MAXIMAL ELEMENTS FOR G_B-MAJORIZED MAPPINGS IN PRODUCT G-CONVEX SPACES AND APPLICATIONS (Ⅰ)

IntroductionItiswell_knownthattheexistenceofmaximalelementsforset_valuedmappingsintopological(vector)spacesanditsimportantapplicationstomathematicaleconomieshavebeenstudiedextensivelybymanyauthorsinbothmathematicsandeconomics.Forexistenceresultsofmaximalelementsofvariousclassesofset_valuedmappingsandtheirapplicationstomathematicaleconomiesandotherbranchesofmathematics,thereadermayconsultRefs.[1～ 2 7]andthereferencestherein .LetXbeatopologicalspaceandY =∏i∈IYibeaproductofnonemptyconvexsetY…     

A Fixed Point Theorem for Set-Valued Mappings

ＩｎｔｒｏｄｕｃｔｉｏｎＳｔｕｄｙｏｆｆｉｘｅｄｐｏｉｎｔｔｈｅｏｒｅｍｆｏｒｍｕｌｔｉｖａｌｕｅｄｍａｐｐｉｎｇｓｉｎｃｏｍｐｌｅｔｅｍｅｔｒｉｃｓｐａｃｅｗａｓｉｎｉｔｉａｔｅｄｂｙＮａｄｌｅｒ[1].ＡｆｔｅｒｈｉｓｒｅｓｕｌｔａｎｕｍｂｅｒｏｆｆｉｘｅｄｐｏｉｎｔｔｈｅｏｒｅｍｓｆｏｒｓｅｔｖａｌｕｅｄａｎｄｍｕｌｔｉｖａｌｕｅｄｍａｐｐｉｎｇｓｗｅｒｅｅｓｔａｂｌｉｓｈｅｄａｓｓｏｃｉａｔｅｄｗｉｔｈｔｈｅｎａｍｅｓｏｆＲｅｉｃｈ[2 ],Ｋｈａｎ[3],ＫａｕｌｇｕｄａｎｄＰａｉ[4 ],Ｆｉｓｈｅｒ…     

The best approximation and coincidence theorems for composites of acyclic mappings

ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｃｅｎｔｌｙｔｈｅｒｅｈａｖｅａｐｐｅａｒｅｄａｎｕｍｂｅｒｏｆｎｅｗｆｉｘｅｄｐｏｉｎｔｔｈｅｏｒｅｍｓａｎｄｃｏｉｎｃｉｄｅｎｃｅｔｈｅｏｒｅｍｓｉｎｖｏｌｖｉｎｇｓｏ＿ｃａｌｅｄＫａｋｕｔａｎｉｆａｃｔｏｒｉｚａｂｌ...     

On a class of generalized nonlinear implicit quasivariational inclusions

ＩｎｔｒｏｄｕｃｔｉｏｎＶａｒｉａｔｉｏｎａｌｉｎｅｑｕａｌｉｔｙｔｈｅｏｒｙａｎｄｃｏｍｐｌｅｍｅｎｔａｒｉｔｙｐｒｏｂｌｅｍｔｈｅｏｒｙｈａｖｅｂｅｃｏｍｅｖｅｒｙｅｆｆｅｃｔｉｖｅａｎｄｐｏｗｅｒｆｕｌｔｏｏｌｓｆｏｒｓｔｕｄｙｉｎｇａｗｉｄｅｒａｎｇｅｏｆｐｒｏｂｌｅｍｓａｒｉｓｉｎｇｉｎｍｅｃｈａｎｉｃｓ,ｍａｔｈｅｍａｔｉｃａｌｐｒｏｇｒａｍｍｉｎｇ,ｏｐｔｉｍｉｚａｔｉｏｎａｎｄｃｏｎｔｒｏｌ,ｅｑｕｉｌｉｂｒｉｕｍｔｈｅｏｒｙｏｆｅｃｏｎｏｍｉｃｓ,ｍａｎａｇｅｍｅｎｔｓｃｉｅｎ…     

NEW COLLECTIVELY FIXED POINT THEOREMS AND APPLICATIONS IN G-CONVEX SPACES

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎ 1 991 ,Ｔａｒａｆｄａｒ[1]ｆｉｒｓｔｅｓｔａｂｌｉｓｈｅｄｔｈｅｆｏｌｌｏｗｉｎｇｃｏｌｌｅｃｔｉｖｅｌｙｆｉｘｅｄｐｏｉｎｔｔｈｅｏｒｅｍｏｎｔｈｅｐｒｏｄｕｃｔｓｐａｃｅｏｆｎｏｎｅｍｐｔｙｃｏｍｐａｃｔｃｏｎｖｅｘｓｕｂｓｅｔｓｏｆｔｏｐｏｌｏｇｉｃａｌｖｅｃｔｏｒｓｐａｃｅｓａｎｄｇａｖｅｉｔｓａｐｐｌｉｃａｔｉｏｎｓｔｏｔｈｅｅｘｉｓｔｅｎｃｅｏｆｅｑｕｉｌｉｂｒｉｕｍｐｏｉｎｔｓｆｏｒａｂｓｔｒａｃｔｅｃｏｎｏｍｉｅｓ.Ｔｈｅｏｒｅｍ 1　Ｌｅｔ Ｘｉ ｉ∈Ｉ…     

On Optimality Conditions for Trusses with Nonuniform Stress Constraints*

ABSTRACT

The optimal design of a truss subjected to a single loading system and stress constraints, which are not necessarily the same in each bar, is considered. Sufficient conditions for global optimality are derived by variational methods. While these optimality criteria lead to a linear programming formulation of the problem, they show in a clear physical way how the optimal design is found, and that advantages accrue from incorporating the optimality criteria in a numerical scheme.     

A Dual Approach to Optimum Truss Design

Abstract

This paper considers the problem of finding member sizes which minimize the weight of a pin-jointed truss of fixed geometry while satisfying constraints upon joint displacements, member stresses, and minimum sizes. Aspects of both mathematical programming methods and optimality criteria methods for designing large trusses are discussed. The optimality criteria approach is further extended and the whole truss design problem is recast into a new dual formulation in which constraint activity levels are used as variables in a mathematical programming solution method. This new dual formulation unifies both the optimality criteria and mathematical programming approaches to the problem of truss design. The paper is theoretical in nature, being largely devoted to a proof of the dual method. A discussion of the likely implications and usefulness of the dual approach to truss design is given with comments upon its possible modes of practical use.     

Optimal compliance criterion for axisymmetric solid plates

The problem of minimum compliance of solid plates is formulated in statical terms. It is shown that a previously derived optimality condition is merely a stationary condition. Additional necessary conditions for optimality that distinguish local minima from local maxima are derived from the second variation on the compliance. Although designs which are local minima may exist, it is shown that an absolute minimum does not. An example is presented for which both a local minimum and a local maximum are obtained.     

以孔边绝对值最大的切向应力最小为优化准则的孔洞形状优化

提出了一个新的孔形优化准则－－孔边绝对值最大的切向应力最小，并给出了了基于这种优化准则寻找最优孔形的方法，在所得的孔洞周边，应力集中程度最小。     

Removing of vortices in incompressible flows by distributed controls

We consider an optimal control problem of fluids flow. The fluid motion is governed by the incompressible time-dependent Navier-Stokes equations. A new optimal control formulation for the reduction and possibly extinction of vortices is proposed. A cost functional based on a local dynamical systems characterization of vortices is investigated. The resulting functional is a non-convex function of the velocity gradient tensor. The optimality system describing first order necessary optimality conditions is derived. The gradient and the second derivative of the cost functional with respect to the distributed control are established.     

Optimal shape of an elastic column on elastic foundation

By using Pontryagin's maximum principle we determine the shape of an elastic compressed column on elastic, Winkler type foundation. We assume that the column has clamped ends. The optimality conditions for the case of bimodal optimization are derived. It is shown that the optimal cross-sectional area function is determined from the solution of a nonlinear boundary value problem. In the special case of a compressed column with no foundation, the optimality condition and the solution obtained earlier are recovered.     

Dynamical systems‐based optimal control of incompressible fluids

For optimal control problems related to fluid flow the choice of an adequate cost functional for suppression of vortices is of significant importance. In this research we propose a cost functional based on a local dynamical systems characterization of vortices. The resulting functional is a non‐convex function of the velocity gradient tensor. The resulting optimality system describing first order necessary optimality conditions is derived, a possible strategy for numerical realization of the optimal control problem is provided and a numerical feasibility study is conducted. Copyright © 2004 John Wiley & Sons, Ltd.     

Optimization of body shape at small reynolds numbers

The problem of the optimization of the shape of a body in a stream of viscous liquid or gas was treated in [1–5]. The necessary conditions for a body to offer minimum resistance to the flow of a viscous gas past it were derived in [1], The necessary optimality conditions when the motion of the fluid is described by the approximate Stokes equations were derived in [2], The shape of a body of minimum resistance was found numerically in [3] in the Stokes approximation. The optimality conditions when the motion of the fluid is described by the Navier—Stokes equations were derived in [4, 5], and in [4] these conditions were extended to the case of a fluid whose motion is described in the boundary-layer approximation. The necessary optimality conditions when the motion of the fluid is described by the approximate Oseen equations were derived in [5] and an asymptotic analysis of the behavior of the optimum shape near the critical points was performed for arbitrary Reynolds numbers.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 1, pp, 87–93, January–February, 1978.     

Optimality Conditions for Mass Design Problems and Applications to Thin Plates

We derive necessary and sufficient optimality conditions for a quite large class of structural design problems which can be formulated as follows: under a given load and a total volume constraint, minimize a suitable notion of compliance among all admissible mass distributions, represented by positive measures with prescribed integral mean. As a special case, we focus attention on the optimization of thin plates; we detail the corresponding optimality conditions and we show how they can be handled in order to determine analytically some optimal plates.     

New Type of Optimal Topologies by Iterative Method

ABSTRACT

Optimal design with thousands of variables is a great challenge in engineering calculations. In this paper beside the short history of optimality criteria methods, a solution technique is introduced for the topology optimization of elastic disks under single parametric static loading. Different boundary conditions and thousands of design variables are applied. Due to a simple mesh construction technique, the checker-board pattern is avoided. The Michell-type problem is investigated minimizing the weight of the structure subjected to a compliance condition. The numerical procedure is based on an iterative formula that is formed by the use of the first-order optimality condition of the Lagrangian function. The application is illustrated by numerical examples. The effect of the different loading conditions is studied for the Michell-type topologies as well.     

Three-phase plane composites of minimal elastic stress energy: High-porosity structures

The paper establishes exact lower bound on the effective elastic energy of two-dimensional, three-material composite subjected to the homogeneous, anisotropic stress. It is assumed that the materials are mixed with given volume fractions and that one of the phases is degenerated to void, i.e., the effective composite is porous. Explicit formula for the energy bound is obtained using the translation method enhanced with additional inequality expressing certain property of stresses. Sufficient optimality conditions of the energy bound are used to set the requirements which have to be met by the stress fields in each phase of optimal effective material regardless of the complexity of its microstructural geometry. We show that these requirements are fulfilled in a special class of microgeometries, so-called laminates of a rank. Their optimality is elaborated in detail for structures with significant amount of void, also referred to as high-porosity structures. It is shown that geometrical parameters of optimal multi-rank, high-porosity laminates are different in various ranges of volume fractions and anisotropy level of external stress. Non-laminate, three-phase microstructures introduced by other authors and their optimality in high-porosity regions is also discussed by means of the sufficient conditions technique. Conjectures regarding low-porosity regions are presented, but full treatment of this issue is postponed to a separate publication. The corresponding “G-closure problem” of a three-phase isotropic composite is also addressed and exact bounds on effective isotropic properties are explicitly determined in these regions where the stress energy bound is optimal.     

Optimal material orientation of linear and non-linear elastic 3D anisotropic materials

Optimal material orientation problems of linear and non-linear elastic three-dimensional anisotropic materials are studied. Most commonly, the energy based formulation is applied for solving orientational design problems of anisotropic materials, considering elastic energy density as a measure of the stress strain state. The same approach is used in the current study, but the strength criteria based approaches are also discussed. A simple relation between the stationary conditions in terms of Euler angles and the optimality conditions in terms of strains is pointed out. The complexity analysis of the different existing optimality conditions has been performed. The solution of the posed optimization problem is decomposed into the strain level solution, search for global extremes and evaluation of Euler angles (parameters). The results obtained are extended to some nonlinear elastic material models.     

KUHN-TUCKER CONDITION AND WOLFE DUALITY OF PREINVEX SET-VALUED OPTIMIZATION

The optimality Kuhn-Tucker condition and the wolfe duality for the prein-vex set-valued optimization are investigated. Firstly, the concepts of alpha-order G-invex set and the alpha-order S-preinvex set-valued function were introduced, from which the properties of the corresponding contingent cone and the alpha-order contingent derivative were studied. Finally, the optimality Kuhn-Tucker condition and the Wolfe duality theorem for the alpha-order S-preinvex set-valued optimization were presented with the help of the alpha-order contingent derivative.     

NUMERICAL SOLUTIONS OF OPTIMAL CONTROL FOR THERMALLY CONVECTIVE FLOWS

We study the numerical solution of optimal control problems associated with two-dimensional viscous incompressible thermally convective flows. Although the techniques apply to more general settings, the presentation is confined to the objectives of minimizing the vorticity in the steady state case and tracking the velocity field in the non-stationary case with boundary temperature controls. In the steady state case we develop a systematic way to use the Lagrange multiplier rules to derive an optimality system of equations from which an optimal solution can be computed; finite element methods are used to find approximate solutions for the optimality system of equations. In the time-dependent case a piecewise-in-time optimal control approach is proposed and the fully discrete approximation algorithm for solving the piecewise optimal control problem is defined. Numerical results are presented for both the steady state and time-dependent optimal control problems. © 1997 John Wiley & Sons, Ltd.     

On Optimal Bang-Bang Control

We consider the problem of optimal control in a class of bang-bang functions. A method for the construction of a special auxiliary system is proposed. Using this method, we formulate optimality conditions for the system considered.