• Korean Journal of Materials Research
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• v.20 no.9
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• pp.478-482
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• 2010

A series of molecular dynamic (MD), finite element (FE) and ab initio simulations are carried out to establish suitable modeling schemes for the continuum-based analysis of aluminum matrix nanocomposites reinforced with carbon nanotubes (CNTs). From a comparison of the MD with FE models and inferences based on bond structures and electron distributions, we propose that the effective thickness of a CNT wall for its continuum representation should be related to the graphitic inter-planar spacing of 3.4${\AA}$. We also show that shell element representation of a CNT structure in the FE models properly simulated the carbon-carbon covalent bonding and long-range interactions in terms of the load-displacement behaviors. Estimation of the effective interfacial elastic properties by ab initio simulations showed that the in-plane interfacial bond strength is negligibly weaker than the normal counterpart due to the nature of the weak secondary bonding at the CNT-Al interface. Therefore, we suggest that a third-phase solid element representation of the CNT-Al interface in nanocomposites is not physically meaningful and that spring or bar element representation of the weak interfacial bonding would be more appropriate as in the cases of polymer matrix counterparts. The possibility of treating the interface as a simply contacted phase boundary is also discussed.

• Journal of Environmental Science International
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• v.20 no.1
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• pp.93-106
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• 2011

Physically-based resampling scheme for roughness coefficient of surface runoff considering the spatial landuse distribution was suggested for the purpose of effective operational application of recent grid-based distributed rainfall runoff model. Generally grid scale(mother scale) of hydrologic modeling can be greater than the scale (child scale) of original GIS thematic digital map when the objective basin is wide or topographically simple, so the modeler uses large grid scale. The resampled roughness coefficient was estimated and compared using 3 different schemes of Predominant, Composite and Mosaic approaches and total runoff volume and peak streamflow were computed through distributed rainfall-runoff model. For quantitative assessment of biases between computational simulation and observation, runoff responses for the roughness estimated using the 3 different schemes were evaluated using MAPE(Mean Areal Percentage Error), RMSE(Root-Mean Squared Error), and COE(Coefficient of Efficiency). As a result, in the case of 500m scale Mosaic resampling for the natural and urban basin, the distribution of surface runoff roughness coefficient shows biggest difference from that of original scale but surface runoff simulation shows smallest, especially in peakflow rather than total runoff volume.

• Journal of the Korea Computer Graphics Society
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• v.25 no.3
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• pp.105-113
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• 2019

Physically-based fluid simulation takes a lot of time for high resolution. To solve this problem, there are studies that make up the limitation of low resolution fluid simulation by using deep running. Among them, Super-resolution, which converts low-resolution simulation data to high resolution is under way. However, traditional techniques require to the entire space where there are no density data, so there are problems that are inefficient in terms of the full simulation speed and that cannot be computed with the lack of GPU memory as input resolution increases. In this paper, we propose a new method that divides and classifies 2D smoke simulation data into the space using the quad tree, one of the spatial partitioning methods, and performs Super-resolution only required space. This technique accelerates the simulation speed by computing only necessary space. It also processes the divided input data, which can solve GPU memory problems.

• Journal of the Korea Society of Computer and Information
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• v.27 no.5
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• pp.85-92
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• 2022

In this paper, we propose a technique that can express low-resolution hair and fur simulations in high-resolution without noise using ConvNet and geometric images of strands in the form of lines. Pairs between low-resolution and high-resolution data can be obtained through physics-based simulation, and a low-resolution-high-resolution data pair is established using the obtained data. The data used for training is used by converting the position of the hair strands into a geometric image. The hair and fur network proposed in this paper is used for an image synthesizer that upscales a low-resolution image to a high-resolution image. If the high-resolution geometry image obtained as a result of the test is converted back to high-resolution hair, it is possible to express the elastic movement of hair, which is difficult to express with a single mapping function. As for the performance of the synthesis result, it showed faster performance than the traditional physics-based simulation, and it can be easily executed without knowing complex numerical analysis.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.414-419
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• 2008

3D rendering is a critical process for a movie production, advertisement, interior simulation, medical and many other fields. Recently, several effective rendering methods have been developed for the photo-realistic image generation. With a rapid performance enhancement of graphics hardware, physically based 3D rendering algorithm can now often be approximated in real-time games. However, the high quality of global illumination, required for the image generation in the 3D animation production community is a still very expensive process. In this paper, we propose a new rendering method to create photo-realistic global illumination effect efficiently by harnessing the high power of the recent GPUs. Final gathering routines in our global illumination module are accelerated by programmable graphics hardware. We also simulate physically based light transport on a ray tracing based rendering algorithm with photon mapping effectively.

• Journal of the Korea Computer Graphics Society
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• v.20 no.2
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• pp.25-32
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• 2014

We present an example-based approach to synthesizing physically simulated Rube Goldberg machines in which a series of rigid body elements are sequentially triggered and driven along the causal chain. Given a set of elements, our goal is to automatically instantiate and arrange those elements to meet the user-specified requirements including the start and end positions, and the boundary of movement. To do so, we first sample small-scale machines consisting of only a few elements randomly, and represent the connectivity between every pair of components as a graph structure. Searching over possible paths in this graph solves our problem by finding a path that can be unrolled to satisfy the given requirements, and then assembling components sequentially along the solution path. In order to ensure that the machine works precisely in a physically simulated environment, we finally elaborate the layout of assembled components by a simple greedy algorithm. We demonstrate the usefulness of our approach by displaying a large diversity of Rube Goldberg machines built with only five kinds of elements.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2079-2088
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• 2014

In this paper, we propose new physically based threshold voltage models for short channel Surrounding Gate Silicon Nanowire Transistor with two different geometries. The model explores the impact of various device parameters like silicon film thickness, film height, film width, gate oxide thickness, and drain bias on the threshold voltage behavior of a cylindrical surrounding gate and rectangular surrounding gate nanowire MOSFET. Threshold voltage roll-off and DIBL characteristics of these devices are also studied. Proposed models are clearly validated by comparing the simulations with the TCAD simulation for a wide range of device geometries.

• Water for future
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• v.29 no.6
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• pp.203-215
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• 1996

A physically based model for rainfall-runoff simulation in agricultural watersheds equipped with tile drains is developed from the TOPMODEL framework. The model is based on detailed topographical information provided by the Digital Elevation Model (DEM), which is available in the Geographic Information System GRASS. Nine possible flow generation scenarions are suggested and used in the development of the model. The storage and delaying effects in the soil matrix and in the tile system are simulated with a second order linear reservoir. The model can identify the portions of the hydrators resulting from tile flow, subsurface flow and surface runoff.

• Journal of Korea Water Resources Association
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• v.30 no.5
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• pp.539-548
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• 1997

A physically based model for rainfall runoff simulation in agricultural watershed equipped with tile drains is presented. This model is developed from the TOPMODEL which is based on the detailed topographic information provided by Digital Elevation Model (DEM). Nine possible flow generation scenarios in the tile drained basin are suggested and used in the development of the model. The model can identify the portions of the hydrograph resulting from tile flow, subsurface flow and surface flow. The performance of the model is assessed through a calibration and validation process. The results of the analysis show that the model describes the physical system well and provides a better insight into the hillslope hydrology of agricultural watersheds with tile drainage.

• Advances in biomechanics and applications
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• v.1 no.1
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• pp.1-14
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• 2014

In this paper, a simple and accurate finite element model coupled to quasi-brittle damage law able to describe the multiple cracks initiation and their progressive propagation is developed in order to predict the complete force-displacement curve and the fracture pattern of human proximal femur under quasi-static load. The motivation of this work was to propose a simple and practical FE model with a good compromise between complexity and accuracy of the simulation considering a limited number of model parameters that can predict proximal femur fracture more accurately and physically than the fracture criteria based models. Different damage laws for cortical and trabecular bone are proposed based on experimental results to describe the inelastic damage accumulation under the excessive load. When the damage parameter reaches its critical value inside an element of the mesh, its stiffness matrix is set to zero leading to the redistribution of the stress state in the vicinity of the fractured zone (crack initiation). Once a crack is initiated, the propagation direction is simulated by the propagation of the broken elements of the mesh. To illustrate the potential of the proposed approach, the left femur of a male (age 61) previously investigated by Keyak and Falkinstein, 2003 (Model B: male, age 61) was simulated till complete fracture under one-legged stance quasi-static load. The proposed finite element model leads to more realistic and precise results concerning the shape of the force-displacement curve (yielding and fracturing) and the profile of the fractured edge.