• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.756-760
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• 1997

In this research, the automatic level measurement system used in land leveling was developed. By using a laser transmitter and a receiver as measuring equipments, level was measured automatically. The driving part of this system was composed of stepping motor, timing belt and pulley. It drived the laser receiver to track laser beam generated form the laser transmitter. The level measuring experiments were performed about three level change shapes (step, random, sine). This system could measure step level change of which amplitude was 40mm in 0.5s, random level change within .+-. mm, maximum measurement error. In case of sine level change, experiment was executed with varying the spatial frequency of level change. As a result, this system was able to measure sine level change of which spatial frequency was 0.5m $^{-1}$ accurately.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.434-435
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• 2008

An in-situ monitoring technique for deposition process of CdS buffer layer was developed in this work. A quartz crystal microbalance (QCM) was used to measure the frequency change during the CdS deposition process and the relation ship between frequency change and film thickness and optical transmittance was investigated. The film thickness shows a linear relationship with frequency change, demonstrating that frequency change measured by QCM can be used a in-situ monitoring tool for CdS deposition process.

• Journal of the Semiconductor & Display Technology
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• v.23 no.1
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• pp.52-55
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• 2024

In this paper, a state change study was conducted through Frequency Domain Reflectometry (FDR) technology for the process chamber of plasma equipment for semiconductor manufacturing. In the experiment, by direct connecting the network analyzer to the RF matcher input of the 300 mm plasma enhanced chemical vapor deposition (PECVD) chamber, S11 was measured in a situation where plasma was not applied, and the frequency domain reacting to the chamber state change was searched. Response factors to changes in the status, such as temperature, spacing of the heating chuck, internal pressure difference, and process gas supply state were confirmed. Through this, the frequency domain in which a change in the reflection value was detected through repeated experiments. The reliability of the measured micro-displacement was verified through reproducibility experiments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.74-76
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• 2006

An external electrode fluorescent lamp (EEFL) has an advantage of a long lifetime in the ear1y stages of the study on plasma discharge, interest in the lamp continues. Researches on the operation of external electrode fluorescent lamps have focused mainly on its use of a type of high frequency (MHz). By performing high brightness using a square wave operation method with the low frequency below 100kHz, which is applied to a narrowed tube type lamp that has several mm of lamp diameter, EEFL presented the possibility of using it as a light source for back-lights. However, because EEFL generates plasma using wall charges, which considers the impedance characteristics of glass based on the structural principle in discharge, it can be significant1y affected by frequency. Thus, this study verified the change in the characteristics of electromagnetic fields according to the change in frequency through a Maxwell's electromagnetic field simulation and examined the relationship between the change in the EEFL frequency and brightness by measuring the optical characteristics. In addition, the characteristics of the transformation of energy orbits were verified by investigating the characteristics of the wavelength according to the change in frequency through the OES.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.1040-1047
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• 2006

Bridges are exposed to constantly changing weather conditions and temperature. The temperature change is induced by a change in atmospheric temperature and solar radiation. Atmospheric temperature change acts on the whole structure. Thus, it is relatively easy to consider in the design. Solar radiation, however, causes un-uniform temperature distribution in the structure, depending on the shape of the structure and its shadows. Un-uniform temperature distribution causes a torsional moment in bridge section and a deformation of bridge. A deformation can make differences of dynamic and static behavior of bridge. In this study, the method for analysis of static and dynamic behavior considering deformation and changes of material properties due to temperature variation was developed. By this method, it is found from dynamic analysis results that the change of frequency in analysis model is similar with test results of public used cable-stayed bridge. When a temperature goes down, a frequency goes up. And it is found that the change of frequency is affected by the change of material properties.

• Journal of radiological science and technology
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• v.41 no.5
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• pp.463-469
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• 2018

Morphological information such as shape and margin of micro lesion is important information for diagnosis of disease in clinical imaging. In this study, we investigated the morphological changes of the micro lesions by comparing the contrast and area in grid suppressed DR images according to grid frequency. In the profile analysis of the image, the mass showed an average intensity variation of 8.6 ~ 72.4 after suppression, The higher the grid frequency, the more the contrast was increased. However, in the images obtained using 103 lp / inch, which is a grid frequency less than the sampling frequency, the contrast of the mass in the vertical direction decreased after suppression. In the binary image, the area change of the mass was also large. As a result, the shape, size, and margin of the mass changed. In the case of very small calcification, the higher the grid frequency is the larger the change in contrast, so that a clear image can be obtained in the post-suppression image. However, we could confirm that the margin of the lesion was blurred and the lesion was lost in some of the images using the 103 lp / inch grid. The higher the frequency of the grid, The change of the contrast of fiber occurred largely and clear boundary was confirmed. The decrease of the number of pixels was small and morphological change was small. In conclusion, when using a grid frequency that is not suitable for the sample frequency, morphological changes or lesion loss of micro lesions in the post- suppression image may give the possibility of misdiagnosis in diagnosis and differentiation of the image.

• Journal of the Korean Graphic Arts Communication Society
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• v.30 no.1
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• pp.47-58
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• 2012

The inorganic powder EL lamp was made by screen printing technique with a phosphor ink and a dielectric ink. Value of color coordinates X and Y increased under the condition of supplying driving power to the inorganic powder EL lamp and changing voltage with constant frequency. When frequency was changed under the constant voltage, value of color coordinates X and Y were decreased with increasing frequency. However, level of change of color coordinates X was different from color coordinates Y. When voltage was increased under constant frequency, changing degree of color coordinates X and Y shows similarity. But under the constant voltage with changing frequency, color coordinates X and Y were differently changed that degree of change of color coordinates Y showed five times more than that of color coordinates X. As increasing thickness of phosphor ink and dielectric ink, level of voltage and frequency, color coordinates X and Y were slightly changed. According to the thickness of phosphor ink and dielectric ink, and level of voltage and frequency, color coordinate of color light was changed. Frequency was most important element influencing on the change of color coordinate.

• Journal of the Korea Society for Simulation
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• v.10 no.1
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• pp.63-65
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• 2001

To investigate the natural frequencies of curved piping systems with various elbow angles conveying flow fluid, a simulation is performed considering Initial tension due to the inside fluid. The system is analyzed by finite element method utilizing straight beam element. Elbow part is meshed using 4 elements, and the initial tension is considered by inserting equivalent terms into the stiffness matrix. Without considering the initial tension, the system becomes unstable, that is, the fundamental natural frequency approaches to zero value fast, as the flow velocity reaches critical value. With the initial tension terms, the system becomes stable where there is no abrupt decrease of the fundamental natural frequency. The change rate of the natural frequency with respect to the flow velocity reduces. As elbow angle increases, the system becomes stiffer, then around 150 degrees of the elbow angle the natural frequency has the largest value, the value decreases after the angle of the largest natural frequency. When angle is between 170 degrees and 179 degrees, the natural frequency is very sensitive. This means that small change of angle results in great change of natural frequency, which is expected to be utilized in the control of the natural frequency of the piping system conveying flow fluid.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.83-85
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• 2007

In this paper is described frequency control of Induction Heating System for using the resonant high-frequency inverter. To follow in output temperature and frequency in order to change, it controls a system and it confirms the electric change of induction heating system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.621-624
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• 2005

Among many auditory feelings for the vehicle interior noise, booming is considered as the most important nuisance to the passenger and developer. Because the main source of booming noise is a power train system including engine, in general, it consists of tonal components related to fundamental engine rotation and its harmonics including the firing frequency. Therefore, it is demanded to extract the effective tonal components only by using pitch extraction algorithm based on the place theory enable to find aurally relevant tonal components. However, there is a difference between booming sensation and pitch perception according to frequency change of tonal component. In this study, subjective listening test using a tracking method was performed to find the difference limen for just noticeable change of booming sensation in frequency. 20 Koreans and 10 Japanese were participated in this test and the results obtained from Koreans and Japanese were compared with each other. Finally, 5Hz was determined as the difference limen for just noticeable change of booming sensation in frequency, and by applying this value to booming analysis using pitch concept, it was confirmed that the degree of prediction of booming sensation was improved.