• 산업기술연구
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• 제22권A호
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• pp.49-57
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• 2002

The accurate wind speed information at the hub height of a wind turbine is very essential to the exact estimation of the wind turbine power performance testing. Several methods on the site calibration, which is a technique to estimate the wind speed at the wind turbine's hub height based on the measured wind data using a reference meteorological mast, are introduced. A site calibration result and the wind resource assessment for the Taekwanryung test site are presented using a one-month wind data from a reference meteorological mast and a temporal mast installed at the site of wind turbine. From this analysis, it turns out that the current location of the reference meteorological mast is wrongly determined, and the self-developed codes for the site calibration are working properly. Besides, an analysis on the uncertainty allocation for the wind speed correction using site calibration is performed.

• 대한안전경영과학회지
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• 제11권2호
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• pp.159-165
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• 2009

Through the understanding of the change of productivity and the ability of error recovery according to aging and the assessment and analysis of them, we may take this research to contribute to make a design for the road-map to help set up the policy of employment for old generation. For this we have taken an experiment of the coordination tester for 100 person who are chosen randomly and analysed the collected data using SAS, which is one of widely used statistical analysis packages. The main results are as follow: $\circledcirc$ The result of regression between the working speed and the length of the correction of error shows independence. (pr>0.2029). $\circledcirc$ The regression between age and working speed is statistically significant. (pr<0.0001) $\circledcirc$ The relation between age and the length of the correction of error is not significant. (pr>0.9123).

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2250-2257
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• 2004

The accurate wind speed information at the hub height of a wind turbine is very essential to the exact estimation of the wind turbine power performance testing. Several methods on the site calibration, which is a technique to estimate the wind speed at the wind turbine's hub height based on the measured wind data using a reference meteorological mast, are introduced. A site calibration result and the wind resource assessment for the TaeKwanRyung test site are presented using three-month wind data from a reference meteorological mast and the other mast temporarily installed at the site of wind turbine. Besides, an analysis on the uncertainty allocation for the wind speed correction using site calibration is performed.

• 한국태양에너지학회 논문집
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• 제30권4호
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• pp.9-14
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• 2010

The main cause of global warming is carbon dioxide generated from the use of fossil fuels, and active research on the reduction of carbon is in progress to slow down the increasing global warming. Wind turbines generate electricity from kinetic energy of wind and are considered as representative for an energy source that helps to reduce carbon emission. Since the kinetic energy of wind is proportional to the cube of the wind speed, the intensity of wind affects wind farm construction validity the most. Therefore, to organize a wind farm, validity analysis should be conducted first through measurement of the wind resources. To facilitate the approval and permission and reduce installation cost, measuring sensors should be installed at locations below the actual wind turbine hub. Wind conditions change in shape with air density, and air density is most affected by the variable sterrain and surface type. So the magnitude of wind speed depends on the ground altitude. If wind conditions are measured at a location below the wind turbine hub, the wind speed has to be extrapolated to the hub height. This correction of wind speed according to height is done with the Deacon equation used in the statistical analysis of previously observed data. In this study, the optimal Deacon equation parameter was obtained through the analysis of the correction of the wind speed error with the Deacon equation based on the characteristics of terrain.

• Wind and Structures
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• 제26권3호
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• pp.129-146
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• 2018

Extreme wind speed analysis has been carried out conventionally by assuming the extreme series data is stationary. However, time-varying trends of the extreme wind speed series could be detected at many surface meteorological stations in China. Two main reasons, exposure change and climate change, were provided to explain the temporal trends of daily maximum wind speed and annual maximum wind speed series data, recorded at Hangzhou (China) meteorological station. After making a correction on wind speed series for time varying exposure, it is necessary to perform non-stationary statistical modeling on the corrected extreme wind speed data series in addition to the classical extreme value analysis. The generalized extreme value (GEV) distribution with time-dependent location and scale parameters was selected as a non-stationary model to describe the corrected extreme wind speed series. The obtained non-stationary extreme value models were then used to estimate the non-stationary extreme wind speed quantiles with various mean recurrence intervals (MRIs) considering changing climate, and compared to the corresponding stationary ones with various MRIs for the Hangzhou area in China. The results indicate that the non-stationary property or dependence of extreme wind speed data should be carefully evaluated and reflected in the determination of design wind speeds.

• 한국통신학회논문지
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• 제24권9A호
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• pp.1372-1382
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• 1999

B-ISDN과 같은 초고속 네트워크에서 전송오류의 주요원인은 과잉밀집 상태에 있어서의 버퍼 오버플로우이며 이로 인해 셀손실을 야기한다. 기존의 통신 프로토콜은 손실된 패킷이나 전송에러들을 다루기 위해 ARQ와 같이 오류탐지와 재전송 기법을 사용하고 있으나 이러한 ARQ 방법들은 재전송으로 인한 전송 지연시간이 매우 크기 때문에 초고속 네트워크에서는 적합하지 않다. 따라서 본 논문은 이러한 문제를 줄이기 위하여 B-ISDN에서 Forward Error Correction(FEC)를 이용하여 셀손실 회복방법의 셀손실율을 수치적으로 분석하였다. FEC 기법은 Two-state Markov 모델인 셀손실 프로세스 모델을 기초한 성능평가에서 상당한 낮은 셀손실율을 나타내었으며 ATM 네트워크에 인터리빙의 적용은 버스티한 트래픽을 랜덤(random)하게 배열하게 함으로서 셀손실율을 개선할 수 있음을 보이고 있다. 이러한 요소들은 향후 오류제어 기법 설계시 고려해야 할 주요요소로 사용될 수 있다. 또한 IP-over-ATM 네트워크에서 신뢰성 있는 IP 패킷의 전달을 위하여 FEC 기법의 효과에 관한 성능을 분석하고 평가하였다. 본 성능평가의 결과로 FEC 기법은 IP-over-ATM 환경에\ulcorner 신뢰성이 있는 IP 전달을 위한 해결책을 제시한다.

• 대한교통학회지
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• 제27권2호
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• pp.47-56
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• 2009

현장에서 수집되는 교통원시자료는 수집장비의 결함 및 주변환경 등에 의해 다양한 이상치가 발생한다. 원시자료의 품질은 추가 가공을 통해 생성되는 교통정보의 신뢰도에 직접적인 영향을 미치는 중요한 요인이다. 실시간으로 수집되는 교통원시자료를 1차 가공하는데 있어서 핵심은 이상치(Outlier)를 검지하고 보정하는 것이라고 할 수 있다. 본 연구에서는 GPS장비를 이용해 얻은 개별차량의 주행속도에서 발생하는 이상치를 제거하고 보정하는 기법을 제안하였다. GPS는 광범위한 교통네트워크상의 차량추적에 용이하게 사용될 수 있는 장점이 있다. 수집된 개별차량의 주행속도에서 이상치를 검지하고 보정하기 위해 국소가중다항회귀분석(LWR: Locally Weighted Regression)을 적용하였다. 또한 국소가중다항회귀분석을 수행하기 위한 파라미터 결정 알고리즘을 개발하여 적용하였다. 개발된 필터링 기법의 성능 평가를 위해 Synthetic Outlier를 생성 및 주입하여 개발된 필터링 기법을 통해 보정시키고 원시자료와 비교 분석 하였고, LWR을 이용한 기법의 상대적 성능 평가를 위해 지수평활화를 이용한 기법과 비교하였다. 평가 결과 LWR기법이 지수평활화를 이용한 기법보다 낮은 오차율을 보여 상대적으로 우수함을 검증하였다. 본 연구에서 제안한 방법론은 교통정보공학 분야의 자료처리 및 정보가공을 위한 도구로서 활용도가 클 것으로 기대된다.

• 한국산학기술학회논문지
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• 제22권3호
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• pp.439-445
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• 2021

영상 센서 및 소형 디스플레이의 발달로 가능해진 저가의 고속 카메라는 영상처리 및 패턴인식 분야에서 유용하게 활용될 수 있다. 본 논문에서는 약간의 시차를 두고 연속적으로 입력되는 고속의 영상으로부터 불규칙적인 조명을 보정한 다음, 조명이 보정된 영상으로부터 사람의 관심 영역인 노출된 피부 색상 영역을 획득하는 알고리즘을 소개한다. 본 연구에서는 먼저 받아들인 고속의 영상으로부터 비 균일하게 발생된 조명적인 효과를 프레임 블렌딩 기법을 사용하여 보정한다. 그런 다음, 사전에 반복적인 학습으로 생성된 타원형의 피부 색상 분포 모델을 적용하여 입력된 고속의 컬러 영상으로부터 관심 영역을 강인하게 획득한다. 실험 결과에서는 본 논문에서 제시된 접근 방법이 입력되는 컬러 영상으로부터 조명을 보정한 다음 관심 영역을 정확하게 획득한다는 것을 보여준다. 본 연구에서 제안된 알고리즘은 얼굴 인식 및 추적, 조명 보정 및 제거, 동영상 색인 및 검색 등과 같은 영상 인식과 연관된 다양한 종류의 실제적인 응용 프로그램에서 매우 유용하게 이용될 것으로 추측된다.

• Wind and Structures
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• 제30권1호
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• pp.55-67
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• 2020

Wind tunnel test is one of the most important means to study the flutter performance of bridges, but there are blockage effects in flutter test due to the size limitation of the wind tunnel. On the other hand, the size of computational domain can be defined by users in the numerical simulation. This paper presents a study on blockage effects of a simplified box girder by computation fluid dynamics (CFD) simulation, the blockage effects on the aerodynamic characteristics and flutter performance of a long-span suspension bridge are studied. The results show that the aerodynamic coefficients and the absolute value of mean pressure coefficient increase with the increase of the blockage ratio. And the aerodynamic coefficients can be corrected by the mean wind speed in the plane of leading edge of model. At each angle of attack, the critical flutter wind speed decreases as the blockage ratio increases, but the difference is that bending-torsion coupled flutter and torsional flutter occur at lower and larger angles of attack respectively. Finally, the correction formula of critical wind speed at 0° angle of attack is given, which can provide reference for wind resistance design of streamlined box girders in practical engineering.

• Geomechanics and Engineering
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• 제32권1호
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• pp.35-47
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• 2023

Deformability of road pavements in the form of ruts represent a safety risk for road users. In the procedures for dimensioning the pavement structure, the requirement that such deformations do not occur is imperatively included, which results in the appropriate selection of elements (material, geometry) of the pavement structure. Deformability and functionality, will depend of the correct design of pavement structure during exploitation period. Nevertheless, there are many examples where deformations are observed on the pavement structure, in the form of rutting at parts of the road with relatively short length, realised in the same climatic and the same geoenvironmental conditions. The performed analysis of deformability led to the conclusion that the level of deformation is a function of the speed of traffic. This effect is observed on city roads, but also outside of urban areas at roads with speed limits are significant, due to the traffic management, traffic jams (intersections, etc.). Still, the lower speed cause greater deformations. The authors tried to describe the deformability of flexible pavement structures, from the aspects of geotechnical problems, as a function of driving speed. Outcome of the analysis is a traffic load correction coefficient, in terms of using the existing methods of flexible pavement structures design.