• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.354-357
• /
• 2008

Drag reduction is one of main concerns for commercial aircraft companies than ever because fuel price has been tripled in ten years. In this research, Natural Laminar Flow airfoil is designed and tested to reduce drag at cruise condition, $c_l$=0.3, Re=3.4${\times}$10$^6$ and M=0.6. NLF airfoil is characterized by delayed transition from laminar to turbulent flow, which comes from maintaining favorable pressure gradient to downstream. Transition is predicted by solving Boundary Layer equations in viscous boundary layer and by solving Euler Equation outside the boundary layer. Once boundary layer thickness and momentum thickness are obtained, $e^N$-method is used for transition point prediction. As results, KARI's NLF airfoil is designed and shows better characteristics than NLF-0115. The characteristics are tested and verified at low Reynolds numbers, but at high Reynolds numbers, laminar flow characteristics are not obtainable because of fully turbulent flow over airfoil surfaces. Precious experiences, however, relating NLF airfoil design, subsonic and transonic tests are acquired.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.275-276
• /
• 2005

Organic Light Emitting Diodes(OLEDs) are attractive as alternative display components because of their relative merits of being self-emitting, having large intrinsic viewing angle and fast switching speed. But because of their relatively short history of development, much remains to be studied in terms of their basic device physics and design, manufacturing techniques, stability and so on. We invested electrical properties of N,N-diphenyl-N,N bis (3-methyphenyl)-1,1'-biphenyl-4,4'-diamine(TPD) and tris-8-hydroxyquinoline aluminum($Alq_3$) when their thicknesses were changed variedly from 3:7 to 7:3 of their thickness ratios. And we also studied properties of OLEDs depend on their deposition rate between 0.05$\sim$0.2 [nm/s].

• Journal of Korea Foundry Society
• /
• v.28 no.4
• /
• pp.184-189
• /
• 2008

Ag-Cd alloy has been widely used as an electrical contact material, since Ag-Cd alloy has a good wear resistance and stable contact resistance. But nowadays Ag-Cd alloy is not considered as electrical contact material any more due to detrimental effect on environments. Currently, active researches are being performed on ($Ag-SnO_2$ and $Ag-SnO_{2}-In_{2}O_{3}$) as an alternative solution which can fix the remaining environmental problems. However, $In_{2}O_{3}$ is relatively expensive and Ag-Sn alloy has low wear resistance. Our recent research results show that Ag-X%Zn-Y%Sn has similar physical and chemical properties. In the present study, so we tried to change and to optimize the Zn oxide content to over 6 wt% and Sn oxide content with 0.5, 1.0, 1.5 wt%. Results obtained from the experiments on the Ag-X%ZnO-Y%$SnO_2$ are discussed.

• Herbal Formula Science
• /
• v.27 no.4
• /
• pp.285-297
• /
• 2019

Objectives : The purpose of this study is to analyze effectiveness of herbal medicine treatment on Dry Eye Syndrome. Methods : We analyze medical records of 114 patients who visited Indara oriental medical clinic for dry eye syndrome. Patients were treated with acupuncture and Inmok-tang, and the ocular surface disease index was evaluated before and after treatment. Results : Analysis of 114 medical records showed a significant decrease in the pre-treatment and post-treatment ocular surface disease index, and a statistically significant positive correlation between the duration of Inmok-tang administration and the change in the ocular surface disease index. Conclusions : Herbal medicine treatment with Inmok-tang reduces the Ocular Surface Disease Index, an indicator of subjective symptoms of dry eye syndrome.

• Journal of Korea Game Society
• /
• v.1 no.1
• /
• pp.55-60
• /
• 2001

With rapid development of graphic hardware, researches on Virtual Reality and 3D Games have received more attention than before. For more realistic 3D graphic scene, objects were to be presented with lots of polygons and the number of objects shown in a scene was remarkably increased. Therefore, for effective visualization of large polygon models like this, view-frustum culling method, that visualizes only objects shown in the screen, has been widely used. In general, the bounding boxes that include objects are generated firstly, and the boxes are intersected with view-frustum to check whether object is in the visible area or not. Recently, an algorithm that can check in-out test of objects using OpenGL's selection mode, which is originally used to select the objects in the screen, is suggested. This algorithm is fast because it can use hardware acceleration. In this study, by implementing and applying this algorithm to large polygon models, we showed the efficiency of OpenGL assisted View-Frustum Culling algorithm. If this algorithm is applied to 3D games that have to process more complicated characters and landscapes, performance improvement can be expected.

• Journal of the Korea Society for Simulation
• /
• v.14 no.2
• /
• pp.57-71
• /
• 2005

A simulation for the analysis of the evasive capability of a conventional costal submarine against a light Anti-Submarine Warfare (ASW) torpedo has been studied. The Torpedo, Submarine Controller, Devoy, and Jammer models of this simulation are analysised and designed using Unified Modeling Language (UML) and in addition they are modeled Discrete Event System Specification (DEVS). We examine maximum speed, acceleration, countermeasure systems capabilities of a submarine, and sonar range of a torpedo as the factors which affect the evasive capability of the submarine. This paper shows the relationships between those various factors and the submarine's evasive capability as the outcome of the simulation. The simulation models can be applied for simulation based acquisition (SBA) of a submarine system.

• Journal of the Korea Society for Simulation
• /
• v.16 no.3
• /
• pp.65-74
• /
• 2007

A tactic manager which can change the behavior of a simulation model according to the tactic definition file has been studied and implemented. Based on the DEVS(discrete event system specification) formalism, we generated a simulation model which is equipped with the inter ace to the tactic manager. To demonstrate the effectiveness of the tactic manager, a target motion analysis simulation of the warfare between a submarine and a surface ship is simulated.

• Proceedings of the PSK Conference
• /
• 2003.10b
• /
• pp.88.3-89
• /
• 2003

Acanthoic acid (AA) is a pimaradiene diterpene isolated from the Korean medicinal plant, Acanthopanax koreanum (Araliaceae), which has been traditionally used as a tonic and sedative as well as in the treatment of rheumatism and diabetes in korea. Proteinase-activated receptor-2 (PAR-2) agonist trypsin plays a role in inflammation, and human leukemic mast cells (HMC-l) express PAR-2. In the present study, the effect of acanthoic acid on production of tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$) and tryptase in trypsin-stimulated HMC-1 was examined. (omitted)

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.4
• /
• pp.31-36
• /
• 2010

Free energy based lattice Boltzmann method (LBM) has been used to simulate the rising bubble flows with large density ratio. LBM with compact discretization is able to reduce the spurious current of the static bubble test and be satisfied with the Laplace law. The terminal rise velocity and shape of the bubbles are dependent on Eotvos number, Morton number and Reynolds number. For single bubble flows, simulations are executed for various Eotvos number, Morton number and Reynolds number, and the results are agreed well with the experiments. For multiple bubbles, the bubble flow characteristics are related by the vortex pattern of the leading bubble. The coalescence of the bubbles are simulated successfully and the subsequent results are presented. The present method is validated for static, dynamic bubble test cases and compared to the numerical, experimental results.

• Journal of Korea Foundry Society
• /
• v.20 no.1
• /
• pp.29-37
• /
• 2000

The purpose of this study is to investigate the effect of misch metal addition on the microstructure and mechanical property of rapidly solidified AZ91 alloy by melt spinning process. As the contents of misch metal(rare earth element:Ce,La, Nd, Pr)was increased, the microstructure of RS ribbons and extrudates became finer than those of AZ91, and RE related phases($Al_{11}RE_3$, $Al_2RE$) were formed. At room temperature, the rapidly solidified AZ91+1 wt%Mm alloy showed the highest tensile strength, 430 MPa due to precipitation strengthening of${\beta}(Mg_{17}Al_{12})$ phase and Al11RE3 phase. At the elevated temperature, the mechanical property of AZ01+3 wt%Mm alloy was higher than those of other Mg alloys. The reasons were that $Al_{11}La_3$ phase was thermally stable and suppressed the grain growth. In contrast with $Al_{11}La_3$ phase, ${\beta}$ phase was thermally unstable and could not suppress the grain growth at the elevated temperature. Therefore, Al11RE3 phase contributed to improve the thermal stability of RS AZ91 Alloy.