Wave Propagation along Axes of Symmetry in Linearly Elastic Media with Initial Stress

The proofs of the Fedorov–Stippes and Fedorov's theorems, which hold for linearly elastic homogeneous bodies in natural configurations, remain valid for any linearly elastic medium with initial stress provided that Hooke's tensor be replaced by a suitable elasticity tensor.     

Relaxations during the postcure of unsaturated polyester networks by ultrasonic wave propagation,dynamic mechanical analysis,and dielectric analysis

Ultrasonic wave propagation, dynamic mechanical analysis, and dielectric analysis were used to monitor relaxation phenomena during the nonisothermal postcure of unsaturated polyester networks. The measurements covered 6 decades of frequency. As a result, the residual reactive groups, immobilized in the glassy state by vitrification during an isothermal cure step, gained molecular mobility, which promoted the formation of additional crosslinks. After the postcure, the reaction was complete, and the maximum achievable glass‐transition temperature was reached. Moreover, the frequency and temperature dependence of the two relaxations, one related to the glass‐transition temperature of the partially cured sample and the other to the glass transition of the fully cured sample, was evaluated. The Williams–Landel–Ferry equation was used to model the frequency dependence of the main α‐relaxation data obtained with the different techniques. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 596–602, 2005     

A review of commonly used analytical and empirical formulae for predicting sound diffracted by a thin screen

This paper reviews some useful analytical and empirical formulae that are used for the calculation of sound diffracted by a barrier. A brief historic overview of the study of spherical waves diffracted by a rigid half plane is presented also. The physical principles of sound diffraction by a thin plane are explained. The mathematical expressions are cast in a convenient form for ease of numerical implementation. Accurate analytical solutions are expressed in terms of standard mathematical functions that can be computed readily. Among the approximate solutions quoted, quite a few empirical formulations are adequate for most engineering purposes. The information presented in this paper should also be helpful for those who are interested in the study of sound diffracted by a barrier in a room or in a long industrial space.     

高浓度镱铒共掺磷酸盐光纤放大器增益特性

在忽略高能级的自发辐射和光纤损耗的情况下，利用速率方程和传输方程理论研究了高浓度Er³⁺/Yb³⁺共掺磷酸盐玻璃光纤放大器的增益特性，讨论了Er³⁺浓度、Yb³⁺浓度、抽运光功率、信号光功率、光纤长度对放大器增益的影响，并与单掺铒光纤放大器进行了比较.由于Yb³⁺的敏化作用降低了铒离子的团簇效应，减少了离子间相互作用，共掺光纤的增益和效率明显高于单掺光纤.数值计算表明，3.2cm长Er³⁺/Yb³⁺共掺光纤在980nm的20dBm(100mW)抽运功率下，1532nm处的增益可达10dB. 关键词： 镱铒共掺光纤放大器 速率方程 传输方程 高浓度     

Reinvestigation of pressure broadening parameters at 60-GHz band and single 118.75 GHz oxygen lines at room temperature

Low pressure measurements of broadening parameters of the 118.75 GHz fine structure line of oxygen molecule have been made by a BWO-based spectrometer with acoustic detector (RAD) at room temperature. Pressure broadening parameters were obtained for the buffer gases O₂, N₂, Ne, He, Ar, H₂O, CO₂, and CO and have the following values 2.23 ± 0.01, 2.245 ± 0.02, 1.375 ± 0.02, 1.62 ± 0.03, 2.005 ± 0.02, 2.52 ± 0.04, 2.66 ± 0.08, and 2.31 ± 0.05 MHz/Torr, respectively. Measured central frequency is 118 750.340 ± 0.007 MHz. The central frequencies and broadenings by O₂ and N₂ of fine structure lines 1⁺, 5⁻, 7⁺, 11⁺, and 15⁻ belonging to the 60-GHz band are also measured. Comparison of previous and recent data on electronic, rotational, and fine structure lines broadenings reveals their close values (within 10%) and dependencies on corresponding rotational quantum numbers for these different oxygen spectra stretching from millimeter through submillimeter up to the optical bands. Such similarity could be used for estimation of the broadenings of not measured yet oxygen lines.     

Absorption Coefficient Measurements of Strongly Scattering Media Using Time-Resolved Transmittance of a Short Pulse in Near-Infrared (NIR) Wavelength Range

Absorption coefficient measurements of strongly scattering and weakly absorbing media have been performed using time resolved transmittance of a 100 fs pulse through a 30 mm slab containing latex spheres suspended in water and absorbing ink solutions. The scattering and absorption coefficients were selected so that the optical properties of the media were similar to those of biological tissues. Measured curves of time-resolved transmittance of the pulse through the media were used to estimate the optical properties of the media. The experiment was made at two different wavelengths, 784 nm and 810 nm. Estimated absorption coefficients were in good agreement with those measured in a nonscattering case by a spectrophotometer.Presented at the 7th International Workshop on Multiple Scattering Lidar/Light Experiments (MUSCLE7), July 21-23 1994, Chiba, Japan.     

基于道格拉斯格式的宽角有限差分光束传播法分析大角度交叉波导

交叉波导是集成光学中的一种重要的器件单元，针对大角度交叉波导的结构及折射率分布，运用基于广义道格拉斯算子的宽角多步有限差分光束传播法模拟大角度交叉波导的传输特性，数值计算出波导中的光场的分布。与Crank-Nicholson格式的有限差分光束传播法相比，该算法在几乎不增加计算时间和计算机内存资源的情况下，结合了广义道格拉斯格式的有限差分光束传播法截断误差小[只有o(△x)^4]和宽角多步法所具有较高精度的优点，是光波导器件理想的数值模拟工具。在此基础上计算分析了大角度交叉波导的输出分支波导的能量与交叉角度的关系，以及交叉角度对波导间能量耦合的影响。这为实际的设计制作光器件的工作提供了极好的基础。     

焊接接头热影响区表面裂纹疲劳扩展速率

给出了数据处理的方法，通过对试验数据的分析，给出了裂纹扩展速率与ΔK的关系，为油田的安全生产提供了依据。     

Parameter uncertainty, sensitivity analysis and prediction error in a water-balance hydrological model

Analysis of uncertainty is often neglected in the evaluation of complex systems models, such as computational models used in hydrology or ecology. Prediction uncertainty arises from a variety of sources, such as input error, calibration accuracy, parameter sensitivity and parameter uncertainty. In this study, various computational approaches were investigated for analysing the impact of parameter uncertainty on predictions of streamflow for a water-balance hydrological model used in eastern Australia. The parameters and associated equations which had greatest impact on model output were determined by combining differential error analysis and Monte Carlo simulation with stochastic and deterministic sensitivity analysis. This integrated approach aids in the identification of insignificant or redundant parameters and provides support for further simplifications in the mathematical structure underlying the model. Parameter uncertainty was represented by a probability distribution and simulation experiments revealed that the shape (skewness) of the distribution had a significant effect on model output uncertainty. More specifically, increasing negative skewness of the parameter distribution correlated with decreasing width of the model output confidence interval (i.e. resulting in less uncertainty). For skewed distributions, characterisation of uncertainty is more accurate using the confidence interval from the cumulative distribution rather than using variance. The analytic approach also identified the key parameters and the non-linear flux equation most influential in affecting model output uncertainty.     

计算机蠕虫病毒传播的数学模型分析

建立了一种计算机病毒传播的数学模型,并利用微分方程理论进行了分析,得到了计算机病毒消除的阈值,并进行了数值模拟.