对英国防结构倒塌设计规范中拉结力法的研究

英国规范中采用的拉结力法被认为是一种有效地防止建筑物发生连续倒塌的方法。用于提高钢框架建筑整体性的拉结力法是以在结构承重柱遭到破坏处梁板通过悬链线作用进行荷载重分配,但对于这一荷载重分配机制的可靠性至今还不是很明确。采用＂抽柱法＂,通过NIDA-NAF软件对某10层的简单钢框架算例进行数值模拟。分析得出：对于传统的简单框架,结构柱失效处梁中产生的拉结力将远远大于英国钢结构设计规范的规定,其相应的抗倒塌安全系数仅为0.46。最后提出一种半刚性连接设计法,该方法能有效地提高结构抗连续倒塌的能力。     

城市高压天然气管道的通球、清管和水压试验与干燥

通过对城镇、输油输气施工验收规范的对比，介绍了城市高压天然气管道施工过程中，进行通球、试压、吹扫及干燥各环节的施工方案、施工方法、工程中遇到的问题及解决方案。     

A ferry-assisted solution for forwarding function in Wireless Sensor Networks

For sure, Wireless Sensor Networks (WSNs) are becoming an ultimate part of next generation mobile networks. They are a master piece for Ubiquitous computing. Indeed, they sustain development of numerous paradigms/ technologies such as distributed ambient intelligence, context-awareness and future mobile networking (e.g., B4G and 5G). Battery life remains one of the crucial problems to handle. In this article we propose an infrastructure-based topology using mobile ferries (mobile micro-base stations). In real life, a ferry could be robot, bus, tram, train or any other engine scrutinizing periodically a given area. Yet, message ferries are moving along concentric annulus and may collect data generated by the static sensors (could be classic sensors, smart meters, wearable devices, etc.) randomly distributed on given area. Next, transmissions are performed in a ferry-to-ferry forwarding scheme till arriving at the sink. Considered ferries could sense themselves data and therefore behave as mobile sensors allowing better awareness on the area state [1], [2], [3]. Our scheme could also assist Machine-to-Machine communications to increase the network lifetime, with potentially some cognitive-radio capabilities and opportunistic detection and access. Our proposal can easily be integrated in a smart-city for better interaction and green communications. Next, we present a queueing model (queues with finite capacity) to handle the generated traffic and to analyze the behavior of mobile ferries. We provided a close-form expression for both end-to-end throughput and end-to-end delay. The main objective of this work is to improve the energy efficiency of the cognitive sensors by asking cognitive sensors to not care about forwarding data of each other except for urgent data, this latter point is out of the scope of the paper. These static sensors will only care about data sensing, which will reduce their individual energy consumption.     

基于COBS串行通信协议的自适应最优帧长分析

针对工业数据通信中通信不及时与可靠性低的问题,本文基于COBS(Consistent Overhead Byte Stuffing)算法构建一种工业数据通信协议,解决了数据通信中的同步问题,缩短了帧的长度,节约了比特资源。分析在工业噪声干扰下,该协议数据帧出错的概率与帧长、误码率之间的定量关系,给出已知误码率的情况下计算最优帧长的公式。在此基础上,利用协议可变帧长的特点制定自适应最优帧长策略,可进一步提高通信的效率。通过仿真与数值分析,说明该方法可以有效提高工业通信的效率与可靠性。     

Convergence Behavior of NLMS Algorithm for Gaussian Inputs: Solutions Using Generalized Abelian Integral Functions and Step Size Selection

This paper studies the mean and mean square convergence behaviors of the normalized least mean square (NLMS) algorithm with Gaussian inputs and additive white Gaussian noise. Using the Price’s theorem and the framework proposed by Bershad in IEEE Transactions on Acoustics, Speech, and Signal Processing (1986, 1987), new expressions for the excess mean square error, stability bound and decoupled difference equations describing the mean and mean square convergence behaviors of the NLMS algorithm using the generalized Abelian integral functions are derived. These new expressions which closely resemble those of the LMS algorithm allow us to interpret the convergence performance of the NLMS algorithm in Gaussian environment. The theoretical analysis is in good agreement with the computer simulation results and it also gives new insight into step size selection.     

Effects of ion irradiation on Zr52.5Cu17.9Ni14.6Al10Ti5 (BAM-11) bulk metallic glass

Bulk metallic glasses are intriguing candidates for nuclear applications due to their inherent amorphous structure, but their radiation response is largely unknown due to the relatively recent nature of innovations in bulk metallic glass fabrication. Here, microstructural and mechanical property evaluations have been performed on a Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ bulk metallic glass (BAM-11) irradiated with 3 MeV Ni⁺ ions to 0.1 and 1.0 dpa at room temperature and 200 °C. Nanoindentation hardness and Young's modulus both decreased by 6–20% in samples irradiated at room temperature, with the sample irradiated to 1.0 dpa experiencing the greatest change in mechanical properties. However, no significant changes in properties were observed in the samples irradiated at 200 °C, and transmission electron microscopy showed no visible evidence of radiation damage or crystallization following ion irradiation at any of the tested conditions. These results suggest that BAM-11 bulk metallic glass may be useful for certain applications in nuclear environments.     

水性环氧底漆在城轨车辆上应用的难点

重点介绍了城轨车辆用水性环氧底漆的涂装工艺、技术要求,探讨了水性环氧底漆防腐性能、施工工艺、配套性3个技术难点。     

基于数字孪生的高动态生产系统联动决策方法

个性化需求引发的随机高动态干扰加大了生产系统高效运作的难度。如何面向随机高动态干扰,构建在线联动决策方法,实现对生产系统的精准决策以支持各生产单元的高效协同成为关键挑战。以模块化生产的多单元联动运作为研究对象,基于数字孪生构建多单元联动决策架构、机制和模型。通过实时精准映像与动态虚拟仿真,实现高动态生产系统的在线协同运作和自主联动决策。最后以某大型化工企业的多单元联动运作为例,验证所提方法可以显著降低系统运作总成本,实现复杂多单元生产系统在高动态干扰下的最优化运作。