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161.
Recently, multi-layered targets have become commonplace in both military and civilian applications, such as marine hulls, armored vehicle bodies, outside structures of bulletproof cars, and aerospace vessels. This paper studies the resistant performance of perforation in multi-layered targets. An estimation procedure is established based on the concepts of the conservation of momentum, impulse-momentum law, and conservation of energy. Experimental results of the test of Almohandes et al. are adopted to check the residual velocity of multi-layered targets. The results of the verification are good in terms of agreement for impact velocities ranging from 700 to 800 m/s, when the ratio of the projectile length to the projectile diameter (i.e. L/D) is 4.2, and the average residual velocity error of single, double- or triple-layered targets range approximately from 4.42 to 8.40%. The ballistic performance is best for the double target when the ratio of the first layer thickness to the total thickness (i.e. t1/(t1+t2)) is about 0.75, and the worse performance occurs when the ratio t1/(t1+t2) is 0.5. An air gap slightly influences the resistant performance of perforation in multi-layered targets. These results may serve as a useful reference for designers. 相似文献
162.
163.
Zuo Qihua Yang Zhengji .
Senior Engieer River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1996,(3)
- The variation of the amplitude of waves with varying incident angles when waves propagate through a typical approach channel is discussed by a numerical calculation method, the result of which shows that the influence of the channel on wave propagation is obvious. When the wave propagation direction is in coincidence with the channel axis, the wave amplitude ratio will decrease with the increase of propagation distance. When the incident angle is 15 - 30 , there appears an area of larger wave amplitude ratio on the side slope facing the waves, but at the another side, the wave amplitude ratio is generally small, indicating that the channel has a shielding effect. When waves propagate across the channel perpendicularly, the wave amplitude ratio can be calculated with the shallow water coefficient. 相似文献
164.
科学计算可视化作为新一代的分析工具 ,正在进入物理海洋学领域。文中介绍对海洋调查数据进行可视化的关键问题——数据建模 ,并从分析海洋调查数据的特点出发提出针对海洋研究中可视化建模的原则和有效途径 ,给出相关的实现方法。其中 ,重点讨论局部体样条建模中必须面对的区域分割优化问题 ,引入遗传算法并给出较好的解决方案。 相似文献
165.
166.
L. D. Wright Z. -S. Yang B. D. Bornhold G. H. Keller D. B. Prior W. J. Wiseman Jr. Y. B. Fan Z. Su 《Geo-Marine Letters》1986,6(2):115-120
Internal waves with periods of about 5 minutes and trough to crest heights of up to 6.2 m were observed acoustically over the actively accreting delta front of the Huanghe (Yellow River) in the western portion of the Gulf of Bohai, Peoples Republic of China. The radian frequency of the internal waves was close to the locally-observed Brunt-Vaisala frequency. Through the relatively short (one hour) duration of an internal wave train, the amplitude was observed to decrease progressively with time. These internal waves may cause resuspension of delta-front sediments. 相似文献
167.
Sand dabs, an important commercial flatfish in the Bohai Sea, has recently decreased gradually in biomass, resulting from overfishing and marine pollution. Artificial culture and multiplication of sand dabs are essential and practical in China. The present paper examines the food habitof this fish to provide detailed information for its culture and multiplication. 相似文献
168.
Multibeam imagery of siliceous sponge reefs (Hexactinellida, Hexactinosida) reveals the setting, form, and organization of five reef complexes on the western Canadian continental shelf. The reefs are built by framework skeleton sponges which trap clay-rich sediments resulting in a distinctive pattern of low intensity backscatter from the reefs that colonize more reflective glacial sediments of higher backscatter intensity. Bathymetry and backscatter maps show the distribution and form of reefs in two large complexes in the Queen Charlotte Basin (QCB) covering hundreds of km2, and three smaller reef complexes in the Georgia Basin (GB). Ridges up to 7 km long and 21 m in height, together with diversely shaped, coalescing bioherms and biostromes form the principal reef shape in the QCB whereas chains of wave-form, streamlined mounds up to 14 m in height have developed in the GB. Reef initiation is dependent on the distribution of high backscatter-intensity relict glacial surfaces, and the variation in reef complex morphology is probably the result of tidally driven, near seabed currents. 相似文献
169.
170.
Generally, the underwater flight vehicle (UFV) depth control system operates with the following problems: it is a multi-input multi-output (MIMO) system, it requires robustness, a continuous control input, and further, it has the speed dependency of controller parameters. To solve these problems, an expanded adaptive fuzzy sliding mode controller (EAFSMC), which is based on the decomposition method designed by using an expert knowledge and the decoupled sub-controllers and composition method designed by using the fuzzy basis function expansions (FBFEs), is proposed. To verify the performance of the EAFSMC, the depth control of UFV in various operating conditions is performed. Simulation results show that the EAFSMC solves all problems experienced in the UFV depth control system online. 相似文献