碎石RPC抗拉性能试验研究

RPC是一种新型的超高性能水泥基复合材料,因其具有超高的抗压性能和远高于普通混凝土的抗拉性能而受到广泛关注。通过试验对碎石RPC的抗折性能和轴心抗拉性能进行了研究,以得到各组分对碎石RPC抗拉性能的影响。     

超载条件下混合式基层沥青路面层底拉应力研究

分析半刚性基层的缺点,提出混合式基层沥青路面结构,并给出超载条件下轴载计算参数。采用Bisar3.0软件,计算在完全连续、部分连续和完全光滑三种界面条件下混合式基层沥青路面各结构层层底拉应力。结果表明,在完全连续条件下沥青层不会产生拉应力,路面内部拉应力最大值出现在半刚性基层底部;当沥青层与半刚性基层之间的接触条件由完全连续向完全光滑转变时,沥青层层底和半刚性基层层底的拉应力逐渐增大;在三种界面条件下,沥青面层表面轮隙中心处都出现较大的拉应力。     

Improvements of elevated temperature strength and creep resistance of Mg-12Zn-4Al based alloy with calcium addition

A series of Mg-12Zn-4Al-0.3Mn (ZA124) based alloys with additions of calcium have been prepared and their microstructure and properties have been investigated. The results show that Mg-12Zn-4Al-0.3Mn alloy consists of the ??-Mg matrix and block quasicrystal and exhibits excellent creep resistance compared to commonly used AZ91 alloy. A small amount of calcium addition to the ZA124 based alloys increased the yield strenghth at both ambient and elevated temperatures as well as creep resistance, although the ductility decreased slightly. Microanalysis indicated that the addition of calcium decreased the quasicrystalline phase and caused the formation of some lamellar precipitates of Al₂Mg₅Zn₂ with orthorhombic crystal structure. This Ca-containing Al₂Mg₅Zn₂ phase with high stability straddled the grain boundaries and strengthened grain boundaries by inhibiting crack propagation during creep tests at elevated temperature.     

高强度快递需求区域移动仓库选址算法

研究了高强度快递需求区域移动仓库选址问题的特点,以移动仓库总建设规模最小为目标函数,以区域需求量和仓库服务能力为约束条件,提出了基于多粒度集合覆盖问题的相遇蚁群算法。将需求点虚拟成粒子,利用K-means算法对粒子聚类,在划分好的粒子群里得到移动仓库备选点,分别应用传统的蚁群算法和相遇蚁群算法进行实例验证。计算结果表明:运用传统的蚁群算法,运算时间为12.714 4s,最优解个数为13,最差解个数为15,平均解个数为13,解的正确率为79%;运用相遇蚁群算法,运算时间为3.806 4s,最优解个数为12,最差解个数为13,平均解个数为12,解的正确率为98%,移动仓库选址方案的建设数量为12,有10个备选移动仓库是多余的。     

西堠门大桥钢箱梁安装

西堠门大桥受桥址恶劣的风环境与复杂的海域环境以及梁段超重等不利因素影响,钢箱梁安装难度大.文中介绍了钢箱梁安装的关键技术与相关施工过程,可供类似工程借鉴.     

大气折光系数修正与高精度三角高程测量

根据三角高程测量原理与误差传播定律及分配原则,推导了大气折光系数反演模型。利用高低棱镜同时对向观测方法,对一个测段上具有偶数务边的闭合网进行观测,消除了仪镜高测量带来的误差。提出了利用闭合网高差闭合差为0及影响参数比例误差的分配原则,采用周期图法求定各方向大气折光系数改正值的方法,提高了三角高程测量精度与可靠性。通过对某大型悬索桥施工监控中塔顶一点的三维坐标分量24h连续监测,其空间几何关系和塔柱的饶度变化完全满足理论变化特征;塔柱各断面应力实测值与空间状态理论应力计算值标准偏差在0．015内,大大优于设计精度要求,验证了此测量方法的正确性。     

水泥混凝土面板脱空的有限元模型分析研究

水泥混凝土路面在实际使用过程中,由于车辆荷载的重复作用,板下基础将产生塑性变形累积而导致面层脱空,地面水沿着接缝下渗而积聚在脱空的空隙内,在车轮荷载作用下变成压力水而形成唧泥,导致水泥混凝土面板局部脱空而产生附加应力,在行车荷载作用下,面层应力将会剧增,从而导致水泥混凝土面板的断裂.通过数值分析对路面板角脱空形成机理以及在行车荷载与脱空耦合导致面层板的断裂机理进行分析,同时讨论了路面厚度、路基土和基层模量变化对路面结构的应力状态的影响.     

驾驶员适应性研究述评

驾驶员适应性的检测对减少交通事故起着至关重要的作用,通过对驾驶员适应性研究现状的介绍以及对驾驶员适应性的指标和标准化的分析．提出驾驶员适应性存在的问题并展望其未来的发展趋势,可为驾驶员适应性研究提供参考。     

公共交通一体化策略措施应用研究

根据广州市公共交通一体化存在的问题,提出公共交通一体化的策略措施,包括线网构建、设施衔接、运营管理等方面,并进行实例分析,验证其实施效果,这对有效实现公共交通系统内部元素的整合及其与外部的有机融合具有重要意义。     

Numerical simulation to reliability analysis of fault-tolerant repairable system

In the traditional method for the reliability analysis of fault-tolerant system, the system structure is described by means of binary decision diagram (BDD) and Markov process, and then the reliability indexes are calculated. However, as the size of system augments, the size of state space will increase exponentially. Additionally, Markov approach requires that the failure and repair time of the components obey an exponential distribution. In this study, by combining dynamic fault tree (DFT) and numerical simulation based on the minimal sequence cut set (MSCS), a new method to evaluate reliability of fault-tolerant system with repairable components is proposed. The method presented does not depend on Markov model, so that it can effectively solve the problem of the state-space combination explosion. Moreover, it is suitable for systems whose failure and repair time obey an arbitrary distribution. Therefore, our method is more flexible than the traditional method. At last, an example is given to verify the method.