• 한국공간구조학회논문집
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• 제15권1호
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• pp.65-73
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• 2015

This paper presents the structural model verification process of whole wind turbine blade including blade model which proposed in Part1 paper. The National Renewable Energy Laboratory (NREL) Phase VI wind turbine which the wind tunnel and structural test data has publicly available is used for the study. In the Part1 of this paper, the processes of structural model development and verification process of blade only are introduced. The whole wind turbine composed by blade, rotor, nacelle and tower. Even though NREL has reported the measured values, the material properties of blade and machinery parts are not clear but should be tested. Compared with the other parts, the tower which made by steel pipe is rather simple. Since it does not need any considerations. By the help of simple eigen-value analysis, the accuracy of structural stiffness and mass value of whole wind turbine system was verified by comparing with NREL's reported value. NREL has reported the natural frequency of blade, whole turbine, turbine without blade and tower only models. According to the comparative studies, the proposed material and mass properties are within acceptable range, but need to be discussing in future studies, because our material properties of blade does not match with NREL's measured values.

• 한국지능시스템학회논문지
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• 제24권1호
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• pp.96-101
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• 2014

풍력은 전 세계적으로 가장 각광을 받고 있는 신재생 에너지이며 당분간 이러한 추세는 계속될 것으로 기대되고 있다. 최근 풍력발전시스템의 O&M(Operation & Maintenance) 비용의 절감에 대한 필요성이 꾸준히 대두되고 있는 실정이다. O&M 비용의 절감을 위한 가장 효율적인 방법은 CMS(Condition Monitoring System)의 도입이며 이는 풍력발전기 부품들의 악화, 적절한 선제적 유지보수, 발전중지시간의 단축 및 궁극적으로 풍력발전기의 운전 효율을 증대시키는 것을 가능케 한다. 풍력발전기의 터빈 로터와 관련하여 질량 불평형 및 공력비대칭과 같은 고장이 발생될 수 있다. 일반적으로 이러한 고장은 다양한 형태의 진동을 야기 시킨다. 이에 본 연구에서는 진동신호에 대한 스펙트럼과 간단한 max-min 진단 로직으로 구성된 고장검출 알고리즘을 제안한다. 또한 제안된 진단기법의 유용성의 확인을 위해 GH-Bladed 프로그램을 이용한 다양한 시뮬레이션 고찰을 수행한다.

• 한국농림기상학회지
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• 제21권4호
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• pp.327-336
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• 2019

콩은 식량작물 중 단백질 함량이 매우 높고 식생활에서 여러가지 형태로 소비되기 때문에 매우 중요한 식량자원 중 하나이다. 콩은 일반적으로 노지에서 재배되기 때문에 콩의 생산량 및 품질은 갑작스런 기후 변화에 큰 영향을 받는다. 최근 폭염 및 폭우 등과 같은 이상기후로 인해 콩의 생산량이 불안정해짐에 따라 콩의 생육을 실시간으로 추정하여 품질저하를 예방할 수 있는 기술 개발이 필요하다. 본 연구에서는 회전익무인기에 장착된 다중분광 센서를 이용하여 콩 생육을 추정하기 위해 수행되었다. 반사값을 이용하여 산출된 정규화 식생지수(NDVI, GNDVI)와 단순비 식생지수(RRVI, GRVI)와 콩 생육 데이터(생체중, 건물중, 엽면적지수)로 선형회귀분석을 실시하여 생육 추정 모델을 개발하였다. 그 결과, 정규화 식생지수인 NDVI를 이용한 엽면적 지수 추정 모델(R²=0.587, RMSE=1.01 ㎡/㎡, RE=48.98%)보다 GNDVI를 이용한 엽면적 지수 추정 모델(R²=0.789, RMSE=0.73 ㎡/㎡, RE=34.91%)이 높은 정밀도가 나타났으며, 단순비 식생지수를 이용한 엽면적 지수 추정 모델 RRVI (R²=0.760, RMSE=0.78 ㎡/㎡, RE=37.26%) GRVI (R²=0.828, RMSE=0.66 ㎡/㎡, RE=31.59%)과 비교 했을 때, 단순비 식생지수에서 높은 정밀도가 나타났다. 기후변화에 대체하기 위해 재식밀도 및 변량 시비와 같은 재배관리법이 적용된다면, 고품질의 콩을 생산하는데 도움이 될 것으로 판단된다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.237.2-237.2
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• 2010

Although oscillating water column type wave energy devices are nearing the stage of commercial exploitation, there is still much to be learnt about many facets of their hydrodynamic performance. The techniques of Computational Fluid Dynamics (CFD) are applied to simulate a wave energy conversion device in free surface such as waves. This research uses the commercially available ANSYS CFX computational fluid dynamics flow solver to model a complete oscillating water column system with savonius turbine incorporated at the rear bottom of the OWC chamber in a three dimensional numerical wave tank. The purpose of the present study is to investigate the effect of an average wave condition on the performance and internal flow of a newly developed direct drive turbine (DDT) model for wave energy conversion numerically. The effects of blade angle and front lip shape on the hydrodynamic efficiency are investigated. The results indicated that the developed models are suitable to analyze the water flow characteristics both in the chamber and in the turbine. For the turbine, the numerical results of torque were compared for the all cases. The results of the testing have also illustrated that simple changes to the front wall aperture shape can provide marked improvements in the efficiency of energy capture for OWC type devices.

• 디지털융복합연구
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• 제12권1호
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• pp.319-324
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• 2014

최근 들어 고성능 비행 드론이 주목받고 있다. 특히, 다중 로터를 장착한 헬기 형태의 비행 드론은 항공촬영, 방송영상제작, 항공구조, 물류배송, 감시, 측량, 방역 방제, 군사용 등으로 그 활용범위를 확장해가고 있다. 그러나 이를 조종하는 제어기의 형태는 매우 단순하다. 따라서 본 연구에서는 모바일 기기에 탑재된 G-센서를 이용하여 사용자의 직관적인 동작으로 비행 드론을 조종할 수 있는 향상된 제어기를 구현한다. 구현된 제어기는 신경망 알고리즘을 사용하여 동작 인식 성능을 향상시켰다.

• Journal of Power Electronics
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• 제15권5호
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• pp.1264-1273
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• 2015

An inverter output power control based power factor correction (PFC) strategy is being extensively used for permanent magnet synchronous motor (PMSM) drives in appliances because such a strategy can considerably reduce the cost and size of the inverter. In this strategy, PFC circuits are removed and large electrolytic DC-link capacitors are replaced with small film capacitors. In this application, the PMSM d-q axes currents are controlled to produce ripples, the frequency of which is twice that of the AC main voltage, to obtain a high power factor at the AC mains. This process indicates that the PMSM operates under periodic magnetic saturation conditions. This paper proposes a back electromotive-force (back-EMF) estimator for the high-speed sensorless control of PMSM operating under periodic magnetic saturation conditions. The transfer function of the back-EMF estimator is analyzed to examine the effect of the periodic magnetic saturation on the accuracy of the estimated rotor position. A simple compensation method for the estimated position errors caused by the periodic magnetic saturation is also proposed in this paper. The effectiveness of the proposed method is experimentally verified with the use of a PMSM drive for a vacuum cleaner centrifugal fan, wherein the maximum operating speed reaches 30,000 rpm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.139-141
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• 1996

The switched reluctance motors(SRM) are simple and robust in structure. Because the wide range of power and speed, their application field is increasing. In order to design the motors and to evaluate the performance of them properly, an accurate study about the analysis of motor characteristics is required. In this paper, for the analysis of SRM characteristics, the finite element method which is based on the solution of combined equations both the electromagnetic field equations and the circuit equations of stator is adopted. The analysis model is to he assumed two-dimensional and the nonlinear property of magnetic materials is considered by Newton-Raphson method. To verify the usefulness of the proposed algorithm, commercial SRM is chosen and simulated. The computed torques obtained by Maxwell Stress Tensor are compared with the experimental data and it is found that they are in good agreement. By applying the proposed algorithm to two cases, currents of stator and torques at every angular positions of rotor are obtained step by step. Comparing them, one can recognize that torque ripple of SRM can he improved by controlling the switching sequences of driving circuits.

• 한국정밀공학회지
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• 제19권2호
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• pp.213-219
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• 2002

A cone-shaped active magnetic healing spindle system for high speed internal grinding with built-in motor that has 7.5kW power and maximum rotational speed of 50,000 rpm is designed and built. Using cone-shaped AMB(Active Magnetic Bearing) system, the axial rotor dick and magnets of conventional 5-axis actuating design can be eliminated. so this concept of design provides a simple magnetic bearing system. In this paper, the cone-shaped electromagnets are designed by magnetic circuit theory, and a de-coupled direct feedback PID controller is applied to control the coupled magnetic bearings. The designed crone-shaped AMB spindle system is built and constructed with a digital control system, which has TMS320C6702 DSP, 16 bit AD/DA, switching power amplifier and gap sensors. As the AMB system provides high damping ratio eliminating overshoot and resonance speed, this spindle runs up to 40,000 rpm stably with about 5${\mu}{\textrm}{m}$ of runout.

• 펄프종이기술
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• 제48권3호
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• pp.14-22
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• 2016

Pulping is a stage that can change fibrous raw materials into pumpable slurry. Recovered paper can be defibrated to individual fibers by shear stress generated by rotation of a rotor and water. Disintegration of recovered paper is more complicated than that of chemical pulp. When disintegration of recovered paper is poor, screening and cleaning efficiency will be worse and properties of paper will also be deteriorated. Therefore, pulping is an important treatment for improvement of availability of recovered paper and process runnability. In this study, degrees of disintegration of KOCC obtained from a linerboard mill was analyzed with a pilot-scale screen. Flake removal of KOCC slurry was performed by a pilot screen. Simple pumping action gave a positive effect on disintegration of KOCC. After pumping for 10 minutes, paper strength increased without the change of water retention value and fibrillation of KOCC slurry. This phenomena can be explained by modification of hornified surface of KOCC fibers by shear stress generated by pumping. Consequently, disintegration efficiency of KOCC can be enhanced by control of retention time at pulper or an agitation power at chests of papermaking process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.170-172
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• 2003

Among low power servo applications, classical DC motors are very popular because they are reasonably cheap and easy to control. The main disadvantage is the mechanical collector which has only a limited life period. Also, brush sparking can destroy the rotor coil, generate EMC problems. So permanent magnet brushless do motors and drives are being used increasingly in a wide range of applications. This has been made possible with the advantages of high performance permanent magnets with high coercively and residual magnetic, which make it possible for the PM to have superior power density, torque to inertia ratio and efficiency, when compared to an induction or conventional dc machine. This paper presents the design of a PM brushless dc motor drive simplistically operates as a classical dc motor. The BLDC motor drive system for this paper composes to the power integrated circuits, the one chip device. And several simple semiconductors add to drive system for a motor drive system simplistically operates as a conventional dc motor. Test results confirmed the feasibility of the proposed motor drive system design.