• 한국구조물진단유지관리공학회 논문집
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• 제27권5호
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• pp.89-96
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• 2023

본 연구에서는 강봉댐퍼의 변위의존성 평가, 강도 및 에너지소산능력을 평가하였다. 실험 변수는 단면형상 및 형상비이며, 총 6개의 실험체를 제작하였다. 실험 결과, 설계기준에서 제시한 변위 의존성 조건을 모든 실험체가 만족하는 것으로 평가되었다. 그리고 단면형상에 따른 강도 영향은 미비하였다. 결과적으로, 형상비 13.7의 강도 및 에너지소산능력이 우수한 것으로 평가되었다.

• Tribology and Lubricants
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• 제18권6호
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• pp.384-388
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• 2002

The adequate design of a passenger car braking system, which is directly related to the safety of a car, is very important since the safety is an essential design parameter of a car to keep men and car from the damage. The thermal behaviors of the ventilated disk has been investigated based on the air cooling effects during repeat braking operations. In this study, the thermal behavior of ventilated disk brake system was investigated by numerical method. The 3-Dimensional unsteady model was simulated by using a general purpose software package “FLUENT” to obtain the temperature distributions of disk and pad. The model includes the more realistic braking method, which repeats braking and release. The effects of aspect ratio of ventilated hole on the heat dissipation was investigated.

• 설비공학논문집
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• 제3권5호
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• pp.395-403
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• 1991

The purpose of this investigation was to characterize nucleate boiling and burn-out heat flux for rectangular free jet with saturated water impinging perpendicularly and upward against a flat uniform heat flux surface. Heat flux measured for Reynolds number based on rectangular nozzle width and for aspect ratio. The result of nucleate boiling heat transfer was presented nondimensional experimental equation including Nusselt, Boiling, Subcooling, Reynolds and Weber number. The effect of aspect ratio of heated surface in the burn-out heat flux had not appeared distinctly. But for the same aspect ratio, burn-out heat flux increased linearly with increment of nozzle exit velocity.

• 한국유체기계학회 논문집
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• 제13권3호
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• pp.30-36
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• 2010

The detailed heat transfer coefficients on a rotating dimpled channel were measured by the hue detection based the transient liquid crystal technique. The dimples were fabricated on the one side of the channel and the tested channel aspect ratio was 4, 6, and 12 with fixed channel width. Tested Reynolds number based on the channel hydraulic diameter was varied from 21,000 to 47,000. A stationary case and two different rotating conditions were tested so that the dimple fabricated surface became leading or trailing surface. For all rotating conditions, the minimum averaged heat transfer coefficient was measured for the channel aspect ratio of 6. Generally, the highest averaged heat transfer coefficient was observed for the highest aspect ratio cases due to increased dimple induced vortex strength.

• 대한기계학회논문집
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• 제16권11호
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• pp.2181-2188
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• 1992

본 연구에서는 크기가 45˚인 부채형 공간내의 자연대류 열전달 특성을 고찰 하기 위하여 간격비, 경사각 그리고 Rayleigh 수를 변수로 하여 유한 차분법으로 수치 해석 하고, 대료적인 간격비 L/r$_{i}$=1.6에서 Ra=2.51*$10^{4}$ 및 Pr=0.71일때, Machzehnder 간섭계를 사용하여 실험 하였으며, 수치해석과 실험결과를 비교하였다.

• Steel and Composite Structures
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• 제9권4호
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• pp.367-380
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• 2009

This study focuses on the experimental evaluation of the flexural-torsional performance of high strength thin-walled composite members. A series of tests on composite members with various sectional aspect ratios subjected to eccentric cyclic loads were conducted. Test results show that the composite member's torsional strength could be approximated using a series of linear segments and evaluated using the superposition of the component steel and reinforced concrete responses. It is also validated from the tests that the strength deterioration of members subjected to combined loads is closely related to the aspect ratios of the sections. An interaction expression between the bending and torsion for high strength thin-walled composite members is proposed for engineering practice references.

• 지구물리와물리탐사
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• 제11권1호
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• pp.41-51
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• 2008

해양성 현무암층에 대해 현장에서의 속도와 공극률의 관계를 알기 위해서 Juan do Fuca 해저산맥의 동쪽 측면으로부터 채취한 현무암 시료들에 대해 최고 40MPa 구속압력(confining pressure)하에서 균열 특성을 고려하며 P파와 S파 속도를 측정하였다. 구속압력에 따른 속도의 변화는 미세균열의 닫힘(microcrack closure)에 기인한다고 가정하고, Kuster-$Toks{\ddot{o}}z$ 이론을 이용하여 미세균열의 개구비 스펙트라(micro-crack aspect ratio spectra)를 측정하였다. 그 결과 서로 다른 시료들의 정규화된 개구비 스펙트라들이 유사한 특성을 갖는다는 것을 보여주었다. 그리고 나서 정규화된 개구비 스펙트럼(spectrum)으로부터, 각 공극률에 대한 개구비 스펙트럼을 계산함으로써 이론적인 속도와 공극률의 관계를 만들었다. 또한 구속압력에 따른 미세균열 닫힘을 고려하여 구속압력의 함수로서의 속도-공극률 관계를 얻을 수 있었다. 개구비 스펙트라를 고려한 이론적인 관계는 대기압하에서 측정된 100개가 넘는 시료들에 대해 관찰된 관계와 잘 일치하고, 넓은 범의의 공극률에 대해 일반적으로 관찰되는 압력 의존적인 관계와도 잘 일치된다. 실험에서 유도된 자료들과 이론적으로 계산된 값들의 일치를 통해 Juan de Fuca 해저산맥의 동쪽 측면으로부터 얻어진 현무암 시료의 속도와 공극률의 관계는 균열의 특성(즉, 정규화된 개구비 스펙트라)과 균열 담힘에 의해 설명되어질 수 있음을 알 수 있다.

• 한국생산제조학회지
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• 제7권4호
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• pp.104-116
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• 1998

This paper provides a review of the performance for SM45C using the CNC lathe. Under the constant cutting area, the tool wear for large feed rate is more than the small feed rate, and the progress goes more rapidly as the cutting speed is increased. This is caused by the friction between the workpiece and the bite. The average cutting force increases as the feedrate increases, and decreases as the cutting speed increases. This is because the effective rake/shear angle becomes smaller as the feedrate becomes larger. The higher is the cutting speed and the aspect ratio (the ratio for depth of cut to feedrate), the lower is the cutting force and the surface roughness. Also, for the optimal selection of the cutting conditions, many experimental graphical data were obtained. That is, the cutting force, the tool life, and the surface roughness were measured and investigated as the depth of cut and the feedrate changed. And the size effect was examined as the depth of the cut varied.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.429-434
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• 2007

This paper presents an experimental and parametric study of a biomimetic fish robot actuated by the Lightweight Piezo-composite Actuator(LIPCA). The biomimetic aspects in this work are the oscillating tail beat motion and shape of caudal fin. Caudal fins that resemble fins of BCF(Body and Caudal fin) mode fish were made in order to perform parametric study concerning the effect of caudal fin characteristics on thrust production at an operating frequency range. The observed caudal fin characteristics are the shape, area, and aspect ratio. It was found that a high aspect ratio caudal fin contributes to high swimming speed. The fish robot was propelled by artificial caudal fins shaped after thunniform-fish and mackerel caudal fins, which have relatively high aspect ratio, produced swimming speed as high as 2.364 cm/s and 2.519 cm/s, respectively, for 300 Vpp input voltage excited at 0.9 Hz. Thrust performance of the biomimetic fish robot was examined by Strouhal number, Froude number, Reynolds number, and Net forward force.

• Environmental Analysis Health and Toxicology
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• 제30권
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• pp.1.1-1.8
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• 2015

Objectives In this study, the effect of tube length and outer diameter (OD) size of hydroxylated-multi walled carbon nanotubes (OH-MWCNTs) on their uptake and toxicity was investigated in the nematode Caenorhabditis elegans using a functional mutant analysis. Methods The physicochemical properties of three different OH-MWCNTs were characterized. Uptake and toxicity were subsequently investigated on C. elegans exposed to MWCNTs with different ODs and tube lengths. Results The results of mutant analysis suggest that ingestion is the main route of MWCNTs uptake. We found that OH-MWCNTs with smaller ODs were more toxic than those with larger ODs, and OH-MWCNTs with shorter tube lengths were more toxic than longer counterparts to C. elegans. Conclusions Overall the results suggest the aspect ratio affects the toxicity of MWCNTs in C. elegans. Further thorough study on the relationship between physicochemical properties and toxicity needs to be conducted for more comprehensive understanding of the uptake and toxicity of MWCNTs.