The influence of thermal damage on macroscopic and microscopic characteristics of different rocks has received much attention in the field of rock engineering.When the rocks are subjected to thermal treatment,the chan...The influence of thermal damage on macroscopic and microscopic characteristics of different rocks has received much attention in the field of rock engineering.When the rocks are subjected to thermal treatment,the change of macroscopic characteristics and evolution of micro-structure would be induced,ultimately resulting in different degrees of thermal damage in rocks.To better understand the thermal damage mechanism of different rocks and its effect on the rock performance,this study reviews a large number of test results of rock specimens experiencing heating and cooling treatment in the laboratory.Firstly,the variations of macroscopic behaviors,including physical parameters,mechanical parameters,thermal conductivity and permeability,are examined.The variations of mechanical parameters with thermal treatment variables(i.e.temperature or the number of thermal cycles)are divided into four types.Secondly,several measuring methods for microstructure,such as polarizing microscopy,fluorescent method,scanning electron microscopy(SEM),X-ray computerized tomography(CT),acoustic emission(AE)and ultrasonic technique,are introduced.Furthermore,the effect of thermal damage on the mechanical parameters of rocks in response to different thermal treatments,involving temperature magnitude,cooling method and thermal cycle,are discussed.Finally,the limitations and prospects for the research of rock thermal damage are proposed.展开更多
In recent years, the spin parity effect in magnetic macroscopic quantum tunneling has attracted extensive attention. Using the spin coherent-state path-integral method it is shown that if the HamiltonianH of a single-...In recent years, the spin parity effect in magnetic macroscopic quantum tunneling has attracted extensive attention. Using the spin coherent-state path-integral method it is shown that if the HamiltonianH of a single-spin system hasM - fold rotational symmetry around z-axis, the tunneling amplitude 〈?S|e Ht |S〉 vanishes when S, the quantum number of spin, is not an integer multiple ofM/2, where |m〉 (m=-S, -S +1, ?, S) are the eigenstates of Sz. Not only is a pure quantum mechanical approach adopted to the above result, but also is extended to more general cases where the quantum system consists ofN spins, the quantum numbers of which can take any values, including the single-spin system, ferromagnetic particle and antiferromagnetic particle as particular instances, and where the states involved are not limited to the extreme ones. The extended spin parity effect is that if the Hamiltonian ? of the system ofN spins also has the above symmetry, then 〈m′N?m′2 m′1|e?H t |m 1 m 2?m N vanishes when ∑ i=1 N (m i?m′1) not an integer multiple ofM, where |m 1 m 2?m N〉=∏ α=1 N |m a 〉 are the eigenstates of S a z . In addition, it is argued that for large spin the above result, the so-called spin parity effect, does not mean the quenching of spin tunneling from the direction of ⊕-z to that of ±z.展开更多
The spin parity effect resulting from time_inversion symmetry is derived by generalizing the pure quantum theory of the effect resulting from finite_fold axial_rotation symmetry. The quantum system concerned may consi...The spin parity effect resulting from time_inversion symmetry is derived by generalizing the pure quantum theory of the effect resulting from finite_fold axial_rotation symmetry. The quantum system concerned may consist of either one spin or many spins with arbitrary spin quantum numbers and the states involved may be any pair of eigenstates of spin operator projected on arbitrary axis with their eigenvalues having opposite signs. The two kinds of spin parity effect, resulting from time_inversion symmetry and from axial_rotation symmetry, are in general not equivalent but complementary to each other.展开更多
Macroscopic organisms lived in the Yangtze Sea of South China during the Late Doushantuo period of the Ediacaran.The results of the specimen collections and statistics within each meter show that the macroscopic biota...Macroscopic organisms lived in the Yangtze Sea of South China during the Late Doushantuo period of the Ediacaran.The results of the specimen collections and statistics within each meter show that the macroscopic biota from the Ediacaran Doushantuo Formation in northeast Guizhou,South China,can be subdivided into Globusphyton,Cucullus,Sectoralga-Longifuniculum, Beltanelliformis,and Baculiphyca-Gesinella paleo-communities.The paleo-community evolution indicates the relationship not only between biota and environment,but also between metaphytes and metazoans.From the Globusphyton paleo-community,through to the Sectoralga-Longifuniculum paleo-community,to the Cucullus paleo-community,the increase in the abundance and diversity of metaphytes（especially the branching macroalgae）and metazoans implies that the oxygen content in the seawater increased gradually.Both the Beltanelliformis and Baculiphyca-Gesinella paleo-communities could be related to a deteriorated environment and fragile ecosystem.The emergence,abundance,and diversity of macroscopic metaphytes,which were closely connected with the environmental microchanges,accelerated the process,improving the environment and increasing oxygen,and established an important platform for the development of macroscopic metazoans.展开更多
The evolution of gas bearing channels in the roof,and their spatial distribution,was studied.A complete consideration of gas flow changes through the stress-strain changes in the roof near a working face is made.The t...The evolution of gas bearing channels in the roof,and their spatial distribution,was studied.A complete consideration of gas flow changes through the stress-strain changes in the roof near a working face is made.The theoretical abutment pressure distribution using displacement monitors and borehole visual recording instruments allow a theoretical analysis.Field test research determined the conditions for formation of macroscopic gas channels.These appear along the working face roof,normally distributed to it.These results show that the coal rock stratification becomes a macroscopic gas channel boundary if its deformation is less than the lower layer,or greater than the layer above it.At the same time the stability is greater than the distance from the roof for hanging dew conditions.The working face advances and the roof gas channels experience a cycle of development.Microscopic channels dominate the initial stage then macroscopic gas channels form,develop,and close.The evolution of the macroscopic channels depends on the ratio between the distances from the new compaction area in the goaf to the initial stress area in front of the working face.The amount of daily advance of the face also affects channel development.The experimental observations in one mining area showed that the main gas channels are located about 2 and 6.2 m above the lower surface of the roof and that they have an evolution period 7 to 11 days long.展开更多
The mesoscopic damage dynamics and damage evolution have been applied to probe theevolutional process induced catastrophe in the earthquake activity.It is a new method.In thispaper,a brief introduction of the basic pr...The mesoscopic damage dynamics and damage evolution have been applied to probe theevolutional process induced catastrophe in the earthquake activity.It is a new method.In thispaper,a brief introduction of the basic principle about damage dynamics and evolution ismade.At the same time,using the theory of the pattern dynamics we studied all earthquakes(M_L≥5.0)which occurred along Zhangjiakou-Bohai Sea earthquake belt in the capitalregion.The result indicates that the preparation and happening of the real earthquakes andthe theory are consistent.There are two kinds of evolutional model according to the finalstate,namely,global stability model(GS)and evolution induced catastrophe model(EIC).The two models haven’t evident boundary.The transitional zone exhibits the indeterminacyof the seismic process and the effect of the random variation.This research proposed newapproaches for earthquake prediction.展开更多
基金supported by the National Key Research and Development Plan(Grant No.2022YFC2905700)Natural Science Foundation of Anhui Province(Grant No.2208085ME120)Key Research and Development Plan of Anhui Province(Grant No.2022m07020001).
文摘The influence of thermal damage on macroscopic and microscopic characteristics of different rocks has received much attention in the field of rock engineering.When the rocks are subjected to thermal treatment,the change of macroscopic characteristics and evolution of micro-structure would be induced,ultimately resulting in different degrees of thermal damage in rocks.To better understand the thermal damage mechanism of different rocks and its effect on the rock performance,this study reviews a large number of test results of rock specimens experiencing heating and cooling treatment in the laboratory.Firstly,the variations of macroscopic behaviors,including physical parameters,mechanical parameters,thermal conductivity and permeability,are examined.The variations of mechanical parameters with thermal treatment variables(i.e.temperature or the number of thermal cycles)are divided into four types.Secondly,several measuring methods for microstructure,such as polarizing microscopy,fluorescent method,scanning electron microscopy(SEM),X-ray computerized tomography(CT),acoustic emission(AE)and ultrasonic technique,are introduced.Furthermore,the effect of thermal damage on the mechanical parameters of rocks in response to different thermal treatments,involving temperature magnitude,cooling method and thermal cycle,are discussed.Finally,the limitations and prospects for the research of rock thermal damage are proposed.
文摘In recent years, the spin parity effect in magnetic macroscopic quantum tunneling has attracted extensive attention. Using the spin coherent-state path-integral method it is shown that if the HamiltonianH of a single-spin system hasM - fold rotational symmetry around z-axis, the tunneling amplitude 〈?S|e Ht |S〉 vanishes when S, the quantum number of spin, is not an integer multiple ofM/2, where |m〉 (m=-S, -S +1, ?, S) are the eigenstates of Sz. Not only is a pure quantum mechanical approach adopted to the above result, but also is extended to more general cases where the quantum system consists ofN spins, the quantum numbers of which can take any values, including the single-spin system, ferromagnetic particle and antiferromagnetic particle as particular instances, and where the states involved are not limited to the extreme ones. The extended spin parity effect is that if the Hamiltonian ? of the system ofN spins also has the above symmetry, then 〈m′N?m′2 m′1|e?H t |m 1 m 2?m N vanishes when ∑ i=1 N (m i?m′1) not an integer multiple ofM, where |m 1 m 2?m N〉=∏ α=1 N |m a 〉 are the eigenstates of S a z . In addition, it is argued that for large spin the above result, the so-called spin parity effect, does not mean the quenching of spin tunneling from the direction of ⊕-z to that of ±z.
文摘The spin parity effect resulting from time_inversion symmetry is derived by generalizing the pure quantum theory of the effect resulting from finite_fold axial_rotation symmetry. The quantum system concerned may consist of either one spin or many spins with arbitrary spin quantum numbers and the states involved may be any pair of eigenstates of spin operator projected on arbitrary axis with their eigenvalues having opposite signs. The two kinds of spin parity effect, resulting from time_inversion symmetry and from axial_rotation symmetry, are in general not equivalent but complementary to each other.
基金supported by the National Science Foundation of China(no40739901 and 40621002)the National Science Foundation of Guizhou Province(J- 2010-2030)the Stadholder Foundation of Guizhou Province
文摘Macroscopic organisms lived in the Yangtze Sea of South China during the Late Doushantuo period of the Ediacaran.The results of the specimen collections and statistics within each meter show that the macroscopic biota from the Ediacaran Doushantuo Formation in northeast Guizhou,South China,can be subdivided into Globusphyton,Cucullus,Sectoralga-Longifuniculum, Beltanelliformis,and Baculiphyca-Gesinella paleo-communities.The paleo-community evolution indicates the relationship not only between biota and environment,but also between metaphytes and metazoans.From the Globusphyton paleo-community,through to the Sectoralga-Longifuniculum paleo-community,to the Cucullus paleo-community,the increase in the abundance and diversity of metaphytes（especially the branching macroalgae）and metazoans implies that the oxygen content in the seawater increased gradually.Both the Beltanelliformis and Baculiphyca-Gesinella paleo-communities could be related to a deteriorated environment and fragile ecosystem.The emergence,abundance,and diversity of macroscopic metaphytes,which were closely connected with the environmental microchanges,accelerated the process,improving the environment and increasing oxygen,and established an important platform for the development of macroscopic metazoans.
基金provided by the State Key BasicResearch Program of China(No.2011CB201204)the National Natural Science Foundation of China(Nos.51204187 and 51234005)
文摘The evolution of gas bearing channels in the roof,and their spatial distribution,was studied.A complete consideration of gas flow changes through the stress-strain changes in the roof near a working face is made.The theoretical abutment pressure distribution using displacement monitors and borehole visual recording instruments allow a theoretical analysis.Field test research determined the conditions for formation of macroscopic gas channels.These appear along the working face roof,normally distributed to it.These results show that the coal rock stratification becomes a macroscopic gas channel boundary if its deformation is less than the lower layer,or greater than the layer above it.At the same time the stability is greater than the distance from the roof for hanging dew conditions.The working face advances and the roof gas channels experience a cycle of development.Microscopic channels dominate the initial stage then macroscopic gas channels form,develop,and close.The evolution of the macroscopic channels depends on the ratio between the distances from the new compaction area in the goaf to the initial stress area in front of the working face.The amount of daily advance of the face also affects channel development.The experimental observations in one mining area showed that the main gas channels are located about 2 and 6.2 m above the lower surface of the roof and that they have an evolution period 7 to 11 days long.
基金This research was the key project sponsored by the Ninth Five-year Plan (95-04-05-03-03) of China Seismological Bureau, China.
文摘The mesoscopic damage dynamics and damage evolution have been applied to probe theevolutional process induced catastrophe in the earthquake activity.It is a new method.In thispaper,a brief introduction of the basic principle about damage dynamics and evolution ismade.At the same time,using the theory of the pattern dynamics we studied all earthquakes(M_L≥5.0)which occurred along Zhangjiakou-Bohai Sea earthquake belt in the capitalregion.The result indicates that the preparation and happening of the real earthquakes andthe theory are consistent.There are two kinds of evolutional model according to the finalstate,namely,global stability model(GS)and evolution induced catastrophe model(EIC).The two models haven’t evident boundary.The transitional zone exhibits the indeterminacyof the seismic process and the effect of the random variation.This research proposed newapproaches for earthquake prediction.
