生物氧化预处理过程中氧化槽温度机理模型及温度场的研究

对生物氧化槽内的温度进行热量分析,建立氧化槽内热量机理模型,在热分析的基础上,增加外界载荷,建立基于时空域的不确定性温度场分布模型,通过对温度场分布模型的分析,为改进氧化槽结构及设计氧化槽温度控制系统提供指导策略。     

三相绕组Y接法单相电容电动机瞬态过程仿真研究

对三相绕组Y接法单相电容电动机的瞬态过程进行仿真分析.为了得到瞬态特性,提出了三相绕组Y接法单相电容电动机在αβ坐标系下的瞬态数学模型,并通过实例对该电动机的瞬态过程进行仿真计算,对仿真结果进行了分析.该电动机能否在最小不平衡条件下运行,与电容的数值密切相关.用对称分量法分析了三相绕组单相电容电动机最小不对称运行时需要满足的条件,并由此初步计算电容的数值,然后通过计算机仿真较准确地加以确定电容的数值.     

适应主导薄弱断面迁移的暂态稳定控制

为适应电网大扰动冲击下,表征机群主导失稳模式的主导薄弱断面动态迁移之复杂场景,需要制定相应暂态稳定控制策略。在薄弱断面关键支路识别方法,以及关键受扰轨迹几何特征判稳方法的基础上,针对大扰动冲击下主导薄弱断面迁移的复杂扰动场景,提出了以交流支路实时受扰电气量为信息源的暂态稳定控制策略,可有效降低系统失稳风险。大容量长距离交直流混联输电系统仿真结果,验证了控制策略的有效性。     

On the predictability of the water-table variation in a ditch-drainage system

The irrigation in regions of brackish groundwater in many parts of the world results in the rise of the water-table very close to the groundsurface. The salinity of the productive soils is therefore increased. A proper layout of the ditch-drainage system and the prediction of the spatio-temporal variation of the water table under such conditions are of crucial importance in order to control the undesirable growth of the water-table. In this paper, an approximate solution of the nonlinear Boussinesq equation has been derived to describe the water-table variations in a ditch-drainage system with a random initial condition and transient recharge. The applications of the solution is discussed with the help of a synthetic example.Notations a lower value of the random variable representing the initial water-table height at the groundwater divide - a+b upper value of the random variable representing the initial water-table height at the groundwater divide - h variable water-table height measured from the base of the aquifer - K hydraulic conductivity - L half width between ditches - m ₀ initial water-table height at the groundwater divide - N(t) rate of transient recharge at time t - N ₀ initial rate of transient recharge - P N ₀/K - S Specific yield - t time of observation - t ₀ logarithmic decrement of the recharge function - T Kt/SL - x distance measured from the ditch boundary - X x/L - Y h/L - Y mean of Y - Y Variance of Y     

手机电磁兼容测试常见问题分析及相关性能改进

针对手机电磁兼容测试中经常出现的问题,包括静电放电抗扰度试验、电快速瞬变脉冲群抗扰度试验、辐射骚扰及传导骚扰性能测试中经常发现的问题进行了分析,并提出了相应的改善手机电磁兼容性能的建议。     

Constructal Enhancement of Heat Conduction with Phase Change

For enhancing the heat energy release from a phase change material (PCM) the conductive fin is designed according to a proposed constructal rule, in which the high conductivity material (HCM) should be located at the place where the heat flux density is the largest. The local temperature gradient integration over time is taken as a criterion to determine where to distribute the limited HCM during a given time period. This rule is applicable to heat conduction of steady and unsteady conditions, as well as to the problems with and without phase change. Numerical simulations show that the constructal design of a conductive fin has much better performance than arbitrary ones. The constructal rule is an effective technique that designs the fin with high performance for enhancing heat conduction.Paper presented at the 7th Asian Thermophysical Properties Conference, August 23–28, 2004, Hefei and Huangshan, Anhui, P. R. China.     

Joining of metal bars by a new process of transformation-diffusion brazing

Within the bonded interface of metal bars joint produced by conventional solid state bonding process （ such as flash welding, resistance butt welding, friction welding and so on）, the inclusions are often present, which degrade the ductility of joint. A new process of transformation-diffusion brazing is proposed, in which an amorphous foil containing melting point depressant is preplaced between the interfaces to be joined, and the assembly is repeatedly heated/cooled without holding time at peak temperature. A low carbon steel bars, BNi-2 amorphous foil and resistance butt welding machine were used. The results show that surfuce contamination can be disrupted by the dissolution of base metal into molten interlayer in comparison with conventional process, and the ductility of joint can be improved by increasing the times of temperature cycles on line. In addition, transformation-diffusion brazing can be done with relatively simple and inexpensive system in comparison with transient liquid phase bonding.     

高压变频器控制器的电磁兼容设计

本文用最短的篇幅从线路设计、印制板设计、设备内部走线、接地设计、屏蔽技术、滤波技术、电缆辐射问题、瞬态干扰抑制等各个方面,介绍了电磁兼容设计要点和关键技术。     

Dissolution Behaviors and Applications of Silicon Oxides and Nitrides in Transient Electronics

Silicon oxides and nitrides are key materials for dielectrics and encapsulation layers in a class of silicon‐based high performance electronics that has ability to completely dissolve in a controlled fashion with programmable rates, when submerged in bio‐fluids and/or relevant solutions. This type of technology, referred to as “transient electronics”, has potential applications in biomedical implants, environmental sensors, and other envisioned areas. The results presented here provide comprehensive studies of transient behaviors of thin films of silicon oxides and nitrides in diverse aqueous solutions at different pH scales and temperatures. The kinetics of hydrolysis of these materials depends not only on pH levels/ion concentrations of solutions and temperatures, but also on the morphology and chemistry of the films, as determined by the deposition methods and conditions. Encapsulation strategies with a combination of layers demonstrate enhancement of the lifetime of transient electronic devices, by reducing water/vapor permeation through the defects.     

综合物探技术在煤矿采空区探测中的应用

小煤窑的无序无证开采,形成的采空区等地质异常体常因富含水或瓦斯而成为影响煤矿安全生产和建设的隐患。为解决上述问题,本文介绍了活性炭测氡法、瞬变电磁法和可控源音频大地电磁法三种勘探方法的原理、特点以及在采空区探测中的应用效果,并以太原煤气化嘉乐泉煤矿周围采空区的探测为例,证明了三种方法互补,互证,定位、定性准确,探测效果明显。