• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2696-2707
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• 2021

The purpose of this study is to investigate the efficiency of various structural modeling schemes for evaluating seismic performances and fragility of the reactor containment building (RCB) structure in the advanced power reactor 1400 (APR1400) nuclear power plant (NPP). Four structural modeling schemes, i.e. lumped-mass stick model (LMSM), solid-based finite element model (Solid FEM), multi-layer shell model (MLSM), and beam-truss model (BTM), are developed to simulate the seismic behaviors of the containment structure. A full three-dimensional finite element model (full 3D FEM) is additionally constructed to verify the previous numerical models. A set of input ground motions with response spectra matching to the US NRC 1.60 design spectrum is generated to perform linear and nonlinear time-history analyses. Floor response spectra (FRS) and floor displacements are obtained at the different elevations of the structure since they are critical outputs for evaluating the seismic vulnerability of RCB and secondary components. The results show that the difference in seismic responses between linear and nonlinear analyses gets larger as an earthquake intensity increases. It is observed that the linear analysis underestimates floor displacements while it overestimates floor accelerations. Moreover, a systematic assessment of the capability and efficiency of each structural model is presented thoroughly. MLSM can be an alternative approach to a full 3D FEM, which is complicated in modeling and extremely time-consuming in dynamic analyses. Specifically, BTM is recommended as the optimal model for evaluating the nonlinear seismic performance of NPP structures. Thereafter, linear and nonlinear BTM are employed in a series of time-history analyses to develop fragility curves of RCB for different damage states. It is shown that the linear analysis underestimates the probability of damage of RCB at a given earthquake intensity when compared to the nonlinear analysis. The nonlinear analysis approach is highly suggested for assessing the vulnerability of NPP structures.

• Advances in Computational Design
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• v.4 no.2
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• pp.119-139
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• 2019

Planning and management building projects should tackle the coordination of works and the management of limited spaces, traffic and supplies. Activities cannot be performed without the resources available and resources cannot be used beyond the capacity of workplaces. Otherwise, workspace congestion will negatively affect the flow of works. Better on-site management allows for substantial productivity improvements and cost savings. The procurement system should be able to manage a wider variety of materials and products of the required quality in order to have less stock, in less time, using less space, with less investment and avoiding multiple storage stations. The objective of this paper is to demonstrate the advantages of using the Chronographic modeling, by combining spatiotemporal technical scheduling with the 4D simulations, the Last Planner System and the Takt-time when modeling the construction of building projects. This paper work toward the aforementioned goal by examining the impact that material flow has on site occupancy. The proposed spatiotemporal model promotes efficient site use, defines optimal site-occupancy and workforce-rotation rates, minimizes intermediate stocks, and ensures a suitable procurement process. This paper study the material flow on the site and consider horizontal and vertical paths, traffic flows and appropriate means of transportation to ensure fluidity and safety. This paper contributes to the existing body of knowledge by linking execution and supply to the spatial and temporal aspects. The methodology compare the performance and procurement processes for the proposed Chronographic model with the Gantt-Precedence diagram. Two examples are presented to demonstrate the benefits of the proposed model and to validate the related concepts. This validation is designed to test the model's graphical ability to simulate construction and procurement.

• Journal of Digital Convergence
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• v.20 no.1
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• pp.185-190
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• 2022

Bluetooth is a common wireless technology that is widely used as a connection medium between various consumer electronic devices. The Bluetooth receiver usually adopts a Viterbi algorithm to improve signal-to-noise ratio performance, but requires complex hardware and calculations for continuous search and estimation for the irrational modulation indexes at the transmission. This paper proposes a non-coherent maximum estimation based 8-State Viterbi FSM to solve these complexity problems. The proposed optimal Viterbi FSM can detect Gaussian frequency-shfit keying symbol without any prior information and estimation for the modulation indexes. The HV1/HV2 packets are used for the estimation of the proposed algorithm and the simulation results have shown performance improvements with about 2dB for 10^-3 BER compared to other ideal approaches such as decision direct method.

• Journal of Wellbeing Management and Applied Psychology
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• v.5 no.4
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• pp.19-31
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• 2022

Purpose: This study was conducted to identify indoor air quality in various living spaces using sensors that can measure noise, vibration, fine dust, and odor in real time and to propose optimal indoor air quality maintenance management using Internet of Things(IoT). Research design, data and methodology: Using real-time sensors to monitor physical factors and environmental air pollutants that affect the comfort of the residential environment, Noise, Vibration, Atmospheric Pressure, Blue Light, Formaldehyde, Hydrogen Sulfide, Illumination, Temperature, Ozone, PM10, Aldehyde, Amine, LVOCs and TVOCs were measured. It were measured every 1 seconds from 4 offices and 4 stores on a small scale from November 2018 to January 2019. Results: The difference between illuminance and blue light for each measuring point was found to depend on lighting time, and the ratio of blue light in total illumination was 0.358 ~ 0.393. Formaldehyde and hydrogen sulphide were found to be higher than those that temporarily attract people in an indoor office space that is constantly active, requiring office air ventilation. The noise was found to be 50dB higher than the office WHO recommendation noise level of 35 ~ 40dB. The most important factors for indoor environmental quality were temperature> humidity> illumination> blue light in turn. Conclusions: Various factors that determine the comfort of indoor living space can be measured with real-time sensors. Further, it is judged that the use of IoT can help maintain indoor air quality comfortably.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2D
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• pp.205-216
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• 2008

Urban freeway is defined as the roadway with 4 lanes or more which requires a high design criteria for handling a large capacity of vehicles rapidly as a high-speed exclusive roadway in the city. However, most of the urban freeways suffer from severe traffic congestion due to the increased traffic exceeding their capacities regardless of the morning and afternoon rushhours or the inbound and outbound directions. The purpose in this study is to collect and investigate the real-time traffic characteristics based on the ramp junction influence areas of the urban freeway connected with the Busan port, compare and analyze the traffic characteristic relationship for each lane within the ramp junction influence areas, and finally assess and suggest the optimal capacity for each lane within the ramp junction influence areas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2D
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• pp.295-303
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• 2009

The purpose of present study is to examine the effect of guideway characteristics on runnability of low and medium speed maglev vehicle. Dynamic governing equation for 2-dof vehicle and optimal feedback control scheme are developed. And then the effect of vehicle speed, rail roughness, guideway deflection, continuity of spans, each span length on dynamic response of the UTM-01 maglev vehicle are investigated. From the numerical simulation, it is found that the gap between bogie and guideway does not increase greatly within design velocity of the vehicle. The response of vehicle are mostly affected by the guideway deflection rather than rail roughness. As a result of the present study, the runnability of maglev vehicle can be improved by reducing the maximum deflection of guideway and adopting the continuous girder systems.

• Journal of the Semiconductor & Display Technology
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• v.22 no.3
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• pp.119-124
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• 2023

In this study, experimental approach of the measurement of condensation and evaporation heat transfer coefficients is discussed for mixed refrigerants using in the ultra low-temperature cooling system for semiconductor etching process. An experimental apparatus was described performing the condensation and evaporation heat transfer measurements for mixed refrigerants. The mixed refrigerant used in this study was composed of the optimal mixture determined in previous research, with a composition of Ar:R14:R23:R218 = 0.15:0.4:0.15:0.3. The experiments were conducted over a temperature range from -82℃ to 15℃ and at pressures ranging from 18.5 bar to 5 bar. The convection heat transfer coefficients of the mixed refrigerant were measured at flow rates corresponding to actual operating conditions. The condensation heat transfer coefficient ranged from approximately 0.7 to 0.9 kW/m2K, while the evaporation heat transfer coefficient ranged from 1.0 to 1.7 kW/m2K. The detailed discussion of the experimental methods, procedures, and results were described in this paper.

• Journal of Technologic Dentistry
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• v.46 no.1
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• pp.1-7
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• 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
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• v.26 no.2
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• pp.181-188
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• 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
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• v.33 no.3
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• pp.149-156
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• 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.