• 한국군사과학기술학회지
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• 제5권3호
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• pp.62-76
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• 2002

This paper describes the design of a Coordinates Tracking algorithm for EOTS and its error analysis. EOTS stabilizes the image sensors such as FLIR, CCD TV camera, LRF/LD, and so on, tracks targets automatically, and provides navigation capability for vehicles. The Coordinates Tracking algorithm calculates the azimuth and the elevation angle of EOTS using the inertial navigation system and the attitude sensors of the vehicle, so that LOS designates the target coordinates which is generated by a Radar or an operator. In the error analysis in this paper, the unexpected behaviors of EOTS that is due to the time delay and deadbeat of the digital signals of the vehicle equipments are anticipated and the countermeasures are suggested. This algorithm is verified and the error analysis is confirmed through simulations. The application of this algorithm to EOTS will improve the operational capability by reducing the time which is required to find the target and support especially the flight in a night time flight and the poor weather condition.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.697-708
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• 2017

The complex battlefield environment makes it difficult to intercept maneuvering targets for guided missiles. In this paper, a finite-time convergent (FTC) guidance law based on the second-order sliding mode (SOSM) control theory is proposed to achieve the requirements of stability, accuracy and robustness. More specifically, a second-order sliding mode observer (SMOB) is used to estimate and compensate for the total disturbance of the controlled system, while the target acceleration is extracted from the line-of-sight (LOS) angle measurement. The proposed guidance law can drive the LOS angular rate converge to zero in a finite time, which means that the missile will accurately intercept the target. Numerical simulations with some comparisons are performed to demonstrate the superiority of the proposed guidance law.

• 천문학논총
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• 제13권1호
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• pp.17-30
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• 1998

To study kinematics of solar prominences, we have made Ha spectrographic study of an eruptive prominence which appeared on the 27th of August, 1992 with a position angle of 270 deg. The observation was carried out by a Littrow type spectrograph and a G1 CCD camera attached to the 25cm coronagraph at Norikura Coronal Station. In taking the spectral data the slit was placed in parallel to the solar limb at 7 different heights, each being separated by 5 arcsec with a time step of 30 sec. The observed eruptive prominence shows a wide range of line of sight Doppler velocity, spanning from $V_{dopp}=-17.5km/s\;to\;V_{dopp}=58.2km/s$. It is also found that the velocity increases with height at the rate of ${\Delta}V= 0.86 km/s/arcsec$.

• 천문학회보
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• 제39권2호
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• pp.62.2-62.2
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• 2014

A relativistic jet associated with active galactic nuclei (AGNs) is almost ubiquitous while its formation mechanism is still not well understood. To get a deeper understanding of how an AGN jet forms and evolves, we have obtained Very Large Baseline Array (VLBA) data of a compact and optically violent variable quasar, OVV 1633+382 which is a small line-of-sight angle version of Fanaroff-Reily type 2 galaxy. Before our data were taken, a pronounced flare had been reported at mm wavelengths, making this object an excellent laboratory to study detailed properties of a radio jet powered by an AGN. The target have been observed in 12 epochs between 2002 and 2005 at 22, 43 and 86 GHz in full polarization mode. Among these observations, in this work, we present 43 GHz total intensity maps of our target for three epochs to discuss kinematics and geometry of the jet.

• 한국분무공학회지
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• 제7권4호
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• pp.9-15
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• 2002

Convolution Fourier transformation tomographically reconstructs the spatially resolved spray injection rate from direct measuring cells. Asymmetric sprays generated from a twin-hole air shroud injector are tested with 12 equiangular projections of measurements. For each projection angle, line of sight integrated injection rate was measured at 35 positions with equal spacing measuring cells of 3 mm in width, 100 mm in length, 55 mm in depth and 0.5 mm thickness of separating wall. Interpolated data between the projection angles effectively increase the number of projections, which significantly enhances the signal-to-noise level in the reconstructed data. This modified convolution Fourier transformation scheme predicts well the structure of asymmetric sprays. Comparative study has been made between sprays with and without air shrouding. Tomograhpic reconstruction of injection rate from direct measuring cells obtained can be used to estimate the accuracy of volume fraction of spray from the LDPA tomographic reconstruction.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.158.2-158
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• 2001

This paper introduces the design and implementation of a signal processing system for an airborne active homing radar system. This airborne active homing radar system uses the pulse Doppler radar of high PRF (Pulse Repetition Frequency) for computation of exact relative velocity of the target. This system carries out two operations mainly. The first is to transmit and receive microwave signal through the antenna. The second is to calculate the relative velocity of the target taking advantage of the Doppler frequency signal reflected from the target and detect the angle error between a target and an antenna LOS (Line Of Sight) to make the antenna direction coincident with the target. The signal processing system has a role of the latter.

• 천문학회보
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• 제43권1호
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• pp.60.3-61
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• 2018

Abell 115 is a renowned cluster merger at z=0.197. It exhibits an asymmetric X-ray distribution with cometary tails and a megaparsec-sized radio relic stretching in the northeastern direction from the core of the northern cluster. Many observations have concluded that this cluster merger has a large impact parameter, but there has been no numerical analysis on the structure of Abell 115. In this study, we simulate Abell 115 with Gadget2 N-body/SPH code to reproduce the X-ray and weak lensing features of Abell 115. We find a new plausible merger scenario of Abell 115, wherein the northern cluster is currently in an outgoing phase. The predicted X-ray emission has a similar morphology to the observed tail of the northern cluster. However, in order to reproduce the observed line-of-sight velocity and projected distance while maintaining the two systems gravitationally bound, the system should possess a large projection angle, which makes the shock look considerably more diffused than the observed radio relic.

• 한국위성정보통신학회논문지
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• 제3권2호
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• pp.26-31
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• 2008

As a multi-mission GEO satellite, Communication, Ocean, and Meteorological Satellite (COMS) is scheduled to be launched in the year 2009. COMS has three different payloads: Ka-band communication payload, Geostationary Ocean Color Imager (GOCI) and Meteorological Imager (MI). Among the three payloads, MI and GOCI have several conflict relationships; one of them is that if MI mirror moves vertically larger than 4 Line Of Sight (LOS) angle while GOCI is imaging, image quality of GOCI becomes degraded. In this paper, MI scheduling algorithm to prevent GOCI's image quality degradation will be presented.

• Journal of electromagnetic engineering and science
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• 제11권1호
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• pp.51-55
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• 2011

Electromagnetic fields, radiated from an intestine-ingested source and propagated through an inhomogeneous human body model, are computed with the finite-difference time-domain (FDTD) method. The calculated results obtained at some receiving points vertically placed according to the abdomen of the human body model show unusual dip patterns in the frequency domain. The frequency of this unusual dip varies according to the location of the receiving points. Thus, the relationship between the frequency of the unusual dip and the incident angle of the line-of-sight is analyzed. The effect of the location of an ingested source on the above relationship is also investigated. The slope of the approximately linear relationship is affected by the location of the ingested source.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.219-220
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• 2007

Image plane상에서의 목표의 크기, 시선각 (Line-of-Sight angle) 및 관측자의 상태 정보 등을 이용하여 목표의 상태를 추정한다. 표적 모델을 Linear Time Varying(LTV) system처럼 다룰 수 있음을 밝히고, 이를 이용하여 가관측성(observability)이 성립하는 조건을 구하고 Kalman filter를 이용하여 비선형 추정기를 설계한다. 그리고 등가속도 표적 추정, 미사일의 정지 표적 공격 등의 모의실험에 적용해 본다.