• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1C
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• pp.43-52
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• 2006

Despite several constitutive models have been proposed and applied, it is still difficult to choose a suitable model and to estimate adequate analysis parameters. Furthermore, a cyclic shear behavior under the volume change caused by the seepage is more complex. None of the constitutive model is available at present in the expression of the cyclic behavior of soil under an additional volume change condition by seepage. Therefore, a new geotechnical hybrid simulation system which can control the pore water immigration was developed. The system enables a quantitative evaluation of the residual deformation such as lateral spreading and settlement caused by the liquefaction. The seismic responses in a one-dimensional slightly inclined multilayered soil system are taken into consideration, and the soils are governed by both equation of motion and the continuity equation. Furthermore, the estimation and the selection of the soil parameter for the representation of the strong nonlinearity of the material are not required, because soil behaviors under the earthquake motions are directly introduced instead of a numerical soil constitutive model. This paper presents the concept and specifications of the system. By applying the system to an example problem, the permeability effect on the seismic response during cyclic shear is studied. The importance of the volume change characteristics of sandy soil during and after cyclic shear is shown in conclusion.

• Journal of the Korean Solar Energy Society
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• v.27 no.3
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• pp.117-125
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• 2007

This study proposes a CFD(Computational Fluid Dynamics) analysis as a method of verification of the designed-data and a supplement of the insufficient experiences in geothermal system, which shows a rapid growth among the renewable energies. The followings are the results. FLUENT 6.2.12 is used as a CFD tool on this study, with the equations of continuity, motion, energy for unsteady flow through pipes and k-epsilon turbulent model. S-type model which has one borehole with diameter 12m by depth 206m and T-type model which has 3 boreholes with $12m{\times}20m{\times}206m$ are proposed, and also the boundary conditions are described. The temperature differences between temperatures by CFD analysis and by on-site measurement are less than 1.5%, this shows a high reliability of CFD analysis process which this study proposes. After 11 days simulation operated 12 hours interval On/Off mode, it is clearly predicted that the outlet temperatures of geothermal pipes are increased by $1.2^{\circ}C$, and $2.2^{\circ}C$ after 4 months. And the outlet temperatures of geothermal pipes increased with increase of the mass flow rates through the pipes. T-type model shows that the 4m distance between boreholes are reasonable because the temperatures at 2m and 6m from boreholes are nearly same.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.12
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• pp.103-112
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• 2005

In this paper, in order to derive the current-voltage characteristics of n-AlGaN/GaN HEMTs with the piezoelectric and spontaneous polarizations, we suggested analytical solutions for the two-dimensional Poisson equation in the AlGaN and GaN regions by taking into account the longitudinal field variation, field-dependent mobility, and the continuity condition of the channel current flowing in the quantum well. Obtained expressions for long and short channel devices would be applicable to the entire operating regions in a unified manner. Simulation results show that the drain saturation current increases and the cutoff voltage decreases as drain voltage increases. Compared with the conventional models, the present model seems to provide more reasonable explanation for the drain-induced threshold voltage roll-off and the channel length modulation effect.

• Water for future
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• v.28 no.1
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• pp.121-132
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• 1995

This paper presents a mathematical model which simulates the Cherepnov water lifter, that can lift water without the use of external energy such as electricity. A theoritical study was conducted to reveal the characteristics of the Cherepnov water lifter that was continuously operated with the aid of the siphon. The mathematical model wal composed of the continuity equation and energy equation, and was coded using FORTRAN language. In this study, the govering flow equation of the lifter were derived and the computer programs of the equations were worked out. The accuracy of the theoretical equations and their solutions was checked by laboratory experimentation. The mathematical model that simulate the Cherepnov water lifter is appeared to be good to predict the behavior of Cherepnov water lifter. Therefore, the mathematical model and the simulation method used in this study could be used in designing of the Cherepnov water lifter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.965-968
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• 2005

Roll drafting operation causes variations in the linear density of bundles because the bundle flow cannot be controlled completely by roll pairs. Defects occurring in this operation bring about many problems successively in the next processes. In this paper, we attempt to analyze the draft dynamics and the linear density irregularity based on the governing equation of a bundle motion that has been suggested in our previous studies. For analyzing the dynamic characteristics of the roll drafting operation, it is indispensable to investigate a transient state in time domain before the bundle flux reaches a steady state. However, since governing equations of bundle flow consisting of continuity and motion equations turn out to be nonlinear, and coupled between variables, the solutions for a transient state cannot be obtained by an analytical method. Therefore, we use the Finite Difference Method(FDM), particularly, the FTBS(Forward-Time Backward-Space) difference method. Then, the total equations system yields to an algebraic equations system and is solved under given initial and boundary conditions in an iterative fashion. From the simulation results, we confirm that state variables show different behavior in the transient state; e.g., the velocity distribution in the flow field changes more quickly the linear density distribution. During a transient flow in a drafting zone, the output irregularity is influenced differently by the disturbances, e.g., the variation in input bundle thickness, the drafting speed, and the draft ratio.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.4
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• pp.1-8
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• 2005

Plasma researches using parallel-plate electrodes are widely used in semiconductor application such as etching and thin film deposition. Therefore, a quantitative understanding and control of plasma behavior are becoming increasingly necessary because their important applications and simulation techniques have been actively carried out in order to solve such problems above. In this paper, we developed a two-dimensional(2D) self-consistent fluid model, because 2D models can deal with real reactor geometries. The fluid model is based on particle continuity equations for taking account of an electrode system in a cylindrical geometry. An pure Ar gas was used at 500[mTorr] and radio-frequency (13.56(MHz)). Four models were simulated under the different electrode geometries which have chamber widths of 5.25, 6.0, 8.0, and 10.0[cm] and we compared their results with each other. Plasma uniformity and a do self-bias voltage were also discussed.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.11
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• pp.98-105
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• 2010

In this paper, double ball-bar is used to estimate the geometric errors of a rotary table, which includes one-axial motion, two-radial motions and two-tilt motions, except the angular positioning error. To simplify the measurement procedures, three measurement steps have been designed and developed. At each measurement step, one end of the double ball-bar is fixed at the nose of spindle and the other end is located on the rotary table. And specific circular test path is planned to keep the distance between two balls as constant at ideal case. The relationship including the geometric errors of a rotary table and the measured distance between two balls which is distorted by the geometric errors is defined by using ball-bar equation. Each geometric error is modeled as $4^{th}$ order polynomial considering $C^1$-continuity. Finally the coefficients of polynomial are calculated by least-square method. Simulation is done to check the validation of the suggested method considering set-up errors and measurement noise. Suggested method is applied to estimate geometric errors of a rotary table of a 5-axis machine tool.

• Wind and Structures
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• v.15 no.6
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• pp.481-494
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• 2012

The greenhouse type metal structures are increasingly used in modern construction of livestock farms because they are less laborious to construct and they provide a more favorable microclimate for the growth of animals compared to conventional livestock structures. A key stress factor for metal structures is the wind. The external pressure coefficient ($c_{pe}$) is used for the calculation of the wind effect on the structures. A high pressure coefficient value leads to an increase of the construction weight and subsequently to an increase in the construction cost. The EC1 in conjunction with EN 13031-1:2001, which is specialized for greenhouses, gives values for this coefficient. This value must satisfy two requirements: the safety of the structure and a reduced construction cost. In this paper, the Navier - Stokes and continuity equations are solved numerically with the finite element method (Galerkin Method) in order to simulate the two dimensional, incompressible, viscous air flow over the vaulted roofs of single span and twin-span with eaves livestock greenhouses' structures, with a height of 4.5 meters and with length of span of 9.6 and 14 m. The simulation was carried out in a wind tunnel. The numerical results of pressure coefficients, as well as, the distribution of them are presented and compared with data from Eurocodes for wind actions (EC1, EN 13031-1:2001). The results of the numerical experiment were close to the values given by the Eurocodes mainly on the leeward area of the roof while on the windward area a further segmentation is suggested.

• Journal of the Korea Computer Graphics Society
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• v.23 no.5
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• pp.1-7
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• 2017

We propose a complex crack generation technique which is represented when impact is applied to glass. The crack patterns expressed when external forces are applied to the glass are classified into dense, radial, and concentric cracks, and we use procedural methods to efficiently represent crack patterns. Based on the input external force, we synthesize the crack example and apply the L-system based on this example to model the propagation shape of the crack in real time. Although physics based crack generation can analyze and model accurate cracks, it has a disadvantage of slow computation because of its high computational cost, and procedural methods have a relatively fast rate of continuity, but are not sufficient to capture accurate crack characteristics. We modeled cracks in glass using L-system to achieve both of these advantages. As a result, it realistically represented the microscopic crack patterns of glass in real time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1128-1140
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• 2009

In this paper, we present a patient real-time vital sign information transmission system to effectively support developing real-time communication service by using a real-time object model named TMO (Time-Triggered Message-Triggered Object). Also, we describe the application environment as the ICU(Intensive Care Unit) to guarantee real-time service message with TMO structure in distributed network systems. We have to design to obtain useful vital sign information, which is generated at parsing data receiver modulor of HIS with TMO structure, that is offered by the central monitor. Vital sign informations of central monitor is composed of the raw data of several bedsite patient monitors. We are willing to maintain vital sign information of real time and continuity that is generated from the bedsite patient monitor. It is able to apply to remote medical examination and treatment. we proposed integration method between a vital sign database systems and hospital information systems. In the real time simulation techniques based on TMO object modeling, We have observed several advantages to the TMO structuring scheme. TMO object modeling has a strong traceability between requirement specification and design.