• Journal of ILASS-Korea
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• v.6 no.4
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• pp.31-38
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• 2001

The Holographic Particle Velocimetry system can be a promising optical tool for the measurements of three dimensional particle velocities. In this study, the holographic panicle velocimetry system was used to measure the sizes and velocities of droplets formed by a commercial full cone spray nozzle. Uncertainty analysis was performed to identify the sources of all relevant errors and to evaluate their magnitude. The droplet velocities ranged from 10.3 to 13.3 m/s with average uncertainty of ${\pm}1.6m/s$, which is ${\pm}14%$ of the mean droplet velocity. Compared with relatively small uncertainties of velocity components in the normal direction to the optical axis, the uncertainty of the optical axis component is ${\pm}3.6m/s$. This is due to the long depth of field of droplet images in the optical axis, which is inherent feature of holographic system using forward-scattering object wave of particles.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.3
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• pp.163-170
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• 1987

It is known that reactive component of AC power in the power system gives no energy to outside and cuses enlargiment of power apparatus, voltage fluctuation and unstability of power system. The power conversion system and control system which are composed of power semiconductor devices such as tyristor, transistor, GTO and so on have been appeared as new sources of reactive power. So the cmpensation of reactive power in power semiconductor systems is one of impending problem on the point of energy conservation and inprovement of power factor. This paper treates the fundamental review of the current type power compensation system that compensates the reactive power by MOSFET inverter. This inverter detects not only the reactive power of fundamental wave but also that of all harmoics created in the power semiconductor system and is scheduled to control by sampled value.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1679-1681
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• 2001

In this paper, As the wavelet transform has the properties of multi-resolution analysis and time-frequency domain localization, application of wavelet transform is used at partial discharge(PD) signal detected by electromagnetic wave detection method to extract PD signal's various frequency component and its time domain. therefore we can analyzed PD signal's time-frequency domain simultaneously. On the other hand, using wavelet transform denoising process, inclued noise signal in detected PD signal is well elimiated. we can propose the true shape of PD signal.

• Proceedings of the Korea Society of Mathematical Education Conference
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• 2010.04a
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• pp.291-306
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• 2010

The study reported here is the Australian component of an international research project which seeks to identify student-reported convictions co-valued by them and their teachers during moments of effective mathematics learning. The 2 teachers and their 12 students in the 2 primary school classes associated effective moments of learning with 13 different values. No gender difference was apparent. Although the teachers planned their lessons together and were teaching similar topics, there were differences in what were co-valued. Of the 13 values, examples, sharing, resources, and multimodal representations were found to be commonly valued by students across the 'ability' groups, while the others related to particular 'ability' groups only.

• Journal of Advanced Marine Engineering and Technology
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• v.12 no.2
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• pp.35-45
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• 1988

In this paper an experimental review of condition monitoring method using time domain vibration signals and statically measured wave forms of a multi-components damaged ball bearing is presented first time. Many investigators studied already about vibration characteristics of a single point damaged ball bearing but they did not make efforts to verify vibration phenomena of a multi-components damaged one. Even in case of a tripple components damaged (i.e, outer race, inner race and rolling element) one, the high frequency resonance technique (HERT) and the displacement time domain technique can be also used for its fault detection. According to experimental results undertaken a static displacement measuring method, the defect locations of components can be proposed confidently with simple calculation of the rotating angles of each component.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.7 s.166
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• pp.1215-1222
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• 1999

It is advantageous to use an NDE method to assess the mechanical properties of materials since the conventional method is time-consuming and sometimes requires cutting of sample from the material/component. This paper shows that the ultrasonic and the Barkhausen noise(BHN) methods can be used to accurately characterize forged reactor vessels. The attenuation coefficient of the ultrasonic wave was changed with heat treatment temperature and condition[as-quenched, tempered, PWHT]. The RMS[root mean square] voltage of Barkhausen noise depended on heat treatment temperature and conditions. The fracture appearance transition temperature(FATT) can be predicted using nondestructive evaluation methods.

• Progress in Medical Physics
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• v.9 no.1
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• pp.37-46
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• 1998

Beta-particle energy distributions of the radionuclides in medicine are calculated for the medical physics applications. The radial component solutions of Dirac wave equations are evaluated for a point-nucleus un screened Coulomb potential. The WKB method is employed to correct the screening due to the orbital-electron cloud. Fierz interference terms are ignored. The radionuclides considered are $\^$32/P, $\^$90/Y, $\^$131/I, $\^$166/Ho, $\^$192/Ir, $\^$198/Au, $\^$153/Sm, $\^$169/Er and $\^$188/Re. A total of 9 beta-spectra for the radionuclides, currently in domestic use or potential use in the near future, are calculated with enough accuracy and presented in graphs and tables.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.310-315
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• 1998

This study includes noise automatic inspection system for washing machine auto-transmission one of modern home necessary. We effort to find and certificate sound noisesource by sound power and sound intensity, and apply to frequency analysis in vibration related sound noise. Still more we have been studying to data acquisition and programming for MS VisualBasic version 5.0. System component is below. 1) Pentium PC for data acquisition. 2) DSO for noise acquisition. 3) S/W for comparison and decision. 4) I/F Board for data communication. Wave form data through the DSO are converting to ASCII code data. The ASCII code through binary converting S/W are to be decision fitness or the badness comparison S/W. Finally, we will making noise monitoring system and automatic inspection system.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.25-38
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• 2009

Local failure of a primary structural component induced by direct air-blast loading may be itself a critical damage and lead to the partial or full collapse of the building. As an extensive research to mitigate blast-induced hazards in steel frame structure, a state-of-art analytical approach or high-fidelity computational nonlinear continuum modeling using computational fluid dynamics was described in this paper. The capability of the approach to produce reasonable blast pressures on a steel wide-flange section column was first evaluated. Parametric studies were conducted to observe the effects of section sizes and boundary conditions on behavior and failure of columns in steel frame structures. This study shows that the analytical approach is reasonable and effective to understand the nature of blast wave and complex interaction between blast loading and steel column behavior.

• Smart Structures and Systems
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• v.14 no.4
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• pp.501-516
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• 2014

The rocking pier system (RPS) allows the columns to rock on beam or foundation surfaces during the attacks of a strong earthquake. Literatures have proved that seismic energy dissipated by the RPS through the column impact is limited. To enhance the energy dissipation capacity of a RPS bridge substructure, frictional hinge dampers (FHDs) were installed and evaluated by shaking table tests. The supplemental FHDs consist of two brass plates sandwiched by three steel plates. The strategy of self-centering design is to isolate the seismic energy by RPS at the columns and then dissipate the energy by FHDs at the bridge deck. Component tests of FHD were first conducted to verify the friction coefficient and dynamic characteristic of the FHDs. In total, 32 shaking table tests were conducted to investigate parameters such as wave forms of the earthquake (El Centro 1940 and Kobe 1995) and normal forces applied on the friction dampers. An analytical model was also proposed to compare with the tested damping of the bridge sub-structure with or without FHDs.