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Various decoupling methods were proposed and investigated for multiple-input multiple-output (MIMO) Base Station (BS) systems. These methods can effectively decouple the dual-polarized co-polar signal but fail to decouple the cross-polarized signal, similarly limiting the BS's overall decoupling performance. In this paper, different antenna arrays are designed to illustrate the coupling mechanism of cross-polarized BS antennas, and a comprehensive study of the relationship between antenna configurations and mutual couplings is conducted. It is shown that compact size antenna elements enlarge the edge-to-edge separation, and the loop-shaped dipole elements reduce the cross-polarization couplings. Finally, the array-antenna decoupling surface (ADS) method is applied in a 2×2 array composed of the designed antennas. Thanks to the improved antenna unit, the decoupling task is eased, and a better decoupling performance is achieved compared with the original ADS work.

Near-field scanning microwave microscopy (SMM) employs microwave radiation to image and characterize samples down to the atomic scale, including soft biological structures or inorganic materials, such as ferroelectric films. However, SMM generally also senses sample topography; hypersensitivity to topography becomes problematic with additional parasitic contributions and may partially or completely mask nontopographic sample features in the data, such as contrast in electrical conductivity or permittivity. This work proposes a simple and effective procedure to remove unwanted parasitic effects from SMM images. Differently from existing procedures, the method is applicable either in postprocessing or in real time, i.e., during the scanning operation. This allows the immediate visualization of nontopographic sample features in the instrument screen. As a proof of concept, hafnium zirconium oxide (HfZrO) ferroelectric film with high surface roughness is studied; unwanted contributions were removed from SMM data, providing a clear map of the sample ferroelectric structure that was originally hidden.

Nowadays, 5G is playing a significant role in the efficiency of network security and creating more and faster channels for communication. 5G is evolving industries such as healthcare, education, marketing, transportation, and V2X (Vehicle-to-everything). In addition, 5G considers a new radio access technology that is adding new applications like the Internet of Things (IoT), Augmented Reality, Virtual Reality, connected cars, connected people-to-people, smart city, connected homes that are considered using higher bandwidth and low latency. Mainly, this paper is focusing on security challenges faced by the Vehicular ad-hoc network (VANET). VANET faces threats in three different fields; security, safety, and infotainment, which further have numerous attacks. More precisely, this research conducted an in-depth study and proposed a VANET trust model. Therefore the proposed model deals specifically with the “location closeness” parameter. Moreover, the trust model integrated with 5G cloud to support greater coverage, effective network density with respect to network infrastructure and IoT as well. Therefore, in this article, an effort has been put forward to implement the model using case studies to validate the trust model based on the “location closeness” parameter. The results proved the valid implementation of the model by identifying the trusted communication between the vehicles.

This paper presents an active mode subtraction method based on the characteristic mode analysis to estimate the forward directivity based on the difference in modal significance curves. This made the optimization of the antenna gain in the design process to be more efficient. To the best of the authors’ knowledge, such method is innovative and proposed in literature for the first time. This method is derived on the basis that the total radiated field of the antenna, and consequently, the directivity is mainly contributed by the excited dominant modes. To demonstrate its effectiveness, three compact, planar, and wearable antennas with increasing complexity will be designed and optimized using this method. The first is a conventional circular patch antenna operating at 5.3 GHz, whereas the second one is a planar loop antenna operating at 3.08 GHz. The third design is a crown-shaped planar antenna (CPA) with a $3\times3$ artificial magnetic conductor (AMC) plane integrated underneath to reduce potential coupling effects from the body. All three antennas are made fully using textiles with the same thicknesses: felt fabric as its substrate and ShieldIt Super as its conductive textile. For all designs, the use of the proposed method, which is validated using the method of moments, has predicted the maximum direction of radiation and its respective gain at the desired frequencies with good accuracy. Besides that, the design of the AMC plane for the CPA is also optimized using CMA prior to the integration with the antenna and a leather wrist strap. Measurements of the final crown-shaped antenna design indicated a good agreement with simulations, with an operating bandwidth of more than 240 MHz, FBR of 15.73 dB and a directional radiation pattern outward from the body.

In this work, the design procedure of a new decoupling network for different antennas is presented for mobile terminals operating in the Sub-1 GHz band (from 0.698 to 0.96 GHz). To evaluate its applicability for different resonant and non-resonant antenna types, two antenna elements have been chosen to be decoupled using the proposed decoupling network: a printed inverted-F antenna and a capacitive coupling element antenna. Simulation and measurement results showed that the decoupling network offer promising improvements in terms of impedance matching, port isolation, envelope correlation coefficient (ECC), and total efficiency. In addition, the antennas are also investigated with the ergodic capacity, multiplexing efficiency, gain, and diversity gain (both calculated using maximal ratio combining technique). Due to the contribution of the decoupling network, the ECC of both types of multiple antennas are less than 0.3, with a 30 % improvement in total efficiency and an inter-element spacing miniaturization of 34 %.

The Internet of things (IoT) and advancements of wireless technology have evolved intelligent transport systems to integrate billion of smart objects ready to connect to the Internet. The modern era of the Internet of things (IoT) has brought significant development in vehicular ad hoc networks (VANETs) which transformed the conventional VANET into the Internet of Vehicle (IoV) to improve road safety and diminished road congestion. However, security threats are increasing due to dependency on infrastructure, computing, dynamic nature, and control technologies of VANET. The security threats of VANETs could be addressed comprehensively by increasing trustworthiness on the message received and transmitting node. Conversely, the presence of dishonest vehicles, for instance, Man in the Middle (MiTM) attackers, in the network sharing malicious content could be posed as a severe threat to VANET. Thus, increasing trustworthiness among nodes can lead to increased authenticity, privacy, accuracy, security, and trusted information sharing in the VANET. In this paper, a lightweight trust model is proposed, presented model identifying dishonest nodes and revoking its credential in the MiTM attack scenario. Furthermore, addressing the privacy and security requirement, the pseudonym scheme is used. All nodes in the VANET established trust provided by initially RSU, which is a trusted source in the network. Extensive experiments are conducted based on a variety of network scenarios to evaluate the accuracy and performance of the presented lightweight trust model. In terms of recall, precision, and F-score, our presented model significantly outperformed compared to MARINE. The simulation results have validated that the proposed lightweight model realized a high trust level with 40% of MiTM attackers and in terms of F-score 95%, whereas the MARINE model has 90%, which leads to the model to attain high detection accuracy.

This paper investigates the performance variation when a different number of antenna elements (AEs) is integrated onto a single MIMO mobile terminal, both in free space and when held in a user hand in data mode. Starting with a minimum of two AEs, this investigation assessed the performance of the MIMO terminal with every additional two AEs (up to 18 AEs) in terms of envelope correlation coefficient (ECC), efficiency, multiplexing efficiency, capacity and maximal ratio combining (MRC). The integrated MIMO antennas are identical and operate between 5 and 6 GHz for 5G applications. Results indicated that ECC increased with the number of AEs. However, ECC remains less than 0.32 for the case of 18 AEs in both free space and with a user hand. Meanwhile, the free space efficiency of about 90 % for the two AEs is observed to decrease with the increasing number of AEs to about 50 % with 18 AEs. However, the efficiency of elements changes with user hand depending on the level of interaction between each element and the hand. Direct blockage of AEs by the hand resulted in efficiencies of as low as 5 %, while at the same time, other AEs retained an efficiency of up to 75 %. At the center frequency of 5.5 GHz, the free space capacity is 11.1, 49.5 and 83.2 bit/s/Hz with two, ten and 18 AEs, respectively. However, the use of the mobile terminal in the proximity of the user hand degraded these levels by 11 % (two AEs), 35 % (10 AEs) and 31 % (18 AEs). Finally, multiplexing efficiency showed that capacity degradation is caused mainly by the degradation of AEs efficiency, whereas the impact of low correlation between AEs is found to be an insignificant factor. In addition to the capacity analysis, gain and diversity gain of the maximal ratio combining technique was also investigated.

Buildings are becoming smarter through the deployment of intelligent and energy-efficient technologies that reduce energy consumption while making buildings easier to manage and operate. Demand for lighting systems, efficient heating, ventilation and air conditioning (HVAC), as well as other types of hardware such as controls and sub-meters, is growing rapidly that needs more attention in terms of the energy efficiency. Moreover, the energy management of micro-generation or poly-generation system has always been very complex. Keeping the balance between demand and production is a challenging task for researchers. This paper investigates a simple yet very effective and intelligent demand response algorithm to mitigate the intermittency problem, providing an uninterrupted power supply to the users. The developed algorithm is fully capable of balancing the consumption and the production by controlling the user pre-defined load patterns that is based on the state of charge (SOC) of the storage system. The algorithm is tested on a microgrid system that consists of different loads, six photovoltaic (PV) solar panels, a small wind turbine system, and a set of lead-acid battery banks. The experimental result shows the maximum use of renewable energy while reducing the peak demand, cost of end-users and low or no carbon emissions. To achieve a significant reduction in energy consumption as well as to keep the balance between production and demand, this algorithm can be implemented for the efficient use of intermittent renewable energy sources.

Recent researches have shown that spectral representation provides a significant speed-up in the massive computation workload of convolution operations in the inference (feed-forward) algorithm of Convolutional Neural Networks (CNNs). This approach results in reducing the computational complexity of the classification task, which makes spectral-based CNN suitable for implementation on embedded platform that typically has constrained resources. However, a major challenge in this approach is that the mathematical formulation of a nonlinear activation function in spectral (frequency) domain is currently not available; hence, computation of the activation functions in each layer has to be performed in the spatial domain. This results in several spatial-frequency domain switchings that are computationally very costly, and as such, it would be advantageous to strictly stay in the frequency domain. Hence, in this work, a novel Spectral Rectified Linear Unit (SReLU) for the activation function is proposed, that makes it possible for the computations to remain in the frequency domain, and therefore avoids the multiple compute-intensive domain transformations. To further optimize the classification speed of the network, an efficient spectral-based CNN model is presented that uses only the lower frequency components by way of fusing the convolutional and sub-sampling layers. Additionally, we provide and utilize a frequency domain equivalent of the conventional batch normalization layer that results in improving the accuracy of the network. Experimental results indicate that the proposed spectral-based CNN model achieves up to 17.02 × and 3.45 × faster classification speed (without considerable accuracy loss) on AT&T face recognition and MNIST digit/fashion classification datasets, respectively, as compared to the equivalent models in the spatial domain, hence outperforming conventional approaches significantly.

Objective:To assess the dental practitioners' use of social media, concerning demographic and social variables and the impact of social media use on dental practice.Methods:The study was a cross-sectional analytical study of dental practitioners in Riyadh, Saudi Arabia. A self-administered 30-items questionnaire was distributed to 438 dentists, which included eight questions related to background and demographic information and 22 questions related to the use of social media within the dental practice. Data were entered and analyzed usingSPSSsoftware. Data analysis included frequency distributions and chi-square tests to assess the association of social media use with demographic and social variables and its impact on dental practice. Significant level was considered ifpwas less than 0.05.Results:Of participating, 338 dentists, 52% were using social media in their practice. Twitter was the most commonly used (35%). Education was the primary purpose of using social media (43%), while entertainment was the least (8%). Approximately 62% and 68% are using social media for marketing of their dental practice and broadcasting treatment outcome, respectively. Social media was observed to be used significantly higher among Non-Saudi, general and private dentists. Participating dentists who used social media in their practice significantly recommended using social media to other dentists.Conclusion:In general, non-Saudis, general practitioners and dentists practicing in private clinics are significantly using more social media during their practice. The majority of dental practitioners indicated that social media has improved their dental practice and become an indicator of successful practice.

A dramatic evolution can be observed in cellular wireless communication. It started from analog 2G (global system for mobile communication) toward high-data-rate systems such as 3G (wideband code-division multiplexing access), 3.5G (high-speed packet access), 4G (long-term evolution (LTE) and LTE advanced), and currently converging in a more optimized and compact 5G (orthogonal frequency-division multiple access) form. The main challenges for designing of mobile terminal antennas are the compact size requirement of the built-in structure, multiband capabilities, and the number of integrated antennas that form a multiple-input multiple-output (MIMO) terminal system. Moreover, they are required to fulfill all performance and safety standards. For mobile antennas, their radiation efficiency may be affected by the interaction of user head/hand, which consequently affects the correlation of MIMO antenna systems. This paper provides an overview of user effect on mobile terminal antennas in the last seven years. An overview of the Cellular Telecommunication and Internet Association specifications for mobile terminal antennas will first be explained. This is followed by a discussion on the user's effects on MIMO parameters, channel capacity on mobile terminal antennas, and millimeter-wave applications prior to the presentation of recent technologies that are aimed at improving the antenna performance. Finally, a perspective and potential future investigations on mobile terminal antennas will be discussed in the conclusion.

In this paper, flexible and deployable double-sided linear-to-circular polarizers designed on polydimethylsiloxane are proposed for the first time to the best of our knowledge. ShieldIt textile is used as the conducting element of the two designs based on two different unit cell arrays: a loaded circular patch unit cell or an unloaded circular patch unit cell, both backed by a generic rectangular element on its reverse side. This is in contrast to conventional frequency-selective structure-based linear-to-circular polarizers implemented using rigid substrates, which are multi-layered and requires inter-layer physical spacing. This complicates their implementation using flexible substrates and in a deployable format. Upon implementation of this double-sided polarizer, their final performances are evaluated in terms of the phase difference, conversion efficiency, 3-dB axial ratio (AR), and ellipticity bandwidth (from 40° to 45°). Measurements indicated good agreements with simulations, and both structures exhibited more than 90% of conversion efficiency from 2.34 to 3 GHz (for the loaded circular unit cell) and from 2.36 to 3 GHz (for the unloaded circular unit cell). In terms of ellipticity, a bandwidth of 8.67% is observed for the unloaded design and 13.82% for the loaded design. The unloaded structure exhibited a fractional 3-dB AR bandwidth of 36.36% (from 1.98 to 2.86 GHz) in simulations, and 32.64 % (from 2.00 to 2.78 GHz) when evaluated experimentally. Conversely, the loaded design showed only 12.58%. An equivalent circuit model is proposed and validated via a comparison between the circuit and full-wave simulations. Finally, the performances of these polarizers are also assessed under different bending conditions due to the use of flexible materials, prior to the proposal of a suitable deployment mechanism.

A compact crown-shaped planar antenna integrated with a 3 × 3 artificial magnetic conductor (AMC) ground is presented for wearable internet of things communications. Simulations were performed using the commercial software FEKO based on two approaches: characteristic mode analysis and the method of moments. This paper aims to optimize the operation of the AMC reflector by studying and understanding its mode behavior. Results show that the proposed antennas operate at 5.8 GHz with acceptable radiation characteristics in terms of reflection coefficients, realized gain of 8 dBi, and a front-to-back ratio of 17.33 dB. Moreover, the flexible features of the antenna make it suitable for wearable IoT applications.

The design of a wearable wideband textile antenna based on a loop structure and fed using a coplanar waveguide line is proposed in this work. Characteristic mode analysis is used to first estimate the radiating modes on the structure. This is to ensure that the optimal mode significance is chosen. Analysis of modal significance enabled the first four modes to be identified from the structure. In this paper, the antenna is proposed to designed with an inverse partial ground (IPG) to enhance the bandwidth. It is shown that this IPG method improved impedance bandwidth to 1560 MHz (60.57%), indicating a bandwidth broadening of about 370 MHz (11.61%). A compact size of 70×70 mm2(0.57 × 0.57 λg) is also maintained, with a realized gain of 4.23 dBi. Finally, the proposed antenna is fabricated and measured to validate the analysis experimentally, indicating a good agreement with simulations.

A 24-48 GHz wideband frequency tripler has been developed based on a 130-nm SiGe BiCMOS technology. The 2-stage tripler employs a compact wideband matching technique for the inter-stage and output matching, leading to a measured 3-dB bandwidth of 24 GHz (24-48 GHz), or 67 % with reference to the center frequency. The obtained peak conversion gain is -2.5 dB at 27 GHz with a -5-dBm input power, and the saturated output power is -0.87 dBm at 33 GHz with a 4.8-dBm input power. The tripler consumes 6.8 mW. The circuit occupies 460 × 300 μm2, excluding probing pads.

Future many-core systems need to handle high power density and chip temperature effectively. Some cores in many-core systems need to be turned off or &lsquo, dark&rsquo, to manage chip power and thermal density. This phenomenon is also known as the dark silicon problem. This problem prevents many-core systems from utilizing and gaining improved performance from a large number of processing cores. This paper presents a dynamic thermal-aware performance optimization of dark silicon many-core systems (DTaPO) technique for optimizing dark silicon a many-core system performance under temperature constraint. The proposed technique utilizes both task migration and dynamic voltage frequency scaling (DVFS) for optimizing the performance of a many-core system while keeping system temperature in a safe operating limit. Task migration puts hot cores in low-power states and moves tasks to cooler dark cores to aggressively reduce chip temperature while maintaining high overall system performance. To reduce task migration overhead due to cold start, the source core (i.e., active core) keeps its L2 cache content during the initial migration phase. The destination core (i.e., dark core) can access it to reduce the impact of cold start misses. Moreover, the proposed technique limits tasks migration among cores that share the last level cache (LLC). In the case of major thermal violation and no cooler cores being available, DVFS is used to reduce the hot cores temperature gradually by reducing their frequency. Experimental results for different threshold temperatures show that DTaPO can keep the average system temperature below the thermal limit. Affirmatively, the execution time penalty is reduced by up to 18% compared with using only DVFS for all thermal thresholds. Moreover, the average peak temperature is reduced by up to 10.8∘C. In addition, the experimental results show that DTaPO improves the system&rsquo, s performance by up to 80% compared to optimal sprinting patterns (OSP) and reduces the temperature by up to 13.6∘C.

This paper presents a single-layered fabric-based flexible linear-to-circular polarizer for GNSS application operating at 1.575 GHz. The structure presented here is based on a square aperture with an E-shaped patch structure on the reverse side. The size of the structure is 0. 21λ 0 ×0. 26λ 0 × 0. 01λ 0 The complete structure is flexible, and the frequency of operation is centered at 1.575 GHz, with a minimum value of the axial ratio achieved is 0.06 dB. The 3 dB axial ratio fractional bandwidth is 3.81% (1.54-1.60 GHz) and the conversion efficiency fractional bandwidth covering 90% is 5.09% (1.53 to 1.61 GHz).

This paper presents a two-dimensional capacitive sensor circuit implemented in 28-nm silicon technology for material characterization. The circuit is based on a 4.5-GHz quadrature oscillator with a single inductor and distributed capacitor array with 12.6-um pitch. The 16×16 sensor array is designed with minimal signal energy loss to enable scalable designs. The quadrature oscillator is embedded in a trans-linear loop for frequency shift amplification up to 36 times with an acquisition bandwidth of 2.4 MHz. The readout time for single pixel drops below the limit set by the quantization noise floor and reaches near optimal window, while the sensor maintains a sensitivity of 3 ppm. A mixer is used to down-convert the high-frequency component to an intermediate frequency. A digital core is used to acquire and process the data.

A wearable textile antenna with dual-band and dual-sense characteristics is presented in this work. It operates at the 2.45 GHz band for WBAN and WLAN applications, and at the 1.575 GHz band for Global Positioning System (GPS) applications. An antenna backing based on an artificial magnetic conductor (AMC) plane operating at 2.45 GHz band is introduced to reduce the backward radiation and to improve antenna gain. It consists of a $3\times 3$ array of square patch unit cells, where each unit cell is integrated with four square slits and a square ring. A square-shaped patch is then located on top of the substrate as its radiator. To enable dual-band operation, two corners of this radiator are truncated, with each of the four corners incorporated with a rectangular slit to enable its circular polarization characteristic in the GPS band. Simulation and experimental results are in good agreement and indicate proper antenna operation with linear polarization in the 2.45 GHz band and circular polarization in the 1.575 GHz band, with realized gain of 1.94 dBi and 1.98 dBic, respectively.

A flexible Kapton-based coplanar waveguide-fed (CPW) patch antenna has been designed in this work to operate in different wireless applications. The wideband operation and compact size of the antenna is enabled using a simple rhombic-shaped integrated onto the monopole which was designed using a rectangular patch. The proposed broadband antenna model operated below -10dB at 2.45 GHz and 3.5 GHz for the WLAN/WBAN and 5G band, respectively. The antenna optimization process is explained when varying the ground structure, patch dimensions, feed width, and substrate thickness using FEKO software. The performance of the antenna is studied in terms of radiation efficiency, gain, bandwidth and current distributions. Results indicate that the proposed antenna operates throughout the 2.45 and 3.5 GHz bands, with a bandwidth of1710 MHz.

A compact and flexible coplanar waveguide-fed (CPW) monopole antenna is presented for operation at four different wireless bands. The antenna design is based on a simple rectangular patch which is then integrated with multiple L-shaped slots to enable multiband operation at 1.22, 1.56, 2.45 and 3.42 GHz, offering a reflection coefficient of -10 dB at these frequencies. Modeling is performed using FEKO, a commercial software, based on two approaches: the method of moments (MoM) and characteristic mode analysis (CMA). Results show satisfactory agreement of the predicted resonant frequencies. In addition, radiation efficiency, realized gain, bandwidth and current distributions are discussed in the paper. Finally, a systematic investigation of the bending effects for the proposed wearable antenna is also presented.

Multilevel converter generally consists of more switching devices than the conventional two-level converter topology. The performance of these multilevel converters tends to increase by using high switching frequency which may also increase the switching loss that is the largest dominating loss of a power converter. This paper proposed a novel modulation strategy with a mixed switching frequency scheme that uses both high and low switching frequency to overcome this problem. Different multilevel converter topology such as Cascaded H- Bridge (CHB), Cascaded H5 (CH5), Neutral point Clamped (NPC), and Flying Capacitor Converter (FCC) topologies are presented for the validation of using proposed mixed switching frequency scheme. The level shifted modulation technique is used for CHB, CH5, NPC, and FCC except for CH5 topology which doesn’t allow level shifting operation. Moreover, it is observed that the zero-voltage state occurs for the CH5 topology during mixed switching condition which may result in reactive power flow from load/grid to the photovoltaic solar panel. Hence a new modified H5 topology is proposed to avoid the reactive power flow. H5 topology has never been implemented into the multilevel converter application. This research work emphasizes the efficiency improvement of different multilevel converter topologies. MATLAB SIMULINK is used for the simulation and the results are carried out clearly to demonstrate the effectiveness and efficient outcomes of the proposed switching scheme for grid- connected multilevel converters.

Recently, there is increasing interest in using behind-the-meter (BTM) solar systems for grid services. However, providing visibility and operational situational awareness of BTM solar systems mainly operated by small-scale solar inverters is challenging due to the requirement of relatively expansive networked observation tools (e.g., micro phasor measurement units (µPMUs)) and consequent cybersecurity threats through networks. This paper presents a secure, cost-effective, µPMUs-like metering method using a blockchain-assisted smart (BAS) inverters for a BTM solar system. The proposed BAS inverter consisting of an internet of things device as a node of a local blockchain network enables the secure provision of inverter measurement data for grid services. The BAS inverter sends the encrypted local measurement data with a timestamp to a local blockchain miner. Once the blockchain miner generates a tamper-resistant metering ledger including the measurements, it is used to assess the situational awareness of the BTM solar system. The concept of the proposed metering using the BAS inverters is validated by experimental studies.

Collaborative Filtering (CF) is a widely used technique in recommendation systems. It provides personal recommendations for users based on their preferences. However, this technique suffers from the sparsity issue which occurs due to a high proportion of missing rating scores in a rating matrix. Several factorization approaches have been used to address the sparsity issue. Such techniques have also been considered to tackle other challenges such as the overfitted predicted scores. Nevertheless, they suffer from setbacks such as drift in user preferences and items’ popularity decay. These challenges can be solved by prediction approaches that accurately learn the long-term and short-term preferences integrated with factorization features. Nonetheless, the current temporal-based factorization approaches do not accurately learn the convergence of the assigned k clusters due to a lower number of short-term periods. Additionally, the use of optimization algorithms in the learning process to reduce prediction errors is time-consuming which necessitates a faster optimization algorithm. To address these issues, a new temporal-based approach named TWOCF is proposed in this paper. TWOCF utilizes the elbow clustering method to define the optimal number of clusters for the temporal activities of both users and items. This approach deploys the whale optimization algorithm to accurately learn short-term preferences within other factorization and temporal features. Experimental results indicate that TWOCF exhibits a superior CF prediction accuracy achieved within a shorter execution time when compared to the benchmark approaches.

This paper compares ASIC and FPGA implementations of two commonly used architectures for 2-dimensional discrete cosine transform (DCT), the parallel and folded architectures. The DCT has been designed for sizes 4x4, 8x8, and 16x16, and implemented on Silterra 180nm ASIC and Xilinx Kintex Ultrascale FPGA. The objective is to determine suitable low energy architectures to be used as their characteristics greatly differ in terms of cells usage, placement and routing methods on these platforms. The parallel and folded DCT architectures for all three sizes have been designed using Verilog HDL, including the basic serializer-deserializer input and output. Results show that for large size transform of 16x16, ASIC parallel architecture results in roughly 30% less energy compared to folded architecture. As for FPGAs, folded architecture results in roughly 34% less energy compared to parallel architecture. In terms of overall energy consumption between 180nm ASIC and Xilinx Ultrascale, ASIC implementation results in about 58% less energy compared to the FPGA.

In recent years, the convolutional neural network (CNN) has found wide acceptance in solving practical computer vision and image recognition problems. Also recently, due to its flexibility, faster development time, and energy efficiency, the field-programmable gate array (FPGA) has become an attractive solution to exploit the inherent parallelism in the feedforward process of the CNN. However, to meet the demands for high accuracy of today's practical recognition applications that typically have massive datasets, the sizes of CNNs have to be larger and deeper. Enlargement of the CNN aggravates the problem of off-chip memory bottleneck in the FPGA platform since there is not enough space to save large datasets on-chip. In this work, we propose a memory system architecture that best matches the off-chip memory traffic with the optimum throughput of the computation engine, while it operates at the maximum allowable frequency. With the help of an extended version of the Roofline model proposed in this work, we can estimate memory bandwidth utilization of the system at different operating frequencies since the proposed model considers operating frequency in addition to bandwidth utilization and throughput. In order to find the optimal solution that has the best energy efficiency, we make a trade-off between energy efficiency and computational throughput. This solution saves 18% of energy utilization with the trade-off having less than 2% reduction in throughput performance. We also propose to use a race-to-halt strategy to further improve the energy efficiency of the designed CNN accelerator. Experimental results show that our CNN accelerator can achieve a peak performance of 52.11 GFLOPS and energy efficiency of 10.02 GFLOPS/W on a ZYNQ ZC706 FPGA board running at 250 MHz, which outperforms most previous approaches.

T eacher education aims to foster a change in perspective in teaching and learning within various educational contexts from prospective teachers to real teachers. This change is often seen to involve three forms of knowing: knowing "that", knowing "how", and knowing "why". Transformative learning has much to do with such a change. When prospective teachers critically reflect on teaching as a process, and are engaged in a rational dialogue within a safe, supportive, collaborative classroom environment, they will be able to accomplish the outcomes coming and then consider them in future practices: elaborating or redefining the existing frames of reference, learning new frames of reference, transforming points of views, and transforming habits of mind. By so doing, they can become transformative teachers who can affect their learners – implicitly or explicitly – to be transformative as well.Therefore, this paper addresses how transformative learning can be activated in teacher education programs in general for constructing a community of knowledge. The paper has four main sections. Section one deals with the relationship between transformative learning, critical reflection and teacher education. Section two tackles the form, the features and the requirements of the pedagogic context for developing transformative learning. The paper concludes with section three which proposes a conceptual model for using transformative learning in teacher education contexts. It ends with section four giving some implications that can be implemented so as to set the proposed transformative learning-based model into practice.

A multiband monopole antenna with minimised ground plane influence for portable devices is presented. This antenna operates at LTE band 13 (0.746-0.787 GHz), GPS, LTE band 11 (1.427-1.495 GHz), LTE band 3 (1.71-1.88 GHz), WLAN (2.4-2.48 GHz) and WiMAX (3.3-3.88 GHz) with at least -6 dB of reflection coefficient. The performance of antennas for portable devices is commonly influenced by the ground plane to result in variation in terms of operating frequency, impedance bandwidth and radiation pattern. Via a parametric investigation of the antenna geometry and its integration with peripherals devices, it is validated that the influence of the ground plane is minimised by adjusting the feed position. This in turn reduces the current distribution on the ground plane. It is also noticed that the impedance matching level is also more robust with the reduction of ground plane influence. The antenna features an omnidirectional radiation pattern across the all operating frequencies. Fabrication and assessment of the fabricated antenna indicated a close agreement with simulations.

Wearable devices present an increasingly attractive solution for numerous applications in sectors ranging from the military to medicine to consumer electronics. They will also play an integral role in the imminent fifth-generation (5G) networks, which are expected to operate with higher bit rates and lower outage probabilities in smaller microcells and picocells covering broader areas than fourth-generation (4G) or older technologies. In addition, beam reconfigurability and beamforming are expected to facilitate spectral and energy efficiencies at both the mobile device and base station levels. In overcoming the limitations of current 4G systems, the new features and capabilities envisioned for 5G networks will radically change applications in transportation, health care, smart homes, and wireless robots, among many others [1], [2].

Cube Satellite (CubeSat) technology is an attractive emerging alternative to conventional satellites in radio astronomy, earth observation, weather forecasting, space research, and communications. Its size, however, poses a more challenging restriction on the circuitry and components as they are expected to be closely spaced and very power efficient. One of the main components that will require careful design for CubeSats is their antennas, as they are needed to be lightweight, small in size, and compact or deployable for larger antennas. This paper presents a review of antennas suitable for picosatellite applications. An overview of the applications of picosatellites will first be explained, prior to a discussion on their antenna requirements. Material and antenna topologies which have been used will be subsequently discussed prior to the presentation of several deployable configurations. Finally, a perspective and future research work on CubeSat antennas will be discussed in the conclusion.

This paper presents the design and characterization of a 0.56 THz frequency synthesizer implemented in standard 65 nm CMOS technology. Its front end consists of triple-push Colpitts oscillators (TPCOs), followed by the first and second stage injection locking frequency dividers (ILFDs) and a divide-by-16 chain. TPCOs are used to triple their fundamental frequencies to 0.53–0.56 THz, while ILFDs and the subsequent divider chain are used to divide such frequencies to 2.7–2.9 GHz. Its back end consists of separate frequency and phase-locked loops with unique CMOS circuit designs to accomplish the desirable frequency/phase locking, including: 1) band-selection inductor switches; 2) simultaneous bulk voltage tuning over TPCOs and the first ILFD; and 3) a dual port injection architecture for the first ILFD. The resultant prototype realizes a 21 GHz frequency locking range with phase noise lower than −74 dBc/Hz at 1 MHz offset, and consumes 174 mW dc power.

This work presents the design of a compact meander-based antenna for search and rescue application. The proposed antenna is designed on a polydimethylsiloxane (PDMS) substrate, which is robust, flexible, waterproof and suitable for use in harsh environments. Due to the need for operation at a relatively low frequency of 406 MHz, antennas for the search and rescue application require an extended electrical length, thus typically resulting in large sizes. This is alleviated by implementing the meander-based structure on the antenna to ensure size compactness. Besides that, to minimize the effects of the human body when worn, the antenna is integrated with a full ground plane on its reverse side to shield the body from electromagnetic coupling. Results indicated that the antenna operated with a center frequency of 406 MHz and bandwidth of 30.88 MHz (7.61 %). A unidirectional radiation is produced and the final size is 190 × 60 × 5 mm (0.257 × 0.081 × 0.0068) λo.

151 GHz CMOS transmitter and receiver are presented for ultra-short distance (~1 mm) contactless connection and plastic waveguide communications. To continue to scale the communication bandwidth, the 4-level pulse amplitude modulation (PAM-4) is utilized by implementing a current-mode PAM-4 modulator in the transmitter. The transmitter and receiver suffer non-linear characteristics and create amplitude distortions on PAM-4 signaling. A digital pre-distortion circuit is integrated in the PAM-4 modulator to correct such system non-idealities. 151 GHz antennas are realized on FR4HR substrate and used as air-to-air/chip-to-waveguide couplers. On top of contactless connection and plastic ribbon waveguide, plastic-embedded PCB channels are introduced by exploiting copper-coated slots on PCB and plastic ribbons to communicate through PCB substrates. The transmitter and receiver are fabricated in 28-nm CMOS process. The demonstrated system consumes 60.2 mW under 1.2 V supply while transferring 30 Gb/s of PAM-4 data, achieving 2.01 pJ/bit energy efficiency.

Near-field scanning microwave microscopy (SMM) is a technique gaining popularity for the study of the electrical properties of both soft and hard matter on the nanometer scale. Despite the current focus on semiconductors, the applications of SMM on new two-dimensional materials such as platinum diselenide (PtSe2) are still in an initial stage. In this work, the imaging capabilities of an innovative SMM and the analysis of the electrical properties of PtSe2 are demonstrated.

This paper presents a two-dimensional capacitive sensor array implemented in a 0.13-µm silicon technology for material characterization. The circuit is based on an oscillator operating at 4.5 GHz with a single inductor and a distributed capacitor. The 6×6 sensor array can be individually selected. When a dielectric material is in the near field of a pixel, it results in a shift of the oscillator frequency. A mixer is used to down-convert the the high-frequency component to an intermediate frequency. A digital core is used to acquire and process the data. The array is capable of detecting capacitance shift with a sensitivity down to 1.25 aF and a spatial resolution of 6 µm.

A flexible planar antennas using substrate gap structure (SG) technique to improve the performance of planar antennas in terms of reduces the reflection coefficient and the backward radiation are presented. Two types of probe-fed microstrip patch antennas are studied using FEKO software to quantify its contributions in terms of surface wave reduction, which is expected to results in reduces the reflection coefficient and the backward radiation. The choice of the microstrip patch antenna is due to its design simplicity, ease of fabrication and integration of the SG element. Simulations indicated that this technique enabled the improvements of reflection coefficients up to -32.27, 25.52 and -28.02 dB operating in the band 5.56, 6.11 and 8.73 GHz respectively. Besides that, the backward radiation is reduced to 7.28 and 27.2 dB at the resonant frequencies 3 and 7.11 GHz respectively.

Most of the cores in future many-core system-on-chip (MCSoC) will be off or ‘dark’ to manage the high power density and chip temperature of future chips. This problem is called dark silicon problem. This paper presents a task scheduling technique for optimizing the MCSoC performance under temperature constraint for dark silicon. The proposed technique uses both task migration and dynamic voltage frequency scaling (DVFS) to optimize many-core system performance, while the system temperature is kept in a safe operating range. Task migration improves system performance and balances heat distribution among cores by moving tasks from active cores to dark cores, while DVFS reduces core speed in case of thermal limit violation. Simulation results show that using both task migration and DVFS techniques reduces peak temperature by 12° C and keeps the average system temperature under the thermal limit, while the execution time increased by 16% compared with 50% when only DVFS technique is used.

A circuit model for a flexible linear-to-circular polarizer is proposed. This linear-to-circular polarizer is designed based on the concept of Frequency Selective Surface (FSS) unit cells on one side and a rectangular-shaped conductive strip (CS) on its reverse side. The overall polarizer is implemented on a felt substrate, whereas ShieldIt Super conductive textile is used to form the conductive elements for operation in the S-band. Its principle of operation and its interaction with different orthogonal polarized wave components are first presented, followed by the generation and study of the surface currents to understand the waves in different polarizations. This study is summarized in the form of an equivalent circuit model. To further assess this model, the textile-based polarizer is then simulated using full wave simulations and compared to the results obtained from the proposed circuit model. Both results indicated satisfactory agreement in terms of transmission coefficient. Further analysis of the proposed polarizer using full wave simulations indicated promising results in terms of conversion efficiency and axial ratio. A fractional bandwidth of 7.35 %, operating from 2.36 to 2.55 GHz and an axial ratio of 1.4 dB indicated its operation in the S-band.

This study is focused on highly coupled multiple antennas with defected ground slot techniques. Two Printed Inverted-F Antenna (PIFA) are positioned at the top edge of chassis symmetrically. Both antennas are operating at low-band Long-Term Evolution (LTE) with center frequency, 829MHz. Rectangular defected ground slot is implemented to reduce the coupling effect between the antennas on the ground plane of the small chassis. Parameter study of the rectangular defected ground slot is studied with different width, W and length, L. Furthermore, the optimized dimensions of rectangular defected ground slot, W and L are simulated and presented. The optimized defected ground slot reduced the mutual coupling up to -4.5 dB. The envelope correlation coefficient (ECC) achieved less than 0.5. The ground plane of the multiple antenna structure has been further investigated by introducing another slot with a gap of 1mm between them. The achieved result is not significant in term of S-parameter and ECC compared to single defected ground slot.

This paper presents a bi-layered textile-based flexible linear-to-circular polarizing surface. The proposed structure is designed based on a loop type structure for CubeSat application in the S-band. Each unit cell is sized at 0.42λg×0.40λg×0.02λg for operation centered at 2.2 GHz. This unit cell is then multiplied into a 4 × 4 array to form the polarizing surface. It features a 3 dB axial ratio bandwidth (ARBW) of 34.31 % in simulations and 29.09 % in measurements. Besides that, an equivalent circuit model of the unit cell and the assessment of the polarizer under oblique incidences are presented. The performance of the proposed surface is validated by placing it in front of a patch antenna operating at 2.2 GHz. The antenna performance indicated an increase in terms of realized gain from 3.21 dB to 7.33 dB when integrated with the polarizing surface, besides successfully converting linearly-polarized waves to circularly-polarized.

An electrically small, low profile, multi-band, wireless USB dongle antenna is proposed in this paper. The antenna is able to operate at LTE 700 in the lower band while in the higher band, it covers GPS (1.6 GHz), DCS 1800/PCS1900 and LTE 2300/2600. Besides that, this antenna also operates over WLAN 2.4/3.6 GHz and WiMAX 3.5 GHz frequency bands. The antenna is designed based on a spiral shaped radiator with an L-shaped stub along its feed line. It is also shown that the proposed antenna has minimized ground plane effect on performance of antenna. It has a compact size of 56 × 9.5 mm2. Fabricated antenna shows a good agreement between simulation and measurement.

This paper presents a comprehensive review of mobile terminal antenna researches performed in the past seven years and the current challenges related to the user's influence on the performance of fifth generation (5G) terminal antennas. The main challenges for the designing of mobile terminal antennas are to meet the compact size requirements of built-in structures and their multiband capabilities. The antenna design techniques that are used to achieve broader operating bandwidths with smaller antenna dimensions will be first discussed. This is followed by the effects of user interactions with the head/hand for mobile antennas in terms of radiation efficiency and, consequently, the correlation of multiple input multiple output (MIMO) antenna systems. The ultimate aims of this paper are as follows: 1) to highlight the different frequencies of mobile terminal antennas for different applications; 2) to highlight mobile terminal antennas that have been developed for 5G application; 3) to study and discuss the effects of user's hand on 5G mobile terminal antennas; and 4) to discuss the research gap, issues, and challenges in the field of user's effects on mobile terminal antennas for 5G applications. In addition to that, an investigation of the users' hand effects on two MIMO mobile terminal antennas operational in the sub-6-GHz 5G band is presented. This investigation performed using two MIMO antennas is an attempt to formulate guidelines on efficient mobile terminal antenna design in the presence of user's hand in C Band (from 3.4 to 3.6 GHz) and LTE-U Band 46 (from 5.15 to 5.925 GHz).

This work presents the design and optimization of an antenna with defected ground structure (DGS) using characteristic mode analysis (CMA) to enhance bandwidth. This DGS is integrated with a rectangular patch with circular meandered rings (RPCMR) in a wearable format fully using textiles for wireless body area network (WBAN) application. For this integration process, both CMA and the method of moments (MoM) were applied using the same electromagnetic simulation software. This work characterizes and estimates the final shape and dimensions of the DGS using the CMA method, aimed at enhancing antenna bandwidth. The optimization of the dimensions and shape of the DGS is simplified, as the influence of the substrates and excitation is first excluded. This optimizes the required time and resources in the design process, in contrast to the conventional optimization approaches made using full wave "trial and error" simulations on a complete antenna structure. To validate the performance of the antenna on the body, the specific absorption rate is studied. Simulated and measured results indicate that the proposed antenna meets the requirements of wideband on-body operation. ispartof: SENSORS vol:21 issue:7 ispartof: location:Switzerland status: published

Recommendation systems suggest peculiar products to customers based on their past ratings, preferences, and interests. These systems typically utilize collaborative filtering (CF) to analyze customers’ ratings for products within the rating matrix. CF suffers from the sparsity problem because a large number of rating grades are not accurately determined. Various prediction approaches have been used to solve this problem by learning its latent and temporal factors. A few other challenges such as latent feedback learning, customers’ drifting interests, overfitting, and the popularity decay of products over time have also been addressed. Existing works have typically deployed either short or long temporal representation for addressing the recommendation system issues. Although each effort improves on the accuracy of its respective benchmark, an integrative solution that could address all the problems without trading off its accuracy is needed. Thus, this paper presents a Latent-based Temporal Optimization (LTO) approach to improve the prediction accuracy of CF by learning the past attitudes of users and their interests over time. Experimental results show that the LTO approach efficiently improves the prediction accuracy of CF compared to the benchmark schemes.

The rating matrix of a personalized recommendation system contains a high percentage of unknown rating scores which lowers the quality of the prediction. Besides, during data streaming into memory, some rating scores are misplaced from its appropriate cell in the rating matrix which also decrease the quality of the prediction. The singular value decomposition algorithm predicts the unknown rating scores based on the relation between the implicit feedback of both users and items, but exploiting neither the user similarity nor item similarity which leads to low accuracy predictions. There are several factorization methods used in improving the prediction performance of the collaborative filtering technique such as baseline, matrix factorization, neighbour-base. However, the prediction performance of the collaborative filtering using factorization methods is still low while baseline and neighbours-base have limitations in terms of over fitting. Therefore, this paper proposes Ensemble Divide and Conquer (EDC) approach for solving 2 main problems which are the data sparsity and the rating scores’ deviation (misplace). The EDC approach is founded by the Singular Value Decomposition (SVD) algorithm which extracts the relationship between the latent feedback of users and the latent feedback of the items. Furthermore, this paper addresses the scale of rating scores as a sub problem which effect on the rank approximation among the users’ features. The latent feedback of the users and items are also SVD factors. The results using the EDC approach are more accurate than collaborative filtering and existing methods of matrix factorization namely SVD, baseline, matrix factorization and neighbours-base. This indicates the significance of the latent feedback of both users and items against the different factorization features in improving the prediction accuracy of the collaborative filtering technique.

This paper provides a brief introduction to high-density interconnect (HDI) technology and its implementation on printed circuit boards (PCBs). The advantages and challenges of implementing 10-Gbps signal transmission on high-density interconnect boards are discussed in detail. The advantages (e.g., smaller via dimension and via stub removal) and challenges (e.g., crosstalk due to smaller interpair separation) of HDI are studied by analyzing the S-parameter, time-domain reflectometry (TDR), and transmission-line eye diagrams obtained by three-dimensional electromagnetic modeling (3DEM) and two-dimensional electromagnetic modeling (2DEM) using Mentor Graphics HyperLynx and Keysight Advanced Design System (ADS) electronic computer-aided design (ECAD) software. HDI outperforms conventional PCB technology in terms of signal integrity, but proper routing topology should be applied to overcome the challenge posed by crosstalk due to the tight spacing between traces.

An on-chip Substrate Integrated Waveguide (SIW) antenna operating in Half (HF) mode and One and a Half (OHF) mode is presented. The antenna is implemented in compliance with design rule of Commercial 65 nm CMOS technology. The proposed antenna shows increased bandwidth (compared to resonant antennas) of 20 GHz (0.54 THz – 0.56 THZ). Moreover, antenna shows a measured directivity of 9.4 dBi, leading to a gain of 2.8 dBi, when calculated with simulated efficiency.