• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.431-436
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• 2001

Lateral confining effect due to the existence of the shear reinforcements in R.C. beam is investigate in a numerical way. For the purpose, a three dimensional constitutive model of concrete is developed based on the elasto-plasticity using non-associated plastic flow rule to control the excessive inelastic dilatancy. The plastic flow direction is determined based on the associated plastic flow direction in a way to adjust the directional angle between the two normal vector components along the hydrostatic and deviatoric axis in a meridian plane in which the loading function prescribed. The current formulation is combined with the four parameter elasto-plastic triaxial concrete model recently developed. The resulting elasto-plastic triaxial concrete model predicts the fundamental behaviors of concrete under different confining levels and the 4-points flexural test of a beam with shear reinforcements, compares with the experimental results.

• Current Optics and Photonics
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• 제2권5호
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• pp.431-435
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• 2018

A modified setup of a CMD technique for high power coherent beam combining was presented to address an issue of low damage threshold of electro-optic modulators. The feasibility of the modified setup was demonstrated by combining eight fiber beams, and it was successfully performed with ${\lambda}/44$ of residual phase error and 100 Hz of control bandwidth. It is expected that the modified CMD setup facilitates ultra-high power coherent beam combination without a limitation caused by the low damage threshold of electro-optic modulators.

• 한국공작기계학회논문집
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• 제16권5호
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• pp.96-100
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• 2007

Condenser lens and objective lens are used to demagnify the image of the crossover to the final spot size. In lens, electrons are focused by magnetic fields. This fields is fringing field. It is important in electron focusing. Electron focusing occurs the radial component field and axial component field. Radial component produces rotational force and axial component produces radial force. Radial force causes the electron's trajectory to curve toward the optic axis and corss it. Focal length decreases as the current of lens increases. In this paper, we use the focal length for desiging the hardware of lens current control and present the results.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.528-529
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• 2008

A new concept based on sample current measurements for detecting of via-hole defects on wafer has been performed by low energy electron beam microcolumn. The microcolumn has been operated at a low voltage of 290 eV with total emission current of 400 nA, and a sample current of 6 nA. The test sample was fabricated with SiO2 layer of 300 nm thickness on a piece of a silicon substrate. Preliminary results of both sample current method and secondary electron method show microcolumn and its control can be useful technology for detecting of via-hole defects on wafer.

• 방사선산업학회지
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• 제2권3호
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• pp.141-148
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• 2008

Beta rays emitted from tritium in titanium tritide film were simulated with cathode rays of a scanning electron microscope to investigate the effect of beta rays from tritium on semiconductor devices. The cathode ray currents, which vary with the change of applied energy and beam spot size, were measured with Faraday cup. The current from the semiconductor device irradiated with cathode rays at various conditions was measured. The cathode ray current increased with the increase of spot size to a maximum then decreased when the spot sized increased further. The magnitude of current produced in the semiconductor device is proportional to the magnitude of cathode ray current. The magnitude of cathode ray current at each energy level was matched to the intensity of beta ray to simulate the tritium beta ray spectrum. Then the semiconductor characteristics were analyzed with I-V curves.

• 반도체디스플레이기술학회지
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• 제10권2호
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• pp.115-119
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• 2011

A tip-type carbon nanotube(CNT)-based field emitter was studied to consider it as electron source for micro-focused x-ray tube. The CNT was grown directly on a metal (tungsten) substrate by using an inductively coupled plasma-chemical vapor deposition (ICP-CVD) method. Prior to CNT growth, the metal substrate was etched to have various tip angles from $10^{\circ}$ to $180^{\circ}C$ (flat-type). The morphologies and microstructures of all the grown CNTs were analyzed via field-emission SEM. Furthermore, the effects of substrate tip-angles on the emission properties of CNT-based field emitters were characterized to estimate the maximum current density, the turn-on voltage, and the spatial distribution of electron beams. Prolonged long-term stability testing of the CNT emitters was also performed. All the experiment results obtained from this study indicated why a tip-type CNT emitter, compared with a flat-type CNT emitter, would be more desirable for a micro-focused x-ray system, in terms of the emission current level, the focused beam area, and the emission stability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.2184-2186
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• 2005

Neutron production is very important to apply fusion energy through SCBF(Spherically Convergent Beam Fusion) device and its rate is Proportional to the square of the ion current$({\propto}I^2)$. Also the ion current has a close relation with the potential well structure in grid cathode. In this paper, the ion current is calculated for the increasement of neutron production rate in a variety of grid cathode geometry. The atomic and molecular collision are taken into account by Monte Carlo Method and Potential is calculated by Finite Element Method. Main processes of the discharge is the ionization of $D_2$ by fast $D_2^+$ ion. As the number of a cathode ring is small and gap distance decreases, the ion current increases and neutron production rate will increase.

• 한국컴퓨터정보학회논문지
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• 제10권4호
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• pp.87-92
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• 2005

본 연구는 레이저빔을 제어하기 위한 전자 셔터의 디지털 I/O 인터페이스와 온도 제어 알고리즘을 개발함으로써 레이저 치료 시 열적 피이드 백을 통한 치료의 가능성을 보여 주었다. 전자셔터는 이러한 전자셔터 구동 인터페이스와 제어 알고리즘의 개발로 경제성은 물론 어느 일정한 범위에서 온도를 자동제어 하도록 설계하였다. 방사선 치료, 고주파 치료 또는 약물치료 등에 의하여 정상세포까지 죽이는 현 치료방법의 문제점을 개선함으로써 어느 일정한 온도 범위에서의 레이저 빔 치료에 의한 환자의 국부적 치료의 가능성을 제시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1530-1533
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• 2005

Total 12 units of high power klystron-modulator systems as microwave source is under operation for 2.5-GeV electron linear accelerator in Pohang Light Source(PLS) linac. RF power and beam power of klystron are precisely measured for the effective control of electron beam. A precise measurement and measurement equipment with good response characteristics are required for this. Input power of klystron is calculated from the applied voltage and the current on its cathode. Tiny measurement error severely effects RF output power value of klystron. Therefore, special care is needed to measure precise beam voltage. Capacitive voltage divider(CVD) unit is intended for the measurement of beam voltage of 400 kV generated from the pulsed klystron-modulator system. Main parameter to determine the standard capacitance in the high arm of CVD is dielectric constant of insulation oil. Therefore CVD should be designed to have a minimum capacitance variation due to voltage, frequency and temperature in the measurement range. This paper will discuss the analysis of capacitive voltage divider for a pulsed high-voltage measurement, and the empirical relations between capacitance and oil temperature variation.

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.731-736
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• 2014

An organic junction transistor with a vertical structure based on an active layer of poly(3-hexylthiophene) was fabricated by facile micro-contact printing combined with the Langmuir-Schaefer technique, without conventional e-beam or photo-lithography. Direct printing and subsequent annealing of Au-nanoparticles provided control over the thickness of the Au electrode and hence control of the electrical contact between the Au electrode and the active layer, ohmic or Schottky. The junction showed similar current-voltage characteristics to an NPN-type transistor. Current through the emitter was simply controllable by the base voltage and a high transconductance of ~0.2 mS was obtained. This novel fabrication method can be applied to amplifying or fast switching organic devices.