长期在地下工作后的塑料排水板的性能研究

塑料排水板在软基工程施工后期及竣工后的工作性状对于工后沉降的控制起着重要作用,目前国内对塑料排水板长期工作后的性能研究几乎是空白。本文通过现场开挖采取在地下工作2年后的塑料排水板试样进行室内检测,并与施工前性能进行对比分析。结果表明:工作2年后,塑料排水板基本无磨损,芯板齿槽保持较好;而排水板复合体干态抗拉强度及滤膜干态抗拉强度明显降低,折减系数分别为81%~88%5、9%~90%;通水量减小,弯折的排水板通水量减小的可能性更大,部分数据达不到设计要求,对工程后期排水固结将产生不利影响。     

新安江模型参数优选的改进粒子群算法

借鉴竞争演化和多种群混合的思想,对粒子群算法(PSO)进行改进,建立并行种群混合进化的粒子群算法(PMSE-PSO)和序列主-从种群混合进行的粒子群算法(SMSE-PSO)。数值模拟结果表明,这两种改进的粒子群算法具有较高的计算效率、较强的自适应性和稳定性。将PMSE-PSO和SMSE-PSO应用于新安江模型的参数优选中,通过与PSO和SCE-UA的比较可以看出,PMSE-PSO和SMSE-PSO不仅具有较好的全局优化性能和稳定性,而且在调用目标函数次数相同的情况下精度较高,是一种有效的新安江模型参数优选方法。     

针梁台车在大花水水电站引水隧洞混凝土衬砌施工中的改进

大花水水电站引水隧洞由于前期开挖工期略有滞后，为加快施工进度，结合全圆断面的施工特点，大部分引水隧洞采用了全圆针梁穿行式钢模台车进行混凝土衬砌。通过各参建单位对针梁台车的运用和改进，有效地提高了引水隧洞混凝土的衬砌速度，并确保了工程质量。     

川中丘陵区一种新型小流域径流输沙模型的建立与应用

径流输沙模型对定量评价水沙的输出响应具有重要的意义。本研究在已有研究成果的基础上，通过对四川盐亭县林山西沟小流域的径流、泥沙进行现场观测与分析，提出含沙量单位线的定义及其确定方法，建立了适应该小流域的径流输沙模型。并应用实测资料进行比较，表明模型的模拟结果可靠，模拟过程确定性系数达0．8以上，为川中丘陵区小流域径流输沙过程的预测预报提供了一个新方法。     

川中地区上三叠统天然气地球化学特征及成藏过程探讨

川中地区上三叠统是一套自生自储的天然气成藏系统，天然气中甲烷含量为88%～96％，重烃（C2＋）含量一般在6％～9％之间，二氧化碳和硫化氢等非烃气体含量普遍较低；天然气干燥系数（C1／C2＋）为5～15，并且随深度增加而呈现升高的趋势；天然气和凝析油轻烃中的甲基环己烷、庚烷和异庚烷值变化表明天然气主要来源于腐殖型母质；天然气甲烷和乙烷碳同位素分别为-39．00‰～-41．00‰和-25．00‰～-27．00‰，具有典型煤成气特征。川中地区上三叠统烃源岩在燕山期持续沉降埋藏过程中，达到高成熟早期阶段；在喜山期，该地区大约2500m地层的剥蚀，使地层温度和压力大幅度降低，故储层中早期低成熟残余天然气的卸压膨胀作用和水溶气的脱溶作用为晚期天然气聚集成藏提供了重要的气源，同时也使气藏中甲烷碳同位素变轻。     

Evaporation and Evolution of Suspended Solution Droplets at Atmospheric and Reduced Pressures

Thermal history and solute precipitation behavior of suspended solution droplets of sodium chloride (NaCl), magnesium sulphate (MgSO₄), and zirconium hydroxychloride (ZrO(OH)Cl) evaporating at atmospheric and reduced pressures are studied. Experimental measurements on the variation of droplet diameter, solution concentration, and temperature during the evaporation period are presented and discussed. The results of solute precipitation behavior in solution droplets observed under an optical microscope are displayed and discussed. Results indicate that reducing the pressure (∼ 33 kPa) results in a change in the solution droplet evaporation rate, but the thermal histories of a particular solution droplet are similar at the atmospheric and reduced pressures. At atmospheric and reduced pressures used in this study, the d² law for solution droplets is valid at early stages of the evaporation and before the solute precipitation initiates. Drying of MgSO₄ and ZrO(OH)Cl solution droplets results in the formation of spherical particles, whereas drying of spherical NaCl solution droplets results in the formation of cubic particles.     

降温集油技术在朝阳沟油田的应用

精确界定油井温度界限值,对回油温度进行自动控制是降低气耗、能耗的有效措施。首先推导了单井温度界限数值模型,然后针对朝阳沟油田的实际情况对油井进行了分类,并选择了有代表性的单(环)井进行了试验。通过现场实测值与利用模型计算的预测值比对,符合率达到了70%以上。在此基础上利用温度界限分析仪进行了进一步的验证试验,结果符合预期。在单(环)井上加装了掺水量自动控制装置,实现了回油温度的自动控制。     

An investigation of water-gas transport processes in the gas-diffusion-layer of a PEM fuel cell by a multiphase multiple-relaxation-time lattice Boltzmann model

In order to study water-gas transport processes in the gas-diffusion-layer (GDL) of a proton exchange membrane (PEM) fuel cell system, a multiphase, multiple-relaxation-time lattice Boltzmann model is presented in this work. The model is based on the mean-field diffuse interface theory and can handle the multiphase flows with large density ratios and various viscosities. By using the standard bounce back boundary condition and an approximate average scheme for the non-slip and wetting boundary walls, respectively, detailed liquid-gas transportation in the GDL, in which exact boundary condition is difficult to be implemented, can be simulated. Unlike most of lattice Boltzmann methods based on the Bhatnagar–Gross–Krook collision operator, the present model shows a viscosity-independent velocity field, which is very important in simulating multiphase flows where various viscosities coexist. We validate our model by simulating a static droplet on a wetting wall and compare with theoretical predictions. Then, we simulate a water-gas flow in the GDL of a PEM fuel cell and investigate the saturation-dependent transport properties under different conditions. The results are shown to be qualitatively consistent with the previous numerical and theoretical works.     

安徽省长江干堤的几种加固措施

安徽省境内765km的长江干堤，由于均是在原来旧堤的基础上经逐年加高培厚的，修筑时均未按设计要求施工，致使堤身密实度不够，新老堤土之间结合不牢，在汛期高水位时易产生渗漏。20世纪70年代以来，安徽省高度重视对长江干堤渗漏隐患的处理，经过长期的实践，逐渐摸索出一套行之有效的除险加固方法，如锥探灌浆、灭杀白蚁、冲抓套吉、垂直铺塑防渗、粘土铺盖及压渗盖重等处理措施。使长江干堤的渗漏隐患得以基本消除，其具体作法可供类似工程借鉴。     

Limit Cycles in a Class of Hybrid Dynamical Systems

This paper deals with qualitative analysis of the so-called switched fluid networks. Such networks are used to model communication, computer, and flexible manufacturing systems. We prove that for any deterministic network from a specific class, there exists a finite number of limit cycles attracting all the trajectories of the system. Furthermore, we determine this number. Date received: March 11, 2000. Date revised: January 19, 2001.