• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.6
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• pp.637-644
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• 2010

The purpose of this study is to analyze characteristics of water quality factor scientifically and develop the multiple regression model predicting dissolved oxygen to save periodic replacement costs for dissolved oxygen sensor. Correlation analysis using the environmental data obtained from 2 different land-based fish farms of the Geogeum-do, Geheung-gun coastal area during the periods from November 2008 to January 2009 shows that water temperature was negatively correlated with dissolved oxygen and pH butpH was positively correlated with salinity and dissolved oxygen. The information of Keumho fish farm in 2009 is presented by the tables which are monthly statistics of water quality factors and seasonable difference by the Duncan's post-test. Also we developed multiple regression model predicting dissolved oxygen, the usefulness of which was verified by the comparison graph between estimates and actual observations. The developed regression model shows that seawater temperature and salinity give negative affect to dissolved oxygen while pH gives positive affect to it. Lastly the seawater temperature has much higher explanatory power than pH factor.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.171-178
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• 2008

Pressure control of hydraulic pump using SRM with pressure predictor and direct torque control method is presented in this paper. Nowadays, high efficiency and high performance motor drive is much interested in hydraulic pump system. But the hydraulic pump system has an inherent defect that its dynamic behavior causes by interaction between the sensor and hydraulic load. It will make low performance of whole system, even unstable and oscillatory. Proposed system integrates pressure predictor and direct instantaneous torque control (DITC). The pressure predictor includes Smith predictor, which is easy to improve unstable or long oscillation in traditional negative feedback control and popular PID control architectures. And DITC method can reduce inherent torque ripple of SRM, and develop smooth torque to load, which can increase stability and improve the torque response of SR drive. So high dynamic performance and stabilization can achieved proposed hydraulic system. At last, the proposed hydraulic system is verified by simulation and experimental results.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.123-131
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• 2009

The emerging display technology has been replaced the previous position of the CRT with the LCD. The nature of hold type display such as LCD, however, causes many problems such as motion blur and motion judder. To resolve the problems, we used frame interpolation technique which improves the image quality by inserting new interpolated frames between existing frames. In this paper, we propose a novel frame interpolation technique that uses dominant MV and variance different value in each block. At first, the proposed algorithm performs unidirectional motion estimation using blocking matching algorithm. The new frame is generated by pixel average using compared block variance or by pixel motion compensation using dominant motion vector, whether the motion estimation find the target area or not. Several experiments with the proposed algorithm shows that the proposed algorithm has better image quality than the existing bidirectional frame interpolation algorithm at the rate of about 3dB PSNR and has low complexity comparing to the unidirectional frame interpolation technique.

• Journal of the Korean Geotechnical Society
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• v.18 no.1
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• pp.141-152
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• 2002

Although a number of constitutive models have been proposed to define the behavior of geotechnical materials including elastic, plastic, and dynamic response, flew numerical models have been developed for the cyclic shear behavior of rock joints or interfaces. Such realistic constitutive models play an important role in analyzing and predicting the response of joints under dynamic loads. The purpose of this research is to verify the constitutive model modified for rough granite joints based on Disturbed State Concept(DSC) model, which has been successfully verified with respect to other materials such as dry sand-steel interface and wet sand-concrete interface. Furthermore, DSC model is compared and verified with respect to cyclic shear tests and numerical analysis results based on Plesha model. Based on the results of this research, it can be stated that DSC model is capable of characterizing the cyclic shear behavior of rough granite joints under dynamic loads.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.10
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• pp.959-965
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• 2011

A modeling and power simulation of a small UAV's electric propulsion systems is described. Each power source is modeled and simulated in Matlab/Simulink and it is compared flight test data during 4 hr 30 min with simulation results about 200 W electric propulsion system using fuel cell and battery as a main power sources. In result, it is properly simulated performance and dynamic characteristic of each electric power source. Through this, it is revealed that the simulation is available as a means of predicting power characteristic variation for electric propulsion systems of different class.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.329-334
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• 2009

The Study of steady performance of orifice must be precede before study of dynamic characteristics with configuration change. So, orifice performance with change of diameter ratio, thickness, expansion and angle predicted by CFD. The analysis algorithm is SIMPLEC. And PRESTO, QUICK scheme is used for dicretization. The $k-{\omega}$ STS turbulent model also used. The discharge coefficient is rapidly increased with increasing of diameter ratio and slowly decreased after rapidly increasing with orifice thicken. In case of expansion angle, the discharge coefficient is the smallest at $45^{\circ}$ of the angle.

• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.193-195
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• 2007

해양생태계로 유입되는 화학물질의 총합적인 평가 및 관리를 위해서는 동 화합물의 해양환경중의 거동 및 운영, 생태계에의 영향, 관리방안에 따른 화학물질의 변화 예측 및 리스크 평가 등을 행할 필요가 있으며, 이를 위하여는 화학물질에 대한 생태계 모델이 유용한 수단이 될 수 있다. 본 연구에서는 여러 화학물질에 적용할 수 있으며, 지역특성, 존재 데이터 상황, 대상 수산물의 특성을 고려하여 여러 상태함수 및 프로세스의 추가와 삭제가 가능한 3차원 생태계 모델(EMT-3D)을 사용하여 해양환경중의 PFCs 관련물질을 대상으로 그 적용성을 검토하였으며, 민감도 분석 및 시나리오 분석을 행하여 영향인자를 판별하고 대안에 따른 영향을 평가하였다.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.351-352
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• 2007

부분방전이 고체절연시스템에서 대부분의 절연고장과 관련된 징후를 알 수 있으므로 부분방전시험은 고전압회전기 고정자권선의 절연특성을 효과적으로 진단할 수 있다. 부분방전시험은 다른 고전적인 절연시험법과는 다르게 고전압회전기가 운전중(On-line)인 상태와 정지중(Off-line)인 상태에서 모두 측정이 가능한 장점이 있다. 정지중 부분방전시험은 고정자권선 절연상태를 평가할 수 있는 잘 알려진 시험법이다. 최근에는 운전중 부분방전시험이 권선의 절연상태를 모니터링하는데 효과적인 방법으로 운영자에게 고장징후를 알려주고, 예측보전이 가능하도록 도움을 주고있다. 이 논문에서는 수력발전기에 설치되어 운영중인 운전중 진단시스템의 각 상별 부분방전데이터를 바탕으로 정지상태에서 운전중 및 정지중 진단시스템을 이용하여 부분방전을 측정하고 시험결과를 분석하였으며, 운전중 시험과 정지중 시험의 유사성과 차이점을 확인할 수 있었다.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.241-251
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• 2007

The observed spectra from Odaesan earthquake were fitted to a point-source spectral model to evaluate the source spectrum and spatial features of the modelling error. The source spectrum was calculated by removing from the observed spectra the path and site dependent responses (Yun, 2007) that were previously revealed through an inversion process applied to a large accumulated spectral dataset. The stress drop parameter of one-corner Brune's ${\omega}^2$ source model fitted to the estimated source spectrum was well predicted by the scaling relation between magnitude and stress drop developed by Yun et al. (2006). In particular, the estimated spectrum was quite comparable to the two-corner source model that was empirically developed for recent moderate earthquakes occurring around the Korean Peninsula, which indicates that Odaesan earthquake is one of typical moderate earthquakes representative of Korean Peninsula. Other features of the observed spectra from Odaesan earthquake were also evaluated based on the commonly treated random error between the observed data and the estimated point-source spectral model. Radiation pattern of the error according to azimuth angle was found to be similar to the theoretical estimate. It was also observed that the spatial distribution of the errors was correlated with the geological map and the $Q_0$ map which are indicatives of seismic boundaries.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.61-69
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• 2013

This research is aimed to evaluate characteristics and dynamic modeling of MR damper for semi-active vibration control. A MR damper of semi-active type was designed and made for the purpose of controlling the vibration of a real-size model structure. Usually a semi-active control system equipped with a MR damper requires a dynamic model which expresses numerical data about the damping capacity and dynamic characteristics generated by a MR damper. To fulfil the requirement, a Power model and a Bingham model were particularly employed among many dynamic models of MR damper. Those models being contrasted with other ones, a dynamic test was carried out on the developed MR damper. In the test, excitation frequencies were conditioned to be 0.15 Hz, 1.0 Hz, and 2.0 Hz, and three different currents were adopted for each frequency. From these test results, it was found that displacement affected control capacity of the MR damper. The test results led to the identification of model variables for each dynamic model, on the basis of which a force-speed relation curve and expected damping force were derived and contrasted to those of the developed MR damper. Therefore, it was proven that the MR damper designed and made in this research was effective as a semi-active controller, and also that displacement of 2mm at minimum was found to be secured for vibration control, through the test using various displacements.