• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.555-567
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• 2013

A finite element formulation for a Rayleigh-damped Bernoulli-Euler beam subjected to support motions, which accompanies quasi-static rigid-body motion, is presented by using the quasi-static decomposition method. Moving support beam elements, one of whose nodes is coincident with the moving support, are developed to represent the effect of a moving support. Statically determinate beams subjected to support motions can be modeled successfully by using moving support elements. Examples of cantilever and simply-supported beams subjected to support motions are illustrated, and the numerical results are compared with the analytical solutions. The comparison shows good agreement.

• Composites Research
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• v.14 no.6
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• pp.16-23
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• 2001

Analysis of mechanical behavior for a pultruded-wound hollow rod is presented. For this purpose, the pultruded-wound hollow rod is manufactured by the new winder attached to the conventional pultrusion system. And the conventional pultrusion process is newly altered to manufacture pultruded-wound specimens. A computer program, POST II, is modified to perform this study, In the nonlinear finite element formulation, the updated Lagrangian description method based on the second Piolar-Kirchhoff stress tensor and the Green strain tensor are used. For the finite element modeling of the composite hollow rod, the eight-node degenerated shell element is utilized. In order to estimate the failure, the maximum stress criterion is adopted to the averaged stress in the each layer of the finite elements. As numerical examples, the behavior of glass/up composite hollow rod is investigated from the initial loading to the final collapse. Present finite element results considering stiffness degradation and stress unload due to failure shows excellent agreement with experiments in the ultimate load, failure and deformations.

• Journal of Advanced Navigation Technology
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• v.20 no.6
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• pp.574-579
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• 2016

Unlike general unmanned aerial vehicles, the quad-rotor is attracting the attention of many people because of simple structure and very useful value. However, as the interest in drones increases, the safety and location of vehicles are becoming more important provide against aviation safety accidents or lost accidents. Therefore, in this paper, we propose a tracking system that stabilizes the model with a simple controller by linearized modeling and grasp tilt angle data from various sensor through the filter. The developed tracking system transmits the position of the quad-rotor in flight to the computer and shows it through the route, so it can check the flight path and various information such as flight speed and altitude at the same time. Then the sensor used in the actual quad-rotor can not measure exact sensor data for disturbance and vibration. So we use sensor fusion of Kalman filter and Complementary filter to overcome this problem and the stability of the quad-rotor hovering is realized by PID control. Through simulation, various information such as the speed, position, and altitude of the quad-rotor were confirmed in real time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.323-335
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• 1992

In this paper, an adaptive cosine transform coding scheme which incorporate human visual properties into the coding scheme is investigated. Human vision is relatively sensitive to mid-frequency band, and insensitive to very low and very high frequency band. These property was mathematically modelled with MTF(Modulation Transfer Function) through many psychovisual experiment. DCT transforms energy in spatial domain into frequency domain, so can exploit the MTF very efficiently. Another well-known visual characteristics is spatial masking effect that visibility of noise is less in regions of high activity than in regions of low activity. Proposed coding scheme imploys quantization matrix which represent the properties of these spatial frequency response of human vision, and adaptively quality of an image. To compute the activity index of an image block, simple operation is performed in spatial domain, and according to activity index. block of low activity region is more exactly quantized relatively than that of high activity region. Results showed that, at low bit rate, the subjective quality of the reconstructed images by proposed coding scheme is acceptible than that of coding scheme without HVS properties.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.3
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• pp.243-250
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• 2009

In order to reduce the time needed for design, enterprises recently need the customizing technology that can modify the functions of existing CAD systems according to the their purposes. So most of the companies developing commercial CAD system are providing API to make possible the preparation of macro or external programs, which allow automatic performance of a series of repeated tasks. The objective of the present paper is to achieve more convenient carrying out of a particular modeling, by developing 3D CAD template of the standardized engineering rule of the particular model in order to establish a knowledge-based product development system. The formula, data and design knowledge which are required for the designing of the components of refrigerator were made into a program by means of Unigraphics' UG/Open API. And examples of such a development were presented. By using them in connection with commercial CAD system, design verification and modification were efficiently applied to the product design business.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.65-73
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• 2013

Ground-coupled heat pump system has attracted attention as a promising renewable energy technology due to its improving energy efficiency and eco-friendly mechanism for space cooling and heating. Pipes buried in the ground play a role of direct thermal interaction between circulating fluid inside the pipe and surrounding soils in the geothermal exchange system. However, both complexities of turbulent flow coupling thermal-hydraulic phenomena and very long aspect ratio of the pipe make it difficult to model the heat exchange system directly. Energy balance for fluid flow inside the pipe was derived to model thermal-hydraulic phenomena, and one-dimensional pipe element was proposed through Galerkin formation and time integration of the equation. Developed element is combined to pre-developed FEM code for THM phenomena in porous media. Numerical results of Thermal Response Test showed that line-source model overestimates equivalent thermal conductivity of surrounding soils due to thermal interaction between adjacent pipes and finite length of the pipe. Thus, inverse analysis for the TRT simulation was conducted to present optimal transformation matrix with utmost convergence.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.9
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• pp.938-943
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• 2014

The scattered field by a gap/crack on the PEC surface of a large object having low-observable RCS cannot be negligible, but may not be analyzed by the known high-frequency technique. If the electrical width of the crack is very small, the crack can be modeled by an impedance strip, whose scattering formulation can be analytically obtained based on a low-frequency approximation. The scattering solution is formulated for the 2D strip and TE(Transverse Electric) or TM(Transverse Magnetic) wave incidence, from which a 3D ILDC(Incremental Length Diffraction Coefficients) can be extracted. Using the ILDC formulation, the scattering by any arbitrary shaped crack can be estimated. In this paper, an improved ILDC equations are proposed, which combine the known TE and TM solutions. The improved accuracy of the proposed solution is numerically verified.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.455-461
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• 2004

Effects of the different strengths and intervals of the periodic outer water intrusions (kyuchos and bottom intrusions) on the dynamics of phytoplankton biomass in a small embayment were examined with a simple numerical model. Environmental conditions of Kitanada Bay in the Bungo Channel were applied to the model. As the interval of the intrusion became longer and the amplitude became smaller, phytoplankton biomass In the bay became higher. On the other hand, as the interval became shorter and the amplitude became larger, the growth rate of the phytoplankton became higher. It suggested that when the intrusion was weaker, water exchange of the bay decreased and the phytoplankton in the bay accumulated at a high density, When water exchange was improved by active intrusions, availability of light would become more efficient and the growth rate of the phytoplankton was enhanced.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1354-1361
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• 2007

The evacuation simulation study was performed with the boundary condition of a fire simulator, referring to Dae-gu Subway Fire Accident which was a real station fire. The subway station was modelled from B3F station building to B2F waiting room in fire simulation. Also, a fire simulation were performed with CFAST and FLUENT. In CFAST, the total 29 zones were divided into 18 station buildings in B3F and 11 station buildings in B2F. In FLUENT, the simulated space had the same establishment as zone of CFAST. The study focused on possibility for application of fire simulation in underground station by comparing the resulted values from two simulators. For application of fire effect, the fire data were loaded directly to EXODUS in the case of CFAST and performed a passenger evacuation simulation. In the case of FLUENT, Out Data values of a fire simulation were difficult to be compatible with EXODUS. Two resulted values of passenger evacuation simulation by fire simulation were compared with the Dae-gu Subway Fire Accident in reality.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.38 no.1
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• pp.45-52
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• 2001

The proximal isovelocity surface area (PISA) method is an effective way of measuring the regurgitant blood flow rate in the mitral valve. This method defines the modelling required to describe the geometry of the isotach of the PISA. In the normal PISA flow model, the flow rate is calculated assuming that the surface of the isotach is either hemispherical or non-hemispherical numerically. However, this paper evaluated the estimate flow rate using a direct surface subdivision flow model based on the height field after isotach extraction using a region-based scheme. To validate the proposed method, the various PISA flow models were compared using pusatile color Doppler images with flow rates ranging from $30\;cm^3/sec\;to\;60\;cm^3/sec$ flow rate. Whereas the hemispherical flow model had a mean value of $29\;cm^3/sec$ and underestimated the measured flow rate by 35%, the proposed model and non-hemispherical model produced a c;ame mean value of $45\;cm^3/sec$, moreover, both flow models produced a similar pulsatile flow rate.