On the existence of positive solutions for a class of singular boundary value problems

In this paper, by the use of a fixed point theorem, many new necessary and sufficient conditions for the existence of positive solutions in C[0,1]∩C¹[0,1]∩C²(0,1) or C[0,1]∩C²(0,1) are presented for singular superlinear and sublinear second-order boundary value problems. Singularities at t=0, t=1 will be discussed.     

用反射法自动测量大尺寸样品的折射率分布

针对大尺寸样品的折射率分布测量,引入自动扫描装置和适时数据处理系统,研究出一种高灵敏度的智能化反射法折射率分布测量仪,可进行快速、自动、准确的折射率分布测量.经理论分析和实验研究提出了一套合理的实验数据处理方法.并具体介绍和详尽分析了实验装置,讨论了有关理论和实验误差,给出了消除各种误差的有效方法,最终得出较为理想的实验结果.     

斐索梯度折射率光纤透镜传感实验

采用LD泵浦的单纵模Nd：YVO4倍频激光器、梯度折射率光纤透镜等器件构成斐索梯度折射率光纤透镜传感实验仪．本文介绍了实验装置和实验原理，并给出了实验结果。     

用迈克耳逊干涉仪测量气体折射率的误差的研究

研究在用迈克尔逊干涉仪测量气体折射率时存在的系统和方法误差，提出了误差修正方法。     

中国农村居民省际间消费结构差异分析

近年来我国农村居民恩格尔系数下降迅速,反映了农村居民的生活水平和生活质量得到了一定的改善。但农村居民恩格尔系数在省际间出现东部高而中西部低的反常现象让人难以理解。本文借助经济计量方法建立农村居民恩格尔系数的Panel Data模型,定量分析了农村居民收入水平、教育收费和粮食价格对各省农村居民恩格尔系数影响的程度,得出教育收费对食品支出的挤占效应是导致农村居民恩格尔系数反常变化的主要原因。     

强色指数的一个新的上界

给出了图的强色指数的一个新的上界，并指出几类恰好达到该上界的图，从而改进了Erodoes和Nesetri的强色指数猜想，在某种意义上证明了这个猜想。     

Scale-free behavior of the Internet global performance

Measurements and data analysis have proved very effective in the study of the Internet's physical fabric and have shown heterogeneities and statistical fluctuations extending over several orders of magnitude. Here we focus on the relationship between the Round-Trip-Time (RTT) and the geographical distance. We define dimensionless variables that contain information on the quality of Internet connections finding that their probability distributions are characterized by a slow power-law decay signalling the presence of scale-free features. These results point out the extreme heterogeneity of Internet delay since the transmission speed between different points of the network exhibits very large fluctuations. The associated scaling exponents appear to have fairly stable values in different data sets and thus define an invariant characteristic of the Internet that might be used in the future as a benchmark of the overall state of “health” of the Internet. Received 25 January 2003 Published online 7 May 2003     

KrF准分子激光激发掺锗光纤折射率扰动的非线性过程

本文采用了一种简单的功率监测法,观察了KrF准分子激光对掺锗光纤折射率影响的非线性过程。观察到子纤芯折射率扰动过程中非稳定现象、饱和现象和折射率扰动的非线性。     

The Existence of Periodic Orbits for Higher Dimensional Autonomous Systemswith Small Perturbations

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群色散光纤中高强度光脉冲传输与压缩的研究

考虑非线性四阶折射率,推导了光脉冲在群色散单模光纤中传输的非线性方程,并得到孤子型解析解.同时指出在Sech型光纤脉冲压缩实验中,光强度的阈值.