bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Associated with Control of Type I Diabetes in Malaysian Adolescents and Young Adults
Authors: Tan S. M. K. , Shafiee Z. , Wu L. L. , Rizal A. M. , Rey J. M.
Published: October 2005

Objectives:

To examine the association between ethnicity, depression, quality of life, and diabetic control in Malaysian adolescents and young adults with type I diabetes mellitus.

Methods:

Fifty-two outpatients with type I diabetes (mean age 15.5 years) who attended a Diabetes Clinic were included. The level of HbA1c was the measure of diabetes control used (better control defined as HbA1c < 10%). Other variables were measured through questionnaires (e.g., depressive symptoms, quality of life), computerized diagnostic interviews (major depression), and medical records (e.g., demographic, family circumstances, compliance with treatment).

Results:

Ethnic Chinese youth showed better diabetic control than Malays and Indians (mean HbA1c 9.1%, 10.3%, and 11.0% respectively). Young people with better diabetic control (HbA1c < 10%) were more likely to have better quality of life and less likely to live in problematic families. When the cut-off for diabetic control was stricter (HbA1c ≤ 8%), the young person's compliance was the main predictor of poor control. Family problems were also associated with poor control but to a lesser extent. The initial association between poorer diabetes control and depression became non-significant when quality of life was taken into account.

Conclusions:

There are ethnic differences in juvenile diabetic control in this Malaysian sample which need to be understood further. Previous findings of an association between quality of life and glycemic control were verified but different definitions of good control showed different associations with individual and environmental variables. Clinicians' awareness and early intervention for psychosocial problems (for example, inadequate family support) could improve diabetes control.
Determinants of Systemic Retention: Implications for Improving Retention Practice in Higher Education
Authors: Caison Amy L.
Published: October 2005

Drawing on Tinto's (1987, 1993) theory of student integration, this research examines students who withdrew from their original institution prior to graduation. Of this group, some of the students who withdraw do so to transfer to another institution, and it is reasonable to assume that these students are different in many ways from students who withdraw and do not continue their education. Thus, the purpose of this effort is to provide a better understanding of the characteristics of students who leave their original institution so that intervention strategies can be more carefully targeted to the individual needs of these two groups. Results of the logistic regression analysis concur with some aspects of the existing literature on institutional departure; however, this study of systemic departure differs on several key points. The implications for the findings are then discussed in terms of their impact on the design institutional retention programs.
An equation‐of‐state contribution for polar components: Dipolar molecules
Authors: Gross Joachim , Vrabec Jadran
Published: October 2005

Accounting for dipolar interactions in a physically based equation of state (EOS) can substantially improve the modeling of phase equilibria of real mixtures. An EOS contribution for dipolar interactions of nonspherical molecules is developed based on a third‐order perturbation theory. Molecular simulation data for vapor–liquid equilibria of the two‐center Lennard–Jones (2CLJ) plus pointdipole fluid is used to determine model constants of the EOS. The resulting model is compared to simulation data of pure dipolar nonspherical molecules and their mixtures and an excellent agreement is found. The proposed dipole term is applied to real substances with the perturbed‐chain statistical associating fluid theory (PC‐SAFT) EOS and it is confirmed that accounting for dipolar interactions not only reduces the binary interaction parameter, but also improves the description of pure component and mixture phase equilibria. Literature values for the dipole moment can thereby be used and no further dipole‐related pure component parameter has to be adjusted. This constitutes an advantage over earlier approaches, where dipole‐related parameters were fitted to pure component data or to mixture data. © 2005 American Institute of Chemical Engineers AIChE J, 2006
Tragverhalten und Bemessung von Befestigungen mit Verbunddübeln unter Zugbeanspruchung – Teil 2: Dübelgruppen und Befestigungen am Bauteilrand
Authors: Eligehausen Rolf , Appl Jörg J. , Lehr Bernhard , Meszaros Juraj , Fuchs Werner
Published: October 2005

Im Bauwesen werden in zunehmendem Maße Dübel zur Einleitung von Lasten in den erhärteten Beton eingesetzt. Vor allem Befestigungssysteme auf der Grundlage chemischer Mörtel werden vermehrt verwendet. Allerdings fehlt bisher ein genügend genaues Berechnungsmodell zur Bemessung von beliebigen Befestigungen mit Verbunddübeln für unterschiedliche Verankerungstiefen und verschiedene chemische Mörtel.

In diesem Beitrag wird das Tragverhalten und die Bemessung von Befestigungen mit Verbunddübeln unter Zugbeanspruchung vorgestellt. Das Bemessungsmodell beruht auf dem CC‐Verfahren [1] und berücksichtigt die wesentlichen Einflußparameter auf die Bruchlast mit ausreichender Genauigkeit. Teil 1 [2] des Beitrages behandelt Einzeldübel mit großem Achs‐ und Randabstand in ungerissenem und gerissenem Beton. In diesem zweiten Teil werden Dübelgruppen mit großem Randabstand sowie Einzeldübel am Bauteilrand diskutiert.
Betontechnik für die Stelen des Holocaust‐Mahnmals in Berlin
Authors: Müller Harald S. , Schlüter Franz‐Hermann
Published: October 2005

Die 2711 Betonstelen des Holocaust‐Mahnmals in Berlin Mitte müssen hohen Anforderungen hinsichtlich ihres Erscheinungsbildes und ihrer Dauerhaftigkeit genügen. Daher sah die Ausschreibung einen zu bewehrenden Konstruktionsbeton, mit einer Mindestdruckfestigkeit von 40 N/mm2 und einer maximal zulässigen Rißbreite an der Oberfläche der Stelen von 0, 1 mm vor. Eingehende Untersuchungen zur Beanspruchung der Stelen zeigten, daß die gestellten Anforderungen wesentlich sicherer erfüllt werden können, wenn auf eine Bewehrung verzichtet wird und unerwünschte Rißbildungen allein durch betontechnologische Maßnahmen auf ein Mindestmaß beschränkt werden. Entwickelt und eingesetzt wurde schließlich ein dunkel gefärbter hochfester Beton mit selbstverdichtenden Eigenschaften.
Kontrolle der Wirksamkeit der Korrosionsschutzwirkung eines Inhibitors durch Online Monitoring
Authors: Büchler Markus , Schiegg Yves , Giessler Sabine
Published: October 2005

Die Instandsetzung von korrosionsgeschädigten Stahlbetonbauwerken ist kosten‐ und zeitintensiv. Die klassische Vorgehensweise besteht aus dem Abtrag von karbonatisiertem oder chloridbelastetem Beton und anschließender Reprofilierung. Unter gewissen Umständen ist dies nicht möglich. So kann beispielsweise die hohe Verkehrsauslastung eine Sperrung des Bauwerks praktisch unmöglich machen. Korrosionsinhibitoren, die durch einfache Sprühapplikation auf die Oberfläche des Betons aufgetragen werden, stellen eine mögliche Alternative dar. Diese Produkte sind in den meisten Fällen jedoch erst seit wenigen Jahren auf dem Markt, und Erfahrungswerte über das Langzeitverhalten liegen noch nicht ausreichend vor. Hinzu kommt, daß bei fehlerhafter Applikation keine genügende Wirksamkeit erreicht werden kann. Durch Kombination von Anwendung und meßtechnischer Überwachung der Makroelementströme und Potentiale ist es möglich, die Wirksamkeit der getroffenen Maßnahme nachzuweisen. Die langjährigen, positiven Ergebnisse einer solchen Inhibierungsmaßnahme am Beispiel von Autobahn‐Galeriestützen werden in diesem Beitrag diskutiert.
NMR evidence of a valinomycin–proton complex
Authors: Kříž Jaroslav , Makrlík Emanuel , Vaňura Petr
Published: October 2005

In addition to the well‐known complexes of valinomycin with alkali metal cations, an equimolar complex of the same compound with proton was found to be formed in nitrobenzene. Hydrogen bis(1,2‐dicarbollylide) cobaltate (HDCC) was used as a proton source. According to NMR spectra, the complex formation is quantitative at proton/valinomycin molar ratios up to 1:1 but there is fast exchange of protons between coordinated and uncoordinated valinomycin molecules at lower ratios. 1H and 13C NMR spectra show a dramatic change in the valinomycin conformation during its coordination with protons, probably from a propeller‐like to a bracelet‐like form. As valinomycin is one of the well‐known ion‐carrying ionophores facilitating especially the K+ ion transport across a biological membrane, the existence of the valinomycin‐proton complex could be important in biochemistry and biology. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 104–109, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
A thermodynamic study on the interaction between magnesium ion and human growth hormone
Authors: Saboury A. A. , Atri M. S. , Sanati M. H. , Moosavi‐Movahedi A. A. , Hakimelahi G. H. , Sadeghi M.
Published: October 2005

A thermodynamic study on the interaction between magnesium ion and human growth hormone (hGH) was studied at 27°C in NaCl solution (50 mM) using different techniques. Two techniques of ionmetry using a Mg2+selective membrane electrode and isothermal titration calorimetry were applied to obtain the binding isotherm for hGHMg2+; results obtained by both techniques were found to be in good agreement. There is a set of three identical and noninteracting binding sites for magnesium ions. The intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 46 μM and −17.7 kJ/mol, respectively. Temperature scanning UV‐visible spectroscopy was applied to elucidate the effect of Mg2+ binding on the protein stability, and circular dichroism (CD) spectroscopy was used to show the structural change of hGH due to the metal ion interaction. Magnesium ion binding increased the protein thermal stability by increasing the α‐helix content as well as decreasing both β and random coil structures. However, the secondary structural change of the protein returns to its native form, including a small change in the tertiary structure, in high concentrations of magnesium ion. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 120–126, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Detailed Structural Examinations of Covalently Immobilized Gold Nanoparticles onto Hydrogen‐Terminated Silicon Surfaces
Authors: Yamanoi Yoshinori , Shirahata Naoto , Yonezawa Tetsu , Terasaki Nao , Yamamoto Noritaka , Matsui Yoshitaka , Nishio Kazuyuki , Masuda Hideki , Ikuhara Yuichi , Nishihara Hiroshi
Published: October 2005

The modification of flat semiconductor surfaces with nanoscale materials has been the subject of considerable interest. This paper provides detailed structural examinations of gold nanoparticles covalently immobilized onto hydrogen‐terminated silicon surfaces by a convenient thermal hydrosilylation to form SiC bonds. Gold nanoparticles stabilized by ω‐alkene‐1‐thiols with different alkyl chain lengths (C3, C6, and C11), with average diameters of 2–3 nm and a narrow size distribution were used. The thermal hydrosilylation reactions of these nanoparticles with hydrogen‐terminated Si(111) surfaces were carried out in toluene at various conditions under N2. The obtained modified surfaces were observed by high‐resolution scanning electron microscopy (HR‐SEM). The obtained images indicate considerable changes in morphology with reaction time, reaction temperature, as well as the length of the stabilizing ω‐alkene‐1‐thiol molecules. These surfaces are stable and can be stored under ambient conditions for several weeks without measurable decomposition. It was also found that the aggregation of immobilized particles on a silicon surface occurred at high temperature (> 100 °C). Precise XPS measurements of modified surfaces were carried out by using a Au–S ligand‐exchange technique. The spectrum clearly showed the existence of SiC bonds. Cross‐sectional HR‐TEM images also directly indicate that the particles were covalently attached to the silicon surface through SiC bonds.
An accurate numerical solution algorithm for 3D velocity–vorticity Navier–Stokes equations by the DQ method
Authors: Lo D. C. , Young D. L. , Murugesan K.
Published: October 2005

A numerical scheme based on a differential quadrature (DQ) method is discussed for the solution of three‐dimensional velocity–vorticity Navier–Stokes equations. Numerical solutions of the six field variables, three velocities and three vorticities are obtained by adopting a coupled numerical solution procedure. Hence, it is required to specify only the velocity boundary conditions, whereas the vorticity values at the boundary are computed implicitly, thus without seeking boundary vorticity values by an iterative procedure followed in other explicit numerical schemes. Since the DQ method approximates a given differential operator with higher‐order polynomials, the vorticity definition is accurately enforced at the boundary. This ensures a divergence‐free solution for the flow field. Flow simulations obtained for a lid‐driven cubic cavity for Stokes flow and Re=100, 400 and 1000 show excellent agreements with other numerical schemes. A grid independence study demonstrates that the present numerical scheme could predict benchmark solutions with coarser meshes than other numerical schemes. Copyright © 2005 John Wiley & Sons, Ltd.
Systematic Control of Nonlinear Optical Processes Using Optimally Shaped Femtosecond Pulses
Authors: Lozovoy Vadim V. , Dantus Marcos
Published: October 2005

This article reviews experimental efforts to control multiphoton transitions using shaped femtosecond laser pulses, and it lays out the systematic study being followed by us for elucidating the effect of phase on nonlinear optical laser–molecule interactions. Starting with a brief review of nonlinear optics and how nonlinear optical processes depend on the electric field inducing them, a number of conclusions can be drawn directly from analytical solutions of the equations. From a Taylor expansion of the phase in the frequency domain, we learn that nonlinear optical processes are affected only by the second‐ and higher‐order terms. This simple result has significant implications on how pulse‐shaping experiments are to be designed. If the phase is allowed to vary arbitrarily as a continuous function, then an infinite redundancy that arises from the addition of a linear phase function across the spectrum with arbitrary offset and slope could prevent us from carrying out a closed‐loop optimization experiment. The early results illustrate how the outcome of a nonlinear optical transition depends on the cooperative action of all frequencies in the bandwidth of a laser pulse. Maximum constructive or destructive interference can be achieved by programming the phase using only two phase values, 0 and π. This assertion has been confirmed experimentally, where binary phase shaping (BPS) was shown to outperform other alternative functions, sometimes by at least on order of magnitude, in controlling multiphoton processes. Here we discuss the solution of a number of nonlinear problems that range from narrowing the second harmonic spectrum of a laser pulse to optimizing the competition between two‐ and three‐photon transitions. This Review explores some present and future applications of pulse shaping and coherent control.
Sc3N@C80: Computations on the Two‐Isomer Equilibrium at High Temperatures
Authors: Slanina Zdeněk , Nagase Shigeru
Published: October 2005

Reported herein are computations on the relative concentrations of the two experimentally known isomers of Sc3N@C80 , that is, those produced by encapsulation of Sc3N in two particular C80 cages that obey the isolated‐pentagon rule, namely, with Ih and D5h symmetries. The calculations are based on density functional methods and have been carried out using the Gibbs energy over a broad temperature interval. It has been computed that, if a relatively free motion of the encapsulate inside the cages is allowed, the observed populations of 10 and 17 % for the D5h Sc3N@C80 species are reached at temperatures of 2100 and 2450 K, respectively. The inclusion of the entropy term is essential as, if it is neglected, the D5h Sc3N@C80 population at a temperature of 2100 K would be a mere 1 %, owing to the relatively large interisomeric separation potential energy of 19 kcal mol−1.
Experimental and Computational Studies of the Phenyl Radical Reaction with Propyne
Authors: Tokmakov Igor V. , Park Joonbum , Lin Ming Chang
Published: October 2005

The kinetics for the gas‐phase reaction of phenyl radical with propyne has been measured by cavity ring‐down spectrometry (CRDS), and the mechanism and initial product branching have been elucidated with the help of quantum chemical calculations. Absolute rate constants measured by the CRDS technique can be expressed by the following Arrhenius equation: (k/cm3 mol−1 s−1): kpropyne(T=301–428 K)=(3.68±0.92)×1011exp[−(1685±80)/T]. The experiment is unable to distinguish between the possible reactive channels, but theory indicates that phenyl radicals preferably add to the unsaturated terminal carbon atom in propyne under our experimental conditions. Theoretical kinetic calculations, employing high‐level G2M(RCC, RMP2) and G3 energetic and IRCMax(RCCSD(T)//B3LYP‐DFT) molecular parameters, reproduce the total experimental rate constants within a factor of three. Calculated total and branching rate constants are provided for high‐T kinetic modeling. Addition reactions of phenyl to C3H4 are estimated to be less important molecular‐growth pathways in high‐T conditions (T>1000 K) in comparison to the C6H5+C2H2 reaction.
SiC Linked Organic Monolayers on Crystalline Silicon Surfaces as Alternative Gate Insulators
Authors: Faber Erik J. , de Smet Louis C. P. M. , Olthuis Wouter , Zuilhof Han , Sudhölter Ernst J. R. , Bergveld Piet , van den Berg Albert
Published: October 2005

Herein, the influence of silicon surface modification via SiCnH2n+1 (n=10,12,16,22) monolayer‐based devices on p‐type 〈100〉 and n‐type 〈100〉 silicon is studied by forming MIS (metal–insulator–semiconductor) diodes using a mercury probe. From current density–voltage (J–V) and capacitance–voltage (C–V) measurements, the relevant parameters describing the electrical behavior of these diodes are derived, such as the diode ideality factor, the effective barrier height, the flatband voltage, the barrier height, the monolayer dielectric constant, the tunneling attenuation factor, and the fixed charge density (Nf). It is shown that the J–V behavior of our MIS structures could be precisely tuned via the monolayer thickness. The use of n‐type silicon resulted in lower diode ideality factors as compared to p‐type silicon. A similar flatband voltage, independent of monolayer thickness, was found, indicating similar properties for all silicon–monolayer interfaces. An exception was the C10‐based monolayer device on p‐type silicon. Furthermore, low values of Nf were found for monolayers on p‐type silicon (≈6×1011 cm−2). These results suggest that SiC linked monolayers on flat silicon may be a viable material for future electronic devices.
Particle Distribution in a Microporous Material: Theoretical Concept
Authors: Meyer Marc , Currao Antonio , Calzaferri Gion
Published: October 2005

Particle distribution and exchange equilibria in a microporous host material, built up of equivalent particle sites, which are grouped in larger subsets, are described. Simplified descriptions evolve from the exact formulae in the thermodynamic limit. We find that, for example, a single zeolite A nanocrystal consisting of about 1000 pseudo‐unit‐cells fixes a lower limit for the use of the approximate formula describing particle distribution. A rational selectivity coefficient, which is approximately constant over the whole exchange range, only results if a single zeolite crystal consists of one million pseudo‐unit‐cells or more, or if a sufficiently large number of smaller crystals is considered. On the basis of the statistical particle distribution model, a closed, simple formula for the ion‐exchange isotherm is then derived, which is valid for systems involving a variable number of coupled‐exchange reactions. Its similarity to the Langmuir isotherm is discussed. The theory on ion‐exchange equilibria is used to derive formulae for the change of free‐energy, enthalpy, and entropy occurring in coupled ion‐exchange reactions. The findings, though applicable to virtually any particle exchanging system with the structural properties described above, are applied to zeolite A, since this material can be treated as a nearly ideal model. The results derived can straightforwardly be used to evaluate experimental data quantitatively, since the common inequivalence of the host sites can be taken into account.
NMR Spectroscopy Investigation of the Cooperative Nature of the Internal Rotational Motions in Acetophenone
Authors: De Luca Giuseppina , Longeri Marcello , Pileio Giuseppe , Lantto Perttu
Published: October 2005

The proton NMR spectrum of the doubly enriched acetophenone‐carbonyl,methyl‐13C2 isotopomer dissolved in a liquid‐crystalline solvent (LXNMR) was analyzed to yield a data set of 19 dipolar couplings. The presence of so many couplings, and in particular the dependence of some of them on the acetyl carbons enabled the investigation of the structure of the acetyl moiety and of possible cooperative motions about the aryl–carbonyl and carbonyl–methyl bonds. Methodological aspects, and approximations relating to the application of the vibrational correction procedure in the presence of large‐amplitude torsional motions, are discussed. Results show that it is possible to discriminate between a continuous and a discrete conformer distribution about the angle ϕ1 but not among a few proposed continuous shapes of Uiso({ϕ}). In this study, the use of dipolar couplings with a non‐negligible contribution from the indirect spin–spin coupling tensor J, (${D_{{\rm{C8C9}}} }$ in our case), for structural determination is extended from rigid to flexible molecules. The ${{1 \over 2}J_{{\rm{C8C9}}}^{{\rm{aniso}}} }$ contribution was derived theoretically using the density functional theory linear response (DFT‐LR) first‐principles calculation of the JC8C9 spin–spin coupling tensor.
Early Stages of ZnS Nanoparticle Growth Studied by In‐Situ Stopped‐Flow UV Absorption Spectroscopy
Authors: Tiemann Michael , Weiß Özlem , Hartikainen Juha , Marlow Frank , Lindén Mika
Published: October 2005

The early stages of ZnS nanoparticle growth from supersaturated solution are investigated in situ by stopped‐flow UV absorption spectroscopy with a time resolution of 1.28 ms. A model for data analysis is suggested which makes it possible to study both the average particle radius and the concentration. The average radii lie in the sub‐nanometer range. During the first 40 ms, growth is predominantly governed by ripening.
Exploiting the innate immune system to control allergic asthma
Authors: Dombrowicz David
Published: October 2005

NKT cells are key actors at the interface between innate and acquired immunity. Indeed, upon activation by glycolipid antigens, they rapidly secrete both Th1 and Th2 cytokines, which affects the development of later immune responses. Previous studies have shown that NKT cells are essential for the development of allergic asthma, a prototypical Th2‐mediated pathology. By contrast, three papers, two of which are published in this issue of the European Journal of Immunology, demonstrate, in mouse models, that treatment with α‐galactosylceramide, a specific NKT ligand, inhibits most of the parameters associated with the disease, including airway hyperreactivity, eosinophilia and IgE production. Increased IFN‐γ synthesis, rather than regulatory IL‐10, accounts for this paradoxical effect.

See accompanying articles: http://dx.doi.org/10.1002/eji.200525994 and http://dx.doi.org/10.1002/eji.200535268
Time‐dependent natural convection in a square cavity: Application of a new finite volume method
Authors: Mahdi Hashim S. , Kinney Robert B.
Published: October 2005

A new finite volume (FV) approach with adaptive upwind convection is used to predict the two‐dimensional unsteady flow in a square cavity. The fluid is air and natural convection is induced by differentially heated vertical walls. The formulation is made in terms of the vorticity and the integral velocity (induction) law. Biquadratic interpolation formulae are used to approximate the temperature and vorticity fields over the finite volumes, to which the conservation laws are applied in integral form. Image vorticity is used to enforce the zero‐penetration condition at the cavity walls. Unsteady predictions are carried sufficiently forward in time to reach a steady state. Results are presented for a Prandtl number (Pr) of 0‐71 and Rayleigh numbers equal to 103, 104 and 105. Both 11 × 11 and 21 × 21 meshes are used. The steady state predictions are compared with published results obtained using a finite difference (FD) scheme for the same values of Pr and Ra and the same meshes, as well as a numerical bench‐mark solution. For the most part the FV predictions are closer to the bench‐mark solution than are the FD predictions.
Finite element analysis of convective heat transfer in porous media
Authors: Rajamani Rajesh , Srinivas C. , Seetharamu K. N.
Published: October 2005

The finite element method is used to analyse convective heat transfer in a porous medium. Convection past a vertical surface embedded in the medium and convection in a confined porous medium enclosure are analysed using the above method. The results are compared with those available in the literature and the agreement is found to be good. The method is applicable for two‐dimensional analysis in a porous body of any arbitrary shape. The restriction of the boundary layer assumption is relaxed.
Finite element solution of the Navier–Stokes equations by a velocity–vorticity method
Authors: Guevremont G. , Habashi W. G. , Hafez M. M.
Published: October 2005

A velocity–vorticity formulation of the Navier–Stokes equations is presented as an alternative to the primitive variables approach. The velocity components and the vorticity are solved for in a fully coupled manner using a Newton method. No artificial viscosity is required in this formulation. The pressure is updated by a method allowing natural imposition of boundary conditions. Incompressible and subsonic results are presented for two‐dimensional laminar internal flows up to high Reynolds numbers.
Analysis of plane and axisymmetric flows of incompressible fluids with the stream tube method: Numerical simulation by trust‐region optimization algorithm
Authors: Clermont J. R. , De La Lande M. E. , Dinh T. Pham , Yassine A.
Published: October 2005

New concepts for the study of incompressible plane or axisymmetric flows are analysed by the stream tube method. Flows without eddies and pure vortex flows are considered in a transformed domain where the mapped streamlines are rectilinear or circular. The transformation between the physical domain and the computational domain is an unknown of the problem. In order to solve the non‐linear set of relevant equations, we present a new algorithm based on a trust region technique which is effective for non‐convex optimization problems. Experimental results show that the new algorithm is more robust compared to the Newton‐Raphson method.
Differential‐equation‐based representation of truncation errors for accurate numerical simulation
Authors: MacKinnon Robert J. , Johnson Richard W.
Published: October 2005

High‐order compact finite difference schemes for two‐dimensional convection‐diffusion‐type differential equations with constant and variable convection coefficients are derived. The governing equations are employed to represent leading truncation terms, including cross‐derivatives, making the overall O(h4) schemes conform to a 3 × 3 stencil. We show that the two‐dimensional constant coefficient scheme collapses to the optimal scheme for the one‐dimensional case wherein the finite difference equation yields nodally exact results. The two‐dimensional schemes are tested against standard model problems, including a Navier‐Stokes application. Results show that the two schemes are generally more accurate, on comparable grids, than O(h2) centred differencing and commonly used O(h) and O(h3) upwinding schemes.
Magnetohydrodynamic steady flow computations in three dimensions
Authors: Lee Seungsoo , Dulikravich George S.
Published: October 2005

A complete three‐dimensional mathematical model has been developed governing the steady, laminar flow of an incompressible fluid subjected to a magnetic field and including internal heating due to the Joule effect, heat transfer due to conduction, and thermally induced buoyancy forces. The thermally induced buoyancy was accounted for via the Boussinesq approximation. The entire system of eight partial differential equations was solved by integrating intermittently a system of five fluid flow equations and a system of three magnetic field equations and transferring the information through source‐like terms. An explicit Runge‐Kutta time‐stepping algorithm and a finite difference scheme with artificial compressibility were used in the general non‐orthogonal curvilinear boundary‐conforming co‐ordinate system. Comparison of computational results and known analytical solutions in two and three dimensions demonstrates high accuracy and smooth monotone convergence of the iterative algorithm. Results of test cases with thermally induced buoyancy demonstrate the stabilizing effect of the magnetic field on the recirculating flows.
Numerical computation of unsteady incompressible flow in complex geometry using a composite multigrid technique
Authors: Hinatsu M. , Ferziger J. H.
Published: October 2005

This paper presents a composite multigrid method and its application to a geometrically complex flow. The treatment of the interior boundary conditions within a composite multigrid strategy is described in detail for a 1D model equation. For the Navier‐Stokes equations a staggered grid technique is adopted for spatial discretization and a fractional step method is used for the time advance. Lid‐driven cavity flows are used to demonstrate the effectiveness of the method.
Numerical simulation of the reflection of a planar shock wave over a double wedge
Authors: Itoh K. , Takayama K. , Ben‐Dor G.
Published: October 2005

A numerical code based on the upwind TVD scheme for simulating the various reflection processes of a planar shock wave over a concave or convex double wedge has been developed. The numerical results were compared with actual experiments and excellent agreement was obtained. The excellent agreement serves also as a validation of the shock‐capturing performance of the numerical scheme.
Time‐dependent solutions of viscous incompressible flows in moving co‐ordinates
Authors: Rosenfeld Moshe , Kwak Dochan
Published: October 2005

A time‐accurate solution method for the incompressible Navier‐Stokes equations in generalized moving coordinates is presented. A finite volume discretization method that satisfies the geometric conservation laws for time‐varying computational cells is used. The discrete equations are solved by a fractional step solution procedure. The solution is second‐order‐accurate in space and first‐order‐accurate in time. The pressure and the volume fluxes are chosen as the unknowns to facilitate the formulation of a consistent Poisson equation and thus to obtain a robust Poisson solver with favourable convergence properties. The method is validated by comparing the solutions with other numerical and experimental results. Good agreement is obtained in all cases.
Higher‐order streamfunction‐vorticity formulation of 2D steady‐state Navier‐Stokes equations
Authors: Liao S. J.
Published: October 2005

Based on regular boundary element method and a kind of linearity invariance under homotopy, a kind of numerical scheme of 2D steady‐state Navier‐Stokes equation in streamfunction‐vorticity formulation is described. The flow inside a square cavity is used to illustrate this numerical scheme.
α‐GMRES: A new parallelizable iterative solver for large sparse non‐symmetric linear systems arising from CFD
Authors: Xu X. , Qin N. , Richards B. E.
Published: October 2005

Linearization of the non‐linear systems arising from fully implicit schemes in computational fluid dynamics often result in a large sparse non‐symmetric linear system. Practical experience shows that these linear systems are ill‐conditioned if a higher than first‐order spatial discretization scheme is used. To solve these linear systems, an efficient multilevel iterative method, the α‐GMRES method, is proposed which incorporates a diagonal preconditioning with a damping factor α so that a balanced fast convergence of the inner GMRES iteration and the outer damping loop can be achieved. With this simple and efficient preconditioning and damping of the matrix, the resulting method can be effectively parallelized. The parallelization maintains the effectiveness of the original scheme due to the algorithm equivalence of the sequential and the parallel versions.
Overlapping grids and multigrid methods for three‐dimensional unsteady flow calculations in IC engines
Authors: Tu J. Y. , Fuchs L.
Published: October 2005

A new computational methodology with emphasis on using an overlapping grid technique and a multigrid method has been developed. The main feature of the present overlapping‐grid system is of extended flexibility to deal with three‐dimensional complex multicomponent geometries. The multigrid method is incorporated into this technique to accelerate the convergence of the numerical solution. The current scheme has been applied for computations of the laminar flows in the multicomponent configuration of internal combusion engines. The flow is governed by three‐dimensional, time‐dependent, incompressible Navier‐Stokes equations with the continuity equation. A time‐independent grid system is constructed for the moving boundary, i.e. the moving piston in the engine. This grid system is entirely different from others for the same problem in previous works. The performance of the present method has been validated by comparing the results with those from an equivalent, single‐grid method and those from experiments. In addition, the flexibility and potential of the method has been demonstrated by calculating several cases which would be very difficult to be handled by other schemes.
Application of generalized differential quadrature to solve two‐dimensional incompressible Navier‐Stokes equations
Authors: Shu Chang , Richards Bryan E.
Published: October 2005

A global method of generalized differential quadrature is applied to solve the two‐dimensional incompressible Navier‐Stokes equations in the vorticity‐stream‐function formulation. Numerical results for the flow past a circular cylinder were obtained using just a few grid points. A good agreement is found with the experimental data.
Numerical simulation of a low‐emission gas turbine combustor using KIVA‐II
Authors: Yang S. L. , Chen R. , Cline M. C. , Nguyen H. L. , Micklow G. J.
Published: October 2005

A numerical study was performed to investigate chemically reactive flows with sprays inside a staged turbine combustor (STC) using a modified version of the KIVA‐II code. This STC consists of a fuel nozzle (FN), a rich‐burn (RB) zone, a converging connecting pipe, a quick‐quench (QQ) zone, a diverging connecting pipe and a lean‐combustion (LC) zone. From the computational viewpoint, it is more efficient to split the STC into two subsystems, called FN/RB zone and QQ/LC zones, and the numerical solutions were obtained separately for each subsystem. This paper addresses the numerical results of the STC which is equipped with an advanced airblast fuel nozzle. The airblast nozzle has two fuel injection passages and four air flow passages. The input conditions used in this study were chosen similar to those encountered in advanced combustion systems. Preliminary results generated illustrate some of the major features of the flow and temperature fields inside the STC. Velocity, temperature and some critical species information inside the FN/RB zone are given. Formation of the co‐ and counter‐rotating bulk flow and the sandwiched‐ring‐shaped temperature field, typical of the confined inclined jet‐in‐cross‐flow, can be seen clearly in the QQ/LC zones. The calculations of the mass‐weighted standard deviation and the pattern factor of temperature revealed that the mixing performance of the STC is very promising. The temperature of the fluid leaving the LC zone is very uniform. Prediction of the NOx emission shows that there is no excessive thermal NOx produced in the QQ/LC zones for the case studied. From the results obtained so far, it appears that the modified KIVA‐II code can be used to guide the low‐emission combustion experiments.
Surface grid generation with a linkage to geometric generation
Authors: Suzuki Masahiro
Published: October 2005

This paper describes a new method to generate surface grids over complex configurations defined by a geometric generation system. The scheme is designed for direct utilization of the surface definition provided by a geometric modeller based on a boundary representation (the so‐called B‐rep modeller). Thus, the conversion of the geometric representation for the surface grid generator is not required. Consequently, this technique eliminates not only laborious tedium in the conversion of data, but also errors in the representation of the surface induced in the process of the conversion.

The proposed method is accomplished over several stages. First, the triangulation is performed on the surface of the geometry, on which the area to be grided is laid. Then linear partial differential equations are mapped and solved on these triangular elements. Finally, the surface grid is constructed by searching for the contours inside the solution domain. After the co‐ordinate values of the grid points are obtained by a linear interpolation within each triangular element, these values are mapped onto the surface of the geometry through surface parametric functions provided by the B‐rep modeller.

An example of generating surface grid over a car configuration is given to illustrate the capability of the method.
Vectorized poisson solvers for the Navier–Stokes equations
Authors: Armfield S. W.
Published: October 2005

The advent of vector and massively parallel computers offers researchers the possibility of enormous gains in execution time for scientific and engineering programs. From the numerical point of view, such programs are frequently based on the inversion of sparse, diagonally banded matrices. Conventional scalar solvers often perform poorly on vector machines due to short effective vector lengths, and thus appropriate methods must be chosen for use with vector machines. In this paper a number of commonly used solvers are tested for the Navier–Stokes equations, in both scalar and vector form, on two vector architecture machines. A new method is presented which performs well in both vector and scalar form on a range of vector architectures.
Identification of shallow sea models
Authors: ten Brummelhuis P. G. J. , Heemink A. W. , van den Boogaard H. F. P.
Published: October 2005

In this paper we consider a parameter estimation procedure for shallow sea models. The method is formulated as a minimization problem. An adjoint model is used to calculate the gradient of the criterion which is to be minimized. In order to obtain a robust estimation method, the uncertainty of the open boundary conditions can be taken into acoount by allowing random noise inputs to act on the open boundaries. This method avoids the possibility that boundary errors are interpreted by the estimation procedure as parameter fluctuations. We apply the parameter estimation method to identify a shallow sea model of the entire European continental shelf. First, a space‐varying bottom friction coefficient is estimated simultaneously with the depth. The second application is the estimation of the parameterization of the wind stress coefficient as a function of the wind velocity. Finally, an uncertain open boundary condition is included. It is shown that in this case the parameter estimation procedure does become more robust and produces more realistic estimates. Furthermore, an estimate of the open boundary conditions is also obtained.
Non‐symmetric CG‐like schemes and the finite element solution of the advection–dispersion equation
Authors: Peters Alexander
Published: October 2005

Seven leading iterative methods for non‐symmetric linear systems (GMRES, BCG, QMR, CGS, Bi‐CGSTAB, TFQMR and CGNR) are compared in the specific context of solving the advection–dispersion equation by a classic approach: The space derivatives are approximated by linear finite elements while an implicit scheme is used to integrate the time derivatives. Convergence formulas that predict the behaviour of the iterative methods as a function of the discretization parameters are developed and validated by experiments. It is shown that all methods converge nicely when the coefficent matrix of the linear system is close to normal and the finite element approximation of the advection–dispersion equation yields accurate results.
Numerical simulation of the head‐on reflection of a regular reflection
Authors: Falcovitz J. , Alfandary G. , Ben‐Dor G.
Published: October 2005

The head‐on collision and subsequent reflection of a Regular Reflection (RR) from the end‐wall of a shock tube has been investigated both experimentally and numerically for two different incident shock wave Mach numbers and two different reflecting wedge angles.

The agreement between the double‐exposure holographic interferograms and the numerical simulations which were obtained using a GRP based numerical code, was found to be excellent in the RR region and very good behind the head‐on reflected RR.

The overall good agreement between the computed and experimental constant‐density contours (isopycnics) constitutes a validation of the computational method, including the oblique‐wall boundary condition.
Iterative solution techniques for the stokes and Navier‐Stokes equations
Authors: Ramage Alison , Wathen Andrew J.
Published: October 2005

The linear system arising from a Lagrange‐Galerkin mixed finite element approximation of the Navier–Stokes and continuity equations is symmetric indefinite and has the same block structure as a system arising from a mixed finite element discretization of a Stokes problem. This paper considers the iterative solution of such a system, comparing the performance of the one‐level preconditioned conjugate residual method for indefinite matrices with that of a more traditional two‐level pressure correction approach. Asymptotic estimates for the amount of work involved in each method are given together with the results of related numerical experiments.
Control volume finite element solution of confined turbulent swirling flows
Authors: Elkaïm D. , McKenty F. , Reggio M. , Camarero R.
Published: October 2005

A control volume finite element method that uses a triangular grid has been applied for solving confined turbulent swirling flows. To treat the velocity‐pressure coupling, the vorticity‐streamfunction formulation has been used. For turbulence effects the k‐ϵ model has been adopted. Consistent with the use of wall functions in the near‐wall regions, a boundary condition for the calculation of the vorticity at computational boundaries is proposed and used effectively. The discretized equations are obtained by making use of an exponential interpolation function. Its use has been beneficial in reducing numerical diffusion. Comparisons of the current predictions with available experimental and numerical data from the literature showed generally fair agreement.
Exact fully 3D Navier–Stokes solutions for benchmarking
Authors: Ethier C. Ross , Steinman D. A.
Published: October 2005

Unsteady analytical solutions to the incompressible Navier–Stokes equations are presented. They are fully three‐dimensional vector solutions involving all three Cartesian velocity components, each of which depends non‐trivially on all three co‐ordinate directions. Although unlikely to be physically realized, they are well suited for benchmarking, testing and validation of three‐dimensional incompressible Navier–Stokes solvers. The use of such a solution for benchmarking purposes is described.
TVD algorithms for the solution of the compressible Euler equations on unstructured meshes
Authors: Lyra P. R. M. , Morgan K. , Peraire J. , Peiró J.
Published: October 2005

The Galerkin finite element method is used as the basis for the construction of schemes for the solution of the two‐dimensional compressible Euler equations on unstructured triangular grids. The use of a side‐based data structure readily allows for the construction of a local (structured) stencil and the incorporation of a high‐resolution shock‐capturing method formulated within the TVD concept. The essential features of the finite element side‐based scheme and the ID TVD approach are described and their numerical implementation is discussed. The choice of limiters and the support for their computation are analysed and the solutions of some inviscid flows, obtained by advancing explicitly in time, are presented.
An unstructured grid algorithm for the solution of Maxwell's equations in the time domain
Authors: Morgan K. , Hassan O. , Peraire J.
Published: October 2005

The solution of problems involving the scattering of plane electromagnetic waves by perfectly conducting obstacles is considered. The governing equations are Maxwell's equations, which are expressed in a conservation form. The solution is then obtained by modifying a technique which was applied originally to the solution of the compressible Euler equations on a mesh consisting of an unstructured assembly of linear triangular elements in 3D. The computed solution can be used to determine the radar cross‐section of the scatterer.
Numerical calculation of the viscous flow around a propeller shaft configuration
Authors: Oh Keon‐je , Kang Shin‐hyoung
Published: October 2005

A viscous flow simulation method is developed to calculate the flow around a marine propeller configuration and applications to propeller flow under uniform flow conditions are presented. The continuity and Reynolds‐averaged Navier‐Stokes equations are solved in a rotating co‐ordinate system using the finite volume method. The turbulent Reynolds stresses are modelled by the modified k‐ϵ turbulence model to account for swirling flows. The general characteristics of propeller flow can be reasonably predicted in the slipstream of the propeller wake and the results of the circumferentially averaged velocity profiles show good agreement with experimental data. The tip vortex can be captured near the tip of the blade, but the strength of the vortex is weakly predicted in comparison with the measured one. The predictions of the boundary layer on the blade show reasonable agreement with measurements in the turbulent boundary layer region. However, the laminar and transitional boundary layers cannot be represented, because the flow is assumed to be turbulent in the calculation. The thrust and torque coefficients are adequately estimated in comparison with measured data for a wide range of advance coefficients.