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排序方式: 共有419条查询结果,搜索用时 171 毫秒
91.
光场相干性对线聚焦均匀性的影响   总被引:1,自引:0,他引:1  
采用高斯-谢尔模型(GSM)光束来模拟部分相干光,研究了具有不同相干多数β的GSM光束经柱透镜列阵系统变换后聚焦场的光强分布,并详细讨论了衍射效应和干涉效应对辐照均匀性的影响。  相似文献   
92.
陈东立 《数学研究》1996,29(3):41-43
在k-饱和的超幂非标准模型中将序列的无穷小延伸定理推广到网的情形并利用网的无穷小延伸定理给出函数空间一致收敛拓扑的一个主要性质的直观简短的离散化证明.  相似文献   
93.
Radiation sensitivities of . pumilus and spores were examined to bremsstrahlung of 5 MeV EB and Cobalt -60 γ rays in order to confirm the effects of radiation and dose rate. Biological indicators (SPORTROL, NAmSA, USA) were irradiated with the X ray in the dose rate range of 4.7–47kGy/h. D-value of spores was 1.4–1.5 kGy, and that of was 1.1–1.3 kGy. The D-values of and have very small dose rate dependences to X ray, and the D-values are similar to those of γ ray. Dose distribution by X-ray and γ irradiation was measured for cartons containing 32 unit dialyzers. The Dmax./Dmin. of the X-ray irradiation (1.2) was smaller than that of γ ray (1.3).  相似文献   
94.
Chalus P  Roggo Y  Walter S  Ulmschneider M 《Talanta》2005,66(5):1294-1302
Near-infrared (NIR) spectroscopy can be applied to determine the active substance content of tablets. Its great advantage lies in the minimal sample preparation required, which helps to reduce the potential for error. The aim of this study is to show the feasibility of this method on low-dosage tablets. The influence of various spectral pretreatments [standard normal variate (SNV), multiplicative scatter correction (MSC), second derivative (D2), orthogonal signal correction (OSC), separately and combined] and regression methods on prediction error are compared. Partial least square (PLS) regression provided better prediction than principal component regression (PCR). SNV was applied to the first data set and SNV and a second derivative to the second set to maximise model accuracy for quantifying the active substance of intact pharmaceutical products using diffuse reflectance NIR. The models yielded standard errors of prediction (SEP) of 0.1768 and 0.0682 mg for the two products. The experiments were conducted with two low-dosage pharmaceutical forms and results of NIR predictions were comparable to currently approved methods. Diffuse reflectance NIR has the potential to become a reliable and robust quality control method for determining active tablet content.  相似文献   
95.
李树  蓝可  赖东显  刘杰 《物理学报》2015,64(14):145203-145203
利用蒙特卡罗方法模拟六孔球形黑腔中的辐射输运, 研究靶球辐照均匀性问题. 对于几何结构简单的解析模型, 研究了不同黑腔靶球半径比的靶球辐照均匀性变化规律, 得出的结论与解析的“视因子”方法给出的一致. 对于几何结构复杂的黑腔模型, 如放置有挡板的模型, 解析方法计算困难, 但利用蒙特卡罗方法仍然能够准确模拟计算. 不同挡板大小的理论模型计算结果表明, 挡板对X光输运到靶球表面的分布状况有明显的影响, 如果设置得当则可以提高X光利用效率并显著改善靶球辐照均匀性, 否则可能严重破坏靶球辐照均匀性. 因此, 黑腔中的挡板位置及大小需要精心设计. 应用表明, 蒙特卡罗方法对于具有复杂结构的黑腔辐射输运问题具有很好的适应性.  相似文献   
96.
Let {X k , 1 k n} be n independent and real-valued random variables with common subexponential distribution function, and let {k, 1 k n} be other n random variables independent of {X k , 1 k n} and satisfying a k b for some 0 < a b < for all 1 k n. This paper proves that the asymptotic relations P (max1 m n k=1 m k X k > x) P (sum k=1 n k X k > x) sum k=1 n P ( k X k > x) hold as x . In doing so, no any assumption is made on the dependence structure of the sequence { k , 1 k n}. An application to ruin theory is proposed.  相似文献   
97.
Finding permutation polynomials with low differential and boomerang uniformity is an important topic in S-box designs of many block ciphers. For example, AES chooses the inverse function as its S-box, which is differentially 4-uniform and boomerang 6-uniform. Also there has been considerable research on many non-quadratic permutations which are modifications of the inverse function. In this paper, we give a novel approach which shows that plenty of existing modifications of the inverse function are in fact affine equivalent to permutations of low Carlitz rank, and those modifications cannot be APN. We also present the complete list of permutations of Carlitz rank 3 having the boomerang uniformity six, and give the complete classification of the differential uniformities of permutations of Carlitz rank 3. As an application, we provide all the involutions of Carlitz rank 3 having the boomerang uniformity six.  相似文献   
98.
Finding permutations with good cryptographic parameters is a good research topic about constructing a secure S-box in substitution-permutation networks. In particular constructing differentially 4-uniform permutations has made considerable progress in recent years. In this paper, we present new differentially 4-uniform permutations from the inverse function composed by disjoint cycles. Our new differentially 4-uniform permutations have high nonlinearity and low differential-linear uniformity. We give the differential spectrum and the extended Walsh spectrum of some of our differentially 4-uniform permutations, and then we can see that they are CCZ-inequivalent to some permutations whose differential spectrum and extended Walsh spectrum are known.  相似文献   
99.
行星夹具膜厚均匀性计算   总被引:6,自引:2,他引:4       下载免费PDF全文
 建立了平板型和球面型行星夹具膜厚均匀性的计算模型。利用根据这些模型编制的计算程序计算了基板表面膜层厚度分布与蒸发源位置、蒸发源发射特性、夹具高度、行星轨半径以及行星夹具的倾角之间的关系。并得到了一组典型结果。  相似文献   
100.
带有定性因素均匀设计的均匀性度量准则   总被引:5,自引:0,他引:5  
我们在文〔3〕中曾讨论了如何用均匀设计来安排含有定性因素的试验。在文〔1〕中所使用的均匀设计表是针对试验中全为连续因素设计的。显然 ,当试验中含有定性因素时 ,均匀性的度量和相应均匀设计表的设计都会有所不同。这是一个值得研究的课题。本文主要探讨均匀性的度量 ,并用文中提出的准则 ,对文〔1〕中一些均匀设计表的均匀性给出了数值性结果  相似文献   
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