Elimination of Fresnel Reflection Boundary Effects and Beam Steering in Pulsed Terahertz Computed Tomography

For the past few decades there has been tremendous innovation and development of Terahertz (THz) science and imaging. In particular, the technique of 3-D computed tomography has been adapted from the X-Ray to the THz range. However, the finite refractive index of materials in the THz range can severally refract probing THz beams during the acquisition of tomography data. Due to Fresnel reflection power losses at the boundaries as well as steering of the THz beam through the sample, refractive effects lead to anomalously high local attenuation coefficients near the material boundaries of a reconstructed image. These boundary phenomena can dominate the reconstructed THz-CT images making it difficult to distinguish structural defect(s) inside the material. In this paper an algorithm has been developed to remove the effects of refraction in THz-CT reconstructed images. The algorithm is successfully implemented on cylindrical shaped objects.     

Memoryless block transceivers with minimum redundancy based on Hartley transforms

This paper proposes real linear transceivers employing minimum redundancy, unlike the standard block transceivers that require, at least, L elements of redundancy, where L is the channel order. In all block-based systems, there is an inherent interblock interference (IBI) that can be eliminated by inserting redundancy. For transceivers based on the discrete Fourier transform (DFT), the redundancy induces a circulant channel matrix, allowing superfast implementations. Although it has been known for some time that the minimum redundancy for IBI-free designs of block transceivers is ⌈L/2⌉, only recently practical DFT-based solutions using minimum redundancy were proposed. However, the extension of these solutions to real transforms, such as the discrete Hartley transform (DHT), is not straightforward. The only known solution imposes a symmetry on the channel model that is unlikely to be met in practice. This paper proposes transceivers with practical zero-forcing (ZF) and minimum mean-squared error (MMSE) receivers using DHT, diagonal, and antidiagonal matrices. The resulting systems are asymptotically as simple as orthogonal frequency-division multiplex (OFDM) and single-carrier with frequency-domain (SC-FD) equalization transceivers. In addition, they do not enforce constraints on the channel model. Several computer simulations indicate the higher throughput of the proposals as compared to the standard solutions.     

A low-voltage low-power threshold voltage monitor for CMOS process sensing

In this paper a low-voltage low-power threshold voltage monitor for CMOS process sensing is presented. This circuit works in weak inversion and it can be used as an elementary circuit block for on-chip compensation of the intra-die or inter-die threshold voltage variations in low-power analog and mixed-signal SoC, since it is robust to temperature and power supply voltage variations (similar to the bandgap voltage reference). The proposed threshold voltage monitor has been successfully verified in a standard 0.35-μm n-well CMOS TSMC process. Experimental results have confirmed that the circuit generates an average reference voltage of 758 mV (very close to the typical threshold voltage when extrapolated to absolute zero) for a 950 mV power supply voltage, with a variation of 39 ppm/°C for the −20 to 80°C temperature range.     

Environmentally Friendly Graphene Inks for Touch Screen Sensors

Graphene-based materials have attracted significant attention in many technological fields, but scaling up graphene-based technologies still faces substantial challenges. High-throughput top-down methods generally require hazardous, toxic, and high-boiling-point solvents. Here, an efficient and inexpensive strategy is proposed to produce graphene dispersions by liquid-phase exfoliation (LPE) through a combination of shear-mixing (SM) and tip sonication (TS) techniques, yielding highly concentrated graphene inks compatible with spray coating. The quality of graphene flakes (e.g., lateral size and thickness) and their concentration in the dispersions are compared using different spectroscopic and microscopy techniques. Several approaches (individual SM and TS, and their combination) are tested in three solvents (N-methyl-2-pyrrolidone, dimethylformamide, and cyrene). Interestingly, the combination of SM and TS in cyrene yields high-quality graphene dispersions, overcoming the environmental issues linked to the other two solvents. Starting from the cyrene dispersion, a graphene-based ink is prepared to spray-coat flexible electrodes and assemble a touch screen prototype. The electrodes feature a low sheet resistance (290 Ω □⁻¹) and high optical transmittance (78%), which provide the prototype with a high signal-to-noise ratio (14 dB) and multi-touch functionality (up to four simultaneous touches). These results illustrate a potential pathway toward the integration of LPE-graphene in commercial flexible electronics.     

In search of computer-aided social support in non-communicable diseases care

Non-communicable diseases burden is well-known and care for these diseases goes beyond patients’ engagement, extending to their family, friends, and acquaintances. The ability of social relations in alleviating the harmful effects of health risks is known as social support. Computing can be used to promote social support to enhance the care of non-communicable diseases. However, it is unclear how computing obtains such enhancement. This paper presents a systematic review, in the form of a mapping study, aiming to answer how computing enhances non-communicable diseases care by using social data and by promoting social support. It also looks for available computing models focused on social support promotion in non-communicable diseases care. The study was guided by a two-phase process review, resulting in 38 reviewed papers from journals, conferences, and chapters in the period from 2010 to 2016. In general, the reviewed papers focus on controlled trials, frameworks and systems, knowledge discovery, simulation models or social media usage analysis. Knowledge discovery was the predominant subject, followed by social media usage analysis, and frameworks and systems.     

Survey and comparison of message authentication solutions on wireless sensor networks

Security is an important concern in any modern network. This also applies to Wireless Sensor Networks (WSNs), especially those used in applications that monitor sensitive information (e.g., health care applications). However, the highly constrained nature of sensors imposes a difficult challenge: their reduced availability of memory, processing power and energy hinders the deployment of many modern cryptographic algorithms considered secure. For this reason, the choice of the most memory-, processing- and energy-efficient security solutions is of vital importance in WSNs. To date, a number of extensive analyses comparing different encryption algorithms and key management schemes have been developed, while very little attention has been given to message authentication solutions. In this paper, aiming to close this gap, we identify cipher-based Message Authentication Codes (MACs) and Authenticated Encryption with Associated Data (AEAD) schemes suitable for WSNs and then evaluate their features and performance on a real platform (TelosB). As a result of this analysis, we identify the recommended choices depending on the characteristics of the target network and available hardware.     

A study of drilling performances with minimum quantity of lubricant using fuzzy logic rules

Nowadays the increasing interest to perform machining operations is in dry/near-dry environments. The reason includes health and safety of operator, cost, ease of chip recyclability, etc. However one important process, which is difficult to perform in dry, is drilling. Without coolant, drilling leads to excessive thermal distortion and poor tool life. In order to tackle these conflicting requirements, the essentiality of study on machining performances with minimum quantity lubricant (MQL) becomes important.Fuzzy logic rules, which are derived based on fuzzy set theory, are used to develop fuzzy rule based model (FRBM). The performance of FRBM depends on two different aspects: structures of fuzzy rules and the associated fuzzy sets (membership function distributions, MFDs). The aim of this study is to investigate the performances of FRBMs based on Mamdani and TSK-types of fuzzy logic rules with different shapes of MFDs for prediction and performance analysis of machining with MQL in drilling of aluminum alloy. A comparison of the model predictions with experimental results and those published in the literature shows that FRBM with TSK-type fuzzy rules describes excellent trade-off with experimental measurements.     

Improved Message Forwarding for Multi-Hop HaRTES Real-Time Ethernet Networks

Nowadays, switched Ethernet networks are used in complex systems that encompass tens to hundreds of nodes and thousands of signals. Such scenarios require multi-switch architectures where communications frequently occur in multiple hops. In this paper we investigate techniques to allow efficient multi-hop communication using HaRTES switches. These are modified Ethernet switches that provide real-time traffic scheduling, dynamic bandwidth management and temporal isolation between real-time and non-real-time traffic. This paper addresses the problem of forwarding traffic in HaRTES networks. Two methods have been recently proposed, namely Distributed Global Scheduling (DGS) that buffers traffic between switches, and Reduced Buffering Scheme (RBS), that uses immediate forwarding. In this paper, we discuss the design and implementation of RBS within HaRTES and we carry out an experimental validation with a prototype implementation. Then, we carry out a comparison between RBS and DGS using worst-case response time analysis and simulation. The comparison clearly establishes the superiority of RBS concerning end-to-end response times. In fact, with sample message sets, we achieved reductions in end-to-end delay that were as high as 80 %.     

A Tutorial on Multiplierless Design of FIR Filters: Algorithms and Architectures

Finite impulse response (FIR) filtering is a ubiquitous operation in digital signal processing systems and is generally implemented in full custom circuits due to high-speed and low-power design requirements. The complexity of an FIR filter is dominated by the multiplication of a large number of filter coefficients by the filter input or its time-shifted versions. Over the years, many high-level synthesis algorithms and filter architectures have been introduced in order to design FIR filters efficiently. This article reviews how constant multiplications can be designed using shifts and adders/subtractors that are maximally shared through a high-level synthesis algorithm based on some optimization criteria. It also presents different forms of FIR filters, namely, direct, transposed, and hybrid and shows how constant multiplications in each filter form can be realized under a shift-adds architecture. More importantly, it explores the impact of the multiplierless realization of each filter form on area, delay, and power dissipation of both custom (ASIC) and reconfigurable (FPGA) circuits by carrying out experiments with different bitwidths of filter input, design libraries, reconfigurable target devices, and optimization criteria in high-level synthesis algorithms.     

Optimized Prototype Filter Based on the FRM Approach for Cosine-Modulated Filter Banks

A design procedure for frequency-response masking (FRM) prototype filters of cosine-modulated filter banks (CMFBs) is proposed. In the given method, we perform minimization of the maximum attenuation level in the filters stopband, subject to intersymbol interference (ISI) and intercarrier interference (ICI) constraints. For optimization, a quasi-Newton algorithm with line search is used, and we provide simplified analytical expressions to impose the interference constraints, which greatly reduce the computational complexity of the optimization procedure. The result is lower levels of ISI and ICI for a predetermined filter order, or a reduced filter complexity for given levels of interferences. It is then illustrated how the FRM-CMFB structure is suitable for implementing filter banks with a large number of bands, yielding sharp transition bands and small roll-off factors, which is an attractive feature for a wide range of practical applications.