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作为一种新兴的检测手段 ,激光光声光谱技术与其他检测技术相比具有很多优点。本文设计的光声光谱仪用激光做光源 ,有两个光声池 ,分别用来放置参考样品和待测样品 ,输出结果为二者光声信号的比值。利用这一比值 ,可以由参考样品的性能参数方便地求出待测样品的相关性能参数。该光声光谱仪有效地减小了本底吸收噪声的影响 ,提高了信噪比 ,扩大了固体光声理论的应用范围。本文还阐述了该光声光谱仪在定性定量分析中的一些应用  相似文献   
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The study aims to exploit incremental analysis or marginal analysis to overcome the drawbacks of ratio scales utilized in various multi-criteria or multi-attribute decision making (MCDM/MADM) techniques. In the proposed 11-step procedure, multiple criteria of alternatives are first reorganized as two categories – benefits and costs – and decision information will be manipulated separately. The performances of alternatives are then evaluated on their incremental benefit–cost ratio, and the rank can be obtained by applying the group TOPSIS (technique for order preference by similarity to ideal solution) model (Shih et al., 2007). Two representations of cost, i.e., a cost index and utility index, are proposed in the model to better-fit real-world situations. In addition, some considerations on costs and input–output relations are also discussed in order to understand the essentials of incremental analysis. In the final part, a case of robot selection demonstrates the suggested model to be both robust and efficient in a group decision-making environment.  相似文献   
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We address the problem of estimating the finite population mean in survey sampling, by exploiting any available auxiliary information in order to increase the precision of classical estimators. The idea is to use any population quantiles of the available auxiliary variables which are known in many real situation from census, administrative files, etc. This is achieved using these known quantities in the construction of the estimators, by modifying the usual ratio estimation methods and afterwards defining a general class of exponentiation ratio estimators. The advantages of the proposed estimators are demonstrated using theoretical asymptotic tools and through a simulation study.  相似文献   
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通过揭示模糊推理的一种CRI算法的逻辑原理,提出了模糊推理的一种新算法.并对单规则的CRI算法(或三Ⅰ算法)的重心(或最大隶属度)去模糊法的有效性进行了研究.发现在单规则的CRI算法(或三Ⅰ算法)的模糊推理中,当大前提的后件取对称模糊集时,采用重心去模糊法使得推理结果无效,而采用最大隶属度去模糊法可使得推理结果有效.  相似文献   
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For X 1 , X 2 , ..., X n a sequence of non-negative independent random variables with common distribution function F(t), X (n) denotes the maximum and S n denotes the sum. The ratio variate R n  = X (n) / S n is a quantity arising in the analysis of process speedup and the performance of scheduling. O’Brien (J. Appl. Prob. 17:539–545, 1980) showed that as n → ∞, R n →0 almost surely iff is finite. Here we show that, provided either (1) is finite, or (2) 1 − F (t) is a regularly varying function with index ρ < − 1, then . An integral representation for the expected ratio is derived, and lower and upper asymptotic bounds are developed to obtain the result. Since is often known or estimated asymptotically, this result quantifies the rate of convergence of the ratio’s expected value. The result is applied to the performance of multiprocessor scheduling.   相似文献   
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本文采用pH指示剂吸光度比法测定喷昔洛韦钠原料药的含量,并与紫外分光光度法和高效液相色谱法两种方法进行了比较。该法简单、准确、快速、灵敏且重现性好,有应用前景。  相似文献   
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Uniform Yb3+ and Er3+-codoped Y2O3 hollow microspheres were synthesized via urea co-precipitation using carbon spheres as templates. Intense red emission (4F9/24I15/2) and weak green emission (2H11/2, 4S3/24I15/2) of Er3+ were observed for the Yb3+ and Er3+-codoped Y2O3 hollow microspheres under 980 nm infrared excitation. The integrated intensity of visible emission and the ratio of red to green were found to be strongly dependent on the amount of carbon sphere templates and the concentration of Yb3+ ions. The amount of carbon sphere templates also plays an important role in adjusting the size of crystallite. Multi-phonon relaxation resulted from the absorbents (OH and CO32−) on the surface of the crystallite, and efficient occur of energy transfer processes and cross-relaxation between Er3+ and Yb3+ are responsible for the enhancement of intensity ratio of red to green emission. Interestingly, for higher concentration of Yb3+ ions, the green emission is assigned to a three-phonon process in Y2O3:Yb/Er hollow microspheres, which also could result in the increase of the red to green emission ratio. An explanation to account for these behaviors was presented.  相似文献   
20.
Electronic speckle interferometry (ESPI) is used to determine the Young's modulus E and Poisson ratio ν of an isotropic material. Micron scale deformations of the surface of the block of polymethyl-methacrylate (PMMA) are induced by normal application of a known near-point force. These deformations are recorded in speckle interferometric fringe patterns. An iterative minimum error inversion technique is developed to obtain the elastic properties from the positions of fringe peaks and troughs observed in the fringe patterns. Sensitivity tests of the method on calculated fringe patterns using measured experimental uncertainties suggest the technique will provide measures of the elastic moduli to better than 5%. In an experimental test on a bloc of PMMA (acrylic) the technique gave values of E and ν that differed from corresponding measures obtained using more conventional strain-gauge methods by less than 4%.  相似文献   
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