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  • Wiley  (59)
  • American Institute of Physics (AIP)  (26)
  • American Physical Society  (17)
  • American Meteorological Society  (9)
  • 1995-1999  (111)
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Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    A dynamic similarity model for large eddy simulation of turbulent combustion (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 10 (1998), S. 1775-1777 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dynamic similarity subgrid-scale (SGS) unmixedness model is presented for large eddy simulation (LES) of turbulent reacting flows. The model is assessed both a priori and a posteriori via data obtained by direct numerical simulations (DNS) of homogeneous compressible turbulent flows involving a single step Arrhenius reaction. The results of a priori analysis indicate that the local values of the SGS unmixedness are accurately predicted by the model. A posteriori results also indicate that the statistics of the resolved temperature and scalars as obtained by LES compare favorably with DNS values. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869696
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  • 2
    Electronic Resource
    Electronic Resource
    Electron paramagnetic resonance detection by time-locked subsampling (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2622-2628 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A detection method for electron paramagnetic resonance spectroscopy is described that permits simultaneous acquisition of multiple in- and out-of-phase harmonics of the response to magnetic-field modulation for both dispersion and absorption: (i) conversion of the microwave carrier to an intermediate frequency (IF) carrier; (ii) subsampling of the IF carrier by an analog-to-digital converter four times in K IF cycles where K is an odd integer; (iii) dividing the digital words into two streams, odd indexes in one and even in the other, followed by sign inversion of every other word in each stream; and (iv) feeding the two streams to a computer for the digital equivalent of phase-sensitive detection (PSD). The system is broadbanded, in the frequency domain, with narrow banding for improved signal-to-noise ratio occurring only at the PSD step. All gains and phases are internally consistent. The method is demonstrated for a nitroxide spin label. A fundamental improvement is achieved by collecting more information than is possible using a single analog PSD. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148989
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  • 3
    Electronic Resource
    Electronic Resource
    Bimodal loop-gap resonator (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1896-1904 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A bimodal loop-gap resonator for use in electron paramagnetic resonance (EPR) spectroscopy at S band is described. It consists of two identical one-loop–one-gap resonators in coaxial juxtaposition. In one mode, the currents in the two loops are parallel and in the other antiparallel. By introducing additional capacitors between the loops, the frequencies of the two modes can be made to coincide. Details are given concerning variable coupling to each mode, tuning of the resonant frequency of one mode to that of the other, and adjustment of the isolation between modes. An equivalent circuit is given and network analysis carried out both experimentally and theoretically. EPR applications are described including (a) probing of the field distributions with DPPH, (b) continuous wave (cw) EPR with a spin-label line sample, (c) cw electron–electron double resonance (ELDOR), (d) modulation of saturation, and (e) saturation-recovery (SR) EPR. Bloch induction experiments can be performed when the sample extends half way through the structure, but microwave signals induced by Mx and My components of magnetization cancel when it extends completely through. This latter situation is particularly favorable for SR, modulation of saturation, and ELDOR experiments, which depend on observing Mz indirectly using a second weak observing microwave source. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147001
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  • 4
    Electronic Resource
    Electronic Resource
    General method for adjusting the quality factor of EPR resonators (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4857-4865 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Instrumentation for remote control of the unloaded quality factor, Q0, of a loop-gap resonator is described. The value of Q0 can be lowered by weak inductive coupling of the resonator to a loop of wire that contains a carbon resistor. Replacement of the resistor by a PIN diode permits remote control. Theoretical analysis and experiments are carried out in a context of electron paramagnetic resonance (EPR) spectroscopy at X band. Equivalent circuits are solved numerically and predicted performance confirmed experimentally. Two applications are demonstrated: (a) superfine control of critical coupling of the incoming transmission line to the resonator in excess of −80 dB, and (b) dynamic Q spoiling for reduction of the dead time after a microwave pulse. Possible degradation of EPR system performance by shot noise from the PIN diode is considered. Scant literature suggests that it is very low, and noise from this source could not be detected experimentally. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146165
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  • 5
    Electronic Resource
    Electronic Resource
    Low-loss polycrystalline silicon waveguides for silicon photonics (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6120-6123 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photonic integrated circuits in silicon require waveguiding through a material compatible with silicon very large scale integrated circuit technology. Polycrystalline silicon (poly-Si), with a high index of refraction compared to SiO2 and air, is an ideal candidate for use in silicon optical interconnect technology. In spite of its advantages, the biggest hurdle to overcome in this technology is that losses of 350 dB/cm have been measured in as-deposited bulk poly-Si structures, as against 1 dB/cm losses measured in waveguides fabricated in crystalline silicon. We report methods for reducing scattering and absorption, which are the main sources of losses in this system. To reduce surface scattering losses we fabricate waveguides in smooth recrystallized amorphous silicon and chemomechanically polished poly-Si, both of which reduce losses by about 40 dB/cm. Atomic force microscopy and spectrophotometry studies are used to monitor surface roughness, which was reduced from an rms value of 19–20 nm down to about 4–6 nm. Bulk absorption/scattering losses can depend on size, structure, and quality of grains and grain boundaries which we investigate by means of transmission electron microscopy. Although the lowest temperature deposition has twice as large a grain size as the highest temperature deposition, the losses appear to not be greatly dependent on grain size in the 0.1–0.4 μm range. Additionally, absorption/scattering at dangling bonds is investigated before and after a low temperature electron-cyclotron resonance hydrogenation step. After hydrogenation, we obtain the lowest reported poly-Si loss values at λ=1.54 μm of about 15 dB/cm. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363686
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  • 6
    Electronic Resource
    Electronic Resource
    Deep level defects in GaAs on Si substrates grown by atomic hydrogen-assisted molecular beam epitaxy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4770-4772 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical activity of defects in GaAs p+n diodes grown on Si and GaAs substrates by both conventional molecular beam epitaxy (MBE) and atomic hydrogen-assisted MBE (H-MBE) were characterized by deep level transient spectroscopy. The well-known electron traps typical of MBE-grown GaAs were detected without the presence of any new levels in the upper half of the band gap. The trap densities and diode reverse saturation currents are significantly reduced in the homoepitaxial GaAs grown by H-MBE compared to that grown by MBE. The trap densities for the heteroepitaxial GaAs-on-Si grown by H-MBE have values higher than those of homoepitaxial GaAs grown by H-MBE at 330 °C, which are possibly affected by the residual dislocation density and stress. The reduction of trap density is attributed to in situ passivation of these defects by atomic H during the growth. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363415
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  • 7
    Electronic Resource
    Electronic Resource
    Raman scattering study of GaN films (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4058-4062 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectra of GaN films grown by molecular-beam epitaxy and hydride vapor-phase epitaxy on GaAs and Al2O3 substrates have been studied. It was found that longitudinal phonon modes disappear from the spectra of n+ films due to screening by free carriers, but coupled plasmon phonon modes of the higher-energy branch are not observed because of strong damping of plasmons. Precise values for phonon frequencies and linewidths are presented. No differences in phonon frequencies for the films of different thicknesses grown on different substrates have been found which indicates that the strain due to lattice and thermal-expansion mismatch is relaxed by the formation of the dislocations very close to the substrate–film interface. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363367
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  • 8
    Electronic Resource
    Electronic Resource
    Growth of epitaxial AlxGa1−xN films by pulsed laser deposition (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1158-1160 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial AlxGa1−xN films have been grown on c-cut sapphire substrates at 800 °C and 10−2 Torr N2 by pulsed laser deposition (PLD) using a KrF laser. Throughout the composition range from x=0 to 0.6, the films show epitaxial patterns in reflection high-energy electron diffraction, in agreement with the results from x-ray diffraction. The lattice constants of the films vary linearly with x. The composition dependence of the band gaps of the films deviates from linearity and bows downward. This letter reports the application of PLD to controlling the lattice constant and band gap by varying the proportion of AlN and GaN in the target mixture. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121033
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  • 9
    Electronic Resource
    Electronic Resource
    New excimer-laser-crystallization method for producing large-grained and grain boundary-location-controlled Si films for thin film transistors (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1513-1515 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Based on the previously elucidated super lateral growth phenomenon, we have developed an excimer-laser-crystallization method that produces large-grained and grain-boundary- location-controlled Si films on SiO2 and which possesses a wide processing window. For the set of experiments reported in this letter, a patterned SiO2 capping layer on top of Si films is utilized as an anti-reflective coating in order to induce artificially controlled super-lateral growth in the film upon being irradiated with a single excimer laser pulse. For a simple SiO2 stripe pattern, the occlusion among the laterally and directionally solidifying grains permits the eventual development of elongated parallel grains with a single perpendicular grain boundary which is localized in the middle of the completely melted regions, provided that the width of the completely molten region is sufficiently narrow so as to avoid the nucleation of solids in the supercooled liquid. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115683
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  • 10
    Electronic Resource
    Electronic Resource
    Hyperfine selectivity using multiquantum electron–nuclear–electron triple resonance (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 9644-9646 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Hyperfine selectivity is demonstrated in a continuous wave electron–nuclear double resonance (ENDOR) experiment. A multiquantum electron–electron double resonance (ELDOR) signal is monitored as a function of the nuclear radio frequency. The signs and relative intensities of the ENDOR lines permit separating the case where both ELDOR and ENDOR frequencies match hyperfine couplings from the cases where this condition is not satisfied. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471671
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