Investigation of path requirements in a water distribution network

One approach in addressing reliability aspects of water distribution networks is to require two paths from a source to a demand point. The problem faced in these approaches is to define the paths and to what degree there is, or should be, dependency, i.e., common links in those paths. This study attempts to examine the implications associated with these dependency issues. Using an optimization formulation which includes minimum path constraints, various path requirements ranging from a single path to two distinct, independent paths (to each demand node) are investigated.     

Operational transfer path analysis

One of the tools used to study the NVH behaviour of a system is the transfer path analysis. It aims to identify the operational forces and the propagation paths of the vibrations and is especially interesting in the case when the system is composed of different subsystems. The classical techniques identify the transfer paths when the system is disassembled. This way one eliminates flanking transfer paths. Yet it is very time-consuming and the boundary conditions are not correct anymore. The presented method makes it possible to identify the transfer paths without disassembling the system. The advantages are that the overall testing time is reduced and that the real boundary conditions are present. In this article the theory will be reviewed and it will be validated using data generated by finite element simulations.     

First-Principles Calculation of the Third Virial Coefficient of Helium

Knowledge of the pair and three-body potential-energy surfaces of helium is now sufficient to allow calculation of the third density virial coefficient, C(T), with significantly smaller uncertainty than that of existing experimental data. In this work, we employ the best available pair and three-body potentials for helium and calculate C(T) with path-integral Monte Carlo (PIMC) calculations supplemented by semiclassical calculations. The values of C(T) presented extend from 24.5561 K to 10 000 K. In the important metrological range of temperatures near 273.16 K, our uncertainties are smaller than the best experimental results by approximately an order of magnitude, and the reduction in uncertainty at other temperatures is at least as great. For convenience in calculation of C(T) and its derivatives, a simple correlating equation is presented.     

《舰艇艉部纵向激励传递特性分析》

采用有限元/边界元方法对艉部的声振特性进行研究。首先建立了包含主推进系统在内的有限元模型，分析流固耦合下结构的振动，并利用边界元技术进行结构水下声辐射预报。然后根据传递路径分析方法，对纵向激励下艉部的传递路径进行分析排序。结果显示，纵向激励下，推力轴承基座是艉部振动的主要传递路径。在确定了潜艇艉部的主要振动传递路径后，在主要传递路径上采取隔振措施，以达到减振降噪的目的。研究表明，改变推力轴承的刚度和基座结构形式，对艉部的减振降噪有一定作用。     

两探测面结构激光粒度仪的接收光路设计

为了扩大激光粒度仪测量的动态范围,采用同轴的两组接收透镜,将两个硅光电探测器阵列分别置于前组透镜的后焦面和两组透镜的组合后焦面上,对测量信号进行组合后用改进共轭梯度法处理数据。通过优化光路结构,采用两组双胶合透镜和探测环半径均不大于45mm的探测器可满足同时测量5～3500μm粒径的要求。     

Finding rectilinear least cost paths in the presence of convex polygonal congested regions

This paper considers the problem of finding the least cost rectilinear distance path in the presence of convex polygonal congested regions. We demonstrate that there are a finite, though exponential number of potential staircase least cost paths between a specified pair of origin–destination points. An upper bound for the number of entry/exit points of a rectilinear path between two points specified a priori in the presence of a congested region is obtained. Based on this key finding, a “memory-based probing algorithm” is proposed for the problem and computational experience for various problem instances is reported. A special case where polynomial time solutions can be obtained has also been outlined.     

Crack initiation and growth path under multiaxial fatigue loading in structural steels

In real engineering components and structures many accidental failures occur due to unexpected or additional loadings, such as additional bending or torsion. There are many factors influencing the fatigue crack paths, such as the material type (microstructure), structural geometry and loading path. It is widely believed that fatigue crack nucleation and early crack growth are caused by cyclic plasticity. This paper studies the effects of multiaxial loading paths on the cyclic deformation behaviour, crack initiation and crack path. Three types of structural steels are studied: Ck45, medium carbon steel, 42CrMo4, low alloy steel and the AISI 303 stainless steel. Four biaxial loading paths were applied in the tests to observe the effects of multiaxial loading paths on the additional hardening, fatigue crack initiation and crack propagation orientation. Fractographic analyses of the plane orientations of crack initiation and propagation were carried out by optical microscope and SEM approaches. It is shown that these materials have different crack orientations under the same loading path, due to their different cyclic plasticity behaviour and different sensitivity to non-proportional loading. Theoretical predictions of the damage plane were conducted using the critical plane approaches, either based on stress analysis or strain analysis (Findley, Smith–Watson–Topper, Fatemi–Socie, Wang–Brown–Miller, etc). Comparisons of the predicted crack orientation based on the critical plane approaches with the experimental observations for the wide range of loading paths and the three structural materials are shown and discussed. Results show the applicability of the critical plane approaches to predict the fatigue life and crack initial orientation in structural steels.     

A bootstrapped switch employing a new clock feed-through compensation technique

Nonlinearity caused by the clock feed-through of a bootstrapped switch and its compensation techniques are analyzed. All kinds of clock feed-through compensation configurations and their drawbacks are also investigated.It is pointed out that the delay path match of the clock boosting circuit is the critical factor that affects the effective-ness of clock feed-through compensation. Based on that, a new clock feed-through compensation configuration and corresponding bootstrapped switch are presented and designed optimally with the UMC mixed-mode/RF 0.18μm 1P6M P-sub twin-well CMOS process by orientating and elaborately designing the switch MOSFETs that influence the delay path match of the clock boosting circuit. HSPICE simulation results show that the proposed clock feed-through compensation configuration can not only enhance the sampling accuracy under variations of process, power supply voltage, temperature and capacitors but also decrease the even harmonic, high-order odd harmonic and THD on the whole effectively.     

振动传递路径的功率流传递度灵敏度分析

摘 要：基于振动的功率流理论和一般概率摄动法，研究振动传递路径的功率流传递概率的度量问题，提出了频域内振动传递路径系统的路径功率流传递度的新概念和方法。在考虑工程中的不确定因素以后，在频域内清晰地描述了振动传递路径系统的路径功率流传递度。研究功率流传递度对这些不确定因素的敏感程度，估计参数变化的效果，从而指导系统结构的优化。     

分层复杂网络的鲁棒性研究

文章针对述分层复杂网络的框架结构，阐述了物理层与逻辑层之间的关系；描述负载定义；分析了负载的重新分配问题及其在不同的路径重新选择对策下，对分层复杂网络鲁棒性的影响。通过对典型分层复杂网络舰艇编队作战系统的仿真发现：面对攻击，逻辑层的影响要大予物理层，路径重新选择对策和负载都对分层复杂网络的攻击效果产生重要影响。