排序方式: 共有75条查询结果,搜索用时 546 毫秒
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Due to its high strength, high density, high hardness and good penetration capabilities, Depleted ura-nium alloys have already shined in armor-piercing projectiles. There should also be a lot of room for improvement in the application of fragment killing elements. Therefore, regarding the performance of the depleted uranium alloy to penetrate the target plate, further investigation is needed to analyze its advantages and disadvantages compared to tungsten alloy. To study the difference in penetration per-formance between depleted uranium alloy and tungsten alloy fragments,firstly, a theoretical analysis of the adiabatic shear sensitivity of DU and tungsten alloys was given from the perspective of material constitutive model. Then, taking the cylindrical fragment penetration target as the research object, the penetration process and velocity characteristics of the steel target plates penetrated by DU alloy frag-ment and tungsten alloy fragment were compared and analyzed, by using finite element software ANSYS/LS-DYNA and Lagrange algorithm. Lastly, the influence of different postures when impacting target and different fragment shapes on the penetration results is carried out in the research. The results show that in the penetration process of the DU and tungsten alloy fragments, the self-sharpening properties of the DU alloy can make the fragment head sharper and the penetrating ability enhance. Under the same conditions, the penetration capability of cylindrical fragment impacting target in vertical posture is better than that in horizontal posture, and the penetration capability of the spherical fragment is slightly better than that of cylindrical fragment. 相似文献
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Mushtaq Ahmad 《The Nonproliferation Review》2013,20(2):285-292
Nearly 95 percent of the world demand for molybdenum-99 (Mo-99)—perhaps the world's most important medical isotope—is met by just four manufacturers, all of whom use highly enriched uranium (HEU) targets in their isotope production programs. Research and development on the use of low-enriched uranium targets and gel generators to produce Mo-99 began in the 1980s; some success has been achieved, but Mo-99 is still mainly produced by irradiating HEU targets in a reactor. Fission-produced Mo-99 has a high specific activity, but activation methods provide low specific activity Mo-99, which is unsuitable for the generators routinely used in most of the world's medical centers. This article evaluates the use of enriched Mo-98 to produce Mo-99 by activation methods; the use of medium specific activity Mo-99 for the preparation of alumina-based generators is also discussed. This article concludes that if support is provided for the production of enriched Mo-98, it may replace to a significant extent the use of HEU and LEU for the production of Mo-99. 相似文献
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介绍了数据仓库和数据挖掘的概念、数据挖掘的过程和方法,简单分析了现代战争中信息处理的特点和需求,阐述了数据挖掘在军事指挥控制系统中的应用必要性,提出了军事应用中数据挖掘系统的层次体系结构,并针对该层次体系结构进一步提出了指挥控制系统中数据挖掘技术的应用模型. 相似文献
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《防务技术》2020,16(5):1062-1072
Recent years have seen an explosion in graph data from a variety of scientific, social and technological fields. From these fields, emotion recognition is an interesting research area because it finds many applications in real life such as in effective social robotics to increase the interactivity of the robot with human, driver safety during driving, pain monitoring during surgery etc. A novel facial emotion recognition based on graph mining has been proposed in this paper to make a paradigm shift in the way of representing the face region, where the face region is represented as a graph of nodes and edges and the gSpan frequent sub-graphs mining algorithm is used to find the frequent sub-structures in the graph database of each emotion. To reduce the number of generated sub-graphs, overlap ratio metric is utilized for this purpose. After encoding the final selected sub-graphs, binary classification is then applied to classify the emotion of the queried input facial image using six levels of classification. Binary cat swarm intelligence is applied within each level of classification to select proper sub-graphs that give the highest accuracy in that level. Different experiments have been conducted using Surrey Audio-Visual Expressed Emotion (SAVEE) database and the final system accuracy was 90.00%. The results show significant accuracy improvements (about 2%) by the proposed system in comparison to current published works in SAVEE database. 相似文献
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Gregory S. Jones 《The Nonproliferation Review》2019,26(1-2):61-81
The claim that reactor-grade plutonium cannot or will not be used to produce nuclear weapons has been used to justify non-nuclear-weapon states’ large stockpiles of plutonium that has been separated from highly radioactive spent fuel. However, by using reduced-mass plutonium cores, it is possible to manufacture reliable nuclear weapons with reactor-grade plutonium. These weapons can have the same design, size, weight, and predetonation probability as weapons using weapon-grade plutonium and would require no special cooling. The increased radiation from reactor-grade plutonium could be easily managed by shielding and operational procedures. Weapons using plutonium routinely produced by pressurized-water reactors could have a lethal area between 40 percent and 75 percent that of weapons using weapon-grade plutonium. In the past, both Sweden and Pakistan considered using reactor-grade plutonium to produce nuclear weapons, and India may be using reactor-grade plutonium in its arsenal today. Despite claims to the contrary, the United States used what was truly reactor-grade plutonium in a successful nuclear test in 1962. The capability of reactor-grade plutonium to produce highly destructive nuclear weapons leads to the conclusion that the separation of plutonium, plutonium stockpiling, and the use of plutonium-based fuels must be phased out and banned. 相似文献
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吴晓尉 《中国人民武装警察部队学院学报》2009,25(9):71-74
基于传统网络化教学系统存在的问题,应用数据挖掘的相关技术,对以往在网络化教学系统中不能对学生练习结果进行科学、客观分析的实际问题给出了初步解决方案。基于数据挖掘技术的网络化教学系统,其目的就是在一定程度上提高教师的教学效率。. 相似文献
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