• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.50.1-50.1
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• 2015

The origin of globular cluster (GC) color bimodality, which is one of the salient phenomena observed in most large galaxies, has not yet been fully resolved. The phenomenon has conventionally been interpreted as a bimodal metallicity distribution based on an assumption of linear GC color-metallicity relations (CMRs). Recent studies however suggest that nonlinear GC CMRs can cause a bimodal color distribution even from a single-peaked metallicity spread. Using photometric and spectroscopic data on GCs in NGC 5128 (Cen A) and NGC 4594 (Sombrero), we investigate the nonlinearity of GC CMRs and compare the observed GC CMRs with the predictions of stellar population simulation models. Our careful selection of old GCs effectively reduces the scatter and reveals the nonlinear nature of the GC CMRs for various colors. The overall shape of the observed CMRs agrees well with that of the modeled CMRs, while offsets are present for some colors. We discuss the implications of our results in terms of the GC color bimodality and GC formation in NGC 5128 and NGC 4594.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.1
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• pp.1-7
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• 1997

Anion concentrations and distributions of airborne fine particles less than 2 $\mu$m in urban atmosphere were determined from Feb. 5 to 16, 1996. The sampling was carried out using 8 stages Hering's low pressure impactor (LPI, aerodynamic cutoff diameters are 0.05, 0.075, 0.11, 0.26, 0.50, 1.0, 2.0, and 4.0$\mu$m) on the top of a five-story building located at Kon-Kuk university in Seoul. Average concentrations if C $l^{[-10]}$ , N $O_3$$^{[-10]}$ and S $O_4$$^{2-}$ were 9.4, 8.4, and 14.5 $\mu\textrm{g}$/㎥, respectively. The distributions of these anion concentrations were bimodal types which showed two peaks in the range of 0.075~0.12 ${\mu}{\textrm}{m}$ and 0.5~1 ${\mu}{\textrm}{m}$ in aerodynamic diameter. These results were 2.5~4.7 times higher than anion concentrations collected by Anderson low volume air sampler.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.452-453
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• 2008

전 차륜 조향 굴절차량의 자동안내제어를 위한 기준경로와의 편차 되먹임 방식은 곡선경로에서 발생하는 정상상태 오차를 줄이기 어렵다. 본 논문은 이 차량의 자동안내제어의 성능향상을 위한 전향보상기 설계에 대해 기술한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.2074-2079
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• 2008

This paper presents a software toolbox with $Matlab^{(R)}$ developed for the various performance analysis of an automatic guidance system of the Bimodal Tram. The Bimodal Tram is a new kind of transportation vehicle which could be an all-wheel steered multiple-articulated vehicle. This vehicle has to be equipped with an automatic guidance, traction/braking, and docking system, In the stage of developing such a system, its validities and performances should be verified under various operation conditions. For the purpose of doing these things through simulation, this toolbox has been developed and demonstrated well by applying it to the KRRI model.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1360-1363
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• 1987

Two edge detection methods are devised and tested. First one makes use of mean-difference between two connected regions after bimodal thresholding within a local window. It appears experimentally to provide reduced edge width maintaining good connectivity. It seems due to the use of the threshold obtained from a larger neighborhood. Second one uses additionally the gradient information to detect approximate zero crossing points of second directional derivative. This provides edges thinned nearly to one pixel width.

• Nuclear Engineering and Technology
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• v.31 no.6
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• pp.608-617
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• 1999

The powder mixture which has a bimodal size distribution, with a large mode corresponding to AUC-UO$_2$ powder and a small one corresponding to ADU-UO$_2$ powder, was prepared, pressed into compacts, and sintered at 1680t for 4 hours in hydrogen gas. The compact density of the powder mixture increases with increasing ADU-UO$_2$content within a content of 20 wt %, since small ADU-UO$_2$ particles can fill interstices between large AUC-UO$_2$particles. The UO$_2$ pellet made using the powder mixture has a lower open porosity than that made using AUC-UO$_2$ powder alone. The mechanism for the formation of a flake-like pore is proposed, and the decrease in open porosity may be ascribed to the decrease in the number of flake-like pores.

• Journal of the Korean Ceramic Society
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• v.32 no.6
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• pp.653-658
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• 1995

Directional effect of applied pressure during sintering on the microstructure and fracture toughness of the heat-treated silicon nitride ceramics has been investigated. The specimens with a composition of 92Si3N4-8Y2O3(in wt%) were sintered at 172$0^{\circ}C$ by a hot press (HP ) and a hot isostatic press (HIP) and heat-treated for grain growth at 1800~20$0^{\circ}C$. The fracture toughness of the HP samples increased with the grain size while the fracture toughness of the HIP treated samples remained the same even though the grain growth occurred. This discrepancy was explained by a bimodal grain size distribution and large aspect ratio of the HPed samples and a monomodal grain size distributjion and samll aspect ratio of the HIP treated samples.

• Transactions on Electrical and Electronic Materials
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• v.8 no.3
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• pp.143-146
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• 2007

Polymer insulators are used widely in variable fields for high voltage insulation and separating people from high voltage charging parts for safety and also supporting overhead power line in electric railway. But it may be broken down by tracking path resulting from continuous surface discharge. This paper has investigated synthetically both the characteristics of electrical aging using precision CT(current transformer) and the thermal aging using thermography method. Electrical aging was analyzed for time-frequency region and thermal aging was illustrated by image processing method. This synthetic method may be an appropriate one to evaluate the surface degradation of polymer insulator.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.525-528
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• 2003

In this paper, we present a novel idea to integrate low cost Inertial Measurement Unit(IMU) and Differential Global Positioning System (DGPS) for Telematics applications. As well known, low cost IMU produces large positioning and attitude errors in very short time due to the poor quality of inertial sensor assembly. To conquer the limitation, we present a bimodal approach for integrating IMU and DGPS, taking advantage of positioning and orientation data calculated from CCD images based on photogrammetry and stereo-vision techniques. The positioning and orientation data from the photogrammetric approach are fed back into the Kalman filter to reduce and compensate IMU errors and improve the performance. Experimental results are presented to show the robustness of the proposed method that can provide accurate position and attitude information for extended period for non-aided GPS information.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1061-1067
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• 2010

In this paper, we propose a simulator for testing of the Navigation Control System(NCS) in Bimodal-tram. NCS uses values of all sorts of sensors installed in vehicle to decide current position, and to control speed and steering of vehicle to go to a next position. Major functions of simulator are input processing of the driver and generation of virtual sensor data and driving profile(navigation path, magnetic information), and the NCS function. Virtual sensor data is generated according to output data from the NCS, driving profile and input processing of the driver, and monitoring systems is operated separatedly to confirm of NCS operation. This paper discusses about the implementation of the simulator, and analyzes and evaluates the simulation results.