• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.27-30
• /
• 2002

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. In this study, 3-dimensional unsteady incompressible Wavier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade' scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.807-810
• /
• 2002

The suitability of high-order accurate, central and upwind-biased compact difference schemes is evaluated for the large-eddy simulations of flows in complex geometry. Two flow geometries are considered: channel and circular cylinder. The effects of numerical dissipation and aliasing error on the evaluation of subgrid scale stress are investigated by extending the analysis by Ghosal (1) to centered and upwind compact schemes. It is shown that the failure of upwind schemes mainly comes from the aliasing error.

• Journal of Mechanical Science and Technology
• /
• v.18 no.2
• /
• pp.230-239
• /
• 2004

A compact model approach of a network of spring elements for elastic loading is presented for the thermal deformation analysis of BGA package assembly. High-sensitivity moire interferometry is applied to evaluate and calibrated the model quantitatively. Two ball grid array (BGA) package assemblies are employed for moire experiments. For a package assembly with a small global bending, the spring model can predict the boundary conditions of the critical solder ball excellently well. For a package assembly with a large global bending, however, the relative displacements determined by spring model agree well with that by experiment after accounting for the rigid-body rotation. The shear strain results of the FEM with the input from the calibrated compact spring model agree reasonably well with the experimental data. The results imply that the combined approach of the compact spring model and the local FE analysis is an effective way to predict strains and stresses and to determine solder damage of the critical solder ball.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.1443-1448
• /
• 2009

Numerical analysis has been carried out to investigate air-side convective heat transfer characteristics in compact heat exchangers with continuous plate fins. Simulation results such as air flow and temperature distributions are presented, and heat transfer characteristics are compared for various inlet conditions. Results from various turbulence models are also compared for applicability. There is large difference between the local heat transfer coefficient distributions along the cylinder wall for circular tubes. Colburn j factors from the calculated results of circular and flat tubes in the heat exchangers are compared for various Reynolds number. The predicted results in this study can be applied to the optimal design of air conditioning system. with compact heat exchanger.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1997.03a
• /
• pp.226-230
• /
• 1997

A plasticity theory applicable to powdered metal compaction is briefly summarized and its variational form for the finite element analysis is described. The compaction processes of axisymmetric solid cylinder are simulated. For the analysis of the friction effect of solid cylinder, the investigations were performed for different compact geometries. Highlights of the results for given geometries are reported in terms of transmitted pressure on the lower punch from the upper punch through the compact and maximum density variation within the compacts. General conclusions from these simulation results are : (1) the friction coefficient could be selected from the transmitted force data during the single acting compaction test with the simulated results ; and (2) density variatioins within the compacts are very much dependent of the compact geometry such as the height to diameter ratio and the frictional condition between compact and dies.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.31A no.4
• /
• pp.84-91
• /
• 1994

A compact electron cyclotron resonance(ECR) plasma system composed of a microwave generator and a magnet coil was fabricated. A Langmuir single probe was used to investigate the plasma characteristics of the system through I-V measurements. The performance of the compact ECR plasma system was tested for the case of silicon etching reaction with $CF_{4}/O_{2}$(30%) mixed gas. Electron density and etch rate increased to maximum values and then decreased with increasing argon gas pressure, but electron temperature changed in the opposite way. The electron density and the electron temperature of argon gas plasma were 0.85${\times}~5.5{\times}10^{10}cm^{-3}$ and 4.5~6.0 eV, respectively, in the pressure range from $3{\times}10^{4}$ to 0.05Torr. The etch rate reached a maximum value at the position of 2.5cm from the bottom of plasma cavity. Etch rate uniformity was $\pm$6% across 6cm wafer. Anisotropic index was 0.75 at 1.5${\times}10^{-4}$Torr.

• Journal of applied mathematics & informatics
• /
• v.19 no.1_2
• /
• pp.447-452
• /
• 2005

Given operators X and Y on a Hilbert space H, an interpolating operator is a bounded operator A such that AX = Y. In this article, we investigate compact interpolation problems for vectors in a tridiagonal algebra. Let L be a subspace lattice acting on a separable complex Hilbert space H and Alg L be a tridiagonal algebra. Let X = $(x_{ij})\;and\;Y\;=\;(y_{ij})$ be operators acting on H. Then the following are equivalent: (1) There exists a compact operator A = $(x_{ij})$ in AlgL such that AX = Y. (2) There is a sequence {$\alpha_n$} in $\mathbb{C}$ such that {$\alpha_n$} converges to zero and $$y_1\;_j=\alpha_1x_1\;_j+\alpha_2x_2\;_j\;y_{2k}\;_j=\alpha_{4k-1}x_{2k\;j}\;y_{2k+1\;j}=\alpha_{4k}x_{2k\;j}+\alpha_{4k+1}x_{2k+1\;j}+\alpha_{4k+2}x_{2k+2\;j\;for\;all\;k\;\epsilon\;\mathbb{N}$$.

• Communications of the Korean Mathematical Society
• /
• v.9 no.2
• /
• pp.293-298
• /
• 1994

It is well known that the approximation property and the compact approximation property are not hereditary properties; that is, a closed subspace M of a Banach space X with the (compact) approximation property need not have the (compact) approximation property. In 1973, A. Davie [2] proved that for each 2 < p < $\infty$, there is a closed subspace $Y_{p}$ of $\ell_{p}$ which does not have the approximation property. In fact, the space Davie constructed even fails to have a weaker property, the compact approximation property. In 1991, A. Lima [12] proved that if X is a Banach space with the approximation property and a closed subspace M of X is locally $\lambda$-complemented in X for some $1\leq\lambda < $\infty$, then M has the approximation property.(omitted)

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.12
• /
• pp.119-124
• /
• 2010

In this paper, thermal stabilization design of a new concept compact machining center has been investigated. A new concept machining center adopted a new X-axis as a NC rotary table. A New concept compact machining center is designed that spindle speed, feed rate and NC Rotary table speed are 12,000rpm, 60m/min and 110rpm each. The analysis is carried out by using FEM simulation Solidworks, CATIA and ANSYS. This paper is focused on the thermal deformation according to temperature distribution of a spindle system and feed drive system. Heat transfer analysis is performed according to heat source and atmosphere contact parts. As a result, this compact machining center is designed as a thermally stable structure.

• The Pure and Applied Mathematics
• /
• v.10 no.1
• /
• pp.25-35
• /
• 2003

We study equivalent definitions and some categorical properties of completely regular quasi-ordered spaces and zero-dimensional quasi-ordered spaces. Using the o-completely regular (resp. o-zero-dimensional) filters on a completely regular (resp. zero-dimensional) quasi-ordered space, we show that the category COMPOS (resp. ZCOMPOS) of compact (resp. compact zero-dimensional) partially ordered spaces is reflective in the category CRQOS (resp. ZQOS) of completely regular (resp. zero-dimensional) quasi-ordered spaces and continuous isotones.