• Korean Journal of Crystallography
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• v.15 no.1
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• pp.44-50
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• 2004

Spinel structured lithium managanese oxide $(LiMn_2O_4)$ powder with well defined facetted morphology was prepared by precipitation-evaporation method. {111}, {110}, and {100} planes are mainly observed in the $LiMn_2O_4$ powder. And powder shape of tetradecahedron and octahedron was observed depending on the calcinations temperature. The observed powder morphology observed seemed to be related to the nonstoichiometry of the oxygen in the $LiMn_2O_4$ spinel structure. Oxygen nonstoichiometry might be responsible for the Jahn-teller effect and structure transition which in turn affects the surface energy of the {111}, {110}, and {100} planes. Powder shape transition from tetradecahedron to octahedron seemed to be related to the surface energy of the {111}, {110}, and {100} planes with oxygen nonstoichiometry.

• Korean Journal of Crystallography
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• v.12 no.2
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• pp.81-87
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• 2001

We have studied the effect of sintering temperature and time on the cation ordering and second phase formation in Ba(Mg/sub 1/3/Nb/sub 2/3/)O₃(BMN) microwave ceramics by using transmission electron microscopy. The relationship between the structural-chemical behavior arid microwave dielectric properties has also been investigated. It is revealed that according to the sintering conditions the BMN ceramics show very diverse local ordering behavior, such as the development of domain twinning and "core-shell"-structured grains and the formation of local disordered domains, though having 1 : 2 cation ordering structure basically. The disordered structure is found in Mg-excess region. Such local chemical variation seems to be caused by the formation of BaNb₂O/sub 6/-like second phase in its neigh-boring grain boundary. The microwave dielectric quality factor of the ceramics decreases greatly with the increase of the structural-chemical inhomogeneity and diversity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.284-287
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• 2001

This paper presents the robust control simulation of a composite beam using self-sensing actuators(SSA). The self-sensing actuator is a new concept for intelligent material, where a single piezoelectric element simultaneously functions as both a sensor and an actuator. In a practical implementation of the self-sensing actuator an electrical bridge circuit is used to measure strain. The circuit could provide significant information about strain in the element if it were well-balanced. Our aim is design a robust controller which guarantees that the performance of a self-sensing actuator is robust against perturbation of the bridge balance and to confirm the advantages of this technique. Simulation results show that the self-sensing actuator driven by the designed controller exhibits excellent performance in suppressing the vibration of a composite beam.

• Korea-Australia Rheology Journal
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• v.21 no.1
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• pp.71-79
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• 2009

The incomplete saturation and the void formation during the resin infiltration into fibrous porous media in the resin transfer molding process cause failure in the final product during its service. In order to better understand flow behavior during the filling process, a finite-element scheme for transient flow simulation across the micro-structured fibrous media is developed in the present work. A volume-of- fluid (VOF) method has been incorporated in the Eulerian frame to capture the evolution of flow front and the vertical periodic boundary condition has been combined to avoid unwanted wall effect. In the microscale simulation, we investigated the transient filling process in various fiber structures and discussed the mechanism leading to the flow fingering in the case of random fiber distribution. Effects of the filling pressure, the shear-thinning behavior of fluid and the volume fraction on the flow front have been investigated for both intra-tow and the inter-tow flows in dual-scale fiber tow models.

• Journal of Welding and Joining
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• v.8 no.2
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• pp.58-69
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• 1990

In conventional arc welding, position error of the weld torch with respect to the weld seam and variation of groove dimension are induced by inaccurate fitup and fixturing. In this study, a vision system has been developed to recognize and compensate the position error and dimensional inaccuracy. The system uses a structured laser light illuminated on the weld groove and perceived by a C.C.D camera. A new algorithm to detect the edge of the reflected laser light is introduced for real time processing. The developed system was applied to arbitarary weld paths with various types of joint in arc welding process. The experimental results show that the proposed system can detect the weld groove parameters within good accuracy and yield good tracking performance.

• Journal of the Korean housing association
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• v.10 no.4
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• pp.23-30
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• 1999

This study has been performed to analyze impacts of urban vs rural residence on later life. In this study, 329 Koreans aged 60 or more were interviewed for their current sociodemographic status and daily life styles. The results are drawn as follows: 1. There is no regional impact on birth order; rate of those born as the first child was not significantly different over regions. 2. For the household composition, the rate of three generations was significantly higher in rural areas than in urban areas. 3. More than 85% of the subjects lived in owned homes in rural areas, while 77% did in urban areas. 4. More than 89% of the subjects lived in single-structured homes in rural areas, while only 45% did in urban areas. The results indicate that in planning public housing for the aged, more social spaces accommodating grandchildren and ownership units need to be allocated for rural facilities. In addition, it is recommended that daily activity schedules need to be differentiated so that rural residents have meals and houseworks earlier than urban residents.

• Journal of Home Health Care Nursing
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• v.3
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• pp.39-52
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• 1996

This study presents results of surveys conducted Incheon area using structured questionaire developed by researcher to determine the degree of knowledge, attitude and practice of breast feeding of mothers of infant. The suvjects were mothers of 84 Childs, 1-6 months of age. Results were as follows : 1. More than half of the subjects started breast feeding and breast-bottle feeding(61.9%) 2. Duration of breast feeding was under one month (9.6%), 1-2months(13.7%), 3-4months(5.5%), 5-6months(23.3%) and had continued breast feeding until they were questioned. 3. The 40.5% of mothers'never got information of breast feeding and 21.4% of mother got information of breart feeding through T. V. or radio. 4. Degree of mothers' knowledge of breast feeding was significantly correlated with mothers' attitude of breast feeding (r=.47, p<0.01) and degree of mothers' attitude of breast feeding was significantly correlated with mothers' practice of breast feeding(r=.34, p<0.01).

• Convergence Security Journal
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• v.5 no.3
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• pp.67-73
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• 2005

Security requirements must be defined well to reduce software vulnerabilities in requirement specification phase. In this paper, we show how to specify security requirements in structured manner for object-oriented development methodology. Our method specifies security requirements through four phases: defining security objectives, identifying the threat, construct attack tree, and specifying security function. This method would help developers to specify security requirements and functions which software have to possess clearly and systematically.

• Child Health Nursing Research
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• v.10 no.1
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• pp.48-58
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• 2004

Purpose: Internet addiction is a newly recognized problem in the adolescents. The purpose of this study was to identify and analyze the educational needs for Internet addiction in middle school students of Korea. Method: The subjects of this study were 450 middle school students. The data were collected from open and structured questionnaire about the educational needs for Internet addiction. Result: As a result of content analysis of educational needs for Internet addiction, 9 domains and 19 themes were categorized from 542 statements. 9 Domains are : Definition, Etiology, Status, Process, Diagnosis, Influence, Coping and Prevention of Internet Addiction and General Information of Internet Use. These results were revealed that middle school students had comprehensive education needs for Internet Addiction. Also, there were the difference of need contents and frequency between school boy and girl students. Most of students had high educational needs for Internet addiction based on school health care program. Conclusion: It would be necessary to develop on Internet addiction prevention program for adolescents concerning these findings. In the future, there should be study to identify the psychological characteristics of adolescent associated with Internet addiction.

• Korean Journal of Occupational Health Nursing
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• v.21 no.3
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• pp.184-191
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• 2012

Purpose: This study was to examine the effects of 3 domains of continuing education (CE) for healthcare managers. Methods: A group of 20 healthcare managers, attending 3 levels of CE, were the subjects. The data were collected by structured questionnaires before and after each education. The data were analyzed by Friedman test, Wilcoxon Signed Ranked Test, and Bonferroni correction. Results: After completing CE, there was significant improvement on the scores of knowledge, attitude, and skills. Conclusion: This study suggests that CE for healthcare managers is an effective strategy to promote the competency of healthcare managers, who take care of the chronically ill patients.