Search

Vector quantization is known widely as a highly efficient coding for image and speech signals. The algorithm proposed by Linde, Buzo, and Gray (the LBG algorithm) is the most fundamental design procedure for this kind of quantizer. However, the LBG algorithm usually gives only the local minimum of the distortion measure based on the quantization error. With such a background, this paper introduces the simulated annealing procedure into the design of the vector quantizer based on the LBG algorithm, which is known as the effective method for the NP-complete probabilistic combinational optimization problem. The widely employed mean-square error is adopted as the distortion measure. Various approaches are considered to derive the global minimum of the measure. In other words, this paper is based on the LBG algorithm and presents a design procedure for the vector quantizer (more generally, the vector quantizer considering the channel error) by introducing simulated annealing. By this approach, a vector quantizer with a better performance than the traditional design as well as a more ideal highly efficient coding is realized. A simulated experiment is executed for the standard image data (SIDBA), and it is demonstrated that the simulated annealing is useful in the design of the vector quantizer. [ABSTRACT FROM AUTHOR]

This paper points out that meta-heuristics should have not only robustness and adaptability to problems with different structure but also adjustability of parameters included in their algorithms. Particle swarm optimization (PSO), whose concept began as a simulation of a simplified social milieu, is known as one of the most powerful optimization methods for solving nonconvex continuous optimization problems. Then, in order to improve adjustability, a new parameter is introduced into PSO on the basis of the proximate optimality principle (POP). In this paper, we propose adaptive PSO and the effectiveness and the feasibility of the proposed approach are demonstrated on simulations using some typical nonconvex optimization problems. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(3): 41–49, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20077 [ABSTRACT FROM AUTHOR]

SUMMARY Structural identification based on analysis of vibration signals is usually formulated as an optimization problem. Nevertheless, identifying a structural system as a whole often involves a great number of unknowns and degrees of freedom, resulting in considerable convergence difficulty and expensive evaluation of objective function. To handle these issues, this paper aims to propose a frequency domain substructural identification method applicable to arbitrary excitations. This is done by introducing the exponential window method in the formulation so that the effect caused by initial condition is alleviated without using zero padding. The proposed identification method is verified through both numerical and experimental studies. It is shown that significant reduction in computer time can be achieved in addition to remarkable identification accuracy. The experimental study also indicates that the proposed strategy is effective in identifying small structural changes. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this paper, we study an algorithm (which we call the support reduction algorithm) that can be used to compute non-parametric M-estimators in mixture models. The algorithm is compared with natural competitors in the context of convex regression and the ‘Aspect problem’ in quantum physics. [ABSTRACT FROM AUTHOR]

This paper presents a modification of the tabu search called gradient tabu search (GTS). It uses analytical gradients for a fast minimization to the next local minimum and analytical diagonal elements of the Hessian to escape local minima. For an efficient blocking of already visited areas tabu regions and tabu directions are introduced into the tabu list (TL). Trials with various well-known test functions indicate that the GTS is a very promising approach to determine local and global minima of differentiable functions. Possible application areas could be optimization routines for force field parameters or conformational searches for large molecules. © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 601–611, 2007 [ABSTRACT FROM AUTHOR]

We derive a formula for the minimal initial wealth needed to hedge an arbitrary contingent claim in a continuous-time model with proportional transaction costs; the expression obtained can be interpreted as the supremum of expected discounted values of the claim, over all (pairs of) probability measures under which the "wealth process" is a supermartingale. Next, we prove the existence of an optimal solution to the portfolio optimization problem of maximizing utility from terminal wealth in the same model; we also characterize this solution via a transformation to a hedging problem: the optimal portfolio is the one that hedges the inverse of marginal utility evaluated at the shadow state-price density solving the corresponding dual problem, if such exists. We can then use the optimal shadow state-price density for pricing contingent claims in this market. The mathematical tools are those of continuous-time martingales, convex analysis, functional analysis, and duality theory. [ABSTRACT FROM AUTHOR]

The paper presents an analytical description of a state-dependent assignment policy, where different assignments of attributes to objects are employed under different states. Various considerations, other than optimizing an objective function, present themselves for such cases—for example, the existence of groups of assignees with certain levels of intragroup assignment uniformity, the stability of the policy over states, the presence of a revealed preference ordering of the assignments, and others. An approach towards a quantitative treatment of such features of a state-dependent assignment policy is discussed, and in particular a uniformity measure is defined and its properties are investigated. Potential uses of the model are suggested for urban emergency services, questionnaire analysis, task allocation, medical diagnosis, and dynamic computer program behavior. Three implementations for questionnaire analysis are reported. [ABSTRACT FROM AUTHOR]

Computing the charge density on the surfaces of conductors is fundamental to many electrostatic applications. Difficulties arise in two-dimensional simulation due to the O(log||r||) potential. Fully understanding the 2D potential problem, and reasonably connecting the mathematical formulation with physical interpretation, are key to handling this difficulty properly. In the absence of these factors it is easy for one to propose an ill-posed problem. In this paper, a complete investigation of potential theory, from 3D to 2D, is made for computing charge density on the surfaces of conductors. Various integral formulations are derived - these are applicable in different situations. It is shown that, in general, the electrostatic potential need not be finite valued at infinity for 2D problems. Numerical examples for the 2D case are constructed to show that the formulations are consistent. Criteria for choosing the most appropriate formulation for a given problem are suggested. [ABSTRACT FROM AUTHOR]

Explains that this special issue of "Numerical Linear Algebra with Applications" is devoted to the 2002 International Conference on "Preconditioning Methods for Optimal Control and Constrained Optimization Problems" held on October 23-25, 2002 in Netherlands. Goal of addressing complex issues related to preconditioning methods for constrained optimization and optimal control.

We propose a novel surface remeshing algorithm. While many remeshing algorithms are based on global parametrization or local mesh optimization, our algorithm is closely related to surface reconstruction techniques and it requires no explicit parameterization. Our approach is based on the advancing-front paradigm, and it can be used to both incrementally remesh the complete surface, or simply to remesh a portion of it with a high-quality mesh. It is accurate, fast, robust, and suitable for use with interactive mesh processing applications that require local remeshing. We show a number of applications, including matching the resolution of meshes when doing Boolean operations such as unions and intersections. We also show how to adapt the algorithm to blend and merge mixed-mode objects — for example, to compute the union of a point-set surface and a triangle mesh. [ABSTRACT FROM AUTHOR]

We give a corrected proof of an extension of the Robinson Splitting Theorem for the d. c. e. degrees. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We survey some results dealing with well-posedness of scalar optimization problems, with applications to the optimal control of ordinary differential equations under plant perturbations. Then we deal with the definition of a condition number for optimization problems. Corresponding distance theorems are discussed, aiming to generalize the Eckart-Young theorem to the infinite-dimensional setting. [ABSTRACT FROM AUTHOR]

We study the relationship between various properties of the real numbers and weak choice principles. [ABSTRACT FROM AUTHOR]

A major difficulty in practicing constrained nonlinear optimization is that different optimization algorithms are effective for different classes of problems. The search algorithms tested were selected because they seemingly had the capability of solving ill-defined problems. The emphasis of this research was on problems that are realistic and do not necessarily satisfy the classical assumptions of convexity, continuity, unimodality, etc. All algorithms were tested on a variety of problems. A problem was described by three types of attributes: the environmental attributes, the objective function attributes, and the constraint set attributes. The results of the study provide selective logic for choosing an effective search algorithm. [ABSTRACT FROM AUTHOR]

In via-minimization in topological routing on a k-layer, an equivalent transformation of a t-terminal net to a collection of two-terminal nets is considered. An equivalent transformation to a special structure of two-terminal nets, which is called a two-terminal net-body, is presented for the case when available vias are through-hole vias and t ≷ k and for the case when available vias are adjacent-layer vias and t=3. The key issue is the proof that the routings of the t-terminal nets in optimum routing are classified into a few fixed number of cases with respect to the division of the layers and that each net is equivalently replaced with a two-terminal net-body. [ABSTRACT FROM AUTHOR]