Different Kinds Of Particles Research Articles

Effect of distribution shape on the melting transition, local ordering, and dynamics in a model size-polydisperse two-dimensional fluid

Abstract We study the effect of particle size polydispersity (δ) on the melting transition (T *), local ordering, solid–liquid coexistence phase and dynamics of two-dimensional Lennard–Jones fluids up to moderate polydispersity by means of computer simulations. The particle sizes are drawn at random from the Gaussian (G) and uniform (U) distribution functions. For these systems, we further consider two different kinds of particles, viz., particles having the same mass irrespective of size, and in the other case the mass of the particle scales with its size. It is observed that with increasing polydispersity, the value of T * initially increases due to improved packing efficiency (ϕ) followed by a decrease and terminates at δ ≈ 8% (U-system) and 14% (G-system) with no significant difference for both mass types. The interesting observation is that the particular value at which ϕ drops suddenly coincides with the peak of the heat capacity (CP ) curve, indicating a transition. The quantification of local particle ordering through the hexatic order parameter (Q 6), Voronoi construction and pair correlation function reveals that the ordering decreases with increasing δ and T. Furthermore, the solid–liquid coexistence region for the G-system is shown to be comparatively wider in the T–δ plane phase diagram than that for the U system. Finally, the study of dynamics reveals that polydisperse systems relax faster compared to monodisperse systems; however, no significant qualitative differences, depending on the distribution type and mass polydispersity, are observed.

Imaging Voids and Defects Inside Li-Ion Cathode LiNi0.6Mn0.2Co0.2O2 Single Crystals.

Li-ion battery cathode active materials obtained from different sources or preparation methods often exhibit broadly divergent performance and stability despite no obvious differences in morphology, purity, and crystallinity. We show how state-of-the-art, commercial, nominally single crystalline LiNi0.6Mn0.2Co0.2O2 (NMC-622) particles possess extensive internal nanostructure even in the pristine state. Scanning X-ray diffraction microscopy reveals the presence of interlayer strain gradients, and crystal bending is attributed to oxygen vacancies. Phase contrast X-ray nano-tomography reveals two different kinds of particles, welded/aggregated, and single crystal like, and emphasizes the intra- and interparticle heterogeneities from the nano- to the microscale. It also detects within the imaging resolution (100 nm) substantial quantities of nanovoids hidden inside the bulk of two-thirds of the overall studied particles (around 3000), with an average value of 12.5%v per particle and a mean size of 148 nm. The powerful combination of both techniques helps prescreening and quantifying the defective nature of cathode material and thus anticipating their performance in electrode assembly/battery testing.

Molecular dynamics simulation of deposition of amorphous carbon films on sapphire surfaces

The growth of amorphous carbon films on a sapphire surface was investigated using classical molecular dynamics simulation. The kinetic energy of carbon particles was set as 10 eV and ReaxFF potential was used to express the interaction between different kinds of particles. The results of the temperature distribution in both deposition time and deposition space are reported. Simulation results reveal that the grown amorphous carbon film consists of four regions, namely interlayer, low density, stable growth, and surface regions. In the interlayer region, the interlayer between substrate and pure carbon film is formed. In the low density region, a pure carbon film is grown while the film density decreases initially and then increases. In the stable growth region, the film density remains almost constant. The film density decreases rapidly in the surface region. The radial distribution function (RDF) analysis suggests that a structure similar to that of diamond exists in the stable growth region of the film. The lower film density in the low density and surface regions was interpreted to indicate the existence of abundant sp1 chain structures, which is supported by the depth profile of the sp fractions. The present results are in good agreement with previous experimental and simulation results and demonstrate the suitability of the ReaxFF potential in the simulation of amorphous carbon growth on sapphire substrate. Our study provides a good starting point for the simulation study of amorphous carbon films on sapphire substrates.

A review of particle detection using scintillation detector

Acquiring properties of microscopic particles helps establish modern physics models and theories, and detectors are the main method. This literature review researches on modern particle physics papers, summarizing the detection principle adopted for four types of particles, concluding the detection principle of the most commonly used detectors, scintillators, and summing up the use of scintillators in the four main kinds of particle detection. Based on the investigation, various kinds of detection materials absorb particles or their secondary particles based on different interaction mechanism in detection, and different kinds of particles have their suitable detectors. Scintillators are classified into three categories based on difference in physical properties, and detect particles by releasing energy during de-excitation in electric pulse signal forms. They can be made into large size, have relatively large detection efficiency and is suitable for ray detection. These ability gain scintillators a wide range of application in detection of the principal types of detectors.

Versatility of the Preparation Method for Macroporous Cryogel Particles Utilizing the Inverse Leidenfrost Effect.

We have investigated the versatility of a two-step preparation method, without a detergent, that combines both the inverse Leidenfrost effect and the cryogelation technique by using the macroporous particles of different kinds of monomers (four vinyl monomers) or a natural polymer (agarose). First, the precursor of polymers was dropped into liquid nitrogen to prepare the spherical frozen droplet by the inverse Leidenfrost effect. Second, the frozen droplets were cryo-polymerized at the frozen temperature; then, cryogel particles were prepared after thawing. Subsequently, the basic characteristics of the macroporous polymer particles obtained above were compared, focusing on the appearances, porous morphologies, and mechanical properties. It was found that the similar polymer particles could be obtained by the two-step preparation method, while there was a slight difference in their characteristics, depending on the type of monomers. Especially for the mechanical properties, the cryogel particles of the hydrophilic polymer exhibited a shape memory function with sponge-like elasticity, whereas the hydrophobic polymer particles were observed to be cracked after compression (i.e., no shape memory function). This work provides a versatile method of adopting various kinds of monomers and natural polymers for the preparation of macroporous particles. Hence, the method possibly has a potential to prepare and design "tailor-made" macroporous polymer particles for the application purpose.

Dynamics of test particles around charged black holes in Einstein-Æther gravity

This paper focuses on the issues of motion of various kinds of charged, magnetized, and neutral test particles in the vicinity of static and spherically symmetric electrically charged black holes in the Einstein-Æther gravitational theory. Our purpose here is to analyze the effects of the free parameters occurring in the Einstein-Æther theory for particle motion in curved spacetime. Specifically, we have studied the stability of circular and radially varying orbits of different kinds of particles by varying the free parameters [Formula: see text] and [Formula: see text], and also varying the particle’s specific energy, specific angular momentum, and electric charge of the black hole. As a special case, we investigate the charged particle motion around the black holes with a uniform magnetic field by checking the characteristics of the particle’s innermost stable circular orbit. Finally, we propose few values of the parameters [Formula: see text] and [Formula: see text] which mimic the behavior of spin of a Kerr black hole to model an astrophysical black hole.

DEM contact model for spherical and polyhedral particles based on energy conservation

The mechanical behaviors of granular materials are greatly influenced by the geometric shapes, which is widely investigated using the discrete element method (DEM). Accurate contact detection is a critical issue in modelling complicated contact types, especially for arbitrary shaped particles. In this study, the contact detection algorithms for spherical and polyhedral particles based on energy conservation are classified into polyhedron-polyhedron and sphere-polyhedron contacts. The polyhedron-polyhedron and sphere-polyhedron contact detection algorithms are developed under the DEM framework of Coupling Simulator (CoSim-DEM). Geometric dualization theory is used in the polyhedron-polyhedron contact detection algorithm to construct the overlapping volume of polyhedral particles. For the sphere-polyhedron contact detection, the algorithm can transfer into the contact between sphere and triangles composed of polyhedron, and the contact forces between arbitrary shaped particles can be calculated based on calculated contact characteristics. Particle collision tests with different particle shapes and contact types are used to validate the aforementioned algorithms. Experiments and simulation studies of deposition tests are conducted to validate the effectiveness and stability of algorithms. Furthermore, the rotating drum tests are used to analyze the influence of particle shapes on the calculation efficiency. Finally, a large-scale rotating drum test involving different kinds of particles with random sizes is performed, demonstrating the robustness of algorithms based on CoSim-DEM.

Comparison of ultrasonic attenuation models for small droplets measurement based on numerical simulation and experiment

Ultrasonic method has developed rapidly in particle measurement. Suitable ultrasonic attenuation theoretical models are very important for measuring different kinds of particles. In this paper, the ultrasonic measurement technique for small droplets in air is studied based on simulation and experiment, and the applicability of some theoretical models is discussed. In simulation method, both pressure acoustic module and thermoviscous acoustic module are compared, and a method of randomly placing small droplets is proposed. Based on the thermoviscous acoustic module, four ultrasonic attenuation theoretical models including ECAH model, McClements model, Hemar model and Qian model are compared. The mechanism of ultrasonic attenuation under different ultrasonic frequency, droplet radius and concentration is analyzed. And the results show that ECAH model and McClements model are closer to the simulation results, but ECAH model is the most consistent with the simulation data. Furthermore, the flowing experiment is carried out to measure the ultrasonic attenuation coefficient of small droplets in air. The experimental results are inverted using above four theoretical models and hybrid particle swarm optimization algorithm to obtain the droplet radius and concentration. Compared with the results of optical photographing method, the error of ECAH model and McClements model is the smallest within ± 10%. Based on the simulation results and experimental results, ECAH model is the most suitable theoretical model for ultrasonic attenuation method to inverse droplet radius and concentration for small droplets in air measurement at low concentrations, and McClements model has a very close performance to ECAH model.

Simple Adhesion Model between Different Kinds of Particles for Representing the Mixing Behavior of Different Food Powders

Simple Adhesion Model between Different Kinds of Particles for Representing the Mixing Behavior of Different Food Powders

Ion therapy guideline (Version 2020)

Ion therapy guideline (Version 2020)

Black swans, extreme risks, and the e-pile model of self-organized criticality

A new model of self-organized criticality (SOC) is described which differs from ordinary sand-pile SOC models in that it uses electrically charged particles of different kinds to propagate activities and to generate the critical state. The model, arguably called the e-pile model (as an alternative to sand-pile, with “e-” standing for “electric charge”), is motivated by the problem of dielectric relaxation in self-asembling random lattices with disorder under the action of electrostatic forces, but in principle it may be applied to different SOC processes with the random injection scheme and charitable lattice-redistribution rule. We show that the critical state is that of self-evolving random percolation clusters at the edge of percolation and is also different from known “self-organized” versions of the percolation problem based on the directed percolation. A set of critical exponents is obtained based on the random walks, using the Kramers-Kronig relation and the formalism of frequency-dependent complex conductivity. The relaxation of a supercritical system to SOC is shown to obey the Mittag-Leffler pattern and fractional relaxation equation, with a broad distribution of durations of relaxation events. A peculiar feature of the e-pile system is that it is characterized by an intrinsic bias disregarding a vast majority of incipient relaxation events (by killing them “in their egg”), while it also favors other events that may, then, grow into extremely large sizes. We use this observation to explain the phenomenon of the “black swan,” by which one means a family of rare, large events, whose sudden occurrence is very difficult to predict, despite the important impact this type of event may have over the entire system. The event-size distribution of the black swans is found to be a power law, with the drop-off exponent being sensitive to the complexity features of the underlying percolation clusters. On the basis of this observation, we show that the black swans are less probable in more complex environments, and we use this argument to explain why driven, dissipative systems would develop complex structures as a result of dynamical evolution. The e-pile model reveals the upper critical dimension dc=6 for which a crossover to mean-field SOC is found. In six and higher dimensions, the probability density to observe a black swan of a given size behaves as the inverse cube of the size. Below dc the decay is always slower than the inverse-cube and is flatter at lower dimensions. The implications of the mean-field law in country risk assessment, business, and finance are discussed. Finally, we show that the occurrence of the power-law tails is limited to the rate of the driving, and that for too high a rate a different branch of extreme events may result, with the defining features enabling to associate this branch with the phenomenon of dragon kings.

Spectral Methods of Control of Impurities, Their Flows and Localization in an Equilibrium Low-Temperature Plasma of Low Pressure

The state-of-art of studies of processes involving small fractions of particles formed as a result of chemical transformations of the source gas or appearing from the outside as an impurity is discussed. Various high-sensitivity methods for measuring the low concentrations of particles are considered. The main focus is on spectral methods, both classical and laser ones. The main modern fields of the application of non-equilibrium plasma, features, and achievements of the diagnostic tools used in them are highlighted. The emphasis is on spectroscopic studies of plasma purity in the low-temperature near-wall layers of thermonuclear reactors. In this case, the issue of the penetration of water molecules into the plasma chamber from the cooling circuits is of particular importance. In view of the limited accessibility to the reactors, new remote versions of spectral emission methods are being developed that are focused on the diagnostics of the ITER near-wall plasma. A new method of multispectral optical actinometry is discussed, in which intermediate chemically unstable particles can play the role of actinometers. This broadens the range of possibilities for quantitative measurements of concentrations of particles of different kinds, and increases the sensitivity. Effective actinometric pairs were found for the objects under consideration, e.g., hydrogen and deuterium atoms. The schemes are worked out on laboratory facilities, and kinetic models of plasma-chemical processes are developed. Scaling of the results of model experiments makes it possible to predict the measurement of the impurity flows at the level (10–9–10–13) Pa m3 s–1 with the localization of sources determined by the spatial resolution of the optical system.

Solar vapor generation using bubbly flow nanofluids with collaborative light-harvesting nanoparticles

Nanotechnology can produce metallic particles of nanometer sizes with unique optical and thermal properties. Utilizing the nanofluid in solar systems has distinct advantages over conventional fluids in light harvesting, thermal generation and heat transport. However, the plasmonic effect only induces strong light absorption around its nature resonance peak, which is not desirable for broadband solar absorption. Herein, we propose a composite nanofluid composed of three different kinds of particles with distinguish absorbance peaks for collaborative light absorption over the entire solar spectrum. Dynamic bubbles are further introduced into the nanofluid to promote the solar vapor generation. With light absorption spanning from ultraviolet, visible to near-infrared wavelengths, these particle-bubble couplings induce multiple scattering events, increasing photon absorption and light flux within local domain, leading to intensive heating that activates phase-change evaporation in the close proximity. The bubbly flow nanofluid exhibits the best photothermal efficiency of 91.2% than that of the other counterparts, enabling fast vapor diffusion with an upward bubble-bursting flow, and therefore achieving a decent steam generation efficiency of 40.8% under one-sun irradiation. Our findings not only suggest a new way to improve solar vapor generation in laden-particle solution, but also shed lights on the development of novel solar thermal systems.

Sampling Device-Dependence of Prokaryotic Community Structure on Marine Particles: Higher Diversity Recovered by in situ Pumps Than by Oceanographic Bottles.

Microbes associated with sinking marine particles play key roles in carbon sequestration in the ocean. The sampling of particle-attached microorganisms is often done with sediment traps or by filtration of water collected with oceanographic bottles, both involving a certain time lapse between collection and processing of samples that may result in changes in particle-attached microbial communities. Conversely, in situ water filtration through submersible pumps allows a faster storage of sampled particles, but it has rarely been used to study the associated microbial communities and has never been compared to other particle-sampling methods in terms of the recovery of particle microbial diversity. Here we compared the prokaryotic communities attached to small (1–53 μm) and large (>53 μm) particles collected from the mesopelagic zone (100–300 m) of two Antarctic polynyas using in situ pumps (ISP) and oceanographic bottles (BTL). Each sampling method retrieved largely different particle-attached communities, suggesting that they capture different kinds of particles. These device-driven differences were greater for large particles than for small particles. Overall, the ISP recovered 1.5- to 3-fold more particle-attached bacterial taxa than the BTL, and different taxonomic groups were preferentially recovered by each method. In particular, typical particle-attached groups such as Planctomycetes and Deltaproteobacteria recovered with ISP were nearly absent from BTL samples. Our results suggest that the method used to sample marine particles has a strong influence in our view of their associated microbial communities.

Above and beyond: holographic tracking of axial displacements in holographic optical tweezers.

How far a particle moves along the optical axis in a holographic optical trap is not simply dictated by the programmed motion of the trap, but rather depends on an interplay of the trap's changing shape and the particle's material properties. For the particular case of colloidal spheres in optical tweezers, holographic video microscopy reveals that trapped particles tend to move farther along the axial direction than the traps that are moving them and that different kinds of particles move by different amounts. These surprising and sizeable variations in axial placement can be explained by a dipole-order theory for optical forces. Their discovery highlights the need for real-time feedback to achieve precise control of colloidal assemblies in three dimensions and demonstrates that holographic microscopy can meet that need.

Experimental investigation of fountain height in a shallow rectangular spouted bed using digital image analysis

The formation of a fountain is a unique phenomenon of spouted beds, which plays a significant role in the reactor design as well as the physical and chemical efficiency of the whole system. The present work investigates the fountain height (Hf) behavior in a rectangular spouted bed (30.2 mm × 101.6 mm) using four different kinds of particles classified in both Geldart groups D (Nylon and Alumina) and B (Glass beads (GB) and High density polyethylene (HDPE)), which is intended as a gap-bridging attempt, given the fact that most of the published fountain height studies were conducted in the cylindrical bed geometry. First, with the determination of Hf by systematic image processing methods, the effects of different variables including, superficial gas velocity (Ug), nozzle size (Deqn), and initial static bed height (H0) on Hf of the Geldart D and B particles are addressed. Secondly, because of the intrinsic periodical behavior of the absolute fountain height (Hfa, i.e. the vertical distance between the fountain surface to the bed bottom), the Fast Fourier Transform (FFT) is applied to characterize the variation of the Hfa for the four particle types. The period of particles’ entry into the spout and the “residence time” of particles in the fountain region are proposed as two possible factors that affect the fountain frequency. Finally, correlations to predict the Hf for both Geldart D and B particles are developed respectively, based on the discussion of different influence factors and frequency analysis. The correlation developed for Geldart B particles indicates that the effect of the nozzle size (Di) can be neglected when the ratio of particle size (dp) to nozzle size (Di) is less than 0.1. The predicted values show good agreement with the experimental data in the present study. In addition, the employment of the equivalent cross-sectional area diameters of the nozzle and rectangular column, namely Di and Dc, ensures the potential extension of the application of the developed correlations to cylindrical spouted beds.

Shape-Controlled Nanoparticles in Pore-Confined Space.

Increasing the catalyst's stability and activity are one of the main quests in catalysis. Tailoring crystal surfaces to a specific reaction has demonstrated to be a very effective way in increasing the catalyst's specific activity. Shape controlled nanoparticles with specific crystal facets are usually grown kinetically and are highly susceptible to morphological changes during the reaction due to agglomeration, metal dissolution, or Ostwald ripening. A strong interaction of the catalytic material to the support is thus crucial for successful stabilization. Taken both points into account, a general catalyst design is proposed, combining the enhanced activity of shape-controlled nanoparticles with a pore-confinement approach for high stability. Hollow graphitic spheres with narrow and uniform bimodal mesopores serve as model system and were used as support material. As catalyst, different kinds of particles, such as pure platinum (Pt), platinum/nickel (Pt3Ni) and Pt3Ni doped with molybdenum (Pt3Ni-Mo), have exemplarily been synthesized. The advantages, limits and challenges of the proposed concept are discussed and elaborated by means of time-resolved, in and ex situ measurements. It will be shown that during catalysis, the potential boundaries are crucial especially for the proposed catalyst design, resulting in either retention of the initial activity or drastic loss in shape, size and elemental composition. The synthesis and catalyst design can be adapted to a wide range of catalytic reactions where stabilization of shape-controlled particles is a focus.

Determining the refractive index of particles using glare-point imaging technique.

A method of measuring the refractive index of a particle is presented from a glare-point image. The space of a doublet image of a particle can be determined with high accuracy by using auto-correlation and Gaussian interpolation, and then the refractive index is obtained from glare-point separation, and a factor that may influence the accuracy of glare-point separation is explored. Experiments are carried out for three different kinds of particles, including polystyrene latex particles, glass beads, and water droplets, whose measuring accuracy is improved by the data fitting method. The research results show that the method presented in this paper is feasible and beneficial to applications such as spray and atmospheric composition measurements.

Heavy-metal detectors based on modified ferrite nanoparticles.

In this work, we analyze artificial heavy-metal solutions with ferrite nanoparticles. Measurements of adsorption effectiveness of different kinds of particles, pure magnetite or magnetite doped with calcium, cobalt, manganese, or nickel ions, were carried out. A dependence of the adsorption efficiency on the composition of the inorganic core has been observed. Ferrites surfaces were modified by phthalic anhydride (PA), succinic anhydride (SA), acetic anhydride (AA), 3-phosphonopropionic acid (3-PPA), or 16-phosphohexadecanoic acid (16-PHDA) to compare the adsorption capability of the heavy metals Cd, Cu and Pb. The obtained nanoparticles were structurally characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Mössbauer spectroscopy. The amounts of Cd, Cu and Pb were measured out by atomic absorption spectroscopy (AAS) and energy dispersive X-ray (EDX) as comparative techniques. The performed study shows that SA linker appears to be the most effective in the adsorption of heavy metals. Moreover, regarding the influence of the composition of the inorganic core on the detection ability, the most effective ferrite Mn0.5Fe2.5O4 was selected for discussion. The highest heavy-metal adsorption capability and universality was observed for SA as a surface modifier.

Experimental study of acoustic agglomeration and fragmentation on coal-fired ash

As the major part of air pollution, inhalable particles, especially fine particles are doing great harm to human body due to smaller particle size and absorption of hazardous components. However, the removal efficiency of current particles filtering devices is low. Acoustic agglomeration is considered as a very effective pretreatment technique for removing particles. Fine particles collide, agglomerate and grow up in the sound field and the fine particles can be removed by conventional particles devices easily. In this paper, the agglomeration and fragmentation of 3 different kinds of particles with different size distributions are studied experimentally in the sound field. It is found that there exists an optimal frequency at 1200 Hz for different particles. The agglomeration efficiency of inhalable particles increases with SPL increasing for the unimodal particles with particle diameter less than 10 μm. For the bimodal particles, the optimal SPLs are 115 and 120 dB with the agglomeration efficiencies of 25% and 55%. A considerable effectiveness of agglomeration could only be obtained in a narrow SPL range and it decreases significantly over the range for the particles fragmentation.