The Experts below are selected from a list of 1914 Experts worldwide ranked by ideXlab platform
Francois Lique - One of the best experts on this subject based on the ideXlab platform.
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rotational excitation of hcn by para and ortho h2
Journal of Chemical Physics, 2014Co-Authors: Mario Hernandez Vera, Thierry Stoecklin, Yulia N Kalugina, Otoniel Denisalpizar, Francois LiqueAbstract:Rotational excitation of the hydrogen cyanide (HCN) molecule by collisions with para-H2( j = 0, 2) and ortho-H2( j = 1) is investigated at low temperatures using a quantum time independent approach. Both molecules are treated as Rigid Rotors. The scattering calculations are based on a highly correlated ab initio 4-dimensional (4D) potential energy surface recently published. Rotationally inelastic cross sections among the 13 first rotational levels of HCN were obtained using a pure quantum close coupling approach for total energies up to 1200 cm−1. The corresponding thermal rate coefficients were computed for temperatures ranging from 5 to 100 K. The HCN rate coefficients are strongly dependent on the rotational level of the H2 molecule. In particular, the rate coefficients for collisions with para-H2( j = 0) are significantly lower than those for collisions with ortho-H2( j = 1) and para-H2( j = 2). Propensity rules in favor of even Δj transitions were found for HCN in collisions with para-H2( j = 0) whereas propensity rules in favor of odd Δj transitions were found for HCN in collisions with H2( j ⩾ 1). The new rate coefficients were compared with previously published HCN-para-H2( j = 0) rate coefficients. Significant differences were found due the inclusion of the H2 rotational structure in the scattering calculations. These new rate coefficients will be crucial to improve the estimation of the HCN abundance in the interstellar medium.
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near resonant rotational energy transfer in hcl h2 inelastic collisions
Journal of Chemical Physics, 2014Co-Authors: Mathieu Lanza, Yulia N Kalugina, L Wiesenfeld, Francois LiqueAbstract:We present a new four-dimensional (4D) potential energy surface for the HCl–H2 van der Waals system. Both molecules were treated as Rigid Rotors. Potential energy surface was obtained from electronic structure calculations using a coupled cluster with single, double, and perturbative triple excitations method. The four atoms were described using the augmented correlation-consistent quadruple zeta basis set and bond functions were placed at mid-distance between the HCl and H2 centers of mass for a better description of the van der Waals interaction. The global minimum is characterized by the well depth of 213.38 cm−1 corresponding to the T-shape structure with H2 molecule on the H side of the HCl molecule. The dissociation energies D0 are 34.7 cm−1 and 42.3 cm−1 for the complex with para- and ortho-H2, respectively. These theoretical results obtained using our new PES are in good agreement with experimental values [D. T. Anderson, M. Schuder, and D. J. Nesbitt, Chem. Phys. 239, 253 (1998)]. Close coupling ...
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the rotational excitation of the interstellar hnc by para and ortho h2
Physical Chemistry Chemical Physics, 2011Co-Authors: Fabien Dumouchel, Jacek Klos, Francois LiqueAbstract:Rotational excitation of the interstellar HNC due to collisions with H2 is investigated. We present a new four dimensional (4D) potential energy surface for the HNC–H2 collisional system. Both molecules were treated as Rigid Rotors. Interaction energy was obtained from the electronic structure calculations using a single and double-excitation coupled cluster method with perturbative contributions from connected triple excitations [CCSD(T)]. The five atoms were described using the aug-cc-pVTZ basis sets. Bond functions were placed at mid-distance between the HNC center of mass and the center of mass of H2 for a better description of the van der Waals interaction. Close coupling calculations of the inelastic integral cross sections of HNC in collisions with para-H2 and ortho-H2 were calculated for kinetic energies up to 800 cm−1. After Boltzmann thermal averaging, rate coefficients were obtained for temperatures ranging from 5 to 100 K. Significant differences exist between para- and ortho-H2 results. The strongest collision-induced rotational HNC transitions are the transitions with Δj = 1 for collisions with para-H2 and with ortho-H2. The new rate coefficients should induce important consequences on the determination of HNC abundance in the interstellar medium. In particular, we expect that they will help to solve the interstellar problem of relative abundance of the HCN and HNC isomers.
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quantum scattering of sis with h2 potential energy surface and rate coefficients at low temperature
Journal of Chemical Physics, 2008Co-Authors: Francois Lique, Jacek KlosAbstract:Rotational excitation of the interstellar species SiS with H2 is investigated. We present a new four dimensional potential energy surface for the SiS–H2 system. Both molecules were treated as Rigid Rotors. Potential was obtained from the electronic structure calculations using a single- and double-excitation coupled cluster method with perturbative contributions from connected triple excitations [CCSD(T)]. The four atoms were described using the aug-cc-pVTZ basis sets. Bond functions were placed at mid-distance between the SiS center of mass and the center of mass of H2 for a better description of the van der Waals interaction. Additionally, at seven characteristic geometries, we calculated perturbational components of the interaction energy using symmetry-adapted perturbation theory approach to explain the anisotropy of the potential energy surface. Coupled-state calculations of the inelastic integral cross sections of SiS in collisions with para-H2 and ortho-H2 were calculated at low energies. After Bol...
David Patterson - One of the best experts on this subject based on the ideXlab platform.
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automated context free assignment of asymmetric rotor microwave spectra
Journal of Chemical Physics, 2019Co-Authors: Lia Yeh, Lincoln Satterthwaite, David PattersonAbstract:We present a new algorithm, Robust Automated Assignment of Rigid Rotors (RAARR), for assigning rotational spectra of asymmetric tops. The RAARR algorithm can automatically assign experimental spectra under a broad range of conditions, including spectra comprised of multiple mixture components, in ≲100 s. The RAARR algorithm exploits constraints placed by the conservation of energy to find sets of connected lines in an unassigned spectrum. The highly constrained structure of these sets eliminates all but a handful of plausible assignments for a given set, greatly reducing the number of potential assignments that must be evaluated. We successfully apply our algorithm to automatically assign 15 experimental spectra, including 5 previously unassigned species, without prior estimation of molecular rotational constants. In 9 of the 15 cases, the RAARR algorithm successfully assigns two or more mixture components.
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automated context free assignment of asymmetric rotor microwave spectra
arXiv: Chemical Physics, 2018Co-Authors: Lia Yeh, Lincoln Satterthwaite, David PattersonAbstract:We present a new algorithm, Robust Automated Assignment of Rigid Rotors (RAARR), for assigning rotational spectra of asymmetric tops. The RAARR algorithm can automatically assign experimental spectra under a broad range of conditions, including spectra comprised of multiple mixture components, in about 100 seconds or less. The RAARR algorithm exploits constraints placed by the conservation of energy to find sets of connected lines in an unassigned spectrum. The highly constrained structure of these sets eliminates all but a handful of plausible assignments for a given set, greatly reducing the number of potential assignments that must be evaluated. We successfully apply our algorithm to automatically assign 15 experimental spectra, including 5 previously unassigned species, without prior estimation of molecular rotational constants. In 9 of the 15 cases, the RAARR algorithm successfully assigns two or more mixture components.
Lia Yeh - One of the best experts on this subject based on the ideXlab platform.
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automated context free assignment of asymmetric rotor microwave spectra
Journal of Chemical Physics, 2019Co-Authors: Lia Yeh, Lincoln Satterthwaite, David PattersonAbstract:We present a new algorithm, Robust Automated Assignment of Rigid Rotors (RAARR), for assigning rotational spectra of asymmetric tops. The RAARR algorithm can automatically assign experimental spectra under a broad range of conditions, including spectra comprised of multiple mixture components, in ≲100 s. The RAARR algorithm exploits constraints placed by the conservation of energy to find sets of connected lines in an unassigned spectrum. The highly constrained structure of these sets eliminates all but a handful of plausible assignments for a given set, greatly reducing the number of potential assignments that must be evaluated. We successfully apply our algorithm to automatically assign 15 experimental spectra, including 5 previously unassigned species, without prior estimation of molecular rotational constants. In 9 of the 15 cases, the RAARR algorithm successfully assigns two or more mixture components.
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automated context free assignment of asymmetric rotor microwave spectra
arXiv: Chemical Physics, 2018Co-Authors: Lia Yeh, Lincoln Satterthwaite, David PattersonAbstract:We present a new algorithm, Robust Automated Assignment of Rigid Rotors (RAARR), for assigning rotational spectra of asymmetric tops. The RAARR algorithm can automatically assign experimental spectra under a broad range of conditions, including spectra comprised of multiple mixture components, in about 100 seconds or less. The RAARR algorithm exploits constraints placed by the conservation of energy to find sets of connected lines in an unassigned spectrum. The highly constrained structure of these sets eliminates all but a handful of plausible assignments for a given set, greatly reducing the number of potential assignments that must be evaluated. We successfully apply our algorithm to automatically assign 15 experimental spectra, including 5 previously unassigned species, without prior estimation of molecular rotational constants. In 9 of the 15 cases, the RAARR algorithm successfully assigns two or more mixture components.
Yahong Fan - One of the best experts on this subject based on the ideXlab platform.
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Nutation and Precession Stability Criterion of Magnetically Suspended Rigid Rotors With Gyroscopic Effects Based on Positive and Negative Frequency Characteristics
IEEE Transactions on Industrial Electronics, 2014Co-Authors: Jiancheng Fang, Yuan Ren, Yahong FanAbstract:For magnetically suspended Rigid Rotors with significant gyroscopic effects and high rotor speed, it is necessary to stabilize the forward whirling (nutation) and backward whirling (precession) modes. This paper derives the necessary and sufficient conditions for marginal stability of the whirling modes and further presents their absolute stability criterion based on the positive and negative frequency characteristics of the control channel. Then, the relative stability judging method of the nutation and precession modes is further developed, describing analytically the rotor speed margin, gain, and phase margins. The key advantage of the criterion is that it is independent from the rotational speed and it can reveal analytically the relationships between the rotor speed stability margins of the different whirling modes and the controller itself. Simulation and experimental results demonstrate the validity and superiority of the proposed stability criterion.
Hanwook Jeon - One of the best experts on this subject based on the ideXlab platform.
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proportional integral derivative control of Rigid rotor active magnetic bearing system via eigenvalue assignment for decoupled translational and conical modes
Journal of Vibration and Control, 2015Co-Authors: Hanwook JeonAbstract:Proportional-integral-derivative (PID) control has been widely adopted for stable and reliable operation of Rigid Rotors supported by a pair of active magnetic bearing systems. Conventional centralized PID control methods manipulate the feedback gains in prescribed forms until they achieve the desired control performance. In this study, an eigenvalue assignment for decoupled translational and conical modes is proposed in the complex domain to yield a unique PID controller in a closed form, preserving the isotropic bearing characteristics. The eigenvalue assignment necessitates the constraints required for decoupling of the translational and conical whirl motions from the complex equation of motion written in the center of gravity coordinates of the Rigid rotor. The complex equation of motion integrates the Rigid rotor and electro-magnetic control force models defined in two different coordinate systems by utilizing complex coordinate transformation relations. A flywheel energy storage system is taken as a...
