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Various Alternatives (various + alternative)
Selected AbstractsInvestigating the Incidence of type i errors for chronic whole effluent toxicity testing using Ceriodaphnia dubiaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2000Timothy F. Moore Abstract The risk of Type I error (false positives) is thought to be controlled directly by the selection of a critical p value for conducting statistical analyses. The critical value for whole effluent toxicity (WET) tests is routinely set to 0.05, thereby establishing a 95% confidence level about the statistical inferences. In order to estimate the incidence of Type I errors in chronic WET testing, a method blank-type study was performed. A number of municipal wastewater dischargers contracted 16 laboratories to conduct chronic WET tests using the standard test organism Ceriodaphnia dubia. Unbeknownst to the laboratories, the samples they received from the wastewater dischargers were comprised only of moderately hard water, using the U.S. Environmental Protection Agency's standard dilution water formula. Because there was functionally no difference between the sample water and the laboratory control/dilution water, the test results were expected to be less than or equal to 1 TUc (toxic unit). Of the 16 tests completed by the biomonitoring laboratories, two did not meet control performance criteria. Six of the remaining 14 valid tests (43%) indicated toxicity (TUc > 1) in the sample (i.e., no-observed-effect concentration or IC25 < 100%). This incidence of false positives was six times higher than expected when the critical value was set to 0.05. No plausible causes for this discrepancy were found. Various alternatives for reducing the rate of Type I errors are recommended, including greater reliance on survival endpoints and use of additional test acceptance criteria. [source] Description for smooth contact conditions based on the internal geometry of contact surfacesPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003Alexander Konyukhov Dr. A kinematical approach, based on the consideration of the contact conditions in the local coordinate system, is proposed for the contact description and for consistent linearization. This leads to a simple structure of the tangent matrix, which is subdivided into main, rotational and curvature parts. Various alternatives neglecting parts of the contact tangent matrix are considered. Representative examples show the effectiveness of the proposed approach for contact problems with arbitrary large deformation. [source] Snap: A time critical decision-making framework for MOUT simulationsCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2008Shang-Ping Ting Abstract Deliberative reasoning based on the rational analysis of various alternatives often requires too much information and may be too slow in time critical situations. In these situations, humans rely mainly on their intuitions rather than some structured decision-making processes. An important and challenging problem in Military Operations on Urban Terrain (MOUT) simulations is how to generate realistic tactical behaviors for the non-player characters (also known as bots), as these bots often need to make quick decisions in time-critical and uncertain situations. In this paper, we describe our work on Snap, a time critical decision-making framework for the bots in MOUT simulations. The novel features of Snap include case-based reasoning (CBR) and thin slicing. CBR is used to make quick decisions by comparing the current situation with past experience cases. Thin slicing is used to model human's ability to quickly form up situation awareness under uncertain and complex situations using key cues from partial information. To assess the effectiveness of Snap, we have integrated it into Twilight City, a virtual environment for MOUT simulations. Experimental results show that Snap is very effective in generating quick decisions during time critical situations for MOUT simulations. Copyright © 2008 John Wiley & Sons, Ltd. [source] Theoretical influences on research on language development and intervention in individuals with mental retardationDEVELOPMENTAL DISABILITIES RESEARCH REVIEW, Issue 3 2004Leonard Abbeduto Abstract In this article, we consider the theoretical debates and frameworks that have shaped research on language development and intervention in persons with mental retardation over the past four decades. Our starting point is the nativist theory, which has been espoused most forcefully by Chomsky. We also consider more recent alternatives to the nativist approach, including the social-interactionist and emergentist approaches, which have been developed largely within the field of child language research. We also consider the implications for language development and intervention of the genetic syndrome-based approach to behavioral research advocated by Dykens and others. We briefly review the impact and status of the debates spurred by the nativist approach in research on the course of language development in individuals with mental retardation. In addition, we characterize some of the achievements in language intervention that have been made possible by the debates spurred by nativism and the various alternatives to it. The evidence we consider provides support for all three alternatives to the nativist approach. Moreover, successful interventions appear to embody elements of several of these approaches as well as other theoretical approaches (e.g., behaviorism). We conclude that language intervention must be theoretically eclectic in its approach, with different strategies appropriate for teaching different features of language, at different points in development, and for children displaying different characteristics or learning histories. © 2004 Wiley-Liss, Inc. MRDD Research Reviews 2004;10:184,192. [source] On the construction of manufactured solutions for one and two-equation eddy-viscosity modelsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2007L. Eça Abstract This paper presents manufactured solutions (MSs) for some well-known eddy-viscosity turbulence models, viz. the Spalart & Allmaras one-equation model and the TNT and BSL versions of the two-equation k,, model. The manufactured flow solutions apply to two-dimensional, steady, wall-bounded, incompressible, turbulent flows. The two velocity components and the pressure are identical for all MSs, but various alternatives are considered for specifying the eddy-viscosity and other turbulence quantities in the turbulence models. The results obtained for the proposed MSs with a second-order accurate numerical method show that the MSs for turbulence quantities must be constructed carefully to avoid instabilities in the numerical solutions. This behaviour is model dependent: the performance of the Spalart & Allmaras and k,, models is significantly affected by the type of MS. In one of the MSs tested, even the two versions of the k,, model exhibit significant differences in the convergence properties. Copyright © 2006 John Wiley & Sons, Ltd. [source] A reconstruction of development of the periodic table based on history and philosophy of science and its implications for general chemistry textbooksJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 1 2005Angmary Brito The objectives of this study are: (a) elaboration of a history and philosophy of science (HPS) framework based on a reconstruction of the development of the periodic table; (b) formulation of seven criteria based on the framework; and (c) evaluation of 57 freshman college-level general chemistry textbooks with respect to the presentation of the periodic table. The historical reconstruction of the periodic table showed that the periodicity of the elements could be construed as an inductive generalization or as a function of the atomic theory. There is considerable controversy with respect to the nature of Mendeleev's contribution, and various alternatives are discussed: ordered domain; empirical law; and a theory with limited explanatory power. Accommodation of the elements according to their physicochemical properties is considered to be the major contribution of the periodic table by all textbooks, followed by contrapredictions of previously unknown elements (30 textbooks), and novel predictions (corrections of atomic mass) of known elements (10 textbooks). The relative importance of accommodation and prediction within an HPS framework is generally ignored. Few textbooks have attempted to explore the possible cause of periodicity in the table and very few textbooks have explored the nature of Mendeleev's contribution. The development of the periodic table as a sequence of heuristic principles in the form of a convincing argument has been ignored. The textbook approach of emphasizing that the development of the periodic table was an inductive generalization, and that Mendeleev had no model or theory, does not facilitate the spirit of critical inquiry that led the scientists to grapple with alternative interpretations, conflicts, and controversies. It is concluded that the development of the periodic table went through a continual critical appraisal (conflict and controversy), in which scientists presented various tentative theoretical ideas to understand the observed phenomena. © 2004 Wiley Periodicals, Inc. J Res Sci Teach 42: 84,111, 2005 [source] Cost-efficient higher-order crossover designs for two-treatment clinical trialsPHARMACEUTICAL STATISTICS: THE JOURNAL OF APPLIED STATISTICS IN THE PHARMACEUTICAL INDUSTRY, Issue 4 2005Ying Yuan Abstract Higher-order crossover designs have drawn considerable attention in clinical trials, because of their ability to test direct treatment effects in the presence of carry-over effects. The important question, when applying higher-order crossover designs in practice, is how to choose a design with both statistical and cost efficiencies from various alternatives. In this paper, we propose a general cost function and compare five statistically optimal or near-optimal designs with this cost function for a two-treatment study under different carry-over models. Based on our study, to achieve both statistical and cost efficiencies, a four-period, four-sequence crossover design is generally recommended under the simple carry-over or no carry-over models, and a three-period, two-sequence crossover design is generally recommended under the steady-state carry-over models. Copyright © 2005 John Wiley & Sons, Ltd. [source] What's Really Wrong with the Limited Quantity View?RATIO, Issue 2 2001Tim Mulgan In Part Four of Reasons and Persons, Derek Parfit seeks Theory X , the Utilitarian account of the morality of choices where the number of people who will ever exist depends upon our actions. Parfit argues that X has yet to be found. The two simplest versions of Theory X are Total Utilitarianism and Average Utilitarianism. Unfortunately, Parfit argues, each of these leads to unacceptable results. Parfit explores various alternatives and finds them all unsatisfactory. This paper deals with one of those alternatives: the Limited Quantity View. I argue that ParfitÃ,s argument against this view fails. However, I then present a new and more general objection which defeats a broad range of utilitarian views, including the Limited Quantity View. [source] On the Ghoudi, Khoudraji, and Rivest test for extreme-value dependenceTHE CANADIAN JOURNAL OF STATISTICS, Issue 4 2009Noomen Ben Ghorbal Abstract Ghoudi, Khoudraji & Rivest [The Canadian Journal of Statistics 1998;26:187,197] showed how to test whether the dependence structure of a pair of continuous random variables is characterized by an extreme-value copula. The test is based on a U -statistic whose finite- and large-sample variance are determined by the present authors. They propose estimates of this variance which they compare to the jackknife estimate of Ghoudi, Khoudraji & Rivest (1998) through simulations. They study the finite-sample and asymptotic power of the test under various alternatives. They illustrate their approach using financial and geological data. The Canadian Journal of Statistics © 2009 Statistical Society of Canada Ghoudi, Khoudraji & Rivest (1998) ont montré comment tester que la structure de dépendance d'un couple d'aléas continus est caractérisée par une copule de valeurs extrêmes. Le test s'appuie sur une U -statistique dont les auteurs déterminent ici la variance asymptotique et à taille finie. Ils proposent des estimations de cette variance qu'ils comparent à l'estimateur jackknife de Ghoudi, Khoudraji & Rivest (1998) à l'aide de simulations. Ils étudient les puissances à taille finie et asymptotique du test sous diverses contre-hypothèses. Ils illustrent leur propos avec des données financières et géologiques. La revue canadienne de statistique © 2009 Société statistique du Canada [source] | ||||||||||||||||