Roaming

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 22656 Experts worldwide ranked by ideXlab platform

Rajendra Reddy - One of the best experts on this subject based on the ideXlab platform.

Wei Peng - One of the best experts on this subject based on the ideXlab platform.

  • NPC - LDAPRoam: A Generic Solution for Both Web-Based and Non-Web-Based Federate Access
    Lecture Notes in Computer Science, 2019
    Co-Authors: Qi Feng, Wei Peng
    Abstract:

    Identity federation technology has been widely used in recent years. But the solution for federate access is totally different between the Web-Based and Non-Web-Based scenarios. Furthermore, it is highly limited for lack of support from Non-Web-Based scenarios now. This paper proposes a generic federate access solution based on LDAP Roaming, which can provide reliable identity Roaming in any internet service. To service providers, our solution is transparent and looks like a LDAP. The paper first presents the difficulties in realizing LDAP Roaming and discusses offers solutions to the implementation of LDAP Roaming. Then it evaluates the easy integration and usability of LDAP Roaming. Finally it compares the Generic Solution with the existing federal access solution.

Stephen J. Klippenstein - One of the best experts on this subject based on the ideXlab platform.

  • Thermal Dissociation and Roaming Isomerization of Nitromethane: Experiment and Theory.
    Journal of Physical Chemistry A, 2015
    Co-Authors: Christopher J. Annesley, John B. Randazzo, Stephen J. Klippenstein, Lawrence B. Harding, Ahren W. Jasper, Yuri Georgievskii, Branko Ruscic, Robert S. Tranter
    Abstract:

    The thermal decomposition of nitromethane provides a classic example of the competition between Roaming mediated isomerization and simple bond fission. A recent theoretical analysis suggests that as the pressure is increased from 2 to 200 Torr the product distribution undergoes a sharp transition from Roaming dominated to bond-fission dominated. Laser schlieren densitometry is used to explore the variation in the effect of Roaming on the density gradients for CH3NO2 decomposition in a shock tube for pressures of 30, 60, and 120 Torr at temperatures ranging from 1200 to 1860 K. A complementary theoretical analysis provides a novel exploration of the effects of Roaming on the thermal decomposition kinetics. The analysis focuses on the Roaming dynamics in a reduced dimensional space consisting of the rigid-body motions of the CH3 and NO2 radicals. A high-level reduced-dimensionality potential energy surface is developed from fits to large-scale multireference ab initio calculations. Rigid body trajectory simulations coupled with master equation kinetics calculations provide high-level a priori predictions for the thermal branching between Roaming and dissociation. A statistical model provides a qualitative/semiquantitative interpretation of the results. Modeling efforts explore the relation between the predicted Roaming branching and the observed gradients. Overall, the experiments are found to be fairly consistent with the theoretically proposed branching ratio, but they are also consistent with a no-Roaming scenario and the underlying reasons are discussed. The theoretical predictions are also compared with prior theoretical predictions, with a related statistical model, and with the extant experimental data for the decomposition of CH3NO2, and for the reaction of CH3 with NO2.

  • Separability of tight and Roaming pathways to molecular decomposition.
    The journal of physical chemistry. A, 2012
    Co-Authors: Lawrence B. Harding, Stephen J. Klippenstein, Ahren W. Jasper
    Abstract:

    Recent studies have questioned the separability of the tight and Roaming mechanisms to molecular decomposition. We explore this issue for a variety of reactions including MgH(2) → Mg + H(2), NCN → CNN, H(2)CO → H(2) + CO, CH(3)CHO → CH(4) + CO, and HNNOH → N(2) + H(2)O. Our analysis focuses on the role of second-order saddle points in defining global dividing surfaces that encompass both tight and Roaming first-order saddle points. The second-order saddle points define an energetic criterion for separability of the two mechanisms. Furthermore, plots of the differential contribution to the reactive flux along paths connecting the first- and second-order saddle points provide a dynamic criterion for separability. The minimum in the differential reactive flux in the neighborhood of the second-order saddle point plays the role of a mechanism divider, with the presence of a strong minimum indicating that the Roaming and tight mechanisms are dynamically distinct. We show that the mechanism divider is often, but not always, associated with a second-order saddle point. For the formaldehyde and acetaldehyde reactions, we find that the minimum energy geometry on a conical intersection is associated with the mechanism divider for the tight and Roaming processes. For HNNOH, we again find that the Roaming and tight processes are dynamically separable but we find no intrinsic feature of the potential energy surface associated with the mechanism divider. Overall, our calculations suggest that Roaming and tight mechanisms are generally separable over broad ranges of energy covering most kinetically relevant regimes.

  • Statistical theory for the kinetics and dynamics of Roaming reactions.
    The journal of physical chemistry. A, 2011
    Co-Authors: Stephen J. Klippenstein, Yuri Georgievskii, Lawrence B. Harding
    Abstract:

    We present a statistical theory for the effect of Roaming pathways on product branching fractions in both unimolecular and bimolecular reactions. The analysis employs a separation into three distinct steps: (i) the formation of weakly interacting fragments in the long-range/van der Waals region of the potential via either partial decomposition (for unimolecular reactants) or partial association (for bimolecular reactants), (ii) the Roaming step, which involves the reorientation of the fragments from one region of the long-range potential to another, and (iii) the abstraction, addition, and/or decomposition from the long-range region to yield final products. The branching between the Roaming induced channel(s) and other channels is obtained from a steady-state kinetic analysis for the two (or more) intermediates in the long-range region of the potential. This statistical theory for the Roaming-induced product branching is illustrated through explicit comparisons with reduced dimension trajectory simulation...

  • Roaming radical pathways for the decomposition of alkanes.
    The Journal of Physical Chemistry Letters, 2010
    Co-Authors: Lawrence B. Harding, Stephen J. Klippenstein
    Abstract:

    CASPT2 calculations predict the existence of Roaming radical pathways for the decomposition of propane, n-butane, isobutane and neopentane. The Roaming radical paths lead to the formation of an alkane and an alkene instead of the expected radical products. The predicted barriers for the Roaming radical paths lie ∼1 kcal/mol below the corresponding radical asymptotes.

Lawrence B. Harding - One of the best experts on this subject based on the ideXlab platform.

  • Thermal Dissociation and Roaming Isomerization of Nitromethane: Experiment and Theory.
    Journal of Physical Chemistry A, 2015
    Co-Authors: Christopher J. Annesley, John B. Randazzo, Stephen J. Klippenstein, Lawrence B. Harding, Ahren W. Jasper, Yuri Georgievskii, Branko Ruscic, Robert S. Tranter
    Abstract:

    The thermal decomposition of nitromethane provides a classic example of the competition between Roaming mediated isomerization and simple bond fission. A recent theoretical analysis suggests that as the pressure is increased from 2 to 200 Torr the product distribution undergoes a sharp transition from Roaming dominated to bond-fission dominated. Laser schlieren densitometry is used to explore the variation in the effect of Roaming on the density gradients for CH3NO2 decomposition in a shock tube for pressures of 30, 60, and 120 Torr at temperatures ranging from 1200 to 1860 K. A complementary theoretical analysis provides a novel exploration of the effects of Roaming on the thermal decomposition kinetics. The analysis focuses on the Roaming dynamics in a reduced dimensional space consisting of the rigid-body motions of the CH3 and NO2 radicals. A high-level reduced-dimensionality potential energy surface is developed from fits to large-scale multireference ab initio calculations. Rigid body trajectory simulations coupled with master equation kinetics calculations provide high-level a priori predictions for the thermal branching between Roaming and dissociation. A statistical model provides a qualitative/semiquantitative interpretation of the results. Modeling efforts explore the relation between the predicted Roaming branching and the observed gradients. Overall, the experiments are found to be fairly consistent with the theoretically proposed branching ratio, but they are also consistent with a no-Roaming scenario and the underlying reasons are discussed. The theoretical predictions are also compared with prior theoretical predictions, with a related statistical model, and with the extant experimental data for the decomposition of CH3NO2, and for the reaction of CH3 with NO2.

  • Separability of tight and Roaming pathways to molecular decomposition.
    The journal of physical chemistry. A, 2012
    Co-Authors: Lawrence B. Harding, Stephen J. Klippenstein, Ahren W. Jasper
    Abstract:

    Recent studies have questioned the separability of the tight and Roaming mechanisms to molecular decomposition. We explore this issue for a variety of reactions including MgH(2) → Mg + H(2), NCN → CNN, H(2)CO → H(2) + CO, CH(3)CHO → CH(4) + CO, and HNNOH → N(2) + H(2)O. Our analysis focuses on the role of second-order saddle points in defining global dividing surfaces that encompass both tight and Roaming first-order saddle points. The second-order saddle points define an energetic criterion for separability of the two mechanisms. Furthermore, plots of the differential contribution to the reactive flux along paths connecting the first- and second-order saddle points provide a dynamic criterion for separability. The minimum in the differential reactive flux in the neighborhood of the second-order saddle point plays the role of a mechanism divider, with the presence of a strong minimum indicating that the Roaming and tight mechanisms are dynamically distinct. We show that the mechanism divider is often, but not always, associated with a second-order saddle point. For the formaldehyde and acetaldehyde reactions, we find that the minimum energy geometry on a conical intersection is associated with the mechanism divider for the tight and Roaming processes. For HNNOH, we again find that the Roaming and tight processes are dynamically separable but we find no intrinsic feature of the potential energy surface associated with the mechanism divider. Overall, our calculations suggest that Roaming and tight mechanisms are generally separable over broad ranges of energy covering most kinetically relevant regimes.

  • Statistical theory for the kinetics and dynamics of Roaming reactions.
    The journal of physical chemistry. A, 2011
    Co-Authors: Stephen J. Klippenstein, Yuri Georgievskii, Lawrence B. Harding
    Abstract:

    We present a statistical theory for the effect of Roaming pathways on product branching fractions in both unimolecular and bimolecular reactions. The analysis employs a separation into three distinct steps: (i) the formation of weakly interacting fragments in the long-range/van der Waals region of the potential via either partial decomposition (for unimolecular reactants) or partial association (for bimolecular reactants), (ii) the Roaming step, which involves the reorientation of the fragments from one region of the long-range potential to another, and (iii) the abstraction, addition, and/or decomposition from the long-range region to yield final products. The branching between the Roaming induced channel(s) and other channels is obtained from a steady-state kinetic analysis for the two (or more) intermediates in the long-range region of the potential. This statistical theory for the Roaming-induced product branching is illustrated through explicit comparisons with reduced dimension trajectory simulation...

  • Roaming radical pathways for the decomposition of alkanes.
    The Journal of Physical Chemistry Letters, 2010
    Co-Authors: Lawrence B. Harding, Stephen J. Klippenstein
    Abstract:

    CASPT2 calculations predict the existence of Roaming radical pathways for the decomposition of propane, n-butane, isobutane and neopentane. The Roaming radical paths lead to the formation of an alkane and an alkene instead of the expected radical products. The predicted barriers for the Roaming radical paths lie ∼1 kcal/mol below the corresponding radical asymptotes.

Qi Feng - One of the best experts on this subject based on the ideXlab platform.

  • NPC - LDAPRoam: A Generic Solution for Both Web-Based and Non-Web-Based Federate Access
    Lecture Notes in Computer Science, 2019
    Co-Authors: Qi Feng, Wei Peng
    Abstract:

    Identity federation technology has been widely used in recent years. But the solution for federate access is totally different between the Web-Based and Non-Web-Based scenarios. Furthermore, it is highly limited for lack of support from Non-Web-Based scenarios now. This paper proposes a generic federate access solution based on LDAP Roaming, which can provide reliable identity Roaming in any internet service. To service providers, our solution is transparent and looks like a LDAP. The paper first presents the difficulties in realizing LDAP Roaming and discusses offers solutions to the implementation of LDAP Roaming. Then it evaluates the easy integration and usability of LDAP Roaming. Finally it compares the Generic Solution with the existing federal access solution.

  • LDAPRoam: A Generic Solution for Both Web-Based and Non-Web-Based Federate Access
    Network and Parallel Computing, 2019
    Co-Authors: Qi Feng
    Abstract:

    Identity federation technology has been widely used in recent years. But the solution for federate access is totally different between the Web-Based and Non-Web-Based scenarios. Furthermore, it is highly limited for lack of support from Non-Web-Based scenarios now. This paper proposes a generic federate access solution based on LDAP Roaming, which can provide reliable identity Roaming in any internet service. To service providers, our solution is transparent and looks like a LDAP. The paper first presents the difficulties in realizing LDAP Roaming and discusses offers solutions to the implementation of LDAP Roaming. Then it evaluates the easy integration and usability of LDAP Roaming. Finally it compares the Generic Solution with the existing federal access solution.

Related terms

Roaming - 15 days free trial to Access Experts & Abstracts