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21.
Acrylamide (AAm) solid state polymerization was induced using argon plasma to improve the pervaporation performance of poly(tetrafluoroethylene) (PTFE) membranes (PTFE‐g‐PAAm) in aqueous alcohol mixtures. The surface morphology, chemical composition, and hydrophilicity changes in the PTFE and PTFE‐g‐PAAm membranes were investigated using ATR‐FTIR, SEM, AFM, X‐ray photoelectron spectroscopy, and water contact angle measurements. The surface hydrophilicity rapidly increased with increasing Ar exposure time, but decreased after longer Ar exposure time because of the degradation in the PTFE‐g‐PAAm membrane grafted layer. Compared with the hydrophilicity of the pristine PTFE membrane (water contact angle = 120°), the argon plasma induced acrylamide (AAm) solid‐state polymerization onto the PTFE surface (water contact angle = 43.3°) and effectively improved the hydrophilicity of the PTFE membrane. This value increases slowly with increasing aging time and then reaches a plateau value of about 50° after 10 days of storage under air. The pervaporation separation performances of the PTFE‐g‐PAAm membranes were higher than that of the pristine PTFE membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:909–919, 2006 相似文献
22.
Abstract In this note, a simple model of a circular cavity with two arcs rotated in opposite directions on the boundary is employed to demonstrate flow patterns of recirculation. A particular streamline “cutting” the domain into two separating eddies is formed as a circular arc. When the rotating angular speed of the arc is proportional to the length of the arc, the streamline degenerates to a straight line. 相似文献
23.
Shyy's multiple one-dimensional adaptive grid method is modified to improve the grid skewness. A test problem of steady isotropic heat conduction illustrates that both the grid distortion and the accuracy of temperature distribution are improved significantly. 相似文献
24.
A realistic modeling of circuit output error patterns with random test inputs is suggested. The model can be used as the basis for accurate evaluation of the probability of aliasing in compact testing. For several example compression techniques, the following aspects are investigated: identification of the error patterns that cause aliasing; asymptotic effectiveness analysis; and comparative simulation study with a limited number of random test vectors applied 相似文献
25.
Poh Chiang Loh Vilathgamuwa D.M. Gajanayake C.J. Yih Rong Lim Chern Wern Teo 《Power Electronics, IEEE Transactions on》2007,22(2):498-507
The newly proposed Z-Source inverter has been proven in the literature to exhibit both steady-state voltage buck and boost capabilities using a unique LC impedance network coupled between the power source and converter circuit. This paper now presents transient modeling and analysis of a voltage-type Z-source inverter. These aspects are found to be challenging and they need to be carefully investigated before attempting to design advanced control algorithms for controlling the Z-source inverter. Through detailed analysis, the paper identifies several phenomena on the dc and ac-sides of the inverter, which would result in the inverter having a non-minimum-phase transient response. The dc-side phenomenon is associated with the Z-source impedance network, which is shown through small-signal and signal-flow-graph analyses to be having a right-half-plane zero in its control-to-output transfer function. Also, the ac-side phenomenon is shown through space vector analysis to depend on the time intervals of inverter states used for reconstructing the desired inverter output voltage. Based on the ac vectorial analysis, a method for improving the inverter transient response is also presented. Last, simulation results obtained using a switching-functional model and experimental results obtained using a laboratory prototype are presented for validating the described theoretical concepts 相似文献
26.
Abstract Two types of GaAs/AIGaAs laser arrays, each consisting of five emitters and suitable for high power operations, have been fabricated and tested. They are easily fabricated, have high yield and deliver high power. The first array structure was fabricated using proton implantation to define the active lasing channels. Damage introduced by proton bombardment provides both electrical and optical confinement for the lasing channels. We have investigated the effect of heat treatment on the performance of these lasers and have found that the heat treated samples had a lower threshold current and higher quantum efficiency. For 400 μm long devices, with uncoated facets, we have measured a threshold current of 200 mA and a peak power of 231 mW/facet. The highest external quantum efficiency is 60%. We have also fabricated laser arrays with a simple, self‐aligned, index guided ridge waveguide structures. We have obtain a pulsed output power of up to 551 mW/facet with a quantum efficiency of 37.4%. The typical threshold current is 370 mA. 相似文献
27.
The fluorinated copolymer emulsions containing different monomers with the reactive groups were successfully prepared at our lab, using emulsion polymerization technique. The water repellency and the durability for the fabrics treated by fluorinated water repellents after 30 and 50 washes were measured and compared. Actually, the combination of the comonomers containing blocked isocyanate or other reactive groups after copolymerization would increase the durability of the water repellency. In addition, the blocked isocyanate crosslinking agent (Jintexguard FCN) does, indeed, substantially increase the durability also. It clearly indicates that the copolymer emulsion prepared by the reaction of fluorinated acrylate, cyclohexyl methacrylate, and 3‐chloro‐2‐hydroxy‐propyl methacrylate(Topolene M) with monomers containing blocked isocyanate group(Jintexan BIA) showed very good durability. More importantly, the combination of this copolymer and Jintexguard FCN will significantly provide excellent water repellency and durability after 50 washes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2451–2457, 2007 相似文献
28.
29.
Jee Weng Tan Kwai Lin Thong Nirmala Devi Arumugam Wai Lian Cheah Yih Wei Lai Kek Heng Chua Raha Abdul Rahim Sabaratnam Vikineswary 《International Journal of Hydrogen Energy》2009,34(17):7538-7541
Molybdenum (Mo) nitrogenases consist of two components: dinitrogenase reductase (encoded by nifH) and the dinitrogenase or MoFe protein (encoded by nifDK). Nitrogenase enzyme of photosynthetic bacteria is responsible for hydrogen production. Therefore, primers were designed for the nitrogenase gene only. In this study, two primers (ND and NH) were designed after comparative genomic analysis of nifH and nifD gene sequences from public databases. The designed primers were used for the amplification of nifH and nifD genes to detect nitrogenase genes in photosynthetic bacteria. Initial detection was done using a monoplex Polymerase Chain Reactions (PCRs) followed by optimization of the PCR protocols. Subsequently, a duplex PCR was designed for amplification and detection of nifH and nifD genes in indigenous photosynthetic bacteria. Evaluation of the duplex PCR on six samples isolated from Palm Oil Mill Effluent (POME) showed that only four isolates contained both the nifH and nifD genes, indicating that these isolates were potential hydrogen-producing bacteria. PCR detection provides a rapid and efficient pre-identification of potential photosynthetic bacterial hydrogen producers. 相似文献
30.
The local implicit scheme of Reddyet al. is extended to the minmod and third-order upwind TVD schemes. Numerical tests show that the proposed scheme is stable. In addition, it is found that if the flow field has a dominant direction, setting the iteration sweep to align with this direction can significantly improve the converging speed. 相似文献