• 천문학논총
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• 제12권1호
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• pp.173-183
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• 1997

We have numerically simulated the evolution of supernova remnant VRO 42.05.01(G166.0+43) in order to understand its morphology m radio and X-ray observations as well as the dynamical interaction of the supernova remnant with the surrounding interstellar medium. The Radio and ROSAT observations suggest that the unusual morphology of VRO 42.05.01 is caused by a supernova blast wave breaking out of the cloud boundary where the supernova event occurred, and expanding into another cloud across a much less dense and presumably hot cavity. Our numerical results are consistent with the interactions of a passing supernova blast wave with the clouds across the cavity. We discuss the implications of our results on the dynamics of VRO 42.05.01 such as the reverse shocks, the rejuvenation of the hot cavity, and the reflected shocks formed by the reverse shock collisions. We have theoretically mapped the radio continuum(1.4 GHz) and X-ray(0.1~2 keV) morphology which are consistent with the observational ones.

• Carbon letters
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• 제14권4호
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• pp.228-233
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• 2013

In this work, we report in-situ observations of changes in catalyst morphology, and of growth termination of individual carbon nanotubes (CNTs), by complete loss of the catalyst particle attached to it. The observations strongly support the growth-termination mechanism of CNT forests or carpets by dynamic morphological evolution of catalyst particles induced by Ostwald ripening, and sub-surface diffusion. We show that in the tip-growth mode, as well as in the base-growth mode, the growth termination of CNT by dissolution of catalyst particles is plausible. This may allow the growth termination mechanism by evolution of catalyst morphology to be applicable to not only CNT forest growth, but also to other growth methods (for example, floating-catalyst chemical vapor deposition), which do not use any supporting layer or substrate beneath a catalyst layer.

• Journal of Astronomy and Space Sciences
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• 제30권1호
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• pp.59-67
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• 2013

We present a spectroscopic study of 343 blue compact galaxies (BCGs) at 0.20 < z < 0.35 from the Sloan Digital Sky Survey (SDSS) DR7 data. We derive gas phase oxygen abundance using the empirical and direct method. Stellar masses of galaxies are derived from the STARLIGHT code. We also derive star formation rates of galaxies based on $H{\alpha}$ emission line from the SDSS as well as far-ultraviolet (FUV) flux from the Galaxy Evolution Explorer GR6 data. Evolution of the luminosity-metallicity and mass-metallicity (M-Z) relations with redshift is observed. At a given luminosity and mass, galaxies at higher redshifts appear to be biased to low metallicities relative to the lower redshift counterparts. Furthermore, low mass galaxies show higher specific star formation rates (SSFRs) than more massive ones and galaxies at higher redshifts are biased to higher SSFRs compared to the lower redshift sample. By visual inspection of the SDSS images, we classify galaxy morphology into disturbed or undisturbed. In the M-Z relation, we find a hint that morphologically disturbed BCGs appear to exhibit low metallicities and high SSFRs compared to undisturbed counterparts. We suggest that our results support downsizing galaxy formation scenario and star formation histories of BCGs are closely related with their morphologies.

• 한국결정성장학회지
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• 제18권5호
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• pp.184-190
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• 2008

단순 침전법으로 타원, 땅콩, 아령, 바디가 있는 구형 모양의 $CaMoO_4$ 결정을 합성하였다. $Ca^{2+}$ 이온과 $MoO_4^{2-}$ 이온 농도가 증가함에 따라서 $CaMoO_4$의 형태는 차원형에서 땅콩 모양과 아령 모양을 거쳐서 마디가 있는 구형 모양으로 전개됨을 확인하였다. 이러한 $CaMoO_4$ 결정의 형태의 전개는 프랙탈 메커니즘에 기인한다. 타원형의 양 끝 부분에서부터 가지를 치면서 결정 성장이 시작된다. 1차와 2차 프랙탈 성장에 의해서 땅콩 모양과 아령 모양이 각각 형성되었다. 아령 모양에서 더 프랙탈 성장을 하여 최종적으로 마디가 있는 구형이 형성되었다.

• 천문학회지
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• 제48권2호
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• pp.139-154
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• 2015

We carry out three-dimensional hydrodynamic simulations of the supernova remnants (SNRs) produced inside molecular clouds (MCs) near their surface using the HLL code (Harten et al. 1983). We explore the dynamical evolution and the X-ray morphology of SNRs after breaking through the MC surface for ranges of the explosion depths below the surface and the density ratios of the clouds to the intercloud media (ICM). We find that if an SNR breaks out through an MC surface in its Sedov stage, the outermost dense shell of the remnant is divided into several layers. The divided layers are subject to the Rayleigh-Taylor instability and fragmented. On the other hand, if an SNR breaks through an MC after the remnant enters the snowplow phase, the radiative shell is not divided to layers. We also compare the predictions of previous analytic solutions for the expansion of SNRs in stratified media with our onedimensional simulations. Moreover, we produce synthetic X-ray surface brightness in order to research the center-bright X-ray morphology shown in thermal composite SNRs. In the late stages, a breakout SNR shows the center-bright X-ray morphology inside an MC in our results. We apply our model to the observational results of the X-ray morphology of the thermal composite SNR 3C 391.

• 한국표면공학회지
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• 제31권6호
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• pp.345-358
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• 1998

The evolution of surface roughness and morphology in epitaxial Si and $Si_{0.7}Ge{0.3}$ alloys grown by UHV opm-beam sputter deposition onto nominally-singular, [100]-, and [110]-mi-scut Si(001) was investigated by stomic force microscopy and trasmission electron microscopy. The evolution of surface roughness of epitaxial Si films grown at $300^{\circ}C$ is inconsistent with conventional scaling and hyperscaling laws for kineti roughening. Unstable growth leading to the formation of mounds separated by a well-defined length scale is observed on all substrates. Contraty to previous high-temperature growth results, the presence of steps during deposition at $300^{\circ}C$ increases the tendency toward unstable growth resulting in a much earlier development of mound structures and larger surface roughnesses on vicival substrates. Strain-induced surface roughening was found to dominate in $Si_{0.7}Ge{0.3}$ alloys grown on singular Si(001) substrates at $T_S\ge450^{\circ}C$ where the coherent islands are prererentially bounded along <100> directions and eshibt {105} facetting. Increasing the film thickness above critical values for strain relaxation leads to island coalescence and surface smoothening. At very low growth temperatures ($T_s\le 250^{\circ}C$), film surfaces roughen kinetically, due to limited adatom diffusiviry, but at far lower rates than in the higher-temperature strain-induced regime. There is an intermediate growth temperature range, however, over which alloy film surfaces remain extremely smooth even at thicknesses near critical values for strain relaxation.

• 한국미생물·생명공학회지
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• 제44권4호
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• pp.488-492
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• 2016

S. fibuligera 균주는 생전분을 분해하는 활성이 있는 효모 균주이다. 본 연구에서는 첨가되는 젖산의 농도가 점차 증가하는 장기간 반복 회분식 배양 방법을 사용하는 적응진화를 통하여 S. fibuligera 균주의 젖산에 대한 내성을 증진시키고자 하였다. 진화된 균주인 S. fibuligera MBY1940 균주는 비성장속도 측정과 평판배지를 사용하는 성장분석을 통하여 모균주가 성장할 수 없는 젖산 농도 2.5%에 대해서도 내성을 나타내는 것을 확인하였다. 전자현미경 관찰을 통하여 젖산이 첨가된 스트레스 조건에서 모균주는 신장된 세포 형태와 세포막에 손상을 입은 것으로 보아 진화된 균주에 비해 젖산에 대하여 상대적으로 취약한 것으로 판단되었다.

• 한국표면공학회지
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• 제49권2호
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• pp.111-118
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• 2016

A method to quantitatively analyze the defects formed by the hydrogen evolution during electroplating was suggested based on the theoretical approach of the small angle neutron scattering technique. In case of trivalent chrome layers, an isolated defect size due to the hydrogen evolution was about 40 nm. Direct and pulse plating conditions gave the average defect size of about 4.9 and $4.5{\mu}m$ with rod or calabash shape, respectively. Current density change of the pulse plating from $1.5A/dm^2$ to $2.0A/dm^2$ enlarged the average defect size from 3.3 to $7.8{\mu}m$. The defect morphology like rod or calabash was originated by inter-connecting the isolated defects. Small angle neutron scattering was useful to quantitatively evaluate defect morphology of the deposit.

• Geomechanics and Engineering
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• 제14권2호
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• pp.107-113
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• 2018

Coal samples with different joints morphology were subjected to uniaxial compression experiments, cracks evolution was recorded by Nikon D5300 and acoustic emission (AE) energy signals were collected by AEwin Test for Express-8.0. During loading process, coal samples deformed elastically with no obvious cracks changes, then they expanded gradually along the trace of the original cracks, accompanied by the formation of secondary cracks, and eventually produced a large-scale fracture. It was more interesting that the failure mode of samples were all shear shape, whatever the original cracks morphology was. With cracks and damage evolution, AE energy radiated regularly. At the early loading stage, micro damage and small scale fracture events only induced a few AE events with less energy, while large scale fracture leaded to a number of AE events with more energy at the later stage. Based on the multifractal theory, the multifractal spectrum could explain AE energy signals frequency responses and the causes of AE events with load. Multifractal spectrum width (${\Delta}{\alpha}$), could reflect the differences between the large and small AE energy signals. And another parameter (${\Delta}f$) could reflect the relationship between the frequency of the least and greatest signals in the AE energy time series. This research is helpful for us to understand cracks evolution and AE energy signals causes.

• 한국유변학회:학술대회논문집
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• 한국유변학회 2002년도 추계학술발표회 논문집
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• pp.67-71
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• 2002