• 한국음향학회지
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• 제37권6호
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• pp.396-403
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• 2018

본 논문에서는 쾌적한 운전 환경을 제공하기 위해 자동차 시트를 냉각시키기 위한 고성능 및 저소음 원심팬을 개발하였다. 먼저 팬 성능 테스터 및 전산유체역학(Computational Fluid Dynamics, CFD) 시뮬레이션을 이용하여 기존 팬 장치의 유동 특성을 분석하였다. 예측한 유동장 분석을 통하여 팬 허브 팁 근처의 와류 및 팬 허브 상단의 정체된 유동 현상이 관측되었다. 이러한 와류 및 정체 유동을 줄이기 위해 두 가지 설계 요소를 고안하였다. 첫째, 팬 날개와 팬 하우징 최소 간극(cut-off)를 증가시켜 난류강도를 줄이고 그 결과로 전체적인 음압 레벨을 줄이고자 하였다. 둘째, 허브 형상은 정체 유동을 줄이기 위해 형상을 변경하였다. 제안된 설계의 타당성을 수치해석을 통해 확인하였다. 수치해석결과를 바탕으로 프로토타입을 제작하고 팬 테스터에서 측정한 성능 곡선(P-Q curve)과 반무향실에서 측정한 음압 레벨의 분석을 통해서 유동과 소음 성능의 향상을 확인하였다.

• 한국음향학회지
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• 제42권6호
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• pp.519-528
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• 2023

본 논문에서는 식기 세척기 내 원심펌프를 대상으로 수치적/실험적 연구를 통해 최적 설계를 수행하였으며 유량 및 소음 성능을 개선하고자 하였다. 먼저 대상 원심펌프의 특성을 실험적으로 분석하기 위해 펌프 성능시험기를 통한 유량 실험과 반 무향실에서의 소음 실험을 진행하였다. 원심펌프 회전에 따른 내부 유동 및 유동 소음 성능을 수치적으로 모사하기 위해 전산유체역학 기반의 Reynolds Averaged Navier-Stokes(RANS) 방정식과 Ffowcs Williams and Hawkings 방정식을 지배 방정식으로 수치해석을 수행하였다. 실험 결과와의 비교를 통해 수치 기법의 유효성을 검증하였으며, 검증된 수치 기법을 활용하여 원심펌프 내 임펠러 형상에 대한 최적 설계를 수행하였다. 수치 기법의 활용을 통해 최적 설계된 임펠러의 개선된 유량 성능을 수치적으로 확인하였으며, 유동장 분석을 통해 임펠러 형상 각도 변화에 따른 유동 특성 변화 및 개선을 확인하였다. 또한, 시제품 제작 및 실험을 통해 개선 유량 성능을 검증하였으며, 팬 법칙에 의거하여 동일 유량에서 소음 수준이 감소함을 확인하였다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2017년도 춘계공동학술대회
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• pp.154-154
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• 2017

Root is an important organ of plant that typically lies below the surface of the soil. Root surface determines the ability of plants to absorb nutrient and water from the surrounding soil. This study describes an application of image processing and computer vision which was implemented for rapid measurement of seed germination such as root length, surface area, average diameter, branching points of roots. A CCD camera was used to obtain RGB image of seed germination which have been planted by wet paper in a humidity chamber. Temperature was controlled at approximately 250C and 90% relative humidity. Pre-processing techniques such as color space, binarized image by customized threshold, removal noise, dilation, skeleton method were applied to the obtained images for root segmentation. The various morphological parameters of roots were estimated from a root skeleton image with the accuracy of 95% and the speed of within 10 seconds. These results demonstrated the high potential of computer vision technique for the measurement of seed germination.

• 대한기계학회논문집B
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• 제27권8호
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• pp.1042-1050
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• 2003

A heating flow discharged from a 4-way ceiling type indoor unit has been investigated to determine the design parameters for the optimal flow control. The flow was measured by a PIV(particle image velocimetry) system and an experimental model of 1/10 scale with a transparent room was devised by satisfying the Archimedes number. This similarity is generally used in cases where the forced convection has similar magnitude of the natural convection. To optimize the heating flow, several vane angles and vane control algorithms of cross and right angle controls were considered. Regarding the vane angle, experimental results show that 30$^{\circ}$is an optimal angle to avoid re-suction flows without significant increase in flow noise. Temperature distribution measured in the environmental chamber ensures the increased thermal comfort when compared to the case, 60$^{\circ}$angle. At the optimal angle, applying open/close control gives rise to more uniform distribution of the heating flow than without control. Especially, the cross-control seems to be satisfactory for thermal comfort.

• Tribology and Lubricants
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• 제13권1호
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• pp.14-20
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• 1997

This paper reports on theoretical study of the pressure overshoot in the delivery ports and pressure rising within balanced type vane pump. Pressure overshoot occur due to the accelerated fluid through the notch, so, result in pressure ripple, flow ripple, and noise. For calculating the pressure rising and fluctuations of pressure, we have modeled mathematically used continuity equation based on compressibility and momentum equation considered fluid inertia in the notch, and analyzed simultaneously. As a results of analysis, we have found oscillation of pressure and compression chamber pressure depend on the rotational speeds, notches. Using the model, notches have been shown to be important design factor in relaxing the rapid pressure rising and reducing the amplitudes of pressure overshoot.

• Journal of Microbiology and Biotechnology
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• 제17권1호
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• pp.5-14
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• 2007

Nanotechnology is the creation and utilization of materials, devices, and systems through the control of matter on the nanometer. The technology has been applied to biodevices such as bioelectronics and biochips to improve their performances. Nanoparticles, such as gold (Au) nanoparticles, are the most widely used of the various other nanotechnologies for manipulation at the nanoscale as well as nanobiosensors. The immobilization of biomolecules is playing an increasingly important role in the development of biodevices with high performance. Nanopatteming technology, which is able to increase the density of chip arrays, offers several advantages, including cost lowering, simultaneous multicomponent detection, and the efficiency increase of biochemical reactions. A microftuidic system incorporated with control of nanoliter of fluids is also one of the main applications of nanotechnologies. This can be widely utilized in the various fields because it can reduce detection time due to tiny amounts of fluids, increase signal-to-noise ratio by nanoparticles in channel, and detect multi-targets simultaneously in one chamber. This article reviews nanotechnologies such as the application of nanoparticles for the detection of biomolecules, the immobilization of biomolecules at nanoscale, nanopatterning technologies, and the microfluidic system for molecular diagnosis.

• 한국자동차공학회논문집
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• 제18권6호
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• pp.145-151
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• 2010

The performance of a direct-injection diesel engine often depends on the strength of swirl or squish, the shape of combustion chamber, the number of nozzle holes, etc. This is natural because the combustion in the cylinder was affected by the mixture formation process. Since the available duration to make the mixture formation of air-fuel is very short, it is difficult to make complete mixture. Therefore, an early stage of combustion is violent, which leads to the weakness of noise and vibration. In this paper, the combustion process of a common-rail diesel engine was studied by employing two kinds of pistons. One has several grooves with inclined plane on the piston crown to generate swirl during the compression and expansion strokes in the cylinder in order to improve the atomization of fuel. The other is a toroidal piston, generally used in high speed diesel engines. To take photographs of flame and flaming duration, a four-stroke diesel engine was remodeled into a two-stroke visible single cylinder engine and a high speed video camera was used.

• 한국연소학회지
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• 제20권3호
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• pp.13-20
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• 2015

The performance of a direct-injection diesel engine often depends on the strength of swirl or squish, the shape of combustion chamber, the number of nozzle holes, etc. This is natural because the combustion in the cylinder was affected by the mixture formation process. Since the available duration to make the mixture formation of air-fuel is very short, it is difficult to make complete mixture. Therefore, an early stage of combustion is violent, which leads to the weakness of noise and vibration. In this paper, the combustion process of a common-rail diesel engine was studied by employing two kinds of pistons. One has several cavities on the piston crown to intensify the squish during the compression stroke in order to improve the atomization of fuel, we call this multi cavity piston in this paper. The other is a toroidal single cavity piston, generally used in high speed diesel engines. To take photographs of flame and flaming duration, a four-stroke diesel engine was remodeled into a two-stroke visible single cylinder engine and a high speed video camera was used.

• 한국의류산업학회지
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• 제10권4호
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• pp.537-543
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• 2008

The purpose of this study was to evaluate the comfort and fabric hand characteristics of selected lining fabrics made of acetate and polyester. The comfort of the linings was determined by human subjects wearing suit blazers constructed with different lining materials in an environmental chamber controlled at $30.6^{\circ}C$ air temperature and 50% relative humidity. The hand characteristics of the lining fabrics were determined by five trained panelists using standard fabric reference samples. The effect of lining fabrics on the subjects' thermal sensations was not statistically significant. But the subjects voted warmer when wearing the polyester surah lined blazer or the polyester taffeta blazer than wearing the acetate blazers. The results of the subjective comfort evaluation indicated that, in general, the subjects rated the acetate linings significantly less sticky, clammy, damp, and non-absorbent than the polyester linings. Acetate surah was rated a little higher than the other acetate fabrics on these comfort descriptors. The results of the subjective hand evaluation indicated that the lining fabrics rated low on the geometric and mechanical hand characteristics and rated moderate on noise. Acetate surah scored the highest on most of the hand characteristics, whereas, polyester taffeta scored the lowest.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.860-865
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• 2000

This Paper Proposes the test pieces of X, Y and Z axes to compensate the shape distortion of Selective Laser Sintering(SLS) parts resulting from the phase change during the sintering process. In no case of the proposed compensation test pieces of X, Y axes the accurate rates of shrinkage can be measured with the reduction of curling which is obtained from adjustment of build orientation and the formula used to get scale factors are proposed with the shrinkage rates of them. The scale factors of X, Y and Z axes are generated by building up proposed compensation test pieces. The generated scale iactors are required to satisfy the dimensional accuracy even if there are changes of the build position and the size of SLS parts in the build chamber. For this reason, it is proposed that the build positions and the size be considered to be noise factors against the compensation test pieces and a method is also proposed that scale factors be selected to robustly maintain the dimensional accuracy of SLS parts under the actual operating conditions with the application of the Taguchi Method.