• Journal of Institute of Control, Robotics and Systems
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• v.8 no.2
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• pp.158-166
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• 2002

A mathematical model and dynamic characteristics ova continuously variable damper for semi-active suspen- sion systems are investigated. After analyzing the geometry of a typical continuously variable damper, mathematical models fur individual components including piston, orifices, spring, and valves are first derived and then the flow equations for extension and compression strokes are investigated. To verify the developed mathematical model, the dynamic response of the model are simulated using MATLAB/SIMULINK and are compared with experimental results. The proposed model can be used not only for mechanical components design but also for control system design.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.06a
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• pp.15.1-21
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• 1999

Radiosity method is a global illumination model for image synthesis. It computes all energy interactions among diffuse elements in a virtual environment. One of the major drawbacks if its time consuming computation. Existing radiosity algorithms for static scene is difficult to be applicable to dynamic environments. In this paper we proposed an hierarchical scene partition scheme to speedup the link update computations in the dynamic environments. Since the proposed spatial data structure is global, it not only can be used to speedup the culling of non-affected links after geometry change, but also can be used to accelerate the subsequent visibility computation. Several empirical tests are given to show the efficiency of our improved algorithm.

• Communications of Mathematical Education
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• v.18 no.2 s.19
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• pp.383-410
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• 2004

DGS(dynamic Geometry System)와 WBI(Web Based Instruction)를 고찰해보고, 동적 기하 프로그램의 대표적인 프로그램인 GSP, Cabri, Cinderella를 이용하여 WBI를 제작해 보고 웹 환경 하에서 세 프로그램의 효율성을 비교 ${\cdot}$ 분석하였으며, 이들 세 프로그램의 장점을 정리하여 웹 환경에서 동적 기하 프로그램의 개선 방향을 제시하였다.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.517-524
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• 1998

A liner numerical model of the wheel-rail interation and the track geometry is developed for multi-body dynamics program. The simulation results are very simulation to these of VAMPIRE simulation. This program can be used for the analysis of train dynamic performance.

• Korean Institute of Interior Design Journal
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• v.19 no.5
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• pp.83-94
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• 2010

Conventionally, ornament has developed around linear thinking based on Euclidean geometry, and been explained as simple and lucid natural Euclidean geometrical phenomena. The modular arrangement with vertical, horizontal and diagonal grids has been an organizing principle of classical ornament, but in digital era ornament is found not to be explained only with the principle of traditional arrangement due to the seemingly irregular complex forms. In that sense, this study presents the concept of digital ornament and examined the backgrounds of ornament in digital age, that are complex system and non-Euclidean geometry. Accordingly, the present study takes an approach by dividing new formal types of ornament into algorithmic form, hybrid form and dynamic form to find out a principle of pattern organization. Lately, architects who actively use computer for their architectural designs take the algorithmic strategies in nature and create various and complex patterns by simple rules. The patterns are not the repetition of the same, but the production of singularities. In addition, hybrid form by morphing shows a topologically flexible evolutionary transformation, and is used to create in-between transitional shapes from the source to target. Finally, the patterns by the interaction between the system components which are corresponded to the embedded forces emerge from dynamic simulation of the natural environment. Rather than objects itself, focus is given to the process of generating forms, and the ornamental patterns as the revelation of such implicit order provide not just the formal beauty but also spatial pathways for lights and air, maximizing the effects of lights.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.5
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• pp.38-48
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• 2004

Recently the use of high-speed equipment in machine-tool industry has greatly increased, which requires the development of prognostics and prediction methods on the design stage. Conversion of the test/experiments stage from real to virtual reality will not only significantly reduce the design and manufacturing cost, but will also increase design quality. This paper shows how it is possible to develop the automated system for the design calculations of the air-bearing spindles. First, the general calculation method is introduced. It contains several steps, namely, geometry identification, pressure calculation, stiffiness calculation, dynamics characteristics calculation. For geometry identification reducing spindle shaft to rings was proposed, which helps to automate the calculation process. For pressure calculation the Peshti method was implemented. For stiffiness calculation the analysis was made, which shown the necessity of correct calculation step selection. Then the system of ordinary differential equations containing influence coefficients was evolved, which is used for trjectories calculation. The graphical representation of the calculation results shows the dynamic behavior of the spindle unit concerning various working conditions. Finally, this automated system is illustrated by an example of the air-bearing spindle calculation.

• School Mathematics
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• v.13 no.3
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• pp.525-542
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• 2011

As teachers need to understand how to select and use technology in mathematics education, analysis on history, characteristics, and effects of various technology used in school mathematics will facilitate effective use of technology. This thesis aims to analyze through literary studies the history, characteristics, and effects of using spreadsheets Excel, dynamic geometry softwares GSP, Cabri and CAS, the most commonly used technology in teaching and learning mathematics in Korea. And we also study the current trends on using technology in mathematics education in Korea by investigating research trend, secondary mathematics curriculums past and present in Korea, mathematics textbooks, and classroom environments.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.10
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• pp.1166-1173
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• 2011

There have been many researches about SUGV (Small Unmanned Ground Vehicle) mechanism regarding off-road mobility and obstacle negotiation. This paper introduces an analysis of geometry parameters to enhance the vertical obstacle negotiation ability for the SUGV. Moreover, this paper proposes an anti-shock structure analysis of wheels to protect the main body of the SUGV when it falls off a vertical obstacle. Major system geometry parameters will be determined under certain constraints. The constraints and optimization problem for maximizing the ability of vertical obstacle negotiation will be presented and discussed. Dynamic simulation results and experiments with manufactured platform will also be presented to validate the analysis. Several types of wheel materials and structures will be compared to determine the best anti-shock wheel design through FEM (Finite Element Method) simulations.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.190-194
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• 2007

The forging process design and microstructure evolution for gas turbine disk of a Waspaloy is investigated in this study. Parameters related to deformation are die and preform geometry, and forging temperature of die and workpiece. Die and preform design are considered to reduce the forging load, and to avoid the forging defects. Blocker and finisher dies for multistage forging are designed and the initial billet geometry is determined. The control of hot forging parameters such as strain, strain rate and temperature also is important because the microstructure change in hot working affects the mechanical properties. The dynamic recrystallization evolution has been studied in the temperature range 900-$1200^{\circ}C$ and strain rate range 0.01-1.0s-1 using hot compression tests. Modeling equations are required represent the flow curve, recrystallized grain size, recrystallized volume fraction by various tests. In this study, we used to thermo-viscoplastic finite element modeling equation of DEFORM-2D to predict the microstructure change evolution during thermo-mechanical processing. The microstructure is updated during the entire thermal and deformation processes in forging.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2838-2858
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• 2019

Traditional channel models for vehicle-to-vehicle (V2V) communication usually assume fixed velocity in static scattering environment. In the realistic scenarios, however, time-variant velocity for V2V results in non-stationary statistical properties of wireless channels. Dynamic scatterers with random velocities and directions have been always utilized to depict the non-stationary statistical properties of the channel. In this paper, a non-stationary geometry-based cooperative scattering channel model is proposed for multiple-input multiple-output (MIMO) V2V communication systems, where a birth-death process is used to capture the appearance and disappearance dynamic properties of moving scatterers that reflect the time-variant time correlation and Doppler spectrum characteristics. Moreover, our model has more straight and concise to study the impact of the vehicular traffic density on channel characteristics and thus avoid complicated procedure in deriving the analytical expressions of the channel parameters and functions. The numerical results validate our analysis and demonstrate that setting important parameters of our model can appropriately build up more purposeful measurement campaigns in the future.