• Journal of Biosystems Engineering
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• 제32권6호
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• pp.395-402
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• 2007

This study was carried out as basic researches to develop the leaf vegetable harvester. This study was conducted to investigate physical and rheological properties of bundled leaf vegetables with stem (Chinese leek, Crown daisy and Chamnamul) as test materials held and picked-up by a machine. Stress-strain behavior, stress relaxation, and strain recovery for the bundled materials were analyzed using simple Maxwell model. Physical and rheological properties of the materials were investigated by measuring rupture load, deformation and stress experimentally. Also, strain recovery time when unloading was measured using super high speed camera. Recorded recovery time for stress-strain behavior was0.026 s for Chinese leek with liner strain recovery, 0.046 s for Crown daisy and 0.05 s for Chamnamul with non-linear strain recovery. Furthermore, the strain recovery time for permanent deformation was 0.026 s, 0.046 s, and 0.05 s for Chinese Leek, Crown daisy and Chamnamul, respectively. Finally, strain recovery time and strain recovery ratio for the test materials were 0.17 s, 60.4% in Chinese leek, 0.12 s, 55.3% in Crown daisy, 0.15 s, 58.7% in Chamnamul. Here strain recovery time means that how fast the test materials are recovered from initial deformation and strain recovery ratio means how much the test materials are recovered from initial deformation. The above results show that the test materials can be held enough and moved by the belts.

• Structural Engineering and Mechanics
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• 제60권2호
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• pp.337-350
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• 2016

Even though extensive researches have been performed for steam explosion due to their complex mechanisms and inherent uncertainties, establishment of severe accident management guidelines and strategies is one of state-of-the arts in nuclear industry. The goal of this research is primarily to examine effects of vessel failure modes and locations on nuclear facilities under typical steam explosion conditions. Both discrete and integrated models were employed from the viewpoint of structural integrity assessment of steel components and evaluation of the cracking and crushing in reinforced concrete structures. Thereafter, comparison of systematic analysis results was performed; despite the vessel failure modes were dominant, resulting maximum stresses at the all steel components were sufficiently lower than the corresponding yield strengths. Two failure criteria for the reinforced concrete structures such as the limiting failure ratio of concrete and the limiting strains for rebar and liner plate were satisfied under steam explosion conditions. Moreover, stresses of steel components and reinforced concrete structures were reduced with maximum difference of 12% when the integrated model was adopted comparing to those of discrete models.

• 대한조선학회지
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• 제24권4호
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• pp.9-18
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• 1987

The hydrodynamic radiation forces acting on a ship travelling in waves have been conventionally treated by strip theories or by direct three dimensional approaches, most of which have been formulated in frequency domain. If the forward speed of a ship varies with time, or if its path is not a straight line, conventional frequency domain analysis can no more be used, and for these cases time domain analysis may be used. In this paper, formulations are made in time domain with applications to some problems the results of which are known in frequency domain. And the results of both domains are compared to show the characteristics and validity of time domain solutions. The radiation forces acting on a three dimensional body within the framework of a linear theory. If the linearity of entire system is assumed, radiation forces due to arbitrary ship motions can be expressed by the convolution integral of the arbitrary motion velocity and the so called impulse response function. Numerical calculations are done for some bodies of simple shapes and Series-60[$C_B=0.7$] ship model. For all cases, integral equation techniques with transient Green's function are used, and velocity or acceleration potentials are obtained as the solution of the integral equations. In liner systems, time domain solutions are related with frequency domain solutions by Fourier transform. Therefore time domain solutions are Fourier transformed by suitable relations and the results are compared with various frequency domain solutions, which show good agreements.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.384-385
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• 2005

Monolayers of lipids on a water surface have attracted much interest as models of biological membranes, but also as precursors of multilayer systems promising many technical applications. Until now, many methodologies have been developed in order to gain a better understanding of the relationship between the structure and function of the monolayers. Maxwell displacement current (MDC) measurement has been employed to study the dielectric property of Langmuir-films. MDC flowing across monolayers is analyzed using a rod-like molecular model. It is revealed that the dielectric relaxation time $\tau$ of mono layers in the isotropic polar orientational phase is determined using a liner relationship between the monolayer compression speed a and the molecular area $A_m$. Compression speed a was about 30, 40, 50mm/min. also, LB layers of Arachidic acid deposited by LB method were deposited onto slide glass as Y-type film. The structure of manufactured device is Au/Arachidic acid/Al, the number of accumulated layers are 9 ~ 21 and we then examined of the Metal-Insulator-Metal(MIM) device by means of I-V.

• Structural Engineering and Mechanics
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• 제55권6호
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• pp.1087-1097
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• 2015

In this paper, the effect of functionally graded material (FGM) coatings on the fracture behavior of semi-elliptical cracks in cylinders is assessed. The objective is to calculate the stress intensity factor (SIF) of a longitudinal semi-elliptical crack on the wall of an aluminum cylinder with FGM coating. A three-dimensional finite element method (FEM) is used for constructing the mechanical models and analyzing the SIFs of cracks. The effect of many geometrical parameters such as relative depth, crack aspect ratio, FG coating thickness to liner thickness as well as the mechanical properties of the FG coating on the SIF of the cracks is discussed. For a special case, the validity of the FE model is examined. The results indicated that there is a particular crack aspect ratio in which the maximum value of SIFs changes from the deepest point to the surface point of the crack. Moreover, it was found that the SIFs decrease by increasing the thickness ratio of the cylinder. But, the cylinder length has no effect on the crack SIFs.

• Journal of Korea Trade
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• 제27권1호
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• pp.19-41
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• 2023

Purpose - Conventional supply chains (SCs) must identify facilitating roles, such as port or terminal operators, shipping companies, and freight forwarders in executing the various logistical activities that support the organizational strategies of shippers. Meanwhile, supply chain collaborative practices can engender a willingness to share relevant and mutually helpful information. To this end, this study seeks to identify the impact of supply chain integration (SCI) on information sharing (IS) and the operational performance (OP) of Korea's container-shipping industry from the perspective of social capital. Design/methodology - We established the research model for this study based on previous studies. In administering the survey, we obtained 149 valid responses from employees working in liner-shipping companies and freight forwarders in Korea. With the collected questionnaires, the study's hypotheses were tested using SPSS 26.0 and AMOS 26.0 Findings - The results indicate the existence of a mediated relationship where the impact of SCI on OP is mediated by IS. The effect of external integration (EI) on OP is fully mediated by information quality (IQ) and information-sharing content (ISC). Furthermore, EI, IQ and ISC partially mediate the relationship between internal integration (II) and OP. Originality/value - This study expands SCI contexts, where ISC and IQ respectively serve as bridges between EI and OP which has crucial implications for container-shipping companies in terms of improving their performance.

• 무역학회지
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• 제47권1호
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• pp.13-24
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• 2022

This study was conducted because the global economic downturn caused by COVID-19 caused a surge in logistics costs and it was no longer possible to predict logistics costs using existing methods. For this study, we made the assumption that economic indicators affect logistics cost. Chapter 2 examines the current status of the liner market and factors affecting logistics costs. Based on this, Chapter 3 collects independent and dependent variables to determine the analysis model. As the independent variable, economic indicators of major countries constituting the SCFI were selected, and the dependent variables were the SCFI Europe Index and the SCFI USA Index. In Chapter 4, a panel analysis was conducted based on this, and it was confirmed that major economic indicators had a negative (-) effect on SCFI. This is contrary to the existing research results, which can be attributed to the special situation caused by COVID-19 and the imbalance of demand and supply by region. The results of this study are meaningful in that they can predict long-term logistics cost volatility without analyzing supply and demand, and can be applied to other studies as well.

• 한국지하수토양환경학회지:지하수토양환경
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• 제13권1호
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• pp.13-23
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• 2008

오염물질로 오염된 퇴적점토의 강도, 변형 및 투수특성 변화를 파악하기 위하여 NaCl 수용액과 매립장 침출수를 시료의 간극수(포화수)로 교체하여 삼축압축시험과 압밀시험을 수행하였다. 또한, 채취된 점토시료의 화학적 특성을 규명하기 위하여 주사전자현미경(SEM) 관찰과 에너지분산분광(EDX) 분석이 수반된다. 화학성분 분석결과 O, C, Si, Al, Fe 크기 순의 구성비가 얻어졌으며, 삼축압축시험 및 압밀시험결과는 NaCl의 농도가 증가할수록 극한응력(강도)은 증가하고 압축성과 투수성이 커지는 경향을 보이는데, 이는 전해질의 농도가 증가할수록 확산이중층(DDL)의 두께가 감소되어 면모화되기 때문인 것으로 판단된다. 또한, 점토 차수재를 투과한 침출수가 지하수 오염에 미치는 영향을 분석하기 위하여 MT3D 해석모델이 이용되었으며, 지하수 오염거동 해석결과 초기 염소이온 농도가 클수록 측정농도도 커지며, 시간경과에 따라 지하수 오염농도는 비선형적으로 증가되었다. 지하수 오염농도 감쇄 관계식을 유도하여 지하수 오염 이동거리를 예측한 결과, 초기농도가 클수록 지하수 오염 이동거리도 크게 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제22권1호
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• pp.129-136
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• 2018

대형 용접 구조물에 대한 피로설계 수명의 예측은 일반적으로 Palmgren Miner과 등가손상도 방법 또는 선형누적손상도 방법을 사용한다. 또한 용접 구조물에서 피로 균열이 발생되면 잔존 수명은 S-N 곡선과 선형 파괴역학에 기초하여 예측되고 있다. 본 연구에서는 면외거셋 용접이음의 3차원 피로균열 진전거동과 피로수명을 예측하기 위하여 피로 시험을 실시하였다. 면외거셋 용접이음의 3차원 피로균열진전해석은 NX NASTRAN 및 FRANC3D를 이용하여 유한요소 해석을 실시하였다. 면외거셋 용접이음의 균열 형상비, 초기균열 크기 및 응력비에 미치는 영향을 검토하기 위하여 피로균열진전 해석을 실시하였다. 또한 초기균열크기, 균열 형상비와 응력비의 변화에 따른 3차원 피로균열진전 해석 결과와 피로시험결과를 비교하였다. 피로균열진전 해석결과, 피로균열 진전속도와 응력확대계수와의 관계에서 피로시험과 유사하게 나타남을 확인하였으며, 면외거셋 용접이음의 피로수명을 추정할 수 있음을 확인하였다.

• 생태와환경
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• 제44권2호
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• pp.195-202
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• 2011

본 연구에서는 일본전국을 연구대상지로 선정하고 대상지에 서식하고 있는 대표 외래어종인 배스와 블루길의 공간적 서식분포 특성을 평가하였다. 또한 GAM, GLM, CTA 등의 세가지 통계 기법을 이용하여 일본전국에서의 해당 어종에 대한 공간적 분포패턴을 예측하였다. 그 결과 배스와 블루길 등의 외래어종은 인구 및 댐 풍의 인위적인 환경인자와 유의한 정의 관계를 보임에 따라 외래어종의 확산에 미치는 인간활동의 부정적인 영향이 확인되었다. 또한 회귀모델을 통한 해당어종의 서식확률 예측을 통한 배스와 블루길의 서식 분포는 각각 GAM (AUC: 0.88, Kappa: 0.42)과 CTA (AUC: 0.92, Kappa: 0.44)에 의해서 가장 정확하게 예측되는 것으로 평가되었고, 가장 유의한 환경인자는 연평균기온으로 나타났다. 따라서 각 생물종별로 서식확률을 추정하고 예측하는데 있어서 적합한 통계모델에 대한 검증은 생물종별로 선행되어야 할 필요가 있을 것으로 판단된다. 비록 본 연구의 연구대상지는 일본이지만 국내의 경우도 최근 들어 어류를 포함한 생물조사가 다수의 조사연구에서 광역적으로 시행되고 있기 때문에 본 연구와 같은 다량자료를 이용한 광역 스케일에서의 생물종의 서식확률 및 출현종수에 대한 연구가 충분히 가능할 것으로 판단된다.