石板尾隧道施工过程的动态仿真数值模拟研究

文章针对石板尾隧道浅埋偏压段台阶分部法施工的特点,采用有限元方法对隧道某一断面动态开挖过程进行数值模拟分析,以配合和指导隧道新奥法施工。通过将数值模拟结果与实测结果进行比较,验证了该数值模拟方法是切实可行的,可供隧道新奥法施工借鉴。     

经济型两相步进电机控制系统的设计

本文介绍基于STC89C52单片机,驱动芯片采用L9110的经济型两相步进电机控制系统,配合软件速度调节算法,满足目前广泛使用的两相混合式步进电机的控制需要,同时采用监控芯片和电源隔离等方式,保证系统稳定可靠运行。     

Snap behaviour in the upheaval buckling of subsea pipelines under topographic step imperfection

Pipelines exposed to high temperature and high pressure with a topographic step imperfection are susceptible to the phenomenon of upheaval buckling potentially leading to a hazard for the structural integrity of the pipeline. To analyse this problem we derive analytical upheaval buckling solutions and obtain the locations of maximum displacement and maximum axial compressive stress. We also analyse the typical post-buckling behaviour and its dependence on step height, axial soil resistance and wall thickness. The difference in behaviour between a pipeline with step imperfection and one with a symmetric prop imperfection is discussed. Our results show that a pipeline with a step imperfection is more prone to upheaval buckling than a perfect pipeline. For sufficiently small step heights the pipeline may suffer a snap-back instability under decreasing thermal loading, raising the possibility of hysteretic snap behaviour under cyclic thermal loading (for instance caused by periodic start-ups and shut-downs). The snap-back buckling disappears for large enough step height and the minimum critical temperature difference decreases with increasing step height and wall thickness or with decreasing axial soil resistance. The maximum compressive stress decreases with increasing step height and axial soil resistance or with decreasing wall thickness. A pipeline with step imperfection is safer than one with a symmetric prop imperfection.     

基于TB6560步进电机驱动系统的设计

步进电机具有惯量低、定位精度高、无累积误差、控制简单等特点,电机驱动系统有基于L297、TA8435等芯片的设计方案,这些驱动系统单相驱动电流一般为2A左右,无法驱动更大功率步进电机。本文介绍了基于东芝公司TB6560芯片步进电机驱动系统设计方案,该芯片功耗低、内部集成双全桥MOSFET驱动;最高耐压可达40V,单相输出最大电流为3．5A（峰值）;具有整步、1／2、1／8、1／16等细分设置;芯片内置温度保护,温度大于150℃时自动切断所有输出;具有过流保护功能。     

拱座台阶基础基底应力计算

依据基础变形协调条件和文可尔假定,提出了拱座等受水平荷载作用的台阶形基础底面和背面应力计算方法。     

Optimal multi-step toll design under general user heterogeneity

This paper studies the optimal multi-step toll design problem for the bottleneck model with general user heterogeneity. The design model is formulated as a mathematical program with equilibrium constraints (MPEC), which is NP-hard due to non-convexity in both the objective function and the feasible set. An analytical method is proposed to solve the MPEC by decomposing it into smaller and easier quadratic programs, each corresponding to a unique departure order of different user classes. The quadratic programs are defined on a polyhedral set, which makes it easier to identify a local optimum. Importantly, each quadratic program is constrained by a set of linear feasibility cuts that define the presence of each user class in the arrival window. We prove that the proposed method ensures global optimality provided that each quadratic program can be solved globally. To obviate enumerating all departure orders, a heuristic method is developed to navigate through the solution space by using the multipliers associated with the feasibility cuts. Numerical experiments are conducted on several small examples to validate the proposed methodology. These experiments show that the proposed heuristic method is effective in finding near-optimal solutions within a relatively small number of iterations.     

电动式调节阀流量参数的评价及应用

介绍了电动式调节阀的流量参数评价及应用方法,即通过试验评价,确定电动式调节阀自盲区当量步数、泄漏当量步数及流出系数。利用这些参数,对流体管道进行闭环控制,可以实现对流体的流量调节。     

台阶对路堑边坡稳定性的影响分析

阐述了强度折减边坡稳定性分析方法的基本原理,应用强度折减法进行路堑边坡的稳定性验算,分析了设置台阶对路堑边坡稳定性的影响,并对台阶的宽度及位置对路堑边坡稳定性的影响做出分析,确定了稳定性最高的台阶宽度及位置,为带台阶路堑边坡设计提供了参考。     

季节性冻土地区牵引变电所接地方案研究

在季节性冻土地区,地面冻土层的土壤电阻率随季节性因素变化很大,将严重影响接地网的安全性能,此时采用参数合适的复合接地网将比水平接地网具有更好的降阻效果及安全性能。以哈牡铁路亚沟牵引变电所为例,采用CDEGS软件进行仿真计算的方法,分析在季节性冻土地区影响接地网安全性能的四个因素(水平均压带网格大小;垂直接地极数量、长度及位置),得出采用水平均压带与垂直接地极相结合的复合接地网方案为工程最佳方案。     

新型科考船发电系统控制策略研究

以某新型综合物探科考船为对象,对其先进发电系统及其控制策略进行研究,介绍发电系统的结构、特点和调频调载策略,并给出具体控制方法。以瞬态阶跃负载为着眼点,提出优化发电机组配置策略和控制程序流程,最后通过实船系泊试验验证其控制策略和方法的可靠性。