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891.
完全液相法与溶胶-凝胶法制备Cu-Zn-Al双功能催化剂对浆态床一步法合成二甲醚的催化性能比较 总被引:1,自引:0,他引:1
采用完全液相法和溶胶-凝胶法分别制备了组成完全相同的Cu-Zn-Al双功能催化剂,用XRD、氮气吸附-脱附实验和XPS等手段对催化剂的性质进行表征,考察了催化剂对浆态床一步法合成二甲醚反应的催化性能.结果表明,两种方法制备的Cu基催化剂中Cu组分的物相和表面Cu含量明显不同,而催化剂的织构性质基本相同.完全液相法制备的... 相似文献
892.
以Racah的群表示论和Slater的波函数理论为基础,分别建立了4f2组态离子Pr~(3+)在三角晶体场C3v和C3h中的91×91完全能量矩阵,并对Pr~(3+)离子掺杂在卤化物CsCdBr_3和GdCl_3中的Stark能级做了计算与分析.结果显示计算值与实验值吻合很好,表明在分析由稀土离子掺杂体系的能级分裂时,完全能量矩阵方法是有效的方法.此外,将两种具有不同点群对称的体系的能级分裂情况作了比较,结果显示六阶晶体场参量对能级分裂的影响是不能忽略的,而且CsCdBr_3:Pr~(3+)和GdCl_3:Pr~(3+)将产生不同程度的畸变. 相似文献
893.
运用时域有限差分法计算了地面有限长电缆在高功率微波、超宽带和核电磁脉冲作用下的外导体感应电流。计算结果表明:场强相同情况下,核电磁脉冲在电缆上感应的电流最大,持续时间最长,高功率微波和超宽带在几m长和几十m长的电缆上感应的电流相差不大;入射角对电缆感应电流也有影响,电场方向与电缆平行时感应最强;地面电缆的感应电流振荡频率比自由空间中电缆的感应电流振荡频率低;随着大地电导率的增大,感应电流反射波衰减加快;电缆任一端接地后,接地端电缆感应电流都会增大。 相似文献
894.
This paper reports the induced growth of high quality ZnO thin film
by crystallized amorphous ZnO. Firstly amorphous ZnO was prepared by
solid-state pyrolytic reaction, then by taking crystallized
amorphous ZnO as seeds (buffer layer), ZnO thin films have been
grown in diethyene glycol solution of zinc acetate at 80℃. X-ray
Diffraction curve indicates that the films were preferentially
oriented [001] out-of-plane direction of the ZnO. Atomic force
microscopy and scanning electron microscopy were used to evaluate
the surface morphology of the ZnO thin film. Photoluminescence
spectrum exhibits a strong ultraviolet emission while the visible
emission is very weak. The results indicate that high quality ZnO
thin film was obtained. 相似文献
895.
An approximate theoretical expression for the current induced by long internal solitary waves is presented when the ocean is continuously or two-layer stratified. Particular attention is paid to characterizing velocity fields in terms of magnitude, flow components, and their temporal evolution/spatial distribution. For the two-layer case, the effects of the upper/lower layer depths and the relative layer density difference upon the induced current are further studied. The results show that the horizontal components are basically uniform in each layer with a shear at the interface. In contrast, the vertical counterparts vary monotonically in the direction of the water depth in each layer while they change sign across the interface or when the wave peak passes through. In addition, though the vertical components are generally one order of magnitude smaller than the horizontal ones, they can never be neglected in predicting the heave response of floating platforms in gravitationally neutral balance. Comparisons are made between the partial theoretical results and the observational field data. Future research directions regarding the internal wave induced flow field are also indicated. 相似文献
896.
A neuron model of the Morris and Lecar form is investigated, which is composed of two individuals and is considered to be functioned by the gap junction coupling. When the level of the reversal potential in the calcium ion channel is small, neurons adjust their activities to the common asymptotic states. However, if we increase the level of the reversal voltage in the calcium ion channel, the exact synchrony firing of neurons is produced. Patterns of synchrony activity and the stability are observed to vary with the choice of time delay, which also enhances the multi-variety of the spike bursting firing rhythm. The lag synchrony of time trajectories of the voltage is illustrated near the boundary of the synchrony regime. 相似文献
897.
In this paper, we show that a generic nonexpansive operator on a closed and convex, but not necessarily bounded, subset of a hyperbolic space has a unique fixed point which attracts the Krasnoselskii-Mann iterations of this operator. 相似文献
898.
We consider the only remaining unsolved case n≡0 (mod k) for the largest kth eigenvalue of trees with n vertices. In 1995, Jia-yu Shao gave complete solutions for the cases k=2,3,4,5,6 and provided some necessary conditions for extremal trees in general cases (cf. [Linear Algebra Appl. 221 (1995) 131]). We further improve Shao's necessary condition in this paper, which can be seen as the continuation of [Linear Algebra Appl. 221 (1995) 131]. 相似文献
899.
图G的一个圈基的长度是该圈基的所有圈的长度之和。设C^-、C^ 分别是G的最小、最大圈基长度,如果对任一偶数C,C^-<C<C^ ,都存在G的一个长为C的圈基,则称G具有偶圈基内插性质,本证明了,完全偶图Km,n具有偶圈基内插性质。 相似文献
900.