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Verification of a mixed high-order accurate DNS code for laminar turbulent transition by the method of manufactured solutions

SILVA, H. G.; SOUZA, L. F.; MEDEIROS, M. A. F.
Fonte: JOHN WILEY & SONS LTD Publicador: JOHN WILEY & SONS LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.82%
This paper presents results on a verification test of a Direct Numerical Simulation code of mixed high-order of accuracy using the method of manufactured solutions (MMS). This test is based on the formulation of an analytical solution for the Navier-Stokes equations modified by the addition of a source term. The present numerical code was aimed at simulating the temporal evolution of instability waves in a plane Poiseuille flow. The governing equations were solved in a vorticity-velocity formulation for a two-dimensional incompressible flow. The code employed two different numerical schemes. One used mixed high-order compact and non-compact finite-differences from fourth-order to sixth-order of accuracy. The other scheme used spectral methods instead of finite-difference methods for the streamwise direction, which was periodic. In the present test, particular attention was paid to the boundary conditions of the physical problem of interest. Indeed, the verification procedure using MMS can be more demanding than the often used comparison with Linear Stability Theory. That is particularly because in the latter test no attention is paid to the nonlinear terms. For the present verification test, it was possible to manufacture an analytical solution that reproduced some aspects of an instability wave in a nonlinear stage. Although the results of the verification by MMS for this mixed-order numerical scheme had to be interpreted with care...

Simultaneous Determination of Choline Citrate and Acetylmethionine in Injectable Solutions by High Performance Liquid Chromatography

ALEXANDRE, Grazielle P.; AURORA-PRADO, Maria S.; KEDOR-HACKMANN, Erika R. M.; SINGH, Anil K.; SANTORO, Maria Ines R. M.
Fonte: COLEGIO FARMACEUTICOS PROVINCIA DE BUENOS AIRES Publicador: COLEGIO FARMACEUTICOS PROVINCIA DE BUENOS AIRES
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.82%
Choline citrate (CC) and acetylmethionine (AM) are lipotropic drugs used in several pharmaceutical formulations. The objective of this research was to develop and validate a high performance liquid chromatographic (HPLC) method for simultaneous determination of CC and AM in injectable solutions, aiming its application in routine analysis for quality control of these pharmaceutical formulations. The method was validated using a Shim-Pack (R) C18 (250 x 4.6 mm, 5 mu m) column. The mobile phase was constituted of 25 mM potassium phosphate buffer solution, pH 5.7, adjusted with 10 % orthophosphoric acid, acetonitrile and methanol (88:10:2, v/v/v). The flow rate was 1.1 mL.min(-1) and the UV detection was made at 210 nm. The analyses were made at room temperature (25 +/- 1 degrees C). The method is precise, selective, accurate and robust, and was successfully applied for simultaneous quantitative determination of CC and AM in injectables.

Microbiological assay for the determination of azithromycin in ophthalmic solutions

Salgado, Hérida Regina Nunes; Roncari, Ana Flávia Ferreira
Tipo: Artigo de Revista Científica Formato: 544-549
ENG
Relevância na Pesquisa
35.88%
The validation of a simple, sensitive and specific agar diffusion bioassay, applying cylinder-plate method, for the determination of the antibiotic azithromycin in ophthalmic solutions is described. Using a strain of Bacillus subtilis ATCC 9372 as the test organism, azithromycin at concentrations ranging from 50.0 to 200.0 μg·mL-1 could be measured in 1.666 7 mg·mL-1 ophthalmic solutions. A prospective validation of the method showed that the method was linear (r = 0.999 9) and precise (RSD = 0.70) and accurate (it measured the added quantities). The results obtained by bioassay method could be statistically calculated by linear parallel model and by means of regression analysis and verified using analysis of variance (ANOVA). We conclude that the microbiological assay is satisfactory for quantification of azithromycin in ophthalmic solutions.

Accuracy of analytical-numerical solutions of the Michaelis-Menten equation

Gonzalez-Parra,Gilberto; Acedo,Luis; Arenas,Abraham
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
26.03%
It is the aim of this paper to investigate a suitable approach to compute solutions of the powerful Michaelis-Menten enzyme reaction equation with less computational effort. We obtain analytical-numerical solutions using piecewise finite series by means of the differential transformation method, DTM. In addition, we compute a global analytical solution by a modal series expansion. The Michaelis-Menten equation considered here describes the rate of depletion of the substrate of interest and in general is a powerful approach to describe enzyme processes. A comparison of the numerical solutions using DTM, Adomian decomposition and Runge-Kutta methods is presented. The numerical results show that the DTM is accurate, easy to apply and the obtained solutions retain the positivity property of the continuous model. It is concluded that the analytic form of the DTM and global modal series solutions are accurate, and require less computational effort than other approaches thus making them more convenient.

General recursive solution for one-dimensional quantum potentials: a simple tool for applied physics

Morelhão,Sérgio L.; Perrotta,André V.
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
35.76%
A revision of the recursive method proposed by S.A. Shakir [Am. J. Phys. 52, 845 (1984)] to solve bound eigenvalues of the Schrödinger equation is presented. Equations are further simplified and generalized for computing wave functions of any given one-dimensional potential, providing accurate solutions not only for bound states but also for scattering and resonant states, as demonstrated here for a few examples.

Millimeter-Scale Contact Printing of Aqueous Solutions Using a Stamp Made Out of Paper and Tape

Whitesides, George M.; Cheng, Chao-Min; Mazzeo, Aaron D.; Gong, Jinlong; Martinez, Andres W.; Phillips, Scott T.; Jain, Nina
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
35.82%
This communication describes a simple method for printing aqueous solutions with millimeter-scale patterns on a variety of substrates using an easily fabricated, paper-based microfluidic device (a paper-based “stamp”) as a contact printing device. The device is made from inexpensive materials, and it is easily assembled by hand; this method is thus accessible to a wide range of laboratories and budgets. A single device was used to print over 2500 spots in less than three minutes at a density of 16 spots per square centimeter. This method provides a new tool to pattern biochemicals—reagents, antigens, proteins, and DNA—on planar substrates. The accuracy of the volume of fluid delivered in simple paper-to-paper printing is low, and although the pattern transfer is rapid, it is better suited for qualitative than accurate, quantitative work. By patterning the paper to which the transfer occurs using wax printing or an equivalent technique, accuracy increases substantially.; Chemistry and Chemical Biology

Searching for solutions: health concerns expressed in letters to an East African newspaper column

Asera, Rosa; Bagarukayo, Henry; Shuey, Dean; Barton, Thomas
Fonte: Health Transition Centre, National Centre for Epidemiology and Population Health, The Australian National University Publicador: Health Transition Centre, National Centre for Epidemiology and Population Health, The Australian National University
Tipo: Artigo de Revista Científica Formato: 34130 bytes; application/pdf
EN_AU
Relevância na Pesquisa
35.86%
This study examined health care questions from an unusual data set: 1252 unsolicited letters written over a three–year period to an advice column in an East African newspaper. Analysis of the letters was a non-intrusive method of ascertaining prevalent health questions and opinions. People wrote seeking information, advice, solutions, and reassurance about health problems. Emotions expressed in the letters ranged from hope to fear and frustration. The written format allowed questions which are generally too embarrassing or stigmatized to present in other public or interpersonal settings. More than half the total letters raised questions about sexual behaviour, sexually transmitted diseases, and HIV/AIDS. The letters present not only personal health concerns, but also expectations of health-care quality and reflections on the medical options presently available in Uganda. As a whole, the letters express dissatisfaction not only with the outcomes of health encounters, but with the process. Of the letter writers with specific physical complaints, more than one-third had already sought medical care and were dissatisfied with the results. The letters were seeking solutions, especially for alleviation of symptoms and discomfort. Almost equally prevalent was a plea for accurate and relevant health information; people not only want to feel better...

Efficient and accurate simulation of integrate-and-fire neuronal networks in the hippocampus

Kellems, Anthony Richard
ENG
Relevância na Pesquisa
36.06%
This thesis evaluates a method of computing highly accurate solutions for network simulations of integrate-and-fire (IAF) neurons. Simulations are typically evolved using time-stepping, but since the IAF model is composed of linear first-order ODEs with hard thresholds, explicit solutions in terms of integrals of exponentials exist and can be approximated using quadrature. The technique presented here utilizes Clenshaw-Curtis quadrature to approximate these integrals to high accuracy. It uses the secant method to more precisely identify spike times, thus yielding more accurate solutions than do time-stepping methods. Additionally, modeling synaptic input with delta functions permits the quadrature method to be practical for simulating largescale networks. I determine general conditions under which the quadrature method is faster and more accurate than time-stepping methods. In order to make these methods accessible to other researchers, I introduce and develop software designed for simulating networks of IAF hippocampal cells.

Analysis and Visualization of Exact Solutions to Einstein's Field Equations

Fonte: Quens University Publicador: Quens University
EN; EN
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36.01%
Einstein's field equations are extremely difficult to solve, and when solved, the solutions are even harder to understand. In this thesis, two analysis tools are developed to explore and visualize the curvature of spacetimes. The first tool is based on a thorough examination of observer independent curvature invariants constructed from different contractions of the Riemann curvature tensor. These invariants are analyzed through their gradient fields, and attention is given to the resulting flow and critical points. Furthermore, we propose a Newtonian analog to some general relativistic invariants based on the underlying physical meaning of these invariants, where they represent the cumulative tidal and frame-dragging effects of the spacetime. This provides us with a novel and intuitive tool to compare Newtonian gravitational fields to exact solutions of Einstein's field equations on equal footing. We analyze the obscure Curzon-Chazy solution using the new approach, and reveal rich structure that resembles the Newtonian gravitational field of a non-rotating ring, as it has been suspected for decades. Next, we examine the important Kerr solution, which describes the gravitational field of rotating black holes. We discover that the observable part of the geometry outside the black hole's event horizon depends significantly on its angular momentum. The fields representing the cumulative tidal and frame-dragging forces change qualitatively at seven specific values of the dimensionless spin parameter of the black hole. The second tool we develop in this thesis is the accurate construction of the Penrose conformal diagrams. These diagrams are a valuable tool to explore the causal structure of spacetimes...

Accurate solution of structured least squares problems via rank-revealing decompositions

Castro González, Nieves; Ceballos Cañón, Johan Armando; Martínez Dopico, Froilán C.; Molera, Juan M.
Fonte: Society for Industrial and Applied Mathematics Publicador: Society for Industrial and Applied Mathematics
Tipo: info:eu-repo/semantics/publishedVersion; info:eu-repo/semantics/article
Relevância na Pesquisa
56.17%
Least squares problems min(x) parallel to b - Ax parallel to(2) where the matrix A is an element of C-mXn (m >= n) has some particular structure arise frequently in applications. Polynomial data fitting is a well-known instance of problems that yield highly structured matrices, but many other examples exist. Very often, structured matrices have huge condition numbers kappa(2)(A) = parallel to A parallel to(2) parallel to A(dagger)parallel to(2) (A(dagger) is the Moore-Penrose pseudoinverse of A) and therefore standard algorithms fail to compute accurate minimum 2-norm solutions of least squares problems. In this work, we introduce a framework that allows us to compute minimum 2-norm solutions of many classes of structured least squares problems accurately, i.e., with errors parallel to(x) over cap (0) - x(0)parallel to(2)/parallel to x(0)parallel to(2) = O(u), where u is the unit roundoff, independently of the magnitude of kappa(2)(A) for most vectors b. The cost of these accurate computations is O(n(2)m) flops, i.e., roughly the same cost as standard algorithms for least squares problems. The approach in this work relies in computing first an accurate rank-revealing decomposition of A, an idea that has been widely used in recent decades to compute...

Effect of Degassing on the Electrical Conductivity of Pure Water and Potassium Chloride Solutions

Francis, Mathew
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.82%
Recently, a significantly higher value was reported for the conductivity of pure water, in the absence of dissolved gases. These initial observations have been repeated in this study but with an improved experimental system, giving more accurate results t

Approximate Solutions of Coupled Ramani Equation by using RDTM with compared DTM and exact solutions

Gubes, Murat; Oturanc, Galip
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.86%
In this paper, we present the new approximate solutions of famous coupled Ramani Equation. In order to obtain the solution, we use the semi-analytic methods differential transform method (DTM) and reduced form of DTM called reduced differential transform method (RDTM). We compare our proposed methods with exact solution and also compare with together. Numerical results show clearly that DTM and RDTM are very effective and also provide very accurate solutions. Additionally, it should be noted that RDTM is applied very easily, fast and more convergent than DTM for these kind of problems.; Comment: 19 pages, 4 figures, Regular paper

Accurate calculation of the solutions to the Thomas-Fermi equations

Amore, Paolo; Boyd, John P.; Fernández, Francisco M.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.89%
We obtain highly accurate solutions to the Thomas-Fermi equations for atoms and atoms in very strong magnetic fields. We apply the Pad\'e-Hankel method, numerical integration, power series with Pad\'e and Hermite-Pad\'e approximants and Chebyshev polynomials. Both the slope at origin and the location of the right boundary in the magnetic-field case are given with unprecedented accuracy.

Structural and spectral properties of a family of deterministic recursive trees: Rigorous solutions

Qi, Yi; Zhang, Zhongzhi; Ding, Bailu; Zhou, Shuigeng; Guan, Jihong
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.76%
As one of the most significant models, the uniform recursive tree (URT) has found many applications in a variety of fields. In this paper, we study rigorously the structural features and spectral properties of the adjacency matrix for a family of deterministic uniform recursive trees (DURTs) that are deterministic versions of URT. Firstly, from the perspective of complex networks, we investigate analytically the main structural characteristics of DURTs, and obtain the accurate solutions for these properties, which include degree distribution, average path length, distribution of node betweenness, and degree correlations. Then we determine the complete eigenvalues and their corresponding eigenvectors of the adjacency matrix for DURTs. Our research may shed light in better understanding of the features for URT. Also, the analytical methods used here is capable of extending to many other deterministic networks, making the precise computation of their properties (especially the full spectrum characteristics) possible.; Comment: Definitive version published in Journal of Physics A: Mathematical and Theoretical

A Nonperturbative Perspective on Inner Product Quantization: Highly Accurate Solutions to the Schr{\"o}dinger Equation

Tymczak, C. J.; Japaridze, G. S.; Handy, C. R.; Wang, Xiao-Qian
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.78%
We devise a new and highly accurate quantization procedure for the inner product representation, both in configuration and momentum space. Utilizing the representation $\Psi(\xi) = \sum_{i}a_i[E]\xi^i R_{\beta}(\xi)$, for an appropriate reference function, $R_{\beta}(\xi)$, we demonstrate that the (convergent) zeroes of the coefficient functions, $a_i[E] = 0$, approximate the exact bound/resonance state energies with increasing accuracy as $i \to \infty$. The validity of the approach is shown to be based on an extension of the Hill determinant quantization procedure. Our method has been applied, with remarkable success, to various quantum mechanical problems.; Comment: Four Pages REVTEX, Three Postscript figures

Development of accurate solutions for a classical oscillator

Amore, Paolo; Sanchez, Nestor
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.89%
We present a method to obtain arbitrarily accurate solutions for conservative classical oscillators. The method that we propose here works both for small and large nonlinearities and provides simple analytical approximations. A comparison with the standard Lindstedt-Poincar\'e method is presented, from which the advantages of our method are clear.; Comment: 11 pages, 2 figures

Highly Accurate Solutions of the Blasius and Falkner-Skan Boundary Layer Equations via Convergence Acceleration

Ganapol, B. D.
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.89%
A new highly accurate algorithm for the solution of the Falkner-Skan equation of boundary layer theory is presented. The algorithm, based on a Maclaurin series representation, finds its coefficients from recurrence. In addition, Wynn-epsilon convergence acceleration and continuous analytical continuation enable an accurate evaluation. The most accurate skin friction coefficients (shooting angle) to date are presented along with comparisons to past and present values found in the literature. The algorithm, coded in FORTRAN, uses neither enhanced precision arithmetic beyond quadruple precision nor computer algebra to achieve results in a timely fashion. Key Words: Falkner-Skan flow; Blasius flow; Wynn-epsilon acceleration; Romberg acceleration; Continuous analytical continuation; Comment: 27 pages and 7 figures

A Study of detonation evolution and structure for a model of compressible two-phase reactive flow

Schwendeman, Donald; Wahle, Christopher; Kapila, Ashwani
Fonte: Taylor and Francis, Ltd Publicador: Taylor and Francis, Ltd
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
35.76%
A two-phase model of heterogeneous explosives, due to Baer and Nunziato, is examined computation- ally by a new numerical approach that is a modification of the standard Godunov scheme. The approach generates well-resolved and accurate solutions economically, and treats rationally the nozzling terms that render the otherwise hyperbolic model incapable of a conservative representation. A broad range of the parameter space is investigated and two possible structures of steady, planar detonations are identified, along with subregions of the parameter space where they exist. The transient processes subsequent to impact by a low-speed piston are studied in detail, for a variety of cases, to describe the transition from a compaction wave to one or the other of the two steady detonation waves. The findings are compared with existing computational results.; RIT community members may access full-text via RIT Libraries licensed databases: http://library.rit.edu/databases/; None

Determination of the effective dielectric constant from the accurate solution of the Poisson equation

Fonte: John Wiley & Sons Inc Publicador: John Wiley & Sons Inc
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.82%
Constant dielectric (CD) and distance-dependent dielectric (DDD) functions are the most popular and widespread in the Molecular Mechanism simulations of large molecular systems. In this article, we present a simple procedure to derive an effective dielectric constant, εout,eff, for these two methods based on numerical solutions of the Poisson equation. It was found that because of the very approximate of the CD and DDD models there is no universal εout,eff which will work equally well for all molecular systems. For example, different MD trajectories of the same molecule can produce different optimal εout,effs. The DDD function was found to yield better agreement with the numerical solutions of the Poisson equation than a CD model does. The reason is that a DDD function gives a better description of the electrostatic interactions short distances the atoms. Another interesting finding of this study is that under certain conditions εout,eff can take negative values for a system of two atoms at a limited distance range, However, in principle, there is nothing to prevent the εout,eff from taking negative values for specific conformations of some molecules.

Contributions from Dispersion and Born Self-Free Energies to the Solvation Energies of Salt Solutions

Bostrom, Mathias Anders; Ninham, Barry
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.76%
That the Born theory provides an accurate means of calculating solvation energies of ions in water has been demonstrated by Rashin and Honig (Rashin, A. A.; Honig, B. J. Phys. Chem. 1985, 89, 5588). They could fit the experimental solvation energies of a