Natural Frequency based delamination estimation in GFRP beams using RSM and ANN

The importance of delamination detection can be understood from aircraft components like Vertical Stabilizer, which is subjected to heavy vibration during the flight movement and it may lead to delamination and finally even flight crash can happen because of that. Any solid structure's vibration behaviour discloses specific dynamic characteristics and property parameters of that structure. This research investigates the detection of delamination in composites using a method based on vibration signals.  The composite material's flexural stiffness and strength are reduced as a result of delaminations, and vibration properties such as natural frequency responses are altered. In inverse problems involving vibration response, the response signals such as natural frequencies are utilized to find the location and magnitude of delaminations. For different delaminated beams with varying position and size, inverse approaches such as Response Surface Methodology (RSM) and Artificial Neural Network (ANN) are utilized to address the inverse problem, which aids in the prediction of delamination size and location

Artificial neural network based delamination prediction in composite plates using vibration signals

Dynamic loading on composite components may induce damages such as cracks, delaminations, etc. and development of an early damage detection technique for delaminations is one of the most important aspects in ensuring the integrity and safety of composite components. The presence of damages such as delaminations on the composites reduces its stiffness and further changes the dynamic behaviour of the structures. As the loss in stiffness leads to changes in the natural frequencies, mode shapes, and other aspects of the structure, vibration analysis may be the ideal technique to employ in this case. In this research work, the supervised feed-forward multilayer back-propagation Artificial Neural Network (ANN) is used to determine the position and area of delaminations in GFRP plates using changes in natural frequencies as inputs. The natural frequencies were obtained by finite element analysis and results are validated by experimentation. The findings show that the suggested technique can satisfactorily estimate the location and extent of delaminations in composite plates

Bulk viscosity in hyperonic star and r-mode instability

We consider a rotating neutron star with the presence of hyperons in its core, using an equation of state in an effective chiral model within the relativistic mean field approximation. We calculate the hyperonic bulk viscosity coefficient due to nonleptonic weak interactions. By estimating the damping timescales of the dissipative processes, we investigate its role in the suppression of gravitationally driven instabilities in the $r$-mode. We observe that $r$-mode instability remains very much significant for hyperon core temperature of around $10^8$K, resulting in a comparatively larger instability window. We find that such instability can reduce the angular velocity of the rapidly rotating star considerably upto $\sim0.04 \Omega_K$, with $\Omega_K$ as the Keplerian angular velocity.Comment: 10 pages including 7 figure

Artificial neural network based delamination prediction in composite plates using vibration signals

Dynamic loading on composite components may induce damages such as cracks, delaminations, etc. and development of an early damage detection technique for delamination prediction is one of the most important aspects in ensuring the integrity and safety of such components. The presence of damages such as delaminations on the composites reduces its stiffness and changes the dynamic behaviour of the structures. As the loss in stiffness leads to changes in the natural frequencies, mode shapes, and other aspects of the structure, vibration analysis may be the ideal technique for delamination prediction. In this research work, the supervised feed-forward multilayer back-propagation Artificial Neural Network is used to determine the position and area of delaminations in glass fiber-reinforced polymer (GFRP) plates using changes in natural frequencies as inputs. The natural frequencies were obtained by finite element analysis and results are validated experimentally. The findings show that the suggested technique can satisfactorily estimate the location and extent of delaminations in composite plates

Combining surplus production and spectral models to define fishery management advisory - a case study using the threadfinbream fishery along Kerala coast

Threadfinbreams have emerged as a very important resource along the west coast of India both as food fish and as raw material for export oriented surimi production. The state of Kerala contributes 30-40% of the total threadfinbream production in the country landed mainly by multiday trawlers. The analysis of the catch and effort of threadfinbreams during 1985-2012 along Kerala revealed that the landing recently showed decline despite increased fishing effort. A simulation study was conducted to examine the effects of restrictions imposed on the total hours of operation of multiday trawlers on the threadfinbream fishery of Kerala. A genetic algorithm was used for simulation of threadfinbream fishery along Kerala coast using surplus production model and spectral time series methods. Numerical simulations were made for selected seven levels of exploitation and the average biomass and average yield were calculated and compared with the maximum sustainable yield (MSY). The results indicated that the optimum level of exploitation is at 85.1% of the current level of exploitation to keep the average annual yields during 2013-2020 just below MSY

Stock structure analysis of Indian mackerel Rastrelliger kanagurta (Cuvier, 1817) from south-east and south-west coasts of India using truss network system

A total of 200 specimens of Indian mackerel (Rastrelliger kanagurta) were collected from Kochi in the south-west coast and Chennai in the south-east coast and they were subjected to truss analysis. A truss network was constructed by interconnecting 10 landmarks to form a total of 21 truss distance variables extracted from the landmarks. The transformed truss measurements were subjected to factor analysis which revealed that there is no separation of the stocks along south-east and south-west coasts. Thus the present study has indicated that the population of Indian mackerel from south-east and south-west coasts remains the same

Stock structure analysis of oil sardine Sardinella longiceps (Valenciennes, 1847) from southeast and southwest coasts of India

A total of 200 specimens of oil sardine Sardinella longiceps collected from Kochi in the southwest coast and Chennai in the southeast coast were subjected to truss analysis. A truss network was constructed by interconnecting 10 landmarks to form a total of 21 truss distance variables extracted from the landmarks. The transformed truss measurements were subjected to factor analysis which revealed that there is no separation of the stocks along southeast and southwest coasts. The marginal differences in shape and form are attributed to the ecological differences in the habitats which is evident from differences in length weight relationships and feeding intensity of the population along these two coasts

Properties of the nuclear medium

We review our knowledge on the properties of the nuclear medium that have been studied, along many years, on the basis of many-body theory, laboratory experiments and astrophysical observations. First we consider the realm of phenomenological laboratory data and astrophysical observations, and the hints they can give on the characteristics that the nuclear medium should possess. The analysis is based on phenomenological models, that however have a strong basis on physical intuition and an impressive success. More microscopic models are also considered, and it is shown that they are able to give invaluable information on the nuclear medium, in particular on its Equation of State. The interplay between laboratory experiments and astrophysical observations are particularly stressed, and it is shown how their complementarity enriches enormously our insights into the structure of the nuclear medium. We then introduce the nucleon-nucleon interaction and the microscopic many-body theory of nuclear matter, with a critical discussion about the different approaches and their results. The Landau Fermi Liquid theory is introduced and briefly discussed. As illustrative example, we discuss neutron matter at very low density, and it is shown how it can be treated within the many-body theory. A section is dedicated to the pairing problem. The connection with nuclear structure is then discussed, on the basis of the Energy Density Functional method. The possibility to link the physics of exotic nuclei and the astrophysics of neutron stars is particularly stressed. Finally we discuss the thermal properties of the nuclear medium, in particular the liquid-gas phase transition and its connection with the phenomenology on heavy ion reactions and the cooling evolution of neutron stars. The presentation has been taken for non-specialists and possibly for non-nuclear physicists.Comment: 90 pages, 29 figures, revised versio

Flow in heavy-ion collisions - Theory Perspective

I review recent developments in the field of relativistic hydrodynamics and its application to the bulk dynamics in heavy-ion collisions at the Relativistic Heavy- Ion Collider (RHIC) and the Large Hadron Collider (LHC). In particular, I report on progress in going beyond second order relativistic viscous hydrodynamics for conformal fluids, including temperature dependent shear viscosity to entropy density ratios, as well as coupling hydrodynamic calculations to microscopic hadronic rescattering models. I describe event-by-event hydrodynamic simulations and their ability to compute higher harmonic flow coefficients. Combined comparisons of all harmonics to recent experimental data from both RHIC and LHC will potentially allow to determine the desired details of the initial state and the medium properties of the quark-gluon plasma produced in heavy-ion collisions.Comment: 8 pages, Invited plenary talk at the 22nd International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2011), May 23-28 2011, Annecy, Franc