• The Journal of the Acoustical Society of Korea
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• v.36 no.1
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• pp.1-11
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• 2017

In this study, novel approximate form of the square-root operator of three dimensional acoustic Parabolic Equation (3D PE) is proposed using a rational approximant for two variables. This form has two advantages in comparison with existing approximation studies of the square-root operator. One is the wide-angle capability. The proposed form has wider angle accuracy to the inclination angle of ${\pm}62^{\circ}$ from the range axis of 3D PE at the bearing angle of $45^{\circ}$, which is approximately three times the angle limit of the existing 3D PE algorithm. Another is that the denominator of our approximate form can be expressed into the product of one-dimensional operators for depth and cross-range. Such a splitting form is very preferable in the numerical analysis in that the 3D PE can be easily transformed into the tridiagonal matrix equation. To confirm the capability of the proposed approximate form, comparative study of other approximation methods is conducted based on the phase error analysis, and the proposed method shows best performance.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.72-78
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• 1996

This thesis deals with a method to solve a two-and-one-half-dimensional ($2\frac12$ D) problem, which means that the ocean environment is two-dimensional whereas the source is fully three-dimensionally propagating, including three-dimensional refraction phenomena and three-dimensional back-scattering, using two-dimensional two-way parabolic equation method combined with Fourier synthesis. Two dimensional two-way parabolic equation method uses Galerkin's method for depth and Crank-Nicolson method and alternating direction for range and provides a solution available to range-dependent problem with wave-field back-scattered from discontinuous interface. Since wavenumber, k, is the function of depth and vertical or horizontal range, we can reduce a dimension of three-dimensional Helmholtz equation by Fourier transforming in the range direction. Thus transformed two-dimensional Helmholtz equation is solved through two-way parabolic equation method. Finally, we can have the $2\frac12$ D solution by inverse Fourier transformation of the spectral solution gained from in the last step. Numerical simulation has been carried out for a canonical ocean environment with stair-step bottom in order to test its accuracy using the present analysis. With this spectral parabolic equation method, we have examined three-dimensional acoustic propagation properties in a specified site in the Korean Straits.

• Journal of Sensor Science and Technology
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• v.16 no.3
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• pp.220-228
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• 2007

For many applications particularly in navigation system, a three-dimensional representation improves the usability of information. This paper introduces 3D Graphical User Interface (GUI) of indoor location tracking system, 3D Navigation View. The application provides users a 3D visualization of the indoor environments they are exploring, synchronized with the physical world through spatial information obtained from indoor location tracking system. It adopts widely used Virtual Reality Modeling Language (VRML) to construct, represent, distribute and render 3D world of indoor environments over Internet. Java, an all-purpose programming language is integrated to comprehend spatial information received from indoor location tracking system. Both are connected through an interface called External Authoring Interface (EAI) provided by VRML. Via EAI, Java is given the authority to access and manipulate the 3D objects inside the 3D world that facilitates the indication of user's position and viewpoint in the constructed virtual indoor environments periodically.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.12
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• pp.1735-1745
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• 1998

Oil-film surface flow visualizations and three-dimensional flow measurements using a straight five-hole probe have been conducted for a circular impinging jet which is normally oriented to the crossflow in a channel. Throughout the experiments, the ratio of channel height to injection hole diameter, H/D, is fixed to be 1.0, and blowing ratio is varied to be 1.0, 2.0, 3.0 and 4.0. From the surface flow visualizations for both top wall(target plate) and bottom wall, impinging jet region on the target plate can be clearly identified, and for the small value of H/D = 1.0, presence of the bottom wall changes the near-hole flow structure, significantly. The three-dimensional flow measurements show that in the dawnstream region of the injection hole, there exist a pair of counter-rotating vortices, called "scarf vortices", and the strength of the vortices strongly depends on the blowing ratio. In addition, a new flow model in the flow symmetry plane has been proposed for H/D = 1.0.

• Journal of information and communication convergence engineering
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• v.19 no.2
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• pp.108-113
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• 2021

Multiview autostereoscopic three-dimensional (MA3D) displays have the disadvantage that the single-view resolution decreases as the number of views increases. Furthermore, the resolution of MA3D displays is relatively degraded, even though the resolution of two-dimensional displays has increased recently. Therefore, it is unattractive to consumers, and the single-view resolution enhancement of MA3D displays is required. In this study, we developed a method for supplementing the single-view resolution of MA3D displays using a plate beam splitter that can show two MA3D displays simultaneously. By applying our proposed method, the resolution of a single view can increase, and the visual obstruction by the optical plate, which is a problem for MA3D displays, can be solved. In addition, an MA3D display was optically designed and fabricated using a parallax barrier. Finally, the experimental optical results obtained using the proposed method and the only MA3D display were compared.

• Clinics in Shoulder and Elbow
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• v.27 no.1
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• pp.72-78
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• 2024

Background: Clinical outcomes after fixation of distal humerus intraarticular fractures are directly related to the quality of reduction. The use of three-dimensional (3D)-printed fracture models can benefit preoperative planning to ensure good reduction. This review aims to determine if surgery performed with 3D printing assistance are faster and result in fewer complications and improved clinical outcomes than conventional methods. We also outline the benefits and drawbacks of this novel technique in surgical management of distal humerus fractures. Methods: A systematic literature search was carried out in various electronic databases. Search results were screened based on title and abstract. Data from eligible studies were extracted into spreadsheets. Meta-analysis was performed using appropriate computer software. Results: Three randomized controlled trials with 144 cases were included in the final analysis. The 3D-printed group had significantly shorter mean operating time (mean difference, 16.25 minutes; 95% confidence interval [CI], 12.74-19.76 minutes; P<0.001) and mean intraoperative blood loss (30.40 mL; 95% CI, 10.45-60.36 mL; P=0.005) compared with the conventional group. The 3D-printed group also tended to have fewer complications and a better likelihood of good or excellent outcomes as per the Mayo elbow performance score, but this did not reach statistical significance. Conclusions: Three-dimensional-printing-assisted surgery in distal humerus fractures has several benefits in reduced operating time and lower blood loss, indirectly decreasing other complications such as infection and anemia-related issues. Future good-quality studies are required to conclusively demonstrate the benefits of 3D printing in improving clinical outcomes.

• Journal of Fashion Business
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• v.15 no.6
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• pp.101-112
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• 2011

Three-dimensional(3D) virtual clothing simulation system may require the use of physical, mechanical, and configurational data in order to mimic the actual clothing with high degree of realism. Therefore the 3-dimensional scanning system based on optical methods was adopted to extract the 3-dimensional data of the fabric surface. In this study, the appearances of the 3-dimensionally transformed textile fabrics via several finishing procedures were investigated using a 3D scanning system. The wool gauze fabrics treated with the shrink-proof finishing and the felting process showed height changes up to 4.5mm. The 3-dimensional configuration may be objectively described by the use of mesh generation from the scanned output. The generated mesh information may further be utilized in the 3D virtual clothing simulation system for accurate description of the fashionable textile materials used in the simulation system.

• The Journal of the Korea Contents Association
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• v.8 no.2
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• pp.91-99
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• 2008

When making a comic film, the comic presentation that uses stress and exaggeration is the important subject among other things. In this study we tried to investigate the comic effect using the movement of three-dimensional shot. To conduct this study, we extracted the shot manufactured through the Flow Motion of a 3D Production Program Virtual Camera and a High Speed Motion Picture Camera. The shot manufactured applying this manufacturing skill and using three-dimensional production method for the video contents efficiently made was classified into several scenes. The focus of this study is to search for the factor that makes the atmosphere of a story comic through three-dimensional production shot. According to the shot analysis, three-dimensional production method plays a role in developing more stories on space and time by visualizing stories in three dimensions, which makes the most use of the movement of camera, lens and the utilization of focus. In addition, in the presentation where many comic and exaggerated factors are provided, we used the technology that stresses a scene using the size of a shot and the lasting time and presented the method that exaggerates space using a 3D Production Program Virtual Camera and a High Speed Motion Picture Camera. By reviewing the qualitative improvement and the efficient method on making comic films through the possibility that the atmosphere of this three-dimensional shot can apply to the effect for comic presentation, we tried to approach the comic presentation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.3
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• pp.283-291
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• 2015

In this paper, the two-dimensional(2D) and three-dimensional(3D) analyses have been performed in order to evaluate the structural integrities and compare 2D and 3D results for nozzles attached to cylindrical shells. Three nozzles, which are currently used in the nuclear power plant, are chosen to evaluate the structural integrities, and each nozzle is subjected to internal pressure, temperature variation and external loads. It is found that the 2D analysis for internal pressure should be performed with a factor of more than 1.5 or a stress concentration factor; 2D and 3D analysis results for temperature variation are almost similar to each other regardless of cladding; and the analysis results for external loads by WRC Bulletin 297 are more conservative than the 3D analysis results.

• Journal of Conservation Science
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• v.38 no.1
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• pp.55-63
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• 2022

The Bigyeokjincheolloe (bomb shell), a scientific cultural heritage, has outstanding historical value for sustaining a gunpowder weapon of Joseon. In this study, the bomb shell was modeled through three-dimensional (3D) scanning centered on the external shape and 𝛾-ray radiography-based on the internal shape. In particular, to improve the contrast in the radiographic image, optimization and image processing were performed. After these processes, the thickness of the inner wall (2.5 cm on average) and the positions of the three mold chaplets were clearly revealed. For exhibition purposes, the 3D model of the bomb shell was output to a 3D printer and the output was rendered realistic by coloring. In addition, the internal functional elements, such as Mokgok, fuse, mud, gunpowder, and caltrops, were reproduced through handwork. The results will contribute to the study of digital heritages in two ways. First, the internal and external shapes of the bomb shell were modeled by fusing two different technologies, namely, 3D scanning and 𝛾-ray radiography. Second, the internal shape of the bomb shell was constructed from the original form data and the reproduction was utilized for museum exhibitions. The developed modeling approach will greatly expand the scope of museum exhibitions, from those centered on historical content to those centered on scientific content.