• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.83.1-83.1
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• 2010

In the last meeting of KAS, we reported the first statistical study of Faraday rotation measure (RM) in the large-scale structure of the universe using the data of cosmological structure formation simulations. With a turbulence dynamo model for the intergalactic magnetic field (IGMF), we predicted that the root mean square of RM through filaments is \sim 1 rad/m^2. Future radio observatories such as the Square Kilometer Array (SKA) could detect this signal level. However, it is known that the typical foreground galactic RM is a few tens and less than ten rad/m^2 in the low and high galactic latitudes, respectively. So the RM in the large-scale structure could be detected only after the foreground galactic RM is removed. In this talk, we show how we remove the foreground galactic RM and what we obtain from the masked data, by using some noise models and masking techniques. Our results can be used to simulate future RM observations by SKA, and eventually to constrain the origin and evolution of the IGMF in the large-scale structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.2
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• pp.131-135
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• 2011

We have been studied the effects of oxidant on the properties of Sr-ferrite magnets using mill scale for motor. The small-added (0.5 wt%) $NaNO_3$ oxidant improved significantly the degree of oxidation and the grindability of mill scale, and then highly enhanced the magnetic properties of anisotropic Sr-ferrite sintered magnets; such as the remanent flux density from 3.55 to 3.80 kG, the intrinsic coercivity from 2.75 to 3.22 kOe, and the maximum energy product from 2.90 to 3.45 MGOe.

• Journal of the Korean Electrochemical Society
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• v.8 no.3
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• pp.125-129
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• 2005

We have investigated the electrochemical factors affecting the magnetic properties of hard magnetic CoP nanowires and soft magnetic CoFe nanowires fabricated by ac electrodeposition into self-made AAO(anodic aluminum oxide) nano-templates. AAO template having nano scale pores of high aspect ratio has been prepared through 2-step anodizing of aluminum foil in sulfuric acid. Hard Magnetic properties of CoP nanowires were highly conditional on the applied ac potential which could be a decisive factor to make CoP nanowires made up of either pure hcp crystals or a mixture of hop crystals and fcc crystals. On the contrary to CoFe films, there was no anomalous codeposition in the electrodeposition of soft magnetic CoFe nanowires which exhibited their best saturation magnetization of 238 emu/g at the composition of $Co_{30}Fe_{70}$.

• Progress in Superconductivity and Cryogenics
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• v.21 no.2
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• pp.31-35
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• 2019

Andong-dam was built up in 1967 and it is one of the biggest dams in Korea. Previous studies showed that the sediments are highly contaminated with heavy metals such as arsenic, cadmium, and lead. Many research projects are going on to find out the source of the contamination, to evaluate the toxicities to ecosystem, to estimate the volume of sediment to be treated and to find out a good remediation method. Reports show that the sediment is highly contaminated and the main contamination source is supposed to be abandoned mines and a zinc refinery located upper stream of the river. A magnetic separation has been tested as a treatment method for the dredged sediment. Lab scale test showed that the magnetically captured portion is about 10% in weight but the contamination of heavy metal is much higher than the contamination of the passed portion. This indicates that a magnetic separation could be applied for the purpose of reduction of sediment to be treated and for increasing the volume of low toxic sediments which can be dumped as general waste. A magnetic separation using a HGMS has been tested for the sediment with variable magnetic field and the results showed the higher magnetic field increase the captured portion but the concentrating effect of heavy metal was weakened. Further study is needed to establish a useful technology and optimization between decontamination and reduction of sediment volume.

• Advances in materials Research
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• v.12 no.3
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• pp.243-261
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• 2023

This study aims to analyze the mechanical buckling behavior of a single-walled carbon nanotube (SWCNT) integrated with a one-parameter elastic medium and modeled as a Kerr-type foundation under a longitudinal magnetic field. The structure is considered homogeneous and therefore modeled utilizing the nonlocal first shear deformation theory (NL-FSDT). This model targets thin and thick structures and considers the effect of the transverse shear deformation and small-scale effect. The Kerr model describes the elastic matrix, which takes into account the transverse shear strain and normal pressure. Using the nonlocal elastic theory and taking into account the Lorentz magnetic force acquired from Maxwell relations, the stability equation for buckling analysis of a simply supported SWCNT under a longitudinal magnetic field is obtained. Moreover, the mechanical buckling load behavior with respect to the impacts of the magnetic field and the elastic medium parameters considering the nonlocal parameter, the rotary inertia, and transverse shear deformation was examined and discussed. This study showed useful results that can be used for the design of nano-transistors that use the buckling properties of single-wall carbon nanotubes(CNTs) due to the creation of the magnetic field effect.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.85-85
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 1999.04a
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• pp.14-15
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• 1999

• The Bulletin of The Korean Astronomical Society
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• v.31 no.2
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• pp.29.2-29.2
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• 2006

• Proceedings of the Korean Magnestics Society Conference
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• 2016.05a
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• pp.144-144
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• 2016

• Publications of The Korean Astronomical Society
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• v.15 no.spc2
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• pp.1-13
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• 2000

Through the coupling between the near-earth space environment and the polar ionosphere via geomagnetic field lines, the variations occurred in the magnetosphere are transferred to the polar region. According to recent studies, however, the polar ionosphere reacts not only passively to such variations, but also plays active roles in modifying the near-earth space environment. So the study of the polar ionosphere in terms of geomagnetic disturbance becomes one of the major elements in space weather research. Although it is an indirect method, ground magnetic disturbance data can be used in estimating the ionospheric current distribution. By employing a realistic ionospheric conductivity model, it is further possible to obtain the distributions of electric potential, field-aligned current, Joule heating rate and energy injection rate associated with precipitating auroral particles and their energy spectra in a global scale with a high time resolution. Considering that the ground magnetic disturbances are recorded simultaneously over the entire polar region wherever magnetic station is located, we are able to separate temporal disturbances from spatial ones. On the other hand, satellite measurements are indispensible in the space weather research, since they provide us with in situ measurements. Unfortunately it is not easy to separate temporal variations from spatial ones specifically measured by a single satellite. To demonstrate the usefulness of ground magnetic disturbance data in space weather research, various ionospheric quantities are calculated through the KRM method, one of the magneto gram inversion methods. In particular, we attempt to show how these quantities depend on the ionospheric conductivity model employed.