• Advances in concrete construction
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• v.16 no.6
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• pp.317-325
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• 2023

Strength prediction and correlation of concrete is done using experimental and analytical methods. Main objective is to correlate the experimental and simulated values of compressive strength of concrete mix using Fly Ash (FA) and Silica Fume (SF) by partial replacement of cement in concrete. Mix proportion was determined using IS method for M40grade concrete. Hundred and forty-seven cubes were cast and tested using Universal Testing Machine (UTM). Genetic Algorithm (GA) model was developed using C++ program to simulate the compressive strength of concrete for various proportions of FA and SF replacements individually at 3% increments. Experiments reveal that 12 percent silica fume replacement produced maximum compressive strength of 35.5 N/mm², 44.5 N/mm² and 54.8 N/mm² moreover 9 percent fly ash replacement produced a maximum strength of 31.9 N/mm², 37.6 N/mm² and 51.8 N/mm² during individual material replacement of concrete mix. Correlation coefficient for each curing period of fly ash and silica fume replaced mix were acquired using trend lines. The correlation coefficient is found to be approximately 0.9 in FA and SF replaced mix irrespective of the mix proportion and age of concrete. A higher and positive correlation was found between the experimental and simulated values irrespective of the curing period in all the replacements.

• Journal of the Korean Society for Nondestructive Testing
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• v.11 no.2
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• pp.22-31
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• 1991

Various types of ultrasonic techniques have been used for the estimation of compressive strength of concrete structures. However, conventional ultrasonic velocity method using only longitudial wave cannot be determined the compressive strength of concrete structures with accuracy. In this paper, by using the introduction of multiple parameter, e. g. velocity of shear wave, velocity of longitudinal wave, attenuation coefficient of shear wave, attenuation coefficient of longitudinal wave, combination condition, age and preservation method, multiple regression analysis method was applied to the determination of compressive strength of concrete structures. The experimental results show that velocity of shear wave can be estimated compressive strength of concrete with more accuracy compared with the velocity of longitudinal wave, accuracy of estimated error range of compressive strength of concrete structures can be enhanced within the range of ${\pm}$10% approximately.

• Korean Journal of Psychosomatic Medicine
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• v.3 no.1
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• pp.49-57
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• 1995

To evaluate body image disturbance in Korea, the Body Image Scale(BIS) was developed and it's reliability and validity was tested. The BIS was administered to 33 subjects of normal controls and 64 patients consisting of mainly neurotic patients. The correlation coefficient, of test-retest reliability with an interval of 2 weeks was 0.88 and internal consistency coefficient Cronbach's alpha, was 0.80. Discriminant validity test indicated that there were significant differences in total BIS score between normal control group and psychiatric patients group after controlling the effects of age, sex, and educational level. Factor analysis showed two distinct dimensions, namely 'physical appearance' and 'physical health and strength'. The BIS appears to be a reliable, internally consistent and valid scale which can be used for assessing body image in Korea pupulations.

• Journal of the Korean Society of Clothing and Textiles
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• v.27 no.11
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• pp.1307-1317
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• 2003

The level of consumer knowledge has been gradually increased with the growth of living standard of consumer and the development of communication technology. The purpose of this study was to investigate the structure and measure of consumer knowledge and to find out relationship between objective knowledge and subjective knowledge. The subjects of this study were female adults from theirs twenties to theirs forties who lived in Seoul, Kyunggi or Incheon areas and Quota sampling method was used age and areas. The data were obtained from 603 questionnaires. Data were statistically analyzed using SPSS 10 and major statistical methods are mean, frequency, Pearson correlation coefficient, and Cronbach's $\alpha$ coefficient. The results are as follows: 1. Objective knowledge consisted of the product knowledge, brand knowledge, purchase knowledge and usage knowledge, and subjective knowledge consisted of experience and self-evaluation knowledge. 2. Consumer knowledge was related to the subjective knowledge and objective knowledge. But, there was relatively a low relationship between subjective knowledge and objective knowledge of apparel.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.6
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• pp.13-19
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• 2004

This study was performed to evaluate permeable properties of eco-concrete using soil, natural coarse aggregate, soil compound and polypropylene fiber. The fIexural strength, ultrasonic pulse velocity and dynamic modulus of elasticity were increased with increasing the content of coarse aggregate, soil compound and polypropylene fiber. The flexural strength, ultrasonic pulse velocity and dynamic modulus of elasticity were 259 MPa, 3,527 m/s and 275 ${\times}$ 102 MPa at the curing age of 28 days, respectively. The coefficient of permeability was decreased with increasing the content of coarse aggregate and soil compound, but it was increased with increasing the content of polypropylene fiber. Accordingly, this concrete can be used for farm road.

• Journal of the Korean Home Economics Association
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• v.20 no.2
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• pp.135-140
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• 1982

As a step preliminary to the factor-analysis of a child-rearing attitude scale under construction, its preliminary form containing a total of 368 self-answered questions was administerd to 88 married women with one or more children in the grade school age. all graduates of colleges and in possession of a home telephone and a house, twice from one week apart. The test-retest correlation coefficients, calculated for each test item based on the subject's choice among the three response alternatives on two test ocasions, ranged from .80 to .10. The cut-off point of r=.41 or lower led to the elimination of 48 items. As a point of incidental interest, the rate of response concordance. The namber of subjects giving the same categroy response on two occasions was calculated for each item and it was correlated with its test. retest correlation coefficient. The two different indices of item test-retest reliability were found not related to each other. Empirical evidence, as well as rational justifications, was presented to show that the correlation coefficient is the better of the tow indices of item test-retest reliability.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.87-91
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• 2009

Recycling demolished concrete as an alternative source of coarse aggregates for the production of new concrete can help solve the growing waste disposal crisis and the problem of depleted natural aggregates. The purpose of this study is to investigate chloride migration of recycled aggregate concrete containing pozzolanic materials by chloride migration coefficient. The specimens were made with recycled coarse aggregate as various replacement ratio(10, 30, 50%) and metakaolin, blast furnace slag, fly ash is replaced for recycled concrete with mixing ratio 20%. The major results are as follows. 1) Compressive strength of recycled aggregate concrete containing pozzolanic materials increase as curing age and chloride migration decrease. 2) When the replacement ratio of recycled coarse aggregate is 30%, the chloride migration coefficient of recycled concrete containing blast furnace slag, metakaolin shows the similar or lower value than plain concrete at all ages.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.549-552
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• 2006

Deicing salt has been generally used for prevention of a road freezing in winter, and the amount is increasing every year. However, deicing salt may induce the decrease of bond strength, surface scaling, and environmental pollution, etc. The purpose of this paper is to suggest the fundamental data on safety and durability for concrete structures through the estimation of characteristics of chloride penetration with deicer types. According to the test results, as age of concrete is increased, chloride penetration depth is also increased independent of deicer types. However, there is no remarkable difference between deicer types. And when the estimation of chloride diffusion is carried out by immersion test, diffusion coefficient is decreased with ages, and short-term estimation may overestimate the coefficient.

• Communications for Statistical Applications and Methods
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• v.12 no.2
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• pp.381-394
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• 2005

In order to estimate the damage of orchards due' to natural disasters such as typhoon, severe rain, freezing or frost, it is necessary to estimate the number of fruit bearing before and after the damage. To estimate the fruit bearing after the damages are easily done by delegations, but it cost too high to survey every insured farm household and calculate the fruit bearing before the damage. In this article, we suggest to use a random coefficient model to predict the numbers of fruit bearing in the orchards before the damage based on the tree age and the area information.

• Women's Health Nursing
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• v.12 no.3
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• pp.204-209
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• 2006

Purpose: The Edinbergh Postnatal Depression Scale (EPDS) has seen widespread use in epidemiological and clinical studies. The objective of this research was to translate and to test the reliability and validity of the 10-item EDPS in Korea. Methods: Subjects were 145 women who were 6 to 10 weeks post delivery. To test reliability, the internal consistency was assessed by Cronbach's alpha coefficient. Validity testing was performed using convergent validity by Pearson's correlation. Data was gathered at 3 hospitals during Oct. 2005 after obtaining an informed consent. Result: The mean age of the subjects was 29.9 years. and the mean parity was 1.46 times. The mean EPDS score was 18.4. Reliability analysis showed a satisfactory result (Cronbach's alpha coefficient=.84). There were significant positive correlations between EPDS and Mills postnatal depression and anxiety check list scores as expected(r=.69, p<.001) and thus supported convergent validity. Conclusion: The study findings showed that the Korean version of the EPDS-10 is a reliable and valid instrument that can be used for measuring postnatal depression in Korea.