Spline-Galerkin Solution of Dynamic Equations for Particle Comminution and Collection

The population balance equation is solved for particles undergoing a combination of growth, comminution, and collection. The approximation method is to use a weighted Galerkin technique with cubic B-splines and an implicit scheme for solving the system of ordinary differential equations. The cubic splines are defined on a graded mesh. The performance of the method is investigated by solving a model problem with simple but nonsmooth kernels. The weight function is chosen so that singularities in the equation can be easily treated. A self-similar solution for comminuted particles is shown to be a useful representation for the solution of the population balance equation provided that this equation is solved over a sufficiently long time interval. Stationary solutions of the equation are obtained for a model that describes both particle comminution and collection.     

管流中注入粒子的非定常波系的数值研究

使用二维有限体积方法,对在管流中固定位置处注入静止固体粒子的可压缩含灰气体流动进行数值模拟,讨论流场和粒子在过程中的耦合,研究质量增加和热量变化所产生的非定常波系,分析物理参数在过程中的变化.结果表明,在添质和加热过程中,流场会产生不同类型和不同强度的非定常波,在分析其物理规律的同时,讨论添质和加热相互作用导致的波系间转换,最后求解流场中各区域的热力学参数,得到不同的流场速度和粒子温度情况下各非定常波波强的相图,定量解释改变参数引起的非定常波变化规律.     

Limiting Fragmentation Behaviours of Correlation and Fluctuation of Particle Produced in High Energy Oxygen-Nucleus Induced Interactions

The limiting fragmentation behaviour of the single-particle pseudo-rapidity distributions and the two-particle correlations in oxygen-nucleus induced interactions in the energy region from 3.7 to 200A GeV is systematically investigated,and that of the dynamical fluctuations of multi-particle distribution is studied by using the relation between the factorial-moments and the multi-particle pseudo-rapidity distributions.     

基于粒子群算法的球磨机情感智能自适应辨识算法

制粉工艺在矿物加工工程技术中极其重要,而球磨机正是其关键设备。针对球磨机系统时变性、非线性的特点,提出了采用大脑情感学习模型(Brain Emotional Learning, BEL)对球磨机系统实现正向模型和逆模型辨识,并利用粒子群算法(PSO)对整个参数空间进行高效并行搜索使参数最优化,并给出球磨机系统数学模型辨识算法。仿真结果表明,改进方法可使模型输出与球磨机系统输出或输入达到一致,具有模型辨识误差小、算法简单的特点。     

压力使固体产生磷光

Recent development of theory ofluminescence demands that latticedefects are directly responsible forthe phenomena of phosphoresccence.There are many evidences supportingthis view.It seems to us there is anew method of testing this theory.This method is to investigate whetherit is possible to produce the phosphores-cence by purely mechanical means.Following is a report of some experi-mental results concerning this question.     

Shapes and shifts in the oxygen Auger spectra

The oxidation of silicon and platinum single crystal faces, of polycrystalline supported catalysts and of some alloy surfaces has been studied by AES and as far as possible by LEED. A comparison of the oxygen Auger spectra obtained during the oxidation process with those found on oxides has been made; it shows that the modification of the fine structure of the oxygen Auger peaks gives some information about the binding state of oxygen. Two different structures, which compete one with the other, are described. In one case, a spectrum where three lines dominate is obtained; in the other case, a “quasi-atomic” spectrum characterized by five features is observed: multiplet splitting in the two-hole final state is predominant. Besides these differences in the fine structure of the Auger spectra one can notice shifts of several eV for the main feature. They have been correlated with the various observed LEED patterns. Physisorption, chemisorption, solution of oxygen in the metal lattice, growth of ordered or amorphous oxides are the different possibilities which are discussed.     

核子与核力决定的核形状(英文)

讨论了最近提出的作为量子多体系统重要潜在机制之一的量子自组织,原子核无疑是最好的实例。由于原子核内核子的单粒子和集体运动共存,它们的相互制约决定了核结构。集体模式因其驱动力,如使椭球形变的四极力及其阻力达到平衡形成,而单粒子能量就是产生阻力的一种根源。当存在较大单粒子能隙时,相关的集体运动更易受到阻碍。因此,一般认为,单粒子运动和集体运动是相互对抗的"天敌"。然而,由于核力的多样和复杂性,单极相互作用使单粒子能量改变也能减小其对集体运动的阻碍而加强集体模式,该现象将通过Zr同位素实例加以说明。这就导致了量子自组织的产生:单粒子能量由两种量子液体（质子和中子）和控制阻力的单极相互作用自组织。于是,不同于朗道费米液体理论的结论,原子核不一定像填装了自由核子的刚性瓶。Ⅱ型壳演化即是包含跨准幻壳能隙激发的直观实例。在重核中,量子自组织因其轨道和核子数更多而更为重要。We discuss the quantum self-organization introduced recently as one of the major underlying mechanisms of the quantum many-body systems. Atomic nuclei are actually a good example, because two types of the motion of nucleons, single-particle states and collective modes, interplay in determining their structure. The collective mode appears as a consequence of the balance between the effect of the mode-driving force (e.g., quadrupole force for the ellipsoidal deformation) and the resistance power against it. The single-particle energies are one of the sources to bring about such resistance power:a coherent collective motion is more hindered by larger spacings between relevant single particle states. Thus, the single-particle state and the collective mode are "enemies" against each other in the usual understanding. However, the nuclear forces are rich and complicated enough so as to enhance relevant collective mode by reducing the resistance power by changing single-particle energies for each eigenstate through monopole interactions. This will be demonstrated with the concrete example taken from Zr isotopes. In this way, the quantum self-organization occurs:single-particle energies can be self-organized by (i) two quantum liquids, e.g., protons and neutrons, (ii) monopole interaction (to control resistance). Thus, atomic nuclei are not necessarily like simple rigid vases containing almost free nucleons, in contrast to the naïve Fermi liquid picture a la Landau. Type Ⅱ shell evolution is considered to be a simple visible case involving excitations across a (sub)magic gap. The quantum self-organization becomes more important in heavier nuclei where the number of active orbits and the number of active nucleons are larger.     

Analysis of Particle Size Distribution by Particle Tracking

Particle tracking is performed using a combination of dark field or fluorescence video microscopy with automatic image analysis. The optical detection together with the image analysis software allows for the time resolved localization of individual particles with diameters between 100 and 1000 nm. Observation of their Brownian motion over a set of time intervals leads to the determination of their mean square displacements under the given room temperature and viscosity. Hereby, the radii of a set of particles visible within a given optical frame are derived simultaneously. Rapid data analysis leads to reliable particle size histograms. The applicability of this method is demonstrated on polystyrene latices and PMMA nanospheres with radii between 51 nm and 202 nm.     

Particle Breakup in Shock Waves Studies by single Particle Light Scattering

The breakup of suspended, agglomerated submicron particles was studied by exposing the aerosol to weak shock waves of varying strength under conditions 400 ms^?1?v?880 ms^?1. A newly developed laser light-scattering diagnostic employing a top hat laser profile was used to size the particles passing through a very small scattering volume. By Comparing the optically measured particle size in front of and behind shock waves, the breakup of agglomerated particles could be clearly identified. The experiments indicate that the aerodynamic forces behind an incident shock overcome the particle binding force resulting in disintegration of the submicron agglomerates. The results are presented in form of a modified Weber number.     

Shapes of heaps and in silos

Experimental investigations on the shape of a heap formed in a Hele Shaw cell either on a flat base or in a two-dimensional silo are presented. We have focused our attention on the shape dependence on mass flux and initial energy of particles poured into the cell. Two kinds of granular media are considered: glass beads and sand and we shall point out their different behaviors. We described the variations of the angle of repose and of the size of the tail as a function of the experimental parameters. We also report the time evolution of the angle of repose during the formation of the heap. Received 28 September 1998 and Received in final form 20 January 1999     

Drop-Size Distributions Produced by Flat-Spray Nozzles

This study deals with measurements of the drop-size distributions of different types of fan spray atomisers using a scattered-light particle size counting analyser. The drop-size distributions were determined at various locations in the spray cone. These local distributions change systematically from the fan's axis to its border. Superimposing these local distributions, adequately weighted, one acquires the entire distribution of all the drops. A comparison of the experimental results is made with those yielded by mathematical equations.     

Iron Halide Species Produced by Laser-Evaporation

Iron halide species were produced by the reaction of laser-evaporated iron atoms with halogen-containing reactant gas, and isolated in low-temperature matrices to obtain their Mössbauer spectra. Iron fluoride (Fe₂F₆, FeF₃ and Fe₂F₄) and iron iodide (FeI₂ and Fe₂I₄) were produced by the reaction of laser-evaporated iron atoms with sulfur hexafluoride SF₆ and methyl iodide CH₃I, respectively. The yields of the products varied depending on the concentration of reactant gas in the Ar matrix. Molecular orbital calculations were performed in order to confirm their assignments.     

Simultaneous Measurement of Particle Size and Particle Velocity by the Spatial Filtering Technique

The objective of this study was to compare the measuring results of a fiber‐optical probe based on a modified spatial filtering technique with given size distributions of different test powders and also with particle velocity values of laser Doppler measurements. Fiber‐optical spatial filtering velocimetry was modified by fiber‐optical spot scanning in order to determine simultaneously the size and the velocity of particles. The fiber‐optical probe system can be used as an in‐line measuring device for sizing of particles in different technical applications. Spherical test particles were narrow‐sized glass beads in the range 30–100 μm and irregularly shaped test particles were limestone particles in the range 10–600 μm. Particles were dispersed by a brush disperser and the measurements were carried out at a fixed position in a free particle‐laden air stream. Owing to the measurement of chord lengths and to the influence of diffraction and divergent angle, the probe results show differences from the given test particle sizes. Owing to the particle‐probe collisions, the mean velocity determined by the probe is smaller than the laser Doppler mean velocity.     

ZnO Nanorods Produced by the Method of Arc Discharge

ZnO nanorods are fabricated by arc discharge with ZnO powder as source materials. The sample is characterized by x-ray diffraction, Raman scattering spectra, scanning electron microscopy and high-resolution transmission electron microscopy. The ZnO nanorods exhibit single crystals with the hexagonal wurtzite structure. Many of them are tetrapod-like. The diameters range from several nanometres to about lOOnm, and the main diameters of the nanorods is around 20nm. The length-to-diameter ratio is more than 5, and the grown directions are along the [001] axis. Photoluminescence spectra show a narrow ultraviolet emission at around 389nm and a broad green emission at around 520 nm. The growth process can be interpreted by the vapour-solid mechanism.     

Particle production by the Čerenkov mechanism

The rate of electron-positron pair creation and rho-meson creation by uniformly moving charges in condensed matter is calculated in the framework of the Schwinger source theory.     

Particle Spectrum Implied by the Dirac Equation

There is a process that starts from the Lagrangian of a set of field equations and leads to a spectrum of particle states. The process is applied in this article to a Lagrangian for the Dirac equation. It leads to a differential equation with solutions that describe particles with definite mass, angular momentum J, charge, and isotopic spin I, having I = J. There is no suggestion of strangeness. The theory is in rough agreement with the masses of many of the 0⁺ (0^–+) and 0⁺ (0⁺⁺) mesons and with the masses of the nonstrange 1/2 (1/2⁺) and 3/2 (3/2⁺) baryons.     

Particle production by charges in condensed matter

The rate of electron-positron pair creation and rho-meson creation by uniform quantum motion of charges in condensed matter is calculated in the framework of the Schwinger source theory.     

Particle Acceleration by Shocks in Supernova Remnants

Particle acceleration occurs on a range of scales from AU in the heliosphere to Mpc in clusters of galaxies and to energies ranging from MeV to exaelectronvolt (EeV). A number of acceleration processes have been proposed, but diffusive shock acceleration (DSA) is widely invoked as the predominant mechanism. DSA operates on all these scales and probably to the highest energies. DSA is simple, robust and predicts a universal spectrum. However, there are still many unknowns regarding particle acceleration. This paper focuses on the particular question of whether supernova remnants (SNR) can produce the Galactic cosmic ray (CR) spectrum up to the knee at a few petaelectronvolt (PeV). The answer depends in large part on the detailed physics of diffusive shock acceleration.     

Nanostructured Y-Fe Alloys Produced by Ball Milling

Ball milling was used to produce nanostructured Y-Fe alloys. Depending on preparation conditions, nanocrystalline and amorphous components are formed to coexist. The transmission Mössbauer spectra exhibit YFe₂ and amorphous components. The influence of superparamagnetic YFe₂ particles was separated from the amorphous part by measuring at 77 K. The thermal stability of the samples and the growth of equilibrium phases was studied by annealing.