• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.181.2-181.2
• /
• 2015

Sputtering is one of the most popular physical deposition methods due to their versatility and reproducibility. Synthesis of Cr thin films by DC magnetron sputtering using glancing angle deposition (GLAD) has been reported. Chromium thin films have been prepared at two different working pressure($2.0{\times}10-2$, 30, $3.3{\times}10-3torr$) on Si-wafer substrate using magnetron sputtering with glancing angle deposition (GLAD) technique. The thickness of Cr thin films on the substrate was adjusted about 1 mm. The electrical property was measured by four-point probe method. For the measurement of density in the films, an X-ray reflectivity (XRR) was carried out. The sheet resistance and column angle increased with the increase of glancing angle. However, nanohardness and density of Cr thin films decreased as the glancing angle increased. The measured density for the Cr thin films decreased from 6.1 to 3.8 g/cc as the glancing angle increased from $0^{\circ}$ to $90^{\circ}$ degree. The low density of Cr thin films is resulted from the isolated columnar structure of samples. The evolution of the isolated columnar structure was enhanced at the conditions of low sputter pressure and high glancing angle. This GLAD technique can be potentially applied to the synthesis of thin films requiring porous and uniform coating such as thin film catalysts or gas sensors.

• Journal of Astronomy and Space Sciences
• /
• v.10 no.2
• /
• pp.163-188
• /
• 1993

On the framework of Tolman spacetime model, the caustics around a local perturbed region in redshift is due to the local expansion rate induced by a local density inhomogeneity in real space. We have compared the caustics in redshift space, which are analytically obtained, with the observed redshift-distance patterns of galaxies which are belonging to Coma and Perseus clusters. For the Abell density distribution model and polytropic density profiles which are well-fitting the optical and X-ray observations, respectively, the size of caustics which is defined by "turnaround radius" of a local density perturbed region should give constraints on the sizes and masses of rich clusters and give also a clue to understand the state of hot X-ray emitting gas.

• Ocean and Polar Research
• /
• v.37 no.4
• /
• pp.333-340
• /
• 2015

The contrast (fish body to medium ratio) of density and sound speed were measured to estimate acoustic scattering from small juvenile cod (Gadus macrocephalus) with the Kirchhoff-Ray Mode backscatter model. The density contrast was measured by the density-bottle method and the sound speed contrast was estimated by the time of flight method. The results revealed that the measured density contrasts of juvenile cod varied between 1.003 and 1.029 (mean = 1.014, S.D. = 0.01). On the other hand, sound speed contrasts varied between 1.039 and 1.041 (mean = 1.041, S.D. = 0.001). The relationship between averaged target strength (TS) and total length (TL) established by the model were <$TS_{38kHz}$> = 20log(TL) - 68.8 and <$TS_{38kHz}$> = 20log(TL) - 69.4, respectively.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.10 no.1
• /
• pp.44-53
• /
• 2006

In this study, the non-destructive computed tomography was adopted to observe the density profile of the needle-punched Carbon/Carbon(C/C) composites nozzle throat. The density profile of C/C was evaluated within ${\pm}0.01g/cm^3$ with 98.74% confidence when the correction of the image and high signal-to-noise ratio were achieved by the optimization of the beam hardening, the electrical noise and the scattered X-ray. The density variation of C/C with the computed tomography was in good agreement with the results obtained by the water immersion method and the observation with scanning electron microscope.

• Korean Journal of Metals and Materials
• /
• v.46 no.6
• /
• pp.370-376
• /
• 2008

The formation of anodic oxide film of titanium (Ti) was studied at a variety of electrolyte concentrations and current density to clarify their effects on morphology, microstructure and composition of Ti oxide layer. For the analysis of the Ti oxide films, a scanning electron microscopy (SEM), X-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS) were used. The results showed that the concentration of phosphoric acid played a crucial role in the crystalline structure of the Ti oxide layer while the current density gave a critical effect on the thickness and diameter of its pore. In particular, the crystalline anatase phase with a thickness larger than $2{\mu}m$, which is quite desirable for a dental implant application, could be readily prepared at the phosphoric acid concentration of 0.5 M and current density higher than $2.0A/dm^2$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2005.11a
• /
• pp.469-474
• /
• 2005

Tn this study, the noll-destructive computed X-ray tomography was adopted to observe the density distribution of the needle-punched C-C composites nozzle throat. The density distribution of the C-C was evaluated within ${\pm}0.01g/cm^3$ with 98.74% confidence when the correction of the image and high signal-to-noise ratio were achieved by the optimization of the beam hardening, the electrical noise and the scattered X-ray. The density variation of the C/C with the computed tomography was in good agreement with the results obtained by the water immersion method and the observation with scanning electron microscope.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.1
• /
• pp.32.2-32.2
• /
• 2014

We present a prediction for 21cm differential brightness temperature (dTb) from a set of strongly clustered sources of Population III and II objects at high redshift, from a suite of numerical simulations of their formation and radiative processes. These objects are located inside a highly biased density environment ("Rarepeak"), which is a rare, high-density peak which extends to ~7 comoving Mpcs. We study the impact on the resulting 21 cm signal from their ultraviolet and X-ray properties. The boost of emission (dTb>0) by high-density environment, moderate leakage of X-ray photons, and strong absorption due to Lyman-alpha pumping contrive to make Rarepeak a discernible, spatially-extended (sky angle~10') object around z~15, which is found to be detectable as a single object by Square Kilometre Array (SKA) with integration time of ~[600-2000] hours. We also examine detectability of many such peaks through SKA precursors.

• Journal of radiological science and technology
• /
• v.2 no.1
• /
• pp.85-88
• /
• 1979

When X-radiation passes through the human body; some is transmitted some is truly absorbed, and some is scattered. In diagnostic radiography, scattered radiation can reach the film if no protective measures are taken. This scattered ray increased density which not necessary for image formation. We studied about absorbtion, scattered ray and the way of get rid of scatter ray according to the x-ray tube kilovoltage and obtained results as follow; 1. Absorbtion ray increased proportion to KVP. 2. Scattered ray increased at high KVP and thick object. 3. Secondary radiation of the primary increased at high KVP and thick object. 4. Remove .ate of scattered ray decreased at thick object and increase at low KVP make use of 6:1 grid ratio

• 한국초전도학회:학술대회논문집
• /
• 2009.07a
• /
• pp.5-5
• /
• 2009

• Geomechanics and Engineering
• /
• v.34 no.4
• /
• pp.449-459
• /
• 2023

The design and development of underground nuclear waste repositories should cover the performance evaluation of the different components such as the construction materials because the long term stability will depend on their response to the surrounding conditions. In South Korea, Gyeonju bentonite has been proposed as a candidate to be used as buffer and backfilling material, especially in the form of blocks to speed up the construction process. In this study, various cylindrical samples were prepared with different dry density and water content, and their physical and mechanical properties were analyzed and correlated with X-ray CT observations. The main objective was to characterize the samples and establish correlations for non-destructive estimation of physical and mechanical properties through the utilization of X-ray CT images. The results showed that the Uniaxial Compression Strength and the P-wave velocity have an increasing relationship with the dry density. Also, a higher water content increased the values of the measure parameters, especially for the P-wave velocity. The X-ray CT analysis indicated a clear relation between the mean CT value and the dry density, Uniaxial Compression Strength, and P-wave velocity. The effect of the higher water content was also captured by the mean CT value. Also, the relationship between the mean CT value and the dry density was used to plot CT dry densities using CT images only. Moreover, the histograms also provided information about the samples heterogeneity through the histograms' full width at half maximum values. Finally, the particle size and heterogeneity were also analyzed using the Madogram function. This function identified small particles in uniform samples and large particles in some samples as a result of poor mixing during preparation. Also, the μ_max value correlated with the heterogeneity, and higher values represented samples with larger ranges of CT values or particle densities. These image-based tools have been shown to be useful on the non-destructive characterization of bentonite samples, and the establishment of correlations to obtain physical and mechanical parameters solely from CT images.