基于填谷电路的恒流式LED高压驱动电源的设计

设计一种基于填谷电路的无源功率因数校正器,详细分析了填谷电路的基本原理,阐述了LED高压驱动电源主电路及过电压／欠电压保护电路的设计原理。该恒流式LED高压驱动电源可将功率因数从0．55提高到0．92～0．965,所对应的总谐波失真（THD）从151％降至42．5％～27．2％,适用于节能环保型LED照明灯具。     

Retention models of capacity factor with different compositions of organic modifier in RP-HPLC

A Chromatographic retention behavior of five deoxyribonucleosides (dCyd, dUrd, dGuo, dThd, and dAdo) with respect to the mobile phase composition was studied under isocratic conditions of reversed phase High Performance Liquid Chromatography (RP-HPLC). The volume fraction (F) of organic modifier was changed from 0.05 to 0.30, and to 0.12 for methanol and acetonitrile, respectively. The experimental data of nitro and steroid compound were also considered for comparison of five retention models with various class of samples. The Langmuir-type retention model (k′= A+B/F) with two parameters shows excellect agreements between the experimental capacity factors and calculated values although the values by the log-scale quadratic model with three parameters (log k′= LF₂+MF+N) are closer. Unlike the other four retention models, the slope B of the Langmuir-type retention model can characterize the properties of solute and organic modifier simultaneously. For each solute, the intercepts A calculated for acetonitrile and methanol as organic modifiers are coincident closely.     

化学法和机械法从大肠杆菌释放人肿瘤坏死因子

对化学法和机械法破碎基因工程大肠杆菌以释放人肿瘤坏死因子的影响因素作了考察。在化学法破菌中研究了破碎时间、试剂浓度、溶剂ｐＨ值、加入表面活性剂等因素的影响。在机械法破碎中研究了停留时间、装珠量、搅拌转速、细胞浓度等的影响，对操作条件进行了优化。通过对二者的比较，发现机械法破碎细胞效率高，但产生细小的碎片不利后分离；化学法释放产物有选择性，但操作时间长。     

浅谈病险水库出险加固工程建设期的环保措施方案

环保措施方案是病险水库出险加固工程建设期的一项重要工作内容,面对日趋严峻的环境问题,有必要把环保措施放在更加突出的位置。本文分析了建设期施工现场环境影响的主要因子,并提出了具体的环保措施方案。     

基于因子分析的内蒙古各盟市文化产业发展的综合评价

文化产业是市场经济条件下繁荣发展社会主义文化的重要载体,也是推动产业结构调整、转变经济发展方式的重要着力点。选取8个反映文化产业发展的有代表性的指标．采用因子分析法．从文化建设投入因子和贡献因子两个方面对内蒙古12个盟市的文化产业进行对比分析,得出各盟市综合评价结果,进而有针对性地提出加快发展文化产业的相应对策。     

Typology of teacher perception toward distance education issues – A study of college information department teachers in Taiwan

The popularity of distance education has grown rapidly over the last decade in Taiwan’s higher education, yet many fundamental teaching–learning issues are still in debate. While teacher–student interaction is a key success factor in distance education, little work has been done on the teachers. The intent of this research was to clarify teacher’s perceptions on key distance education issues and to develop a discernible typology of different groups of teachers based on their perceptions. Because there may be a gulf between teachers and the technology used in distance education, the target of this study was teachers in information related departments in Taiwan’s colleges, who were more familiar with current technology. Factor analysis and cluster analysis were used to derive the typology. Five higher-level issue constructs emerged from the factor analysis: learning effect, customization, administrative challenges, geographic and resource integration, and instructional design challenges. Four groups of teachers, namely the skeptics, the optimists, the mild-promising group, and the outlier, were identified using cluster analysis of teachers’ perceptions on these five higher-level issue constructs. The profiles of the four groups of teachers were summarized and implications were discussed, which should provide useful insights to the policy makers of higher education on distance education decisions.     

面向污水处理过程因子分析故障诊断方法的研究

污水生化处理过程是一个典型的多变量、非线性、具有强外部干扰的复杂工业过程,基于主元分析(PCA)的方法在污水处理过程的故障诊断中已经得到了广泛的应用和发展.但是,主元分析存在着噪声和不确定信息描述能力不足的问题.针对污水过程的特点提出了因子分析(FA)故障诊断方法,同时拓展了因子分析监控指标以及解决了故障辨识贡献图的控制问题,为污水处理过程的有效监控提供了可行性.所提出方法在国际水协会BSM1模型上得到了有效的验证,与PCA的对比研究表明FA提供了更低的故障误报警率和更完整的不确定信息描述能力.     

航空发动机加工现场生产制造网络化协同系统

为解决航空发动机加工现场存在的物料管理手段缺乏、物料无法拉动、生产要素采集少、可视化手段少等问题,本文实现了一套面向航空发动机生产制造过程的网络化协同环境,对生产过程关键要素数据的采集、追踪、分析和处理,通过物料拉动配送系统、生产要素采集系统、可视化看板系统,实现物料线边拉动优化、数据展示端业务报表优化、生产关键要素信息采集、制造端数据集成等内容。     

Pricing Loss Leaders Can be Hard

Consider the problem of pricing n items under an unlimited supply with m single minded buyers,each of which is interested in at most k of the items.The goal is to price each item with profit margin p1,p2,...,pn so as to maximize the overall profit.There is an O(k)-approximation algorithm by Balcan and Blum when the price on each item must be above its margin cost;i.e.,each pi > 0.We investigate the above problem when the seller is allowed to price some of the items below their margin cost.It was shown by Balcan et al.that by pricing some of the items below cost,the seller could possibly increase the maximum profit by Ω(log n) times.These items sold at low prices to stimulate other profitable sales are usually called "loss leader".It is unclear what kind of approximation guarantees are achievable when some of the items can be priced below cost.Understanding this question is posed as an open problem by Balcan and Blum.In this paper,we give a strong negative result for the problem of pricing loss leaders .We prove that assuming the Unique Games Conjecture (UGC),there is no constant approximation algorithm for item pricing with prices below cost allowed even when each customer is interested in at most three items.Conceptually,our result indicates that although it is possible to make more money by selling some items below their margin cost,it can be computationally intractable to do so.     

面向微博内容的信息抽取模型研究

社会媒体是人们用来分享意见、见解、观念和经验的平台或工具,目前已经发展成具有重大影响力的新媒体。而微博作为社会媒体的一个重要部分,对信息的传播起到了很大的作用。面向微博内容的信息抽取就是要从充满噪音的、零碎的、非结构化的微博内容的自由文本中提取有价值的结构化的信息,以利于从微博内容中有效地获取信息。提出了一种基于因子图的微博事件抽取方法来准确地抽取微博中所反映的事件。最后通过实验验证了该方法在性能和准确性上都比其他的方法要高。