Smart Behavior of Carbon Fiber Reinforced Cement-based Composite

The electrical characteristics of cement-based material can be remarkably improved by the addition of short carbon fibers. Carbon fiber reinforced cement composite (CFRC) is an intrinsically smart material that can sense not only the stress and strain, but also the temperature. In this paper, variations of electrical resistivity with external applied load, and relation of thermoelectric force and temperature were investigated. Test results indicated that the electrical signal is related to the increase in the material volume resistivity during crack generation or propagation and the decrease in the resistivity during crack closure. Moreover, it was found that the fiber addition increased the linearity and reversibility of the Seebeck effect in the cement-based materials. The change of electrical characteristics reflects large amount of information of inner damage and temperature differential of composite, which can be used for stress-strain or thermal self-monitoring by embedding it in the concrete structures.

High-Performance and Multifunctional Cement-Based Composite Material

Concrete is a continuously evolving material, and even the definition of high-performance concrete has changed over time. In this paper, high-performance characteristics of concrete material are considered to be those that support the desirable durability, resilience, and sustainability of civil infrastructure that directly impact our quality of life. It is proposed that high-performance material characteristics include tensile ductility, autogenous crack-width control, and material “greenness.” Furthermore, smart functionalities should be aimed at enhancing infrastructure durability, resilience, and sustainability by responding to changes in the surrounding environment of the structure in order to perform desirable functions, thus causing the material to behave in a manner more akin to certain biological materials. Based on recent advances in engineered cementitious composites (ECCs), this paper suggests that concrete embodying such high-performance characteristics and smart multifunctionalities can be designed, and holds the potential to fulfill the expected civil infrastructure needs of the 21st century. Highlights of relevant properties of ECCs are provided, and directions for necessary future research are indicated.

A comprehensive layered approach for implementing internet of things-enabled smart grid:A survey

The current power grid confronts severe challenges in satisfying customers'demands.Fast transition to the much more flexible power grid enriched with renewable energies,micro-grid,and distributed energy resources has been considered as a straightforward solution to the customers’high demand.Using smart equipment and renewable energies,electric power generation and storage through the power grid domains will be facilitated,which enables bi-directional energy and information flows.The power grid with such enhanced features is called Smart Grid(SG).Controlling and managing the diverse sets of variables in the SG requires precise measuring,monitoring,communicating,and analytic systems which increase the complexity of the grid.This complexity is the main barrier to the realization of the SG up to now.The emergence of the Internet of Things(IoT)simplifies monitoring,communications,and data processing among smart things to connect to anything in the world.This motivates the SG stakeholders and researchers to proceed with the best way to exploit the IoT technologies in the SG.In this survey paper,we summarize various efforts in this regard to highlight the advantages of the IoT-enabled SG and its probable gaps.To this end,a comprehensive layered approach has been proposed in this paper to classify various applications of the IoT technologies in the SG.Investigating IoT opportunities in each architecture layer facilitates the role of each technology and its relationship with other technologies.Also,open issues and future measures for the realization of IoT-enabled SG have been discussed in the paper.

Embedded TLS 1.2 Implementation for Smart Metering & Smart Grid Applications

Digital networked communications are the key to all Internet-of-things applications, but especially to smart metering systems and the smart grid. In order to ensure a safe operation of systems and the privacy of users, the transport layer security （TLS） protocol, a mature and well standardized solution for secure communications, may be used. We implemented the TLS protocol in its latest version in a way suitable for embedded and resource-constrained systems. This paper outlines the challenges and opportunities of deploying TLS in smart metering and smart grid applications and presents performance results of our TLS implementation. Our analysis shows that given an appropriate implementation and configuration, deploying TLS in constrained smart metering systems is possible with acceptable overhead.

基于联邦学习的医疗数据共享与隐私保护

针对医疗数据共享中的“数据孤岛”问题,提出一个基于联邦学习的医疗数据共享与隐私保护方案。利用差分隐私技术对各个医疗机构的本地模型参数添加噪声,解决参数泄露的问题;全局模型通过编写的智能合约聚合并上传区块链,避免过度依赖中心聚合服务器;针对提出的隐私保护方案对差分隐私噪声的添加位置进行实验和讨论。实验结果表明,该方案可以在去中心化的同时保护数据的隐私,达到了较高的准确度,找到了合适的噪声添加位置。

智能电网中基于密钥生成的物理层安全技术研究

电网作为国家重要基础设施,其安全性至关重要。无线通信在智能电网的发展中体现了重要作用,是实现智能电网泛在环境感知、嵌入式计算、网络通信等系统工程的重要保障。然而,在突破传统物理连接设备限制的同时,无线电磁传播的开放性也给智能电网带来了严峻的安全挑战。为了确保智能电网无线终端间的通信安全,文中提出了一种基于密钥生成的增强型物理层安全策略。该策略综合利用电网设备的物理标识、无线信道的随机特性以及时间戳功能,既可以实现“一次一密”的轻量级加密效果,又能够有效鉴别合法网络设备,从通信安全和设备识别两个角度为智能电网提供高效可靠的安全通信保障。仿真实验结果表明,文中所提出的物理层密钥生成方法可以充分保障无线通信安全,在实际应用中可以有效对抗窃听者的窃听攻击,同时针对恶意干扰攻击也具有很强的鲁棒性。

面向多业务场景的区块链数据存证系统

针对区块链存证系统多需对不同业务场景的存证内容开发特定智能合约及对关系型数据存证操作不便的问题,提出了面向多业务场景的智能合约分层架构、设计模式及基于集合论的智能合约对关系型数据的操作方法。通过对不同智能合约间及智能合约同数据表间的解耦,提高了智能合约代码的可扩展性,并能有效支持以键值对数据库为底层存储的区块链对关系型数据库表及数据的存证操作,实现对已有政务业务数据的存证。实验结果表明,提出的存证方案具备可行性和有效性,并可大幅减少智能合约的开发工作量。

有源智能反射面辅助的无线安全网络能效优化

由于“双重衰落”效应,使得含有IRS系统的链路传输过程面临两段较大的链路损耗,为了解决该效应,引入有源IRS辅助系统安全。基于此提出了物理层安全领域下有源IRS辅助系统安全保密能量效率优化问题,并考虑用户保密速率约束、基站发射功率约束、IRS功率约束以及反射原件放大系数约束。为了解决该多变量耦合的非线性优化问题,采用交替优化技术、Dinkelbach方法、SDR技术联合处理。对比有源IRS、无源IRS以及无IRS辅助三种方案,仿真结果显示,所提出的有源IRS辅助方案能够达到更好的保密能效,从而使系统安全性得到保证。

基于无人机遥感技术的电力巡检方案研究

随着我国电力基础设施的快速发展和电网规模的不断扩大,传统的人工巡检方式已难以适应现代电力系统的高效运维需求。本研究基于“一体三翼”的思想,提出一套多层次、多维度的无人机电力巡检方案,借助顶层设计达成主体建设目标,然后通过“设备层—数据层—平台层”三层协同巡检方式实现对电力设施的智能化、精细化巡检。

继电保护技术在智能电网中的应用分析

大量新能源接入电网对电网运行安全、稳定提出了更高要求。在此背景下,继电保护作为主流的智能电网保护方案,对保障智能电网安全可靠运行有着重要意义。继电保护可以有效解决电网故障问题,并发出故障警报。运维人员可在短时间内发现故障情况,快速处理故障问题,缩短停电时间,降低电力公司损失。对于电力公司而言,如何正确应用继电保护技术,保证智能电网安全、可靠运营,是需要重点考虑的问题。基于此,分析了智能变电站结构与特点,并探究了继电保护技术在智能电网中的应用方案以及过程层组网方式,旨在保障智能变电站安全、稳定运行。

基于CRSN的智能电网资源跨层分配算法改进

由于用户的增多,导致智能电网的频谱资源紧张,严重影响了智能电网运行的稳定性,同时也降低了供电能力。为了解决这一问题,提出基于CRSN的智能电网资源跨层分配算法改进研究。将认知无线传感器网络(Cognitive Radio Sensor Networks,CRSN)引入智能电网中,通过认知节点感知智能电网主用户的频谱资源,找出可用的空闲频谱。借助图论着色将智能电网资源进行跨层分配建模,利用改进猫群算法求取分配模型最优解,得到智能电网资源跨层分配方案。实验结果表明,所研究算法求解到的方案是全局最优解,能够实现智能电网频谱资源的跨层分配。

全维智能可重构无线通信系统设计与实现

【目的】通过探讨智能无线环境和智能可重构物理层的应用需求和发展趋势,构建全维智能可重构无线通信模型和体系结构。【方法】首先,将物理层参数和无线传播环境等无线通信链路的各个维度纳入智能可重构范畴,解决了由于硬件条件与无线环境限制引起的传统通信技术难以实现更高维调控自由度的问题。然后,利用优化和定制物理层与无线环境所需的感知数据,提出一种允许根据不同无线环境和PHY参数在人工智能算法之间动态切换的全维可重构结构。【结果】仿真和分析结果表明,该系统在误码率和可达速率等指标上均优于传统方法。【结论】将智能可重构的思想延伸到无线传播环境和整个通信链路的各个维度,构建了高效的全维智能可重构无线通信系统,可以为6G移动通信系统提供工程应用指导。

Salt freezing resistance improvement of cement-based materials incorporated with calcined layered double hydroxide

Salt freezing damage has severe impacts on durability of cement-based materials(CBMs).Calcined layered double hydroxide(CLDH),as an efficient environmental-friendly adsorption material,can impart excellent salt freezing resistance to CBMs.In this work,salt freezing resistance improvement of CBMs incorporated with CLDH was experimentally evaluated by chloride binding capacity,mass loss rate,relative dynamic elastic modulus,setting time,compressive strength,and micro structure tests.Beside these,the salt freezing damage model was established to effectively express the quantitative relationship between influencing factors and evaluation indexes of the salt freezing resistance of CBMs.Results show that CLDH can reconstruct its original layered structure to form reconstructed layered double hydroxide(RLDH).RLDH combines with chloride ions to form RLDH-Cl recrystallization,which can improve chloride binding capacity and pore structures of CBMs to relieve the salt freezing damage.The salt freezing damage model indicates that the suitable CLDH content can evidently alleviate the salt freezing damage,which facilitates the quantitative analysis of the effect of CLDH on the salt freezing resistance of CBMs.

基于220 kV智能变电站的网络信息流分析及应用

智能变电站增加了过程层设备,对应的网络结构也发生了相应变化。通过梳理220 kV智能变电站的网络架构及各个间隔的信息流向图,并结合某一智能变电站的异常进行应用,得出了智能变电站的网络信息流处理方法,为现场解决GOOSE、SV断链等异常提供了参考。

基于分布式同步方法的智能变电站采样值组网技术

通过对国内外智能变电站过程层采样值传输组网方式的研究,重点对点对点传输方式和交换机组网传输方式加以分析,总结分析了常见组网方式的特点,并针对其不足,提出了智能变电站分布式同步采样值组网技术方案。与原组网方案相比,新方案的主要长处在于不依赖全局同步系统,从而进一步提高了过程层网络的可靠性。该方案的研究成果已应用于苏州110kV沈巷变电站智能化改造。

智能变电站过程层组网方案分析

智能变电站是智能电网建设的重要环节,过程层网络则是智能变电站的重要基础,直接关系到全站数据采集和开关控制的可靠性和实时性。总结分析了智能变电站建设过程层设备所涉及的网络报文,针对数据采样和通用面向对象变电站事件(GOOSE)通信的不同组合方式所形成的网络方案进行了对比分析,讨论了采用IEEE 1588标准对时的三网合一组网方案和混合模式组网方案,针对500kV等级变电站过程层组网方式进行了实例讨论,最后介绍了虚拟网络划分所涉及的虚拟局域网(VLAN)和组播注册协议(GMRP)技术。

智能变电站过程层冗余组网模式及网络延时累加技术研究

当前智能变电站过程层采用双网架构,IED设备的处理器同时处理双网数据,存在处理器负荷高的问题。SV采用光纤直连传输方式、存在布线复杂、IED设备光口多、成本高、装置发热量大、信息共享困难及链路无法监视等各种问题。同时GOOSE采用网络传输方式,过程层网络与光纤直连方式并存,结构不清晰问题。针对高可靠性无缝冗余协议(High Reliablity Seamless Redundant Protocol,HSR)和并行冗余协议(Parallel Redundant Protocol,PRP)的智能变电站过程层组网进行了研究,并基于该组网基础上进行了HSR和PRP的延时累加技术研究及测试。该研究为将来在国内智能变电站进行推广应用此技术提供了坚实的理论分析和测试结果参考数据。

基于OPNET的智能变电站通信建模与组网研究

智能变电站通信组网方式决定了其通信性能,现阶段尚缺乏有效的智能变电站通信网络性能分析模型与手段,对此,基于OPNET软件平台搭建了适用于智能变电站网络性能分析的过程层、间隔层、站控层设备通信模型,并在此基础上,对智能变电站的组网方式开展研究。设置不同网络场景,通过对过程层网络与站控层网络分别组网方式以及采样值、通用面向对象的变电站事件、制造业信息规范网"三网合一"的方式进行仿真,获取不同组网方式的网络性能。仿真结果表明,两种组网方式均能适用于不同状态下的网络性能要求,能够应用于智能变电站的通信组网。

智能变电站采样值组网分布式同步技术及应用

在分析常规采样值组网技术的基础上,提出了一种智能变电站过程层采样值组网分布式同步技术。该技术的具体思路为:每个采样值输出设备内具有1个IEEE 1588主时钟,该时钟无需接受外同步,按本地晶振频率运行;采样值接收设备中各从时钟对应跟踪相应的主时钟,在接收到采样值输出设备的采样值后,利用回溯插值算法实现采样数据的同步。与常规的采样值组网方式相比,该技术省去了全局外同步系统,可靠性更高。现场测试结果表明,所提技术可以保证采样的同步性,性能稳定。

智能结构中光纤智能夹层系统的研究

根据光纤自诊断系统模块化、集成化要求,提出并研制了光纤智能夹层。这种智能夹层易于制作,且制作过程中光纤传感器完好率达100%,智能夹层的埋入对复合材料拉伸强度影响较小。在此基础上,对光纤智能夹层试件进行了轴向拉伸试验。试验表明,在一定应变范围内,单膜交错光纤中光强-应变之间具有良好的线性关系,可以在埋入复合材料之前进行标定。利用智能夹层内的光纤传感器网络和先进的信息处理技术,可以建立结构损伤主动、在线和实时监测系统。