铝对大蒜根尖细胞有丝分裂的影响

用不同浓度的三氯化铝分别处理大蒜根尖6h,18h,24h,结果表明:各处理组均对大蒜根尖细胞有丝分裂产生抑制.随着处理液中铝浓度的升高及处理时间的加长,有丝分裂指数呈现规律性的变化:染毒的根尖细胞有丝分裂指数明显低于对照组,并随着作用时间的延长快速下降,随着浓度的升高先减后增再减,说明三氯化铝具有细胞分裂抑制剂的作用.不同浓度的三氯化铝在不同处理时间内均能诱使大蒜根尖细胞发生染色体畸变.     

Approach to Weighted Geometric Evaluation Based on Projection Pursuit

Weighted geometric evaluation approach based on Projection pursuit （PP） model is presented in this paper to optimize the choice of schemes. By using PP model, the multi-dimension evaluation index values of schemes can be synthesized into projection value with one dimension. The scheme with a bigger projection value is much better, so the schemes sample can be an optimized choice according to the projection value of each scheme. The modeling of PP based on accelerating genetic algorithm can predigest the realized process of projection pursuit technique, can overcome the shortcomings of large computation amount and the difficulty of computer programming in traditional projection pursuit methods, and can give a new method for application of projection pursuit technique to optimize choice of schemes by using weighted geometric evaluation. The analysis of an applied sample shows that applying PP model driven directly by samples data to optimize choice of schemes is both simple and feasible, that its projection values are relatively decentralized and profit decision-making, that its applicability and maneuverability are high. It can avoid the shortcoming of subjective weighing method, and its results are scientific and objective.     

Expected Value Method for Fuzzy Multiple Attribute Decision Making

Introduction Multiple attribute decision making (MADM), which entails decision making problems with multi- alternatives and multi-attributes, is widely applied in engineering, economics, management, military affairs society, and so on. In many real-world …     

Some evidence of drying trend over northern China from 1951 to 2004

The surface wetness index, Palmer drought sererity index and the retrieval of soil moisture over China were calculated using monthly precipitation and monthly mean surface air temperature. Based on the contrast analysis of the variation of the above three indices and precipitation, the dry/wet spatio-temporal pattern of northern China in the last 54 years was revealed, and the evidence of drying trend over northern China was analyzed, especially. The results show the following four facts: (1) The drying trend is the main characteristic of the eastern part of Northwest China and the central part of North China since the 1980s and it was enhanced in the last 15 years mainly due to the precipitation decrease and the temperature increase; (2) During the last 54 years, there was only one dry/wet shift at the interdecadal scale occurring in the eastern part of Northwest China and the central part of North China in the late 1970s, which was related to 1977/1978 global abrupt change, whereas there were three shifts in Northeast China, one was in the mid 1990s and the other two were in 1965 and 1983, respectively; (3) Unlike the variation trend of other subregions of northern China, the western part of Northwest China is currently located in a relatively wetting period, which is weak-ened due to the temperature increase; (4) The extreme drought frequency is obviously increasing in the eastern part of Northwest China, the central part of North China and Northeast China since the 1980s, which is closely related to the precipitation decrease and temperature increase in these subregions.     

最大公因数闭集上平方矩阵的行列式的整除性

设S={x1,…,xn}是由n个不同正整数组成的最大公因数闭集．得到的主要结果是：（1）如果n≤3，则det（S）n^2整除det[S]n^2；（2）如果max{xi si∈S}〈12，则det（S）n^2整除det[S]m^2；（3）当n=4时，存在最大公因数闭集．S，有det（S）n^2不整除det[S]n^2．     

盐酸吗啉胍对蚕豆根尖细胞的遗传毒性效应

以不同浓度的盐酸吗啉胍为诱变剂，运用蚕豆根尖微核检测技术和染色体畸变实验方法，测定蚕豆根尖细胞的有丝分裂指数、微核率和染色体畸变率．结果表明：盐酸吗啉胍能够降低蚕豆根尖细胞有丝分裂指数，能诱发较高频率的微核和染色体畸变，产生染色体断片、滞后染色体和染色体桥．随着盐酸吗啉胍处理浓度的增加，有丝分裂指数降低，而微核率和染色体畸变率均升高；随着盐酸吗啉胍浓度的进一步增加，染色体畸变率却下降，但仍明显高于对照组．     

基于特征域词频的邮件过滤方法的研究

出了根据邮件特征域信息和特征词频进行垃圾邮件过滤的新方法，并介绍在该方法中的文本特征选取、特征词典构造以及基于TF的权值计算等相关技术，以及改进的文本相似度计算概率模型.实验表明该方法在邮件过滤的查全率、查准率等几个性能评价指标上，比传统的Rocchio方法有了明显改善.     

奇异二阶微分方程边

利用拓扑度理论研究了奇异二阶Neumann边值问题.在有关其线性算子方程对应的第一特征值的条件下得到了边值问题正解及多解的存在性.     

不完全信息下概率决策的扩展粗糙集方法

为了从不完备多属性决策系统中获取概率决策规则，提出了一种不完全信息下概率决策的扩展粗糙集方法. 给出了容差关系下相容度的概念，通过设定相容阈值给出知识的粗糙下近似、上近似和边界域，然后讨论了粗糙近似的基本性质和概率决策规则的获取.通过实例说明这个新方法的可行性和有效性.