LED环氧树脂封装材料研究进展

针对封装材料在使用中的缺陷,综述了对环氧树脂的增韧、提高耐热性、改善透明性、改善加工性能的研究现状,并介绍了LED环氧树脂封装材料的发展前景。     

圆环挡板振荡流反应器浓度场的数值模拟

采用有限体积元方法对五腔室圆环挡板振荡流反应器(OFR)的三维浓度场进行了数值模拟研究,考察了腔室中心注入模式下的示踪剂浓度场的分布形态及其在不同振荡条件下的演化情况.研究表明,示踪剂在OFR中运动是由振荡流反应器中主体流动与漩涡构成的二次流动对腔室中心区域的交替控制促成的.定义一个腔室中的浓度方差C作为判断混合效率的依据,结果表明,C值是腔室内混合和腔室间混合共同作用的结果.参数表征的混合效率说明振荡雷诺数越大,混合效率越高.统计分析结果表明,基于长程对流混合和短程湍流扩散双模式传递模式的二项指数衰减曲线方程能够较好地描述踪剂浓度分布方差值随时间的变化.     

Preparation of activated carbons by utilizing solid wastes from palm oil processing mills

Feasibility of producing activated carbons by utilizing solid wastes (extracted flesh fibre and seed shell) from palm oil processing mills was investigated. The effects of activation conditions (CO₂ flow rate, activation temperature and retention time) on the characteristics of the activated carbons, i.e. density, porosity, BET surface area, pore size distribution and surface chemistry were studied. In this study, the optimum conditions for activation were an activation temperature of 800 °C and a retention time of 30 min for fiber or 50 min for shell, which gave the maximum BET surface area. Pore size distribution revealed that the shell-based activated carbons were predominantly microporous whilst fiber activated carbon had predominant mesopores and macropores, suggesting the application of shell and fiber activated carbon as adsorbents for gas-phase and liquid-phase adsorption, respectively. This was confirmed by further gas- and liquid-phase adsorption tests.     

Low-temperature H2S removal from gas streams with SBA-15 supported ZnO nanoparticles

Mesoporous silica SBA-15 with zinc oxide (ZnO) nanoparticles was prepared via incipient wetness impregnation and ultrasonic method, followed by in situ activation at 523 K. The mesoporous materials obtained were characterized by ICP, XRD, FTIR, nitrogen adsorption, TEM and XPS. The prepared materials showed a superior ability to remove H₂S down to parts per billion (ppb) from gas stream at lower temperature (298 K), and the highest H₂S breakthrough capacity, 436 mg S/g adsorbent, was observed for SBA-15 with 3.04 wt% zinc loading. The enhancement of H₂S removal capacity was attributed to the integration of the high surface area of the mesoporous material and the promising desulphurization properties of ZnO nanoparticles. It was believed that ZnO-modified SBA-15 is a promising adsorbent for H₂S cleaning at ambient conditions, which will extend the application of the mesoporous materials to the environmental protection area.     

110kV主变压器间隙保护误动作原因分析及处理措施

介绍110kV千根变电站主变压器失压故障,分析故障排查的过程,认为低压侧违规小电源是造成主变间隙保护误动的原因,提出排查用户自备应急电源、完善保护配合、定位自备电源等措施。     

直接甲醇燃料电池及系统模型研究进展

对直接甲醇燃料电池(DMFC)进行数学模拟,有利于进一步了解电池内部的物理化学过程,为优化电池结构,确定最优操作条件提供参考依据。综述了近几年DMFC数学模型的研究进展,介绍了DMFC的一维、二维和三维单电池模型,电池组和系统的模型,并分析了直接甲醇燃料电池建模的发展方向。     

卫星电源控制中霍尔非接触测量技术

1879年,美国物理学家爱德华·海博特·霍尔发现霍尔效应以来,霍尔技术越来越多地应用于工业控制的各个领域,特别是随着二十世纪中叶第三次产业革命产生的科学技术大爆发,使得基于霍尔效应原理研制而成的霍尔电流传感器,彻底改变了工业应用中对电压、电流的测量方法。霍尔电流传感器是一种新型磁敏传感器,介绍霍尔电流传感器的使用原理,及在卫星电源控制器中应用的典型霍尔电流传感器基本技术条件和在小卫星中对整星方阵电流、负载电流、放电电流的测量举例。     

氢氧化铝阻燃剂的表面改性

为改善氢氧化铝阻燃剂与聚合物间的相容性,对氢氧化铝进行了改性研究,确定了量佳工艺条件,并对改性后的氢氧化铝粉体进行了性能测试。结果表明,最佳改性剂为硬脂酸,改性剂的量佳用量为1.5%。改性后的氢氧化铝粉体的表面性质发生了明显变化,沉降速度减慢,吸油值降低,活化指数增大,分散性好。     

硬脂酸钠原位改性碳酸钙的研究

采用原位法制备改性碳酸钙,即在改性剂存在条件下,由氢氧化钙经过碳酸化制备改性碳酸钙.研究了改性剂种类、改性剂加入时间、改性剂用量对改性效果的影响.结果显示:硬脂酸钠的改性效果相对较好;产品活化度显示改性碳酸钙是憎水性的;当在消化时加入3%的硬脂酸钠(以碳酸钙质量计)时,改性碳酸钙的活化度可达97.1%.FT-IR,DTA分析表明:其憎水性是由于硬脂酸钠以离子键的形式结合到碳酸钙表面形成难溶硬脂酸钙结果所致.     

Delay-independent decentralized stabilizer design for large interconnected power systems based on WAMS

Recent stabilizer design using wide-area measurement systems (WAMS) signals has been suggested to enhance the dynamic performance of large interconnected power systems. However, there is an unavoidable delay involved before these signals are received at the stabilizer site. Long time-delay may be detrimental to system stability and may degrade system performance. Therefore, the delay-independent robust control problem of large interconnected power systems based on WAMS is studied via H_∞ fuzzy control method. First, a set of equivalent Takagi–Sugeno (T–S) fuzzy model is employed to represent the large interconnected power systems. A wide-area state feedback decentralized control scheme is developed to stabilize the T–S fuzzy systems without any wide-area signals delay information such that the H_∞ performance is achieved. The H_∞ fuzzy robust control design problem is parameterized in terms of a linear matrix inequality (LMI) problem, and the LMI problem can be solved very efficiently using the convex optimization techniques. Finally, the performance of the robust control is studied using a fourteen-machine interconnected power system example.