微型碳纳米管NH3气体检测系统

基于制备得到的微型碳纳米管NH3传感器,研制了一种便携式气体浓度检测系统。此系统由恒流源驱动,通过微控制单元实现自动检测。为了便于安装、维修与调试,该系统所有电路均采用模块化设计,检测系统可以比较精确地测量25 kΩ以内电阻的变化,可以精确检测5×10－6～50×10－6范围内NH3气体浓度。     

A novel algorithm for selective current limit used in AMOLED panel

A selective current limit algorithm based on color space conversion is proposed in this paper. There are mainly two advantages for this algorithm. Firstly, only the luminance component Y is decreased, and the color component Cb or Cr is not changed; thus, the color distortion is avoided in the process of current limit. Secondly, the current of pixels with high luminance is limited while that of those pixels with low luminance is not, which means current limit is executed selectively. For the same value of mean square error, the simulation results show that the ratio of pixels with high luminance of the image processed by the proposed algorithm is zero, and that processed by the net power control and the algorithm based on color space conversion is 0.081 and 0.0854, respectively. This algorithm is implemented on a field‐programmable gate array to drive the image display on the AMOLED panel.     

低压增安型异步电动机热过载保护的改进

低压增安型三相异步电动机是适用于工厂2区内具有爆炸危险场所的防爆电机,其防爆技术原理是在保证电机正常运行的条件下,不产生电弧、火花,或在可能点燃爆炸性混合物的高温的基础上,进一步采取电磁和机械方面的措施,以提高安全性,避免在正常和认可的过载条件下出现问题。随着增安型异步电动机被广泛采用、数字技术的不断发展和新一代低压电动机智能综合保护器的逐步普及,增安型电动机的热过载保护（TE时间保护）已日趋完善。     

超大规模集成电路电源完整性设计中的滤波电容选择

集成电路技术的迅速发展,对电源完整性设计提出了更高的要求,设计者通常通过放置各种电容来降低电源噪声以及应对负载瞬态大电流的需求。讨论了电容技术发展对电源完整性设计带来的影响,同时通过对几种典型电容特性的分析,给出了在电源完整性设计中合理选择使用各种滤波电容的解决方案。     

微电流电解对尿素降解的机理及影响因素研究

采用微电流电解技术对模拟游泳池水中的尿素进行降解处理,探索了电解对尿素的去除机理,研究了电流密度和氯离子浓度等因素对电解去除尿素效果的影响。结果表明:以钌钛和不锈钢分别做阳极和阴极材料,当水溶液中有较高浓度的氯离子存在时,电解过程中产生的活性氯使得尿素被氧化,尿素降解产物中无氨氮、氯胺等二次污染物,尿素极有可能通过电解生成了N2等气体挥发到空气中。电流密度和氯离子浓度对尿素的去除效率有很大影响,随着电流密度和氯离子浓度的增加,尿素去除效率逐渐上升。在500 mg/L的氯离子浓度条件下,电流密度为12 m A/cm2时,电解处理30 min时尿素去除率可达99.5%。将微电流电解技术应用于游泳池水中的尿素去除,无需添加电解质,即能达到较高的尿素去除效果,采用该技术对游泳池水中的尿素进行降解去除完全可行。     

矿山井下低压IT接地系统设计规范探讨

介绍了矿山井下低压IT接地系统第一次接地故障的原理,指出GB 50070—2009《矿山电力设计规范》要求"配电系统相导体和外露可导电部分之间第一次出现阻抗可忽略的故障时,故障电流不应大于5A"的规定是没有实际意义的;通过计算比较IT系统和TN系统单相接地故障时的触电电压和电流,可知在采用IT系统时直接触电的人身触电电流与采用TN系统时基本相同,而在间接触电的情况下IT系统优于TN系统。     

基于分布参数的煤矿井下直流杂散电流研究

直流杂散电流是引起井下瓦斯爆炸的重要原因之一,对煤矿安全生产具有很大威胁。针对这一问题,从杂散电流的产生机理着手,建立了井下直流杂散电流的分布参数模型;在该模型的基础上,仿真分析了各个参数对杂散电流的影响,得出了如下结论:随着机车电流的增加、供电区间的延长及轨道电阻的增大,杂散电流也会线性增加,可通过减小机车电流、缩短供电区间长度及减小轨道电阻来减小杂散电流;轨道与大地间过渡电阻低于安全值时会造成杂散电流急剧增大,保证轨道与地之间的绝缘是限制杂散电流的一种有效措施。     

Spatial and functional relationships between air conduits and blood capillaries in the pulmonary gas exchange tissue of adult and developing chickens

The documented data regarding the three-dimensional structure of the air capillaries (ACs), the ultimate sites of gas exchange in the avian lung is contradictory. Further, the mode of gas exchange, described as cross-current has not been clearly elucidated. We studied the temporal and spatial arrangement of the terminal air conduits of the chicken lung and their relationship with the blood capillaries (BCs) in embryos as well as the definitive architecture in adults. Several visualization techniques that included corrosion casting, light microscopy as well as scanning and transmission electron microscopy were used. Two to six infundibulae extend from each atrium and give rise to numerous ACs that spread centrifugally. Majority of the ACs are tubular structures that give off branches, which anastomose with their neighboring cognates. Some ACs have globular shapes and a few are blind-ending tapering tubes. During inauguration, the luminal aspects of the ACs are characterized by numerous microvillus-like microplicae, which are formed during the complex processes of cell attenuation and canalization of the ACs. The parabronchial exchange BCs, initially inaugurated as disorganized meshworks, are reoriented via pillar formation to lie predominantly orthogonal to the long axes of the ACs. The remodeling of the retiform meshworks by intussusceptive angiogenesis essentially accomplishes a cross-current system at the gas exchange interface in the adults, where BCs form ring-like patterns around the ACs, thus establishing a cross-current system. Our findings clarify the mode of gas exchange in the parabronchial mantle and illuminate the basis for the functional efficiency of the avian lung.     

Bed morphology, flow structure, and sediment transport at the outlet of Lake Huron and in the upper St. Clair River

An integrated multibeam echo sounder and acoustic Doppler current profiler field survey was conducted in July 2008 to investigate the morphodynamics of the St. Clair River at the outlet of Lake Huron. The principal morphological features of the upper St. Clair River included flow-transverse bedforms that appear weakly mobile, erosive bedforms in cohesive muds, thin non-cohesive veneers of weakly mobile sediment that cover an underlying cohesive (till or glacio-lacustrine) surface, and vegetation that covers the bed. The flow was characterized by acceleration as the banks constrict from Lake Huron into the St. Clair River, an approximately 1500-m long region of flow separation downstream from the Blue Water Bridge, and secondary flow connected to: i) channel curvature; ii) forcing of the flow by local bed topography, and iii) flow wakes in the lee side of ship wrecks. Nearshore, sand-sized, sediment from Lake Huron was capable of being transported into, and principally along, the banks of the upper St. Clair River by the measured flow. A comparison of bathymetric surveys conducted in 2007 and 2008 identifies that the gravel bed does undergo slow downstream movement, but that this movement does not appear to be generated by the mean flow, and could possibly be caused by ship-propeller-induced turbulence. The study results suggest that the measured mean flow and dredging within the channel have not produced major scour of the upper St. Clair River and that the recent fall in the level of Lake Huron is unlikely to have been caused by these mechanisms.     

中国水利投资的发展路径分析

通过数据分析,总结出改革开放以来我国水利投资的基本变化趋势：从长期来看,我国水利投资处于不断上升的趋势．并且投资增速呈现不稳定波动的态势。1998年以来水利投资总量虽大幅度提高,但水利投资仍存在投资总量与实际需求差距过大、增长速度缓慢、区域差异较大等问题。针对以上问题,从公共财政保障机制缺失、财政支持政策缺乏、中央地方事权和财权不匹配等三方面,着重分析我国水利投资变化的原因,从建立公共财政投资稳定增长的投入机制、保障地方投入机制、利用市场融资等方面,提出未来我国水利投资的发展路径。