Particle Coordinates Research Articles

Development of multi-cycle rainbow particle tracking velocimetry improved by particle defocusing technique and an example of its application on twisted Savonius turbine

Rainbow particle tracking velocimetry (PTV) is a PTV method that enables three-dimensional (3D) three-component flow measurement using a single camera. Despite the advantage of its simple setup, the accuracy of the particle depth is restricted due to false color caused by image sensor arrays, such as Bayer arrangement. Since the false color occurs near sharp edges in the color gradient of in-focus individual particle images, we here introduced a defocusing technique to rainbow PTV to remove these false colors. Defocusing led to moon-shaped distorted particle images, which we applied an adaptive mask correlation technique to detect. Multi-cycle rainbow illumination was realized as an additional improvement on the defocusing technique. In particular, individual particle coordinates were obtained by a combination of the color and constitution of pixels. This dramatically increased the depth resolution of the 3D particle tracking. The feasibility of the proposed method was demonstrated by a flow driven by rotating impellers and a wake behind a twisted Savonius turbine. By the demonstration, it is confirmed that the twisted turbine suppresses the loss of kinetic energy by shedding streamwise vortices in the wake.

Thermophoretic collection of virus-laden (SARS-CoV-2) aerosols.

Detecting the existence of SARS-CoV-2 in the indoor atmosphere is a practical solution to track the prevalence and prevent the spread of the virus. In this work, a thermophoretic approach is presented to collect the novel coronavirus-laden aerosols from the air and accumulate to high concentrations adequate for the sensitivity of viral RNA detection. Among the factors, the density and particle size have negligible effects on particle trajectory, while the vertical coordinates of particles increase with the rise in heating source temperature. When the heating temperature is higher than , all of the particles exit the channel from one outlet; thus, the collecting and accumulating of virus-laden aerosols can be realized. This study provides a potential approach to accelerate the detection of SARS-CoV-2 and avoid a false negative in the following RNA test.

Wheeler–DeWitt quantization for point-particles

We present the Hamiltonian formulation of a relativistic point-particle coupled to Einstein gravity and its canonical quantization \`a la Wheeler-DeWitt. In the resulting quantum theory, the wave functional is a function of the particle coordinates and the 3-metric. It satisfies a particular Hamiltonian and diffeomorphism constraint, together with a Klein-Gordon-type equation. As usual in the Wheeler-DeWitt theory, the wave function is time-independent. This is also reflected in the Klein-Gordon-type equation, where the time derivative is absent. Before considering gravity, we consider the coupling of a particle with electromagnetism, which is treated similarly, but simpler.

A novel approach for investigation of collision mechanisms between fine particles in electrostatic precipitator under consideration of Brownian effect

In this paper, a novel approach based on the Lagrangian particle tracking method which adopted the accumulated displacement of particles as judgment standard was proposed to investigate the particle collision mechanism under the influence of non-contact external forces in a typical wire-plate electrostatic precipitator. The accumulated displacement of different diameter particles could reflect the range of particle motion and the collision probability inside the ESP, which was obtained from the calculated trajectory coordinates of particles under the influence of Brownian force and electric force. Results showed that the electric force controlled the particle’s trajectory direction while the Brownian force only made particles fluctuate along with the main track. The binary collision models with the determination of the dominant force were developed, which can be divided into two areas respectively called the electric force dominant region and the Brownian force dominant region. The total accumulated displacement of the submicron particle presented a U-shape curve, which matched well with the grade collection efficiency of fine particles in various experiments and demonstrated the validity of the proposed method. Also, the approach had good expansibility in investigating the role of other external forces in particle collision and could provide references for the design and working condition selection of ESP.

A novel radioactive particle tracking algorithm based on deep rectifier neural network

Radioactive particle tracking (RPT) is a minimally invasive nuclear technique that tracks a radioactive particle inside a volume of interest by means of a mathematical location algorithm. During the past decades, many algorithms have been developed including ones based on artificial intelligence techniques. In this study, RPT technique is applied in a simulated test section that employs a simplified mixer filled with concrete, six scintillator detectors and a137Cs radioactive particle emitting gamma rays of 662 keV. The test section was developed using MCNPX code, which is a mathematical code based on Monte Carlo simulation, and 3516 different radioactive particle positions (x,y,z) were simulated. Novelty of this paper is the use of a location algorithm based on a deep learning model, more specifically a 6-layers deep rectifier neural network (DRNN), in which hyperparameters were defined using a Bayesian optimization method. DRNN is a type of deep feedforward neural network that substitutes the usual sigmoid based activation functions, traditionally used in vanilla Multilayer Perceptron Networks, for rectified activation functions. Results show the great accuracy of the DRNN in a RPT tracking system. Root mean squared error for x, y and coordinates of the radioactive particle is, respectively, 0.03064, 0.02523 and 0.07653.

Numerical Analysis of the Nanoparticle Dynamics in a Viscous Liquid: Deterministic Approach

We study the deterministic dynamics of single-domain ferromagnetic nanoparticles in a viscous liquid induced by the joint action of the gradient and uniform magnetic fields. It is assumed that the gradient field depends on time harmonically and the uniform field has two components, perpendicular and parallel to the gradient one. We also assume that the anisotropy magnetic field is so strong that the nanoparticle magnetization lies along the anisotropy axis, i.e., the magnetization vector is "frozen" into the particle body. With these assumptions and neglecting inertial effects we derive the torque and force balance equations that describe the rotational and translational motions of particles. We reduce these equations to a set of two coupled equations for the magnetization angle and particle coordinate, solve them numerically in a wide range of the system parameters and analyze the role of the parallel component of the uniform magnetic field. It is shown, in particular, that nanoparticles perform only periodic rotational and translational motions if the perpendicular component of the uniform magnetic field is absent. In contrast, the nanoparticle dynamics in the presence of this component becomes non-periodic, resulting in the drift motion (directed transport) of nanoparticles. By analyzing the short and long-time dependencies of the magnetization angle and particle coordinate we show that the increase in the parallel component of the uniform magnetic field decreases both the particle displacement for a fixed time and its average drift velocity on each period of the gradient magnetic field.

Influence of Particle Shape on the Macroscopic and Mesolevel Mechanical Properties of Slip Zone Soil Based on 3D Scanning and 3D DEM

The macroscopic and mesolevel mechanical mechanisms of slip zone soil are a crucial subject for the research of landslide deformation evolution and slope control, but the effects of the shape and psephicity of coarse particles in a slip zone soil on the mechanical properties of the slip soil zone still need to be explored. Discrete element method (DEM) can effectively monitor and track the mesolevel mechanical parameters of geotechnical materials, such as displacement vector field, contact force chain, and particle coordination number. The rock blocks in the medium‐sized shear test undergo a sophisticated process by 3D scanning technology, and a database of the blocks is established and accurately modeled by combining 3D DEM to simulate the indoor medium‐sized shear test for numerical investigation in line with the test conditions. The numerical simulation results demonstrate that the psephicity and particle shape of the rock blocks significantly affect the dilatancy and mesolevel mechanical parameters of the slip zone soil specimens. In addition, the numerical models featured by poorer psephicity and more irregular particle shape display more evident dilatancy, larger particle coordination numbers, as well as better contact density inside the model. Some references for the study of the macroscopic and mesolevel mechanical mechanisms of slip zone soil are provided.

Characteristics of semiconductor pion stop tagging system

A determination of the coordinates of charged particle stops is one of the tasks that have to be solved in a wide class of experiments. A method based on the use of semiconductor detectors (SCD) to determine the stops of particles (muons and pions) was proposed and experimentally tested. The dependence that allows calculating the stopping point of the pions in the tagging system was obtained experimentally. This dependence can be used to optimize the thickness values of monitor detectors.

Numerical simulation study on formation mechanism of void distributions of proppant particles

Investigations of void distributions and formation mechanisms of proppant particles in closure fractures have extremely major significance for improving the production of coalbed methane. In this study, a numerical method was developed to simulate compaction processes of a proppant-filled fracture under different closure stresses. The particle trajectories, force chains and coordination numbers of proppants were extracted to analyze and investigate void ratio distributions and associated formation mechanisms. The results showed that during fracture closures from the top to bottom, some particles in the top layer of the proppant-filled fracture moved into the middle layer, which made the middle layer particles formed solid force-bearing structures. The greatest force was transmitted between particles in the middle layer. This was followed by particles in the top layer and finally, the bottom layer. In addition, the proportions of large coordination numbers, and average coordination numbers of the middle layer were the largest, followed by those of the top and bottom layers, which reflected that the particles of the middle layer were denser than those of the other two layers. The above factors caused the void ratios of the middle layer to be the lowest, followed by those of the top and bottom layer, respectively.

Relativistic Symmetries and Hamiltonian Formalism

The relativistic (Poincaré and conformal) symmetries of classical elementary systems are briefly discussed and reviewed. The main framework is provided by the Hamiltonian formalism for dynamical systems exhibiting symmetry described by a given Lie group. The construction of phase space and canonical variables is given using the tools from the coadjoint orbits method. It is indicated how the “exotic” Lorentz transformation properties for particle coordinates can be derived; they are shown to be the natural consequence of the formalism.

Practical aspects in modeling the air conveying modes of small–piece food products

A mathematical and physical model of the critical pneumatic conveying modes has been developed to ensure the calculation and construction of pneumatic product pipelines of continuous operation. The model takes into consideration the technological conditions of gas suspension movement; the laws of movement of individual fine particles, accounting for their impact interaction and decompression, as well as the actual boundary conditions for a food product movement. The parameters of the zone of dynamic destruction of the layer of a small-piece food product by impact airwave were experimentally studied; the results of the calculation have been compared with the experimental data. The process of managing critical pneumatic conveying modes has been theoretically described, based on the proportional elements and feedback (a current loop of 4‒20 mA); the process of destruction of the cluster of products by airwave and controlled decompression has been studied. The process of pneumatic conveying of a small-piece product at the experimental bench system has been examined. As well as the process of moving the material in the product pipeline, which is controlled by compressed air pulses, to maintain the modes of operation. The following has been established: pressure losses caused by the movement of clean air; additional pressure losses resulting from the movement of the material; the loss of pressure required for transporting in a suspended state on a vertical stretch. A model has been developed to calculate the coordinates of a product particle when it collides with the inner surface of the product pipeline, as well as a change in its kinematic characteristics. The developed model makes it possible to determine the rational modes of pneumatic conveying and possible energy costs in the processing of various small-piece materials. The rational pneumatic conveying regimes have been determined, as well as possible energy costs in the processing of small-piece materials. As the time of supplying compressed air in the product pipeline increases, the number of product particles reaches a maximum in the range of 0.1...0.2 s. The compressed air flow rate, depending on the value of inlet mainline pressure P (0.1…0.3 MPa), is 80…160 (Nl/min). A general approach to the modeling of pneumatic conveying systems has been proposed

Impact of the competition between aggregation and surface growth on the morphology of soot particles formed in an ethylene laminar premixed flame

Soot particle surface growth may have a significant impact on aggregation kinetics, particle morphology, and both aggregate and monomer size distributions. Particularly, the morphological effects of surface growth are currently poorly understood. This is complex since surface growth also affects the kinetics of aggregation resulting in a time-dependent competition between both phenomena, producing very different morphological markers. The present study aims at improving our understanding of the morphological impact of surface growth by implementing this effect in a Monte Carlo discrete element code for the simulation of soot formation in an ethylene premixed flame. An asymptotic average primary particle overlapping ∼30% is observed for different flame conditions. The primary particle coordination number is highly sensitive to surface growth rate and particle volume fraction, and maximum values are on average within the 4 - 8 range. The particle local compacity, as quantified by the packing factor, is also considerably increased when aggregates experience surface growth, contrarily to the fractal structure of individual aggregates that seems more dependent on the aggregation regime. Finally, surface growth narrows both the primary particle and aggregate size distributions.

General metaheuristic-based methodology for computation and decomposition of LMPs

Locational marginal prices (LMPs) are economic signals paramount to the deliberations, policy designs, and planning judgments of most electricity markets. This paper presents a general metaheuristic-based methodology applied in the scope of two subproblems to compute and decompose the LMPs considering the incorporation of a distributed slack bus model in the power flow formulation. The deterministic core of the methodology is governed by a process of sequential setting of maximum number of metaheuristic iterations based on load disharmony indices (LDIs) in the context of the initial subproblem. The metaheuristic crux of the methodology is anchored in a random initialization strategy based on time-traveling parameters in the environment of both subproblems. In the introductory arrangement of the optimization sequence, the chain order of the operating horizon periods is defined based on the LDIs. Due to its notorious merits and the breadth of its applications in power system problems, a particle swarm optimization (PSO) algorithm model is used to solve the mentioned subproblems. For the practical purposes of this paper, in the PSO algorithm model instance the particle coordinates are adopted as time-traveling metaheuristic parameters. Numerical simulations on a 3-bus system and on the IEEE 30-bus test system corroborate the efficiency and adequacy of the proposed methodology.

The structure and collective oscillations of electron systems consisting of several chains

The collective properties of surface electron systems consisting of several lines of charges are considered. To simulate the system, its characteristic frequencies of oscillations are found by applying Fourier analysis to the average coordinates of particles along and across the lines. The frequencies are compared with the theoretically obtained dispersion laws of plasma modes, calculated according to the equations of motion for small displacements of electrons from equilibrium. The dispersion laws of collective oscillations are calculated for two-, three-, and four-chain systems of electrons, and in the latter case, configurations with both identical and different distances between the charge lines are examined. There is good agreement between the simulation results and the frequency values that follow from the dispersion laws.

Numerical Investigation of the Cushion and Size Effects During Single-Particle Crushing via DEM

This paper uses the discrete element method to model the size and cushion effects during single-particle crushing tests. We propose simplified numerical modeling to examine the effects of particle size and coordination number on particle breakage behavior. We validate the proposed modeling by comparing the numerical results with the experimental data reported in the literature, in terms of the variability of particle tensile strength and axial force–displacement responses. Based on the numerical results, it is clear that a larger particle size entails a higher tensile strength with a larger discreteness. In addition, the characteristic tensile strength increases linearly with an increasing coordination number. Moreover, smaller particles are more susceptible to the cushion effect than larger particles. The numerical results also indicate that an increasing coordination number induces a more ductile mode of failure. Based on these results, we propose an empirical equation for calculating tensile strength, incorporating both the cushion effect and the size effect.

Assessing the Reactive Surface Area of Soils and the Association of Soil Organic Carbon with Natural Oxide Nanoparticles Using Ferrihydrite as Proxy.

Assessment of the surface reactivity of natural metal-(hydr)oxide nanoparticles is necessary for predicting ion adsorption phenomena in soils using surface complexation modeling. Here, we describe how the equilibrium concentrations of PO4, obtained with 0.5 M NaHCO3 extractions at different solution-to-soil ratios, can be interpreted with a state-of-the-art ion adsorption model for ferrihydrite to assess the reactive surface area (RSA) of agricultural top soils. Simultaneously, the method reveals the fraction of reversibly adsorbed soil PO4 (R-PO4). The applied ion-probing methodology shows that ferrihydrite is a better proxy than goethite for consistently assessing RSA and R-PO4. The R-PO4 pool agrees well with ammonium oxalate (AO)-extractable phosphorus, but only if measured as orthophosphate. The RSA varied between ∼2 and 20 m2/g soil. The corresponding specific surface area (SSA) of the natural metal-(hydr)oxide fraction is ∼350–1400 m2/g, illustrating that this property is highly variable and cannot be represented by a single value based on the AO-extractable oxide content. The soil organic carbon (SOC) content of our top soils increases linearly not only with the increase in RSA but remarkably also with the increase in mean particle size (1.5–5 nm). To explain these observations, we present a structural model for organo-mineral associations based on the coordination of SOC particles to metal-(hydr)oxide cores.

Regioselective Generation of Single‐Site Iridium Atoms and Their Evolution into Stabilized Subnanometric Iridium Clusters in MWW Zeolite

AbstractPreparation of supported metal catalysts with uniform particle size and coordination environment is a challenging and important topic in materials chemistry and catalysis. In this work, we report the regioselective generation of single‐site Ir atoms and their evolution into stabilized subnanometric Ir clusters in MWW zeolite, which are located at the 10MR window connecting the two neighboring 12MR supercages. The size of the subnanometric Ir clusters can be controlled by the post‐synthesis treatments and maintain below 1 nm even after being reduced at 650 °C, which cannot be readily achieved with samples prepared by conventional impregnation methods. The high structure sensitivity, size‐dependence, of catalytic performance in the alkane hydrogenolysis reaction of Ir clusters in the subnanometric regime is evidenced.

Impact of IN718 bimodal powder size distribution on the performance and productivity of laser powder bed fusion additive manufacturing process

Bimodal powders of IN718 were obtained by adding a fine powder (D10–D90: 6.2–16.9 μm) to a typical laser powder bed fusion (L-PBF) powder (coarse powder, D10–D90: 26.5–50.5 μm) in various volume fractions. The fine powder was selected to generate an Alpha (Rosin-Rammler fit parameter) of 3.17 based on literature data and powder availability. The 83.75/16.25 Vol% of coarse/fine blend was chosen for the combination of reduced interparticle spacing/improved particle coordination number while retaining free flowing behavior. A new index, termed Raking Index (R), is defined to incorporate apparent density and Confined Specific Flow Energy as one parameter for assessing rakeability. Our results show that when R > 36 mJ/cm3 IN718 forms a dense and rakeable powder bed. After L-PBF processing, the use of the 83.75/16.25 blend resulted in 10% increase in process productivity, higher IN718 tensile strength, and reduced mechanical anisotropy.

DEM modelling to assess internal stability of gap-graded assemblies of spherical particles under various relative densities, fine contents and gap ratios

It is believed that the relative density (Dr) can affect the internal stability of the gap-graded soils and hence the erosion of their fine particles (i.e. susceptibility to suffusion). This paper investigates the influence of Dr on the contribution of fine particles to soil fabric. A new procedure is proposed to produce samples with target Dr using the discrete element method (DEM). DEM simulations were carried out using spherical particles. Particulate scale analysis of variation of stress reduction factor (αDEM), the evolution of contact type and fine particle coordination number (Zfine) with Dr reveals how Dr affects packing stability. The results show that packings with a fine content of 35% and the gap ratio in a range of 4–7 are in the transitional zone in which they are unstable initially and become internally stable as Dr increases. The behaviour of gap-graded soil in the transitional zone is governed by fine-coarse contacts, but fine-fine contacts dominate the behaviour when soil becomes internally stable. Both αDEM and Zfine are reliable parameters in determining internal stability of gap-graded soils. Finally, the correlation between the results and macro-scale matrix phase diagrams confirms the validity of micro-scale information to describe the underlying phenomenon.

Motion Compensated Virtual View Synthesis Using Novel Particle Cell

Due to the wide interest in advanced multimedia experience, free-viewpoint communication is being greatly developed in recent years. In the free-viewpoint communication, viewers can perceive a view from any angle and any position of a scene. Even though the preferred views are not captured, we can generate the views through virtual view synthesis that synthesizes an arbitrary view from captured reference view(s). For daily use, only one or few cameras in baseline distance are given to capture the scene that makes the virtual view synthesis challenging. The task is more difficult when the camera is continuously moving. In this paper, we propose a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">particle cell</i> to model a reference view sequence to a set of moving particles for virtual view synthesis. Using our novel hybrid motion estimation scheme, the projected coordinates of particles in each frame are obtained even they are occluded. The particles are warped to a virtual view and synthesized as a virtual view sequence. Our method is applicable for both dynamic camera setting and static camera setting. The experimental results show our method outperforms the state-of-the-art algorithms in dynamic camera datasets and presents improvement in static camera datasets in general.