• Journal of Biosystems Engineering
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• v.24 no.3
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• pp.253-258
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• 1999

This study was conducted to develop an automatic egg inspection system for detecting creaked eggs based on acoustic impulse response. This system includes a sound generator, a sound sensor with signal conditioner, and a computer. The sound generator that hit the sharp of the dull edges of an egg was constructed with a ceramic ball pendulum attached to a rotary type solenoid. The signal conditioner included a pre-amplifier and a digital signal processing (DSP) board. The parameters for distinguishing cracked and normal eggs were the area, the geometric centroid and the resonance frequency of power spectrum of the acoustic signal generated. An algorithm for on-line detection of the continuous transferring eggs was developed. The performance tests resulted with 91% success rate to separate cracked and normal eggs at the rate of 1 second per an egg.

• Journal of the Korean Geotechnical Society
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• v.17 no.5
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• pp.97-105
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• 2001

현장타설말뚝의 건전도 평가에서 충격반향, 충격응답기법과 같은 비검측공 시험법을 적용하는 사례가 점차로 증가되는 추세에 있다. 비검측공시험법의 적용성을 체계적으로 평가하기 위해 수행된 일련의 연구결과 중에서 본 논문에서는 시험법의 결함탐지 능력을 평가하기 위해 수행된 해석적 연구결과에 관해 논한다. 이 연구에서는 시험법의 결함탐지능력에 대한 제반 영향인자 중에서 결함의 유형, 위치 및 크기의 영향을 평가하고자 하였다. 이를 위해서 여러 가지 조건에서 말뚝머리에 작용하는 충격하중에 대한 흙-말뚝 구조의 동적응답을 ABAQUS를 이용한 유한요소법으로 해석하였다. 이로부터 얻은 신호를 충격반향 혹은 충격응답기법으로 처리.분석하여 각 시험법의 결함탐지 능력을 평가해 보았다. 연구결과 이들 두 기법 모두 결함의 위치와 유형은 비교적 정확하게 탐지하는 것으로 나타났다. 그러나 충격응답기법을 이용하여 추정한 결함 크기는 신뢰도가 매우 낮았다. 이 문제를 해소하여 시험법의 적용성을 향상시키기 위해서는 측정된 동적응답신호를 이용하여 적절한 역계산 기법을 개발하여 적용할 필요가 있다는 결론을 얻었다.

• Journal of the Korean Geotechnical Society
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• v.17 no.5
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• pp.107-114
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• 2001

비검측공 시험법을 현장타설말뚝의 건전도 평가 목적으로 적용함에 있어서 시험법의 적용성을 향상시키기 위한 연구가 진행되어 오고 있다. 본 논문에서는 같은 맥락에서 수행되어 온 일련의 해석적 연구 결과 중 시험법의 해상도에 관한 문제와 말뚝 주변 및 선단지반의 강성이 비검측공 시험결과에 미치는 영향에 관해 다루었다. 본 논문에서 수행한 연구결과에 의하면 충격응답기법의 해상도를 평가하기 위해서는 말뚝재료에 대한 지반의 강성비($V_{s}$ /$V_{c}$)와 말뚝의 길이에 대한 직경의 비(L/D)에 의존하는 기존 평가기준에 부가하여 말뚝의 상대적인 체적변화가 필히 고려되어야 한다는 결론을 얻었다. 한편, 말뚝이 수평으로 층이 진 주변 지반을 통과하여 말뚝선단부를 지지하는 지반(선단지반)에 근입되거나 지지되는 경우에 말뚝의 자유단 혹은 고정단 경계 조건은 주변 지반과 선단 지반의 강성비와 선단 지반에 대한 말뚝의 근입깊이에 따라 변화한다는 사실을 규명하였다. 말뚝의 건전도 평가 시에 사용하게 되는 말뚝의 공진주파수가 이들 조건에 따라 변화하므로 결과적으로 시험결과분석에 있어서 이들 영향이 필히 고려되어야 한다는 결론을 얻었다.

• Tunnel and Underground Space
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• v.9 no.1
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• pp.36-47
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• 1999

For cautious controlled blasting, it is necessary to understand characteristics of the blasting vibration. In this study, a series of tests were carried out to investigate the several characteristics of blasting vibration waveform by vibration time history analysis. Separation between impulse vibration and free vibration from blasting vibration, duration time, effects of overlap of free vibration upon the level of vibration and changes of waveform according to increase of charge weight per delay etc. were studied with waveform analysis.

• International Journal of Aerospace System Engineering
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• v.2 no.2
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• pp.1-5
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• 2015

The powder propellant rocket which uses micron-sized particles as fuel is storable and costly. Functions like thrust control and multiple-ignition can be realized by changing powder mass flow rate. In this paper, we discuss the theoretical performance of bi-propellant and mono-propellant powder rocket. When used as the fluidization gas, helium can improve specific impulse dramatically. The stability of the powder feeding device is preliminarily quantified through metal/N2O powder rocket hot fire tests.

• 전기의세계
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• v.27 no.6
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• pp.76-83
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• 1978

This paper reveals the results of fundamental experiments with the breakdown strength- and treeing phenomena, by A.C voltage and impulse voltage, of cross-linked polyethylene insulator, respectively compared in each case of the various specimens; nonvoid, air void, water void, oil void and oil impregnated one, all articially made. In this research, the V-t and V-n characteristics are investigated by means of the Weibull distribution and are analysed the characteristics of fatigue breakdown caused by the A.C and impulse voltage. Based on numerous tests, treeing effect and treeing breakdown mechanism is investigated through microscopic photographs taken to clarify the shapes of each tree and treeing breakdown phenomena.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.235-242
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• 2008

An innovative Panel ExTension SATellite(PETSAT) and propulsion system for PETSAT, are presented in this paper. First, we outline what PETSAT is. Next, based on PETSAT ethos, design policy of the propulsion system is provided. According to the policy, we designed propulsion system and concretely estimated and assembled mono-propellant and bi-propellant systems, and it indicated that mono-propellant propulsion with 50-60 seconds of specific impulse and 1 N of thrust is probable. In the case of bi-propellant, 120-150 seconds of specific impulse is valid even based on the design policy. We conducted captive tests of mono-propellant and bi-propellant propulsions with a breadboard model of propulsion system for PETSAT, and obtained good operations and performances. Based on the test results, we designed and manufactured flight model propulsion system for PETSAT. We are planning to demonstrate it in SOHLA-2L project progressed by the Space Oriented Higashiosaka Leading Association(SOHLA). SOHLA-2L will be the first on-orbit demonstrator of PETSAT in 2008.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.443-451
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• 2023

Machine Learning has introduced many solutions in data science, but its application in IoT faces significant challenges, due to the limitations in memory size and processing capability of constrained devices. In this paper we design an automatic gamma radiation detection and identification embedded system that exploits the power of TinyML in a SiPM micro radiation sensor leveraging the Edge Impulse platform. The model is trained using real gamma source data enhanced by software augmentation algorithms. Tests show high accuracy in real time processing. This design has promising applications in general-purpose radiation detection and identification, nuclear safety, medical diagnosis and it is also amenable for deployment in small satellites.

• The Journal of Asian Finance, Economics and Business
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• v.1 no.1
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• pp.5-14
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• 2014

This paper empirically examines the short-run and long-run causal relationship between stock market prices and exchange rates in Chinese stock markets using monthly data from January 2002 to December 2012 retrieved from the National Bureau of Statistics of the People's Republic of China. Unit root, cointegration tests, vector error correction estimates, block exogeneity Wald tests, impulse responses, variance decomposition techniques and structural break tests are employed. This study found 1) long-run causality from exchange rates to stock prices in Chinese stock markets and 2) short-run causality from Japanese yen and Korean won exchange rates to stock prices in the Shanghai Stock Exchange strongly prevails while in the Shenzhen Stock Exchange weakly prevails. The impact of the global financial crisis from 2007 to 2009 on Chinese stock markets was insignificant.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.10
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• pp.82-88
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• 2014

This paper presents the results of model tests for the attachment process of lightning leader to ground which is one of poorly understood processes of cloud-to-ground lightning discharges. In order to simulate the attachment process of lightning leader to ground, we investigated the discharge characteristics of air gap between the tip of needle-shaped electrode and the soil surface as a parameter of moisture content in soils when the positive and negative $1.2/50{\mu}s$ lightning impulse voltages are applied. The breakdown voltage and the discharge light were observed. As a result, the attachment processes of lightning leader to ground are strongly dependent on the grain size and the moisture content of soils. The time to breakdown was shortened with increasing the magnitude of incident impulse voltages. The delay time from application of the highest voltage to breakdown in sand is shortened with increasing the moisture content. The delay time from application of the voltage to breakdown in gravel varied from about $0.5{\mu}s$ to several ${\mu}s$. As the moisture content in soil increases, the breakdown voltages are decreased and the breakdown voltage versus time to breakdown curves are shifted toward the lower side. The results obtained in this work are similar to those for non-uniform air gap stressed by lightning impulse voltages.