• The Journal of the Acoustical Society of Korea
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• v.18 no.7
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• pp.56-66
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• 1999

Thermoacoustic oscillation is a significant problem in cylindrical-type combustors such as common internal combustion engines, industrial furnaces, gas turbine, etc. This kind of low frequency oscillation can lead to serious consequences such as destruction of the combustor and production of strong noise. The accurate numerical simulation of thermoacoustic phenomena is a complex and challenging problem, especially when considering the chemical reaction of mixtures. As with other simulations of aerodynamics and aeroacoustics, the direct computation of thermoacoustic phenomena requires that Navier-Stokes equations be solved using accurate numerical differentiation and time-marching schemes, with non-reflecting boundary conditions. The numerical approach used here aims at qualitative analysis and efficient prediction of those problems, not at the development of an accurate scheme. The numerical prediction developed in this work is shown to be reasonably matched with experimental result.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.190-200
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• 1991

Certain structural components are exposed to high temperatures. At high temperature, under thermal and mechanical loading, metal components exhibit both creep and plastic behavior. The unified constitutive theory is to model both the time-dependent behavior(creep) and the time-independent behavior(plasticity) in one set of equations. Microscopically both creep and plasticity are controlled by the motion of dislocations. A finite element method is presented encorporating a unified constitutive model for the transient analysis of viscoplastic behavior of structures exposed to high temperature.

• Aerospace Engineering and Technology
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• v.2 no.2
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• pp.142-150
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• 2003

Turbulent flows and related heat transfer in a square heated duct is investigated by a turbulence model and a large eddy simulation. The cooling channel of calorimeter is modeled to the square duct. The nonlinear k-ε-fμ model of Park et al. [3] is slightly modified and their explicit heat flux model is employed. The Reynolds number is varied in the range 4000≤Reｂ≤20000. The heat transfer is closely linked to the secondary flows which driven by the turbulent motion. Its magnitude is 1~3% of the mean streamwise velocity. The relation of Nu~Re0.8Pr0.34 is validated by comparing with the predicted Nu of k-ε-fμ model. Finally, the coherent structures and thermal fluctuations are scrutinized.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.281-286
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• 2004

The vacuum cleaner motor runs on very high speed for the suction power. Specially, the motive power is provided by the impeller being rotate on very high speed. And centrifugal fan consists of the impeller, the diffuser, and the circular casing. Due to the high rotating speed or the impeller and small gap distance between the impeller and diffuser, the centrifugal fan makes very high noise level at BPF and harmonic frequencies. In order to calculate the sound pressure of centrifugal fan, the unsteady flow data is needed. And Noise cause is dividing to fluid noise by exhaust flow of fan and vibration noise by rotational vibration of vacuum cleaner fan motor. Until now, measuring method has been used to measure vibration by the accelerometer; this method has been not measured for the vibration in some parts of brush and commutator because of motor construction and 3-D vibrating mode. This paper was purposed on the accurate analysis, using laser vibration analyzer,. By using this measured data of noise cause against the difficult part in old times, we would like to use for the design of silent fan motor.

• Journal of Life Science
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• v.18 no.10
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• pp.1325-1330
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• 2008

Salix koriyanagi is a deciduous shrub and native to Korea. The spatial distribution of multilocus allelic frequencies and geographical distances of the natural population in upper swampy area at the Namgang River in Korea were studied. The species showed a significant positive and negative spatial autocorrelation according to geographical distances as measured by Moran's I. Genetic similarity of individuals was found among subpopulations at up to a scale of a 12 m distance, and this was partly due to a combination of allelic frequencies, and therefore, a significant spatial autocorrelation was composed of a scale of 12 m intervals. Within S. koriyanagi in swampy area at the Namgang River, a strong spatial structure was observed for allozyme markers, indicating a migration within subpopulations.

• Journal of Korea Foundry Society
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• v.29 no.1
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• pp.33-37
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• 2009

Cartesian grid system has mainly been used in the casting simulation even though it does not nicely represent sloped and curved surfaces. These distorted boundaries cause several problems. A special treatment is necessary to clear these problems. In this paper, we propose a new method that can consider the cutting cells which are cut by casting and mold based on the partial cell treatment (PCT). This method provides a better representation of geometry surface and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian grid system. Various test examples for several casting process were computed and validated. The analysis results of more accurate fluid flow pattern and less momentum loss owing to the stepped boundaries in the Cartesian grid system were confirmed. By using the cut cell method, performance of computation gets better because of reducing the whole number of meshes.

• Solar Energy
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• v.10 no.1
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• pp.47-56
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• 1990

The aerodynamic performances of Darrieus wind turbine were studied through the wind tunnel model tests and its analytical aerodynamic streamtube model. Hence, analytical streamtube model which is based on momentum and blade element theory is considered and the formulated model was generalized in non-dimensional type to predict the aerodynamic characteristics of Darrieus wind turbine. The analytical model was justified through the wind tunnel model tests for several experimental conditions but in the limited rages. These satisfactory comparative studies between the wind tunnel tests and the analytical predictions can be utilized for the basic reliable design of Darrieus wind turbine.

• Journal of Korean Medical classics
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• v.18 no.3 s.30
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• pp.1-8
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• 2005

${\lceil}$소문(素問) 장기법시론(藏氣法時論)${\rfloor}$적오장병지일중간심적주석중(的五藏病的日中間甚的注釋中), 관어비병여폐병정적주석(關於脾病與肺病靜的注釋), 가분이하삼조(可分以下三條), 기일시(其一是), 비병정(脾病靜), 당작일중정(當作日中靜), 폐병정(肺病靜), 당작일질정, 기이시(其二是), 하포여야반(下哺與夜半), 제기적사(制其賊邪), 소이병정(所以病靜), 기삼시(其三是), 자어자기왕(資於子氣旺), 모기역왕(母氣亦旺). 논자이기지경향성해석본문(論者以氣之傾向性解釋本文), 기내용여하(其內容如下), 기일시(其一是), 평단여간유동양적기지경향성(平旦與肝有同樣的氣之傾向性), 소이병상(所以病爽). 하포여간유상반적기지경향성, 소이병심(所以病甚). 야반시보충간지기(夜半是補充肝之氣), 소이병정((所以病靜), 기이시(其二是), 일중여심(日中與心), 기기능유사(其機能有似), 소이병상(所以病爽). 야반여심(夜半與心), 유상반적기류(有相反的氣流), 소이병심((所以病甚). 평단보심적활동(平旦輔心的活動), 소이병정(所以病靜). 기삼시(其三是), 일질여비공유화적특성, 소이병상(所以病爽). 일출여화(日出與化), 유상반적기지특성(有相反的氣之特性), 소이병심((所以病甚). 하포시수렴적시기, 유관여화적작용(有關與化的作用), 소이병정(所以病靜). 기사시(其四是). 하포여폐, 공유수렴적특성(共有收斂的特性), 소이병상(所以病爽). 일중유상반적기류(日中有相反的氣流), 소이병심(所以病甚). 야반여금(夜半與金), 공유음적기류(共有陰的氣流), 소이병정(所以病靜). 기오시(其五是), 야반여신(夜半與 腎하), 공유장적기능(共有藏的 機能), 소이병상(所以病爽). 사계포용만물(四季包容萬物), 여장정미적신(與藏精微的腎), 유상반적특성(有相反的特性), 소이병심(所以病甚). 하포유수렴숙살기능, 보신지장적기능(補腎之藏的機能), 소이병정(所以病靜). 신병심적시기(腎病甚的時期), 작사계이불작일질, 저취설명료 신병적위중성(這就說明了 腎病的危重性).

• Journal of Life Science
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• v.18 no.11
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• pp.1465-1470
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• 2008

Salix koriyanagi is a deciduous shrub and native to Korea. The spatial distribution of multilocus allelic frequencies and geographical distances of the natural population in upper swampy area at the Namgang River in Korea were studied. The species showed a significant positive and negative spatial autocorrelation according to geographical distances as measured by Moran's I. Genetic similarity of individuals was found among subpopulations at up to a scale of a 12 m distance, and this was partly due to a combination of allelic frequencies, and therefore, a significant spatial autocorrelation was composed of a scale of 12 m intervals. Within S. koriyanagi in swampy area at the Namgang River, a strong spatial structure was observed for allozyme markers, indicating a migration within subpopulations.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.559-564
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• 2008

A prediction of binary droplets collision is important in the formation of falling drops and the evolution of sprays. The droplet velocity, impact parameter and drop-size ratio have influence on the interaction of the droplets. By the effect of these parameter, the collision processes are generated with the complicated phenomena. The droplet collision can be classified into four interactions such as the bouncing, coalescence, reflexive separation and stretching separation. In this study, the two-phase flow of the droplet collision was simulated numerically by using the Level Set method. 2D axi-symmetric simulations on the head-on collisions in the coalescence and reflexive separation, and 3D simulation on the off-center collisions in the coalescence and stretching separation were performed. These numerical results showed good agreements with the experimental and analytical results. For tracking the identity of droplets after the collision, transport equation for the volume fraction of the each initial droplet were used. From this, the identities of droplets were analyzed on the collision of droplets having different size.