The combination of the dipping effect and hydromechanical(H-M)coupling effect can easily lead to water inrush disasters in water-rich roadways with different dip angles in coal mines.Therefore,H-M coupling tests of be...The combination of the dipping effect and hydromechanical(H-M)coupling effect can easily lead to water inrush disasters in water-rich roadways with different dip angles in coal mines.Therefore,H-M coupling tests of bedded sandstones under identical osmotic pressure and various confining pressures were conducted.Then,the evolution curves of stress-strain,permeability and damage,macro-and mesoscopic failure characteristics were obtained.Subsequently,the mechanical behaviour was characterized,and finally the failure mechanism was revealed.The results showed that:(1)The failure of the sandstone with the bedding angle of 45°or 60°was the structure-dominant type,while that with the bedding angle of 0°,30°or 90°was the force-dominant type.(2)When the bedding angle was in the range of(0°,30°)or(45°,90°),the confining pressure played a dominant role in influencing the peak strength.However,withinβ∈(30°,45°),the bedding effect played a dominant role in the peak strength.(3)With the increase in bedding angle,the cohesion increased first,then decreased and finally increased,while the internal friction angle was the opposite.(4)When the bedding angle was 0°or 30°,the“water wedging”effect and the“bedding buckling”effect would lead to the forking or converging shear failure.When the bedding angle was 45°or 60°,the sliding friction effect would lead to the shear slipping failure.When the bedding angle was 90°,the combination of the“bedding buckling”effect and shear effect would lead to the mixed tension-shear failure.The above conclusions obtained are helpful for the prevention of water inrush disasters in water-rich roadways with different dips in coal mines.展开更多
The quantitative determination and evaluation of rock brittleness are crucial for the estimation of excavation efficiency and the improvement of hydraulic fracturing efficiency.Therefore,a“three-stage”triaxial loadi...The quantitative determination and evaluation of rock brittleness are crucial for the estimation of excavation efficiency and the improvement of hydraulic fracturing efficiency.Therefore,a“three-stage”triaxial loading and unloading stress path is designed and proposed.Subsequently,six brittleness indices are selected.In addition,the evolution characteristics of the six brittleness indices selected are characterized based on the bedding effect and the effect of confining pressure.Then,the entropy weight method(EWM)is introduced to assign weight to the six brittleness indices,and the comprehensive brittleness index Bcis defined and evaluated.Next,the new brittleness classification standard is determined,and the brittleness differences between the two stress paths are quantified.Finally,compared with the previous evaluation methods,the rationality of the proposed comprehensive brittleness index Bcis also verified.These results indicate that the proposed brittleness index Bccan reflect the brittle characteristics of deep bedded sandstone from the perspective of the whole life-cycle evolution process.Accordingly,the method proposed seems to offer reliable evaluations of the brittleness of deep bedded sandstone in deep engineering practices,although further validation is necessary.展开更多
Fluidized beds have been widely used for processing granular materials. In this paper, we study the effect of plasma on the fluidization behavior of a bubbling fluidized bed with an atmospheric pressure plasma dischar...Fluidized beds have been widely used for processing granular materials. In this paper, we study the effect of plasma on the fluidization behavior of a bubbling fluidized bed with an atmospheric pressure plasma discharger. Experiment results show that the bubbling fluidized bed is stabilized with the discharge of plasma. When the discharge current reaches a minimum stabilization current Cms, air bubbles in the bed will disappear and the surface fluctuation is completely suppressed.A simplified model is proposed to consider the effect of electric Coulomb force generated by the plasma. It is found that the Coulomb force will propel the particles to move towards the void area, so that the bubbling fluidized bed is stabilized with a high enough plasma discharge.展开更多
Analyses made among four radiotherapy schedules for NPC in order to determine whether there is an impact of radiotherapy course length on treatment results.A series of 320 NPC patients were divided into four radiati...Analyses made among four radiotherapy schedules for NPC in order to determine whether there is an impact of radiotherapy course length on treatment results.A series of 320 NPC patients were divided into four radiation treatment branches each with a schedule, this clinical trial was non-randomized.Radiotherapy course length factor was considered with a derivative LQ model formula that biological effective dose(BED)=nd[1 +d/(α/β)]-(T-28).The four branches were:1.split-course 103 cases, with an intermediary rest of 3-4 weeks,mean total dose 70Gy/35fx,73d, BED 51.6 Gy; 2.continuous 115 cases, 72Gy/36fx, 61d, BED 62.6 Gy;3.hyperfractionation I 52 cases, 1.5 Gy b.i.d.,time interval(Ti)≥6 hr, 75Gy/49fx,57d,BED 65.5Gy;4. hyperfractionation Ⅱ 50 cases, 1.2 Gy b.i.d., Ti≥6hr,76Gy/60fx,59d,BED 63.0 Gy.Treatment results were compared with 1-, and 3-year loco-regional recurrent rates,and 1-,and 3-year survival rates, and these rates were of a negative interrelation with prolonged course duration, but of a positive one with BED valas.Continuous branch was of a course mean 12 days shorter than the spilt-course one, its treatment results were nearly 10% higher in some subgroups;and hyperfractionation branches were slightly better than continuous one.展开更多
Simulations of fixed beds having column to particle diameter ratio (D/dp) of 3, 5 and 10 were performed in the creeping, transition and turbulent flow regimes, where Reynolds number (dpVLρL/μL) was varied from 0...Simulations of fixed beds having column to particle diameter ratio (D/dp) of 3, 5 and 10 were performed in the creeping, transition and turbulent flow regimes, where Reynolds number (dpVLρL/μL) was varied from 0.1 to 10,000. The deviations from Ergun's equation due to the wall effects, which are important in D/dp 〈 15 beds were well explained by the CFD simulations. Thus, an increase in the pressure drop was observed due to the wall friction in the creeping flow, whereas, in turbulent regime a decrease in the pressure drop was observed due to the channeling near the wall. It was observed that, with an increase in the D/dp ratio, the effect of wall on drag coefficient decreases and drag coefficient nearly approaches to Ergun's equation. The predicted drag coefficient values were in agreement with the experimental results reported in the literature, in creeping flow regime, whereas in turbulent flow the difference was within 10-15%.展开更多
Expanded fluidization behavior in liquid-solid mini-fluidized beds (MFBs) was experimentally investigated using visual measurements. Wall effects in the liquid-solid MFBs were identified and explained. The measured ...Expanded fluidization behavior in liquid-solid mini-fluidized beds (MFBs) was experimentally investigated using visual measurements. Wall effects in the liquid-solid MFBs were identified and explained. The measured incipient]minimum fluidization liquid velocity (Umf) in the MFBs was 1.67 to 5.25 times higher than that calculated using the Ergun equation when the ratio of solid particle diameter to bed diameter varied from 0.017 to 0.091. The ratio of the Richardson-Zaki (R-Z) exponent obtained by fitting with experimental data to that calculated using the R-Z correlation varied from 0.92 to 0.55. A wider solid particle size distribution resulted in a smaller R-Z exponent. The influence of the solid particle material on Umf and R-Z exponent was negligible.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52034009 and 51974319)the Yue Qi Distinguished Scholar Project(Grant No.2020JCB01).
文摘The combination of the dipping effect and hydromechanical(H-M)coupling effect can easily lead to water inrush disasters in water-rich roadways with different dip angles in coal mines.Therefore,H-M coupling tests of bedded sandstones under identical osmotic pressure and various confining pressures were conducted.Then,the evolution curves of stress-strain,permeability and damage,macro-and mesoscopic failure characteristics were obtained.Subsequently,the mechanical behaviour was characterized,and finally the failure mechanism was revealed.The results showed that:(1)The failure of the sandstone with the bedding angle of 45°or 60°was the structure-dominant type,while that with the bedding angle of 0°,30°or 90°was the force-dominant type.(2)When the bedding angle was in the range of(0°,30°)or(45°,90°),the confining pressure played a dominant role in influencing the peak strength.However,withinβ∈(30°,45°),the bedding effect played a dominant role in the peak strength.(3)With the increase in bedding angle,the cohesion increased first,then decreased and finally increased,while the internal friction angle was the opposite.(4)When the bedding angle was 0°or 30°,the“water wedging”effect and the“bedding buckling”effect would lead to the forking or converging shear failure.When the bedding angle was 45°or 60°,the sliding friction effect would lead to the shear slipping failure.When the bedding angle was 90°,the combination of the“bedding buckling”effect and shear effect would lead to the mixed tension-shear failure.The above conclusions obtained are helpful for the prevention of water inrush disasters in water-rich roadways with different dips in coal mines.
基金supported by the National Natural Science Foundation of China(Nos.52034009 and 51974319)the Yue Qi Distinguished Scholar Project(No.2020JCB01)。
文摘The quantitative determination and evaluation of rock brittleness are crucial for the estimation of excavation efficiency and the improvement of hydraulic fracturing efficiency.Therefore,a“three-stage”triaxial loading and unloading stress path is designed and proposed.Subsequently,six brittleness indices are selected.In addition,the evolution characteristics of the six brittleness indices selected are characterized based on the bedding effect and the effect of confining pressure.Then,the entropy weight method(EWM)is introduced to assign weight to the six brittleness indices,and the comprehensive brittleness index Bcis defined and evaluated.Next,the new brittleness classification standard is determined,and the brittleness differences between the two stress paths are quantified.Finally,compared with the previous evaluation methods,the rationality of the proposed comprehensive brittleness index Bcis also verified.These results indicate that the proposed brittleness index Bccan reflect the brittle characteristics of deep bedded sandstone from the perspective of the whole life-cycle evolution process.Accordingly,the method proposed seems to offer reliable evaluations of the brittleness of deep bedded sandstone in deep engineering practices,although further validation is necessary.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11035005 and 11034010)
文摘Fluidized beds have been widely used for processing granular materials. In this paper, we study the effect of plasma on the fluidization behavior of a bubbling fluidized bed with an atmospheric pressure plasma discharger. Experiment results show that the bubbling fluidized bed is stabilized with the discharge of plasma. When the discharge current reaches a minimum stabilization current Cms, air bubbles in the bed will disappear and the surface fluctuation is completely suppressed.A simplified model is proposed to consider the effect of electric Coulomb force generated by the plasma. It is found that the Coulomb force will propel the particles to move towards the void area, so that the bubbling fluidized bed is stabilized with a high enough plasma discharge.
文摘Analyses made among four radiotherapy schedules for NPC in order to determine whether there is an impact of radiotherapy course length on treatment results.A series of 320 NPC patients were divided into four radiation treatment branches each with a schedule, this clinical trial was non-randomized.Radiotherapy course length factor was considered with a derivative LQ model formula that biological effective dose(BED)=nd[1 +d/(α/β)]-(T-28).The four branches were:1.split-course 103 cases, with an intermediary rest of 3-4 weeks,mean total dose 70Gy/35fx,73d, BED 51.6 Gy; 2.continuous 115 cases, 72Gy/36fx, 61d, BED 62.6 Gy;3.hyperfractionation I 52 cases, 1.5 Gy b.i.d.,time interval(Ti)≥6 hr, 75Gy/49fx,57d,BED 65.5Gy;4. hyperfractionation Ⅱ 50 cases, 1.2 Gy b.i.d., Ti≥6hr,76Gy/60fx,59d,BED 63.0 Gy.Treatment results were compared with 1-, and 3-year loco-regional recurrent rates,and 1-,and 3-year survival rates, and these rates were of a negative interrelation with prolonged course duration, but of a positive one with BED valas.Continuous branch was of a course mean 12 days shorter than the spilt-course one, its treatment results were nearly 10% higher in some subgroups;and hyperfractionation branches were slightly better than continuous one.
基金One of us (Rupesh Kumar Reddy Guntaka) acknowledges the fellowship support given by the university Grant Commission (UGC),Government of India
文摘Simulations of fixed beds having column to particle diameter ratio (D/dp) of 3, 5 and 10 were performed in the creeping, transition and turbulent flow regimes, where Reynolds number (dpVLρL/μL) was varied from 0.1 to 10,000. The deviations from Ergun's equation due to the wall effects, which are important in D/dp 〈 15 beds were well explained by the CFD simulations. Thus, an increase in the pressure drop was observed due to the wall friction in the creeping flow, whereas, in turbulent regime a decrease in the pressure drop was observed due to the channeling near the wall. It was observed that, with an increase in the D/dp ratio, the effect of wall on drag coefficient decreases and drag coefficient nearly approaches to Ergun's equation. The predicted drag coefficient values were in agreement with the experimental results reported in the literature, in creeping flow regime, whereas in turbulent flow the difference was within 10-15%.
文摘Expanded fluidization behavior in liquid-solid mini-fluidized beds (MFBs) was experimentally investigated using visual measurements. Wall effects in the liquid-solid MFBs were identified and explained. The measured incipient]minimum fluidization liquid velocity (Umf) in the MFBs was 1.67 to 5.25 times higher than that calculated using the Ergun equation when the ratio of solid particle diameter to bed diameter varied from 0.017 to 0.091. The ratio of the Richardson-Zaki (R-Z) exponent obtained by fitting with experimental data to that calculated using the R-Z correlation varied from 0.92 to 0.55. A wider solid particle size distribution resulted in a smaller R-Z exponent. The influence of the solid particle material on Umf and R-Z exponent was negligible.