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51.
Matthew R. Gibson Jeffrey W. Ohlmann Michael J. Fry 《Computers & Operations Research》2010,37(3):598-609
We examine a situation in which a decision-maker executes a sequence of resource allocation decisions over time, but the availability of the indivisible resources at future epochs is uncertain due to actions of competitors. We cast this problem as a specialized type of stochastic knapsack problem in which the uncertainty of item (resource) availability is induced by competitors concurrently filling their own respective knapsacks. Utilizing a multi-period bounded multiple-choice knapsack framework, we introduce a general discrete stochastic optimization model that allows a nonlinear objective function, cardinality constraints, and a knapsack capacity constraint. Utilizing a set of greedy selection rules and agent-based modeling to simulate the competitors’ actions, we solve the problem with a stochastic ruler approach that incorporates beam search to determine item selection of the types specified by the solution representation. We illustrate the computational effectiveness of our approach on instances motivated by a sports league draft as well as generic problem instances based on the knapsack literature. 相似文献
52.
Technology-aided participative methods in environmental assessment: An international perspective 总被引:1,自引:0,他引:1
Ainhoa Gonzlez Alan Gilmer Ronan Foley John Sweeney John Fry 《Computers, Environment and Urban Systems》2008,32(4):303
Provisions for citizen involvement in the assessment of potential environmental effects of certain plans, programmes and projects are present in current legislation. An international survey revealed that public participation is common practice in European and some other countries worldwide. However, a number of issues are observed to affect public involvement in EIA/SEA processes and expert opinion differs when evaluating the effectiveness of existing participative methods.Results suggest that technology-aided methods can improve traditional participation processes. In particular, GIS has the potential to increase community knowledge and enhance involvement by communicating information more effectively. Variable accessibility to technology and data quality remain issues. Combining technology with more conventional ways of gathering, evaluating and presenting data are seen as offering a solution to the need to promote the integration of public perceptions in environmental assessment procedures. Recommendations to improve current public participation methods and measures for making GIS available to the general public are provided. 相似文献
53.
H Tanaka CA Desouza PP Jones ET Stevenson KP Davy DR Seals 《Canadian Metallurgical Quarterly》1997,83(6):1947-1953
Using a meta-analytic approach, we recently reported that the rate of decline in maximal oxygen uptake (VO2 max) with age in healthy women is greatest in the most physically active and smallest in the least active when expressed in milliliters per kilogram per minute per decade. We tested this hypothesis prospectively under well-controlled laboratory conditions by studying 156 healthy, nonobese women (age 20-75 yr): 84 endurance-trained runners (ET) and 72 sedentary subjects (S). ET were matched across the age range for age-adjusted 10-km running performance. Body mass was positively related with age in S but not in ET. Fat-free mass was not different with age in ET or S. Maximal respiratory exchange ratio and rating of perceived exertion were similar across age in ET and S, suggesting equivalent voluntary maximal efforts. There was a significant but modest decline in running mileage, frequency, and speed with advancing age in ET. VO2 max (ml . kg-1 . min-1) was inversely related to age (P < 0.001) in ET (r = -0.82) and S (r = -0.71) and was higher at any age in ET. Consistent with our meta-analysic findings, the absolute rate of decline in VO2 max was greater in ET (-5.7 ml . kg-1 . min-1 . decade-1) compared with S (-3.2 ml . kg-1 . min-1 . decade-1; P < 0. 01), but the relative (%) rate of decline was similar (-9.7 vs -9. 1%/decade; not significant). The greater absolute rate of decline in VO2 max in ET compared with S was not associated with a greater rate of decline in maximal heart rate (-5.6 vs. -6.2 beats . min-1 . decade-1), nor was it related to training factors. The present cross-sectional findings provide additional evidence that the absolute, but not the relative, rate of decline in maximal aerobic capacity with age may be greater in highly physically active women compared with their sedentary healthy peers. This difference does not appear to be related to age-associated changes in maximal heart rate, body composition, or training factors. 相似文献
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During the development of an automated cost estimating system, several factors led to the selection of the triangular probability-density function to model historical construction costs. The triangular-density function is customarily used when function parameters are directly estimated by experts. A typical example is for estimating activity durations by identifying a minimum value, a most likely value, and a maximum value. These values are then used to construct triangular-density functions to represent uncertain activity durations. For this work, however, it was necessary to estimate parameters of the triangular-density function using historical cost data. A methodology was developed to generate test data and compare three methods of parameter estimation—maximum likelihood, moment matching, and least-squares curve-fitting techniques. It is concluded that optimized moment matching and least-squares techniques produce more accurate parameter estimates, while maximum likelihood estimation yields less accurate results. It is further concluded that the least-squares minimization method always performed as well as or better than the optimized moment matching technique and was therefore selected as the method of choice for the project. 相似文献
57.
本文对精密放大器的电压失调误差进行分析,并给出了基于电阻网络解决方案,分别提供了分立和集成方案。 相似文献
58.
E Cornillot RV Nair ET Papoutsakis P Soucaille 《Canadian Metallurgical Quarterly》1997,179(17):5442-5447
Degeneration is the process whereby Clostridium acetobutylicum ATCC 824 loses the capacity to produce acetone and butanol after repeated vegetative transfers or in continuous culture. Two degenerate mutants (M5 and DG1) of C. acetobutylicum ATCC 824 do not contain the four genes (ctfA, ctfB, adc, and aad) for acetone and butanol formation. Strain ATCC 824 contains a 210-kb plasmid (pSOL1) which is absent in M5 and DG1. pSOL1 carries the four acetone and butanol formation genes. A restriction map of pSOL1 was constructed by using ApaI, SmaI, SstII, and NarI digestions. M5 and DG1 could be complemented for acetone and butanol formation by expressing the corresponding genes (ctfA, ctfB, and adc for acetone; aad for butanol) on the plasmid. Degeneration of this strain thus appears to be the result of pSOL1 loss. 相似文献
59.
Dr. Zsofia Lengyel-Zhand Dr. Liam R. Marshall Maximilian Jung Megha Jayachandran Dr. Min-Chul Kim Austin Kriews Prof. Dr. Olga V. Makhlynets Dr. H. Christopher Fry Prof. Dr. Armin Geyer Prof. Dr. Ivan V. Korendovych 《Chembiochem : a European journal of chemical biology》2021,22(3):585-591
The self-assembly of short peptides into catalytic amyloid-like nanomaterials has proven to be a powerful tool in both understanding the evolution of early proteins and identifying new catalysts for practically useful chemical reactions. Here we demonstrate that both parallel and antiparallel arrangements of β-sheets can accommodate metal ions in catalytically productive coordination environments. Moreover, synergistic relationships, identified in catalytic amyloid mixtures, can be captured in macrocyclic and sheet-loop-sheet species, that offer faster rates of assembly and provide more complex asymmetric arrangements of functional groups, thus paving the way for future designs of amyloid-like catalytic proteins. Our findings show how initial catalytic activity in amyloid assemblies can be propagated and improved in more-complex molecules, providing another link in a complex evolutionary chain between short, potentially abiotically produced peptides and modern-day enzymes. 相似文献
60.
Fabrega J Tantra R Amer A Stolpe B Tomkins J Fry T Lead JR Tyler CR Galloway TS 《Environmental science & technology》2012,46(2):1128-1135
We studied the effects of ZnO nanoparticles [ZnO NPs, primary particle size 35 ± 10 nm (circular diameter, TEM)], bulk [160 ± 81 nm (circular diameter, TEM)], and Zn ions (from ZnCl(2)) on mortality, growth, and reproductive endpoints in the sediment dwelling marine amphipod Corophium volutator over a complete lifecycle (100 days). ZnO NPs were characterized by size, aggregation, morphology, dissolution, and surface properties. ZnO NPs underwent aggregation and partial dissolution in the seawater exposure medium, resulting in a size distribution that ranged in size from discrete nanoparticles to the largest aggregate of several micrometers. Exposure via water to all forms of zinc in the range of 0.2-1.0 mg L(-1) delayed growth and affected the reproductive outcome of the exposed populations. STEM-EDX analysis was used to characterize insoluble zinc precipitates (sphaerites) of high sulfur content, which accumulated in the hepatopancreas following exposures. The elemental composition of the sphaerites did not differ for ZnO NP, Zn(2+), and bulk ZnO exposed organisms. These results provide an illustration of the comparable toxicity of Zn in bulk, soluble, and nanoscale forms on critical lifecycle parameters in a sediment dwelling organism. 相似文献