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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Computing 41 (1989), S. 163-166 
    ISSN: 1436-5057
    Keywords: Primary 65 C 10 ; Random variables ; acceptance-rejection ; logarithm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Bei der Erzeugung nicht-gleichverteilter Zufallszahlen muß häufig der Logarithmus einer gleichverteilten Zufallszahl mit einer Testgröße verglichen werden. Es wird gezeigt, daß dieser Vergleich ohne den Aufruf einer Logarithmusroutine effizient durchführbar ist; zwei Prozeduren für diese Aufgabe werden vorgestellt und verglichen.
    Notes: Abstract In many algorithms for sampling from non-uniform distributions the logarithm of a uniform deviate must be compared with some test quantity. It is shown that all these comparisons can be done efficiently without calling a logarithm subprogram: two procedures for this task are presented and compared.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Computing 42 (1989), S. 159-170 
    ISSN: 1436-5057
    Keywords: Primary 65C10 ; Random numbers ; normal distribution ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die effizientesten Algorithmen für Stichproben von der Standardnormalverteilung benötigen lange Listen von Konstanten. Die Größe dieser Tafeln wächst mit der verwendeten Präzision. Durch eine Anpassung der “Aliasmethode” von A.J. Walker an die Normalverteilung wird eine Stichprobenprozedur entwicklet, die nur drei feste Tafeln von je 128 Bytes braucht. Die neue Methode ist ebenso schnell wie ihre Konkurrenten und leichter zu implementieren.
    Notes: Abstract The most efficint algorithms for sampling from the standard normal distribution require long lists of constants. The size of these tables grows with the employed precision. By adapting A.J. Walker's “alias method” to the normal distribution a sampling procedure is developed which needs only three fixed tables of 128 bytes each. The new method is as fast as its competitors and easier to implement.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Computing 54 (1995), S. 127-146 
    ISSN: 1436-5057
    Keywords: 65C10 ; 65C05 ; Random number generation ; table method ; acceptance-rejection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Für die Erzeugung von Stichproben aus weitgehend beliebigen VerteilungenF mit Dichtefunktionenf(x) oder Wahrscheinlichkeitenp k (in diskreten Fällen) wird eine praxisnahe Methode entwickelt. Die hohe Effizienz der Stichprobengewinnung wird mittels einer einzigen Hilfstafel erreicht, die eine Unterteilung des Bereiches vonF enthält. Beispiele stetiger und diskreter Verteilungen zeigen, daß die Prozedur einfach zu handhaben ist und daß ihre Geschwindigkeit nicht sehr von der speziellen VerteilungF abhängt.
    Notes: Abstract A practical method for sampling from largely arbitrary distributionsF with density functionsf(x) or probabilitiesp k (in discrete cases) is developed. The high efficiency of the sampling routine is achieved by means of only one auxiliary table which contains a subdivision of the range ofF. Examples of continuous and discrete distributions demonstrate that the procedure is easy to apply and that its speed does not much depend on the particular target distributionF.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Computing 12 (1974), S. 223-246 
    ISSN: 1436-5057
    Keywords: Random numbers ; pseudorandom ; normal distribution ; gamma distribution ; bei distribution ; Poisson distribution ; binomial distribution ; simulation ; numerical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Zur Erzeugung nicht-gleichverteilter Zufallszahlen braucht man Methoden, die gleichverteilte Zufallszahlen in Größen der gegebenen Verteilung transformieren. Es werden Transformationen untersucht, die Gamma-, Beta-, Poisson- oder Binomial-verteilte Zufallszahlen produzieren. Approximative Verfahren werden nicht behandelt. Die bisher bekannten Algorithmen sind langsam, wenn die Parameter der Verteilungen groß sind. Daher werden neue Methoden eingeführt, die diesen Nachteil weitgehend vermeiden. In allen Verfahren dürfen die Parameter beliebig und jedesmal neu gewählt werden. Für manche Transformationen werden normalverteilte Zufallszahlen als Zwischenschritt benötigt; die hierfür verwendete Methode ist ebenfalls angegeben.
    Notes: Abstract Accurate computer methods are evaluated which transform uniformly distributed random numbers into quantities that follow gamma, beta, Poisson, binomial and negative-binomial distributions. All algorithms are designed for variable parameters. The known convenient methods are slow when the parameters are large. Therefore new procedures are introduced which can cope efficiently with parameters of all sizes. Some algorithms require sampling from the normal distribution as an intermediate step. In the reported computer experiments the normal deviates were obtained from a recent method which is also described.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 33 (1984), S. 59-62 
    ISSN: 1432-0630
    Keywords: 7.77 ; 29.25
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A pulsed LINAC is used for pair production in a tantalum target of 2.5 radiation lengths in an energy range from 80 to 260 MeV. Several well-annealed tungsten vanes are placed immediately behind the target and thermalize a small fraction of the fast positrons. The slow positrons are extracted from the target region and magnetically guided over a distance of 17 m to the detector at the end of an S-shaped solenoid. Two Nal detectors with well-known detection efficiency are used to register the 511 keV annihilationγ-rays. To reduce pile-up effects 50 mm of Pb were placed in front of the detectors. At an average electron current of 1 μA we could detect about 107 slow positrons per second. The positron yield is proportional to the electron current, and shows an increase with the electron energy for our target. The positron energy distribution has a FWHM of ∼ 1.8 eV.
    Type of Medium: Electronic Resource
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