高功率半导体激光端面泵浦方形掺Nd3+离子激光晶体热形变研究

为了解决高功率半导体激光器端面泵浦激光晶体引起的热效应问题,激光晶体泵浦端面的热形变必须进行准确的计算.通过对于全固态激光器中激光晶体的工作特点分析,建立了矩形截面激光晶体热分析模型.基于热传导方程,提出了泊松方程的一种新解,并获得了矩形截面激光晶体端面热形变分布的一般解析表达式.同时讨论了半导体激光器偏心泵浦激光晶体给端面热形变带来的影响.与有限元分析方法以及其他数值分析方法相比,解析分析方法不会给计算引入任何的误差.热形变的解析分析为解决激光晶体的热效应问题以及提高激光器的性能提供了理论的依据.     

Long-term prediction of compressive creep development in expanded polystyrene

The results obtained in investigating the creep of expanded polystyrene (EPS) boards under compressive stress are presented. Power and exponential equations were used for describing creep compliance. It was found that the curves of creep compliance approximated by both equations adequately represent the research results, taking into account the scatter of the experimental data. Based on the calculation and empirical estimate of long-term creep of EPS under compressive stress σ_c=(0.25–0.45)σ_10%, its creep compliance was determined for a period of 10 years in the future. The dependence of on the density of polystyrene boards and the value of long-term compressive stress σ_c was established. The expected values of creep strain development in expanded polystyrene boards EPS 80–EPS 250 under constant compressive stress σ_c=(0.25–0.45)σ_10% are presented for the prediction period of 10 years. To obtain the expected creep values for any other period of time in the interval of 5T50 years, the values of should be multiplied by the empirical coefficient .     

Mikroprozessor-Interface zur on-line Erfassung von Wägedaten

Zusammenfassung Als ergänzender Schritt für die Automatisierung der Flüssigkeitschromatographie wurde in unseren analytischen Laboratorien für Routinemessungen die automatische Erfassung von Wägedaten während der Probenvorbereitung eingeführt. Zu diesem Zweck wurde ein von einem Mikroprozessor gesteuertes Datenerfassungsgerät entwickelt, welches die Gewichtswerte von der Analysenwaage on-line in das Hewlett-Packard Lab-Data-System 3354 übermittelt. Das bedienungsfreundliche Konzept bringt eine wesentliche Arbeitserleichterung und schließt Fehlermöglichkeiten weitgehendst aus. Mit Geräten, welche seit über einem Jahr in Betrieb stehen konnten die Erwartungen voll erfüllt werden.

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Microprocessor-interface for the on-line aquisition of weight data

Summary With the on-line data aquisition of sample weights an additional step to the automation of liquid chromatography was introduced in our analytical laboratories. A new developed microprocessor controlled equipment connects a balance to the Hewlett-Packard Lab-Data-System 3354 and controls the on-line transfer of the weight data. The design is based on an easy application for users and gives essential reductions of workload and of error possibilities. Equipment are now in use with excellent results for over one year.

     

Analysis of herbicides

Herbicides, like other pesticides, leave undesirable residues on the treated plants. To analyze them, the plant material is extracted and the herbicidal residues are separated from the bulk of the co-extractives of natural origin, about which too little is known. Quantitative determinations at the ppm level are best performed by gas chromatography with highly sensitive, specific detectors. In food control, where the history of the sample is unknown, the herbicide residues are identified and determined quantitatively together with the residues of other pesticides.     

Organic Compounds in Nature: Limits of Our Knowledge

Current geochemical and environmental research reveals the presence in soils and sediments of extremely complex assemblages of organic compounds. Their recognition has long been delayed by both conceptual and analytical limitations. Even today the best techniques cannot fully resolve these mixtures into their individual components. Yet, the knowledge of their structures and abundances is needed in geochemistry, and especially for the assessment of their potential biological effect and ecological impact. The classical “natural products approach” is unlikely to provide this information; therefore, I foresee the need for a more realistic assessment of nature, that acknowledges the limitations of our present analytical powers and of our knowledge.     

Radioimmunoassay

Biologically active substances are often effective in nanogram or even smaller quantities. Investigations of their mode of action therefore require highly sensitive microanalytical methods of detection. Chemical, chromatographic or spectrometric methods frequently lack the required sensitivity; it was only after the discovery of the radioimmunoassay (RIA) that quantitative determination of minute amounts of substances in the presence of a millionfold excess of other compounds became possible. The radioimmunoassay combines the extreme sensitivity of detection of radioactively labeled substances with the high specificity of immunological reactions. The superiority of radioimmunological methods over other analytical techniques rests upon their sensitivity, specificity, facile application, and especially their broad general scope.     

基于Buchadhl象差系数和解析偏导数的光学优化设计

本文以基于 Buchadhl 象差系数得到的点列图为目标函数,只需追迹少许光线就可得到近似点列图,大大减少了计算量;同时采用了目标函数对结构参数偏导数解析求导原理并应用于光学自动设计,这样得到的解析偏导数不仅不存在原理误差,同时极大地减少了求得所需的时间;最后给出了使用 DFP-BFGS 优化方法设计一个双高斯物镜的实例.     

An Apparatus for Titrations in Liquid Ammonia

An apparatus for titrations in liquid ammonia is described. The titrations can be carried out in the absence of air, and the utility of the apparatus is demonstrated for a number of conductometric and potentiometric titrations.     

A square-wave wavelength modulation system for automatic background correction in carbon furnace atomic emission spectrometry

A square-wave wavelength modulation system, based on a rotating quartz chopper with four quadrants of different thicknesses, has been developed and evaluated as a method for automatic background correction in carbon furnace atomic emission spectrometry. Accurate background correction is achieved for the residual black body radiation (Rayleigh scatter) from the tube wall and Mie scatter from particles generated by a sample matrix and formed by condensation of atoms in the optical path. Intensity modulation caused by overlap at the edges of the quartz plates and by the divergence of the optical beam at the position of the modulation chopper has been investigated and is likely to be small.