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Complex Equations (complex + equation)

Distribution by Scientific Domains

Engineering	60%

Selected Abstracts

China and Northeast Asia: A Complex Equation for ,Peaceful Rise'

POLITICS, Issue 3 2007
Jae Ho Chung
This article tackles the question: has China become more proactive and willing to resolve regional problems unilaterally, bilaterally or multilaterally? It suggests that, while China has clearly become more proactive in facilitating regional stability and co-operation, it still has to overcome certain perceptual hurdles and constrain its impulse to be the ,centre' of the world. Consisting of three sections, this article first discusses the nexus between post-Mao China's ,new' diplomacy and Beijing's proactive posture towards Asia and notes the troublesome nature of the regional dynamics in Northeast Asia. It then explores three case studies in which China's activism has varied in resolving intricate regional and inter-state problems: namely, Sino,Japanese discord, the Koguryo controversy between South Korea and China and the North Korean nuclear conundrum. The final section offers some concluding observations regarding China's diplomacy towards Northeast Asia. [source]

Numerical simulation of dense gas flows on unstructured grids with an implicit high resolution upwind Euler solver

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2004
P. Colonna
Abstract The study of the dense gas flows which occur in many technological applications demands for fluid dynamic simulation tools incorporating complex thermodynamic models that are not usually available in commercial software. Moreover, the software mentioned can be used to study very interesting phenomena that usually go under the name of ,non-classical gasdynamics', which are theoretically predicted for high molecular weight fluids in the superheated region, close to saturation. This paper presents the numerical methods and models implemented in a computer code named zFlow which is capable of simulating inviscid dense gas flows in complex geometries. A detailed description of the space discretization method used to approximate the Euler equations on unstructured grids and for general equations of state, and a summary of the thermodynamic functions required by the mentioned formulation are also given. The performance of the code is demonstrated by presenting two applications, the calculation of the transonic flow around an airfoil computed with both the ideal gas and a complex equation of state and the simulation of the non-classical phenomena occurring in a supersonic flow between two staggered sinusoidal blades. Non-classical effects are simulated in a supersonic flow of a siloxane using a Peng,Robinson-type equation of state. Siloxanes are a class of substances used as working fluids in organic Rankine cycles turbines. Copyright © 2004 John Wiley & Sons, Ltd. [source]

FOIST: Fluid,object interaction subcomputation technique

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 9 2009
V. Udoewa
Abstract Our target is to develop computational techniques for studying aerodynamic interactions between multiple objects. The computational challenge is to predict the dynamic behavior and path of the object, so that separation (the process of objects relatively falling or moving away from each other) is safe and effective. This is a very complex problem because it has an unsteady, 3D nature and requires the solution of complex equations that govern the fluid dynamics (FD) of the object and the aircraft together, with their relative positions changing in time. Large-scale 3D FD simulations require a high computational cost. Not only must one solve the time-dependent Navier,Stokes equations governing the fluid flow, but also one must handle the equations of motion of the object as well as the treatment of the moving domain usually treated as a type of pseudo-solid. These costs include mesh update methods, distortion-limiting techniques, and remeshing and projection tactics. To save computational costs, point force calculations have been performed in the past. This paper presents a hybrid between full mesh-moving simulations and the point force calculation. This mesh-moving alternative is called FOIST: fluid,object subcomputation interaction technique. Copyright © 2009 John Wiley & Sons, Ltd. [source]

A general Riemann solver for Euler equations

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2008
Hao Wu
Abstract In this paper, we present a general Riemann solver which is applied successfully to compute the Euler equations in fluid dynamics with many complex equations of state (EOS). The solver is based on a splitting method introduced by the authors. We add a linear advection term to the Euler equations in the first step, to make the numerical flux between cells easy to compute. The added linear advection term is thrown off in the second step. It does not need an iterative technique and characteristic wave decomposition for computation. This new solver is designed to permit the construction of high-order approximations to obtain high-order Godunov-type schemes. A number of numerical results show its robustness. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Fluoropolyethers end-capped by polar functional groups.

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002

Abstract The kinetics of the dibutyltin dilaurate (DBTDL)-catalyzed urethane formation reactions of cyclohexyl isocyanate (CHI) with model monofunctional fluorinated alcohols and fluoropolyether diol Z-DOL H-1000 of various molecular weights (100,1084 g mol,1) in different solvents were studied. IR spectroscopy and chemical titration methods were used for measuring the rate of the total NCO disappearance at 30,60 °C. The effects of the reagents and DBTDL catalyst concentrations, the solvent and hydroxyl-containing compound nature, and the temperature on the reaction rate and mechanism were investigated. Depending on the initial reagent concentration and solvent, the reactions could be well described by zero-order, first-order, second-order, or more complex equations. The reaction mechanism, including the formation of intermediate ternary or binary complexes of reagents with the tin catalyst, could vary with the concentration and solvent and even during the reaction. The results were treated with a rate expression analogous to those used for enzymatic reactions. Under the explored conditions, the rate of the uncatalyzed reaction of fluorinated alcohols with CHI was negligible. Moreover, there was no allophanate formation, nor were there other side reactions, catalysis by urethane in the absence of DBTDL, or a synergetic effect in the presence of the tin catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3771,3795, 2002 [source]