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  • Articles  (1,386)
  • Engineering  (1,378)
  • Fisheries
  • 2020-2024  (6)
  • 1980-1984  (1,380)
  • 1925-1929
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  • 1
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    American Association for the Advancement of Science (AAAS)
    Publication Date: 1981-12-18
    Description: Women have made tremendous strides in educational attainment in science and engineering over the past decade, increasing their proportion of doctorate awards in these fields from 7 percent in 1965 to 23 percent in 1980. But they still have higher unemployment rates and lower salaries than men in all fields of science and engineering, at all degree levels, and at all levels of experience; and the disparities between men and women widen with higher degree levels and with years of experience. Graduate enrollments indicate continuing increases over at least the next several years in degree awards to women, but their access to equal employment and advancement opportunities is not assured.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Vetter, B M -- New York, N.Y. -- Science. 1981 Dec 18;214(4527):1313-21.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7313688" target="_blank"〉PubMed〈/a〉
    Keywords: Education, Graduate ; Employment ; Engineering ; Female ; Humans ; Salaries and Fringe Benefits ; *Science ; *Women
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2024-01-11
    Description: The 60–80s of the last century were the period of the most rapid development of commercial oceanology in the Azov and Black Sea Scientific Research Institute of Marine Fisheries and Oceanography (AzCherNIRO, further renamed YugNIRO). In addition to the monitoring of oceanographic processes, it was involved in the areas of general marine ecology, monitoring of marine pollution, and space oceanology. Oceanographic information is used in forecasting the state of aquatic ecosystems at various timescales and is crucial for fishing forecasts. In 1981, a satellite data reception center was established in AzCherNIRO. In the 80–90s, in YugNIRO, an optimal procedure was created for multidimensional predictive monitoring of the state of the Black Sea ecosystem. In September 1986, within the Laboratory of Commercial Oceanology of the Black Sea, a group for the conservation of marine ecosystems was created, which turned into a sector in January 1989, and into a separate laboratory in December 1996. Its reasearchers carried out multidisciplinary environmental studies, investigating the ecological status of the aquatic areas affected by the facilities of the marine industry during their operation, monitoring the level of soil contamination, and excercising the toxicological control of fish and fish products. YugNIRO oceanological studies conducted in the World Ocean from the early 1970s to the early 1990s made it possible to link the productivity and catches of exploitable species to the atmospheric circulation, changes in the climatic fields of currents, as well as to the geo- and heliophysical factors, which enabled the fishing predictions with a one-year lead time or more for the fishing areas of the Central, Southeastern and Southwestern Indian Ocean, the Patagonian Shelf, and the Indian Ocean sector of Antarctica. In the 70–90s and early 2000s, YugNIRO conducted marine geological studies facilitating fishing operations and environmental protection in the Gulf of Aden, on the bottom elevations of the tropical and subtropical parts of the Indian Ocean, in the Antarctic Shelf area, and in the Black and Azov Seas. This article lays down the current major goals and prospects of commercial oceanology.
    Description: 60–80-е годы прошедшего столетия были в АзЧерНИРО (ЮгНИРО) периодом наиболее активного развития промысловой океанологии. Кроме мониторинга океанографических процессов она начала внедряться в сферы общей экологии моря, мониторинга загрязнения моря, космической океанологии. Океанографическая информация используется при разработке прогнозов состояния водных экосистем различной заблаговременности и является неотъемлемой составляющей рыбопромысловых прогнозов. В 1981 г. в АзЧерНИРО был создан центр приема спутниковой информации. В 1980–1990-х гг. в ЮгНИРО была создана оптимальная для Черного моря схема комплексного прогностического мониторинга состояния его экосистемы. В сентябре 1986 г. в составе лаборатории промысловой океанологии Черного моря была создана группа, в январе 1989 г. — сектор, в декабре 1996 г. — лаборатория охраны морских экосистем. Сотрудниками лаборатории проводились комплексные экологические исследования состояния акваторий предприятий морехозяйственого комплекса в условиях их производственной деятельности, контроль уровня загрязненности почв, токсикологический контроль рыбы и рыбопродукции. Океанологические исследования ЮгНИРО, проводимые в Мировом океане с начала 1970-х до начала 1990-х гг., позволили получить систему связей урожайности и вылова промысловых объектов с особенностями атмосферной циркуляции, изменениями макромасштабных полей течений, гео- и гелиофизическими факторам для прогноза промысловых характеристик с заблаговременностью год и более в промысловых районах центральной, юго-восточной и юго-западной частей Индийского океана, в районе Патагонского шельфа, в индоокеанском секторе Антарктики. Выполнение морских геологических работ в рыбопромысловых и природоохранных целях проводилось ЮгНИРО в 1970–1990-х и в начале 2000-х гг. в Аденском заливе, на поднятиях тропической и субтропической частей Индийского океана, на шельфе Антарктиды, в Черном и Азовском морях. В статье формулируются основные современные цели и пути развития промысловой океанологии.
    Description: Published
    Description: Non Refereed
    Keywords: Commercial oceanography ; Marine geology ; Ecosystems ; Fisheries ; Промысловая океанография ; Морская геология ; Экосистемы ; АзЧерНИРО ; ЮгНИРО ; Промысловые прогнозы ; Океанографическая информация ; Океанологические исследования ; YugNIRO ; AzCherNIRO ; ASFA_2015::F::Fishery oceanography ; ASFA_2015::F::Forecasting ; ASFA_2015::F::Fishery institutions ; ASFA_2015::M::Monitoring
    Repository Name: AquaDocs
    Type: Journal Contribution
    Format: pp.159-169
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  • 3
    Publication Date: 2024-01-25
    Description: La producción de ostión en Cuba aumenta hacia el este, y los máximos de abundancia y captura se presentan en la zona costera cercana a la cuenca del río Cauto, en la región correspondiente al municipio Manzanillo, provincia de Granma. En esta región habitan el ostión de mangle antillano (Crassostrea rhizophorae Guilding, 1828), y el ostión americano (Crassostrea virginica Gmelin, 1791). Aunque la tendencia histórica ha sido al incremento, posterior a 2013 (853 t) la producción promedio anual disminuye a 307 t. El objetivo de esta investigación fue evaluar el estado actual del recurso ostión y su aprovechamiento industrial en la región del golfo de Guacanayabo, en relación a la situación ambiental de sus hábitats. Se realizó un diagnóstico de la pesquería de ostión y de la gestión ambiental de la pesca extractiva para determinar impactos ecosistémicos. Se identificaron como principales factores de impacto negativo, que inciden sobre las poblaciones de ostión y sus hábitats, el incumplimiento del periodo de veda, el manejo inadecuado de la pesca extractiva, y eventos de contaminación, que afectan los bienes y servicios ecosistémicos del manglar y reducen las poblaciones de ostión. Se propone la ostricultura artesanal como alternativa pesquera sostenible y se proyectó un plan de producción de ostión para 2023-2030. Se estimó que a calidad ambiental de la región donde se desarrollan las especies de interés es adecuada para su desarrollo.
    Description: Oyster production in Cuba increases to the east, and the maximum abundance and catch occur in the coastal zone near the Cauto river basin, in the region corresponding to the Manzanillo municipality, Granma province. The West Indian mangrove oyster (Crassostrea rhizophorae Guilding, 1828), and the American oyster (Crassostrea virginica Gmelin, 1791) inhabit this region. Although the historical trend has been to increase, after 2013 (853 t) the average annual production decreases to 307 t. The objective of this research was to evaluate the current state of the oyster resource and its industrial use in the region of the Guacanayabo Gulf, in relation to the environmental situation of its habitats. A diagnosis of the oyster fishery and the environmental management of extractive fishing was carried out to determine ecosystem impacts. The main factors of negative impact, which affect oyster populations and their habitats, were identified as non-compliance with the closed season, inadequate management of extractive fishing, and pollution events, which affect the goods and ecosystem services of the mangrove and reduce oyster populations. Artisanal oyster farming is proposed as a sustainable fishing alternative and an oyster production plan was projected for 2023-2030. It is estimated that the environmental quality of the region where the species of interest develop is adequate for their development.
    Description: Published
    Description: Refereed
    Keywords: Golfo de Guacanayabo ; Gestión ambiental ; Pesquería ; Ostricultura ; Gulf of Guacanayabo ; Environmental management ; Fisheries ; Ostrich farming
    Repository Name: AquaDocs
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  • 4
    Publication Date: 2024-03-05
    Description: Con sus 220 km2 la región geográfica de Bahía de Nipe es el mayor acuatorio en su tipo en Cuba, donde se encuentran representaciones de diversos ecosistemas a lo largo de sus costas. Los asentamientos humanos y sus múltiples actividades productivas de importancia y magnitud, le dan a esta bahía relevancia como recurso natural que sustenta usos estratégicos para el país.
    Description: Other
    Keywords: Contaminación ; Metales pesados ; Fuentes contaminantes ; Pesquerías ; Pollution ; Heavy metals ; Plaguicides ; Fisheries ; Plaguicidas ; Sources pollution
    Repository Name: AquaDocs
    Type: Thesis/Dissertation
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  • 5
    Publication Date: 2024-05-20
    Description: To ensure the long-term sustainable use of African Great Lakes (AGL), and to better understand the functioning of these ecosystems, authorities, managers and scientists need regularly collected scientific data and information of key environmental indicators over multi-years to make informed decisions. Monitoring is regularly conducted at some sites across AGL; while at others sites, it is rare or conducted irregularly in response to sporadic funding or short-term projects/studies. Managers and scientists working on the AGL thus often lack critical long-term data to evaluate and gauge ongoing changes. Hence, we propose a multi-lake approach to harmonize data collection modalities for better understanding of regional and global environmental impacts on AGL. Climate variability has had strong impacts on all AGL in the recent past. Although these lakes have specific characteristics, their limnological cycles show many similarities. Because different anthropogenic pressures take place at the different AGL, harmonized multilake monitoring will provide comparable data to address the main drivers of concern (climate versus regional anthropogenic impact). To realize harmonized long-term multi-lake monitoring, the approach will need: (1) support of a wide community of researchers and managers; (2) political goodwill towards a common goal for such monitoring; and (3) sufficient capacity (e.g., institutional, financial, human and logistic resources) for its implementation. This paper presents an assessment of the state of monitoring the AGL and possible approaches to realize a long-term, multi-lake harmonized monitoring strategy. Key parameters are proposed. The support of national and regional authorities is necessary as each AGL crosses international boundaries.
    Description: Published
    Description: 101988
    Description: JCR Journal
    Keywords: Fisheries ; Limnology ; Pollution ; Biodiversity ; Climate change ; Erosion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
    Publication Date: 2024-06-13
    Description: In a marine environment that is rapidly changing due to anthropogenic activities and climate change, area-based management tools are often used to mitigate threats and conserve biodiversity. Marine protected areas (MPAs) are amongst the most widespread and recognized marine conservation tools worldwide, however, MPAs alone are inadequate to address the environmental crisis. The promotion of other effective area-based conservation measures (OECMs) under draft Target 3 of the Post-2020 Global Biodiversity Framework, i.e., conserving 30% of marine areas by 2030, holds promise to acknowledge sites and practices occurring beyond MPAs that contribute to conservation. Here, we evaluate the potential recognition of OECMs into Indonesia's national policy framework on marine resource management and provide the first-ever overview of distribution and types of potential marine OECMs in Indonesia, including a review of the existing evidence on conservation effectiveness. We identified 〉 390 potential marine OECMs, led by government, customary and local communities, or the private sector, towards diverse management objectives, including habitat protection, traditional/customary management, fisheries, tourism, or other purposes. While some evidence exists regarding the conservation effectiveness of these practices, the long-term impacts on biodiversity of all potential marine OECMs in Indonesia are unknown. Many OECM elements have been included in several national policies, yet there are no established mechanisms to identify, recognize and report sites as OECMs in Indonesia. We propose four transformational strategies for future OECM recognition in Indonesia, namely: (i) safeguard customary and traditional communities, (ii) leverage cross-sector and cross-scale collaboration, (iii) focus on delivering outcomes, and (iv) streamline legal frameworks. Our study shows that OECMs have the potential to play a significant role in underpinning marine area-based conservation in Indonesia, including supporting the Government of Indonesia in reaching national and international conservation targets and goals.
    Keywords: Area-based management ; Biodiversity conservation ; Customary management ; Fisheries ; Co-management ; Sustainable marine management
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 7
    Publication Date: 2024-06-10
    Description: This draft White Paper has been prepared as part of the Vision 2030 process of the United Nations (UN) Decade of Ocean Science for Sustainable Development (hereafter, Ocean Decade). The Vision 2030 process aims to identify tangible measures of success for each of the ten Ocean Decade Challenges by 2030. From a starting point of existing initiatives underway in the Ocean Decade and beyond, and through a lens of priority user needs, the process determines critical gaps in science and knowledge, needs for capacity development, priority datasets, infrastructure, and technology for each Challenge. Focusing investments in science and knowledge to address these needs will help ensure progress towards meeting each critical Challenge by the end of the Ocean Decade in 2030. The results of the process will contribute to the scoping of future Decade Actions, identification of resource mobilisation priorities, and ensure relevance of the Challenges over time. This draft White Paper is one of a series of ten White Papers, all of which have been authored by an expert Working Group and discussed at the 2024 Ocean Decade Conference. A synthesis report, authored by the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific, and Cultural Organization (UNESCO/IOC), will accompany the White Papers. With a substantial portion of people depending on the ocean as a primary source of nutrition and livelihood, a significant challenge comes into focus: How can we ensure that the ocean's resources continue to effectively nourish an expanding global population? The Ocean Decade responds to this critical concern through its Challenge 3: “Sustainably nourish the global population”.
    Description: Published
    Description: Refereed
    Keywords: Food ; Agriculture ; Sustainable economy ; Fisheries ; World population ; Ocean economy ; Nutrition ; Aquatic foods ; Aquaculture ; Sustainable production ; Forward look ; Vision paper
    Repository Name: AquaDocs
    Type: Report
    Format: 33pp.
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  • 8
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    Springer
    Environmental management 7 (1983), S. 151-160 
    ISSN: 1432-1009
    Keywords: Grass carp ; Biological control ; Nuisance aquatic weeds ; Fisheries ; Aquaculture ; Reproductive requirements ; Arkansas management plan ; Sterile hybrids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Grass carp (Ctenopharyngodon idella Val.) were introduced into the United States in 1963 as potential biological control agents for nuisance aquatic weeds. Since that time an oftentimes bitter controversy has raged over its effects on sportfishing, and its possible natural reproduction and naturalization in North America. This review considers the history, ecology, and present status of grass carp in the United States in light of the voluminous scientific research conducted since its importation. Particular attention is given to the role of grass carp in the fisheries management plans of Arkansas. Recent development of a sterile, triploid grass carp hybrid may lead to widespread use of grass carp to control nuisance aquatic weeds in culturally eutrophicated waters of the United States.
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  • 9
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    Environmental biology of fishes 7 (1982), S. 177-180 
    ISSN: 1573-5133
    Keywords: Temperature ; Behavior ; Ecology ; Fisheries ; Fish ; Marine juveniles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Sixteen yearling winter flounder, tested individually for 3-day periods in electronic shuttleboxes, voluntarily occupied an 8–27°C range of temperature, with a modal final thermal preferendum of 18.5°C (mean 18.7°C, median 19°C, midpoint 17.5°C, s.d. 1.9°C, S k + 0.33). The locomotor activity pattern of the yearling fish in the laboratory was markedly nocturnal, with mean hourly nocturnal activity exceeding mean hourly diurnal activity by a factor of 3.4. Maximum activity occurred at 0300 EST, minimum activity at 1400 EST. While activity generally increased with temperature, a local activity minimum occurred at 18.7°C, coinciding with the 24-hour mean final thermal preferendum. Comparison of these laboratory data with previously published field data suggest that behavioral responses to temperature and light play significant roles in determining age- and size-specific differences in seasonal depth stratification and onshore-offshore distributions in this species.
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  • 10
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1-11 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The distribution of the first-passage time is of decisive importance in lift (elevator) design. It yields the easure of performance of the system, the expected number of stops, the interval (i. e. time elapsed between two successive departures from a given floor) and many other parameters and factors determining the required number of lifts in a building. The derivation is based on the transition probability matrix of the operation policy, and consists in solving a system of linear equations.
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  • 11
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 55-62 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Fourier analysis of numerical accuracy has traditionally concentrated on the propagation behaviour of various methods. When systems of equations in more than one unknown are involved, analysis of propagation accuracy alone is shown to be incomplete. A distribution factor is introduced to complement the Fourier analysis in these cases, and application of the concept to two problems commonly encountered in the water resources field is demonstrated. The distribution factor is shown to provide important information which cannot be obtained from the customary analysis of propagation accuracy.
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  • 12
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 177-188 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple approximation by nonconforming finite elements is presented that passes the patch test of Irons and Strang but does not yield approximate solutions converging to the solution of the given boundary value problem. It is constructed from continuous piecewise linear functions perturbed by step functions. Further, strange convergence properties of such approximations are explained in all details because they may be typical for the behaviour of nonconforming finite elements violating the basic precondition for convergence.
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  • 13
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 209-223 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The solution of incompressible, viscous flow problems using the primitive variable finite element approach is formulated in a coherent and physically reasoned exposition. In particular, it is shown that terms associated with changes in momentum caused by lack of mass conservation should logically be included in the governing equations. Previous formulations have not considered this possibility. Numerical results are presented to show the effect of inclusion of these extra terms; however, it is concluded from the numerical results for the specific case which was tested that there is no obvious benefit obtained by including these terms.
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  • 14
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 237-247 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A dual load method of truss analysis is presented that allows highly nonlinear member behaviour to be followed. In particular, a brittle type of strut behaviour is considered. The method assumes that the inelastic strut response is known and that piecewise linearization of the behaviour is acceptable. An example is given to illustrate the type of problem that can be handled. The example involves negative stiffness of the members and consequently attention must be given to the equation solving procedure for the structure. A comparison is made with some observed test results.
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  • 15
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 291-295 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical Laplace transform inversion technique is described, which is a modification of the inversion method using an exponential series representation. By adding an auxiliary function and using Erdélyi's inversion formula, the proposed technique provides the inverse approximation with improved accuracy near t = 0. Numerical illustrations shows that this procedure also works in cases when the original method of schapery fails to give satisfactory results.
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  • 16
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 308-318 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new method for interpolating in triangles is described. Bivariate cubic polynomials are utilized to define an interpolant which assumes arbitrary position and slope on the entire boundary of a triangular domain. Some examples and applications are discussed.
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  • 17
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 351-360 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Numerical convergence of first- and second-order plate-bending elements is investigated. Using iso-parametric formulation, general bilinear and biquadratic quadrilaterals, with the three moment components and the transverse deflection as dependent variables, are obtained. The same elements are also used as degenerate triangles by collapsing one side. A constant bending moment patch test, applied numerically to the elements, indicated poor performance for linear triangles, while the bilinear, quadratic and biquadratic elements behaved well, with exact results in uniform meshes. Further numerical examples showed the same general trend as the patch test. Although bilinear, quadratic and biquadratic elements were always able to yield the correct solutions with mesh refinements, the linear triangles were in general unable to do so.
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  • 18
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 381-404 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The complete two-dimensional partial differential equations for developing laminar flow in a circular tube have been treated by a finite difference analysis. Property variation with temperature, especially that of viscosity, is allowed for in a flexible manner. The continuity and momentum equations, and then the energy equations, are solved by direct elimination at each axial step, and marching procedure used in the axial direction. A new technique is that the stepwise energy balance is rigidly satisfied throughout by using it as a constituent equation in place of the ‘explicit’ wall thermal boundary condition normally used.The analysis predicts the complete developing hydrodynamic and thermal fields, together with friction factors and heat transfer coefficients. It has been tested for a range of fluid velocity and thermal boundary conditions and for various fluids, including high viscosity oils, water and air.Data for constant wall heat flux have already been published. 1,2 Predictions for constant wall temperature presented here are for forced and combined convection and are compared with experimental data of Test3 and Zeldin and Schmidt4.
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  • 19
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 464-469 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical method for solving two-point boundary value problems associated with systems of first-order nonlinear ordinary differential equations is described. It needs four function evaluations at each point and is of order h6, where h is the space chop. Results of computational experiments, which include perturbation of the initial conditions, comparing this method with other known methods are given.
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  • 20
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 470-476 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An algorithm is given to discretize a polygon or curved surface into triangular arrays. The method first involves the manual division of the array into quadrilaterals with specified numbers on rows and columns. The individual points are then filled in automatically and elements are automatically generated. A point of particular importance is that the number of columns or rows may be made to change. A subroutine is given to perform this task.
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  • 21
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 483-494 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An approximate analysis method for calculating local and system geometric imperfection influences on the displacements, stresses and buckling load of imperfect truss structures, is developed. The structural response, as a function of the design variables, is expressed in this approximate analysis which is much faster and cheaper than the ‘accurate’ analysis. The accurate analysis for a particular design is used as a base for each approximate analysis which then gives the response information needed for other designs in the neighbourhood about the base point design. Comparison of the approximate behaviour predictions with accurate results based on the more refined analysis methods shows that the quality of the proposed approximate analysis procedure is adequate for guiding a structural design procedure. It is evident that the approximate analysis is capable of describing the nonlinear behaviour of the structure, but when nonlinearity increases, the quality of the approximate analysis tends to deteriorate.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 575-582 
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    Keywords: Engineering ; Engineering General
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    Notes: The usual linear shape function for approximating axial displacement in beam finite elements used as eccentric stiffeners leads to an inconsistency which can result in large errors in the deflection of plates or composite beams. The introduction of an additional degree-of-freedom for these elements circumvents this problem.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 639-648 
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    Keywords: Engineering ; Engineering General
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    Notes: A boundary-location method is developed for finite element simulation of steady, two-dimensional flows of Newtonian liquid with free boundaries. In the method, boundary shape and position and the velocity and pressure fields are determined simultaneously. Inertial, viscous, gravitational, and surface tension effects are included in the development. The complete set of nonlinear finite element equations is solved by a modified frontal method combined with Newton-Raphson iteration to speed convergence. The finite element used to illustrate the method approximates the pressure as a piecewise constant function and the velocity and free boundaries as piecewise linear functions. Example calculations for flow from a slit show that the method can be effective.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 685-699 
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    Notes: The choice on an efficient direct integration procedure for linear structural dynamic equations of motion is discussed. It is suggested that as accuracy parameter the truncation error on the exponential terms contained in the modal contributions of the exact solution be assumed. This error does not always coincide with the local truncation error. These considerations were used to design an unconditionally stable one-step method whose accuracy is 0(h4). Numerical comparisons with some well-known integration schemes showed the efficiency of the proposed method.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 713-731 
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    Keywords: Engineering ; Engineering General
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    Notes: This paper presents a generalized method which generates linear, triangular, quadrilateral and pentahedral elements for the finite element method. Depending on geometrical and material variations, the region to be discretized is manually divided into blocks such as lines, triangles, quadrilaterals, pentahedrons and hexahedrons in several appropriate co-ordinate systems. However, no connectivity information of the adjacent blocks is required by the user as input. The continuity of the generated nodal co-ordinates and element configurations at the block interface are automatically maintained to describe the geometry of structures, no matter how these five types of blocks are connected. Furthermore, a mesh grading algorithm which generates reliable mesh grade distributions in the interior of the triangular and quadrilateral blocks is established corresponding to the arbitrarily defined subdivision numbers for each edge line of blocks. This algorithm is extended to the mesh grading in the interior of the hexahedral and pentahedral blocks. Element numbers are also renumbered in this scheme, in addition to node numbers, in order to increase the computational efficiency of the global matrix assembly. Additional facilities, i.e. loading data generation, boundary condition data generation and so on, are also discussed. An illustrative and a practical example are given to demonstrate the capabilities of this scheme.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 773-778 
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    Notes: The shape functions of serendipity rectangular elements had originally to be found by inspection. More recently an algorithm has been developed to formalize the construction of these shape functions. Here a simple expression is found for the interpolation function of the most general serendipity element. The shape functions can be derived immediately.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 955-980 
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    Notes: A series of finite element algorithms for the calculation of the post-buckling behaviour of structures are proposed. The algorithms represent a finite element implementation of a variational principle for nonlinear eigenvalue problems. Incremental amplitude solution schemes are defined. Numerical results are presented for the post-buckling behaviour of specific structures with linear and nonlinear pre-buckling states.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1041-1052 
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    International Journal for Numerical Methods in Engineering 15 (1980) 
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 935-942 
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 991-1020 
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    Notes: This paper presents isoparametric formulation for the three-dimensional transition finite elements. The transition finite elements are necessary for applications requiring the use of three-dimensional isoparametric solid elements and the curved shell elements. These elements provide proper connections between the two portions of the structure modelled with three-dimensional solids and the curved shell elements. The element properties are derived and presented in detail. Numerical examples are also presented to demonstrate the accuracy and the applications of such elements in three-dimensional stress analysis.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1261-1278 
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    Notes: A hybrid-stress element is developed for the analysis of thin and moderately thick plates. The independent transverse displacement and rotations are interpolated by the 12-node cubic Serendipity shape functions. All components of stress are included and 36β stress assumption is used. The element stiffness possesses correct rank and numerical results indicate that the element does not lock in the thin-plate limit. Results obtained using the present element are compared with those obtained using a 12-node assumed-displacement based Mindlin plate element with reduced integration; the present hybrid-stress element is shown to yield superior accuracy for all cases considered. In addition, the accuracy of the present element is compared against that of analogous 4-node and 8-node hybrid-stress Mindlin plate elements.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1280-1280 
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1083-1094 
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    Notes: This paper is concerned with the solution of the three-dimensional potential problem for electromagnetic river gauging. It extends previous ideas of joining finite elements in an interior region to one infinite external element treated by the boundary integral method1,2 to this case where there are two external infinite elements representing the river and the ground. The boundary continuity conditions on the infinite river-ground interface, as well as the internal-external interfaces, are dealt with by introducing a variational principle with relaxed continuity requirement3.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1107-1107 
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1129-1148 
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1113-1127 
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    Notes: Various boundary methods are considered for the numerical solution of the linear wave equation. The solution in the interior region is obtained using the Lax-Wendroff method. The theory of Gustafsson, Kreiss and Sundström is used to establish stability and the theory of Sköllermo is used to compare the accuracies of the various methods. The accuracy predictions are compared with computed results.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1161-1175 
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    Notes: The technique of fixed-interface modal synthesis used to solve large structural eigenvalue problems is extended to fluid-structure eigenvalue problems with a view to efficient solution of problems involving localized modifications. Three cases are considered: namely, those fluid or fluid-structure vibration problems directly analogous to the structural case; the modification of the fluid model of a structure enclosing a compressible fluid; and the modification of fluid and structural models of a structure enclosing an incompressible fluid. Examples of the three cases are given, as are estimates of the computation that can be saved when using the methods to avoid resolving modified eigenvalue problems. It is also shown that the hard-walled modes of a fluid enclosure can be used to modify the incompressible-fluid modes of the fluid-structure system to account for a degree of compressibility in the fluid. An example and computation estimates are given.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1239-1260 
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    Notes: The assumed-stress hybrid finite element model is examined for application to the bending analysis of thin plates. A hybrid-stress functional is defined by using a Mindlin-type displacement assumption and including all components of stress. The Euler equations and matrix formulation corresponding to this functional are examined to assess the effects of plate thickness, and a rationale is presented for the selection of stress assumptions so that locking is avoided in the thin plate limit. To illustrate these concepts, a series of linear displacement quadrilateral elements are derived and tested, and the best of these elements is identified for suggested implementation in general-purpose computer programs.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1315-1324 
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    Notes: An algorithm is presented for reducing the frontwidth of finite element meshes. The technique takes an arbitrary input scheme and reorders the elements so as to reduce the frontwidth. A number of examples are presented to demonstrate the reliability and effectiveness of the method.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1335-1341 
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    Notes: This review attempts to place in perspective the wide variety of computer methods which are available for constructing irregular computational grids. Several different approaches exist for each aspect of the construction task: creation of the points, recognition of neighbouring points that define grid elements, enumeration of the points with indices, optimization of the positions of the points for computational advantage, and variation of point density throughout the grid.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1381-1393 
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    Notes: The finite element method is used to analyse heat and mass transfer problems in porous media, in which the thermophysical properties are allowed to vary as functions of temperature and moisture. An example is given of the application of the method to the problem of timber drying.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1570-1574 
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    Notes: A method is presented for solving field problems using a finite element formulation, to be executed with the aid of a micro-computer. In order to reduce the requirements regarding memory space, the coefficients of the matrix defining the system of equations are not stored, but calculated when they are needed, in a modification of the usual finite element procedure. The method is applicable to all problems for which Gauss-Seidel iteration converges, and can handle problems involving more than 100 degrees-of-freedom on a computer with 8,000 bytes memory. Computing time may run up to several minutes per cycle of iteration, but on a small, personal computer, this is still acceptable.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1659-1680 
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    Notes: A finite element formulation for the adhesive of a lap joint is presented. The element is based on the assumptions common to the theories of Goland and Reissner and Ojalvo and Eidinoff. Deficiencies of the lap joint theories of those workers and of a previous finite element formulation of the adhesive are pointed out and the covergence of the new formulation to their results is discussed. Experimentally determined extreme fibre strains in the adherends are compared with those determined numerically using the new finite element formulation.
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    International Journal for Numerical Methods in Engineering 15 (1980) 
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1730-1733 
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1747-1769 
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    Notes: Finite elements with polynomial interpolation functions of a degree higher than 2 are used comparatively little on large FEM systems, except in shell elements. However, the author has had several years' experience in the use of the so-called ‘isoparametric, reduced Hermitian element’,4 Which has behaved excellently in an industrial as well as an educational environment. The reason for the interest in the Hermitian concept is that the overcompatibility of the element reduces the number of unknowns, the solution time and the discontinuities in stresses between elements.Explicit formulae for the family of interpolation polynomials of order q and degree p = 2q + 1 are given and hierarchical Hermite elements are introduced. The families of Hermite and serendipity elements are isomorphic and the latter may thus be extended to arbitrary high order.For some problems the equidistant node configuration in Lagrange elements of degree 3 and higher is not optimal with respect to smoothness, and a new type of element, the ‘Lobatto element’, is introduced.The methods consistently produce results of an accuracy which is above the requirements of usual engineering applications, but in graphics smoothness of curves is important for a convincing representation. The methods are of particular interest in industries working with structures composed of almost linear materials with well-known properties.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1771-1812 
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    Notes: An assessment of flat triangular plate bending elements with displacement degrees-of-freedom at the three corner nodes only is presented, with the purpose of identifying the most effective for thin plate analysis. Based on a review of currently available elements, specific attention is given to the theoretical and numerical evaluation of three triangular 9 degrees-of-freedom elements; namely, a discrete Kirchhoff theory (DKT) element, a hybrid stress model (HSM) element and a selective reduced integration (SRI) element. New and efficient formulations of these elements are discussed in detail and the results of several example analyses are given. It is concluded that the most efficient and reliable three-node plate bending elements are the DKT and HSM elements.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1613-1626 
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    Notes: The method of infinite elements is briefly reviewed. New more logical and general formulations of infinite elements are presented. The simplicity of the programming is emphasized. Results are given for elasticity and potential problems. Future extensions are discussed.
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    International Journal for Numerical Methods in Engineering 15 (1980), S. 1681-1689 
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    Notes: Convection-diffusion equations are difficult to solve when the convection term dominates because most solution methods give solutions which oscillate in space. Previous criteria based on the one-dimensional convection-diffusion equation have shown that finite difference and Galerkin (linear or quadratic basis functions) will not give oscillatory solutions provided the Peclet number times the mesh size (Pe Δx) is below a critical value. These criteria are based on the solution at the nodes, and ensure that the nodal values are monotone. Similar criteria are developed here for other methods: quadratic Galerkin with upwind weighting, cubic Galerkin, orthogonal collocation on finite elements with quadratic, cubic or quartic polynomials using Lagrangian interpolation, cubic or quartic polynominals using Hermite interpolation, and the method of moments. The nodal values do not oscillate for collocation or moments methods with Hermite cubic polynomials regardless of the value of Pe Δx.A new criterion is developed for all methods based on the monotonicity of the solutions throughout the domain. This criterion is more restrictive than one based only on the nodal values. All methods that are second order (Δx2) or better in truncation error give oscillatory solutions (based on the entire domain) unless Pe Δx is below a critical value. This value ranges from 2 for finite difference methods to 4·6 for Hermite, quartic, collocation methods.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 15-41 
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    Notes: The governing equations for large strain analysis of elastic-plastic problems are reconsidered. An improved form of these equations is derived, which is valid for small increments of strain and large increments of rotation. Special attention is paid to the integration procedures for these equations in the deformation history. It is shown that the tangent modulus procedure for integration of the constitutive equations is conditionally stable, and that implicit methods, such as the ‘mean normal’ method, are to be preferred. A novel procedure is introduced for the treatment of nonlinear geometric effects. The performance of various element types is examined, with specific attention to effects of ‘locking’ and distortion. Several applications are discussed to illustrate the various aspects of the formulation developed ein this paper.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 97-112 
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    Notes: In this paper we analyse a simple but non-trivial steady-state creeping elasto visco-plastic (Maxwell fluid) radial flow problem, paying particular attention to the effects of the boundary conditions. Solutions are obtained by integration of a governing equation on stress, using the Runge-Kutta method for initial value problems and finite differences for boundary value problems. A more general approach by the finite element method, which solves for the velocity field rather than the stress field, and which is applicable to a wide range of problems, is presented and tested using the radial flow example.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 133-139 
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    Notes: Some new formulae are presented for numerical integration over triangular regions. These formulae, which are triangularly symmetric, involve four, six, and seven integration points, respectively. They were derived by determining co-ordinates and weight factors for which polynomial functions of up to a certain degree are integrated exactly. The effectiveness of the formulae is demonstrated by applying them to the integration of five non-polynomial functions, two of which are singular within the region of integration. Results obtained with the new formulae are compared with results obtained with other, comparable formulae. It is seen that the new formulae are more accurate than some existing ones with the same numbers of points.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 156-156 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 159-170 
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    Notes: A finite element anaylysis to predict the sloshing dislacements and hydrodynamic pressures in liquid-filled tanks subjected to earthquake ground motions is presented. Finite element equations were derived using the Galerkin formulation, and the predicted results were checked against the test data, showing a good agreement between the test and finite element results.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 213-229 
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    Notes: Minimum cost design of a framed structure is considered by using the mini-mas dual method. Stress and/or displacement constraints are imposed as behavioural constraints. The minimum cost design problem has a discrete objective function and discrete design variables. A sequence of approximate optimization problems in created by using the first-order Taylor series expansion for displacements with respect to the reciprocals of cross-sectional areas and moments of inertia. Each approximate problem is solved in the dual space. Two simple structural examples are given to show the appropriateness and efficiency of the proposed procedure. Approximate solutions are obtained within five structural analysis.
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    International Journal for Numerical Methods in Engineering 16 (1980), S. 149-170 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The purpose of the paper is two-fold: Firstly, we develop stream function--vorticity and primitive variable finite element models of two-dimensional barotropic equations that satisfy the conservation of mean vorticity, mean squared vorticity (or enstrophy) and mean kinetic energy, and scondly, we present a comparative study of a number of numerical schemes for their accuracy in phase speed as well as in amplitude calculations for a two-dimensional, time-dependent, stream function--vorticity equation for periodic fluid motion in a channel. A circular vortex is placed in a uniform channel flow of a constant velocity (U) as an initial condition. An analytic solution exists for the problem such that the vortex moves with a constant speed U conserving the shape of the vortex: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {\psi \left({x,y,0} \right) = - Uy + \psi _0 \exp \left[{ - a^2 \left({x^2 + y^2 } \right)} \right] \equiv F\left({x,y} \right)} \hfill \\ {\psi \left({x,y,t} \right) = F\left({x - Ut,y} \right)} \hfill \\ \end{array} $$\end{document} where U, ψ0 a are constants. This example makes it easier to identify the cause of phase speed error, either due to linear or non-linear processes, and furthermore, to find a satisfactory scheme for time integration. The numerical schemes compared include: Arakawa Jacobian,1 Arakawa-Matsuno scheme, Galerkin finite element, Lax-Wendroff, leap-frog, and Crank-Nicholson. The effect of a variational adjustment (see Sasaki16) is also studied. Computational time, RMS errors in stream function and vorticity, and the conservation of the mean kinetic energy and enstrophy are compared at the end of 120 (one period) and 240 (two periods) time steps. The study indicates that the numerical scheme that employs finite elements in space (same as Arakawa Jacobian) and Crank-Nicholson in time is the most accurate among the schemes studied.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 123-132 
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    Keywords: Engineering ; Engineering General
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    Notes: A kinematically nonlinear analysis of unbraced, rigid-jointed, portal frames, rotationally restrained at the base and subjected to eccentric concentrated and/or uniformly distributed loads, is presented. Through this analysis the complete behaviour, including the primary path and postbuckling path (whenever it exists), is evaluated. Moreover, through parametric studies, the effects of bar slenderness ratio, load eccentricity and amount of rotational restraint are assessed. Through this method it is also possible to assess the effect of member lengths and member lengths and member bending stiffnesses.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 145-153 
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    Keywords: Engineering ; Engineering General
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    Notes: Numerical evaluations of elliptic integral solutions of some large deflection beam and frame problems are presented. The values are given in tabular form with up to six significant figures. The numerical technique used for evaluating the elliptic integrals is described.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 156-156 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 187-198 
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    Keywords: Engineering ; Engineering General
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    Notes: This paper presents the details of a unified numerical algorithm and the associated computer program developed for the efficient determination of natural frequencies and modes of free vibration of structures. Both spinning and nonspinning structures with or without viscous and/or structural damping may be solved by the current procedure; in a addition, the program is capable of solving static problems with multiple load cases as well as the quadratic matric eigenproblem associated with a finite dynamic element structural discretization. A special symmetric matrix decomposition scheme has been adopted for matrix triangularization, which renders the program rather efficient and economical. Also, a novel bisection scheme is described that further accelerates the solution convergence rate, particularly for the case of repeated roots.The associated computer program adopts and out-of-core solution strategy, thereby enabling effective solutions to be achieved for large, complex, practical structures. A complete listing of the program written in FORTRAN V, for the UNIVAC 1100/82 computer, along with the source deck is available for ready use.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 271-279 
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    Keywords: Engineering ; Engineering General
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    Notes: A FORTRAN subroutine is presented to integrate a function given only by a set of tabular values at unequal intervals. It uses the trapezoidal rule and a generalization of Simpson's rule, obtaining a conservative error estimate by comparing the two results.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 301-305 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 309-309 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 312-312 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 335-346 
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    Notes: Splitting methods for time-dependent partial differential equations usually exhibit a drop in accuracy if boundary conditions become time-dependent. This phenomenon is investigated for a class of splitting methods for two-space dimensional parabolic partial differential equations. A boundary-value correction discussed in a paper by Fairweather and Mitchell for the Laplace equation with Dirichlet conditions, is generalized for a wide class of initial boundary-value problems. A numerical comparison is made for the ADI method of Peaceman-Rachford and the LOD method of Yanenko applied to problems with Dirichlet boundary conditions and non-Dirichlet boundary conditions.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 357-365 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 445-464 
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    Notes: A singular finite element is developed for direct calculation of combined modes I and II stress intensity factors for planar rectilinear anisotropic structures subject to arbitrary loading. Twelve-node conventional elements are used in conjunction with a linear elastic fracture mechanics enrichment of the same element which is formed into a four-element macro-element. Example problems show this formulation to be exceptionally accurate and results are presented for a variety of modern fibre-reinforced composites in simple mode I extension and in mixed mode I and II situations. In addition, it is shown that the meshes for accurate results are relatively coarse and thus calculations are quite economical.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 477-477 
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    International Journal for Numerical Methods in Engineering 17 (1981) 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 527-541 
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    Notes: This paper is concerned with conventional and mixed finite element analysis of large deflection bending and free vibration of axisymmetric circular plates including shear deformation. Conventional and mixed finite element formulations are presented. Numerical results are included for isotropic as well as orthotropic, circular and annular plates under various edge conditions and loadings.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 601-613 
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    Notes: The general problem of optimum design of trusses composed of tubular elements requires the determination of cross-sectional dimensions for each element which satisfy a set of side constraints on those dimensions as well as Euler and local buckling constraints. A formulation is presented which eliminates the necessity to use mathematical programming methods for the determination of feasible cross-sectional dimensions. The minimization problem is shown to be expressible in terms of area variables only, with each area subject to bounds which are functions of truss stiffness but which may be obtained by explicit analysis of the element ‘desing space’ for any design. This‘direct’ formulation is completely general and compatible with any minimization algorithm. The formulation also leads to a simple and efficient recursive procedure for producing near-optimal fully-constrained designs. Several examples illustrate results obtained by both the direct and recursive procedures.
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    International Journal for Numerical Methods in Engineering 17 (1981) 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 707-718 
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    Notes: The use of quasi-Newton methods is studied for the solution of the nonlinear finite element equations that arise in the analysis of incompressible fluid flow. An effective procedure for the use of Broyden's method in finite element analysis is presented. The quasi-Newton method is compared with the commonly employed successive substitution and Newton-Raphson procedures, and it is concluded that the use of Broyden's method can constitute an effective solution strategy.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 747-771 
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    Notes: This paper discusses computational strategies for elastic-plastic-creep behaviour. These computational strategies, based on the tangent stiffness and initial strain techniques, include solution algorithms, modelling techniques and constitutive relations.A predictor-corrector iterative and non-iterative scheme is presented for combined plasticity and creep. This scheme has been incorporated into the three-dimensional, isoparametric element, module (HEX) of the Grumman PLANS finite element program for nonlinear analysis and used for the problems presented in this paper.The concept of modelling for inelastic behaviour is demonstrated by introducing a variable set of inelastic integration points within a finite element at which stresses and strains are monitored.In order to perform a meaningful analysis, one must understand and justify the employed constitutive relations. To this end, work at Oak Ridge National Laboratory in justifying constitutive relations for high-temperature nuclear reactor components is referred to.An analysis of a test model of a nuclear reactor inlet nozzle operating at high temperatures is presented to demonstrate some of the computational strategies discussed.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 1407-1426 
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    Keywords: Engineering ; Engineering General
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    Notes: The displacement and strain fields of thin-walled pretwisted beams are prescribed in terms of generalized displacements for extension, bending, torsion and warping. Differential equations and boundary conditions are obtained from the elastic potential energy functional without assuming coincidence of the beam axis with any of the structural axes. This procedure gives a unique consistent definition of sectional moments and generalized forces. Some simple explicit formulae are derived for homogeneous tension-torsion. For the general case a computer code is developed on the basis of discretized generalized displacements and a modified energy functional, devised to obtain consistent lengthwise variation of the stresses and a unique decomposition of the torsional moment. Examples show agreement with analytical results for cylindrical beams and illustrate the various coupling effects for beams with pretwist. They also demonstrate the usefulness of the explicit formulae for homogeneous tension-torsion.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 1443-1453 
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    Notes: A computationally efficient and accurate solution technique for large-order eigenvalue problems with small to medium bandwidth is presented. The algorithm - called the Sub-Polynomial Iteration (SPI) method - solves for the eigenvalues and corresponding eigenvectors. directly without any transformation to the standard form. The method is an efficient combination of several separate techniques including Sturm sequence, Lagrangian polynomial interpolation, inverse iteration with shift and Gram-Schmidt orthogonalization. Computer run times for a set of sample solution indicate the efficiency of the SPI method.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 1647-1657 
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    Notes: A method for solving boundary value problems for thin plate flexure as described by Kirchhoff's theory is proposed. An integral formulation leads to a system of boundary integral equations involving values of deflection, slope, bending moment and transverse shear force along the edge. A discretization leading to a matrix formulation is proposed. To solve problems with inner conditions in the plate domain, an elimination of boundary unknowns proves successful. The degenerate case where the boundary is free (which leads to a non-invertible matrix) is investigated. Three examples illustrate the efficiency of the method.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 1740-1742 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 1743-1748 
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 1779-1789 
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    Notes: The following work proposes the use of a special description-language for producing input data of finite element programs. The programs now used require a detailed description of the structure to be analysed, and they require it in a form which is unfavourable to the user and which promotes errors. Therefore, a language was designed which allows a short and compact description of the structure. This description is then automatically transformed into the input data. In this paper, the design process and the characteristics of the language are presented. Some comments on its implementation, that is on the development of a special preprocessor, are made. As target system, the finite element program SAP IV has been chosen. Finally, we want to present an example of the improvements achieved by the use of this language and the SAP IV preprocessor, respectively.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 1791-1810 
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    Notes: Two alternative hybrid-stress-based functionals are examined for the incremental elastic-plastic static analysis of single layer plates. Material nonlinear effects are incorporated via the initial-stress approach so that an equivalent nodal force vector is defined and the stiffness remains constant throughout the incremental loading. The alternative functionals differ in the incremental stress which is assumed to satisfy equilibrium; in the first, it is the actual stress increment, and in the second it is the elastic stress increment. Results are presented for two example problems, and comparisons of the alternative functionals and plausible iteration schemes are given. The effects of variation of pertinent solution parameters are also shown. A 4-node hybrid-stress plate element based on a Mindlin-type displacement field is used for most cases; however, limited results are also presented using an 8-node plate element, thus permitting comparisons of the relative efficiencies of the two elements.
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    International Journal for Numerical Methods in Engineering 17 (1981), S. 1888-1889 
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    International Journal for Numerical Methods in Engineering 18 (1982) 
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    International Journal for Numerical Methods in Engineering 18 (1982), S. 41-66 
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    Notes: A system for describing three-dimensional surfaces in a form suitable for finite element analysis is described. The system makes extensive use of real-time interactive computer graphics techniques for both input and display. Discrete transfinite mappings are used as the mathematical basis for the surface representation. The mathematical basis and the reasons for choosing this form of representation are discussed. Explicit forms of the mappings based on Lagrange polynomial interpolation functions are presented. Finally, the interactive graphics procedures for defining finite element meshes are described.
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    International Journal for Numerical Methods in Engineering 18 (1982), S. 99-109 
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    Notes: Two highly accurate implicit Padé approximations to the transient heat conduction equation are investigated using the conjugate gradient method to solve, for the temperatures. The accuracy and stability of the approximations are discussed and numerical examples are presented showing the relative performance. Comparisons with the Crank-Nicolson method are also presented.
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    International Journal for Numerical Methods in Engineering 18 (1982), S. i 
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    International Journal for Numerical Methods in Engineering 18 (1982), S. 195-210 
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    Notes: A clearer insight into the ‘shear locking’ phenomenon, which appears in the development of C0 continuous element using shear-flexible or penalty type formulations, is obtained by a careful study of the Timoshenko beam element. When a penalty type argument is used to degenerate thick elements to thin elements, the various approximations of the shear related energy terms act as different types of constraints and, depending on the formulation, two types of constraints which are classified as true or spurious may emerge. The spurious constraints, where they exist, are responsible for the ‘shear locking’ phenomenon, and its manifestation and elimination is demonstrated in a very simple example. The source of difficulty is shown to be the mathematical operations involved in the various shape function definitions and subsequent integration of functionals. It is seen that formulations that ensure only true constraints in the extreme penalty limit cases display far superior performance in the thick element situation as well, and thus guidelines for the development of efficient elements are drawn. A similar type of behaviour is observed in a shallow curved beam element and here ‘inplane locking’ can be eliminated by selective integration to obtain an improved curved beam element. However, ‘inplane locking’ does not cause a spurious constraint as the error quickly vanishes with the reduction of element size for a reasonable radius of curvature conforming with shallow shell theory.
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    International Journal for Numerical Methods in Engineering 18 (1982), S. 321-322 
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    International Journal for Numerical Methods in Engineering 18 (1982), S. 323-341 
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    Notes: The rate of convergence of the finite element method is a function of the strategy by which the number of degrees-of-freedom are increased. Alternative stragegies are examined in the light of recent theoretical results and computational experience.
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    International Journal for Numerical Methods in Engineering 18 (1982), S. 381-396 
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    Notes: Upwind finite element schemes remove spurious oscillations that occur in the solution of diffusion convection equations. Up to now these schemes lose part of their accuracy when the Peclet is large. As an improvement, it is proposed to move the integration nodes along the ‘streamlines’ before evaluating the elementary convection matrices. The displacements of the nodes along the streamlines, which are one-dimensional manifolds, are calculated analogously to well-known one-dimensional formulae. The last section of this paper illustrates this new method with the help of four examples which show its validity.
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    International Journal for Numerical Methods in Engineering 18 (1982), S. 314-320 
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    Notes: Quarter-point elements are used very frequently for fracture mechanics computations, because the quarter-point technique yields the required singular interpolation without any modification to existing software. This advantage is particularly significant for three-dimensional stress intensity factor computations because of the difficulty of implementing other techniques. However, in practical 3-D applications, the crack front is usually curved, and this note proves that a crack front distortion leads to a negative Jacobian in the region surrounding the crack front. The numerical difficulties to be expected depend on the aspect ratio of the elements.
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    International Journal for Numerical Methods in Engineering 18 (1982), S. 343-350 
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    Notes: The paper presents a smoothing technique to the oscillated contact pressure obtained by penalty methods for a class of unilateral contact problems in linear elasticity. The main result is to show that the smoothed contact pressure satisfies the so-called Babuska-Brezzi condition which dominates the convergence of the penalty method. One numerical example is described.
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 18 (1982), S. 435-444 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A method for the exploitation of screw translation symmetry for the vibration analysis of structures is presented. The method is capable of providing significant computational economies over the use of the lower axial translational symmetry of such structures.
    Additional Material: 4 Ill.
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  • 95
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 18 (1982), S. 629-630 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 96
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 18 (1982), S. 632-634 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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  • 97
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 18 (1982), S. 661-673 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Optimal structural desingn generally deals with frame or shell structures where the optimization is limited to resizing of structural members to obtain optimum cross-sections or thicknesses. Shape optimization solves another class of problems involving continuous structural components where the optimum shape (the shape of the boundaries and the surfaces of the components) is determined. This report describes shape optimization of three-dimensional structural components. The finite element method of analysis is used employing the 20-noded isoparametric element. The objective function, mass, is minimized by the direct use of nonlinear mathematical programming, specifically the feasible direction method. Numerical shape representation and the selection of design variables are the most important aspects of the problem. The problem is addressed from a practical standpoint and techniques are presented to minimize the number of desingn variables. Isoparametric representation of the surfaces and the numerical superposition of shapes are discussed. These techniques are compared and demonstrated on simple cantilever beams and their minimum mass designs are obtained. In one example, the optimum shape of a non-uniform cross-sectinal beam is obtained under stress constraint. The final design has a crosssectional shape varying over the length of the beam which could not be predicted using the bending theory of beams. One major difficulty encountered in some problems was that the shape changes during the optimization process may require a change in the finite element mesh because the initial configuration of the finite element mesh may result in very distorted elements for the new shape. The analyis with a mesh containing distorted elements may not be possible at all or the results of the analysis may be inaccurate.
    Additional Material: 14 Ill.
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  • 98
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 18 (1982), S. 727-735 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Vector functions having a constant or zero divergence over a quadrilateral domain are derived using a parametric co-ordinate formulation. Expansion functions with a constant curl, defined over parallelograms and triangles, which can be used in moments-based investigations of electromagnetic wave interactions with surfaces and apertures, are then obtained. Finally, two basis functions, which have appeared in the literature and have been used to solve field problems associated with rectangular apertures and arbitrary surfaces, are identified as special cases of these expansion functions.
    Additional Material: 4 Ill.
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  • 99
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 18 (1982), S. 927-944 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Finite element formulation for stress analysis of a twisting beam is developed. The formulation is effective for a prismatic beam with solid section as well as a thin-walled beam, and can be applied both to a pure-torsion problem and a warping-torsion problem. The formulation is of a great advantage to an elastic-plastic torsion problem. The formulation does not stand on the assumption of a thin-walled structure, and therefore torsional rigidity of the section can be evaluated exactly without using the so-called Saint-Venant's torsional constant. Torsional rigidity is, in this paper, evaluated directly by a warping function of the section. Warping function is evaluated numerically due to shape of the section, due to progress of plastic region and due to effect of finite displacement (finite rotation, small strain). Pure-torsion and warping-torsion of a rectangular beam and an H-beam, which have an elastic-plastic material property, are analysed, and the extension to the finite displacement problem is discussed. Many numerical examples are provided in order to check the accuracy of the formulation.
    Additional Material: 10 Ill.
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  • 100
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    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 18 (1982), S. 955-957 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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