• Structural Engineering and Mechanics
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• 제89권1호
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• pp.47-59
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• 2024

In this study, a new sustainable material was proposed to prepare precast tunnel lining segments (TLS), which were produced using a fiber-reinforced slag-based geopolymer composite. Slag was used as the geopolymer binder. In addition, polypropylene and carbon fibers were added to reinforce TLSs. TLSs were examined in terms of flexural performance, load-deflection response, ductility, toughness, crack characteristics, and tunnel boring machine (TBM) thrust force. Simultaneously, numerical simulation was performed using finite element analysis. The mechanical characteristics of the geopolymer composite with a fiber content of 1% were used. The results demonstrated that the flexural performance and load-deflection response of the precast TLSs were satisfactory. Furthermore, the numerical results were capable of predicting and realistically capturing the structural behavior of precast TLSs. Therefore, fiber-reinforced slag-based geopolymer composites can be applied as precast TLSs.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.410-413
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• 2012

A traditional fabrication method is very difficult to make small robots using embedded sensors, actuators and connectors. Fortunately, Shape Deposition Manufacturing can provide an alternative method, and it has many benefits. Firstly, the weight of robot can be lighter, as it can be consisted of composite materials. Secondly, SDM can make simple robot structures because this approach does not need to use connectors and fasteners. Lastly, SDM gives stiffness and flexibility at the specific parts. Therefore, in this paper, we present a design of 3 segment legs organized by SDM, what the SDM approach is, and compare SDM method with 3 segment prototype legs which uses a traditional approach and made by DGIST.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.161-164
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• 2004

In these days, composite materials are applied to the military field like parts of air crafts, rockets, ammunitions and so on. As high pressure is loaded on the composite body, however, cracks or delamination phenomena can be occurred between layers of laminate. These cracks or delamination usually cause a deterioration of mechanical properties under the complicated loads. In this study, methods for improvement of the inter-laminar bonding strength of thick carbon/epoxy composite structures are suggested and discussed in terms of segment bending test.

• 한국재난정보학회 논문집
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• 제12권4호
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• pp.422-431
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• 2016

본 연구에서는 프리스트레스트 강합성 거더의 콘크리트 케이싱 분절부 상세에 따른 연결부 성능 평가를 위해 각각 다른 분절부를 가진 실험체를 제작하여 실험하였다. 분절부가 없는 일반 강합성 거더와 분절부에 이음철근 보강 유무 및 이음철근 상세를 변수로 하는 총 4본의 비교 실험체를 제작하여 구조적 거동 평가하였다. 또한, 분절형 강합성 거더의 비균열등급 설계 가능 여부 및 균열발생 후 루프철근 상세에 따른 강성과 강도 영향에 대해 분석하고, 매립강판면과 타설접합면에 따른 균열폭 제어 적정성을 평가하였다.

• Archives of Plastic Surgery
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• 제49권1호
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• pp.70-75
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• 2022

Background Fingertip injuries are very common; however, the reconstruction of volar pulp defects with nail bed defects is challenging in the absence of the amputated segment. We reconstructed fingertip amputations with nail bed defects using a new surgical approach: a subcutaneous flap and composite graft. Methods We treated 10 fingertip amputation patients without an amputated segment, with exposed distal phalangeal bone and full-thickness nail bed defects between February 2018 and December 2020. All patients underwent two-stage surgery: in the first stage, a subcutaneous flap was performed to cover the exposed distal phalanx, and in the second stage, a composite graft, consisting of nail bed, hyponychium, and volar pulp skin, was applied over the subcutaneous flap. Results All flaps survived and all composite grafts were successful. The wounds healed without any significant complications, including the donor site. The average follow-up duration was 11.2 months (range, 3-27 months). The new nail and the shape of the volar pulp were evaluated during follow-up. All patients were satisfied with their natural fingertip shapes and the new nails did not have any serious deformities. Conclusions A subcutaneous flap in combination with a composite graft fitting the shape of the defect could be another option for fingertip injuries without amputated segments.

• 멤브레인
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• 제15권1호
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• pp.44-51
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• 2005

유기증기에 대한 PDMS의 단점을 보완하기 위해 4,4'-diphenylmethane diisocyanate (MDI)와 1,4-butanediol(BD)를 이용하여 poly(dimethylsiloxane)를 기초로 한 polyurethane-polysiloxanes (PU/PDMS)를 합성하였다. 그리고 poly(tetrafluoroethylene) (PTFE)를 다공성 지지체로 이용하여 복합막을 제조하여 SEM 분석으로 코팅층의 존재와 두께를 확인하였다. 증기투과실험에서 투과온도와 feed의 농도가 증가할수록 flux는 점차 증가하였고, separation factor는 이와 반대로 점차 감소하는 'trade-off'현상을 보였다. 본 연구에서의 PU/PDMS는 soft segment의 함량보다는 비교적 hard segment의 함량이 높기 때문에 투과온도의 증가에 따른 영향이 크지 않았던 것으로 사료된다. PU/PDMS막은 VOCs와 상대적으로 높은 친화도를 가지고 있기 때문에 PU/PDMS 균질막과 비교하여 복합막의 형태에서도 향상된 flux와 높은 separation factor를 나타내었다.

• Journal of Chest Surgery
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• 제15권2호
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• pp.222-229
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• 1982

The aneurysmal dilatation of ascending aorta with the aortic regurgitation presents typical surgical problems. Over the years, various surgical procedures had been used for the management of the dilated segment of sending aorta and the aortic regurgitation. The surgical technique Is still in the state of evolution. The one method is the super coronary replacement of the ascending aorta with vascular graft and replacement of the aortic valve with preservation of the coronary ostia as advocated by Miller and his colleague at Stanford University, so called conventional technique". The other is the replacement of aortic valve and the dilated segment of the ascending aorta using a composite graft and transplantation of the coronary ostia as described by Bentall and DeBono in 1968. The controversy appears to evolve around 3 technical problems. One is bleeding from the grafted area. Two is later development of the aneurysmal dilatation of the subcoronary aortic wall when non-composite graft is employed. Three is a management of the coronary arteries. The purpose of this article is to present our experience with 7 cases of annuloaortic ectasia in whom both of these surgical techniques at that employed and to review some of the problems that encountered during the management of these patients .

• Wind and Structures
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• 제16권3호
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• pp.241-248
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• 2013

The wind turbine blade is a very important part of the rotor. Extraction of energy from wind depends on the design of blade. In this work, the analysis is done on a blade of length 38.95 m which is designed for V82-1.65 MW horizontal axis wind turbine (supplied by Vestas). The airfoil taken for the blade is NACA 634-221 which is same from root to tip. The analysis of designed blade is done in flap-wise loading. Two shapes of the spar are taken, one of them is of square shape and the other one is combination of square and cross shape. The blade and spar are of the same composite material. The Finite element analysis of designed blade is done in ANSYS. This work is focused on the two segments of blade, root segment and transition segment. Result obtained from ANSYS is compared with the experimental work.

• Steel and Composite Structures
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• 제33권2호
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• pp.163-180
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• 2019

A semi analytical method is employed to analyze free vibration characteristics of uniform and stepped functionally graded circular cylindrical shells under complex boundary conditions. The analytical model is established based on multi-segment partitioning strategy and first-order shear deformation theory. The displacement functions are handled by unified Jacobi polynomials and Fourier series. In order to obtain continuous conditions and satisfy complex boundary conditions, the penalty method about spring technique is adopted. The solutions about free vibration behavior of functionally graded circular cylindrical shells were obtained by approach of Rayleigh-Ritz. To confirm the dependability and validity of present approach, numerical verifications and convergence studies are conducted on functionally graded cylindrical shells under various influencing factors such as boundaries, spring parameters et al. The present method apparently has rapid convergence ability and excellent stability, and the results of the paper are closely agreed with those obtained by FEM and published literatures.

• 대한원격탐사학회지
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• 제35권2호
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• pp.343-346
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• 2019

이 연구에서는 2019년 4월 4일 발생한 고성-속초 산불과 강릉-동해 산불의 피해지를 신뢰할 만한 수준으로 신속하게 파악하기 위하여, 고해상도 영상 기반의 산림고사지수를 개발하고 이를 Sentinel-2 영상에 적용한 결과를 소개하고자 한다. 고사한 산림과 건강한 산림은 매우 다른 분광특성을 보이는데, 특히 R-NIR-G 위색조합(false color composite)에서 그 차이가 뚜렷이 나타난다. 이러한 특성에 기초하여 개발된 산림고사지수를 적용한 결과, 고성-속초 산불의 피해면적은 약 701.16 ha, 강릉-동해 산불의 피해면적은 약 710.60 ha로 추정된다. 정확한 피해면적은 현장조사 등의 과정을 거쳐 추후에 공식적으로 확정되겠지만, 이러한 위성영상 분석은 신속한 피해현황 파악을 가능하게 하는 장점이 있다.