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  • 1
    Electronic Resource
    Electronic Resource
    Complexity aspects of guessing prefix codes (1994)
    Springer
    Algorithmica 12 (1994), S. 409-419 
    Details
    ISSN: 1432-0541
    Keywords: Prefix codes ; Huffman codes ; Encryption ; Complexity ; NP-completeness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Given a natural language cleartext and a ciphertext obtained by Huffman coding, the problem of guessing the code is shown to be NP-complete for various variants of the encoding process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01185434
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  • 2
    Electronic Resource
    Electronic Resource
    Vertical drift mobility of excited carriers in multi quantum well structures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 3536-3543 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the vertical mobility of photo-excited carriers in quantum well infrared detectors are reported. The low temperature mobility is extracted by means of a photo geometrical magnetoresistance technique. This approach is most suitable for the multi quantum well structure geometry. Both rectangular and stepped well structures were studied. They exhibit asymmetry with regard to bias polarity for both gain and mobility. This asymmetry is shown to be contributed by both well structure, and growth induced inequivalent interfaces. The low field mobility is governed mainly by unscreened ionized impurity scattering in the barriers. The well interfaces act as additional anisotropic scattering centers. We observe clear correlation between the extracted drift velocity and the optical gain. It is postulated that anisotropic well recapture causes polarity dependent energy distribution above the barriers. In addition, we conclude that intervalley scattering of the hot electrons has a substantial influence on the detector performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356117
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of band nonparabolicity on two-dimensional electron gas (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4382-4384 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Energy band nonparabolicity is present in the majority of materials used in heterojunctions, quantum wells, and superlattices. In the present work we derive a simplified dispersion relation for electrons using the k⋅p model. We demonstrate that this dispersion relation can account for nonparabolicity in both narrow and wide gap isotropic semiconductors. We then calculate the carrier effective mass and densities of states for both two- and three-dimensional electron systems. Finally, we derive a simple analytical relation between the carrier concentration and the Fermi energy in a nonparabolic two-dimensional electron gas. Agreement with a numerical model is demonstrated, while the traditional, parabolic approximation results in a large error. The simplicity of the new approximation allows an intuitive understanding of the nonparabolicity effect in two-dimensional systems. Therefore, the new approach should be useful for design, characterization, and modeling of quantum semiconductor devices with nonparabolic energy bands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350775
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  • 4
    Electronic Resource
    Electronic Resource
    Lifetime and carrier-concentration profile of B+-implanted p-type HgCdTe (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 3916-3922 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The lifetime and carrier-concentration profile of Hg1−xCdxTe photodiodes (x=0.2–0.3) formed by implantation of B+ ions (100 keV, 1013–1014 cm−2) into a p-type substrate was investigated. Using graded C-V measurements, concentration of carriers around the n+p junction was obtained. It was found that the junction is located at a depth of 0.7–1.5 μm, depending on the bulk hole concentration. The technique enables profiling of the same sample after annealing. The annealing process was shown to make the electron concentration shallower and thus to bring the junction closer to the surface. Various techniques were used to measure excess carrier lifetimes. All indicate that the extent of degradation of the excess electron lifetime in the p region is very limited. For all tested samples, an etch of 2 μm was enough to recover the bulk lifetime. These results contradict the general assumption of deep damages in the p-type substrate. Thus, the contribution of the n+ side to the saturation current and to the R0A product cannot be neglected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337514
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  • 5
    Electronic Resource
    Electronic Resource
    Current induced intersubband absorption in GaAs/GaAlAs quantum wells (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2513-2515 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The observation of intersubband (e1–e2) absorption induced by current injection in GaAs/GaAlAs multiquantum wells is reported. The new technique enables sensitive measurement of intersubband transitions in undoped quantum wells. The carrier concentration in the wells is easily controlled by varying the current density. The technique is demonstrated on undoped multiquantum well layers sandwiched in a p-i-n laser-diodelike structure. The lowest confined level was populated by biasing the junction and hence injecting carriers into the quantum wells. The spectra were taken by a Fourier transform infrared (FTIR) spectrometer, modulating the current and using the double modulation method. The dependence of the absorption on current intensity was examined and excess carrier concentration and lifetime were calculated. The induced absorption saturates at current densities higher than 100 mA/cm2. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113151
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  • 6
    Electronic Resource
    Electronic Resource
    Bias dependence of responsivity and transport in asymmetric quantum well infrared detectors (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1341-1343 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new type of asymmetric stepped GaAs/AlGaAs multiquantum well infrared detector is reported. These asymmetric detectors utilize the usual bound-to-continuum transition. The current responsivity is remarkably asymmetric with regard to the voltage polarity. In contrast with rectangular wells, in which responsivity is saturated in both bias polarities, these wells exhibit saturation only for negative bias. The responsivity increases monotonously with positive electric field. This is attributed to changes induced by the field on the transport properties of the excited electrons. In particular, the bias affects the dwell time spent by the carrier wave packet in the well region. Employing this model, we achieve a very good fit with experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107585
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  • 7
    Electronic Resource
    Electronic Resource
    Geodetic contraction games on graphs (1989)
    Springer
    International journal of game theory 18 (1989), S. 327-338 
    Details
    ISSN: 1432-1270
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract LetG = (V, E) be a finite graph. The setL of labeled vertices is initially empty. Two players A and B move alternately (A first), by choosing an unlabled vertexu ε ∈V\L; thenu itself and all vertices on shortest paths betweenu and any vertex ofL are adjoined toL. WhenL =V, the game is over. Innormal play, the first player unable to move loses and his opponent wins. The outcome is reversed formisère play. We resolve the game by determining its winning strategies for the following cases: trees in normal play; cycles in normal and misère play; and complete graphsK m with rays all of lengthn, in normal play.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01254296
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  • 8
    Electronic Resource
    Electronic Resource
    Partizan octal games: Partizan subtraction games (1987)
    Springer
    International journal of game theory 16 (1987), S. 145-154 
    Details
    ISSN: 1432-1270
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract A subtraction gameS=(s 1, ...,s k)is a two-player game played with a pile of tokens where each player at his turn removes a number ofm of tokens providedmεS. The player first unable to move loses, his opponent wins. This impartial game becomes partizan if, instead of one setS, two finite setsS L andS R are given: Left removes tokens as specified byS L, right according toS R. We say thatS L dominatesS R if for all sufficiently large piles Left wins both as first and as second player. We exhibit a curious property of dominance and provide two subclasses of games in which a dominance relation prevails. We further prove that all partizan subtraction games areperiodic, and investigatepure periodicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01780638
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  • 9
    Electronic Resource
    Electronic Resource
    Ueber den respiratorischen Gasaustausch im Fieber (1879)
    Springer
    Virchows Archiv 76 (1879), S. 136-211 
    Details
    ISSN: 1432-2307
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01955886
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  • 10
    Electronic Resource
    Electronic Resource
    Allgemeine Therapie (1937)
    Springer
    Journal of cancer research and clinical oncology 45 (1937), S. 52-60 
    Details
    ISSN: 1432-1335
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01619003
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