• Composites Research
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• v.19 no.5
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• pp.1-6
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• 2006

In this study, a closed-form analysis has been developed for the transverse shear behavior of thin-walled composite beams with closed cross-sections. The shear flow distributions and cross-section stiffness coefficients are derived analytically by using a mixed beam approach. The theory has been applied to single-celled composite box-beams with elastic couplings. The location of the shear center and the effect of transverse shear deformation on the static behavior of composite beams are investigated in the framework of the analysis. The present results are validated against those of a two-dimensional finite element analysis and a good correlation has been obtained for box-beam cases considered in this study.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.451-458
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• 2004

The study was focused on the development of computational scheme in three dimensional configurations by applying effective heat capacity model to the numerical procedure in order to predict the temperature profiles of a buried pipeline and the frozen penetration depth(FPD) of a freezing soil medium. To realize this, the investigator conducted the unsteady state heat transfer analysis, using the commercial code ABAQUS, for the freezing granite soil medium including a pipeline in a closed system. The proposed model took into consideration the phase change effect of in situ pore water in the frozen fringe. The comparison of results obtained by the proposed model and the actual performances was valuable in establishing a level of confidence in the application of introduced theory.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.971-977
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• 2015

Because foam metal has the excellent physical characteristics and mechanical performance, they are applied extensively into a lot of advanced technology areas. The aluminum foam with closed cell is one of the foam metals. It is applied widely into automobile and airplane because of the excellent absorption performance of impact energy. In this study, the mechanical characteristics by thickness was analyzed through the impact experiment of closed-cell aluminum foam, and the simulation analysis was performed for the verification. As the simulation analysis method, a finite-element analysis was carried under the same boundary conditions as the experiment by using ANSYS. By comparing with the results of experiment and simulation, it was thought that the case of thickness of 20mm was the most efficient of among the cases of thicknesses of 10mm, 20mm and 30mm. At the case of thickness of 20mm, the absorption energy by comparing with the specimen thickness is shown to become the most among three models. By using the result of this study, it is thought that it can apply the material necessary to develop the mechanical structure with aluminum foam.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.3
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• pp.219-228
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• 2003

Numerical and experimental studies were conducted on the temperature distribution of a buried steel pipe and surrounding granite frozen soils in the closed system. The relationship between unfrozen water content and temperatures was analysed by laboratory test. The thermal conductivity measurements were made to compare the results with a formula presented by Lachenbruch. A steel container model that consists of a freezing chamber and a buried circular steel pipe was built for the laboratory temperature measurements. The time temperature records were measured experimentally, and those records were compared with numerical results obtained from FEM analysis in order to verify the feasibility. The latent heat effect on the granite frozen soils in the numerical study was considered.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.104-106
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• 2004

GIS의 금속으로 차폐된 폐쇄형 스페이서(barrier)의 에폭시 주입구를 통해 방사되는 극초단파 부분방전 신호를 검출할 수 있는 외장형 UHF PD 센서를 제작하였다. 센서에 내장되는 패치안테나는 모노폴(monopole)과 다이폴(dipole) 형태로 설계하여 고주파 전자기장 해석 툴을 이용하여 각각의 특성을 계산하고 분석하였다. 제작된 센서는 362kV GIS의 차폐형 스페이서의 에폭시 주입구에 장착하고 각 센서의 PD 검출 감도와 주파수 특성을 측정하고 비교하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.4
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• pp.470-476
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• 2010

The thermodynamic performance of closed ocean thermal energy conversion (OTEC) cycle with 1 MW gross power was evaluated to obtain the basic data for the optimal design of OTEC. The basic thermodynamic model for OTEC is Rankine cycle and the thermal effluent from power plant was used for the heat source of evaporator. The cycle performance such as efficiency, heat exchanger capacity, etc. was analyzed on the temperature variation of thermal effluent. The saturated pressure of evaporator increased with respect to the increase of thermal effluent temperature, so the cycle efficiency increased and necessary capacity of evaporator and condenser decreased under 1 MW gross power. As the thermal effluent temperature increases about $15^{\circ}C$, the cycle efficiency increased approximately 44%. So, it was revealed that thermal effluent from power plant is important heat source for OTEC plant. Also, if there is an available waste heat, it can be transferred heat to the working fluid form the evaporator through heat exchanger and cycle efficiency will be increased.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.69-77
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• 2017

By producing pre-engineered modular system in the factory, It is enable to expedite construction and can be distinguished from two types by the method resisting load. One is the open-sided modular system composed of beams and columns. The other is enclosed modular system composed of panels and studs. Of the modular systems, the open-sided modular system buildings the connection between modules are difficult due to closed member sections, and the overall strength is reduced as a result of local buckling. In this study, in order to solve these problems, a modular system with folded steel members filled with concrete are proposed. The capacity spectrum method presented in ATC 40 is used for seismic performance assessment of the proposed model structure and the structure with conventional steel members. The analysis results show that at the performance point of each model the number and rotation of plastic hinge formed in the proposed modular system are smaller than those in the conventional system. Based on this observation it is concluded that the proposed system with composite sections has superior seismic capacity compared with conventional system.

• Informatization Policy
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• v.27 no.1
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• pp.72-91
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• 2020

In this study, we classified SNS into open and closed types, and empirically examined in which SNS activity the privacy paradox holds. The idea comes from the argument that privacy paradox may be observed differently in the open SNS, which is more vulnerable to the leakage of personal information due to public profiles, and the closed SNS, which is relatively less vulnerable by limiting the range of acquaintances, The results of the empirical analysis are as follows. First, in case of SNS usage, the privacy paradox holds in the overall SNS activities, but different conclusions are drawn according to open and closed SNS. In particular, it is found that as privacy concerns increase, individuals respond in a reasonable and desirable way to reduce SNS activity in the open SNS, which is more susceptible to infringement. Second, in the case of SNS activity intensity, (i) heavy users are more seriously aware of the probability of privacy infringement than light users, so there is a reasonable response to reducing the intensive margin with increasing privacy concerns, and (ii) this tendency is more clearly observed in open SNS, which is more vulnerable to privacy infringement. Accordingly, insisting that the privacy paradox is empirically established by observing only the overall SNS activities without distinguishing them into open and closed SNS may be interpreted as a "Fallacy of Composition."

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.105-114
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• 2018

Modular system can be divided into two types based on the methods of resisting load. The one is the open-sided modular system composed of beams and columns. The other is the enclosed modular system composed of panels and studs. Of the Modular systems, the use of open-sided modular system is limited because it consists of closed member sections. In order to solve this problem, Choi et al.(2017) proposed a composite modular system with folded steel members filled with concrete. However, it was assumed in the previous study that the connections between modules are composed of rigid joint. Therefore it didn't identify the effect of connection behavior in structure. This study used finite element analysis to calculate stiffness of the connections in the proposed modular system. The linearization method presented in FEMA 440 is used for seismic performance assessment of structures, considering the connection stiffness computed in this study. The result of analysis shows that the capacity and story drift ratio obtained in the model considering stiffness of connection are less than those in the model not considering connection stiffness. Based on this observation, it is concluded that the stiffness of connection has a considerable effect on structural behavior.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.9-18
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• 2019

Modular system can be divided into two types based on the methods of resisting load. The one is the open-sided modular system composed of beams and columns. The other is the enclosed modular system composed of panels and studs. Of the Modular systems, the use of open-sided modular system is limited because it consists of closed member sections. In order to solve this problem, Choi et al.(2017) proposed a composite modular system with folded steel members filled with concrete. However, it was assumed in the previous study that the connections between modules are composed of rigid joint. Therefore it didn't identify the effect of connection behavior in structure. This study used finite element analysis to calculate stiffness of the connections in the proposed modular system. The linearization method presented in FEMA 440 is used for seismic performance assessment of structures, considering the connection stiffness computed in this study. The result of analysis shows that the capacity and story drift ratio obtained in the model considering stiffness of connection are less than those in the model not considering connection stiffness. Based on this observation, it is concluded that the stiffness of connection has a considerable effect on structural behavior.