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101.
按照IEC 61000-4-4/GB 17626.4—1998的要求,首先应用PSPICE仿真确定电路中各元件的参数值,然后基于拉普拉斯变换用MATLAB求解二阶电路验证各元件参数。在此基础上研制了一台以开关电源作为高压直流电源、以氢闸流管作为主控开关的脉冲群电源。该电源体积小、重量轻、效率高、成本低廉。试验结果表明,其输出信号符合标准要求,可用于快速瞬变脉冲群抗扰度试验。 相似文献
102.
研究了Pt,Ru,Ni为活性金属的负载型催化剂上甲醇质量分数为5%的水溶液的液相重整反应。在合适的温度、体积空速下,Pt基催化剂表现出较好的反应性能,甲醇转化率可达99%,H2选择性达98%以上,产物中CO体积分数小于0.01%。Ni/Al2O3催化剂可使甲醇转化率最高达到98%以上,H2选择性随转化率升高而下降,但不低于80%。Ru/Al2O3催化剂上甲醇的转化率最高,可达到98%以上,但其H2选择性随着转化率的升高,从68%快速下降至20%,明显与Pt、Ni基催化剂上的反应机理不同。根据反应条件和产物组成变化,进一步探讨甲醇反应路径,当产物中H2与CH4选择性比值高于2/3时,反应路径以重整制氢为主;当比值低于2/3时,反应路径以甲烷化为主。 相似文献
103.
徐宝成 《石油化工安全环保技术》2006,22(1):31-34
有机过氧化物是烯烃聚合工业中重要的引发剂。针对烯烃聚合工业用有机过氧化物自分解温度低、易发生反应失控引发火灾爆炸等情况,简要叙述了有机过氧化物的结构、分类、化学性质以及反应特性,重点对其储存、使用、管理等过程中的危险性进行了分析。提出过氧化物储存、运输、使用、报废等方面的风险消减与事故预防措施。 相似文献
104.
The electron spin resonance (ESR) spectra of end‐group spin labelled poly(ethylene oxide) (SLPEO) using 2,2,6,6‐tetramethyl‐piperdine‐1‐oxyl nitroxide and its blends with poly(styrene‐co‐4‐vinylphenol) (STVPhs) of different hydroxyl contents were recorded over a wide temperature range. For a blend of SLPEO and pure polystyrene (PS), the ESR spectrum was composed of a single motion component, indicating that PS was immiscible with PEO. For blends composed of SLPEO and different‐hydroxyl‐content STVPhs, two spectral components with different motion rates were observed over a certain temperature range. The difference between the motion rates should be attributed to micro‐heterogeneity in the blends, with the faster rate corresponding to a nitroxide radical motion trapped in the PEO‐rich domain and the slower rate corresponding to a nitroxide radical motion trapped in the STVPh‐rich domain. Variations in the values of a number of the ESR parameters (Ta, Td and T50G) and the apparent activation energy (Ea) with hydroxyl content in the blends indicated that the miscibility of the blends increased with increasing hydrogen‐bonding density due to specific interactions between the hydroxyl groups in STVPh and the ether oxygens in PEO. Copyright © 2004 Society of Chemical Industry 相似文献
105.
Yu. F. Smirnov 《Measurement Techniques》2007,50(3):293-297
Metrological characteristics of active hydrogen frequency standards are investigated on the basis of internal and external
comparisons. The stability of random changes and drift of hydrogen frequency standards and also the potential capabilities
of time scale preservation with effective consideration of systematic changes in their frequency are demonstrated.
__________
Translated from Izmeritel’naya Tekhnika, No. 3. pp. 42–45, March, 2007. 相似文献
106.
107.
Akbar Eslami Simin Nasseri Bahram Yadollahi Alireza Mesdaghinia Foroogh Vaezi Ramin Nabizadeh Shahrokh Nazmara 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(11):1447-1453
BACKGROUND: Over the past several decades methyl tert‐butyl ether (MTBE) as additive to gasoline, intended to either boost ratings of fuel or to reduce air pollution, has been accepted worldwide. Since MTBE has high water solubility, the occurrence of fuel spills or leaks from underground storage tanks or transferring pipeline has led to the contamination of natural waters. In this study the degradation of aqueous MTBE at relatively high concentrations was investigated by a UV‐visible/ZnO/H2O2 photocatalytic process. The effects of important operational parameters such as pH, amount of H2O2, catalyst loading and irradiation time were also investigated. Concentration of MTBE and intermediates such as tert‐butyl formate and tert‐butyl alcohol were measured. RESULTS: Time required for complete degradation increased from 20 to 150 min when the initial concentration was increased from 10 to 500 mg L?1. The first‐order rate constants for degradation of MTBE were estimated to be 0.183–0.022 min?1 as the concentration increased from 10 to 500 mg L?1. Study of the overall mineralization monitored by total organic carbon analysis showed that at an initial concentration of 100 mg L?1 MTBE complete mineralization was obtained after 100 min under UV‐visible/ZnO/H2O2 photocatalysis. CONCLUSION: The data presented in this paper clearly indicated that UV‐visible/ZnO/O2 as an advanced oxidation process provides an efficient treatment alternative for the remediation of MTBE‐contaminated waters. Copyright © 2008 Society of Chemical Industry 相似文献
108.
109.
A Ml (NiCoMnA1)5 hydrogen storage alloys was prepared by double-roller rapid quenching.Its microstructure, electrochemically and kinetic characteristic were studied.A uniform crystal phase with CaCu5 structure could be detected by XRD analyses, whose average grain size is 30 ~ 50 nm and the ratio of c/a of nano-crystal hydrogen storage alloy is larger.The hydrogen absorption/desertion p - C isotherms of alloy show that its fiat-performance is perfect and the magnetic stagnant effect is very little.An simulate cell is used for electrochemical measurement.Electrode is 10C, the capacity decreasing rate via the 450 cycles at 7C is less than 20%. 相似文献
110.
The effect of hydrogen heat treatment on impurity contents in aluminum nitride powder of different fineness is studied. Thermodynamic calculations are provided pointing to the possibility of forming gaseous hydrogen compounds with impurity elements. It is established that as a result of treatment the contents of impurity elements, i.e. oxygen, carbon, sulfur, are reduced by a factor of 3-13. The optimum hydrogen heat treatment regime is determined: a temperature of 1323 K and an exposure time of 30 min. 相似文献