• Journal of the Korea Concrete Institute
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• v.13 no.3
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• pp.195-205
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• 2001

This Paper describes a numerical method to evaluate the flexural strength of reinforced concrete members exposed to fire. An analytical method is developed for the moment-curvature relationship for the cross section which is subjected to high temperature. The method performs heat-transfer analysis for the cross sections and subsequently performs numerical analysis using the stress-strain relationships of concrete and reinforcing steel in various heat conditions. The results of the numerical studies are ; 1) the residual flexural strength exposing at high temperature is affected by the heating time, the depth of concrete cover and reinforcement ratio, 2) the residual flexural strength after exposed at high temperature is recovered of its original strength at minimum ratio of reinforcement, while members having half of maximum ratio and maximum ratio of reinforcement do not recover its original strength, 3) furthermore, the concrete may reach its maximum capacity before reinforcement yields in reinforced concrete members having maximum ratio of reinforcement.

• Journal of the Korean Society of School Health
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• v.33 no.3
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• pp.203-212
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• 2020

Purpose: The purpose of this study was to investigate the relationship between relative handgrip strength (HGS/BMI) and obesity (BMI above 95th percentile) in adolescents. Methods: The subjects of the study were 637 out of 701 adolescents aged 10~18 who participated in the 2018 National Health and Nutrition Survey (KNHANES), excluding those with missing values in body mass index (BMI) and handgrip strength (HGS). The relative handgrip strength (HGS/BMI) value was divided by quartile and composite sample logistic regression analysis was performed to see its relationship with obesity (BMI above 95th percentile). The collected data were analyzed using SPSS 18.0. Results: As a result of analyzing HGS according to gender-specific quartiles, age, height, and weight of male adolescents increased significantly as HGS/BMI increased (p trend<.001). In addition, as HGS/BMI increased, total cholesterol, triglycerides, and HDL cholesterol decreased significantly (p trend<.001). In the case of female adolescents, age and height increased significantly as HGS/BMI increased (p trend<.001). HGS/BMI was lower in the obese group (p=.023), while total cholesterol was higher in the obese group(BMI above 95th percentile) than in the non-obese group. As a result of the composite sample logistic regression analysis, the odds ratio (OR) decreased significantly as the quartile increased in both male and female adolescents. Conclusion: According to these results, a follow-up study is needed to confirm the factors affecting muscle strength of adolescents. In addition, this study intends to be used as basic data to conduct further research and to develop programs that can improve muscle strength and reduce obesity in adolescents.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.683-692
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• 2023

This research assesses the mechanical properties of concrete, utilizing both normal and lightweight aggregates, through measurements of compressive strength and ultrasonic pulse velocity. The study observed that concrete with normal aggregates exhibited higher compressive strength in its initial stages, whereas concrete with lightweight aggregates showed increased strength over time, likely attributed to the higher water absorption rate of lightweight aggregates. Ultrasonic pulse velocity generally registered higher in normal aggregate concrete, barring a specific duration, presumably due to variations in the internal pore structure of the aggregates. The correlation coefficient(R²) for the strength prediction equation, derived from the relationship between compressive strength and ultrasonic pulse velocity, exceeds 0.95. This high correlation suggests that the predictive equation based on these experimental findings is a reliable method for estimating concrete strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.77-82
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• 1994

The maturity concept proposes that concrete of the same mix at the same maturity has the same strength, whatever combination of temperature and time makes up that maturity. Maturity is the integral of time and temperature of concrete above a datum temperature. Tests are conducted in order to determine a datum temperature and to measure compressive strengths and maturity of test specimens. This study also proposes some appropriate functions to represent the relationship between maturity and strength development.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.169-174
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• 2002

We can consider that the study on early evaluation of compressive strength and durability of concrete is useful to raise safety of quality control of concrete. In this paper, was proposed to method early to predict strength and durability of concrete with parameter, such as Water/cement(W/C) ratio and steam curing conditions. Through analyzing the relationship between the compressive strength and the amount of chloride penetration into concrete specimens, a new formula early estimating durability of the concrete structure was suggested.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.321-329
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• 2013

Recently, the medium-low level radioactive waste from nuclear power plant must be transported from temporary storage to the final repository. Medium-low level radioactive waste, which is composed mainly of the liquid ion exchange resin, has been consolidated with cementitious material in the plastic or iron container. Since cementitious material is brittle, it would generate cracks by impact load during transportation, signifying leakage of radioactive ray. In order to design the safety transporting equipment, there is a need to check the compressive strength of the current waste. However, because it is impossible to measure strength by direct method due to leakage of radioactive ray, we will estimate the strength indirectly by the dynamic modulus of elasticity. Therefore, it must be identified the relationship between of strength and dynamic modulus of elasticity. According to the waste acceptance criteria, the compressive strength of cement based solid is defined as more than 3.44 MPa (500 psi). Compressive strength of the present solid is likely to be significantly higher than this baseline because of continuous hydration of cement during long period. On this background, we have tried to produce the specimens of the 28 day's compressive strength of 3 to 30 MPa having the same material composition as the solid product for the medium-low level radioactive waste, and analyze the relationship between the strength and the dynamic modulus of elasticity. By controling the addition rates of AE agent, we made the mixture containing the ion exchange resin and showing the target compressive strength (3~30 MPa). The dynamic modulus of elasticity of this mixtures is 4.1~10.2 GPa, about 20 GPa lower in the equivalent compressive strength level than that of ordinary concrete, and increasing the discrepancy according to increase strength. The compressive strength and the dynamic modulus of elasticity show the liner relationship.

• Journal of Convergence for Information Technology
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• v.11 no.5
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• pp.242-250
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• 2021

The subjects of this study were 514 people aged 65 and older who voluntarily participated in the senior welfare center in Seoul and Gyeonggi. The purpose of this study is to analyze the relationship between muscular strength, cognitive function, activities of daily living, depression variables of elderly people in a comprehensive evaluation. As for the data collection methods, were measured the upper and lower body strength, grip strength(left, right), cognitive function(mini-mental state examination, trail marking test, digit span test, stroop test), activities of daily living and depression was measured using a questionnaire. The results are as follows First, there was a statistically significant correlation between the elderly's muscular strength, cognitive function, daily living ability, and depression. Second, the statistical significance was found among all the variables as a result of the analysis of the elderly's integrated muscular strength, cognitive function, activities of daily living and depression. This study can provide basic data for successful aging and independent retirement life of the elderly by confirming the relationship between the elderly's muscular strength, cognitive function, Activities of daily living, and depression.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.1-12
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• 2017

This paper concerns the structural behavior of high-strength concrete beams with compressive strength of 80 MPa subjected to flexure. Main test variables were nominal yielding strength of longitudinal rebar including normal strength rebar(SD 400) and high strength rebar(SD 600), reinforcement ratio from 0.98 to 1.58% and beam section size with $200{\times}250$, $200{\times}300mm$. The nine beams were cast and tested under flexure. The study investigated ultimate flexural strength, load-deflection relationship, crack patterns, failure patterns and ductility of the test beams. Test results indicate that when rebar ratio increased flexural strength increased and ductility decreased. In addition, the number of cracks increased and the crack width decreased as the reinforcement ratio increased. The yield strength of rebar did not affect significantly load-crack width relationship. Nonlinear analysis of test beams was performed and then test results and analytical results of ultimate load were compared. Analytical results of high-strength concrete beams overall underestimated flexural strength of test beams.

• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.12
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• pp.1412-1423
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• 2003

본 연구는 소비자-기업간 관계마케팅모델을 개발하는 데 주된 목적을 갖고 있다. 본 연구모델은 소비자를 단순한 환경변수의 하나로 인식해왔던 기존 마케팅의 통합적 관점을 비판하고 소비자를 사업의 동반자로써 인식하는 소비자 중심의 관계마케팅 모델을 제안하였다. 소비자 중심의 관계모델은 소비자를 기업 이익의 원천으로 보는 통합적 관점이 아닌, 소비자를 사업관계의 동반자로 인식하는 내부화 (internalization)를 관계마케팅의 궁극적인 목표로 제시하였다. 소비자들의 관계 내부화를 위한 관계강도(relationship strength)와 4개의 선행변수-analogy, approbation, availability, stakes-로 구성된 관계마케팅구조방정식 모델을 유통경로의 최종 단계인 소비자-소매업자(C-R)그리고 소비자-제조업자(C-M)관계에 적용하였다 서울의 5개 백화점 소비자들로부터 수집된 자료는 AMOS 4.0과 SPSS 10.0프로그램을 통해 분석한 결과, 본 연구의 제안모델은 통계적으로 검증되었고, 검증된 결과는 나아가 소매업자-소비자-제조업자의 3자 네트웍을 바탕으로 한 총체적 관점의 관계 내부화 모델 설계를 위한 하나의 실증 예로 사용 될 수 있음을 시사하고 있다.

• Journal of Information Technology Applications and Management
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• v.19 no.4
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• pp.1-18
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• 2012

This paper identifies technology trends of national research and development (national R&D) by exploiting Korean national R&D patents, ranging from 2007 to 2010. In this paper, co-word analysis (CWA), which is a method to identify the relationship among technology terms by using their co-occurrences, is incorporated into network analysis to visualize the relationships among technology keywords of national R&D patents and calculate network indexes concerning inter-relationship diversity and strength of technology keywords. As a result, this research found that inter-relationship among technology keywords in national R&D are getting increasingly strengthening in an overall sense. In addition, the keyword inter-relationship diversity-strength map proposed in this paper revealed some significant technological keywords of national R&D : core technology keywords including "sensor", "film" and "fuel" and emerging keywords including "biosensor" and "thermoelectric". Because the proposed approach helps identify interdisciplinary trends of technology keywords from a massive volume of national R&D patents in a visual and quantitative way, we expect that the approach can be incorporated as a preliminary into the R&D planning process to assist R&D policy makers to understand technology convergence of national R&D and develop relevant R&D policies.