• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.601-604
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• 2001

The insulation materials of cables used for underground power transmission requires a higher insulating capability, and the most popular method to examine the cable is partial discharge test due to applying variation voltage. In the thesis, air void, silicone oil, of which may possibly exist real cables, are simulated by Electro 2D program. Also the relations between calculated field strength and the void defect type in the cable joint materials. In the modeling, eclectic field inner to the cable joint material composed by XLPE and EPDM is modeling simulated. We obtained the electric field distribution in void due to two conditions.

• Computers and Concrete
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• v.3 no.4
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• pp.197-212
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• 2006

Modeling of physically non-linear behavior becomes more and more important for the analysis of SFRC structures in practical applications. From this point of view we will present an effective, three-dimensional constitutive model for SFRC, that is also easy to implement in commercial finite element programs. Additionally, the finite element analysis should only require standard material parameters which can be gained easily from conventional experiments or which are specified in appropriate building codes. Another important point is attaining the material parameters from experimental data. The procedures to determine the material parameters proposed in appropriate codes seem to be only approximations and are unsuitable for precise structural analysis. Therefore a finite element analysis of the test itself is used to get the material parameters. This process is also denoted as inverse analysis. The efficiency of the proposed constitutive model is demonstrated on the basis of numerical examples and their comparison to experimental results. In the framework of material parameter identification the idea of a new, indirect tension testing procedure, the "Modified Tension Test", is adopted and extended to an easy-to-carry-out tension test for steel fiber reinforced concrete specimens.

• Structural Engineering and Mechanics
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• v.46 no.2
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• pp.213-229
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• 2013

Although performance based assessment procedures are mainly developed for reinforced concrete and steel buildings, URM (Unreinforced Masonry) buildings occupy significant portion of buildings in earthquake prone areas of the world as well as in IRAN. Variability of material properties, non-engineered nature of the construction and difficulties in structural analysis of masonry walls make analysis of URM buildings challenging. Despite sophisticated finite element models satisfy the modeling requirements, extensive experimental data for definition of material behavior and high computational resources are needed. Recently, nonlinear equivalent frame models which are developed assigning lumped plastic hinges to isotropic and homogenous equivalent frame elements are used for nonlinear modeling of URM buildings. The equivalent frame models are not novel for the analysis of masonry structures, but the actual potentialities have not yet been completely studied, particularly for non-linear applications. In the present paper an effective tool for the non-linear static analysis of 2D masonry walls is presented. The work presented in this study is about performance assessment of unreinforced brick masonry buildings through nonlinear equivalent frame modeling technique. Reliability of the proposed models is tested with a reversed cyclic experiment conducted on a full scale, two-story URM building at the University of Pavia. The pushover curves were found to provide good agreement with the experimental backbone curves. Furthermore, the results of analysis show that EFM (Equivalent Frame Model) with Dolce RO (rigid offset zone) and shell element have good agreement with finite element software and experimental results.

• Proceedings of the Korea Society for Simulation Conference
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• 1997.04a
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• pp.23-28
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• 1997

We discuss development of a simulator for automated manufacturing systems (AMSs) which have sophisticated automated material handling equipments and complicated work flows. The simulator is designed to satisfy the following requirements. A user should be able to easily configure or specify an AMS through a graphical user interface (GUI) and minimal data input. The user should be able to model diverse and complied control logic for automated material handling systems like automated guided vehicle (AGV) systems, robot workcell systems and conveyor systems as well as complicated job flow program. Real time animation is desired. Finally, the simulator should be easily maintained and extended. To satisfy the requirements, we use an object-oriented paradigm for modeling, designing, and programming of the simulator. We use an object-oriented modeling framework to design the modeling elements library, and take the process interaction approach for scheduling processes and events. To model a user-defined diverse control logic, we also develop a script language and its interpreter. We explain design and implementation strategies. We implement the simulator using Visual C++ 4.2 and Open GL on Windows NT and the Windows95. Some modeling examples will be demonstrated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.557-561
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• 2014

In this work, Altair Engineering's vibroacoustic modeling approach is used to simulate the acoustic signature of a simplified automobile in a wind tunnel. The modeling approach relies on a two step procedure involving simulation and extraction of acoustic sources using a high fidelity Computational Fluid Dynamics (CFD) simulation followed by propagation of the acoustic energy within the structure and passenger compartment using a structural dynamics solver. The tools necessary to complete this process are contained within Altair's HyperWorks CAE software suite. The CFD simulations are performed using AcuSolve and the structural simulations are performed using OptiStruct. This vibroacoustics simulation methodology relies on calculation of the acoustic sources from the flow solution computed by AcuSolve. The sources are based on Lighthill's analogy and are sampled directly on the acoustic mesh. Once the acoustic sources have been computed, they are transformed into the frequency domain using a Fast Fourier Transform (FFT) with advanced sampling and are subsequently used in the structural acoustics model. Although this approach does require the CFD solver to have knowledge of the acoustic simulation domain a priori, it avoids modeling errors introduced by evaluation of the acoustic source terms using dissimilar meshes and numerical methods. The aforementioned modeling approach is demonstrated on the Hyundai Simplified Model (HSM) geometry in this work. This geometry contains flow features that are representative of the dominant noise sources in a typical automobile design; namely vortex shedding from the passenger compartment A-pillar and bluff body shedding from the side view mirrors. The geometry also contains a thick poroelastic material on the interior that acts to reduce the acoustic noise. This material is modeled using a Biot material formulation during the structural acoustic simulation. Successful prediction of the acoustic noise within the HSM geometry serves to validate the vibroacoustic modeling approach for automotive applications.

• Composites Research
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• v.32 no.5
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• pp.206-210
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• 2019

As the use of composite materials of woven structure has expanded to various fields such as automobile and aviation industry, there has been a need for reliability problems and prediction of mechanical properties of woven composites. In this study, finite element analysis for predicting the mechanical properties of composite materials with different weaving structures was conducted to verify similarity with experimental static properties and an effective modeling method was developed. To reflect the characteristics of the weave structure, the meso-scale representative volume element (RVE) was used in modeling. Three-dimensional modeling was carried out by separating the yarn and the pure matrix. Hashin's failure criterion was used to determine whether the element was failed, and the simulation model used a progressive failure model which was suitable for the composite material. Finally, the accordance of the modeling and simulation technique was verified by successfully predicting the mechanical properties of the composite material according to the weave structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.51-51
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• 2009

In this paper, we proposed GaN trench Static Induction Transistor(SIT). Because The compound semiconductor had superior thermal characteristics, GaN and SiC power devices is next generation power semiconductor devices. We carried out modeling of GaN SIT with 2-D device and process simulator. As a result of modeling, we obtained 340V breakdown voltage. The channel thickness was 3um and the channel doping concentration is 1e17cm-3. And we carried out thermal characteristics, too.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.70-73
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• 2001

The layup optimization by genetic algorithm (GA) for the interlaminar strength of laminated composites with free edge is presented. For the calculation of interlaminar stresses of composite laminates with free edges, extended Kantorovich method is applied. In the formulation of GA, repair strategy is adopted for the satisfaction of given constraints. In order to consider the bounded uncertainty of material properties, convex modeling is used. Results of GA optimization with scattered properties are compared with those of optimization with nominal properties. The GA combined with convex modeling can work as a practical tool for maximum interlaminar strength design of laminated composite structures, since uncertainties are always encountered in composite materials and the optimal results can be changed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.12
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• pp.1018-1022
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• 2009

In this paper, we proposed GaN trench Static Induction Transistor(SIT). Because The compound semiconductor had superior thermal characteristics, GaN and SiC power devices is next generation power semiconductor devices. We carried out modeling of GaN SIT with 2-D device and process simulator. As a result of modeling, we obtained 340 V breakdown voltage. The channel thickness was 3 urn and the channel doping concentration is $1e17\;cm^{-3}$. And we carried out thermal characteristics, too.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1057-1062
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• 2007

The purpose of this study is to find out design parameters of vibrating screen, such as particles motion, specific gravity, shape, and kinetic friction. In order to approach this problem, four materials of construction wastes, wood, styrofoam, concrete, and sand are used for dynamic modeling. To present friction between the particles material and tilt plates material, these particles model is applied in order to verify effectively. Generally, the vibrating screen is composed of three assemblies such as screen, wastes guide, supported of screen. This model regards vibrator as system of screen fixed tilt plates. The model is analyzed to present what kind of particles motion while the system is vibrating. and this vibration system has been implemented in a ADAMS dynamaic program. This modeling is consist of dynamic model separation state on particle size. This study make good technique to verify in theory.