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排序方式: 共有558条查询结果,搜索用时 125 毫秒
41.
Caliane B.B. Costa Elmer A.C. Rivera Mylene Cristina Alves Ferreira Rezende Maria Regina Wolf Maciel Rubens Maciel Filho 《Chemical engineering science》2007,62(17):4780-4801
This work presents an extension of a previous proposed procedure [Costa, C.B.B., Wolf Maciel, M.R., Maciel Filho, R., 2005. Factorial design technique applied to genetic algorithm parameters in a batch cooling crystallization optimization. Computers and Chemical Engineering 29, 2229-2241] to be adopted as a prior analysis in optimization problems to be solved using genetic algorithm (GA). Chemical engineering problems are commonly highly non-linear and possess a large number of variables, sometimes with significant interactions among them. Such characteristics make the optimization problems really difficult to be solved by deterministic methods. GA is an increasing tool for solving this sort of problems. However, no systematic approach to establish the best set of GA parameters for any problem was found in the literature and a relatively easy to use and meaningful approach is proposed and proved to be of general application. The proposed approach consists of applying factorial design, a well-established statistical technique to identify the most meaningful information about the influences of factors on a specific problem, as a support tool to identify the GA parameters with significant effect on the optimization problem. This approach is very useful in conducting further optimization works, since it discharges GA parameters that are not statistically significant for the evolutionary search for the optimum, saving time and computation burden in evolutionary optimization studies. 相似文献
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BACKGROUND: Traditionally, patients presenting with uncomplicated dyspepsia have been managed using empiric antisecretory therapy, followed by endoscopy in the event of persistent symptoms or complication. Since Helicobacter pylori is now accepted as an important and potentially reversible cause of ulcer disease, it is important to reevaluate the management of dyspepsia. The goal of this study is to evaluate seven outpatient strategies for the management of dyspeptic patients using a cost-utility analysis. METHODS: The study design was that of a cost-utility analysis. The model assumes that an adult patient with signs of dyspepsia but no signs of complication presents to the outpatient office of a primary care physician. Seven strategies are modeled: empiric antisecretory therapy; empiric H pylori eradication using oral omeprazole (20 mg [corrected] twice daily), clarithromycin (500 mg twice daily), and amoxicillin (1000 mg twice daily); use of either upper endoscopy, an upper gastrointestinal barium study (an upper GI), or the serum titer for H pylori as a diagnostic test to identify patients for H pylori eradication; or use of an initial diagnostic test followed by the serum titer for H pylori. The primary outcome was the cost per quality-adjusted life year (QALY) for each strategy for a 1-year period from presentation; secondary outcomes included the probability of symptomatic ulcer recurrence, cost per ulcer cure, and mortality. RESULTS: Three strategies were similarly cost-effective: empiric H pylori eradication ($1198 per QALY), use of a serum H pylori titer as an initial diagnostic test ($1214 per QALY), and empiric antisecretory therapy ($1288 per QALY). Empiric antisecretory therapy, however, was associated with significantly more symptomatic ulcer recurrences and deaths than any other strategy. CONCLUSIONS: This cost-utility analysis suggests that two strategies are reasonable for patients presenting with dyspepsia: (1) empiric H pylori eradication and (2) use of a serum H pylori titer to identify patients who might benefit from H pylori eradication. The latter strategy may be preferable because it is less likely to lead to antibiotic resistance. Strategies utilizing an upper GI or upper endoscopy (either with or without serum H pylori titer) or empiric antisecretory therapy do not improve outcomes and are associated with greater cost, morbidity, and/or mortality. 相似文献
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Effects of repeated practice and contextual-writing experiences on college students' writing skills.
Johnstone Karla M.; Ashbaugh Hollis; Warfield Terry D. 《Canadian Metallurgical Quarterly》2002,94(2):305
The authors examined the effects of both general and task-specific writing experiences on college students' writing-skill development. On the basis of theories of expertise development and a cognitive process theory of writing-skill development, the authors predicted that repeated practice would be associated with superior writing skills and that after controlling for repeated practice, writing within a specific task domain would be associated with superior writing skills. Undergraduate students participated in a field experiment in which 279 students practiced their writing skills in a professionally relevant task domain, whereas another group of 385 students practiced their writing skills in a more general domain. The results were consistent with the predictions. The authors discuss implications for teaching writing skills and for general theories of expertise development in writing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
Polymeric supports based on divinylbenzene (DVB) were prepared by aqueous suspension polymerization in presence or absence of styrene (S), using toluene and n‐heptane as diluents of the monomers. Poly(S–DVB) and poly(DVB) were sulfonated with sulfuric acid in presence of 1,2‐dichloroethane. The influence of the morphological structure of the supports and as a consequence of the catalyst on the esterification reaction of acetic acid with n‐butanol was evaluated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3616–3627, 2006 相似文献
47.
Denis Alcides Rezende Gilberto dos Santos Madeira Leonardo de Souza Mendes Gean Davis Breda Bruno Bogaz Zarpelão Frederico de Carvalho Figueiredo 《Telematics and Informatics》2014
Making information and telecommunications available is a permanent challenge for cities concerned to their social, urban and local planning and development, focused on life quality of their citizens and on the effectiveness of public management. Such a challenge requires the involvement of everyone in the city. The objective is to describe the information and telecommunications project from the planning of a digital city carried out in Vinhedo-SP, Brazil. It was built as a telecommunications infrastructure of the kind of “open access metropolitan area networks” which enables the integration of citizens in a single telecommunications environment. The research methodology was emphasized by a case study which turned to be a research-action, comprising the municipal administration and its local units. The results achieved describe, by means of a methodology, the phases, sub-phases, activities, approval points and resulting products, and formalize their respective challenges and difficulties. The contributions have to do with the practical feasibility of the project and execution of its methodology. The conclusion reiterates the importance of the project, collectively implemented and accepted, as a tool to help the management of cities, in the implementation of Strategic Digital City Projects, in the decisions of public administration managers, and in the quality of life of their citizens. 相似文献
48.
Christine J. Frandsen Karla S. Brammer Kunbae Noh Laura S. Connelly Seunghan Oh Li-Han Chen Sungho Jin 《Materials science & engineering. C, Materials for biological applications》2011,31(8):1716-1722
Electrochemical formation of tunable nanoscale oxide layers on biomedical metallic surfaces has recently drawn much attention in biomaterials research. In this study, we report on the cellular response to a unique vertically aligned, laterally spaced nanotube nanostructure made of zirconium oxide (ZrO2) fabricated by anodization. The growth, morphology, and functionality of osteoblasts cultured on ZrO2 nanotubes have been investigated. The initial adhesion and spreading was considerably improved on the nanotube surface as compared to a flat zirconium (Zr) surface without a nanostructure. The morphology of the adhered cells on the nanotube surface elicited a highly organized cytoskeleton with crisscross patterned actin, which was lacking on the flat Zr. Increased alkaline phosphatase activity levels and the formation of calcified extracellular matrix implied improved osteoblast functionality and mineralization on the nanotube substrate. This in vitro study suggests that the ZrO2 nanotubes provided an enhanced osteoblast response and demonstrated their apparent role in providing a platform for bone growth. 相似文献
49.
Microwave absorption properties of a
conductive thermoplastic blend based on
polyaniline 总被引:1,自引:0,他引:1
Cristiane Reis Martins Roselena Faez Mirabel Cerqueira Rezende Marco-A. De Paoli 《Polymer Bulletin》2004,51(4):321-326
Summary Conductive thermoplastic blends of polystyrene and
polyaniline doped with dodecylbenzene sulfonic acid, DBSA and
polystyrene sulfonic acid were prepared in an internal mixer. We
used a block copolymer of styrene and butadiene as
compatibilizer. Different formulations were tested according to
a statistical response surface method. The electrical
conductivity and the microwave radiation absorbing properties of
the blends were evaluated. The concentration of the
compatibilizer and polyaniline and the blend film thickness
affect the attenuation properties of the materials. 相似文献
50.