• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.467-469
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• 2009

In this study, fatigue samples were prepared from cylinder head parts that are actually used in domestic (A) and foreign (B) automobiles; high-temperature, high-cycle, and low-cycle fatigue characteristics were then evaluated and compared. A study on the correlation between the microstructural factor and high temperature fatigue characteristic was attempted. The chemical compositions of the heat resistant aluminum alloys above represented A356 (A) and A319 (B), respectively. The result of the tensile strength test on material B at $250^{\circ}C$ was higher by 30.8MPa compared to material A. On the other hand, elongation was 8.5% higher for material A. At $130{\circ}C$, material B exhibited high fatigue life given high cycle fatigue under high stress, whereas material A showed high fatigue life when stress was lowered. With regard to the low-cycle fatigue result ($250^{\circ}C$) showing higher fatigue life as ductility is increased, material A demonstrated higher fatigue life. Through the observation of the differences in microstructure and the fatigue fracture surface, an attempt to explain the high-temperature fatigue deformation behavior of the materials was made.

• 한국치위생학회지
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• 제17권5호
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• pp.889-898
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• 2017

Objectives: This study was conducted in order to identify the various influencing factors of dental caries according to the socio-economic characteristics and oral health behaviors across the life cycle among Koreans. Methods: The data were extracted from the 6th Korea National Health and Nutrition Examination Survey (2013-2015) and a total of 4,871 subjects with ages of 7 and over were selected. The data were analyzed using SPSS 21.0 for ${\chi}^2$-test and multi-logistic regression. Results: Significant differences were observed in the socio-economic characteristics, health behaviors and in the dental caries across the life cycle. The influencing factors of DT includes the type of health insurance (p<0.05) in school aged & adolescence, Oral health examination/year (p<0.01), Residence (p<0.05) in early adults, type of health insurance (p<0.001), Oral health examination/year (p<0.001), use of oral hygiene products (p<0.01) in late Adults, Oral health examination/year (p<0.05) and Gender (p<0.05) in old age. Conclusions: This study suggests that dental health promotion can be enhanced by regular checkup. The government must provide the people with better quality of oral health care and promotion across the life cycle in the near future.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2004년도 추계학술대회
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• pp.229-235
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• 2004

This paper treats accelerated life tests for automotive connector. The contact resistance of connector is explained by some factors; the use time(calender time, real cycle), stresses and loads adapted in auto test. The relationships between contact resistance and some factors are compared and analyzed by regression models in various test conditions; field use-environment, manufacturer's test environment, and accelerated test condition. The consistency between of manufacturer's test and field test is examined. Finally, the future study on accelerated test for automotive connector is presented.

• 가정과삶의질연구
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• 제10권1호통권19호
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• pp.53-74
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• 1992

The purpose of this study was to analyse the factors that influence marital conflicts and family life statisfaction, and to predict the future stage of establishment family and extending family, bsed on the theretical model by system approach. For this pourpose, 336 couples of urban households in Seoul were selected. The data were analysed through statistical methods such as, Frequency, percentile, T-test, F-test, ANOVA, Pearson's correlation analysis. The results were as follow : The Martial Conflict and family life satisfaction of surveyed couples were above middle level. It had significantly differences according to family life cycle, husband and wife's educationed levels, husband and wife's occupations, and family income. And Family life satisfaction had significantly differences according to marital conflict. The marital conflict is higher, life satisfaction is lower. In this study, it were appeared that the amount of marital conflict and life satisfaction had differences according to life cycle stages, husband and wife's educational level, husband and wife occupations, and family income, and so that the conflict of phsycho-social system was more affected on family life satisfaction that of managerial system. Such results were indicated that the birth of children was the critical family event affecting on family life satisfaction on and the marital conflict. But the conflict by family's given resources and situational differences also as an environment affection on the family system.

• 가정과삶의질연구
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• 제7권2호
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• pp.163-178
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• 1989

This study was mainly concerned providing a basic of data for the more reasonable home management. The purpose study was to investigate the relationship of husbands and wives self-actualization and degree of joint decision-making. For the purpose of this study 500 questionaire were distributed to the marital in seoul. The 412 data were analized by Frequency, Percentage, T-test, ANOVA, Scheffe-test. The major findings of this study were as follows: 1) Over one and half of husbands and wives are try to be self-actualized. 2) The tendency of the husbands and wives decision-making was joint decision-making. 3) The important influential variables on the husbands and wives self-actualization husbands were age, life-cycle, job employment motivation. And wives were life-cycle, education, income, job, employment motivation. 4) The important influential variables on the joint decision-making were age, number of child, life-cycle. 5) A marital joint decision-making level differs significantly, according to the degree of husbands and wives self-actualization. The higher level of husbands and wives self-actualization, the higher degree of marital joint decision-making. The result of this study implies that a marital joint-making necessary in order to carry on happy home management and the reasonable home administration.

• Steel and Composite Structures
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• 제34권1호
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• pp.35-51
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• 2020

Integral abutment bridges (IABs) are those bridges without expansion joints. A single row of steel H-piles (SHPs) is commonly used at the thin and stub abutments of IABs to form a flexible support system at the bridge ends to accommodate thermal-induced displacement of the bridge. Consequently, as the IAB expands and contracts due to temperature variations, the SHPs supporting the abutments are subjected to cyclic lateral (longitudinal) displacements, which may eventually lead to low-cycle fatigue (LCF) failure of the piles. In this paper, the potential of using finite element (FE) modeling techniques to estimate the LCF life of SHPs commonly used in IABs is investigated. For this purpose, first, experimental tests are conducted on several SHP specimens to determine their LCF life under thermal-induced cyclic flexural strains. In the experimental tests, the specimens are subjected to longitudinal displacements (or flexural strain cycles) with various amplitudes in the absence and presence of a typical axial load. Next, nonlinear FE models of the tested SHP specimens are developed using the computer program ANSYS to investigate the possibility of using such numerical models to predict the LCF life of SHPs commonly used in IABs. The comparison of FE analysis results with the experimental test results revealed that the FE analysis results are in close agreement with the experimental test results. Thus, FE modeling techniques similar to that used in this research study may be used to predict the LCF life of SHP commonly used in IABs.

• International Journal of Automotive Technology
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• 제5권4호
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• pp.297-302
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• 2004

This paper presents the low cycle thermal fatigue of the engine exhaust manifold subject to thermo-mechanical cyclic loading. As a failure of the exhaust manifold is mainly caused by geometric constraints of the less expanded inlet flange and cylinder head, the analysis is based on the exhaust system model with three-dimensional temperature distribution and temperature dependent material properties. The result show that large compressive plastic deformations are generated at an elevated temperature of the exhaust manifold and tensile stresses are remained in several critical zones at a cold condition. From the repetition of these thermal shock cycles, maximum plastic strain range (0.454%) could be estimated by the stabilized stress-strain hysteresis loops. It is used to predict the low cycle thermal fatigue life of the exhaust manifold for the thermal shock test.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2001년도 정기학술대회
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• pp.91-97
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• 2001

These Study are for the development of the reliability assessment test code and test equipment and test procedures of the heavy sluice gate hydraulic cylinder. Because there is no reliability test code for the heavy sluice gate hydraulic cylinder inside and outside of the country, the modified reliability test code is made reference for the related existing standards like as ISO, JIS, MIL, TUV, DIN, KS and etc. In this study, the novel method is proposed to evaluate efficiency of the heavy sluice gate hydraulic cylinder on the loading conditions and established the conditions of the acceleration life test to reduce the testing time and cycles. The testing equipments for life test, lode operating test, high and low temperature test and salt spray test have been established for 8 month, and the reliability tests are accomplished. The test results of the heavy sluice gate hydraulic cylinder which is produced and tested initially in Korea are satisfied the durability life cycle on the using conditions.

• Steel and Composite Structures
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• 제33권6호
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• pp.777-792
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• 2019

This paper presents a new efficient approach to estimate the S-N type fatigue life assessment curve for S550 high strength steels under low-cycle actions at -60℃. The proposed approach combines a single set of monotonic tension test and one set of fatigue tests to determine the key material damage parameters in the continuum damage mechanics framework. The experimental program in this study examines both the material response under low-cycle actions. The microstructural mechanisms revealed by the Scanning Electron Microscopy (SEM) at the low temperature, furthermore, characterizes the effect due to different strain ratios and low temperature on the low-cycle fatigue life of S550 steels. Anchored on the experimental results, this study validates the S-N curve determined from the proposed approach. The S-N type curve determined from one set of fatigue tests and one set of monotonic tension tests estimates the fatigue life of all specimens under different strain ratios satisfactorily.

• International journal of advanced smart convergence
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• 제11권4호
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• pp.104-119
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• 2022

Life safety awareness level diagnosis is necessary for customized safety education and continuous safety awareness. As the starting stage of safety education for each life cycle, a scale that has verified the reliability and validity of high school students' life safety awareness has not yet been developed. In this context, the purpose of this study is to develop and validate the life safety awareness scale of high school students and to analyze interindividual differences. Questionnaire data was collected from April to June 2022 from 834 students in the first, second, and third grades of high schools in △△ city in Jeollabuk-do. A final 25-item scale was developed using the preliminary survey, preliminary test, the main test, descriptive statistical analysis, and exploratory and confirmatory factor analysis. This scale consists of four sub-factors: 'safety prevention', 'safety knowledge', 'safety preparation', and 'safety protection'. Good reliability and validity were verified by analysis of content validity and construct validity. The generalizability of the scale was verified by crossover validation between the search group and the crossover group. Based on the interindividual differences analysis, although there was a difference between genders in life safety awareness, there was no difference by grade level and academic achievement. This study is significant in developing the first valid scale that can measure high school students' life safety awareness and providing the necessity and rationale for life safety education by life cycle considering individual gender differences.