Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La2O3, ZnO, Y2O3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepare...Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La2O3, ZnO, Y2O3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepared by impregnation method. Their properties were characterized by X-ray diffraction （XRD）, NH3 temperature-programmed desorption （NH3-TPD）, He temperature-programmed reduction （He-TPR）, N2 adsorption/desorption, and CO-chemisorption. The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust gas from lean-burn natural gas vehicles with and without water vapor. The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts, compared with the Pd catalyst supported on the unmodified ZrA1. The addition of ZnO or Y203 promoted the conversion of CH4. In the absence of water vapor, Pd/ZnZrA1 exhibited the best activity for CH4 conversion with the light-off temperature （Tso） of 275 ℃ and the complete conversion temperature （T90） of 314 ℃, respectively. However, in the presence of water vapor, Pd/YZrA1 was the best one over which the light-off temperature （Tso） of methane was 339 ℃ and the complete conversion temperature （T90） was 371 ℃. These results indicated that Pd catalyst supported on the modified composite ZrA1 support showed excellent catalytic activity at low temperature and high resistance to H20 poisoning for the exhaust purification of lean-burn natural gas vehicles.展开更多
1 INTRODUCTIONMany attempts to develop semipermeable membranes for gas separation have beendone over the past twenty years [1,2].However,it is still difficult to prepare apolymer film which makes certain gas separatio...1 INTRODUCTIONMany attempts to develop semipermeable membranes for gas separation have beendone over the past twenty years [1,2].However,it is still difficult to prepare apolymer film which makes certain gas separation processed within range of being econ-omically and technically feasible,since most polymeric materials are relativelyimpermeable to gases.Facilitated transport concept which was first proposed展开更多
The introduction of surface engineering is expected to be an effective strategy against fretting damage. A large number of studies show that the low gas multi-component （such as carbon, nitrogen, sulphur and oxygen, ...The introduction of surface engineering is expected to be an effective strategy against fretting damage. A large number of studies show that the low gas multi-component （such as carbon, nitrogen, sulphur and oxygen, etc） thermo-chemical treatment（LTGMTT） can overcome the brittleness of nitriding process, and upgrade the surface hardness and improve the wear resistance and fatigue properties of the work-pieces significantly. However, there are few reports on the anti-fretting properties of the LTGMTT modified layer up to now, which limits the applications of fretting. So this paper discusses the fretting wear behavior of modified layer on the surface of LZ50 （0.48%C） steel prepared by low temperature gas multi-component thermo-chemical treatment （LTGMTT） technology. The fretting wear tests of the modified layer flat specimens and its substrate （LZ50 steel） against 52100 steel balls with diameter of 40 mm are carried out under normal load of 150 N and displacement amplitudes varied from 2 μm to 40 μm. Characterization of the modified layer and dynamic analyses in combination with microscopic examinations were performed through the means of scanning electron microscope（SEM）, optical microscope（OM）, X-ray diffraction（XRD） and surface profilometer. The experimental results showed that the modified layer with a total thickness of 60 μm was consisted of three parts, i.e., loose layer, compound layer and diffusion layer. Compared with the substrate, the range of the mixed fretting regime（MFR） of the LTGMTT modified layer diminished, and the slip regime（SR） of the modified layer shifted to the direction of smaller displacement amplitude. The coefficient of friction（COF） of the modified layer was lower than that of the substrate in the initial stage. For the modified layer, the damage in partial slip regime（PSR） was very slight. The fretting wear mechanism of the modified layer both in MFR and SR was abrasive wear and delamination. The modified layer presented better wear resistance than the substrate in PSR and MFR; however, in SR, the wear resistance of the modified layer decreased with the increase of the displacement amplitudes. The experimental results can provide some experimental bases for promoting industrial application of LTGMTT modified layer in anti-fretting wear.展开更多
Pure ZnO thick film, prepared by screen-printing technique, was almost insensitive to NH3. Pure ZnO thick films were surface modified with MnO2 by dipping them into 0.01 M aqueous solution of manganese chloride (MnCl2...Pure ZnO thick film, prepared by screen-printing technique, was almost insensitive to NH3. Pure ZnO thick films were surface modified with MnO2 by dipping them into 0.01 M aqueous solution of manganese chloride (MnCl2) for different intervals of time and fired at 500℃ for 12 h. The grains of MnO2 would disperse around the grains of ZnO base material. The MnO2 modified ZnO films dipped for 30 min were observed to be sensitive and highly selective to NH3 gas at room temperature. An exceptional sensitivity was found to low concentration (50 ppm) of NH3 gas at room temperature and no cross sensitivity was observed even to high concentrations of other hazardous and polluting gases. The effects of surface microstructure and MnO2 concentrations on the sensitivity, selectivity, response and recovery of the sensor in the presence of NH3and other gases were studied and discussed. The better performance could be attributed to an optimum number of surface misfits in terms of MnO2 on the ZnO films.展开更多
Intrinsic time quantum geometrodynamics is a formulation of quantum gravity naturally adapted to 3 + 1 dimensions. In this paper we construct its analogous 2 + 1 formulation, taking note of the mathematical structures...Intrinsic time quantum geometrodynamics is a formulation of quantum gravity naturally adapted to 3 + 1 dimensions. In this paper we construct its analogous 2 + 1 formulation, taking note of the mathematical structures which are preserved. We apply the resulting construction to convert the BTZ black hole metric to ITQG framework. We then modify the BTZ black hole in order to investigate the existence of the P-V criticality in ITQG theory.展开更多
Measuring gas content is an essential step in estimating the commerciality of gas reserves. In this study,eight shale core samples from the Mouye-1 well were measured using a homemade patented gas desorption apparatus...Measuring gas content is an essential step in estimating the commerciality of gas reserves. In this study,eight shale core samples from the Mouye-1 well were measured using a homemade patented gas desorption apparatus to determine their gas contents. Due to the air contamination that is introduced into the desorption canister, a mathematical method was devised to correct the gas quantity and quality.Compared to the chemical compositions of desorbed gas, the chemical compositions of residual gas are somewhat different. In residual gas, carbon dioxide and nitrogen record a slight increase, and propane is first observed. This phenomenon may be related to the exposure time during the transportation of shale samples from the drilling site to the laboratory, as well as the differences in the mass, size and adsorptivity of different gas molecules. In addition to a series of conventional methods, including the USBM direct method and the Amoco Curve Fit(ACF) method, which were used here for lost gas content estimation, a Modified Curve Fit(MCF) method, based on the 'bidisperse' diffusion model, was established to estimate lost gas content. By fitting the ACF and MCF models to gas desorption data, we determined that the MCF method could reasonably describe the gas desorption data over the entire time period, whereas the ACF method failed. The failure of the ACF method to describe the gas desorption process may be related to its restrictive assumption of a single pore size within shale samples. In comparison to the indirect method, this study demonstrates that none of the three methods studied in this investigation(USBM, ACF and MCF) could individually estimate the lost gas contents of all shale samples and that the proportion of free gas relative to total gas has a significant effect on the estimation accuracy of the selected method. When the ratio of free gas to total gas is lower than 45%, the USBM method is the best for estimating the lost gas content, whereas when the ratio ranges from 45% to 75% or is more than 75%, the ACF and MCF methods, are the best options respectively.展开更多
A CFD code has been developed based on the conservation principles describing gas and solid flow in fluidized beds. This code is employed to simulate not only the spatiotemporal gas and solid phase velocities and v...A CFD code has been developed based on the conservation principles describing gas and solid flow in fluidized beds. This code is employed to simulate not only the spatiotemporal gas and solid phase velocities and voidage profiles in a two dimensional bed but also fluid dynamics in the jet region. The computational results show that gas flow direction is upward in the entire bed accompanied with random local circulations, whilst solid flow direction is upward at the center and downward near the wall. The radical reason of strong back mixing of solid particles and good transfer behavior between two phases is that the jet entrains solid particles. Numerical calculation indicates that gas velocity, solid velocity and pressure profile have a significant change when the voidage is 0 8. The simulated time averaged voidage profiles agree with the experimental results and simulated data reported by Gidaspow and Ettehadieh(1983). Therefore, CFD model can be regarded as a useful tool to study the jet characteristics in dense gas solid fluidized beds.展开更多
A modified particle bed model derived from the two-fluid momentum balance equations was employed to predict the gas-fluidised bed behaviour. Additional terms are included in both the fluid and the particle momentum ba...A modified particle bed model derived from the two-fluid momentum balance equations was employed to predict the gas-fluidised bed behaviour. Additional terms are included in both the fluid and the particle momentum balance equations to take into account the effect of the dispersed solid phase. This model has been extended to two-dimensional formulations and has been implemented in the commercial code CFX 4.3. The model correctly simulates the homogeneous fluidisation of Geldart Group A and the bubbling fluidisation of Geldart Group B in gas-solid fluidised beds.展开更多
We use the work of de Vega, Sanchez, and Comes (1997), to approximate the “particle density” of a “graviton gas”. This “particle density” derivation is compared with Dolgov’s (1997) expression of the Vacuum ene...We use the work of de Vega, Sanchez, and Comes (1997), to approximate the “particle density” of a “graviton gas”. This “particle density” derivation is compared with Dolgov’s (1997) expression of the Vacuum energy in terms of a phase transition. The idea is to have a quartic potential, and then to utilize the Bogomol’nyi inequality to refine what the phase transition states. We utilize Ng, Infinite quantum information procedures to link our work with initial entropy and other issues and close with a variation in the HUP: at the start of the expansion of the universe.展开更多
基金supported by the National Natural Science Foundation of China (21173153)Science and Technology Department of Science and Technology Support Project of Sichuan Povince,China (2011GZ0035)
文摘Composite supports Zr0.5Al0.5O1.75 modified by metal oxides, such as La2O3, ZnO, Y2O3 or BaO, were prepared by co-precipitation method, and palladium catalysts supported on the modified composite supports were prepared by impregnation method. Their properties were characterized by X-ray diffraction （XRD）, NH3 temperature-programmed desorption （NH3-TPD）, He temperature-programmed reduction （He-TPR）, N2 adsorption/desorption, and CO-chemisorption. The catalytic activity and the resistance to water poisoning of the prepared Pd catalysts were tested in a simulated exhaust gas from lean-burn natural gas vehicles with and without water vapor. The results demonstrated that the modified supports had an apparent effect on the performance of Pd catalysts, compared with the Pd catalyst supported on the unmodified ZrA1. The addition of ZnO or Y203 promoted the conversion of CH4. In the absence of water vapor, Pd/ZnZrA1 exhibited the best activity for CH4 conversion with the light-off temperature （Tso） of 275 ℃ and the complete conversion temperature （T90） of 314 ℃, respectively. However, in the presence of water vapor, Pd/YZrA1 was the best one over which the light-off temperature （Tso） of methane was 339 ℃ and the complete conversion temperature （T90） was 371 ℃. These results indicated that Pd catalyst supported on the modified composite ZrA1 support showed excellent catalytic activity at low temperature and high resistance to H20 poisoning for the exhaust purification of lean-burn natural gas vehicles.
文摘1 INTRODUCTIONMany attempts to develop semipermeable membranes for gas separation have beendone over the past twenty years [1,2].However,it is still difficult to prepare apolymer film which makes certain gas separation processed within range of being econ-omically and technically feasible,since most polymeric materials are relativelyimpermeable to gases.Facilitated transport concept which was first proposed
基金ACKNOWLEDGMENT Financial support of the work by the Natural Science Foundation of China （NO. 21176108） and the National High Technology Research and Development Program of China （863 Program） （NO. 2011AA06A106） is greatly acknowledge. We also would like to thank the key Laboratory of Kunming University of Science and Technology for characterization analysis.The heading of the Acknowledgment section and the References section must not be numbered.
基金supported by National Natural Science Foundation of China (Grant No. 50521503)National Basic Research Program of China (973 Program, Grant No. 2007CB714704)National Hi-tech Research and Development Program of China (863 Program, Grant No. 2006AA04Z406)
文摘The introduction of surface engineering is expected to be an effective strategy against fretting damage. A large number of studies show that the low gas multi-component （such as carbon, nitrogen, sulphur and oxygen, etc） thermo-chemical treatment（LTGMTT） can overcome the brittleness of nitriding process, and upgrade the surface hardness and improve the wear resistance and fatigue properties of the work-pieces significantly. However, there are few reports on the anti-fretting properties of the LTGMTT modified layer up to now, which limits the applications of fretting. So this paper discusses the fretting wear behavior of modified layer on the surface of LZ50 （0.48%C） steel prepared by low temperature gas multi-component thermo-chemical treatment （LTGMTT） technology. The fretting wear tests of the modified layer flat specimens and its substrate （LZ50 steel） against 52100 steel balls with diameter of 40 mm are carried out under normal load of 150 N and displacement amplitudes varied from 2 μm to 40 μm. Characterization of the modified layer and dynamic analyses in combination with microscopic examinations were performed through the means of scanning electron microscope（SEM）, optical microscope（OM）, X-ray diffraction（XRD） and surface profilometer. The experimental results showed that the modified layer with a total thickness of 60 μm was consisted of three parts, i.e., loose layer, compound layer and diffusion layer. Compared with the substrate, the range of the mixed fretting regime（MFR） of the LTGMTT modified layer diminished, and the slip regime（SR） of the modified layer shifted to the direction of smaller displacement amplitude. The coefficient of friction（COF） of the modified layer was lower than that of the substrate in the initial stage. For the modified layer, the damage in partial slip regime（PSR） was very slight. The fretting wear mechanism of the modified layer both in MFR and SR was abrasive wear and delamination. The modified layer presented better wear resistance than the substrate in PSR and MFR; however, in SR, the wear resistance of the modified layer decreased with the increase of the displacement amplitudes. The experimental results can provide some experimental bases for promoting industrial application of LTGMTT modified layer in anti-fretting wear.
文摘Pure ZnO thick film, prepared by screen-printing technique, was almost insensitive to NH3. Pure ZnO thick films were surface modified with MnO2 by dipping them into 0.01 M aqueous solution of manganese chloride (MnCl2) for different intervals of time and fired at 500℃ for 12 h. The grains of MnO2 would disperse around the grains of ZnO base material. The MnO2 modified ZnO films dipped for 30 min were observed to be sensitive and highly selective to NH3 gas at room temperature. An exceptional sensitivity was found to low concentration (50 ppm) of NH3 gas at room temperature and no cross sensitivity was observed even to high concentrations of other hazardous and polluting gases. The effects of surface microstructure and MnO2 concentrations on the sensitivity, selectivity, response and recovery of the sensor in the presence of NH3and other gases were studied and discussed. The better performance could be attributed to an optimum number of surface misfits in terms of MnO2 on the ZnO films.
文摘Intrinsic time quantum geometrodynamics is a formulation of quantum gravity naturally adapted to 3 + 1 dimensions. In this paper we construct its analogous 2 + 1 formulation, taking note of the mathematical structures which are preserved. We apply the resulting construction to convert the BTZ black hole metric to ITQG framework. We then modify the BTZ black hole in order to investigate the existence of the P-V criticality in ITQG theory.
文摘Measuring gas content is an essential step in estimating the commerciality of gas reserves. In this study,eight shale core samples from the Mouye-1 well were measured using a homemade patented gas desorption apparatus to determine their gas contents. Due to the air contamination that is introduced into the desorption canister, a mathematical method was devised to correct the gas quantity and quality.Compared to the chemical compositions of desorbed gas, the chemical compositions of residual gas are somewhat different. In residual gas, carbon dioxide and nitrogen record a slight increase, and propane is first observed. This phenomenon may be related to the exposure time during the transportation of shale samples from the drilling site to the laboratory, as well as the differences in the mass, size and adsorptivity of different gas molecules. In addition to a series of conventional methods, including the USBM direct method and the Amoco Curve Fit(ACF) method, which were used here for lost gas content estimation, a Modified Curve Fit(MCF) method, based on the 'bidisperse' diffusion model, was established to estimate lost gas content. By fitting the ACF and MCF models to gas desorption data, we determined that the MCF method could reasonably describe the gas desorption data over the entire time period, whereas the ACF method failed. The failure of the ACF method to describe the gas desorption process may be related to its restrictive assumption of a single pore size within shale samples. In comparison to the indirect method, this study demonstrates that none of the three methods studied in this investigation(USBM, ACF and MCF) could individually estimate the lost gas contents of all shale samples and that the proportion of free gas relative to total gas has a significant effect on the estimation accuracy of the selected method. When the ratio of free gas to total gas is lower than 45%, the USBM method is the best for estimating the lost gas content, whereas when the ratio ranges from 45% to 75% or is more than 75%, the ACF and MCF methods, are the best options respectively.
文摘A CFD code has been developed based on the conservation principles describing gas and solid flow in fluidized beds. This code is employed to simulate not only the spatiotemporal gas and solid phase velocities and voidage profiles in a two dimensional bed but also fluid dynamics in the jet region. The computational results show that gas flow direction is upward in the entire bed accompanied with random local circulations, whilst solid flow direction is upward at the center and downward near the wall. The radical reason of strong back mixing of solid particles and good transfer behavior between two phases is that the jet entrains solid particles. Numerical calculation indicates that gas velocity, solid velocity and pressure profile have a significant change when the voidage is 0 8. The simulated time averaged voidage profiles agree with the experimental results and simulated data reported by Gidaspow and Ettehadieh(1983). Therefore, CFD model can be regarded as a useful tool to study the jet characteristics in dense gas solid fluidized beds.
基金Supported by EU Comm ission(No.ENK5 - CT2 0 0 0 - 0 0 314 )
文摘A modified particle bed model derived from the two-fluid momentum balance equations was employed to predict the gas-fluidised bed behaviour. Additional terms are included in both the fluid and the particle momentum balance equations to take into account the effect of the dispersed solid phase. This model has been extended to two-dimensional formulations and has been implemented in the commercial code CFX 4.3. The model correctly simulates the homogeneous fluidisation of Geldart Group A and the bubbling fluidisation of Geldart Group B in gas-solid fluidised beds.
文摘We use the work of de Vega, Sanchez, and Comes (1997), to approximate the “particle density” of a “graviton gas”. This “particle density” derivation is compared with Dolgov’s (1997) expression of the Vacuum energy in terms of a phase transition. The idea is to have a quartic potential, and then to utilize the Bogomol’nyi inequality to refine what the phase transition states. We utilize Ng, Infinite quantum information procedures to link our work with initial entropy and other issues and close with a variation in the HUP: at the start of the expansion of the universe.
