• Composites Research
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• v.15 no.6
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• pp.30-37
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• 2002

A stiffness model has been proposed to predict elastic constants of twisted yam composites. The model is based upon the unit cell structure, the coordinate transformation, and the volume averaging of compliance constants for constituent materials. For the correlation of analytic results with experiments, composite samples of various yam twist angles were tested, and strength and Young's modulus under tensile, compressive, and shear loading have been obtained. The sample was fabricated by the RTM process using glass yarns and epoxy resin. The correlations of elastic constants showed relatively good agreements. The model provides the predictions of the three-dimensional engineering constants, which are valuable input data for the analytic characterization of textile composites made of twisted yam.

• Korean Journal of Adult Nursing
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• v.24 no.1
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• pp.31-37
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• 2012

Purpose: This Study was to examine to applicability of the Maslach Burnout Inventory on measuring burnout of the nurses who works in Korean university hospitals. Methods: The sample included 200 nurses and nurse managers. We used 22-item Maslach Burnout Inventory to evaluate the reported burnout. We evaluated the convergent validity through the factor analysis, and evaluated the discriminant validity through the Pearson's correlation analysis. Also, we evaluated the reliability for three subscales of Maslach Burnout Inventory with the Cronbach's ${\alpha}$, which assesses the internal consistency. Results: Factor analysis revealed three factors being extracted from the 22-item Maslach Burnout Inventory, and item loading for each factor is higher than 0.5. Therefore, the Maslach Burnout Inventory demonstrated high convergent validity. Also, emotional exhaustion, personal accomplishment, and depersonalization showed low correlation leading to the conclusion that there was discriminant validity. The Cronbach's ${\alpha}$ coefficients in the 22-item Maslach Burnout Inventory and three subscales were higher than 0.7. Conclusion: Maslach Burnout Inventory can be used as a valid instrument to measure the burnout level of the nurses working in Korean university hospitals.

• Journal of Korean Society for Quality Management
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• v.25 no.1
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• pp.80-99
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• 1997

This paper considers designing the simple (2-level) constant-and step-stress ALTs minimizing the asymptotic variance of the maximum likelihood estimator of the accelaeration factor, which is defined as the ratio of the 100qth percentile at use stress to that a specified stress, for items having lognormally-distributed lives. It is assumed that (i) the log-linear relationship exists between the stress and the mean log life, (ii) the standard deviation of the log life is constant, and (iii) the cumulative exposure model holds for the effect of changing stress. For the constant-stress ALT the low stress and the sample proportion allocated to low stress are determined and for two modes of stress loading of step-stress ALTs, the low-to-high and high-to-low, the low stress and the stress change time are determined. For selected values of the design parameters the optimum plans are figured, two modes of step-stress ALTs and the constant-stress ALT are compared to each other, and the effects of the incorrect pre-estimates of the design parameters are investigated.

• Journal of Korean Society of Steel Construction
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• v.22 no.2
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• pp.197-208
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• 2010

An under-tension system is frequently employed for large-span structures to reduce the deflection and member size. In this study, a microgenetic algorithm was used to find the optimum cross-section of truss structures with an undertension cable under transverse loading. Maximum deflection, allowable stress, and buckling were considered constraints. The proposed approach was verified using a 10-bar truss sample that shows good agreement with the previous results. In the numerical results, minimum-weight design of the under-tension structure was performed for various magnitudes of pretension.

• Journal of the Korean Geosynthetics Society
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• v.8 no.2
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• pp.41-46
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• 2009

In this paper, a series of model tests were performed in laboratory to evaluate promoting consolidation of compaction pile methods for soft ground improvement. For the model tests, composite soil samples that have 10% replacement area ratio were prepared by using sand, gravel, and sandy gravel for the materials of compaction piles. After loading to each composite soil sample, the excess pore pressure dissipation and settlement were investigated. In addition, the behavior of clay mixed with each compaction pile was also monitored at the end of consolidation to evaluate clogging phenomenon. As a test result, the effects for decreasing settlement and promoting consolidation by GCP were prominent, and the mixed clay was not monitored in all of the three compaction piles.

• Korean Medical Education Review
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• v.22 no.2
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• pp.57-66
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• 2020

The purpose of this study was to examine teaching strategies from cognitive learning theory applied to medical education and to present specific applications of the strategies and cases. The results of this study yielded (1) seven teaching strategies and specific sample activities that instructors can use based on learning processes in medical schools; (2) nine instructional events to which cognitive learning strategies were applied; (3) principles of curriculum design from a cognitive perspective; and (4) instruction cases employing cognitive teaching strategies. Cognitive learning theory has two implications: first, if instructors in medical schools apply the results of the study to design a class and curriculum, it would be possible for them to minimize cognitive loading of the learners that may stem from ineffective teaching strategies or curricula; second, cognitive teaching strategies that seek improvement in thinking skills could provide useful teaching strategies for medical education, which aims to develop experts with high-level thinking processes. In this sense, cognitive learning theory is not an out-of-date learning theory, but one that can be effectively applied in current medical education.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.402.1-402.1
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• 2014

Photonic force microscopy (PFM) is an optical tweezers-based scanning probe microscopy, which measures the forces in the range of fN to pN. The low stiffness leads proper to measure single molecular interaction. We introduce a novel photonic force microscopy to stably map various chemical properties as well as topographic information, utilizing weak molecular bond between probe and object's surface. First, we installed stable optical tweezers instrument, where an IR laser with 1064 nm wavelength was used as trapping source to reduce damage to biological sample. To manipulate trapped material, electric driven two-axis mirrors were used for x, y directional probe scanning and a piezo stage for z directional probe scanning. For resolution test, probe scans with vertical direction repeatedly at the same lateral position, where the vertical resolution is ~25 nm. To obtain the topography of surface which is etched glass, trapped bead scans 3-dimensionally and measures the contact position in each cycle. To acquire the chemical mapping, we design the DNA oligonucleotide pairs combining as a zipping structure, where one is attached at the surface of bead and other is arranged on surface. We measured the rupture force of molecular bonding to investigate chemical properties on the surface with various loading rate. We expect this system can realize a high-resolution multi-functional imaging technique able to acquire topographic map of objects and to distinguish difference of chemical properties between these objects simultaneously.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.160-160
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• 2017

Commercially pure titanium (Cp-Ti) and Ti alloys (typically Ti-6Al-4V) display excellent corrosion resistance and biocompatibility. Although the chemical composition and topography are considered important, the mechanical properties of the material and the loading conditions in the host have, conventionally. Ti and its alloys are not bioactive. Therefore, they do not chemically bond to the bone, whereas they physically bond with bone tissue. The electrochemical deposition process provides an effective surface for biocompatibility because large surface area can be served to cell proliferation. Plasma electrolyte oxidation (PEO) enables control in the chemical composition, porous structure, and thickness of the TiO2 layer on Ti surface. Silicon (Si) in particular has been found to be essential for normal bone and cartilage growth and development. Zinc (Zn) plays very important roles in bone formation and immune system regulation, and is also the most abundant trace element in bone. The objective of this work was to study on electrochemical behaviors of PEO-treated Ti-6Al-4V Alloy in solution containing Zn and Si ions. The morphology, the chemical composition, and the microstructure analysis of the sample were examined using FE-SEM, EDS, and XRD. The potentiodynamic polarization and AC impedance tests for corrosion behaviors were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat. The promising results successfully demonstrated the immense potential of Si/Zn-TiO2 coatings in dental and biomaterials applications.

• Preventive Nutrition and Food Science
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• v.4 no.1
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• pp.79-83
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• 1999

A potentiometric biosensor employing a CO3-2 ion-selective electrode(ISE) and malic enzyme immobilization in al flow injection analysis (FIA) system was constructed. Analytical parameters were optimized for L-malate determination . The CO3-2 -ISE-FIA system was composed of a pump, an injector, a malic enzyme (EC1.1.1.40) reactor, a CO3-2 ion-selective electrode, a pH/mV meter and a recorder. Cofactor NADP was also injected with substrate for theenzyme reaction into the system. Optimized analytical parameters for L-malate determination in the CO3-2 ISE-FIA system were as follows ; flow rate, 14.5ml/hr ; sample injection volume, 100ul; enzyme loading in the reactor, 20 units ; length of the enzyme reactor , 7 cm ; tubing length form the enzyme reactor to the detector as a geometric factor in FIA, 15 cm . The response time for measuring the entire L-malate concentration range (10-2 ~10-5 mol/L ; 4 injections )was <15minutes . In this CO3-2 -ISE-FIA system, the potential differences due to th eformation of CO3-2 by the reaction of malic enzyme on L-malate were correlated to L-malate concentration in the range of 10-2 ~10-5mol/L ; the detection limit was 10-5 mol/L. This potentionmetric CO3-2 ISE--FIA system was found to be useful for L-malate measurement.

• Journal of the Korean Society of School Health
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• v.22 no.2
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• pp.137-146
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• 2009

Purpose: This study was performed to identify the socioeconomic factors, the health behavior factors and dietary pattern that have an influence on abdominal obesity, as measured by using the waist circumference in children and adolescents. Methods: This study used data collected from 1998, 2001, 2005 Korean National Health and Nutrition Examination Survey (NHANES). Final sample included 3,596 subjects from 10 to 19 years old who had completed necessary health examinations, health behaviors survey, and nutrition survey. Results: 12 dietary patterns emerged from factor analysis with different factor loading. Logistic regression analysis of the factors that affect abdominal obesity showed that the education level, BMI(Body Mass Index) and dietary pattern, 'Kimchi' including Korean cabbage and radish affected the abdominal obesity in children and adolescents. Conclusions: Abdominal obesity is a risk factor for morbidity and mortality, and it is associated with chronic diseases, including cardiovascular disease and diabetes. Based on the findings, it is essential to modify dietary pattern for preventing abdominal obesity, which is a condition associated with the incidence of chronic disease in adults.