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排序方式: 共有3172条查询结果,搜索用时 15 毫秒
51.
Chanho Pak Seung Jae Lee Seol-Ah Lee Hyuk Chang 《Korean Journal of Chemical Engineering》2005,22(2):214-218
To reduce the effect of methanol permeated from the anode, the structure of the cathode was modified from a single layer with
Pt black catalyst to two-layer with PtRh black and Pt black catalysts, respectively. The current density of the direct methanol
fuel cell (DMFC) using the two-layer cathode was improved to 228 mA/cm-2 compared to that (180 mA/cm-2) of the DMFC using the single layer cathode at 0.3 V and 303 K. From the cyclic voltammograms (CVs), it is indicated that
the amount of adsorbates on the metal catalyst in the two-layer cathode is less than that of adsorbates in the single layer
cathode after methanol test. In addition, the adsorbates were removed very rapidly by electrochemical oxidation from the two-layer
cathode. It is suggested fromex situ X-ray absorption near edge structure analysis that the d-electron vacancy of Pt atom in the two-layer cathode is not changed
by the methanol test. Thus, Pt is not covered with the adsorbates, which agrees well with the results of CV. 相似文献
52.
Effect of Mode of Drying on Microstructure of Potato 总被引:2,自引:0,他引:2
Potato v. Irga was subjected to blanching, and thereafter was dried by convection, puff-drying, and freeze-drying. Microstructure of raw, blanched, and dried tissue was analyzed under the light microscope using computer image analysis. It was found that the tissue of the investigated variety is built up from cells much smaller than those described in literature for other cultivars. Blanching caused starch gelatinization and increase of cross-sectional area of cells. There was no evidence of broken cell walls. Convective drying resulted in cell shrinkage and some breaking of cell walls. It was estimated that some 12% of cells lost integrity during drying. Limited disintegration of the tissue caused by convective drying is attributed to small size of cells, large contact area, and high cohesive forces between cells. Puff-drying damaged the tissue much more than the convective drying. The most devastating to tissue microstructure was freeze-drying, probably freezing per se. 相似文献
53.
针对无线传感器网络能量受约束的问题,为实现节点均衡能耗,平衡网络簇头分布,并最大限度地延长网络寿命,提出一种基于细胞膜优化算法的无线传感器网络能量均衡分簇协议。细胞膜优化算法具有良好的全局寻优和快速收敛能力,通过浓度与能量因素对节点进行划分,并结合距离因素完成全局均衡分簇,能够解决传感器网络中簇头分布不均匀、全局能耗不均衡等问题。实验结果表明,该协议具有对无线传感器网络进行快速全局均衡分簇的能力,且与LEACH算法和LEAH-C算法相比,在均衡节点能耗和延长网络生存周期等方面具有更好的性能。 相似文献
54.
55.
Electrochemical cell current requirements for toxic organic waste destruction in Ce(IV)-mediated electrochemical oxidation process 总被引:1,自引:0,他引:1
Vasily V. Kokovkin Sang Joon Chung Subramanian Balaji Manickam Matheswaran Il-Shik Moon 《Korean Journal of Chemical Engineering》2007,24(5):749-756
The electrochemical cell for cerium oxidation and reactor for organic destruction are the most important operation units for
the successful working mediated electrochemical oxidation (MEO) process. In this study, electrochemical cells with DSA electrodes
of two types, single stack and double stack connected in series, were used. The performances towards the electrochemical generation
of Ce(IV) in nitric acid media at 80 °C were studied. The current-voltage curves and cerium electrolysis kinetics showed the
dependence on number of cell stacks needed to be connected in series for the destruction of a given quantity of organic pollutant.
The presence of an optimum region for Ce(III) oxidation with a contribution of oxygen evolution, especially at low Ce(III)
concentration (high conversion ratios), was found. The cells were applied for the Ce(IV) regeneration during the organic destruction.
The cell and reactor processes were fitted in a simple model proposed and used to calculate the current needed in terms of
Ce(III) oxidation rate and the number of cell stacks required for maintaining Ce(IV)/Ce(III) ratio at the same level during
the organic destruction. This consideration was based on the kinetic model previously developed by us for the organic destruction
in the MEO process. 相似文献
56.
The first use of nickel foam (NF) as electrocatalytic negative electrode in a polysulfide/bromine battery (PSB) is described. The performance of a PSB employing NF and polyacrylonitrile (PAN)-based carbon felt (CF) as negative and positive electrode materials, respectively, was evaluated by constant current charge-discharge tests in a single cell. Charge/discharge curves of the cell, positive and negative electrodes show that the rapid fall in cell voltage is due to the drop of positive potential caused by depletion of Br2 dissolved in the catholyte at the end of discharge. Cell voltage efficiency was limited by the relatively high internal ohmic resistance drop (iR drop). Polarization curves indicated that both NF and CF have excellent catalytic activity for the positive and negative redox reactions of PSB. The average energy efficiency of the single cell designed in this work could be as high as 77.2% at 40 mA cm−2 during 48 charge-discharge cycles. 相似文献
57.
目的获得高质量的中国流行株HIV-1B/C重组亚型包膜蛋白抗原。方法改造表达载体,以构建中国流行株HIV-1B/C重组亚型包膜蛋白基因带有筛选标记的真核细胞表达质粒,将所构建质粒转染真核细胞,用含有抗性的培养基筛选出能够高效、持续表达包膜蛋白的稳定表达细胞株。结果所构建的表达载体pVRPEnv转染细胞后可表达目的蛋白,并建立了稳定表达细胞系。结论获得了可以高效、持续稳定表达中国流行株HIV-1B/C重组亚型包膜蛋白的细胞株。 相似文献
58.
59.
Eun-Yong Ko Eun Duck Park Kyung Won Seo Hyun Chul Lee Doohwan Lee Soonho Kim 《Korean Journal of Chemical Engineering》2006,23(2):182-187
Selective CO oxidation in the presence of excess hydrogen was studied over supported Pt catalysts promoted with various transition
metal compounds such as Cr, Mn, Fe, Co, Ni, Cu, Zn, and Zr. CO chemisorption, XRD, TPR, and TPO were conducted to characterize
active catalysts. Among them, Pt-Ni/γ-Al2O3 showed high CO conversions over wide reaction temperatures. For supported Pt-Ni catalysts, Alumina was superior to TiO2 and ZrO2 as a support. The catalytic activity at low temperatures increased with increasing the molar ratio of Ni/Pt. This accompanied
the TPR peak shift to lower temperatures. The optimum molar ratio between Ni and Pt was determined to be 5. This Pt-Ni/γ A12O3 showed no decrease in CO conversion and CO2 selectivity for the selective CO oxidation in the presence of 2 vol% H2O and 20 vol% CO2. The bimetallic phase of Pt-Ni seems to give rise to stable activity with high CO2 selectivity in selective oxidation of CO in H2-rich stream. 相似文献
60.