• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.955-962
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• 2002

According to the trends of construction of large size vessel with high power, the natural frequencies of the bending modes of propeller blades have been lower than the past. Therefore, it is expected that the noise and vibration problems of the marine propeller are frequently occurred. As main issue of the propeller noise and vibration problem, the cavitation noise and singing noise due to the flow induced excitation of the bending modes of propeller blade in the high frequency range has been studied by the hydrodynamic researchers in the view point of the excitation force reduction. In this paper, the vibration mode characteristics of propeller with a large diameter in very large vessel are investigated by the vibration analysis of the finite element method using MSC/Nastran and the vibration measurement by the impact test on the propeller blade. According to the results, the natural frequencies of various blade bending modes in water entrained condition could be estimated from the natural frequencies taken by the measurement and free vibration analysis in the dry condition, and it could be estimated how the high frequency noise such as singing is generated from the blade bending modes.

• Journal of Magnetics
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• v.1 no.1
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• pp.24-30
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• 1996

The relationship between effective permeability and the remanence ratio of an Fe-based amorphous alloy (Metglas 2605S3A) is investigated over a wide frequency range, in an effort to understand magnetization behavior of the alloy. In the frequency range from 1 to 200 kHz, the permeability is maximum at the remanence ratio of 0.4-0.5 and, at frequencies over 500 kHz, the correlation with negative coefficients emerges indicating that the permeability decreases with the remanent ratio, except for the ribbon coated with an insulating layer of MgO which exhibits both high values of the effective permeability and remanence ratio. It is considered from the correlation results that the boundary at which the dominant magnetization mechanism changes from domain wall motion to spin rotation is near 500 kHz. The core loss is also investigated as a function of annealing time when the samples are annealed at a fixed temperature of $435^{\circ}C$. The core loss in most cases decreases with the annealing time, the degree of the loss may consist of the hysteresis loss and anomalous eddy current loss. The two loss components are considered to be of similar magnitudes at low frequencies while, at high frequencies, the dominant contribution to the total loss is the anomalous loss.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.97-106
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• 2005

According to the trends of construction of large size vessel with high power the natural frequencies of the bending modes of propeller blades have been lower than the past. Therefore, it is expected that the noise and vibration problems of the marine propeller are frequently occurred. As main issue of the propeller noise and vibration problem, the cavitation noise and singing noise due to the flow induced excitation of the bending modes of propeller blade in the high frequency range has been studied by the hydrodynamic researchers in the view point of the excitation force reduction. In this paper, the vibration mode characteristics of propeller with a large diameter in very large vessel are investigated by the vibration analysis of the finite element method using MSC/Nastran and the vibration measurement by the impact test on the propeller blade. According to the results, the natural frequencies of various blade bending modes in water entrained condition could be estimated from the natural frequencies taken by the measurement and free vibration analysis in the dry condition, and it could be estimated how the high frequency noise such as singing is generated from the blade bending modes.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.6
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• pp.1544-1548
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• 2008

The aim of this study is to learn the effects of ST36 ST44 and ST25 ST36 electroacupuncture stimulation on high fat diet-induced obese mouse. The control group was provided with high fat diet without electroacupuncture stimulation, while the experimental group received a electroacupuncture stimulation on ST36 ST44 and ST25 ST36 with three frequencies (10Hz, 100Hz, 200Hz) for 5 times a week during five week periods with the high fat diet. We investigated the body weight, weight gain, and food intake. After the electroacupuncture stimulation, a significant inhibition of increase in weight was found in the experimental group compared with the high fat diet group. But there were no significant differences made by the change of acupoint combinations and frequencies. After the electroacupuncture stimulation, no significant change was found in the food intakes, but the weight gain a week was decreased compared with the high fat diet group. Electroacupuncture stimulation may be effective in treatments of obesity to high fat diet, But no significant difference was found between three frequencies.

• Journal of electromagnetic engineering and science
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• v.18 no.1
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• pp.29-34
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• 2018

An antipodal Vivaldi antenna with a compact parasitic patch to overcome radiation performance degradations in the high-frequency band is proposed. For this purpose, a double asymmetric trapezoidal parasitic patch is designed and added to the aperture of an antipodal Vivaldi antenna. The patch is designed to efficiently focus the beam toward the end-fire direction at high frequencies by utilizing field coupling between the main radiating patch and the inserted parasitic patch. As a result, this technique considerably improves the gain and stability of radiation patterns at high frequencies. The proposed antenna has a peak gain greater than 9 dBi over the frequency range of 6-26.5 GHz.

• Journal of Nutrition and Health
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• v.46 no.1
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• pp.26-33
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• 2013

The purpose of this study was to investigate the sodium intake of office workers using 24-hour urine analysis and to analyze the correlation matrix between variables. The sodium intake of the subjects (n = 137), based on a 24-hr sodium excretion period, was male (n = 56) 6072.4 mg and female (n = 81) 5,168.2 mg. Urinary sodium excretion showed significant positive correlation with BMI, frequency of eating out, expenditure of eating out, salty taste assessment and high-salt dietary behavior. Analysis of urinary sodium excretion showed significant positive correlation with intake frequencies of cabbage kimchi, broiled fish, feast noodle and rice with leaf wraps. Based on the results of multiple regression, urinary sodium excretion was found to be related to intake frequencies of cabbage kimchi, broiled fish, rice with leaf wraps and high score of high-salt dietary behavior.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.209-210
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• 2006

Digital technology has been applied to marine seismic survey to develop data processing technology and multi-channel marine seismic survey. In result, high-resolution marine seismic survey ended in a success. Surveys are conducted for various purposes using various frequencies of acoustic sources. A low frequency source is used for deeper penetration and a high frequency source is used for higher resolution survey. In this study, a multi-source system was used for multi-channel marine seismic survey to acquire seismic sections of both low and high frequencies. Variations of depth of penetration and resolution would be used to achieve more accurate analysis of formations. In this study, the multi-source system consists of Bubble Pulser(400 Hz) for low frequency source and Sparker(1.5 kHz) for high frequency source.

• Journal of Information Display
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• v.12 no.2
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• pp.109-113
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• 2011

This paper summarizes the recent fabrication and characterizations of flexible high-speed radio frequency (RF) transistors, PIN-diode single-pole single-throw switches, as well as flexible inductors and capacitors, based on single-crystalline Si nanomembranes transferred on polyethylene terephthalate substrates. Flexible thin-film transistors (TFTs) on plastic substrates have reached RF operation speed with a record cut-off/maximum oscillation frequency ($f_T/f_{max}$) values of 3.8/12 GHz. PIN diode switches exhibit excellent ON/OFF behaviors at high RF frequencies. Flexible inductors and capacitors compatible with high-speed TFT fabrication show resonance frequencies ($f_{res}$) up to 9.1 and 13.5 GHz, respectively. Robust mechanical characteristics were also demonstrated with these high-frequency passives components.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1273-1279
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• 2000

A new concept of piezoelectric smart panels for noise reduction in wide band frequencies is proposed and their possibility is experimentally investigated. The proposed panels are based on active and passive methods. They use piezoelectric smart structure technology for active noise reduction at low band frequencies and passive sound absorbing materials for mid-range of noise frequencies. To prove the concept of piezoelectric smart panels, an acoustic measurement experiment was performed. The smart panels exhibit a good noise reduction in middle and high frequency ranges due to the mass effects of absorbing materials or/and the air gap. The use of piezoelectric smart panel renders noise reduction large at resonance frequency. Another concept of smart panel that uses piezoelectric damping is experimentally investigated. Since piezoelectric dampings can reduce vibration and noise at resonance frequencies with simple shunt circuit, they have merits in terms of economy and simplicity. Dissipated energy method(DEM) is adopted to tune the shunt circuit precisely in piezoelectric dampings. Noise reduction at multiple resonance frequencies is demonstrated.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.4
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• pp.372-376
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• 2008

We report experimental results on the correlations between welding penetration depth and the frequencies of the radiation from the welding pool. Various welding samples such as SUS304, brass, SUS316, etc. have been investigated with 2 kW CW Nd:YAG laser welding machine. The radiation signals from the plume generated by the interactions between the welding sample and laser with respect to the defocusing length was measured with fiber system collecting the plume signal. Analysis of the frequencies by using fast Fourier transform (FFT) shows that the penetration depth is deep as plume signal frequencies are low, shallow penetration depth for high frequencies. Frequencies up to 250 Hz for obtained signals can be analyzed with the discrete FFT. This is the useful method fur closed loop control of the laser power with respect to the welding penetration depth and is used for real time inspection of the welding quality.