• Journal of the Korean GEO-environmental Society
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• v.24 no.9
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• pp.15-24
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• 2023

The behavior of buried pipes is directly influenced by the nonlinearity and complex characteristics of the surrounding soil. However, the simplified beam-spring model, which ignores the nonlinearity and complex behavior of soil, is commonly used in practice. In response, several studies have employed continuum analysis methods to account for the nonlinear and complex behavior of the soil. This paper presents various numerical continuum analysis techniques and verifies their comparison with full-scale tests. The study found that reaction force results close to the full-scale test could be obtained by applying contact surface characteristics that take into account the interaction between the ground and the buried pipe. In the case of sharing pipe and soil node method and ignoring the interaction between pipe and soil, excessive reaction force was derived, and the failure shapes were different. In addition, this study applied the dynamic explicit analysis method, ALE method, and CEL method. It was confirmed that the displacement-reaction relationship and failure shape are similar to those of the static analysis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.5
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• pp.488-496
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• 2023

Ship and bridge structures are a type of long box-shaped structure, and resistance to vertical bending moment is a key factor in their structural design. In particular, because box girders are repeatedly exposed to irregular wave loads for a long time, the continuous collapse behavior of structural members must be accurately predicted. In this study, plastic collapse behavior, including buckling according to load changes of the box girder receiving pure bending moments, was analyzed using a numerical analysis method. The analysis targets were selected as three box girders used in the Gordo experiment. The cause of the difference was considered by comparing the results of the structural strength experiment with those of non-linear finite element analysis. This study proposed a combination of the entire and local sagging shape to reflect the effect of the initial sagging caused by welding heat that is inevitably used to manufacture carbon steel materials. The procedures reviewed in the study and the contents of the initial sagging configuration can be used as a good guide for analyzing the final strength of similar structures in the future.

• Nuclear Engineering and Technology
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• v.27 no.6
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• pp.877-887
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• 1995

YGN 3 is the first nuclear power plant to use the Core Protection Calculator (CPC) as the core protection system and the Core Operating Limit Supervisory System (COLSS) as the core monitor-ing system in Korea. The CPC is designed to provide on-line calculations of Departure from Nucleate Boiling Ratio (DNBR) and Local Power Density (LPD) and to initiate reactor trip if the core conditions exceed the DNBR or LPD design limit. The COLSS is designed to assist the operator in implementing the Limiting Conditions for Operation (LCOs) in Technical Specifications for DNBR/Linear Heat Rate (LHR) margin, azimuthal tilt, and axial shape index and to provide alarm when the LCOs are reached. During YGN 3 initial startup testing, extensive CPC/COLSS related tests ore peformed to ver-ify the CPC/COLSS performance and to obtain optimum CPC/COLSS calibration constants at var, -ious core conditions. Most of test results met their specific acceptance criteria. In the case of missing the acceptance criteria, the test results ore analyzed, evaluated, and justified. Through the analysis and evaluation of each of the CPC/COLSS related test results, it can be concluded that the CPC/COLSS are successfully Implemented as designed at YGN 3.

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.243-249
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• 2023

The occurrence of cavitation on the propeller is directly linked to the naval ship's survivability, and it is necessary to design a propeller shape that delays the cavitation inception. However, the propeller cavitation can occur under various operating conditions, thus it is important to identify whether the propeller cavitation exists during operation as well as in the design phase. To this end, it is necessary to use noise or vibration signals on board to monitor the cavitation inception. In this study, a hydrophone and an accelerometer were installed on the ship hull right above the propeller to compare the performance of analyzing cavitation inception between acoustic and vibration signals. Also, a high speed camera was used to visually observe the occurrence of cavitation through an observation window. The measured results showed that the spectral shapes between acoustic and vibration signals were different, but the level increases at each frequency band and the overall level of the frequency band from 1 kHz to 10 kHz showed a similar tendency. The Detection of Envelope Modulation On Noise (DEMON) analysis also showed similar results for both acoustic and vibration signals, confirming that both hydrophones and accelerometers can be utilized in the analysis of cavitation inception.

• Journal of Internet of Things and Convergence
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• v.9 no.3
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• pp.93-98
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• 2023

In this paper, an artificial neural network based on simulated annealing was constructed. The mapping relationship between the parameters of micro-scaled flow channels electrochemical machining and the channel shape was established by training the samples. The depth and width of micro-scaled flow channels electrochemical machining on stainless steel surface were predicted, and the flow channels experiment was carried out with pulse power supply in NaNO3 solution to verify the established network model. The results show that the depth and width of the channel predicted by the simulated annealing artificial neural network with "4-7-2" structure are very close to the experimental values, and the error is less than 5.3%. The predicted and experimental data show that the etching degree in the process of channels electrochemical machining is closely related to voltage and current density. When the voltage is less than 5V, a "small island" is formed in the channel; When the voltage is greater than 40V, the lateral etching of the channel is relatively large, and the "dam" between the channels disappears. When the voltage is 25V, the machining morphology of the channel is the best.

• Korea Science and Art Forum
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• v.23
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• pp.149-162
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• 2016

Here are background, method, scope, main contents of this research. As the interests increased in recent about the construction in complex and diverse areas, construction is locally connected to human life like to coexistence of the technology and culture. The local development should not be fragmentary construction to improve local recycling ability. Local society should be inherited by modern cultural perspective through a variety of local culture and coexistence. Effective decision making analysis is necessary to build a livable area with a combination of high-tech industry. For this reason, this paper will study the political analysis for decision making at the planning stage of construction in point of fusion of technology and culture by using unstructured data analysis. Conclusion is as in the following. Local planning stage of construction describes diverse meanings of intangible and intangible factors as political factor. Technology factors have various qualitative and quantitative factors in construction field. Understanding decision making at the planning stage of construction means not only visible 'technology factor' such as structure, method, shape, and so on, but also invisible 'culture factor' such as spirit of age, religion, learning, and life-style reflected in formation process of space, and insight of brain power about art.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.394-400
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• 2023

In this study, the tuning phenomena, gas storage capacity, and thermal expansion behaviors of binary (cyclopentylamine + CH₄) and (cyclopropylamine + CH₄) clathrate hydrates were investigated for the potential applications of clathrate hydrates to gas storage. To understand the tuning behaviors of binary (cyclopentylamine + CH₄) and (cyclopropylamine + CH₄) clathrate hydrates, ¹³C solid-state NMR spectroscopy was used, and the results confirmed that maximum tuning factors for the binary (cyclopentylamine + CH₄) and (cyclopropylamine + CH₄) clathrate hydrates were achieved at 0.5 mol% and 1.0 mol% of guest concentration, respectively. The gas storage capacity of binary (cyclopentylamine + CH₄) and (cyclopropylamine + CH₄) clathrate hydrates were also checked, and the results showed the CH₄ capacity of our hydrate systems was superior to that of binary (tetrahydrofuran + CH₄) and (cyclopentane + CH₄) clathrate hydrates. The synchrotron diffraction patterns of these hydrates collected at 100, 150, 200, and 250 K confirmed the formation of a cubic Fd-3m hydrate. In addition, the lattice constant of clathrate hydrates with cyclopentylamine and methane were larger than that with cyclopropylamine and methane due to the effects of molecular size and shape.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.441-452
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• 2009

This paper describes the evaluation technique for climate change effect on daily precipitation frequency using daily precipitation generator that can use outputs of the climate model offered by IPCC DDC. Seoul station of KMA was selected as a study site. This study developed daily precipitation generation model based on two-state markov chain model which have transition probability, scale parameter, and shape parameter of Gamma-2 distribution. Each parameters were estimated from regression analysis between mentioned parameters and monthly total precipitation. Then the regression equations were applied for computing 4 parameters equal to monthly total precipitation downscaled by K-NN to generate daily precipitation considering climate change. A2 scenario of the BCM2 model was projected based on 20c3m(20th Century climate) scenario and difference of daily rainfall frequency was added to the observed rainfall frequency. Gumbel distribution function was used as a probability density function and parameters were estimated using probability weighted moments method for frequency analysis. As a result, there is a small decrease in 2020s and rainfall frequencies of 2050s, 2080s are little bit increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.1-13
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• 2010

This paper presents an investigation on the geometric nonlinear behavior of cable-stayed bridges using geometric nonlinear finite element analysis method. The girder and mast in cable-stayed bridges show the combined axial load and bending moment interaction due to horizontal and vertical forces of inclined cable. So these members are considered as beam-column member. In this study, the nonlinear finite element analysis method is used to resolve the geometric nonlinear behavior of cable-stayed bridges in consideration of beam-column effect, large displacement effect (known as P-${\delta}$ effect) and cable sag effect. To analyze a cable-stayed bridge model, nonlinear 6-degree of freedom frame element and nonlinear 3-degree of freedom equivalent truss element is used. To resolve the geometric nonlinear behavior for various live load cases, the initial shape analysis is performed for considering dead load before live load analysis. Then the geometric nonlinear analysis for each live load case is performed. The deformed shapes of each model, load-displacement curves of each point and load-tensile force curves for each cable are presented for quantitative study of geometric nonlinear behavior of cable-stayed bridges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6A
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• pp.789-798
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• 2008

The stiffness method provides a framework to calculate the structural deformations directly from solving the equilibrium state. However, to use the displacement shape functions leads to approximate estimation of stiffness matrix and resisting forces, and accordingly results in a low accuracy. The conventional flexibility method uses the relation between sectional forces and nodal forces in which the equilibrium is always satisfied over all sections along the element. However, the determination of the element resisting forces is not so straightforward. In this study, a new fiber finite element mixed method has been developed for nonlinear anaysis of steel-concrete composite structures in the context of a standard finite element analysis program. The proposed method applies the Newton method based on the load control and uses the incremental secant stiffness method which is computationally efficient and stable. Also, the method is employed to analyze the steel-concrete composite structures, and the analysis results are compared with those obtained by ABAQUS. The comparison shows that the proposed method consistently well predicts the nonlinear behavior of the composite structures, and gives good efficiency.