Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of t...Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of the tensile steel tube is 0.252 during the using stage,and the average crack space of beams depends on the ratio of the sum of the bottom chord steel tube's outside diameter and the secondary bottom chord steel tube's section area to the effective tensile concrete area. The coefficient of uneven crack distribution is 1.68 and the formula for the calculation of crack width is established. Test results indicate that the ultimate stress increment of unbonded tendon in the beams decreases in linearity with the increase of the composite reinforcement index β0. The pure bending region of beams accords with the plane section assumption from loading to failure. The calculation formula of ultimate stress increment of the unbonded tendon and the method to calculate the bearing capacity of normal section of beams have been presented. Besides,the method to calculate the stiffness of this sort of beams is brought forward as well.展开更多
An analysis is made of the effect of Doppler broadening on gain without inversion （GWI） from different aspects in a closed lambda-type three-level system with an incoherent pump. It is shown that, regardless of the ...An analysis is made of the effect of Doppler broadening on gain without inversion （GWI） from different aspects in a closed lambda-type three-level system with an incoherent pump. It is shown that, regardless of the driving field being on resonance or not, for the counter- or co-propagating of the probe and driving fields （PDF）, GWI does not monotonically decrease or increase with increasing Doppler width. Except for the case of counter-propagating PDF with off-resonance driving field, at a suitable Doppler width one can obtain a gain maximum value much larger than that without Doppler broadening; especially in the situation of the resonant driving field, the co-propagating geometry leads to a larger GWI. In addition, for the counter-propagating geometry, when Doppler width is larger enough, GWI oscillation occurs, and the oscillation amplitude and region increase with increasing Doppler width. These conclusions are very different from that obtained in previous investigation （Lukin et al, Laser Phys. 6 436 （1996））.展开更多
This study was conducted to study the effects of the addition of encapsulated and non-encapsulated compound acidifiers （in a diet based on corn-soybean meal-extruded soybean） on growth performance and incidence of d...This study was conducted to study the effects of the addition of encapsulated and non-encapsulated compound acidifiers （in a diet based on corn-soybean meal-extruded soybean） on growth performance and incidence of diarrhea in weaning piglets. Sixty-four 28-day-old, crossbred piglets （Landrace × Large White）, weighing an average of 7.004- 0.10 kg, were randomly assigned to four treatments with four replicates per pen, according to the single-factor design principle. The feeding trial lasted for 35 days. The results showed that, when compared to non-encapsulated acidifiers, encapsulated compound acidifiers not only improved the average daily gain and the feed efficiency （P 〈 0.01）, but also reduced the incidence of diarrhea. However, the addition of encapsulated compound acidifiers in piglet diets had no significant effect on the average daily food intake （P〉0.05）. These results indicated that the encapsulated compound acidifiers enhanced the intestinal adaptation, and subsequently improved the growth performance and reduced the incidence of diarrhea in weaning piglets.展开更多
文摘Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of the tensile steel tube is 0.252 during the using stage,and the average crack space of beams depends on the ratio of the sum of the bottom chord steel tube's outside diameter and the secondary bottom chord steel tube's section area to the effective tensile concrete area. The coefficient of uneven crack distribution is 1.68 and the formula for the calculation of crack width is established. Test results indicate that the ultimate stress increment of unbonded tendon in the beams decreases in linearity with the increase of the composite reinforcement index β0. The pure bending region of beams accords with the plane section assumption from loading to failure. The calculation formula of ultimate stress increment of the unbonded tendon and the method to calculate the bearing capacity of normal section of beams have been presented. Besides,the method to calculate the stiffness of this sort of beams is brought forward as well.
基金Project supported by the National Natural Science Foundation of China （Grant No 10675076）, the Natural Science Foundation of Shandong Province of China （Grant No Y2006A21） and the State Key Laboratory of High Field Laser Physics, Shanghai Institute of 0ptics and Fine Mechanics, Chinese Academy of Sciences.
文摘An analysis is made of the effect of Doppler broadening on gain without inversion （GWI） from different aspects in a closed lambda-type three-level system with an incoherent pump. It is shown that, regardless of the driving field being on resonance or not, for the counter- or co-propagating of the probe and driving fields （PDF）, GWI does not monotonically decrease or increase with increasing Doppler width. Except for the case of counter-propagating PDF with off-resonance driving field, at a suitable Doppler width one can obtain a gain maximum value much larger than that without Doppler broadening; especially in the situation of the resonant driving field, the co-propagating geometry leads to a larger GWI. In addition, for the counter-propagating geometry, when Doppler width is larger enough, GWI oscillation occurs, and the oscillation amplitude and region increase with increasing Doppler width. These conclusions are very different from that obtained in previous investigation （Lukin et al, Laser Phys. 6 436 （1996））.
文摘This study was conducted to study the effects of the addition of encapsulated and non-encapsulated compound acidifiers （in a diet based on corn-soybean meal-extruded soybean） on growth performance and incidence of diarrhea in weaning piglets. Sixty-four 28-day-old, crossbred piglets （Landrace × Large White）, weighing an average of 7.004- 0.10 kg, were randomly assigned to four treatments with four replicates per pen, according to the single-factor design principle. The feeding trial lasted for 35 days. The results showed that, when compared to non-encapsulated acidifiers, encapsulated compound acidifiers not only improved the average daily gain and the feed efficiency （P 〈 0.01）, but also reduced the incidence of diarrhea. However, the addition of encapsulated compound acidifiers in piglet diets had no significant effect on the average daily food intake （P〉0.05）. These results indicated that the encapsulated compound acidifiers enhanced the intestinal adaptation, and subsequently improved the growth performance and reduced the incidence of diarrhea in weaning piglets.
