• Clinical and Experimental Pediatrics
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• 제52권4호
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• pp.458-463
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• 2009

목 적 : 뇌갈림증은 연질막 표면에서 외측 뇌실까지 대뇌 피질이 갈라져 열구를 이루며 회색질로 둘러 싸여 있는 드문 대뇌 기형으로서 본 연구에서는 국내 소아에서 발생한 뇌갈림증 환아의 임상양상, 방사선 소견에 대해 전반적으로 고찰하여 질환의 특징을 알아보고자 하였다. 방 법 : 2005년 1월부터 2007년 12월까지 세브란스 어린이 병원과 영동 세브란스 병원 소아과에 방문 및 입원 치료한 뇌갈림증 환자 13예의 환아를 대상으로 의무 기록을 후향적으로 고찰하였다 결 과 : 진단 시의 연령은 0-30개월 사이로 평균 연령은 $9.08{\pm}9.61$ 개월이었고, 남녀비 3.33:1로 남아에서 호발 하였다. 뇌갈림증은 일측성이 8예(61.5%), 양측성이 5예(38.5%)였고, 개방형이 4예(30.8%), 폐쇄형이 5예(38.5%), 개방형과 폐쇄형 모두 보이는 혼합형이 4예(30.8%)였다. 모든 환아에서 다른 뇌기형이 동반되었는데 투명 중격 결손이 9예(69.2%), 거미막 낭종이 4예(30.8%), 시신경 형성 부전이 4예(30.8%), 대뇌 피질 형성부전이 4예(30.8%), 뇌실 확장이 3예(23.1%), 뇌량 무형성이 1예(7.7%) 순이었다. 운동장애는 편측 근력 약화는 모든 유형에서 관찰되었고 편마비는 4예에서 사지마비는 3예에서 관찰되어 열구의 유형과 운동 장애의 정도의 상관관계는 알아 볼 수 없었다. 발달 지연이 모든 환아에서 조사되다. 간질 발작은 13예의 환아 중 7예(53.8%)에서 발병하였는데 일측성에서 5예, 양측성에서 2예로 조사되었고 그 중 난치성 간질은 3예(42.8%)였다. 결 론 : 우리나라 소아에서 뇌갈림증의 임상 양상과 신경영상 소견은 열구의 위치, 유형 및 동반기형에 따라 매우 다양하게 나타났다. 뇌갈림증의 조기 진단과 간질 발생에 대한 주의 깊은 관찰이 반드시 필요하며 이와 관련된 보다 많은 환자군을 대상으로 하는 심도 있는 연구가 장기적으로 이루어 져야 할 것이다.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.14-20
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• 2014

Recent developments for high altitude, long endurance conventional UAVs(HALE UAVs) have revealed new issues regarding aircraft structure design and analysis. First of all, due to intensive mission requirements, the structures of HALE UAVs have lightweight and very flexible main wing with high aspect ratio, and slender fuselage. For this kind of structures, aeroelastic characteristics are different from conventional aircrafts. Hence, currently developed analysis methods are not suitable to fully understand strucutral dynamics of the very flexible aircraft, and to guarantee structural reliability. Therefore, various structural studies considering nonlinear behaviors which are generally ignored for the conventional aircraft strucutral analyis have been attracting researchers interests. Nonlinear flutter of the very flexible wing is one of the subject to be studied in combination with strong coupling between aeroelastic characteristics and flight dynamics. Herein, as preliminary study, modeling and nonlinear system analysis of the 2D airfoild with torsional nonlinearity have been discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.226-231
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• 2013

Recent developments for high altitude, long endurance conventional UAVs (HALE UAVs) have revealed new issues regarding aircraft structure design and analysis. First of all, due to intensive mission requirements, the structures of HALE UAVs have lightweight and very flexible main wing with high aspect ratio, and slender fuselage. For this kind of structures, aeroelastic characteristics are different from conventional aircrafts. Hence, currently developed analysis methods are not suitable to fully understand strucutral dynamics of the very flexible aircraft, and to guarantee structural reliability. Therefore, various structural studies considering nonlinear behaviors which are generally ignored for the conventional aircraft strucutral analyis have been attracting researchers interests. Nonlinear flutter of the very flexible wing is one of the subject to be studied in combination with strong coupling between aeroelastic characteristics and flight dynamics. Herein, as preliminary study, modeling and nonlinear system analysis of the 2D airfoild with torsional nonlinearity have been discussed.

• Archives of Plastic Surgery
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• 제32권5호
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• pp.667-670
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• 2005

Congenital facial cleft is a rare entity and appears along by the line of different processes of the facial development. An isolated cleft of the nose has been reported not often in the literature. We treated a patient with an isolated nasal cleft associated with undefined cranial anomaly. On 3D CT scan was seen a bony cleft traversing the pyriform aperture lateral to the anterior nasal spine. The nasal septum and frontal process of the maxilla were intact. There also was found bilateral bony defects in the frontal bone and bilateral frontal boss. The nasal cleft and frontal defect and boss were corrected by two stages: anterior two-third of the cranial vault with bilateral frontal boss was remodeled at the age of two years and the nasal cleft was repaired with a local rotation flap at age 3.

• 대한기계학회논문집
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• 제19권2호
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• pp.495-508
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• 1995

The self-excited vibrations of airfoil is related to the classical flutter problems, and it has been studied as a system with linear stiffness and small damping. However, since the actual aircraft wing and the many mechanical elements of airfoil type have various design variables and parameters, some of these could have strong nonlinearities, and the nonlinearities could be unexpectedly strong as the parameters vary. This abrupt chaotic behavior undergoes ordered routes, and the behaviors after these routes are uncontrollable and unexpectable since it is extremely sensitive to initial conditions. In order to study the chaotic behavior of the system, three parameters are considered, i.e., free-stream velocity, elastic distance and zero-lift angle. If the chaotic parameter region can be identified from the mathematically modeled nonlinear differential equation system, the designs which avoid chaotic regions could be suggested. In this study, by using recently developed dynamically system methods, and chaotic regions on the parameter plane will be found and the safe design variables will be suggested.

• Journal of Welding and Joining
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• 제6권2호
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• pp.56-63
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• 1988

The effects of PWHT (poste weld heat treatment) and stress simulating the residual stress during PWHT in weld HAZ of low and high strength steels on corrosion fatigue crack growth were evaluated. The obtained results are summarized as follows. 1. Fatigue crack growth rate of HAZ in air and 3.5% NaCl solution was slower than that of parent due to the signgularity in weld HAZ. 2. In the case of HT-80, 3.5% NaCl solutio nacts to accelerate the crack growth for all specimens, and the sensitivity of as-weld to corrosion environment was the greatest among other PWHT specimens. 3. Corrosion fatigue crack growth of parent, as-weld and PWHT speciments ofr SS41 as well as SM53B was retarded in comparison with the fatigue crack growth in air. 4. There was a tendency that crack growth of PWHT specimens subjected $10kg/mm^2$ was faster than that of PWHT specimens without stress during PWHT. 5. The retardation phenomenon of crack growth in corrosion environment is attributed to the crack branching decreased .DELTA.K due to the corrosion products and multi-cracks.

• 한국항공운항학회지
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• 제21권4호
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• pp.47-52
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• 2013

In this paper, limit cycle flutter induced by Hopf bifurcation is studied with nonlinear system analysis approach and observed for the critical slowing down phenomenon. Considering an attractor of the dynamics of a system, when a small perturbation is applied to the system, the dynamics converge toward the attractor at some rate. The critical slowing down means that this recovery rate approaches zero as a parameter of the system varies and the size of the basin of attraction shrinks to nil. Consequently, in the pre-bifurcation regime, the recovery rates decrease as the system approaches the bifurcation. This phenomenon is one of the features used to forecast bifurcation before they actually occur. Therefore, studying the critical slowing down for limit cycle flutter behavior would have potential applicability for forecasting those types of flutter. Herein, modeling and nonlinear system analysis of the 2D airfoil with torsional nonlinearity have been discussed, followed by observation of the critical slowing down phenomenon.

• 한국진공학회지
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• 제21권5호
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• pp.249-257
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• 2012

1차원 유체 모델을 사용하는 수치 코드를 개발하여 Pierce 다이오드에서 플라즈마에 대한 비선형 동력학적 거동을 연구하였다. Pierce 다이오드에서 플라즈마는 전극에서 방출되는 전자 전류와 전극 사이의 거리로 결정되는 Pierce 매개 변수가 변화함에 따라 안정하기도 하고 불안정해지기도 한다. 중성 및 비중성 Pierce 시스템의 동력학적 특성에 대해 해석적 및 수치적으로 연구하였다. Pierce 매개 변수의 값에 따라 플라즈마는 증폭 모드 또는 진동 모드를 가질 수 있으며, 진동 모드에서는 매개 변수가 감소함에 따라 계속적인 주기 배가 쌍갈림(period doubling bifurcation)을 일으키며 카오스 상태에 도달하게 된다. 이러한 거동에 대한 분석은 보다 복잡한 구조에서의 빔-플라즈마 상호작용에 대한 기본적인 이해를 위한 모델 및 카오스 제어를 위한 자료로서 사용될 수 있다.

• 대한두개안면성형외과학회지
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• 제13권2호
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• pp.135-138
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• 2012

Purpose: Reconstruction of the cleft earlobe is challenging. Several procedures are available to reconstruct congenital earlobe deformities. However, for large defective type, surgical procedures and designs are complex and tend to leave a visible scar. We present a simple method of reconstruction for defective type congenital cleft earlobe using a one stage technique with infraauricular transposition flap. This allows for easy and accurate size estimation and good aesthetic outcomes. Methods: A 4-year-old male patient has congenital cleft earlobe and antihelical deformity. Otoplasty for antihelical deformity correction and one stage infra-auricular transposition flap for earlobe reconstruction were performed. The flap was designed from the inferoanterior margin of the earlobe. The size of the flap was determined based on the normal side, and the width and length of the flap was 1 cm and 3 cm in size, respectively. An incision was made at the midline of the defective lobule. Further, the elevated flap was inserted. The elevated flap and the incision margins of the lobule were sutured together. Then, the donor site was closed primarily. Results: The volume and shape of the reconstructed earlobe were natural. There was no flap necrosis. The donor site had no morbidities and scar was not easily notable. Conclusion: Infra-auricular transposition flap can be designed easily and offer sufficient volume of earlobe. Furthermore, the scar is inconspicuous. In conclusion, infra-auricular transposition flap can be a good option for reconstructing a large defect type cleft earlobe.

• 콘크리트학회논문집
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• 제17권1호
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• pp.3-10
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• 2005

콘크리트 구조물은 다양한 요인으로 인하여 골재노출, 탈락, 표면박리, 균열발생, 철근노출 및 부식, 강도저하, 염소이온침투, 공극률 증가, 팽창 및 수축 등과 같은 여러가지 열화현상이 나타나는 문제점을 가지고 있다. 특히 상$\cdot$하수도 시설을 포함한 수처리 구조물의 경우에는 일반적인 콘크리트 구조물보다 더욱 가혹한 환경에 노출되어있기 때문에 콘크리트의 열화는 더욱 심하다고 볼 수 있다. 본 연구는 시멘트 혼입 폴리머와 에폭시수지를 복합한 내균열성 방수$\cdot$방식재를 이용한 콘크리트구조물용 방수$\cdot$방식공법을 개발하여 실용화하는데 목적이 있다. 콘크리트구조물용 방수$\cdot$방식공법의 평가를 위하여 흡수 및 투수성, 부착성, 인장강도, 내잔갈림성, 내충격성, 냉온반복성능, 내화학성능, 음용수 용출성 등 방수$\cdot$방식재에 요구되는 성능을 평가하였다. 그 결과 KS의 규격에서 규정하는 성능기준을 모두 만족하는 것으로 나타났으며, 특히 부착성능이 우수한 것으로 확인되었다. 또한 본 탄성층을 보완한 방수$\cdot$방식공법의 적용에 의해서 최대 1.49mm까지의 균열에 대하여 저항성이 있는 것으로 평가되어 내균열성 측면에서 높은 성능을 확보하고 있는 것으로 평가되었다.