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  • 1
    Electronic Resource
    Electronic Resource
    Electron transport through GaAlAs barriers in GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 341-345 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have analyzed electronic transport through a single, 200-A(ring)-thick, Ga0.74Al0.36As barrier embedded in GaAs. At low temperatures and high electric field, the Fowler–Nordheim regime is observed, indicating that the barrier acts as insulating layers. At higher temperatures the thermionic regime provides an apparent barrier height, decreasing with the field, which is equal to the expected band offset when extrapolated to zero field. However, for some samples, the current is dominated by the presence of electron traps located in the barrier. A careful analysis of the temperature and field behavior of this current allows to deduce that the mechanism involved is field-enhanced emission from electron traps. The defects responsible are tentatively identified as DX centers, resulting from the contamination of the barrier by donor impurities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354114
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    COMPATIBILITE ENTRE LA COMPRESSION DE L'INFORMATION SISMIQUE ET SON TRAITEMENT (1975)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 23 (1975), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Some time ago, we described and implemented two methods of seismic data compression. In the first method a seismic trace is considered as being the convolution of a distribution made up of the trace peak values with a Gaussian pseudo-pulse. The second method is performed through a truncation of the sequential (Walsh, Paley or Haar) spectrum of each trace.In this paper it is shown that neither method has adverse effects on quality when traces with their information compressed undergo conventional data processing, such as stacking and deconvolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1975.tb01553.x
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  • 3
    Electronic Resource
    Electronic Resource
    CORRELATION A DISTANCE (1971)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 19 (1971), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The automatic picking of seismic sections becomes delicate with the presence of blind zones breaking up the continuity of horizons. This makes it difficult to establish correlations between reflections coming from above and below these blind zones.With the help of a certain number of characteristic parameters, a computer capable of storing a great quantity of data makes it possible to identify the horizons bounding a blind zone. Once this investigation has been made, the coherence between these horizons still has to be measured by making a factorial analysis of these different parameters. The statistical decision functions involved in this analysis are well adapted to computer logic. They enable the probability to be given with which the horizons located above and below blind zones correspond.A program has been worked out to provide the degree of coherence between such horizons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1971.tb00903.x
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  • 4
    Electronic Resource
    Electronic Resource
    DETERMINATION DE L'IMPULSION SISMIQUE (1968)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 16 (1968), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Determining the shape of a pulse generated by an explosion solely from the data provided by the recorded seismic trace is a difficult and even ambitious task.Knowledge of parameters such as length and number of “arches” of the pulse under study is, in fact, indispensable in solving this problem.These parameters cannot be found directly in the seismic trace, which nevertheless contains a great amount of information. Autocorrelation, with its mathematical and statistical properties, is an efficient way of making the best of this information.We compute all the autocorrelations of reflections having a given number of arches which fulfil certain conditions determined in advance. Then, after statistical testing of some parameters pertaining to the autocorrelations (abcissae of zeros, of extrema …), we select only those with a maximum likelihood. It is sufficient to consider only the reflections whose autocorrelations have been selected and to arrange them in groups according to their shape and arch number in order to obtain average pulses.In so doing several solutions are arrived at, but when considering a given number of traces, a single record for instance, it is possible by comparing these results with each other to considerably reduce their number.In the last part of the paper the nature of the impulse obtained with our method is examined in order to find out whether it is “minimum phase” for carrying out deconvolutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1968.tb01958.x
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  • 5
    Electronic Resource
    Electronic Resource
    INFLUENCE DE LA LARGEUR DU PAS D'ECHANTILLONNAGE DU CAROTTAGE CONTINU DE VITESSES SUR LES SISMOGRAMMES SYNTHETIQUES A MULTIPLES (1965)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 13 (1965), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Attenuation caused by transmission is known to be the greater the closer the samples are taken together. As a result, the amplitudes of seismograms with multiple reflections can be expected to be negligible within a more or less brief time interval, as is the case for seismograms without multiple reflections with attenuation. This paper examines the process by which multiple reflections regenerate these greatly attenuated reflections. It is also ascertained that a sampling interval of one ms for continuous velocity logs is valid for any survey. For economic reasons, we recommend the selection of a larger interval without, however, overdoing things and thus losing too much information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1965.tb01923.x
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  • 6
    Electronic Resource
    Electronic Resource
    DETERMINATION OF THE NATURE OF RESERVOIRS BY USE OF PATTERN RECOGNITION ALGORITHM WITH PRIOR LEARNING (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 29 (1981), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The determination of the nature of reservoirs containing hydrocarbons is approached via a pattern-recognition method with prior learning. This method consists of comparing the nature of a reservoir that has been drilled into with an unknown reservoir. The known reservoir plays the part of a monitor for the learning process. To this end an algorithm is compiled using the Burg method of the features represented by different portions of traces contained in the reservoirs. An analysis of the dots representing these different features serves as a criterion for deciding whether the two reservoirs have identical or different natures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1981.tb00703.x
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  • 7
    Electronic Resource
    Electronic Resource
    DÉCONVOLUTION RAPIDE (1973)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 21 (1973), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: During the last ten years data processing has enabled the geophysicist to seriously attack the problem of how to improve the quality of seismic sections. For instance new processing methods have been proposed for improving the resolving power of the seismic pulse. These methods are based on deconvolution and they require lengthy computations.The method discussed here for pulse contraction is based on the use of Hadamard transforms. It is very fast but nevertheless the quality of the result stands comparison with that of conventional methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1973.tb00055.x
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  • 8
    Electronic Resource
    Electronic Resource
    ESSAI DE DETERMINATION AUTOMATIQUE DES VITESSES SISMIQUES PAR MESURES ENTRE PUITS (1971)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 19 (1971), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Large memory computers create new possibilities for seismic interpretation in well-drilled areas, and more generally in problems involving deep sources.Records obtained by well-to-surface, surface-to-well and/or well-to-well propagation contain a large amount of information, owing to the great number of seismic rays travelling throughout the subsurface.This paper considers two successive steps:— direct case: computation of the first arrival times of seismic rays propagating through a two-dimensional subsurface with given vertical and horizontal velocity variations;— inverse case: computation of a two-dimensional velocity distribution, knowing the travel times of seismic rays through the subsurface.A computer program has been elaborated to solve both direct and inverse problems. There are no difficulties with the direct case; a certain number of uncertainties remain with the inverse case.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1971.tb00585.x
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  • 9
    Electronic Resource
    Electronic Resource
    ETUDE STATISTIQUE DE LA CONTRIBUTION DES MULTIPLES AUX SISMOGRAMMES SYNTHETIQUES ET REELS (1963)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 11 (1963), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Une étude statistique par secteurs des coefficients de réflexion permet de préciser leur homogénéité et de donner des renseignements sur l'importance de la contribution des multiples et de l'atténuation due aux coefficients de transmission.Elle permet également de montrer que les multiples tendent à rendre normale la répartition des amplitudes des sismogrammes impulsionnels et que le filtrage par l'impulsion provoque le même phénomène sur les amplitudes des sismogrammes syntliétiques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1963.tb02041.x
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Electron relaxation time measurements in GaAs/AlGaAs quantum wells: Intersubband absorption saturation by a free-electron laser (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6492-6495 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The intersubband absorption saturation in GaAs/AlGaAs quantum wells as a function of the incident power has been measured, using picosecond micropulses with a power density up to 1 GW/cm2 delivered by a free-electron laser. The absorption in a sample with a bound-to-bound transition was compared to the absorption in a sample with a bound-to-resonant transition, and it was found that the electron relaxation time in the bound-to-bound transition is about four times shorter than for the bound-to-resonant transition. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359125
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