基于改进蚁群算法的变压器诊断数据的约简

针对变压器故障诊断提出的各种算法,多数不能从激增的诊断数据中提取有效的信息,无法实现快速准确诊断.为提高变压器故障诊断的速度,基于蚁群算法基本原理和模糊信息熵理论,对蚁群算法从局部搜索策略、蚂蚁内部状态、信息素更新策略及状态转移规则四方面进行了改进,提出诊断数据约简新方法.经过变压器故障诊断实例验证,使用改进方法将数据约简后,具有较高的诊断正确率,而与传统的算法相比,诊断速度快.     

基于参数自适应调整的光伏阵列最大功率控制

针对最大功率的控制问题,采用自适应调整控制方法中的参数寻优来实现功率跟踪控制,目的是解决自适应因子的选取问题.基于晶体物理模型的等效电路,建立光伏阵列仿真模型,考虑光照和温度对光伏发电的影响,采用干扰观察法和PWM技术控制DC-DC电路实现最大功率输出.此外,分析了基于模糊控制方式和基于自适应调整方式的光伏阵列功率输出的优劣点,采用定步长和不定步长两种控制方式,实施光伏功率动态响应仿真.仿真结果表明,基于自适应调整方式的参数作为不定步长,不仅能快速有效地跟踪最大功率输出,相对于采用定步长方式,还能有效减免系统的波动性.     

两步碱催化法制备尿素和三聚氰胺改性PF胶粘剂

采用两步碱催化法探讨了尿素(U)、三聚氰胺(M)和无机黏土等对酚醛树脂(PF)胶粘剂性能的影响.结果表明:适宜的n(甲醛):n(苯酚)比例是3.00:1或2.00:1;尿素改性可降低PF胶粘剂的生产成本,但其粘接强度减弱;三聚氰胺改性可提高PF胶粘剂的粘接强度,但其成本较高;无机黏土的加入可改善PMUF(苯酚-三聚氰胺...     

双水相分离纯化荷叶中黄酮类化合物

采用PEG/硫酸铵双水相体系分离纯化荷叶黄酮。实验结果表明：在PEG 4000的质量分率为25%,（NH4）2SO4的质量分率为10%,加入粗提液3 mL,在常温下,荷叶黄酮的萃取率可达97%以上。     

影响橡胶增韧塑料的主要因素

综述了影响橡胶增韧塑料的主要因素,着重探讨了粒子间距对橡胶增韧塑料的影响,最后总结了橡胶增韧塑料的研究重点。     

基于SPA-PLSR的回收油鉴别研究

近年来回收油(地沟油)事件频繁出现,为寻找快速、无损、高效的鉴别方法,防止回收油再次流回餐桌.本文采集到10种回收油以及10种正常食用油样品,建立光谱技术结合SPA-PLSR组合模型,选取因变量苯环(270nm)、多环芳烃类(225nm),提取特征吸收波长个数为8,分别为:195,197,209,245,255,270,310和830nm.利用最低PRESS法确定潜变量个数:LV225=4,LV270=3,建立PLSR回归方程Y225,Y270,预测相关度分别为R225=0.994119,R270=0.9886,均方根残差分别为RMSEC225=0.033654,RMSEC270=0.0336.最后利用Fisher有监督模式分类器实现对8种正常食用油和8种回收油的投影,以及对2种回收油和2种正常食用油的有效辨别,准确率为100％.可作为鉴别回收油与正常食用油的一种办法.     

基于FPGA的高速加密卡设计与实现

为增强数据信息的安全性,设计了一种基于FPGA的高性能加密卡。该加密卡通过PCI Express总线与主机通信,由FPGA芯片内置的NiosII软核处理器和PCI-E硬核分别实现控制器模块与通信接口模块功能;采用SM1、RSA算法对数据进行加密或解密。将加密卡的数据通信和算法控制等功能集成在单片FPGA芯片上实现,优化了电路结构、提高了加密卡的稳定性和可靠性。实际测试结果表明,所设计的加密卡功能正确,运算速度快,达到了预期的目标,具有良好的应用前景。     

钢包旋转塔回转轴承连接螺栓预紧力计算

钢包旋转塔是连铸机的关键设备,而回转轴承是钢包旋转塔的重要部件,回转轴承的连接螺栓的紧固情况直接关系到轴承的使用寿命.对螺栓的预紧力进行了计算,并采用有限单元法对螺栓的变形进行了分析.实践证明,计算的预紧力能够保证轴承正常运转和较长的使用寿命.     

Effect of properties of zirconia powder on performance of planar oxygen sensor chip北大核心CSCD

Three kinds of powders were used in the experiment. Chemical composition, phase composition, particle morphology, surface area, and sintering properties, Suitability for cast taping, performance of prepared planar oxygen sensor chip were studied comprehensively. The results showed that POWDER A was suitable for tape casting, but the sintering temperature (1500 ℃) is highest among those three powder, and there exist a lot of small-sized pores in sintered ceramics. The reason for this phenomenon is the presence of two-phase composition in POWDER A. But this powder can be prepared to planar oxygen sensor which has good response for oxygen. The substrate prepared by tape casting using POWDER C is very soft, which resulting in the follow-up process is difficult, and there is no measured signal for the preparaed planar oxygen sensor chip samples. Substrate prepared by POWDER B is brittle, and the impurity content also is high, sample signal is not detected for the prepared sensor chip. The requirement of planar oxygen sensor by tape-casting for YSZ powder is: Si and Fe content should be as low as possible; particles have a small particle diameter, monodisperse size distribution; specific surface area should be controlled at 12 m2/g~15 m2/g. ©, 2014, The Editorial Office of Chinese Journal of Sensors and Actuators. All right reserved.     

Enhancement of weld line mechanical strength using a novel ejector‐pins compression system

This study proposes a novel ejector‐pins compression system (EPCS) to improve the mechanical strength of weld lines that are formed in the injection molding process. Weld lines are significant defects that affect injection molding quality, causing the poor appearance and low mechanical strength of injection‐molded parts. In this experiment, several ejector pins are placed intentionally near the weld lines appearing, and are initially sunken beneath the cavity surface to form a reflow trap such that some of the molten plastics are allowed to flow into it during the filling process. These molten plastics are then compressed by the arisen ejector pins. Accordingly, the compressed molten plastics reflow through the weld lines, disordering the molecular orientation. Experimental verification revealed that the use of an EPCS can efficiently eliminate the orientation of the molecules parallel to the weld line. The specimens' impact strength of using EPCS can increase to between one and two times than that of conventionally injection‐molded. Therefore, this simple and novel method is feasible for greatly improving the mechanical strength of weld lines. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013