• Bulletin of the Korean Chemical Society
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• 제35권10호
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• pp.2935-2940
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• 2014

Monodispersed $Bi_2O_2CO_3$ nanoplates with an average width of 320 nm and thicknesses of 50-90 nm were successfully synthesized by a simple solvothermal method in a mixture solution of polyethylene glycol and $H_2O$. The obtained nanoplates were characterized by means of XRD, FT-IR, SEM and TEM. The effect of surfactant sodium dodecyl benzene sulfonate on the morphology of $Bi_2O_2CO_3$ product was investigated. Under simulated solar light irradiation, $Bi_2O_2CO_3$ nanoplates exhibited superior photocatalytic activities towards the degradation of RhB as well as high chemical stability upon cycling photocatalytic test. The nanoplates also showed promising photodegradation ability for eliminating refractory pollutant of phenol. The excellent photocatalytic performance of $Bi_2O_2CO_3$ nanoplates as compared with P25-$TiO_2$ endows them as promising high efficiency photocatalysts.

• 한국세라믹학회지
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• 제43권12호
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• pp.798-804
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• 2006

Co-planar type single chamber solid oxide fuel cell with patterned electrode on a surface of electrolyte has been fabricated by robo-dispensing method and microfluidic lithography. The cells were composed of NiO-GDC-Pd or NiO-SDC cermet anode, $(La_{0.7}Sr_{0.3})_{0.95}MnO_3$ cathode, and yttria stablized zirconia electrolyte. The cell performance at $900^{\circ}C$ was investigated as a function of electrode geometries, such as anode-to-cathode distance, numbers of electrode pairs. Relationship between OCV and I-V characteristics at the optimized operation condition was also studied by DC source meter under the mixed gas condition of methane, air, and nitrogen. An increase of anode-facing-cathode area leads to lower OCV due to intermixing between product gases of anode and cathode, which in turn decreases the oxygen partial pressure difference.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.3.1-3.1
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• 2009

Normal sintering process of producing porous ceramics is not to sinter perfectly, i.e., stop sintering in middle-process. Our porous ceramic materials are a product of complete sintering. For example if one want to make a porous carborundum, raw carborundum powder is sintered at either lower temperatures than normal sintering temperature or shorter sintering periods than normal sintering time to obtain incompletely sintered materials, i.e., porous carborundum. This implies normally sintered porous ceramic materials can mot be used in high vacuum conditions due to dust coming out from uncompleted sintering. We could produce completely sintered porous ceramic materials. For example, we can produce porous carborundum material by using carborundum particles bonded by glassy material. The properties of this material are similar to carborundum. We could make quasi-zero thermal expansion porous material by using carborundum and particles of negative thermal expansion materials bonded by the glassy material. We apply to sinter them also by microwave to sinter quickly. We also use HIP process to introduce closed pores. We could sinter them in large size to produce $2.5m{\times}2.5m$ ceramic plate to use as a precision plate for flat display industries. This flat ceramic plate is the world largest artificial ceramic plate. Precision plates are basic importance to any advanced electronic industries. The produced precision plate has lower density, lower thermal expansivity, higher or similar damping properties added extra properties such as vacuum vise, air sliding capacity. These plates are highly recommended to use in flat display industries. We could produce also cylindrical porous ceramics materials, which can applied to precision roller for polymer film precision motion for also electronic industries.

• The Korean Journal of Ceramics
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• 제6권3호
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• pp.250-257
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• 2000

The feasibility of synthesizing SiC-AlN solid solution by field-activated combustion synthesis was demonstrated. At lower fields of 8-16.5V/cm, composites of AlN-rich and SiC-rich phases were synthesized, but at fields of 25-30 V/cm, the product was a 2H structure solid solution. Combustion synthesis of the solid solution by nitridation of aluminum with silicon carbide under a nitrogen gas pressure of 4-8 MPa was also investigated. The maximum combustion temperature and wave propagation velocity were found to be influenced by the electric field in the field-activated combustion synthesis, and by the green density and nitrogen pressure in the combustion nitridation. In both cases the formation of solid solutions is complete within seconds, considerably faster than in conventional methods which require hours.

• Journal of Advanced Marine Engineering and Technology
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• 제20권2호
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• pp.75-75
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• 1996

The rapid expansion for the auto-industry and the worldwide trend toward non-asbestos friction materials for brake lining force our industry to transfer into non-asbestos ones from asbestos-based friction materials. Furthermore, it is imperative for the friction materials to have technological excellence and lower production cost to be competitive in the world market. There is no known theoretical procedures to formulate friction materials. It, rather, depends on the trial and error process. Thus, it is quite clear how important it is to accumulate the know-how on the formulation and manufacturing the friction material. This study concerns the practical ways of conceptualizing the formulation and optimizing the manufacturing process. This study focused on the development of formulation for non-asbestos friction material as well as deriving the physical properties of the trial product to prove its validity and applicability. Elaboration of the formula and optimizing scheme of the manufacturing process to get better quality are also sought. Physical properties were obtained by constant velocity test dynamotest, hardness test and strength test. Differential scanning calorimeter was also used to analyze the thermal reactions of organic constituents, microstructures, bond effects, and degree of mixture.

• Journal of Advanced Marine Engineering and Technology
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• 제20권2호
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• pp.7-14
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• 1996

The rapid expansion for the auto-industry and the worldwide trend toward non-asbestos friction materials for brake lining force our industry to transfer into non-asbestos ones from asbestos-based friction materials. Furthermore, it is imperative for the friction materials to have technological excellence and lower production cost to be competitive in the world market. There is no known theoretical procedures to formulate friction materials. It, rather, depends on the trial and error process. Thus, it is quite clear how important it is to accumulate the know-how on the formulation and manufacturing the friction material. This study concerns the practical ways of conceptualizing the formulation and optimizing the manufacturing process. This study focused on the development of formulation for non-asbestos friction material as well as deriving the physical properties of the trial product to prove its validity and applicability. Elaboration of the formula and optimizing scheme of the manufacturing process to get better quality are also sought. Physical properties were obtained by constant velocity test dynamotest, hardness test and strength test. Differential scanning calorimeter was also used to analyze the thermal reactions of organic constituents, microstructures, bond effects, and degree of mixture.

• 대한치과기공학회지
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• 제21권1호
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• pp.67-75
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• 1999

The purpose of this study is to evaluate the friction coefficients between abutment materials and clasp materials, and to an estimation formula for retention force. The coefficients of friction between three clasp materials and four abutment materials were measured under various conditions, polished and sandblasted and wet and dry. The measurement was repeated for each combination up to a total measurement of 1200 times. Estimation formula for retention force is measured as sum of two terms, which the one time is proportional to the product of friction coefficient ${\mu}$ and undercut u and the other term is proportional to u-squared. Two proportional coefficient were obtained by least square method. The results are as follows: 1. Friction coefficients were ranged from 0.08 to 0.53 under various conditions. 2. Friction coefficients of non-metal abutment materials are greater in wet conditions than dry conditions. 3. Friction coefficients of sandblasted clasp against abutment are greater than that of polished clasp. 4. Clasp retention force can be estimated with the model as F=$F_d(3.0{\mu}u+1.5u^2/h)$ with minor error.

• Journal of Animal Science and Technology
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• 제65권3호
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• pp.490-510
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• 2023

Feed safety is needed to produce and provide safe animal feeds for consumers, animals, and the environment. Although feed safety regulations have been set for each country, there is a lack of clear feed safety regulations for each livestock. Feed safety regulations are mainly focused on heavy metals, mycotoxins, and pesticides. Each country has different safe levels of hazardous materials in diets. Safe levels of hazardous materials in diets are mostly set for mixed diets of general livestock. Although there is a difference in the metabolism of toxic materials among animals, the safe level of feed is not specific for individual animals. Therefore, standardized animal testing methods and toxicity studies for each animal are needed to determine the correct safe and toxic levels of hazardous materials in diets. If this goal is achieved, it will be possible to improve livestock productivity, health, and product safety by establishing appropriate feed safety regulations. It will also provide an opportunity to secure consumer confidence in feed and livestock products. Therefore, it is necessary to establish a scientific feed safety evaluation system suitable for each country's environment. The chance of outbreaks of new hazardous materials is increasing. Thus, to set up appropriate toxic levels or safe levels in feed, various toxicity methods have been used to determine toxic levels of hazardous materials for humans and animals. Appropriate toxic testing methods should be developed and used to accurately set up and identify toxicity and safe levels in food and feed.

• 유통과학연구
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• 제22권1호
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• pp.115-125
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• 2024

Purpose: This study is to analyze the purchasing process and distribution management requirements for teaching materials that have important meaning in the practical field of preschool education. Research design, data and methodology: A structured questionnaire was used to survey 103 childcare staffs regarding the purchasing process and distribution managements. The collected data underwent Likert's 5-point scale analysis and keyword grouping. Additionally, ANOVA was conducted to examine the distribution management demands based on demographic characteristics. Results: The purchasing of teaching materials involved more offline channels than online, and the purchase decisions were predominantly made by principals rather than teachers. Although the purchasing process is similar to that of general businesses, there are difficulties in purchasing due to the disorganized distribution channels and limited accessibility to product information. Additionally, the management of inventory for teaching materials is challenging due to limited personnel and storage. Childcare staffs have requirements for classification systems, evaluation criteria, environments and policies related to teaching materials distribution. The need to introduce a teaching material evaluation and certification system to ensure quality was not high. Conclusions: Most of the respondents recognized that strict management and measures should be taken for the distribution of teaching materials. There were differences in the demand of teaching material distribution depending on the respondents' status, age, education, and experience.

• Nutrition Research and Practice
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• 제14권2호
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• pp.152-159
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• 2020

BACKGROUND/OBJECTIVES: Hypertriglyceridemia may be a more important predictor of cardiovascular disease in Asian population consuming carbohydrate-rich foods than in Western populations. Dairy products are known to play a beneficial role in obesity, dyslipidemia, and metabolic syndrome, but the results vary depending on gender and obesity. In this study, we investigated the associations between dairy product intake and hypertriglyceridemia in Korean adults. SUBJECTS/METHODS: The participants were selected from the Korea National Health and Nutrition Examination Survey 2007-2012 (KNHANES IV and V). A total of 22,836 participants aged 19-64 years were included in the analysis. A food frequency questionnaire used to determine the frequency of consumption of products (milk and yogurt). Multivariable logistic regression was used to assess the associations between dairy product intake and hypertriglyceridemia. RESULTS: A significantly decreased risk of hypertriglyceridemia was detected in the highest dairy product intake frequency group (≥ 1 time/day) (odd ratio [OR] = 0.79; 95% confidence interval [CI] 0.64-0.97, P for trend = 0.022) compared to that for the lowest dairy product intake frequency group. Among obese participants, the group with the highest intakes of milk (in men, OR = 0.64; 95% CI: 0.46-0.91, P for trend = 0.036) and yogurt (in women; OR = 0.53; 95% CI: 0.29-0.94, P for trend = 0.019) showed inverse associations with hypertriglyceridemia. No associations were detected in normal weight participants. CONCLUSION: The association between dairy product intake and hypertriglyceridemia differed by gender and obesity status. Further prospective studies are needed to confirm these associations.