• Geophysics and Geophysical Exploration
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• v.19 no.1
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• pp.11-19
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• 2016

Two representative residual static methods of traveltime decomposition and stack-power maximization are discussed in terms of application to land seismic data. For the model data with synthetic shot/receiver statics (time shift) applied and random noises added, continuities of reflection event are much improved by stack-power maximization method, resulting the derived time-shifts approximately equal to the synthetic statics. Optimal parameters (maximum allowable shift, correlation window, iteration number) for residual statics are effectively chosen with diagnostic displays of CSP (common shot point) stack and CRP (common receiver point) stack as well as CMP gather. In addition to removal of long-wavelength time shift by refraction statics, prior to residual statics, processing steps of f-k filter, predictive deconvolution and time variant spectral whitening are employed to attenuate noises and thereby to minimize the error during the correlation process. The reflectors including horizontal layer of reservoir are more clearly shown in the variable-density section through repicking the velocities after residual statics and inverse NMO correction.

• Journal of the KSME
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• v.29 no.2
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• pp.175-183
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• 1989

오늘날 널리 연구되고 있고 공학자들에게 많은 관심을 끌고있는 압전 세라믹(ceramic)을 이용 하여 자연계에서 일어나는 각종 진동현상을 측정하고 해석하기 위한 센서(sensor)의 설계, 제작은 이미 선진국에서도 보편화된지 오래이다. 특히 압전형 가속도계(piezo type accelerometer)는 진동의 절대 측정에 가장 유용한 센서로 널리 알려져 있다. (1) 아주 넓은 사용 주파수 범위 (2) 넓은 동적범위(dynamic range)에 걸친 뛰어난 선형성(linearity) (3) 측정된 가속도 신호를 전기적으로 적분하여 속도와 변위에 대한 자료 제공 용이 (4) 높은 정확성 (5) 자발 전(self-generating)이므로 외부 전원 공급이 불필요 (6) 수명과 뛰어난 내구성 (7) 작은 크기와 가벼운 무게 등이다. 현재 기계 구조물 진동 측정에 이용되고 있는 스트레인 게이지 형(strain gage-type)의 가속도계는 감도가 좋고 저주파 진동 측정에는 편리한 반면 충격이나 높은 주파수 전동 측정에는 적합하지 않으며 내부 구조가 다소 복잡하다(2). 반면에 압전형 가 속도계는 압전 소자와 관성 질량의 조합 설계로서 저주파 진동 측정에 적합한 고감도의 가속도 계와, 감도는 떨어지나 아주 높은 주파수 범위의 진동까지 측정이 가능한 가속도계를 손쉽게 설계, 제작할 수 있다. 본 글에서는 선진국에 비해 낙후된 국내의 센서 설계, 제작 기술을 고 양시키고자 최근 한국과학기술원에서 시도된 압전형 가속도계의 개발 연구 사례를 중심으로 설계 및 제작시 고려 사항과 보정 문제를 소개하고자 한다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.802-803
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• 2011

매입형 영구자석 동기전동기는 강건한 회전자 구조와 릴럭턴스 토크를 사용할 수 있다는 점, 악계자 제어를 하기 쉽다는 점에서 넓은 속도와 토크를 필요로하는 하이브리드 차량이나 전기 차량에 적합한 전동기이다. 영구자석의 감자곡선은 온도에도 의존하기 때문에 온도에 따라 전동기의 자속과 토크가 변하게 된다. 이 논문은 전기 스쿠터에 사용되는 매입형 영구자석 동기전동기의 온도에 따른 지령 전류 보정에 의한 제어법에 대해 연구하였다. 토크 리플을 줄이기 위해서 속도-토크 곡선과 감자곡선을 이용하여 구하였으며, 보정된 지령 전류를 구하기 위해 Lagrange 보간법과 재귀 최소자승(Recursive Least Square : RLS) 법을사용하여 전류맵을 만들었다.이 지령 전류는 토크와 인버터 출력 전류값을 계산하는데 사용된다. 전류맵을 만들기 위해서 측정한 온도는 20, 80, 100도이다. 본 논문에서 제안한 제어법을 이용하여 토크 리플이 줄어듬을 시뮬레이션과 실험을 통해서 확인할 수 있었다.

• Fire Science and Engineering
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• v.16 no.2
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• pp.33-37
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• 2002

This study has investigated hydrodynamic of torque characteristics for disc of butterfly valve that is used in control for fire-protection water, The free-streamline theory is applied to predict hydrodynamic of torque characteristics. The torque characteristics of disc are corrected for the angles of attack of valve disc and surrounding velocity of flow by theoretical torque equation, and correction equation is added. The torque characteristics of disc are investigated for the ratio of hub thickness to the valve diameter. The result of prediction are shown to be successful as that show typical torque characteristics of butterfly valve. Since the velocity distribution around the disc is confirmed in a visualization, it is confirmed that the free-streamline theory can be used to predict the torque characteristics of disc.

• Journal of Astronomy and Space Sciences
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• v.11 no.1
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• pp.107-114
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• 1994

This paper describes a method for the determination of wind parameters as mass-loss rate, wind velocity, stochastic velocity in Zeta Aurigae type binaries. We have modified the Baade's (1989) computer code to analyze the wind parameters of Zeta Aurigae type binaries according to the least squares criterion. The modified program adjusts the wind parameters by the method of differential corrections. We have appled this method to the IUE observations of 32 Cygni. We have fitted a theoretical line profile to the IUE observations of Fe II resonance line at various phases. The mass-loss rate, wind velocity and stochastic velocity of 32 Cygni obtained in this paper are $2.18{\times}10^{-8}M_{\odot}/yr$, 132.14km/s, 39.82km/s, respectively.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.635-643
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• 2015

In this study, the experimental test results are given to confirm the control efficiency of the linear control algorithm used for designing the active mass dampers(AMD) which are supposed to be installed at Incheon international airport control tower. The comparison between the results from test and numerical analysis is conducted and it was observed that the AMD showed the control performance expected by the numerical model. The effects of the gain scheduling and constant-velocity signal added to the control signal calculated by the algorithm is identified through the observation that the AMD always show behavior within the given stroke limit without any loss of the desired control performance. The phase difference between the accelerations of the structure and the AMD were almost close to 90 degree, which implies that the AMD absorbed the structural energy effectively.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.70-79
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• 2017

This study proposes a method to quickly and accurately acquire distance information on direction signs. The proposed method is composed of the recognition of the sign, pre-processing to facilitate the acquisition of the road sign distance, and the acquisition of the distance data. The road sign recognition uses color detection including gamma correction in order to mitigate various noise issues. In order to facilitate the acquisition of distance data, this study applied tilt correction using linear factors, and resolution correction using Fourier transform. To acquire the distance data, morphological operation was used to highlight the area, along with labeling and template matching. By acquiring the distance information on the direction sign through such a processes, the proposed system can be output the distance remaining to the next junction. As a result, when the proposed method is applied to system it can process the data in real-time using the fast calculation speed, average speed was shown to be 0.46 second per frame, with accuracy of 0.65 in similarity value.

• Geophysics and Geophysical Exploration
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• v.5 no.3
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• pp.150-156
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• 2002

In this study, a software for crosswell seismic tomography is developed. The software consists of first arrival picking and adjusting module, crosswell traveltime tomography module, and imaging module. This software allows saying the picked first arrival times into the header of seismic data, and using this data directly to the input of crosswell seismic tomography. With an imaging module, velocity structures and ray path can be imaged directly from the output of the tomography module. Because it is developed on the basis of the SU under the Linux and the GUI environment for user, this software can be carried out directly the first arrival picking, inversion and tomogram for crosswell tomography data in the field. Therefore, this software can be improved the applicability of site investigation by tomography method.

• Journal of Korean Society of Transportation
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• v.26 no.2
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• pp.101-107
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• 2008

Traffic speed data may be missed due to detector malfunction or network problems. In this paper we have proposed effective methods to estimate the data which could not be collected through loop detectors. Our proposed algorithm has three steps. First step is to find the most similar neighbor data record by coefficient of correlation. Second step is to make some data records which is calculated by the 5 kinds of estimation methods. Third step is to compare the data records with history data record of observation link and thus the best method is selected. The proposed method is useful for estimating travel time.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.5
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• pp.60-66
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• 2008

Each weapon system's muzzle velocity can be used as basic data for operating accurate automatic firing control system. Even among the same kind of ammunition, despite taking into consideration various battlefield parameters, irregular performance causes difficulties in obtaining accurate muzzle velocity data. In this study, pressure in the gun barrel was measured, the experimental relationship between chamber pressure and the projectile's base pressure was found, and a method of obtaining muzzle velocity was researched. Through this method, data regarding muzzle velocity is offered that corrects irregular performance.