• Tunnel and Underground Space
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• v.31 no.6
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• pp.593-609
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• 2021

We proposed a numerical method for the thermo-mechanical behavior of rock fracture using a grain-based distinct element model (GBDEM) and simulated thermally induced fracture slip. The present study is the benchmark simulation performed as part of DECOVALEX-2023 Task G, which aims to develop a numerical method to estimate the coupled thermo-hydro-mechanical processes within the crystalline rock fracture network. We represented the rock sample as an assembly of Voronoi grains and calculated the interaction of the grains (blocks) and their interfaces (contacts) using a distinct element code, 3DEC. Based on an equivalent continuum approach, the micro-parameters of grains and contacts were determined to reproduce rock as an elastic material. Then, the behavior of the fracture embedded in the rock was characterized by the contacts with Coulomb shear strength and tensile strength. In the benchmark simulation, we quantitatively examined the effects of the boundary stress and thermal stress due to heat conduction on fracture behavior, focusing on the mechanism of thermally induced fracture slip. The simulation results showed that the developed numerical model reasonably reproduced the thermal expansion and thermal stress increment, the fracture stress and displacement and the effect of boundary condition. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study experiments.

• Journal of the Korean Society of Radiology
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• v.16 no.7
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• pp.843-849
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• 2022

In this study, the probability of secondary carcinogenesis was analyzed by measuring the exposure dose of surrounding normal organs during radiosurgery using a gamma knife. A pediatric phantom (Model 706-G, CIRS, USA) composed of human tissue-equivalent material was set to four tumor volumes of 0.25 cm³, 0.51 cm³, 1.01 cm³, and 2.03 cm³, and the average dose was 18.4 ± 3.4 Gy. After installing the Rando phantom on the table of the gamma knife surgical equipment, the OSLD nanoDot dosimeters were placed in the right eye, left eye, thyroid, thymus gland, right lung, and left lung to measure each exposure dose. The probability of cancer occurrence due to radiation exposure of surrounding normal organs during gamma knife radiosurgery for acoustic schwannoma disease was 4.08 cancers per 100,000 at a tumor volume of 2.03 cm³. This study is expected to be used as useful data in relation to stochastic effects in the future by studying the risk of secondary radiation exposure that can occur during stereotactic radiosurgery.

• Proceedings of the KSAR Conference
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• 2001.03a
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• pp.30-30
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• 2001

The culture of preantral follicles has important biotechnological implications through its potential to produce the large quantity of oocytes for embryo production, transgenesis research, conservation of rare breed, and a potential source of ovarian genetic material. The present study was conducted to establish the optimal conditions of in vitro culture for intact bovine preantral follicles; and to examine the developmental ability of oocytes derived from the in vitro-grown preantral follicles; and to investigate the effects of various concentrations of FSH and LH on these processes. Bovine preantral follicles (150 $\pm$ 1.2${\mu}{\textrm}{m}$), surrounded by theca cell, were isolated enzymetically and mechanically from ovarian cortical slides in Leibovitz L-15 medium containing 1 mg/$m\ell$ collagens and 0.2 mg/$m\ell$ DNase I and cultured for 25 days in the presence of different concentrations of bovine FSH and LH in $\alpha$MEM medium with insulin, transferrin, and selenite. The survival was tested by frypan Blue and Hematoxylin. The survival and growth rates of follicles were higher in FSH treatment groups than these in control (P<0.001), but there were no significant differences between the LH treatment groups and the control. In 25 days, the survival and growth rates of follicles in FSH and LH treatment group (50%, 300$\pm$1.0${\mu}{\textrm}{m}$) were higher than in FSH treatment group (40%, 244$\pm$0.5${\mu}{\textrm}{m}$) and the control group (25%, 160$\pm$ 1.0${\mu}{\textrm}{m}$). Fifty-five percent of healthy antral follicles were obtained, and 60% of the oocytes complete meiotic maturation to the metaphase II stage. Twenty-two percent of the mature oocytes underwent cleavage, and 9% developed to the blastocyst stage. In this study, in vitro-grown oocytes (111 $\pm$ $1.5mutextrm{m}$), under our culture conditions, were not equivalent in size to the in vivo-grown oocytes (130$\pm$1.3${\mu}{\textrm}{m}$). Therefore, these results suggest that bovine preantral follicles with intact theca cell can grow to the antral stage in 25days, and that oocytes from those follicles can acquire the meiotic competence and normally undergo fertilization and development to the blastocyst stage. However, the developmental capacity of in vitro-grown oocytes is presumably not comparable to those of the in vivo counterparts.

• Journal of the Korean Society of Radiology
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• v.17 no.4
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• pp.497-506
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• 2023

In the case of radiation workers in medical institutions, radiation exposure is made for patient protection and accurate procedures, so they have a problem of low dose exposure. Low-dose radiation exposure occurs mainly in parts of the body other than the Apron area, and the most frequent place is the skin of the back of the hand. In particular, since the medical personnel's hands require senses and fine movements during the procedure, they are defenseless in the radiation exposure area and are at risk of exposure. It can solve the problem of shielding such as lead gloves, and it is difficult to use by suggesting the activity of the hand during the procedure. To solve this problem, a shielding cream capable of obtaining a functional radiation protection effect was developed and its shielding performance was compared with lead equivalent of 0.1 mmPb. In the process of manufacturing shielding cream, the shielding performance was improved by adding a defoaming process to reduce air holes to increase the density of the cream. Therefore, the shielding cream using barium sulfate as the main material has a lower shielding rate than the lead plate, and in the realm of effective energy, it is 59%, At high effective energy, a difference of about 37% was shown, indicating that there is a functional radiation protection effect. The advantage is that it can be used directly on the skin, and it is considered that it can be used before wearing surgical gloves and has a permanent protective effect.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.16-24
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• 2023

Coal ash generated from thermal power plants using briquettes contains Si, Al, and Fe components. These components are the main components required for the manufacture of cement clinker. In particular, Al and Fe components form the interstitial phase of cement clinker and have an important effect on the sintering of cement clinker. In this study, a large amount of coal ash was applied as a raw material for cement clinker by content, and the mineral formation process of cement clinker to which coal ash was applied was confirmed by sintering temperature. It was confirmed that the intermediate phase was generated in the sintering temperature range of 1050 ~ 1150 ℃ in the cement clinker to which a large amount of coal ash was applied. As the content of coal ash increased, the production amount of the intermediate phase increased. The phase produced by the addition of coal ash is expected to be converted to calcium silicate phase and interstitial phase and disappear above 1350 ℃. The cement clinker applied with a large amount of coal ash at 1450 ℃ formed well-developed minerals equivalent to the standard cement clinker.

• Journal of the Korean Society of Radiology
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• v.17 no.2
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• pp.243-248
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• 2023

This study aims to analyze the secondary carcinogenesis rate caused by exposure of organs at risk of damage using a glass dosimeter during radiosurgery in vestibular schwannoma disease. Using a pediatric phantom of human tissue equivalent material, the volume of the tumor was set to a total of three volumes: 0.506 cm³, 1.008 cm³, and 2.032 cm³, and a radiosurgery plan was established with an average dose of 18.4 ± 3.4 Gy. After mounting the human body phantom on the table of surgical equipment, glass dosimeters were placed on the right eye, left eye, thyroid gland, thymus, right lung, and left lung to measure the exposure dose, respectively. In this study, the incidence of secondary cancer due to exposure to damaged organs during gamma knife radiosurgery in vestibular schwannoma disease with the largest tumor volume of 2.032 cm³ was measured with a glass dosimeter. This study studies the risk of secondary radiation exposure dose that can occur during stereotactic radiosurgery, and it is considered that it will be used as basic data in the field of radiation damage related to the stochastic effect of radiation in the future.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.2
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• pp.185-195
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• 2017

Two byproducts, brewer's spent grain (BSG; germinated rice and malt) and brewer's spent material (BSM; Achyranthes japonica Nakai), were collected during the manufacture of pilsner beer using A. japonica Nakai and germinated rice. Water extracts of BSG and BSM were prepared at different temperatures ($25^{\circ}C$, $60^{\circ}C$, and $100^{\circ}C$) for 5 h, and their nutritional and functional properties were investigated. ${\gamma}-Aminobutyric$ acid (GABA), saponin, and niacin contents were higher in extracts prepared at $60^{\circ}C$ for more than 3 h than the other extracts, whereas total polyphenol content, DPPH radical scavenging activity, and reducing power were higher in samples extracted at $100^{\circ}C$ for 1 h compared to the other ones. Overall, water extraction at $60^{\circ}C$ for 3 h was desirable to effectively collect both nutritional and functional components from BSG and BSM. Under these conditions, BSM extracts showed 4~18 times high niacin and folate contents, 1.4 times high total phenolic content, and 11~60 times high antioxidant activities compared to BSG extracts. This study shows that pilsner beer byproducts would be good sources of health beneficial components, especially GABA, saponin, water soluble vitamins, and polyphenolics.

• Progress in Medical Physics
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• v.25 no.1
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• pp.46-52
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• 2014

Liquid ionization chamber is filled with liquid equivalent material unlike air filled ionization chamber. The high density material allow very small-volume chamber to be constructed that still have a sufficiently high sensitivity. However liquid ionization chamber should be considered for both initial recombination and general recombination. We, therefore, studied using the Co-60 beam as the continuous beam and the microLion chamber (PTW) for comparing the ion collection efficiency by Greening theory, two-dose rate method and our experiment method. The measurements were carried out using Theratron 780 as the cobalt machine and water phantom and 0.6 cc Farmer type ionization chamber was used with microLion chamber in same condition for measuring the charge of microLion chamber according to the dose rates. Dose rate was in 0.125~0.746 Gy/min and voltages applied to the microLion chamber were +400, +600 and +800 V. As the result, the collection efficiency by three method was generally less than 1%. In particular, our experimental collection efficiency was in good agreement within 0.3% with Greening theory except the lowest two dose rates. The collection efficiency by two-dose rate method also agreed with Greening theory generally less than 1%, but the difference was about 4% when the difference of two dose rates were lower. The ion recombination correction factors by Greening theory, two-dose rate method and our experiment were 1.0233, 1.0239 and 1.0316, respectively, in SSD 80 cm, depth 5 cm recommended by TRS-398 protocol. Therefore we confirmed that the loss by ion recombination was about 3% in this condition. We think that our experiment method for ion recombination correction will be useful tool for radiation dosimetry in continuous beam.

• Korean Journal of Medicinal Crop Science
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• v.13 no.6
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• pp.255-260
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• 2005

For selecting a new candidate as functional material, this study was conducted on in vitro antioxidant activity and total phenol content of methanol and water extracts prepared from two Mentha species (M viridis L. (M spicata L.) and Mentha piperita L, Extracts of M. viridis showed more efficient scavenging activity on superoxide and DPPH ${({\alpha},{\alpha}-diphenyl-{\beta}-picrylhydrazyl)}$ radical and inhibitory activity on oxidation of human low density lipoprotein (LDL) induced by $CuSO_4$ and auto-oxidation of linoleic acid than those of M piprita. Methanol extract $(65.88%{\sim}77.59%)$ and water extract $(37.69%{\sim}87.21%)$ of M. viridis also exhibited more potent inhibitory activity on LDL oxidation than that of ${{\alpha}-tocopherol\;(28.37%{\sim}66.54%)}$ at ${1{\sim}100\;{\mu}g/ml}$ of final concentration. The total phenol contents of methanol extract and water extract of Mviridis (17.95% & 10.18%, respectively) as tannic acid equivalent were higher than those of M piperita (15.44% & 9.19%). But the yields of methanol and water extracts of M. viridis (13.3 % & 13.5%) were lower than those of M. piperita (14.1 % & 14.6%). The results implies that the extracts from M. viridis (spicata) is more useful material for industrialization as functional food than those from M. piperita.

• Restorative Dentistry and Endodontics
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• v.35 no.6
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• pp.445-452
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• 2010

Objectives: The aim of this study was to compare apical sealing ability and physical properties of MTA, MTA - AH-plus mixture (AMTA) and experimental Portland cement - Epoxy resin mixture (EPPC) for a development of a novel retro-filling material. Materials and Methods: Forty-nine extracted roots were instrumented and filled with gutta-percha. Apical root was resected at 3 mm and the retro-filling cavity was prepared for 3 mm depth. Roots were randomly divided into 3 groups of 15 roots each. The retro-filling was done using MTA, AMTA, and EPPC as the groups divided. Four roots were used as control groups. After setting in humid condition for 24 hours, the roots were immersed in 1% methylene blue dye solution for 72 hours to test the apical leakage. After immersion, the roots were vertically sectioned and photos were taken to evaluate microleakage. Setting times were measured with Vicat apparatus and digital radiographs were taken to evaluate aluminum equivalent thickness using aluminum step wedge. The results of microleakage and setting time were compared between groups using one-way ANOVA and Scheffe's post-hoc comparison at the significance level of 95%. Results: AMTA and EPPC showed less microleakage than MTA group (p < 0.05). AMTA showed the highest radio-opacity than other groups and the novel EPPC showed 5 mm aluminum thickness radio-opacity. EPPC showed the shortest initial and final setting times than other groups while the MTA showed the longest (p < 0.05). Conclusions: Under the condition of this study, the novel composite using Portland cement-Epoxy resin mixture may useful for retro-filling with the properties of favorable leakage resistance, radio-opacity and short setting time.