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Selected AbstractsA note on the prospective analysis of outcome-dependent samplesJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 2 2003Hua Yun Chen Summary. Two likelihood representations corresponding to the prospective and retrospective analyses of the case,control design are derived for general outcome-dependent samples with arbitrary discrete or continuous outcomes and possibly non-multiplicative models. Parameter identification in the general outcome-dependent design is reduced to the simple problem of parameter identification in the general odds ratio function. Both likelihoods are shown to generate the same profile likelihood for the common parameter of interest. Maximum like- lihood estimators based on either likelihood are semiparametric efficient for the identifiable parameters. [source] Input impedance calculation of dipole antenna using FDTD methodMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2008Wenhua Yu Abstract Since the input impedance of half wavelength dipole antenna is well known, therefore, a dipole antenna is frequently used to validate the computational electromagnetic method. Though its structure is relatively simple, it is not a simple problem for the most computational electromagnetic methods. In this article, we investigate the input impedance of half wavelength dipole antenna using the FDTD method. Numerical experiments have demonstrated that the FDTD method can be used to accurately calculate its input impedance using uniform mesh, nonuniform mesh, or subgridding. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2335,2337, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23631 [source] Mechanics with variable-order differential operatorsANNALEN DER PHYSIK, Issue 11-12 2003C.F.M. Coimbra Abstract This work presents the novel concept of Variable-Order (VO) Calculus through the description of a simple problem in Mechanics. A mathematical definition for the VO-differential operator that is suitable to mechanical modelling is proposed, and an example concerning the effect of nonuniform viscoelastic frictional forces is described. A numerical method for the solution of Variable Order Differential Equations (VODEs) is proposed. The physical model under study requires mathematical tools that lie beyond the traditional methods of Constant-Order (CO) differential equations. The VO-Calculus formulation is compared to a CO-Calculus model in order to show the limitations of the latter in resolving the transition between the relevant dynamic regimes. [source] Has the guest arrived yet?BUSINESS ETHICS: A EUROPEAN REVIEW, Issue 3 2007Emmanuel Levinas, a stranger in business ethics To what extent can business ethics be ,hospitable' to Levinasian ethics? This paper raises questions about how business ethics relates to its guests, in this case the guest called ,Levinas'; the idea of introducing or inviting the work of an author into a field, as its guest, is by no means a simple problem of transference. For Jacques Derrida, there is hospitality only when the stranger's introduction to our home is totally unconditional. Such a conceptualisation of hospitality becomes even more demanding when the ,stranger' that is near our ,home' is an ethics also demanding hospitality, such as the ethics proposed by Levinas. An invitation puts in place particular circumstances that allow only for an arrival of the one invited. These conditions precede the so-called stranger, thereby predetermining the route to be taken, the destination to be reached and the correct manner of self-presentation. An invitation already reduces the Other to that which is expected by the inviter, that is to the Same. The hospitality of the field of business ethics becomes an endorsement of a particular version of the stranger, therefore recognisable by the field. Perhaps conceptualising Levinasian ethics as an ethics that cannot be invited might protect it from procedures that reduce the ,strangeness' of the stranger, making it knowable. That is the argument presented in this paper. [source] An MPI Parallel Implementation of Newmark's MethodCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2000Ali Namazifard The standard message-passing interface (MPI) is used to parallelize Newmark's method. The linear matrix equation encountered at each time step is solved using a preconditioned conjugate gradient algorithm. Data are distributed over the processors of a given parallel computer on a degree-of-freedom basis; this produces effective load balance between the processors and leads to a highly parallelized code. The portability of the implementation of this scheme is tested by solving some simple problems on two different machines: an SGI Origin2000 and an IBM SP2. The measured times demonstrate the efficiency of the approach and highlight the maintenance advantages that arise from using a standard parallel library such as MPI. [source] Adaptive through-thickness integration for accurate springback predictionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2008I. A. Burchitz Abstract Accurate numerical prediction of springback in sheet metal forming is essential for the automotive industry. Numerous factors influence the accuracy of prediction of this complex phenomenon by using the finite element method. One of them is the numerical integration through the thickness of shell elements. It is known that the traditional numerical schemes are very inefficient in elastic,plastic analysis and even for simple problems they require up to 50 integration points for an accurate springback prediction. An adaptive through-thickness integration strategy can be a good alternative. The main characteristic feature of the strategy is that it defines abscissas and weights depending on the integrand's properties and, thus, can adapt itself to improve the accuracy of integration. A concept of an adaptive through-thickness integration strategy for shell elements is presented in this paper. Its potential is demonstrated using two examples. Calculations of a simple test,bending a beam under tension,show that for a similar set of material and process parameters the adaptive rule with seven integration points performs significantly better than the traditional trapezoidal rule with 50 points. Simulations of an unconstrained cylindrical bending problem demonstrate that the adaptive through-thickness integration strategy for shell elements can guarantee an accurate springback prediction at minimal costs. Copyright © 2007 John Wiley & Sons, Ltd. [source] The effect of overall discretization scheme on Jacobian structure, convergence rate, and solution accuracy within the local rectangular refinement methodNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 8 2001Beth Anne V. Bennett Abstract The local rectangular refinement (LRR) solution-adaptive gridding method automatically produces orthogonal unstructured adaptive grids and incorporates multiple-scale finite differences to discretize systems of elliptic governing partial differential equations (PDEs). The coupled non-linear discretized equations are solved simultaneously via Newton's method with a Bi-CGSTAB linear system solver. The grids' unstructured nature produces a nonstandard sparsity pattern within the Jacobian. The effects of two discretization schemes (LRR multiple-scale stencils and traditional single-scale stencils) on Jacobian bandwidth, convergence speed, and solution accuracy are studied. With various point orderings, for two simple problems with analytical solutions, the LRR multiple-scale stencils are seen to: (1) produce Jacobians of smaller bandwidths than those resulting from the traditional single-scale stencils; (2) lead to significantly faster Newton's method convergence than the single-scale stencils; and (3) produce more accurate solutions than the single-scale stencils. The LRR method, including the LRR multiple-scale stencils, is finally applied to an engineering problem governed by strongly coupled, highly non-linear PDEs: a steady-state lean Bunsen flame with complex chemistry, multicomponent transport, and radiation modeling. Very good agreement is observed between the computed flame height and previously published experimental data. Copyright © 2001 John Wiley & Sons, Ltd. [source] What a reviewer wantsPEDIATRIC ANESTHESIA, Issue 12 2008ANDREW J. DAVIDSON MBBS MD Summary Understanding what a reviewer wants helps authors write better papers and design better research studies. Central to any research study is the research question. This is the first thing the reviewer looks for. The question, or research aim, should be relevant, original and very clearly defined. The paper should also be scientifically valid; the methods should achieve the aim by addressing the question, and the conclusions should match the results. The statistical analysis often attracts criticism, especially the relatively simple problems arising with the use of P -values and the concepts of statistical and clinical significance. There are several agreed guidelines describing exactly how studies should be reported. Following these is a great help to reviewers. [source] Why use CFD for explosion studies?PROCESS SAFETY PROGRESS, Issue 2 2008David D. Herrmann Abstract This article provides an overview showing the value of CFD for the study of explosions. Although computational fluid dynamics finds a great deal of use in solving very complex problems, its value is not limited to complex problems. Many relatively simple problems can be solved quickly and economically with the use of CFD. The intent of this article is to show industry the possibilities that exist for improving safety when the physics of explosions are better understood. © 2007 American Institute of Chemical Engineers Process Saf Prog, 2008 [source] Modellierung und Simulation von Chemiereaktoren , Aspekte einer zeitgemäßen IngenieurausbildungCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 1-2 2005J. Hagen Prof. Abstract Die Durchführung chemischer Prozesse in der Technik unter möglichst optimalen Bedingungen setzt ein Grundverständnis für die Arbeitsweise von Chemiereaktoren voraus. Grundlage der Modellierung von Chemiereaktoren sind die Stoff- und Wärmebilanz und die Kinetik der Reaktion. Nur in einfachen Fällen lassen sich analytische Lösungen für Problemstellungen aus der Praxis durch Integration der Differentialgleichungen finden. Das in der Chemieingenieurausbildung eingesetzte Softwarepaket POLYMATH ist sehr anwenderfreundlich und einfach zu erlernen. Es wird u.,a. eingesetzt, um gekoppelte Differentialgleichungen simultan zu lösen und Datenanalyse durch Regression durchzuführen. Mit einem einmal aufgestellten Modell lässt sich der Einfluss verschiedener Reaktionsparameter auf den Gesamtprozess leicht nachvollziehbar simulieren. Modeling and Simulation of Chemical Reactors , Aspects of a Modern Education of Engineers Understanding how chemical reactors work lies at the heart of almost every chemical processing operation. Basis information for modeling and simulation of chemical reactors is needed from mass transfer, heat transfer and chemical kinetics. Only simple problems from practice can be solved analytically by means of integration of the differential equations. POLYMATH is a extremely user-friendly software package which makes modeling easy for the education of chemical engineers and chemists. POLYMATH is used to numerically solve coupled differential equations simultaneously or to find kinetic parameters in rate expressions by regression. Using an identified model the influence of various reaction parameters on the overall process can be simulated easily. [source] | ||||||||||||||||