Multi-Objective Genetic Algorithm Based Optimization of Age Hardening for AA6063 Alloy

The present article attempts to optimize the process parameters of artificial ageing for an AA6063 Al-Mg-Si alloy using multi-objective genetic algorithm (MOGA) to simultaneously achieve the maximum ultimate tensile strength (UTS) and percentage of elongation (El). For this, a feed-forward multi-layered perceptron artificial neural network (ANN) has been developed which is trained by the scale conjugate gradient back propagation algorithm. The dataset required for the model has been compiled from the experimental results of this study, as well as, from the open literature. The network consists of solutionizing time and temperature, storage time/pre-ageing, rate of quenching, ageing time and temperature as input variables and UTS, El as their outputs. The developed ANN model establishes the interrelationships between the input and output variables which can serve as objective functions for the optimization, following the theory of Pareto-optimality. The Pareto solution generated from MOGA between UTS and El assists to conclude that the desired combination of high strength and ductility has been achieved through slow cooling after solutionizing, high pre-ageing time and high temperature of ageing. Furthermore, the designed heat treatment schedule through MOGA has been applied to the selected alloy on an experimental basis which shows satisfactory results. © Published under licence by IOP Publishing Ltd

Critical behavior of loops and biconnected clusters on fractals of dimension d < 2

We solve the O(n) model, defined in terms of self- and mutually avoiding loops coexisting with voids, on a 3-simplex fractal lattice, using an exact real space renormalization group technique. As the density of voids is decreased, the model shows a critical point, and for even lower densities of voids, there is a dense phase showing power-law correlations, with critical exponents that depend on n, but are independent of density. At n=-2 on the dilute branch, a trivalent vertex defect acts as a marginal perturbation. We define a model of biconnected clusters which allows for a finite density of such vertices. As n is varied, we get a line of critical points of this generalized model, emanating from the point of marginality in the original loop model. We also study another perturbation of adding local bending rigidity to the loop model, and find that it does not affect the universality class.Comment: 14 pages,10 figure

Electrical conduction in composites containing copper core-copper oxide shell nanostructure in silica gel

Composites of nanometre-sized copper core-copper oxide shell with diameters in the range 6.1 to 7.3 nm dispersed in a silica gel were synthesised by a technique comprising reduction followed by oxidation of a suitably chosen precursor gel. The hot pressed gel powders mixed with nanometre-sized copper particles dispersed in silica gel showed electrical resistivities several orders of magnitude lower than that of the precursor gel. Electrical resistivities of the different specimens were measured over the temperature range 30 to 300°C. Activation energies for the coreshell nanostructured composites were found to be a fraction of that of the precursor gel. Such dramatic changes are ascribed to the presence of an interfacial amorphous phase. The resistivity variation as a function of temperature was analysed on the basis of Mott's small polaron hopping conduction model. The effective dielectric constant of the interfacial phase as extracted from the data analysis was found to be much higher than that of the precursor glass. This has been explained as arising from the generation of very high pressure at the interface due to the oxidation step to which the copper nanoparticles are subjected

Modulus stabilization of generalized Randall Sundrum model with bulk scalar field

We study the stabilization of inter-brane spacing modulus of generalized warped brane models with a nonzero brane cosmological constant. Employing Goldberger-Wise stabilization prescription of brane world models with a bulk scalar field, we show that the stabilized value of the modulus generally depends on the value of the brane cosmological constant. Our result further reveals that the stabilized modulus value corresponding to a vanishingly small cosmological constant can only resolve the gauge hierarchy problem simultaneously. This in turn vindicates the original Randall-Sundrum model where the 3-brane cosmological constant was chosen to be zero.Comment: 12 Pages, 1 figure, Revtex, Version to appear in Euro. Phys. Let

High spin states of 204^{204}At: search for isomeric states and evaluation of shears band structure

High spin states of neutron deficient Trans-Lead nucleus $^{204}$At were populated up to $E_x \sim 8\,{\rm MeV}$ through the $^{12}$C + $^{197}$Au fusion evaporation reaction. Decay of the high spin states including prompt and delayed gamma ray emission were studied to understand the underlying nuclear structure. The level scheme, which was partly known from earlier studies, was extended further through our experiment and analysis of spin and parity of the associated levels. An isomeric $16^+$ level $(\tau=52(5)\, {\rm ns})$, corresponding to $M2$ transition, was established from our measurements. Attempts were made at interpretation of the excited states based on multi quasiparticle and hole structure involving $2f_{5/2}$, $1h_{9/2}$, and $1i_{13/2}$ shell model states, along with moderate core excitation. Magnetic dipole band structure over the spin parity range:~$16^+ - 23^+$, which was found in the earlier Gammasphere study, was confirmed and explored in more detail, including the missing cross-over $E2$ transitions. Band-crossing along the shears band was observed and compared with the evidence of similar phenomena in the neighboring neutron deficient $^{202}$Bi, $^{205}$Rn isotones and the neighbouring $^{203}$At isotope. Based on comparison of the measured $B(M1)/B(E2)$ values for transitions along the band with the semiclassical model based estimates, the shears band of $^{204}$At was firmly established along with the level scheme

Bacteriological examination of drinking water in Burdwan, India with reference to coliforms

Most probable number (MPN) test was done to detect the coliform in water samples collected from mobile vendors, sweet shops and tap water supplied from Burdwan municipality. The study revealed that the number of coliforms was very high (1600) in water samples collected from mobile vendors. The bacteria were identified as Escherichia coli. Bacteriological examination of water samples collected from different sources showed that the water of mobile vendors and sweet shops of Burdwan marketarea was not potable while the municipal tap water was found to be safe for drinking

Mathematical Modelling of ductile erosion behaviour of impacted fly ash particles on steel components of coal fired boiler

In coal-fired power stations about 20% of the ash prod-uced in the boilers is deposited on the boiler walls, economisers, air-heaters and super-heater tubes. An abinitio, first principle based mathematical model emb-odying the mechanisms of erosion involving cutting, wear, plastic deformation wear and effect of temperature on erosion behaviour has been developed to predict erosion rates on the coal fired boiler components such as boiler tubes, economiser and air-preheater assembles at room & elevated temperature

Mathematical modelling of ductile erosion behaviour of impacted fly ash particles on steel components of a coal fired boiler

In coal-fired power stations about 20% of tie ash produced in the boilers is deposited on the boiler walls, economisers, air-heaters and super-heater tubes. An abin-itio, first principle based mathematical model embodying the mechanisms of erosion involving cutting, wear, plastic deformation wear and effect of temperature on erosion behaviour has been developed to predict erosion rates on the coal fired boiler components such as boiler tubes, economiser and air-preheater assemblies at room and elevated temperature

Comparing the spatio-temporal variability of remotely sensed oceanographic parameters between the Arabian Sea and Bay of Bengal throughout a decade

The spatio-temporal variability of sea-surface temperature (SST), photosynthetically active radiation (PAR), chlorophyll-a (Chl-a), particulate organic carbon (POC) and particulate inorganic carbon (PIC) was evaluated in the Arabian Sea (ABS) and Bay of Bengal (BoB), from July 2002 to November 2014 by means of remotely sensed monthly composite Aqua MODIS level-3 data having a spatial resolution of 4.63 km. Throughout the time period under consideration, the surface waters of ABS (27.76 ± 1.12°C) were slightly cooler than BoB (28.93 ± 0.76°C); this was observed during all the seasons. On the contrary, the availability of PAR was higher in ABS (45.76 ± 3.41 mol m-2 d-1) compared to BoB (41.75 ± 3.75 mol m-2 d-1), and its spatial dynamics in the two basins was mainly regulated by cloud cover and turbidity of the water column. The magnitude and variability of Chl-a concentration were substantially higher in ABS (0.487 ± 0.984 mg m-3), compared to BoB (0.187 ± 0.243 mg m-3), and spatially higher values were observed near the coastal waters. Both POC and PIC exhibited higher magnitudes in ABS compared to BoB; however, the difference was substantially high in case of POC. None of the parameters showed any significant temporal trend during the 12-year span, except PIC, which exhibited a significant decreasing trend in ABS

Attenuation of electromagnetic radiation in Nuclear Track Detectors

A systematic study of the attenuation of electromagnetic radiation in Nuclear Track Detectors (NTDs) is carried out. The attenuation of gamma-ray, X-ray, UV, visible, and infrared radiation in NTDs are investigated using NaI(Tl) detector, Gas Electron Multiplier (GEM) detector, UV-Vis spectrophotometer, and FTIR spectrophotometer respectively. The values of some important parameters (e.g., optical depth, attenuation coefficient, etc.) of three commercially available NTDs (PET, Makrofol r and CR-39 r ), at the relevant region of the electromagnetic spectrum, is determined. The details of the experimental techniques and the results are also presented in this paper.Comment: 10 page