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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical study of the effect of reagent rotation on the reaction of F+H2(ν=0,J) (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 8884-8890 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quasiclassical calculations on the Muckerman V potential energy surface were carried out on the reaction F+H2(ν=0, J)→FH+H at a relative energy of 2 kcal/mol for J=0 to 10. This surface is, to use the classification of Levine and co-workers, very oblate; for a given distance Rc.m. from F to the center of mass of H2 the potential energy is much lower for the collinear configuration (χ=0) than for the perpendicular configuration (χ=90 deg). The goal of the work was to understand the effect of molecular rotation on such an extremely oblate surface. It proved useful to decompose the reactive cross section QR(J) into the product of a hitting cross section Q≠hit(J) for F hitting H2 times the probability PR(J) of reaction occurring once F hits H2. Both Q≠hit(J) and PR(J) go through minima at J≈4–5. We determined that Q≠hit(J=0) is increased by about a factor of 2 by "reorientation'' of the H2 molecule towards a linear configuration by the F atom as it approaches. For J(approximately-greater-than)0 Q≠hit(J) declines due both to loss of this reorientation effect as well as to the more oblique approach of the trajectory to the reactant valley. Many trajectories bounce off the repulsive wall near χ=90 deg before the F atom can hit H2; this effect has been discussed by other authors. The initial decline of PR(J) with J is due to a relatively unusual feature of the potential surface, whereby rotation of the H2 molecule away from a linear F–H–H configuration can easily switch the system from the product region back to the reactant region of the system. Both Q≠hit(J) and PR(J) increase above J=5 because the H2 molecule now has enough rotational energy to rotate through the barrier at χ=90 deg rather than bounce off it. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470077
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  • 2
    Electronic Resource
    Electronic Resource
    Two hard sphere models for the reaction A+BC (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 4885-4894 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In an attempt to understand the mechanism of chemical reactions such as A+BC→AB+C or AC+B, we have constructed two models based upon the assumption that A, B, and C are hard spheres with B and C initially touching. Both models include an accurate estimate of the total cross section for A+BC collisions, the proper angular dependence of the activation energy, and a set of reasonable procedures for selecting the product state (AB+C, AC+B, A+BC, or A+B+C) once the final velocities of the three atoms have been computed. The two models differ in that one uses the sequential impulse model to calculate the final velocities, whereas the other uses the direct interaction with product repulsion (DIPR) model to obtain the velocities. The two models are used to study the O(3P)+H2 system, and the results are compared with quasiclassical trajectory (QCT) calculations on this system. At high energies the DIPR model appears to give better overall agreement with the QCT results. In particular, the QCT calculations show that at high energy the major product channel is the knockout reaction, where the O atom first hits one H atom but then goes on to react with the other atom. This effect is predicted by the DIPR model, but not by the sequential impulse model. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469536
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  • 3
    Electronic Resource
    Electronic Resource
    Theoretical study of the intramolecular isotope effect in the reaction of F+HD (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 5834-5844 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quasiclassical trajectory calculations on the Muckerman V potential energy surface were carried out for the reaction F+HD(υ=0, J)→FH+D or FD+H. The reactive cross sections for the two product channels as well as the isotope effect were calculated for J=0 over the relative collision energy range 0.8–900 kcal/mol and also for 0≤J≤10 at a collision energy of 2 kcal/mol. The results are compared to those for F+H2→FH+H. The goal of this work was to understand the remarkable isotope effect behavior in both sets of calculations. It proved useful to decompose the reactive cross sections QR(FH) and QR(FD) into the product of three factors; the cross sections for F hitting the H end and the D end of HD, Qhit(FHD) and Qhit(FDH); the probabilities of reacting to give either FH or FD once the H end or D end is hit, PR(FHD) and PR(FDH); and the corrections for knockout collisions at both ends of the molecule, CKO(FHD) and CKO(FDH). (A knockout collision is one where the F atom initially hits the H end but reacts to form FD or vice versa.) All three factors make important contributions to the isotope effect. At low collision energies for J=0 FD is favored over FH because F hits the D end of HD more often and because the overall reactivity is higher at the D end. Both effects become less important at higher energies, but above 30 kcal/mol knockout reactions strongly favor the production of FD. The isotope effect as a function of J is quite remarkable. Although FD is favored for J=0 at E=2 kcal/mol, by J=3 no trajectories hit the D end, and no DF is formed. But at J=7 DF product reappears, coinciding with the onset of knockout reactions and an increase in reactivity at both ends of HD. We attribute all of these effects to the ability of the system at high J to rotate through the barrier separating the reactant valleys at each end of HD. The results obtained in this paper are explained by reference to special features of the potential energy surface and to the displacement of the HD center of mass towards the D atom. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471314
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of classical and quantal calculations for the reaction O+H2(υ=0, J)→OH(υ′, J′)+H near threshold (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 10429-10435 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: State-to-state reaction probabilities have been calculated for the reaction O+H2(υ=0,J) →OH(υ′,J′)+H near threshold using the quasiclassical trajectory technique. In most cases the total classical angular momentum J of the system was held equal to zero. The procedure for "quantizing'' the product vibrational energy is somewhat ambiguous, and two procedures were used. The results were compared with the quantal calculations of Chatfield et al. on the same system for J=0. Both the classical and quantal calculations give very state-specific product distributions. The agreement between the classical and quantal calculations is reasonably good, particularly for the classical procedure which conserves the total product internal energy during the quantization procedure. The agreement is worst for J=0. For the case J=14 we have also carried out a calculation for all J values (i.e., all impact parameters and initial orientations) of the product density distribution P(Evib′,Erot′) and compared it with the comparable distribution for J=0. Here, Evib′ and Erot′ are the product vibrational and rotational energies. The results for all J show a peaked product distribution, but it is broader than that for J=0 and it has a somewhat different correlation between Evib′ and Erot′. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472988
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical study of the intramolecular isotope effect in the reaction of O(3P)+HD. The importance of molecular reorientation (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 5117-5125 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A quasiclassical trajectory study has been made of the intramolecular isotope effect for the reaction of O(3P)+HD (v=0, J=0) on the potential energy surface of Johnson and Winter for relative energies E between 15 and 150 kcal/mol. In this energy range OD+H is the favored product channel. During each trajectory the OH and OD bond lengths were monitored to determine which end of the HD molecule was "hit'' by the O atom. The results show unambiguously that the O atom exerts a torque on the molecule that rotates the H atom away from O, increasing the likelihood that O will hit and react with D. The effect of this torque increases as the HD molecule stretches during the reactive process. The reorientation of HD is important even at collision energies as high as E=100 kcal/mol. Plots of the potential energy surface for this reaction confirm the importance of the intermolecular torque exerted on HD by O.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466013
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  • 6
    Electronic Resource
    Electronic Resource
    The investigation into the Schwarz–Korteweg–de Vries equation and the Schwarz derivative in (2+1) dimensions (2000)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 41 (2000), S. 4747-4751 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: In this note, we shall introduce a new integrable equation and the Schwarz derivative in (2+1) dimensions. First we show the existence of the Lax pair for an equation which has the relation to the Schwarz–Korteweg–de Vries (SKdV) equation. Next we derive a new equation in (2+1) dimensions by using a well-known higher-dimensional manner to the Lax pair for the SKdV equation. The (2+1) dimensional Schwarz derivative is defined here. Finally we briefly discuss various results which we have obtained about the new equation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.533374
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  • 7
    Electronic Resource
    Electronic Resource
    Reducing tilt errors in moiré linear encoders using phase-modulated grating (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 2296-2300 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new hardware compensation method reducing displacement measurement errors, caused by tilt of the index scale in a moiré linear encoder, has been developed. In conventional moiré linear encoders, the detectors are aligned perpendicular to the line of the moiré fringes and this structure is very sensitive to an unwanted tilt of the gratings. In this article, a newly designed grating, called a phase-modulated grating, is developed to compensate for nonorthogonal errors. By using the phase-modulated grating instead of a conventional index, it is possible to reduce nonorthogonal errors of the moiré linear encoder. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1150445
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  • 8
    Electronic Resource
    Electronic Resource
    Prediction of Slip Displacement in Nuclear Fuel Fretting Wear (2005)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 297-300 (Nov. 2005), p. 1365-1370 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Slipping characteristic on the contacts between the tubes and the supports is investigated to study the fretting wear of a vibratory tube. Tests were carried out to simulate the vibration of the fuel rods supported by the springs and dimples. A tube was forced to vibrate with 30Hz. The supporting condition was varied artificially: positive contact force or gap existence. During the tube vibration, amplitudes were measured continuously in the vicinity of the supports. Simple equations were derived to evaluate the slip displacement on the contacts. As a result, it was found that the supporting condition affected the vibration characteristic near the contacts. In the positive contact condition, the phase difference of the vibration signals at both sides of the contact was 180 degrees. It is altered in the gap condition and the higher frequency components than 30Hz appeared. The severer wear in the case of the gap existence is discussed with the evaluated slip distance per cycle
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/50/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.297-300.1365.pdf
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  • 9
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    Reducing tilt errors in moiré linear encoders using phase-modulated grating (2000)
    American Institute of Physics
    Details
    Publication Date: 2000-06-01
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics
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  • 10
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    Phosphoproteome-based kinase activity profiling reveals the critical role of MAP2K2 and PLK1 in neuronal autophagy (2017)
    Taylor & Francis
    Details
    Publication Date: 2017-10-04
    Print ISSN: 1554-8627
    Electronic ISSN: 1554-8635
    Topics: Biology
    Published by Taylor & Francis
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