• 한국조경학회지
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• 제40권5호
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• pp.33-42
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• 2012

본 연구는 자연형 경관석 GFRC를 대상으로 성능기준을 설정하기 위해 국내 외 성능관련 문헌 및 사례 등의 고찰을 통해 요구성능인 재료성능, 구조안전성능, 내구성능, 경관성능의 항목을 40인의 전문가 설문을 통해 선정하였고, 검증된 항목 및 성능기준을 제안하였다. 전문가 설문을 통해 요구 성능 중 재료성능(유리섬유 함유율, 기건비중), 구조안전성능(휨강도, 압축강도) 그리고 내구성능(균열, 내부식성), 경관성능(질감, 백화)을 각각 선정하였다. 기준이 존재하는 재료성능과 구조안전성능의 경우, 시험을 거쳐 기존 기준사례와 비교하여 최종 성능평가기준을 제시하였으며, 기준이 존재하지 않은 내구성능과 경관성능은 기 시공된 인공폭포 등의 경관조형물을 대상으로 현지조사를 통해 직접 측정하여 검증하였다. 본 연구에서는 재료성능, 구조안전성능, 내구성능, 경관성능 등 자연형 경관석 GFRC의 재료 및 시공 후 평가 가능한 항목에 대한 성능기준을 제안하였으나, 추후 시공사례지에 대한 지속적인 모니터링을 통해 최근에 대두되고 있는 친환경적이고, 생태적인 성능기준에 관한 후속 연구가 필요하다.

• 비파괴검사학회지
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• 제30권5호
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• pp.464-470
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• 2010

고온, 고압에서 운용되고 있는 설비의 안전성을 평가하기 위해서는 사용시간 동안 열화된 역학물성을 정기적으로 점검하여야 한다. 비파괴적으로 열화된 설비의 역학적 특성을 점검하기 위하여 표면형 프로브(surface type probe)를 사용한 가역투자율 측정방법이 제시된다. 가역투자율 측정방법은 가역투자율이 자기 이력곡선의 미분값임에 근거하고 있다. 가역투자율은 교류 섭동 자기장의 주파수에 동조된 록-인 증폭기로 측정된 탐지코일에 유도된 전압의 제 1 고조파이다 가역투자율의 첨두값은 보자력 영역에서 나타난다. 실험에 사용된 강재는 12Cr 페라이트 내열강으로 $700^{\circ}C$의 등온에서 열처리 시간을 달리한 11개의 시편을 제작하였다. 가역투자율 첨두값 사이의 간격 (peak interval of reversible permeability: PIRP), 비커스 경도 및 인장강도는 열화가 진행됨에 따라 초기에는 급격하게, 후반에는 완만하게 감소하였다. PIRP가 감소함에 따라 인장강도와 비커스 경도가 선형적으로 감소하였고 이 상관관계를 이용하면 측정한 가역투자율로 12Cr 페라이트 내열강의 열화된 역학적 물성을 비파괴적으로 평가할 수 있다.

• 한국재료학회지
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• 제27권12호
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• pp.705-709
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• 2017

The electronic and optical characteristics of molybdenum disulphide ($MoS_2$) film significantly vary with its thickness, and thus a rapid and accurate estimation of the number of $MoS_2$ layers is critical in practical applications as well as in basic researches. Various existing methods are currently available for the thickness measurement, but each has drawbacks. Transmission electron microscopy allows actual counting of the $MoS_2$ layers, but is very complicated and requires destructive processing of the sample to the point where it will no longer be useable after characterization. Atomic force microscopy, particularly when operated in the tapping mode, is likewise time-consuming and suffers from certain anomalies caused by an improperly chosen set point, that is, free amplitude in air for the cantilever. Raman spectroscopy is a quick characterization method for identifying one to a few layers, but the laser irradiation causes structural degradation of the $MoS_2$. Optical microscopy works only when $MoS_2$ is on a silicon substrate covered with $SiO_2$ of 100~300 nm thickness. The last two optical methods are commonly limited in resolution to the micrometer range due to the diffraction limits of light. We report here a method of measuring the distribution of the number of $MoS_2$ layers using a low voltage field emission electron microscope with acceleration voltages no greater than 1 kV. We found a linear relationship between the FESEM contrast and the number of $MoS_2$ layers. This method can be used to characterize $MoS_2$ samples at nanometer-level spatial resolution, which is below the limits of other methods.

• 국제초고층학회논문집
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• 제6권3호
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• pp.279-284
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• 2017

The purpose of structural health monitoring is to evaluate structural behavior due to various external loads through installation of appropriate measurement. Accordingly, a guideline for monitoring standards is necessary to evaluate the safety and performance of a structure. This paper introduces preliminary design of SHM for high-rise buildings, which is the stage creating a guideline. As for preliminary design of SHM, first step is to calculate the displacement and member force through structural analysis. After that, limitations or qualifications are proposed for management. Secondly, based on the results from first step, issues related monitoring such as monitoring method, measurement type, or installation location are determined. This method leads building managers to reasonably define the structural safety over the whole life cycle. Furthermore, this experience contributes to development of SHM forward and it is expected to be useful for other types of structures as well such as spatial structures or irregular buildings.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.375-375
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• 2009

For many large-scale applications of high-temperature superconducting materials, large critical current density($J_c$) in high applied magnetic fields are required. A number of methods have been reported to introduce artificial pinning centers(APCs) in $YBa_2Cu_3O_{7-\delta}$(YBCO) films for enhancement of their $J_c$. We report measurements of critical current in $YBa_2Cu_3O_{7-\delta}$ films deposited by PLD on $SrTiO_3$ substrates decorated with Au nanoparticles. Au nanoparticles were synthesized on STO substrates with self assembled monolayer. Microstructural analysis of the obtained YBCO films was performed by using cross-section transmission electron microscopy(TEM). Phase and textural analysis was done using X-ray diffraction. The surface morphology and surface roughness(Ra) of the layers was measured by atomic force microscopy(AFM).

• Korea-Australia Rheology Journal
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• 제12권2호
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• pp.107-117
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• 2000

Prediction of the product shape in sheet casting process is performed from the numerical simulation. A three-dimensional finite element method is used to investigate the flow behavior and to examine the effects of processing conditions on the sheet produced. Effects of inertia, gravity, surface tension and non-Newtonian viscosity on the thickness profile of the sheet are considered since the edge bead and the flow patterns in the chill roll region have great influence on the quality of the products. In the numerical simulation with free surface flows, the spine method is adopted to update the free surface, and the force-free boundary condition is imposed along the take-up plane to avoid severe singularity problems existing at the take-up plane. From the numerical results of steady isothermal flows of a generalized Newtonian fluid, it is shown that the draw ratio plays a major role in predicting the shape of the final sheet produced and the surface tension has considerable effect on the bead thickness ratio and the bead width fraction, while shear-thinning and/or tension-thickening viscosity affect the degree of neck-in.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1774-1779
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• 2005

Most of materials receive force in using, therefore, the characteristics of materials must be considered in system design not to occur deformation or destruction. Mechanical properties about materials can be expressed as responsible level of material itself under the exterior operation. Main mechanical properties is strength, hardness, ductility and stiffness etc. Currently, among major measure facilities to measure such mechanical properties, advanced indentation technique has focused in industrial areas as reason of nondestructive and easy applications for mechanical tensile properties and evaluation of residual stress of materials. This study is to find the optimum experimental condition about residual stress advanced indentation technique for accurate analysis of the welded joint of steel materials through indentation load-depth curve obtained from cruciform specimen experiment. Optimum selection was applied to the welded joint of real steel materials to give non-equi-biaxial stress state and compared with general residual stress analyzing method for verification.

• 한국자동차공학회논문집
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• 제20권4호
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• pp.10-15
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• 2012

The design of automobile occupant seat belt system has been studied by using MADYMO. Based on the FMVSS 208 (Federal Motor Vehicle Safety Standards 208) and the USNCAP (United States New Car Assessment Program) regulations, seat belt design parameters were chosen for the design improvement to the 5th percentile female dummy: limit force of load limiter, time to fire of shoulder belt, inlet length of shoulder belt, inlet length of lap belt. The design of experiment method was employed to optimize the design parameters of passenger seat belt. Range of injury probability due to the change of H-point position was estimated by the simulation.

• 한국식생활문화학회지
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• 제15권4호
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• pp.307-312
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• 2000

The purpose of this study is to understand the Chinese noodles(mian tiao). Wheat seems to have been cultivated 3-4,000 years before according to the archaeological evidences from the neolithic sites. The five grains(rice, millet, beans, barley, barnyard millet) already appeared in the period prior to Chin dynasty and were used as whole grain, but it was not until Chun Chu Zhan Guo period that the introduction of the flouring method stimulated the cultivation of wheat. In Chin-Han period, when water power and animal force were put into usage to facilitate the mass production of wheat flour, 'Bing', a designation for all the food made of wheat first appeared in the literature, and it was this 'Bing' that had later developed into noodles. In Wei Chin Nan Bei Chao period, roasted 'Bing', namely 'Kao-Bing' made its first appearance, and in Tang period, various noodles were created with the increase of restaurants specialized in noodles. In Song dynasty, 'La-Mian', the noodles stretched and beat from noodle dough, was first introduced, and in Yuan period, invention of drying method made the appearance of dried noodles, 'Gua-Mian', possible, which was good for easy and long preservation. Qing dynasty developed the noodles with a variety of assorted ingredients. The Chinese noodles are classified by various standards such as main ingredients, cooking methods, kinds of sauce, secondary ingredients, shape, eating method, flavor, and look.

• Steel and Composite Structures
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• 제15권6호
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• pp.679-703
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• 2013

This paper presents experimental investigations of the fundamental behavior of concrete filled steel tube (CFT) beam-columns under fire loading. A total of thirteen specimens were tested to determine the axial force-moment-curvature-temperature behavior of CFT beam-columns. The experimental approach involved the use of: (a) innovative heating and control equipment to apply thermal loading and (b) digital image correlation with close-range photogrammetry to measure the deformations (e.g., curvature) of the heated region. Each specimen was sequentially subjected to: (i) constant axial loading; (ii) thermal loading in the expected plastic hinge region following the ASTM E119 temperature-time T-t curve; and (iii) monotonically increasing flexural loading. The effects of various parameters on the strength and stiffness of CFT beam-columns were evaluated. The parameters considered were the steel tube width, width-tothickness ratio, concrete strength, maximum surface temperature of the steel tube, and the axial load level on the composite CFT section. The experimental results provide knowledge of the fundamental behavior of composite CFT beam-columns, and can be used to calibrate analytical models or macro finite element models developed for predicting behavior of CFT members and frames under fire loading.