采用正交分集的灵巧噪声干扰对抗方法

针对数字射频存储干扰机多通道宽带转发模式下的灵巧噪声干扰,提出了基于混沌调制信号、多谐波相位调制线性调频信号的正交分集抗干扰方法。混沌调制信号与多谐波相位调制线性调频信号具有"图钉"形模糊函数,除了具有良好的距离、多普勒分辨力,还对回波频率敏感,通过正交分集设计,能够更好地适应宽带转发灵巧噪声干扰。通过计算机仿真对新方法的抗干扰性能进行了分析和验证,结果表明:在多通道宽带转发灵巧噪声干扰环境下,新方法的抗干扰改善因子能够达到10 d B以上,抗干扰性能明显优于传统的频率捷变、斜率捷变方法。     

多输入多输出雷达恒模稳健波形联合优化算法

针对目标冲激响应及杂波冲激响应分布特性先验知识不准确导致的多输入多输出雷达检测性能下降的问题,提出恒模稳健波形与接收机滤波器联合优化算法。将目标冲激响应及杂波冲激响应分布特性先验知识不准确时的优化问题建模为一个极大极小化问题。运用迭代优化算法将联合优化问题分解为两个子优化步骤:将波形固定时的接收机滤波器权值优化问题建模为广义瑞利商模型,求解得到相应的接收机滤波器权值矢量;利用半正定松弛技术对权值固定时的波形优化问题进行求解,获得对应的波形矩阵,并根据得到的波形矩阵,通过高斯随机化的方法获得所需的恒模波形。对所提算法的收敛性进行了证明,仿真结果表明所提算法有效。     

星箭分离相对位姿摄影测量方法

提出一种基于视觉的星箭分离相对位姿测量方法。在相机内参数已知的情况下,将相机安装于运载火箭,并在卫星上固连不少于6个合作标志,利用相机对合作标志实时成像;基于单目位姿估计的基本原理,采用高效n点渗透与正交迭代结合的方式解算卫星与火箭之间的相对位姿关系。仿真实验结果、半实物仿真实验结果证明了所提测量方法的可行性和准确性。     

机载MIMO雷达稳健非均匀样本选择方法

针对杂波训练样本中混入干扰目标,导致空时自适应处理技术的杂波抑制性能下降问题,提出一种基于目标知识进行局部稀疏恢复的稳健训练样本挑选方法。该方法利用先验知识确定待检测单元中的目标区域,对整个角度-多普勒平面进行遍历,获得稀疏超完备基。通过变换矩阵对超完备基中对应的目标区域进行"挖空"处理,局部稀疏恢复出超分辨的杂波空时谱,获得杂波协方差矩阵估计。结合广义内积算法,实现非均匀训练样本挑选的过程。与常规结合广义内积方法相比,该方法对于不同干扰强度的训练样本,均有良好的检测效果。经仿真验证,所提方法的检验统计量之间区分度更加明显,对于干扰样本的挑选更加彻底,从而有效地提高了空时自适应处理技术的目标检测性能。     

军民融合产业内涵及范畴

发展军民融合产业是各级政府落实军民融合发展国家战略的重要抓手之一。针对军民融合产业界定不清等问题,从理论研究和实践工作层面梳理既有观点及演变趋势,形成对军民融合产业的客观认识。在此基础上,剖析军民融合产业的属性特征,从指导实践工作角度出发提出三种界定军民融合产业范畴及相关统计工作的合理化思路,并提出建立两级联动工作机制、开展国家工业基础中国防科研生产能力普查工作、试点开展军民融合产业分类标准及指标体系建设工作、加强军民融合产业统计数据质量监测等政策建议。     

国防科技助力“一带一路”建设

国防科技能够为"一带一路"沿线国家的经济、政治、安全、科技、文明等方面的发展进步做出重要贡献,我国可以将核能、航空、航天、船舶等国防科技领域作为重点先导领域推进实施。要着眼面临的机遇与挑战,着重从促进战略对接、打造品牌优势、推进军民融合、加强人才培养和关注人文交流等方面搞好战略应对。     

The Illusion of Afghanistan’s Electoral Representative Democracy: The Cases of Afghan Presidential and National Legislative Elections

This article is the latest in a series of published articles systematically examining Afghan Presidential and legislative elections. Structural problems including fraud, ethno-linguistic block voting, and the Single Non-Transferable Vote have had significant impacts on the development of Afghan democratic elections. The challenge now facing the current Afghan government and future elections is the daunting task of uniting the Afghan people while not repeating the electoral mistakes of the past. The tricky balancing act of fostering an overarching national identity without being perceived as privileging particular identities requires strong leadership and a willingness to challenge traditional ethnic, linguistic, and religious norms when need be. Karzai and Ghani Administrations have seriously failed relative to this dynamic.     

The Organization of the Defense Support System: An Economic Geography Perspective

In the context of restricted budgetary resources and the growing cost of maintenance, repair, and overhaul (MRO) activities, a major issue for modern armed forces is to sustain defense platforms. A possible method consists of realizing economies of scale through the concentration of maintenance activities, which involves the spatial reorganization of existing industrial sites dedicated to MRO. This article provides a formalized framework to discuss the optimal organization for the MRO of defense platforms in space. The public planner organizes the maintenance of defense platforms with only two possible spatial configurations. In the dispersed configuration, two industrial production units in charge of the maintenance optimally cover space, whereas in the concentrated configuration, a unique industrial unit covers space. Focusing on the tipping point between the two configurations, the balance of forces between agglomeration and dispersion in defense support activities is described and discussed. On the one hand, economies of scale provide an opportunity to optimize defense support costs, favoring concentration in a unique industrial unit. On the other hand, space causes dispersion to reduce both transport costs and operational social costs. This trade-off illustrates a general principle in spatial economics with an application to MRO production in the French case.     

Humanitarians at sea: Selective emulation across migrant rescue NGOs in the Mediterranean sea

Between 2014 and 2017, no less than 10 different non-governmental organizations (NGOs) conducted maritime Search and Rescue (SAR) operations off the coast of Libya. By rescuing over 100,000 migrants in three years, these NGOs became the largest provider of SAR in the Mediterranean. The theory of institutionalism suggests that organizations conducting similar activities are likely to converge in a process of mimetic isomorphism, deliberately imitating one another to increase their effectiveness and cope with uncertainty. These 10 SAR NGOs, however, developed two different rescue models: While some rescued migrants and disembarked them in Italian ports, others only simply assisted those in distress until the arrival of another ship transporting them to land. They also cooperated with Italian and European authorities to different degrees. Why did SAR NGOs imitated many elements of existing non-governmental rescue models, but discarded some others? This article argues that differences in material capabilities and organizational role conceptions are crucial to explain why newer SAR NGOs have imitated most but not all of their predecessors’ policies, engaging in a process of “selective emulation.”     

Geopolitical Risks and Movements in Islamic Bond and Equity Markets: A Note

This study applies a non-parametric causality-in-quantiles test to examine the causal effect of geopolitical risks on return and volatility dynamics of Islamic equity and bond markets. Geopolitical risks are generally found to impact Islamic equity market volatility measures, rather than returns. However, geopolitical risks tend to predict both returns and volatility measures of Islamic bonds. Interestingly, causality, when it exists for returns and/or volatility of Islamic equities and bonds, is found to hold over entire conditional distributions of returns and volatilities, barring the extreme ends of the same.