• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.278.2-278.2
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• 2008

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.73.1-73.1
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• 2008

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.236.2-236.2
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• 2008

• 천문학회지
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• 제37권5호
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• pp.455-460
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• 2004

There have been many speculations about the presence of cosmic ray protons (CRps) in galaxy clusters over the past two decades. However, no direct evidence such as the characteristic $\gamma$-ray signature of decaying pions has been found so far. These pions would be a direct tracer of hadronic CRp interactions with the ambient thermal gas also yielding observable synchrotron and inverse Compton emission by additionally produced secondary electrons. The obvious question concerns the type of galaxy clusters most likely to yield a signal: Particularly suited sites should be cluster cooling cores due to their high gas and magnetic energy densities. We studied a nearby sample of clusters evincing cooling cores in order to place stringent limits on the cluster CRp population by using non-detections of EGRET. In this context, we examined the possibility of a hadronic origin of Coma-sized radio halos as well as radio mini-halos. Especially for mini-halos, strong clues are provided by the very plausible small amount of required CRp energy density and a matching radio profile. Introducing the hadronic minimum energy criterion, we show that the energetically favored CRp energy density is constrained to $2\%{\pm}1\%$ of the thermal energy density in Perseus. We also studied the CRp population within the cooling core region of Virgo using the TeV $\gamma$-ray detection of M 87 by HEGRA. Both the expected radial $\gamma$-ray profile and the required amount of CRp support this hadronic scenario.

• 천문학회지
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• 제37권5호
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• pp.349-353
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• 2004

Magnetic fields are an important ingredient of galaxy clusters and are indirectly observed on cluster scales as radio haloes and radio relics. One promising method to shed light on the properties of cluster wide magnetic fields is the analysis of Faraday rotation maps of extended extragalactic radio sources. We developed a Fourier analysis for such Faraday rotation maps in order to determine the magnetic power spectra of cluster fields. In an advanced step, here we apply a Bayesian maximum likelihood method to the RM map of the north lobe of Hydra A on the basis of our Fourier analysis and derive the power spectrum of the cluster magnetic field. For Hydra A, we measure a spectral index of -5/3 over at least one order of magnitude implying Kolmogorov type turbulence. We find a dominant scale of about 3 kpc on which the magnetic power is concentrated, since the magnetic autocorrelation length is ${\lambda}_B = 3 {\pm} 0.5\;kpc$. Furthermore, we investigate the influences of the assumption about the sampling volume (described by a window function) on the magnetic power spectrum. The central magnetic field strength was determined to be ${\~}7{\pm}2{\mu}G$ for the most likely geometries.

• Journal of Korean Society for Atmospheric Environment
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• 제24권E1호
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• pp.12-23
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• 2008

Relationship between the optimum soil water content and clay content on soil samples from mid-latitude European forest was tested. Soil samples from 4 different experimental sites (two forest sites in the Netherlands and a Danish forest) were collected, and analyzed for the soil physical and chemical characteristics. Water retention curves for the soil samples were determined according to the standard procedure ISO 11274, and pF decreased with increase in soil water contents. NO is simultaneously produced and consumed by microbiological processes, which comprise of nitrification and denitrification. NO consumption and production rates were determined from the soil samples and compared to their corresponding water retention curves in order to find the optimum soil water content and matric potential for maximum NO release from mid-latitude soils. NO consumption rate coefficient (k) in Hollandse Hout was significantly lower than those in other soil sites. Maximum NO production was observed at an intermediate soil moisture ($0.2{\sim}0.3kg/kg$) in all the soil samples. Resulting from the NO consumption and production rates for the soils, the empirical NO fluxes of the different soils were calculated in the laboratory.

• 천문학회보
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• 제46권1호
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• pp.34.2-34.2
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• 2021

SPT-CL J2106-5844 is the most massive galaxy cluster at z>1 discovered to date. It has been known to be an isolated system with a singular, well-defined halo. However, recent studies provide lines of evidence for its merging state. We strengthen the case with the multi-wavelength observations from ALMA, ACA, ASKAP, ATCA, and Chandra. With the sensitive, high resolution ALMA+ACA observations, we reconstruct the ICM pressure map from the thermal SZ effect. It reveals two main gas components that are associated with the mass clumps inferred from the weak-lensing analysis. Furthermore, the X-ray hardness map supports the bimodal gas distribution. With these multi-wavelength data, we probe the merger phase in SPT-CL J2106-5844.

• 천문학회지
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• 제37권5호
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• pp.439-446
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• 2004

A critical discussion of our knowledge about extragalactic cosmic rays and magnetic fields is at-tempted. What do we know for sure? What are our prejudices? How do we confront our models with the observations? How can we assess the uncertainties in our modeling and in our observations? Unfortunately, perfect answers to these questions can not be given. Instead, I describe efforts I am involved in to gain reliable information about relativistic particles and magnetic fields in extragalactic space.

• 마이크로전자및패키징학회지
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• 제12권1호
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• pp.27-33
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• 2005

The effect of microstructure on alternating current-induced damage in 200 and 300 nm thick polycrystalline sputtered Cu lines on Si substrates has been investigated. Alternating currents were used to generate temperature cycles (with ranges from 100 to $300^{\circ}C$) and thermal strains (with ranges from 0.14 to $0.42\%$) in the Cu lines at a frequency of 10 kHz. Fatigue loading caused the development of severe surface roughness that was localized within individual grains which depends severely on grain orientations.

• 한국재료학회지
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• 제5권3호
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• pp.310-315
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• 1995

기계적으로 연마한 고속도강과 구리 두 종류의 서로 다른 기판상에 dc 마그네트론 스파터법으로 TiN 박막을 성막시켜 코팅층의 비커스 미소경도를 측정하였다. 압입체의 침투깊이와 시험하중과의 관계를 log-log 좌표상에 도시함으로써 기판의 영햐응ㄹ 받지 않고 코팅층만의 경도를 측정할수 있는 최대하중인 임계하중(critical load)을 구할수 있었다. 임계하중을 가했을 때 압입체의 침투깊이와 코팅층 두께간의 비율은 코팅층의 두께에 무관하였고 기판의 경도에 크게 의존하였다.