• 천문학회보
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• 제36권2호
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• pp.85.1-85.1
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• 2011

The magnetic field at the surface of the Sun is concentrated in magnetic features that often have spatial extents of 100 km or less. The study of the fine scale structure of the Sun's magnetic field has been hampered by the limited spatial resolution of the available observations. This has recently changed thanks to various new high-resolution facilities, among them the SUNRISE observatory, built around the largest solar telescope to leave the ground, and containing two science instruments. SUNRISE successfully had its first long-duration science flight on a stratospheric balloon in June 2009 and a host of scientific results have been obtained from the data. After a brief introduction to the Sunrise mission, an overview of selected results obtained so far will be given. A reflight at higher solar activity is currently being prepared.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.53-56
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• 1987

Gyroscope is a key sensor for inertial navigation system (INS) which is a navigational instrument necessary to guide and control a free vehicle, and an important instrument for defense, aeronautical, and space industries that is and will be actively involved. In this study, design parameters, scale factor and linearity, of torquer which is one of the components of two degree of freedom dynamically tuned gyroscope (DTG) are presented. The magnetic circuit of torquer is so complicated that it is difficult to analyze it with analytic method. Thus these parameters are calculated by using finite element method with analysis of magnetic vector potential for axisymmetric 3-dimension magnetic field.

• Smart Structures and Systems
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• 제25권6호
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• pp.707-717
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• 2020

In this paper, analysis of thermal post-buckling behaviors of sandwich nanobeams with two layers of multi-phase magneto-electro-thermo-elastic (METE) composites have been presented considering geometric imperfection effects. Multi-phase METE material is composed form piezoelectric and piezo-magnetic constituents for which the material properties can be controlled based on the percentages of the constituents. Nonlinear governing equations of sandwich nanobeam are derived based on nonlocal elasticity theory together with classic thin beam model and an analytical solution is provided. It will be shown that post-buckling behaviors of sandwich nanobeam in thermo-electro-magnetic field depend on the constituent's percentages. Buckling temperature of sandwich nanobeam is also affected by nonlocal scale factor, magnetic field intensity and electrical voltage.

• Structural Engineering and Mechanics
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• 제75권6호
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• pp.659-674
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• 2020

The present paper employs nonlocal strain gradient theory (NSGT) to study buckling behavior of functionally graded magneto-electro-thermo-elastic (FG-METE) nanoshells under various physical fields. NSGT modeling of the nanoshell contains two size parameters, one related to nonlocal stress field and another related to strain gradients. It is considered that mechanical, thermal, electrical and magnetic loads are exerted to the nanoshell. Temperature field has uniform and linear variation in nanoshell thickness. According to a power-law function, piezo-magnetic, thermal and mechanical properties of the nanoshell are considered to be graded in thickness direction. Five coupled governing equations have been obtained by using Hamilton's principle and then solved implementing Galerkin's method. Influences of temperature field, electric voltage, magnetic potential, nonlocality, strain gradient parameter and FG material exponent on buckling loads of the FG-METE nanoshell have been studied in detail.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.583-588
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• 2008

A spacecraft propulsion system utilizing the energy of the solar wind was reviewed. The first plasma sail concept was proposed by Prof. Winglee in 2000, and that was called M2P2(mini-magnetospheric plasmapropulsion). However, the first M2P2 design adopting a small(20-cm-diamter) coil and a small helicon plasma source design was criticized by Dr. Khazanov in 2003. He insisted that: 1) MHD is not an appropriate approximation to describe the M2P2 design by Winglee, and with ion kinetic simulation, it was shown that the M2P2 design could provide only negligible thrust; 2) considerably larger sails(than that Winglee proposed) would be required to tap the energy of the solar wind. We started our plasma ssail study in 2003, and it is shown that moderately sized magnetic sails can produce sub-Newton-class thrust in the ion inertial scale(${\sim}70$ km). Currently, we are continuing our efforts to make a feasibly sized plasma sail(Magnetoplasma sail) by optimizing the magnetic field inflation process Winglee proposed.

• 한국초전도ㆍ저온공학회논문지
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• 제23권3호
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• pp.26-31
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• 2021

Advanced classification of Cs contaminated soil by using a magnetic force-assisted selection pipe was investigated. A selection pipe is a device that sort particles depending on their particle size, based on the relationship between buoyancy, drag, and gravity force acting on the particles. Radioactive cesium is concentrated in small-particle size soil components with a large specific surface area. Hence, the volume of the Cs contaminated soil can be reduced by recycling the large-particle size soil components with low radioactive concentration. One of the problems of the selection pipe was that the radioactive concentration of the stayed soil in the selection pipe exceeds 8000 Bq/kg, which is the standard value of recycling of Cs contaminated soil, due to low classification accuracy. In this study, magnetic fields were applied to the lab-scale selection pipe from upper side to improve the classification accuracy and to reduce the radioactive concentration of the stayed soil.

• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.347-357
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• 2018

Steady shear response of a magnetorheological fluid (MRF) system containing porous mono-disperse magnetite ($Fe_3O_4$) spheres synthesized by solvothermal method is demonstrated. In applied magnetic field the interaction between the spherical particles leads to form strong columnar structures enhancing the yield strength and viscosity of the MRFs. The yield strengths of the MRFs also scale up with the concentration of magnetic particles in the fluid. Considering magnetic dipolar interaction between the particles the magneto-mechanical response of the MRFs is explained. Unlike metallic iron particles, the low-density corrosion resistant soft-ferrimagnetic $Fe_3O_4$ spherical particles make our studied MRF system efficient and reliable for shock-mitigation/vibration-isolation applications.

• 한국초전도ㆍ저온공학회논문지
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• 제24권1호
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• pp.1-7
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• 2022

So far, large-scale scientific devices such as nuclear fusion tokamaks and high energy circular accelerators were constructed using high-current conductors made of metallic superconducting wires. Recently, as REBCO superconducting wires usable in high magnetic fields have been developed by several companies, researchesto apply high current cable type REBCO conductors to next-generation large superconducting magnets were also started. High critical currents of several kA or more in high magnetic fields have been successfully demonstrated on test samples of REBCO cable conductors by several research groups. In this review article, the main features and properties of the representative high current REBCO conductors such as CORC(Conductor On Round Core), TSTC(Twisted Stacked-Tape Cable) and RACC(Roebel-Assembled Coated Conductor), which are currently being developed at abroad are briefly introduced. Research activities of high-current density REBCO MHOS(Multi HTS layers on One Substrate) conductor at KERI, whose structure is different from other cable type REBCO conductors are also shortly introduced.

• 천문학회보
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• 제45권1호
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• pp.42.1-42.1
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• 2020

Filamentary structures pervade the whole kind of molecular clouds from low- to high-mass star-forming clouds, and the non-star-forming clouds. It is supposed to be a prerequisite stage of star formation, and hence how filaments and dense cores form is one of the critical questions in the early star formation study. We investigated the dynamics and chemistry of dense cores in IC5146 using TRAO FUNS (TRAO Survey of the nearby Filamentary molecular clouds, the Universal Nursery of Stars) data. In addition, we performed polarization observation using JCMT Pol-2 polarimetry to investigate the magnetic field morphology within a core-scale. In the presentation, we will present the result of TRAO FUNS and JCMT/Pol2 observation toward the filaments and dense cores in the IC5146. We aim to reveal the roles of gravity, turbulence, and magnetic field in the formation of dense cores in the western hub-filament structure of IC5146.

• 천문학회보
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• 제46권2호
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• pp.39.3-40
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• 2021

The Faraday rotation measure (RM) of extragalactic radio sources is one of tools that can explore the magnetic field in the cosmic web. We have investigated the statistical properties of the RM using the data of simulations for the large-scale structure formation of the universe. Various modelings for the cosmic magnetic field including the redshift dependence, and the intrinsic RM of radio sources have been considered. We here present the structure functions (SFs) of simulated RMs for small angular separations, and compare the SFs with observations, specifically those from the NRAO VLA Sky Survey (NVSS) and LOFAR Two-Metre Sky Survey (LoTSS). We then discuss the implications of our work.