An investigation on terahertz response in electro-optic crystals excited at 1.03 lm wavelength

We theoretically investigate terahertz(THz)emission and detection from h110i-oriented electro-optic(EO) crystals adapted for Yb-doped femtosecond pulse laser.According to the principles of phase-matching condition, the dispersion relation between optical velocity and THz pulse,THz absorption spectra, and coherence lengths of CdTe, GaP,and GaAs crystals below the phonon resonant frequency are calculated correspondingly. The optical rectification and EO sampling process of above crystals with the same thickness of0.1 mm are simulated. As a consequence, we found that the optimal emission frequency of CdTe is at 2.65 THz, however,it reaches 6.56 THz of GaAs and 4.77 THz of GaP. With the help of frequency response function, the calculated cut-off frequency of CdTe is only 3.45 THz, while GaAs and GaP achieve 7.15 and 6.37 THz correspondingly. Finally, the EO sampling sensitivity of GaAs is higher than CdTe and GaP when the crystal's thickness exceeds 1.58 mm. The strong THz absorption of CdTe saturates distinctly the EO sampling sensitivity with its thickness increasing.     

数据包络分析方法的灵敏度分析

本文对数据包络分析方法的有效决策单元作了灵敏度分析。文中首先提出一种只考虑乎一投入量变化时的灵敏度分析方法,然后在此基础上研究几个报入量同时变化时的灵敏度分析。进而扩展到产出量变化投入产出量同时变化时的灵敏度分析,最后用数例进行了说明。     

降雨历时和重现期对洪涝风险的敏感性和转移——以济南市大寺河流域起步区段大桥分区为例

为研究降雨历时和重现期对洪涝风险的敏感性和转移影响,构建了3种降雨历时和7种重现期的芝加哥降雨雨型,并建立了相应的MIKE FLOOD耦合模型,模拟了21种降雨情景下的洪涝过程;基于模拟结果,分别从洪涝空间分布、水动力特性等方面开展分析。结果表明：（1）1风险级主要位于城镇道路,5风险级主要分布于耕地、绿地和林地等径流系数较低的用地处。（2）各风险级积水总量峰值和积水总峰值均随降雨历时和降雨重现期的增加而增加,且对低重现期和短降雨历时更为敏感。（3）各洪涝等级的积水峰值面积随洪涝等级的增大逐渐增大,均随降雨历时增加而增加,增幅整体上为增长趋势。2风险级的积水峰值面积对重现期的变化敏感性最强,5风险级的积水峰值面积对重现期的变化敏感性最低。1、2风险级的积水面积峰值对短降雨历时更敏感,3、4、5风险级的积水面积峰值对长降雨历时更敏感。（4）当降雨历时相同时,随着重现期的增加,只发生无风险等级向有风险等级和从高等级向低等级转移的过程。随着降雨重现期的增大,研究区主要发生无风险到5级、5级到4级两个转移过程,且对低重现期的变化更敏感。本研究可为雨洪管理研究提供科学参考。     

应用最优化设计提高石墨炉原子吸收光谱法测定生铁中锌的灵敏度

本文采用最优化设计实验手段 ,研究了石墨炉原子吸收光谱法中石墨炉参数和时间常数对锌分析信号的影响 ,确定了最优测定条件。通过方差分析 ,进一步揭示了灰化温度、灰化时间、原子化温度、原子化时间、时间常数与吸光度的内在规律 ,明显提高了分析灵敏度。该法操作简单 ,测定范围 0 .0 0 3—0 .0 15μg/ m L ,回收率 95 %— 110 % ,相对标准偏差小于 2 5 %。     

触觉美感的美学依据——论书法艺术的触觉美感其二

触觉美感是一个被美学忽视的问题。西方理性主义传统美学错误地认为触觉只是本能的官能感觉。而其宗教视之更不在话下。中国审美文化也避讳或忽略这个问题,但从其整体思维与全面体味的思维方式和审美情趣上看,似乎隐隐地透露出触觉美的一些信息。马克思关于整体的人和人的本质力量以及人与自然、人与工具等重要思想是我们思考触觉美感最重要的理论基础。     

Variational inequalities applied to the study of paradoxes in equilibrium problems frl:† $f:† This work was supported by MURST and CNR $ef:

In this paper, starting from examples exhibited by some authors. (see [I], [3], [4], [6]j, we determine set of values such that, when certain parameters belong to them, counter-intuitive rewlts occur. By means of some properties of the variaiionai iiiequali:y associated to the nptirnization problem, we can generali~eth e previous results     

Synthesis,crystal structure,thermal decomposition,and explosive properties of [Bi(tza)3] n (tza = tetrazole acetic acid)

A coordination compound based on tetrazole acetic acid (Htza) and bismuth(III), [Bi(tza)₃] _n , was synthesized and characterized by single crystal X-ray diffraction analysis, elemental analysis, FT-IR, and ¹H NMR spectroscopy. The crystallographic data show that the crystal belongs to monoclinic, P2₁/n space group, a?=?0.91968(19)?nm, b?=?0.94869(19)?nm, c?=?1.7824(4)?nm, β?=?101.488(3)°, and Z?=?4. The central bismuth(III) is nine-coordinate by three nitrogens from three tetrazole rings and six oxygens of the carboxylate of another three tza^? ions, with each tza^? tridentate, chelating, bridging coordination. The coordination bonds and the intramolecular hydrogen bonds make the complex pack into a layered structure in polymer form. The thermal decomposition mechanism of the title complex was investigated by DSC and TG-DTG techniques. Under nitrogen at a heating rate of 10°C?min^?1, thermal decomposition of the complex contains two intense exothermic processes between 217.4°C and 530.3°C in the DSC curve; the final decomposed residue at 570°C was Bi₂O₃. Sensitivity tests showed that [Bi(tza)₃] _n was sensitive to impact and flame stimulus.     

Mechanical and electronic approaches to improve the sensitivity of microcantilever sensors

Advances in the field of micro electro mechanical systems and their uses now offer unique opportunities in the design of ultrasensitive analytical tools. The analytical community continues to search for cost-effective, reliable, and even portable analytical techniques that can give reliable and fast response results for a variety of chemicals and biomolecules. Microcantilevers （MCLs） have emerged as a unique platform for label-free chem-sensor or bioassay. Several electronic designs, including piezoresistive, piezoelectric, and capacitive approaches, have been applied to measure the bending or frequency change of the MCLs upon exposure to chemicals. This review summarizes mechanical, fabrication, and electronics approaches to increase the sensitivity of MCL sensors.     

Uncertainties in Solubility Calculations

Summary.  When considering the possible migration of hazardous elements in groundwater, one has to take into account several phenomena, e.g. solubility, ion exchange, adsorption, matrix diffusion, and transport paths. Here, we focus upon the solubility which in turn depends on several more or less uncertain chemical properties. Uncertainties in the data during laboratory experiments aiming at measurements of thermodynamic constants may cause uncertainties in the amount of some species of several tenths of the relative mass fraction. The thermodynamic data may then be used for solubility calculations under different conditions and water compositions. Clearly, there are several uncertainties associated with solubility calculations in the rock-water system. First, there is the effect of uncertainties in thermodynamic data such as stability and solubility constants, and also enthalpies of reaction if the water is not at room temperature. Furthermore, there are the rock-water interactions which will change the water composition as different minerals come in contact with the water flowing through a system of fractures. Studies in mineralogy to an accuracy good enough for modeling of water evolution are difficult to perform, and therefore the mineral composition of the rock and thus the water composition should be treated as parameters subjected to uncertainties. In addition, there are also conceptual uncertainties with respect to input data. The calculation of a solubility should be an easy task for every chemist, but in fact results differing by orders of magnitude are found even when the modelers have used the same computer program and the same data. In this paper, uncertainties associated with solubility calculations are discussed. The results are exemplified on the calculated solubilities of some actinides in groundwater from crystalline rock. Received August 21, 2000. Accepted (revised) May 18, 2001