A new estimator of covariance matrix via partial Iwasawa coordinates

This paper is concerned with the problem of improving the estimator of covariance matrix under Stein’s loss. By the partial Iwasawa coordinates of covariance matrix, the corresponding risk can be split into three parts. One can use the information in the weighted matrix of weighted quadratic loss to improve one part of risk. However, this paper indirectly takes advantage of the information in the sample mean and reuses Iwasawa coordinates to improve the rest of risk. It is worth mentioning that the process above can be repeated. Finally, a Monte Carlo simulation study is carried out to verify the theoretical results.     

Ruin probabilities with pairwise quasi-asymptotically independent and dominatedly-varying tailed claims

This paper considers the nonstandard renewal risk model in which a part of surplus is invested into a Black-Scholes market whose price process is modelled by a geometric Brownian motion, claim sizes form a sequence of not necessarily identically distributed and pairwise quasi-asymptotically independent random variables with dominatedly-varying tails.The authors obtain a weakly asymptotic formula for the finite-time and infinite-time ruin probabilities.In particular,if the claims are identically distributed and consistently-varying tailed,then an asymptotic formula is presented.     

Characterization of microbe cementitious materials

A new generation of cement, microbe cement, has been developed in response to the ever increasing awareness of environmental protection. Microbe cement is a new strengthening material based on microbiologically induced precipitation of calcium carbonate. This paper confirms the feasibility of binding loose sand particles using microbe cement and details the cementation mechanism of microbe cement. We have also prepared microbe cementitious materials (biosandstones). The compressive strength of the bio-sandstone, which depends on the content of calcium carbonate produced by microbially induced precipitation and the bio-mediated calcite crystal size, could be up to 12 MPa at an age of 20 days. By increasing the precipitated calcite content, the compressive strength and microstructure of bio-sandstone could be improved.     

全站仪进行水准控制测量的实现

利用全站仪进行水准测量,则可以克服水准仪视准轴不能倾斜的特点,从而快速地完成水准传递的任务,同时,也可以减少由于水准仪多次转站而增加的观测误差.     

Initializing K-means Batch Clustering: A Critical Evaluation of Several Techniques

K-means clustering is arguably the most popular technique for partitioning data. Unfortunately, K-means suffers from the well-known problem of locally optimal solutions. Furthermore, the final partition is dependent upon the initial configuration, making the choice of starting partitions all the more important. This paper evaluates 12 procedures proposed in the literature and provides recommendations for best practices.     

Genomic and genic sequence variation in synthetic hexaploid wheat （AABBDD） as compared to their parental species

In order to understand the genomic changes during the evolution of hexaploid wheat, two sets of synthetic hexaploid wheat from hybridization between maternal tetraploid wheat （AABB） and paternal diploid goat grass （DD） were used for DNA-AFLP and single strand conformation polymorphism （SSCP） analysis to determine the genomic and genic variation in the synthetic hexaploid wheat. Results indicated that more DNA sequences from paternal diploid species were eliminated in the synthetic hexaploid wheat than from maternal tetraploid wheat, suggesting that genome from parental species of lower ploidity tends to be eliminated preferentially. However, sequence variation detected by SSCP procedure was much lower than those detected by DNA-AFLP, which indicated that much less variation in the genic regions occurred in the synthetic hexaploid wheat, and sequence variations detected by DNA-AFLP could be derived mostly from non-coding regions and repetitive sequences. Our results also indicated that sequence variation in 4 genes can be detected in hybrid F1, which suggested that this type of sequence variation could be resulted from distant hybridization. It was interesting to note that 3 out of the 4 genes were mapped and clustered on the long arm of chromosome 2D, which indicated that variation in genic sequences in synthetic hexaploid wheat might not be a randomized process.     

A fast pseudorandom number generator with BLAKE hash function

This paper presents a fast pseudorandom generation algorithm, which is based on the BLAKE hash function and can pass the random test of the NIST (National Institute of Standards and Technology) Statistical Test Suite. Through theoretical analysis and experimental imitation, our new algorithm is proven to be more secure and efficient than G-SHA1. Simultaneously, we introduce and discuss the BLAKE in detail. Its security shows that can be utilized to generate pseudorandom bit sequences, which the experimental results show the BLAKE hash function has excellent pseudorandomness. Therefore, we believe the BLAKE is one of the most potential candidate algorithms of SHA-3 program.     

NECESSARY AND SUFFICIENT CONDITION FOR GLOBAL CONTROLLABILITY OF A CLASS OF AFFINE NONLINEAR SYSTEMS

In this paper, we investigate the global controllability of a class of n-dimensional affine nonlinear systems with n- 1 controls and constant control matrix. A necessary and sufficient condition for its global controllability has been obtained by using the methods recently developed. Furthermore, we generalize the above result to a class of affine nonlinear systems with a block-triangular-like structure. Finally, we will give three examples to show the applications of our results.     

大学生体质测试系统应用于专业运动领域探讨——以四川省女子水球代表队的应用为例

应用大学生体质监测系统对四川女子水球队现役队员进行体质监测,并对不同位置球员的各项指标进行对比。结果发现:(1)中锋身高、体重及身体成分体重等指标均显著高于外线球员,台阶试验得分显著低于外线球员;(2)中锋反应时、体重等指标显著高于守门员,横向滑动次数显著低于守门员;(3)外线球员的身高显著低于守门员,反应时显著高于守门员。因此,大学生体质测试仪器可应用于专业运动领域,教练员可根据测试结果选择运动员、制定技战术。     

田径运动员左心收缩时间间期的分析与评价

采用MCA-3心脏功能综合检测仪,测量田径运动员静态心脏收缩时间间期各指标,分析其特点并与非运动员进行比较,从而对田径运动员的左心功能作出系统的评价。结果发现,田径运动员的LVET、EMT、MSTI、CT及PEP等指标值均比一般人群的指标值高。田径运动员的左心功能呈现机能节省化。