• Journal of Welding and Joining
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• 제18권1호
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• pp.97-103
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• 2000

Time series analysis results show the SVD is a candidate of on-line monitoring of welding penetration when the covariance matrix of a full penetration is used as a mapping function. As the reconstructed embedding vectors from the chaotic scalar time series are manipulated by the covariance matrix, the mapped tim series lie on a hyper-ellipsoid which the lengths of semi-axes are the squared eigenvalues of the covariance matrix in the case of full penetration. These visualize by two dimensional stroboscope views. The other cases like partial penetration, are different in the sense of sizes and shapes. Here we test two types of time series; the ion current and the X-ray. The ion current is better than the X-ray as an on-line monitoring signal, because the difference of the eigenvalue spectrum of the ion(between the pull penetration and partial penetration) is bigger than those of the X-ray.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2003년도 추계학술대회 논문집
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• pp.45-46
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• 2003

The x-ray micro-imaging technique was employed to measure the size and velocity of micro-bubbles moving in an opaque tube simultaneously. Phase contrast images were obtained at interfaces of micro-bubbles between water and air due to different refractive index. Micro-bubbles of $20\~120{\mu}m$ diameter moving upward in an opaque tube $(\phi=2.7mm)$ were tested. For two different working fluids of tap water and DI water, the measured velocity of micro-bubbles is roughly proportional to the square of bubble size.

• 진공이야기
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• 제3권4호
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• pp.4-7
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• 2016

An X-ray Free Electron laser facility (PAL-XFEL) has been built in Pohang Accelerator Laboratory to provide X-ray FEL radiations for photon users. The machine consists of a 10 GeV normalconducting S-band linear accelerator and two undulator beamlines. The hard and soft X-ray beamlines will provide FEL radiations with wavelengths of 0.6 to 0.1 nm and 4.5 to 1 nm, respectively. Beam commissioning of PAL-XFEL is ongoing and user service will start in 2017. In this report, the PAL-XFEL layout and the working principle are discussed.

• 천문학회지
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• 제29권spc1호
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• pp.41-42
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• 1996

A possible cosmic X-ray background(XRB) radiation related to original antimatter is considered. If the universe is made of separating domains of antimatter and matter, the photons produced by the annihilation of electron-positron and proton-antiproton on the last scattering surface would reach us in the energy $\~$0.45 keV and $\~$60 keV respectively because of the redshift. The spectrums of X-ray radiation from annihilation are deduced and a possible observational figure is described also.

• Journal of the Optical Society of Korea
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• 제7권4호
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• pp.230-233
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• 2003

This study describes the conceptual design of a soft x-ray microscope system based on a laserbased source for biomedical application with high resolution (${\leq}$50nm). The laboratory scale soft x-ray microscope consists of high power laser plasma x-ray source and grazing incidence mirrors with high reflectivity. The laser plasma source used for developing this system employs Q-switched Nd-YAG pulsed laser. The laser beam is focused on a tantalum (Ta) target. The Wolter type I mirror was used as condenser optics for sample illumination and as objective mirror for focusing on a detector. The fabrication of the Wolter type I mirror was direct internal cutting using ultraprecision DTM. A hydrated biological specimen was put between the two silicon wafers, the center of which was $Si_3N_4$ windows of 100㎚ thickness. The main issues in the future development work are to make a stable, reliable and reproducible x-ray microscope system.

• Carbon letters
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• 제4권1호
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• pp.10-13
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• 2003

The structural studies of amorphous isotropic carbon prepared from pyrolysis of phenol formaldehyde resin have been carried out using X-ray diffraction. X-ray diffraction from as prepared sample at $1000^{\circ}C$ and a sample treated at $1900^{\circ}C$ revealed that both are amorphous even though there are small differences in short range order. It is found that both are graphite like carbon (GLC) with predominantly $sp^2$ hybridization. Small angle X-ray scattering results show that as prepared sample mainly consists of thin two dimensional platelets of graphitic carbon whereas they grow in thickness to become three dimensional materials of nano dimensions.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2009년도 정보통신설비 학술대회
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• pp.262-265
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• 2009

최근 각광받고 있는 위치기반 서비스의 모델인 긴급 SOS 시스템은 기지국망을 이용한 광역위치추적과 IEEE 802.15.4를 기반으로 하는 근거리 위치추적 시스템이 결합된 새로운 형태의 하이브리드형 위치추적 기법이다. 본 시스템에서 근거리 위치추적 범위를 정확히 추정하는 것은 중요한 이슈라 할 수 있다. 따라서 본 논문에서는 IEEE 8020.15.4를 기반으로 하는 Zigbee 통신방식을 추정 할 수 있는 최대 거리를 log distance model과 two ray ground 모델을 기반으로 추정 하였다.

• Applied Microscopy
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• 제45권3호
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• pp.131-134
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• 2015

Here we show how by processing energy dispersive X-ray spectrometry (EDS) data obtained using highly sensitive, new generation EDS detectors in the AZtec LayerProbe software we can obtain data of sufficiently high quality to non-destructively measure the number of layers in two-dimensional (2D) $MoS_2$ and $MoS_2/WSe_2$ and thereby enable the characterization of working devices based on 2D materials. We compare the thickness measurements with EDS to results from atomic force microscopy measurements. We also show how we can use electron backscatter diffraction (EBSD) to address fabrication challenges of 2D materials. Results from EBSD analysis of individual flakes of exfoliated $MoS_2$ obtained using the Nordlys Nano detector are shown to aid a better understanding of the exfoliation process which is still widely used to produce 2D materials for research purposes.

• Journal of the Korean Wood Science and Technology
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• 제37권6호
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• pp.531-536
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• 2009

주요 국산 수종인 잣나무재와 일본잎갈나무재의 횡단면상 방사조직 밀도 및 접선단면상 복열방사조직 출현 빈도수에 대한 변이성을 조사하였다. 방사조직의 밀도는 잣나무재 4.6개/mm, 일본잎갈나무재 9.0개/mm로 일본잎갈나무재의 방사조직 밀도가 더 높게 나타났다. 또한, 방사조직 밀도는 수 부근에서 높았고, 수피 쪽으로 이행함에 따라 점차 감소하는 경향을 나타냈다. 한 연륜 내에서의 복열방사조직 출현 빈도수는 일본잎갈나무재가 잣나무재보다 높았다. 잣나무재의 복열방사조직은 복열의 수가 1세포고인 것(B+1)이, 일본잎갈나무재는 2세포고인 것(B+2)이 가장 많았다. 일반적으로 복열방사조직의 출현 빈도수는 조재부가 만재부보다 높았는데 일본잎갈나무재의 경우 복열의 수가 6~7세포고에 달하는 것(B+6~B+7)도 있었다. 본 연구 결과, 방사조직 밀도의 변이성은 성숙재와 미성숙재를 구분하는 기초 자료로뿐만 아니라 방사조직의 출현 빈도와 함께 두 수종을 식별하는 자료로도 활용될 수 있을 것으로 생각되었다.

• 한국항행학회논문지
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• 제11권4호
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• pp.454-460
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• 2007

본 논문에서는 실내 환경에서 전파의 전달특성을 모델링하기 위해 광선추적법을 이용한 2차원 ray-tracing 시뮬레이터를 구현하였고, 이를 통해 다중 벽면으로 구성된 환경에서 ray의 전파 경로를 분석하고 평가하였다. 실험 결과, 구현된 광선추적법의 경로 패턴 및 시간지연 분포는 동일한 무선 환경에서 수행된 이전의 실험 결과와 비슷한 결과가 나타남을 확인하였으며, 송수신 거리 및 방사각에 따른 수신반경의 조절이 타당함을 확인하였다. 특히 비가시거리 송수신 환경에서 다중 벽면을 투과한 ray가 반사와 투과를 형성하여 수신기에 도달할 때까지의 channel profile은 기존 연구의 실험 결과와 유사함을 확인하였다.