Differentially amplitude and phase-encoded QAM for the correlatedRayleigh-fading channel with diversity reception

This paper studies the differentially amplitude and phase-encoded (DAPE) quadrature amplitude modulation (QAM) transmission over correlated Rayleigh channels with diversity reception. Operating over two successive received symbols, the optimum and an asymptotic maximum-likelihood (AML) differentially coherent receiver are developed and compared with a conventional switched diversity combining (SDC) grid receiver. It is shown that the AML and SDC grid receivers are much simpler in complexity than the optimum receiver in that no channel side information is required in their realization. An exact expression of the bit-error probability (BEP) is obtained for the SDC grid receiver. Based on a union bound argument, a BEP upper bound for the AML receiver is also derived and verified by simulation. Numerical results on 16- and 64-point constellations show that the AML receiver exhibits an almost optimum performance and the SDC grid receiver with a small level of diversity is nearly optimum. It is also shown by simulation that the conventional equal-gain diversity receiver is almost optimal for demodulating a 16-point DAPE QAM signal     

Analysis of singular systems using Taylor series approach

The Taylor series approach to the analysis of singular systems is considered. An example is given to demonstrate the use of this method.     

Catalyst layer-free carbon-coated steel—An easy route to bipolar plates of polymer electrolyte membrane fuel cells: Characterization on structure and electrochemistry

Stainless steel coated with carbon by CVD process has been evaluated as a low-cost and small-volume substitute for graphite bipolar plate in polymer electrolyte membrane fuel cell (PEMFC). Carbon film was grown at 690–930 °C under gas-mixture of C₂H₂–H₂. Scanning electron microscopy and X-ray diffractometry were used to characterize surface morphology and crystal structure of resultant carbon films, which were found to depend much on reaction temperature. Interfacial contact resistance (ICR), hydrophobicity and chemical stability of obtained specimens were measured to compare with commercial highly oriented pyrolytic graphite (HOPG). All carbon films investigated in this study show improved ICR and hydrophobicity of SUS304 substrate to the level of HOPG. Amorphous carbon layer with continuous film structure prepared at 810 °C shows the best protection of SUS304 substrate against the attack of H_(aq)⁺ (anodic side) and the best resistance of the coated carbon from gasification (cathodic side) in the simulated PEMFC environment.     

Room-temperature growth of high-purity titanium nitride by laser ablation of titanium in a nitrogen atmosphere

Thin films of titanium nitride (TiN) were deposited on glass substrates by KrF excimer laser ablation of titanium over a very broad nitrogen pressure range with different target–substrate distances at room temperature. The as-deposited TiN thin films were analyzed by X-ray diffraction and transmission electron microscopy. It was found that the as-deposited thin films are normally a mixture of TiN and metallic titanium, and the TiN-to-Ti ratio of the as-deposited thin film depends on both the nitrogen pressure and the target–substrate distance. High-purity TiN thin films can be obtained only in a very narrow deposition parameter range. A compound parameter (the product of the nitrogen pressure and the target–substrate distance) is proposed to optimize the deposition of high-purity TiN thin films, and the possible mechanism is also discussed. It was also revealed that the as-deposited TiN thin films are polycrystalline with an average grain size of about 20 nm.     

An analytical model for breakdown voltage of surface implanted SOIRESURF LDMOS

An analytical model for the breakdown voltage of the surface implanted silicon-on-insulator (SOI) REduced SURface Field (RESURP) LDMOS is presented, which allows useful design curves of breakdown voltage in terms of the device parameters, including the substrate bias voltage. Improvement on both the breakdown voltage and the on-resistance of the device due to the surface implantation is demonstrated. Numerical simulations are shown to support the analytical results     

Purification and characterization of recombinant human erythropoietin from milk of transgenic pigs

BACKGROUND: Human erythropoietin (hEPO), a hydrophobic acidic glycoprotein responsible for the regulation of red blood cell production in mammals, is used for the treatment of anemia. In general, the purification of transgenic animal‐derived therapeutic proteins is not easy due to their low titer concentrations and abundant contaminant proteins. For the first time, here the purification and characterization of rhEPO from the milk of transgenic pigs are described. RESULTS: The rhEPO was purified by heparin chromatography, reverse‐phase chromatography, and gel filtration chromatography, resulting in a 16.5% yield and > 98% purity. The rhEPO purified from the milk of transgenic pigs contained less acidic isoforms and was underglycosylated in contrast to CHO‐derived rhEPO. Cell proliferation of the F‐36/EPO‐dependent cell line was proportional to the dose of transgenic pig‐derived rhEPO. CONCLUSION: Transgenic pig‐derived rhEPO with high purity was achieved after three‐step chromatography following two‐step precipitation. The transgenic pig‐derived rhEPO was demonstrated to have comparable potency with CHO‐derived rhEPO. Transgenic pig‐derived rhEPO may not be therapeutically feasible because of different glycosylation, and thus further studies are required to elucidate the effect of this aberrant glycosylation on the biological activity and stability in vivo. Copyright © 2008 Society of Chemical Industry     

Computational fluid dynamic analyses of catalytic combustors for 100 kW-class molten carbonate fuel cell

The asymmetric inner structure of a catalytic combustor causes wall cracking because of regional overheating. Thus, a symmetric shape is proposed in the present work and analyses of the computational fluid dynamics of the existing combustor and the proposed type have been performed. A simulation of the revised combustor without a swirl device revealed that the flow of gases is concentrated on the center of the combustor and only catalysts around the center are used. In the revised combustor with a swirl device, the overall temperatures were estimated to be uniform. However, near the swirl device, high temperature exceeding 1,700 K was measured. Therefore, a heatproof surface coating on the swirl device is necessary for protection of the material. At the initial start-up of the catalytic combustor, hydrogen and natural gas are used. When only natural gas is used, the simulation indicated that the gas does not burn in the revised combustor without a swirl device. However, in the combustor with the swirl device, methane of 34.8% volume burns in the simulation. On the other hand, when hydrogen and natural gas are burned together, methane of 91.7% volume burns in the simulation.     

Effects of light wavelength and intensity on the production of ethanol by Saccharomyces cerevisiae in batch cultures

BACKGROUND: Photoreceptors have been identified in Saccharomyces cerevisae, however, the influence of light on the performance of ethanol fermentation of S. cerevisiae is not yet clear. The aims of this study are to elucidate the influence of light wavelength and intensity on the growth and ethanol production of S. cerevisiae and to describe a novel two‐stage LED light process to optimize ethanol fermentation. RESULTS: Experimental results indicated that maximum biomass concentration X_max of the batch under red LED light increased monotonically with light intensity, and the optimal specific product yield Y_p/x was 13.2 g g^?1 at 600 lux. Maximum ethanol concentration P_max of the batch under blue LED light increased monotonically with light intensity, and the optimal Y_p/x was 18.4 g g^?1 at 900 lux. A novel two‐stage LED light process achieved maximum P_max, of 98.7 g dm^?3 resulting in 36% improvement compared with that of the batch in the dark. CONCLUSION: The light wavelength and its intensity significantly affected cell growth and ethanol formation of S. cerevisiae. Red LED light (630 nm) stimulated cell growth but slightly inhibited ethanol formation. In contrast, blue LED light (470 nm) significantly inhibited cell growth but stimulated ethanol formation. A novel two‐stage LED light process has been successfully demonstrated to optimize ethanol fermentation of S. cerevisiae. Copyright © 2009 Society of Chemical Industry     

Direct simulation of effective conductivity of porous silicon: Fourier treatments

The effective thermal conductivity of anisotropic porous-silicon layers is predicted using the simulated pore structure from a two-dimensional, diffusion-limited model along with the Fourier conduction. The low-dimensionality effect due to the phonon boundary scattering is included through an available modified solid conductivity. It is shown that for the highly branched columnar structure, the effective conductivity across the layer is small and yet much larger than that along the layer. Good agreement is found with available experimental results. It is predicted that the combination of a small pore size and a high porosity leads to a very small effective conductivity. This makes porous-silicon layer an attractive insulator and readily integrable in silicon-based microstructures. In a following paper, the low-dimensionality effect is directly included in a Boltzmann treatment of phonon transport.