We theoretically investigate the electricity storage/generation in a reversible solid oxide cell stack. The system heat is for the first time tentatively stored in a phase-change metal when the stack is operated to ge...We theoretically investigate the electricity storage/generation in a reversible solid oxide cell stack. The system heat is for the first time tentatively stored in a phase-change metal when the stack is operated to generate electricity in a fuel cell mode and then reused to store electricity in an electrolysis mode. The state of charge （H2 frication in cathode） effectively enhances the open circuit voltages （OCVs） while the system gas pressure in electrodes also increases the OCVs. On the other hand, a higher system pressure facilitates the species diffusion in electrodes that therefore accordingly improve electrode polarizations. With the aid of recycled system heat, the roundtrip efficiency reaches as high as 92% for the repeated electricity storage and generation.展开更多
The microstructure, dielectric properties and chemical state of Ti element on BaTi_4O_9 (f)/(0.64 BaTi_4O_9-0.36BaPr_2Ti_4O_(12)) composites sample surface were characterized by X-ray diffraction (XRD), Transmission e...The microstructure, dielectric properties and chemical state of Ti element on BaTi_4O_9 (f)/(0.64 BaTi_4O_9-0.36BaPr_2Ti_4O_(12)) composites sample surface were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), LCR meter method and X-ray photoelectron spectroscopy (XPS). The results show that the system is composed of BaTi_4O_9 and BaPr_2Ti_4O_(12) two phases. Pr ions are distributed in the BaWi_4O_9 grains and the segregation of Pr ions was observed on the grain boundaries of BaTi_4O_9/BaTi_4O_9. The content of Ti^(3+) and Ti^(2+) decrease in the BPT system composites due to the addition of BaTi_4O_9 fibers, which improved the dielectric properties of the system. BPT10 sample with 10% BaTi_4O_9 fibers, has the best dielectric properties in the system, its ε_r = 64, tan δ= 1×10^(-4)(at 1 MHz) , and it may be a potential candidate for microwave dielectric ceramics.展开更多
The surface and interface electronic states of tris (8 hydroxyquinoline) aluminum (Alq 3)/indium tin oxide (ITO) were measured and analyzed by X ray photoelectron spectroscopy (XPS). The results indicated that, in Alq...The surface and interface electronic states of tris (8 hydroxyquinoline) aluminum (Alq 3)/indium tin oxide (ITO) were measured and analyzed by X ray photoelectron spectroscopy (XPS). The results indicated that, in Alq 3 molecule, the binding energy ( E b) of Al atoms is 70.7 eV and 75.1 eV, corresponding to Al(O) and Al(Ⅲ), respectively; The binding energy of C is 285.8 eV, 286.3 eV, and 286.8 eV, corresponding to C of C-C group, C-O, and C-N bond, respectively. N is the main peak locating at 401.0 eV, corresponding to N atom of C-N=C. O atoms mainly bond to H atom, with the binding energy of 533.2 eV. As the sputtering time of Ar + ion beam increases, Al 2p , C 1s , N 1s , O 1s , In 3d 5/2 and Sn 3d 5/2 peaks slightly shift towards lower binding energy, and Al 2p , C 1s and N 1s peaks get weaker, which contributes to diffusing the oxygen, indium and tin in ITO into Alq 3 layer.展开更多
In this paper, online security warning and risk assessment of power grid are proposed, based on data from EMS （Energy Management System）, combined with information of real-time operation state, component status and ...In this paper, online security warning and risk assessment of power grid are proposed, based on data from EMS （Energy Management System）, combined with information of real-time operation state, component status and external operating environment. It combines the two factors, contingency likelihood and severity, that determine system reliability, into risk indices on different loads and operation modes, which provide precise evaluation of the power grid＇s security performance. According to these indices, it can know the vulnerable area of the system and whether the normal operating mode or repair mode is over-limited or not, and provide decision-making support for dispatchers. Common cause outages and equipment-aging are considered in terms of the establishment of outage model. Multiple risk indices are defined in order to reflect the risk level of the power grid more comprehensively.展开更多
Stretchable color-changing fibers are urgently demanded for smart textiles/clothing due to their perfect implantability,permeability of vapor and heat,and flexibility/stretchability.Herein,stretchable electrothermochr...Stretchable color-changing fibers are urgently demanded for smart textiles/clothing due to their perfect implantability,permeability of vapor and heat,and flexibility/stretchability.Herein,stretchable electrothermochromic fibers were fabricated with unconventional stretchable conductive fibers as core layers and thermochromic coatings as shell layers.In the stretchable conductive fibers,hierarchical porous structures with percolative one-dimensional(1 D)conductive networks were constructed through phase inversion of carbon nanotube/polyurethane(CNT/PU)solutions.With the deposition of silver nanoparticles(AgN Ps)on the surface of micro-pores,electrically conductive dual-pathways consisting of0 D AgN Ps and 1 D CNTs were formed to significantly enhance the electric conductivity and thus improve the electrothermal performance of the fibers.More importantly,because of the connective CNTs and AgN Ps,such dual-pathways ensured the electron transport under the stretching state,preventing the sharp decay of conductivity and electrothermal performance.Through the continuous wet-spinning method,the stretchable conductive fibers can be easily obtained with the length up to several meters.At last,stretchable electrothermochromic fibers were prepared with two color-changing modes and implanted into textile perfectly,advancing their applications in wearable display and military adaptive camouflage of smart clothing.展开更多
Cr_2Ge_2Te_6is an intrinsic ferromagnetic semiconductor with van der Waals type layered structure,thus represents a promising material for novel electronic and spintronic devices.Here we combine scanning tunneling mic...Cr_2Ge_2Te_6is an intrinsic ferromagnetic semiconductor with van der Waals type layered structure,thus represents a promising material for novel electronic and spintronic devices.Here we combine scanning tunneling microscopy and first-principles calculations to investigate the electronic structure of Cr_2Ge_2Te_6.Tunneling spectroscopy reveals a surprising large energy level shift and change of energy gap size across the ferromagnetic to paramagnetic phase transition,as well as a peculiar double-peak electronic state on the Cr-site defect.These features can be quantitatively explained by density functional theory calculations,which uncover a close relationship between the electronic structure and magnetic order.These findings shed important new lights on the microscopic electronic structure and origin of magnetic order in Cr_2Ge_2Te_6.展开更多
A transfer-reaction experiment of ~9Be(~9Be,^(10)Be)~8Be was performed at a beam energy of 45 Me V.Excited states in ^(10)Be up to 18.80 Me V are produced using missing mass and invariant mass methods.Most of the obse...A transfer-reaction experiment of ~9Be(~9Be,^(10)Be)~8Be was performed at a beam energy of 45 Me V.Excited states in ^(10)Be up to 18.80 Me V are produced using missing mass and invariant mass methods.Most of the observed high-lying resonant states,reconstructed from theα+~6He and t+~7Li decay channels,agree with the previously reported results.In addition,two new resonances at 15.6 and 18.8 Me V are identified from the present measurement.The 18.55 Me V state is found to decay into both the t + ~7Lig:s: and t + ~7Li?(0.478 MeV) channels, with a relative branching ratio of 0:93 ± 0:33. Further theoretical investigations are encouraged to interpret this new information on cluster structure in neutron-rich light nuclei.展开更多
The energy-saving analytics of coal-fired power units in China is confronting new challenges especially with even more complicated system structure, higher working medium parameters, time-dependent varying operation c...The energy-saving analytics of coal-fired power units in China is confronting new challenges especially with even more complicated system structure, higher working medium parameters, time-dependent varying operation conditions and boundaries such as load rate, coal quality, ambient temperature and humidity. Compared with the traditional optimization of specific operating parameters, the idea of the energy-consumption benchmark state was proposed. The equivalent specific fuel consumption(ESFC) analytics was introduced to determine the energy-consumption benchmark state, with the minimum ESFC under varying operation boundaries. Models for the energy-consumption benchmark state were established, and the endogenous additional specific consumption(ASFC) and exogenous ASFC were calculated. By comparing the benchmark state with the actual state, the energy-saving tempospacial effect can be quantified. As a case study, the energy consumption model of a 1000 MW ultra supercritical power unit was built. The results show that system energy consumption can be mainly reduced by improving the performance of turbine subsystem. This nearly doubles the resultant by improving the boiler system. The energy saving effect of each component increases with the decrease of load and has a greater influence under a lower load rate. The heat and mass transfer process takes priority in energy saving diagnosis of related components and processes. This makes great reference for the design and operation optimization of coal-fired power units.展开更多
文摘We theoretically investigate the electricity storage/generation in a reversible solid oxide cell stack. The system heat is for the first time tentatively stored in a phase-change metal when the stack is operated to generate electricity in a fuel cell mode and then reused to store electricity in an electrolysis mode. The state of charge （H2 frication in cathode） effectively enhances the open circuit voltages （OCVs） while the system gas pressure in electrodes also increases the OCVs. On the other hand, a higher system pressure facilitates the species diffusion in electrodes that therefore accordingly improve electrode polarizations. With the aid of recycled system heat, the roundtrip efficiency reaches as high as 92% for the repeated electricity storage and generation.
文摘The microstructure, dielectric properties and chemical state of Ti element on BaTi_4O_9 (f)/(0.64 BaTi_4O_9-0.36BaPr_2Ti_4O_(12)) composites sample surface were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), LCR meter method and X-ray photoelectron spectroscopy (XPS). The results show that the system is composed of BaTi_4O_9 and BaPr_2Ti_4O_(12) two phases. Pr ions are distributed in the BaWi_4O_9 grains and the segregation of Pr ions was observed on the grain boundaries of BaTi_4O_9/BaTi_4O_9. The content of Ti^(3+) and Ti^(2+) decrease in the BPT system composites due to the addition of BaTi_4O_9 fibers, which improved the dielectric properties of the system. BPT10 sample with 10% BaTi_4O_9 fibers, has the best dielectric properties in the system, its ε_r = 64, tan δ= 1×10^(-4)(at 1 MHz) , and it may be a potential candidate for microwave dielectric ceramics.
文摘The surface and interface electronic states of tris (8 hydroxyquinoline) aluminum (Alq 3)/indium tin oxide (ITO) were measured and analyzed by X ray photoelectron spectroscopy (XPS). The results indicated that, in Alq 3 molecule, the binding energy ( E b) of Al atoms is 70.7 eV and 75.1 eV, corresponding to Al(O) and Al(Ⅲ), respectively; The binding energy of C is 285.8 eV, 286.3 eV, and 286.8 eV, corresponding to C of C-C group, C-O, and C-N bond, respectively. N is the main peak locating at 401.0 eV, corresponding to N atom of C-N=C. O atoms mainly bond to H atom, with the binding energy of 533.2 eV. As the sputtering time of Ar + ion beam increases, Al 2p , C 1s , N 1s , O 1s , In 3d 5/2 and Sn 3d 5/2 peaks slightly shift towards lower binding energy, and Al 2p , C 1s and N 1s peaks get weaker, which contributes to diffusing the oxygen, indium and tin in ITO into Alq 3 layer.
文摘In this paper, online security warning and risk assessment of power grid are proposed, based on data from EMS （Energy Management System）, combined with information of real-time operation state, component status and external operating environment. It combines the two factors, contingency likelihood and severity, that determine system reliability, into risk indices on different loads and operation modes, which provide precise evaluation of the power grid＇s security performance. According to these indices, it can know the vulnerable area of the system and whether the normal operating mode or repair mode is over-limited or not, and provide decision-making support for dispatchers. Common cause outages and equipment-aging are considered in terms of the establishment of outage model. Multiple risk indices are defined in order to reflect the risk level of the power grid more comprehensively.
基金supported by the National Natural Science Foundation of China(51672043)Donghua University Distinguished Young Professor Program(LZB2019002)+1 种基金Young Elite Scientists Sponsorship Program by China Association for Science and Technology(2017QNRC001)the Fundamental Research Funds for the Central Universities(CUSF-DH-D-2018006)。
文摘Stretchable color-changing fibers are urgently demanded for smart textiles/clothing due to their perfect implantability,permeability of vapor and heat,and flexibility/stretchability.Herein,stretchable electrothermochromic fibers were fabricated with unconventional stretchable conductive fibers as core layers and thermochromic coatings as shell layers.In the stretchable conductive fibers,hierarchical porous structures with percolative one-dimensional(1 D)conductive networks were constructed through phase inversion of carbon nanotube/polyurethane(CNT/PU)solutions.With the deposition of silver nanoparticles(AgN Ps)on the surface of micro-pores,electrically conductive dual-pathways consisting of0 D AgN Ps and 1 D CNTs were formed to significantly enhance the electric conductivity and thus improve the electrothermal performance of the fibers.More importantly,because of the connective CNTs and AgN Ps,such dual-pathways ensured the electron transport under the stretching state,preventing the sharp decay of conductivity and electrothermal performance.Through the continuous wet-spinning method,the stretchable conductive fibers can be easily obtained with the length up to several meters.At last,stretchable electrothermochromic fibers were prepared with two color-changing modes and implanted into textile perfectly,advancing their applications in wearable display and military adaptive camouflage of smart clothing.
基金supported by the Basic Science Center Project of NSFC(51788104)the MOST of China(2015CB921000)+6 种基金the support from Tsinghua University Initiative Scientific Research Program and NSFC(11774196)S.H.Z.is supported by the National Postdoctoral Program for Innovative Talents of China(BX201600091)the China Postdoctoral Science Foundation(2017M610858)the support of the National Key Research and Development Program(2016YFA0300404)NSFC Grant(11674326)the Joint Funds of NSFC and the Chinese Academy of Sciences’Large-Scale Scientific Facility(U1432139)supported in part by the Beijing Advanced Innovation Center for Future Chip(ICFC)
文摘Cr_2Ge_2Te_6is an intrinsic ferromagnetic semiconductor with van der Waals type layered structure,thus represents a promising material for novel electronic and spintronic devices.Here we combine scanning tunneling microscopy and first-principles calculations to investigate the electronic structure of Cr_2Ge_2Te_6.Tunneling spectroscopy reveals a surprising large energy level shift and change of energy gap size across the ferromagnetic to paramagnetic phase transition,as well as a peculiar double-peak electronic state on the Cr-site defect.These features can be quantitatively explained by density functional theory calculations,which uncover a close relationship between the electronic structure and magnetic order.These findings shed important new lights on the microscopic electronic structure and origin of magnetic order in Cr_2Ge_2Te_6.
基金supported by the National Basic Research Program of China (Grant No. 2013CB834402)the National Natural Science Foundation of China (Grant Nos. 11535004, 11275011, 11375017, and 11275001)
文摘A transfer-reaction experiment of ~9Be(~9Be,^(10)Be)~8Be was performed at a beam energy of 45 Me V.Excited states in ^(10)Be up to 18.80 Me V are produced using missing mass and invariant mass methods.Most of the observed high-lying resonant states,reconstructed from theα+~6He and t+~7Li decay channels,agree with the previously reported results.In addition,two new resonances at 15.6 and 18.8 Me V are identified from the present measurement.The 18.55 Me V state is found to decay into both the t + ~7Lig:s: and t + ~7Li?(0.478 MeV) channels, with a relative branching ratio of 0:93 ± 0:33. Further theoretical investigations are encouraged to interpret this new information on cluster structure in neutron-rich light nuclei.
文摘The energy-saving analytics of coal-fired power units in China is confronting new challenges especially with even more complicated system structure, higher working medium parameters, time-dependent varying operation conditions and boundaries such as load rate, coal quality, ambient temperature and humidity. Compared with the traditional optimization of specific operating parameters, the idea of the energy-consumption benchmark state was proposed. The equivalent specific fuel consumption(ESFC) analytics was introduced to determine the energy-consumption benchmark state, with the minimum ESFC under varying operation boundaries. Models for the energy-consumption benchmark state were established, and the endogenous additional specific consumption(ASFC) and exogenous ASFC were calculated. By comparing the benchmark state with the actual state, the energy-saving tempospacial effect can be quantified. As a case study, the energy consumption model of a 1000 MW ultra supercritical power unit was built. The results show that system energy consumption can be mainly reduced by improving the performance of turbine subsystem. This nearly doubles the resultant by improving the boiler system. The energy saving effect of each component increases with the decrease of load and has a greater influence under a lower load rate. The heat and mass transfer process takes priority in energy saving diagnosis of related components and processes. This makes great reference for the design and operation optimization of coal-fired power units.
