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Governing Parameters (governing + parameter)
Selected AbstractsThe influence of grout and bentonite slurry on the process of TBM tunnelling.GEOMECHANICS AND TUNNELLING, Issue 3 2009Der Einfluss von Ringspaltmörtel und Bentonitsuspension auf den TBM-Vortrieb Abstract The bentonite and grout flow around a TBM is elaborated, as well as grout flow along the lining. The calculated grout flow along the lining is compared with the results of measurements. Measurement data for the flow around the TBM are not available. Both the bentonite and the grout are modelled as a Bingham liquid and it will be shown that, due to the relatively low flow velocities, the yield stress is the governing parameter. The results of the calculations show that both the flow around the TBM and the flow around the lining may significantly influence loading on the TBM, the soil, and the lining. The bentonite and grout flow around the TBM may result in a lower volume loss than calculated when assuming that the soil follows the tapered TBM. The grout flow and especially grout consolidation lead to lower pressures around the lining if the tunnel is constructed in sandy soil. Der Bentonit- und Mörtelfluss um eine TBM und der Mörtelfluss entlang der Auskleidung werden diskutiert. Der berechnete Mörtelfluss entlang der Auskleidung wird mit Messdaten verglichen. Für die Strömungen um eine TBM existieren keine Messdaten. Sowohl der Bentonit als auch der Mörtel werden als Bingham Flüssigkeit modelliert, und es wird gezeigt, dass wegen der relativ niedrigen Strömungsgeschwindigkeiten die Fließspannung der bestimmende Parameter ist. Die Ergebnisse der Berechnungen zeigen, dass sowohl die Strömung um die TBM als auch entlang der Auskleidung einen bedeutenden Einfluss auf die Belastung der TBM, des Bodens und der Auskleidung haben. Der Bentonit- und Mörtelfluss um die TBM kann einen niedrigeren Volumenverlust zur Folge haben als berechnet, wenn man annimmt, dass der Boden der konisch zulaufenden TBM folgt. Der Mörtelfluss und besonders die Mörtelverfestigung führen zu einem niedrigeren Druck auf die Auskleidung wenn der Tunnel in sandigem Boden errichtet wird. [source] The influence of electrospinning parameters on the structural morphology and diameter of electrospun nanofibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Valencia Jacobs Abstract Electrospinning is a simple method of producing nanofibers by introducing electric field into the polymer solutions. We report an experimental investigation on the influence of processing parameters and solution properties on the structural morphology and average fiber diameter of electrospun poly ethylene oxide (PEO) polymer solution. Experimental trials have been conducted to investigate the effect of solution parameters, such as concentration, molecular weight, addition of polyelectrolyte in PEO solution, solvent effect, as well as governing parameter, such as applied voltage. The concentration of the aqueous PEO solution has shown noteworthy influence on the fiber diameter and structural morphology of electrospun nanofibers. At lower concentrations of PEO polymer solution, the fibers showed irregular morphology with large variations in fiber diameter, whereas at higher concentrations, the nanofibers with regular morphology and on average uniform fiber diameter were obtained. We find that the addition of polyelectrolytes, such as sodium salt of Poly acrylic acid (PAA) and Poly allylamine hydrochloride (PAH), increases the conductivity of PEO solutions and thereby decreases the bead formation in electrospun nanofibers. The increase in applied voltage has been found to affect the structural morphology of nanofiber while the addition of ethanol in PEO solution diminishes the bead defects. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Prediction of Onset of Corrosion in Concrete Bridge Decks Using Neural Networks and Case-Based ReasoningCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2005G. Morcous It is based on the integration of artificial neural network (ANN), case-based reasoning (CBR), mechanistic model, and Monte Carlo simulation (MCS). A probabilistic mechanistic model is used to generate the distribution of the time to corrosion initiation based on statistical models of the governing parameters obtained from field data. The proposed ANN and CBR models act as universal functional mapping tools to approximate the relationship between the input and output of the mechanistic model. These tools are integrated with the MCS technique to generate the distribution of the corrosion initiation time using the distributions of the governing parameters. The proposed methodology is applied to predict the time to corrosion initiation of the top reinforcing steel in the concrete deck of the Dickson Bridge in Montreal. This study demonstrates the feasibility, adequate reliability, and computational efficiency of the proposed integrated ANN-MCS and CBR-MCS approaches for preliminary project-level and also network-level analyses. [source] Effect of double stratification on mixed convection heat and mass transfer from a vertical surface in a fluid-saturated porous mediumHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2010V.J. Bansod Abstract This paper presents the mixed convection heat and mass transfer near a vertical surface in a stratified porous medium using an integral method. The conservation equations that govern the problem are reduced to a system of coupled non-linear ordinary differential equations, which is then reduced into a single algebraic equation using exponential profiles for the temperature and concentration. The results for heat and mass transfer rates in terms of Nusselt and Sherwood number are presented for a wide range of governing parameters like the buoyancy ratio (N), Lewis number (Le), flow driving parameter (Ra/Pe), in addition to both thermal and solutal parameters (S and R). The results indicate that the stratification effects have considerable influence on both the heat and mass transfer rates. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/htj.20300 [source] On the analytical solution of the Bejan-Khair equation arising in free convection in porous mediaHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2010V.J. Bansod Abstract This paper revisits the fundamental problem of free convection heat and mass transfer over a heated vertical surface embedded in a porous medium using analytical techniques. An integral procedure is applied to the boundary layer similar equation for the combined heat and mass transfer from a vertical surface in a porous medium. The analytical approximations have covered a wide range of governing parameters of the problem. The results for both Nusselt and Sherwood numbers agree well with numerical results published in the literature. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20297 [source] Modeling particle inflation from poly(amic acid) powdered precursors.POLYMER ENGINEERING & SCIENCE, Issue 5 2007Morphological characteristics of polyimide microstructures obtained by solid-state powder foaming determine the geometric properties of the unit cell, in polyimide foams prepared by this process. Morphological analysis of precursor particles has shown that particle size and shape, as well as the presence of embedded microvoids, exert a strong influence on the final microstructure morphology. Of equal importance in the morphological development are processing conditions such as heating rate and primary blowing agent content in the particles, prior to thermal treatment. In the present paper, the first of two numerical schemes is presented. A numerical model has been developed to study the preliminary stages that lead to particle inflation. Based on this model, a parametric analysis is performed for pertinent governing parameters, with the purpose of determining their effect on the onset of particle inflation and the potential morphological characteristics of polyimide microstructures. It has been found that precursor particle morphology and nuclei density are the key parameters in determining the potential morphology of the microstructures, by limiting the number of bubbles that grow within each particle. POLYM. ENG. SCI., 47:560,571, 2007. © 2007 Society of Plastics Engineers. [source] Quantitative analogue flume-model study of river,shelf systems: principles and verification exemplified by the Late Quaternary Colorado river,delta evolutionBASIN RESEARCH, Issue 3 2001M. W. I. M. Van Heijst ABSTRACT Physical modelling of clastic sedimentary systems over geological time spans has to resort to analogue modelling since full scaling cannot be achieved within the spatial and temporal restrictions that are imposed by a laboratory set-up. Such analogue models are suitable for systematic investigation of a sedimentary system's sensitivity to allocyclic changes by isolating governing parameters. Until now, analogue models of landscape evolution were mainly qualitative in nature. In this paper, we present a quantitative approach. The quantitative experimental results are verified and discussed by comparison with high-resolution data from the Colorado river,shelf system of the Texas shelf that we used as a prototype. The model's dimensions are proportionally scaled to the prototype, except for a vertical exaggeration. Time is scaled using a Basin Response factor to maintain a similar ratio between the period of change and the system's equilibrium time for model and prototype. A Basin Fill factor was used to compare the ratio between the time-averaged sedimentation rate and the rate of change in accommodation space of model and prototype. The flume-model results are in the form of sediment budgets that are related to shelf cannibalism and fluvial supply, which are compared with the ancestral Colorado river,delta evolution of the last 40 kyr. Model and prototype have similarities in delta evolution in response to one cycle of sea-level change. With sea-level change as the isolated variable, the flume model generates a significant supply pulse caused by headward erosion of the shelf in response to the sea-level fall. This pulse adds to the yield of the hinterland. The supply induced by sea-level change persists during the early rise, although its rate declines. A similar trend is observed on the east Texas shelf. We argue that shelfal and fluvial degradation cycles induced by sea-level changes can significantly influence the timing and amount of sediment supply to basins and must therefore be taken into consideration. [source] | |||||||||||||