• 한국자동차공학회논문집
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• 제3권6호
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• pp.96-111
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• 1995

A bellows is a component installed in the automobile exhaust system to reduce the impact from an engine. It's stiffness has a great influence on the natural frequency of the system. Therefore, it must be designed to keep the specified stiffness that requires in the system. This study present the finite element analysis of U-typed bellows using a curved conical frustum element and the shape optimal design with specified stiffness. The finite element analysis is verified by comparing with the experimental results. In the shape optimal design, the weight is considered as the cost function. The specified stiffness from the system design is transformed to equality constraints. The formulation has inequality constraints imposed on the fatigue limit, the natural frequencies, the buckling load and the manufacturing conditions. A procedure for shape optimization adopts a thickness, a corrugation radius, and a length of annular plate as optimal design variables. The external loading conditions include the axial and lateral loads with a boundary condition fixed at an end of the bellows. The recursive quadratic programming algorithm is selected to solve the problem. The result are compared with the existing bellows, and the characteristics of the bellows is investigated through the optimal design process. The optimized shape of the bellows are expected to give quite a good guideline to the practical design.

• Clinical and Experimental Pediatrics
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• 제49권2호
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• pp.208-211
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• 2006

Dyke-Davidoff-Masson 증후군은 일측성 대뇌 반구의 위축과 동측의 대상성 골비대, 반대측의 편마비 등을 특징으로 하는 드문 신경질환이다. 본 증례는 17개월 남아가 좌측 국소적 경련외에 좌측 편마비 및 기타 발달지연을 동반한 경우이다. 당시 시행한 뇌 자기공명영상에서 우측 대뇌 반구의 진행성 위축과 뇌실 확장, 두꺼워진 두개관과 동측 전두부 부비동의 확장, 추체 접형골의 거상을 보였고 뇌 SPECT 촬영상에 우측 대뇌 반구의 위축 및 혈류감소를 보였다. 이 같은 소견들은 Dyke-Davidoff-Masson 증후군에 합당하여 이에 저자들은 본 증례를 문헌 고찰과 함께 보고한다.

• Steel and Composite Structures
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• 제34권1호
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• pp.35-51
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• 2020

Integral abutment bridges (IABs) are those bridges without expansion joints. A single row of steel H-piles (SHPs) is commonly used at the thin and stub abutments of IABs to form a flexible support system at the bridge ends to accommodate thermal-induced displacement of the bridge. Consequently, as the IAB expands and contracts due to temperature variations, the SHPs supporting the abutments are subjected to cyclic lateral (longitudinal) displacements, which may eventually lead to low-cycle fatigue (LCF) failure of the piles. In this paper, the potential of using finite element (FE) modeling techniques to estimate the LCF life of SHPs commonly used in IABs is investigated. For this purpose, first, experimental tests are conducted on several SHP specimens to determine their LCF life under thermal-induced cyclic flexural strains. In the experimental tests, the specimens are subjected to longitudinal displacements (or flexural strain cycles) with various amplitudes in the absence and presence of a typical axial load. Next, nonlinear FE models of the tested SHP specimens are developed using the computer program ANSYS to investigate the possibility of using such numerical models to predict the LCF life of SHPs commonly used in IABs. The comparison of FE analysis results with the experimental test results revealed that the FE analysis results are in close agreement with the experimental test results. Thus, FE modeling techniques similar to that used in this research study may be used to predict the LCF life of SHP commonly used in IABs.

• 대한기계학회논문집A
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• 제31권6호
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• pp.665-670
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• 2007

Alpha-phase alumina TGO(Thermally Grown Oxide) forms on the interface between zirconia top coat and bond coat of thermal barrier coating system for superalloys during exposure to high temperature over $1000^{\circ}C$. It is known to provide a good protection against hot corrosion and to cause surface failure such as rumpling and cracking due to difference in thermal expansion coefficient from the substrate metal and the lateral growth. Consequently, mechanical properties of the alumina TGO at the high temperature are the key parameters determining the integrity of TBC system. In this work, by using Fecralloy foils as the alumina forming substrate, creep tests and tensile tests have been performed with various TGO thicknesses$(h=0{\sim}4{\mu}m)$ and yttrium contents(0, 200ppm) at $1200^{\circ}C$. Displacement-time curves and load-displacement curves for each TGO thickness(h=1,2,..) were measured from the creep and tensile tests, respectively, and compared with the curves without TGO thickness(h=0). As the result, the intrinsic tensile and creep properties of TGO itself were determined.

• Structural Engineering and Mechanics
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• 제59권2호
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• pp.209-226
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• 2016

Integral bridges are typically designed with flexible foundations that include one row of piles. The construction of integral bridges solves difficulties due to the maintenance of expansion joints and bearings during serviceability. It causes integral bridges to become more economic comparing with conventional bridges. Research has been focused not only to enhance the seismic performance of newly designed bridges, but also to develop retrofit strategies for existing ones. The local performance of the pile to abutment connection will have a major effect on the performance of the structure and the embedment length of pile inside the abutment has a key role to provide shear and flexural resistance of pile-abutment connections. In this paper, a simple method was developed to estimate the initial value of embedment length of the pile for retrofitting of specimens. Four specimens of pile-abutment connections were constructed with different embedment lengths of pile inside the abutment to evaluate their performances. The results of the experimentation in conjunction with numerical and analytical studies showed that retrofitting pile-abutment connections with CFRP wraps increased the strength of the connection up to 86%. Also, designed connections with the proposed method had sufficient resistance against lateral load.

• 한국광학회지
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• 제17권2호
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• pp.159-164
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• 2006

원통형의 압접소자를 이용한 광지연선을 사용하여 광 간섭형 단층촬영 시스템을 제작하였다. 광지연선은 18 m 길이의 단일 모드 광섬유를 압전소자의 둘레에 134회 감아 구성하였으며 0.78 mm의 광경로 길이변화를 얻었다. 제작한 광 간섭형 단층촬영 시스템은 신호 대 잡음비 96.9 dB, 종방향 분해능 $18.6{\pm}0.5\;{\mu}m$, 횡방향 분해능 $5\;{\mu}m$의 특성을 보였다.

• 한국진공학회지
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• 제17권6호
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• pp.555-559
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• 2008

순방향 전압-온도 (forward voltage-temperature)법을 이용하여 양자점 레이저 다이오드의 접합온도를 측정하였다. 식각 깊이가 깊은 mesa 구조의 경우 입력전류에 대한 접합온도의 증가율은 0.05 K/mA인 반면, 식각 깊이가 낮은 mesa 구조의 경우 0.07 K/mA로서 상대적으로 높게 측정되었다. 깊은 mesa 구조에서의 상대적으로 낮은 접합온도 증가율은 mesa 측면 방향으로의 열확산 효과 때문인 것으로 설명된다.

• 대한건축학회논문집:구조계
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• 제35권1호
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• pp.21-28
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• 2019

This study investigates the applicability of composite polyurea to contain fiber reinforcement like fiber glass, steel fiber and carbon nanotube. Polyurea as elastomer is an excellent water-proofing material with many mechanical characteristics such as high tensile strength, ductility, high rate of expansion and contraction, and so on. The reinforcing fibers can be utilized for improving the load-carrying capacity of concrete structures. The polyurea plays a role to improve the ductility and toughness. Composite polyurea takes the mechanical advantages of the fibers and the polyurea. The test variables include the type of reinforcing fiber, its spraying thickness, and its weight ratio contained in the composite polyurea. It is observed that the load-carrying capacity, and the ductility and toughness are improved with the increase in the spraying thickness and the weight ratio contained in the composite polyurea. It is expected that the composite polyurea can be widely utilized in enhancing the structural and seismic performance.

• 대한소아치과학회지
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• 제31권2호
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• pp.169-179
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• 2004

이 연구의 목적은 함치성 낭의 임상적 및 방사선적 특성을 세 그룹으로 나누어 살펴보고자 하였다. I, II, III군으로 나누었으며 첫 번째 I군은 함치성 낭에 이환된 부위가 유치 하방의 계승 영구치인 군이며, II군는 이환부위가 영구 대구치 부위인 군이며, III군은 이환부위가 상악 전치부의 과잉치인 경우로 나누었다. 저자는 I군의 49증례와 II군의 36증례, III군의 15증례들에 대하여 이들의 병록지와 파노라마 방사선 사진에 기초하여 임상적 및 방사선적 특성을 비교, 관찰하였다. 연구 결과는 다음과 같았다. 1. 유치 하방의 영구 계승치를 포함하는 I 군이 49증례로 가장 많았고, II군과 III군이 각각 36증례, 15증례였다. 2. 함치성 낭은 전체적으로 10대에 가장 호발하였으며, 계승치군인 I군에서는 10대 이전과 초반에 87.8%, 대구치 군과 과잉치 군인 II군과 III군에서는 이보다 늦은 시기에 호발하였다. 3. 남자가 여자보다 2.5배 높은 발생 빈도를 보였다. 4. 환자의 내원 동기는 종창이 50%로 가장 많았고, 정기 검진 (32%), 동통(9%) 순이었다. 5. 낭의 유형은 I군에서 lateral type이 71.4%로 많았고, II군과 III군에서는 central type이 각각 94.4%, 100%로 많았다. 6. 병소의 크기는 I군에서는 2치관 크기가 II군에서는 1치관 크기가, III군에서는 4치관 크기 이상이 많았다. 7. 이환된 치아의 대부분은 변위를 보였고 변위된 치아의 일부에서 치근 발육이 지연되거나 치근 만곡 경 향을 보였다. 8. 낭의 성장에 의한 치조골 반응은 I군에서는 협측골 팽창(67.3%)이 많았고, II군에서는 골팽창이 일어나지 않은 경우(66.7%)가 많았으며, III군에서는 구개측 골팽창(60.0%)이 많았다. 9. 낭에 포함되는 치아로는 하악 제 3대구치가 31%로 가장 많았고 하악 제 2소구치 (30%), 상악 전치부 과잉치 (15%), 상악 견치 (8%), 하악 제 1소구치 (5%) 순이었다. 10. I군에서 추정되는 낭의 발생 원인으로는 치수절단술을 받은 유치가 59.2%로 가장 많았고 이외에 심한 우식 및 치료 받지 않은 외상 병력등 기타 가능한 원인들이 있었다. 11.함치성 낭의 치료법으로는 I군의 경우 61.2%에서 조대술이 시행되었고, II군과 III군의 경우 61.1%, 80.0%에서 적출술이 시행되었다.

• Archives of Plastic Surgery
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• 제38권3호
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• pp.295-299
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• 2011

Purpose: It is generally believed that alopecia is caused by various factors such as scars, stress, genetical factors, androgens, etc. Androgenic alopecia is one of the most common cause of alopecia and found mainly in males. Propecia (Merck & Co., USA) and Minoxidil (McNEIL-PPC, Inc, USA) were the drugs approved from FDA for treatment of androgenic alopecia. Surgical treatments such as flap, tissue expansion, scalp reduction and hair transplantation can be considered if necessary. Hair micrograft techniques were developed for natural hair shapes and minimal adverse effect. There were attempts to measure the length of the forehead of the Korean young adults. However attempts to classify the shape and location of forehead hairline were rare. This study attempted to find out standard hairlines of young adults in their 20s & 30s and the result would be the guideline of the hairline in hair replacement surgery of male patients in their 40s & 50s. Methods: 200 male adults in 20s and 30s were photographed and measured the length of 11 vertical index lines to determine hairline. The indexes are the distances from hairline to intercanthal midpoint (A), to medial canthus (B), to upper eyelid fissure (C), to lower eyelid fissure (D), to lateral canthus (E) and distance from lateral highest point to medial lowest point, if the hairline is M-shape (F). Additionally, we classified the hairlines into 4 groups, M, horizontal, inverted U and irregular shapes. Results: The most common hairline of male adults in their 20s is inverted U-shape (53.3%), followed by horizontal-shape, M-shape, irregular-shape. In their 30s, inverted U-shape (59%) is followed by irregular-shape, M-shape, horizontal-shape. The M-shape is more frequently found in males in 30s than those in 20s. The mean values of the indexes in their 20s are as follows: A (76.14 mm), B (Rt: 75.78 mm, Lt:76.41 mm), C (Rt: 69.43 mm, Lt: 69.92 mm), D (Rt: 76.92 mm, Lt:77.46 mm), E (Rt: 64.16 mm, Lt: 64.73 mm), F (4.09 mm). Those in their 30s are as follows: A (76.13 mm), B (Rt: 76.114 mm, Lt: 76.02 mm), C (Rt: 69.87 mm, Lt: 70.37 mm), D (Rt: 77.37 mm, Lt: 77.58 mm), E (Rt: 69.63 mm, Lt: 69.85 mm), F (6.14 mm). Conclusion: The knowledge about human body measurement is indispensable to plastic surgeons. In this study, inverted U shape is the most common type of hairline in 30s, and similar distribution is found in 20s. The percentage of M shape in their 30s is elevated more than 10% compared to that in their 20s. The study of hairline shapes and 11 indexes of hairlines can be useful for planning of the hair transplantation and postoperative evaluation. This study being based on photogrammetry, there may be differences between actual distance of curved face and projected distance on flat photographs.