四能级原子系统中泵浦场位相涨落对激光增益的影响(英文)

针对四能级系统中的无反转激光，分析了驱动场中位相变化对系统的影响，结果表明：位相涨落不仅引起粒子囚禁数目减少，并且导致激光增益减少。     

贾府的衰败与赖家的兴盛谫论

宁荣二国公所创造的辉煌基业,因其生齿日繁,事务日盛,主仆上下安富尊荣,生活过分奢糜,缺乏运筹谋划之人．造成一代不如一代的颓势,致使贾府由盛而衰,大厦倾倒。与其相反的是：赖家虽为贾府的世仆,因其在贾府管家时间长,权势重,善于拍马逢迎主子,钻了贾府管理混乱的孔子,渐次发迹,超越常人,最后连主子也要向其乞借遭冷遇。这一主仆贫富易位的典型事例给世人留下颇值得深思回味的人生课题。     

Multisim 2001在模拟电路教学中的应用研究

本文利用Multisim2001电路仿真软件分析了电压串联负反馈放大电路的各项性能指标，证明采用电路设计仿真软件进行仿真实验教学可有效地对理论教学起到辅助作用。利用电路仿真技术的先进教学手段进行教学，提高学生学习兴趣和课堂教学效果，是值得广大教师研究的又一新课题。     

一种恒定跨导、摆率和增益的轨至轨运放

提出了一种新型的通用低压轨至轨CMOS运放．该运放在整个输入共模电压范围内获得了恒定的跨导、摆率和恒定的高增益．所提出的电路有应用于深亚微米工艺的潜力,因为运放电路的运行不依赖于晶体管平方率或线性率的约束．因此该电路比较紧凑,适用于VLSI单元的应用．轨至轨CMOS运放采用DPDM CMOS混合信号工艺设计,模拟结果表明在整个输入共模电压范围内,跨导、摆率和增益的波动分别为1％,2．3％和1．36dB．在此基础上进行了版图设计和流片测试,版图面积为0．072mm^2,实际测试结果与模拟结果基本一致．     

Information gain and divergence-based feature selection for machine learning-based text categorization

Most previous works of feature selection emphasized only the reduction of high dimensionality of the feature space. But in cases where many features are highly redundant with each other, we must utilize other means, for example, more complex dependence models such as Bayesian network classifiers. In this paper, we introduce a new information gain and divergence-based feature selection method for statistical machine learning-based text categorization without relying on more complex dependence models. Our feature selection method strives to reduce redundancy between features while maintaining information gain in selecting appropriate features for text categorization. Empirical results are given on a number of dataset, showing that our feature selection method is more effective than Koller and Sahami’s method [Koller, D., & Sahami, M. (1996). Toward optimal feature selection. In Proceedings of ICML-96, 13th international conference on machine learning], which is one of greedy feature selection methods, and conventional information gain which is commonly used in feature selection for text categorization. Moreover, our feature selection method sometimes produces more improvements of conventional machine learning algorithms over support vector machines which are known to give the best classification accuracy.     

院校研究与中国高等学校的发展

起源于美国的院校研究经历了萌芽阶段、雏形阶段、成型阶段和完善普及化阶段。院校研究因其具有参谋咨询、信息中枢和知识管理的功能而受到各国的重视。在目前我国高等教育走向普及化、国际化的进程中,加强院校研究对我国各高等学校具有更为现实的意义。借鉴国际院校研究的新方法、新成果,我国必须成立全国性的院校研究机构,制定院校研究的基本原则,建立院校研究的平台,确立院校研究的重点。     

税收目的再探

税乃国家财政收入之源，税收是以国家为主体，以满足国家需要为目的，凭借国家政治权力而实现的分配和再分配，一般认为，税收的重要目的是聚财，也可分为政治目的、经济目的和社会目的。但社会主义市场经济条件下的税收还有其独特的一面，即税收的根本目的应该是促进社会生产力的高速发展，不断提高国民的物质和化生活水平。     

无线扩频技术及应用

随着科学技术的进步，各类无线数据通信设备的不断推出，无线数据通信事业的发展取得长足进展，同时无线电频率资源却日益紧张，通信干扰现象也较为严重，造成传输速率低下、可靠性降低；迫切需要一种新的技术手段加以解决；通过介绍扩频通信的基本原理、技术特点、实现方案、和在现代高速数据通信中的广泛应用，揭示了扩频技术在解决常规数据通信传输速率低下和频谱利用不合理等方面，起到的主要作用，阐述了扩频技术的广泛应用在无线电频谱资源管理工作中的重大意义和通信技术的优良性能和广阔的发展前景。     

A comparison of feature selection methods for an evolving RSS feed corpus

Previous researchers have attempted to detect significant topics in news stories and blogs through the use of word frequency-based methods applied to RSS feeds. In this paper, the three statistical feature selection methods: χ², Mutual Information (MI) and Information Gain (I) are proposed as alternative approaches for ranking term significance in an evolving RSS feed corpus. The extent to which the three methods agree with each other on determining the degree of the significance of a term on a certain date is investigated as well as the assumption that larger values tend to indicate more significant terms. An experimental evaluation was carried out with 39 different levels of data reduction to evaluate the three methods for differing degrees of significance. The three methods showed a significant degree of disagreement for a number of terms assigned an extremely large value. Hence, the assumption that the larger a value, the higher the degree of the significance of a term should be treated cautiously. Moreover, MI and I show significant disagreement. This suggests that MI is different in the way it ranks significant terms, as MI does not take the absence of a term into account, although I does. I, however, has a higher degree of term reduction than MI and χ². This can result in loosing some significant terms. In summary, χ² seems to be the best method to determine term significance for RSS feeds, as χ² identifies both types of significant behavior. The χ² method, however, is far from perfect as an extremely high value can be assigned to relatively insignificant terms.     

带选频滤波功能的程控高增益音频放大器

为了对传感器产生的微弱信号同时进行选频滤波和大增益放大,研制了一种带选频滤波功能的程控高增益音频放大器.该系统主要包括控制中心(单片机12LE5A60S2)、放大器模块(VCA810和两级固定放大)和选频滤波模块(LTC1068和FPGA).测试结果表明:该系统的增益在80 dB～120 dB范围内可按1 dB步长调整,选频带通滤波器的中心频率在200Hz～3.1 KHz范围内可按1Hz步进,且通频带宽度不大于100Hz.