• Journal of Yeungnam Medical Science
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• v.40 no.3
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• pp.302-307
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• 2023

With recent developments in digital dentistry, research on techniques and materials for three-dimensional (3D) printing is actively underway. We report the clinical applications and outcomes of 3D printing of temporary crowns fabricated with polylactic acid (PLA) using a fused deposition modeling (FDM) printer. Five participants were recruited from among patients scheduled to be treated with a single full-coverage crown at a dental clinic in a university medical center from June to August 2022. We used 3D-printed crowns fabricated with PLA using an FDM printer as temporary crowns and were assessed for discomfort, fracture, and dislodging. The 3D-printed temporary crowns were maintained without fracture, dislodging, or discomfort until the permanent prosthesis was ready. The average time required for printing the temporary crowns was approximately 7 minutes. The 3D printing of temporary crowns with PLA using an FDM printer is a convenient process for dentists. However, these crowns have some limitations, such as rough surface texture and translucency; therefore, the 3D printing process should be improved to produce better prostheses.

• Steel and Composite Structures
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• v.43 no.1
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• pp.91-106
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• 2022

This paper has focused on presenting a three dimensional theory of elasticity for free vibration of 3D-graphene foam reinforced polymer matrix composites (GrF-PMC) cylindrical panels resting on two-parameter elastic foundations. The elastic foundation is considered as a Pasternak model with adding a Shear layer to the Winkler model. The porous graphene foams possessing 3D scaffold structures have been introduced into polymers for enhancing the overall stiffness of the composite structure. Also, 3D graphene foams can distribute uniformly or non-uniformly in the shell thickness direction. The effective Young's modulus, mass density and Poisson's ratio are predicted by the rule of mixture. Three complicated equations of motion for the panel under consideration are semi-analytically solved by using 2-D differential quadrature method. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibration analysis of cylindrical panels with two opposite axial edges simply supported and arbitrary boundary at the curved edges. It is explicated that 3D-GrF skeleton type and weight fraction can significantly affect the vibrational characteristics of GrF-PMC panel resting on two-parameter elastic foundations.

• Journal of the Korean Physical Society
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• v.81
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• pp.516-524
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• 2022

Recently, three-dimensional (3D) nano-processing technology that can increase design freedom and space efficiency of devices has been being rapidly developed, and is highly expected to provide a key path for the development of next-generation optical devices. This technology has shown a high possibility of success in realizing the future devices, but still are facing many challenges in the popularization and practical application. In particular, the ability of quickly, precisely, and stably fabricating complex 3D nanostructures composed of many individual elements is strongly demanded. In recent years, the so-called four-dimensional (4D) nanofabrication technology is attracting attention. The 4D nanofabrication is achieved by applying an external force to manufactured two-dimensional nanostructures, inducing deformation in time, and then precisely transforming them into 3D nanostructures. The 4D nanofabrication technology with excellent flexibility, versatility, functionality, and reconfiguration properties provides a new paradigm enabling effectively control the mechanical, electrical, and optical properties of existing materials. In this review, we examine the conventional methods for fabricating 3D nanostructures, and then investigate 4D nanofabrication technology in detail.

• Structural Engineering and Mechanics
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• v.32 no.3
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• pp.399-406
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• 2009

A three-dimensional panel system, which was offered as a new method for construction in Jordan using relatively high strength modular panels for walls and ceilings, is investigated in this paper. The panel consists of two steel meshes on both sides of an expanded polystyrene core and connected together with a truss wire to provide a 3D system. The top face of the ceiling panel was pored with regular concrete mix, while the bottom face and both faces of the wall panels were cast by shotcreting (dry process). To investigate the structural performance of this system, an extensive experimental testing program for ceiling and wall panels subjected to static and dynamic loadings was conducted. The load-deflection curves were obtained for beam and shear wall elements and wall elements under transverse and axial loads, respectively. Static and dynamic analyses were conducted, and the performance of the proposed structural system was evaluated and compared with a typical three dimensional reinforced concrete frame system for buildings of the same floor areas and number of floors. Compressive strength capacity of a ceiling panel is determined for gravity loads, while flexural capacity is determined under the effect of wind and seismic loading. It was found that, the strength and serviceability requirements could be easily satisfied for buildings constructed using the three-dimensional panel system. The 3D panel system is superior to that of conventional frame system in its dynamic performance, due to its high stiffness to mass ratio.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.317-328
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• 2002

A numerical investigation on the turbulent flows over a three-dimensional steep hill is presented. The numerical model developed for the present work is based on the finite volume method and the SIMPLE algorithm with a non-staggered grid system. Standard $k-{\varepsilon}$ model and Shih's non-linear model are tested for the validation of the prediction accuracy in the 3D separated flow. Comparisons of the mean velocity and turbulence profiles between the numerical predictions and the measurements show good agreement. The Shih's non-linear model is found to predict mean flow and turbulence better than the Standard $k-{\varepsilon}$. Flow patterns have also been examined to explain the difference in the cavity zone between 2D and 3D hills.

• Journal of Broadcast Engineering
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• v.11 no.4 s.33
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• pp.483-494
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• 2006

In this paper, we propose a novel program specific information structure(PSI) in MPEG-2 system for a three-dimensional broadcasting system while guaranteeing compatibility with the conventional digital broadcasting system. The proposed PSI structure including a descriptor of contents type, 2D or 3D, provides service providers with a function of combining 2D and 3D contents freely. However the descriptor is ignored in the conventional digital broadcasting set-top box. With the proposed PSI structure, we designed and implemented a three-dimensional broadcasting system. The proposed system has 2D or 3D display mode for providing user's preference in a three-dimensional broadcasting environment.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.8
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• pp.15-25
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• 1997

The integration method of carier concentrations to redcue the discretization error of th box integratio method used in the discretization of the three-dimensional poisson's equation is presented. The carrier concentration is approximated in the closed form as an exponential function of the linearly varying potential in the element. The presented method is implemented in the three-dimensional poisson's equation solver running under the windows 95. The accuracy and the convergence chaacteristics of the three-dimensional poisson's equation solver are compared with those of DAVINCI for the PN junction diode and the n-MOSFET under the thermal equilibrium and the DC reverse bias. The potential distributions of the simulatied devices from the three-dimensional poisson's equation solver, compared with those of DAVINCI, has a relative error within 2.8%. The average number of iterations needed to obtain the solution of the PN junction diode and the n-MOSFET using the presented method are 11.47 and 11.16 while the those of DAVINCI are 21.73 and 23.0 respectively.

• Journal of information and communication convergence engineering
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• v.17 no.1
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• pp.60-66
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• 2019

In this paper, we propose a new free-view three-dimensional (3D) computational reconstruction of integral imaging to improve the visual quality of reconstructed 3D images when low-resolution elemental images are used. In a conventional free-view reconstruction, the visual quality of the reconstructed 3D images is insufficient to provide 3D information to applications because of the shift and sum process. In addition, its processing speed is slow. To solve these problems, our proposed method uses a pixel rearrangement technique (PERT) with locally selective elemental images. In general, PERT can reconstruct 3D images with a high visual quality at a fast processing speed. However, PERT cannot provide a free-view reconstruction. Therefore, using our proposed method, free-view reconstructed 3D images with high visual qualities can be generated when low-resolution elemental images are used. To show the feasibility of our proposed method, we applied it to optical experiments.

• Current Applied Physics
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• v.18 no.11
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• pp.1235-1239
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• 2018

We present a novel process to fabricate three-dimensional (3D) metallic patterns from 3D printed polymeric structures utilizing different hygroscopic swelling behavior of two different polymeric materials. 3D patterns are printed with two different polymers as cube shape. The surface of the 3D printed polymeric structures is plated with nickel by an electroless plating method. The nickel patterns on the surface of the 3D printed cube shape structure are formed by removing sacrificial layers using the difference in the rate of hygroscopic swelling between two printing polymer materials. The hygroscopic behavior on the interfaced structure was modeled with COMSOL Multiphysics. The surface and electrical properties of the fabricated three-dimensional patterns were analyzed and characterized.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1127-1130
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• 2008

Integral imaging is a three-dimensional display technique which has 100 years of history. The method is characterized by offering full parallax, almost-continuous viewpoints and easiness of moving picture display. In this paper, the history of the method is briefly explained and overview of its current status is provided.