• Journal of Power Electronics
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• v.12 no.4
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• pp.632-642
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• 2012

This paper presents a filter analysis of conducted Electro-Magnetic Interference (EMI) in switching power converters (SPC) based on noise impedances. The EMI characteristics of SPC can be analytically deduced from a circuit theoretical viewpoint. The analytical noise model is investigated to get a full understanding of the EMI mechanism. It is shown that with suitable and justified model, filters pertinent to EMI noise is investigated. The EMI noise is identified by time domain measurements associated with an isolated half-bridge ac-dc converter. Practical filters like LC filter, ${\pi}$ filter and complete EMI filters are investigated. The proposed analysis and results can provide a guideline for improving the effectiveness of filtering schemes in SPC. Experimental results are also included to verify the validity of the proposed method. The results obtained satisfy the Federal Communications Commission (FCC) class A and class B regulations.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.8
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• pp.371-375
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• 2001

We attempted to fabricate polyurethane derivatives (PU-CN, PU-DCM) LB films by using LB method. Also, we investigated the monolayer behavior at the air-water interface by surface pressure-area (${\pi}$-A) isotherms. The surface morphologies and the physicochemical properties of LB films were investigated by atomic force microscopy(AFM) and UV-vis spectroscopy, respectively. And, the electrical properties of polyurethane derivatives LB films were investigated by using the conductivity and the dielectric constant. In the surface morphologies, physicochemical and electrical properties of polyurethane derivatives LB films, the properties is different as to the polyurethane derivatives, it is considered that this phenomena could be described by the difference of lumophore pendant which was adhered at PU main chain.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.1
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• pp.12-19
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• 2001

In this study, the physical properties of the piezoelectric sounder with metal-piezoelectric ceramics were analyzed. The dielectric and piezoeletric properties of 0.5wt% MnO$_2$ and NiO doped 0.1Pb(Mg$\_$1/3/Nb$\_$2/3/)O$_3$-0.45PbTiO$_3$-0.45PbZrO$_3$ ceramics were investigated aiming at acoustic transducer applications. The acoustic characteristics of a thin circular disc-type with metal-piezoceramics have been investigated. Also, the acoustic characteristics for the geometrical form of case were investigated. The piezoelectric sounder with 200kHz resonant frequency and 20kHz bandwidth was designed by considering the sharp directivity and the sound pressure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.85-88
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• 1998

Light-emitting diode(LEDs), diode arrays, and phosphor display panels are finding increased use in a variety of commercial applications. Present and anticipated application of these devices include solid state indicator(e.g., digital clocks, meter readout) and display systems(e.g., instrument panels, TV display), the application being determined by the light -output capability and size availability(cost) of the particular device. In this work, Phosphor based on ZnS:Cu are used. Relation by luminance with the thickness of insulating layer and phosphor layer are discussed. Increased thickness of insulating layer are stable on voltage to 300V. By considering thickness and voltage, optimal structure and thickness are investigated. Also in order to maximize even surface emission, various sieving process are introduced. Very similar phosphor particle size is selected. Luminance by various wave intensity is also investigated. 150cd/m$^2$ luminance are investigated in stable voltage and frequency.

• Journal of Fisheries and Marine Sciences Education
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• v.19 no.3
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• pp.478-490
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• 2007

A technology of ultrasonic biotelemetry for tracking fish behavior is investigated. The ultrasonic biotelemetry system is constituted by a transmitter and a receiving system. Because a pinger was mainly used for the transmitter, the capability for pinger to possess was investigated and the efficient usage for pinger was examined. A source pressure level and a frequency were synthetically examined so that pinger could realize small size, a light weight, and a long life time. The receiving system is divided roughly into directional hydrophone systems and acoustic positioning systems by the receiving method. The directional hydrophone system is divided into single beam and multiple beam with the number of hydrophone, and the acoustic positioning systems is divided into LBL (Long Base Line), SBL (Short Base Line), and SSBL (Super Short Base Line) on the basis of base line. The present situation, the merits and demerits, and the principle of each receiving method were investigated in detail, and the efficient usage for each receiving method were examined.

• Journal of the Korean Society of School Health
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• v.21 no.1
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• pp.43-51
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• 2008

Background: Although school footpaths must guarantee pedestrians’ safety and pleasantness, even facilities installed according to standards provided in “Rules on the Designation and Management of School Zones” are not maintained and managed properly and as a result they are not effective for securing the safety of school footpaths. Purpose: The present study surveyed the physical environment of elementary school footpaths and investigated problems posed by the absence of facilities. Methods: First, the current state of street structure was investigated using maps as well as field surveys, and the current state of street furniture was surveyed by checking if it has been installed and photographing it. In addition, traffic characteristics were investigated by measuring traffic safety while children’s going to school and home, and children’s behaviors on school footpaths were surveyed by observing their behaviors when going to school and home. Result: This study surveyed the installation and state of safety facilities on school footpaths around elementary schools in B City, analyzed items to be improved, and presented materials for reducing accidents among elementary students.

• Tribology and Lubricants
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• v.20 no.2
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• pp.102-108
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• 2004

In this paper, friction and wear behaviors between monocrystalline, defect-free copper and carbon on the atomic scale are investigated by using 2-dimensional molecular dynamics simulation. It is assumed that all interatomic forces are given by Morse potential. The deformation of carbon is assumed to be neglected and vacuum condition is also assumed. Average friction and normal forces for various surface conditions, various scratch speeds and scratch depths are obtained from simulations. Changes of wear behaviors for various scratch speeds and surface conditions are investigated by observing snapshots in scratch process. The effects of surface conditions, scratch speeds, and scratch depths on the friction force, normal force, and friction coefficient are also investigated.

• Transactions of Materials Processing
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• v.10 no.7
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• pp.551-557
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• 2001

In the present study, several design parameters of the flat-die extrusion process are investigated using the finite element method. The effects of the location of an extrusion profile, arrangement of multiple extrusion profiles, and the design of various die land have been investigated through the analysis. Several numerical examples of flat-die extrusion of such as C-section, multiple U-shape, and a window guide section, are analyzed. From the comparative study, the effect of design parameters is investigated. In each example, comparing the velocity distribution with that of the original design, it has been shown that the design modification affords more uniform distribution.

• Transactions of Materials Processing
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• v.13 no.4
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• pp.374-381
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• 2004

In this study, the deformation behavior of semi-solid Al-Si alloy was investigated by nanoindenter as a part of the research on the surface crack behavior in thixoformed automobile component. The microstructure of semi-solid Al-Si alloy consists of primary and eutectic regions. In eutectic regions the crack initiation begins with initial fracture of the eutectic silicon particles and inside other intermetallic phases. Nano-deformation characteristics in the eutectic and primary phase of semi-solid aluminium alloy were investigated through the nano-indentation experiments and the AFM observation. In addition, mechanical properties of each region were investigated and compared with each other.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.537-540
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• 2006

In previous study, the effect of specimen sizes and shapes on the compressive strength of concrete specimens was experimentally investigated based on fracture mechanics. In this study, the relationship between the cube compressive strength and the cylinder strength for representative specimen sizes was investigated by linear regression analyses. And, by reanalyzing the compressive strength prediction equations with specimen size and shape obtained in previous studies, the compressive strength prediction equations were generalized. In addition, its verification was investigated by comparing with the results obtained from other researchers.