一种用于多方通信的新的SMC安全协议*

对主流安全协议在多方通信环境下的应用进行分析,总结其各自优缺点。在综合各个协议优点的基础上,提出并介绍了一个用于多方通信环境下的SMC(securing multiparty communications)协议,该协议工作在传输层之上,具有更强的可部署性。SMC协议被设计用来取代当前用于多方通信环境的MSEC协议族。通过将SMC协议与MSEC协议族进行比较,证明SMC协议具有与MSEC协议族一致的安全性,并且具有更强的可部署性。     

基于纹理切换的虚拟战斗人员三维显示方法

为了解决形象化模型显示方法硬件依赖性过高、不易实现推广等问题,从“分队指挥模拟对抗演练系统”虚拟战斗人员显示的实际需要出发,提出了一种基于纹理切换的虚拟战斗人员三维显示方法. 重点叙述了这种纹理切换显示方法的基本思路、算法思想、技术路线以及具体实现;并且对实现过程中涉及到的在视点角度发生变化的条件下,如何同时保持纹理框架朝向不变以及如何保持虚拟战斗人员逻辑方向不变两个纹理切换的关键问题进行了重点研究.     

雅安市旅游WebGIS的构建及其存在问题探讨*

基于ArcIMS9.0系统,并结合ArcXML、JavaScript等编程技术、数据库技术及空间数据库引擎ArcSDE,构建了雅安市旅游WebGIS系统。在WebGIS基础平台上,对雅安市旅游资源信息进行采集、存储、管理、分析和图形处理显示,并由图形、图像、文字和声音等多种形式综合展示。针对系统构建过程中遇到的一些主要问题提出了有效的解决方案。针对目前尚未有适合中国国情的地址编码方案问题,率先编制了中国式的地址标准化规则文件和匹配规则文件;利用MapObjects＋VB 6.0开发了地址匹配软件,不仅提高了地址匹配成功率,还大幅度提升了匹配效率;利用TM和DEM等多源信息融合技术解决了三维＂近自然＂地形的显示问题。     

凝胶法制备Cu-BTC块体及其吸附脱除二甲基二硫醚性能

金属有机骨架材料Cu-BTC具有高孔隙率、易调控的骨架结构以及含过渡金属等特点,是吸附脱除硫化物的优异材料。采用凝胶法在常温条件下制备块状样品Cu-BTC-g,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)、红外光谱(FT-IR)、拉曼光谱(Raman)、X射线光电子能谱(XPS)、N₂吸附-脱附等手段对其进行分析表征,同时测定Cu-BTC-g样品对模型硫化物二甲基二硫醚(DMDS)的静态吸附容量、吸附热力学和动力学特性。结果表明：凝胶法制备的Cu-BTC-g样品晶体平均尺寸约为0.2μm、比表面积为901 m²/g、孔体积为0.40 cm³/g,晶体尺寸、比表面积和孔体积均小于溶剂热法合成的样品Cu-BTC-s;在吸附温度298 K下,Cu-BTC-g样品的DMDS吸附容量为110.8 mg/g,比Cu-BTC-s样品提高12%。     

Electric field assisted solid-state interfacial joining of TaC-HfC ceramics without filler

The application of ultra-high-temperature ceramics (UHTCs) demands effective ways of joining in overcoming the problems associated with the fabrication of complex-shaped components. In this study, we choose to investigate a new method of rapidly joining pre-sintered TaC and HfC ceramics without any filler material using the spark plasma sintering (SPS) technique. A well-bonded TaC–HfC interface was observed with no apparent cracking and porosity at the joint. The joining mechanisms were predominantly driven by solid-state diffusion and localized plastic deformation. The nanomechanical properties of the TaC-HfC joint are better than the HfC while comparable to that of the TaC. High-load indentation (up to 200 N) results suggest that the TaC–HfC interface is stronger than the parent UHTCs with no crack propagating at the interface. Upon comparison with the parent UHTCs, the damaged area and the average crack length at the interface, reduced up to ~94% and ~56%, respectively. This study shows that the SPS technique can also apply to joining other UHTCs without any filler, resulting in the new field of developing complex components for the thermal protection system (TPS).     

Simultaneously achieved high-energy storage density and efficiency in (K,Na)NbO3-based lead-free ferroelectric films

With the development of advanced electrical and electronic devices and the requirement of environmental protection, lead-free dielectric capacitors with excellent energy storage performance have aroused great attention. However, it is a great challenge to achieve both large energy storage density and high efficiency simultaneously in dielectric capacitors. This work investigates the energy storage performance of sol-gel-processed (K,Na)NbO₃-based lead-free ferroelectric films on silicon substrates with compositions of 0.95(K_0.49Na_0.49Li_0.02)(Nb_0.8Ta_0.2)O₃-0.05CaZrO₃-x mol% Mn (KNN-LT-CZ5-x mol% Mn). The appropriate amount of Mn-doping facilitates the coexistence of orthorhombic and tetragonal phases, suppresses the leakage current, and considerably enhances the breakdown strengths of KNN-LT-CZ5 films. Consequently, large recoverable energy storage density up to 64.6 J cm⁻³ with a high efficiency of 84.6% under an electric field of 3080 kV cm⁻¹ are achieved in KNN-LT-CZ5-5 mol% Mn film. This, to the best of our knowledge, is superior to the majority of both the lead-based and lead-free films on silicon substrates and thus demonstrates great potentials of (K,Na)NbO₃-based lead-free films as dielectric energy storage materials.     

Valence-induced effects on the electrical properties of NiMn2O4 ceramics with different Ni sources

Spinel-structured NiMn₂O₄ ceramics, with different valence Ni sources, were originally prepared using Ni₂O₃ and NiO as raw materials, and the effects of different valence Ni sources on their electrical properties were first investigated. XRD patterns show that both Ni₂O₃-based and NiO-based NiMn₂O₄ ceramics are single cubic spinel structures. SEM/EDS images indicate that the NiMn₂O₄ ceramics exhibited high density at the experiment-determined sintering temperatures. XPS results and Raman drifts prove that the Ni valence-induced changes in Mn ions at B sites played a significant role in the electrical properties and thermal stability of NiMn₂O₄ ceramics. Compared with NiO-based NiMn₂O₄, the resistivity at 25°C (ρ_25°C) of Ni₂O₃-based NiMn₂O₄ increased dramatically from 3109 to 106958 Ω cm, the thermal constant (B_25/50) increased from 3264 to 4473 K, and the resistance shifts after annealing for 1000 h at 150°C decreased from 0.80% to 0.74%. The investigation of the relationship between the material properties and valence of Ni sources has provided a new and effective way for designing the spinel-structured negative temperature coefficient (NTC) materials by modulating the valence of ions at A sites in the raw materials.     

Preparation of ZrO2 beads by an improved micro-droplet spray forming process

Monodisperse ZrO₂ ceramic beads with size larger than 1 mm have been prepared by an improved micro-droplet spray forming process, through which a compressor and a dispenser were employed to produce droplets continuously. Furthermore, the slurry recipe and drying temperature have been optimized to enhance the sphericity and smoothness of the beads. The sintered ZrO₂ ceramic beads present promising mechanical performance, including a relative density of 84.6%, a crush strength of 256.2 ± 36.6 N as well as a Vickers hardness of 1344.4 ± 58.3 HV. Such procedure reveals great potential in mass production of ceramic beads.     

Ti4+ modified MgZrNb2O8 microwave dielectric ceramics with an ultra-high quality factor

Ti⁴⁺-modified MgZrNb₂O₈ (MgZr_1-xTi_xNb₂O₈, x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were synthesized using the traditional solid-state reaction method. Pure MgZr_1–xTi_xNb₂O₈ was detected without any secondary phase via the X-ray diffraction patterns. According to the sintering behavior and the surface morphology results, the introduction of Ti⁴⁺ reduced the sintering temperature and promoted the grain growth. The correlations between the dielectric properties and the crystal structure were analyzed through the Rietveld refinement and Raman spectroscopy. The slight shifts of the Raman peaks, corresponding to different vibration modes, were induced by the substitution of Ti⁴⁺ for Zr⁴⁺ and related to the improved quality factor. In general, the sample of MgZr_0.9Ti_0.1Nb₂O₈ sintered at 1320°C for 4 h exhibited promising microwave dielectric properties with an ultra-high Q × f value of 130 123 GHz (at 7.308 GHz, 20°C), which is potential for 5G communication applications.     

Electrochemical investigation of La0.4Sr0.6TiO3 synthesized in air for SOFC application

Journal of Applied Electrochemistry - La-doped titanate materials have been widely investigated as alternative Ni-free anodes for solid oxide fuel cells (SOFCs). In this study, La0.4Sr0.6TiO3 (LST)...