995 resultados para 209-1274
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本文研究了一种多级气动喷嘴对水煤浆燃料的喷雾特性。采用实验的方法研究了水煤浆性质(动态表面张力和表观粘度)、喷嘴操作工况和喷嘴几何结构对射流雾化细度的影响,给出喷嘴雾炬轴向粒度分布,并对相关结果进行了分析。
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建立了水中悬浮隧道在冲击载荷作用下的简化计算模型。用等效质量法将圆柱壳分布质量折算成冲击点处的集中质量,模型中考虑流体附加质量和系统阻尼的影响。根据碰撞过程中的动量守恒、变形过程中的能量守恒以及结构的位移与内力关系,得到问题的解析解。为验证解析解,在ANSYS/LS-DYNA中建立了动态冲击有限元分析模型。通过算例分别考察了在忽略和考虑流体附加质量两种情况下,冲击点位置和冲击速度对冲击点处最大径向位移的影响,将解析解与数值解进行对比,结果吻合较好。然后采用数值模拟方法得到了系统阻尼对计算结果的影响规律。数值模拟过程中还可以得到冲击点处的最大Mises应力。
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209 p. : graf.
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本文在对热工模具进行失效分析的基础上,利用激光熔覆技术,在5CrMnMo基础上设计并制备强韧兼备的抗高温磨损涂层。
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Relatório das atividades da Comissão de Direitos Humanos da Câmara dos Deputados no ano de 2000.
Receptivity to free-stream disturbance waves for blunt cone axial symmetry hypersonic boundary layer
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Based on high-order compact upwind scheme, a high-order shock-fitting finite difference scheme is studied to simulate the generation of boundary layer disturbance waves due to free-stream waves. Both steady and unsteady flow solutions of the receptivity problem are obtained by resolving the full Navier-Stokes equations. The interactions of bow-shock and free-stream disturbance are researched. Direct numerical simulation (DNS) of receptivity to free-stream disturbances for blunt cone hypersonic boundary layers is performed.
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Tension leg platform (TLP) is an important kind of working station for deep water exploration and development in ocean, whose dynamic responses deserve a serious thought. It is shown that for severe sea state, the effects of nonlinearities induced by large displacements of TLP may be noteworthy, and then employment of small displacements model should be restrained. In such situation, large amplitude motion model may be an appropriate alternative. The numerical experiments are performed to study the differences of dynamic responses between the two models. It is shown that for most cases, differences between results of the two models are significant. The variances of the differences vs. the wave period are the most remarkable, and that of the differences vs. wave heading angle are also apparent.
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Eterio Pajares, Raquel Merino y José Miguel Santamaría (eds.)
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Raquel Merino Álvarez, José Miguel Santamaría, Eterio Pajares (eds.)
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本书阐明了板壳断裂理论的基础。论证了Reissner型板壳断裂理论的科学性、经典板壳断裂理论的缺陷及在一定范围内仍具有的实用价值;介绍了作者所创意的研究Reissner型板壳断裂纹尖端场的方法等。
目录
- §1.1 板壳弯曲断裂问题
- §1.2 Kirchhoff经典板壳弯曲断裂理论
- §1.3 Reissner型板壳弯曲断裂理论
- §1.4 Kirchhoff与Reissner型板壳弯曲断裂理论的比较
- §1.5 含裂纹有限尺寸板壳断裂分析的局部-整体法
- §1.6 含表面裂纹板壳
- §2.1 Kirchhoff板的基本概念和基本假定
- §2.2 基本公式与弹性曲面微分方程
- §2.3 边界条件
- §2.4 弹性薄板的应变能
- §2.5 极坐标下的挠曲面微分方程与内力公式
- §2.6 裂纹尖端场特征展开式通项公式
- §2.7 Kirchhoff板弯曲应力强度因子
- §3.1 基本方程和公式的复变函数表示
- §3.2 所引入函数的确定程度与一般形式
- §3.3 坐标变换与边界条件
- §3.4 运用保角变换方法求解孔口问题
- §3.5 应力强度因子与函数Φ(z)的关系
- §3.6 复变-主部分析法之应用简例
- §3.7 共直线裂纹问题的一般解答
- §3.8 典型弯曲裂纹问题的解答及弯曲应力强度因子公式
- §3.9 共圆曲线裂纹问题的解答及弯曲应力强度因子公式
- §4.1 裂纹尖端奇异元的位移模式与弯曲应力强度因子
- §4.2 裂纹尖端奇异元的刚度矩阵
- §4.3 裂纹尖端奇异元与常规单元的连接
- §4.4 解析法与数值法的结果比较与讨论
- §4.5 两共线半无限裂纹问题的定解条件及解的实用价值
- §5.1 Reissner型板的基本假定
- §5.2 Reissner型板的基本公式与平衡微分方程
- §5.3 基本方程的简化
- §5.4 边界条件
- §5.5 极坐标下的基本公式与平衡微分方程
- §5.6 两种平板理论用于无裂纹板时的比较
- §5.7 两种乎板理论用于含裂纹板时的比较
- §6.1 基本方程和一般求解方法
- §9.1 局部-整体法与其它解析和数值法的结果比较
- §9.2 边界对应力强度因子的影响
- §9.3 板的支承条件及长宽比的影响
- §9.5 计算Reissner型板应力强度因子的一组近似方程与近似解法
- §9.4 Reissner型板理论与Kirchhoff板理论所得应力强度因子的比较
- §9.6 关于数值计算的几点讨论
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Quarterly ichthyoplankton sampling was conducted at 16 estuarine and 24 inshore stations along the Florida Everglades from May 1971 to February 1972. The area is one of the most pristine along lhe Florida coast. The survey provided the first comprehensive information on seasonal occurrence, abundance (under 10 m' of surface area), and distribution of fish eggs and larvae in this area. A total of 209,462 fish eggs and 78,865 larvae was collected. Eggs were identified only as fish eggs, but among the larvae, 37 families, 47 genera, and 37 species were identified. Abundance of eggs and larvae, and diversity of larvae, were greatest in the inshore zone. The 10 most abundant fish families which together made up 90.7% of all larvae from the study area were, in descending order of abundance: Clupeidae, Engraulidae, Gobiidae, Sciaenidae, Carangidae, Pomadasyidae, Cynoglossidae, Gerreidae, Triglidae, and Soleidae. Clupeidae, Engraulidae, and Gobiidae made up 59.9% of all larvae. The inshore zone (to a depth of about 10 m) was a spawning ground and nursery for many fishes important to fisheries. The catch of small larvae (<>3.5 mm SL) indicated that most fishes identified from the 10 most abundant families spawned throughout the inshore zone at depths of <> 10 m, but Orthopristis chrysoptera, Gerreidae, and Prionotus spp. spawned at depths > 10 m, with offshore to inshore (eastward) larval transport. Salinity was one of several environmental factors that probably limited the numbers of eggs and larvae in the estuarine zone. Abundance of eggs and larvae at inshore stations was usually as great as, and sometimes greater than, the abundance of eggs and larvae at offshore stations (due west of the Everglades). (PDF file contains 81 pages.)
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209 p. : il., gráf.
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A preliminary survey of the helminth fish parasites was carried out in Imo River (Nigeria). A total of 191 fishes belonging to 15 genera were examined and only 13.6% were infested with various species of helminth parasites which is low percentage of infection. The following helminth parasites were recorded. Wenyonia virilis, kainji; Wenyonia sp., Procamallanus laeviconchus; Procamallanus sp., Sprionoura congolense; Spironoura sp., Cucullanus sp. and Serradacnitis serrata. It was found that helminth parasites showed some degree of specificity in their distribution within their fish hosts. This specificity could be as a result of the physiochemical and physiological factors operating in the gut such as pH, osmotic tension, oxygen tension and nutrient levels. The results also revealed that age and sex influence helminth parasites infections in fishes
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Sex ratio and fecundity variations of Chrysichthys nigrodigitatus and Chrysichthys walkeri from Asejire Lake (Nigeria) were examined. The Logarithm transformation of weight (W) against standard length (SL) gave a straight-line graph represented by the following equations: 1) C. nigrodigitatus LogW =-0.66 + 2.13 Log SL; = 0.854; (P < 0.001) n = 209; 2) C. walkeri LogW = -1.23 + 2.63 Log SL; = 0.759; (P < 0.001) n = 237. Males were generally more than females in both species. The ratio of males:females was higher in C. nigrodigitatus (1:0.18) than in C. walkeri (1:0.8). C. walkeri attained sexual maturity at a smaller size of 20.0 g (12.0 cm Standard Length) compared with C. nigrodigitatus maturity size of 45.0 g (14.0 cm Standard Length). Relative fecundity was not dependent on body weight and standard length for C. walkeri but it was significant at P < 0.05 and P < 0.01 respectively for C. nigrodigitatus