Effect of (n, γ) and (n, α) reactions of framework atoms on the (n, γ) recoils in Ba and Cs cations in high-silica zeolites

The effects of (n, γ) and (n, α) reactions of framework atoms on the fate of (n, γ) recoil species ¹³¹Ba²⁺ and ¹³⁴Cs⁺ from Ba²⁺ and Cs⁺ loaded in high-silica aluminosilicate and borosilicate zeolites (boron-zeotypes) have been studied. Studies were made of the recoil from “open to locked-in” and “locked-in to open” sites. In open to locked-in recoil, target ions were eluted with efficiencies of 90% where only (n, γ) processes were in operation, but in the presence of (n, γ) and (n, α) reactions, the efficiency fell to 80%. For locked-in to open site recoil, the corresponding efficiencies were in the ranges 50–60% and 40–50%. The effect of calcination temperature on the exchange of cations present was also ascertained. The high-silica zeolites used were synthesized according to published methods and were characterized by XRD, i.r., SEM, and t.g.-d.t.g./d.s.c. techniques, and all were found to be crystalline. In boron-zeotype materials, the magnitude of (n, α) damage was increased by the use of ¹⁰B isotope.     

由感应电压引起的电压异常原因分析与处理措施

针对外高桥三厂启动调试过程中导致断路器无法合闸的高感应电压现象,基于电磁暂态程序(EMTP)建立了外高桥三厂的感应电压分析模型,研究了外高桥三厂在各种工况下的桥引线感应电压,并提出了调度操作中应注意的问题和解决措施.     

Performance of Polymer Modified Asphalt Bridge Expansion Joints in Low-Temperature Regions

Conventional asphalt bridge expansion joints used in low-temperature regions generally show cracking within the first 2?years. To improve the low-temperature performance of these joints, the commercial MEIJIA asphalt binder commonly used in bridge expansion joint construction was modified with two polymers: thermoplastic rubber and rubber. The goal is to find an optimum combination of polymers, binders, and aggregates to improve the performance of asphalt expansion joints in low-temperature regions. The polymer modified binders and mixtures were evaluated for their low-temperature properties using ductility, penetration, indirect tension, and bending tests. The study indicates that performance of these joints at low temperature can be enhanced significantly with the right combinations of polymers, binders, and aggregates. Four expansion joints made with the polymer modified asphalt mixtures were installed on two bridges in a cold region. A construction procedure was also developed to install these joints properly to minimize low-temperature cracking along the interface between the joint and bridge deck. After 7?years of service, the four joints show good performance without any visible cracking or rutting.     

基于Ayada损伤模型的板料冲裁过程数值模拟

使用DEFORM-2D软件对AISI-1045钢的冲裁工艺过程进行弹塑性大变形有限元数值模拟,采用Ayada断裂准则,预测了材料变形过程中静水应力、等效应力和等效应变的分布以及发展趋势、冲裁最后阶段微裂纹产生发展和最终断裂,模拟结果中的材料断裂和冲裁力的变化与实验结果一致.     

基于VFW视频会议系统开发

计算机科学技术的发展不仅极大地促进了整个科学技术的发展,而且明显加快经济信息化和社会信息化的进程。在这基础上发展起来的网络视频会议是一个新型的会议方式,在企业、医学界等方面发挥着重要的作用。本文主要从系统的需求分析、体系结构、视频／音频的实现及相关界面的组成功能等方面详细介绍了此系统的功能模块。     

基于能量法的双线下穿既有隧道沉降研究

针对双线隧道穿越施工造成的复杂影响问题,基于能量方法,提出了考虑地层损失率差异的双线下穿开挖作用下既有隧道沉降的计算方法。基于经典的Peck和Mair理论,在计算新建隧道开挖引起的地层位移时,引入Hunt双线开挖沉降修正系数,考虑双线隧道先后穿越引起的地层损失率差异性所造成的影响;基于Rayleigh-Ritz法和弹性地基梁理论,写出系统各部分功能关系式,建立系统总势能方程;利用变分法求解总控制方程,得到考虑地层损失率差异的双线隧道下穿引起既有隧道沉降的理论解析,并将理论计算结果与已有文献报道的工程实测沉降数据进行对比验证;以双线隧道下穿既有隧道为例,对双线中心间距、新建隧道直径以及新旧隧道净距展开参数分析。研究结果表明：理论计算结果与实测数据整体趋势一致,二者吻合较好,验证了所提方法的可行性;新建隧道先后下穿引起的地层损失率差异对既有隧道的沉降有显著影响;随着新建双线中心间距和新旧隧道净距的增大,既有隧道的沉降量随之减小;随着新建隧道直径的增大,既有隧道的沉降量随之增加,且第二次下穿施工产生的沉降影响会越发明显。研究成果可快速且合理评估既有隧道受新建隧道穿越施工影响时的纵向变形响应,对类似的双线隧道工程起到一定的理论支持和指导意义。     

离网小型风力发电系统的研究

离网小型风力发电系统是边远缺电地区一种重要的电力生产方式.给出了一种典型的小型风力发电系统的拓扑结构.着重对风机变流器环节进行了分析研究,应用电力电子专用仿真软件PSIM完成了系统建模、仿真分析和实验研究,验证了方案的可行性和优越性.