Simulated annealing and greedy search for multi-objective optimisation

Copyright © 2009 University of ExeterSimulated annealing generalises greedy or elitist search methods by permitting states which are not an improvement over previous solutions, and for single-objective problems these exploratory moves permit escape from local minima. We examine two classes of multi-objective simulated annealing algorithm: those in which a single solution comprises the state and those in which a set of mutually non-dominating solutions form the state. We compare ways of determining the `energy' of the state in simulated annealing, including the dominated volume and we relate the greedy versions of these annealers (zero computational temperature) to well-established multi-objective optimisation algorithms. Empirical tests on the DTLZ test problems show that (a) a single solution state is often more efficient than a set-based state; and (b) that exploratory algorithms are out-performed by their greedy counterparts. These results lead to an examination of the role of local fronts. Problems for which the Pareto front cannot be located via a sequence of infinitesimal perturbations are defined to be noninfinitesimally greedy searchable. We present examples of non-infinitesimally greedy searchable test problems, which are nonetheless searchable using finite perturbations, but which may be adjusted to be arbitrarily hard even with large finite perturbations.Department of Computer Science, University of Exete

Dominance Measures for Multi-Objective Simulated Annealing

Copyright © 2004 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Simulated annealing (SA) is a provably convergent optimiser for single-objective (SO) problems. Previously proposed MO extensions have mostly taken the form of an SO SA optimising a composite function of the objectives. We propose an MO SA utilising the relative dominance of a solution as the system energy for optimisation, eliminating problems associated with composite objective functions. We also propose a method for choosing perturbation scalings promoting search both towards and across the Pareto front.We illustrate the SA's performance on standard test problems. The new SA is shown to promote rapid convergence to the true Pareto front with a good coverage of points across it

Drift Lithology in Relation to Bedrock Geology, Long Island Lake Quadrangle, Cook County, Minnesota

A Thesis submitted to the faculty of the Graduate School of the University of Minnesota by Curtis I. Everson in partial fulfillment of the requirements for the degree of Master of Science, June 1977. Plate 1 referenced in the thesis is also attached to this record, along with the Explanation for Plate 1.Lithologic studies in northeastern Minnesota suggest that drift prospecting is a useful tool for mapping drift-covered bedrock. A detailed study of till clasts composition in the Long Island Lake Quadrangle revealed a significant relationship between drift lithology and bedrock geology. The Long Island Lake Quadrangle is a suitable area for this study for the following reasons: (1) outcrops are numerous enough to have allowed the construction of a detailed geologic map; (2) the area contains eight distinctive rock units; (3) the local bedrock experienced glacial erosion, indicated by the existence of glacially abraded and quarried outcrops. The distribution of glacial sediments, mainly till and outwash, were mapped and one hundred and one samples of drift were collected along traverses parallel to ice flow (perpendicular to strike of the bedrock). Both till and outwash contain a large quantity of local bedrock clasts in the size ranges greater than 1mm in diameter. Clasts smaller than 1mm are mainly minerals, and therefore not so diagnostic of local bedrock. As a test, boulders greater than 1 meter in diameter were used in the field for inferring bedrock contacts. These contacts were found to be within 60 meters (200 ft.) of contacts placed by outcrop mapping. Lack of local bedrock clasts in the smaller size fractions indicate either high resistance of local bedrock to crushing, or lack of opportunity for crushing because of short residence time in the glacial system (short distance transport). In either case, the fine-grained fraction therefore represents a contribution to the glacial load from more distant sources and the coarse-grained fraction represents a contribution form local sources

SRB Environment Evaluation and Analysis. Volume 3: ASRB Plume Induced Environments

Contract NAS8-37891 was expanded in late 1989 to initiate analysis of Shuttle plume induced environments as a result of the substitution of the Advanced Solid Rocket Booster (ASRB) for the Redesigned Solid Rocket Booster (RSRB). To support this analysis, REMTECH became involved in subscale and full-scale solid rocket motor test programs which further expanded the scope of work. Later contract modifications included additional tasks to produce initial design cycle environments and to specify development flight instrumentation. Volume 3 of the final report describes these analyses and contains a summary of reports resulting from various studies

Dominance-Based Multiobjective Simulated Annealing

Copyright © 2008 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Simulated annealing is a provably convergent optimizer for single-objective problems. Previously proposed multiobjective extensions have mostly taken the form of a single-objective simulated annealer optimizing a composite function of the objectives. We propose a multiobjective simulated annealer utilizing the relative dominance of a solution as the system energy for optimization, eliminating problems associated with composite objective functions. We also propose a method for choosing perturbation scalings promoting search both towards and across the Pareto front. We illustrate the simulated annealer's performance on a suite of standard test problems and provide comparisons with another multiobjective simulated annealer and the NSGA-II genetic algorithm. The new simulated annealer is shown to promote rapid convergence to the true Pareto front with a good coverage of solutions across it comparing favorably with the other algorithms. An application of the simulated annealer to an industrial problem, the optimization of a code-division-multiple access (CDMA) mobile telecommunications network's air interface, is presented and the simulated annealer is shown to generate nondominated solutions with an even and dense coverage that outperforms single objective genetic algorithm optimizers

A preliminary investigation of the water use efficiency of sweet sorghum for biofuel in South Africa

Sweet sorghum (Sorghum bicolor (L.) Moench) has been recognized globally as a potential biofuel crop for ethanol production. Sweet sorghum is a drought-tolerant crop that is widely adapted to different environmental growing conditions. The aim of this study was to determine the water use efficiency (utilisable yield per unit amount of water used) of drip-irrigated sweet sorghum (variety Sugargraze) under two different climatic conditions in South Africa. The sweet sorghum trials were conducted at Ukulinga research farm (University of KwaZulu-Natal, Pietermaritzburg) and Hatfield experimental farm (University of Pretoria, Pretoria), South Africa. Field trials were conducted in two successive seasons, viz., 2010/11 and 2011/12. Seasonal water use was estimated using eddy covariance and surface renewal methods. Fresh and dry aboveground biomass yield, stalk yield and stalk Brix % were measured at final harvest. Theoretical ethanol yield was calculated from fresh stalk yield and Brix %. Water use for the two growing seasons was 415 mm at Ukulinga and 398 mm at Hatfield. The ethanol water use efficiency (WUE) values for the sweet sorghum at Ukulinga were 0.27 and 0.60 L∙m-3 for 2010/11 and 2011/12 growing seasons, respectively. The ethanol WUE estimate of the sweet sorghum at Hatfield was 0.53 L∙m-3 for the 2010/11 season and 0.70 L∙m-3 for the 2011/12 growing season. WUE estimates of the sweet sorghum crop were higher for Hatfield compared to Ukulinga research farm. The results from this study showed that the WUE of sweet sorghum was sensitive to plant density. The WUE values confirm that sweet sorghum has high WUE under different climatic conditions.Keywords: water use efficiency; ethanol yield; biofuel crop; plant density, sweet sorghum, South Afric

Setting a precautionary catch limit for Antarctic krill

A revised precautionary catch limit for Antarctic krill (Euphausia superba) in the Scotia Sea of 4 million tons was recently adopted by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). The limit was based on a total biomass of 44.3 million tons, as estimated from an acoustic and net survey of krill across the Scotia Sea sector of the Southern Ocean, and a harvest rate of 9.1%, as determined from an analysis of the risks of exceeding defined conservation criteria. We caution, however, that before the fishery can expand to the 4-inillion-ton level it will be necessary to establish mechanisms to avoid concentration of fishing effort, particularly in proximity to colonies of land-breeding krill predators, and to consider the effects of krill immigrating into the region from multiple sources

Anomalous asymmetry of magnetoresistance in NbSe3_3 single crystals

A pronounced asymmetry of magnetoresistance with respect to the magnetic field direction is observed for NbSe$_3$ crystals placed in a magnetic field perpendicular to their conducting planes. It is shown that the effect persists in a wide temperature range and manifests itself starting from a certain magnetic induction value $B_0$, which at $T=4.2$ K corresponds to the transition to the quantum limit, i.to the state where the Landay level splitting exceeds the temperature.Comment: 4 pages, 6 figures, to be appeared in JETP Let