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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical study of electron transport in gallium nitride (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2834-2836 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper describes characteristic electron transport properties for GaN in bulk and quantum well structures. First, ensemble Monte Carlo calculations of steady-state electron drift velocity in bulk GaN are presented as a function of applied electric field for different lattice temperatures. At 300 K, the calculated peak steady-state drift velocity is 2.8×107 cm/s and the threshold field is 160 kV/cm. It is found that the peak steady-state electron drift velocity decreases only slightly by about 20% as the temperature increases from 300 to 600 K while the threshold field increases slightly by about 20%. Therefore, in addition to its high temperature stability, GaN has a low temperature coefficient making it ideal for high temperature applications. For electron transport in heterostructures, quantum mechanical calculations of the electron capture rate in GaN-based quantum wells as a function of well thickness are also presented. An oscillatory behavior of the electron capture rate as a function of quantum well thickness is observed. It is found that the electron capture time oscillates between 2 and 30 ps, which is about an order of magnitude greater than capture times in GaAs quantum wells. The amplitude of oscillations decreased as the well thickness increased. These results suggest that electron transport and carrier collection in GaN are efficient processes for improved electronic and optoelectronic devices. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358696
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  • 2
    Electronic Resource
    Electronic Resource
    Carrier capture in quantum well embedded quantum wire structures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 360-362 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose a novel quantum wire (QWR) laser structure with improved carrier capture characteristics, where the carriers are injected into a quantum well (QWL) and subsequently recombine within an embedded QWR. The corresponding electron capture rates via polar optical phonon scattering are calculated for this system. An oscillatory behavior of the electron capture rate is observed as a function of the QWR thickness at the temperatures considered (77 K and 300 K). The amplitude of these oscillations also increases as the QWR width decreases. Our calculations show that the electron capture rate in the QWL embedded QWR structure can be improved by more than 30% when compared to single QWLs. Therefore, the proposed QWR laser design provides improved modulation bandwidth and optical gain over conventional QWL and QWR structures. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118060
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  • 3
    Electronic Resource
    Electronic Resource
    Nozzleless droplet formation with focused acoustic beams (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3441-3447 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the use of focused acoustic beams to eject discrete droplets of controlled diameter and velocity from a free-liquid surface. No nozzles are involved. Droplet formation has been experimentally demonstrated over the frequency range of 5–300 MHz, with corresponding droplet diameters from 300 to 5 μm. The physics of droplet formation is essentially unchanged over this frequency range. For acoustic focusing elements having similar geometries, droplet diameter has been found to scale inversely with the acoustic frequency. A simple model is used to obtain analytical expressions for the key parameters of droplet formation and their scaling with acoustic frequency. Also reported is a more detailed theory which includes the linear propagation of the focused acoustic wave, the coupling of the acoustic fields to the initial surface velocity potential, and the subsequent dynamics of droplet formation. This latter phase is modeled numerically as an incompressible, irrotational process using a boundary integral vortex method. For simulations at 5 MHz, this numerical model is very successful in predicting the key features of droplet formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342663
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  • 4
    Electronic Resource
    Electronic Resource
    Carrier capture in cylindrical quantum wires (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3480-3482 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present quantum mechanical calculations of electron capture rates in cylindrical quantum wires via polar-optical phonon scattering. The capture rate dependence on quantum wire radius and lattice temperature is investigated. An oscillatory behavior of the electron capture rate is observed as a function of the quantum wire radius at the temperatures considered in this study (20–300 K). However, the amplitude of these oscillations decreases significantly at large wire radii and high lattice temperatures. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115253
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  • 5
    Electronic Resource
    Electronic Resource
    Direct numerical simulation of a three-dimensional turbulent boundary layer (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1846-1853 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of transverse strain on an initially two-dimensional turbulent boundary layer are studied in a direct numerical simulation of a planar channel flow with impulsively started transverse pressure gradient. Consistent with experiments in three-dimensional boundary layers, the simulation shows a decrease in the Reynolds shear stress with increasing transverse strain. Also, the directions of the Reynolds shear stress vector and the mean velocity gradient vector were found to differ. In addition, the simulation shows a drop in the turbulent kinetic energy. Terms in the Reynolds stress transport equations were computed. The balances indicate that the decrease in turbulent kinetic energy is a result of a decrease in turbulence production, along with an increase in turbulent dissipation. Intuitive reasoning and current turbulence models would predict an increase in kinetic energy along with increases in production and dissipation rates as a result of increased mean-flow strain rate. Later in the evolution of the flow, both turbulence production and dissipation increase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857658
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  • 6
    Electronic Resource
    Electronic Resource
    Auriculo-emetic reflex? (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 44 (1989), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2044.1989.tb09167.x
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  • 7
    Electronic Resource
    Electronic Resource
    Coughing and laryngospasm with the laryngeal mask (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 44 (1989), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2044.1989.tb09120.x
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  • 8
    Electronic Resource
    Electronic Resource
    Isolation of putative acetylcholine receptor proteins from housefly brain (1977)
    s.l. : American Chemical Society
    Biochemistry 16 (1977), S. 4126-4132 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00637a028
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  • 9
    Electronic Resource
    Electronic Resource
    Transient ballistic transport in GaN (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 2901-2903 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Monte Carlo simulations have been used to study the spatial scales of electron ballistic transport in GaN. The large optical phonon energy (92 meV) and the large intervalley energy separation between the Γ and satellite conduction band valleys (≥1.5 eV) suggest an increasing role for ballistic electron effects in GaN, especially when compared with most III–V semiconductors such as GaAs. However, the concomitant high polar optical phonon scattering rate in GaN tends to diminish the desirable electron transport properties. The relationships between these two factors have been studied for the range of electric fields up to 140 kV/cm and lattice temperatures between 300 and 600 K. We demonstrate that in most cases electrons in GaN lose their directed average velocity over distances of only 100−200 Å, and ballistic transport occurs only over such short distances. The main cause for the small spatial scales of ballistic transport in GaN is the strong electron–optical phonon coupling which results in rapid relaxation of the directed electron velocity.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363952
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  • 10
    Electronic Resource
    Electronic Resource
    Decay of isotropic turbulence at low Reynolds number (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 808-814 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Decay of isotropic turbulence is computed using direct numerical simulations. Comparisons with experimental spectra at moderate and low Reynolds numbers (Rλ〈70) show good agreement. At moderate to high Reynolds numbers (Rλ(approximately-greater-than)50), the spectra are found to collapse with Kolmogorov scaling at high wave numbers. However, at low Reynolds numbers (Rλ〈50) the shape of the spectra at the Kolmogorov length scales is Reynolds number dependent. Direct simulation data from flowfields of decaying isotropic turbulence are used to compute the terms in the equation for the dissipation rate of the turbulent kinetic energy. The development of the skewness and the net destruction of the turbulence dissipation rate in the limit of low Reynolds numbers are presented. The nonlinear terms are found to remain active at surprisingly low Reynolds numbers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868319
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