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  • 1
    Electronic Resource
    Electronic Resource
    Studies of synthesis and cationic photopolymerization of three isomeric monoterpene diepoxides (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1881-1890 
    Details
    ISSN: 0887-624X
    Keywords: cationic polymerization ; photopolymerization ; epoxy monomers ; terpene epoxides ; isoascaridole ; limonene diepoxide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The monoterpene diepoxides isoascaridole (III), γ-terpinene diepoxide (V), and limonene diepoxide (VIII) were prepared from the corresponding hydrocarbons and their reactivity in photoinitiated cationic polymerization examined. Both V and VIII underwent facile and rapid polymerization to give crosslinked polyethers III, but although highly reactive, did not undergo crosslinking polymerization. With the aid of model compounds it was determined that the rearrangement of one of the epoxy groups of III takes place in the presence of photogenerated acid to give an epoxy ketone (XIII) as the primary product. XIII undergoes very sluggish polymerization. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080331116
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  • 2
    Electronic Resource
    Electronic Resource
    On Some Polyhedra Covering Problems (2000)
    Springer
    Journal of combinatorial optimization 4 (2000), S. 437-447 
    Details
    ISSN: 1573-2886
    Keywords: computational geometry ; polyhedra covering ; NP-hard
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Let P 0, P 1 be two simple polyhedra and let P 2 be a convex polyhedron in E 3. Polyhedron P 0 is said to be covered by polyhedra P 1 and P 2 if every point of P 0 is a point of P 1 ∪ P 2. The following polyhedron covering problem is studied: given the positions of P 0, P 1, and P 2 in the xy-coordinate system, determine whether or not P 0 can be covered by P 1 ∪ P 2 via translation and rotation of P 1 and P 2; furthermore, find the exact covering positions of these polyhedra if such a cover exists. It is shown in this paper that if only translation is allowed, then the covering problem of P 0, P 1 and P 2 can be solved in O(m 2 n 2(m + n)l)) polynomial time, where m, n, and l are the sizes of P 0, P 1, and P 2, respectively. The method can be easily extended to the problem in E d for any fixed d 〉 3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009833410742
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  • 3
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    Theoretical approach to obtaining dynamic characteristics of noncontacting spiral-grooved seals (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The dynamic characteristics of spiral-grooved seals are theoretically obtained by using the Navier-Stokes equation. First, with the inertia term of the fluid considered, the flow and pressure in the steady state are obtained for the directions parallel to and perpendicular to the groove. Next, the dynamic character is obtained by analyzing the steady state and by analyzing the labyrinth seal. As a result, the following conclusions were drawn: (1) As the land width becomes shorter or the helix angle decreases, the cross-coupling stiffness, direct and cross-coupling damping, and add mass coefficients decrease; (2) As the axial Reynolds number increases, the stiffness and damping coefficients increase. But the add mass coefficient is not influenced by the axial Reynolds number; (3) The rotational Reynolds number influences greatly the direct and cross-coupling stiffness and direct damping coefficients; and (4) As the journal rotating frequency increases, the leakage flow decreases. Therefore zero net leakage flow is possible at a particular rotating frequency.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery, 1986; p 155-188
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Static and dynamic characteristics of parallel-grooved seals (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Presented is an analytical method to determine static and dynamic characteristics of annular parallel-grooved seals. The governing equations were derived by using the turbulent lubrication theory based on the law of fluid friction. Linear zero- and first-order perturbation equations of the governing equations were developed, and these equations were analytically investigated to obtain the reaction force of the seals. An analysis is presented that calculates the leakage flow rate, the torque loss, and the rotordynamic coefficients for parallel-grooved seals. To demonstrate this analysis, we show the effect of changing number of stages, land and groove width, and inlet swirl on stability of the boiler feed water pump seals. Generally, as the number of stages increased or the grooves became wider, the leakage flow rate and rotor-dynamic coefficients decreased and the torque loss increased.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery, 1986; p 99-127
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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