• Journal of the Korean Magnetics Society
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• v.22 no.3
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• pp.85-90
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• 2012

Oxidation of the $Nd_2Fe_{14}B$ compound crystal and its effect on the coercivity of the fine $Nd_2Fe_{14}B$ crystal particles were investigated. Oxidation kinetics of the $Nd_2Fe_{14}B$ compound crystal was investigated using an excessively grown $Nd_2Fe_{14}B$ grains in the $Nd_{15}Fe_{77}B_8$ alloy ingot. Oxidation of the $Nd_2Fe_{14}B$ compound crystal occurred by dissociation of the phase into multi-phase mixture of ${\alpha}$-Fe, $Fe_3B$, and Nd oxides. Oxidation rate of the $Nd_2Fe_{14}B$ compound crystal showed no dependence on the crystallographic direction. The oxidation reaction was modeled according to simple linear relationship. Activation energy for the oxidation of $Nd_2Fe_{14}B$ compound crystal was calculated to be approximately 26.8 kJ/mol. Fine $Nd_2Fe_{14}B$ crystal particles in near single domain size was prepared by ball milling of the HDDR-treated $Nd_{15}Fe_{77}B_8$ alloy, and these particles were used for investigating the effect of oxidation on the coercvity. The near single domain size $Nd_2Fe_{14}B$ crystal particles (${\fallingdotseq}0.3\;{\mu}m$) had high coercivity over 9 kOe. However, the coercivity was radically reduced as the temperature increased in air (<2 kOe at $200^{\circ}C$). This radical coercivity reduction was attributed to the soft magnetic phases, ${\alpha}$-Fe and $Fe_3B$, which were formed on the surface of the fine particles due to the oxidation.

• Korean Journal of Veterinary Research
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• v.41 no.2
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• pp.203-210
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• 2001

Here, we compared the effectiveness of 50 MeV($p{\to}RBe^+$) cyclotron fast neutrons versus $^{60}Co$ ${\gamma}$-rays by the apoptotic fragment frequency in both rat peripheral lymphocytes and crypt cells to check a radiobiological endpoint. The incidence of apoptotic cell death was increased in all irradiated groups, and radiation at all doses trigger rapid changes in both crypt cells and peripheral lymphocytes. These data suggest that apoptosis may play an important role in homeostasis of damaged radiosensitive target organ by removing damaged cells. The curve of dose-effect relationship for these data of apoptotic fragments frequencies was $y=0.3+(6.512{\pm}0.279)D(r^2=0.975)$ after neutrons, while $y=0.3+(4.435{\pm}0.473)D+(-1.300{\pm}0.551)D^2(r^2=0.988)$ after ${\gamma}$-rays. In addition, $y=3.5+(118.410{\pm}10.325)D+(-33.548{\pm}12.023)D^2(r^2=0.992)$ after ${\gamma}$-rays in rat lymphocytes. A significant dose-response relationship was found between the frequency of apoptotic cell and dose. These data show a trend towards increase of the numbers of apoptotic cells with increasing dose. Dose-response curves for high and low linear energy transfer (LET) radiation modalities in these studies were different. The relative biological effectiveness (RBE) value for crypt cells was 1.919. In addition, there were significant peaks on apoptosis induction at 4 and 6h after irradiation, and the morphological findings of the irradiated groups were typical apoptotic fragments in crypt cells that were hardly observed in the control group. Thus, apoptosis induction in both crypt cells and peripheral lymphocytes could be a useful endpoint of rat model for studying screening test and microdosimetic indicator to evaluate the biological effects of radiation-induced cell damage.

• Radiation Oncology Journal
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• v.16 no.3
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• pp.251-258
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• 1998

Purpose : This study was performed to analyze the factors affecting local control in malignant tumors of the parotid gland treated with surgery and postoperative radiation. Materials and methods : Twenty-six patients were treated for malignant tumors of the parotid gland from 1986 to 1995 at Department of Therapeutic Radiology, Chonnam University Hospital. Age of the patients ranged from 14 to 72 years (median : 55 years). Histologically 10 patients of mucoepidermoid carcinoma, 7 of squamous cell carcinoma, 4 of acinic cell carcinoma, 4 of adenoid cystic carcinoma and 1 of adenocarcinoma were treated. Total parotidectomy was performd in 15 of 26 patients, superficial in 7, subtotal in 4. Facial nerve was sacrificed in 5 patients. Postoperatively 4 patients had residual disease, 4 had positive resection margin. Radiation was delivered through an ipsilateral wedged pair of photon in 11 patients. High energy electron beam was mixed with photon in 15 patients. Electron beam dose ranged from 900 cGy to 3800 cGy (median 1700 cGy). Total radiation dose ranged from 5000 cGy to 7560 cGy (median : 6020 cGy). Minimum follow-up period was 2 years. Local control and survival rate were calculated using Kaplan-Meier method. Generalized Wilcoxon test and Cox proportional hazard model were used to test factors affecting local control. Results : Five (19$\%$) of 26 patients had local recurrence. Five year local control rate was 77$\%$. Overall five year survival rate was 70$\%$. Sex, age, tumor size, surgical involvement of cervical lymph node, involvement of resection margin, surgical invasion of nerve, and total dose were analyzed as suggested factors affecting local control rate. Among them patients with tumor size less than 4 cm (p=0.002) and negative resection margin (p=0.011) were associated with better local control rates in univariate analysis. Multivariate analysis showed only tumor size factor is associated with local control rate (p=0.022). Conclusion : This study suggested that tumor size is important in local control of malignant tumors of parotid gland.

• Journal of Conservation Science
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• v.32 no.4
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• pp.579-588
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• 2016

This study analyzed nonmetallic inclusions in iron swords with a ring pommel excavated in the Ipbuk-dong, Suwon. Scanning electron microscopy with energy dispersive spectroscopy(SEM-EDS) was used to estimate the iron-making temperature, and we compared the oxide with $SiO_2$ to investigate the heat-treatment technology in the production of iron swords with a ring pommel by investigating the artificial insertion of a slag former and the metallurgical structure. From the wustite observed in most of the specimens, it is judged that these swords were produced by heating and forging iron smelted at a low temperature using the solid reduction method. In addition, judging from the partial presence of $P_2O_5$, it is assumed that they were smelted directly with natural ore, not calcined. From the ratios of $CaO/SiO_2$ and $TiO_2/SiO_2$, it is judged that the raw material for iron-making was iron ore and that a calcareous slag former was not artificially inserted. The structure of the blade part on the front end was pure iron. From the high carbon content of the blade part on the ring pommel and the formation of a martensitic structure and pearlite colony, it is judged that they were tempered after carburizing and that the back, handle part, and ring pommel were unintentionally carburized. Judging from the structure of these specimens, it was noted that they were produced by applying artificial partial heat-treatment technology. This study attempted to present a more scientific analysis by using the method of interpretation through component analysis of nonmetallic inclusions appearing in one relic by the ratio of the oxide divided by $SiO_2$. It is judged that reinterpreting the arguments by the results of the existing analysis and research in this way can obtain different interpretations.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.2
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• pp.306-314
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• 2002

The purpose of this study is to examine the relation between vegetarian diet and the risk factors of cardiovascular disease. The subjects of the study were 127 Buddhist nuns (age: 23 ~79 yr) for vegetarians and 235 healthy female adults (age: 23 ~79 yr) for non-vegetarians. This study covers food consumption survey, anthropometric measurement, amount of energy expenditure, physical activity and clinical examination. Average body mass index (BMI) of vegetarians and non-vegetarians were 22.47 and 21.08, waist/hip ratio (WHR) was 0.85 and 0.84, percentage of body fat (%BF) was 28.79 and 26.55, respectively. Average duration of vegetarian diet of the vegetarians was 13.16 years. The triglyceride levee of the vegetarians was significantly lower for those who take nutrient tablet compared to those who either take vitamins or who do not take any nutrient supplement. Taking vitamins or nutrient tablet did not give any significant difference in total-cholesterol and LDL-cholesterol for vegetarians, while significantly high triglyceride was observed for the non-vegetarians taking nutrient tablet than the ether non-vegetarians. Taking vitamins or nutrient tablet did not affect the lever of HDL-cholesterol for either vegetarians or non-vegetarians. Athrogenic index (AI) was lower for the vegetarian group tailing nutrient tablet and for the non-vegetarian group not taking vitamins and nutrient tablet, than the other respective groups. Blood sugar of the vegetarians who take nutrient tablet was significantly lower than those tailing vitamins, while blood sugar of the non-vegetarians not taking any nutrient supplement was significantly lower than those taking nutrient tablet.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.2
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• pp.39-44
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• 2020

Recently, numerous researches are being conducted in flexible substrate to apply to wearable devices. Particularly, Conductive substrate researches that can implement the wearable devices on clothing are massive. In this study, we formed fiber substrate spraying CNT and Pd mixed solution on it and plated metal layer with electroless plating. Used SEM equipment and EDS analysis to analysis structure of the plated fiber substrate and discovered Ni layer was created. For check electrical properties, mapping was performed to check surface resistance and distribution of resistance of electroless plated fiber substrate with 4-point probe. It was confirmed that conductivity was improved as the duration of electroless plating was increased, and it was found that distribution of resistance by surface location was uniform. Changes in resistance due to mechanical stress were measured through tensile, bending, and twisting tests. As a result, it was confirmed that resistance change of flexible substrate gradually disappeared as plating time increased. Using UTM (Universal testing machine), it was analyzed mechanical properties of the electroless plated substrate with respect to changes in plating time were improved. In the case of conductive fiber substrate in which electroless plating was performed for 2 hours, tensile strength was increased by 16 MPa than fiber substrate. Based on these results, we found that Ni-CNT-Fabric flexible substrate is adequate for clothing-intergrated conductive substrate and we positively expect that this experiment shows flexible substrate can adapt to and develop not only a wearable device technology but also other fields needing flexibility such as battery, catalyst and solar cell.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.91-93
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• 2003

A comprehensive numerical study is carried out to investigate for the understanding of the flow evolution and flame development in a supersonic combustor with normal injection of ncumally injecting hydrogen in airsupersonic flows. The formulation treats the complete conservation equations of mass, momentum, energy, and species concentration for a multi-component chemically reacting system. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations and detailed chemistry of H2-Air is considered. It also accommodates a finite-rate chemical kinetics mechanism of hydrogen-air combustion GRI-Mech. 2.11[1], which consists of nine species and twenty-five reaction steps. Turbulence closure is achieved by means of a k-two-equation model (2). The governing equations are spatially discretized using a finite-volume approach, and temporally integrated by means of a second-order accurate implicit scheme (3-5).The supersonic combustor consists of a flat channel of 10 cm height and a fuel-injection slit of 0.1 cm width located at 10 cm downstream of the inlet. A cavity of 5 cm height and 20 cm width is installed at 15 cm downstream of the injection slit. A total of 936160 grids are used for the main-combustor flow passage, and 159161 grids for the cavity. The grids are clustered in the flow direction near the fuel injector and cavity, as well as in the vertical direction near the bottom wall. The no-slip and adiabatic conditions are assumed throughout the entire wall boundary. As a specific example, the inflow Mach number is assumed to be 3, and the temperature and pressure are 600 K and 0.1 MPa, respectively. Gaseous hydrogen at a temperature of 151.5 K is injected normal to the wall from a choked injector.A series of calculations were carried out by varying the fuel injection pressure from 0.5 to 1.5MPa. This amounts to changing the fuel mass flow rate or the overall equivalence ratio for different operating regimes. Figure 1 shows the instantaneous temperature fields in the supersonic combustor at four different conditions. The dark blue region represents the hot burned gases. At the fuel injection pressure of 0.5 MPa, the flame is stably anchored, but the flow field exhibits a high-amplitude oscillation. At the fuel injection pressure of 1.0 MPa, the Mach reflection occurs ahead of the injector. The interaction between the incoming air and the injection flow becomes much more complex, and the fuel/air mixing is strongly enhanced. The Mach reflection oscillates and results in a strong fluctuation in the combustor wall pressure. At the fuel injection pressure of 1.5MPa, the flow inside the combustor becomes nearly choked and the Mach reflection is displaced forward. The leading shock wave moves slowly toward the inlet, and eventually causes the combustor-upstart due to the thermal choking. The cavity appears to play a secondary role in driving the flow unsteadiness, in spite of its influence on the fuel/air mixing and flame evolution. Further investigation is necessary on this issue. The present study features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous works. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is not related to the cavity, but rather to the intrinsic unsteadiness in the flowfield, as also shown experimentally by Ben-Yakar et al. [6], The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The work appears to be the first of its kind in the numerical study of combustion oscillations in a supersonic combustor, although a similar phenomenon was previously reported experimentally. A more comprehensive discussion will be given in the final paper presented at the colloquium.

• Journal of the Korean Society of Food Science and Nutrition
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• v.15 no.2
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• pp.181-189
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• 1986

This nutrition survey was carried out twice(Spring and autumn) in Sam Chung-Ri, Song Kwang Myun, Soong Ju-Gun. The food intakes of 92 family members were measured by weighing method. Also 45 adults were examined for anthropometric, blood content and blood pressure. The results abtained were summarized as follows; In vegetable foods, the intake of rice was high, but that of legumina and other cereals was low. In animal foods, the intake of milk and eggs was low, and that of oils and fats was very low. However, the food intake between spring and autumn showed remarkable difference. The average intake of calorie, protein, Ca, Fe and vitamin $B_2$ except vitamin $B_1$ and niacin was below the RDAs. The percentage of carbohydrate, protein and fat for energy was 82.2, 11.6 and 6.2%, respectively. The results of anthropometry of height, weight and chestcircumference showed that both sexes Were below Korean Standards. The concentration of Hb & Hct was normal in both sexes, and the rate of anemia was low. The concentrations of plasma glucose, protein, lipids, and blood pressure were normal in both sexes. In case of male, the correlation between plasma albumin and nutrients intake was significant, but the case of female showed different tendency. In case of male, the correlation between weight, height and plasma protein was also significant but the case of female showed different tendency. The rate of parasite infection was very low $(2.17%{\ldots}3.26%)$

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.656-662
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• 2007

Fuel reformer using plasma and shift reactor for CO oxidation were designed and manufactured as $H_2$ supply device to operate a polymer electrolyte membrane fuel cell (PEMFC). $H_2$ selectivity was increased by non-thermal plasma reformer using GlidArc discharge with Ni catalyst simultaneously. Shift reactor was consisted of steam generator, low temperature shifter, high temperature shifter and preferential oxidation reactor. Parametric screening studies of fuel reformer were conducted, in which there were the variations of the catalyst temperature, gas component ratio, total gas ratio and input power. and parametric screening studies of shift reactor were conducted, in which there were the variations of the air flow rate, stema flow rate and temperature. When the $O_2/C$ ratio was 0.64, total gas flow rate was 14.2 l/min, catalytic reactor temperature was $672^{\circ}C$ and input power 1.1 kJ/L, the production of $H_2$ was maximized 41.1%. And $CH_4$ conversion rate, $H_2$ yield and reformer energy density were 88.7%, 54% and 35.2% respectively. When the $O_2/C$ ratio was 0.3 in the PrOx reactor, steam flow ratio was 2.8 in the HTS, and temperature were 475, 314, 260, $235^{\circ}C$ in the HTS, LTS, PrOx, the conversion of CO was optimized conditions of shift reactor using simulated reformate gas. Preheat time of the reactor using plasma was 30 min, component of reformed gas from shift reactor were $H_2$ 38%, CO<10 ppm, $N_2$ 36%, $CO_2$ 21% and $CH_4$ 4%.

• Clean Technology
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• v.20 no.4
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• pp.375-382
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• 2014

This work investigated the plasma-catalytic decomposition of isopropyl alcohol (IPA) and the behavior of the byproduct compounds over monolith-supported metal oxide catalysts. Iron oxide ($Fe_2O_3$) or copper oxide (CuO) was loaded on a monolithic porous ${\alpha}-Al_2O_3$ support, which was placed inside the coaxial electrodes of plasma reactor. The IPA decomposition efficiency itself hardly depended on the presence and type of metal oxides because the rate of plasma-induced decomposition was so fast, but the behavior of byproduct formation was largely affected by them. The concentrations of the unwanted byproducts, including acetone, formaldehyde, acetaldehyde, methane, carbon monoxide, etc., were in order of $Fe_2O_3/{\alpha}-Al_2O_3$ < $CuO/{\alpha}-Al_2O_3$ < ${\alpha}-Al_2O_3$ from low to high. Under the condition (flow rate: $1L\;min^{-1}$; IPA concentration: 5,000 ppm; $O_2$ content: 10%; discharge power: 47 W), the selectivity towards $CO_2$ was about 40, 80 and 95% for ${\alpha}-Al_2O_3$, $CuO/{\alpha}-Al_2O_3$ and $Fe_2O_3/{\alpha}-Al_2O_3$, respectively, indicating that $Fe_2O_3/{\alpha}-Al_2O_3$ is the most effective for plasma-catalytic oxidation of IPA. Unlike plasma-alone processes in which tar-like products formed from volatile organic compounds are deposited, the present plasma-catalyst hybrid system did not exhibit such a phenomenon, thus retaining the original catalytic activity.