• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.322-331
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• 2013

This paper describes the development of the pilot plant of distributed intelligent management system for a microgrid. For optimal control and management of microgrids, intelligent agents area applied to the microgrid management system. Each agent includes intelligent algorithms to make decisions on behalf of the corresponding microgrid entity such as distributed generators, local loads, and so on. To this end, each agent has its own resources to evaluate the system conditions by collecting local information and also communicating with other agents. This paper presents key features of the data communication and management of the developed pilot plant such as the construction of mesh network using local wireless communication techniques, the autonomous agent coordination schemes using plug-and-play functions of agents and contract net protocol (CNP) for decision-making. The performance of the pilot plant and developed algorithms are verified via real-time microgrid test bench based on hardware-in-the-loop simulation systems.

• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.627-639
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• 2004

The objective of this research was to evaluate the performance of metal-plate-connected truss joints subjected to cyclic loading conditions that simulated seismic events in the lives of the joints. We also investigated the duration of load factor for these joints. We tested tension splice joints and heel joints from a standard 9.2-m Fink truss constructed from $38-{\times}89-mm$ Douglas-fir lumber: 10 tension splice joints for static condition and for each of 6 cyclic loading conditions (70 joints total) and 10 heel joints for static condition and for each of 3 cyclic loading conditions (40 joints total). We evaluated results by comparing the strengths of the control group (static) with those of the cyclic loading groups. None of the cyclic loading conditions showed any strength degradation; however, there was significant stiffness degradation for both types of joint. The results of this research show that the current duration of load factor of 1.6 for earthquake loading is adequate for these joints.

• Advances in concrete construction
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• v.6 no.5
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• pp.485-507
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• 2018

Concrete-Filled Steel Tube (CFST) columns are an increasingly popular means to support great compressive loads in buildings. The residual strength capacity of CFST stub columns may be utilized to assess the potential damage caused by fire and calculate the structural fire protection for least post-fire repair. Ten specimens under room conditions and 10 specimens under fire exposure to the Eurocode smouldering slow-growth fire were tested to examine the effects of diameter to thickness D/t ratio and reinforcing bars on residual strength capacity, ductility and stiffness of CFST stub columns. On the other hand, in sixteen among the twenty specimens, three or six reinforcing bars were welded inside the steel tube. The longitudinal strains in the steel tube and load-displacement relationships were recorded throughout the subsequent compressive tests. Corresponding values of residual strength capacity calculated using AISC 360-10 and EC4 standards are presented for comparison purposes with the experimental results of this study. The test results showed that after exposure to $750^{\circ}C$, the residual strength capacity increased for all specimens, while the ductility and stiffness were slightly decreased. The comparison results showed that the predicted residual strength using EC4 were close to those obtained experimentally in this research.

• Advances in concrete construction
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• v.10 no.2
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• pp.141-149
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• 2020

In the present study, a mechanical model is applied to account the effects of the surrounding viscoelastic media on the buckling behavior of single microfilament within the cell. The model immeasurably associates filament's bending rigidity, neighboring system elasticity, and cytosol viscosity with buckling wavelengths, buckling growth rates and buckling amplitudes of the filament. Cytoskeleton components in living cell bear large compressive force and are responsible in maintaining the cell shape. Actually these filaments are surrounded by viscoelastic media consisting of other filaments network and viscous cytosole within the cell. This surrounding, viscoelastic media affects the buckling behavior of these filaments when external force is applied on these filaments. The obtained results, indicate that the coupling of viscoelastic media with the viscous cytosol greatly affect the buckling behavior of microfilament. The buckling forces increased with the increase in the intensity of surrounding viscoelastic media.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2117-2122
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• 2004

The main objective of the present study is to investigate the performance characteristics of a ground source heat pump (GSHP) system with a 130 m vertical 60.5 mm nominal diameter U-bend ground heat exchanger. In order to evaluate the performance analysis, the GSHP system connected to a test room with 90 $m^2$ floor area in the Korea Institute of Construction Technology ($37^{\circ}39'$ N, $126^{\circ}48'$ E) was designed and constructed. This GSHP system mainly consisted of ground heat exchanger, indoor heat pump and measuring devices. The cooling and heating loads of the test room were 5.5 and 7.2 kW at design conditions, respectively. The experimental results were obtained from July to January in cooling and heating season of $2003{\sim}2004$. The cooling and heating performance coefficients of the system were determined from the experimental results. The average cooling and heating COPs for the system were obtained to be 4.82 and 3.02, respectively. The temperature variations in ground and the ground heat exchanger surface at different depths were also measured.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.5
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• pp.467-473
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• 2007

Cavitation phenomena appearing on ship propellers have long been interested and recent theoretical analysises give good results comparing with model tests. In accordance with a continuous rise in heavy powered and high speed ships, hull forms have been changed and loads acting on the propeller surface have also been increased, and they result in various and particular cavitations. In some cases, cavitation appears not only on the back but also on the face of the propeller and it causes additive pressure fluctuations and erosion of the propeller and reduces propulsion efficiency of the ship. In this study, we predict the face cavity inception using unsteady propeller analysis based on the panel method and compare the results with experimental observations.

• Steel and Composite Structures
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• v.2 no.1
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• pp.67-84
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• 2002

Traffic decks of steel or composite motorway bridges sometimes provide the opportunity of using the composite action between an existing steel deck and a reinforced concrete plate (RC plate) in the process of rehabilitation, i.e., to increase the load-carrying capacity of the deck for concentrated traffic loads. The steel decks may be orthotropic decks or also unstiffened steel plates, which during the rehabilitation are connected with the RC plate by shear studs, such developing an improved local load distribution by the joint behaviour of the two plate elements. Investigations carried out, both experimentally and numerically, were performed in order to quantitatively assess the combined static behaviour and to qualitatively verify the usability of the structure for dynamic loading. The paper reports on the testing, the numerical simulation as well as the comparison of the results. Conclusions drawn for practical design indicated that the static behaviour of these structures may be very efficient and can also be analysed numerically. Further, the results gave evidence of a highly robust behaviour under fatigue equivalent cyclic traffic loading.

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.249-256
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• 2013

In accordance with the US Nuclear Regulatory Commission (US NRC), Regulatory Guide 1.20, the reactor vessel internals comprehensive vibration assessment program (RVI CVAP) has been developed for an Advanced Power Reactor 1400 (APR1400). The purpose of the RVI CVAP is to verify the structural integrity of the reactor internals to flow-induced loads prior to commercial operation. The APR1400 RVI CVAP consists of four programs (analysis, measurement, inspection, and assessment). Thoughtful preparation is essential to the measurement program, because data acquisition must be performed only once. The optimized design of a vibration and stress measurement system for the RVI CVAP is essential to verify the integrity of the APR1400 RVI. We successfully designed a vibration and stress measurement system for the APR1400 RVI CVAP based on the design materials, the hydraulic and structural analysis results, and performance tests of transducers in an extreme environment. The measurement system designed in this paper will be utilized for the APR1400 RVI CVAP as part of the first construction project in Korea.

• Land and Housing Review
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• v.6 no.1
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• pp.21-29
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• 2015

Coupling beams posses proper strength, stiffness and ductility capacities to resist efficiently under seismic loads. The strength, stiffness and ductility capacities for special diagonally reinforced concrete coupling beam with a span-to-depth ratio 2.0 or less is higher than those of coupling beam with conventionally reinforced concrete coupling beam. However, diagonally reinforced detailing creates major construction problem. In this study, design alternatives for diagonally reinforced concrete coupling beams were experimentally investigated. The results show that angle reinforced coupling beam(specimen SA) exhibited a better stable behavior in comparison with non-diagonally coupling beams(specimens SB-series) and sustained corresponding drift ratio, peak-to-peak stiffness and cumulative dissipated energy in comparison to diagonally coupling beam(specimen CA).

• Journal of the Korean Society for Precision Engineering
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• v.33 no.8
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• pp.623-628
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• 2016

This article describes the determination of the dynamic stability for a heavy press, particularly considering rotational speed. A finite element model of the driving parts for the heavy press was generated. We also applied boundary conditions and dynamic loads considering the driving conditions. Modal analysis was conducted using the finite element construction model. Therefore, no resonance was identified with the comparison between the results of the modal analysis and vibration excitation frequency by the gear tooth. In addition, the stress distribution of the driving parts for press was determined using transient analysis. As compared to the yield strength of the material, the dynamic stability the heavy press was confirmed.