改变规则以提升高等院校理工类实验课的授课效果

分析了高等院校理工类实验课多年来无法达到预期目标的原因,提出了改变现有实验课的授课方法,以提高学生对实验课的重视程度,激励学生自主完成实验的全部环节,使学生的实践操作能力、分析问题和解决问题的能力有较大程度地提高;提出的实验课考核新方式,不仅可以较为公正地评判每名学生的实验技能,还可以减轻学生的课业负担,给学生更多的自主学习及实践锻炼的机会。     

基于地形梯度的典型小流域景观类型分布特征分析——以高建堡流域为例

地形在一定程度上对土地利用方向和方式的变化以及土地利用空间格局的形成有着重要影响.以彭阳县高建堡流域为例,按生态恢复措施将流域划分成14种景观类型,利用GIS空间分析功能,借助DEM提取高程和坡度,分析高建堡流域2013年景观类型在不同高程带、坡度带的结构特征及在地形位梯度带上的分布特征,以期为该地区生态恢复及水土保持措施优化提供决策依据.结果表明:景观类型在1 722~1 822 m高程带分布最多;坡向以斜、陡坡居多,急、缓坡次之;荒山自然修复、混交林、沟谷景观分布的优势区间集中于低地形位区间,经果林、水平梯田、建设用地、乔木林及生物围栏等景观分布的优势区间集中于中地形位区间,退耕还林(草)及鱼鳞坑等分布的优势区间集中于中高地形位区间.     

近海大气环境下低矮RC剪力墙抗震性能试验

为了解近海大气环境下低矮RC剪力墙的抗震性能,采用人工气候实验室对6片剪跨比1.0的低矮RC剪力墙试件进行模拟近海大气环境腐蚀试验,进而对其进行拟静力试验,得到不同轴压比和不同锈胀裂缝宽度下腐蚀试件的滞回曲线,绘制出各个试件的骨架曲线,分析轴压比和锈胀裂缝宽度对腐蚀试件强度、刚度、延性、耗能能力等抗震性能指标的影响.结果表明:随轴压比增加,腐蚀试件的承载力和刚度不断提高,而延性和变形恢复能力却降低,表明在近海大气环境下对低矮RC剪力墙进行抗震设计时需要严格控制其轴压比;随锈胀裂缝宽度的增加,试件的开裂荷载和峰值荷载不断降低,刚度、延性和耗能能力均变差,当遭受腐蚀较为严重时,脆性破坏更为显著,说明在近海大气环境下低矮RC剪力墙内部钢筋锈蚀越来越严重,抗震性能越来越差.     

Dynamic cluster member selection method for multi-target tracking in wireless sensor network简

Multi-target tracking（MTT） is a research hotspot of wireless sensor networks at present.A self-organized dynamic cluster task allocation scheme is used to implement collaborative task allocation for MTT in WSN and a special cluster member（CM） node selection method is put forward in the scheme.An energy efficiency model was proposed under consideration of both energy consumption and remaining energy balance in the network.A tracking accuracy model based on area-sum principle was also presented through analyzing the localization accuracy of triangulation.Then,the two models mentioned above were combined to establish dynamic cluster member selection model for MTT where a comprehensive performance index function was designed to guide the CM node selection.This selection was fulfilled using genetic algorithm.Simulation results show that this method keeps both energy efficiency and tracking quality in optimal state,and also indicate the validity of genetic algorithm in implementing CM node selection.     

气溶胶和氡浓度变化对氡子体影响的探讨

为了得到气溶胶变化后对氡子体产生的影响,实验通过气溶胶粒径谱仪SMPS测试氡室内不同浓度气溶胶,分析气溶胶的变化情况,根据AlphaGUARD测氡仪以及AlphaPM子体仪测试变化的氡浓度不同气溶胶下子体变化情况。实验结果表明：在两个NaCl浓度的气溶胶条件下,气溶胶的总量随着气溶胶发生器中的NaCl浓度的增大而变大,由于氡子体结合态随气溶胶浓度改变,氡子体浓度也随气溶胶浓度的增大而增大。并且在相同气溶胶浓度情况下,氡子体的浓度随着氡浓度的增大而增大。     

基于流固耦合的闸板防喷器建模及有限元分析

为了更加准确地分析流体对闸板剪切力的影响规律,需要对闸板防喷器剪切钻杆进行流固耦合分析。以钻杆窜动和扭转2种动态工况为例,利用SolidWorks建立闸板防喷器三维模型,并对防喷器内部流体域进行有限元建模,输出到ANSYS Fluent进行有限元分析。结果表明:在闸板剪切钻杆过程中,流体达到稳态后,在钻杆窜动工况下,流体力随钻杆受载荷力增大而减小; 在钻杆扭转工况下,流体力随钻杆扭转角度而变化,在扭转90°时流体力最大。研究结果可为防喷器剪切闸板的剪切能力分析及结构设计提供参考。     

Effect of characteristic scale on the extrudate swelling behavior of polypropylene melt in a micro-extrusion process

The swelling behavior in micro-extrusion has a significant effect on the dimensional and shape accuracy of microproducts. In this study, the effect of characteristic scale, defined as the gap of die land in an annular micro-extrusion die, on the extrudate swelling behavior of viscoelastic melt is analyzed through numerical simulations and micro-extrusion experiments. The results show that the swelling behavior displays an obvious dependence on the characteristic scale. An increase in the characteristic scale reduces the swell ratio and retards the process to reach the equilibrium state. In contrast, a decrease in the characteristic scale results in a larger magnitude of change in velocity field and faster relaxation development of stress field. The location of the maximum velocity layer for the laminar flow gradually deviates from the geometric center of channel toward the wall of mandrel with the increase in the characteristic scale. Moreover, an increase in the flow rate results in a larger swell ratio for a constant characteristic scale. The elastic effect plays a more dominant role than the viscous effect in determining the viscoelastic swell behavior. It is imperative to consider the complicated swelling behavior and remarkable viscoelastic effect simultaneously in micro-extrusion process.     

含电动汽车充电的配电网运行可靠性评估算法

现有方法难以对不同充电状态下的配电网运行状态进行准确评估,为此设计含电动汽车充电的配电网运行可靠性评估算法.通过计算配电网运行情况与配电网元件使用状态,实现配电网运行可靠性评估指标的选取.同时,设定充电周期,计算电动汽车充电功率,并将此作为评估参考因素之一.采用模拟法构建评估模型,将运行可靠性评估指标与电动汽车充电功率融入此模型中,实现对含电动汽车充电的配电网运行可靠性的评估.算例测试结果表明,在慢充和快充状态下的评估计算响应时间明显低于现有方法,并且评估结果的准确性较高.算法更适用于电动汽车配电网运行状态的评估.     

Moire Patterns of θ''''Precipitates in Al-Cu Alloy

A θ＇precipitate in an Al-Cu alloy was imaged.Its Moire patterns shown by TEM were discussed.     

Dislocation Structures in a BulkPb－doped Bi－SrCa－Cu－O High Temperature Superconductor

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