• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.205-210
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• 2001

In this work, virtual material characterization of 3D orthogonal woven composites is performed to predict the elastic properties by a full scale FEA. To model the complex geometry of 3D orthogonal woven composites, an accurate unit structure is first prepared. The unit structure includes warp yarns, filler yarns, stuffer yams and resin regions and reveals the geometrical characteristics. For this virtual experiments by using finite element analysis, parallel multifrontal solver is utilized and the computed elastic properties are compared to available experimental results and the other analytical results. It is founded that a good agreement between material properties obtained from virtual characterization and experimental results. Using the method of this virtual material characterization, the effects of inconsistent filler yarn distribution on the in-plane shear modulus and filler yarn waviness on the transverse Young's modulus are investigated. Especially, the stiffness knockdown of 3D woven composite structures is simulated by virtual characterization. Considering these results, the virtual material characterization of composite materials can be used for designing the 3D complex composite structures and may supplement the actual experiments.

• Journal of Fashion Business
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• v.17 no.1
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• pp.30-41
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• 2013

Augmented reality techniques have been increasingly employed in the textile and fashion industry as well as computer graphics sectors. Three-dimensional virtual clothing CAD systems have also been widely used in the textile industries and academic institutes. Motion tracking techniques are grafted together in the 3D and augmented reality techniques in order to develop the virtual three-dimensional clothing and fitting systems in the fashion and textile industry sectors. In this study, three-dimensional virtual clothing sample has been prepared using a 3D virtual clothing CAD along with a 3D scanning and reconstruction system. Motion of the user has been captured through an RGB-D sensor system, and the virtual clothing fitted on the user's body is allowed to move along with the captured motion flow of the user. Acutal fabric specimens are selected for the material characterization. This study is a primary step toward building a comprehensive system for the user to experience interactively virtual clothing under real environment.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.911-914
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• 2005

Soft tissue characterization and modeling based on living tissues has been investigated in order to provide a more realistic behavior in a virtual reality based surgical simulation. In this paper, we characterize the nonlinear viscoelastic properties of intra-abdominal organs using the data from in vivo animal experiments and inverse FE parameter estimation algorithm. In the assumptions of quasi-linear-viscoelastic theory, we estimated the nonlinear material parameters to provide a physically based simulation of tissue deformations. To calibrate the parameters to the experimental results, we developed a three dimensional FE model to simulate the forces at the indenter and an optimization program that updates new parameters and runs the simulation iteratively. The comparison between simulation and experimental behavior of pig intra abdominal soft tissue are presented to provide a validness of the tissue model using our approach.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.12
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• pp.1054-1059
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• 2002

A great deal of research has been done in the field of characterization for piezoelectric thin films after the first report on the measurement for the piezoelectric coefficient of thin films in 1990. The main idea of this research is to provide a distinctive solution for the measurement and standardization of both the longitudinal and the transverse piezoelectric d-coefficients, d33 and d31, of ferroelectric thin films. In general, to get these two coefficients of thin films, two different measuring systems are required. Here, we propose the improved method for the evaluation of these two coefficients with single equipment and with the relatively convenient procedure. The two-step loading process of applying the both positive and the negative pressure has been introduced to acquire the piezoelectric coefficients. These results have been calibrated for both the longitudinal and 4he transverse piezoelectric d-coefficients, d33 and 431, of thin films by comparison with the virtual standard created from FEM. In this experiments, we have obtained d33 of 331pC/N and 031 of -92.2pC/N for the PZT thin films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.47-51
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• 2000

A modified direct bonding technique employing a wet chemical deposition of $SiO_2$ film on a wafer surface to be bonded is proposed for the fabrication of Si-$SiO_2$-Si structures. Structural and electrical quality of the bonded wafers is studied. Satisfied insulating properties of interfacial $SiO_2$ layers are demonstrated. Elastic strain caused by surface morphology is investigated. The diminution of strain in the grooved structures is semi-quantitatively interpreted by a model considering the virtual defects distributed over the interfacial region.

• Journal of Practical Engineering Education
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• v.14 no.3
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• pp.479-489
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• 2022

In order to understand how to increase the use of virtual training content at K University's online lifelong education institute, this study examined the use experience, content recognition, field practice replacement, and requirements, focusing on the examples of operating institutions. To this end, 12 institutions that operated virtual training contents distributed by the K University Online Lifelong Education Center in 2020 were selected for in-depth interviews and qualitative analysis was conducted on the interviews of 11 institutions. As a result of the analysis, first, the experience of using the contents of the virtual training operating institution was aimed at changing the educational environment, supplementing theoretical learning, and improving the sense of practice. Second, according to a survey on the recognition of virtual training content, if the importance and utilization of the content are high, it can be replaced by on-site practice in non-face-to-face classes, such as experiences of facilities and equipment, attracting interest and attention. Third, in many cases, the perception of replacement for field practice is not unreasonable to use as a pre-training material for field practice, but it is difficult to replace field practice. Fourth, content quality improvements can be summarized as content quality improvement, content access and manipulation improvement, dedicated device development, training for instructors, and curriculum systematization. Fifth, institutional requirements include improving the quality of virtual training content itself, equipment support, curriculum systemization and characterization, systematic curriculum and detailed content sharing, detailed guidance on using virtual training content, introducing how to use content, and recruiting instructors. This study is meaningful in that it sought ways to improve the utilization of virtual training content based on the perception of virtual training content operating institutions.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.170-174
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• 2002

In this study, the material characterization and the dynamic behavior of 3D orthogonal woven composite materials has been studied under transverse central low-velocity impact condition by means of the micromechanical model using finite elements. To build up the micromechanical model considering tow spacing and waviness, an accurate unit structure is stacked in x-y-z direction repeatedly. First, the mechanical properties of 3D orthogonal woven composites are obtained by means of virtual experiment using full scale Finite Element Analysis based on the DNS concepts, and the computed elastic properties are validated by comparison to available experimental results[9]. Second, using the implementation of this validated micromechanical model, 3D transient finite-element analysis is performed considering contact and impact, and the impact behavior of 3D orthogonal woven composite is investigated. A comparison study will be carried out in terms of energy absorption capabilities.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.53-56
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• 2005

In this study, the material characterization and the dynamic behavior of 3D orthogonal woven composite materials has been studied under transverse central low-velocity impact condition by means of the micromechanical model using finite elements. To build up the micromechanical model considering tow spacing and waviness, an accurate unit structure is stacked in x-y-z direction repeatedly. First, the mechanical properties of 3D orthogonal woven composites arc obtained by means of virtual experiment using full scale Finite Element Analysis based on the DNS concepts, and the computed elastic properties arc validated by comparison to available experimental results. Second, using the implementation of this validated micromechanical model, 3D transient finite-clement analysis is performed considering contact and impact, and the impact behavior of 3D orthogonal woven composite is investigated. A comparison study with the homogenized model will be carried out in terms of global and local behaviors.

• Composites Research
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• v.21 no.4
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• pp.7-14
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• 2008

Prediction of the load-bearing capacity of an adhesive-bonded Joint is of practical importance for engineers. This paper introduces interface fracture mechanics approach to predict the load-bearing capacity of composite metal bonded joints. The adhesion strength of composite/steel bonding is evaluated in terms of the energy release rate of an interfacial crack and the fracture toughness of the interface. Virtual track closure technique (VCCT) is used to calculate energy release rates, and hi-material end-notched flexure (ENF) specimens are devised to measure the interfacial fracture toughness. Bi-material ENF specimens gave consistent mode II fracture toughness $(G_{IIc})$ values of the composite/steel interface regardless of the thickness of specimens. The critical energy release rates of double-lap joints showed a good agreement with the measured fracture toughness. Therefore. the energy-based interfacial fracture characterization can be a practical engineering tool for predicting the load-bearing capacity of bonded joints.