A review of the Effect of α/W ratio on fracture toughness （Ⅱ） experimental investigation in LEFM

In part I of this series, experimental investigation in EPFM （elastic-plastic fracture mechanics） had been discussed. In this paper, experimental investigation in LEFM （ linear elastic fracture mechanics） is given. Fracture toughness tests had been carried out on three different strength steels, using both through-cracked specimens with different α/W ratio and semi-elliptical cracked specimens with variable crack size and shape. Results show that the fracture toughness KIC increases with decreasing α/W when α/W 〈 0.3 for three-point-bend specimens, and that for α/W 〉 0.3, it is independent of α/W. Shallow crack specimens, both through-cracked and surface-cracked, gave markedly higher values than deeply notched specimens. However, the effect of crack shape on fracture toughness is negligible. Results also show that the LEFM approach to fracture is not tenable for design stresses where αc is often very small, far less than 2.5 （ KIC/σy）^2.     

城市轨道交通车辆段物业开发研究

通过对车辆段上盖物业开发必要性、方案可行性的分析,提出车辆段物业开发的几种主要模式:屋顶绿化、库上物业开发、落地物业开发、库上库下同时开发以及地下车辆段开发等,并相应列举了有代表性的车辆段开发案例 从确保轨道交通车辆段使用功能和运营安全的角度出发,着重分析上盖物业开发对车辆段的影响,从专业设计角度提出各方面的应对措施,一方面应尽量消除车辆段运营期间的振动、噪声,避免对车辆段上盖及周边开发造成负面影响;另一方面应最大限度地解决好车辆段的通风、采光问题,保证车辆段的使用功能和工作环境,尽可能降低物业开发对车辆段运营的不利影响 随着车辆段物业开发经验的不断积累,将早期开发遇到的各种问题在设计之初就协调解决好,使车辆段运营与物业开发良性共融,以期城市轨道交通车辆段物业开发建设日趋向土地集约型、环境友好型方向发展,有效促进城市轨道交通的可持续发展.     

基于网络文件共享服务的双机数据同步方法

介绍了以Windows网络文件共享服务为基础,并结合Ping、文件读写等技术,在双机热备系统中实现了数据同步的方法。该技术已在铁路调度指挥系统中得到应用。     

电磁式道岔融雪装置设计及干扰问题解决方案

提出了一种新型的道岔融雪方法,融雪装置采用新型电磁感应加热。对融雪装置的安装进行了详细设计,分析了道岔融雪装置存在的现场干扰问题,并提出了一系列的解决方案。     

宁波南站深基坑承压水抽水试验及数值分析

为降低深基坑工程设计与施工风险,对现场实际水文地质情况进行抽水试验,取得准确水文地质参数(承压含水层),建立深基坑降水三维渗流与沉降的数学模型,利用抽水试验期间监测数据对水文地质计算参数进行反演,进而对降水运行期间引起的渗流与地面沉降进行趋势预测。该抽水试验指导进行了基坑突涌性评价和实际工况运行控制,为降水运行提供依据,对类似工程的设计、施工及风险控制具有借鉴意义。     

一种新型调车信号机灯丝转换报警电路

针对传统调车信号机灯丝转换报警电路存在不能实时监测副灯丝状态、报警显示不能精确到具体故障灯位等缺点,提出一种新型调车信号机灯丝转换报警方法。采用单片机作为中心控制器、电压互感器为监测元件、电压跟随器和反相比较器组成断丝信号处理电路、RS-485总线为报警信号传输电路。该方法与传统电路相比增加了灯丝暖丝电路、故障灯位显示和故障信号处理电路,提高电路性能,降低电路成本,增强电路的实用性。     

Micro-Grinding Performance of Hard-Brittle Chip Materials in Precision Micro-Grinding Microgroove

The micro-structure on hard-brittle chip materials (HBCMs) surface can produce predominant functions and features. The micro-grinding with diamond wheel micro-tip is an efficient method to machine microstructure on HBCMs. However, different HBCMs and crystal orientation may have a significant influence on the micro-grinding performance. In this paper, the micro-grinding performance along different crystal orientation of HBCMs is investigated. First, a dressed 600^# diamond grinding wheel is used to micro-grind micro-structure on HBCMs. Then, the experiment of micro-grinding force test is completed. Finally, the quality of microgroove, the grinding ratio and the micro-grinding force are investigated and they are related to the crystal orientation of HBCMs. It is shown that the stronger resistance to the micro-crack propagation has the best quality of microgroove and the smallest grinding ratio. Moreover, the hardest single-crystal SiC has the best machinability and the micro-grinding force is 38.9%, 10.8% and 46.8% less than the one of sapphire, single-crystal Si and quartz glass, respectively. The direction to micro-grind easily is the crystal orientation 〈10\(\overline 1 \)0〉 for single-crystal SiC and sapphire. In addition, the micro-grinding force increases with the increase of the micro-grinding depth and feed rate and decreases with the increase of the grinding wheel speed.     

Lattice-based group signature with verifier-local revocation

Among several post quantum primitives proposed in the past few decades, lattice-based cryptography is considered as the most promising one, due to its underlying rich combinatorial structure, and the worst-case to average-case reductions. The first lattice-based group signature scheme with verifier-local revocation(VLR) is treated as the first quantum-resistant scheme supported member revocation, and was put forward by Langlois et al. This VLR group signature(VLR-GS) has group public key size of O(nm log N log q), and a signature size of O(tm log N log q log β). Nguyen et al. constructed a simple efficient group signature from lattice, with significant advantages in bit-size of both the group public key and the signature. Based on their work, we present a VLR-GS scheme with group public key size of O(nm log q) and signature size of O(tm log q). Our group signature has notable advantages: support of membership revocation, and short in both the public key size and the signature size.     

基于Multi-Agent的分布式计算机联锁系统研究

目前计算机联锁系统多采用集中式控制结构,为适应铁路大提速,以及信号系统智能化、网络化、分散化发展要求,讨论一种新型的基于Multi-Agent的分布式计算机联锁系统,实现了地理上和功能上的分散控制,有助于分散危险,增强系统的可靠性。在对该系统的体系结构进行探讨的基础上,着重对其通信机制与协作机制进行了研究。     

ZPW-2000A故障的分析处理

随着ZPW-2000A设备的迅速推广,其作为主要的区间闭塞信号设备在全路得到了普遍的应用,设备的正常运行对运输生产显得至关重要。当区间闭塞设备发生故障时,因站内距离区间的路途一般较远,加之判断、处理失误,往往造成故障延时过长,甚至上升为事故,严重影响运输生产。作为现场电务维护人员如何迅速判断、处理,使故障设备尽快投入正常使用值得认真思考。