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41.
Using capacitance measurement and Mott-Schottky analysis, the semiconducting properties of passive films formed on chromium within the passive potential range under different conditions were investigated. The study reveals a p-type behavior of the passive layers. Two semiconductive parameters, i.e., the acceptor density (NA) and the flatband potential (EFB), which are mainly related to composition and surface charges of the passive films, have been measured. The effect of film formation potential, passivation time, pH and composition of solutions on the parameters are discussed. NA increases either with lowering film formation potentials or with prolonging passivation times. This is attributed to the transformation of a less hydrated oxide film into a more hydrated form. The changes of EFB are discussed as a function of adsorptive anions and pH values of electrolyte solution. 相似文献
42.
运动目标跟踪技术是未知环境下移动机器人研究领域的一个重要研究方向。该文提出了一种基于主动视觉和超声信息的移动机器人运动目标跟踪设计方法,利用一台SONY EV-D31彩色摄像机、自主研制的摄像机控制模块、图像采集与处理单元等构建了主动视觉系统。移动机器人采用了基于行为的分布式控制体系结构,利用主动视觉锁定运动目标,通过超声系统感知外部环境信息,能在未知的、动态的、非结构化复杂环境中可靠地跟踪运动目标。实验表明机器人具有较高的鲁棒性,运动目标跟踪系统运行可靠。 相似文献
43.
Cyclic deformations of annealed pure polycrystalline -iron with and without further mutually immiscible silver-ion implantation (90 keV, 6×1016 ions cm–2) were studied in a plastic strain-controlled tension-compression fatigue test (triangular loading waveform, frequency 0.02–0.3 Hz, and plastic strain range 3×10–3–1.2×10–2). The obtained plastic strain-life (p-N
f) curves showed that the iron specimens could survive for a greater number of cycles before failure when implanted. Comparison of the cyclic stress-strain curves suggested that the implanted specimens had maintained a relatively more stable microstructural change than those unimplanted ones which had undergone a violent cyclic hardening during cyclic deformation. This is proposed to be a strong indication that the fatigue ductility has been improved and the cross slip of screw dislocations, which leads to the evolution of the persistent slip bands for fatigue damage, was hindered to some extent after ion implantation. 相似文献
44.
碳中和、碳达峰的践行,零碳园区是重点之一。新型电力系统背景下,园区的电力能源供应具有水/电/气/热高度融合、源网荷储强不确定、一二次拓扑结构复杂多样等特点,现有的规划设计技术较难满足其应用需求。为此,以零碳园区为主要研究对象,对其优化规划设计的研究现状、关键技术与未来发展趋势展开讨论。首先,从能源互联的角度阐述了零碳园区的内涵架构与其规划设计技术研究现状;其次,归纳并阐述了零碳园区包括能源-交通系统耦合、多能互补、能量梯级利用、需求响应、渐进式规划等优化规划关键技术;最后,从共享理念、数字孪生与云储能等方面分析了园区规划未来的发展趋势,从理念应用、学科交叉、信息融合与态势感知等角度指明了园区规划的技术挑战与研究方向,以期为我国面向能源互联网的零碳园区的发展提供更有力的技术支撑。 相似文献
45.
The stress corrosion cracking (SCC) initiation process for 4340 high strength steel in distilled water at room temperature was studied using a new kind of instrument: an environmental scanning electron microscope (ESEM). It was found that the applied stress accelerated oxide film formation which has an important influence on the subsequent SCC initiation. SCC was observed to initiate in the following circumstances: (1) cracking of a thick oxide film leading to SCC initiation along metal grain boundaries, (2) the initiation of pits initiating SCC in the metal and (3) SCC initiating from the edge of the specimen.All these three SCC initiation circumstances are consistent with the following model which couples SCC initiation with cracking of a surface protective oxide. There is a dynamic interaction between oxide formation, the applied stress, oxide cracking, pitting and the initiation of SCC. An aspect of the dynamic interaction is cracks forming in a protective surface oxide because of the applied stress, exposing to the water bare metal at the oxide crack tip, and oxidation of the bare metal causing crack healing. Oxide crack healing would be competing with the initiation of intergranular SCC if an oxide crack meets the metal surface at a grain boundary. If the intergranular SCC penetration is sufficiently fast along the metal grain boundary, then the crack yaws open preventing healing of the oxide crack. If intergranular SCC penetration is not sufficiently fast, then the oxidation process could produce sufficient oxide to fill both the stress corrosion crack and the oxide crack; in this case there would be initiation of SCC but only limited propagation of SCC. Stress-induced cracks in very thin oxide can induce pits which initiate SCC, and under some conditions such stress induced cracks in a thin oxide can directly initiate SCC. 相似文献
46.
Z. Y. Ma J. H. Li S. X. Li X. G. Ning Y. X. Lu J. Bi 《Journal of Materials Science》1996,31(3):741-747
The in situ formed Al2O3, TiB2 and Al3Ti mixture-reinforced aluminium composites were successfully fabricated by the reaction sintering of the TiO2-B-Al system in a vacuum. With increasing boron content in the TiO2-B-Al system, the amount of generated TiB2 in the composites increased and Al3Ti content decreased. At the same time the distribution uniformity of the in situ formed Al2O3 and TiB2 particulates was obviously improved, and the size of the Al3Ti particles was reduced. The in situ Al2O3 and TiB2 particulates had sizes from 0.096–1.88 m. The interface between the in situ formed particulates and the aluminium matrix was clean, and no consistent crystallographic orientation relationship was found. The strength and elastic modulus of the composites was significantly improved by lowering the Al3Ti content. When the boron content in the TiO2-B-Al system rose, the morphology of the tensile fracture surface of the composites was changed from large fractured Al3Ti blocks and fine dimples, to fine dimples and pulled-out particulates. The strengthening and fracture of the composites have been modelled. 相似文献
47.
GIS环境下的最佳路径规划 总被引:7,自引:0,他引:7
本文从沈阳市消防通信指挥系统的实际需要出
发,在GIS环境下求解从消防中队到火灾发生地的最佳路径.采用了离线搜索、建立最佳路
径库来解决实际应用中对实时性的要求,叙述了如何建立最佳路径的数学模型和利用遗传算
法通过样本路径来求解模型中的参数. 相似文献
48.
Microsoft NetMeeting的技术特点及其底层服务在远程医疗系统中的应用 总被引:1,自引:0,他引:1
本文详细介绍并分析了Microsoft NetMeeting的各种功能特点及实现策略,重点研究了NetMeeting提供的底层服务的技术特点及其应用潜力,在此基础上提出了一个基于NetMeeting底层服务的远程医疗管理系统的实现方案.并对方案中的技术实现进行了阐述, 相似文献
49.
50.
Effects of hydrogen on mechanical properties and fracture mechanism of 8090 Al-Li alloy 总被引:2,自引:0,他引:2
Lian Chen Wenxiu Chen Zhonghao Liu Yuxia Shao Zhuangqi Hu 《Metallurgical and Materials Transactions A》1993,24(6):1355-1361
The effects of hydrogen and strain rate on the mechanical properties and fracture mechanism of 8090 Al-Li alloy under electrochemical
charging conditions have been studied. Experimental results demonstrate that the tensile strength [ultimate tensile strength
(UTS) and yield strength (YS)] and plasticity [reduction of area (RA) and elongation (EL)] drop linearly with the decrease
of strain rate. The charged hydrogen increases the tensile strength but markedly impair the plasticity. The susceptibility
of hydrogen embrittlement increases with the decreases of strain rate, and the susceptibility of the charged specimens was
larger than that of the uncharged ones over the strain-rate range. Observation by scanning electron microscope (SEM) reveals
that the charged hydrogen enhances intergranular delamination cracking on the fracture surface. The fracture model of charged
specimens at low strain rates
is grain boundary brittle fracture (GBBF), while that of other conditions is grain boundary ductile fracture (GBDF). Secondary
ion mass spectroscopy (SIMS) study shows that the atomic binding energy of Al and Li in the alloy decreased after hydrogen
charging, and the atomic binding energy drop of the former is more than the latter. In this article, the hydrogen transport
through the mobile dislocation mechanism of hydrogen-induced fracture and the hydrogen effect on atomic binding energy were
also discussed in detail. 相似文献