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  • 1
    Electronic Resource
    Electronic Resource
    The plane stress crack-tip field for an incompressible rubber material (1994)
    Springer
    Applied mathematics and mechanics 15 (1994), S. 499-506 
    Details
    ISSN: 1573-2754
    Keywords: incompressible material ; plane stress condition ; crack-tip field fully nonlinear ; equilibrium theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The crack-tip field under plane stress condition for an incompressible rubber material[1] is investigated by the use of the fully nonlinear equilibrium theory. It is found that the crack-tip field is composed of two shrink sectors and one expansion sector. At the crack-tip, stress and strain possess the singularity of R−1 and R−1 n, respectively, (R is the distance to the crack-tip before deformation. n is the material constant). When the crack-tip is approached, the thickness of the sheet shrinks to zero with the order of R1 4n. The results obtained in this paper are consistent with that obtained in[8] when s→∞.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02451500
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Extrusion, fiber formation, and characterization of thermotropic copolyesters (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 179-200 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The flow behavior and the effect of the spinning conditions on the fiber properties and structure of poly(ethylene terephthalate) modified with 60 mol% p-hydroxybenzoic acid (PET/60PHB) were investigated. PET and its copolyesters with 28 and 80 mol% PHB were used as control samples. The melt of PET/60PHB at temperatures above 265°C exhibited extremely low viscosity and low flow activation energy. High birefringence, indicating the presence of a mesophase, was observed between 265 and 300°C on a hot-stage polarizing light microscope. The maximum tensile strength and initial modulus, 438 MPa and 37 GPa, respectively, were obtained at 275°C for a 0.69 IV polymer. The fiber strength and modulus were significantly lowered when extrusion was conducted at temperatures below 265°C. The fiber properties could also be improved when a high extrusion rate and/or a high draw down ratio was used. Scanning electron microscopy revealed that the fibers spun at temperatures above 265°C had a well-developed, highly oriented fibrillar structure. The fibers spun at lower temperatures, however, were poorly oriented and nonfibrillar in character. The high orientation and superior mechanical performance achieved at high temperatures were attributed to the presence of the nematic mesophase in the polymer melt.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260110
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  • 3
    Electronic Resource
    Electronic Resource
    Characteristics and design procedure of hyperbolic dies (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 557-561 
    Details
    ISSN: 0887-6266
    Keywords: extrusion from hyperbolic dies, characteristics and design procedures in ; strain rate in extrusion procedures, hyperbolic die design and ; filament production with constant extensional strain rate with hyperbolic dies ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Nozzle profiles capable of generating constant extensional strain rates are termed hyperbolic dies. When used in polymer extrusion, they exhibit greater potential in inducing and retaining polymer molecular orientation than conventional capillary dies. Most mathematical expressions found in the literature involve several processing variables in describing and designing such nozzle profiles. This report reveals that a hyperbolic die profile, although rather complicated, can be expressed with equations in terms of two ordinary geometrical parameters - the exit diameter and the hyperbolic length. This finding greatly simplifies the design procedure of hyperbolic dies. The extensional strain rate of a hyperbolic die can be related to the length-to-diameter ratio for any given exit diameter. Examples of various types of die profiles are presented and their constant extensional strain-rate characteristics are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090300606
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of spinning conditions on morphology and properties of polyethylene terephthalate fibers spun at high speeds (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 447-458 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fiber spinning of polyethylene terephthalate (PET) was studied at take-up speeds ranging from 2000 m/min to 7000 m/min under various spinning conditions. Effects of changes in process variables on the molecular orientation, crystallinity, and properties of as-spun PET fibers are reported. Conventional cross-flow quench in high-speed spinning yields fibers with undesirable crimp and asymmetric structure with respect to the fiber axis. Radial-flow quench eliminates these problems. Changes in other spinning conditions, such as extrusion temperature, throughput or take-up denier, and molecular weight, may also affect the development of PET fiber structure in the high-speed threadline.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070440310
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  • 5
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    A51F-0123: Model Analysis of Tropospheric Aerosol Variability and Sources over the North Atlantic During NAAMES 2015-2016 (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: The North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) is a five-year Earth-Venture Suborbital-2 Mission to characterize the plankton ecosystems and their influences on remote marine aerosols, boundary layer clouds, and their implications for climate in the North Atlantic. While marine-sourced aerosols have been shown to make important contributions to surface aerosol loading, cloud condensation nuclei and ice nuclei concentrations over remote marine and coastal regions, it is still a challenge to differentiate the marine biogenic aerosol signal from the strong influence of continental pollution outflow. We examine here the spatiotemporal variability and quantify the sources of tropospheric aerosols over the North Atlantic during the first two phases (November 2015 and May-June 2016) of NAAMES using a state-of-the-art chemical transport model (GEOS-Chem). The model is driven by the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) from the NASA Global Modeling and Assimilation Office (GMAO). It includes sulfate-nitrate-ammonium aerosol thermodynamics coupled to ozone-NOx-hydrocarbon-aerosol chemistry, mineral dust, sea salt, elemental and organic carbon aerosols, and especially a recently implemented parameterization for the marine primary organic aerosol emission. The simulated aerosols over the North Atlantic are evaluated with available satellite (e.g., MODIS) observations of aerosol optical depths (AOD), and aircraft and ship aerosol measurements. We diagnose transport pathways for continental pollution outflow over the North Atlantic using carbon monoxide, an excellent tracer for anthropogenic pollution transport. We also conduct model perturbation experiments to quantify the relative contributions of terrestrial and oceanic sources to the aerosol loading, AOD, and their variability over the North Atlantic.
    Keywords: Earth Resources and Remote Sensing
    Type: ARC-E-DAA-TN38154 , 2016 AGU Fall Meeting; Dec 12, 2016 - Dec 16, 2016; San Francisco, CA; United States
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  • 6
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    Constraints from Airborne (210)Pb Observations on Aerosol Scavenging and Lifetime in a Global Chemical Transport Model (2016)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Lead-210 distribution and lifetime in the atmosphere are not sensitive to ice in-cloud scavenging in convective updraft. Ice in-cloud scavenging in stratiform clouds reduce tropospheric (210)Pb lifetime by approximately 1 day and results in better agreements with observed surface observations and aircraft measured profiles. However, the process results in significant underestimate of (210)Pb in UT/LS.
    Keywords: Earth Resources and Remote Sensing
    Type: NF1676L-25449 , AeroCOM/AeroSAT Workshop; Sep 19, 2016 - Sep 27, 2016; Beijing; China
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  • 7
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    Model Analysis of Tropospheric Aerosol Variability and Sources over the North Atlantic During NAAMES 2015-2016 (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The North Atlantic Aerosols and Marine Ecosystems Study (NAAMES; http://naames.larc.nasa.gov) is a five year NASA Earth-Venture Suborbital-2 Mission to characterize the plankton ecosystems and their influences on remote marine aerosols, boundary layer clouds, and their implications for climate in the North Atlantic, with the 1st field deployment in November 2015 and the 2nd in May 2016.
    Keywords: Earth Resources and Remote Sensing
    Type: NF1676L-26208 , AGU Fall Meeting; Dec 12, 2016 - Dec 16, 2016; San Francisco, CA; United States
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  • 8
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    Evaluating A Priori Ozone Profile Information Used in TEMPO Tropospheric Ozone Retrievals (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Ozone (O3) is a greenhouse gas and toxic pollutant which plays a major role in air quality. Typically, monitoring of surface air quality and O3 mixing ratios is primarily conducted using in situ measurement networks. This is partially due to high-quality information related to air quality being limited from space-borne platforms due to coarse spatial resolution, limited temporal frequency, and minimal sensitivity to lower tropospheric and surface-level O3. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite is designed to address these limitations of current space-based platforms and to improve our ability to monitor North American air quality. TEMPO will provide hourly data of total column and vertical profiles of O3 with high spatial resolution to be used as a near-real-time air quality product. TEMPO O3 retrievals will apply the Smithsonian Astrophysical Observatory profile algorithm developed based on work from GOME, GOME-2, and OMI. This algorithm uses a priori O3 profile information from a climatological data-base developed from long-term ozone-sonde measurements (tropopause-based (TB) O3 climatology). It has been shown that satellite O3 retrievals are sensitive to a priori O3 profiles and covariance matrices. During this work we investigate the climatological data to be used in TEMPO algorithms (TB O3) and simulated data from the NASA GMAO Goddard Earth Observing System (GEOS-5) Forward Processing (FP) near-real-time (NRT) model products. These two data products will be evaluated with ground-based lidar data from the Tropospheric Ozone Lidar Network (TOLNet) at various locations of the US. This study evaluates the TB climatology, GEOS-5 climatology, and 3-hourly GEOS-5 data compared to lower tropospheric observations to demonstrate the accuracy of a priori information to potentially be used in TEMPO O3 algorithms. Here we present our initial analysis and the theoretical impact on TEMPO retrievals in the lower troposphere.
    Keywords: Earth Resources and Remote Sensing
    Type: ARC-E-DAA-TN38040 , AGU Fall Meeting; Dec 12, 2016 - Dec 16, 2016; San Francisco, CA; United States
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  • 9
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    Using Satellite Observations of Cloud Vertical Distribution to Improve Global Model Estimates of Cloud Radiative Effect on Key Tropospheric Oxidants (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Clouds directly affect tropospheric photochemistry through modification of solar radiation that determines photolysis frequencies. This effect is an important component of global tropospheric chemistry-climate interaction, and its understanding is thus essential for predicting the feedback of climate change on tropospheric chemistry.
    Keywords: Earth Resources and Remote Sensing
    Type: NF1676L-27058 , International GEOS-Chem Meeting (IGC8); May 01, 2017 - May 04, 2017; Cambridge, MA; United States
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  • 10
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    Evaluating a Priori Ozone Profile Information Used in TEMPO Tropospheric Ozone Retrievals (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: Ozone (O3) is a greenhouse gas and toxic pollutant which plays a major role in air quality. Typically, monitoring of surface air quality and O3 mixing ratios is primarily conducted using in situ measurement networks. This is partially due to high-quality information related to air quality being limited from space-borne platforms due to coarse spatial resolution, limited temporal frequency, and minimal sensitivity to lower tropospheric and surface-level O3. The Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite is designed to address these limitations of current space-based platforms and to improve our ability to monitor North American air quality. TEMPO will provide hourly data of total column and vertical profiles of O3 with high spatial resolution to be used as a near-real-time air quality product.TEMPO O3 retrievals will apply the Smithsonian Astrophysical Observatory profile algorithm developed based on work from GOME, GOME-2, and OMI. This algorithm uses a priori O3 profile information from a climatological data-base developed from long-term ozone-sonde measurements (tropopause-based (TB) O3 climatology). It has been shown that satellite O3 retrievals are sensitive to a priori O3 profiles and covariance matrices. During this work we investigate the climatological data to be used in TEMPO algorithms (TB O3) and simulated data from the NASA GMAO Goddard Earth Observing System (GEOS-5) Forward Processing (FP) near-real-time (NRT) model products. These two data products will be evaluated with ground-based lidar data from the Tropospheric Ozone Lidar Network (TOLNet) at various locations of the US. This study evaluates the TB climatology, GEOS-5 climatology, and 3-hourly GEOS-5 data compared to lower tropospheric observations to demonstrate the accuracy of a priori information to potentially be used in TEMPO O3 algorithms. Here we present our initial analysis and the theoretical impact on TEMPO retrievals in the lower troposphere.
    Keywords: Earth Resources and Remote Sensing
    Type: ARC-E-DAA-TN37773 , American Geophysical Union (AGU) Fall Meeting; Dec 12, 2016 - Dec 16, 2016; San Francisco, CA; United States
    Format: application/pdf
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