This paper investigates mechanical behaviours of sandstone during post-peak cyclic loading and unloading subjected to hydromechanical coupling effect, confirming the peak and residual strengths reduction laws of sands...This paper investigates mechanical behaviours of sandstone during post-peak cyclic loading and unloading subjected to hydromechanical coupling effect, confirming the peak and residual strengths reduction laws of sandstone with water pressure, and revealing the influence of water pressure on the upper limit stress and deformation characteristics of sandstone during post-peak cyclic loading and unloading.Regarding the rock strength, the experimental study confirms that the peak strength σ_(p) and residual strength σ_(r) decrease as water pressure P increases. Especially, the normalized strength parameters σ_(p)/σ_(pk) and σ_(r)/σ_(re) was negatively and linearly correlated with the P/σ_(3). Moreover, the Hoek-Brown strength criterion can be applied to describe the relationship between effective peak strength and effective confining stress. During post-peak cyclic loading and unloading, both the upper limit stress σ_(p(i)) and crack damage threshold stress σ_(cd(i)) of each cycle tend to decrease with the increasing cycle number. A hysteresis loop exists among the loading and unloading stress–strain curves, indicating the unloading deformation modulus E_(unload) is larger than the loading deformation modulus E_(load). Based on experimental results,a post-peak strength prediction model related to water pressure and plastic shear strain is established.展开更多
This paper presents the experimental results to understand the performance of moderately loaded high speed single stage transonic axial flow compressor subjected to various configurations of axial extensions of bend s...This paper presents the experimental results to understand the performance of moderately loaded high speed single stage transonic axial flow compressor subjected to various configurations of axial extensions of bend skewed casing treatment with moderate porosity.The bend skewed casing treatment of 33%porosity was coupled with rectangular plenum chamber of depth equal to the slots depth.The five axial extensions of 20%,40%,60%,80%and 100%were used for the experimental evaluations of compressor performance.The main objective was to identify the optimum extension of the casing treatment with reference to rotor leading edge which results in maximum stall margin improvements with minimum loss in the stage efficiency.At each axial extension the compressor performance is distinctive.The improvement in the stall margin was very significant at some axial extensions with 4%–5%penalty in the stage efficiency.The compressors stage shows recovery in terms of efficiency at lower axial extensions of 20%and 40%with increase in the peak stage efficiency.Measurements of flow parameters showed the typical behaviors at near stall flow conditions.Hot wire sensor was placed at the rotor upstream in the tip region to capture the oscillations in the inlet axial and tangential velocities at stall conditions.In the absence of casing treatment the compressor exhibit abrupt stall with very high oscillations in the inlet axial and tangential velocity of the flow.The extents of oscillations reduce with bend skewed casing treatment.Few measurements were also performed in the plenum chamber and salient results are presented in this paper.展开更多
[Objective] This study was to reveal the differences in two terminal oxdiases,so as to provide theoretical basis for the selection of upland and sea-land hybrid materials. [Methods] Using 7 shares of upland cotton cul...[Objective] This study was to reveal the differences in two terminal oxdiases,so as to provide theoretical basis for the selection of upland and sea-land hybrid materials. [Methods] Using 7 shares of upland cotton cultivars and 4 shares of sea-land cultivars as experimental materials,the change differences in AAO and PPO activities during whole growth period of the materials tested were studied. [Results] Two terminal oxdiases both in upland and sea-land cotton cultivars assumed similar change laws during whole growth period. AAO activity assumed a low-high trend,and there is a peak at the early stage. PPO activity presented two peaks,and that at the early stage was higher than at the late stage; the first peak is obviously higher than the second for sea-land cultivars,and two peaks are not remarkably different for upland cultivars. [Conclusion] The differences in AAO and PPO activities of sea-land and upland cotton cultivars observed on Jul.4th and Aug.6th,may provide guidance for the selection of upland and sea-land hybrids.展开更多
In this article,the post-peak softening stage of the constitutive relation and the elastic stiffness degradation of concrete are investigated,and a highly reasonable constitutive relation curve is proposed.At the mate...In this article,the post-peak softening stage of the constitutive relation and the elastic stiffness degradation of concrete are investigated,and a highly reasonable constitutive relation curve is proposed.At the material level,the energy change in the concrete failure process is studied based on the different stress-strain curves of concrete under uniaxial tension and compression.The concrete failure criterion based on elastic strain energy density is deemed suitable and consistent with the experimental phenomena.The hysteresis phenomenon(lags behind the peak strength)is also discussed.At the structure level,the strength reduction method is employed for the stability analysis,the energy change in the failure process of the Long Xi-Kou Dam is examined,and the results show that the dam failure criterion based on elastic strain energy shows a greater significance in practical applications compared with other conventional structural failure criteria in engineering.This criterion is objective and can avoid subjective arbitrariness.展开更多
With validamycin A.（0.2 billion spores/ml） Paenibacillus polymyxa DN-1 3% AS as the test agent, the effects of different dosage and different application time on the control efficacy for＇ rich sheath blight were in...With validamycin A.（0.2 billion spores/ml） Paenibacillus polymyxa DN-1 3% AS as the test agent, the effects of different dosage and different application time on the control efficacy for＇ rich sheath blight were investigated. The results of two- year test showed that when the application amount was in the range of 45-90 g.a.i/ hm^2, the field efficacy of validamycin A-（0.2 billion spores/ml） P. polymyxa DN-1 3% AS in the initial infection stage of rich sheath blight （Le., the diseased plant rate was below 5%） reached 80.38%-89.06%, and that in the peak infection stage （i.e., the diseased plant rate was higher than 10%） reached only 41.12%-53.26%. The field efficacy of validamycin A.（0.2 billion spores/ml） P. polymyxa DN-1 3% AS at the early onset of rich sheath blight was significantly better than that at the onset, so that the application time of validamycin A .（0.2 billion spores/ml） P. polymyxa DN-1 3% AS should be appropriately brought forward in the prevention and control of rice sheath blight.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52274118 and 52274145)the Construction Project of Chenzhou National Sustainable Development Agenda Innovation Demonstration Zone(No.2021sfQ18).
文摘This paper investigates mechanical behaviours of sandstone during post-peak cyclic loading and unloading subjected to hydromechanical coupling effect, confirming the peak and residual strengths reduction laws of sandstone with water pressure, and revealing the influence of water pressure on the upper limit stress and deformation characteristics of sandstone during post-peak cyclic loading and unloading.Regarding the rock strength, the experimental study confirms that the peak strength σ_(p) and residual strength σ_(r) decrease as water pressure P increases. Especially, the normalized strength parameters σ_(p)/σ_(pk) and σ_(r)/σ_(re) was negatively and linearly correlated with the P/σ_(3). Moreover, the Hoek-Brown strength criterion can be applied to describe the relationship between effective peak strength and effective confining stress. During post-peak cyclic loading and unloading, both the upper limit stress σ_(p(i)) and crack damage threshold stress σ_(cd(i)) of each cycle tend to decrease with the increasing cycle number. A hysteresis loop exists among the loading and unloading stress–strain curves, indicating the unloading deformation modulus E_(unload) is larger than the loading deformation modulus E_(load). Based on experimental results,a post-peak strength prediction model related to water pressure and plastic shear strain is established.
基金Authors take this opportunity to thank Director,CSIRNAL,for funding the research program through elevenths five year plan and allow publishing the results.
文摘This paper presents the experimental results to understand the performance of moderately loaded high speed single stage transonic axial flow compressor subjected to various configurations of axial extensions of bend skewed casing treatment with moderate porosity.The bend skewed casing treatment of 33%porosity was coupled with rectangular plenum chamber of depth equal to the slots depth.The five axial extensions of 20%,40%,60%,80%and 100%were used for the experimental evaluations of compressor performance.The main objective was to identify the optimum extension of the casing treatment with reference to rotor leading edge which results in maximum stall margin improvements with minimum loss in the stage efficiency.At each axial extension the compressor performance is distinctive.The improvement in the stall margin was very significant at some axial extensions with 4%–5%penalty in the stage efficiency.The compressors stage shows recovery in terms of efficiency at lower axial extensions of 20%and 40%with increase in the peak stage efficiency.Measurements of flow parameters showed the typical behaviors at near stall flow conditions.Hot wire sensor was placed at the rotor upstream in the tip region to capture the oscillations in the inlet axial and tangential velocities at stall conditions.In the absence of casing treatment the compressor exhibit abrupt stall with very high oscillations in the inlet axial and tangential velocity of the flow.The extents of oscillations reduce with bend skewed casing treatment.Few measurements were also performed in the plenum chamber and salient results are presented in this paper.
基金Supported by Sub-project of Key Project in the National Science &Technology Pillar Program in the Eleventh Five-year Plan Period(2006BAD01A05-27)the Starting Program for High-level Talents in Henan Institute of Science and Technology (6009)~~
文摘[Objective] This study was to reveal the differences in two terminal oxdiases,so as to provide theoretical basis for the selection of upland and sea-land hybrid materials. [Methods] Using 7 shares of upland cotton cultivars and 4 shares of sea-land cultivars as experimental materials,the change differences in AAO and PPO activities during whole growth period of the materials tested were studied. [Results] Two terminal oxdiases both in upland and sea-land cotton cultivars assumed similar change laws during whole growth period. AAO activity assumed a low-high trend,and there is a peak at the early stage. PPO activity presented two peaks,and that at the early stage was higher than at the late stage; the first peak is obviously higher than the second for sea-land cultivars,and two peaks are not remarkably different for upland cultivars. [Conclusion] The differences in AAO and PPO activities of sea-land and upland cotton cultivars observed on Jul.4th and Aug.6th,may provide guidance for the selection of upland and sea-land hybrids.
基金supported by The National Natural Science Foundation of China(No.51739006,11132003).
文摘In this article,the post-peak softening stage of the constitutive relation and the elastic stiffness degradation of concrete are investigated,and a highly reasonable constitutive relation curve is proposed.At the material level,the energy change in the concrete failure process is studied based on the different stress-strain curves of concrete under uniaxial tension and compression.The concrete failure criterion based on elastic strain energy density is deemed suitable and consistent with the experimental phenomena.The hysteresis phenomenon(lags behind the peak strength)is also discussed.At the structure level,the strength reduction method is employed for the stability analysis,the energy change in the failure process of the Long Xi-Kou Dam is examined,and the results show that the dam failure criterion based on elastic strain energy shows a greater significance in practical applications compared with other conventional structural failure criteria in engineering.This criterion is objective and can avoid subjective arbitrariness.
基金Supported by National Agricultural Science and Technology Achievement Transformation Fund of China(2010GB2C300196)Modern Agricultural Production Development Fund(Rice Industry)Project of Anhui Academy of Agricultural SciencesIntegration and Demonstration of Chemical Fertilizer and Agrochemical Reduction and Efficiency Increasing Technology for Rice in Rice-wheat(rape)Rotation Areas in Anhui(2016YFD0200806)~~
文摘With validamycin A.（0.2 billion spores/ml） Paenibacillus polymyxa DN-1 3% AS as the test agent, the effects of different dosage and different application time on the control efficacy for＇ rich sheath blight were investigated. The results of two- year test showed that when the application amount was in the range of 45-90 g.a.i/ hm^2, the field efficacy of validamycin A-（0.2 billion spores/ml） P. polymyxa DN-1 3% AS in the initial infection stage of rich sheath blight （Le., the diseased plant rate was below 5%） reached 80.38%-89.06%, and that in the peak infection stage （i.e., the diseased plant rate was higher than 10%） reached only 41.12%-53.26%. The field efficacy of validamycin A.（0.2 billion spores/ml） P. polymyxa DN-1 3% AS at the early onset of rich sheath blight was significantly better than that at the onset, so that the application time of validamycin A .（0.2 billion spores/ml） P. polymyxa DN-1 3% AS should be appropriately brought forward in the prevention and control of rice sheath blight.
