ALBERT

Description: Gold nanorods (GNRs) with surface plasmon resonance peak at 1063.8 nm were fabricated and experimentally exploited as the single and combined saturable absorber (SA) in a $Q$ -switched Nd:YAG laser for the first time. In the situation using GNRs as a single SA, the maximum pulse energy of 19 $muhbox{J} $ was achieved at a pulse repetition rate of 20 kHz. However, due to the small effective modulation depth of the GNRs, microsecond pulses were generated in such a GNRs-based passively $Q$ -switched laser. A novel configuration using GNRs as a combined SA in an acoustooptic $Q$ -switched Nd:YAG laser was proposed. The small nonlinear loss modulation induced by the GNRs played a distinctive role in flexibly manipulating the nanosecond pulse waveforms. Our study demonstrated the feasibility of generating high-energy pulses by singly using GNRs-based SA in all solid-state lasers. Meanwhile, a new application mode incorporating GNRs as a combined SA was studied, providing an alternative method to take advantage of the nanomaterial-based SA with a relatively small modulation depth.

Description: Commercial, industrial, and military aerospace designs are increasingly deploying MEMS micro inertial measurement unit (MIMU) for motion control, automation, and positioning applications, such as the unmanned aerial vehicle (UAV), robot, and smart phone. On the one hand, MIMU has the merit of low cost, small size, low-power consumption, and high shock resistance, but on the other hand, low-cost MIMU is affected by systematic error caused by the instability of the drift, scaling factors, and axes misalignment, which may lead to large errors in the position and attitude’s determination from time to time. That means calibration before use is an effective way to improve the practical precision of MIMU. However, many customers have no precise turntable to calibrate the MIMU before they use it. To address these problems, this paper presents an easy self-calibration method to implement calibration of the MIMU on a common table only with an inclined surface, no precise turntable is needed. The calibration method is based on the following principles. First, the module of the output vector of the orthogonal configured three-axis accelerometers is equal to unit gravity. Second, when IMU rotates to a known gesture with a stable axis, the angles can be calculated through integration. Third, when the accelerometers’ parameters are calculated, it can act as a level datum. Furthermore, the accelerometers on the inclined surface are used to determine the rotating heading datum. Finally, after a series static positions test and rotating test, the parameters can be extracted and estimated. To demonstrate the success and the convenience of the proposed method, comparison experiments with the precision turntable have been made on an ADI’s MIMU. The calibration results show that the accuracy and precision of this method is quite equivalent with the turntable-based calibration, and the scale factors error with an order of magnitude always equal or less than $10^{-5}$ . The observed static and dynamic yaw maximum angular error in a certain period is <0.8°, the pitch maximum angular error is <0.5°, and the roll maximum angular error is <0.3°.

Description: Time–frequency packing (TFP) transmission provides the highest achievable spectral efficiency with a constrained symbol alphabet and detector complexity. In this paper, the application of the TFP technique to fiber-optic systems is investigated and experimentally demonstrated. The main theoretical aspects, design guidelines, and implementation issues are discussed, focusing on those aspects which are peculiar to TFP systems. In particular, adaptive compensation of propagation impairments, matched filtering, and maximum a posteriori probability detection are obtained by a combination of a two-dimensional equalizer and four eight-state parallel Bahl–Cocke–Jelinek–Raviv (BCJR) detectors. A novel algorithm that ensures adaptive equalization, channel estimation, and a proper distribution of tasks between the equalizer and BCJR detectors is proposed. A set of irregular low-density parity-check codes with different rates is designed to operate at low error rates and approach the spectral efficiency limit achievable by TFP at different signal-to-noise ratios. An experimental demonstration of the designed system is finally provided with five dual-polarization QPSK-modulated optical carriers, densely packed in a 100-GHz bandwidth, employing a recirculating loop to test the performance of the system at different transmission distances.

Description: We investigated nonlinear optical characteristics of Tungsten disulfide (WS 2 ) films and experimentally demonstrated their high potential for application as nonlinear saturable absorbers in passively mode-locked fiber lasers. Side polished fiber (SPF) was fabricated and WS 2 film was overlaid to provide an efficient evanescent field interaction. The WS 2 film was prepared using two methods: liquid phase exfoliation to form few-layer nano-sheets, and chemical vapor deposition (CVD) to grow uniform multilayer WS 2 on a SiO 2 substrate. Two SPF saturable absorbers were prepared by either spin coating WS 2 solution or lifting off the multilayer CVD WS 2 on SPF. An all-fiber ring cavity was built and the WS 2 film overlaid on SPF was employed as a mode locker along with Er-doped fiber as a gain medium. Using the spin-coated WS 2 SPF, stable soliton-like pulses were generated with a spectral width of 5.6 nm and 467 fs pulse duration. The fiber laser cavity containing CVD WS2 SPF generated a transform-limited soliton pulse train with a spectral width of 8.23 nm and a pulse duration of 332 fs. Our study confirmed a high potential of WS 2 film as a novel 2-D nonlinear optical material for laser applications.

Description: We propose and experimentally demonstrate an on-chip all-optical differential-equation solver capable of solving second-order ordinary differential equations (ODEs) characterizing continuous-time linear time-invariant systems. The photonic device is implemented by a self-coupled microresonator on a silicon-on-insulator platform with mutual coupling between the cavity modes. Owing to the mutual mode coupling within the same resonant cavity, the resonance wavelengths induced by different cavity modes are self-aligned, thus avoiding precise wavelength alignment and unequal thermal wavelength drifts as in the case of cascaded resonators. By changing the mutual mode coupling strength, the proposed device can be used to solve second-order ODEs with tunable coefficients. System demonstration using the fabricated device is carried out for 10-Gb/s optical Gaussian and super-Gaussian input pulses. The experimental results are in good agreement with theoretical predictions of the solutions, which verify the feasibility of the fabricated device as a tunable second-order photonic ODE solver.

Description: We demonstrate a 100 Gb/s short reach system using a multicarrier transmitter based on a gain switched monolithically integrated laser. An optical comb source with 12.5-GHz free spectral range is achieved by gain-switching an integrated passive feedback laser. The 100 Gb/s wavelength division multiplexed, single sideband, direct detection, orthogonal frequency division multiplexed (WDM-SSB-DD-OFDM) system operates over 25 km standard single mode fiber exhibiting a spectral efficiency of 1.8 b/s/Hz. Receiver sensitivity of –14.2 dBm is achieved after 25 km transmission. Performance optimization with phase and amplitude precompensation is employed to improve the SSB OFDM modulation thereby reducing the interchannel interference and overcoming the power fading induced by the optical filter. We also present a theoretical analysis of the SSB-OFDM modulation.

Description: In this paper, narrow-band emission lines are generated by means of two random distributed feedback fiber laser schemes. Spectral line-widths as narrow as 3.2 pm have been measured, which significantly improves previous reported results. The laser is analyzed with the aim of obtaining a spectral line-width as narrow as possible. Additionally a variation of this setup for multi-wavelength operation is also validated. Both schemes present a simple topology that use a combination of phase-shifted fiber Bragg gratings and regular fiber Bragg gratings as filtering elements.

Description: We report on the fabrication and characterization of 19-cell hypocycloid-shape Kagome fibers with core size larger than 100 μm. These inhibited coupling fibers present low propagation loss (100 dB/km) over broad transmission range with low chromatic dispersion combined with ultra-low power overlap with silica surround, making them an efficient solution for ultra-high power laser handling, ultra-fast laser delivery, and plasma photonics applications.

Description: The iterative demodulation and decoding algorithm introduced in 2005 by Colavolpe, Barbieri, and Caire to cope with channels affected by phase noise needs pilot symbols to bootstrap. However, pilot symbols reduce the spectral efficiency of the system and, consequently, system's throughput. The aim of this paper is to show that trellis-based demodulation can be used to bootstrap the iterative process without the need of pilot symbols. Also, the complexity issue of trellis-based demodulation is addressed in this paper. The result is that the performance of iterative demodulation and decoding after the iterations is virtually unaffected by complexity reduction, provided that the reduced-complexity demodulator guarantees cycle-slip-free operation. From the numerical results presented in this paper, we show that cycle-slip-free operation can be achieved with substantial complexity reduction also for phase noise associated with linewidths of practical interest.

Description: The optical pulse evolution in a highly nonlinear normal dispersion-increasing fiber has been considered, both experimentally and theoretically. It was found that large spectral broadening in tapered waveguides could occur without temporal instabilities and impose the linear frequency modulation, i.e., chirp, required for high-quality pulse compression. The pedestal-free pulses have been demonstrated after dechirping in a standard single-mode fiber.

Description: This work proposes a novel localized surface plasmon resonance (LSPR) biochemical sensor featuring high sensitivity and a high resolution. The sensor was divided into two subcomponents according to their distinct functions; namely, single-mode fiber and metal array. Single-mode fibers located on the left and right sides of the sensors function as the input and output for optical fiber signals. A metal array comprising an arrangement of cylindrical nanometal particles served as the detection area of the sensor. To effectively reduce the memory capacity and calculation time, two innovative techniques (i.e., object meshing and boundary meshing) were integrated with the finite element method. With the area of the triangular elements used as a basis, the object boundary, small object, medium object, and large objects were meshed at a ratio of 1:8:160:1600. The improved numerical simulation methods and six design procedures were adopted to develop and analyze the proposed LSPR biochemical sensor. The results show that the novel LSPR biochemical sensor outperformed two current high-performance biochemical sensors and provided additional advantages such as short length (approximately 430 μm), high resolution (approximately –120 dB), and high sensitivity (approximately 127 604 nm/RIU).

Description: We propose an ultra-broadband super light absorber by integrating different-sized tapered hyperbolic metamaterial (HMM) waveguides, each of which has a different and wide absorption band due to broadband slow-light response, into a unit cell. We numerically demonstrate that such an absorber is superior to a single-sized HMM absorber in terms of absorption bandwidth, while maintaining a comparable absorption efficiency. A three different-sized HMM absorber presents the capability of working with an ultra-wide frequency band ranging from 1 to 30 THz, which is much larger than previously proposed absorbers working in the same spectral region. Such a design shows great promise for a broad range of applications such as thermal emitters, photovoltaics, optical-chemical energy harvesting, and stealth technology, where ultra-wideband absorption is in very high demand.

Description: This paper proposes a ring-based integrated wireless optical network architecture and an associated protocol that involves Ethernet passive optical network (EPON) and long term evolution (LTE) wireless network. The architecture along with the proposed protocol is instrumental toward the reduction of handover delay. The proposed ring-based EPON architecture facilitates the implementation of the X2 interface for LTE network by enabling the optical network units of the EPON backhaul to directly communicate with each other. The work further discusses about an open access network architecture where a single EPON can be used by multiple mobile service providers without compromising information security. Extensive simulations have been carried out to evaluate the performance of the proposed network. An analytical model has been introduced to calculate the queuing delay experienced by the X2 interface. The model has been validated with the simulations results.

Description: High spectrum efficiency and fast restoration speed are highly desired for survivable elastic optical networks (EONs). In this paper, we take the advantages of failure-independent path-protecting preconfigured cycles (FIPP p -cycles) and investigate how to realize spectrum efficient resilience design with them. We first study the problem of offline service provisioning with FIPP p -cycles. We formulate an integer linear programming model and prove that the problem is $mathcal{NP}$ hard. Then, several time-efficient heuristics are designed for FIPP p -cycle formulation and related routing, modulation format, and spectrum assignment. Extensive simulations on offline provisioning verify that the heuristics can obtain near-optimal solutions. Next, we consider online service provisioning with FIPP p -cycles in dynamic EONs. In order to overcome the decrease of protection efficiency during dynamic network operation, we propose a p -cycle reconfiguration scheme to reoptimize protection structures on-the-fly. Simulation results demonstrate that the proposed algorithms can improve spectrum efficiency and reduce bandwidth blocking probability simultaneously.

Description: Photo-thermo-refractive (PTR) glasses are the class of polyfunctional materials that combine the properties of several monofunctional materials such as photo-refractive, laser, luminescent, and plasmonic ones. Based on PTR glasses, various diffractive holographic elements and photonic devices were developed in both the volume and fiber versions. In this paper, the fabrication of optical planar waveguides on PTR glass by low-temperature ion exchange is reported for the first time. Planar waveguides were fabricated through substituting the sodium ions in glass by silver, potassium, rubidium, and cesium ones from the nitrate melts. The silver waveguides were shown to have the largest depth (27 μm) and reveal no birefringence. For the silver waveguides, an increase in the refractive index is caused by differences in the polarizabilities of cations exchanged. The maximum increment of the refractive index was observed in the cesium waveguides (0.0512). An increase in the refractive index and also appearing the birefringence in potassium, rubidium, and cesium waveguides are found to be due to the compressive mechanical stresses and their relaxation. The potentialities of the ion exchange technology for fabricating, in PTR glasses, planar gradient waveguides with low losses (0.5 dB/cm) are demonstrated, the potentialities extending the application field of PTR glasses in photonics.

Description: A multi-sensor addressing method for fiber Bragg grating aided fiber loop ringdown (FBG-FLRD) sensor array is proposed. It is capable of simultaneous measurement of temperature and force. Light from a wavelength-swept fiber laser (WSFL) is modulated into pulsed light to illuminate FBG-FLRD sensor array. Based on the time sequence of pulsed lights reflected by fiber Bragg grating array, each FBG-FLRD sensor can be distinguished. The time interval between the trigger signal of the WSFL and the pulsed light reflected by FBG offers temperature variation information. By measuring the ringdown time of each FBG-FLRD, the loss of fiber ring induced by temperature and force can be obtained. And then simultaneous measurement can be implemented in real time. To prove the validity of the proposed system, a six elements array is experimentally validated with interrogation frequency of 27.5 Hz.

Description: Low-energy technologies in the Internet of Things (IoTs) era are still unable to provide the reliability needed by the industrial world, particularly in terms of the wireless operation that pervasive deployments demand. While the industrial wireless performance has achieved an acceptable degree in communications, it is no easy task to determine an efficient energy-dimensioning of the device in order to meet the application requirements. This is especially true in the face of the uncertainty inherent in energy harvesting. Thus, it is of utmost importance to model and dimension the energy consumption of the IoT applications at the pre-deployment or pre-production stages, especially when considering critical factors, such as reduced cost, life-time, and available energy. This paper presents a comprehensive model for the power consumption of wireless sensor nodes. The model takes a system-level perspective to account for all energy expenditures: communications, acquisition and processing. Furthermore, it is based only on parameters that can empirically be quantified once the platform (i.e., technology) and the application (i.e., operating conditions) are defined. This results in a new framework for studying and analyzing the energy life-cycles in applications, and it is suitable for determining in advance the specific weight of application parameters, as well as for understanding the tolerance margins and tradeoffs in the system.

Description: With the development of Internet of Things (IoT), a large amount of machine-to-machine (M2M) devices produce the data from a huge number of M2M communications. A massive access congestion control scheme in M2M communication is important in a wireless M2M network, where a wireless M2M network is constituted by a large number of wireless M2M devices. In this paper, we developed a spiderweb-based massive access management protocol for M2M wireless networks. The wireless M2M network topology considered, in this paper, is a spiderweb-based topology, which belongs to a regular topology. The spiderweb-based topology is split into a number of sub-spiderweb, while each sub-spiderweb can be seen as a small reservoir. The main function of the small reservoir is to temporarily store the massive access if the congestion problem is occurred due to the massive assess has been suddenly happened from the M2M devices. When the congestion problem is alleviated gradually, the temporarily-stored massive assess can be digested from these small reservoirs. The contribution of the proposed scheme is to reduce the packet loss rate and prolong the wireless M2M network lifetime. In addition, a dynamically adjustment of the different sub-spiderweb size is developed based on the amount of different data traffics. Simulation result finally illustrates that the proposed mechanism significantly reduces the packet loss rate and keeps the maximum network lifetime.

Description: The paper presents the methodology including the deployment of a structure comprising of C-clamp magnetic stripes and a self-calibration scheme using a four-coil design to resolve the issues of the interference and misplacement problems existing in the flexible nonintrusive current sensor tag for the current detection of household two-wire power lines. Experimental results show that the stripe structure can effectively screen out the magnetic flux originating from the nearby power line for the reduction of sensing error caused by the electromagnetic field interference and the calibration scheme containing the correction of horizontal misplacement and the analysis of power cable thickness via the four-coil design can provide the information of sensor location for accurate current sensing. Less than 4% of sensing error indicates that the proposed methodology can indeed facilitate the flexible current sensor tag for practical use.

Description: Rapidly emerging batteryless sensors are creating tremendous opportunities for truly wearable sensors for activity recognition. However, data streams from such sensors are characterized by sparsity and noise, which make activity recognition a challenging task. In this paper, we study the feasibility of passive computational RFID sensors for ambulatory monitoring. In particular, we focus on recognizing transfers out of beds or chairs and walking. Ideally, all these activities need to be monitored by movement sensor alarm systems to alert caregivers to provide supervision during the ambulation of older people in hospitals and nursing homes to prevent a fall. Our novel approach to partition continuous sensor data on natural activity boundaries and to identify transfers out of beds or chairs and walking as transitions between sequences of movements overcomes issues posed by the sparsity and the noise. We demonstrate through in-depth experiments the high performance (F-score > 93%) and the responsiveness of our approach.

Description: A common-mode (CM) active filter was designed in a compact package to suppress CM conducted emissions at a switching mode power supply (SMPS). Based on the analytical expressions considering both stability and performance, the design and optimization rules for the proposed active filter have been presented. After verifying its performance by measurements using vector network analysis, the proposed filter was installed in a 200-W SMPS board with 64 and 110 kHz switching frequencies, demonstrating its usefulness by experiments. The performance degradation due to the magnetic saturation and the AEF grounding impedance was also analyzed and investigated.

Description: This paper proposes an approach to design multiple-input multiple-output radar waveforms that are orthogonal on both the transmitter and receiver. The proposed method jointly utilizes the direct sequence spread spectrum coding and orthogonal frequency division multiplexing (OFDM) chirp signaling techniques. We name it spread spectrum-coded OFDM chirp waveform diversity design. The performance of the designed waveforms is analyzed by examining the ambiguity function and correlation function. The influences of the spread spectrum code choice and the OFDM chirp parameters are also investigated. It is verified that the proposed design scheme can ensure these waveforms stay orthogonal on the receiver and have large time-bandwidth product which is beneficial to separate closely spaced targets.

Description: Studies have presented that the driver vigilance level has serious implication in the causation of road accidents. This paper focuses on integrating both the vehicle-based control behavior and physiological state to predict the driver vigilance index which is evaluated by using a smartwatch. The vehicle control behavior can be observed from the steering wheel movement. Our study utilized the smartwatch motion sensors to study the steering wheel behavior. Meanwhile, physiological state of driver reflects the driver capability of safety alert driving which is estimated by photoplethysmogram (PPG) and respiration signals in this paper. The PPG sensor is integrated in a sport wristband with a Bluetooth low energy module, transmitted the PPG signals to smartwatch in real time. The steering angle is derived by the reading from smartwatch built-in accelerometer and gyroscope sensors. On the other hand, the respiration is derived using the PPG peak baseline method. In order to utterly investigate the sleepiness-induced factors, the time, spectral, and phase space domain features are calculated. Considering the smartwatch processing capability, mutual-information technique is applied to designate the ten most descriptive features. Then, the extracted descriptive features are serve as parameters to a classifier to determine the driver aptitude status. The features are analyzed for their correlation with the subjective Koralinska sleepiness scale and through recorded video observations. The experimental results reveal that our system is capable of estimating driver hypervigilance at average of 96.5% accuracy rate by evaluating on both driving behavior and driver physiological state, provided a novel and low-cost implementation.

Description: A cavitating two-phase flow of water in a pipe with area shrinkage was experimentally investigated, acquiring at high sampling rate pressure signals and images of the cavitating flow field. The time series of the pressure fluctuations was analyzed in terms of power spectral density and related to the cavitation regimes. Furthermore, the fluctuations of the pressure measurements were also decomposed using the wavelet transform to analyze the frequency distribution of the signals energy with respect to the flow behavior. The energy content at each frequency band of the acquire signals is well related to cavitation flow-field behavior. Moreover, the artificial neural network and the least squares support vector machine (LS-SVM) were implemented to identify the cavitation regime, using, as inputs, the power spectral density distributions of the pressure fluctuations, and some features of the decomposed signals, as the wavelet energy for each decomposition level and wavelet entropy. Results indicate the most accurate model to be used in the cavitation regime identification, underlining the enhanced capability of LS-SVM trained with the input data set based on the wavelet decomposition features.

Description: In this paper, we present a novel silicon-on-insulator (SOI) complementary metal–oxide–semiconductor (CMOS) microelectromechanical-system thermal wall shear stress sensor based on a tungsten hot-wire and a single thermopile. Devices were fabricated using a commercial 1- $mu text{m}$ SOI-CMOS process followed by a deep reactive ion etching back-etch step to release a silicon dioxide membrane, which mechanically supports and thermally isolates heating and sensing elements. The sensors show an electrothermal transduction efficiency of $50~mu text{W}$ /°C, and a very small zero flow offset. Calibration for wall shear stress measurement in air in the range of 0–0.48 Pa was performed using a suction type, 2-D flow wind tunnel. The sensors were found to be extremely sensitive, up to 4 V/Pa for low wall shear stress values. Furthermore, we demonstrate the superior signal-to-noise ratio (up to five times higher) of a single thermopile readout configuration compared with a double thermopile readout configuration (embedded for comparison purposes within the same device). Finally, we verify that the output of the sensor is proportional to the cube root of the wall shear stress and we propose an accurate semiempirical formula for its modeling.

Description: A kind of low-cost electric and magnetic field simulators, which are used to produce simulative lightning electromagnetic pulse (LEMP) with adjustable waveforms and intensity output, are presented. The lightning electric field can be produced within the GTEM cell by feed-in of impulse voltage output by a Marx generator. The lightning magnetic field can be produced within the coil by feed-in of surge current from the lightning surge generator. The simulated magnetic field is measured by a “B-dot” coil. The measured results show that the lightning electric field simulator and magnetic field simulator could provide relatively homogeneous LEMP environment within certain area in the GTEM cell and the coil within 3 dB deviation. The effects of the simulated lightning electric fields on some electronic devices and the influence of the turns and size of the coil on the homogeneity of the simulated magnetic fields are also investigated.

Description: This paper presents a detailed model of devices utilizing many nanotubes and the coupling between them based on the electromagnetic model of a device using one nanotube. Empirical equations are proposed to link the device conductance with the number of nanotubes per device. Then, a circuit model is developed to predict the effect of the number of nanotubes per device on the overall conductance, capacitance, and the frequency response of the device. A prototype structure is fabricated. Its performance is tested and compared with the proposed model, and it shows promising agreements. The model is flexible and can be integrated with quantum transport models.

Description: A full-wave analysis of the fundamental quasi-TEM modes supported by multiple graphene nanoribbons above a ground plane is presented, aimed at characterizing crosstalk in graphene multiconductor lines. A method-of-moments discretization of the relevant electric-field integral equation is performed. Assuming first a local scalar conductivity, an efficient spatial-domain approach with subsectional basis functions is assuming first a local scalar conductivity, a spatial-domain approach with subsectional basis functions is developed. This allows for the efficient treatment of nanoribbons with wide transverse separations, and can be expanded to include in the simulation model spatial nonuniformity of the graphene conductivity. This spatial-domain formulation is then extended to treat the case of weakly nonlocal conductivity, via an original integro-differential approach derived by approximating a recent full spectral graphene conductivity model in the limit of low wavenumbers. Numerical results are provided for propagation constants and characteristic impedances of two identical coupled graphene nanoribbons; on this basis, a crosstalk analysis is performed by means of the modal decomposition method.

Description: We propose an optical fiber hydrostatic pressure sensor based on micro-cavities generated by the fiber fuse effect. The presented sensor is manufactured through the recycling of optical fiber destroyed by the fiber fuse effect, being, therefore, a cost-effective solution, when compared with other similar micro-cavity-based solutions. The developed sensor was characterized for pressures up to 20 kPa, showing a linear sensitivity coefficient of $0.47pm 0.03~{rm nm}cdot {rm kPa}^{-1}$ , for pressure values below 8 kPa. Furthermore, we propose a new theoretical model to describe the behavior of the microcavities embedded in optical fibers. This allows us to solve the discrepancies, already identified by other authors, between the experimental results and the ones attained with the flat mirrors Fabry-Perot model. By this way, we were able to describe the sensor response, within the full dynamic range.

Description: The monitoring and control of crops in precision agriculture sometimes requires a high collection frequency of information (e.g., temperature, humidity, and salinity) due to the variability in crops. Data acquisition and transmission are generally achieved thanks to wireless sensor networks. However, sensor nodes have limited resources. Thus, it is necessary to adapt the increase in sampling frequency for different crops, under application constraints (reliability, packet delay, and lifetime duration). In this paper, we propose to properly tune IEEE 802.15.4 MAC parameters ( macMinBE and macMaxCSMABackoffs ) and the sampling frequency of deployed sensor nodes. An analytical model of network performance is derived and used to perform the tuning of these tradeoff parameters. Simulation analysis shows that our scheme provides an efficient increase of sampling frequency of sensor nodes while satisfying application requirements.

Description: Sensors based on the magnetoelectric (ME) effect have the potential to be genuine alternatives for measuring bio-magnetic signals. Unfortunately, the sensor structure usually inhibits the problem that several non-magnetic types of noise couple mechanically into the sensor: in this contribution, we will focus on undesired acoustic coupling. Therefore, an adaptive cancellation approach based on a computationally efficient gradient estimation algorithm with a pseudo-optimally control scheme is proposed. The approach is using a microphone as a noise reference sensor and is implemented in real time. An evaluation in terms of measurements is performed inside a magnetically shielded chamber. For a particular scenario, which is characterized by double excitation, an algorithm with binary control-scheme improves the signal-to-noise ratio (SNR) only by around 4dB. If the proposed control scheme is used instead, an improvement of the SNR of around 13dB is achieved.

Description: Target detection is an important issue in the unattended ground sensors. In this paper, inspired by the idea of subspace-based direction of arrival estimation algorithms, a new target detection algorithm called subspace-based target detection (SBTD) is proposed to detect moving targets. The SBTD employs the SNR of the acoustic signals to decide whether moving targets are exiting or not. Although the SBTD has good detection performance, its cost maybe a little high for unattended sensors with low-cost hardware and long-term monitoring. To relieve the cost, we propose the hierarchical detection scheme and develop a two-stage detection method based on the SBTD for target detection in the wild, in which the first stage detection algorithm is chosen from current detection algorithms, while the second stage detection algorithm employs the SBTD. Experiments are conducted to verify the proposed detection method through acoustic signals gathered by the micro-electro-mechanical systems (MEMS) microphone array in the wild. Results show that the detector constructed by our two-stage detection method cannot only estimate the SNR of the acoustic signals but also can reduce the false alarm rate significantly with the detection rate almost unchanged in comparison with the detector chosen by its first-stage detection algorithm. The results indicate that a better detection performance is achieved in terms of the receiver operator characteristic curves.

Description: Crosstalk within cable bundles can degrade system performance. In aircraft systems that use shielded twisted pairs, the crosstalk occurs primarily in the connector where individual signal wires are not shielded or twisted. In many cases, the parameters which determine crosstalk within the connector are unknown because the connector is closed and wires cannot be easily accessed. Expanding on prior research [14] , a methodology for measuring coupling parameters and modeling crosstalk within aircraft cable connectors at low frequencies (〈400 MHz) was developed. The values of mutual inductance and capacitance were extracted from measurements made with a vector network analyzer (VNA). The characteristics of the individual wires were extracted from VNA-measured TDR response. The accuracy of the model was evaluated through comparison of simulated and measured results. Additionally, a closed-form solution was developed to estimate the worst-case envelope of the differential crosstalk. The calculated results match the measured peak values well. This worst-case crosstalk estimate allows effective evaluation of the impact of crosstalk within different connectors. The developed method can be effective for analyzing complex aircraft cable assemblies and connectors without requiring extensive knowledge of the assembly procedure.

Description: Surface roughness topography of printed circuit boards (PCBs) needs to be included in signal integrity simulations in order to accurately predict the insertion loss of the structure and its delay time. An effective roughness dielectric (ERD) model can be used to substitute an inhomogeneous interface between copper foil and laminate dielectric in a PCB. Herein, this approach is tested for verification using 3-D full-wave numerical simulations. These ERD layers with the appropriate complex permittivity are included in the modeling of stripline examples. The parameters of an ambient laminate dielectric refined from conductor roughness in the stripline are determined using differential extrapolation roughness measurement technique. The agreement of the results of 3-D full-wave modeling simulations and measurements on multiple test structures justifies the proposed approach. Based on the extracted ERD parameters “design curves” can be built and used in numerical simulations of PCB high-speed designs.

Description: Biometric systems provide a valuable service in helping to identify individuals from their stored personal details. Unfortunately, with the rapidly increasing use of such systems [1], there is a growing concern about the possible misuse of that information. To counteract the threat, the European Union (EU) has introduced comprehensive legislation [2] that seeks to regulate data collection and help strengthen an individual?s right to privacy. This article looks at the implications of the legislation for biometric system deployment. After an initial consideration of current privacy concerns, the definition of ?personal data? and its protection is examined in legislative terms. Also covered are the issues surrounding the storage of biometric data, including its accuracy, its security, and justification for what is collected. Finally, the privacy issues are illustrated through three biometric use cases: border security, online bank access control, and customer profiling in stores.

Description: The articles in this special section were conceived to champion recent developments in the rapidly evolving field of biometrics and also to encourage research in new signal processing solutions to security and privacy protection. Biometrics is the science of recognizing individuals based on their behavioral and biological characteristics such as face, fingerprints, iris, voice, gait, and signature. The past decade has witnessed a rapid increase in biometrics research in addition to the deployment of large-scale biometrics solutions in both civilian and law enforcement applications. Example applications that incorporate biometric recognition include: logical and physical access systems; surveillance operations to fight against fraud and organized crime; immigration control and border security systems; national identity programs; identity management systems; and the determination of friend or foe in military installations.

Description: A small amount of jitter can quickly eat up timing budgets and create timing issues. Precise characterization of deterministic and crosstalk-induced jitter can help isolate and solve issues within high-speed links. Characterizing deterministic and crosstalk-induced jitter is challenging, however, because many types of jitter work together to create the overall jitter profile. Methods are presented in this paper to characterize the deterministic and crosstalk-induced jitter from measurements of total jitter. An improved tail-fit deconvolution method is proposed for characterizing the impact of deterministic jitter in the presence of random jitter. The contribution of random jitter to total jitter is found first, and then that contribution is accounted for to find deterministic jitter. A Wiener filter deconvolution method is also presented for extracting the characteristics of crosstalk-induced jitter from measurements of total jitter made when the crosstalk sources were and were not present. The Wiener filter allows for accurate deconvolution of the measured histograms for total jitter even in the presence of the measurement noise. The proposed techniques are shown to work well both in simulations and in measurements of a high-speed link.

Description: This paper proposes a new control structure for tasks where explicit disturbance compensation is not only critical for overcoming poor feedback performance but is also challenging due to the complexity and nonrepetitive nature of the interaction between the plant and the environment. The approach proposed uses a particular form of iterative learning control (ILC) to estimate the previous disturbances, which are used as a preview of the disturbance in the next iteration. A disturbance observer is used to compensate for the difference between the ILC prediction and the true disturbance. The controller is evaluated and compared with a proportional controller, with ILC, and with an observer-based controller in extensive field trials using an automated excavator.

Description: This paper explored the possibility of building channel emulators by utilizing fused deposition modeling (FDM) three-dimensional (3-D) printing technology. The FDM 3-D printing provides a rapid and economic method to produce parts with different shapes. An optimizing algorithm was developed for obtaining the printing pattern and loss profile. Parts with different dielectric constants and loss tangents can be printed. Those parts will be placed or directly printed on a low-loss transmission line to modify its transmission or reflection. As a result, different channel emulators can be built to emulate the S -parameter and eye diagrams of a target channel with the advantage of avoiding complicated electronic components and only being limited in the frequency range by the transmission line and attached connectors.

Description: In this paper, we present general considerations for the application of the multiconductor transmission-line theory for simulating shielded spacecraft harness cable assemblies. Some of the practical issues that occur in the modeling process of various components of cable assemblies in spacecraft applications, namely connectors, pigtails, and backshells are discussed. The overall transfer impedance of the assembly measured through a current injection with a pseudomicrostrip line is used as a figure of merit to evaluate the total shielding provided by the harness. Some of the parameters of the model were available from the manufacturers’ datasheets, while others were determined either experimentally or empirically. The position of the cables along the cross section was randomly assigned by the simulation tool. In general, the obtained simulation results are found to be in reasonable agreement with the experimental data. It is found that the generally overlooked contact impedances between the cable shields and connectors play a significant role, especially at low frequencies. The presented simulation results also emphasize the importance of the inductance and resistance of the connector backshell interconnection to the spacecraft chassis.

Description: Encryptions are used in almost all standards to ensure the confidentiality of the data. Encryptions can be and indeed are implemented in the different layers of a network protocol stack. Conventional encryption performs the bitwise XOR operation between one message bit and one key stream bit to generate one ciphertext bit. Huo et al. have recently proposed to provide confidentialities on the user data by performing the phase encryption on the time domain OFDM samples in LTE system. Phase encryption is performed on the modulated symbols, different from the bit level of XOR encryption, i.e., stream cipher encryption. In this paper, we extend their study. We first generalize the phase encryption to general communication systems independent of the underlying modulation scheme. Then, we formulate the mathematical models for XOR and phase encryptions. Based on our model, we compare these two encryption methods in terms of their security and encryption efficiency. We also show phase encryption can resist traffic analysis attack when implemented in the physical layer. Finally, we conduct simulations to compare the performance of these two methods in terms of their decoding symbol error rate.

Description: In this paper, an adaptive hierarchical sparse grid collocation (ASGC) method combined with the discontinuous Galerkin time-domain method is leveraged to quantify the impacts of random parameters on the electromagnetics systems. The ASGC method approximates the stochastic observables of interest using interpolation functions over a set of collocation points determined by the Smolyak's algorithm integrated with an adaptive strategy. Instead of resorting to a full-tensor product sense, the Smolyak's algorithm constructs the collocation points in a hierarchical scheme with the interpolation level. Enhanced by an adaptive strategy, the Smolyak's algorithm will sample more points along important dimensions with sharp variations or discontinuities, resulting in a nonuniform sampling scheme. To flexibly handle different stochastic systems, either piecewise linear or Lagrange polynomial basis functions are applied. With these strategies, the number of collocation points is significantly reduced. The statistical knowledge of stochastic observables including the expected value, variance, probability density function, and cumulative distribution function are presented. The accuracy and robustness of the algorithm are demonstrated by various examples.

Description: Signal integrity (SI) analysis based on state-of-the-art measurements can be difficult to perform especially when the structures of interest are on inner layers of multilayer boards or are enclosed by IC packages. To enable an SI analysis in such cases the authors have recently developed a method that is based on the extraction of accurate simulation models from computed tomography (CT) scans. These models can be used in electromagnetic (EM) field simulators for computer-aided SI analyses. Such CT-based models include geometry variations or defects due to the manufacturing process so that computed EM field simulation results have a good correlation with common measurements. In order to identify the potential of the method an analysis of the required voxel resolution for the extraction of single-ended and differential striplines is presented. The analysis is based on the measurement uncertainty of length measurements in CT scans and an analysis of the propagation of uncertainty for the characteristic impedances of single-ended and differential striplines. This analysis shows that the voxel resolution of industrial CT scans is well suited for the extraction of accurate simulation models which can be used for an SI analysis.

Description: In the millimeter wave (mmW) frequency range, the root mean square height of the through silicon via (TSV) sidewall roughness is comparable to the skin depth, and hence, becomes a critical factor for TSV modeling and analysis. In this paper, the impact of the TSV sidewall roughness on electrical performance, such as the loss and impedance alteration in the mmW frequency range, is examined and analyzed. The second-order small analytical perturbation method is applied to obtain a simple closed-form expression for the power absorption enhancement factor of the TSV. In this study, we propose an electrical model of the TSV, which considers the TSV sidewall roughness effect, the skin effect, and the metal oxide semiconductor effect. The parameters of the proposed circuit model can be determined analytically; the accuracy of the model is validated through a comparison of circuit model behavior for full wave electromagnetic field simulations up to 100 GHz.

Description: Histopathological grading of cancer not only offers an insight to the patients’ prognosis but also helps in making individual treatment plans. Mitosis counts in histopathological slides play a crucial role for invasive breast cancer grading using the Nottingham grading system. Pathologists perform this grading by manual examinations of a few thousand images for each patient. Hence, finding the mitotic figures from these images is a tedious job and also prone to observer variability due to variations in the appearances of the mitotic cells. We propose a fast and accurate approach for automatic mitosis detection from histopathological images. We employ area morphological scale space for cell segmentation. The scale space is constructed in a novel manner by restricting the scales with the maximization of relative-entropy between the cells and the background. This results in precise cell segmentation. The segmented cells are classified in mitotic and non-mitotic category using the random forest classifier. Experiments show at least 12% improvement in $F_{1}$ score on more than 450 histopathological images at $40times $ magnification.

Description: This paper proposes a fast multi-band image fusion algorithm, which combines a high-spatial low-spectral resolution image and a low-spatial high-spectral resolution image. The well admitted forward model is explored to form the likelihoods of the observations. Maximizing the likelihoods leads to solving a Sylvester equation. By exploiting the properties of the circulant and downsampling matrices associated with the fusion problem, a closed-form solution for the corresponding Sylvester equation is obtained explicitly, getting rid of any iterative update step. Coupled with the alternating direction method of multipliers and the block coordinate descent method, the proposed algorithm can be easily generalized to incorporate prior information for the fusion problem, allowing a Bayesian estimator. Simulation results show that the proposed algorithm achieves the same performance as the existing algorithms with the advantage of significantly decreasing the computational complexity of these algorithms.

Description: In recent years, baggage screening at airports has included the use of dual-energy X-ray computed tomography (DECT), an advanced technology for nondestructive evaluation. The main challenge remains to reliably find and identify threat objects in the bag from DECT data. This task is particularly hard due to the wide variety of objects, the high clutter, and the presence of metal, which causes streaks and shading in the scanner images. Image noise and artifacts are generally much more severe than in medical CT and can lead to splitting of objects and inaccurate object labeling. The conventional approach performs object segmentation and material identification in two decoupled processes. Dual-energy information is typically not used for the segmentation, and object localization is not explicitly used to stabilize the material parameter estimates. We propose a novel learning-based framework for joint segmentation and identification of objects directly from volumetric DECT images, which is robust to streaks, noise and variability due to clutter. We focus on segmenting and identifying a small set of objects of interest with characteristics that are learned from training images, and consider everything else as background. We include data weighting to mitigate metal artifacts and incorporate an object boundary field to reduce object splitting. The overall formulation is posed as a multilabel discrete optimization problem and solved using an efficient graph-cut algorithm. We test the method on real data and show its potential for producing accurate labels of the objects of interest without splits in the presence of metal and clutter.

Description: Feature point matching is a fundamental and challenging problem in many computer vision applications. In this paper, a robust feature point matching algorithm named spatial order constraints bilateral-neighbor vote (SOCBV) is proposed to remove outliers for a set of matches (including outliers) between two images. A directed ${k}$ nearest neighbor ( knn ) graph of match sets is generated, and the problem of feature point matching is formulated as a binary discrimination problem. In the discrimination process, the class labeled matrix is built via the spatial order constraints defined on the edges that connect a point to its knn . Then, the posterior inlier class probability of each match is estimated with the knn density estimation and spatial order constraints. The vote of each match is determined by averaging all posterior class probabilities that originate from its associative inliers set and is used for removing outliers. The algorithm iteratively removes outliers from the directed graph and recomputes the votes until the stopping condition is satisfied. Compared with other popular algorithms, such as RANSAC, RSOC, GTM, SOC and WGTM, experiments under various testing data sets demonstrate strong robustness for the proposed algorithm.

Description: Acoustic localization is an essential technique in speech capturing, speech enhancement, video conferencing, and human–robot interaction. However, in practical situations, localization has to be performed in abominable environments, where the presence of reverberation and noise degrades the performance of available position estimates. Besides, the designed systems should be adaptive to locomotion of targets with low computational complexity. In the context, this paper introduces a robust hierarchical acoustic localization method via time-delay compensation (TDC) and interaural matching filter (IMF). Firstly, interaural time-delay (ITD) and interaural level difference (ILD), which are cues involved in first two layers, respectively, are yielded by TDC all at once. Then, a novel feature named IMF, which can eliminate the difference between binaural signals, is proposed in the third layer. The final decision making is based on a Bayesian rule. The relationships among the three layers are that the former layer provides candidate directions for later ones such that the searching space becomes gradually smaller to reduce matching time. Experiments using both a public database and a real scenario verify that TDC and IMF are robust for acoustic localization, and hierarchical system has less consumption time.

Description: Canonical correlation analysis (CCA) is a widely used data analysis tool that allows to assess the correlation between two distinct sets of signals. It computes optimal linear combinations of the signals in both sets such that the resulting signals are maximally correlated. The weight vectors defining these optimal linear combinations are referred to as “principal CCA directions”. In addition to this particular type of data analysis, CCA is also often used as a blind source separation (BSS) technique, i.e., under certain assumptions, the principal CCA directions have certain demixing properties. In this paper, we propose a distributed CCA (DCCA) algorithm that can operate in wireless sensor networks (WSNs) with a fully connected or a tree topology. The algorithm estimates the $Q$ principal CCA directions from the sensor signal observations collected by the different nodes in the WSN and extracts the corresponding sources. These network-wide principal CCA directions are estimated in a time-recursive fashion without explicitly constructing the corresponding network-wide correlation matrices, i.e., without the need for data centralization. Instead, each node locally computes smaller CCA problems and only transmits compressed sensor signal observations (of dimension $Q$ ), which significantly reduces the bit rate over the wireless links of the WSN. We prove convergence and optimality of the DCCA algorithm, and we demonstrate its performance by means of numerical simulations in a blind source separation scenario.

Description: This paper proposes the improved design of an ultraviolet (UV)- and-blue-light-inhibited white light-emitting diode for use as a safe and practical light source. Covered with a glass substrate coated with a photocatalyst resin on one side and a reflectance film on the other side, wavelengths below 400 nm are reflected back to re-excite the red–green–blue phosphors and, consequently, enhance luminous efficiency. The absorption spectrum of bismuth oxide photocatalysts is below 521 nm, and the leaked UV and blue light can be absorbed, thereby exciting electron–hole pairs and producing the photocatalytic effect. Thus, blue light and UV leakage can be suppressed appreciably, and the luminous efficiency can be increased markedly. Experimental results showed a UV suppression ratio of 88.43% and a visible light increasing ratio of 21.66%. The Commission International de L'Eclairage chromaticity coordinates $(x,y)$ were (0.343, 0.404), the correlated color temperature and the deviation from de Blackbody locus were (5201 K, 0.0250), and the color rendering index was 93.16. In addition, the photocatalyst coating layer can act as a diffuser to provide a comfortable visual experience and facilitate environmental purification.

Description: Metamaterial-based perfect absorbers have attracted considerable attention due to their potential for practical applications. The existing absorbers, however, are mostly polarization insensitive or only sensitive to one direction, which is inapplicable in some areas. Polarization tunable or high absorption in two orthogonal directions is very useful and necessary. Herein, we present a polarization tunable absorber formed by an asymmetric patch and a dielectric layer on top of a metallic board. With this structure, the frequency of the absorber can be tuned by merely changing the polarization of the incident. The tunable mechanism originates from the different length of the patch along the two orthogonal directions. The concept is rather general and applicable to various absorbers, as long as the asymmetric design is valid. The absorber can find practical applications in manipulation of the polarization of the light and detecting waves with specific polarization.

Description: The major activity during speech production is glottal activity and is earlier detected using strength of excitation (SoE). This work uses the normalized autocorrelation peak strength (NAPS) and higher order statistics (HOS) as additional features for detecting glottal activity. The three features, namely, SoE, NAPS, and HOS, are, respectively indicators of different attributes of glottal activity, namely, energy, periodicity, and asymmetrical nature of the resulting source signal. The effectiveness of these features is analyzed using the differential electroglottograph signal, zero-frequency filtered signal, and integrated linear prediction residual, as representatives of source signal. The combination of glottal activity information from the three features outperforms any single of them, demonstrating different information represented by each of these features.

Description: This letter addresses the texture classification problem through a pixel-based local binary pattern (LBP) statistics aggregation mechanism. Real-world texture images often present challenges for classification algorithms in terms of intra-class variability due, among others, to variable illumination. The LBP operator, a state-of-the-art texture descriptor, possesses key properties for tackling real-world texture images: discriminative power and invariance against monotonic gray level changes. We propose a novel texture classification approach that increases the robustness of LBP-based methods with respect to any type of intra-class variations. The method locally characterizes each pixel with an LBP code histogram and globally computes the label of a textured image by aggregating pixel labels through a voting process. Our approach can be in principle applied to any LBP version, as it focuses on how statistics are computed from LBP codes. We show that the proposed pixel-based approach improves upon traditional LBP block-based approaches in terms of classification accuracy by up to 5.1 p.p. on the public Outex database for the classic LBP with various neighborhoods as well as for various LBP extensions.

Description: We present a new trigonometric basis function that is capable of perfectly reproducing circles, spheres and ellipsoids while at the same time being interpolatory. Such basis functions have the advantage that they allow to construct shapes through a sequence of control points that lie on their contour (2-D) or surface (3-D) which facilitates user-interaction, especially in 3-D. Our piecewise exponential basis function has finite support, which enables local control for shape modification. We derive and prove all the necessary properties of the kernel to represent shapes that can be smoothly deformed and show how idealized shapes such as ellipses and spheres can be constructed.

Description: We demonstrate low-voltage waveguide-coupled germanium avalanche photodetectors (APDs) with a (wafer-scale mean) gain $times$ bandwidth product of 140 GHz at $-$ 5 V by utilizing a 185-nm-thick Ge layer. An optical receiver based on such an APD operating up to 25 Gb/s is demonstrated.

Description: The realization of high-efficiency organic small molecule: Fullerene solar cells are challenging but become more and more feasible due to the rapid development in donor materials and device fabrication techniques. In the past several years, the optimization in the processing techniques, such as, solvent vapor annealing (SVA), the use of solvent additives had led to superior improvement in the device performance of organic solar cells from different donor systems, but at an expense of reduction in the open-circuit voltage ( $V_{{rm OC}}$ ). In this paper, we report that the overall device performance of the organic small molecule solar cells (SMSCs) can be significantly enhanced through a two-step process consisting of SVA and thermal annealing (TA) (short for SVA+TA), especially the reduction in $V_{{rm OC}}$ can be effectively avoided in case of exclusive use of SVA. The carrier dynamics is determined by transient photovoltage and transient photocurrent measurements, which can provide information on the origin of enhanced device performance upon the two-step annealing. The observed $V_{{rm OC}}$ recovery is attributed to the preferable change in charge dynamic, thus, leading to a superior overall device performance. Furthermore, the SVA and the consequential TA are complementary to each other; thus, the two-step annealing method represents a feasible route to simultaneously improve the $V_{{rm OC}}$ , $J_{{rm SC}}$ , FF, and PCE of SMSCs.

Description: We report a fast and efficient method for permanently correcting fabrication-induced phase errors in silicon photonic circuits. The method uses femtosecond laser pulses at 400-nm wavelength to amorphize a thin layer of crystalline silicon near the waveguide surface, thereby inducing a change in the effective index of the waveguide. Using a single femtosecond laser pulse, we reduced the polarization-dependent frequency shift between the two interferometers of a polarization diversity differential phase shift keying silicon demodulator from 11 GHz to less than 0.5 GHz, thereby restoring the polarization diversity operation of the circuit with little degradation to the circuit performance.

Description: A refined model of a mid-IR amplifier, constituted by a tapered chalcogenide fiber coupled to an erbium-doped chalcogenide microsphere, is integrated with a global solution search procedure based on particle swarm optimization approach. It is implemented in a computer code in order to obtain an inversion algorithm useful to evaluate the spectroscopic parameters of rare-earth-doped glass microspheres. The rare earth parameters can be recovered by means of the optical gain measurement. The error in evaluation of the erbium lifetime $tau _{41}$ is <3.5%. It is <0.5% for the other lifetimes and ion–ion interaction parameters. These excellent results are obtained since whispering gallery mode electromagnetic field interacts with rare earth for long effective distances.

Description: We demonstrate an integrated spectral shaper based on a Sagnac loop incorporating a chirped Bragg grating in silicon photonics for the photonic generation of chirped microwave pulses. The technique is based on optical spectral shaping combined with linear frequency-to-time mapping. By tuning the central wavelength of the input optical pulse, we obtain chirped microwave pulses with central frequencies ranging from $sim 10$ GHz to $sim 30$ GHz and an RF chirp rate of $sim 20$ GHz/ns with both positive and negative signs.

Description: Internet of Things (IoTs) is a technology to connect machines, objects, and people with electronic devices. Many researchers have focused their works on architecture design from different perspectives. The deployment of IoT applications contains a variety of things that are attached with end-point devices, such as sensors, actuators, and radio frequency identification tags to perform sensing, controlling, and/or identifying things. The GS1 EPCglobal Architecture and IEEE 1451 standards are adopted as the cornerstone of our IoT architecture framework. In this paper, we focus on how to resolve the heterogeneity and dynamic characteristics of this variety of things. A uniform expression mechanism based on electronic product coding (EPC) scheme is introduced. The practical facilities are presented and examples of how to generate EPC scheme for transducers are illustrated. By integrating the IEEE 1451 compatible transducers, based on transducer electronic data sheet, to the identify layer of the extended GS1 EPCglobal Architecture, we can process more versatile data of different things in IoT applications. The uniform EPC scheme of heterogeneous things in the identify layer will make a consistent expression of things and compatible with the upper layer. This mechanism plays a fundamental role to support transducer capability in GS1 EPCglobal Architecture.

Description: Provides a listing of current staff, committee members and society officers.

Description: A novel planar multilayered epsilon-near-zero (ENZ) tunnel sensor based on fully laminated surface integrated waveguide (SIW) technology is proposed for the microwave measurement of dispersive materials. The proposed sensor is designed and optimized using parametric analysis to obtain the multilayered ENZ tunnel dimensions. It is observed that the width of the upper tunnel of the designed two-tunnel sensor should be at least half of the SIW width of the actual SIW structure for the multiband operation. The complex permittivity measurement using the proposed sensor is possible at two frequencies with a single set of measurement data. The proposed method is based on perturbation of the squeezed electric field having constant magnitude and high intensity inside the multilayered ENZ tunnel, which eventually increases the sensitivity of the proposed sensor. The sensitivity and accuracy of the proposed sensor are tested using both the simulated and the experimented data. It is found that the proposed sensor is highly sensitive, and typically demonstrates 6% error under ideal conditions, thus making it a good candidate for the microwave measurement of dispersive materials.

Description: A system based on phase-sensitive optical time domain reflectometry is proposed for simultaneously strain and vibration sensing. The strain of fiber is detected by comparing the patterns of signal for different laser frequencies, and the vibration of fiber is detected simultaneously from the signals for any certain laser frequency. During the measurement, frequencies of the probe optical pulses are modulated sequentially in ascending or descending order. Using the signals generated by optical pulses with the same frequency, the vibration of fiber is detected with fast response speed; using that with different frequencies, the strain of fiber is detected with high resolution. In our experiment, a sensing system with 2-m spatial resolution, up to 1-kHz frequency measurement range and 10- $text{n}{{varepsilon }}$ strain resolution is realized for a 9-km sensing fiber length.

Description: The following is included in this newsletter: IEEE Young Professionals, Lahore Section Win World Class Award "Hall of Fame 2015"; Distinguished Lecturer Tour of Nei Kato in China, May 2015; Distinguished Lecturer Tour of Tom Hou to Beijing and Nanjing, China; European Wireless 2015 in Budapest; Novel In-Band Full-Duplex Communication Prototype for 5G Systems, Finland, May 2015

Description: Wireless vehicular networks offer the promise of connectivity to vehicles that could provide a myriad of safety and driving-enhancing services to drivers and passengers. With wireless technology available in each car, it is expected that huge amounts of information will be exchanged between vehicles or between vehicles and roadside infrastructure. Due to defective sensors, software viruses, or even malicious intent, legitimate vehicles might inject untrustworthy information into the network. Besides relying on the public key infrastructure, this article proposes a social network approach to study trustworthy information sharing in a vehicular network. We first cover recent research progress in measuring direct trust and modeling indirect trust in online social networks, and then discuss how to apply them to vehicular social networks despite several pressing research challenges.

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

Description: The mobile crowdsourcing network (MCN) is a promising network architecture that applies the principles of crowdsourcing to perform tasks with human involvement and powerful mobile devices. However, it also raises some critical security and privacy issues that impede the application of MCNs. In this article, in order to better understand these critical security and privacy challenges, we first propose a general architecture for a mobile crowdsourcing network comprising both crowdsourcing sensing and crowdsourcing computing. After that, we set forth several critical security and privacy challenges that essentially capture the characteristics of MCNs. We also formulate some research problems leading to possible research directions. We expect this work will bring more attention to further investigation on security and privacy solutions for mobile crowdsourcing networks.

Description: Presents the ComSoc conference calendar of events.

Description: Energy harvesting technologies have gained widespread attention for their perpetual energy supply for sensor nodes. However, the energy resources are still insufficient while the harvesting module is added on the node. To prolong the network lifetime and meet the demand of a green wireless network, a dynamic gradient-aware hierarchical packet forwarding mechanism is designed. According to the relative positions of nodes, gradient-aware clusters are established. Consequently, considering the energy conversion efficiency and relative distance, cluster heads are selected reasonably. Furthermore, by exploiting the available energy and the number of cluster members, packets can be forwarded to the sink in an energy-efficient manner. Results show that the network lifetime can be noticeably improved.

Description: Recently, there has been substantial research interest in the subject of simultaneous wireless information and power transfer (SWIPT) due to its cross-disciplinary appeal and its wide-ranging application potential, which motivates this overview. More explicitly, we provide a brief survey of the state of the art and introduce several practical transceiver architectures that may facilitate its implementation. Moreover, the most important link-level as well as system-level design aspects are elaborated on, along with a variety of potential solutions and research ideas. We envision that the dual interpretation of RF signals creates new opportunities as well as challenges requiring substantial research, innovation and engineering efforts.

Description: The emerging trends of 2014 have continued to dominate the developments in the first half of 2015: 1. The packet optical transport system (P-OTS) concept supports the service provider goal to build a common network infrastructure by integrating Ethernet, IP/MPLS, and DWDM 2. There has been intensifying focus and attention on network functions virtualization (NFV) and softwaredefined networking (SDN) to provide service providers with the tools for more effective operation and management of communications networks in general, and optical communications networks in particular.

Description: In June 2015, the ComSoc Board of Governors approved a revision of ComSoc Constitution. The IEEE approved the revision in July 2015, and ComSoc Membership approval is currently pending.

Description: The directivity factor (DF) of a beamformer describes its spatial selectivity and ability to suppress diffuse noise which arrives from all directions. For a given array constellation, it is possible to select beamforming weights which maximize the DF for a particular look-direction, while enforcing nulls for a set of undesired directions. In general, the resulting DF is dependent upon the specific look- and null directions. Using the same array, one may apply a different set of weights designed for any other feasible set of look- and null directions. In this contribution, we show that when the optimal DF is averaged over all look directions, the result equals the number of sensors minus the number of null constraints. This result holds regardless of the positions and spatial responses of the individual sensors and regardless of the null directions. The result generalizes to more complex wave-propagation domains (e.g., reverberation).

Description: We report on the design, fabrication, and optical characterization of InN-based optical waveguides aiming at their application as all-optical limiters at 1.55 $mu text{m}$ . The InN guiding layers are grown by radio frequency (RF) sputtering on sapphire substrates. Experimental cutback method and nonlinear optical transmittance measurements were performed for the developed devices. The waveguides present nonlinear behavior associated with two photon absorption process. A nonlinear absorption coefficient ranging from $sim 43$ to 114 cm/GW is estimated from optical measurements. These results open the possibility of using RF sputtering as a low cost and thermally harmless technique for the development and overgrowth of InN-based optical waveguides in future III-nitride all-optical integrated circuits working at telecom wavelengths.

Description: A new simple structure of ultrahigh birefringent and ultrahigh nonlinear slot silicon microfiber with highly efficient dispersion reduction is proposed and numerically simulated using the full-vector finite-element method with anisotropic perfectly matched layers. Benefiting from the slot effect-induced sub-wavelength mode confinement, ultrahigh birefringence up to the order of $10^{mathrm {{-1}}}$ can be realized within a wide wavelength range from 1.4 to 1.7 $mu text{m}$ , which is comparable with the results in these ultrahigh birefringent photonic crystal fibers, but cannot be achieved in traditional microfibers. Meanwhile, the nonlinear coefficients of quasi-TE mode and quasi-TM mode at the wavelength of 1.55 $mu text{m}$ are as high as 969.58 $text{W}^{mathrm {{-1}}}text{m}^{mathrm {{-1}}}$ and 156.74 $text{W}^{mathrm {{-1}}}text{m}^{mathrm {{-1}}}$ , respectively. Furthermore, the dispersion value of quasi-TE mode at 1.55 $mu text{m}$ can be decreased from $1.2358times 10^{mathrm {{3}}}$ ps/(nm $cdot $ km) to 0 ps/(nm $cdot $ km) simply by modifying the slot size. Owing to its excellent performance, the proposed slot silicon microfiber will have great potential for polarization maintaining nonlinear signal processing applications.

Description: Hierarchical routing in wireless sensor networks (WSNs) is a very important topic that has been attracting the research community in the last decade. Typical hierarchical routing is called clustering routing, in which the network is divided into multiple clusters. Recently, some types of atypical hierarchical routing arise, including chain-based, tree-based, grid-based routing, and area-based routing. There are several survey papers that present and compare the hierarchical routing protocols from various perspectives, but a survey on atypical hierarchical routing is still missing. This paper makes a first attempt to provide a comprehensive review on atypical hierarchical routing. We offer a classification of atypical hierarchical routing of WSNs, and give detailed analysis of different logical topologies. The most representative atypical hierarchical routing protocols are described, discussed, and qualitatively compared. In particular, the advantages and disadvantages of different atypical hierarchical routing protocols are analyzed with respect to their significant performances and application scenarios. Finally, we put forward some open issues concerning the design of hierarchical WSNs. This survey aims to provide useful guidance for system designers on how to evaluate and select appropriate logical topologies and hierarchical routing protocols for specific applications.

Description: A novel fiber-optic relative humidity (RH) sensor with thermal compensation based on a fiber Bragg grating (FBG) is presented. Changes in the RH are transduced to the FBG properties by an ORMOCER coating. The cross sensitivity to temperature is compensated by inscribing the Bragg grating in a highly birefringent fiber and using the individual Bragg peaks of each polarization direction for separation (discrimination) of temperature and humidity influences.

Description: This paper focuses on the nondestructive dielectric measurement for thin dielectric material using open-ended coaxial probe. The probe calibration procedure requires only a measurement of a half-space air and three open standard kits. The measured reflection coefficient for thin sample, which is backed by metal plate, is taken with a vector network analyzer up to 7 GHz and the reflection coefficient is converted to relative dielectric constant and tangent loss via closed form capacitance model and simple calibration process.

Description: We present a physical model to study the dark current and noise characteristics of quantum-dot infrared photodetectors (QDIPs). This model considers both carrier’s thermoexcitaion and carrier’s field-assisted tunneling, which are the main origin of dark current and noise in QDIPs. We use this model to analyze the effect of different structural parameters, such as QDs lateral size and density of QD, and environmental parameters, such as bias voltage and operating temperature on the dark current and the noise of QDIP. The theoretical results obtained from our model are in excellent agreement with reported experimental data. Therefore, the validity of the model is proven for these reasons. This model can be extended to other quantum structure detectors to evaluate the noise and dark current characteristics.

Description: This paper presents a new approach for the definition and identification of a transistor model suitable for low-noise amplifier (LNA) design. The resulting model is very robust to layout modifications (i.e., source degeneration) providing accurate predictions of device noise-performance and small-signal parameters. Moreover, the described procedure is very robust since it does not require any numerical optimization, with possibly related problems like local minima and unphysical model parameters. The adopted model topology is based on a lumped element parasitic network and a black-box intrinsic device, which are both identified on the basis of full-wave electromagnetic simulations, as well as noise and ${ S}$ -parameter measurements. The procedure has been applied to three GaN HEMTs having different peripheries and a Ku-band LNA has been designed, demonstrating a very good agreement between measurements and predicted results.

Description: Novel design of a shielded vertically stacked ring resonator (VSRR) is presented in this paper. The use of a shielded VSRR with a layer of the low-loss liquid that fills the partial space between the fed patch and the parasitic patch have been investigated. Dependencies of the resonating frequency and input impedance of the shielded VSRR on structure size and material properties of the test liquid layer are discussed. The method, of finding the complex permittivity (CP), particularly of petroleum liquids, is verified using electromagnetic modeling with full wave simulation software ANSYS HFSS-15 and confirmed experimentally. The proposed new design of the resonator will improve the sensitivity of single ring boxed resonator in terms of the quality factor, and in turn, increase the CP measurement sensitivity.

Description: This paper proposes a design scheme for extending the bandwidth of a three-stage Doherty power amplifier (DPA) based on symmetric devices for broadband applications. The proposed bandwidth enhancement scheme provides an optimized solution for the load combiner parameters while operating the auxiliary power amplifier (PA) at lower current values as compared to the main PA at saturation. The proposed scheme promises 30.3% fractional bandwidth in terms of efficiency enhancement up to 9.54-dB back-off. The proposed design methodology is validated with the design of a broadband three-stage DPA using three 10-W packaged GaN HEMT devices. Measurement results show more than 51.6% drain efficiency at 6-dB output power back-off (OPBO) over the entire frequency range from 700 to 950 MHz. At 9.54-dB OPBO, the drain efficiency is better than 50.2% over this 250-MHz band. The peak drain efficiency at saturation is better than 60.04% over the entire band of operation. Measurement with 5-MHz WCDMA modulated signal shows the average drain efficiency of about 57.6% at 33.97-dBm average output power at the center frequency of operation. The corresponding adjacent channel power ratio is better than ${-}{hbox{45.6}}$ dBc after applying digital predistortion. The circuit is realized with microstrip technology, which can be easily fabricated using conventional printed circuit processes.

Description: In this work, the design of an inductorless, high-isolation, and high conversion gain fully differential subharmonic down-conversion mixer for 2.4-GHz wireless application is presented. A complementary current-reuse technique is adopted between the transconductance and the local oscillator (LO) switching stage to boost the conversion gain without additional power consumption in the concept of reusing the dc current of the LO switching stage. The LO switching transistors are driven by a 25% duty cycle input to further enhance the conversion gain and improve the noise-figure performance. An active balun is integrated in the design for single-balanced to differential conversion or vice-versa, along with an RC poly phase filter to generate quadrature LO signals from a differential input signal. The subharmonic mixer is fabricated in a 0.13- $mu{hbox{m}}$ standard CMOS technology with a core chip dimension of 313 $mu{hbox{m}}times,$ 372 $mu{hbox{m}}$ and a power consumption of 5.82 mW from a supply voltage of 1.2 V. Experimental results show a conversion gain of 13.61 dB, an input-referred third-order intercept point of $-{hbox{4.46 dBm}}$ , a noise figure of 20 dB, and an isolation greater than 50 dB between the LO, RF, and IF ports. The proposed inductorless subharmonic mixer has a competitive performance in size with high isolation performance and highest conversion gain in comparison to other published works.

Description: This paper presents a novel method to design filtering rat-race hybrids with wide-stopband bandpass responses. Four ${pm} K$ -inverters with bandpass functions are utilized to replace the one or three quarter-wavelength transmission lines in the conventional rat-race hybrid. The ${pm} K$ -inverters consist of transmission lines and capacitors, which can reduce the area occupied and suppress the high-order harmonics. Furthermore, the isolation performance is enhanced by embedding the ${pm} K$ -inverters. Theoretical analysis is carried out and design equations are derived. For demonstration, a filtering rat-race hybrid with bandpass responses is implemented. The center frequency is located at 470 MHz with the insertion loss of 1.2 dB. Good in-phase and out-of-phase characteristics are observed. Comparisons between the measured and simulated results are also presented to verify the theoretical analysis. The overall size is only 4.6% of the conventional hybrid and stopband is extended to $5f_{0}$ .

Description: An approach that can be used for exploiting the sensing capabilities of RF identification (RFID) is presented and formulated. In this approach, sensor information is carried through the modulation frequency of RFID. The aim of this work is to investigate the sensor concept and to characterize the sensor performance both theoretically and experimentally. Furthermore, the operation of the sensor RF parts and oscillator are described analytically, and the equations are verified by simulations and measurements. The concept is experimentally demonstrated at a single carrier frequency to test its suitability for ultra-high-frequency RFID applications, and shown to be feasible for implementing sensors that can be read across distances up to 14 m.

Description: Based on advanced industrial fabrication processes and on specialized design strategies, a new class of ferroelectric metal–insulator–metal (MIM) capacitors with high tunability and high quality factor ( $Q$ -factor) is here presented. Modeled by means of lumped element equivalent circuits and experimentally validated up to 67 GHz, a maximum tunability of 81% (0–20-V bias), and a $Q$ -factor improvement up to 30% (at 0 V) could be demonstrated at 1 GHz. These varactors have been exploited in the design of reconfigurable filters, with a center frequency at around 1 GHz that can be tuned up to 112%, and a figure of merit (FoM) per applied bias better than ${hbox{31.5}}~{hbox{dB}}^{-1} /{hbox{kV}}$ . Owing to their promising features, these materials have been exploited to design small-size capacitors suitable for millimeter-wave frequencies. The results demonstrate tunabilities and FoMs superior to the state-of-the-art. Based on this, two 60-GHz tunable phase shifters are proposed. They represent the first example of such devices based on MIM $({hbox{Ba,Sr}}){hbox{TiO}}_{3}$ (BST) capacitors. In terms of insertion loss, size, FoM, and FoM per bias they show a remarkable improvement with respect to the state-of-the-art of ferroelectric-based devices, thus proving that the BST represents a promising candidate to operate into the millimeter frequency band.

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Description: There has been much research on shrinkage methods for real-valued covariance matrices and their inverses (precision matrices). In spectral analysis of $p$ -vector-valued time series, complex-valued spectral matrices and precision matrices arise, and good shrinkage methods are often required, most notably when the estimated complex-valued spectral matrix is singular. As an improvement on the Ledoit-Wolf (LW) type of spectral matrix estimator we use random matrix theory to derive a Rao-Blackwell estimator for a spectral matrix, its inverse being a Rao–Blackwellized estimator for the spectral precision matrix. A random matrix method has previously been proposed for complex-valued precision matrices. It was implemented by very costly simulations. We formulate a fast, completely analytic approach. Moreover, we derive a way of selecting an important parameter using predictive risk methodology. We show that both the Rao–Blackwell estimator and the random matrix estimator of the precision matrix can substantially outperform the inverse of the LW estimator in a time series setting. Our new methodology is applied to EEG-derived time series data where it is seen to work well and deliver substantial improvements for precision matrix estimation.

Description: In this paper, the state estimation problem for discrete-time linear systems influenced by multiplicative and time-correlated additive measurement noises is considered where the multiplicative noises are zero-mean white noise sequences, and the time-correlated additive noise is described by a linear system model with white noise. An optimal linear estimator for the system under consideration is proposed, which does not require computing the inverse of state transition matrix. The proposed estimator has a recursive structure, and has time-independent computation and storage load. Computer simulations are carried out to demonstrate the performance of the proposed estimator. The simulation results show the superiority of the proposed estimator.

Description: In this paper, we start with the standard support vector machine (SVM) formulation and extend it by considering a general SVM formulation with normalized margin. This results in a unified convex framework that allows many different variations in the formulation with very diverse numerical performance. The proposed unified framework can capture the existing methods, i.e., standard soft-margin SVM, $ell_{1}$ -SVM, and SVMs with standardization, feature selection, scaling, and many more SVMs, as special cases. Furthermore, our proposed framework can not only provide us with more insights on different SVMs from the “energy” and “penalty” point of views, which help us understand the connections and differences between them in a unified way, but also enable us to propose more SVMs that outperform the existing ones under some scenarios.

Description: The Electric Reliability Council of Texas (ERCOT) serves as the independent system operator for most of the state of Texas. There is more than 74,000-MW capacity for peak demand and over 11,000 MW of operating wind generation capacity in ERCOT. In February 2015, wind generation reached a record output of 11,154 MW, which was 34% of the load at the time.