基于自收缩效应液态金属限流器中电弧行为特性的实验研究

研究基于自收缩效应液态金属限流器(LMCL)中的电弧行为特性。设计了具有LMCL基本结构特征的实验模型。利用高速摄影技术获得的起弧和燃弧过程的影像以及通过数字示波器记录的电弧电压和电流波形,揭示了液态金属中电弧起弧机理,分析了电流对弧前自收缩过程的影响,研究了在单孔条件下电弧形态随电弧电压的演变规律。同时在实验过程中发现了电弧对电极的侵蚀现象,并通过分析其成因提出一种能够有效避免侵蚀的电极结构改进方法。该研究对进一步提高LMCL限流性能具指导意义。     

低压开关电器稳态电弧特性的仿真

研究了低压开关电器稳态电弧特性仿真。在磁流体动力学基础上,针对低压断路器简化灭弧室建立了稳态空气电弧等离子体模型,并引入了P1辐射模型进行仿真分析,分析了低压稳态空气电弧等离子体内各项参数的分布。该成果为电弧等离子体动态特性研究提供了帮助。     

电动力作用下万能式断路器操作机构运动特性仿真及试验

分析了短路分闸时电弧的运动过程,根据不同触头开距建立了多种类型的电弧模型。基于有限元方法计算了不同模型下动触头受到的电动力,将计算的最小和最大电动力数据导入ADAMS空载仿真模型,从而建立了DW45型万能式断路器(ACB)短路条件下的运动特性仿真模型。仿真结果得到了ACB在电动力作用下的最慢、最快分闸过程。试验测量验证了实际分闸过程处于仿真范围内,证明了模型的有效性。     

石英砂熔断器弧前时间数值仿真

分析了熔体熔断过程的电流场和温度场的变化,并根据能量守恒定律将电流场和温度场方程联立起来,建立了描述熔体熔断过程的热电耦合数学模型。采用有限元分析软件Ansys对该模型进行分析求解,为熔断器的选择以及熔断器在使用过程中带来的热效应和过电压问题的解决提供依据。     

永磁机构的微机控制系统

利用ＣＰＵ技术,对配有永磁操动机构的真空断路器控制回路进行了研制,通过信号采集和处理,实现了电器的智能控制,并与上位ＰＣ机通讯传递数据,生成报表。     

Simulation and Experimental Study of Arc Column Expansion After Ignition in Low-Voltage Circuit Breakers

The dynamic process of arc pressure and corresponding arc column expansion, which is the main feature after arc ignition and has a significant effect on the breaking behaviour of low -voltage circuit breakers, is studied. By constructing a three dimensional mathematical model of air arc plasma and adopting the Control Volume Method, the parameters of arc plasma including temperature and pressure are obtained. The variations of pressure field and temperature field with time are simulated. The result indicates that there are six stages for the process of arc column expansion according to the variation of pressure in arc chamber. In the first stage, the maximal pressure locates in the region close to cathode, and in the second stage the maximal pressure shifts to the region close to the anode. In the third stage, the pressure difference between the middle of arc column and the ambient gas is very large, so the arc column begins to expand apparently. In the fourth stage, the pressure wave propagates towards both ends and the maximal pressure appears at the two ends when the pressure wave reaches both sidewalls. In the fifth stage, the pressure wave is reflected and collides in the middle of the arc chamber. In the last stage, the propagation and reflection of pressure wave will repeat several times until a steady burning state is reached. In addition, the experimental results of arc column expansion, corresponding to the arc pressure variation, are presented to verify the simulation results.     

Influence of Copper Vapor on Low-Voltage Circuit Breaker Arcs During Stationary and Moving States

The influence of copper vapor on the low-voltage circuit breaker arcs is studied. A three-dimensional （3-D） magnetohydrodynamics（MHD） model of arc motion under the effect of external magnetic field is built up. By adopting the commercial computational fluid dynamics （CFD） package FLUENT based on control-volume method, the above MHD model is solved. For the mediums of air-1% Cu and air-10% Cu, the distributions of stationary temperature, pressure, electrical potential and the arc motion processes are compared with those of a pure air arc. The copper vapor diffusion process in the arc chamber and the distribution of copper vapor mass concentration are also simulated. The results shows that the copper vapor has a cooling effect on the arc plasma and can decrease the stationary voltage as well. Moreover, the presence of copper vapor can decelerate the arc motion in the quenching chambers. The maximal copper vapor concentration locates behind the arc root because of the existence of a ＂double vortex＂ near the electrodes.     

新的流形学习方法统一框架及改进的拉普拉斯特征映射方法

流形学习是多个领域的重要研究课题.通过考察各种流形学习方法,提出了一种新的流形学习方法的统一框架,并在此框架下对拉普拉斯特征映射方法(Laplacian eigenmap,LE)进行了分析.进一步,基于此框架,提出了一种改进拉普拉斯特征映射方法(improved Laplacian eigenmap,ILE).它建立在LE方法和最大差异延展算法(maximum variance unfolding,MVU)的基础上,在保持流形谱图拉普拉斯特征的同时,以最大化任意两点之间的差异为目标.ILE有效地解决了拉普拉斯特征映射方法对邻域选择敏感以及MVU方法大计算量、局部限制过强等问题.且能够保持数据聚类性质,挖掘数据内蕴特征.通过实验说明了ILE的有效性.     

基于最优一维分解的图像超分辨方法

提出了一种用分离变量的一维函数乘积形式逼近二维图像数据的方法，通过在一维空间的超分辨处理，很容易实现对图像的超分辨处理。从理论上证明了这种表达是最优的。实际结果显示了超分辨的效果好，计算量小。这种方法也可应用于图像处理的其他领域和海量数据信息特征提取。     

关于工程量清单计价模式下的施工合同管理研究与探析

国家推行工程量清单计价后,对于施工合同管理带来了新的挑战和机遇。本文从工程量清单计价模式下合同管理的优点入手,对工程量清单计价模式下的计价方式、工程量的调整、工程变更、材料价格风险、工程索赔的处理、工程结算等进行了探讨,并针对施工合同管理改进,提出几点有效的措施。