• Elastomers and Composites
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• v.48 no.3
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• pp.181-189
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• 2013

Unfilled, carbon black-filled, and silica-filled natural rubber (NR) composites were aged with a circular deformation at $60-90^{\circ}C$ and the recovery behaviors were investigated. The samples were aged under the altering aging medium systems of air and distilled water every day for 10 days. The order of the recoveries according to the filler systems was unfilled > silica > carbon black. The recoveries of the samples aged in the air to water altering system were greater than those of the samples aged in the water to air altering system. The initial aging medium dominantly influenced the deformation level.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.707-710
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• 2010

The most important things in the KSLV-I Kick Motor nozzle is a development of flexible seal that is utilized to drive a movable nozzle. Especially, a manufacturing technology of flexible seal is one of the key element in the Kick Motor nozzle development. The method used to produce flexible seal in the Kick Motor is injection method. Mold design technology, rubber injection technic and molding process through flexible seal manufacture has been established. After manufacturing, X-Ray inspection have been carried out to confirm a adhesive and internal array of flexible seal.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.161-176
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• 1999

A powerful numerical method that can be used for modeling rock-structure interaction is the Discontinuous Deformation Analysis (D D A) method developed by Shi in 1988. In this method, rock masses are treated as systems of finite and deformable blocks. Large rock mass deformations and block movements are allowed. Although various extensions of the D D A method have been proposed in the literature, the method is not capable of modeling water-block interaction, sequential loading or unloading and rock reinforcement; three features that are needed when modeling surface or underground excavation in fractured rock. This paper presents three new extensions to the D D A method. The extensions consist of hydro-mechanical coupling between rock blocks and steady water flow in fractures, sequential loading or unloading, and rock reinforcement by rockbolts, shotcrete or concrete lining. Examples of application of the D D A method with the new extensions are presented. Simulations of the underground excavation of the \ulcornerUnju Tunnel\ulcorner in Korea were carried out to evaluate the influence of fracture flow, excavation sequence and reinforcement on the tunnel stability. The results of the present study indicate that fracture flow and improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is found that, in general, the D D A program with the three new extensions can now be used as a practical tool in the design of underground structures. In particular, phases of construction (excavation, reinforcement) can now be simulated more realistically.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1193-1202
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• 2000

The paper describes the use of genetic algorithms (GA's) to the minimum weight design of stiffened composite panels for buckling constraints. The proposed design problem is characterized by mixture of continuous and discrete design variables corresponding to panel elements and stacking sequence of laminates, respectively. Design space is multimodal and non-convex, thereby introducing the need for global search strategies. Advanced strategies in GA's such as directed crossover, multistage search and separated crossover are adopted to improve search ability and to save computational resource requirements. The paper explores the effectiveness of genetic algorithms and their advanced strategies in designing stiffened composite panels under various uniaxial compressive load conditions and the linrlit on stacking sequence of laminates.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.477-485
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• 2012

Geometric configurations such as hull shape, wall thickness, stiffener layout, and type of construction materials are the key factors influencing the structural performance of pressure hulls. Traditional theoretical approach provides quick and acceptable solutions for the design of pressure hulls within specific geometric configuration and material. In this paper, alternative approaches that can be used to obtain optimal geometric shape, wall thickness, construction material configuration and stiffener layout of a pressure hull are presented. CAE(Computer Aided Engineering) based design optimization tools are utilized in order to obtain the required structural responses and optimal design parameters. Optimal elliptical meridional profile is determined for a cylindrical pressure hull design using metamodel-based optimization technique implemented in a fully-integrated parametric modeler-CAE platform in ANSYS. While the optimal composite laminate layup and the design of ring stiffener for a thin-walled pressure hull are obtained using gradient-based optimization method in OptiStruct. It is noted that the proposed alternative approaches are potentially effective for pressure hull design.

• Journal of the Korea Convergence Society
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• v.8 no.12
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• pp.55-62
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• 2017

The Named Entity Recognition system is a system that recognizes words or phrases with object names such as personal name (PS), place name (LC), and group name (OG) in the document as corresponding object names. Traditional approaches to named entity recognition include statistical-based models that learn models based on hand-crafted features. Recently, it has been proposed to construct the qualities expressing the sentence using models such as deep-learning based Recurrent Neural Networks (RNN) and long-short term memory (LSTM) to solve the problem of sequence labeling. In this research, to improve the performance of the Korean named entity recognition system, we used a hand-crafted feature, part-of-speech tagging information, and pre-built lexicon information to augment features for representing sentence. Experimental results show that the proposed method improves the performance of Korean named entity recognition system. The results of this study are presented through github for future collaborative research with researchers studying Korean Natural Language Processing (NLP) and named entity recognition system.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.231-237
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• 2008

This study was performed to evaluate joint behavior of prestressed concrete(PSC)-steel mixed girders through the flexural test of 14 beams according to embedded length, amount of reinforcing steel, stud arrangement, and prestressing force. All test beams were failed by turns of desertion of reinforcing steel, stud, and steel plate. From test results, prestressing force was more effective on performance of connection than stud arrangement and reinforcing steel. And the spacing of stud is also more effective than embedding length. This paper also presented 3D nonlinear analysis considering the slip of composite section as well as the static load tests of PSC-steel mixed girders. According to the slip modulus, the nonlinear analysis showed that the behavior of hybrid girders could be divided into three parts as full-composite, partial-composite and non-composite. However, the experimental results showed that the PSC-steel hybrid girders with shear connectors took the part of partial composite action in ultimate load stage. In addition, it was founded that stud shear connectors and welded reinforcements were contributed to improve the ultimate strength of hybrid girders for about 20%.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.119-128
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• 2004

Environmental impact of waste tires as gound-reinforcing material is studied. Analysis for chemical compounds and toxic effect were performed on effluents from twelve lysimeters in which waste tires were mixed with sand and three initially different environmental solutions of acidic, neutral, and basic circulated through the mixture. The test results of effluents collected from the lysimeters provided that the contaminant concentrations were lower than those of Korean drinking water standards for all the selected and tested metal elements. While iron concentration increased slightly with the exposure period, other metal concentrations decreased with the number of circulation times. From the comparison with previous investigations, the contaminant concentration decreased with the increase of tire size, i.e. increases with the increase of the exposed surface of tire metals. From the toxicity tests, no deteriorative effect was observed and it could be concluded that waste tires are not biologically hostile materials.

• Journal of the Korean Geotechnical Society
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• v.25 no.7
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• pp.11-21
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• 2009

This paper presents a new high-performance supporting system of the shallow tunnel. In order to perform this research the mechanism of new supporting system is suggested and compared with the conventional existing supporting system. It is found that the new supporting system as pre-support system has several advantages such as improvement of ground before tunnel excavation and increment of capacity of the tunnel support. The construction procedures of this supporting system are also reviewed. In addition, the numerical simulation is carried out to evaluate the new supporting system. It is found that the new high-performance supporting system is very applicable in shallow depth tunnel such as portal area, tunnel in soil and weak zone, and so on.

• Proceedings of the Korean Society of Community Living Science Conference
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• 2009.09a
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• pp.94-94
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• 2009

농업계고등학교 교과서는 농촌어메니티를 학습할 수 있는 최적의 교재로서 농촌어메니티 교육내용을 개발함으로써 청소년의 올바른 농업 농촌 가치관 형성 및 국민적 공감대 확산에 이바지하고자 한다. 대상 교과서는 농업계고등학교 교과서 39종으로 이루어졌으며, 연구방법으로는 우선적으로 1~5단계의 내용분석 척도를 설정하여(1단계는 어메니티 개념에 따라 반드시 수정이 필요한 내용, 2단계는 어메니티 개념에 따라 수정이 필요한 내용, 3단계는 어메내티 개념이 포함되었는지 판단할 때 크게 문제가 없는 내용, 4단계는 어메니티 개념이 포함되어 있는 좋은 내용, 5단계는 어메니티 개념이 포함되어 있는 교과서의 모델이 될 수 있는 내용) 판정하였다. 그 결과 1단계 어메니티 개념에 따라 반드시 수정이 필요한 내용을 선정하여 교과내용을 개발하였으며, 이는 어메니티 관점에 맞추어 실시하였다. 또한 내용분석을 통한 교과서 구분을 하여 A, B, C 유형으로 나타내었다. A유형은 내용분석의 결과 판정 1 또는 2의 분석 내용이 20개 이상 나온 교과서, B유형은 내용분석의 결과 판정 1 또는 2의 분석 내용이 10~19개 나온 교과서, C유형은 내용분석의 결과 평정 1또는 2의 분석 내용이 10개 미만으로 나온 교과서를 의미한다. 교과내용 개발 결과 총 262건의 교과내용 개발이 이루어졌으며, 문장 132개로 50.38%, 사진 105개 40.47%, 삽화 22개 8.35, 그래프 0.76%, 표 0.38% 등의 순서로 나타났다. 총 262개 개발내용중에서 '사회자원의 시설'부분에 대한 관점 77개로, '사회자원의 경제활동'에 대한 관점 64개, '문화자원의 경관'에 대한 관점 50개 순으로 집계되었다. 그 다음은 '자연자원의 자연'에 대한 관점이 47개, 문화자원의 역사'에 대한 관점이 9개, '사회자원의 공동체 활동'에 대한 관점이 14개 순으로 나타났다. 자연적 자원 18.31%, 문화적 자원 22,52%, 사회적 자원 관점이 59.16%로 '사회적 자원 관점이 가장 많은 것으로 나타났다. 이는 농업계고등학교 교과서에서는 농촌어메니티의 사회적 자원이 강조되어야 하며, 문화적 자원, 자연적 자원의 순서로 강조될 필요성이 있다는 것을 뜻한다. 즉 농촌어메니티개념의 확립을 이하여 현재 농업계 고등학교 교과서에서는 시설, 경제활동, 공동체활동 같은 '사회적 자원'을 보강하여 강조할 필요가 있음을 나타낸다.