In order to burn a hydrocarbon fuel efficiently using conventional cycles,very high temperatures are required.Chemical looping combustion（CLC）offers an alternative cycle for large scale power production.In CLC a car...In order to burn a hydrocarbon fuel efficiently using conventional cycles,very high temperatures are required.Chemical looping combustion（CLC）offers an alternative cycle for large scale power production.In CLC a carrier molecule is used to transport oxygen between two redox reactions,one where the carrier is oxidised and another where it is reduced by reaction with a fuel.Separation of the oxygen carrier from fuel ash can be aided by means of phase difference and this is a key advantage of fluid phase CLC where the carrier medium proposed is sodium,potassium or zinc.The principle exploited in fluid phase CLC is the recirculation of both energy and entropy.High thermal efficiencies,circa 75% at 35 bar are theoretically achievable taking into account component efficiencies,with separation of nitrogen and carbon dioxide,in combination with the water shift gas reaction,as an inherent part of the cycle if air is used as the oxygen source.展开更多
For the purpose of improving the electrochemical cycle stability of the La-Mg-Ni based A2BT-type electrode alloys, both reducing Mg content and substituting La with Pr were adopted. The Lao.8-xPrxMg0.2Ni3.15Co0.2A10.1...For the purpose of improving the electrochemical cycle stability of the La-Mg-Ni based A2BT-type electrode alloys, both reducing Mg content and substituting La with Pr were adopted. The Lao.8-xPrxMg0.2Ni3.15Co0.2A10.1Si0.05 （x=0, 0.1, 0.2, 0.3, 0.4） electrode alloys were fabricated by casting and annealing. The investigation on the structures and electrochemical performances of the alloys was performed. The obtained results reveal that the as-cast and annealed alloys comprise two major phases, （La, Mg）2Ni7 phase with the hexagonal Ce2NiT-type structure and LaNi5 phase with the hexagonal CaCus-type structure, as well as a little residual LaNi3 phase. It is also found that the addition of Pr element observably affects the electrochemical hydrogen storage characteristics of the alloys, just as the discharge capacity and high rate discharge ability （HRD） first rise then fall with the growing of Pr content, and among all the alloys, the as-cast and annealed （x=0.3） alloys generate the largest discharge capacities of 360.8 and 386.5 mA.h/g, respectively. Additionally, the electrochemical cycle stability of all the alloys markedly grows with the increase of Pr content. The capacity retaining rate （S100） at the 100th charging and discharging cycle is enhanced from 64.98% to 77.55% for the as-cast alloy, and from 76.60% to 95.72% for the as-annealed alloy by rising Pr content from 0 to 0.4. Furthermore, the substitution of Pr for La results in first increase and then decrease in the hydrogen diffusion coefficient （D）, the limiting current density （IL） as well as the electrochemical impedance.展开更多
We report a theoretical scheme using a B-spline basis set to improve the poor computational accuracy of circular Rydberg states of hydrogen atoms in the intermediate magnetic field. This scheme can produce high accura...We report a theoretical scheme using a B-spline basis set to improve the poor computational accuracy of circular Rydberg states of hydrogen atoms in the intermediate magnetic field. This scheme can produce high accuracy energy levels and valid for an arbitrary magnetic field. Energy levels of hydrogen are presented for circular Rydberg states with azimuthal quantum numbers ｜m｜ =10-70 as a function of magnetic field strengths ranging from zero to 2.35 × 10^9 T. The variation of spatial distributions of electron probability densities with magnetic field strengths is discussed and competition between Coulomb and magnetic interactions is illustrated.展开更多
文摘In order to burn a hydrocarbon fuel efficiently using conventional cycles,very high temperatures are required.Chemical looping combustion（CLC）offers an alternative cycle for large scale power production.In CLC a carrier molecule is used to transport oxygen between two redox reactions,one where the carrier is oxidised and another where it is reduced by reaction with a fuel.Separation of the oxygen carrier from fuel ash can be aided by means of phase difference and this is a key advantage of fluid phase CLC where the carrier medium proposed is sodium,potassium or zinc.The principle exploited in fluid phase CLC is the recirculation of both energy and entropy.High thermal efficiencies,circa 75% at 35 bar are theoretically achievable taking into account component efficiencies,with separation of nitrogen and carbon dioxide,in combination with the water shift gas reaction,as an inherent part of the cycle if air is used as the oxygen source.
基金Projects(51161015,50961009) supported by the National Natural Science Foundation of ChinaProject(2011AA03A408) supported by the National High Technology Research and Development Program of ChinaProjects(2011ZD10,2010ZD05) supported by the Natural Science Foundation of Inner Mongolia,China
文摘For the purpose of improving the electrochemical cycle stability of the La-Mg-Ni based A2BT-type electrode alloys, both reducing Mg content and substituting La with Pr were adopted. The Lao.8-xPrxMg0.2Ni3.15Co0.2A10.1Si0.05 （x=0, 0.1, 0.2, 0.3, 0.4） electrode alloys were fabricated by casting and annealing. The investigation on the structures and electrochemical performances of the alloys was performed. The obtained results reveal that the as-cast and annealed alloys comprise two major phases, （La, Mg）2Ni7 phase with the hexagonal Ce2NiT-type structure and LaNi5 phase with the hexagonal CaCus-type structure, as well as a little residual LaNi3 phase. It is also found that the addition of Pr element observably affects the electrochemical hydrogen storage characteristics of the alloys, just as the discharge capacity and high rate discharge ability （HRD） first rise then fall with the growing of Pr content, and among all the alloys, the as-cast and annealed （x=0.3） alloys generate the largest discharge capacities of 360.8 and 386.5 mA.h/g, respectively. Additionally, the electrochemical cycle stability of all the alloys markedly grows with the increase of Pr content. The capacity retaining rate （S100） at the 100th charging and discharging cycle is enhanced from 64.98% to 77.55% for the as-cast alloy, and from 76.60% to 95.72% for the as-annealed alloy by rising Pr content from 0 to 0.4. Furthermore, the substitution of Pr for La results in first increase and then decrease in the hydrogen diffusion coefficient （D）, the limiting current density （IL） as well as the electrochemical impedance.
基金Support from National Science Foundation of USA under Grant No. 0630370National Natural Science Foundation of China under Grant Nos. 90403028 and 11074260
文摘We report a theoretical scheme using a B-spline basis set to improve the poor computational accuracy of circular Rydberg states of hydrogen atoms in the intermediate magnetic field. This scheme can produce high accuracy energy levels and valid for an arbitrary magnetic field. Energy levels of hydrogen are presented for circular Rydberg states with azimuthal quantum numbers ｜m｜ =10-70 as a function of magnetic field strengths ranging from zero to 2.35 × 10^9 T. The variation of spatial distributions of electron probability densities with magnetic field strengths is discussed and competition between Coulomb and magnetic interactions is illustrated.
