In the first step, the Ehrenfest reasoning concerning the adiabatic invariance of the angular orbital momentum is applied to the electron motion in the hydrogen atom. It is demonstrated that the time of the energy emi...In the first step, the Ehrenfest reasoning concerning the adiabatic invariance of the angular orbital momentum is applied to the electron motion in the hydrogen atom. It is demonstrated that the time of the energy emission from the quantum level n+1 to level n can be deduced from the orbital angular momentum examined in the hydrogen atom. This time is found precisely equal to the time interval dictated by the Joule-Lenz law governing the electron transition between the levels n+1 and n. In the next step, the mechanical parameters entering the quantum systems are applied in calculating the time intervals characteristic for the electron transitions. This concerns the neighbouring energy levels in the hydrogen atom as well as the Landau levels in the electron gas submitted to the action of a constant magnetic field.展开更多
The geological tectonic zone is closely related to outburst.Taking the outburst coal bodies in tectonic zones as the research object,combined with DIC and AE monitoring technologies and discrete element simulation,the...The geological tectonic zone is closely related to outburst.Taking the outburst coal bodies in tectonic zones as the research object,combined with DIC and AE monitoring technologies and discrete element simulation,the mechanical response,crack evolution and energy characteristics of coal bodies under different loading rates(impact disturbances)were studied.The results show that both the uniaxial compressive strength and elastic modulus are positively correlated with the loading rate,with a maximum increase in compressive strength of 25.15%.The uniaxial compressive strength is more sensitive to impact disturbances.The failure modes of coal bodies can be divided into the“slip-crack synchronization(S&C)type”and the“crack-first-then-slip(C&S)type”.The slip in tectonic zones is more severe at high loading rates.At low loading rates,shear cracks dominate(60.01%),while the proportion of tensile cracks increases significantly(70.52%)at high loading rates.Additionally,the rate of axial crack growth decreases as the loading rate increases.The peak values of total energy and dissipated energy increase significantly with the loading rate,and the peak energy of the C&S type is greater than that of the S&C type.Energy is preferentially released through the slip of tectonic zones and the propagation of radial cracks.展开更多
Strength and deformability characteristics of rock with pre-existing fissures are governed by cracking behavior. To further research the effects of pre-existing fissures on the mechanical properties and crack coalesce...Strength and deformability characteristics of rock with pre-existing fissures are governed by cracking behavior. To further research the effects of pre-existing fissures on the mechanical properties and crack coalescence process, a series of uniaxial compression tests were carried out for rock-like material with two unparallel fissures.In the present study, cement, quartz sand, and water were used to fabricate a kind of brittle rock-like material cylindrical model specimen. The mechanical properties of rock-like material specimen used in this research were all in good agreement with the brittle rock materials. Two unparallel fissures（a horizontal fissure and an inclined fissure） were created by inserting steel during molding the model specimen.Then all the pre-fissured rock-like specimens were tested under uniaxial compression by a rock mechanics servocontrolled testing system. The peak strength and Young＇s modulus of pre-fissured specimen all first decreased and then increased when the fissure angle increased from 0？to 75？.In order to investigate the crack initiation, propagation and coalescence process, photographic monitoring was adopted to capture images during the entire deformation process.Moreover, acoustic emission（AE） monitoring technique was also used to obtain the AE evolution characteristic of prefissured specimen. The relationship between axial stress, AE events, and the crack coalescence process was set up： when a new crack was initiated or a crack coalescence occurred, thecorresponding axial stress dropped in the axial stress–time curve and a big AE event could be observed simultaneously.Finally, the mechanism of crack propagation under microscopic observation was discussed. These experimental results are expected to increase the understanding of the strength failure behavior and the cracking mechanism of rock containing unparallel fissures.展开更多
Formaldehyde emissions from medium-density fiberboard(MDF)are significantly influenced by humidity.However,existing emission models predominantly rely on static humidity or instantaneous equilibration assumptions,ther...Formaldehyde emissions from medium-density fiberboard(MDF)are significantly influenced by humidity.However,existing emission models predominantly rely on static humidity or instantaneous equilibration assumptions,thereby neglecting the effects of dynamic moisture transfer.This study investigated the impact of moisture transfer on formaldehyde emissions using a combined experimental and modeling approach.MDF samples were exposed to equilibrium and moisture transfer conditions in controlled chambers,respectively.Key emission parameters—initial emittable concentration(C0),diffusion coefficient(Dm),and partition coefficient(K)—were regressed based on dynamic measurement data.The results indicated that humidity had a positive correlation with formaldehyde emissions,increasing C0 values more significantly compared to other emission parameters.Moisture transfer introduced directional biases in parameter estimation:inward transfer(from environment to material)reduced Dm by 61%but increased C0 by 136%,whereas outward transfer(from material to environment)elevated Dm by 40%and decreased C0 by 13%.These deviations substantially distorted indoor formaldehyde predictions,with simulations underestimating peak concentrations by 6%for inward transfer scenario and overestimating them by 20%for outward transfer scenario.The findings emphasize the necessity of incorporating transient humidity gradients into emission models to improve the accuracy of indoor air quality assessments.展开更多
文摘In the first step, the Ehrenfest reasoning concerning the adiabatic invariance of the angular orbital momentum is applied to the electron motion in the hydrogen atom. It is demonstrated that the time of the energy emission from the quantum level n+1 to level n can be deduced from the orbital angular momentum examined in the hydrogen atom. This time is found precisely equal to the time interval dictated by the Joule-Lenz law governing the electron transition between the levels n+1 and n. In the next step, the mechanical parameters entering the quantum systems are applied in calculating the time intervals characteristic for the electron transitions. This concerns the neighbouring energy levels in the hydrogen atom as well as the Landau levels in the electron gas submitted to the action of a constant magnetic field.
基金supported by the National Natural Science Foundation of China(Nos.52374122 and 51874165)the Liaoning Revitalization Talents Program(No.XLYC1902106).
文摘The geological tectonic zone is closely related to outburst.Taking the outburst coal bodies in tectonic zones as the research object,combined with DIC and AE monitoring technologies and discrete element simulation,the mechanical response,crack evolution and energy characteristics of coal bodies under different loading rates(impact disturbances)were studied.The results show that both the uniaxial compressive strength and elastic modulus are positively correlated with the loading rate,with a maximum increase in compressive strength of 25.15%.The uniaxial compressive strength is more sensitive to impact disturbances.The failure modes of coal bodies can be divided into the“slip-crack synchronization(S&C)type”and the“crack-first-then-slip(C&S)type”.The slip in tectonic zones is more severe at high loading rates.At low loading rates,shear cracks dominate(60.01%),while the proportion of tensile cracks increases significantly(70.52%)at high loading rates.Additionally,the rate of axial crack growth decreases as the loading rate increases.The peak values of total energy and dissipated energy increase significantly with the loading rate,and the peak energy of the C&S type is greater than that of the S&C type.Energy is preferentially released through the slip of tectonic zones and the propagation of radial cracks.
基金supported by the National Natural Science Foundation of China (Grant 51179189)the National Basic Research 973 Program of China (Grant 2013CB036003)+2 种基金the Program for New Century Excellent Talents in University (Grant NCET-120961)Outstanding Innovation Team Project in China University of Mining and Technology (Grant 2014QN002)the Fundamental Research Funds for the Central Universities (Grants 2014YC10 and 2014XT03)
文摘Strength and deformability characteristics of rock with pre-existing fissures are governed by cracking behavior. To further research the effects of pre-existing fissures on the mechanical properties and crack coalescence process, a series of uniaxial compression tests were carried out for rock-like material with two unparallel fissures.In the present study, cement, quartz sand, and water were used to fabricate a kind of brittle rock-like material cylindrical model specimen. The mechanical properties of rock-like material specimen used in this research were all in good agreement with the brittle rock materials. Two unparallel fissures（a horizontal fissure and an inclined fissure） were created by inserting steel during molding the model specimen.Then all the pre-fissured rock-like specimens were tested under uniaxial compression by a rock mechanics servocontrolled testing system. The peak strength and Young＇s modulus of pre-fissured specimen all first decreased and then increased when the fissure angle increased from 0？to 75？.In order to investigate the crack initiation, propagation and coalescence process, photographic monitoring was adopted to capture images during the entire deformation process.Moreover, acoustic emission（AE） monitoring technique was also used to obtain the AE evolution characteristic of prefissured specimen. The relationship between axial stress, AE events, and the crack coalescence process was set up： when a new crack was initiated or a crack coalescence occurred, thecorresponding axial stress dropped in the axial stress–time curve and a big AE event could be observed simultaneously.Finally, the mechanism of crack propagation under microscopic observation was discussed. These experimental results are expected to increase the understanding of the strength failure behavior and the cracking mechanism of rock containing unparallel fissures.
基金supported by the National Natural Science Foundation of China(Grant No.52278109).
文摘Formaldehyde emissions from medium-density fiberboard(MDF)are significantly influenced by humidity.However,existing emission models predominantly rely on static humidity or instantaneous equilibration assumptions,thereby neglecting the effects of dynamic moisture transfer.This study investigated the impact of moisture transfer on formaldehyde emissions using a combined experimental and modeling approach.MDF samples were exposed to equilibrium and moisture transfer conditions in controlled chambers,respectively.Key emission parameters—initial emittable concentration(C0),diffusion coefficient(Dm),and partition coefficient(K)—were regressed based on dynamic measurement data.The results indicated that humidity had a positive correlation with formaldehyde emissions,increasing C0 values more significantly compared to other emission parameters.Moisture transfer introduced directional biases in parameter estimation:inward transfer(from environment to material)reduced Dm by 61%but increased C0 by 136%,whereas outward transfer(from material to environment)elevated Dm by 40%and decreased C0 by 13%.These deviations substantially distorted indoor formaldehyde predictions,with simulations underestimating peak concentrations by 6%for inward transfer scenario and overestimating them by 20%for outward transfer scenario.The findings emphasize the necessity of incorporating transient humidity gradients into emission models to improve the accuracy of indoor air quality assessments.
