用模拟万用表测电容

介绍了用模拟万用表和秒表测量电容的简单方法，对测量结果的误差原因进行了分析，给出了提高测量精度的几点措施。     

逆变器预置开关角误差对输出谐波的影响

针对数字控制技术的特点，分析了在选择性谐波消除法的理论计算结果与实际开关角数字控制结果出现偏差时，对逆变器输出电压谐波含量的影响。并研究了开关角数量对逆变器性能的影响，结果表明：开关角控制误差对逆变器输出谐波有一定影响，但可以在计算时修正；而开关角数量的增加有利于减小电流脉动，提高输出电压质量，但开关频率随之增加。     

Sol-gel preparation of a silica enhanced hydrophobicity and antireflective coating with optical stability in vacuum

A new silica antireflective coating with improved hydrophobicity and optical stability in a vacuum is obtained by a two-step route. Firstly, silica sols are prepared with a sol-gel process, in which tetraethyl orthosilicate is utilized as a precursor. And by introduction of fluorine containing glycol into the sols, the porosity of silica particles and surface polarity of the coatings are decreased. Afterward, coatings are constructed with low surface roughness by modification of PMBA-PMMA. The coatings retain transmission of up to 99.6%, and laser damage threshold of about 50 J/cm^2 at a wavelenth of 532 nm （1-on-1. 10 ns）     

着好底色 精心打磨 巧妙融合——谈一道几何填空题的命制

以一道几何填空题的命制过程为例,阐述从选择基本图形到确定研究主题的命题设想,介绍打磨试题的几点优化策略,提出“着好底色、精心打磨、巧妙融合”的命题主张.     

关于建立高校科研管理创新体系的思考

知识经济对高校科研管理工作提出了更高要求。克服现行科研管理的不足,高校科研管理应做到:顶层设计,实施教育、科技和经济一体化战略;以人为本,大力加强科技管理体制创新;科教互动,科技工作和学科建设、人才培养协调发展;注重原始创新,实施“人才、专利和标准”战略;建立技术转移中心,实现科研成果的快速转化。     

几种保鲜药在柑桔贮藏中的防病效果

选取4类有代表性的防腐保鲜剂对柑桔的两大品种进行了贮藏试验,在常温等相同环境条件下,观察记录各自的褐疤果、腐烂果及发病果并统计相关指标.结果表明:防病效果相对较好的仍是各药(纳他霉素、多菌灵、抑霉唑)与2,4-D联用的处理.对98天贮期的温州蜜柑而言,5号处理(多菌灵加2,4-D)的总病率最低(5.4%),其腐烂率为5.07%;对136天贮期的447而言,9号处理(纳他霉素加2,4-D)效果最好,腐烂率仅为4.76%.生物防腐剂纳他霉素的防腐效果前期很好,它与2,4-D合用的增效作用体现在贮藏后期;植物源中药3与微生物制剂纳他霉素单用的防病效果接近,而且都存在药力持久性问题.     

Mechanism of micro-waviness induced KH2PO4 crystal laser damage and the corresponding vibration source

The low laser induced damage threshold of the KH₂PO₄ crystal seriously restricts the output power of inertial confinement fusion. The micro-waviness on the KH₂PO₄ surface processed by single point diamond turning has a significant influence on the damage threshold. In this paper, the influence of micro-waviness on the damage threshold of the KH₂PO₄ crystal and the chief sources introducing the micro-waviness are analysed based on the combination of the Fourier modal theory and the power spectrum density method. Research results indicate that among the sub-wavinesses with different characteristic spatial frequencies there exists the most dangerous frequency which greatly reduces the damage threshold, although it may not occupy the largest proportion in the original surface. The experimental damage threshold is basically consistent with the theoretical calculation. For the processing parameters used, the leading frequency of micro-waviness which causes the damage threshold to decrease is between 350^-1 μ^-1 and 30^-1 μ^-1, especially between 90^-1 μ^-1 and 200^-1 μ^-1. Based on the classification study of the time frequencies of micro-waviness, we find that the axial vibration of the spindle is the chief source introducing the micro-waviness, nearly all the leading frequencies are related to the practical spindle frequency (about 6.68 Hz, 400 r/min) and a special middle frequency (between 1.029 Hz and 1.143 Hz).     

如何用模拟万用表测量电容容量

对一个原来不带电的电窬进行充电的过程是一个零状态响应的过程,在此过程中电容可以看成是阻值随时间变化的动态电阻,其变化范围是由零增至无穷大的。因此,当用万用表对电容进行测量（充电）时,必须有一个时刻其大小与万用表的内阻相等,而其内阻又与中值电阻相等,可由表盘直接读出,依据有关公式便可很快计算出待测电容大小。     

核心素养下初中数学章前导学课程的开发研究

随着我国教育与国际教育的不断接轨,关于核心素养的讨论热潮也蔓延到了我国.学生核心素养的培养一直是我国政府及教育部门重点关注的问题,在教育领域的多个方面都开始把学生核心素养的培养列入研究范围,其中就囊括了教学方式创新、教材改革及教师专业能力评定等方面.     

高校科研管理信息化建设探讨

科研管理信息化是通过在科研管理中引入先进的管理思想和应用成熟的信息技术,对高校科研管理流程进行全面整合、优化,为科研管理者和科研工作者提供运行、决策管理平台,从而大大地简化了工作程序,提高了管理效率和服务水平,是高校科研管理发展趋势。