Finite Groups Acting on Homology 3-Spheres: On a Result of M. Reni

 We give a list including all finite groups G which admit smooth orientation preserving actions on homology 3-spheres (arbitrary actions, i.e. possibly with fixed points; if the action is free then the group G has periodic cohomology and the classification of such groups is well known). The main work in this direction is due to M. Reni. In the present paper, we complete and extend his results for the case of nonsolvable groups G. Received 19 March 2001; in revised form 15 September 2001     

A topological aspect of Sobolev mappings

Let be a connected open set, . We give a sufficient condition for a mapping , , to have the property that sgn is almost everywhere of one sign. Following the work of Müller, Spector, and Tang [MST], we give an application of our results to the theory of non-linear elasticity. Received: 13 October 2000 / Accepted: 23 January 2001 / Published online: 4 May 2001     

关于Delphi7的Zlib压缩库的应用

在数据库应用过程中,往往要对一些文件进行保存,如果直接保存,会浪费很多数据库空间,势必造成对数据库处理速度的影响。介绍利用Delphi7提供的Zlib压缩库在数据库存取文件时可以直接进行压缩和解压缩处理,使得在数据库中存取文件变得越来越方便。     

A C + + computational environment for biomolecular sequence management

The wide production of biomolecular data of the last 30 years, mainly due to the rapid evolving of technologies as well as to the accomplishment of the Genome Projects, led to the necessity of appropriate computational approaches for data storage, manipulation and analyses, giving place to a fast evolving area of Biology: Computational Biology or Bioinformatics.We propose here a new method for the storage of the sequences and their analyses using the C + + programming language, checking the effectiveness of an object oriented approach for new models, suitable to manage data representation and analyses, to improve the efficiency of computational methodologies to solve problems of general interest in bioinformatics. We developed a framework with the aim to decrease the computational costs for the storage and some basic manipulations of nucleic acid sequences. The remarkable reduction of memory requirements with no loss of efficiency makes this approach a first well promising step in order to get a more efficient environment for the manipulation and the management of nucleic acid data sets, in a field of research with hard challenges for Computer and Life Sciences.Mathematics Subject Classification: 68U99G. Toraldo, via Universita’ 100, 80055 Portici, Napoli, Italy     

一维应变压缩下TC4钛合金绝热剪切研究

 利用内径为57 mm的压缩气炮，在撞击速度为0.2~1.2 km/s（相应的靶中压力为3~15 GPa）范围内进行对称碰撞实验，以研究TC4（Ti-Al6-V4）钛合金在一维应变冲击压缩条件下的绝热剪切现象。对回收得到的受冲击样品，在扫描电镜（SEM）下进行细观金相分析。结果指出，一维应变冲击压缩条件下，TC4钛合金中绝热剪切带产生的对称碰撞速度阈值为500 m/s（相当于样品中的压力为5.87 GPa）；主剪切带与冲击方向约为45°角，带上有圆形和椭圆形两种孔洞且随碰撞速度的增大而增多和长大，这是典型的韧性损伤特征。随碰撞速度增大，产生与主剪切带成15°角的支剪切带。这些与理论预言相符。X射线能谱分析结果指出，剪切带内材料发生了(α+β)→β相的转变，是典型的相变带。剪切带的温度估算与实验提供的信息吻合。     

cdma200O 1X系统正向前馈线性功率放大器设计

本文采用简单实用的自适应控制技术,设计了用于cdma2000 1X系统的正向前馈线性功率放大器.输出功率大于20W(43dBm),双音IMD3低于-50dBc,cdma20001X信号测试ACPR低于-51dB·±750kHz.     

On the Metrical Theory of Continued Fraction Mixing Fibred Systems and Its Application to Jacobi-Perron Algorithm

 We study the metrical theory of fibred systems, in particular, in the case of continued fraction mixing systems. We get the limit distribution of the largest value of a continued fraction mixing stationary stochastic process with infinite expectation and some related results. These are analogous to J. Galambos, W. Philipp, and H. G. Diamond–J. D. Vaaler theorems for the regular continued fractions. As an application, we see that these theorems hold for Jacobi-Perron algorithm. Received September 30, 2001; in revised form January 8, 2002     

Lower Bounds for the Height and Size of the Ideal Class Group in CM-Fields

 We prove that, under the assumption of the Generalized Riemann Hypothesis, the exponent of the ideal class group of a CM-field goes to infinity with its absolute discriminant. This gives a positive answer to a question raised by Louboutin and Okazaki [4]. Received September 10, 2001; in revised form April 5, 2002     

基于Karhunen-Loève变换和小波谱特征矢量量化的三维谱像数据压缩

提出了基于Karhunen Lo埁ｖｅ变换的小波谱特征矢量量化三维谱像数据压缩方法耍幔颍瑁酰睿澹?Lo埁ｖｅ变换 /小波变换 /小波谱特征矢量量化方法应用了Karhunen Lo埁ｖｅ变换的消除谱相关性优良性能 ,应用二维小波变换消除空间相关性 ,在小波变换域内应用二维集分割嵌入块编码和一维谱特征矢量量化对三维谱像数据压缩 ,获得较高的压缩性能。实验结果表明 :Karhunen Lo埁ｖｅ变换 /小波变换 /小波谱特征矢量量化编码比Karhunen Lo埁ｖｅ变换 /小波变换 /改进对块零树编码和Karhunen Lo埁ｖｅ变换 /小波变换 /快速矢量量化编码方法在同样压缩比条件下 ,峰值信噪比提高 2dB和 1dB以上 ,而速度提高了 1.5和 8倍 ,整体压缩性能有较大的提高