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  • Cambridge University Press  (9)
  • International Union of Crystallography  (3)
  • American Institute of Physics (AIP)  (2)
  • Blackwell Science Pty
  • Springer Science + Business Media
Collection
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    Effect of surface treatment on visible luminescence of porous silicon: Correlation with hydrogen and oxygen terminators (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3032-3034 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of hydrogen and oxygen surface termination atoms on the visible luminescence of porous Si was investigated for underlying physical mechanism. Atmospheric thermal treatment up to 1000 °C was carried out to study the functional relationship between the surface coverage and photoluminescence (PL). The results show that oxygen incorporation induces surface modification that enhance the PL efficiency after the removal of all SiHx (x=1–3) species. The presence of oxygen atoms can also account for the observed PL redshift along with the usual blueshift. The molecular orbital calculations on the cluster modeling showed the significance of oxygen atoms in modifying the electronic structure of porous Si.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110249
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Sensitivity of the central Asian climate to uplift of the Tibetan Plateau in the coupled climate model (MRI-CGCM1) (2005)
    Melbourne, Australia : Blackwell Science Pty
    The @island arc 14 (2005), S. 0 
    Details
    ISSN: 1440-1738
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract  The relationship between the altitude of the Tibetan Plateau and climate change in central Asia was investigated through a numeric experiment using the Meteorological Research Institute (MRI) coupled atmosphere–ocean general circulation model I (MRI-CGCM1). The results suggest that summer precipitation in central Asia decreased significantly as the Tibetan Plateau rose in height. Spring precipitation, however, increased during initial growth stages when the plateau height was up to 40% of its present-day height, and then decreased with further plateau growth. During the Tibetan Plateau uplift, the difference between precipitation and evaporation was minimal during spring. When the plateau attained a height exceeding 60% of its present height, relatively low precipitation but high evaporation in spring led to a lower amount of ground moisture. In the case of the high plateau, sensible heat flux during summer and fall largely exceeded latent heat flux. Change was particularly significant for cases when the plateau reached 40–60% of its present-day height. The duration of the predominant sensible heat flux became longer with the uplift of the Tibetan Plateau. The period in which latent heat exceeded sensible heat seems to have been restricted to winter and early spring. The numeric experiments suggest that a significant drying of central Asia corresponded to the period in which the Tibetan Plateau exceeded approximately half its present-day height.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1738.2005.00493.x
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  • 3
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    FMO3-LCMO study of electron transfer coupling matrix element and pathway: Application to hole transfer between two tryptophans through cis- and trans-polyproline-linker systems (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-09-17
    Description: The linear-combination of fragment molecular orbitals with three-body correction (FMO3-LCMO) is examined for electron transfer (ET) coupling matrix elements and ET pathway analysis, with application to hole transfer between two tryptophans bridged by cis - and trans -polyproline linker conformations. A projection to the minimal-valence-plus-core FMO space was found to give sufficient accuracy with significant reduction of computational cost while avoiding the problem of linear dependence of FMOs stemming from involvement of bond detached atoms.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 4
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    Experimental study on mean velocity and turbulence characteristics of plane Couette flow: low-Reynolds-number effects and large longitudinal vortical structure (2005)
    Cambridge University Press
    Details
    Publication Date: 2005-09-05
    Description: Experimental work to investigate plane Couette flow has been performed in the Reynolds number range of 750 ≤ Re (=hUb/(2v)) ≤ 5000 or 50 ≤ Re* (=hu*/v) ≤ 253 where Ub, u* and h are moving wall speed, friction velocity and channel half-height, respectively. The low-Reynolds-number effect on the wall friction coefficient Cf, mean velocity profile and statistical turbulence quantities is discussed in relation to the turbulent Poiseuille flow properties. Since the shear stress is constant in Couette flow, the flow is free from the effect of shear stress gradient and the Reynolds number effect therefore can be seen explicitly, uncontaminated by this effect. A flow region diagram is given to show how the low-Reynolds-number effect penetrates into the wall region. The area of the buffer region is contracted by the low-Reynolds-number effect when Re* ≤ 150, so that the additive constant B of the log law decrease as Re* decreases. Also, Cf has a larger value than in Poiseuille flow in the low Re* range. The log-law area in Couette flow is 2-3 times as wide as that in Poiseuille flow. The defect law is Re*-dependent and the non-dimensional velocity gradient at the core, Rs = (dU1/ dx2(h/u*), increases from 3 to 4.2 as Re* increases from 50 to 253. The peak value of streamwise turbulence intensity u1p + has a constant value of 2.88 but decreases sharply as Re* reduces below 150. The large longitudinal vortices extending the entire height of the channel are shown to be sustained in Couette flow that is oscillating around their average position. This causes a slow fluctuation with large amplitude in the streamwise velocity component. These vortices make the Couette flow three-dimensional and the skin friction coefficient varies 20% sinuously in the spanwise direction, for example. Also, the zero-crossing time separation of streamwise velocity auto-correlation R11(τ) becomes longer as τ =40h/Ub, which is 3 times as long as that in Poiseuille flow. © 2005 Cambridge University Press.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 5
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    Turbulence characteristics of two-dimensional channel flow with system rotation (2005)
    Cambridge University Press
    Details
    Publication Date: 2005-04-10
    Description: Turbulence quantities have been measured for a low-Reynolds-number fully developed two-dimensional channel flow subjected to system rotation. Turbulence intensities, Reynolds shear stress, correlation coefficient, skewness and flatness factors, four-quadrant analysis, autocorrelation coefficient and power spectra are investigated. According to the dimensional analysis, the relevant parameters of this flow are the Reynolds number Re* = u* D/v and the Coriolis parameter Rc = Ω v/u*2 for the wall region, and Re* and Ω D/u* for the turbulent core-region. The existence of a Coriolis region where turbulence intensities are defined by a new variable yc* = y/δc has been clarified on the pressure side in the rotating channel flow. The amount of turbulent kinetic energy transported by the Coriolis term is extremely small compared to the production term in the transport equation of Reynolds normal stress. However, the Coriolis term makes a large contribution to Reynolds shear stress transport on the pressure side of the channel. It is caused by the strong ejection which occurs periodically on the pressure side even though the ejection frequency is low. The strong ejection is conjectured to be caused by a large-scale longitudinal structure like a roll cell on the pressure side of the channel. © 2005 Cambridge University Press.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 6
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    Low Reynolds number fully developed two-dimensional turbulent channel flow with system rotation (1996)
    Cambridge University Press
    Details
    Publication Date: 1996-05-25
    Description: Theoretical and experimental studies have been performed on fully developed two-dimensional turbulent channel flows in the low Reynolds number range that are subjected to system rotation. The turbulence is affected by the Coriolis force and the low Reynolds number simultaneously. Using dimensional analysis, the relevant parameters of this flow are found to be Reynolds number Re* = u* D/v (u* is the friction velocity, D the channel half-width) and Ωv/u2* is the angular velocity of the channel) for the inner region, and Re* and ΩD/u* for the core region. Employing these parameters, changes of skin friction coefficients and velocity profiles compared to non-rotating flow can be reasonably well understood. A Coriolis region where the Coriolis force effect predominates is shown to exist in addition to conventional regions such as viscous and buffer regions. A flow regime diagram that indicates ranges of these regions as a function of Re* and Ωv/u2* is given from which the overall flow structure in a rotating channel can be obtained. Experiments have been made in the range of 56 ≤ Re* ≤ 310 and -0.0057 ≤ Ωv/u2* ≤ 0.0030 (these values correspond to Re = 2Um D/v from 1700 to 10000 and rotation number Ro = 2*/D/Um up to 0.055 ; Um is bulk mean velocity). The characteristic features of velocity profiles and the variation of skin friction coefficients are discussed in relation to the theoretical considerations.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 7
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    Similarity laws of velocity profiles and turbulence characteristics of CouettePoiseuille turbulent flows (2004)
    Cambridge University Press
    Details
    Publication Date: 2004-05-25
    Description: Similarity laws of mean velocity profiles and turbulence characteristics of Couette-Poiseuille turbulent flow (C-P flow) have been studied experimentally. The global parameters of C-P flow are the Reynolds number Re* and the dimensionless shear stress gradient μ and flow parameter β. The effects of these parameters on the turbulence structure have also been considered in the wall region and turbulent core region, respectively. In the wall region, the wall law varies greatly with μ but slightly with Re*. Typically, the additive constant B of the logarithmic law (or Van Driest damping factor A+) is shown to depend only on μ. Turbulence characteristics are also strongly influenced by μ, but not much by Re*. Because the relation μ = -Re* holds in plane Poiseuille flow and Re* has little effect on the similarity laws for C-P flows, the low-Reynolds-number effect on the additive constant and turbulence quantities for plane Poiseuille flow can be attributed to the μ effect. In the turbulent core region, however, there is a great difference in the defect law of the velocity profile and the distribution of turbulence intensity between Poiseuille (P)- and Couette (C)-types flows. For P-type flow, an effective friction velocity u*e and a new coordinate η = y -hs are recommended for the universal profile, where y = hs = δp is the position of τ = 0 and δp is considered to be appropriate as a characteristic length scale of turbulence. For C-type flow, a different effective friction velocity u*c, the characteristic length scale 2h and the wall coordinate y are preferred. The turbulence activity away from the wall is extremely high for μ 〉 0 and low for μ 〈 0. A strong sweep event plays a dominant role in the Reynolds shear stress when 0 〈 μ 〈 50, whereas strong ejection from the near-wall region prevails in the case of negative μ with a small absolute value. © 2004 Cambridge University Press.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 8
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    Swirling flow through a bend (1987)
    Cambridge University Press
    Details
    Publication Date: 1987-02-01
    Description: An analytical study is made of a flow with swirling motion through a bend in a pipe with circular cross-section. The intensity of the swirl and the axial velocity distribution may change along a curved path according to the conservation law of angular momentum that is the basic principle used in this analysis. The analysis deals with the variation of angular-momentum flux components of the flow along the pipe. Approximate inviscid solutions indicate that, depending on the inlet conditions of the flow and the configuration of the bend, different types of swirling motion appear in the bend. The sign of a constant C appearing in the analysis is a governing parameter determining the flow type. Comparisons are made with the experimental results of other investigators. Finally, examples of swirling motion appearing in a real curved duct are discussed. © 1987, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 9
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    Experimental study of turbulent swirling flow in a straight pipe (1991)
    Cambridge University Press
    Details
    Publication Date: 1991-04-01
    Description: Swirling flow through a pipe is a highly complex turbulent flow and is still challenging to predict. An experimental investigation is performed to obtain systematic data about the flow and to understand its physics. A free-vortex-type swirling flow is introduced in a long straight circular pipe. The swirling component decays downstream as a result of wall friction. The velocity distributions are continuously changing as they approach fully developed parallel flow. The swirl intensity £2, defined as a non-dimensional angular momentum flux, decays exponentially. The decay coefficients, however, are not constant as conventionally assumed, but depend on the swirl intensity. The wall shear stresses are measured by a direct method and, except in a short inlet region, are a function only of the swirl intensity and the Reynolds number. The velocity distributions and all Reynolds stress components are measured at various axial positions in the pipe. The structure of the tangential velocity profile is classified into three regions: core, annular and wall regions. The core region is characterized by a forced vortex motion and the flow is dependent upon the upstream conditions. In the annular region, the skewness of the velocity vector is noticeable and highly anisotropic so that the turbulent viscosity model does not work well here. The tangential velocity is expressed as a sum of free and forced vortex motion. In the wall region the skewness of the flow becomes weak, and the wall law modified by the Monin-Oboukhov formula is applicable. Data on the microscale and the spectrum are also presented and show quite different turbulence structures in the core and the outer regions. © 1991, Cambridge University Press. All rights reserved.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Cambridge University Press
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  • 10
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    5-Isopropyl-5-methyl-2-sulfanylideneimidazolidin-4-one (2013)
    International Union of Crystallography
    Details
    Publication Date: 2013-05-25
    Electronic ISSN: 1600-5368
    Topics: Chemistry and Pharmacology , Geosciences
    Published by International Union of Crystallography
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