A numerical study based on direct thermal to electric energy conversion was performed in a reciprocal flow porous media burner embedded with two layers of thermoelements. The burner lean combustibility limit was sough...A numerical study based on direct thermal to electric energy conversion was performed in a reciprocal flow porous media burner embedded with two layers of thermoelements. The burner lean combustibility limit was sought in order to maximize global efficiency of thermal to electrical energy conversion by minimizing fuel consumption. Once the pairs of operational variables, composition and filtrational velocity of gas inlet mixture were found, the optimal length and placement of thermoelectric elements within the reactor high thermal gradients were sought to maximize the electric current, thermoelements and system overall efficiency. A two temperature-resistance model for finite time thermodynamics was developed for the thermoelectric elements energy fluxes. Results indicate a distribution of current and efficiencies that presents a maximum at different themoelements length. Maximum values for current and system efficiency obtained were 44.3 m A and 2.5%, respectively.展开更多
We present an analytical analysis of the spatial resolution of quantum ghost imaging implemented by entangled photons from a general, spontaneously parametric, down-conversion process. We find that the resolution is a...We present an analytical analysis of the spatial resolution of quantum ghost imaging implemented by entangled photons from a general, spontaneously parametric, down-conversion process. We find that the resolution is affected by both the pump beam waist and the nonlinear crystal length. Hence, we determined a method to improve the resolution for a certain imaging setup. It should be noted that the resolution is not uniquely related to the degree of entanglement of the photon pair since the resolution can be optimized for a certain degree of entanglement. For certain types of Einstein-Podolsky-Rosen(EPR) states——namely the momentum-correlated or momentum-positively correlated states——the resolution exhibits a simpler relationship with the pump beam waist and crystal length. Further, a vivid numerical simulation of ghost imaging is presented for different types of EPR states,which supports our analysis. This work discusses applicable references to the applications of quantum ghost imaging.展开更多
A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K0.09MnO3 （LCKMO）/zinc oxide （ZnO） heterojunction bilayers grown on ITO substrate by pulsed laser deposition ...A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K0.09MnO3 （LCKMO）/zinc oxide （ZnO） heterojunction bilayers grown on ITO substrate by pulsed laser deposition （PLD） at relative low growth temperature. The heterostructure ITO/LCKMO/ZnO/A1 exhibits reproducible rectifying characteristics and light cur- rent under continuous laser irradiation of 2 = 325 nm. We report here the influence of LCKMO/ZnO bilayers＇ thickness on the electrical and photoelectric properties of the heterostructure at room temperature. The power conversion efficiency （PCE） is achieved when the LCKMO and ZnO layers are thin enough or the full space charge layer is sufficient. We obtained the maximum value of PCE of 0.0145% when the thicknesses of LCKMO and ZnO layers are 25 and 150 nm, respectively. The open circuit voltage is 0.04 V under this condition due to the internal photoemission.展开更多
文摘A numerical study based on direct thermal to electric energy conversion was performed in a reciprocal flow porous media burner embedded with two layers of thermoelements. The burner lean combustibility limit was sought in order to maximize global efficiency of thermal to electrical energy conversion by minimizing fuel consumption. Once the pairs of operational variables, composition and filtrational velocity of gas inlet mixture were found, the optimal length and placement of thermoelectric elements within the reactor high thermal gradients were sought to maximize the electric current, thermoelements and system overall efficiency. A two temperature-resistance model for finite time thermodynamics was developed for the thermoelectric elements energy fluxes. Results indicate a distribution of current and efficiencies that presents a maximum at different themoelements length. Maximum values for current and system efficiency obtained were 44.3 m A and 2.5%, respectively.
基金supported by the National Natural Science Foundation of China(Grant Nos.11174121,11321063,91121001,and 91321312)the National Program on Key Basic Research Project(Grant No.2012CB921802)
文摘We present an analytical analysis of the spatial resolution of quantum ghost imaging implemented by entangled photons from a general, spontaneously parametric, down-conversion process. We find that the resolution is affected by both the pump beam waist and the nonlinear crystal length. Hence, we determined a method to improve the resolution for a certain imaging setup. It should be noted that the resolution is not uniquely related to the degree of entanglement of the photon pair since the resolution can be optimized for a certain degree of entanglement. For certain types of Einstein-Podolsky-Rosen(EPR) states——namely the momentum-correlated or momentum-positively correlated states——the resolution exhibits a simpler relationship with the pump beam waist and crystal length. Further, a vivid numerical simulation of ghost imaging is presented for different types of EPR states,which supports our analysis. This work discusses applicable references to the applications of quantum ghost imaging.
基金supported by the National Natural Science Foundation of China (No. 90922034 and No. 21131002)Specialized Research Fund for the Doctoral Program of Higher Education (No. 20110061130005)
文摘A novel photovoltaic phenomenon of internal photoemission was found in a low cost manganite La0.62Ca0.29K0.09MnO3 （LCKMO）/zinc oxide （ZnO） heterojunction bilayers grown on ITO substrate by pulsed laser deposition （PLD） at relative low growth temperature. The heterostructure ITO/LCKMO/ZnO/A1 exhibits reproducible rectifying characteristics and light cur- rent under continuous laser irradiation of 2 = 325 nm. We report here the influence of LCKMO/ZnO bilayers＇ thickness on the electrical and photoelectric properties of the heterostructure at room temperature. The power conversion efficiency （PCE） is achieved when the LCKMO and ZnO layers are thin enough or the full space charge layer is sufficient. We obtained the maximum value of PCE of 0.0145% when the thicknesses of LCKMO and ZnO layers are 25 and 150 nm, respectively. The open circuit voltage is 0.04 V under this condition due to the internal photoemission.
