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31.
This paper considers a general class of continuous, nonlinear, and nonseparable knapsack problems, special cases of which
arise in numerous operations and financial contexts. We develop important properties of optimal solutions for this problem
class, based on the properties of a closely related class of linear programs. Using these properties, we provide a solution
method that runs in polynomial time in the number of decision variables, while also depending on the time required to solve
a particular one-dimensional optimization problem. Thus, for the many applications in which this one-dimensional function
is reasonably well behaved (e.g., unimodal), the resulting algorithm runs in polynomial time. We next develop a related solution
approach to a class of continuous, nonlinear, and nonseparable multiple-choice knapsack problems. This algorithm runs in polynomial
time in both the number of variables and the number of variants per item, while again dependent on the complexity of the same
one-dimensional optimization problem as for the knapsack problem. Computational testing demonstrates the power of the proposed
algorithms over a commercial global optimization software package. 相似文献
32.
The traditional Generalized Assignment Problem (GAP) seeks an assignment of customers to facilities that minimizes the sum of the assignment costs while respecting the capacity of each facility. We consider a nonlinear GAP where, in addition to the assignment costs, there is a nonlinear cost function associated with each facility whose argument is a linear function of the customers assigned to the facility. We propose a class of greedy algorithms for this problem that extends a family of greedy algorithms for the GAP. The effectiveness of these algorithms is based on our analysis of the continuous relaxation of our problem. We show that there exists an optimal solution to the continuous relaxation with a small number of fractional variables and provide a set of dual multipliers associated with this solution. This set of dual multipliers is then used in the greedy algorithm. We provide conditions under which our greedy algorithm is asymptotically optimal and feasible under a stochastic model of the parameters. 相似文献
33.
R. D. Lipscomb W. H. Sharkey 《Journal of polymer science. Part A, Polymer chemistry》1970,8(8):2187-2196
The thioketo and thioenol tautomers of thioacetone have been separated by gas chromatography and characterized by infrared and NMR spectra at low temperatures. The pure thioketo tautomer polymerizes rapidly at room temperature, but the thioenol tautomer does not. At room temperature, the thioenol gradually disappears, probably by tautomerization to the reactive thioketo form, which then polymerizes. Attempts to copolymerize thioacetone with vinyl and diene monomers were not successful. 相似文献
34.
Dr. W. W. Sharkey 《International Journal of Game Theory》1981,10(2):101-106
A convex game without side payments is defined and discussed. It is shown that such a game is totally balanced. With a second and more restrictive definition of convexity it is shown that the core coincides with the von Neumann-Morgenstern solution. 相似文献
35.
Shankai Zhao Kasi V. Somayajula Andrew G. Sharkey David M. Hercules 《Fresenius' Journal of Analytical Chemistry》1990,338(5):588-592
Summary A simple method for obtaining laser mass spectra (LMS) of liquids is described using a nitrocellulose membrane or fibrous material as the sample substrate. Laser mass spectra of liquids are presented along with those of solutes in aqueous systems. The use of a liquid matrix with the laser soft ionization method enhances molecular ion formation. Results are presented for charge-transfer derivatization and the influence of solution pH on LMS. 相似文献
36.
Gurmit Singh Brian C. Wilson Sheila M. Sharkey George P. Browman Paula Deschamps 《Photochemistry and photobiology》1991,54(2):307-312
A degree of resistance to photodynamic therapy (PDT) has been induced in radiation-induced fibrosarcoma-1 (RIF-1) tumor cells by repeated photodynamic treatment with Photofrin (4 or 18 h incubation) in vitro to the 0.1-1% survival level, followed by regrowth from single surviving colonies. The resistance is shown as increased cell survival in the strain designated RIF-8A, compared to the wild-type RIF-1 cells, when exposed to increasing Photofrin concentration for 18 h incubation and fixed light exposure. No difference was found between RIF-1 and RIF-8A in the uptake of Photofrin per unit cell volume at 18 h incubation. Resistance to PDT was also observed in Chinese hamster ovary-multi-drug resistant (CHO-MDR) cells compared to the wild-type CHO cells, possibly associated with decreased cellular concentration of Photofrin in the former. By contrast, the PDT-resistant RIF-8A cells did not show any cross-resistance to Adriamycin, nor was there any significant drug concentration difference between RIF-1 and RIF-8A. These findings suggest that different mechanisms are responsible for PDT-induced resistance and multi-drug resistance. 相似文献
37.
Sacha J. Pidot Marion Herisse Liam Sharkey Liselle Atkin Jessica L. Porter Torsten Seemann Benjamin P. Howden Mark A. Rizzacasa Timothy P. Stinear 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):4036-4041
The nargenicin family of antibiotics are macrolides containing a rare ether‐bridged cis‐decalin motif. Several of these compounds are highly active against multi‐drug resistant organisms. Despite the identification of the first members of this family almost 40 years ago, the genetic basis for the production of these molecules and the enzyme responsible for formation of the oxa bridge, remain unknown. Here, the 85 kb nargenicin biosynthetic gene cluster was identified from a human pathogenic Nocardia arthritidis isolate and this locus is solely responsible for nargenicin production. Further investigation of this locus revealed a putative iron‐α‐ketoglutarate‐dependent dioxygenase, which was found to be responsible for the formation of the ether bridge from the newly identified deoxygenated precursor, 8,13‐deoxynargenicin. Uncovering the nargenicin biosynthetic locus provides a molecular basis for the rational bioengineering of these interesting antibiotic macrolides. 相似文献
38.
Wilco Van den Heuvel O. Erhun Kundakcioglu Joseph Geunes H. Edwin Romeijn Thomas C. Sharkey Albert P. M. Wagelmans 《Mathematical Programming》2012,134(2):395-424
Emphasis on effective demand management is becoming increasingly recognized as an important factor in operations performance. Operations models that account for supply costs and constraints as well as a supplier’s ability to influence demand characteristics can lead to an improved match between supply and demand. This paper presents a class of optimization models that allow a supplier to select, from a set of potential markets, those markets that provide maximum profit when production/procurement economies of scale exist in the supply process. The resulting optimization problem we study possesses an interesting structure and we show that although the general problem is ${\mathcal{NP}}$ -complete, a number of relevant and practical special cases can be solved in polynomial time. We also provide a computationally very efficient and intuitively attractive heuristic solution procedure that performs extremely well on a large number of test instances. 相似文献
39.
Anna?Maria?Barlow Christian?Rohrbeck Paul?Sharkey Rob?ShooterEmail authorView authors OrcID profile Emma?S.?Simpson 《Extremes》2018,21(3):431-439
This paper concerns our approach to the EVA2017 challenge, the aim of which was to predict extreme precipitation quantiles across several sites in the Netherlands. Our approach uses a Bayesian hierarchical structure, which combines Gamma and generalised Pareto distributions. We impose a spatio-temporal structure in the model parameters via an autoregressive prior. Estimates are obtained using Markov chain Monte Carlo techniques and spatial interpolation. This approach has been successful in the context of the challenge, providing reasonable improvements over the benchmark. 相似文献
40.
Faison B. D. Clark T. M. Lewis S. N. Ma C. Y. Sharkey D. M. Woodward C. A. 《Applied biochemistry and biotechnology》1991,(1):237-251
Paecilomyces sp. TLi, a coal-solubilizing fungus, was shown to degrade organic sulfur-containing coal substructure compounds. Di-benzothiophene
was degraded via a sulfur-oxidizing pathway to 2,2′-dihydroxybiphenyl. No further metabolism of that compound was observed.
Ethyl phenyl sulfide and diphenyl sulfide were degraded to the corresponding sulfones. A variety of products were formed from
dibenzyl sulfide, presumably via free radical intermediates. Diphenyl disulfide and dibenzyl disulfide were cleaved to the
corresponding thiols and other single-ring products. It was concluded that degradation of organic sulfur compounds byPaecilomyces involves an oxidative attack localized at the sulfur atom. 相似文献