Test and computational results for the ISS's GPS antenna inducate that the truss structures do not have a significant effect on the upper-hemisphere portion of the GPS antenna patterns; truss structures instead af...
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Test and computational results for the ISS's GPS antenna inducate that the truss structures do not have a significant effect on the upper-hemisphere portion of the GPS antenna patterns; truss structures instead affect GPS lower-hemisphere portion patterns. The GPS antenna's choke-ring, which is designed to minimize multipath effects at low elevation angles, may reduce the signal interference from the truss structures. (AIAA)
In this work we analyse the fed-batch operation of a biochemical reactor. In the first part of the work we consider a repeated fed-batch operation. The reaction is assumed to follow Haldane kinetics, i.e. it is charac...
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In this work we analyse the fed-batch operation of a biochemical reactor. In the first part of the work we consider a repeated fed-batch operation. The reaction is assumed to follow Haldane kinetics, i.e. it is characterised by substrate inhibition. The feed rate of the substrate is chosen as the control variable. The entire duration of the operation is divided into different subintervals. We optimise the system performance by approximating the feed flow rate using (i) discrete pulses, (ii) a constant flow rate over different sub-intervals. In the first strategy the equations lend themselves to an analytical solution. For the second case we use a shooting method coupled with a sequential quadratic programming technique to obtain the constant flow rates in the different sub-intervals. This has been analysed for two scenarios: (i) equal duration of sub-intervals and (ii) unequal duration of sub-intervals. The objective here is to maximise the biomass production over one cycle. The effect of converting a non-linear constraint to a linear constraint by reformulating the problem on the numerical convergence has also been investigated. In the second part of this work we have extended our method to investigate a non-repeated fed-batch reactor operation. Here the objective is to maximise the product formed. (C) 1997 Elsevier Science Ltd.
In this paper we develop new Newton and conjugate gradient algorithms on the Grassmann and Stiefel manifolds. These manifolds represent the constraints that arise in such areas as the symmetric eigenvalue problem, non...
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In this paper we develop new Newton and conjugate gradient algorithms on the Grassmann and Stiefel manifolds. These manifolds represent the constraints that arise in such areas as the symmetric eigenvalue problem, nonlinear eigenvalue problems, electronic structures computations, and signal processing. In addition to the new algorithms, we show how the geometrical framework gives penetrating new insights allowing us to create, understand, and compare algorithms. The theory proposed here provides a taxonomy for numerical linear algebra algorithms that provide a top level mathematical view of previously unrelated algorithms. It is our hope that developers of new algorithms and perturbation theories will benefit from the theory, methods, and examples in this paper.
In this paper we describe a new version of a sequential equality constrained quadraticprogramming method for general nonlinear programs with mixed equality and inequality constraints. Compared with an older version [...
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In this paper we describe a new version of a sequential equality constrained quadraticprogramming method for general nonlinear programs with mixed equality and inequality constraints. Compared with an older version [P. Spellucci, Han's method without solving QP, in: A. Auslender, W. Oettli, J. Steer (Eds), Optimization and Optimal Control, Lecture Notes in Control and Information Sciences, vol. 30, Springer, Berlin, 1981, pp. 123-141.] it is much simpler to implement and allows any kind of changes of the working set in every step. Our method relies on a strong regularity condition. As far as it is applicable the new approach is superior to conventional SOP-methods, as demonstrated by extensive numerical tests. (C) 1998 The Mathematical programming Society, Inc. Published by Elsevier Science B.V.
Camera system calibration and related problems are considered as least squares parameter estimation problems based on error-in-variables regression models. The interrelationship between different methods for solving t...
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ISBN:
(纸本)0819431125
Camera system calibration and related problems are considered as least squares parameter estimation problems based on error-in-variables regression models. The interrelationship between different methods for solving these problems is investigated. In addition, the origin and interrelationship of some approximate methods is also discussed.
The physical problem considered in this paper is that of a non-linear elastic body being indented by a rigid punch. The treatment is based on finite element discretization and sequential quadratic programming (SQP). T...
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The physical problem considered in this paper is that of a non-linear elastic body being indented by a rigid punch. The treatment is based on finite element discretization and sequential quadratic programming (SQP). The finite element formulation is obtained through a variational formulation, which generalizes to frictionless contact a three-field principle which involves deformation, volume strain and hydrostatic pressure as independent fields. We compare an incremental load method and a method where the indentation for the final load is sought directly. Crucial for the second method is the use of a line search with respect to a merit function which measures the infeasibility in the optimality criteria for the problem;this line search also includes a check of the orientation-preserving condition of a positive determinant of the deformation gradient. Each iteration within an SQP method requires the solution of a quadraticprogramming (QP) subproblem, and four different methods for the solution of these subproblems are compared. The performance of the overall procedure is also compared to that of a commercially available system. Test examples ranging from 23 to 770 displacement degrees of freedom are treated. The computational results show that the proposed solution concept is feasible and efficient. Furthermore, it can be applied to general non-linear elastic contact problems, since it does not include any ad hoc rules.
This paper discusses a strategy for performing aerodynamic single-point and multipoint optimization studies. The approach uses a combination of three methods: an Euler computational fluid dynamics (CFD) code that prov...
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This paper discusses a strategy for performing aerodynamic single-point and multipoint optimization studies. The approach uses a combination of three methods: an Euler computational fluid dynamics (CFD) code that provides accurate information at one chosen point in the design space, a linear approximation method of the quasianalytic type that rapidly evaluates data at many design points, and a function-fitting algorithm that maps aerodynamic and geometric data across the whole design space. As the method proceeds, a good quality database of aerodynamic and geometric quantities is rapidly constructed at a fraction of the cost of using conventional methods. The availability of this database and the analytic representation of the quantities over the whole design space permits optimizations to be performed using constraints on specific aerodynamic parameters, e.g,, maximum surface Mach number and pressure gradients, over chosen regions of the aerofoil, The approach is also highly flexible, enabling optimization problems of increasing complexity to be built up quickly, and is easily integrated within modern engineering methods. Results are presented for a typical transonic aerofoil giving comparisons with individual CFD analyses.
The feasibility of using the solar electric propulsion (SEP) for a Mercury mission is investigated by computing the optimal orbit transfer that maximize the spacecraft payload mass at Mercury rendezvous. The proposed ...
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The feasibility of using the solar electric propulsion (SEP) for a Mercury mission is investigated by computing the optimal orbit transfer that maximize the spacecraft payload mass at Mercury rendezvous. The proposed Mercury rendezvous is a Discovery-class mission that utilizes Delta and Med-lite launch vehicles for injection into heliocentric space. The EP system consists of 30-cm ion thrusters are similar to the proposed thrusters for the first New Millennium mission. The orbital transfer is governed by two-body dynamics, and gravity assist from Venus is included to reduce further the orbital energy enroute to the Mercury rendezvous. Numerical results are presented for maximum payload trajectories.
The paper is dedicated to the problem of planning and management of water resources systems. The tasks are formulated as time-discrete dynamic optimal control problem and transformed to a large-scale structured nonlin...
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The paper is dedicated to the problem of planning and management of water resources systems. The tasks are formulated as time-discrete dynamic optimal control problem and transformed to a large-scale structured nonlinear optimisation problem with sparse data structures. The solving procedure is an SQP-type algorithm. Two different hydrological scenarios were investigated applying the proposed approach and compared with an existing reservoir management plan. The simulative management in an extraordinary situation was also performed.
An error is pointed out in the local convergence proof in the quoted paper [J. L. Zhou and A. L. Tits, SIAM J. Optim., 6 (1996), pp. 461--487]. A correct proof is given.
An error is pointed out in the local convergence proof in the quoted paper [J. L. Zhou and A. L. Tits, SIAM J. Optim., 6 (1996), pp. 461--487]. A correct proof is given.
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