• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.2
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• pp.177-184
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• 2011

In this paper the nonlinear analysis that include time-dependent characteristics of materials and geometric nonlinearity of elements for the cable-stayed PSC bridges is presented. Analysis models for finite element method were developed based on the flexibility based fiber beam-column model originally proposed by Spacone et al.(1996). The developed analysis model implemented in general purpose object-oriented finite element analysis program named HFC(Cho 2009). The performance of proposed analysis models is evaluated by comparing with the former results of the design data. The deflection of time dependent analysis is larger than time ignored analysis on construction sequences, and the bridge is destructed at a smaller deflection than the time ignored analysis on failure behavior.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1671-1676
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• 2006

홍수범람은 무제부에서의 하천수위 상승으로 인해 제내로 서서히 침수해가는 것과 월류로 인한 제방의 파괴를 동반하는 급격한 범람의 두 가지 형태가 있다. 기존연구들은 대부분이 월류에 의한 제방붕괴를 고려할 경우, 제방붕괴가 점진적으로 발생함에도 불구하고 이를 수치모형에 적용할 경우 갑작스럽게 지형을 낮추거나 초기지형으로써 제방붕괴를 가정하여 이를 고려해왔다. 본 연구에서는 제방붕괴를 시간의존적인 함수로 가정하고 이를 고려할 수 있는 서브프로그램의 개발을 통해 기존의 방법과 비교하여 그 영향을 검토하였다. 본 연구에 사용된 수치모형은 비선형의 2차원 천수방정식을 비구조적 격자계가 적용된 유한체적법을 이용하였으며, Riemann 해를 계산하기 위하여 approximate HLLC Riemann solver를 이용하였다. 기연구된 제방붕괴 고려방법과 본 연구의 시간의존적인 제방붕괴 고려방법을 통해 월류량을 비교하였을 때, 기존연구들의 홍수범람 해석결과가 과다예측 되었음을 알 수 있었다. 추후의 이루어질 연구들에서는 시간의존적인 제방붕괴를 반드시 고려해야됨과 동시에 이를 자연현상과 좀더 가깝고 효과적으로 고려할 수 있도록 연구가 필요하다.

• Journal of the Korean Geotechnical Society
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• v.19 no.3
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• pp.15-22
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• 2003

The appropriate description of the stress-anisotropy and time-dependent behavior of cohesive soils is very important in representing the real soil behavior. In this study, two constitutive relations have been incorporated based on the generalized viscous theory: one is the plastic constitutive relation adopted to capture the stress-anisotropy with a few model parameters; the other is the rate-dependent constitutive relation adopted to describe the strain rate-dependent behavior, an important time-dependent behavior in cohesive soils. The incorporated and proposed constitutive model has relatively a few model parameters and their values need not to be re-evaluated at different strain rates. The proposed model has been verified and investigated with the anisotropic triaxial test results obtained by using the artificial homogeneous specimens.

• The Journal of the Korea Contents Association
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• v.14 no.2
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• pp.294-307
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• 2014

The purpose of this study is to examine the trajectory of early adolescent aggression and to assess the effects of perceived family factors on it. This study investigated the changes in aggression over time and the effects of three family factors, parental attachment, parental monitoring, and family conflict, on the changes using multilevel modeling. The data from Korea Youth Panel Survey(KYPS) of fourth graders who were followed over five years were analyzed. The results indicated that there was a significant average increase followed by a slight decrease in aggression over time; that is, the data followed a quadratic trend. Parental attachment, parental monitoring, and family conflict had significant time-independent effects on aggression, while only family conflict had a significant time-dependent effect on aggression. These results imply that family factors need to be emphasized in planning prevention and intervention programs to reduce aggression during adolescence.

• Journal of Food Hygiene and Safety
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• v.3 no.1
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• pp.37-40
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• 1988

A great deal of attention has been directed recently at the roles played by lipidperoxides in the mediation of pathogenesis and complications of various disease. In view of the strong inhibitory activity of Brazilin on the lipidperoxidation, we examined the effect of Brazilin on the lipidperoxidation in diabetic states. Brazilin inhibited the lipidperoxidation of liver mitochondrial and microsomal fraction in alloxan-induced diabetic ICR mice in the dose and time dependent manner. In the light of the present results, further elucidation of the inhibitory activities of Brazilin on the liver and blood plasma is warrented.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.1-12
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• 1994

This paper deals with the time-dependent analysis of reinforced and prestressed concrete beams. Based on the age-adjusted effective modulus method, the structural behavior in accordance with time is analyzed using the force equilibrium and strain compatibility condition within a typical section. Unlike most of presented approaches adopting some assumptions, such as non-cracking of concrete and consideration of steel effect as a transformed concrete area only, more accurate results can be obtained at all loading conditions since all materials are considered together so as to be maintained their given properties and the cracking effect is included at the same time. Several parameter studies are conducted with the objective to identify the significance of various effects on the time-dependent response of concrete members, i.e., stress re-distribution of each material and occurrance of long-term deflection, etc. Moreover, the obtained results can be used at design and/or construction stage for the purpose of more accurate prediction of structural response with time.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.99-106
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• 2012

This study presents estimation method of temperature-dependent thermal conductivity by using solution of inverse heat conduction problem. Time and depth temperature distribution data from full-scale fire test were used for estimating temperature-dependent thermal conductivity on hybrid-fiber reinforced shield tunnel lining. At short heating time, estimated thermal conductivity sharply decreased within $100^{\circ}C$. On the other hand, it reflected thermal properties of concrete and effect of steel fiber at heating time of measured maximum heating temperature. Thus arbitrary time should be determined to estimate temperature-dependent thermal conductivity in time zone of measured maximum heating temperature. Estimated temperature-dependent thermal conductivity is similar to results of other study.

• Korean Journal of Child Studies
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• v.31 no.6
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• pp.1-13
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• 2010

This study examined the time-dependent effects of changes in private education on the trajectories of academic achievement among early adolescents. Five-wave data was employed from the KYPS; the participants being 2844 (1524 boys, 1320 girls). All were 4th graders in 2004 and became 8th graders in 2008. Latent growth curve model indicated that academic achievement significantly decreased over the five time points, but there were significant individual differences as well. Participants who reported higher initial levels of academic achievement tended to decrease in academic achievement more slowly over time compared to participants who reported lower levels of initial academic achievement. The effects of private education on academic achievement were at their most powerful when participants were in the 4th grade. Private educational experiences among 6th graders had relatively less influence upon the academic achievement of 7th graders.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.2
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• pp.155-162
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• 2012

Recently, building of long span bridge is increasing and cable stayed bridges have large portion in civil projects. As the spans of bridges become longer, steel cable-stayed bridges have been constructed mainly for slim structure. But in many case, pylons are constructed by concrete for the stability of structures and the economy. Concrete is greatly influenced by the long-term behavior like creep and drying shrinkage, so analysis of stress redistribution and structural change in construction is required. In this study, as a cable stayed bridge with concrete pylon, Incheon Bridge is analyzed by nonlinear FEM analysis program RCAHEST. Through this analysis, time dependent effect of concrete pylon to whole cable stayed bridge system is studied.

• Journal of Acupuncture Research
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• v.27 no.5
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• pp.59-68
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• 2010

목적 : 최근 한의학에서 널리 사용되며, 신경계 질환에도 응용되고 있는 봉약침의 농도의존적 효과를 알아보기 위하여, 대표적인 신경 퇴행성 질환인 파킨슨병의 동물모델을 통해 세포보호효과와 세포사멸 및 신경염증 기전을 관찰하였다. 방법 : C57BL/6 mice에 신경독소인 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine(MPTP)를 4번 복강내 주입하여 중뇌의 흑질 도파민 신경세포를 파괴하여 Parkinson 질병동물 모델을 만든 후, 2개의 군에는 마지막 MPTP 투여 2시간 후에 1차, 그 후로 48시간이 지날 때마다 양측 신수에 각각 0.06mg/kg 농도와 0.6mg/kg 농도의 봉약침을 시행하여 총 4회 시술한 후, 도파민 세포를 측정하는 TH 면역조직 화학법을 통해 세포의 보존 정도를 관찰하고, 세포사멸과 관련된 양상을 확인하기 위하여 Caspase 3, 신경염증과 관련된 양상을 확인하기 위하여 iNOS의 발현여부를 면역 조직화학법을 이용하여 관찰하였다. 결과 : 관찰결과 MPTP 투여 후 MPTP 투여군의 흑질의 도파민 세포 수는 감소하였으나 0.6mg/kg 봉약침을 투여한 경우에는 유의성 있게 세포 수가 유지되었다. Caspase-3와 iNOS 발현억제 실험에서 0.6mg/kg 봉약침군은 MPTP 투여군과 0.06mg/kg의 봉약침군과 비교하여 Caspase-3, iNOS 발현을 유의하게 억제하였다. 결론 : 봉약침은 MPTP 투여로 인한 신경세포 손상에 대하여 농도에 따라 세포사멸 기전과 신경염증 기전을 억제함으로 신경세포를 보호하는 것으로 추정되며, 추후 적절한 경혈점 및 최적의 봉약침 농도를 찾는데 지속적인 연구가 필요할 것이다.