共查询到20条相似文献,搜索用时 31 毫秒
1.
Nikola Toljic K. Adamiak G.S.P. Castle Hong-Hsiang Kuo Hua-Tzu Fan 《Journal of Electrostatics》2011,69(3):189-194
Charge to mass ratio is a crucial parameter that governs the behavior of particle trajectories in a charged cloud of particles. The complex nature of the charging process limits our ability to accurately determine the charging level when particles of varying size are present. Using a numerical approach, it is possible, however, to take into account predefined values for this parameter. In this paper, the average charge to mass ratio and the distribution of the charge to mass ratio in the coating of a flat target were systematically varied to demonstrate their effect on the motion of the charged particles. The results show that the transfer efficiency increases as the average charge to mass ratio increases. It was found that the transfer efficiency is a weak function of the average particle size in the range tested and that it increases as the width of the size distribution increases. 相似文献
2.
3.
M. Lackowski A. Krupa A. Jaworek 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(3):377-382
Charging of aerosol droplets and solid particles is applied in many
industrial processes such as electrostatic painting, particle separation and
electrostatic precipitation. In most of charging devices, electrical
discharges are used as a source of ions, which are deposited onto the
particles. In the present paper, the charging process by ionic current in
alternating electric field was optimized experimentally. Alternating
electric field charger was used as a charging device in these experiments.
The current voltage characteristics of electrical discharge in this device,
and the charge imparted to the particles were determined. The level of
charge was measured at the outlet of the charger and was compared to the
Pauthenier limit for different supply voltages, and frequencies. MgO powder
was used as a source of particles in these experiments. It was noticed that
higher supply voltage of the charger gives higher level of particle charge,
but at the same time, the particle deposition on the charger elements was
increased, decreasing the particle penetration. A compromise between these
two tendencies is therefore necessary. As a result we have proposed a
criterion maximizing the total charge born by the particles which is a
product of relative particle charge and particle penetration. 相似文献
4.
L. J. Landau 《Journal of statistical physics》1994,77(1-2):259-309
A quantum particle observed on a sufficiently large space-time scale can be described by means of classical particle trajectories. The joint distribution for large-scale multiple-time position and momentum measurements on a nonrelativistic quantum particle moving freely inR
v is given by straight-line trajectories with probabilities determined by the initial momentum-space wavefunction. For large-scale toroidal and rectangular regions the trajectories are geodesics. In a uniform gravitational field the trajectories are parabolas. A quantum counting process on free particles is also considered and shown to converge in the large-space-time limit to a classical counting process for particles with straight-line trajectories. If the quantum particle interacts weakly with its environment, the classical particle trajectories may undergo random jumps. In the random potential model considered here, the quantum particle evolves according to a reversible unitary one-parameter group describing elastic scattering off static randomly distributed impurities (a quantum Lorentz gas). In the large-space-time weak-coupling limit a classical stochastic process is obtained with probability one and describes a classical particle moving with constant speed in straight lines between random jumps in direction. The process depends only on the ensemble value of the covariance of the random field and not on the sample field. The probability density in phase space associated with the classical stochastic process satisfies the linear Boltzmann equation for the classical Lorentz gas, which, in the limith0, goes over to the linear Landau equation. Our study of the quantum Lorentz gas is based on a perturbative expansion and, as in other studies of this system, the series can be controlled only for small values of the rescaled time and for Gaussian random fields. The discussion of classical particle trajectories for nonrelativistic particles on a macroscopic spacetime scale applies also to relativistic particles. The problem of the spatial localization of a relativistic particle is avoided by observing the particle on a sufficiently large space-time scale. 相似文献
5.
To simulate the intense bunched beam transport, a computer
program LEADS-3D has been developed. The particle trajectories are
analysed with the Lie algebraic method. The third order
approximation of the trajectory solutions is made with space charge
forces off, and the second order approximation is made with space
charge forces on. The particle distribution in the 3D ellipsoid is
uniform or Gaussian. Most of the conventional beam optical elements
are incorporated in the code. The optimization procedures are
provided to fit the beam lines to satisfy the given optical
conditions. 相似文献
6.
This work is focused on analysing effect of accumulated dust particles' charge on PV module performance. In the Dundee University's laboratory, dust particles have been created through epoxy powder and charged by using corona and tribo-electric charging methods by varying the charge levels of the accumulated dust particles. The PV module output has analysed for finding a relation between charge levels of the accumulated dust particles and its output voltage. Obtained experimental results have shown that charge level of accumulated dust particles on PV module's have significant impact on its output and dust particle accumulations are not associated with panel tilt angle. 相似文献
7.
Mahmoud Hachemane Mohamed Abdelwahab Benbitour Abdallah Smida 《Foundations of Physics》1997,27(4):579-594
Along the lines of a previous work, the geometrical structure of Hibert bundles describing extended quantum free particles
is repeated with Galilei external and internal independent symmetries. Then, in order to introduce the interaction, this structure
is extended by replacing configuration and momentum spaces by the socelled spaces of trajectories and extended velocity boosts,
respectively. These provide representations giving the probability amplitudes for the particle to follow certain trajectories.
The interaction can be introduced in the transformation law from functions on the space of trajectories (free dynamics) to
functions on spacetime (intracting dynamics). This transformation law, which makes use of a universal distribution, is seen
as a functional in our work according to a quantum functional theory which generalizes the ideas of de Broglie. Intertwining
of induced representations gives the free propagator in the space of trajectories and, henceforth, the propagator with interaction
in space-time for the extended particle. 相似文献
8.
9.
粉末冶金高温合金中元素偏析以及粉末原始颗粒边界是影响材料性能的重要因素,由于其颗粒粒径通常为几十微米,宏观的成分分布分析方法无法实现粉末原始颗粒边界处成分分布的精细表征。微束X射线荧光光谱(μ-XRF)是近年来发展起来的无损微区成分分布分析技术,可实现材料较大范围内元素快速、高分辨分布分析,目前在地质、考古、生物等领域有了较多的应用,但在复杂块状金属成分定量分布表征方面还存在一定困难,在粉末冶金工业领域还未见有应用报道。该试验研究了高温合金中各元素的荧光光谱行为,通过类型匹配的高温合金块状标准样品对元素定量模型进行了校正,建立了基于μ-XRF的高温合金成分定量分布分析方法,满足了粉末冶金工业对于较大范围内粉末边界成分分布精细定量表征的需求。该实验以经高纯钴合金化处理的放电等离子体烧结(SPS)粉末高温合金样品为研究对象,对经不同球磨时间混合处理后的粉末烧结样品中的Ni,Co,Cr,Mo,W,Ta,Ti和Al进行了定量统计分布分析,探讨了不同球磨时间对烧结样品成分分布的影响规律;发现样品中存在大量原始颗粒边界,且成分分布较不均匀,颗粒中心处仍然为原始高温合金颗粒成分,经球磨混合加入的纯Co粉颗粒仅存在于高温合金颗粒的外层,导致颗粒边缘Co含量明显高于颗粒中心。当球磨时间较短时,原始颗粒边界处存在很多Co富集区,当球磨时间增加到24 h时,由于在机械混粉过程中超细钴粉与高温合金的合金化,使烧结样品成分分布均匀性有了较大改善,原始颗粒边界处Co的含量显著下降,而其他元素的含量有所增加,说明球磨时间的延长,样品中各元素发生了明显的扩散,这将有助于元素偏析的改善,据此,该粉末冶金高温合金的制备工艺将得以改进。该法亦可应用于其他各种粉末冶金工业产品的成分定量分布表征,可为粉末冶金工艺优化、产品质量的改进提供数据支撑。 相似文献
10.
No Heading A hydrodynamic analogy for quantum mechanics is used to develop a phase-space representation in terms of a quasi-probability distribution function. Averages over phase space using this approach agree with the usual expectation values of quantum mechanics for a certain class of observables. We also derive the equations of motion that particles in an ensemble would have in phase space in order to mimic the time development of this probability distribution, thus giving the position and momentum of particles in the ensemble as a function of time. The equations of motion separate into position and momentum components. The position component reproduces the de Broglie-Bohm equation of motion. As a simple example, we calculate the phase space trajectories and entropy of a free particle wave packet. 相似文献
11.
M. Girardi 《Physica A》2010,389(21):4520-4527
In this work we employ event-driven particle dynamics simulations for a system of spherical insulating grains interacting with an external electric field. This system resembles the electrostatic particle separation present on some industrial processes. Here, the particles collide inelastically with each other and with the container walls, for a constant normal and tangential restitution coefficients. During the collisions, the grains can acquire electric charge due to triboelectric contact charging, since two different species of insulating particles are mixed. Particle-particle electric interactions are not considered. Grains are also subjected to the gravitational field and rotation, and are confined in a cubic box with thermal walls in order to prevent the static equilibrium state. We calculate the mass and charge density profile, and the particle charge distribution for different values of the electric field and temperature of the walls. The particle charge distribution and the effect of particle sizes on the separation process were also investigated. 相似文献
12.
Based on the contact charge transfer model between two particles due to a single collision proposed by Apodaca, the contact charges carried on a particle is derived due to multiple collisions, including the repeat collisions between two particles and the collisions with different particles, in mixed-size granular system of identical material. The effect of the particle size on the charges carried on the particle is simulated. The results indicate that for a mixed-size granular system, due to multiple collisions among particles, there exists a threshold particle radius, the particles with radius higher than which and the particles with radius lower than which carry opposite charges. The threshold particle radius is equal to mean value of particle size in the mixed-size granular system. Basically, the polarity of the charges carried on the largest particle is same as the polarity of the transfer charge carrier, and in case of the positive charge transferred, the largest particle will be positively charged and the smallest particle will be negatively charged, and vice versa. In the same size region, the more dispersive the particle size is, the more the net charges can be produced. In normal-distributed granular system, the magnitude of contact charge is determined mainly by the particle size distribution, size region, total particle number and the relative impact velocity. 相似文献
13.
E. Borie S. Illy T. Westermann 《International Journal of Infrared and Millimeter Waves》1997,18(1):1-22
Numerical modelling of an electron gun in the space charge limited regime requires determining the current density distribution
as well as the electric fields and electron trajectories. This is a rather complicated self-consistent problem, since the
space charge influences the electric field, which in turn influences the electron trajectories. Previous simulations of magnetron
electron guns using the BFCPIC and BFCRAY codes used a simple emission model (constant current density) that is approximately
valid for thermionic emission. The code has been modified to include space charge limited emission. Several different ways
of doing this are considered.
One of the models considered uses Gauss’s law to force the electric field on the emitter to vanish; it was used in the original
version of BFCPIC for the simulation of ion diodes. A second is based on the use of Child’s law (locally), which may be more
appropriate for extension to fully electromagnetic particle-in-cell (PIC) codes. Calculations were performed with both models,
and the results compared with each other and with experiments performed at FZK. 相似文献
14.
The effects of powder properties on in-flight particle velocity and deposition process during low pressure cold spray process 总被引:1,自引:0,他引:1
Xian-Jin Ning 《Applied Surface Science》2007,253(18):7449-7455
In cold spray process, impacting velocity and critical velocity of particles dominate the deposition process and coating properties for given materials. The impacting velocity and critical velocity of particles depend on the powder properties and cold spray conditions. In the present study, the in-flight particle velocity of copper powder in low pressure cold spraying was measured using an imaging technique. The effects of particle size and particle morphology on in-flight particle velocity and deposition efficiency were investigated. The critical velocity of copper powder was estimated by combining the in-flight particle velocity and deposition efficiency. The effect of annealing of feedstock powder on deposition and critical velocity was also investigated. The results showed that the irregular shape particle presents higher in-flight velocity than the spherical shape particle under the same condition. For irregular shape particles, the in-flight velocity decreased from 390 to 282 m/s as the particle size increases from 20 to 60 μm. Critical velocities of about 425 m/s and more than 550 m/s were estimated for the feedstock copper powder with spherical and irregular shape morphology, respectively. For the irregular shape particles, the critical velocity decreased from more than 550 to 460 m/s after preheating at 390 °C for 1 h. It was also found that the larger size powder presents a lower critical velocity in this study. 相似文献
15.
《Journal of Electrostatics》2006,64(6):345-354
Powder coating has several key advantages over liquid coating, and fine powder coating makes the surface finish quality comparable with liquid coating. This work reports on the numerical simulation of a fine powder-coating process in comparison with coarse powder coating, using a commercial computational fluid dynamic code, Fluent v6.1. The purpose of the study is to understand the gas and particle flow fields inside the coating booth for various operating conditions and the effect of reducing particle size on the coating process. The air and powder particle flows in a coating booth were modeled as a three-dimensional turbulent continuous gas flow with solid particles as a discrete phase. The continuous gas flow was calculated by solving the Navier–Stokes equations, including the standard k–ε turbulence model with non-equilibrium wall function. The discrete phase was modeled based on the Lagrangian approach. In addition to drag force and gravity, the electrostatic force including the effect of space charge due to free ions was considered in the equation of motion and implemented using user-defined scalars and user-defined functions. The governing equations were solved using a second-order upwind scheme. This study demonstrates that the use of finer particles of size 15 μm or lower can give a very smooth and uniform surface finish, which may serve the requirement of automotive top-clear coating. This also provides useful information about optimum operating conditions such as the airflow rate, the applied external voltage and the powder-spray rate. The numerical model can also be used to optimize the gun-booth design for a better coating efficiency. 相似文献
16.
Chan Soo Kim Li Bao Kikuo Okuyama Manabu Shimada Hitoshi Niinuma 《Journal of nanoparticle research》2006,8(2):215-221
The filtration efficiency for nanoparticles down to 1 nm in size through glass fibrous filters was measured using an improved PSM-CNC system. In addition, the effects of relative humidity and particle charge were investigated for various nanoparticle diameters. The results show that the filtration efficiencies were independent of humidity and affected by particle charge in the case of particles below 100 nm in size. For particles smaller than 2 nm, the particle penetrations increased with decreasing particle size. These results suggest that the thermal rebound phenomena would be operative for nanoparticles with diameters below 2 nm, even though it would depend on the states of both the particles and the filter media. These results are particularly important for experimental investigations of the behavior of nanoparticles on a filter. 相似文献
17.
Particles inside electrolytes with ion-specific interactions,their effective charge distributions,and effective interactions
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In this work, we explore the statistical physics of colloidal particles that interact with electrolytes via ion-specific interactions. Firstly we study particles interacting weakly with electrolyte using linear response theory. We find that the mean potential around a particle is linearly determined by the effective charge distribution of the particle, which depends both on the bare charge distribution and on ion-specific interactions. We also discuss the effective interaction between two such particles and show that, in the far field regime, it is bilinear in the effective charge distributions of two particles. We subsequently generalize the above results to the more complicated case where particles interact strongly with the electrolyte.Our results indicate that in order to understand the statistical physics of non-dilute electrolytes, both ion-specific interactions and ionic correlations have to be addressed in a single unified and consistent framework. 相似文献
18.
激光熔覆中金属粉末粒子与激光相互作用模型 总被引:4,自引:1,他引:3
为了对同轴激光熔覆过程中运动的金属粉末粒子的速度和温度进行理论分析,并研究各工艺参量的影响,建立了运动中金属粉末粒子的运动模型和热模型.模拟结果表明,粉嘴几何尺寸、粒子直径以及气/粉两相流初始速度是影响粒子运动行为的重要因素;粉嘴几何尺寸、激光焦点位置、激光发散角、激光功率、粒子直径以及气/粉两相流初始速度是影响粒子热行为的重要因素.在相同的工艺参量下(粉嘴出口内径r=2 mm,粉嘴倾角α=60°,初始气流速度v0=0.8 m/s),基于数字粒子图像测速(DPIV)技术,对316L不锈钢粉末粒子运动模型进行了实验验证.结果表明,运动理论模型是可靠的.该模型是掌握同轴激光熔覆过程中金属粉末粒子运动行为的有效工具;同时,热模型也是分析粉末粒子温度随不同参量变化的重要工具. 相似文献
19.
Chuen‐Jinn Tsai Jyh‐Shyan Lin C. G. Deshpande Li‐Chun Liu 《Particle & Particle Systems Characterization》2005,22(5):293-298
An aerosol charge analyzer has been constructed to measure the charge distribution of NaCl particles generated in the laboratory. A radioactive electrostatic charge neutralizer utilizing Po‐210 was used to neutralize the electrostatic charge of the particles. The atomization technique was used to generate NaCl particles with diameters of 0.2 to 0.8 μm, while the evaporation and condensation method was adopted to generate particles of 0.01 to 0.2 μm in diameter. The experimental data demonstrates that the absolute average particle charge depends on the particle diameter, and is higher than that calculated by the Boltzmann charge equilibrium for particles within the range of 0.2 to 0.8 μm. The charge increases with decreasing NaCl concentration. When these particles are neutralized using the Po‐210 neutralizer, it is found that the electrostatic charge reaches the Boltzmann charge equilibrium. For 0.01 to 0.2 μm NaCl particles generated using the evaporation and condensation method, test results show that the absolute average particle charge is higher than that calculated by the Boltzmann charge equilibrium for particles larger than 0.03 to 0.05 μm in diameter, while it is lower than that predicted by the Fuchs theory [1], for particles smaller than 0.03 to 0.05 μm. However, after charge neutralization, particles with diameter above 0.05 μm reach the Boltzmann charge equilibrium condition, and the charges for particles with diameters of 0.010 to 0.05 μm, agree well with Fuchs' theory. 相似文献
20.
Jian-Xin Nie 《中国物理 B》2022,31(4):44703-044703
The combustion mechanism of aluminum particles in a detonation environment characterized by high temperature (in unit 103 K), high pressure (in unit GPa), and high-speed motion (in units km/s) was studied, and a combustion model of the aluminum particles in detonation environment was established. Based on this model, a combustion control equation for aluminum particles in detonation environment was obtained. It can be seen from the control equation that the burning time of aluminum particle is mainly affected by the particle size, system temperature, and diffusion coefficient. The calculation result shows that a higher system temperature, larger diffusion coefficient, and smaller particle size lead to a faster burn rate and shorter burning time for aluminum particles. After considering the particle size distribution characteristics of aluminum powder, the application of the combustion control equation was extended from single aluminum particles to nonuniform aluminum powder, and the calculated time corresponding to the peak burn rate of aluminum powder was in good agreement with the experimental electrical conductivity results. This equation can quantitatively describe the combustion behavior of aluminum powder in different detonation environments and provides technical means for quantitative calculation of the aluminum powder combustion process in detonation environment. 相似文献