288 research outputs found
Validation of a magneto- and ferro-hydrodynamic model for non-isothermal flows in conjunction with Newtonian and non-Newtonian fluids
This work focuses on the validation of a magnetohydrodynamic (MHD) and ferrohydrodynamic
(FHD) model for non-isothermal flows in conjunction with Newtonian and non-
Newtonian fluids. The importance of this research field is to gain insight into the interaction of
non-linear viscous behaviour of blood flow in the presence of MHD and FHD effects, because
its biomedical application such as magneto resonance imaging (MRI) is in the centre of research
interest. For incompressible flows coupled with MHD and FHD models, the Lorentz force and
a Joule heating term appear due to the MHD effects and the magnetization and magnetocaloric
terms appear due to the FHD effects in the non-linear momentum and temperature equations,
respectively. Tzirtzilakis and Loukopoulos [1] investigated the effects of MHD and FHD for
incompressible non-isothermal flows in conjunction with Newtonian fluids in a small rectangular
channel. Their model excluded the non-linear viscous behaviour of blood flows considering
blood as a Newtonian biofluid. Tzirakis et al. [2, 3] modelled the effects of MHD and FHD for
incompressible isothermal flows in a circular duct and through a stenosis in conjunction with
both Newtonian and non-Newtonian fluids, although their approach neglects the non-isothermal
magnetocaloric FHD effects. Due to the fact that there is a lack of experimental data available
for non-isothermal and non-Newtonian blood flows in the presence of MHD and FHD effects,
therefore the objective of this study is to establish adequate validation test cases in order to assess
the reliability of the implemented non-isothermal and non-Newtonian MHD-FHD models.
The non-isothermal Hartmann flow has been chosen as a benchmark physical problem to study
velocity and temperature distributions for Newtonian fluids and non-Newtonian blood flows in
a planar microfluidic channel. In addition to this, the numerical behaviour of an incompressible
and non-isothermal non-Newtonian blood flow has been investigated from computational
aspects when a dipole-like rotational magnetic field generated by infinite conducting wires. The
numerical results are compared to available computational data taken from literature
A unified fractional-step, artificial compressibility and pressure-projection formulation for solving the incompressible Navier-Stokes equations
This paper introduces a unified concept and algorithm for the fractionalstep (FS), artificial compressibility (AC) and pressure-projection (PP) methods for solving the incompressible Navier-Stokes equations. The proposed FSAC-PP approach falls into the group of pseudo-time splitting high-resolution methods incorporating the characteristics-based (CB) Godunov-type treatment of convective terms with PP methods. Due to the fact that the CB Godunov-type methods are applicable directly to the hyperbolic AC formulation and not to the elliptical FS-PP (split) methods, thus the straightforward coupling of CB Godunov-type schemes with PP methods is not possible. Therefore, the proposed FSAC-PP approach unifies the fully-explicit AC and semi-implicit FS-PP methods of Chorin including a PP step in the dual-time stepping procedure to a) overcome the numerical stiffness of the classical AC approach at (very) low and moderate Reynolds numbers, b) incorporate the accuracy and convergence properties of CB Godunov-type schemes with PP methods, and c) further improve the stability and efficiency of the AC method for steady and unsteady flow problems. The FSAC-PP method has also been coupled with a non-linear, full-multigrid and full approximation storage (FMG-FAS) technique to further increase the efficiency of the solution. For validating the proposed FSAC-PP method, computational examples are presented for benchmark problems. The overall results show that the unified FSAC-PP approach is an efficient algorithm for solving incompressible flow problems
Equilibrium molecular dynamics modeling of diffussion and adsorption of fluids in armchair single walled carbon-nanotube
The aim of this paper is to study adsorption and diffusion of gases and liquids especially Argon and Carbon-dioxide in single walled carbonnanotube at room temeperature using equilibrium molecular dynamic simulation. The simulation domain is developed by the large atomic/molecular massively parallel simulator (LAMMPS). The domain consists of a simulation box of volume 100 x 100 x 100 A having periodic boundary conditions at the x. y and z direction.The adsorption and diffusion of different chiral- ity of carbonnanotubes are reported. The Molecular Dynamics Simulation (MD) result shows that single walled carbonnanotube have affinity to attract carbon dioxide to itself than argon, with argon acting as a catalyst for adsorption of more C02 confirming a high adsorption at higher loading. The highest adsorption and diffussion inside the Single-walled carbon-naotube (SWCNT) was determined at certain loading and temperature. The SWCNT is as-sumed to be rigid due to the fact that, flexibility is insignificant and can increase computational time. This study will bring about a better understanding of storage and filtering of gases in SWCNTs and so leading its usefullness in applications such as gasification for jet engines, Co2 removal in the international space station, desalination for water systems, air purification, longer space batteries and enhanced oil recovery
Computation of the conformal algebra of 1+3 decomposable spacetimes
The conformal algebra of a 1+3 decomposable spacetime can be computed from
the conformal Killing vectors (CKV) of the 3-space. It is shown that the
general form of such a 3-CKV is the sum of a gradient CKV and a Killing or
homothetic 3-vector. It is proved that spaces of constant curvature always
admit such conformal Killing vectors. As an example, the complete conformal
algebra of a G\"odel-type spacetime is computed. Finally it is shown that this
method can be extended to compute the conformal algebra of more general
non-decomposable spacetimes.Comment: 15 pages Latex, no figures. Minor mistakes correcte
Phase regeneration of optical signals
We present recent advances in phase-sensitive amplification technology and its application to the regeneration of phase-encoded signals. Using a combination of parametric effects in fibers and optical injection locking of lasers, it is possible to observe phase regeneration in signals with multiple levels of phase encoding
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Hybrid Segmentation of Anatomical Data
We propose new hybrid methods for automated segmentation of radiological patient data and the Visible Human data. In this paper, we integrate boundary-based and region-based segmentation methods which amplifies the strength but reduces the weakness of both approaches. The novelty comes from combining a boundary-based method, the deformable model-based segmentation with region-based segmentation methods, the fuzzy connectedness and Voronoi Diagram-based segmentation, to develop hybrid methods that yield high precision, accuracy and efficiency. This work is a part of a NLM funded effort to provide a fully implemented and tested Visible Human Project Segmentation and Registration Toolkit (Insight)
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Chapter 1 : Hybrid Segmentation Methods
We propose a Hybrid Segmentation Engine that consists of component modules, for automated segmentation of radiological patient and the Visible Human data. We integrate boundary-based and region-based segmentation methods to exploit the strength of each method hopefully to cover the weakness of the other method
Non-Markovian entanglement dynamics in coupled superconducting qubit systems
We theoretically analyze the entanglement generation and dynamics by coupled
Josephson junction qubits. Considering a current-biased Josephson junction
(CBJJ), we generate maximally entangled states. In particular, the entanglement
dynamics is considered as a function of the decoherence parameters, such as the
temperature, the ratio between the reservoir cutoff
frequency and the system oscillator frequency , % between
the characteristic frequency of the %quantum system of interest, and
the cut-off frequency of %Ohmic reservoir and the energy levels
split of the superconducting circuits in the non-Markovian master equation. We
analyzed the entanglement sudden death (ESD) and entanglement sudden birth
(ESB) by the non-Markovian master equation. Furthermore, we find that the
larger the ratio and the thermal energy , the shorter the
decoherence. In this superconducting qubit system we find that the entanglement
can be controlled and the ESD time can be prolonged by adjusting the
temperature and the superconducting phases which split the energy
levels.Comment: 13 pages, 3 figure
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