反应结合SiC电热材料的高温氧化特征

研究了反应结合SiC电热材料在1100～1580℃空气介质中加热时的氧化特征。结果表明：加热温度高于1420℃后，材料基体中的残留Si熔化并流动到表面形成SiO2。氧化后形成的SiO2与表面氧化层融为一体，提高了表面氧化层的致密度，有利于材料的抗氧化性能。1500℃左右为材料的抗氧化性能转折温度。在1500℃以下氧化时，反应结合SiC的抗氧化行为与重结晶SiC接近；高于1500℃氧化时，材料表面发生破坏性氧化，引起电热材料的失效。1500℃氧化后的表面氧化层中同时存在低温石英、方石英和非晶态SiO2。     

预应力锚索在水利大坝下游冲坑边坡防护工程中的应用

结合了国外工程(巴基斯坦高摩赞水利大坝边坡防护工程)实例,详细介绍了预应力锚索技术在水利大坝下游防护工程的应用,有效提高了边坡的稳定性.     

不同灌溉处理对水稻产量及水分利用效率的影响

以吉林省岔路河镇灌溉试验站水稻试验田为研究对象,结合当地实际情况,探求作物产量与水分的定量关系,提出适合当地实际的满足节水增产双重目标的灌溉管理模式,得出控制灌溉能够提高农田作物水分生产效率,减少了单位灌溉面积的用水量,获得了较高的作物产量和用水效益,适宜大力推广。     

Numerical investigation on flow and convective heat transfer of aviation kerosene at supercritical conditions

In this paper,characteristics of flow and convective heat transfer of China RP-3 kerosene in straight circular pipe were numerically studied.Navier-Stokes equations were solved using RNG k-turbulence model with low Reynolds number correction.The thermophysical and transport properties of the China RP-3 kerosene were calculated with a 10-species surrogate and the extended corresponding state method(ECS) combined with Benedict-Webb-Rubin equation.The independence of grids was first studied and the numerical results were then compared with experimental data for validation.Under flow conditions given in the paper,the results show that deterioration of convective heat transfer occurs when the wall temperature is slightly higher than the pseudo-critical temperature of kerosene for cases with wall heat flux of 1.2 and 0.8 MW/m 2.The degree of the heat transfer deterioration is weakened as the heat flux decreases.The deterioration,however,does not happen when the heat flux on the pipe wall is reduced to 0.5 MW/m 2.Based on the analysis of the near-wall turbulent properties,it is found that the heat transfer deterioration and then the enhancement are attributed partly to the change in the turbulent kinetic energy in the vicinity of pipe wall.The conventional heat transfer relations such as Sieder-Tate and Gnielinski formulas can be used for the estimation of kerosene heat convection under subcritical conditions,but they are not capable of predicting the phenomenon of heat transfer deterioration.The modified Bae-Kim formula can describe the heat transfer deterioration.In addition,the frictional drag would increase dramatically when the fuel transforms to the supercritical state.     

Wave–current interaction with a vertical square cylinder at different Reynolds numbers

Railway Engineering Science - Large eddy simulation is performed to study three-dimensional wave–current interaction with a square cylinder at different Reynolds numbers, ranging from 1,000...     

燕子崖砂石加工系统技术创新及运行管理

龙开口水电站大规模采用白云岩作为高强度碾压混凝土砂石骨料生产的母岩,属国内首创,因此缺少相关实验数据和实际生产经验,另外,燕子崖砂石系统自身存在高落差等特点,给砂石系统加工工艺带来了困难.通过采用3个竖井、3个平洞连续阶梯式运输直接将600 m超高落差半成品料输送至半成品堆料场,采用长距离空间曲带式输送机输送成品骨料至坝区转料堆的方案,以及调整爆破参数、干法生产改为湿法生产等工艺措施,解决了骨料高落差、长距离运输,半成品含泥量大,骨料级配不平衡等问题,圆满完成了各阶段浇筑所需砂石骨料的供应任务.     

基于分级加载的高面板堆石坝应力变形分析

依据非线性弹性K-G模型理论对天池上水库面板堆石坝进行了应力变形分析。首先采用CAD图形和程序控制相结合方法建立坝体与地基模型,考虑了断层构造和岸坡变化,得到了较为精细的三维有限元模型。然后在模型计算中采用了施工逐级加载的方法对坝体进行了模拟,应用修正后的分级加载位移变形公式,对竣工期和正常水位蓄水期的应力变形进行三维有限元分析,得出了两种工况下断层对该高面板坝应力变形影响一般规律。     

厌氧/缺氧/好氧膜生物反应器处理城市污水效能研究

采用厌氧/缺氧/好氧膜生物反应器对北京某城市污水处理厂的初沉池出水进行中试试验,约200 d的研究表明,在水力停留时间保持12.5 h后,化学需氧量、生物需氧量及总有机碳的去除率分别稳定在92%、98%、85%左右,其中生化降解部分与膜过滤部分对COD去除的贡献率分别为89%和11%;NH4+-N、总氮(total nitrogen,TN)的去除率分别为98%、79%左右,出水ρ(TN)平均在10 mg/L左右;系统在污泥龄为40 d左右时,总磷(totalphosphorus,TP)平均去除率为85%,出水ρ(TP)在0.93 mg/L左右;反硝化除磷、好氧吸磷、膜截留对总磷的去除所占的比例分别为44.6%、51.8%、3.6%;出水浊度极低且几乎无悬浮物,可直接回用于城市杂用水.间歇抽吸、曝气冲刷、在线水力反冲及定期药洗保证了该系统的可持续运行.     

基于SharePoint的专家群协作与决策系统设计

结合专家群协作特点与决策要求,提出了基于SharePoint技术构建专家群协作与决策系统,设计了系统的整体框架以及决策流程。在此基础上,提出了基于MOSS2007的专家群协作与决策系统的技术架构,并对系统实现的关键技术及应用层功能进行了说明。最后,以奥运科技信息通信专项产业化潜力评价的专家协作与决策过程为例,对该系统进行了验证。     

不同模量比对复合材料储能飞轮强度的影响

以材料的环向与径向模量比λ作为参量,利用ANSYS有限元分析软件,对给定尺寸不同材料的单层及双层异构复合材料飞轮转子进行强度计算,得出飞轮转子在高速旋转时的径向和环向应力分布规律。进而利用强度比方程求解各种结构的强度比,分析材料参数对飞轮转子强度的影响。