激光淬火基体对镀铬层界面剪切强度的影响

为了揭示激光淬火预处理基体提高镀铬身管寿命的机理,采用多裂纹拉伸技术分别对激光淬火处理和激光未处理基体上的镀铬层界面剪切强度进行了测量,发现激光淬火基体可以提高镀铬层界面剪切强度77.7%,并从基体与铬层的界面材料结构和力学两个方面进行了分析。结果表明,激光预处理的界面是连续过渡的,而原始基体的界面存在一个过渡;激光淬火基体表面残余压应力的存在提高了铬层的断裂应力;基体表面硬度的提高减小了最大裂纹间距。     

Pure CuBi2O4 Photoelectrodes with Increased Stability by Rapid Thermal Processing of Bi2O3/CuO Grown by Pulsed Laser Deposition

A new method for enhancing the charge separation and photo‐electrochemical stability of CuBi₂O₄ photoelectrodes by sequentially depositing Bi₂O₃ and CuO layers on fluorine‐doped tin oxide substrates with pulsed laser deposition (PLD), followed by rapid thermal processing (RTP), resulting in phase‐pure, highly crystalline films after 10 min at 650 °C, is reported. Conventional furnace annealing of similar films for 72 h at 500 °C do not result in phase‐pure CuBi₂O₄. The combined PLD and RTP approach allow excellent control of the Bi:Cu stoichiometry and results in photoelectrodes with superior electronic properties compared to photoelectrodes fabricated through spray pyrolysis. The low photocurrents of the CuBi₂O₄ photocathodes fabricated through PLD/RTP in this study are primarily attributed to their low specific surface area, lack of CuO impurities, and limited, slow charge transport in the undoped films. Bare (without protection layers) CuBi₂O₄ photoelectrodes made with PLD/RTP shows a photocurrent decrease of only 26% after 5 h, which represents the highest stability reported to date for this material. The PLD/RTP fabrication approach offers new possibilities of fabricating complex metal oxides photoelectrodes with a high degree of crystallinity and good electronic properties at higher temperatures than the thermal stability of glass‐based transparent conductive substrates would allow.     

He-Ne激光器功率调谐位移传感激光器

阐述了一种新型的HeNe激光位移传感器,具有自校准功能以及没有原理上的误差。利用频率分裂技术,将一个纵模间隔分为4个宽度相等的区间,在这4个区间内激光器具有不同的光功率输出。当一个频率移动过这样的一个区间,相当于激光器的一个腔镜移动了λ/8。可移动的反射镜与被测工件相连。这样,一支HeNe激光器变成了一个不用干涉现象的位移传感器,其测量范围可达10mm,测量精度可达0.079μm,并具有判向的功能。     

激光透射焊接聚碳酸酯接头性能研究

为研究聚碳酸酯激光透射焊接接头性能,采用10W半导体端抽运全固态(DPSS)激光器进行了聚碳酸酯材料的激光透射焊接。采用光学金相显微镜(OM)、场发射扫描电子显微镜(SEM)和电子万能实验拉力机分析了接头的显微形貌、断口形貌和拉伸剪切强度。结果表明,在激光功率8 W、激光频率50kHz、焊接速度350mm/s、激光扫描间距0.1mm时,试样的拉伸剪切强度达到44MPa,为母材强度的68%,焊缝内部的分层和气孔是影响接头力学性能和断裂机制的主要原因,通过激光塑料透射焊接技术,可以获得接头力学性能良好的焊接试样。     

激光修复热影响区深度对TC17-TC11双合金拉伸性能的影响

以TC17合金锻件为基材,采用激光修复工艺方法,在其上沉积TC11合金粉末,制备TC17-TC11双合金修复试样,在双合金界面处靠近TC17锻件基体一侧观察到一定深度的热影响区。通过调整激光修复工艺参数(激光功率、扫描速度、送粉率),构造不同深度的热影响区,探讨热影响区深度对激光修复试样高温拉伸性能的影响。研究结果表明,高温拉伸时,修复试样表现为滑移分离型断裂,由于α/β两相的应变不协调,拉伸时裂纹萌生于TC11合金α/β相界面,其中热影响区深度为5 mm修复试样的强度和塑性匹配度好。随着热影响区深度的增加,修复试样的强度值呈现先升后降的趋势,热影响区深度为2 mm修复试样的抗拉强度最大,但其塑性较差。     

成缆工序对光缆拉伸性能的影响

光缆拉伸性能是检验光缆质量的重要指标之一,成缆工序对光缆的拉伸性能起着至关重要的作用。结合现有的实际生产经验,从成缆设备和成缆生产工艺的控制等方面探讨了影响光缆拉伸性能的因素,以期提高光缆的拉伸性能。     

Highly Porous Materials as Tunable Electrocatalysts for the Hydrogen and Oxygen Evolution Reaction

The facile preparation of highly porous, manganese doped, sponge‐like nickel materials by salt melt synthesis embedded into nitrogen doped carbon for electrocatalytic applications is shown. The incorporation of manganese into the porous structure enhances the nickel catalyst's activity for the hydrogen evolution reaction in alkaline solution. The best catalyst demonstrates low onset overpotential (0.15 V) for the hydrogen evolution reaction along with high current densities at higher potentials. In addition, the possibility to alter the electrocatalytic properties of the materials from the hydrogen to oxygen evolution reaction by simple surface oxidation is shown. The surface area increases up to 1200 m²g^?1 after mild oxidation accompanied by the formation of nickel oxide on the surface. A detailed analysis shows a synergetic effect of the oxide formation and the material's surface area on the catalytic performance in the oxygen evolution reaction. In addition, the synthesis of cobalt doped sponge‐like nickel materials is also delineated, demonstrating the generality of the synthesis. The facile salt melt synthesis of such highly porous metal based materials opens new possibilities for the fabrication of diverse electrode nanostructures for electrochemical applications.     

Hierarchical Nanowire Arrays Based on ZnO Core−Layered Double Hydroxide Shell for Largely Enhanced Photoelectrochemical Water Splitting

Well‐aligned hierarchical nanoarrays containing ZnO core and layered double hydroxide (LDH) nanoplatelets shell have been synthesized via a facile electrosynthesis method. The resulting ZnO@CoNi–LDH core?shell nanoarray exhibits promising behavior in photoelectrochemical water splitting, giving rise to a largely enhanced photocurrent density as well as stability; much superior to those of ZnO‐based photoelectrodes. This is attributed to the successful integration of photogenerated electron–hole separation originating from the ZnO core and the excellent electrocatalytic activity of LDH shell. This work provides a facile and cost‐effective strategy for the fabrication of multifunctional nanoarrays with a hierarchical structure, which can be potentially used in energy storage and conversion devices.     

虚拟软件定义网络中采用优化备份拓扑的抗毁虚拟网络映射(英)

Software-Defined Network architecture offers network virtualization through a hypervisor plane to share the same physical substrate among multiple virtual networks.However,for this hypervisor plane,how to map a virtual network to the physical substrate while guaranteeing the survivability in the event of failures,is extremely important.In this paper,we present an efficient virtual network mapping approach using optimal backup topology to survive a single link failure with less resource consumption.Firstly,according to whether the path splitting is supported by virtual networks,we propose the OBT-Ⅰ and OBT-Ⅱ algorithms respectively to generate an optimal backup topology which minimizes the total amount of bandwidth constraints.Secondly,we propose a Virtual Network Mapping algorithm with coordinated Primary and Backup Topology(VNM-PBT)to make the best of the substrate network resource.The simulation experiments show that our proposed approach can reduce the average resource consumption and execution time cost,while improving the request acceptance ratio of VNs.     

Dynamic Multicast Session Provisioning in WDM Optical Networks with Sparse Splitting Capability

In this work, we study dynamic provisioning of multicast sessions in a wavelength-routed sparse splitting capable WDM network with an arbitrary mesh topology where the network consists of nodes with full, partial, or no wavelength conversion capabilities and a node can be a tap-and-continue (TaC) node or a splitting and delivery (SaD) node. The objectives are to minimize the network resources in terms of wavelength-links used by each session and to reduce the multicast session blocking probability. The problem is to route the multicast session from each source to the members of every multicast session, and to assign an appropriate wavelength to each link used by the session. We propose an efficient online algorithm for dynamic multicast session provisioning. To evaluate the proposed algorithm, we apply the integer linear programming (ILP) optimization tool on a per multicast session basis to solve off-line the optimal routing and wavelength assignment given a multicast session and the current network topology as well as its residual network resource information. We formulate the per session multicast routing and wavelength assignment problem as an ILP. With this ILP formulation, the multicast session blocking probability or success probability can then be estimated based on solving a series of ILPs off-line. We have evaluated the effectiveness of the proposed online algorithm via simulation in terms of session blocking probability and network resources used by a session. Simulation results indicate that our proposed computationally efficient online algorithm performs well even when a fraction of the nodes are SaD nodes.