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81.
Cold spraying is a thermal spray process enabling the production of metallic and metal-ceramic coatings with low porosity
and low oxygen content, capable of, e.g., resisting corrosion. The aim of this study was to characterize the microstructural
and mechanical properties of cold-sprayed Ni-20Cr+Al2O3 coatings and to clarify the effect of the hard particles on different coating properties. Accordingly, the research focused
on the microstructure, denseness (impermeability), adhesion strength, and hardness of the coatings. Scanning electron microscopy
(SEM) analysis and corrosion tests were run to gain information on the through-porosity. Ceramic addition in cold-sprayed
Ni-20Cr+Al2O3 coatings improved their quality by lowering their porosity. Moreover, hardness was slightly higher than those of cold-sprayed
Ni-20Cr coating, indicating a hardening effect by the ceramic particles. The addition of Al2O3 also made it possible to use high gas temperatures without nozzle clogging, which affects coating properties, such as coating
thickness, denseness, and hardness. 相似文献
82.
大气气柱内水汽总含量的红外光谱遥测 总被引:4,自引:0,他引:4
我们研制了一台太阳红外光谱仪,在地面连续自动地记录了晴天的太阳红外光谱,利用3.434μm(2912cm^-1)波段附近水汽对太阳光谱的吸收反演出整层大气中水汽的总含量,遥测结果与无线电探空相当吻合,经过近一年半的观测,得到了合肥地区垂直气柱中可降水含量的日变化和季节变化规律,并发现气柱中可降水含量与地面露点温度有较好的相关,并对结果进行了讨论。 相似文献
83.
84.
本文介绍作者进一步研究双滤膜法测~(222)Rn 的工作结果。主要讨论了由过滤法测氡子体的基本方程推导出测定~(222)Rn 浓度的一般公式和衰变、扩散校正系数的计算公式。这些公式同时考虑了衰变和扩散对测定结果的影响。采用壁沉积方法,测得 RaA 的扩散系数 D=0.071cm~2/s。文中还分析了双滤膜法测~(222)Rn 的误差传递问题,结果表明,随着μ值(μ=0.06πDL/q,L 为采样管长度)的减小’D和取样流速 q 的误差对~(222)Rn 浓度测定结果的影响也显著减小。试从理论上解释该方法用于低μ条件时精密度和准确度都较高的特点。 相似文献
85.
Microstructural Studies of Cold Sprayed Copper,Nickel, and Nickel-30% Copper Coatings 总被引:1,自引:0,他引:1
Heli Koivuluoto Juha Lagerbom Petri Vuoristo 《Journal of Thermal Spray Technology》2007,16(4):488-497
Cold spraying enables to produce metallic coatings with low porosity level and low oxygen content. Several material properties
such as electrical conductivity and corrosion resistance rely on these properties. Aim of this study was to characterize microstructural
properties of cold sprayed copper, nickel, and nickel-30%copper coatings. Microstructures, denseness, and deformation of particles
were investigated. SEM analysis and corrosion tests were done to get information of through-porosity. Open porosity has an
important role on protectiveness of anodically protective coatings, such coating materials like copper and nickel. In this
study, cold-sprayed Cu coating was fully dense. However, cold-sprayed Ni and Ni-30%Cu coatings seemed to be microstructurally
dense but some porosity in some areas of the coatings especially in some parts of particle boundaries was noticed after corrosion
tests. Furthermore, effect of annealing to microstructure and corrosion test behavior was studied. Cold sprayed Ni coating
became denser during heat treatment. 相似文献
86.
改性铸造Ni3Al基合金MX246组织与性能研究 总被引:2,自引:0,他引:2
研究了合金元素W,Mo,Y和Hf对Ni3Al基金属间化合物MX246高温力学性能与氧化性能的影响.实验结果表明,W和Mo的加入有利于合金高温力学性能的提高,成分为Ni-8.2Al-7.8Cr-0.1C-1Ti-0.5Hf-0.05B-4Mo-2W-0.01Y(质量分数,%)的No.6合金的高温强度和持久性能远优于MX246合金,其1100℃/100h氧化速率为0.0639g/(m2·h),远低于MX246合金的0.2683g/(m2·h),高温抗氧化性能的提高则主要归功于Y和Hf的作用.分析讨论了这些元素对合金性能的影响机制.优异的高温综合性能使研制的新型MX246合金在高温结构材料应用领域极具潜力. 相似文献
87.
Moving data from cloud to the edge network can effectively reduce traffic burden on the core network, and edge collaboration can further improve the edge caching capacity and the quality of service ( QoS). However, it is difficult for various edge caching devices to cooperate due to the lack of trust and the existence of malicious nodes. In this paper,blockchain which has the distributed and immutable characteristics is utilized to build a trustworthy collaborative edge caching scheme to make full use of the storage resources of various edge devices. The collaboration process is described in this paper, and a proof of credit (PoC) protocol is proposed, in which credit and tokens are used to encourage nodes to cache and transmit more content in honest behavior. Untrusted nodes will pay for their malicious actions such as tampering or deleting cached data. Since each node chooses strategy independently to maximize its benefits in an environment of mutual influence, a non-cooperative game model is designed to study the caching behavior among edge nodes. The existence of Nash equilibrium (NE) is proved in this game, so the edge server (ES) can choose the optimal caching strategy for all collaborative devices, including itself, to obtain the maximum rewards. Simulation results show that the system can save mining overhead as well as organize a trusted collaborative edge caching effectively. 相似文献
88.
89.
Li2MoO4‐based composite ceramics fabricated from temperature‐ and atmosphere‐sensitive MnZn ferrite at room temperature 下载免费PDF全文
Maria Väätäjä Hanna Kähäri Jari Juuti Heli Jantunen 《Journal of the American Ceramic Society》2017,100(8):3626-3635
The first magnetic ceramic composites manufactured, using the room‐temperature densification method are reported. The samples were prepared at room temperature using Li2MoO4 as a matrix and MnZn ferrite with loading levels of 10‐30 vol‐% followed by postprocessing at 120°C. The method utilizes the water solubility of the dielectric Li2MoO4 and compression pressure instead of high temperatures typical of conventional solid‐state sintering. Hence, composite manufacturing using temperature‐ and atmosphere‐sensitive materials is possible without special conditions. This was demonstrated with MnZn ferrite, which is prone to oxidation when heat treated in air. Samples manufactured with room‐temperature densification showed no signs of reactivity during processing, whereas reference samples sintered at 685°C suffered from oxidation and formation of an additional reaction phase. The densities achieved with different loading levels of MnZn ferrite with both methods were very similar. Measurements up to 1 GHz showed relatively high values of relative permittivity (21.7 at 1 GHz) and permeability (2.6 at 1 GHz) with 30 vol‐% loading of MnZn ferrite in the samples manufactured by room‐temperature densification. In addition, pre‐granulation is proposed to improve the processability of the composite powders in room‐temperature densification. 相似文献
90.
Jinhuan Ge Heli Sun Chenhao Xue Liang He Xiaolin Jia Hui He Jiyin Chen 《Computational Intelligence》2021,37(1):484-510
Traditional community detection methods in attributed networks (eg, social network) usually disregard abundant node attribute information and only focus on structural information of a graph. Existing community detection methods in attributed networks are mostly applied in the detection of nonoverlapping communities and cannot be directly used to detect the overlapping structures. This article proposes an overlapping community detection algorithm in attributed networks. First, we employ the modified X‐means algorithm to cluster attributes to form different themes. Second, we employ the label propagation algorithm (LPA), which is based on neighborhood network conductance for priority and the rule of theme weight, to detect communities in each theme. Finally, we perform redundant processing to form the final community division. The proposed algorithm improves the X‐means algorithm to avoid the effects of outliers. Problems of LPA such as instability of division and adjacent communities being easily merged can be corrected by prioritizing the node neighborhood network conductance. As the community is detected in the attribute subspace, the algorithm can find overlapping communities. Experimental results on real‐attributed and synthetic‐attributed networks show that the performance of the proposed algorithm is excellent with multiple evaluation metrics. 相似文献