Experimental study of forced convective boiling for non-azeotropic refrigerant mixtures R-22/R-124 in horizontal smooth tube

In this article, the experiment is carried out with four stages of test section and new experimental data of non-azeotropic refrigerant mixtures R-22/R-124 are presented. Existing correlations are analysed and new ones are proposed for pure refrigerants. The nucleate boiling correlation of the refrigerant mixtures is modified so as to obtain the evaporation heat transfer coefficient of the refrigerant mixtures in a smooth tube. The result shows that the majority of the predictions fall within ±30% of the experiments.     

On a transistor-type hydrogen gas sensor prepared by an electrophoretic deposition (EPD) approach

A Pd/GaN/AlGaN heterostructure field-effect transistor (HFET)-type hydrogen gas sensor, based on an electrophoretic deposition (EPD) approach, is fabricated and studied. Due to the formation of good Schottky gate contact by an EPD approach, the studied HFET shows improved DC performance including the suppressed gate current and better thermal stabilities on current–voltage (I–V) characteristics. This is mainly attributed to the reduction of interface trap density and improved Pd morphology. The EPD-based Pd morphologies are examined by X-ray diffraction, energy dispersive spectroscopy, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. For the used gate-dimension of 1 μm × 100 μm, an EPD-based HFET shows low gate current of 2.9 nA, maximum drain saturation current of 490 mA/mm, and maximum extrinsic transconductance of 78.9 mS/mm at room temperature. Also, solid thermal stabilities on maximum drain saturation current (−0.46 mA/mm K) and maximum extrinsic transconductance (−0.08 mS/mm K) are found as the temperature is increased from 300 to 600 K. For hydrogen gas sensing application, at 370 K, the maximum hydrogen sensitivity of 600.1 μA/mm ppm H₂/air under a 5 ppm H₂/air ambiance and fast response time (30 s) and recovery time (47 s) under a 10,000 ppm H₂/air ambiance are obtained. The EPD approach also demonstrates advantages of low cost, simple apparatus, easy process, little restriction on the shaped substrate, composited deposition, and adjustable alloy grain size. Therefore, the proposed EPD approach gives the promise for fabricating high-performance HFET devices and hydrogen gas sensors.     

Energy-Efficient Dual-Edge-Triggered Level Converting Flip Flops With Symmetry in Setup Times and Insensitivity to Output Parasitics

Level converting flip-flops (LCFFs) are crucial components for multisupply systems as interfaces between different voltage islands. The proposed energy-efficient LCFFs reduce the power consumption of clock networks with dual-edge triggering, support sleep mode of power management mechanisms with data retention, and have symmetry in setup times and insensitivity to output parasitics. With all these features, the proposed LCFFs have 19% and 38% lower power-delay product than the conventional LCFF, as demonstrated by postlayout simulation results.     

Comparison of potential water supply and demand in Taiwan

The authors estimated the potential water supply in Taiwan based on hydrologic and water resource data sets pertaining to 233 rainfall stations, 145 stage stations and 109 reservoirs. The comparison between potential water supply estimates and predicted water demand indicated a slight water shortage, even though Taiwan normally receives a large amount of rainfall. This predicted water shortage likely occurred due to the uneven distribution of rainfall in Taiwan. Taken together, the results of this study demonstrate the importance of conservation of forests and paddy fields for the maintenance of base flow and effective management of reservoirs in Taiwan.     

Comparison of the pulsed field gel electrophoresis patterns and virulence profiles of the multidrug resistant strains of Salmonella enterica serovar Schwarzengrund isolated from chicken meat and humans in Taiwan

Salmonella Schwarzengrund is one of the frequent serovars isolated from chicken meat in Taiwan. This organism is also one of the invasive Salmonella serovars which may cause human salmonellosis and animal infections. In this study, a total of 466 strains of S. Schwarzengrund including 232 retail chicken meat isolates and 234 human isolates in Taiwan were analyzed for their antibiotic resistance and pulsed field gel electrophoresis (PFGE) patterns. For XbaI-digested DNA, a total of 110 PFGE patterns were obtained. When patterns from both origins were analyzed, of these patterns, 21 were shared by isolates from chicken meat samples and humans. In these 21 patterns, 153 (32.8%) isolates from both origins shared the top five patterns. Since ACSSXTT R-type strains are the major concern worldwide and they accounted for 74.5% of total strains used in this study, such R-type strains in the top five XbaI-digested patterns were then further analyzed with AvrII digestion followed by PFGE and PCR assay targeted to 10 Salmonella virulence genes, i.e., avrA, ssaQ, mgtC, siiD, sopB, gipA, sodC1, sopE1, spvC, and bcfC. When PFGE patterns and virulence gene profiles were combined for the analysis of ACSSXTT R-type strains of S. Schwarzengrund, 29 strains from both origins showed the same pattern combinations. Such results suggested the possible transmission of S. Schwarzengrund from chicken meat to humans.     

A full code-patterns coverage high-speed embedded ROM using dynamic virtual guardian technique

Crosstalk between bitlines induces read failure and limits the coverage of applicable code-patterns for high-speed contact/via-programming read-only memories (ROMs) in SoC. Owing to the variation in bitline loading across code-patterns, the amount of coupled noise on an accessed bitline is code-pattern-dependent. This crosstalk effect worsens, with larger coupling capacitance and smaller intrinsic loading, as the technology node shrinks. This study proposes dynamic virtual guardian (DVG) techniques for contact/via-programming ROM macros and compilers to eliminate the crosstalk-induced read failure and increase the code-patterns coverage. Compared with conventional ROMs, DVG techniques achieve higher speed, lower power consumption and better design for manufacturing (DFM) capability with full code-patterns coverage. Experiments on fabricated designs, a conventional ROM and two 256 Kb DVG ROMs, using 0.18 /spl mu/m 1P5M CMOS technology have demonstrated that DVG techniques achieve 100% code-pattern coverage under a small sensing margin.     

Miscibility of SAN with polyacrylates and polymethacrylates

Styrene-acrylonitrile copolymers, SAN, are known to be miscible with poly(methyl methacrylate). Based on the presence of a single composition dependent glass transition and lower critical solution temperature behaviour, it is shown that SAN is also miscible with poly(ethyl methacrylate). However, the SAN does not appear to be miscible with other polymethacrylates or polyacrylates.     

A simple simultaneous geometric and intensity correction method for echo-planar imaging by EPI-based phase modulation

A technique, based on Echo planar imaging (EPI)-based phase modulation factor maps, is described for correction of EPI distortions resulting from field inhomogeneity. In this paper, a phase modulation factor was employed to remove the distortions. The phase modulation factor was obtained experimentally by collecting EPI images with a spin-echo (TE) spacing, deltaTE, equal to the inter-echo time interval, T(i). Then, the distortions resulting from the field inhomogeneity were removed by modulating the kappa-space data with the phase modulation factor. One of the advantages of this method is that it requires only a few extra scans to collect the information on field inhomogeneity. The proposed method does not require a phase unwrapping procedure for field inhomogeneity correction and, hence, is easier to implement, compared to other techniques. In addition, it corrects geometric distortion as well as intensity distortions simultaneously, which is robust to external noise or estimation error in severely distorted images. In this work, we also compared the proposed technique with others including, a) interpolation method with EPI-based displacement maps, and b) modulation method with phase modulation factor maps generated from spin-echo images. The results suggest the proposed technique is superior in correcting severely distorted images.     

The effect of polyimide passivation on the electromigration of Cu multilayer interconnections

Electromigration damage (EMD) is one of the major causes for the failures of interconnect. In this study, the electromigration (EM) of Cu multilayer (TiWN/Cu/TiWN) with polyimide passivation is investigated with an isothermal resistance change method. The EM measurements were carried out on a wafer level at various temperatures (170–230 °C) and current densities (2.28–4.0 ). The activation energy for passivated Cu multilayer is larger than that of the unpassivated ones. The lifetime of passivated specimens are from two to 16 times those of the unpassivated ones. Resistance oscillation, which is attributed to the formation and closing of Cu gap, is observed during EM test. The TiWN interlayer helps to maintain the electrical continuity when a local Cu gap is formed. Hence, the lifetime of Cu metallization is further enhanced by the presence of the interlayer. Copper multilayer interconnect has better EMD resistance than Cu monolayer interconnect does.     

A closed-cycle capillary polymerase chain reaction machine

A novel thermocycling machine based on a microcapillary equipped with bidirectional pressure-driven flow and in situ optical position sensors is described. A 1-microL droplet of reaction mixture moves between three heat zones in a 1-mm-i.d., oil-filled capillary using a multielement scattered light detector and active feedback. Dwell times and accelerations can be adjusted independently. As a demonstration of the device, 30 cycles of a 500-base pair product were performed in 23 min with 78% amplification efficiency. This result compares well with previous high-speed thermocyclers. Theoretically, the arrangement can approach a time of 2.5 min for 30 cycle amplifications of a 500-base pair product.