• 한국지형학회지
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• 제23권1호
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• pp.117-128
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• 2016

High resolution aerial photographs and digital elevation models for Bangpo beach using UAV were generated in this study to analyze the thematic and geometric characteristics of coastal features. Based on 728 aerial images acquired on September 10, 2016 by the UAV, a image mosaic at 2.2 cm spatial resolution and a digital elevation model at 4.4 cm spatial resolution were developed. This study found out that Bangpo beach consisted of intertidal zone and supratidal zone. The intertidal zone can be subdivided into lower part and upper part with distinctive geomorphological characteristics. While the lower part included sand bars and ripple marks along the coastline, the cusps and sand dunes were the major coastal features of the upper part. Part of the intertidal zone was occupied by shore platform with average slope of 0.9 degree containing various sizes of gravels. The supratidal zone slanted toward ocean with berms on the surface with an interval of 15 m. These coastal features indicated the flow intensity towards to the land and tidal effect. It validated that the UAV application in coastal research was very effective analyzing to examine coastal processes.

• 대한금속재료학회지
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• 제46권10호
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• pp.672-682
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• 2008

The resistance spot welding of TRIP590 steels was investigated to enhance understanding of weld fracture during tensile-shear strength (TSS) test. The main failure modes for spot welds of TRIP590 steels were nugget pullout and interfacial fracture. The peak load to cause a weld interfacial failure was found to be related to fracture toughness of the weld and the weld diameter. Although interfacial fracture occurred in the samples, the load carrying capacity of the weld was high and not significantly affected by the fracture mode. Substantial part of the weld exhibits the characteristic dimple (or elongated dimple) fractures on interfacial fractured surface, in spite of the high hardness values associated with the martensite microstructures. The high load-bearing ability of the weld is directly associated with the area of ductile fracture occurred in weld. Therefore, the judgment of the quality of resistance spot welds in TRIP590 steels, the load carrying capacity of the weld should be considered as an important factor than fracture mode.

• 한국정보통신학회논문지
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• 제26권3호
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• pp.436-442
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• 2022

본 논문은 수중 주파수 선택적 채널에서 주파수 다이버시티의 채널 선택 판정법에 따른 선택 합성법 (selective combining)의 성능을 평가하였다. 천해 수중 음향 채널은 경계면 반사와 수온 층에 따른 음파 굴절 등의 다양한 환경요인이 결합하여 복잡한 다중경로의 특성을 가진다. 특히, 다중경로에 의한 주파수 선택성 (frequency selectivity)는 통신 채널의 에너지 변동을 발생시키고, 이로 인해 SNR (Signal to Noise Ratio)가 감소하여 통신성능이 저하된다. 본 논문에서는 다중경로의 주파수 선택성에 따른 통신성능 확보를 위해 다수의 채널을 이용하는 주파수 다이버시티 기법을 적용하였다. 각 채널은 4-FSK (Frequency Shift Keying)과 선택 합성법을 적용하였으며, 선택 합성법의 복조 채널 선택 판정을 위해 신호의 최댓값, 평균값 그리고 심벌 비교 판정 (majority decision)을 적용하여 성능을 평가하였다.

• 복식문화연구
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• 제30권2호
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• pp.262-280
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• 2022

The purpose of this study is to analyze the organic forms, expressions, and characteristics of Alexander McQueen's fashion design and to present various materials for understanding and utilizing this organic design style. The criteria for organic design expressions and characteristics were classified through a literature review, and the organic design characteristics of Alexander McQueen's fashion were then analyzed. The results are as follows: First, the morphological characteristics of nature's forms are used as objects in Alexander McQueen's fashions to represent organic characteristics. Second, abstraction through the application of organic forms means creating an abstract representation of the object being represented. Abstracting organic forms occurs by partially modifying the structural features of the human body to show characteristics or by visualizing these characteristics within the surface of the natural object. Third, continuity through the expression of the formation process of organisms is characteristic of the expression of the gradual growth of organisms; this reinterpretation is based on the concept that the internal elements of natural objects affect their external forms. Fourth, the structure of using natural materials, as well as regional and cultural characteristics, is shown in the designs through use of the physical characteristics of expressions and materials that use natural elements. Fifth, symbolism through subjective thinking implies that the element of nature that an object expresses is the element that appears in nature; this includes created organisms along with environmental factors. These characteristics are best demonstrated in fashion designs that express themselves through creativity.

• 한국지하수토양환경학회지:지하수토양환경
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• 제27권6호
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• pp.22-36
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• 2022

Water resources in Jeju Island are dependent virtually entirely on groundwater. For groundwater resources, drought damage can cause environmental and economic losses because it progresses slowly and occurs for a long time in a large area. Therefore, this study quantitatively evaluated groundwater level fluctuations using principal component and cluster analyses for 42 monitoring wells in Jeju Island, and further identified the types of groundwater fluctuations caused by drought. As a result of principal component analysis for the monthly average groundwater level during 2005-2019 and the daily average groundwater level during the dry season, it was found that the first three principal components account for most of the variance 74.5-93.5% of the total data. In the cluster analysis using these three principal components, most of wells belong to Cluster 1, and seasonal characteristics have a significant impact on groundwater fluctuations. However, wells belonging to Cluster 2 with high factor loadings of components 2 and 3 affected by groundwater pumping, tide levels, and nearby surface water are mainly distributed on the west coast. Based on these results, it is expected that groundwater in the western area will be more vulnerable to saltwater intrusion and groundwater depletion caused by drought.

• 한국컴퓨터정보학회논문지
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• 제27권8호
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• pp.211-218
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• 2022

광반사 변조 분광법에서 측정된 결과를 해석하기 위하여 전산모사 프로그램을 개발하였다. 개발된 프로그램은 광반사 변조 분광 특성해석에 필요한 인자들을 사용자가 손쉽게 바꿀 수 있으며, 그 값에 따른 결과를 실제 측정 결과와 동시에 확인할 수 있도록 구현하였다. 광반사 변조 분광법에서 얻어지는 결과는 밴드갭 주변에서 변조되어 나타나는 TDFF(Third Derivative Function Form)와 밴드갭보다 높은 에너지에서 나타나는 표면 및 계면에서의 전기장에 기인한 FKO(Franz-Keldysh Oscillation)신호가 혼합하여 나타난다. 전산모사 프로그램을 통하여, 실제로 단일층으로 형성된 GaSb Epi 층에서 나타나는 광변조 특성에 대하여 해석하였으며, 광변조 분석에 특화되어 매우 유용한 결과를 얻을 수 있었다. 또한, FFT (Fast Fourier Transform) 해석 Tool을 추가하여 FKO의 주파수 특성분석을 보다 용이하게 하였다.

• 자원리싸이클링
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• 제31권6호
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• pp.73-80
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• 2022

본 연구에서는 국내 부존 몰리브덴광을 대상으로 광물학적 특성 및 부유선별 기초특성을 파악하였다. 몰리브덴의 근원광물은 휘수연석으로 확인되었으며 원광 내 주요 맥석광물은 규산염광물이었다. 구리, 납 및 아연 등은 극미량으로 나타났다. 부유선별 기초특성 결과, 휘수연석의 제타전위는 pH 전영역에서 음전하를 나타내었다. 휘수연석의 접촉각은 pH의 증가에 따라 증가하였고 최대값은 pH 9에서 74°을 나타내었다. 단위부선의 최적조건에서 정광의 품위와 회수율은 각각 MoS2 82.4%와 92.04%를 나타내었다. 정광내 불순물 조사결과, 정광의 품위를 저하시킬 수 있는 휘수연석과 유사한 특성을 보이는 황화광물, 그리고 휘수연석과 결합된 규산염광물이 관찰되었다. 따라서, 정광의 품위향상을 위해 재분쇄/단체분리 향상을 통한 규산염광물의 제어와 미립자광물 선별 효율을 높일 수 있는 컬럼부선등이 요구된다.

• Geomechanics and Engineering
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• 제28권2호
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• pp.181-195
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• 2022

Roughness and joint inclination angle are the important factors that affect the strength and deformation characteristics of jointed rock mass. In this paper, 3D printer has been employed to make molds firstly, and casting the jointed specimens with different joint roughness coefficient (JRC), and different joint inclination angle (α). Conventional triaxial compression tests were carried out on the jointed specimens, and the influence of JRC on the strength and deformation parameters was analyzed. At the same time, acoustic emission (AE) testing system has been adopted to reveal the AE characteristic of the jointed specimens in the process of triaxial compression. Finally, the morphological of the joint surface was observed by digital three-dimensional video microscopy system, and the relationship between the peak strength and JRC under different confining pressures has been discussed. The results indicate that the existence of joint results in a significant reduction in the strength of the joint specimen, JRC also has great influence on the morphology, quantity and spatial distribution characteristics of cracks. With the increase of JRC, the triaxial compressive strength increase, and the specimen will change from brittle failure to ductile failure.

• 한국산업융합학회 논문집
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• 제25권2_2호
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• pp.289-297
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• 2022

Deterioration in durability of structures due to the steel corrosion is difficult to determine whether or not corrosion is initiated and how much propagated, and moreover, repair and maintenance are not easy to deal with. Therefore, preventive treatments can be the best option to avoid the deterioration. Various methods for preventing corrosion of steel, such as electrochemical treatments, anti-corrosion agents and steel surface coatings, are being developed, but economic and environmental aspects make it difficult to apply them to in-situ field. Thus, the purpose of this study was to improve corrosion resistance by using CA-based clinker that are relatively simple and expected to be economically profitable Existing CA-based clinkers had problems such as flash setting and low strength development during the initial hydration process, but in order to solve this problem, CA clinker with low initial reactivity were used as binder in this study. The cement paste used in the experiments was replaced with CA₂ clinker for 0%, 10%, 20%, and 30% in OPC. And the mixture used in the chloride binding test for the extraction of water-soluble chloride was intermixed with Cl- 0.5%, 1%, 2%, and 3% by weight of binder content. To evaluate characteristic of hydration heat evolution, calorimetry analysis was performed and simultaneously chloride binding capacity and acid neutralization capacity were carried out. The identification of hydration products with curing ages was verified by X-ray diffraction analysis. The free chloride extraction test showed that the chlorine ion holding ability improved in order OC 10 > OC 30 > OC 20 > OC 0 and the pH drop resistance test showed that the resistance capability in pH 12 was OC 0 > OA 10 > OA 20 > OA 30. The XRD analyses showed that AFm phase, which can affect the ability to hold chlorine ions, tended to increase when CA₂ was mixed, and that in pH12 the content of calcium hydroxide (Ca(OH)₂), which indicates pH-low resistance, decreased as CA₂ was mixed

• Composites Research
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• 제36권3호
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• pp.141-153
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• 2023

본 리뷰 논문에서는 일반 접촉 역학 이론과 더불어 유기탄성체 마찰에 관한 이론 및 배경을 소개한다. 특히 Greenwood & Williamson 접촉 역학 이론을 확장하여 거친 표면을 자기-아핀(self-affine) 특성으로 고려한 접촉 역학 및 마찰의 수학적 모델을 제시한 Klüppel & Heinrich 이론을 중심으로 유기탄성체 복합재료의 마찰 거동에 대해 살펴본다. 자기-아핀 특성에 의한 노면의 멀티스케일 거칠기로 인해 미끄러짐 마찰 시 유기탄성체 복합재료는 다양한 주파수에 따른 동적 변형이 가해지며 이때 재료가 나타내는 점탄성이 마찰 거동에 주요한 영향을 미친다. 따라서 유기탄성체 복합재료의 비선형 점탄성을 고려하여 광범위한 주파수 영역에서의 점탄성 거동인 마스터커브를 구축하는 원리 및 방법을 제시하였다. 마지막으로 유기탄성체 복합재료 마찰 이론을 타이어 트레드 컴파운드와 노면 간의 마찰에 응용한 실험적 결과와 그 물리적 의미를 이론과 접목하여 설명하였다.