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51.
Hajime Kabashima Hideto Tsuji Hideshi Hattori 《Reaction Kinetics and Catalysis Letters》1996,58(2):255-259
All the alkaline earth oxides exhibit activities for double, bond isomerization of 5-vinylbicyclo[2.2.1]hept-2-ene (VBH) to 5-ethylidenebicyclo[2.2.1]hept-2-ene (EBH) at a reaction temperature of 273 K. The order of the activity on the basis of unit weight of catalyst was CaO>MgO>SrO>BaO when compared under optimum pretreatment conditions. The E/Z ratio in the products is determined by the reaction temperature regardless of the type of catalyst; the ratios were 82/18 and 88/12 for the reaction temperatures of 323 and 273 K, respectively. 相似文献
52.
采用时域有限差分方法,对水平极化电磁脉冲模拟器所产生的电磁场进行数值模拟,在时域中计算了电磁场的时间 空间分布。讨论了电磁脉冲模拟器产生的电磁脉冲波形和场的空间变化、均匀性等重要因素。结果表明,模拟器产生的电磁脉冲前沿为10ns,接近脉冲电压前沿,波形与脉冲电压波形(双指数波)相差较大;峰值场强在对称轴上并非与距离成反比,而是随距离增大而迅速减弱;该模拟器的双锥 笼形天线能在大范围内(大于等于50m,水平方向)产生均匀分布、高峰值场强、快前沿的电磁脉冲。 相似文献
53.
54.
Shuang-Shuang Yang Ming-Jiang Xie Yu Shen Yong-Zheng Wang Xue-Feng Guo Bin Shen 《中国化学快报》2016,27(4):507-510
Chemical doping of nickel hydroxide with other cations(e.g. Al~(3+)) is an efficient way to enhance its electrochemical capacitive performances. Herein, a simple cation–anion(Ni~(2+)and AlO_2) double hydrolysis method was developed toward the synthesis of nickel–aluminum(Ni–Al) composite hydroxides. The obtained composite hydroxides possesses a porous structure, large surface area(121 m~2/g) and homogeneous element distribution. The electrochemical test shows that the obtained composite hydroxides exhibits a superior supercapacitive performances(specific capacitance of 1670F/g and rate capability of 87% from 0.5 A/g to 20 A/g) to doping-free nickel hydroxide(specific capacitance of 1227 F/g and rate capability of 47% from 0.5 A/g to 20 A/g). Moreover, the galvanostatic charge/discharge test displays that after 2000 cycles at large current density of 10 A/g, the composite hydroxides achieves a high capacitance retention of 98%, indicative of an excellent electrochemical cycleability. 相似文献
55.
In the dynamics analysis and synthesis of a con-trolled system, it is important to know for what feedback gains can the controlled system decay to the demanded steady state as fast as possible. This article presents a sys-tematic method for finding the optimal feedback gains by taking the stability of an inverted pendulum system with a delayed proportional-derivative controller as an example. First, the condition for the existence and uniqueness of the stable region in the gain plane is obtained by using the D-subdivision method and the method of stability switch. Then the same procedure is used repeatedly to shrink the stable region by decreasing the real part of the rightmost charac-teristic root. Finally, the optimal feedback gains within the stable region that minimizes the real part of the rightmost root are expressed by an explicit formula. With the optimal feedback gains, the controlled inverted pendulum decays to its trivial equilibrium at the fastest speed when the initial val-ues around the origin are fixed. The main results are checked by numerical simulation. 相似文献
56.
钟摆系统是一类典型的分段光滑系统,结合Filippov系统刻画语言,解释了当钟摆无能量补充时,钟摆最终会停止在滑动集上的原因.利用数值模拟的方法,给出钟摆系统在有能量补充时,存在极限环的条件.最后,结合环域定理证明了一般的钟摆模型存在唯一稳定的极限环. 相似文献
57.
All-organic composites are widely used in energy storage application due to the high breakdown strength performance, but the improvement of energy storage was limited by the relatively low dielectric constant. Therefore, to satisfy the high demands of dielectric materials, energy storage properties of polymer composites should be further enhanced. In this article, poly(vinylidene fluoride-co-chlorotrifluoroethylene) (P(VDF-CTFE)) and polyurea (PUA), which are known as high dielectric ferroelectric material and linearly high energy storage efficiency material respectively, are composited through double layer (DL) casting method for the first time. The properties of DL structured composite film is contrasted with solution blending structure especially in energy storage efficiency, and the results demonstrate that DL structure design can make great use of advantages of two materials and also can avoid the influence of phase separation between P(VDF-CTFE) and PUA efficiently. Moreover, high breakdown strength (6180 kV/cm) and high energy storage efficiency (77%) of DL composites can be realized simultaneously by incorporating PUA as an insulating layer, and the mechanism is discussed in detail. This work provides an effective route to improve the energy storage properties of polymer dielectric materials and shows great application potential. 相似文献
58.
Resonant tunneling quantum structures consist of asymmetric wells and barriers have been investigated to find their optimized geometrical parameters and potential profile by the numerical calculations. The results show that the widths and the depths of the asymmetric wells have a significant effect on the transmission coefficient and the dwell time. The properties exhibited in this work may establish guidance to the device applications. 相似文献
59.
通过对全液体空分装置不同流程组织形式进行分析和模拟计算、能耗与投资的比较,根据不同规格的产品要求,进行合适的流程形式选择,以可达到节能降耗的目的。 相似文献
60.
An improved watermarking method, based on the double random phase encoding technique and the cascaded-phases iterative algorithm and random-phase-shift algorithm, is proposed. This method can significantly reduce the needs of watermarking information storage for different multimedia products, and provide a reasonable criterion of determining the authenticity of a product for the copyright owner. This method can also be applied to track the source of copies. The effectiveness of this method was verified through numerical simulations. 相似文献