• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.570-572
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• 2003

In this paper, a method of vegetation spectrum measurement using multi spectrum camera was studied. Each pixel in taken images using multi spectrum camera have spectrum data, the relationship between spectrum data and distribution, structure, etc. are directly turned out. In other words, detailed spectrum data information of object including spatial distribution can be obtained from those images. However, the camera has some problems for applying field measurement and data analysis. In this study, those problems are solved.

• 전자공학회논문지
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• 제54권3호
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• pp.63-69
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• 2017

NNPS(normalized noise power spectrum)는 획득한 x선 영상에서 평판형 방사선 디텍터의 잡음 특성을 spectrum을 관찰하기 위해 측정한다. 그러나 NNPS 측정은 획득한 영상에 따라 일관적이지 못한 성질을 가지고 있어서 안정된 측정이 필요하다. 디텍터의 NNPS 측정은 표본 periodogram을 구하여 평균을 내는 방법을 사용하는데, 일반적으로 표본의 개수를 충분히 늘리면 정확하면서 안정된 값을 구할 수 있다. 본 논문에서는 periodogram과 같은 표본 spectrum의 평균으로 유한한 개수의 영상이 주어졌을 때 일관적이고 효율적인 NNPS 값을 제공 할 수 있는 두 가지 방법을 제안하고 그 성능을 비교하고 분석했다. 실제 두 종류의 방사선 디텍터로부터 획득한 x선 영상을 사용하여 제안한 방법을 실험하였으며, 주어진 영상을 사용하여 표본 spectrum의 최대 가지 수를 갖는 조합으로 NNPS를 구하고 평균을 내는 방법이 기존 방법에 비하여 안정된 NNPS 측정이 가능함을 보였다.

• 한국콘텐츠학회논문지
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• 제14권9호
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• pp.589-597
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• 2014

전파자원을 이용한 다양한 무선 서비스에 대한 급증하는 수요는 더 많은 주파수 자원의 확보를 요구한다. 그러나 주파수 자원의 희소성과 고대역 주파수 발굴의 어려움을 감안하면, 늘어나는 전파자원의 수요를 충족시킬 수 있는 유일한 방법은 기존 전파자원의 이용 효율을 극대화시키는 것이다. 이러한 상황에서, 전파자원에 대한 초과 수요를 해결하기 위한 다양한 주파수 공유 방안이 최근 활발히 논의되고 있다. 이와 더불어, 주파수 공유의 실효성 검증과 무선시스템의 성과 예측을 위해, 주파수 이용효율 측정의 중요성이 높아지고 있다. 본 연구에서는 전파자원 이용효율의 합리적 측정 방법을 제안한다. 국제전기통신연합(ITU) 권고안을 토대로 전파자원 이용효율의 다양한 측정 방법을 고찰하고, 대기행렬모형을 이용한 전파 자원 이용효율 측정의 대안 모델을 제시한다. 이를 통해, 주파수 공유 시 전파자원의 이용효율이 어느 정도 증대되는지를 합리적으로 예측할 수 있다.

• 한국정밀공학회지
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• 제31권2호
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• pp.141-148
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• 2014

In this work, effects of plasma on different hardness of welding steel using laser-induced breakdown spectroscopy were investigated. The ratios of ionic to atomic spectrum peaks were related to its material hardness. The major spectrum peak (Fe) and minor spectrum peak (Mn) were considered as monitoring elements. The stronger repulse plasma was generated, the harder material it was. The ratios of ionic to atomic spectrum peaks increased with respect to the material hardness as well. The correlation of minor spectrum peaks was stronger than that of major spectrum peaks. However, the major spectrum peaks indicated a similar trend, which could be used to estimate the hardness, too. Based on this result, the method could be used as a non-contact remote measurement of material properties.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1656-1658
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• 1998

This paper deals with a measurement system of a distance between lightning strokes and observatory station and spectrum analysis of electric fields radiated from lightning discharges. The distance measurement system, which consists of a loop type magnetic field sensor, a microphone and one chip microprocessor, is connected to a personal computer through RS232 port to acquire and process the data. This system is to use a difference of propagation velocity between an electromagnetic wave and a sonic wave produced by lightning discharge. Also, an electric field waveform and a frequency spectrum were investigated by an electric field measurement system with a hemisphere antenna and a spectrum analyzer with a biconical antenna and a log-periodic antenna, respectively. The results would be used as a basic reference to protect the power systems and electric circuits from lightning overvoltages.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.75-77
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• 2005

When measuring impedance of electronic component and so on, even the small size can reject the interference to shielding object. But, the interference through human body is grown when measuring bioimpedance without establishing shield specially. Consequently, when measuring bioimpedance in this paper, it proposed impedance measurement method to take advantage of spread spectrum technology, so that can reject the interference without establishing shield specially. Spread spectrum impedance measurement method to propose in this paper can reject the interference signal that occurring from medical instruments in the human body, the interference signal that is flowed in from surrounding environment when measuring impedance. It improved SJR(signal to jamming ratio) about 22dB than conventional method that actually realize and experiment spread spectrum impedance measurement method.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.184-184
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• 2012

We proposed a new measurement method of cutoff probe using the reactance spectrum of the plasma in cutoff probe system instead of transmission spectrum. The high accurate reactance spectrum of the plasma which is expected in previous circuit simulation of cutoff probe [1] was measured by using the automatic port extension method of the network analyzer. The measured reactance spectrum is good agreement with E/M wave simulation result (CST Microwave Studio). From the analysis of the measured reactance spectrum based on the circuit modeling, not only the electron density but also electron-neutral collision frequency can be simply obtained. The obtained results of electron density and e-n collision frequency were presented and discussed in wide range of experimental conditions, together with comparison result with previous methods (a previous cutoff probe using transmission spectrum and a single langmuir probe).

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.266-272
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• 2021

In the pulsed electron beam generators, such as plasma focus devices and linear induction accelerators whose electron pulse width is in the range of nanosecond and less, as well as in cases where there is no direct access to electron beam, like runaway electrons in Tokamaks, measurement of the electron energy spectrum is a technical challenge. In such cases, the indirect measurement of the electron spectrum by using the bremsstrahlung radiation spectrum associated with it, is an appropriate solution. The problem with this method is that the matrix equation between the two spectrums is an ill-conditioned equation, which results in errors of the measured X-ray spectrum to be propagated with a large coefficient in the estimated electron spectrum. In this study, a method based on the neural network and the MCNP code is presented and evaluated to recover the electron spectrum from the X-ray generated by collision of the electron beam with a target. Multilayer perceptron network showed good accuracy in electron spectrum recovery, so that for the X-ray spectrum with errors of 3% and 10%, the network estimated the electron spectrum with an average standard error of 8% and 11%, on all of the energy intervals.

• 한국해양공학회지
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• 제26권2호
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• pp.8-13
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• 2012

This paper investigates the statistical properties of waves in the sea area of Uljin, which is located in the East Sea area of Korea. The wave data were measured using AWAC (Acoustic Wave and Current Meter), which was installed at a 16-m water depth from November 2010 to March 2011. The wave data acquisition rate, Hmax, monthly mean Hs, Tz, Tp, and wave direction are summarized. The distributions of Hs and Tz were analyzed using the Hs-Tz scatter diagrams. The measurement wave data were analyzed to investigate freak wave characteristics. By comparing the wave spectrum using the measurement wave data with the wave spectrum obtained by varying the JONSWAP wave spectrum, it was possible to approximate the wave spectrum shape at the Uljin Sea area.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.30-30
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• 2011

The wave-cutoff tool is a new diagnostic method to measure electron density and electron temperature. Most of the plasma diagnostic tools have the disadvantage that their application to processing plasma where toxic and reactive gases are used gives rise to many problems such as contamination, perturbation, precision of measurement, and so on. We can minimize these problems by using the wave-cutoff method. Here, we will present the results obtained through the development of the wave-cutoff diagnostic method. The frequency spectrum characteristics of the wave-cutoff probe will be obtained experimentally and analyzed through the microwave field simulation by using the CST-MW studio simulator. The plasma parameters are measured with the wave-cutoff method in various discharge conditions and its results will be compared with the results of Langmuir probe. Another disadvantage is that other diagnostic methods spend a long time (~ a few seconds) to measure plasma parameters. In this presentation, a fast measurement method will be also introduced. The wave-cutoff probe system consists of two antennas and a network analyzer. The network analyzer provides the transmission spectrum and the reflection spectrum by frequency sweeping. The plasma parameters such as electron density and electron temperature are obtained through these spectra. The frequency sweeping time, the time resolution of the wave-cutoff method, is about 1 second. A short pulse with a broad band spectrum of a few GHz is used with an oscilloscope to acquire the spectra data in a short time. The data acquisition time can be reduced with this method. Here, the plasma parameter measurement methods, Langmuir probe, pulsed wave-cutoff method and frequency sweeping wave-cutoff method, are compared. The measurement results are well matched. The real time resolution is less than 1 ?sec. The pulsed wave-cutoff technique is found to be very useful in the transient plasmas such as pulsed plasma and tokamak edge plasma.