• 한국항공우주학회지
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• 제36권11호
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• pp.1039-1048
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• 2008

본 논문에서는 새로운 비선형 와류격자법 계산 과정이 제안된다. 기존의 계산 과정은 자유와의 형태 계산을 위해 내부 반복계산 및 하향이완법을 포함한다. 하지만 본 논문에서는 유사 정상 개념에 기초한 새로운 수식을 제안하여 자유와의 형태를 계산함으로써, 계산 과정에서 내부 반복계산 및 하향이완법을 생략한다. 또한 반복계산이 진행됨에 따라 각 분절에 유도되는 유속도를 적절히 평균해 줌으로써 알고리듬의 수치적 안정성을 향상시킨다. 그리고 낮은 종횡비 날개에 대한 수치실험을 수행하여 분절의 길이, 와류중심반경, 후류영역 계산범위 등과 같은 중요 인자들의 적절한 기준을 경험적으로 결정한다.

• Archives of Reconstructive Microsurgery
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• 제14권1호
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• pp.37-41
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• 2005

Purpose: The purpose of this study was to evaluate the effectiveness of internal transport using Ilizarov apparatus with free flap surgery for infected tibial nonunion. Materials and Methods: We reviewed 8 patients of infected tibial nonunion treated with internal transport using Ilizarov apparatus and free flap surgery. Seven of eight patients were available for at least 1 year follow-up. All patients were male. The mean age at the time of the surgery was All fractures were Gustilo's type III B open fracture. The mean length of the bone defect was 8.5 cm. All used flaps for covering the soft tissue defect were free rectus abdominis muscle flap. We evaluated bone and functional results with use of the Paley and Catagni's classification. And we classified the complication with use of the Paley's classification. Results: Acceptable length and solid union of bone was achieved in all cases. The mean size of the bone length was 7.2 cm. The mean healing index was 69.5 days/cm. All but one case needed bone graft at docking site. All flaps were survived. There was no recurrence of infection. According to Paley and Catagni's classification, all cases showed excellent or good results. Complications were pin tract infection in 3 cases, persistent pain in 2 cases and limitation of joint motion in 2 cases. Conclusion: Simultaneous free-tissue transfer and Ilizarov distraction osteogenesis was thought to be an attractive treatment modality for infected nonunion of the tibia.

• 전자공학회논문지SC
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• 제48권2호
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• pp.86-90
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• 2011

전계효과 트랜지스터(FETs)를 이용한 전하 검출형 DNA센서는 DNA가 가지고 있는 음전하를 중성화 시키는 양이온의 영향은 매우 중요하다. 본 논문에서는 양이온 농도에 의존하는 Debye length에 관한 연구를 통해 DNA 검출감도를 평가하였다. Debye length는 낮은 농도의 NaCl 용액에서 긴 거리를 유지하며, Debye length가 높은 용액에서 DNA가 가지고 있은 음전하는 게이트 채널에 보다 많은 영향을 미친다. 용액내 NaCl농도가 1 mM인 버퍼 용액에서 상보적 DNA의 hybridization에 의한 전계효과 트랜지스터의 게이전압은 21 mV 시프트 했으며, NaCl 농도가 10 mM인 버퍼 용액에서는 7.2 mV, NaCl농도가 100 mM인 버퍼 용액에서는 전계효과 트랜지스터의 게이트 전압이 5.1 mV 각각 시프트 하였다. 이러한 결과를 바탕으로 전계효과 트랜지스터를 이용한 전하 검출형 DNA센서의 검출 감도는 Debye length에 의존하는 것을 규명하였다.

• Archives of Reconstructive Microsurgery
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• 제22권2호
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• pp.63-68
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• 2013

Purpose: In case of the failed replantation, if the patients want to preserve the length of amputated stump, toe transfer is the ideal choice. However, reconstruction of these amputated stump with a free flap can be a useful method when the patients refuse sacrificing their toe. Our purpose of this study is to evaluate availability of functional results and patient satisfaction after this procedure. Materials and Methods: From March 2008 to February 2012, we reconstructed the amputated stump with free flap by patients demand. Eleven patients were included, medial plantar artery perforator flap in seven cases and great toe pulp flap in five cases. Follow-up range 12 to 24 months and we evaluate patient satisfaction by using a visual analogue scale (VAS; 1=unsatisfied, 5=excellent) and functional recovery by measuring the range of motion of remaining joint at 12 months after operation. Results: During follow-up period, all transferred free flaps survived and no major complications were noted. Range of motion of remaining joint appeared satisfactory result ($15^{\circ}$ to $100^{\circ}$). The VAS patient satisfaction score for aesthetic were five in six patients, four in four patients, and three in one patient. Conclusion: In case of the failed digital replantation, if patient refuse toe transfer, it could be useful method to reconstruction with the free flap to preserving maximal length of amputated stump.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1340-1347
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• 2006

Dynamic response of buried pipelines both in the axial and the transverse directions on concrete pipe and steel pipe, FRP pipe were investigated through a free vibration analysis. End boundary conditions considered herein consist of free ends, fixed ends, and fixed-free ends in the axial and the transverse direction. Guided ends, simply supported ends, and supported-guided ends were added to the transverse direction. The buried pipeline was regarded as a beam on an elastic foundation and the ground displacement of sinusoidal wave was applied to it. Natural frequencies and mode shapes were determined according to end boundary conditions. In addition, the effects of parameters on the natural frequency were evaluated. The natural frequency is affected most significantly by the soil stiffness and the length of the buried pipelines. The natural frequency increases as the soil stiffness increases while it decreases as the length of the buried pipeline increases. Such behavior appears to be dominant in the axial direction rather than in the transverse direction of the buried pipelines.

• 대한토목학회논문집
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• 제28권6A호
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• pp.827-833
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• 2008

이 논문은 elastica형 아치의 자유진동에 관한 연구이다. Elastica형 아치의 선형은 항상 일정한 곡선길이를 갖는 후좌굴 기둥의 정확탄성곡선을 이용하였다. 이 Elastica형 아치의 곡률항을 일반아치의 자유진동을 지배하는 미분방정식에 적용하여 고유진동수 및 진동형을 산출하였다. 수치해석 예에서는 회전-회전, 회전-고정 및 고정-고정의 지점조건을 고려하였다. 회전관성이 고유진동수에 미치는 영향을 분석하고, 아치의 높이비 및 세장비와 고유진동수와의 관계를 그림에 나타내었다. Elastica형 아치와 포물선형 아치의 고유진동수를 비교한 결과, elastica형 아치의 고유진동수가 포물선 아치의 고유진동수보다 매우 크게 나타나는 동적 특성을 보였다. 진동형의 전형적인 예를 그림에 나타내었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.337-344
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• 2000

A modified k-$\epsilon$ model is proposed for calculation of transitional boundary layer flows. In order to develop the eddy viscosity model for the problem, the flow is divided into three regions; namely, pre-transition region, transition region and fully turbulent region. The pre-transition eddy-viscosity is formulated by extending the mixing Length concept. In the transition region, the eddy-viscosity model employs two length scales, i.e., pre-transition length scale and turbulent length scale pertaining to the regions upstream and the downstream, respectively, and a university model of stream-wise intermittency variation is used as a function bridging the pre-transition region and the fully turbulent region. The proposed model is applied to calculate three benchmark cases of the transitional boundary layer flows with different free-stream turbulent intensity ( $1\%{\~}6\%$ ) under zero-pressure gradient. It was found that the profiles of mom velocity and turbulent intensity, local maximum of velocity fluctuations, their locations as well as the stream-wise variation of integral properties such as skin friction, shape factor and maximum velocity fluctuations are very satisfactorily Predicted throughout the flow regions.

• 생태와환경
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• 제41권3호
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• pp.320-330
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• 2008

소하천에 서식하는 수서곤충 29 분류군에 대한 몸길이와 건조질량, 그리고 회분외질량에 관한 회귀식이 자연 log로 변환된 멱함수를 이용하여 구해졌다. 수서곤충은 강원도 북부지방의 산간계류에서 채집되었다. 각 분류군에서 주어진 몸길이에 대해 회귀식이 예측하는 건조질량은 기 보고된 다른 저자들의 예측값과 대체로 유사하였지만, 체벽이 연하고 이동할 때 몸을 수축-이완하는 분류군에서는 다른 저자들이 예측값에 비해 높았다. 수서곤충의 평균 회분율은 건조질량의 10%였으며, 섭식기능군간 차이는 인정되지 않았다.

• Structural Engineering and Mechanics
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• 제73권2호
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• pp.109-121
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• 2020

This study aims to estimate crack location and crack length in damaged beam structures using transfer matrix formulations, which are based on analytical solutions of governing equations of motion. A single variable shear deformation theory (SVSDT) that considers parabolic shear stress distribution along beam cross-section is used, as well as, Timoshenko beam theory (TBT). The cracks are modelled using massless rotational springs that divide beams into segments. In the forward problem, natural frequencies of intact and cracked beam models are calculated for different crack length and location combinations. In the inverse approach, which is the main concern of this paper, the natural frequency values obtained from experimental studies, finite element simulations and analytical solutions are used for crack identification via plots of rotational spring flexibilities against crack location. The estimated crack length and crack location values are tabulated with actual data. Three different beam models that have free-free, fixed-free and simple-simple boundary conditions are considered in the numerical analyses.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.971-976
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• 2002

The differential equations governing free vibrations of the elastic arches with unsymmetric axis are derived in rectangular coordinates rather than in polar coordinates, in which the effect of rotatory inertia is included. Frequencies and mode shapes are computed numerically for parabolic arches with both clamped ends and both hinged ends. Comparisons of natural frequencies between this study and SAP 2000 are made to validate theories and numerical methods developed herein. The convergent efficiency is highly improved under the newly derived differential equations in Rectangular coordinates. The lowest four natural frequency parameters are reported, with and without the rotatory inertia, as functions of three non-dimensional system parameters: the rise to chord length ratio, the span length to chord length ratio, and the slenderness ratio. Also typical mode shapes of vibrating arches are presented.