考虑腐蚀因素的船体结构寿命预测方法

为建立考虑腐蚀因素的船体结构寿命预测方法,在分析现有常用的船体结构腐蚀损伤时变模型的基础上,根据舰船维修保障实际情况建立了考虑腐蚀防护系统作用时间和维修时间等因素的腐蚀时变模型。根据相关规范选择了船体结构腐蚀寿命标准,并建立了一种计算船体结构腐蚀寿命的方法。该方法建立了船体结构腐蚀寿命与腐蚀防护系统作用时间和修理时间等因素之间的量化关系,可以用于预测均匀腐蚀条件下船体结构寿命,也可以反过来指导腐蚀防护系统设计指标的选择和船体结构维修策略的确定。     

Storage life prediction under pre-strained thermally-accelerated aging of HTPB coating using the change of crosslinking density

In order to predict the storage life of a certain type of HTPB (hydroyl-terminated polybutadiene) coating at 25 C and analyze the influence of pre-strain on the storage life, the accelerated aging tests of HTPB coating at 40 C, 50 C, 60 C, 70 C with the pre-strain of 0%, 3%, 6%, 9%, respectively were carried out. The variation regularity of the change of crosslinking density was analyzed and the aging model of HTPB coating under pre-strained thermally-accelerated aging was proposed. The storage life of HTPB coating at 25 C was estimated by using the Berthelot equation as the end point of the aging life with a 30% decrease in maximum elongation. The results showed that the change of crosslinking density of HTPB coating increased with the increase of aging temperature and aging time, and decreased with the in-crease of pre-strain. Under 0% pre-strain, the relationship between the change of crosslinking density of HTPB coating and the aging time can be described by the logarithmic model with the confidence probability greater than 99%.The stress relaxation phenomenon existed under 3%, 6% and 9% pre-strained aging. The aging model considering chemical aging and pre-strain was established with the confidence probability greater than 90%. The storage life of HTPB coating was 15.2935 years at 25 C under 0% pre-strain, which was reduced by 13.9007%, 75.6949% and 89.7859% under 3%, 6% and 9% pre-strain, respectively. The existence of pre-strain has a serious impact on the storage life of HTPB coating, therefore, the pre-strain should be avoided as much as possible during the actual storage.     

Weapon effectiveness and the shapes of damage functions

This paper provides a review of methods of assessing a fragmentation weapon's effectiveness against a point target or an area target with keeping the focus on the necessity of using the Carleton damage function with the correct shape factor.First,cookie-cutter damage functions are redefined to preserve the shape factor of and to have the same lethal area as the corresponding Carleton damage function.Then,closed-form solutions of the effectiveness methods are obtained by using those cookie-cutter damage functions and the Carleton damage function.Finally,the closed-form solutions are applied to calculate the probability of damaging a point target and the expected fractional damage to an area target for several attack scenarios by using cookie-cutter damage functions and the Carleton damage functions with different shape factors.The comparison of the calculation results shows that using cookie-cutter damage functions or the Carleton damage function with a wrong shape factor results in quite signifi-cant differences from using the original Carleton damage function with a correct shape factor when weapon's delivery error deviations are less than or comparable to the lengths of the lethal area and the aim point is far from a target.The effectiveness methods improved in this paper will be useful for mission planning utilizing the precision-guided munitions in circumstances where the collateral damage should be reduced.     

无源雷达GPS卫星信号模糊函数研究

研究了GPS卫星信号作为照射信号的双基无源雷达信号模糊函数性能,论述了雷达系统结构和信号模型,分析了GPS信号的模糊函数特性,给出了计算机仿真。理论分析和仿真结果表明,GPS信号作为无源雷达照射源具有良好的目标分辨力。     

基于生物视觉原理的图像结构信息变化检测方法

为克服多时相遥感图像变化检测中照度差异和配准误差的影响,采用边缘结构信息进行变化检测。利用多方向Gabor函数从图像梯度强度图中提取边缘结构信息,称之为边缘标记(Edge Tag,ET),通过比较多时相遥感图像中ET的互相关系数实现变化检测。为减小差异较小的边缘对检测结果的影响,在相关系数的计算中引入抑制因子。仿真图像和真实图像的实验结果表明,该方法能克服图像照度差异和配准误差对变化检测的影响,取得了较好的检测效果。     

战术情报系统模型化分析方法

针对未来联合作战活动中陆军作战部队的战术应用需求,提炼出陆军战术情报系统建设的组织体系模型和情报生产区域模型,同时,以某一陆军战术作战单位为例,提出并深入分析对应情报系统节点的功能参考模型,建立了基于组织体系模型和功能参考模型的陆军战术情报系统模型化分析方法,详细描述了该模型化分析方法涉及的陆军战术情报系统的6个主要功能单元;最后简要分析了该模型化分析方法的军事应用前景.     

从艺术客体的选择看中国古代戏剧家表现社会生活内容的广阔性

中国古代戏剧家在戏剧人物艺术客体的选择上,同古希腊悲喜剧和印度梵剧迥然不同,表现出别具一格的建树和开拓性,初步形成了具有中国作风和中国气派的戏剧文化,并在这种戏剧文化中体现了中国古代剧作家们主体精神的独立不羁的自由品格和表现社会生活内容的无限广阔性。     

A stochastic model for burn‐in procedures in accelerated environment

Burn‐in procedure is a manufacturing technique that is intended to eliminate early failures of system or product. Burning‐in a component or system means to subject it to a period of use prior to being used in field. Generally, burn‐in is considered expensive and so the length of burn‐in is typically limited. Thus, burn‐in is most often accomplished in an accelerated environment in order to shorten the burn‐in process. A new failure rate model for an accelerated burn‐in procedure, which incorporates the accelerated ageing process induced by the accelerated environmental stress, is proposed. Under a more general assumption on the shape of failure rate function of products, which includes the traditional bathtub‐shaped failure rate function as a special case, upper bounds for optimal burn‐in time will be derived. A numerical example will also be given for illustration. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

差分跳频码性能检验研究

差分跳频是一种新的扩展频谱通信技术.在介绍差分跳频基本原理的基础上,将差分跳频的频率跳变过程建模成齐次马尔可夫链.分析了G函数的功能,重点讨论了差分跳频码性能的检验方法,包括不可约性、频隙滞留、均匀性和随机性检验,其中频隙滞留是首次提出应用于差分跳频码性能的检验.这些检验方法对于差分跳频G函数的设计具有一定的指导意义.     

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。