For the accurate extraction of cavity decay time, a selection of data points is supplemented to the weighted least square method. We derive the expected precision, accuracy and computation cost of this improved method...For the accurate extraction of cavity decay time, a selection of data points is supplemented to the weighted least square method. We derive the expected precision, accuracy and computation cost of this improved method, and examine these performances by simulation. By comparing this method with the nonlinear least square fitting （NLSF） method and the linear regression of the sum （LRS） method in derivations and simulations, we find that this method can achieve the same or even better precision, comparable accuracy, and lower computation cost. We test this method by experimental decay signals. The results are in agreement with the ones obtained from the nonlinear least square fitting method.展开更多
A novel series of Ce^3＋-doped Yb3 Al（5-x）GaxO（12）（x = 0, 1,2, 3,4, 5） powders of ytterbium aluminum gallium garnets were synthesized by high temperature solid-state reaction in a carbon reducing atmosphere. The...A novel series of Ce^3＋-doped Yb3 Al（5-x）GaxO（12）（x = 0, 1,2, 3,4, 5） powders of ytterbium aluminum gallium garnets were synthesized by high temperature solid-state reaction in a carbon reducing atmosphere. The ytterbium aluminum garnets were characterized by X-ray powder diffraction, UV-Vis diffuse reflectance spectra, photoluminescence spectra and decay curves. Moreover, the substitution effect for the Al^3＋ sites with Ga^3＋ in 0.5 at%Ce：Yb3 Al（5-x）GaxO（12）（x = 0,1, 2, 3, 4, 5） garnets were discussed. With the increase of Ga^3＋ ion concentration, the visible absorption peaks within 400-450 nm have blue shift phenomenon,while the absorption peaks in the range of 330-350 nm and the absorption band edge red shifts.Furthermore, the short decay times are very short with less than 10 ns due to the Yb^3＋ ＋ Ce^3＋→ Yb^2＋ ＋ Ce^4＋ electron transfer reaction.展开更多
In this review article, we present recent developments and improvements in magnetic resonance sounding （MRS）, a newly established geophysical exploration method that provides unique information about hydrogeophysica...In this review article, we present recent developments and improvements in magnetic resonance sounding （MRS）, a newly established geophysical exploration method that provides unique information about hydrogeophysical properties due to its direct sensitivity to hydrogen protons and proton dynamics. Starting with the most sophisticated and complete MRS formulation, we give a detailed view on how to solve the equation, i.e., inverting exactly for all model parameters： water content, decay time, and resistivity. Giving a short review of general inversion schemes used in geophysics, the special properties of MRS inversion are evaluated and the development of MRS inversion over recent years is shown. We present the extension of MRS to magnetic resonance tomography （MRT）, i.e., the extension to two-dimensional investigations and appropriate inversions. Finally, we address restrictions, limitations, and inconsistencies as well as future developments.展开更多
The photoplethysmogram(PPG) of a pulse wave,similar in appearance to the arterial blood pressure(ABP) waveform,contains rich information about the cardiovascular system.The decay time constant RC,equal to the product ...The photoplethysmogram(PPG) of a pulse wave,similar in appearance to the arterial blood pressure(ABP) waveform,contains rich information about the cardiovascular system.The decay time constant RC,equal to the product of peripheral resistance R and total arterial compliance C,is a meaningful cardiovascular model parameter in vascular assessment.Using or ameliorating the existing ABP methods does not achieve a satisfactory estimation of RC from the PPG volume pulse(VRC).Thus,a novel non-iterative shape method(NSM) of evaluating VRC is introduced in this paper.The mathematic expression between a novel,readily available morphological parameter called the area difference ratio(ADR) and VRC was established.As it was difficult to calculate VRC from the complicated expression analytically,we recommend estimating it using a piecewise linear interpolation criterion.Also,since the effect of the PPG magnitude is eliminated in the calculation of ADR,precaliberation or normalization is dispensable in the NSM.Results of human experiments indicated that the NSM was computationally efficient,and the simulation experiments confirmed that the NSM was theoretically available for ABP.展开更多
We study the theoretical effect of k-cubic （i.e, cubic-in-momentum） Dresselhaus spin-orbit coupling on the decay time of persistent spin helix states in semiconductor two-dimensional electron gases. We show that the...We study the theoretical effect of k-cubic （i.e, cubic-in-momentum） Dresselhaus spin-orbit coupling on the decay time of persistent spin helix states in semiconductor two-dimensional electron gases. We show that the decay time of persistent spin helix states may be suppressed substantially by k-cubic Dresselhaus spin-orbit coupling, and after taking the effect of k-cubic Dresselhaus spin-orbit interaction into account, the theoretical results obtained accord both qualitatively and quantitatively with other recent experimental results.展开更多
We developed a procedure to prepare luminescent LiYF_(4):Yb/LiYF_(4) and LiYF_(4):Yb,Er/LiYF_(4) core/shell nanocrystals with a size of approximately 40 nm revealing luminescence decay times of the dopant ions that ap...We developed a procedure to prepare luminescent LiYF_(4):Yb/LiYF_(4) and LiYF_(4):Yb,Er/LiYF_(4) core/shell nanocrystals with a size of approximately 40 nm revealing luminescence decay times of the dopant ions that approach those of high-quality laser crystals of LiYF_(4):Yb(Yb:YLF)and LiYF_(4):Yb,Er(Yb,Er:YLF)with identical doping concentrations.As the luminescence decay times of Yb^(3+)and Er^(3+)are known to be very sensitive to the presence of quenchers,the long decay times of the core/shell nanocrystals indicate a very low number of defects in the core particles and at the core/shell interfaces.This improvement in the performance was achieved by introducing two important modifications in the commonly used oleic acid based synthesis.First,the shell was prepared via a newly developed method characterized by a very low nucleation rate for particles of pure LiYF_(4) shell material.Second,anhydrous acetates were used as precursors and additional drying steps were applied to reduce the incorporation of OH−in the crystal lattice,known to quench the emission of Yb^(3+)ions.Excitation power density(P)-dependent absolute measurements of the upconversion luminescence quantum yield(ΦUC)of LiYF_(4):Yb,Er/LiYF_(4) core/shell particles reveal a maximum value of 1.25%at P of 180 W·cm^(−2).Although lower than the values reported for NaYF4:18%Yb,2%Er core/shell nanocrystals with comparable sizes,theseΦUC values are the highest reported so far for LiYF_(4):18%Yb,2%Er/LiYF_(4) nanocrystals without additional dopants.Further improvements may nevertheless be possible by optimizing the dopant concentrations in the LiYF_(4) nanocrystals.展开更多
In this paper, we first show the global existence, uniqueness and regularity of weak solutions for the hyperbolic magnetohydrodynamics(MHD) equations in R^3. Then we establish that the solutions with initial data belo...In this paper, we first show the global existence, uniqueness and regularity of weak solutions for the hyperbolic magnetohydrodynamics(MHD) equations in R^3. Then we establish that the solutions with initial data belonging to H^m(R^3) ∩ L^1(R^3) have the following time decay rate:║▽~mu(x, t) ║~2+║ ▽~mb(x, t)║~ 2+ ║▽^(m+1)u(x, t)║~ 2+ ║▽^(m+1)b(x, t) ║~2≤ c(1 + t)^(-3/2-m)for large t, where m = 0, 1.展开更多
In this paper, we show the existence and regularity of mild solutions depending on the small initial data in Besov spaces to the fractional porous medium equation. When 1 < <em>α</em> ≤ 2, we prove gl...In this paper, we show the existence and regularity of mild solutions depending on the small initial data in Besov spaces to the fractional porous medium equation. When 1 < <em>α</em> ≤ 2, we prove global well-posedness for initial data <img src="Edit_b7b43d4c-00d8-49d6-9066-97151fb5c337.bmp" alt="" /> with 1 ≤ <em>p</em> < ∞, 1 ≤ <em>q</em> ≤ ∞, and analyticity of solutions with 1 < <em>p</em> < ∞, 1 ≤ <em>q</em> ≤ ∞. In particular, we also proved that when <em>α</em> = 1, both <em>u</em> and <img src="Edit_a5af0853-8adc-4a08-b8a2-b9a70ea0f409.bmp" alt="" /> belong to <img src="Edit_03a932cc-aa58-4568-83ad-f16416cc7b71.bmp" alt="" />. We solve this equation through the contraction mapping method based on Littlewood-Paley theory and Fourier multiplier. Furthermore, we can get time decay estimates of global solutions in Besov spaces, which is <img src="Edit_083986e9-4e1c-4494-ac5d-a7d30a12df97.bmp" alt="" /> as <em>t</em> → ∞.展开更多
In this study,we comprehensively characterized and optimized a cryogenic pure CsI(pCsI)detector.We utilized a 2 cm×2 cm×2 cm cube crystal coupled with a HAMAMATSU R11065 photomultiplier tube,achieving a rema...In this study,we comprehensively characterized and optimized a cryogenic pure CsI(pCsI)detector.We utilized a 2 cm×2 cm×2 cm cube crystal coupled with a HAMAMATSU R11065 photomultiplier tube,achieving a remarkable light yield of 35.2 PE/ke V_(ee)and an unprecedented energy resolution of 6.9%at 59.54 ke V.Additionally,we measured the scintillation decay time of pCsI,which was significantly shorter than that of CsI(Na)at room temperature.Furthermore,we investigated the impact of temperature,surface treatment and crystal shape on light yield.Notably,the light yield peaked at approximately 20 K and remained stable within the range of 70–100 K.The light yield of the polished crystals was approximately 1.5 times greater than that of the ground crystals,whereas the crystal shape exhibited minimal influence on the light yield.These results are crucial for the design of the 10 kg pCsI detector for the future CLOVERS(coherent elastic neutrino(V)-nucleus scattering at China Spallation Neutron Source(CSNS))experiment.展开更多
This study investigates the effect of the magnetic field on the transient density of excess minority charge carriers in the base of a series-connected vertical junction silicon solar cell. The solar cell is presented ...This study investigates the effect of the magnetic field on the transient density of excess minority charge carriers in the base of a series-connected vertical junction silicon solar cell. The solar cell is presented in open circuit transient operation. The magnetic field through the Laplace force which deflects the photogenerated carriers from their initial trajectory towards the lateral surfaces reducing their mobility, diffusion and conduction, will certainly influence the decay time of the transient regime. The transient density of excess minority carriers in the base is a sum of infinite terms whose decay time of the different harmonics is studied.展开更多
In this paper,we study the global existence and decay rates of strong solutions to the three dimensional compressible Phan-Thein-Tanner model.By a refined energy method,we prove the global existence under the assumpti...In this paper,we study the global existence and decay rates of strong solutions to the three dimensional compressible Phan-Thein-Tanner model.By a refined energy method,we prove the global existence under the assumption that the H^(3) norm of the initial data is small,but that the higher order derivatives can be large.If the initial data belong to homogeneous Sobolev spaces or homogeneous Besov spaces,we obtain the time decay rates of the solution and its higher order spatial derivatives.Moreover,we also obtain the usual L^(p)-L^(2)(1≤p≤2)type of the decay rate without requiring that the Lpnorm of initial data is small.展开更多
In this paper, we study the non-isentropic compressible magnetohydrodynamic system with a time periodic external force in R^n. Under the condition that the optimal time decay rates are obtained by spectral analysis, w...In this paper, we study the non-isentropic compressible magnetohydrodynamic system with a time periodic external force in R^n. Under the condition that the optimal time decay rates are obtained by spectral analysis, we show that the existence, uniqueness and time-asymptotic stability of time periodic solutions when the space dimension n 〉 5. Our proof is based on a combination of the energy method and the contraction mapping theorem.展开更多
We consider the global existence and decay of integral solutions to the parabolic-parabolic Keller-Segel system in d-dimension.On the one hand,by Banach fixed point theorem and some properties of heat kernel,we prove ...We consider the global existence and decay of integral solutions to the parabolic-parabolic Keller-Segel system in d-dimension.On the one hand,by Banach fixed point theorem and some properties of heat kernel,we prove the local existence and the global existence of integral solutions for the different initial data under some conditions that involve the size of the initial data.On the other hand,in the case of global solutions,we obtain their optimal time decay by Gronwall’s lemma.展开更多
In this manuscript,we consider two kinds of the Fokker-Planck-type systems in the whole space.The first part involves proving the global existence and the algebraic time decay rates of the mild solutions to the Fokker...In this manuscript,we consider two kinds of the Fokker-Planck-type systems in the whole space.The first part involves proving the global existence and the algebraic time decay rates of the mild solutions to the Fokker-Planck-Boltzmann equation near Maxwellians if initial data satisfies some smallness in the function space L_(k)^(1)L_(T)^(∞)L_(v)^(2)∩L_(k)^(p)L_(T)^(∞)L_(v)^(2).The second part proves the global existence of the mild solutions to the Vlasov-Poisson-Fokker-Planck system in the function space L_(k)^(1)L_(T)^(∞)L_(v)^(2),and we also obtain the exponential time decay rates,which are different from the algebraic time decay rates of the Fokker-Planck-Boltzmann equation.Our analysis is based on Lk1LT∞Lv2function space introduced by Duan et al.(Comm Pure Appl Math,2021,74:932-1020),the L_(k)^(1)∩L_(k)^(p) approach developed by Duan et al.(SIAM J Math Anal,2024,56:762-800),and the coercivity property of the Fokker-Planck operator.However,it is worth pointing out that the L_(k)^(1)∩L_(k)^(p)approach is not required for the Vlasov-Poisson-Fokker-Planck system,due to the influence of the electric field term,which is different from the Fokker-Planck-Boltzmann equation in this paper and in the work of Duan et al.(SIAM J Math Anal,2024,56:762-800).展开更多
Oxygen/glucose deprivation （OGD） has been widely used as an in vitro model of focal ischemia, where the blood flow is severely reduced and neurons rapidly die. However, adjacent to the focal region is ‘penumbra＇, ...Oxygen/glucose deprivation （OGD） has been widely used as an in vitro model of focal ischemia, where the blood flow is severely reduced and neurons rapidly die. However, adjacent to the focal region is ‘penumbra＇, where residual blood flow remains oxygen and glucose supplies are at low levels. To model this pathological genesis, we developed a partial OGD （pOGD） protocol in a rat brain slice. This model met two requirements： oxygen was partially deprived and glucose was reduced in the perfusion buffer. Therefore we investigated the effect of pOGD on gama-aminobutyric acid （GABAA） receptor-mediated inhibitory postsynaptic currents （IPSCs） in CA1 neurons of a hippocampal slice through whole-cell patch-clamp technique. We found that the amplitude and decay time of IPSCs were increased immediately during pOGD treatment. And the enhancement of IPSCs amplitude resulted from an increase of the synaptic conductance without a significant change in the reversal potential of chloride. These results suggested that the nervous system could increase inhibitory neurotransmission to offset excitation by homeostasis mechanisms during the partial oxygen and glucose attack.展开更多
A novel red-emitting K2（Ge,Si）F6：Mn^4＋ phosphor with uniform morphology was synthesized by co-precipitation method. The pure K2GeF6 phase with P63 mc space group other than P3m1 space group was affirmed just by in...A novel red-emitting K2（Ge,Si）F6：Mn^4＋ phosphor with uniform morphology was synthesized by co-precipitation method. The pure K2GeF6 phase with P63 mc space group other than P3m1 space group was affirmed just by incorporation of Si in K2GeF6 at room temperature according to XRD characterization. SEM images showed lamellar and octahedron grain morphology for K2GeF6：Mn^4＋ and K2（Ge,Si）F6：Mn^4＋ phosphors, respectively. It was also found that the photoluminescence excitation（PLE） and photoluminescence（PL） showed slight displacement in K2GeF6：Mn^4＋ and K2（Ge,Si）F6：Mn^4＋ system. And the zero-phonon line（ZPL） of the PL spectrum of K2GeF6：Mn^4＋ with Si showed a strong peak. Meanwhile crystalline field surrounding Mn^4＋ changes could affect the decay time in this fluoride system. The color gamut of the LED devices based on K2（Ge,Si）F6：Mn^4＋ and K2GeF6：Mn^4＋ reached up to 94.58% NTSC（National Television Standards Committee） and 94.386% NTSC, respectively, that was much higher than that based on nitride red phosphors. All these original characteristics in K2（Ge,Si）F6：Mn^4＋ phosphor are desirable for potential applications as a red phosphor for improving lighting and display quality of conventional white LEDs.展开更多
Eu3＋ doped borophosphate glasses with the chemical composition 20Li2O-30Al2O3-10B2O3-40P2O5-xEu2O3（where x=0.05 mol.%, 0.1 mol.%, 1.0 mol.%, 1.5 mol.% and 2.0 mol.%） were prepared by conventional melt quenching tec...Eu3＋ doped borophosphate glasses with the chemical composition 20Li2O-30Al2O3-10B2O3-40P2O5-xEu2O3（where x=0.05 mol.%, 0.1 mol.%, 1.0 mol.%, 1.5 mol.% and 2.0 mol.%） were prepared by conventional melt quenching technique. The structural and luminescence properties of the prepared Eu3＋ doped borophosphate glasses were studied and compared with reported results. The XRD pattern showed the amorphous nature of the prepared glasses. Whereas, the FTIR spectra revealed the vibrational modes in the prepared glasses. The bonding parameters（ β and ？） were calculated through the excitation spectra. Judd-Ofelt（J-O） intensity parameters were calculated from the emission spectra and were used to determine transition probability（A）, stimulated emission cross-section（σE P）, radiative lifetime（τR） and branching ratios（βexp） for the transition 5D0→7Fj（j=1, 2, 3 and 4） of Eu3＋ ions. Furthermore, the luminescence intensity ratio（R） of 5D0→7F2 to 5D0→7F1 transition was also calculated. Transition 5D0→7F2 had the highest value of stimulated emission cross-section and branching ratios and the results were comparable with the reported values. This indicated that the present glass is promising host material for Eu3＋ doped fiber amplifiers.展开更多
In this article upconversion luminescence of silver nanoparticles（AgNPs） coated NaYF4：Er3＋/Yb3＋phosphor nano-particles was investigated.The prepared samples were characterized through various techniques.The surfa...In this article upconversion luminescence of silver nanoparticles（AgNPs） coated NaYF4：Er3＋/Yb3＋phosphor nano-particles was investigated.The prepared samples were characterized through various techniques.The surface plasmon band is observed for prepared AgNPs by analyzing UV-vis measurements and is used to enhance the upconversion emission.From the upconversion measurement the emission bands are observed at 522,546,and 656 nm corresponding to the 2 H11/2→ 4115/2,4 S3/2→4 I15/2and 4 F9/2→4 I15/2 levels,respectively.The upconversion emission intensity of the above bands is found to enhance for sample containing 1 mmol AgNPs.Decay time of 4 S3/2 and 4F9/2 levels is found to decrease on coating of AgNPs and hence intensity enhancement is assumed due to the surface plasmon resonance（SPR） effect.展开更多
The single crystal of this compound has been grown from melt by using a conventional Czochralski technique. The temperature dependent luminescence spectra were measured using a 265 nm laser as an exciting source in th...The single crystal of this compound has been grown from melt by using a conventional Czochralski technique. The temperature dependent luminescence spectra were measured using a 265 nm laser as an exciting source in the range of 10-300 K. The scintillation decay time profile was measured and found to have three components. The influence of the trap centers on the luminescence properties was studied by means of thermoluminescence（TL） glow peak analysis. Low temperature TL glow peaks were measured in the temperature range of 10-300 K at the heating rate of 0.1 K/s for X-ray irradiated sample. The TL glow peak consists of two dominant peaks at 88 and 109 K. Several glow peaks with a complex nature causes the decrease in the light yield at temperatures below 250 K, and along with long scintillation decay components were observed. The trap parameters such as activation energy（E）, frequency factor（s）and order of kinetics（b） were calculated using various standard methods such as peak shape（PS）,variable heating rate（VHR）, initial rise（IR） and computerized glow curve deconvolution（CGCD）.展开更多
Upconversion （UC） phosphor Tm3＋ doped YF3 nano-erystals were prepared by hydrothermal method under different conditions and characterized by Field Transmission electron microscopy （TEM）, Scanning electron microsc...Upconversion （UC） phosphor Tm3＋ doped YF3 nano-erystals were prepared by hydrothermal method under different conditions and characterized by Field Transmission electron microscopy （TEM）, Scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Their UC luminescence properties were studied by fluorescence spectrophotometer with 980 nm diode laser excitation, and impact of different grain sizes and morphology on the UC luminescence intensity was discussed. The fluorescence decay lifetime was calculated by Multi-exponential function fitting method. Results show that UC emission intensity was enhanced with the reduction of grain size, and the decay lifetime is 0.60 us.展开更多
基金supported by the Preeminent Youth Fund of Sichuan Province,China(Grant No.2012JQ0012)the National Natural Science Foundation of China(Grant Nos.11173008,10974202,and 60978049)the National Key Scientific and Research Equipment Development Project of China(Grant No.ZDYZ2013-2)
文摘For the accurate extraction of cavity decay time, a selection of data points is supplemented to the weighted least square method. We derive the expected precision, accuracy and computation cost of this improved method, and examine these performances by simulation. By comparing this method with the nonlinear least square fitting （NLSF） method and the linear regression of the sum （LRS） method in derivations and simulations, we find that this method can achieve the same or even better precision, comparable accuracy, and lower computation cost. We test this method by experimental decay signals. The results are in agreement with the ones obtained from the nonlinear least square fitting method.
基金Project supported by National Natural Science Foundation of China(11475242,51272263)K.C.Wong Magna Fund in Ningbo University
文摘A novel series of Ce^3＋-doped Yb3 Al（5-x）GaxO（12）（x = 0, 1,2, 3,4, 5） powders of ytterbium aluminum gallium garnets were synthesized by high temperature solid-state reaction in a carbon reducing atmosphere. The ytterbium aluminum garnets were characterized by X-ray powder diffraction, UV-Vis diffuse reflectance spectra, photoluminescence spectra and decay curves. Moreover, the substitution effect for the Al^3＋ sites with Ga^3＋ in 0.5 at%Ce：Yb3 Al（5-x）GaxO（12）（x = 0,1, 2, 3, 4, 5） garnets were discussed. With the increase of Ga^3＋ ion concentration, the visible absorption peaks within 400-450 nm have blue shift phenomenon,while the absorption peaks in the range of 330-350 nm and the absorption band edge red shifts.Furthermore, the short decay times are very short with less than 10 ns due to the Yb^3＋ ＋ Ce^3＋→ Yb^2＋ ＋ Ce^4＋ electron transfer reaction.
基金supported by the German Scientific Council as part of a program on Magnetic Resonance
文摘In this review article, we present recent developments and improvements in magnetic resonance sounding （MRS）, a newly established geophysical exploration method that provides unique information about hydrogeophysical properties due to its direct sensitivity to hydrogen protons and proton dynamics. Starting with the most sophisticated and complete MRS formulation, we give a detailed view on how to solve the equation, i.e., inverting exactly for all model parameters： water content, decay time, and resistivity. Giving a short review of general inversion schemes used in geophysics, the special properties of MRS inversion are evaluated and the development of MRS inversion over recent years is shown. We present the extension of MRS to magnetic resonance tomography （MRT）, i.e., the extension to two-dimensional investigations and appropriate inversions. Finally, we address restrictions, limitations, and inconsistencies as well as future developments.
基金Project (No.81070885) supported by the National Natural Science Foundation of China
文摘The photoplethysmogram(PPG) of a pulse wave,similar in appearance to the arterial blood pressure(ABP) waveform,contains rich information about the cardiovascular system.The decay time constant RC,equal to the product of peripheral resistance R and total arterial compliance C,is a meaningful cardiovascular model parameter in vascular assessment.Using or ameliorating the existing ABP methods does not achieve a satisfactory estimation of RC from the PPG volume pulse(VRC).Thus,a novel non-iterative shape method(NSM) of evaluating VRC is introduced in this paper.The mathematic expression between a novel,readily available morphological parameter called the area difference ratio(ADR) and VRC was established.As it was difficult to calculate VRC from the complicated expression analytically,we recommend estimating it using a piecewise linear interpolation criterion.Also,since the effect of the PPG magnitude is eliminated in the calculation of ADR,precaliberation or normalization is dispensable in the NSM.Results of human experiments indicated that the NSM was computationally efficient,and the simulation experiments confirmed that the NSM was theoretically available for ABP.
基金Project supported by the National Natural Science Foundation of China (Grant No.10874049)
文摘We study the theoretical effect of k-cubic （i.e, cubic-in-momentum） Dresselhaus spin-orbit coupling on the decay time of persistent spin helix states in semiconductor two-dimensional electron gases. We show that the decay time of persistent spin helix states may be suppressed substantially by k-cubic Dresselhaus spin-orbit coupling, and after taking the effect of k-cubic Dresselhaus spin-orbit interaction into account, the theoretical results obtained accord both qualitatively and quantitatively with other recent experimental results.
基金We thank the German Science Foundation DFG for financial support(grants RE 1203/18-1 and HA 1649/7-1).
文摘We developed a procedure to prepare luminescent LiYF_(4):Yb/LiYF_(4) and LiYF_(4):Yb,Er/LiYF_(4) core/shell nanocrystals with a size of approximately 40 nm revealing luminescence decay times of the dopant ions that approach those of high-quality laser crystals of LiYF_(4):Yb(Yb:YLF)and LiYF_(4):Yb,Er(Yb,Er:YLF)with identical doping concentrations.As the luminescence decay times of Yb^(3+)and Er^(3+)are known to be very sensitive to the presence of quenchers,the long decay times of the core/shell nanocrystals indicate a very low number of defects in the core particles and at the core/shell interfaces.This improvement in the performance was achieved by introducing two important modifications in the commonly used oleic acid based synthesis.First,the shell was prepared via a newly developed method characterized by a very low nucleation rate for particles of pure LiYF_(4) shell material.Second,anhydrous acetates were used as precursors and additional drying steps were applied to reduce the incorporation of OH−in the crystal lattice,known to quench the emission of Yb^(3+)ions.Excitation power density(P)-dependent absolute measurements of the upconversion luminescence quantum yield(ΦUC)of LiYF_(4):Yb,Er/LiYF_(4) core/shell particles reveal a maximum value of 1.25%at P of 180 W·cm^(−2).Although lower than the values reported for NaYF4:18%Yb,2%Er core/shell nanocrystals with comparable sizes,theseΦUC values are the highest reported so far for LiYF_(4):18%Yb,2%Er/LiYF_(4) nanocrystals without additional dopants.Further improvements may nevertheless be possible by optimizing the dopant concentrations in the LiYF_(4) nanocrystals.
基金Supported by NSFC(11271290)GSPT of Zhejiang Province(2014R424062)
文摘In this paper, we first show the global existence, uniqueness and regularity of weak solutions for the hyperbolic magnetohydrodynamics(MHD) equations in R^3. Then we establish that the solutions with initial data belonging to H^m(R^3) ∩ L^1(R^3) have the following time decay rate:║▽~mu(x, t) ║~2+║ ▽~mb(x, t)║~ 2+ ║▽^(m+1)u(x, t)║~ 2+ ║▽^(m+1)b(x, t) ║~2≤ c(1 + t)^(-3/2-m)for large t, where m = 0, 1.
文摘In this paper, we show the existence and regularity of mild solutions depending on the small initial data in Besov spaces to the fractional porous medium equation. When 1 < <em>α</em> ≤ 2, we prove global well-posedness for initial data <img src="Edit_b7b43d4c-00d8-49d6-9066-97151fb5c337.bmp" alt="" /> with 1 ≤ <em>p</em> < ∞, 1 ≤ <em>q</em> ≤ ∞, and analyticity of solutions with 1 < <em>p</em> < ∞, 1 ≤ <em>q</em> ≤ ∞. In particular, we also proved that when <em>α</em> = 1, both <em>u</em> and <img src="Edit_a5af0853-8adc-4a08-b8a2-b9a70ea0f409.bmp" alt="" /> belong to <img src="Edit_03a932cc-aa58-4568-83ad-f16416cc7b71.bmp" alt="" />. We solve this equation through the contraction mapping method based on Littlewood-Paley theory and Fourier multiplier. Furthermore, we can get time decay estimates of global solutions in Besov spaces, which is <img src="Edit_083986e9-4e1c-4494-ac5d-a7d30a12df97.bmp" alt="" /> as <em>t</em> → ∞.
基金supported by the National Key R&D Program of China(No.2022YFA1602204)the National Natural Science Foundation of China(Nos.12175241,12221005)+2 种基金the Fundamental Research Funds for the Central Universitiesthe International Partnership Program of the Chinese Academy of Sciences(No.211134KYSB20200057)the Double First-Class University Project Foundation of USTC。
文摘In this study,we comprehensively characterized and optimized a cryogenic pure CsI(pCsI)detector.We utilized a 2 cm×2 cm×2 cm cube crystal coupled with a HAMAMATSU R11065 photomultiplier tube,achieving a remarkable light yield of 35.2 PE/ke V_(ee)and an unprecedented energy resolution of 6.9%at 59.54 ke V.Additionally,we measured the scintillation decay time of pCsI,which was significantly shorter than that of CsI(Na)at room temperature.Furthermore,we investigated the impact of temperature,surface treatment and crystal shape on light yield.Notably,the light yield peaked at approximately 20 K and remained stable within the range of 70–100 K.The light yield of the polished crystals was approximately 1.5 times greater than that of the ground crystals,whereas the crystal shape exhibited minimal influence on the light yield.These results are crucial for the design of the 10 kg pCsI detector for the future CLOVERS(coherent elastic neutrino(V)-nucleus scattering at China Spallation Neutron Source(CSNS))experiment.
文摘This study investigates the effect of the magnetic field on the transient density of excess minority charge carriers in the base of a series-connected vertical junction silicon solar cell. The solar cell is presented in open circuit transient operation. The magnetic field through the Laplace force which deflects the photogenerated carriers from their initial trajectory towards the lateral surfaces reducing their mobility, diffusion and conduction, will certainly influence the decay time of the transient regime. The transient density of excess minority carriers in the base is a sum of infinite terms whose decay time of the different harmonics is studied.
基金partially supported by the National Natural Science Foundation of China(11926354,11971496)Natural Science Foundation of Guangdong Province(2019A1515011320,2021A1515010292,2214050001249)+2 种基金Innovative team project of ordinary universities of Guangdong Province(2020KCXTD024)Characteristic innovation projects of ordinary colleges and universities in Guangdong Province(2020KTSCX134)the Education Research Platform Project of Guangdong Province(2018179)。
文摘In this paper,we study the global existence and decay rates of strong solutions to the three dimensional compressible Phan-Thein-Tanner model.By a refined energy method,we prove the global existence under the assumption that the H^(3) norm of the initial data is small,but that the higher order derivatives can be large.If the initial data belong to homogeneous Sobolev spaces or homogeneous Besov spaces,we obtain the time decay rates of the solution and its higher order spatial derivatives.Moreover,we also obtain the usual L^(p)-L^(2)(1≤p≤2)type of the decay rate without requiring that the Lpnorm of initial data is small.
基金Supported by National Natural Science Foundation of China(11271305)
文摘In this paper, we study the non-isentropic compressible magnetohydrodynamic system with a time periodic external force in R^n. Under the condition that the optimal time decay rates are obtained by spectral analysis, we show that the existence, uniqueness and time-asymptotic stability of time periodic solutions when the space dimension n 〉 5. Our proof is based on a combination of the energy method and the contraction mapping theorem.
文摘We consider the global existence and decay of integral solutions to the parabolic-parabolic Keller-Segel system in d-dimension.On the one hand,by Banach fixed point theorem and some properties of heat kernel,we prove the local existence and the global existence of integral solutions for the different initial data under some conditions that involve the size of the initial data.On the other hand,in the case of global solutions,we obtain their optimal time decay by Gronwall’s lemma.
基金supported by the National Natural Science Foundation of China(11801285,12326337)。
文摘In this manuscript,we consider two kinds of the Fokker-Planck-type systems in the whole space.The first part involves proving the global existence and the algebraic time decay rates of the mild solutions to the Fokker-Planck-Boltzmann equation near Maxwellians if initial data satisfies some smallness in the function space L_(k)^(1)L_(T)^(∞)L_(v)^(2)∩L_(k)^(p)L_(T)^(∞)L_(v)^(2).The second part proves the global existence of the mild solutions to the Vlasov-Poisson-Fokker-Planck system in the function space L_(k)^(1)L_(T)^(∞)L_(v)^(2),and we also obtain the exponential time decay rates,which are different from the algebraic time decay rates of the Fokker-Planck-Boltzmann equation.Our analysis is based on Lk1LT∞Lv2function space introduced by Duan et al.(Comm Pure Appl Math,2021,74:932-1020),the L_(k)^(1)∩L_(k)^(p) approach developed by Duan et al.(SIAM J Math Anal,2024,56:762-800),and the coercivity property of the Fokker-Planck operator.However,it is worth pointing out that the L_(k)^(1)∩L_(k)^(p)approach is not required for the Vlasov-Poisson-Fokker-Planck system,due to the influence of the electric field term,which is different from the Fokker-Planck-Boltzmann equation in this paper and in the work of Duan et al.(SIAM J Math Anal,2024,56:762-800).
文摘Oxygen/glucose deprivation （OGD） has been widely used as an in vitro model of focal ischemia, where the blood flow is severely reduced and neurons rapidly die. However, adjacent to the focal region is ‘penumbra＇, where residual blood flow remains oxygen and glucose supplies are at low levels. To model this pathological genesis, we developed a partial OGD （pOGD） protocol in a rat brain slice. This model met two requirements： oxygen was partially deprived and glucose was reduced in the perfusion buffer. Therefore we investigated the effect of pOGD on gama-aminobutyric acid （GABAA） receptor-mediated inhibitory postsynaptic currents （IPSCs） in CA1 neurons of a hippocampal slice through whole-cell patch-clamp technique. We found that the amplitude and decay time of IPSCs were increased immediately during pOGD treatment. And the enhancement of IPSCs amplitude resulted from an increase of the synaptic conductance without a significant change in the reversal potential of chloride. These results suggested that the nervous system could increase inhibitory neurotransmission to offset excitation by homeostasis mechanisms during the partial oxygen and glucose attack.
基金Project supported by the Major State Basic Research Development Program of China(National Basic Research Program of China)(2014CB643801973)
文摘A novel red-emitting K2（Ge,Si）F6：Mn^4＋ phosphor with uniform morphology was synthesized by co-precipitation method. The pure K2GeF6 phase with P63 mc space group other than P3m1 space group was affirmed just by incorporation of Si in K2GeF6 at room temperature according to XRD characterization. SEM images showed lamellar and octahedron grain morphology for K2GeF6：Mn^4＋ and K2（Ge,Si）F6：Mn^4＋ phosphors, respectively. It was also found that the photoluminescence excitation（PLE） and photoluminescence（PL） showed slight displacement in K2GeF6：Mn^4＋ and K2（Ge,Si）F6：Mn^4＋ system. And the zero-phonon line（ZPL） of the PL spectrum of K2GeF6：Mn^4＋ with Si showed a strong peak. Meanwhile crystalline field surrounding Mn^4＋ changes could affect the decay time in this fluoride system. The color gamut of the LED devices based on K2（Ge,Si）F6：Mn^4＋ and K2GeF6：Mn^4＋ reached up to 94.58% NTSC（National Television Standards Committee） and 94.386% NTSC, respectively, that was much higher than that based on nitride red phosphors. All these original characteristics in K2（Ge,Si）F6：Mn^4＋ phosphor are desirable for potential applications as a red phosphor for improving lighting and display quality of conventional white LEDs.
基金Project supported by the Ministry of Higher Education(MOHE),the Ministry of Science,Technology and Innovation(MOSTI)and Universiti Teknologi Malaysia via Research University Grant Project(R.J130000.7826.4F140)Nanofund Grant(J.130000.7926.4H007)
文摘Eu3＋ doped borophosphate glasses with the chemical composition 20Li2O-30Al2O3-10B2O3-40P2O5-xEu2O3（where x=0.05 mol.%, 0.1 mol.%, 1.0 mol.%, 1.5 mol.% and 2.0 mol.%） were prepared by conventional melt quenching technique. The structural and luminescence properties of the prepared Eu3＋ doped borophosphate glasses were studied and compared with reported results. The XRD pattern showed the amorphous nature of the prepared glasses. Whereas, the FTIR spectra revealed the vibrational modes in the prepared glasses. The bonding parameters（ β and ？） were calculated through the excitation spectra. Judd-Ofelt（J-O） intensity parameters were calculated from the emission spectra and were used to determine transition probability（A）, stimulated emission cross-section（σE P）, radiative lifetime（τR） and branching ratios（βexp） for the transition 5D0→7Fj（j=1, 2, 3 and 4） of Eu3＋ ions. Furthermore, the luminescence intensity ratio（R） of 5D0→7F2 to 5D0→7F1 transition was also calculated. Transition 5D0→7F2 had the highest value of stimulated emission cross-section and branching ratios and the results were comparable with the reported values. This indicated that the present glass is promising host material for Eu3＋ doped fiber amplifiers.
基金Project supported by the Indian Institute of Technology(Indian School of Mines),Dhanbad,Indiathe Council of Scientific&Industrial Research(CSIR),New Delhi,India(03(1303)13/EMR)
文摘In this article upconversion luminescence of silver nanoparticles（AgNPs） coated NaYF4：Er3＋/Yb3＋phosphor nano-particles was investigated.The prepared samples were characterized through various techniques.The surface plasmon band is observed for prepared AgNPs by analyzing UV-vis measurements and is used to enhance the upconversion emission.From the upconversion measurement the emission bands are observed at 522,546,and 656 nm corresponding to the 2 H11/2→ 4115/2,4 S3/2→4 I15/2and 4 F9/2→4 I15/2 levels,respectively.The upconversion emission intensity of the above bands is found to enhance for sample containing 1 mmol AgNPs.Decay time of 4 S3/2 and 4F9/2 levels is found to decrease on coating of AgNPs and hence intensity enhancement is assumed due to the surface plasmon resonance（SPR） effect.
基金Project supported by the National Research Foundation of Korea(NRF) funded by the Ministry of Science and Technology,Korea(MEST)(NRF2017M2A8A4018678)
文摘The single crystal of this compound has been grown from melt by using a conventional Czochralski technique. The temperature dependent luminescence spectra were measured using a 265 nm laser as an exciting source in the range of 10-300 K. The scintillation decay time profile was measured and found to have three components. The influence of the trap centers on the luminescence properties was studied by means of thermoluminescence（TL） glow peak analysis. Low temperature TL glow peaks were measured in the temperature range of 10-300 K at the heating rate of 0.1 K/s for X-ray irradiated sample. The TL glow peak consists of two dominant peaks at 88 and 109 K. Several glow peaks with a complex nature causes the decrease in the light yield at temperatures below 250 K, and along with long scintillation decay components were observed. The trap parameters such as activation energy（E）, frequency factor（s）and order of kinetics（b） were calculated using various standard methods such as peak shape（PS）,variable heating rate（VHR）, initial rise（IR） and computerized glow curve deconvolution（CGCD）.
文摘Upconversion （UC） phosphor Tm3＋ doped YF3 nano-erystals were prepared by hydrothermal method under different conditions and characterized by Field Transmission electron microscopy （TEM）, Scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Their UC luminescence properties were studied by fluorescence spectrophotometer with 980 nm diode laser excitation, and impact of different grain sizes and morphology on the UC luminescence intensity was discussed. The fluorescence decay lifetime was calculated by Multi-exponential function fitting method. Results show that UC emission intensity was enhanced with the reduction of grain size, and the decay lifetime is 0.60 us.
