• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.762-769
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• 2016

The dynamic modulation transfer function (MTF) for image degradation caused by sinusoidal vibration is formulated based on a Bessel function of the first kind. The presented method makes it possible to obtain an analytical MTF expression derived for arbitrary frequency sinusoidal vibration. The error obtained by the use of finite order sum approximations instead of infinite sums is investigated in detail. Dynamic MTF exhibits a stronger random behavior for low frequency vibration than high frequency vibration. The calculated MTFs agree well with the measured MTFs with the slant edge method in imaging experiments. With the proposed formula, allowable amplitudes of any frequency vibration are easily calculated. This is practical for the analysis and design of the line-of-sight stabilization system in the remote sensing camera.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.241-245
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• 2015

In this work we present the results of light curve analysis for two cataclysmic variables detected recently in the SDSS project: SDSS J090350.73+330036.1 and J150240.98+333423.9. Photometric observations of the first were obtained during a superoutburst in May 2010. Our observations clearly indicate the presence of superhumps in the light curves, suggesting SDSS J090350.73+330036.1 is an SU UMa dwarf nova. We determined the period of the superhumps. We also carried out fitting using a spiral-arm model in order to determine parameters of the accretion disk, hot line, and other components of this system. Photometric observations of the second, J150240.98+333423.9, were obtained during the post-maximum decline, during April-June 2012. Photometric variability of this system has been studied in an inactive state. We obtained its parameters via a combined model fitted to the observed light curves by ${\chi}^2$ minimization.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.88-90
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• 2009

Extremely-Low-Frequency(ELF) magnetic fields are generated around power cables and bus bars in power systems. Such the stray fields may cause disturbances to nearby electronic apparatus and affect even human health. In order to seeking out a proper way to reducing the fields, the first thing to do is to accurately predict field distribution around analysis models of interest. Then, optimization techniques should be applied for finding a more improved design than the initial one. To achieve this goal, commercial electromagnetic software, MagNet, is combined with evolution strategy algorithm. For verification of the proposed method, three-phase power line cables and busbar systems have been tested.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1418-1423
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• 2007

The topology of LLC half bridge resonant converter provides ZVS characteristic. The voltage stress and current stress are smaller than that of the general resonant converters. So the LLC HB resonant converter can be considered as a optimal circuit for the notebook computer adapter. In the adapter design, we should consider the weight, the size and the overheat of the adapter. Thus the higher efficiency is an essential particular. First of all, the optimal design of transformer is the most important facts. Some parameters should be considered in order to get the highest efficiency. The adapter is designed through the considering of these parameters including the PFC circuit as the pre-regulator. It converts AC line input into about DC 390V link voltage of the LLC HB converter input and the converter has 16V/90W ratings. The efficiency measured is about up to 93%.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.6-8
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• 1995

In this paper, we study the computation of the electric field of dielectric analysis models with the conductivity on its surface. The finite element formulation describes a sinusoidal electrodynamic field computation. One term is added to this functional in order to take the conductivity on its surface into accounts. The electric field computations of the dielectric analysis model are done first with the surface conductivity and second with the volume conductivity. Also, it is shown that a surface conductor with sufficiently large conductivity can be substituted with a floating equipotential line. This method is applied to an insulator in arbitrary shape with the conductivity on its surface.

• Proceedings of the KIEE Conference
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• 2004.05a
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• pp.138-140
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• 2004

This paper mainly deals with the dynamic walking of a biped robot. At first, in order to walk in various environments, it is desirable to adapt to such ground conditions with a suitable foot motion, and maintain the stability of the robot by a smooth hip motion. A method to plan a walking pattern consisting of a foot trajectory and a hip trajectory is presented. The effectiveness of the proposed method is illustrated by simulation results. Secondly, the paper brings forward a balance control technique based on off-line walking pattern with real-time modification. At last, the concept of Zero Moment Point (ZMP) is used to evaluate dynamic stability.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.4
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• pp.126-137
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• 1994

Performance management of computer networks is intended to improve a given network performance in order for more efficient information exchange between subsystems of an integrated large-scale system. Importance of perfomance management is growing as many functions of the large- scale system depend on the quality of communication services provided by the network. The role of performance management is to manipulate the adjustable protocol parameters on line so that the network can adapt itself to a dynamic environment. This can be divided into two subtasks : performance evaluation to find how changes in protocol parameters affect the network performance and decision making to determine the magnitude and direction of parameter adjustment. This paper is the first part of the two papers focusing on conceptual design, development, and evaluation of performance management for token bus networks. This paper specifically deals with the task of performance evaluation which utilizes the principle of perturbation analysis of discrete event dynamic systems. The developed algorithm can estimate the network performance under a perturbed protocol parameter setting from observations of the network operations under a nominal parameter setting.

• Journal of Intelligence and Information Systems
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• v.6 no.1
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• pp.113-128
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• 2000

This paper presents a first year report of an ongoing multi-year project to develop a systolic parallel simulation system for dynamic traffic assignment. The fundamental approach to the simulation is systolic parallel processing based on autonomous agent modeling. Agents continuously act on their own initiatives and access to database to get the status of the simulation world. Various agents are defined in order to populate the simulation world. In particular existing modls and algorithm were incorporated in designing the behavior of relevant agents such as car-following model headway distribution Frank-Wolf algorithm and so on. Simulation is based on predetermined routes between centroids that are computed off-line by a conventional optimal path-finding algorithm. Iterating the cycles of optimization-then-simulation the proposed system will provide a realistic and valuable traffic assignment. Gangnum-Gu district in Seoul is selected for the target are for the modeling. It is expected that realtime traffic assignment services can be provided on the internet within 3 years.

• Bulletin of the Korean Chemical Society
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• v.22 no.4
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• pp.383-387
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• 2001

The kinetics and mechanism of the reactions of thiophenyl dimethylacetates (TDA) and trimethylacetates (TTA) with benzylamines in acetonitrile are studied. The reactions are first order in both the amine and the substrate. Relatively large values of ${\beta}X(\betanuc$ = 1.1-1.5; TDA and 1.1-1.5; TTA) and ${\beta}Z({\beta}lg$ = -1.8~-2.0; DTA and -1.3~-1.6; TTA) for benzylamines, significantly large kH/kD values (=1.2-1.5; DTA and 1.2-1.5; TTA) involving deuterated benzylamines, and large ${\rho}XZ$ (=0.82; TDA and 1.05; TTA) values are interpreted to indicate stepwise acyl transfer mechanism, but with the hydrogen bonded four center type transition state for benzylamine. The relatively greater magnitudes of ${\rho}XZ$ and the secondary kinetic isotope effects involving deuterated nucleophiles are in line with the proposed mechanism.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.4
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• pp.566-572
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• 2019

This paper proposes a new composite guidance law that can intercept moving targets and satisfy look angle rate constraint. In order to obtain the composite guidance law, we first develop a new look angle rate control guidance law which can maintain the maximum look angle rate limitation. And then, we propose the composite guidance scheme on the basis of the look angle rate control guidance and the proportional navigation guidance. To investigate the capturablity and characteristics of the proposed guidance, we also derive closed-form solutions and perform various numerical simulations. The proposed composite guidance only requires the line-of-sight rate, closing velocity, and missile's speed, thereby easily implementing in practical homing missiles.