自适应模拟退火遗传算法在薄膜厚度及光学常数反演中的应用

准确的测量薄膜的厚度和光学常数,在薄膜的制备、研究和应用中都是十分重要的。借助Cauchy色散模型,通过薄膜透过率测量曲线,用改进的自适应模拟退火遗传算法对透过率曲线进行全光谱拟合,从而反演得到薄膜的厚度和光学常数。对由电子束蒸发制备的TiO2单层膜和SiO2/TiO2双层膜的厚度和光学常数进行了测量计算。实验结果表明,计算得到的光学参数与实测结果相一致,厚度误差小于2nm,在560nm波长处折射率误差小于0.03。     

利用LED的量子特性设计新型普朗克常数测定仪

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.     

Improving microwave dielectric properties of La2.98/3Sr0.01(Mg0.5Sn0.5)O3 ceramics with CuO additive

The microwave dielectric properties of CuO-doped La_2.98/3Sr_0.01(Mg_0.5Sn_0.5)O₃ ceramics were investigated with a view to their application in microwave devices. CuO-doped La_2.98/3Sr_0.01(Mg_0.5Sn_0.5)O₃ ceramics were prepared by the conventional solid-state method. The X-ray diffraction patterns of CuO-doped La_2.98/3Sr_0.01(Mg_0.5Sn_0.5)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 τ_f (−77.0 ppm/°C) were obtained when La_2.98/3Sr_0.01(Mg_0.5Sn_0.5)O₃ ceramics were sintered at 1500 °C for 4 h.     

激光雷达湍流大气探测

基于湍流对激光束的扩散和漂移效应,提出了一种采用激光雷达观测湍流强度的方法。湍流对光束产生扩散和飘移作用,使激光光束偏离激光雷达接收视场,造成后向散射光能量损失。对比常规散射回波信号与畸变回波信号的差别可以测量湍流强度。实验表明该方法与其他方法的测量结果具有一致性,证明了该方法的有效性。     

Feedback control in a coupled Brownian ratchet

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.     

Comparative study of kinetics isomerization of substituted polyacetylene (Cl,F and I): Ab initio and DFT calculations

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 E_a=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 ΔE_barrier 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.     

Interaction of new polyamine ligand N,N , N ′ , N ′ -tetrakis(2-salicylideneaminoethyl)butane-1,4-diamine with iodine in chloroform and dichloromethane solutions

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.     

Prediction dielectric constant of different ternary liquid mixtures at various temperatures and compositions using artificial neural networks

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.