Air Table Research Articles

Binary random cellular structures

A topological model for binary random cellular structures under neighbor-switching is presented. Performing exact analytical calculations, one obtains a bimodal cell shape distribution, whereas Aboav's law for the correlations between neighboring cells holds for each species separately. The binary character of the tessellation is reduced with increasing disorder. The calculated topological properties are analyzed in comparison with recent experimental studies of binary disc assemblies on an air table.

エアテーブルによる廃電線破砕物の分別

The dry separation of polyvinyl chloride resin from shredded copper wire scrap using an air table has been studied. The air table has a shaking motion similar to that of a wet table, and instead of water acting as the medium of distribution, a blast of air is driven through a perforated deck. Using a mixture of 62.8% polyvinyl chloride resin and 37.2% copper wire, each shredded to less than 4 mm, separation experiments were carried out. The influences of frequency, inclination angle of the shaking deck and the air flow velocity were mainly examined. The optimum treatment conditions were as follows: the frequency of the shaking deck was from 8.9 to 9.3 Hz, the inclination angle was from 7.0 to 10.0 degrees and the air flow velocity was from 1.6 to 2.0 m/s. The separation efficiency at that time was nearly 1.0.

A pneumatic air table realized by micro-EDM

This paper presents a one-dimensional (1-D) pneumatic actuator fabricated by combining several micromachining technologies such as microelectrodischarge machining (micro-EDM) as well as isotropic and anisotropic wet etching. Unlike the existing pneumatic actuators, which usually convey the object by means of friction, this device employs the dynamic pressure of inclined driving jets in order to enhance the horizontal transportation performance. Typical slider speeds of up to 5 cm/s can be obtained. Comparisons between different types of sliders are presented. By an appropriate patterning of the slider bottom surface, the speed could be increased by 50%-60%. Similarly, a maximum tangential force of 20 /spl mu/N (equivalent shear stress: 2.2 /spl mu/N/mm/sup 2/) was obtained using this dynamic pressure concept. The latter is about two times larger than that of a slider with a smooth surface.

廃電子部品破砕物のエアテーブルによる分別

Precious metals are recycled from electric devices. In this study, metallic fragments from shredded mixture were separated using an air table. The air table has a shaking deck motion similar to a wet table and a blast of air is driven through a perforated deck. Several experiments were carried out to demonstrate the effect of frequency, slope angle of the inclined deck and air velocity on separation efficiency. The results indicated that the end slope of inclined deck exerted a great influence of the separation of metallic fragments. The optimum treatment condition was as follows: The angle of slope was 6.5 degrees, frequency of shaking deck was 500 min -1, and air velocity were 1.0-2.0 m·Es-1. The overall separation efficiency at that time was 0.95.

Thermodynamic properties of ideal gas air

The thermodynamic properties of ideal gas air at low pressure (0.1 MPa) are newly calculated, using the most recent spectroscopic data for its components. The components of the 'ideal air' are nitrogen, oxygen and argon, with appropriate volume fractions. The thermodynamic properties of the components are computed by means of statistical thermodynamics using the molecular, physical and spectroscopic data in the new set of Joint Army-Navy-Air Force (JANAF) tables. Therefore, the resulting air table is thermodynamically consistent with the JANAF tables. The reference temperature of enthalpy and entropy is zero degrees kelvin and the reference pressure is 0.1 MPa. The temperature range of the table is 100-4000 K, which covers most engineering interests. In order to speed up the computation, approximate models are developed without any significant loss of accuracy. The new air tables are available in interactive computer codes format for microcomputers as well as in the conventional number-listing tables format. The enthalpy and specific heat of this study are within 0.05% of those of Keenan et al. (1980). The entropy of this study differs from that of Keenan et al. by a constant (=1.164 kJ kg -l K -l ). If the entropy of Keenan et al. is augumented by 1.164 kJ kg -1 K -1 , thermodynamic properties of Keenan et al. are in full agreement with those of this study. The enthalpy, specific heat and entropy of this study are also in full agreement with those of the NBS table and Vargaftik's table (1975) for real gas air.

Arrangement of discs in 2d binary assemblies

We study arrangements of the two species of discs in binary assemblies at an intermediate scale. Small discs rearrange along large ones in clusters whose mass and compactness are analyzed with the tools of percolation. The assemblies are generated analogically on an air table or numerically from RSA or Powell algorithms. At a given packing fraction, an infinite cluster of small discs exists above a critical composition; a phenomenological expression for this threshold is proposed. Like in usual percolation problems, the number of inner links in a cluster is a linear function of its mass, with a slope depending both on the packing fraction, the composition of the mixture and the building procedure. An approximate expression is derived for it.

Two-dimensional harmonic oscillator on an air table

The very important and interesting topic of coupled, harmonic oscillations is studied both theoretically and experimentally with a moving disk on a horizontal air table under the action of two identical springs. Attention is paid to the study of the normal modes and, with adequate and easily reproducible initial conditions, the beats phenomenon.

エアテーブルによるパーライト中の未発泡体の分別

The removal of unexpanded materials from a commercial perlite product was studied using an air table. The air table has shaking motion similar to that of a wet table and a blast of air is driven through a perforated deck. The sample used was the perlite product containing 20% of unexpanded materials. The unexpanded materials and expanded perlites were almost the same in size and shape, however the density of unexpanded materials was slightly greater than that of expanded perlites. The authors tried to separate unexpanded materials on the basis of density difference using the air table. Several experiments were carried out to clarify the effect of frequency, slope angles of perforated deck and air flow on separation efficiency. The results indicated that the end slope angle of deck exerted a great influence on the removal of unexpanded materials.

The effect of viscosity on the height of disks floating above an air table

A similarity solution is used to analyse the flow in the thin gap between a floating disk and an air table, the similarity solution being that for an axisymmetric stagnation point but with an upper boundary condition within the boundary layer. Viscous effects increase the height of the floating disk by 20% even at a Reynolds number of 50. Theoretical predictions are compared with experimental observations. The effect of the pressure distribution under the disk on the air flux through the table is examined.

A model of binary assemblies of dises and its application to segregation study

We propose a theoretical model of random binary assemblies of discs which is the extension at any packing fraction of a model previously described by Dodds for dense packings. In dilute assemblies, the notion of contact between the grains must be replaced by that of neighbourhood of the grains. We define the neighbours of a disc through the radical tesselation. The model is tested on packings built grain after grain, obtained from numerical simulations. Its results are then compared with experimental results obtained on assemblies built on an air table: this shows that the possibility of rearrangement in those assemblies leads to segregation at a local scale

Shock simulation with magnetic pucks

Magnetic pucks on an air table create a two dimensional ‘‘gas.’’ The pucks are accelerated around a race track forming a strong shock and a rarefaction wave. The shock density reaches the limit given by the Rankine Hugoniot equations. A shock front instability is observed.

A Study on Distributed Micro Robotic System. 3rd Report. Micro Optical Robotic System with Cordless Optical Power Supply.

This paper deals with the Micro Optical Robotic System (MORS) with cordless optical power supply system. The MORS is the robotic system, which utilizes the concept of the Micro Cellular Robotic System (μ-CEBOT). The purposes of developing the MORS are to develop the prototype of μ-CEBOT and to solve the problems such as the friction and the power supply which hinder the development of the micro electro mechanical systems. The MORS consists of a floating robot and an air table : the former is driven by the cordless optical power supply system, and the latter works as the air bearing. The optical power supply system converts from the optical energy to electrical energy using the pyroelectric element. The optical power supply system generates the electric voltage, and the electric voltage generates the electrostatic force between the electrodes of the robot and the blocks of the air table, which work as the electrodes. The electrostatic force generated drives the robot above the table. In this paper, we propose the design of the MORS, and show the mathematical model of MORS and the some experimental results.

Experimental study of radical tesselations of assemblies of discs with size distribution

We had previously shown that topological and metric properties of 2d mosaics obtained from the Voronoitesselation of monosize packings of discs deviate from those of a totally random mosaic. Here, we describe a mosaic obtained from the radical tesselation of a two-size mixture of dises at different packing fractions. Two kinds of packings are considered, experimental (dises moving on an air table) and numerical. The deviations are even more striking, particularly at large packing fraction where neither Aboav's nor Lewis' law hold ; moreover, some distributions, such as the distribution of the number of sides of the cells, or distribution of the cell area, are split into two parts, each of them related to one species of dises. Finally, we consider polydisperse packings : as to their topological properties, the mosaics obtained from those packings obey approximately the laws of random mosaics but this is not so for their metric properties, which are still largely affected by steric exclusion.

Arrangement of cells in Voronoi tesselations of monosize packing of discs

Abstract We describe a two-dimensional mosaic obtained by the Voronoi tesselation of a monosize assembly of discs at different packing fractions. The experimental device (hard discs moving on an air table) produces, for every concentration of the discs, a succession of mosaics in statistical equilibrium, which constitutes a statistical ensemble. This ensemble is large enough for fluctuations from the most probable distributions to be negligible. Both topological and metric properties show deviations from those of a totally random mosaic. These deviations can be ascribed to steric exclusions. In particular, distributions of the numbers of sides, of the perimeters and of the areas of the polygons differ from those observed in biological celi assemblies. The Aboav law holds, but with a slope which can be as Iow as 4–66. The Lewis law is obeyed only for smali packing fractions. The variance of the distribution of the number n of polygon sides is a universal function of p 6, the probability of finding a six-si...

Gravity-Driven Flows of Smooth, Inelastic Disks Between Parallel Bumpy Boundaries

The problem of a steady gravity-driven granular flow of identical, smooth, slightly inelastic, circular disks between parallel bumpy boundaries is analyzed. The balance laws, constitutive equations and boundary conditions obtained by the kinetic theory (Richman and Chou, 1988) are utilized. Both collisional and transport contributions to the fluxes of momentum and fluctuation energy are considered. The problem is reduced to a system of coupled differential equations governing the transverse variations of granular temperature, shear stress, and solid fraction with the appropriate boundary conditions. The numerical procedure is developed using a variation of shooting method in order to simultaneously satisfy all of the boundary conditions. The particle flux (discharge) calculated using the present theory compares favorably with the data from numerical simulations and air table experiments reported by Sanders et al. (1988).

Universal properties of Voronoi tessellations of hard discs

The authors describe a 2D mosaic obtained by the Voronoi tessellation of a monosize assembly of discs at different packing fractions. The experimental device (hard discs moving on an air table) produces, for every packing fraction, a succession of mosaics in statistical equilibrium, which constitutes a statistical ensemble. This ensemble is large enough for fluctuations from the most probable distributions to be negligible. They use the maximum entropy principle to get the distribution of the polygons in 2D mosaics generated from an assembly of hard discs. Steric exclusion yields an extra conservation law, which is sufficient to give a good agreement with the experimental data. A similar behaviour in the six-fold parameter seems to hold for other mosaics.

An air table designed to study two-dimensional disc packings: preliminary tests and first results

The authors describe in detail the characteristics of an air table designed to study two-dimensional packings of a 'large' number (up to 2500) of particles (discs). The particles are submitted mainly to hard core, and more weakly to hydrodynamic, interactions. The suspension height of a disc is studied theoretically and experimentally as a function of the air flow through the table. They also examine the dynamic properties of the system in the case of a dilute packing (evolution of the velocity of a disc and the number of collisions it has against the walls and the other discs). Then they study experimentally the spatial distribution of the discs on the table for increasing densities. The hydrodynamic interactions are hard to control and some care would be needed for further hydrodynamic studies. On the other hand, the working part of their table is sufficiently homogeneous and is appropriate to the geometrical study of densifying systems.

Equilibrium configurations of parallel repulsive permanent magnets placed inside a circle

The equilibrium configurations of a plane system of N equal, parallel, repulsive, permanent magnets constrained inside a circle of radius R are considered. Simple demonstration experiments with permanent magnets gliding on an air table are described. One finds that the magnets can gather in various stable patterns, either symmetrical or nonsymmetrical, the actual configuration being a function of the system’s history. The theoretical analysis has been restricted to a comparison between the energies of the following configurations: (A) All N magnets uniformly distributed around the circumference of radius R; (B) N−1 magnets uniformly distributed around the circumference of radius R plus one magnet at the center. It is shown that the energy of configuration A is lower than that of configuration B only for N smaller than a critical value Nc.

A method of recording rotational motion on a conventional air table

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Potential energy of interaction for two magnetic pucks

An air table experiment is described in which the interaction force and potential energy for a pair of magnetic pucks are measured as functions of the separation of the pucks. The relation between the force and potential energy is demonstrated by graphical integration. The experiment is also well suited to an air track.