In this paper, A fluid vector rudder flying-wing UAV is employed as the design object, so as to study the nonlinear design method and flight validation. For the maneuvering flight control, this paper presents a contro...In this paper, A fluid vector rudder flying-wing UAV is employed as the design object, so as to study the nonlinear design method and flight validation. For the maneuvering flight control, this paper presents a control structure. This control structure included the inner loop linearization decoupling methods to eliminate the known negative coupling and the outer loop backstepping methods for trajectory tracking control. The stability of the control structure has been proved in this paper. Compared with the traditional backstepping control method, this controller increases the inner loop decoupling structure and retains the aerodynamic damping term which makes the linearized system a weak nonlinear system.This structure can not only reduce the conservatism of the outer loop controller design, but also is convenient for engineering implementation. Simulation and flight validation results show that the proposed control scheme is effective.展开更多
The field shift and mass shift parameters of the 2s2p3,1P1→ 2s2 1S0 transitions in Be-like ions(70 ≤ Z≤ 92)are calculated using the multi-configuration Dirac–Hartree–Fock and the relativistic configuration intera...The field shift and mass shift parameters of the 2s2p3,1P1→ 2s2 1S0 transitions in Be-like ions(70 ≤ Z≤ 92)are calculated using the multi-configuration Dirac–Hartree–Fock and the relativistic configuration interaction methods with the inclusion of the Breit interaction and the leading QED corrections. We find that the mass shift parameters of these two transitions do not change monotonously along the isoelectronic sequence in the high-Z range due to the relativistic nuclear recoil effects. A minimum value exists for the specific mass shift parameters around Z= 80, especially for the 2s2p3,1P1→ 2s2 1S0 transition. In addition, the field shifts and mass shifts of these two transitions are estimated using an empirical formula, and their contributions are compared along the isoelectronic sequence.展开更多
Systematic calculations and assessments are performed for the magnetic dipole(M1)transition energies and rates between the ^(2)F^(o)_(5/2,7/2) levels in the ground configuration 4d104f along the Ag-like isoelectronic ...Systematic calculations and assessments are performed for the magnetic dipole(M1)transition energies and rates between the ^(2)F^(o)_(5/2,7/2) levels in the ground configuration 4d104f along the Ag-like isoelectronic sequence with 62≤Z≤94 based on the second-order many-body perturbation theory implemented in the Flexible Atomic Code.The electron correlations,Breit interaction and quantum electrodynamics effects are taken into account in the present calculations.The accuracy and reliability of our results are evaluated through comprehensive comparisons with available measurements and other theoretical results.For transition energies,our results are in good agreement with the recent experimental data obtained from the electron beam ion traps within 0.18%.The maximum discrepancy between our results and those obtained with the large-scale multiconfiguration Dirac–Hartee–Fock calculations by Grumer et al.[Phys.Rev.A 89062501(2014)]is less than 0.13%along the isoelectronic sequence.Furthermore,the corresponding M1 transition rates are also reported.The present results can be used as the benchmark and useful for spectra simulation and diagnostics of astrophysical and fusion plasmas.展开更多
We present a method that the atomic transition frequency measurement relies on the accurate wavemeter,optical frequency comb and stable Fabry–Pérot cavity to precise determination of stable even isotope shift on...We present a method that the atomic transition frequency measurement relies on the accurate wavemeter,optical frequency comb and stable Fabry–Pérot cavity to precise determination of stable even isotope shift on single Yb+ion(A=168,170,172,174,176).The 6s^(2)S_(1/2)←→6p^(2)P_(1/2)and 5d^(2)D_(3/2)←→6s^(3)[3/2]_(1/2)resonance dipole transition frequencies are preliminarily measured by using a wavemeter which is calibrated by the 729 nm clock laser of ^(40)Ca^(+).Meanwhile,those frequencies are double checked by using optical frequency comb for correction of deviation.Ultimately,by changing frequency locking points at an ultralow expansion cavity more slightly and monitoring the corresponding atomic fluorescence changing with 17%,we finally improve the resonant frequency uncertainty to±6 MHz,which is one order of improvement in precision higher than previously published measurements on the same transitions.A King-plot analysis with sensitivity to coupling between electrons and neutrons is carried out to determine the field and mass shift constants.Our measurement combined with existing or future isotope shift measurements can be used to determine basic properties of atomic nuclei,and to test new forces beyond the Standard Model.展开更多
Layered rare-earth hydroxides(LREHs) draw wide research interest because of their peculiar crystal structure,rich interlayer chemistry and abundant functionality of the RE element,but are limited to the two categories...Layered rare-earth hydroxides(LREHs) draw wide research interest because of their peculiar crystal structure,rich interlayer chemistry and abundant functionality of the RE element,but are limited to the two categories of RE_(2)(OH)_(5)A·nH_(2)O(A:typical of Cl^(-)or NO_(3)^(-)) and RE_(2)(OH)_(4)SO_(4)·nH_(2)O.On the other hand,rare-earth oxysulfates(RE_(2)O_(2)SO_(4)) have attracted attention due to their properties of large-capacity oxygen storage,low-temperature magnetism and luminescence,but their preparation procedure mostly involves toxic SO_(x) gases and/or complicated procedures.In this work,RE_(2)(OH)_(2)CO_(3)SO_(4)·nH_(2)O as a new family of LREHs(RE=Gd-Lu lanthanides and Y) were produced via hydrothermal reaction,from which phase-pure RE_(2)O_(2)SO_(4) was derived via subsequent annealing at 800℃ in air without the involvement of SO_(x),The compounds were thoroughly characterized to reveal the intrinsic influence of lanthanide contraction(RE^(3+) radius) on crystal structure,thermal behavior(dehydroxylation/decarbonation/desulfurization),vibrational property and crystallite morphology.Through analyzing the photoluminescence of Eu^(3+) and Sm^(3+)in the Gd_(2)O_(2)SO_(4) typical host it is found that the 617 nm(Eu^(3+),λ_(ex)=275 nm) and 608 nm(Sm^(3+),λ_(ex)=407 nm) main emissions can retain as high as ^(7)9.6% and 85.5%of their room-temperature intensities at 423 K,with activation energies of ~0.19 and 0.21 eV for thermal quenching,respectively.Application also indicates that both the phosphors have the potential for optical temperature sensing via the fluorescence intensity ratio(FIR) technology,whose maximum relative sensitivity reaches ^(2).70%/K for Eu^(3+)and 1.73%/K for Sm^(3+) at 298 K.展开更多
Phosphor-converted near-infrared light-emitting diodes(NIR pc-LEDs) are finding applications in various fields including food quality analysis,biomedical imaging,night vision,and biomedicine.The crucial factor in the ...Phosphor-converted near-infrared light-emitting diodes(NIR pc-LEDs) are finding applications in various fields including food quality analysis,biomedical imaging,night vision,and biomedicine.The crucial factor in the development of NIR pc-LEDs devices lies in the advancement of high-performance broadband NIR phosphors,In this work,novel Cr^(3+)-activated silicate phosphors NaRESi_(3)O_(9)(RE=Y,Lu,Sc) are reported.This silicate has a special 3D network structure in which RE has four different sites,forming four octahedrons and providing suitable occupation sites for Cr^(3+).The phosphors demonstrate a wide emission spectrum ranging from 750 to 1450 nm when excited by light at 468 nm.The full width at half maximum(FWHM),which benefits from the presence of Cr^(3+)ions occupying multiple sites,is measured to be 203 nm.Notably,the strongest emission peak is observed at a longer wavelength of 984 nm compared to most other systems activated by Cr^(3+).The Na_(3)ScSi_(3)O_(9) lattice provides a weak crystal field(Dq/B=1.97) and weak phonon-photon coupling for Cr^(3+),and the integrated emission intensity of Na_(3)ScSi_(3)O_(9):0,03Cr^(3+)is 4.66 times stronger than that of Na_(3)YSi_(3)O_(9):0.03Cr^(3+).展开更多
A chemical co-precipitation strategy was employed to synthesize a series of(Gd_(0.95−x)Lu_(x)Eu_(0.05))_(3)Al_(5)O_(12)(x=0.1−0.95)powder phosphors,followed by vacuum sintering to achieve transparent garnet ceramic ph...A chemical co-precipitation strategy was employed to synthesize a series of(Gd_(0.95−x)Lu_(x)Eu_(0.05))_(3)Al_(5)O_(12)(x=0.1−0.95)powder phosphors,followed by vacuum sintering to achieve transparent garnet ceramic phosphors.The density functional theory indicated Lu_(3)Al_(5)O_(12) was formed in priority compared with Gd_(3)Al_(5)O_(12) during solid-phase reaction.Upon high-temperature sintering,the Lu^(3+)substitution for Gd^(3+)suppressed point mass diffusion leading to a smaller grain size.The in-line transmittances of bulk specimens with x=0.1,0.3,0.5,0.7,and 0.95 nm were~83.5%,80.1%,68.8%,73.7%,and 82.2%at 710 nm(Eu^(3+)emission center),respectively,among which the sample of x=0.1 exhibited the optical grade with near-zero optical loss in agreement with the defect-free single crystal(~100%of the theoretical transmittance).The resulting particle and ceramic materials both presented characteristic Eu^(3+)emission arising from 5D0→7FJ(J=1−4)transition,where the dominant far-red emission at~710 nm arising from ^(5)D_(0)→^(7)F_(4) transition overlapped with the absorption of phytochrome(PFR).The photoluminescence excitation and photoluminescence intensities of(Gd_(0.95−x)Lu_(x)Eu_(0.05))_(3)Al_(5)O_(12) powders and ceramics generally increased at a higher Gd^(3+)/Lu^(3+)ratio.Lu^(3+)dopants delayed the fluorescence lifetime while the bulk samples had shorter lifetime compared to the particle counterparts.The transparent(Gd_(0.85)Lu_(0.1)Eu_(0.05))3Al_(5)O_(12) ceramic phosphor exhibited good thermal stability with a high thermal quenching temperature above 533 K.The designed ceramic phosphor-converted light-emitting diode had a saturation injection current of 435 mA and a current-dependent color rendering index.More importantly,our report marked the developmental stage of transparent ceramic materials towards zero optical loss.展开更多
Understanding the coking behaviors has been considered to be really essential for developing better vacuum residue processing technologies.A battery of thermal cracking tests of typical vacuum residue at 410℃ with va...Understanding the coking behaviors has been considered to be really essential for developing better vacuum residue processing technologies.A battery of thermal cracking tests of typical vacuum residue at 410℃ with various reaction time were performed to evaluate the coke formation process.The total yields of ideal components including naphtha,atmospheric gas oil(AGO)and vacuum gas oil(VGO)of thermal cracking reactions increased from 10.89%to 40.81%,and the conversion ratios increased from8.05%to 43.33%with increasing the reaction time from 10 to 70 min.The asphaltene content increased from 12.14%to a maximum of 22.39%and then decreased,and this maximum of asphaltene content occurred at the end of the coking induction period.The asphaltenes during the coking induction period,at the end and after coking induction period of those tested thermal cracking reactions were characterized to disclose the structure changing rules for coke formation process,and the coke formation pathways were discussed to reveal the coke formation process at molecular level.展开更多
文摘In this paper, A fluid vector rudder flying-wing UAV is employed as the design object, so as to study the nonlinear design method and flight validation. For the maneuvering flight control, this paper presents a control structure. This control structure included the inner loop linearization decoupling methods to eliminate the known negative coupling and the outer loop backstepping methods for trajectory tracking control. The stability of the control structure has been proved in this paper. Compared with the traditional backstepping control method, this controller increases the inner loop decoupling structure and retains the aerodynamic damping term which makes the linearized system a weak nonlinear system.This structure can not only reduce the conservatism of the outer loop controller design, but also is convenient for engineering implementation. Simulation and flight validation results show that the proposed control scheme is effective.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11874090,11604385,91536106 and 11204374the Research Project of National University of Defense Technology under Grant No ZK17-03-11
文摘The field shift and mass shift parameters of the 2s2p3,1P1→ 2s2 1S0 transitions in Be-like ions(70 ≤ Z≤ 92)are calculated using the multi-configuration Dirac–Hartree–Fock and the relativistic configuration interaction methods with the inclusion of the Breit interaction and the leading QED corrections. We find that the mass shift parameters of these two transitions do not change monotonously along the isoelectronic sequence in the high-Z range due to the relativistic nuclear recoil effects. A minimum value exists for the specific mass shift parameters around Z= 80, especially for the 2s2p3,1P1→ 2s2 1S0 transition. In addition, the field shifts and mass shifts of these two transitions are estimated using an empirical formula, and their contributions are compared along the isoelectronic sequence.
基金the National Natural Science Foundation of China(Grant Nos.11874090,11934004,11404180,11604052,and 11774037)the National Key Research and Development Program of China(Grant No.2017YFA0402300).
文摘Systematic calculations and assessments are performed for the magnetic dipole(M1)transition energies and rates between the ^(2)F^(o)_(5/2,7/2) levels in the ground configuration 4d104f along the Ag-like isoelectronic sequence with 62≤Z≤94 based on the second-order many-body perturbation theory implemented in the Flexible Atomic Code.The electron correlations,Breit interaction and quantum electrodynamics effects are taken into account in the present calculations.The accuracy and reliability of our results are evaluated through comprehensive comparisons with available measurements and other theoretical results.For transition energies,our results are in good agreement with the recent experimental data obtained from the electron beam ion traps within 0.18%.The maximum discrepancy between our results and those obtained with the large-scale multiconfiguration Dirac–Hartee–Fock calculations by Grumer et al.[Phys.Rev.A 89062501(2014)]is less than 0.13%along the isoelectronic sequence.Furthermore,the corresponding M1 transition rates are also reported.The present results can be used as the benchmark and useful for spectra simulation and diagnostics of astrophysical and fusion plasmas.
基金Supported by the National Natural Science Foundation of China(Grant Nos.12204491 and 12121004)the National Basic Research Program of China(Grant No.2021YFF0603801)+3 种基金Wuhan Young Talent Program(Grant No.R22H000106)the Natural Science Foundation of Hubei Province(Grant No.2022CFA013)the CAS Youth Innovation Promotion Association(Grant Nos.Y201963 and 2018364)CAS Project for Young Scientists in Basic Research(Grant No.YSBR-055)。
文摘We present a method that the atomic transition frequency measurement relies on the accurate wavemeter,optical frequency comb and stable Fabry–Pérot cavity to precise determination of stable even isotope shift on single Yb+ion(A=168,170,172,174,176).The 6s^(2)S_(1/2)←→6p^(2)P_(1/2)and 5d^(2)D_(3/2)←→6s^(3)[3/2]_(1/2)resonance dipole transition frequencies are preliminarily measured by using a wavemeter which is calibrated by the 729 nm clock laser of ^(40)Ca^(+).Meanwhile,those frequencies are double checked by using optical frequency comb for correction of deviation.Ultimately,by changing frequency locking points at an ultralow expansion cavity more slightly and monitoring the corresponding atomic fluorescence changing with 17%,we finally improve the resonant frequency uncertainty to±6 MHz,which is one order of improvement in precision higher than previously published measurements on the same transitions.A King-plot analysis with sensitivity to coupling between electrons and neutrons is carried out to determine the field and mass shift constants.Our measurement combined with existing or future isotope shift measurements can be used to determine basic properties of atomic nuclei,and to test new forces beyond the Standard Model.
基金supported in part by the National Natural Science Foundation of China (52172112,51972047)。
文摘Layered rare-earth hydroxides(LREHs) draw wide research interest because of their peculiar crystal structure,rich interlayer chemistry and abundant functionality of the RE element,but are limited to the two categories of RE_(2)(OH)_(5)A·nH_(2)O(A:typical of Cl^(-)or NO_(3)^(-)) and RE_(2)(OH)_(4)SO_(4)·nH_(2)O.On the other hand,rare-earth oxysulfates(RE_(2)O_(2)SO_(4)) have attracted attention due to their properties of large-capacity oxygen storage,low-temperature magnetism and luminescence,but their preparation procedure mostly involves toxic SO_(x) gases and/or complicated procedures.In this work,RE_(2)(OH)_(2)CO_(3)SO_(4)·nH_(2)O as a new family of LREHs(RE=Gd-Lu lanthanides and Y) were produced via hydrothermal reaction,from which phase-pure RE_(2)O_(2)SO_(4) was derived via subsequent annealing at 800℃ in air without the involvement of SO_(x),The compounds were thoroughly characterized to reveal the intrinsic influence of lanthanide contraction(RE^(3+) radius) on crystal structure,thermal behavior(dehydroxylation/decarbonation/desulfurization),vibrational property and crystallite morphology.Through analyzing the photoluminescence of Eu^(3+) and Sm^(3+)in the Gd_(2)O_(2)SO_(4) typical host it is found that the 617 nm(Eu^(3+),λ_(ex)=275 nm) and 608 nm(Sm^(3+),λ_(ex)=407 nm) main emissions can retain as high as ^(7)9.6% and 85.5%of their room-temperature intensities at 423 K,with activation energies of ~0.19 and 0.21 eV for thermal quenching,respectively.Application also indicates that both the phosphors have the potential for optical temperature sensing via the fluorescence intensity ratio(FIR) technology,whose maximum relative sensitivity reaches ^(2).70%/K for Eu^(3+)and 1.73%/K for Sm^(3+) at 298 K.
基金supported by the Natural Science Foundation of The Educational Department of Liaoning Province (JYTMS20231627)the Natural Science Foundation of Liaoning Province (2020-MS-286)。
文摘Phosphor-converted near-infrared light-emitting diodes(NIR pc-LEDs) are finding applications in various fields including food quality analysis,biomedical imaging,night vision,and biomedicine.The crucial factor in the development of NIR pc-LEDs devices lies in the advancement of high-performance broadband NIR phosphors,In this work,novel Cr^(3+)-activated silicate phosphors NaRESi_(3)O_(9)(RE=Y,Lu,Sc) are reported.This silicate has a special 3D network structure in which RE has four different sites,forming four octahedrons and providing suitable occupation sites for Cr^(3+).The phosphors demonstrate a wide emission spectrum ranging from 750 to 1450 nm when excited by light at 468 nm.The full width at half maximum(FWHM),which benefits from the presence of Cr^(3+)ions occupying multiple sites,is measured to be 203 nm.Notably,the strongest emission peak is observed at a longer wavelength of 984 nm compared to most other systems activated by Cr^(3+).The Na_(3)ScSi_(3)O_(9) lattice provides a weak crystal field(Dq/B=1.97) and weak phonon-photon coupling for Cr^(3+),and the integrated emission intensity of Na_(3)ScSi_(3)O_(9):0,03Cr^(3+)is 4.66 times stronger than that of Na_(3)YSi_(3)O_(9):0.03Cr^(3+).
基金supported by Zhejiang Provincial Natural Science Foundation of China(Grant No.LY23F050007).
文摘A chemical co-precipitation strategy was employed to synthesize a series of(Gd_(0.95−x)Lu_(x)Eu_(0.05))_(3)Al_(5)O_(12)(x=0.1−0.95)powder phosphors,followed by vacuum sintering to achieve transparent garnet ceramic phosphors.The density functional theory indicated Lu_(3)Al_(5)O_(12) was formed in priority compared with Gd_(3)Al_(5)O_(12) during solid-phase reaction.Upon high-temperature sintering,the Lu^(3+)substitution for Gd^(3+)suppressed point mass diffusion leading to a smaller grain size.The in-line transmittances of bulk specimens with x=0.1,0.3,0.5,0.7,and 0.95 nm were~83.5%,80.1%,68.8%,73.7%,and 82.2%at 710 nm(Eu^(3+)emission center),respectively,among which the sample of x=0.1 exhibited the optical grade with near-zero optical loss in agreement with the defect-free single crystal(~100%of the theoretical transmittance).The resulting particle and ceramic materials both presented characteristic Eu^(3+)emission arising from 5D0→7FJ(J=1−4)transition,where the dominant far-red emission at~710 nm arising from ^(5)D_(0)→^(7)F_(4) transition overlapped with the absorption of phytochrome(PFR).The photoluminescence excitation and photoluminescence intensities of(Gd_(0.95−x)Lu_(x)Eu_(0.05))_(3)Al_(5)O_(12) powders and ceramics generally increased at a higher Gd^(3+)/Lu^(3+)ratio.Lu^(3+)dopants delayed the fluorescence lifetime while the bulk samples had shorter lifetime compared to the particle counterparts.The transparent(Gd_(0.85)Lu_(0.1)Eu_(0.05))3Al_(5)O_(12) ceramic phosphor exhibited good thermal stability with a high thermal quenching temperature above 533 K.The designed ceramic phosphor-converted light-emitting diode had a saturation injection current of 435 mA and a current-dependent color rendering index.More importantly,our report marked the developmental stage of transparent ceramic materials towards zero optical loss.
文摘Understanding the coking behaviors has been considered to be really essential for developing better vacuum residue processing technologies.A battery of thermal cracking tests of typical vacuum residue at 410℃ with various reaction time were performed to evaluate the coke formation process.The total yields of ideal components including naphtha,atmospheric gas oil(AGO)and vacuum gas oil(VGO)of thermal cracking reactions increased from 10.89%to 40.81%,and the conversion ratios increased from8.05%to 43.33%with increasing the reaction time from 10 to 70 min.The asphaltene content increased from 12.14%to a maximum of 22.39%and then decreased,and this maximum of asphaltene content occurred at the end of the coking induction period.The asphaltenes during the coking induction period,at the end and after coking induction period of those tested thermal cracking reactions were characterized to disclose the structure changing rules for coke formation process,and the coke formation pathways were discussed to reveal the coke formation process at molecular level.