• Journal of the Korean Institute of Gas
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• v.7 no.2 s.19
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• pp.48-53
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• 2003

This study is to look at the effect for deformation of carbon steel for high-presure pipe, on the AE signals produced by tensile test. Acoustic emission(AE) has been widely used in various fields because of its extreme sensitivity, dynamic detection ability and location of growing defects. We investigated a relationship failure mode and AE signals by tensile test, From the tensile test, we could divide into four ranges of the failure modes of elastic range, yield range, plastic range before $\sigma$u, plastic range after $\sigma$u. And failure behaviors of elastic range, yield range, plastic range before $\sigma$u, plastic range after $\sigma$u could be evaluated in tensile test by AE counts, accumulation counts and time frequency analysis. It is expected to be basic data that can protect a risk according to tensile test and bending of pipe material for pressure vessel, as a real time test of AE.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.5
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• pp.373-379
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• 2019

If two signals with the same single-tone frequency and differing phases impinge simultaneously on an antenna at slightly differing angles, then a large error in the angle estimation might occur if the phase difference is either $0^{\circ}$ or $180^{\circ}$. This phenomenon might arise with an airborne fire-control radar, which has a relatively small bandwidth, for a low-flying target over the sea or terrain surface. In this paper, we show that the $Cram{\acute{e}}r$-Rao lower bound for such a target can be significantly lowered with the use of two frequencies.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.2
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• pp.136-141
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• 2021

Heating cables, widely used in office buildings, factories, streets and railways, deteriorate in electrical insulation during operation. The insulation deterioration of heating cables leads to electric discharges that can cause electrical fires. With this background, this paper dealt with a condition monitoring technique for heating cables by the analysis of discharge signals to prevent electrical fires. Insulation deterioration was simulated using an arc generator specified in UL1699 under AC operation, and the characteristic and propagation of discharge signals were analyzed on a 100 meter-long heating cable. Discharge signals produced by insulation deterioration were detected as a voltage pulse because they are as small as a few mV and they are attenuated through propagation path. The frequency spectrum of discharge signals mainly existed in the range from 70 kHz to 110 kHz, and the maximum attenuation of the signal was 84.8% at 100 meters away from the discharge point. Based on the experimental results, a monitoring device, which is composed of a high pass filter with the cut-off frequency of 70 kHz, a comparator, a wave shaper and a microprocessor, was designed and fabricated. Also, an algorithm was designed to discriminate the discharge signal in the presence of noise, compared with the pulse repetition period and the number of pulse counts per 100ms. In the experiment, the result showed that the prototype monitoring device could detect and discriminate the discharge signals produced at every discharge point on a heating cable.

• Science of Emotion and Sensibility
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• v.20 no.3
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• pp.39-48
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• 2017

In order to verify the effectiveness of marketing in the basketball stadium, this study measured and analyzed the gaze frequency and interest when the pupil was expanded by using the eye-tracking technology among various neuro marketing techniques of marketing. To analyze the section where the pupil size get expanded, interval of pupil size was higher than 2.275% (2 sigma data) and higher than 0.135% high (3 sigma data). Overall the valid data was analyzed by inflection points according to gaze frequency. We also analyzed the correlation between overall valid data and the ranges where the pupil size was significantly increased. The result showed that the correlation between overall valid data and pupil size 2 sigma data showed the highest correlation with 0.805. The pupil size 2 sigma data and pupil size 3 sigma data showed a correlation with 0.781, overall the valid data and pupil size 2 sigma data showed a correlation with 0.683. Therefore, it is concluded that, the section where the pupil size was expanded and the section at which gaze frequency is higher in the eye-tracking data were similar. However, the correlation between data of pupil size is determined to be significantly expanded and overall the valid data is decreased.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.5-13
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• 2017

Noise complaints among neighbors in apartment building are mainly caused by floor impact noise that is structure born noise due to occupant induced floor vibration. To control this noise problems many researchers have investigated floor systems and finishing materials. Light-weight impact noise affects by finishing materials, but heavy-weight impact noise induced by heel impacts during normal walking or jumping of children is concerned with structural system and floor vibration. To figure out the characteristics of floor impact noise and transmission of floor vibration due to human activities, vibration tests were conducted in apartment buildings. Impact hammer, heel drop and walking activities were loaded at center of upstairs living room, and accelerations of slabs for both upstairs and downstairs and sound pressure levels for downstairs were measured. The acceleration ratio of transmitted floor vibration to downstairs and human induced vibration in upstairs was between 0.5 and 1.0 according to slab size, wall, and load type. And floor impact noise occurred in the range of natural frequency of slab.

• Journal of the Korean Society of Safety
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• v.25 no.4
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• pp.36-41
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• 2010

This paper seeks to survey and analyze the status of obligatory execution from key institutional aspects that have taken effect according to laws on creating safe environment for laboratory and of general details such as the level of satisfaction on the part of people engaged in research activity regarding the laws after they have taken effect. The subjects of this study were MA and PhD graduate students in science and engineering who are primarily involved in research. This questionnaire survey was focused on finding basic data required for safety education for researcher and for efficient safety management by examining the correlation between education time and level of satisfaction. The collected data were analyzed by using frequency analysis, descriptive statistics, one way anova by SPSS12 package. The results obtained by this study are as follow. 1) Awarences of safety management rules, ordinary inspection, safety education were around 70% and other law clauses were around 50%. 2) The general satisfaction after the Laboratory Safety Act enforcement was usual level with 4.72 points in 7. 3) Researchers demanded ordinary inspection and protective equipment in a safe environmental composition. 4) The safety education time for improvement of a safe consciousness level was needed 12h or 24h at 1 years.

• Journal of the Korean Institute of Oriental Medical Informatics
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• v.15 no.2
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• pp.93-99
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• 2009

Objective: The aim of this study is to show one case of cerebral infarction patient with chest discomfort, insomnia and constipation improved by Daehwanghwangryeonsasim-tang. Methods: The patient was treated with herbal medicine (Daehwanghwangryeonsasim-tang) and acupuncture. Changes in symptoms for treatment period were observed. Result: Intensity and frequency of chest discomfort was decreased. Sleep time was increased and constipation was improved. Conclusion: Daehwanghwangryeonsasim-tang is effective on symptoms of the pattern of heart heat and fire-heat.

• Korean Journal of Optics and Photonics
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• v.20 no.2
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• pp.65-70
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• 2009

In this paper, a THz Yagi-Uda antenna with high input impedance is designed. By placing the antenna on a thin substrate, end-fire radiation patterns with high antenna impedance can be obtained even when the substrate has high relative dielectric constant. The proposed Yagi-Uda antenna has high input resistance of approximately $4,400{\Omega}$ at the resonance frequency which is obtained by using a U-shaped dipole as a driver element. It is expected that the Yagi-Uda antenna on a thin substrate can achieve much higher terahertz output power than the conventional THz antennas.

• The Korean Journal of Emergency Medical Services
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• v.8 no.1
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• pp.161-168
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• 2004

The workers of limestone industry have relatively higher rate of accident and injury than other industry workers. This survey was conducted to provide the informations for the planning of safety and health educations to prevent the accident and injury. The purpose of this study is to identify the morbidity rate per month and to determine the related health factors, and to find accident experiences of the limestone workers and to analyze the reasons and types of that accidents. The study design was a descriptive survey. Self reporting questionnaires developed by researcher were used for data collection. The subjects of this study were 225 workers in limestone industries in Jecheon city. The statistical methods utilized for data analysis were frequency analysis, $x^2$-test with SPSS-pc(ver.9.0). The results are as follows, 1. The workers morbidity rate per month was 22%, and morbid factors were Flu., G-I trouble, hypertension, orthopedic trauma, external wound, burn, etc., and the related health factors are self-assessment for health, exercise, accessability for medical facilities. 2. 40% of the subjects have experienced the accidents during last 6 months. The types of the accidents were safety violations, traffic accidents and fire accidents. Injury types were external wounds, fracture/amputation and burn. The workers of limestone industry have higher morbidity rate and experiences of accidents. Therefore the more increased safety and health educations than now for both the workers and the managers are needed. And this study could be helpful to increase the quality and the quantity of the educations needed.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.479-483
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• 1997

In general, motor parameters can be divided into mechanical/electrical parameters and harmonic parameters. Mechanical/electrical parameters identification of motor have been studying systematically for a long time. But, systematical study on harmonic parameters analysis for efficient motor drive system are very poor. The goal of this paper is to propose analyzing method of harmonic parameters for motor drive system with various experimental graphic screens and numerical results and to develope harmonic parameters analyzer. A developed analyzer is made up 586-PC and DSP (digital signal processor) board, motor drive system, power and harmonic parameters analyzing software for windows. Harmonic parameters are analyzed using correlation signal processing techniques based on the correlation between voltage and current waveforms. Analysis results are visualized by 3-D current coordinates, and it is compared and evaluated with conventional time/frequency domain. To verify the validity of the proposed system, 1/4HP capacitor run type single phase induction motor and thyristor speed controller is used for analyzing. Harmonic parameters of motor drive system is analyzed and verified, with varying fire angle of thyristor speed controller, and the proposed approach is to confirm validity.