A Method for Determining the Dielectric Constant of Microwave PCB Substrates

This paper presents a simple method for determining the dielectric constant of microwave PCB substrates. In the presented method, a bandpass microstrip filter designed on the PCB substrate with a user-predicted dielectric constant value is implemented for a given center frequency. The simulation results of the designed bandpass filter are obtained by the help of microwave design software; XFDTD?. Experimental results regarding the filter frequency characteristic are accomplished by means of a vector network analyzer. The simulation results of the designed filter are modified to overlap with the experimental ones by varying the dielectric constant value. When the simulation and experimental results are overlapped, the value of dielectric constant is accurately selected. In order to illustrate the validity of proposed method, the dielectric constant values of flame resistant-4 (FR4) substrates are acquired at IEEE 802.11b/g and IEEE 802.11a wireless local area network (WLAN) application frequencies. The results obtained by using the presented method agree with the previous studies in the literature.     

原子核的单粒子共振态

采用基于相对论平均场的耦合常数解析延拓方法研究球形核的单粒子共振态.具体计算了Zr同位素链中巨晕核的核芯核122Zr阈值附近的中子共振态的能量、宽度和波函数,其结果同相应的散射相移法的结果一致. Using analytic continuation in the coupling constant (ACCC) method within the framework of the self-consistent relativistic mean field (RMF) theory, the energies, widths and wave functions for single-particle resonant states close to the continuum threshold are evaluated. Predictions are also compared with corresponding results obtained by the scattering phase shift method.     

不同算法原子电荷下的~1J_(CH)理论计算

用一种计算直接键连原子核自旋耦合常数的半经验公式,结合量子化学计算得到的32种有机分子稳定几何构型的7种不同算法下的原子电荷,探究原子电荷算法的不同对1JCH理论计算的影响,拟合出基于7种原子电荷的耦合常数计算公式,并利用拟合公式对5种分子进行了检验.计算结果表明拟合的32种分子及检验的5种分子的耦合常数的计算值均与实验值较好的符合,拟合得到的基于7种原子电荷的计算公式均可以对其他分子体系的耦合常数进行预测.另外,计算结果同样显示原子电荷算法的不同对1JCH理论计算值有一定的影响却不显著,其中基于电荷均衡方法电荷(QEq)得出的耦合常数计算值与实验值的偏差较其它6种原子电荷的小,结果更可靠.     

聚酯薄膜复合材料带状脉冲形成线传输介质

介绍了一种电气绝缘柔软复合材料——DMD膜,通过对膜结构的分析,设计了一种串联等效电路模型对其进行分析。运用该模型,对DMD膜在浸渍前和浸渍后两种情况下的介电常数和介电强度进行了求解并给出计算公式。从公式可以看出:DMD膜的介电常数在浸渍前后有明显的变化,浸渍后的介电常数得到了显著的提高,并且变化率较小;浸渍后DMD膜的介电强度高于未浸渍DMD膜的介电强度。当浸渍料介电常数愈大,聚酯材料上承受的电场强度愈大,浸渍料上承受的电场强度愈小,由于聚酯材料的耐压强度很高,所以整个传输线的介电强度得到提高。     

First-principles study of elastic and thermo-physical properties of kesterite-type Cu2ZnSnS4

The lattice constants and elastic constants of the kesterite-type Cu₂ZnSnS₄ have been calculated using density-functional theory (DFT). The calculated lattice constants are in good agreement with the experimental data. The calculated elastic constants indicate that the bonding strength along the [1 0 0] and [0 1 0] directions is as strong as the one along the [0 0 1] direction. The high B/G ratio shows that the kesterite-type Cu₂ZnSnS₄ compound has ductile behavior. Finally, using the Debye model, the volume, bulk modulus and heat capacity as a function of temperature for the kesterite-type CZTS have been estimated at different pressures. The Debye temperature and Gruneisen parameter are 157 K and 2.28 at 300 K temperature, respectively. The present results can give some information for the design of the kesterite-type CZTS compounds, and these can also be used to stimulate future experimental and theoretical work.     

Modulated photophysics of 2-anthracene sulphonate in micellar assembly

The association of a non-ionic surfactant of polyoxyethylene-p-(1,1,3,3-tetramethylbutyl)phenyl ether (Triton X) series with 2-AS in aqueous solution has been studied by means of steady-state, time-resolved fluorescence and fluorescence anisotropy techniques. The effect of the hydrophobic chain length on the structural dynamism of the fluorophore has been reported. Experimental results demonstrate that the equilibrium of this dynamism is sensitive to the environment. The association constant of the probe molecule with the non-ionic micelles of Triton X (TX), location of the probe in the micellar environment, have been determined from the change in emission characteristics of the probe as a function of surfactant concentration. The rate constant of quenching and mode of quenching of probe in micellar media have been ascertained. Quantitative estimates of the micropolarity at the binding sites of the probe molecule have been determined. Some of the environment-dependent relevant fluorescence parameters, fluorescence anisotropy (r), have been monitored for exploring the imposed motional restriction of the microenvironment around the probe. An attempt has been made to correlate the steady-state results with time resolved study.     

分光计测定光栅常数

针对分光计测定光栅常数实验中入射光线偏离光栅法线的情形,提出了计算光栅常数的一个近似表达式。在不增加额外测量的前提下,使实验结果更接近于实际值。     

分光仪测衍射光栅常量的实验设计与数据处理

不等精密度测量在实验中是很普遍的现象,而在现行的本科基础实验教学中对此的强调是不足的.本文以分光仪测衍射光栅常量的实验为例,针对光学实验在设计与数据处理上强化不等精密度测量进行探索研究.     

PN结伏安特性的实验研究

介绍了验证PN结伏安关系特性实验的实验原理,并利用绘图软件Origin7.5对实验数据进行处理.结果表明,PN结的扩散电流和两端的正向电压之间满足指数关系.通过与理论公式的比较,准确地测出了玻尔兹曼常数.     

Application of quantitative structure-activity relationship to the determination of binding constant based on fluorescence quenching

Quantitative structure-activity relationship (QSAR) model was used to predict and explain binding constant (log K) determined by fluorescence quenching. This method allowed us to predict binding constants of a variety of compounds with human serum albumin (HSA) based on their structures alone. Stepwise multiple linear regression (MLR) and nonlinear radial basis function neural network (RBFNN) were performed to build the models. The statistical parameters provided by the MLR model (R²=0.8521, RMS=0.2678) indicated satisfactory stability and predictive ability while the RBFNN predictive ability is somewhat superior (R²=0.9245, RMS=0.1736). The proposed models were used to predict the binding constants of two bioactive components in traditional Chinese medicines (isoimperatorin and chrysophanol) whose experimental results were obtained in our laboratory and the predicted results were in good agreement with the experimental results. This QSAR approach can contribute to a better understanding of structural factors of the compounds responsible for drug-protein interactions, and can be useful in predicting the binding constants of other compounds.