大截面架空导线输电技术的研究与分析

随着我国电力需求的增长,输电容量日益增大,大截面架空导线输电技术的应用将日益广泛。本文分析了大截面架空导线输电技术的优势及其不利因素;探讨了采用大截面架空导线输电技术后对系统的影响;并指出大截面架空导线输电技术的适宜范围及注意问题。     

500kV温南变电所接地网安全性问题的探讨

文章从接地阻抗、地电位升、接触电压和跨步电压的角度综合分析探讨了地处高土壤电阻率地区的500kV温南变电所接地网安全性问题,并提出了相应的安全防范措施,如通往变电所外的金属管加绝缘段隔离、通信电缆全部采用光缆、验算接触电压和跨步电压、降低电缆的感应电压以及避雷针采用集中接地等,最终使地网接地阻抗可放宽到0·5Ω仍能确保变电所安全运行和人身安全。     

对公务员招聘问题的思考

本文利用层次分析法和0-1型整数规划建立了一个公务员招聘的数学模型,并结合实际提出了通用可行的算法。首先利用层次分析法确定了招聘人员面试成绩对用人部门的权重,再把笔试成绩转化为相应的权重,然后将笔试成绩和面试成绩对用人部门的权重结合起来,建立了权重计算模型。再把应聘人员的志愿转化为用人单位对应聘人员的权重,建立了双向选择的权重计算模型。然后确定最优方案模型,被选人员对用人单位的权重之和最大时的人员选取即为所求,从而建立了应聘人员最优选取的0-1整数规划模型,制定出最优的分配方案,并对一般情况即N个应聘人员M个用人单位时,对模型做了推广。最后利用Matlab和Lingo编程对上述模型和算法进行了实践求解。针对实际本文还充分考虑了多种情况下各种因素对人员招聘的影响,较完满地解决了公务员招聘问题,并检验了模型的合理性,文章分析了模型的优缺点和改进方向,同时提出了一些实用性建议。     

金属喷射成型过程大量液滴的统计模型研究

通过概率模拟的方法,建立了金属喷射成型过程中大量金属液滴的统计模型.应用该模型对喷射成型过程中钢液的喷射过程进行了研究,给出了在喷射过程中不同尺寸液滴的分布,以及不同液滴产生的位置、初速度分布.通过大量液滴的统计,确定出整个喷射过程液滴的产生、运动情况,为进一步研究液滴在沉积面上的沉积情况提供前提和依据.     

CCD离散性对面积测量的影响

分析了电荷耦合器件(CCD)在空间和彩色(或灰度)的离散特性对面积测量的影响。通过统计特定区域的边界点和分析图像分割的效果,提出了一种评价CCD相关误差的方法。举例说明了图像分割方法对面积测量的影响很大,为此,讨论了正确使用CCD和提高面积测量精度的相应措施。     

Luminaries-level structure improvement of LEDs for heat dissipation enhancement under natural convection

Heat dissipation enhancement of LED luminaries is of great significance to the large-scale application of LED. Luminaries-level structure improvement by the method of boring through-hole is adopted to intensify heat dissipation. Furthermore, the natural convection heat transfer process of LED luminaries is simulated by computational fluid dynamics (CFD) model before and after the structural modification. As shown by computational results, boring through-hole is beneficial to develop bottom-to-top natural convection, eliminate local circumfluence, and finally form better flow pattern. Analysis based on field synergy principle shows that boring through-hole across LED luminaries improves the synergy between flow field and temperature field, and effectively decreases the thermal resistance of luminaries-level heat dissipation structure. Under the same computational conditions, by luminaries-level structure improvement the highest temperature of heat sink is decreased by about 8°C and the average heat transfer coefficient is increased by 45.8%.     

中线平移互交视线测设法在斜交桥梁定位的应用

以福建某高速公路尤溪段源湖中桥为例,阐述了中线平移互交视线测设法在斜交桥梁墩台定位的应用情况,实践证明该方法能很好地解决斜交桥梁墩台定位的问题。     

Study on photocatalysis of TiO 2 nanotubes prepared by methanol-thermal synthesis at low temperature

TiO₂ nanotubes were synthesized by the solvothermal process at low temperature in a highly alkaline water–methanol mixed solution. Their characteristics were identified by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), specific surface area (BET), Fourier transform infrared spectroscopy (FTIR) and UV–Vis absorption spectroscopy. The as-prepared samples were tested by the photodegradation reaction of methylene blue (MB) dye under visible-light irradiation. The ratios of methanol and water, as well as calcination temperature, affected the morphology, nanostructure and photocatalytic performance. The methanol solvent plays an important role in improving crystallization of the anatase phase, which affects the photocatalytic reaction. Titanate nanotubes were synthesized in methanol–water volume ratios of 10:90, 20:80 and 30:70 which still had high absorbability. Titania nanotubes formed at a calcination temperature of 300 °C using methanol–water volume ratio of 30:70 showed highest photocatalytic performance, much higher than that using water solvent and TiO₂–P25 powder.     

中压区域补偿型动态电压调节器设计

对适用于10kV配电网区域电压跌落治理的动态电压恢复器进行了设计,给出了基于级联H桥的主电路、取电装置、无变压器耦合电路的设计方法,并针对中性点不接地配网系统中电压跌落的特点,提出了一种仅需补偿电压跌落相电压即可恢复负载侧线电压的参考值计算方法。最后,基于PSCAD搭建了仿真模型,分析了不同故障类型下动态电压调节器(DVR)的补偿效果以及取电装置对系统的影响,通过实验验证了DVR硬件设计与参考电压计算方法的正确性和有效性。