992 resultados para 152-919
Resumo:
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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Analisa a importância das atividades da Comissão de Direitos Humanos e Minorias, bem como a atuação política na promoção da igualdade e as inovações legislativas para os direitos humanos.
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Paralarval and juvenile cephalopods collected in plankton samples on 21 western North Atlantic cruises were identified and enumerated. The 3731 specimens were assigned to 44 generic and specific taxa. This paper describes their spatial and temporal distributions and their developmental morphology. The smallest paralarvae recognized for a number of species are identified and illustrated. The two most abundant and most frequently collected taxa were identifiable to species based on known systematic characters of young, as well as on distribution of the adults. These were the neritic squids Loligo pealeii and Illex illecebrosus collected north of Cape Hatteras, both valuable fishery resources. Other abundant taxa included two morphotypes of ommastrephids, at least five species of enoploteuthids, two species of onychoteuthids, and unidentified octopods. Most taxa were distributed widely both in time and in space, although some seasonal and mesoscale-spatial patterns were indicated. The taxa that appeared to have distinct seasonal distribution included most of the neritic species and, surprisingly, the young of the bathypelagic cranchiids. In eight seasonal cruises over the continental shelf of the middle U.S. Atlantic states, neritic taxa demonstrated approximately the same seasonal patterns during two consecutive years. Interannual differences in the oceanic taxa collected on the shelf were extreme. The highest abundance and diversity of planktonic cephalopods in the oceanic samples were consistently found in the vicinity of the Gulf Stream. Only eight of the oceanic taxa appeared to have limited areal distributions, compared with twelve taxa that were found throughout the western North Atlantic regions sampled in this study. Many taxa, however, were not collected frequently enough to describe seasonal or spatial patterns. Comparisons with published accounts of other cephalopod surveys indicate both strengths and weaknesses in various sampling techniques for capturing the young of oceanic cephalopods. Enoploteuthids were abundant both in our study and in other studies using midwater trawls in several areas of the North Atlantic. Thus, this family probably is adequately sampled over its developmental range. In contrast, octopoteuthids and chtenopterygiids are rare in collections made by small to medium-sized midwater trawls but are comparatively common in plankton samples. For families that are relatively common in plankton samples, paralarval abundance, derived similarly to the familiar ichthyoplankton surveys of fisheries science, may be the most reliable method of gathering data on distribution and abundance. (PDF file contains 58 pages.)
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ENGLISH: In a previous Bulletin of this Commission, Griffiths (1960) discussed two indices of population density and an index of concentration of fishing effort of bait boats for yellowfin tuna in the Eastern Tropical Pacific for the 1951-1956 period. Yellowfin and skipjack tuna occur in the same general fishing areas and many of the commercial catches are composed of a mixture of the two species. It is desirable, therefore, to extend the investigation to skipjack and to the two species combined. SPANISH:En un Boletín anterior de esta Comisión, Griffiths (1960) se refiere a dos índices de la densidad de la población y a un índice de la concentración del esfuerzo de pesca de los barcos de carnada sobre el atún aleta amarilla en el Pacífico Oriental Tropical, correspondientes al período 1951-1956. Los atunes aleta amarilla y barrilete se encuentran en las mismas áreas generales de pesca y muchas de las pescas comerciales están compuestas de una mezcla de las dos especies. Es deseable, por lo tanto, ampliar la investigación en lo que se refiere al barrilete y a las dos especies combinadas.
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El objetivo principal del trabajo es el diseño, utilizando técnicas de bajo consumo, del algoritmo de cifrado estándar AES (Advanced Encryption Standard) y su implementación sobre dispositivos reconfigurables, en particular sobre una FPGA.
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152 p. : il.
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Analisa as dinâmicas de interação entre coalizão e oposição nas atividades legislativas da Comissão de Constituição e Justiça e de Cidadania e da Comissão de Finanças e Tributação da Câmara dos Deputados em perspectiva comparada às atividades legislativas da Comissão de Constituição, Justiça e Cidadania e da Comissão de Assuntos Econômicos do Senado, no primeiro ano da 54ª legislatura, 2011.
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The preliminary results obtained from the study of stomach contents of specimens of Gymnarchus niloticus of a size ranging from 56 cm (66 grams) to 152 cm (12.0 kg.) from August to December, 1982 indicate for these sizes an exclusively piscivorous diet. The predominant prey species in Lake Chad are Tilapia/Sarotherodon , and Clarias . The prey is often cut in two parts before it is swallowed. Small prey may be swallowed whole. The implication of this prey capture method on prey-predator relationship and therefore the impact of the predator is discussed. The breeding season of Gymnarchus niloticus in Lake Chad has been deduced from observation of changes in gonad maturity stages and the results indicate that breeding takes place between August and November. Data are also presented on the fecundity, size of ripe eggs and probable size at maturity
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Biological studies of Heterotis niloticus were conducted for three years in the middle River Niger. Scales were found to be the most suitable structure in ageing Heterotis which was validated by length/histogram curve. Annual rings were found to be formed between March to June. Growth was rapid in the first two years and they reached sexual maturity at 2 years. The male grow longer while the female are bulkier. The length-weight relationship of male and female Heterotis did not differ significantly and the resulting equation for male was W = 1.25L super(2.5) and W = 1.6L super(2.7) for females respectively where W = weight (g) and L = total length. The total length to body scale relationship was found to be L = 14.3R super(2.6) where (R = oral radius of scale Heterotis growth was found to be allometric
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在衡量单个细胞力学行为的研究中,越来越多地采用结合实验的数值模拟方法.在连续介质力学框架下,发展了一种新的心肌细胞本构模型,并与微管吮吸实验结合,探讨了心肌细胞的力学特性.本构模型是对普遍使用的仅能用于小变形分析的标准线性固体模型的一种扩展,它将超弹性性能引入到黏弹性模型中,用以描述细胞的大变形黏弹性效应.基于改进的本构模型,对心肌细胞微管吮吸实验过程进行了有限元模拟,并将计算结果与实验结果以及经典理论解进行了对比.结果显示发展的本构模型适合细胞大变形问题的有限元数值模拟.
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The impact of radio as a medium of communication in all human endeavours cannot be over emphasized. It is the cheapest means of reaching large number of people in illiterate society. Thus, the Kainji Lake Fisheries Promotion Project used radio in reaching fishers around Kainji Lake basin (Nigeria). Two radio stations namely Radio Niger (Koro station in New Bussa) and Federal Radio Corporation (FRCN), Kaduna were used. Open broadcast using Hausa language, which is commonly spoken among the target group, was used for the broadcast.A total of 152 programmes were produced and broadcasted 720 times.After five years of broadcast, impact assessment studies were carried out using focus group discussion method in 25 randomly selected fishing villages out of 309 villages. The paper reports the result of the impact of the radio broadcast on fishing and related activities and how this affects management strategies adopted by the Project
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Blue-green algae (cyanobacteria) have had a profound and unparalled impact on the aquatic environment because of the phenomenon of bloom formation. In many countries, water management is threatened with extensive and persistent noxious blooms of blue-green algae in surface and near-surface mesotrophic and eutrophic waters. In view of this, ecological and physiological factors responsible for blue-green algal dominance are discussed. The implications of cyanobacterial blooms are highlighted and recommendations made to combat this menace
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在现有的工业控制系统中经常使用PLC实现顺序控制、定时等功能.控制程序经常需要执行同步操作且输入开关量的触发时机具有不确定性,因此无法充分描述真实的执行过程.为此提出下述解决方法:首先在控制程序的编译阶段,使用Petri网建立网模型以表示程序执行逻辑,其次在控制程序的执行阶段,根据程序真实执行状况动态运行上述网模型,当程序运行结束时网模型停止执行,由此判断程序中存在的逻辑错误.