高速电弧喷涂耐磨涂层性能研究

将低碳马氏体和3Cr13+AlRE伪合金高速电弧喷涂层进行了性能和组织结构的对比分析。实验结果表明,与伪合金涂层相比,低碳马氏体涂层呈现出更优异的力学性能、耐磨性能和机械加工性能。该涂层可用于发动机曲轴等零件的再制造。     

基于解析算法的声纳浮标搜潜系统定位精度分析

针对基于位置时间参数解析算法的声纳浮标阵搜潜系统的定位精度问题,采用定性和定量分析相结合的方法展开了研究。从解析定位模型出发,首先定性分析浮标自身的定位误差与传感器测时误差对航速及航向角计算的影响;然后选取评价指标,采用蒙特卡洛方法进行了仿真分析,得到了不同仿真条件下各个因素对定位精度具体的影响关系,这些结论为根据精度参数合理选择浮标阵的数量及布放阵型提供了依据。     

一种RetinaNet与SE融合的航空取证目标检测算法

针对在开展航空侦察取证时缺乏自动化、智能化取证手段的情况,提出了一种基于Reti-naNet与SE融合的航空取证目标检测算法,解决目标尺度变化大、数据集中类别不均衡的问题,并通过SE (squeeze-excitations)模块引入注意力机制进一步改进性能.该改进算法中的特征金字塔网络FPN可有效应对目标尺寸变化较大...     

Limiting cyberwarfare: applying arms-control models to an emerging technology

ABSTRACT

An arms race in cyberspace is underway. US and Western government efforts to control this process have largely been limited to deterrence and norm development. This article examines an alternative policy option: arms control. To gauge whether arms-control models offer useful lessons for addressing cyber capabilities, this article compiles a new dataset of predominantly twentieth-century arms-control agreements. It also evaluates two case studies of negotiated agreements that regulate dual-use technologies, the 1928 Geneva Protocol prohibiting chemical- and biological-weapon use and the 1944 Chicago Convention on International Civil Aviation. The analysis underscores the limits of norm development for emerging technologies with both civilian and military applications. It finds lessons for developing verifiable, international cooperation mechanisms for cyberwarfare in the regulatory model of international aviation. Conventionally, arms-control agreements take advantage of transparent tests or estimates of arms. To restrict cyberwarfare activities, experts and policy makers must adapt arms-control models to a difficult-to-measure technology at an advanced stage of development and use. Further investigation of international regulatory schemes for dual-use technology of similar diffusion and development to the internet, such as international civil aviation, is needed.     

新型铝水燃烧无人水下航行器混合动力系统优化设计

铝水燃烧无人水下航行器混合动力系统利用铝水燃烧产生的热量来加热水产生高温气流带动涡轮做功从而产生动力,研究表明其具有较高的能量密度。在原混合动力系统基础上,提出三种新的系统方案,分别对其建立数学模型并进行求解,得到并比较各个系统方案净输出功率、能量密度、系统效率等性能参数。计算结果表明:采用直接返回的高温气流与铝进行反应,虽然提高了水蒸气温度,但系统性能有所下降;增加蒸发器和固体换热器系统后充分利用固体氧化剂的热量,使得系统性能提升;采用双燃烧室加壁面冷却换热构型,减少了高温压缩机组件且解决了燃烧室热防护问题,同时系统性能有所提升。研究结果可为今后铝水燃烧无人水下航行器混合动力系统总体设计提供参考。     

Effect of fusion welding processes on tensile properties of armor grade,high thickness,non-heat treatable aluminium alloy joints

AA5059 is one of the high strength armor grade aluminium alloy that finds its applications in the military vehicles due to the higher resistance against the armor piercing (AP) threats. This study aimed at finding the best suitable process among the fusion welding processes such as gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) by evaluating the tensile properties of AA5059 aluminium alloy joints. The fracture path was identified by mapping the low hardness distribution profile (LHDP) across the weld cross section under tensile loading. Optical and scanning electron microscopies were used to characterize the microstructural features of the welded joints at various zones. It is evident from the results that GTAW joints showed superior tensile properties compared to GMAW joints and this is primarily owing to the presence of finer grains in the weld metal zone (WMZ) and narrow heat-affected zone (HAZ). The lower heat input associated with the GTAW process effectively reduced the size of the WMZ and HAZ compared to GMAW process. Lower heat input of GTAW process results in faster cooling rate which hinders the grain growth and reduces the evaporation of magnesium in weld metal compared to GMAW joints. The fracture surface of GTAW joint consists of more dimples than GMAW joints which is an indication that the GTAW joint possess improved ductility than GMAW joint.     

基于能力的远程航空通信用频需求获取策略

提出一种基于能力的远程航空通信用频需求获取策略。分析了远程航空通信用频需求获取的基本思路。在此基础上,将远程航空通信用频需求自顶而下划分为任务需求、能力需求、效果需求3个层级,通过对层级进行定义和关系分析,给出基于能力的远程航空通信用频需求获取框架,最后对需求获取准则进行定义,得出一套较为科学有效的远程航空通信用频需求获取流程。     

有机羧酸在中性腐蚀介质中对铸铝的缓蚀性能研究

通过电化学方法研究了不同浓度的有机羧酸对偶接及非偶接状态下铸铝的缓蚀性能,并对其缓蚀机理作了初步探讨.结果表明:常温状态下,该有机羧酸对铸铝有着很好的缓蚀效果,且随着其浓度的提高,缓蚀效果增加.此缓蚀剂对铸铝主要表现为几何覆盖效应,为抑制阳极型缓蚀剂.     

2A12铝合金焊接接头超声冲击处理前后拉伸性能分析

为克服铝合金薄板焊接接头强度偏低、韧性不足的缺点,用ER5356焊丝对不同厚度的2A12铝合金板材进行了手工氩弧焊接,并采用超声冲击处理对焊接接头进行全覆盖强化处理。采用金相显微镜观察了处理和未处理焊接接头的显微组织结构,对接头的力学性能进行了测试分析,分析了超声冲击处理改善2A12铝合金焊接接头力学性能的机理。结果表明：铝合金焊接接头经超声冲击强化处理后,6 mm和4 mm厚板材对接接头的抗拉强度分别提高了17.4%和23.7%,延伸率分别提高了28%和44%,焊缝表层组织得到明显细化。分析认为：晶粒大幅细化、组织致密化和缺陷减少,是超声冲击处理改善铝合金焊接接头抗拉伸性能的主要原因。     

航空燃料冰点快速测定方法

冰点是表征航空燃料低温使用性能的重要指标。常规冰点测定方法操作步骤复杂,测定时间长,影响航空燃料质量检测效率。基于光散射原理,将温度传感和光电检测技术应用于航空燃料冰点测定,利用燃料结晶对光散射和透射的影响,实现航空燃料冰点快速测定。该方法操作简单快速,检测1个油样用时少于15 min,大幅提高了冰点检测效率;试样体积仅需2 mL,有利于试验环境保护;测定结果重复性好,与标准方法 GB/T2430—2008具有良好的相关性。