不同裂纹倾角下岩桥拉张破裂数值模拟研究

以预制于岩体中不同倾角的裂纹及其组成的岩桥为研究对象,采用可模拟拉张开裂的有限元软件,对不同裂纹倾角岩桥模型的拉张破坏过程进行数值模拟。结果显示:在单轴压缩条件下,对于相同尺寸、等距离的平行预制裂纹,裂纹的倾角不同,拉张裂纹的扩展形态不同;预制裂纹倾角越大,岩桥越容易拉张破坏;八字形裂纹比平行裂纹更稳定。     

基于位移突变判据的强度折减法边坡稳定分析

通过对有限元强度折减法失稳判据的探讨得出,相对于塑性应变贯通和不收敛判据,位移突变判据更符合边坡失稳机理,提出了基于三点位移突变判据为主,结合位移云图及塑性变形综合判定边坡稳定性的有限元强度折减法。确定了位移突变标准的两个关键点,并指出参考的位移比值应取"纯"滑坡位移比值,该值越大,边坡滑动幅度越大,边坡向危险滑动状态变化。     

基于动态规划的水电站机组间负荷分配程序开发

水电站机组间负荷分配计算中的阶段变量与状态变量的个数越多,计算量就越大,且计算程序也越复杂,因而仅用手工计算很难做到。为此,利用动态规划法建立了水电站厂内经济运行流量分配数学模型。使用编程软件Visual Basic开发了水电站机组间负荷分配程序;该程序界面友好,使用方便,且能大大提高计算速度。应用该程序,对水电站机组间的负荷分配进行了实际应用计算,得出了经济效益最优的负荷分配方案。     

基于神经元PID的风力发电机组独立变桨控制

依据风力机空气动力学原理,设计了神经元PID控制器,实现了风力发电机组3个桨叶的独立变桨控制。通过神经元PID控制,计算出桨距角,并与Park变换得到的附加桨距角相加,作为独立桨距角的设定值。基于Fast软件平台,以2 MW变速变桨风力发电机组为验证对象,对提出的控制策略与传统的统一变桨距控制策略进行仿真比较。结果表明,相对于统一变桨距控制,所提出的方法能有效确保在额定转速下机组输出功率稳定,同时也能有效降低风力发电机组各零部件的疲劳载荷。     

EFFECT OF ESCAPE DEVICE FOR SUBMERGED FLOATING TUNNEL （SFT） ON HYDRODYNAMIC LOADS APPLIED TO SFT

This paper presents a potential approach to settle the problem of surviving major safety accidents in Submerged Floating Tunnel (SFT) that detachable emergency escape devices are set up outside SFT. The Computational Fluid Dynamics (CFD) technology is used to investigate the effect of emergency escape devices on the hydrodynamic load acting on SFT in uniform and oscillatory flows and water waves by numerical test. The governing equations, i.e., the Reynolds-Averaged Navier-Stokes (RANS) equations and standard turbulence equations, are solved by the Finite Volume Method (FVM). Analytic solutions for the Airy wave are applied to set boundary conditions to generate water wave. The VOF method is used to trace the free surface. In uniform flow, hydrodynamic loads, applied to SFT with emergency escape device, reduce obviously. But, in oscillatory flow, it has little influence on hydrodynamic loads acting on SFT. Horizontal and vertical wave loads of SFT magnify to some extend due to emergency escape devices so that the influence of emergency escape devices on hydrodynamic loads of SFT should be taken into consideration when designed.     

基于逆建模技术的淮河干流长台关-息县段入河污染负荷评估

以淮河上游长台关-息县段为研究对象,以2008年为算例,根据研究区域汇流特征,建立分布式源模型,基于贝叶斯统计方法进行逆建模,利用断面水质序列实测资料,测算区域入河污染负荷及主要水质因子降解系数。结果表明:淮河上游长台关-息县段NH3-N、COD入河污染负荷总量分别为1.7万t/a、8.9万t/a;受主要入流面源污染负荷季节性影响,NH3-N入河污染负荷为657.55～2 014.99 t/月,COD入河污染负荷为3897.73～13311.83 t/月;研究区域水体环境NH3-N、COD降解系数分别为0.356/d、0.202/d,NH3-N、COD负荷模拟值和实测值的相关系数分别为0.943、0.979。     

乌金峡水电站灯泡贯流机组初期运行问题分析

乌金峡水电站灯泡贯流式机组投运初期,因设计、制造、安装等诸多原因导致机组故障率较高,经过2 a多来的消缺、技改,机组运行可靠性、稳定性逐步提高,逐步取得了一定的效果。文章针对具体问题产生原因及相关改进措施予以阐述,并进行相关优化分析探讨。     

陕西电网建设抽水蓄能电站的初步探讨

抽水蓄能电站在电力系统中具有调峰填谷、调频、事故备用和黑启动等多种功能,成为现代电力系统中有效的调节工具。文章结合陕西电网规划期调峰能力研究成果,对陕西电网建设抽水蓄能电站进行了初步探讨。     

Movements with Lateral Constraint

Abstract

The literature on terminal control tasks and continuous tracking tasks suggests a possible model for tasks where the subject must guide a vehicle at his own speed along a course defined by a tolerance band. The model predicts a linear relationship between the average velocity and the width of the tolerance band. Throe experiments are described which simulate vehicle guidance by pencil-and-paper experiments for courses consisting of straight lines and circles. The predictions of the model were confirmed, suggesting that a general measure for the ease of control of a vehicle (or other controlled system) is possible using this technique.     

Eye-strain and changes in accommodation of the eye and in visual evoked potential following quantified visual load

The measurements were made of the muscular contractions and relaxations of accommodation (infrared optometer) and of visual evoked potential (VEP) (photic stimulation) before and after one hour's visual load, checking calculations (1800 questions/hour and 900 questions/hour). The results showed that the relaxation time in accommodation lengthened and the latency of the positive wave appearing at about 100 ms in VEP increased with the increase in visual load. In addition, the complaint rate for eye-strain was higher in the group given heavier visual work. In this group, there was no significant difference in amplitude of VEP before and after the visual task. The difference in the relaxation time before and after the visual task tended to be negatively correlated to the difference in amplitude of VEP and positively related to that in the latency. In the group given lighter visual work there were significant differences in the latency and the amplitude of VEP before and after the visual task, neither were correlated to the difference in the relaxation time. These results suggest that not only peripheral hypofunction but also the decrease of centrencephalic activity level may be responsible for the development of eye-strain caused by visual tasks.