulation (CPM) partial response signals is of special importance in systems in which phase coherence is very difficult to establish and/or maintain (e.g., mobile communications systems). The authors propose a Tomlinson-based approach which copes with the intersymbol interference (ISI) introduced by the baseband partial response frequency modulating pulses of the CPM schemes, (e.g., GTFM, GMSK, raised cosine (RC)). In this approach, the ISI equalization is divided between the transmitter and the receiver. The authors investigate, through simulation, the detectability performance and spectral properties of a number of CPM signals and receiver structures with special emphasis on the Tomlinson approach. It is shown that this novel application of the Tomlinson configuration allows the use of relatively simple receivers which exhibit almost the same performance as more complex Viterbi structured receivers. It is shown that a bandwidth-efficient narrow-band quaternary CPM-2RC modulation with either a Viterbi, a DFE or a Tomlinson receiver structure outperforms classical binary FSK (discriminator-integrate and dump detection) by approximately one db. It is pointed out in the paper that in general it is also possible to achieve detectability results similar to that of classical discriminator (integrate and dump) detection of binary CPFSK, for a number of bandwidth-efficient binary CPM schemes (e.g., GMSK) using the aforementioned receiver structures. >

This paper describes an economic dispatch formulation for a power system control area with high penetration of renewable generation and energy storage. We develop a comprehensive objective function that is unbiased to both the conventional and renewable generation sources. Operating constraints of conventional sources are considered, wind turbine generation is treated as a dispatchable source, and solar photovoltaic generation as negative load. A simulated annealing and particle swarm optimization algorithm are separately applied to minimize the objective function. The results obtained by the proposed economic dispatch formulation show that even a variable energy resource like wind can be dispatched in a manner that benefits the control area as a whole.

This paper proposes a visualizing methodology of iron loss generation in a magnetic material using its visualized domain images, i.e., SEM, Kerr and Faraday effects. Based on the differential equations for dynamic image, the material behavior is visualized. The state transition matrix of the Helmholtz equation, for which is derived from a series of distinct visualized domain images representing magnetized state. This makes it possible to visualize the magnetizing mechanism as well as iron loss generation. In the present paper, visualization of iron loss generation on a grain-oriented electrical steel sheet is worked out using a set of SEM images. As a result of our image analysis, magnetization curves at the particular points can be estimated.

System identification of vessel steering associated with unstructured uncertainties is considered in this paper. The initial model of vessel steering is derived by a modified second-order Nomoto model (i.e., nonlinear vessel steering with stochastic state-parameter conditions). However, that model introduces various difficulties in system identification, due to the presence of a large number of states and parameters and system nonlinearities. Therefore, partial feedback linearization is proposed to simplify the proposed model, where the system-model unstructured uncertainties can also be separated. Furthermore, partial feedback linearization reduces the number of states and parameters and the system nonlinearities, given the resulting reduced-order state model. Then, the system identification approach is carried out, for both models (i.e., full state model and reduced-order state model), resorting to an extended Kalman filter (EKF). As illustrated in the results, the reduced-order model was able to successfully identify the required states and parameters when compared to the full state model in vessel steering under persistent excitation maneuvers. Therefore, the proposed approach can be used in a wide range of system identification applications.

In this paper, we propose a boundary structure for improving performances of Single-sided Linear Induction Motors (SLIMs). In such machines, solid-plate conductors and back irons are usually used for secondary stators throughout operating regions. However, to take account of deformation due to thermal expansions, secondary stators are constructed from some sections of limited length. Therefore, a propulsive force characteristic declines when the primary armature crosses the boundary between secondary sections. In this study, by adopting a three-dimensional finite element method, detailed phenomena at the boundary between secondary sections have been clarified from the viewpoint of propulsive force and secondary current distributions. Besides the validity of calculated results is verified by the measured results. Further, to suppress the aggravation of characteristic caused by the secondary structural transition, we connect the secondary sections electrically. Finally, the propulsive force characteristic has been improved in spite of the existence of the boundary.

Since the safety and multimedia-related functions of automobile are getting increased and complex, In-vehicle network has become important. Even though FlexRay has emerged as the de-facto standard for the network, the message delay analysis problem has not been solved yet. In this paper, we propose the probabilistic delay model of message transmission in the FlexRay dynamic segment considering the variable length of messages that share identical Frame Identifier (ID). Based on the model, we analyze frame delay probability and empty minislot distribution as performance metric, which can be used during the design phase of a FlexRay network, and also derive transmission probabilities for different length of frames from the empty minislot probability. Finally, through simulation experiments, we verify the models, and show that previous model only considering fixed frame length causes pessimistic delay compared to the proposed model.

A key measure of wireless network performance is the amount of signaling information needed to deliver calls to mobile users. Estimates of the signaling system loading are widely available in recent literature. However, in all of the available publications the results are heavily dependent upon assumptions about user density, velocity, cell sizes, and other quantities related to the system and users. This paper presents a methodology to evaluate the signaling system loading that can produce general results that are independent of these assumptions. The technique relies upon the definition of an index of mobility which aggregates several key quantities in a single measure. With this index as the independent variable, graphical results reveal the behavior of a system. This paper evaluates three protocols: GSM Pan-European Cellular, IS-41 North American Cellular, and Bellcore's PCS Access Service for Networks. The method is general and can be easily applied to a new system.

This paper describes a strategy of backward motion control in a tractor-trailer system. The backward motion of a tractor-trailer requires skilled control, because the position and orientation of the trailer can only be controlled by an input to the tractor. When a driver changes orientation while driving backward, the steering angle must be skillfully controlled. This operation is different in the case of a single vehicle moving backward. An uncontrollable situation of a tractor-trailer motion often happens, for example, the "jackknife phenomenon." Such a situation is often induced by the nonholonomic constraint of a wheeled system. In this research, virtual steering is introduced to a trailer. This virtual steering controls the orientation of the trailer and suppresses the nonholonomic equivalent disturbance. With this virtual steering, the tractor-trailer is able to track a straight trajectory in backward driving independently of the nonholonomic constraint. Several numerical and experimental results are shown to confirm the validity of the proposed approach.

The manufacturing era is going through an evolutionary phase from Industry 3.0 to Industry 4.0 (I4.0). In 2011, Germany initiated I4.0 during the Hanover fair in collaboration with industrialists, academicians and researchers. The benefits of implementing I4.0 are attracting the curiosity of practitioners. In current academic literature, there is little discussion related to analysing potential roadblocks of I4.0 implementation using mathematical modelling. This paper has identified roadblocks through an extensive literature review and validation has been carried out by gathering experts’ opinions. As per the findings, the identified roadblocks have been categorized into five sections: management roadblocks, operational roadblocks, human resource roadblocks, procedural and behavioural roadblocks. A case study of the automobile industry has been discussed. The data was collected from experts in the area of I4.0. A Graph Theory and Matrix Approach (GTMA) was applied to evaluate the relative intensity of the roadblocks, Comprehensive I4.0 Index (CII) and its range for each category of roadblock. Implications for industrialists, practitioners and academicians are provided.

Hydraulic turbines are widely used to meet real-time electricity demands. Computational fluid dynamic (CFD) techniques have played an important role in the design and development of such turbines. The simulation of a complete turbine requires substantial computational resources. A specific approach that is applied to investigate the flow field of one turbine may not work for another turbine. A series of Francis-99 workshops have been planned to discuss and explore the CFD techniques applied within the field of hydropower with application to high-head Francis turbines. The first workshop was held in December 2014 at the Norwegian University of Science and Technology, Norway. The steady-state measurements were conducted on a model Francis turbine. Three operating points, part load, best efficiency point, and high load, were investigated. The complete geometry, meshing, and experimental data concerning the hydraulic efficiency, pressure, and velocity were provided to the academic and industrial research groups. Various researchers have conducted extensive numerical studies on the high-head Francis turbine, and the obtained results were presented during the workshop. This paper discusses the presented numerical results and the important outcome of the extensive numerical studies on the Francis turbine. The use of a wall function assuming equilibrium between the production and dissipation of turbulence is widely used in the simulation of hydraulic turbines. The boundary layer of hydraulic turbines is not fully developed because of the continuously-changing geometry and large pressure gradients. There is a need to develop wall functions that enable the estimation of viscous losses under boundary development for accurate simulations. Improved simulations and results enable reliable estimation of the blade loading. Numerical investigations on leakage flow through the labyrinth seals were conducted. The volumetric efficiency and losses in the seals were determined. The seal leakage losses formulated through analytical techniques are sufficient.

In the paper, we studied specific features of adaptive testing implementation by means of different methods for the purpose of increasing an objective character of results of such tests and decreasing labor-intensiveness of their creation. We chosen an optimal structure for a hybrid neural network.

This paper presents two benchmark systems for time-domain simulation of a thyristor-based static transfer switch (STS). The objectives are: (1) to provide guidelines for digital simulation of STS systems, (2) to provide a basis for performance evaluation of simulation programs used for STS analysis, and (3) to benchmark performance of various detection/control strategies adopted for STS systems. Each benchmark system is composed of: (1) a supply system, (2) STS, and (3) sensitive load. The two benchmark systems are referred to as STS-1 and STS-2. Simulated performances of the two systems, based on the use of the PSCAD/EMTDC software package, are provided. Simulation results corresponding to STS-2 are also compared with the corresponding measurement results.

In this paper, we propose a new ultra-wideband (UWB) antenna for UWB applications. The proposed antenna is designed to operate from 3.2 to 12 GHz. It consists of a rectangular patch with two steps, a single slot on the patch, and a partial ground plane. Details of the proposed antenna design and measured results are presented and discussed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 399–401, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11392

Active structural methods constitute a promising way to mitigate chatter vibrations in milling. This paper presents an active system integrated into a spindle unit. Two different optimal control strategies are investigated. The first one only considers the dynamics of the machine structure in the controller design and minimizes the influence of cutting forces on tool tip deviations. The second one takes explicitly the process interaction into account and attempts to guarantee the stability of the overall closed-loop system for specific machining conditions. The modeling and formulation used for both strategies are presented in this first part. A simulation allows the comparison of their respective working principle. The validation of the proposed concept in experimental conditions is described in the second part.

A new concept for wire-length prediction, the semi-individual wire-length prediction, is introduced. Structural metrics, such as mutual contraction and net range, are used to predict which interconnects have a tendency to be long or short in the final layout. The very good correlation of the prelayout measures with the postlayout interconnect lengths is demonstrated. The prelayout wire-length-prediction techniques are applied in logic synthesis, targeting wiring cost, and congestion minimization. This paper focuses on technology mapping and fan-out optimization. Experiments on LGSyn93 and ITC'99 benchmark suites show that the wire-length-prediction-based technology mapping and fan-out-optimization algorithms produce layout-friendly netlists. After placement and global routing, the netlists yield smaller total wire length, are more routable, and achieve better timing than the netlists obtained using traditional logic-synthesis flow in SIS.

This paper presents a new space vector pulse width modulation (SVPWM) to eliminate common-mode voltage (CMV) for multilevel inverters. The proposed SVPWM is performed in a new coordinate system, in which the converter voltage vectors have only integer entries and the absolute coordinate increment between adjacent vectors is equal to 1. The location of the reference vector, detection of the nearest three CMV vectors, and duty cycles of the nearest three CMV vectors are all obtained by simple calculations, no lookup table is needed and the SVPWM is computationally fast. Compared with earlier pulse width modulations (PWMs), the realization of the CMV vectors is very simple, and the CMV of multilevel inverters are limited to zero with any modulation index. Because the SVPWM is independent of the level number of the inverter, the proposed SVPWM is suitable for any level of inverter. This paper also thoroughly compares the proposed SVPWM with prior PWMs. Experimental results are also given in the paper.

This paper presents an approach for incorporating actual voltage stability operating limits (VSOL) in the composite power system adequacy evaluation. The VSOL curves are fitted into simplex-type straight lines and added in the linear programming model for minimizing load curtailment as additional constraints. The incorporated voltage stability limits are those calculated for the operators in the power system control center. The introduction of the actual limits therefore leads to adequacy evaluation closer to the operation reality with very little overhead since the voltage stability operating limits are pre-calculated for system operation. The case studies for BC Hydro's 500/230 kV system are given and discussed.

The paper reports on a practical backward motion strategy for a vehicle pushing several passive trailers with any combination of on- and off-axle hitches. The last trailer is defined as a virtual tractor that can be guided along paths of varying curvature like a single non-holonomic vehicle. Then, kinematic relationships are proposed to translate the resulting motion commands to the actual tractor. The paper extends previous work by specifically addressing propagation of virtual set-points through on-axle hitches. This case is difficult because direct propagation cannot be achieved due to kinematic restrictions imposed by current joint angles. The method has been experimentally applied for both autonomous path-tracking and online operator steering using a tracked mobile robot with two different off- and on-axle combinations of dissimilar trailers. Results indicate applicability in autonomous vehicles and advanced driver assistance systems.

Condition Based Maintenance (CBM) is a new maintenance strategy and interest of utilities for reliable operation of aged power equipments. Although CBM has been tried to apply for various equipments, since an affection of accuracies of condition information from sensor have not sufficiently discussed, specification of reliable information is still not clear and CBM has not widely applied in actual power substation. The affection of accuracies of condition information for the criteria of failure recognition is treated in this paper. Authors retrace to the potential—failure curve (P-F curve) in original Reliability Centered Maintenance (RCM) concept and explain the affection. The explanation is proved using comparison with original sensor for CBM and existing sensor in SF6 gas slow leakage detection experiment. As a result of experiment SF6 gas leakage less than 0.1%/year might be detected using CBM sensor. The authors concluded that special performances in sensitivity and long term stability of sensor are very important for reliable operation of power substation under CBM strategy.

This paper reports wireless microfluidic control enabled by the selective operation of multiple bulk-micromachined shape-memory-alloy actuators using external radiofrequency magnetic fields. Each shape-memory-alloy actuator is driven by a wireless resonant heater which generates heat only when the field frequency is tuned to the resonant frequency of the heater. Multiple actuators coupled with the heater circuits that are designed to have different resonant frequencies in the range of 135–295 MHz are selectively and simultaneously controlled by modulating the field frequency to the resonant frequencies of the corresponding heaters. A wireless microsyringe device that has three actuator–heater components and a flexible parylene reservoir is developed. The 5 µl reservoir is squeezed by the 5 mm long cantilever-type actuators to eject controlled amount of liquid from the reservoir. Using the device with an acidic solution loaded in the reservoir, sequential modifications of the pH level in the liquid are experimentally demonstrated through the selective control of the three actuators. The thermal characterization of the actuator using infrared imaging shows a temperature increase of 50 °C in 4 s and the full activation of the actuator in 8 s with 300 mW field output power.

Poor adherence to prescription medication can compromise treatment effectiveness and cost the billions of dollars in unnecessary health care expenses. Though various interventions have been proposed for estimating adherence rates, few have been shown to be effective. Digital systems are capable of estimating adherence without extensive user involvement and can potentially provide higher accuracy with lower user burden than manual methods. In this paper, we propose a smartwatch-based system for detecting several motions that may be predictors of medication adherence, using built-in triaxial accelerometers and gyroscopes. The efficacy of the proposed technique is confirmed through a survey of medication ingestion habits and experimental results on movement classification.

This paper presents two expert systems designed to serve as a control center operator's assistant. The first is designed to assist operators in solving overload problems and the second is to assist in solving voltage problems. Both systems use the distribution factor concept to create indices for the decision-making process. A new improved technique to obtain the distribution factors is presented. That technique circumvents part of the problems introduced by the linearization implicit in the use of distribution factors and makes them suitable to be used to solve voltage problems. A 634-bus model of an actual electrical system and its interconnections is used so that the results can be realistically compared with the action that would be taken in the control center. Results are reached in a manner consistent with the operation of the control center and in a time frame that makes these expert systems feasible for real-time applications.

Commonly, three-phase diode bridge rectifiers with an LC filter at the DC side are often used to convert AC input into a DC voltage. It is well known that they generate large amounts of harmonic currents. This paper proposes an analytical method for calculating the harmonic currents for both the continuous and discontinuous current conductions. The equations for the harmonic currents are derived, taking into account the effects of the DC and AC side impedances. All the calculations are conducted only by algebraic calculation with high accuracy. The validity of the proposed method is demonstrated by comparison to the results of time simulation. >

In this paper, we propose a case study of field programmable gate array (FPGA)-implemented self-checking circuits. In particular, we propose the design, implementation and experimental measurements of the Transmission and Reception Blocks of a Track-side Control System for railway applications. Our scheme is designed to feature on-line testing ability with respect to possible functional errors affecting the received and transmitted words, as well as with respect to a wide set of possible internal faults, representative of the most likely faults for FPGA-implemented systems. It negligibly impacts system's performance and features a more compact structure with respect to its alternative design making a massive use of the duplicate and compare technique. A prototype has been implemented, whose correct operation has been verified by means of post-layout simulations and experimental measurements.

The biggest concern in the use of radio-over-fiber (ROF) links in wireless access is their limited dynamic range due to nonlinear distortion (NLD). In this paper, a higher order adaptive filter based nonlinearity compensation scheme is proposed. Pre-compensation is done for the downlink while post-compensation is done for the uplink to result in asymmetry with respect to complexity. Thiscentralized signal processing is attractivein thatit keeps the remote unit simple. Accurate measurements of ROF link parameters are not required with this approach because the filters are adapted from the distortion of the input/output base band signal. This technique also facilitates fast tracking of modifications and drifts in the link characteristics. Measurements and simulation results show that gradually saturating amplitude nonlinearity can be adequately linearized with some backoff from the clipping limit. A 42% backoff is required for pre-compensation to protect the laser while only a 16.7% backoff is required for post-compensation. Phase pre-compensation is accomplished with a higher accuracy than phase post-compensation.

This paper presents the analysis of the voltage error caused by a finite resolution of the modulator of a three-phase PWM invertor. A suitable algorithm is proposed in order to eliminate offsets and to reduce parasitic components for as much as 15 dB. Essentially, the algorithm represents the numerical procedure of rounding the high-resolution amplitude products into lower resolution digital words that are to be loaded into the PWM counters. For a given resolution of the modulator, the suggested procedure considers the coupling between the phase residual errors and selects counter loads in such a way that the minimum voltage vector error is obtained. The presented analytical considerations are verified by experimental results. The spectra of the inverter output voltage, obtained in an experimental setup, illustrate the efficiency of the proposed algorithm in suppressing undesired spectral components of the inverter output. >

Designing energy-efficient cognitive radio sensor networks is important to intelligently use battery energy and to maximize the sensor network life. In this paper, the problem of determining the power allocation that maximizes the energy-efficiency of cognitive radio-based wireless sensor networks is formed as a constrained optimization problem, where the objective function is the ratio of network throughput and the network power. The proposed constrained optimization problem belongs to a class of nonlinear fractional programming problems. Charnes-Cooper Transformation is used to transform the nonlinear fractional problem into an equivalent concave optimization problem. The structure of the power allocation policy for the transformed concave problem is found to be of a water-filling type. The problem is also transformed into a parametric form for which a ε-optimal iterative solution exists. The convergence of the iterative algorithms is proven, and numerical solutions are presented. The iterative solutions are compared with the optimal solution obtained from the transformed concave problem, and the effects of different system parameters (interference threshold level, the number of primary users and secondary sensor nodes) on the performance of the proposed algorithms are investigated.

Many commercial wireless mesh network (WMN) products are available in the marketplace with their own proprietary standards, but interoperability among the different vendors is not possible. Open source communities have their own WMN implementation in accordance with the IEEE 802.11s draft standard, Linux open80211s project and FreeBSD WMN implementation. While some studies have focused on the test bed of WMNs based on the open80211s project, none are based on the FreeBSD. In this paper, we built an embedded system using the FreeBSD WMN implementation that utilizes two channels and evaluated its performance. This implementation allows the legacy system to connect to the WMN independent of the type of platform and distributes the load between the two non-overlapping channels. One channel is used for the backhaul connection and the other one is used to connect to the stations to wireless mesh network. By using the power efficient 802.11 technology, this device can also be used as a gateway for the wireless sensor network (WSN).

In this paper, we present an analytic model for thickness resonating plate ultrasound energy receivers, which we have derived from the piezoelectric and the wave equations and, in which we have included dielectric, viscosity and acoustic attenuation losses. Afterwards, we explore the optimal electric load predictions by the zero reflection and power maximization approaches present in the literature with different acoustic boundary conditions, and discuss their limitations. To validate our model, we compared our expressions with the KLM model solved numerically with very good agreement. Finally, we discuss the differences between the zero reflection and power maximization optimal electric loads, which start to differ as losses in the receiver increase.

Wireless sensors are increasingly penetrating every domain of our lives through integration with Internet of Things, e.g., such devices are widely incorporated into smart buildings and for monitoring critical industrial infrastructure. Sensing, collecting and communication of sensor data, however, are under threat from various attacks due to the difficulty in implementing proper protection mechanisms and limited computational resources available in these cost-sensitive devices. This paper expands on recent research on physical unclonable function (PUF) sensors to secure sensing by taking the advantage of inherent physical randomness. In particular, PUF unreliability originates from its sensitivity to ambient parameter variations that is usually undesirable for elementary PUF applications—such as authentication and key generation—is exploited to guarantee the veracity of the sensed value. In this paper, a PUF naturally acting as a sensor or a PUF explicitly integrated with a sensor is called a PUF sensor. Security of sensing in a PUF sensor is attributed to the natural merging of cryptography and sensing to eschew the need for a standalone crypto module. Thus, the PUF sensor is appealing for low-cost applications. To obtain the sensed value, we develop an authenticated sensing protocol that is robust against eavesdropping, also capable of detecting man-in-the-middle manipulation of the sensed value. Compared to initial investigations of PUF sensors, we avoid the stringent requirements of a strong PUF. We validate the feasibility of the proposed authenticated sensing protocol based on an experimental implementation of a ring oscillator PUF sensor. To improve the sensing capability, we present an efficient approach to select sensitive responses and only employ them for sensing. Significantly improved efficacy is validated through comprehensive experimental results.

Massive multiple-input-multiple-output (MIMO) systems use few hundred antennas to simultaneously serve large number of wireless broadband terminals. It has been incorporated into standards like long term evolution (LTE) and IEEE802.11 (Wi-Fi). Basically, the more the antennas, the better shall be the performance. Massive MIMO systems envision accurate beamforming and decoding with simpler and possibly linear algorithms. However, efficient signal processing techniques have to be used at both ends to overcome the signaling overhead complexity. There are few fundamental issues about massive MIMO networks that need to be better understood before their successful deployment. In this paper, we present a detailed review of massive MIMO homogeneous, and heterogeneous systems, highlighting key system components, pros, cons, and research directions. In addition, we emphasize the advantage of employing millimeter wave (mmWave) frequency in the beamforming, and precoding operations in single, and multi-tier massive MIMO systems. Keywords: 5G wireless networks; massive MIMO; linear precoding; encoding; channel estimation; pilot contamination; beamforming; HetNets

In this paper, a 48-200 MHz CMOS hybrid tracking low-pass filter with low power and high dynamic range is presented to solve a local oscillator harmonic-mixing problem for Advanced Television Systems Committee terrestrial digital TV tuner integrated circuits. For low power consumption, the first-order passive RC filter and the second-order transconductor-C filter are combined to implement the third-order Chebyshev tracking low-pass filter. A transconductor linearization technique based on a method of multiple gated transistors is adopted to achieve high dynamic range. Fabricated in a 0.18 μm CMOS process, it achieves a maximum in-band input-referred noise density of 5.1 nV/√Hz and maximum in-band output-referred third-order intercept point of 17.3 dBm, while dissipating 23.4 mW with 1.8 V. The total chip area is 0.6 mm × 0.4 mm.

In harsh environments, Fe-based amorphous coatings can provide effective protection for equipment. A method of thickness measurement of thin layer and quality evaluation based on high-frequency water-immersion ultrasonic testing and imaging is proposed here. In this paper, because of the interface echoes of the micron-scale coating in the aliasing of ultrasonic testing signals, wavepacket decomposition and extraction technology proposed according to the matching pursuit theory is used to separate the interface echoes. After using the narrow pulse replacement method, the coating structure imaged is reconstructed. The decomposed interface echoes will not be mixed again, thus reflecting the coating thickness information more accurately. Consequently it can be used to evaluate the coating quality. Finally, the experimental results show that the coating structure image can be reconstructed after the high-frequency water-immersion ultrasonic scanning signals are processed with the above method. The relative error of the coating thickness detection is only 3.13% compared with the scanning electron microscope (SEM) results. At the same time, the coating spraying quality can be evaluated effectively through the imaged results.

Wireless local area network (WLAN) is a technology that combines computer network with wireless communication technology. The 2.4 GHz and 5 GHz frequency bands in the Industrial Scientific Medical (ISM) band can be used in the WLAN environment. Because of the development of wireless communication technology and the use of the frequency bands without the need for authorization, the application of WLAN is becoming more and more extensive. As the key part of the WLAN system, the antenna must also be adapted to the development of WLAN communication technology. This paper designs two new dual-frequency microstrip antennas with the use of electromagnetic simulation software—High Frequency Structure Simulator (HFSS). The two antennas adopt ordinary FR4 material as a dielectric substrate, with the advantages of low cost and small size. The first antenna adopts microstrip line feeding, and the antenna radiation patch is composed of a folded T-shaped radiating dipole which reduces the antenna size, and two symmetrical rectangular patches located on both sides of the T-shaped radiating patch. The second antenna is a microstrip patch antenna fed by coaxial line, and the size of the antenna is diminished by opening a stepped groove on the two edges of the patch and a folded slot inside the patch. Simulation experiments prove that the two designed antennas have a higher gain and a favourable transmission characteristic in the working frequency range, which is in accordance with the requirements of WLAN communication.

This paper deals with static transfer stability limits (STSL) of network branches and their relation with singularity of the power flow Jacobian. It describes the effect of large transfers on the branch complex flows and shows that when a transfer takes place in the system, at least one branch must reach its STSL before the singularity is encountered. Numerical examples confirm this necessary condition and show that the first STSL appears close to the singularity. Therefore, it is possible to monitor the proximity to the power flow Jacobian singularity by supervising the complex flow in individual transmission lines.

This paper presents some distinctive features of a power system which is composed of a generator and a large power system connected to it through relatively long tie-line. The generator is closely connected to an induction machine which is regarded as a dynamic load. The phenomena-affected with dynamic load are explored by extending the approach developed by deMello and Concordia [1], and the laboratory field tests. The features are compared with the case of impedance load to which many studies have already been conducted.

A new magnetorheological piston head design inspired by toroidal electromagnets was proposed in previous work as an alternative to conventional annular dampers. A prototype with a circular valve array integrated inside the piston head was built and tested to measure its passive performance. The mechanical, electromagnetic, and hydraulic models used in the new design were explained, and the relevant parameters of the actuator were analyzed to construct a mathematical model to estimate its performance. These works showed the feasibility of the concept and its potential as an alternative to current damper technology, but lacked a baseline for comparison. This paper reviews and widens this groundwork. It adds a magnetic finite element method study to address the previously found leakage, and a new set of experiments, including a force controller, to compare its performance against a conventional annular piston head. The new findings show how the current force limitations can be overcome by striking a balance between the coil space and the size of electromagnet cores to achieve the performance of current dampers. They also highlight its potential in force control applications to provide a wider range of customization options, such as number and size of holes, electromagnets, and coils, and a better use of the active area of the gap.

The paper presents a method for optimizing the mean confirmation time of a bistatic track (in bistatic range, bistatic velocity coordinates) in passive radar by adjusting the processing parameters. The track confirmation method is a standard cascaded logic, or "m out of n" logic. To provide high reliability of the confirmed tracks, the expected rate of confirmed false tracks is calculated, and it is used as a constraint during the optimization process. The optimization is based on a joint analysis of several parts of the processing chain of the passive radar, including the correlator, detector, and tracker. The parameters tuned to obtain minimum confirmation time are integration time, probability of false alarm (set by detection threshold), and parameters of the initialization logic m and n. Because the results depend on the signal-to-noise ratio, a parallel processing structure is proposed with different parameters in each branch to accommodate varying echo signal strengths. As a result, one can obtain improvement in track confirmation time with assumed number of confirmed false tracks per second. The developed procedures are tested on a simulated signal as well as on real-life data recorded with the experimental passive system PaRaDe.

Economical delivery of power from the terminals of large electric generators to transmission transformers may require forced cooling. This paper presents a method for calculating the cooling requirements. Operating characteristics of typical self-cooled and forced-cooled buses for 13,000 amp (amperes) are tabulated. Experimental results on a 10,000-amp liquid-cooled assembly demonstrate the validity of this method of calculation.

Permanent-magnet generators (PMG) have rapidly become important in renewable energy systems, portable and standby generating systems, and in many new applications in industrial, utility, aerospace and automotive sectors. While there has been some discussion of “fault tolerance,” and fault testing of an 8MW machine has recently been reported [5], understanding the behavior of faulted PMGs remains far from complete. This paper addresses the important case of the sudden short-circuit applied to large PMG machines. It explains key differences in short-circuit behavior between the PMG and wound-field generator (WFG). The subtransient reactances and time-constants of the PMG are calculated by both analytical and finite-element methods, and applied to the classical circuit-theory simulation of the short-circuit fault. The finite-element method is also used to assess in detail the risk of loss of magnetization in the magnets. The complexity of the transient magnetic field requires transient nonlinear circuit-coupled finite-element analysis in three dimensions with voltage-source excitation. The paper concludes with a review of the methods of calculation and a discussion of implications for future design and application of the PMG, including factors relevant to the application of standard tests and specifications.

This paper presents an AC-AC power converter integrated with techniques that provide environmental harmony. The voltage source PWM inverter has been established as the major motor drive equipment. However, it is associated with issues pertaining to PWM switching as well as issues related to the input harmonics caused by capacitor input-type rectification. Hence, there is need for a converter that addresses these problems and provides an environmentally harmonious solution. The matrix converter has a topology that inherently exhibits sinusoidal input current waveforms and less stressful output voltage waveforms. Combining the matrix converter with certain filter topologies is shown to provide an environmentally harmonious solution. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(8): 1–10, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10129

A single wafer silicon condenser microphone with a novel single deeply corrugated diaphragm is presented in this paper. The microphone diaphragm with corrugation depth of 100 μm is only 1 mm2 in area, while the open‐circuit sensitivity as high as 9.8 mV/Pa under a bias voltage of 6 V has been obtained. The recorded frequency bandwidth is about 20 kHz. The measurements show reasonable agreements with the theoretical predictions.

This paper presents a semianalytical technique that predicts the propagation characteristics of high-voltage (HV) transient pulses along a single-wire electric fence line with an earth return. The technique models the fence line in the frequency domain to facilitate an analytical solution for the propagation of HV pulses along the line. The frequency-domain solution is then transformed into time domain through a numerical Laplace inversion algorithm to determine the propagation characteristics of the line at a given location and time. For various line conditions, the propagation characteristics of HV pulses are investigated, and results indicate that the parameters of fence lines are frequency dependent, and an accurate insight into the propagation characteristics of HV pulses along single-wire fence lines can only be achieved through a frequency-dependent fence model. As confirmed by simulations of power systems computer-aided design, the proposed technique based on a frequency-dependent fence model is accurate, and can be considered an invaluable tool for designing complicated electric fence networks.