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  • Polymer and Materials Science  (1,307)
  • Chemical Engineering  (552)
  • FLUID MECHANICS AND HEAT TRANSFER  (326)
  • Fisheries
  • GENERAL
  • 1985-1989  (1,876)
  • 1955-1959  (337)
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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 36 (1985), S. 624-627 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Unter Hernziehung unterschiedlicher Präparationsmethoden wurde die Struktur verdünnter und konzentrierter (0,01 bis 9,8%) Lösungen des starkettigen Polyamidohydrazid (PAH) mittels Elektronenmikroskopie in zwei Lösungsmitteln (DMSO und DMAA) untersucht. Beginnend mit der Konzentration 0,01% erfolgt unterschiedliche Strukturierung in diesen Lösungsmitteln, die bezüglich des Polymers eine unterschiedliche Güte aufweisen. Die Ergebnisse wurden früheren Untersuchungen zur Rheologie konzentrierter PAH-Lösungen in den genannten Lösungsmitteln gegenüber gestellt.
    Notes: The structure of dilute and concentrated solutions (0.01-9.8%) of rigid-chain polyamidohydrazide (PAH) in dimethylsulphoxide and dimethylacetamide was investigated by electron microscopy using various preparation techniques. Starting with a 0.01% concentration, PAH shows two distinct types of structuration in the solvents. The results are compared with previously studied rheological properties of PAH in these solvents.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2013-08-31
    Description: A brief overview of flow separation phenomena is provided. Langley has many active research programs in flow separation related areas. Three cases are presented which describe specific examples of flow separation research. In each example, a description of the fundamental fluid physics and the complexity of the flow field is presented along with a method of either reducing or controlling the extent of separation. The following examples are discussed: flow over a smooth surface with an adverse pressure gradient; flow over a surface with a geometric discontinuity; and flow with shock-boundary layer interactions. These results will show that improvements are being made in the understanding of flow separation and its control.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Langley Symposium on Aerodynamics, Volume 1; p 361-374
    Format: application/pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1215-1218 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Transparent dimethyl siloxane network polymers with refractive indices near 1.40 may be applied to fused silica fibers (n = 1.458) as they are drawn to produce plastic-clad silica (PCS) optical fibers. The evanescent tail of the light energy propagating in the core of such fibers extends into the silicone cladding, where it interacts with chemical species present in the polymer. If the silicone is doped with a dye, the absorption spectrum or fluorescence spectrum of the dye is reflected in the transmission spectrum of the fiber. Further, if the dye changes its absorption spectrum or fluorescence spectrum as a result of diffusion of a chemical species into the silicone, the change is detectable in the fiber output. The polymer material properties which determine the performance of these sensors are described, along with examples of sensors for ammonia and oxygen which utilize either color changing or fluorescent dyes.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 2541-2551 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Trichroic infrared absorption has been measured for oriented phase I poly(vinylidene fluoride). In addition to intensity differences, frequency shifts in the plane transverse to the draw direction are apparent. Shifts up to 10 cm-1 in one-way drawn phase I are found for the CF2 stretching vibration (880 cm-1) between the direction normal to the film surface (thickness direction) and the remaining directions. Annealing the highly oriented films produces no major changes in the unique three-dimensional structure. A model based on crystal defect structures is proposed to explain the unusual frequency shift behavior in the phase I PVDF. Possible conformations and a mechanism of formation of the defects are discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 571-589 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study was performed to test the feasibility of using a biodegradable delivery system for the local controlled release of sodium fluoride as a mechanism for the stimulation of local bone growth. Sodium fluoride grains were mixed with poly-DL-lactic acid (PLA), and the mixture was then dissolved in acetone. After driving off the solvent, sheets of this material were rolled into rods 3.2 mm in diameter and 28.6 mm long. These were inserted into the intramedullary canals of the right femora of adult New Zealand White rabbits. A sham implant, made the same way but containing no fluoride, was inserted into the contralateral left leg. The effects of three different concentrations of sodium fluoride, 0.125 g NaF/g PLA, 0.250 g NaF/g PLA, and 0.500 g NaF/g PLA, were determined after a 4-week implantation period. In a second set of experiments, the concentration was fixed at 0.500 g NaF/g PLA with implantation durations of 4, 8, and 16 weeks. Expressed in terms of property ratios (experimental/control), bending strengths of the femora were significantly raised in most groups with the notable exception of Group 3 (0.500 g NaF/g PLA, 4 weeks). Cross-sectional area ratios in the distal femora were increased in all groups compared to right/left values for a normal unoperated group (p 〈 0.05), with the highest ratio being 1.50 (SD = 0.44) for Group 4 (0.500 g NaF/g PLA, 8 weeks). Only Group 4 animals showed significant (p 〈 0.05) increases in midshaft area ratio and none had responses proximally. Growth rates, measured by sequential fluorochrome labeling of bone followed the area ratio data and were only significant for the distal femora.
    Additional Material: 7 Ill.
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  • 6
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch die Synthese von cyclischen Acrylaten wurde eine Reihe von Monomeren erhalten, die hohe Reaktivitäten der Copolymerisation bei gleichzeitiger Fähigkeit zur radikalischen Ringöffnungspolymerisation aufweisen. Sie wurden polymerisiert, um einen Pyruvatester in die Polymerkette einzuführen. Eine Reihe von Spiromethylencyclohexadienen wurde hergestellt, um neben der Carbonylgruppe und gespannten Ringen weitere Gruppen zu finden, die die radikalische Ringöffnungspolymerisation fördern. Bei ihrer Polymerisation wurden Polymere mit einer p-Phenylengruppe in der Kette erhalten.
    Notes: In order to find a series of monomers with high reactivities in copolymerization and still undergo free radical ringopening polymerization, a series of cyclic acrylates were synthesized and polymerized to insert a pyruvate ester into the backbone of the polymer. In order to discover groups other than the carbonyl groups and strained rings that would promote free radical ring-opening polymerization, a series of spiro methylenecyclohexadienes were prepared and polymerized to give a polymer with a p-phenylene group in the backbone.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 9 (1988), S. 139-143 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effect of filler content and applied electrical field on the electrical resistivity of poly(methyl methacrylate) (PMMA) filled with aluminum particles was investigated. The resistivity of such composite suddenly decreases by several orders of magnitude at a critical volume concentration φc. In addition, for filler contents lower than φc, the PMMA/Al composite undergoes a transition from a high to a low resistance material in correspondence of a critical value of the external applied electrical field. This value has been related to thermal breakdown occurring in the regions between conductive particles. Moreover, the permittivity spectrum as a function of frequency is reported for composites of several filler contents, and the Lal and Parshad law was used to correlate the experimental data.
    Additional Material: 8 Ill.
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  • 8
    Publication Date: 2019-06-28
    Description: A titanium multiwall/reusable surface insulation (MW/RSI) TPS concept designed to prevent local erosion of the RSI tiles on the upper surface of the Space Shuttle Orbiter body flap was investigated. The concept, which consisted of a combination of a titanium multiwall tile and an RSI tile, was evaluated by thermal analysis and structural and thermal testing of one configuration to assess the attachment scheme and thermal behavior. Results indicate that the MW/RSI concept will remain attached to the vehicle and provide the required thermal protection.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-87589 , NAS 1.15:87589
    Format: application/pdf
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  • 9
    Publication Date: 2019-06-28
    Description: A numerical model based on a transformed, conservative form of the three dimensional Navier-Stokes equation and an analytical model based on lumped fluid parameters are presented and compared with studies of modeled rotor bearing seal systems. The rotor destabilizing factors are related to the rotative character of the flow field. It is shown that these destabilizing factors can be reduced through a decrease in the fluid average circumferential velocity. However, the rotative character of the flow field is a complex three dimensional system with bifurcated secondary flow patterns that significantly alter the fluid circumferential velocity. By transforming the Navier-Stokes equations to those for a rotating observer and using the numerical code PHOENICS-84 with a nonorthogonal body fitted grid, several numerical experiments were carried out to demonstrate the character of this complex flow field. In general, fluid injection and/or preswirl of the flow field opposing the shaft rotation significantly intensified these secondary recirculation zones and thus reduced the average circumferential velocity; injection or preswirl in the direction of rotation significantly weakened these zones.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-100268 , E-3903 , NAS 1.15:100268
    Format: application/pdf
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 773-781 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A second example of insertion of a water molecule into the helical backbone of an apolar peptide is presented here and compared to a similar occurrence in a longer peptide with the same type of sequence of residues, i.e., Boc-Aib-(Ala-Leu-Aib)3-OMe. The backbone of the title compound assumes an approximate 310-helical form with three 4 → 1 hydrogen bonds. In the place of a fourth 4 → 1 hydrogen bond, a water molecule is inserted between O(1) and N(4), and acts as a bridge by forming hydrogen bonds N(4) … W(1) (2.95 Å) and W(1) … O(1) (2.81 Å). The water molecule participates in a third hydrogen bond with a neighboring peptide molecule, W(1) … O(4) (2.91 Å). The insertion of the water molecule causes the apolar peptide to mimic an amphiphilic helix. Crystals grown from ethyl acetate/petroleum ether (reported here) or from methanol/water solution are in space group P212121 with a = 12.024(4) Å, b = 15.714(6) Å, c = 21.411(7) Å, Z = 4 and dcalc = 1.124 g/cm3 for C32H58N6O9 · H2O. The overall agreement factor R is 6.3% for 2707 reflections observed with intensities 〉 3σ(F) and the resolution is 0.90 Å.
    Additional Material: 4 Ill.
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