• Smart Structures and Systems
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• v.1 no.1
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• pp.83-101
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• 2005

This paper summarizes the application of a rational methodology for the structural assessment of older reinforced concrete Tunisian bridges. This methodology is based on ambient vibration measurement of the bridge, identification of the structure's modal signature and finite element model updating. The selected case study is the Boujnah bridge of the Tunis-Msaken Highway. This bridge is made of a continuous four-span simply supported reinforced concrete slab without girders resting on elastomeric bearings at each support. Ambient vibration tests were conducted on the bridge using a data acquisition system with nine force-balance accelerometers placed at selected locations of the bridge. The Enhanced Frequency Domain Decomposition technique was applied to extract the dynamic characteristics of the bridge. The finite element model was updated in order to obtain a reasonable correlation between experimental and numerical modal properties. For the model updating part of the study, the parameters selected for the updating process include the concrete modulus of elasticity, the elastic bearing stiffness and the foundation spring stiffnesses. The primary objective of the paper is to demonstrate the use of the Enhanced Frequency Domain Decomposition technique combined with model updating to provide data that could be used to assess the structural condition of the selected bridge. The application of the proposed methodology led to a relatively faithful linear elastic model of the bridge in its present condition.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.3
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• pp.213-229
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• 2005

Nuclides in radioactive wastes are assumed to be transported in the geosphere by groundwater and probably discharged into the biosphere. Quantitative evaluation of doses to human beings due to nuclide transport in the geosphere and through the various pathways in the biosphere is the final step of safety assessment of the radioactive waste repository. To calculate the flux to dose conversion factors (DCFs) for nuclides appearing at GBIs with their decay chains, a template ACBIO which is an AMBER case file based on mathematical model for the mass transfer coefficients between the compartments has been developed considering material balance among the compartments in biosphere and then implementing to AMBER, a general and flexible software tool that allows to build dynamic compartment models. An illustrative calculation with ACBIO is shown.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.2
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• pp.183-194
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• 2002

The clustering environment with heterogeneous workstations provides the cost effectiveness and usability for executing applications in parallel. Load balancing is considered a necessary feature for a cluster of heterogeneous workstations to minimize the turnaround time. Previously, static load balancing that assigns a predetermined weight for the processing capability of each workstation, or dynamic approaches which execute a benchmark program to get relative processing capability of each workstation were proposed. The execution of the benchmark program, which has nothing to do with the application being executed, consumes the computation time and the overall turnaround time is delayed. In this paper, we present efficient methods for task distribution and task migration, based on the relative load index. We designed and implemented a load balancing system for the clustering environment with heterogeneous workstations. Turnaround times of our methods and the round-robin approach, as well as the load balancing method using a benchmark program, were compared. The experimental results show that our methods outperform all the other methods that we compared.

• Safety and Health at Work
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• v.6 no.3
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• pp.206-210
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• 2015

Background: Fatigue has a strong impact on workers' performance and safety, but expedient methods for assessing fatigue on the job are not yet available. Studies discuss posturography as an indicator of fatigue, but further evidence for its use in the workplace is needed. The purpose of the study is to examine whether posturography is a suitable indicator of fatigue in clerical workers. Methods: Thirty-six employees (${\emptyset}$ 34.8 years, standard deviation = 12.5) participated in postural tasks (eyes open, eyes closed, arm swinging, and dual task) in the morning and afternoon. Position of their center of pressure (COP) was registered using a Nintendo Wii Balance Board and commercial software. From registered COP time series, we calculated the following parameters: path length (mm), velocity (mm/s), anterior-posterior variance (mm), mediolateral variance (mm), and confidence area ($mm^2$). These parameters were reduced to two orthogonal factors in a factor analysis with varimax rotation. Results: Statistical analysis of the first factor (path length and velocity) showed a significant effect of time of day: COP moved along a shorter path at a lower velocity in the afternoon compared with that in the morning. There also was a significant effect of task, but no significant interaction. Conclusion: Data suggest that postural stability of clerical workers was comparable in the morning and afternoon, but COP movement was greater in the morning. Within the framework of dynamic systems theory, this could indicate that the postural system explored the state space in more detail, and thus was more ready to respond to unexpected perturbations in the morning.

• Journal of the Korean Geotechnical Society
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• v.32 no.12
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• pp.5-13
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• 2016

In this study, Coupled Eulerian-Lagrangian (CEL) analysis, which is one of the large deformation analyses, was incorporated to investigate excavation damage zone (EDZ) under TBM advancement. Considering the quasi-static condition, the dynamic analysis was performed to simulate the real TBM advancement and subsequently a case study on mesh and TBM excavation rate was carried out for satisfying a balance of accuracy and economic computational time. Based on this, a series of parametric studies were performed for different rock types and tunnel diameters. From the numerical analysis results, it is found that EDZ was taken to range within 0.4D(D=tunnel diameter) for most rocks. It is also found that the EDZ tends to increase as the tunnel diameter increases.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.2
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• pp.152-160
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• 2011

The electromagnetic characteristics of FCEVs (fuel cell electric vehicles) are much different from the existing combustion engine cars as well as hybrid, plug-in-hybrid, and pure electric vehicles due to the high voltage/current generated by a fuel cell stack which uses a compressed hydrogen gas reacted with oxygen. To operate fuel cell stack efficiently, BOP (Balance of Plant) which is consisted of many motors in water pump, air blower, and hydrogen recycling pump as well as inverters for these motors is essential. Furthermore, there are also electric systems for entertainment, information, and vehicle control such as navigation, broadcasting, vehicle dynamic control systems, and so on. Since these systems are connected by high voltage or general cables, EMC (Electromagnetic compatibility) analysis for high voltage and general cable of FCEV is the most important element to prevent the possible electric functional safety errors. In this paper, electromagnetic fields by high voltage and general cables for FCEVs is studied. From numerical analysis results, total time harmonic electromagnetic field strength from high voltage and general cables have difference of 13~16 dB due to ground effect by impedance matching. The EMI results of FECV at 10 m distance shows difference of 41 dB at 30 MHz and 54 dB at 230 MHz compared with only general cable routing.

• Journal of architectural history
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• v.21 no.2
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• pp.7-20
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• 2012

As the corner of wooden pagoda forms the roof by closely bordering left and right eaves on the various purlins and angle rafters, it is designed for every face to be recognized as front whose structure system increases load to bear proportionally. The corner of wooden pagoda is inseparable with the corner bracket set as it becomes stable thanks to the corner bracket set structurally and load burden under restrained structure makes the corner bracket set really important. Accordingly, this study could figure out some facts by analyzing corner bracket sets of Palsangjeon of Beobjusa Temple in Korea, Seokgatap of Bulgungsa Temple in China and Ojungtap of Beobryungsa Temple in Japan which were constructed with pure wooden structure. This study demonstrated that corner bracket set played a pivotal role in keeping balance of concentrated load of corner (corner of opening) in each floor that contributed to the stability of wooden pagoda structurally despite multiple duplications of floors and also figured out the outfit of corner bracket set was subject to the floor type and the cross section of Gongpo installed on top of Pyeongju. Wooden pagodas in 3 countries were two floor types of octagon and square, and employed different connection method between upper and lower floors. The difference between floor and duplication method determines the method of corner, but even different methods were sufficient to have entirety in every side by completing dynamic principle of corner bracket set even though old method had to solve the problem of concentrated load and it also confirms that it was essential Gongpo to prevent any deformation of corner.

• Korean Journal of Construction Engineering and Management
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• v.12 no.5
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• pp.35-45
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• 2011

Establishing housing supply strategies in Korean housing market is a crucial issue due to contradictory but concurrent two problems in market; one is the unstable working-class residential and the other is the high vacancy rate by the low-level of sales rate. Although government has been continuously implementing various supply policies in an attempt to evenly distribute houses as well as to keep supply and demand in balance, it is difficult to satisfy all of stakeholders, such as housing consumers, housing owners and housing suppliers. This paper, therefore, applies a system dynamics methodology and offers a dynamic and integrated model encompassing for-profit behaviors of each market participants. The proposed model simulates the future trends of house prices, the balances between supply and demand, construction companies earnings and vacancy rate when applying various housing supply scenarios. From the simulation result, recent governmental small-size rental housing supplies in bulks should utilize private construction companies to stabilize housing distribution rate and private supply system as well as the supply and demand are well balanced.

• Aerospace Engineering and Technology
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• v.3 no.2
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• pp.217-228
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• 2004

This paper presents the rotating test techniques and the results of the roating test of the small-scaled hingeless rotor system with composite paddle blades in hover and forward flight conditions. The small-scaled rotor system was designed using froude-scaled properties of full scale rotor system. Metal flexures and composite flexures were made as hub flexures by the same dynamic properties of rotor system. The rotating tests of hingeless rotor system installed in GSRTS at KARI were carried out to get lead-lag damping ratios and aerodynamic loads of the hingeless rotor system. MBA(Moving Block Analysis) technique was used for the estimation of lead-lag damping ratio. 6-components balance was installed between hub and main shaft and straingauges on blades were instrumented for the measurements of aerodynamic loads of rotor system. Tests were performed on the ground and in the wind tunnel according to the test conditions of hover and forward flight, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.659-665
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• 2010

This paper proposes a control algorithm for quadruped robots moving on irregularly sloped uneven surfaces. Since the body balance of a quadruped robot is controlled by the forces acting on its feet during touchdown, the ground reaction force (GRF) is controlled for stable running. The desired GRF for each foot is generated on the basis of the desired galloping pattern; this GRF is then compared with the actual contact force. The difference between the two forces is used to modify the foot trajectory. The desired force is realized by considering a combination of the rate change of the angular and linear momenta at flight. Then, the amplitude of the GRF to be applied at each foot in order to achieve the desired linear and angular momenta is determined by fuzzy logic. Dynamic simulations of galloping motion were performed using RecurDyn; these simulations show that the proposed control method can be used to achieve stable galloping for a quadruped robot on irregularly sloped uneven surfaces.