• Structural Engineering and Mechanics
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• v.75 no.3
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• pp.377-387
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• 2020

Modern long-span floor system typically possesses low damping and low natural frequency, presenting a potential vibration sensitivity problem induced by human activities. Field test and numerical analysis methods are available to study this kind of problems, but would be inconvenient for design engineers. This paper proposes a simplified method to determine the acceleration amplitudes of long-span floor system subjected to walking or running load, which can be carried out manually. To theoretically analyze the acceleration response, the floor system is simplified as an anisotropic rectangular plate and the mode decomposition method is used. To facilitate the calculation of acceleration amplitude a_P, a coefficient α_wmn or α_Rmn is introduced, with the former depending on the geometry and support condition of floor system and the latter on the contact duration t_R and natural frequency. The proposed simplified method is easy for practical use and gives safe structural designs.

• Journal of Welding and Joining
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• v.18 no.1
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• pp.52-58
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• 2000

Spot welding, namely a kind of electric resisting welding has been used widely in field of automobile and aircraft industries because of easiness to apply. Specimens used in this study was a mild steel of 1.2mm thickness and the electrode was a Cu-Cr alloy of 6mm diameter. The surface sheared of specimens after testing of tensile shear was observed by SEM(scanning electron microscope) after ultrasonic cleaning for 10min., and microstructures and grain size of all specimens were measured with using of O.M.(Optical microscope). By the means of measurement and observations of tensile shear load, fatigue strength and share surface, the weldability of spot welding was evaluated. When tensile shearing testing, fracture starting point in all specimens was took place at the bond between HAZ(Heat affected zone) and nugget. With increasing in number of layers, fatigue strength was decreased. With increasing in electric current, grain size in the HAZ became more fine.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.552-555
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• 2004

The reliability issue of the probe tip/recording media interface is one of the most crucial concerns in the Atomic Force Microscope (AFM)-based recording technology. In this work, the tribological characteristics of the probe/media interface were investigated by performing wear tests using an AFM. The ranges of applied normal load and sliding velocity for the wear test were 10 to 50nN and 2 to 20$\mu$m/s respectively. The damage of the probe tip was quantitatively as well as qualitatively characterized by Field Emission Scanning Probe Microscope (FESEM) analysis and calculated based on Archard s wear equation. It was shown that the wear coefficient of the probe tip was in the order of 10$^{-4}$ ~ 10$^{-3}$ , and significant contamination at the end of the probe tip was observed. Thus in order to implement the AFM-based recording technology, tribological optimization of the probe/media interface must be achieved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1429-1433
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• 2004

Recently, a dangerous event occurred at the field industry and mechanical system. At developed by SUNGGOK corp. a R-L clutches of a small and high capacity serves safety device from a variety environment of mechanical system, it permits transmission of driving torque form input to output shaft in both directions of rotation, but restrains any feedback torque of the driven load from rotating the output shaft in either direction. This study was carried out to demonstrate through finite element methode and durability estimation for safety of the R-L clutches without sliding during the engagement process. As results, we organized about endurance test methode when applied rated torque.

• Journal of the Korean Society for Precision Engineering
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• v.1 no.2
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• pp.47-57
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• 1984

The porous matterials are used both to control the flow of the compressed gas and to serve as the bearing surface. This porous design offers several advantages over the conventional externally pressurized gas bearings. It can simplify the construction, lower the gas consumption, and make the cleaning of the gas supply less critical. Test apparatus was cinstructed to experi- mentally investigate maximum load capacity of thrust bearing was measured 200 Kg (15Kg/$\mu$m), and radial bearing was 36 Kg/$\mu$m. And a rotation accuracy of face waving was 0.0127$\mu$m, and center waving was measured 0.5 $\mu$m. Finally, the use of this method of design and manufacturing will contribute to many practical application in the field required for precision and high stability.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.387-392
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• 2002

In many years, post-tensioning method has been used for structural reinforcement of RC structures due to easy installation and good quality control. This study presents practical application results for the effectiveness of structural post-tensioning reinforcement of the FCM bridge girders, cement silos and building girders. For the FCM bridges deflected excessively at the end of girders, for cement silos cracked vertically at silo surface and for building girders deflected due to heavy load from roof, the external post-tensioning method was used for uplifting deflected girders and closing cracks with increasing resisting capacity of the structures. It was demonstrated that all the items were rehabilitated nearly to the initial construction status according to the field test results.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.450-454
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• 1994

From a point of view in energy saving and improvement of productivity, inverter for large power induction motor drive is very important. In this thesis, we developed high voltage inverter for large power induction motor drive. We experimented the inverter with R-L series load, successfully, and are going to do the field test in the real plant.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1284-1286
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• 2001

In this paper, the operating characteristics of a 3 kW class grid-interactive photovoltaic(PV) power system was analysed from January 1998 to December 2000. The construction of the PV system includes a DC/AC inverter for grid connection, PV module, and data Monitoring & Acquisition system. The major results of the field test of the 3 kW class grid-interactive PV system showed that the system utilization rate was 13.83% the conversion efficiency of the inverter was 88% at an over half load, and the PV system generated the electricity more then 300 kWh per month.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.722-729
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• 2010

In this study, we considered the development for degree of compaction for intelligent compaction. In practice, any direct or indirect method can be used as a intelligent compaction method. A series of field tests was conducted using an accelerometer. This is quick and simple indirect methods of measuring soil stiffness. Each result was compared with the results from a plate load test. A prototype device for intelligent compaction was developed, and we evaluated its performance.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.1047-1048
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• 2008

The objective of this paper is to build a decision method of the shape quality for the stainless steel and ensure reducibility of working-load for next rolling process. The criterion of the shape quality is derived from the customer needs, and Automatic Shape Decision System is implemented in SPM (Skin Pass Mill). The methods of shape decision are based on curve fitting and frequency analysis and so on. The Field Test with concerned customers is successful. The performance of right decision is 99% and the claims from the customer have been largely reduced.