Search

Electrostatic forces can be used to control the motion of charged particles. In this article, particle charging and motion in an electric field under ultraviolet (UV) irradiation were investigated. When the particle layers deposited on an insulating substrate were irradiated with UV light in a downward electric field, photoelectrons were emitted, and positive charges moved to the bottom of the particle layers. Subsequently, by reversing the direction of the electric field, the positive charges in the bottom moved upward; thus, the particles in the top layer were positively charged and levitated by Coulomb forces. The flux of the levitated particles increased with an increase in the strength of the electric field (downward and upward). As the upward electric field strength increased, the number of agglomerated particles in the levitation increased; however, the particle charge decreased. As the thickness of the particle layers increased, the time delay for particle levitation increased; however, the flux of the levitated particles decreased. The ratio of agglomerated particles to the total levitated particles increased. These results can be explained by the mechanisms of charge transfer and particle levitation. [ABSTRACT FROM AUTHOR]

The charging and levitation of particles using UV irradiation in an upward electric field were investigated. Glass beads with a mass median diameter of 61 μm were used for the experiments. The particle layers formed on a glass plate were irradiated by UV light with wavelengths ranging from 240 to 400 nm. The particles in the top layer were positively charged by photoemission and levitated by the electrostatic forces. The fluxes and motions of the levitated particles were analyzed by digital processing of the images obtained with a high-speed camera. The charge of each levitated particle was determined by fitting the results calculated using the equation of motion to the experimentally obtained particle motion. The charge of the particles beginning to be levitated was determined by the force balance and thus was not affected by the UV irradiance. The positive charge of the levitated particles could be increased by continuous photoemission from the particles and decreased by the capture of photoelectrons emitted by other particles. Approximately 40% of the levitated particles descended because of the negative charge clouds formed by the photoemission from the particle layers and the levitated particles. Furthermore, in a second set of experiments, an upward electric field was applied after UV irradiation. In these experiments, the particles in the top layer were levitated after applying the electric field. These particles could be gain more excess charges than the particles for which the levitation was governed by the force balance. [ABSTRACT FROM AUTHOR]

The corrosion of ceramic chamber parts causes particles in plasma etching process, so that the production yield and the overall equipment effectiveness (OEE) at LSI mass production line are decreased. We have developed magnesium oxide (MgO)-based ceramics whose corrosion resistance in reactive plasma is higher than conventional ceramic materials. In this study, we have prepared a shower-head-type electrode by using MgO-based ceramics, and demonstrated that the number of particles generated from the electrode is much lower than that generated from a conventional electrode made from aluminium oxide. The MgO-based ceramics contributes to improvement of the production yield and the OEE. [ABSTRACT FROM AUTHOR]

In modern semiconductor manufacturing, one type of measured particle count data contains excess zeros, and the ratio of zeros in the measurements is usually larger than 50%. This type of particle count sample data cannot be well modeled by popular defect models such as Poisson, zero-inflated Poisson, generalized zero-inflated Poisson, and Neyman and Gamma-Poisson models. In this paper, a threshold-Poisson model was proposed to describe the particles with excess zero counts, and the method for parameter estimation was developed. Via comparison with those popular models by using 15 measured samples, it showed that the measurements are better modeled by the threshold-Poisson model. A control chart called threshold-c control chart was proposed and the control limits were derived. A reasonable minimum sample size for constructing control chart was also discussed based on simulations. [ABSTRACT FROM AUTHOR]

This paper presents the numerical analysis and experiments on the electromechanical behavior of conducting wired-shape particles. We investigate the effects of particle ending profiles and orientation on the initial motion. The boundary element method is used to analyze the electric field, forces, and torques on the particles. The calculated liftoff electric field is smaller than the estimated value based on a model of infinitely long cylinder, and slightly decreases for a particle with a sharp end when the sharp tip is separated from the electrode. The measured liftoff electric field agrees with the tendency obtained from the numerical analysis. Particles mostly began the motion at either end. When the sharp tip was separated from the electrode, the initial motion almost exclusively took place at the sharp end. On the other hand, the probability was slightly higher for the motion at the rounded end when the sharp tip was close to the electrode. The numerical calculation clarifies that the electrostatic and gravitational torques contribute to such liftoff behavior. [ABSTRACT FROM AUTHOR]

Aerosol deposition (AD) method is technique for forming high density ceramic films on substrate material surface at room temperature. The yttrium oxide films formed by the AD method (AD-Y2O3 films) have been developed as plasma resistance coating used for the plasma etching equipment. In recent years, plasma eroded particles from chamber components of the etching devices are regarded as a serious issue that they reduce the semiconductor device yield rate. AD-Y2O3 films which have excellent plasma resistance can reduce the eroded particles in the plasma etching equipment and greatly have contributed to manufacturing high integrated semiconductor devices. In this paper, the plasma erosion behavior of AD-Y2O3 films were investigated compared with sintered Al2O3, sintered Y2O3 and thermal splayed Y2O3 in order to clarify the reason why AD Y2O3 films were superior as plasma resistance material. The plasma etching rates of AD-Y2O3 films were not significantly different from other samples. It was assumed that the etching rates were dependent on the chemical stability to fluorine plasma of material. On the other hand, the surface roughness difference before and after plasma exposure of AD-Y2O3 films were much smaller than other samples. It was assumed that the surface roughness difference is dependent on the crystalline size of material. The structure of AD-Y2O3 films, which had high density and nano-crystalline structure, were eroded homogeneously and smoothly. It suggests AD-Y2O3 films do not generate large eroded particles and are superior to reduce the eroded particles in the etching devices. [ABSTRACT FROM AUTHOR]

Considering an actual collection of spherical particles dispersing in a medium, we study in detail the polarization of particles and the effective static dielectric constant by two general models. Particles embedded in a medium lead to core-shell structure. The shell is the interface layer between the particle and the medium. With the effect of the interface layer included, these models are exactly solved with some details for metallic particles and non-metallic particles, respectively. The effective static permittivity of the composite material is approximated by Maxwell-Garnett method. The significant change of the effective permittivity is given by a term in proportional to the volume ratio of the interface layer, which is big for nano-sized particles. The permittivity of the interface layer plays an important role in the dependence of the effective permittivity of the composite material on particle size. [ABSTRACT FROM PUBLISHER]

The deactivation of free particles is an important issue for improving the insulating capability and reliability of high-voltage systems. In this work, we carry out experiments to investigate the electromechanical behavior of the non-spherical conducting particles for different particle orientations on either bare or coated electrode. Spheroidal and wire-shaped particles are used for the experiments. The particle motion is observed for two principal orientations with respect to the applied electric field in air. The results show that on a bare electrode, both kinds of particles exhibit the liftoff motion when the particle axis is aligned with electric field gradient. The field nonuniformity enhances the upward rotation of the particle tip subjected to the higher electric field. When the particle axis is parallel with a constant field line, the wire-shaped particle is more readily to make a rolling motion to the region of stronger electric field in comparison with the spheroidal particle, which shows higher occurrence rate of liftoff. The motion onset electric field decreases with increasing field nonuniformity. On the insulated electrode, the wire-shaped particle shows exclusively the rolling motion, whereas the spheroidal particle may make a rolling motion or rotate horizontally so as to align its axis with electric field gradient. [ABSTRACT FROM PUBLISHER]

The frequent forest fires become a serious threat to the performance of transmission lines' external insulation. Gap breakdown in forest fire relates to many factors, such as flame temperature, conductivity and particles. Large quantities of smoke (carbon black) and flying ash are produced during the combustion of vegetation, causing the dielectric strength of gap to decrease drastically. In order to analyze the influence of forest fire particles on the breakdown characteristics of air gap, the experimental setup consisting of a conductor-plane was built to simulate the effect of forest fire particles. At the same time, a theoretical model was developed to analyze the influence mechanism of multiple particles on the discharge characteristics of gap. Experimental results show that, a chain of carbon particles has been formed between flame and conductor by the action of electric field. The gap's insulation strength decreases significantly, which is about 40% of that in the pure air under AC voltage. The particles movement and the breakdown characteristics of air gap have an evident effect of polarity characteristic under DC voltage and the breakdown voltage is reduced to about 29% of that in the air gap under negative DC voltage. The simulation results show that, the electric field distribution between conductor and plane become uneven, and the distortion degree of the elongated particle to the background electric field is not related to the distance between particles with high-voltage electrode. According to the electric field diagram, it is obvious that the particles make the background electric field distortion, and the maximum field strength increased by about 100%. More close to the conductor, the greater electric field strength is at the both ends of particles. [ABSTRACT FROM AUTHOR]

Microelectromechanical systems (MEMS) that require contact of moving parts to implement complex functions exhibit limits to their performance and reliability. Here, we advance our particle tracking method to measure MEMS motionin operandoat nanometer, microradian, and millisecond scales. We test a torsional ratcheting actuator and observe dynamic behavior ranging from nearly perfect repeatability, to transient feedback and stiction, to terminal failure. This new measurement capability will help to understand and improve MEMS motion. [2018-0118] [ABSTRACT FROM AUTHOR]

An overview of cyclotron development in research laboratories worldwide and the impressive growth of commercial cyclotrons during the last 50 years are summarized. The role of the superconducting cyclotrons, the return of the synchrocyclotrons, the flourishing interest in the fixed field alternating gradient (FFAG), and finally the proposed design for 10-MW class cyclotrons are also presented. [ABSTRACT FROM PUBLISHER]

This paper presents a numerical method to simulate the particle trajectory in the head–disk interface (HDI). The simulator solves the reduced Navier–Stokes equation with the second-slip boundary conditions to get the air velocity distribution, then solves the motion equations of particles and obtains the trajectories of the particles in the HDI using the binary Lagrange interpolation and the fourth-order Runge–Kutta method. The calculated trajectories of particles follow well with the air streamlines in the recessed regions. The particle density, diameter, and initial entering velocity have different effects on particle movement. Furthermore, particle velocity behaviors in the recessed regions are investigated for the first time. The particle is accelerated or decelerated by the action of the drag force and becomes close to the velocity of local air flow. Such effects are more obvious for small particles than large particles. The particle velocity becomes very small when it is close to the leading edge of the trailing pad. The numerical results also show that the particle goes up when it crosses the transition regions, and the particle moves upward more sharply with higher initial entrance height due to the larger vertical velocity of the local air flow. [ABSTRACT FROM AUTHOR]

Particle filters provide a general framework for dynamic state estimation (DSE) in nonlinear systems. The scope for particle filter-based DSE can be significantly enhanced by exploiting data from phasor measurement units (PMUs) when available at higher sampling frequencies. In this paper, we present a particle filtering approach to dynamically estimate the states of a synchronous generator in a multi-machine setting considering the excitation and prime mover control systems. The filter relies on typical output measurements assumed available from PMUs stationed at generator buses. The performance of the proposed filter is illustrated with dynamic simulations on IEEE 14-bus system including: 1) generators models with subtransient dynamics, 2) excitation units (IEEE DC1A, DC2A, AC5A), and 3) turbine-governor models (steam and hydro). The estimation accuracy of the proposed filter is assessed for three classes of disturbances assuming noisy PMUs' measurements and comparative results are presented with the unscented Kalman filter (UKF). The accuracy-computational burden trade-off is also analyzed and the results strengthen the feasibility of using particle filters for dynamic state estimation. [ABSTRACT FROM PUBLISHER]