单片开关电源的原理及应用

TOPSwitch系列三端单片开关电源集成电路是由控制电压源、带隙基准电压源、振荡器、脉宽调制器等部分组成的。其工作原理是利用反馈电流来调节占空比达到稳压目的。在光电反馈式开关电源中由于增加了光电反馈电路 ,使输出电压的精度与调整率均得到明显提高。 TOP1 0 0系列还能构成固定频率、非连续式功率因数校正升压预调节器 ,可用于提高功率因数、降低无功功率、减少谐波及防止输出波形失真等作用。     

A DEA Approach to Understanding the Productivity Growth of Malaysia's Manufacturing Industries

This paper seeks to explain the productivity growth performance of Malaysia's manufacturing sector using a panel data of 28 industries from 1981–1996. Here, the data envelopment analysis technique is used to calculate and decompose the Malmquist index of total factor productivity (TFP) growth into technical change, change in technical efficiency and change in scale efficiency. This allows the identification of the sources of productivity growth which is crucial for policy formulation. It was found that the annual TFP growth of the Malaysian manufacturing sector was low at 0.8% and this was driven by small gains in both technical change and technical efficiency, with industries operating close to optimum scale.     

75kW中频感应加热电源的研制

针对中频感应加热电源对油田油井加热问题,本文采用PWM控制技术实现了功率可调。为使系统的功率因数较高,采用串联谐振和频率跟踪技术。中频感应加热电源采用IGBT作为开关器件,可工作在10 Hz-10 kHz频段。它充分利用中频趋肤效应、邻近效应和圆环效应原理,通过感应加热器和油管柱,使电能有效的转化为热能,从而达到原油降粘降稠、稳产高产的目的。     

影响投标决策的典型因素

基于美国斯坦福大学Boyd C．Paulson．Jr．教授所准备的材料，本介绍了影响招标决策的典型因素，包括：企业的目标和现有能力，工程项目位置，投标时间和地点，如何获得设计图和规范，法定的和其他官方要求，工程特定范围，资源比较的决策。     

天然气压缩因子对流量计量的影响

探讨了速度式和容积式流量计用于天然气计量时,天然气压缩因子对其计量结果的影响;同时也探讨了无压缩因子修正或修正不当而造成的二次仪表计量误差.     

农业产业化经营中的风险要素及其规避

成熟的农业产业化经营在很大的程度上弱化了农业风险。但作为一种尚不成熟的农业产业化经营,潜藏着各种经营风险,包括市场风险、技术风险、违约风险和自然风险。农业产业化经营风险具有客观性、多样性和隐含性,农业产业化经营主体应针对不同风险,采取不同措施,有效化解和规避风险。     

论税收撤销权

税务机关如何正确行使撤销权,有关的法律规定过于简单。因而,需要从理论和实践相结合的角度对税收撤销权的成立要件、税收撤销权的行使及效力、税收撤销权的冲突等问题给予明确,以期对税收实践有所裨益。     

我国基金选股选时能力实证分析

本文运用西方基金绩效评价中较为常见的选股选时能力模型及其FF3改进模型对我国证券投资基金进行实证研究,在处理过程中考虑了不同取样频率和不同样本区间的影响.研究结果表明:(1)我国基金只存在很小程度的选股能力,而基本不存在选时能力,更没有基金同时具有选时能力和选股能力;(2)多因素改进模型与原模型相比显著提高了解释能力,说明在可能的情况下应尽可能使用多因素模型;(3)加快取样频率后基金表现出更强一些的选股能力,但在各年度内基金的选股能力有所差异.     

International Transmission Channels of U.S. Quantitative Easing: Evidence from Canada

The U.S. Federal Reserve responded to the great recession by implementing quantitative easing, or large‐scale asset purchases, when its conventional policy rate reached the zero lower bound. We assess the international spillover effects of this quantitative easing program on the Canadian economy in a factor‐augmented vector autoregression (FAVAR) framework, by considering a counterfactual scenario in which the Federal Reserve's long‐term asset holdings do not rise in response to the recession. We find that U.S. quantitative easing boosted Canadian output, mainly through the financial channel.     

Financial Stress Regimes and the Macroeconomy

Some financial stress events lead to macroeconomic downturns, while others appear to be isolated to financial markets. We identify financial stress regimes using a model that explicitly links financial variables to macro‐economic outcomes. The stress regimes are identified using an unbalanced panel of financial variables with an embedded method for variable selection. Our identified stress regimes are associated with corporate credit tightening and with NBER recessions. An exogenous deterioration in our financial conditions index has strong negative effects in economic activity, and negative amplification effects on inflation in the stress regime. These results are obtained with a novel factor‐augmented vector autoregressive model with smooth‐transition regimes (FASTVAR).