• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.193-200
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• 2006

To perform the finish grinding process of ferrules which are widely used as fiber optic connectors, a high-precision centerless grinding machine is necessary. The high-precision centerless grinding machine is consisted of the hydrostatic GW and RW spindle systems, hydrostatic RW feeding mechanism, RW swivel mechanism, on-machine GW and RW dressers, and concrete-filled steel bed. In this study, the thermal characteristics of the high-precision centerless grinding machine such as the temperature distribution, temperature rise and thermal deformation, are estimated based on the virtual prototype of the grinding machine and the heat generation rates of heat sources related to the machine operation conditions. The reliability of the predicted results is demonstrated by the temperature characteristics measured from the physical prototype. Especially, the predicted and measured results show the fact that the high-precision centerless grinding machine has very stable thermal characteristics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.6-9
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• 2005

In this study, the ultra precision centerless grinder for ferrule grinding was designed. As the good-qualified ferrule is required a precise and fine grinding, grinding machine for ferrule must have a high accuracy and a sufficient stiffness. The centerless grinder is composed of the high damping concrete bed, grinding wheel spindle unit, regulating wheel spindle unit, feeding table and dressing unit. For a newly developed centerless grinder, hydrostatic system with high precision feeding and high stiffness was proposed. The grinding and regulating wheel spindle units were composed of hydrostatic spindle and feeding table was hydrostatic table. The prototype of hydrostatic table was manufactured and tested.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.1
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• pp.32-37
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• 2007

The outer diameter finishing grinding process required for ferrules, which are widely used as fiber optic connectors, is carried out by high-precision centerless grinding machines. In this study, the thermal characteristics of such a machine, for example, the temperature distribution, temperature rise, and thermal deformation, were estimated based on a virtual prototype and the heat generation rates of heat sources related to normal operating conditions. The prototype consisted of a concrete-filled bed. hydrostatic grinding wheel (GW) and regulating wheel (RW) spindle systems, a hydrostatic RW feed mechanism, a RW swivel mechanism, and on-machine GW and RW dressers. The reliability of the predicted results was demonstrated using temperature characteristics measured from a physical prototype. The predicted and measured results indicated that this particular high-precision centerless grinding machine had very stable thermal characteristics.

• Journal of the Korean Professional Engineers Association
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• v.19 no.2
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• pp.21-25
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• 1986

Structure-borne noise due to forced vibration which is originated from subway operation and transmitted to buildings in order of rail-wood tie-concrete bed-structure-soil-building foundations-members of building results in social problem of environmental pollution. Moreover this becomes a serious problem because of the increment of surface traffic and subway operation made by meeting traffic system in crowded cities. Since subway is constructed along the principal road or through the residential area and as the worst case may be, building foundations is contact with top part of subway structure, it is possible that vibration resonance results in fatal damage of buildings. And, structure-borne vibration noise due to subway operation at late and early hours have the residents suffer from insonmia, restlessness and so on. Therefore, to satisfy the future need concerning the environmental protection, this report deals with the influence of structure-borne vibration noise on the basis of the characteristics of Seoul Subway System.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.92-97
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• 1994

The there axis CNC grinding machine tool for ultra-precison mirror surface grinding of advanced materials such as ceramics and other hard and brittle materials was designed and manufactured. The grinding machine is composed of the air spindle, the high damping resin concrete bed, and the three axis CNC controller with the high resolution AC servo motor. To investigate the dynamic properties of the grinding machine, the natural frequencies of the spindle and the headstock were experimentally measured. The truing method using the break truer to revise the shape of the metal bonded diamond wheel was developed. Form the results of the machining using the prototype three axis CNC grinding machine manufactured, the mirror surface were achieved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.557-558
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• 2006

In this study, the ultra precision centerless grinder for ferrule grinding was designed. As the good-qualified ferrule is required a precise and fine grinding, grinding machine for ferrule must have a high accuracy and a sufficient stiffness. The centerless grinder is composed of the high damping concrete bed, grinding wheel spindle unit, regulating wheel spindle unit, feeding table and dressing unit. For a newly developed centerless grinder, hydrostatic system with high precision feeding and high stiffness was proposed.

• International Journal of Railway
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• v.6 no.2
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• pp.78-84
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• 2013

This paper is about the first experiment in Korea that was conducted on speeding increase up with rail speeds at 430km/h at high speed railway of designed 350km/h. and analysis data collected on vibration accelerations of roadbed. There are barely references on roadbed behavior measurement with rail speeds more than 350 km/h in Korea as it has never been conducted the experiment on it. So the experiments were confirmed the reliability through crosschecking the figures/values from respective sensors and measuring devices after measuring EMS and ICP types. Based on the study, values of vibration acceleration were less than 12% compared with the ones that conducted while speeding up of HEMU-430X. Also, figures of HSB for concrete bed tracks were 52% against the standard. According to the results, all the performance evaluation of vibration acceleration for roadbeds in transition zones is under the standard.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.35-36
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• 2018

Korea has many problems due to the asphalt pavement or impermeable pavement. Many methods are being implemented to improve water circulation. Among them, permeable packaging materials are used. However, existing permeable packaging materials have a problem of causing efflorescence and clogging the pores. The pores of the permeable packing material are clogged and the permeability is lost. This leads to economic problems and product problems. The purpose of this study was to develop a block to prevent efflorescence.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1087-1091
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• 2004

In this study, the ultra precision centerless grinder for ferrule grinding was designed. The centerless grinder is composed of the high damping concrete bed, grinding wheel spindle unit, regulating wheel spindle unit, feeding table and dressing unit. For a newly developed centerless grinder, hydrostatic system with high precision feeding and high stiffness was proposed. The grinding and regulating wheel spindle units were composed of hydrostatic spindle and feeding table was hydrostatic table. The prototype of hydrostatic table was manufactured and tested.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4D
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• pp.565-569
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• 2011

This paper presents minimum area repair method that is one of the preventive maintenance techniques in asphalt concrete pavements. In this method, a 70cm-width as an effective repair zone was suggested considering the conventional longitudinal damages (rutting and fatigue cracking) in early stages. In addition, the repair zone can be readjusted according to the pavement damage levels. A field test bed was constructed to verify the adaptness for the repair method. Test results revealed that the minimum area repair method can be adopted as a preventive maintenance technique in flexible pavements to recover an appropriate serviceability level. The preventive maintenance method may be one of the major maintenance methods of flexible pavements with an appropriate application. It is also noted that the method may be a long term maintenance cost effective and pavement life ensuring one.