CO_(2) methanation has a potential in the large-scale utilization of carbon dioxide.It has also been considered to be useful for the renewable energy storage.The commercial pipeline for natural gas transportation can ...CO_(2) methanation has a potential in the large-scale utilization of carbon dioxide.It has also been considered to be useful for the renewable energy storage.The commercial pipeline for natural gas transportation can be directly applied for the methane product of CO_(2) methanation.The supported ruthenium(Ru)catalyst has been confirmed to be active and stable for CO_(2) methanation with its high ability in the dissociation of hydrogen and the strong binding of carbon monoxide.CO_(2) methanation over the supported Ru catalyst is structure sensitive.The size of the Ru catalyst and the support have significant effects on the activity and the mechanism.A significant challenge re-mained is the structural controllable preparation of the supported Ru catalyst toward a sufficiently high low-temperature activity.In this review,the recent progresses in the investigations of the supported Ru catalysts for CO_(2) methanation are summarized.The challenges and the future devel-opments are also discussed.展开更多
The development of open-pit mines can adversely affect and even damage existing access tunnels. To ensure the safety and serviceability of them, it is essential to know potential adverse effects of the mining sequence...The development of open-pit mines can adversely affect and even damage existing access tunnels. To ensure the safety and serviceability of them, it is essential to know potential adverse effects of the mining sequence on existing tunnels such as displacements of the lining and additional loads on the lining. In this paper, three-dimensional numerical parametric study is performed to explore this complex interaction. This study investigates the effects of different parameters that may affect the tunnel response. These parameters are： excavation sequence method, horizontal/vertical stress ratio, slope angle, and tunnel diameter. This study shows that the mining sequence affects the stability of the tunnels. The open-pit mining activities lead to both higher axial forces in rock bolts and normal forces and bending moments in the lining. The results of the analysis also demonstrate that the mining sequence causes tunnel heave and significant tensile forces in the lining. Based on the study in this paper a better understanding of the interaction between oDen-oit minin~ seouence and tunnels will he ohtained展开更多
Using an MTS816.03 test system and self-designed seepage apparatus, seepage tests of saturated broken rocks were conducted, and the influence of lithology, axial stress, grain size distribution and loading rate on see...Using an MTS816.03 test system and self-designed seepage apparatus, seepage tests of saturated broken rocks were conducted, and the influence of lithology, axial stress, grain size distribution and loading rate on seepage characteristics was analyzed. The results show that： （1） Under the same axial stress （12 MPa）, the permeability of different lithologic samples increases in the order： gangue 〈 mudstone 〈 sandstone 〈 limestone. The permeability of gangue is 3 magnitudes lower than that of limestone. The absolute value of the non-Darcy coefficient β increases in the order： limestone 〈 sandstone 〈 mudstone 〈 gangue. The non-Darcy coefficient β of limestone, which is positive, is 5 magnitudes lower than that of gangue. （2） With increasing axial stress, the permeability of saturated broken sandstone decreases, and the absolute value of the non-Darcy coefficient β increases. After the axial stress exceeds 12 MPa, the curves of permeability and non-Darcy coefficient β all tend to be stable. （3） With increasing Talbol power exponent, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. （4） With increasing loading, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. When the loading rate is 0.5 kN/s, the non-Darcy coefficient β is positive.展开更多
Additional displacement of the building foundations over old goaf are prone to happen under the addi- tional loads induced by new buildings, weakening-rock mass by mining and seismic actions, which will cause serious ...Additional displacement of the building foundations over old goaf are prone to happen under the addi- tional loads induced by new buildings, weakening-rock mass by mining and seismic actions, which will cause serious damage to the buildings. In order to analyze the safety of the building foundations safety over the old goaf. the structure characteristics of the strata over the old goaf was investigated and the instability conditions of overhanging rocks upon old goaf were also analyzed in this paper. The results indicate that the stability of overhanging rocks is remarkably decreased by the interactions of mining fractures, earthquake force and building load, in addition, the settlement of the foundations over old goal is increased by the instability of overhanging rocks. According to the location of a new power plant in Yima Mine and its ambient conditions, we defined the influence scope of old goal via resistivity tomography. Based on the seismic parameters of the construction site, a numerical FLAC3d model of the building foundation under the seismic actions and building load was developed. The numerical results are obtained as follows： the foundation of the main power house meets the requirement of 6° seismic fortification intensity： however, under 7° seismic fortification intensity, the maximum differential settlement of foundation between the neighboring pillars is close to the maximum allowable value, while the seismic fortification intensity reaches 8°, but the safety requirements will not be satisfied.展开更多
The damage evolution in steel reinforced high strength concrete(SRHSC) frame columns was studied based on the test results of cyclic reversed loading experiment of 12 frame column specimens with various axial compress...The damage evolution in steel reinforced high strength concrete(SRHSC) frame columns was studied based on the test results of cyclic reversed loading experiment of 12 frame column specimens with various axial compression rations,stirrups ratios,steel rations and loading histories.The variation law of the ultimate bearing capacity,ultimate deformation and ultimate hysteretic energy dissipation of specimens under different loading protocols was obtained.The seismic damage characteristics,as well as strength and stiffness degradation,of SRHSC frame columns were analyzed.Based on the analysis of the nonlinear double parameters combination of deformation and energy,a damage model that can well reflect the mechanical characteristics of members subjected to a horizontal earthquake action was established by considering the effects of the number of the loading cycles on the ultimate resistance capacity(ultimate deformation and ultimate energy dissipation capacity) of members,and the loading history on damage,etc.According to the test results,the related parameters of the damage model were proposed.Finally,the damage model proposed was validated by the test results.Results indicated that the proposed damage model is theoretically more reasonable and can accurately describe the seismic damage evolution of the SRHSC frame columns.The results also can be used as a new theoretic reference for the establishment of damage-based earthquake-resistant design method of SRHSC members.展开更多
A W-band traveling-wave tube (TWT) with double-groove loaded folded waveguide structure (FWSWS) has been designed and numerically modelled. The nonlinear performance of such a TWT is investigated by a particle-in-cell...A W-band traveling-wave tube (TWT) with double-groove loaded folded waveguide structure (FWSWS) has been designed and numerically modelled. The nonlinear performance of such a TWT is investigated by a particle-in-cell code MAGIC3D. Simulation results indicate this TWT produces a saturated electromagnetic power of 170.2 W at 90 GHz, corresponding to 36.9 dB gain and 69.6 mm interaction distance. A comparison between the novel folded waveguide traveling-wave tube (FWTWT) and the conventional one is also carried out to verify the effect of groove loading on the large-signal performance of TWT. Within the same working conditions, the double groove-loaded FWTWT could obtain higher saturated output power and gain in a shorter interaction length. The maximum of output power and gain of this novel TWT is 58.6% and 10% higher than those of the conventional FWTWT, while the 3-dB bandwidth of TWT is reduced to 4 GHz. With the additional advantage of ease of fabrication based on micro-electro-mechanical systems (MEMS) technologies, the double-groove loaded FWSWS is suitable for a millimeter-wave TWT with high power capacity and gain.展开更多
文摘CO_(2) methanation has a potential in the large-scale utilization of carbon dioxide.It has also been considered to be useful for the renewable energy storage.The commercial pipeline for natural gas transportation can be directly applied for the methane product of CO_(2) methanation.The supported ruthenium(Ru)catalyst has been confirmed to be active and stable for CO_(2) methanation with its high ability in the dissociation of hydrogen and the strong binding of carbon monoxide.CO_(2) methanation over the supported Ru catalyst is structure sensitive.The size of the Ru catalyst and the support have significant effects on the activity and the mechanism.A significant challenge re-mained is the structural controllable preparation of the supported Ru catalyst toward a sufficiently high low-temperature activity.In this review,the recent progresses in the investigations of the supported Ru catalysts for CO_(2) methanation are summarized.The challenges and the future devel-opments are also discussed.
文摘The development of open-pit mines can adversely affect and even damage existing access tunnels. To ensure the safety and serviceability of them, it is essential to know potential adverse effects of the mining sequence on existing tunnels such as displacements of the lining and additional loads on the lining. In this paper, three-dimensional numerical parametric study is performed to explore this complex interaction. This study investigates the effects of different parameters that may affect the tunnel response. These parameters are： excavation sequence method, horizontal/vertical stress ratio, slope angle, and tunnel diameter. This study shows that the mining sequence affects the stability of the tunnels. The open-pit mining activities lead to both higher axial forces in rock bolts and normal forces and bending moments in the lining. The results of the analysis also demonstrate that the mining sequence causes tunnel heave and significant tensile forces in the lining. Based on the study in this paper a better understanding of the interaction between oDen-oit minin~ seouence and tunnels will he ohtained
基金provided by the National Basic Research Program of China (No.2013CB227900)the Ordinary University Graduate Student Research Innovation Project in Jiangsu Province for 2014 (No.KYLX_1370)the National Natural Science Foundation of China (Nos.11502229 and 51404266)
文摘Using an MTS816.03 test system and self-designed seepage apparatus, seepage tests of saturated broken rocks were conducted, and the influence of lithology, axial stress, grain size distribution and loading rate on seepage characteristics was analyzed. The results show that： （1） Under the same axial stress （12 MPa）, the permeability of different lithologic samples increases in the order： gangue 〈 mudstone 〈 sandstone 〈 limestone. The permeability of gangue is 3 magnitudes lower than that of limestone. The absolute value of the non-Darcy coefficient β increases in the order： limestone 〈 sandstone 〈 mudstone 〈 gangue. The non-Darcy coefficient β of limestone, which is positive, is 5 magnitudes lower than that of gangue. （2） With increasing axial stress, the permeability of saturated broken sandstone decreases, and the absolute value of the non-Darcy coefficient β increases. After the axial stress exceeds 12 MPa, the curves of permeability and non-Darcy coefficient β all tend to be stable. （3） With increasing Talbol power exponent, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. （4） With increasing loading, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. When the loading rate is 0.5 kN/s, the non-Darcy coefficient β is positive.
基金the Funds of the State Key Development Program for Basic Research of China (Nos. 2013CB227900, 2010CB226800)the National Natural Science Foundation of China (Nos. 51108161, 51374201)+2 种基金the Open Laboratory Foundation for Deep Mine Construction of Henan Province of China (No. 2011KF-09)the Doctor Foundation in Henan Polytechnic University of China (No. Q2013-065)the Key Program for Science and Technology Research of Henan Province of China (Nos. 14A560002, 14B560021).
文摘Additional displacement of the building foundations over old goaf are prone to happen under the addi- tional loads induced by new buildings, weakening-rock mass by mining and seismic actions, which will cause serious damage to the buildings. In order to analyze the safety of the building foundations safety over the old goaf. the structure characteristics of the strata over the old goaf was investigated and the instability conditions of overhanging rocks upon old goaf were also analyzed in this paper. The results indicate that the stability of overhanging rocks is remarkably decreased by the interactions of mining fractures, earthquake force and building load, in addition, the settlement of the foundations over old goal is increased by the instability of overhanging rocks. According to the location of a new power plant in Yima Mine and its ambient conditions, we defined the influence scope of old goal via resistivity tomography. Based on the seismic parameters of the construction site, a numerical FLAC3d model of the building foundation under the seismic actions and building load was developed. The numerical results are obtained as follows： the foundation of the main power house meets the requirement of 6° seismic fortification intensity： however, under 7° seismic fortification intensity, the maximum differential settlement of foundation between the neighboring pillars is close to the maximum allowable value, while the seismic fortification intensity reaches 8°, but the safety requirements will not be satisfied.
基金supported by the National Natural Science Foundation of China (Grant Nos. 90815005, 50978218)Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20106120110003)the Educational Office of Shan'xi Province in China (Grant No.2010JK633)
文摘The damage evolution in steel reinforced high strength concrete(SRHSC) frame columns was studied based on the test results of cyclic reversed loading experiment of 12 frame column specimens with various axial compression rations,stirrups ratios,steel rations and loading histories.The variation law of the ultimate bearing capacity,ultimate deformation and ultimate hysteretic energy dissipation of specimens under different loading protocols was obtained.The seismic damage characteristics,as well as strength and stiffness degradation,of SRHSC frame columns were analyzed.Based on the analysis of the nonlinear double parameters combination of deformation and energy,a damage model that can well reflect the mechanical characteristics of members subjected to a horizontal earthquake action was established by considering the effects of the number of the loading cycles on the ultimate resistance capacity(ultimate deformation and ultimate energy dissipation capacity) of members,and the loading history on damage,etc.According to the test results,the related parameters of the damage model were proposed.Finally,the damage model proposed was validated by the test results.Results indicated that the proposed damage model is theoretically more reasonable and can accurately describe the seismic damage evolution of the SRHSC frame columns.The results also can be used as a new theoretic reference for the establishment of damage-based earthquake-resistant design method of SRHSC members.
基金supported by the National Natural Science Foundation of China(Grant No. 60971038)the Talent Fund of Chinese Education Administration
文摘A W-band traveling-wave tube (TWT) with double-groove loaded folded waveguide structure (FWSWS) has been designed and numerically modelled. The nonlinear performance of such a TWT is investigated by a particle-in-cell code MAGIC3D. Simulation results indicate this TWT produces a saturated electromagnetic power of 170.2 W at 90 GHz, corresponding to 36.9 dB gain and 69.6 mm interaction distance. A comparison between the novel folded waveguide traveling-wave tube (FWTWT) and the conventional one is also carried out to verify the effect of groove loading on the large-signal performance of TWT. Within the same working conditions, the double groove-loaded FWTWT could obtain higher saturated output power and gain in a shorter interaction length. The maximum of output power and gain of this novel TWT is 58.6% and 10% higher than those of the conventional FWTWT, while the 3-dB bandwidth of TWT is reduced to 4 GHz. With the additional advantage of ease of fabrication based on micro-electro-mechanical systems (MEMS) technologies, the double-groove loaded FWSWS is suitable for a millimeter-wave TWT with high power capacity and gain.
