基于退化速率跟踪粒子滤波的剩余使用寿命预测框架

毋庸置疑,剩余使用寿命预测对于设备的健康管理越来越重要。近年来粒子滤波方法被越来越多地应用到设备寿命预测技术当中,这是因为粒子滤波方法能更好的解决非线性非高斯系统滤波问题,而且能够获得不确定度信息。但该方法的预测性能却过度依赖于预测模型,并且对于模型参数的初始分布也比较敏感,这在一定程度上限制了粒子滤波预测方法的进一步发展。本文针对基本粒子滤波预测方法的不足,提出了一种基于退化速率跟踪粒子滤波的通用预测框架,以历史观测数据的退化速率统计规律作为指导来跟踪目标数据的退化速率,实现对粒子滤波预测方法的简化。并将该方法用于轴承和锂离子电池的剩余使用寿命预测,验证了方法的有效性。     

MIDDLE EAST NONPROLIFERATION

The Middle East is a crucial region for the global nonproliferation regime. In 2010, the state parties to the Treaty on the Non-Proliferation of Nuclear Weapons proposed a conference on a Middle East Weapons of Mass Destruction-Free Zone. The nuclear weapon-free zone model, on which this idea builds, has achieved important results in other regions, but faces especially stark challenges in the Middle East. However, the attempt to apply the boldly imaginative zone approach to the Middle East holds promise for building a more inclusive dialogue on nonproliferation and regional security.     

基于自适应阈值的FAST特征点提取算法

FAST特征提取算法阈值选取固定,因此不能满足不同图像的特征点抽取要求,并且提取的结果存在着多个特征点块的现象。针对这些缺陷,首先采用动态全局阈值对原始灰度图像进行初步提取得到候选特征点,然后采取动态局部阈值和非极大值抑制法进一步对候选特征点进行筛选,从而达到自适应选取阈值和抑制多个特征点块的目的。实验表明,改进后的算法稳定性高,对不同光照和对比度情况下有一定的适应能力,并且运算量相对比于其他一些特征提取算法要小得多,满足实时应用的要求。     

业务流程建模中流程校验的研究与实现

随着计算机网络技术的迅速发展,企业的信息化程度不断提高,以自动化流程为核心理念的工作流管理系统应用越来越普及,对工作流管理系统的可靠性和正确性要求也越来越高.提出了一种工作流建模时的验证方法:在工作流管理系统的工作流建模环境中加入流程验证模块,对建模过程中可能产生的错误进行验证,进而建立简洁实用的流程;通过分析流程中的异常和失败的类型,增强系统的纠错能力,减少引擎处理的压力;对有着特殊应用的建模过程,能够方便地添加自定义的验证条件,为流程的正确运行提供有效的保障;向基于规则化的工作流系统提供建模完整性的方案,获得系统工作流的稳健性.     

基于信息流的中枢疲劳脑电分析

为充分利用多导脑电信息,首次提出运用有向传递函数（DTF）方法,对不同中枢疲劳状态下导联间信息流的强度和方向的变化进行分析。研究结果表明,脑电功能耦合中额一到一顶方向的信息流是大脑皮层联系的一个固有特征,可以有效地刻画安静清醒和疲劳两个状态,长时间脑力劳动任务引起中枢疲劳的增加,进而导致整个频率段占优势的信息流的方向发生了反转,信息流占优势的方向从实验前的顶一到一额方向,转变为实验后的额一到一顶方向。     

Thermal hazard assessment of TKX-50-based melt-cast explosive

In the present study, thermal hazards of TNT and DNAN used as the molten binder in TKX-50-based melt-cast explosives were comparatively studied through accelerating rate calorimeter (ARC) and Cook-off experiments. Two kinds of ARC operation modes were performed to investigate the thermal safety performance under adiabatic conditions (HWS mode) and constant heating (CHR mode). The obtained results demonstrated that at both heating modes, DNAN/TKX-50 outperformed TNT/TKX-50 from the thermal safety point of view. However, the sensitivity to heat of the samples was reverse because of the different heating modes. In addition, the results of thermal hazard assessment obtained from the cook-off experiment complied with ARC analysis which indicated the molten binder TNT replaced by DNAN would reduce the hazard of the TKX-50 melt cast explosive. Furthermore, the results of cook-off experiments also showed that DNAN/TKX-50 outperformed TNT/TKX-50 from the aspect of thermal stability, which was consistent with the result of CHR mode because of the similar heating process.     

Formation of adiabatic shearing band for high-strength Ti-5553 alloy: A dramatic thermoplastic microstructural evolution

By using split Hopkinson pressure bar, optical microscopy and electronic microscopy, we investigate the influence of initial microstructures on the adiabatic shear behavior of high-strength Ti–5Al–5V–5Mo–3Cr (Ti-5553) alloy with lamellar microstructure and bimodal microstructure. Lamellar alloy tends to form adiabatic shearing band (ASB) at low compression strain, while bimodal alloy is considerably ASB-resistant. Comparing with the initial microstructure of Ti-5553 alloy, we find that the microstructure of the ASB changes dramatically. Adiabatic shear of lamellar Ti-5553 alloy not only results in the formation of recrystallized β nano-grains within the ASB, but also leads to the chemical redistribution of the alloying elements such as Al, V, Cr and Mo. As a result, the alloying elements distribute evenly in the ASB. In contrast, the dramatic adiabatic shear of bimodal alloy might give rise to the complete lamination of the globular primary α grain and the equiaxial prior β grain, which is accompanied by the dynamic recrystallization of α lamellae and β lamellae. As a result, ASB of bimodal alloy is composed of α/β nano-multilayers. Chemical redistribution does not occur in ASB of bimodal alloy. Bimodal Ti-5553 alloy should be a promising candidate for high performance armors with high mass efficiency due to the processes high dynamic flow stress and excellent ASB-resistance.     

On the Road to the 2015 NPT Review Conference

The second session of the Preparatory Committee for the 2015 Review Conference (RevCon) of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) highlighted two issues in particular—progress toward a Middle East Weapons of Mass Destruction–Free Zone and the Joint Statement on the humanitarian impact of nuclear weapons—that may not only greatly affect the health and vitality of the NPT and the 2015 RevCon, but possibly also have implications for the international nonproliferation regime as a whole. Dr. William Potter, director of the James Martin Center for Nonproliferation Studies, interviewed Ambassador Cornel Feruta, chairman of the 2013 PrepCom, to discuss these and other issues related to the meeting and the future of the treaty and its review process.     

切向空气气流对激光辐照碳纤维复合材料的影响

实验研究了靶材表面存在和不存在切向空气气流时,975nm连续激光对碳纤维增强树脂基复合材料的辐照效应,发现切向气流的加载有利于激光对碳纤维复合材料的破坏.从理论上对激光辐照下碳纤维复合材料的破坏机理进行了初步分析,基于碳的氧化特性和氧化反应机理,推导了碳纤维的氧化速率方程.采用改进的光滑粒子方法,对激光辐照下复合材料树...     

如何估计软件的MTBF

软件剩余初始故障个数No、平均无故障时间MTBF、故障暴露率λ和软件运行的成功率θ等是衡量软件可靠性的重要参数.其中对高可靠性软件(包括军用软件等)MTBF是最重要的.传统的MTBF计算方法有2种一是计算发生故障的平均时间间隔二是通过软件可靠性模型进行估计.前者代价较大,后者不太准确.本文从软件的失败率入手研究软件的MTBF,这是一个比较贴近实际的方法.