• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.251-252
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• 2022

Chemical crosslinking is the most widely used method for hydrogel preparations. We prepared a hydrogel using chitosan catechol/polyvinyl alcohol and sodium tetraborate decahydrate (Na₂B₄O₇·10H₂O). The formation of hydrogels often presents inconsistent results and issues according to the reaction scale. Therefore, we measured and analyzed the self-healing property and viscoelasticity of hydrogels attributed to scale-up synthesis using a rheometer.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.307-314
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• 2000

In order to study the effect of the magnetic anisotropy on the giant magnetoresistance (GMR), the angle dependent magnetoresistance (MR) was measured. The experimental results show that the maximum MR ratio depends on the angle between the direction of the applied field and that of the easy axis. The angular modulation of the MR ratio can be explained by the alignments of the two 'effective' magnetization vectors that are bound to their own easy axes. The typical property of MR loops at 2$\^$nd/ antiferromangtic maximum (AFM) such as two maxima was discussed in relation with the magnetic anisotropy (MA). The simulated results under an assumption of the two in-plane easy axes, which exist in the sample, were compared with the experiments.

• 융복합기술연구소 논문집
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• 제5권1호
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• pp.13-17
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• 2015

In wafer level molding progress, the thermal releasing failure phenomenon is shown up as the important problem. This phenomenon can cause the problem including the warpage, crack of the molded wafer. The thermal releasing failure is due to the insufficiency of adhesion strength degradation of the molding tape. To solve this problem, we studied experimental method increasing the release property of the molding tape through the plasma surface treatment on the wafer substrate. In this research, the vacuum plasma treatment system is used for release property improvement of the molding tape and controls the operating condition of the hydrophilic($O_2$, 100kW, 10min) and hydrophobic($C_2F_6$, 200kW, 10min). In order to perform the peeling test for measuring the releasing force precisely, we remodel the micro scale material property evaluation system developed by Korea institute of industrial technology. In case of hydrophilic surface treatment on the wafer substrate, we can figure out the releasing property of molding tape increase. In order to grasp the effect that it reaches to the release property increase when repeating the hydrophilic treatment, we make an experiment with twice treatment and get the result to increase about 12%. We find out the hydrophilic surface treatment method using plasma can improve releasing property of molding tape in the wafer level molding process.

• 한국터널지하공간학회 논문집
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• 제9권4호
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• pp.343-349
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• 2007

터널 화재와 관련된 축소모형실험연구는 기본적인 데이터는 제공할 수 있지만, 축소모형과 실물화재간의 정확한 이론적 상사관계가 정립되어 있지 않기 때문에 실물화재에 대한 직접적인 분석을 하기에는 어려움이 따른다. 이에 산소소모율법을 적용하여 열방출율과 같은 물리량의 측정이 가능한 실물화재실험장치인 대형칼로리미터를 개발하였다. 이를 이용하여 차량의 화재시 열방출율을 측정하기 위한 실물실험을 실시하였으며, 그 결과 차량의 열방출율은 $2.3{\sim}3.4\;MW$로 측정되었다. 이는 PIARC에서 권고하는 차량의 열방출율과 유사한 범위로서 개발된 실물화재평가장치의 신뢰성을 확인할 수 있음은 물론이고 향후 관련 연구에 매우 유용하게 이용될 수 있을 것이다.

• Journal of Biosystems Engineering
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• 제39권4호
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• pp.377-388
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• 2014

Purpose: Determining the spatial structure of data is important in understanding within-field variability for site-specific crop management. An understanding of the spatial structures present in the data may help illuminate interrelationships that are important in subsequent explanatory analyses, especially when site variables are correlated or are a combined response to multiple causative factors. Methods: In this study, correlation, principal component analysis, and single and nested variogram models were applied to soil electrical conductivity and chemical property data of two fields in central Missouri, USA. Results: Some variables that were highly correlated, or were strongly expressed in the same principal component, exhibited similar spatial ranges when fitted with a single variogram model. However, single variogram results were dependent on the active lag distance used, with short distances (30 m) required to fit short-range variability. Longer active lag distances only revealed long-range spatial components. Nested models generally yielded a better fit than single models for sensor-based conductivity data, where multiple scales of spatial structure were apparent. Gaussian-spherical nested models fit well to the data at both short (30 m) and long (300 m) active lag distances, generally capturing both short-range and long-range spatial components. As soil conductivity relates strongly to profile texture, we hypothesize that the short-range components may relate to the scale of erosion processes, while the long-range components are indicative of the scale of landscape morphology. Conclusion: In this study, we investigated the effect of changing active lag distance on the calculation of the range parameter. Future work investigating scale effects on other variogram parameters, including nugget and sill variances, may lead to better model selection and interpretation. Once this is achieved, separation of nested spatial components by factorial kriging may help to better define the correlations existing between spatial datasets.

• Smart Structures and Systems
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• 제26권3호
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• pp.331-343
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• 2020

In this paper, based on the CPT, motion equations for a sandwich plate containing a core and two integrated face-sheets have derived. The structure rests on the Visco-Pasternak foundation, which includes normal and shear modules. The piezo-magnetic core is made of CoFe₂O₄ and also is subjected to 3D magnetic potential. Two face sheets at top and bottom of the core are under electrical fields. Also, in order to obtain more accuracy, the effect of flexoelectricity has took into account at face sheets' relations in this work. Flexoelectricity is a property of all insulators whereby they polarize when subject to an inhomogeneous deformation. This property plays a crucial role in small-scale rather than macro scale. Employing CPT, Hamilton's principle, flexoelectricity considerations, the governing equations are derived and then solved analytically. By present work a detailed numerical study is obtained based on Piezoelectricity, Flexoelectricity and modified couple stress theories to indicate the significant effect of length scale parameter, shear correction factor, aspect and thickness ratios and boundary conditions on natural frequency of sandwich plates. Also, the figures show that there is an excellent agreement between present study and previous researches. These finding can be used for automotive industries, aircrafts, marine vessels and building industries.

• 한국지반공학회지:지반
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• 제13권6호
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• pp.147-164
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• 1997

본 논문은 절리 암반물성의 크기효과가 암반의 불균질성 및 불연속성에 기인한다고 가정하였다. 이를 위해 대표체적요소의 개념이 적용되는 일반적인 등가물성이론을 탈피하여 불규칙적인 절리기하와 임의의 절리수 및 임의의 절리 방향성을 고려할 수 있는 등가물성이론에 대해서 연구하였다. 이론적인 연구를 바탕으로 이 이론을 실제 문제에 적용한 결과 암반요소의 크기에 따라 달라지는 물성 변화를 관찰하고, 크기효과에 관한 여러 가지 연구를 수행하였다. 특히, 수치해석적인 방법으로 크기효과를 증명하는 과정의 타당성을 입증하고 크기효과의 구체적인 원인을 알아보기 위해서 4개의 모델에 대해서 전산실험을 수행하였다. 이 실험으로부터 증명된 내용을 토대로 실제 3차원 구조물을 대상으로 크기효과 실험을 수행하였다. 이 실험 과정 중 절리의 여러 역학적인 성질들이 암반강도 및 탄성계수의 크기효과에 미치는 영향을 관찰해 보았다. 또 크기효과가 특정 절리구조에서 발생되는 것이 아니고 절리를 포함하는 모든 경우에서 발생됨을 증명하기 위해 절리 구조가 다른 두 모델을 대상으로 크기효과 실험을 수행하였다.

• 대한토목학회논문집
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• 제26권6D호
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• pp.917-926
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• 2006

수송 규모의 경제 효과는 허브 네트워크의 특수한 현상이다. 허브 네트워크의 중요한 특성은 규모의 경제 효과로 인한 비용 절감과 허브 시설 운영 및 수송량 집화에 따른 지체와 관련한 비용들을 정량화하는 것이다. 그럼에도 불구하고 허브 입지 문제의 NP-complete 특성으로 인하여, 대부분의 기존 연구자들은 근사해 도출을 위한 휴리스틱 알고리즘 개발에 초점을 맞추었다. 본 연구의 목적은 규모의 경제 효과를 반영하는 허브 네트워크 설계 모형을 개발하는 것이다. 모형은 허브 네트워크의 특수성을 고려하고 다양한 비용요소들을 결정할 수 있도록 설계된다. 개발된 모형식을 반영하는 휴리스틱 알고리즘이 개발되며 모형의 결과들은 실제 데이터를 이용하여 최근 발표된 연구결과들과 비교된다. 분석 결과, 제안된 모형은 수송량 집화에 따른 규모의 경제 효과를 잘 반영할 수 있는 것으로 확인되었다. 본 연구는 효율적이고 합리적인 네트워크 설계의 이론적 기반을 구성함과 동시에 현재 및 계획 중인 물류시스템의 평가에도 기여할 수 있을 것으로 사료된다.

• 한국의류학회지
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• 제31권9_10
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• pp.1453-1464
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• 2007

The purpose of this study is to examine the hand of spring/fall fabrics for 'Saenghwal Hanbok' on subjective hand, objective hand and the preference. In this study, 28 varieties of spring/fall fabrics such as cotton fabrics, synthetic fabrics, blended fabrics and a silk fabric for 'Saenghwal Hanbok' are used. To evaluate the subjective hand of fabrics, the holistic touch and preferences, 33 seven ranks' segmentic differential scale questions are developed with adjective pairs and are gathered by surveying experts on clothes. The mechanical properties, HV and THV of them are measured and calculated by KES-FB system. Through subjective hand, items could be classified into six hand expressions: 'bulky/extensibility', 'stiffness', 'feeling of weight', 'surface property', 'drapability' and 'moisture property'. Through mechanical properties, the results indicated that the character of cotton fabrics are slight flexible, tough, rough, uneven, a bit heavy, thick and low resilience on tensile and compression, and then those of synthetic fabrics, blended fabrics and a silk fabric are thin and light, smooth, flat and bulkless. In correlation on subjective evaluations and the preference for 'Saenghwal Hanbok', cotton fabrics mainly depend on 'surface property' and 'moisture property' and then synthetic fabrics, blended fabrics and a silk depend on 'bulky/extensibility' and 'surface property' In correlation on objective hand and the preference for 'Saenghwal Hanbok'. people aren't satisfied with low resilience. high stiffness and low drape.

• Carbon letters
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• 제12권3호
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• pp.177-179
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• 2011

The use of carbon nanotubes (CNTs) as a reinforcing material in a polymer matrix has increased in various industries. In this study, the flexural behavior of CNT-modified epoxy/basalt (CNT/epoxy/basalt) composites is investigated. The effects of CNT modification with silane on the flexural properties of CNT/epoxy/basalt composites were also examined. Flexural tests were performed using epoxy/basalt, oxidized CNT/epoxy/basalt, and silanized CNT/epoxy/basalt multi-scale composites. After the flexural tests, the fracture surfaces of the specimens were examined via scanning electron microscopy (SEM) to investigate the fracture mechanisms of the CNT/epoxy/basalt multi-scale composites with respect to the CNT modification process. The flexural properties of the epoxy/basalt composites were improved by the addition of CNTs. The flexural modulus and strength of the silane-treated CNT/epoxy/basalt multi-scale composites increased by approximately 54% and 34%, respectively, compared to those of epoxy/basalt composites. A SEM examination of the fracture surfaces revealed that the improvement in the flexural properties of the silane-treated CNT/epoxy/basalt multi-scale composites could be attributed to the improved dispersion of the CNTs in the epoxy.