Home About us Contact
|
Home About us Contact | ||
|
|
||
Correct Solution (correct + solution)
Selected AbstractsSolutions of pore pressure build up due to progressive wavesINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2001L. Cheng Abstract The analytical solution of soil pore pressure accumulations due to a progressive wave is examined in detail. First of all, the errors contained in a published analytical solution for wave-induced pore pressure accumulation are addressed, and the correct solution is presented in a more general form. The behaviour of the solution under different soil conditions is then investigated. It is found that the solution for deep soil conditions is sensitive to the soil shear stress in the top thin layer of the soil. However the solution is significantly influenced by the shear stress in the thin layer of soil near the impermeable base, for shallow and finite depth soil conditions. It is also found that a small error in the soil shear stress can lead to a large error in the accumulated pore pressure. An error analysis reveals the relationships between the accuracy of the pore pressure accumulation and the accuracy of the soil shear stress. A numerical solution to the simplified Biot consolidation equation is also developed. It is shown that the error analysis is of significant value for the numerical modelling of pore pressure buildup in marine soils. Both analytical and numerical examples are given to validate the error estimation method proposed in the present paper. Copyright © 2001 John Wiley & Sons, Ltd. [source] An assumed-gradient finite element method for the level set equationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 8 2005Hashem M. Mourad Abstract The level set equation is a non-linear advection equation, and standard finite-element and finite-difference strategies typically employ spatial stabilization techniques to suppress spurious oscillations in the numerical solution. We recast the level set equation in a simpler form by assuming that the level set function remains a signed distance to the front/interface being captured. As with the original level set equation, the use of an extensional velocity helps maintain this signed-distance function. For some interface-evolution problems, this approach reduces the original level set equation to an ordinary differential equation that is almost trivial to solve. Further, we find that sufficient accuracy is available through a standard Galerkin formulation without any stabilization or discontinuity-capturing terms. Several numerical experiments are conducted to assess the ability of the proposed assumed-gradient level set method to capture the correct solution, particularly in the presence of discontinuities in the extensional velocity or level-set gradient. We examine the convergence properties of the method and its performance in problems where the simplified level set equation takes the form of a Hamilton,Jacobi equation with convex/non-convex Hamiltonian. Importantly, discretizations based on structured and unstructured finite-element meshes of bilinear quadrilateral and linear triangular elements are shown to perform equally well. Copyright © 2005 John Wiley & Sons, Ltd. [source] Iterative algorithm for optimal fiducials under weak perspective projectionINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2009Alfred M. Bruckstein Abstract In previous work, we designed space fiducials with the aim of making camera pose determination as noise-insensitive as possible. These fiducials turned out to be sets of points that formed concentric regular polyhedra. Here, we apply an idea of Dementhon and Davis and test and analyze an iterative linear algorithm in conjunction with our optimal fiducials to increase the accuracy of the computed camera pose. We also analyze under what circumstances this iterative algorithm is guaranteed to converge to the correct solution. Comprehensive computer simulations illustrate the behavior of the algorithm and the degree of improvement in pose determination in case of convergence. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 27,36, 2009 [source] About the efficiency of the early FOMs in ab initio protein phasingJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2004Maria C. Burla All ab initio techniques for solving protein crystal structures use multisolution approaches. Several figures of merit that are found in the literature are efficient in the last steps of the phasing process, when some trials converge to the correct solution with a relatively small average phase error. Early figures of merit are much more critical; they should be able to recognize useful trials when the phase error is still large, and their efficiency determines the efficiency of the program. In the present work, a wide variety of known figures of merit at atomic and quasi-atomic (,1.4,Å) resolution have been tested; new figures have also been devised and tested. Their application to a large set of test structures allows the study of their properties at different data resolutions and the selection of the most efficient figures within the SIR2003-N framework. [source] Time,accurate Modular CFD-CSD Coupling for Aeroelastic Rotor SimulationsPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003A. Altmikus Dipl.-Ing. This paper addresses the timewise accuracy of different coupling approaches applied to instationary aeroelastic simulations of rotors in forward flight. Two different approaches which are widely discussed in literature are examined: the tight or strong coupling, and the fully integrated or monolithic coupling. Strong coupling means an exchange of fluid loads and structural deformations at each time step which is effectuated in a fully modular manner. We will address aspects of conservativity and time-accuracy, and will present results for a helicopter forward flight scenario. However, objections concerning the correct solution of the global non-linear three field problem , structure, grid deformation, aerodynamics , remain. These objections are normally rejected by the monolithic approach. Here, a common set of partial differential equations is derived and solved in a single code. However, a truly monolithic system of equations is only needed for stability analysis, and it can be decomposed in a three field problem respecting appropriate boundary conditions for each domain. Thus, modularity can be maintained, conceiving a quasi-monolithic procedure, when both domains are simultaneously solved in a common non-linear iteration loop on a per time-step basis. First results will be shown for a 2D flutter testcase. [source] The pair-functional method for direct solution of molecular structures.ACTA CRYSTALLOGRAPHICA SECTION A, Issue 2 2001The pair-functional principle shows how to construct a unique statistical ensemble of strongly interacting atoms that corresponds to any feasible measured set of X-ray intensities. The ensemble and all its distribution functions are strictly periodic in the crystal lattice, so that each unit cell has exactly the same arrangement of atoms at all times. The mean particle density in the cell is uniform because the ensemble has undefined phases and the origin is not fixed. The atoms in this maximum-entropy ensemble interact through pairwise additive periodic statistical forces within the unit cell. The ensemble average pair-correlation function is matched to the observed originless Patterson function of the crystal. The derived pairing force then becomes approximately proportional to the Ornstein,Zernicke direct correlation function of the ensemble. The atoms have a many-body Boltzmann distribution and the logarithm of the likelihood of any particular conformation is related to its total pairing potential. The pairing potential of a group of atoms acts like a local field in the cell. This property is used in the pair-functional method. Molecular structures can be solved by a direct search in real space for clusters of atoms with high pair potentials. During a successful search, the atoms move from their original random positions to form larger and larger clusters of correctly formed fragments. Finally, every atom belongs to a single cluster, which is the correct solution. [source] Cluster analysis for phasing with molecular replacement: a feasibility studyACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2009Andreas Buehler Molecular replacement can fail to find a solution, namely a unique orientation and position of a search model, even when many search models are tested under various conditions. Simultaneous use of the results of these searches may help in the solution of such difficult structures. A closeness between the peaks of several calculated rotation functions may identify the model orientation. The largest and most compact cluster of such peaks usually corresponds to models which are oriented similarly to the molecule under study. A search for the optimal translation may be more problematic and both individual translation functions and straightforward cluster analysis in the space of geometric parameters such as rotation angles and translation vectors may give no result. An improvement may be obtained by performing cluster analysis of the peaks of several translation functions in phase-set space. In this case, the Fourier maps computed using the observed structure-factor magnitudes and the phases calculated from differently positioned models are compared. Again, as a rule, the largest and the most compact cluster corresponds to the correct solution. The result of the updated procedure is no longer a single search model but an averaged Fourier map. [source] A common European foreign policy after Iraq?INTERNATIONAL AFFAIRS, Issue 3 2003Brian Crowe Taking as read the wide range of other instruments that the EU has for international influence (enlargement, aid, trade, association and other arrangements, etc.), the Common Foreign and Security Policy (CFSP), under pressure from the Kosovo conflict, has been shaped by two important decisions in 1999: the creation of the European Security and Defence Policy (ESDP) to give the EU a military capability when NATO as a whole is not engaged, and the appointment as the new High Representative for the CFSP of a high-profile international statesman rather than a senior civil servant. A major European effort will still be needed if Europe is to be effective militarily, whether in the EU/ESDP or NATO framework. The management of the CFSP has been held back by the doctrine of the equality of all member states regardless of their actual contribution. This in turn leads to a disconnect between theory (policy run by committee in Brussels) and practice (policy run by the High Representative working with particular member states and other actors, notably the US). It has been difficult for Javier Solana to develop the authority to do this, not in competition with the Commission as so widely and mistakenly believed, as with member states themselves, and particularly successive rotating presidencies. It is important that misdiagnosis does not lead to politically correct solutions that end up with the cure worse than the disease. Ways need to be found to assure to the High Representative the authority to work with third countries and with the member states making the real contribution, while retaining the support of all. Then, with its own military capability, the EU can have a CFSP that is the highest common factor rather than the lowest common denominator, with member states ready to attach enough priority to the need for common policies to give Europeans a strong influence in the big foreign policy issues of the day. [source] Using pop-up windows to improve multimedia learningJOURNAL OF COMPUTER ASSISTED LEARNING, Issue 2 2006S. Erhel Abstract The aim of the present study is to evaluate the effects on learning of the spatial integration of textual information incorporated into illustrations in the form of pop-up windows that are opened by the user. Three groups of students viewed illustrated texts depicting the functioning of the heart and the replication of the AIDS virus either with textual information presented below the picture, with textual information integrated within the picture, or with textual information integrated within the picture with pop-up windows. The results showed that the integrated formats were more effective than the separated format when we tested the retention of textual information, comprehension and the matching of textual elements to the appropriate illustrated elements. Furthermore, they indicated that the group working with pop-up windows performed better than the integrated groups on the retention test for illustrated information as well as when asked to find correct solutions to problems in a comprehension test. Consequently, these findings support the use of pop-up windows in learning with this kind of illustrated explanatory text. [source] Molecular replacement: the probabilistic approach of the program REMO09 and its applicationsACTA CRYSTALLOGRAPHICA SECTION A, Issue 6 2009Rocco Caliandro The method of joint probability distribution functions has been applied to molecular replacement techniques. The rotational search is performed by rotating the reciprocal lattice of the protein with respect to the calculated transform of the model structure; the translation search is performed by fast Fourier transform. Several cases of prior information are studied, both for the rotation and for the translation step: e.g. the conditional probability density for the rotation or the translation of a monomer is found both for ab initio and when the rotation and/or the translation values of other monomers are given. The new approach has been implemented in the program REMO09, which is part of the package for global phasing IL MILIONE [Burla, Caliandro, Camalli, Cascarano, De Caro, Giacovazzo, Polidori, Siliqi & Spagna (2007). J. Appl. Cryst.40, 609,613]. A large set of test structures has been used for checking the efficiency of the new algorithms, which proved to be significantly robust in finding the correct solutions and in discriminating them from noise. An important design concept is the high degree of automatism: REMO09 is often capable of providing a reliable model of the target structure without any user intervention. [source] Explaining the modality and contiguity effects: New insights from investigating students' viewing behaviourAPPLIED COGNITIVE PSYCHOLOGY, Issue 2 2010Florian Schmidt-Weigand The study examined viewing behaviour and learning outcome during multimedia learning in order to explore split-attention processes in modality and spatial contiguity effects. Fourty students viewed a computer instruction depicting the process of lightning. Exploratory text was spoken, written near or written far from accompanying animations. Students who received spoken text outperformed students who received written text in recalling the major steps (retention) and in identifying correct solutions to problems (transfer), replicating a modality effect. Differences between near and far written text presentation in retention (d,=,0.51) and transfer (d,=,0.68) tests failed statistical significance. Two major characteristics concerning the learners' viewing behaviour were identified: (a) in written text presentation, learning was largely text directed and (b) learning success was related to the time learners' spent looking at animations, indicating that the processing of animations is a crucial factor in explanations of modality and spatial contiguity effects. Copyright © 2009 John Wiley & Sons, Ltd. [source] Feasibility of one-shot-per-crystal structure determination using Laue diffractionACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2010Sterling Cornaby Crystal size is an important factor in determining the number of diffraction patterns which may be obtained from a protein crystal before severe radiation damage sets in. As crystal dimensions decrease this number is reduced, eventually falling to one, at which point a complete data set must be assembled using data from multiple crystals. When only a single exposure is to be collected from each crystal, the polychromatic Laue technique may be preferable to monochromatic methods owing to its simultaneous recording of a large number of fully recorded reflections per image. To assess the feasibility of solving structures using single Laue images from multiple crystals, data were collected using a `pink' beam at the CHESS D1 station from groups of lysozyme crystals with dimensions of the order of 20,30,µm mounted on MicroMesh grids. Single-shot Laue data were used for structure determination by molecular replacement and correct solutions were obtained even when as few as five crystals were used. [source] | |||||||||||||