• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년 영문 학술대회
• /
• pp.255-259
• /
• 2008

This paper presents the spray characteristics of the oxidizer rich preburner injector which can be used in the high-thrust rocket system. We designed the basic shape of the liquid-liquid coaxial swirl injector for the rocket oxidizer rich preburner injection system. To understand the spray angle variation with the high pressure environment, the spray visualization in the high pressure chamber was preformed. Also we measured the droplet velocity, the Sauter Mean Diameter(SMD), the volume flux and the number density with the PDPA system by using water in atmospheric pressure. The results show that the spray angle is reduced by increasing ambient pressure and maximum droplet velocity is shown from a nozzle tip and then the droplet velocity decreases as a spray moves to the downstream. The SMD decreases on the axial distance from 20 mm to 50 mm but it increases over 50 mm. That is due to the increasing number of collision with each droplet and interaction with ambient air on going downstream direction.

• 대한조선학회논문집
• /
• 제31권1호
• /
• pp.121-132
• /
• 1994

본 연구에서는 선저보강판부재의 좌초시 손상거동특성을 규명하기 위하여 시리즈 실험을 수행하였다. 즉, 강체웨지가 선저보강판을 연직방향에서 준정적으로 진입할 때 여러가지 파라메타 즉 1) 판의 종횡비, 2)웨지각도, 3)판두께, 4)웨지형상 및 5)종 횡보강재의 변화에 따른 시리즈 실험을 수행하고, 좌초시 선저보강판의 좌초하중-진입량 관계와 흡수에너지-진입량 관계 등에 관한 파라메타들의 영향을 분석하였다.

• 한국기계가공학회지
• /
• 제19권11호
• /
• pp.23-28
• /
• 2020

In general, lithography techniques are applied when machining single-crystal silicon in nanoscale applications; however, these techniques involve low degrees of freedom for the vertical shapes. By applying mechanical techniques to machine silicon, nanopatterns having various types of vertical shapes can be manufactured. In this study, we determined the ductile-brittle machining transition point and analyzed the- variation of the specific cutting resistance within the ductile machining region in nanoscale applications. When brittle fracture occurred during the nanoscale cutting, the depth of cut and cutting force increased and decreased rapidly, respectively. The first point of rapid increase in the depth of cut was defined as the ductile-brittle machining point. Subsequently, the shape of the machining tool was observed using a scanning electron microscope to calibrate the machining area, considering the tip blunting. The specific cutting resistance decreased continuously and converged to a certain value during the nanoscale cutting. The decrease and convergence in the value can be attributed to the decrease in the ratio of the arc length to the area of the machining tool and silicon.

• 한국지열·수열에너지학회논문집
• /
• 제17권1호
• /
• pp.23-32
• /
• 2021

Conventional wind power generators have limited installation sites due to low efficiency due to reverse resistance or high cut-in speed. To compensate for these problems, this study proposed another new type of tilting wind turbine. The key to this method is the structural design of a cylindrical cam with a guide groove that allows the blade to tilt. As the blade rotates by the cam, it tilts according to the angle. In the section that generates torque by receiving drag, the blade is made perpendicular to the wind. And it is a structure that creates a parallel state with the wind in the section where reverse resistance occurs. We prepared six types of cams considering the length of the section subject to drag, reverse resistance, tilting section. The performance was analyzed as the maximum value of the output, torque coefficient, and efficiency coefficient, which is indicated by setting different wind speed and low TSR.

• Archives of Plastic Surgery
• /
• 제48권1호
• /
• pp.44-48
• /
• 2021

Previously reported nipple-areolar complex reconstruction (NAR) methods involve multiple incisions and wide skin redraping, which increase retraction forces and heighten the risk of nipple-areolar complex (NAC) flattening. We introduce a NAR method using the long V-Y advancement technique that can overcome these disadvantages. A V-shaped flap is designed with the width of the flap base 4-5 mm larger than the diameter of the normal nipple. The flap length is designed to be at least 2.5 times its width. Dissection is performed to the top of the artificial dermal matrix or muscle layer. The nipple is constructed with the same projection as the contralateral side by folding the elevated flap. The tip of the elevated flap is apposed in the middle of the donor defect to minimize the deformity during donor site closure. A 3-point skin suture is applied to the upper third of the folded flap to mold its shape. Using this long V-Y advancement technique, we successfully decreased skin tension in NAC flaps and improved the maintenance of reconstructed nipple projection. The long V-Y advancement technique provides an easy, simple NAR method, effectively maintaining longer nipple projections and reducing breast deformities, especially in Asian women with relatively large nipples.

• Design & Manufacturing
• /
• 제16권4호
• /
• pp.46-51
• /
• 2022

The piercing process of creating holes in sheet metals for mechanical fastening generates high shear force. Real-time monitoring technology could predict tool damage and product defects due to this severe condition, but there are few applications for piercing high-strength aluminum. In this study, we analyzed the load signal to predict the punch's wear level during the process with a piezoelectric sensor installed piercing tool. Experiments were conducted on Al6061 T6 with a thickness of 3.0 mm using piercing punches whose edge angle was controlled by reflecting the wear level. The piercing load increases proportionally with the level of tool wear. For example, the maximum piercing load of the wear-shaped punch with the tip angle controlled at 6 degrees increased by 14% compared to the normal-shaped punch under the typical clearance of 6.7% of the aluminum piercing tool. In addition, the tool wear level increased compression during the down-stroke, which is caused by lateral force due to the decrease in the diameter of pierced holes. Our study showed the predictability of the wear level of punches through the recognition of changes in characteristic elements of the load signal during the piercing process.

• Applied Microscopy
• /
• 제39권1호
• /
• pp.41-48
• /
• 2009

본 연구는 색조화장품에 사용되는 진주광택안료의 특성을 주사전자현미경과 에너지분산분광분석기 및 열분석기를 사용하여 규명하였다. 본 연구에 사용된 인공합성 진주광택안료를 여성의 볼과 눈두덩 부위에 화장을 한 후 육안으로 관찰하였을 때 진주 광택안료는 보는 각도에 따라 흰색에서 보라색까지 다양한 색조로 빛을 반사하였다. 진주광택안료의 주사전자현미경 관찰 결과 안료는 얇은 판상의 다각형의 형태를 하고 있었으며 크기는 규격화된 모양이 아니고 다양하게 관찰되었다. 이런 조각의 크기는 약 $30{\mu}m$에서 $300{\mu}m$까지 측정되었고 안료 조각은 끝이 뾰족하거나 각진 상태로 존재하였다. 고배율의 주사전자현미경상에서 안료조각의 모서리 부위와 측면은 날카롭지 않은 타원형의 형태로 나타났으며 두께는 약 $9{\mu}m$로 측정되었다. 안료조각 표면은 직경이 약 60 nm의 이산화티탄 입자들에 의해서 피복되어 있었다. 진주광택안료의 에너지분산분석기를 사용하여 구성 원소 성분을 분석한 결과 안료의 표면은 O, Si, C, Na, Ca, Ti, Zn 등이 검출되었고 안료의 측면 부위도 동일한 성분들이 검출되었다. 이들 안료는 운모 티타니아(mica titania)로 확인되었다. 진주광택안료의 열분석 결과 초기 $100^{\circ}C$부터 $800^{\circ}C$까지 중량 감소는 큰 차이를 보이지 않았다. 열분석 결과 $115^{\circ}C$에서 1.1% 중량 감소를 하였고 $416^{\circ}C$에서 1.7% 감소하였으며 $797^{\circ}C$ 에서 1.9%의 중량이 감소된 것을 확인하였다.

• 한국진공학회지
• /
• 제18권2호
• /
• pp.97-101
• /
• 2009

현대의 반도체 산업에서 공정 중 가장 큰 비중을 차지하며, 가장 많은 자본과 인력을 소비하는 것이 바로 세정 공정이다. 세정공정은 소자의 작동에 영향을 미치고 기능을 저하시킬 수 있는 이물질 입자들을 제거하는 것이다. 특히 소자를 식각하기 위한 Photoresist(PR) 과정이 끝날 때마다 항상 세정 과정이 포함되어야 했다. 또한, Photoresist(PR) 공정 중 생성된 HDI-PR(high dose implanted photoresist)은 세정 과정에서 제거가 힘들기 때문에 현대의 고밀도 집적회로 세정 공정에서는 건식 세정과 습식 세정을 혼용하여 여러 단계의 세정 공정을 거치게 된다. 이 논문에서는 기존 플라즈마 방식으로 대표되는 건식 세정과 약액으로 대표되는 습식 세정을 동시에 사용하는 방식을 사용하여 약액활성화 방법(Plasma Liquid-Vapor Activation; PLVA)을 제안하여 실험을 실시하였고 HDI-PR을 활성화된 용액에 담근 후 Nano-Indenter를 이용하여 표면강도와 탄성계수를 측정했다. Nano-indenter는 특정한 기하학적 형태를 가지는 Tip을 표면에 압입한 후 압입하중과 압입깊이를 측정함으로서 시료의 표면강도와 탄성계수를 측정하였다. 그 결과 plasma로 활성화된 PR stripper 용액으로 strip한 후의 시료의 표면 강도가 크게 줄어든 것을 확인하였다. 이는 이후 물리적 표면 세정 공정을 후 공정으로 사용한다면 보다 효율적인 HDI-PR을 제거할 수 있을 것으로 사료된다.

• 수산해양기술연구
• /
• 제29권3호
• /
• pp.200-213
• /
• 1993

A model experiment on a midwater rope trawl net which is used in the North Pacific to catch alaska pollack is carried out in the circulating tank to examine the basic efficiency of the net. The prototype is the net used by M/S Hanil(1, 179GT, 2, 700PS), a Korean trawler. The model net was made according to the Tauti's Similarity Law of Fishing Gear in 1/100 scale by considering the condition of the tank. To measure the basic efficiency of the standard model net, the vertical opening and width between some points marked on the net were measured, and the hydrodynamic resistance were determined. Then the constructive conditions of the net were varied as follows and the factors were measured again to compare the efficiency of those nets with that of the standard net(A-1 type) front weight multiplied 1.5 times: A-2 type. buoyancy and depressing force multiplied 1.7 times: A-3 type. front weight multiplied 1.5 times on A-3 type: A-4 type. depressors rigged at ground rope: B type. cod-end stuffed with cashmylon wad: C type. The results obtained can be summarized as follows: 1. The vertical opening at the center of head rope was steeply decreased with the flow velocity increasing and the vertical opening H(m) can be expressed in H=1.2v super(-1.2)(v : flow velocity in m/sec). The width of the net varied a little when the flow velocity was over 0.4m/sec, and the width of net mouth showed about 37% of the distance between the fore tips of net pendant. The shape of net mouth was almost a circle at 0.2m/sec and then steeply flatted elliptically with the flow velocity increasing and the area of mouth S(m super(2)) can be expressed in S=(1.65-2.3v)$\times$10 super(-2). The hydrodynamic resistance of the net increased almost linearly with the flow velocity increasing and the resistance R(kg) can be expressed in R=3.2$\times$d/l$\times$abv. where d/l denotes the mean of d(diameter of netting twine) and l(length of a leg in a mesh) from wing tip to the end of bag-net except cod-end on the side pannel, and a denotes the strectched circumference of the net at the fore end of a meshed part and b the stretched length of the whole net from wing tip to the end of cod-end. 2. In the condition-varied nets, the vertical opening of head rope showed some increase in every type net except the C type, and the increase showed the greatest in the B type by 30~54%, whereas it showed decrease in the C type by 5~10%. Variation of the area of net mouth showed almost the same tendency as the vertical opening and the increase showed the greatest in the B type by 20%, whereas it showed decrease in the C type by 12%. Hydrodynamic resistance showed some increase in every type compared with the standard net, and the rate of increase indicated 5~10% in the A-2, A-3 and A-4 type, 22% in the B type and 3% in the C type.

• 대한기계학회논문집B
• /
• 제35권8호
• /
• pp.781-787
• /
• 2011

본 연구에서는 4단으로 구성된 LNG 플랜트용 프로판 냉매 원심 압축기 각 단의 설계점에 대해 상용 코드를 이용하여 공력설계를 하였다. 1차원 공력 설계 결과와 3차원 유로 형상의 타당성은 유동해석을 통해 확인하였다. 특히 입구전압이 높고 회전수가 큰 4단 압축기 임펠러의 유로와 베인리스 디퓨저 내부 유동에 대한 속도장, 압력장 및 엔트로피 등의 유동특성에 대해 고찰하였고, 아울러 익단 간극이 유동장에 미치는 영향에 대해서도 알아보았다. 본 연구 결과는 프로판 냉매 압축기의 시스템 제작에 활용될 것이며 추후 실제 실험결과와 비교하고자 한다. 향후 설계된 프로판 냉매압축기에 대한 LNG 플랜트에서의 실증시험을 통해 구체적인 설계결과에 대한 평가 및 설계 개선이 이루어지리라 생각한다.