零电压准谐振开关电源的设计

介绍了准谐振开关电源的组成、零电压准谐振变换器的工作原理、移相全桥两桥臂开关管实现ZVS的条件、移相全桥PWM控制和驱动的原理,研究了移相全桥ZVS变换器的控制和输出特性.利用UC3875控制器研制了3kW、6kW移相全桥零电压高频通信开关电源.     

基于DSP数字控制的零电压全桥三电平DC-DC变换器实验装置研制

设计并开发了一种基于DSP控制的零电压全桥三电平DC-DC变换器。该实验装置是对电力电子技术中多电平和软开关技术的学习和实践,是在全桥结构DC-DC变换器的基础上进行改进,加入了三电平技术和ZVS技术。以DSP为控制器,通过采用移相斩波的控制方法,实现各只MOS管零电压开关。该实验装置具有技术先进、安全可靠、操作简便等优点,尤其适合在实验教学中应用,让学生动手实践,测量观察三电平和软开关技术的相应实验波形。重点分析了变换器的工作原理以及系统的设计方案。     

零电压开前谐振变换器设计

针对传统型PWM控制开关电源是硬开关 ,开关损耗大 ,不易提高开关频率 ,不利开关电源向小型化、轻量化发展等问题 ,提出利用零电压开关谐振技术实现功率开关管的软开关技术设计 ,从而降低开关损耗。以SG35 2 5为核心设计控制电路 ,提高系统的动态响应性能     

一种基于全桥移相ZVS-PWM直流变换器的设计

提出了一种能在全负载范围内实现零电压开关的改进型全桥移相ZVS—PWMDC／DC变换器．该电路简单高效,超前臂、滞后臂都能在很宽的范围实现软开关．介绍和分析了变换器的工作原理,最后给出了实验结果和两个主要波形,并做出了详细的说明．     

软开关PWM boost全桥变换器

本文系统提出boost全桥变换器的一族共 9种PWM控制方式 .根据一对斜对角开关管开通情况的不同 ,将这 9种PWM控制方式分成 2类切换方式 .为了实现软开关 ,引入超前管和滞后管的概念 .在此基础上 ,将软开关PWMboost全桥变换器分成ZCS和ZCZVS两类 .计算机仿真结果证实了所做的分析 .     

结实型谐振支路及其在软开关变换器中的应用

本文给出了结实型谐振支路实现软开关的工作原理和运行特性 ,详细讨论了结实型谐振支路拓扑在软开关直直变换器和软开关逆变器中的各种应用 .结实型谐振支路可构成升降压软开关直直变换器、具有输出功率自动限制特性的隔离型软开关直直变换器 ,可实现部分串联谐振直直变换器功率管的零电压、零电流开关 ,可用于移相控制全桥直直变换器实现滞后桥臂功率管的软开关 ,可构成结实型谐振极逆变器和结实型谐振直流环节逆变器 .本文对各变换器的工作原理、特性、实现软开关的条件进行了讨论 ,给出了实验和仿真波形 .     

零时间企业作业层面零时间点研究

零时间企业是按照零时间理念运作的企业，是21世纪企业的发展方向。基于时间的竞争要求零时间企业选择适当的零时间点。然而，零时间点作为零时间概念框架中的一个基础概念，目前尚未得到系统研究。章试图进行零时间点的理论分析．并着重从作业层面界定零时间企业的零时间点，弥补零时间概念框架中的缺憾。     

高频软开关通讯电源电路的设计

介绍了一种新型双正激高频软开关通讯电源,该电源电路的拓扑结构利用主功率变压器漏感和串接的电容、电感作为谐振元件来完成谐振过程,从而实现功率管的零电压或零电流开关转换,大大降低了功率器件的开关损耗。分析了电路工作原理,建立了各个工作模式的数学模型,设计了电路主要参数。实验表明该系统能安全、可靠运行,达到了高频、高效率和高功率密度等各项设计指标的要求,电路最大输出功率500 W,输出电压24 V,开关频率50 kHz,额定输出时效率达到93%。     

RLC并联二阶网络的零输入响应和零状态响应实验

用RLC并联二阶网络进行零输入响应和零状态响应实验,在理论上进行推导,论证,对电路元件的具体参数进行计算,并借助示波器得到与计算结果相一致的数据。     

强诣零Armendariz环

结合环尺称为强诣零Armendariz的如果对于R[x]中任意两个多项式f(x),g(x)当f(x)g(x)∈Nil*+(R)[x]时,有ab∈Nil*(尺),这里a,b分别是f(x),g(x)的任何系数,而N*(R)为R的素根.证明了强诣零Armendariz环R的素根与上诣零根一致;强诣零Armendariz环足诣零Amlendariz环;证明了R是强诣零Amaendariz环当且仪当R的每个子环是强诣零Armendariz环,当且仪当R的多项式环R[x]是强诣零Armendariz环,当且仪当R的上三角矩阵环Tn(R)是强诣零Armendariz环;R是强诣零Armendariz环当且仪当R/Nil*(R)是Armendariz环.并推广了弱Armendariz环的两个结果.     

热力学基本方程的适用条件

根据是否有与之相对应的状态参量,将功分为两种类型：第一种类型有相应的状态参量,如弹簧或橡皮筋的变形功、表面功、电介质的极化功、磁介质的磁化功;第二种类型没有对应的状态参量,如搅拌功、电功。通过对热力学基本关系式的适用条件的详细讨论,总结得到：无论过程是否可逆,也不管过程中是否有第二种类型的功,热力学基本关系式均适用。     

Assessing the assessments: Taking stock of learning outcomes data in India

Data on learning outcomes is essential for tracking progress in achieving education goals, understanding what education policies work (and don’t work), and holding public officials accountable. We assess the accuracy and reliability of India’s two nationally representative surveys on learning outcomes, ASER and NAS, so that users of these datasets may better understand when, and for what purposes, these two datasets can reasonably be used. After restricting our sample to maximize comparability between the two datasets, we find that NAS state averages are significantly higher than ASER state averages and averages from an independently conducted and nationally representative survey (IHDS). In addition, state rankings based on NAS data display almost no correlation with state rankings based on ASER, IHDS, or net state domestic product per capita. We conclude that NAS state averages are likely artificially high and contain little information about states’ relative performance. The presence of severe bias in the NAS data suggests that this data should be used carefully or not at all for comparisons between states, constructing learning profiles, or any other purpose. We then analyze the internal reliability of ASER data using variance decomposition methods. We find that while ASER data is mostly reliable for comparing state averages, it is less reliable for looking at district averages, or changes in district and state averages over time. We conclude that analysts may use ASER data with confidence for comparisons between states in a single year, constructing learning profiles, and assessing learning inequality but should exercise caution when comparing changes in state scores and avoid using ASER district-level data.     

Teacher professionalism in educational reform: the experiences of Hong Kong and Shanghai

Beginning in the 1990s, the education departments of Hong Kong and Shanghai began to actively initiate reform with a focus on the quality of education. In reviewing the implementation of educational reform in these two societies, we found that Hong Kong teachers tended to only adopt those policies which they felt were beneficial for students' learning, whereas Shanghai teachers tended to conform more to the state's requirements. Teachers in Hong Kong strongly expressed their frustration over the intensification of their work, while teachers in Shanghai seldom expressed disagreement over the state initiatives. Concerning the meaning of teacher professionalism, teachers in Hong Kong were more able than their counterparts in Shanghai to develop their own interpretations. However, at the same time, teachers' work in Hong Kong was still being monitored by the emerging schooling market, while the work of Shanghai teachers was monitored by the state. Teachers' work in both societies can be interpreted as ‘confined professionalism’. In addition, in both of the two societies teachers' awareness of their professionalism was comparatively weak. Further empowerment in this area is needed.     

中国现代化进程中的国家与社会走向

国家与社会是两种不同的人类组织,但是由于多种因素的影响和作用,长期以来人们的思想和实践中都存在着将两者混同的倾向,结果就形成了国家与社会关系的失衡,主要表现为社会自主性的缺失和国家权威性的不足.当代中国政府的职能改革,通过个人权利与公共权力之间的界分,合理地设定政府职能的行使范围和方式等,从而进一步深化国家与社会之间关系的调整.无论是经济体制的转换还是政治体制的改革,以及政府职能的改革都需要法治的保障.通过市场的中间作用,可以构建适合中国国情的新型国家与社会关系.     

教师生存状态异化现象透视

当前,很多教师的生存状态是倦怠的、被动的和疏离的.倦怠的生存表现为对工作情感耗竭,对学生冷漠迁怒,对自己消极评价;被动的生存表现为在教学过程中、事务工作中和自我发展中的被动;疏离的生存表现为与教学过程的疏离、与学生的疏离和与生活世界的疏离.透视异化的教师生存状态,对于教师回归生存之本真状态具有重要意义.     

创作：在幻梦中寻找自我拯救的力量——蒲松龄《聊斋志异》创作心理分析

《聊斋志异》是蒲松龄在失意痛苦中的“孤愤”之作,其作品除了对科举制度的批判外,还以如下情节反映了蒲松龄消除内心痛苦、维持心理平衡的努力：即反复出现鬼狐花妖所化女性青睐于落魄男性,并大大改变了男性处境。蒲松龄主要选择了女性作为虚幻世界的拯救力量,这与男权社会中女性的存在本质相关。     

“中国梦”与政治认同的关系

实现"中国梦"对提高公民政治认同、使国家政治体系获得合法性并保持长久稳定具有重要意义,而政治认同又制约着"中国梦"的实现效果,两者之间存在着密切关系。实现"中国梦"与提高公民政治认同两者相互作用,因此,在实际工作中必须将两者结合起来,从国家、社会和个人层面把提高政治认同贯穿于实现"中国梦"的全过程,为中国的进一步发展并成为人民所期待的国家提供更广阔的空间。     

高校学报编辑的工作应激及应对策略

影响我国高校学报编辑心理状态的主要因素来自于工作应激源。个体在高应激状态下如果缺乏良好的应对方式,心理受损的危险程度是普通人群的两倍,而成熟的应对方式有助于工作者积极理性地面对工作应激。根据CPT理论,抵抗工作应激的措施,一方面可采取降低对应激源危险性的评估,另一方面应重视应对方法的了解及应用。全面提升高校学报编辑的心理素质,需要学报出版单位和编辑个人采取多种措施,掌握更多专业的、科学的工作应激应对资源。     

Meeting the Challenge of Diversity through Cooperative Learning

During the last two decades the use of group work in British primary classrooms has been a ‘neglected art’. This paper begins by considering the reasons for this ‘state of affairs’ and concludes that teachers often give up too early because of lack of initial success. The advantages of group work over other forms of classroom organisation are then considered, particularly in classes where there is a wide range of ability. Drawing from research findings obtained in the United Kingdom and the United States, the paper concludes with practical advice on how this grouping strategy can be used to develop higher level thinking skills. Three key factors are required. First, pupils must be taught necessary social skills. Second, a suitable ‘scaffold’ for thinking must be provided. Third, a mutually supportive classroom ethos must be created.     

《学生体质健康标准》测试工作的研究分析

为了贯彻落实“健康第一”的指导思想,教育部、国家体育总局联合颁布了《学生体质健康标准(试行方案)》(以下简称《标准》),根据新疆维吾尔自治区实施《标准》,结合本校实际情况先后对在校学生进行了两次学生体质健康测试,通过对测试结果分析和《标准》实施工作的总结,探讨实施学生体质健康测试工作的有关问题。