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In-line imaging measurements of particle size,velocity and concentration in a particulate two-phase flow

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Particuology 2014年第2期12卷 106-113页

作者： Xiaozhen Chen Wu Zhou Xiaoshu Cai Mingxu Su Hailong Liu institute of particle and two-phase flow measurement University of Shanghai for Science and Technology

A novel method is developed for in-line measurements of particle size, velocity and concentration in a dilute, particulate two-phase flow based on trajectory image processing. The measurement system consists of a common industrial CCD camera, an inexpensive LED light and a telecentric lens. In this work, the image pre-processing steps include stitching, illumination correction, binarization, denoising, and the elimination of unreal and defocused particles. A top-hat transformation is found to be very effective for the binarization of images with non-uniform background illumination. particle trajectories measured within a certain exposure time are used to directly obtain particle size and velocity. The particle concentration is calculated by using the statistics of recognized particles within the field of view. We validate our method by analyzing experiments in a gas-droplet cyclone separator. This in-line image processing method can significantly reduce the measurement cost and avoid the data inversion process involved in the light scattering method.

关键词： In-line measurements particle trajectory Image processing Multi-parameters

Fast nanoparticle sizing by image dynamic light scattering

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Particuology 2015年第2期13卷 82-85页

作者： Chengze Xu Xiaoshu Cai Jie Zhang Lili Liu institute of particle and two-phase flow measurement University of Shanghai for Science and Technology

In this paper, an image dynamic light scattering method for nanoparticle sizing is introduced. The spatial distribution of the scattered lights from nanoparticles undergoing Brownian motion was captured at a high frame rate by a digital camera within one second, which is considerably faster than the conven- tional photon correlation spectroscopy method. The captured series of photographs were meshed into thousands of small units for calculating the intensity autocorrelation functions in parallel. Experimental results from the measurements of three reference nanoparticle samples （27, 80, and 352 nm in diameters） demonstrated the feasibility of this method.

关键词： Nanoparticle sizing Image dynamic light scattering Real-time acquisition Brownian motion

Resonance scattering characteristics of double-layer spherical particles

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Particuology 2012年第1期10卷 117-126页

作者： Xuejin Dong Mingxu Su Xiaoshu Cai institute of particle and two-phase flow measurement University of Shanghai for Science and Technology Shanghai 200093 China

Based on the principle of ultrasonic resonance scattering, sound-scattering characteristics of double-layer spherical particles in water were numerically studied in this paper. By solving the equations of the scat- tering matrix, the scattering coefficient determined by the boundary conditions can be obtained, thus the expression for the sound-scattering function of a single double-layer spherical particle can be derived. To describe the resonance scattering characteristics of a single particle, the reduced scattering cross section and reduced extinction cross section curves were found through numerical calculation. Similarly, the numerically calculated sound attenuation coefficient curves were used to depict the resonance scattering characteristics of monodisperse and poIydisperse particles. The results of numerical calculation showed that, for monodisperse particles, the strength of the resonance was mainly related to the particle size and the total number of particles; while for polydisperse particles, it was primarily affected by the particle size, the coverage of the particle size distribution and the particle concentration.

关键词： UltrasonicResonance scatteringDouble-layerPolydisperseVisco-elastic

particle size characterization by ultrasonic attenuation spectra

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Particuology 2008年第4期6卷 276-281页

作者： Mingxu Su, Minghua Xue, Xiaoshu Cai, Zhitao Shang, Feng Xu institute of particle and two-phase flow measurement, University of Shanghai for Science and Technology, Shanghai 200093, China institute of particle and two-phase flow measurement University of Shanghai for Science and Technology Shanghai 200093 China

This paper contributes to extracting information from signals of broadband ultrasonic attenuation spectrum for effective utilization in particle size characterization. The single particle scattering model and the coupled-phase model are formulated simultaneously, the relationship between particle size distribution and ultrasonic spectrum is established, and a convergence criterion for calculation is quantified. Demonstration inversion by the optimum regularization factor method is carried out to yield typical numerical results for discussion. With the experimental set-up developed by the institute of particle and two-phase flow measurement (IPTFM) at the University of Shanghai for Science and Technology, sand sediment particle size is measured by attenuation spectrum and analyzed using the above inversion algorithm and theoretical models. To validate the proposed ultrasonic spectrum particle sizing method, results are compared with those obtained by microscopy.

关键词： Ultrasonic spectrum particle Size Inversion

particle sizing in dense two-phase droplet systems by ultrasonic attenuation and velocity spectra

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Science China(Technological Sciences) 2009年第6期52卷 1502-1510页

作者： SU MingXu CAI XiaoShu XUE MingHua DONG LiLi XU Feng institute of particle and two-phase flow measurement University of Shanghai for Science and TechnologyShanghai 200093China

Size and size distribution of particles in particulate two-phase flow play an important role in a wide variety of industrial areas,while their measurement still remains a hard task till *** wave as a mechanical vibration contains plenty of information about medium when it passes *** the size distribution could be extracted from the measured ultrasonic attenuation and velocity spectra by means of well established models and data processing *** paper contributes to the extraction of information of droplet size of a two-phase fat emulsion simultaneously from signals of broad-band ultrasonic attenuation and velocity *** to the formulated single particle scattering model,the relationship between particle size distribution and ultrasonic spectrum is *** sensitivities of ultrasonic spectra to the variation of particle size are ***-guishing features for attenuation and velocity spectra are *** calculations of inversion by optimum regularization factor method are carried out to yield the typical numerical results for *** on the proposed inversion algorithm and theoretical model,a fat emulsion sam-ple with a volume fraction up to 20% is measured and *** validate the proposed ultrasonic spectrum particle sizing method,the results are compared to those obtained from optical measure-ment.

关键词： two-phase flow ultrasonic particle sizing inversion

Magnetic and luminescent properties of bifunctional composite Fe_(3)O_(4)@Y_(2)O_(2)S:Eu^(3+)

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Journal of Rare Earths 2024年第8期42卷 1568-1576,I0006页

作者： Zhiqi Liang Zhili Zhang Liu Li Wen Xu Decai Li School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China Beijing Key Laboratory of flow and Heat Transfer of phase Changing in Micro and Small Scale Beijing100044China State Key Laboratory of Tribology Tsinghua UniversityBeijing100084China

As a kind of non-destructive testing method,magnetic particle inspection is widely used in the fields of aviation and high-speed *** properties of magnetic fluorescent bifunctional composites,such as fluorescence intensity and magnetic properties,have increasing demands in magnetic particle *** earth compounds offer potential as novel materials for fluorescent magnetic bifunctional composites due to their excellent optical properties and extremely narrow emission *** this work,the rare earth fluorescent material Y_(2)O_(2)S:Eu^(3+) was synthesized by solid-state reaction ***_(3)O_(4)nanoparticles prepared by hydrothermal method were uniformly coated on the Y_(2)O_(2)S:Eu^(3+) particles through physical adsorption of *** obtained Fe_(3)O_(4)@Y_(2)O_(2)S:Eu^(3+) exhibits dark red color under the ultraviolet *** additio n,X-ray diffractio n,morphology,photoluminescence and hyste resis loop of Fe_(3)O_(4)@Y_(2)O_(2)S:Cu^(3+) were *** luminescence mechanism of Y_(2)O_(2)S:Eu^(3+) is described in detail Fe_(3)O_(4)@Y_(2)O_(2)S:Cu^(3+) displays good paramagnetism and has a good controllability under a magnetic *** magnetic particle inspection of Fe_(3)O_(4)@Y_(2)O_(2)S:Eu^(3+) was performed using a 4-pole electromagnet and a test piece *** magnetic fluorescent bifunctional composite presented in this work can be applied for non-destructive testing.

关键词： Bifunctional material Fe_(3)O_(4) Y_(2)O_(2)S:Eu^(3+) Luminescence Solid-state reaction Rare earths

Mitigating set-stuck failure in 3D phase change memory: substituting square pulses with surge pulses

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Science China(Information Sciences) 2024年第5期67卷 295-301页

作者： Ninghua LI Wang CAI Jun XIANG Hao TONG Weiming CHENG Xiangshui MIAO School of Integrated Circuits Huazhong University of Science and Technology Hubei Yangtze Memory Laboratories Hubei institute of measurement and Testing Technology

In the devices that integrate phase change memory(PCM) and ovonic threshold switching(OTS),the OTS threshold voltage often surpasses the RESET operation voltage of PCM. The conventional application of square pulses hinders the successful completion of the SET operation in these integrated devices. To address this challenge, a novel pulse called the surge pulse is introduced, which comprises a high amplitude pulse for OTS activation and a low amplitude pulse for PCM operation. By employing COMSOL simulation,the operational effectiveness of both square pulses and surge pulses is validated. Test results reveal that using a square pulse to operate the integrated device accelerates the occurrence of SET-stuck failure(SSF).In contrast, the surge pulse enables the integrated device to operate for at least 1000 cycles while preserving the essential cyclic characteristics. Additionally, an investigation into the overshoot component of the surge pulse is conducted, revealing that an increase in overshoot amplitude and pulse width also accelerates the emergence of SSF. By applying the theory of ion migration induced by the electric field, the root cause of SSF in integrated devices is explained, and the accuracy of the theory is validated through the application of a reverse pulse. In summary, this study elucidates the rationality of replacing the square pulse with a surge pulse, presenting a superior approach for operating PCM and OTS integrated devices.

关键词： surge pulse phase change memory (PCM) integration SET-stuck failure (SSF) square pulse

Modeling and prediction of ultrasonic attenuations in liquid-solid dispersions containing mixed particles with Monte Carlo method

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Particuology 2019年第2期17卷 84-91页

作者： Jianfei Gu Fengxian Fan Yunsi Li Huinan Yang Mingxu Su Xiaoshu Cai institute of particle and two-phase flow measurement/Shanghai Key Laboratory of Multiphase flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology Shanghai 200093 China

We develop a theoretical model for predicting the ultrasonic attenuation in the liquid-solid system containing mixed particles. The ultrasonic attenuation coefficient is obtained by counting the number of phonons that reach the receiver. Using the Monte Carlo method (MCM), numerical simulations were performed to predict the ultrasonic attenuations with not only a single particle type but also monodisperse and polydisperse mixed particles. The simulation results for the systems with a single particle type were compared with various standard models. The results show that they agree well at relatively low particle volume concentrations (within 10%). For systems with mixed particles, the particle volume concentrati on was found to in crease to around 10%, and the variation of the ultrasonic attenuation agai nst the mixing ratio yields a nonlinear trend. Moreover, the ultrasonic attenuation is significantly affected by particle properties. The numerical results also show that both the particle type and particle size distribution should be carefully taken into account in the dispersions with polydisperse mixed particles, where the MCM can give a more direct description of the physics of sound propagation compared with the conventional models.

关键词： Ultrasound Ultrasonic attenuation Monte Carlo method particle size measurement

Comprehensive Euler/Lagrange modelling including particle erosion for confined gas-solid flows

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Particuology 2024年第1期84卷 209-235页

作者： Guiherme A.Novelletto Ricardo Martin Sommerfeld Multiphase flow Systems Institute of Process EngineeringOtto-von-Guericke-University MagdeburgHoher Weg 7b06120Halle(Saale)Germany

The present research aims to assess the capability of a comprehensive Euler/Lagrange approach for predicting gas-solid flows and the associated solid particle *** open-source code OpenFOAM®4.1 was used to carry out the numerical simulations,where the standard Lagrangian libraries were substantially extended to account for all necessary *** are tracked considering both translational and rotational motion as well as all relevant forces,such as gravity/buoyancy,drag and transverse lift due to shear and particle *** tracking time step was dynamically adapted ac-cording to the locally relevant time scales,which drastically reduces computational *** approaches are adopted to model particle turbulent dispersion,particle collisions with rough walls and particle-particle *** solid particle erosion models,available in the literature,were considered to estimate pipe bend *** study cases are provided to validate the adopted nu-merical approach and erosion models *** first case intends to evaluate the ability of the extended CFD code to predict the behaviour of gas-solid flows in pneumatic conveying *** goal is achieved by comparing the numerical results with the experimental data obtained by Huber(1997)and Huber and Sommerfeld(1994,1998)in a pneumatic conveying ***,the importance of considering inter-particle collisions and surface roughness for predicting particle velocity,mass flux and mean diameter distributions in gas-solid flows is *** second and third case intend to evaluate the ability of the erosion models in estimating bend erosion in diluted gas-solid *** erosion data obtained experimentally by Mazumder et al.(2008)and Solnordal et al.(2015)in very dilut pneumatic conveying systems is used for validating the numerical results,neglecting now inter-particle collisions and two-way *** a comprehensive analysis of the different influential properti

关键词： Pneumatic conveying Pipe bend Numerical calculation(CFD) Euler/Lagrange approach Erosion models Wall roughness