思维可视化工具的教学应用

思维可视化是利用图形化、形象化的形式来表达人们头脑中形成的概念、知识、思想等,把隐性知识显性化、可视化,方便人们思考、表达、理解并能促进交流的一种图形技术。该文在阐述思维可视化定义的基础上,研究了思维可视化工具在教学中的应用。     

空镜头在影视作品中的运用研究

从空镜头的基本内涵出发,就如何在影视作品中艺术地运用空镜头,使得“空镜头不空”作一探究,并对运用空镜头应注意的问题进行了初步讨论。     

基于IPv6的视频资源服务平台构建

介绍了基于IPv6视频资源服务平台的工作原理和关键技术,设计并开发了基于IPv6的视频资源服务平台,该平台能实现视频教学、影视娱乐、交流答疑、视频直播、视频点播等功能。     

Effect of welding current on strength and microstructure in resistance spot welding of AZ31 Mg alloy

In this paper, resistance spot welding were performed on lmm-thickness magnesium AZ31B plates. The effect of welding current on the microstructure and tensile shear force was investigated. It was found that the welding current governed the nugget growth, and the nugget could not form if current levels were insufficient. The nugget revealed a homogeneous, equiaxed, fine-grained structure, which consisted of non-equilibrium microstructure of α-phase dendrites surrounded by eutectic mixtures of α and β（ Mg17All2 ） in the grain boundaries. With increasing welding current, the size of grains in nugget would be more smaller and uniform, and the width of plastic rings would be larger. Tensile shear tests showed that tensile shear force of the joints increased with increasing welding current when the welding current was smaller than 17 000 A. The maximum tensile shear force was up to 1980 N.     

无线城域网无线局域网安全机制分析与比较

阐述了无线城域网和无线局域网的安全机制,着重分析了它们在身份认证和数据加密方面的异同．总结了它们的应用现状和对未来的展望。     

基于分水岭变换和图割的彩色图像快速分割

基于图割理论的图像分割具有结合多种知识的统一图像分割框架,可获取全局最优解,但海量的像素级处理单元以及为达到一定分割精度而采用的迭代求解模式,导致算法分割效率不高。以GrabCut算法为基础,通过分水岭变换,将图像划分成区域内颜色相似的若干分块,以各个块内像素的RGB均值代表所在分块的全部像素点来估计高斯混合模型参数,使问题规模减小,算法效率得到提高。     

Electron beam braze-welding of vanadium alloy to stainless steel with electroplated Cu/Ag coatings

Cracks may easily occur in the fusion weld between vanadium alloys and stainless steel due to the brittle intermetallics and welding stress.The high vacuum electron beam braze-welding has been successfully used to join vanadium alloy(V-5Cr-5Ti) to stainless steel(HR-2) with electroplated Cu and Ag coating.To investigate the effects of electroplated coating on the weldability,the joint appearance,the microstructure and the mechanical properties of the joints have been thoroughly analyzed.The results show that the joint surface configuration was good and root reinforcement was full and smooth.A reaction zone(RZ) was gained on the interface between the VSCrSTi alloy and HR-2 stainless steel base metals.The width of reaction zone at the top of the joint was up to 0.65 mm,wider than that in the bottom of the joint(0.46 mm).The reaction zone consisted of considerably smaller dendritic structures with an average grain size of less than 10 μm.Element Ag and Cu almost enriched the interface between V-5Cr-5Ti alloy substrate and RZ,serving as a physical barrier which decreases or avoids the formation of intermetallics.The maximum tensile strength of vanadium alloy/stainless steel dissimilar alloy joint was more than 300 MPa.The joint was defects free.     

Li(Al1-xBex)SiO4陶瓷的结构及微波介电性能

采用传统的固相反应法合成了Li(Al_1-xBe_x)SiO₄(x=0.005,0.01,0.02,0.03)陶瓷,为了确定Be²⁺进入晶格后所占据的位置,通过CASTEP提供的第一性原理的密度泛函理论计算了Be²⁺所占据的LiAlSiO₄(LAS)不同位置的缺陷形成能和体系总能量,结果表明,Be²⁺占据Al位的LAS体系能量最低,最稳定。探究Be²⁺取代Al³⁺对Li(Al_1-xBe_x)SiO₄(x=0.005,0.01,0.02,0.03)陶瓷的体密度、相组成、烧结特性、微观形貌和微波介电性能的影响。在掺杂Be²⁺之后,烧结温度从1300℃(x=0)降低到1225℃(x=0.03),同时显著提升了LAS陶瓷的品质因数(Q×f)值和谐振频率温度系数(τ_f),能有效降低其介电常数。Li(...     

焊后热处理对2A14高强铝合金电子束焊接头组织及力学性能的影响

轻质化的需求使得人们把关注的焦点集中于轻质材料,高强铝合金作为钢结构材料的最佳替代品,受到越来越广泛的关注,利用电子束焊接高强铝合金,为获得性能优良的2A14高强铝合金电子束焊接接头,采用焊后热处理,通过组织观察(光学显微镜和扫描电镜)、维氏硬度测试、接头拉伸性能测试等方法研究焊后热处理对2A14电子束焊接接头显微组织和性能的影响。结果表明,通过焊后热处理,焊缝中心原晶界分布的网状共晶组织回溶于基体组织中消失,焊缝内部析出大量弥散强化项,基体强化效果增强,显微硬度显著升高,由焊态下低于母材硬度直接升高至超过母材硬度。接头抗拉强度由原来的355MPa提高到465 MPa,超过了母材强度。接头断裂均发生在焊缝,由断口分析发现热处理后接头韧性增强,韧窝深度增加,且有第二相质点出现。     

激光焊接HR-2抗氢不锈钢的性能及组织

为研究HR-2抗氢不锈钢的激光焊接性,对焊接接头的力学性能、试样断口扫描电镜形貌、焊缝金相组织及焊缝内气孔的形貌与成分进行了试验与分析.结果表明,激光焊接HR-2抗氢不锈钢,虽然焊接接头的抗拉强度有所升高,断面收缩率和缺口冲击韧性值有所降低,但试样的微观断裂机制与母材一样是按微坑聚集型的韧性断裂方式进行的,表明焊接接头仍然具有较好的韧塑性;焊缝中未出现明显的合金元素烧损或过多的氧化及脱氧产物,焊缝热影响区很窄,与基体的结合界面良好;激光深熔焊接HR-2抗氢不锈钢,焊缝中除了容易出现常见的析出性气孔和反应性气孔外,更容易出现激光焊接所特有的小孔型气孔.