并联混合型有源滤波器单周控制

针对目前有源滤波器容量限制,提出一种新型的并联混合型有源滤波器SHAPF的结构,SHAPF结合有源滤波器和无源滤波器,大大减少了有源滤波器的容量,有利于工程实现.在分析SHAPF的数学模型的基础上,应用了一种新型的非线性控制方法--单周控制,此方法是控制直流侧电压来达到控制谐波输出,克服了目前一般PWM控制方法的缺陷,实现简单,仿真验证了此方法的可行性.     

Ventilation performance prediction for buildings: Model assessment

Designing ventilation systems for buildings requires a suitable tool to assess the system performance. This investigation assessed seven types of models (analytical, empirical, small-scale experimental, full-scale experimental, multizone network, zonal, and CFD) for predicting ventilation performance in buildings, which can be different in details according to the model type. The analytical model can give an overall assessment of a ventilation system if the flow could be approximated to obtain an analytical solution. The empirical model is similar to the analytical model in terms of its capacities but is developed with a database. The small-scale model can be useful to examine complex ventilation problems if flow similarity can be maintained between the scaled model and reality. The full-scale model is the most reliable in predicting ventilation performance, but is expensive and time consuming. The multizone model is a useful tool for ventilation design in a whole building, but cannot provide detailed flow information in a room. The zonal model can be useful when a user has prior knowledge of the flow in a room. The CFD model provides the most detailed information about ventilation performance and is the most sophisticated. However, the model needs to be validated by corresponding experimental data and the user should have solid knowledge of fluid mechanics and numerical technique. Thus, the choice for an appropriate model is problem-dependent.     

Luminescence properties of blue and green dual wavelength InGaN/GaN multi-quantum well light-emitting diode

Blue and green dual wavelength InGaN/GaN multi-quantum well (MQW) light-emitting diode (LED) has wide applications in full color display, monolithic white LED and solid state lighting, etc. Blue and green dual wavelength LEDs, which consist of InGaN strain-reduction layer, green InGaN/GaN MQW and blue InGaN/ GaN MQW, were grown by metal-organic chemical vapor deposition (MOCVD), and the luminescence properties of dual wavelength LEDs with different well arrangements were studied by photoluminescence and electrolumines-cence. The experimental results indicated that well position played an important role on the luminescence evolvement from photoluminescence to electroluminescence.     

电磁力平衡传感器的磁缸温度稳定控制方法研究

未温度补偿过的电磁力平衡传感器温度漂移达200×10-6 g/℃,远不能满足万分之一克及以上的电子分析天平计量性能要求。详细分析了电磁力平衡传感器磁缸温度变化对传感器输出的影响,根据传感器结构及热传递路径,设计了一种基于高精度数字温度传感器的温度检测模块;利用正弦波信号在线圈上做功发热但产生电磁力合力为零的特点,提出了一种基于脉冲宽度调制(pulse width modulation,PWM)控制的电磁力平衡传感器磁缸温度稳定控制方法。该方法根据磁缸温度变化量以及加载物体质量大小,不断地调节PWM输出的占空比,控制正弦波信号导通时间,改变线圈的发热量,实时调节磁缸的热平衡。实验研究表明,基于电磁力平衡传感器的电子分析天平应用上述研究方法后,温度漂移降低至15×10-6 g/℃,有效地改善了传感器温度稳定性,大大降低了天平温度漂移补偿的难度。     

储罐内防腐蚀涂层鼓泡分析

经过对中间产品油储罐内防腐蚀施工过程的观察与分析,认为导致该储罐涂层产生鼓泡和流挂等缺陷的影响因素主要有储罐表面预处理、涂装工艺、涂层厚度和防腐蚀施工监理四个方面.提出了从涂料、储罐表面预处理、涂装工艺、施工队伍资质、现场施工监理和施工质量检测等方面严格控制储罐内防腐蚀施工质量的建议.     

In situ growth monitoring of AlGaN/GaN distributed Bragg reflectors at 530 nm using a 633 nm laser

The metal-organic chemical vapor deposition(MOCVD) growth of AlGaN/GaN distributed Bragg reflectors (DBR) with a reflection peak at 530 nm was in situ monitored using 633 nm laser reflectometry.Evolutions of in situ reflected reflectivity for different kinds of AlGaN/GaN DBR were simulated by the classical transfer matrix method.Two DBR samples,which have the same parameters as the simulated structures,were grown by MOCVD.The simulated and experimental results show that it is possible to evaluate the DBR...     

基于TRIZ理论的电磁驱动式机械密封创新设计

基于TRIZ理论,提出一种改善非接触式机械密封在低转速状态下密封面相对转速低且不稳定的方法.通过对传统机械密封整体原理和结构的分析,运用TRIZ理论,以“速度”为改善的参数,“组件的复杂性”和“测量的准确性”为恶化的参数,由矛盾矩阵得到发明原理号,经分析选取“调节器原理”和“置换机械系统原理”,并由此采取设置中间旋转环及采用电磁驱动该中间旋转环的方法,提高了机械密封的工作稳定性和使用寿命.     

搞好雨水排放消除工业废水污染来源

文章针对火法、湿法冶炼工艺并存的重金属冶炼企业工业、废水中重金属污染物的来源、危害 ,分析、探讨了实现工业废水无污染排放的途径。认为搞好雨水排放既是从根本上消除重冶企业工业废水中重金属污染的需要 ,又是实现工业废水无污染排放的关键。     

固定式直流融冰装置在贵州输电线路的应用

2008年至2012年共配备了28套固定式直流融冰装置,并在2011年首次实现了直流融冰技术的大规模应用,该技术证明了直流融冰装置是应对线路覆冰的最有效手段,同时能有效地提高电网抵御极端气候的能力。     

树枝状硅钛杂化纳米球负载金纳米颗粒催化性能研究

树枝状纳米球独特的三维中心辐射状孔道结构使其具有出色的比表面积和孔体积。客体物质可负载于多级孔道内,形成新型的载体/递送/反应平台。本研究设计构筑了一类具有高稳定性的多功能复合材料——树枝状硅钛杂化纳米球负载金纳米颗粒催化剂。使其经过系列化学反应及改性过程,树枝状硅钛杂化纳米球依旧保持中心辐射状纹理结构,孔道内成功负载了锐钛矿二氧化钛和超细金纳米粒子。结果表明,相较于树枝状二氧化硅纳米球负载金纳米颗粒材料(对比样),设计合成的催化剂展现出更加优越的多功能催化性能。在模拟太阳光下,其光解水产氢量为210.01μmol·g^-1,约为对比样的10倍。无光条件下,其降解对硝基苯酚的表观动力学常数为2.150×10^-3 s^-1,约是对比样(0.111×10^-3 s^-1)的19倍。