图C_（4n＋2）×P_（4k＋3）的优美性

图Ｃ＿（４ｎ＋２）×Ｐ＿（４ｋ＋３）的优美性杨燕昌，王广选（北京工业大学应用数学系，北京１０００２２）（北京密云县医院计算机室，北京　１０１５００）关键词乘积图，标号，优美图．分类号ＡＭＳ（１９９１）０５Ｌ７８／ＣＣＬＯ１５７．５关于一般乘积图Ｃ＿ｌ...     

Approximate indexing of icosahedral polyhedra with fibonacci numbers

In general, indexing faces of icosahedral face-forms requires irrational numbers. However, for many practical purposes an approximate indexing based on triplets of integer numbers can be used. Two possible approaches called, respectively, “Fibonacci Matrix Methods” (FMM) and the “Linear Combination Method” (LCM) are described. FMM relies on the use of “auxiliary” matrices F_n, F² _n, F³ _n and F⁴ _n which have Fibonacci numbers as their elements. These matrices allow good approximation of the results usually obtained using the standard five-fold rotation matrices which are typical of icosahedral symmetry. LCM is based on the use of a classical crystallographic rule i.e. the so-called “Goldschmidt Complication Law” which is just a particular case of linear combination of triplets of face indices, with integers as coefficients. The occurrence of large integer indices is remarked.     

加速度计的全组合标定方法

阐述了在重力场上用全组合法标定单加速度计的方法,并且推导了加速度计全组合标定法测试原理。这种方法剔出了测试设备的确定性角位置误差对加速度计误差模型系数标定精度的影响,提高了加速度计的标定精度。结合上述的理论分析,对某型号加速度计进行了实际测试和误差分析,实验结果证明本方法对于提高加速度计标定精度是非常有效的。     

科技文献主题词的自动标引法

本文介绍利用后邻字符树方法对文献进行计算机自动处理，对主题词表进行重排，再结合位置信息实现科技文献主题词的自动标引．     

Powder pattern indexing using the weighted crosscorrelation and genetic algorithms

X-ray diffraction is a powerful technique for investigating the structure of crystals and crystalline powders. Unfortunately, for powders, the first step in the structure elucidation process, retrieving the unit cell parameters (indexing), is still very critical. In the present article, an improved approach to powder pattern indexing is presented. The proposed method matches peak positions from experimental X-ray powder patterns with peak positions from trial cells using a recently published method for pattern comparison (weighted crosscorrelation). Trial cells are optimized with Genetic Algorithms. Patterns are not pretreated to remove any existing zero point shift, as this is determined during optimization. Another improvement is the peak assignment procedure. This assignment is needed for determining the similarity between lines from trial cells and experiment. It no longer allows calculated peaks to be assigned twice to different experimental peaks, which is beneficial for the indexing process. The procedure proves to be robust with respect to false peaks and accidental or systematic absensences of reflections, and is successfully applied to powder patterns originating from orthorhombic, monoclinic, and triclinic compounds measured with synchrotron as well as with conventional laboratory X-ray diffractometers.     

一种语言文档自动检索方法

提出了一种基于潜在语义索引的多语言文档自动检索方法,讨论了多语言环境下概念空间的构造,文档,词语相似度的计算及文档的查询。