In the present study an attempt has been made to carry out the detailed petrographic characterization of the Karharbari coals of Talcher coalfield and to reconstruct the paleoenvironment conditions of coal formation u...In the present study an attempt has been made to carry out the detailed petrographic characterization of the Karharbari coals of Talcher coalfield and to reconstruct the paleoenvironment conditions of coal formation using macerals and microlithtotypes as a tool. For these purposes a large number of samples were collected following the pillar sampling method and were subjected to detailed petrographic study. The petrographic observation shows that these coals are vitrinite rich followed by the liptinite and inertinite group of macerals. On microlithotype scale, these coals shows the dominance of the vitrite followed by clarite, vitrinertite and inertite. The concentration of liptite, clarodurite, duroclarite and vitriner- toliptite are insignificant. The vitrinite reflectance ranks the Karharbari coal as high volatile bituminous ＇C＇ to high volatile ＇B＇ bituminous. Coal petrography based depositional models suggest peat accumulation in forested telmatic swamp. Moreover, during the time of their evolution, there were alternate phases of oxic and anoxic moor conditions with good tissue preservation.展开更多
The Mo modified Ni/Al_2O_3 catalysts were prepared and sulfided at different temperatures, and their catalytic activity for thioetherification of mercaptans and olefins(or dienes), hydrogenation of dienes and olefins ...The Mo modified Ni/Al_2O_3 catalysts were prepared and sulfided at different temperatures, and their catalytic activity for thioetherification of mercaptans and olefins(or dienes), hydrogenation of dienes and olefins in the thioetherification process using fluidized catalytic cracking(FCC) naphtha as the feedstock was investigated. In order to disclose the correlation between the physicochemical characteristics of catalysts and their catalytic activity, the surface structures and properties of the catalysts sulfided at different temperatures were characterized by the high resolution transmission electronic microscopy(HRTEM), X-ray photoelectron spectroscopy(XPS) and H2-temperature programmed reduction(H_2-TPR) technique. The results showed that an increase of sulfurization temperature not only could promote the sulfurization degree of active metals on the catalysts, but also could adjust the micro-morphology of active species. These changes could improve the catalytic performance of thioetherification, and hydrogenation of dienes and olefins. However, an excess sulfurization temperature was more easily to upgrade the ability of the catalyst for hydrogenation of olefins, which could lead to a decrease of the octane number of the product. It was also showed that a moderate sulfurization temperature not only could improve the catalytic performance of thioetherification and hydrogenation of dienes but also could control hydrogenation of olefins.展开更多
High density vertically aligned and high aspect ratio silicon nanowire （SiNW） arrays have been fabricated on a Si substrate using a template and a catalytic etching process. The template was formed from polystyrene ...High density vertically aligned and high aspect ratio silicon nanowire （SiNW） arrays have been fabricated on a Si substrate using a template and a catalytic etching process. The template was formed from polystyrene （PS） nanospheres with diameter 30-50 nm and density 10^10/cm^2, produced by nanophase separation of PS-containing block-copolymers. The length of the SiNWs was controlled by varying the etching time with an etching rate of 12.5 nm/s. The SiNWs have a biomimetic structure with a high aspect ratio （-100）, high density, and exhibit ultra-low reflectance. An ultra-low reflectance of approximately 0.1% was achieved for SiNWs longer than 750 nm. Well-aligned SiNW/poly（3,4-ethylenedioxy-thiophene）：poly（styrenesulfonate） （PEDOT：PSS） heterojunction solar cells were fabricated. The n-type silicon nanowire surfaces adhered to PEDOT：PSS to form a core-sheath heterojunction structure through a simple and efficient solution process. The large surface area of the SiNWs ensured efficient collection of photogenerated carriers. Compared to planar cells without the nanowire structure, the SiNW/PEDOT：PSS heterojunction solar cell exhibited an increase in short-circuit current density from 2.35 mA/cm^2 to 21.1 mA/cm^2 and improvement in power conversion efficiency from 0.4% to 5.7%.展开更多
Thermal protection systems are very essential for high temperature thermal conductivity measurement system to reduce the heat loss to environment at the range of 600-1800 K. A compound multi-layer insulations structur...Thermal protection systems are very essential for high temperature thermal conductivity measurement system to reduce the heat loss to environment at the range of 600-1800 K. A compound multi-layer insulations structure which composed of inner carbon fibrous materials and outer alternately arranged alumina fibrous materials and high reflectivity foils is proposed for use in high temperature cylinder thermal protection systems. A coupled conductive and radiation governing equations is presented for heat transfer analysis of the structure. The finite volume method and the discrete ordinate method are used to solve the goveming equations. The optimization structure of the compound multi-layer insulations is investigated by considering the pressure of the gas, the density of the carbon fibrous materials, the density of the alumina fibrous materials, the number of reflective foil layers and the emissivity of reflective foils. The results show that the compound structure has the best thermal insulation performance when the pressure of the gas is below 0.01 kPa, the density of carbon fibrous materials is 180 kg m^-3, the density of alumina fibrous materials is 256 kg m^-3 and the number of reflective foil layers is 39. In addition, the thermal insulation performance is much better when the emissivity of reflective foils is lower.展开更多
The simulation of wave phenomena in unbounded domains generally requires an artificial boundary to truncate the unbounded exterior and limit the computation to a finite region.At the artificial boundary a boundary con...The simulation of wave phenomena in unbounded domains generally requires an artificial boundary to truncate the unbounded exterior and limit the computation to a finite region.At the artificial boundary a boundary condition is then needed,which allows the propagating waves to exit the computational domain without spurious reflection.In 1977,Engquist and Majda proposed the first hierarchy of absorbing boundary conditions,which allows a systematic reduction of spurious reflection without moving the artificial boundary farther away from the scatterer.Their pioneering work,which initiated an entire research area,is reviewed here from a modern perspective.Recent developments such as high-order local conditions and their extension to multiple scattering are also presented.Finally,the accuracy of high-order local conditions is demonstrated through numerical experiments.展开更多
SiC nanowires with thickness-controlled SiO2 shells have been obtained by a simple and efficient method, namely treatment of SiC/SiO2 core-shell nanowires in NaOH solution. The products were characterized by transmiss...SiC nanowires with thickness-controlled SiO2 shells have been obtained by a simple and efficient method, namely treatment of SiC/SiO2 core-shell nanowires in NaOH solution. The products were characterized by transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）, Raman spectroscopy, infrared （IR） spectroscopy, and photoluminescence spectroscopy. The thickness of the SiO2 shell can be effectively controlled by selecting the appropriate processing time, and pure SiC nanowires were also obtained by alkaline cleaning in 1 mol-L-1 NaOH solution for 40 min at 70 ~C. A mechanism for the removal of the SiO2 shells has been proposed, and a two-phase reaction kinetic equation was derived to explain the rate of the removal of the SiO2 shells. The validity of this equation was verified by experiment. This work not only describes an effective experimental method for achieving SiC nanowires with thickness-controlled SiO2 coatings but also provides a fundamental theoretical equation with a certain level of generality. In addition, photoluminescence （PL） measurement results showed that the SiC nanowires sheathed with an optimum SiO2 thickness （3.03 nm） have better photoluminescence properties than either the bare SiC nanowires or SiC nanowires with thicker coatings of SiO2.展开更多
文摘In the present study an attempt has been made to carry out the detailed petrographic characterization of the Karharbari coals of Talcher coalfield and to reconstruct the paleoenvironment conditions of coal formation using macerals and microlithtotypes as a tool. For these purposes a large number of samples were collected following the pillar sampling method and were subjected to detailed petrographic study. The petrographic observation shows that these coals are vitrinite rich followed by the liptinite and inertinite group of macerals. On microlithotype scale, these coals shows the dominance of the vitrite followed by clarite, vitrinertite and inertite. The concentration of liptite, clarodurite, duroclarite and vitriner- toliptite are insignificant. The vitrinite reflectance ranks the Karharbari coal as high volatile bituminous ＇C＇ to high volatile ＇B＇ bituminous. Coal petrography based depositional models suggest peat accumulation in forested telmatic swamp. Moreover, during the time of their evolution, there were alternate phases of oxic and anoxic moor conditions with good tissue preservation.
基金support provided by the National Natural Science Foundation of China(Granted No.21276276)
文摘The Mo modified Ni/Al_2O_3 catalysts were prepared and sulfided at different temperatures, and their catalytic activity for thioetherification of mercaptans and olefins(or dienes), hydrogenation of dienes and olefins in the thioetherification process using fluidized catalytic cracking(FCC) naphtha as the feedstock was investigated. In order to disclose the correlation between the physicochemical characteristics of catalysts and their catalytic activity, the surface structures and properties of the catalysts sulfided at different temperatures were characterized by the high resolution transmission electronic microscopy(HRTEM), X-ray photoelectron spectroscopy(XPS) and H2-temperature programmed reduction(H_2-TPR) technique. The results showed that an increase of sulfurization temperature not only could promote the sulfurization degree of active metals on the catalysts, but also could adjust the micro-morphology of active species. These changes could improve the catalytic performance of thioetherification, and hydrogenation of dienes and olefins. However, an excess sulfurization temperature was more easily to upgrade the ability of the catalyst for hydrogenation of olefins, which could lead to a decrease of the octane number of the product. It was also showed that a moderate sulfurization temperature not only could improve the catalytic performance of thioetherification and hydrogenation of dienes but also could control hydrogenation of olefins.
文摘High density vertically aligned and high aspect ratio silicon nanowire （SiNW） arrays have been fabricated on a Si substrate using a template and a catalytic etching process. The template was formed from polystyrene （PS） nanospheres with diameter 30-50 nm and density 10^10/cm^2, produced by nanophase separation of PS-containing block-copolymers. The length of the SiNWs was controlled by varying the etching time with an etching rate of 12.5 nm/s. The SiNWs have a biomimetic structure with a high aspect ratio （-100）, high density, and exhibit ultra-low reflectance. An ultra-low reflectance of approximately 0.1% was achieved for SiNWs longer than 750 nm. Well-aligned SiNW/poly（3,4-ethylenedioxy-thiophene）：poly（styrenesulfonate） （PEDOT：PSS） heterojunction solar cells were fabricated. The n-type silicon nanowire surfaces adhered to PEDOT：PSS to form a core-sheath heterojunction structure through a simple and efficient solution process. The large surface area of the SiNWs ensured efficient collection of photogenerated carriers. Compared to planar cells without the nanowire structure, the SiNW/PEDOT：PSS heterojunction solar cell exhibited an increase in short-circuit current density from 2.35 mA/cm^2 to 21.1 mA/cm^2 and improvement in power conversion efficiency from 0.4% to 5.7%.
基金supported by the National Natural Science Foundation of China(Grant No.51225602)
文摘Thermal protection systems are very essential for high temperature thermal conductivity measurement system to reduce the heat loss to environment at the range of 600-1800 K. A compound multi-layer insulations structure which composed of inner carbon fibrous materials and outer alternately arranged alumina fibrous materials and high reflectivity foils is proposed for use in high temperature cylinder thermal protection systems. A coupled conductive and radiation governing equations is presented for heat transfer analysis of the structure. The finite volume method and the discrete ordinate method are used to solve the goveming equations. The optimization structure of the compound multi-layer insulations is investigated by considering the pressure of the gas, the density of the carbon fibrous materials, the density of the alumina fibrous materials, the number of reflective foil layers and the emissivity of reflective foils. The results show that the compound structure has the best thermal insulation performance when the pressure of the gas is below 0.01 kPa, the density of carbon fibrous materials is 180 kg m^-3, the density of alumina fibrous materials is 256 kg m^-3 and the number of reflective foil layers is 39. In addition, the thermal insulation performance is much better when the emissivity of reflective foils is lower.
文摘The simulation of wave phenomena in unbounded domains generally requires an artificial boundary to truncate the unbounded exterior and limit the computation to a finite region.At the artificial boundary a boundary condition is then needed,which allows the propagating waves to exit the computational domain without spurious reflection.In 1977,Engquist and Majda proposed the first hierarchy of absorbing boundary conditions,which allows a systematic reduction of spurious reflection without moving the artificial boundary farther away from the scatterer.Their pioneering work,which initiated an entire research area,is reviewed here from a modern perspective.Recent developments such as high-order local conditions and their extension to multiple scattering are also presented.Finally,the accuracy of high-order local conditions is demonstrated through numerical experiments.
基金The work reported here was supported by the National Natural Science Foundation of China under Grant Nos. 51272117, 51172115, and 50972063, the Natural Science Foundation of Shandong Province under Grant Nos. ZR2011EMZ001, and ZR2011EMQ011, the Specialized Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20123719110003, the Application Foundation Research Program of Qingdao under Grant No. 13-1-4- 117-jch, and the Tackling Key Program of Science and Technology in Shandong Province under Grant No. 2012GGX10218. We express our grateful thanks to them for their financial support.
文摘SiC nanowires with thickness-controlled SiO2 shells have been obtained by a simple and efficient method, namely treatment of SiC/SiO2 core-shell nanowires in NaOH solution. The products were characterized by transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）, Raman spectroscopy, infrared （IR） spectroscopy, and photoluminescence spectroscopy. The thickness of the SiO2 shell can be effectively controlled by selecting the appropriate processing time, and pure SiC nanowires were also obtained by alkaline cleaning in 1 mol-L-1 NaOH solution for 40 min at 70 ~C. A mechanism for the removal of the SiO2 shells has been proposed, and a two-phase reaction kinetic equation was derived to explain the rate of the removal of the SiO2 shells. The validity of this equation was verified by experiment. This work not only describes an effective experimental method for achieving SiC nanowires with thickness-controlled SiO2 coatings but also provides a fundamental theoretical equation with a certain level of generality. In addition, photoluminescence （PL） measurement results showed that the SiC nanowires sheathed with an optimum SiO2 thickness （3.03 nm） have better photoluminescence properties than either the bare SiC nanowires or SiC nanowires with thicker coatings of SiO2.
