• Korean Journal of Dental Materials
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• v.45 no.4
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• pp.257-274
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• 2018

The purpose of this study was to evaluate the effect of acid-treatment conditions on the surface properties of the RBM (Resorbable Blast Media) treated titanium. Disk typed cp-titanium specimens were prepared and RBM treatments was performed with calcium phosphate ceramic powder. Acid solution was mixed using HCl, $H_2SO_4$ and deionized water with 4 different volume fraction. The RBM treated titanium was acid treated with different acid solutions at 3 different temperatures and for 3 different periods. After acid-treatments, samples were cleaned with 1 % Solujet solution for 30 min and deionized water for 30 min using ultrasonic cleanser, then dried in the electrical oven ($37^{\circ}C$). Weight of samples before and after acid-treatment were measured using electric balance. Surface roughness was estimated using a confocal laser scanning microscopy, crystal phase in the surface of sample was analyzed using X-ray diffractometer. Surface morphology and components were evaluated using Scanning Electron Microscope (SEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoemission Spectroscopy (XPS). Values of the weight changes and surface roughness were statistically analyzed using Tukey-multiple comparison test (p=0.05). Weight change after acid treatments were significantly increased with increasing the concentration of $H_2SO_4$ and temperature of acid-solution. Acid-treatment conditions (concentration of $H_2SO_4$, temperature and time) did not produce consistent effects on the surface roughness, it showed the scattered results. From XRD analysis, formation of titanium hydrides in the titanium surface were observed in all specimens treated with acid-solutions. From XPS analysis, thin titanium oxide layer in the acid-treated specimens could be evaluated. Acid solution with $90^{\circ}C$ showed the strong effect on the titanium surface, it should be treated with caution to avoid the over-etching process.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.122-127
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• 2010

Purpose: The Xpress3.$cardiac^{TM}$ which is a kind of wide beam reconstruction (WBR) method developed by UltraSPECT (Haifa, Israel) enables the acquisition of at quarter time while maintaining image quality. The purpose of this study is to investigate the usefulness of WBR method for decreasing scan times and to compare to it with filtered back projection (FBP), which is the method routinely used. Materials and Methods: Phantom and clinical studies were performed. The anthropomorphic torso phantom was made on an equality with counts from patient's body. The Tl-201 concentrations in the compartments were 74 kBq (2 ${\mu}Ci$)/cc in myocardium, 11.1 kBq (0.3 ${\mu}Ci$)/cc in soft tissue, and 2.59 kBq (0.07 ${\mu}Ci$)/cc in lung. The non-gated Tl-201 myocardial perfusion SPECT data were acquired with the phantom. The former study was scanned for 50 seconds per frame with FBP method, and the latter study was acquired for 13 seconds per frame with WBR method. Using the Xeleris ver. 2.0551, full width at half maximum (FWHM) and average image contrast were compared. In clinical studies, we analyzed the 30 patients who were examined by Tl-201 gated myocardial perfusion SPECT in department of nuclear medicine at Asan Medical Center from January to April 2010. The patients were imaged at full time (50 second per frame) with FBP algorithm and again quarter-time (13 second per frame) with the WBR algorithm. Using the 4D MSPECT (4DM), Quantitative Perfusion SPECT (QPS), and Quantitative Gated SPECT (QGS) software, the summed stress score (SSS), summed rest score (SRS), summed difference score, end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were analyzed for their correlations and statistical comparison by paired t-test. Results: As a result of the phantom study, the WBR method improved FWHM more than about 30% compared with FBP method (WBR data 5.47 mm, FBP data 7.07 mm). And the WBR method's average image contrast was also higher than FBP method's. However, in result of quantitative indices, SSS, SDS, SRS, EDV, ESV, EF, there were statistically significant differences from WBR and FBP(p<0.01). In the correlation of SSS, SDS, SRS, there were significant differences for WBR and FBP (0.18, 0.34, 0.08). But EDV, ESV, EF showed good correlation with WBR and FBP (0.88, 0.89, 0.71). Conclusion: From phantom study results, we confirmed that the WBR method reduces an acquisition time while improving an image quality compared with FBP method. However, we should consider significant differences in quantitative indices. And it needs to take an evaluation test to apply clinical study to find a cause of differences out between phantom and clinical results.

• Korean Journal of Animal Reproduction
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• v.25 no.3
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• pp.269-275
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• 2001

This study was carried out to investigate the general characteristics such as volume, sperm concentration, sperm motility, sperm abnormality on whole semen, RSP-S and RSP-T semen and fractional semen of small size dogs, and the effect of temperature and preservation time and cryoproservation on motility of whole and RSP-S and RSP-T semen. Multiple ejaculates were collected from small dogs by the digital manipulation of penis. 1. The volume per ejaculate semen, sperm of concentration and motility and abnormal sperm rate of 1st fractional semen were 0.65$\pm$0.09 $m\ell$, 4.52$\pm$0.35$\times$10$^{6}$ cells/$m\ell$, 15.64$\pm$3.85% and 5.50$\pm$0.62%. Also, 2nd fractional semen were 1.25$\pm$0.20$m\ell$, 3.35$\pm$0.48$\times$10$^{6}$ cells/$m\ell$, 96.25$\pm$4.65% and 4.24$\pm$0.46%. And 3rd fractional semen were 1.45$\pm$0.21$m\ell$, 3.55$\pm$0.52$\times$10$^{6}$ cells/$m\ell$, 92.82$\pm$4.24% and 4.66 $\pm$0.58%, respectively. 2. The sperm of concentration and motility and abnormal sperm rates of whole, RSP-S and RSP-T semen were 5.45$\pm$0.82$\times$10$^{6}$ cells/$m\ell$, 95.55 $\pm$4.65%, 4.58$\pm$0.45% and 4.82$\pm$0.36$\times$10$^{6}$ cells/$m\ell$, 90.10$\pm$3.42%, 6.48$\pm$0.68% and 4.55$\pm$0.45$\times$10$^{6}$ cells/$m\ell$, 93.25$\pm$3.85%, 4.82$\pm$0.58%, respectively. 3. The motility of whole, RSP-S and RSP-T semen were higher at 4$^{\circ}C$ than at 38$^{\circ}C$. When preservation temperature was at 4$^{\circ}C$, survival rates of RSP-S and RSP-T sperm were 97.54~6.25% at 1~72 hrs, 97.40~5.62% at 1~100 hrs, respectively. 4. The survival rates of slow and rapid frozen 2nd fraction, RSP-S and RSP-T semen were 67.3$\pm$4.45%, 88.8$\pm$4.46% and 46.4$\pm$3.84%, 74.4$\pm$4.20%, respectively. Survival rates was significantly higher in frozen RSP-S and RSP-T semen than that in control group(8.5$\pm$2.12%).

• Korean Journal of Materials Research
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• v.4 no.8
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• pp.906-914
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• 1994

Plastic behavior of two-phase intermetallic compounds based on $LI_{2}$-type $(Al, Cr)_3$ Ti was investigated using compression test at R.T. and 77K. $LI_{2}$ single phase alloys and two-phase alloys consisting of mainly $LI_{2}$ phase and a few or 20% second phases were selected from AI-Ti-Cr phase diagram. In general, compared with Llz single phase, two-phase alloys consisting of 20% second phase showed relatively high yield strength and poor ductility. Among the alloys, however, AI-21Ti-23Cr alloy consisting of 20% $Cr_{2}Al$ phase showed available ductility as well as high yield strength. Plastic behavior of $LI_{2}$ single phase alloys and two-phase alloys consisting of a few% $Cr_{2}Al$ was also investigated. Homogenization of arc melted ingots substantially reduced the amount of second phases but introduced extensive pore. When Cr content increased in $Ll_{2}$ single phase alloys after the homogenization, the volume fraction of pore in the alloys decreased, and no residual pore was observed in two-phase alloys consisting of a few% $Cr_{2}Al$ phase. Environmental effect on the ductility of the alloys was investigated using compression test at different strain rates($1.2 \times 10^{-4}/s$ and $1.2 \times 10^{-2}/s$). Environmental embrittlement was least significant in A1-25Ti-10Cr alloy consisting of LIZ single phase among the alloys tested in this study. However, based on the combined estimation of the pore formation, environmental embrittlement and ingot cast structure, AI-21Ti-23Cr alloy consisting of 20% $Cr_{2}Al$ as the second phase is expected to show the best tensile elongation behavior.

• Journal of Chest Surgery
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• v.39 no.8 s.265
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• pp.611-618
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• 2006

Background: There have been controversies whether mitral valvular surgery is necessary in the patients with moderate ischemic mitral regurgitation undergoing coronary artery bypass grafting. The purpose of this study is to evaluate the long term clinical results of patients with moderate ischemic mitral regurgitation. Material and Method: Between January 1992 and February 2005, 44 patients with moderate ischemic mitral regurgitation underwent coronary artery bypass grafting. Concomitant mitral valvular procedure was performed in 20 patients (group 1) and isolated coronary artery bypass grafting was performed in 24 patients (group 2). There were no significant difference between groups except cardiopulmonary bypass time (p<0.01). Postoperative follow up duration was $30.1{\pm}29.6$ months and last follow up echocardiographic examination was performed at $21.2{\pm}28.0$ months. Result: There was no difference in operative mortality between groups (group 1 vs group 2, 15.0% vs 8.3%, p=0.493). Grade of mitral regurgitation ${(0.81{\pm}0.91\;vs\;1.50{\pm}0.05,\;p=0.046)}$ and reduction in regurgitation grade ${(1.75{\pm}0.93\;vs\;0.70{\pm}1.26,\;p=0.009)}$ were different between two groups. But there were no significant differences in left ventricular ejection fraction ${(34.1{\pm}11.4%\;vs\;41.6{\pm}12.9%)}$, left ventricular end systolic volume ${(118.2{\pm}63.9\;ml%\;vs\;85.6{\pm}281\;ml)}$, New York Heart Association functional class ${(2.1{\pm}0.2\;vs\;2.4{\pm}1.2)}$ and 5 year survival rate ${(85{\pm}8%\;vs\;82{\pm}8%)}$. There was no risk factor for operative mortality and the only risk factor for late death was preoperative atrial fibrillation (p=0.042). There was no significant correlation between mitral valvular surgery and late death. Conclusion: Concomitant mitral valvular procedure in patients with moderate ischemic mitral regurgitation undergoing coronary artery bypass grafting had no significant positive effect on survival and ventricular function compared with isolated coronary artery bypass grafting. Prospective randomized study may be needed to evaluate the necessity of concomitant mitral procedure and to find more effective method for the improvement of ventricular function.

• Journal of the Mineralogical Society of Korea
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• v.23 no.4
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• pp.367-375
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• 2010

Understanding the interactions between earth materials and fluids is essential for studying the diverse geological processes in the Earth's surface and interior. In order to better understand the interactions between earth materials and fluids, we explore the effect of specific surface area and porosity on structural parameters of pore structures. We obtained 3D pore structures, using random packing simulations of porous media composed of single sized spheres with varying the particle size and porosity, and then we analyzed configurational entropy for 2D cross sections of porous media and cube counting fractal dimension for 3D porous networks. The results of the configurational entropy analysis show that the entropy length decreases from 0.8 to 0.2 with increasing specific surface area from 2.4 to $8.3mm^2/mm^3$, and the maximum configurational entropy increases from 0.94 to 0.99 with increasing porosity from 0.33 to 0.46. On the basis of the strong correlation between the liquid volume fraction (i.e., porosity) and configurational entropy, we suggest that elastic properties and viscosity of mantle melts can be expressed using configurational entropy. The results of the cube counting fractal dimension analysis show that cube counting fractal dimension increases with increasing porosity at constant specific surface area, and increases from 2.65 to 2.98 with increasing specific surface area from 2.4 to $8.3mm^2/mm^3$. On the basis of the strong correlation among cube counting fractal dimension, specific surface area, and porosity, we suggest that seismic wave attenuation and structural disorder in fluid-rock-melt composites can be described using cube counting fractal dimension.