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  • American Institute of Physics (AIP)
  • American Meteorological Society
  • 2015-2019  (7)
  • 1985-1989  (11)
  • 2019  (7)
  • 1987  (11)
Collection
Publisher
Years
  • 2015-2019  (7)
  • 1985-1989  (11)
Year
  • 1
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    Tropical Cloud Cluster Environments and Their Importance for Tropical Cyclone Formation (2019)
    American Meteorological Society
    Details
    Publication Date: 2019-06-18
    Description: This study uses a nonhierarchical cluster analysis to identify the major environmental circulation patterns associated with tropical cloud cluster (TCC) formation in the western North Pacific. All TCCs that formed in July–October 1981–2009 are examined based on their 850-hPa wind field around TCC centers. Eight types of environmental circulation patterns are identified. Of these, four are related to monsoon systems (trough, confluence, north of trough, and south of trough), three are related to easterly systems (low-latitude zone, west of subtropical high, and southwest of subtropical high), and one is associated with low-latitude cross-equatorial flow. The genesis potential index (GPI) is analyzed to compare how favorable the environmental conditions are for tropical cyclone (TC) formation when TCCs form. Excluding three cluster types with the GPI lower than the climatology of all samples, TCCs formed in monsoon environments have larger sizes, lower brightness temperatures, longer lifetimes, and higher GPIs than those of TCCs formed in easterly environments. However, for TCCs formed in easterly environments, the average GPI for those TCCs that later develop into TCs (developing TCCs) is higher than that for other TCCs (nondeveloping TCCs). This difference is nonsignificant for TCCs formed in monsoon environments. Conversely, the average magnitudes of GPI are similar for developing TCCs, regardless of whether TCCs form in easterly or monsoon environments. In summary, the probability of a TCC to develop into a TC is more sensitive to the environmental conditions for TCCs formed in easterly environments than those formed in monsoon environments.
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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  • 2
    Electronic Resource
    Electronic Resource
    Hg incorporation in CdTe during the growth of HgTe-CdTe superlattices by molecular beam epitaxy (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1545-1547 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: HgTe-CdTe superlattices and other microstructures such as single and double barrier tunneling structures are commonly grown by molecular beam epitaxy with the mercury flux continuously on the sample during the growth. This means that some mercury will be incorporated in the CdTe layers. We present here, for the first time, a measurement of the amount of mercury incorporated in thin layers of CdTe. X-ray photoelectron spectroscopy was used to measure the amount of mercury. The amount of mercury was found to be between 3 and 9% for CdTe (111)B, depending on the growth conditions. The amount of mercury was found to increase with mercury flux and to decrease as the substrate temperature was increased. Under the same conditions, it was found that much more mercury was incorporated in the (100) orientation. The type of substrate (CdTe or GaAs) was not found to influence the results. These results indicate that the amount of mercury in the CdTe layers of HgTe-CdTe superlattices is not quite as low as expected from measurements of thick CdTe layers, but it can be low enough that it does not influence significantly the results on the superlattice system in the (111) orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98630
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  • 3
    Electronic Resource
    Electronic Resource
    AlGaAs/GaAs quantum wells with high carrier confinement and luminescence efficiencies by organometallic chemical vapor deposition (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 120-125 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Single and multiple quantum wells with well widths ranging from 10 to 135 A(ring) were grown by atmospheric pressure organometallic chemical vapor deposition and characterized by photoluminescence (PL) and electrical measurements. Compared with single layers of high-purity GaAs and AlGaAs which have high intensity near band-edge excitonic transitions, the quantum well (QW) structures exhibit very strong luminescence of the discrete QW eigenstates. The intense QW signals indicate that the carrier confinement efficiency of the wells is very high, which is also supported by significant mobility enhancement in the samples. The sharp PL lines suggest high quality and smoothness of the well interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339170
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  • 4
    Electronic Resource
    Electronic Resource
    Photoluminescence characteristics of selectively grown GaAs and AlGaAs/GaAs quantum wells (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2466-2469 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs and AlGaAs/GaAs multiple quantum wells (MQW) were selectively deposited on GaAs substrates patterned with native oxide, and photoluminescence (PL) characteristics of both the single crystal grown in open windows and the polycrystalline material deposited on the oxide masks were studied. Well-resolved distinct quantum-well (QW) transition peaks indicate no degradation of the epitaxial material quality in the small single-crystal areas. The PL of polycrystalline GaAs is very weak and the peak is centered around the near-band-edge transition energy of GaAs. Polycrystalline MQW structures exhibit much stronger PL signals, and the peak position shifts corresponding to the widths of the QWs grown. These results suggest that the quantum size effect is preserved in the polycrystalline material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339455
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement of ultrasound velocity in the spin-glass CuMn (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 2074-2077 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrasound velocity measurements may be used to study the dynamics of the spin-glass phase. Near the transition temperature, the sound speed deviates slightly from that of the pure nonmagnetic host. We measured the velocity anomaly in a 1-at. % CuMn sample near the transition temperature (12 K) as a function of frequency from 5 to 100 MHz and found its size to be frequency independent. We also found changes in the anomaly when the sample was field cooled in transverse 4.7- and 14.2- kG fields. These results are discussed in light of previously published theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338947
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  • 6
    Electronic Resource
    Electronic Resource
    Damage induced by CHF3+C2F6 plasma etching on Si-implanted GaAs(100) (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 1729-1733 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The damage induced by CHF3+C2F6 plasma etching on GaAs(100) was studied. We exposed GaAs(100) surfaces to various etching conditions and monitored sheet resistance, carrier concentration, and Hall mobility. Significant losses of Hall mobility and carrier concentration, and an increase in sheet resistance were observed only when CHF3 was introduced into the plasma. After annealing at 400 °C for 55 min, sheet resistance was restored nearly to the value obtained before the plasma exposure. We believe that the damage was produced by hydrogen atoms or ions dissociated from CHF3 in the plasma. In contrast to the general belief that plasma etching induces the least damage among dry etching techniques [such as reactive ion etching (RIE) and reactive ion beam etching (RIBE)], our plasma etching damage was comparable to previously reported RIE or RIBE damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339601
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  • 7
    Electronic Resource
    Electronic Resource
    The tokamak equilibrium profile (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 1221-1224 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fully relaxed magnetohydrodynamic (MHD) equilibrium is obtained by imposing nonideal MHD perturbations constrained by the total plasma current. The minimum energy state governed by Δ*ψ+CF exp(ψ/λ)+CpR2 exp(5ψ/4λ) =0 reveals properties of profile consistency, bifurcated solutions, and a loss of equilibrium condition. It predicts the transport coefficient peaked at the plasma edge and a unique current profile for given q0 and ql.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866273
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  • 8
    Electronic Resource
    Electronic Resource
    Hamiltonian four-field model for nonlinear tokamak dynamics (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 3204-3211 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Hamiltonian four-field model is a simplified description of nonlinear tokamak dynamics that allows for finite ion Larmor radius physics, as well as other effects related to compressibility and electron adiabaticity. Much simpler than some previous descriptions of the same physics, it still preserves essential features of the underlying exact dynamics. In particular, because it is a Hamiltonian dynamical system it conserves the appropriate Casimir invariants, as well as avoiding implicit, unphysical dissipation. Here the model is derived and interpreted, its Hamiltonian nature is demonstrated, and its constants of motion are extracted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866527
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  • 9
    Electronic Resource
    Electronic Resource
    Nonperturbative theory of temperature-dependent optical dephasing in crystals. IV. Microscopic model for pseudolocal phonons (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 54-59 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We continue our study of the optical dephasing of impurities by phonons. The pure dephasing contribution to the homogeneous linewidth is calculated to all orders in the excitation–phonon interaction. We introduce a microscopic model for the pseudolocal phonon spectral density when the impurity is in the ground electronic state. This microscopic model improves upon our previous phenomenological model. The model is applied to several experimental systems—in all cases, the theoretical results provide a reasonably accurate description of the temperature-dependent linewidth with no adjustable parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453603
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  • 10
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    Effective Cloud Detection and Segmentation Using a Gradient-Based Algorithm for Satellite Imagery: Application to Improve PERSIANN-CCS (2019)
    American Meteorological Society
    Details
    Publication Date: 2019-05-01
    Description: The effective identification of clouds and monitoring of their evolution are important toward more accurate quantitative precipitation estimation and forecast. In this study, a new gradient-based cloud-image segmentation algorithm is developed using image processing techniques. This method integrates morphological image gradient magnitudes to separate cloud systems and patches boundaries. A varying scale kernel is implemented to reduce the sensitivity of image segmentation to noise and to capture objects with various finenesses of the edges in remote sensing images. The proposed method is flexible and extendable from single to multispectral imagery. Case studies were carried out to validate the algorithm by applying the proposed segmentation algorithm to synthetic radiances for channels of the Geostationary Operational Environmental Satellite (GOES-16) simulated by a high-resolution weather prediction model. The proposed method compares favorably with the existing cloud-patch-based segmentation technique implemented in the Precipitation Estimation from Remotely Sensed Information Using Artificial Neural Networks–Cloud Classification System (PERSIANN-CCS) rainfall retrieval algorithm. Evaluation of event-based images indicates that the proposed algorithm has potentials comparing to the conventional segmentation technique used in PERSIANN-CCS to improve rain detection and estimation skills with an accuracy rate of up to 98% in identifying cloud regions.
    Print ISSN: 1525-755X
    Electronic ISSN: 1525-7541
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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