• International Journal of Aeronautical and Space Sciences
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• v.17 no.2
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• pp.204-213
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• 2016

A differential game theory based approach is used to develop an automated maneuver generation algorithm for Within Visual Range (WVR) air-to-air combat of unmanned combat aerial vehicles (UCAVs). The algorithm follows hierarchical decisionmaking structure and performs scoring function matrix calculation based on differential game theory to find the optimal maneuvers against dynamic and challenging combat situation. The score, implying how much air superiority the UCAV has, is computed from the predicted relative geometry, relative distance and velocity of two aircrafts. Security strategy is applied at the decision-making step. Additionally, a barrier function is implemented to keep the airplanes above the altitude lower bound. To shorten the simulation time to make the algorithm more real-time, a moving horizon method is implemented. An F-16 pseudo 6-DOF model is used for realistic simulation. The combat maneuver generation algorithm is verified through three dimensional simulations.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.768-773
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• 2005

We present an overview of our new method of liquid crystal (LC) alignment based on the anisotropic etching of the alignment layers with a directed plasma flux. The method is realized by the use of anode layer source of "race track" geometry generating two "sheets" of accelerated plasma. These sheets are directed obliquely to the treated substrates. The static and dynamic irradiation regimes have been explored. The optimized processing conditions and materials are discussed. The technique yields an excellent uniformity of liquid crystal alignment of planar, tilted and vertical types. It is shown that the new method can be easily adapted for the alignment treatment of large area substrates used in the modern LCD manufacturing process.

• Journal of Ship and Ocean Technology
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• v.4 no.2
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• pp.13-23
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• 2000

A low-order potential based boundary element method is applied to the prediction of the flow around the cavitating propeller in steady or in unsteady inflow. For given cavitation number, the cavity shape is determined in an iterative manner until the kinematic and the dynamic boundary conditions are both satisfied on the approximate cavity boundary. In order to improve the solution behavior near the tip region, a hyperboloidal panel geometry and a modified split panel method are applied. The method is then extended to include the analysis of time-varying cavitating flows around the propeller blades via a time-step algorithm in time domain. In the method, the steady state oscillatory solution is obtained by incremental stepping in the itme domain. Finally, the present method is validated through comparison with other numerical results and experimental data.

• International Journal of Railway
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• v.7 no.2
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• pp.46-56
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• 2014

The superstructure of the railway track undertakes the forces that develop during train passage and distributes them towards its seating. The track panel plays a key role in terms of load distribution, while at the same time it maintains the geometrical distance between the rails. The substructure and ballast undergo residual deformations under high stresses that contribute to the deterioration of the so-called geometry of the track. The track stiffness is the primary contributing factor to the amount of the stresses that develop on the substructure and is directly influenced by the fastening resilience. Four methods from the international literature are used in this paper to calculate the loads and stresses on the track substructure and the results are compared and discussed. A parametric investigation of the stresses that develop on the substructure of different types of railway tracks (i.e. balastless vs ballasted) is performed and the results are presented as a function of the total static track stiffness.

• East Asian mathematical journal
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• v.30 no.4
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• pp.475-491
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• 2014

We can easily see the 'cycloid slide' in the many mathematics and science museums. The educational materials, however, do not give us any mathematical principle. For this reason, we, in this thesis, first study the brachistochrone problem in the history of mathematics, and suggest a method of how to teach the principle using 'the dynamic geometry software GSP5' in order to help students understand the idea that the cycloid is the brachistochrone. Secondly, we examine the origin of the calculus of variations and apply it to prove the brachistochrone problem in order to build up the teachers' background knowledge. This allows us to increase the worth of history of mathematics and recognize how useful the learning is which uses technological tools or materials, and we can expect that the learning which makes use of cycloid slide will be meaningful.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.458-461
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• 2009

Thermo-mechanical simulation of the Friction Stir Spot Welding (FSSW) processes was performed for the AA5083-H18 sheets, utilizing commercial Finite Element Method (FEM) and Finite Volume Method (FVM) which are based on Lagrangian and Eulerian formulations, respectively. The Lagrangian explicit dynamic FEM code, PAM-CRASH, and the Eulerian Computational Fluid Dynamics (CFD) FVM code, STAR-CD, were utilized to understand the effect of pin geometry on weld strength and material flow under the unsteady state condition. Using FVM code, material flow pattern near the tool boundary was analyzed to explain the weld strength difference between the weld by cylindrical pin and the weld by triangular pin, while the frictional energy concept using the FEM code had limitation to explain the weld strength difference.

• The Mathematical Education
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• v.42 no.2
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• pp.177-191
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• 2003

In this paper, we present the theory of computers and mathematics education based on the concept of microworlds for mathematics education. We lust look back some previous papers published in the journal of the Korea society of mathematical education series A and else where. Then we present the new view points regarding mircroworlds and mathematics curriculems, microworlds and mathematics teaching and teaming, microworld based problem centered teaming, and microworld based diagnostics and debuggings. We use JavaMAL microworld that is designed to make LOGO and dynamic geometry system in one microworld to give some examples to explain the necessary mathematics educational needs fur designing microworlds for mathematics education. The JavaMAL microworld is a web based microworld that is programmed using JAVA, and the user on use script language, menus, keyboard, and mouse interaction to use the environment.

• Journal of the Korean Society of Combustion
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• v.14 no.4
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• pp.48-53
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• 2009

This paper describes the forced flame response in a turbulent premixed gas turbine combustor. The fuel was premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. To impose the inlet flow velocity, a siren type modulation device was developed using an AC motor, rotating and static plates. Measurements were made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The test results showed that flame length as well as geometry was strongly dependent upon modulation frequency in addition to operating conditions such as inlet velocity. Convection delay time between the velocity perturbation and heat release fluctuations was calculated using phase information of the transfer function, which agreed well with the results of flame length measurements. Also, basic characteristics of the flame nonlinear response shown in the current test conditions were introduced.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.370-376
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• 2005

This paper is described the program algorithm which can easily estimate dynamics of test support system by using mathematica tool based on the finite element method. We can determine the geometry, dimensions of the test support system, through tool stated in this paper for a certain test conditions. As a result of computer simulation and manufactured test support system's experiment in oder to verify suggested program, the dynamics of the test support system was well correspondent each other.

• Wind and Structures
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• v.4 no.4
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• pp.315-332
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• 2001

Presented herein is a numerical study for evaluating the aerodynamic behaviour of equipped bridge deck sections. In the first part, the method adopted is described, in particular concerning turbulence models, meshing requirements and numerical approach. The validation of the procedure represents the aim of the second part of the paper: the results of the numerical simulation in case of two-dimensional, steady, incompressible, turbulent flow around a realistic bridge deck are compared to the data collected from wind-tunnel tests. In order to demonstrate the influence of the section details and of the partial streamlining of the deck geometry on its aerodynamic behaviour, in the third part of the paper the effect of the fairings and of each item of equipment of the section (such as central barriers, side railings and sidewalks) is evaluated. The study has been applied to the deck section of the Normandy cable-stayed bridge.