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51.
Chengcong Zhang 《Science & Technology of Welding & Joining》2018,23(5):394-399
The longitudinal residual stresses in the friction stir-welded plates of 5A06 aluminium and pure copper were determined using the contour method. The results revealed the presence of high tensile and compressive residual stresses on the aluminium and copper sides, respectively. The residual stresses were detected on the weld zone as well as the thermo-mechanically affected zone (TMAZ) of the aluminium plate. In contrast, the compressive residual stresses in the copper plate had a much narrower width along the weld line. Peak tensile stresses up to 240?MPa were found in the TMAZ of the aluminium plate. 相似文献
52.
The process of cemented carbides manufacturing requires rapid and field elemental analytical techniques to control and evaluate the properties of products. Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is such a potential elemental analytical technique. In this work, a portable LIBS instrument combined with a CF method was developed for the analysis of cemented carbides. Three batches of cemented compact carbides without reference samples were analyzed. Qualitative and quantitative analysis of the samples were achieved by using the portable LIBS instrument combined with CF method. To validate the analysis results, X-ray fluorescence spectrometry (XRF) was used to analyze the samples as well. The results of CF-LIBS agreed well with the results of XRF, with relative errors between ?29.53 and 24.70%. The results demonstrated that the portable LIBS instrument combined with CF method was capable for direct and rapid analysis without any need of standard measurements. Notably, with the portable LIBS instrument combined with CF method, acceptable accuracy could be obtained, which is promising for practical field applications. 相似文献
53.
54.
Devendrasinh Darbar M.R. Anilkumar Vijayaraghavan Rajagopalan Indranil Bhattacharya Hendry Izaac Elim T. Ramakrishnappa F.I. Ezema Rajan Jose M.V. Reddy 《Ceramics International》2018,44(5):4630-4639
Optimization of electrodes for charge storage with appropriate processing conditions places significant challenges in the developments for high performance charge storage devices. In this article, metal cobaltite spinels of formula MCo2O4 (where M = Mn, Zn, Fe, Ni and Co) are synthesized by oxalate decomposition method followed by calcination at three typical temperatures, viz. 350, 550, and 750 °C and examined their performance variation when used as anodes in lithium ion batteries. Phase and structure of the materials are studied by powder x-ray diffraction (XRD) technique. Single phase MnCo2O4,ZnCo2O4 and Co3O4 are obtained for all different temperatures 350 °C, 550 °C and 750 °C; whereas FeCo2O4 and NiCo2O4 contained their constituent binary phases even after repeated calcination. Morphologies of the materials are studied via scanning electron microscopy (SEM): needle-shaped particles of MnCo2O4 and ZnCo2O4, submicron sized particles of FeCo2O4 and agglomerated submicron particle of NiCo2O4 are observed. Galvanostatic cycling has been conducted in the voltage range 0.005–3.0 V vs. Li at a current density of 60 mA g?1 up to 50 cycles to study their Li storage capabilities. Highest observed charge capacities are: MnCo2O4 – 365 mA h g?1 (750 °C); ZnCo2O4 – 516 mA h g?1 (550 °C); FeCo2O4 – 480 mA h g?1 (550 °C); NiCo2O4 – 384 mA h g?1 (750 °C); and Co3O4 – 675 mA h g?1 (350 °C). The Co3O4 showed the highest reversible capacity of 675 mA h g?1; the NiO present in NiCo2O4 acts as a buffer layer that results in improved cycling stability; the ZnCo2O4 with long needle-like shows good cycling stability. 相似文献
55.
聚类混合型数据,通常是依据样本属性类别的不同分别进行评价。但这种将样本属性划分到不同子空间中分别度量的方式,割裂了样本属性原有的统一性;导致对样本个体的相似性评价产生了非一致的度量偏差。针对这一问题,提出以二进制编码样本属性,再由海明差异对属性编码施行统一度量的新的聚类算法。新算法通过在统一的框架内对混合型数据实施相似性度量,避免了对样本属性的切割,在此基础上又根据不同属性的性质赋予其不同的权重,并以此评价样本个体之间的相似程度。实验结果表明,新算法能够有效地聚类混合型数据;与已有的其他聚类算法相比较,表现出更好的聚类准确率及稳定性。 相似文献
56.
身份基加密(IBE)需要提供一种有效的成员撤销机制,然而,现有可撤销成员的IBE方案存在密钥更新和加密运算量过大的问题,可能使执行该操作的设备成为系统的瓶颈。将完全子树方法和在线离线技术相结合,通过修改指数逆类型IBE的密钥生成和加密算法,提出了一种高效可撤销的身份基在线离线加密方案。方案利用完全子树方法生成更新钥,使得撤销用户无法获得更新钥,进而失去解密能力;利用在线离线技术,将大部分加密运算在离线阶段进行预处理,使得在线阶段仅执行少量简单计算即可生成密文。与相关知名方案相比,该方案不仅提高密钥生成中心的密钥更新的效率,而且极大减少了轻量级设备的在线加密工作量,适合于轻量级设备保护用户隐私信息。 相似文献
57.
专家发现是实体检索领域的一个研究热点,针对经典专家发现模型存在索引术语独立性假设与检索性能低的缺陷,提出一种基于贝叶斯网络模型的专家发现方法。该方法模型采用四层网络结构,能够实现图形化的概率推理,同时运用词向量技术能够实现查询术语的语义扩展。实验结果显示该模型在多个评价指标上均优于经典专家发现模型,能够有效实现查询术语语义扩展,提高专家检索性能。 相似文献
58.
标准LoRaWAN协议中定义的纯ALOHA信道接入方法在网络负载较大时会造成大量碰撞,使LoRa网络的可扩展性和可靠性受到极大挑战。为此提出了一种将先听后说与模拟退火相结合(Listen Before Talk combined with Simulated Annealing,LBT-SA)的LoRa信道接入方法。该方法通过在设备发送之前先监听信道,降低信道被同时接入的概率,并以成功传输所需退避时间为初始值,搜索更小的退避时间。仿真结果表明,LBT-SA和基于二元指数退避算法的先听后说(Listen Before Talk,LBT)方法在包成功传输率方面保持了高度的一致,并且LBT-SA在周期传输过程中逐渐减少了不必要的退避时间,从而减少了时延。在多达10 000个终端接入单个网关的场景中,该算法的平均退避时间至少降低了16.38%。 相似文献
59.
60.
In this article, an analytical technique is introduced to obtain the excitation coefficients of uniformly spaced linear antenna arrays in order to achieve a desired array factor. By integration of the prescribed array factor, the array factor dependency to the progressive phase shift is eliminated. A new system of linear equations is consequently obtained whose solution represents the excitation coefficients of the array. Some examples are presented to verify the accuracy of the introduced method. The performance of this strategy is compared with those obtained by the other well‐known techniques such as Woodward‐Lawson and Fourier transform. It is shown that the presented method estimates the desired array pattern with a very good precision. 相似文献