An accelerated decay test and a natural decay test were conducted synchronically to explore the strength degradation of decaying wood members under long-term exposure to natural environment.A natural decay test was ca...An accelerated decay test and a natural decay test were conducted synchronically to explore the strength degradation of decaying wood members under long-term exposure to natural environment.A natural decay test was carried out to measure the bending strength,compressive strength parallel to grain and modulus of elasticity of the wood members,with 6 groups of specimens decayed in natural environment for 3 to 18 months respectively.To compare with corresponding decay test,in which 6 other groups of specimens were measured under accelerated conditions.The experimental data collected were evaluated by Pearson productmoment for the correlation.The results indicate that the mechanical properties of the accelerated decay were highly correlated with those in natural environment,both of which decreased in the same trend.Under the given test conditions,the mean value of the accelerated decay test data were curve-fitted to achieve the time-dependent degradation model of the bending strength,the compressive strength parallel to grain,as well as the modulus of elasticity.Due to the high correlation,the acceleration shift factors(ASF)of the two tests were derived,where the bending strength of 2.934,the compressive strength parallel to grain of 2.519 and the elastic modulus of 2.346 were employed to formulate the strength degradation models in the long-term natural environment.The results verify that the exponential functionσ=σ0e^(-βt)enables to exactly capture the degradation of the mechanical properties of wood members decayed in natural environment.展开更多
Blocks of Moso bamboo were used as experimental materials to test the toxicity of CuAz preservative on decay fungi by the lab test in this paper. The result showed that the natural decay resistance of 4-year-old Mao b...Blocks of Moso bamboo were used as experimental materials to test the toxicity of CuAz preservative on decay fungi by the lab test in this paper. The result showed that the natural decay resistance of 4-year-old Mao bamboo is moderate, and the resistance to brown fungi is stronger than that to white fungi. The anti-fungi properties of CuAz preservative at the retention of 3.3 kg/m3 are equal to those of CCA-C and ACQ-B at the retention of about 4.0 kg/m3 , and obviously superior to those of organic acids preservatives.展开更多
In this paper,an improved discharging circuit was proposed to quicken the decay of the current in the drive coil in a reluctance accelerator when the armature reaches the center of the coil.The aim of this is to preve...In this paper,an improved discharging circuit was proposed to quicken the decay of the current in the drive coil in a reluctance accelerator when the armature reaches the center of the coil.The aim of this is to prevent the suck-back effect caused by the residual current in drive coil.The method is adding a reverse charging branch with a small capacitor in the traditional pulsed discharging circuit.The results under the traditional circuit and the improved circuit were compared in a simulation.The experiment then verified the simulations and they had good agreement.Simulation and experiment both demonstrated the improved circuit can effectively prevent the suck-back effect and increase the efficiency.At the voltage of 800 V,an efficiency increase of 36.34% was obtained.展开更多
In this study,we investigate the generation of parametric decay instability,Langmuir turbulence formation,and electron acceleration in ionospheric heating via a two-fluid model using the Fokker-Planck equation and Vla...In this study,we investigate the generation of parametric decay instability,Langmuir turbulence formation,and electron acceleration in ionospheric heating via a two-fluid model using the Fokker-Planck equation and Vlasov-Poisson system simulations.The simulation results of both the magnetofluid model and the kinetic model demonstrate the dynamics of electron acceleration.Further,the results of the Vlasov-Poisson simulations suggest the formation of electron holes in phase space at the same spatial scale as the Langmuir wave,which are shown to be related to electron acceleration.In addition,electron acceleration is enhanced through the extension of the wavenumber spectrum caused by strong Langmuir turbulence,leading to more electron holes in phase space.展开更多
基金supported by a grant from the National Natural Science Foundation of China(No.51208399)Natural Science Foundation of Hubei province of China(No.2018CFB645)Hubei Key Laboratory of Roadway Bridge and Structure Engineering(Wuhan University of Technology)(No.DQJJ201706).
文摘An accelerated decay test and a natural decay test were conducted synchronically to explore the strength degradation of decaying wood members under long-term exposure to natural environment.A natural decay test was carried out to measure the bending strength,compressive strength parallel to grain and modulus of elasticity of the wood members,with 6 groups of specimens decayed in natural environment for 3 to 18 months respectively.To compare with corresponding decay test,in which 6 other groups of specimens were measured under accelerated conditions.The experimental data collected were evaluated by Pearson productmoment for the correlation.The results indicate that the mechanical properties of the accelerated decay were highly correlated with those in natural environment,both of which decreased in the same trend.Under the given test conditions,the mean value of the accelerated decay test data were curve-fitted to achieve the time-dependent degradation model of the bending strength,the compressive strength parallel to grain,as well as the modulus of elasticity.Due to the high correlation,the acceleration shift factors(ASF)of the two tests were derived,where the bending strength of 2.934,the compressive strength parallel to grain of 2.519 and the elastic modulus of 2.346 were employed to formulate the strength degradation models in the long-term natural environment.The results verify that the exponential functionσ=σ0e^(-βt)enables to exactly capture the degradation of the mechanical properties of wood members decayed in natural environment.
基金National Forestry Key Technology Program during the 11th Five-Year Plan Period (2006BAD19B0404).
文摘Blocks of Moso bamboo were used as experimental materials to test the toxicity of CuAz preservative on decay fungi by the lab test in this paper. The result showed that the natural decay resistance of 4-year-old Mao bamboo is moderate, and the resistance to brown fungi is stronger than that to white fungi. The anti-fungi properties of CuAz preservative at the retention of 3.3 kg/m3 are equal to those of CCA-C and ACQ-B at the retention of about 4.0 kg/m3 , and obviously superior to those of organic acids preservatives.
基金This work was supported by the Fundamental Research Funds for the Central Universities[Grant number 2019XJ01].
文摘In this paper,an improved discharging circuit was proposed to quicken the decay of the current in the drive coil in a reluctance accelerator when the armature reaches the center of the coil.The aim of this is to prevent the suck-back effect caused by the residual current in drive coil.The method is adding a reverse charging branch with a small capacitor in the traditional pulsed discharging circuit.The results under the traditional circuit and the improved circuit were compared in a simulation.The experiment then verified the simulations and they had good agreement.Simulation and experiment both demonstrated the improved circuit can effectively prevent the suck-back effect and increase the efficiency.At the voltage of 800 V,an efficiency increase of 36.34% was obtained.
基金supported by the National Natural Science Foundation of China (NSFC Grant Nos. 42104150, 42074187, 41774162, and 41704155)the Foundation of the National Key Laboratory of Electromagnetic Environment (Grant No. 6142403200303)+3 种基金the Chinese Academy of Sciences, Key Laboratory of Geospace Environmentthe University of Science & Technology of China (Grant No. GE2020-01)the Fundamental Research Funds for the Central Universities (Grant No. 2042021kf0020)the Excellent Youth Foundation of Hubei Provincial Natural Science Foundation (Grant No. 2019CFA054)
文摘In this study,we investigate the generation of parametric decay instability,Langmuir turbulence formation,and electron acceleration in ionospheric heating via a two-fluid model using the Fokker-Planck equation and Vlasov-Poisson system simulations.The simulation results of both the magnetofluid model and the kinetic model demonstrate the dynamics of electron acceleration.Further,the results of the Vlasov-Poisson simulations suggest the formation of electron holes in phase space at the same spatial scale as the Langmuir wave,which are shown to be related to electron acceleration.In addition,electron acceleration is enhanced through the extension of the wavenumber spectrum caused by strong Langmuir turbulence,leading to more electron holes in phase space.
