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SAR技术的发展现状 总被引:5,自引:0,他引:5
文章以表格形式来说明民用空载和机载合成孔径雷达(SAR)技术的发展现状。表中列出了一些用户需求和目前系统的一些特性,并给出了一些特殊的应用结果。 相似文献
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冷战后我周边一些国家和地区的军费明显上升,出现与世界裁减军费的主流逆发展的趋向。本文着重研究了东南亚一些国家和印度、韩国、日本等,以及我国台湾地区的军费增长问题,对其增长原因和性质进行了较深入的分析,并提出了自己的一些看法。 相似文献
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1 概述自从1989年底一些院校引进MASSCOMP微巨机(以下简称M机)以来,我南京计算机维修服务中心已为大部分用户提供了维修服务。通过工作实践和研究讨论,不仅取得了经验,提高了维修服务水平,更主要的是发现了一些问题,找到了一些故障的主要原因,并针对一些问题提出了解决的方法。 相似文献
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本文根据计算机基础教学的情况,简要分析了计算机基础教育面临的一些问题,并结合个人多年来教学经验,提出了一些解决方法。 相似文献
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本文探讨了当前大学英语教学中存在的一些问题,针对全球进入信息化时代,提出了在信包网络环境下改革英语课程体系、教学模式和标准化考试的一些设想。 相似文献
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回顾了混沌控制产生的背景 ,重点介绍了OGY方法的思想、原理和特点 ,简要概括了十年来的一些重要进展 ,并对今后的发展方向和可能存在的困难提出了一些见解。 相似文献
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《防务技术》2020,16(3):668-677
The formation and separation behaviors of tandem EFPs are studied by the combination of experiments and simulations. The results show that different formation and separation processes can be obtained by adjusting the double-layer liners, and simulations agree with experiments well. Then, the interaction process between the two liners is discussed in details, and the formation and separation mechanism are revealed. It can be found that there are four phases in the formation and separation processes, including impact phase, propulsion phase, slide phase and free flight phase. During the impact phase, the velocities of two liners rise in turns with kinetic energy exchange. In the propulsion phase, the axial impact becomes insignificant, but the radial interaction between two liners influences the appearance of tandem EFPs. Meanwhile, it should be mentioned that the inner surface of foregoing EFP remains to be in contact with the outer surface of following EFP in the propulsion phase, and the following one would continue to push the foregoing one for about 10μ to 20 μs, causing the velocities of following and foregoing EFPs gradually decreasing and increasing respectively. In the slide phase, an obvious relative movement occurs between the two EFPs, and there would be barely kinetic energy exchange. Then, the two EFPs separate gradually and get into the phase of free flight. Generally, if the outer and inner liners have the same thickness, the outer copper-inner copper liners form two long EFPs, the outer copper-inner steel liners become a foregoing short steel EFP and a following long copper EFP, and the outer steel-inner copper liners produce a foregoing long copper EFP and a following conical steel EFP. In addition, thickness match also has an important impact on formation appearance and separation process for both outer copper-inner copper liners and outer steel-inner copper liners. With the thickness ratio of outer liner to inner liner decreasing, the length and length-diameter ratio of both foregoing and following EFPs increase gradually. 相似文献
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根据chirp信号在模糊域的特点,本文提出了线性核时频表示方法。这种方法在提高分辨率、消除交叉项以及抑制噪声等方面都具有较高的性能。理论分析和实验结果都证实了这种方法的有效性 相似文献
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David Santoro 《The Nonproliferation Review》2013,20(3-4):319-332
This viewpoint takes stock of the changes in the strategic nuclear landscape in recent decades and reflects on its consequences on the policy community. It finds that the number and scope of issues have expanded considerably; they have manifested themselves in many more regions of the world; and they have become deeply politicized and polarized. The consequences have been twofold: the nuclear policy field has seen the development of an increasingly diverse expert community composed of highly specialized functionalists and regionalists, and it has become ever more divided into two entirely separate ideological camps—one that believes in deterrence, the other in disarmament. The stove-piping of expertise and the widening gap between deterrence and disarmament ideologies are immensely problematic because, in different ways, they stand in the way of the emergence of a better and safer nuclear future. Looking ahead, it is critical to “bust the silos of expertise” and to build bridges between the deterrence and disarmament ideological camps. Only such a community-building effort will help solve today’s and tomorrow’s nuclear challenges. 相似文献
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作为生物信息学的重要研究内容,近年来代谢网络结构特征方面的研究取得了许多成果。回顾了代谢网络的重构和表示方法,重点综述了代谢网络宏观结构特征所蕴含的生物学意义,以及拓扑特征所揭示的网络演化过程和网络稳健性信息,提出了目前研究中仍然存在的问题及可能的解决思路,并对将来的研究趋势进行了阐述。 相似文献
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John P. Cann 《Small Wars & Insurgencies》2013,24(1):103-128
The lessons from the two French counterinsurgencies, Indochina and Algeria, give rise to a new understanding of the projection of airpower in remote and hostile environments and the purpose, design, and use of aircraft in counterinsurgency. In both Indochina and Algeria, the campaigns were ones of poverty, and it is their imaginative management under severe resource constraints that provides thoughtful and applicable lessons for today. In both cases, airpower held the promise of delivering victory and solving the resource issue. In Indochina, acquisition of the needed aircraft, operating knowledge, and experience came too slowly to realize this promise. In Algeria, the French embraced the lessons from Indochina and were quite successful and innovative in the use of airpower. The lessons can be reduced to four requirements: (1) a network of airfields for liaison, ground-support, and intra-theater airlift to enable effective air support of ground forces; (2) a solid, reliable, and simple ground-support aircraft capable of operating from forward airfields within range of ground engagements; (3) a capable intra-theater heavy-lift transport to supply the extended ground forces; and (4) helicopter capability to enhance tactical troop mobility and support. 相似文献
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刘占军 《中国人民武装警察部队学院学报》2011,27(1):64-66
当代中国以人为本的理念,不但建立在马克思主义人学理论基础之上,而且是以当代中国和世界社会实践为现实根据的,只有把握和理解以人为本的理论源泉和现实根据,弄清以人为本的价值取向,才能真正实现以人为本。 相似文献
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Stephen A. Emerson 《Small Wars & Insurgencies》2013,24(4):669-687
This article provides an in-depth examination and analysis of the 2006–2009 Tuareg rebellion in Mali and Niger. It identifies the underlying reasons behind the rebellion, explores contrasting counter-insurgency (COIN) strategies employed by the two governments, and presents some lessons learned. While both COIN approaches ultimately produced similar peace settlements, the article argues that the Malian strategy of reconciliation combined with the selective use of force was far more effective than the Nigerien iron fist approach at limiting the size and scope of the insurgency and producing a more sustainable peace. It concludes by looking at the role of external actors, particularly the United States, and how the failure to internationalize the conflict was actually more beneficial to the local COIN effort, as well as to the longer strategic interests of the United States in the region. 相似文献
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张晓雅 《武警工程学院学报》2014,(3):41-45
武警职权的配置是武警部队依法行使权力、完成任务的基础,武警职权的行使又是实现武警职能的途径。从宏观上确定武警职权的配置与行使的基本原则,是保障武警部队正确行使权力、合法用权的前提。通过对武警职权的属性、配置原则、行使原则三个问题的探讨,从理论研究的角度对相关问题一一提出了相应的观点。 相似文献
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Ian G.Crouch 《防务技术》2021,17(6):1887-1894
The ballistic performance, and behaviour, of an armour system is governed by two major sets of variables, geometrical and material. Of these, the consistency of performance, especially against small arms ammunition, will depend upon the consistency of the properties of the constituent materials. In a body armour system for example, fibre diameter, areal density of woven fabric, and bulk density of ceramic are examples of critical parameters and monitoring such parameters will form the backbone of associated quality control procedures. What is often overlooked, because it can fall into the User’s domain, are the interfaces that exist between the various products; the carrier, the Soft Armour Insert (SAI), and the one or two hard armour plates (HAP1 and HAP2). This is especially true if the various products are sourced from different suppliers.There are between 30 and 150 individual layers within a typical body armour system, and each of the interfaces between each of those layers will, in some way or another, contribute to the ballistic performance of the system. For example, consider the following interfaces/interlayers: (i) the frictional, sliding, inter-ply surfaces within a soft armour pack, and also between the pack and the carrier, (ii) the air-gaps that may develop within the soft armour pack, (iii) the interconnecting space between the soft armour pack and the hard armour plate, (iv) the nature of the interfaces between adjacent plies of a multiplied backing laminate, even in a highly compressed Ultra High Molecular Weight Polyethylene (UHMWPE) variant, (v) the interlayer between the ceramic and its substrate, within a HAP, and (vi) the geometrical fit between two hard armour plates within a stacked body armour system. This paper will provide a User-friendly overview of all such interfaces and provide unique guidance as to their criticality and influence. 相似文献
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将指数极坐标系建立在运动的圆柱上,推导了运动坐标中剪切来流条件下,涡生振荡的涡量-流函数守恒方程及其初始和边界条件,圆柱表面的水动力表达式以及圆柱振荡方程。对圆柱从静止开始振荡,到发展为稳定振荡状态进行了计算和讨论,描述了脱体涡街的发展过程,升阻力相图的连续变形和漂移,圆柱振荡和平衡位置的变化过程。并研究了涡生振荡终态随剪切度K的变化。结果表明,剪切来流给流场加入了背景涡,使圆柱的上涡增强而下涡减弱,流场的对称性被破坏。随着剪切度K的增大,涡街的倾斜程度增大,压力曲线的漂移量增大,由此导致升力的绝对值增大,圆柱的振幅增大且平衡位置向圆柱下侧的漂移也越大。 相似文献