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  • Institute of Physics  (128)
  • Springer  (68)
  • 1
    Electronic Resource
    Electronic Resource
    Projections in minimax algebra (1976)
    Springer
    Mathematical programming 10 (1976), S. 111-123 
    Details
    ISSN: 1436-4646
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract An axiomatic theory of linear operators can be constructed for abstract spaces defined over (R, ⊕, ⊗), that is over the (extended) real numbersR with the binary operationsx ⊕ y = max (x,y) andx ⊗ y = x + y. Many of the features of conventional linear operator theory can be reproduced in this theory, although the proof techniques are quite different. Specialisation of the theory to spaces ofn-tuples provides techniques for analysing a number of well-known operational research problems, whilst specialisation to function spaces provides a natural formal framework for certain familiar problems of approximation, optimisation and duality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01580656
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  • 2
    Electronic Resource
    Electronic Resource
    Discrete-event dynamic systems: The strictly convex case (1995)
    Springer
    Annals of operations research 57 (1995), S. 45-63 
    Details
    ISSN: 1572-9338
    Keywords: Discrete dynamic systems ; max-algebra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Given the observed outputg j of a discrete-event system, a classical problem is to find a matrix realisationg j =cA jb withA of least possible dimension. When the sequenceg j is convex and ultimately 1-periodic, a linear-time algorithm suffices to construct such a realisation over the algebra (R, max, +). When the transient is strictly convex, this realisation is minimal-dimensional.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02099690
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  • 3
    Electronic Resource
    Electronic Resource
    Aeolian regime of the surface of Venus (1970)
    Springer
    Astrophysics and space science 8 (1970), S. 59-65 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent probes of the planet Venus reveal a probable surface temperature exceeding 700K and a pressure exceeding 100 atm. A very dusty lower atmosphere may exist which is composed of micron-sized particles kept airborne by mild turbulence and a gentle circulation of deep adiabatic currents. A study of surface conditions responsible for generation and persistence of surface dust clouds is of fundamental importance in the radiative and dynamic properties of the atmosphere. Also spurious radar echoes may be caused by suspended particulate matter, thus explaining the high relief reported by radar altimeters. Equations describing transportation and deposition of dust and sand have been solved for the surface conditions of Venus. It is concluded that the minimum wind velocity for initiating grain movement is about one order of magnitude smaller than on Earth. In addition, this minimum wind velocity occurs for smaller particles on Venus than on Earth. Once the particles are raised, they can be maintained aloft for longer periods of time and over a larger size range on Venus. Surface structures such as ripples evolved from aeolian deposition are likely to be of smaller vertical dimensions but larger horizontally when compared with equivalent structures on Earth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651655
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  • 4
    Electronic Resource
    Electronic Resource
    The use of the cooling-history of thick intrusive sheets for the study of the secular variation of the earth's magnetic field (1956)
    Springer
    Pure and applied geophysics 35 (1956), S. 49-53 
    Details
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Numerical results are given which show the way in which thc Curie temperature moves inwards from the margin during the cooling of a thick intrusive sheet. The time taken to move from the margin to the centre varies as the square of the thickness of the sheet, being about 6500 years for a sheet 1000 m thick on reasonable assumptions as to the thermal properties of the material. This implies that the secular variation of the Earth's magnetic field over periods of time of 1000 years or more may be studied by measuring the directions of magnetisation at a series of points across the thickness of such a sheet. Some measurements on a Tasmanian sill about 430 m thick of Jurassic or Cretaceous age suggest a change from maximum to minimum inclination in a time of about 200 years. Since the margins of the sill are not available this figure may be considerably in error but the results suggest the general practicability of the method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02122865
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  • 5
    Electronic Resource
    Electronic Resource
    How lesioning the nucleus praeeminentialis affects electrolocation behavior in the weakly electric fish, Apteronotus leptorhynchus (1996)
    Springer
    Journal of comparative physiology 179 (1996), S. 353-361 
    Details
    ISSN: 1432-1351
    Keywords: Behavior ; Electric fish ; Electrolocation ; Feedback pathways ; Nucleus praeeminentialis dorsalis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The ability to orient to and track moving electrolocation targets was assessed in normal Apteronotus leptorhynchus and in those with unilateral lesions of the nucleus praeeminentialis dorsalis. 1. Each fish was trained to hover between two vertical metal rods and track their movement. Two aspects of this behavior were measured: a) the hovering position of the fish relative to stationary rods; b) the latency between the onset of rod motion and the fish's tracking response. Control fish hovered midway between stationary rods, while lesioned fish hovered closer to the rod ipsilateral to the lesion. Response latency varied negatively with rod diameter in both sets of fish, and lesioned fish exhibited shorter latencies than control fish. While the response latencies of control fish were shortest when their starting position was midway between the rods, lesioned animals' latencies were shortest when they hovered closer to the rod ipsilateral to their lesion. 2. Control fish responded to the approach of a single metal ball to either side of the body with nearly equal latencies and fish-to-object distances. After lesioning, response latency increased and fish-to-object distance decreased for approaches to the side ipsilateral to the lesion; opposite changes occurred for contralateral approaches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194989
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  • 6
    Electronic Resource
    Electronic Resource
    A chart for designing modal analysis by point counting (1966)
    Springer
    International journal of earth sciences 55 (1966), S. 844-848 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract Developing the work ofHasofer (1963) andSolomon (1963) concerning the factors controlling the precision of point counting, the authors have designed a chart to facilitate the choice of grid-spacing and sample area for individual minerals. After determining the grain radius, and making a rough estimate of the percentage of the mineral under investigation, suitable combinations of grid-spacing and number of counts can be rapidly determined from the chart.
    Abstract: Résumé Développant le travail deHasofer (1963) et deSolomon (1963) sur les facteurs qui déterminent la précision du „compte par points“, les auteurs ont élaboré un diagramme pour faciliter le choix du quadrillage et de la superficie d'essai pour des minéraux particuliers.
    Notes: Zusammenfassung Diese Arbeit stellt eine Weiterentwicklung derjenigen vonHasofer (1963) undSolomon (1963) dar, die sich mit den Faktoren befaßten, welche die Genauigkeit der Punktezählung bestimmen. Die Autoren haben eine Tabelle entworfen, welche die Wahl der graphostatischen Abstände und des Mustergebietes für einzelne Mineralien erleichtert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02029658
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  • 7
    Electronic Resource
    Electronic Resource
    Seismic refraction observations in the Transkei Basin and adjacent areas (1977)
    Springer
    Marine geophysical researches 3 (1977), S. 197-208 
    Details
    ISSN: 1573-0581
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Some seismic refraction observations undertaken during the IGY are reported here together with a summary of other refraction studies carried out within the Transkei Basin, the Mozambique Ridge and the South African continental shelf area. A 2.5 km section of Cretaceous and younger rocks is associated with profiles observed on the continental shelf; directly below this group are rocks with velocities in the range 4.0–5.5 km s-1, probably representatives of the Karroo and Cape supergroups. The basement material velocity variations were from 5.3 to 6.5 with an average of 5.9 km s-1, and is correlated with granite or Malmesbury Formation plus granite. This crustal structure is similar to that found on the eastern continental shelf of southern South America. The profiles in the Transkei Basin show a thick layer of sediment with velocity range 1.50 to 3.50 km s-1, underlain by a refracting layer in which the average velocity is 4.5 km s-1. The velocity of 6.6 km s-1 obtained for the oceanic layer is similar to the velocities of the crustal layer measured in the Argentine Basin. The mantle velocity (8.1 km s-1) is consistent with the average mantle velocity for the Indian Ocean but significantly lower than the Pacific Ocean average of 8.20 km s-1. The depth to Moho is about 12.0 km and the crustal section is typical oceanic. A plate tectonic model of the early opening of the South Atlantic is used to describe the evolution of the Transkei Basin. On the Mozambique Ridge the thin sediments (0.7 km) are underlain by rocks with velocities averaging 5.6 km s-1. This is more than 1.0 km s-1 faster than the velocity for layer 2 from the Transkei Basin and the Agulhas Plateau, indicating rocks of a younger age or of a different type. Moreover the crustal section of the Ridge has a thickness in excess of 22 km and is in isostatic equilibrium when compared with the adjacent Transkei Basin and Agulhas Plateau. DSDP site 249, situated on the Ridge, penetrated basalt at a depth of 0.4 km. Whether this is continental or oceanic basalt is not known; when this site 249 basalt was compared to the cored basalts of the adjacent Mozambique Basin, inconclusive results were obtained. The essential constitution of the Mozambique Ridge remains an enigma, but solution of this problem is vital for the proper understanding of the Mesozoic history of this oceanic region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310110
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  • 8
    Electronic Resource
    Electronic Resource
    Analysis of exceptionally large tremors in two gold mining districts of South Africa (1989)
    Springer
    Pure and applied geophysics 129 (1989), S. 295-307 
    Details
    ISSN: 1420-9136
    Keywords: Large mine tremors ; source parameters ; ground motion parameters ; Klerksdorp mining district ; Carletonville mining district
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An investigation of ground motion, recorded using broad-band, wide dynamic-range digital seismographs, of large mine tremors from two South African mining districts with different geologic settings, reveals some essential differences in both seismic source and ground motion parameters. In the Klerksdorp district where the strata are offset by major throughgoing normal faults, the largest tremors, with magnitudes ranging as high as 5.2, tend to be associated with slip on these pre-existing faults. Moreover, the seismic source and ground motion parameters are quite similar to those of natural crustal earthquakes. In the Carletonville district, by contrast, where substantial faults do not exist, the large-magnitude tremors appear to result from the failure of relatively intact rock and cause seismic stress drops and ground motion parameters higher than normally observed for natural shocks. Additionally, there appears to be an upper magnitude limit of about 4 in the Carletonville district. Detailed analyses of an exceptionally large event recorded locally from each of these districts serve to highlight these contrasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874511
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  • 9
    Electronic Resource
    Electronic Resource
    Changes in the early part of the seismic coda due to localized scatterers: The estimation ofQ in a stope environment (1989)
    Springer
    Pure and applied geophysics 129 (1989), S. 497-511 
    Details
    ISSN: 1420-9136
    Keywords: Seismic coda ; quality factorQ ; localized scatterers ; fractured rock ; stope environment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A single scattering model was used to analyse the temporary changes in the mean density of scattered waves in a discrete random medium. The model of the mean energy density, originally proposed bySato (1977) for spherical radiation and isotropic scattering, has been modified and applied to a medium in which the scatterers are confined to a specified volume. The time variation of the early part of the mean energy density function for the different source durations was investigated. The dominant effect on the theoretical mean energy density is caused by the specified volume containing scatterers. The duration of the source pulse influences the early part of the coda fort/t 0〈1.2, wheret is the lapse time measured from the source origin time, andt 0is arrival time of the body wave. The analysis of the coda signal of micro-events occurring immediately in front of the face enables us to estimate the size of the fracture zone induced by the stope. The model of the mean energy density of coda for a medium containing scatterers close to the seismic source was used to analyse a large number of events recorded close to an advancing mine face in a deep level gold mine in South Africa. The coda decay rate has two trends: the first, with a steep decay of coda, is produced by a larger deviation of rock parameters and/or larger size of the scatterers; the second trend, which decays more slowly, has the corresponding mean-free path ranging from 20 m to 200 m. The analysis indicates that the rock mass about 15–20 m from the stope contains a large proportion of fractured and blocked rock, which is the source of scattering. The scattering of theS-wave was much stronger and more stable, with the mean-free path varying from 11 m to 45 m. This is due to the shorter wavelength of theS wave in comparison with theP wave. The quality factor for theP coda wave varies from 30 to 100 in the fracture zone of stope and outside this zone it has a value of 300. The quality factor of theS wave varies from 20 to 78 in the equivalent volume. For rock surrounding the stope the ratioQ sp −1 /Q ss −1 varied from 0.31 to 0.69. This suggests that the radii of scatterers are smaller than 3.5 m.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874521
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of adrenergic amines on the membrane potential of guinea-pig liver parenchymal cells in short term tissue culture (1972)
    Springer
    Cellular and molecular life sciences 28 (1972), S. 1073-1074 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Mit Hilfe der intrazellulären Mikroelektrodentechnik wirk gezeigt, dass Parenchymzellen der Meerschweinchenleber in der Gewebekultur hyperpolarisieren, wenn sympathomimetische Drogen ionophoretisch appliziert werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01918681
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