ALBERT

Description: In 2013, Switzerland and Italy started using wide area monitoring (WAM) systems as an additional tool for power-system operation and analysis. One of the driving forces behind this was the need for the comprehensive observation of highly loaded transmission corridors. Another important target was setting up a systemwide stability-monitoring tool with respect to interarea oscillations.

Description: Of the many electric power grid characteristics that contribute to its strength and effectiveness, there are two attributes that truly illustrate the nature of the grid?its fibrousness and its scale. Continental interconnectivity allows for fast, affordable, and reliable energy delivery but comes at the cost of complexity. In this way, the properties of the grid that embody its magnitude also contribute to the challenge of monitoring, operation, and control.

Description: The two-, three-, and four-channel mapping multiplexing technique (MMT) is demonstrated to increase the data capacity of multilevel intensity-modulated transmission formats to 2, 3, and 4 bits/symbol with a substantial reduction in power penalty. This paper outlines the $N$ -channel MMT design metric consideration influence on the performance enhancement of higher order amplitude modulated systems in terms of power penalty, receiver sensitivity, and spectral efficiency. The signal space model has been developed for $N$ -channel MMT, where the average electrical and optical power expressions are derived. Transmission of 2, 3, and 4 bits/symbol using MMT system shows better performance in terms of the average optical power penalty, in comparison with pulse amplitude modulation (M-PAM) formats, with respect to the information capacity. The proposed scheme can be considered as an alternative to M-PAM systems with enhanced power efficiency.

Description: This paper presents a novel low-complexity motion estimation and mode decision algorithm for encoding multiple quality layers following the H.264/scalable video coding standard, considering both coarse grain scalability (CGS) and medium grain scalability (MGS). The proposed algorithm conducts motion estimation and mode decision only at the base layer (BL) and enforces the higher layers to inherit the motion and mode decisions of the BL. In order for the decision made at the BL to be nearly optimal for all layers, we use the highest layer reconstructed frame as the reference frame for motion estimation and set the Lagrangian multipliers according to the quantization parameter of the current and higher layers. We also propose a simple early skip/direct decision to further boost the encoding speed. Mode decision and motion estimation is conducted at a higher layer only if the layer below it uses the skip/direct mode for a block. Significant complexity reduction can be achieved because the mode and motion estimation is performed at most once for each macroblock. Because the mode and motion information only needs to be transmitted once, we also achieve a slightly better rate-distortion (R–D) performance for typical videos. Experiments have shown more than $2times $ (up to $5times $ ) speedup for a three-layer encoder against the conventional R–D optimized reference software JSVM on both CIF and HD sequences, and for both CGS and MGS, with the tradeoff of the coding efficiency measured by the Bjontegaard delta rate.

Description: This paper proposes a new simplified model of a doubly fed induction generator (DFIG) that is integrated with a rotor-side converter for studies of large-scale transient stability. This model accurately considers the rotor field dynamics of an induction generator to yield simulation results that are more accurate in terms of voltage stability, as well as angle stability. The purpose of this paper is to provide a simple but effective DFIG model for the study of large-scale transient stability, and to examine the important aspects of rotor voltage and rotor slip power. This new simplified DFIG model with an electric/turbine control system was tested against a six-machine and 23-bus system, and the responses obtained in case studies of transient stability were compared with those of a PSS/E program. Finally, the proposed DFIG model was also validated by comparing the simulation results for a single-machine and infinite-bus system with those of PSCAD/EMTDC.

Description: Power fluctuation caused by wind speed variations may be harmful for the stability of the power system as well as the reliability of the wind power converter, since it may induce thermal excursions in the solder joints of the power modules. Using the wind turbine rotor inertia energy for power leveling has been studied before, but no quantified analysis or generic design method have been found. In this paper, the transfer functions from the wind speed to electrical power, electromagnetic torque, and rotating speed are built based on which the rotating speed controller is designed in the frequency domain for power leveling. Moreover, the impact of other parameters on power leveling, including the time constant of maximum power point tracking (MPPT) and the rotor inertia, are also studied. With the proposed optimal design, the power fluctuations are mitigated as much as possible, while the stability of the rotating speed is still guaranteed. Moreover, the oscillation of the electromagnetic torque is also reduced, and the performance of the MPPT is only weakened slightly.

Description: The precise estimation of efficiency of induction motors is crucial in industries for energy savings, auditing, and management. This paper presents a novel method for in situ induction motors efficiency estimation by applying the genetic algorithm and utilizing IEEE Form F2-Method F1 calculations with pretested motor data. The method requires a dc test, full-load operating point rms voltages, currents, input power, and speed measurements. The proposed algorithm uses a sensorless technique to determine motor speed. The algorithm is not only an in situ tool; it can also be used as an on-site efficiency estimation tool that might replace the expensive dynamometer procedure. The method was validated by testing 30 induction motors.

Description: It has recently been shown that spectrum analysis of instantaneous power can provide sensitive online detection of rotor faults in induction motors compared with current, torque, speed, or vibration spectrum analysis. However, it was reported that monitoring of the twice slip frequency, $2sf_{s}$ , components induced by the fundamental component can produce false rotor fault alarms due to asymmetry in the rotor or low frequency load oscillations. In this paper, the rotor fault components induced in the power spectrum by the stator fifth and seventh space harmonics are derived to evaluate their immunity to false alarms. It is shown that the $(6 - 8s)f_{s}$ component can provide reliable detection of rotor faults under cases where existing methods produce false alarms. An experimental study performed on custom built rotor samples shows that the new components are capable of detecting rotor faults immune to false alarms produced by rotor axial air ducts, rotor anisotropy, and low frequency load oscillations for cases where existing methods fail. The components derived in this paper can also be applied to vibration, speed, torque, or acoustic monitoring for reliable detection of rotor faults.

Description: Analytical models of electric machinery often utilize Carter's coefficient to account for the increased airgap reluctance due to flux entering the sides of the stator teeth. In this letter, a modified coefficient is proposed to account for wide stator slots, wherein a component of flux directly enters the stator backiron. The proposed coefficient is implemented in an analytical model of a wound rotor synchronous machine and is validated using two-dimensional (2-D) finite element analysis.

Description: Design aspects of the trans-rotary magnetic gear (TROMAG) integrated rotary machine are discussed in this paper, with particular focus on optimizing system cost and weight. Analytical models are used for design of the TROMAG. Optimal designs of the rotary machine are found by using a population-based genetic algorithm and two-dimensional finite-element analysis and thermal considerations. Weight, volume, and cost of the resultant system are then compared with the Pareto-optimal set of a permanent magnet linear tubular machine that is designed for the same force and speed specification. It is shown in this paper that, for high-force low-speed reciprocating motion applications, an electromechanical motion system consisting of a TROMAG and a rotary electric machine can far surpass a conventional direct drive linear machine in terms of weight, volume, and initial and operating cost.

Description: This paper presents a decentralized current control approach for a nine-phase wind turbine generator. This type of generator has three different three-phase stators sharing the same machine yoke and connected to the grid by means of three different voltage source back-to-back power converters. Due to the machine configuration, magnetic couplings are present between the three stators, complicating the design and implementation of the machine current controllers. Rather than a centralized control approach, this paper proposes a methodology to design a decentralized machine control to regulate the active and reactive power flowing through each stator independently. A complete dynamic analysis is performed in order to design the controller to reduce the coupling effects within the machine, while ensuring a proper dynamic performance. The control strategy is validated through simulation and experimental results.

Description: The papers in this special section cover the advances in multi-objective design and optimization based on genetic algorithms, surrogate, polynomial regression, and particle swarm optimization techniques. Design of novel trans-rotary magnetic gear, hybrid machines for dc generation, and two degrees of freedom split-stator induction machines highlight new magnetic configurations and their performance evaluations. Multiphysics analysis of magnetothermal and magnetostructural behavior of Switched Reluctance Machine (SRM) and brushless doubly fed machines shed light on analytical and practical aspects of design in electromechanical converters. Finally, control of torque undulation, loss minimization, low speed high torque operation, and advanced digital control of adjustable speed motor drives conclude this unique collection of papers.

Description: We consider multiple-antenna signal detection of primary user transmission signals by a secondary user receiver in cognitive radio networks. The optimal detector is analyzed for the scenario where the number of primary user signals is no less than the number of receive antennas at the secondary user. We first derive exact expressions for the moments of the generalized likelihood ratio test (GLRT) statistic, yielding approximations for the false alarm and detection probabilities. We then show that the normalized GLRT statistic converges in distribution to a Gaussian random variable when the number of antennas and observations grow large at the same rate. Further, using results from large random matrix theory, we derive expressions to compute the detection probability without explicit knowledge of the channel, and then particularize these expressions for two scenarios of practical interest: 1) a single primary user sending spatially multiplexed signals, and 2) multiple spatially distributed primary users. Our analytical results are finally used to obtain simple design rules for the signal detection threshold.

Description: Paralleling the increasing traffic and the associated degradation of services in operators' networks, there have been numerous research initiatives to explore potential solutions to better optimize network resources and maintain a high quality of experience (QoE) for subscribers. Although several possible solutions do exist, the focus of this paper is to survey one specific emerging family of solutions, called offload. Offloading's primary goal is to avoid transporting low priority traffic in costly networks in order to avoid degrading the perceived QoE. In particular, mobile operators target traffics that cause network congestion without creating any additional revenue. Offloading is based on traffic redirection from parts of the network where congestion could occur to other low-cost parts of the network where capacity is available and less expensive. In this paper, we present a survey on the offload approaches at different parts of the global network (access, core, and gateway). The aim of these approaches is to help mobile operators to face challenges such as capacity crunch, radio access saturation, average revenues per user decrease, and lack of indoor coverage.

Description: Optical networks-on-chips (ONoCs) are burgeoning structures of communication that can give a solution to the bandwidth and latency for multiprocessor systems-on-chips. Furthermore, photonic devices are widely used in ONoCs but suffer from crosstalk noise. Therefore, crosstalk noise is the critical factor that affects signal transmission and limits the network scale of ONoCs. To reduce the crosstalk noise sharply, an angle optimization that uses the cross angle of 60 $^{circ}$ or 120 $^{circ}$ instead of the conventional angle of 90 $^{circ} $ is proposed to optimize the Crux router. Furthermore, we present a signal transmission system simulation model for the mesh-based ONoC. For different routers applied to the mesh-based ONoC, the simulation model can present the time-domain waveform, eye diagram, and bit-error-rate (BER) curve clearly. On the basis of the analytical model, the results show that the minimum signal-to-noise ratio (SNR) of a 7 $times$ 7 mesh-based ONoC is 20.9 dB when using optimized Crux routers, and the injection power is equal to 0 dBm, which is 2.1 dB better than using Crux routers. Therefore, the application of angle optimization to the Crux router and mesh network can minimize crosstalk noise and improve the scalability of mesh-based ONoCs.

Description: Pulse-amplitude-modulated discrete multitone (PAM-DMT) modulation is an optical orthogonal frequency division multiplexing scheme, which is compatible with intensity modulation and direct detection channel. In the conventional receiver for PAM-DMT, only the imaginary parts of subcarriers are detected, while the real parts are considered as clipping noise and simply discarded, causing insufficient usage of the received power. This letter proposes a new receiver characterizing temporal and spectral diversity combining for PAM-DMT, which extracts the effective information in clipping noise to recover the data. The proposed receiver achieves a better performance than the conventional receiver with a gain of at least 2.3 dB in ${E_{b}}/{N_{0}}$ at the system bit error rate of $10^{-5}$ in additive white Gaussian noise channel by simulation when using 4-PAM modulation.

Description: Information-Centric Networking (ICN) is a novel networking paradigm that attracts increasing research interests in recent years. In-network caching has been viewed as an attractive feature of ICN because it can reduce network traffic, alleviate server bottleneck, and reduce the user access latencies. Because of this, the network community has proposed many in-network caching mechanisms that aim at optimizing various performance metrics such as cache hit ratio and cache hit distance. In this survey, we present a comprehensive overview of the recently proposed in-network caching mechanisms for ICN. For each caching mechanism, we describe it in detail, present examples to illustrate how it works, and analyze its possible benefits and drawbacks. We also compare some typical in-network caching mechanisms through extensive simulations and discuss the remaining research challenges.

Description: Wireless sensor networks (WSNs) are a key part of the Internet of Things vision which aims at bridging together the physical and the digital worlds in several application domains. In the building automation field, WSNs are widely adopted for energy optimization, safety and security purposes, and could greatly benefit from existing information already available in preexisting building information models (BIMs). Such BIMs are normally developed during the building design phase and reused continuously during the construction and operation phases of the building life-cycle. In current deployments, however, due to lack of interoperability such information (e.g., walls geometry, materials, and so on) must often be recollected and reinputed by WSN commissioning specialists. Open development and planning tools and methodologies can play a key role in fostering interoperability and convergence of BIM and WSN systems. This paper aims at demonstrating how increased interoperability between WSN development-support tools and BIM systems could provide advantages to developers, integrators, domain specialist, and BIM users. The methodology is validated by applying a newly proposed tool exploiting BIM interoperability to support the planning of the topology of a WSN based on ultrawideband technologies. The proposed approach is evaluated through a small-scale experimentation held in a historical building in Torino (Italy).

Description: Sample preparation plays an essential role in most biochemical reactions. Raw reactants are diluted to solutions with desirable concentration values in this process. Since the reactants, like infant’s blood, DNA evidence collected from crime scenes, or costly reagents, are extremely valuable, their usage should be minimized whenever possible. In this paper, we propose a two-phased reactant minimization algorithm (REMIA), for sample preparation on digital microfluidic biochips. In the former phase, REMIA builds a reactant-minimized interpolated dilution tree with specific leaf nodes for a target concentration. Two approaches are developed for tree construction; one is based on integer linear programming (ILP) and the other is heuristic. The ILP one guarantees to produce an optimal dilution tree with minimal reactant consumption, whereas the heuristic one ensures runtime efficiency. Then, REMIA constructs a forest consisting of exponential dilution trees to produce those aforementioned specific leaf nodes with minimal reactant consumption in the latter phase. Experimental results show that REMIA achieves a reduction of reactant usage by 32%–52% as compared with three existing state-of-the-art sample preparation approaches. Besides, REMIA can be easily extended to solve the sample preparation problem with multiple target concentrations, and the extended version also effectively lowers the reactant consumption further.

Description: The 3-D integrated dynamic random-access memory (DRAM) structure with a processor is being widely studied due to advantages, such as a large band-width and data communication power reduction. In these structures, the massive heat generation of the processor results in a high operating temperature and a high refresh rate of the DRAM. Thus, in the 3-D DRAM over processor architecture, temperature-aware refresh management is necessary. However, temperature determination is difficult, because in the 3-D DRAM, the temperature changes dynamically and temperature variation in a DRAM die is complicated. In this paper, a thermal guard-band set-up method for 3-D stacked DRAM is proposed. It considers the latency of the temperature data and the position difference between the temperature sensor and the DRAM cell. With this method, the data reliability of the on-chip temperature sensor-dependent adaptive refresh control is guaranteed. In addition, an efficient temperature sensor built-in and refresh control method is analyzed. The expected refresh power reduction is examined through a simulation.

Description: There are many kinds of permanent-magnet (PM) motors, which are widely used in modern industry, but the problem of temperature rise is likely to affect the operation performance and even the life of the motor. The semiclosed structure of the PM spherical motor (PMSM) tends to increase the temperature when it works, so the thermal analysis of the PMSM is considered necessary. Based on double Fourier series decomposition, this paper establishes a three-dimensional (3-D) analytical model of PM eddy current loss in the PMSM, which considers the effect of time and space harmonics. Meanwhile, the heat sources such as hysteresis loss and copper loss are discussed. With those heat sources, a 3-D equivalent thermal network model is established. The thermal resistances are calculated. By applying the thermal network model, the influence of different speed and load on temperature rise is analyzed, and a steady-state thermal analysis of the motor is performed by using finite element analysis. The structure of stator is improved and good heat dissipation effect is achieved. This paper provides the theoretical basis for the design of ventilation and cooling system of the PMSM.

Description: This paper presents a comprehensive investigation of various reference frames and their relative speeds in cascaded doubly-fed induction machines (CDFIMs). Then, a compact space-phasor model of CDFIMs in the natural and arbitrary reference frames is presented that is useful for performance analysis of CDFIMs based on rotating phasors. The merits of the proposed model compared with existing models are using a common (single) reference frame for all machines and parts of CDFIMs, and the model formulation is independent of the rotor angle position. The reference frames in the suggested model can be fixed on the common rotor of the CDFIM machines for dynamic analysis or it can be fixed on the stator/rotor flux of each cascaded machines useful for CDFIMs controller design. A two-axes equivalent circuit for a CDFIM is also presented, which enables analysis of CDFIMs in commercially available power circuit simulation software tools. The validity of the model is verified via the investigation of an experimental setup and consists of two mechanically coupled 4-kW DFIMs and a 4-kW dc machine as a load. The setup is investigated under various test scenarios, including free acceleration, load (torque) change, and frequency step change conditions.

Description: Discusses the ramifications from a privacy and network security point of view given today's systems that offer access to huge amounts of data and database systems. These information and data sharing interactions capture varied aspects of our lives, such as our shopping behavior, our mental and physical health, our likes and dislikes, political and religious opinions, products we shop for, how we drive our cars, how much energy we use, and even more nebulous things such as our hopes and aspirations. Credit card companies record every purchase we make, with the time and place of purchase; companies like Amazon and Netflix not only record our purchases but also our interest in things we merely peruse on their websites. Loyalty cards and digital profiles of our purchases even in brick-and mortar stores such as Target and Walmart and our local supermarkets create a record of all our purchases, easily being able to infer our shopping patterns.

Description: In various disciplines, information about the same phenomenon can be acquired from different types of detectors, at different conditions, in multiple experiments or subjects, among others. We use the term “modality” for each such acquisition framework. Due to the rich characteristics of natural phenomena, it is rare that a single modality provides complete knowledge of the phenomenon of interest. The increasing availability of several modalities reporting on the same system introduces new degrees of freedom, which raise questions beyond those related to exploiting each modality separately. As we argue, many of these questions, or “challenges,” are common to multiple domains. This paper deals with two key issues: “why we need data fusion” and “how we perform it.” The first issue is motivated by numerous examples in science and technology, followed by a mathematical framework that showcases some of the benefits that data fusion provides. In order to address the second issue, “diversity” is introduced as a key concept, and a number of data-driven solutions based on matrix and tensor decompositions are discussed, emphasizing how they account for diversity across the data sets. The aim of this paper is to provide the reader, regardless of his or her community of origin, with a taste of the vastness of the field, the prospects, and the opportunities that it holds.

Description: Multimodal data are ubiquitous in engineering, communications, robotics, computer vision, or more generally speaking in industry and the sciences. All disciplines have developed their respective sets of analytic tools to fuse the information that is available in all measured modalities. In this paper, we provide a review of classical as well as recent machine learning methods (specifically factor models) for fusing information from functional neuroimaging techniques such as: LFP, EEG, MEG, fNIRS, and fMRI. Early and late fusion scenarios are distinguished, and appropriate factor models for the respective scenarios are presented along with example applications from selected multimodal neuroimaging studies. Further emphasis is given to the interpretability of the resulting model parameters, in particular by highlighting how factor models relate to physical models needed for source localization. The methods we discuss allow for the extraction of information from neural data, which ultimately contributes to 1) better neuroscientific understanding; 2) enhance diagnostic performance; and 3) discover neural signals of interest that correlate maximally with a given cognitive paradigm. While we clearly study the multimodal functional neuroimaging challenge, the discussed machine learning techniques have a wide applicability, i.e., in general data fusion, and may thus be informative to the general interested reader.

Description: A novel low cost and simple temperature sensor based on multimode interference (MMI) is formed by a successive singlemode fiber (SMF)-bent multimode fiber (MMF)-SMF structure. Due to the small curvature radius of bent MMF section mimicking a balloon shape, MMI effect from the core is spreading into coating. The high temperature sensitivity is mainly due to the large thermo-optical coefficient of the existing acrylate coating of the MMF fiber. A temperature sensitivity of up to −2060 pm/°C and −25.1 nW/°C for wavelength- and intensity-based interrogation, respectively, have been achieved in the range between 27 °C and 31 °C. This sensor is most suitable in high sensitivity and low-temperature application such as the measurement of human body temperature.

Description: We reported the observation of whispering gallery modes (WGMs) from silicon microspheres in $C$ -band with a biconical tapered fiber-microsphere coupled system. We experimentally studied the resonant transmission spectra with broadband light source and optical spectrum analyzer, and measured the X-ray diffraction pattern of silicon microspheres. We analyzed the WGMs of silicon microspheres, the full-width at half-maximum was 0.12 nm, and the dip of the transmission spectra was 3.5 dB (55% of the incident power). The $Q$ factor of the silicon microsphere was $1.3 times 10 ^{4}$ . The Raman gain coefficient in silicon is rather strong and the energy density of microsphere resonator is rather high, so the silicon microsphere resonator possesses broad application prospect in optical communication fields, including filter, modulator, switch, wavelength converter, amplifier, Raman laser source, and so on.

Description: A working small-footprint asymmetrically and vertically coupled hybrid Si/GaN microring resonator (HMR) was demonstrated. The HMR of a minimum radius of 20 $muhbox{m}$ was fabricated in a high-yield ( $sim$ 90%) hybrid nanophotonic platform that allowed interactions between the GaN microring and the underlying Si waveguide circuit. The HMR's spectral response across the telecommunication C- and L-bands was measured. The high extinction ratio of up to 17 dB, the resonance linewidth as narrow as 40 pm, and the intrinsic quality factor of up to 70 000, which was the highest value for GaN microring reported so far, were achieved. The explicit analytical model for the high-index-contrast HMR was developed. Our basic study opened new possibilities for exploring GaN–Si nonlinear phenomena and for developing complex on-chip optical interconnects.

Description: It is difficult to manipulate the pulse distribution of a multipulse passively mode-locked fiber laser, and an effective solution is yet to be demonstrated. Here, we all-optically manipulate the pulsing of a mode-locked fiber ring laser at a telecommunication window (1.5 $mu text{m}$ ) by an optical pattern at 1 $mu text{m}$ . It can be demonstrated as an effective solution by examining different optical patterns modulated on an external laser source. In particular, the minimum pulse separation being manipulated by the external optical pattern can be shorter than 20 ps. It is noted that, with such a large wavelength separation between the cavity and the external sources, i.e., $sim 1550$ and 1060 nm, respectively, our scheme can simultaneously serve as an ultra-wideband wavelength convertor.

Description: AlGaN multiple quantum well lasers for optical pumping have been grown by metal-organic vapor phase epitaxy on high and low dislocation density AlN/sapphire templates. Lasers on planar templates exhibited high dislocation densities and high V-pit densities, but a smooth surface morphology leading to inefficient, but laterally very homogeneous optical emission. Lasing was not observed when optically pumped with up to 50 MW/cm 2 . Epitaxially laterally overgrown templates on patterned sapphire showed much lower dislocation densities, but also step bunching on the surface. This resulted in good photoluminescence efficiencies of up to 20%, but also in a higher lateral inhomogeneity of the emission. Lasers on these templates exhibited lasing at $sim 240$ nm with low full-width at half-maximum of 1 nm and threshold power densities of 11–15 MW/cm 2 .

Description: In the light-emitting-diode (LED) industry, it is a great challenge to simultaneously achieve high efficiency values and excellent light quality in practical applications. In this paper, we have designed microscale-roughness-controlled-surface modules to optimize rectified mellowness index, quantum efficiency, correlated color temperature, and color rendering index; we have also discovered a mechanism that reduces the total internal reflection trapped within the diffuser, maximizes phosphor fluorescence probabilities, and randomizes photon emissions. The first effect subsequently leads to the photon-propagation-direction rectification, such that incident photons are allowed to escape from the top but are discouraged to reversely exit from the bottom. In addition to the discovery of this mechanism, we have proposed a previously undefined criterion that evaluates the uniformity of various optical parameters exemplified by wavelengths, solid angles, and spatial distributions. Current findings offer a guide on future research for human-eye-comfort-related uniformities.

Description: In this paper, we propose a novel unifying framework using a Markov network to learn the relationships among multiple classifiers. In face recognition, we assume that we have several complementary classifiers available, and assign observation nodes to the features of a query image and hidden nodes to those of gallery images. Under the Markov assumption, we connect each hidden node to its corresponding observation node and the hidden nodes of neighboring classifiers. For each observation-hidden node pair, we collect the set of gallery candidates most similar to the observation instance, and capture the relationship between the hidden nodes in terms of a similarity matrix among the retrieved gallery images. Posterior probabilities in the hidden nodes are computed using the belief propagation algorithm, and we use marginal probability as the new similarity value of the classifier. The novelty of our proposed framework lies in the method that considers classifier dependence using the results of each neighboring classifier. We present the extensive evaluation results for two different protocols, known and unknown image variation tests, using four publicly available databases: 1) the Face Recognition Grand Challenge ver. 2.0; 2) XM2VTS; 3) BANCA; and 4) Multi-PIE. The result shows that our framework consistently yields improved recognition rates in various situations.

Description: Ellipse fitting is widely applied in the fields of computer vision and automatic manufacture. However, the introduced edge point errors (especially outliers) from image edge detection will cause severe performance degradation of the subsequent ellipse fitting procedure. To alleviate the influence of outliers, we develop a robust ellipse fitting method in this paper. The main contributions of this paper are as follows. First, to be robust against the outliers, we introduce the maximum correntropy criterion into the constrained least-square (CLS) ellipse fitting method, and apply the half-quadratic optimization algorithm to solve the nonlinear and nonconvex problem in an alternate manner. Second, to ensure that the obtained solution is related to an ellipse, we introduce a special quadratic equality constraint into the aforementioned CLS model, which results in the nonconvex quadratically constrained quadratic programming problem. Finally, we derive the semidefinite relaxation version of the aforementioned problem in terms of the trace operator and thus determine the ellipse parameters using semidefinite programming. Some simulated and experimental examples are presented to illustrate the effectiveness of the proposed ellipse fitting approach.

Description: State-of-the-art web image search frameworks are often based on the bag-of-visual-words (BoVWs) model and the inverted index structure. Despite the simplicity, efficiency, and scalability, they often suffer from low precision and/or recall, due to the limited stability of local features and the considerable information loss on the quantization stage. To refine the quality of retrieved images, various postprocessing methods have been adopted after the initial search process. In this paper, we investigate the online querying process from a graph-based perspective. We introduce a heterogeneous graph model containing both image and feature nodes explicitly, and propose an efficient reranking approach consisting of two successive modules, i.e., incremental query expansion and image-feature voting, to improve the recall and precision, respectively. Compared with the conventional reranking algorithms, our method does not require using geometric information of visual words, therefore enjoys low consumptions of both time and memory. Moreover, our method is independent of the initial search process, and could cooperate with many BoVW-based image search pipelines, or adopted after other postprocessing algorithms. We evaluate our approach on large-scale image search tasks and verify its competitive search performance.

Description: We propose to exploit filter stopband for high sensitivity radio frequency (RF) interferometer operation by utilizing reflection scattering parameters. Combined with passband filter operation, the modified RF interferometer effectively expands its frequency coverage. A simple model is described to analyze and predict interferometer performance. A high-pass filter and a low-pass filter are designed and built to demonstrate the interferometer operation as well as to verify the model over a frequency of 1–4 GHz. Lossy materials are shown to significantly degrade filter sensitivity enhancement effects due to reduced group delay and lower RF fields. Further work is needed to address the issue.

Description: Power grids have become more complex to plan and operate. With grid changes arise new challenges: renewable generation, energy conservation, electric vehicles, energy storage, and load growth. Challenges facing the electric industry today include balancing capacity, reliability, economics, environmental, and other public objectives. Recent cascading outages have demonstrated the challenges faced when operating a system near its limits. These outages over the last few years have had large social and economic impacts. In 2012, an outage in India affected over 620 million people. In 2009, a blackout in Brazil and Paraguay impacted 87 million. In 2011, a power blackout affecting 3 million people in Southern California and Mexico lasted 12 hours and was estimated to have cost over US$100 million in lost revenue. It is a balancing act to meet today?s electricity consumer expectations in a changing landscape.

Description: Conventional model-predictive torque control (MPTC) requires tedious and time-consuming tuning work for stator flux weighting factor, and presents relatively high torque ripples. To solve these problems, this paper proposes a model-predictive flux control (MPFC) for two-level inverter-fed induction motor (IM) drives. The references of stator flux magnitude and torque in conventional MPTC are converted into an equivalent reference of stator flux vector in the proposed MPFC. As only the tracking error of stator flux vector is required in the cost function, the use of weighting factor is eliminated. The optimal voltage vector is selected based on the principle of stator flux error minimization and its switching instant is optimized rather than being in the beginning of each control period. The proposed MPFC with and without switching instant optimization are both implemented in a 32-bit floating digital signal processor, and they are compared in detail in terms of torque ripple, current harmonics, and average switching frequency. Both digital simulations and experimental tests were carried out on a two-level inverter-fed IM drive, and the obtained results validate the effectiveness of the proposed method.

Description: A generic model of grid-connected doubly-fed induction generator (DFIG)-type wind turbines represented by differential-algebraic equations (DAE) is proposed for short-term transient-stability analysis. From the view of analytical research, vital simplifications are made to the complex physical model of DFIGs, whereas characteristic dynamics are still preserved. When the connection between the wind turbine and grid is weak, transient voltage collapse caused by singularity-induced instability (SII) is observed and analyzed adopting the generic model. In addition, it is shown that collapse might also occur when state variables of the dynamical system get out of control when the connection between the wind turbine and grid is stiff, where fast drop of dc-bus voltage occurs. Critical indices for evaluating transient-stability performances of the DFIG are proposed and parameter sensitivity analysis is carried out. Physical meanings of SII in generators/units with power–electronic interface in vector-oriented control frame are generalized. Novel interaction between the grid and these nonconventional generators/units is highlighted.

Description: Analytical models of electric machinery often utilize a two-axis lumped-circuit approach, wherein the inductance parameters are obtained by applications of Ampere's law in a two-dimensional (2-D) cross section of the machine. A method of incorporating end-effects in the magnetizing inductance calculations of wound rotor synchronous machines is presented, allowing machines with high diameter-to-length ratios to be modeled more accurately. The method is verified using three-dimensional (3-D) finite element analysis.

Description: This paper provides a theoretical analysis on the energy loss of a battery–ultracapacitor hybrid energy storage system based on the equivalent series resistances and a pulsed current load profile. The optimal current distribution that minimizes the overall energy loss is proved to be solely determined by the ratio of internal resistances between battery and ultracapacitor packs. Due to a large difference in the internal resistances, a quasi-optimal current distribution can be considered to let the battery pack provide the average load current and ultracapacitor pack supply the entire dynamic load current. This result clearly demonstrates that the ultracapacitor pack should supply the most of the dynamic load current not only because of battery protection, but also for energy loss minimization. Finally, the theoretical analysis is validated by both simulation and experimental results. Additional discussions, such as sensitivity analysis, the influence of the sizing of ultracapacitors, and a realistic test cycle are also added for reference purposes.

Description: Applications for low-speed high-torque machines include marine propulsion and wind power generation. Since electric machinery size is more directly related to required torque than to required power, high required torque leads to large machines. Mechanical gears increase the speed and lower the required torque of the machine to reduce size. This, however, results in increased noise and maintenance, and decreased reliability. Magnetic gears offer the advantages of mechanical gears without the disadvantages created by physical contact. Integrating magnetic gears into the machine structure offers additional mass savings. This study proposes a novel machine architecture, which integrates magnetic gearing and a permanent magnet synchronous machine to create an inner rotor flux-modulated permanent magnet synchronous machine. Unlike previous arrangements, the proposed machine utilizes a more desirable inner rotor configuration and avoids multiple magnet arrays. This study presents a finite–element-based design model of the proposed machine to be utilized in an optimization-based design environment. A multiobjective design study is presented for a laboratory scale application. The resulting tradeoff between mass and loss is compared with that of a permanent magnet synchronous machine for the same application.

Description: Developing the control algorithms of electric machine drives for less noise and harmonics is proposed here for design improvements. Modern control algorithms for electric machine drives are implemented, and their radiated magnetic fields are measured and imported into a digital signal processing unit. The measurement was implemented using magnetic field antennas which cover low frequencies. A digital signal processing unit was designed for online and real-time measurement and processing of the fields, and categorizing the harmonics. The controller compares the desired and measured signals and modifies the duty cycle of the switches to suppress the existing harmonics. The manual and automatic suppressions of some critical harmonics were implemented in two switching techniques using a defined procedure. Consequently, the modified control algorithm of the drive would radiate the electromagnetic stray field with less noise and harmonics. This leads to lower electromagnetic interference from the machine drive. Since there is no need to locate any sensor inside the machine or the converter, this can be considered as a nondestructive method for industry implementations, where it is impossible to access the parameters of components for online monitoring.

Description: This paper studies the unbalanced magnetic pull in the brushless doubly fed machine (BDFM) caused by both static and dynamic rotor eccentricities. Several parallel winding designs for the two stator windings are proposed, and the practicality of such designs is discussed with respect to direct coupling between the stator windings and with rotor undesirable harmonic fields. Once practical parallel winding designs are established, their effects on reducing deflection as a result of static and dynamic eccentricities are shown and compared with series wound stator. This study has been carried out on a prototype D400 250-kW BDFM.

Description: The nonlinear induction motor model is appropriately integrated by incorporating the dynamics of the power electronic converter in a manner that permits the design of stable field-oriented control (FOC) operating with minimum losses. As already proven, the challenging issue of operating the induction machine with minimum copper losses requires a varying rotor flux opposed to the standard FOC technique, which keeps the rotor field magnitude constant and tracks the electric torque to the desired level. To this end, exploiting the Hamiltonian structure of the developed motor/converter model, an innovated nonlinear controller is proposed that guarantees the technical limits of the converter (linear modulation) and simultaneously operates under FOC at steady state to achieve accurate speed regulation with varying rotor flux according to the minimal losses requirements. Under these circumstances, the conventional FOC stability analysis does not hold anymore, and therefore for the first time, a new rigorous analysis is provided that proves stability and convergence to the desired equilibrium for the complete closed-loop motor converter system. Finally, the theoretical contribution is examined in comparison to the traditional FOC operation by simulations obtained for an industrial size induction motor, while it is further evaluated by real-time results of a motor with similar parameters.

Description: The study of fluid flow through solid matter by computed tomography (CT) imaging has many applications, ranging from petroleum and aquifer engineering to biomedical, manufacturing, and environmental research. To avoid motion artifacts, current experiments are often limited to slow fluid flow dynamics. This severely limits the applicability of the technique. In this paper, a new iterative CT reconstruction algorithm for improved a temporal/spatial resolution in the imaging of fluid flow through solid matter is introduced. The proposed algorithm exploits prior knowledge in two ways. First, the time-varying object is assumed to consist of stationary (the solid matter) and dynamic regions (the fluid flow). Second, the attenuation curve of a particular voxel in the dynamic region is modeled by a piecewise constant function over time, which is in accordance with the actual advancing fluid/air boundary. Quantitative and qualitative results on different simulation experiments and a real neutron tomography data set show that, in comparison with the state-of-the-art algorithms, the proposed algorithm allows reconstruction from substantially fewer projections per rotation without image quality loss. Therefore, the temporal resolution can be substantially increased, and thus fluid flow experiments with faster dynamics can be performed.

Description: Most existing approaches for RGB-D indoor scene labeling employ hand-crafted features for each modality independently and combine them in a heuristic manner. There has been some attempt on directly learning features from raw RGB-D data, but the performance is not satisfactory. In this paper, we propose an unsupervised joint feature learning and encoding (JFLE) framework for RGB-D scene labeling. The main novelty of our learning framework lies in the joint optimization of feature learning and feature encoding in a coherent way, which significantly boosts the performance. By stacking basic learning structure, higher level features are derived and combined with lower level features for better representing RGB-D data. Moreover, to explore the nonlinear intrinsic characteristic of data, we further propose a more general joint deep feature learning and encoding (JDFLE) framework that introduces the nonlinear mapping into JFLE. The experimental results on the benchmark NYU depth dataset show that our approaches achieve competitive performance, compared with the state-of-the-art methods, while our methods do not need complex feature handcrafting and feature combination and can be easily applied to other data sets.

Description: Out-of-focus blur occurs frequently in multispectral imaging systems when the camera is well focused at a specific (reference) imaging channel. As the effective focal lengths of the lens are wavelength dependent, the blurriness levels of the images at individual channels are different. This paper proposes a multispectral image deblurring framework to restore out-of-focus spectral images based on the characteristic of interchannel correlation (ICC). The ICC is investigated based on the fact that a high-dimensional color spectrum can be linearly approximated using rather a few number of intrinsic spectra. In the method, the spectral images are classified into an out-of-focus set and a well-focused set via blurriness computation. For each out-of-focus image, a guiding image is derived from the well-focused spectral images and is used as the image prior in the deblurring framework. The out-of-focus blur is modeled as a Gaussian point spread function, which is further employed as the blur kernel prior. The regularization parameters in the image deblurring framework are determined using generalized cross validation, and thus the proposed method does not need any parameter tuning. The experimental results validate that the method performs well on multispectral image deblurring and outperforms the state of the arts.

Description: This paper presents an optimized low-complexity and high-throughput MIMO signal detector core for detecting spatially multiplexed data streams. The core architecture supports various layer configurations up to 4, while achieving near-optimal performance, and configurable modulation constellations up to 256-QAM on each layer. The core is capable of operating as a soft-input soft-output log-likelihood ratio (LLR) MIMO detector which can be used in the context of iterative detection and decoding. High area-efficiency is achieved via algorithmic and architectural optimizations performed at two levels. First, distance computations and slicing operations for an optimal 2-layer maximum a posteriori MIMO detector are optimized to eliminate use of multipliers and reduce the overhead of slicing in the presence of soft-input LLRs. We show that distances can be easily computed using elementary addition operations, while optimal slicing is done via efficient comparisons with soft decision boundaries, resulting in a simple feed-forward pipelined architecture. Second, to support more layers, an efficient channel decomposition scheme is presented that reduces the detection of multiple layers into multiple 2-layer detection subproblems, which map onto the 2-layer core with a slight modification using a distance accumulation stage and a post-LLR processing stage. Various architectures are accordingly developed to achieve a desired detection throughput and run-time reconfigurability by time-multiplexing of one or more component cores. The proposed core is applied also to design an optimal multiuser MIMO detector for LTE. The core occupies an area of 1.58 MGE and achieves a throughput of 733 Mbps for 256-QAM when synthesized in 90-nm CMOS.

Description: Mobile social networks (MSNs) have become increasingly popular in supporting many novel applications since emerging in the recent years. Their applications and services are of great interest to service providers, application developers, and users. This paper distinguishes MSNs from conventional social networks and provides a comprehensive survey of MSNs with regard to platforms, solutions, and designs of the overall system architecture. We review the popular MSN platforms and experimental solutions for existing MSN applications and services and present the dominant mobile operating systems on which MSNs are implemented. We then analyze and propose the overall architectural designs of conventional and future MSN systems. In particular, we present the architectural designs from two perspectives: from the client side to the server side, and from the wireless data transmission level to the terminal utilization level. We further introduce and compare the unique features, services, and key technologies of two generations of architectural designs of MSN systems. Then, we classify the existing MSN applications and propose one special form of MSN, i.e., vehicular social network, and demonstrate its unique features and challenges compared with common MSNs. Finally, we summarize the major challenges for on-going MSN research and outline possible future research directions.

Description: Resource allocation and link adaptation in Long-Term Evolution (LTE) and LTE Advanced are discussed with focus on the location and formatting of the pertinent reference and control signals, as well as the decisions they enable. In particular, after reviewing the units for resource allocation and the time-frequency resource grid, the enabled resource-allocation modes and their purposes are reviewed. A detailed description of the way the resource allocations are encoded under these different modes is also given. Similarly, the various methods of link adaptation, including power control and rate control, both through the use of adaptive modulation and coding and hybrid automatic repeat request, are reviewed. The control signaling encoding for link adaptation is provided in detail, as is the encoding of channel state feedback for the purposes of link adaptation and resource allocation.

Description: Mobile Opportunistic Network (MON) is characterized by intermittent connectivity where communication largely depends on the mobility pattern of the participating nodes. In MON, a node can take the custody of a packet for a long time and carry it until a new forwarding path has been established, unlike mobile adhoc network (MANET), where a node must drop the packet otherwise. Therefore, routing in MON depends on the repeated make-and-break of communication links, which again depends on the mobility of the nodes as they encounter and drift away from each other. MONs can simply be formed by humans carrying hand-held devices (like Personal Digital Assistant [PDAs] or cell phones) or on-board devices installed in vehicles. Therefore, with mobility playing a major role in the performance of MON, researchers have repeatedly tried to understand the nature of mobility with respect to humans, vehicles, and wild animals. To study the nature of mobility, researchers have collected mobility traces, proposed mobility models, and analyzed the performance of MON with respect to various mobility parameters. This article provides a detailed survey of different mobility models which have been proposed to date and how mobility largely determines the performance of opportunistic routing. We divide the article into four major sections. First, we provide a detailed survey of all the synthetic mobility models which have been developed to date. Second, we study the various mobility traces which have been collected and analyzed. Third, we study how mobility parameters affect the performance of MON. Finally, we highlight on some of the research areas and open challenges which yet remain unsolved.

Description: We experimentally investigate the wavelength-division multiplexing (WDM) transmission of single-carrier 400G based on an orthogonal optical time-division multiplexed (orth-OTDM) 80-GBd polarization-division multiplexed (PDM) 8 quadrature-amplitude modulation (QAM) signal. The 80-GBd 8QAM signal is generated using the OTDM method based on two tributaries of time-domain orthogonal pulses with 40-GBd 8QAM signals. Full-band coherent detection is utilized with digital signal processing based on a single broadband receiver for the 80-GBd signals. The WDM transmission performance of single-carrier 400G signals within different channel grids and carrier spacing is also investigated. Finally, four 400G channels, each carrying an 80-GBd PDM-8QAM signal within 100-, 80-, and 75-GHz grids, are successfully transmitted over 1600-, 800-, and 400-km standard single-mode fibers with Erbium-doped fiber amplifier (EDFA)-only amplification below a pre-Forward error correction (FEC) bit-error rate (BER) of $2.4times10^{-2} $ (20% soft-decision FEC) , respectively. The achieved spectral efficiency for the 400G channel can be 4, 5, and 5.33 bit/s/Hz, respectively.

Description: In this paper, we present a radar sensor system for real-time blast furnace burden surface imaging inside a fully operative blast furnace, called BLASTDAR, the blast furnace radar. The designed frequency-modulated continuous-wave (FMCW) radar sensor array operates in the frequency band around 77 GHz and consists of several nonuniformly spaced receive and transmit antennas, making it a multiple-input multiple-output radar system with large aperture. Mechanical steering is replaced by digital array processing techniques. Off-the-shelf automotive-qualified multichannel monolithic microwave integrated circuits are used. By means of this configuration, a virtual antenna array with 256 elements was developed that guarantees the desired angular resolution of better than 3°, and a range resolution of about 15 cm. Based on the single-channel FMCW signal model, this paper will derive a multichannel signal model in combination with a digital beamforming approach and further advanced signal processing algorithms. The implementation of a simulation tool covering the whole design process is shown. Based on these simulation results, a system configuration is chosen and the obtained setup is defined and presented. A description of the manufactured cost-efficient radio frequency and baseband boards together with the housing design shows the practical implementation of the sensor. For the system calibration, two different methods are listed and compared regarding their performance. Verification measurements confirm the predicted performance of the developed sensor. Several measurements inside a fully operational blast furnace demonstrate the proper long-term functionality of the system, to the best of our knowledge, for the first time worldwide. It is in continuous operation since about two years in blast furnace #5 of voestalpine Stahl GmbH, Linz.

Description: Indoor lighting systems with wireless sensor-equipped luminaires are considered as an infrastructure for offering location-based illumination control. Wireless occupancy and light sensors transmit sensing information to a lighting controller, which then adapts artificial illumination from luminaires to user occupancy and daylight changes. Such wireless sensor transmissions can be used to collect received signal strength indicator (RSSI) values at a user device. We propose to use the RSSI measurements at the user device, in combination with accelerometer sensor data, to determine user location zone when a user seeks personalized light control. Based on its location zone, the user is granted control of associated luminaires. The performance of the proposed system and positioning method is evaluated in a large indoor lighting open-plan office model.

Description: In this paper, a Pd–TiO 2 nanofiber structure with photoactivation capability for H 2 gas sensing is made using the electrospinning procedure. The solution which was stacked into the syringe for electrospinning Pd–TiO 2 nanofibers consisted of titanium tetraisopropoxide, acetic acid, ethanol, polyvinyl pyrrolidone, and different amounts of Pd solution. The X-ray diffraction, field emission scanning microscopy, transmission electron microscopy, and spectrophotometry techniques were employed to analyze the crystalline structure and surface morphology of the nanofibers. Moreover, Fe 2 O 3 and HNO 3 were also used as additional additives and the effect of additives in the absorption spectrum shift towards the visible light spectrum was investigated. About 95-nm red shift toward visible light from 370 to 465 nm for TiO 2 /Pd/N/Fe 2 O 3 was observed in comparison with the pure TiO 2 nanofibers. By using additives and visible light irradiation, the operating temperature lowered from 290 °C to 130 °C and the response increased from 11 to 368. At an operating temperature of 150 °C, the response time also reduced from 25 to 0.9 s and recovery times reduced from 40 to 2 s. The response dropped only by $sim 30$ %, 12%, and 5% after nine months for the TiO 2 , TiO 2 /Pd, and TiO 2 /Pd/N/Fe 2 O 3 samples, respectively.

Description: Over the years, several QRS complex detection algorithms have been proposed with different features, but the remaining problem is their implementation in low-cost portable platforms for real-time applications, where hardware resources are limited, still providing the accuracy level required for medical applications. The proposed algorithm copes at the same time with both requirements: 1) accuracy and 2) low resource consumption. In this paper, a real-time QRS complex detector is proposed. This algorithm is based on a differentiation at the pre-processing stage combined with a dynamic threshold to detect R peaks. The thresholding stage is based on a finite-state machine, which modifies the threshold value according to the evolution of the signal and the previously detected peak. It has been evaluated on several databases, including the standard ones, thus resulting sensitivities and positive predictivities better than 99.3%. In order to analyze the computational complexity of the algorithm, it has been compared with the well-known Pan and Tompkins’ algorithm. As a result, the proposed detector achieves a reduction in processing time of almost 50% by using only the 25% of hardware resources (memory, adders, and multipliers).

Description: 1-D oxide nanostructures-based metal-insulator–metal structures represent potential gas sensor devices, owing to their vertical electron transport feature. In this paper, we demonstrate that for achieving optimum gas sensing by a TiO 2 nanotube (NT) array in vertical mode, tuning of NTs (1-D) surface area as well as carrier transport path length by tailoring the NT length can be a valuable approach. For anodization times of 1, 4, 8, 12, and 16 h, the corresponding NT length was found to be 280–320, 506–514, 1730–1790, 2000–2200, and 2380–2420 nm, respectively, with almost no variation in tube diameters or separations. The carrier concentrations of the NTs were found to be decreasing with increasing tube length. The vertical device structure, employing NT arrays of different lengths as the sensing layer, was investigated in the temperature range of 50 °C–250 °C for sensing acetone, as a test gas/vapor, in the concentration range of 10–1000 ppm. The response magnitude of the sensor was increased with increased NT length, possibly owing to the availability of larger amounts of gas interaction sites due to higher surface area at increased length. The response time and recovery time of the developed sensor also increased with increasing tube length and became excessively sluggish after the critical tube length exceeded 2250 nm owing to slower adsorption/desorption and diffusion kinetics.

Description: The growth in Internet usage has been phenomenal over the last decade. During the last few years, more and more of this growth has come from mobile broadband access. The most widely used types of mobile broadband access are based on the standards defined by the Third Generation Partnership Project (3GPP). This phenomenal growth, and the introduction of the always-on network paradigm in cellular networks, has put a strain on the Internet infrastructure itself—it has caused the exhaustion of the Internet address space. This paper surveys the relevant 3GPP and Internet Engineering Task Force specifications, and by looking at the research and standardization experience of the authors, it addresses the factors leading up to this strain, and it describes how the solution—Internet Protocol version 6 (IPv6)—has been implemented in the 3GPP architecture and its specifications. It also analyzes what still needs to be done and suggests the possible focus areas of the future for IPv6 in 3GPP networks.

Description: Cooperative communication is capable of forming a virtual antenna array for each node (user) in a network by allowing the nodes (users) to relay the messages of others to the destination. Such a relay aided network may be viewed as a distributed multiple-input multiple-output (MIMO) system relying on the spatially distributed single antennas of the cooperating mobiles, which avoids the correlation of the antenna elements routinely encountered in conventional MIMO systems and hence attains the maximum achievable diversity gain. Therefore, the family of cooperative communication techniques may be regarded as a potential solution for future wireless networks. However, constrained by the half-duplex transmit/receive mode of most practical transceivers, the cooperative networks may impose a severe 50% throughput loss. As a remedy, successive relaying can be employed, which is capable of mimicking a full-duplex relay and thereby recovering much of the 50% throughput loss. Furthermore, for the sake of bypassing power-hungry and potentially excessive-complexity channel estimation, noncoherent detection techniques may be employed for multiple-antenna aided systems, because estimating all the associated channels may become unrealistic. Explicitly, the mobile-stations acting as relays cannot be realistically expected to estimate the source-to-relay channels. To motivate further research on noncoherent successive relaying aided systems, a comprehensive review of its basic concepts, fundamental principles, practical transceiver designs and open challenges is provided.

Description: Visible Light Communication (VLC) is an emerging field in Optical Wireless Communication (OWC) which utilizes the superior modulation bandwidth of Light Emitting Diodes (LEDs) to transmit data. In modern day communication systems, the most popular frequency band is Radio Frequency (RF) mainly due to little interference and good coverage. However, the rapidly dwindling RF spectrum along with increasing wireless network traffic has substantiated the need for greater bandwidth and spectral relief. By combining illumination and communication, VLC provides ubiquitous communication while addressing the shortfalls and limitations of RF communication. This paper provides a comprehensive survey on VLC with an emphasis on challenges faced in indoor applications over the period 1979–2014. VLC is compared with infrared (IR) and RF systems and the necessity for using this beneficial technology in communication systems is justified. The advantages of LEDs compared to traditional lighting technologies are discussed and comparison is done between different types of LEDs currently available. Modulation schemes and dimming techniques for indoor VLC are discussed in detail. Methods needed to improve VLC system performance such as filtering, equalization, compensation, and beamforming are also presented. The recent progress made by various research groups in this field is discussed along with the possible applications of this technology. Finally, the limitations of VLC as well as the probable future directions are presented.

Description: This letter presents a multiplexed fiber-optic sensor array suitable for detection of liquid intrusions, spills, and leaks. The proposed detection systems is based on active heating and observation of temperature changes in short sections of optically absorbing (vanadium-doped) optical fibers that were interconnected into a sensing array by a standard single-mode optical fiber. The heating of the vanadium-doped fiber sections was achieved by application of a common 980-nm pump laser source. The associated signal processing and integration utilizes a simple, custom-designed optical time domain reflectometry that relies on only a few low-cost standard telecom components.

Description: A method for mitigating local oscillator (LO) phase noise-induced impairment, also known as equalization-enhanced phase noise, in coherent optical systems is discussed. The method is suitable for real-time implementation and requires hardware with a bandwidth much lower than the signal baud rate, even for a system utilizing conventional semiconductor laser as LO. We evaluate the required parameters like interpolation technique, electrical signal-to-noise ratio at digital coherence enhancement (DCE) front end, for long haul transmission links having quadrature phase shift keying and 16-quadrature amplitude modulation formats. We show that the method can be implemented using a low-speed DCE front end and a simple digital linear interpolator with small (<1 dB) implementation penalty even in cases that would otherwise result in error floor.

Description: One of the key studies in the cognitive radio networks is maximizing some important metrics such as transmission/energy efficiencies or throughput with respect to network parameters such as sensing and transmission time. There is always a tradeoff between sensing time and transmission time. While longer sensing times results in higher detection accuracy, it loses transmission opportunities and hence decreases transmission efficiency. Many works have been done to find the best transmission and sensing time to maximize the efficiencies such as transmission and energy, but the interference and hence the probability of collision was not defined and formulated correctly. In this paper, we consider the trilateral tradeoff between sensing, transmission, and contention times. To do this, the interference between primary user (PU) and secondary user (SU) is formulated. We consider interference due to both imperfect sensing and PU-return. Furthermore, the interference among SUs has been also formulated. These metrics are used in defining transmission efficiency and probability of collision as a constraint.

Description: This letter presents a low-power, 40-Gb/s optical receiver front-end fabricated in a 65-nm CMOS technology. Using an inverter-based topology for both the transimpedance amplifier and the post amplifier, high energy efficiency has been obtained. Cascaded amplifiers with transconductance and transimpedance combinations are utilized to acquire a bandwidth of 29.6 GHz. A low-dropout voltage regulator is applied to reduce the supply noise of the single-ended amplifiers. The prototype chip excluding output buffer consumes only 12.4 mW (310 fJ/b) at a 1.2 V single supply, and the integrated input referred noise is 9.2 $mu text{A}_{mathrm { {rms}}}$ .

Description: A new type of electric machine with two free rotating rotors [dual mechanical port (DMP)] is investigated in this paper. Since this DMP machine has a squirrel-cage outer rotor, it is named as SCDMP machine. First, the electromagnetic characteristic of the SCDMP machine is analyzed. Then, the transient model and steady-state model of the SCDMP machine are derived. The proposed machine models are verified by finite element method and simulation. The results show that the proposed models accurately represent the unique electromagnetic characteristics of the SCDMP machine.

Description: Design of power delivery system has great influence on the power management in many-core processor systems. Moving voltage regulators from off-chip to on-chip gains more and more interest in the power delivery system design, because it is able to provide fine-grained dynamic voltage scaling. Previous works are proposed to implement power efficient on-chip voltage regulators. It is important to analyze the characteristics of the entire power delivery system to explore the tradeoff between the promising properties and costs of employing on-chip voltage regulators, especially the on-chip buck converters. In this paper, we present a novel analysis and design optimization platform of power delivery system called power supply on-chip (PowerSoC). It employs an analytical model to provide an accurate and fast evaluation of important characteristics, e.g., power efficiency, output stability, and dynamic voltage scaling, for the entire power delivery system consisting of on-chip/off-chip buck converters and power delivery network. Based on our model, geometric programming is utilized to find the optimal design for different power delivery systems and explore the tradeoff of using on-chip converters. Compared with SPICE simulations, our model achieves a simulation time reduction of six to seven orders of magnitude within 5% model error for the characteristic evaluation of different power delivery systems. By using PowerSoC, various architectures of power delivery systems are optimized for power efficiency under constraints of output stability, area, etc. Simulation results show that the hybrid architecture, consisting of both on-chip and off-chip converters, achieves 1.0% power efficiency improvement and 66.4% area reduction of converters, compared to the conventional design. We conclude the hybrid architecture has potential for efficient dynamic voltage scaling, small area, and the adaptability of the change of power delivery network parasitic, but ca- eful account for the overhead of on-chip converters is needed.

Description: As the technology sizes of integrated circuits (ICs) scale down rapidly, current transistor densities on chips dramatically increase. While nanometer feature sizes allow denser chip designs in each technology generation, fabricated ICs become more susceptible to wear-outs, causing operation failure. Even a single link failure within an on-chip fabric can halt communication between application blocks, which makes the entire chip useless. In this paper, we aim to make faulty chips designed with network-on-chip (NoC) communication usable. Specifically, we present fault-tolerant irregular topology-generation method for application-specific NoC designs. Designed NoC topology allows different routing path if there is a link failure on the default routing path. Additionally, we present a simulated annealing-based application mapping algorithm aiming to minimize total energy consumption of the NoC design. We compare fault-tolerant topologies with nonfault-tolerant application-specific irregular topologies on energy consumption, performance, and area using multimedia benchmarks and custom-generated graphs. Our results demonstrate that our method is able to determine fault-tolerant topologies with negligible area increase and better energy values.

Description: Three-dimensional (3-D) integration is an attractive technology platform for next-generation ICs. Despite the benefits offered by 3-D integration, test cost remains a major concern, and analysis and tools are needed to understand test flows and minimize test cost. We propose a generic cost model to account for various test costs involved in 3-D integration and present a formal representation of the solution space to minimize the overall cost. We present an algorithm based on A*—a best-first search technique—to obtain an optimal solution. An approximation algorithm with provable bounds on optimality is proposed to further reduce the search space. In contrast to prior work, which is based on explicit enumeration of test flows, we adopt a formal optimization approach, which allows us to select an effective test flow by systematically exploring an exponentially large number of candidate test flows. Experimental results highlight the effectiveness of the proposed method. Adopting a formal approach to solving the cost-minimization problem provides useful insights that cannot be derived via selective enumeration of a smaller number of candidate test flows.

Description: This paper focuses the analysis around a grid-connected converter that operates under unbalanced voltage and current conditions. Two different scenarios have been selected to validate the proposed algorithms. In the first scenario, the converter operates as a reactive power compensator, exchanging reactive power with the grid, and minimizing the dc bus voltage oscillations. The second scenario is more challenging, since it operates as a load balancer. In this application, the unbalanced current consumption of the load is compensated by the converter, exchanging positive and negative sequence currents with the grid. Another objective in this second scenario is to compensate the reactive power of the unbalanced load. It is important to highlight that in both scenarios, any maximum limit of the converter can be exceeded due to the specific unbalanced voltage and current conditions. Three variables are considered critical for the converter: 1) output ac current limit; 2) output ac voltage limit; and 3) dc bus voltage oscillation limit. Thus, this paper proposes a control method, which limits online the reactive power reference in the first scenario and the exchanged current references in the second scenario in order not to exceed any of the mentioned critical variables. The corresponding experimental results are shown in Part II of this paper so as to validate the limitation algorithm obtained by means of the mathematical analysis carried out in Part I.

Description: The fault current contribution of the doubly fed induction generator-based wind turbines (DFIG-WTs) is dictated by a combination of factors, including the electrical parameters of the machine and the controller configuration of the converters. This paper presents an analytical derivation of short-circuit current quantities considering the controller influences. Mathematical models of the short-circuit current were first developed based on the closed-loop transfer functions, and approximate expressions for time constants and frequencies were derived. The mathematical models and the expressions for time constants and frequencies were later validated using a manufacturer-based simulation model and a nonlinear optimization for parameter extraction.

Description: A mesh-based magnetic equivalent circuit has been derived to model the dynamics of wound rotor synchronous machines (WRSMs). A particular focus has been placed on the derivation of flux tubes to model machines with an arbitrary number of damper bars placed at an arbitrary depth in the rotor pole tip. Faraday's Law is applied to establish a state model in which winding and damper bar flux linkages are selected as state variables. The resulting coupled magnetic equivalent circuit/state model is solved to predict machine dynamics. An important attribute of the model is that saturation is represented without the need for a relaxation factor, which enables its use as a practical tool in machine design. Data obtained from hardware experiment and a finite-element model are used to validate the proposed methods.

Description: The maximum capacity, the amount of maximal electric charge that a battery can store, not only indicates the state of health, but also is required in numerous methods for state-of-charge estimation. This paper proposes an alternative approach to perform online estimation of the maximum capacity by solving the recursive total-least-squares (RTLS) problem. Different from prior art, the proposed approach poses and solves the RTLS as a Rayleigh quotient optimization problem. The Rayleigh quotient-based approach can be readily generalized to other parameter estimation problems including impedance estimation. Compared with other capacity estimation methods, the proposed algorithm enjoys the advantages of existing RTLS-based algorithms for instance, low computation, simple implementation, and high accuracy, and thus is suitable for use in real-time embedded battery management systems. The proposed method is compared with existing methods via simulations and experiments.

Description: The high power pulsed charging power supply is usually necessary for the pulsed power devices with high power repetitive discharge. This paper first introduces a new topology structure of a charge and discharge system for high voltage capacitor and its operating principle, then comes up with technical requirements for the pulsed alternator. Afterward, design features of the inductor pulsed alternator, including the structure, main dimensions, and sizes of rotor teeth and slots are studied, and the main parameters of homopolar inductor pulsed alternator (HIPA) prototype are provided. The choice of rotor material and bearing failure phenomenon are also investigated to find a responsible solution. Finally, the experimental waveforms of HIPA prototype without and rated load when charging capacitor are given. The research shows that the pulsed power supply based on the inductor pulsed alternator is competitive for its high energy storage density, moderate power density, and high reliability, which is suited to the charging power supply of pulsed capacitor.

Description: This paper presents an unexpected fluctuation of voltage for a 30-kW wound rotor brushless doubly-fed machine (BDFM) in a standalone power generation system. To address this issue, an improved method of harmonic injection is introduced. A voltage and current double closed-loop control strategy, based on control winding (CW) current decoupling, is applied through the entire experiment. Consequently, the experimental outcomes are fairly aligned with the dynamic simulations in most conditions. However, the voltage fluctuation in the power winding (PW) can be observed for a certain speed range. Harmonic analysis is then carried out on experimental data of PW voltage and CW current. A pair of interharmonic waves, which are symmetric with respect to the fundamental wave, is demonstrated to exist in PW voltage and CW current. Due to the analysis, these harmonic conjugate waves are caused by the high-order magnetomotive force tooth harmonics and current harmonics within a specific speed range. Accordingly, the control strategy of harmonic injection is employed to effectively eliminate these harmonic conjugate waves. The experimental results further highlight that the voltage amplitude can be maintained with less harmonic contents by our tailored control scheme. In addition, the formation and presence of harmonic conjugate waves may lead to the voltage amplitude fluctuation of BDFM in the standalone power generation system.

Description: Application of electric machines in the traction and transmission systems of hybrid/electric vehicles has been studied for many years. The hybrid vehicle based on dual mechanical port (DMP) electric machine has gained more and more attention, because it eliminates the need for planetary gear and combines the motor and the generator into a compact electric machine. The DMP machine with a squirrel-cage outer rotor (SCDMP) is investigated in this paper. Due to its unique electromagnetic characteristics, control algorithms for conventional machines cannot be applied to the SCDMP machine. The methods to calculate the correct current commands and estimate the outer rotor flux position are proposed. Based on these two methods, a control algorithm for the SCDMP machine is proposed and estimated by simulation. The results show that the proposed control algorithm is able to independently control the torque productions and the flux levels of the two rotors of the SCDMP machine.

Description: We study a tandem of agents who make decisions about an underlying binary hypothesis, where the distribution of the agent observations under each hypothesis comes from an uncertainty class defined by a 2-alternating capacity. We investigate both decentralized detection rules, where agents collaborate to minimize the error probability of the final agent, and social learning rules, where each agent minimizes its own local minimax error probability. We then extend our results to the infinite tandem network, and derive necessary and sufficient conditions on the uncertainty classes for the minimax error probability to converge to zero when agents know their positions in the tandem. On the other hand, when agents do not know their positions in the network, we study the cases where agents collaborate to minimize the asymptotic minimax error probability, and where agents seek to minimize their worst-case minimax error probability (over all possible positions in the tandem). We show that asymptotic learning of the true hypothesis is no longer possible in these cases, and derive characterizations for the minimax error performance.

Description: Various blind synchronization methods built on the maximum likelihood (ML) principle have been proposed, where the addressed scenarios include additive white Gaussian noise (AWGN), single-path fading, and multipath fading channels. We consider ML blind synchronization over wide-sense stationary uncorrelated scattering (WSSUS) channels. Different from existing studies, we exploit a more complete signal correlation function and find the carrier frequency offset estimate to be the solution of a quartic equation, rather than the phase angle of a complex number. As the truly ML synchronizer (dubbed MLE) is very complicated, we also derive a reduced-complexity alternative (dubbed RCE). It is found that the RCE yields indistinguishable performance from the MLE, at a somewhat lower complexity than an existing rival. We also present an in-depth theoretical analysis and comparison of the performance of various methods. Simulations show that the proposed methods yield rather robust performance in modeling errors of the fading rate and the channel power-delay profile (PDP).

Description: We report the results of a study of an optical sensor based on a channel-drop technique with two cascaded cavities in photonic-crystal slabs. Quality factors and intensities of the resonant modes of the sensor were analyzed with three-dimensional simulations. With the introduction of a reflector in the bus-channel and by control of the coupling between the two cavities and the drop-channel, the drop efficiency can be remarkably increased. In addition to the simulation, the two cavity sensor is fabricated and tested for optical response to water and oil infiltration. Both direct visual imaging and quantitative analysis were applied in experiment. A difference of refractive index $Delta n = 0.12$ between water and oil samples results in a wavelength shift of 18.3 nm, which greatly matches the simulation result of 20 nm and indicates a sensitivity of 153 nm RIU −1 . Both resonant peaks for water and oil infiltration have good selectivity in their transmission spectrum. The contrast between the broadband output of the bus-channel and the highly wavelength-selective outputs of the drop-channel opens opportunities for the two cascaded-cavity system as a fundamental building block for a multiplex drop-channel array for all-optical sensing, which can be widely used for bio/chemical detection and environmental monitoring.

Description: Nonlinearity-induced phase noise has become a major obstacle in long-haul coherent fiber-optic communication systems. Such phase noise has been shown to be signal dependent, and correlated over time. We propose a code-aided expectation-maximization algorithm to mitigate such nonlinear phase noise, iteratively utilizing both the time correlation of the nonlinearity-induced impairments and a soft-decision error-control code. Simulation and experimental results show that on a dual-polarization wavelength-division-multiplexed 16 QAM system, launch-power tolerance can be increased by ${1.5}$ dB, and the optical signal-to-noise ratio requirement can be relaxed by ${0.3}$ dB to achieve the same ${Q^2}$ -factor.

Description: Microring resonators have been the fundamental building blocks of integrated photonic networks. They play key roles in a number of on-chip photonic elements, such as filters, modulators, switches, and sensors. However, the applications of microring resonators in these components are hindered by the evanescent coupling, which requires very precise position control and is hard to be realized in standard photolithography. Here, we demonstrate a novel, general, and robust mechanism to achieve microdisk-based end-fire injection and collection devices. Instead of coupling light via evanescent waves, here the light is injected into the cavity by connecting a waveguide and a deformed microdisk directly. The light on resonance can be reflected back and detected at the same waveguide, making the devices to be “easy come easy go.” The reflectance is as high as 95% and can be periodically obtained from the long-lived resonances with free spectral range around 18 nm. The proposed mechanism is found to be robust to cavity shape, refractive index, and waveguide width and all the parameters can be larger than 500 nm, making the designed devices to be easier realized by standard photolithography. We believe this research will boost the development of low-cost silicon photonic devices.

Description: We proposed theoretically analyzed and experimentally demonstrated novel 1 × 4 channel flatband optical multiplexer/demultiplexer (MUX/DeMUX) that is based on Si-nanowire microring-assisted multiple delaylines. The proposed optical MUX/DeMUX scheme, which includes all-pass microring-type phase controllers and a Banyan-type 4 × 4 coupler, exhibits superior spectral flatness to any Si-nanowire optical DeMUXs that have previously been experimentally demonstrated.

Description: Analysis of the experimental data on microscopic, absorptive, fluorescent, and Raman-scattering properties of Bismuth (Bi)-doped yttria-alumino-silicate glass (Y-Al-SiO 2 :Bi)-based nanoengineered optical fibers, exhibiting broadband near-infrared fluorescence, is presented. Among the other well-established characteristics, inherent to Bi-doped silica fibers codoped with Aluminum (Al), a trend of spatial distributions of Bi atoms and Bi-related fluorescence-active centers is determined, being their concentrating in ring-like areas around the core's center, at approximately a half-distance to core/cladding interface. At the same time, the formation in this region of nanosized Bi clusters, supposedly weakly or nonfluorescing, is revealed for the fibers. These phenomena are argued to underlie worsening of the pump-to-signal overlap factor, which deteriorates efficiency of lasers and amplifiers based on such or similar Bi-doped alumino-silicate fibers.

Description: The paper develops a statistical model for the signals received in phase-sensitive optical time domain reflectometry (OTDR) probed by highly coherent sources. The backscattering process is modelled by a set of discrete scatterers with properly chosen parameters. Explicit equations for calculating the amplitude and the phase of the backscattered signal are obtained. The developed model predicts spectral and autocorrelation characteristics of the amplitude signals that are validated by experimental results. Characteristics of the phase signals, practicable for studying the sensing applications of the OTDR system, are presented and studied as well, demonstrating good correspondence with experiment. A more detailed modelling of distributed vibration sensing systems and their response to disturbances along an optical fiber will be possible as an extension of the developed formalism.

Description: A five channel step index plastic optical fiber proposal for a multiplexer/demultiplexer having insertion losses ( IL ) of 2.9–4 dB, pass bandwidths at −3 dB > 30 nm, crosstalk attenuation >30 dB and size of ∼65 mm × 55 mm, is demonstrated. It is based on a reflective diffraction grating with blazed profile and an aspheric lens. The theoretical analysis presented is used to further reduce the system size to ∼37 mm × 30 mm and to increase the number of channels to 8 keeping ILs 〈 4.5 dB. Experimental results have good agreement with theoretical expectations.

Description: Presents an historical account of the Abbey Road recording studios in England where the Beatles recorded their music. Abbey Road Studios have been an iconic landmark in London ever since The Beatles decided to name their latest album according to the street where their recording studio was located???and illustrate its cover with its now-famous pedestrian crossing. However, on 1 April 2015, there was another kind of success celebrated there. A new IEEE Historic Milestone plaque has been unveiled to commemorate the numerous inventions of engineer Alan Dower Blumlein on stereo sound recording and reproduction. Reports on this event.

Description: Systems employing biometric traits for people authentication and identification are witnessing growing popularity due to the unique and indissoluble link between any individual and his/her biometric characters. For this reason, biometric templates are increasingly used for border monitoring, access control, membership verification, and so on. When employed to replace passwords, biometrics have the added advantage that they do not need to be memorized and are relatively hard to steal. Nonetheless, unlike conventional security mechanisms such as passwords, biometric data are inherent parts of a person?s body and cannot be replaced if they are compromised. Even worse, compromised biometric data can be used to have access to sensitive information and to impersonate the victim for malicious purposes. For the same reason, biometric leakage in a given system can seriously jeopardize the security of other systems based on the same biometrics. A further problem associated with the use of biometric traits is that, due to their uniqueness, the privacy of their owner is put at risk. Geographical position, movements, habits, and even personal beliefs can be tracked by observing when and where the biometric traits of an individual are used to identify him/her.

Description: Prospective authors are requested to submit new, unpublished manuscripts for inclusion in the upcoming event described in this call for papers.

Description: Reports on future SPSS events and conferences.

Description: In this paper, a unified control framework is proposed to realize a robotic ball catching task with only a moving single-camera (eye-in-hand) system able to catch flying, rolling, and bouncing balls in the same formalism. The thrown ball is visually tracked through a circle detection algorithm. Once the ball is recognized, the camera is forced to follow a baseline in the space so as to acquire an initial dataset of visual measurements. A first estimate of the catching point is initially provided through a linear algorithm. Then, additional visual measurements are acquired to constantly refine the current estimate by exploiting a nonlinear optimization algorithm and a more accurate ballistic model. A classic partitioned visual servoing approach is employed to control the translational and rotational components of the camera differently. Experimental results performed on an industrial robotic system prove the effectiveness of the presented solution. A motion-capture system is employed to validate the proposed estimation process via ground truth.

Description: An article by W.L. Everitt in the 1962 50th anniversary issue of Proceedings of the IEEE, ?Engineering Education?Circa 2012 A.D.,? was one of many predictive articles that appeared in that issue [1]. One of Everitt?s observations was the distinction between training and education. He then predicted that, in the future, training will be done primarily with computers, remarking, ?Relieved of the necessity of spending most of their time on the training function, devoted teachers will be able to concentrate their efforts on ?education?.?