The undrained shear strength （su） of fine-grained soils that can be measured in situ and in laboratory isone of the key geotechnical parameters. The unconfined compression test （UCT） is widely used in laboratoryto...The undrained shear strength （su） of fine-grained soils that can be measured in situ and in laboratory isone of the key geotechnical parameters. The unconfined compression test （UCT） is widely used in laboratoryto measure this parameter due to its simplicity; however, it is severely affected by sampledisturbance. The vane shear test （VST） technique that is less sensitive to sample disturbance involves acorrection factor against the soil plasticity, commonly known as the Bjerrum＇s correction factor, m. Thisstudy aims to reevaluate the Bjerrum＇s correction factor in consideration of a different approach and arelatively new method of testing. Atterberg limits test, miniature VST, and reverse extrusion test （RET）were conducted on 120 remolded samples. The effect of soil plasticity on undrained shear strength wasexamined using the liquidity index instead of Bjerrum＇s correction factor. In comparison with the resultobatined using the Bjerrum＇s correction factor, the undrained shear strength was better representedwhen su values were correlated with the liquidity index. The results were validated by the RET, whichwas proven to take into account soil plasticity with a reliable degree of accuracy. This study also showsthat the RET has strong promise as a new tool for testing undrained shear strength of fine-grained soils.展开更多
The granular dynamic shear strength is the same as that of the static one in nature, as found from numerous experiments and investigations. The shear strength is equal to the sum of the internal frictional force and t...The granular dynamic shear strength is the same as that of the static one in nature, as found from numerous experiments and investigations. The shear strength is equal to the sum of the internal frictional force and the cohesive force. The influences of type, shape, size distribution, pore ratio, moisture content and variation of vibration velocity on the dynamic shear strength of granules were studied. Based on numerous vibration shear experiments, the authors investigate the mechanism of dynamic shear strength in granules in terms of the fundamental principle and the relevant theory of modern tribology.展开更多
Objective:To determine the effect of antiparallel phosphorothioate triplex-forming oligonucleotide(apsTFO),which was designed according to shear stress response element(SSRE) in tissue factor(TF) gene promoter region,...Objective:To determine the effect of antiparallel phosphorothioate triplex-forming oligonucleotide(apsTFO),which was designed according to shear stress response element(SSRE) in tissue factor(TF) gene promoter region,on the expression of endothelial TF in carotid artery stenosis rats.Methods:Rat model of severe carotid artery stenosis were inflicted by silica gel tube ligation.Half an hour before the model infliction,GT20-apsTFO,GT20-psTFO and GT21-apsTFO labeled with green fluorescence(FITC) were injected into the vena caudalis of rat at a dose of 0.5 mg/kg.Half an hour,4 or 9 h after the ligation,the distribution of TFO in the common carotid artery,the liver and the kidney was detected with aid of fluorescence microscopy.And the mRNA and protein expressions of TF,Egr-1 and Sp1 in the above-mentioned organs were determined with in situ hybridization and immunohistochemical assay respectively in 6 h after the model establishment,and the results were analyzed with an image analysis system.Results:Only in 1 h after TFO injection,fluorescent granules appeared in the liver,the kidney and the vascular wall and lumen of carotid artery,and then in 4.5 h,they still deposited in above sites except the vascular lumen.GT20-apsTFO and GT21-apsTFO significant down-regulated the mRNA and protein expressions of TF compared to the rats without treatment(P<0.05),and the former apsTFO had a more stronger effect than the later(P<0.05).GT20-psTFO had no such effect(P>0.05).The 3 TFOs had no inhibition on the mRNA and protein expressions of Egr-1 and Sp1.Conclusion:Pretreated apsTFO can partly come into the vascular endothelial cells,and inhibit TF expression induced by shear stress,but had no effect on Egr-1 and Sp1 gene expressions.展开更多
The caustic method is applied to compressive shear experiment and used to detect the stress intensity factors of cracks prefabricated on plexiglass sample. Loading, friction of crack planes and influence among cracks ...The caustic method is applied to compressive shear experiment and used to detect the stress intensity factors of cracks prefabricated on plexiglass sample. Loading, friction of crack planes and influence among cracks are not needed to know as they are combined and transformed into the caustic shadow used in detecting the stress intensity factor. Even boundary condition is not necessary. Therefore it is effective to determine the stress intensity factor of compressive shear crack.展开更多
Previous researches on the mixed mode fracture initiation criteria were mostly focused on opening mode fracture. In this study, the authors proposed a new criterion for mixed mode sliding fracture initiation, which is...Previous researches on the mixed mode fracture initiation criteria were mostly focused on opening mode fracture. In this study, the authors proposed a new criterion for mixed mode sliding fracture initiation, which is the maximum twin shear stress factor criterion. The authors studied a finite width plate with central slant crack, subject to a far field uniform uniaxial tensile or compressive stress.展开更多
文摘The undrained shear strength （su） of fine-grained soils that can be measured in situ and in laboratory isone of the key geotechnical parameters. The unconfined compression test （UCT） is widely used in laboratoryto measure this parameter due to its simplicity; however, it is severely affected by sampledisturbance. The vane shear test （VST） technique that is less sensitive to sample disturbance involves acorrection factor against the soil plasticity, commonly known as the Bjerrum＇s correction factor, m. Thisstudy aims to reevaluate the Bjerrum＇s correction factor in consideration of a different approach and arelatively new method of testing. Atterberg limits test, miniature VST, and reverse extrusion test （RET）were conducted on 120 remolded samples. The effect of soil plasticity on undrained shear strength wasexamined using the liquidity index instead of Bjerrum＇s correction factor. In comparison with the resultobatined using the Bjerrum＇s correction factor, the undrained shear strength was better representedwhen su values were correlated with the liquidity index. The results were validated by the RET, whichwas proven to take into account soil plasticity with a reliable degree of accuracy. This study also showsthat the RET has strong promise as a new tool for testing undrained shear strength of fine-grained soils.
基金TheNationalNaturalScienceFoundationofChina (No .5 0 0 74 0 34)
文摘The granular dynamic shear strength is the same as that of the static one in nature, as found from numerous experiments and investigations. The shear strength is equal to the sum of the internal frictional force and the cohesive force. The influences of type, shape, size distribution, pore ratio, moisture content and variation of vibration velocity on the dynamic shear strength of granules were studied. Based on numerous vibration shear experiments, the authors investigate the mechanism of dynamic shear strength in granules in terms of the fundamental principle and the relevant theory of modern tribology.
基金the National Natural Science Foundation of China (39970269)
文摘Objective:To determine the effect of antiparallel phosphorothioate triplex-forming oligonucleotide(apsTFO),which was designed according to shear stress response element(SSRE) in tissue factor(TF) gene promoter region,on the expression of endothelial TF in carotid artery stenosis rats.Methods:Rat model of severe carotid artery stenosis were inflicted by silica gel tube ligation.Half an hour before the model infliction,GT20-apsTFO,GT20-psTFO and GT21-apsTFO labeled with green fluorescence(FITC) were injected into the vena caudalis of rat at a dose of 0.5 mg/kg.Half an hour,4 or 9 h after the ligation,the distribution of TFO in the common carotid artery,the liver and the kidney was detected with aid of fluorescence microscopy.And the mRNA and protein expressions of TF,Egr-1 and Sp1 in the above-mentioned organs were determined with in situ hybridization and immunohistochemical assay respectively in 6 h after the model establishment,and the results were analyzed with an image analysis system.Results:Only in 1 h after TFO injection,fluorescent granules appeared in the liver,the kidney and the vascular wall and lumen of carotid artery,and then in 4.5 h,they still deposited in above sites except the vascular lumen.GT20-apsTFO and GT21-apsTFO significant down-regulated the mRNA and protein expressions of TF compared to the rats without treatment(P<0.05),and the former apsTFO had a more stronger effect than the later(P<0.05).GT20-psTFO had no such effect(P>0.05).The 3 TFOs had no inhibition on the mRNA and protein expressions of Egr-1 and Sp1.Conclusion:Pretreated apsTFO can partly come into the vascular endothelial cells,and inhibit TF expression induced by shear stress,but had no effect on Egr-1 and Sp1 gene expressions.
基金The Specialized Funds for National Key Basic Study (G1998040704), the Dual Project of China Earthquake Admini-stration (9691309020301), and National Natural Sciences Foundation of China (46764010).
文摘The caustic method is applied to compressive shear experiment and used to detect the stress intensity factors of cracks prefabricated on plexiglass sample. Loading, friction of crack planes and influence among cracks are not needed to know as they are combined and transformed into the caustic shadow used in detecting the stress intensity factor. Even boundary condition is not necessary. Therefore it is effective to determine the stress intensity factor of compressive shear crack.
文摘Previous researches on the mixed mode fracture initiation criteria were mostly focused on opening mode fracture. In this study, the authors proposed a new criterion for mixed mode sliding fracture initiation, which is the maximum twin shear stress factor criterion. The authors studied a finite width plate with central slant crack, subject to a far field uniform uniaxial tensile or compressive stress.
