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준설 실트질 점토를 이용한 경량기포혼합토의 압축강도 특성
김동규(Donggyu Kim),윤여원(Yeowon Yoon),윤길림(Gillim Yoon) 한국지반환경공학회 2017 한국지반환경공학회논문집 Vol.18 No.5
본 연구에서는 실트질 점토와 동물성 기포제 및 시멘트로 제작한 경량기포혼합토의 공학적 특성을 고찰하는 시험을 수행하였다. 현장의 경량기포혼합토는 도로를 위한 연약지반상 성토 및 기존도로의 확장 구간에 성토재료로 사용되어 왔다. 현장에서는 주로 제작 직후의 단위중량과 흐름치를 측정하여 품질관리를 하고 있으며, 실내 시험을 통해 압축강도시험으로 확인한다. 본 연구의 주목적은 경량혼합토의 다른 특성과 흐름치 관계와 더불어 흐름치로부터 시방서에서 요구하는 압축강도를 예측하고자 하는 것이 주요 목적이다. 연구 결과, 준설토의 함수비가 클수록 높은 유동성으로 인해 흐름치가 증가하였고 재료분리로 인해 타설 깊이에 따른 단위중량이 증가하였다. 60cm의 시료 하부는 상부에 비하여 약 2배의 압축강도를 나타내었다. 현장에서의 품질관리는 주로 흐름치에 의존하게 되므로 흐름치와 혼합토의 압축강도를 선행적으로 예측할 수 있도록 Yoon & Kim(2004)이 제시한 정규화계수와 의 상관관계를 제시함으로써 흐름치로부터 압축강도를 예측할 수 있도록 하였다. 또한, 흐름치와 정규화계수와의 관계를 제시하였으며 이관계로부터 정규화계수를 산정하고, 이로부터 계산한 압축강도와 실내시험 압축강도를 비교한 결과, 준설토의 초기함수비가 높을수록 유사한 관계가 나타났다. 따라서, 흐름치와 정규화계수의 상관관계를 통해 압축강도를 사전에 예측하여 설계 단계에서 반영할 필요성이 있다고 판단된다. In this research, laboratory tests were carried out to investigate the engineering properties of Light-Weight Air Foamed Soil (LWAS) based on silty clays with the animal foaming agent and cement. LWAS has been used as an embankment material over soft ground for road and side extension of the existing road. In field, unit weight and flow value is measured right after producing in mixing plant in order to control the quality of LWAS, and laboratory tests are carried out to confirm the quality through compressive strength of LWAS as well. In this research, direct estimation of the specification requirement of strength using flow values in field is the main purpose of the study together with other characteristics. From the test results, it can be seen that flow values increase with the initial water content and unit weight increases with the depth due to material segregation. Compared to the upper specimen, lower end of 60 cm specimen shows about 2 times higher compressive strength. Relationship between flow values and normalized factor presented by Yoon & Kim (2004) was presented. With that relationship, compressive strength can be predicted from flow values in field. From the relationship, the normalized factor was calculated. Thereafter calculated compressive strengths according to the flow values were compared to measured strengths in the laboratory. The higher the initial water content of the dredged soil has, the better relationship between predicted and measured shows. Therefore it is necessary to predict the compressive strength in advance through the relationship between the flow value and the normalized factor to reflect it in the design stage.
Jusik Park,Donggyu Yoon,Minjeong Kim,Mingyun Son J-INSTITUTE 2022 Kinesiology Vol.7 No.1
Purpose: In this study, the number of students enrolled in the practical classes is decreasing as the academic year increases due to the reduction of required courses and the expansion of major electives in order to give stu-dents voluntary class options unlike in the past for Taekwondo students. Considering that as a result, physical strength and practical skills may decrease, this study intends to compare and analyze the differences by grade level by measuring the physique and physical strength of students enrolled in the Department of Taekwondo. In addition, the results of this study are intended to be used as basic data for organizing and reorganizing the curriculum by grade level. Method: The subjects of this study were Taekwondo majors enrolled at K University in D city, 27 first graders, 26 second graders, and 26 third graders (total 79), and the characteristics of body composition and physical fit-ness factors were compared and analyzed. Results: As a result of body composition measurement, body fat percentage and body mass index were statis-tically significantly higher in second grade than in first grade. As a result of measuring the physical fitness factors, it was found that the first graders were statistically significantly higher than the third graders in the Harvard Step test, which is an evaluation item for cardiorespiratory endurance. The sound reaction time was found to be statis-tically significantly faster in the first year students than in the second year students. The stand-up long jump, which is a quickness evaluation item, was statistically significantly higher in first-year students than in third-year students. Conclusion: In conclusion, it is considered that the decrease in the frequency of use of the practical practice space and face-to-face classes in the university due to COVID-19 had a negative effect on the physical composi-tion and development of physical fitness of Taekwondo students. Based on the results of this study, it is thought that it is necessary to seek ways to improve the physical strength and practical ability of Taekwondo students.
Hahm, Yeankyoung,Yoon, Heeyeun,Jung, Donggyu,Kwon, Hyunsook Elsevier 2017 Habitat international Vol.70 No.-
<P><B>Abstract</B></P> <P>This study aims to reveal components of built environments that influence pedestrians' walking patterns and potential consumption in a retail district. We conducted a Global Positioning System (GPS) experiment observing 82 pedestrians' choices of walking routes in Hongdae, a campus-oriented retail district near Hongik University in Seoul, South Korea, and assessed their causal relationships with built environments using a structural equation model (SEM). We revealed that all four categories of built environments studied—accessibility, diversity, design, and density—affected pedestrians’ choices of walking route, controlling for retail attributes. Specifically, pedestrians prefer shaded streets and openness, confirming the importance of design quality in pedestrian retail environments. Contrary to conventional wisdom, however, shorter distances from public transportation would not guarantee more pedestrian traffic in specialized shopping areas such as Hongdae, unlike what we have observed in residential neighborhoods. Additionally, pedestrians prefer streets with concentrations of similar types and high-density retails, affirming the agglomeration economies theory.</P>