• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.4
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• pp.242-247
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• 2009

AILU type preconditioners for a two-dimensional combined P2P1 finite element formulation of the interaction of rigid cylinder with incompressible fluid flow have been devised and tested by solving fluid-structure interaction (FSI) problems. The FSI code simulating the interaction of a rigid cylinder with an unsteady flow is based on P2P1 mixed finite element formulation coupled with combined formulation. Four different preconditioners were devised for the two-dimensional combined P2P1 finite element formulation extending the idea of Nam et al., which was proposed for the preconditioning of a P2P1 mixed finite element formulation of the incompressible Navier-Stokes equations. It was found that PC-III or PC-IV among them perform well with respect to computational memory and convergence rate for some bench-mark problems.

• Journal of the Korean Mathematical Society
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• v.41 no.2
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• pp.345-368
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• 2004

A preconditioning algorithm is developed in this paper for the iterative solution of the linear system of equations resulting from the p-version boundary element approximation of the three dimensional integral equation with hypersingular operators. The preconditioner is derived by first making the nodal and side basis functions locally orthogonal to the element internal bases, and then by decoupling the nodal and side bases from the internal bases. Its implementation consists of solving a global problem on the wire-basket and a series of local problems defined on a single element. Moreover, the condition number of the preconditioned system is shown to be of order $O((1＋ln/p)^{7})$. This technique can be applied to discretization with triangular elements and with general basis functions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1581-1593
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• 2001

An efficient variable-reordering method for finite element meshes is used and the effect of variable-reordering is investigated. For the element renumbering of unstructured meshes, Cuthill-McKee ordering is adopted. The newsy reordered global matrix has a much narrower bandwidth than the original one, making the ILU preconditioner perform bolter. The effect of variable reordering on the convergence behaviour of saddle point type matrix it studied, which results from P2/P1 element discretization of the Navier-Stokes equations. We also propose and test 'level(0) preconditioner'and 'level(2) ILU preconditioner', which are another versions of the existing 'level(1) ILU preconditioner', for the global matrix generated by P2/P1 finite element method of incompressible Navier-Stokes equations. We show that 'level(2) ILU preconditioner'performs much better than the others only with a little extra computations.

• Journal of the Korean Society of Tobacco Science
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• v.11 no.1
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• pp.79-85
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• 1989

For the Purpose of this study, were researched the optimum condition preconditioning condition of orient tobacco leaves . The loss of 3-methyl pentanoic acid (3-MP) component of BASMA leaves in the treatment process amount to about 60% , but the loss of 3-MP At the optimum conditions of BASMA CTC treatment, the temperature was 45-$65^{\circ}C$ and the treatment time 25-35 minutes. And further, the physical properties of BASMA after CTC treatment was remarkably similar to the control's. Since VTC minimized the loss, it is suggested that CTC method should be changed by VTC method.

• Journal of Chest Surgery
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• v.29 no.8
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• pp.807-815
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• 1996

The protective effect of'ischemic preconditioning'on ischemid-reperfusion injury of heart has been reported in various animal species. but without known mechAnism in detail, In An attempt to investigate the cardioprotective mechanism of ischemic preconditioning, we examined the effects of nitric oxide(UO) synthesis in preconditioned heart of rat The isolated hearts perfused by Langendorfr's method were ex- posed to 30min global ischemia followed by 30min reperfusion with oxygenated Krebs-Henseleit(K-H) sol- ution. Ischemic preconditioning was performed with three episodes of Sm n ischemia and Smin repeyfusion before the induction of prolong ischemia(30min)-reperfusion(30min). Ischemic preconditioning prevented the depression of cardiac function(left ventricular pressure .K heart rate) observed in the ischemia- reperfusion hearts and reduced the release of lactate dehydrogenase during the reperfusion period. On electromicroscopic pictures, myocardial ultrastructures wore relatively well preserved in isthemic preconditioned hearts. N6_nitro-L-arginine methyl ester(L-NAME) an inhibitor of L-arginine citric oxide pathway, was infused at a rate O.Smllmin In a dose of 10mg kg-1 before the initial ischemic preconditioning. neither the protection of cardiac function nor the reduction of LDH releAse in ischemic preconditioning hearts was altered in the presence of added L-NAME On ultrastructural finding, the preservation of morphology in ischemic preconditioning heart was not change by the pretreatment of L-UAME. The failure of the WO synthesis inhibitor to reduce t e effect of ischemic preconditioning may be related to be species specific in that NO may allot be the trigger for ischemic preconditioning in rats.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.183-195
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• 2007

Comprehensive mathematical comparison of numerical dissipation vector was made for a compressible and the preconditioned version Roe's Riemann solvers. Choi and Merkle type preconditioning method was selected from the investigation of the convergence characteristics of the various preconditioning methods for the flows over a two-dimensional bump. The investigation suggests a way of migration from a compressible code to a preconditioning code with a minor changes in Eigenvalues while maintaining the same code structure. Von Neumann stability condition and viscous Jacobian were considered additionally to improve the stability and accuracy for the viscous flow analysis. The developed code was validated through the applications to the standard validation problems.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.5
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• pp.30-40
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• 2004

In the present study, a numerical method has been developed for the calculation of the gust response of an airship using unstructured meshes. A preconditioning method is incorporated for accurate and efficient computations of the Euler equations at the low Mach number range. A simple sharp-edged gust is used as a gust model. The accuracy of the present method is demonstrated through comparisons with an exact line theory. The numerical results show that the variation of lift is relatively larger than that of moment. It is also shown that the static stability of the airship is enhanced with the use of control fins.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.260-265
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• 2008

A numerical scheme for solid propellant rocket has been studied using preconditioning method to research unsteady combustion processes for the double-base propellant with a converging-diverging nozzle. The Navier-Stokes equation is solved by dualtime stepping method with finite volume method. The turbulence model uses a shear stress transport modeling. The species equation follows up the method of Xinping WI, Mridul Kumar and Kenneth K. Kuo. A preconditioned algorithm is applied to solve incompressible regime inside the combustor and compressible flow at nozzle. Mass flux was evaluated using modified advective upwind splitting method. The simulated result the comparison a fully coupled implicit method and a semi implicit method in terms of accuracy and efficiency. This report shows the result of solid rocket propellant combustion.

• Journal of applied mathematics & informatics
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• v.8 no.2
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• pp.305-326
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• 2001

We introduce a class of multilevel recursive incomplete LU preconditioning techniques (RILUM) for solving general sparse matrices. This techniques is based on a recursive two by two block incomplete LU factorization on the coefficient martix. The coarse level system is constructed as an (approximate) Schur complement. A dynamic preconditioner is obtained by solving the Schur complement matrix approximately. The novelty of the proposed techniques is to solve the Schur complement matrix by a preconditioned Krylov subspace method. Such a reduction process is repeated to yield a multilevel recursive preconditioner.

• 한국전산유체공학회:학술대회논문집
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• 2001.05a
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• pp.195-202
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• 2001

In this paper, the convergence characteristics of preconditioned multigrid methods are investigated. The preconditioning method is introduced to reduce the condition number of discrete governing equations. 6 preconditioners including a point, line and diagonalized line solvers are implemented and applied to 2-dimensional inviscid flow problems. Theoretical fourier analyses and numerical results are presented for the preconditioners.