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Selected AbstractsMicrofluidics simulation using adaptive unstructured gridsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 9 2004Jacob Waltz Abstract A methodology for microfluidics simulation is presented. The methodology solves the three-dimensional incompressible Navier,Stokes equations with an adaptive unstructured Finite Element method. A semi-implicit Fractional Step procedure is used for time integration. The entire methodology has been parallelized for shared-memory architectures via an algebraic domain decomposition. Results from both verification problems and prototypical applications are included. Copyright © 2004 John Wiley & Sons, Ltd. [source] A numerical scheme for strong blast wave driven by explosionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2006Kaori Kato Abstract After the detonation of a solid high explosive, the material has extremely high pressure keeping the solid density and expands rapidly driving strong shock wave. In order to simulate this blast wave, a stable and accurate numerical scheme is required due to large density and pressure changes in time and space. The compressible fluid equations are solved by a fractional step procedure which consists of the advection phase and non-advection phase. The former employs the Rational function CIP scheme in order to preserve monotone signals, and the latter is solved by interpolated differential operator scheme for achieving the accurate calculation. The procedure is categorized into the fractionally stepped semi-Lagrangian. The accuracy of our scheme is confirmed by checking the one-dimensional plane shock tube problem with 103 times initial density and pressure jump in comparison with the analytic solution. The Sedov,Taylor blast wave problem is also examined in the two-dimensional cylindrical coordinate in order to check the spherical symmetry and the convergence rates. Two- and three-dimensional simulations for the blast waves from the explosion in the underground magazine are carried out. It is found that the numerical results show quantitatively good agreement with the experimental data. Copyright © 2006 John Wiley & Sons, Ltd. [source] Large eddy simulation of turbulent flows via domain decomposition techniques.INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2005Part 1: theory Abstract The present paper discusses large eddy simulations of incompressible turbulent flows in complex geometries. Attention is focused on the application of the Schur complement method for the solution of the elliptic equations arising from the fractional step procedure and/or the semi-implicit discretization of the momentum equations in velocity,pressure representation. Fast direct and iterative Poisson solvers are compared and their global efficiency evaluated both in serial and parallel architecture environments for model problems of physical relevance. Copyright © 2005 John Wiley & Sons, Ltd. [source] Large eddy simulation of turbulent flows via domain decomposition techniques.INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2005Part 2: applications Abstract The present paper discusses the application of large eddy simulation to incompressible turbulent flows in complex geometries. Algorithmic developments concerning the flow solver were provided in the companion paper (Int. J. Numer. Meth. Fluids, 2003; submitted), which addressed the development and validation of a multi-domain kernel suitable for the integration of the elliptic partial differential equations arising from the fractional step procedure applied to the incompressible Navier,Stokes equations. Numerical results for several test problems are compared to reference experimental and numerical data to demonstrate the potential of the method. Copyright © 2005 John Wiley & Sons, Ltd. [source] Combining a polarizable force-field and a coarse-grained polarizable solvent model: Application to long dynamics simulations of bovine pancreatic trypsin inhibitorJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2008Michel Masella Abstract The dynamic coupling between a polarizable protein force field and a particle-based implicit solvent model is described. The polarizable force field, TCPEp, developed recently to simulate protein systems, is characterized by a reduced number of polarizable sites, with a substantial gain in efficiency for an equal chemical accuracy. The Polarizable Pseudo-Particle (PPP) solvent model represents the macroscopic solvent polarization by induced dipoles placed on mobile Lennard-Jones pseudo-particles. The solvent-induced dipoles are sensitive to the solute electric field, but not to each other, so that the computational cost of solvent,solvent interactions is basically negligible. The solute and solvent induced dipoles are determined self-consistently and the equations of motion are solved using an efficient iterative multiple time step procedure. The solvation cost with respect to vacuum simulations is shown to decrease with solute size: the estimated multiplicative factor is 2.5 for a protein containing about 1000 atoms, and as low as 1.15 for 8000 atoms. The model is tested for six 20 ns molecular dynamics trajectories of a traditional benchmark system: the hydrated Bovine Pancreatic Trypsin Inhibitor (BPTI). Even though the TCPEp parameters have not been refined to be used with the solvent PPP model, we observe a good conservation of the BPTI structure along the trajectories. Moreover, our approach is able to provide a description of the protein solvation thermodynamic at the same accuracy as the standard Poisson-Boltzman continuum methods. It provides in addition a good description of the microscopic structural aspects concerning the solute/solvent interaction. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Syntheses of oxazolo[4,5- c]pyridine and 6-azaindoleJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2008Freddy Tjosaas The preparation of oxazolo[4,5- c]pyridine and 6-azaindole from 4-bromo-3-pivaloylaminopyridine (8) is reported. The oxazolopyridine 2- tert -butyl-oxazolo[4,5- c]pyridine (9) was successfully prepared from 8 in 78% yield by a new base/TBAB promoted non-catalyzed microwave cyclisation strategy (10 min) or, alternatively, in 54% yield by conventional heating (48 hrs) and CuI catalysis. The 6-azaindole 2-phenyl-1-(trimethylacetyl)-6-azaindole (13) was prepared from 8 in a two step procedure, including a Sonogashira coupling reaction. [source] Restoration of PSD from Chord Length Distribution Data using the Method of Projections onto Convex SetsPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 2 2005Jörg Worlitschek Abstract The interpretation of chord length distributions (CLDs) is essential in many fields and has been discussed by various authors. Here, the technique of the Focused Beam Reflectance Measurement (FBRM) is considered as on-line and in-situ measurement device of the CLD of particle dispersions and emulsions. Though useful in general, this measurement cannot be converted directly into a particle size distribution (PSD), unless the physics of the measurement method is described and accounted for. In this work we present a new tool to carry out such a conversion once the particle shape is known a priori and can be fixed, which is based on a two step procedure: (1) the computation of a matrix that converts the PSD of a population of particles with given shape into the corresponding CLD using a 3-dimensional geometric model; (2) the calculation of the PSD from the resulting linear matrix equation for the measured CLD. Here, the method of Projections onto Convex Sets (POCS) is applied to solve the PSD restoration problem, which is a mathematically ill-posed inverse problem. We study the effect of particle shape and matrix dimension on the ill-posed character of the inverse problem. A detailed error analysis of the CLD allows for a predictive description of a posteriori constraints in the POCS framework. We discuss the application of this method to the characterization of simulated test cases and experimentally obtained data. [source] Effectiveness of software training using simulations: An exploratory studyPERFORMANCE IMPROVEMENT QUARTERLY, Issue 4 2009Arnold D. McElroy Jr. This study was designed to explore the effectiveness in student performance and confidence of limited and full device simulators. The 30 employees from an information technology company who participated in this study were assigned to one of three groups. Each group received practice for learning a complex software procedure using traditional interactions, a limited device simulator, or a full device simulator. A training portal was created for each practice method. Measurements of performance included the number of times the participants repeated the assigned practice activity, the total time required to complete the procedure, a test score representing the number of mistakes made in the 20-step procedure, and the average time between mouse clicks as they selected items from menus or clicked buttons. Preliminary results indicated that a limited device simulator appears to be as effective as a full device simulator. Recommendations for further research and limitations of the study are also addressed. [source] 1H-HRMAS NMR study of smoked Atlantic salmon (Salmo salar)MAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2010David Castejón Abstract High-resolution magic angle spinning (HRMAS) NMR spectroscopic data of smoked Atlantic salmon (Salmo salar) were fully assigned by combination of one- and two-dimensional-HRMAS experiments. Complete representative spectra, obtained after few minutes of analysis time, revealed a large number of minor and major compounds in the sample. The methodology is limited by the low sensitivity of NMR, and therefore HRMAS only enables the determination of the most relevant components. These were fatty acids (FAs), carbohydrates, nucleoside derivatives, osmolytes, amino acids, dipeptides and organic acids. For the first time, spectra were resolved sufficiently to allow semiquantitative determination in intact muscle of the highly polyunsaturated FA 22:6 ,-3. Additionally, the feasibility of 1H-HRMAS NMR metabolite profiling was tested to identify some bioactive compounds during storage. This profiling was carried out by the non-destructive and direct analysis (i.e. without requiring sample preparation and multiple step procedures) of intact salmon muscle. The proposed procedure can be applied to a large number of samples with high throughput due to the short time of analysis and quick evaluation of the data. Copyright © 2010 John Wiley & Sons, Ltd. [source] Synthesis of potentially photoactivatable coumarin derivatives via a 1,3-dipolar cycloadditionJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2008Elodie-Denise Chenot A copper (1)-catalyzed 1,3-dipolar cycloaddition reaction was used to prepare a series of mono and disubstituted 1,2,3-triazolyl-coumarins using a 1,3-cycloaddition ("Click Chemistry"). Starting coumarins were synthesized using classical or modified Pechmann's reaction. The propargyl group was introduced as either propargylether or as a propargylamide. Azides were prepared in a three steps procedure. Cycloaddition products, containing a coumarin and a photoactivatable moiety, were obtained in good yields. [source] Synthesis of self-healing supramolecular rubbers from fatty acid derivatives, diethylene triamine, and ureaJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2008Damien Montarnal Abstract We describe the synthesis of supramolecular self-healing elastomers from vegetable oil fatty acid derivatives, diethylene triamine, and urea. Our strategy to obtain materials that are self-healing but do not flow relies on the use of a wide molecular distribution of randomly branched oligomers equipped with self-complementary and complementary hydrogen bonding groups. We prepared such oligomers with a two steps procedure. In the first step, diethylene triamine was condensed with dimer acids. In the second step, the oligomers obtained were allowed to react with urea. The molecules were characterized by NMR and IR spectroscopies and Monte-Carlo simulations were used to analyze the molecular size distribution. The sensitivity to small variations of the experimental conditions has been examined and the robustness of the synthetic procedure optimized. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7925,7936, 2008 [source] | |||||||||||||