• Restorative Dentistry and Endodontics
• /
• v.47 no.1
• /
• pp.10.1-10.11
• /
• 2022

Objectives: This study aimed to investigate the color stability, solubility, and surface characteristics of 3 calcium silicate-based cements (CSCs) after immersion in different solutions. Materials and Methods: ProRoot white mineral trioxide aggregate (MTA), Biodentine, and Endosequence Root Repair Material (ERRM) were placed in cylindrical molds and stored at 37℃ for 24 hours. Each specimen was immersed in distilled water, 5% sodium hypochlorite (NaOCl), 2% chlorhexidine, or 0.1% octenidine hydrochloride (OCT) for 24 hours. Color changes were measured with a spectrophotometer. Solubility was determined using an analytical balance with 10^-5 g accuracy. The surface characteristics were analyzed using scanning electron microscopy and energy-dispersive spectroscopy. Data were analyzed using 2-way analysis of variance, the Tukey test, and the paired t-test. Results: MTA exhibited significant discoloration in contact with NaOCl (p < 0.05). White precipitation occurred on the surfaces of Biodentine and ERRM after contact with the solutions, and none of the materials presented dark brown discoloration. All materials showed significant solubility after immersion in the solutions (p < 0.05), irrespective of the solution type (p > 0.05). The surface topography and elemental composition of the samples showed different patterns of crystal formation and precipitation depending on the solution type. Conclusions: All materials presented some amount of solubility and showed crystal precipitation after contact with the solutions. Biodentine and ERRM are suitable alternatives to ProRoot MTA as they do not exhibit discoloration. The use of OCT can be considered safe for CSCs.

• Journal of the Korean Society of Radiology
• /
• v.11 no.7
• /
• pp.547-553
• /
• 2017

In the current medical field, lead is widely used as a radiation shield. However, the lead weight is very heavy, so wearing protective clothing such as apron is difficult to wear for long periods of time and there is a problem with the danger of lethal toxicity in humans. Recently, many studies have been conducted to develop substitute materials of lead to resolve these problems. As a substitute materials for lead, barium(Ba) and iodine(I) have excellent shielding ability. But, It has characteristics emitting characteristic X-rays from the energy area near 30 keV. For patients or radiation workers, shielding materials is often made into contact with the human body. Therefore, the characteristic X-rays generated by the shielding material are directly exposured in the human body, which increases the risk of increasing radiation absorbed dose. In this study, we have developed the FLUKA transport code, one of the most suitable elements of radiation transport codes, to remove the characteristic X-rays generated by barium or iodine. We have verified the reliability of the shielding fraction of the structure of the structure shielding by comparing with the MCPDX simulations conducted as a prior study. Using the MCNPX and FLUKA, the double layer shielding structures with the various thickness combination consisting of barium sulphate ($BaSO_4$) and bismuth oxide($Bi_2O_3$) are designed. The accuracy of the type shown in IEC 61331-1 was geometrically identical to the simulation. In addition, the transmission spectrum and absorbed dose of the shielding material for the successive x-rays of 120 kVp spectra were compared with lead. In results, $0.3mm-BaSO_4/0.3mm-Bi_2O_3$ and $0.1mm-BaSO_4/0.5mm-Bi_2O_3$ structures have been absorbed in both 33 keV and 37 keV characteristic X-rays. In addition, for high-energy X-rays greater than 90 keV, the shielding efficiency was shown close to lead. Also, the transport code of the FLUKA's photon transport code was showed cut-off on low-energy X-rays(below 33keV) and is limited to computerized X-rays of the low-energy X-rays. But, In high-energy areas above 40 keV, the relative error with MCNPX was found to be highly reliable within 6 %.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.16 no.3
• /
• pp.112-115
• /
• 2006

The red emission properties of $Bi^{3+}$ co-doped $Y_2O_3:Eu^{3+}$ prepared by the solid-state reaction was investigated, in order to verify its potential to act as the red emitting phosphor of white LEDs. The emission spectrum consisted of a weak band at 581, 587, 5931 and 599 nm, with maximum sharp peaks occurring at about 611 nm due to the $^5D_0{\rightarrow}^7F_2$ transition of $Eu^{3+}$, while the excitation spectrum exhibited a broad band between 290 and 430 mm with peaks occurring in the range of $310{\sim}390nm$. Also, SEM image of the sample containing 0.43 mol% $H_3BO_3$ and 2.08 mol% $BaCl_2{\cdot}2H_2O$ phosphor particles grew to achieve diameters of $700{\sim}800nm$.

• Journal of the Korean Society of Radiology
• /
• v.14 no.2
• /
• pp.149-155
• /
• 2020

Most of radiation protection clothing is made of lead with excellent radiation shielding because it has excellent process ability and economic efficiency and has a high atomic number. However, lead is classified as a hazardous heavy metal, and there is a risk of lead poisoning. Recently, research to replace lead has been actively conducted. In this study, a research on a shielding sheet with improved physical properties while maintaining the radiation shielding ability equivalent to that of conventional materials by mixing two materials that are harmless to the human body, such as BaSO₄ and Bi₂O₃, and a silicone material binder Was performed. For comparison evaluation with the existing lead shielding sheet, the shielding rate was evaluated using a 40 degree shielding sheet having the highest porosity. As a result, it was analyzed that the shielding rate was superior to 9 % or more at the same thickness. In addition, as a result of studies to improve the physical properties of the shielding sheet, it was analyzed that the shielding sheet mixed with BaSO₄/nylon/Bi₂O₃ was the best.

• Economic and Environmental Geology
• /
• v.29 no.4
• /
• pp.411-419
• /
• 1996

The Janggun magnetite deposits occur as the lens-shaped magnesian skarn, magnetite and base-metal sulfide orebodies developed in the Cambrian Janggun Limestone Formation. The K-Ar age of alteration sericite indicates that the mineralization took place during late Cretaceous age (107 to 70 Ma). The ore deposition is divided into two stages as a early skarn and late hydrothermal stage. Mineralogy of skara stage (107 Ma) consists of iron oxide, base-metal sulfides, Mg-Fe carbonates and some Mg- and Ca-skarn minerals, and those of the hydrothermal stage (70 Ma) is deposited base-metal sulfides, some Sb- and Sn-sulfosalts, and native bismuth. Based on mineral assemblages, chemical compositions and thermodynamic considerations, the formation temperature, $-logfs_2$, $-logfo_2$ and pH of ore fluids progressively decreased and/or increased with time from skarn stage (433 to $345^{\circ}C$, 8.8 to 9.9 atm, 29.4 to 31.6 atm, and 6.1 to 7.2) to hydrothermal stage (245 to $315^{\circ}C$, 11.2 to 12.3 atm, 33.6 to 35.4 atm, and 7.3 to 7.8). The ${\delta}^{34}S$ values of sulfides have a wide range between 3.2 to 11.6‰. The calculated ${\delta}^{34}S_{H_2S}$ values of ore fluids are relatively homo-geneous as 2.9 to 5.4‰ (skam stage) and 8.7 to 13.5‰ (hydrothermal stage), which are a deep-seated igneous source of sulfur indicates progressive increasing due to the mixing of oxidized sedimentary sulfur with increasing paragenetic time. The ${\delta}^{13}C$ values of carbonates in ores range from -4.6 to -2.5‰. Oxygen and hydrogen isotope data revealed that the ${\delta}^{38}O_{H_2O}$ and ${\delta}D$ values of ore fluids decreased gradually with time from 14.7 to 1.8‰ and -85 to -73‰ (skarn stage), and from 11.1 to -0.2‰ and -87 to -80‰ (hydrothermal stage), respectively. This indicates that magmatic water was dominant during the early skarn mineralization but was progressively replaced by meteoric water during the later hydrothermal replacement.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.48 no.3
• /
• pp.280-290
• /
• 2021

Color stability of pulp-capping material is considered vital to the final aesthetic result since the material is placed in the coronal area. The purpose of this study was to compare the color stability of various pulp-capping materials by analyzing color change of tooth over time. A cavity was formed in the crown of the extracted premolar, and 4 types of pulp-capping materials were filled. Color assessment was performed with a spectrophotometer at different intervals: before placement; immediately after material placement; 1 day, 1 week, 2 weeks, 4 weeks, 8 weeks, 12 weeks, and 16 weeks after placement. Proroot white MTA^® and TheraCal LC^® showed a significant decrease in the L^* value and an increase in the ∆E^* value over time. In contrast, Biodentine^® and Well-Root^TM PT showed no significant change in the L^* value and maintained a steady ∆E^* value. The application of pulp-capping materials containing bismuth oxide as a radiopacifier may result in a color change of teeth. Long-term color stability of pulp-capping materials should be considered when treating teeth with thin enamel thickness or in aesthetically important area.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.37 no.4
• /
• pp.457-463
• /
• 2024

(Bi_1/2Na_1/2)TiO₃(BNT) piezoelectric ceramics are one of the promising materials that can replace Pb(Zr, Ti)O₃(PZT) piezoelectric ceramics due to the high electromechanical strain properties. However, it is still difficult to use practical applications because the required electric field for inducing electromechanical strain is relatively higher than that of PZT ceramics. To overcome this problem, it has been intensively studied on doping impurity or modifying other ABO₃ for BNT-based piezoelectric ceramics. Therefore, this study investigated the effects of La₂O₃ doping on the phase transition behavior and electromechanical strain properties in BNT-SrTiO₃ (BNT-ST) lead-free piezoelectric ceramics. In the case of the temperature-dependent dielectric properties, it was confirmed that a phase transition from ferroelectrics to relaxors is induced with increasing La₂O₃ content. As a result, the electromechanical strain properties of BNT-ST ceramics were improved. The highest S_max/E_max value corresponding to 300 pm/V was obtained at 2 mol% La₂O₃-dopped BNT-ST ceramics. Accordingly, this study successfully demonstrated that La₂O₃ doping is effective on the inducing phase transition from ferroelectrics to relaxors and the improving electromechanical strain properties of BNT-ST lead-free piezoelectric ceramics.

• The Korean Journal of Nuclear Medicine
• /
• v.30 no.4
• /
• pp.548-559
• /
• 1996

A series of performance measurements of positron emission tomography (PET) were performed following the recommendations of the Computer and Instrumentation Council of the Society of Nuclear Medicine and the National Electrical Manufacturers Association. We investigated the performance of the General Electric $Advance^{TM}$ PET. The measurements include the basic intrinsic tests of spatial resolution, scatter fraction, sensitivity, and count rate losses and randoms. They also include the tests of the accuracy of corrections: count rate linearity correction, uniformity correction, scatter correction and attenuation correction. GE $Advance^{TM}$ PET has bismuth germanate oxide crystals (4.0mm transaxial ${\times}$ 8.1mm axial ${\times}$ 30.0mm radial) in 18 rings, which form 35 imaging planes spaced by 4.25mm. The system has retractable tungsten septa 1mm thick and 12cm long. Transaxial resolution was 4.92mm FWHM in 2D and 5.14mm FWHM in 3D at the center. Average axial resolution in 2D decreased from 3.91mm FWHM at the center to 6.49mm FWHM at R=20cm. Average scatter fraction of direct and cross slices was 9.57%. Dead-time losses of 50% corresponded to a radioactivity concentration of $4.86{\mu}Ci/cc$ and a true count rate of 519 kcps in 2D. The accuracy of count rate linearity correction was 1.84% at the activity of $4.50{\mu}Ci/cc$. Non-uniformity was 2.06% in 2D and 2.93% in 3D. Remnant errors after scatter correction were 0.55% in 2D and 4.12% in 3D. The errors of attenuation correction were 6.21% (air), 0.20% (water), -6.32% (teflon) in 2D and 5.00% (air), 6.94% (water), 3.01% (teflon) in 3D. The results indicate the performance of GE $Advance^{TM}$ PET scanner to be well suited for clinical and research applications.