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Desired Accuracy (desired + accuracy)
Selected AbstractsAn Adaptive Strategy for the Local Discontinuous Galerkin Method Applied to Porous Media ProblemsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2008Esov S. Velázquez DG methods may be viewed as high-order extensions of the classical finite volume method and, since no interelement continuity is imposed, they can be defined on very general meshes, including nonconforming meshes, making these methods suitable for h-adaptivity. The technique starts with an initial conformal spatial discretization of the domain and, in each step, the error of the solution is estimated. The mesh is locally modified according to the error estimate by performing two local operations: refinement and agglomeration. This procedure is repeated until the solution reaches a desired accuracy. The performance of this technique is examined through several numerical experiments and results are compared with globally refined meshes in examples with known analytic solutions. [source] Sentinel lymph node biopsy in patients with melanoma and breast cancerINTERNAL MEDICINE JOURNAL, Issue 9 2001R. F. Uren Abstract Sentinel lymph node biopsy (SNLB) is a new method for staging regional node fields in patients with cancers that have a propensity to metastasise to lymph nodes. The majority of early experience has been obtained in patients with melanoma and breast cancer. The technique requires the close cooperation of nuclear medicine physicians, surgical oncologists and histopathologists to achieve the desired accuracy. It involves: (i) identification of all lymph nodes that directly drain a primary tumour site (the sentinel nodes) by the use of pre-operative lymphoscintigraphy, (ii) selective excision of these nodes by the surgeon, guided by pre-operative blue dye injection and a gamma detecting probe intra-operatively and (iii) careful histological examination of the sentinel nodes by the histopathologist using serial sections and immunohistochemical stains. If the nodes are normal it can be inferred with a high degree of accuracy that all nodes in the node field are normal. This means that radical dissections of draining node fields can be avoided in patients with normal lymph nodes. A further advantage of lyamphatic mapping is that drainage to sentinel nodes in unusual locations is identified, leading to more accurate nodal staging than could be achieved with routine dissection of the closest node field. (Intern Med J 2001; 31: 547,553) [source] Equilibrium real gas computations using Marquina's schemeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2003Youssef Stiriba Abstract Marquina's approximate Riemann solver for the compressible Euler equations for gas dynamics is generalized to an arbitrary equilibrium equation of state. Applications of this solver to some test problems in one and two space dimensions show the desired accuracy and robustness. Copyright © 2003 John Wiley & Sons, Ltd. [source] Approximate lower bounds of the Weinstein and Temple varietyINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2007M. G. Marmorino Abstract By using the Weinstein interval or coupling the Temple lower bound to a variational upper bound one can in principle construct an error bar about the ground-state energy of an electronic system. Unfortunately there are theoretical and calculational issues which complicate this endeavor so that at best only an upper bound to the electronic energy has been practical in systems with more than a few electrons. The calculational issue is the complexity of ,H2, which is necessary in the Temple or Weinstein approach. In this work we provide a way to approximate the ,H2, to any desired accuracy using much simpler ,H,-like information so that the lower bound calculations are more practical. The helium atom is used as a testing ground in which we obtain approximate error bars for the ground-state energy of [,2.904230, ,2.903721] hartree using the variational energy with the Temple lower bound and [,2.919098, ,2.888344] hartree for the Weinstein interval. For comparison, the slightly larger error bars using the exact value of ,H2, are: [,2.904358, ,2.903721] hartree and [,2.919765, ,2.887677] hartree, respectively. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Amplitude estimation for near-sinusoidal oscillators by using a modified Barkhausen criterionINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2005H. Jardón-Aguilar Abstract By using an approach based on the Taylor/Volterra series, nonlinear amplifier characteristics can be introduced into the Barkhausen criterion in order to estimate the amplitude for near-sinusoidal oscillators. The characteristic equation is similar to the 1st -order determining equation obtained by Chua. This new method includes all desirable features of Chua's equation and lets us generalize the linear approach directly to a nonlinear one without losing the mathematical simplicity of the Barkhausen criterion. It also allows us to determine the oscillation amplitude with a desired accuracy. Moreover, this method investigates the influence of the feedback factor and the voltage supply on the oscillation amplitude. Employing only the 3rd -order nonlinearity of the amplifying element, the amplitude of the oscillation predicted by the modified Barkhausen criterion was compared to the one estimated using the transient analysis of SPICE, the harmonic balance analysis of Serenade, and by measurements. The amplitudes obtained by these four approaches for several feedback factors and supply voltages are in good agreement. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source] Numerical direct kinematic analysis of fully parallel linearly actuated platform type manipulatorsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 8 2002Li-Chun T. Wang This article presents a new numerical approach for solving the direct kinematics problem of fully parallel, linearly actuated platform manipulators. The solution procedure consists of two stages. The first stage transforms the direct kinematics problem into an equivalent nonlinear programming program, and a robust search algorithm is developed to bring the moving platform from arbitrary initial approximation to a feasible configuration that is near to the true solution. The second stage uses the Newton-Raphson iterative method to converge the solution to the desired accuracy. This approach is numerically stable and computationally efficient. In addition, by randomly perturbing the initial approximations, it can be implemented successively to find multiple solutions to the direct kinematics problem. Two numerical examples are presented to demonstrate the stability and efficiency of this approach. © 2002 Wiley Periodicals, Inc. [source] Richardson extrapolation techniques for the pricing of American-style optionsTHE JOURNAL OF FUTURES MARKETS, Issue 8 2007Chuang-Chang Chang In this article, the authors reexamine the American-style option pricing formula of R. Geske and H.E. Johnson (1984), and extend the analysis by deriving a modified formula that can overcome the possibility of nonuniform convergence (which is likely to occur for nonstandard American options whose exercise boundary is discontinuous) encountered in the original Geske,Johnson methodology. Furthermore, they propose a numerical method, the Repeated-Richardson extrapolation, which allows the estimation of the interval of true option values and the determination of the number of options needed for an approximation to achieve a given desired accuracy. Using simulation results, our modified Geske,Johnson formula is shown to be more accurate than the original Geske,Johnson formula for pricing American options, especially for nonstandard American options. This study also illustrates that the Repeated-Richardson extrapolation approach can estimate the interval of true American option values extremely well. Finally, the authors investigate the possibility of combining the binomial Black,Scholes method proposed by M. Broadie and J.B. Detemple (1996) with the Repeated-Richardson extrapolation technique. © 2007 Wiley Periodicals, Inc. Jrl Fut Mark 27:791,817, 2007 [source] | ||||||||||