排序方式: 共有120条查询结果,搜索用时 15 毫秒
21.
2,3,5—三甲基吡啶合成路线的述评 总被引:2,自引:0,他引:2
2,3,5-三甲基吡啶是合成奥美担唑的重要中间体,文章介绍了2,3,5-三甲基吡啶常见的合成方法,对其优缺点作了评价。 相似文献
22.
用细粉末Raney-Ni催化剂研究了木糖水溶液加氢的本征反应动力学。在考察的温度(373~393K)、压力(1~6MPa)和木糖浓度(0.02~1.3mol/dm3)范围内,速率与木糖浓度成1级。氢压低于4~5MPa时,符合Langmuir-Hinshewood形式的方程,用非线性优化法关联其参数,得到本征速率方程。反应机理推测为吸附氢原子与吸附木糖分子反应,表面反应生成的中间物被木糖解吸而成产物是控制步骤。373K以上在高压区出现的速率剧增现象可能与低能吸附位的激活有关 相似文献
23.
Enantioselective hydrogenation of ethyl 2-oxo-4-phenylbutyrate to ethyl (R)-2-hydroxy-4-phenyl- bu- tyrate on Pt/γ-Al2O3 modified by 10,11-dihydrocinchonidine was studied by investigating the influences of the amount of modifier, initial concentration of reactant, pressure and temperature on conversion and enantiometric excess in a stirred autoclave and the effects of the liquid velocity, gas velocity, modifier concentration and various catalytic beds in a trickle-bed reactor. The maximum optical yields were about 50% and 60% in the two types of reactors, respectively. It was assumed that the total hydrogenation rate included the reaction rates over the unmodified and modified active sites on platinum surface and a kinetic model, which fitted the experimental data well in autoclave, was obtained. A simplified plug-flow model was proposed to describe the bed average efficiency of trickle-bed reactor. 相似文献
24.
25.
26.
针对人体对真实空间中三维立体虚拟图像的成像和直接交互问题,提出了包含虚拟立体成像和基于线绳的力反馈设备的立体交互系统设计方法。立体图像的产生方法是通过编程建立一个VC工程,实现了三维对象模型的导入和左右视差图像的产生;人手指末端位置的检测是通过电机的增量式光电编码器测量出线绳长度,进而利用线绳的空间几何关系求出的;根据手指末端位置与虚拟图像的位置关系,利用空间几何关系来合成线绳拉力。在系统中导入对象模型并且进行交互的实验表明:系统具有良好的成像效果和交互效果。 相似文献
27.
The electroencephalogram(EEG)characters value of observers can be deduced by collecting brain electrical information when the observers are watching parallax stereo video.The characters value will change clearly when watching asthenopia appear.To investigate the characters of parallax stereo watching asthenopia,the EEG of observers were recorded through the whole watching process of parallax stereo films until watching asthenopia appeared.The recorded EEG data of observers belongs to time-domain information.Fourier transform can process these data to frequency spectrum information.Theαandβwaves average power can be got by Newton-Cotes equation from the information.The ratio ofβpower to the sum ofαandβpower,CV,can be defined as EEG characters value of parallax stereo watching asthenopia and used to estimate the asthenopia degree of observers.Our experiments show that the smaller the CVis,the more serious the asthenopia is. 相似文献
28.
对硝基苯甲酸催化加氢本征动力学 总被引:8,自引:0,他引:8
用活性炭载钯催化剂,在排除扩散影响的条件下,研究了对硝基苯甲酸加氢的动力学。实验测定了氢气压力、温度、催化剂浓度等因素对反应速率的影响。研究结果表明:对硝基苯甲酸催化加氢反应为一级反应,表面化学反应活化能E=25.910kJ/mol,原子氢吸附热QH=38.487kJ/mol,其总括动力学方程为r=Kc2TKHαPH(1+KHα·PH)2·cA其中:c2TK=4.035×103exp[-25909.49/RT],min-1αKH=5.013×10-6exp(38486.93/RT),MP 相似文献
29.
30.
大豆磷脂酰胆碱在硅胶柱中的色谱特性 总被引:2,自引:0,他引:2
为研究大豆磷脂酰胆碱的色谱分离过程,建立了考虑轴向扩散、液膜传质阻力和内扩散阻力的一般性速率模型,用有限元和正交配置法求解该模型.模拟结果与实验数据吻合,并得到了液膜传质系数与流速的关系及孔内有效扩散系数.采用乙醇 水体系分离了大豆浓缩磷脂中的磷脂酰胆碱,考察了流动相组成和流速对分离效果的影响.随着流动相中水质量分数的增加,磷脂酰胆碱的容量因子和分离度减小.流动相中的水质量分数以20%为最佳. 相似文献