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水雷是一种布设在水中或海底,当舰船与其碰撞或进入其引信作用范围时,或由人工控制、或自动控制而起爆的水中武器。它由水面舰艇、潜艇或飞机布放,具有隐蔽性好、威胁时间长、布放简便、扫除困难、效费比较高、用途广泛等特点,是一种可以发挥战略作用的常规武器。 相似文献
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利用微气泡减小平板摩擦阻力的数值模拟 总被引:2,自引:0,他引:2
假定气-液两相流体均匀混合且微气泡在水流中存在滑移运动,运用混合多相流模型对水中运动平板的微气泡减阻过程进行了数值计算,研究了微气泡流的减阻机理,分析了主流速度及气体流量率等对减阻率的影响规律,同时构建了一个减阻率预报数学模型,并指出在微气泡减阻中存在一个与主流速度相对应的饱和气流量. 相似文献
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反水雷装备的冤家对头——水雷反水雷与水雷是一对相互共存的矛盾体,谈到反水雷,就不能不先谈谈水雷。粗略地说,水雷就是水中“地雷”。由于使用环境的特殊性及打击对象的多样性,水雷的品种、样式尤其是所依赖的技术又比地雷复杂得多。按水中状态可分为锚系于水下的锚雷、漂浮于水中的漂雷、沉没在海底的沉底雷;按水雷布放方式分为舰布、潜 相似文献
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微槽平板热管传热性能的实验研究 总被引:4,自引:0,他引:4
系统地研究小充液率条件下重力对微槽平板热管传热性能的影响,分析了工作温度、冷却方式等影响因素.发现重力对热管径向液膜的分布影响比较小,而对轴向的影响比较明显,从而使得倾角较大地影响了热管的传热能力.进一步证明了深槽平板热管具有良好的传热性能. 相似文献
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拟定的制导方法重点在于通过最小二乘法和卡尔曼滤波对随时间变化的目标状态进行估算。这为提前表明目标的未来位置提供了基础。从而我们能解决预测拦截点问题,并且将拦截器直接对准拦截点,由此产生了一个碰撞路线导引方案。为了实现这个方案,提出了一个分层结构。在这一结构的外层回路中,首先寻求预测拦截点问题,然后在拦截点附近用古典比例导引方法对拦截点作一些小的修正。本文给出了目标状态的估算方法和预测拦截点问题的显式解;接着,提出了一种基于修正拦截点位移的制导算法;然后,提供了“重力下沉”的修正项。本文的贡献在于给出了拦截点的修正方法,这个方法可用于补偿拦截过程中发现的拦截点的位移和重力下沉。 相似文献
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潜艇规避被动声纳浮标阵方法及期望驶离时间 总被引:2,自引:0,他引:2
基于对反潜巡逻机布放被动声纳浮标阵的研究,对方形阵的布放建立了模型。利用该模型研究了我潜艇规避被动浮标声纳阵的方法。通过计算,得出潜艇驶离被动声纳浮标阵搜索范围的期望时间,用选取的声纳浮标阵间距和潜艇规避速度对结果进行分析,为潜艇的下一步行动提供辅助决策。 相似文献
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高速方尾水面舰船兴波问题计算方法研究 总被引:7,自引:4,他引:3
将Dawson型兴波阻力计算方法推广用于高速方尾水面舰船兴波问题计算,在计算中同时计入了尾封板0静压力、尾倾与下沉等因素的影响.以两高速方尾水面舰船为例计算了兴波问题,将兴波阻力计算值与剩余阻力模型试验值进行了比较,求出了相应的相关系数.结果表明,本方法可较好地求解高速方尾水面舰船的兴波问题,兴波阻力相关系数可用于修正理论计算结果,以提高计算精度. 相似文献
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介绍了用CCD器件完成玻璃管外径和壁厚在线测量的实现方法,测试系统的结构和硬件及软件设计思想。本测试系统也适合于对其它透明或非透明管材及线材的在线测量。 相似文献
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AbstractWe study the differential impacts of combat and humanitarian assistance/disaster relief (HA/DR) missions on the mental health of U.S. Marine Corps members. The deployment experiences of any individual Marine are plausibly random conditional on the observable characteristics which are used to assign Marines into units. Leveraging this exogenous variation, we compare the incidence of post-traumatic stress disorder (PTSD) and suicide deaths among Marines who deployed to either Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF) or HA/DR missions between 2001 and 2011. We find that the hazard of PTSD is close to eight times higher among Marines returning from OEF/OIF compared to those never deployed, and just 1.33 times higher among those returning from HA/DR (and never participated in OEF/OIF). Those returning from OEF/OIF missions are 1.81 times more likely than those never deployed to die by suicide when they were still active duty, and the hazard increases to almost 3 after they have left the military. In contrast, we find no difference in the hazards of suicide death between those that deployed to only HA/DR missions and non-deployed Marines. 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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Godfrey Maringira 《Defence Studies》2016,16(3):299-311
The paper reveals how Zimbabwean soldiers who fought in the Democratic Republic of the Congo (1998–2002) were challenged by the terrain of war. While soldiers are trained to live and fight in dreadful wars, I argue that immersing oneself in the war terrain is neither mathematical nor calculative; rather, war tactics to be employed are defined by the context in which soldiers operate in. When soldiers reflect on and about the war, they unconsciously produce accounts that are often not completely heroic, but a life lived in fear as well an issue that they had never anticipated when they set out to war. A main finding of this study is that while these soldiers were deployed to fight against the rebels, they find difficulties in locating physical features from map reading to the ground, distinguishing the enemy from civilian people and deployed for days without eating a proper meal as well as seeing their fellow soldiers dying in the context of war. The paper provides a vantage point in which we can also understand that trained soldiers do not exert total power over war terrains, they are sometimes challenged by the war situation itself. 相似文献
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Li-zhi Xu Cheng-xin Du Chun Cheng Xiao-dong Wang Jiang-bo Wang Zhong-hua Du Guang-fa Gao 《防务技术》2021,17(3):859-873
When a penetrator with enhanced lateral effect (PELE) impacts on a reinforced concrete (RC) target, the target is damaged with a large opening. An understanding of how PELE projectile parameters affect the opening dimension, is essential for effective design of the PELE projectile. In this study, under the condition that the impact velocity and target parameters (strength and thickness) were fixed values, the important influence factors of the PELE (jacket wall thickness B, jacket material strength Y1, filling material strength Y2 and angle of monolithic jacketθ) were determined by a dimensional analysis. Tests and simulations of the PELE penetrating the RC target were conducted to analyze the influence of these factors on opening diameter ((D), an equivalent diameter under relative kinetic energy). Based on the test and simulation results, it is found that the influence of these factors B, Y1 andθon the deformation mode of the jacket shows a similar trend:as values of the three factors decrease, the jacket deforms from small bending deformation to large one, and then to curling deformation. This causes the opening diameter to first increase with the decrease of these three factors, and then decreases. It is well known that the bending resistance of the jacket is related to these factors B, Y1 andθ. Therefore, a plastic limit bending moment (M0) of the jacket was quoted to characterize the influence of these factors on the bending deformation of the jacket and the opening diameter of the target. The influence factor Y2 causes (D) to first increase with the increase of Y2, and then decreases. A formula was developed to predict the opening diameter, whose influence parameters were considered in a dimensionless way. It has been shown that the dimensionless opening diameter (D)/d1 is dependent on two dimensionless parameters Q = (d31fc/M0) and G = (fc/Y2), where d1 and fc are the outer diameter of the projectile and the compressive strength of the target, respectively. 相似文献
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二级迭代法由内、外迭代和内迭代次数三部分组成。给出了线性方程组二级迭代法R1-收敛因子的一个上界,这个上界由内、外迭代的R1-收敛因子和内迭代次数所决定,其主部为外迭代的R1-收敛因子。在矩阵单调性条件下,对于任何内迭代方法和任意内迭代次数,证明了外迭代的R1-收敛因子也是二级迭代法R1-收敛因子的下界。所得结果反映了内、外迭代的收敛速度以及内迭代次数对于二级迭代法收敛速度的综合影响。 相似文献
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美国地基中段防御(GMD)系统虽然于2004年底完成了初始部署,但是目前仍然没有完全移交给军方,而由美国导弹防御局负责管理和维护.通过对GMD系统进行成熟度评估,得出其发展状态仍然处于系统发展和验证阶段. 相似文献
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This article analyzes how the conflict environment in which a civilian monitoring mission is deployed influences the monitors' assessment of the operation. It draws on unique empirical material from the experience of the Sri Lanka Monitoring Mission (SLMM), deployed to oversee a ceasefire agreement in Sri Lanka 2002–2008. With material from a survey and in-depth interviews, experiences of the monitors are analyzed and changes over time are traced in relation to the monitors' assessment of the mandate and organizational set-up of the mission. The study points to the difficulty of monitoring missions to address escalation during an ongoing peace process. Its function is dependent on the goodwill of the parties. In essence, monitoring missions have the potential to strengthen peace when there is momentum in favor of progress, but when relations between the parties turn sour and the conflict escalates a civilian monitoring mission basically loses its potential. During the final stages of the war, which saw a very large number of civilian casualties, the war-torn areas were closed to international observers. Moreover, international pressure for a short-term ceasefire to alleviate the humanitarian situation was dismissed by the Sri Lankan government, which also saw the backing of several important actors, not the least China. 相似文献