为了提高光伏电池转换效率、降低能量损失,有必要研究最大功率点跟踪(maximum power point tracking,MPPT)方法。针对传统扰动观察法(perturbation observation method,P&O)存在无法兼顾跟踪速度与稳态精度、在光照度发生较大变化...为了提高光伏电池转换效率、降低能量损失,有必要研究最大功率点跟踪(maximum power point tracking,MPPT)方法。针对传统扰动观察法(perturbation observation method,P&O)存在无法兼顾跟踪速度与稳态精度、在光照度发生较大变化时会产生误判现象的问题,文中提出一种能适应环境变化的变步长P&O控制策略。首先,利用光伏电池刚启动时类似恒流源的特性获取当前光照度下的短路电流,通过固定电流法推导出最大功率点(maximum power point,MPP)的参考电压;其次,当光照度突变时,提出功率修正方法,并给出突变时的变步长调整策略;最后,设计基于线性扩张状态观测器(linear extended state observer,LESO)的分数阶比例积分微分(fractional order proportion integration differentiation,FOPID)控制器,可以对算法输出的参考电压进一步进行跟踪补偿。仿真结果表明,所提控制策略可以提高稳态精度和跟踪速度,有效提高光伏电池的输出功率。展开更多
It has been an established practice to estimate the Θ-temperature of a polymer solution from thedisappearance of the interchain interactions (A_2 = 0) Recently, in studies of the temperature dependence ofthe chain co...It has been an established practice to estimate the Θ-temperature of a polymer solution from thedisappearance of the interchain interactions (A_2 = 0) Recently, in studies of the temperature dependence ofthe chain conformation in solution, we found that the change of the chain conformation clearly underwentthree different stages which could be viewed as the 'gas'. 'liquid' and 'solid' states in terms of the freedomof the 'blobs' on the chain. The transition temperature between the first and second stages corresponds nicelyto the Θ-temperature determined by the conventional method. It reveals, for the first time, that the Θ-temperature can be deduced from the conformation change of a single polymer chain in solution, which isimportant not only in conception, but also in practice.展开更多
Using the secondary spinel standard, the authors have precisely measured theFe^(3+)/SIGMA Fe values of spinels in mantle xenoliths from Cenozoic basalts in eastern China, andestimated the oxygen fugacities recorded by...Using the secondary spinel standard, the authors have precisely measured theFe^(3+)/SIGMA Fe values of spinels in mantle xenoliths from Cenozoic basalts in eastern China, andestimated the oxygen fugacities recorded by 63 mantle xenoliths through olivine-orthopyroxene-spineloxygen barometry. The results indicate that the oxygen fugacities of the lithospheric mantle ineastern China are higher in the south than in the north. Among them, the oxygen fugacity of theNorth China craton lithospheric mantle is the lowest, similar to that of the oceanic mantle, whilethat of Northeast and South China are the same as that of the global continental mantle. Thevariations of mantle redox state in eastern China are mainly controlled by the C-O-H fluids derivedfrom the asthenospheric mantle. According to the mantle oxidation state, it can be concluded thatthe C-O-H fluids in the lithospheric mantle of eastern China consist mainly of CO_2 and minor H_2O,but CH_4-rich fluids should come from the asthenosphere where the oxidation state is lower.展开更多
We conducted measurement and calculation to resolve the long-standing large discrepancy in the metastable state lifetime for the ^(88)Sr atom between theoretical and experimental results. The present lifetime τ = 830...We conducted measurement and calculation to resolve the long-standing large discrepancy in the metastable state lifetime for the ^(88)Sr atom between theoretical and experimental results. The present lifetime τ = 830_(-240)^(+600)s,measured using the magneto-optical trap as a photon amplifier to detect the weak decay events, is approximately60% larger than the previous experimental value τ = 520_(-140)^(+310)s. By considering the electron correlation effects in the framework of the multiconfiguration Dirac–Hartree–Fock theory, we obtained a theoretical lifetime of 1079(54) s, which lies in the range of measurements with error bars. Furthermore, we considered the higher-order electron correlation and Breit interaction to control the uncertainty of the theoretical calculation. The significant improvement in the agreement between calculations and measurements is attributed to the updated blackbody radiation-induced decay rate.展开更多
olid state reactions of o-aminobenzoic acid (HOAB) with Cu (OAc)_2·H_2O,Cu(HCOO)_2 · 4H_2O, anhydrous Cu (OAc)_2 and Cu (HCOO)_2 at room or close toroom temperature have been investigated. The product Cu(OAB...olid state reactions of o-aminobenzoic acid (HOAB) with Cu (OAc)_2·H_2O,Cu(HCOO)_2 · 4H_2O, anhydrous Cu (OAc)_2 and Cu (HCOO)_2 at room or close toroom temperature have been investigated. The product Cu(OAB)_2 with a high yieldwas synthesized very conveniently compared witb the solution phase method. Thekinetic behavior was studied by means of the isothermal electrical conductivity mea-surement. The reactivity was found to decrease in the order : Cu(OAc)_2· H_2O>Cu(OAc)_2>Cu (HCOO)_2 ·4H_2O>Cu (HCOO)_2, which was attributable to the crystalstructures of the copper salts.展开更多
We study the electronic and magnetic properties of an oxygen-deficient perovskite Ca2Mn2O5 based on the first principle calculations. The calculations show that the ground state of Ca2Mn2O5 is a D-type anti-ferromagne...We study the electronic and magnetic properties of an oxygen-deficient perovskite Ca2Mn2O5 based on the first principle calculations. The calculations show that the ground state of Ca2Mn2O5 is a D-type anti-ferromagnetic structure with the anti-ferromagnetic spin coupling along the c-direction. The corresponding electronic structure of the D-type state is investigated, and the results display that Ca2Mn2O5 is an insulator with an indirect energy gap of -2.08eV. By the partiM density-of-state analysis, the valence band maximum is mainly contributed to by the 0-213 orbitMs and the conduction band minimum is contributed to by the 0-213 and Mn-3d orbitals. Due to the Coulomb repulsion interaction between electrons, the density of state of Mn-3d is pulled to -6--4.5eV.展开更多
A self-consistent-field—configuration interaction(SCF-CI)procedure of studying highly excited vibrational states of bent triatomic molecules is suggested and its application to O_3 is investigated.
We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_（8＋δ）（Bi2212） superconductor in the superconducting and pseudogap states by super-high resolution laser-based an...We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_（8＋δ）（Bi2212） superconductor in the superconducting and pseudogap states by super-high resolution laser-based angleresolved photoemission spectroscopy. The precise determination of the superconducting gap for the nearly optimally doped Bi2212（T_c= 91 K） at low temperature indicates that the momentum-dependence of the superconducting gap deviates from the standard d-wave form（cos（2Φ））. It can be alternatively fitted by including a high-order term（cos（6Φ）） in which the next nearest-neighbor interaction is considered. We find that the band structure near the antinodal region smoothly evolves across the pseudogap temperature without a signature of band reorganization which is distinct from that found in Bi_2Sr_2CuO_（6＋δ） superconductors. This indicates that the band reorganization across the pseudogap temperature is not a universal behavior in cuprate superconductors.These results provide new insights in understanding the nature of the superconducting gap and pseudogap in high-temperature cuprate superconductors.展开更多
The Fe(OH) 3 precursor was prepared by solid-state reaction with Fe(NO 3 ) 3 ·9H 2 O,NaOH and dispersed poly-ethylene glycol at low heating temperature(25℃).Synthesis of iron oxide(γ-Fe 2 O 3 )nanoparticle was ...The Fe(OH) 3 precursor was prepared by solid-state reaction with Fe(NO 3 ) 3 ·9H 2 O,NaOH and dispersed poly-ethylene glycol at low heating temperature(25℃).Synthesis of iron oxide(γ-Fe 2 O 3 )nanoparticle was achieved by thermal decomposition of Fe(OH) 3 ·xH 2 O precursor.The nanoparticle was characterized by TG-DTA,X-ray diffra-ction,TEM etc.The results showed that the nanoparticle was composed ofγ-Fe 2 O 3 and was a better absorber for electromagnetic wave within the low frequency band.展开更多
文摘为了提高光伏电池转换效率、降低能量损失,有必要研究最大功率点跟踪(maximum power point tracking,MPPT)方法。针对传统扰动观察法(perturbation observation method,P&O)存在无法兼顾跟踪速度与稳态精度、在光照度发生较大变化时会产生误判现象的问题,文中提出一种能适应环境变化的变步长P&O控制策略。首先,利用光伏电池刚启动时类似恒流源的特性获取当前光照度下的短路电流,通过固定电流法推导出最大功率点(maximum power point,MPP)的参考电压;其次,当光照度突变时,提出功率修正方法,并给出突变时的变步长调整策略;最后,设计基于线性扩张状态观测器(linear extended state observer,LESO)的分数阶比例积分微分(fractional order proportion integration differentiation,FOPID)控制器,可以对算法输出的参考电压进一步进行跟踪补偿。仿真结果表明,所提控制策略可以提高稳态精度和跟踪速度,有效提高光伏电池的输出功率。
基金The support of the National Distinguished Young Investigator Fund(1996,29625410)is gratefully acknowledged
文摘It has been an established practice to estimate the Θ-temperature of a polymer solution from thedisappearance of the interchain interactions (A_2 = 0) Recently, in studies of the temperature dependence ofthe chain conformation in solution, we found that the change of the chain conformation clearly underwentthree different stages which could be viewed as the 'gas'. 'liquid' and 'solid' states in terms of the freedomof the 'blobs' on the chain. The transition temperature between the first and second stages corresponds nicelyto the Θ-temperature determined by the conventional method. It reveals, for the first time, that the Θ-temperature can be deduced from the conformation change of a single polymer chain in solution, which isimportant not only in conception, but also in practice.
基金the Nationa1 Natural Science Foundation(Grant No.49673185)the Ministry of Science and Technology of China(Grant No.95-Pre-39).
文摘Using the secondary spinel standard, the authors have precisely measured theFe^(3+)/SIGMA Fe values of spinels in mantle xenoliths from Cenozoic basalts in eastern China, andestimated the oxygen fugacities recorded by 63 mantle xenoliths through olivine-orthopyroxene-spineloxygen barometry. The results indicate that the oxygen fugacities of the lithospheric mantle ineastern China are higher in the south than in the north. Among them, the oxygen fugacity of theNorth China craton lithospheric mantle is the lowest, similar to that of the oceanic mantle, whilethat of Northeast and South China are the same as that of the global continental mantle. Thevariations of mantle redox state in eastern China are mainly controlled by the C-O-H fluids derivedfrom the asthenospheric mantle. According to the mantle oxidation state, it can be concluded thatthe C-O-H fluids in the lithospheric mantle of eastern China consist mainly of CO_2 and minor H_2O,but CH_4-rich fluids should come from the asthenosphere where the oxidation state is lower.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11874090, 91536106, 61127901, 11404025, and U1530142)the Strategic Priority Research Program of CAS (Grant No. XDB21030100)+1 种基金the Key Research Project of Frontier Science of CAS (Grant No. QYZDB-SSW-JSC004)the West Light Foundation of CAS (Grant No. XAB2018B17)。
文摘We conducted measurement and calculation to resolve the long-standing large discrepancy in the metastable state lifetime for the ^(88)Sr atom between theoretical and experimental results. The present lifetime τ = 830_(-240)^(+600)s,measured using the magneto-optical trap as a photon amplifier to detect the weak decay events, is approximately60% larger than the previous experimental value τ = 520_(-140)^(+310)s. By considering the electron correlation effects in the framework of the multiconfiguration Dirac–Hartree–Fock theory, we obtained a theoretical lifetime of 1079(54) s, which lies in the range of measurements with error bars. Furthermore, we considered the higher-order electron correlation and Breit interaction to control the uncertainty of the theoretical calculation. The significant improvement in the agreement between calculations and measurements is attributed to the updated blackbody radiation-induced decay rate.
文摘olid state reactions of o-aminobenzoic acid (HOAB) with Cu (OAc)_2·H_2O,Cu(HCOO)_2 · 4H_2O, anhydrous Cu (OAc)_2 and Cu (HCOO)_2 at room or close toroom temperature have been investigated. The product Cu(OAB)_2 with a high yieldwas synthesized very conveniently compared witb the solution phase method. Thekinetic behavior was studied by means of the isothermal electrical conductivity mea-surement. The reactivity was found to decrease in the order : Cu(OAc)_2· H_2O>Cu(OAc)_2>Cu (HCOO)_2 ·4H_2O>Cu (HCOO)_2, which was attributable to the crystalstructures of the copper salts.
基金Supported by the National Basic Research Program of China under Grant No 2014CB931703the National Natural Science Foundation of China under Grant Nos 11404172,51101088,and 51171082the Fundamental Research Funds for the Central Universities
文摘We study the electronic and magnetic properties of an oxygen-deficient perovskite Ca2Mn2O5 based on the first principle calculations. The calculations show that the ground state of Ca2Mn2O5 is a D-type anti-ferromagnetic structure with the anti-ferromagnetic spin coupling along the c-direction. The corresponding electronic structure of the D-type state is investigated, and the results display that Ca2Mn2O5 is an insulator with an indirect energy gap of -2.08eV. By the partiM density-of-state analysis, the valence band maximum is mainly contributed to by the 0-213 orbitMs and the conduction band minimum is contributed to by the 0-213 and Mn-3d orbitals. Due to the Coulomb repulsion interaction between electrons, the density of state of Mn-3d is pulled to -6--4.5eV.
文摘A self-consistent-field—configuration interaction(SCF-CI)procedure of studying highly excited vibrational states of bent triatomic molecules is suggested and its application to O_3 is investigated.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0300300the National Natural Science Foundation of China under Grant No 11334010+1 种基金the National Basic Research Program of China under Grant No2015CB921300the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant No XDB07020300
文摘We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_（8＋δ）（Bi2212） superconductor in the superconducting and pseudogap states by super-high resolution laser-based angleresolved photoemission spectroscopy. The precise determination of the superconducting gap for the nearly optimally doped Bi2212（T_c= 91 K） at low temperature indicates that the momentum-dependence of the superconducting gap deviates from the standard d-wave form（cos（2Φ））. It can be alternatively fitted by including a high-order term（cos（6Φ）） in which the next nearest-neighbor interaction is considered. We find that the band structure near the antinodal region smoothly evolves across the pseudogap temperature without a signature of band reorganization which is distinct from that found in Bi_2Sr_2CuO_（6＋δ） superconductors. This indicates that the band reorganization across the pseudogap temperature is not a universal behavior in cuprate superconductors.These results provide new insights in understanding the nature of the superconducting gap and pseudogap in high-temperature cuprate superconductors.
文摘The Fe(OH) 3 precursor was prepared by solid-state reaction with Fe(NO 3 ) 3 ·9H 2 O,NaOH and dispersed poly-ethylene glycol at low heating temperature(25℃).Synthesis of iron oxide(γ-Fe 2 O 3 )nanoparticle was achieved by thermal decomposition of Fe(OH) 3 ·xH 2 O precursor.The nanoparticle was characterized by TG-DTA,X-ray diffra-ction,TEM etc.The results showed that the nanoparticle was composed ofγ-Fe 2 O 3 and was a better absorber for electromagnetic wave within the low frequency band.
