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An elasto-plastic constitutive model for rockfill materials considering particle breakage is proposed. Although numerous constitutive models have been proposed for rockfill materials, most of them are mainly based on empirical results, without consideration of the physical meaning of their parameters. In the present work, a yield function is derived based on the evolution of microstructures formed by rockfill particles. The dilatancy equation is derived based on both the theory of breakage mechanics and the energy dissipation equations. The breakage-induced hardening is also formulated to account for both the volumetric and shearing hardening of rockfill materials. It is demonstrated that, without compromising the simplicity of the model, most of the parameters in the proposed constitutive model have concrete physical meanings. Comparison of the model simulation with experimental data shows that the proposed model can describe reasonably the static loading characteristics of rockfill materials within a wide range of confining stresses.

In the present paper, we have studied the dependence of thermal conductivity on shape, size and dimension of nanomaterial. By using the quantitative expression of melting temperature, the expression for thermal conductivity is deduced in this work. Kapitza resistance term is also considered in the study to better explain the thermal conductivity variation in nanomaterials with scattering effect on thermal properties. The thermal conductivity is found to decreased as size of nanomaterials decease. The variation in thermal conductivity with size is calculated for nanowire, nanofilm, spherical, regular tetrahedral particle, regular octahedral particle, and regular icosahedral particle shapes. The results calculated in the present work are compared with the available experimental results to judge the validity of the present model.

Abrasive flow jet machining (ASJM) is modern manufacturing technique which uses comparatively low-pressure abrasive flow jet for machining various machined surfaces like holes, channels and intricate shapes which is not possible from conventional machining processes. The effect of abrasive particle concentration on the impacting slurry velocity on the surface was examined in the present CFD simulation, resulting in target surface erosion. To predict the impact velocity of abrasive particles hitting the surface, a 2D CFD model was used. The depth of machined surface, surface irregularity and surface removal rate at normal incidence mainly depend on the KE of particle, impact angle, etc. in line with previously published research work on highly pressurised air and water driven abrasive jet. In the present work CFD simulation is performed to predict the effect of solid particle concentration on the impacting slurry jet velocity at the target surface and also turbulence kinetic energy near the surface is studied. As per the CFD results the simulation model predictions the velocity of impacting particle goes on decreasing due to internal frictional resistance between solid and liquid phase and it shows scope of further parametric analysis in this area.

Recycling CO2 into light olefins is a promising approach to reduce CO2 emissions. To promote this technology, an efficient catalyst with high activity and selectivity towards light olefins is imperative. In this work, a series of Fe–Co–K supported on micro-mesoporous carbon (MMC) and microporous carbon (MC) with different metal loading contents (20–80 wt%) were prepared for CO2 hydrogenation to light olefins. Impregnating mixed metal oxides on both MMC and MC reduced particle sizes and enhanced their dispersion and reducibility, yielding a higher CO2 conversion compared to the unsupported Fe–Co–K catalyst. The metal oxides were highly dispersed inside the micropores of MC support, achieving the highest CO2 conversion. However, the high dispersion of metal oxides inside micropores led to the formation of isolated particles with a low interfacial contact with each other, resulting in a low light olefins selectivity. The MMC support provided a lower degree of metal dispersion, creating more interfacial contact area, promoting the selectivity towards olefins. Overall, the 60 wt% Fe–Co–K supported on MMC catalyst exhibited the highest light olefins yield of 10.8% at 400 °C and 20 bar and excellent stability.

Inspired by the viscoelastic displacement theory, we have developed a product called preformed particle gel (PPG) as conformance control agent to enhance oil recovery and control excess water production. The migration law of PPG suspension in porous media is related to its deep profile control and displacement capability. Laboratory experiments indicate that PPG suspension has good viscosity increasing, and the apparent viscosity decreases with the increase of shear rate. PPG suspension is mainly elastic, and its network structure makes it have certain shear stability. PPG particles realize migration in porous media in the way of “accumulation and blockage→pressure increase→deformation and migration”. When the ratio of the PPG particle size to the pore throat diameter δ ranges from 35.52 to 53.38, the particles can match through the porous medium. When the permeability difference of the parallel model is 5, PPG suspension has the highest profile improvement rate, 69.10%. PPG suspension can adjust the planar heterogeneity, and increase the oil recovery rate by 20.75%. The PPG suspension can effectively start “cluster"、 “film” and “blind end residual oil”, and has a high oil washing efficiency. The core NMR T2 spectrum shows that PPG suspension mainly reduces oil saturation in mesopores and macropores. After PPG flooding, the EOR capacity of small pores is the highest, 39.11%.

Particle Impact Drilling (PID) is a new technology to effectively improve the rate of penetration (ROP) for oil and gas drilling in hard and strongly abrasive formations. In this paper, numerical simulation method is used to analyse the motion characteristics and the modulation method of particle swarm in high-pressure tank for the particle injection system based on differential pressure ejection in PID. The numerical simulation results show that: when there is no modulation elements, the motion of particle swarm in the high-pressure tank follows an asymmetric funnel flow with pulsating state, which could be divided into vertical flow domain, fast flow domain, slow flow domain and stagnation domain. The unstable dynamic arching effect of the funnel flow, the viscous effect of the liquid bridge force and the collapsing effect of the particle swarm could probably lead to the blockage of the discharge port of the high-pressure tank. When the semiapex angles of the high-pressure tank decreases, the volume flow rate of particles increases and the stagnation domain becomes smaller, but it becomes easier to form arching and blockage. The modelling results indicate that the pulsation of the funnel flow is minimum when the semiapex angle is 45° without the mutilation element, which means the funnel flow of the particle swarm is relatively stable. By introducing a conical modulating element above the discharge port, the unstable funnel flow of the particle swarm could be transformed to an overall uniform flow. The modelling results indicate that the installation height of the modulation element has the greatest influence on the pulsation degree. The optimized parameters for the conical modulation element based on numerical modelling tests are 70° for the vertex angle, 35 mm for the length of the flank and 70 mm for the installation heigh.

The microstructure of primary Mg 2 Si and the interface of Mg 2 Si / α -Mg modified by Sn and Sb elements in an as-cast Mg-5Sn-2Si-1.5Al-1Zn-0.8Sb (wt.%) alloy were investigated. In the primary Mg 2 Si phase not only the Si atoms but also the Mg atoms could be substituted by Sn and Sb atoms, resulting in the slightly reduced lattice constant a of 0.627 nm. An OR of Mg 2 Si phase and α -Mg in the form of [ 001 ] Mg 2 Si ∥ [ 01 1 ¯ 1 ] α , ( 220 ) Mg 2 Si ∥ ( 0 1 ¯ 12 ) α was discovered. Between primary Mg 2 Si phase and α -Mg matrix two transitional nano-particle layers were formed. In the rim region of primary Mg 2 Si particle, Mg 2 Sn precipitates sizing from 5 nm to 50 nm were observed. Adjacent to the boundary of primary Mg 2 Si particle, luxuriant columnar crystals of primary Mg 2 Sn phase with width of about 25 nm and length of about 100 nm were distributed on the α -Mg matrix. The lattice constant of the Mg 2 Sn precipitate in primary Mg 2 Si particle was about 0.756 nm. Three ORs between Mg 2 Sn and Mg 2 Si were found, in which the Mg 2 Sn precipitates had strong bonding interfaces with Mg 2 Si phase. Three new minor ORs between Mg 2 Sn phase and α -Mg were found. The lattice constant of primary Mg 2 Sn phase was enlarged to 0.813 nm owing to the solution of Sn and Sb atoms. Primary Mg 2 Sn had edge-to-edge interfaces with α -Mg. Therefore, the primary Mg 2 Si particle and α -Mg were united and the interfacial adhesion was improved by the two nano-particles layers of Mg 2 Sn phase.

Laboratory experiments were performed to study the impact of the relative particle protrusion P/D (P is the protrusion height and D is the diameter of the target particle) on the mechanism of entra...

Strontium aluminate nanophosphor doped with Praseodymium was synthesized by sol–gel method. The above synthesized SrAl4O7:Pr material was characterized by SEM, PXRD, EDAX, TG and PL. By Xray diffraction analysis monoclinic structure was confirmed. Particle size was calculated by using Scherrer formula. Obtained nano particles are round interlinked shaped and leads to the formation of bigger particle. Under excitation for 360 nm, Photolumiscence emission obtained were at 395 nm, 520 nm 790 nm for UV and Green and IR regions respectively. The TG curve illustrates the three key weight loss measures for Pr doped SrAl4O7.

Ferrite Cobalt (CoFe2O4) is a recognized attractive material with normal implementation and normal size of polarization. It has unmistakable substance security and motorized hardness. It is an eager promoter for the strategy of tactile gadgets and actuators, as an authoritative fixing, attractive medication gadgets electrical and having a broad scope of researching in materialistic innovation or science for mechanical uses and applications. These nanoparticles cobalt and ferrite on an ensnared viably handled on surrounding temperature by a basic process of co-precipitation. This precious stone structures and architecture of image was controlled through X-ray diffraction and SEM. The range of XRD affirms that composite nano-particles were shaped by ideal structure of spinel. This normal pace of precious stones was controlled through methods for Modified Scherer (54 nm) and Williamson-Hall (49 nm) techniques. A SEM view demonstrated nanoparticles CoFe2O4 being assembled in close-by structures. This visual and bond highlights was depicted by FTIR and UV–Vis Spectrum. As the temperature of the production rises, so does the magnetics period for the NPs and the magnetization of the concentration improves monotonously from 2.6 μB to 16 μB plus from 37 to 66 emu/g. According to the actions of both SPM and attendance of a dead layer (surface amorphous shell layer), which systemically decreases as the synthesis temperature increases, the optimum curve-appropriate of M-H statistics is due to the reduced particle/particle interaction.

Aluminium-wood particle composites were formed by casting method. Different weight fractions of wood particle as reinforcement to the Aluminium alloys were used to produce the composites. The physical and mechanical properties such as density, impact strength, tensile strength, hardness and microstructure were investigated. The results showed that the density decreases with the percentage increase in reinforcement. Also, a significant enhancement in the ultimate tensile strength (UTS) of the composite compared to that of pure aluminium was achieved. The maximum UTS of the Aluminium -wood composite is 97.69 MPa and occurred at 20%wt wood particulate addition reinforcement while that of the unreinforced Aluminium is 40.189 MPa. The impact energy varies from 47.00 J to 89.00 J with a maximum value at 10%wt wood particulate addition while the hardness varies from 52.33BHN to 62BHN with a maximum value at 10%wt. All the mechanical behaviours investigated in the study generally showed that the Aluminium -wood composite exhibited better mechanical properties than the pure Aluminium. The microstructure examination revealed that the wood particles were uniformly distributed in the metal matrix composite.

Granular matter can exhibit solid or liquid behavior, which contains complex physical mechanisms. In this work, we experimentally investigated the structural relaxation and avalanche dynamics of particle piles under vertical vibration. The influence of vibration parameters on the avalanche process was studied. The morphological features of avalanches were recorded and classified using high-speed camera. The effects of vibration parameters and particle properties on the relaxation mode are obtained. It is found that the evolution of particle pile height with time can be described by an exponential decay function. The relaxation rate and avalanche characteristics of four types of particles with different sizes are discussed. At the same acceleration level, for two larger particles, a smaller amplitude (A = 0.025 mm) leads to a faster relaxation rate, while for two smaller particles, a large amplitude (A = 0.500 mm) leads to a faster relaxation rate. The analogy powder surface tension is introduced to address the cohesion and flowability evolution of particles under vibration.

To study the effects of the morphology of ZnO particles on the properties of asphalt binder and asphalt mixture, the micro ZnO particles with different morphologies (agglomerate, sphere, rod and flower), whose average size were 2 µm, were made by the homogeneous precipitation and hydrothermal methods. A series of tests, including the softening point, bending beam rheometer (BBR), dynamic shear rheological (DSR), Marshall test, rutting test and so on, were used for evaluating the properties of asphalt binder and asphalt mixture. The analysis of variance (ANOVA) and the maximum relative difference (MRD) were introduced to study the effects of the morphology of ZnO particles on the properties of asphalt binder and asphalt mixture. Finally, the optimal morphology of the ZnO particle was recommended. The results show that the morphology of the ZnO particle has a significant effect on the rutting factor, has an effect on the viscosity in the situation of the dosages of SBS are 0% and 4%, has no effect on the low temperature ability of asphalt binder. In terms of asphalt mixture, the morphology of the ZnO particle has a noticeable effect on the high temperature stability, has an effect on the low temperature ability, has almost no effect on the water stability of asphalt mixture. Furthermore, the rod-like ZnO particles are more conducive to promote the properties of asphalt binder and asphalt mixture. As a result, the rod-like ZnO particle is recommended.

Liquid–solid fluidized beds (LSFB) modeling validation is crucial for establishing design rules and monitoring tools. However, it generally relies on comparing global variables, which overlook dynamic features that influence reaction outputs. This work aims to implement time series analysis tools to compare Radioactive Particle Tracking data with a simulation consisting of Computational Fluid Dynamics coupled with Discrete-Element Method. Experiments have been performed in a pilot-scale LSFB of calcium alginate spheres fluidized with a calcium chloride solution. The Diks’ test indicates that the simulation can capture the LSFB behavior. It also allows diagnosing flow regime transitions from the simulation. Trends of solid dispersion coefficients and mixing times predicted by the simulation are in good agreement with the experiments.

Fe3O4 nanoparticles have been a research focus area for many years and have been applied in fields like medical treatment, catalysis and sensors. Particularly, they can be coated and dispersed in a solvent to prepare magnetic fluids. Magnetic fluid sealing is a high-performance sealing method but still not capable of extreme working conditions such as elevated temperatures. Here we present a new sealing method with nano-micro magnetic powders as a sealing medium. Fe3O4 particles with an average size of 20 nm, 200 nm and 25 μm are prepared by the chemical co-precipitation method. The fluid permeability of magnetic powders is estimated by Darcy’s Law. Finally, a static sealing prototype is designed and optimized based on magnetic field distribution analysis. Sealing experiments show a strong relevance between particle sizes and leakage rate. The mixture of nano and micron-sized Fe3O4 particles leads to a significant decrease in leakage rate, making magnetic powder sealing a promising novel sealing method.

In many energy and combustion applications, particles experience large temperature gradients, which can affect the coagulation process due to thermophoresis. This study presents a rigorous theory of thermophoretically modified Brownian coagulation in the entire particle size regime. The theoretical derivations are based on the kinetic theory for the free-molecular regime and the harmonic mean method for the transition regime. The coagulation kernels in different size regimes can be expressed as the basic Brownian coagulation kernel times an enhancement factor. The enhancement factor represents the coagulation rate enhancement induced by thermophoresis and is a function of specific dimensionless numbers. Based on the enhancement factor, the thermophoretic enhancement effects on particle coagulation are further analyzed under a wide range of gas and particle conditions. The results show that thermophoretic enhancement effects are ignorable in the free-molecular regime, but need to be considered in the continuum regime and the transition regime. In addition, the enhancement effects increase significantly with increase of gas temperature and temperature gradient while decrease with increase of gas pressure. The present study can improve understanding of thermophoretic effects on Brownian coagulation in the entire size regime and provide a useful tool to calculate the coagulation rates in presence of thermophoresis.

Static electricity has an important effect on gas–solid fluidized bed reactor fluidization performance. In the process of fluidization, electrostatic interaction between particles will obviously accelerate particle agglomerate formation, which consequently reduces the fluidization performance. Pulsed gas flow injection is an efficient method to enhance particle mixing, thereby weakening the occurrence of particle agglomerate. In this study, the two-dimensional hybrid pulsed fluidized bed is established. The flow characteristics are studied by using the coupled CFD-DEM numerical simulation model considering electrostatic effects. Influences of different pulsed frequencies and gas flow ratios on fluidized bed fluidization performance are investigated to obtain the optimal pulsed gas flow condition. Results show that in the presence of static electricity, the bubble generation position is lower, which is conducive to the particle flow. Pulsed gas flow can increase the particle velocity and improve the diffusion ability. The bubble generation time is different at different frequencies, and the frequency of 2.5 Hz has the most obvious effect on the flow characteristics. Different gas flow ratios have significant impacts on the particle movement amplitude. When the pulse gas flow accounts for a large ratio, the particle agglomerate tends to be larger. Therefore, in order to improve the fluidization effect, the ratio of pulsed gas flow to stable gas flow should be appropriately reduced to 0.5 or less.

Water-based fire extinguishing agent is the main means to deal with smoldering fires. However, due to the hydrophobic properties of the particle surface, the porous medium channel provide resistance and slow down the extinguishing agent flow during the downward permeation process. To promote the liquid permeation process in such porous media, this work studied liquid imbibition process and analyzed the oscillating and attenuating process of liquid level in capillary channel by theoretical, experimental, and numerical methods. An empirical mathematical equation was proposed to describe the oscillating process, and the effects of the capillary diameter and contact angle parameters on the transportation process were analyzed. Based on this, the “relay-mode” was proposed to promote the liquid transportation forward. Finally, the transient simulation results of liquid permeation in coal stacks showed when the liquid flowed through the channel with changed diameter from large to small ones, the transportation distance was several times longer than that through the unidiameter ones. The trend of liquid “relay-mode” in capillaries can be used to promote the permeation in granular materials porous media stacks. The relevant results also provide new thoughts to develop the water-based fire extinguishing agents and then improve the firefighting efficiency of deep-seated fire in porous media stacks.

Gadolinium (III)-based T1 contrast agent have been widely used in clinical MRI. In this study, salicylic acid-gadolinium chelate was prepared via directly coordination reaction of gadolinium ion and salicylic acid. Then, three polyethylene glycols with different molecular weight were modified on the surface of salicylic acid-gadolinium by simple chemical coupling to construct three core-shell structural Gd based composites. The SEM and TEM characterization results show that the composite is a spherical particle with a diameter of about 100–200 nm. The longitudinal relaxation rate r1 of the Gal-PEG-2000 is 11.097 (mmol/L)–1/s, and the ratio of r2/r1 is as low as 2.53. The composite shows good liver and intestines MRI performances after being used in in vivo imaging, showing a good prospect of biological application.

As the demand for lithium-ion batteries increases, a better understanding of the complex phenomena involved in their operation becomes crucial. In this work, we propose a coupled thermo-chemo-mechanical model for electrode particles of Li-ion batteries. To this end, we start with a general finite strain continuum framework for the coupled thermo-chemo-mechanical problem and then narrow it down to cathode active particles of Li-ion batteries, particularly to lithium manganese oxide particles. Electrochemical kinetics at the surface of the particle and also heat generation due to current exchange are taken into account. Next, the numerical treatment of the problem using the finite element method is presented. Specific line elements are needed to evaluate the flux of ions at the surface of the particle. Finally, the performance of the proposed model is evaluated using a few representative boundary value problems., Deutsche Forschungsgemeinschaft, Projekt DEAL

Screw conveyors are extensively used in modern industry such as metallurgy, architecture and pharmaceutical due to their high-efficiency in the transportation of granular materials. And substantial efforts have been devoted to the study of the screw conveyors. Numerical method is an effective way to study screw conveyor. However, previous studies have mainly focused in the regime of spherical particles while the in-depth investigations for non-spherical particles that should be the most encountered in practical applications are still limited. In view of the above situations, discrete element method (DEM), which has been widely accepted in simulating the discrete systems, is utilized to investigate the conveying process of non-spherical particles in a horizontal screw conveyor, with particles being modeled by super-ellipsoids. In addition, a wear model called SIEM (Shear Impact Energy Model) is incorporated into DEM to predict the wear of screw conveyor. The DEM simulation results demonstrate that the particle shape is influential for the flow behaviors of particles and the wear of conveyor. The conveying performance evaluated quantitatively of both mass flow rate and power consumption is subsequently obtained to investigate the effect of sphericity of particle with different operation parameters. Moreover, particle collision frequency and collision energy consumption are acquired to investigate the possible particle breakage between particles and screw blade. The comparisons between particle–particle collision and particle–wall collision reveal that particles with large shape index have more possibility to be damaged in particle–wall impingement.

Fluidized Carbon Bed Cooling (FCBC) is an innovative investment casting process for directional solidification of superalloy components. It takes advantage of a fluidized bed with a base of small glassy carbon beads for cooling and other low-density particles that form an insulating layer by floating to the bed surface. This so-called “Dynamic Baffle” protects the fluidized bed from the direct heat input from the high-temperature heating zone and provides the basis for an improved bed microstructure. The prerequisites for a stable casting process are stable fluidization conditions where neither collapse of the bed nor particle blow out at excessive bubble formation occur. This work aimed to investigate the fluidization behavior of spherical carbon bed material in argon and air at temperatures between 20 to 350 °C. Systematic studies at reduced pressures using the FCBC prototype device were performed to understand the stable fluidization conditions at all stages of the investment casting process. The particle shape factor and size distribution characterization and the measurement of the powder’s minimum fluidization velocity and bed voidage show that this material can be fully utilized as a cooling and buoyancy medium during the FCBC process.

Heat transfer is of vital importance because of its application in industries. A new nanofluid class called "hybrid nanofluid" is being used to boost ordinary fluids' heat transfer capabilities and has a higher heat exponent than nanofluids. The hybrid nanofluids (HNFs) are associated with two-element nanoparticles immersed in a base fluid. The steady hybrid nanofluid flowing and thermal transport characteristics passed overhead a slippery surface are investigated in this research. The impact of nanosolid particle shapes, Porosity material, heat source, viscous dissipative flow, and radiative flux are also involved in this examination. In a regime of partial-differential equations (PDEs), the predominant flow equations are formulated. Keller-box's computational technique is the utilized method to detect the self-similar solution for formulas transformed into ordinary-differential equations (ODEs) through appropriate transmutations. Williamson hybrid nanofluid has been considered for this work, which consists of double diverse kinds of nanoparticle, Copper (Cu) and Silicon dioxide (SiO2) in the rich viscous based fluid of kind EO (Engine Oil). The noteworthy result of this analysis is that the comparing thermal transmission level of such kind of fluid (SiO2-Cu/EO) which has progressively more upsurges as compared to traditional nanofluids (Cu-EO). The lamina-shaped elements cause the utmost important thermal conductivity in the boundary- layer, whilst the lowermost thermal conductivity is detected in sphere shaped nanoparticles.

The discrete element method (DEM) is widely used in the realistic simulation of the shapes of particles. Researchers have considered the simplification of particle shapes owing to the high computational cost of such simulation. In this regard, the modeling of calibrated particles is a major challenge owing to the simultaneous effects of particle properties. The angle-of-repose test is a standard test method used to calibrate the bulk behavior of simulated particles. In the present study, the hollow-cylinder (slump) test was modeled for the verification of discrete element simulations. In this regard, a sensitivity analysis was conducted for all effective parameters, namely the static friction, rolling friction, restitution coefficient, sphericity, roundness, particle size distribution, and number of ballast particles. The results indicate that the rolling friction, roundness, number of particles, and size of particles are the most important parameters in the determination of the angle of repose (AOR). For particles in the range of ballast (20–60 mm), the effect of the number of particles on the angle of repose is reduced when the number is greater than 426. Additionally, it is concluded that angular particles can be replaced with sub-angular particles (R ≈ 0.2–0.45) with a higher rolling friction coefficient (μr > 0.14).

The different carbon nanotube (CNT) particles (@A and @V) were bed materials in the pseudo-2D tapered fluidized bed (TFB) with/without a distributor. A detailed investigation of the motion mechanism of bubbles was carried out. The high-speed photography and image analysis techniques were used to study bubble characteristic and mixing behavior in the tapered angle of TFB without a distributor. The fractal analysis method was used to analyze the degree of particles movement. Results showed that an S-shaped motion trajectory of bubbles was captured in the bed of @V particles. The population of observational bubbles in the bed of @V particles was more than that of @A particles, and the bubble size was smaller in the bed of @V particles than that of @A particles. The motion mechanism of bubbles had been shown to be related to bed materials and initial bed height in terms of analysis and comparison of bubble diameter, bubble aspect ratio and bubble shape factor. Importantly, compared to the TFB with a distributor, the TFB without a distributor had been proved to be beneficial to the CNT fluidization according to the study of bubble characteristic and the degree of the particle movement. Additionally, it was found that the mixing behavior of @V particles was better than @A particles in the tapered angle of TFB without a distributor.

The droplet velocity and diameter significantly affect both the spatial drift loss and the interfacial deposition behaviors, thus determining the ultimate utilization efficiency during pesticide spraying. Investigating the spatial velocity and diameter evolutions can reveal the mechanism of drift loss and guide to design regulation strategy. Here, we explored the spatial velocity distribution of droplets after leaving the nozzle by particle image velocimetry technology and particle tracking model, considering that the effect of nozzle configuration and the air velocity. It shows that all droplets decelerate rapidly with the velocity attenuation ratio ranging from 50% to 80% within the region of 200 mm below the nozzle. The spatial velocity evolution differences between droplets in crossflow are determined by the competition of vertical drag force and net gravity, and the drag force sharply increases as the droplet diameter decreases, especially for that smaller than 150 μm. Based on the spatial evolution differences of the droplet velocity and diameter, a functional adjuvant was added to the liquid for improving the diameter distribution. And the drift loss was significantly reduced due to the reduction of the proportion of easily drifting droplets.

This study aimed to quantitatively identify the influence of the block impact angle and block shape on the impact effect of reinforced concrete (RC) sheds. The smooth particle hydrodynamic (SPH) method and finite element method (FEM) were coupled and used to solve the simulation difficulty of large deformation of the sand buffer layer in the RC shed. SPH was used to simulate the sand buffer layer in the impact area that experienced large deformation. Concrete, reinforced, bedrock, block and sand buffer layer in the non-impact area were simulated by FEM. The accuracy of the coupled model was verified by the full-scale test data. Finally, the impact forces and the dynamic responses of the RC shed were analyzed, focusing on the effects of the block impact angle and shape. The numerical results show that the coupled SPH-FEM method is effective for simulating how block impacts the RC shed. The block impact angle and shape can significantly influence the normal and tangential impact forces. The design of the RC shed based on the assumption of blocks as free-falling spherical projectiles can lead to inaccuracy in some impact scenarios, and an appropriate correction was put forward in available empirical calculating formulae to include the effect of the irregular shape and impact angle of the block. The sand buffer layer dissipates a large part of the energy, which accounts for at least 58% of the initial impact energy.

In this paper, we present the design, development, and characteristics of the novel aerosol mass spectrometer ERICA (ERC Instrument for Chemical composition of Aerosols; ERC – European Research Council) and selected results from the first airborne field deployment. The instrument combines two well-established methods of real-time in situ measurements of fine particle chemical composition. The first method is the laser desorption and ionization technique, or laser ablation technique, for single-particle mass spectrometry (here with a frequency-quadrupled Nd:YAG laser at λ = 266 nm). The second method is a combination of thermal particle desorption, also called flash vaporization, and electron impact ionization (like the Aerodyne aerosol mass spectrometer). The same aerosol sample flow is analyzed using both methods simultaneously, each using time-of-flight mass spectrometry. By means of the laser ablation, single particles are qualitatively analyzed (including the refractory components), while the flash vaporization and electron impact ionization technique provides quantitative information on the non-refractory components (i.e., particulate sulfate, nitrate, ammonia, organics, and chloride) of small particle ensembles. These techniques are implemented in two consecutive instrument stages within a common sample inlet and a common vacuum chamber. At its front end, the sample air containing the aerosol particles is continuously injected via an aerodynamic lens. All particles which are not ablated by the Nd:YAG laser in the first instrument stage continue their flight until they reach the second instrument stage and impact on the vaporizer surface (operated at 600 ∘C). The ERICA is capable of detecting single particles with vacuum aerodynamic diameters (dva) between ∼ 180 and 3170 nm (d50 cutoff). The chemical characterization of single particles is achieved by recording cations and anions with a bipolar time-of-flight mass spectrometer. For the measurement of non-refractory components, the particle size range extends from approximately 120 to 3500 nm (d50 cutoff; dva), and the cations are detected with a time-of-flight mass spectrometer. The compact dimensions of the instrument are such that the ERICA can be deployed on aircraft, at ground stations, or in mobile laboratories. To characterize the focused detection lasers, the ablation laser, and the particle beam, comprehensive laboratory experiments were conducted. During its first deployments the instrument was fully automated and operated during 11 research flights on the Russian high-altitude research aircraft M-55 Geophysica from ground pressure and temperature to 20 km altitude at 55 hPa and ambient temperatures as low as −86 ∘C. In this paper, we show that the ERICA is capable of measuring reliably under such conditions.

In this study, functionally graded foam made of Inconel 625 superalloy was successfully produced using the template replication method, with open-cell polyurethane foams as a precursor. The products have a similar pore morphology as the templates and adjacent layers were successfully sintered together by particle bonding. Sound absorption experiments on graded metallic foams reveal that the sound absorption at particular frequency ranges can be improved by various permutations of foam layers. For graded foam of two distinct pore sizes, a mathematical equation was proposed to predict the location of the intersection point of the sound absorption curves, thereby aiding in graded foam design. An increase in sound absorption coefficients by resonance-like effects can be introduced before the intersection points by placing the foam layer of smaller pore size nearer to the sound source. The sound absorption performances can be further customized when the thickness proportion of the pore sizes is changed and when the number of distinct pore sizes used is increased. The sound absorption performance at lower frequencies is generally boosted by resonance-like effects when the layer of foam with the largest pore size is placed furthest from the sound source. Given the same composition of foam with a fixed thickness proportion of pore sizes, one can introduce resonance-like effects to improve the sound absorption performance compared to other permutations while possibly satisfying weight requirements in practical applications. This study provides valuable insights and mathematical guidelines in the design and manufacturing of functionally graded metallic foam for specific applications.

The phenomenon of adsorption of solid particles at fluid interfaces to stabilize emulsions or foams have been known for more than a century. Today, particle-stabilized emulsions, often referred to as Pickering emulsions, are receiving growing attention as they are encountered in oil recovery and have long been used in personal care products and food industry. In the past 10 years the focus of the Pickering emulsion has also increasingly shifted to biomedical applications with thanks to novel syntheses of a wide range of biocompatible particle stabilizers. Here, a brief overview of the development of biocompatible particles is given for Pickering emulsion stabilization, including alginate, poly(lactic-co-glycolic acid) (PLGA), and protein-based particles. The materials capable of being prepared by templating from emulsion stabilized with biocompatible particles include colloidal capsules and hierarchically porous materials. It is hoped that the understanding gained from the recent intense activity in the field will enable more researchers to modify existing materials and design new formulations, which would be beneficial for exploring more biological applications.

Experiments have been performed to explore the combustion behaviors of spherical micron-sized aluminum (μAl) particles and liquid water for Al particle sizes in the range of 3.5–25 μm. The ignitio...

Pickering emulsions are emulsions stabilized by colloidal surfactants, i.e. solid particles. Compared with traditional molecular surfactant-stabilized emulsions, Pickering emulsions show many advantages, such as high resistance to coalescence, long-term stability, good biocompatibility and tunable properties. In recent years, Pickering emulsions are widely applied in scientific researches and industrial applications. In this review, we focus on the influences of particle properties on Pickering emulsions, including particle amphiphilicity, concentration, size and shape, and summarize the strategies developed for the preparation of amphiphilic Janus particles. The applications of Pickering emulsions in food industry, cosmetic industry, material science, drug delivery, biomedical research and vaccine adjuvant will also be covered. Pickering emulsions are a unique system for multi-disciplinary studies and will become more and more important in the future.

Emulsions are liquid–liquid dispersions with one liquid phase dispersed in the other liquid phase as small droplets. Nanoemulsions are nano-sized emulsions with sizes ranging from tens to hundreds of nanometers, and have great potential applications in pharmaceutics, foods and cosmetics due to their attractive properties, such as small sizes, high surface area per unit volume, improved dispersion of active hydrophobic components and enhanced absorption. The article provides an overview of nanoemulsions for drug delivery, starting with an introduction of emulsion types, nanoemulsion preparation and nanoemulsion stability. Surfactants play critical roles in producing and stabilizing nanoemulsions. Different types of surfactants are summarized including small molecule surfactants, particle surfactants, phospholipids, peptide and protein surfactants. Then the applications of nanoemulsions as nanomedicine in drug delivery are presented. Finally, clinical applications of nanoemulsions are discussed.

In order to mimic hierarchical nanostructures in nature, particles of polymer blends consisting of poly(4-butyltriphenylamine) (PBTPA), poly(methyl methacrylate) (PMMA) and PBTPA-block-PMMA were fabricated by a solvent evaporation method. Effects of the molecular weight and the chemical composition of PBTPA-b-PMMA, molecular weights of homopolymers, and the composition of the blend on the morphology were investigated. The polymer blend particle consisting of PBTPA and PMMA homopolymers exhibited thermodynamically favored core-shell structure, in which more hydrophilic PMMA-shell surrounded PBTPA-core. The addition of 10 wt% of PBTPA-b-PMMA caused the morphological transition from core-shell to Janus or inversed core-shell, in which PBTPA-shell surrounded PMMA-core, depending on the molecular weight of PBTPA segment in PBTPA-b-PMMA. When the molecular weight of PMMA segment was higher than that of PMMA homopolymer, watermelon-like particles in which small PBTPA domain less than 80 nm dispersed in the PMMA domain surrounded by PBTPA shell were observed. As the ratio of PBTPA-b-PMMA increased, the interface of the macrophase separation became obscure. At 50 wt% of the PBTPA-b-PMMA, only microphase separation was observed. The measurement of interfacial tension by pendant drop method demonstrated that PBTPA-b-PMMA lower the interfacial tension between PBTPA and the aqueous phase to the value similar to that of PMMA with the aqueous phase.

The bubble formation dynamics and size manipulation in the slurry of polystyrene microspheres in the microfluidic T-junction were visually investigated by a high-speed camera. Based on the evolution law of the bubble neck width with time, the formation process of bubbles is divided into three stages: filling, squeezing and pinch-off. The particle concentration has an obvious effect on the squeezing stage, while less impact on the filling and pinch-off stages. In the squeezing stage, the evolution of the dimensionless minimum neck width of bubbles with time could be described by a power-law relationship. The increase of the particle concentration or continuous phase flow rate could lead to the increase of body flow of the continuous phase flow rate and the enhancement of the squeezing force acted on the bubble neck, correspondingly, the power-law index α in the squeezing stage enlarges. Moreover, the bubble size increases with the increase of the gas phase flow rate and the decrease of the particle concentration and continuous phase flow rate. However, the effect of the particle concentration on the bubble size weakens with the increase of the continuous phase flow rate. In addition, a new prediction correlation of the bubble size for the slurry system in a T-shape microchannel was proposed with good prediction accuracy.

The evolution of the hydrate particle structure during growth and agglomeration under flowing condition affects the particle as well as flow characteristic, which plays an important role in the flow assurance as well as heat transfer in refrigeration systems. Therefore, this article conducts experiments to study and observe the growth and agglomeration process in the main forming stage of hydrate. It was found that the growth of tetrahydrofuran hydrate was anisotropic and in a layered growth pattern. Single crystals generally transformed from octahedral structure to octahedral skeleton structure with growth, however some single crystals also deformed into plate type particles. The thickness of the plate type particles increased gradually during growth, and the edge part increased earlier than the middle part. During agglomeration, the hydrate particles contacted and sintered together. Sand as the impurity didn’t serve as the nucleation center but affected the agglomeration of hydrate particles by collisions. In addition, the effect increased as the sand size decreased. Finally, a microstructure model for hydrate growth and agglomeration was proposed, which showed the hydrate structure evolution in these processes and could lay a foundation for studying the flow assurance of hydrate slurry.

Understanding of nanoplastic prevalence and toxicology is limited by imaging challenges resulting from their small size. Fluorescence microscopy is widely applied to track and identify microplastics in laboratory studies and environmental samples. However, conventional fluorescence microscopy, due to diffraction, lacks the resolution to precisely localize nanoplastics in tissues, distinguish them from free dye, or quantify them in environmental samples. To address these limitations, we developed techniques to label nanoplastics for imaging with Stimulated Emission Depletion (STED) microscopy to achieve resolution at an order of magnitude superior to conventional fluorescence microscopy. These techniques include (1) passive sorption; (2) swell incorporation; and (3) covalent coupling of STED-compatible fluorescence dyes to nanoplastics. We demonstrate that our labeling techniques, combined with STED microscopy, can be used to resolve nanoplastics of different shapes and compositions as small as 50 nm. The longevity of the dye labeling is demonstrated in different media and conditions of biological and environmental relevance. We also test STED imaging of nanoplastics in exposure experiments with the model worm C. elegans. These techniques will allow more precise localization and quantification of nanoplastics in complex matrices.SynopsisWe show that Stimulated Emission Depletion (STED) microscopy can be used to image single nanoplastics of different compositions and shapes. This will allow researchers to study environmentally-relevant nanoplastics and their interactions with organisms in relevant exposure scenarios.TOC Graphic

Supercritical water (SCW) fluidized bed reactors convert biomass to fuels without pollutants emission. In this work, experimental studies were carried out to investigate voidage distribution in an SCW fluidized bed by capacitance probes. Quartz sands with different particle sizes were fluidized by SCW under system pressure of 20–27 MPa and temperature of 410–570 °C. The effect of operation conditions on voidage distributions of the emulsion phase (e.g. averaged voidage and probability density) is discussed. A predicting correlation between voidage and superficial velocity in emulsion phase is proposed. The relative error of the correlation is within ±25%. These research results provide useful guidance for the optimization of supercritical water gasification technology.

A computational study was carried out on bubble dynamic behaviors and bubble size distributions in a pressurized lab-scale gas-solid fluidized bed of Geldart A particles. High-resolution 3-D numerical simulations were performed using the two-fluid model based on the kinetic theory of granular flow. A fine-grid, which is in the range of 3-4 particle diameters, was utilized in order to capture bubble structures explicitly without breaking down the continuum assumption for the solid phase. A novel bubble tracking scheme was developed in combination with a 3-D Detection and Tracking Algorithm (MS3DATA) and applied to detect the bubble statistics, such as bubble size, location in each time frame and relative position between two adjacent time frames, from numerical simulations. The spatial coordinates and corresponding void fraction data were sampled at 100Hz for data analyzing. The bubble coalescence/break-up frequencies and the daughter bubble size distribution were evaluated by using the new bubble tracking algorithm. The results showed that the bubble size distributed non-uniformly over cross-sections in the bed. The equilibrium bubble diameter due to bubble break-up and coalescence dynamics can be obtained, and the bubble rise velocity follows Davidson’s correlation closely. Good agreements were obtained between the computed results and that predicted by using the bubble break-up model proposed in our previous work. The computational bubble tracking method showed the potential of analyzing bubble motions and the coalescence and break-up characteristics based on time series data sets of void fraction maps obtained numerically and experimentally.

Fly ash (FA) is a complex and abundant solid waste created by humans, and has caused environmental issues, for which flotation is an effective technique employed before its comprehensive utilization. However, the complex and hydrophilic characteristics of FA particles cannot naturally fulfill the selective separation by common flotation. Therefore, this study aims to provide an insight into fluid intensification effects on flotation to achieve the enhancement of FA surface property and decarburization. The relevant effects and mechanisms are investigated, based on the measurements of zeta potential, infrared spectroscopy, contact/wrap angle, induction time, size distribution and scanning electron microscopy–energy dispersive spectrometry. Experimental results manifested that the maximum unburned carbon recovery (73.25%) and flotation rate (0.2037 s–1) were achieved with preconditioning energy inputs of 14.23 and 6.57 W·kg–1 respectively. With increasing preconditioning energy inputs, fluid intensification effects could promote the inter-particle collision/attrition, detachment of hydrophilic existence and collector adsorption on particles. Correspondingly, absorbance of some hydrophobic and hydrophilic functional groups was strengthened and weakened respectively, which accounted for the improved interfacial properties, reflected as the increased contact and wrap angles, together with declined induction time. Overall, this article revealed the positive influences of fluid intensification based preconditioning process on rendering particle surface hydrophobic and improving separation performance.

In this study, a system of automatic microparticle patterning that could enable the separation, trapping, and translation of single microbeads in liquid suspension using negative dielectrophoresis (DEP) tweezers was presented to form a single-bead pattern. A microchip with integrated electrodes was flipped and placed above the substrate through a micromanipulator. Microparticles laying on the substrate could be displaced to different positions relative to the electrodes on the microchip, and only the selected particles would be trapped by the electric fields generated from electrodes. Vision-based approaches were used to evaluate the necessary information, such as the gap distance and the positions of electrodes and microparticles in the image. A strategy for separating nearby particles was proposed to achieve single-bead patterning with high accuracy. A controller was used to guide the microparticles toward the position for trapping while avoiding flow disturbance. Different strategies were simulated to decrease the patterning time and find the minimum traveling distance and the best route of movement. The optimization problem is NP-hard. Hence, global optimization algorithms, such as genetic algorithm, particle swarm optimization, and ant colony optimization (ACO), were simulated, and the results were compared with those of the local optimization method. The comparison results showed that ACO obtained the best performance among the methods. The strategy for constructing high-quality microparticle patterns was also examined through experiments. Orange fluorescent polystyrene beads suspended in 6-aminohexanoic acid solution were considered and successfully patterned on a glass substrate by using the proposed system.

Triaxial experiments were conducted on granular materials presenting uniform, graded and fractal particle distributions in order to investigate how the broadness of the distribution affects the phenomenon of strain localisation. The shear band thickness evolution is assessed by digital image correlation (DIC) using three cameras placed at different angles around a transparent triaxial cell. From the field of deformation, Gaussian distributions have made it possible to fit the data satisfactorily and determine the shear band width evolution. The latter exhibits a rapid decrease in the softening regime until a residual value is reached in all cases. In the conditions of the experiments, it is shown that the residual shear band thickness scales with the mean grain size and the ratio between the two increases with the broadness of the distribution. Samples with uniform distribution exhibit an average residual thickness of ∼ 10D50, samples with graded distribution exhibit an average residual thickness of ∼ 12·5D50 and samples with fractal distribution exhibit an average residual thickness of ∼ 17D50.

Poor ductility is the primary concern of magnesium matrix composites (MMCs) inflicted by non-deformable ceramic particle reinforcements. Metal particles which melt at elevated temperature can be used as reinforcement to improve the deformation characteristics. Ti-6Al-4V particles reinforced AZ31 MMCs were produced through friction stir processing (FSP) which was carried out in a traditional vertical milling machine. The microstructural features as well as the response to external tensile load were explored. A homogenous distribution of Ti-6Al-4V was achieved at every part of the stir zone. There was no chemical decomposition of Ti-6Al-4V. Further, Ti-6Al-4V did not react with Al and Zn present in AZ31 alloy to form new compounds. A continuous strong interface was obtained around Ti-6Al-4V particle with the matrix. Ti-6Al-4V particles underwent breakage during processing due to severe plastic strain. There was a remarkable refinement of grains in the composite caused by dynamic recrystallization in addition to the pinning of smaller size broken particles. Dense dislocations were observed in the matrix because of plastic deformation and the associated strain misfit. Ti-6Al-4V particles improved the tensile behavior and assisted to obtain appreciable deformation before fracture. Brittle mode of failure was avoided.

With the enhancement of the people consciousness of environment protection, soot particulates (PM) elimination has drawn wide attention in recent years. Efficient after-treatment with well-designed catalysts is one of the best ways to eliminate soot particulates that come from diesel engines. Catalysts coated on the DPF (diesel particulate filter) are considered as the main factor to lower soot ignition temperature. Improvement of the structures of the catalysts is significantly important in order to achieve good catalytic performance and high stability. Based on the structures, soot combustion catalysts can be mainly divided into three types: particle-based catalysts, 3DOM catalysts and nanoarray catalysts. This review mainly summarized recent advances in soot combustion catalysts with different designedmicro-structures, each category is explained with critical assessment and several typical examples, aiming to guide the synthesis of advanced soot combustion catalysts.

The effect of mechanical strength of the dispersed particle gels (DPG) on their macro plugging performances is significant, however, little study has been reported. In this paper, DPG particles with different mechanical strengths were obtained by mechanical shearing of bulk gels prepared with different formula. Young's moduli of DPG particles on the micro and nano scales were measured by atomic force microscope for the first time. The mapping relationship among the formula of bulk gel, the Young's moduli of the DPG particles and the final plugging performance was established. The results showed that when the Young's moduli of the DPG particles increased from 82 to 328 Pa, the plugging rate increased significantly from 91.46% to 97.10% due to the distinctly enhanced stacking density and strength at this range. While when the Young's moduli of the DPG particles surpassed 328 Pa, the further increase of plugging rate with the Young's moduli of the DPG particles became insignificant. These results indicated that the improvement of plugging rate was more efficient by adjusting the Young’s moduli of the DPG particles within certain ranges, providing guidance for improving the macroscopic application properties of DPG systems in reservoir heterogeneity regulation.

Gas atomization is now an important production technique for Fe-based amorphous alloy powders used in additive manufacturing, particularly selective laser melting, fabricating large-sized Fe-based bulk metallic glasses. Using the realizable k-e model and discrete phase model theory, the flow dynamics of the gas phase and gas-melt two-phase flow fields in the close-wake condition were investigated to establish the correlation between high gas pressure and powder particle characteristics. The locations of the recirculation zones and the shapes of Mach disks were analyzed in detail for the type of discrete-jet closed-coupled gas atomization nozzle. In the gas-phase flow field, the vortexes, closed to the Mach disk, are found to be a new deceleration method. In the two-phase flow field, the shape of Mach disk changes from “S”-shape to “Z”-shape under the impact of the droplet flow. As predicted by the wave model, with the elevation of gas pressure, the size of the particle is found to gradually decrease and its distribution becomes more concentrated. Simulation results were compliant with the Fe-based amorphous alloy powder preparation tests. This study deepens the understanding of the gas pressure impacting particle features via gas atomization, and contributes to technological applications.