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Programming Algorithms (programming + algorithms)

Distribution by Scientific Domains
Engineering50%

Selected Abstracts

On the convergence of stationary sequences in topology optimization

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2005
Anton Evgrafov
Abstract We consider structural topology optimization problems including unilateral constraints arising from non-penetration conditions in contact mechanics. The resulting non-convex non-smooth problems are instances of mathematical programs with equilibrium constraints (MPEC), or bi-level programs. Applying nested (implicit programming) algorithms to this class of problems is problematic owing to the singularity of the feasible set. We propose a perturbation strategy combining the relaxation of the equilibrium constraint with the restriction of the design domain to its regular part only. This strategy allows us to attack the problem numerically using standard non-linear programming algorithms. We rigorously study the optimality conditions for the original singular problem as well as the convergence of stationary points and globally optimal solutions to approximating problems towards respective stationary points and globally optimal solutions to the original problem. A limited numerical benchmarking of the algorithm is performed. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A nonlinear minimization approach to multiobjective and structured controls for discrete-time systems

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 16 2004
Kwan Ho Lee
Abstract In this paper, a nonlinear minimization approach is proposed for multiobjective and structured controls for discrete-time systems. The problem of finding multiobjective and structured controls for discrete-time systems is represented as a quadratic matrix inequality problem. It is shown that the problem is reduced to a nonlinear minimization problem that has a concave objective function and linear matrix inequality constraints. An algorithm for the nonlinear minimization problem is proposed, which is easily implemented with existing semidefinite programming algorithms. The validity of the proposed algorithm is illustrated by comparisons with existing methods. In addition, applications of this work are demonstrated via numerical examples. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Credit cards scoring with quadratic utility functions

JOURNAL OF MULTI CRITERIA DECISION ANALYSIS, Issue 4-5 2002
Vladimir Bugera
Abstract The paper considers a general approach for classifying objects using mathematical programming algorithms. The approach is based on optimizing a utility function, which is quadratic in indicator parameters and is linear in control parameters (which need to be identified). Qualitative characteristics of the utility function, such as monotonicity in some variables, are included using additional constraints. The methodology was tested with a ,credit cards scoring' problem. Credit scoring is a way of separating specific subgroups in a population of objects (such as applications for credit), which have significantly different credit risk characteristics. A new feature of our approach is incorporating expert judgments in the model. For instance, the following preference was included with an additional constraint: ,give more preference to customers with higher incomes.' Numerical experiments showed that including constraints based on expert judgments improves the performance of the algorithm. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Implantable Cardioverter-Defibrillator Shock: Appropriate or Inappropriate?

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2010
F.R.C.P.C., Michael A. Nault M.D.
A 76-year-old female with a single chamber implantable cardioverter-defibrillator implanted for secondary prevention was referred due to multiple discharges. The device was programmed for ventricular tachycardia (VT) detection at 400 ms, fast VT detection at 280 ms, and ventricular fibrillation detection at 320 ms. Antitachycardia pacing (ATP) during charge was enabled. Interrogation revealed a VT episode with a mean cycle length of 270 ms, which was successfully terminated with ATP during charge. Seconds later, the device delivered a shock. This case illustrates the importance of understanding programming algorithms as part of troubleshooting when facing a scenario of device discharge. Ann Noninvasive Electrocardiol 2010;15(2):181,183 [source]