• Geomechanics and Engineering
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• v.27 no.6
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• pp.537-550
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• 2021

There are various technical problems need to be solved in the construction process of pre-setting an isolation wall into a double lane in the outburst prone mine. This study presents a methodology that pre-setting an isolation wall into a double lane without a coal pillar. This requires the excavation of two small section roadways to dig a wide section roadway, followed by construction of the separation wall. During this process the connecting lane is reserved. In order to ensure the stability of the separation wall, the required bearing capacity of the isolation wall is 4.66 MN/m and the deformation of the isolation wall is approximately 25 cm. To reduce the difficulty of implementing support the roadway is driven by 5 m/d. After the construction of the separation wall, the left side coal wall is brushed 1.5 m to make the width of the gas roadway reach 2.5 m and the roadway support utilizes anchor rod, ladder beam, anchor cable beam and net configuration. During construction, the concrete pump and removable self-propelled hydraulic wall mold are used to pump and pour the concrete of the isolation wall. In the process of mining, the stress distribution of coal body and isolation wall is detected and measured on site. The results demonstrate that the deformation of the surrounding rock of roadway and separation of roof in the roadway is small. The stress of the bolt and anchor cable is within equipment tolerance validating their selection. The roadway is well supported and the intended goal is achieved. The methodology can be used for reference for similar mine gas control.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.12
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• pp.1351-1359
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• 2012

Due to the development of electric and hybrid vehicles, the trend has changed from hydraulic power steering system to electric power steering system (EPS). In this paper, design parameters are deduced through the structural analysis based on the finite element analysis for the intermediate shaft of the EPS on the market. By analyzing the design parameters, the structure design is improved to support the required high torque on the EPS. The numerical analysis is performed to obtain the improved design of the intermediate shaft model and the analysis results are compared with the existing model. It is noted through this numerical approach that the improved design of the intermediate shaft can be acquired the structural safety and high stiffness than existing model.

• ETRI Journal
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• v.38 no.4
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• pp.787-797
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• 2016

Mining, construction, and other special vehicles for heavy use are designed to work under high-performance and off-road working conditions. The driving and executive mechanisms of the support structures and superstructures of these vehicles frequently operate under high loads. Such high loads place the equipment under constant risk of an accident and can jeopardize the dynamic stability of the machinery. An experimental investigation was conducted on a refuse collection vehicle. The aim of this research was to determine the working conditions of a real vehicle: the kinematics of the waste container, that is, a hydraulic rotate drum for waste collection; the dynamics of the load manipulator (superstructure); the vibrations of the vehicle mass; and the strain (stress) of the elements responsible for the supporting structure. For an examination of the force (weight) on the rear axle of a heavy vehicle, caused by its own weight and additional load, a universal measurement system is proposed. As a result of this investigation, we propose an alternative system for continuous vehicle weighing during waste collection while in motion, that is, an on-board weighing system, and provide suggestions for measuring equipment designs.

• Environmental Engineering Research
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• v.14 no.4
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• pp.238-242
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• 2009

This study investigated the effects of organic loading rates on simultaneous carbon and nitrogen removal in an innovative fixed-film aerobic bioreactor. The fixed-film bioreactor (FFB) was composed of a two-compartment aeration tank, in which a synthetic filamentous carrier was submerged as biofilm support media, and a settling tank which polyvinylidene media (Saran) was used as settling aid for suspended solids. Three different organic loading rates, ranging from 0.92-2.02 kg chemical oxygen demand/$m^3$/day were applied by varying hydraulic retention time (HRT). The total soluble organic carbon removal efficiencies were in the range of 90-97%. The removal efficiency of ammonia was found to be in the range of 70-84%. Total nitrogen removal efficiency was found to be in the range of 40-45%, which indicates that denitrification reactions occurred simultaneously in the attached biofilm on the fibrous media in the aeration tank. The settling performance of suspended solids was significantly improved due to the presence of Saran media in the settling compartment, even for a short HRT. The fixed-film aerobic bioreactor used in this study demonstrated efficient treatment efficiency even at higher organic loading rates and at short HRTs.

• International Journal of High-Rise Buildings
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• v.5 no.3
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• pp.167-176
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• 2016

This paper describes a large tuned mass damper (TMD) developed as an effective seismic control device for an existing highrise building. To realize this system, two challenges needed to be overcome. One was how to support a huge mass that has to move in any direction, and the second was how to control mass displacement that reaches up to two meters. A simple pendulum mechanism with strong wires was adopted to solve the first problem. As a solution to the important latter problem, we developed a high-function oil damper with a unique hydraulic circuit. When the mass velocity reaches a certain value, which was predetermined by considering the permissible displacement, the damper automatically and drastically increases its damping coefficient and limits the mass velocity. This velocity limit function can effectively and stably control the mass displacement without any external power. This paper first examines the requirements of the TMD using a simple model and clarifies the constitution of the actual TMD system. Then the seismic upgrading project of an existing high-rise building is outlined, and the developed TMD system and the results of performance tests are described. Finally, control effects for design earthquakes are demonstrated through response analyses and construction progress is introduced.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.641-646
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• 2008

Long and slender body with or without flexible supports under severe operating condition can be unstabilized even by the small cross flow. Turbulent flow mixer, which actually increases thermal-hydraulic performance of the nuclear fuel by boosting turbulence, disturbs the flow field around the fuel rod and affects dynamic behavior of the nuclear fuel rods. Few studies on this problem can be found in the literature because these effects depend on the specific natures of the support and the design of the system. This work shows how the dynamics of a multi-span fuel rod can be affected by the turbulent flow, which is discretely activated by a flow mixer. By solving a state-space form of the eigenvalue equation for a multi-span fuel rod system, the critical velocity at which a fuel rod becomes unstable was established. Based on the simulation results, we evaluated how stability of a multi-spanned nuclear fuel rod with mixing vanes can be affected by the coolant flow in an operating reactor core.

• Transactions of Materials Processing
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• v.20 no.7
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• pp.512-517
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• 2011

TRB(Tailor Rolled Blank) is an emerging manufacturing technology by which engineers are able to change blank thickness continuously within a sheet metal. TRB door inner panels with required larger thicknesses can be used to support localized high loads. In this study, the aluminum alloy 5J32 TRB sheet is used for a door inner panel application. The TRB material properties were varied by using three heat treatment conditions. In order to predict the failure of the aluminum TRB during simulation, the forming limit diagram, which is used in sheet metal forming analysis to determine the criterion for failure, was investigated. Full-field photogrammetric measurement of the TRB deformation was performed with an ARAMIS 3D system. A FE model of the door inner panel was created using Autoform software. The material properties obtained from the tensile tests were used in the numerical model to simulate the door inner of AA 5J32 for each heat treatment condition. After finite element analysis for the evaluation of formability, a prototype front door panel was manufactured using a hydraulic press.

• Journal of Environmental Science International
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• v.9 no.1
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• pp.49-55
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• 2000

An EMERGY analysis of the main energy flows driving the economy of humans and life support systems consists of environmental energies, fuels, and imports, all expresses as solar emjoules. Total EMERGY use(720.0 E20 sej/yr) of the Nakdong River Basin is 96 per cent from imported sources, fuels and goods and services. EMERGY flows from the environment such as rain and geological uplift flux accounted for only 4 percent of total EMERGY use. Consequently, the ratio of outside investment to attracting natural resources was large, like other industrialized areas. EMERGY use per person in the Nakdong River Basin indicates a moderate EMERGY standard of living, even though the indigenous resources are very poor. Population of 6.66 million people in 1996 is already in excess of carrying capacity of the basin. Carrying capacity for steady state based on its renewable sources in only 0.226 million people. EMERGY yield ratio and environment loading ratio were 1.07 and 28.52, respectively. EMERGY sustainability index, a ratio of EMERGY yield ratio to environment loading ratio, is therefore less than one, which is indicative of highly developed consumer oriented economies. This study suggests that the economic structure of the Nakdong River Basin should be transformed from the present industrial structure to the social-economic structure based on an ecological-recycling concept for the sustainable use of the Nakdong River.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.84-91
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• 2003

Flow-Induced Vibration of steam generator tubes may result in fretting wear damage at the tube-to-support locations. KSNP(Korean Standard Nuclear Power plant) steam generators experienced fretting wear in the upper part of U-bend above the central cavity region of steam generators. This region has conditions susceptible to the flow-induced vibration, such as high flow velocity, high void fraction, and longer unsupported span. To improve its performance, APR1400 steam generator is designed with additional supports in this region to reduce unsupported span and to reduce peak velocity in the central cavity region. In this paper, we examined its performance improvement using ATHOS code. The thermal-hydraulic condition in the region of secondary side of APR1400 steam generator is obtained using the ATHOS3 code. The effective mass for modal analysis is calculated using the void fraction, enthalpy, and operating pressure information from ATHOS3 code result. With the effective mass distribution along the tube, natural frequency and mode shape is obtained using ANSYS code. Finally, stability ratios and real mean squared displacements for selected tubes of the APR1400 steam generator are computed. From these results, the current design of the APR1400 steam generator are examined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.399-401
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• 2014

The comprehensive vibration assessment program(CVAP) of APR+ nuclear power plant(NPP) is classified as non-prototype, category II with Palo Verde NPP as valid prototype. In this paper, CVAP for first plant of APR+ NPP is proposed. The Control Element Assembly(CEA) shroud of APR+ NPP is different from that of Palo Verde NPP. And the Core Support Barrel(CSB) outer diameter and the flow rate of normal operation of APR+ NPP are larger than those of Palo Verde NPP. Vibration and stress analysis program should be conducted to establish test acceptance criteria. Limited vibration measurement program should be implemented to establish the margin of safety, demonstrate the satisfaction of test acceptance criteria and confirm the similar vibratory response between the APR+ and Palo Verde NPP. Because of the change of normal operation condition, the nominal differences between APR+ and Palo Verde NPP in the structural and hydraulic analysis are studied to determine the measurement locations.