• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.347-348
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• 2013

To obtain high conversion efficiency in InGaN-based solar cells, it is critical to grow high indium (In) composed InGaN layer for increasing sun light absorption wavelength rage. At present, most InGaN-based solar cells adopt InGaN/GaN multi-quantum-well (MQW) structure for high crystalline quality of InGaN with high In composition. In this study, we fabricated and compared the performances of two types of InGaN/GaN MQW solar cells which have the 15% (SC 15) and 25% (SC 25) of In composition at quantum well layer. Although both devices showed similar dark current density and leakage current, SC 15 showed better performance under AM 1.5G illumination as shown in Fig. 1. It is interesting to note that SC 25 showed severe current density decrease as increasing voltages. As a result, it lowered short circuit current density and fill factor of the device. However, SC 15 showed steady current density and over 75 % of fill factor. To investigate these differencesmore clearly, we analyzed their photoluminescence (PL) spectra under various applied voltages as shown in Fig. 2. At the same time, photocurrent, which was generated by PL excitation, was also measured as shown in Fig. 3. Further, we investigated the relationship between piezoelectric field and performance of InGaN based solar cell varying indium composition.

• Journal of Family Resource Management and Policy Review
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• v.19 no.4
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• pp.121-140
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• 2015

This study tried to develop and suggest the program for the family friendly culture in Healthy Families Center. This study focused on specially the cooking program on which entire family member can participate. To develop the program two theoretical perspectives were applied : 1. healthy families perspectives and family leisure, 2. child development perspectives. In the process for developing the program the related literatures were investigated and the proceding cases were analized. The developed program consisted of 4 parts : 1. today, I(child) am the chef, 2. today, daddy(or mommy) is the chef, 3. for my parents and for my kids, 4. let's take a familytrip with snacks. This program is to be made suitable for the families with child(ren) in school age. We suggested various strategies for the effective management the program in Healthy Families Center such as the program manual and workbook, the time duration of program, three steps(introduction-performance-closing) of each session and using the professionals. We suggested the pilot performance of this program for the confirmation the effectiveness of the program. The evaluation index can be used before and after the program implementation. Further research needs to investigate the program for another family life cycle, such as the family with the child(ren) of preschool age or youth child(ren). In addition, for the enhancement of professionals quality who lead the program in field the professionals academy or education program need to be offered.

• Journal of Family Resource Management and Policy Review
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• v.13 no.1
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• pp.147-168
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• 2009

The purpose of this study is to research support systems of the community child care services for optimum work-family balance. For this purpose, the questionnaire to be completed combined four areas: the workplace, school, community and home. Then questions concerning demographic factors and community-related aspects were analysed for this article. After analyzing 197 questionnaires, supplementary questions were asked, by interview to 10 samples. Full-time working wives (eg. working from 9am to 6pm) who have 1 or more children under 10 years old, living in Seoul and Gyeonggi province were collected as samples. The results were as follows: First, child care from family and relatives, and community services was properly used during the week, but dual working parents took complete charge of child care on Saturdays. Second, emergency child care was usually provided by the family, while relatives and community child care services were used less. Third, parents spent 17% of their monthly income on total child care expenditure. Fourth, community child care services were not used often, but the level of satisfaction with them was very high. Finally, they used relatives' services for safety reasons and community services for location, and only based on informed decisions. Therefore, Saturday child care programmes need to be initiated to help physically and mentally tired parents, with more general provision of positive and diverse public support systems.

• Quality Improvement in Health Care
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• v.3 no.1
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• pp.78-93
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• 1996

Background : The goal of this study was to establish the QA items and guidelines for preventing and improving of safety management. Therefore we investigated the nurses' recognition and knowledge of the safety and risk procedures and policies, and the agreement between the nurses beliefs on the degree of importance of those procedures and policies, with actual implementation in hospitals. Method : The subjects of this study were 201 nurses who participated in a program called continuing education for nurses, which held in December, 1993. Result: The results of this study were as follows: 1. Among 18 types of hospital risks, the items that scored highest or the need of closer attention in safety management was the needle stick, medication errors, falling, and bed sores. 2. In most questions of the 18 incidences, the nurses showed that the estimated result would have positive signs except for hospital infections, burns, and bed sores. 3. Even though the survey shows that incidences and types of occurences varies according to the person's age and the time of incident, they mostly occur between midnight to 6AM. Falls and bed sores can be seen more in the elderly. Medications errors, hospital infections and burns are frequently found between the ages of one through twenty. 4. There was a higher mean score for recognizing the importance of those items than the importance of implementing them. Conclusion : In summary, nurses did perceive the need of safety management but the hospital policy for proper safety management was not established. So we recommended that the hospital administration would undertake an early detection and proper management system for hospital precautions, based on QA items & guidelines presented in this study.

• Journal of Korea Foundry Society
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• v.31 no.5
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• pp.293-301
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• 2011

Representative magnesium alloys applied to the die-casting are AZ91, AM60, etc., and the application of these alloys is restricted to components operating at moderate temperatures, due to grain boundary siding of ${\beta}$-phase($Mg_{17}Al_{12}$) at temperatures above $120^{\circ}C$. Heat-resistant magnesium alloys such as AE42, AE44 have been developed, but that have been too burdensome to produce because of the expensive rare earth materials. Research work for the development of low-priced heat-resistant magnesium alloy is actively in progress and positive results are being reported. This study aims to investigate the effect of Ca additions on mechanical properties of Mg-4Al-2Sn heat resistant magnesium alloys. Mg-4Al-2Sn alloys with Ca (0wt.%, 0.3wt.%, 0.7wt.%, 1wt.%) have been produced through the die-casting process for the development of low-priced heat-resistant magnesium alloy, and high temperature tensile tests are performed using the specimens. The results showed that mechanical properties of Mg-4Al-2Sn-xCa increased with the addition of Ca up to 0.7wt.% Ca and further addition of Ca deteriorated the mechanical properties of the alloys. A significant amount of porosity was observed at the sample with 1wt%. Ca and the longer freezing range of the alloy was believed to cause the formation of porosity.

• Journal of Aerospace System Engineering
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• v.11 no.1
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• pp.14-21
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• 2017

A Linear parameterized Sigma-Pi neural network (SPNN) is applied to a tilt-duct unmanned aerial vehicle (UAV) which has a very large longitudinal stability ($C_{L{\alpha}}$). It is uncontrollable by a proportional, integral, derivative (PID) controller due to heavy stability. It is shown that the combined inner loop and outer loop of SPNN controllers could overcome the sluggish longitudinal dynamics using a method of dynamic inversion and pseudo-control to compensate for reference model error. The simulation results of the way point guidance are presented to evaluate the performance of SPNN in comparison to a PID controller.

• Korean Journal of Plant Taxonomy
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• v.38 no.1
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• pp.43-50
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• 2008

The pollination system of Bupleurum latissimum Nakai (Apiaceae) was investigated in the natural population of Korea. The various insects of 19 species, 11 families, 5 orders visited the flowers of B. latissimum. Episyrphus balteatus and Lasioglossum occidens were considered as the most effective pollen vector which have associated specially with B. latissimum. The visitation frequency peaked at 10 AM - 13 PM and no visitor was recognized during night time. The flowers of B. latissimum last during only three days and they are protandry. It is also confirmed that the flower of B. latissimum is self-compatible and cross-pollination by vectors is critical for successful seed setting.

• Journal of Acupuncture Research
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• v.17 no.3
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• pp.176-187
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• 2000

Objectives : This study was purposed to investigate the antioxidative effects of Paeoniae radix aqua-acupuncture solution(PR) on culture liver cell system, lipid peroxidation and antioxidative enzyme activities in tert-butyl hydroperoxide(t-BHP) treatmented conditions. Methods : Cultured normal rat liver cell(Ac2F) were prepared and incubated with or without PR(at 2% volume in culture medium). After 16~18hr, cells placed in DMEM medium without serum, and then incubated with 1mM t-BHP for 2hr. Viable cells were detected by MTT assay, and the levels of lipid peroxide(LPO) were measured by TBA method. And catalase activity was measured as the decrease in hydrogen peroxide absorbance at 240nm on spectrophotometer using 30mM hydrogen peroxide. Superoxide dismutase(SOD) were assayed by recording the inhibition of nitro blue tetrazolium reduction with xanthine and xanthine oxidase. Glutathione peroxidase(GPX) activity was determined by the modified coupled assay developed by Paglia and Lawrence. The reaction was started by addition of 2.2mM hydrogen peroxide as substrate. The change in absorbance at 340nm was measured for 1min on spectrophotometer. Glutathione-S-transferase(GST) activity was assayed with CDNB as substrate and enzyme activity of GST towards the glutathione conjugation of CDNB. Results : Cell killing was significantly enhanced by addition of t-BHP compared to those of untreated group. PR pretreated cell resisted the toxic effects of t-BHP. LPO levels of t-BHP treatment group were significantly higher than other groups. This increased level was significandy reduced by PR pretreatment. The t-BHP treatment resulted in a decrease of catalase, GPX and GST activities. By contrast, PR pretreatment markedly increased compare to those of untreated groups. Conclusions : T-BHP which can produce intracellular free radical was used for inducer of the peroxidation of cellular lipids. PR protected the cell death induced by t-BHP and significantly increased cell viabiliry in the normal rat liver cell, and showed effective inhibition of lipid peroxidation, and elevations of catalase, GPX and GST activities. These results suggested that PR might play a protective role in lipid peroxidation by free radicals.

• Journal of the Korean Chemical Society
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• v.13 no.1
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• pp.49-55
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• 1969

X-ray Fluorescence Spectrographic method has been applied for the rapid determination of main components, such as $SiO_2$, $Al_2O_3$, $Fe_2O_3$, CaO, MgO and $K_2O$ in Silicate Minerals. In this method, Boric Acid was used as a binder after fusion with Lithium Tetraborate in the briquet-making process. The Lithium Flubride, Ammonium di-Hydrogen Phosphate and Ethylene Diamine d-Tartrate crystals were used with Scintillation counter and Gas Flow counter as the detectors. Several influences on this method were discussed, including the particle size of samples and reducing of the matrix effects by dilution with Boric Acid and addition of Lanthanum Oxide with the diluent. In order to test the reproducibility of this method described above, the determination of the same kind of samples were carried out repeatedly, and the results obtained were presented in the table. Calibration curves for each element were presented, and the application of the method was tested with International Rock Standard T-Ⅰ. All the results obtained by X-Ray Fluorescence Spectrographic method were compared with the results by conventional chemical method.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.65-69
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• 2003

The kinetic and chemical mechanisms of AChE-catalyzed hydrolysis of short-chain thiocholine esters are relatively well documented. Up to propanoylthiocholine (PrTCh) the chemical mechanism is general acid-base catalysis by the active site catalytic triad. The chemical mechanism for the enzyme-catalyzed butyrylthiocholine(BuTCh) hydrolysis shifts to a parallel mechanism in which general base catalysis by E199 of direct water attack to the carbonyl carbon of the substrate. [Selwood, T., et al. J. Am. Chem. Soc. 1993, 115, 10477- 10482] The long chain thiocholine esters such as hexanoylthiocholine (HexTCh), heptanoylthiocholine (HepTCh), and octanoylthiocholine (OcTCh) are hydrolyzed by electric eel acetylcholinesterase (AChE). The kinetic parameters are determined to show that these compounds have a lower Michaelis constant than BuTCh and the pH-rate profile showed that the mechanism is similar to that of BuTCh hydrolysis. The solvent isotope effect and proton inventory of AChE-catalyzed hydrolysis of HexTCh showed that one proton transfer is involved in the transition state of the acylation stage. The relationship between the dipole moment and the Michaelis constant of the long chain thiocholine esters showed that the dipole moment is the most important factor for the binding of a substrate to the enzyme active site.