The primary goal of this study is the design and construction of semi-flexible pavement(SFP)mixture in accordance with the engineering and mechanical criteria.This study involves the use of a range of gradation curves...The primary goal of this study is the design and construction of semi-flexible pavement(SFP)mixture in accordance with the engineering and mechanical criteria.This study involves the use of a range of gradation curves,air void contents,cellulose and synthesized fibers,and neat and modified asphalt binders to prepare the open-graded asphalt(OGA)mixtures.To analyze the characteristics of these mixtures,a variety of test,namely binder drainage,semi-circular bending(SCB),Cantabro,wheel tracking,indirect tensile strength(ITS),and permeability tests were conducted.Additionally,to analyze the prepared grouting material,flexural strength,compressive strength,and fluidity tests were conducted.In the final stage,SFP was compared to HMA in terms of engineering characteristics and performance.According to the results,SFP was more resistant to skid,rutting,fire,and moisture damage,while HMA had a better performance in fracture tests,including SCB test.According to the results of the mechanical performance tests conducted on OGA mixtures,the highest and lowest values for air void content to achieve the highest mechanical performance level were 30%-35%and 25%,respectively.Also,based on the laboratory results,it was determined that the required void ratio for constructing OGA mixtures was 24%-26%based on the bitumen type and fibers amount in the mixture.Finally,SFP mixture can be regarded as a viable alternative to common pavements thanks to its high resistance to rutting and moisture damage,long freezing-thawing fatigue life,and adequate fire and skid resistance.展开更多
Background:Low cardiorespiratory fitness is an independent predictor of all-cause and cardiovascular mortality,and interventions that increase fitness reduce risk.Water-walking decreases musculoskeletal impact and ris...Background:Low cardiorespiratory fitness is an independent predictor of all-cause and cardiovascular mortality,and interventions that increase fitness reduce risk.Water-walking decreases musculoskeletal impact and risk of falls in older individuals,but it is unclear whether water-walking improves aerobic fitness in the same way as weight-dependent land-walking.This randomized controlled trial involved 3 intervention groups—a no-exercise control group(CG),a land-walking(LW)group,and a water-walking(WW)group—to investigate the comparative impacts of LWandWWto CG on fitness.Methods:Both exercise groups attended individually tailored,center-based,intensity-matched 3×weekly sessions for 24 weeks,which progressed to 150 min of exercise per week.This was followed by a 24-week no-intervention period.Maximal graded exercise tests were performed on a treadmill at Weeks 0,24,and 48.Results:Maximal oxygen uptake increased from Week 0 to Week 24 in both exercise groups(0.57±0.62 mL/kg/min,0.03±0.04 L/min for LW;0.93±0.75 mL/kg/min,0.06±0.06 L/min for WW,mean±SE)compared to the CG(-1.75±0.78 mL/kg/min,-0.16±0.05 L/min)(group×time,p<0.05).Time to exhaustion increased significantly following LW only(123.4±25.5 s),which was significantly greater(p=0.001)than the CG(24.3±18.5 s).By Week 48,the training-induced adaptations in the exercise groups returned to near baseline levels.Conclusion:Our study supports current physical-activity recommendations that 150 min/week of moderate-intensity exercise produces improvements in fitness in previously sedentary older individuals.Also,LW andWW elicit similar improvements in fitness if conducted at the same relative intensities.Exercise-na?ve older individuals can benefit from the lower impact forces and decreased risk of falls associated withWWwithout compromising improvements in cardiorespiratory fitness.展开更多
The mix design method of asphalt rubber open-graded friction course （AR-OGFC） by the Marshall test and key technologies of AR-OGFC overlay are studied. Based on the draindown test, the stripping test and the Marshal...The mix design method of asphalt rubber open-graded friction course （AR-OGFC） by the Marshall test and key technologies of AR-OGFC overlay are studied. Based on the draindown test, the stripping test and the Marshall test by different beating times, the asphalt content estimating method and Marshall beat criterion are studied. It is found that the asphalt content of AR-OGFC can be estimated by the formula of Arizona, and the proper Marshall test criterion for AR-OGFC is 50 beats on both sides. By analyzing the influence of gradation on OGFC performance, the gradation of AR-OGFC is recommended, and the amount of aggregate passing 4. 75 mm should be minimized for AR-OGFC. Through investigation of AR-OGFC overlay projects, key technologies such as the treatment of underlying pavement and the selection of tack coat are advanced, and modified emulsified asphalt should be used in AR-OGFC overlay tack coat.展开更多
The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up...The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.展开更多
Introducing N_2 during sputtering and pre-oxidation of substrate were investigated to improve the adhesion of sputtered TiC coating to steel substrate. The results show that yeactive gas N_2 increases the adhesion of ...Introducing N_2 during sputtering and pre-oxidation of substrate were investigated to improve the adhesion of sputtered TiC coating to steel substrate. The results show that yeactive gas N_2 increases the adhesion of TiC coating to steel because of a graded interface existing between coating and substrate. The interaction of discharge plasma with the surface of substrate was discussed. Pre-oxidation of substrate is effective for improving the adhesion due to the fomation of FeTi0_3 which appeared as an inteylayer between coating and pre-oxidized substrate.展开更多
Mud inrush in mountain tunnel is an independent geological hazard type different from water inrush,landslide and debris flow.The intrinsic factor of mud inrush is the instability failure of disaster medium.Its essence...Mud inrush in mountain tunnel is an independent geological hazard type different from water inrush,landslide and debris flow.The intrinsic factor of mud inrush is the instability failure of disaster medium.Its essence is that when the cohesion decreases gradually with the increase of void ratio to the point where the movement of soil particles cannot be restricted,soil particles and groundwater form slurry and gush out.Thus,accurate calculation of cohesion with variable void ratios is crucial for analyzing the reliability of disaster medium.In this study,the disaster medium was regarded as graded soil and a structural model was established wherein soil particles were simplified as cubes and the inter-particle pores were represented by the clearance between cubes.On the basis of the structure model of disaster medium,a function between the soil particle distance and void ratio was derived.Cohesion is equivalent to the resultant force between soil particles per unit area;thus,a cohesion function was derived in which the void ratio is the main variable.This function considers the influence of gradation characteristics on cohesion variation and is generally applicable to various types of disaster medium.A series of direct shear tests were carried out to determine the cohesion variation for different types of disaster medium with variable void ratios.By comparing the variation of cohesion obtained through direct shear tests with those deduced by the proposed cohesion function,we verified the validity and general applicability of the cohesion function.It is of great significance because the cohesion function can accurately predict the variation of cohesion by using the void ratio,and effectively evaluate the possibility of mud inrush according to the initial mechanical properties of disaster medium.展开更多
文摘The primary goal of this study is the design and construction of semi-flexible pavement(SFP)mixture in accordance with the engineering and mechanical criteria.This study involves the use of a range of gradation curves,air void contents,cellulose and synthesized fibers,and neat and modified asphalt binders to prepare the open-graded asphalt(OGA)mixtures.To analyze the characteristics of these mixtures,a variety of test,namely binder drainage,semi-circular bending(SCB),Cantabro,wheel tracking,indirect tensile strength(ITS),and permeability tests were conducted.Additionally,to analyze the prepared grouting material,flexural strength,compressive strength,and fluidity tests were conducted.In the final stage,SFP was compared to HMA in terms of engineering characteristics and performance.According to the results,SFP was more resistant to skid,rutting,fire,and moisture damage,while HMA had a better performance in fracture tests,including SCB test.According to the results of the mechanical performance tests conducted on OGA mixtures,the highest and lowest values for air void content to achieve the highest mechanical performance level were 30%-35%and 25%,respectively.Also,based on the laboratory results,it was determined that the required void ratio for constructing OGA mixtures was 24%-26%based on the bitumen type and fibers amount in the mixture.Finally,SFP mixture can be regarded as a viable alternative to common pavements thanks to its high resistance to rutting and moisture damage,long freezing-thawing fatigue life,and adequate fire and skid resistance.
基金supported by the National Health and Medical Research Council(NHMRC)of Australia(1045204)supported by an NHMRC Principal Research Fellowship(APP1080914)supported by a National Heart Foundation of Australia Future Leader Fellowship(ID 101895)。
文摘Background:Low cardiorespiratory fitness is an independent predictor of all-cause and cardiovascular mortality,and interventions that increase fitness reduce risk.Water-walking decreases musculoskeletal impact and risk of falls in older individuals,but it is unclear whether water-walking improves aerobic fitness in the same way as weight-dependent land-walking.This randomized controlled trial involved 3 intervention groups—a no-exercise control group(CG),a land-walking(LW)group,and a water-walking(WW)group—to investigate the comparative impacts of LWandWWto CG on fitness.Methods:Both exercise groups attended individually tailored,center-based,intensity-matched 3×weekly sessions for 24 weeks,which progressed to 150 min of exercise per week.This was followed by a 24-week no-intervention period.Maximal graded exercise tests were performed on a treadmill at Weeks 0,24,and 48.Results:Maximal oxygen uptake increased from Week 0 to Week 24 in both exercise groups(0.57±0.62 mL/kg/min,0.03±0.04 L/min for LW;0.93±0.75 mL/kg/min,0.06±0.06 L/min for WW,mean±SE)compared to the CG(-1.75±0.78 mL/kg/min,-0.16±0.05 L/min)(group×time,p<0.05).Time to exhaustion increased significantly following LW only(123.4±25.5 s),which was significantly greater(p=0.001)than the CG(24.3±18.5 s).By Week 48,the training-induced adaptations in the exercise groups returned to near baseline levels.Conclusion:Our study supports current physical-activity recommendations that 150 min/week of moderate-intensity exercise produces improvements in fitness in previously sedentary older individuals.Also,LW andWW elicit similar improvements in fitness if conducted at the same relative intensities.Exercise-na?ve older individuals can benefit from the lower impact forces and decreased risk of falls associated withWWwithout compromising improvements in cardiorespiratory fitness.
文摘The mix design method of asphalt rubber open-graded friction course （AR-OGFC） by the Marshall test and key technologies of AR-OGFC overlay are studied. Based on the draindown test, the stripping test and the Marshall test by different beating times, the asphalt content estimating method and Marshall beat criterion are studied. It is found that the asphalt content of AR-OGFC can be estimated by the formula of Arizona, and the proper Marshall test criterion for AR-OGFC is 50 beats on both sides. By analyzing the influence of gradation on OGFC performance, the gradation of AR-OGFC is recommended, and the amount of aggregate passing 4. 75 mm should be minimized for AR-OGFC. Through investigation of AR-OGFC overlay projects, key technologies such as the treatment of underlying pavement and the selection of tack coat are advanced, and modified emulsified asphalt should be used in AR-OGFC overlay tack coat.
文摘The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.
文摘Introducing N_2 during sputtering and pre-oxidation of substrate were investigated to improve the adhesion of sputtered TiC coating to steel substrate. The results show that yeactive gas N_2 increases the adhesion of TiC coating to steel because of a graded interface existing between coating and substrate. The interaction of discharge plasma with the surface of substrate was discussed. Pre-oxidation of substrate is effective for improving the adhesion due to the fomation of FeTi0_3 which appeared as an inteylayer between coating and pre-oxidized substrate.
基金funded by the National Natural Science Foundation of China(Grant No.U1706223)the Natural Science Foundation of Shandong Province(Grant No.ZR2017MEE070)
文摘Mud inrush in mountain tunnel is an independent geological hazard type different from water inrush,landslide and debris flow.The intrinsic factor of mud inrush is the instability failure of disaster medium.Its essence is that when the cohesion decreases gradually with the increase of void ratio to the point where the movement of soil particles cannot be restricted,soil particles and groundwater form slurry and gush out.Thus,accurate calculation of cohesion with variable void ratios is crucial for analyzing the reliability of disaster medium.In this study,the disaster medium was regarded as graded soil and a structural model was established wherein soil particles were simplified as cubes and the inter-particle pores were represented by the clearance between cubes.On the basis of the structure model of disaster medium,a function between the soil particle distance and void ratio was derived.Cohesion is equivalent to the resultant force between soil particles per unit area;thus,a cohesion function was derived in which the void ratio is the main variable.This function considers the influence of gradation characteristics on cohesion variation and is generally applicable to various types of disaster medium.A series of direct shear tests were carried out to determine the cohesion variation for different types of disaster medium with variable void ratios.By comparing the variation of cohesion obtained through direct shear tests with those deduced by the proposed cohesion function,we verified the validity and general applicability of the cohesion function.It is of great significance because the cohesion function can accurately predict the variation of cohesion by using the void ratio,and effectively evaluate the possibility of mud inrush according to the initial mechanical properties of disaster medium.
