• 한국재료학회지
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• 제11권8호
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• pp.664-664
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• 2001

$\sigma$-VFe 금속간화합물에 대한 기계적 합금화(MA) 효과를 중성자 및 X선 회절법으로 조사하였다. MA 분말의 구조분석은 X선 회절(Cu-K$\alpha$) 린 중성자회절(HRPD, λ=1.835$\AA$)을 이용하여 행하였다. $\sigma$-VFe화합물의 MA시 큰 구조변화가 관찰되었으며, MA 60시간의 경우 Fe-Fe 훤자분포는 unit cell에 30개의 원자를 포함하고 있는 $\sigma$상의 tetragonal구조에서 $120^{\circ}C$이상에서 안정하게 존재하는 $\alpha$-(V,Fe) 고용체의 bcc 구조로 상변화함을 알 수 있었다. 또한 $\alpha$-VFe 화합물에 대한 중성자 및 X선 회절패턴의 비교분석을 행하였으며 그 결과 $\sigma$상이 가지는 화학적 규칙성에 기인하는 (101)과 (111) 회절 피크가 중성자 회절에서 뚜렷하게 관찰됨을 알 수 있었다.

• KSBB Journal
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• 제19권2호
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• pp.159-163
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• 2004

$\AA$의 분해능을 가진 Bacillus macerans에서 분리 정제한 cyclodextrin glucanotransferase의 결정 구조를 X-ray를 이용하여 분자 대치법을 사용하여 밝혔다. 정확한 구조는 16.6% ( $R_{free}$ = 20.5%)의 결정학적 R-factor를 가지고 있다. 두 개의 $Ca^{2+}$$_{-}$/ 이온이 점유된 새로운 금속 결합자리는 활성 자리의 도달 채널에서 발견되었다. $Ca^{2+}$$_{-}$/ 이온에 결합하는 음의 하전을 띤 아미노산 잔기들이 많이 밀집되어 있고 이 때, domain A ($\alpha$H에서 아미노산 잔기 283-297)의 중심부에 연결 부분은 $\beta$ 13-$\alpha$G 이었다. $\beta$13-$\alpha$G 부분은 활성 자리의 입구에 위치한 subsite 1에서 -1 과 Tyr260 (subsite 2)사이에 있는 촉매 부위 Glu258을 포함하고 있다. 비록 $\alpha$-CGTase 부류에서 잘 보존되어 있지는 않으나, 새로운 $Ca^{2+}$$_{-}$/ 자리 3a,b가 이 $\alpha$-CGTase의 활성도와 생성물의 특이성에 중요한 역할을 하리라 추측된다.다.

• Bulletin of the Korean Chemical Society
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• 제33권6호
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• pp.1845-1850
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• 2012

Layered metal hydroxides (LMHs) containing calcium were synthesized by coprecipitation in solution having two different trivalent metal ions, iron and aluminum. Two mixed metal solutions ($Ca^{2+}/Al^{3+}$ and $Ca^{2+}/Fe^{3+}$ = 2/1) were added to sodium hydroxide solution and the final pH was adjusted to ~11.5 and ~13 for CaAl-and CaFe-LMHs. Powder X-ray diffraction (XRD) for the two LMH samples showed well developed ($00l$) diffractions indicating 2-dimensional crystal structure of the synthesized LMHs. Rietveld refinement of the X-ray diffraction pattern, the local structure analysis through X-ray absorption spectroscopy, and thermal analysis also confirmed that the synthesized precipitates show typical structure of LMHs. The chemical formulae, $Ca_{2.04}Al_1(OH)_6(NO_3){\cdot}5.25H_2O$ and $Ca_{2.01}Fe_1(OH)_6(NO_3){\cdot}4.75H_2O$ were determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Particle morphology and thermal behavior for the synthesized LMHs were examined by field emission scanning electron microscopy and thermogravimetricdifferential scanning calorimetry.

• 한국정밀공학회지
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• 제19권2호
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• pp.65-71
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• 2002

Turbine blade is subject to cyclic bending force by steam pressure. Stress analysis by fractography is already established technology as means far seeking cause of fracture and has been widely employed. In the X-ray frctography, plastic deformation and residual stress near the fracture surface can be determined and information of internal structure of material can be obtained. Therefore, to find a fracture mechanism of torsion-mounted blade in nuclear power plant, based on the information from the fracture surface obtained by fatigue test, the correlation of X-ray parameter and fracture mechanics parameter was determined and then the stress intensity factor to actual broken turbine blade was predicted.

• 천문학회지
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• 제38권1호
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• pp.1-6
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• 2005

We searched for X-ray emission from the 665 galaxies inside and towards the nearby voids by analyzing the ROSAT All-Sky Survey (RASS) data as well as the ROSAT pointed observations (PSPC). As a result we have detected six X-ray emitting galaxies. Two (UGC 10205 and NGC 7509) are in the high density region in the local void, three (UGC 749, MCG +11-10-073, and Mrk 464) are towards the nearby voids, and UGC 32 is located in the low density region. We carried out a timing analysis for both Mrk 464 and UGC 32, and a spectral analysis for Mrk 464. The light curve of Mrk 464 shows the possibility of periodic X-ray flux variation and UGC 32 shows weak, but rapid variation.

• 대한화학회지
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• 제42권3호
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• pp.345-349
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• 1998

• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.521-523
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• 2003

• 대한화학회지
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• 제47권4호
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• pp.427-431
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• 2003

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2009년도 Korea Superconductivity Society Meeting 2009
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• pp.5-5
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• 2009

• International Journal of Concrete Structures and Materials
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• 제7권2호
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• pp.95-110
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• 2013

We report various synchrotron radiation laboratory based techniques used to characterize cement based materials in nanometer scale. High resolution X-ray transmission imaging combined with a rotational axis allows for rendering of samples in three dimensions revealing volumetric details. Scanning transmission X-ray microscope combines high spatial resolution imaging with high spectral resolution of the incident beam to reveal X-ray absorption near edge structure variations in the material nanostructure. Microdiffraction scans the surface of a sample to map its high order reflection or crystallographic variations with a micron-sized incident beam. High pressure X-ray diffraction measures compressibility of pure phase materials. Unique results of studies using the above tools are discussed-a study of pores, connectivity, and morphology of a 2,000 year old concrete using nanotomography; detection of localized and varying silicate chain depolymerization in Al-substituted tobermorite, and quantification of monosulfate distribution in tricalcium aluminate hydration using scanning transmission X-ray microscopy; detection and mapping of hydration products in high volume fly ash paste using microdiffraction; and determination of mechanical properties of various AFm phases using high pressure X-ray diffraction.