bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance and limitations of the unsteady RANS approach
Authors: Schwarze Rüdiger , Obermeier Frank 
Published: January 2007

AbstractTurbulent flows in complex geometries often exhibit an oscillating behavior of large coherent structures, even in the case of steady state boundary conditions. Recently, numerous efforts have been made to resolve these oscillations by means of numerical simulations. Unfortunately, large‐eddy simulations are often very time‐ and memory‐consuming in the case of complex flows. Therefore, the unsteady RANS (URANS) approach is an attractive alternative, especially when numerical simulations are used as a design and optimization tool.Here, two complex flow situations are presented, the tundish flow and a jet in a crossflow. For these flows, relationships between the Strouhal number and important flow parameters are known from experiments. In the paper, URANS models are applied to resolve those relationships also numerically. The evaluation of the numerical results demonstrates the abilities and the limitations of the URANS approach when resolving the dynamics of large coherent structures in complex flows. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of the Propagation Direction for an Acoustic Wave Interacting with a Turbulent Premixed Flame
Authors: Shalaby Hemdan , Thévenin Dominique 
Published: January 2007

AbstractWe investigate in this work the conditions leading to amplification or damping of a planar, Gaussian acoustic wave interacting with a CO/H2/Air turbulent premixed flame. We examine in particular the influence of the direction of propagation. In a first case the acoustic wave is coming from the right direction (starting in burnt gas zone), while it propagates from the left direction (starting in fresh gas zone) in the second case. This investigation is based on fully compressible Direct Numerical Simulation (DNS) results. Chemical processes are computed using a complete reaction scheme and accurate transport properties are taken into account. A local version of the classical Rayleigh's criterion is used to analyze the results, based on the single assumption that the celerity of sound is independent of time and only function of the spatial coordinates. We observe that, after the interaction, the wave is wrinkled leading to a non‐planar geometry, similar to that of the initial flame front. For both cases the heat release fluctuation is concentrated in very small zones, associated either with positive or negative values. Rayleigh's criterion is then used to localize large positive and negative values (amplification resp. damping conditions). This criterion shows that wave amplification occurs only inside well‐located small zones in the two cases. The propagation direction has no influence on these results, confirming that amplification or damping is mainly controlled by a coupling process between pressure and heat release fluctuations through the chemical reactions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaporation and condensation of a binary mixture of vapors
Authors: Yasuda Shugo , Takata Shigeru , Aoki Kazuo 
Published: January 2007

AbstractHalf‐space problem of evaporation and condensation of a binary mixture of vapors is investigated on the basis of the linearized Boltzmann equation for hard‐sphere molecules with the complete condensation condition. The problem is analyzed numerically by a finite‐difference method, in which the complicated collision integrals are computed by the extension of the method proposed by Y. Sone, T. Ohwada, and K. Aoki [Phys. Fluids A 1, 363 (1989)] to the case of a gas mixture. As a result, the behavior of the mixture is clarified not only at the level of the macroscopic quantities but also at the level of the velocity distribution function. In addition, accurate formulas of the temperature, pressure, and concentration jumps caused by the evaporation and condensation are constructed for arbitrary values of the concentration of the background reference state by the use of the Chebyshev polynomial approximation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling free surfaces in oscillating pipe flows
Authors: Adler Katrin , Schwarze Rüdiger , Chaves Humberto 
Published: January 2007

AbstractAn oscillating pipe flow with a free surface is investigated numerically and experimentally. The pipe diameter is 12mm. Due to this small diameter capillary forces play an important role. Therefore special attention has to be paid to the flow field near the free surface. The numerical model is based on the fundamental flow equations. The free surface is resolved according to the volume‐of‐fluid method. The model equations are solved on a moving grid. In the experiment, pictures of the flow field are taken near the free surface. The effects occuring near the interface will be presented here. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimentelle Untersuchung des Temperaturfelds in einem Extruder
Authors: Conzen Carsten , Wünsch Olaf 
Published: January 2007

AbstractExtruder werden im Maschinenbau und in der Verfahrenstechnik zur Förderung und Homogenisierung von hochviskosen Flüssigkeiten, wie z. B. Kunststoffschmelzen verwendet. Diese besitzen neben der temperatur‐ und schergeschwindigkeitsabhängigen Viskosität eine sehr geringe thermische Leitfähigkeit. Durch Dissipation im Fluid bildet sich so ein Temperaturfeld aus. Mit dem verwendeten Doppelschneckenextruder wird das Temperatur‐ und Druckfeld sowie integrale Größen wie Durchsatz und Leistung untersucht. Die Ergebnisse werden mit numerischen Simulationen verglichen. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bistable Resonance In Gravity‐driven Film Flows
Authors: Heining C. , Wierschem A. , Aksel N. 
Published: January 2007

AbstractWe study the flow of a viscous liquid down an inclined plane with a sinusoidal bottom profile. Applying the integral boundarylayer method leads to a nonlinear ordinary differential equation for the film thickness. Linear resonance between the free surface and the bottom contour is observed via a regular perturbation approach. Considering nonlinear contributions, the resonance curve shows a foldover effect which is typical for nonlinear oscillators. In order to understand the origin of this bistable behaviour we derive a simple model equation and show an analogy to the Duffing oscillator. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pressure distributions in a channel with a backward facing step
Authors: Jonáš Pavel , Mazur Oton , Uruba Václav 
Published: January 2007

AbstractUnderstanding of the process of a turbulent shear flow separation and reattachment is an important task of fluid dynamics. Channel flow with a step expansion on one wall is the simplest reattaching flow in view of the facts that the separation line is defined, the flow region geometry is easy to describe for the mathematical and physical modelling requirements, the experimental arrangement design is not difficult and it is repeatable in another laboratory exactly. These reasons were the motivation for the introductory experiments reported in [1] and for the continuation in the investigation of the assembly of new configurations using more sophisticated experimental methods. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Admixture stratification in the stagnation region of two streams
Authors: Lebedeva N. A. , Osiptsov A. N. 
Published: January 2007

AbstractA self‐similar 2D steady‐state flow of two immisible viscous fluids with inertial particles is considered. It is assumed that two viscous streams, one of which contains the particles, collide forming a flat interface with a stagnation point. The general case is discussed, when the fluids have different viscosities and densities and the streams are directed at arbitrary angles. The far field corresponds to inviscid vortex flow near an “oblique” stagnation point. The limiting case of viscous dusty flow near a rigid plane is studied in detail within one‐way and two‐way coupling approximations. Thin zones of particle accumulation are detected. Threshold parameters corresponding to the change of flow regime are found. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shear Viscosity of the Gaussian Core Model Fluid
Authors: Mausbach P. , May H.‐O. 
Published: January 2007

AbstractBy means of molecular dynamics simulations we investigated the shear viscosity of the Gaussian Core Model fluid. We observed anomalous viscous behaviour for dimensionless densities greater than 0.3 and dimensionless temperatures below 0.04. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wavelets on Regular Surfaces Generated by Stokes Potentials
Authors: Mayer Carsten 
Published: January 2007

AbstractBy means of the limit and jump relations of potential theory with respect to the Stokes equations the framework of a tensorial wavelet approach on a regular (Lyapunov‐) surface is established. The setup of a multiresolution analysis is defined by interpreting the kernel functions of the limit and jump integral operators as scaling functions on the regular surfaces. The distance of the parallel surface to the surface under consideration thereby represents the scale level in the scaling function. Tensorial scaling functions and wavelets show space localizing properties. Thus, they can be used to represent vector fields locally on a regular surface. Furthermore, these functions can be used as ansatz functions for the discretization of Fredholm integral equations of the second kind which result from the Stokes boundary‐value problems with respect to a regular surface. By this, scaling functions and wavelets enable us to give a multiscale representation of the solution of the Stokes problem. This representation will be demonstrated in a concrete example. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Viscosity Characterisation for Rubber Blends from Die Swell Data by means of a Genetic Algorithm
Authors: Müllner Herbert W. , Eberhardsteiner Josef , Hofstetter Karin 
Published: January 2007

AbstractThe goal of this contribution is the identification of the interaction of the typical swelling behaviour of viscoelastic fluids and the viscosity of the investigated rubber blends in the context of an extrusion process. By adaptation the fitness equation of the used genetic algorithm it is possible to study the influence of the die swell on viscous properties. With this knowledge a more realistic simulation of the die swell phenomenon and its influence on the resulting profile geometry is possible. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of the filling behavior of a Non‐Newtonian Fluid
Authors: Rudert Alexander , Schwarze Rüdiger 
Published: January 2007

AbstractA numerical model for free surface flows of non‐newtonian liquids which are injected into a cavity is presented. These flows are regarded as a basic model of injection molding. Model experiments of the injection process are performed with a water‐based gel.The flow equations are integrated according to the finite‐volume‐method. The volume of fluid method (VoF) is employed in order to describe the free surface flow of two incompressible phases, the phase interface is resolved by the method of geometric reconstruction. The Herschel‐Bulkley model is used in order to describe shear‐thinning behavior of the molding material and the effects of a yielding point.Different patterns of the filling flow depending on the injection parameters are evident in the experiment and the simulation. They are characterized and arranged with respect to the similarity parameters of the flow. Again, the results of the simulation are found to agree well with the experimental observations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mixed Convection Flow Past a Horizontal Plate: The Trailing Edge
Authors: Savić Lubomir , Steinrück Herbert 
Published: January 2007

AbstractThe mixed convection flow past a horizontal plate which is aligned under a small angle of attack to a uniform free stream will be considered in the limit of large Reynolds number and small Richardson number close to the trailing edge. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flow instabilities in thermocapillary liquid pools
Authors: Schoisswohl U. , Kuhlmann H. 
Published: January 2007

AbstractThe instability of steady axisymmetric thermocapillary flow in liquid pools heated from above is investigated numerically. The conditions for the onset of three‐dimensional motion depend on the thermal conditions as well as the geometrical constraints. The critical Reynolds number is calculated as a function of the Prandtl number for a cylindrical pool of unit aspect ratio. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mixed Convection Flow Past a Horizontal Plate: The Global Flow
Authors: Steinrück Herbert , Savić Ljubomir 
Published: January 2007

AbstractThe mixed convection flow past a horizontal plate which is aligned under a small angle of attack to a uniform free stream will be considered in the limit of large Reynolds number and small Richardson number. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of amyl acetate sorption on mechanical and thermal properties of polypropylene packaging
Authors: Safa Laurent , Abbès Boussad , Zaki Oussama 
Published: January 2007

AbstractSorption kinetics of amyl acetate in polypropylene is studied at 23, 40 and 55°C. Diffusion (D) and partition (Kp) coefficients were determined by fitting the sorption curves with a theoretical curve calculated from Fick's diffusion equation. The role of temperature and concentration of amyl acetate was investigated. The results show that D is not affected and Kp decreases with increasing concentration of amyl acetate in the solution. The sorption rate or total amount absorbed increased considerably with temperature. Concentration profiles were calculated by using a numerical algorithm based on a finite element method. The effect of amyl acetate concentration on the mechanical and thermal properties of the polymer was investigated. Copyright © 2007 John Wiley & Sons, Ltd.
Which constructs can predict emotional exhaustion in a working population? A study into its determinants
Authors: Michielsen Helen J. , Croon Marcel A. , Willemsen Tineke M. , De Vries Jolanda , Van Heck Guus L. 
Published: January 2007

AbstractThe main objective of this study was to examine the psychosocial stress model developed by Taylor and Aspinwall with emotional exhaustion as the outcome variable. Respondents, 409 men and 346 women, who had a paid job for at least 20 hours per week, completed questionnaires concerning demographic variables, personality, temperament, work pressure, workload, perceived social support, appraisal, coping, and emotional exhaustion. Structural equation analyses provided only partial support for the validity of the model. First, on theoretical and statistical grounds, one more path linking external resources to social support was added. Second, contrary to expectations, coping styles did not predict emotional exhaustion. To conclude, when coping is measured retrospectively, it does not add to our understanding of emotional exhaustion. It is suggested that future studies should be longitudinal and include objective measures of stressors and psychosocial health outcomes in addition to self‐reports. Copyright © 2007 John Wiley & Sons, Ltd.
Performance may predict natural killer cell activity after an acute time‐limited stressor
Authors: Lamkin Donald M. , Bloom Christopher M. , Michaels Zachary J. , Hunter Evelyn , Aguilar Miriam , Venard Jacob , Barnett Jeanne K. 
Published: January 2007

AbstractMuch attention has been given to natural killer cell activity (NKCA) in acute stressor research. While many studies show that acute stressors increase NKCA, fewer studies have investigated the variability in NKCA within an experimental group that is associated with performance. In his ‘Toughness’ theory of arousal, Richard Dienstbier suggests that behavioural performance during an acute stressor task could account for a variability in NKCA. We were not aware of any human studies that had investigated this possibility. Thus, in the present study we tested Dienstbier's proposal in a group of male and female human participants (n = 25) who completed a 4‐min serial subtraction mental arithmetic task. Blood samples were taken before and after the task. Controlling for baseline NKCA, performance score significantly predicted post‐task NKCA, β = 0.455, p = 0.01, and accounted for 25 per cent of the variance. Coincidence test showed no significant difference between men and women in predicting post‐task NKCA on performance score. Thus, in addition to evidence in the animal literature, the present study provides evidence that performance on an acute stressor is associated with enhanced NKCA in humans. Copyright © 2007 John Wiley & Sons, Ltd.
Productivity and optimum plant density of pigeonpea in different environments in Tanzania
Authors: MLIGO J. K. , CRAUFURD P. Q. 
Published: January 2007

SUMMARYThe objective of the present study was to determine the optimum plant density of four pigeonpea genotypes, representing early, medium and late maturing types, grown in five contrasting environments in Tanzania. ICPL 86005 (early), Kat 50/3 and QP 37 (medium) and Local (late) were grown at four plant densities (40 000–320 000 plants/ha) in irrigated and rainfed conditions at Ilonga and under rainfed conditions at Kibaha, Selian and Ismani. At maturity, total above-ground biomass and seed yield (SY) were measured. The highest yields were obtained in the irrigated experiment at Ilonga, where the medium/late genotypes produced 25 t biomass/ha and 5·6 t seed/ha. The lowest SY were at Kibaha, 0·58 to 1·76 t/ha, where a severe drought occurred. In nearly all cases the response to density was linear or asymptotic. The response of ICPL 86005 was significantly different from the other three genotypes. The optimum density for SY varied from 37 000 to 227 000 plants/ha in ICPL 86005, compared with 3000 to 101 000 plants/ha in the medium/late genotypes. The highest optimum density was at Selian and Ismani and the lowest at Ilonga and Kibaha, where drought occurred. Optimum densities therefore varied greatly with genotype (duration) and environment, and this variation needs to be considered when planning trials.
Immobilization antibodies of tiger puffer Takifugu rubripes induced by i.p. injection against monogenean Heterobothrium okamotoi oncomiracidia do not prevent the infection
Authors: UMEDA N. , HATANAKA A. , HIRAZAWA N. 
Published: January 2007

SUMMARYWe examined whether infection by the monogenean Heterobothrium okamotoi induces production of specific antibodies against oncomiracidia and their cilia, larvae on the gills, and adults on the branchial cavity wall of tiger puffer Takifugu rubripes. We also investigated whether specific antibody production participates in acquired protection against H. okamotoi. Sera from persistently infected fish immobilized H. okamotoi oncomiracidia 89 days after exposure and antibody levels (measured by enzyme-linked immunosorbent assays) in the sera against oncomiracidia and their cilia increased compared with sera from control (naïve) fish. Antibody levels in these sera against the larvae and adult stages did not increase. The number of H. okamotoi on persistently infected fish was significantly lower than for control fish (P<0·05) when persistently infected fish and control fish were exposed to oncomiracidia in the same tank. Thus tiger puffer produced specific antibodies against oncomiracidia and their cilia, and acquired partial protection against H. okamotoi. Intraperitoneal injection of proteins of sonicated oncomiracidia or their cilia with an adjuvant also produced oncomiracidium agglutination antibodies in sera from tiger puffer; the antibody levels in these sera against oncomiracidia and their cilia increased compared with sera from control fish (injection of BSA with an adjuvant) at 14, 44, and 75 days after the booster immunization. However, in a parasite challenge at 54–58 days after the booster immunization, the infection levels of fish immunized with parasites of sonicated oncomiracidia or their cilia were the same as the control fish. Western blot showed that sera from persistently infected fish and fish immunized with sonicated oncomiracidia or their cilia recognized similar antigenic bands, suggesting that tiger puffer tends to react against these antigens compared with other antigens. These results indicated that specific antibodies against these cilia and oncomiracidia induced by i.p. injection do not prevent H. okamotoi infection.
Comparative genomics and disorder prediction identify biologically relevant SH3 protein interactions
Authors: Beltrao Pedro , Serrano Luis 
Published: January 2007

AbstractProtein interaction networks are an important part of the post-genomic effort to integrate a part-list view of the cell into system-level understanding. Using a set of 11 yeast genomes we show that combining comparative genomics and secondary structure information greatly increases consensus-based prediction of SH3 targets. Benchmarking of our method against positive and negative standards gave 83% accuracy with 26% coverage. The concept of an optimal divergence time for effective comparative genomics studies was analyzed, demonstrating that genomes of species that diverged very recently from Saccharomyces cerevisiae (S. mikatae, S. bayanus, and S. paradoxus), or a long time ago (Neurospora crassa and Schizosaccharomyces pombe), contain less information for accurate prediction of SH3 targets than species within the optimal divergence time proposed. We also show here that intrinsically disordered SH3 domain targets are more probable sites of interaction than equivalent sites within ordered regions. Our findings highlight several novel S. cerevisiae SH3 protein interactions, the value of selection of optimal divergence times in comparative genomics studies, and the importance of intrinsic disorder for protein interactions. Based on our results we propose novel roles for the S. cerevisiae proteins Abp1p in endocytosis and Hse1p in endosome protein sorting.
Improved usability of the minimal model of insulin sensitivity based on an automated approach and genetic algorithms for parameter estimation
Authors: Morbiducci Umberto , Di Benedetto Giacomo , Kautzky-Willer Alexandra , Pacini Giovanni , Tura Andrea 
Published: January 2007

Minimal model analysis of glucose and insulin data from an IVGTT (intravenous glucose tolerance test) is widely used to estimate insulin sensitivity; however, the use of the model often requires intervention by a trained operator and some problems can occur in the estimation of model parameters. In the present study, a new method for minimal model analysis, termed GAMMOD, was developed based on genetic algorithms for the estimation of model parameters. Such an algorithm does not require the fixing of initial values for the parameters (that may lead to unreliable estimates). Our method also implements an automated weighting scheme not requiring manual intervention of the operator, thus improving the usability of the model. We studied a group of 170 women with a history of previous gestational diabetes. Results obtained by GAMMOD were compared with those obtained by MINMOD (a traditional gradient-based algorithm for minimal model analysis). Insulin sensitivity by GAMMOD was (3.86±0.19) compared with (4.33±0.20)×10−4 μ-units·ml−1·min−1 by MINMOD; glucose effectiveness was 0.0236±0.0005 compared with 0.0229±0.0005 min−1 respectively. The difference in the estimation by the two methods was within the precision expected for such metabolic parameters and is probably of no clinical relevance. Moreover, both the coefficient of variation of the estimated parameters and the error of fit were generally lower in GAMMOD, despite the fact that it does not require manual intervention. In conclusion, the GAMMOD approach for parameter estimation in the minimal model provides a reliable estimation of the model parameters and improves the usability of the model, thus facilitating its further use and application in a clinical context.