脉冲电沉积对低温气体渗氮及耐蚀性能的影响

利用脉冲电沉积(PED)预处理,在纯铁和45钢表面形成由厚度50 nm左右的片状结构组成的含Cr、Ni预处理层,然后再在480℃进行9 h气体渗氮。采用扫描电镜(SEM)和电子探针(EPMA)对预处理层和氮化层的表面形貌和成分进行表征,采用X射线衍射(XRD)对氮化层进行物相分析,结果表明:通过脉冲电沉积预处理,纯铁和45钢都实现了低温、快速气体渗氮。通过硬度测量及电化学方法测试表明,脉冲电沉积预处理不仅提高了气体渗氮后纯铁及45钢表面硬度,改善了脆性,引入的Cr、Ni元素及Ni-Cr-Fe合金层还提高了氮化层的耐蚀性能。     

基于实时电价的用户用电响应行为研究

随着智能电网的发展,电网开放性不断增强,需求响应(demand response,DR)策略被提出,并被广泛应用于电力市场的运营模式中。各国相继推出需求响应的实时电价(real-time pricing,RTP)策略,来提高电网的有效性与电力市场的可靠性。合理地分析实时电价下用户的用电响应行为,对制定更高效的实时电价机制,实施需求响应策略具有重要意义。因此,基于用户的需求价格弹性(price elasticity of electricity demand,PED)模型,通过回归模型学习需求价格弹性,模拟用户响应行为。实验表明,学习获得的用户价格弹性可以很好地实现用户响应行为的拟合,较传统的调查问卷方式获得固定的用户价格弹性,回归模型克服时间与空间的变化问题,更高效地实现用户响应行为的学习,为实时电价提供决策支持。     

A precession electron diffraction study of α, β phases and Dauphiné twin in quartz

Precession electron diffraction is used to distinguish between the hexagonal β high-temperature and the trigonal α low-temperature phases of SiO₂ quartz. The structures just differ by a kink of the SiO₄ tetrahedra arranged along spiraling chains, which induces a loss of the two-fold axis and subsequent twinning in the low-temperature phase. Conventional selected-area electron diffraction (SAED) does not enable the phases distinction since only the intensity of reflections is different. It becomes possible with precession that reduces the dynamical interactions between reflections and makes their intensity very sensitive to small variations of the electron structure factors. Distinction between the twinned individuals in the low-temperature phase is then easily made and the twin law is characterized using stereographic projections. The actual symmetry of precessed zone axis patterns is also examined in detail. Using dynamical intensity simulations, it is shown that under certain thickness conditions, the diffraction class symmetry can be observed on selected area patterns that are to be used in the case of beam sensitive materials such as quartz.     

Microscale 3D Printing of Nanotwinned Copper

Nanotwinned (nt)‐metals exhibit superior mechanical and electrical properties compared to their coarse‐grained and nanograined counterparts. nt‐metals in film and bulk forms are obtained using physical and chemical processes including pulsed electrodeposition (PED), plastic deformation, recrystallization, phase transformation, and sputter deposition. However, currently, there is no process for 3D printing (additive manufacturing) of nt‐metals. Microscale 3D printing of nt‐Cu is demonstrated with high density of coherent twin boundaries using a new room temperature process based on localized PED (L‐PED). The 3D printed nt‐Cu is fully dense, with low to none impurities, and low microstructural defects, and without obvious interface between printed layers, which overall result in good mechanical and electrical properties, without any postprocessing steps. The L‐PED process enables direct 3D printing of layer‐by‐layer and complex 3D microscale nt‐Cu structures, which may find applications for fabrication of metamaterials, sensors, plasmonics, and micro/nanoelectromechanical systems.     

Pulse and pulse reverse plating—Conceptual, advantages and applications

A review on pulse and pulse reverse techniques for electrodeposition have been attempted. Pulse electrodeposition (PED) of some metals and alloys are reported. The effects of mass, transport, electrical double layer pulse parameters and current distribution on surface roughness and morphology are presented. Applications, advantages and disadvantages of PC and PRC techniques are discussed along with theoretical aspects and mechanism.     

国内煤矿无线电通信技术的综述和展望

概述了国内煤矿井下无线通信系统的现状,介绍了煤矿井下目前使用的无线通信系统的性能和特点,并对井下无线通信系统的发展趋势进行了分析。     

CPM信号的定时-相位联合估计算法

针对CPM信号同步问题,在判决数据辅助的基础上提出一种联合定时-相位估计算法。该算法用Laurent分解表示CPM信号,由定时-相位联合似然函数得到定时误差检测器和相位误差检测器,找出瞬时梯度,迭代求解恢复出定时和相位信息。通过分析二进制部分响应CPM中的常见形式PCM/FM信号,提出一种联合定时-相位估计的实现方案。在加性高斯白噪声信道上的仿真结果表明,该算法适用于二进制部分响应CPM信号,定时和相位估计性能都逼近理想曲线。     

一种改进的移动Agent通信模型

移动Agent系统的通信问题是阻碍其广泛应用于实践的最重要的因素之一。通过对已有的移动Agent系统通信机制的研究与分析,提出了一种改进的移动Agent通信参考模型。该参考模型分别从移动Agent命名与定位、移动Agent通信安全和移动Agent通信失效三个方面进行分析,在某种程度上解决了移动Agent的通信问题,并提高了移动Agent通信安全性。最后,对未来的工作做了展望。     

Security systems of point-of-sales devices

Security is a systematic issue which covers product design, implementation, logistic, manufacture and management. With the exponential growth of electronic business in recent years, the security of e-payment which is an important part of e-supply chain management (eSCM), becomes a critical issue. A large amount of payment in transactions is made via POS (point of sales) devices. The security of the POS system has its own specialties. However, few research papers focus on POS device security. This paper provides comprehensive investigation into security on POS devices. Firstly, it offers first-hand information on hardware and design of physical security. In particular, attacks, countermeasures and practical implementation are studied. Secondly, secure key management and security management in manufacture are investigated. Further research directions have been discussed according to the authors’ analysis.     

原丝卷绕断丝报警系统的工作原理及故障排除方法

对原丝卷绕中的断丝报警传感器进行了详细的分析，提出了处理故障的有效方法。