• 대한조선학회논문집
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• 제50권5호
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• pp.355-363
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• 2013

Panel methods are essential tools for analyzing a fluid-flow problem around complex three dimensional bodies, but they lack ability to solve viscous effects. On the other hand, CFD methods are considered as powerful tools for analyzing fluid-flow characteristics including viscosity. However, they also have short falls, requiring more computing time and showing different results depending on the selection of turbulence models and grid systems. In this paper a hybrid scheme combining a panel method and a CFD method is suggested. The scheme adopts a panel method for far-field solution where viscous effects are negligible and a CFD method for the solution of RANS equations in near-field where viscous effects are relatively strong. The intermediate region between the far-field and near-field is introduced where the calculated field point velocities by the panel method are given as boundary velocities for the CFD method. To verify the scheme, calculated results, by a panel method, a CFD method and the hybrid scheme, for a two dimensional foil section are compared. The suggested hybrid scheme gives reasonable results, while computation time and memory can be dramatically reduced. By using the hybrid scheme efforts can be concentrated for the local flow near the leading and trailing edges, by providing more dense grid system, where detailed flow characteristics are required.

• 한국지반환경공학회 논문집
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• 제13권8호
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• pp.5-13
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• 2012

본 연구는 최근 개발된 알칼리성 실리카졸 그라우팅재의 적용성 및 주입효과를 규명한 것으로서 연구에 사용된 그라우트재는 3차원겔 형성재인 알칼리성 실리카졸 그라우팅재와 규산나트륨 그라우팅재에 대한 공학적 특성을 비교하기 위하여 실내시험을 실시하여 강도특성 및 환경영향성을 검토하였으며, 현장시험 등을 통해 차수성과 주입효과를 검토하여 현장적용성을 규명하고자 하였다. 실내시험결과 알칼리성 실리카졸의 일축압축강도는 규산나트륨에 비해 약 5배 정도 증가하는 현상이 나타났고 용탈시험결과 용탈되는 원소의 총량도 극히 작아 친환경적인 재료임이 입증되었다. 현장시험결과 동수층에서도 상당한 투수계수 저감효과를 확인하였고, 시방기준인 $10^{-5}cm/sec$보다 낮은 투수계수를 확보하였다. 주입확인시험결과 페놀프탈레인 반응시험, 전기비저항탐사에서 주입효과가 양호한 것으로 나타났다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.743-750
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• 2008

Asymmetric tip clearance in an axial compressor induces pressure and velocity redistributions along the circumferential direction in an axial compressor. This paper presents the mechanism of the flow redistribution due to the asymmetric tip clearance with a simple numerical modeling. The flow field of a rotor of an axial compressor is predicted when an asymmetric tip clearance occurs along the circumferential direction. The modeling results are supported by CFD results not only to validate the present modeling but also to investigate more detailed flow fields. Asymmetric tip clearance makes local flow area and resultant axial velocity vary along the circumferential direction. This flow redistribution 'seed' results in a different flow patterns according to the flow coefficient. Flow field redistribution patterns are largely dependent on the local tip clearance performance at low flow coefficients. However, the contribution of the main flow region becomes dominant while the tip clearance effect becomes weak as the flow coefficient increases. The flow field redistribution pattern becomes noticeably strong if a blockage effect is involved when the flow coefficient increases. The relative flow angle at the small clearance region decreases which result in a negative incidence angle at the high flow coefficient. It causes a recirculation region at the blade pressure surface which results in the flow blockage. It promotes the strength of the flow field redistribution at the rotor outlet. These flow pattern changes have an effect on the blade loading perturbations. The integration of blade loading perturbation from control volume analysis of the circumferential momentum leads to well-known Alford's force. Alford's force is always negative when the flow blockage effects are excluded. However when the flow blockage effect is incorporated into the modeling, main flow effects on the flow redistribution is also reflected on the Alford's force at the high flow coefficient. Alford's force steeply increases as the flow coefficient increases, because of the tip leakage suppression and strong flow redistribution. The predicted results are well agreed to CFD results by Kang and Kang(2006).

• 대한예방한의학회지
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• 제19권2호
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• pp.83-101
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• 2015

Objective : In order to establish the scientific research methods to prove the effects of korean traditional medicine about ultraviolet induced skin damage, we investigated the research on ultraviolet induced skin damage in the korean traditional medicine field. Method : We searched the papers about ultraviolet induced skin damage published in the journals of korean traditional medicine. The searching end date was on June 29, 2015. Results : Thirty papers about ultraviolet induced skin damage were found. Twenty nine papers were experimental research, and one paper was clinical research. Sixty-three percent of papers were written the years after 2011. Fifty-seven percent of papers were published in the korean journal of oriental physiology & pathology and the journal of korean oriental medical ophthalmology & otolaryngology & dermatology. Main outcome measures of experimental research were anti-wrinkle effects, anti-oxidant capacity, anti-apoptosis effects, whitening effects and anti-inflammatory effects. Conclusion : We need more systematic research in order to prove the effects of korean traditional medicine, and use extensively.

• 한국토양비료학회지
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• 제47권5호
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• pp.340-344
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• 2014

Compost and gypsum can be used to ameliorate soil physicochemical properties in reclaimed tidal lands as an organic and inorganic amendment, respectively. To evaluate effects of compost and gypsum on soil water movement and retention as a soil physical property, we measured the soil's saturated hydraulic conductivity and field capacity after treating the soil collected in a reclaimed tidal land with compost and gypsum. Saturated hydraulic conductivity of soil increased when compost was applied at the conventional application rate of $30Mg\;ha^{-1}$. However, the further application of compost insignificantly (P > 0.05) increased saturated hydraulic conductivity. On the other hand, additional gypsum application significantly increased soil saturated hydraulic conductivity while it decreased soil field capacity, implying the possible effect of gypsum on flocculating soil colloidal particles. The results in this study suggested that compost and gypsum can be used to improve hydrological properties of reclaimed tidal lands through increasing soil water retention and movement, respectively.

• 아동학회지
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• 제26권6호
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• pp.237-245
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• 2005

The purpose of this study is to investigate the effects of field-trip based environmental education on young children's environmental literacy. The subjects for the study Were the 40 children of five years old at two nursery centers in province. The questionnaire and checklist for parents and the children developed by the researcher were used in this study. The conclusion were as follows. First, the care center environmental education improved the young children's saving, and anti-pollution depending on their mother is reported. Second, the care center environmental education improved the young children's saving, recycling and anti-pollution depending on their teacher is reported. Results showed that the field-trip based environmental education improved environmental literacy.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.136-142
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• 2011

The equations of motion for composite plates incorporating magneto-thermo-elastic effects have been derived via Hamilton's principle. In order to get the insight into the implications of a number of geometrical and physical features of the system, the vibrational responses of finite composite rectangular plates immersed in a transversal magnetic field are investigated by applying the extended Galerkin method. The vibration response characteristics of a composite plate are exploited in connection with the magnetic field intensity, thermal load, and electric conductivity of fibrous composite materials. Some pertinent conclusions, which highlight the various effects induced by the magneto-thermo-elastic couplings, are outlined.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
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• pp.23-23
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• 1998

High resolution field emission dispplay(FED) devices of 5 inch diagonal in size are fully developped for the applications of near-future flat ppanel dispplays. Under the unique gate-switching drive scheme electron trajectory pprofiles are simulated and tested by considering leakage effects of each ppixel. Uniquely-pprinted sppacer with high asppect ratio are fabricated on real ITO glass for high vacuum ppackaging. In addition new gas aging scheme of stabilizing field emitting array are extensively investigated during the sealing and exhausting pprocess in order to pprevent oxidation effects on the micro tipp. Finally fulll color images of 64 gray scale will be demonstrated.

• 대한전기학회논문지
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• 제40권5호
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• pp.496-500
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• 1991

The effects of annealing with and without magnetic field on magnetic properties of amorphous Fe-B-Si cores have been investigated as a function of toroidal stress. By decreasing the toroidal stress, the magnetic properties of the amorphous ribbon have beenimproved. Near 180 domain walls exist in the thermally annealed toroidal cores, but the domain walls exist in the thermally annealed toroidal cores, but the domain walls are not parallel to the longitudinal direction of the ribbon. In the specimen annealed with a magnetic field strength of 10 Oe in the longitudinal ribbon length axis, the domains are nearly parallel to the longitudinal direction due to the field induced uniaxial anisotropy resulting in further increase in the remanent magnetization and decrease in the coercive force and loss.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 E
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• pp.1648-1650
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• 1997

The effects of power frequency electric and magnetic fields have been a source of concern for many years. Electromagnetic fields can pose a theat to both signal system of electrified railways and human body around railways. It is believed that, though the electromagnetic fields do no serious harm to human health, they do induce biological effects. This paper estimates the electromagnetic fields near Kyeongbu high speed railways with numerical data. The charge simulation method and surface charge method are used to calculate the electric field of 2 dimensional power distribution lines and rails and magnetic field is calculated on the base of Biot-Sarart's law.