Home About us Contact
|
Home About us Contact | ||
|
|
||
Formulation Used (formulation + used)
Selected AbstractsPower function decay of hydraulic conductivity for a TOPMODEL-based infiltration routineHYDROLOGICAL PROCESSES, Issue 18 2006Jun Wang Abstract TOPMODEL rainfall-runoff hydrologic concepts are based on soil saturation processes, where soil controls on hydrograph recession have been represented by linear, exponential, and power function decay with soil depth. Although these decay formulations have been incorporated into baseflow decay and topographic index computations, only the linear and exponential forms have been incorporated into infiltration subroutines. This study develops a power function formulation of the Green and Ampt infiltration equation for the case where the power n = 1 and 2. This new function was created to represent field measurements in the New York City, USA, Ward Pound Ridge drinking water supply area, and provide support for similar sites reported by other researchers. Derivation of the power-function-based Green and Ampt model begins with the Green and Ampt formulation used by Beven in deriving an exponential decay model. Differences between the linear, exponential, and power function infiltration scenarios are sensitive to the relative difference between rainfall rates and hydraulic conductivity. Using a low-frequency 30 min design storm with 4·8 cm h,1 rain, the n = 2 power function formulation allows for a faster decay of infiltration and more rapid generation of runoff. Infiltration excess runoff is rare in most forested watersheds, and advantages of the power function infiltration routine may primarily include replication of field-observed processes in urbanized areas and numerical consistency with power function decay of baseflow and topographic index distributions. Equation development is presented within a TOPMODEL-based Ward Pound Ridge rainfall-runoff simulation. Copyright © 2006 John Wiley & Sons, Ltd. [source] Eight-node shell element based on incompatible modesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 2 2009Desheng Xu Abstract This paper concerns the shell element formulation used for linear analysis. Introduction of hierarchical incompatible modes into the ordinary 8-node solid element is very effective to obtain the rational deflection,rotation relationship. An efficient revision scheme without using numerical volume integration is developed to ensure the satisfaction of the patch test. A lot of numerical tests are carried out for the validation of the present element. Numerical results show that the element can give satisfactory accuracy and convergence, especially for moderately thick shells. Copyright © 2008 John Wiley & Sons, Ltd. [source] A variationally consistent mesh adaptation method for triangular elements in explicit Lagrangian dynamicsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 9 2010Sudeep K. Lahiri Abstract In this paper a variational formulation for mesh adaptation procedures, involving local mesh changes for triangular meshes, is presented. Such local adaptive changes are very well suited for explicit methods as they do not involve significant computational expense. They also greatly simplify the projection of field variables from the old to the new meshes. Crucially, the variational nature of the formulation used to derive the equilibrium equations at steps where adaptation takes place ensures that conservation of linear and angular momentum is obtained (Int. J. Numer. Meth. Engng 2000; 49:1295,1325). Several examples in 2-D showing the application of the proposed adaptive algorithms are used to demonstrate the validity of the methodology proposed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Variance-reduced Monte Carlo solutions of the Boltzmann equation for low-speed gas flows: A discontinuous Galerkin formulationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2008Lowell L. Baker Abstract We present and discuss an efficient, high-order numerical solution method for solving the Boltzmann equation for low-speed dilute gas flows. The method's major ingredient is a new Monte Carlo technique for evaluating the weak form of the collision integral necessary for the discontinuous Galerkin formulation used here. The Monte Carlo technique extends the variance reduction ideas first presented in Baker and Hadjiconstantinou (Phys. Fluids 2005; 17, art. no. 051703) and makes evaluation of the weak form of the collision integral not only tractable but also very efficient. The variance reduction, achieved by evaluating only the deviation from equilibrium, results in very low statistical uncertainty and the ability to capture arbitrarily small deviations from equilibrium (e.g. low-flow speed) at a computational cost that is independent of the magnitude of this deviation. As a result, for low-signal flows the proposed method holds a significant computational advantage compared with traditional particle methods such as direct simulation Monte Carlo (DSMC). Copyright © 2008 John Wiley & Sons, Ltd. [source] Kinetic parameters for step and flash imprint lithography photopolymerizationAICHE JOURNAL, Issue 2 2006Michael D. Dickey Abstract Step and Flash Imprint Lithography (SFIL) is a high-resolution, yet low-cost nanopatterning technique that employs an acrylate-based, free-radical photo-polymerization to replicate a patterned template onto a substrate. Modeling the photo-polymerization requires knowledge of the values of several reaction parameters, which are unique to the acrylate formulation used in SFIL. The values of these parameters were experimentally determined for use in a previously described kinetic model. The rate coefficient for initiation, kI, was determined by measuring the absorbance spectrum of the initiator, Darocur® 1173, and convolving it with the intensity spectrum from the irradiation source. The reaction coefficients kp and kt were measured using the dark polymerization method. The experimental values of both parameters were then mathematically modeled to reflect the changes that occur as a function of conversion. Measuring the kinetic parameters provides insight into the fundamental steps involved in the polymerization. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] TEOS,colloidal silica,PDMS-OH hybrid formulation used for stone consolidationAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2010Carmen Salazar-Hernández Abstract The consolidation of materials concept, which consists of introducing a chemical substance (consolidant) into degraded stone, has been applied to architectural conservation. Silicon compounds such as tetraethoxysilane (TEOS) are frequently used as a base for commercial consolidant formulations due to their ability to form a siloxane polymer such as SiO2. However, the silica xerogels deposited into the stone show poor performance and the gels obtained are non-porous and tend to crack during the drying stage. In order to avoid the fractures and to improve gel properties, we propose the synthesis of a hybrid consolidant based on TEOS and fillers such as colloidal silica (200 nm in diameter) and hydroxy-terminated polydimethylsiloxane (PDMS-OH). Both additives enhance gel properties such as porosity and elasticity, leading to the formation of non-fractured and permeable gels. Characterization of the hybrid xerogel was carried out by nitrogen adsorption and 29Si MAS-NMR. The properties of the hybrid xerogels were compared with those prepared from a formulation based on TEOS (T-ME) with a composition similar to a commercial product. In order to evaluate the effectiveness of the hybrid consolidant, it was applied to tuff-stone of historical monuments in the city of Guanajuato, Mexico. The tuff-stone was also treated with the formulation T-ME. Both treatments were studied by determining the percentage of consolidant deposited, evaluating changes in porosity and hardness of the treated stone. The applicability of the hybrid consolidant for the decayed tuff-stone is under study. Copyright © 2010 John Wiley & Sons, Ltd. [source] | |||||||||||||