• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.2
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• pp.45-53
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• 2002

This paper presents an algorithm for the appropriate parameter selection of a power system stabilizer and power converters in two-area power systems with a series HVDC links. The method for PSS is one of the classical techniques by allocating properly poly-zero positions to fit as closely as desired the ideal phase lead and by changing the gain to produce a necessary damping torque. Proper parameter of power converters are obtained in order to have sufficient speed and stability margin to cope with changing reference values and disturbances based on the Root-locus technique. The small signal and transient stability studies using the PSS and power converters parameters obtained from these methods show that a natural oscillation frequency of the study case system is adequately damped. The simulation used in the paper was performed by the Power System Toolbox software program based on MATLAB.

• Journal of the Korean Magnetics Society
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• v.23 no.2
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• pp.54-61
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• 2013

Ferromagnetic material's residual magnetization is remained because of the interaction between domains from external apply field, so the electrical and electronic industry and area of defense development request deperm protocol which makes the residual magnetization to 0. But the deperm protocols which are used theses days are developed by using only experience and experiment, so we have to develop deperm protocol considering hysteresis curve. In this paper, Anhysteretic Deperm, Deperm-ME, Flash-Deperm were analyzed using two dimensional finite element method and Preisach model that was formulated by property of magnetic materials. From that analysis, the relations between hysteresis curve and deperm variable are compared by analyzing the trace of Preisach plane. Also, an efficient current ratio of deperm protocol, is proposed.

• Communications of Mathematical Education
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• v.15
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• pp.273-280
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• 2003

1983년 말 중국 형주시 소재 강릉장가산 247호 묘에서 죽간의 형태로 출토된 ${\ulcorner}$산수소${\lrcorner}$ 는 그것이 엮어진 시점이 유휘의 ${\ulcorner}$구장산술${\lrcorner}$ 보아 최소한 450년 가량이나 거슬러 올라간다는 점에서 동야수학사의 기원을 크게 앞당기게 하는 막중한 의의를 지니는 문서가 아닐 수 없다. 그러나 석문 자체가 최근 들어와서야 겨우 공개되었을 뿐, 현재로서는 자료에 대한 평가와 내용 분석은 물론, 변역마저도 제대로 이루어지지 못한 상태에 있다. 이 글은 ${\ulcorner}$산수서${\lrcorner}$ 와 ${\ulcorner}$구장산술${\lrcorner}$ 의 내용을 배교하여 ${\ulcorner}$산수서${\lrcorner}$ 의 특징을 밝히는 동시에 동양수학의 초창기 발달의 궤적을 더듬어 보려는 시도이다. ${\ulcorner}$산수서${\lrcorner}$ 는 '상승(相乘)'에서 '이전(里田)'까지 이어지는 70개 제명(題名)하에 서술되어 있는데, 제명들은 주제를 나타내는 것과 산법을 나타내는 것을 혼재하는 것으로 나타난다. 내용 가운데에는 '여직(女織)', '우시(羽矢)', '소광(少廣)' 등이 문제처럼 ${\ulcorner}$구장산술${\lrcorner}$ 의 그것들과 기본적으로 같거나 유사한 것들이 다수 발견되어 고대수학 전통의 연속성을 엿볼 수 있게 하지만, 동시에 의료수가 문제인 '의(醫)'처럼 ${\ulcorner}$산수서${\lrcorner}$에서만 발견되는 것들도 더러 눈에 띈다. ${\ulcorner}$산수서${\lrcorner}$ 와 ${\ulcorner}$구장산술${\lrcorner}$ 사이에 이루어진 수학 발달은, 이를테면, 제급근 사이에 있어서 전자의 경우에는 $\sqrt{240}$을 $15\frac{15}{31}$로 계산한 데서도 드러나듯이 보간법에 의존한 반면, 후자의 경우에는 온답을 제시하는 데 하등의 어려움을 겪지 않았다는 차에서도 확인된다.

• Atmosphere
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• v.24 no.2
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• pp.245-251
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• 2014

Statistical trajectory analysis has been widely used to identify potential source regions for chemically and radiatively important chemical species in the atmosphere. The most widely used method is a statistical source-receptor model developed by Stohl (1996), of which the underlying principle is that elevated concentrations at an observation site are proportionally related to both the average concentrations on a specific grid cell where the observed air mass has been passing over and the residence time staying over that grid cell. Thus, the method can compute a residence-time-weighted mean concentration for each grid cell by superimposing the back trajectory domain on the grid matrix. The concentration on a grid cell could be used as a proxy for potential source strength of corresponding species. This technical note describes the statistical trajectory approach and introduces its application to estimate potential source regions of $CO_2$ enhancements observed at Korean Global Atmosphere Watch Observatory in Anmyeon-do. Back trajectories are calculated using HYSPLIT 4 model based on wind fields provided by NCEP GDAS. The identified $CO_2$ potential source regions responsible for the pollution events observed at Anmyeon-do in 2010 were mainly Beijing area and the Northern China where Haerbin, Shenyang and Changchun mega cities are located. This is consistent with bottom-up emission information. In spite of inherent uncertainties of this method in estimating sharp spatial gradients within the vicinity of the emission hot spots, this study suggests that the statistical trajectory analysis can be a useful tool for identifying anthropogenic potential source regions for major GHGs.

• Journal of the Korea Society for Simulation
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• v.20 no.1
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• pp.51-59
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• 2011

This paper is concerned with locomotion of dog-like quadruped robots that can adapt to various terrains, mainly dealing with implementation methods and characteristics of static and dynamic gaits. To this end, a 12-DOF robot is built in house, motional trajectories of its body and feet are generated mimicking biological life, and the corresponding leg joint angles are analytically obtained by inverse kinematics. Such joint angle data are then applied to the robot's ADAMS model for computer simulations so that the planned walk and trot gaits are both confirmed dynamically stable. However, contrary to the simulation results, previous trot patterns showed unstable behavior during experiments. This problem led us to analyze the reason, and in the course we discovered the importance of maximally utilizing the concept of WSM rather than ZMP and therefore reducing the gait period to secure the stability of dynamic gaits such as trot.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.6
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• pp.749-754
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• 2009

Two gait generation methods using GP(genetic programming) and CPG(Central Pattern Generator) are compared to develop a fast locomotion for quadruped robot. GP based technique is an effective way to generate few joint trajectories instead of the locus of paw positions and lots of stance parameters. The CPGs are neural circuits that generate oscillatory output from a input coming from the brain. Optimization for two proposed methods are executed and analysed using Webots simulation for the quadruped robot which is built by Bioloid. Furthermore, simulation results for two proposed methods are experimented in real quadruped robot and performances and motion features of GP and CPG based methods are investigated.

• Journal of Navigation and Port Research
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• v.28 no.8
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• pp.735-743
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• 2004

A bridge which connects Mokpo North Harbor and Goha Island is going to be constructed until 2009. For the bridges being built in the navigable water area, it is indispensible to carry out vessel traffic safety assessment from the viewpoint of shiphandlers, however, there exist no specific guidelines for the necessary conditions which the bridge designers can rely on. In this paper, traffic safety assessment procedures for the layout of the bridge are briefly introduced, and the conditions which should be taken into account at the initial design stage of the bridge are surveyed For the safety assessment of the bridge design, ship navigation simulations, such as RTS( real time simulation) and FTS(fast time simulation), are carried out, the results of which are statistically analysed to estimate the probability of collision between the ship and the pier of the bridge.

• Journal of the Korea Society of Computer and Information
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• v.16 no.7
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• pp.25-34
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• 2011

In this paper, we propose a new golf putting training system which we call "X-Putt". X-Putt analyzes putting strokes by measuring putter face angle and path. To do this, we improved the sonar-based localization scheme used by previous localization techniques. As a result, X-Putt can measure putter's location within the error range, ${\pm}0.9cm$ and putter face angle within ${\pm}1.5^{\circ}$. Additionally, we built an user application that has an easy-to-use interface for analyzing the strokes after training.

• Journal of the Korea Convergence Society
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• v.11 no.5
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• pp.175-182
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• 2020

The calculation of the optimal trajectory of the stepped top-down robot was made using a genetic algorithm and a computational torque controller. First, the total energy efficiency was minimized using the Red-Cold Generic Algorithm (RCGA) consisting of reproductive, cross, and mutation. The reproducibility condition related to the position assembly of the start and end of the stride and the joints, angles, and angular velocities are linear constraints. Next, the unequal constraint accompanies the condition for preventing the collision of the swing leg at the corner with the outer surface of the stairs, the condition of the knee joint for preventing kinematic peculiarity, and the condition of no moment in safety in the traveling direction. Finally, the angular trajectory of each joint is defined by fourth-order polynomial whose coefficient is to approximate chromosomes. This is to approximate walking. In this study, the energy efficiency of the optimal trajectory was analyzed by computer simulation through a biped robot with seven degrees of freedom composed of seven links.

• Journal of Biomedical Engineering Research
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• v.19 no.5
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• pp.495-502
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• 1998

A mathematical model of viscoelasticity on the material property of human pharyngeal tissue utilizing Y.C. Fung's Quasi-linear viscoelastic theory is proposed based on cyclic load, stress relaxation, incremental load, and uniaxial tensile load tests. The material properties are characterized and compared with other biological materials' results. The mathematical model is proposed by combining two characteristic functions determined from the stress relaxation and uniaxial tensile load tests. The reduced stress relaxation function G(t) and elastic response function S(t) are obtained from stress relaxation test and uniaxial tensile load test results respectively. Then the model describing stress-time history of the tissue is implemented utilizing two functions. The proposed model is evaluated and validated by comparing the model's cyclic behaviour with experimental results. The model data could be utilized as an important information for constructing 3-dimensional biomechanical model of human pharynx using FEM(Finite Element Method).