Based on a modified-Darcy-Maxwell model, two-dimensional, incompressible and heat transfer flow of two bounded layers, through electrified Maxwell fluids in porous media is performed. The driving force for the instabi...Based on a modified-Darcy-Maxwell model, two-dimensional, incompressible and heat transfer flow of two bounded layers, through electrified Maxwell fluids in porous media is performed. The driving force for the instability under an electric field, is an electrostatic force exerted on the free charges accumulated at the dividing interface. Normal mode analysis is considered to study the linear stability of the disturbances layers. The solutions of the linearized equations of motion with the boundary conditions lead to an implicit dispersion relation between the growth rate and wave number. These equations are parameterized by Weber number, Reynolds number, Marangoni number, dimensionless conductivities, and dimensionless electric potentials. The case of long waves interfaciaJ stability has been studied. The stability criteria are performed theoreticaily in which stability diagrams are obtained. In the limiting cases, some previously published results can be considered as particular cases of our results. It is found that the Reynolds number plays a destabilizing role in the stability criteria, while the damping influence is observed for the increasing of Marangoni number and Maxwell relaxation time.展开更多
Preparation of a high flux of hydrogen molecules in a specific vibrationally excited state is the major prerequisite and challenge in scattering experiments that use vibrationally excited hydrogen molecules as the tar...Preparation of a high flux of hydrogen molecules in a specific vibrationally excited state is the major prerequisite and challenge in scattering experiments that use vibrationally excited hydrogen molecules as the target. The widely used scheme of stimulated Raman pumping suffers from coherent population return which severely limits the excitation efficiency. Re- cently we successfully transferred D2 molecules in the molecular beam from （v=0, J=0） to （v=1, J=0） level, with the scheme of Stark-induced adiabatic Raman passage. As high as 75% of the excitation efficiency was achieved. This excitation technique promise to be a unique tool for crossed beam and beam-surface scattering experiments which aim to reveal the role of vibrational excitation of hydrogen molecules in the chemical reaction.展开更多
This paper summarizes the selected results of an extensive investigation of application of two methods （hydrothermal and mechanochemical） assisted by calcination for synthesizing belite cement from reactive mixtures...This paper summarizes the selected results of an extensive investigation of application of two methods （hydrothermal and mechanochemical） assisted by calcination for synthesizing belite cement from reactive mixtures （CaO/SiO2 molar ratio of 2） consisting of various waste kinds from fluidized brown coal combustion in Slovakian power plant and CaO addition. Based on XRD diffraction patterns and infrared spectra ofpre-treatment products, the formation of the new profiles corresponding to CSH phases with low degree of ordering as belite precursors after hydrothermal treatment as well as metastables calcium silicates and aluminosilicates in mechanosynthesized products was confirmed. Calcination of hydrothermally treated products led to transformation of CSH phases to wollastonite （CS）, belite and gehlenite phase, whereas creation oft^- and I^-C2S or wollastonite in milled reactive mixture took place. Differences in phase composition of products before and after calcination depend upon waste quality and precursor＇s synthesis conditions. Bottom ash isn＇t suitable as raw material for synthesizing belite phase because of high CaO content fixed in anhydrite form （44.1%）. Coal fly ash with low CaO content in anhydrite form （4.2%） and its mechanochemical or hydrothermal treatment in combination with subsequent heating offer opportunities for the utilization of coal fly ash as raw material for belite production.展开更多
In structure of manufacture of PFER （primary fuel and energy resources） in Central Asia region the leading place occupies now organic fuel. Thus about half of total amount of power resources it is necessary on the n...In structure of manufacture of PFER （primary fuel and energy resources） in Central Asia region the leading place occupies now organic fuel. Thus about half of total amount of power resources it is necessary on the natural gas which basic stocks are concentrated in Turkmenistan and Uzbekistan. More than 95% of all electric power in Tajikistan is developed by hydroelectric power stations. Use of hydrogen as energy carrier allows to consider and solve power problems in close connection with ecological. At a large factory electrolysis of water with capacity of 450 t/day and more expenses of the electric power on 1 m3 hydrogen can be finished by capacity up to 4.0-4.5 kWt.h. At such expense of the electric power in a number of power situations electrolysis of water, even in modem conditions can become a competitive method of obtaining of hydrogen.展开更多
The idea of the transformation of coal in underground into synthetic gas so-called syngas is interested in world in many centuries. Underground Coal Gasification （UCG） is an in-situ technique to recover the fuel or ...The idea of the transformation of coal in underground into synthetic gas so-called syngas is interested in world in many centuries. Underground Coal Gasification （UCG） is an in-situ technique to recover the fuel or feedstock value of coal that is not economically available through conventional recovery technologies. Today, less than one sixth of the world＇s coal is economically accessible. Today, similarly to all other countries in the world also in Slovakia there is an interest in the revival and perfection of the UCG technology. From the viewpoint of content the research is directed toward to increasing heating capacity of syngas. From the standpoint of the methods used the research can be divided into 2 approaches： experiments in UCG laboratory and mathematical modeling, including simulation studies. Both approaches have helped to discover complicated relationships during UCG and they will be the subject of this paper. The most important factors are methods, the humidity of the coal, heat losses, temperatures in relevant zones, the composition of oxidation agents and the permeability of the coal. The calorific value of syngas was found generally to be 0.55-4.45 MJ.Nm^-3 with a maximum of 25.51 MJ.m^-3 if only air is used as the oxidation agent. Where a mixture of air and oxygen is used, calorific values in the range 0.43-6.38 MJ.m^-3 were generally obtained, with maximum 27.53 MJ·m^-3. Analysis was carried out on these big differences in order to improve UCG.展开更多
Mathematical model for Maxwell fluid flow in rotating frame induced by an isothermal stretching wall is explored numerically. Scale analysis based boundary layer approximations are applied to simplify the conservation...Mathematical model for Maxwell fluid flow in rotating frame induced by an isothermal stretching wall is explored numerically. Scale analysis based boundary layer approximations are applied to simplify the conservation relations which are later converted to similar forms via appropriate substitutions. A numerical approach is utilized to derive similarity solutions for broad range of Deborah number. The results predict that velocity distributions are inversely proportional to the stress relaxation time. This outcome is different from that observed for the elastic parameter of second grade fluid. Unlike non-rotating frame, the solution curves are oscillatory decaying functions of similarity variable. As angular velocity enlarges, temperature rises and significant drop in the heat transfer coefficient occurs. We note that the wall slope of temperature has an asymptotically decaying profile against the wall to ambient ratio parameter. From the qualitative view point, temperature ratio parameter and radiation parameter have similar effect on the thermal boundary layer. Furthermore, radiation parameter has a definite role in improving the cooling process of the stretching boundary.A comparative study of current numerical computations and those from the existing studies is also presented in a limiting case. To our knowledge, the phenomenon of non-linear radiation in rotating viscoelastic flow due to linearly stretched plate is just modeled here.展开更多
Applying Clausius relation with energy-supply defined by the unified first law of thermodynamics formalism to the apparent horizon of a massive gravity model in cosmology proposed lately, the corrected entropic formul...Applying Clausius relation with energy-supply defined by the unified first law of thermodynamics formalism to the apparent horizon of a massive gravity model in cosmology proposed lately, the corrected entropic formula of the apparent horizon is obtaJned with the help of the modified Friedmann equations. This entropy-area relation, together with the identified Misner-Sharp internal energy, verifies the first law of thermodynamics for the apparent horizon with a volume change term for consistency. On the other hand, by means of the corrected entropy-area formula and the Clausius relation δQ = T dS, where the heat flow δQ is the energy-supply of pure matter projecting on the vector ξ tangent to the apparent horizon and should be looked on as the amount of energy crossing the apparent horizon during the time interval dt and the temperature of the apparent horizon for energy crossing during the same interval is 1/（2πτA）, the modified Friedmann equations governing the dynamical evolution of the universe are reproduced with the known energy density and pressure of massive graviton. The integration constant is found to correspond to a cosmological term which could be absorbed into the energy density of matter. Having established the correspondence of massive cosmology with the unified first law of thermodynamics on the apparent horizon, the validity of the generalized second law of thermodynamics is also discussed by assuming the thermal equilibrium between the apparent horizon and the matter field bounded by the apparent horizon. It is found that, in the limit Hc → 0, which recovers the Minkowski reference metric solution in the fiat case, the generalized second law of thermodynamics holds if α3 ＋ 4α4 〈 0. Without this condition, even for the simplest model of dRGT massive cosmology with α3= α4 = 0, the generalized second law of thermodynamics could be violated.展开更多
文摘Based on a modified-Darcy-Maxwell model, two-dimensional, incompressible and heat transfer flow of two bounded layers, through electrified Maxwell fluids in porous media is performed. The driving force for the instability under an electric field, is an electrostatic force exerted on the free charges accumulated at the dividing interface. Normal mode analysis is considered to study the linear stability of the disturbances layers. The solutions of the linearized equations of motion with the boundary conditions lead to an implicit dispersion relation between the growth rate and wave number. These equations are parameterized by Weber number, Reynolds number, Marangoni number, dimensionless conductivities, and dimensionless electric potentials. The case of long waves interfaciaJ stability has been studied. The stability criteria are performed theoreticaily in which stability diagrams are obtained. In the limiting cases, some previously published results can be considered as particular cases of our results. It is found that the Reynolds number plays a destabilizing role in the stability criteria, while the damping influence is observed for the increasing of Marangoni number and Maxwell relaxation time.
文摘Preparation of a high flux of hydrogen molecules in a specific vibrationally excited state is the major prerequisite and challenge in scattering experiments that use vibrationally excited hydrogen molecules as the target. The widely used scheme of stimulated Raman pumping suffers from coherent population return which severely limits the excitation efficiency. Re- cently we successfully transferred D2 molecules in the molecular beam from （v=0, J=0） to （v=1, J=0） level, with the scheme of Stark-induced adiabatic Raman passage. As high as 75% of the excitation efficiency was achieved. This excitation technique promise to be a unique tool for crossed beam and beam-surface scattering experiments which aim to reveal the role of vibrational excitation of hydrogen molecules in the chemical reaction.
文摘This paper summarizes the selected results of an extensive investigation of application of two methods （hydrothermal and mechanochemical） assisted by calcination for synthesizing belite cement from reactive mixtures （CaO/SiO2 molar ratio of 2） consisting of various waste kinds from fluidized brown coal combustion in Slovakian power plant and CaO addition. Based on XRD diffraction patterns and infrared spectra ofpre-treatment products, the formation of the new profiles corresponding to CSH phases with low degree of ordering as belite precursors after hydrothermal treatment as well as metastables calcium silicates and aluminosilicates in mechanosynthesized products was confirmed. Calcination of hydrothermally treated products led to transformation of CSH phases to wollastonite （CS）, belite and gehlenite phase, whereas creation oft^- and I^-C2S or wollastonite in milled reactive mixture took place. Differences in phase composition of products before and after calcination depend upon waste quality and precursor＇s synthesis conditions. Bottom ash isn＇t suitable as raw material for synthesizing belite phase because of high CaO content fixed in anhydrite form （44.1%）. Coal fly ash with low CaO content in anhydrite form （4.2%） and its mechanochemical or hydrothermal treatment in combination with subsequent heating offer opportunities for the utilization of coal fly ash as raw material for belite production.
文摘In structure of manufacture of PFER （primary fuel and energy resources） in Central Asia region the leading place occupies now organic fuel. Thus about half of total amount of power resources it is necessary on the natural gas which basic stocks are concentrated in Turkmenistan and Uzbekistan. More than 95% of all electric power in Tajikistan is developed by hydroelectric power stations. Use of hydrogen as energy carrier allows to consider and solve power problems in close connection with ecological. At a large factory electrolysis of water with capacity of 450 t/day and more expenses of the electric power on 1 m3 hydrogen can be finished by capacity up to 4.0-4.5 kWt.h. At such expense of the electric power in a number of power situations electrolysis of water, even in modem conditions can become a competitive method of obtaining of hydrogen.
文摘The idea of the transformation of coal in underground into synthetic gas so-called syngas is interested in world in many centuries. Underground Coal Gasification （UCG） is an in-situ technique to recover the fuel or feedstock value of coal that is not economically available through conventional recovery technologies. Today, less than one sixth of the world＇s coal is economically accessible. Today, similarly to all other countries in the world also in Slovakia there is an interest in the revival and perfection of the UCG technology. From the viewpoint of content the research is directed toward to increasing heating capacity of syngas. From the standpoint of the methods used the research can be divided into 2 approaches： experiments in UCG laboratory and mathematical modeling, including simulation studies. Both approaches have helped to discover complicated relationships during UCG and they will be the subject of this paper. The most important factors are methods, the humidity of the coal, heat losses, temperatures in relevant zones, the composition of oxidation agents and the permeability of the coal. The calorific value of syngas was found generally to be 0.55-4.45 MJ.Nm^-3 with a maximum of 25.51 MJ.m^-3 if only air is used as the oxidation agent. Where a mixture of air and oxygen is used, calorific values in the range 0.43-6.38 MJ.m^-3 were generally obtained, with maximum 27.53 MJ·m^-3. Analysis was carried out on these big differences in order to improve UCG.
文摘Mathematical model for Maxwell fluid flow in rotating frame induced by an isothermal stretching wall is explored numerically. Scale analysis based boundary layer approximations are applied to simplify the conservation relations which are later converted to similar forms via appropriate substitutions. A numerical approach is utilized to derive similarity solutions for broad range of Deborah number. The results predict that velocity distributions are inversely proportional to the stress relaxation time. This outcome is different from that observed for the elastic parameter of second grade fluid. Unlike non-rotating frame, the solution curves are oscillatory decaying functions of similarity variable. As angular velocity enlarges, temperature rises and significant drop in the heat transfer coefficient occurs. We note that the wall slope of temperature has an asymptotically decaying profile against the wall to ambient ratio parameter. From the qualitative view point, temperature ratio parameter and radiation parameter have similar effect on the thermal boundary layer. Furthermore, radiation parameter has a definite role in improving the cooling process of the stretching boundary.A comparative study of current numerical computations and those from the existing studies is also presented in a limiting case. To our knowledge, the phenomenon of non-linear radiation in rotating viscoelastic flow due to linearly stretched plate is just modeled here.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10747155, 11205131, 11175270, 11005164, and 10935013, ChongqingChongqing Science and Technology Commission under Grant No. 2010BB0408Local Support from Argonne National Laboratory
文摘Applying Clausius relation with energy-supply defined by the unified first law of thermodynamics formalism to the apparent horizon of a massive gravity model in cosmology proposed lately, the corrected entropic formula of the apparent horizon is obtaJned with the help of the modified Friedmann equations. This entropy-area relation, together with the identified Misner-Sharp internal energy, verifies the first law of thermodynamics for the apparent horizon with a volume change term for consistency. On the other hand, by means of the corrected entropy-area formula and the Clausius relation δQ = T dS, where the heat flow δQ is the energy-supply of pure matter projecting on the vector ξ tangent to the apparent horizon and should be looked on as the amount of energy crossing the apparent horizon during the time interval dt and the temperature of the apparent horizon for energy crossing during the same interval is 1/（2πτA）, the modified Friedmann equations governing the dynamical evolution of the universe are reproduced with the known energy density and pressure of massive graviton. The integration constant is found to correspond to a cosmological term which could be absorbed into the energy density of matter. Having established the correspondence of massive cosmology with the unified first law of thermodynamics on the apparent horizon, the validity of the generalized second law of thermodynamics is also discussed by assuming the thermal equilibrium between the apparent horizon and the matter field bounded by the apparent horizon. It is found that, in the limit Hc → 0, which recovers the Minkowski reference metric solution in the fiat case, the generalized second law of thermodynamics holds if α3 ＋ 4α4 〈 0. Without this condition, even for the simplest model of dRGT massive cosmology with α3= α4 = 0, the generalized second law of thermodynamics could be violated.
