This paper discusses the future power system consisting of distributed generations connected to local loads in the form of micro-grid systems.The benefits of having energy storage systems and the role of power electro...This paper discusses the future power system consisting of distributed generations connected to local loads in the form of micro-grid systems.The benefits of having energy storage systems and the role of power electronics in micro-grid systems are presented.This paper also examines how micro-grids have a key role to play in the development of the smart grid.展开更多
Although already scientists in recent years have reported some experimental and theoretical results of LaNi-Al series of tritium-storage alloys, several key aspects remain the subject of considerable debate. In an eff...Although already scientists in recent years have reported some experimental and theoretical results of LaNi-Al series of tritium-storage alloys, several key aspects remain the subject of considerable debate. In an effort to interpret some of these unknowns, we have performed experimental and theoretical investigations for LaNi（5-x）Alx（x = 0, 0.25, 0.5, 0.75 and 1.0） tritium-storage alloys. Firstly, the XRD characterization indicates that the unit cell volumes of LaNi（5-x）Alx increase with Al content in alloys. Secondly, the PCisotherm measurement of LaNi（5-x）Alxalloys shows that their hydrogen absorption/desorption plateau pressures reduce with the increase of Al content while their plateau widths narrow simultaneously. The deuterium absorption/desorption plateaus have a similar trend to hydrogen＇s except for their plateaus being higher than hydrogen＇s. To explain the above experimental findings, a series of calculations based on density functional theory（DFT） and frozen phonon approach have been performed. The results manifest that：（1） the partial substitutions of Al for Ni reduce the hydrogen formation energies of LaNi（5-x）AlxH and the number of available interstitial sites, and therefore lead to the absorption/desorption plateau pressures being reduced and the plateau widths being narrowed down at the same experimental temperatures;（2） the covalent interaction between H and Ni is an important factor for estimating the stability of LaNi（5-x）Alx-H system;（3） since the calculated enthalpy change H is generally more accurate than the calculated entropy change S with respect to the corresponding experimental value for each LaNi（5-x）AlxH（or D）, the curves of H vs. hydrogen storage capacity instead of Van＇t Hoff relation, can be used to predict the experimental plateau pressures of LaNi（5-x）Alx-H（D or T） at a given temperature;（4） the hydrogen isotope effect of LaNi（5-x）Alx-H（D or T） system can be quantitatively described as a linearity relation between ⊿ZPE ＋ ⊿H^（vib） and 1/√mQ（Q = H, D, T）. From the good agreement between the predicted and experimental ln（PH/P0） and ln（PD/P0）, it is deduced that predicting ln（PT/P0） of LaNi（5-x）Alx T is feasible. The procedure of pre-computing and comparing curves of H vs. hydrogen storage capacity proposed in this paper provided an attractive tool to increase the efficiency of experimental alloying design of hydrogen（deuterium or tritium） storage materials.展开更多
Hybrid improper ferroelectric Ca3Ti2O7 and Ca3Tii 9RuO.iO7 ceramics were successfully synthesized by conventional solid-state reaction method.Two strongest diffraction peaks located around 2θ=33°shifted towards ...Hybrid improper ferroelectric Ca3Ti2O7 and Ca3Tii 9RuO.iO7 ceramics were successfully synthesized by conventional solid-state reaction method.Two strongest diffraction peaks located around 2θ=33°shifted towards the lower angle region with Ru substitution,reflecting structure variation.Grain growth and higher oxygen vacancy concentration after doping resulted in a reduction in the coercive field about 20 kV/cm.Optical bandgap estimated by UV-vis diffuse reflectance(DR)spectrum and X-ray photoelectron spectroscopy(XPS)valence band spectra showed a decreasing trend due to the existence of impurity energy level upon Ru doping,which was consistent with the results of first-principles calculations.The origin of the unexpected induced magnetic moments in Ru-dope Ca3Ti2O7 is also discussed.展开更多
GaAs-based polarization modulators （PolMs） exhibit the unique characteristic of simultaneous intensity and complementary phase modulation owing to the linear electro-optic （LEO） effect determined by crystallograph...GaAs-based polarization modulators （PolMs） exhibit the unique characteristic of simultaneous intensity and complementary phase modulation owing to the linear electro-optic （LEO） effect determined by crystallographic orientations of the device. In this paper, we reviewed the principle of operation, the design and fabrication flows of a GaAs-based PolM. Analytical models are established, from which the features of a PolM are derived and discussed in detail. The recent advances in PolM-based multifunctional systems, in particular the PolM-based optoelectronic oscillator （OEO） are demonstrated with an emphasis on the remarkable development of applications for frequency conversion, tunable microwave photonic filter （MPF）, optical frequency comb （OFC）, arbitrary waveform generation （AWG） and beamforming. Challenges in practical implementation of the PolM-based systems and their promising future are discussed as well.展开更多
基金funded by the ARC Linkage Grant LP100100618,Country Energy and the University of Wollongong
文摘This paper discusses the future power system consisting of distributed generations connected to local loads in the form of micro-grid systems.The benefits of having energy storage systems and the role of power electronics in micro-grid systems are presented.This paper also examines how micro-grids have a key role to play in the development of the smart grid.
基金support from the National Natural Science Foundation of China under the grant No. 51271176
文摘Although already scientists in recent years have reported some experimental and theoretical results of LaNi-Al series of tritium-storage alloys, several key aspects remain the subject of considerable debate. In an effort to interpret some of these unknowns, we have performed experimental and theoretical investigations for LaNi（5-x）Alx（x = 0, 0.25, 0.5, 0.75 and 1.0） tritium-storage alloys. Firstly, the XRD characterization indicates that the unit cell volumes of LaNi（5-x）Alx increase with Al content in alloys. Secondly, the PCisotherm measurement of LaNi（5-x）Alxalloys shows that their hydrogen absorption/desorption plateau pressures reduce with the increase of Al content while their plateau widths narrow simultaneously. The deuterium absorption/desorption plateaus have a similar trend to hydrogen＇s except for their plateaus being higher than hydrogen＇s. To explain the above experimental findings, a series of calculations based on density functional theory（DFT） and frozen phonon approach have been performed. The results manifest that：（1） the partial substitutions of Al for Ni reduce the hydrogen formation energies of LaNi（5-x）AlxH and the number of available interstitial sites, and therefore lead to the absorption/desorption plateau pressures being reduced and the plateau widths being narrowed down at the same experimental temperatures;（2） the covalent interaction between H and Ni is an important factor for estimating the stability of LaNi（5-x）Alx-H system;（3） since the calculated enthalpy change H is generally more accurate than the calculated entropy change S with respect to the corresponding experimental value for each LaNi（5-x）AlxH（or D）, the curves of H vs. hydrogen storage capacity instead of Van＇t Hoff relation, can be used to predict the experimental plateau pressures of LaNi（5-x）Alx-H（D or T） at a given temperature;（4） the hydrogen isotope effect of LaNi（5-x）Alx-H（D or T） system can be quantitatively described as a linearity relation between ⊿ZPE ＋ ⊿H^（vib） and 1/√mQ（Q = H, D, T）. From the good agreement between the predicted and experimental ln（PH/P0） and ln（PD/P0）, it is deduced that predicting ln（PT/P0） of LaNi（5-x）Alx T is feasible. The procedure of pre-computing and comparing curves of H vs. hydrogen storage capacity proposed in this paper provided an attractive tool to increase the efficiency of experimental alloying design of hydrogen（deuterium or tritium） storage materials.
基金the National Natural Science Foundation of China(51572193)the Natural Science Foundation of Tianjin(20JCZDJC00210).
文摘Hybrid improper ferroelectric Ca3Ti2O7 and Ca3Tii 9RuO.iO7 ceramics were successfully synthesized by conventional solid-state reaction method.Two strongest diffraction peaks located around 2θ=33°shifted towards the lower angle region with Ru substitution,reflecting structure variation.Grain growth and higher oxygen vacancy concentration after doping resulted in a reduction in the coercive field about 20 kV/cm.Optical bandgap estimated by UV-vis diffuse reflectance(DR)spectrum and X-ray photoelectron spectroscopy(XPS)valence band spectra showed a decreasing trend due to the existence of impurity energy level upon Ru doping,which was consistent with the results of first-principles calculations.The origin of the unexpected induced magnetic moments in Ru-dope Ca3Ti2O7 is also discussed.
基金Acknowledgements This work was supported in part by the National Basic Research Program of China （No. 2012CB315705）, the National Natural Science Foundation of China （Grant Nos. 61422108 and 61527820）, Fundamental Research Funds for the Central Universities （Nos. NP2015404, NE2012002） and a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘GaAs-based polarization modulators （PolMs） exhibit the unique characteristic of simultaneous intensity and complementary phase modulation owing to the linear electro-optic （LEO） effect determined by crystallographic orientations of the device. In this paper, we reviewed the principle of operation, the design and fabrication flows of a GaAs-based PolM. Analytical models are established, from which the features of a PolM are derived and discussed in detail. The recent advances in PolM-based multifunctional systems, in particular the PolM-based optoelectronic oscillator （OEO） are demonstrated with an emphasis on the remarkable development of applications for frequency conversion, tunable microwave photonic filter （MPF）, optical frequency comb （OFC）, arbitrary waveform generation （AWG） and beamforming. Challenges in practical implementation of the PolM-based systems and their promising future are discussed as well.
