• Advances in aircraft and spacecraft science
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• 제7권2호
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• pp.151-168
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• 2020

The present study deals with the repair of composite structures by bonding composite patches. The composite structure is a carbon/epoxy laminate with stacking sequence [45/-45/0/90]S. The damaged zone is simulated by a central crack and repaired by bonding symmetrical composite patches. The repair is carried out using composite patches laminated from the same elemental folds as those of the cracked specimen. Three-dimensional finite element method is used to determine the energy release rate along the front of repaired crack. The effects of the repair technique used single or double patch, the stacking sequence of the cracked composite patch and the adhesive properties were highlighted on the variations of the fracture energy in mode I and mixed mode I + II loading.

• Structural Engineering and Mechanics
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• 제7권6호
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• pp.575-588
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• 1999

A boundary element method is applied to the analysis of crack trajectory in materials with complex microstructure, such as discontinuously reinforced composite materials, and systems subjected to complex loading, such as indentation. The path followed by the crack(s) has non-trivial geometry. A study of the stress intensity factors and fracture toughness of such systems must therefore be accompanied by an analysis of crack trajectory. The simulation is achieved using a dual boundary integral method in planar problems, and a single boundary integral method coupled with substructuring in axisymmetric problems. The direction of crack propagation is determined using the maximum mechanical energy release rate criterion. The method is demonstrated by application to (i) a composite material composed of components having the elastic properties of aluminium (matrix) and silicon carbide (reinforcement), and (ii) analysis of contact damage induced by the action of an indenter on brittle materials. The chief advantage of the method is the ease with which problems having complex geometry or loading (giving rise to complex crack trajectories) can be treated.

• 한국콘텐츠학회논문지
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• 제16권7호
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• pp.221-230
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• 2016

대다수의 국민은 부동산정책을 접할 때 정부의 보도자료 보다는 언론기사를 주로 접하며 정보를 얻는다. 하지만 이러한 정보는 언론사의 성향과 독자의 계층에 따라 다른 프레임으로 전달 될 수 있다. 언론사는 정부의 부동산 정책에 대하여 언론사의 성향에 따라 기대와 찬성 또는 우려와 비판의 프레임으로 기사를 보도한다. 따라서 어떤 성향의 언론보도를 접하느냐에 따라 국민의 부동산 정책에 대한 기대와 우려는 바뀌게 될 가능성이 있다. 본 연구에서는 정부의 부동산 정책이 언론사의 성향에 따라 어떤 프레임을 가지고 신문보도에 투영되는지 '부동산 3법에 대한 여야합의 및 국회통과'와 관련된 기사를 분석하여 살펴보았다. 분석결과 보수성향의 언론사는 부동산 3법의 국회통과에 대하여 긍정적 논조의 보도 및 정책에 대한 호의적 전망 프레임의 비율이 높았고, 진보성향의 언론사는 국회통과에 대한 중립적 또는 부정적 논조의 보도 및 정책에 대한 부정적 전망 프레임의 비율이 높은 것으로 나타났다. 이를 통하여 부동산 정책과 관련하여 여야가 합의한 사안이라 하더라도 보수와 진보로 구분되는 언론매체들 사이에 보도프레임에 대하여 차이가 존재하고 있다는 것을 확인하였다.

• 한국정보관리학회:학술대회논문집
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• 한국정보관리학회 2006년도 제13회 학술대회 논문집
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• pp.281-288
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• 2006

2000년 이후 우리나라 언론보도에 나타난 도서관 관련 기사에 대한 계량적 분석을 통해 우리나라 도서관에 대한 사회적 인식과 요구가 어떤 것인지를 파악해 보았다. 그 중에서 기적의 도서관 관련한 내용에 대한 내용분석을 시도하였다. 이러한 분석결과를 기반으로 향후 도서관계의 언론홍보 방안을 제시하였다.

• Membrane and Water Treatment
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• 제6권3호
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• pp.225-235
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• 2015

During low-pressure membrane treatments of cyanobacterial cells, including microfiltration (MF) and ultrafiltration (UF), there have reportedly been releases of intracellular compounds including cyanotoxins and compounds with an earthy-musty odor into the water, probably owing to cyanobacterial cell breakage retained on the membrane. However, to our knowledge, no information was reported regarding the effect of growth phase of cyanobacterial cells on the release of the intracellular compounds. In the present study, we used a geosmin-producing cyanobacterium, Anabaena smithii, to investigate the effect of the growth phase of the cyanobacterium on the release of intracellular geosmin during laboratory-scale MF experiments with the cells in either the logarithmic growth or stationary phase. Separate detection of damaged and intact cells revealed that the extent of cell breakage on the MF membrane was almost the same for logarithmic growth and stationary phase cells. However, whereas the geosmin concentration in the MF permeate increased after 3 h of filtration with cells in the logarithmic growth phase, it did not increase during filtration with cells in the stationary phase: the trend in the geosmin concentration in the MF permeate with time was much different between the logarithmic growth and stationary phases. Adsorption of geosmin to algogenic organic matter (AOM) retained on the MF membrane and/or pore blocking with the AOM were greater when the cells were in the stationary phase versus the logarithmic growth phase, the result being a decrease in the apparent release of intracellular geosmin from the stationary phase cells. In actual drinking water treatment plants employing membrane processes, more attention should be paid to the cyanobacterial cells in logarithmic growth phase than in stationary phase from a viewpoint of preventing the leakage of intracellular earthy-musty odor compounds to finished water.

• Structural Engineering and Mechanics
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• 제87권1호
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• pp.47-56
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• 2023

Any pre-existed delamination defect present during manufacturing or induce during service loading conditions in the wingskin adherend invariably shows a greater loss of structural integrity of the spar wingskin joint (SWJ). In the present study, inter-laminar delamination propagation at the critical location of the SWJ has been carried out using contact and multi-point constraint finite elements available with commercial FE software (ANSYS APDL). Strain energy release rates (SERR) based on virtual crack closure technique have been computed for evaluation of the opening (Mode-I), sliding (Mode-II) and cross sliding (Mode-III) modes of delamination by sequential release of multi point constraint elements. The variations of different modes of SERR are observed to be significant by considering varied delamination lengths, material properties of adherends and radius of curvature of the SWJ panel. The SERR rates are seen to be much different at the two pre-embedded delamination ends. This shows dissimilar delamination propagation rates. The maximum is seen to occur in the delamination front in the unstiffened region of the wingskin. The curvature geometry and material anisotropy of SWJ adherends significantly influences the SERR values. Increase in the SERR values are observed with decrease in the radius of curvature of wingskin panel, keeping its width unchanged. SWJs made with flat FRP composite adherends have superior resistance to delamination damage propagation than curved composite laminated SWJ panels. SWJ made with Boron/Epoxy (B/E) material shows greater resistance to the delamination propagation.

• 방사성폐기물학회지
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• 제16권1호
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• pp.123-136
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• 2018

본 연구의 목적은 고준위폐기물 처분기술 개발과 관련하여 현장실증 연구를 위해 사용될 공학규모 이상의 균질 완충재 블록을 제작하기 위한 새로운 방법론을 제시하는 것이다. 이와 관련하여 플롯팅 다이(floating die) 방식의 프레스 재하 및 냉간등방압프레스(CIP; Cold Isostatic Press) 기법을 국내 최초로 완충재 제작에 적용하였다. 또한 소요 밀도기준을 충족하는 완충재 블록을 생산하기 위한 최적의 제작조건(프레스 및 CIP의 소요 압력)과 현장 적용성을 분석하였다. 상기 기법의 적용을 통해 완충재 블록 내 밀도분포 편차가 현저히 감소하였으며, 이와 동시에 평균 건조밀도가 소폭 상승하고 약 5%의 크기가 감소하였다. 또한 CIP 적용을 통해 응력이완(stress release) 현상이 감소하고, 이로 인해 시간 경과에 따른 표면균열 발생이 현저히 저감됨을 시험제작을 통해 확인하였다. 본 연구에서 제시된 방법론은 공학규모 이상의 균질한 완충재 블럭을 성형할 수 있으며, 또한 이는 선진핵주기 고준위폐기물처분시스템(AKRS; Advanced Korea Reference Disposal System of HLW)의 완충재 소요 밀도기준을 충족하는 것으로 분석되었다.

• 디지털융복합연구
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• 제14권6호
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• pp.187-197
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• 2016

본 연구는 정부의 메시지 제시 유형 즉, 텍스트 형태의 보도자료와 대량의 정보를 시각적으로 표현하기 위한 인포그래픽 그리고 어렵고 난해한 정보를 흥미롭게 제공하기 위한 웹툰이 환경의식 따른 정보의 이해 용이성과 정보습득에는 차이가 있는지 상호작용효과는 있는지 확인하였다. 연구결과, 정보의 메시지 제시 유형과 환경의식에 따른 정보이해 용이성에는 주효과와 상호작용효과가 있는 것으로 확인되었다. 또한 정부의 메시지 제시 유형과 환경 의식에 따른 정보습득에는 각각의 변인에 관한 주효과는 확인되었으나 상호작용효과는 나타나지 않았다. 이상의 연구결과는 정부 3.0시대를 맞이하여 정보 수용자들에게 제공되는 정부의 메시지 제시 유형 정보의 효용성과 유용성을 획득하기 위한 기초자료를 제공하였다는 것에 의의를 두고자 한다.

• 한국운동역학회지
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• 제27권2호
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• pp.117-124
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• 2017

Objective: The purpose of this study was to examine the effect of changes in degrees of freedom of the fingers (i.e., the number of the fingers involved in tasks) on the task performance during force production and releasing task. Method: Eight right-handed young men (age: $29.63{\pm}3.02yr$, height: $1.73{\pm}0.04m$, weight: $70.25{\pm}9.05kg$) participated in this study. The subjects were required to press the transducers with three combinations of fingers, including the index-middle (IM), index-middle-ring (IMR), and index-middle-ring-little (IMRL). During the trials, they were instructed to maintain a steady-state level of both normal and tangential forces within the first 5 sec. After the first 5 sec, the subjects were instructed to release the fingers on the transducers as quickly as possible at a self-selected manner within the next 5 sec, resulting in zero force at the end. Customized MATLAB codes (MathWorks Inc., Natick, MA, USA) were written for data analysis. The following variables were quantified: 1) finger force sharing pattern, 2) root mean square error (RMSE) of force to the target force in three axes at the aiming phase, 3) the time duration of the release phase (release time), and 4) the accuracy and precision indexes of the virtual firing position. Results: The RMSE was decreased with the number of fingers increased in both normal and tangential forces at the steady-state phase. The precision index was smaller (more precise) in the IMR condition than in the IM condition, while no significant difference in the accuracy index was observed between the conditions. In addition, no significant difference in release time was found between the conditions. Conclusion: The study provides evidence that the increased number of fingers resulted in better error compensation at the aiming phase and performed a more constant shooting (i.e., smaller precision index). However, the increased number of fingers did not affect the release time, which may influence the consistency of terminal performance. Thus, the number of fingers led to positive results for the current task.

• Structural Engineering and Mechanics
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• 제16권3호
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• pp.241-257
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• 2003

The first seismically isolated structure in Taiwan was completed in early 1999. Seven new bridges of the Second National Freeway located at Bai-Ho area, a region which is considered to be of high seismic risk, have been designed and constructed with lead-rubber seismic isolation bearings. Since this is the first application of seismic isolation method to the practical construction in Taiwan, field tests were conducted for one of the seven bridges to evaluate the assumptions and uncertainties in the design and construction. The test program is composed of ambient vibration tests, forced vibration tests, and free vibration tests. For the free vibration tests, a special test setup composed of four 1000 kN hydraulic jacks and a quick-release mechanism was designed to perform the function of push-and-quick release. Valuable results have been obtained based on the correlation between measured and analytical data so that the analytical model can be calibrated. Based on the analytical correlation, it is concluded that the dynamic characteristics and free vibration behavior of the isolated bridge can be well captured when the nonlinear properties of the bearings are properly considered in the modeling.