Nonlinear behaviors are investigated for a structure coupled with a nonlinear energy sink. The structure is linear and subject to a harmonic excitation, modeled as a forced single-degree-of-freedom oscillator. The non...Nonlinear behaviors are investigated for a structure coupled with a nonlinear energy sink. The structure is linear and subject to a harmonic excitation, modeled as a forced single-degree-of-freedom oscillator. The nonlinear energy sink is modeled as an oscillator consisting of a mass,a nonlinear spring, and a linear damper. Based on the numerical solutions, global bifurcation diagrams are presented to reveal the coexistence of periodic and chaotic motions for varying nonlinear energy sink mass and stiffness. Chaos is numerically identified via phase trajectories, power spectra,and Poincaré maps. Amplitude-frequency response curves are predicted by the method of harmonic balance for periodic steady-state responses. Their stabilities are analyzed.The Hopf bifurcation and the saddle-node bifurcation are determined. The investigation demonstrates that a nonlinear energy sink may create dynamic complexity.展开更多
QUANTIZED radiation fields exhibiting nonclassical properties have been of great theoretical andexperimental interest in the last two decades. It is shown that various nonclassical states suchas squeezed state and Sch...QUANTIZED radiation fields exhibiting nonclassical properties have been of great theoretical andexperimental interest in the last two decades. It is shown that various nonclassical states suchas squeezed state and Schrodinger cat state can be generated out of coherent state in thenonlinear process of the interaction of atom and field although the radiation field in a展开更多
The existing research of the electro-hydraulic vibrator mainly focuses on system stability, working frequency width and output waveform distortion. However, this high frequency performance of the electro-hydraulic vib...The existing research of the electro-hydraulic vibrator mainly focuses on system stability, working frequency width and output waveform distortion. However, this high frequency performance of the electro-hydraulic vibrator is difficult to be improved greatly due to fast insufficiently frequency response of the servo valve itself and limited compensation capability of the control structure in the vibrator system. In this paper, to realize high frequency vibration, an improved two-dimensional valve （here within defined as a 2D valve） as a main control component is adopted to the parallel connection with a servo valve to control the electro-hydraulic vibrator, Because the output waveforms of this electro-hydraulic vibrator are incapable to be verified through timely feedback as in the conventional electro-hydraulic servo system, the analysis to the output waveform becomes crucial to the design and control of the electro-hydraulic vibrator. The mathematical models of hydraulic actuation mechanism and the orifice area of the parallel valves connection are established first. And then the vibration process is divided into two sections in terms of the direction of the flow, the analytical expression of the excited waveform is solved. Based on relationships exist between working states and the control parameters the analytical results, the vibration boundary positions and the are derived. Finally an experimental system was built to validate the theoretical analysis. It is verified that this electro-hydraulic vibration system could achieve high working frequency, up to 2 000 Hz. The excited waveform is similar to the sinnsoidal waveform. And the ascent and decent slopes of the waveforms are somewhat asymmetrical. This asymmetry is not only caused by the change of the direction of the elastic force but also dependent on the bias position of the vibration. Consequentky the distortion of effective working waveform is less tha~ 10%. This electro-hydraulic vibrator controlled by the multiple valves could not only greatly en展开更多
Geometry and vibrational frequencies of the ground state of Si2O2 molecule are studied using density function theory （DFT） at the level of cc-pvtz and 6-311-k＋G^＊＊. It is found that the optimizing value by B31yp/...Geometry and vibrational frequencies of the ground state of Si2O2 molecule are studied using density function theory （DFT） at the level of cc-pvtz and 6-311-k＋G^＊＊. It is found that the optimizing value by B31yp/cc-pvtz is closer to the experimental data. The excited properties under different external electric fields are also investigated by the time-dependent-DFT method. Transitions from the ground state of Si2O2 molecule to the first singlet state under different external electric fields can take place more easily. The corresponding absorption spectral line is about 360 nm in wavelength and the excitation energy is about 3.4 eV.展开更多
The research of propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial targets from underwater.In order to study the propagation characteristics of air-to-wate...The research of propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial targets from underwater.In order to study the propagation characteristics of air-to-water sound transmission in shallow water,State Key Laboratory of Acoustics,Institute of Acoustics,conducted an experiment in the South China Sea in March,2013.During the experiment,multi-frequency signals transmitted by a hooter hung on a research ship were received by an underwater hydrophone,and the distance between the hooter and the hydrophone was from 2.4 km to 9.8 km approximately.Through analyzing experimental data in this work,the experimental air-to-water transmission loss at frequencies128 Hz and 256 Hz is estimated up to 9.8 km in range,and its oscillation structure is evident.The wave-number integration approach is used to simulate theoretical air-to-water transmission losses,which are in good agreement with experimental values and to explain the experimental air-to-water sound transmission characteristics.展开更多
We developed adjustable and movable droplet microlenses consisting of a liquid with a high refractive index.The microlenses were prepared via ultrasonic shaking in deionized water,and the diameter of the microlenses r...We developed adjustable and movable droplet microlenses consisting of a liquid with a high refractive index.The microlenses were prepared via ultrasonic shaking in deionized water,and the diameter of the microlenses ranged from 1 to 50μm.By stretching the microlenses,the focal length can be adjusted from 13 to 25μm.With the assistance of an optical tweezer,controllable assembly and movement of microlens arrays were also realized.The results showed that an imaging system combined with droplet microlenses could image 80 nm beads under white light illumination.Using the droplet microlenses,fluorescence emission at 550 nm from Cd Se@Zn S quantum dots was efficiently excited and collected.Moreover,Raman scattering signals from a silicon wafer were enhanced by^19 times.The presented droplet microlenses may offer new opportunities for flexible liquid devices in subwavelength imaging and detection.展开更多
This paper considers the dynamical behavior of a Duffing-Mathieu type system with a cubic single-well potential during the principal parametric resonance. Both the cases of constant and time-dependent excitation ampli...This paper considers the dynamical behavior of a Duffing-Mathieu type system with a cubic single-well potential during the principal parametric resonance. Both the cases of constant and time-dependent excitation amplitude are used to observe the variation of the extent and the rate of the erosion in safe basins. It is evident that the appearance of fractal basin boundaries heralds the onset of the losing of structural integrity. The minimum value of control parameter to prevent the basin from erosion is given along with the excitation amplitude varying. The results show the time-dependence of excitation amplitude can be used to control the extent and the rate of the erosion and delay the first occurrence of heteroclinic tangency.展开更多
Ratiometric luminescence thermometry with trivalent lanthanide ions and their 4f^(n) energy levels is an emerging technique for non-invasive remote temperature sensing with high spatial and temporal resolution.Convent...Ratiometric luminescence thermometry with trivalent lanthanide ions and their 4f^(n) energy levels is an emerging technique for non-invasive remote temperature sensing with high spatial and temporal resolution.Conventional ratiometric luminescence thermometry often relies on thermal coupling between two closely lying energy levels governed by Boltzmann’s law.Despite its simplicity,Boltzmann thermometry with two excited levels allows precise temperature sensing,but only within a limited temperature range.While low temperatures slow down the nonradiative transitions required to generate a measurable population in the higher excitation level,temperatures that are too high favour equalized populations of the two excited levels,at the expense of low relative thermal sensitivity.In this work,we extend the concept of Boltzmann thermometry to more than two excited levels and provide quantitative guidelines that link the choice of energy gaps between multiple excited states to the performance in different temperature windows.By this approach,it is possible to retain the high relative sensitivity and precision of the temperature measurement over a wide temperature range within the same system.We demonstrate this concept using YAl_(3)(BO_(3))_(4)(YAB):Pr^(3+),Gd^(3+)with an excited 6 PJ crystal field and spin-orbit split levels of Gd^(3+)in the UV range to avoid a thermal black body background even at the highest temperatures.This phosphor is easily excitable with inexpensive and powerful blue LEDs at 450 nm.Zero-background luminescence thermometry is realized by using blue-to-UV energy transfer upconversion with the Pr^(3+)−Gd^(3+)couple upon excitation in the visible range.This method allows us to cover a temperature window between 30 and 800 K.展开更多
Eu3＋-activated B2O3-GeO2-37Gd2O3-3Eu2O3-（15-x）GdF3-xBaF2 （0≤x≤15） scintillating glasses with the density of 6.1-6.3 g/cm3 were synthesized by a melt-quenching method. The substitution of BaF2 for expensive GdF3...Eu3＋-activated B2O3-GeO2-37Gd2O3-3Eu2O3-（15-x）GdF3-xBaF2 （0≤x≤15） scintillating glasses with the density of 6.1-6.3 g/cm3 were synthesized by a melt-quenching method. The substitution of BaF2 for expensive GdF3 in oxyfluoride borogermanate glasses slightly decreased the glass density within 3.0%. Their optical properties were characterized by transmittance, photolumines- cence （excitation and emission）, and X-ray excited luminescence （XEL） spectra in detail. The emission intensity of Eu3＋ ions increased with the elevated x values. The Eu-O covalancey nature and the local environment of Eu3＋ ions were evaluated by Judd-Ofelt results. It was found that the covalency property of Eu-O bond increased with increasing x values.展开更多
Photoreceptor phytochrome B(phy B)mediates a variety of light responses in plants.To further elucidate the molecular mechanisms of phy B-regulated hypocotyl elongation,we performed firefly luciferase complementation i...Photoreceptor phytochrome B(phy B)mediates a variety of light responses in plants.To further elucidate the molecular mechanisms of phy B-regulated hypocotyl elongation,we performed firefly luciferase complementation imaging(LCI)screening for phy B-interacting transcription factors(TFs).LCI assays showed that phy B possibly interacts with brassinazoleresistant 1(BZR1),BZR2,AUXIN RESPONSE FACTOR 6(ARF6),and several WRKY DNA-binding TFs in a red light-dependent manner.Furthermore,biochemical assays demonstrated that photoexcited phy B specifically interacts with nonphosphorylated BZR1,the physiologically active form of a master TF in brassinosteroid(BR)signaling,and this interaction can be competitively interfered by phytochrome-interacting factor 4.Furthermore,we showed that phy B can directly interact with the DNA-binding domain of BZR1 and affect the enrichment of BZR1 on the chromatin of target genes.Moreover,our genetic evidence and RNA-seq analysis demonstrated that phy B negatively regulates BR signaling.Together,we revealed that photoexcited phy B directly interacts with the TF BZR1 to repress BR signaling in Arabidopsis.展开更多
ZnO nanorods prepared by a solution-phase method are annealed at different temperatures in oxygen ambient.The luminescence properties of the samples are investigated.In the same excitation condition,the photoluminesce...ZnO nanorods prepared by a solution-phase method are annealed at different temperatures in oxygen ambient.The luminescence properties of the samples are investigated.In the same excitation condition,the photoluminescence(PL) spectra of all samples show an ultraviolet(UV) emission and a broad strong visible emission band.The asymmetric visible emis-sion band of annealed samples has a red-shift as the annealing temperature increasing from 200 ℃ to 600 ℃ and it can be deconvoluted into two subband emissions centered at 535 nm(green emission) and 611 nm(orange-red emission) by Gaussian-fitting analysis.Analyses of PL excitation(PLE) spectra and PL spectra at different excitation wavelengths reveal that the green emission and the orange-red emission have a uniform initial state,which can be attributed to the electron transition from Zn interstitial(Zni) to oxygen vacancy(Vo) and oxygen interstitial(Oi),respectively.展开更多
Using time-resolved techniques of 337 and 248 nm laser flash photolysis, the photo physical and photochemical processes of riboflavin (RF, vitamin B2) were studied in detail in aqueous solution. The excited triplet st...Using time-resolved techniques of 337 and 248 nm laser flash photolysis, the photo physical and photochemical processes of riboflavin (RF, vitamin B2) were studied in detail in aqueous solution. The excited triplet state of riboflavin (3RF*) was produced with 337 nm laser, while under 248 nm irradiation, both3RF* and hydrated electron (eaq) formed from photoionization could be detected. Photobiological implications have been inferred on the basis of reactivity of3RF* including energy transfer, electron transfer and hydrogen abstraction. The RF·+ was generated by oxidation of SO4 ·-radical with the aim of confirming the results of photolysis.展开更多
This paper investigates the excited states of Si3O molecule by using the single-excitation configuration interaction and density functional theory. It finds that the visible light absorption spectrum of Si3O molecule ...This paper investigates the excited states of Si3O molecule by using the single-excitation configuration interaction and density functional theory. It finds that the visible light absorption spectrum of Si3O molecule comprises the yellow and the purple light without external electric field, however all the visible light is included except the green light under the action of external electric field. Oxygen-deficient defects, which also can be found in Si3O molecule, have been used to explain the 1 from silicon-based materials but the microstructures of the materials are still uncertain Our results accord with the experimental values perfectly, this fact suggests that the structure of Si3O molecule is expected to be one of the main basic structures of the materials, so the oxygen-deficient defect structural model for Si3O molecule also has been provided to research the structures of materials.展开更多
As this is the first time a large volume airgun has been excited in the "Yangtse River Geoscience Project",it is necessary to study the time-frequency characteristic based on the linear stacked seismic data ...As this is the first time a large volume airgun has been excited in the "Yangtse River Geoscience Project",it is necessary to study the time-frequency characteristic based on the linear stacked seismic data from records from portable stations near the fixed fields and seismic stations. Airgun signal propagation distances were detected using stacked seismic data to analyze the environmental impact on signal propagation distance. The results showed that:( 1) the airgun signal produced by bubble pulses,pressure pulses and the surface wave can be received by a portable station near the fixed field;( 2) the dominant frequency of a bubble at 5Hz or so can be received by both near-field stations and far-field stations,pressure pulses rapidly weaken and the dominant frequency bands get narrower as epicentral distance increases;( 3) the longest spread distance of signal is 260 km,the nearest is 180 km,and the signal can travel further in the evening.展开更多
We develop a method for creating two- and one-dimensional （2D and 1D） self-trapped modes in bi- nary spin-orbit-coupled Bose-Einstein condensates with the contact repulsive interaction, whose local strength grows su...We develop a method for creating two- and one-dimensional （2D and 1D） self-trapped modes in bi- nary spin-orbit-coupled Bose-Einstein condensates with the contact repulsive interaction, whose local strength grows sufficiently rapidly from the center to the periphery. In particular, an exact semi-vortex （SV） solution is found for the anti-Gaussian radial modulation profile. The exact modes are included in the numerically produced family of SV solitons. Other families, in the form of mixed modes （MMs）, as well as excited states of SVs and MMs, are also produced. Although the excited states are unstable in all previously studied models, they are partially stable in the present one. In the 1D version of the system, exact solutions for the counterpart of SVs, namely, semi-dipole solitons, are also found. Families of semi-dipoles, as well as the 1D version of MMs, are produced numerically.展开更多
We analyzed the excited-state structures and emission spectra of firefly emitter, the anionic keto form of firefly oxyluciferin（keto-l）, determined by the time dependent-density functional theory（TD-DFT） approach....We analyzed the excited-state structures and emission spectra of firefly emitter, the anionic keto form of firefly oxyluciferin（keto-l）, determined by the time dependent-density functional theory（TD-DFT） approach. The analysis is based on a direct comparison with the highly correlated CASSCF（MS-CASPT2） ab initio approach. 49 DFT functionals were considered and applied to the study. Among the tested functionals, mPW3PBE, B3PW91 and B3P86 give the best performance for ground-state geometry, absorption spectrum, excited-state geometry and emis- sion spectrum.展开更多
Dy：Lu2O3 was grown by the float-zone （Fz） method. According to the absorption spectrum, the Judd-Ofelt （JO） parameters Ω2, Ω4, and Ω6 were calculated to be 4.86 × 10-20 cm2, 2.02 × 10-20 cm2, and 1.7...Dy：Lu2O3 was grown by the float-zone （Fz） method. According to the absorption spectrum, the Judd-Ofelt （JO） parameters Ω2, Ω4, and Ω6 were calculated to be 4.86 × 10-20 cm2, 2.02 × 10-20 cm2, and 1.76 ×10-20 cm2, respectively. The emission cross-section at 574 nm corresponding to the 4F9/2 →6H13/2 transition was calculated to be 0.53 ×10 20 cm2. The yellow （4F9/2 →6H13/2 transition） to blue （4F9/2 →6H15/2 transition） intensity ratio ranges up to 12.9. The fluorescence lifetime of the 4F9/2 energy level was measured to be 112.1 μs. These results reveal that Dy：Lu2O3 is a promising material for use in yellow lasers.展开更多
Organic scintillators that efficiently generate bright triplet excitons are of critical importance for highperformance X-ray-excited luminescence in radiation detection.However,the nature of triplet-singlet spinforbid...Organic scintillators that efficiently generate bright triplet excitons are of critical importance for highperformance X-ray-excited luminescence in radiation detection.However,the nature of triplet-singlet spinforbidden transitions in these materials often result in long-lived phosphorescence,which is undesirable for ultrafast X-ray detection and imaging.Here we demonstrate that the effect of hybridized local and charge-transfer(HLCT)excited states enables organic scintillators to exhibit highly efficient and fast radioluminescence(RL)in response to X-ray irradiation.Our experimental and theoretical investigation shows that the oxidized 1,8-naphthalimide-phenothiazine dyad(OMNI-PTZ 2)with HLCT-excited states has an enhanced overlap integral of the highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)on MNIπ-orbitals,and moderate donor–acceptor electron interactions.As a result,the RL of these crystals exhibits a 61-fold increase and its monoexponential decay lifetime is three orders of magnitude faster compared to its corresponding thermally activated delayed fluorescence(TADF)molecule MNI-PTZ 1.We further demonstrate the practical utility of the OMNI-PTZ 2(G)in high-performance X-ray detection and imaging,achieving an X-ray dose sensitivity of 97 nGy s−1 and an exceptional spatial resolution of 20 lp/mm.Our study provides a promising molecular design principle for utilizing triplet excitons to develop high-efficiency and fast X-ray scintillators for the development of next-generation flexible and stretchable X-ray imaging detectors.展开更多
Solar-driven N_(2) fixation using a photocatalyst in water presents a promising alternative to the traditional Haber-Bosch process in terms of both energy efficiency and environmental concern.At present,the product of...Solar-driven N_(2) fixation using a photocatalyst in water presents a promising alternative to the traditional Haber-Bosch process in terms of both energy efficiency and environmental concern.At present,the product of solar N_(2) fixation is either NH_(4)^(+)or NO_(3)^(-).Few reports described the simultaneous formation of ammonia(NH_(4)^(+))and nitrate(NO_(3)^(-))by a photocatalytic reaction and the related mechanism.In this work,we report a strategy to photocatalytically fix nitrogen through simultaneous reduction and oxidation to produce NH_(4)^(+)and NO_(3)^(-)byW18O49 nanowires in pure water.The underlying mechanism of wavelength-dependent N_(2) fixation in the presence of surface defects is proposed,with an emphasis on oxygen vacancies that not only facilitate the activation and dissociation of N_(2) but also improve light absorption and the separation of the photoexcited carriers.Both NH_(4)^(+)and NO_(3)^(-)can be produced in pure water under a simulated solar light and even till the wavelength reaching 730 nm.The maximum quantum efficiency reaches 9%at 365 nm.Theoretical calculation reveals that disproportionation reaction of the N_(2) molecule is more energetically favorable than either reduction or oxidation alone.It is worth noting that the molar fraction of NH_(4)^(+)in the total product(NH_(4)^(+)plus NO_(3)^(-))shows an inverted volcano shape from 365nm to 730 nm.The increased fraction of NO_(3)^(-)from 365 nm to around 427 nm results from the competition between the oxygen evolution reaction(OER)at W sites without oxygen vacancies and the N_(2) oxidation reaction(NOR)at oxygen vacancy sites,which is driven by the intrinsically delocalized photoexcited holes.From 427nm to 730 nm,NOR is energetically restricted due to its higher equilibrium potential than that of OER,accompanied by the localized photoexcited holes on oxygen vacancies.Full disproportionation of N_(2) is achieved within a range of wavelength from~427nm to~515 nm.This work presents a rational strategy to efficiently utilize the photoex展开更多
基金supported by the National Natural Science Foundation of China (Grants 11402151 and 11572182)
文摘Nonlinear behaviors are investigated for a structure coupled with a nonlinear energy sink. The structure is linear and subject to a harmonic excitation, modeled as a forced single-degree-of-freedom oscillator. The nonlinear energy sink is modeled as an oscillator consisting of a mass,a nonlinear spring, and a linear damper. Based on the numerical solutions, global bifurcation diagrams are presented to reveal the coexistence of periodic and chaotic motions for varying nonlinear energy sink mass and stiffness. Chaos is numerically identified via phase trajectories, power spectra,and Poincaré maps. Amplitude-frequency response curves are predicted by the method of harmonic balance for periodic steady-state responses. Their stabilities are analyzed.The Hopf bifurcation and the saddle-node bifurcation are determined. The investigation demonstrates that a nonlinear energy sink may create dynamic complexity.
文摘QUANTIZED radiation fields exhibiting nonclassical properties have been of great theoretical andexperimental interest in the last two decades. It is shown that various nonclassical states suchas squeezed state and Schrodinger cat state can be generated out of coherent state in thenonlinear process of the interaction of atom and field although the radiation field in a
基金supported by National Natural Science Foundation of China(Grant No.50675204)Zhejiang Provincial Natural Science Foundation of China(Grant No.D1080667)
文摘The existing research of the electro-hydraulic vibrator mainly focuses on system stability, working frequency width and output waveform distortion. However, this high frequency performance of the electro-hydraulic vibrator is difficult to be improved greatly due to fast insufficiently frequency response of the servo valve itself and limited compensation capability of the control structure in the vibrator system. In this paper, to realize high frequency vibration, an improved two-dimensional valve （here within defined as a 2D valve） as a main control component is adopted to the parallel connection with a servo valve to control the electro-hydraulic vibrator, Because the output waveforms of this electro-hydraulic vibrator are incapable to be verified through timely feedback as in the conventional electro-hydraulic servo system, the analysis to the output waveform becomes crucial to the design and control of the electro-hydraulic vibrator. The mathematical models of hydraulic actuation mechanism and the orifice area of the parallel valves connection are established first. And then the vibration process is divided into two sections in terms of the direction of the flow, the analytical expression of the excited waveform is solved. Based on relationships exist between working states and the control parameters the analytical results, the vibration boundary positions and the are derived. Finally an experimental system was built to validate the theoretical analysis. It is verified that this electro-hydraulic vibration system could achieve high working frequency, up to 2 000 Hz. The excited waveform is similar to the sinnsoidal waveform. And the ascent and decent slopes of the waveforms are somewhat asymmetrical. This asymmetry is not only caused by the change of the direction of the elastic force but also dependent on the bias position of the vibration. Consequentky the distortion of effective working waveform is less tha~ 10%. This electro-hydraulic vibrator controlled by the multiple valves could not only greatly en
基金Project supported by the National Natural Science Foundation of China (Grant No. 10774039)the Natural Science Foundation of Henan Province,China (Grant No. 092300410249)+1 种基金the Natural Science Foundation of the Education Bureau of Henan Province,China (Grant No. 2010A140008)the Foundation for University Young Core Instructors of Henan Province,China (Grant No. 2009GGJS-044)
文摘Geometry and vibrational frequencies of the ground state of Si2O2 molecule are studied using density function theory （DFT） at the level of cc-pvtz and 6-311-k＋G^＊＊. It is found that the optimizing value by B31yp/cc-pvtz is closer to the experimental data. The excited properties under different external electric fields are also investigated by the time-dependent-DFT method. Transitions from the ground state of Si2O2 molecule to the first singlet state under different external electric fields can take place more easily. The corresponding absorption spectral line is about 360 nm in wavelength and the excitation energy is about 3.4 eV.
基金supported by the National Natural Science Foundation of China(11434012,41561144006)Public Science and Technology Research Funds Projects of Ocean(201405032)
文摘The research of propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial targets from underwater.In order to study the propagation characteristics of air-to-water sound transmission in shallow water,State Key Laboratory of Acoustics,Institute of Acoustics,conducted an experiment in the South China Sea in March,2013.During the experiment,multi-frequency signals transmitted by a hooter hung on a research ship were received by an underwater hydrophone,and the distance between the hooter and the hydrophone was from 2.4 km to 9.8 km approximately.Through analyzing experimental data in this work,the experimental air-to-water transmission loss at frequencies128 Hz and 256 Hz is estimated up to 9.8 km in range,and its oscillation structure is evident.The wave-number integration approach is used to simulate theoretical air-to-water transmission losses,which are in good agreement with experimental values and to explain the experimental air-to-water sound transmission characteristics.
基金National Natural Science Foundation of China(11874183,61827822,61905092)Fundamental Research Funds for the Central Universities(21619321)。
文摘We developed adjustable and movable droplet microlenses consisting of a liquid with a high refractive index.The microlenses were prepared via ultrasonic shaking in deionized water,and the diameter of the microlenses ranged from 1 to 50μm.By stretching the microlenses,the focal length can be adjusted from 13 to 25μm.With the assistance of an optical tweezer,controllable assembly and movement of microlens arrays were also realized.The results showed that an imaging system combined with droplet microlenses could image 80 nm beads under white light illumination.Using the droplet microlenses,fluorescence emission at 550 nm from Cd Se@Zn S quantum dots was efficiently excited and collected.Moreover,Raman scattering signals from a silicon wafer were enhanced by^19 times.The presented droplet microlenses may offer new opportunities for flexible liquid devices in subwavelength imaging and detection.
基金the National Science Foundation of ChinaPSF of China
文摘This paper considers the dynamical behavior of a Duffing-Mathieu type system with a cubic single-well potential during the principal parametric resonance. Both the cases of constant and time-dependent excitation amplitude are used to observe the variation of the extent and the rate of the erosion in safe basins. It is evident that the appearance of fractal basin boundaries heralds the onset of the losing of structural integrity. The minimum value of control parameter to prevent the basin from erosion is given along with the excitation amplitude varying. The results show the time-dependence of excitation amplitude can be used to control the extent and the rate of the erosion and delay the first occurrence of heteroclinic tangency.
基金D.Y.is grateful to Prof.Wei Wei from Nanjing University of Posts and Telecommunication for useful suggestions.Moreover,Q.Z.acknowledges funding from the National Science Foundation of China(U1601205,51472088,and 51125005)while D.Y.and A.M.acknowledge funding from the Nederlandse Organisatie voor Wetenschappelijk Onderzoek(NWO,Grant No.731.017.302)A.M.and M.S.additionally gratefully acknowledge funding from the EU-Horizon 2020 FET-Open project NanoTBTech(grant agreement no.:801305).
文摘Ratiometric luminescence thermometry with trivalent lanthanide ions and their 4f^(n) energy levels is an emerging technique for non-invasive remote temperature sensing with high spatial and temporal resolution.Conventional ratiometric luminescence thermometry often relies on thermal coupling between two closely lying energy levels governed by Boltzmann’s law.Despite its simplicity,Boltzmann thermometry with two excited levels allows precise temperature sensing,but only within a limited temperature range.While low temperatures slow down the nonradiative transitions required to generate a measurable population in the higher excitation level,temperatures that are too high favour equalized populations of the two excited levels,at the expense of low relative thermal sensitivity.In this work,we extend the concept of Boltzmann thermometry to more than two excited levels and provide quantitative guidelines that link the choice of energy gaps between multiple excited states to the performance in different temperature windows.By this approach,it is possible to retain the high relative sensitivity and precision of the temperature measurement over a wide temperature range within the same system.We demonstrate this concept using YAl_(3)(BO_(3))_(4)(YAB):Pr^(3+),Gd^(3+)with an excited 6 PJ crystal field and spin-orbit split levels of Gd^(3+)in the UV range to avoid a thermal black body background even at the highest temperatures.This phosphor is easily excitable with inexpensive and powerful blue LEDs at 450 nm.Zero-background luminescence thermometry is realized by using blue-to-UV energy transfer upconversion with the Pr^(3+)−Gd^(3+)couple upon excitation in the visible range.This method allows us to cover a temperature window between 30 and 800 K.
基金supported by the National Natural Science Foundation of China(11165010,11465010)Natural Science Foundation of Jiangxi Province(20142BAB202006,20152ACB21017)+2 种基金the Training Program of Young Scientists(Jing Gang Star)in Jiangxi Province(20133BCB23023)the Key Subject of Atomic&Molecular Physics in Jiangxi Province(2011-2015)the Open Fund of Key Laboratory of Transparent Opto-functional Inorganic Materials,SICCAS
文摘Eu3＋-activated B2O3-GeO2-37Gd2O3-3Eu2O3-（15-x）GdF3-xBaF2 （0≤x≤15） scintillating glasses with the density of 6.1-6.3 g/cm3 were synthesized by a melt-quenching method. The substitution of BaF2 for expensive GdF3 in oxyfluoride borogermanate glasses slightly decreased the glass density within 3.0%. Their optical properties were characterized by transmittance, photolumines- cence （excitation and emission）, and X-ray excited luminescence （XEL） spectra in detail. The emission intensity of Eu3＋ ions increased with the elevated x values. The Eu-O covalancey nature and the local environment of Eu3＋ ions were evaluated by Judd-Ofelt results. It was found that the covalency property of Eu-O bond increased with increasing x values.
基金supported by Institute of Crop SciencesChinese Academy of Agricultural Sciences(CAAS)+1 种基金the Agricultural Science and Technology Innovation Program of CAASYouth Talent Plan of CAAS。
文摘Photoreceptor phytochrome B(phy B)mediates a variety of light responses in plants.To further elucidate the molecular mechanisms of phy B-regulated hypocotyl elongation,we performed firefly luciferase complementation imaging(LCI)screening for phy B-interacting transcription factors(TFs).LCI assays showed that phy B possibly interacts with brassinazoleresistant 1(BZR1),BZR2,AUXIN RESPONSE FACTOR 6(ARF6),and several WRKY DNA-binding TFs in a red light-dependent manner.Furthermore,biochemical assays demonstrated that photoexcited phy B specifically interacts with nonphosphorylated BZR1,the physiologically active form of a master TF in brassinosteroid(BR)signaling,and this interaction can be competitively interfered by phytochrome-interacting factor 4.Furthermore,we showed that phy B can directly interact with the DNA-binding domain of BZR1 and affect the enrichment of BZR1 on the chromatin of target genes.Moreover,our genetic evidence and RNA-seq analysis demonstrated that phy B negatively regulates BR signaling.Together,we revealed that photoexcited phy B directly interacts with the TF BZR1 to repress BR signaling in Arabidopsis.
基金supported by the National Natural Science Foundation of China(Nos.60877029,10904109,60977035 and 60907021)the Natural Science Foundation of Tianjin(Nos.09JCYBJC01400 and 10SYSYJC28100)+1 种基金the Key Subject for Materials Physics and Chemistry of Tianjinthe Open Foundation of Key Laboratory of Luminescence and Optical Information of Ministry of Education(Nos.2010LOI02 and 2010LOI11)
文摘ZnO nanorods prepared by a solution-phase method are annealed at different temperatures in oxygen ambient.The luminescence properties of the samples are investigated.In the same excitation condition,the photoluminescence(PL) spectra of all samples show an ultraviolet(UV) emission and a broad strong visible emission band.The asymmetric visible emis-sion band of annealed samples has a red-shift as the annealing temperature increasing from 200 ℃ to 600 ℃ and it can be deconvoluted into two subband emissions centered at 535 nm(green emission) and 611 nm(orange-red emission) by Gaussian-fitting analysis.Analyses of PL excitation(PLE) spectra and PL spectra at different excitation wavelengths reveal that the green emission and the orange-red emission have a uniform initial state,which can be attributed to the electron transition from Zn interstitial(Zni) to oxygen vacancy(Vo) and oxygen interstitial(Oi),respectively.
基金the National Natural Science Foundation of China (Grant No. 39830090).
文摘Using time-resolved techniques of 337 and 248 nm laser flash photolysis, the photo physical and photochemical processes of riboflavin (RF, vitamin B2) were studied in detail in aqueous solution. The excited triplet state of riboflavin (3RF*) was produced with 337 nm laser, while under 248 nm irradiation, both3RF* and hydrated electron (eaq) formed from photoionization could be detected. Photobiological implications have been inferred on the basis of reactivity of3RF* including energy transfer, electron transfer and hydrogen abstraction. The RF·+ was generated by oxidation of SO4 ·-radical with the aim of confirming the results of photolysis.
基金Project supported by the Foundation for University Young Core Instructors of Henan Province,China(Grant No.2009GGJS-044)the Natural Science Foundation of the Education Bureau of Henan Province,China(Grant No.2010A140008)+1 种基金the Natural Science Foundation of Henan Province,China(Grant No.092300410249)the Natural Science Foundation of the Education Bureau of Henan Province,China(Grant No.2010A140008)
文摘This paper investigates the excited states of Si3O molecule by using the single-excitation configuration interaction and density functional theory. It finds that the visible light absorption spectrum of Si3O molecule comprises the yellow and the purple light without external electric field, however all the visible light is included except the green light under the action of external electric field. Oxygen-deficient defects, which also can be found in Si3O molecule, have been used to explain the 1 from silicon-based materials but the microstructures of the materials are still uncertain Our results accord with the experimental values perfectly, this fact suggests that the structure of Si3O molecule is expected to be one of the main basic structures of the materials, so the oxygen-deficient defect structural model for Si3O molecule also has been provided to research the structures of materials.
基金jointly sponsored by the Special Fund for Earthquake Scientific Research in the Public Welfare of China Earthquake Administration(2015419015)the National Natural Science Foundation of China(41474071)
文摘As this is the first time a large volume airgun has been excited in the "Yangtse River Geoscience Project",it is necessary to study the time-frequency characteristic based on the linear stacked seismic data from records from portable stations near the fixed fields and seismic stations. Airgun signal propagation distances were detected using stacked seismic data to analyze the environmental impact on signal propagation distance. The results showed that:( 1) the airgun signal produced by bubble pulses,pressure pulses and the surface wave can be received by a portable station near the fixed field;( 2) the dominant frequency of a bubble at 5Hz or so can be received by both near-field stations and far-field stations,pressure pulses rapidly weaken and the dominant frequency bands get narrower as epicentral distance increases;( 3) the longest spread distance of signal is 260 km,the nearest is 180 km,and the signal can travel further in the evening.
基金This work was supported in part by the National Natural Science Foundation of China through Grant Nos. 11575063, 61471123, and 61575041, the Joint Program in Physics of the NSF and the Binational （US-Israel） Science Foun- dation through Project No. 2015616, the Israel Science Founda- tion （project No. 1287/17）, and the Natural Science Foundation of Guangdong Province through Grant No. 2015A030313639. B.A.M. is grateful for a foreign-expert grant from Guangdong province （China） and a Ding-Ying professorship provided by the SouthChina Agricultural University （Guangzhou） at its College of Elec- tronic Engineering.
文摘We develop a method for creating two- and one-dimensional （2D and 1D） self-trapped modes in bi- nary spin-orbit-coupled Bose-Einstein condensates with the contact repulsive interaction, whose local strength grows sufficiently rapidly from the center to the periphery. In particular, an exact semi-vortex （SV） solution is found for the anti-Gaussian radial modulation profile. The exact modes are included in the numerically produced family of SV solitons. Other families, in the form of mixed modes （MMs）, as well as excited states of SVs and MMs, are also produced. Although the excited states are unstable in all previously studied models, they are partially stable in the present one. In the 1D version of the system, exact solutions for the counterpart of SVs, namely, semi-dipole solitons, are also found. Families of semi-dipoles, as well as the 1D version of MMs, are produced numerically.
基金Supported by the National Natural Science Foundation of China（Nos.21173099, 20973078, 51164017）, the Applied Basic Research Plans Program of Yunnan Province, China（No.2011FZ040）, the Scientific Research Fund of Yunnan Provincial Educa- tion Department, China（No.2012Y545）, the Training Foundation for Talents of Kunming University of Science and Technolo- gy（No.KKSY201232040） and the Foundation of State Key Laboratory of Theoretical and Computational Chemistry, China.
文摘We analyzed the excited-state structures and emission spectra of firefly emitter, the anionic keto form of firefly oxyluciferin（keto-l）, determined by the time dependent-density functional theory（TD-DFT） approach. The analysis is based on a direct comparison with the highly correlated CASSCF（MS-CASPT2） ab initio approach. 49 DFT functionals were considered and applied to the study. Among the tested functionals, mPW3PBE, B3PW91 and B3P86 give the best performance for ground-state geometry, absorption spectrum, excited-state geometry and emis- sion spectrum.
基金Project supported by the Fund of Key Laboratory of Optoelectronic Materials Chemistry and Physics,Chinese Academy of Sciences(Grant No.2008DP173016)the National Key Research and Development Program of China(Grant No.2016YFB1102202)the National Key Research and Development Program of China(Grant No.2016YFB0701002)
文摘Dy：Lu2O3 was grown by the float-zone （Fz） method. According to the absorption spectrum, the Judd-Ofelt （JO） parameters Ω2, Ω4, and Ω6 were calculated to be 4.86 × 10-20 cm2, 2.02 × 10-20 cm2, and 1.76 ×10-20 cm2, respectively. The emission cross-section at 574 nm corresponding to the 4F9/2 →6H13/2 transition was calculated to be 0.53 ×10 20 cm2. The yellow （4F9/2 →6H13/2 transition） to blue （4F9/2 →6H15/2 transition） intensity ratio ranges up to 12.9. The fluorescence lifetime of the 4F9/2 energy level was measured to be 112.1 μs. These results reveal that Dy：Lu2O3 is a promising material for use in yellow lasers.
基金supported by the National Key R&D Program of China(grant no.2020YFA0709900)the National Natural Science Foundation of China(grant nos.21971041,22201042,22027805,62134003,and 22104016)+2 种基金the Natural Science Foundation of Fujian Province(grant nos.2020J01447,2022J06008,and 2022J0121)the Research Foundation of Education Bureau of Fujian Province(grant no.JAT210001)the Fuzhou University Testing Fund of Precious Apparatus(grant no.2022T001).
文摘Organic scintillators that efficiently generate bright triplet excitons are of critical importance for highperformance X-ray-excited luminescence in radiation detection.However,the nature of triplet-singlet spinforbidden transitions in these materials often result in long-lived phosphorescence,which is undesirable for ultrafast X-ray detection and imaging.Here we demonstrate that the effect of hybridized local and charge-transfer(HLCT)excited states enables organic scintillators to exhibit highly efficient and fast radioluminescence(RL)in response to X-ray irradiation.Our experimental and theoretical investigation shows that the oxidized 1,8-naphthalimide-phenothiazine dyad(OMNI-PTZ 2)with HLCT-excited states has an enhanced overlap integral of the highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)on MNIπ-orbitals,and moderate donor–acceptor electron interactions.As a result,the RL of these crystals exhibits a 61-fold increase and its monoexponential decay lifetime is three orders of magnitude faster compared to its corresponding thermally activated delayed fluorescence(TADF)molecule MNI-PTZ 1.We further demonstrate the practical utility of the OMNI-PTZ 2(G)in high-performance X-ray detection and imaging,achieving an X-ray dose sensitivity of 97 nGy s−1 and an exceptional spatial resolution of 20 lp/mm.Our study provides a promising molecular design principle for utilizing triplet excitons to develop high-efficiency and fast X-ray scintillators for the development of next-generation flexible and stretchable X-ray imaging detectors.
基金The research was financially supported by the National Key R&D Program of China(2016YFB0700600)the Guangdong Innovation Team Project(No.2013N080)+2 种基金the Soft Science Research Project of Guangdong Province(No.2017B030301013)the Shenzhen Science and Technology Research Grant(ZDSYS201707281026184)the Shenzhen Peacock Plan(KQTD2014062714543296).
文摘Solar-driven N_(2) fixation using a photocatalyst in water presents a promising alternative to the traditional Haber-Bosch process in terms of both energy efficiency and environmental concern.At present,the product of solar N_(2) fixation is either NH_(4)^(+)or NO_(3)^(-).Few reports described the simultaneous formation of ammonia(NH_(4)^(+))and nitrate(NO_(3)^(-))by a photocatalytic reaction and the related mechanism.In this work,we report a strategy to photocatalytically fix nitrogen through simultaneous reduction and oxidation to produce NH_(4)^(+)and NO_(3)^(-)byW18O49 nanowires in pure water.The underlying mechanism of wavelength-dependent N_(2) fixation in the presence of surface defects is proposed,with an emphasis on oxygen vacancies that not only facilitate the activation and dissociation of N_(2) but also improve light absorption and the separation of the photoexcited carriers.Both NH_(4)^(+)and NO_(3)^(-)can be produced in pure water under a simulated solar light and even till the wavelength reaching 730 nm.The maximum quantum efficiency reaches 9%at 365 nm.Theoretical calculation reveals that disproportionation reaction of the N_(2) molecule is more energetically favorable than either reduction or oxidation alone.It is worth noting that the molar fraction of NH_(4)^(+)in the total product(NH_(4)^(+)plus NO_(3)^(-))shows an inverted volcano shape from 365nm to 730 nm.The increased fraction of NO_(3)^(-)from 365 nm to around 427 nm results from the competition between the oxygen evolution reaction(OER)at W sites without oxygen vacancies and the N_(2) oxidation reaction(NOR)at oxygen vacancy sites,which is driven by the intrinsically delocalized photoexcited holes.From 427nm to 730 nm,NOR is energetically restricted due to its higher equilibrium potential than that of OER,accompanied by the localized photoexcited holes on oxygen vacancies.Full disproportionation of N_(2) is achieved within a range of wavelength from~427nm to~515 nm.This work presents a rational strategy to efficiently utilize the photoex
