• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.823-831
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• 2011

According to the development of loading equipments, it is usual to change or replace the existing stores. It has been known that pylon-mounted under stores strongly affect aircraft dynamics characteristics due to the change of aerodynamics. To predict the aerodynamics and aero-elasticity is essentially requested with considering the configuration and shape of external stores during the development of aircraft and/or external stores. In this paper, computational fluid dynamics and computational structure dynamics interaction methodology are applied for prediction of aerodynamic characteristics for F-5 aircraft's horizontal tail with various shape of external stores. FLUENT and ABAQUS were used to calculate fluid and structural dynamics. Code-bridge was made base on the globally supported radial basis function to execute interpolation and mapping. As a result, even though the aeroelasticity of the horizontal tail slightly changes according to the shape of external store, the flutter was not occurred at the considered flight conditions in this study.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.5 s.170
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• pp.130-137
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• 2005

Recently, the importance of CAE research is growing with the advances of the automotive and computer industry. In addition, multi-body dynamics and powertrain analysis are the most important factors in improving the vehicle design. Since engine torque with curve-data was used for analyzing full car simulation in the multi-body dynamics system for many years, it is impossible to assess the concurrent analysis of the engine and powertrain element included in a real full car system. In powertrain, since vehicle are usually modeled as a simple mass and a inertia, they can not be seen as real cars. Moreover, it is hard to obtain additional dynamics data other than the longitudinal velocity value in movement. Because of the reason that was previously discussed, it is necessary to consolidate the two parts as one routine program for design and development through the coordinate system connectivity, and presented here is a program named O-DYN. Using an object-oriented language C++, this program has a good structure with the valuable characteristics of objectivity, inheritance, and reusability. The reliability of this multi-body dynamics program is examined by DADS, which is the general dynamics program, using DAE solver and PECE integral function with the common coordinator separation method. As a result, we can obtain a better solution and total dynamics data in either area through this process. This program will be useful for analyzing full car simulation with powertrain.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.343-348
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• 2007

Molecular dynamics study of thermal NIL (Nano Imprint Lithography) process is performed to examine stamp-resist interactions. A layered structure consists of Ni stamp, poly-(methylmethacrylate) thin film resist and Si substrate was constructed for isothermal ensemble simulations. Imposing confined periodicity to the layered unit-cell, sequential movement of stamp followed by NVT simulation was implemented in accordance with the real NIL process. Both vdW and electrostatic potentials were considered in all non-bond interactions and resultant interaction energy between stamp and PMMA resist was monitored during stamping and releasing procedures. As a result, the stamp-resist interaction energy shows repulsive and adhesive characteristics in indentation and release respectively and irregular atomic concentration near the patterned layer were observed. Also, the spring back and rearrangement of PMMA molecules were analyzed in releasing process.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.4
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• pp.730-734
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• 2013

The dynamic simulation of machine tools and motion control systems has been widely used for optimization, design verification, control design, etc. There are three main streams in dynamic simulation: structural dynamic analysis based onthe finite element method, dynamic motion analysis based on equations of motion, and control system analysis based on transfer functions. Generally, one of these dynamic simulation methods is chosen and employed for specific purposes. In this study, an integrated dynamic simulation is introduced, in which the structure, motion, and control dynamics are combined together. Commercially well-known software is used in the integrated dynamic simulation: ANSYS, ADAMS, and Matlab/Simulink. Using the integrated dynamic simulation, the dynamics of a magnetic bearing stage is analyzed and the causes of oscillation and noise are identified. A controller design for suppressing a flexible dynamic mode is carried out and verified through the integrated dynamic simulation.

• Journal of Technology Innovation
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• v.11 no.2
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• pp.283-314
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• 2003

The transformation of sector system in Information and Communications Technology (ICT), a prominent character in sector system, has been paid much attention in innovation theory with rapid change in information technologies and technological environment. In this context, we explore how Sectoral Innovation System (SIS) in ICT has been transformed since 1970 by employing US patent data and Proxy variables which measures the basic elements for SIS and its technological characteristics. By utilizing patent data, it is demonstrated that technological regimes, key links and Schumpeterian patterns of innovation in overall ICT sector have drastically transformed over the last three decades. We also reviewed how changes of knowledge bases and technological characteristics driving forces of dynamics in ICT help heterogeneous agents interact with environmental factors (Industrial structure and institutions), leading to industrial or economic growth and its dynamics in the historical perspective over ICT sector (Telecommunication, Computer and Semiconductor). Consequently, our research shows clearly that Schumpeterian patterns of innovation have shifted from Mark I to Mark II in ICT. Our study also provides a glimpse picture of dynamics patent data.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.1
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• pp.15-20
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• 2022

An improvement of computational resources with a large scale cluster service is available to the individual person, which has been limited to the original industry and research institute. Therefore, the application of powerful computational resources to the engineering design has been increased fast. In naval and marine industry, the application of Computational Fluid Dynamics, which requires a huge computational effort, to a design of ship and offshore structure has been increased. Floating bodies such as the ship or offshore structure is exposed to ocean waves, current and wind in the ocean, therefore the precise modelling of those environmental disturbances is important in Computational Fluid Dynamics. Especially, ocean waves has to be nonlinear rather than the linear model based on the superposition due to a nonlinear characteristics of Computational Fluid Dynamics. In the present study, a fast reconstruction technique is suggested and it is validated from a series of simulations by using the Computational Fluid Dynamics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.299-299
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• 2011

In this study, transonic aeroelastic response analyses have been conducted for the business jet aircraft configuration considering shockwave and flow separation effects. The developed fluid-structure coupled analysis system is applied for aeroelastic computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. It can give very accurate and useful engineering data on the structural dynamic design of advanced flight vehicles. For the nonlinear unsteady aerodynamics in high transonic flow region, Navier-Stokes equations using the structured grid system have been applied to wing-body configurations. In transonic flight region, the characteristics of static and dynamic aeroelastic responses have been investigated for a typical wing-body configuration model. Also, it is typically shown that the current computation approach can yield realistic and practical results for aircraft design and test engineers.

• Korean System Dynamics Review
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• v.1 no.1
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• pp.103-131
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• 2000

If a system such as a port has a large boundary and complexity, and the system's substance is considered as a black box, forecast accuracy will be very low. Futhermore various components in a port exert significant influence on each other. To copy with these problem the form of structure models were introduced by using SD method. The Competitive Ports Model had several sub-systems consisting of each Unit Port models, and each Unit Port model was made by quantitative, qualitative factors and their feedback loops. The fact that all components of one port have influence on the components of the other ports should be taken into account to construct Competitive Port Models. However, with the current approach that is impossible, and in this paper therefore, models were simplified by HFP adapted to integrate level variables of unit port models. Although many studies on modelling of port competitive situation have been conducted, both theoretical frame and methodology are still very weak. In this study, a new algorithm called ESD(Extensional System Dynamics) for the evaluation of port competition was presented, and applied to simulate port systems in northeast asia.

• Interaction and multiscale mechanics
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• v.6 no.2
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• pp.157-172
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• 2013

This paper presented an investigation of macromolecular suspension in a grooved channel by using the dissipative particle dynamics (DPD) with finitely extensible non-linear elastic (FENE) bead spring chains model. Before studying the movement and evolution of macromolecules, the DPD method was first validated by modeling the simple fluid flow in the grooved channel. For both simple fluid flow and macromolecular suspension, the flow fields were analyzed in detail. It is found that the structure of the grooved channel with sudden contraction and expansion strongly affects the velocity distribution. As the width of the channel reduces, the horizontal velocity increases simultaneously. Vortices can also be found at the top and bottom corners behind the contraction section. For macromolecular suspension, the macromolecular chains influence velocity and density distribution rather than the temperature and pressure. Macromolecules tend to drag simple fluid particles, reducing the velocity with density and velocity fluctuations. Particle trajectories and evolution of macromolecular conformation were investigated. The structure of the grooved channel with sudden contraction and expansion significantly influence the evolution of macromolecular conformation, while macromolecules display adaptivity to adjust their own conformation and angle to suit the structure so as to pass the channel smoothly.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1469-1478
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• 2014

Use of acetonitrile in electrolytes promotes better operation of supercapacitors. Recent efforts show that electrolytes containing acetonitrile can also function in a wide range of operating temperatures. Therefore, this paper addresses the dielectric relaxation processes, structure and dynamic properties of the bulk acetonitrile at various temperatures. Systems of acetonitrile were modeled using canonical ensemble and simulated by employing Molecular Dynamics method. Results show that interactions among the molecules were correlated within a cut-off radius while parallel and anti-parallel arrangements are observed beyond this radius at relatively high and low temperatures respectively. Furthermore, effects of C-C-N and C-H bending modes were greatly appreciated on the power spectral density of time rate change of dipole-dipole correlations whereas frequency shifts were observed on all modes at the lowest temperature under consideration. Linear variations with temperature were depicted for reorientation times and self-diffusion coefficients. Shear viscosity was also computed with a good accuracy within a certain range of the temperature as well.