An Efficient Reliability Evaluation Approach for Networks with Simultaneous Multiple‐Node‐Pair Flow Requirements

This paper proposes an efficient approach for reliability evaluation of multiple‐sources and multiple‐destinations flow networks. The proposed approach evaluates multiple node pair capacity related reliability. The proposed approach is a three‐step approach; in the first step, it enumerates network minimal cut sets. These network minimal cut sets are then used to enumerate subset cuts in the second step. Third step involves the evaluation of multiple node pair capacity related reliability from the enumerated subset cuts using a multi‐variable inversion sum‐of‐disjoint set approach. The proposed approach can be used for optimal network design as it combines multiple performance requirements, that is, flow requirements between multiple node pairs and network reliability, in a single criterion. Copyright © 2016 John Wiley & Sons, Ltd.     

Deformation,diffusion and ductility during creep – continuous void nucleation and creep-fatigue damage

Abstract

It is shown that the assumption of unit (negative) slope in the well known Monkman–Grant plot of time to failure against minimum creep rate is too restrictive. By acknowledging observed slopes in the range 0.8–1, a ductility–strain-rate relation is deduced where ductility decreases with reducing strain rate. This in turn has implications for the ductility exhaustion method as applied during stress relaxation in the dwell period of low cycle fatigue tests of austenitic steels at elevated temperature. The simple method is used to calculate the cyclic creep damage in typical tests on austenitic steels in the region 550–650 °C and is compared to other calculations as employed in the R5 high temperature assessment procedure. The assumption of a uniform nucleation rate of grain boundary voids with creep strain goes some way to predicting the slope of the ductility–strain-rate relation. Both the ‘unconstrained’ and ‘constrained’ (lower shelf) regions of void growth are discussed.     

Effect of multi-directional forging and ageing on fracture toughness of Al–Zn–Mg–Cu alloys

Strength, ductility and fracture toughness are the most important mechanical properties of engineering materials. In this work, an Al–Zn–Mg–Cu alloy was subjected to multi-directional forging (MF) and ageing treatment. Microstructural evolution was studied by optical and electron microscopy and strength, ductility and fracture toughness were researched. After MF, the dislocation density was increased and the microstructure was refined. The strength and fracture toughness were increased, while the ductility was decreased sharply. Without compromising the strength, the ductility was improved significantly after ageing. The fracture toughness was increased further. The coarse and discontinuously distributed grain boundary precipitates were found to be responsible for higher fracture toughness of the fine-grained structure Al–Zn–Mg–Cu alloy.     

基于SNS型双路约瑟夫森结阵驱动方法研究

根据SNS型双路约瑟夫森结阵的驱动原理以及结阵分段特点,提出了平衡三进制驱动算法,实现了双路约瑟夫森结阵偏置状态的快速计算。根据约瑟夫森结阵的偏置状态以及组合方式,采用节点电压法,准确合成了双路阶梯波交流量子电压的台阶电压值,最终实现了最小分辨率为2个结,有效位为15位的交流量子电压输出。双路交流量子电压互测实验结果表明,合成交流量子电压的最大误差为0.06 μV,双路信号同步性测试实验中,两个通道的相位差为-0.01 μrad,证明了合成双路交流量子电压具有较高的幅值准确度和相位同步性。     

基于非对称往返测距的海洋无线传感网络节点定位算法

提出一种新的基于非对称往返测距的海洋无线传感网络节点定位(LMARR)算法,该算法利用节点间非对称的接收与发送测距信息的时间差,推算出节点间海水声速以及未知节点与其邻居参考节点之间的距离,将三维距离信息转换成二维,运用最小二乘法完成定位计算。与SWN和ARTL算法相比较,仿真结果表明:LMARR算法能有效地提高节点定位的精度,特别是在深度为20～120m海水声速持续变化的区域,定位精度比SWN算法提高了20%,比ARTL算法提高了33%;此外,LMARR算法还具有较高的稳定性。     

Automatic PV Grid Fault Detection System with IoT and LabVIEW as Data Logger

Fault detection of the photovoltaic (PV) grid is necessary to detect serious output power reduction to avoid PV modules’ damage. To identify the fault of the PV arrays, there is a necessity to implement an automatic system. In this IoT and LabVIEW-based automatic fault detection of 3 × 3 solar array, a PV system is proposed to control and monitor Internet connectivity remotely. Hardware component to automatically reconfigure the solar PV array from the series-parallel (SP) to the complete cross-linked array underneath partial shading conditions (PSC) is centered on the Atmega328 system to achieve maximum power. In the LabVIEW environment, an automated monitoring system is developed. The automatic monitoring system assesses the voltage drop losses present in the DC side of the PV generator and generates a decimal weighted value depending on the defective solar panels and transmits this value to the remote station through an RF modem, and provides an indicator of the faulty solar panel over the built-in Interface LabVIEW. The managing of this GUI indicator helps the monitoring system to generate a panel alert for damaged panels in the PV system. Node MCU in the receiver section enables transmission of the fault status of PV arrays via Internet connectivity. The IoT-based Blynk app is employed for visualizing the fault status of the 3 × 3 PV array. The dashboard of Blynk visualizes every array with the status.     

中国爆破安全网

中国爆破安全网是由中国工程爆破协会主办的涉爆行业信息专业网 ,开通于 2 0 0 3年 4月。该网是民爆器材生产流通主管部门、使用部门和公安机关实施联网监控和规范化管理的有力工具 ,最主要的功能是为涉爆行业管理部门和从业单位提供一个功能完善的管理和办公平台。该网的开通 ,有利于民爆器材生产、销售、购买、使用流向监控制度的贯彻实行。文章介绍了网络的组成、建设原则 ,并给出了中国爆破安全网网络拓扑图     

Network Invulnerability Enhancement Algorithm Based on WSN ClosenessCentrality

Wireless Sensor Network (WSN) is an important part of the Internet of Things (IoT), which are used for information exchange and communication between smart objects. In practical applications, WSN lifecycle can be influenced by the unbalanced distribution of node centrality and excessive energy consumption, etc. In order to overcome these problems, a heterogeneous wireless sensor network model with small world characteristics is constructed to balance the centrality and enhance the invulnerability of the network. Also, a new WSN centrality measurement method and a new invulnerability measurement model are proposed based on the WSN data transmission characteristics. Simulation results show that the life cycle and data transmission volume of the network can be improved with a lower network construction cost, and the invulnerability of the network is effectively enhanced.     

某直升机主减传动系统振动能量传递特性研究

基于超单元方法和节点有限元法建立考虑轴系柔性和机匣柔性的齿轮-转子-机匣耦合系统动力学模型,推导了各类齿轮副的啮合关系,以直升机主减速器为研究对象,通过振动响应试验验证了模型的有效性。从振动能量的角度研究耦合和不耦合柔性机匣两种情况下,齿轮副作为振动激励源时系统模型中产生的多级齿轮激励现象和作为传递结构时对振动能量的传递特性。研究结果表明:耦合机匣后,各级齿轮振动能量贡献占比的极值点数量减少,与目标点相邻的齿轮激励源在该节点处振动能量贡献占比整体上升,不相邻的齿轮激励源在该节点处能量贡献占比整体下降;齿轮啮合刚度和啮合阻尼比的增加会提高齿轮副对振动能量的传递能力,啮合误差的增加会降低其对振动能量的传递能力,而耦合柔性机匣会放大齿轮啮合特性对其振动能量传递能力的影响。