Full Non-rigid Group of Sponge and Pina

The non-rigid molecule group theory (NRG) in which the dynamical symmetry operations are defined as physical operations is a new field in chemistry. Smeyers and Villa computed the r-NRG of the triple equivalent methyl rotation in pyramidal trimethylamine with inversion and proved that the r-NRG of this molecule is a group of order 648, containing a subgroup of order 324 without inversions (see J. Math. Chem. 28(4) (2000) 377–388). In this work, a computational method is described, by means of which it is possible to calculate the symmetry group of molecules. We study the full non-rigid group (f-NRG) of Sponge and Pina molecules with C ₂ and C _i point groups, respectively. It proved that these are groups of order 162 and 13122 with 54 and 3240 conjugacy classes, respectively. The character tables of these groups are also computed.     

内蒙古地区沙生植物--沙枣对亚硝酸盐分解作用的研究

利用分光光度法研究了内蒙古地区沙生植物———沙枣对亚硝酸盐的分解作用。结果表明,沙枣中富含的维生素C、维生素E和脯氨酸等抗氧化剂可以作为还原剂与亚硝酸盐作用,从而降低亚硝酸盐的含量;加入的沙枣量愈多,随时间延长对亚硝酸盐的分解能力亦增强,但不呈线性关系。试验结果表明,沙枣不仅可以作水土保持、防沙造林的先锋树种,还由于它富含抗氧化物,可作为人体降低体内亚硝胺生成的良好补充源。     

Topological Space of the Chemical Elements and its Properties

We carried out a mathematical study of 72 chemical elements taking advantage of the chemotopological method. We selected 128 properties to define the elements (physico-chemical, geochemical and chemical properties). Then, we looked for correlated properties and we reduced the number of them to 90. In this way we defined each element as a 90-tuple. Afterwards, we applied principal component analysis and cluster analysis (4 similarity functions and 5 grouping methodologies). Then, we calculated a consensus tree for the 20 dendrograms generated by the CA. Afterwards, we extracted the similarity relationships from the consensus tree and built up a basis for a topology on the set of chemical elements. Finally, we calculated some topological properties (closures, derived sets, boundaries, interiors and exteriors) of several subsets of chemical elements. We found that alkali metals, alkaline earth metals and noble gases appear not related to the rest of the elements. Also, we found that the boundary of non-metals are the semimetals with a stair-shape on the periodic table     

爆炸冲击震动模拟平台的研制

为了模拟核爆、化爆冲击震动环境,根据能量守恒和弹性碰撞原理,研制了悬挂式爆炸冲击震动模拟平台。该平台能够完成水平向和垂直向冲击试验,通过对锤重、锤高和垫层厚度等参数的合理选择,性能指标可达到:水平向冲击加速度峰值5~1 500 m/s2,作用时间50~4 ms;垂直向冲击加速度峰值10~1 000 m/s2,作用时间60~4 ms。性能试验表明,该平台能够为防护工程结构抗震及其他有关冲击振动问题的研究提供安全、方便、经济、可靠的试验手段。     

三轴模拟台的交叉耦合及其控制方法的研究

本文主要从三轴转台的模型出发，研究了采用状态反馈的最优控制及状态观测器来提高控制系统的自适应能力，以解决三轴台特有的不确定非线性耦合问题和变结构解耦控制。     

惯性系统三轴综合测试转台总体设计若干问题的探讨

本文从框架形式、总体布局、轴承的种类和布置方式等方面，讨论了惯性系统三轴综合测试转台总体设计中的若干问题，从设计、制造和使用等方面阐述了各种总体布局形式的优缺点，并提出了自己的相应看法，最后讨论了目前惯导测试设备研究领域需要研究的关键技术。     

Predicting USCS soil classification from soil property variables using Random Forest

Soil classification systems are widely used for quickly and easily summarizing soil properties and provide a shorthand method of communication between scientists, engineers, and end-users. Two of the most widely used soil classification systems are the United States Department of Agriculture (USDA) textural soil classification system and the Unified Soil Classification System (USCS). Unfortunately, not all soil map units are classified according to the USDA or USCS systems, and previous attempts to provide a crosswalk table have been inconsistent. Random Forest machine learning model was used to create a USCS prediction model using USDA soil property variables. Important variables for predicting USCS code from available soil properties were USDA soil textures, percent organic material, and available water storage. Prediction error rates less than 2% were achieved compared to error rates of approximately 40% using crosswalk methods.     

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本文用概率函数分析方法研究了乒乓球拍形状和尺寸对乒乓球迎击概率的影响．基于将球拍的外轮廓线视为一条等概率曲线，导出了满足最高迎击球概率的球拍外轮廓线的数学表达式，给出了相应的计算结果．计算结果表明，现有球拍平面形状和尺寸有待进一步改进和完善，减小打漏球的失误，使其具有最大的迎击球概率．     

Detection of the support damage of spatial steel structures under earthquakes based on shaking table test

There are always some local damages in spatial steel structures induced by strong earthquakes, such as welding cracks of steel nodes, anchor loose of supports etc. If these local damages of spatial steel structures occur, there will be serious dangers to the structural safety. In order to detect the position of local damage under earthquake quickly and accurately, the method of support damage diagnosis of spatial steel structures under earthquakes is studied by using wavelet packet decomposition, data fusion and cluster analysis. Furthermore, a scale model of spatial steel structure was tested on a seismic simulation shaking table to detect the position of damaged support. Results show that the damaged support position can be detected accurately by using the method proposed in this paper, which has practical applications to the damage detection of spatial steel structures.