Flow of linear molecules through a 4:1:4 contraction-expansion using non-equilibrium molecular dynamics: Extensional rheology and pressure drop

Abstract

We present a study of a quantum controlled-controlled-not gate, implemented in a chain of three nuclear spins weakly Ising interacting between all of them, that is, taking into account first and second neighbour spin interactions. This implementation is done using a single resonant ?-pulse on the initial state of the system (digital and superposition). The fidelity parameter is used to determine the behaviour of the CCN quantum gate as a function of the ratio of the second neighbour interaction coupling constant to the first neighbour interaction coupling constant (J?/J). We found that for J?/J ? 0.02 we can have a well-defined CCN quantum gate. " 2006 IOP Publishing Ltd.",,,,,,"10.1088/0953-4075/39/18/019",,,"http://hdl.handle.net/20.500.12104/43259","http://www.scopus.com/inward/record.url?eid=2-s2.0-33748798917&partnerID=40&md5=fcb55c25bc61050a65b19d03fc2bcdd7",,,,,,"18",,"Journal of Physics B: Atomic, Molecular and Optical Physics",,"3897

3904",,"39",,"Scopus

WOS",,,,,,,,,,,,"Numerical simulation of a controlled-controlled-not (CCN) quantum gate in a chain of three interacting nuclear spins system",,"Article" "43337","123456789/35008",,"Castillo-Tejas, J., Facultad de Ciencias Básicas, Ingeniería y Tecnología, Universidad Autónoma de Tlaxcala, Calzada Apizaquito S/N, Apizaco, Tlaxcala, 90300, Mexico; Rojas-Morales, A., Facultad de Ciencias Básicas, Ingeniería y Tecnología, Universidad Autónoma de Tlaxcala, Calzada Apizaquito S/N, Apizaco, Tlaxcala, 90300, Mexico; López-Medina, F., Facultad de Ciencias Básicas, Ingeniería y Tecnología, Universidad Autónoma de Tlaxcala, Calzada Apizaquito S/N, Apizaco, Tlaxcala, 90300, Mexico; Alvarado, J.F.J., Departamento de Ingeniería Química, Instituto Tecnológico de Celaya, Avenida Tecnologico García Cubas S/N, Celaya, Guanajuato, 38010, Mexico; Luna-Bárcenas, G., Centro de Investigación y Estudios Avanzados, Instituto Politécnico Nacional, Unidad Querétaro, Libramiento Norponiente No. 2000, Real de Juriquilla, Queretaro Queretaro, 76230, Mexico; Bautista, F., Departamento de Ingeniería Química CUCEI, Universidad de Guadalajara, Boulevard M. García Barragan No. 1451, Guadalajara, Jalisco 44430, Mexico; Manero, O., Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Ciudad Universitaria, Mexico, D.F. 04510, Mexico",,"Castillo-Tejas, J.

Rojas-Morales, A.

Lopez-Medina, F.

Alvarado, J.F.J.

Luna-Barcenas, G.

Bautista, F.

Manero, O.",,"2009",,"In this work, non-equilibrium molecular dynamics simulations are used to generate the flow of linear polymer chains (monomer-springs with FENE potential) and a Lennard-Jones fluid (Newtonian fluid) through a contraction-expansion (4:1:4) geometry. An external force field simulating a constant pressure gradient upstream the contraction region induces the flow, where the confining action of the walls is represented by a Lennard-Jones potential. The equations of motion are solved through a multiple-step integration algorithm coupled to a Nosí-Hoover dynamics [S. Nose, A unified formulation of the constant temperature molecular dynamics methods, J. Chem. Phys. 81 (1984) 511-519], i.e., to simulate a thermostat, which maintains a constant temperature. In this investigation, we assume that the energy removed by the thermostat is related to the viscous dissipation along the contraction-expansion geometry. A non-linear increasing function between the pressure drop and the mean velocity along the contraction for the linear molecules is found, being an order of magnitude larger than that predicted for the Lennard-Jones fluid. The pressure drop of both systems (the linear molecules and Lennard-Jones fluid) is related to the dissipated energy at the contraction entry. The large deformation that the linear molecules experience and the evolution of the normal stress at the contraction entry follow a different trajectory in the relaxation process past the contraction, generating large hysteresis loops. The area enclosed by these cycles is related to the dissipated energy. Large shear stresses developed near the re-entrant corners as well as the vortex formation, dependent on the Deborah number, are also predicted at the exit of the contraction. To our knowledge, for the first time, the excessive pressure losses found in experimental contraction flows can be explained theoretically. " 2009 Elsevier B.V. All rights reserved.