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This study explored the use of parasternal second intercostal space and lower intercostal space surface electromyogram (sEMG) and surface mechanomyogram (sMMG) recordings (sEMGpara and sMMGpara, and sEMGlic and sMMGlic, respectively) to assess neural respiratory drive (NRD), neuromechanical (NMC) and neuroventilatory (NVC) coupling, and mechanical efficiency (MEff) noninvasively in healthy subjects and chronic obstructive pulmonary disease (COPD) patients. sEMGpara, sMMGpara, sEMGlic, sMMGlic, mouth pressure (Pmo), and volume (Vi) were measured at rest, and during an inspiratory loading protocol, in 16 COPD patients (8 moderate and 8 severe) and 9 healthy subjects. Myographic signals were analyzed using fixed sample entropy and normalized to their largest values (fSEsEMGpara%max, fSEsMMGpara%max, fSEsEMGlic%max, and fSEsMMGlic%max). fSEsMMGpara%max, fSEsEMGpara%max, and fSEsEMGlic%max were significantly higher in COPD than in healthy participants at rest. Parasternal intercostal muscle NMC was significantly higher in healthy than in COPD participants at rest, but not during threshold loading. Pmo-derived NMC and MEff ratios were lower in severe patients than in mild patients or healthy subjects during threshold loading, but differences were not consistently significant. During resting breathing and threshold loading, Vi-derived NVC and MEff ratios were significantly lower in severe patients than in mild patients or healthy subjects. sMMG is a potential noninvasive alternative to sEMG for assessing NRD in COPD. The ratios of Pmo and Vi to sMMG and sEMG measurements provide wholly noninvasive NMC, NVC, and MEff indices that are sensitive to impaired respiratory mechanics in COPD and are therefore of potential value to assess disease severity in clinical practice. [ABSTRACT FROM AUTHOR]

This article studies design guidelines to optimize the inductive coils for electric vehicles by replacing the standard compact ferrite core with a compound of polymers, nanoparticles, and tile-links of ferrite and by reviewing different aspects of the winding to improve mechanical behavior and efficiency. A system composed of the studied vehicle assembly and ground assembly from the society of automotive engineers’ recommended practice is defined. Fast three-dimensional (3-D) finite element simulations are performed by evaluating different geometric aspects of the vehicle assembly. In doing so, the variation of coupling factor and inductance related to the geometry can be observed and compared in order to analyze the performance when the amount of compact ferrite is reduced. The polymer bonded magnetic is, then, incorporated to improve the decreased magnetic behavior due to the reduction in ferrite. In previous works, the modeling of the litz-wire and polymer bonded magnetic were developed to accelerate the simulations. In this article, we include the modeling of the compact ferrite tile-links to further reduce the time consumption of these simulations. Moreover, simple two-dimensional simulations are described to study the windings’ parasitic capacitances. The design guidelines, based on fast 3-D simulations, are detailed and validated with particular prototypes. [ABSTRACT FROM AUTHOR]

This article is a contribution to answer the following question: Is it possible to design a permanent magnet machine with the performance expected from rare-earth magnets but at a lower cost? Performance being understood as torque, size, efficiency, demagnetization, and temperature rise together. The question is addressed with a systematic exploration of different interior permanent magnet machine topologies mixing rare-earth and ferrite permanent magnets. The study starts from a production baseline, the Prius 2010 traction motor, with interior magnets placed in a single V pattern. It investigates various rotor designs, most specifically, single V and double V patterns as well as spoke configurations. The stator cross-section design and winding selection are fixed, providing a solid comparison basis from the point of view of machine cooling. For each rotor design, torque potential and machine material cost are assessed, the latter expressed as torque per dollar. A promising configuration was found based on a spoke pattern for which further modeling was performed to assess efficiency as well as mechanical strength and resistance to short circuits and to demagnetization. It reduces the rare-earth magnet volume by over 60%. [ABSTRACT FROM AUTHOR]

Robotic ankle-foot prostheses aim to improve the mobility of individuals with belowknee amputations by closely imitating the biomechanical function of the missing biological limb. To accomplish this goal, they must provide biomechanically accurate torque during ambulation. In addition, they must satisfy further requirements such as build height, range of motion (ROM), and weight. These requirements are critical for determining the potential number of users, range of activities that can be performed, and clinical outcomes. Previous studies have proposed addressing this challenge through the use of advanced actuation systems with series and parallel elastic actuators, clutchable leverages, and pneumatic artificial muscles. These ad vanced actuation systems have shown improved mechanical and electrical efficiency compared to conventional servo motors, making powered ankle prostheses possible. However, the improved efficiency comes at the expense of a tall build height, reduced ROM, and significant increase in weight, thus limiting the clinical viability of currently available powered prostheses. [ABSTRACT FROM AUTHOR]

The conversion efficiency of piezoelectric energy harvesters (EH) have been improved by several approaches including frequency up-conversion (FUC) techniques that trigger the high-frequency (HF) piezoelectric resonators using low-frequency (LF) mechanical inputs. This work proposes a new time-domain multiplexing technique to further improve the harvesting efficiency for random mechanical impacts using commercially available microfabrication processes. The FUC is implemented by a slowly moving shuttle beam, which represents the LF mechanical inputs, that triggers the free ends of piezoelectric cantilever beams. Mechanical impacts by the LF shuttle lead to the cantilever beams vibrating at their higher natural resonance frequencies. In the proposed approach, resonators are exposed to the LF mechanical input at unequal distances, which results in sequential HF vibrations. As a result, the HF electrical outputs fit sequentially within the long period of the LF input. Analytical and experimental comparisons support the increased electrical output using time domain multiplexing. [ABSTRACT FROM AUTHOR]

This paper discusses systematic efficiency considering the efficiency of both a motor and airflow in an inverter-driven single-phase brushless direct-current (BLDC) motor with two different lamination designs for a cordless vacuum cleaner. In other words, multi-physical lamination design has to be conducted, and hence, the shape and placement of a whole electromagnetic structure are investigated in terms of a tradeoff between the electrical and mechanical efficiencies. In this paper, a single-phase BLDC motor for cordless vacuum cleaners is designed to satisfy starting and continuous torques by means of asymmetric air gap, and fluid analysis is performed to determine which shape of a single-phase BLDC motor has better system efficiency. The prototype of a single-phase BLDC motor has been tested, and the speed of the operation is ranged from 84468 r/min up to the rated speed of 100020 r/min. The motor efficiency of 94.7% has been measured to verify a good match with the estimated efficiency of 94.5%. [ABSTRACT FROM AUTHOR]

This paper presents research work on a 12-slot ten-pole tapered axial-flux permanent-magnet machine utilizing amorphous magnetic material in the stator core. Novel loss separation techniques are described, including mechanical loss and locked-rotor tests. Mechanical loss estimation is based on a combination of experimental tests and 3-D finite-element model analysis using an uncut stator. The locked-rotor test is introduced to separate the stator and rotor losses by eliminating the uncertainty associated with mechanical loss. High rotor yoke losses were identified in the baseline design. The rotor design was modified and a significant improvement in efficiency was demonstrated. [ABSTRACT FROM PUBLISHER]

Nonorthogonal multiple access (NOMA) can effectively improve the spectral efficiency by exploiting the power difference and employing successive interference cancellation (CSI) at receivers. In NOMA, the power allocation is crucial and can be performed with known CSI. It is also possible to carry out the power allocation with statistical CSI to meet target outage probabilities for given transmission rates. In this paper, we consider joint rate and power allocation to minimize the total transmission power with individual throughput constraints in NOMA when statistical CSI is available. An approach to find the optimal solution to the joint rate and power allocation problem is proposed. Based on simulation results, it is shown that NOMA can have a much lower total transmission power than OMA for given target throughput of each user. [ABSTRACT FROM AUTHOR]

The design strategies and the implementation of a two-stage concurrent dual-band (DB) microwave harmonic-tuned power amplifier (PA) are presented in this paper. The power stage and the driver stage of this circuit are designed to operate under DB class-F conditions and DB inverse class-F conditions, respectively. The proposed DB harmonic control network of the power stage is implemented by combining a composite right/left-handed transmission line and a DB biasing line with harmonic tuning. A novel DB interstage matching network is developed to transfer the optimum fundamental output impedances of the driver stage to optimum fundamental input impedances of the power stage, as well as suppress the third harmonics at two frequency bands of interest. In the nonconcurrent mode (CM), the measured output power of the two-stage DB PA achieves two peaks of 40.2 and 40 dBm at 1.62 and 2.08 GHz with the maximum power-added efficiencies (PAEs) of 71.5% and 73%, respectively. In the CM, the maximum average PAE is up to 62%. To our best knowledge, the implementation of the two-stage concurrent DB harmonic-tuned PA is reported for the first time in the literature. [ABSTRACT FROM PUBLISHER]

This paper presents verification of frequency-response analysis (FRA) and vibroacoustic-method (VM) test methods complementarity for the assessment of the mechanical condition of a transformer's active part. Experiments performed on real power transformers under field conditions are discussed. The presented results cover three cases of faults which would be difficult to detect or correctly interpret with the application of a single method only. The first case shows the interfering influence of radiators on VM results. In the second case, a loosened winding with unchanged geometry, which cannot be detected by the FRA method, is discussed. The third presented case shows the results of an experiment based on introducing faults into the active part followed by FRA and VM tests. These faults were loosening of the core and loosening of winding with its slight stretching. The first fault could only be detected, as expected by VM results analysis, while the second one was confirmed by both methods; however, FRA assessment quality depends on the method of test data comparison. [ABSTRACT FROM PUBLISHER]

Cooling failure in data centers (DCs) is a complex phenomenon due to the many interactions between the cooling infrastructure and the information technology equipment (IT). To fully understand it, a system integration philosophy is vital to the testing and design of experiment. In this paper, a facility-level DC cooling failure experiment is run and analyzed. An airside cooling failure is introduced to the facility during two different cooling set points as well as in open and contained environments. Quantitative instrumentation includes pressure differentials, tile airflow, external contour and discrete air inlet temperature, intelligent platform management interface (IPMI), and cooling system data during failure recovery. Qualitative measurements include infrared imaging and airflow visualization via smoke trace. To our knowledge of current literature, this is the first experimental study in which an actual multi-aisle facility cooling failure is run with real IT (compute, network, and storage) load in the white space. This will establish a link between variations from the facility to the central processing unit (CPU). The results show that using the external IT inlet temperature sensors, the containment configuration shows a longer available uptime (AU) during failure. However, the IPMI data show the opposite. In fact, the available uptime is reduced significantly when the external sensors are compared to internal IT analytics. The response of the IT power, CPU temperature, and fan speed shows higher values during the containment failure. This occurs because of the instantaneous formation of external impedances in the containment during failure, which renders the contained aisle to be less resilient than the open aisle. The tradeoffs between PUE, OPEX, and AU are also explained. [ABSTRACT FROM PUBLISHER]

International efficiency testing standards, such as the IEEE 112-B and IEC 34-2-1, can determine the efficiency of an induction machine (IM) accurately at the cost of hindering the machine's productivity. Alternatively, various methods used to determine a machine's efficiency in situ do so at the cost of accuracy. This paper proposes a method that determines an IM's efficiency over a range of load conditions from tests conducted and centered around one thermally stable load point in the least intrusive manner possible. The results are then compared to those of the IEEE 112-B and IEC 34-2-1 motor testing standards using segregated loss analysis. It was found that despite the proposed algorithm being unable to accurately determine core losses, the efficiency of a machine can be estimated to within 0.5%–2.1% and 1.1%–1.7% error, when compared to the IEEE 112-B and IEC 34-2-1 standards, respectively over a 25%–150% machine load profile (dependent upon the proposed method's implementations). [ABSTRACT FROM PUBLISHER]

Rejection rates of upper limb prostheses are high (23%–45%). Amputees indicate that the highest design priority should be reduction of the mass of the prosthetic device. Despite all efforts, the mass of the new prosthetic hands is 35%–73% higher than that of older hands. Furthermore, current hands are thicker than a human hand, they operate slower and do not provide proprioceptive force and position feedback. This study presents the Delft Cylinder Hand, a body powered prosthetic hand which mass is 55%–68% lower than that of the lightest current prosthetic hands, operates faster, has an anthropomorphic shape, and provides proprioceptive force and position feedback. The hand has articulating fingers, actuated by miniature hydraulic cylinders. The articulating fingers adapt to the shape of the grasped object. Its functional scores are similar to that of current prosthetic devices. The hand has a higher mechanical performance than current body-powered hands. It requires 49%–162% less energy from the user and it can deliver a higher maximum pinch force (30–60 N). [ABSTRACT FROM AUTHOR]

Power losses in high-efficiency dc–dc step up converters based on the synchronous three-level neutral-point-clamped (TLNPC) configuration were investigated. TLNPC converters benefit from the reduced stress on components and from the non-insulated stacked-boost output stage to provide reduced power losses and large voltage gains. Several prototypes with increasing efficiency were produced and tested; voltage gains larger than $20\times$ were achieved by means of hard-switched prototypes with composite switches consisting of both low- R_{ds(ON)} and high-speed MOSFETs. At lower voltage gains conversion efficiencies exceeding 98% were demonstrated. A thorough loss analysis is reported, extended to subtle power dissipation processes, which in high efficiency converters grow in relevance after weakening of the major loss mechanisms. The related model is proven capable to accurately predict circuit performance in a wide range of operating conditions. [ABSTRACT FROM PUBLISHER]

Approximate efficiency of a linear regulator, if the power consumed by the control circuits is negligible, can be expressed by the ratio of Vo/Vin. A very low frequency supercapacitor circulation technique can be combined with commercial low-dropout (LDO) regulator integrated circuits to achieve significantly high end-to-end efficiency, and the result could be closer to the efficiencies of practical switching regulators. In this technique, supercapacitors are used as lossless voltage droppers, and the energy reuse occurs at very low frequencies such as from few hertz to few hundred hertz only, eliminating any radio-frequency interference/electromagnetic interference issues, compared to the switching regulators which utilize bulky inductors. Also, the technique is not a variation of charge pump converters due to nine clear reasons. Fundamental concepts related to this supercapacitor-assisted LDO regulator technique are discussed with experimental details of 12–5 V and 5–3.3 V versions together with a discussion on fundamental secondary losses associated with this novel technique. [ABSTRACT FROM PUBLISHER]

To gain insight into cyclic motor learning processes, hand rim wheelchair propulsion is a suitable cyclic task, to be learned during early rehabilitation and novel to almost every individual. To propel in an energy efficient manner, wheelchair users must learn to control bimanually applied forces onto the rims, preserving both speed and direction of locomotion. The purpose of this study was to evaluate mechanical efficiency and propulsion technique during the initial stage of motor learning. Therefore, 70 naive able-bodied men received 12-min uninstructed wheelchair practice, consisting of three 4-min blocks separated by 2 min rest. Practice was performed on a motor-driven treadmill at a fixed belt speed and constant power output relative to body mass. Energy consumption and the kinetics of propulsion technique were continuously measured. Participants significantly increased their mechanical efficiency and changed their propulsion technique from a high frequency mode with a lot of negative work to a longer-slower movement pattern with less power losses. Furthermore a multi-level model showed propulsion technique to relate to mechanical efficiency. Finally improvers and non-improvers were identified. The non-improving group was already more efficient and had a better propulsion technique in the first block of practice (i.e., the fourth minute). These findings link propulsion technique to mechanical efficiency, support the importance of a correct propulsion technique for wheelchair users and show motor learning differences. [ABSTRACT FROM AUTHOR]

Numerical and experimental studies on a coaxial vircator with radial dual-cavity premodulation are presented. The physics of mechanisms on microwave frequency determination and effects on microwave generating efficiency are discussed. It is proved that the microwave frequency is mainly determined by the modulation frequency, while the optimum operating frequency is determined by the intrinsic frequency of the beam itself. When the two frequencies match, the maximum efficiency is yielded. A structure capable of generating 6.0 GW microwave, 17% efficiency, and 50% frequency tuning bandwidth has been obtained by numerical simulations. The preliminary experiments were carried out on the MC55 accelerator. A 2.0 GW output microwave was experimentally obtained and the corresponding device efficiency is about 7%. [ABSTRACT FROM PUBLISHER]

The performance of a 2\,\times\,2 microstrip patch array under crumpling conditions is presented. The antenna array was manufactured on textile material, and three cases of crumpling resembling real applications are discussed. The performance of the individual patch elements correlate with the overall performance of the array. Frequency shifts of up to 6% are measured for the array when crumpled, the boresight gain is reduced by up to 6 dB with significant changes in directivity and efficiency, up to 20%. The overall efficiency for the textile array increases for crumpling in one plane but falls in the other. [ABSTRACT FROM PUBLISHER]

Effective means of delivering wireless power to volumes of spaces will enable users the freedom and mobility to seamlessly power and recharge their devices in an unencumbered fashion. This has particular importance for consumer electronic, medical, and industrial applications, where usage models focus on unstructured and dynamic environments. However, existing wireless power technology falls short of this vision. Inductive charging solutions are limited to near-contact distances and require a docking station or precise placement for effective operation. Far-field wireless power techniques allow much greater range, but require complicated tracking systems to maintain a line-of-sight connection for high-efficiency power delivery to mobile applications. Recent work using magnetically coupled resonators (MCRs) for wireless power delivery has shown a promising intersection between range (on the order of a meter), efficiency (over 80%), and delivered power (up to tens of watts). However, unpredictable loads rapidly change system operating points, and changes in position disrupt system efficiency, which affects the ultimate usability of these systems. Dynamic adaptation to these changes in operating conditions and power transfer range is a critical capability in developing a fully functional and versatile wireless power solution. This paper provides an overview of methods used to adapt to variations in range, orientation, and load using both wideband and fixed-frequency techniques. [ABSTRACT FROM PUBLISHER]

Efficient wireless power transfer across tissue is highly desirable for removing bulky energy storage components. Most existing power transfer systems are conceptually based on coils linked by slowly varying magnetic fields (less than 10 MHz). These systems have many important capabilities, but are poorly suited for tiny, millimeter-scale implants where extreme asymmetry between the source and the receiver results in weak coupling. This paper first surveys the analysis of near-field power transfer and associated strategies to optimize efficiency. It then reviews analytical models that show that significantly higher efficiencies can be obtained in the electromagnetic midfield. The performance limits of such systems are explored through optimization of the source, and a numerical example of a cardiac implant demonstrates that millimeter-sized devices are feasible. [ABSTRACT FROM PUBLISHER]

Several tribocharging devices are commonly used for charging insulating particles in order to separate granular plastic mixtures using a vertical triboelectric separator. However, there is no comparative analysis of these devices when tribocharging is achieved using identical samples of insulating particles. The objective of this paper is to carry out an experimental study that compares several tribocharging devices built up in the laboratory: a rotating cylinder, a tribo-cyclone, a static tribocharger, a propeller-type unit, and a fluidized bed. The study was performed using two granular samples of polyvinyl chloride (PVC) and high-density polyethylene (HDPE), for two different particle sizes: 1 and 2 mm. Experimental results showed that, when tribocharging pure samples of either PVC or HDPE, tribo-cyclone is the most efficient. However, when mixed samples are processed, the fluidized bed device gives the best results in terms of electric charge and separation efficiency. [ABSTRACT FROM PUBLISHER]

In this paper, the efficiency optimization of an axial flux permanent-magnet synchronous generator with concentrated pole windings is examined for a 3.6 kW/2000 rpm combined heat and power application. Because the efficiency of the machine is important, specific measures are taken in order to reduce losses in the machine: thin laminated grain oriented material in the teeth, concentrated pole windings, and segmented magnets. A study of the influence of a limited set of geometry parameters on the efficiency of this type of machine is done, using both analytical and finite-element methods. In the analytical as well as in the finite-element model, the inherent 3-D geometry of the axial flux machine is approximated by multiple 2-D models at different radii in circumferential direction. Afterwards, the influence of mass on the optimal values of the geometry parameters and the efficiency is considered, and it is found that mass can be seriously decreased with only a small reduction in efficiency. Finally, the results of both methods are compared with measurements on a prototype to evaluate their validity. [ABSTRACT FROM AUTHOR]

The international standards for determining induction motor efficiency are not in agreement with each other. At the heart of the differences is the stray load loss (SLL). The way this loss is quantified is continuously debated. For many years, the IEC standard for motor efficiency measurement has assigned a fixed percentage to stray load loss. This fixed percentage value has been criticized throughout the history of the standard. A new version of the standard published in September 2007 replaced the fixed percentage with one that is dependent on motor kW rating through a specific relationship. One of the goals of this paper is to determine whether the new formula for assigning the SLL can be confirmed with actual test data. This paper presents a collection of test data on about 1000 motors to show the distribution of stray load losses in induction motors. The analysis clearly demonstrates the need for determining stray loss from test measurements rather than assigning an arbitrary value. [ABSTRACT FROM PUBLISHER]

One of the methods to improve efficiency and torque performance of the single-phase brushless dc (BLDC) motor is to find out the optimum commutation angle at each different speed. We used the finite-element method (FEM) to simulate the back-EMF voltage and the coil current for the single-phase BLDC motor, and then adjust the conduction time of switches by detecting the waveform of coil current. The motor can improve its efficiency, noise, and vibration when it obtains the optimal shift angle of each speed. We used PSPICE to verify the exactness of FEM simulation results of the single-phase BLDC motor. We adopted Microchip's dsPIC30F4011 digital signal processor (DSP) to process the Hall signal and the driving signals of switches of the driving system prototype of the single-phase BLDC fan motor. Finally, we used the related experimental results to confirm the feasibility and effectiveness of the proposed driver. [ABSTRACT FROM AUTHOR]

Recent research has shown that electromechanical (E/M) impedance-based techniques are an efficient strategy for damage sensing in the context of structural health monitoring (SHM). The basic principle is to excite the lead zirconate titanate (PZT) sensors attached to the structure and to measure the corresponding electrical impedance. A variation in the electrical impedance indicates a variation in the mechanical impedance and, consequently, structural damage. To measure the electrical impedance, most universities and research centers use expensive, bulky, heavy, and high-powered impedance analyzers, which limit new developments and practical applications. To overcome these issues, this paper presents an efficient and inexpensive methodology for electrical impedance measurement. To verify the efficiency and accuracy of the new methodology, practical tests were carried out, and the results were compared with those obtained using a conventional impedance analyzer. [ABSTRACT FROM AUTHOR]

When spectrum is shared among multiple radio systems, spectrum admission control (SAC) can be performed via a centralized spectrum manager to meet their respective traffic demands. The adopted policy will determine the admission of service requests and, in turn, affect the overall spectrum utilization efficiency. The design of SAC policies becomes more challenging when each radio system provides a grade of service (GoS) in the form of a blocked service guarantee to its users. Given such constraints, we study the admission region, which indicates the maximum amount of supported traffic for the given resources. We first study the performance based on a simple first-come-first-serve (FCFS) policy. Our studies show that the admission region is, in general, limited by the radio system that first violates its prescribed GoS guarantee (i.e., the performance-limiting radio). We propose three SAC policies to enhance the total offered traffic and compare them against the FCFS policy. The first is a random discard (RD) policy, where requests from other systems are discarded with some predetermined probabilities so that a larger portion of the spectrum is made available to the performance-limiting radio. The second SAC uses a reservation (RES) policy, where a suitable amount of spectrum is reserved for the performance-limiting radio. In the third policy, SAC is formulated as a discrete-time constrained Markov decision process (MDP). We analyzed the performance of each policy at low and high request rates and show how the additional design parameters in each policy can be optimized to enhance the offered traffic. As admission decisions are jointly made with traffic predictions, the MDP admission policy shows superior performance over the other policies due to its flexibility to operate both radios at the bound of the respective GoS constraint. [ABSTRACT FROM AUTHOR]

An energy-efficient adaptive transmission protocol for ultrawideband (UWB) wireless sensor networks (WSNs), called ATP-UWSN, is described and evaluated over time-varying multipath fading channel conditions and multinode interference. Since wireless channels may greatly change from one transmission to the next, the use of fixed transmission parameters for such channels results in wasted energy when channel conditions are good. Adaptation of transmission parameters reduces energy consumption and interference. The proposed ATP-UWSN permits each of the sensor nodes to adapt its code rate and spreading code length (the number of pulses used per data bit) to match the predicted channel-state information (CSI). The transmission parameters are selected in accordance with the predicted CSI characteristics of the communication links in the network to achieve the desired quality of service given by the target bit-error probability. Subsequently, we develop a mathematical adaptation framework for the analytical evaluation of ATP-UWSN. Communication performance is evaluated in terms of average information throughput efficiency, which is a relevant progress-related measure for multihop WSNs that is associated with the energy consumption and throughput of a packet transmission. The analytical expression of this performance metric is defined and is used to assess the benefits of the proposed ATP-UWSN when compared with a nonadaptive transmission protocol (NATP) with fixed transmission parameters. Our results show that the ATP-UWSN outperforms the NATP and can improve the robustness of the link and reduce energy consumption by adapting the transmission parameters in response to changes in the predicted CSI. [ABSTRACT FROM AUTHOR]

We describe a theoretical analysis of the excitation of the fundamental HE11 surface wave mode on an infinite dielectric rod by a magnetic ring current that is interior to the rod. Earlier work has provided results for an external ring source. Results obtained by us show that for an interior source excitation efficiencies close to 100% are possible for high permittivity dielectrics and launching efficiencies greater than 90% can be achieved over bandwidths greater than 20%. This is a higher efficiency than is possible with an exterior source. Simulation results verifying the theoretical analysis are presented for the practical case of a coaxial waveguide exciting the dielectric rod. [ABSTRACT FROM AUTHOR]

We review and formalize the mathematical background of time-modulated linear arrays (TMLAs); then, a number of issues are examined. First, for signal transmission applications, restrictions to the frequencies involved in the procedure are highlighted. Second, the sideband power losses associated to the technique are thoroughly examined, introducing a coefficient appropriate to evaluate the efficiency of the procedure. Finally, a closed form expression for the total power associated to sideband radiation is obtained, very convenient for the implementation of real-time optimization of the system. Relevance of additional research on the subject is highlighted. [ABSTRACT FROM AUTHOR]

A vehicle stability enhancement control algorithm for a four-wheel-drive hybrid electric vehicle (HEV) is proposed using rear motor driving, regenerative braking control, and electrohydraulic brake (EHB) control. A fuzzy-rule-based control algorithm is proposed, which generates the direct yaw moment to compensate for the errors of the sideslip angle and yaw rate. Performance of the vehicle stability control algorithm is evaluated using ADAMS and MATLAB Simulink cosimulations. HEV chassis elements such as the tires, suspension system, and steering system are modeled to describe the vehicle's dynamic behavior in more detail using ADAMS, whereas HEV power train elements such as the engine, motor, battery, and transmission are modeled using MATLAB Simulink with the control algorithm. It is found from the simulation results that the driving and regenerative braking at the rear motor is able to provide improved stability. In addition, better performance can be achieved by applying the driving and regenerative braking control, as well as EHB control. [ABSTRACT FROM AUTHOR]

This brief discusses the design and practical implementation of an Internet-based predictive control strategy. This novel control strategy can compensate for the random network delay and data dropout in an active way. In order to test the performance of the proposed control scheme, the offline simulation and practical implementation of an Internet-based servo control system are carried out. At the same time, the stability of the control scheme is also studied. The simulation and experimental results illustrate the feasibility and efficiency of the proposed Internet-based predictive control scheme. [ABSTRACT FROM AUTHOR]

We report on time-domain measurement and statistical analysis of field transients that are caused by mechanical transitions between the stationary states of an over-moded resonant cavity. These transitions and field transients are produced by the stepwise rotation of a mode tuner (reflective paddle wheel) inside a reverberation chamber excited by an uninterrupted time-harmonic source. It is shown that the cross-correlation function between the so-called stir sequences enables the reconstruction of the averaged mechanical motion of the mode tuner. Evolutions of the probability distribution and statistics of the transmission S-parameter show correlation with tuner motion and demonstrate nonstationarity of the cavity field. The influence of the operating frequency and various motor parameters is investigated. In estimating the evolving maximum-to-average ratio, the variations in the underlying (parent) distribution are shown to be considerably more influential than the variations of the number of independent samples. Semi. and fully empirical estimates of this ratio are compared with the directly measured values, and fully empirical estimation allows for more accurate prediction. It is shown that the measured local minima and local maxima of this ratio can be identified with short- and long- tailed instantaneous parent distributions, respectively. The effect is physically interpreted as modal bunching and dilation. The results are relevant to EMC immunity testing in reverberation chambers. [ABSTRACT FROM AUTHOR]

Two new models used to characterize polarization diversity at the mobile are presented and discussed. The first model is built upon existing theoretical models at a base station to demonstrate how those principles apply to the mobile fading environment. Due to limitations of antennas at the mobile, this extended model, although relevant, is not sufficient to characterize polarization diversity of the antennas; therefore, this paper moves on to show how a new approach to polarization diversity at the mobile exists as an inherent feature within an angular diversity system. Results show that, for two polarizations in a fading environment, the best overall output occurs with a ±45° element configuration, although the diversity combiner itself has optimum performance with a ±67.5° configuration due to lower correlation at the input. The second model is also used to demonstrate how differently polarized dipoles are using polarization diversity inherent within an angular diversity system. [ABSTRACT FROM AUTHOR]

We report on the fabrication and characterization of high-speed, single photon detectors using superconducting NbN nanowires at a wavelength of 1064 nm. A 15 by 15 microns detector with a detector efficiency of 40% has been measured. Due to kinetic inductance, the recovery time of such large area detectors is longer than that of smaller or single wire detectors. The recovery time of our detectors (50 ns) has been characterized by measuring the inter-arrival time statistics of our detector. [ABSTRACT FROM AUTHOR]

Agility is key for telecommunication operators to survive in a deregulated, competitive, and converging telecommunications environment. Openness and reusability have emerged as leading concepts to realize such agility. These concepts have both a business perspective and an operational perspective. Handling both perspectives in concert may provide competitive success. This article describes a strategy for managing commercial and operational agility in an open telecommunication value chain, using a structured approach for service orientation. [ABSTRACT FROM AUTHOR]

Condition monitoring of electric motors avoids severe economical losses resulting from unexpected motor failures and greatly improves the system reliability and maintainability. Efficiency estimation, which shares many common requirements with condition monitoring in terms of data collections, is expected to be implemented in an integrated product. This brings more considerations into the selection of the efficiency-estimation methods. This paper presents the results of an up-to-date literature survey on efficiency-estimation methods of in-service motors, particularly with considerations of the motor-condition-monitoring requirements. More than 20 of the most commonly used methods are briefly described and classified into nine categories according to their physical properties. Six categories of these methods are more related to in-service testing and are compared in a table summarizing the required tests and measurements, intrusion level, and average accuracy. Estimation of the rotor speed and the stator resistance, the two stumbling blocks of various efficiency-estimation methods, is also carefully studied; commonly used methods are summarized. Based on the survey results, four efficiency-estimation methods are suggested as candidates for nonintrusive in-service motor-efficiency estimation and condition-monitoring applications. Another contribution of this paper is that a general approach for developing nonintrusive motor-efficiency-estimation methods is proposed, incorporating rotor speed, stator resistance, and no-load loss estimations. [ABSTRACT FROM AUTHOR]

This paper describes an extensive induction motor rewind study. The consequent effects during the rewind process on loss components and efficiency are investigated. All the tests are conducted in accordance with the IEEE 112-B method, and some results are justified by the calorimetric approach. The conclusions drawn from the study show a little impact of rewinding or repeated rewinding on the motor losses and efficiency if ‘good practice’ is followed strictly. The efficiency results presented for most rewind studies apply for the full load condition. Changes in the balance between the load-independent losses and the load losses resulting from rewinding can, however, cause the maximum efficiency point to occur at a load, which differs from that of the original design. This may or may not be a disadvantage. Since few motors actually operate continuously at a full load, the comparisons of efficiency should really be made at the load point that applies specifically to the individual motor being rewound. The question that then arises is whether, there is a chance of improving the energy efficiency by modifying the motor design during rewinding, so that, a maximum efficiency occurs at the actual load point of the motor when used for its particular application. [ABSTRACT FROM AUTHOR]

The interest in methods that are able to efficiently compress microarray images is relatively new. This is not surprising, since the appearance and fast growth of the technology responsible for producing these images is also quite recent. In this paper, we present a set of compression results obtained with 49 publicly available images, using three image coding standards: lossless JPEG2000, JBIG, and JPEG-LS. We concluded that the compression technology behind JBIG seems to be the one that offers the best combination of compression efficiency and flexibility for microarray image compression. [ABSTRACT FROM AUTHOR]

Disk drive spindle motors require accurate speed control and highly efficient drive controllers. Small-volume and high-efficiency converters are of particular interest for portable data storage applications. Quasi-resonant voltage controllers are described in this paper and the experimental results are presented. In contrast to the conventional pulsewidth-modulated voltage controller, this technique reduces the switching loss and enables the controller to operate at very high frequencies. Three types of resonant converters are built and tested for the application. A comparison of performance in terms of losses and voltage regulation is given. [ABSTRACT FROM AUTHOR]