Grey Particles Research Articles

A full spectrum k-distribution based non-gray radiative property model for fly ash particles

Particle radiation characteristics have a strong wavelength-dependence. However, the gray particle assumption is widely used for coal combustion simulations, which cannot reflect the non-gray radiative property of the particles. In this study, based on the measured complex index of refraction from literatures (Gupta and Wall, 1985, Goodwin and Mitchner, 1989, and Lohi et al., 1992), a new non-gray particle radiative property model for fly ash is proposed by combining the features of full-spectrum k-distribution (FSK) model with the weighted sum of gray gases (WSGG) model. Four gray particles with different absorption and scattering efficiencies are used to replace the non-gray particles, for which absorption efficiency, scattering efficiency and weighting factor are directly obtained from the k-distribution, with model parameters obtained based on rational polynomials. Simultaneously, a gray particle model based on the Planck’s law is also obtained for comparison. The new model is systematically validated by comparing the radiative source terms and radiative heat fluxes, with those predicted by the line-by-line (LBL) integration of Mie-data in a one-dimensional plane-parallel slab system. The maximum relative error of radiative source term is 8% for the new non-gray radiative property model, 13% for Planck mean coefficients, 14% for modified Johansson model (Johansson, 2017), and 18% for empirical-constant model in non-isothermal inhomogeneous particle media, respectively. Combining the new non-gray radiative property model with the non-gray formulation of WSGG-SK model (Guo et al., 2015), the prediction accuracy is further validated by LBL solutions in the gas and particle mixture. Moreover, the contribution of gases and particles to radiative heat transfer is discussed at different path lengths, which shows the accuracy of the particle radiative property model determines the prediction accuracy of the radiative heat transfer in large-scale furnace.

Bio-production of selenium nanoparticles with diverse physical properties for recovery from water

Biological reduction of soluble selenate to insoluble elemental selenium enables the removal and recovery of selenium from aqueous streams. Economic, efficient biological selenium recovery depends on properties of selenium particles such as size, density, stability, hydrophilic character and attachment to the biomass. In batch and fed-batch reactors using anaerobic sludge, the influence of pH (6-9) and temperature (20–50°C) on the morphology, structure and stability of the biologically produced selenium particles were studied using SEM, XRD, and light microscopy. At a high pH or a high temperature these experiments resulted in grey crystalline hexagonal acicular selenium particles, while at a low pH combined with a low temperature red amorphous nanospheres were dominant. Particle stability tests were carried out by changing the temperature or pH after the particles had formed. Red amorphous selenium spheres (produced at pH=7 and 30°C) transformed gradually towards the grey hexagonal structure at 50°C over a period of three weeks, whereas the transformation was less or not detected under other process conditions (according XRD). We show here that biological selenium particle crystallinity, shape and color can be controlled by temperature and pH. However, the choice for the temperature and pH in the bioreactor should not limit the biomass' reduction capacity of selenate. The production of crystalline particles is an important first step to grow larger selenium particles in the future in order to reduce costs for selenium recovery in bioreactors.

VC and Cr3C2 doped WCoB-TiC ceramic composites prepared by hot-pressing

The grain growth inhibitors (GGIs) VC and Cr3C2 doped WCoB-TiC ceramic composites were fabricated by hot-pressing. The microstructure, hardness, transverse rupture strength (TRS), fracture toughness (KIC) and wear-resistance of WCoB-TiC ceramic composites were investigated. The results reveal that the grains can obviously become refined and the densification temperature of WCoB-TiC ceramic composites will be increased due to the VC and Cr3C2. The typical microstructure of WCoB-TiC ceramic composites mainly consist of bright W2CoB2 grains, gray TiC particles, dark TiB2 and pores. WCoB-TiC ceramic composites doped with 0.3wt% VC and 0.3wt% Cr3C2 hot-pressing at 1420°C show the optimum mechanical properties (hardness, TRS and KIC are 92.6 HRA, 1976MPa and 14.8MPam1/2, respectively) and the best dry sliding wear-resistance.

The formation mechanism and bio-corrosion properties of Ag/HA composite conversion coating on the extruded Mg-2Zn-1Mn-0.5Ca alloy for bone implant application

In this study, a silver and hydroxyapatite (Ag/HA) composite coating was generated on an extruded Mg-2Zn-1Mn-0.5Ca magnesium alloy through a chemical conversion process. Scanning electron microscopy (SEM) observation showed that a gray conversion coating was formed with white snow-like and gray globular particles or crystals located randomly above the coating. X-ray diffraction (XRD) combined with X-ray photoelectron spectroscopy (XPS) analysis indicated that the conversion coating was mainly composed of Ca10(PO4)6(OH)2 with limited quantities of Ag/Ag2CO3, CaHPO4·2H2O and CaSiO3. The formation mechanism of the Ag/HA composite conversion coating is discussed in this work. The electrochemical polarization and EIS tests showed that the conversion coating markedly improved the bio-corrosion resistance of the Mg-2Zn-1Mn-0.5Ca alloy in Hank's solution. Adhesion test showed that the coating has a strong bonding strength. The bactericidal activity was assessed with the zone of inhibition method, and the composite coating on the Mg alloy substrates exhibits good antibacterial performance.

Effect of Rare Earth Metals, Sr, and Ti Addition on the Microstructural Characterization of A413.1 Alloy

The present work was performed on A413.1 alloy containing 0.2–1.5 wt% rare earth metals (lanthanum or cerium), 0.05–0.15% Ti, and 0–0.02 wt% Sr. These elements were either added individually or combined. Thermal analysis, image analysis, and electron probe microanalysis were the main techniques employed in the present study. The results show that the use of the depression in the eutectic temperature as a function of alloy modification cannot be applied in the case when the alloy is treated with rare earth metals. Increasing the concentration of RE increases the solidification zone especially in Sr-modified alloys leading to poor feeding ability. This observation is more prominent in the case of Ce addition. Depending upon the amount of added Ti, two RE based intermetallics can be formed: (i) a white phase, mainly platelet-like (approximately 2.5 μm thick), that is rich in RE, Si, Cu, and Al and (ii) a second phase made up of mainly grey sludge particles (star-like) branching in different directions. The grey phase is rich in Ti with some RE (almost 20% of that in the white phase) with traces of Si and Cu. There is a strong interaction between RE and Sr leading to a reduction in the efficiency of Sr as a eutectic Si modifier causing particle demodification.

Characteristics study of projectile’s lightest fragment for 84Kr36–emulsion interaction at around 1 A GeV

The present article significantly investigated projectiles lightest fragments (proton) multiplicity distribution and probability distribution with 84Kr36 emulsion collision at around 1 A GeV. The multiplicity and normalized multiplicity of projectiles lightest fragments (proton) is correlated with the compound particles, shower particles, black particles, grey particles, helium fragments particles and heavily ionizing charged particles. It is found that projectiles lightest fragments (proton) are strongly correlated with compound particles and shower particles rather than other particles and the average multiplicity of projectiles lightest fragments (proton) increases with increasing compound, shower and heavy ionizing particles. Normalized projectiles lightest fragments (proton) are strongly correlated with compound particles, shower particles and heavy ionizing charge particles. The multiplicity distribution of the projectiles lightest fragments (proton) emitted in the 84Kr36 + emulsion interaction at around 1 A GeV with different target has well explained by KNO scaling. The mean multiplicity of projectiles lightest fragments (proton) depends on the mass number of the projectile and does not significantly dependent of the projectile energy. The mean multiplicity projectiles lightest fragment (proton) increases with increasing the target mass number.

Centrality dependence of total disintegration of target nuclei in high energy nucleus–nucleus interactions

A study of centrality dependence of target fragmentation and multiparticle production has been carried out in 16O–AgBr, 22Ne–AgBr, and 28Si–AgBr interactions at 4.1–4.5 AGeV/c for the total disintegrated (TD) events. Average multiplicity of black particles increases linearly with decreasing centrality while average multiplicity of grey and shower particles decreases with decreasing centrality for the TD events. The decrease of average multiplicity of grey particles is linear; on the other hand, in the case of shower particles, the increase is nonlinear. With the increase of the mass of the projectile beam, the average multiplicity of black particles decreases and the average multiplicity of grey particles increases for the TD events. This observation has been explained on the basis of the fireball model; however, in the case of shower particles, average multiplicity increases with increase of projectile mass.

A Real-Time Renewable Plastic Particles Sorting Algorithm Based on Image Processing

According to the demand of harmonia renewable particles sorting in domestic plastics recycling industry,mainly for white and gray recycled plastic particles,a mathematical model is built in RGB color space and a kind of high accuracy, real-time sorting algorithm based on image processing is proposed.This algorithm is intended to use related multiplication, addition and comparison operations of particles pixels R, G, B component,,instead of sorting algorithm based on the difference and threshold processing commonly used in domestic products,and verify its effectiveness through simulation.

Complete Destruction of Ag Br Emulsion Nuclei BY<sup>28</sup>Si Ions with 4.5 GeV/Nucleon Energy

The main experimental characteristics (multiplicity characteristics) of secondary particles have been investigated in interactions of 28Si with emulsion at 4.5 GeV/c per nucleon at rest of emulsion, nuclei. The complete destruction of the heavy target nuclei (Ag, Br) has been studied. The average of shower particles s > is weakly dependent on the target mass whereas the average multiplicity of grey particles g > is strongly dependent on it. The correlations between the multiplicities of the charged secondaries at different mass number of the projectile and center-of-mass-available energy are investigated.

Target productions in forward and backward hemispheres in the interactions of 28Si-EM at 14.6A GeV

This paper search for the results and properties of slow particle productions, appear as a gray and black tracks in nuclear emulsions, producing secondary charged particles which are emitted from [Formula: see text]Si interactions with emulsion nuclei at 14.6[Formula: see text] GeV. The forward particles emission of interactions, ([Formula: see text]) as well as the backward ones ([Formula: see text]), have been investigated. It includes the effect of both projectile mass number and energy on the production and multiplicities of these particles. The results compared with other experiments for the same target but with different projectiles and energies. The experimental data show that there are two different mechanisms responsible for the production of gray particles for the chosen channels of emission angles and each are energy dependence. This dependence is weakly on the projectile mass number. The same investigations are applied for black tracks producing particles. The experimental results show the production of these particles is purely target fragments independent on both projectile mass number and its energy. The anisotropy ratio of angular distribution (F/B) is applied for both kinds of particles which are found the value for gray particle production depends on the direction of emissions while it is unchanged for black particles.

Study of multiplicity correlations in nucleus–nucleus interactions at high energy

In the present paper, some results on the correlations of the nucleus–nucleus interactions, at high energy, between different particle multiplicities are reported. The correlations between the multiplicities of the different charged particles emitted in the interactions of 22 Ne and 28 Si nuclei with emulsion at (4.1–4.5)A GeV/c have been studied. The correlations of the compound multiplicity nc, defined as the sum of both numbers of the shower particles ns and grey particles ng, have been investigated. The experimental data have been compared with the corresponding theoretical ones, calculated according to the modified cascade evaporation model (MCEM). An agreement has already been fairly obtained between the experimental values and the calculated ones. The dependence of the average compound multiplicity, on the numbers of shower, grey, black and heavy particles is obvious and the values of the slope have been found to be independent of the projectile nucleus. On the other hand, the variation of the average shower, grey, black and heavy particles is found to increase linearly with the compound particles. A strong correlation has been observed between the number of produced shower particles and the number of compound particles. Moreover, the value of the average compound multiplicity is found to increase with the increase of the projectile mass. Finally, an attempt has also been made to study the scaling of the compound multiplicity distribution showing that the compound multiplicity distribution is nearly consistent with the KNO scaling behavior.

Study of Compound Particle Production in <sup>28</sup>Si and <sup>32</sup>S-Emulsion Collisions at 14.6 and 200 AGeV

This work displays a study of the compound multiplicity characteristics of 14.6 and 200 AGeV/c 28Si and 32S-emulsion interactions, where the number of shower and grey particles taken together is termed as compound multiplicity, Nc. It has been found that the average compound multiplicity depends on the mass number of the projectile, Ap, and energy of the projectile. A positive linear dependence of the compound multiplicity on the black, grey, heavy and shower particles has been found. Also the scaling of compound multiplicity distributions produced in these interactions has been studied in order to check the validity of KNO-scaling. A simplified universal function has been used to represent the experimental data. The experimental results have been compared with those obtained by analyzing events generated with the computer code FRITIOF based on Lund Monte Carlo model.

Modeling radiation in particle clouds: on the importance of inter-particle radiation for pulverized solid fuel combustion

The importance of inter-particle radiation for clusters of gray and diffuse particles is investigated. The radiative cooling of each individual particle is found to vary strongly with its position in the cluster, and a “mean” radiative particle cooling term is proposed for single particle simulations of particle clusters or for high detail simulation, like Direct Numerical Simulations of small sub-volumes of large clusters of particles. Radiative cooling is shown to be important both for furnaces for coal gasification and coal combustion. Broadening the particle size distribution is found to have just a minor effect on the radiative particle cooling. This is particularly the case for large and dense particle clusters where there is essentially no effect of size distribution broadening at all. For smaller and more dilute particle clusters, the effect of distribution broadening is clear but still not dominant.

Experimental Investigation of a New Triboelectrostatic Separation Process for Mixed Fine Granular Plastics

Triboelectrostatic separation of millimeter-size particles is a well-known process, which is widely used in the recycling industry. However, when processing fine particles with an average diameter of 0.1 mm or less, this technique is still inefficient. The aim of this paper is the experimental investigation of a patent-pending triboelectrostatic separation process based on a fluidized bed tribocharging system where the fine granules to be sorted are exposed to the electric field generated between a pair of rotating metallic disks connected to two high-voltage supplies of opposite polarities. The lower parts of the disk electrodes are immersed in the fluidized bed. The experiments were carried out on a granular mixture composed of fine white and gray PVC particles of average size 20 μm. The particles to be separated are positively and negatively tribocharged using the fluidization air provided by a variable-speed blower, and then they are pinned to the disk electrodes of opposite polarities. The separation outcome, in terms of recovery and purity, is highly efficient and depends on several factors: the high-voltage level, the rotating speed of the disks, the interelectrode gap, the thickness of the fluidized bed, and the fluidization rate.

CHARACTERISTICS OF PARTICLES PRODUCED IN HADRON-NUCLEUS COLLISIONS

A detailed study on mean multiplicities of secondary charged particles is presented. The average number of grey, black and heavy particles are found to be independent of energy in proton-nucleus interactions whereas for pion-nucleus collisions the data deviates from its independence with energy. The ratio of mean number of charged particles produced in pion-nucleus collisions to its number in proton-nucleus interactions at almost the same energy is found to be similar at different energies.

Cytological changes during luminescence production in lanternshark (Etmopterus spinax Linnaeus, 1758) photophores

Studying an organism’s photogenic structures at the ultrastructural level is a key step in the understanding of its light-emission process. Recently, the photophore ultrastructure of the deep-sea lanternshark Etmopterus spinax Linnaeus, 1758 was described. The photocytes appeared to be divided into three areas including an apical granular area, which contains inclusions and was hypothesized to be the light-producing reaction site. In this study, we investigated the morphological changes occurring within the granular area during the bioluminescent emissions induced by two hormones: prolactin and melatonin. Prolactin provoked the formation of new structures in the granular area, the “grey particles”, whose number was proportional to the amount of light produced by the reaction. An increase in the number of granular inclusions was also detected at the end of the prolactin-induced light emission. Conversely, melatonin induced a decrease in the number of granular inclusions and an increase in their diameter. An effect of hormones was also observed on the iris-like structure where they triggered pigment retraction and hence an increase in the iris aperture diameter. This is consistent with previous findings and is shown for the first time at the cellular level. The possible role of grey particles in E. spinax light-emission mechanism is discussed, while granular inclusion is considered to be E. spinax’s intracellular luminescence site. Regarding typical shark long-lasting glows, a new term (“glowon”) is proposed to characterize this novel membrane-free microsource.

Scaling of multiplicity distribution in high energy hadron-nucleus interactions

Analysis of 50 and 340 GeV pion-nucleus and 400 GeV proton- nucleus interactions data for multiplicity scaling study has been carried out. The multiplicity distribution of compound(sum of shower and grey particles in an event), slow (black tracks) particles and target protons ( grey tracks) are found to obey a KNO type scaling law. Keywords: Multiplicity scaling, compound multiplicity, relativistic charged particles, multiparticle production, multiplicity distribution Subject classification PACS 13.85 - Hadron - induced high - and superhigh - energy interactions, energy > 10 GeV. I. Introduction During the last many years, the work on high energy experiments was carried out by several workers(1-8) mostly for shower particles which are fast moving charged particles or we can say that relativistic charged particles in hadron-nucleus (hA) and nucleus-nucleus (AA) collisions. The investigation of hA collisions is fundamental for understanding the nature of the interaction process. It is believed that these interactions may provide some very useful information about the dynamics of multiparticle production. An important feature noticed in these interactions is that the nucleus plays the role of target for the incident hadron. For the present study nuclear emulsion technique has been used to collect the data. Nuclear emulsion is a material which memorises the tracks of charged particles. When a particle, let us call it as a primary particle, is incident on the nuclei of the emulsion, secondary particles are produced in the form of tracks. These particles are termed as shower, grey and black particles; and their number in an event/interaction is given as ns, ng and nb. We have tried to study the compound particle (nc) multiplicity distribution also. A compound particle is defined as the sum of number of shower (ns) and grey (ng) particles in an event, i.e., nc=ns+ng. The study on compound particle multiplicity was first done by Jurak and Linscheid (9). We studied some aspects of compound multiplicity distribution in our earlier publication (10), this paper is in continuation to that (10). Many workers (12-20) have studied various characteristics of compound multiplicity distributions for high energy interactions. An attempt has also been made to study the multiplicity distributions of the slow particles (black tracks) and target protons (grey particles). In the present paper an effort is made to test the validity of hypothesis of Koba, Neilsen and Olesen (11) which is referred to as KNO scaling in the case of compound as well as slow particles. II. Experimental details In order to collect the experimental data, a stack of Ilford-G5 emulsion pellicles exposed to a 340 GeV negative pion beam was used. The events/interactions were picked up after leaving 3 mm from the leading edges of the pellicles to avoid any distortion effects. The measurement was carried out using an oil immersion objective of 100X magnification. To rule out any contamination of primary events with secondary interactions, the primaries of all the events were followed back up to the edge of the plates and only those events whose primary remained parallel to the main direction of the beam and which did not show any significant change in their ionization were finally picked up as genuine primary events. In these interactions the secondary particles appear in the form of a track. The particles associated with different tracks were classified according to emulsion terminology (21) on the basis of their specific ionization g*(=g/go), where g is the ionization of the track and go is the ionization of the primary. The tracks with g* 10 were named as grey and black tracks respectively. The particles associated with grey and black tracks are also called as slow particles, grey tracks are mostly target protons. In this study two more data sets were used, one at 50 GeV (18) pion-nucleus interactions and the other at 400 GeV (18) proton-nucleus interactions. Thus the analysis is based at three energies i.e., 50, 340 and 400 GeV. Other details may be found in our earlier publications(10,18).

Some aspects of multiparticle production in high energy nuclear interactions

We report some results on mean normalized multiplicity (RA). This quantity shows independence with energy for pion-nucleus and proton-nucleus interactions both. The variation of RA4 with mean number of collisions made by incident hdaron inside the nucleus has also been studied. Keywords: Mean normalized multiplicity, multiparticle production, created charged particles and nuclear emulsion. Subject classification PACS 13.85 - Hadron - induced high - and superhigh - energy interactions, energy > 10 GeV. I. Introduction The main concern of high energy physics is the study of fundamental particles. After having understood the properties of fundamental particles and the laws governing their interactions, one can apply these to more complex system of particles. Going back to the last many decades, one finds that there has been a growing realization that nuclear targets can give snapshots of the space-time development of a strong interaction process. Hence, it was thought that collisions of hadrons with nuclei may provide some information regarding elementary particles and their interactions which can never be known using a simple hydrogen target. People use complex atomic nuclei in high energy experiments as targets because of the fact that it gives quite unexpected and interesting results. From theoretical point of view it is believed that at high energy a nuclear collision forces the projectile to interact with the whole lot of hadronic matter within a very short period of time. Therefore, by studying the penetration of projectile in nuclear matter, one may get some very useful informations of high energy reactions within very small distances and quite short times from impact which is definitely not possible in normal particle-particle reactions. In the present investigation nuclear emulsion technique was used to collect the interactions/events which is when seen under a compound microscope look like a star. Nuclear emulsion is a material which memorises the tracks of charged particles. When a particle (projectile) collides with the nuclei (target) of emulsion, a large number of secondary particles are produced. There are three categories of secondary particles which are produced. First are the shower particles, they are mostly pions and are produced in forward cone, the other two are grey and black particles. The grey and black particles are also called as slow particles. The number of shower, grey and black particles in an interaction/event are termed as Ns, Ng and Nb. When grey and black particles are taken together, they are called as heavy tracks/particles and their number is written by Nh(=Ng+Nb). Many workers (1-12) have studied nuclear interactions using this technique. In this paper we report some results on mean multiplicity, its dependence on energy and average number of collisions made by the incident particle inside the nucleus.

Corrigendum: Characteristics of the total disintegration events of emulsion heavy target nuclei caused by O16 and 28Si nuclei at high energies

The present paper deals with the interactions of 16 O and 28 Si nuclei with emulsion heavy target nuclei (silver (Ag) and bromine (Br)) at 4.5A GeV/c. The results have been analyzed to identify interesting characteristics of the total disintegration (TD) events produced in these interactions. Events having a number of heavily ionizing particles Nh 28 have been selected in this study. The integral multiplicity distributions for the disintegrated particles from the target nuclei have been used to separate the inelastic interactions with the free hydrogen (H), the light (CNO), and the heavy (AgBr) nuclei. The average multiplicities of the different secondary particles emitted in these interactions have been compared with the corresponding ones of different projectiles nearly at the same momentum. The average multiplicity of the grey particles is found to increase with the mass of the projectile, while the average multiplicity of the black particles is found to decrease with increasing mass of the projectile; this result agrees with the prediction of the fireball model. Also, the dependence of the shower, grey, and black particles produced in the TD events on the mass of the projectile has been studied. Moreover, the dependence of the probability of the TD for the projectile mass as well as the target fragments has also been discussed. The results show that the multiplicity distributions of the shower, grey, and black particles present a Gaussian distribution. Finally, the linear dependence of the grey and compound multiplicities on the black, heavy, and shower particles has also been observed.

Shower and Slow Particle Productions in Nucleus-Nucleus Collisions at High Energy

The multiplicity distributions of shower, grey, and black particles produced in interactions of4He,12C,16O,22Ne, and28Si with emulsion (Em) at 4.1–4.5 A GeV/c beam energies, and their dependence on target groups (H, CNO, and AgBr) is presented and has been reproduced by multisource thermal model. The multiplicity and the angular distributions of the three types of particles have been investigated. The experimental results are compared with the corresponding ones from the model. We found that the experimental data agrees with theoretical calculations using multisource thermal model.