• Steel and Composite Structures
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• 제26권3호
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• pp.375-386
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• 2018

Existing design codes for steel-concrete composite structures give only general information about the shear connection provided by headed studs in group arrangement. Grouting of the openings in prefabricated concrete slabs, where the grouped headed studs are placed in the deck pockets is alternative to cast-in-place decks to accomplish fast execution of composite structures. This paper considers the possibility to reduce the distance between the studs within the group, bellow the Eurocode limitations. This may lead to increased competitiveness of the prefabricated construction because more studs are placed in the group if negative effectives of smaller distances between studs are limited. The main purpose of this work is to investigate these limits and propose an analytical calculation model for prediction of the shear resistance of grouped stud arrangements in the deck pockets. An advanced FEA model, validated by results of push-out experiments, is used to analyze the shear behavior of the grouped stud with smaller distance between them than recommended by EN 1994-1. Calculation model for shear resistance, which is consistent with the existing Eurocode rules, is proposed based on a newly introduced equivalent diameter of the stud group, $d_G$. The new calculation model is validated by comparison to the results of FE parametric study. The distance between the studs in the longitudinal direction and the number of stud rows and columns in the group are considered as the main variables.

• Journal of the Korean Wood Science and Technology
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• 제28권3호
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• pp.14-24
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• 2000

본 연구에서는 향후 공급량이 증가될 것으로 예상되는 라디아타소나무와 국산 낙엽송의 두 수종을 이용하여 합판을 제조하고 구조용 합판 및 콘크리트 거푸집용 합판으로서의 사용 가능성을 검토하고자 하였다. 먼저, 기초적인 재질을 평가하기 위하여 합판의 재질시험 및 못성능 등의 시험을 실시하였고, 콘크리트조 주택 혹은 목조주택 등의 구조용 재료로의 사용을 검토하기 위해 집중하중과 균일분포하중에 의한 구조성능 시험 및 콘크리트 거푸집용으로서의 성능시험을 실시하였다. 합판의 기초 재질에 해당되는 비중, 너비 굽음, 길이 굽음 비틀림에 대한 실험 결과, 구조용 재료로서의 기준을 만족하였다. 못 측면 저항력, 못 인발 저항력 그리고 못머리 관통력에 대한 실험 결과, 구조용 재료로서의 벽체나 지붕재에 대한 표준성능을 만족하였다. 이들 두 수종으로 제조한 합판의 경우, 집중하중과 균일 분포하중에 의한 구조성능 평가, 콘크리트 거푸집용으로서의 성능 평가 결과를 볼 때 구조용 덮개재, 바탕바닥 마감재, 콘크리트 거푸집용 재료로의 사용이 가능하다고 판단되었다.

• Journal of Communications and Networks
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• 제14권2호
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• pp.162-168
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• 2012

This paper considers the scenario in which a set of nodes share a common channel. Some nodes have a rechargeable battery and the others are plugged to a reliable power supply and, thus, have no energy limitations. We consider two source-destination pairs and apply the concept of cognitive radio communication in sharing the common channel. Specifically, we give high-priority to the energy-constrained source-destination pair, i.e., primary pair, and low-priority to the pair which is free from such constraint, i.e., secondary pair. In contrast to the traditional notion of cognitive radio, in which the secondary transmitter is required to relinquish the channel as soon as the primary is detected, the secondary transmitter not only utilizes the idle slots of primary pair but also transmits along with the primary transmitter with probability p. This is possible because we consider the general multi-packet reception model. Given the requirement on the primary pair's throughput, the probability p is chosen to maximize the secondary pair's throughput. To this end, we obtain two-dimensional maximum stable throughput region which describes the theoretical limit on rates that we can push into the network while maintaining the queues in the network to be stable. The result is obtained for both cases in which the capacity of the battery at the primary node is infinite and also finite.

• 농촌계획
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• 제26권2호
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• pp.39-49
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• 2020

This study was attempted to grasp the push-pull factors of urban to rural migrants in relation to services and infrastructure of rural welfare and culture. Online and offline survey were conducted for urban residents who were willing to return to the rural area and those who were already returning to the rural area. In the fields of health care, social welfare, and education, it was found that the satisfaction level of urban-to-rural migrants was relatively higher than those of latent urban-to-rural migrants. In the field of culture, leisure and sports, the level of satisfaction and concern were similar, so it was found that the expectations for the field were relatively high before returning rural area. As for the agreement degree to expand support, the demand for emergency medical facilities and dementia care program was the highest, and the demand for health care was found to be relatively high. The results of the survey on the top priority items indicate that latent urban-to-rural migrants require support of facility and space item and expansion of program item, and urban-to-rural migrants have high demand for expansion of program item in all field except healthcare field. The results of this study are expected to provide useful information for establishing the direction of the rural area development project in connection with the revitalization of policy of people return to rural area.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.380-386
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• 2008

The development of a new railway vehicle is under progress through the Next Generation High-Speed Rail Development Project in Korea. Its aim is to develope fundamental technology of the vehicle that can run over 400km/h. The new distributed traction bogie system, 'HEMU'(High-speed Electric Multiple Unit), will be used and is different from that of previously developed high speed railway vehicles. Previous vehicles adopted push-pull type system, which means one traction-car drives rest all of the vehicle. Due to the difference, investigation on dynamic behavior and its safety evaluation are necessary, as a part of verification of the design specification. In the paper, current progresses of researches are presented. And the High-Speed Railway vehicle system is evaluated for a dynamic characteristic simulation. Proper dynamic models including air-suspension system, wheel-rail, bogie and car-body is developed according to the vehicle simulation scenario. The basic platform for the development of dynamic solver is prepared using nodal, modal coordinate system and wheel-rail contact module. Operating scenario is prepared using commercial dynamic analysis program and used for development of dynamic model, which contains many parts such as carbodies, bogies and suspension systems. Furthermore, international safety standard is applied for final verification of the system. Finally, the reliability of the dynamic model will be verified with test results in the further researches. This research will propose a better solution when test results shows a problem in the parts and elements. Finally, the vehicle that has excellent performance will be developed, promoting academic achievement and technical development.

• Advances in concrete construction
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• 제11권5호
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• pp.429-445
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• 2021

With regard to economic efficiency, composite fix beams are widely used to pass longitudinal shear forces across the interface. The current knowledge of the composite beam load-slip activity and shear capability are restricted to data from measurements of push-off. Modelling and analysis of the composite beams based on Euro-code 4 regarding to shear, bending, and deflection under differing loads were carried out using Finite Element through an efficient computer simulation and the final loading and sections capacity based on the failure modes was analysed. In bending, the section potential was increased by an improvement of the strength in both steel and concrete, but the flexural and compressive resistance growth is very weak (3.2% 3.1% and 3.0%), while the strength of the concrete has increased respectively from 25 N/mm² to 30, 35, and 40 N/mm² compared to the increment of steel strength by 27% and 21% when it was raised from 275 to 355 and 460 N/mm², respectively. It was found that the final flexural load capacity of fix beams was declined with increase in the fix beam span for both three steel strength. The shear capacity of sections was remained unchanged at constant steel strength and different length, but raised with final yield strength increment of steel sections by 29%, and 67% when it was raised from 275 N/mm² to 355 N/mm² and 460 N/mm², respectively.

• 한국응용과학기술학회지
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• 제38권6호
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• pp.1606-1615
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• 2021

본 연구에서는 남자 실업팀 핸드볼 선수들을 대상으로 플라이휠 운동을 적용한 웨이트 트레이닝 프로그램을 개발하여 상해예방과 경기력 향상을 위한 기초자료를 제공하는데 그 목적이 있다. 12주간 복합 플라이휠 운동 프로그램을 적용하여 신체조성, 체력요인, 무산소성파워, 등속성근기능에 미치는 영향을 분석한 결과는 다음과 같다. 팔굽혀펴기는 그룹 간 유의한 차이가 나타났다. 체지방률, 무산소성 파워는 시기별 상호작용에서 유의한 차이가 나타났다. 제자리멀리뛰기, 제자리높이뛰기, 악력, 배근력, 무산소성평균파워 그리고 등속성근기능검사는 좌굴근과 우굴근에서 시기별로 유의한 차이가 나타났다. 따라서 12주간 플라이휠 운동을 활용한 웨이트 트레이닝 결과는 상해예방과 경기력 향상을 위한 기초자료로 제공할 수 있을 것으로 판단된다.

• 한국인터넷방송통신학회논문지
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• 제21권2호
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• pp.125-130
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• 2021

축산 스마트팜의 구현이 사물인터넷 기술이 발전함에 따라 더욱 효율적으로 이루어질 수 있게 되었다. IoT 기술을 이용한 소의 질병 및 발정을 판단하여 자동적으로 소의 관리자 스마트폰으로 그 판단 결과를 푸시메지시로 알려주면 유용한 축산관리 시스템 구축이 가능해진다. 소의 질병 및 발정시기를 판단하는 방식은 온도센서 및 3축가속도 센서를 이용하여 가축의 생체데이터를 수집하여 IoT 통신과 인터넷을 이용해서 서버로 데이터를 전송하고 이 데이터는 인공지능 머신러닝 학습에 의해 이루어진다. 본 논문에서는 이와 같은 사물인터넷 기반 소관리 시스템을 구축하기 위한 전체 시스템 구조를 보여준다. 또한 객체지향방법을 이용한 사용자 요구사항 분석과 플로우차트 및 화면 설계를 보여줌으로써 이 시스템 소프트웨어를 개발하기 위한 효율적인 분석 및 설계 방법을 제시한다.

• Steel and Composite Structures
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• 제42권5호
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• pp.633-647
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• 2022

This paper presents the results from reliability analyses of the current Eurocode 4 (EN 1994-1-1) and AISC 360-16 design models for predicting the resistance of headed stud shear connectors within profiled steel sheeting, when the ribs are oriented transverse to the supporting beam. For comparison purposes, the performance of the alternative "Luxembourg" and "Stuttgart" model were also considered. From an initial database of 611 push-out tests, 269 cases were included in the study, which ensured that the results were valid over a wide range of geometrical and material properties. It was found that the current EN 1994-1-1 design rules deliver a corrected partial safety factor γ_M^* of around 2.0, which is significantly higher than the target value 1.25. Moreover, 179 tests fell within the domain of the concrete-related failure design equation. Notwithstanding this, the EN 1994-1-1 equations provide satisfactory results for re-entrant profiled sheeting. The AISC 360-16 design equation for steel failure covers 263 of the tests in the database and delivers 𝛾_M^*≈2.0. Conversely, whilst the alternative "Stuttgart" model provides an improvement over the current codes, only a corrected partial safety factor of 𝛾_M^*=1.47 is achieved. Finally, the alternative "Luxembourg" design model was found to deliver the required target value, with a corrected partial safety factor 𝛾_M^* between 1.21 and 1.28. Given the fact that the Luxembourg design model is the only model that achieved the target values required by EN 1990, it is recommended as a potential candidate for inclusion within the second generation of Eurocodes.

• 대한통합의학회지
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• 제6권4호
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• pp.39-45
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• 2018

Purpose : The purpose of this study is to investigate the effect of core motion pattern on abdominal muscle thickness on unstable support surface using sling suspension system and to provide an effective exercise program for therapeutic rehabilitation in clinical practice. Methods : In this study, we used the flank exercise using a sling. It was intended for 21 healthy men and 9 healthy women. Before and after the exercise of the subjects, abdominal muscles (EO, IO, TrA the thickness of the muscle) was determined using a diagnostic ultrasonic apparatus. The period of exercise was 3 times a week for 6 weeks. The exercise for each group started with 3 sets per week and 1 set per week was added. A description of the method and attitude of each exercise is as follows. First, the push-up flank 's exercise position is to put both feet on the sling and hold the floor with both hands. Second, the side flank's exercise postures take the side flanks, while the two legs hang on the sling and one arm supports the body with an articulated bend (about $90^{\circ}$). Third, the elbow flank's exercise position is to put the two legs on the sling, and take a flank posture with the arms bent and joint bending (about $90^{\circ}$). Results : There was a significant difference in the thickness of the muscle in the three flank movements after the exercise (p<.05). The most significant difference was in the change of the muscle thickness in the abdominal muscle, the outer muscle, and the stomach in the elbow flank exercise after exercise. There was a significant difference between the mean thickness of the abdominal muscles according to the flank type after exercise (p<.05). Conclusion : In flank exercise for core stabilization using sling, it is considered effective to strengthen the abdominal muscles by considering the support surface, difficulty level, change of movement pattern.