• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.939-946
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• 2023

Comprehensive Research Facility for Fusion Technology (CRAFT) is an integration of different demonstrating or testing facilities, which aim to develop the critical technology or composition system towards the fusion reactor. Due to the importance and challenge of the negative ion based neutral beam injection (NNBI), a NNBI test facility is included in the framework of CRAFT. The initial object of CRAFT NNBI test facility is to obtain a H⁰ beam power of 2 MW at the energy of 200-400 keV for the pulse duration of 100 s. Inside the negative ion accelerator of NNBI system, the interactions of the negative ions with the background gas and electrodes can generate abundant stray electrons. The stray electrons can be further accelerated and dumped on the electrodes or eject from the accelerator. The stray electrons, including the ejecting electrons, cause the unwanted particle and heat flux onto the electrodes and the inner components of beamline (especially the temperature sensitive cryopump). The suppression of the stray electrons from the CRAFT accelerator is carried out via a series of design and simulation works. The paper focuses the influence of different magnetic field configurations on the stray electrons and the character of the ejecting electrons.

• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.357-364
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• 2008

For the purpose of possibility study on development of an acoustic tweezer using standing waves and very high frequency ultrasound focused beams, a system which can manipulate the position of particles in water has been constructed. It can move the particles to near focal point of a focused beam by the radiation force of standing waves, and then the particles would be trapped by the radiating force of the focused beam. The results show that micro sphere particles were trapped well at nodes of the standing waves and their position can be easily manipulated by frequency control. And, even though the radiation force by single focused beam pushes a particle away from the transducer, two focused confronted beams can trap it at near center.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.35 no.1
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• pp.38-50
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• 2013

Purpose: The aim of this study is to evaluate the effect and potential of electron beam (E-beam) irradiation treatment to the synthetic bony mixtures composed of hydroxyapatite (HA; Bongros$^{(R)}$, Bio@ Co., Korea) and tricalcium phosphate (${\beta}$-TCP, Sigma-Aldrich Co., USA), mixed at various ratios and of type I collagen (Rat tail, BD Biosciences Co., Sweden) as an organic matrix. Methods: We used 1.0~2.0 MeV linear accelerator and 2.0 MeV superconductive linear accelerator (power 100 KW, pressure 115 kPa, temperature $-30{\sim}120^{\circ}C$, sensor sensitivity 0.1~1.2 mV/kPa, generating power sensitivity 44.75 mV/kPa, supply voltage $5{\pm}0.25$ V) with different irradiation dose, such as 1, 30 and 60 kGy. Structural changes in this synthetic bone material were studied in vitro, by scanning electron microscopy (SEM), elementary analysis and field emission scanning electron microscope (FE-SEM), attenuated total reflection (ATR), and electron spectroscopy for chemical analysis (ESCA). Results: The large particular size of HA was changed after E-beam irradiation, to which small particle of TCP was engaged with organic collagen components in SEM findings. Conclusion: The important new in vitro data to be applicable as the substitutes of artificial bone materials in dental and medical fields will be able to be summarized.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.55-56
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• 2008

본 연구에서는 볼빔 시스템 제어에 대해 particle swarm optimization을 이용한 최적 퍼지 cascade 제어기 설계 방법을 소개한다. 볼빔 시스템은 모터, 빔과 움직이는 볼로 구성되며 볼의 위치를 제어하는 시스템이다. 본 논문에서는 많은 분야에서 제어 성능이 우수한 퍼지제어기를 cascade 형식으로 설계하여 볼빔 시스템을 제어한다. 퍼지 cascade 제어구조는 1차 제어기와 2차 제어기로 구성되어 있다. 최적 퍼지 제어기를 설계하기 위하여 PSO를 사용한다. PSO는 초기값에 영향이 석고 일반적인 탐색알고리즘과 달리 조기 수렴의 문제점을 극복한다. 본 논문에서 퍼지 제어기와 기존의 PB 제어기의 성능을 비교 분석한다.

• Journal of the Korean Society of Visualization
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• v.9 no.4
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• pp.63-68
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• 2011

The flow-field of a liquid-metal system is very important for the safety analysis and the design of the steam generator of liquid-metal fast breeder reactor. Dynamic neutron radiography (DNR) is suitable for a visualization and measurement of a liquid metal flow and a two-phase flow in a metallic duct. However, the three dimensional DNR techniques is not enough to obtain the velocity information in the wide channel up to now. In this research, a high speed DNR technique was applied to visualize the heavy liquid-metal flow field in the narrow channel with the HANARO-beam facility. The images were taken with a high frame-rate neutron radiography at 250 fps and analyzed with a Particle Image Velocimetry(PIV) method. The images were compared with the results of the commercial CFX code to study the feasibility of DNR technique for the measuring the heavy liquid-metal flow field. The PIV images could discern the turbulent vortex flow in the two-dimensional narrow channel.

• Communications for Statistical Applications and Methods
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• v.5 no.2
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• pp.503-515
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• 1998

When a neutral particle beam(NPB) aimed at the object and receive a small number of neutron signals at the detector, it follows approximately Poisson distribution. Under the four assumptions in the presence of errors and uncertainties for the Poisson parameters, an exact probability distribution of neutral particles have been derived. The probability distribution for the neutron signals received by a detector averaged over the three sources of errors is expressed as a four-dimensional integral of certain data. Two of the four integrals can be evaluated analytically and thereby the integral is reduced to a two-dimensional integral. The monotone likelihood ratio(MLR) property of the distribution is proved by using the Cauchy mean value theorem for the univariate distribution and multivariate distribution. Its MLR property can be used to find a criteria for the hypothesis testing problem related to the distribution.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1990.11a
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• pp.58-62
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• 1990

The size and concentration of wear debris in lubricating oil often reveal the operating condition of the rotating machinery. To evaluate the possible application of light attenuation measurement for the estimation of wear debris concentration in the lubricating oil, the light transmittance through the lubricating oil cell contaminated with various concentrations of diatomite particles was measured, the attenuation coefficient was estimated from the transmittance measurement and the coefficients were compared with those obtained from the scattering theory. The comparision showed good agreements between them. It is also noted that the experimentally determined attenuation coefficient showed almost linear relation with particle weight concentrations for the concentrations within the range of 2000 ppm. For the case of 0 ppm weight concentration of diatomite particles in the lubricating oil cell, the thickness of the cell required to give $100 \mu W$ light attenuation is 7.75 mm. This result indicates that the light attenuation method will be one of the possible candidates of machine failure diagnostic sensors for the estimation of wear debris concentration in the lubricating oil.

• Journal of the Korean Society of Visualization
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• v.8 no.3
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• pp.22-28
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• 2010

In the present study, we performed the velocity field measurement in a microchannel using a focal length variable micro liquid lens. The liquid lens is used as a beam expander in a micro-PIV system to acquire the scatter image of the seeded particle. A thin film-type micro liquid lens was made of PDMS material and it was attached on top of the 700-micron-wide working fluid supply channel trench. As a result, the focal length and contact angle of the liquid lens changed with variations in applied pressure.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1948-1949
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• 2011

본 논문은 볼빔시스템 제어에 대해 입자군집최적화(Particle Swarm Optimization; PSO)을 이용한 최적 퍼지제어기 설계방법을 연구한다. 볼빔 시스템은 모터와 빔, 움직이는 볼로 구성되며 볼의 위치제어를 기본 동작으로 한다. 본 논문에서는 제어성능이 우수한 퍼지제어기를 사용하여 제어시스템을 설계하는데, 퍼지제어구조는 1차 제어기와 2차 제어기로 구성되고, 최적 퍼지제어기 설계를 위해 PSO를 사용하며 PSO는 초기값에 영향이 적고 일반적인 탐색알고리즘과 달리 초기 수렴의 문제를 극복한다. 본 논문에서는 퍼지제어기와 기존의 PD 제어기의 성능비교를 시도 하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.62-66
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• 2008

Spacecrafts such as most of commercial satellites that are operating in the geostationary orbit can be subjected to intense irradiation by charged particles. The surface made of dielectric materials can therefore become probable sites for damaging electrostatic discharges. Thanks to a specially equipped chamber, the spatial environment can be reproduced experimentally in the laboratory. In this paper, the behavior of high energy electrons injected in polymers such as PolyMethylMetaAcrylate (PMMA) and Kapton is studied. Results obtained by surface potential technique, pulse-electro acoustic device and a cell based on the split Faraday cup system are analyzed and discussed.