• Journal of Science Education
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• v.35 no.2
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• pp.283-294
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• 2011

The purpose of this study were to develop a tutorial for secondary students to understand of basic concepts of special relativity, which is appropriate for the cognition level of secondary student. We developed the concept evaluation tool and the tutorial material. Result from pretest and post-test are presented to verify the effect of the tutorial for helping student understanding of the concept such as time, event, reference frame, relativity of simultaneity. Secondary student had intense cognitive conflict about the complex concepts such as simultaneity, length contraction and time expansion. This tutorial could be proposed methodology to overcome cognitive difficulty for understanding these concepts.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.271-275
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• 2014

A New Single Phase Active Power Filter Controller is proposed using Rotating Synchronous Frame d-q transformation. Instantaneous Active Power is calculated using d-q transformation. Average Value of Instantaneous Active Power is obtained using Low Pass Filter. Because power factor is corrected, source current is in phase with source voltage. Amplitude of source current is calculated using single phase power formula. Reference signal of compensated current of Active power filter is obtained from source current reference signal minus load current. Simulation is performed using hysteresis current controller in proposed new controller. Simulation result shows that because active power filter compensates load current, source current is in phase with source voltage and source current is sinusoidal. And Hilbert transformer is builded using all pass filter.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.3
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• pp.20-31
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• 2008

In this paper, we propose a single view-based technique for the estimation of human height and position. Conventional techniques for the estimation of 3D geometric information are based on the estimation of geometric cues such as vanishing point and vanishing line. The proposed technique, however, back-projects the image of moving object directly, and estimates the position and the height of the object in 3D space where its coordinate system is designated by a marker. Then, geometric errors are corrected by using geometric constraints provided by the marker. Unlike most of the conventional techniques, the proposed method offers a framework for simultaneous acquisition of height and position of an individual resident in the image. The accuracy and the robustness of our technique is verified on the experimental results of several real video sequences from outdoor environments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.437-442
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• 2012

To analyze a multibody system, this paper proposes an implicit numerical integration method for joint coordinates subsystem synthesis method. To verify the proposed method, a multibody model for an unmanned robot vehicle, which consists of six identical independent suspension systems, is developed. The symbolic method is applied to compute the system Jacobian matrix for the implicit integration method. The proposed method is also verified by performing rough terrain run-over simulation in comparison with the conventional implicit integration method. In addition, to evaluate the efficiency of the proposed method, the CPU time obtained by using this method is compared with that obtained by using the conventional implicit method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.22-30
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• 1989

Wave propagation is changed by the effect of shoaling, current-depth refraction and shelter-ing etc. To solve these problems. numerous models have been developed. In the present study, a coordinate system is proposed based on the wave ray equation with the wave number equation including diffraction effects . The governing equation for the study was derived from the mild slope wave equation in non-steady state, including current effects (Kirby, 1986a) and trans-formed into an orthogonal curvilinear coordinate system on the basis of the wave ray equation. To obtain a numerical solution, an explicit finite difference scheme was used, and solved by the relaxation method. This model was tested for various cases: Firstly a submersed circular shoal and a constant unit depth. Secondly a submerged elliptic shoal on a slope, and finally a breakwater harbour with obliquely incident waves on a slope. The model was found to simulate the experimental results and other theoretical results in wave height and wave angle fairy well, and the applicability of the model around an arbitrary shaped coastal structure was also verified. To demonstrate the general usefullness of the present approach , the model is to be applied to a field situation with a complex bed topography.

• Journal of the Korea Society of Computer and Information
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• v.16 no.8
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• pp.49-56
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• 2011

Recently, animation contents has become extensively available along with the development of cultural industry. In this paper, we propose a method to analyze a face of animation character and extract 3D rotational information of the face. The suggested method first generates a dominant color model of a face by learning the face image of animation character. Our system then detects the face and its components with the model, and establishes two coordinate systems: base coordinate system and target coordinate system. Our system estimates three dimensional rotational information of the animation character face using the geometric relationship of the two coordinate systems. Finally, in order to visually represent the extracted 3D information, a 3D face model in which the rotation information is reflected is displayed. In experiments, we show that our method can extract 3D rotation information of a character face reasonably.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.40.1-40.1
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• 2009

미래 한국의 달궤도선 임무에 대비하여 달 근접 궤도 전파기인(orbit propagator) YSPLOP ver. 1(Yonsei Lunar Precise Orbit Propagator version 1)을 개발 하였다. 개발된 궤도 전파기의 성능은 상용 소프트웨어인 STK Astrogator를 이용하여 검증되었다. 개발된 궤도 전파기를 이용, 달 궤도선의 운용에 있어서 다양한 섭동력들이 궤도선의 수명(orbital decay)에 미치는 영향을 분석하였다. YSPLOP ver. 1은 정밀한 달 중심 탐사선의 위치산출을 위하여 M-EME2000 (Moon-Centered, Earth Mean Equator and Equinox of J2000) 좌표계, M-MME2000 (Moon-Centered, Moon Mean Equator and IAU vector of epoch J2000) 좌표계 그리고 M-MEPMD (Moon-Centered, Moon Mean Equator and Prime Meridian) 좌표계를 이용하여 탐사선의 상태(state) 정보를 산출한다. 또한 태양, 지구, 달, 화성, 목성의 중력에 의한 섭동력 및 태양풍에 의한 영향을 포함할 수 있도록 설계되었으며, 달 근접 궤도선의 궤도 운동에 가장 큰 영향을 미칠 수 있는 섭동력인 달의 비대칭 중력장에 의한 영향 또한 고려하도록 하였다. 달의 비대칭 중력장 모델 (Lunipotential model)은 LP165p 모델이 사용되었으며 행성의 정밀한 위치 산출을 위하여 JPL의 DE405 천체력이 사용되었다. 개발된 궤도 전파기를 이용, 달고도 100 km, 궤도 경사각 $90^{\circ}$인 달 중심의 극궤도를 약 30일 동안 전파한 결과, YSPLOP ver. 1의 성능은 STK Astrogator와 비교하여 보았을 때 약 수 m의 오차를 보이는 것으로 확인되었다. 달의 극궤도 탐사선의 궤도 수명을 분석한 결과, 최소한 달의 비대칭 중력장이 70 by 70 이상으로 고려되어야 함을 확인하였으며 이때 달 궤도선의 수명은 약 160일으로 나타났다. 아울러 달 근접 환경에서의 지구 중력에 의한 섭동력은 달 궤도선의 운동에 있어서 무시 할 수 없는 정도의 많은 영향을 끼치고 있음을 확인하였다. 이 연구를 통하여 개발된 궤도 전파기는 미래 한국의 달 궤도선 및 착륙선의 임무 설계시 사용 될 수 있다. 또한 이 연구에서 제시된 달 근접 환경에서의 다양한 섭동력들이 달 궤도선의 운동에 미치는 영향에 대한 해석 결과는 추후 달 근접 임무 설계시 고려되어야 하는 섭동력들의 기본 사양을 제공할 것이다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.1
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• pp.39-45
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• 2007

In this paper, a research has been conducted to find out the optimal combination of central meridian and scale factor of UTM-K to apply for the whole area of Korean peninsula. For this research, various combinations of central meridian and stale factor are set up and the cumulated level or distortion for each combination has been computed and compared to each other. In the case of using the central meridian and scale factor defined in the present UTM-K, the level of distortion shows about $47.0837{\times}10^{-2}$. On the other hand, the minimum distortion which is about $21.0495{\times}10^{-2}$ can be obtained when the $127^{\circ}26'$ for the central meridian and 0.99991 for scale factor are used for computation. Consequently, we can conclude that later result is the optimum combination of central meridian and scale factor for the Korean peninsula.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.80-86
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• 1994

A numerical method for simulations of inviscid incompressible flow fields around a ship advancing on the free surface is developed. A body fitted coordinate system, generated by numerically solving elliptic type partial differential equations is used to conform the ship and free surface configurations. Three dimensional Euler equations transformed to the non-staggered body fitted coordinate system are discretised by finite difference method. Time and spatial derivatives are discretised by forward and centered differencings, respectively, and artificial dissipations are added to discretised convection terms for improvements of numerical stability. At each time steps, free surface elevations are recomputed to satisfy nonlinear free surface conditions. Poisson equations for pressure field are solved iteratively and the velocity field for next time step is extrapolated. To verify the developed numerical method, flow fields around a Wigley model are simulated(Fn=0.250-0.408) and compared with experimental data to show good agreements.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.4
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• pp.548-555
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• 2022

This paper describes the hardware implementation of elliptic curve cryptography (ECC) used as a core operation in elliptic curve digital signature algorithm (ECDSA). The ECC processor supports eight operation modes (four point operations, four modular operations) on the NIST P-521 curve. In order to minimize computation complexity required for point scalar multiplication (PSM), the radix-4 Booth encoding scheme and modified Jacobian coordinate system were adopted, which was based on the complexity analysis for five PSM algorithms and four different coordinate systems. Modular multiplication was implemented using a modified 3-Way Toom-Cook multiplication and a modified fast reduction algorithm. The ECC processor was implemented on xczu7ev FPGA device to verify hardware operation. Hardware resources of 101,921 LUTs, 18,357 flip-flops and 101 DSP blocks were used, and it was evaluated that about 370 PSM operations per second were achieved at a maximum operation clock frequency of 45 MHz.