Intensity Fluctuations Research Articles

Mechanism investigation on gear vibration-cavitation caused by tooth-pair lubricated contact

Elastohydrodynamic contact of gears under the influence of vibration induces cavitation and jet impact. To predict the evolution of cavitation and the degree of cavitation erosion in the gear contact region, the multi-phase flow cavitation model and gear dynamic model are coupled for simulating the cavitation effect in the gear lubrication region and the jet stresses at the tooth boundary under different load torques and rotational speeds. Moreover, the proposed model is confirmed to be valid through comparing to experimental results. The cavitation and jet impact intensity increase and mainly distribute at the outlet of tooth contact under high speed. Load torque mainly affects the cavitation oscillation, but there exists an expectation value that makes both the amplitude and intensity of the cavitation fluctuation and erosion low.

Orbital- and millennial-scale Asian winter monsoon variability across the Pliocene–Pleistocene glacial intensification

Intensification of northern hemisphere glaciation (iNHG), ~2.7 million years ago (Ma), led to establishment of the Pleistocene to present-day bipolar icehouse state. Here we document evolution of orbital- and millennial-scale Asian winter monsoon (AWM) variability across the iNHG using a palaeomagnetically dated centennial-resolution grain size record between 3.6 and 1.9 Ma from a previously undescribed loess-palaeosol/red clay section on the central Chinese Loess Plateau. We find that the late Pliocene–early Pleistocene AWM was characterized by combined 41-kyr and ~100-kyr cycles, in response to ice volume and atmospheric CO2 forcing. Northern hemisphere ice sheet expansion, which was accompanied by an atmospheric CO2 concentration decline, substantially increased glacial AWM intensity and its orbitally oscillating amplitudes across the iNHG. Superposed on orbital variability, we find that millennial AWM intensity fluctuations persisted during both the warmer (higher-CO2) late Pliocene and colder (lower-CO2) early Pleistocene, in response to both external astronomical forcing and internal climate dynamics.

Evolution of weathering intensity in the Qaidam Basin, northeastern Tibetan Plateau, since the middle Miocene: Insights from clay mineral records

Terrestrial silicate weathering records from the tectonically active Tibetan Plateau are crucial to explore the interactions among climate change, tectonic uplift and chemical weathering during the Cenozoic. However, the complex sedimentary facies changes and frequent occurrence of coarse lithologies related to intense tectonic uplift of the Tibetan Plateau have largely limited the reliability of bulk chemical weathering indexes to reveal the silicate weathering history. Here, we present detailed records of clay minerals and geochemical compositions from clay-sized (< 2 μm) sediments collected from the well-dated Huaitoutala section (ca. 15.3–1.8 Ma) in the NE Qaidam Basin to reconstruct the chemical weathering history of the NE Tibetan Plateau during the late Cenozoic. The relatively high (illite–smectite mixed layers + smectite)/(chlorite + illite) ratio indicates a strong silicate weathering intensity from 15.3 to 12.6. Ma, while a continuous decrease in this ratio since 12.6 Ma reflects a long-term decreasing intensity of silicate weathering. By comparing the clay mineral records with the climatic reconstruction and the tectonic events in the NE Tibetan Plateau, the results reveal that middle Miocene global cooling-related drying exerted a significant influence on the decreasing weathering intensity since ca. 12.6 Ma. Furthermore, the late Cenozoic episodic and persistent uplift of the NE Tibetan Plateau may have exerted an additional influence on the long-term decrease in weathering intensity. Specifically, the dramatic fluctuation in the silicate weathering intensity during ∼11–9.6 Ma is mainly due to uplift-induced provenance changes. Moreover, the fluctuating increase in the silicate weathering intensity during ∼8–5 Ma may have been caused by intensified East Asian summer monsoon precipitation. Our study suggests that both climate change and tectonic deformation controlled the chemical weathering intensity in the NE Tibetan Plateau during the late Cenozoic.

Tunable on-chip optical traps for levitating particles based on single-layer metasurface

Abstract Optically levitated multiple nanoparticles have emerged as a platform for studying complex fundamental physics such as non-equilibrium phenomena, quantum entanglement, and light–matter interaction, which could be applied for sensing weak forces and torques with high sensitivity and accuracy. An optical trapping landscape of increased complexity is needed to engineer the interaction between levitated particles beyond the single harmonic trap. However, existing platforms based on spatial light modulators for studying interactions between levitated particles suffered from low efficiency, instability at focal points, the complexity of optical systems, and the scalability for sensing applications. Here, we experimentally demonstrated that a metasurface which forms two diffraction-limited focal points with a high numerical aperture (∼0.9) and high efficiency (31 %) can generate tunable optical potential wells without any intensity fluctuations. A bistable potential and double potential wells were observed in the experiment by varying the focal points’ distance, and two nanoparticles were levitated in double potential wells for hours, which could be used for investigating the levitated particles’ nonlinear dynamics, thermal dynamics and optical binding. This would pave the way for scaling the number of levitated optomechanical devices or realizing paralleled levitated sensors.

Lake-level responses to climate change in an inland basin in the Japanese Islands during the last 16 kyr

During the last deglaciation and middle Holocene, rapid climatic changes occurred repeatedly. Previous research has primarily focused on investigating these periods in East Asia's coastal and inland regions of the Eurasian continent. In contrast, a limited number of studies have reported on climate change and its environmental impacts in island areas near the Pacific Ocean. This study aims to reconstruct paleosol drainage conditions and lake water level fluctuations in the Suwa Basin, an inland basin in central Japan, after the last deglaciation. We utilize the identification of paleosols and the geochemistry of lacustrine sediments to discuss climate change and its impacts on terrestrial environments in the East Asian coastal region. During the Last Glacial Maximum, the basin experienced a lowstand period; meandering fluvial systems led to the development of dry and well-drained paleosols. The lacustrine environment expanded between ca. 16 cal kyr BP and 5 cal kyr BP during a transgressive period. Short-term lake-level fluctuations were reconstructed by examining repeated paleosol development and changes in the bulk SiO2 content originating from biogenic silica in lacustrine sediments. Our data suggest that the lake's water level fell at ca. 12 cal kyr BP, 8 cal kyr BP, and 7 cal kyr BP. After 5 cal kyr BP, thin paleosols repeatedly formed during short exposure times due to the rapid sedimentation rate in the delta system, which corresponds to the highstand period. Short-term fluctuations between 16 kyr BP and 5 kyr BP, in the lake water level in the inland basin of the Japanese Islands was influenced by drying and cooling trends in the East Asian coastal region, as well as declines in sea surface temperatures in the western tropical Pacific Ocean. These fluctuations roughly synchronize with the Younger Dryas stadial and an 8.2 ka cooling event. Changes in precipitation, which responded to fluctuations in the East Asian summer monsoon intensity and tropical depressions, likely regulated the lake water level. These findings imply the predominant influence of paleoclimate fluctuations over thousands of years on the hydrological regime of lake systems across the island area of the East Asia.

Thermal Hydraulic Analysis of Turbulent Flow of Superheated Steam Through Multiple Configurations of 3D Angular Piping Bend in Power Plant Installations

Abstract One of the most vulnerable parts in high-pressure and temperature pipeline networks in steam turbine power plant installations is pipe bends, due to intense fluctuation of velocity and pressure of the superheated steam flowing through the piping bend. On the other hand, because of unique chemical and physical properties, the transportation of superheated steam can adversely effect on the integrity of the pipe bends in the piping network. Therefore, the potential risk of pipeline failure becomes more probable at bends. Therefore, to ensure the survivability of the piping network, thorough investigations of the superheated steam flowing through pipe bends are of great significance in better understanding its flow behavior. However, to predict flow behavior at piping bend, intensive research by direct experiment at high temperature and pressure might not be possible to some extent. In that case, computer codes and models can help us analyze flow behavior of superheated steam at pipe bends. The current work is a computational fluid dynamics investigation, where numerical examination is carried out by commercial code ansys fluent for thermal hydraulic analysis of flow behavior of superheated steam through multiple configurations of 3D angular piping bend: 90 deg, 120 deg, and 135 deg. Validation of credibility of the computational approach is done against Sudo et al.'s experiment. With relatively good agreement between the experiment and numerical result using air flowing through 90 deg elbow, single-phase turbulent flow of superheated steam is examined by the application of realizable turbulence model (k–ɛ). The final assessment of the computed results has been done using qualitative and quantitative analyses. The study reveals that unlike the pressure profiles, the radial velocity profiles at the bend exit are noticeably different from those at the bend inlet, since they exhibit more rounded peaks and gentler velocity gradients. The study also shows that the radial pressure and velocity profiles do not display any sign of the existence of a pair of vortices.

Variable-frequency phase-shifting algorithm with least-squares iteration for hybrid errors reduction under structured-light illumination

In this paper, a novel variable-frequency phase-shifting algorithm is proposed to reduce hybrid errors under structured-light illumination, which combines a least-squares iteration with regularization processing. Theoretical formulas and related calculation techniques for the variable-frequency fringe model are respectively derived and proposed considering phase-shifting errors, temporal intensity fluctuations and Gamma distortion. From the perspective of theoretical model, it is successfully verified and implemented to establish a minimal and sufficient system of equations using a least number of fringe patterns. To tackle the challenge of solving numerous unknown parameters in the derived model caused by these sources, a grouped step-by-step strategy is adopted during the least-squares iteration process. Error point determination and compensation tricks are further developed to reduce the phase jump problem caused by underdetermined solution. A Gamma prediction technique based on bi-frequency single-frame fringe patterns is also put forward to enhance the accuracy of phase retrieval results. Corresponding simulation and experimental results have demonstrated that the proposed algorithm with attractive potentiality can achieve a significant enhancement in accuracy using the least number of phase-shifting fringe patterns (taking bi-frequency two-step as an example in this study) compared to other existing competitive techniques.

Experimental investigation of the characteristics of the plasma flow generated in quasi-stationary plasma accelerator using optical methods

The spatial and temporal dependencies of the characteristics of the hydrogen plasma flow generated in quasi-stationary plasma accelerator were investigated. The spatiotemporal structure of discharge radiation in the interelectrode gap was studied. The range of changes in the length of the plasma glowing region in the interelectrode gap during the discharge pulse was determined. The region with bright plasma radiation located in the output face of the accelerator electrode system was observed. The presence of impurities and increased electron concentration values were observed in this region. Fluctuations in the radiation intensity of the plasma flow were detected along the entire length of its propagation. The spatial and temporal characteristics of these fluctuations were determined. The electron concentration values near the output face of the electrode system were obtained by measuring the Stark broadening of the Hβ line. For the first time, the time dependence of the electron concentration of free plasma flow was obtained using two methods simultaneously. The measurements were conducted at a distance, which significantly exceeds the characteristic size of the electrode system and where the influence of interelectrode processes of plasma flow generation is reduced. The first is based on measuring the Stark broadening of Hβ. As a second method, heterodyne interferometry was used.

An LES investigation on turbulent flow in a centrifugal impeller affected by normal-distributed inflow perturbations

The inflow of a rotating centrifugal impeller is normally perturbed by an upstream stationary component; therefore, the development of turbulent flow is different from the case with steady and uniform inflow. In this work, we performed a large-eddy simulation on turbulent flow in a centrifugal impeller, considering perturbation from the inflow and emphasizing the development of perturbation and its influence on flow in the impeller. The inflow perturbation is applied for the streamwise (w-) velocity and is time-varying as generated by a random number generator. A normal-distributed pattern of perturbation is always assumed with the intensity of perturbation, defined as the ratio between the perturbation amplitude and the mean velocity, set as fv = 0%, 5%, 10%, and 20%, where fv denotes the perturbation intensity. The inflow perturbation notably affects the passage flow. The velocity fluctuation and secondary flow increase in intensity as the perturbation intensity increases from fv = 0% to 10%, while a further increase to fv = 20% slightly weakens the velocity fluctuation. Although this phenomenon is less obvious in terms of the time-averaged characteristics of velocity, the Reynolds stress terms CtCa and CrCa under time-averaging still reflect a clear variation trend, and the Reynolds stresses are observed significantly on the blade suction surface.

Direct numerical simulations of supersonic flat-plate turbulent boundary layers with uniform blowing

The effect of uniform blowing on a spatially developing flat-plate turbulent boundary layer at Mach 2.25 is investigated using direct numerical simulations. Two values of the wall blowing ratio are considered, corresponding to low and high blowing rates. Uniform blowing is found to significantly reduce the near-wall turbulence anisotropy, although the turbulent kinetic energy still exhibits near-wall asymptotic behavior and the Reynolds analogy is relatively insensitive to changes in the blowing ratio. The pre-multiplied spectra of turbulent kinetic energy production demonstrate that increasing the blowing ratio significantly energizes the large-scale structures in the outer region, while suppressing the inner small-scale structures. An increase in the blowing ratio also has a strong influence on the behavior of the fluctuating wall pressure, amplifying the fluctuation intensity and reducing the dominant frequencies in the power spectrum. Two-point space–time correlations indicate that the characteristic length scale of the pressure fluctuations increases with increasing blowing ratio, whereas the convection velocity exhibits the opposite trend. Analysis of the reduced mean wall heat flux reveals that it is dominated by the relative balance between the work of the Reynolds stress and the turbulent transport of heat, but is insensitive to uniform blowing. Importantly, bidimensional empirical mode decomposition of the turbulent structures highlights the increasingly dominant contributions related to the significantly energized outer large-scale structures in the blowing region.

A red-emitting carborhodamine for monitoring and measuring membrane potential

Biological membrane potentials, or voltages, are a central facet of cellular life. Optical methods to visualize cellular membrane voltages with fluorescent indicators are an attractive complement to traditional electrode-based approaches, since imaging methods can be high throughput, less invasive, and provide more spatial resolution than electrodes. Recently developed fluorescent indicators for voltage largely report changes in membrane voltage by monitoring voltage-dependent fluctuations in fluorescence intensity. However, it would be useful to be able to not only monitor changes but also measure values of membrane potentials. This study discloses a fluorescent indicator which can address both. We describe the synthesis of a sulfonated tetramethyl carborhodamine fluorophore. When this carborhodamine is conjugated with an electron-rich, methoxy (-OMe) containing phenylenevinylene molecular wire, the resulting molecule, CRhOMe, is a voltage-sensitive fluorophore with red/far-red fluorescence. Using CRhOMe, changes in cellular membrane potential can be read out using fluorescence intensity or lifetime. In fluorescence intensity mode, CRhOMe tracks fast-spiking neuronal action potentials (APs) with greater signal-to-noise than state-of-the-art BeRST 1 (another voltage-sensitive fluorophore). CRhOMe can also measure values of membrane potential. The fluorescence lifetime of CRhOMe follows a single exponential decay, substantially improving the quantification of membrane potential values using fluorescence lifetime imaging microscopy (FLIM). The combination of red-shifted excitation and emission, mono-exponential decay, and high voltage sensitivity enable fast FLIM recording of APs in cardiomyocytes. The ability to both monitor and measure membrane potentials with red light using CRhOMe makes it an important approach for studying biological voltages.

Judging Rainfall Intensity from Inter-Tip Times: Comparing ‘Straight-Through’ and Syphon-Equipped Tipping-Bucket Rain Gauge Performance

The inter-tip times (ITTs) of tipping-bucket rain gauges (TBRGs) potentially provide the highest-resolution intensity data that can be acquired from this type of gauge. At an intensity of 100 mm h−1, a typical gauge with a sensitivity of 0.2 mm of rainfall would be expected to tip every 7.2 s. However, TBRGs are often equipped with syphons to reduce the dynamic calibration error that results from continued (and unmeasured) inflow to a bucket as it tips. This increases the accuracy of rainfall depth recording, but the time to fill and empty the syphon can reduce the ability of a TBRG to respond to (and for the ITTs to reflect) short-term intensity fluctuations. This ability is already limited by the discretisation arising from the filling and emptying of the buckets themselves. Laboratory tests with controlled water inflow rates were performed using two high-quality TBRGs, one a ‘straight-through’ design and the other syphon-equipped. These confirmed that at all intensities at which the syphon operates, a regular sequence of fixed-duration ITTs (such as the 7.2 s mentioned above) does not occur. Rather, the ITTs are perturbed by the syphon cycling. The gauges were also co-located in the field and linked to carefully synchronised event data loggers. Data collected during several rainfall events revealed differences in the ITTs and again confirm that the ITT sequence of a syphon-equipped TBRG exhibits artefacts related to syphon operation that are not present in the ‘straight-through’ data. These artefacts can result in ITT differences of many minutes, depending on the rainfall intensity and are problematic for the use of ITTs to estimate intensity. Peaks and troughs in the intensity profile also differed between the two gauges. It is recommended that in the application of TBRGs for studies where short-term intensity data are required, ‘straight-through’ gauges should be used, and syphon-equipped gauges should be avoided.

Investigation on the unstable flow characteristic and its alleviation methods by modifying the impeller blade tailing edge in a centrifugal pump

In the field of the pumped storage plants, the unstable flow is universally caused by the rotating stall in the hydro-energy machinery, which further deteriorates the performance curves. To explore the alleviation method of the unstable flow, flow characteristic in a centrifugal pump with different impeller blade geometries is numerically investigated using a modified SST k-ω partially averaged Navier-Stokes model in this study. Numerical validation on the characteristic curves is carried out, which appears in accord with the experimental data of the test pump. Four types of available modification methods are attempted based on theoretical analysis, i.e., trimming the section side of the blade at trailing edge (TE) (named model A), decreasing the blade angle at TE (named model B), trimming the blade TE in spanwise direction with 45 degree (named model C) and adopting large lean angle blades (named model D). Results on the characteristic curves are first compared. In the test pump and model B, one positive slope region is observed under the same operation condition, while it is brought forward in the model A. On the contrary, the positive slope region is completely alleviated in model C and model D. Further exploration on the flow pattern in the impeller is conducted to give a comprehensive explanation. Due to the sudden increment of the energy loss, the flow pattern tends to be deteriorated, which further has impact on the characteristic curves. At last, unstable flow analysis in the impeller of the model D is carried out with emphasis on the evolution of the rotating stall. By using large lean angle blades, the rotating stall in the blade-to-blade passage of impeller is alleviated significantly with lower pressure fluctuation intensity.

Angularly offset multiline dispersive optical phased array enabling large field of view and plateau envelope

We propose and demonstrate an angularly offset multiline (AOML) dispersive silicon nitride optical phased array (OPA) that enables efficient line beam scanning with an expanded field of view (FOV) and plateau envelope. The suggested AOML OPA incorporates multiline OPA units, which were seamlessly integrated with a 45° angular offset through a thermo-optic switch based on a multimode interference coupler, resulting in a wide FOV that combines three consecutive scanning ranges. Simultaneously, a periodic diffraction envelope rendered by the multiline OPA units contributes to reduced peak intensity fluctuation of the main lobe across the large FOV. An expedient polishing enabling the angled facet was diligently accomplished through the implementation of oblique polishing techniques applied to the 90° angle of the chip. For each dispersive OPA unit, we engineered an array of delay lines with progressively adjustable delay lengths, enabling a passive wavelength-tunable beam scanning. Experimental validation of the proposed OPA revealed efficient beam scanning, achieved by wavelength tuning from 1530 to 1600 nm and seamless switching between multiline OPAs, yielding an FOV of 152° with a main lobe intensity fluctuation of 2.8 dB. The measured efficiency of dispersive scanning was estimated at 0.97°/nm, as intended.

Effect of suction temperature on the internal flow characteristics of hydrogen circulation pump

This paper explores the effects of suction temperature (ST) on the internal flow and pressure pulsation characteristics of a roots hydrogen circulation pump (HCP). The study analyzes the suction and discharge chamber pressure pulsation, as well as the inlet and outlet flow pulsation, at different STs. The research finds that an increase in ST leads to a decrease in the amplitude and fluctuation intensity of the pressure pulsation in both suction and discharge chambers. Moreover, the average flow rate of the HCP decreases with increasing ST, while the frequency and waveform remain unchanged. The maximum and minimum values of the inlet flow pulsation decrease, while the maximum value of the outlet flow pulsation decreases, and the minimum value increases, indicating a reduction in fluctuation intensity. The turbulent energy within the discharge and transport chambers also changes with increasing ST. The inter-lobe leakage flow (ILF) is slightly affected by ST, while the radial leakage flow (RLF) and axial leakage flow (ALF) exhibit slight increases. Overall, these findings reveal the importance of considering ST as a critical design parameter for optimizing the performance and stability of the HCP.

Localization landscape of optical waves in multifractal photonic membranes

In this paper, we investigate the localization properties of optical waves in disordered systems with multifractal scattering potentials. In particular, we apply the localization landscape theory to the classical Helmholtz operator and, without solving the associated eigenproblem, show accurate predictions of localized eigenmodes for one- and two-dimensional multifractal structures. Finally, we design and fabricate nanoperforated photonic membranes in silicon nitride (SiN) and image directly their multifractal modes using leaky-mode spectroscopy in the visible spectral range. The measured data demonstrate optical resonances with multiscale intensity fluctuations in good qualitative agreement with numerical simulations. The proposed approach provides a convenient strategy to design multifractal photonic membranes, enabling rapid exploration of extended scattering structures with tailored disorder for enhanced light-matter interactions.

Numerical Investigations of Stirring Induced Flow on Solidification and Interface Behavior in Continuous Casting Mold With Bifurcated Nozzle

Abstract Electromagnetic stirring (EMS) is a technique that has the potential to improve steel quality with fine microstructure by fragmentation of dendrites and enhancing the inclusion removal. The success of implementing the EMS lies in the selection of key input parameters such as position, frequency, and current density of the stirrer. In the present study, an integrated mathematical model consisting of liquid steel solidification and two phase interface is numerically developed with the use of EMS. The enthalpy porosity and volume of fluid (VOF) model are adopted for numerical modeling analysis of solidification and interface level fluctuation, respectively. The results reveal that on moving EMS downwards decreases the maximum magnetic field value, widens the mushy zone, and promotes the stability of the interface. Current intensity and frequency are seen to have the opposite effect on stirring intensity and interface fluctuation. With an increase in frequency, both stirring intensity and interface level fluctuations decrease while the high liquid fraction region increases. Moreover, current density enhances the swirling flow intensity and homogenizes the liquid fraction, thereby promoting equiaxed grain formation. Interface fluctuation is seen to increase with current density.

A universal dual-channel ratiometric photoelectrochemical sensing platform with integrated ionic liquid-sensitized In2S3@BiOBr0.8I0.2/PEDOT photoanode and Cu@Cu2O photocathode

The generation, separation and interfacial reaction of photogenerated carriers are crucial to realize efficient photoelectrochemical (PEC) detection. However, fast electron-hole recombination and slow interfacial reaction dynamics remain challenges for constructing advanced PEC platforms. Herein, ionic liquids (i.e. 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF4) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm]PF6)) are introduced as morphology modulator and supporting electrolyte into the synthesis of Cu@Cu2O and the heterogeneous combination of In2S3@BiOBr0.8I0.2 with electrochemically polymerized 3,4-ethylenedioxythiophene (PEDOT), for constructing a PEC sensing platform. As their unique microstructure, the formed p-n junction and the doped ionic liquids benefit the charge separation/transfer, the resulted [BMIm]BF4 − In2S3@BiOBr0.8I0.2/ [BMIm]PF6 − PEDOT/AuNPs (i.e. Au nanoparticles) photoanode material and [BMIm]PF6 − Cu@Cu2O photocathode material show enhanced interfacial reaction dynamics and photo-conversion efficiency. In order to improve the accuracy and reliability of PEC detection, the potentially responsive photocathode and photoanode materials are integrated on the same indium tin oxide electrode for potential-resolved two-channel ratiometric PEC detection. By tuning the bias voltage, the cathode and anode currents can be well distinguished, and dual signals can be obtained during a single detection run and used as reference for each other. Then, a biometric sensing platform for vascular endothelial growth factor and epithelial cell adhesion factor is constructed by combining with aptamers and it demonstrates excellent analytical performance. Compared with the traditional PEC biosensors, the platform can effectively eliminate the detection errors caused by the fluctuation of excitation light intensity and preparation conditions. In addition, the platform is universal, by changing the recognition element, it can be applied to the detection of a variety of biomarkers.

Experimental investigation of wet particle flow characteristics in a pseudo two-dimensional fluidized bed

The flow characteristics of wet particles in a fluidized bed are extremely complicated due to the presence of moisture. It is essential to understand the complex behavior and flow characteristics of wet particles in the drying, coating and granulation process for optimizing the process efficiency and product quality. Thus, the flow characteristics of wet particles, such as pressure fluctuation, bubble size and bubble fraction, in a pseudo two-dimensional fluidized bed were investigated through the multi-resolution time-frequency analysis of the pressure signal combined with the high-speed camera images. Results show that the critical fluidization velocity increases after the particles are wetted, and it shows a slight increase with higher moisture content levels. Besides, there are two main characteristic frequencies, which correspond to the gas-solid flow state of the gas channel and the large bubble in the bed, respectively. Notably, higher gas velocities promote the dominance of large bubbles. And increasing particle moisture inhibits bubble expansion and reduces bubble size, while dense particle areas expand vertically due to enhanced bonding. The bed height increases with the increase of moisture, and the fluctuation of bubble fraction decreases. In the drying experiment, two characteristic frequencies also appear and the pressure drop reduce slightly due to the reduction of water. During the drying process, both the average bubble fraction and fluctuation intensity increase.

Transient X-Ray Absorption Near Edge Structure Spectroscopy Using Broadband Free-Electron Laser Pulses.

A new method for time-resolved X-ray absorption near edge structure (XANES) spectroscopy that enables faster data acquisition and requires smaller sample quantities for high-quality data, thus allowing the analysis of more samples in a shorter time is introduced. The method uses large bandwidth free electron laser pulses to measure laser-excited XANES spectra in transmission mode. A beam-splitting grating configuration allows simultaneous measurements of the spectra of the incoming X-ray Free Electron Laser (XFEL) pulses and transmission XANES, which is crucial for compensating the pulse-dependent intensity and spectrum fluctuations due to the self-amplified spontaneous emission operation. The implementation of this new methodology is applied on a liquid solution of ammonium iron(III) oxalate jet and is compared to previous results, showing great improvements in the speed of acquisition and spectral resolution, and the ability to measure a large 2-D spectral-time map quickly.