• Korean Journal of Materials Research
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• v.16 no.5
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• pp.318-322
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• 2006

Short-term high temperature degradation test was conducted on Hastelloy X, a candidate tube material for high temperature gas-cooled reactors (HTGR), to evaluate the variation of microstructure and mechanical property in air at $1050^{\circ}C$ during 2000 h. The dominant oxide layer was Cr-oxide and a very shallow Cr-depleted region was observed below the oxide layer. At the beginning of degradation, the island shape $M_6C$ precipitate (M=Mo-rich, Fe, Ni, Cr) was observed in matrix region. After 2000 h degradation, precipitate shape was changed to the chain shape and increased amount of precipitate. These results influenced mechanical property of the specimen which exposed in high temperature. Yield strength was decreased from 115MPa to 89 MPa after 24 h and 2000 h exposure, respectively.

• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.52-57
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• 2008

The short-term high temperature creep rupture behavior of Ni-based Alloy718 steel was investigated at the elevated temperatures range of 550 to $700^{\circ}C$ under constant stress conditions. The creep rupture characteristics such as creep stress, rupture time, steady state creep rate, and initial strain were evaluated. Creep stress has a quantitative correlation between creep rupture tim and steady state creep rate. The stress exponents (n, m) of the experimental data at 550, 600, 650 and $700^{\circ}C$ were derived as 33.5, -24.9, 26.1, -21.2, 16.8, -12.8 and 10, -8.2, respectively. The stress exponent decreased with increasing creep temperature. The creep lift prediction was derived by the Larson-Miller parameter (LMP) method and the resultant equation was obtained as follows: T($logt_r$+20)=-0.00252 ${\sigma}^2$-1.377${\sigma}$+-22718.

• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.58-63
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• 2008

The short-term high temperature creep rupture behavior of Ni-based Alloy718 steels jointed by friction welding wasinvestigated at the elevated temperatures of 550 to $700^{\circ}C$ under constant stress conditions. The creep rupture characteristics such as creep stress, rupture time, steady state creep rate, and initial strain were evaluated. Creep stress has a quantitative correlation between creep rupture time and steady state creep rate. The stress exponents (n, m) of the experimental data at 550, 600, 650 and $700^{\circ}C$ were derived as 26.1, -22.4, 22.5, -18.5, 17.4, -14.3 and 6.9, -8.1, respectively. The stress exponents decreased with increasing creep temperature. The creep life prediction was derived by the Larson-Miller parameter (LMP) method and the result equation obtained is as follows: T(logtr+20)=-0.00148${\sigma}^2$-3.089${\sigma}$+23232. Finally, the results were compared with those of the base metal for Alloy718.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.195-202
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• 2004

In this study, it was founded to make the optimal mixture for producing concrete which is self-compacting, yet, and generates low heat of hydration by using flyash, blast furnace slags and limestone powders as binders in addition to cement while using super-plasticizers and viscosity agents as admixture agents. The structural behaviors of the concrete produced with the selected mixture were compared with those of the concrete currently using for construction of nuclear power plants. The study shows that the blended high fluidity concrete including limestone is better in workability and durability than the concrete currently in use for nuclear power plants.

• The Korean Journal of Food And Nutrition
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• v.29 no.3
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• pp.313-326
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• 2016

The aim of this study was to evaluate the effects of a nutrition education program for the elderly at a public health center located in Jinhae city. The one group pretest and posttest design was conducted using self-administered questionnaire survey. Nutrition education lessons based on social cognitive theory (2 hours/lesson, 3 times) were provided to 27 female elderly(${\geq}65$ yrs) for a month. After the nutrition education, number of exercise increased and preference for sweetness decreased significantly (p<0.05). The outcome expectations, the knowledge of nutrition (p<0.001), and behavioral capability (p<0.05) score were significantly increased. There were significant increases in all nutrient intake. NAR was increased significantly in protein, calcium and vitamin C (p<0.01), dietary fiber, iron, zinc, thiamin, niacin and folic acid (p<0.001), and riboflavin (p<0.05). INQ was increased significantly in thiamin, vitamin B6 and niacin (p<0.05), and dietary fiber (p<0.01). The score of nutrition education satisfaction was high (4.52). The results of this study suggested that the nutritional education program based on social cognitive theory had a positive effect on dietary behavior changes, and nutrition intake status among female elderly even after short-term intervention.

• Corrosion Science and Technology
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• v.19 no.4
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• pp.174-188
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• 2020

Atmospheric corrosion is a natural surface degradation process of metal due to changes in environmental parameters in the surrounding atmosphere. It is very sensitive to environmental parameters such as temperature, relative humidity, sulphur dioxide, and chloride, making it a major global economic challenge. Existing forecasting empirical corrosion models including the ISO standard are based on statistical analysis of experimental studies without considering the behavior of atmospheric parameters. The present study proposes a reliable global empirical model for estimating short and long-term atmospheric corrosion rates based on environmental parameters and corrosion mechanisms obtained from a parametric study. Repercussion of atmospheric corrosion rate due to individual and combined influences of environmental parameters specifies their importance in the estimation. New global empirical coefficients obtained for environmental parameters are statistically established (R² =0.998) with 95% confidence limit. They are validated using experimental datasets of existing studies observed at 88 different continental locations. The current proposed model can predict atmospheric corrosion by means of corrosion formation mechanisms influenced by combined effects of environmental parameters, further abating applicability limitations of location and time.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.67-69
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• 2003

The magnetic properties of single- and poly-crystalline $La_{0.7}Sr_{0.3}MnO_3/Pr_{0.65}Ca_{0.35}MnO_3$ multilayered (ML) films, and composite (CP) $(La_{0.7}Sr_{0.3})_{0.5}(Pr_{0.65}Ca_{0.35}_{0.5}MnO_3$ films, prepared by laser ablation, have been investigated in a wide temperature range. It was shown that the transformation from an incoherent to a coherent interface in the ML films leads to an enhancement of the ferromagnetic coupling between layers and to a single-phase magnetic transition. The amorphous CP films demonstrate a paramagnetic behavior of the magnetization with a sharp peak at $T_{G}\approx$45 K, which was interpreted as the formation of Griffiths phase. A short-term annealing at $750^{\circ}C$ induced the complete crystallization of film, and a recovery of the ferromagnetic and the metal-insulator transitions.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.749-752
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• 1993

This paper deals with the development of three phase 440[V], 500[KVA] Inverter system using the IGBT Devices. IGBT's have been used very successfully in variable frequency induction motor drive equipment. Problems associated with power devices characteristics when power devices are operated in parallel, such as balanced switching behavior and thermal stability, can be solved by using NPT type IGBT's. By Experimental results, it is confirmed that the voltage overshoot and reverse recovery current was very low. The equipment had proved to be reliable and short circuit proof. In addition, the performances in term of thermal characteristics, protection functions and stability are satisfactory.

• Journal of Korean Medicine for Obesity Research
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• v.3 no.1
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• pp.1-6
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• 2003

Background: Recently, Obesity has become a social problem in all over the world including Korea. Dietary regulation, exercise and behavior modification therapy are used in the treatment of obesity, but until now, there have been many difficulties in treating it. Objectives: To examine in obese pre-menopausal Korean females the short-term efficacy for weight loss of an herbal formula (Slim-diet). Design: A 6-week longituidinal evaluation of a herbal formula (Slim-diet) in 35 pre-menopausal females (baseline age $31.6\;{\pm}\;6.1$) with body mass index > $25kg/m^2$. Body composition was measured using bioimpedence analysis (BIA) and dual energy X-ray absorptiometry (DXA). Anthropometry was done by same observer. Total cholesterol, total lipid, triglyceride, and LDL-cholesterol were measured. Results: Herbal formula (Slim-diet) treatment produced significant loss of weight (P < 0.001), percent of body fat (P < 0.001, both BIA and DXA) and waist circumference (P < 0.001). It also produced significant reduction of total cholesterol and total lipid levels (P < 0.05).

• The Korean Journal of Food & Health Convergence
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• v.8 no.4
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• pp.1-10
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• 2022

The term "Organic Food" is no longer strange to consumers around the world. Many people are concerned about their safety and health, so they have chosen this safe food. However, the decision to buy this product still faces some difficulties and challenges, such as the high price of organic products, short-time use, supply of products and so on. This study conducted an analysis to investigate the determinants of Danang City consumers' intention to purchase organic foods in Vietnam. The results show that, there are 6 influencing factors, including: subjective norm, food safety & health consciousness, consumer knowledge & environment consciousness, price of the product, availability product and trust in brands and certifications. The study uses a combination of 2 qualitative and quantitative methods. Qualitative methods are used through analysis, evaluation and synthesis of previous studies to build research models and scales for variables. Quantitative method with 250 samples applied SPSS 25.0 to test the scale by Cronbach's Alpha coefficients, to analyze the discovery factor EFA and regression analysis. The findings of the study provide useful information for consumers to buy organic foods and for marketers to increase sale of organic foods in Vietnam in general and Danang city in particular.