• Korean Journal of Optics and Photonics
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• v.8 no.5
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• pp.362-365
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• 1997

This paper presents a new optical phase stabilization technique for interferometric such as Mach-Zehnder interferometers or Homodyne detectors. The proposed technique can lock such interferometric systems in their maximum/minimum optical outputs without using a dither signal. The phase control scheme is a modified steepest decent algorithm, and is analyzed in terms of a delta modulation approach. It is also applicable to low-repetition rate pulsed interferometric systems in which conventionally used dithering method is difficult to be applied.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.4
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• pp.209-221
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• 2008

In this paper, we propose a subcarrier allocation method and a composite linear minimum mean square error (LMMSE) channel estimator to increase spectrum efficiency in orthogonal frequency division multiplexing (OFDM) transmit diversity. The pilot symbols for OFDM transmit (Alamouti) diversity are exclusively allocated in two OFDM symbols in different antennas, which causes serious degradation of spectrum efficiency. To reduce the number of pilot symbols, our subcarrier allocation method uses repetition-coded data symbols, and the proposed channel estimator maintains good bit error rate (BER) performance.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.988-989
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• 2008

This paper describes a rapid pulsed power charging system for pulsed power application. It is capable of charging 35kJ/s energy up to 0.47uF 25kV within 3ms and maximum pulse repetition rate of 300 pps can be achieved. The charger is designed based on three-phase series resonant inverter followed by air cooled set-up transformers thus it has many advantages of lower weight, small size and high efficiency compared with large bulky traditional pulse charger system. Detail design procedure of resonant inverter and high voltage transformers is explained. Experimental results carried out at different condition and its results shows 90% efficiency at full load condition.

• International Journal of Reliability and Applications
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• v.5 no.1
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• pp.15-24
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• 2004

Folder type electronic devices have hinge to support the rotational motion of folder. This hinge is stressed by the rotational inertia moment of folder at the maximum open limit position of folder. This stress is repeated whenever the folder is open, and it is a cause of hinge fracture. In this paper, the reliability evaluation for the hinge fracture in the folder type cellular phone is discussed. For this, the durability testing machine using crank-rocker mechanism is developed to evaluate the life cycle of the hinge, and the degradation after repetitions of opening and shutting is evaluated from the deformation around the hinge, where the deformation is measured by ESPI (electronic speckle pattern interferometer). Experimental results showed that ESPI was able to measure the deformation of hinge precisely, so we could monitor the change of deformation around the hinge as the repetition number of folder open is increased.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.213-214
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• 2001

This paper describes a power supply for a rapid pulse power charging system designed for charging a $0.35{\mu}F$ capacitor to 20kV in approximately 3ms. The power supply should be capable of recharging the load capacitor maximum 300 times within one second. This power supply is based on a series resonant 3-phase inverter followed by the step-up transformers. The experiments have been carried out at different repetition rates and charging voltages.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.2
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• pp.73-78
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• 2001

With the increasing demands for clean environment, development of air cleaning systems has been received increasing attention. One of the key technologies in the electrostatic precipitator(EP) is high voltage pulsed power supply, which affects the performance of the overall system. In this study, a high voltage microsecond pulse power supply for the pilot EP is developed. The power supply has a dc source and a pulsed one. The ratings of the dc and the pulse source are 60kV and 70kV respectively. The width of pulse voltage is 140us and the maximum pulse repetition frequency is 200Hz.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.69-73
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• 2002

A study on photovoltaic system has a lot of problems. Such as repetition experiment in the same condition, development of MPPT(Maximum Power Point Tracking) algorithm, development of islanding detection algorithm and so forth. The reason Is that solar cell output characteristics are varied by insolarion and surface temperature of solar cell. Therefore, the assistance equipment is required which emulates the solar cell characteristics. In this paper, propose the new modeling of solar cell and verify this modeling using MATLAB simulation. And experiment virtual implement of solar cell system using this modeling.

• International Journal of Computer Science & Network Security
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• v.21 no.2
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• pp.40-43
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• 2021

In the article of instability on the peak power level, duration and repetition period of a multifrequency space-time signal, we calculated the maximum values of the errors of the parameters of the laws of spatial-phase-frequency control. Requirements for the accuracy of the location of the phase centers of the emitters in a cylindrical phased array antenna with pyramidal horns; it is advisable to calculate the radiation field using single-stage and multi-stage distribution laws. The phase centers of individual radiation sources of a cylindrical phased array antenna have been studied; they have almost no effect on the duration and period of recurrence.

• 한국해양학회지
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• v.22 no.2
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• pp.105-118
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• 1987

A series of anchor stations were occupied along the Keum EAstuary during six different periods of tidal and fluvial regimes. The results clearly show that the formation and evolution of the turbidity maximum play an important role in the sedimentary processes in this environment. The turbidity maximum in the Keum Estuary is primarily related to the tidal range at the mouth and is caused by the resuspension of bottom sediments. In this estuary, the turbidity maximum is not a permanent feature and shows semidiurnal, fortnightly and seasonal variations. Repetition of deposition and resuspension of fine sediments occur in response to the variation in current velocity associated with semidiurnal tidal cycles. The core of turbidity maximum shifts landward or seaward accordion to the flood-ebb succession. The turbidity maximum also shows a fortnightly variation in response to the spring-neap cycles. Thus, the turbidity maximum degenerates during neap-tide and regenerates during spring-tide. The freshwater discharge is also an important factor in the formation and destruction of the turbidity maximum. The increase in freshwater discharge in rainy season can create an ebb-dominant current pattern which enhances the seaward transport of suspended sediments, resulting in the shortening of residence time of suspended materials in the estuary. Thus, under this high discharge condition, the turbidity maximum exists only during spring-tide and starts to disappear as the tidal amplitude decreases.

• Journal of Life Science
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• v.19 no.4
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• pp.492-501
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• 2009

The purpose of this study was to examine the most effective weight training (WT) intensity for the improvement of metabolic syndrome factors in overweight high school students. Sixty overweight high school students were randomly divided into 4 groups (15 subjects/group) according to WT intensity: A group - control group, B group - 40-55% repetition maximum (RM) group, C group - 60-75% RM group, and D group - 80-90% RM group. They exercised between 60-70 minutes a day, three times a week, for eight weeks. In order to determine the most effective WT intensity, five metabolic syndrome factors--waist size, fasting glucose, triglyceride (TG), high-density lipoprotein-cholesterol (HDL-C) and blood pressure--were measured for each subject prior to and after the experiment. Waist size decreased in all exercise groups, but the results were more prominent in the 40-55% RM and 60-75% RM groups. TG levels also decreased in all groups but results were more prominent in the 40-55% RM group. HDL-C levels in the 80-90% RM group were significantly higher than the control group. Groups did not show any significant difference in the diastolic blood pressure, but the 40-55% RM group's systolic blood pressure significantly decreased compared to other groups. Groups did not show significant difference in the fasting glucose level. These results indicate that lower-intensity weight training is generally more effective than the higher-intensity weight training in improving metabolic syndrome factors in overweight high school students and that the most effective WT intensity is 40-55% RM.