• 한국지구과학회지
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• 제41권3호
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• pp.211-221
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• 2020

이 연구는 SDSS DR7의 적색이동(z)<0.05이고, 동시에 R_pet>6 arcsec, 단축과 장축의 비(b/a)>0.6인 외부은하 25,308개를 분류하고, 색 영상을 육안으로 조사하여 고리 모양의 구조를 가진 531개 은하를 선별했다. 이 은하들이 일차적 표본으로 사용되었고, 이 중 90개의 외부고리 은하 후보를 선택했다. 후보 은하의 u, g, r, i, z 영상에 대한 표면 측광으로부터 도출한 특성을 조사하여 최종으로 69개의 외부고리 은하를 결정했다. 외부고리 은하는 국부은하의 0.3%를 차지하는 것으로 나타났으며, 두 개의 환경 인자, 즉, 가장 가까운 은하까지의 투영 거리와 국부 배경 은하 밀도를 이용하여, 외부고리 은하의 환경 특성을 조사했다. 외부고리 은하의 환경이 다른 은하의 경우와 비교하여 눈에 띄는 차이의 결과는 보이지 않았다.

• Tribology and Lubricants
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• 제39권4호
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• pp.123-132
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• 2023

In this study, the expansion, stress, and operating clearance of bearing elements during operation are observed using the inner/outer ring temperature test data of a 3.0×10⁶ DN-class roller bearing. The operating clearance characteristics of inner-/outer-ring cooling (IORC) bearings are compared to those of inner-ring cooling (IRC) bearings. For IRC bearings, the thermal expansion of the outer ring is the most important factor in clearance variation. As a result, the operating clearance is less than the initial clearance of 61 ㎛, and the operating clearance decreases to 0.5 ㎛ at 25,500 rpm. Conversely, the temperature of the outer ring of IORC bearings is lower than that of IRC bearings, so the operating clearance is kept smaller. When the coolant flow rate to the outer ring is approximately 1.5 to 2.0 L/min, the temperature difference between the inner and outer rings is minimized and the operating clearance is maintained at a significantly lower level than IRC bearings. Small operating clearances are expected to be effective in reducing cage slip and skid damage in roller bearings. The results and analysis procedures of this study can be utilized to design of bearing clearance, lubricant flow rate, and assembled interference in the early design stage of aerospace roller bearings.

• 천문학회보
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• 제38권2호
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• pp.53.2-53.2
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• 2013

외부 고리를 갖는 은하들(Outer ring galaxies)을 SDSS dr7 목록에서 분류하여, 이들이 갖는 특징과 링 구조(Ring structure)를 형성하는데 외부환경의 요인이 있는지 조사하고자 했다. z<0.05, b/a>0.6, R>6"의 조건에서 25,308개의 은하들을 추출하였고, SDSS image tool을 이용하여 531개의 외부 고리 은하(Outer ring galaxies)또는 외부고리를 갖고 있는 것처럼 보이는 은하(Ring-like galaxies)를 육안으로 분류하였다. 5개(u, g, r, i, z)의 필터로 관측되어진 CCD 이미지의 분석으로 최종적으로 69개의 외부고리 은하(Outer ring galaxies)를 선정하였다. 통계적으로 전체 은하에서 외부 고리 은하가 차지하는 비율이 약 0.2726%라는 결과를 얻게 되었고, 은하들의 주변의 환경을 조사한 결과 배경밀도와 비리얼 반경에 있어서 다른 형태의 고리를 갖고 있는 은하들과의 유의미한 특이점은 보이지 않았다.

• 한국기계가공학회지
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• 제16권4호
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• pp.38-45
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• 2017

A finite element analysis-based approach which investigates the causes of the breakdown in the outer ring of the choke at hot rod rolling mill is presented. Two-dimensional drawings of the whole vertical-type mill stand are transformed into three-dimensional CAD models. Non-linear elasto-plastic deformation analysis of material at the roll gap is performed for computing roll force and torque of the work roll. Then, the reaction forces of the bearing rings together with a set of roller bearings that support the work roll are obtained by means of rigid body motion analysis. Finally, stress behaviors in the bearing rings together with a set of roller bearings that support the work roll are investigated by linear elastic analysis. Results reveal that stress at the contact area between the outer ring and roller bearing is extraordinary high when an internal gap between an external surface of the outer ring and the internal surface of the chock due to wear of the inside of the chock occurs.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1398-1401
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• 2004

This paper proposes a new approach for the shape design of the rotating outer-ring type epicycloid plate gear by using instant velocity center. First, this method defines the instant velocity centers for rotating outer-ring type epicycloid plate gear and calculates the contact angles and the contact points by using the geometric relationships and the kinematic properties of the reducer. Second, it generates the full shape of the cycloidal plate gear. Finally, the paper develops CAD-program for construction of the design automation using the proposed method. This CAD-program is developed to have the functions of the friendly user interface and the simulation of the real operation for the cycloid reducer.

• 대한기계학회논문집A
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• 제36권12호
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• pp.1613-1618
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• 2012

자동차용 휠 베어링은 동력을 전달하고 차량의 무게를 지지해주는 중요한 부품으로써 너클에 체결된다. 이때 체결 토크에 의하여 시일 압입부와 궤도부를 포함하는 휠 베어링 외륜의 변형이 발생한다. 본 연구에서는 휠 베어링 외륜의 변형을 유한요소법을 이용하여 해석하였다. 상용 소프트웨어 MSC.MARC 를 이용하였고, 외륜, 볼트, 너클의 체결거동을 보다 정확하게 예측하기 위하여 탄소성 해석과 접촉 해석을 수행하였다. 외륜 플랜지는 가공에 따라서 다소 오목하게 형성될 수 있으며, 이는 너클과의 체결 시 틈새 발생을 유발하여 변형에 영향을 줄 수 있다. 따라서, 본 연구에서는 외륜의 오목한 정도를 변화시키면서 변형 해석을 수행하였다. 해석 결과를 검증 하기 위하여 시험을 수행하였고, 해석과 시험 결과를 비교한 결과 비교적 유사함을 알 수 있었다.

• 한국산학기술학회논문지
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• 제16권2호
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• pp.952-962
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• 2015

열간 링 롤링 공법은 열간단조 후의 잠열을 이용하기 때문에 가공 부하가 적고 최종 환형제품에 가까운 제품을 제조하는 장점이 있다. 본 연구에서는 열간 링 롤링 공법에 의한 대형 직경의 환형 부품의 다중형상 링 제조를 목표로 AFDEX2D 및 AFDEX3D/HEXA/RING 시뮬레이터(simulator)를 이용하여 열간 단조공정부터 링 롤링 공정까지 연계된 공정을 유한요소 해석하였다. 또한 링 롤링공정의 유한요소해석 시간을 줄이기 위해 소성변형이 일어나고 있는 영역에서만 요소망을 조밀하게 재구성하는 이중요소 시스템을 적용하였다. 이 유한요소해석 결과를 바탕으로 실제 공정을 설계하고 실험하여 개발된 제품이 품질 규격을 만족하는지를 확인하였다. 또한 링 롤링 실험 완성품을 통하여 부품의 품질수준 및 공정능력을 평가하였다. 그 결과, 개발된 환형 부품은 40%의 투입재료 감소과 최종 제품의 원소재 회수율이 24% 증가하였다. 또한 링 롤링 제품은 내, 외경의 진원도가 0.5mm로 우수하였으며 공정능력 분석결과 외경 Cpk 1.49, 내경 Cpk 0.85를 확보하여 환형 부품의 다중 형상 열간 링 롤링 공정의 최적화를 실현하였다.

• 대한치과보철학회지
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• 제38권2호
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• pp.214-225
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• 2000

The purpose of this study was to investigate the effects of investing conditions on the marginal discrepancy of conical telescope outer crown with Co-Cr-Ti alloy(Dentitan) and to compare the marginal discrepancy and the retention force of outer crowns using different pattern materials(plastic foil, casting wax, pattern resin). To evaluate the effects of investing conditions on the marginal discrepancy, patterns with plastic foil were invested under three different liquid/powder ratio conditions using phosphate bonded investment(Univest-nonprecious): standard, 10% decreased and 10% increased. At each liquid/powder ratio condition, metal ring was lined with single or double layers of ceramic ring liner. The marginal discrepancy of outer crown at different investing conditions was measured by ${\times}100$ compact measuring microscope(STM5, Olympus, Japan). For measurement of the marginal discrepancy and the retention force of outer crown using different pattern materials, the investing condition of 10% decreased liquid/powder ratio and double layers of ring liner was selected because this investing condition resulted in the best fit of outer crown. Marginal discrepancy was measured in the same way above and retention force on universal testing machine. Under the conditions of this study, the following conclusions were drawn: 1. The thickness of ring liner had more influence on the marginal discrepancy of outer crown than the liquid/powder ratio, and the acceptable marginal fitness could not be expected at the investing condition directed by investment manufacturer 2. There were no differences in the marginal discrepancy of outer crown among three different pattern materials(P>0.05). 3. Casting wax showed the greatest retention force(1640g) of outer crown, followed by pattern resin(1110g), plastic foil(820g). However, there was no significant difference between plastic foil and pattern resin(P>0.05). 4. Plastic foil showed the least variation in marginal discrepancy and retention force.

• 한국생산제조학회지
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• 제19권5호
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• pp.609-615
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• 2010

Angular contact ball bearings in a high speed spindles are under the extreme conditions, such as high temperature, big centrifugal force and thrust cutting forces. So, the assembly contacts between spindle shaft and inner ring bearings, bearing housing and outer ring of bearings are occasionally unstable at high speed revolution. Furthermore, the ball contact angle of a bearing, which influence stiffness and lifetime of bearings, are changed according to loads and rotational speed. To analyze internal forces of a bearing under high speed revolution, the ball contact are calculated using nonlinear equations in consideration of rotational speed, thrust loads and raceway form. Diameter increase of inner and outer ring by influence factors, such as internal forces to inner and outer ring, centrifugal force and temperature of inner and outer rings are calculated to establish stable state in bearing assembly in high speed spindle. Finally, contribution ratio of influence factor to assembly design tolerance of inner and outer rings are shown and the stable assembly design tolerance are proposed.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(3)
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• pp.265-270
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• 1996

The temperature distribution in the pellet was obtained from beginning the general heat conduction equation. The thermal conductivity of pellet used the SIMFUEL data that made clear the effect of burnup on the thermal conductivity degradation. Since the pellet rim acts as the thermal barrier to heat flow. the pellet was subdivided into several rings in which the outer ring was adjusted to play almost the same role as the rim. The local burup in each ring except the outer ring was calculated from the power depression factor based on FASER results. whereas the rim burnup at the outer ring was achieved by the pellet averaged burnup based on the empirical relation. The rim changed to the equivalent Xe film so the predicted temperature shooed the thermal jump across the rim. The observed temperature profiles depended on linear heat generation rate. fuel burnup. and power depression factor. The thermal conductivity degradation modelling can be applied to the fuel performance code to high burnup fuel,