• Proceedings of the Korea Water Resources Association Conference
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• 2002.05a
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• pp.27-40
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• 2002

Developed at Colorado State University, CASC2D-SED is a physically-based model simulating the hydrologic response of a watershed to a distributed rainfall field. The time-dependent processes include: precipitation, interception, infiltration, surface runoff and channel routing, upland erosion, transport and sedimentation. CASC2D-SED is applied to Goodwin Creek, Mississippi. The watershed covers 21 $\textrm{km}^2$ and has been extensively monitored both at the outlet and at several internal locations by the ARS-NSL at Oxford, MS. The model has been calibrated and validated using rainfall data from 16 meteorological stations,6 stream gaging stations and 6 sediment gaging stations. Sediment erosion/deposition rates by size fraction are predicted both in space and time. Geovisualization, a powerful data exploration technique based on GIS technology, is used to analyze and display the dynamic output time series generated by the CASC2D-SED model.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.284-289
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• 1996

The predictions of the COBRA-IV-I code with the modified turbulent mixing and void drift models have been compared with the diabatic two-phase flow data on equilibrium quality. The turbulent mixing model based on an equal mass exchange of the existing COBRA-IV-I code has been modified to that based on an equal volume exchange between adjacent subchannels, and a void drift model has been newly incorporated in the code. To evaluate the performance of the equal volume exchange turbulent mixing model and the effects of the void drift model, the diabatic steam-water two-phase flow data obtained for the 9-rod bundle test under the typical operating conditions of the boiling water reactor(BWR) conducted by the General Electric (GE) were analyzed by the modified COBRA-IV-I code. The analysis indicates that the equal volume exchange turbulent mixing model with void drift predicts the observed two-phase flow data trends better than the equal mass exchange model, and to predict the correct data trends a more physically based void drift model need to be developed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.624-627
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• 2002

Experimental study showed that the existing mathematical model doesn't fully describe the lateral motion of a moving web fur different operating conditions. So, a physically interpretable model of lateral motion of a moving web in a typical web guidance system, operated at Konkuk Univ., was developed using the system identification technique. A well-known Least Square Method based on ARX model was used for the system identification. Lateral displacement of the web was measured at the exit of each span by infrared sensors. The model obtained from identifying a linear time-invariant system for a typical operating condition yields an improved prediction capability of the lateral dynamics of the moving web compared to other mathematical models proposed in literature.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.6
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• pp.37-45
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• 2005

Almost every year, Korea has been suffered from serious damages of lives and properties, due to landslides that are triggered by heavy rains in monsoon season. In this paper, we systematized the physically based landslide prediction model which consisted of 3 parts, infinite slope stability analysis model, groundwater flow model and soil depth model. To evaluate its applicability to the prediction of landslides, the data of actual landslides were plotted on the predicted areas on the GIS map. The matching rate of this model to the actual data was $84.8\%$. And the relation between hydrological and land form factors and potential landslide were analyzed.

• Transactions on Electrical and Electronic Materials
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• v.12 no.1
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• pp.7-10
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• 2011

High voltage (HV) integrated circuits are viable alternatives to discrete circuits in a wide variety of applications. A HV device generally used in these circuits is a lateral double diffused metal oxide semiconductor (LDMOS) transistor. Attempts to model LDMOS devices are complicated by the existence of the lightly doped drain and by the extension of the poly-silicon and the gate oxide. Several physically based investigations of the bias-dependent drift resistance of HV devices have been conducted, but a complete physical model has not been reported. We propose a new technique to model HV devices using both the BSIM3 SPICE model and a bias dependent resistor model (sub-circuit macro model).

• Water Engineering Research
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• v.2 no.1
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• pp.49-61
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• 2001

A grid-based KIneMatic wave soil-water EROsion and deposition Model(KIMEROM) that predicts temporal variation and spatial distribution of sediment transport in a watershed was developed. This model uses ASCII-formatted map data supported from the regular gridded map of GRASS (U.S. Army CERL, 1993)-GIS(Geographic Information Systems), and generates the distributed results by ASCII-formatted map data. For hydrologic process, the kinematic wave equation and Darcy equation were used to simulated surface and subsurface flow, respectively (Kim, 1998; Kim et al., 1998). For soil erosion process, the physically-based soil erosion concept by Rose and Hairsine (1988) was used to simulate soil-water erosion and deposition. The model adopts single overland flowpath algorithm and simulates surface and subsurface water depth, and sediment concentration at each grid element for a given time increment. The model was tested to a 162.3 $\textrm{km}^2$ watershed located in the tideland reclaimed ares of South Korea. After the hydrologic calibration for two storm events in 1999, the results of sediment transport were presented for the same storm events. The results of temporal variation and spatial distribution of overland flow and sediment areas are shown using GRASS.

• Journal of Hydrospace Technology
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• v.2 no.2
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• pp.80-87
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• 1996

A creep-buckling analysis is studied for a simply-supported viscoelastic column. The fluid-type four-parameter model is employed because of its general applicability to creep materials. Using the imperfection-based incremental approach, a nonlinear load deflection equation is derived. Safe load and critical (or life) time which characterize the stability of the viscoelastic column are obtained mathematically and interpreted physically. A finite difference algorithm is applied to solve the second-order differential equation of the viscoelastic stress-strain relation. Numerical calculation has been made and discussed far a SUS316 stainless steel column.

• Proceedings of the Korea Water Resources Association Conference
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• 2001.05a
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• pp.35-44
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• 2001

As one of advanced uses of radar, a physically based rainfall prediction method which uses a conceptual rainfall model assimilated by information from volume scanning radar is shown. As another example of advanced utilization of weather radar, results from analyzing a hierarchical time-scale structure in dependency of rainfall distribution en topography are shown.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.289-298
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• 2007

A nonlinear dynamic simulation model from cranking to idle speed is developed to optimize the cold start process of a diesel engine. Physically-based first order nonlinear differential equations and some algebraic equations describing engine dynamics and starter motor dynamics are used to model the performance of cold starting process which is very complex and involves many components including the cold start aiding method. These equations are solved using numerical schemes to describe the starting process of a diesel engine and to study the effects of cold starting parameters. The validity of this model is examined by a cold start test at $-20^{\circ}C$. Using the developed model the effects of the important starting variables on the cold starting processes were investigated. This model can be served as a tool for designing computer aided control systems that improve cold start performance.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.668-673
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• 2008

In this paper, we developed a physically-based micromechanical model for inelastic deformation of ceramic powders. The aggregate response of ceramic particles was modeled using the two-surface yield function which considered the shear-induced dilatancy caused by friction, rolling resistance and cohesion between powder particles and consolidation caused by plastic deformation of powder themselves under high compression. The constitutive equations were implemented into the user-subroutine VUMAT of finite element program ABAQUS/Explicit. The material parameters in the constitutive model were identified by calibrating the model to reproduce data from triaxial compression tests and simple compression tests. The density distribution obtained by using the proposed model was in good quantitative agreement with the experimental results of the triaxial compression and cold isostaic compression as well.