Computers in Physics
Index of content:
Volume 5, Issue 4, July 1991
- PEER-REVIEWED PAPERS
5(1991); http://dx.doi.org/10.1063/1.168412View Description Hide Description
This paper describes a general visualization model for 3‐D scalar data fields based on linear transport theory that contains common volume rendering models as special cases and/or approximations. The concept of ‘‘virtual’’ particles for the extraction of information from data fields is introduced. The role of different types of interaction of the data field with those particles such as absorption, scattering, source, and color shift are discussed and demonstrated. Special attention is given to possible tools for the enhancement of interesting data features. Random distortions or noise of the data field are mapped onto the image plane in a well‐defined way such that picture processing methods can be used to reconstruct the appearance of the undistorted data set. Random texturing can provide visual insights as to the magnitude and distribution of deviations of related data fields, e.g., originating from analytic models and measurements, or in the noise content of a given data field. Hidden symmetries of a data set can often be identified visually by allowing it to interact with a preselected beam of ‘‘physical’’ particles with the attendant appearance of characteristic structural effects such as channeling.
5(1991); http://dx.doi.org/10.1063/1.168413View Description Hide Description
An analysis program for x‐ray and γ‐ray spectra, incorporating a new peak search routine, is described. This routine is very fast and conceptually simple, and is based on the execution of Gaussian interpolations assuming certain characteristics of the analyzed spectrum. A satisfactory comparison is presented between the results of the routine and those of a well‐known, efficient method.
5(1991); http://dx.doi.org/10.1063/1.168397View Description Hide Description
An efficient algorithm is presented that calculates the Debye–Scherrer electron diffraction pattern, in the kinematical approximation, for clusters with several thousand atoms. The algorithm creates a histogram of interatomic distances in the cluster and applies a fast Fourier transform to it, to calculate the diffraction pattern. The approximation of binning interatomic distances into discrete, evenly spaced, histogram classes is discussed. When the class width is small, the distortion introduced to the diffraction pattern can be represented by a pseudotemperature factor, analogous to thermal movement of the cluster.
5(1991); http://dx.doi.org/10.1063/1.168398View Description Hide Description
A high‐performance parallel processor utilizing 60 Inmos T800 transputers and 60 Mbytes of memory has been designed and constructed. Intended especially for applications in nuclear medicine imaging, the system has several unique features, including a global broadcast address mode via a VME bus interface and nonalgorithmic generation of random numbers in hardware. Initial performance tests demonstrate near‐linear speedup for image reconstructions using the simulated annealing algorithm, and a processing speed that is over 60 times that of a VAX 8600.