• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.169-172
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• 2005

A flywheel system is an electromechanical energy storage device that stores energy by rotating a rotor. The rotating part, supported by magnetic bearings, consists of the metallic shaft, composite rims of fiber-reinforced materials, and a hub that connects the rotor to the shaft. The delamination in the fiber wound composite rotor often lowered the performance of the flywheel energy storage system. In this work, an advanced hybrid composite rotor with a split hub was designed to both overcome the delamination problem in composite rim and prevent separation between composite rim and metallic shaft within all range of rotational speed. It was analyzed using a three-dimensional finite clement method. In order to demonstrate the predominant perfom1ance of the hybrid composite rotor with a split hub, a high spin test was performed up to 40,000 rpm. Four radial strains and another four circumferential strains were measured using a wireless telemetry system. These measured strains were in excellent agreement with the FE analysis. Most importantly, the radial strains were reduced using the hybrid composite rotor with a split hub, and all of them were compressive. As a conclusion, a compressive pressure on the inner surface of the proposed flywheel rotor was achieved, and it can lower the radial stresses within the composite rotor, enhancing the performance of the flywheel rotor.

• The Mathematical Education
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• v.58 no.4
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• pp.507-518
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• 2019

The OECD launched the Education 2030 project to develop a learning framework and to conduct the international comparative study on curriculum. As a part of the OECD international curriculum analysis, Korea Institute for Curriculum and Evaluation(KICE) conducted a main study of Curriculum Content Mapping (hereafter, CCM) in the 7 learning areas/subject areas such as national languages, mathematics, humanities/social sciences, natural science, physical education/health, arts, and technologies. The CCM study aimed to identify how the competencies on CCM framework were reflected in the Korea curriculum. For this purpose, KICE identified the competencies on CCM framework, revised the coding framework, and undertook the mapping process. In this study, we gathered the CCM data as an evidence of how competencies on CCM framework were embedded in the 2015 revised mathematics curriculum. For this purpose, experts in mathematics education undertook the mapping process, we summarized the results of CCM main study in mathematics. As the results, numeracy, critical thinking, problem solving, anticipation, action, reflection were perfectly embedded in the 2015 revised mathematics curriculum. the competencies on CCM framework were embedded in the 2015 revised mathematics curriculum, and but literacy, physical/health literacy, trust, learning to learn, reconciling tension and dilemmas, literacy for sustainable development, financial literacy, and entrepreneurship/enterprising were not clearly related to mathematics curriculum. The mapping results should help the Korea Ministry of Education and KICE for preparing the future curriculum revision and development.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.453-462
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• 1990

The interaction of forced convection-conduction with thermal radiation in laminar boundary layer over a plate fin is studied numerically. The analysis is based on complete solution whereby the heat conduction equation for the fin is solved simultaneously with the conservation equations for mass, momentum and energy in the fluid boundary layer adjacent to the fin. The fluid is a gray medium and diffusion(Rosseland) approximation is used to describe the radiative heat flux in the energy equation. The resulting boundary value problem are convection-conduction parameter N$_{c}$ and radiation-conduction parameter m, Prandtl number Pr. Numerical results are presented for gases with the Prandtl numbers of 0.7 & 5 with values of N$_{c}$ and M ranging from 0 to 10 respectively. The object of this study is to provide the first results on forced convection-radiation interaction in boundary layer flow over a semi-infinite flay plate which can be used for comparisons with future studies that will consider a more accurate expression for the radiative heat flux. The agreement of the results from the complete solution presented by E. M. Sparrow and those from this paper for the special case of M=0 is good. The overall rate of heat transfer from the fin considering radiative effect is higher than that from the fin neglecting radiative effect. The local heat transfer coefficient with radiative effect is higher than that without radiative effect. In the direction from tip to base, those coefficients decrease at first, attain minimum, and then increase. The larger values of N$_{c}$ M, Pr give rise to larger fin temperature variations and the fin temperature without radiative effect is always higher than that with radiative effect.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.4
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• pp.353-360
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• 2011

The prediction of binary droplet collisions is important in the formation of falling drops and the evolution of sprays. The droplet velocity, impact parameter, and drop-size ratio influence the interaction between the droplets. The effect of these parameters results in complicated collision phenomena. Droplet collisions can be classified into four types of interactions: bouncing, coalescence, reflexive separation, and stretching separation. In the present study, the interfacial flow problem of the droplet collision was numerically simulated by using the level set method. 2D axisymmetric simulations on the head-on collisions and 3D simulation on the off-center collisions were performed. The numerical results of droplet behavior after the collision agreed well with the experimental and analytical results. The mixing of the mass of the initial droplets after the collision was also predicted by using different species index of colliding droplets.

• Journal of the Korean School Mathematics Society
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• v.9 no.1
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• pp.19-40
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• 2006

There are various efforts to alleviate problems about the learning disabilities each year, however, the number of the learning disabilities has been increasing. Therefore, we need to consider and develop practical methods to help them. In this aspect, we review and examine previous research regarding the learning disabilities which are known to be general and comprehensive. Then we suggest math clinic as one of the methods to alleviate the problem. There are purposes of the math clinic. The first is to make a comprehensive diagnosis for basic (emotional, environmental, psychological) reasons as well as the learning anxiety; not only the lower achievement in learning. The second is to provide them suitable corrective programs which would help them to gain a better understanding about mathematics and a positive learning attitude. The third is to provide them applicabilities in their learning and potentialities so that we have given them foundation in mathematics. In this article, we operate math clinic for the learning disabilities, and then make an analysis of the student's error occurred in learning, and finally we suggest a demonstrative operating program of math clinic for learning disabilities.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.497-503
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• 2016

In this study, we formulate an acoustical topology optimization problem to optimally design a partition layout inside the expansion chamber of a muffler. The lower-limit insertion loss value at a target frequency is constrained, and the partition volume is selected as an object function. In this study, we calculate the insertion loss outside the duct, while to determine the noise-attenuation performance, we use the insertion loss value calculated inside the duct or transmission loss value obtained in a previous study. We employ the finite-element model for acoustical analysis, and we determine the transmission of an incident acoustic wave through each finite element using the functions of design variables that change continuously between "0" and "1." The rigid body elements, which totally reflect incident waves, build up partitions. Finally, we compare optimal topologies that depend on the target frequency and the allowed lower-limit value of insertion loss.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.85-96
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• 2020

The effect of an aluminum scrap addition ratio on the tensile and solidification cracking properties of the AC4A aluminum alloy in the as-cast state and heat-treated state were investigated in this study. Generally, the expected problem of using scrap in aluminum casting is an increase of hydrogen and Fe element inside the aluminum melt. Another issue is an oxide film which has a weak interface with the molten aluminum and acts as potent nucleation sites for internal porosity and crack initiation. Solidification cracking is one of the critical defects that must be resolved to produce high quality castings. A conventional evaluation method for solidification cracking is a relative and qualitative analysis method which does not provide quantitative data on the thermal stress in the solidification process. Therefore, a newly designed solidification cracking test apparatus was used in this study, and the device can provide quantitative data. As a result, after conducting experiments with different scrap addition ratios (0%, 20%, 35%, 50%), the tensile strengths and elongations in the as-cast state were 214, 187.7, 182.1 and 170.4MPa and 4.6%, 3.4%, 3.1% and 2.3%, respectively. In the case of the T6 heat-treated state, the tensile strengths and elongations were 314.9, 294.6, 293.1 and 271.1MPa and 5.4%, 4.6%, 3.8% and 3.1%, respectively. The strength of the solidification cracking was 3.1, 2.4, 2.2and 1.6MPa as the scrap addition ratio increases.

• Asian Oncology Nursing
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• v.3 no.2
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• pp.103-111
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• 2003

The purpose of this study was to identify the effect of imagery therapy on "coping mechanism and type C personality of the women with mastectomy. To achieve this purpose, 2 hours sessions of imagery therapy were given to the patients with breast cancer twice a week for 6 weeks. The period of data collection was from July, 7th to August, 12th 2002. The participants were 30 patients, 15 experimental group, 15 control group who were treated at the G University hospital in J City. This study was designed using a quasi-experimental approach with non-equivalent Pre test-Post test Design. The themes for the Imagery Therapy Program were composed of Leuner's(1969) 12 Imagery Themes: flower, green-field, stream, mountain, house, woods, significant figures, rose, lion, ideal self-image, cave and volcano. The data were analyzed with ${\chi}2-test$ and MANOVA using the SPSS program. The course of image change of the 12 imagery themes was analyzed by content analysis. The results of this study are as follows: First Hypothesis, 'The score of type C personality in the women with mastectomy who received imagery therapy will be significantly lower than that of the control group' was supported(p<.05). Second Hypothesis, 'The score of coping mechanism' in the women with mastectomy who received imagery therapy will be significantly higher than that of the control group' was rejected. In conclusion, imagery therapy is suggested as an effective nursing intervention to change type C personality of the women with mastectomy, but not effective to improve coping mechanism. Therefore, the program for the women with mastectomy should be developed to change their coping mechanism, method of problem solving and Quality of life.

• The Journal of Pediatrics of Korean Medicine
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• v.18 no.2
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• pp.119-126
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• 2004

Objective : We used herbal medicine to treat various disease and also to keep good general condition of children. We aimed to evaluate the effect of herbal medicine on the growth of children treated with herbal medicine. Method: We studied 187 children who visited the department of Pediatrics, KyungHee Oriental Medical Hospital from March 2004 to August 2004. They meet condition as follows; they were treated for more than 6 months and they visited our clinic more than 3 times. Whenever patients visited our hospital, we measured their height, body weight and obesity degree using DS-102(dszenix, Seoul). We measured height percentile of first time visit, and that of last time visit. And we compared them using the Growth Statistics Curve made by the Korean Association of Pediatrics, 1998. Results : The mean growth of total children showed 4.04 percentile upwardly; the growth- up percentile of boys was 4.52 and that of girls was 3.26. Analysis according to disease resulted as follows; children with respiratory disease showed 10.29 percentile growth-up, digestive disease 4.21percentile, urinary disease 4 percentile, allergic disease 2.65 percentile, weak children 2.52 percentile and other disease 3.19 percentile. Conclusion : Herbal medical treatment helped growth not only in children who took medicine for growth retardation problem but children with various disease. Moreover herbal medical treatment applied to keep good general condition of children also gave positive effect on the growth of children.

• Korean Journal of Biological Psychiatry
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• v.25 no.3
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• pp.72-78
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• 2018

Objectives The high suicide rate has risen as a main concern in South Korea. Given the complexity of the mechanism resulting in complete suicide, studies targeting various populations are needed for broader understanding of its risk factors. This study aims to analyze the factors affecting the suicidal tendency in the population of the elderly living alone in Seoul depending on basic elderly-care services. Methods A total number of 415 people participated in the study. Home-visit interviews were administered by trained interviewers. Suicidal tendency was measured by the Korean version of mini international neuropsychiatric interview (K-MINI). Health-related quality of life was measured by a brief version of the World Health Organization Quality-of-life Scale (WHOQOL-BREF). Alcohol problem was assessed by the Korean version of the alcohol use disorders identification test (AUDIT-K). Among total subjects of 415 interviewees, the actual responses of 408 people were used for the final analysis. Results The result showed that the suicide risk was high in persons isolated from social support [odds ratio (OR) = 4.49], having depression (OR = 14.85), and having low quality of life (OR = 4.39). Conclusions We found that social support, depression and health-related quality of life are associated with suicidal tendency in the elderly living alone on basic services. Our evidence will contribute to suicide prevention policy for the elderly living alone on care services.