Time-resolved ultra-small-angle X-ray scattering beamline(BL10U1)at SSRF

The construction of a new beamline,BL10U1,was completed at the Shanghai synchrotron radiation facility in 2020.This multipurpose beamline was designed to provide X-ray scattering techniques such as ultra-small-angle X-ray scattering(USAXS),small-angle X-ray scattering(SAXS),wide-angle X-ray scattering,and microfocus SAXS(μSAXS)for a broad user community.To realize fast time-resolved USAXS experiments,the beamline adopted an in-vacuum undulator with a total length of 1.6 m as the photon source.An in-house cryogenic-cooled double multilayer monochromator was installed to deliver a photon flux of approximately 10^(13) photons/s at a photon energy of 10 keV.The three-year successful operation of this beamline demonstrated that the monochromator operated smoothly,as expected.BL10U1 has three end stations in succession:USAXS end station,μSAXS end station,and end station for industrial applications.The minimum scattering vector q~0.0042 nm^(-1) at 10 keV can be achieved at the USAXS end station equipped with a 28 m-long and 1.8 m-diameter vacuum flight tube.At theμSAXS end station,a beam spot of less than 10×8μm was achieved for micro-SAXS experiments.In contrast,in situ experimental instruments up to 5 m high and 8 m wide can be mounted at the industrial application end station,which offers industrial scientists the opportunity to use their large industrial equipment.BL10U1 opens up a new capability to investigate phenomena such as non-equilibrium and dynamic processes of materials with a wide length scale from angstroms to micrometers with millisecond time resolution.In this paper,we also report beamline design considerations and commissioning results.

New Time-resolved-Tween 80 Chemiluminescent System for Simultaneous Determination of Trace Gold and Osmium

A time resolved chemiluminescent analysis for simultaneous determination of trace Au(Ⅲ) and Os(Ⅳ) was proposed. The method is based on the kinetic distinction of Au(Ⅲ) and Os(Ⅳ) in Tween 80 KOH chemilumescent system. The detection limits were 1.1×10 -9 g/ml for Au(Ⅲ) and 1.0×10 -8 g/ml for Os(Ⅳ), with the linear ranges of 1.0×10 -8 ～1.0×10 -5 g/ml for Au(Ⅲ) and 1.0×10 -7 ～1.0×10 -6 g/ml for Os(Ⅳ). The method was applied to the determination of Au(Ⅲ) and Os(Ⅳ) in the sample of metallurgical materials of noble metals with satisfactory results.

TIME RESOLVED SPECTRA OF Eu(MBA)_3 PHEN COMPLEXES

Time-resolved fluorescence spectra of europium methylbenzoates (MBA)with 1,10-phenanthroline(phen)have been measured at room temperature.For each of the europium chelates,where the ligand triple states lie above the ~5D_1 level of Eu^(3-),the spectra providc evidence that the Eu^(3-) ~5D_0 state is populated by nonradiative energy transfer from the higher-lying ~5D_1,state.The relaxation time for energy decay from ~5D_1 state is measured in the microcrystals to bc of the order of a few microseconds.It is suggested that the ligand C=0 and C=C stretching vibrations and Eu-O vibrations,chclate ring and benzene ring vibrations make important contributions to the relaxation process.The ~5D\-1—~5D\-0 relaxation time of Eu- (p-MBA)_3phen is shorter than those of Eu(m-MBA)_3phen and Eu(o-MBA)_3phen since nonradiative degradation to ~5D_0 from ~5D_1 appears to be more strongly influenced by the E_u^(3+)sites in the former.

垂直及斜出水流场的二维及三维TR-PIV试验

本文对钝头回转体垂直及斜出水流场采用TR-(Time-Resolved)PIV技术进行测量,并对斜出水流场进行3D-StereoPIV(三维体视PIV)测量。文中介绍了测试技术及测量结果,揭示了出水过程中流动结构及其演变,展示了TR-PIV技术对具有瞬态历程特征的出水流场研究的适应性。

Experimental study of the wake characteristics of a two-blade horizontal axis wind turbine by time-resolved PIV

Wind tunnel experiments of the wake characteristics of a two-blade wind turbine, in the downstream region of 0

Fast-sweeping Langmuir probes:what happens to theⅠ–Ⅴtrace when sweeping frequency is higher than the ion plasma frequency?

Limited particle transit time is one of several limiting factors which determine the maximum temporal resolution of a Langmuir probe.In this work,we have revisited the known fast sweep Langmuir probe techniques in a uniform,quiescent multi-dipole confined hot cathode discharge with two operation scenarios:one in which the probe sweeping frequency fsweepis much lower than the ion plasma frequency fpi,another one where fsweepis much greater than fpi,respectively.This allows investigation into the effect of limited ion-motion on I–V traces.Serious distortions of I–V traces at high frequencies,previously claimed to be an ion-motion limitation effect,were not found unless shunt resistance is sufficiently high,despite a f;/f;ratio of~3.On the other hand,evidences of sheath capacitance on the I–V traces have been observed.Distortions of I–V traces qualitatively agree with predictions of sheath capacitance response to the sweeping voltage.Additionally,techniques in fast sweep Langmuir probe are briefly discussed.The comparison between the high-speed dual Langmuir probe(HDLP)and the single probe setup shows that the capacitive response can be removed via subtracting a leakage current for the single probe setup almost as effectively as using the HDLP setup,but the HDLP setup does remain advantageous in its facilitation of better recovery of weak current signal commonly in low density plasma.

Exciton emission dynamics in single InAs/GaAs quantum dots due to the existence of plasmon-field-induced metastable states in the wetting layer

A very long lifetime exciton emission with non-single exponential decay characteristics has been reported for single InA-s/GaAs quantum dot(QD)samples,in which there exists a long-lived metastable state in the wetting layer(WL)through radiative field coupling between the exciton emissions in the WL and the dipole field of metal islands.In this article we have proposed a new three-level model to simulate the exciton emission decay curve.In this model,assuming that the excitons in a metastable state will diffuse and be trapped by QDs,and then emit fluorescence in QDs,a stretchedlike exponential decay formula is derived as I(t)=At^(β−1)e^(−(rt)^(β)),which can describe well the long lifetime decay curve with an analytical expression of average lifetime(τ)=1/rГ(1/β+1),where G is the Gamma function.Furthermore,based on the proposed three-level model,an expression of the second-order auto-correlation function g^(2)(t)which can fit the measured g^(2)(t)curve well,is also obtained.

Kinetics Study on Reaction of Atenolol with Singlet Oxygen by Directly Monitoring the^(1)O_(2)Phosphorescence

The pharmaceuti-cally active com-pound atenolol,a kind of β-blockers,may result in ad-verse effects both for human health and ecosystems if it is excreted to the surface water resources.To e ectively remove atenolol in the environ-ment,both direct and indirect photodegradation,driven by sunlight play an important role.Among indirect photodegradation,singlet oxygen(^(1)O_(2)),as a pivotal reactive species,is likely to determine the fates of atenolol.Nevertheless,the kinetic information on the re-action of atenolol with singlet oxygen has not been well investigated and the reaction rate constant is still ambiguous.Herein,the reaction rate constant of atenolol with singlet oxy-gen is investigated directly through observing the decay of the^(1)O_(2)phosphorescence at 1270 nm.It is determined that the reaction rate constant between atenolol and^(1)O_(2)is 7.0×10^(5)(mol/L)^(-1)·s^(-1)in D2O,8.0×10^(6)(mol/L)^(-1)·s^(-1)in acetonitrile,and 8.4×10^(5)(mol/L)^(-1)·s^(-1)in EtOH,respectively.Furthermore,the solvent effects on the title reaction were also inves-tigated.It is revealed that the solvents with strong polarity and weak hydrogen donating ability are suitable to achieve high rate constant values.These kinetics information on the reaction of atenolol with singlet oxygen may provide fundamental knowledge to the indirect photodegradation of β-blockers.

Temperature dependent terahertz giant anisotropy and cycloidal spin wave modes in BiFeO3 single crystal

THz time-domain spectroscopy(THz-TDS)is used to study the THz-optical properties of a single crystal bismuth ferrite BiFeO3(BFO).It can be found that the anisotropy of BiFeO3 is strongly dependent on the temperature.A giant birefringence up to around 3.6 is observed at 1 THz.The presence of a spatially modulated cycloidal antiferromagnetic structure leads to spin cycloid resonances(SCR)ψandΦ,corresponding to the out-of-plane and in-plane modes of the spin cycloid,respectively.We distinguish the SCR with respect to their response to orthogonal polarizations of the electric fields of the incident THz beam.In addition,we observe a resonance appearing below 140 K,which might be interpreted as an electromagnon mode and related to a spin reorientation transition.Our present observations present that the temperature and polarization,as the external control parameters,can be used to modulate the THz optical properties of BFO single crystal.

DEEP-UV CONFOCAL FLUORESCENCE IMAGING AND SUPER-RESOLUTION OPTICAL MICROSCOPY OF BIOLOGICAL SAMPLES

A wide range of techniques has been developed to image biological samples at high spatial and temporal resolution.In this paper,we report recent results from deep-UV confocal fAuorescence microscopy to image inherent emission from fuorophores such as tryptophan,and structured ilumination microscopy(SIM)of biological materials.One motivation for developing deep-UV fhuorescence imaging and SIM is to provide methods to complement our measurements in the emerging field of X-ray coherent diffractive imaging.

旋转状态边界层速度场及温度场特性实验

针对涡轮转子叶片内冷技术,使用TR-PIV(time resolved particle image velocimetry)技术与热线技术同步原位测量了壁面加热条件下旋转通道内边界层速度场和温度场特性。结果显示:旋转数大于0.48时前缘面附近出现了回流现象,并从受力分析的角度给出了解释;回流区一般出现于流场下游、较大密度比、较高旋转数下,可以利用回流区的影响达到增强前缘面换热的目的;得到了旋转条件下无量纲温度型、温度脉动量和努塞尔数的变化规律,可以看出湍流边界层内部的温度场分布在旋转效应的影响下产生了强烈的不对称性,与静止条件下的标准规律相比会产生一定的偏差。

Effect of a transverse plasma jet on a shock wave induced by a ramp

We conducted experiments in a wind tunnel with Mach number 2 to explore the evolution of a transverse plasma jet and its modification effect on a shock wave induced by a ramp with an angle of 24°. The transverse plasma jet was created by arc discharge in a small cylindrical cavity with a 2 mm diameter orifice. Three group tests with different actuator arrangements in the spanwise or streamwise direction upstream from the ramp were respectively studied to compare their disturbances to the shock wave. As shown by a time-resolved schlieren system, an unsteady motion of the shock wave by actuation was found： the shock wave was significantly modified by the plasma jet with an upstream motion and a reduced angle. Compared to spanwise actuation, a more intensive impact was obtained with two or three streamwise actuators working together. From shock wave structures, the control effect of the plasma jet on the shock motion based on a thermal effect, a potential cause of shock modification, was discussed. Furthermore, we performed a numerical simulation by using the Improved Delayed Detached Eddy Simulation（IDDES） method to simulate the evolution of the transverse plasma jet plume produced by two streamwise actuators. The results show that flow structures are similar to those identified in schlieren images. Two streamwise vortices were recognized, which indicates that the higher jet plume is the result of the overlap of two streamwise jets.

Application of Bioinspired Superhydrophobic Surfaces in Two-phase Heat Transfer Experiments

This paper addresses the potential to use Lotus leafbioinspired surfaces in applications involving heat transfer with phase change, namely pool boiling and spray impingement. Besides describing the role of bioinspired topographical features, using an innovative technique combining high-speed visualization and time-resolved infrared thermography, surface durability is also addressed. Water is used for pool boiling and for spray impingement systems （simplified as single droplet impact）, while HFE7000 is used in a pool boiling cooler for electronic components. Results show that surface durability is quickly compro- mised for water pool boiling applications, as the chemical treatment does not withstand high temperatures （T 〉 100 ℃） during long time intervals （3 h - 4 h）. For HFE7000 pool boiling （depicting lower saturation temperature - 34 ℃）, heat transfer en- hancement is governed by the topography. The regular hierarchical pattern of the bioinspired surfaces promotes the heat transfer coefficient to increase up to 22.2%, when compared to smooth surfaces, while allowing good control of the interaction mechanisms until a distance between micro-structures of 300 gm- 400 Ixm. Droplet impingement was studied for surface temperatures ranging between 60 ℃ - 100 ℃. The results do not support the use of superhydrophobic surfaces for cooling applications, but reveal great potential for other applications involving droplet impact on heated surfaces （e.g. metallurgy in- dustry）.

Large-eddy simulation and experimental study on the turbulent wake flow characteristics of a two-bladed wind turbine

Large-eddy simulation(LES) with fully resolved rotor method(FRM) is applied to explore the turbulent wake flow characteristics and vortex evolution laws of a two-bladed horizontal-axis wind turbine. Relevant wind tunnel experiments have been done based on time resolved particle image velocimetry(TRPIV) technique. The simulation results are validated by the experimental data and they are in good agreement. The axial average velocity, turbulent kinetic energy, shear Reynolds stress, and vortex structure of the wind turbine wake are analyzed based on the comparison of LES results and experimental data. It is observed that the wake diameter of wind turbine enlarges with the increase of tip speed ratio(TSR). Turbulent kinetic energy meets its minimum value when x/R=2.0. Shear Reynolds stress appears a positive peak in the near wake when x/R<2.0, and the value of shear Reynolds stress decreases along the axial direction. The blade tip vortex dissipates more quickly than the central vortex in the wind turbine wake, and the gradient of the relationship curve between the blade tip vortex core position and the vortex age decreases as the TSR increases. With the increase of TSR, the thrust coefficient increases, and the power coefficient increases first and then decreases.The present work proves that LES with FRM could calculate wind turbine turbulent wake flow with a high accuracy.

The Reduction Square Root and Perturbation for a Class of Strongly Continuous Operator Families

We introduce the concept of a times C-second resolvent families and present the rela- tionship between a times C-resolvent families and a times C-second resolvent families. Moreover, the perturbation and square root for a times C-resolvent families are considered in this paper which generalize the counterparts of C-Cosine operator functions.

Bubble Dynamics and Heat Transfer on Biphilic Surfaces:Experiments and Numerical Simulation

Wettability is known to play a major role in enhancing pool boiling heat transfer.In this context bioinspired surfaces can bring significant advantages in pool boiling applications.This work addresses a numerical investigation of bubble growth and detachment on a biphilic surface pattern,namely in a superhydrophobic region surrounded by a hydrophilic region.Surface characteristics resemble bioinspired solutions explored in our research group,mainly considering the main topographical characteristics.This numerical approach is intended to provide additional information to an experimental approach,allowing to obtain temperature,pressure and velocity fields in and around the bubble,which help to describe bubble dynamics.The model was validated based on experimental data obtained with extensive image processing of synchronized high-speed video and high-speed thermographic images.The results obtained here clearly evidence that combining enhanced direct numerical simulations with high-resolution transient experimental measurements is a promising tool to describe the complex and intricate hydrodynamic and heat transfer phenomena governing pool boiling on heated biphilic surfaces.

Spot size diagnostics for flash radiographic X-ray sources at LAPA

Spot size is one of the parameters to characterize the performance of a radiographic X-ray source. It determines the degree of blurring due to magnification directly. In recent years, a variety of measurement methods have been used to diagnose X-ray spot size at Laboratory of Accelerator Physics and Application (LAPA). Computer simulations and experiments showed that using a rolled-edge to measure the spot size are more accurate, and the intensity distribution of X-ray source was obtained by a device with a square aperture. Experimental and simulation results on a flash X-ray source at our laboratory are presented and discussed in this paper. In addition, a new method for time resolved diagnostics of X-ray spot size is introduced too.

Spectra of ZnO nanoparticles under low photon energy excitation

Time-integrated photoluminescence （PL） spectra between 1.2 and 2.25 eV of ZnO nanoparticles were observed at ambient temperatures when they were excited by a picosecond （ps） laser pulse at a low photon energy of 2.33 eV/532 rim, to show clear red shift when the excitation intensiW increased. Gaussian analysis shows that the red shift is due to increase of the relative magnitudes of the Gaussian combination in the low energy region. Temporal evolution of the dominant emissions exhibited a similar double-exponential decay process, in which the respective two distinct decay durations of 189 ps at the corresponding amplitude of 82% and 2081 ps at 18% were identified. Speculation based on the surfacestate emission due to the large surface-to-volume ratio of nanoscale materials is used to explain the phenomena.