方钢管混凝土压弯构件可靠度分析

以方钢管混凝土压弯构件为研究对象,应用可靠度最优化方法,分析荷载偏心距为常量时构件可靠性。将偏心距视为基本随机变量,同时考虑轴向力和弯矩相关性影响下构件承载力的可靠性,得到相关结论。     

Safety threshold of high-speed railway pier settlement based on train-track-bridge dynamic interaction

This paper presents a method to determine the safety threshold of bridge pier settlement in high-speed railways.An analytical expression of the mapping relationship between the pier settlement and the rail deformation is derived theoretically for the double block ballastless track-bridge system.By adopting the superposition of the track random irregularity and the rail deformation caused by the pier settlement as the excitation inputs,the variations of vehicle dynamics indices with pier settlement are comparatively analyzed.Then,the safety threshold of the bridge pier settlement is obtained according to the limit of vehicle running safety and ride comfort indices of the high-speed trains.Results show that the dynamics indices of different trains have different sensitivities to the pier settlement,and the train CRH2C is the most sensitive one among all the types of Chinese high-speed trains.When passing through the bridges in common span with pier settlement at the speed of 250–350 km/h,the trains suffer the low-frequency excitations,and the vertical acceleration of car body is most sensitive to the pier settlement of all the dynamics indices.When the car body vertical acceleration just exceeds the allowable limit,the critical settlement value is 23.4 mm,which is much bigger than the pier differential settlement limit in the current code for Chinese high-speed railways.     

芳胺与芳醛希夫碱化合物的合成与表征

以3-硝基-4-羟基吡啶为原料,经过溴化、硝化、还原等反应,合成了5-溴-3,4-二氨基吡啶。然后分别以各种芳氨和芳醛为原料,以无水甲醇和离子液体为溶剂,合成了6种新型杂环希夫碱化合物6a～6f。所得化合物用IR和1 H NMR进行了确证,并考察了离子液体等对希夫碱收率的影响因素。     

镍基单晶高温合金凝固组织特征的研究进展

镍基单晶高温合金的凝固组织对其最终的高温力学性能有着重要的影响,由于制造工艺条件限制,单晶高温合金的制备和加工中总会出现杂晶,保持单晶结构的完整性对提高单晶合金的冶金质量和降低维护成本具有重要意义.综述了镍基单晶高温合金在铸造、焊接、表面熔凝工艺条件下的凝固组织特征的研究现状,分析了工艺条件、工艺参数等对凝固组织和性能的影响,并展望了杂晶缺陷的控制、实现单晶叶片连接区的单晶化.     

基于基准流量的气体泄漏测量方法

该文阐述了一种基于基准流量的并联接入式离线气体泄漏测量方法.与传统的测量方法相比,该方法使用简单,只需将测量装置并联接入到被测管路.为消除无法测量的设备气动回路容积的影响,设计了多段基准流量跟泄漏流量匹配,基准流量发生时,管路中气体压力发生变化,根据这种变化,可以得到管路的泄漏量.试验结果表明,这种方法响应快,测量精度达到士5%F.S..     

航空装备保障任务规划系统体系结构研究

航空装备保障任务规划系统,采用基于三层结构的数据管道方法,用MSSQL Server2000作为数据库开发平台,并利用SQL自带的OLAP Server建立大型多维数据库,前台软件选用Delphi7,通过开放式数据接口实现连接。系统由数据源,数据的知识化处理、辅助决策、可视化表达4部分组成,通过建立多维数据库,利用数据库分析工具从大量数据中提取有效信息。     

Effects of Drought Stress on Photosynthetic Characteristics of Pioneer Plant Neyraudia reynaudiana on Soil and Water Conservation

以水土保持先锋植物类芦为研究材料,通过4个不同梯度干旱胁迫的盆栽试验,测定类芦的光合色素、叶绿素荧光参数和光合参数.研究干旱胁迫对类芦的光台特性的影响.结果表明:中度、轻度干旱胁迫类芦叶绿素含量增加,叶绿素a/b比值下降,干旱胁迫下叶绿素荧光参数F0、Fm,Fv提高,Fv/Fm、Fv/F0下降.类芦叶片的胞问CO2浓度随千旱程度加重而逐渐增加,日变化表现为上午缓慢上升,下午快速上升,到16:00达到最高.净光合速率、气孔导度、蒸腾速率日变化均表现为"单峰型",为先升后降,12:00达到高峰,日均值随着干旱程度加重而逐渐下降.中度、轻度干旱胁迫下WUE提高,重度干旱WUE稍有下降,类芦具有较强的耐干旱能力.     

交替隐式时域有限差分分析有耗介质电磁波传播

针对电磁波在有耗介质中的传播特点,提出了改进的交替方向隐式时域有限差分(ADI-FDTD)算法来研究电磁波在有耗介质中的传播特性。改进后的算法可改善传统ADI-FDTD为提高计算效率导致的计算精度下降的缺点。证明了算法的无条件稳定性,并分析了算法的数值色散。通过算例对比验证了算法的有效性和对计算精度的改善。将算法应用到金属球体在空气中、地面上方和海平面上方的电磁散射分析中,仿真结果表明:介质损耗在一定程度增大电磁散射的同时,会加大电磁散射的震荡。     

PCC升降式反应器的两种新式进料结构

Based on the analysis of flow characteristics of the FCC riser feedstock injection zone, two novel feedstock injection structures are put forward. By investigating three flow parameters in the feedstock injection zone under the three different structures (the traditional and the novel No. 1, No. 2 structures): the local density, the particle backmixng ratio, and the jet eigen-concentration, the flow feature under three structures were obtained. The experimental results demonstrate that the flow features under both proposed structures are obviously improved comparing with those under the traditional structure. Especially, the performance of the deflector-structured No. 2 is more desirable than that of No. 1.