Particle Density Distribution Research Articles

On the single-lane TASEP with generalized update and open boundary conditions

We report on numerical simulation results for the stationary properties of the totally asymmetric simple exclusion process (TASEP) with generalized update (GU) on a simple chain with open boundary conditions (OBC). We note that the application of TASEP to biomolecular processes can be traced back to [1], see also [2,3], where the model was used to describe directed motion of molecular motors along twisted filaments. The model with generalized update, suggested and studied on a ring in [4,5], includes interaction between nearest-neighbor particles. The implementation of OBC leads to a variety of stationary properties of the TASEP with GU, which cannot be observed on a ring. We introduce here a modified left boundary condition which controls the input of particles in the chain, which allows for a smooth transition from the standard updates to the extreme case of particles gluing in stable clusters. The density distribution of particles along the chain, nearest-neighbor particle-particle correlations, and the fundamental relationship between particle current and density were studied at different values of the parameters. Our numerical simulations reveal broad and quite unexpected modes of behavior of the system. Simple analytical models for the description of some of the unusual types of behavior are suggested. Finally, the possibilities for different applications are mentioned. [1] C. T. MacDonald, J. H. Gibbs, and A. C. Pipkin, Biopolymers 6, 1 (1968). [2] Y.-M. Yuan et al., J. Phys. A 40, 12351 (2007). [3] A. E. Derbyshev et al, J. Stat. Mech., 2012, P05014 (2012); Phys. Rev. E 91, 022125 (2015).

Fractal structures for the Jacobi Hamiltonian of restricted three-body problem

We study the dynamical chaos and integrable motion in the planar circular restricted three-body problem and determine the fractal dimension of the spiral strange repeller set of non-escaping orbits at different values of mass ratio of binary bodies and of Jacobi integral of motion. We find that the spiral fractal structure of the Poincaré section leads to a spiral density distribution of particles remaining in the system. We also show that the initial exponential drop of survival probability with time is followed by the algebraic decay related to the universal algebraic statistics of Poincaré recurrences in generic symplectic maps.

Particle density distribution in a fluvial floodplain

The mechanisms that determine the formation of a floodplain are very well known. At the same time, there is an established correspondence between the sedimentary deposits and density of the particles, whose distribution in the plain is until now poorly constrained. In this work we therefore highlight the spatial distribution of the particle density of soils from the Padania Po Plain in relation to the depositional sub-environment where they have been sampled.

Determination of partition surface of grained material by means of non-classical approximation methods of distributions functions of particle size and density

Abstract In this paper, the grained material analyzed was hard coal collected from one of the mines located in Upper Silesia. Material was collected from a dust jig where it was separated in industrial conditions by concentrate and waste. It was then screened in sieves and it was separated in dense media into density fractions. Both particle size distribution and particle density distribution for feed and concentrate were approximated by several classical distribution functions. The best results were obtained by means of the Weibull (RRB) distribution function. However, because of the unsatisfying quality of approximations it was decided to apply non-parametric statistical methods, which became more and more popular alternative methods in conducting statistical investigations. In the paper, the kernel methods were applied to this purpose and the Gauss kernel was accepted as the kernel function. Kernel method, which is relatively new, gave much better results than classical distribution functions by means of the least squared method. Both classical and non-parametric obtained distribution functions were evaluated by means of mean standard error, the values of which proved that they sufficiently well approximate the empirical data. Such function forms were then applied to determine the theoretical distribution function for vector (D, P), where D is the random variable describing particle size and P – its density. This approximation was sufficiently acceptable. That is why it served to determine the equation of partition surface dependent on particle size and particle density describing researched material. The obtained surface proves that it is possible to evaluate material separation which occurs during mineral processing operations, such as jigging, by means of more than one feature of researched material. Furthermore, its quality confirms that it is justified to apply non-parametric statistical methods instead of commonly used classical ones.

Experimental study on the effect of dust deposition on solar photovoltaic panels in desert environment

The accumulation of dust particles deteriorates the performance of solar cells and results in appreciable losses in the generated power due to the sun irradiance scattering effects on the surface of the solar panel. This study investigates the impact of dust accumulation on photovoltaic solar modules in Baghdad city in Iraq. For this purpose an experiment has been conducted to quantify losses caused by the accumulation of dust on the surface of three identical photovoltaic solar modules. The modules have been installed with direct exposure to weather conditions, in a well controlled experimental setup. Subsequently, measurements of dust accumulation on modules have been taken on daily, weekly and monthly basis. The dust density and size distribution of aerosol particles and fibers have been also investigated and measured by a highly sensitive aerosols measuring system. The dusted module and another similar clean module have been then exposed to constant radiation and constant temperature using a solar simulator as light source. The deposition of the dust on the surface of the photovoltaic solar modules showed a reduction in both the short circuit current (Isc) and the output power compared to the same parameters of the clean module. The average degradation rate of the efficiencies of the solar modules exposed to dust are; 6.24%, 11.8% and 18.74% calculated for exposure periods of one day, one week and one month. The experimental results are well compared with the calculations obtained by a theoretical model recently developed by the authors.

A preliminary numerical model of the Geminid meteoroid stream

Last year the work on the qualitative model of the Geminid meteoroid stream was finished [1, 2]. The mentioned publications summarized the results of 20-years efforts. This model explained most of the Geminid’s structural features, including bimodality, but to find quantitative spatial density distribution of particles we need a more precise model. The first runs of the new numerical model were made, and some preliminary results have been obtained.

Surface fitting and position-pose measurements based on an improved SA-PSO algorithm

Scattered point pattern matching is an important issue in computer vision and pattern recognition,which is widely used for target recognition,medical and remote sensing image registration,and position and pose measurements. This paper describes an algorithm for use in an explosive ordnance disposal robot for when the target object is partial exposed.A simulated annealing-particle swarm optimization(SA-PSO)algorithm based on particle density distribution changes for scattered point pattern matching is developed.The algorithm is more accurate and faster than previous algorithms.The fitness function is constructed from a series of scattered points collected from the local surface of a rotated object.Accurate surface fitting and pose parameters are found using coordinate transforms.The factors that affect the accuracy and applicability are discussed in detail.Tests show that this method is accurate and efficient,with less points needed and less sensitivity to point errors compared with the traditional least squares method.

Primary Fragmentation Characteristics of Coal Particles during Rapid Pyrolysis

Experiments were carried out to investigate the rapid pyrolysis of Nei-meng (NM) lignite, Shen-fu (SF) bituminous coal, and Jin-cheng (JS) anthracite with the duration time of 0–500 ms and the temperature of 1173–1773 K using a high-frequency induction furnace. Interest was centered on the primary fragmental characteristics of particles, including the changes of mass loss, particle density, and size distribution, during the pyrolysis. A pair of fragmental parameters, i.e., dimensionless particle diameter δ and particle distribution Sf, was proposed to characterize the fragmentation during the different stages of pyrolysis. The result showed that the pyrolysis progress increases with time and temperature. The fragmentation extent is also positively related to the time and temperature. The progress of primary fragmentation is lignite ≈ bituminous coal > anthracite. However, the particle morphology changes little during the pyrolysis fragmentation. Evidence reveals that major fragmentations of NM and SF occu...

Investigations of Droplet‐Plasma Interaction using Multi‐Dimensional Coupled Model

AbstractRecently developed multi‐dimensional coupled fluid‐droplet model is used to investigate the behavior of complex interaction between the liquid precursor droplets and atmospheric pressure plasma (APP). The significance of this droplet‐plasma interaction is not well understood under diverse realm of working conditions in two‐phase flow. In this study, we explain the implication of vaporization of liquid droplets in APP which are subsequently responsible to control major characteristics of surface coating depositions. Coalescence of water droplets is more dominant than Hexamethyldisiloxane (HMDSO) droplets because of its sluggish rate of evaporation. A disparity in the performance of evaporation is identified in two independent mediums, such as gas mixture and discharge plasma using HMDSO precursor. The length of evaporation of droplets is amplified by an increment of gas flow rate indicating with a reduction in the gas temperature and electron mean energy. In particular, the spatio‐temporal density distributions of charged particles show a clear pattern in which the typical nitrogen impurity ions are primarily effective as compared to other helium ionic species along the pulse of droplets in APP. Finally, we contrast the behavior of discharge species in the pure helium and He‐N2 gas mixtures revealing the importance of stepwise and Penning ionization processes. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Numerical simulation of flow characteristics for non-spherical particle mixture flowing in moving bed

Environmental pollution problems are more serious with the rapid economic development. The study of particle flow characteristics is a hot issue for scholars. In many ways to tackle air pollution and solid waste, the particle flow characteristics can play a decisive role. Then in the actual process, the non-spherical particle such as active carbon and solid waste were always treated as spherical particles during the simulation. It could cause large errors. This study was mainly to simulate the non-spherical particles. Three kinds of non-spherical particles including corn-shaped particle, cylinder paritcle and ellipsoidal particle were developed by multi-element particle model. The motion equation for non-spherical particle mixture was founded based the analysis on the collision mechanism and the typical collision mode. The flowing condition of non-spherical particle mixture in moving bed was simulated through experiment, which verified the the reliability of multi-element particle model. The discharge rate, flow pattern, particle density distribution and voidage variation for non-spherical particle mixture were discussed further. The results showed that the discharge rate for non-spherical particle mixture was fundamentally the same as single non-spherical particle. However, the value for spherical particle was larger than that of spherical and non-spherical particle mixture. The MFI values (the particle speed ratio of bedside to centre in moving bed) of nonspherical particles mixture were closer to the corresponding homogeneous particles. The particle density distribution of spherical and spherical-nonspherical mixture generally had one peak, while that of non-spherical particle and non-spherical particle mixture always had two peaks. The wall effect and the average voidage of three kinds of non-sphercial particle mixture were almost the same. The average voidage of three kinds of non-sphercial particle mixture are almost the same.

On the bipolar charge distribution used for mobility particle sizing: Theoretical considerations

An essential part of mobility particle size spectroscopy is the prediction of the aerosol charge distribution in a highly concentrated bipolar ion environment. This charge distribution can be readily calculated, but is depending on several environmental conditions. These influences are investigated theoretically.The first part of this work deals with a sensitivity analysis using the Fuchs model (Fuchs, 1963) to determine the variation of the resulting charge distributions depending on the input parameters. It is demonstrated, that the main influencing variable is the difference between the positive and negative ion mobility. A sensitivity analysis reveals that a reasonable variation of the ion mobilities may lead to variations of the particle density distribution up to±20%.The second part investigates the evolution of the charge distribution along the tubing downstream of the bipolar charger exit starting with equal ion concentrations for positive and negative ions. Due to wall losses depending on ion mobility a non-equilibrium charge distribution is developing along the plumbing. The evolution of the particle charge distribution is determined using a coupled population balance model. Even though the non-equilibrium character is clearly shown, it turns out that this effect is negligible at conditions typical for particle size measurements.

Quantum walks on graphene nanoribbons using quantum gates as coins

Both discrete and continuous quantum walks on graphs are universal for quantum computation. We define and use discrete quantum walks on the graphene honeycomb lattice to investigate the possibility of using graphene armchair and zigzag nanoribbons to implement quantum gates. The probability distribution of the quantum walker location represents the particle (electron) density distribution on the graphene lattice. We use a universal set of quantum gates as coins that drive the quantum walk and show that different quantum gates result in distinguishable particle distributions on the graphene lattice.

Resputtering effect during MgO buffer layer deposition by magnetron sputtering for superconducting coated conductors

In this study, MgO thin films were deposited by radio-frequency magnetron sputtering. The film thickness in the deposition area directly facing the target center obviously decreased compared with that in other areas. This reduction in thickness could be attributed to the resputtering effect resulting from bombardment by energetic particles mainly comprising oxygen atoms and negative oxygen ions. The influences of deposition position and sputtering pressure on the deposition rate were investigated. Resputtering altered the orientation of the MgO film from (111) to (001) when the film was deposited on a single crystal yttria-stabilized zirconia substrate. The density distribution of energetic particles was calculated on the basis of the measured thicknesses of the MgO films deposited at different positions. The divergence angle of the energetic particle flux was estimated to be approximately 15°. The energetic particle flux might be similar to the assisting ion flux in the ion beam assisted deposition process and could affect the orientation of the MgO film growth.

Nanoparticle analysis of cancer cells by light transmission spectroscopy

We have measured the optical properties of cancer and normal whole cells and lysates using light transmission spectroscopy (LTS). LTS provides both the optical extinction coefficient in the wavelength range from 220 to 1100nm and (by spectral inversion using a Mie model) the particle distribution density in the size range from 1 to 3000nm. Our current work involves whole cells and lysates of cultured human oral cells in liquid suspension. We found systematic differences in the optical extinction between cancer and normal whole cells and lysates, which translate to different particle size distributions (PSDs) for these materials. Specifically, we found that cancer cells have distinctly lower concentrations of nanoparticles with diameters less than 100nm and have higher concentrations of particles with diameters from 100 to 1000nm—results that hold for both whole cells and lysates. We also found a power-law dependence of particle density with diameter over several orders of magnitude.

Density distribution of particles upon jamming after an avalanche in a 2D silo

We present a complete analysis of the density distribution of particles in a two dimensional silo after discharge. Simulations through a pseudo-dynamic algorithm are performed for filling and subsequent discharge of a plane silo. Particles are monosized hard disks deposited in the container and subjected to a tapping process for compaction. Then, a hole of a given size is open at the bottom of the silo and the discharge is triggered. After a clogging at the opening is produced, and equilibrium is restored, the final distribution of the remaining particles at the silo is analyzed by dividing the space into cells with different geometrical arrangements to visualize the way in which the density depression near the opening is propagated throughout the system. The different behavior as a function of the compaction degree is discussed.Received: 9 December 2014, Accepted: 13 April 2015; Edited by: L. A. Pugnaloni; Reviewed by: F. Vivanco, Dpto. de Física, Universidad de Santiago de Chile, Chile; DOI: http://dx.doi.org/10.4279/PIP.070007Cite as: R. O. Uñac, J. L. Sales, M. V. Gargiulo, A. M. Vidales, Papers in Physics 7, 070007 (2015)This paper, by R. O. Uñac, J. L. Sales, M. V. Gargiulo, A. M. Vidales, is licensed under the Creative Commons Attribution License 3.0.

A Theory of Solvation Effects on Viscosity

We formulate a theory for calculating the viscosity of a dilute solution, considering the solute–solvent interaction. We consider an inhomogeneous density distribution of solvent particles caused by the interaction, using the equilibrium solute–solvent radial distribution function. The theory is a microscopic extension of Einstein’s viscosity formula. We formulate the theory by a perturbation expansion, assuming that a solvent particle is much smaller than a solute particle. From the perturbation theory, we obtain hydrodynamic equations with new boundary conditions on the surface of the solute. The theory is applied to a system with a simple radial distribution function.

Study of the mechanism of fine coal beneficiation in air table

Abstract Beneficiation of fine (−1.0 mm) coal in air table was studied both from theoretical and experimental angles. Experiments were performed according to Response Surface Method with high ash (43%) coal fines using air table. The features of separation were established and favorable operating regimes identified for the targeted product. About 10% (absolute) reduction in the ash level was achieved in single stage operation with a reasonably high product yield. Separation in air table was described by a set of mathematical equations. It was established that the vertical stratification and horizontal segregation are the two phenomena responsible for separation. Both these phenomena are described mathematically from a fundamental standpoint using force balance approach. Simulation performed using the model equations led to the identification of the trajectories of various particles with different size and density over the deck surface. Following the trajectories and using the size and density distribution of the coal particles the mass yield and the ash level of the product are computed. The computed data and the experimental observations were found to be in good agreement.

An analytic expression for the sheath criterion in magnetized plasmas with multi-charged ion species

The generalized Bohm criterion in magnetized multi-component plasmas consisting of multi-charged positive and negative ion species and electrons is analytically investigated by using the hydrodynamic model. It is assumed that the electrons and negative ion density distributions are the Boltzmann distribution with different temperatures and the positive ions enter into the sheath region obliquely. Our results show that the positive and negative ion temperatures, the orientation of the applied magnetic field and the charge number of positive and negative ions strongly affect the Bohm criterion in these multi-component plasmas. To determine the validity of our derived generalized Bohm criterion, it reduced to some familiar physical condition and it is shown that monotonically reduction of the positive ion density distribution leading to the sheath formation occurs only when entrance velocity of ion into the sheath satisfies the obtained Bohm criterion. Also, as a practical application of the obtained Bohm criterion, effects of the ionic temperature and concentration as well as magnetic field on the behavior of the charged particle density distributions and so the sheath thickness of a magnetized plasma consisting of electrons and singly charged positive and negative ion species are studied numerically.

Run-and-tumble dynamics of self-propelled particles in confinement

Run-and-tumble dynamics is a wide-spread mechanism of swimming bacteria. The accumulation of run-and-tumble microswimmers near impermeable surfaces is studied theoretically and numerically in the low-density limit in two and three spatial dimensions. Both uni-modal and exponential distributions of the run lengths are considered. Constant run lengths lead to peaks and depletions regions in the density distribution of particles near the surface, in contrast to exponentially distributed run lengths. Finally, we present a universal accumulation law for large channel widths, which applies not only to run-and-tumble swimmers, but also to many other kinds of self-propelled particles.

Sheath structure in plasmas with nonextensively distributed electrons and thermal ions

Sheath region of an electropositive plasma consisting of q-nonextensive electrons and singly charged positive ions with finite temperature is modeled. Using Sagdeev's pseudo potential technique to derive the modified sheath formation criterion, it is shown that the velocity of ions at the sheath edge is directly proportional to the ion temperatures and inversely proportional to the degree of nonextensivity of electrons (q-parameter). Using the modified Bohm criterion, effect of degree of nonextensivity of electrons and temperature of positive ions on the characteristics of the sheath region are investigated numerically. It is shown that an increase in the ion temperature gives rise to an increase in the electrostatic potential and the velocity of ions in the sheath regardless of the value of q. Furthermore, it is seen that the sheath width and the density distribution of the charged particles decrease by increasing the temperature of positive ions. In addition, it is found that the positive ion temperature is less effective on the sheath structure for higher values of the q-parameter. Finally, the results obtained for a thermal plasma with nonextensively distributed electrons are compared with the results of a cold plasma with nonextensive electrons and an extensive (Maxwellian) plasma with thermal ions.