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1

Digitale Medien

Separation of losses in low-alloy, nonoriented electrical steels (1985)

Stephenson, E. T.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 57 (1985), S. 4226-4228

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A recent study on low-alloy, nonoriented, semiprocessed electrical steels indicated that at 60 Hz and 15 and 17 kG the anomalous loss per cycle Wa increased linearly with t2/ρ, i.e., Wa=Wao+kt2/ρ, where t is sheet thickness, ρ is resistivity, and Wao and k are empirical constants. The present study explores the above relationship over inductions B of 5 to 17 kG and frequencies f of 20 to 200 Hz. A separation of hysteresis loss Wh into synchronous and asynchronous components is also considered. Six laboratory heats with Si+Al〈1.1 wt. % were hot and cold rolled to 0.035, 0.07, and 0.11 cm. The sheets were annealed, critically strained, and decarburized. Longitudinal strips were tested with dc as well as ac current in a 25-cm Epstein frame. The above linear equation was generally valid. At each combination of B and f, the intercepts Wao were always positive, but the slopes k were negative at 5 and 10 kG and positive at 15 and 17 kG. Furthermore, a fifth of the Wa values were negative. The negative Wa and k were associated with lack of flux penetration. Wh, but not Wa, increased with increasing oxygen and decreasing grain size, and these effects resided in the B1.6 component of Wh.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.334621

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2

Digitale Medien

Energy distribution in the nitric oxide fragments from the ν7 vibrational predissociation of NO–C2H4 (1985)

King, David S. ; Stephenson, John C.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 82 (1985), S. 5286-5288

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: The rotational level distribution of the NO fragments formed as a result of the predissociation of the vibrationally excited NO–C2H4 (ν7) van der Waals molecule was measured by laser excited fluorescence techniques. The distribution was found to be Boltzmann in character, described by the rotational temperature 75±15 K. An average kinetic energy release of ≈105 cm−1 per fragment, in an isotropic flux distribution, was determined from Doppler profiles of the NO fragments in selected rotational levels.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.448604

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3

Digitale Medien

Infrared multiphoton dissociation of methyl nitrite in a molecular beam: Internal states of the nitric oxide fragment (1985)

King, David S. ; Stephenson, John C.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 82 (1985), S. 2236-2239

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: The rotational-, spin-, and lambda doublet-state distributions for nitric oxide (NO) formed in the CO2 laser multiphoton dissociation of methyl nitrite, CH3ONO, in a pulsed molecular beam are reported. Upon methyl nitrite photolysis by temporal square wave infrared laser pulses at 983 cm−1 of 50 ns duration and 800 MW/cm2 intensity, the low-lying rotational levels of the nitric oxide fragments formed in the 2Π1/2 (F1) and 2Π3/2 (F2) spin-orbit states exhibited Boltzmann-like population distributions, characterizable by the rotational temperatures TR (F1)=400±10 K and TR (F2)=530±100 K; the integrated populations for J〈30.5 of the two spin components were in the ratio F1/F2=2.7 : 1. For those highly rotationally excited levels with J(approximately-greater-than)24.5 there is no measurable spin preference, the level population depending solely on total internal energy Eint. There is no apparent preference for formation of either lambda doublet component and there is no observable fragment alignment, the nascent NO species exhibiting an isotropic distribution of angular momentum vectors.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.448317

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4

Digitale Medien

Vibrational deactivation of surface OH chemisorbed on SiO2: Solvent effects (1985)

Heilweil, E. J. ; Casassa, M. P. ; Cavanagh, R. R. ; [weitere]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 82 (1985), S. 5216-5231

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: Picosecond infrared transmission spectroscopy was used to directly measure the vibrational energy relaxation time T1 of hydroxyl groups chemisorbed on the surface of colloidal silica (SiO2). T1 was obtained for OH(νstretch=1) in the strongly bound "isolated sites'' of fumed silica particles in vacuum and dispersed in several liquids at T=293 K. At the SiO2/vacuum interface, T1=204±20 ps. When the SiO2 particles are surrounded by solvents, the relaxation time of the surface OH(v=1) groups decreases: for the liquids CCl4, CF2Br2, CH2Cl2, and C6H6, T1(ps)=159±16, 140±30, 102±20, and 87±30, respectively. T1 does not depend on the size of the SiO2 particles for the range 70 A(ring)≤ diameter ≤150 A(ring), or on the surface OH coverage up to an average density of 4 OH/100 A(ring)2. Significant amounts of physisorbed water (5 H2O/100 A(ring)2) decreased T1 for the isolated OH(v=1) to T1=56±10 ps. For comparison to the surface hydroxyls, the vibrational deactivation time for OH(v=1) groups in the bulk of fused silica (OH/SiO2≈130 ppm by weight) was determined to be T1=109±11 ps. These observations are discussed in terms of the possible mechanisms of vibrational energy flow in these systems. The observed T1 values demonstrate that the spectral linewidths (e.g., IR and Raman) observed for these surface vibrations are too large (by factors of 200–2000) to be caused solely by T1 uncertainty broadening. The slow transfer of vibrational energy between surface and lattice vibrations may have important implications for surface chemistry.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.448646

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5

Digitale Medien

Darstellung und Eigenschaften von Tetrakis(trifluormethyl)-1,3-dithietan-S-oxiden und des Bis(trifluormethyl)sulfins (1985)

Elsäßer, Andreas ; Sundermeyer, Wolfgang ; Stephenson, David S.

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 116-123

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ISSN: 0009-2940

Schlagwort(e): Chemistry ; Inorganic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Beschreibung / Inhaltsverzeichnis: Synthesis and Properties of Tetrakis(trifluoromethyl)-1,3-dithietane S-Oxides and Bis(triflouromethyl)sulfineThe corresponding S-oxides 2-6 could be obtained by oxidation of 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane (1). Similar oxidation of 2,2,4,4-tetrakis(trifluoromethyl)thiirane (8) yields the episulfoxide 12, but not the episulfone 14. Pyrolysis of 2, 3, 5, and 6 have been investigated and bis(trifluoromethyl)sulfine (7) could be isolated as the first member of perfluoroalkylsulfines as well as the sulfonylfluoride 13 being the product of isomerization of bis(trifluoromethyl)-sulfene (9). 7 could also be obtained by ring opening from 3 with bases and by oxidation of hexafluorothioacetone (11), respectively. Solvolytic ring opening in 5 and 6 yields the sulfones 16 and 17.

Notizen: Durch Oxidation des 2,2,4,4-Tetrakis(trifluormethyl)-1,3-dithietans (1) erhält man dessen S-Oxide 2-6. Auf gleiche Weise gelingt die Oxidation des 2,2,4,4-Tetrakis(trifluormethyl)thiirans (8) zum Episulfoxid 12, nicht jedoch zum Episulfon 14. Die Pyrolysen von 2, 3, 5 und 6 wurden untersucht, wobei als erster Vertreter der Perfluoralkylsulfine das Bis(trifluormethyl)sulfin (7) sowie das Sulfonylfluorid 13 als Isomerisierungsprodukt des Bis(trifluormethyl)sulfens (9) isoliert wurden. 7 entsteht auch durch Ringöffnung aus 3 mit Basen bzw. bei der Oxidation des Hexafluorthioacetons (11). Die Solvolyse von 5 und 6 liefert unter Ringöffnung die Sulfone 16 und 17.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/cber.19851180112

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6

Digitale Medien

High-order difference schemes for two-dimensional elliptic equations (1985)

Gupta, Murli M. ; Manohar, Ram P. ; Stephenson, John W.

New York, NY [u.a.] : Wiley-Blackwell

Numerical Methods for Partial Differential Equations 1 (1985), S. 71-80

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ISSN: 0749-159X

Schlagwort(e): Mathematics and Statistics ; Numerical Methods

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Mathematik

Notizen: A high-order finite-difference approximation is proposed for numerical solution of linear or quasilinear elliptic differential equation. The approximation is defined on a square mesh stencil using nine node points and has a truncation error of order h4. Several test problems, including one modeling convection-dominated flows, are solved using this and existing methods. The results clearly exhibit the superiority of the new approximation, in terms of both accuracy and computational efficiency.

Zusätzliches Material: 4 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/num.1690010108

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