• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.201-210
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• 2023

This study is to evaluate the ductility strengthening effect of aramid fiber sheets on piloti-type structures. Two piloti-type structure specimens were prepared and tested under statical cyclic lateral loads. The ductility strengthening effect was validated from the analysis of lateral load-displacement relationship, displacement ductility ratio, work damage index and torsion behavior. Test results showed that the post-peak behavior of piloti-type structures with columns strengthened with aramid fiber sheets tended to be ductile resulting from preventing shear failure and minimizing torsion due to the effective lateral confinement of column concrete by aramid fiber sheet. Consequently, the displacement ductility ratio and work damage index of piloti-type structures with columns with strengthened with aramid fiber sheets were 4.63 and 42.81 times higher than those of non strengthened piloti-type structures.

• Journal of The Korean Association For Science Education
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• v.29 no.8
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• pp.861-873
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• 2009

This study investigated the types of analogies generated by science-gifted students, mapping errors on the chromatography, and the perceptions on generating analogy. The subjects were science-gifted eighth-graders (N=68) enrolled at four gifted-education centers in Seoul. Analyses of the results revealed that most science-gifted students represented the analogies using verbal and pictorial forms based on concrete and everyday experiences, and they elaborately explained them including the functional attributes and the causal relationships of the target concept. Science-gifted students selected the analogies having rich similarities or similar structure and principle between the target concept and the analogy as the best of the self-generated analogies. And they used mainly their 'school life' as analogy materials. The results of the mapping test showed that many science-gifted students had mapping errors such as 'failure to map' and 'overmapping'. They were found to have the positive perceptions on generating analogy. The present study will provide the basic information to develop an instructional model in generating analogy in an education program for science-gifted students.

• Steel and Composite Structures
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• v.51 no.5
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• pp.509-527
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• 2024

Bonding carbon fiber-reinforced polymer (CFRP) laminates have been extensively employed in the restoration of steel constructions. In addition to the mechanical properties of the CFRP, the bond strength (P_U) between the CFRP and steel is often important in the eventual strengthened performance. Nonetheless, the bond behavior of the CFRP-steel (CS) interface is exceedingly complicated, with multiple failure causes, giving the P_U challenging to forecast, and the CFRP-enhanced steel structure is unsteady. In just this case, appropriate methods were established by hybridized Random Forests (RF) and support vector regression (SVR) approaches on assembled CS single-shear experiment data to foresee the P_U of CS, in which a recently established optimization algorithm named Aquila optimizer (AO) was used to tune the RF and SVR hyperparameters. In summary, the practical novelty of the article lies in its development of a reliable and efficient method for predicting bond strength at the CS interface, which has significant implications for structural rehabilitation, design optimization, risk mitigation, cost savings, and decision support in engineering practice. Moreover, the Fourier Amplitude Sensitivity Test was performed to depict each parameter's impact on the target. The order of parameter importance was t_c> L_c > E_A > t_A > E_c > b_c > f_c > f_A from largest to smallest by 0.9345 > 0.8562 > 0.79354 > 0.7289 > 0.6531 > 0.5718 > 0.4307 > 0.3657. In three training, testing, and all data phases, the superiority of AO - RF with respect to AO - SVR and MARS was obvious. In the training stage, the values of R² and VAF were slightly similar with a tiny superiority of AO - RF compared to AO - SVR with R² equal to 0.9977 and VAF equal to 99.772, but large differences with results of MARS.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.109-115
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• 2008

As structures are getting super-rise and large-sized, introducing the construction methods such as prefabrication of bar-meshes and complex method are being actively discussed to pursue the high quality of reinforced concrete, the simplification of field works, and the reduction of duration, as well as the study on how to connect reinforcing rods, which occurs while applying the same methods, is in progress Also, the pressure welded joint is a kind of method that heats the ends of reinforced bars locally and joint them, and after the pressure welding, the vulnerable part in the reinforced bar occur. Thus, in the construction field, the throughout quality control is necessary because of the delayed duration and the lowered construct ability. In this study, of the traditional lap splice method and the mechanical splice one, the screw coupler, we tried to look into through experiments the prefabrication method of bar-meshes, a typical joint method usually used for the joint parts for PSC structures applying the reinforced bar with its big diameter, and a newly-developed up-set coupler method. And we also examined the characteristic of tensile.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.79-86
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• 2008

Four RC shear wall specimens with a/d of 2.2 are designed. And a flexural retrofitting is performed for one specimen by both enlarging wall section and adding additional vertical reinforcements. Also the effectivity of jaketting wall sides is evaluated for the two methods using only steel plate or welded wire mesh with enlargement of section. Cyclic loads are applied to the retrofitted specimens according to the loading history proposed by ACI under constant axial force. Test result showed that the strength and ductility of specimen were improved where the section was enlarged after the installation of additional vertical reinforcements. Confining the ends of wall by U shape W.W.F. with enlargement of section showed most excellent structural capacity regarding to the strength and ductility. Retrofitting by using steel plate was much effective not only to protect the abrupt decrease of strength after yield but also to improve the deformation capacity.

• Journal of The Korean Association For Science Education
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• v.24 no.3
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• pp.519-531
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• 2004

In recent years, there has been an increased emphasis on performance assessment to evaluate students' abilities. Our nation has introduced a change in testing and assessment. Additional work on the efficacy, reliability, and comparability in order to develop the performance assessment item has been needed in the enforcement of the 7th National Science Curriculum. Also, criteria for professional and technical standards has been needed to be developed. The purpose of this study was to draw out various key concepts and to develop achievement standards, assessment standards and performance assessment items based on the 7th National Science Curriculum on the subject matter of reproduction(chapter 13) and biological accumulation(chapter 17). And also, this study examined the validity of completed performance assessment items based on classical test theory and polytomous item response theory. Twelve key concepts in chapter 13(reproduction) and four from chapter 17(biological accumulation) were abstracted. Twenty-six achievement standards in chapter 13(reproduction), and nine in chapter 17(biological accumulation) were developed. The achievement standards were determined in terms of knowledge(K), process skill(P) and attitude(A). Twenty-five assessment standards in chapter 13(reproduction) and nine in chapter 17(biological accumulation) were developed. Based on the developed achievement standards and assessment standards, twenty-two performance assessment items(seventeen open-ended questions, three essays, and two portfolios) with concrete grading criteria were developed. Eight open-ended items were applied to 240 10th graders to evaluate reliabilities of the test which consisted of four items per each chapter. The results would be suggested that the applied items were valid for performance assessment because item difficulties and item discriminations were proper. There was not much differences in item discrimination between interpretation from classical test theory and that from polytomous item response theory. However, there were some differences in item difficulties between the interpretations of two theories because the characteristics of examinees were reflected in classical test theory.

• Journal of the Korea Concrete Institute
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• v.18 no.1 s.91
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• pp.21-28
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• 2006

This paper presents both experimental and analytical studies for the development of an ECC(Engineered Cementitious Composites) using ground granulated blast furnace slag(slag). This material has been focused on achieving moderately high composite strength while maintaining high ductility, represented by strain-hardening behavior in uniaxial tension. In the material development, micromechanics was adopted to properly select optimized range of the composition based on steady-state cracking theory and experimental studies on matrix, and interfacial properties. A single fiber pullout test and a wedge splitting test were employed to measure the bond properties of the fiber in a matrix and the fracture toughness of mortar matrix. The addition of the slag resulted in slight increases in the frictional bond strength and the fracture toughness. Subsequent direct tensile tests demonstrate that the fiber reinforced mortar exhibited high ductile uniaxial tension behavior with a maximum strain capacity of 3.6%. Both ductility and tensile strength(~5.3 MPa) of the composite produced with slag were measured to be significantly higher than those of the composite without slag. The slag particles contribute to improving matrix strength and fiber dispersion, which is incorporated with enhanced workability attributed to the oxidized grain surface. This result suggests that, within the limited slag dosage employed in the present study, the contribution of slag particles to the workability overwhelms the side-effect of decreased potential of saturated multiple cracking.

• Journal of the Korean Society of School Health
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• v.12 no.2
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• pp.357-375
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• 1999

The purpose of this study is to find out methods to control, regulate and prevent sexual violence and provide guidelines for sex education in middle school. This study was conducted to examine factors in relation to sexuality, attitudes toward women, experience of sexual contact, frequencies and kinds of pornography with which they had contact, and sex education. For the data collection, a survey was conducted from September 25 to October 1, 1997 by using prepared questionnaires. Questionnaires were given to 503 students from three different kinds of middle schools in Seoul, Boys, Girls, and Coeducation schools. The data analyses used a PC-SAS. Each item was examined by frequencies and percentage. To compare Boys with Girls, I applied a T-test. In addition, with the kinds of school type, I applied anANOVA, ${\chi}^2$. Moreover, For investigating and analyzing each category, I categorized knowledge and attitude of sexuality, with precautionary measures of sexual violence. After that I applied T-test, ANOVA, and a Pearson's correlation for each category. The instruments of this study consisted of 9 domains. (1) General characteristics of the respondents (2) 9 questions about the interaction between he/she and his/her parent. (3) 12 questions, concerning A Scale for Attitudes of Adolescents Toward women(AWSA). (4) 26 questions related to sexual knowledge. (5) 25 questions about sexual attitude (6) strategies for prevention of sexual violence-33 questions (7) 5 questions related to sexual behavior (8) the experience of contact with pronography. (9) the experience of sex-education. The major results were summarized as follows; 1. Like many researches, This study shows that the girls are more eqalitarian than boys. The girls mean ($40.90{\pm}3.67$) is significantly higher than boys ($34.72{\pm}3.77$). Most Koreans have believed that there are many differences between men's roles and women's ones, because of confucianism which had been implied in most thought and ideas since the Lee dynasty. Therefore, the result is not surprising at all. 2. Most students answered correctly the questions of sexual knowledge. The girl's score was higher ($Mean{\pm}SD$ : $48.88{\pm}2.39$) than the boys' ($Mean{\pm}SD$ : $46.95{\pm}3.90$)(p 0.001). Nevertheless, the hypothesis that sexual knowledge influences sexual attitude and its behavior was rejected. 3. When twenty-five questions were asked about sexual attitude, the girl students investigated were found to have a more propre sexual attitude than that of the boys. A significant difference was found between boys and girls(p=0.001). The result shows that a person who has more experience in viewing pornography and who smokes will have a more distorted view of sexuality. 4. There are many students who have experienced of sexual contact. They need to take a sex education program about contraception and prevention of sexually transmitted diseases. Systematic and concrete sex education is one way to lead them to proper sexual behavior. 5. Most respondents rejected stereotyped attitudes towards women. Boys, however, were more likely to accept stereotypes of Women. The girl's mean($Mean{\pm}SD$ : $40.90{\pm}3.67$) is higher than the boys($Mean{\pm}SD$ : $34.72{\pm}3.77$)(p=0.0001). 6. Many boys ignored the rules for prevention of sexual violence. A boy or a girl who has more experience of sexual contact over kiss and sex-typed neglected the rules, too(p=0.001). Today, there is increasing juvenile delinquency related to sexuality. This study provided the basic material for a preventive education system. I believe that a systematic and concrete sex education system can be helpful for adolescents and promote their responsibility as well as cultivate morality about sexuality. As a result, juvenile delinquency can be decreased. This study is basically aimed to provide information for a prevenative education system of sexual violence. Further research is recommended to evaluate programs in schools.

• The Journal of Korean Society for School & Community Health Education
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• v.5
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• pp.85-105
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• 2004

The purpose of this study is to provide basic data for practical and concrete program development, which can give students satisfaction in sex education. To achieve this purpose, an actual status of sex education for high school student and their sexual experience were investigated. And then tried to find out if there is difference of satisfaction in sex education and contents that they want to learn based on having sexual experience or not. For this study, a questionnaire of sexual awareness was conducted on 562 students among first graders and second graders of high school located in Kongju city, from on October 4th, 2004 to on October 15th. But only 550 answer sheets among 562 were analyzed, for 12 answer sheets were not proper enough to apply to this study. The collected data was computerized using SPSS WIN in frequency and percentage for actual condition of sex education and sexual experience and for satisfaction at the result of sex education based on having sexual experience or not. And then the $x^2$-test was verify the difference. The requirement for sex education, based on having sexual experience or not, was analyzed using t-test by computerizing the average and standard deviation. The conclusion of this study are as followings; 1. 93.8% students have ever been taught for sex education by teachers, but nursing teacher among them was the higher percentage than any other teachers. They took courses for sex education in discretion class, and the teaching method was a kind of lecture. 2. After taking sex education, 37.6% students said that it was boring, for they had already known the contents of the courses, and 43.8% students said that they acquired sex knowledge through the Internet and mass media. 3. It was highest percentage that 36.9% students had no agony about sex. The most serious worry was a sexual impulse and the sexual psychology of the opposite sex. To solve these worries, 61.6% students said that they consulted with their friends. 4. It showed that 89.9% male students and 71.6% female students had experiences various lascivious materials, 81.4% male students, 7.2 female students experienced masturbation, 52.7% female student and 44.8% male students experienced kissing or hugging, and 13.7% male students and 9.9% female students experienced sexual intercourse. 5. The satisfaction for sex education based on having sexual experience or not was different. In short, it showed that the students who experienced sexual experiences such as accessing to lascivious materials, kissing, hugging, and sexual intercourse except masturbation thought that sex education was important than the students who didn't experience sexual experiences. On the other hand, the students who didn't experience sexual experiences were more satisfied with the contents and level of sex education than the students who experienced sexual experiences. 6. The requirement for sex education based on having sexual experience or not was also different. The students who experienced sexual experiences wanted to learn an acquaintance with the other sex than the others. On the other hand, the students who didn't experience sexual experience wanted to learn friendship and love. The students who experienced sexual experience except masturbation was more desirable for taking sex education than the other students. In conclusion, it is fully required that sex education should be regular subject in school and teachers who are charge of sex education should be experts in this field, for only expert can teach systematic and adequate sex knowledge to students. In addition, it is also essential to understand contents of sex education which can be satisfactory for students' requirement. So we should develop concrete and practical programs for sex education.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.50-58
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• 2014

Due to the cost burden of new construction, the necessity of repair and retrofitting of aged structures is sharply increasing as the domain of repair and retrofitting construction is expanding. Because of the necessity, new technologies for repair and retrofitting are continuously studied in Korea and foreign countries. Steel adhesive method, fiber reinforced plastic (FRP) surface adhesive method, and external prestressing method are used to perform the repair and retrofitting works in Korea. In order to consider a repair method using steel mesh reinforced cement mortar (SMCM), 3-point flexural member test was conducted considering repair area and layer number of SMCM. Five types of specimens including ordinary reinforced concrete (RC) specimen with dimensions of $1400{\times}500{\times}200$ (mm) were cast for testing the deflection measurement, a LVDT was installed at the top center of the specimens. Also, a steel strain gauge and a concrete strain gauge were placed at the center of the specimens. A steel strain gauge was also installed on the shear reinforcement. The 3 point flexural member test results showed that the maximum load of SMCM reinforced specimen was higher than that of basic RC specimen in all of the load-displacement curves. Also, the results showed that, when the whole lower part of the basic RC specimen was reinforced, the maximum load and strain were 1.18 and 1.37 times higher than that of the basic RC specimen, respectively. Each specimen showed a slightly different failure behavior where the difference of the results was caused by the difference in the adhesive level between SMCM and RC. Particularly, in SM-B1 specimen, SMCM spalled off during the experiment. This failure behavior showed that the adhesive performance for RC must be improved in order to utilize SMCM as repair and retrofitting material.