• Nuclear Engineering and Technology
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• 제55권1호
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• pp.229-237
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• 2023

The mechanics underlying photon and electron interactions was validated using our developed Brachytherapy computer code for high Dose Rate (HDR). By comparing the photon cross-section utilizing multiple physics libraries in the developed code, the results were benchmarked against experimental and theoretical findings. Klein-Nishina and experimental cross-section results were in good agreement with the Livermore library results. For two therapeutically relevant materials, the first scattered electron range was measured within 1 mm and 2 mm, which has significant implications for the interpretation of the kernel dose spikes observed in previous research.

• 천문학회보
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• 제43권1호
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• pp.56.3-56.3
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• 2018

The present study formulates the theory of spontaneously emitted electromagnetic fluctuations in magnetized plasmas containing particles with an anisotropic suparthermal (bi-Kappa) velocity distribution function. The formalism is general applying for an arbitrary wave vector orientation and wave polarization, and for any wave-frequency range. As specific applications, the high-frequency electromagnetic fluctuations emitted in the upper-hybrid and multiple harmonic electron cyclotron frequency range are evaluated. The fluctuations for low-frequency are also applied, which include the kinetic $Alfv\acute{e}n$, fast magnetosonic/whistler, kinetic slow mode, ion Bernstein cyclotron modes, and higher-order modes. The model predictions are confirmed by a comparison with particle-in-cell simulations. The study describes how energetic particles described by kappa velocity distribution functions influence the spectrum of high and low frequency fluctuations in magnetized plasmas. The new formalism provides quantitative analysis of naturally occurring electromagnetic fluctuations, and contribute to an understanding of the electromagnetic fluctuations observed in space plasmas, where kappa-distributed particles are ubiquitous.

• 정보저장시스템학회논문집
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• 제7권2호
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• pp.80-84
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• 2011

In this paper, we propose the integrated design method that enables multi-physics modeling and coupled-field analysis by connecting an electromagnetic field and a structural field. We design the 3-axis moving magnet type actuator that has the high structural stiffness and the effective electromagnetic circuit generating large electromagnetic force. Through design of experiments (DOE) and optimization, the designed actuator is optimized and satisfies high dynamic characteristics over the desired specifications.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2466-2473
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• 2023

A superconducting ion-Linac (iLinac), which is supposed to work as the injector in the High Intensity heavy-ion Accelerator Facility project, is under development at the Institute of Modern Physics (IMP), Chinese Academy of Sciences. The iLinac is a superconducting heavy ion linear accelerator approximately 100 meters long and contains 96 superconducting cavities in two types of 17 cyromodules. Two types of superconducting resonators (quarter-wave resonators with a frequency of 81.25 MHz and an optimal beta β = v/c = 0.07 called QWR007 and half-wave resonators with a frequency of 162.5 MHz and an optimal beta β = 0.15 called HWR015) have been investigated. The cavity design included extensive multi-parameter electromagnetic simulations and mechanical analysis, and its results are described in details. The fundamental power coupler and cavity dynamic tuner designs are also presented in this article. The prototypes are under manufacturing and expected to be ready in 2023.

• Nuclear Engineering and Technology
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• 제49권1호
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• pp.82-91
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• 2017

Liquid alloy systems have a high degree of thermal conductivity, far superior to ordinary nonmetallic liquids and inherent high densities and electrical conductivities. This results in the use of these materials for specific heat conducting and dissipation applications for the nuclear and space sectors. Uniquely, they can be used to conduct heat and electricity between nonmetallic and metallic surfaces. The motion of liquid metals in strong magnetic fields generally induces electric currents, which, while interacting with the magnetic field, produce electromagnetic forces. Electromagnetic pumps exploit the fact that liquid metals are conducting fluids capable of carrying currents, which is a source of electromagnetic fields useful for pumping and diagnostics. The coupling between the electromagnetics and thermo-fluid mechanical phenomena and the determination of its geometry and electrical configuration, gives rise to complex engineering magnetohydrodynamics problems. The development of tools to model, characterize, design, and build liquid metal thermomagnetic systems for space, nuclear, and industrial applications are of primordial importance and represent a cross-cutting technology that can provide unique design and development capabilities as well as a better understanding of the physics behind the magneto-hydrodynamics of liquid metals. First studies for the development of computational tools for the design of liquid metal electromagnetic pumps are discussed.

• Journal of Magnetics
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• 제17권1호
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• pp.13-18
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• 2012

Starting with Kubo's formula and using the projection operator technique introduced by Kawabata, EPR lineprofile function for a $Mn^{2+}$-doped wurtzite structure GaN semiconductor was derived as a function of temperature at a frequency of 9.49 GHz (X-band) in the presence of external electromagnetic field. The line-width is barely affected in the low-temperature region because there is no correlation between the resonance fields and the distribution function. At higher temperature the line-width increases with increasing temperature due to the interaction of electrons with acoustic phonons. Thus, the present technique is considered to be more convenient to explain the resonant system as in the case of other optical transition systems.

• 천문학회보
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• 제36권1호
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• pp.33.1-33.1
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• 2011

The plasma sheet of the Earth's magnetosphere is a sheet of hot plasmas in the magnetotail region, dividing the two (northern and southern) lobes of the Earth's magnetic field. It is the key region that is often closely linked to various electromagnetic dynamics in the Earth's magnetosphere-ionosphere system. In particular, it is the region that is most crucial for substorms, which is one of the most dynamic phenomena in the Earth's magnetosphere. The question of substorm triggering remains highly controversial until today, and at the center of the controversy there are several critical physics issues of the plasma sheet. In this talk I will introduce some of the physics issues of the plasma sheet. The specific topics that this talk will cover are (i) the general properties of the plasma sheet, (ii) fast plasma jets and plasma transport problem, (iii) stability/instability problem, and (iv) effects of thin current sheet. I will also present some of our group's recent findings regarding these topics, as obtained by comprehensive analyses of various observational data. The level and content of this talk are designed to be comprehensible to not only space physicists but also the scientists in a related field such as solar and heliospheric physics.

• 소성∙가공
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• 제28권3호
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• pp.135-144
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• 2019

Electromagnetic impulse welding (EMIW) is a type of solid state welding using the Lorentz force generated by interaction between the magnetic field of the coil and the current induced in the workpiece. Although many experimental studies have been investigated on the expansion and compression welding of tube using the EMIW process, studies on the EMIW process of lap joint between flat sheets are uncommon. Since the magnetic field enveloped inside the tube can be controlled with ease, the electromagnetic technique has been widely used for tube welding. Conversely, it is difficult to control the magnetic field in the flat sheet welding so as to obtain the required welding velocity. The current study analyzed the effects of coil shape on the impulse velocity for suitable flat one-turn coil for the EMIW of the flat sheets. The finite element (FE) multi-physics simulation involving magnetic and structural field of EMIW were conducted with the commercial software LS-DYNA to evaluate the several shape variables, viz., influence of various widths, thicknesses, gaps and standoff distances of the flat one-turn coil on the impulse velocity. To obtain maximum impulse velocity, the flat one-turn coil was designed based on the FE simulation results. The experiments were performed using an aluminum alloy 1050 sheets of 1.0mm thickness using the designed flat one-turn coil. Through the microscopic interfacial analysis of the welded specimens, the interfacial connectivity was observed to have no defects. In addition, the single lap joint tests were performed to evaluate the welding strength, and a fracture occurred in the base material. As a result, a flat one-turn coil was successfully designed to guarantee welding with bond strength equal to or greater than the base material strength.

• 한국전자파학회논문지
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• 제24권5호
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• pp.515-524
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• 2013

유전체 세라믹 도파관 필터를 설계할 수 있는 DWFD 프로그램이 ${\lambda}/2$ 스텝 임피던스 타입의 직접 결합 도파관 필터 이론을 사용하여 개발되었다. 1 GHz 대역의 필터 크기를 줄이기 위하여 3차원 적층 형태로 설계하였다. 이에 필요한 S-매개변수값은 개발한 프로그램을 이용하였다. 적층형에 필요한 인덕티브 아이리스들의 치수는 HFSS 시뮬레이션 도구를 사용하였다. 필터는 중심 주파수 881.5 MHz에서 25 MHz 대역폭을 가지는 8단으로 설계하였다. 설계된 도파관 필터는 유전율 35.4의 세라믹을 사용하여 크기를 폭 50 mm에 높이 48 mm로 제작하였다. 측정한 주파수 반응은 시뮬레이션 결과와 일치하였다. 개발한 시뮬레이션 프로그램을 통하여 원하는 형태의 유전체 세라믹 도파관 필터를 쉽고 효율적으로 설계, 제작이 가능하도록 하였다.

• Carbon letters
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• 제14권1호
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• pp.40-44
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• 2013

The bipolar plate is the most important and most costly component of proton exchange membrane fuel cells. The development of a suitable low density bipolar plate is scientifically and technically challenging due to the need to maintain high electrical conductivity and mechanical properties. Here, bipolar plates were developed from different particle sizes of natural and expanded graphite with phenolic resin as a polymeric matrix. It was observed that the particle size of the reinforcement significantly influences the mechanical and electrical properties of a composite bipolar plate. The composite bipolar plate based on expanded graphite gives the desired mechanical and electrical properties as per the US Department of Energy target, with a bulk density of 1.55 $g.cm^{-3}$ as compared to that of ~1.87 $g.cm^{-3}$ for a composite plate based on natural graphite (NG). Although the bulk density of the expanded-graphite-based composite plate is ~20% less than that of the NG-based plate, the I-V performance of the expanded graphite plate is superior to that of the NG plate as a consequence of the higher conductivity. The expanded graphite plate can thus be used as an electromagnetic interference shielding material.