• 대한토목학회논문집
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• 제3권2호
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• pp.109-117
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• 1983

구속응력(拘束應力), 전단변형율진폭(剪斷變形率振幅), 다짐함수비(含水比), 다짐에너지, 간극비(間隙比) 및 포화도(飽和度)가 다짐점성토(粘性土)의 동적전단탄성계수(動的剪斷彈性係數)에 끼치는 영향(影響)을 연구(硏究)하기 위하여 도주공진시험(圖柱工振試驗)을 하였다. 이들 각각(各各)의 요소(要素)들은 다짐 흙의 동적전단탄성계수(動的剪斷彈性係數)에 큰 영향(影響)을 나타내며 그 원인(原因)은 다짐에 의한 흙의 여러 가지 변화(變化)로서 설명(說明)할 수 있다. 흙의 동적전단탄성계수(動的剪斷彈性係數)는 다짐에 의해서 크게 증가(增加)되며 최적함수비(最適含水比) 건조측(乾燥側)의 함수비(含水比)에서 다지는 것이 훨씬 더 효과적(効果的)이다. 그리고 동적(動的) 전단탄성계수(剪斷彈性係數)와 정적(靜的) 전단탄성도(剪斷彈性度)는 좋은 상관관계(相關關係)를 나타내며 이를 이용(利用)하여 어떤 일정(一定)한 구속응력(拘束應力)에 대한 동적전단탄성계수(動的剪斷彈性係數)를 일축압축강도(一軸壓縮强度)로부터 쉽게 구할 수가 있다.

• Geomechanics and Engineering
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• 제37권3호
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• pp.253-262
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• 2024

Dynamic properties are pivotal in soil analysis, yet their experimental determination is hampered by complex methodologies and the need for costly equipment. This study aims to predict dynamic soil properties using static properties that are relatively easier to obtain, employing machine learning techniques. The static properties considered include soil cohesion, friction angle, water content, specific gravity, and compressional strength. In contrast, the dynamic properties of interest are the velocities of compressional and shear waves. Data for this study are sourced from 26 boreholes, as detailed in a geotechnical investigation report database, comprising a total of 130 data points. An importance analysis, grounded in the random forest algorithm, is conducted to evaluate the significance of each dynamic property. This analysis informs the prediction of dynamic properties, prioritizing those static properties identified as most influential. The efficacy of these predictions is quantified using the coefficient of determination, which indicated exceptionally high reliability, with values reaching 0.99 in both training and testing phases when all input properties are considered. The conventional method is used for predicting dynamic properties through Standard Penetration Test (SPT) and compared the outcomes with this technique. The error ratio has decreased by approximately 0.95, thereby validating its reliability. This research marks a significant advancement in the indirect estimation of the relationship between static and dynamic soil properties through the application of machine learning techniques.

• Geomechanics and Engineering
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• 제38권4호
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• pp.421-437
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• 2024

The soil nailing method entails the utilisation of nails to reinforce and stabilise a zone of soil mass. This is widely used for various applications due to its effective performance under various loading conditions. The seismic response of 6m high vertical soil-nailed cut in various site classes under dynamic excitations has been investigated in this study considering various lengths and inclinations of nails. The influence of frequency content of dynamic excitation on the response of structure has been assessed through finite element analysis using time history data of three different earthquakes. The seismic stability of the nailed cut in retaining soil in various sites under El Centro, Kobe and Trinidad earthquake ground motion is evaluated based on maximum acceleration response, maximum horizontal deformation, earth pressure distribution on the wall and maximum axial force mobilised in nails. The optimum nail inclination is identified as 15° and a minimum nail length ratio of 0.7 is essential for a stable vertical cut under dynamic excitations.

• 한국지반신소재학회논문집
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• 제13권3호
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• pp.21-30
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• 2014

본 연구에서는 남원 사면현장에서 채취된 화강풍화토를 이용하여 경량 동적콘관입시험기의 국내 사면현장에서 적용성을 조사하였다. 그리고 다짐도와 함수비 변화에 따른 경량 동적콘관입시험을 수행하고, 다짐도, 간극비, 포화도와 콘관입 저항치와의 상관성을 분석하였다. 그 결과로 최적함수비의 건조측에서 함수비 증가와 더불어 관입저항치가 급격히 증가하고 습윤측에서 크게 감소하는 경향을 나타내었다. 또한 물리적 특성과의 상관관계에서 다짐도 및 포화도가 클수록 콘 저항치가 선형적으로 증가하는 것을 확인하였다. 이로 인해 역학특성 변화에 따른 함수비, 간극비, 포화도와 콘관입저항치 사이에 높은 상관성을 보여 사면조사시 경량 동적콘관입시험기의 현장적용이 가능할 것으로 판단된다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.283-292
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• 1996

This study was performed to determine the physical properties of rice hull and straw which could be used for an optimum design and operation of the handling facilities for these rice crop by-products. The properties measured were kinetic friction coefficient , bulk density, and dynamic and static angle of repose. Rice hulls with moisture content of 13% and 21% were used throughout the test while rice straws of 10% and 16% moisture were chopped into 10mm length and used for the test. Friction coefficient was calculated from the horizontal traction forces measurement when a container holding the mass of rice hull and straw was pulled over mild steel. PVC, stainless steel, and galvanized steel surface by a universal testing machine. Bulk density was measured by an apparatus consisting of filling fundel and a receiving vessel. Dynamic angle of repose which is the angle at which the material will stand when piled was calculated from the photos of bulk samples after they were flowed by gravity and accumulated on a circular surface. Static angle of repose which is the angle between the horizontal and the sloping side of the material left in the container when discharging was also measured in the similar way. Results and conclusions from this study are summarized as follows . 1. Kinetic friction coefficient of both rice hull and straw were in the range of 0.26 -0.52 and increased with the moisture content. The magnitude of friction increased in the order of galvanized steel, stainless steel, PVC ,and mild steel. 2. Bulk densities of rice hull decreased while those of rice straw increased with moisture content increase . Average bulk densities of rice hull and straw were 96.8 and 74.7kg/㎥, respectively. 3. Average dynamic angle of repose for rice straw was 32.6$^{\circ}$ and those for 13% and 21% moisture rice hull were 38.9$^{\circ}$ and 44.9$^{\circ}$ , respectively. 4. Static angles of repose for both rice hull and straw showed increase with the moisture content. The values were 75.2\ulcorner and 80.2$^{\circ}$ for 13% and 21% moisture rice hull, respectively. Rice straws having 10% and 16% moisture content showed 87.3% and 89.2$^{\circ}$ static angle of repose, respectively.

• Elastomers and Composites
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• 제46권3호
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• pp.186-194
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• 2011

셀룰로오스계 천연섬유인 kenaf를 천연고무와 함께 균일하게 배합한 후 압축성형 방법을 사용하여 천연섬유/천연고무 복합재료를 제조하였으며, 이들의 가황거동, 경도, 인장특성, 인열강도 및 정적, 동적 특성에 미치는 kenaf 섬유함량의 영향을 조사하였다. 복합재료를 구성하는 천연섬유의 함량은 천연고무 및 배합제 대비 0, 5, 10, 15, 20 phr이었다. 실험결과 천연고무의 여러 가지 특성이 kenaf 섬유의 함량에 의존한다는 것을 나타내었다. Kenaf 섬유함량이 증가함에 따라 천연고무의 가황에 요구되는 토크는 높아진 반면 가황시간은 감소되었다. Kenaf/천연고무 복합재료의 경도, 인장탄성률과 인열강도는 섬유함량이 증가할수록 점차적으로 증가한 반면, 인장강도와 파단신장률 은 감소하는 경향을 보여주었다. 또한 kenaf 섬유함량이 증가함에 따라 천연고무의 정적 특성보다는 동적 특성의 변화가 더욱 크게 나타났다. 고무에 가해지는 에너지의 감쇄 또는 흡수와 밀접한 관계가 있는 손실인자도 섬유함량에 비례하여 증가하였다.

• Journal of Biosystems Engineering
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• 제41권4호
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• pp.342-356
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• 2016

Purpose: The drying of a thin layer of native cassava starch in a tray dryer was modeled to establish an equation for predicting the drying behavior under given conditions. Methods: Drying tests were performed using samples of native cassava starch over a temperature range of $40-60^{\circ}C$. We investigated the variation in the drying time, dynamic equilibrium moisture content, drying rate period, critical moisture content, and effective diffusivity of the starch with temperature. The starch diffusion coefficient and drying activation energy were determined. A modification of the model developed by Hii et al. was devised and tested alongside fourteen other models. Results: For starch with an initial moisture content of 82% (db), the drying time and dynamic equilibrium moisture content decreased as the temperature increased. The constant drying rate phase preceded the falling rate phase between $40-55^{\circ}C$. Drying at $60^{\circ}C$ occurred only in the falling rate phase. The critical moisture content was observed in the $40-55^{\circ}C$ range and increased with the temperature. The effective diffusivity of the starch increased as the drying temperature increased from 40 to $60^{\circ}C$. The modified Hii et al. model produced randomized residual plots, the highest $R^2$, and the lowest standard error of estimates. Conclusions: Drying time decreased linearly with an increase in the temperature, while the decrease in the moisture content was linear between $40-55^{\circ}C$. The constant drying rate phase occurred without any period of induction over a temperature range of $40-55^{\circ}C$ prior to the falling rate period, while drying at $60^{\circ}C$ took place only in the falling rate phase. The effective diffusivity had an Arrhenius relationship with the temperature. The modified Hii et al. model proved to be optimum for predicting the drying behavior of the starch in the tray dryer.

• ETRI Journal
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• 제36권2호
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• pp.197-205
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• 2014

This paper proposes a novel framework for virtual content delivery networks (CDNs) based on cloud computing. The proposed framework aims to provide multimedia content delivery services customized for content providers by sharing virtual machines (VMs) in the Infrastructure-as-a-Service cloud, while fulfilling the service level agreement. Furthermore, it supports elastic virtual CDN services, which enables the capabilities of VMs to be scaled to encompass the dynamically changing resource demand of the aggregated virtual CDN services. For this, we provide the system architecture and relevant operations for the virtual CDNs and evaluate the performance based on a simulation.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2007년도 한국컴퓨터종합학술대회논문집 Vol.34 No.1 (D)
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• pp.411-414
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• 2007

본 논문에서는 Content의 배급 및 구독을 위해 등장한 시맨틱 웹의 대표적인 기술인 RSS 를 통하여 모바일 환경에서의 사용자가 원하는 Content를 전달 받을 수 있는 시스템을 제안하고 있다. 이 시스템은 DCD Server를 사용하여 각 Content에 대한 정보를 담고 있게 되며, UDDI를 이용하여 사용자가 원하는 Content를 키워드 검색으로 통해 지정할 수 있게 된다. 또한 사용자가 선택한 각각의 Content는 RSS를 통하여 사용자의 모바일 Client로 전달되게 된다.

• 한국전자통신학회논문지
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• 제10권3호
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• pp.327-332
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• 2015

교육용 로봇은 과학의 기초 원리를 배우고 과학적 창의성을 키우는 것에 효과적인 교육 도구로 소개되면서 방과 후 학습에 적용되어 과학 교육을 위한 교육용 키트의 구성이 바뀌고 있다. 중소기업을 중심으로 과학적 창의성을 키우는 도구로서 다양한 교육용 로봇 기술과 학생들을 위한 다양한 범주의 게임로봇기술이 개발되고 있고, 기존의 mp3 음악이나 e-Learning 콘텐츠의 제공과 같이 로봇용 전문콘텐츠를 다운받아 학습에 활용하는 기술을 개발 중에 있으나 아직 전문 커뮤니티 형성이 미흡한 편이다. 현재는 사용자가 손쉽게 제어가 가능한 인터페이스 모듈용 모터가 개발이 되어있지 않아 1포인트 드래그 연동 스마트터치 제어용 다이나믹 모터 개발이 필요하다.