• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.31 no.5
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• pp.390-398
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• 2005

Purpose: The aim of this study was to evaluate the skeletal and dentoalveolar dimensional changes following surgically-assisted rapid maxillary expansion (SARME). Patients & methods: Thirteen adults who had been treated by SARME for transverse maxillary deficiency from May 2000 to December 2003 were evaluated. The SARME procedure was the subtotal Le Fort I osteotomy combined with pterygomaxillary separation and anterior midpalatal osteotomy. Dental study casts and posteroanterior cephalometric radiographs were taken before operation, after removal of expansion device, and follow up period. Nasal cavity width, skeletal and dentoalveolar parameters were measured pre- and post-operatively. Results: 1. Mean nasal cavity width was increased 12%$(0{\sim}21%)$ of total expansion after retention. 2. Mean maxillary interdental width was increased 70%$(47{\sim}99%)$, 95%$(84{\sim}115%)$, and 77%$(57{\sim}94%)$ of total expansion in the canine, the first premolar, and the first molar region, respectively after retention. 3. Mean maxillary alveolar bone width was increased 66%$(42{\sim}84%)$, 74%$(42{\sim}94%)$, and 57%$(31{\sim}78%)$ of total expansion in the canine, the first premolar, and the first molar region, respectively after retention. 4. Mean palatal vault depth was decreased 1.3 mm ($0.5{\sim}2.0$ mm) after retention. 5. Mean interdental and alveolar bone width of the mandibular canine and intermolar width of mandible were slight increased as maxilla was expanded after retention. 6. There were statistical differences between preoperative and postoperative values of nasal cavity, all maxillary interdental and interalveolar widths, palatal vault depth, mandibular interdental and interalveolar width of canine(paired t-test, p<0.05). 7. The maxillary interdental and alveolar bone width were decreased approximately 25% of total expansion by relapse at follow up period. Conclusion: In conclusion, most amounts of maxillary interdental expansions were acquired with the expansion of the maxilla by SARME. For preventing the relapse, approximately 25% of the overexpansion was needed.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.148-155
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• 2013

The steam generators of OPR-1000 plants have Alloy 600 and Alloy 690 as the tube material and its tube expansion method is the explosive expansion method. According to the experience of these plants, circumferential cracks were largely occurred in steam generator tubes expanded by the explosive expansion method and their locations were the outer surface of tube expansion transition region surrounding with piled-up sludge. But even though tubes have the same conditions, tubes with the hydraulic expansion method shows the prevail trend of axial cracks compared to circumferential cracks. Therefore in this study, in order to identify the difference of such phenomena as above, configurations of tube and tubesheet were modeled and at operating conditions, stress values applied in the tube expansion transition area in accordance with tube expansion methods were calculated by using computational program and the direction and the predominance of cracks were evaluated.

• The korean journal of orthodontics
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• v.49 no.3
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• pp.150-160
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• 2019

Objective: This study aimed to analyze the effect of changing various parameters of the bone-borne rapid palatal expander (RPE) using the finite element method (FEM). Methods: In eight experimental groups, we investigated the effect of the number, position, and length of miniscrews; positional changes of the expander; and changes in the hook length on maxillary expansion. In finite element analysis, we compared the magnitude and distribution of stress, and the displacement changes following expansion of the bone-borne RPE. Results: When we compared the number and position of miniscrews, placing miniscrews in the anterior and posterior sides was advantageous for maxillary expansion in terms of stress distribution and displacement changes. Miniscrew length did not significantly affect stress distribution and displacement changes. Furthermore, anteroposterior displacement of the expander did not significantly affect transverse maxillary expansion but had various effects on vertical changes of the maxilla. The maxilla rotated clockwise when the miniscrews were placed in the anterior region. The hook length of the expander did not show consistent results in terms of changes in stress distribution and magnitude or in displacement changes. Conclusions: The findings of this study suggest that changes in the location and length of the miniscrews and displacement of the bone-borne RPE could affect the pattern of the maxillary expansion, depending on the combination of these factors.

• Nuclear Engineering and Technology
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• v.30 no.4
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• pp.377-385
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• 1998

Many nuclear power plants have experienced unscheduled shutdown due to the leakage of steam generator tubes. The leakages are normally due to the crack, possibly stress corrosion cracking (SCC) near the tube expansion at the top of tubesheet or at the tangential point of the row-1 U-bend region. The conventional eddy current technique, which makes use of a differential bobbin coil, has been found to be inadequate for the early detection of SCC. During the in-service inspection, therefore, it is a general practice that the rotating pancake coil (RPC) is used for detecting the cracks. Even in using RPC, however, it is difficult to determine the depth of the cracks quantitatively. This paper attempts to determine the detectability and sizing ability of RPC technique for axial or circumferential cracks at the tube expansion region. The simulated cracks with various dimensions were fabricated by electro-discharge machining (EDM) method. Experimental results are discussed with theoretical calculations.

• The korean journal of orthodontics
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• v.53 no.4
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• pp.241-253
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• 2023

Objective: To evaluate the following null hypothesis: the skeletal and dentoalveolar expansion patterns in the coronal and axial planes are not different with two different types of microimplant-assisted rapid palatal expansion (MARPE) systems. Methods: Pretreatment (T0) and post-MARPE (T1) cone-beam computed tomography (CBCT) images of 32 patients (14 males and 18 females; mean age, 19.37) were analyzed. We compared two different MARPE systems. One MARPE system included the maxillary first premolars, maxillary first molars, and four microimplants as anchors (U46 type, n = 16), while the other included only the maxillary first molars and microimplants as anchors (U6 type, n = 16). Results: In the molar region of the U6 and U46 groups, the transverse expansion at the midnasal, basal, alveolar, and dental levels was 2.64, 3.52, 4.46, and 6.32 mm and 2.17, 2.56, 2.73, and 5.71 mm, respectively. A significant difference was observed in the posterior alveolar-level expansion (p = 0.036) and posterior basal-bone-level expansion (p = 0.043) between the groups, with greater posterior skeletal and alveolar expansion in the U6 group. Conclusions: Compared with the U46 group, the U6 group showed greater posterior expansion at the alveolar and basal-bone levels, with an almost parallel split. Both groups showed a pyramidal expansion pattern in the coronal view.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.167-168
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• 2008

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.50.4-51
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• 2020

We report our discovery of Raman-scattered He II λ6545 feature in young planetary nebulae NGC 6886 and NGC 6881 which indicates the existence of atomic hydrogen components. Considering sharply increasing cross-section of hydrogen atom near the resonance, Raman-scattered He II features are a useful diagnostic tool to investigate the distribution and kinematics of H I region in planetary nebulae. The high-resolution spectroscopic observation was carried out using BOES installed on the 1.8 m telescope of BOAO. We estimate the column density of H I region and its expansion velocity using our grid-based Monte-Carlo radiative transfer code. We assume that the H I region is uniformly distributed in spherical shell geometry with an opening angle and expands with constant speed. Our best-fit model is shown with the column density NHI = 3 × 1020 cm-2 and expansion speed vexp = 25 km s-1 with the opening angle ~ 25° for NGC 6886, and NHI = 4 × 1020 cm-2 and vexp = 30 km s-1 with the opening angle ~ 35° for NGC 6881. We present brief discussions on the late-stage of evolution of stars with mass > 3 M⊙.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.39-46
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• 2019

This paper proposes an adaptive threshold watershed algorithm, which is the method used for image segmentation and boundary detection, which extends the region on the basis of regional minimum point. First, apply adaptive thresholds to determine regional minimum points. Second, it extends the region by applying adaptive thresholds based on determined regional minimum points. Traditional watershed algorithms create over-segmentation, resulting in the disadvantages of breaking boundaries between regions. These segmentation results mainly from the boundary of the object, creating an inaccurate region. To solve these problems, this paper applies an improved watershed algorithm applied with adaptive threshold in regional minimum point search and region expansion in order to reduce over-segmentation and breaking the boundary of region. This resulted in over-segmentation suppression and the result of having the boundary of precisely divided regions. The experimental results show that the proposed algorithm can apply adaptive thresholds to reduce the number of segmented regions and see that the segmented boundary parts are correct.

• Korean Journal of Agricultural and Forest Meteorology
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• v.23 no.4
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• pp.356-365
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• 2021

The nationwide expansion of the agricultural early warning service for agrometeorological disaster would require assessment of geographical and agricultural environmental characteristics by individual region. The development of an efficient computing environment would facilitate such services for the area of study region to deal with various crops and varieties for many farms. In particular, the design of the computing environment would have a considerable impact on the service quality of agriculture meteorology when the scale of computing environments increases for extended service areas. The objectives of this study were to derive the issues on the current computing environment under which services are provided by each region and to seek the solutions to these problems. The self-evaluation through experimental operation for about a year indicated that integration of the early warning service system distributed over different regions would reduce redundant computing procedures and ensure efficient storage and comprehensive management of data. This suggested that the early warning service for agrometeorological disaster would become more stable even when the service areas are to be expanded to the national scale. This would contribute to higher quality services for individual farmers.

• Journal of the Korean Society of Safety
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• v.32 no.4
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• pp.46-52
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• 2017

Sediment exchange in river has been affected by artificial changes such as dredging and abnormal climate changes like intense rainfall. Over last decades in Korea, there were many constructions, restoration or rehabilitation in rivers. Therefore, deposition and erosion become more actively occurred than before, which may threaten the river safety such as flood defense. For safety's sake, the dredging of river bed, which is considered as the most typical measure, has been increased to extend hydraulic conveyance compared with previous conditions. However, since it might change the sediment mechanism, there would be another risk at which unexpected side effects such as headward erosion could be occurred. Particularly, sedimentation at abrupt expansion region is able to lead to hydraulic characteristics like water elevation in the upstream region in the beginning of dredging, which, however, has been barely studied in this field. Therefore in this study, the relationship between sediment mechanism at dredging section and hydraulic characteristics in upstream region were presented through numerical simulations in the idealized abruptly widen channel using Delft3D. The ideal channel of 2,000 m length with each side angle of 45 degrees at abruptly widen expansion region was employed to consider the sediment angle of repose. The sensitivity analysis was performed on the dimensionless factors consisted of upstream and downstream depths($h_u$, $h_d$), width($w_u$, $w_d$), water level(H), flow rate(Q) and discharge of sediment($Q_s$). And the sedimentation amount at dredging and the upstream hydraulic characteristics were investigated through that analysis. It showed that $h_d/h_u$, $H/h_u$ and $w_d/w_u$ were more influential in sequence of effect on sedimentation amount, while $h_d/h_u$, $w_d/w_u$ and $H/h_u$ on upstream region. It means that $h_d/h_u$ was revealed as the most significant factors on sedimentation, also it would most highly affect the rising of water level upstream.