• Journal of the Korean Society of Radiology
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• v.14 no.5
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• pp.603-612
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• 2020

This study has a purpose to look into the effect of the relationship between the Tube current (mA) and SOD(Source to Object Distance), which is a parameter of lower limb angiography examination, and the dilution rate of the contrast medium concentration (300, 320, 350) on the image. To that end, using 3 mm vessel model water phantom, a vessel model custom made in the size of peripheral vessel diameter, this study measured relationships between change of parameters, such as tube current (mA), SOD and varying concentrations (300, 320, 350) of contrast medium dilution into SNR and CNR values while analyzing the coefficients of variance(cv<10). The software used to measure SNR and CNR values was Image J 1.50i from NIH (National Institutes of Health, USA). MPV (mean pixel value) and SD (standard deviation) were used after verifying numerically the image signal for region of interest (ROI) and background on phantom from the DICOM (digital imaging and communications in medicine) 3.0 file transmitted to PACS. As to contrast medium dilution by the change of tube current, when 146 mA and 102 mA were compared, For both SNR and CNR, the coefficient of variation value was less than 10 until the section of CM: N/S dilution (100% ~ 30% : 70%) but CM: N/S dilution rate (20%: 80% ~ 10% : 90%) the coefficient of variation was 10 or more. As to contrast medium dilution by concentration for SOD change, when SOD's (32.5 cm and 22.5 cm) were compared,For both SNR and CNR, the coefficient of variation value was less than 10 until the section of CM: N/S dilution (100% ~ 30% : 70%) but CM: N/S dilution rate (20%: 80% ~ 10% : 90%) the coefficient of variation was 10 or more. As to contrast medium dilution by concentration for SOD change, when SOD's (32.5 cm and 12.5 cm) were compared,For both SNR and CNR, the coefficient of variation value was less than 10 until the section of CM: N/S dilution (100% ~ 30% : 70%) but CM: N/S dilution rate (20%: 80% ~ 10% : 90%) the coefficient of variation was 10 or more. As a result, set a low tube current value in other tests or procedures including peripheral angiography of the lower extremities in the intervention, and make the table as close as possible to the image receiver, and adjust the contrast agent concentration (300) to CM: N/S dilution (30%: 70%). ) Is suggested as the most efficient way to obtain images with an appropriate concentration while simultaneously reducing the burden on the kidney and the burden on exposure.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.5-14
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• 2023

In this study, the load transfer characteristics of the base and skin of drilled shafts were analyzed and the load sharing ratio was calculated by performing a load transfer large-scale model test and three-dimensional numerical analysis considering the similarity of drilled shafts, which is the design target. From the linear behavior of drilled shafts shown in the large-scale model test and 3D numerical analysis results, the skin load transition curve for the design conditions of this study was proposed by Baquelin et al., and the base load transition curve was proposed by Baquelin et al. For the horizontal load transition curve, the formula proposed by Reese et al. was confirmed to be appropriate. The test value was slightly larger than the numerical analysis value for the axial load at the rock socketing, but the load sharing ratio at the rock socketing increased, on average, about 27.8% as the vertical load increased. The analysis value of the vertical settlement of the pile head under the vertical load was evaluated to be slightly smaller than the test value, and the maximum vertical settlement of the pile head in the model test and analysis maximum vertical load was 10.6 mm in the test value and 10.0 mm in the analysis value, and the maximum vertical settlement value at the base of the pile was found to be a test value of 2.0 mm and an analysis value of 1.9 mm. The horizontal displacement at the head of the column (ground surface) and the head of the pile during the horizontal load was found to agree relatively well with the test value and the analysis value. As a result of the model soil test, the horizontal load measured at the maximum horizontal displacement of 38.0 mm was evaluated to be 24,713 kN, and the horizontal load in the numerical analysis was evaluated to be 26,073 kN.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.167-180
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• 2019

Friction piles are being constructed in Southeast Asia (Myanmar, Cambodia, Vietnam, etc.) where the soft ground is deep, and many cases of friction piles are accumulated in terms of experience. In this study, we used the results of four static load test and load transfer test conducted in Myanmar sites to analyze the skin friction of soil layer. In addition, we proposed a relationship chart with skin friction measured in the N-value of Standard Penetration Test (SPT) and the load transfer test result of the single drilled shaft. In the case of Myanmar sites, the range of soil layers was deeper than domestic sites, so the conventional formula of skin friction using the N-value of SPT is different from domestic sites. In sandy layer, fs = 0.096 N in Myanmar sites showed a similar result of the domestic fs = 0.106 N. In clayey layer, fs = 0.315 N, in Myanmar sites showed about 5.0 times higher than the domestic fs = 0.062 N. The results of this study are based on limited data. Therefore, if we analyze the results of more load transfer tests, we can suggest a conventional formula for skin friction according to the N-value. It is expected to be used as important basic data in the future.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.3
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• pp.89-93
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• 2014

In this study, effects of the V/III ratio on a-plane GaN epitaxial on r-plane grown by HVPE have been investigated. According to increasing of V/III ratio, the value of FWHM of a-plane (11-20) GaN and the value of surface roughness (Ra) were decreased. Growth rate of a-plane GaN epitaxial layer were increased until V/III ratio = 7 as the increasing of V/III ratio, but it was reduced at V/III ratio = 10. At V/III ratio = 10, the FWHM of a-plane (11-20) GaN RC and the surface roughness (Ra) were 829 arcsec and 1.58 nm, respectively, as the lowest value in this study. Also for V/III ratio = 10, cracks under surface or voids were observed the lowest values in images of optical microscope. An M-shaped azimuthal dependence over $360^{\circ}$ angle range was observed for all samples. At V/III ratio = 10, the difference of FWHM of a-plane GaN between $0^{\circ}$ and $90^{\circ}$ was 439 arcsec revealed as the lowest value in the 4 samples.

• Macromolecular Research
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• v.11 no.6
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• pp.425-430
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• 2003

Two types of poly(n-butyl acrylate) copolymer/silicate nanocomposites have been produced: poly(n-butyl acrylate-co-methyl methacrylate) [P(BA-co-MMA)]/silicate nanocomposites and poly(n-butyl acrylate-co-styrene) [P(BA-co-ST)]/silicate nanocomposites. The P(BA-co-MMA)/silicate nanocomposites shows the exfoliated structures but a P(BA-co-ST)/silicate nanocomposites have intercalated structures, because the BA/MMA comonomer has a higher polarity (e-value in Q-e scheme) than the BA/ST comonomer. The BA/MMA comonomer expanded the interlayer space of the silicate wider than did the BA/ST comonomer. The thermal degradation onset point of the P(BA-co-MMA)/silicate nanocomposites was 43$^{\circ}C$ higher than that of pure P(BA-co-MMA). P(BA-co-MMA)T5%, P(BA-co-MMA)T10%, and P(BA-co-MMA)T20% exhibit 134,302, and 195% increases, respectively, in their storage moduli at -20$^{\circ}C$ relative to the pure copolymer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.31-33
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• 1992

This paper is studies the addition effects of $La_2O_3$ on the magnetic properties of Sr ferrite. Compositions were chosen according to the formula $[SrO{\cdot}nFe_2O_3]_{100-x}(La_2O_3)_x$. where n was varied between 5.8~6.1 and x between 0~3. The composition of the best value $(BH)_{max}$=1.48MGOe was n=6(stoichiometric composition) and x=2 at $La_2O_3$ addition. This value was higher than that of ordinary isotropic strontium ferrite.

• Electrical & Electronic Materials
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• v.9 no.10
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• pp.1013-1018
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• 1996

The annealing effects of Au/Te/Au/n-GaAs structure was investigated by using x-ray diffraction, scanning electron microscope, the specific contact resistance and I-V measurement. Increasing the annealing temperature, the intensity of Au-Ga peak by X-ray diffraction was increased. The Ga$\_$2/Te$\_$3/peak got evident for the samples annealed at 400.deg. C and GaAs peak by recrystallization appeared for the samples annealed at 500.deg. C. The variation from the schottky to low resistance contact was confirmed by I-V curve. The lowest value of the specific contact resistance of the samples annealed at 500.deg. C was 3.8*10$\^$-5/.ohm.-cm$\^$2/ but the value increased above 600.deg. C.

• East Asian mathematical journal
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• v.35 no.1
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• pp.67-75
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• 2019

We investigate the averaging value of a random sampling of a Dirichlet series with some condition using Poisson distribution. Our result is the following: Let $L(s)={\sum}^{\infty}_{n=1}{\frac{a_n}{n^s}}$ be a Dirichlet series that converges absolutely for Re(s) > 1. If $X_t$ is an increasing random sampling with Poisson distribution and there exists a number $0<{\alpha}<{\frac{1}{2}}$ such that ${\sum}_{n{\leq}u}a_n{\ll}u^{\alpha}$, then we have $${\mathbb{E}}L(1/2+iX_t)=O(t^{\alpha}{\sqrt{{\log}t}})$$, for all sufficiently large t in ${\mathbb{R}}$. As a result, we get the behaviour of $L({\frac{1}{2}}+it)$ such that L is a Dirichlet L-function or a modular L-function, when t is sampled by the Poisson distribution.

• Journal of The Korean Society of Grassland and Forage Science
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• v.4 no.2
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• pp.158-163
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• 1983

The purpose of this experiment was to find out fundamental data for the cultivation of sorghum-sudangrass hybrid. Leaf area index and dry matter accumulation were investigated with 3-levels of nitrogen application,15, 25, 35kg per 10a during the period of initial growth from the 8th leaf emergence to the late blooming stage. The results obtained were as follows: Leaf emergence increased as growth progressed and in the same pattern at all N-levels. After the heading stage, the value was 15 at all N-levels. Leaf area index (LAI) increased as growth progressed and rapidly till the booting stage. At 15kg N-level the values were larger till the ear formation stage, and at 35tg N-level the values were larger than other N-levels after the booting stage. At the late blooming stage LAI reached 8.13 at 35kg N-level. The value of dry matter accumulation was the highest at 35kg N-level at the late blooming stage, and as was the same in the value of crop growth rate (CGR). There was a tendency that before the booting stage the enlargement of leaf area contributed to dry matter accumulation and after the booting stage did the increase of net assimilation rate (NAR) .

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.6
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• pp.283-287
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• 2002

We have studied Zr(Si)N film as a diffusion barrier between Cu metal and Si substrate for application of interconnection metal in ULSI circuits. Zr(Si)N film was deposited with reactive DC magnetron sputtering system using $Ar/N_2$mixed gas. The value of the resistivity was the lowest for the ZrN film using 29 : 1 of Ar : $N_2$reactant gas ratio at room temperature and decreased with increasing of Si substrate temperature. As the value of ZrN film resistivity was decreased, the direction of crystal growth was toward to (002) plane. The barrier property of ZrN film added with Si was improved. But Si was added too much in ZrN film, the barrier property was degraded. The adhesive property was improved with increasing of Si in ZrN. For the analysis of the film, XRD, Optical microscopy, Scretch tester, so on were used.