Optimal Solutions for the Temporal Precedence Problem

Abstract. In this paper we refer to the Temporal Precedence Problem on Pure Pointer Machines . This problem asks for the design of a data structure, maintaining a set of stored elements and supporting the following two operations: insert and precedes . The operation insert (a) introduces a new element a in the structure, while the operation precedes (a,b) returns true iff element a was inserted before element b temporally. In [11] a solution was provided to the problem with worst-case time complexity O (log log n ) per operation and O(n log log n) space, where n is the number of elements inserted. It was also demonstrated that the precedes operation has a lower bound of Ω (log log n ) for the Pure Pointer Machine model of computation. In this paper we present two simple solutions with linear space and worst-case constant insertion time. In addition, we describe two algorithms that can handle the precedes (a,b) operation in O (log log d ) time, where d is the temporal distance between the elements a and b .     

预测井眼稳定性的力学化学耦合方法

在井眼力学稳定性评价的基础上，将硬脆性页岩水化后岩石强度等参数的变化规律用于页岩水化前后坍塌压力变化的对比分析，结果表明，地层坍塌压力当量密度随页岩水化程度的增加逐渐升高。给出了预测井眼稳定性的力学化学耦合方法，并将该方法应用于现场生产中，取得了较好的预测效果     

Synchronization models for multimedia presentation with user participation

This paper addresses the key issue of providingflexible multimedia presentation with user participation and suggests synchronization models that can specify the user participation during the presentation. We study models like the Petrinet-based hypertext model and the object composition Petri nets (OCPN). We suggest adynamic timed Petri nets structure that can model pre-emptions and modifications to the temporal characteristics of the net. This structure can be adopted by the OCPN to facilitate modeling of multimedia synchronization characteristics with dynamic user participation. We show that the suggested enhancements for the dynamic timed Petri nets satisfy all the properties of the Petri net theory. We use the suggested enhancements to model typical scenarios in a multimedia presentation with user inputs.     

整体式预热器U型管蒸汽发生器数学模型及动态模拟

本文针对整体式预热器Ｕ型管蒸汽发生器建立了热工数学模型并进行了动态模拟。该模型是一个２５阶、非线性、可移动边界模型。包括：一、二次侧的质量与能量平衡方程以及确定二次侧下降段流量的动量守恒方程。对所建立的模型利用Ｇｅａｒ方法作了蒸汽阀门开度阶跃１０％的瞬态模拟，所得结果和国外所公布的结果吻合得很好。由此可见。本文所建立的模型可以为这种蒸汽发生器的设计、运行、控制提供理论依据。     

Pullout tests of epoxy-coated reinforcement in concrete

The bond strength and slip of epoxy-coated reinforcing bars in concrete have been evaluated by carrying out single pullout and double pullout tests. In extended single pullout tests, slip measurements were made while tensile force was applied to reinforcing bars embedded in concrete. In double pullout tests, 20 cycles of load were applied at levels of steel stress between zero and 0·5 times characteristic steel strength. Strains were measured by electrical resistance strain gauges glued inside the bars. Both epoxy-coated and uncoated bars were used in the investigation, to obtain comparative results. The strain gradient along the bar was found to be less for the coated reinforcement. In general, the epoxy coating was found to increase slip in bond and thereby reduce the bond performance of coated bars.     

几种高强度钢腐蚀疲劳裂纹扩展行为的研究

本文研究了ＧＣ－４，３０ＣｒＭｎＳｉＮｉ２Ａ和３００Ｍ超高强钢的腐蚀疲劳裂纹扩展行为。考虑了环境，热处理制度，应力比和频率对裂纹扩展的影响。研究结果表明：腐蚀环境和热处理制度对疲劳裂纹扩展有显著影响。在侵蚀性环境中随频率降低，裂纹扩展大幅度上升，随应力比提高，环境影响加剧。利用扫描电镜对试样断口形貌进行了分析，并讨论了高强钢的腐蚀疲劳机理。     

峒室爆破CAD设计方法研究

本文对峒室爆破断面布药计算机辅助设计参数驱动方法进行了探讨围绕断面布药主要参数的变化，提出一种基于参数驱动的计算机辅助设计方法，利用ｗｉｎｄｏｗｓ操作系统下的动态数据交换特性，对断面布药进行布药参数优化，实现了交互调整布药，形成一套断面布的计算机软件，为工程爆破设计实现计算机提供了一种可行的方法。     

结构陶瓷的高温疲劳强度衰减理论

提出了陶瓷材料疲劳强度衰减理论并由此导出了各种疲劳关系式。建立了疲劳基本方程ｄσ＿ｒ／ｄ＿ｉ＝一Ａσ（ｔ）￣ｎｔ￣（－ｍ），得出了疲劳寿命公式Ｔ＝Ｍ（σ＿０－σ）／Ａσ￣ｎ（静疲劳时Ｍ＝１，连续增载疲劳时Ｍ＝ｎ＋１，循环疲劳时Ｍ＝（ｎ＋１）／（１＋Ｒ＋Ｒ￣２＋……＋Ｒ￣ｎ），逐级加载时，并导出不同疲劳方式下疲劳寿命间的关系。同时，用多种Ｓｉ＿３Ｎ＿４材料在高温中作了论证试验，结果与理论一致。     

微量Ag对CP276合金性能和组织的影响

研究添加不同含量的Ａｇ对ＣＰ２７６合金的拉伸性能和时效组织的影响。对拉伸强度、延伸率测试及透射电镜观察表明：０．１１ｗｔ％加入可促进Ｔ１相析出，使合金强度值升高；０．３５ｗｔ％Ａｇ的加入可在时效前期生成富Ａｇ、Ｍｇ的稳定的ＧＰ区，从而降低合金中Ｃｕ的固溶度，阻碍Ｔ１相析出，时效后期，ＧＰ区分解，生成大量Ｔ１相，使合金强度值显著升高。     

反向凝固法生产H90-钢-H90复合带

研究H90-钢-H90反向凝固复合过程中复合层厚度的变化规律以及复合带的组织和性能，探讨界面结合机理。结果表明：随着浸渍时间的增加，复合层的厚度变化经历了凝固生长、平衡相持和回熔3个阶段，钢带的预热温度越低，获得的最大复合层厚度越厚；H90复合层的组织为等轴晶粒，复合界面处Cu和Fe发生了扩散，而Zn未发生明显扩散，扩散层较薄，约为4μm；复合带的界面结合牢固；不同复合层厚度的复合带，其力学性能略有差异，但均达到GB5213——85所规定的F级深冲钢板的力学性能要求。