Experimental Measuring of Bright Spots on Complex Shape Object Surface with Decomposition Method

Abstract A method has been developed to decompose a polyhedral delta volume, which is the volume difference between the raw material and the finished part, into maximal convex volumes by intersecting the halfspaces of the faces of the delta volume. The hypothesis behind this effort is that in machining a delta volume of complex shape it is more efficient to divide it into volumes of simple shapes and remove volume by volume with large cutters than to remove it as a single volume with a single small cutter. The maximality of a maximal convex volume represents the possibility of using a large cutter and its convexity represents the simplicity of the shape of the volume. To prove the utility of maximal convex volumes, a small computer program was developed that sequences the maximal convex volumes based on a few heuristics on machining efficiency and tested it with a few objects. It generated good machining sequences. The basic idea of the decomposition method is to intersect a polyhedral delta volume with the halfspaces of its faces having concave edges. The combinations of such halfspaces that result in maximal convex volumes when they are intersected with the delta volume are determined efficiently by examining the relationships among the halfspaces. This basic idea works well for polyhedral delta volumes but does not work for delta volumes having curved faces since curved faces cannot always be extended infinitely. To cope with the delta volumes having cylindrical faces, a separate decomposition method has been developed. This method works only for the delta volumes that can be decomposed into 2½D machining volumes.

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On the Configuration of the Magnetic Field of β CrB

International Astronomical Union Colloquium ◽

10.1017/s0252921100080933 ◽

1976 ◽

Vol 32 ◽

pp. 613-622

Author(s):

I.A. Aslanov ◽

Yu.S. Rustamov

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Radial Velocity ◽

Magnetic Field Strength ◽

Complex Shape ◽

Rotation Period ◽

Field Variation ◽

Magnetic Field Variation ◽

Secular Variations ◽

The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

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Analysis of Dark-Field Images of Disordered Materials

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096059 ◽

1972 ◽

Vol 30 ◽

pp. 560-561

Author(s):

J. M. Cowley

Keyword(s):

Amorphous Materials ◽

Careful Analysis ◽

Dark Field ◽

Minimum Diameter ◽

Statistical Fluctuations ◽

Bright Spots ◽

Sufficient Detail ◽

Random Arrangement ◽

Diffraction Patterns ◽

Imaging Conditions

Recently a number of authors have reported detail in dark-field images obtained from diffuse-scattering regions of electron diffraction patterns. Bright spots in images from short-range order diffuse peaks of disordered binary alloys have been interpreted as evidence for the existence of microdomains of ordered lattice or of segragated clusters of one component. Spotty contrast in dark field images of near-amorphous materials has been interpreted as evidence for the existense of microcrystals. Without a careful analysis of the imaging conditions such conclusions may be invalid. Usually the conditions of the experiment have not been specified in sufficient detail to allow evaluation of the conclusions.Elementary considerations show that even for a completely random arrangement of atoms the statistical fluctuations of density will give a spotty contrast with spots of minimum diameter determined by the dark field aperture size and other factors influencing the minimum resolvable distance under darkfield imaging conditions, including fluctuations and drift over long exposure times (resolution usually 10Å or more).

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A photoelectron microscope study of surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100152021 ◽

1989 ◽

Vol 47 ◽

pp. 10-11

Author(s):

W. Engel ◽

M. Kordesch ◽

A. M. Bradshaw ◽

E. Zeitler

Keyword(s):

Electron Microscopy ◽

High Pressure ◽

Field Strength ◽

Uv Light ◽

Physical Property ◽

Photon Flux ◽

Mercury Lamp ◽

Object Surface ◽

The Sixties ◽

Physical Features

Photoelectron microscopy is as old as electron microscopy itself. Electrons liberated from the object surface by photons are utilized to form an image that is a map of the object's emissivity. This physical property is a function of many parameters, some depending on the physical features of the objects and others on the conditions of the instrument rendering the image.The electron-optical situation is tricky, since the lateral resolution increases with the electric field strength at the object's surface. This, in turn, leads to small distances between the electrodes, restricting the photon flux that should be high for the sake of resolution.The electron-optical development came to fruition in the sixties. Figure 1a shows a typical photoelectron image of a polycrystalline tantalum sample irradiated by the UV light of a high-pressure mercury lamp.

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