• The Journal of Advanced Prosthodontics
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• v.10 no.2
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• pp.128-131
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• 2018

PURPOSE. This study aimed to evaluate the marginal discrepancy of full-arch frameworks in implant-supported prostheses fabricated using pre-sintered soft alloy (PSA). MATERIALS AND METHODS. Full-arch metal frameworks were fabricated on the edentulous implant model using casting alloy (CA), fully-sintered hard alloy (FHA), and PSA (n = 4 in each group). To evaluate the misfit of the framework to the abutments, the absolute marginal discrepancy (AMD) values of the frameworks were measured in cross-sectional images that had been drawn as part of the triple-scan protocol. The AMD values were compared among the tested alloy groups using the Kruskal-Wallis test, with a post hoc Mann-Whitney U test (${\alpha}=.05$). RESULTS. The FHA and PSA groups showed lower marginal discrepancies than the CA group (P<.001). However, the FHA group did not differ significantly from the PSA group. CONCLUSION. Soft alloy milling is comparable to hard alloy milling, and it is more precise than casting in terms of the marginal fit of implant-supported, full-arch prostheses.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.3
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• pp.85-93
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• 2001

In this study, a computer program considering shape imperfections of arch under dynamic loading was developed. The shape imperfection of arch was assumed as higher degree polynomial expressed as $\omega$$_{i}$ = $\omega$$_{o}$ (1-(2$\chi$/L)$^{m}$ )$^n$and sinusoidal curve such as $\omega$$_{i}$ = $\omega$$_{o}$ sin(η$\pi$$\chi$/L). In finite element formulation, the material nonlinear behavior was assumed the elasto-viscoplastic model highly corresponding to the real behavior of the material and the geometrically nonlinear behavior was modeled using Lagrangian description of motion. Also, the behavior of steel was modeled by applying yield criteria of Von Mises. The developed program was applied to the analysis of the dynamic behavior for the clamped beam subjected to the concentrated load at midspan and the results were compared with those from other research to investigate accuracy of the presented finite element program. In numerical examples, the shape imperfections of L/500, L/1,000 and L/2,000 were considered and the modes of shape imperfections of the symmetric and antisymmetric were adopted. The effects of the shape imperfections on the dynamic behavior of arch were conspicuous and results of analysis indicate that the reasonable values of arch rise to arch span ratio ranged between 0.1 and 0.3.

• Structural Engineering and Mechanics
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• v.36 no.4
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• pp.401-419
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• 2010

This paper focuses on the development, verification and application of a three-dimensional nite element code for coupled thermal and structural analysis of roller compacted concrete arch dams. The Ostour Arch dam located on Ghezel-Ozan River, Iran, which was originally designed as conventional concrete arch dam, has been taken for the purpose of verication of the nite element code. In this project, RCC technology has been ascertained as an alternative method to reduce the cost of the project and make it competitive. The thermal analysis has been carried out taking into account the simulation of the sequence of construction, environmental temperature changes, and the wind speed. In addition, the variation of elastic modulus with time has been considered in this investigation using Concard's model. An attempt was made to compare the stresses developed in the dam body five years after the completion of the dam with those of end of the construction. It was seen that there is an increase in the tensile stresses after five years over stresses obtained immediately at the end of construction by 61.3%.

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.84-92
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• 2021

Purpose: The purpose of this study was to compare the dimension safety evaluation between a general ultrasonic cleaner and an ultrasonic cleaner equipped with UV-C (ultraviolet-C). Methods: An edentulous model was prepared. A denture base and an occlusal rim were fabricated, and scanning was performed. After scanning, a denture base and full arch artificial teeth were designed. The full arch artificial teeth were printed using a three-dimensional printer (n=10). The residual resin was washed with alcohol and then scanned (reference data). The printed specimens were classified and cleaned using a general ultrasonic cleaner (GU group) and an ultrasonic cleaner equipped with UV-C (UC group). After each washing, a rescan was performed (scan data). Reference data and scan data were superimposed using overlapping software. Data were statistically analyzed using the Mann-Whitney test (α=0.05). Results: In the deviation values of full arch artificial teeth, the GU group showed a high deviation of 18.02 ㎛ and the UC group showed a low deviation of 15.02 ㎛. The two groups demonstrated a statistically significant difference (p<0.05). Conclusion: Full arch artificial teeth prepared using photopolymerized resin were deformed according to the temperature of water generated in the ultrasonic cleaner. It is judged that there is no deformation according to the UV-C ultrasonic cleaner.

• Advances in concrete construction
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• v.7 no.1
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• pp.11-22
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• 2019

A comprehensive assessing approach for durability of reinforced concrete structures dealing with the corrosion process of rebar subjected to the attack of aggressive agent from environment was proposed in this paper. Corrosion of rebar was suggested in the form of combination of global corrosion and pitting. Firstly, for the purposed of considering the influence of rebar's radius, a type of Plane Corrosion Model (PCM) based on uniform corrosion of rebar was introduced. By means of FE simulation approach, global corrosion process of rebar regarding PCM and LCM (Linear Corrosion Model) was regressed and compared according to the data from Laboratoire $Mat{\acute{e}}riaux$ et $Durabilit{\acute{e}}$ des Constructions (LMDC). Secondly, pitting factor model of rebar in general descend law with corrosion degree was introduced in terms of existing experimental data. Finally, with the comprehensive numerical simulation, the durability of an existing arch bridge was studied in depth in deterministic way, including diffusion process and sectional strength of typical cross section of arch, crossbeam and deck slab. Evolution of structural capacity considering life-cycle rehabilitation strategy indicated the degradation law of durability of reinforced arch bridges.

• Journal of Korean society of Dental Hygiene
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• v.12 no.6
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• pp.1082-1089
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• 2012

Objectives : The aim of this study was to determine the accuracy of digitized stone models, impression materials compared to the master model and the reliability of the computer aided analysis. Methods : A master model(500B-1, Nissin dental product, Japan) with the prepared lower full arch tooth was used. Ten vinyl polysiloxane impressions(Examix$^{(R)}$, GC Industrial Corp, Japan) of master model were taken and type IV stone(aesthetic-base gold$^{(R)}$, Dentona, Germany) were poured in stone models. The linear distance between the reference points were measured and analyzed on the Delcam Copycad$^{(R)}$(Delcam plc, UK). The t-student test for paired samples was used for statistical analysis. Results : The mean differences to master model for stone model and impression material were 0.11~0.19mm, and 0.19~0.29mm, respectively. There were statistical differences in dimensional accuracy for full arch impression between master model and stone model/impressions(p<.05). Conclusions : Two different scanning methods showed clinically acceptable accuracy of full arch digital impression produced by them. These results will have to be confirmed in further clinical studies.

• Steel and Composite Structures
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• v.10 no.6
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• pp.541-561
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• 2010

This paper presents finite element analyses, experimental measurements and finite element model updating of an arch type steel laboratory bridge model using semi-rigid connections. The laboratory bridge model is a single span and fixed base structure with a length of 6.1 m and width of 1.1m. The height of the bridge column is 0.85 m and the maximum arch height is 0.95 m. Firstly, a finite element model of the bridge is created in SAP2000 program and analytical dynamic characteristics such as natural frequencies and mode shapes are determined. Then, experimental measurements using ambient vibration tests are performed and dynamic characteristics (natural frequencies, mode shapes and damping ratios) are obtained. Ambient vibration tests are performed under natural excitations such as wind and small impact effects. The Enhanced Frequency Domain Decomposition method in the frequency domain and the Stochastic Subspace Identification method in the time domain are used to extract the dynamic characteristics. Then the finite element model of the bridge is updated using linear elastic rotational springs in the supports and structural element connections to minimize the differences between analytically and experimentally estimated dynamic characteristics. At the end of the study, maximum differences in the natural frequencies are reduced on average from 47% to 2.6%. It is seen that there is a good agreement between analytical and experimental results after finite element model updating. Also, connection percentages of the all structural elements to joints are determined depending on the rotational spring stiffness.

• Journal of the Korean Geotechnical Society
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• v.32 no.10
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• pp.31-40
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• 2016

In order to investigate the change in soil arch structure developed within the soil subjected to trapdoor movement, various responses in the deformed particle assembly were observed via photoelastic measurement technique. The particle assembly was composed of the regularly stacked model particles coated by thin photoelastic material. Variation of the internal structure transmitting contact forces were observed by taking images showing the photoelastic responses and compared with the change in slip lines and pressures measured by load cells placed beneath the assembly. Initial soil arch structure established immediately after the trapdoor movement collapsed progressively and meanwhile a new extended structure was developed against further movement of the trapdoor. For the sufficient movement of the trapdoor, initially identical regions bounded by the soil arch structure and slip lines were separated and the region enclosed by slip lines became a part of the region loosing the transmitting contact forces identified by photoelastic measurement.

• Korea Real Estate Review
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• v.27 no.3
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• pp.41-50
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• 2017

Previous studies, especially that by Lee (2014), showed how time series volatility models can be applied to the house price series. As the regional housing market trends, however, have shown significant differences of late, analysis with national data may have limited practical implications. This study applied volatility models in analyzing and forecasting regional house prices. The estimation of the AR(1)-ARCH(1), AR(1)-GARCH(1,1), and AR(1)-EGARCH(1,1,1) models confirmed the ARCH and/or GARCH effects in the regional house price series. The RMSEs of out-of-sample forecasts were then compared to identify the best-fitting model for each region. The monthly rates of house price changes in the second half of 2017 were then presented as an example of how the results of this study can be applied in practice.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1363-1372
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• 2014

In the previous study, the structural performance of proposed precast concrete arch with reinforced joint was evaluated by structural experiment. In this paper, finite element analysis considering both material and contact nonlinearity was carried out on the specimens of the previous study. Based on the result of analysis and experiment, friction coefficient between concrete blocks was determined. To evaluate the strength of sectional member, elastic analysis was carried out on the arch using linear elastic analysis program. The section force was compared with the nominal strength of arch section. It was concluded that the maximum load of all the specimens exceed the nominal strength of arch section. Those results of the strength evaluation were similar to the results of structural experiments. Therefore, it is concluded that the elastic analysis and ultimate strength model can effectively evaluate the strength for the proposed precast concrete arch composed of concrete blocks and reinforced joint in design.