• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.7-17
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• 2019

With increasing demand for large offshore infrastructures, suction cofferdams have been large, and the lid stiffener arrangement for a suction cofferdam has become a key element in cofferdam design to constrain the flexural deformation effectively. This study analyzed the changes in the structural behavior of a lid for a suction cofferdam due to lid stiffeners to provide insights into effective stiffener arrangements. By investigating conventional suction anchors, several stiffener patterns of a lid for a polygonal suction cofferdam were determined and analyzed. The structural performance of the stiffened lids was estimated by comparing the stress and deformation, and the reaction distributions on the edge of lid were investigated to analyze the effects of the stiffener arrangement on the lid-wall interface. Finite element analysis showed that radial stiffeners contribute dominantly to decreasing the stress and vertical deflection of the lids, but the stiffeners cause an increase in shear forces between the lid and wall; the forces are concentrated on the lid near the areas reinforced with radial stiffeners, which is negative to lid-wall connection design. On the other hand, inner and outer circumferential stiffeners show little reinforcement effects in themselves, while they can help reduce the stress and deformation when arranged with partial radial stiffeners simultaneously.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.413-418
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• 2021

Nano-materials with high effective surface areas have been applied to functional materials, such as high sensitive gas sensors and biosensors and high-efficiency catalytic materials. In this study, titanate sheets with a 3D nano-wall-like structure, high effective surface area, were synthesized vertically to the substrate by a chemical bath deposition (CBD) process using a Ti sheet and urea. The synthesis temperature and synthesis duration time were controlled to the optimal conditions of a 3D nano-wall-like structure in the CBD process. The synthesized ammonium titanate sheets with a 3D nano-wall-like structure were annealed in air to transform to TiO2 with a 3D nano-wall-like structure for various applications. As a result, the optimal temperature in the CBD process for the synthesis of a uniform ammonium titanate sheet with a 3D nano-wall-like structure was 90 ℃. TiO2 with a 3D nano-wall-like structure was obtained from the ammonium titanate sheet with a 3D nano-wall-like structure by annealing above 550 ℃ for three hours. In particular, TiO2 with a 3D nano-wall-like structure with a dominant rutile phase was obtained by post-annealing at 700 ℃. On the other hand, damage to the 3D nano-wall edge was observed after 700 ℃ post-annealing.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.54-62
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• 2023

Flapping-wing air vehicles, well known for their free vertical take-off and excellent flight capability, are currently under intensive development and research. While most of the studies have explored the effect of various parameters of synchronized motions on the unsteady aerodynamics of flapping wings, limited attention has been given to the effect of nonsynchronous motions on the unsteady aerodynamic characteristics of flapping wings. In the present study, we conducted a numerical analysis to investigate the unsteady aerodynamic characteristics of an airfoil flapping with different frequency ratios between pitch and heave oscillations. We identified the motions and angle of attacks due to nonsynchronous motions. It was found that the synchronous motion produced thrust with zero lift, but the nonsynchronous motion generated a large lift with little drag. The aerodynamic characteristics of the airfoil undergoing the non-synchronous motion were also analyzed using the vorticity distributions and the pressure coefficient around and on the airfoil. When r was equal to 0.5, larger leading and trailing edge vortices were observed compared to the case when r was equal to 1.0, and these vortices significantly affected the aerodynamic characteristics of the airfoil undergoing the nonsynchronous motion. In future, the effect of pitch amplitude on the unsteady aerodynamic characteristics of the airfoil will be studied.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.4
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• pp.350-359
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• 2005

Sagittal split ramus osteotomy(SSRO) has been commonly performed in the mandibular prognathism. The previous studies of the mandibular anatomy for SSRO have mostly been used in dry skull without consideration of age, sex or jaw relationship of patients. This study was performed to evaluate the location of mandibular canal and the anatomy of ramus, such as the location of mandibular lingula and the ramal bone marrow, which were associated with SSRO procedures, in the patients with mandibular prognathism and normal young adults by using computerized tomographs(CT) and 3D images. The young adults at their twenties, who were considered to complete their skeletal growth, and seen in the Department of Orthodontics and Oral and Maxillofacial Surgery in Chonnam National University Hospital between March 2000 and May 2003, were selected. This study was performed in 30 patients (15men, 15women) who were diagnosed as skeletal class I normal relationship, and another 30 patients (15men, 15women) who were diagnosed as skeletal class III relationship upon clinical examination and lateral cephalometric radiographs. The patients were divided into 2 groups : Class I group, the patients who had skeletal class Ⅰ normal relationship(n=30, 15men, 15women), and Class III group, the patients who had skeletal class III relationship(n=30, 15men, 15women). Facial CT was taken in all patients, and pure 3D mandibular model was constructed by V-works version 4.0. The occlusal plane was designed by three points, such as the mesiobuccal cusp of both mandibular 1st molar and the incisal edge of the right mandibular central incisor, and used as a reference plane. Distances between the tip of mandibular lingula and the occlusal plane, the sigmoid notch, the anterior and the posterior borders of ramus were measured. The height of ramal bone marrow from the occlusal plane and the distance between mid-point of mandibular canal and the buccal or lingual cortex of the mandible in the 1st and 2nd molars were measured by V-works version 4.0. Distance(Li-OP) between the occlusal plane and the tip of mandibular lingula of Class III Group was longer than that of Class I Group in men(p<0.01), but there was no significant difference in women between both groups. Distance(Li-SN) between the sigmoid notch and the tip of mandibular ligula of Class III group was longer than that of Class I Group in men(p<0.05), but there was no significant difference in women between both groups. Distance(Li-RA) between the anterior border of ramus and the tip of mandibular lingula of Class III Group was shorter than that of Class I Group in men and women(p<0.01). Distance(Li-RP) between the posterior border of ramus and the tip of mandibular lingula of Class III Group was slightly shorter than that of Class I Group in men(p<0.05), but there was no significant difference in women between both groups. Distance(RA-RP) between the anterior and the posterior borders of ramus of Class III Group was shorter than that of Class I Group in men and women(p<0.01). Longer the distance(SN-AN) between the sigmoid notch and the antegonial notch was, longer the vertical ramal length above occlusal plane, higher the location of mandibular lingula, and shorter the antero-posterior ramal length were observed(p<0.01). Height of ramal bone marrow of Class III Group was higher than that of Class I Group in men and women(p<0.01). Distance between mandibular canal and buccal cortex of Class III Group in 1st and 2nd lower molars was shorter than that of Class I Group in men and women (p<0.05 in 1st lower molar in men, p<0.01 in others). These results indicate that there are some anatomical differences between the normal occlusal patients and the mandibular prognathic patients, such as the anterior-posterior length of ramus, the height of ramal bone marrow, and the location of mandibular canal.

• Cartoon and Animation Studies
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• s.50
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• pp.101-130
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• 2018

Since the advent of the Smart Devices, the smartphone has become a popular tool to view Webtoon. This phenomenon has caused the convergence of cutting-edge technologies and Webtoons in diverse forms, creating unique versions of Webtoons including, but not limited to Smart-toon, Effect-toon, Cut-toon, Dubbing-toon, Moving-toon, AR-toon, VR-toon, and Interaction-toon. By comparison to these rich diversities of Webtoons in the online industry, there is a lack of academic research on this topic. There are some papers which talk about the different types of multimedia technology conversion and its case presentation or the effectiveness and problems of visual effect, but the effects of these convergence technologies on comic readers' concentration and reading effectiveness have never been investigated so far. Therefore, this paper will discuss the unique method of immersive storytelling that is often used in comics and analyze each aspects of immersive method in technology-converged Webtoons along with its problems. Furthermore, this paper will analyze different aspects of "immersion" and interaction elements that can be found in the popular Interaction-toon, (Encountered). Through this, this paper discusses the positive influence of the interaction elements on comic readers' immersion level and its limitation. To classify the technology-converged Webtoons in terms of the immersion level, the Effect-toon sometimes interferes viewer's flow by using excessive use of multimedia effect, creating information overload. The Smart-toon which applied motions to each frame under horizontal mode of smartphones was a good try, but it hindered the readers' activeness and made it hard for the readers to be fully absorbed in the story. The VR-toon, which utilizes virtual reality gadgets to allow viewers to explore the world of Webtoon was also a nice try to overcome the limitation of vertical screens. However, it often caused dispersion of user's attention and reduced the users' immersion level. The Moving-toon which only emphasized the reading convenience also invaded readers' activeness and disturb users' concentration. On the other hand, the cartoonist Il-Kwon Ha applied high technologies such as face recognition technology, augmented reality techniques, 360-degree panorama technology, and haptic technology to his cartoon (Encountered). This allowed the readers to form a sense of closeness towards the cartoon characters which let the readers to identify themselves with the characters and interact with them. By this way, the readers can be fully immersed in the story. However, technology abuse, impractical production and hackneyed storylining often showed later in the story remains as its limitations.