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Generation Approach (generation + approach)

Distribution by Scientific Domains
Business, Economics, Finance and Accounting42%
Polymers and Materials Science28%

Selected Abstracts

Stochastic unit commitment problem

INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 1 2004
Takayuki Shiina
Abstract The electric power industry is undergoing restructuring and deregulation. We need to incorporate the uncertainty of electric power demand or power generators into the unit commitment problem. The unit commitment problem is to determine the schedule of power generating units and the generating level of each unit. The objective is to minimize the operational cost which is given by the sum of the fuel cost and the start-up cost. In this paper we propose a new algorithm for the stochastic unit commitment problem which is based on column generation approach. The algorithm continues adding schedules from the dual solution of the restricted linear master program until the algorithm cannot generate new schedules. The schedule generation problem is solved by the calculation of dynamic programming on the scenario tree. [source]

State space sampling of feasible motions for high-performance mobile robot navigation in complex environments

JOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 6-7 2008
Thomas M. Howard
Sampling in the space of controls or actions is a well-established method for ensuring feasible local motion plans. However, as mobile robots advance in performance and competence in complex environments, this classical motion-planning technique ceases to be effective. When environmental constraints severely limit the space of acceptable motions or when global motion planning expresses strong preferences, a state space sampling strategy is more effective. Although this has been evident for some time, the practical question is how to achieve it while also satisfying the severe constraints of vehicle dynamic feasibility. The paper presents an effective algorithm for state space sampling utilizing a model-based trajectory generation approach. This method enables high-speed navigation in highly constrained and/or partially known environments such as trails, roadways, and dense off-road obstacle fields. © 2008 Wiley Periodicals, Inc. [source]

Pressure-Assisted Spinning: A Versatile and Economical, Direct Fibre to Scaffold Spinning Methodology

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2007
Sumathy Arumuganathar
Abstract Spinning composite polymer fibres by means of electric fields has been investigated for well over a century. These spun fibres have been explored across many areas of research, spanning the physical to the life sciences; however, electrospinning has the hazardous nature of the high voltage at the spinning needle. We demonstrate here a competing direct fibre to scaffold preparation method, completely determined by an applied pressure. Our technique reported here removes the hazardous high-voltage element from the fibre/scaffold formation technique and has the ability to form uniaxial fibres and scaffolds comparable to those fabricated by electrospinning. We refer to this fibre generation approach as "pressure-assisted spinning (PAS)", which will have a tremendous impact in a range of applications, spanning the physical through to the life sciences. PAS joins the techniques for fibre to scaffold generation with a view to significantly and globally contributing to the micro- and nanosciences. [source]

A column generation approach for SONET ring assignment

NETWORKS: AN INTERNATIONAL JOURNAL, Issue 3 2006
Elder M. Macambira
Abstract In this article we consider the SONET ring assignment problem (SRAP) presented in 7. The authors pointed out the inadequacy of solving SRAP instances using their integer programming formulation and commercial linear programming solvers. Similar experiences with IP models for SRAP are reported in 1. In this article we reformulate SRAP as a set partitioning model with an additional knapsack constraint. This new formulation has an exponential number of columns and, to solve it, we implemented a branch-and-price/column generation algorithm. Extensive computational experiments showed that the new algorithm is orders of magnitude faster than standard branch-and-bound codes running on compact IP models introduced earlier. Instances taken from 1, 7, which could not be solved there in hours of computation were solved here to optimality in just a few seconds. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 47(3), 157,171 2006 [source]

Structural, thermal, micromechanical and electrical study of polyimide composite thin films incorporating indium tin oxide

POLYMER INTERNATIONAL, Issue 9 2010
Anand Kumar Gupta
Abstract Studies of composite films incorporating inorganic materials are of immense importance for current technological applications. Polyimide (PI) composite thin films incorporating indium tin oxide (ITO) at various weight ratios were processed using an in situ generation approach. The resultant product was imidized up to 350 °C to test the ability of the material to endure high temperatures without affecting the host matrix. The morphological behaviour of the PI/ITO composite films was investigated using Fourier transform infrared, scanning electron microscopy and atomic force microscopy characterization techniques. The degrees of crystallinity and ITO particle size within the PI matrix were studied using X-ray diffraction. The thermal, structural and electrical properties were analysed using thermogravimetric analysis, differential scanning calorimetry, UV-visible spectroscopy and the four-probe technique. The micromechanical properties of the composites were evaluated in terms of tensile strength, tensile modulus and elongation. An overall improvement in the properties of the composite films was observed in comparison to those of pure PI. The synergistic improvement in the composite films is associated with the interaction mechanism between ITO and PI, where ITO becomes dispersed and interacts within the PI matrix. This leads to a decrease in available free-space volume and increases the surface enrichment providing reinforcement to the matrix. Copyright © 2010 Society of Chemical Industry [source]

THE ECONOMICS OF FISCAL DECENTRALIZATION

JOURNAL OF ECONOMIC SURVEYS, Issue 4 2010
Duc Hong Vo
Abstract There is no complete overview or discussion of the literature of the economics of federalism and fiscal decentralization, even though scholarly interest in the topic has been increasing significantly over recent years. This paper provides a general, brief but comprehensive overview of the main insights from the literature on fiscal federalism and decentralization. In doing so, literature on fiscal federalism and decentralization is grouped into two main approaches: ,first generation approach' and ,an emerging second generation approach'. The discussion generally covers the two notions of fiscal decentralization: ,fiscal autonomy' and ,fiscal importance' of subnational governments as the background of the most recently developed index of fiscal decentralization in Vo. The relevance of this discussion to any further development of a fiscal decentralization index is briefly noted. [source]