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  • 1
    Electronic Resource
    Electronic Resource
    COMPARISON OF ASYNCHRONOUS AND DEMAND PACING (1969)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 167 (1969), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1969.tb34159.x
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  • 2
    Electronic Resource
    Electronic Resource
    Integration of reduction and expansion processes in layout optimization (1996)
    Springer
    Structural and multidisciplinary optimization 11 (1996), S. 13-18 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A tw0-stage layout optimization procedure, consisting of reduction and expansion processes, is presented. The object in developing this procedure is to use the advantages of both processes. In the reduction process, a reduced structure with a limited number of members and joints is established by solving large scale idealized problems. An expansion process is then employed, where members and joints are added to the initial reduced structure. At this stage, relatively small problems are solved, considering general variables, all relevant constraints and the real objective function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279649
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  • 3
    Electronic Resource
    Electronic Resource
    Alternative formulations of structural optimization (1994)
    Springer
    Structural and multidisciplinary optimization 7 (1994), S. 32-41 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several alternative, but equivalent, formulations of structural optimization problems are critically reviewed and compared. The various formulations differ in the independent variables chosen, the analysis equations employed, and the form of the resulting constraints. With regard to the method of analysis used, the displacement method, force method and mixed method of analysis are considered. The problem formulations discussed include (i) those in the Design Variable Space (DVS), (ii) Simultaneous Analysis and Design (SAND), and (iii) Optimality Criteria (OC). Some simplified formulations, approximate approaches and dual methods are also reviewed. Moreover, typical characteristics, advantages and drawbacks of various formulations are discussed and their effect on the solution process pointed out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01742501
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  • 4
    Electronic Resource
    Electronic Resource
    Improved optimum structural design by passive control (1989)
    Springer
    Engineering with computers 5 (1989), S. 13-22 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract The problem of optimum structural design by passive control is stated in a nonlinear programming form. A solution procedure, based on a successive selection of design and control variables, is presented. Neglecting the implicit analysis equations, the solution becomes independent of the control variables and a lower bound (LB) on the optimum can easily be obtained. The control variables are then selected to satisfy all constraints. If this cannot be achieved, the LB constraints are modified and the control variables are chosen for the revised optimal design. These two steps are repeated until the final optimum is reached. Employing the proposed procedure on various structural systems subjected to static loads showed that the final optimum has been achieved after a very small number of iteration cycles. The numerical examples illustrate a solution with two types of control devices: a linear spring device and a limited displacement device. It has been found that the final optimum is often identical or close to the initial LB solution. Savings of 14 to 63 percent in weight, compared with conventional optima without control, have been demonstrated for some common structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01201994
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  • 5
    Electronic Resource
    Electronic Resource
    On optimal topology of grillage structures (1986)
    Springer
    Engineering with computers 1 (1986), S. 229-243 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Two problems of optimum topological design of grillages are discussed: (1) the Equilibrium Linear Programming (ELP), where the analysis model is based only on equilibrium conditions and (2) the Nonlinear Program (NLP), where the ELP formulation is extended to include compatibility conditions. The structural topology is optimized by allowing elimination of elements. Three different force method formulations are presented for each of the problems. It is shown that the optimal topology for the NLP problem might correspond to a singular point in the design space. The optimal topology for the ELP problem is obtained by solving a linear program (LP). Conditions for selecting a geometry of Multiple Optimal Topologies (MOT) are derived. The objective function for the MOT geometry is shown to be independent of the redundant forces, and some of the optimal topologies are usually statically determinate structures. In such cases the lower bound on the optimal value obtained by the ELP solution is equal to the final global optimum. Examples are given to illustrate how the optimal topology and its corresponding load path change with the geometric parameters. Design procedures that combine automated optimization and CAD techniques are most suitable for solving the presented problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200139
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  • 6
    Electronic Resource
    Electronic Resource
    Combined approximations – a general reanalysis approach for structural optimization (2000)
    Springer
    Structural and multidisciplinary optimization 20 (2000), S. 97-106 
    Details
    ISSN: 1615-1488
    Keywords: Key words: approximate analysis, structural optimization, structural reanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract. The Combined Approximations (CA) method developed recently, is an effective reanalysis approach providing high quality results. In the solution process the terms of the binomial series, used as basis vectors, are first calculated by forward and back substitutions. Utilizing a Gram–Schmidt orthogonalization procedure, a new set of uncoupled basis vectors is then generated and normalized. Consequently, accurate results can be achieved by considering additional vectors, without modifying the calculations that were already carried out. In previous studies, the CA method has been used to obtain efficiently accurate approximations of the structural response in problems of linear reanalysis. It is shown in this paper that the method is most suitable for a wide range of structural optimization problems including linear reanalysis, nonlinear reanalysis and eigenvalue reanalysis. Some considerations related to the efficiency of the solution process and the accuracy of the results are discussed, and numerical examples are demonstrated. It is shown that efficient and accurate approximations are achieved for very large changes in the design.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001580050141
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  • 7
    Electronic Resource
    Electronic Resource
    Reanalysis of trusses using modified initial designs (2000)
    Springer
    Structural and multidisciplinary optimization 19 (2000), S. 105-112 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract. This paper presents a solution procedure for reanalysis using a mixed exact-approximate approach. The procedure, which is based on the reduced basis method, uses an efficient exact reanalysis method to handle a limited number of dominant member area and topological changes. A modified initial design (MID), associated with which is a recalculated inverse of the modified stiffness matrix, is the starting point for the approximate technique. Local geometrical changes may be accounted for within the modified initial design. An approximate technique is then used to handle the rest of the changes. This solution procedure significantly improves the accuracy of the approximation and conveniently accommodates geometrical and topological changes which occur in layout optimization of structures. The main purpose of this paper is to exploit, for a better balance between efficiency and accuracy, the advantages of the exact approach for reanalysis which is efficient for a small number of changes and the approximate approach for reanalysis which is efficient for a large number of changes of small magnitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001580050090
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  • 8
    Electronic Resource
    Electronic Resource
    On the relationship between optimum structural topologies and geometries (1990)
    Springer
    Structural and multidisciplinary optimization 2 (1990), S. 39-45 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The relationship between two optimal design problems is investigated: (a) The fixed geometry problem, where the topology is optimized for a predetermined geometry. (b) The fixed topology problem, where the geometry is optimized for a given topology. Assuming approximate linear programming formulations, conditions of optimality are derived and geometries of multiple optimal topologies are studied. Some considerations related to a general design procedure for optimization of topology, geometry and cross-sections are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01743519
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  • 9
    Electronic Resource
    Electronic Resource
    On singular topologies in optimum structural design (1990)
    Springer
    Structural and multidisciplinary optimization 2 (1990), S. 133-142 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A major obstacle to topological optimization is that the optimal topology might correspond to a singular point in the design space. Despite its crucial importance, the phenomenon of singular optimal topologies is not well understood. The main objects of this paper are: (a) to clarify some properties of singular optimal topologies; (b) to discuss the effect of various constraints on the optimum; and (c) to present some design considerations related to the particular difficulties involved in topological optimization. It is shown that singular solutions are obtained mainly due to the nature of stress constraints. Displacement constraints might significantly affect the optimal cross-sections, but not necessarily the optimal topology. The effect of lower bounds on cross-sections is demonstrated and several two-stage solution procedures are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01836562
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  • 10
    Electronic Resource
    Electronic Resource
    Exact structural reanalysis by a first-order reduced basis approach (1995)
    Springer
    Structural and multidisciplinary optimization 10 (1995), S. 153-158 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract It is shown in this article that in truss structures, the first-order (two-term) reduced basis expressions provide exact displacements and stresses in terms of the cross-sectional variables. For changes inm members theexact solution is achieved by considering them first-order basis vectors. Each of the latter vectors is shown to be the constant sensitivity vector multiplied by a scalar variable. The multipliers of the reduced basis equations can readily be determined by solving anm × m set of equations. The main advantages of the method presented are as follows: (a) It is more efficient than the common exact analysis in cases where a limited number of members is changed. (b) Unlike the common approximations, the exact solution is achieved. This is particularly important in cases where the accuracy of the results obtained by approximate methods is not adequate. (c) The method can be used also in cases of changes in the structural layout (topological and geometrical optimization), where approximate methods might provide poor or meaningless results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01742586
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