38 research outputs found
Application of smart classification techniques to non-destructive testing of composites
Composites manufactured for applications in the automotive industry were non-destructively tested to determine damage using the following techniques:
(1) Low frequency tapping.
(2) High frequency (C-Scan).
(3) Visual imaging.
(4) Low and high temperature pulse video thermography.
Various levels of impact energy were applied to the following types of composites
(I) RIM: Reaction injection moulded.
(II) Woven Glass.
(III) GMT: Glass mat thermoplastic.
Some interesting results were obtained which could be explained through analytical and numerical modelling. These results were analyzed through developments of the following algorithms:
(a) A novel approach to damage detection using wavelength variation and sequence grouping software.
(b) Correlation of the various NDT techniques through one mathematical equation and software.
(c) The introduction of the uniformity factor concept and software to account for variations among samples quality in relation to experimental results.
(d) The development of smart classification system together with standard neural network algorithms for prediction and classification.
The objectives of this research were all achieved
Application of Neural Networks to Matlab Analyzed Hyperspectral Images for Characterization of Composite Structures
MATHEMATICAL MODELING OF THE PROGRAMING FIELD IN A NEURAL SWITCH USING THE SEMI-INFINITE COPLANAR ELECTRODE APPROXIMATION
The design and mathematical modeling of the programing electric field in a neural switch is carried out. The specified function for the switch is to operate as a synaptic processor behaving in an adaptive manner and suitable to be used as a compact programable device with other artificial neural network hardware. Modeling of the switch is carried out by means of complex mathematical analysis employing the Schwarz–Christoffel transform. The effect of inter-electrode separation on the field strength is analyzed in two dimensions. The realized power law function of the programing field is discussed and explained.Neural, mathematical modeling, synapse, memory, information processing
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Abyssal circulation in the Indian Ocean from a 1 / 12 ∘ resolution global hindcast
Abyssal pathways and volume transports in the Indian Ocean obtained from a
1
/
12
∘
global data assimilative hindcast for the years 2004–2006 are presented. The known features of bottom water circulation such as boundary currents and inter-basin exchanges are well represented in the hindcast solution. Further, the hindcast solution reveals a basin-wide, anti-cyclonic deep circulation pattern with the main inflow located in the east, in the Perth Basin, and outflow in the west along the African continent and Madagascar. Inter-basin westward transport at
10
∘
S
across the Ninetyeast Ridge and along the Mascarene Plateau connect the inflow and outflow locations. The model develops a net bottom water inflow of
10
±
8
Sv
(
mean
±
standard deviation
) across
32
∘
S
, below approximately 3500
m of which
4
±
7
Sv
are returned south across the same latitude in the deep layers between 2000 and 3500
m. Significant variability on intra-seasonal, semi-annual and annual time scales is present in the abyssal flow fields. The vertical mixing algorithm, based on resolved vertical shear, suggests enhanced diapycnal upwelling in the vicinity of the Central Indian Ridge
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Performance of two-equation turbulence closures in three-dimensional simulations of the Red Sea overflow
Mixing of overflows released from polar and marginal seas is a key process shaping the structure of the meridional overturning circulation. Ocean general circulation models have difficulty in resolving the overflows, and therefore they must rely on parameterizations. In this study, the performance of a set of turbulence closures in reproducing mixing of an overflow is quantified. We simulate the Red Sea overflow by employing standard
k–
ε,
k–
ω and Mellor–Yamada schemes with various stability functions, as well as a modified
k–
ε model that relies on the prescription of the turbulent Prandtl number rather than on stability functions. The simpler KPP mixing scheme and experiments without turbulent fluxes serve as useful references. To our knowledge, this is the first time that the performance of two-equation turbulence models has been examined so closely using data from an overflow.
It is found that without turbulence closures, the hydrodynamic model has difficulty in reproducing the correct three-dimensional pathway of the Red Sea overflow, consisting of a distinct bifurcation into two diverging channels. All turbulence models capture the vertical structure of this overflow consisting of an interfacial layer, characterized by the density gradient, and a well-mixed bottom layer. Mean eddy diffusivity values from most closures are comparable those from observations. But we find that KPP leads to eddy diffusivity values that are too small while those from Mellor–Yamada with Galperin [Galperin, B., Kantha, L.H., Hassid, S., Rosati, A., 1988. A quasi-equilibrium turbulent energy model for geophysical flows. J. Atmos. Sci. 45, 55–62] stability functions are too large. Such high diffusivities lead to excessive mixing in the bottom layer of the overflow, ultimately resulting in a salinity deficit of approximately 1
psu in the product water mass. Salinity deviations between the models and observations are quantified using both data taken along the channels and two sections across the overflow. KPP and Mellor–Yamada with Galperin (1988) stability functions produce the largest deviations from the observations, while the modified
k–
ε exhibits the smallest deviations. The other four closures fall in between, showing results similar to one another. The performance of the Mellor–Yamada turbulence closure is improved considerably by using the stability functions by Kantha and Clayson [Kantha, L.H., Clayson, C.A., 1994. An improved mixed layer model for geophysical applications. J. Geophys. Res. 99 (December), 25235–25266], which allow for a stationary Richardson number of 0.21. In conclusion, we find that most turbulence closures lead to a satisfactory reproduction of the Red Sea overflow, within the temporal and spatial sampling uncertainties of the REDSOX data, provided that fairly high-resolution regional models are used
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Very large eddy simulation of the Red Sea overflow
Mixing between overflows and ambient water masses is a critical problem of deep-water mass formation in the downwelling branch of the meridional overturning circulation of the ocean. Modeling approaches that have been tested so far rely either on algebraic parameterizations in hydrostatic ocean circulation models, or on large eddy simulations that resolve most of the mixing using nonhydrostatic models.
In this study, we examine the performance of a set of turbulence closures, that have not been tested in comparison to observational data for overflows before. We employ the so-called very large eddy simulation (VLES) technique, which allows the use of
k
–
ε
models in nonhydrostatic models. This is done by applying a dynamic spatial filtering to the
k
–
ε
equations. To our knowledge, this is the first time that the VLES approach is adopted for an ocean modeling problem.
The performance of
k
–
ε
and VLES models are evaluated by conducting numerical simulations of the Red Sea overflow and comparing them to observations from the Red Sea Outflow Experiment (REDSOX). The computations are constrained to one of the main channels transporting the overflow, which is narrow enough to permit the use of a two-dimensional (and nonhydrostatic) model. A large set of experiments are conducted using different closure models, Reynolds numbers and spatial resolutions.
It is found that, when no turbulence closure is used, the basic structure of the overflow, consisting of a well-mixed bottom layer (BL) and entraining interfacial layer (IL), cannot be reproduced. The
k
–
ε
model leads to unrealistic thicknesses for both BL and IL, while VLES results in the most realistic reproduction of the REDSOX observations