ALBERT

Description: A very efficient boundary-element method for the calculation of the quasi-static port inductances of vertical interconnections within parallel-plate structures is developed. It requires only a one-dimensional discretization along the contour of the plate pair and can be applied to arbitrary geometries. The algorithm is validated by the exact analytical solution for the circular geometry. The low-frequency response of an arbitrary multiport structure can be directly analyzed by the coupled port-inductance network together with the plate capacitance. As examples a circular-shaped and two irregularly shaped plane pairs are considered. The comparison with exact analytical solutions and three-dimensional-full-wave field simulation shows a very good agreement.

Description: The leader progression model (LPM) is a tool for estimating the lightning performance of transmission lines. However, the large computation time remains a problem for the engineering application of this model. An analytical method is proposed in this paper to mitigate the aforementioned problem. First, nonlinear trajectory equations describing the movement of upward and downward leaders are obtained, starting with differential equations. Based on the trajectory equations, the average electric field between the upward and downward leader tips is represented with a comprehensive nonlinear equation. The final strike point is determined by solving the equations. Results show that the proposed method effectively mitigates the large computation time problem of traditional (numerical) LPM.

Description: Principal component analysis (PCA) and independent component analysis (ICA) for radiated emissions from printed circuits are critically intercompared, revealing similarities and differences of the extracted components between both methods. The input data in this analysis are measured wideband complex-valued magnetic radiated and evanescent fields with quasi-Gaussian spatial distributions. PCA and ICA lead to similar maps of their components when considered as spatial eigenmodes, but independent components exhibit simpler field structure than principal components.

Description: Closed-form expressions for the approximation of frequency variations of per-unit-length resistance and inductance of microstrip transmission lines are presented. The provided expressions guarantee causality of the time-domain response. They are valid from dc up to the highest frequencies for which the quasi-static analysis of microstrip transmission lines is applicable. Additionally, the expressions take into account the finite width of the ground plane and can deal with a broad range of dimensions of microstrip lines. The correctness of the formulas is experimentally verified.

Description: This paper investigates the convergence and error evaluation of the distributed analytical representation and iterative technique (DARIT-field) which is a new approach for the analysis of field coupling to multiconductor transmission lines. The DARIT-field method has the advantage of high computational efficiency over the other methods. In order to know the convergence speed and the error at each iteration step of DARIT-field, an analytic expression of iterative error is derived by combining the two telegrapher's equations into a matrix equation and using the euclidean norm to explore its upper bound. The expression shows that the convergence speed is mainly influenced by three parameters, namely coupling factor (CF), terminal loads, and the line length to excitation field wavelength ratio $(d/lambda)$ . The convergence speed is a function of CF, terminal loads, and the line length to excitation field wavelength ratio $(d/lambda)$ . These results allow the users to make a compromise between computational cost and accuracy by selecting the number of iterations.

Description: This paper presents an efficient evaluation method for multiconductor transmission lines with random translation over an infinite and perfectly conducting ground under a plane wave. Based on the assumption of small translation quantity, the equations for the estimation of average induced voltage, induced voltage variation, and the probability distribution of the voltage variation are derived. The average induced voltages and the probability distribution of the voltage variation estimated by the proposed method are in a good agreement with those via the Monte Carlo method but the proposed method is more efficient. The relative sensitivity of the induced voltage to the height approximately equals the inverse of the line height, which can be applied to evaluate the influence induced by the random translation of the line quickly, especially in the low frequency range.

Description: A passive and inherently stable multiport equivalent circuit for lossy transmission lines is presented. The convergence of the infinite modal representation is accelerated by appropriate inductances, for which an exact closed-form expression is developed. The order number of the truncated modal circuit is estimated by a simple relation, according to the required signal bandwidth. The coupling of arbitrary external electromagnetic fields is incorporated by a limited number of corresponding modal sources. The accuracy and versatility of the suggested SPICE-compatible equivalent circuit is demonstrated by examples in frequency and time-domain, including nonlinear terminations.

Description: Carson's, Pollaczek's, Wise's, and Sunde's earth-return impedances of an overhead line have been examined, and errors involved in the formulas are explained. Modified Pollaczek's and Carson's/Sunde's formulas are described. Wave propagation characteristics on a multiconductor in a high-frequency region are evaluated by adopting the modified earth-return impedance and Wise's earth-return admittance. Sommerfeld–Goubau propagation in a high-frequency region, which shows transition between transverse electromagnetic and transverse magnetic propagation, has been confirmed in the calculated results which agree with those predicted by Kikuchi for a single conductor. On a multiconductor system, it is found that the aerial mode also shows Sommerfeld–Goubau propagation when the separation between conductors is large and the earth resistivity is high.

Description: This paper deals with the electromagnetic interaction of a straight thin wire located inside a cylinder with the cylinder walls. The wire runs parallel to the cylinder axis and connects its two opposite caps. A lumped source is chosen, which feeds the terminated conductor. For this configuration, an exact analytical solution for the induced current on the conductor is presented. On the basis of a two-sum Green's function expressed in cylindrical coordinates, the current is derived from the boundary conditions for the total electrical field on the surface of the conductor and the Fourier expansion series for the unknown current and the (known) exciting electrical field. The obtained analytical results are compared to those obtained from a full-wave method and show excellent agreement. They clearly document that the electromagnetic interaction between the cylinder and wire can strongly influence the shape of the transmitted signal. In particular, at higher frequencies, more and more resonance frequencies of the cylinder occur in the current spectrum. Therefore, the application of classical transmission-line theory on conductors, which are housed in resonators, is not allowed in general.

Description: The aim of this paper is the definition of an equivalent two-port model of a transmission line that is able to take into account high frequency radiation effects. Such a model is particularly useful when one has to represent the line into a more complex power system, modeled in a lumped way. To reach this goal, it is necessary to produce a reliable and computationally effective solution to the problem of the high-frequency electromagnetic field coupling with a terminated transmission line. From a mathematical standpoint, this problem can be presented by means of an integral equation whose solution can be achieved with regularization procedures for linear inverse problems. In order to obtain a computationally efficient result, the unknown current is first developed in a Fourier series and then the Landweber iterative algorithm is applied to identify the series coefficients. The proposed method is then tested taking as reference the numerical results obtained using the Numerical Electromagnetics Code (NEC-2), reaching a good agreement.

Description: Mixed carbon nanotube bundles (MCBs) are considered to be highly potential interconnect solutions in the current nanoscale regime. Different MCBs with random and spatial arrangements are proposed based on the placements of single- and multiwalled carbon nanotubes (CNTs) (SWNTs and MWNTs) in a bundle. Propagation delay and dynamic crosstalk performances are analyzed using the modified equivalent single conductor model of proposed MCB topologies. Encouragingly, a significant reduction in propagation delay and crosstalk delay is observed for a spatial arrangement of an MCB wherein MWNTs are placed peripherally to the centrally located SWNTs. Typically, the average delay with and without crosstalk is improved by 82.8% and 80%, respectively, compared to the MCB having randomly distributed SWNTs and MWNTs.

Description: The continuous increase of the operating frequency and density of integrated circuits leads to consider single-wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs) as the most promising candidates for future interconnect technology because of their high current-carrying capacity and conductivity in the nanoscale, and immunity to electromigration. Several modeling methods for SWCNT and MWCNT interconnects have been based on the multiconductor transmission line (MTL) theory. These methods are limited to nanostructures with predefined values of electrical and geometrical parameters. Since process technology continues to scale downward and physical interconnect dimensions become smaller, the impact of design parameters (e.g., layout features) on the system behavior has to be carefully investigated for a successful design by performing design space exploration, optimization, and variability analysis. These design activities require multiple system simulations for different values of design parameters, and using MTL-based solvers is not an efficient choice. Parametric macromodels can be used to accurately and efficiently model these parameter effects, avoiding the brute-force use of MTL-based solvers.

Description: As the key devices of an HVDC transmission system, converter valves should bear different forms of overvoltage. Additionally, the wideband frequency electromagnetic noises caused by the switching of thyristor may impact the normal operation of the communication and control systems in an HVDC converter substation. Consequently, it is of great significance to build the model that is suitable for wide frequency range for the key components of converter valve system. Based on the elementary wideband model, the integrated wideband model is proposed and the estimation method for corresponding parameters is also addressed for different kinds of components in this paper. The theoretical analysis and simulation results show that the integrated wideband model has high accuracy and simplicity; it also can provide the results with rigorous passivity and specific physical meaning. As for the application, the proposed method is used to model the key components of an HVDC converter valve and proved to be correct and effective.

Description: The paper discusses the effect of frequency dependence of soil electrical parameters (also called soil dispersion) on lightning currents induced on the shield of buried cables. To this aim, a full-wave approach based on the finite element method is used in which soil dispersion is incorporated into the model using available analytical formulae obtained from experimental data. It is shown that the soil dispersion can affect the induced currents only for soils with very low conductivities ( $leq 0.003, {rm S/m}$ ). It is also shown that, depending on the burial depth of the cable, for poorly conducting soils with conductivities lower than 0.0005 S/m or so, the soil dispersion can result either in an increase or in a decrease of the induced current peak.

Description: This study evaluates the immunity of a low-noise amplifier (LNA) using a transient voltage suppressor (TVS) diode under direct current injection high-power microwave (HPM) pulses. The ac behavior of the TVS diode is examined. Both experiments and analysis demonstrate that the injected HPM power to failure of the LNA is increased by a factor of about 6 through the introduction of a TVS diode, the power to failure of the LNA is also related to the proportion of the direct current injected into the TVS diode and LNA. This analysis is useful for further discussion regarding semiconductor protection under HPM pulses.

Description: Many studies were devoted to the analysis and the detection of electromagnetic attacks against critical electronic systems at the system or the component levels. Some attempts have been made to correlate effects scenarios with events logged by the kernel of the operating system (OS) of commercial-off-the-shelf computer running Windows. Due to the closed principle of the last OS, we decided to perform such an analysis on a computer running a Linux distribution in which a complete access to logs is available. It will be demonstrated that a computer running such an open OS allows detecting the perturbations induced by intentional electromagnetic interferences at different levels of the targeted computer.

Description: The December page is devoted to IEEE Communications Society Awards and the Awards Committee that receives the nominations and processes them to identify the recipients. ComSoc Awards are meant to honor colleagues who in some ways, either via scientific/technical contributions or exemplary services, have reached significant, widely recognized achievements in our telecommunications community. Owing to their high significance and value, they need to be awarded through a fair and transparent process, and this is the essential, yet difficult and heavy task of the Awards Committee. It is my pleasure to introduce Lajos Hanzo, the Chair of the IEEE Communications Society Awards Committee, who will describe the awards and the procedure followed by the Awards Committee.

Description: Presents the front cover for this issue of the publication.

Description: Cellular phone networks are often paralyzed after a disaster, as damage to fixed infrastructure, loss of power, and increased demand degrade coverage and quality of service. To ensure disaster victims and first responders have access to reliable local and global communication, we propose EmergeNet, a portable, rapidly deployable, small-scale cellular network. In this article, we describe EmergeNet, which addresses the challenges of emergency and disaster areas. EmergeNet provides free voice calling and text messaging within a disaster area, and enables users of unmodified GSM handsets to communicate with the outside world using the Skype VoIP network. We evaluate EmergeNet???s ability to provide robust service despite high load, limited bandwidth, and software or hardware failures. EmergeNet is uniquely well suited to providing reliable, fairly allocated voice and text communication in emergency and disaster scenarios.

Description: A wireless sensor network is liable to suffer faults for several reasons, which include faulty nodes or even the fact that nodes have been destroyed by a natural disaster, such as a flood. These faults can give rise to serious problems if WSNs do not have a reconfiguration mechanism at execution. It should be noted that many WSNs designed to detect natural disasters are deployed in inhospitable places and depend on multihop communication to allow the data to reach a sink node. As a result, a fault in a single node can leave a part of the system inoperable until the node recovers from this failure. In light of this, this article outlines a solution that entails employing unmanned aerial vehicles to reduce the problems arising from faults in a sensor network when monitoring natural disasters like floods and landslides. In the solution put forward, UAVs can be transported to the site of the disaster to mitigate problems caused by faults (e.g., by serving as routers or even acting as a data mule). Experiments conducted with real UAVs and with our WSN-based prototype for flood detection (already deployed in S??o Carlos, State of S??o Paulo, Brazil, have proven that this is a viable approach.

Description: The last 15 years have heralded many developments and advances in consumer communications, from early developments of device-specific challenges in interoperability and configuration that are well captured by the concept of plug and play to a more recent emphasis on mobility and service personalization. The one constant technical challenge, and to a great extent a business success, is home networking in its many forms. There is not a modern home without some variant of a set-top box. The three articles in this issue provide a good overview of current and topical requirements in consumer communications.

Description: With the ratification of the IEEE 802.11ad amendment to the 802.11 standard in December 2012, a major step has been taken to bring consumer wireless communication to the millimeter wave band. However, multi-gigabit-per-second throughput and small interference footprint come at the price of adverse signal propagation characteristics, and require a fundamental rethinking of Wi-Fi communication principles. This article describes the design assumptions taken into consideration for the IEEE 802.11ad standard and the novel techniques defined to overcome the challenges of mm-Wave communication. In particular, we study the transition from omnidirectional to highly directional communication and its impact on the design of IEEE 802.11ad.

Description: Although it performs an increasingly important role in our lives, the home network remains a bit of a mystery when end users wish to know what is ???happening on the inside.??? This article introduces Homenet3D, an open source project that allows users to view their home network???s state as objects in 3D space within a web browser window. Homenet3D maps quantitative state to the shape, size, spin, bounce, and/or color of selected objects to qualitatively communicate what is happening on the network. We describe our Homenet3D implementation for routers running OpenWRT, and discuss the potential for visualizing multirouter/ multi-subnet home networks.

Description: Millimeter-wave communication is one way to alleviate the spectrum gridlock at lower frequencies while simultaneously providing high-bandwidth communication channels. MmWave makes use of MIMO through large antenna arrays at both the base station and the mobile station to provide sufficient received signal power. This article explains how beamforming and precoding are different in MIMO mmWave systems than in their lower-frequency counterparts, due to different hardware constraints and channel characteristics. Two potential architectures are reviewed: hybrid analog/digital precoding/combining and combining with low-resolution analog- to-digital converters. The potential gains and design challenges for these strategies are discussed, and future research directions are highlighted.

Description: Virtual traffic lights (VTL) is a new technology that holds the promise of revolutionizing traffic control in urban areas. The original VTL idea was based on 100 percent penetration of VTL technology. In this article, contrary to conventional wisdom, it is shown that 100 percent penetration is not a necessary condition for deploying VTL technology as it can be implemented with partial or low levels of penetration. Furthermore, based on game-theoretic arguments, it is shown that the adoption of VTL technology can be accelerated by providing incentives to vehicles equipped with VTL technology.

Description: Cognitive radio technology allows the reuse of the underutilized frequency spectrum on an opportunistic and non-interfering basis by means of introducing, besides the legitimate primary users of the spectrum, a new kind of users called cognitive or secondary users. Thus, reliable spectrum sensing is critical to dynamically detect available licensed frequency bands and mitigate the primary signals, but it remains realistically difficult to carry out. In fact, although distributed collaborative sensing has turned out to be fruitful for the cognitive radio environment, its accuracy is often affected by the selfish and autonomous behavior of users. In this article, we model distributed spectrum sensing and channel allocation as a non-cooperative game, and apply the minority game to bring forth and study the cooperative behavior of users. The novelty brought by our study consists of alleviating the number of users contending for primary channels by giving them the opportunity to choose between the two, either sensing the channel or being inactive during the time slot. To address the trade-off faced by the SUs, we evaluate the performance of two secondary systems in a green communications context: energy consumption and transmission delay.

Description: In this 14th issue of the Automotive Networking and Applications Series, we are pleased to present three articles that address ??? Release 1 of the cooperative intelligent transport systems (C-ITS) standards in Europe ??? The implementation of a virtual traffic lights application with only partial market penetration ??? The usage of multihop wireless communications for intra-car sensor networking By timely information exchanges among vehicles, and between vehicles and roadway infrastructure, vehicles can transform from autonomous systems into cooperative systems, thereby enabling applications such as active road safety and traffic efficiency. Cooperative intelligent transport systems (C-ITS) standards are crucial to achieve interoperability among communications equipment made by different manufacturers for vehicles and roadway infrastructure. Release 1 of the C-ITS standards was completed in early 2014, and it covers base standards for ITS-G5 radio (also named wireless access in vehicular environment, or WAVE, in the United States), ad hoc networking and transport with GeoNetworking and Basic Transport Protocol (BTP), the facilities layer such as messaging protocols CAM and DENM, security, privacy and requirements for applications, among others. The first article, "Cooperative Intelligent Transport Systems Standards in Europe" by A. Festag, provides a comprehensive overview of release 1 of the C-ITS standards in Europe. The article first gives a brief overview of the C-ITS core standards set and compares it with the U.S. dedicated short-range communications (DSRC) standards in IEEE 1609 and SAE J2735. The author then provides more detailed overviews of the Release 1 C-ITS standards covering the access layer, the networking and transport layers, the facilities layer, and applications, security, and management in the subsequent sections of the article. The article concludes with a brief outlook on the expected C-ITS corridor pilots in Europe starting in 2015, as well- as future standardization directions.

Description: A review of a number of ongoing SDN standardization and open-source activities, this article also discusses the interactions both actual and potential in various standards bodies.

Description: I am honored to have been given the opportunity to initiate this supplement on Communications Standards. It is clear to me that standards enable the global market place to offer interoperable products and services at affordable cost. Standards Development Organizations (SDOs) bring together stake holders to develop consensus standards for use by a global industry. The importance of standards to the work and careers of communications practitioners motivated the creation of this publication on standards. This new quarterly publication will be incubated as a Communication Standards Supplement to IEEE Communications Magazine, which if successful, may transition into a new magazine. It is a platform for presenting and discussing standards-related topics in the areas of communications, networking, and related disciplines.

Description: As I serve the remaining days of my tenure as the president of the IEEE Standards Association (IEEE-SA), I ponder the future of technology: what's been achieved today and where would this amazing world be without standards?

Description: As Vice President of Standards Activities of the IEEE Communications Society, I want to welcome you to the first issue of the IEEE Communications Magazine supplement on Communications Standards. This supplement is the culmination of the efforts of many people to create a publication that serves the interests of the members of the global standards community who develop, use, or are otherwise interested in communications and networking standards. The aim of this publication is to cover a broad spectrum of communications and networking standards as well as standards-related disciplines, including innovation and standardization theory and methodologies, standards-related research, and standards regulations, as well as the intellectual property and socio-economic aspects of standards.

Description: The modal analysis is needed for the design of photonic waveguide devices to determine propagation constants of guided modes and their field pattern. Rigorous methods based on finite-difference or finite-element methods for the approximation of wave equations rely on the solution of eigenvalue problems. Imaginary-distance beam propagation methods require the solution of matrix equations of high order. The computation time needed for both approaches can be tedious. A modal analysis method based on a beam propagation scheme is proposed, which allows an efficient computation of field patterns and propagation constants, as the resulting algorithm is based on simple matrix vector multiplications. This allows the choice of a large number of discretization points and a dense discretization. The beam propagation operator is designed to include the eigenvalue spectrum of corresponding guided modes only. For this reason, the method can be interpreted as a subdomain propagation method. The concept will be validated by utilizing a single-mode and multimode rib waveguide.

Description: Self-Organizing Networks (SON) is a common term for mobile network automation, critical to the cost-efficient deployment, operation and maintenance of mobile networks. This article provides an overview of SON standardization in 3GPP, including both existing and planned functionalities. It also provides an operator perspective on the relevance and use of 3GPP SON functionalities at different stages of the network design-and-operations cycle. In the long-term it is envisaged that automation will become a natural component in network operations, although the success of SON will depend on automation???s benefits in relation to its cost.

Description: We have investigated the dependence of modal behavior on the structures of 2-D implant-defined coherently coupled vertical cavity surface-emitting laser (VCSEL) arrays experimentally and theoretically. 2-D VCSEL arrays with different interelement spacing have been designed and fabricated. Through the experimental analysis of near-field and far-field distribution, in-phase and out-of-phase mode are obtained from the arrays, depending on the interelement spacing. Considering the effect of thermal and carrier injection, the refractive index distribution of the arrays under operation is calculated. Then, FDTD Solutions software is employed to calculate the near-field distributions of the arrays through establishing a simplified refractive index model. The simulation results agree well with the experiments. Meanwhile, according to the phase characteristics of in-phase and out-of-phase mode, as observed from the near-field profiles, the far-field distributions are calculated, in an excellent agreement with the experiments.

Description: We present experimental investigations of the intensity noise properties of injection-locked midinfrared emitting quantum cascade lasers. Following the theoretical approach by Simos et al. , the injection locking is realized below and near the threshold of the free running slave laser, resulting in an efficient technique to achieve low-noise operation. We find that below the threshold, the locking characteristics as locking range, shape and bandwidth, are different in comparison with those above threshold. In addition, we also investigate injection locking into longitudinal side modes of the slave laser apart by several longitudinal mode hops, and observe similar characteristics, however, with the potential to achieve higher relative intensity noise suppression. The measurements are confirmed by additional numerical simulations with a new model, which considers the multimode spectrum of the slave laser and the spectral profile of the material gain. Under the actual experimental conditions, a reduction of the relative intensity noise of the slave laser of up to 10 dB (above threshold) and up to 20 dB (below threshold) in comparison to the free running slave laser noise level is achieved.

Description: The high accuracy of lasing wavelength spacing is one of the key requirements of a distributed feedback (DFB) semiconductor laser array. However, the nonuniformity of the wavelength spacing is increasingly deteriorating with the increase in the channel number in the laser array. In this paper, theoretical study was made to investigate the effects of sampling pattern deviation and seed grating, as well as waveguide dispersion on the wavelength-spacing uniformity for multiwavelength DFB semiconductor laser arrays (MLAs) fabricated using the reconstruction equivalent chirp (REC) technique. A simple measurement method of dispersion for DFB semiconductor lasers based on the REC technique is also proposed. With the dispersion compensation being included in the sampling period design and small deviation in the seed grating period being guaranteed, a high-channel-count (16-channel) DFB laser array with precise channel spacing of 0.7944 nm/channel (design value of 0.80 nm/channel) was achieved in our experiment. It shows excellent channel-spacing uniformity, and most wavelength residuals are within $pm$ 0.10 nm.

Description: An equivalent–asymmetric coupling coefficient (EACC) distributed feedback laser (DFB) semiconductor laser with equivalent-half apodization grating (EHAG) structure is proposed and experimentally demonstrated for the first time; the EHAG profile is equivalently realized by linearly changing the duty cycle of a sampled Bragg grating along the one half cavity, while that of the other half cavity is kept uniform. Compared with the equivalent–symmetric coupling coefficient DFB laser, the simulated intensity distribution of the EACC DFB laser shows that the light power is concentrated not only on near the phase-shift region and that the power at the front end is enlarged. Therefore, the longitudinal spatial hole burning may be reduced; the output efficiency and the single-mode stability may be improved. The experimental results show that the output power ratio between the front and rear facets is about 2.17 and the side-mode suppression ratios are over 50 dB when the injection current is in the range from 60 to 200 mA.

Description: A theoretical and experimental study of all-solid-state barium borate (BBO)-based optical parametric oscillator with wide tunability from visible to near-infrared by means of intracavity second-order cascaded nonlinear interaction has been demonstrated for simultaneous generation of multicolor radiation. Radiations in the wavelength range of 600–661 nm in the visible and 892–1322 nm in the near-infrared range are generated by a combination of optical parametric oscillation and simultaneous second harmonic generation in BBO crystal. The effective third-order susceptibility is measured to be 885.18 $mathrm{pm}^{2}$ / $mathrm{V}^{2}$ , which is greater than intrinsic third-order susceptibility by one order of magnitude.

Description: In finite-size high-contrast gratings (HCGs) guided modes with low $Q$ values can occur. On the one hand, this is a resonant mode with a $Q$ value of some hundreds only, on the other hand it can transform part of the finite-size incident wave into the in-plane direction. Such finite-size HCGs with guided modes are proposed here for optical sensors with an on-chip integrated p-i-n photodiode in the same HCG layer. The mode characteristics of the guided mode and the performance of the proposed integrated HCG-based optical sensors are investigated. The proposed integrated HCG-based optical sensors are compact, cost-effective, label-free, and highly sensitive, and can be extended to an array format increasing the throughput.

Description: This paper presents the fabrication, modeling, and characterization of a micromachined piezoelectric directional microphone. The microphone structure consists of a 20- $mu $ m-thick semirigid beam structure that rotates about torsional pivots in response to in-plane pressure gradients across the length of the beam. The motion of the beam structure is transduced by piezoelectric cantilevers, which deflect when the structure rotates. While the structure has been introduced in prior publications, this is the first paper summarizing rigorous acoustic characterization of first generation prototypes. An analytical model and multimode, multiport network model utilizing finite-element analysis for parameter extraction are presented and compared with acoustic sensitivity measurements. Directivity measurements are interpreted in terms of the multimode model. A noise model for the sensor and readout electronics is presented and compared with measurements.

Description: An increase in world population along with a significant aging portion is forcing rapid rises in healthcare costs. The healthcare system is going through a transformation in which continuous monitoring of inhabitants is possible even without hospitalization. The advancement of sensing technologies, embedded systems, wireless communication technologies, nano technologies, and miniaturization makes it possible to develop smart systems to monitor activities of human beings continuously. Wearable sensors detect abnormal and/or unforeseen situations by monitoring physiological parameters along with other symptoms. Therefore, necessary help can be provided in times of dire need. This paper reviews the latest reported systems on activity monitoring of humans based on wearable sensors and issues to be addressed to tackle the challenges.

Description: Three-dimensional ultrasound imaging is a promising medical imaging technology because of its ease of use and improved accuracy in diagnosis. However, its high computational complexity and resulting high power consumption has precluded its use in hand-held applications. In this paper, we present a separable beamforming method that greatly reduces computational complexity. Our method is based on decomposing the delay term in a way that minimizes the root-mean-square error caused by the decomposition. We analyze tradeoffs between the approximation error caused by the decomposition and computational complexity. Then, we present enhancements to the Sonic Millip3De hardware accelerator for ultrasound beamforming to implement separable beamforming. Using hardware synthesis targeting standard cells in 45 nm, we show that the proposed method allows us to boost the Sonic Millip3De frame rate from 1–2 Hz to 32 Hz while maintaining power consumption at 15 W. We validate image quality of our method using cyst phantom simulations in Field II. Our evaluation demonstrates that the proposed separable beamforming method can produce 3-D images with high quality that are comparable to those generated by non-separable beamforming.

Description: For MIMO systems, due to the deployment of multiple antennas at both the transmitter and the receiver, the design variables, e.g., precoders, equalizers, and training sequences, are usually matrices. It is well known that matrix operations are usually more complicated compared with their vector counterparts. In order to overcome the high complexity resulting from matrix variables, in this paper, we investigate a class of elegant multi-objective optimization problems, namely matrix-monotonic optimization problems (MMOPs). In our work, various representative MIMO optimization problems are unified into a framework of matrix-monotonic optimization, which includes linear transceiver design, nonlinear transceiver design, training sequence design, radar waveform optimization, the corresponding robust design and so on as its special cases. Then, exploiting the framework of matrix-monotonic optimization the optimal structures of the considered matrix variables can be derived first. Based on the optimal structure, the matrix-variate optimization problems can be greatly simplified into the ones with only vector variables. In particular, the dimension of the new vector variable is equal to the minimum number of columns and rows of the original matrix variable. Finally, we also extend our work to some more general cases with multiple matrix variables.

Description: This paper investigates the bias of the maximum likelihood target location estimate resulting from the Gaussian data measurement noise and sensor position errors. The bias components from them are interrelated, except when they are independent and identically distributed. The bias behaviors of time of arrival, time difference of arrival, and angle of arrival positionings are contrasted, and geometric conditions under which the location bias becomes zero are elaborated.We illustrate the developed results for bias compensation in improving the performance of target tracking.

Description: In a collaborative sensor network (CSN), the conventional target tracking algorithms employed are Kalman filtering (KF) or extended Kalman filtering (EKF). However, these techniques have a presumed probability distribution of the system noise and prediction noise. They also need some a priori information that may be unavailable in some circumstances. Therefore, the system is not flexible for a complicated scenario. With the help of a machine learning technique called expert prediction (EP), a novel target tracking approach for CSNs is developed. This scheme makes use of the aforementioned EP in parameter estimation course for the target of interest, instead of exploiting the filtering method as typically found in available literature. This idea is further unfolded with comparisons regarding the CSN using Kalman filters, extended Kalman filters, and decentralized sigma-point information filters (DSPIFs). The new tracking algorithm is investigated with both linear and nonlinear prediction methods. Simulation results demonstrate that this proposed measure will deliver forecasting output with more precision because of the built-in multimodel mode among different experts, the learning ability, and the self-perfection characteristic. Not only does this performance occur in a more robust way than those of the existing approaches – particularly in the presence of heavy clutter, highly maneuvering targets, and/or multiple targets – but it simultaneously requires the least a priori information and imposes the least limitation on the observation model.

Description: Hybrid aerial-terrestrial communication networks based on low-altitude platforms are expected to meet optimally the urgent communication needs of emergency relief and recovery operations for tackling large-scale natural disasters. The energy-efficient operation of such networks is important given that the entire network infrastructure, including the battery-operated ground terminals, exhibits requirements to operate under power-constrained situations. In this paper, we discuss the design and evaluation of an adaptive cooperative scheme intended to extend the survivability of the battery-operated aerial-terrestrial communication links. We propose and evaluate a real-time adaptive cooperative transmission strategy for dynamic selection between direct and cooperative links based on the channel conditions for improved energy efficiency. We show that the cooperation between mobile terrestrial terminals on the ground could improve energy efficiency in the uplink, depending on the temporal behavior of the terrestrial and aerial uplink channels. The corresponding delay in having cooperative (relay-based) communications with relay selection is also addressed. The simulation analysis corroborates that the adaptive transmission technique improves overall energy efficiency of the network whilst maintaining low latency, enabling real-time applications.

Description: In this paper, a reduced-rank scheme with joint iterative optimization is presented for direction of arrival estimation. A rank-reduction matrix and an auxiliary reduced-rank parameter vector are jointly optimized to calculate the output power with respect to each scanning angle. Subspace algorithms to estimate the rank-reduction matrix and the auxiliary vector are proposed. Simulations are performed to show that the proposed algorithms achieve enhanced performance over existing algorithms in the studied scenarios.

Description: Using the dynamic inversion philosophy, a nonlinear partial integrated guidance and control approach is presented in this paper for formation flying. It is based on the evolving philosophy of integrated guidance and control. However, it also retains the advantages of the conventional guidance then control philosophy by retaining the timescale separation between translational and rotational dynamics explicitly. Simulation studies demonstrate that the proposed technique is effective in bringing the vehicles into formation quickly and maintaining the formation.

Description: The use of ground-based transmitters (so-called pseudolites) for outdoor and indoor navigation has been under consideration since the origin of the Global Positioning System (GPS). However, one significant limitation of the use of code division multiple access (CDMA) was immediately obvious: one CDMA transmitter signal interferes with another CDMA transmitter signal. This is called the ""near-far problem."" Different methods have been studied in order to mitigate such jamming. This paper presents a new mitigation method based on a principle that can be summed up as follows: the signal and a delayed replica of the signal are broadcast by a ground transmitter antenna. At the receiver stage, the replica signal is used to eliminate the interference caused by the direct signal. This is called the double transmission technique (DTT), and it presents interesting performance features regarding interference mitigation. A signal processing technique corresponding to this method is presented in this paper, considering a GPS L1 C/A-code pseudolite. Performance simulations are also presented.

Description: This paper describes a novel framework to determine the relative pose and range of a solid-of-revolution-shaped spacecraft from a single image without any artificial beacons. The translation and the symmetry axis of the spacecraft can be estimated from the imaged cross sections of the spacecraft body. Then the pose and range of the spacecraft are fully determined by means of the images of its solar panels and asymmetric feature. Our method has been validated by both synthetic and real images.

Description: Data association, the problem of reasoning over correspondence between targets and measurements, is a fundamental problem in tracking. This paper presents a graphical model formulation of data association and applies an approximate inference method, belief propagation (BP), to obtain estimates of marginal association probabilities. We prove that BP is guaranteed to converge, and bound the number of iterations necessary. Experiments reveal a favourable comparison to prior methods in terms of accuracy and computational complexity.

Description: The objective of this paper is to present a methodology for identifying the current flow in the capacitors of a multiphase buck converter by synchronously measuring the capacitor currents. A multiphase buck converter uses multiple parallel buck converters with different switching times to source a large amount of current. Currents in the primary capacitors of a multiphase buck converter are drawn by all phases of the converter; however, the phases switch asynchronously. Synchronizing to the switching of a specific phase reveals how the current from that phase is distributed among the capacitors throughout a circuit board. The proposed measurement method is illustrated by comparing an initial printed circuit board design to a new design to show the effect of better capacitor placement and the addition of a ground plane. The new design confines the phase currents to the capacitors close to the field effect transistors of the specific phase.

Description: Research and development are currently being performed to transform the US's utility electric grid into a “smart grid [1] , [2] .” Smart meters are among the first intelligent metering devices used within the “smart grid” concept. They have been deployed in thousands of commercial and residential electrical installations around the US [3] , [4] . While the wide-scale deployment of these devices has initially proven very successful, there is still much that is unknown about how they will impact the long-term operation of a large utility grid or the electrical devices sourced by them [5] . One such device, whose operation appears to be impacted by the smart meter, under specific conditions, is a ground-fault circuit interrupter (GFCI). It has been reported that the RF transmissions from smart meters can induce false tripping events on GFCI outlets installed on temporary construction poles. In an effort to understand why this may happen, a research study, which is presented here, has been performed to understand the correlation between RF transmissions and GFCI tripping events on construction poles.

Description: A locating system based on an advanced time difference of arrival (TDOA) estimation method is developed to locate the position of a discharge source to avoid pulsed electromagnetic interference (PEMI) with the surrounding radio communication environment. In general, from the waveforms of PEMI waves received by an antenna array, the source position can be located or the direction of arrival (DOA) of the EM waves can be estimated by applying TDOA-based methods. However, owing to noises and multipath waves that occur at the metal surfaces of electric power equipment, the estimation accuracy of the TDOA may decrease, and the location accuracy will be degraded. To improve the accuracy of TDOA estimation, we propose a new TDOA estimation technique. In our developed locating system, PEMI waves are received by a four-antenna-square array and the DOA is estimated from the TDOA, which is estimated using the generalized cross-correlation phase transform method in combination with the proposed technique. A PEMI source is ultimately located by aiming a charge-coupled device camera, installed at the center of the antenna array, at the estimated DOA. The estimation accuracy of the locating system is evaluated through experimental measurements. The results show that the developed locating system can locate the position of a PEMI source existing within about 30 m from the system with high accuracy.

Description: High-frequency signals on interconnects can cause significant radiated electromagnetic emissions. An intermediate level modeling method aimed at providing a faster solution with less computing resources to allow designers to obtain rapid approximations is desirable. This paper presents a modeling technique to speed up the evaluation of radiated fields from interconnect cables. Based on the Hertzian dipole radiation theory and transmission-line frequency-dependant solutions, the radiating source is modeled by the sum of a large number of short dipoles. This model allows the contributions of line-end discontinuities to be included through a vector network analyzer measurement together with a monopole approximation. The proposed method is verified by open-line and RG 58 coaxial cable measurements.

Description: An efficient approach to achieve the shielding effectiveness (SE) by using a frequency-selective surface (FSS) is presented. This FSS, which consists of cross dipoles and rings printed on the opposite sides of a single-layer FR-4 substrate, exhibits a wide, 7.5-GHz stopband to provide simultaneous shielding in both X- and Ka-bands. Experimental results confirm SE of the prototype over an ultra-wide band with more than 20-dB measured attenuation. The design is compact and suitable to provide shielding against the radiation interference caused by license-free and other radio systems.

Description: The household appliances in buildings have increased rapidly in the recent years. However, the surge withstanding capability of these household appliances has not been increased. Therefore, it is necessary to install surge protection device (SPD) to prevent serious damage of household electrical appliances caused by the in-rushing surges. In order to avoid the oscillation phenomenon, the effective protection distance of SPDs should be addressed before installing SPDs in the buildings. This paper discussed the influence of a group of common household electrical appliances connected in parallel on the effective protection distance of an SPD to a household appliance. The surges impinging on the household appliances connected to a distribution system are analyzed using electromagnetic transient analysis software. It is found that the SPD's protection distance increases when multiple household appliances are connected in parallel. The SPD's effective protection distance for one specific household appliance, which is determined from the case in which only this household appliance is used, is a conservative value; even if other household appliances are connected with this appliance, the SPD still provides an effective protection to this specific appliance.

Description: In this paper, we propose a novel sparse representation (SR)-based model for wideband direction-of-arrival (DOA) estimation. Different from the classical SR-based DOA model, which only explores the sparsity of sources in spatial space, the proposed model exhibits the sparsity through the fact that any individual wideband source is characterized as a unique oblique line passing through the origin in the 2-D frequency plane of the temporal-spatial array data. To further reduce the computation complexity during the use of such sparse property, the 2-D direction information is projected into a 1-D space. Simulations show the superior performance of our approach, even in the noise corruption and less temporal samples condition.

Description: In this paper, we propose the modeling, the design, and the development of a high sensitivity cheap optical sensor for chlorophyll a and water transparency based on chlorophyll fluorescence and turbidity due to scattering for in situ monitoring of trophic status of seawater. The sensor is designed in order to detect very low chlorophyll concentration and low level turbidity by means of a numeric lock-in amplifier technique, with a common resonant input stage. The sensor is designed and implemented by considering a proper layout suitable for a good light source coupling. The presented prototype integrates on a board two LED sources emitting red and blue light to measure both chlorophyll- a and turbidity. The system assures a chlorophyll sensitivity of 1 mV/ (2.5~mu ) g/l, a detectivity of (0.2~mu ) g/l, with a 40-dB minimum attenuation of all the other light sources. It is attractive with respect to commercial systems because it guarantees considerable reliability with low manufacturing costs.

Description: The target damage efficiency is a key content in weapon testing field to assess new weapon damage performance, this paper researches the projectile multiburst location optical testing method based on double area array camera and assessment arithmetic of target damage efficiency. The optical testing model of 3-D coordinate on the projectile multiburst location is set up using double area array camera. Based on the 3-D coordinates of projectile multiburst location and finite element analysis theory, the calculation method of target vulnerability area was researched and analyzed by dividing the target vulnerable area into many unit areas to develop assessment arithmetic of target damage efficiency. The relationship of fragments size, impact angle, and vulnerable surface unit area size and the calculation methods of the target vulnerable area and damage sensitivity were discussed. The target damage probability was also calculated and analyzed using projectile fragments distribution density, number of fragments, and fragment cloud scattering radius. Through the calculation and experiment, the result shows that the assessment of target damage efficiency is closely related to 3-D coordinates of the projectile multiburst location, fragments size and velocity, vulnerable surface unit area size, and effective number of fragments per unit area.

Description: Several projects have tracked the movement of swimmers in pools using body worn inertial measurement units. In swimming, inertial sensing is subject to large amounts of drift and accumulated error which can only be corrected for after a complete length has been swum. In this paper, we present a new method for tracking swimmers by detecting variations in the magnetic field caused by the structure of pools. This method is complementary to inertial positioning, as it allows the direct extraction of position without requiring postprocessing, and unlike inertial sensing which loses accuracy over time, magnetic field tracking becomes increasingly accurate toward the end of a length.

Description: A small ( (30~{rm mm} times 50~{rm mm} times 8~{rm mm}) ), waterproof 2.45 GHz wireless sensor with a standard meander line printed monopole has poor radiation characteristics when placed against the human body. A suitably optimized H-shape (step impedance resonator) parasitic element was added next to the antenna of the sensor on outer surface of clothing fabric. The parasitic element was placed on the outside of a fabric armband and was found to increase the total efficiency of the antenna by 13% in simulation results and enhanced the measured gain by 3 dB. The technique ensures that the armband is comfortable, washable, flexible, and operates successfully without wired connectors. The technique was optimized using simulation and experimental measurements with an adhesive aluminum strip. As the wireless sensor is waterproof and there is no access to the port of the antenna in the sensor, a two ray ground reflection model was used to match the received power in the spectrum analyzer using least rms curve fitting.

Description: In this paper, microbolometers with different geometric designs were fabricated using polycrystalline silicon (polysilicon) films from TSMC (0.35~mu ) m (D35 type) and (0.18~mu ) m (T18 type). D35 microbolometers with high-resistance films showed negative temperature coefficient of resistance (TCR) values, whereas T18 microbolometers with low-resistance films showed positive TCR values. Results indicate that conventional designs with large areas of infrared absorbers can be optimized using uniform suspended arms throughout the microbolometer in the two types of devices. Finite element modeling indicates that the heat flux of microbolometers with uniform beams is evenly distributed and thus results in improved TCR values.

Description: A continuously wavelength-tunable light source with constant-power output is presented. The unwanted optical power modulation companying with the wavelength modulation of the distributed feedback laser diode by the injection current is successfully offset by the external amplitude modulation of electro-optic modulator. The optical power stability has been experimentally demonstrated better than 1.2% in a wavelength-tunable range of 0.876 cm (^{-1}) . The background baseline appearing in the direct absorption spectrum can be removed with the new light source. Not only that, the spectral distortion of the second harmonic signal caused by residual-amplitude modulation can also be largely eliminated. Experimental results have shown that the new light source is more suitable to be served as a pure wavelength-tuning reference source for different modes of spectroscopic measurement.

Description: The combination of the all solid-state terahertz (THz) technology and synthetic aperture radar imaging technique leads to small imaging sensors of high resolution. In this paper, we present an active frequency-modulated continuous-wave THz imaging radar system with inverse aperture synthesis technique to image objects in centimeter-scale resolution in two dimensions. Its high-range resolution is achieved through the use of broadband sweep signal, whose frequency ranges from 336.6 to 343.8 GHz, and the 1-D aperture synthesis enables the improvement of the cross-range resolution. In order to optimize the range resolution, a nonlinearity calibration approach is presented to solve the signal distortion. To verify the imaging performance of the THz radar, the inverse synthetic aperture radar experiments are performed and the imaging results obtained by the 2-D fast Fourier transform method and back-projection algorithm, respectively, show that the THz radar can achieve high resolution in the range and azimuth dimensions.

Description: We study the problem of controlling multiple 2-D directional sensors while maximizing an objective function based on the information gain corresponding to multiple target locations. We assume a joint prior Gaussian distribution for the target locations. A sensor generates a (noisy) measurement of a target only if the target lies within the field-of-view of the sensor, where the statistical properties of the measurement error depend on the location of the target with respect to the sensor and direction of the sensor. The measurements from the sensors are fused to form global estimates of target locations. This problem is combinatorial in nature—the computation time increases exponentially with the number of sensors. We develop heuristic methods to solve the problem approximately, and provide analytical results on performance guarantees. We then improve the performance of our heuristic approaches by applying an approximate dynamic programming approach called rollout. In addition, we address a variant of the above problem, where the goal is to map the sensors to the targets while maximizing the abovementioned objective function. This mapping problem also turns out to be combinatorial in nature, so we extend one of the above heuristics to solve this mapping problem approximately. We compare the performance of these heuristic approaches analytically and empirically.

Description: This paper illustrates the characterization of a fabric resistance temperature (RTD) detector made from electrospun nylon-6 functionalized with multiwalled carbon nanotubes (MWCNTs) and polypyrrole (PPy) for use in supracutaneous applications like smart clothing, prosthetic sockets, and other medical devices where a temperature detecting fabric is better suited than a rigid detector. The nanocomposite material acts like a RTD, because the conductivity increases linearly with temperature. The empirically determined temperature coefficient of resistance (TCR) is reported for this material, and is –0.204 ± 0.008%/C. Development of a simple and scalable process for constructing the detector utilized electrospinning nylon-6 as a membrane style substrate, vacuum filtration of MWCNTs onto the nylon scaffold, and vapor phase polymerization of pyrrole to PPy onto the MWCNT functionalized nylon nanofibers. The optimal loading of MWCNTs is 6.6 wt%. The conductivity of the device follows a percolative behavior and TCR values indicate this is a viable option for temperature detection. Resistance decreases with increasing temperature, which indicates this is a negative TCR material.

Description: In this paper, we present a novel framework to predict events through time-series analysis of sensor data streams. The framework is capable of producing and visualizing event prediction probabilities, uncertainties around the predictions, and the actual decision being taken based on the prediction. We have tested the analytical framework on predicting closure events in shellfish farms in Tasmania. Reasonably high prediction accuracy is achieved. The visualization was able to capture prediction, uncertainty, and actual decision being taken (i.e., three-in-one).

Description: We proposed and demonstrated an innovative magnetic field optical fiber sensor utilizing magnetic ferrofluid and a thin-core fiber (TCF)-based modal interferometer. The modal interferometer was fabricated by splicing a TCF between two single mode fibers. Two TCF interferometers with different dip wavelength were connected in a fiber to demonstrate the sensors multiplexing capability. The transmission dip wavelength of interferometer is shifting with a maximum sensitivity of 11.8 pm/Oe.

Description: Some mobile sensor network applications require the sensor nodes to transfer their trajectories to a data sink. This paper proposes an adaptive trajectory (lossy) compression algorithm based on compressive sensing. The algorithm has two innovative elements. First, we propose a method to compute a deterministic projection matrix from a learnt dictionary. Second, we propose a method for the mobile nodes to adaptively predict the number of projections needed based on the speed of the mobile nodes. Extensive evaluation of the proposed algorithm using six data sets shows that our proposed algorithm can achieve submeter accuracy. In addition, our method of computing projection matrices outperforms two existing methods. Finally, comparison of our algorithm against a state-of-the-art trajectory compression algorithm shows that our algorithm can reduce the error by 10–60 cm for the same compression ratio.

Description: Heat flux sensors fabricated using Direct Write Thermal Spray are thin, surface-based devices that can operate at high temperatures. In this paper, Direct Write heat flux sensors are calibrated over a temperature range of 25 °C–860 °C. A substitution-based quartz lamp configuration is used to measure the steady-state sensitivity and transient response of Direct Write sensors at ambient temperatures, with repeatability confirmed over a 10-month period and after thermal aging. A matched heat flow approach is used to characterize the sensors at operating temperatures up to 860 °C. The sensitivity is found to increase by a factor of two from 25 °C to 650 °C, after which it plateaus up to the maximum tested temperature of 860 °C. A cubic polynomial calibration function captures the temperature dependence of the sensitivity and provides a good agreement for the measured data.

Description: This paper presents a novel approach of an absolute rotary and linear optical encoder codding patterns. The concept is based on the analysis of 2-D images to find a unique sequence that allows to unambiguously determine an angular shaft position. The adopted coding method allows to achieve a very high data density for specified number of tracks on the code pattern disc. Encoders based on the proposed solution enable the production from readily available and inexpensive components. Nevertheless, encoders retain high measuring accuracy and high dependability obtained in the classical approach. The optical device and a design of processing system is proposed. Finally, the feasibility of the pattern coding method is further proved with encoder prototype.

Description: This paper reports the design of a self-powered telemetric wireless sensor node for temperature measurement. The device is realized with a conventional off-the-shelf thermoelectric generator as a power source. It is sandwiched between two aluminum core printed circuit boards (PCBs). One board is exposed to the heat source and has the role of a heat collector, whereas another one with the mounted low profile heatsink acts as a heat spreader. Electronic components of the node are placed on the inner surfaces of the boards. Implemented step-up circuitry is accommodated to achieve stabile cold boot of the node at a low temperature difference between its hot side and ambient (less than 15 °C), even when it is in thermally inefficient position. Operational autonomy of the node in the absence of the heat source is extended by 30% comparing with the common step-up circuitry implementation. The aluminum core PCBs provide node simplicity and compactness, with small overall dimensions.

Description: In this paper, we report on the development of a highly sensitive, relatively low-temperature ethanol sensor based on sol–gel derived p-TiO 2 thin film. The p-type anatase TiO 2 thin film was deposited by sol–gel technique on a thermally oxidized <100> p-Si (resistivity (5~Omega ) cm) substrate. Anatase TiO 2 phase with <101> nanocrystallinity was confirmed with an average particle size of (sim 11) nm from X-ray diffraction and field emission scanning electron microscopic study. Ethanol sensor study, in the resistive mode, was carried out at a relatively low operating temperature range (75 °C–175 °C) for sensing low concentrations of ethanol in air (5–100 ppm). Response magnitude of (sim 146) % was observed at 150 °C toward 100-ppm ethanol (in air) with corresponding response time and recovery time of 39 and 15 s, respectively. The sensor showed appreciably high-response magnitude (129%) even at low ethanol concentration (5 ppm) with acceptable response and recovery time (54 and 22 s, respectively) at the same operating temperature (150 °C). At a particular temperature, for all the ethanol concentrations, sensor showed minimal base line resistance drift, thereby offering highly repeatable and stable sensing performance. Ethanol selectivity study against other volatile organic compounds, such as methanol, acetone, and 2-butanone, was also investigated and was found to be quite promising. Ethanol sensing mechanism for such p-type TiO 2 has also been discussed in the light of corresponding oxygen vacancy model.

Description: A new phase-based technique for localization and tracking of items moving along a conveyor belt and equipped with ultrahigh frequency-radio frequency identification (UHF-RFID) tags is described and validated here. The technique is based on a synthetic-array approach that takes advantage of the fact that the tagged items move along a conveyor belt whose speed and path are known a priori . In this framework, a joint use is done of synthetic-array radar principles, knowledge-based processing, and efficient exploitation of the reader-tag communication signal. The technique can be easily implemented in any conventional reader based on an in-phase and quadrature receiver and it does not require any modification of the reader antenna configurations usually adopted in UHF-RFID portals. Numerical results are used to investigate the performance analysis of such methods, and also to furnish system design guidelines. Finally, the localization capability is also demonstrated through a measurement campaign in a real conveyor belt scenario, showing that a centimeter-order accuracy in the tag position estimation can be achieved even in a rich multipath environment.

Description: This paper represents the extended version of the conference paper “Developing highly-integrated subcutaneous biochips for remote monitoring of human metabolism” presented at the IEEE Sensors Conference 2012, and presents data on assembly, packaging and short term in vitro and in vivo biocompatibility evaluation of a fully implantable biosensor array. The device was realized integrating three building blocks: 1) a multielectrode platform; 2) an inductive coil; and 3) an integrated circuit. The entire system measures 2.2 mm $times 2.2$ mm $times 15$ mm. Corrosion of electronic components and leaking of potentially hazardous substances in the body is prevented with a conformal coating of Parylene C, while an outer package of medical grade silicone was employed to create a soft shell suitable for implantation. Biocompatibility experiments did not show in vitro cytotoxicity in the considered period of 7 days, while comparison between 7 and 30 days in vivo implantations showed significant reduction of the inflammatory response in time, suggesting normal host recovery.

Description: A fundamental challenge in realizing body-worn sensors is in providing an effective and long-lasting power supply. Issues regarding batteries have prompted researchers to investigate powering devices by extracting energy from the inertial movement of the human body. While previous studies have investigated the effect of generator location and wearer activity on harvestable power, they have not considered the orientation of the generator; this is the focus of this paper. Acceleration data collected across a sample population (10 participants) during different activities (walking and running) and generator location (five locations on the body) are presented. These data are processed to analyze the effect of orientation, and we find that it can significantly reduce the harvestable power. Subsequently, we propose and analyze how two degree-of-freedom generators can improve tolerance to rotation; results indicate that it can be improved by one order of magnitude.

Description: This paper develops a magnetoelectric (ME) heterostructure FeCuNbSiB/Ni/Rosen-type piezoelectric transformer (RPT)/Ni/FeCuNbSiB consisting of a RPT Pb(Zr 1- x Ti x )O 3 with its drive-end sandwiched between two graded-magnetostrictive layers of FeCuNbSiB/Ni. The graded-magnetostrictive layer FeCuNbSiB/Ni is made up of Fe-based nanocrystalline alloy FeCuNbSiB (Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 ) and pure Nickel (Ni). Due to the different magnetic characteristics of FeCuNbSiB and Ni (such as permeability, saturation magnetization and magnetostriction), the FeCuNbSiB/Ni layer exhibits an internal magnetic bias field, which results in the large self-biased ME properties. An amplified output voltage can be obtained between the two electrodes of the generator-end due to the step-up voltage-gain effect of the RPT. Consequently, the maximum zero-biased ME voltage coefficients of generator-end are $sim 4.06$ V/Oe at the first resonance frequency of $sim 41$ kHz, and $sim 4.22$ V/Oe at the second resonance frequency of $sim 102$ kHz. The results show that this heterostructure is of interest for high-sensitive magnetic field sensors.

Description: This letter proposes a novel framework to detect common salient objects in a group of images automatically and efficiently. Different from most existing co-saliency models which directly redesign algorithms for multiple images, the saliency model for a single image is fully exploited under the proposed framework to guide the co-saliency detection. Given single image saliency maps, a two-stage guided detection pipeline led by queries is proposed to obtain the guided saliency maps of the image set through a ranking scheme. Then the guided saliency maps generated by different queries are fused in a way that takes advantages of both averaging and multiplication. The proposed model makes existing saliency models work well in co-saliency scenarios. Experimental results on two benchmark databases demonstrate that the proposed framework outperforms the state-of-the-art models in terms of both accuracy and efficiency.

Description: A method based on the Bivariate Empirical Mode Decomposition (BEMD) is addressed to facilitate radar scene analysis for cognitive radar, building and expanding upon a previous contribution. The method exploits the response of BEMD to the fractional Gaussian character of coherent sea clutter returns. Second–order properties of the intrinsic mode functions are used to form a null hypothesis, which indicates the absence of target(s) if accepted. Extensive experiments on real–world radar data show that the proposed radar scene analysis procedure leads to significantly enhanced statistical separability for target+clutter and clutter–alone data. The results are judged from an information–theoretic perspective using the Kullback–Leibler distance as well as by visual inspection.

Description: In this letter we propose simple and robust features to distinguish continuous-phase frequency shift keying from quadrature amplitude modulation and phase shift keying modulations. The features are based on sample mean and sample variance of the imaginary part of the product of two consecutive complex signal values. Root raised cosine pulses are used to generate the linearly modulated signals. Support vector machines are employed to distinguish the signals. One benefit of using support vector machines is that it requires very few realizations for training. Moreover, no a priori information is required about carrier amplitude, carrier phase, carrier offset, symbol rate, pulse shape, initial symbol phase (timing offset) and channel impulse response. Effectiveness of the features and signal separation by support vector machines is tested by observing the joint effects of additive white Gaussian noise, carrier offset, lack of symbol and sampling synchronization, and either fast or slow fading. In the course of doing that, the proposed classifier is compared to the wavelet based classifier, equipped by support vector machines.

Description: In this paper, we report an integrated single-chip surface acoustic wave sensor with the capability of measuring magnetic field, temperature, and humidity. The sensor is fabricated using a thermally sensitive LiNbO 3 substrate, a humidity sensitive hydrogel coating, and a magnetic field sensitive impedance load. The sensor response to individually and simultaneously changing magnetic field, temperature and humidity is characterized by connecting a network analyzer directly to the sensor. Analytical models for each measurand are derived and used to compensate noise due to cross sensitivities. The results show that all three measurands can be monitored in parallel with sensitivities of 75 ppm/°C, 0.13 dB/%R.H. (at 50%R.H.), 0.18 dB/Oe and resolutions of 0.1 °C, 0.4%R.H., 1 Oe for temperature, humidity and magnetic field, respectively. A passive wireless measurement is also conducted on a current line using, which shows the sensors capability to measure both temperature and current signals simultaneously.

Description: In this paper, the capacity of OFDM/OQAM with isotropic orthogonal transfer algorithm (IOTA) pulse shaping is evaluated through information theoretic analysis. In the conventional OFDM systems the insertion of a cyclic prefix (CP) decreases the system’s spectral efficiency. As an alternative to OFDM, filter bank based multicarrier systems adopt proper pulse shaping with good time and frequency localisation properties to avoid interference and maintain orthogonality in real field among sub-carriers without the use of CP. We evaluate the spectral efficiency of OFDM/OQAM systems with IOTA pulse shaping in comparison with conventional OFDM/QAM systems, and our analytical model is further extended in order to gain insights into the effect of utilizing the intrinsic interference on the performance of our system. Furthermore, the spectral efficiency of OFDM/OQAM systems is analyzed when the effect of inter-symbol and inter-carrier interference is considered.

Description: Algebraic Pursuit (ALPS) is an effective class of iterative hard thresholding algorithms for compressed sensing, with 1-ALPS(2) being the most computationally efficient variant of ALPS. We present a proof of convergence, using restricted isometry constants, for 1-ALPS(2) as well as the recently introduced Fast Iterative Hard Thresholding (FIHT). Large scale empirical testing shows FIHT is superior to 1-ALPS(2) in terms of both the sizes of the problems that are recoverable and overall computational time.

Description: Resistive sensor arrays have been increasingly adopted in wearable electronic applications, which require low-complexity and low-energy circuits. However, current readout strategies for resistive sensor arrays require additional electrical components, such as transistors, diodes, multiplexers, op-amps, switches, current sources, and A/D converters, leading to a considerable increase in circuit complexity, power consumption, system instability, and crosstalk error. To address the problem, this paper proposes a new approach, which determines sensor resistance values by establishing and solving resistance matrix equations of sensor arrays. Unlike conventional approaches, it allows crosstalk currents in arrays to avoid additional components that are originally used for eliminating crosstalk currents and minimizing crosstalk error. Meanwhile, it takes advantage of on-chip resources of wearable platforms, thereby reducing redundant chips. It was implemented on a prototype of $10times 10$ textile resistive sensor array, which was taken in a sensing cushion for sitting pressure monitoring of chair bound people. Experimental results on this array platform showed the new approach achieved a satisfactory accuracy (0.61% ± 0.41%), as well as a low crosstalk error (2.77% ± 0.61%). The fabricated sensing cushion also exhibited a relatively low pressure measurement error (6.30% ± 0.75%). Compared with other approaches, the proposed approach demonstrated the lowest circuit complexity on a microcontroller based wearable platform, and a sufficient sensor capacity. It is ideal for a wide range of applications like wearable or implantable sensing, presenting a reference for the design of low-complexity and low-crosstalk error wearable systems based on resistive sensor arrays.

Description: In this letter, we consider the problem of distributed Bayesian detection in the presence of Byzantine data. The problem of distributed detection is formulated as a binary hypothesis test at the fusion center (FC) based on 1-bit data sent by the sensors. Adopting Chernoff information as our performance metric, we study the detection performance of the system under Byzantine attack in the asymptotic regime. The expression for minimum attacking power required by the Byzantines to blind the FC is obtained. More specifically, we show that above a certain fraction of Byzantine attackers in the network, the detection scheme becomes completely incapable of utilizing the sensor data for detection. When the fraction of Byzantines is not sufficient to blind the FC, we also provide closed form expressions for the optimal attacking strategies for the Byzantines that most degrade the detection performance.

Description: This letter examines a variation of the canonical distributed detection system: a sensor may overhear other sensors’ transmissions and thus may choose to refine its output in the hope of achieving a better detection performance. We show that while this is indeed possible for the fixed sample size test, asymptotically (in the number of samples) there is no performance gain, as measured by the Kullback-Leibler distance achievable at the fusion center, provided that the observations are conditionally independent. For conditionally dependent observations, however, we demonstrate that asymptotic detection performance may indeed be improved when overhearing is utilized.

Description: Conventional speech enhancement methods typically utilize the noisy phase spectrum for signal reconstruction. This letter presents a novel method to estimate the clean speech phase spectrum, given the noisy speech observation in single-channel speech enhancement. The proposed method relies on the phase decomposition of the instantaneous noisy phase spectrum followed by temporal smoothing in order to reduce the large variance of noisy phase, and consequently reconstructs an enhanced instantaneous phase spectrum for signal reconstruction. The effectiveness of the proposed method is evaluated in two ways: phase enhancement-only and by quantifying the additional improvement on top of the conventional amplitude enhancement scheme where noisy phase is often used in signal reconstruction. The instrumental metrics predict a consistent improvement in perceived speech quality and speech intelligibility when the noisy phase is enhanced using the proposed phase estimation method.

Description: In this paper, we present the design of an intelligent monitoring system consisting of physical sensors and intelligent software for the automatic identification of the concentration of natural gas odorants in the environment. An optical-based sensor array was proposed comprising the hardware module. The software module employs wavelets filters and artificial neural networks to recognize the concentration of odorant in a natural gas sample. The objective is to help the natural gas odorization process by means of end point monitoring through the recognizing of the odorant concentration. The recognizing process uses a benchmark index, which measures the degrees of human perception of gas in the environment. In this way, the proposed system tries to mimic the human perception of a natural gas leak and helps one to indicate if more or less amount of odorant should be added into the gas pipeline. Experiments were conducted comparing the performance of the system with human performance, which is normally used to deal with this problem. The proposed system demonstrated promising results and improvements are presented.

Description: We consider the classical 1D phase retrieval problem. In order to overcome the difficulties associated with phase retrieval from measurements of the Fourier magnitude, we treat recovery from the magnitude of the short-time Fourier transform (STFT). We first show that the redundancy offered by the STFT enables unique recovery for arbitrary nonvanishing inputs, under mild conditions. An efficient algorithm for recovery of a sparse input from the STFT magnitude is then suggested, based on an adaptation of the recently proposed GESPAR algorithm. We demonstrate through simulations that using the STFT leads to improved performance over recovery from the oversampled Fourier magnitude with the same number of measurements.

Description: In the aforementioned letter, the authors indicate that with a $2M + 1$ sensor uniform linear array (ULA), up to $2M - 1$ sources can actually be localized by the proposed algorithm. In this comment, however, we prove that the algorithm will no longer be valid if the number of sources exceeds $M$ . A numerical simulation is performed to verify this conclusion.

Description: Mode characteristics of AlGaInAs/InP square resonator microlasers laterally confined by a bisbenzocyclobutene layer, with an output waveguide connected to one vertex or the midpoint of one side, are investigated numerically and experimentally. Numerical simulation results indicate that the square resonator with the midpoint output waveguide has a better single-mode property, but a lower mode ({Q}) -factor than that with the vertex output waveguide. For a 20- (mu ) m-side-length square microlaser with a 1.5- (mu ) m-wide vertex output waveguide, lasing spectra with multiple transverse modes are observed with the mode wavelength intervals agreeing with the 2-D-finite difference time domain simulation results. In contrast, single-mode operation with a side-mode suppression ratio of 42 dB is obtained for a 20- (mu ) m-side-length square microlaser with a 1.5- (mu ) m-wide midpoint output waveguide. The results indicate that output waveguide can result in a mode selection in addition to realizing unidirectional emission.

Description: Properly designed oxide-confined vertical cavity surface emitting laser (VCSEL) allows leakage of the optical modes from the all-semiconductor core region to the selectively oxidized periphery if the orthogonality between the core mode and the modes on the periphery is broken by the oxidation-induced optical field redistribution. The leakage losses are stronger for high-order transverse modes, which have a higher field intensity close to the oxidized region. Single mode lasing in the fundamental mode can thus proceed up to large aperture diameters. The 850-nm GaAlAs thick oxide aperture VCSEL based on this concept is designed, modeled, and fabricated, showing single-mode lasing with the aperture diameters up to 5 (mu mathrm {m}) . Side mode suppression ratio >20 dB is realized at the current density of (sim 10) kA/cm (^{2}) in devices with the series resistance of 90 (Omega ) .

Description: A GaN-based light-emitting diode (LED) grown on a nanocomb-shaped patterned sapphire substrate (PSS) is fabricated and studied. Nanocomb-shaped patterns are transferred on a sapphire substrate using a well-ordered anodized aluminum oxide (AAO) thin film as a mask for the inductively coupled plasma etching process. This well-ordered AAO thin film with a high aspect ratio is grown on a sapphire substrate by an oxalic acid-based electrochemical system and a three-step anodization. The strain state generated during epitaxial growth could be effectively alleviated by the use of nanocomb-shaped PSS. The treading dislocation density could be reduced. Thus, the enhanced crystalline quality is obtained. In addition, due to the presence of photonic crystal-like air buffer layer, part of reflected photons upward the top side could be scattered by this layer. Therefore, more photons could be extracted outside. Experimentally, at 20 mA, as compared with a conventional LED grown on a planar sapphire substrate, the studied LED grown on a nanocomb-shaped PSS shows 53.8% and 43.7% enhancements in light output power and external quantum efficiency as well as a reduced leakage current.

Description: This paper presents a novel example-based single-image superresolution procedure that upscales to high-resolution (HR) a given low-resolution (LR) input image without relying on an external dictionary of image examples. The dictionary instead is built from the LR input image itself, by generating a double pyramid of recursively scaled, and subsequently interpolated, images, from which self-examples are extracted. The upscaling procedure is multipass, i.e., the output image is constructed by means of gradual increases, and consists in learning special linear mapping functions on this double pyramid, as many as the number of patches in the current image to upscale. More precisely, for each LR patch, similar self-examples are found, and, because of them, a linear function is learned to directly map it into its HR version. Iterative back projection is also employed to ensure consistency at each pass of the procedure. Extensive experiments and comparisons with other state-of-the-art methods, based both on external and internal dictionaries, show that our algorithm can produce visually pleasant upscalings, with sharp edges and well reconstructed details. Moreover, when considering objective metrics, such as Peak signal-to-noise ratio and Structural similarity, our method turns out to give the best performance.

Description: Bag-of-features (BoFs) representation has been extensively applied to deal with various computer vision applications. To extract discriminative and descriptive BoF, one important step is to learn a good dictionary to minimize the quantization loss between local features and codewords. While most existing visual dictionary learning approaches are engaged with unsupervised feature quantization, the latest trend has turned to supervised learning by harnessing the semantic labels of images or regions. However, such labels are typically too expensive to acquire, which restricts the scalability of supervised dictionary learning approaches. In this paper, we propose to leverage image attributes to weakly supervise the dictionary learning procedure without requiring any actual labels. As a key contribution, our approach establishes a generative hidden Markov random field (HMRF), which models the quantized codewords as the observed states and the image attributes as the hidden states, respectively. Dictionary learning is then performed by supervised grouping the observed states, where the supervised information is stemmed from the hidden states of the HMRF. In such a way, the proposed dictionary learning approach incorporates the image attributes to learn a semantic-preserving BoF representation without any genuine supervision. Experiments in large-scale image retrieval and classification tasks corroborate that our approach significantly outperforms the state-of-the-art unsupervised dictionary learning approaches.

Description: In image classification, recognition or retrieval systems, image contents are commonly described by global features. However, the global features generally contain noise from the background, occlusion, or irrelevant objects in the images. Thus, only part of the global feature elements is informative for describing the objects of interest and useful for the image analysis tasks. In this paper, we propose algorithms to automatically discover the subgroups of highly correlated feature elements within predefined global features. To this end, we first propose a novel mixture sparse regression (MSR) method, which groups the elements of a single vector according to the membership conveyed by their sparse regression coefficients. Based on MSR, we proceed to develop the autogrouped sparse representation (ASR), which groups correlated feature elements together through fusing their individual sparse representations over multiple samples. We apply ASR/MSR in two practical visual analysis tasks: 1) multilabel image classification and 2) motion segmentation. Comprehensive experimental evaluations show that our proposed methods are able to achieve superior performance compared with the state-of-the-art classification on these two tasks.