• 한국강구조학회 논문집
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• 제25권1호
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• pp.93-102
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• 2013

본 연구에서는 철근콘크리트 벽과 강판 콘크리트 벽이 서로 수직면의 이질접합 형태로 만나는 벽의 면외 휨 거동 특성을 검토하기 위하여, L형 실험체를 제작하고 휨 실험을 수행하였다. 실험 시, 실험체의 동적특성을 확인하기 위하여 Push 및 Pull 하중을 반복하는 싸이클 하중을 구현하고자 하였다. Push 하중에 의한 실험 결과, 실험체의 공칭강도를 초과하는 휨 성능을 발휘하였으며, 이에 따라 설계에 적용된 수직철근의 미겹침 이음길이의 타당성을 확인할 수 있었다. 한편, Pull 하중 가력 시에는 수직철근이 최대 내력을 발휘하기 전에 접합부 콘크리트에서 전단 파괴 거동이 나타나, 이에 대한 보강이 필요함을 확인하였다.

• Computers and Concrete
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• 제21권3호
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• pp.249-259
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• 2018

The use of recycled aggregate in concrete is gaining much attention due to the growing need for sustainability in construction. In the present study, Self Compacting Concrete (SCC) is made using both natural and recycled aggregate (crushed recycled concrete aggregate from building demolished waste) and performance of recycled aggregate based SCC for the bond behaviour of reinforcement is evaluated. The major factors that influence the bond like concrete compressive strength (Mix-A, B and C), diameter of bar ($D_b=10$, 12 and 16 mm) and embedment length of bar ($L_d=2.5Db$, $5D_b$ and full depth of specimen) are the parameters considered in the present study in addition to type of aggregates (natural and recycled aggregates). The mix proportions of Natural Aggregate SCC (NASCC) are arrived based on the specifications of IS 10262. The mix proportions also satisfy the guidelines of EFNARC. In case of Recycled Aggregate SCC (RASCC), both the natural coarse and fine aggregates are replaced 100% by volume with that of recycled aggregates. These mixes are also evaluated for fresh properties as per EFNARC. The hardened properties like compressive strength, split tensile strength and flexural strength are also determined. The pull-out test is conducted as per the specifications of IS 2770 (Part-1) for determining the bond strength of reinforcement. Bond stress versus slip curves were plotted and a typical comparison of RASCC is made with NASCC. The fracture energy i.e., area under the bond stress slip curve is determined. With the use of recycled aggregates, reduction in maximum bond stress is noticed whereas, the normalised maximum bond stress is higher in case of recycled aggregates. Based on the experimental results, regression analysis is conducted and an equation is proposed to predict the maximum bond stress of RASCC. The equation is in good agreement with the experimental results. The available models in the literature are made use to predict the maximum bond stress and compare the present results.

• 한국사회정책
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• 제19권2호
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• pp.69-97
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• 2012

이 연구는 중고령자의 근로여부와 근로시간 선호에 영향을 미치는 요인을 국가비교적 관점에서 경험적으로 분석하였으며, 특히 계층효과, 일에 대한 관점, 노동시장 구조의 배출효과와 사회보장제도 등의 유인요인 효과 등의 가설을 검증하기 위해 국제인식조사자료를 이용하여 18개국에 대한 다층분석을 수행하였다. 주요결과는 다음과 같다. 첫째, 계층과 관계없이 대다수의 고령자들이 일하기를 원하며, 따라서 대다수 중고령자의 비근로는 일을 하지 않으려는 자발적인 선택이 아닐 수 있는 가능성을 보여준다. 둘째, 55-64세 집단에 있어서는 계층이 높을수록 일을 계속할 가능성이 높은 계층간 불평등이 발견되었다. 셋째, 근로여부와 근로시간 선호는 사회보장제도의 관대성보다는 시간제 근로비중 등 고령자에게 적합한 유연한 일자리가 제공되느냐에 더 영향을 받음을 확인하였다. 결론적으로, 적어도 국가 비교적 관점에서 볼 때 고령자 근로의 핵심적인 문제는 노동공급측의 문제(즉 고령자의 근로의욕)라기보다는 노동수요측의 문제, 퇴직 유인의 문제보다는 일자리 상황과 구조의 문제라고 보여진다.

• 한국경영과학회지
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• 제27권4호
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• pp.185-205
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• 2002

In this study, we consider infinite supply of raw materials and backlogged demands as given two boundary conditions. And we need not make any specific assumptions about the inter-arrival of external demand and service time distributions. Under these situations, the ultimate objective of this study is to prove the variability propagation principle in a pull serial line and is to measure it in terms of the first two moments of the inter-departure process subject to number of cards in each cell. Two preparations are required to achieve this objective : The one is to derive a true lower bound of variance of the inter-departure process. The other is to establish a constrained discrete minimax problem for the no backorder (backlogging) probabilities in each cell. We may get some fundamental results necessary to a completion for the proof through the necessary and sufficient conditions for existence of optimal solution of a constrained discrete minimax problem and the implicit function theorem. finally, we propose a numeric model to measure the variability propagation principle. Numeric examples show the validity and applicability of our study.

• Steel and Composite Structures
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• 제33권1호
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• pp.1-18
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• 2019

In the present study, the behavior of steel plate shear walls (SPSW) with variable column flexural stiffness is experimentally and numerically investigated. Altogether six one-bay one-story specimens, three moment resisting frames (MRFs) and three SPSWs, were designed, fabricated and tested. Column flexural stiffness of the first specimen pair (one MRF and one SPSW) corresponded to the value required by the design codes, while for the second and third pair it was reduced by 18% and 36%, respectively. The quasi-static cyclic test result indicate that SPSW with reduced column flexural stiffness have satisfactory performance up to 4% story drift ratio, allow development of the tension field over the entire infill panel, and cause negligible column "pull-in" deformation which indicates that prescribed minimal column flexural stiffness value, according to AISC 341-10, might be conservative. In addition, finite element (FE) pushover simulations using shell elements were developed. Such FE models can predict SPSW cyclic behavior reasonably well and can be used to conduct numerical parametric analyses. It should be mentioned that these FE models were not able to reproduce column "pull-in" deformation indicating the need for further development of FE simulations with cyclic load introduction which will be part of another paper.

• 한국정보시스템학회지:정보시스템연구
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• 제30권4호
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• pp.43-69
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• 2021

Purpose Although companies occupied the network market take the advantageous position first and can be successful in securing users over a certain size, it is important to satisfy the customers' demand and prevent the outflow of users toward a new alternative SNS. What is more, there are frequent changes in the flow of users toward new SNSs. Despite these dynamic market circumstances, there is a lack of research to explain the switching behaviors of SNS users. Design/methodology/approach The objective of this study is to explain and verify a specified migration theory(Push-Pull-Mooring model) focused on SNS fatigue in the psychological point of view, as well as reviewing previous studies on functional and technical characteristics of SNSs themselves. Moreover, this study tried to highlight factors affecting users actual SNS switch rather than their switching intention. Findings According to the statistical analysis, the most influenced pull factor to switch SNS was the alternative attractiveness. On the other hand, undesired relationship burden, service innovation and important mooring factors to prevent users' SNS switch. This study has a significant contribution to the theory, which analyzed users' actual SNS switch, and examined SNS users' psychological factors(SNS fatigue), reviewing the characteristics of existing services. To secure more users and to keep them, companies providing social network service need to develop differentiated strategies by analyzing psychological characteristics of various users.

• 한국도로학회논문집
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• 제20권1호
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• pp.87-95
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• 2018

PURPOSES : A geo-grid pavement, e.g., a stress-absorbing membrane interlayer (SAMI), can be applied to an asphalt-overlay method on the existing surface-pavement layer for pavement maintenance related to reflection cracking. Reflection cracking can occur when a crack in the existing surface layer influences the overlay pavement. It can reduce the pavement life cycle and adversely affect traffic safety. Moreover, a failed overlay can reduce the economic value. In this regard, the objective of this study is to evaluate the bonding properties between the rigid pavement and a SAMI by using the direct shear test and the pull-off test. The predicted fractural energy functions with the shear stress were determined from a numerical analysis of the moving average method and the polynomial regression method. METHODS : In this research, the shear and pull-off tests were performed to evaluate the properties of mixtures constructed using no interlayer, a tack-coat, and SAMI with fabric and without fabric. The lower mixture parts (describing the existing pavement) were mixed using the 25-40-8 joint cement-concrete standard. The overlay layer was constructed especially using polymer-modified stone mastic asphalt (SMA) pavement. It was composed of an SMA aggregate gradation and applied as the modified agent. The sixth polynomial regression equation and the general moving average method were utilized to estimate the interlayer shear strength. These numerical analysis methods were also used to determine the predictive models for estimating the fracture energy. RESULTS : From the direct shear test and the pull-off test results, the mixture bonded using the tack-coat (applied as the interlayer between the overlay layer and the jointed cement concrete) had the strongest shear resistance and bonding strength. In contrast, the SAMI pavement without fiber has a strong need for fractural energy at failure. CONCLUSIONS : The effects of site-reflection cracking can be determined using the same tests on cored specimens. Further, an empirical-mechanical finite-element method (FEM) must be done to understand the appropriate SAMI application. In this regard, the FEM application analy pavement-design analysis using thesis and bonding property tests using cored specimens from public roads will be conducted in further research.

• 한국생활과학회지
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• 제16권6호
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• pp.1243-1250
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• 2007

The purpose of this study was to compare government guidelines and foreign guidelines related to furniture design for elderly. Future elderly will increasingly accustomed to the provisions of improved housing, education and welfare in comparison with our forebears. Also, there will be upgrading and different need for elderly furniture in our market. The results were as follows. The height of bed was based on the height of wheelchair seat, commonly. A adjustable bed was recommended for abled and disabled elderly. A pull-down shelf, drawer, empty space under chest, folding or sliding door in wardrobe and so on were recommended as a elderly furniture. It were good adjustable sink on human scale. There were need the empty space under sink for wheelchair users, one-touch or lever faucet, etc. There have given a little furniture design guidelines for elderly in Korea until now. But those guidelines haven't been considered enough human scale of elderly including wheelchair user. Because the close investigations have not made about abled and disabled elderly for their furniture design. So first of all, the government should be examined elderly physical size more accurately for elderly furniture design. The guideline for elderly furniture design should be for abled elderly and the disabled, too.

• 한국조리학회지
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• 제19권4호
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• pp.193-210
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• 2013

본 연구는 창업에 관심 있는 외식관련전공 대학생들을 대상으로 유인 요인과 추진 요인의 동기 이론을 통해 창업동기를 고찰하였으며, 창업동기가 창업의도에 미치는 영향을 규명하고 이러한 영향관계에서 성별의 조절효과를 검증하였다. 실증연구를 수행하기 위해 확보된 317개의 표본을 바탕으로 탐색적 요인분석, 신뢰도 분석, 상관관계 분석, 다중회귀 분석 및 위계적 조절회귀분석을 사용하여 총 2개의 가설을 검증하였다. 연구결과, 창업동기의 유인 요인 중 성취욕구(p<0.001)와 자아실현(p<0.01)이 창업의도에 유의한 정(+)의 영향을 미치는 것으로 조사되어 외식관련전공 대학생들은 긍정적인 창업동기로 창업의도가 증진된다는 것을 확인 할 수 있었다. 한편 창업동기가 창업의도에 미치는 영향관계에서 성별과 창업교육 경험의 조절효과를 분석한 결과, 성별의 조절효과는 없는 것으로 조사되었다. 이러한 연구결과를 통해 이론적 시사점과 더불어 대학에서의 창업 활성화 및 창업의욕 고취를 위한 정책적 방안을 제시하였으며, 연구의 한계 및 향후 연구방향에 대해서도 논의하였다.

• 한국해안·해양공학회논문집
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• 제30권6호
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• pp.298-305
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• 2018

본 연구에서는 해양 항만 콘크리트 구조물의 보수작업을 위한 수중코팅제의 부착 특성을 조사하기 위하여 실험적 연구를 수행하였다. 고려된 실험변수는 코팅제의 종류, 코팅대상 모재의 표면 거칠기, 도포 작업환경(육상 혹은 수중)으로 부착 강도는 Pull-off 방식으로 측정하였다. 코팅제의 부착 강도는 각 수중코팅제의 도포 작업 완료 24시간 후에 ASTM C1583 규정에 따라 측정하였다. 또한, 콘크리트 모재와 코팅제 간의 부착파괴 거동(코팅제, 계면, 콘크리트 모재)을 육안으로 관찰하였으며 측정된 부착 강도 수치에 근거하여 각 실험요인의 비교분석을 수행하였다. 실험결과, 수중에서 도포한 코팅제의 부착 강도가 육상의 경우에 비해 감소하는 경향을 보였으며 수중환경에서는 부착 강도에 미치는 모재 표면 거칠기의 영향이 육상의 경우에 비하여 미비하였다. 마지막으로 수중코팅제의 선정, 사용 시에 유의할 점에 대하여 설명하였다.