Roles of organic acids during exectrooxidation reaction over Pt-supported carbon electrodes in direct methanol fuel cells

A comprehensive study has been made to explore the role of organic acids on electrocatalytic performances of platinum (Pt) nanoparticles supported on carbon porous materials (CPMs) in proton exchange membrane fuel cells (PEMFCs). In particular, the effects of carboxylic acids (R–COOH), viz. formic acid, acetic acid, propionic acid, and butyric acid on catalytic activity, stability, and durability of anodic Pt/CPM electrocatalyst in direct methanol fuel cells (DMFCs) were investigated. In the presence of doped carboxylic acids, the electrooxidative activity of Pt/CPM follows the trend: HCOOH < CH₃COOH < C₂H₅COOH < C₃H₇COOH, revealing a consistent increase in the severity of catalyst deactivation with the number of carbons on the alkyl chain of the dopant. The Pt/CPM was found to exhibit electrocatalytic performances and tolerance for poisoning than a commercial Pt/XC-72 catalyst with a similar Pt loading (20 wt%). Moreover, a notable increase in mass activity up to ca. 150% over the spent Pt/CPM catalyst was observed up on removing the organic acid in the feed stream, indicating that catalyst poisoning by deactivation may be revived, even to its “intrinsic” activity.     

Transient Temperature and Thermal Stress Distributions in a Hollow Disk Subjected to a Moving Uniform Heat Source

This study presents numerical analyses of transient temperature and thermally induced stress distributions in a stationary hollow steel disk partially heated by a moving uniform heat source from its outer surface under stagnant ambient conditions. The moving heat source applied on a certain angular segment of the processed surface rotates with a constant angular speed (ω). The peak levels of the temperature gradients and the thermal stress ratios at the heated segments do not rise very much after 2–3 cycles. When the value of ω is increased, the maximum effective thermal stress ratio can be decreased in a considerable amount.     

A VLSI architecture for variable block size video motion estimation

With the advent of new video standards such as MPEG-4 part-10 and H.264/H.26L, demands for advanced video coding, particularly in the area of variable block size video motion estimation (VBSME), are increasing. In this paper, we propose a new one-dimensional (1-D) very large-scale integration architecture for full-search VBSME (FSVBSME). The VBS sum of absolute differences (SAD) computation is performed by re-using the results of smaller sub-block computations. These are distributed and combined by incorporating a shuffling mechanism within each processing element. Whereas a conventional 1-D architecture can process only one motion vector (MV), this new architecture can process up to 41 MV sub-blocks (within a macroblock) in the same number of clock cycles.     

Bend,Twist, and Turn: First Bendable and Malleable Toughened PLA Green Composites

The future of green electronics possessing great strength and toughness proves to be a promising area of research in this technologically advanced society. This work develops the first fully bendable and malleable toughened polylactic acid (PLA) green composite by incorporating a multifunctional polyhydroxybutyrate rubber copolymer filler that acts as an effective nucleating agent to accelerate PLA crystallization and performs as a dynamic plasticizer to generate massive polymer chain movement. The resultant biocomposite exhibits a 24‐fold and 15‐fold increment in both elongation and toughness, respectively, while retaining its elastic modulus at >3 GPa. Mechanism studies show the toughening effect is due to an amalgamation of massive shear yielding, crazing, and nanocavitation in the highly dense PLA matrix. Uniquely distinguished from the typical flexible polymer that stretches and recovers, this biocomposite is the first report of PLA that can be “bend, twist, turn, and fold” at room temperature and exhibit excellent mechanical robustness even after a 180° bend, attributes to the highly interconnected polymer network of innumerable nanocavitation complemented with an extensively unified fibrillar bridge. This unique trait certainly opens up a new horizon to future sustainable green electronics development.     

Modelling of the thermal behaviour of an ultracapacitor for a 42-V automotive electrical system

A three-dimensional modelling approach is used to study the effects of operating and ambient conditions on the thermal behaviour of a NESSCAP 2.7 V/3500 F ultracapacitor cell for a 42-V automotive electrical system. The rate of heat generation of the ultracapacitor during charge and discharge is measured with a calorimeter. The transient temperature distribution of the ultracapacitor during cycling is obtained by using the finite element method with an implicit predictor-multicorrector algorithm. The results show that the temperature of the ultracapacitor cell increases during the first 50 cycles after which it reaches a periodic steady-state value that increases with increasing ambient temperature.     

Nonlinear support vector machine visualization for risk factor analysis using nomograms and localized radial basis function kernels

Nonlinear classifiers, e.g., support vector machines (SVMs) with radial basis function (RBF) kernels, have been used widely for automatic diagnosis of diseases because of their high accuracies. However, it is difficult to visualize the classifiers, and thus difficult to provide intuitive interpretation of results to physicians. We developed a new nonlinear kernel, the localized radial basis function (LRBF) kernel, and new visualization system visualization for risk factor analysis (VRIFA) that applies a nomogram and LRBF kernel to visualize the results of nonlinear SVMs and improve the interpretability of results while maintaining high prediction accuracy. Three representative medical datasets from the University of California, Irvine repository and Statlog dataset-breast cancer, diabetes, and heart disease datasets-were used to evaluate the system. The results showed that the classification performance of the LRBF is comparable with that of the RBF, and the LRBF is easy to visualize via a nomogram. Our study also showed that the LRBF kernel is less sensitive to noise features than the RBF kernel, whereas the LRBF kernel degrades the prediction accuracy more when important features are eliminated. We demonstrated the VRIFA system, which visualizes the results of linear and nonlinear SVMs with LRBF kernels, on the three datasets.     

Superposition Coding with Unequal Error Protection for the Uplink of Overloaded DS-CDMA System

The overloaded CDMA schemes exploited in direct sequence CDMA (DS-CDMA) systems are mainly to accommodate a greater number of users than the available spreading factor N. In this paper, a superposition coding CDMA (SPC-CDMA) with unequal error protection (UEP) is proposed as one of the overloaded CDMA schemes for the next generation mobile communication systems. It exploits the available power control in most base stations to adapt the transmitted power of active users in the uplink channel. In this scheme, the active users are divided into G groups and each group consists of K users. The K users share the same spreading sequence and are distinguished by different received power levels. At the receiver side, the system first performs despreading for group detection followed by multiuser receiver to estimate the K user signals in each group. It is shown through simulations that better performance are achieved compared to the conventional DS-CDMA and existing overloaded collaborative spreading CDMA (CS-CDMA) schemes, in additive white Gaussian noise (AWGN) and fading channels. Hence, the proposed scheme maximizes the system capacity K-fold compared to conventional DS-CDMA system without requiring extra spreading codes, with average signal to noise ratio (SNR) cost of only 1dB and 2 dB over AWGN and fading channels respectively at BER of 10^?3. On the other hand, for the same N, K and power constraints, SPC-CDMA scheme achieves twofold increase in data rate with 0.7 and 4 dB gains over AWGN and fading channels respectively, compared with overloaded CS-CDMA scheme in the same system capacity. In addition, the proposed scheme can also attain different levels of UEP for different users?? requirements by adjusting their fractions of transmitted powers.     

Mode selective interpolation for stereoscopic 3D video in frame-compatible top-bottom packing

As a transition stage from a conventional 2D TV to a full stereoscopic 3D TV system, a frame-compatible format of fitting stereoscopic left and right images to a single frame of the existing 2D TV is required to utilize existing codec and transmission infrastructure. To meet this requirement, a frame-compatible top-bottom packing with a horizontal line offset is proposed, where the vertical resolutions of the stereoscopic left and right images are reduced by half. Then, the optimal interpolation mode for each line segment of the sub-sampled horizontal line is determined by exploiting parallax-compensated data as well as undeleted neighboring upper and lower horizontal lines. At the receiver, the discarded horizontal lines for the left and right images are reconstructed by the interpolation modes provided by the sender. Experimental results show that the proposed algorithm improves the PSNR as much as 1.5–3dB comparing to conventional interpolation filters.     

Study of Low-Temperature Thermocompression Bonding in Ag-In Solder for Packaging Applications

Low-temperature solders have wide applications in integrated circuits and micro-electromechanical systems packaging. In this article, a study on Ag-In solder for chip-to-chip thermocompression bonding was carried out. The resulting joint consists of AgIn₂ and Ag₉In₄ phases, with the latter phase having a melting temperature higher than 400°C. Complete consumption of In solder into a Ag-rich intermetallic compound is achieved by applying a bond pressure of 1.4 MPa at 180°C for 40 min. We also observe that the bonding pressure effect enables a Ag-rich phase to be formed within a shorter bonding duration (10 min) at a higher pressure of 1.6 MPa. Finally, prolonged aging leads to the formation of the final phase of Ag₉In₄ in the bonded joints.     

FTIR characterization of tropical wood–polymer composites

Wood–polymer composites (WPC) of Geronggang (Cratoxylon arborescens), a light tropical hardwood, impregnated with methyl methacrylate (MMA), methyl methacrylate-co-acrylonitrile (1 : 1; MAN), and styrene-co-acrylonitrile (3 : 2; STAN), were prepared by in situ polymerization using gamma radiation or the catalyst–heat treatment. The FTIR spectra of the three types of WPC, with polymer loadings ranging from 10 to 70%, were compared with that of the wood itself and the respective polymers. Characteristic peaks due to C?O vibration of MMA, C?N stretching of acrylonitrile, and ring stretching and bending of styrene monomers, were prominent in the samples that had higher polymer loadings. For the copolymeric systems, quantitation of the FTIR spectra of these characteristic peaks enabled calculations of incorporated acrylonitrile and styrene monomers in the composites to be made. The FTIR spectra of the residues remaining, after exhaustive extraction to remove homopolymer, showed that graft copolymerization of wood components with acrylonitrile and styrene monomers was possible, but not with MMA. Composites prepared by the two methods, gamma radiation and the catalyst–heat treatment, were shown to be chemically very similar.