Efficient Implicit Finite-Element Hydrodynamic Model for Dam and Levee Breach

This technical paper presents the development and application of a pseudo-transient continuation (PTC)– inspired flow model for the simulation of dam and levee failure. The unstructured, implicit, Petrov-Galerkin finite-element model relies on computed residuals to automatically adjust the time-step size. The implicit time integration, together with the automatic time-step size selection through PTC, makes the model computationally efficient. The model is verified and applied to several analytic and real-world test cases that exercise model behavior and accuracy for several critical, transcritical, and subcritical flows. The result is an efficient and accurate prediction of both the speed and depth of shock waves as the dam-break flow passes over initially dry and wet land.     

Acoustic failure analysis of windows in buildings

Poor acoustic insulation of building façades is largely influenced by the component assembly of the window and by the installation of the window in the wall. For the first, a poor gasket design and poor gasket installation during the window assembly will usually lead to whistle noises inside the rooms, especially next to busy roads. For the latter, the choice and installation of obturating materials in the cavity between the window and the wall may lead to a decrease in acoustic insulation in a wider range of frequencies. Consequently, the objectives of this investigation are to evaluate different methods to detect acoustical failures in openable windows in walls, and to present an efficient approach to optimise the sound insulation of a façade.By means of experimental measurements on a standard openable window, two different and complimentary approaches are compared to evaluate the acoustical quality and failures of the gaskets and the final setup of the window. More specifically, the first type of measurement is based on a standard sound insulation measurement of the façade according to ISO 140-5, and the second consists of ultrasonic measurements.The acoustic impact of the cavity between the window and the wall is evaluated in the laboratory according to ISO 140-3. For this research two different and most common materials are used to obturate the gap: polyurethane foam and mineral wool. The impact of these different types of materials is evaluated against different types of glazing.On the one hand side, standard sound insulation measurements enable to evaluate the quantitative impact of different parameters governing acoustical failures, such as discontinuity, incorrect placement and wrong selection of both gaskets and obturating material. On the other hand, ultrasonic measurements enable a quick qualitative assessment that is very efficient to determine the exact position of the acoustic leaks in the façade.Finally, a combined use of standard and ultrasonic measurements is proposed to deliver an efficient approach to detect acoustical failures of windows. The ultrasonic approach is a quick and cost-effective way to instantly track workmanship deficiencies of a window on site, whereas the standard measurements are more time consuming but needed to guarantee the performance of a building element.     

自动化仪表安装要求及常见故障分析

文章通过对现场反应温度、物料流量、容器压力、控制阀门、液位料位等控制仪表,安装是否符合规范及蓝图要求,是否满足工艺操作与检测,来分析系统调试与生产过程中现场仪表故障原因。     

Analytical modelling of the electromechanical behaviour of surface-bonded piezoelectric actuators including the adhesive layer

The behaviour of a piezoelectric actuator is strongly affected by the bonding condition along the interface between the actuator and the host structure. The current paper represents an analytical study of the static effect of the mechanical and geometrical properties of the adhesive layer on the coupled electromechanical behaviour of a thin piezoceramic actuator bonded to an elastic medium. An actuator model with an imperfect adhesive bonding layer, which undergoes a shear deformation, is proposed to simulate the two dimensional electromechanical behaviour of the integrated system. Analytical solution of the problem is provided by solving the resulting integral equations in terms of the interfacial stress. Numerical simulation is conducted to study the effect of the bonding layer upon the actuation process. The effect of interfacial debonding on the response of the layered structure and on the interlaminar strain and stress transfer mechanisms is discussed.     

卧式车床车削振动主动控制系统设计与实验研究

分析了车削加工时振动的一般模型,并根据不同车削振动来源建立了它们各自的振动力与振动位移关系模型.针对机床运动失衡下的周期性振动,提出了一种振动主动控制方法.设计了基于PID控制算法与超磁致执行器的车削振动主动控制系统.通过数字仿真与现场试验,表明所设计的车削振动主动控制系统能有效地降低车削振动,提高车削加工精度.     

基于复杂事件处理技术的连锁故障诊断

连锁故障难以预测,如果能在连锁故障过程的初期,诊断或辨识出连锁故障的开始,将有助于阻止或削弱故障的进一步发展.为此,文中将复杂事件处理技术应用于连锁故障的辨识,建立了分层的复杂事件处理和关联分析模型.针对连锁故障典型模式和初始阶段触发保护隐藏故障这2种连锁故障模式,对连锁故障初始阶段的相继故障事件进行了时间、空间以及电气的关联聚合分析,建立了事件之间不同的关联规则.算例分析结果表明该方法实用有效.     

计及维修因素的牵引变电站电气主接线可靠性分析

牵引变电站的可靠性直接关系到铁路运输安全,其电气主接线的可靠性是牵引变电站可靠性研究的重要内容。为此建立了牵引变电站电气主接线在不可维修和可维修情况下的2种可靠性模型,给出了2种不同模型下的平均无故障工作时间（TMTBF）和平均首次故障前工作时间（TMTTFF）的计算方法。计算结果表明：牵引变电站电气主接线可维修时,T...     

北川110kV智能变电站监控系统调试工作研究与分析

针对北川110 kV智能变电站监控系统调试工作,阐述了北川智能变电站的特点和调试的各个阶段的工作内容。并对智能变电站监控系统调试工作中间遇到的一些故障和问题进行了分析,并归纳提出了解决方案。     

对抗社会网络级联失效的减缓策略研究(英文)

Cascading failures are common phenomena in many of real-world networks,such as power grids,Internet,transportation networks and social networks.It's worth noting that once one or a few users on a social network are unavailable for some reasons,they are more likely to influence a large portion of social network.Therefore,an effective mitigation strategy is very critical for avoiding or reducing the impact of cascading failures.In this paper,we firstly quantify the user loads and construct the processes of cascading dynamics,then elaborate the more reasonable mechanism of sharing the extra user loads with considering the features of social networks,and further propose a novel mitigation strategy on social networks against cascading failures.Based on the realworld social network datasets,we evaluate the effectiveness and efficiency of the novel mitigation strategy.The experimental results show that this mitigation strategy can reduce the impact of cascading failures effectively and maintain the network connectivity better with lower cost.These findings are very useful for rationally advertising and may be helpful for avoiding various disasters of cascading failures on many real-world networks.     

Actuation Spaces Synthesis of Lower-Mobility Parallel Mechanisms Based on Screw Theory

The lower-mobility parallel mechanism has been widely used in the engineering field due to its numerous excellent characteristics.However,little work has been devoted to the actuator selection and placement that best satisfy the system's functional requirements during concept design.In this study,a unified approach for synthesizing the actua-tion spaces of both rigid and flexure parallel mechanisms has been presented,and all possible combinations of inputs could be obtained,laying a theoretical foundation for the subsequent optimization of inputs.According to the linear independence of actuation space and constraint space of the lower-mobility parallel mechanism,a general expres-sion of actuation spaces in the format of screw systems is deduced,a unified synthesis process for the lower-mobility parallel mechanism is derived,and the efficiency of the method is validated with two selective examples based on screw theory.This study presents a theoretical framework for the input selection problems of parallel mechanisms,aiming to help designers select and place actuators in a correct and even optimal way after the configuration design.