• Journal of Powder Materials
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• v.29 no.5
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• pp.382-389
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• 2022

A typical trade-off relationship exists between strength and elongation in face-centered cubic metals. Studies have recently been conducted to enhance strength without ductility reduction through surface-treatment-based ultrasonic nanocrystalline surface modification (UNSM), which creates a gradient microstructure in which grains become smaller from the inside to the surface. The transformation-induced plasticity effect in Fe-Mn alloys results in excellent strength and ductility due to their high work-hardening rate. This rate is achieved through strain-induced martensitic transformation when an alloy is plastically deformed. In this study, Fe-6%Mn powders with different sizes were prepared by high-energy ball milling and sintered through spark plasma sintering to produce Fe-6%Mn samples. A gradient microstructure was obtained by stacking the different-sized powders to achieve similar effects as those derived from UNSM. A compressive test was performed to investigate the mechanical properties, including the yielding behavior. The deformed microstructure was observed through electron backscatter diffraction to determine the effects of gradient plastic deformation.

• Korean Journal of Materials Research
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• v.32 no.2
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• pp.57-65
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• 2022

Herein a rich, Se-nanoparticle modified Mo-W₁₈O₄₉ nanocomposite as efficient hydrogen evolution reaction catalyst is reported via hydrothermal synthesized process. In this work, Na₂SeSO₃ solution and selenium powder are used as Se precursor material. The structure and composition of the nanocomposites are characterized by X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), EDX spectrum analysis and the corresponding element mapping. The improved electrochemical properties are studied by current density, and EIS analysis. The as-prepared Se modified Mo-W₁₈O₄₉ synthesized via Na₂SeSO₃ is investigated by FE-SEM analysis and found to exhibit spherical particles combined with nanosheets. This special morphology effectively improves the charge separation and transfer efficiency, resulting in enhanced photoelectric behavior compared with that of pure Mo-W₁₈O₄₉. The nanomaterial obtained via Na₂SeSO₃ solution demonstrates a high HER activity and low overpotential of -0.34 V, allowing it to deliver a current density of 10 mA cm^-2.

• Nutrition Research and Practice
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• v.18 no.4
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• pp.554-566
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• 2024

BACKGROUND/OBJECTIVES: Urban-rural inequities in health and mortality exist in Korea, a highly centralized developed country. The potential impact of multiple health-related lifestyle behaviors on mortality and difference between urban and rural areas is not fully understood. This study aimed to investigate the effect of high-risk health behaviors on all-cause mortality among residents living in urban and rural in Korea. SUBJECTS/METHODS: Cross-sectional analyses were conducted on 8,298 adults aged 40 yrs and older from the Korea National Health and Nutrition Examination Survey 2013-2015. High-risk behaviors were defined as having poor diet quality, current smoking, high-risk drinking, or insufficient physical activity. Mortality status was linked to the Cause of Death data followed up to December 31, 2019. The associations between all-cause mortality and high-risk behaviors were evaluated using Cox proportional hazard regression models adjusted for age, sex, education, income, and survey year. Population attributable fractions (PAFs) were calculated, and effect modification analysis was conducted. Participants were stratified by residential area (urban or rural). RESULTS: During the follow-up (median: 5.4 yrs), 313 deaths occurred. A higher proportion of rural residents than urban residents engaged in multiple high-risk behaviors (28.9% vs. 22.6%; P < 0.0001). As individual factors, a greater risk of mortality was associated with poor diet quality, current smoking, and inadequate physical activity, and these tendencies persisted in rural residents, especially for diet quality. Multiple high-risk behaviors were positively associated with a higher risk of mortality in Koreans living in urban and rural areas. PAF (95% confidence interval) was 18.5% (7.35-27.9%) and 29.8% (16.1-40.2%) in urban and rural residents, respectively. No additive or multiplicative effect of the region was observed. CONCLUSION: The higher prevalence of multiple high-risk lifestyle behaviors in rural residents may explain the higher mortality in rural areas compared to urban areas. Comprehensive public health policies to improve health-related behaviors in rural populations may be needed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.1 s.53
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• pp.186-194
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• 2009

This is a part of the extensive ongoing investigation being carried out by author to develop appropriate design procedure of the concrete member reinforced with FRP rebars instead of conventional steel rebars. This study presents the experimental results of a research programme to assess the structural characteristics of spliced rebar in reinforced concrete members with FRP reinforcement. The test variables are the diameter of FRP rebar and the embedment length. The development length (ld) was calculated according to the ACI 440 for FRP rebars in concrete. A total of 14 concrete beams reinforced with spliced FRP rebars and 4 reference beams reinforced with non-spliced FRP rebars were tested. The effects of bar size (10, 13, 16 and 19 mm) and splice length (from 0.72 to 1.58ld) on the bond strength were empirically evaluated. The test results indicate that a modification factor of 1.3 and 1.6 is relatively sufficient for the bond development length of glass FRP rebars in order to achieve an adequate tension lap splice length.

• Journal of the Korean Geotechnical Society
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• v.27 no.10
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• pp.81-92
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• 2011

The rheological properties of Wyoming bentonites are strongly influenced by the size of particles, cation exchangeable capacity, arrangement and morphology of clay mineral. This paper presents the results of rheological investigations on the Wyoming bentonites aqueous dispersions: two types of particle flocculation were considered. For the Wyoming bentonite, 0g/L and 30g/L NaCl equivalent salinity were added in fresh and salt water to examine the rheological behavior. This paper examined the general rheological characteristics, compatibility of rheological models and correlation between soil structure and change in rheological properties of Wyoming bentonite caused by increasing salinity. From flow curves of bentonites hydrated with fresh water and salt water, the observed general flow behavior is very close to shear thinning with yield stress (or ideal Bingham fluid with yield stress and plastic viscosity). However, the change of shear stress at the same shear rate is clear, particularly for lower shear rate. Well-known rheological models are used to fit the data. There is a good agreement between rheological model and data: Carreau, Herschel-Bulkley and power-law for S=0g/L and bilinear, Herschel-Bulkley and power-law for S=30g/L. It may be due to the fact that the internal structural bonding (strong modification of particle-particle interactions from edge-to-edge and/or edge-to-face to face-to-face) in soil matrix is affected from the evolution of rheological properties with different salinities.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.593-604
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• 2007

Although composite construction has more mechanical advantages compared to noncomposite construction, the design of noncomposite construction for skew bridges with large skew angels has been often checked because composite construction may cause large stresses in the bridge deck. In this study, the analytical model considered dynamic behaviors for noncomposite skew bridges was proposed. Using the proposed analytical model, the validity of the application of noncomposite construction to skew bridges was checked. Also, the effects of interactions between the concrete deck and steel girders such as composite construction, partial composite construction, and noncomposite construction on the dynamic characteristics and dynamic behaviors of simply supported skew bridges were investigated. A series of parametric studies for the total 27 skew bridges was conducted with respect to parameters such as girder spacing, skew angle, and deck aspect ratio. Although the slip at the interfaces between the concrete deck and steel girders results in the reduction of seismic total base shear in the transverse direction due to period elongation, it causes an undesirable behavior of skew bridges by the modification in mode shapes and distributions of stiffness. Shear connectors placed by minimum requirements for partial composite action have an effect on reducing the girder stresses and deck stresses; except case of some skew bridges, the magnitude of the girder stresses and deck stresses obtained from partial composite skew bridges is similar to or slightly more than those acquired from composite skew bridges.

• Journal of Nutrition and Health
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• v.45 no.4
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• pp.315-323
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• 2012

Korean undergraduate students attempt to lose weight but often fail due to utilizing ineffective weight loss strategies. Some diet programs have succeeded, yet, they have not provided adequate skills for long-term weight maintenance. The aim of the study was to determine the effect of a low calorie diet and exercise with nutritional education on weight loss, serum lipid profiles, nutrient intakes, and dietary behavior modification in overweight and obese undergraduate students. The subjects in the low calorie diet group (LCD; n = 12) and the low calorie diet plus exercise group (LCDE; n = 13) had the same goal of losing 4 kg during a 12 week program. Nutrient intakes were assessed by the 24 hour recall method. Also, food habits and dietary behaviors were investigated by self-administered questionnaires before and after the weight control program and one month after completing the program. LCD and LCDE groups lowered body weight by 2 kg and 1 kg, respectively, although they decreased calorie intake by 355 and 287 kcal per day compared to intakes prior to the study. Body fat mass decreased in both the LCD and LCDE groups; however, the decrease was greater in the LCDE group. In addition, only the LCDE group increased muscle mass. The LCD group had a slightly better effect in reducing body weight, body fat, and waist circumference than the LCDE group. However, their decrease was reversed after the mid-study check in the LCD group; the reduction was better maintained and decreased more in the LCDE group. However, serum lipid profiles were already in borderline prior to the study; moreover, they were not modified after losing weight. The dietary behavior program helped students to develop better dietary habits. In conclusion, the combination of a low calorie diet and exercise is necessary in order to maintain longer weight loss by increasing muscle mass and decreasing body fat.

• Journal of Distribution Research
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• v.12 no.2
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• pp.103-129
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• 2007

One of the most enduring concepts in the history of marketing thought relates to the classification of consumer goods. The product classification theory first proposed by Copeland(1923) has, with little modification, survived to the present day, and continues to be endorsed by the American Marketing Association and other related institutions some 80 years after it was first published. In truth, Copeland's classification is now outdated and bears little, if any, relevance to modern product advertising, retailing and consumption. In particular, it can not accommodate the fact that, in modern societies, consumer preoccupations with style, personal identity and status have meant that the social characteristics of goods, heavily promoted by brand managers who understand their markets, are key determinants of consumer choice and buyer behavior. In this respect, the author attempted to explore the reasons why product classification theory has been unresponsive to changes in market conditions over so many years and argue that its failure to embrace the many social influences on consumption and on consumer behavior is now its most serious weakness. And also, the author proposed the new categorization system of goods, based on the several existing literatures.

• Korean Journal of Materials Research
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• v.14 no.10
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• pp.731-736
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• 2004

Herein, we report on the co-firing of a low-K wiring substrate and a middle-K functional substrate in LTCC. Firstly, we researched the sintering behavior and dielectric properties of the low-k wiring substrate comprised by alumina and glass frit with ${\varepsilon}_r$, of $\sim7$ and the middle-k functional substrate comprised by $Ba_{5}Nb_{4}O_{15}$ and glass frit with ${\varepsilon}_r$, of $20\sim30$. The warpage and delamination between the hetero layers of the low-K and the middle-K composition were also studied. In particular, physical matching of the hetero layers could be possible by adjusting of the sintering properties of the composition. We observed that an introduction of the glass frit to the low- and middle-K substrate gives rise to a minimization of an effect given by separation of the hetero layers, and modification of the fraction of the glass frit accompanied by a variation of the composition could control the sintering behavior and its beginning temperature. In the case of co-firing of the L03 as the low-K wiring substrate composition and the M03 as the middle-K functional substrate composition at $875^{\circ}C$, we could fabricate a desirable structure of hetero layers without any kinds of structural defects such as separation, warpage, delamination, pore trap, etc. We suppose that the co-firing techniques described in this study would provide a helpful method to fabricate a LTCC multi-functional for the next generation.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.6 no.3
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• pp.477-492
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• 1999

The disease patterns among the Korean was shifted from acute and infectious diseases to chronic diseases. According to the these disease patterns trends, people have concerned about the health promotion and health behaviors. Pender's(1996) revised health promotion model(HPM) is consist of three categories; Individual characteristics and experiences, Behavior-specific cognitions and affect, behavioral outcome. Of these categories, individual characteristics and experiences, this category of variables is considered to be of biological, psychological and socio-cultural personal factors, especially, individual fatigue. Futhermore. these variables constitute a critical core for nursing intervention, as they are subject to modification through nursing actions. But there is no few the research of the relationship between the fatigue and health promotion. Therefore, the purpose of this study is to investigate the correlation between the fatigue and health promoting life style among a rural college students. Additionally, this descriptive correlational study identified the relation of demographic factors and fatigue, health promoting life style. From June 20 to 26, 1998, a convenience sample of 270 college students completed the questionnaire of the fatigue and health promoting life style profile which were developed by the Yoshitake(1978) and Walker, et al.(1987), respectively. The descriptive correlational statistics, mean, t-test, ANONA, Pearson correlation coefficient were used to analyze the data gathered with SAS pc+ program. The results were as it follows: 1. The average fatigue score of the subjects was $64.93{\pm}12.89$. Fatigue scores by subcategory were physical symptoms($23.5{\pm}4.87$). psychological symptoms($22.11{\pm}4.66$) and neuro-sensory symptoms($19.32{\pm}5.14$). With the respect to the demographic characteristics of the subjects, there were statistically significant differences between the demographic factors and fatigue, especially, sex(t==3.69 p<0.01), major(t=-2.89 p<0.01). the experience of family illness(t=2.76 p<0.01). 2. The average health promoting life style item score of the subjects was $2.33{\pm}0.33$. In the subcategories, the highest degree of performance was self-actualization(2.94), following interpersonal support(2.81). stress management(2.33), exercise(2.20), nutrition(2.10), and the lowest degree was health responsibility(1.73). There were the significant differences on the learning of health education(t=2.00 p<0.01). religion(F=3.01, p<0.05), circle activity(t=2.07, p<0.05), nutrition control(t=5.25, p<0.01) of demographical factors with the health promoting life style. 3. The correlation between the fatigue and health promoting life style made statistically no significance(r=-0.09731, p>0.05). But there was negative significant relationship between health promoting life style and psychological symptom as a fatigue subcategory(r=-0.15721, p<0.05). The self-actualization showed negative significant correlation with all fatigue subcategory. The health responsibility showed significant relationship with total fatigue(r=0.13050. p<0.05). For further research, it suggests to replicate the correlational and causal study between the fatigue and the health promoting life style using the another fatigue scale which is able to measure the subjective and objective fatigue degree. And it needs to develop the nursing intervention program for maintaining and promoting the health behavior as well as for decreasing the college students's fatigue.