Broadband high-gain optical parametric chirped-pulse amplification near 780 nm with LBO-I near-degenerate near-collinear phase match

Near-degenerative near-collinear phase-match geometry for broadband optical parametric chirped-pulse amplification (OPCPA) at approximate to 780 nm is calculated in comparison with nondegenerate noncollinear phase-match geometry. In an experiment on LBO-I near-degenerate near-collinear OPCPA, high gain with broad gain bandwidth (approximate to 71 nm, FWHM) at approximate to 780 nm is achieved by using an approximate to 390-nm pumping pulse. The stretched broadband chirped signal pulse near 780 nm is amplified to approximate to 412 mu J with a pumping energy of approximate to 15 mJ, and the total gain is > 3.7 X 10(6), which agrees well with the calculation. For a broadband (covering approximate to 100 nm) chirped signal pulse, the theoretical gain bandwidth has been attained experimentally for the first time. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Broadband high-gain optical parametric chirped-pulse amplification near 780 nm with LBO-I near-degenerate near-collinear phase match

Near-degenerative near-collinear phase-match geometry for broadband optical parametric chirped-pulse amplification (OPCPA) at approximate to 780 nm is calculated in comparison with nondegenerate noncollinear phase-match geometry. In an experiment on LBO-I near-degenerate near-collinear OPCPA, high gain with broad gain bandwidth (approximate to 71 nm, FWHM) at approximate to 780 nm is achieved by using an approximate to 390-nm pumping pulse. The stretched broadband chirped signal pulse near 780 nm is amplified to approximate to 412 mu J with a pumping energy of approximate to 15 mJ, and the total gain is > 3.7 X 10(6), which agrees well with the calculation. For a broadband (covering approximate to 100 nm) chirped signal pulse, the theoretical gain bandwidth has been attained experimentally for the first time. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Theoretical research on noncollinear match conditions of the type I optical parametric process

Broad bandwidth group match conditions are reported for a noncollinear type I optical parametric process. The theoretical calculations corresponding to two special situations in practice were made, respectively, which are in accordance with the published experimental results. Furthermore, we provide a method to not only achieve maximal parametric bandwidth output but also match the group velocities between three waves. (c) 2006 Optical Society of America.

Beam match and preparation of SFC-CSR

In order to match the beam from the injection machine SFC of the HIRFL to the main ring of HIRFL-CSR, both beam emittance confining method and beam energy spread reducing method are proposed. The beam preparation principles and calculation results are presented

基于I-Match算法的垃圾邮件过滤研究

电子邮件(Electronic Mail，E-Mail)是目前使用最广泛的互联网应用。随着互联网络以惊人的速度增长，电子邮件成为发布恶意信息的一个重要途径，垃圾邮件已经成为危害互联网络的最大毒瘤。针对方式多样的垃圾邮件技术，垃圾邮件过滤系统往往也需要综合多种过滤技术以提高系统的有效性。其中摘要技术已经成为重要的垃圾邮件过滤方法之一：通过摘要技术判断一个邮件和已知垃圾邮件的相似度，从而对邮件进行分类。判断一个垃圾邮件过滤算法是否有效，要综合考虑算法的召回率、准确率以及时间性能。I-Match算法通过摘要值的精确匹配来判断两个邮件文本内容是否相似，算法在效率方面表现突出。但是I-Match算法在实际的应用中还存在很多问题，其中包括字典生成制约算法的性能以及面对攻击时算法表现出的鲁棒性不足。因此，优化算法的字典生成过程以及提高算法的鲁棒性成了算法应用于实际系统的两个重要问题。本文的主要工作包含以下内容： 对垃圾邮件进行相似性分析，包括垃圾邮件相似性的起因、垃圾邮件在时间和内容两方面所表现出的相似性特征。垃圾邮件体现出的相似性特征是使用摘要算法进行垃圾邮件过滤的必要条件之一。 改进I-Match算法的字典生成过程。提出利用特征的互信息作为特征选择依据改进字典生成过程，并对比几种不同的特征选择方式对算法性能的影响。 分析I-Match算法的鲁棒性以及几种I-Match改进算法对算法鲁棒性的提升，在实际的邮件语料上对各种改进算法进行评测，并综合分析各个算法的实用性。 完成了KSpam系统原型，以插件的形式综合多种邮件过滤方法，并给出了I-Match算法在KSpam系统中的实现方案。同时，系统实现了一种新式的邮件自动回收功能，有效减少邮件管理员的邮件语料收集工作。