• Smart Structures and Systems
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• 제17권4호
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• pp.611-629
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• 2016

This study presents a new approach of surrogate modeling for time-consuming finite element analysis. A surrogate model is widely used to reduce the computational cost under an iterative computational analysis. Although a variety of the methods have been widely investigated, there are still difficulties in surrogate modeling from a practical point of view: (1) How to derive optimal design of experiments (i.e., the number of training samples and their locations); and (2) diagnostics of the surrogate model. To overcome these difficulties, we propose a sequential surrogate modeling based on Gaussian process model (GPM) with self-adaptive sampling. The proposed approach not only enables further sampling to make GPM more accurate, but also evaluates the model adequacy within a sequential framework. The applicability of the proposed approach is first demonstrated by using mathematical test functions. Then, it is applied as a substitute of the iterative finite element analysis to Monte Carlo simulation for a response uncertainty analysis under correlated input uncertainties. In all numerical studies, it is successful to build GPM automatically with the minimal user intervention. The proposed approach can be customized for the various response surfaces and help a less experienced user save his/her efforts.

• 소성∙가공
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• 제27권1호
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• pp.28-36
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• 2018

Electromagnetic forming is a type of high-speed forming process to deform a workpiece through a Lorentz force. As the high strain rate in an electromagnetic-forming simulation causes infeasibility in determining constitutive parameters, we employed inverse parameter estimation in the previous study. However, the inverse parameter estimation process required us to spend considerable time, which leads to an increase in computational cost. To overcome the computational obstacle, in this research, we applied two types of surrogate modeling methods and compared them to each other to evaluate which model is best for the electromagnetic-forming simulation. We exploited an artificial neural network and we reduced-order modeling methods. During the construction of a reduced-order model, we extracted orthogonal bases with proper orthogonal decomposition and predicted basis coefficients by utilizing an artificial neural network. After the construction of the surrogate models, we verified the artificial neural network and reduced-order models through training and testing samples. As a result, we determined the artificial neural network model is slightly more accurate than the reduced-order model. However, the construction of the artificial neural network model requires a considerably larger amount of time than that of the reduced-order model. Thus, a reduced order modeling method is more efficient than an artificial neural network for estimating the electromagnetic forming and for the rapid approximation of structural simulations which needs repetitive runs.

• 한국CDE학회논문집
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• 제15권1호
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• pp.60-69
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• 2010

Outfitting systems in marine vessels have many kinds of standard parts. Ship CAD system should support the designers with an efficient tool for the modeling of outfitting parts such as pipes and valves. We develop a practical procedure for a part master model that combines ship CAD systems with the industrial standard. Part master or catalogue database of standard equipments is included in the database of ship CAD. The part master makes the associations of three dimensional modeling with the industrial standard. Moreover, it reflects the automatic modeling to maintain attributes that are disclosed in the entity of each part master in order to reduce the modeling time. Entity and attributes of pipe and valves are chosen from JIS(Japanese Industrial Standards) in order to explain the proposed procedure. Suggested procedure explains that three dimensional model of equipment is generated by parsing the pre-defined attributes after the entities of part masters is stored in database.

• International Journal of CAD/CAM
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• 제11권1호
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• pp.18-26
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• 2011

This paper proposes a new solid-shape modeling system based on a lusterware-image illustration. The proposed method reconstructs a three dimensional solid shape from a set of rough sketches that are typically drawn in the early stages of the design process. The sketches do not have to be strictly accurate, and this tolerance to the roughness of the input sketches is one of the major advantages of the proposed method. The proposed system creates an initial shape based on the silhouette of the input lusterware-images. Then the user can edit the initial shape with intuitive cutting and dishing-up operations, which are based on sketching user interface. To achieve the goal, the system retains the geometric model with two representations: a point-set data and a volume data. This dual data structure allows the program to create an initial shape from the input images with little computational cost, and the user can apply cutting and dishing-up operations without substantially increasing computational and memory requirements. In this research, we have tested the proposed system by reconstructing solid models of some mechanical parts from rough sketches. The experimental results indicate that the proposed method is useful for the prototyping of a solid shape.

• Nuclear Engineering and Technology
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• 제56권9호
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• pp.3512-3527
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• 2024

Seismic quantification of nonstructural components like electrical cabinets is essential to ensure the uninterrupted operation of nuclear facilities during earthquake events. This process requires experimental tests, which can be expensive, time-consuming, and limited by safety concerns and precision. As an alternative to that, numerical simulations should be done in such a way that they are capable of capturing the global dynamic behavior with minimum computational efforts. However, in the case of complex interconnected cabinets, the simplification of numerical models often poses difficulties in illustrating the real-time behavior of combined cabinet systems. On the other hand, detailed three-dimensional (3D) numerical models require lengthy time and sophisticated computational setup, indicating their expensive computational efforts. To resolve this issue, a simplified and efficient 3D modeling approach has been proposed in this study. The accuracy of the results from the new model showed an excellent match with that obtained from the responses of the experimental test. After the validation and observation of the numerical efficiency, a practical application is implemented by considering the impacts of earthquake frequency contents on the behavior of cabinet systems. From the outcomes, it is evident that this proposed modeling methodology has the potential to replace the complex combined nuclear cabinet models for earthquake evaluation.

• 융복합기술연구소 논문집
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• 제10권1호
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• pp.37-40
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• 2020

Automotive battery system consists of various components such as battery cells, mechanical structures, cooling system, and control system. Recently, various computational technologies are required to develop an automotive battery system. Physics-based cell modeling is used for designing a new battery cell by conducting optimization of material selection and composition in electrodes. Structural analysis plays an important role in designing a protective system of battery system from mechanical shock and vibration. Thermal modeling is used in development of thermal management system to maintain the temperature of battery cells in safe range. Finally, vehicle simulation is conducted to validate the performance of electric vehicle with the developed battery system.

• 한국전산유체공학회지
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• 제8권2호
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• pp.42-48
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• 2003

The issues associated with the application of CFD for ship design are addressed. Doubtlessly at the moment, CFD tools are very useful in evaluating hull forms prior to traditional towing tank tests. However, time-consuming pre-processing is an obstacle in the daily application of CFD tools to improve hull forms. The accuracy of computational modeling without sacrificing the usability of CFD system is also to be assessed. The wave generation is still predicted by using potential panel methods, while velocity profiles entering into propeller plane is solved using turbulent flow solvers. The choice of turbulence model is a key to predict nominal wake distribution within acceptable accuracy. The experimental data for CFD validation are invaluable to improve physical and numerical modeling. Other applications of CFD for ship design than hull form improvement are also given. It is certain that CFD can be a cost-effective tool for the design of new and better ships.

• Wind and Structures
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• 제2권4호
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• pp.305-323
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• 1999

Accurate turbulence modeling is an essential prerequisite for the use of Computational Fluid Dynamics (CFD) in Wind Engineering. At present the most popular turbulence model for general engineering flow problems is the ${\kappa}-{\varepsilon}$ model. Models such as this are based on the isotropic eddy viscosity concept and have well documented shortcomings (Murakami et al. 1993) for flows encountered in Wind Engineering. This paper presents an objective assessment of several available alternative models. The CFD results for the flow around a full-scale (6 m) three-dimensional surface mounted cube in an atmospheric boundary layer are compared with recently obtained data. Cube orientations normal and skewed at $45^{\circ}$ to the incident wind have been analysed at Reynolds at Reynolds number of greater than $10^6$. In addition to turbulence modeling other aspects of the CFD procedure are analysed and their effects are discussed.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1998년도 춘계 학술대회논문집
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• pp.117-122
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• 1998

A numerical study is carried out to investigate the transient process of combustion phenomena associated with hypersonic propulsion devices. Reynolds averaged Navier-Stokes equations for reactive flows are used as governing equations with a detailed chemistry mechanism of hydrogen-air mixture and two-equation SST turbulence modeling. The governing equations are discretized by a high order accurate upwind scheme and solved in a fully coupled manner with a fully implicit time accurate method. At first, oscillating shock-induced combustion is analyzed and the comparison with experimental result gives the validity of present computational modeling. Secondly, the model ram accelerator experiment was simulated and the results show the detailed transient combustion mechanisms. Thirdly, the evolution of oblique detonation wave is simulated and the result shows transient and final steady state behavior at off-stability condition. Finally, shock wave/boundary layer interaction in combustible mixture is studied and the criterion of boundary layer flame and oblique detonation wave is identified.

• Molecules and Cells
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• 제25권3호
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• pp.397-406
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• 2008

Computational modeling of signal transduction is currently attracting much attention as it can promote the understanding of complex signal transduction mechanisms. Although several mathematical models have been used to examine signaling pathways, little attention has been given to crosstalk mechanisms. In this study, an attempt was made to develop a computational model for the pathways involving growth-factor-mediated mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3'-kinase/protein kinase B (PI3K/Akt). In addition, the dynamics of the protein activities were analyzed based on a set of kinetic data. The simulation approach integrates the information on several levels and predicts systems behavior. The in-silico analysis conducted revealed that the Raf and Akt pathways act independently.