• Journal of Technologic Dentistry
• /
• v.46 no.1
• /
• pp.1-7
• /
• 2024

Purpose: The goal of this study was to determine the clinical acceptability of various cement space settings for the marginal and internal fit of a zirconia core manufactured using additive manufacturing. Methods: The maxillary right incisor served as the master model. After scanning the maxillary right incisor with a dental 3D (three-dimensional) scanner, the stereo lithography file was created using different cement space settings of 40, 120, and 200 ㎛ using computer-aided design software (Dental System 2018; 3Shape). The marginal and internal fit of the 3 groups were determined using the silicon replica technique. Measurement points were divided into the following three categories: margin, axial wall, and incisal. To ensure more accurate measurements, these three measurement points were divided into 8 points. The Shapiro-Wilk, one-way ANOVA, and Tukey's honestly significant difference test (for all tests α=0.05) were the statistical analyses that were included in the study. Results: The CS (cement space)-200 group had better marginal and internal fit than the CS-40 and CS-120 groups, and there were statistically significant differences at the marginal and incisal points, except for the axial wall points. CS-200 group, both marginal and internal fit were within 120 ㎛, which is the clinically acceptable value. Conclusion: This study suggests that a 200 ㎛ cement space setting is ideal for optimal marginal and internal fit of 3D-printed ceramic crowns.

• Journal of the Korea Concrete Institute
• /
• v.26 no.2
• /
• pp.181-188
• /
• 2014

In this study, an interactive analysis considering column-pile interaction is performed on the basis of an equivalent base spring model for supplementing virtual fixed point design of bent pile structures. Through this analytical method, the application of the minimum steel reinforcement ratio of the pile (0.4%) is analyzed by taking into account the major influencing parameters. Furthermore, the limit depth for steel reinforcement ratio is proposed through the relationships between column and pile conditions. To obtain the detailed information, it is found that an interactive analysis is intermediate in theoretical accuracy between the virtual fixed point model analysis and full-modeling analysis. Base on this study, it is also found that the maximum bending moment is located within cracking moment of the pile when material nonlinearity is considered. Therefore, the minimum steel reinforcement ratio is appropriately applicable for the optimal design of bent pile structures. Finally, the limit depth for steel reinforcement ratio ($L_{As=x%}$) is proposed by considering the field measured results. It is shown that the normalized limit depth ratio for steel reinforcement ratio ($L_{As=x%}/L_P$) decreases linearly as the length-diameter ratio of pile ($L_P/D_P$) increases, and then converges at a constant value.

• Journal of Korean Society of Environmental Engineers
• /
• v.33 no.3
• /
• pp.149-156
• /
• 2011

This experimental design and response surface methodology (RSM) have been applied to the investigation of the electro-UV-ultrasonic complex process for the disinfection of E. coli in the water. The disinfection reactions of electro-UV-ultrasonic process were mathematically described as a function of parameters power of electrolysis ($X_1$), UV ($X_2$), and ultrasonic process ($X_3$) being modeled by use of the Box-Behnken technique, which was used for fitting 2nd order response surface model. The application of RSM yielded the following regression equation, which is empirical relationship between the residual E. coli number (Ln CFU) in water and test variables in coded unit: residual E. coli number (Ln CFU) = 23.69 - 3.75 Electrolysis - 0.67 UV - 0.26 Ultrasonic - 0.16 Electrolysis UV + 0.05 Electrolysis Ultrasonic + 0.27 $Electrolysis^2$ + 0.14 $UV^2$ - 0.01 $Ultrasonic^2$). The model predictions agreed well with the experimentally observed result ($R^2$ = 0.983). Graphical 2D contour and 3D response surface plots were used to locate the optimum range. The estimated ridge of maximum response and optimal conditions for residual E. coli number (Ln CFU) using 'numerical optimization' of Design-Expert software were 1.47 Ln CFU/L and 6.94 W of electrolysis, 6.72 W of UV and 14.23 W of ultrasonic process. This study clearly showed that response surface methodology was one of the suitable methods to optimize the operating conditions and minimize the residual E. coli number of the complex disinfection.

• The Journal of Korean Medicine
• /
• v.28 no.4
• /
• pp.74-85
• /
• 2007

Objective : In this study we wanted to confirm if proper stimulation and de-Qi of traditional Korean medical acupuncture could increase hot flash relief efficacy. Design : A randomized controlled, single blind study. We used two modalities of acupuncture, one with optimal stimulation [Study group; Korean medical acupuncture (TKMA)] and one with minimal stimulation [Control group; Minimal acupuncture (MA)]. Same acupoints [PC6(內關), HT8(少府), HT7(神門), LI4(合谷), ST36(足三里), SP6(三陰交), Ren4(關元)] were used in both groups. Fifty-two patients were treated twice a week for 8 weeks, and follow up was done after 4 weeks from the last treatment. Patients were checked hot flash VAS (visual analog scale), frequency and duration every time they visited. Results : Hot flash relief efficacy by 100mm hot flash VAS was obvious in both groups. Hot flash VAS scores of study group were smaller than the scores of control group at the early stage (3rd, $4^{th}$ and $8^{th}$ visit), but there wasn't a remarkable difference between study and control group at the end of the trial. Besides, diminution of hot flash VAS was faster and more even in the study group than control group by visualization using 'Box plot'. We compared frequency and duration of hot flash, 100mm sweating, palpitation, sleep disturbance VAS, and Kupperman Index, MENQOL, Patient's global assessment score. Both groups showed definite decrease from the baseline, but the difference was not statistically significant. There wasn't any adverse event. Hot flash relief efficacy was kept in most patients after 4 weeks' follow-up. Conclusion : Acupoint combination by Traditional Korean medical theory is effective on hot flashes and hot flash relief efficacy was faster and more even in optimal stimulation than minimal stimulation.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.4
• /
• pp.545-560
• /
• 2019

During EPB TBM tunnelling, an appropriate application of additives such as foam and polymer is an essential factor to secure the stability of TBM as well as tunnelling performance. From the '90s, there have been many studies on the optimal injection of additives worldwidely contrary to the domestic situation. Therefore, in this paper, the foam, which is widely adopted for soil conditioning, was selected as an additive in order to investigate the effect of foam injection on TBM performance through a series of laboratory excavation tests. The excavation experiments were carried out on artificial sandy soil specimens with consideration of the variance of FIR (Foam Injection Ratio), FER (Foam Expansion Ratio) and $C_f$ (Surfactant Concentration), which indicate the amount and quality of the foam. During the tests, torque values were measured, and the workability of conditioned soil was evaluated by comparing the slump values of muck after each experiment. In addition, a weight loss of the replaceable aluminum cutter bits installed on the blade was measured to estimate the degree of abrasion. Finally, the foam injection ratio for the optimal TBM excavation for the typical soil specimen was determined by comparing the measured torque, slump value and abrasion. Note that the foam injection conditions satisfying the appropriate level of machine load, mechanical wear and workability are essential in the EPB TBM operational design.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.5
• /
• pp.617-626
• /
• 2019

This study analyzes the optimal location of gas detectors through the gas dispersion in a cargo compressor room of a 174K LNG carrier equipped with high-pressure cargo handling equipment; in addition, we propose a reasonable method for determining the safety regulations specified in the new International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC). To conduct an LNG gas dispersion simulation in the cargo compressor room-equipped with an ME-GI engine-of a 174 K LNG carrier, the geometry of the room as well as the equipment and piping, are designed using the same 3D size at a 1-to-1 scale. Scenarios for a gas leak were examined under high pressure of 305 bar and low pressure of 1 bar. The pinhole sizes for high pressure are 4.5, 5.0, and 5.6mm, and for low pressure are 100 and 140 mm. The results demonstrate that the cargo compressor room will not pose a serious risk with respect to the flammable gas concentration as verified by a ventilation assessment for a 5.6 mm pinhole for a high-pressure leak under gas rupture conditions, and a low-pressure leak of 100 and 140 mm with different pinhole sizes. However, it was confirmed that the actual location of the gas detection sensors in a cargo compressor room, according to the new IGC code, should be moved to other points, and an analysis of the virtual monitor points through a computational fluid dynamics (CFD) simulation.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.27 no.1
• /
• pp.25-35
• /
• 2023

Considering the non-linear behavior of structure and soil when evaluating a nuclear power plant's seismic safety under a beyond-design basis earthquake is essential. In order to obtain the nonlinear response of a nuclear power plant structure, a time-domain SSI analysis method that considers the nonlinearity of soil and structure and the nonlinear Soil-Structure Interaction (SSI) effect is necessary. The Boundary Reaction Method (BRM) is a time-domain SSI analysis method. The BRM can be applied effectively with a Perfectly Matched Layer (PML), which is an effective energy absorbing boundary condition. The BRM has a characteristic that the magnitude of the response in far-field soil increases as the boundary interface of the effective seismic load moves outward. In addition, the PML has poor absorption performance of low-frequency waves. For this reason, the accuracy of the low-frequency response may be degraded when analyzing the combination of the BRM and the PML. In this study, the accuracy of the analysis response was improved by adjusting the PML input parameters to improve this problem. The accuracy of the response was evaluated by using the analysis response using KIESSI-3D, a frequency domain SSI analysis program, as a reference solution. As a result of the analysis applying the optimal PML parameter, the average error rate of the acceleration response spectrum for 9 degrees of freedom of the structure was 3.40%, which was highly similar to the reference result. In addition, time-domain nonlinear SSI analysis was performed with the soil's nonlinearity to show this study's applicability. As a result of nonlinear SSI analysis, plastic deformation was concentrated in the soil around the foundation. The analysis results found that the analysis method combining BRM and PML can be effectively applied to the seismic response analysis of nuclear power plant structures.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.26 no.2
• /
• pp.113-121
• /
• 2013

The structural steel produced in domestic is classified into 5 grades. For economic structural design, the structural engineers need to choose optimal steel grades for structural member types, but the related data is not sufficient. Recently, high strength steel with yield strength in 650MPa was developed in domestic. It provides structural engineers with the wider range of structural steel strength, which leads to the larger difference in economic evaluation. In this paper, the economic evaluation of high-strength steel in building structures is investigated, by applying structural steel with 235MPa, 325MPa and 650MPa in yield strength to various types of structural members, and can be used as basic data for economic structural design.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.1
• /
• pp.506-514
• /
• 2014

Recently the interest about the vortex intakes are rapidly increased because of its performance to drain a plenty of collected storm water at a time. The tangential intake a kind of vortex intakes is very applicable because this type is very simple and little against other types, but it has a big weakness that the vortex flow is not been rarely created below the design discharge. In this study, the characteristics of a tangential intake and two kinds of a newly suggested compound section type intake are analyzed by the 3D numerical modeling based on theories about the control shift and free drainage condition. The analysis focused on the flow condition, flow surface formation, depth-discharge relation, area ratio of air core. Based on this study, the mild-sloped compound section type intake is the optimal, but steep-sloped compound section type is also the optional for the small design discharge.

• Journal of Energy Engineering
• /
• v.29 no.3
• /
• pp.18-24
• /
• 2020

In this study, a lightweight wide impeller for large-area surface treatment was designed and structural stability was confirmed based on finite element(FE) analysis. A lightweight bracket FE model was established through topology optimization, and the optimal FE model was selected after structural analysis. The bending deformation FE analysis was performed, and bending deformation was included in the allowable deformation range. In addition, FE modal analysis was performed, and the range of safe speed(RPM) by rotation was suggested. Ultimately, it was confirmed that this analytical technique is effective for design the lightweight wide impeller.