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전용백,권준환,백홍렬 대구대학교 과학기술연구소 1998 科學技術硏究 Vol.5 No.1
This study about consolidated undrain test are performed for the different preconsolidation stress, the void ratio and shear strength parameter versus of the clay which make use of the Data Logger and Computer System and the existing theories are compared with existing theories. The summary of experiments as follows 1. The preconsolidation stress and shear strength appeared as r= σ_(e)tan 11.46˚+ σtan 19.44˚ this equation enables to know the shear strength when the preconsolidation strength and the confining stress are know. 2. The shear strength parameter decrease in proportion to void ratio at the degree of over consolidation, and the void ratio decrease in proportion to preconsolidation stress, so the change of preconsolidation ratio is equal to the change of shear strength parameter. The preconsolidation stress has no effect on the internal friction angle but has direct effect on the change of cohesive force, and the relation between preconsolidation stress and cohesive force is c= 0.2288P- 0.0541. 3. The internal friction angles are equal at the same sample by the Mohr-Coulomb's theory, but in this experiment, it was appeared that the cohesive strength decrease in proportion to void ratio through the variation of void ratio and the internal friction angle has nothing to do with void ratio.
Heat stress during summer reduced the ovarian aromatase expression of sows in Korea
Hwan-Deuk Kim,Sung-Ho Kim,Sang-Yup Lee,Tae-Gyun Kim,Seong-Eun Heo,Yong-Ryul Seo,Jae-Keun Cho,Min Jang,Sung-Ho Yun,Seung-Joon Kim,Won-Jae Lee 한국동물위생학회 2023 韓國家畜衛生學會誌 Vol.46 No.3
It has been addressed that heat stress due to high atmospheric temperature during summer in Korea induces impaired release of reproductive hormones, followed by occurring abnormal ovarian cyclicity, lower pregnancy ratio, and reduced litter size. Therefore, the present study attempted to compare seasonal change (spring versus summer) of the ovarian aromatase expression, an enzyme for converting testosterone into estrogen. While serum estrogen level in summer group was significantly lower than that of spring group, testosterone was not different between groups. Consistent with estrogen level, the ovarian aromatase expression in summer at follicular phase was significantly lower than the counterpart of spring. The ovarian aromatase expression was positively related with serum estrogen level significantly (r=0.689; P =0.008) and strongly negative correlation was identified (r=−0.533; P=0.078) with atmospheric temperature. The ovarian aromatase expression was not detected in immature ovarian follicles but specifically localized in the granulosa cell layers in both seasons. However, the aromatase intensity in the granulosa cell layers was stronger in spring than summer. Because testosterone level was not different between groups, it could be concluded that the lower level of estrogen during summer might be derived by not lack of substrate but lower expression of ovarian aromatase by heat stress.
Molecular thermodynamic model of the glass transition temperature: dependence on molecular weight
Kim, Yong Woo,Park, Jung Tae,Koh, Joo Hwan,Min, Byoung Ryul,Kim, Jong Hak John Wiley Sons, Ltd. 2008 Polymers for advanced technologies Vol.19 No.8
<P>A new molecular thermodynamic model to predict the dependency of the glass transition temperature (T<SUB>g</SUB>) of polymer on its molecular weight was developed based on the configurational entropy model and the Flory–Huggins theory. In this model, the disorientation entropy of the polymer (S<SUB>dis</SUB>) has been taken into account. Quantitative descriptions according to the proposed model are consistent with experimental T<SUB>g</SUB> data of several polymers against the number of chain segment (r). At the same T<SUB>g.∞</SUB> (T<SUB>g</SUB> of polymer at a infinite r value), the degree of polymer disorientation is strongly correlated with the slope of straight line at lower r regions in the T<SUB>g</SUB> versus r plot, which is quantitatively identified by physical parameter (γ<SUB>dis</SUB>) in this model. Copyright © 2008 John Wiley & Sons, Ltd.</P>
A Position based Kinematic Method for the Analysis of Human Gait
Ahn Ryul Choi,Yong Hoon Rim,Youn Soo Kim,Joung Hwan Mun 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.10
Human joint motion can be kinematically described in three planes, typically the frontal, sagittal, and transverse, and related to experimentally measured data. The selection of reference systems is a prerequisite for accurate kinematic analysis and resulting development of the equations of motion. Moreover, the development of analysis techniques for the minimization of errors, due to skin movement or body deformation, during experiments involving human locomotion is a critically important step, without which accurate results in this type of experiment are an impossibility. The traditional kinematic analysis method is the Angular-based method (ABM), which utilizes the Euler angle or the Bryant angle. However, this analysis method tends to increase cumulative errors due to skin movement. Therefore, the objective of this study was to propose a new kinematic analysis method, Position-based method (PBM), which directly applies position displacement data to represent locomotion. The PBM presented here was designed to minimize cumulative errors via considerations of angle changes and translational motion between markers occurring due to skin movements. In order to verify the efficacy and accuracy of the developed PBM, the mean value of joint dislocation at the knee during one gait cycle and the pattern of three dimensional translation motion of the tibiofemoral joint at the knee, in both flexion and extension, were accessed via ABM and via new method, PBM, with a Local Reference system (LRS) and Segmental Reference system (SRS), and then the data were compared between the two techniques. Our results indicate that the proposed PBM resulted in improved accuracy in terms of motion analysis, as compared to ABM, with the LRS and SRS.