956 resultados para Aperture height index


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Esta coleção, geralmente conhecida por Grineu, foi compilada por Johann Huttich e publicada por Simon Grineu, que também escreveu e assinou o prefácio. A primeira edição, "muito e rara e de inestimável valor", segundo Borba de Moraes, foi publicada na Basiléia por Jo. Hervagium, em 1532. Dessa edição, a Biblioteca Nacional do Rio de Janeiro possui um exemplar que pertencia à Biblioteca da Ajuda. A obra foi reimpressa em Paris, em 1532, e novamente na Basiléia, em 1537. Esta edição foi acrescida da carta de Maximilianus Transilvanus, secretário de Carlos V, ao Cardeal de Salzburgo. Dentre as várias ediçoes, a mais completa é a de 1555. Relata as grandes navegações e as expedições de Cristovão Colombo, Pedro Alonso, Pinzoni, Americo Vespucio, dentre outros

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This report describes the working of National Centers for Coastal Ocean Service (NCCOS) Wave Exposure Model (WEMo) capable of predicting the exposure of a site in estuarine and closed water to local wind generated waves. WEMo works in two different modes: the Representative Wave Energy (RWE) mode calculates the exposure using physical parameters like wave energy and wave height, while the Relative Exposure Index (REI) empirically calculates exposure as a unitless index. Detailed working of the model in both modes and their procedures are described along with a few sample runs. WEMo model output in RWE mode (wave height and wave energy) is compared against data collected from wave sensors near Harkers Island, North Carolina for validation purposes. Computed results agreed well with the wave sensors data indicating that WEMo can be an effective tool in predicting local wave energy in closed estuarine environments. (PDF contains 31 pages)

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Presentación (p. 9-27). Index Verborum (p.65-89). Letra "P" (extraido del CD-Rom, p.1-184)

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height="142" align="left" />《边界层理论讲义》是郭永怀先生为中国科学技术大学近代力学系第一届学生讲授边界层理论所著的,经徐书轩和尹协远教授精心校订后,即将在庆祝中国科学技术大学成立50周年和纪念郭永怀先生牺牲40周年之际付印出版了。这是一件十分值得庆贺的事。
郭永怀先生是我国著名的力学和应用数学家,在流体力学和边界层理论方面有极深的造诣和重要的贡献。他又是一位热心的教育家。他和钱学森先生共同创建了中国科学技术大学近代力学系,积极倡导要在加强基础科学教育的同时把同学们带到学科的前沿。《边界层理论讲义》十分鲜明地体现了这种精神,在回顾流体力学基本方程和详细讲述低速边界层基本理论之后,紧接着便讲授低速湍流边界层和高速层流与湍流边界层理论,把同学们直接带进高速飞行面临的前沿科学领域。
“讲义”还体现了郭永怀先生一贯的严谨和精炼的作风和求实的科学精神。在短短的一百多页中,郭先生严密地论证和推导了边界层方程,讲述了湍流的基本特点及其在边界层方程式中的体现,介绍了基本的解法和典型解以及近似解法,指出了它们的适用范围。就其涉及内容的广度和深度而言,“讲义"已经超出教材的范围而成为一本学习和随时参考的专著了。“讲义”虽然著于四十余年前,但即使在计算技术高度发展的今天,仍不失其作为重要著作的价值。
“讲义”是郭先生留给我们的一份重要遗产,相信将受到广大读者的欢迎并进入我国科学家著作的宝库。

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height="232" align="left" />This book elucidates the methods of molecular gas dynamics or rarefied gas dynamics which treat the problems of gas flows when the discrete molecular effects of the gas prevail under the circumstances of low density, the emphases being stressed on the basis of the methods, the direct simulation Monte Carlo method applied to the simulation of non-equilibrium effects and the frontier subjects related to low speed microscale rarefied gas flows. It provides a solid basis for the study of molecular gas dynamics for senior students and graduates in the aerospace and mechanical engineering departments of universities and colleges. It gives a general acquaintance of modern developments of rarefied gas dynamics in various regimes and leads to the frontier topics of non-equilibrium rarefied gas dynamics and low speed microscale gas dynamics. It will be also of benefit to the scientific and technical researchers engaged in aerospace high altitude aerodynamic force and heating design and in the research on gas flow in MEMS

  • 目次内容                                                                
[1]  Molecular structure and energy states (21)  
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[2]  Some basic concepts of kinetic theory (51)  
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[3]  Interaction of molecules with solid surface (131)  
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[4]  Free molecular flow (159)  
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[5]  Continuum models (191)  
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[6]  Transitional regime (231)  
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[7]  Direct simulation Monte-Carlo (DSMC) method (275)  
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[8]  Microscale slow gas flows, information preservation method (317)  
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[App. I]  Gas properties (367)  
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[App. II]  Some integrals (369)  
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[App. III]  Sampling from a prescribed distribution (375)  
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[App. IV]  Program of the couette flow (383)  
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Subject Index (399)  

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height="210" align="left" />目录

第一部分总论

环境流体力学――它的意义,内容与方法 李家春

用于大气环流模式的陆面物理过程参数化研究进展 戴永久,曾庆存,欧阳兵

植被-陆面过程耦合模式的动力框架 欧阳兵

第二部分均匀下垫面的陆面过程

干旱地区陆面过程的研究 李家春,姚德良,沈卫明

阿克苏地区陆面蒸发的数值研究 沈卫明,姚德良,李家春

塔里木盆地陆气水热交换数值模拟 姚德良,沈卫明,李家春

植物固沙区土壤水热运移耦合模型研究 姚德良,李家春,沈卫明

Numerical simulation of watercycling and heat balance in agricultural ecosystems D.L.Yao,W.M.Shen and J.C.Li

在植物耗水条件下土壤水分动态的数值模拟 姚德良,邱克俭,冀伟,孙菽芬

干旱地区陆面过程耦合模式及其应用 李家春,姚德良,沈卫明

Modelling of terrestrial ecosystem B.Ouyang

森林生态系统生物循环过程的耦合模型(BCM)及其数值模拟 欧阳兵

森林生态系统生物能流的瞬态分析 欧阳兵

第三部分非均匀下垫面的陆面过程

Turbulence in the atmosphere and ocean J.C.Li

非均匀下垫面上大气边界层的研究进展 徐大鹏

非均匀植被的群体蒸发 徐大鹏

第四部分 区域尺度以上的陆面过程与水文模型

Sensitivity of IAP two-level AGCM to surface albedo variations Z.H.Lin,Q.C.Zeng and B.Ouyang

估算区域蒸发的能量法研究 聂松媛,徐丰

用卫星数据估算区域水资源蒸发研究 聂松媛

负轮分析法在水环境规划与管理中的应用 聂松媛

第五部分 陆面过程观测的指标体系

Mathematical modelling and index system in ecology J.C.Li

陆面过程的观测指标体系研究 欧阳兵,李家春,姚德良

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height="153" align="left" />Adiabatic shear localization is a mode of failure that occurs in dynamic loading. It is characterized by thermal softening occurring over a very narrow region of a material and is usually a precursor to ductile fracture and catastrophic failure. This reference source is the first detailed study of the mechanics and modes of adiabatic shear localization in solids, and provides a systematic description of a number of aspects of adiabatic shear banding. The inclusion of the appendices which provide a quick reference section and a comprehensive collection of thermomechanical data allows rapid access and understanding of the subject and its phenomena. The concepts and techniques described in this work can usefully be applied to solve a multitude of problems encountered by those investigating fracture and damage in materials, impact dynamics, metal working and other areas. This reference book has come about in response to the pressing demand of mechanical and metallurgical engineers for a high quality summary of the knowledge gained over the last twenty years. While fulfilling this requirement, the book is also of great interest to academics and researchers into materials performance.

Table of Contents

1Introduction1
1.1What is an Adiabatic Shear Band?1
1.2The Importance of Adiabatic Shear Bands6
1.3Where Adiabatic Shear Bands Occur10
1.4Historical Aspects of Shear Bands11
1.5Adiabatic Shear Bands and Fracture Maps14
1.6Scope of the Book20
2Characteristic Aspects of Adiabatic Shear Bands24
2.1General Features24
2.2Deformed Bands27
2.3Transformed Bands28
2.4Variables Relevant to Adiabatic Shear Banding35
2.5Adiabatic Shear Bands in Non-Metals44
3Fracture and Damage Related to Adiabatic Shear Bands54
3.1Adiabatic Shear Band Induced Fracture54
3.2Microscopic Damage in Adiabatic Shear Bands57
3.3Metallurgical Implications69
3.4Effects of Stress State73
4Testing Methods76
4.1General Requirements and Remarks76
4.2Dynamic Torsion Tests80
4.3Dynamic Compression Tests91
4.4Contained Cylinder Tests95
4.5Transient Measurements98
5Constitutive Equations104
5.1Effect of Strain Rate on Stress-Strain Behaviour104
5.2Strain-Rate History Effects110
5.3Effect of Temperature on Stress-Strain Behaviour114
5.4Constitutive Equations for Non-Metals124
6Occurrence of Adiabatic Shear Bands125
6.1Empirical Criteria125
6.2One-Dimensional Equations and Linear Instability Analysis134
6.3Localization Analysis140
6.4Experimental Verification146
7Formation and Evolution of Shear Bands155
7.1Post-Instability Phenomena156
7.2Scaling and Approximations162
7.3Wave Trapping and Viscous Dissipation167
7.4The Intermediate Stage and the Formation of Adiabatic Shear Bands171
7.5Late Stage Behaviour and Post-Mortem Morphology179
7.6Adiabatic Shear Bands in Multi-Dimensional Stress States187
8Numerical Studies of Adiabatic Shear Bands194
8.1Objects, Problems and Techniques Involved in Numerical Simulations194
8.2One-Dimensional Simulation of Adiabatic Shear Banding199
8.3Simulation with Adaptive Finite Element Methods213
8.4Adiabatic Shear Bands in the Plane Strain Stress State218
9Selected Topics in Impact Dynamics229
9.1Planar Impact230
9.2Fragmentation237
9.3Penetration244
9.4Erosion255
9.5Ignition of Explosives261
9.6Explosive Welding268
10Selected Topics in Metalworking273
10.1Classification of Processes273
10.2Upsetting276
10.3Metalcutting286
10.4Blanking293
 Appendices297
AQuick Reference298
BSpecific Heat and Thermal Conductivity301
CThermal Softening and Related Temperature Dependence312
DMaterials Showing Adiabatic Shear Bands335
ESpecification of Selected Materials Showing Adiabatic Shear Bands341
FConversion Factors357
 References358
 Author Index369
 Subject Index375

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height="200" align="left" />本书以结构分析有限元为主要内容,围绕杆、梁、弹性力学平面问题和空间问题、平板弯曲问题,系统地介绍了有限元位移法的基本思想和编程实现步骤,并在计算机代数系统MAPLE环境下编制了二维、三维杆单元程序,二维、三维梁单元程序,弹性力学平面问题和空间问题程序,平板弯曲有限元程序等。在给出理论分析结果和自编有限元程序计算结果的同时,还给出了ANSYS程序的求解结果,以及这三种结果的比较。
本书注重从简单问题入手,利用手工计算理解有限元基本思想,编程实现体会实现过程,ANSYS验证说明自编程序的有效性。采用计算机代数系统编程环境大大简化了代码编制,使读者能够将更多的注意力集中在实现程序编制的具体步骤上。ANSYS验证也是读者掌握商用有限元程序的捷径。
本书的使用能够使读者在较短的时间内,理解有限元基本思想和实现过程,同时学会使用计算机代数系统和ANSYS软件。
本书适合大学本科二年级以上的学生和研究生使用,也可供从事结构分析和设计的其他人员参考。

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ENGLISH: In the eastern Pacific Ocean nearly all of the commercial catches of yellowfin tuna (Thunnus albacares) and skipjack (Katsuwonus pelamis) are taken by two types of vessels, baitboats, which use pole and line in conjunction with live-bait, and purse-seiners. From its inception until very recently (1959), this fishery was dominated by baitboats. This method of fishing has been described by Godsil (1938) and Shimada and Schaefer (1956). From 1951 through 1958 baitboats caught between 66.4 and 90.8 per cent of the yellowfin and between 87.2 and 95.3 per cent of the skipjack landed by the California-based fleet. These vessels fished for tuna throughout the year and covered virtually all of the area from southern California to northern Chile. The purse-seine fishery for tunas developed out of the round-haul net fisheries for California sardines and other species. Scofield (1951) gives a detailed description of the development of gear and fishing methods. Prior to 1959 many of the seiners engaged in other fisheries during the fall and early winter months and consequently most of the fishing effort for tuna occurred in the period February-August. The vessels were quite small, averaging approximately 120 tons carrying capacity (Broadhead and Marshall, 1960), in comparison to the baitboats, of which the most numerous size-class was 201-300 tons. The seiners were naturally more restricted in range than the baitboats and most of their effort was restricted to the northern grounds. During the period 1959-61 most of the large baitboats were converted for purse-seining and the existing seiner fleet was modernized. These developments increased the range of the seiner fleet and resulted in a wider and more nearly even spatial and temporal distribution of effort. By the early part of 1961, the purse-seine fleet approximated the level of the preconversion baitboat fleet in amount of effort applied and area covered. The changes in the purse-seine fishery and the fishing methods employed in the modernized fleet are described by Orange and Broadhead (1959), Broadhead and Marshall (1960), McNeely (1961) and Broadhead (1962). The change in the relative importance of the two gears is illustrated by the decline in the proportion of the total logged tonnage landed by California-based baitboats, in comparison to the proportion landed by seiners. In 1959 baitboats landed 49.5 per cent of the yellowfin and 87.8 per cent of the skipjack. In 1960 these percentages were 22.9 and 74.7 respectively and in 1961 the decline continued to 12.6 per cent of the yellowfin and 30.0 per cent of the skipjack (Schaefer, 1962). In previous Bulletins of this Commission (Griffiths, 1960; Calkins, 1961) the baitboat catch and effort statistics were used to compute two indices of population density and an index of concentration of fishing effort and the fluctuations of these indices were analyzed in some detail. Due to the change in the relative importance of the two gears it is appropriate to extend this investigation to include the purse-seine data. The objectives of this paper are to compute two indices of population density and an index of concentration of fishing effort and to examine the fluctuations in these indices before and after the changes in the fishery. A further objective is to compare the purse-seine indices with those of the baitboats for the same time periods. SPANISH: En el Océano Pacífico Oriental casi todas las capturas comerciales del atún aleta amarilla (Thunnus albacares) y del barrilete (Katsuwonus pelamis) son efectuadas por dos tipos de barcos, los barcos de carnada que emplean la caña y el anzuelo en conjunto con la carnada viva, y los barcos rederos. Desde su comienzo hasta hace poco tiempo (1959), esta pesquería estaba dominada por los barcos de carnada. El método de pesca usado por estos barcos ha sido descrito por Godsil (1938) y por Shimada y Schaefer (1956). De 1951 a 1958, los barcos de carnada pescaron entre el 66.4 y el 90.8 por ciento del atún aleta amarilla y entre el 87.2 y el 95.3 por ciento del barrilete descargados por la flota que tiene su base en California. Estos barcos pescaron atún durante todo el año y cubrieron virtualmente toda el área de California meridional hasta la parte norte de Chile. La pesquería del atún con redes de cerco se originó en las pesquerías de las sardinas de California y otras especies, con redes que se remolcaban circularmente. Scofield (1951) dá una descripción detallada del desarrollo de los métodos y del equipo de pesca. Antes de 1959 muchos de los rederos se dedicaban a otras pesquerías durante los meses del otoño y a principios del invierno y consecuentemente, la mayor parte del esfuerzo depesca para la producción del atún ocurría en el período febrero-agosto. Las embarcaciones eran bastante pequeñas, con un promedio de aproximadamente 120 toneladas de capacidad para el transporte (Broadhead y Marshall, 1960) en comparación con los barcos de carnada, de los cuales la clase de tamaño más numerosa era de 201 a 300 toneladas. Los rederos estaban naturalmente más restringidos en su radio de acción que los barcos de carnada y la mayor parte de su esfuerzo se limitaba a las localidades del norte. Durante el período 1959-61, la mayoría de los grandes barcos de carnada fueron convertidos al sistema de pesca con redes de cerco, y se modernizó la flota existente de los rederos. Estos cambios aumentaron el alcance de la flota de los barcos rederos dando como resultado una distribución más amplia y casi más uniforme del esfuerzo espaciado y temporal. En la primera parte del año 1961, la flota de rederos se aproximó al nivel de la preconversión de la flota de clipers, en la cantidad de esfuerzo aplicado y al área comprendida. Los cambios en la pesquería con red y los métodos de pesca empleados en la flota modernizada, han sido descritos por Orange y Broadhead (1959), Broadl1ead y Marshall (1960), McNeely (1961) y Broadhead (1962). El cambio en la importancia relativa de los dos sistemas de pesca está ilustrado por la declinación en la proporción del tonelaje total registrado, como descargado por los barcos de carnada que tienen su base en California, comparado con la proporción desembarcada por los barcos rederos. En 1959 los clipers descargaron el 49.5 por ciento del atún aleta amarilla y el 87.8 por ciento del barrilete. En 1960 estos porcentajes fueron del 22.9 y 74.7 respectivamente, y en 1961 continuó la reducción hasta el 12.6 por ciento del atún aleta amarilla y el 30.0 por ciento del barrilete (Schaefer, 1962). En Boletines anteriores de la Comisión (Griffiths, 1960; Calkins, 1961) las estadísticas de la pesca y el esfuerzo de los clipers se utilizaron para computar dos índices de la densidad de población y un índice de la concentración del esfuerzo de pesca, y se analizaron algo detalladamente las fluctuaciones de estos índices. Debido al cambio en la importancia relativa de los dos sistemas de pesca, es conveniente extender esta investigación para incluir los datos correspondientes a los barcos rederos. Los objetivos del presente estudio son de computar dos índices de la densidad de población y un índice de la concentración del esfuerzo de pesca, y examinar las fluctuaciones en estos índices, antes y después de los cambios en la pesquería. Otro objetivo es de comparar los índices de los barcos rederos, con aquellos de los clipers en los mismos períodos de tiempo.

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This study is concerned with the measurement of total factor prodnctivity in the marine fishing industries in general and in the Pacific coast trawl fishery in particular. The study is divided into two parts. Part I contains suitable empirical and introductory theoretical material for the examination of productivity in the Pacific coast trawl Deet. It is self-contained, and contains the basic formulae, empirical results, and discussion. Because the economic theory of index numbers and productivity is constantly evolving and is widely scattered throughout the economics literature, Part D draws together the theoretical literature into one place to allow ready access for readers interested in more details. The major methodological focus of the study is upon the type of economic index number that is most appropriate for use by economists with the National Marine Fisheries Service. This study recommends that the following types of economic index numbers be used: chain rather than fIxed base; bilateral rather than multilateral; one of the class of superlative indices, such as the Tornqvist or Fisher Ideal. (PDF file contains 40 pages.)

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The following series of fishery publications produced in calendar years 1980-85 by the Scientific Publications OffIce of the National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), are listed numerically and indexed by author and subject: Circular, Fishery BuUetin, Marine Fisheries Review, Special Scientific Report-Fisheries, and Technical Report NMFS. Also included is an alphanumeric listing of the NOAA Technical Memorandum NMFS series published in calendar years 1972-85 by NMFS regional offices and fisheries centers. Authors and subjects for the Memoradum series are indexed with the other publication series. (PDF file contains 156 pages.)

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本文首先对饱和砂土在动载荷下的液化、密实和结构破坏等方面做了文献综述,同时也叙述了化工冶金中的液固流态化的有关情况。本文探讨了饱和砂土中产生水平裂缝和纵向通道等现象的机理。为此,进行了扁平砂柱的落锤冲击实验和模拟圆柱落锤冲击实验中产生水平裂缝和纵向通道等现象的底部加压实验。扁平砂柱落锤冲击实验的目的是为了更清楚地观察饱和砂土结构破坏和孔隙水流动的情况,观察纵向通道和水平裂缝的产生和发展,以及水平裂缝和纵向通道之间的联系。为了探讨水平裂缝和纵向通道产生的条件和机理,设计和进行了底部加压实验,用来模拟落锤冲击实验的后期变形和渗流效应,测量出现水平裂缝和纵向通道时的超孔隙水压力和平均水流速度,统计分析采用什么样的参数可以表征水平裂缝和纵向通道的出现及其特性,发现液化指数等于1是出现水平裂缝的必要条件。此外,针对含有细砂层的饱和砂土在该层出现水平裂缝的现象,提出了一个简化模型,推导出砂柱的液化指数一维分布,根据液化指数等于1才能出现水平裂缝,能够说明水平裂缝出现的条件和位置。

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Polymer optical fibers (POFs) doped with organic dyes can be used to make efficient lasers and amplifiers due to the high gains achievable in short distances. This paper analyzes the peculiarities of light amplification in POFs through some experimental data and a computational model capable of carrying out both power and spectral analyses. We investigate the emission spectral shifts and widths and on the optimum signal wavelength and pump power as functions of the fiber length, the fiber numerical aperture and the radial distribution of the dopant. Analyses for both step-index and graded-index POFs have been done.