• Korean Journal of Crystallography
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• v.14 no.1
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• pp.25-31
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• 2003

Accelerated electric charge is the source of electromagnetic waves. If electric charge is accelerated, the electric field set up by the electric charge is also accelerated. A changing electric field produces a changing magnetic field and the changing magnetic field produces an electric field and the process is self-perpetuating. The lines of B as well as E thus occurred form closed loops that move away from the source with speed c. These traveling electric and magnetic fields. which are strongly interdependent, constitute electromagnetic radiation. All the properties of electromagnetic waves can be deduced mathematically from Maxwell's equations.

• Journal of the Korea Society of Computer and Information
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• v.5 no.4
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• pp.112-119
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• 2000

In this paper, it aims at two different situation such that a preventive control which means, it never has network information in case of occurring congestion in network, and a reactive control which means, after the congestion simply happens. it is not effective to recover with congestion just because of extensive delay for an electric wave. To solve the problems, threshold is set up with buffer in multiplex system, and executes a congestion control by FBLB which is FeedBack Leaky Bucket Algorithm. As suggested by FBLB Algorithm. the outcome of performance could be compared with Buffered Leaky Bucket Algorithm.

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1611-1620
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• 2005

This paper shows the use of wavelet transformation combined with inverse acoustics to reconstruct the surface velocity of a noise source. This approach uses the boundary element analysis based on the measured sound pressure at a set of field points, the Helmholtz integral equations and wavelet transformation for reconstructing the normal surface velocity field. The reconstructed field can be diverged due to the small measurement errors in the case of nearfield acoustic holography (NAH) using an inverse boundary element method. In order to avoid this instability in the inverse problem, the reconstruction process should include some form of regularization for enhancing the resolution of source images. The usual method of regularization has been the truncation of wave vectors associated with small singular values, although the order of an optimal truncation is difficult to determine. In this paper, a wavelet transformation is applied to reduce the computation time for inverse acoustics and to enhance the reconstructed vibration field. The computational speed-up is achieved, with solution time being reduced to $14.5\%$.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.293-296
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• 2005

The tensile properties of GFRP(glass fiber reinforced polymer) rods with various surface deformation produced by RTM(resin transfer molding) process were analyzes experimentally. Two types of GFRP rods with different surface deformation manufactured by RTM process in domestic area and two types of GFRP rods imported were considered in this study. All testing procedures including specimens preparation, set-up of test equipments and measuring devices were made according to the ASTM D3916-02 recommendations. From the test results, it was found that wave-type GFRP rod made by RTM process showed the highest tensile strength due to the highest fiber volume ratio.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.297-300
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• 2005

The bond characteristics of GFRP(glass fiber reinforced polymer) rods with various surface deformation produced by RTM(resin transfer molding) process were analyzes experimentally. Two types of GFRP rods with different surface deformation manufactured by RTM process in domestic area and two types of GFRP rebars imported were considered in this study. All testing procedures including specimens preparation, set-up of test equipments and measuring devices were made according to the CSA S806-02 recommendations. From the test results, it was found that deformed-type GFRP rod manufactured by RTM process showed the highest bond strength among test specimen. But, wave-type GFRP rod made by RTM process show the lowest value due to the splitting failure of concrete caused by the wedge action of waved surfaces on GFRP rods.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.10
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• pp.879-883
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• 2009

This paper was provided to help in detecting defects in power transformer. For this purpose, a partial discharge cell was designed and manufactured as a discharge source to simulate particle defected paper-oil insulation in power transformer. Experimental set-up for measuring PD signals was described. Magnitude of electromagnetic wave signals and corresponding amount of apparent discharge were measured simultaneously against phase of applied voltage to the discharge cell. Frequency range and pattern of PRPD(Phase Resolved Partial Discharge) of partial discharge signals were examined and analyzed. The results will be contributed to build the defect database of power transformer and to decrease the substation faults.

• Applied Science and Convergence Technology
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• v.25 no.3
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• pp.47-50
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• 2016

Low temperature test for half-wave resonator (HWR) cryomodule is performed at the superfluid helium temperature of 2 K. The effective temperature is defined for non-uniform temperature distribution. Helium leak detection techniques are introduced for cryogenic system. Experimental set up is shown to make the low temperature test for the HWR cryomodule. The cooldown procedure of the HWR cryomodule is shown from room temperature to 2 K. The cryomodules is precooled with liquid nitrogen and then liquid helium is supplied to the helium reservoirs and cavities. The pressure of cavity and chamber are monitored as a function of time. The vacuum pressure of the cryomodule is not increased at 2 K, which shows leak-tight in the superfluid helium environment. Static heat load is also measured for the cryomodule at 2.5 K.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.140.1-140.1
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• 2015

Currently, As Plasma application is expanded to the industrial and medical industrial, Low temperature plasma characteristics became important. Especially in Medical industrial, Low temperature plasma directly adapted to human skin, so their plasma parameter is important. One of the plasma parameters is electron density, some kinds of method to measuring electron density are Thomson scattering spectroscopy and Millimeter-wave transmission measurement. But most methods is expensive to composed of experiment system. Heterodyne interferometer system is cheap and simple to setting up, So we tried to measuring electron density by Laser heterodyne interferometer. To measuring electron density at atmospheric pressure, we need to obtain the phase shift signal. And we use a heterodyne interferometer. Our guiding laser is Helium-Neon laser which generated 632 nm laser. We set up to chopper which can make a laser signal like a pulse. Chopper can make a 4 kHz chopping. We used Needle jet as Ne plasma sources. Interference pattern is changed by refractive index of electron density. As this refractive index change, phase shift was occurred. Electron density is changed from Townsend discharge's electron bombardment, so we observed phenomena and calculated phase shift. Finally, we measured electron density by refractive index and electron density relationship. The calculated electron density value is approximately 1015~1016 cm-3. And we studied electron density value with voltage.

• Research in Community and Public Health Nursing
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• v.30 no.4
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• pp.528-538
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• 2019

Purpose: The purpose of this study was to follow-up the frailty of the old who received home health care by Registered Nurse in Public Health Center over 8 years. Methods: We used the second wave data which was a comprehensive longitudinal data set, Public Health Information System of a public health center located in Seoul from 2010 to 2018. For statistical analysis, a mixed model of repeated measures by R program was used. Results: Frailty (range: 0~31) was getting worse significantly from 5.38 on registration to 6.54 on 4th year, 7.40 on 7th year, 7.69 on 8th year with adjustment for age, sex, economic status, the number of family, and the number diseases. The coefficient of parameters with frailty change was serviced year (β=0.29, p<.001), age (70~79 to 60~69; β=0.98, p=.018) and sex (female to male; β=2.55, p<.001). Conclusion: This study showed that the home visiting health service needs to take attention to aged 70s and over, female. The home health care of public health center need to be extended more practical and effective services in terms of 'community care'and 'ageing in place'.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1183-1188
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• 2011

The novel metal position detection method is proposed where conventional techniques, in high temperature, moisture and particle environment, are not able to be applied. It is known that electronic devices, utilizing microwave, ultrasonic or optical technique, are hard to apply for sensing application where temperature is exceeding above 300 degree centigrade. Metal position detection technique, which was consisted with passive elements facing hot sensing surface, utilizing electromagnetic wave was investigated, and the metal detection sensitivity was measured by varying sensor frequency and sensing distance. Measurement result in laboratory test set-up showed position measurement resolution up to 1mm, when distance between two sensing elements were 500mm, and possibility to measure position of hot metal sheet having very high surface temperature.