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981.
982.
采用发光二极管的量子发光原理,通过测两发光二极管的伏安特性,确定阈值电压,根据相关半导体理论,计算出普朗克常数,通过对红黄绿三种颜色的发光二极管进行实验测量,结果表明误差稍大,但作为一种设计性实验开发学生的创新思维还是值得肯定的. 相似文献
983.
Improving microwave dielectric properties of La2.98/3Sr0.01(Mg0.5Sn0.5)O3 ceramics with CuO additive
Yih-Chien Chen 《Current Applied Physics》2012,12(2):483-488
The microwave dielectric properties of CuO-doped La2.98/3Sr0.01(Mg0.5Sn0.5)O3 ceramics were investigated with a view to their application in microwave devices. CuO-doped La2.98/3Sr0.01(Mg0.5Sn0.5)O3 ceramics were prepared by the conventional solid-state method. The X-ray diffraction patterns of CuO-doped La2.98/3Sr0.01(Mg0.5Sn0.5)O3 ceramics exhibited no significant variation of phase with sintering temperature. By adding 0.75 wt.% CuO, a dielectric constant of 20.07, a quality factor (Q × f) of 63,000 GHz, and a temperature coefficient of resonant frequency τf (−77.0 ppm/°C) were obtained when La2.98/3Sr0.01(Mg0.5Sn0.5)O3 ceramics were sintered at 1500 °C for 4 h. 相似文献
984.
985.
On the basis of the double-well ratchet potential which can be calculated theoretically and implemented experimentally, the influences of the time delay, the coupling constant, and the asymmetric parameter of the potential on the performance of a delayed feedback ratchet consisting of two Brownian particles coupled mutually with a linear elastic force are investigated. The centre-of-mass velocity of two coupled Brownian particles, the average effective diffusion coefficient, and the Pe number are calculated. It is found that the parameters are affected by not only the time delay and coupling constant but also the asymmetric parameter of the double-well ratchet potential. It is also found that the enhancement of the current may be obtained by varying the coupling constant of the system for the weak coupling case. It is expected that the results obtained here may be observed in some physical and biological systems. 相似文献
986.
Ab initio and DFT methods were used to investigate the interconversions of substituted polyacetylene conformers C10H6X6 (X=F, Cl and I) in the vapour phase. The rates of this geometrical isomerization have been calculated and the Arrhenius parameters evaluated. In the case of unsubstituted polyacetylene as the reference, the B3LYP Arrhenius parameters obtained are A1=2.99 × 1017 s–1 and Ea=17.30 kcal mol–1. The values of the equilibrium constant for the reaction have also been determined at various temperatures between 300 and 500 K and the value of the energies change calculated. The results also suggest that the straightforward kinetics characterizing the majority of substituted polyacetylene isomerizations above 300 K. The isomerization energies are positive and the barrier heights ΔEbarrier are expected to be sensitive for the magnitude of halogens effects. According to geometries features the Cis → Trans isomerization in the gas phase occurs by a rotational mechanism. 相似文献
987.
988.
989.
《Physics and Chemistry of Liquids》2012,50(4):372-378
The kinetics of complex formation reaction of iodine with N,N,N′,N′-tetrakis(2-salicylideneaminoethyl)butane-1,4-diamine have been studied spectrophotometrically at various temperatures in chloroform and dichloromethane solutions. The results indicate the formation of an electron donor–acceptor complex (EDA), which is followed by two relatively slow consecutive reactions. Pseudo-first order rate constants at various temperatures for the formation of the ionic intermediate, and the final product have been evaluated by computer fitting of the absorbance time data to appropriate equations. 相似文献
990.
《Physics and Chemistry of Liquids》2012,50(4):471-478
Artificial neural networks (ANNs) were successfully developed for the modeling and prediction dielectric constant of different ternary liquid mixtures at various temperatures (?10°C?≤?t?≤?80°C) and over the complete composition range (0?≤?x 1,?x 2,?x 3?≤?1). A three-layered feed forward ANN with architecture 7-16-1 was generated using seven parameters as inputs and its output is dielectric constant of media. It was found that properly selected and trained neural network could fairly represent the dependence of dielectric constant of different ternary liquid mixtures on temperature and composition. For the evaluation of the predictive power of the generated ANN, an optimized network was applied for predicting the dielectric constant in the prediction set, which were not used in the modeling procedure. Squared correlation coefficient (R 2) and root mean square error for prediction set are 0.9997 and 0.2060, respectively. The mean percent deviation (MPD) for the property in the prediction set is 0.8892%. The results show nonlinear dependence of dielectric constant of ternary mixed solvent systems on temperature and composition is significant. 相似文献