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  • Articles  (41)
  • 78.70  (36)
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  • Springer  (41)
  • 1975-1979  (41)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (36)
  • Mathematics  (5)
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  • Articles  (41)
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  • Springer  (41)
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  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (36)
  • Mathematics  (5)
  • Physics  (40)
  • Biology  (2)
  • 1
    Electronic Resource
    Electronic Resource
    A secant method for multiple roots (1977)
    Springer
    BIT 17 (1977), S. 321-328 
    Details
    ISSN: 1572-9125
    Keywords: 5.15 ; nonlinear equation ; root finding ; multiple root ; secant method ; Steffensen procedure ; order of convergence ; efficiency ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A superlinear procedure for finding a multiple root is presented. In it the secant method is applied to the given function divided by a divided difference whose increment shrinks toward zero as the root is approached. Two function evaluations per step are required, but no derivatives need be calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01932152
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  • 2
    Electronic Resource
    Electronic Resource
    Crystallinity of pure silica glass studied by positron annihilation (1978)
    Springer
    Applied physics 16 (1978), S. 231-233 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.10 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The crystallinity of silica glass fused from Brasilian quartz is demonstrated by positron annihilation lineshape measurements using a high resolution Ge(Li)-detector as well as by positron lifetime measurement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885117
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  • 3
    Electronic Resource
    Electronic Resource
    Phase transformations and vacancy formation energies of transition metals by positron annihilation (1979)
    Springer
    Applied physics 20 (1979), S. 135-140 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 71.60 ; 61.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The technique of the coincidence count rate at the peak of the angular correlation curve (CCR) in positron annihilation has been applied to the investigation of vacancy formation energies in thermal equilibrium in nickel, cobalt, and iron. The monovacancy formation energyE 1v/F has been determined to (1.55±0.05) eV and (1.34±0.07) eV for nickel and cobalt, and (1.60±0.10) eV for α-iron, and (1.40±0.15) eV for γ-iron, respectively. The structural phase transformations in cobalt (693 K) and iron (1183 K, 1663 K) are exhibited by discontinuities of the CCR. In the case of cobalt the CCR follows exactly the change of the thermal expansion at the transition temperature. The temperature dependence of the CCR in the prevacancy region is found to be proportional to the thermal expansion for all metals investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885934
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  • 4
    Electronic Resource
    Electronic Resource
    Annihilation gamma-ray lineshape parameters (1977)
    Springer
    Applied physics 13 (1977), S. 365-369 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The S-parameter, introduced by MacKenzie et al., is now widely used to describe annihilation gamma-ray lineshapes recorded with Ge(Li) spectrometers. This paper discusses four descriptive parameters, their statistical properties and their sensitivity to positron trapping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00882612
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  • 5
    Electronic Resource
    Electronic Resource
    A new positron source for positron annihilation lifetime experiments (1979)
    Springer
    Applied physics 18 (1979), S. 305-306 
    Details
    ISSN: 1432-0630
    Keywords: 06.60 ; 78.70 ; 71.60
    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 method using ion-implantation of Na22 to produce source-sample systems applicable to positron annihilation lifetime experiments at elevated temperatures in metals is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885519
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  • 6
    Electronic Resource
    Electronic Resource
    Positron trapping and self-diffusion activation energies in chromium (1979)
    Springer
    Applied physics 19 (1979), S. 149-152 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 66.30 F
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The activation energy for self-diffusion in chromium is found to be 3.51±0.13 eV from positron trapping measurements. The 4.51 eV activation energy seen in tracer diffusion work is therefore ascribed to divacancies, theQ 2/Q 1 ratio being typical of the bcc refractory group. The positron data give 0.55 for the ratioH 1v M /H 1v F of vacancy migration and formation energies, in agreement with quenching data for tungsten.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00932389
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  • 7
    Electronic Resource
    Electronic Resource
    Some investigations of moderators for slow positron beams (1979)
    Springer
    Applied physics 19 (1979), S. 247-255 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 82.65 ; 79.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Measurements were made on a low-energy positron beam apparatus in an attempt to increase the efficiency of the slow positron yield from radioisotopes. A study was made to sweep thermalized positrons to the surface of a silicon wafer with an applied electric field at 298 and 140 K. Temperature studies were also made on more conventional Pt and Pt+MgO powder moderators and the results are discussed. The role of the MgO powder has been clarified, though fundamental questions remain. The positron apparatus beam and relevant information regarding sources, temperature and magnetic fields are discussed in sufficient detail so that such a slow positron beam utilizing a “conventional” slow positron moderator could be easily duplicated for use in solid state studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00900467
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  • 8
    Electronic Resource
    Electronic Resource
    Evidence for a positron-exciton insulator in alkali-halide crystals (1976)
    Springer
    Applied physics 10 (1976), S. 227-229 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 71.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The angular correlation of annihilation photons for single crystals of 60% KCl-40% KBr solid solutions and X-irradiated NaBr crystals were measured. For 60% KCl-40% KBr samples the measurements of the angular correlation curves were carried out under an external magnetic field of 13.0 kG. The experimental data and theoretical estimations show that thermalized positrons, captured by free cation vacancies, form the positron centre of F4-type; if the positrons are localized near the complex defects, containing the cation vacancies, the formation of peculiar “positron-exciton complex” of the positronium-like type is realized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00897220
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  • 9
    Electronic Resource
    Electronic Resource
    Integrated source-specimen system for high-temperature positron annihilation experiments (1976)
    Springer
    Applied physics 11 (1976), S. 197-199 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    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 technique to prepare metal specimens containing sealed positron sources which permit Doppler broadening and lifetime measurements up to high temperatures (close to the melting point in the investigated metals Cd, Au, Cu) is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00920606
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  • 10
    Electronic Resource
    Electronic Resource
    Positron lifetime as a function of grain size (1977)
    Springer
    Applied physics 12 (1977), S. 217-218 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Published data on positron annihilation lifetime in copper as a function of grain size have been analyzed to show that there is a linear relationship between the internal grain boundary surface area, per unit volume,S v, and the positron lifetime, τ. The analysis indicates that grain boundaries are important in the trapping of positrons. It is suggested that the slope of the resulting straight line,dS v/dτ, can be used to determine the annihilation rate of the grain boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00896153
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  • 11
    Electronic Resource
    Electronic Resource
    A study of mono and divacancies in Cu and Au by positron annihilation (1977)
    Springer
    Applied physics 13 (1977), S. 67-70 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The peak counting rate of the angular correlation curve was measured for Cu and Au in the temperature range between −196°C and 1200°C. The experimental data were analysed by means of the trapping model under consideration of positron trapping by mono-and divacancies and detrapping of positrons from monovacancies. Such an analysis leads to acceptable results for both monovacancy and divacancy parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890723
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  • 12
    Electronic Resource
    Electronic Resource
    Measurement of positron-rare gas total cross-sections at intermediate energies (1976)
    Springer
    Applied physics 11 (1976), S. 321-325 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Total scattering cross-sections for positrons in the rare gases in the energy range of 2–960 eV have been measured using a time-of-flight system for which the uncertainty arising from forward scattering is substantially lower than in the 1974 experiment of Canter et al. A comparison of these cross-sections with current theoretical estimates is made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00919360
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  • 13
    Electronic Resource
    Electronic Resource
    Heat treatment of pure silica glass studied by positron annihilation (1978)
    Springer
    Applied physics 16 (1978), S. 119-120 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.10 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The crystallinity of silica glass fused from Brazilian quartz was studied by Doppler-broadening techniques after heat treatment in the temperature range between 1000°C and 1500°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00931432
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  • 14
    Electronic Resource
    Electronic Resource
    Positron trapping in indium (1977)
    Springer
    Applied physics 13 (1977), S. 51-54 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The positron annihilation lineshape was measured in indium in the temperature range between 74 K and the melting point (430 K). A model based on self-trapping of positrons and trapping by vacancies was fitted through the data. A vacancy formation enthalpy of (0.48±0.03) eV was obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00890720
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  • 15
    Electronic Resource
    Electronic Resource
    Another method of deconvoluting positron annihilation spectra obtained by the solid-state detector (1978)
    Springer
    Applied physics 16 (1978), S. 413-416 
    Details
    ISSN: 1432-0630
    Keywords: 06 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The use of various methods processing Doppler broadened annihilation spectra taking into account the detector resolution function and the restoration of the electronpossitron pair momentum distribution is discussed. A statistic regularisation method is proposed. The method is found to be effective particularly for the study of electron momentum distribution in metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885868
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  • 16
    Electronic Resource
    Electronic Resource
    The influence of several parameters on the lifetimes and intensities of positron lifetime spectra of metals (1979)
    Springer
    Applied physics 18 (1979), S. 165-168 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The influence of the instrumental time-resolution function and the source-surface spectrum on the lifetimes and intensities of positron lifetime spectra is studied by a computer simulation of such spectra. The prompt curve is described not by a sum of Gaussian curves but by the convolution of a Gaussian curve with a double-sided exponential. It is shown that the fitted lifetimes and intensities considerably depend on these parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00934411
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  • 17
    Electronic Resource
    Electronic Resource
    Positrons trapped in polyethylene: Electric field effect (1978)
    Springer
    Applied physics 17 (1978), S. 203-205 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 71.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The intensity of the τ2-component of positrons annihilated in polyethylene is found to increase with increasing electric field, while the formation probability of the positron state responsible for this component remains independent of the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885257
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  • 18
    Electronic Resource
    Electronic Resource
    Positron trapping in cobalt and trapping threshold temperature correlations (1979)
    Springer
    Applied physics 19 (1979), S. 269-273 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The monovacancy formation energy of Co is measured as 1.91 eV from a trapping model analysis of theT-dependence of the lineshape parameter. Previously discussed linear relationships between trapping threshold temperature and monovacancy parameters are refined; these relationships can now be regarded as well-established.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00900470
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  • 19
    Electronic Resource
    Electronic Resource
    The formation of positronium in molecular substances (1976)
    Springer
    Applied physics 10 (1976), S. 67-79 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The theories regarding the formation of positronium in molecular substances are discussed. A modified theory based upon the “spur” theory is described. Theoretical derivation and experimental results suggest that the fraction of the long lifetime component due too-positronium annihilation has a complex origin. Initially, the electron of the positron-electron pair is likely to be separated from the positron by medium molecules even when the total kinetic energy of the pair is less than the potential energy between them. The formation of positronium depends on the mobilities of the positron and electron, the slowing down process and the potential energy between them. Positronium is formed in less than 10 ps. Then the positronium produced may react with the radicals created in the “spur” due to the positron. Only the fraction ofo-positronium able to escape the “spur” will have a long lifetime. Therefore, positronium formation is highly related to the fast reactions in the “spur” during the first 100 ps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00929530
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  • 20
    Electronic Resource
    Electronic Resource
    Positron annihilation study of voids in a neutron irradiated aluminum single crystal (1976)
    Springer
    Applied physics 10 (1976), S. 85-90 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have measured the lifetimes of positrons in an aluminum single crystal which was irradiated to a fast neutron fluence of 1.5·1021 n/cm2 (〉0.18 MeV) at 50°C. These irradiation conditions produced 4.2·1014 voids/cm3 with a mean diameter of 330 Å, as determined by both small-angle x-ray scattering and transmission electron microscopy. The positron lifetime spectra were resolved into three lifetime components of 100, 300, and 500 ps. The short lifetime component is a result of fast trapping of positrons by the voids; the long lifetime components result from annihilations within the voids. The intensity of the long lifetime components increases with temperature in the range 80 to 300 K and supports the model of a positron state at the void surface. The positron diffusion coefficient appears to have aT 1/2-dependence. A magnetic quenching experiment shows no indication of positronium formation. Finally, an isochronal heat treating sequence shows that the voids anneal out between 200 and 300°C, and that the lifetime spectrum after annealing is described by a single component of 170 ps, the observed lifetime in unirradiated aluminum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00929532
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  • 21
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    Electronic Resource
    Studies of martensitic transformation in Cu-Al alloys by positron annihilation (1977)
    Springer
    Applied physics 12 (1977), S. 179-181 
    Details
    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reverse martensitic transformations in Cu-23.5at-%Al, and Cu-25.3at-%Al have been studied by means of positron annihilation. The coincidence counting rates of angular correlation were measured as a function of the specimen temperature. The change of counting rates in heating run was rather different from that in cooling run due to the influence of tempering of martensitic structure. The results were interpreted by the change of the formation energy of a vacancy with phase transition. Influence of heating rate is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00896144
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  • 22
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    The relationship between void size and positron lifetime in neutron irradiated molybdenum (1977)
    Springer
    Applied physics 12 (1977), S. 187-189 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.80
    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 number of molybdenum specimens, each containing a characteristic void size spectrum, have been subjected to positron lifetime measurements. Although the average void size varied in radius from 9 Å to 45 Å the long positron lifetime in the specimens was remarkably constant with τ2 = 465±5 ps. Therefore for the range of void sizes examined, this parameter appears to be independent of the void size.
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    URL: http://dx.doi.org/10.1007/BF00896146
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  • 23
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    Positronlifetimes in deformed and annealed copper (1977)
    Springer
    Applied physics 13 (1977), S. 387-389 
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    ISSN: 1432-0630
    Keywords: 78.70 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The positron lifetime method was used for studying the recovery and recrystallization processes occurring in deformed copper on isochronal annealing, the purity of the copper, the percentage of plastic deformation and the annealing treatment being varied. Comparisons were made with the results of resistivity measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00882615
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  • 24
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    Estimates of uncertainties in analysis of positron lifetime spectra for metals (1978)
    Springer
    Applied physics 15 (1978), S. 65-71 
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    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The effects of uncertainties and errors in various constraints used in the analysis of multi-component life-time spectra of positrons annihilating in metals containing defects have been investigated in detail using computer simulated decay spectra and subsequent analysis. It is found that the errors in the fitted values of the main components lifetimes and intensities introduced from incorrect values of the instrumental resolution function and of the source-surface components can easily exceed the statistical uncertainties. The effect of an incorrect resolution function may be reduced by excluding the peak regions of the spectra from the analysis. The influence of using incorrect source-surface components in the analysis may on the other hand be reduced by including the peak regions of the spectra. A main conclusion of the work is that extreme caution should be exercised to avoid introducing large errors through the constraints used in the analysis of experimental lifetime data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00896892
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  • 25
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    A two-parameter measurement of the correlation of positron age with the momentum of the annihilating positron-electron pair (1976)
    Springer
    Applied physics 10 (1976), S. 245-249 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 29
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The momentum spectrum of annihilating positron-electron pairs is normally analysed in terms of two or more momentum groups. If the medium is heterogeneous, or if it permits the formation of positronium, the annihilation time spectrum also becomes complex with as many as four resolvable exponential components. The interrelationship of these groups is difficult to establish because the usual measurements of time and momentum spectra are done with instruments of low absolute efficiency. We have made simultaneous measurements of time and energy spectra using a Ge(Li) spectrometer as a momentum analyser, obtaining an approximate hundredfold increase in data output at a cost of a factor of 3 in momentum resolution. The momentum spectrum of the intermediate lifetime component in a plastic scintillator is shown to be very similar to that of the long-lived orthopositronium. Recent developments in fast timing and in high purity Ge detectors should improve both the quality and quantity of data from these techniques, making them feasible for routine studies of polymers, chemical solutions and metallic voids.
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    URL: http://dx.doi.org/10.1007/BF00897223
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  • 26
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    Dependence of ortho-positronium pick-off annihilation lifetime on free volume in organic molecular liquids calculated by Kincaid Eyring method, and positronium bubble formation (1978)
    Springer
    Applied physics 16 (1978), S. 71-74 
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    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Sizes of free volume were quantitatively calculated for 42 organic liquids by means of the Kincaid and Eyring method. The results were discussed in relation to the pick-off annihilation lifetime of ortho-positronium in molecular liquids. The presence of strong correlation was found between them, this fact made us conclude that the free volume size was the most essential physical parameter, which determines the pick-off annihilation rate of ortho-positronium. The problem that the calculated free volume was too small for the existence of ortho-positronium could be eliminated by the equilibristic formation of a bubble around ortho-positronium. Correlation was shown between the free volume radii and bubble radii. Our discussion will likely apply to a wider area for the analysis of empirical data on pick-off rate of ortho-positronium in organic liquids and to the experimental investigation of the pick-off process of ortho-positronium annihilation.
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    URL: http://dx.doi.org/10.1007/BF00931424
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  • 27
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    Temperature dependence of positron annihilation in iron and vanadium (1978)
    Springer
    Applied physics 16 (1978), S. 29-34 
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    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The Doppler broadened lineshape is measured as a function of temperature for iron and vanadium; vacancies produce a strong trapping effect in γ-Fe, but a weak effect in V. Threshold temperaturesT t for trapping are 1280±25 and 1370±30 K. Empirical linear relationships betweenT t , self-diffusion energyQ SD and monovacancy formation energyH 1v F are discussed and used to determineH 1v F values for γ-Fe and V.
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    URL: http://dx.doi.org/10.1007/BF00931417
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    Positron annihilation studies on molybdenum irradiated with neutrons at temperatures from 350° C to 1000° C (1978)
    Springer
    Applied physics 16 (1978), S. 39-42 
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    ISSN: 1432-0630
    Keywords: 78.70 ; 29
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We performed measurements of positron lifetimes and the lineshape parameter on molybdenum samples irradiated with neutrons at temperatures from 350° to 1000° C. The results show that the correlation between swelling and positron characteristics depends strongly on irradiation temperature. From 350° to 500° C, ΔS, and notI 2, correlates with sweelling; from 500° to 800° C, both ΔS andI 2 correlate with swelling; and at higher temperatures, none of them correlates with swelling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00931419
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    An investigation of polymorphism in MBBA by positron annihilation (1978)
    Springer
    Applied physics 16 (1978), S. 433-434 
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    ISSN: 1432-0630
    Keywords: 78.70 ; 64.70 ; 61.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The solid-state behavior of MBBA has been studied by the technique of positron lifetime measurements. The positron data support the exitence of at least two metastable forms of MBBA, one of which may be glassy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885871
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    The use of running integrated difference curves for analysing momentum distributions from positron annihilation experiments (1979)
    Springer
    Applied physics 19 (1979), S. 87-96 
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    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In positron annihilation measurements it is often necessary to compare annihilation line shapes or angular distributions obtained from a single sample subjected to different experimental conditions, or from a range of samples subjected to different mechanical or metallurgical treatments. The difference of the normalised, distributions provides a convenient, easily visualised, and comprehensive summary of the experimental results. Changes in the shape of these difference curves can be shown to arise only when within the material under examination competition occurs between different types of positron trap. Some of the factors affecting the shape of these difference curves are discussed in terms of trapping model concepts. By using the running integrals of the difference curves (RID curves) a representation is obtained which is very little affected by the number of channels spanning the line, provided that there are enough, leads naturally to an optimised determination of the line shape parameterS, leads to the definition of a number of parameters related to the shape of the difference curve and has well defined statistical properties. Examples of RID curves show the range of shapes encountered, shape changes associated with competition between different types of positron trap, and artefact shapes associated with rate dependent effects in the detector and electronics.
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    URL: http://dx.doi.org/10.1007/BF00900544
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    Temperature dependence of positron annihilation parameters in solid gallium (1976)
    Springer
    Applied physics 10 (1976), S. 121-123 
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    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron annihilation measurements between 80 and 300 K indicate that in gallium positrons are not trapped in thermally induced vacancies. Also no clear evidence is obtained for self-trapping of positrons in gallium. The slight temperature dependence of the lineshape measurements is probably due to thermal expansion.
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    URL: http://dx.doi.org/10.1007/BF00896331
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    Delayed electrical response of polyethylene observed in positronium formation (1977)
    Springer
    Applied physics 12 (1977), S. 93-96 
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    ISSN: 1432-0630
    Keywords: 78.70 ; 71.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The transient and steady effects of positronium yield in polyethylene, due to the application and removal of an external electric field, have been studied. The time-dependent electric field effective in the Ps formation region was deduced from yield measurements.
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    URL: http://dx.doi.org/10.1007/BF00900074
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    Positron and positronium annihilation in benzene solutions (1976)
    Springer
    Applied physics 11 (1976), S. 247-251 
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    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron annihilation in nitrobenzene and manganese oleate solutions in benzene was studied in the liquid and solid states using both lifetime and angular correlation methods. It was found that a long lifetime component (τ2~1.3 ns) appeared in the lifetime spectrum for the solid state of a nitrobenzene solution in benzene but not in the liquid state. The results are briefly discussed.
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    URL: http://dx.doi.org/10.1007/BF00897060
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    The effect of impurities on the lifetime of positrons in voids in molybdenum (1977)
    Springer
    Applied physics 12 (1977), S. 183-185 
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    ISSN: 1432-0630
    Keywords: 78.70 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Following the work of Thrane, Petersen and Evans which showed that positron lifetimes for voids in molybdenum were independent of void size, it seemed necessary to re-examine earlier results where larger positron lifetimes had been obtained during the annealing of specimens containing voids. This paper outlines the problem and presents the result of an experiment pointing strongly to impurity effects being responsible for the increased values of τ2.
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    URL: http://dx.doi.org/10.1007/BF00896145
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    Positron lifetimes in V3Si (1978)
    Springer
    Applied physics 17 (1978), S. 421-422 
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    ISSN: 1432-0630
    Keywords: 78.70 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract From positron annihilation lifetime measurements on V3Si single crystals we estimated that about 17.2% of the positrons annihilate with core electrons.
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    URL: http://dx.doi.org/10.1007/BF00886216
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    A positron annihilation study of carbon black and carbon-black-filled polybutadiene (1979)
    Springer
    Applied physics 18 (1979), S. 85-92 
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    ISSN: 1432-0630
    Keywords: 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Studies have been made on positron lifetimes in carbon blacks and carbon black filled polybutadiene. The results for the carbon blacks can be interpreted with the aid of the theoretical results of Brandt and Paulin: Phys. Rev. B5, 2430 (1972) and show that while positron annihilation occurs principally from a bound state, diffusion in the carbon black is extremely small. A numerical upper limit on the diffusion coefficient has been obtained. The data from the rubber is discussed with the aid of a specially developed extension of the previous theory. Here one finds that whereas the variations in the long-component intensity with carbon black loading can be very satisfactorily explained, there is again no evidence for any diffusion effects in the rubber, and an upper limit can be placed on the diffusion coefficient here also. Indeed the variation in the long-component intensity with particle size goes the opposite way to what one would expect if diffusion were dominant. This effect is attributed to the increase in the amount of bound rubber as the particle size is reduced, and the consequent increase in the number of annihilation sites.
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    URL: http://dx.doi.org/10.1007/BF00935908
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    Total cross-sections for the scattering of positrons by helium, neon, and argon at intermediate energies (1979)
    Springer
    Applied physics 19 (1979), S. 431-437 
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    ISSN: 1432-0630
    Keywords: 34 ; 78.70
    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 slow positron beam time of flight system in which scattering is localised to a region of the flight path close to the slow positron source is described. Total cross-sections measured in helium, neon, and argon at intermediate energies are presented. The results for helium and neon are in agreement with the recent results of Brenton et al. While significant disagreement still exists in the argon data. The helium and neon data are in agreement with the sum rule predictions of Bransden et al.
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    URL: http://dx.doi.org/10.1007/BF00930108
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    Stability, prediction-correction, and dynamic programming (1975)
    Springer
    Journal of optimization theory and applications 17 (1975), S. 239-250 
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    ISSN: 1573-2878
    Keywords: Dynamic programming ; approximation methods ; Bolza problem ; stability ; prediction-correction ; reduction of dimensionality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It is proven here that a bounded perturbation of the discrete dynamic programming functional equation arising from the Bolza problem yields a bounded change in its solution. This stability property encourages the development of approximation techniques for solving such equations. One such technique, involving the backward solution of an approximate functional equation as a prediction step, followed by a forward reconstruction using true equations as a correction step, is then discussed. Bounds for the errors arising from such an approximation procedure are derived. Successive approximations is suggested, in conclusion, as a means for obtaining improved solutions.
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    URL: http://dx.doi.org/10.1007/BF00933878
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    On a class of linear differential games (1975)
    Springer
    Journal of optimization theory and applications 17 (1975), S. 511-522 
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    ISSN: 1573-2878
    Keywords: Differential games ; pursuit-evasion ; stability ; uncertain systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Saddlepoint strategies are deduced for a class of linear, single-input differential games. Conditions necessary for a saddle-point, as well as sufficient conditions, are discussed. The results are illustrated with a simple example. For the case of one control subject to a norm bound and the other to a quadratic penalty, the results are extended to the vector case and applied to the stabilization of a system subject to norm-bounded input disturbance.
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    URL: http://dx.doi.org/10.1007/BF00932787
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    Stabilization through taxation inn-person games (1977)
    Springer
    Journal of optimization theory and applications 23 (1977), S. 277-284 
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    ISSN: 1573-2878
    Keywords: n-person games ; stability ; grand coalition ; taxation systems ; nondominated imputation ; multicriteria framework
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In formulating solutions forn-person cooperative games, the concept of stability has played a dominant role. Although the core concept has the strongest stability, the core of a game is often empty. In this paper, the taxation system is incorporated into our framework, so that a modified solution concept, which enjoys the stability of core, can be developed. Various formulations based on principles such astaxation proportional to income andequity after tax are given.
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    URL: http://dx.doi.org/10.1007/BF00933052
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    Complete stability of noncooperative games (1978)
    Springer
    Journal of optimization theory and applications 25 (1978), S. 485-505 
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    ISSN: 1573-2878
    Keywords: Game theory ; stability ; contraction mappings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper is concerned with a class of noncooperative games ofn players that are defined byn reward functions which depend continuously on the action variables of the players. This framework provides a realistic model of many interactive situations, including many common models in economics, sociology, engineering, and political science. The concept of Nash equilibrium is a suitable companion to such models. A variety of different sufficient conditions for existence, uniqueness, and stability of a Nash equilibrium point have been previously proposed. By sharpening the noncooperative aspect of the framework (which is really only implicit in the original framework), this paper attempts to isolate one set of “natural” conditions that are sufficient for existence, uniqueness, and stability. It is argued thatl ∞ quasicontraction is such a natural condition. The concept of complete stability is introduced to reflect the full character of noncooperation. It is then shown that, in the linear case, the condition ofl ∞ quasicontraction is both necessary and sufficient for complete stability.
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    URL: http://dx.doi.org/10.1007/BF00933516
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