• Structural Engineering and Mechanics
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• 제66권4호
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• pp.477-485
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• 2018

This study aims to investigate the influence of individual and hybrid fiber on the local bond-slip behavior of medium and high strength concrete after exposure to different high temperatures. Tests were conducted on local pullout specimens (150 mm cubes) with a reinforcing bar embedded in the center section. The embedment lengths in the pullout specimens were three times the bar diameter. The parameters investigated include concrete type (control group: ordinary concrete; experimental group: fiber concrete), concrete strength, fiber type and targeted temperature. The test results showed that the ultimate bond stress in the local bond stress versus slip curve of the high strength fiber reinforced concrete was higher than that of the medium strength fiber reinforced concrete. In addition, the use of hybrid combinations of steel fiber and polypropylene fiber can enhance the residual bond strength ratio of high strength concrete.

• 한국결정학회지
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• 제12권2호
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• pp.81-87
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• 2001

We have studied the effect of sintering temperature and time on the cation ordering and second phase formation in Ba(Mg/sub 1/3/Nb/sub 2/3/)O₃(BMN) microwave ceramics by using transmission electron microscopy. The relationship between the structural-chemical behavior arid microwave dielectric properties has also been investigated. It is revealed that according to the sintering conditions the BMN ceramics show very diverse local ordering behavior, such as the development of domain twinning and "core-shell"-structured grains and the formation of local disordered domains, though having 1 : 2 cation ordering structure basically. The disordered structure is found in Mg-excess region. Such local chemical variation seems to be caused by the formation of BaNb₂O/sub 6/-like second phase in its neigh-boring grain boundary. The microwave dielectric quality factor of the ceramics decreases greatly with the increase of the structural-chemical inhomogeneity and diversity.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.357-362
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• 2001

The pipe fracture tests were performed on 102mm-Sch.80 carbon steel pipe with various local wall thinning shapes, in order to understand failure behavior of thinned pipe. Pipe specimens were subjected to monotonic bending moment, using 4-points loading system, under internally pressurized condition. From the results of experiment, the failure mode, load carrying capacity, and deformability of local wall thinning pipe were investigated. Failure mode of thinned pipe depended on magnitude of internal pressure and thinning length as well as loading direction and thinning depth and angle. The variation in load carrying capacity and deformability of thinned pipe with length of thinned area was determined by stress type appled to thinning region and circumferential thinning angle. Also, the effect of internal pressure on failure behavior was dependent on failure mode of thinned pipe, and it promoted crack occurrence and mitigated local buckling at thinned area.

• 국제강구조저널
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• 제18권5호
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• pp.1761-1771
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• 2018

In this paper, a hysteretic model of rectangular hollow section (RHS) columns that includes the deteriorating range caused by local buckling is proposed. The proposed model consists of the skeleton curve, the Bauschinger part that appears before reaching the maximum strength, the strength increasing part of the deteriorating range, and the unloading part. Of these, the skeleton curve, including the deterioration range caused by local buckling, which is considered to be equivalent to the load-deformation relationship under monotonic loading, is obtained through an analytical method. Bi-linear hysteretic models based on experimental results are applied to the Bauschinger part and the strength increasing part. The elastic stiffness is applied to the unloading part. The proposed model is verified by comparing with experimental results of RHS columns under monotonic and cyclic loading.

• 한국강구조학회 논문집
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• 제17권2호통권75호
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• pp.139-149
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• 2005

소성설계에 있어서 국부좌굴 후의 거동은 매우 중요한 고려사항이며, 최종 붕괴상태에 이르는 거동을 설명한다. 지진과 같은 복잡한 하중에 대하여 구조물의 실질적인 신뢰성을 얻기 위해, 국부좌굴 이후의 구조물의 점진적인 소재의 약화와 강성과 강도의 감소, 에너지 소실능력을 평가하여야 한다. 본 연구에서는, two-surface 모델에 근거하여 반복 불비례 하중에서의 국부좌굴 후 거동을 예측하기 위하여 제시된 stress resultant model을 이용하여, 단순화된 국부좌굴해석모델을 제안하였다. 이 모델을 사용한 해석적 모멘트-곡률관계는 일정한 반복 사이클 내에서 실험결과와 적절히 부합하며, 내진설계에 있어 중요한 선형 분포된 에너지 감소를 제안 모델로부터 예측할 수 있다.

• 한국학교ㆍ지역보건교육학회지
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• 제15권1호
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• pp.121-140
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• 2014

Objectives: Recently, the rate of death by chronic disease, is increasing steadily. To prevent this, the public health center will have taken a leading role in the local community medical business through an establish to the national health promotion act and an amendment to the law of public health center in Korea. Results: Accordingly this research, using the Pender's health promotion model which is related with subject health behavior who government employees serve at the public health center have taken important position in the local community health promotion, have comprehended the actual condition of health behavior. For increasing the health behavior practice of subject to comprehend the factor which have effect on health behavior practice, which can be a correct role model in the local community health promotion. A survey was performed on 406 government employees who serve at five public health centers in Seoul. The period of survey was from 25th October, 2010 to 15th November, 2010. The results of this study were summarized as below. 1. Work-related stress, perceptible beneficial obstacle, and self-efficacy were composed by 5 points measure. The results show those work-related stress were $3.06{\pm}0.469$, 74perceptible beneficial obstacle were $3.74{\pm}0.471$, and self-efficacy were $3.49{\pm}0.469$. 2. As for the health behavior by general characteristic, the results have specific differences on age, education level, state of marriage, rank of the position, field of the occupation and employment forms in statics analysis. 3. As for the past health behavior by health behavior characteristic, work-related stress have specific differences on the past frequency of drinking (p<.05) in statics analysis, perceptible beneficial obstacle have specific differences on the past frequency of having breakfast(p<.05), having snacks(p<.05) and doing exercise(p<.05) in statics analysis. Self-efficacy have specific difference on the past frequency drinking(p<.01) in statics analysis. 4. According to the correlation between the factors related with health behavior and health behavior, the health behavior have specific differences on perceptible health condition(p<.01), the past health behavior and perceptible beneficial obstacle(p<.05). Work-related stress and self-efficacy don't have specific relation in health behavior practice. 5. The factors, which effect on health behavior practice have specific differences on the past health behavior, employment forms and field of the occupations. The ability of explanation occupied 54.8% what explained of the health behavior practice by general characteristic, perceptible health condition, employment forms and perceptible beneficial obstacle. Conclusions: According to the correlation between the factors related with health behavior, the health behavior have specific differences on perceptible health condition(p<.01), the past health behavior and perceptible beneficial obstacle(p<.05). The factors, which effect on health behavior practice have specific differences on the past health behavior, employment forms and field of the occupations.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.5-8
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• 2000

This paper presents the analytical investigation pertaining to the local buckling behavior of orthotropic open section thin-walled compression members with asymmetric edge stiffeners. In the analysis, 3 different cases of the second moment of inertia are considered to find the asymmetric edge stiffener effect on the local buckling strength. The analytical study results are presented in the graphical form so that the edge stiffener effects on the local buckling strength can be easily found.

• Advances in concrete construction
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• 제10권1호
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• pp.71-79
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• 2020

Ultra-high-performance concrete (UHPC) is recognized as a promising material in future civil engineering projects due to its outstanding mechanical and durability properties. However, the lack of local UHPC materials and official standards, especially for prestressed UHPC structures, has limited the application of UHPC. In this research, a large-scale prestressed bridge girder composed of nonproprietary UHPC is produced and investigated. This work has two objectives to develop the mixing procedure required to create UHPC in large batches and to study the flexural behavior of the prestressed girder. The results demonstrate that a sizeable batch of UHPC can be produced by using a conventional concrete mixing system at any precast factory. In addition, incorporating local aggregates and using conventional mixing systems enables regional widespread use. The flexural behavior of a girder made by this UHPC is investigated including flexural strength, cracking pattern and development, load-deflection curve, and strain and neutral axis behaviors through a comprehensive bending test. The experimental data is similar to the theoretical results from analytical methods based on several standards and recommendations of UHPC design.

• 한국지능시스템학회논문지
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• 제16권1호
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• pp.8-17
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• 2006

군집 로봇시스템에서 로봇들 간의 협조행동 및 군 행동을 하기 위해서는 로봇의 센싱과 통신 기능은 필수적이다. 일반적으로 대역적 통신 시스템에서 로봇의 대수가 증가하면 통신자원의 제한과 정보의 범람이 발생한다. 따라서 이 경우 지역적 통신방법이 유리하다. 본 논문에서는 지역적 통신 방식을 제안하고, 정보의 전파(propagation) 해석을 통하여 최적의 통신 반경을 찾는 방법들을 제시한다. 또한 로봇이 정보를 획득하고 소실할 경우 발생하는 군(group)의 카오스 행동을 피하기 위한 최적의 조건을 제시한다.

• 펄프종이기술
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• 제31권3호
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• pp.105-109
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• 1999

The purpose of this experiment was to see the effect of local basis weight on the local strain during changing moisture content in handsheets. The averaged strain value of the whole size of paper sheet did not give more valuable information to explain non uniform deformation in the paper sheet. The combination of intact strain measurement system KISA (Linear Image Strain Analysis) and local basis weight measurement method using a scanner made it possible to compare local basis weight with local strain to explain moisture induced paper deformation . Usually higher basis weight local area showed higher moisture induced local strain. However, the hygro-induced strain values were highly affected by the behavior of neighbor local areas. Well distributed local basis weight paper would give more uniform local strains than those of non-uniformed local basis weight paper.