基于DSC控制的移相全桥DC/DC变换器

数字控制由于高集成度带来的低成本、设计沿继性、控制灵活等优点而应用逐渐广泛,电力电子应用逐渐朝着高频化方向发展,这也对高频开关电源的数字控制提出了要求。利用Freescale新型号数字信号控制器(DigitalSingnalController,DSC)MC56F8323的高性能特性,完成了基于DSC的带同步整流的高频软开关移相全桥变换器的数字控制,描述了DSC产生软件移相控制策略,并给出了详细的数字控制系统设计和软件结构设计,最后用一台500W实验样机验证了数字控制所带来的优良的系统性能。     

基于统计参数开展天然岩石节理粗糙度非均匀性和节理尺寸效应关联性研究

岩体结构面粗糙度的准确表征对结构面力学性质的精准描述具有重要意义。为查明天然岩石节理粗糙度评价结果中正负尺寸效应相互矛盾的发现,以浙江省青石镇采石场大尺寸岩体结构面为例,采用三维激光扫描技术,基于4个二维粗糙度统计参数(Z2、S_F、R_p和θ~*_max/(C+1)2D)对大型天然岩石节理面粗糙度进行量化。通过与变异函数方法中的分形参数进行比较,得到高度一致的结果。研究表明：节理表面粗糙度具有明显的非均匀性,且非均匀性对不同节理尺寸下粗糙度参数的计算结果具有重要影响;节理尺寸相关的尺度效应随着粗糙度均匀性的增加而减小。这表明节理尺寸引起的尺度效应一定程度上是源于节理表面粗糙度的非均匀性。     

适用于微机电系统的自适应红外探测器的可调谐滤光器设计与开发

微机电系统与高品质红外探测技术联合运用为国防、商业、通信、生物医学检测及环境监测等许多应用领域面临的一系列具有挑战性的问题提供了唯一可行的解决方案．可调谐法布里．玻罗滤光片是适用于微机电系统的红外探测器的核心部件．滤光片的结构设计和关键结构件的材料对于滤光片的性能和整个装置的完善性有重要影响．阐述了利用有限元建模进行法布里-玻罗滤光片机械设计和分析的方法．报告了滤光片的结构材料——用低温等离子增强化学沉积法制造的氮化硅的结构表征和机械性能测定方法和结果．最后展示了一些所制作的滤光片阵列．     

Prediction of Losses in Flow Through the Last Stage of LP Steam Turbine

The aim of presented work was the prediction of the losses in the wet steam flow through the last stage of 200MW steam turbine LP part.To this end,three numerical tools were used.The first method was the streamline curvature method (SCM) used on the meridional plane with losses correlations.The next two methods,TASCflow commercial CFD code and an in-house CFD code,based on the solution of the Reynolds- averaged Navier-Stokes equations (RANS).Ap- plication of three independent numerical tools al- lowed to make the more reliable losses analysis and made possible to compare applied numerical methods with each other. For the flow modeling in the last stage of LP steam turbine the various two-phase flow models were used and compared.The equilibrium model and non-equi- librium models with homogeneous and/or heterogeneous condensation were considered.The boundary conditions at the inlet and outlet from the stage were selected in such way to get the beginning of the homogeneous condensation process in the sta- tot.It corresponded to the part load of the turbine, i.e.140MW power and pressure in condenser 2.7kPa.     

高职院校“浸润式”党史学习教育模式研究

党史学习教育是在建党100周年之际党中央提出的一项重大决策部署,它是高职院校的政治要求和思政教育的重要内容,可以增强学生的民族自豪感和自信心,帮助他们树立正确的世界观、人生观和价值观。但是,有些高职院校党史学习教育流于形式、方式简单、片面化。针对高职学生基础薄弱、注重专业知识学习等特点,努力探寻出“五层面三主体一平台”的“浸润式”党史学习教育模式,在潜移默化中将党史知识更好地传导给学生。     

太平洋板块的晚始新世古地磁极

海山磁异常反转以及DSDP(深海钻探计划)所获的古地磁和赤道沉积相的资料,都清楚地表明,在晚始新世,太平洋板块存在着一个古地磁极。磁极的位置在77.5°N、21.2°E。这说明在最近的41±5百万午内,太平洋板块的视磁极移动了12.5±1.6°。晚始新世的古磁极与置信度为95％的太平洋马斯特里赫特磁极的位置相差甚远,这表明在距今69百万年到41百万年间,太平洋视磁极移动了7.2°。晚始新世古地磁极的数据采集地散布在北太平洋的广大地区,因此,数据的一致性便支持着这样一种假说:始新世以来,中太平洋北部板块一直是刚性的。晚始新世磁极与根据热点模式预测的太平洋运动的一致性,意味着自那时以来,自转轴与热点间的相对运动已经很小。此外,这一发现还证明,其它作者推得的白垩纪以来所发生的大量热点对自转轴的运动,必定是以更快的速率发生,且是在始新世以前结束的。     

High Temperature Oxidation of FGH96 P/M Superalloy

High temperature oxidation behaviors of FGH96 P/M superalloy have been studied in air at temperatures ranging from 600 to 1000℃. By means of isothermal oxidation testing,X-ray diffraction,SEM(scanning electron microscopy),and EDS(energy dispersive X-ray spectroscopy) analyses,the oxidation kinetics as well as the composition and morphology of scales were investigated. Thermodynamic calculations were used to explain the oxidation mechanism. The results showed that as the oxidation temperature increased,the oxidation rate,the scale thickness,and scale spallation increased. FGH96 P/M superalloy exhibits good oxidation resistance at temperature below 800℃. The oxidation kinetics follows an approximately parabolic rate law,and the oxide layer was mainly composed of Cr2O3,TiO2,and a little amount of NiCr2O4. The oxidation is controlled by the transmission of chromium,titanium,and oxygen through the oxide scale.     

PROPERTIES OF W/Cu FGMS CONTAINING 1%TiC OR 1%La2O3 PREPARED USING GSUHP

W / Cu functionally gradient materials (FGMs) containing 1%La_2O_3 and 1%TiC were prepared using graded sintering under ultra-high pressure (GSUHP). The specimens have been found to exhibit low porosity (11.57% and 11.35%, respectively). Shearing strength of the specimens between layers is good. Moreover, the specimens have still demonstrated good performance in testing thermal-shock resistance. When power density of laser is 200MWm~(-2), the specimens have been tested for thermal-shock resistance (1000 times); the specimens that contained 1%La_2O_3 were not subjected to damage, whereas those that contained 1%TiC began to crack. Finally, effect of additives on thermal-shock resistance was also preliminarily discussed.     

四川盆西平原区裸土扬尘中Pb、Cd化学形态的生物有效性

为探究四川盆西平原区裸土扬尘中Pb、Cd总质量分数与其生物有效性的规律,在构建的"阳离子型污染物土壤表层运移行为研究系统"内进行模拟起尘试验,对土壤样品进行Pb、Cd模拟污染试验,结果表明:试验条件下,四川盆西平原区裸土扬尘颗粒物中Pb、Cd的总质量分数随着粒径的减小而增大,其中Pb的化学形态以碳酸盐结合态为主(44....     

Use of the radiofrequency-intermodulation distortion technique to investigate intrinsic nonlinearity at the electrode-electrolyte interface

We report on investigations of nonlinear radiofrequency responses of electrolytes with Na(+) and Cl(-) ions placed within gold electrodes of a capacitor. The sample was part of a frequency-adjustable inductance-capacitance-resistance (LCR) parallel resonant circuit, and measurements were carried out using the two frequencies intermodulation distortion technique. We employed double layer model to analyze the observed nonlinearities and their dependence on ionic concentration. Electrode-electrolyte interface polarization was found to be a predominant cause of this intrinsic nonlinearity and to be dependent on electrolytic ion concentration. We also measured and calculated coefficients of resistive and capacitive components of the observed nonlinearity.