Abstract: A confocal optical microscopy system for storing and retrieving optical information recorded in multiple layers in an optical disk. The invention includes a system utilizing the principle of confocal optical microscopy for accurately focusing a light beam onto a plane of a layer within a multi-layer disk. Optical information is thereby retrieved from the layer within the multi-layer disk. The invention also includes a method for recording optical data onto the multi-layer disk which comprises stacked multiple layers of transparent material having a distribution of discrete areas of metal film deposited between the layers. The distribution of metal film represents the recorded optical information.

Abstract: A method and apparatus for measuring the tensile strength of aggregate material comprising a device in which a layer of dust is applied to a metal electrode, and an electric field is applied in such a way as to induce a charge (negative or positive) on the outer surface of the dust layer. The electric field is then increased until particles break away from the upper surface as a result of the electrostatic force acting on the induced charge. From the balance of forces between the electrostatic (which is easily calculated from the configuration and applied voltage) and the cohesive attraction between the particles, the tensile force of the dust layer is determined. The breakaway point may be observed directly, or it may be detected by a photoelectric device designed to respond to light scattered by the particles as they are lofted from the surface. Alternatively, the breakaway point may be detected by sensing an electric current concomitant with the ejection of surface charge residing in the lofted particles.

Abstract: An electrostatic precipitator for the removal of dust having a resistivity of from 10.sup.9 to 5.times.10.sup.12 ohm cm from a gas wherein negatively biased discharge rods are arranged in a plane between grounded plates, and wherein the rods are of a diameter of approximately 3/8" (approximately 0.375 inch) enabling increased level of electrical field to be employed without the problem of back corona discharge.

Abstract: An apparatus and method for reducing back corona effects while charging high resistivity dust or the like in a corona field, includes a corona discharge electrode, a passive electrode and a screen electrode, the screen electrode being positioned between the discharge electrode and the passive electrode. The screen electrode is positioned more closely to the passive electrode than the discharge electrode and is supplied with an electrical potential which is of the same polarity as and a fraction of the magnitude of the discharge electrode relative to the passive electrode. Gas having entrained therein the particulate material, which is to be removed, flows between the screen and discharge electrode and thence to a particulate material collection stage. The space between the screen and corona discharge electrode remains essentially a unipolar ion field, while ions of the opposite polarity originating at passive electrode due to back corona are collected by the screen electrode.