Bibliothek

feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    The @journal of organic chemistry 53 (1988), S. 5379-5381 
    ISSN: 1520-6904
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 84 (1980), S. 2441-2446 
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2274-2282 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We compare the sensitivities to initial conditions for both direct (regular) and long-lived (chaotic) trajectories in classical scattering calculations with the corresponding properties of trajectories of position and momentum expectation values for quantum wave packets. The collinear H+H2 reaction is used as an example. The results show that the high sensitivity seen in chaotic trajectories is not reflected in the quantum dynamics. We conclude that it is possible for a classical ensemble consisting of only regular trajectories to respond trajectory by trajectory to perturbations in much the same way as a quantum wave packet. (There will of course be cases that are exceptions to this rule.) The response of an ensemble consisting of chaotic trajectories may on the average be similar to that of a wave packet, but not at the level of individual trajectories. In addition, the sensitivities of these trajectories to variations in the potential are analyzed. We conclude that the large contributions to the sensitivities from particular long-lived trajectories must approximately cancel when an exact ensemble average is taken. An algorithm is presented to smoothly account for the contributions to the sensitivities from these trajectories.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2263-2273 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The corresponding effects of features in the potential on classical, semiclassical, and quantum mechanics are probed using the technique of functional sensitivity analysis. It is shown that the classical and quantum functional sensitivities are equivalent in the classical (small (h-dash-bar)) and harmonic limits. Classical and quantum mechanics are known to react in qualitatively similar ways provided that features on the potential are smooth on the length scale of oscillations in the quantum wave function. By using functional sensitivity analysis, we are able to show in detail how the classical and quantum dynamics differ in the way that they sense the potential. Two examples are given, the first of which is the harmonic oscillator. This problem is well understood by other means but is useful to examine because it illustrates the detailed information about the interaction of the potential and the dynamics which can be provided by functional sensitivity analysis, simplifying the analysis of more complex systems. The second example is the collinear H+H2 reaction. In that case there are a number of detailed and striking differences between the ways that classical and quantum mechanics react to features on the potential. For features which are broad compared to oscillations in the wave function, the two react in qualitatively the same way. The sensitivities are oscillatory, however, and there are phasing differences between the classical and quantum sensitivity functions. This means that using classical mechanics plus experimental data in an inversion scheme intended to find the "true'' potential will necessarily introduce sizeable errors.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 3170-3178 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Functional sensitivity analysis is used to study the effect of potential structure upon the elastic scattering of He atoms from a one-dimensional surface. The calculations are implemented by computing the total scattering wave functions from a wave packet calculation by a Møller wave operator method. The functional sensitivities of the various diffraction probabilities for several angles of incidence and surface corrugation are studied. The method is extended to examine the role of potential structure for a surface with adsorbed impurities. It was observed that the various diffraction processes draw from local regions of the potential in very different ways. At high angles of incidence for back scattering and particularly for strong surface corrugation, the large protruding portions of the surface cast a "shadow'' of lower dynamical sensitivity. Results of this type should ultimately be insightful for the inversion of experimental data to obtain the interaction potential.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6814-6817 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A model to simulate electron transport through the base region of abrupt heterojunction bipolar transistors has been developed taking into account the finite probability for electrons in the base to tunnel through the emitter-base spike back into the emitter. The average base transit time is calculated as a function of the emitter-base voltage using the impulse response technique. For all biases, the average base transit time is found to be smaller than its value computed while neglecting the finite probability for electrons with energy below the emitter-base spike to tunnel back into the emitter. For the case of an AlGaAs/GaAs structure, the average base transit time is found to increase with the forward emitter-base voltage. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5786-5792 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A hybrid model is developed to simulate electron transport through the emitter-base heterojunction and the base region of abrupt heterojunction bipolar transistors. The energy distribution of the injected electron flux through the emitter-base junction is calculated using a rigorous quantum-mechanical treatment of electron tunneling and thermionic emission across the spike at the emitter-base junction. The results are compared with those predicted by the conventional thermionic-field-emission model. For both models, the electron fluxes injected across the emitter-base junction are used as initial energy distributions in a regional Monte Carlo calculation to model electron transport through the base. The average base transit times are calculated using the impulse response technique as a function of the emitter-base voltage. The differences between the thermionic-field-emission model and the rigorous quantum-mechanical approaches to model electron transport through abrupt heterojunction bipolar transistors are pointed out. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 8
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2435-2437 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We first report on migration-enhanced molecular beam epitaxial (MEMBE) growth and characterization of the GaAs layer on Si substrates (GaAs/Si). Excellent surface morphology GaAs layers were successfully grown on (100)Si substrates misoriented 4° toward the [110] direction. The MEMBE growth method is described, and material properties are compared with those of normal two-step MBE-grown or in situ annealed layers. Micrographs of cross-section view transmission electron microscopy (TEM) and scanning surface electron microscopy (SEM) of MEMBE-grown GaAs/Si showed dislocation densities of 1×107 cm−2, over ten times lower than those of normal two-step MBE-grown or in situ annealed layers. AlGaAs/GaAs double heterostructures have been successfully grown on MEMBE GaAs/Si by both metalorganic chemical vapor deposition and liquid phase epitaxy.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 9
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1201-1203 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Al0.3Ga0.7As/Al0.05Ga0.95As double-heterostructure light-emitting diodes (LED's) were successfully grown for the first time by liquid phase epitaxy on a GaAs-coated Si substrate that was prepared by a sequential process of migration-enhanced epitaxy and molecular beam epitaxy. The edge-emitting LED's had diode ideality factors of 1.54 at a forward-biased voltage higher than 0.9 V and external quantum efficiencies of 3.3×10−3 W/A per facet. This efficiency is 50 times higher than the previously reported value, and is on the same order as that of AlGaAs homojunction LED's fabricated on the GaAs substrates by liquid phase epitaxy.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 3671-3671 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effects of a new heat treatment technique and a conventional annealing process on the high-frequency core losses (20 kHz) of Fe76Mo3(SiB)21 amorphous alloys have been investigated. The result shows that the remanence and the high-frequency losses can be reduced remarkably by this special treatment. Meanwhile, its coercivity remains lower in the range of 2.39–4.79 (A/m). In studying, it is found that under the condition of this special treatment the phenomena of the enrichment and the depletion of atoms (Fe, Si, B) become more heavier, and the state between the surface layers of metallic glass core is changed, and the degree of partial crystallization of α-Fe can be controlled. The magnetic properties of Fe76Mo3(SiB)21 metallic glasses obtained by the treatment under the technological parameters selected properly are satisfied, as follows: Fe76Mo3(SiB)21—I P2/20 K =5.27 w/kg, P5/20 K =32.61 w/kg, B1=1.043 T, Hc1 =2.88 A/m, Br1/B1 =0.18. Fe76Mo3(SiB)21—I P2/20 K =5.59 w/kg, P5/20 K =37.25 w/kg, B1=0.656 T, Hc1 =4.79 A/m, Br1/B1 =0.11, in which the properties of high-frequency losses are superior to those of the conventional annealed alloys (P2/20 K =12–14 w/kg), and are comparable to those of VITROVAC Co66Fe4(MoSiB)30 and others.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...