• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.50.2-50.2
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• 2017

We have been carrying out the long-term (3-5 years) AGN monitoring project since October 2015 to investigate the variability and measure the H beta line time lag of 69 nearby (0.06 < z < 0.47) AGNs based on the reverberation mapping method. Our targets have B band magnitudes of 14.4-18.6, luminosities of log L5100 = 45.6-48.1 erg/s, and the expected time lags of 28-597 light days. BVR band images are being taken with ~20-day cadence using MDM 1.3m, LOAO 1m and MDM 2.4m telescopes. Recently, Nickel 1m at Lick and DOAO 1m at Deokheung observatory are joined with photometric observations. Follow-up spectroscopic observations are on-going using the Lick 3m and MDM 2.4m telescopes. In this poster, we will describe our project including sample selection and the observational strategy, and present the preliminary results based on the 1st year photometry.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.76.4-77
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• 2017

We have been performing a long term AGN Monitoring project, to measure the time lag of H beta line with respect to AGN optical continuum based on the reverberation mapping method. From October 2015, 69 AGNs have been monitored with BVR band photometry, using the MDM 1.3m & 2.4m and LOAO 1m telescopes, and long-slit spectroscopy, using the Lick 3m and MDM 2.4m telescopes. In this poster, we report the preliminary results of the variability study of a subsample of 9 AGNs, particularly with a few of tentative time rag measurements between B band magnitude and H beta luminosity based on the 1st year data set from February 2016 - January 2017.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.1
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• pp.28-34
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• 2007

In this research, the characteristics of the DC discharge that was the logical gate input of discharge logic gate PDP newly proposed was considered. The logical output is induced by controlling the potential difference of inter-electrode according to the discharge path in the discharge logic gate. From the experimental result the discharge time lag was shortened to 1/3 and the voltage has decreased to 1/2 in the case to apply priming discharge for improving stability of these DC discharges compared with the case when it is not applied. Moreover, after the priming discharge ends, the space charge generated by this discharge influences it up to about $30[{\mu}s]$. And, as a measured result of the influence that the space charge exerts on the DC discharge with the change in time and spatial distance, it has been understood that there is a possibility that going away spatially can slip out the influence of the discharge easily as for going away from the discharge time-wise. Therefore the conclusion that the discharge logic gates of each scanning electrode can be operated independently is obtained.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.1
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• pp.74-80
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• 2006

This paper addresses the trajectory optimization of Unmanned Aerial Vehicles(UAVs) under multiple ground threats like enemy's anti-air radar sites. The power of radar signal reflected by the vehicle and the flight time are considered in the performance cost to be minimized. The bank angle is regarded as control input for a 1st-order lag vehicle, and input parameter optimization method based on Sequential Quadratic Programming (SQP) is used for trajectory optimization. The proposed path planning method provides more practical trajectories with enhanced survivability than those of Voronoi diagram method.

• Structural Engineering and Mechanics
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• v.85 no.3
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• pp.305-314
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• 2023

The article is about the theoretical analysis of the transmission and reflection of elastic waves through the interface of perfectly connected materials. The solid continuum mediums considered are piezoelectric semiconductors and transversely isotropic in nature. The connection among the mediums is considered in such a way that it holds the continuity property of field variables at the interface. The concept of strain and stress introduced by non-local theory is also being involved to make the study more applicable It is found that, the incident wave results in the generation of four reflected and three transmitted waves including the thermal and elastic waves. The thermal waves generated in the medium are encountered by using the concept of three phase lag heat model along with fractional ordered time thermoelasticity. The results obtained are calculated graphically for a ZnO material with piezoelectric semiconductor properties for medium M₁ and CdSc material with transversely isotropic elastic properties for medium M₂. The influence of fractional order parameter, non-local parameter, and steady carrier density parameter on the amplitude ratios of reflected and refraction waves are studied graphically by MATLAB.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.3
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• pp.203-211
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• 2016

In contrast with STT missiles, the guidance law design for BTT missiles should be based on 3-dimensional pursuit kinematics, since the pitch and roll channels of BTT missiles are coupled dynamically. More generally than the prior works, the dynamics of pitch and roll channels, as well as 3-dimensional pursuit kinematics are considered in the design of our terminal-phase optimal guidance law for BTT missiles proposed in this paper. Thereby, the proposed optimal guidance law guarantees high capturability with small miss distance without significant performance degradation due to time-lag effect even in case of relatively slow autopilot dynamics. Moreover, the resulting optimal guidance law is expressed explicitly in feedback-form with the coefficients given as the functions of time-to-go. The effectiveness and practicality of our work is demonstrated through various simulation results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.100-106
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• 2022

Ships are built according to the purpose and operated with individual goals. Operational goals are reflected in the design of the ships and become the main criterion for determining the required ship ability. In general, cargo ships and passenger ships are objectively evaluated in terms of the operation part of the ship and the capacity part of the cargo or passenger, centering on their transportation ability. In consideration of the required ship ability, the built ship can expect effects such as economic feasibility and eco-friendliness in addition to basic characteristics such as stability. Accordingly, the concept of ship ability is expected to be effectively used in the field of training-only ship management by each institution, which plays a pivotal role in training ship-officers. In this study, the basic direction was verified for the ship ability evaluation criteria of training-only ships through the analysis of the internal space of two training-only ships of the Korea Institute of Maritime and Fisheries Technology, which were recently built with a time lag. In the process of building training-only ship or general-purpose training ship, the possibility of using the ship ability standards in securing budget and designing was derived.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.29-36
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• 2004

In this work, the effect of composite couplings on hub loads of a hingeless rotor in forward flight is investigated. The hingeless composite rotor blade is idealized as a laminated thin-walled box-beam. The nonclassical effects such as transverse shear, torsional warping are considered in the structural formulation. The nonlinear differential equations of motion are obtained by applying Hamilton's principle. The blade response and hub loads are calculated using a finite element formulation in space and time. The aerodynamic forces acting on the blade are calculated by quasi-steady strip theory. The theory includes the effects of reversed flow and compressibility. The magnitude of elastic couplings obtained by MSC/NASTRAN is compared with the classical pitch-flap $({\delta}3)$ or $pitch-lag({\alpha}1)$ coupling. It is found that the elastic couplings have a substantial effect on the behavior of $N_b/rev$ hub loads. Nearly 10 to 40% of hub loads is reduced by appropriately tailoring the fiber orientation angles in the laminae of the composite blade.

• Geophysics and Geophysical Exploration
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• v.3 no.2
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• pp.70-75
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• 2000

In the seismic migration, Kirchhoff and reverse time migration are used in general. In the reverse time migration using wave equation, two-way and one-way wave equation are applied. The approach of one-way wave equation uses approximately computed downward continuation extrapolator, it need tess amounts of calculations and core memory in compared to that of two-way wave equation. In this paper, we applied one-way wave equation to pre-stack reverse time migration. In the frequency-space domain, forward propagation of source wavefield and back propagration of measured wavefield were executed by using monochromatic one-way wave equation, and zero-lag cross correlation of two wavefield resulted in the image of subsurface. We had implemented prestack migration on a massively parallel processors (MPP) CRAYT3E, and knew the algorithm studied here is efficiently applied to the prestck migration due to its suitability for parallelization.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.105-115
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• 2022

The platform for displaying cars has been changing with the times. From the popularity of paper media to the rise of computer graphics, the improvement of technology has brought more space and possibilities to the automotive industry. Yiming Zhong proposed the workflow of car configurator through Unreal Engine 4 to implement the basic functions of configuration in 2021, according to Yiming Zhong's final presentation, there is still room to improve the realism of graphics and functionality of the car configurator. Therefore, in this paper we propose to upgrade the car shaders and lighting environments according to the real-world physics and add multi-scenes switching function to car configurator. However the multi-scenes switching function also brings a large amount of data, which leads to the problem of display lag. At the end of the paper, we use the level of details(LOD) process to reduce the amount of data for real-time computing in Unreal Engine 4 and the increase of frames per second(FPS) values verifies the feasibility of our optimization solution.