Collocation methods: More efficient procedures for applying collocation

In recent years, new and more effective procedures for applying collocation have been published. This article is devoted to present a revision of this subject and complement its developments. From the general theory two broad approaches are derived, which yield the direct and the indirect TH-collocation methods. The former approach had not been published before, and it is a dual of the indirect approach. In particular, second order differential equations of elliptic type are considered and several orthogonal collocation algorithms are developed for them. In TH-collocation, the approximations on the internal boundary and in the subdomain interiors are completely independent. This yields clear computational advantages that are illustrated through the construction of such algorithms. In the implementations presented, three dimensional problems are included. In passing, single-point-collocation methods that have been the subject of several recent publications are revised.     

The reduction of chromite in the presence of silica flux

The mechanism and kinetics of the carbothermic reduction of a natural chromite was studied at 1300–1500 °C in the presence of silica. Thermogravimetry, X-ray diffraction (XRD) analysis, energy dispersive X-ray analysis (EDAX) and metallography were the experimental techniques used. Silica affected the reduction at and above 1400 °C. A two stage reduction mechanism was established. The first stage, up to about 40% reduction, is primarily limited to iron metallization and zoning is observed in partially reduced chromites. In this stage silica does not interfere with the reduction. The second stage is mainly confined to chromium metallization and formation of a silicate slag alters the reduction mechanism. Ion-exchange reactions between the reducible cations (Cr³⁺ and Fe²⁺) in the spinel and the dissolved cations (A1³⁺ and Mg²⁺) in the slag allow further reduction. Due to the very high driving force for the diffusion, the overall process is shifted toward a more chemical reaction controlled mechanism. A generalized rate equation was then applied to the individual metallization curves of iron and chromium from which respective rate constants and diffusion coefficients were derived. The rate constants were in the range 6.74 × 10⁻⁴–9.01 × 10⁻⁴ s⁻¹ for iron and 7.20 × 10⁻⁴–8.50 × 10⁻⁴ s⁻¹ for chromium reduction at 1500 °C in the presence of silica. At 1500 °C, the corresponding diffusion coefficients were in the range 3.14 × 10⁻⁸–4.78 × 10⁻⁸ m²/s for Fe²⁺ diffusion in the spinel and in the range 1.70 × 10⁻⁸–2.03 × 10⁻⁸ m²/s for the respective diffusion of Cr³⁺. Finally using Arrhenius plots activation energies were derived.     

泰安天地广场游人行为研究

作为泰山西路登山之始的泰安天地广场,具有游客集散、市民游憩休闲、泰山文化展示等职能.利用实地观察、抽样调查问卷及访谈等研究方法,对广场游人使用状况进行了评价,并针对问题提出了相应的改进性建议.     

装配式集装箱结构体系优化及节点性能

为建立装配式集装箱结构的标准体系并掌握其力学性能,以一个典型的集装箱建筑方案为基础,以规范要求为评价指标,对其进行了6种不同结构方案的静力分析和抗震分析,研究了设置横梁立柱、辅助拉杆等构造措施对结构性能的影响,结果表明:该集装箱建筑体系对风荷载较为敏感,构件截面主要由风荷载控制,地震作用不起控制作用,增加局部立柱和横梁对于提高集装箱建筑的抗侧移刚度作用不明显,而设置侧向拉杆则能有效加强结构抗侧移刚度.最后采用多尺度分析方法对结构所采用的装配式集装箱建筑节点进行了模拟分析,结果表明该节点在结构各种工况下均能保持良好的工作状态,可为类似集装箱建筑的节点选用提供技术参考.     

计算机网络信息安全影响因素及防范浅析

在计算机网络信息技术成为社会进步助力的同时,网络信息安全也面临着严重的威胁。本文简要分析了影响计算机网络信息安全的主要因素,并就这些问题对网络信息的安全防范进行了探讨。     

宽垄沟灌垄上覆膜条件下土壤水分运移试验研究

为研究宽垄沟灌时灌水前后且有覆膜条件下水分在垄沟间的运移及再分布,采用对比试验方法,在大棚内模拟宽垄沟灌垄上栽培条件和灌水方案,采用中子仪进行水分观测。试验数据显示,采用垄上覆膜,灌水后垄沟水分的侧向入渗,表现出明显的侧向运移变化。垄背剖面两观测点表层,在灌水后144 h（6 d）,覆膜条件下分别达到田间持水量的80%...     

基于遗传算法的流水线车间工序调度问题研究

流水线作业是现代生产线最常用的技术.在流水线生产过程中,某种产品需要很多工序按照一定的顺序才能完成,根据生产计划每台设备可以为同一工件做相对应的工序,而根据实际情况有的工人可以熟练操作多个工序.因此建立好车间加工工序与人员之间的优化配置就显得尤为重要,它可以缩短工期,增加经济效益.基于遗传算法给出人员与工序的最优调度决策,并采用一个简单的例子进行了仿真验证.     

拉筋对两层两跨钢-混凝土组合框架结构抗震性能的影响

该文开展了2榀2层2跨缩尺比例为2/5的水平往复荷载下方钢管混凝土柱-钢混凝土组合梁平面框架滞回性能试验研究,分析了柱端拉筋强柱构造对钢-混凝土组合框架结构抗震性能的影响。运用有限元软件ABAQUS建立该平面框架有限元模型,在试验验证的基础上开展柱端拉筋等效配箍率对组合平面框架抗震性能影响规律的研究。分析结果表明：柱端拉筋降低了钢管与混凝土之间的滑移、约束混凝土并加强了钢管对混凝土的约束作用,进而提高了柱端抗弯承载力与耗能能力,间接改变了梁柱线刚度比和抗弯承载力比,挖掘了钢梁的耗能潜力;柱端拉筋强柱构造措施有效提高了钢-混凝土组合平面框架结构的刚度、承载力和耗能能力,分别达70%、20%和50%以上。     

无线传感器网络簇级拓扑演化模型研究

复杂网络理论研究表明,复杂系统的容错能力不仅仅存在于具有冗余组件的系统之中;而且也同样存在于具有无标度(scale-free)特征的网络之中;文章借助于复杂网络理论和偏好依附机制提出一种无线传感器网络簇级拓扑演化模型;拓扑动态分析表明,该模型能够很好地体现无线传感器簇间的拓扑生长过程,由该模型演化成的无线网络拓扑具有无标度网络的性质,所以该拓扑模型具有很强的容错性。     

平面设计Photoshop教学的探索与研究

计算机平面设计行业作为知识型的服务产业,在竞争日益激烈的商业社会中发挥着举足轻重的作用。Photoshop(以下简称PS)是一门实践性很强的课程,使用传统的教学方法无法达到满意的教学效果。在教学方法的探索与实践中,采用抛砖引玉引导学习法、案例教学法、情景教学法、先成果后教学法等多种教学方法,引发学生的学习兴趣,培养学生的模仿和创新能力。同时,采用分阶段教学方法,使学生更好地掌握该软件,进一步提高教学质量。