井筒中钻柱系统非线性螺旋屈曲稳定性分析

针对钻井过程中钻柱工作载荷或钻压超过某一临界值导致钻柱失稳现象,建立了钻柱非线性稳定性问题的分析模型,用数值分析的方法对整个钻柱系统的非线性屈曲过程进行了有限元仿真分析,解释了钻柱的失稳机理以及钻柱自重、钻压、转速、扭矩和井斜角等因素对钻柱屈曲的影响规律,研究了钻柱在井筒中发生屈曲时的位移、受力状况和各种工况下的失稳临界载荷。结果表明，在相同条件下钻柱螺旋屈曲临界载荷随井斜角增大而增大,呈非线性变化;临界载荷随扭矩的增大而减小,井斜角较大时临界载荷减小的幅度较小。对钻柱在井筒中的非线性屈曲行为研究和钻具组合设计的优化具有一定的参考价值。     

Managing Electricity Peak Loads in Make‐To‐Stock Manufacturing Lines

In this article, we study the control of stochastic make‐to‐stock manufacturing lines in the presence of electricity costs. Electricity costs are difficult to manage because unit costs increase with the total load, that is, the amount of electricity needed by the manufacturing line at a certain point in time. We demonstrate that standard methods for controlling manufacturing lines cannot be used and that standard analytic results for stochastic manufacturing lines do not hold in the presence of electricity costs. We develop a control policy that balances electricity costs with inventory holding and backorder costs. We derive closed‐form expressions and analytic properties of the expected total cost for manufacturing lines with two workstations and demonstrate the accuracy and robustness of the policy for manufacturing lines with more than two workstations. The results indicate that avoiding electricity peak loads requires additional investment in manufacturing capacity and higher inventory and backorder costs. Our approach also applies to companies which aim at reducing their carbon emissions in addition to their operating costs.     

The sensitivity of job mix and load capacity bottlenecks on inventory and due date performance in a manufacturing system

Based on a benchmark job-lot manufacturing system a simulation study was carried out to compare the performance of just-in-time (JIT) shop control system Kanban with conventional job-shop control procedures. The shop control policies were tested under a good manufacturing environment and the effects of job mix and load capacity bottlenecks on various shop control policies were tested. From the simulation results, it is inferred that there are shop control procedures that perform better than the Kanban in a job shop. It has been observed that even with adequate capacity, bottleneck areas surface due to fluctuations in the shop load. Kanban is not appropriate in such a situation because capacity bottlenecks can significantly reduce the ell'ectiveness of a pull system. The disparateness in the processing requirements for jobs can seriously undermine the performance of the shop. This is the type of shop environment where the shop control procedures will be most effective. Although Kanban came out best when the load capacity bottlenecks and the disparateness of the job mix were removed, the selected shop control variable combinations closely approximated the Kanban result. Although many features of JIT can be implemented in any system, companies trying to adopt JIT should remember that Kanban requires a rigid system intolerant of any deviation.     

扩能运输对朔黄铁路桥梁的影响及维管对策研究

随着朔黄铁路扩能运输的快速推进，单元列车轴重从21 t逐步提升到25 t，年运量即将突破2亿t，荷载与疲劳效应的增加对既有铁路桥梁特别是中小跨径桥梁的安全运营要求越来越高。分析重载运输对桥梁的主要影响因素，采取桥梁检查、安全状态评估、快速维修加固、加强维修质量验收相结合等系列应对措施，提出桥梁科学维管的对策，为建立桥梁安全运营保障体系奠定基础。     

基于支持向量机的中长期电力负荷预测研究与应用

采用一种新的机器学习方法——支持向量机,建立了中长期电力负荷预测模型.阐述了支持向量机的基本内容,对影响电力负荷诸多因素的样本集进行了标准化处理和主因素分析(PCA).采用Libsvm训练了数据集,并与灰色预测GM(1,1)模型、多元线性回归模型、模糊ISODATA聚类模型和BP神经网络进行对比.结果表明,此算法有更高的准确性,可为电力负荷预测提供有效依据.     

BP模型的改进算法及其在负荷预测中的应用

分析了BP模型学习算法——累积误差进传播算法在接近极小点时收敛速度变得异常缓慢的原因,并通过对连接权值的调整量引入权重系数,提出了一种改进的BP模型学习算法,大大加快了收敛速度,提高了收敛性。还利用提出的改进算法对某省中期负荷进行了预测,算例结果表明了该算法的有效性。     

轻型桥墩稳定性的非线性分析

轻型桥墩是桥梁工程中常用到的一种桥墩。本文利用柔性桥墩失稳临界荷载非线性分析原理，分析了墩顶位移在非线性阶段对桥墩稳定性的影响。     

Investigation into the subjectively perceived significance of various strain dimensions for informational load

The currently available uni- or multidimensional inquiry techniques employed in determining the psychological strain resulting from informational load only permit recording of the strain which occurs in each case according to particular aspects. A prerequisite for the targeted employment of such methods is therefore knowledge about the relevant strain foci. The present investigation is based on the assumption that such strain foci can be determined via an analysis of a person's perception of the relevance of particular strain dimensions. The experimental subjects in the present investigation used the method of paired comparison to repeatedly assess five strain dimensions (motor, visual, temporal, mental, and memory strain) which had been preselected using a task analysis on the basis of their significance for the strain occurring during the performance of simple arithmetical tasks (concentration performance test). In the further evaluation it was possible to identify two subgroups which were homogeneous in terms of their respective assessments of the significance of the strain dimensions. They differed above all in the importance they attached to the temporal strain. The present findings permit the conclusion that strain foci can be determined via an assessment of the significance of strain dimensions.     

基于眼动认知负荷实验的知识地图可获取性研究

知识地图的可获取性是近年来越来越被重视的评价指标。采用E-Prime呈现视觉刺激材料,ASL眼动仪采集30名被试者的眼动实验数据,考察被试者的首视点在不同界面以及隐含分区的分布,用实验的手段证实了信息出现在界面的不同位置带给使用者的认知负荷不同。针对信息密集的知识地图,合理降低认知负荷是增强知识地图可获取性的有效途径。     

成本倒逼，利益引导——合理运用排污权制度消解经济与环境的矛盾

针对重载运输过程中出现的既有线钢桁梁桥高强螺栓节点螺栓断裂问题,以长东黄河桥为工程背景,采用ANSYS软件建立了带螺栓的实际节点板局部有限元模型,对其在轴力作用下的传力性能进行了研究,并分析了螺栓缺失所造成的影响。结果表明：长列高强螺栓接头在轴力作用下各排传力比呈马鞍型分布;在螺栓连接的计算中应考虑一排内螺栓传力的不均匀性;螺栓缺失后只对局部范围内的螺栓传力比有影响,影响最大的是其相邻的两排螺栓,但若传力比较大的螺栓排缺失数量达到一定程度后,极易使剩余螺栓所受剪力超过其抗剪承载力而出现剪切破坏。