SMA490BW耐候钢手工焊与自动焊接头低温性能对比

以CRH2型动车组转向架专用材料SMA490BW耐候钢为母材,分别制备手工焊接头和自动焊接头,对比分析两种接头在不同温度条件下,尤其是低温条件下的强度、韧性之间的差异,开展了两种接头在不同温度条件下的余高试样疲劳试验。试验结果表明:自动焊接头在平均抗拉强度、平均屈服强度方面稍优于手工焊接头,在焊缝区和焊接热影响区的冲击功要明显劣于手工焊接头;在相同温度条件下,两种接头的疲劳性能相当。     

A robust control strategy for a grid-connected multi-bus microgrid under unbalanced load conditions

The increasing presence of inverter-based distributed generation (DG) units in microgrid application requires control methods that achieve high performance not only during normal operating conditions, but also under unbalanced conditions. These conditions can occur permanently due to distribution of unbalanced loads on the three phases of the microgrid. This paper proposes a robust control strategy for a grid-connected multi-bus microgrid containing several inverter-based DG units. Each of the DG units can supply a combination of balanced and unbalanced local loads. The proposed control strategy employs an adaptive Lyapunov function based control scheme to directly compensate the negative-sequence current components caused by unbalanced loads in some part of microgrid; and a sliding mode based control scheme to directly regulate the positive-sequence active and reactive power injected by DG units to the microgrid. The control method proposed in this paper is shown to be robust and stable under load disturbances and microgrid parameter uncertainties even in the presence of nonlinear and time-variant unbalanced loads. The effectiveness of the presented controller is validated through time-domain simulation studies, under the MATLAB/Simulink software environment.     

线性MMDS固态功率放大器

介绍了ＳＭ２５２７－４１Ｌ线性ＭＭＤＳ固态功率放大器，其性能类似于１００Ｗ的补偿型ＨＰＡ，而功耗更低、体积更小。     

基于SM9的匿名广播加密方案

广播加密允许数据拥有者通过不安全的公开信道将数据安全地发送给一组指定的用户, 只有组内用户（授权用户）利用自身私钥才能正确解密密文, 恢复出明文数据, 不在组内的用户（非授权用户）即使合谋也无法获取数据内容。标识加密是一种非对称加密体制, 可利用能够唯一标识用户身份的任意字符串作为用户的公钥, 消除了传统公钥体制中用于绑定用户公钥的证书。匿名标识广播加密不仅能充分继承标识加密的优点实现多用户数据的安全共享, 而且能有效保护接收者的身份信息。本文以国产商用标识密码算法SM9为基础, 采用多项式技术构造了首个基于SM9的匿名广播加密方案。方案具有与SM9加密算法相同的私钥生成算法, 用户私钥由一个群元素组成。方案的密文由(n+3)个元素组成, 与接收者数量(n)线性相关, 解密仅包含一次双线性对计算。基于q类型的GDDHE困难假设, 在随机谕言器模型中证明方案在静态选择明文攻击下具有不可区分的安全性且满足接收者匿名性。比较分析表明本文方案的计算开销和通信代价与现有高效匿名标识广播加密方案是可比的。最后, 对方案进行编程实验, 在相同安全级别下, 本文方案对比其他方案具有较优的密文长度, 实验结果表明本文方案是可行的。     

基于SM2的无证书盲签名方案

针对现有无证书盲签名方案计算复杂度过高的问题,基于国密算法SM2,提出了一种高效无证书盲签名方案,该方案不需要双线性对操作。基于椭圆曲线离散对数问题(ECDLP)的困难性,在随机预言模型下对该方案进行了形式化分析,能够对类型Ⅰ和类型Ⅱ攻击均具有可证明的安全性。与现有无证书盲签名方案进行性能对比,分析结果表明,该方案计算开销远低于其他几种同类型的方案。     

SM4算法门限掩码方案设计与实现

侧信道分析已严重威胁到密码算法应用安全,为提高SM4算法抵御侧信道分析的能力,提出一种门限掩码方案。首先,完成对SM4算法S盒的复合域分解;其次,基于二共享设计门限掩码方案,使用随机数将S盒输入进行二共享拆分,通过复合域运算和S盒门限掩码进行电路重构,并基于S盒复用降低硬件开销;最后进行线性层操作后将两个输出结果通过异或完成去掩码操作。对SM4算法门限掩码方案的FPGA实现仿真结果和安全性测试结果表明,本掩码方案能够有效抵抗CPA攻击,实现面积相对较低。     

基于区块链的电子医疗记录安全共享

针对电子医疗记录（EMR）共享面临的数据提供商集权化、患者数据管理显被动、互操作效率低、恶意传播等问题,提出一种基于区块链的电子医疗记录安全共享方法。首先,基于商用密码SM2数字签名算法提出一种更加安全高效的泛指定验证者签名证明（UDVSP）方案;然后,设计具有上传、验证、检索、撤销等功能的智能合约,构造基于区块链的电子医疗记录安全共享系统;最后,通过安全性分析和性能分析论证UDVSP方案和共享系统的可行性。安全性分析结果表明,所设计的UDVSP方案满足可证明安全性。性能评估结果表明,与现有常用的UDVSP/UDVS方案相比,节省至少87.42%的计算开销和93.75%的通信代价。区块链智能合约原型系统的仿真结果进一步论证了共享系统的安全性和高效性。     

基于B/S架构的工业主机卫士软件设计与实现

为了保护工业现场主机软件运行环境安全,设计了一款基于B/S架构的工业主机软件。该软件可对进程和外设进行实时监控,在发现主机存在异常风险行为时能及时告警并阻断。工业主机卫士主要是基于白名单可执行文件控制,还包括U盘、网卡等外接设备管控,可多位一体地保障主机安全。根据国密SM3算法生成唯一指纹信息,形成各条白名单规则。相对于传统的主机卫士软件,该软件创新性地采用B/S架构,主机卫士软件系统和管理平台通过Redis消息中间件通信。用户可以通过统一的管理平台Web界面同时对数十台甚至百台的主机卫士进行运维管理,实时查看各主机节点的安全事件告警信息,统一配置主机白名单规则,一键下发主机安全策略,处理告警风险行为,保障主机安全。B/S架构的主机卫士软件,不仅满足了用户对主机安全保护功能的需求,还减轻了用户的运维工作量,切实解决了用户工作中的痛点。     

Compressed sensing channel estimation for STBC‐SM based hybrid MIMO‐OFDM system for visible light communication

This paper presents the idea of sparse channel estimation using compressed sensing (CS) method for space–time block coding (STBC), and spatially multiplexing (SM) derived hybrid multiple‐input multiple‐output (MIMO) Asymmetrically clipped optical‐orthogonal frequency division multiplexing (ACO‐OFDM) optical wireless communication system. This hybrid system accounts multiplexing gain of SM and diversity gain of STBC technique. We present a new variant of sparsity adaptive matching pursuit (SaMP) algorithm called dynamic step‐size SaMP (DSS‐SaMP) algorithm. It makes use of the inherent and implicit structure of SaMP, along with dynamic adaptivity of step‐size feature which is compatible with the energy of the input signal, thus the name dynamic step size. Existing CS‐based recovery algorithms like orthogonal matching pursuit, SaMP, adaptive step‐size SaMP, and proposed DSS‐SaMP were compared for hybrid MIMO‐ACO‐OFDM visible light communication system. The performance analysis is demonstrated through simulation results with respect to bit error rate, symbol error rate, mean square error, computational complexity, and peak‐to‐average power ratio. Simulation results show that the proposed technique gives improved performance and lesser computational complexity in comparison with conventional estimation algorithms.