56 research outputs found
A Hybrid Model Approach for Achieving the Highest Level of Matching Between the “Print and Original” in the Sheet-Fed Offset Pr
This study was designed to explore an optimized hybrid system through dual measurement approach of contrast measurement method and CIE L*a*b* measurement method to arrive a logical interface for achieving the highest matching between the print and original in sheet fed offset printing process. The work was started with the detailed study of contrast measurement, CIE L*a*b* measurement method, visual and computational intelligence based assessment and control. The master was designed in such a way that value of density and other values can be measured easily in effective way. X-Rite eXact instrument is used for capturing the readings, the 10 standard observers were selected initially by manual method and finally by using on line Fransworth-Munsell 100 Hue Colour Vision Test and visual assessments and judgement were done on X-Rite’s Macbeth Lighting Booth and their visual assessments are recorded, analyzed and represented. All the parameters like Paper, Ink, Measuring Conditions and Measuring Instruments etc. were maintained in compliance with ISO specifications. After the analysis of data, the study reached to the following main conclusion i.e. It is observed that almost in all the cases, preference of the Standard Observers are for Delta E Value leading to the higher contrast value instead of Minimum Delta E with less contrast value. Therefore the dual approach of “Hybrid System” will help us to arrive at the most convincing, measurable and perceptually acceptable print result which will be the highest (closest) match to the original by clubbing the best of “CIE Lab, Contrast Method and Standard Observers Visual Perception” as there are positives and negatives in all these three when one approaches individually. The objective of this paper was to develop a dual measurement approach of CIE Lab & Contrast to arrive at a logical inference for the highest level of matching between the original and print in the sheet fed offset printing
On the Applicability of Low-Dimensional Models for Convective Flow Reversals at Extreme Prandtl Numbers
Constructing simpler models, either stochastic or deterministic, for
exploring the phenomenon of flow reversals in fluid systems is in vogue across
disciplines. Using direct numerical simulations and nonlinear time series
analysis, we illustrate that the basic nature of flow reversals in convecting
fluids can depend on the dimensionless parameters describing the system.
Specifically, we find evidence of low-dimensional determinism in flow reversals
occurring at zero Prandtl number, whereas we fail to find such signatures for
reversals at infinite Prandtl number. Thus, even in a single system, as one
varies the system parameters, one can encounter reversals that are
fundamentally different in nature. Consequently, we conclude that a single
general low-dimensional deterministic model cannot faithfully characterize flow
reversals for every set of parameter values.Comment: 9 pages, 4 figure
Probing turbulent superstructures in Rayleigh-B\'{e}nard convection by Lagrangian trajectory clusters
We analyze large-scale patterns in three-dimensional turbulent convection in
a horizontally extended square convection cell by Lagrangian particle
trajectories calculated in direct numerical simulations. A simulation run at a
Prandtl number Pr , a Rayleigh number Ra , and an aspect ratio
is therefore considered. These large-scale structures, which are
denoted as turbulent superstructures of convection, are detected by the
spectrum of the graph Laplacian matrix. Our investigation, which follows
Hadjighasem {\it et al.}, Phys. Rev. E {\bf 93}, 063107 (2016), builds a
weighted and undirected graph from the trajectory points of Lagrangian
particles. Weights at the edges of the graph are determined by a mean dynamical
distance between different particle trajectories. It is demonstrated that the
resulting trajectory clusters, which are obtained by a subsequent -means
clustering, coincide with the superstructures in the Eulerian frame of
reference. Furthermore, the characteristic times and lengths
of the superstructures in the Lagrangian frame of reference agree
very well with their Eulerian counterparts, and ,
respectively. This trajectory-based clustering is found to work for times
. Longer time periods require a
change of the analysis method to a density-based trajectory clustering by means
of time-averaged Lagrangian pseudo-trajectories, which is applied in this
context for the first time. A small coherent subset of the pseudo-trajectories
is obtained in this way consisting of those Lagrangian particles that are
trapped for long times in the core of the superstructure circulation rolls and
are thus not subject to ongoing turbulent dispersion.Comment: 12 pages, 7 downsized figures, to appear in Phys. Rev. Fluid
Role of Bulk flow in Turbulent Convection
In this paper we present scaling of large-scale quantities like Pecl\'{e}t
and Nusselt numbers, and the dissipation rates of kinetic energy and entropy.
Our arguments are based on the scaling of bulk quantities and earlier
experimental and simulation results. We also present the inertial-range
properties of spectra and fluxes of kinetic energy and entropy.Comment: 15 pages, to Appear in the proceedings of "Senfest, International
Conference on Complex Processes in Plasmas and Nonlinear Dynamical Systems
Turbulent superstructures in Rayleigh-B\'enard convection
Turbulent Rayleigh-B\'enard convection displays a large-scale order in the
form of rolls and cells on lengths larger than the layer height once the
fluctuations of temperature and velocity are removed. These turbulent
superstructures are reminiscent of the patterns close to the onset of
convection. They are analyzed by numerical simulations of turbulent convection
in fluids at different Prandtl number ranging from 0.005 to 70 and for Rayleigh
numbers up to . For each case, we identify characteristic scales and
times that separate the fast, small-scale turbulent fluctuations from the
gradually changing large-scale superstructures. The characteristic scales of
the large-scale patterns, which change with Prandtl and Rayleigh number, are
also found to be correlated with the boundary layer dynamics, and in particular
the clustering of thermal plumes at the top and bottom plates. Our analysis
suggests a scale separation and thus the existence of a simplified description
of the turbulent superstructures in geo- and astrophysical settings.Comment: 16 pages (incl. Supplementary Material), 12 figures (all with
downsized figure size
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