Series of TiO 2-ZnO heterojunction composite films with different n(Zn)/n(Ti) ratios were prepared by UDP450 magnetron sputter ion plating equipment, and the mole ratio of Zn to Ti was controlled by adjusting the ...Series of TiO 2-ZnO heterojunction composite films with different n(Zn)/n(Ti) ratios were prepared by UDP450 magnetron sputter ion plating equipment, and the mole ratio of Zn to Ti was controlled by adjusting the current values of sputtering target. The effects of n(Zn)/n(Ti) on the microstructures of TiO2-ZnO films were investigated by SEM, AFM, Raman and XPS, and their photocatalytic decomposition of methyl orange solutions was evaluated. The results show that an increase in n(Zn)/n(Ti) typically results in a decrease in the grain size of composite films firstly and then an increase of grain size, while an increase in n(Zn)/n(Ti) leads to an increase in film roughness firstly and then a decrease in film roughness. Both grain size and roughness of TiO2-ZnO films reach the maximum and minimum at n(Zn)/n(Ti) of 1/9.3, respectively. The n(Zn)/n(Ti) shows little effect on the valences of Zn and Ti elements, which mainly exist in the form of TiO2 and ZnO phases. The n(Zn)/n(Ti) has influence on the amount of anatase/rutile TiO2 heterojunction in the film. With increase of the n(Zn)/n(Ti), the absorption intensity of the composite film increases and the absorption region extends to 450 nm, which is redshifted as much as 150 nm in comparison with the pure TiO2 films. However, the photocatalytic abilities of heterogeneous composite films do not depend on the n(Zn)/n(Ti) but rather on the microstructures of the TiO2-ZnO composite films. Degradation rate of the film reaches the maximum and the photocatalytic decomposition of pollutants works best when n(Zn)/n(Ti)=1:9.3.展开更多
Microstructure of GaAs/SiO 2 nanogranular thin films fabricated by radio frequency magnetron co sputtering technique and postannealing are investigated via atomic force microscope,X ray diffraction,and Rutherford b...Microstructure of GaAs/SiO 2 nanogranular thin films fabricated by radio frequency magnetron co sputtering technique and postannealing are investigated via atomic force microscope,X ray diffraction,and Rutherford backscattering spectroscopy.The results show that GaAs nanocrystals with average diameters from 1 5nm to 3 2nm (depending on the annealing temperature) are uniformly dispersed in the SiO 2 matrices.GaAs and SiO 2 are found in normal stoichiometry in the films.The nonlinear optical refraction and nonlinear optical absorption are studied by Z scan technique using a single Gaussian beam of pulse laser.The third order nonlinear optical refractive index and nonlinear absorption coefficient are enhanced due to the quantum confinement effects and estimated to be 4×10 -12 m 2/W and 2×10 -5 m/W respectively in nonresonant condition,while 2×10 -11 m 2/W and -1×10 -4 m/W respectively in quasi resonant condition.展开更多
A series of BiOX(X=Cl,Br) were prepared by simple hydrolysis and then calcined at various temperatures and they were characterized by XRD,Raman,SEM,DSC-TGA,BET and UV-Vis.The photocatalytic activity was evaluated by p...A series of BiOX(X=Cl,Br) were prepared by simple hydrolysis and then calcined at various temperatures and they were characterized by XRD,Raman,SEM,DSC-TGA,BET and UV-Vis.The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange(MO) solution under simulated solar light irradiation.The results show that the phase structure,crystallite size,morphology,specific surface area,porous structure,and the absorption band-edges are related to the calcination temperature.For BiOBr,it has completely transformed to Bi24O31Br10 at 600℃ and begins to transform to Bi2 O3 at 800℃.As for BiOCl,it begins to transform to Bi24O31Cl10 at 600℃ and completely transforms to Bi24O31Cl10 at 800℃.Finally,the photocatalytic activity of BiOCl decreases with the temperature increasing owing to decrease of the specific surface areas and pore size,while the photocatalytic activity of BiOBr increases in the first stage and then decreases,which is related to good crystallization and three-dimensional structure.展开更多
This experiment obtained different laser energy density(LED) by changing SLM molding process parameters.The surface morphology, surface quality, and microstructure of as-fabricated samples were studied. The effects of...This experiment obtained different laser energy density(LED) by changing SLM molding process parameters.The surface morphology, surface quality, and microstructure of as-fabricated samples were studied. The effects of scanning speed, hatching space, and laser power on surface quality were analyzed, and the optimal LED range for surface quality was determined. The results show that pores and spherical particles appear on the sample’s surface when low LED is applied, while there are lamellar structures on the sides of the samples. Cracks appear on the sample’s surface,and the splash phenomenon increases when a high LED is taken. At the same time, a large amount of unmelted powder adhered to the side of the sample. The surface quality is the best when the LED is 150-170 J/mm^(3). The preferred hatch space is currently 0.05-0.09 mm, the laser power is 200-350 W, and the average surface roughness value is(15.1±3) μm.The average surface hardness reaches HV404±HV3, higher than the forging standard range of HV340-HV395.Increasing the LED within the experiment range can increase the surface hardness, yet an excessively high LED will not further increase the surface hardness. The microstructure is composed of needle-like α’-phases with a length of about 20μm, in a crisscross ‘N’ shape, when the LED is low. The β-phase grain boundary is not obvious, and the secondaryphase volume fraction is high;when the LED is high, the α’-phase of the microstructure is in the form of coarse slats, and the secondary-phase is composed of a small amount of secondary α’-phase, the tertiary α’-phase and the fourth α’-phase disappear, and the volume fraction of the secondary-phase becomes low.展开更多
The Al-3.40Mg-1.08Sc alloy plates were manufactured by selective laser melting(SLM) at platform temperatures of 35 ℃ and 200 ℃, respectively, and the corrosion performance of them was studied along height direction....The Al-3.40Mg-1.08Sc alloy plates were manufactured by selective laser melting(SLM) at platform temperatures of 35 ℃ and 200 ℃, respectively, and the corrosion performance of them was studied along height direction. The results show that the corrosion resistance of the alloy plate built at platform temperature of 35 ℃ along height direction is basically the same due to a uniform microstructure;While the corrosion resistance of the alloy plate built at platform temperature of 200 ℃ along height direction is different. The evolution of microstructure and the distribution of secondary phases are investigated, and the results show that the Cu-rich phases in alloy play a key role on corrosion performance. At higher platform temperature, the cooling rate is relative slow and a certain degree of in situ ageing leads to the significantly different distribution of Cu-rich phases along grain boundary. Specimens built at the platform temperature of 200 ℃ are inclined to locate at the crossed grain boundary, rather than continuous segregation of Cu-rich phases along grain boundary that is built at platform temperature of 35 ℃. Therefore, the corrosion resistance of Al-3.40Mg-1.08Sc alloy plate manufactured at platform temperature of 200 ℃ is higher, and presents a gradually decreasing trend along height direction.展开更多
The House of the Seven Gables (1981), Hawthorne's second romance, is his another masterpiece after The Scarlet Letter (1956). The achievement of its themes and narrative skills has been greatly complimented by re...The House of the Seven Gables (1981), Hawthorne's second romance, is his another masterpiece after The Scarlet Letter (1956). The achievement of its themes and narrative skills has been greatly complimented by readers, especially its descriptions and analyses of the characters' psychological activities and their personalities. The notorious Salem Witch Trials of Hawthorne's family has a great effect on Hawthorne's formation of his views about the good and evil, the sin and penalty, and the psychological descriptive style in his works. In The House of the Seven Gables, Hawthorne takes this family history as the original writing background. Through exploring modem people's spiritual essence, using history as narrative original, Hawthorne's theme illustrates the past's influence on the present. By exploring the changes of the characters' psychologies and values, especially those of Holgrave, the narrator proposes a conception of general love to eradicate the actual contradictions. Hawthorne actually provides an alternative way--a nonpolitical solution to the national problems, which demonstrates not only his artistic pursuit but also his culturally political view in his writing. This paper consists of five parts.展开更多
The effects of cooling rates corresponding to different diameters of the steel mould and laser surface melting(LSM)on the as-cast microstructures of Mg-9Al-xSi(x=1,3)(mass fraction,%)alloys were investigated by XRD an...The effects of cooling rates corresponding to different diameters of the steel mould and laser surface melting(LSM)on the as-cast microstructures of Mg-9Al-xSi(x=1,3)(mass fraction,%)alloys were investigated by XRD and OM.The results show that obvious refinement of the alloy microstructure is obtained with increasing cooling rate by conventional ingot metallurgy.However, no evident modified morphologies of both dendritic primary Mg2Si and Chinese script eutectic Mg2Si in the Mg-Al-Si alloy occurs. Surprisingly,the morphologies of Mg2Si phases within the laser-melted Mg-Al-Si alloy transform drastically from both coarse Chinese script shape for the eutectic Mg2Si and dendrite for the primary Mg2Si to fine spherical particles with an average size of about 3μm due to the rapid cooling of the melted layer,and the Mg2Si particulates distribute more uniformly in theα-Mg matrix.展开更多
In order to investigate the characteristics of re-oxidation of residual coal in goafs in close coal seam mining,scanning electron microscope and infrared spectrometer are used to study the changes of coal microstructu...In order to investigate the characteristics of re-oxidation of residual coal in goafs in close coal seam mining,scanning electron microscope and infrared spectrometer are used to study the changes of coal microstructure and chemical reaction of functional groups of eight coal samples at different ranks.Result shows that after initial oxidation,the surface morphology of pore are different,and the porosity of coal is increased and the oxygen adsorption capacity of coal is improved.The change of coal molecular structure and presence of a large amount of active oxygen-containing functional groups lead to increasing tendency of coal to further oxidation.In addition,the higher lever of the initial oxidation is,the easier the re-oxidation occurs.展开更多
In this study,nano-graphene reinforced titanium matrix composites(GNPs/Ti)with a honeycomb porous structure were fabricated by selective laser melting(SLM).The effects of graphene on the microstructure,mechanical prop...In this study,nano-graphene reinforced titanium matrix composites(GNPs/Ti)with a honeycomb porous structure were fabricated by selective laser melting(SLM).The effects of graphene on the microstructure,mechanical properties and corrosion performance of the SLM GNPs/Ti were systematically investigated.Results of microstructure characterization show that:1)the density of the SLM GNPs/Ti was improved as compared to that of the SLM Ti;2)abundant TiC particles were formed in the SLM GNPs/Ti.The hardness and compressive strength of the composite increased by 90%(from HV 236 to HV 503)and 14%(from 277 MPa to 316 MPa),respectively,attributed to the uniformly distributed TiC and fine GNPs in the Ti matrix.Electrochemical tests reveal that the corrosion current density of the SLM GNPs/Ti is only 0.328μA/cm^(2),that is about 25%less than that of the SLM Ti.The results indicate that the incorporation of nano-graphene is a potential method to strengthen the Ti by SLM.展开更多
This paper describes a geographic information system(GIS)-based method for observing changes in topography caused by the initiation, transport, and deposition of debris flows using highresolution light detection and r...This paper describes a geographic information system(GIS)-based method for observing changes in topography caused by the initiation, transport, and deposition of debris flows using highresolution light detection and ranging(LiDAR) digital elevation models(DEMs) obtained before and after the debris flow events. The paper also describes a method for estimating the volume of debris flows using the differences between the LiDAR DEMs. The relative and absolute positioning accuracies of the LiDAR DEMs were evaluated using a real-time precise global navigation satellite system(GNSS) positioning method. In addition, longitudinal and cross-sectional profiles of the study area were constructed to determine the topographic changes caused by the debris flows. The volume of the debris flows was estimated based on the difference between the LiDAR DEMs. The accuracies of the relative and absolute positioning of the two LiDAR DEMs were determined to be ±10 cm and ±11 cm RMSE, respectively, which demonstrates the efficiency of the method for determining topographic changes at an scale equivalent to that of field investigations. Based on the topographic changes, the volume of the debris flows in the study area was estimated to be 3747 m3, which is comparable with the volume estimated based on the data from field investigations.展开更多
Catalytic converting CO2 into fuels with the help of solar energy is regarded as‘dream reaction’,as both energy crisis and environmental issue can be mitigated simultaneously.However,it is still suffering from low e...Catalytic converting CO2 into fuels with the help of solar energy is regarded as‘dream reaction’,as both energy crisis and environmental issue can be mitigated simultaneously.However,it is still suffering from low efficiency due to narrow solar-spectrum utilization and sluggish heterogeneous reaction kinetics.In this work,we demonstrate that catalytic reduction of CO2 can be achieved over Au nanoparticles(NPs)deposited rutile under full solar-spectrum irradiation,boosted by solar-heating effect.We found that UV and visible light can initiate the reaction,and the heat from IR light and local surface-plasmon resonance relaxation of Au NPs can boost the reaction kinetically.The apparent activation energy is determined experimentally and is used to explain the superior catalytic activity of Au/rutile to rutile in a kinetic way.We also find the photo-thermal synergy in the Au/rutile system.We envision that this work may facilitate understanding the kinetics of CO2 reduction and developing feasible catalytic systems with full solar spectrum utilization for practical artificial photosynthesis.展开更多
After exposure of one-year old seedlings of Swietenia macrophylla to an overnight temperature (13 C, 19 C, 25 C, 31 C or 35 C), the leaf net photosynthetic rate (Pn) was researched through measuring photosynthetic lig...After exposure of one-year old seedlings of Swietenia macrophylla to an overnight temperature (13 C, 19 C, 25 C, 31 C or 35 C), the leaf net photosynthetic rate (Pn) was researched through measuring photosynthetic light-response curves at 360 mmolmol-1 CO2, and photosynthetic CO2-response curves at light-saturated intensity (1500 mmolm-2 s-1). The optimal temperature for photosynthesis measured at 360 mmol穖ol-1 CO2 was from 25 C to 31 C, but which was from 31C to 35 C at saturating CO2 concentration. At temperature of below 25 C, the decline in Pn was mainly due to the drop in carboxylation efficiency (Ce), while as temperature was over 31 C, the reduction in Pn resulted from both decrease in Ce and increase in leaf respiration. The CO2-induced stimulation of photosynthesis was strongly inhibited at temperatures below 13 C. The results showed that, the leaf photosynthesis of tropical evergreen plants should not be accelerated at low temperature in winter season with elevated CO2 concentration in the future.展开更多
Based on the experimental results of Chen et al. to use the solar furnace and medium frequency induction furnace to extract boron impurity from metallurgical silicon, we propose a strong radiation catalysis mechanism ...Based on the experimental results of Chen et al. to use the solar furnace and medium frequency induction furnace to extract boron impurity from metallurgical silicon, we propose a strong radiation catalysis mechanism to explain the difference of reaction rates in these two furnaces. The postulate assuming the photons striking on the material not only increase the thermal energy of the molecules of reactants but also lower down the energy barrier of the reaction to speed up the chemical reaction. It is believed the photon catalysis mechanism is unlversall in most of high temperature chemical reactions and looking forward to more evidences for the postulate proposed in this article.展开更多
To research the influence of oxygen flow rate on the structural and optical properties of TiO2 thin film,TiO2 films on glass were deposited by reactive magnetron sputtering.The microstructure and optical properties we...To research the influence of oxygen flow rate on the structural and optical properties of TiO2 thin film,TiO2 films on glass were deposited by reactive magnetron sputtering.The microstructure and optical properties were measured by X-ray diffractometry,AFM and UV-VIS transmittance spectroscopy,respectively.The results show that the films deposited at oxygen flow rate of 10 mL/min has the lowest roughness and the highest transmittance.The absorption angle shifts to longer wavelengths as oxygen flow rates increase from 5 to 10 mL/min,then to shorter ones as the oxygen flow rate increase from 10 to 30 mL/min.The band gap is 3.38 eV,which is nearly constant in the experiment.For the TiO2 thin films deposited at 10 mL/min of oxyge flow rate,there are nano-crystalline structures,which are suitable for anti-reflection(AR) coating in the solar cells structure system.展开更多
Tourist agriculture, based on agriculture,is a new cross combination of agriculture and tourism from 1970s.Ithas appeared some original features by now, and weshould use the successful experience of the tourist agricu...Tourist agriculture, based on agriculture,is a new cross combination of agriculture and tourism from 1970s.Ithas appeared some original features by now, and weshould use the successful experience of the tourist agriculture in Taiwan of China for reference to standardize all the aspects of work.Support it more in policy,fund, technology, and propaganda, and strengthen the combination of the program of city and suburb to promote the development of the tourist agriculture in Mianyang.展开更多
The g-C_3N_4 with different structures was prepared by heat treatment using urea(CN-U) and thiourea(CN-T) as precursors under the same conditions. The microstructure and optical properties of the photocatalyst were an...The g-C_3N_4 with different structures was prepared by heat treatment using urea(CN-U) and thiourea(CN-T) as precursors under the same conditions. The microstructure and optical properties of the photocatalyst were analyzed with advanced tools. The results showed that the CN-U has a porous structure, a high specific surface area and a wide band gap in comparison with CN-T. The in situ FT-IR technique was used to monitor the adsorption and reaction process of visible photocatalytic NO oxidation on g-C_3N_4. The corresponding reaction mechanism was proposed based on the results of reaction intermediate observation and electron paramagnetic resonance(EPR) radical scavenging. It was revealed that(1) the presence of defective sites favored the adsorption of gas molecules and electronically compensated it leading to promoted formation of the final products;(2) the high separation efficiency of photogenerated electron-hole pairs enhanced the production of radicals during the photocatalytic reaction;(3) the hydroxyl radicals(-OH) are not selective for the decomposition of pollutants, which are favorable to the complete oxidation of the reaction intermediates. The above three aspects are the main reasons for the CN-U possessing the efficient visible light photocatalytic activity. The present work could provide new insights and methods for understanding the mechanism of photocatalysis.展开更多
基金Project (2010JQ6008) supported by the Natural Science Foundation of Shaanxi Province,China
文摘Series of TiO 2-ZnO heterojunction composite films with different n(Zn)/n(Ti) ratios were prepared by UDP450 magnetron sputter ion plating equipment, and the mole ratio of Zn to Ti was controlled by adjusting the current values of sputtering target. The effects of n(Zn)/n(Ti) on the microstructures of TiO2-ZnO films were investigated by SEM, AFM, Raman and XPS, and their photocatalytic decomposition of methyl orange solutions was evaluated. The results show that an increase in n(Zn)/n(Ti) typically results in a decrease in the grain size of composite films firstly and then an increase of grain size, while an increase in n(Zn)/n(Ti) leads to an increase in film roughness firstly and then a decrease in film roughness. Both grain size and roughness of TiO2-ZnO films reach the maximum and minimum at n(Zn)/n(Ti) of 1/9.3, respectively. The n(Zn)/n(Ti) shows little effect on the valences of Zn and Ti elements, which mainly exist in the form of TiO2 and ZnO phases. The n(Zn)/n(Ti) has influence on the amount of anatase/rutile TiO2 heterojunction in the film. With increase of the n(Zn)/n(Ti), the absorption intensity of the composite film increases and the absorption region extends to 450 nm, which is redshifted as much as 150 nm in comparison with the pure TiO2 films. However, the photocatalytic abilities of heterogeneous composite films do not depend on the n(Zn)/n(Ti) but rather on the microstructures of the TiO2-ZnO composite films. Degradation rate of the film reaches the maximum and the photocatalytic decomposition of pollutants works best when n(Zn)/n(Ti)=1:9.3.
文摘Microstructure of GaAs/SiO 2 nanogranular thin films fabricated by radio frequency magnetron co sputtering technique and postannealing are investigated via atomic force microscope,X ray diffraction,and Rutherford backscattering spectroscopy.The results show that GaAs nanocrystals with average diameters from 1 5nm to 3 2nm (depending on the annealing temperature) are uniformly dispersed in the SiO 2 matrices.GaAs and SiO 2 are found in normal stoichiometry in the films.The nonlinear optical refraction and nonlinear optical absorption are studied by Z scan technique using a single Gaussian beam of pulse laser.The third order nonlinear optical refractive index and nonlinear absorption coefficient are enhanced due to the quantum confinement effects and estimated to be 4×10 -12 m 2/W and 2×10 -5 m/W respectively in nonresonant condition,while 2×10 -11 m 2/W and -1×10 -4 m/W respectively in quasi resonant condition.
基金Projects(21676178,21506144,21706179)supported by the National Natural Science Foundation of ChinaProject(2019L0138)supported by the Science and Technology Innovation Program of Higher Education Institutions in Shanxi Province,ChinaProject(201901D211100)supported by the Natural Science Foundation of Shanxi Province for Young Scientists,China
文摘A series of BiOX(X=Cl,Br) were prepared by simple hydrolysis and then calcined at various temperatures and they were characterized by XRD,Raman,SEM,DSC-TGA,BET and UV-Vis.The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange(MO) solution under simulated solar light irradiation.The results show that the phase structure,crystallite size,morphology,specific surface area,porous structure,and the absorption band-edges are related to the calcination temperature.For BiOBr,it has completely transformed to Bi24O31Br10 at 600℃ and begins to transform to Bi2 O3 at 800℃.As for BiOCl,it begins to transform to Bi24O31Cl10 at 600℃ and completely transforms to Bi24O31Cl10 at 800℃.Finally,the photocatalytic activity of BiOCl decreases with the temperature increasing owing to decrease of the specific surface areas and pore size,while the photocatalytic activity of BiOBr increases in the first stage and then decreases,which is related to good crystallization and three-dimensional structure.
基金Projects(51975006, 51505006) supported by the National Natural Science Foundation of China。
文摘This experiment obtained different laser energy density(LED) by changing SLM molding process parameters.The surface morphology, surface quality, and microstructure of as-fabricated samples were studied. The effects of scanning speed, hatching space, and laser power on surface quality were analyzed, and the optimal LED range for surface quality was determined. The results show that pores and spherical particles appear on the sample’s surface when low LED is applied, while there are lamellar structures on the sides of the samples. Cracks appear on the sample’s surface,and the splash phenomenon increases when a high LED is taken. At the same time, a large amount of unmelted powder adhered to the side of the sample. The surface quality is the best when the LED is 150-170 J/mm^(3). The preferred hatch space is currently 0.05-0.09 mm, the laser power is 200-350 W, and the average surface roughness value is(15.1±3) μm.The average surface hardness reaches HV404±HV3, higher than the forging standard range of HV340-HV395.Increasing the LED within the experiment range can increase the surface hardness, yet an excessively high LED will not further increase the surface hardness. The microstructure is composed of needle-like α’-phases with a length of about 20μm, in a crisscross ‘N’ shape, when the LED is low. The β-phase grain boundary is not obvious, and the secondaryphase volume fraction is high;when the LED is high, the α’-phase of the microstructure is in the form of coarse slats, and the secondary-phase is composed of a small amount of secondary α’-phase, the tertiary α’-phase and the fourth α’-phase disappear, and the volume fraction of the secondary-phase becomes low.
基金Project(51901207) supported by the National Natural Science Foundation of ChinaProject(2018M632796) supported by the China Postdoctoral Science FoundationProjects(19A430024, 21A430037) supported by the Plan of Henan Key Scientific Research Project of Universities,China。
文摘The Al-3.40Mg-1.08Sc alloy plates were manufactured by selective laser melting(SLM) at platform temperatures of 35 ℃ and 200 ℃, respectively, and the corrosion performance of them was studied along height direction. The results show that the corrosion resistance of the alloy plate built at platform temperature of 35 ℃ along height direction is basically the same due to a uniform microstructure;While the corrosion resistance of the alloy plate built at platform temperature of 200 ℃ along height direction is different. The evolution of microstructure and the distribution of secondary phases are investigated, and the results show that the Cu-rich phases in alloy play a key role on corrosion performance. At higher platform temperature, the cooling rate is relative slow and a certain degree of in situ ageing leads to the significantly different distribution of Cu-rich phases along grain boundary. Specimens built at the platform temperature of 200 ℃ are inclined to locate at the crossed grain boundary, rather than continuous segregation of Cu-rich phases along grain boundary that is built at platform temperature of 35 ℃. Therefore, the corrosion resistance of Al-3.40Mg-1.08Sc alloy plate manufactured at platform temperature of 200 ℃ is higher, and presents a gradually decreasing trend along height direction.
文摘The House of the Seven Gables (1981), Hawthorne's second romance, is his another masterpiece after The Scarlet Letter (1956). The achievement of its themes and narrative skills has been greatly complimented by readers, especially its descriptions and analyses of the characters' psychological activities and their personalities. The notorious Salem Witch Trials of Hawthorne's family has a great effect on Hawthorne's formation of his views about the good and evil, the sin and penalty, and the psychological descriptive style in his works. In The House of the Seven Gables, Hawthorne takes this family history as the original writing background. Through exploring modem people's spiritual essence, using history as narrative original, Hawthorne's theme illustrates the past's influence on the present. By exploring the changes of the characters' psychologies and values, especially those of Holgrave, the narrator proposes a conception of general love to eradicate the actual contradictions. Hawthorne actually provides an alternative way--a nonpolitical solution to the national problems, which demonstrates not only his artistic pursuit but also his culturally political view in his writing. This paper consists of five parts.
基金Project(LRB05-311)supported by the Postdoctoral Foundation of Heilongjiang Province,ChinaProject(HEUFT05038)supported by the Basic Research Foundation of Harbin Engineering University,ChinaProject(2009AA03Z423)supported by the National High-TechResearch and Development Program of China
文摘The effects of cooling rates corresponding to different diameters of the steel mould and laser surface melting(LSM)on the as-cast microstructures of Mg-9Al-xSi(x=1,3)(mass fraction,%)alloys were investigated by XRD and OM.The results show that obvious refinement of the alloy microstructure is obtained with increasing cooling rate by conventional ingot metallurgy.However, no evident modified morphologies of both dendritic primary Mg2Si and Chinese script eutectic Mg2Si in the Mg-Al-Si alloy occurs. Surprisingly,the morphologies of Mg2Si phases within the laser-melted Mg-Al-Si alloy transform drastically from both coarse Chinese script shape for the eutectic Mg2Si and dendrite for the primary Mg2Si to fine spherical particles with an average size of about 3μm due to the rapid cooling of the melted layer,and the Mg2Si particulates distribute more uniformly in theα-Mg matrix.
基金the National Key Foundation for Exploring Scientific Instruments of China(No.2012YQ24012705)the National Natural Science Foundation of China(No.51174113)+2 种基金the special fund for Scientific Research Institutes of China(Nos.2013EG122192 and 2014EG122293)CCTEG Innovation Foundation of China(No. 2014MS030)Shenhua Innovation Foundation of China(No. SHGF-13-07)
文摘In order to investigate the characteristics of re-oxidation of residual coal in goafs in close coal seam mining,scanning electron microscope and infrared spectrometer are used to study the changes of coal microstructure and chemical reaction of functional groups of eight coal samples at different ranks.Result shows that after initial oxidation,the surface morphology of pore are different,and the porosity of coal is increased and the oxygen adsorption capacity of coal is improved.The change of coal molecular structure and presence of a large amount of active oxygen-containing functional groups lead to increasing tendency of coal to further oxidation.In addition,the higher lever of the initial oxidation is,the easier the re-oxidation occurs.
基金Projects(51504191,51671152,51874225)supported by the National Natural Science Foundation of ChinaProject(2019GY-188)supported by the Key R&D Projects of Shaanxi,China+2 种基金Project(18JC019)supported by the Industrialization Project of Shaanxi Education Department,ChinaProject(PMMSLKL-901)supported by the State Key Laboratory of Metal Porous Materials,ChinaProject(2020ZDLGY13-10)supported by the Science&Technology Project of Shaanxi,China。
文摘In this study,nano-graphene reinforced titanium matrix composites(GNPs/Ti)with a honeycomb porous structure were fabricated by selective laser melting(SLM).The effects of graphene on the microstructure,mechanical properties and corrosion performance of the SLM GNPs/Ti were systematically investigated.Results of microstructure characterization show that:1)the density of the SLM GNPs/Ti was improved as compared to that of the SLM Ti;2)abundant TiC particles were formed in the SLM GNPs/Ti.The hardness and compressive strength of the composite increased by 90%(from HV 236 to HV 503)and 14%(from 277 MPa to 316 MPa),respectively,attributed to the uniformly distributed TiC and fine GNPs in the Ti matrix.Electrochemical tests reveal that the corrosion current density of the SLM GNPs/Ti is only 0.328μA/cm^(2),that is about 25%less than that of the SLM Ti.The results indicate that the incorporation of nano-graphene is a potential method to strengthen the Ti by SLM.
基金supported by the Public Welfare & Safety Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (Grant No. 2012M3A2A1050979)
文摘This paper describes a geographic information system(GIS)-based method for observing changes in topography caused by the initiation, transport, and deposition of debris flows using highresolution light detection and ranging(LiDAR) digital elevation models(DEMs) obtained before and after the debris flow events. The paper also describes a method for estimating the volume of debris flows using the differences between the LiDAR DEMs. The relative and absolute positioning accuracies of the LiDAR DEMs were evaluated using a real-time precise global navigation satellite system(GNSS) positioning method. In addition, longitudinal and cross-sectional profiles of the study area were constructed to determine the topographic changes caused by the debris flows. The volume of the debris flows was estimated based on the difference between the LiDAR DEMs. The accuracies of the relative and absolute positioning of the two LiDAR DEMs were determined to be ±10 cm and ±11 cm RMSE, respectively, which demonstrates the efficiency of the method for determining topographic changes at an scale equivalent to that of field investigations. Based on the topographic changes, the volume of the debris flows in the study area was estimated to be 3747 m3, which is comparable with the volume estimated based on the data from field investigations.
基金supported by the Belt and Road Initiative by Chinese Academy of Sciencesthe National Natural Science Foundation of China(21673052,11404074)
文摘Catalytic converting CO2 into fuels with the help of solar energy is regarded as‘dream reaction’,as both energy crisis and environmental issue can be mitigated simultaneously.However,it is still suffering from low efficiency due to narrow solar-spectrum utilization and sluggish heterogeneous reaction kinetics.In this work,we demonstrate that catalytic reduction of CO2 can be achieved over Au nanoparticles(NPs)deposited rutile under full solar-spectrum irradiation,boosted by solar-heating effect.We found that UV and visible light can initiate the reaction,and the heat from IR light and local surface-plasmon resonance relaxation of Au NPs can boost the reaction kinetically.The apparent activation energy is determined experimentally and is used to explain the superior catalytic activity of Au/rutile to rutile in a kinetic way.We also find the photo-thermal synergy in the Au/rutile system.We envision that this work may facilitate understanding the kinetics of CO2 reduction and developing feasible catalytic systems with full solar spectrum utilization for practical artificial photosynthesis.
文摘After exposure of one-year old seedlings of Swietenia macrophylla to an overnight temperature (13 C, 19 C, 25 C, 31 C or 35 C), the leaf net photosynthetic rate (Pn) was researched through measuring photosynthetic light-response curves at 360 mmolmol-1 CO2, and photosynthetic CO2-response curves at light-saturated intensity (1500 mmolm-2 s-1). The optimal temperature for photosynthesis measured at 360 mmol穖ol-1 CO2 was from 25 C to 31 C, but which was from 31C to 35 C at saturating CO2 concentration. At temperature of below 25 C, the decline in Pn was mainly due to the drop in carboxylation efficiency (Ce), while as temperature was over 31 C, the reduction in Pn resulted from both decrease in Ce and increase in leaf respiration. The CO2-induced stimulation of photosynthesis was strongly inhibited at temperatures below 13 C. The results showed that, the leaf photosynthesis of tropical evergreen plants should not be accelerated at low temperature in winter season with elevated CO2 concentration in the future.
文摘Based on the experimental results of Chen et al. to use the solar furnace and medium frequency induction furnace to extract boron impurity from metallurgical silicon, we propose a strong radiation catalysis mechanism to explain the difference of reaction rates in these two furnaces. The postulate assuming the photons striking on the material not only increase the thermal energy of the molecules of reactants but also lower down the energy barrier of the reaction to speed up the chemical reaction. It is believed the photon catalysis mechanism is unlversall in most of high temperature chemical reactions and looking forward to more evidences for the postulate proposed in this article.
基金Project(08FJ1002) supported by the Hunan Province Key Project of Science and Technology,China
文摘To research the influence of oxygen flow rate on the structural and optical properties of TiO2 thin film,TiO2 films on glass were deposited by reactive magnetron sputtering.The microstructure and optical properties were measured by X-ray diffractometry,AFM and UV-VIS transmittance spectroscopy,respectively.The results show that the films deposited at oxygen flow rate of 10 mL/min has the lowest roughness and the highest transmittance.The absorption angle shifts to longer wavelengths as oxygen flow rates increase from 5 to 10 mL/min,then to shorter ones as the oxygen flow rate increase from 10 to 30 mL/min.The band gap is 3.38 eV,which is nearly constant in the experiment.For the TiO2 thin films deposited at 10 mL/min of oxyge flow rate,there are nano-crystalline structures,which are suitable for anti-reflection(AR) coating in the solar cells structure system.
基金Partachievementsof the projectof the science and research fund in MianyangNormal University.
文摘Tourist agriculture, based on agriculture,is a new cross combination of agriculture and tourism from 1970s.Ithas appeared some original features by now, and weshould use the successful experience of the tourist agriculture in Taiwan of China for reference to standardize all the aspects of work.Support it more in policy,fund, technology, and propaganda, and strengthen the combination of the program of city and suburb to promote the development of the tourist agriculture in Mianyang.
基金supported by the National Key Research and Development Plan (2016YFC02047)the National Natural Science Foundation of China (51478070, 21777011 and 21501016)+1 种基金the Innovative Research Team of Chongqing (CXTDG201602014)the Natural Science Foundation of Chongqing (cstc2017jcyj BX0052, cstc2016jcyj A0481)
文摘The g-C_3N_4 with different structures was prepared by heat treatment using urea(CN-U) and thiourea(CN-T) as precursors under the same conditions. The microstructure and optical properties of the photocatalyst were analyzed with advanced tools. The results showed that the CN-U has a porous structure, a high specific surface area and a wide band gap in comparison with CN-T. The in situ FT-IR technique was used to monitor the adsorption and reaction process of visible photocatalytic NO oxidation on g-C_3N_4. The corresponding reaction mechanism was proposed based on the results of reaction intermediate observation and electron paramagnetic resonance(EPR) radical scavenging. It was revealed that(1) the presence of defective sites favored the adsorption of gas molecules and electronically compensated it leading to promoted formation of the final products;(2) the high separation efficiency of photogenerated electron-hole pairs enhanced the production of radicals during the photocatalytic reaction;(3) the hydroxyl radicals(-OH) are not selective for the decomposition of pollutants, which are favorable to the complete oxidation of the reaction intermediates. The above three aspects are the main reasons for the CN-U possessing the efficient visible light photocatalytic activity. The present work could provide new insights and methods for understanding the mechanism of photocatalysis.