对偶模型的巴黎型破产

研究了风险理论中对偶模型的巴黎型破产问题,给出了巴黎型破产时间的拉普拉斯变换,进一步利用Gaver-Stefest算法给出巴黎型破产时间分布的数值解,当跳分布为指数分布时,给出了巴黎型破产时间的拉普拉斯变换的具体表达公式,并作了一些数值计算。     

采煤机螺旋滚筒最佳截线距的探讨

针对螺旋滚筒可能产生的几种排列形式,以利用最小比能耗为基本原则,推导出了截齿的实际最大切削厚度及最佳截线距的理论计算公式,并以镐型齿为例,分析计算了在具体的工况下．三头螺旋滚筒的三种可能排列形式最佳截线距及切屑断面积,最后综合切削图(影响煤的块度)及切削面积选定其排列形式。该推导公式对截齿排列形式的选择有一定的理论指导意义。     

Shanghai synchrotron radiation facility ready for service

A research team led by Prof. Wang Xiaolin with the Institute of Vertebrate Paleontology and Paleoanthropology （IVPP） under the Chinese Academy of Sciences （CAS） completed the preliminary renovation of the largest dinosaur egg in Tiantai, Zhejiang province on April 24.     

一种新型土遗址加固材料的制备及加固效果评价

通过合成一种丙烯酸-有机硅-环氧树脂体系的土遗址加固材料,将其应用于成都金沙土遗址土样的加固试验.通过对加固前后土样的重量、颜色、透气性、耐溶剂性、抗水解性和耐盐安定性等主要性能的分析,评价了加固效果.结果表明,所合成的加固材料对土样具有良好的加固效果.在不影响土样颜色和透气性的前提下,其耐溶剂性、抗水解性和安定性有明显改善.加固后土样在盐酸和氯化钠溶液中长期浸泡半个月无任何开裂,而且能够经历10个抗水解性循环和5个抗硫酸钠溶液循环而不会开裂崩塌.     

弯晶的引出效率与同步加速器的束流动力学稳定性

近年来,弯晶的束流控制技术得到了迅速发展．在加速器物理中,粒子能量和束流强度一直是人们追求的目标,而引出技术和引出效率则是保证柬流强度的关键．在经典力学框架内和偶极近似下,导出了粒子在弯晶中的一般运动方程．在准静态近似下,利用哈密顿原理分析了系统的稳定性;在相空间密度均匀分布假设下,利用相面积概念讨论了弯晶的引出效率．用Melnikov方法描述了系统的混沌行为及临界性质,给出了常曲率和变曲率弯晶的退道长度．     

A new method for splice site prediction based on the sequence patterns of splicing signals and regulatory elements

It is of significance for splice site prediction to develop novel algorithms that combine the sequence patterns of regulatory elements such as enhancers and silencers with the patterns of splicing signals. In this paper, a statistical model of splicing signals was built based on the entropy density profile （EDP） method, weight array method （WAM） and K test; moreover, the model of splicing regulatory elements was developed by an unsupervised self-learning method to detect motifs associated with regulatory elements. With two models incorporated, a multi-level support vector machine （SVM） system was devised to perform ab initio prediction for splice sites originating from DNA sequence in eukaryotic genome. Results of large scale tests on human genomic splice sites show that the new method achieves a comparative high performance in splice site prediction. The method is demonstrated to be with at least the same level of performance and usually better performance than the existing SpliceScan method based on modeling regulatory elements, and shown to have higher accuracies than the traditional methods with modeling splicing signals such as the GeneSplicer. In particular, the method has evident advantage over splice site prediction for the genes with lower GC content.     

Structure properties for the superconductor MgCNi3 under high pressure with synchrotron radiation

The recent discovery of superconductivity at 39 K in the superconductor MgB2[1] shows that intermetallic compounds with simple structure types are worth serious reconsideration as sources of new superconducting mate-rials. Subsequent to this discovery, He et al. observed a new intermetallic superconductor MgCNi3[2] at about 8 K. The perovskite crystal structure for MgCNi3 is shown in Fig. 1, with the atomic positions: Mg: 1a (0,0,0), C: 1b (0.5,0.5,0.5) and Ni: 3c (0,0.5,0.5). This mater…