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  • 1
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    Introduction to CAUSES: Description of weather and climate models and their near-surface temperature errors in 5-day hindcasts near the Southern Great Plains (2018)
    Wiley
    Details
    Publication Date: 2018-02-17
    Description: We introduce the Clouds Above the United States and Errors at the Surface (CAUSES) project with its aim of better understanding the physical processes leading to warm screen-temperature biases over the American Midwest in many numerical models. In this first of four companion papers, 11 different models, from 9 institutes, perform a series of 5-day hindcasts, each initialised from reanalyses. After describing the common experimental protocol and detailing each model configuration, a gridded temperature data set is derived from observations and used to show that all the models have a warm bias over parts of the Midwest. Additionally, a strong diurnal cycle in the screen-temperature bias is found in most models. In some models the bias is largest around midday, while in others it is largest during the night. At the Department of Energy Atmospheric Radiation Measurement Southern Great Plains (SGP) site, the model biases are shown to extend several kilometers into the atmosphere. Finally, to provide context for the companion papers, in which observations from the SGP site are used to evaluate the different processes contributing to errors there, it is shown that there are numerous locations across the Midwest where the diurnal cycle of the error is highly correlated with the diurnal cycle of the error at SGP. This suggests that conclusions drawn from detailed evaluation of models using instruments located at SGP will be representative of errors that are prevalent over a larger spatial scale.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    CAUSES: Attribution of Surface Radiation Biases in NWP and Climate Models near the U.S. Southern Great Plains (2018)
    Wiley
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    Publication Date: 2018-03-06
    Description: Many numerical weather prediction and climate models exhibit too warm lower tropospheres near the mid-latitude continents. The warm bias has been shown to coincide with important surface radiation biases that likely play a critical role in the inception or the growth of the warm bias. This paper presents an attribution study on the net radiation biases in 9 model simulations, performed in the framework of the CAUSES project (Clouds Above the United States and Errors at the Surface). Contributions from deficiencies in the surface properties, clouds, water vapor and aerosols are quantified, using an array of radiation measurement stations near the ARM SGP site. Furthermore, an in-depth analysis is shown to attribute the radiation errors to specific cloud regimes. The net surface shortwave radiation is overestimated in all models throughout most of the simulation period. Cloud errors are shown to contribute most to this overestimation, although non-negligible contributions from the surface albedo exist in most models. Missing deep cloud events and/or simulating deep clouds with too weak cloud-radiative effects dominate in the cloud-related radiation errors. Some models have compensating errors between excessive occurrence of deep cloud, but largely underestimating their radiative effect, while other models miss deep cloud events altogether. Surprisingly, even the latter models tend to produce too much and too frequent afternoon surface precipitation. This suggests that rather than issues with the triggering of deep convection, cloud-radiative deficiencies are related to too weak convective cloud detrainment and too large precipitation efficiencies.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    CAUSES: On the role of surface energy budget errors to the warm surface air temperature error over the Central U.S. (2018)
    Wiley
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    Publication Date: 2018-02-28
    Description: Many weather forecast and climate models simulate warm surface air temperature (T 2m ) biases over mid-latitude continents during the summertime, especially over the Great Plains. We present here one of a series of papers from a multi-model intercomparison project (CAUSES: Cloud Above the United States and Errors at the Surface), which aims to evaluate the role of cloud, radiation, and precipitation biases in contributing to the T 2m bias using a short-term hindcast approach during the spring and summer of 2011. Observations are mainly from the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) sites. The present study examines the contributions of surface energy budget errors. All participating models simulate too much net shortwave and longwave fluxes at the surface but with no consistent mean bias sign in turbulent fluxes over the Central U.S. and SGP. Nevertheless, biases in the net shortwave and downward longwave fluxes, as well as surface evaporative fraction (EF) are contributors to T 2m bias. Radiation biases are largely affected by cloud simulations, while EF bias is largely affected by soil moisture modulated by seasonal accumulated precipitation and evaporation. An approximate equation based upon the surface energy budget is derived to further quantify the magnitudes of radiation and EF contributions to T 2m bias. Our analysis ascribes that a large EF underestimate is the dominant source of error in all models with a large positive temperature bias, whereas an EF overestimate compensates for an excess of absorbed shortwave radiation in nearly all the models with the smallest temperature bias.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
    Electronic Resource
    Electronic Resource
    Excimer-Fluoreszenz von Polymeren mit aromatischen Substituenten. 1. Mitt. Abhängigkeit der Excimer-Bildung von der Polymerstruktur (1977)
    Springer
    Colloid & polymer science 255 (1977), S. 821-821 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01664549
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  • 5
    Electronic Resource
    Electronic Resource
    Photoluminescence as a Function of Aggregated Size from n-Butyl-Terminated Silicon Nanoclusters (2000)
    Springer
    Journal of cluster science 11 (2000), S. 423-431 
    Details
    ISSN: 1572-8862
    Keywords: silicon nanoparticles ; nanoclusters ; photoluminescence ; TEM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Photoluminescence (PL) from alkyl-terminated silicon nanocrystallites as a function of size has been studied. Ultraviolet–blue luminescence (390–410 nm) is observed from as-prepared silicon nanoclusters with diameters from 3 to 8 nm. After 1 h of annealing at 162°C in 2-methoxyethyl ether (diglyme), the λ max of PL shifts from 360 to 420 nm. High-resolution transmission electron microscopy (HRTEM) images show that individual silicon nanoparticles are fused to form pairs of nanoparticles. FTIR spectra show that the alkyl groups remain on the surface of silicon nanoparticles. As the temperature is raised to 250°C for 1 h, the PL no longer shows any peak in the visible light region. TEM images show that the silicon nanoparticles are aggregated and fused uniformly in one single dimension, to form a strip, and these strips parallel each other. When the temperature is raised to 350°C these silicon nanoparticles form a large piece of silicon textile network, showing that functionalized alkyl surface does not persist above this temperature. A strong Si–O–Si asymmetric stretching vibration appears between 1000 and 1100 cm−1 at the expense of the C–H vibrational modes and there is no more change after 3 h of annealing at 250 or 350°C. These results provide strong evidence that the PL originates from quantum confinement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009099416195
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanisms of iron acquisition from siderophores by microorganisms and plants (1991)
    Springer
    Plant and soil 130 (1991), S. 179-198 
    Details
    ISSN: 1573-5036
    Keywords: chelate ; ecology ; membrane transport ; plant iron nutrition ; plant-microbial interactions ; rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Most bacteria, fungi, and some plants respond to Fe stress by the induction of high-affinity Fe transport systems that utilize biosyrthetic chelates called siderophores. To competitively acquire Fe, some microbes have transport systems that enable them to use other siderophore types in addition to their own. Bacteria such as Escherichia coli achieve this ability by using a combination of separate siderophore receptors and transporters, whereas other microbial species, such as Streptomyces pilosus, use a low specificity, high-affinity transport system that recognizes more than one siderophore type. By either strategy, such versatility may provide an advantage under Fe-limiting conditions; allowing use of siderophores produced at another organism's expense, or Fe acquisition from siderophores that could otherwise sequester Fe in an unavailable form. Plants that use microbial siderophores may also be more Fe efficient by virtue of their ability to use a variety of Fe sources under different soil conditions. Results of our research examining Fe transport by oat indicate parity in plant and microbial requirements for Fe and suggest that siderophores produced by root-colonizing microbes may provide Fe to plants that can use the predominant siderophore types. In conjunction with transport mechanisms, ecological and soil chemical factors can influence the efficacy of siderophores and phytosiderophores. A model presented here attempts to incorporate these factors to predict conditions that may govern competition for Fe in the plant rhizosphere. Possibly such competition has been a factor in the evolution of broad transport capabilities for different siderophores by microorganisms and plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011873
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  • 7
    Electronic Resource
    Electronic Resource
    Structural and chemical characteristics and oxidation behaviour of chromium-implanted single crystal silicon carbide (1995)
    Springer
    Journal of materials science 30 (1995), S. 2668-2674 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract High-dose chromium implantation resulted in complex changes in the structure, chemistry, and oxidation behaviour of beta-type single-crystal silicon carbide. Detailed analytical studies indicated that, in addition to the primary process of surface doping, chromium implantation of silicon carbide to 3.90×1017 ions cm−2 at 200 keV was accompanied by many secondary processes such as surface sputtering, lattice damaging, and silicon depletion/carbon enrichment in the implanted region. These changes resulted in accelerated oxidation of the implanted samples by a factor of 1.14 as compared with the unimplanted crystals in 1 atm of flowing oxygen at 1100°C. The oxidation layer exhibited interesting structural and compositional inhomogeneity which could be explained based upon chromium mobility variation in the implanted region. The presence of densely populated chromium oxide precipitates in the outer region of the oxidation layer played a significant role in keeping the degree of oxidation acceleration low under the detrimental influence of lattice damages and silicon deletion/carbon enrichment. It was concluded that the potential of chromium implantation to improve the oxidation resistance of silicon carbide can be realized only when the implantation-induced secondary effects are suppressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00362150
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  • 8
    Electronic Resource
    Electronic Resource
    Small-scale crack blunting at a bimaterial interface with Coulomb friction (1991)
    Springer
    International journal of fracture 52 (1991), S. 293-306 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The deformation field near the tip of a tensional crack impinging upon a normally loaded bimaterial frictional interface is studied. By allowing the two materials to slide with respect to each other along the interface the high stresses around the crack tip are relaxed. The region of slip as well as the stress distribution inside the slip zone is obtained as a function of the far field loading parameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034085
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  • 9
    Electronic Resource
    Electronic Resource
    Alteration of oxidation behaviour of silicon carbide by aluminium implantation (1995)
    Springer
    Journal of materials science 14 (1995), S. 460-463 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00665902
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  • 10
    Electronic Resource
    Electronic Resource
    Estimation of thermal stresses in the region with an eccentric hole by means of an analogy (1985)
    Springer
    Experimental mechanics 25 (1985), S. 251-254 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The analogy used to solve some thermoelastic problems is extended to include a region with an eccentric hole. The relation is shown to be a little more complicated in this case than in the one for the concentric hole. Three bending tests of an analogous thin plate are required. As an experimental proof, an eccentric circular region is considered and mental proof, an eccentric circular region is considered and the analogous thin plate is prepared. The heat-conduction equation is first solved to give the required temperature terms. The measured strains on the plate and the coefficients specified from the transverse loads and moments applied to the plate are combined effectively to get the estimated thermal stress. The experimentally estimated thermal stress of the region and the numerical result are shown to be in agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325094
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