We explore the excitonic effects in chiral graphene nanoribbons (cGNRs), whose edges are composed alternatively of armchair-edged and zigzag-edged segments. For cGNRs dominated by armchair edges, their energy gaps and...We explore the excitonic effects in chiral graphene nanoribbons (cGNRs), whose edges are composed alternatively of armchair-edged and zigzag-edged segments. For cGNRs dominated by armchair edges, their energy gaps and exciton energies decrease with increasing chirality angles, and they, as functions of widths, oscillate with the period of three, while the exciton binding energies do not have such distinct oscillation. On the other hand, for cGNRs dominated by zigzag edges, all the energy gaps, exciton energies, and exciton binding energies show oscillation properties with their widths, due to the interactions between the edge states localized at the opposite zigzag edges. In addition, the triplet excitons are energy degenerate when the electrons are spin-unpolarized, while the degeneracy split when the electrons are spin-polarized. All the studied cGNRs show strong excitonic effects with the exciton binding energies of hundreds of meV.展开更多
Hydrogenated Cr-incorporated carbon films （Cr/a-C：H） are deposited successfully by using a dc reactive mag- netron sputtering system. The structure and mechanical properties of the as-deposited Cr/a-C：H films are ...Hydrogenated Cr-incorporated carbon films （Cr/a-C：H） are deposited successfully by using a dc reactive mag- netron sputtering system. The structure and mechanical properties of the as-deposited Cr/a-C：H films are characterized systematically by field-emission scanning electron microscope, x-ray diffraction, Raman spectra, nanoindentation and scratch. It is shown that optimal Cr metal forms nanocrystalline carbide to improve the hardness, toughness and adhesion strength in the amorphous carbon matrix, which possesses relatively higher nano-hardness of 15. 7 CPa, elastic modulus of 126.8 GPa and best adhesion strength with critical load （Lc） of 36 N for the Cr/a-C：H film deposited at CH4 flow rate of 20sccm. The friction and wear behaviors of as-deposited Cr/a-C：H films are evaluated under both the ambient air and deionized water conditions. The results reveal that it can achieve superior low friction and anti-wear performance for the Cr/a-C：H film deposited at CH4 flow rate of 20sccm under the ambient air condition, and the friction coetllcient and wear rate tested in deionized water condition are relatively lower compared with those tested under the ambient air condition for each film. Superior combination of mechanical and tribological properties for the Cr/a-C：H film should be a good candidate for engineering applications.展开更多
This paper established the axle load distribution model of overload axes by practical axle-meter investigations. To study the effects of overload axes on pavement distress, deflection and deflection basin tests with a...This paper established the axle load distribution model of overload axes by practical axle-meter investigations. To study the effects of overload axes on pavement distress, deflection and deflection basin tests with axle load from 60kN to 190kN were conducted on different pavement structures. The relationship between axle load and its deflection as well as its deflection basin curvature was obtained by statistical analyses. A methodology for deriving the equivalent conversion factors of overload axes to equivalent standard axle loads (ESAL) of 100kN is developed, obtaining the relationship between the equivalent conversion factors and the axle loads. Comparing the calculated defiections with the measured deflections, that elastic layered system theory is suitable for analyzing overload vehicles was verified. Consequently, the stresses and strains caused by overload axes were calculated by elastic layered system theory. The results showed that overload axes led to greater stresses and strains causing premature pavement fatigue distress. To guarantee the expected performance in overload axes pavement, the structure thickness needed increasing was obtained. The results are of referential values in the control of semi-rigid pavement overloadings.展开更多
A new Monte Carlo simulation of the track structure of low-energy electrons （〈10keV） in liquid water is presented. The feature of the simulation is taken into consideration of the condensed-phase effect of liquid w...A new Monte Carlo simulation of the track structure of low-energy electrons （〈10keV） in liquid water is presented. The feature of the simulation is taken into consideration of the condensed-phase effect of liquid water on electron elastic scattering with the use of the Champion model, while the dielectric response formalism incorporating the optical-data model developed by Emfietzoglou et al. is applied for calculating the electron inelastic scattering. The spatial distributions of energy deposition and inelastic scattering events of low-energy electrons with different primary energies in liquid water are calculated and compared with other theoretical evaluations. The present work shows that the condensed-phase effect of liquid water on electron elastic scattering may be of the influence on the fraction of absorbed energy and distribution of inelastic scattering events at lower primary energies, which also indicate potential effects on the DNA damage induced by low-energy electrons.展开更多
The stability of a backfill wall is critical to implement gob-side entry driving technology in which a small coal pillar is substituted by a waste backfill wall. Based on features of surrounding rock structures in the...The stability of a backfill wall is critical to implement gob-side entry driving technology in which a small coal pillar is substituted by a waste backfill wall. Based on features of surrounding rock structures in the backfill wall, we propose a mechanical model on the structural effect of a soft-hard backfill wall using theory analysis, physical experiments and a numerical simulation. The results show thatChe deformation of the structure of the soft-hard backfill wall is coordinated with the roof and floor. The soft structure on the top of the backfill wall can absorb the energy in the roof by its large deformation and adapt to the given deformation caused by the rotation and subsidence of a key rock block. The hard structure at the bottom of the backfill wall can absorb the strong supporting resistance from the top surrounding rock. The soft structure on the top protecting the hard bottom structure by its large deformation contributes to the stability of the entire backfill wall. An application indicated that the stress in the backfill wall effec- tively decreased and its deformation was significantly reduced after the top coal remained. This ensured the stability of the backfill wall.展开更多
Large-scale gas accumulation areas in large oil-gas basins in central and Western China have multiple special accumulation mechanisms and different accumulation effects.Based on the geological theory and method of nat...Large-scale gas accumulation areas in large oil-gas basins in central and Western China have multiple special accumulation mechanisms and different accumulation effects.Based on the geological theory and method of natural gas reservoir formation,this study examined the regional geological and structural background,formation burial evolution,basic characteristics of gas reservoirs,and fluid geology and geochemistry of typical petroliferous basins.The results show that the geological processes such as structural pumping,mudstone water absorption,water-soluble gas degasification and fluid sequestration caused by uplift and denudation since Himalayan stage all can form large-scale gas accumulation and different geological effects of gas accumulation.For example,the large-scale structural pumping effect and fluid sequestration effect are conducive to the occurrence of regional ultra-high pressure fluid and the formation of large-scale ultra-high pressure gas field;mudstone water absorption effect in the formation with low thickness ratio of sandstone to formation is conducive to the development of regional low-pressure and water free gas reservoir;the water-soluble gas degasification effect in large-scale thick sandstone can not only form large-scale natural gas accumulation;moreover,the degasification of water-soluble gas produced by the lateral migration of formation water will produce regional and regular isotopic fractionation effect of natural gas,that is,the farther the migration distance of water-soluble gas is,the heavier the carbon isotopic composition of methane formed by the accumulation.展开更多
In this paper, a novel magnetoelectric（ME） composite structure is proposed, and the ME response in the structure is measured at the bias magnetic field up to 2000 Oe（1 Oe = 79.5775 A·m^（-1）） and the excitat...In this paper, a novel magnetoelectric（ME） composite structure is proposed, and the ME response in the structure is measured at the bias magnetic field up to 2000 Oe（1 Oe = 79.5775 A·m^（-1）） and the excitation frequency of alternating magnetic field ranging from 1 kHz to 200 kHz. The ME voltage of each PZT layer is detected. According to the measurement results, the phase differences are observed among three channels and the multi-peak phenomenon appears in each channel. Meanwhile, the results show that the ME structure can stay a relatively high ME response within a wide bandwidth.Besides, the hysteretic loops of three PZT layers are observed. When the frequency of alternating current（AC） magnetic field changes, the maximum value of ME coefficient appears in different layers due to the multiple vibration modes of the structure. Moreover, a finite element analysis is performed to evaluate the resonant frequency of the structure, and the theoretical calculating results accord well with the experimental results. The experiment results suggest that the proposed structure may be a good candidate for designing broadband magnetic field sensors.展开更多
In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding ...In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding medium, which not only transmits visible light but also inhibits the transmission of microwaves, despite the fact that the total thickness of the Ag film is much larger than the skin depth in the visible range and less than that in the microwave region. Theoretical results suggest that a high dielectric/metal thickness ratio can enhance the broadband and improve the transmittance in the optical range. Accordingly, the central wavelength was found to be red-shifted with increasing dielectric/metal thickness ratio. A physical mechanism behind the controlling transmission of visible light is also proposed. Meanwhile, the electromagnetic shielding effectiveness of the prepared structures was found to exceed 40 dB in the range from 0.1 GHz to 18 GHz, even reaching up to 70 dB at 0.1 GHz, which is far higher than that of a single ITO film of the same thickness.展开更多
In order to study the permeability and water-resisting ability of the strata on the top of the Ordovician in Longgu Coal Mine, this paper tested the permeability and porosity of the strata, investigated the fracture a...In order to study the permeability and water-resisting ability of the strata on the top of the Ordovician in Longgu Coal Mine, this paper tested the permeability and porosity of the strata, investigated the fracture and pore structure features of the strata, and identified the main channels which govern the permeability and water-resisting ability of the strata. The permeability of the upper, central and lower strata shows as 2.0504 × 10^-3-2.782762× 10^-3, 4.1092 × 10^-3 -7.3387 × 10^-3 and 2.0891 ×10^-3-3.2705 × 10-3 μm^2, respectively, and porosity of that is 0.6786-0.9197%, 0.3109-0.3951% and 0.9829-1.8655%, respectively. The results indicate that： （I） the main channels of the relative water-resisting layer are the pore throats with a diameter more than 6 μm; （2） the major proportion of pore throats in the vertical flow channel and the permeability first increases and then sharply decreases; （3） the fractures occurring from the top to 20 m in depth of the strata were filled and there occurred almost no fracture under the depth of 40 m; and （4） the ratio of turning point of the main flow channel in the strata on top of Ordovician can be used to confirm the thickness of filled water-resisting lavers.展开更多
In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12...In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12）Co_7 series, R_3 Co series and RCu_2series）, which have been investigated in detail in the past several years. The R–T compounds are studied by means of magnetic measurements, heat capacity measurements, magnetoresistance measurements and neutron powder diffraction measurements. The R–T compounds show complex magnetic transitions and interesting magnetic properties.The types of magnetic transitions are investigated and confirmed in detail by multiple approaches. Especially, most of the R–T compounds undergo more than one magnetic transition, which has significant impact on the magnetocaloric effect of R–T compounds. The MCE of R–T compounds are calculated by different ways and the special shapes of MCE peaks for different compounds are investigated and discussed in detail. To improve the MCE performance of R–T compounds,atoms with large spin（S） and atoms with large total angular momentum（J） are introduced to substitute the related rare earth atoms. With the atom substitution, the maximum of magnetic entropy change（？SM）, refrigerant temperature width（Twidth）or refrigerant capacity（RC） is enlarged for some R–T compounds. In the low temperature range, binary R–T（R = Pr, Gd,Tb, Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series,R_（12）Co_7 series, R_3 Co series and RCu_2series） show excellent performance of MCE, indicating the potential application for gas liquefaction in the future.展开更多
The 0.8 Me V copper （ Cu） ion beam irradiation-induced effects on structural, morphological and optical properties of tin dioxide nanowires （Sn02 NWs） are investigated. The samples are irradiated at three differen...The 0.8 Me V copper （ Cu） ion beam irradiation-induced effects on structural, morphological and optical properties of tin dioxide nanowires （Sn02 NWs） are investigated. The samples are irradiated at three different doses 5 × 10^12 ions/cm2, 1 ×10^13 ions/cm2 and 5 × 10^13 ions/em2 at room temperature. The XRD analysis shows that the tetragonal phase of Sn02 NWs remains stable after Cu ion irradiation, but with increasing irradiation dose level the crystal size increases due to ion beam induced coalescence of NWs. The FTIR spectra of pristine Sn02 NWs exhibit the chemical composition of SnO2 while the Cn-O bond is also observed in the FTIR spectra after Cu ion beam irradiation. The presence of Cu impurity in SnO2 is further confirmed by calculating the stopping range of Cu ions by using TRM/SRIM code. Optical properties of SnO2 NWs are studied before and after Cu ion irradiation. Band gap analysis reveMs that the band gap of irradiated samples is found to decrease compared with the pristine sample. Therefore, ion beam irradiation is a promising technology for nanoengineering and band gap tailoring.展开更多
Structural and magnetic properties are investigated for Fe1-xMnxV2O4 （0≤ x ≤ 1） spinels. As orbital-active Fe^2＋ is substituted with Mn^2＋, the cubie-to-tetragonM transition TsI and the tetragonal-to-orthorhombi...Structural and magnetic properties are investigated for Fe1-xMnxV2O4 （0≤ x ≤ 1） spinels. As orbital-active Fe^2＋ is substituted with Mn^2＋, the cubie-to-tetragonM transition TsI and the tetragonal-to-orthorhombic transition Ts2 gradually decrease. These structural transitions originate from the Fe^2＋ ferro-orbital order （F-OO）. Below Yafet-Kittel （YK） magnetic transition TN2, V^3＋ orbital order （V-OO） plays an important role on global structure. Here x = 0.6 is a critical point. Fe^2＋ F-OO and V^3＋ F-OO coexist for 0 ≤ x ≤ 0.5. For x≥ 0.6, the orbital pattern of V^3＋ is antiferro （AF）-00, and Fe^2＋ F-OO disappears. Structural transition Ts3, accompanied by YK magnetic transition TN2, decreases initially, and then increases at x = 0.6. A scenario for the complex phase diagram arising from the cooperation or competition of Fe^2＋ and V^3＋ orbitals is proposed.展开更多
The stress hardening characteristics of the reinforced rock mass in uniaxial compression tests were revealed by means of the experimental study on mechanical characteristics of cracked rock mass reinforced by bolting ...The stress hardening characteristics of the reinforced rock mass in uniaxial compression tests were revealed by means of the experimental study on mechanical characteristics of cracked rock mass reinforced by bolting and grouting. And the load-beating mechanism of the reinforced rock mass was perfectly reflected by the experiment. The results can offer some useful advice for support design and stability analysis of deep drifts in unstable strata.展开更多
基金Supported by the National Key Scientific Research Projects of China under Grant No 2015CB932400the National Natural Science Foundation of China under Grant Nos 11504158,61474059,and U1432129+1 种基金the Program for New Century Excellent Talents in University of Ministry of Education of China under Grant No NCET-11-1003the Jiangxi Provincial'Ganpo Talentes 555Projects'
文摘We explore the excitonic effects in chiral graphene nanoribbons (cGNRs), whose edges are composed alternatively of armchair-edged and zigzag-edged segments. For cGNRs dominated by armchair edges, their energy gaps and exciton energies decrease with increasing chirality angles, and they, as functions of widths, oscillate with the period of three, while the exciton binding energies do not have such distinct oscillation. On the other hand, for cGNRs dominated by zigzag edges, all the energy gaps, exciton energies, and exciton binding energies show oscillation properties with their widths, due to the interactions between the edge states localized at the opposite zigzag edges. In addition, the triplet excitons are energy degenerate when the electrons are spin-unpolarized, while the degeneracy split when the electrons are spin-polarized. All the studied cGNRs show strong excitonic effects with the exciton binding energies of hundreds of meV.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51302116 and 51365016the Open Fund Item of State Key Laboratory of Solid Lubrication of Lanzhou Institute of Chemical Physics of Chinese Academy of Sciences under Grant No LSL-1203
文摘Hydrogenated Cr-incorporated carbon films （Cr/a-C：H） are deposited successfully by using a dc reactive mag- netron sputtering system. The structure and mechanical properties of the as-deposited Cr/a-C：H films are characterized systematically by field-emission scanning electron microscope, x-ray diffraction, Raman spectra, nanoindentation and scratch. It is shown that optimal Cr metal forms nanocrystalline carbide to improve the hardness, toughness and adhesion strength in the amorphous carbon matrix, which possesses relatively higher nano-hardness of 15. 7 CPa, elastic modulus of 126.8 GPa and best adhesion strength with critical load （Lc） of 36 N for the Cr/a-C：H film deposited at CH4 flow rate of 20sccm. The friction and wear behaviors of as-deposited Cr/a-C：H films are evaluated under both the ambient air and deionized water conditions. The results reveal that it can achieve superior low friction and anti-wear performance for the Cr/a-C：H film deposited at CH4 flow rate of 20sccm under the ambient air condition, and the friction coetllcient and wear rate tested in deionized water condition are relatively lower compared with those tested under the ambient air condition for each film. Superior combination of mechanical and tribological properties for the Cr/a-C：H film should be a good candidate for engineering applications.
文摘This paper established the axle load distribution model of overload axes by practical axle-meter investigations. To study the effects of overload axes on pavement distress, deflection and deflection basin tests with axle load from 60kN to 190kN were conducted on different pavement structures. The relationship between axle load and its deflection as well as its deflection basin curvature was obtained by statistical analyses. A methodology for deriving the equivalent conversion factors of overload axes to equivalent standard axle loads (ESAL) of 100kN is developed, obtaining the relationship between the equivalent conversion factors and the axle loads. Comparing the calculated defiections with the measured deflections, that elastic layered system theory is suitable for analyzing overload vehicles was verified. Consequently, the stresses and strains caused by overload axes were calculated by elastic layered system theory. The results showed that overload axes led to greater stresses and strains causing premature pavement fatigue distress. To guarantee the expected performance in overload axes pavement, the structure thickness needed increasing was obtained. The results are of referential values in the control of semi-rigid pavement overloadings.
文摘A new Monte Carlo simulation of the track structure of low-energy electrons （〈10keV） in liquid water is presented. The feature of the simulation is taken into consideration of the condensed-phase effect of liquid water on electron elastic scattering with the use of the Champion model, while the dielectric response formalism incorporating the optical-data model developed by Emfietzoglou et al. is applied for calculating the electron inelastic scattering. The spatial distributions of energy deposition and inelastic scattering events of low-energy electrons with different primary energies in liquid water are calculated and compared with other theoretical evaluations. The present work shows that the condensed-phase effect of liquid water on electron elastic scattering may be of the influence on the fraction of absorbed energy and distribution of inelastic scattering events at lower primary energies, which also indicate potential effects on the DNA damage induced by low-energy electrons.
基金Financial supports for this work, provided by the New Century Excellent Talents in University (No.NCET-05-0480)the Research Fund of the State Key Laboratory of Coal Resources and Mine Safety of CUMT (No.09KF06)the Scientific Research Fund of CUMT (No.OA090239)
文摘The stability of a backfill wall is critical to implement gob-side entry driving technology in which a small coal pillar is substituted by a waste backfill wall. Based on features of surrounding rock structures in the backfill wall, we propose a mechanical model on the structural effect of a soft-hard backfill wall using theory analysis, physical experiments and a numerical simulation. The results show thatChe deformation of the structure of the soft-hard backfill wall is coordinated with the roof and floor. The soft structure on the top of the backfill wall can absorb the energy in the roof by its large deformation and adapt to the given deformation caused by the rotation and subsidence of a key rock block. The hard structure at the bottom of the backfill wall can absorb the strong supporting resistance from the top surrounding rock. The soft structure on the top protecting the hard bottom structure by its large deformation contributes to the stability of the entire backfill wall. An application indicated that the stress in the backfill wall effec- tively decreased and its deformation was significantly reduced after the top coal remained. This ensured the stability of the backfill wall.
基金Supported by the National Science and Technology Major Project(2016ZX05003-002)Scientific Research Project of Petro China Company Limited(2016E-0601)
文摘Large-scale gas accumulation areas in large oil-gas basins in central and Western China have multiple special accumulation mechanisms and different accumulation effects.Based on the geological theory and method of natural gas reservoir formation,this study examined the regional geological and structural background,formation burial evolution,basic characteristics of gas reservoirs,and fluid geology and geochemistry of typical petroliferous basins.The results show that the geological processes such as structural pumping,mudstone water absorption,water-soluble gas degasification and fluid sequestration caused by uplift and denudation since Himalayan stage all can form large-scale gas accumulation and different geological effects of gas accumulation.For example,the large-scale structural pumping effect and fluid sequestration effect are conducive to the occurrence of regional ultra-high pressure fluid and the formation of large-scale ultra-high pressure gas field;mudstone water absorption effect in the formation with low thickness ratio of sandstone to formation is conducive to the development of regional low-pressure and water free gas reservoir;the water-soluble gas degasification effect in large-scale thick sandstone can not only form large-scale natural gas accumulation;moreover,the degasification of water-soluble gas produced by the lateral migration of formation water will produce regional and regular isotopic fractionation effect of natural gas,that is,the farther the migration distance of water-soluble gas is,the heavier the carbon isotopic composition of methane formed by the accumulation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11702120,11372120,11421062,and 11572143)the Fundamental Research Funds for the Central Universities,China(Grant No.lzujbky-2016-106)
文摘In this paper, a novel magnetoelectric（ME） composite structure is proposed, and the ME response in the structure is measured at the bias magnetic field up to 2000 Oe（1 Oe = 79.5775 A·m^（-1）） and the excitation frequency of alternating magnetic field ranging from 1 kHz to 200 kHz. The ME voltage of each PZT layer is detected. According to the measurement results, the phase differences are observed among three channels and the multi-peak phenomenon appears in each channel. Meanwhile, the results show that the ME structure can stay a relatively high ME response within a wide bandwidth.Besides, the hysteretic loops of three PZT layers are observed. When the frequency of alternating current（AC） magnetic field changes, the maximum value of ME coefficient appears in different layers due to the multiple vibration modes of the structure. Moreover, a finite element analysis is performed to evaluate the resonant frequency of the structure, and the theoretical calculating results accord well with the experimental results. The experiment results suggest that the proposed structure may be a good candidate for designing broadband magnetic field sensors.
基金Project supported by the International Science&Technology Cooperation Program of China(Grant No.2014DFR10020)the Science Foundation of Shanxi Province,China(Grant Nos.201701D121050 and 201701D121007)
文摘In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding medium, which not only transmits visible light but also inhibits the transmission of microwaves, despite the fact that the total thickness of the Ag film is much larger than the skin depth in the visible range and less than that in the microwave region. Theoretical results suggest that a high dielectric/metal thickness ratio can enhance the broadband and improve the transmittance in the optical range. Accordingly, the central wavelength was found to be red-shifted with increasing dielectric/metal thickness ratio. A physical mechanism behind the controlling transmission of visible light is also proposed. Meanwhile, the electromagnetic shielding effectiveness of the prepared structures was found to exceed 40 dB in the range from 0.1 GHz to 18 GHz, even reaching up to 70 dB at 0.1 GHz, which is far higher than that of a single ITO film of the same thickness.
基金Financial supports for this work provided by the National Basic Research Program of China(2013CB227900)the Innovation of Graduate Student Training Project in Jiangsu Province of China(CXZZ13_0934)
文摘In order to study the permeability and water-resisting ability of the strata on the top of the Ordovician in Longgu Coal Mine, this paper tested the permeability and porosity of the strata, investigated the fracture and pore structure features of the strata, and identified the main channels which govern the permeability and water-resisting ability of the strata. The permeability of the upper, central and lower strata shows as 2.0504 × 10^-3-2.782762× 10^-3, 4.1092 × 10^-3 -7.3387 × 10^-3 and 2.0891 ×10^-3-3.2705 × 10-3 μm^2, respectively, and porosity of that is 0.6786-0.9197%, 0.3109-0.3951% and 0.9829-1.8655%, respectively. The results indicate that： （I） the main channels of the relative water-resisting layer are the pore throats with a diameter more than 6 μm; （2） the major proportion of pore throats in the vertical flow channel and the permeability first increases and then sharply decreases; （3） the fractures occurring from the top to 20 m in depth of the strata were filled and there occurred almost no fracture under the depth of 40 m; and （4） the ratio of turning point of the main flow channel in the strata on top of Ordovician can be used to confirm the thickness of filled water-resisting lavers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274357,51501005,51590880,and 11674008)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-15-010A1)+1 种基金the China Postdoctoral Science Foundation(Grant No.2016M591071)the Key Research Program of the Chinese Academy of Sciences(Grant No.KJZD-EW-M05)
文摘In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12）Co_7 series, R_3 Co series and RCu_2series）, which have been investigated in detail in the past several years. The R–T compounds are studied by means of magnetic measurements, heat capacity measurements, magnetoresistance measurements and neutron powder diffraction measurements. The R–T compounds show complex magnetic transitions and interesting magnetic properties.The types of magnetic transitions are investigated and confirmed in detail by multiple approaches. Especially, most of the R–T compounds undergo more than one magnetic transition, which has significant impact on the magnetocaloric effect of R–T compounds. The MCE of R–T compounds are calculated by different ways and the special shapes of MCE peaks for different compounds are investigated and discussed in detail. To improve the MCE performance of R–T compounds,atoms with large spin（S） and atoms with large total angular momentum（J） are introduced to substitute the related rare earth atoms. With the atom substitution, the maximum of magnetic entropy change（？SM）, refrigerant temperature width（Twidth）or refrigerant capacity（RC） is enlarged for some R–T compounds. In the low temperature range, binary R–T（R = Pr, Gd,Tb, Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series,R_（12）Co_7 series, R_3 Co series and RCu_2series） show excellent performance of MCE, indicating the potential application for gas liquefaction in the future.
基金Supported by the Department of Physics,the University of AJKHigh Tech.Centralized Instrumentation Lab,the University of AJK,Pakistanthe Experimental Physics Division,and the National Center for Physics,Islamabad Pakistan
文摘The 0.8 Me V copper （ Cu） ion beam irradiation-induced effects on structural, morphological and optical properties of tin dioxide nanowires （Sn02 NWs） are investigated. The samples are irradiated at three different doses 5 × 10^12 ions/cm2, 1 ×10^13 ions/cm2 and 5 × 10^13 ions/em2 at room temperature. The XRD analysis shows that the tetragonal phase of Sn02 NWs remains stable after Cu ion irradiation, but with increasing irradiation dose level the crystal size increases due to ion beam induced coalescence of NWs. The FTIR spectra of pristine Sn02 NWs exhibit the chemical composition of SnO2 while the Cn-O bond is also observed in the FTIR spectra after Cu ion beam irradiation. The presence of Cu impurity in SnO2 is further confirmed by calculating the stopping range of Cu ions by using TRM/SRIM code. Optical properties of SnO2 NWs are studied before and after Cu ion irradiation. Band gap analysis reveMs that the band gap of irradiated samples is found to decrease compared with the pristine sample. Therefore, ion beam irradiation is a promising technology for nanoengineering and band gap tailoring.
基金Supported by the National Basic Research Program of China under Grant Nos 2011CB921904 and 2012CB927402the National Natural Science Foundation of China under Grant Nos 11074142 and 11021464+1 种基金the Key Project of Chinese Ministry of Education under Grant No 309003the Tsinghua TNList Cross-discipline Foundation
文摘Structural and magnetic properties are investigated for Fe1-xMnxV2O4 （0≤ x ≤ 1） spinels. As orbital-active Fe^2＋ is substituted with Mn^2＋, the cubie-to-tetragonM transition TsI and the tetragonal-to-orthorhombic transition Ts2 gradually decrease. These structural transitions originate from the Fe^2＋ ferro-orbital order （F-OO）. Below Yafet-Kittel （YK） magnetic transition TN2, V^3＋ orbital order （V-OO） plays an important role on global structure. Here x = 0.6 is a critical point. Fe^2＋ F-OO and V^3＋ F-OO coexist for 0 ≤ x ≤ 0.5. For x≥ 0.6, the orbital pattern of V^3＋ is antiferro （AF）-00, and Fe^2＋ F-OO disappears. Structural transition Ts3, accompanied by YK magnetic transition TN2, decreases initially, and then increases at x = 0.6. A scenario for the complex phase diagram arising from the cooperation or competition of Fe^2＋ and V^3＋ orbitals is proposed.
基金Projects50490273 and 50474063 supported by National Natural Science Foundation of China
文摘The stress hardening characteristics of the reinforced rock mass in uniaxial compression tests were revealed by means of the experimental study on mechanical characteristics of cracked rock mass reinforced by bolting and grouting. And the load-beating mechanism of the reinforced rock mass was perfectly reflected by the experiment. The results can offer some useful advice for support design and stability analysis of deep drifts in unstable strata.
