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  • Chemistry  (42)
  • General Chemistry  (4)
  • Polymer and Materials Science  (4)
  • Fluid Mechanics and Thermodynamics  (3)
  • 1990-1994  (31)
  • 1980-1984  (9)
  • 1960-1964  (3)
  • 1925-1929  (2)
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  • 1
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    Comparison of Coupled Radiative Navier-Stokes Flow Solutions with the Project Fire II Flight Data (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: A nonequilibrium, axisymmetric, Navier-Stokes flow solver with coupled radiation has been developed to use in the design of thermal protection systems for vehicles where radiation effects are important. The present method has been compared with an existing flow and radiation solver and with the Project Fire II experimental data. Very good agreement has been obtained over the entire Fire II trajectory with the experimentally determined values of the stagnation radiation intensity in the .2 to 6.2 eV range and with the total stagnation heating. The agreement was significantly better than previous numerical predictions. The effects of a number of flow models are examined to determine which combination of physical models produces the best agreement with the experimental data. These models include radiation coupling, multi-temperature thermal models, finite-rate chemistry, and a quasi-steady-state or Boltzmann assumption for the calculation of the excited electronic states. Finally, the computational efficiency of the present model is evaluated. The radiation properties model developed for this study is shown to offer significant computational savings compared to existing codes.
    Keywords: Fluid Mechanics and Thermodynamics
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Development of a Nonequilibrium Radiative Heating Prediction Method for Coupled Flowfield Solutions (1991)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A method for predicting radiative heating and coupling effects in nonequilibrium flow-fields has been developed. The method resolves atomic lines with a minimum number of spectral points, and treats molecular radiation using the smeared band approximation. To further minimize computational time, the calculation is performed on an optimized spectrum, which is computed for each flow condition to enhance spectral resolution. Additional time savings are obtained by performing the radiation calculation on a subgrid optimally selected for accuracy. Representative results from the new method are compared to previous work to demonstrate that the speedup does not cause a loss of accuracy and is sufficient to make coupled solutions practical. The method is found to be a useful tool for studies of nonequilibrium flows.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AIAA Paper 91-1406 , AIAA 26th Thermophysics Conference; Jun 24, 1991 - Jun 26, 1991; Honolulu, HI; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Radiation Transport Around Axisymmetric Blunt Body Vehicles Using a Modified Differential Approximation (1992)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: A moment method for computing 3-D radiative transport is applied to axisymmetric flows in thermochemical nonequilibrium. Such flows are representative of proposed aerobrake missions. The method uses the P-1 approximation to reduce the governing system of integro-di erential equations to a coupled set of partial di erential equations. A numerical solution method for these equations given actual variations of the radiation properties in thermochemical nonequilibrium blunt body flows is developed. Initial results from the method are shown and compared to tangent slab calculations. The agreement between the transport methods is found to be about 10 percent in the stagnation region, with the difference increasing along the flank of the vehicle.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: AIAA Paper 92-0119 , AIAA 30th Aerospace Sciences Meeting; Jan 06, 1992 - Jan 11, 1992; Reno, NV; United States
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    NASA TECHNICAL REPORTS
  • 4
    Electronic Resource
    Electronic Resource
    A New Route to Alkoxy Radicals  -  Photochemical Reactions with (Alkylperoxy)cobaloximes (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 387-390 
    Details
    ISSN: 0009-2940
    Keywords: Peroxy compounds ; Cobaloximes ; Oxygen insertion ; Radicals, alkoxy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alkoxy radicals have been generated by photochemical reactions of (alkylperoxy)cobaloximes 1. The occurrence of alkoxy radicals has been proved by characteristic cyclization and β-scission reactions of the reactive intermediates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240223
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  • 5
    Electronic Resource
    Electronic Resource
    Polar Effects in Halogen Abstraction Reactions of Alkyl Radicals (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1777-1779 
    Details
    ISSN: 0009-2940
    Keywords: Polar effects ; Radical clock ; Cobaloximes, alkyl ; Radicals, alkyl ; Chlorine abstraction ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a series of structurally similar alkyl radicals 1a-c the tertiary 1,1-dimethyl-5-hexenyl radical 1c reacts 30 times faster with carbon tetrachloride than the primary 5-hexenyl radical 1a. The reactivity of the secondary 1-methyl-5-hexenyl radical 1b aligns itself in between the primary and the tertiary radical 1a and 1c. The results indicate that the increasing nucleophilicity of the alkyl radicals is the major factor contributing to the reactivity.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250734
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  • 6
    Electronic Resource
    Electronic Resource
    What is Different in Photochemical Reactions of Primary and Secondary Alkylcobaloximes with and without Radical Traps? (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1187-1191 
    Details
    ISSN: 0009-2940
    Keywords: Cobaloximes, alkyl- ; 5-Hexenyl, cyclization to cyclopentylmethyl ; Radicals, alkyl ; Abstraction of bromine and chlorine ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical cyclization and halogen abstraction reactions of secondary alkylcobaloximes 1b and 1d compared to their primary counterparts 1a and 1c show an enhanced reactivity of secondary alkylcobaloximes: Thus, cyclohexylcobaloxime 1d reacts 13 times faster with CCl4 than n1-hexylcobaloxime 1c, 6-hepten-2-yl-cobaloxime 1b rearranges 58 times faster to its cyclopentylmethyl isomer 4b than 5-hexenylcobaloxime 1a. Although free alkyl radicals are reactive intermediates in photolytic conversions of alkylcobaloximes 1 in organic solvents, the presence of BrCCl3 or bromobenzene in photoreactions of primary alkylcobaloximes 1a and 1c seems to cause a more efficient homolytic cleavage of the Co - C bond.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260519
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  • 7
    Electronic Resource
    Electronic Resource
    Preparation and Properties of Alkylbis(dimethylglyoximato)rhodium(III) ComplexesDedicated to Professor Dr. Klaus Hafner on the occasion of his 65th birthday. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1193-1200 
    Details
    ISSN: 0009-2940
    Keywords: Alkylrhodoximes ; Radicals, alkyl ; Halogen abstraction ; Carbon-carbon bond formation ; Stereochemistry ; Photoreactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Primary, secondary, and tertiary alkylrhodoximes 1 were prepared from alkyl bromides and tosylates 4 and the trans1-dichlororhodium complex 3. X-ray crystallography of the previously unknown tert1-butylrhodoxime 1k reveals structural features of this tert-s̰1-alkylrhodium compound. Photochemical homolytic cleavage of the Rh - C bond in alkylrhodoximes 1 only occurs in the presence of efficient radical traps which allow further mechanistic studies.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260520
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  • 8
    Electronic Resource
    Electronic Resource
    Zum Konformationsverhalten substituierter Benzoesäurephenylester - Molekül- und Kristallstruktur der nematogenen Verbindung 4-n-Pentoxybenzoesäure-4′-(ß-cyanethyl)-phenylester (1983)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 325 (1983), S. 742-752 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Conformational Behaviour of Substituted Phenylbenzoates - Molecular and Crystal Structure of the Nematogenic Compound 4′-(ß-Cyanoethyl)-phenyl-4-n-pentoxybenzoateThe title compound crystallizes in the monoclinic space group P21/n with a = 1567.6(2) pm, b = 915.5(1) pm, c = 1459.1(1) pm, β = 115.30(1)°, and four molecules per unit cell. The structure has been solved by direct methods and refined to R = 0.104. The molecules adopt a markedly stretched form and show a parallel arrangement of their long axes in the crystal lattice. The molecular and crystal structure is discussed in relation to the mesomorphic behaviour of the compound.A theoretical conformational analysis has been performed for the isolated phenylbenzoate molecule using the EPEN/2 method, its results are compared with the experimental torsion angles in a series of substituted phenylbenzoates.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19833250508
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  • 9
    Electronic Resource
    Electronic Resource
    Zum Konformationsverhalten isomerer Phenylpyrimidine  -  Molekül- und Kristallstruktur von 5-Chlor-2-(4-n-hexyloxyphenyl)-pyrimidin (1983)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 325 (1983), S. 489-495 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On the Conformational Behaviour of Isomeric Phenyl Pyrimidines  -  Molecular and Crystal Structure of 5-Chloro-2-(4-n-hexyloxyphenyl)-pyrimidineThe title compound crystallizes in the triclinic space group P1 with a = 979.6(1) pm, b = 1048.8(3) pm, c = 1629.9(1) pm, α = 89.51(1)°, β = 100.62(1)°, γ = 71.50(1)° and four molecules per unit cell. The structure has been solved by direct methods and refined to a final R value of 0.058. The molecules adopt a fully stretched and nearly planar form and show a parallel arrangement in the crystal lattice. The results are discussed in relation to the conformational and mesomorphic behaviour of isomeric substituted phenyl pyrimidines.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19833250319
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  • 10
    Electronic Resource
    Electronic Resource
    Two dimensional TLC determination of PAH in diluted automobile exhaust gasesBased on a paper delivered at the 2nd International Symposium on Instrumental High Performance Thin Layer Chromatography, May, 1982, at Interlaken. (1982)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 5 (1982), S. 489-494 
    Details
    ISSN: 0935-6304
    Keywords: Thin-layer chromatography ; Gas chromatography ; Exhaust gas emissions ; Polycyclic aromatic hydrocarbons (PAH) ; Dilution tunnel ; Langmuir adsorption model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the determination of polycyclic aromatic hydrocarbons (PAH) in the diluted exhaust gas of diesel vehicles. Sampling is done by drawing off proportional streams from the dilution tunnel. The particulates deposited on filters are sublimed, and the sublimate is purified and prefractionated on silica gel. Further separation and quantitative determination of the PAH is performed by two dimensional TLC in conjunction with In situ fluorescence spectrometry. Results of theoretical considerations and experimental data on the distribution of the emitted PAH between particulate matter and the corresponding gas phase in diluted exhaust are presented. A modified Langmuir adsorption model is used to explain the effects of dilution ratio and sample temperature in the dilution tunnel. Comparison of the emission values for PAH obtained from diluted and undiluted exhaust shows good agreement. Furthermore, the PAH contents of the exhaust gas of several diesel-engined cars are also compared for various driving cycles.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240050907
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