Open AccessArticle
Online Optimal Switching Frequency Selection for Grid-Connected Voltage Source Inverters
Electronics 2017, 6(4), 110; doi:10.3390/electronics6040110 (registering DOI) -
Abstract
Enhancing the performance of the voltage source inverters (VSIs) without changing the hardware structure has recently acquired an increased amount of interest. In this study, an optimization algorithm, enhancing the quality of the output power and the efficiency of three-phase grid connected VSIs
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Enhancing the performance of the voltage source inverters (VSIs) without changing the hardware structure has recently acquired an increased amount of interest. In this study, an optimization algorithm, enhancing the quality of the output power and the efficiency of three-phase grid connected VSIs is proposed. Towards that end, the proposed algorithm varies the switching frequency (fsw) to maintain the best balance between switching losses of the insulated-gate-bipolar-transistor (IGBT) power module as well as the output power quality under all loading conditions, including the ambient temperature effect. Since there is a contradiction with these two measures in relation to the switching frequency, the theory of multi-objective optimization is employed. The proposed algorithm is executed on the platform of Altera® DE2-115 field-programmable-gate-array (FPGA) in which the optimal value of the switching frequency is determined online without the need for heavy offline calculations and/or lookup tables. With adopting the proposed algorithm, there is an improvement in the VSI efficiency without degrading the output power quality. Therefore, the proposed algorithm enhances the lifetime of the IGBT power module because of reduced variations in the module’s junction temperature. An experimental prototype is built, and experimental tests are conducted for the verification of the viability of the proposed algorithm. Full article
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Open AccessArticle
Characteristics of Anisotropic Conducting Polymers Suggest Feasibility of Test Fixtures up to 110 GHz
Electronics 2017, 6(4), 109; doi:10.3390/electronics6040109 -
Abstract
Applications and volume of integrated circuits operating at frequencies up to 100 GHz are steadily increasing. This establishes serious challenges, especially for temporarily contacting such products during manufacturing tests with appropriate signal integrity. At present, existing test socket concepts have reached their applicability
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Applications and volume of integrated circuits operating at frequencies up to 100 GHz are steadily increasing. This establishes serious challenges, especially for temporarily contacting such products during manufacturing tests with appropriate signal integrity. At present, existing test socket concepts have reached their applicability limit. The most promising candidates to meet the requirements of future microwave device interfacing are thin, anisotropic conducting polymers. This paper reports a survey covering measurement methodology for signal integrity properties of conducting polymers, model parameter extraction, measurement results from various materials, reliability issues, and a prototype application. Full article
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Open AccessFeature PaperArticle
Experimental Characterization of a Dual-Polarised Parasitic Patch Antenna
Electronics 2017, 6(4), 108; doi:10.3390/electronics6040108 -
Abstract
The aim of this paper is to present the experimental characterization of a reconfigurable parasitic patch antenna for Multiple Input Multiple Output (MIMO) applications. The proposed antenna is able to work with two different polarizations, providing separate control of the antenna pattern of
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The aim of this paper is to present the experimental characterization of a reconfigurable parasitic patch antenna for Multiple Input Multiple Output (MIMO) applications. The proposed antenna is able to work with two different polarizations, providing separate control of the antenna pattern of each of the two polarizations. Both numerical and experimental results show the adaptive capabilities of the antenna, proving its effectiveness for MIMO applications. Full article
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Open AccessFeature PaperArticle
Substrate-Integrated Waveguide PCB Leaky-Wave Antenna Design Providing Multiple Steerable Beams in the V-Band
Electronics 2017, 6(4), 107; doi:10.3390/electronics6040107 -
Abstract
A periodic leaky-wave antenna (LWA) design based on low loss substrate-integrated waveguide (SIW) technology with inset half-wave microstrip antennas is presented. The developed LWA operates in the V-band between 50 and 70 GHz and has been fabricated using standard printed circuit board (PCB)
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A periodic leaky-wave antenna (LWA) design based on low loss substrate-integrated waveguide (SIW) technology with inset half-wave microstrip antennas is presented. The developed LWA operates in the V-band between 50 and 70 GHz and has been fabricated using standard printed circuit board (PCB) technology. The presented LWA is highly functional and very compact supporting 1D beam steering and multibeam operation with only a single radio frequency (RF) feeding port. Within the operational 50–70 GHz bandwidth, the LWA scans through broadside, providing over 40° H-plane beam steering. When operated within the 57–66 GHz band, the maximum steering angle is 18.2°. The maximum gain of the fabricated LWAs is 15.4 dBi with only a small gain variation of +/−1.5 dB across the operational bandwidth. The beam steering and multibeam capability of the fabricated LWA is further utilized to support mobile users in a 60 GHz hot-spot. For a single user, a maximum wireless on-off keying (OOK) data rate of 2.5 Gbit/s is demonstrated. Multibeam operation is achieved using the LWA in combination with multiple dense wavelength division multiplexing (WDM) channels and remote optical heterodyning. Experimentally, multibeam operation supporting three users within a 57–66 GHz hot-spot with a total wireless cell capacity of 3 Gbit/s is achieved. Full article
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Open AccessFeature PaperArticle
Fractional Calculus Based FDTD Modeling of Layered Biological Media Exposure to Wideband Electromagnetic Pulses
Electronics 2017, 6(4), 106; doi:10.3390/electronics6040106 -
Abstract
Electromagnetic fields are involved in several therapeutic and diagnostic applications such as hyperthermia and electroporation. For these applications, pulsed electric fields (PEFs) and transient phenomena are playing a key role for understanding the biological response due to the exposure to non-ionizing wideband pulses.
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Electromagnetic fields are involved in several therapeutic and diagnostic applications such as hyperthermia and electroporation. For these applications, pulsed electric fields (PEFs) and transient phenomena are playing a key role for understanding the biological response due to the exposure to non-ionizing wideband pulses. To this end, the PEF propagation in the six-layered planar structure modeling the human head has been studied. The electromagnetic field and the specific absorption rate (SAR) have been calculated through an accurate finite-difference time-domain (FDTD) dispersive modeling based on the fractional derivative operator. The temperature rise inside the tissues due to the electromagnetic field exposure has been evaluated using both the non-thermoregulated and thermoregulated Gagge’s two-node models. Moreover, additional parametric studies have been carried out with the aim to investigate the thermal response by changing the amplitude and duration of the electric pulses. Full article
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Open AccessFeature PaperArticle
A Pattern-Reconfigurable Slot Antenna for IoT Network Concentrators
Electronics 2017, 6(4), 105; doi:10.3390/electronics6040105 -
Abstract
In this paper, a directional pattern-reconfigurable slot antenna at 2.4 GHz is presented. The antenna can provide three evenly-separated directional patterns and one omnidirectional pattern. The proposed solution is fully suitable for the integration in Internet of things (IoT) network base stations to
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In this paper, a directional pattern-reconfigurable slot antenna at 2.4 GHz is presented. The antenna can provide three evenly-separated directional patterns and one omnidirectional pattern. The proposed solution is fully suitable for the integration in Internet of things (IoT) network base stations to increase the communication range and reduce packet collisions. The performance of the proposed antenna is numerically and experimentally assessed. Full article
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Open AccessArticle
X-Band GaN Power Amplifier MMIC with a Third Harmonic-Tuned Circuit
Electronics 2017, 6(4), 103; doi:10.3390/electronics6040103 -
Abstract
This paper presents an X-band GaN HEMT power amplifier with a third harmonic-tuned circuit for a higher power density per area and a higher power-added efficiency (PAE) using a 0.25 μm GaN HEMT process of WIN semiconductors, Inc. The optimum load impedances at
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This paper presents an X-band GaN HEMT power amplifier with a third harmonic-tuned circuit for a higher power density per area and a higher power-added efficiency (PAE) using a 0.25 μm GaN HEMT process of WIN semiconductors, Inc. The optimum load impedances at the fundamental and third harmonic frequencies are extracted from load-pull simulations at the transistor’s extrinsic plane, including the drain-source capacitance and the series drain inductance. The third harmonic-tuned circuit is effectively integrated with the output matching circuit at the fundamental frequency, without complicating the whole output matching circuit. The input matching circuit uses a lossy matching scheme, which allows a good return loss and a simple LC low-pass circuit configuration. The fabricated power amplifier monolithic microwave integrated circuit (MMIC) occupies an area of 13.26 mm2, and shows a linear gain of 20 dB or more, a saturated output power of 43.2~44.7 dBm, and a PAE of 35~37% at 8.5 to 10.5 GHz. Full article
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Open AccessFeature PaperArticle
Development of a Multisensory Wearable System for Monitoring Cigarette Smoking Behavior in Free-Living Conditions
Electronics 2017, 6(4), 104; doi:10.3390/electronics6040104 -
Abstract
This paper presents the development and validation of a novel multi-sensory wearable system (Personal Automatic Cigarette Tracker v2 or PACT2.0) for monitoring of cigarette smoking in free-living conditions. The contributions of the PACT2.0 system are: (1) the implementation of a complete sensor suite
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This paper presents the development and validation of a novel multi-sensory wearable system (Personal Automatic Cigarette Tracker v2 or PACT2.0) for monitoring of cigarette smoking in free-living conditions. The contributions of the PACT2.0 system are: (1) the implementation of a complete sensor suite for monitoring of all major behavioral manifestations of cigarette smoking (lighting events, hand-to-mouth gestures, and smoke inhalations); (2) a miniaturization of the sensor hardware to enable its applicability in naturalistic settings; and (3) an introduction of new sensor modalities that may provide additional insight into smoking behavior e.g., Global Positioning System (GPS), pedometer and Electrocardiogram(ECG) or provide an easy-to-use alternative (e.g., bio-impedance respiration sensor) to traditional sensors. PACT2.0 consists of three custom-built devices: an instrumented lighter, a hand module, and a chest module. The instrumented lighter is capable of recording the time and duration of all lighting events. The hand module integrates Inertial Measurement Unit (IMU) and a Radio Frequency (RF) transmitter to track the hand-to-mouth gestures. The module also operates as a pedometer. The chest module monitors the breathing (smoke inhalation) patterns (inductive and bio-impedance respiratory sensors), cardiac activity (ECG sensor), chest movement (three-axis accelerometer), hand-to-mouth proximity (RF receiver), and captures the geo-position of the subject (GPS receiver). The accuracy of PACT2.0 sensors was evaluated in bench tests and laboratory experiments. Use of PACT2.0 for data collection in the community was validated in a 24 h study on 40 smokers. Of 943 h of recorded data, 98.6% of the data was found usable for computer analysis. The recorded information included 549 lighting events, 522/504 consumed cigarettes (from lighter data/self-registered data, respectively), 20,158/22,207 hand-to-mouth gestures (from hand IMU/proximity sensor, respectively) and 114,217/112,175 breaths (from the respiratory inductive plethysmograph (RIP)/bio-impedance sensor, respectively). The proposed system scored 8.3 ± 0.31 out of 10 on a post-study acceptability survey. The results suggest that PACT2.0 presents a reliable platform for studying of smoking behavior at the community level. Full article
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Open AccessReview
SoC Estimation for Lithium-ion Batteries: Review and Future Challenges
Electronics 2017, 6(4), 102; doi:10.3390/electronics6040102 -
Abstract
Energy storage emerged as a top concern for the modern cities, and the choice of the lithium-ion chemistry battery technology as an effective solution for storage applications proved to be a highly efficient option. State of charge (SoC) represents the available battery capacity
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Energy storage emerged as a top concern for the modern cities, and the choice of the lithium-ion chemistry battery technology as an effective solution for storage applications proved to be a highly efficient option. State of charge (SoC) represents the available battery capacity and is one of the most important states that need to be monitored to optimize the performance and extend the lifetime of batteries. This review summarizes the methods for SoC estimation for lithium-ion batteries (LiBs). The SoC estimation methods are presented focusing on the description of the techniques and the elaboration of their weaknesses for the use in on-line battery management systems (BMS) applications. SoC estimation is a challenging task hindered by considerable changes in battery characteristics over its lifetime due to aging and to the distinct nonlinear behavior. This has led scholars to propose different methods that clearly raised the challenge of establishing a relationship between the accuracy and robustness of the methods, and their low complexity to be implemented. This paper publishes an exhaustive review of the works presented during the last five years, where the tendency of the estimation techniques has been oriented toward a mixture of probabilistic techniques and some artificial intelligence. Full article
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Open AccessFeature PaperArticle
Reduced-Area Constant-Coefficient and Multiple-Constant Multipliers for Xilinx FPGAs with 6-Input LUTs
Electronics 2017, 6(4), 101; doi:10.3390/electronics6040101 -
Abstract
Multiplication by a constant is a common operation for many signal, image, and video processing applications that are implemented in field-programmable gate arrays (FPGAs). Constant-coefficient multipliers (KCMs) are often implemented in the logic fabric using lookup tables (LUTs), reserving embedded hard multipliers for
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Multiplication by a constant is a common operation for many signal, image, and video processing applications that are implemented in field-programmable gate arrays (FPGAs). Constant-coefficient multipliers (KCMs) are often implemented in the logic fabric using lookup tables (LUTs), reserving embedded hard multipliers for general-purpose multiplication. This paper describes a two-operand addition circuit from previous work and shows how it can be used to generate and add pre-computed partial products to implement KCMs. A novel method for pre-computing partial products for KCMs with a negative constant is also presented. These KCMs are then extended to have two to eight coefficients that may be selected by a control signal at runtime to implement time-multiplexed multiple-constant multiplication. Synthesis results show that proposed pipelined KCMs use 27.4% fewer LUTs on average and have a median LUT-delay product that is 12% lower than comparable LogiCORE IP KCMs. Proposed pipelined KCMs with two to eight selectable coefficients use 46% to 70% fewer LUTs than the best LogiCORE IP based alternative and most are faster than using a LogiCORE IP multiplier with a coefficient lookup function. They also outperform the state-of-the-art in the literature, using 22% to 57% fewer slices than the smallest pipelined adder graph (PAG) fusion designs and operate 7% to 30% faster than the fastest PAG fusion designs for the same operand size and number of selectable coefficients. For KCMs and KCMs with selectable coefficients of a given operand size, the placement and routing of LUTs remains the same for all positive and negative constant values, which is advantageous for runtime partial reconfiguration. Full article
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Open AccessArticle
Performance Evaluation of Downlink Multi-Beam Massive MIMO with Simple Transmission Scheme at Both Base and Terminal Stations
Electronics 2017, 6(4), 100; doi:10.3390/electronics6040100 -
Abstract
Multi-beam massive multiple-input–multiple-output (MIMO) configurations that utilize high-power beam selection in the analog parts and blind algorithms such as the constant modulus algorithm (CMA), which do not require channel state information (CSI), in the digital parts, have been proposed in the literature to
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Multi-beam massive multiple-input–multiple-output (MIMO) configurations that utilize high-power beam selection in the analog parts and blind algorithms such as the constant modulus algorithm (CMA), which do not require channel state information (CSI), in the digital parts, have been proposed in the literature to improve the transmission rates and efficiency. In this paper, we evaluate the transmission performance in the downlink, with simple control at the base station (BS) and user terminal (UTs), for massive MIMO transmissions. Through computer simulations, it is shown that the analog multi-beam selection at the BS and the application of CMA at the UT with two antennas can effectively realize transmissions with high-order modulation schemes. In addition, the weight update switching by the CMA is proposed in order to obtain fast and stable performance with a realistic data size. Full article
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Open AccessFeature PaperReview
THz Rectennas and Their Design Rules
Electronics 2017, 6(4), 99; doi:10.3390/electronics6040099 -
Abstract
The increasing demand for more efficient energy harvesting solutions has urged research for better harvesting solutions than the presently-available ones. While p-n junction solar cells have become commercially widespread, they are expensive and suffer from poor efficiency figures hardly reaching 20%. Other radiation-electricity
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The increasing demand for more efficient energy harvesting solutions has urged research for better harvesting solutions than the presently-available ones. While p-n junction solar cells have become commercially widespread, they are expensive and suffer from poor efficiency figures hardly reaching 20%. Other radiation-electricity converters such as rectennas have a theoretical limit in excess of 80%. However, no efficient rectenna solution for the terahertz frequency band has been commercialized or presented in the academic literature. In fact, there are many obstructions to an efficient solution. The aim of this paper is to address the key points towards an efficient and commercially-available solution by briefly reviewing the relevant literature and so identifying five factors that should be addressed in order to reach an efficient solution. Full article
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Open AccessArticle
An Energy Box in a Cloud-Based Architecture for Autonomous Demand Response of Prosumers and Prosumages
Electronics 2017, 6(4), 98; doi:10.3390/electronics6040098 -
Abstract
The interest in the implementation of demand response programs for domestic customers within the framework of smart grids is increasing, both from the point of view of scientific research and from the point of view of real applications through pilot projects. A fundamental
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The interest in the implementation of demand response programs for domestic customers within the framework of smart grids is increasing, both from the point of view of scientific research and from the point of view of real applications through pilot projects. A fundamental element of any demand response program is the introduction at customer level of a device, generally named energy box, able to allow interaction between customers and the aggregator. This paper proposes two laboratory prototypes of a low-cost energy box, suitable for cloud-based architectures for autonomous demand response of prosumers and prosumages. Details on how these two prototypes have been designed and built are provided in the paper. Both prototypes are tested in the laboratory along with a demonstration panel of a residential unit, equipped with a real home automation system. Laboratory tests demonstrate the feasibility of the proposed prototypes and their capability in executing the customers’ loads scheduling returned by the solution of the demand-response problem. A personal computer and Matlab software implement the operation of the aggregator, i.e., the intermediary of the energy-integrated community constituted by the customers themselves, who participate in the demand response program. Full article
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Open AccessFeature PaperReview
High Efficiency Power Amplifiers for Modern Mobile Communications: The Load-Modulation Approach
Electronics 2017, 6(4), 96; doi:10.3390/electronics6040096 -
Abstract
Modern mobile communication signals require power amplifiers able to maintain very high efficiency in a wide range of output power levels, which is a major issue for classical power amplifier architectures. Following the load-modulation approach, efficiency enhancement is achieved by dynamically changing the
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Modern mobile communication signals require power amplifiers able to maintain very high efficiency in a wide range of output power levels, which is a major issue for classical power amplifier architectures. Following the load-modulation approach, efficiency enhancement is achieved by dynamically changing the amplifier load impedance as a function of the input power. In this paper, a review of the widely-adopted Doherty power amplifier and of the other load-modulation efficiency enhancement techniques is presented. The main theoretical aspects behind each method are introduced, and the most relevant practical implementations available in recent literature are reported and discussed. Full article
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Open AccessFeature PaperReview
Electromagnetic Characterisation of Materials by Using Transmission/Reflection (T/R) Devices
Electronics 2017, 6(4), 95; doi:10.3390/electronics6040095 -
Abstract
An overview of transmission/reflection-based methods for the electromagnetic characterisation of materials is presented. The paper initially describes the most popular approaches for the characterisation of bulk materials in terms of dielectric permittivity and magnetic permeability. Subsequently, the limitations and the methods aimed at
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An overview of transmission/reflection-based methods for the electromagnetic characterisation of materials is presented. The paper initially describes the most popular approaches for the characterisation of bulk materials in terms of dielectric permittivity and magnetic permeability. Subsequently, the limitations and the methods aimed at removing the ambiguities deriving from the application of the classical Nicolson–Ross–Weir direct inversion are discussed. The second part of the paper is focused on the characterisation of partially conductive thin sheets in terms of surface impedance via waveguide setups. All the presented measurement techniques are applicable to conventional transmission reflection devices such as coaxial cables or waveguides. Full article
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Open AccessFeature PaperArticle
Correction of the Unobtrusive ECG Using System Identification
Electronics 2017, 6(4), 94; doi:10.3390/electronics6040094 -
Abstract
Unobtrusively acquired electrocardiograms (ECG) could substantially improve the comfort of patients. However, such ECGs are not used in clinical practice because (among other reasons) signal deformations impede correct diagnosis of the ECG. Here, methods are proposed for correction of the unobtrusive ECG, based
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Unobtrusively acquired electrocardiograms (ECG) could substantially improve the comfort of patients. However, such ECGs are not used in clinical practice because (among other reasons) signal deformations impede correct diagnosis of the ECG. Here, methods are proposed for correction of the unobtrusive ECG, based on system identification. Knowing the reference ECG, models were developed to correct the unobtrusively acquired ECG. A finite impulse response (FIR) model, a state space model and an autoregressive model were developed. The models were trained and evaluated on the Goldberger leads recorded from an ECG T-shirt with dry electrodes, and from a gold standard ECG. It was found that the FIR model corrects the unobtrusive ECG with good agreement (ρaVR = 0.84 ± 0.10, ρaVL = 0.65 ± 0.24, ρaVF = 0.88 ± 0.04), while the other models do not yield significant improvements, or become unstable. The R-peaks were also accurately corrected by the FIR model (MSEaVR = 0.10 ± 0.10, MSEaVL = 0.14 ± 0.27, MSEaVF = 0.03 ± 0.02). To conclude, the proposed FIR method succeeded in significantly correcting the unobtrusive ECG signal. Full article
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Open AccessArticle
μRTZVisor: A Secure and Safe Real-Time Hypervisor
Electronics 2017, 6(4), 93; doi:10.3390/electronics6040093 -
Abstract
Virtualization has been deployed as a key enabling technology for coping with the ever growing complexity and heterogeneity of modern computing systems. However, on its own, classical virtualization is a poor match for modern endpoint embedded system requirements such as safety, security and
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Virtualization has been deployed as a key enabling technology for coping with the ever growing complexity and heterogeneity of modern computing systems. However, on its own, classical virtualization is a poor match for modern endpoint embedded system requirements such as safety, security and real-time, which are our main target. Microkernel-based approaches to virtualization have been shown to bridge the gap between traditional and embedded virtualization. This notwithstanding, existent microkernel-based solutions follow a highly para-virtualized approach, which inherently requires a significant software engineering effort to adapt guest operating systems (OSes) to run as userland components. In this paper, we present μRTZVisor as a new TrustZone-assisted hypervisor that distinguishes itself from state-of-the-art TrustZone solutions by implementing a microkernel-like architecture while following an object-oriented approach. Contrarily to existing microkernel-based solutions, μRTZVisor is able to run nearly unmodified guest OSes, while, contrarily to existing TrustZone-assisted solutions, it provides a high degree of functionality and configurability, placing strong emphasis on the real-time support. Our hypervisor was deployed and evaluated on a Xilinx Zynq-based platform. Experiments demonstrate that the hypervisor presents a small trusted computing base size (approximately 60KB), and a performance overhead of less than 2% for a 10 ms guest-switching rate. Full article
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Open AccessArticle
Fiber Bragg Grating Sensors for Mainstream Industrial Processes
Electronics 2017, 6(4), 92; doi:10.3390/electronics6040092 -
Abstract
This paper reviews fiber Bragg grating sensing technology with respect to its use in mainstream industrial process applications. A review of the various types of sensors that have been developed for industries such as power generation, water treatment and services, mining, and the
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This paper reviews fiber Bragg grating sensing technology with respect to its use in mainstream industrial process applications. A review of the various types of sensors that have been developed for industries such as power generation, water treatment and services, mining, and the oil and gas sector has been performed. A market overview is reported as well as a discussion of some of the factors limiting their penetration into these markets. Furthermore, the author’s make recommendations for future work that would potentially provide significant opportunity for the advancement of fiber Bragg grating sensor networks in these mainstream industries. Full article
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Open AccessArticle
Effectiveness of Implicit Beamforming with Large Number of Antennas Using Calibration Technique in Multi-User MIMO System
Electronics 2017, 6(4), 91; doi:10.3390/electronics6040091 -
Abstract
This paper examines the effectiveness of implicit beamforming (IBF), which enables transmission without channel state information (CSI) feedback in multi-user multiple-input multiple-output (MU-MIMO) systems with a large number of antennas. First, we explain why CSI feedback from terminal stations to the base station
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This paper examines the effectiveness of implicit beamforming (IBF), which enables transmission without channel state information (CSI) feedback in multi-user multiple-input multiple-output (MU-MIMO) systems with a large number of antennas. First, we explain why CSI feedback from terminal stations to the base station produces a very large overhead. A calibration technique is then introduced, which compensates for the difference between the complex amplitudes of the transmitters and receivers to facilitate CSI-feedback-free beamforming; this technique is called IBF. The efficacy of this calibration technique is demonstrated by measuring the amplitude and phase errors obtained using a 16-element array testbed and by performing a channel capacity evaluation. Finally, the throughput under IEEE802.11ac-based massive MIMO transmission, both with and without CSI feedback, is obtained in terms of the medium access control efficiency. Full article
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Open AccessFeature PaperReview
Advances in Electronics Prompt a Fresh Look at Continuous Wave (CW) Nuclear Magnetic Resonance (NMR)
Electronics 2017, 6(4), 89; doi:10.3390/electronics6040089 -
Abstract
Continuous Wave Nuclear Magnetic Resonance (CW-NMR) was a popular method for sample interrogation at the birth of magnetic resonance but has since been overlooked by most in favor of the now more popular pulsed techniques. CW-NMR requires relatively simple electronics although, for most
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Continuous Wave Nuclear Magnetic Resonance (CW-NMR) was a popular method for sample interrogation at the birth of magnetic resonance but has since been overlooked by most in favor of the now more popular pulsed techniques. CW-NMR requires relatively simple electronics although, for most designs, the execution is critical to the successful implementation and sensitivity of the system. For decades there have been reports in the literature from academic groups showing the potential of magnetic resonance relaxation time measurements in industrial applications such as the production of food and drink. However, the cost, complexity and power consumption of pulsed techniques have largely consigned these to the literature. Advances in electronics and developments in permanent magnet technology now require a fresh look at CW-NMR to see if it is capable of providing cost effective industrial solutions. In this article, we review the electronics that are needed to undertake a continuous wave NMR experiment starting with early designs and journeying through the literature to understand the basic designs and limitations. We then review the more recent developments in this area and present an outlook for future work in the hope that more of the scientific community will take a fresh look at CW-NMR as a viable and powerful low-cost measurement technique. Full article
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