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  • 1
    Electronic Resource
    Electronic Resource
    Design optimization of axially laminated rotors for synchronous reluctance motors (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6298-6300 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article describes a design optimization of an axially laminated rotor of the synchronous reluctance motor, using the optimization method combined with the magnetic field analysis. The magnetic flux distribution in the synchronous reluctance motor is distorted due to the complicated rotor configuration and the influence of magnetic saturation, which results in a large number of local minimum solutions. Therefore, taking account of the magnetic saturation by the finite element method, the authors propose a novel optimization approach by coupling the stochastic search method with the deterministic one. In the optimization process a suitable objective function for the stability of machine performances is also proposed. Finally some numerical results that demonstrate the validity of the proposed approach are presented. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372685
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of electron–hole interaction on electron spin relaxation in GaAs/AlGaAs quantum wells at room temperature (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3394-3398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated electron spin relaxation with respect to the spatial electron–hole separation in GaAs/AlGaAs quantum wells at room temperature. The polarization dependent time-resolved photoluminescence method was used to measure the electron spin relaxation time by applying an electric field perpendicular to the quantum wells. The spin relaxation time had a strong electric field dependence and largely increased with an increase in the spatial electron–hole separation. These results cannot be explained by only the D'yakonov–Perel process, which has often been considered the cause of spin relaxation. We discuss the possible mechanisms that cause the spin relaxation by taking into account the electron–hole exchange interaction. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372356
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  • 3
    Electronic Resource
    Electronic Resource
    Direct observation of optical anisotropy in a GaAs/AlAs quantum well wire array (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2969-2971 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using reflectance difference spectroscopy and transmittance difference spectroscopy, optical anisotropy in a quantum well wire array is directly observed at room temperature. The quantum wire array is a fractional-layer superlattice grown by metalorganic chemical vapor deposition on a vicinal (001)GaAs substrate. The size for quantum confinement of the wires is nominally 4×4 nm. Polarization dependence of optical absorption and refractive index is clearly observed between the directions parallel and perpendicular to the wires.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104711
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  • 4
    Electronic Resource
    Electronic Resource
    Spin relaxation of excitons in zero-dimensional InGaAs quantum disks (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1341-1343 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of spin relaxation of excitons in zero-dimensional semiconductor nanostructures. The spin relaxation is measured in InGaAs quantum disks by using a polarization dependent time-resolved photoluminescence method. The spin relaxation time in a zero-dimensional quantum disk is as long as 0.9 ns at 4 K, which is almost twice as long as the radiative recombination lifetime and is considerably longer than that in quantum wells. The temperature dependence of the spin relaxation time suggests the importance of exciton–acoustic phonon interaction. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120988
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  • 5
    Electronic Resource
    Electronic Resource
    Nonlinear optical absorption in an n-InGaAsP/p-InP heterodoping superlattice (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 359-361 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Absorptive optical nonlinearity in an n-InGaAsP/p-InP heterodoping superlattice grown by vapor phase epitaxy is investigated. Although change in the absorption coefficient per an excited carrier obtained for the doping superlattice is comparable to that of bulk material, larger nonlinear absorption is induced by unit-intensity light illumination. This enhancement is attributable to prolonged carrier recombination lifetime due to the separation of electrons and holes in space. The nonlinear absorption caused by accumulated photocarriers can be explained by the combination of two effects: blocking of direct band-to-band transition in real space (band filling effect), and change in probability of indirect transition in real space (Franz–Keldysh effect) due to a modified internal electric field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99464
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  • 6
    Electronic Resource
    Electronic Resource
    Soft heating for hyperthermia using temperature-sensitive magnetic powders and fine metal rings (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5866-5866 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In local hyperthermia it is important to leave the temperature of surrounding normal tissues essentially unchanged while increasing the temperature of tumors to a desired level. Soft heating1 with temperature-sensitive magnetic materials is advantageous in heating deep-seated tumors because of the self-limiting ability. In order for the method to become available for large-scale tumors we have proposed to use temperature-sensitive magnetic powders, in which fine metal rings are dispersed. As the magnetic flux distribution varies with the temperature of the powders, the fine rings immersed in the powders with low temperatures generate heat more than rings located in the powders with high temperatures. Furthermore, the transition from the ferromagnetic to the nonferromagnetic state becomes sharp effectively. As a result it is expected to make the temperatures of powders in a broad region uniform. Figure 1 shows the temperature dependence of the magnetic powders used in experiments. Figure 2 shows the relation between the attained temperature of the powders and the ring resistances, comparing them in the case of iron powder. The figure reveals that it exists appropriate combination between the ring resistance, and the magnetic permeability of the powders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342183
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  • 7
    Electronic Resource
    Electronic Resource
    Temperature dependence of nonlinear absorption in InP doping superlattices (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3641-3646 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Absorptive optical nonlinearity in InP doping superlattices grown by vapor-phase epitaxy is investigated in a 2–300 K temperature range. The absorption spectra have tails below InP band-gap energy, caused by the Franz–Keldysh effect due to the internal electric field. The absorption tail is almost temperature independent. This means that the periodic electric potential in the doping superlattice, responsible for the nonlinearity, is unchanged across this temperature range. Nonlinear absorption is evaluated by the pump-probe method. The large reduction in absorption coefficient is obtained even with a weak excitation light intensity. This enhancement in nonlinearity is due to prolongation of the excited-carrier lifetime. Nonlinear absorption increases as temperature decreases. This is due to the temperature dependence of the carrier lifetime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341403
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  • 8
    Electronic Resource
    Electronic Resource
    Polarization properties of a vertical cavity surface emitting laser using a fractional layer superlattice gain medium (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3082-3084 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the polarization properties of a vertical cavity surface emitting laser that uses an (Al0.5Ga0.5As)1/2(GaAs)1/2 fractional-layer superlattice (FLS) as an anisotropic gain medium. The anisotropy in the gain enables us to both control and switch the polarization state of the optically pumped lasing output. We obtain room-temperature lasing for wavelengths from 690 to 720 nm. The output is linearly polarized and the polarization direction is fixed, either parallel or perpendicular to the FLS layers. By tuning the cavity resonance wavelength, we demonstrate high contrast switching between two orthogonal linear polarization states in the FLS surface emitting laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109142
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  • 9
    Electronic Resource
    Electronic Resource
    Polarization-dependent optical nonlinearities in fractional-layer superlattices (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2654-2656 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We measure the room-temperature polarization-dependent nonlinear absorption and refractive-index spectra of a (Al0.5Ga0.5As)1/2(GaAs)1/2 fractional-layer superlattice (FLS) structure grown by metalorganic chemical vapor deposition. The anisotropic nonlinear effects between the directions parallel and perpendicular to the superlattice give rise to a nonlinear optical birefringence in the plane of the growth surface. From our measurements using a femtosecond optical pulse, we derive the magnitude and spectral shape of the nonlinear optical birefringence. We describe the basis of an all-optical polarization rotation switch using the FLS structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105928
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  • 10
    Electronic Resource
    Electronic Resource
    Quantum wire microcavity laser made from GaAs fractional layer superlattices (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1759-1761 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the first demonstration of lasing action in a quantum wire microcavity semiconductor laser made from an array of (AlAs)1/4(GaAs)3/4 fractional-layer superlattice (FLS) quantum wires. The FLS growth method produces uniform, densely packed, damage-free arrays of nanometer-size quantum wires which are integrated into an optical microcavity that is the size of the wavelength of the light. We obtain room temperature optically pumped lasing for wavelengths from 670 to 690 nm. The lasing output is linearly polarized parallel to the quantum wires, reflecting the higher optical gain for polarization direction parallel to the wires. The combination of a semiconductor quantum wire active material with an optical microcavity offers the possibility of ultimately compact, highly efficient laser sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111799
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