• Maxillofacial Plastic and Reconstructive Surgery
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• v.37
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• pp.11.1-11.5
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• 2015

Rapid palatal expansion(RPE) with the tooth-born appliance is not sufficient to apply to the patients with periodontal problem or insufficient tooth anchorage, and it leads to tipping of the anchorage teeth and increasing teeth mobility and root resorption. To avoid these disadvantages, we present the case using palatal screws and custommade palatal expander. A 23-year-old patient underwent surgically assisted rapid maxillary expansion with the Hyrax expansion using 4 tent screws. The study models were used to measure the pre-/-post surgical width of the anterior and posterior dental arches with a digital sliding caliper. In the result, the custom-made palatal expander with 4 tent screws is suitable for delivering a force to the mid-palatal suture expansion. And it is low cost, small sized and simply applied. The results indicated that maxillary expansion with the custom-made palatal anchorage device is predictable and stable technique without significant complications in patients.

• The korean journal of orthodontics
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• v.51 no.3
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• pp.217-227
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• 2021

Maxillary transverse deficiency often manifests as a posterior crossbite or edge-to-edge bite and anterior crowding. However, arbitrary arch expansion in mature patients has been considered to be challenging due to the possible periodontal adverse effects such as alveolar bone dehiscence and gingival recession. To overcome these limitations, nonsurgical maxillary expansion of the basal bone has been demonstrated in young adults. However, the age range for successful orthopedic expansion has remained a topic of debate, possibly due to the underlying individual variations in suture maturity. This case report illustrates nonsurgical, miniscrew-assisted rapid palatal expansion (MARPE) in a 60-year-old patient with maxillary transverse deficiency accompanied by anterior and posterior crossbites, crowding, and gingival recession. The use of MARPE allowed relief of crowding and correction of the crossbite without causing significant periodontal adverse effects.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.997-1002
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• 2009

The local loosening of ballast supporting railway tract cause a differential vertical tract settlement. In the bridge, the temperature change make bridge deck to contract and expand, and this movement cause local loosening of ballast on the bridge expansion joint. Therefore, the evaluation of the status of ballast on the bridge expansion joint is important for the track maintenance of the high-speed railway. In this paper, hwaw method was applied to evaluate the status of ballast on the bridge expansion joint. HWAW method is non-destructive test to evaluate 2-D shear wave velocity map along the railway. Shear wave velocity is directly related with status of ballast. In this research, hwaw method was applied two different types of bridges and determine the degree and the range of the ballast loosening caused by movement of the bridge expansion joint.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.160-163
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• 2004

The hub hole in a wheel of vehicles usually formed with hole expansion process. Formability of material, especially the hole expansion ratio, is important to produce a fine hub hole. The hub hole expansion process is different from general forming process or bore expansion process in the viewpoint of forming a thick plate. In the hole expansion process of the plate with a hole, as the hole being expanded, the crack is occurred to outward direction at the boundary of a hole. Therefore, it is need to apply the fracture criterion in the hub hole expansion process. In this paper, the hub hole expansion process is simulated with commercial elasto-plastic finite element code, LS-DYNA3D considering some ductile fracture criteria. Fracture mode and hole expansion ratio is compared with respect to the fracture criteria. Analysis results demonstrate that only the effective plastic strain is not adequate to predict the fracture mode in the hub hole. And the analysis results also indicate that the ductile fracture criteria properly predict the fracture mode but hole expansion ratio is different with the result of each other because of their different characteristics.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.42-49
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• 2018

In this study, we have developed a prediction model for expansion and contraction behaviors of expansion joint in Gwangan Bridge using machine learning techniques and bridge monitoring data. In the development of the prediction model, two famous machine learning techniques, multiple regression analysis (MRA) and artificial neural network (ANN), were employed. Structural monitoring data obtained from bridge monitoring system of Gwangan Bridge were used to train and validate the developed models. From the results, it was found that the expansion and contraction behaviors predicted by the developed models are matched well with actual expansion and contraction behaviors of Gwangan Bridge. Therefore, it can be concluded that both MRA and ANN models can be used to predict the expansion and contraction behaviors of Gwangan Bridge without actual measurements of those behaviors.

• International Journal of Highway Engineering
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• v.20 no.3
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• pp.65-73
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• 2018

PURPOSES : In this study, the propriety of expansion joint spacing of airport concrete pavement was examined by using weather and material characteristics. METHODS : A finite element model for simulating airport concrete pavement was developed and blowup occurrence due to temperature increase was analyzed. The critical temperature causing the expansion of concrete slab and blow up at the expansion joint was calculated according to the initial vertical displacement at the joint. The amount of expansion that can occur in the concrete slab for 20 years of design life was calculated by summing the expansion and contraction by temperature, alkali-silica reaction, and drying shrinkage. The effective expansion of pavement section between adjacent expansion joints was calculated by subtracting the effective width of expansion joint from the summation of the expansion of the pavement section. The temperature change causing the effective expansion of pavement section was also calculated. The effective expansion equivalent temperature change was compared to the critical temperature, which causes the blowup, according to expansion joint spacing to verify the propriety of expansion joint applied to the airport concrete pavement. RESULTS : When an initial vertical displacement of the expansion joint was 3mm or less, the blowup never occurred for 300m of joint spacing which is used in Korean airports currently. But, there was a risk of blow-up when an initial vertical displacement of the expansion joint was 5mm or more due to the weather or material characteristics. CONCLUSIONS : It was confirmed that the intial vertical displacement at the expansion joint could be managed below 3mm from the previous research results. Accordingly it was concluded that the 300m of current expansion joint spacing of Korean airports could be used without blowup by controling the alkali-silica reaction below its allowable limit.

• Transactions of Materials Processing
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• v.14 no.7 s.79
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• pp.601-606
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• 2005

A hole expansion process is an important process in producing a hub-hole in a wheel disc of a vehicle. In this process, the main parameter is the formability of a material that is expressed as the hole expansion ratio. In the process, a crack is occurred in the upper edge of a hole as the hole is expanded. Since prediction of the forming limit by hole expansion experiment needs tremendous time and effort, an appropriate fracture criterion has to be developed for finite element analysis to define forming limit of the material. In this paper, the hole expansion process of a hub-hole is studied by finite element analysis with ABAQUS/standard considering several ductile fracture criteria. The fracture mode and hole expansion ratio are compared with respect to the various fracture criteria. These criteria do not predict its fracture mode or hole expansion ratio adequately and show deviation from experimental results of hole expansion. A modified ductile fracture criterion is newly proposed to consider the deformation characteristics of a material accurately in a hole expansion process. A fracture propagation analysis at the hub-hole edge is also performed for high accuracy of prediction using the new fracture criterion proposed.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.1559-1563
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• 2009

Despite the serious lack of parking lots, studies on parking lot expansion are insufficient; research on users' satisfaction following parking lot expansion is practically nonexistent. Therefore, this study sought to provide basic data for the parking lot expansion of old apartments by comparatively analyzing users' satisfaction before and after the parking lot expansion through a questionnaire survey that targeted residents benefiting from the expanded parking lot. Results revealed a low post-occupancy satisfaction with the parking lot expansion despite the parking lot expansion and improvement of the parking lot environment. This was because the parking lot was not expanded up to the second basement floor due to the lack of appropriate parking space. Other factors included the construction cost burden and lack of connectivity of the basement parking lot with elevators. The results actually raise the need for the establishment of an optimally suitable expansion plan and development of method and technology requiring lower cost and shorter construction period in the design and construction processes for parking lot expansion. Through post-occupancy evaluation (POE) after parking lot expansion, this study quantitatively identified the problems associated with the parking lots of old apartments and ensuing expansion effects. The findings in this study can be used as basic data to seek a suitable diagnosis and evaluation method for the parking lots of old apartments.

• Archives of Plastic Surgery
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• v.44 no.6
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• pp.523-529
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• 2017

Background Serial tissue expansion is performed to remove giant congenital melanocytic nevi. However, there have been no studies comparing the expansion rate between the subsequent and preceding expansions. In this study, we analyzed the rate of expansion in accordance with the number of surgeries, expander location, expander size, and sex. Methods A retrospective analysis was performed in pediatric patients who underwent tissue expansion for giant congenital melanocytic nevi. We tested four factors that may influence the expansion rate: The number of surgeries, expander location, expander size, and sex. The rate of expansion was calculated by dividing the 'inflation amount' by the 'expander size'. Results The expansion rate, compared with the first-time group, was 1.25 times higher in the second-or-more group (P=0.04) and 1.84 times higher in the third-or-more group (P<0.01). The expansion rate was higher at the trunk than at other sites (P<0.01). There was a tendency of lower expansion rate for larger expanders (P=0.03). Sex did not affect the expansion rate. Conclusions There was a positive correlation between the number of surgeries and the expansion rate, a positive correlation between the expander location and the expansion rate, and a negative correlation between the expander size and the expansion rate.

• The korean journal of orthodontics
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• v.25 no.6 s.53
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• pp.733-746
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• 1995

In narrow maxillary arch, midpalatal suture can be readily opened in growing children with maxillary palatal expansion. In adult patients, narrow maxilla is generally treated surgically because their growth are deemed completed due to their age. However, in patients under 25, midpalatal suture may not be closed. In addition, maxillary expansion may depend upon the closure of other maxillary sutures, which generally remain open at this stage. The present study attempted suture openings with palatal expansion on 5 female patients in their early 20's. The opening was successful in 4 patients, while only one patient showed no suture opening. In all 4 subjects, no discomfort or pain was present during s\expansion, and the successful suture opening was confirmed on occlusal x-rays. Therefore, for those patients with narrow maxilla in their early 20's, rapid palatal expansion or slow palatal expansion may offer a simple and less complicated option which, if successful, may preclude the need for surgery and thereby circumvent the psychological and financial burdens for the patients.