• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.233-234
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• 2004

각종 재료의 음향투과손실을 간단히 비교 시험할 수 있는 관내법이 향후 국제규격으로 제정될 것에 대비하여 우선 KS 규격 제정을 목적으로 제반 특성평가를 수행하였다. 이를 위해 임피던스관을 제작하고, 관 벽을 따라 시편을 지나 마이크로폰 위치까지 전달되는 진동량, 무반사처리부의 흡음률 등 기본적인 특성을 살펴보았다. 최종적인 검증을 위해 몇 가지 시편에 대해 투과손실을 측정하고 이론적 해석에 의한 예측 값과 비교하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.179-188
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• 1990

The characteristic of volumetric efficiency considering gas exchange process in a reciprocating engine is presented in this paper. The characteristic method is used for solving gas exchange problems of engine system in theoretical studies. The validity of the simulation is investigated by a comparison with the results obtained by the experiment which have been performed on the practical 4-cycle, 4-cylinder gasoline engine. The relationship between the volumetric efficiency and the intake pressure variation according to configuration of intake pipe, position of branch point, valve timing, compression ratio is clarified through simulation and experiment. The results predicted by the simulation are found to be in approximate agreement with those obtained by the experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.340-343
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• 2000

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.692-693
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• 2004

We introduce a new velocity sensor, micro-flown sensor, which was developed by H-E de Bree. The sound absorption coefficients of a fiber material with the conventional pressure microphones and the micro-flown sensors were measured and compared. The experimental results show that both sensors could be well applied to measure the sound absorption coefficient but the pressure sensor was rather stable than micro-flown sensor

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.295-307
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• 1988

In order to predict performance of the intake manifold, which is dependent on the length and diameter of a resonance pipe, the Fluid Dynamic Model for 4-cylinder diesel engine is developed using two step Lax-Wendroff method to solve the governing equations of air flow in the intake system. Boundary conditions at the intake valve, branch at the manifolds, and pipe end are also modeled. The results of the models are compared with the experimental results of a motored engine. The model is capable of predicting the real phenomena satisfactorily with reasonable computing time.

• The Korean Journal of Rheology
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• v.8 no.1
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• pp.1-10
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• 1996

본 논문에서는 협착이 발생된 원관내 뉴턴유체와 비뉴턴유체의 정상 및 맥동유동특 서을 유한요소법으로 해석하였다. 본연구는 맥동유동특성에서 협착관 형상의 변화, 협착이 주기적으로 발생된 협착관에서 협착부사이의 거리와 협착부의 수가유동특성에 미치는 영향 을 검토하였다. 레이놀즈수가 일정할 때 협착이 발생된 원형관내 뉴턴유체와 비뉴턴유체의 맥동유동특성은 정상유동의 경우와 크게 다르게 나타난다. 맥동유동에서는 정상유동보다 관 중앙부에서 속도분포가 훨씬 평탄하고 맥동유동의 속도분포는 감속시에 비하여 가속시에 관 중앙부의 속도분포가 더 평탄하게 나타난다. 정상유동과 맥동유동으 감속시에서는 협착부 하류의 벽면에서 재순환영역이 발생된다. 협착부의 수가 증가하면 각 협착부 주위의 속도장 은 유사하게 나타나지만 전체 압력손실은 크게 증가한다. 협착부사이의 거리가 변화될 경우 맥동유동속도의 국소최대치와 국소최소치의 차이가 가속시에는 거의 없지만 감속시에는 협 착부사이의 거리에 따라 다르게 나타난다.

• Composites Research
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• v.28 no.6
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• pp.389-394
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• 2015

The sound absorption coefficient and sound transmission loss of graphite intercalation compound (GIC) included epoxy composites were investigated. Epoxy resin was infused into the expanded GIC and the impedance tube method was employed to measure the sound absorption coefficient and sound transmission loss. Scanning electron microscopy photographs showed uniform distribution of the GIC in the epoxy matrix. The surface density of epoxy/GIC (20 wt%) composites decreased about 56% compared to that of pure epoxy. The sound absorption coefficient of composites increased about 3 times at the frequency range of 500~1000 Hz compared to the pure epoxy. The sound transmission loss of composites decreased with increasing the GIC content and it is attributed to the increase of pores in the composites.

• Journal of Energy Engineering
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• v.6 no.1
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• pp.52-57
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• 1997

Dynamic characteristics of compressible flow fields in super-circled constricted tube have been studied numerically. By applying MacCormack's explicit scheme, time marching method with predictor/corrector step, Euler equation is solved to find characteristics of fluid flow in a constricted tube where a two-dimensional inviscid compressible flow is assumed. The effects of tube diameter and aspect ratios on the pressure variations are discussed extensively. The results of the developed numerical schemes are compared with those of commercial FLUENT code, and show a good agreement.

• Korean Journal of Microbiology
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• v.24 no.2
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• pp.147-153
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• 1986

Viable potential of Mycobacterium smegmatis, a slow grower in vitro cultivation and of M. leprae, an obligate intracellular parasitic bacterium, which can not be cultured yet in vitro was assessed by fluorospectrophotometry. Bacterial cells in different numbers and under various physiological status were incubater with fluorescein diacetate(FDA). After an incubation of the bacterial preparations with FDA at specified conditions, amount of fluorescein inside bacteria was measured by a fluorospectrophotometer at 470nm and 510nm of excitation and emission wavelengths, respectively. Fluorounit given by such bacteria showed a correlation with assessment of viability of the same preparations made by other methods, such as optical density and colony forming units of M. smegmatis and intracellular ATP content of M. leprae. The possible use of fluorospectrophotometry in assessing viability or physiological potential of bacteria, particularly intracellular parasites and fastidious organisms to culture in vitro is discussed in relation to other methods.

• Biomedical Science Letters
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• v.4 no.1
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• pp.35-42
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• 1998

The effects of CRP purified from human ascites fluid on phagocytic activity of the human macrophage were investigated. CRP was purified using affinity chromatography including absorption on p-diazonium phosphocholine or C-polysaccharide coupled sepharose 4B and gel filtration on hydroxylapatite column chromatography. Macrophage was separated ficoll hypaque gradient density and absorption method, and then was confirmed phagocytic uptake test using latex method. CRP was able either to inhibit or to enhance phagocytic activity of human macrophage against bacteria in vitro. The effects of CRP on phagocytic activity of human macrophage were in time and dose-dependent manners. The additional sequence of reaction mixture against bacteria in vitro shows a threshold stimulus on the activation of phagocytic response upon the CRP.