Soft Switched Synchronous Rectifier with Phase-Shifted Full Bridge Converter and Its Small-Signal Analysis

BY USING THE OUTPUT INDUCTORS AND BODY CAPACITANCES WITHOUT ADDING ANY COMPONENT COMPARED WITH HARD SWITCHING SYNCHRONOUS RECTIFIER,THE TOPOLOGY OF A SOFT SWITCHED SYNCHRONOUS RECTIFIER WITH PHASE-SHIFTED FULL BRIDGE ZERO VOLTAGE SWITCHING DC/DC CONVERTER IS PROPOSED. THE CONVERTER EFFICIENCY IS MAXIMIZED DUE TO SOFT SWITCHING OF THE FULL BRIDGE MOSFETS AND THE SYNCHRONOUS MOS-FETS, AND ALSO THE LOW CONDUCTION LOSS OF SYNCHRONOUS MOSFET. THE OPERATION PRINCIPLES OF THE CIRCUIT ARE ANALYZED IN DETAIL AND THE SMALL-SIGNAL MODEL IS DERIVED, ALSO THE CONVERTER DYNAMIC CHARACTERISTICS ARE ANALYZED. FREQUENCY RESPONSES OF TRANSFER FUNCTIONS UNDER DIFFERENT VALUES OF TRANSFORMER PRIMARY LEAKAGE INDUCTANCE ARE DISCUSSED. THE EXPERIMENTAL RESULTS WERE OBTAINED FROM A 400 V INPUT AND 100 A/12 V OUTPUT DC/DC CONVERTER OPERATING AT 100 KHZ. THE RESULTS SHOW THAT THE CONVERTER EFFICIENCY IS 2% HIGHER IN RATED POWER THAN TRADITIONAL DIODE RECTIFIER.     

江西省中小企业电子商务发展情况调查与研究

本文主要探讨扮演江西省经济发展重要角色的中小企业在面对国际化的趋势及电子商务时代的来临之际，能否把握住电子商务这一千载难逢的历史机遇，促进自身发展，提升江西省整体的经济水平和国际霓争力。     

规模扩张与收缩:国际企业发展新特点探析

20世纪90年代以来的国际企业发展,表现出规模扩张和规模收缩相互交织的特点,即大型企业的快速扩张与中小企业的蓬勃发展同时并存。本文认为,这二者之间存在着内在的一致性,即购并手段的运用可以同时促进大企业和中小企业的发展,而对核心能力的追求则是这一现象的本质根源。     

薄利多销价格策略的条件

薄利多销价格策略的条件包括:商品富有价格弹性、消费者具有与薄利多销相应的消费心理、竞争者之间避免价格大战、企业应达到的基本素质以及把握好薄利多销的最佳时机。     

Peer assessment in a project-based engineering course: comparing between on-campus and online learning environments

As the number of participants in online distance learning courses increases, peer assessment is becoming a popular strategy for evaluating open assignments and for breaking the social isolation surrounding distance education. Yet, the quality and characteristics of peer assessment in massive online courses has received little attention. Hence, this study was set to examine peer feedback quality and grading accuracy in a project-based course. The study applied a sequential exploratory mixed methods design. It included 339 participants who studied the same engineering course, but in three different modes: on-campus (n = 77), small private online course (n = 110), and massive open online course (MOOC) (n = 152). Content analysis of feedback comments identified four categories: reinforcement, statement, verification and elaboration, arranged in an ascending scale of cognitive ability. The findings indicated that the MOOC participants provided more feedback comments and volunteered to assess more projects than their counterparts did. However, the on-campus students provided higher quality feedback and their peer grading was better correlated with the grades assigned by the teaching assistants.     

小微企业智力资本创新力与区域创新氛围的贡献研究——以江苏省小微企业为例

依据智力资本理论、区域创新理论,研究分解出智力资本的核心创新力与区域创新氛围的逻辑联结。结合江苏小微企业调研数据设计的指数与子指标,衡量了小微企业智力资本创新力对区域创新氛围的贡献关系与价值。分析表明,单个小微企业的智力资本创新力对区域创新影响有限,而小微"群"的智力资本创新力才是区域创新氛围形成的重要支撑,其中知识与技术创新力不可分割,对组织内创新的产生和延续至关重要;而环境创新力则需要依靠小微"群"的组织资本,充分利用区域资源禀赋协同组织外创新支持来共同促成。     

浅谈中小企业品牌形象建设的途径

中小型企业在市场竞争中越来越深刻的认识到品牌形象建设的重要性,但是,对于企业品牌形象应怎样建设还存在很多误区。通过对区域内多家中小型企业的调研、分析及研究,提出中小型企业品牌形象建设的有效途径,为企业做大做强提供参考。     

改革实验教学,走绿色化学之路——以无机化学实验教学为例

在化学实验教学中进行绿色化研究,引进多媒体和现代实验新技术手段,将常量实验改为微型、小量-半微量实验,以求从源头阻止污染,培养学生的环境保护意识和创新意识。     

中小国有企业建筑工程项目委托管理与风险控制

项目委托管理作为一个新兴事物在建筑工程工艺日益复杂的今天为非建筑专业企业的管理提供了良好的方式,特别是对中小企业,更有节约成本、提高管理质量等重要意义。它既可以避免单一的招投标制度对于规模不大的企业所带来的费时、费力等缺点,又可以有效补充中小国有企业项目管理经验不足、相关人才缺乏的困难。分析项目委托管理可能带来的风险,引入竞争性谈判是对于风险有效控制的方法。     

临夏回族村镇经济的历史考察与发展对策

临夏回族村镇经济自明清以来就比较发达，商业经济更具特色，在商贸交往中，对西北和西藏地区的民族经济的发展起了促进作用作用，面对西部大开发，临夏回族村镇经济应结合当地的实际，调整产业结构，发挥优势，带动整个周边地区少数民族经济的发展。