• ETRI Journal
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• v.35 no.6
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• pp.1164-1167
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• 2013

We correlate the failure in miniature X-ray tubes with the field emission gate leakage current of gated carbon nanotube emitters. The miniature X-ray tube, even with a small gate leakage current, exhibits an induced voltage on the gate electrode by the anode bias voltage, resulting in a very unstable operation and finally a failure. The induced gate voltage is apparently caused by charging at the insulating spacer of the miniature X-ray tube through the gate leakage current of the field emission. The gate leakage current could be a criterion for the successful fabrication of miniature X-ray tubes.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.20 no.2
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• pp.289-297
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• 1990

The purpose of this study was to assess the resolution and focal spot size of dental X-ray machines. Fifty dental X-ray machines were selected for measuring resolution and focal spot size. These machines were used in general dental clinics. The time of installation of the X-ray machine varies from 1 year to 10 years. The resolution of these machines was measured with the test pattern. The focal spot size of these machines was measured with the star test pattern. The following results were obtained: 1. The resolution of dental intraoral X-ray machines was not significantly changed in ten years. 2. The focal spot size of dental intraoral X-ray machines was not significantly increased in ten years. The statistical analysis between the mean focal spot size and nominal focal spot size was significant at the 0.05 level about the more than 3 years used machines.

• Proceedings of the Optical Society of Korea Conference
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• 1998.08a
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• pp.192-193
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• 1998

At Rutherford Appleton Laboratory(RAL), a high-repetition rate ps exicmer laser-plasma x-ray source has been developed for x-ray lithography with a calibrated output of up to 1 watt X-ray average power at 1nm wavelength. In a previous reports this compact x-ray source was used to print 0.18$\mu$m lines for a gate on Si-FET devices and deep three-dimensional structure with 100$\mu$m length, 25$\mu$m width, and 48 $\mu$m depth for a nanotechnology. The deep X-ray lithography is called as LIGA thchnology and getting a wide interest as a new technology for a nano-device. In this report all this works are summarized.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.141-150
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• 1994

The residual stress is inevitably introduced into composites because of the mismatch of the coefficient of thermal expansion, and it is different in each phase. The X-ray technique can detect separately the stress in each phase, so will wield useful information for analyzing the toughening mechanisms of composites. In order to apply the law of mixture to alloy steels with composite microstructures, two phase stainless steel, consisted of ferrite (.alpha.-Fe) and austenite (.gamma.-Fe) structures, was selected. The tensile elastic deformation was loaded, and then the X-ray diffraction technique was used to measure the X-ray elastic constants, the X-ray stress constants and the phase stresses. The law of mixture was investigated and the separation of macrostress and microstress was carried out. The phase stresses (the residual stresses of phase) in each phase, which were measured by X-ray technique, was directly proportional to the applied stress. The macrostress calculated from the phase stresses by using the law of mixture was nearly equal to the applied stress.

• Journal of the Korean Wood Science and Technology
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• v.33 no.5 s.133
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• pp.1-6
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• 2005

The anatomical structure of fusiform ray was examined by scanning electron microscopy (and microscopic images were analysed by image analyser) to explain the differences in radial fluid uptake between the extremes in the radial treatment data, i.e. between the selected trees of QCI (Queen Charlotte Islands in Rhondda, South Wales) and SO (South Oregon in Dalby, North-East England) planted in the UK. The ray structure of these two seed origins was examined microscopically and different patterns of ray composition were observed. The most important anatomical features influencing radial permeability were the nature of fusiform ray, and the condition of the resin canals, epithelial cells and intercellular spaces in particular.

• Journal of the Korean Wood Science and Technology
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• v.26 no.2
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• pp.24-28
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• 1998

Ray cells with perforations are recorded for the first time in the Korean Celastraceae species of Euonymus sieboldiana and Tripterygium regelii and the Oleaceae species of Abeliophyllum distichum, Forsythia ovata, Ligustrum japonicum, and Osmanthus heterophylla, All these anomalous ray cells have simple perforations, and the vessel elements of all these species have simple perforation plates, Thus, in the Korean Celastraceae and Oleaceae, the perforations of ray cells appear to be identical with the types of perforation plates in the vessel elements of the same wood, The diagnostic value of the perforated ray cells is also discussed.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.29-31
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• 2007

In this paper we propose an directional analytic approach in image data space for X-ray image which is detected from the X-ray projection system. Such a radiographic nondestructive testing has long been used for steel-tube inspection and weld monitoring. The welded area and thickness of steel-tube are detected from gradient radiating mechanism based on the evaluation of biased X-ray source position. The welded area is an ellipse type on low contrast X-ray image including noise. Noise originates from most of elements of the system. such as shielding CCD camera, imaging screen, X-ray source, inspected object, electronic circuits and etc.. Projection incorrectness and noise influence on imaging quality is to be represented by vertical pixels' distribution. Space analysis due to vertical direction also shows the segmental possibility between regions by visual edge evaluation.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.108.1-108.1
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• 2014

제품의 고성능 사양을 위해 초미소 크기(Nano Size)의 구조를 갖는 제품들이 일상에서 자주 등장한다. 대표 제품은 주변에서 쉽게 접할 수 있는 전자제품의 반도체 칩이다. 반도체 칩 소자 구조는 크기를 줄이는 것 외에도 적층을 통해 소자의 집적도를 높이는 방향으로 진화를 하고 있다. 복잡한 구조로 인해 발생되는 여러 반도체 결함 중에 TSV 결함은 현재 진화하는 반도체 칩의 구조를 대변하는 대표 결함이다. 이 결함을 효율적으로 검출하고 다루기 위해서는 초미소 크기(Nano Size)의 결함을 비파괴적인 방법으로 가시화하고 분석하는 장비가 필요하다. X-ray 시스템은 이러한 요구를 해결하는 훌룡한 한 방법이다. 이 논문에서는 X-ray 시스템의 구성 및 위의 TSV 결함을 검출하고 분석하기 위한 시스템의 특징에 대해 설명을 한다. X-ray 시스템은 크게 X선을 발생시키는 X선튜브와 대상 물체를 투과한 X선을 영상화하는 디텍터, 대상물체의 영상화를 위해 물체를 적절하게 구동시키는 이동장치로 구성되어 있다. 초미소크기(Nano Size)의 결함 검출을 위해서는 X선 튜브, 디텍터, 이동장치에 요구되는 사양의 복잡도, 정밀도는 이러한 시스템의 개발을 어렵게 만든다. 이 논문에서는 이러한 시스템을 개발 시에 시스템 핵심 요소의 특징을 분석한다.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.431-435
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• 1998

This paper deals with the output characteristics of resonant PWM inverter type X-ray generators connected to different DC power units i.e. a single phase full bridge rectifier, a three phase full bridge rectifier and a power storage unit(PSU). The quality of X-ray beam depend on the pulsation waveforms of DC voltage supplied to the X-ray tulbe. In a X-ray generator, the waveforme of DC output voltage can be affected from hramonic distortion of DC input power. When a tube voltage waveform is distorded, the property of X-ray beam such as reproducibility, direcibility and doesage can be reduced. Therefore, we compared DC output waveforms and doesages with three thpe of DC power units and show the experimental results in this paper

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.305-306
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• 2005

The effects of As addition In amorphous selenium (a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating (MPG) technique We have found an increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As X-ray device. The fabricated a-Se (0.3%As) based X-ray detector exhibited the highest X-ray sensitivity of 5 samples.