• 대한화학회지
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• 제58권6호
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• pp.524-527
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• 2014

We report a simple yet efficient method to assemble large-scale aligned graphene nanoribbons (GNRs) with a width as small as 30 nm. The $V_2O_5$ nanowires (NWs) were aligned on a graphene surface via spraying a solution of the $V_2O_5$ NWs, and the graphene was selectively etched by the reactive ion etching method using the $V_2O_5$ NWs as a shadow mask. This process allowed us to prepare large scale patterns of the aligned GNRs on a $SiO_2$ substrate. The orientation of the aligned and randomly oriented GNRs was compared by the atomic force microscope (AFM) images. We achieved the highly aligned GNRs along the flow direction of the $V_2O_5$ NWs solution. Furthermore, we successfully fabricated a field effect-transistor with the aligned GNRs and measured its electrical properties. Since our method enable to prepare the aligned GNRs over a large area, it should open up new way for the various applications.

• 천문학회지
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• 제29권spc1호
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• pp.155-158
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• 1996

Magnetic fields correlated on several kiloparsec scales are seen in spiral galaxies. Their origin could be due to the winding up of a primordial cosmological field or due to amplification of a small seed field by a turbulent galactic dynamo. Both options have difficulties: There is no known battery mechanism for producing the required primordial field. Equally the turbulent dynamo may self destruct before being able to produce the large scale field, due to excess generation of small scale power. The current status of these difficulties is discussed. The resolution could depend on the nature of the saturated field produced by the small scale dynamo. We argue that the small scale fields do not fill most of the volume of the fluid and instead concentrate into intermittent ropes, with their peak value of order equipartition fields, and radii much smaller than their lengths. In this case these fields neither drain significant energy from the turbulence nor convert eddy motion of the turbulence on the outer scale to wave like motion. This preserves the diffusive effects needed for the large scale dynamo operation.

• 제어로봇시스템학회논문지
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• 제15권4호
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• pp.413-419
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• 2009

A decentralized adaptive control method is proposed for large-scale systems with unknown time-delayed nonlinear interconnections unmatched in control inputs. It is assumed that the time-delayed interaction terms are bounded by unknown nonlinear bounding functions. The nonlinear bounding functions and uncertain nonlinear functions of large-scale systems are compensated by the function approximation technique using neural networks. The dynamic surface control method is extended to design the proposed memoryless local controller for each subsystem of uncertain nonlinear large-scale time delay systems. Therefore, although the interconnected systems consist of a large number of subsystems, the proposed controller can be designed simply. We prove that all the signals in the total closed-loop system are semiglobally uniformly bounded and the control errors converge to an adjustable neighborhood of the origin. Finally, an example is given to demonstrate the effectiveness and applicability of the proposed scheme.

• Wind and Structures
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• 제9권6호
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• pp.419-440
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• 2006

This article synthesizes the literature on the meteorology, experimental simulation, and wind engineering ramifications of intense downburst outflows. A novel design of a large-scale test facility and experimental evidence of its validity are presented. A two-dimensional slot jet is used to simulate only the outflow region of a downburst. Profiles of mean velocity and turbulence quantities are acquired using hot-wire anemometry. Comparison with the literature provides empirical evidence that supports the current approach. A geometric analysis considers the validity of applying a two-dimensional approximation for downburst wind loading of structures. This analysis is applicable to power transmission lines in particular. The slot jet concept can be implemented in a large boundary layer wind tunnel to enable large-scale laboratory experiments of thunderstorm wind loads on structures.

• 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.

• 응용통계연구
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• 제23권1호
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• pp.197-206
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• 2010

본 논문에서는 대용량 자료 혹은 시간에 따라 순차적으로 들어오는 자료의 분류를 위한 부스팅(boosting) 알고리즘을 제안한다. 대용량 자료나 순차적 자료의 경우 분석시 모든 훈련 자료(training data)들을 한번에 이용하기 어려우므로 보통의 부스팅 알고리즘은 적절하지 못하다. 이러한 상황을 극복하기 위해 AdaBoost와 Arc-x4와 같은 부스팅 알고리즘을 수정하여 제안한다. 모의 실험과 실제 자료 분석을 통해 대용량 자료나 순차적 자료에 제안된 알고리즘이 잘 적용됨을 보였다.

• 터널과지하공간
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• 제19권1호
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• pp.52-63
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• 2009

대규모 암반 절리면의 거칠기를 구하는 여러 가지 방법이 있으나, 길이 10 cm의 절리를 Barton 등이 제안한 표준절리면곡선과 비교하여 절리면 거칠기계수 JRC (joint roughness coefficient)를 결정하고 대규모 절리의 길이에 따라 보정하는 것이 가장 일반적인데, 적합한 표준 절리면곡선을 선택할 때 측정자에 따라 달라자는 경우가 많다. 따라서 대규모 암반 절리면의 거칠기 JRC는 길이에 따른 보정 없이 직접 측정하는 것이 정확할 것이나 측정방법에 한계가 있다. 본 연구에서는 대규모 암반절리를 LIDAR (light detection and ranging)로 스캔하고 절리의 길이 L과 절리면 상의 돌출부(asperity) 높이의 진폭 a를 이용하여 대규모 암반 절리의 거칠기계수 JRC를 구하였다. 그 결과 대규모의 암반 절리면에서도 절리의 길이 증가에 따라 거칠기 계수 JRC가 감소하는 비 정상상태(non-stationary)의 치수효과와 거칠기 측정방향에 따라 절리면 거칠기계수 JRC가 다른 것을 확인하였다.

• Journal of the Korean Data and Information Science Society
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• 제25권6호
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• pp.1283-1291
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• 2014

본 논문에서는 대용량이거나 시간에 따라 순차적으로 들어오는 데이터의 분류를 위한 전진적 단계 알고리즘을 제안한다. Adaboost 알고리즘은 노이즈가 있는 데이터에 대하여 성능이 떨어지는 것으로 알려져 있다. 이를 해결하기 위한 한 가지 방법으로 전진적 단계 선형 회귀 방법을 사용한다. 대용량 데이터나 순차적 배치 데이터의 경우에도 이러한 상황을 극복하기 위해 전진적 단계 알고리즘 방법을 적용한 방법을 제안한다. 모의실험과 실제 자료 분석을 통해 제안된 알고리즘이 좋은 성능을 보임을 알 수 있었다.

• 한국산업융합학회 논문집
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• 제9권3호
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• pp.191-197
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• 2006

Prepare need in each branch for a large scale event. especially prepare for transportation problem is very important. most research for until at now parking prepare according city management however, parking prepare for large event is a necessity which it will parking characteristic. accordingly this research is conducted study for parking prepare subject of large event. this study result, vehicle demand for parking by stadium have many but vehicle demand for parking off stadium have few. accordingly large parking supply is ineffective. shuttle bus service in principal position of city is effective. study result showed that it included 85% parking at 6~7hour before large event start time. accordingly disposition time of parking manager is desirable 6~7hour before large event start time.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.360-363
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• 2006

The red tide related with Cochlodinium Polykrikoides bloom has been frequently occurred around the South Sea of Korea and caused the economic loss in the coastal breeding grounds. The outbreak scale was usually change by physical, biological and environmental condition at each years. Relatively large-scale red tide occurred in 1995, 1997, 1999, 2001, 2002 and 2003 through spatial scale, duration and maximum density. Compared the scale of red tide with physical condition around the South Sea, the lower coastal temperature on August around the South Sea corresponded with the large scale red tide. By serial oceanographic investigations on August in the South Sea and estimated wide area temperature information by satellite, SSTA around the South Sea and wide area was negative when the outbreak of red tide was large scale. From the results of temperature difference between surface and 30m layers, the occurrence of enormous red tide has a tendency when the temperature gradient around the seasonal thermocline was weakened. Larger Kuroshio volume transport in the upstream was also corresponded with the large scale red tide.