Low temperature synthesis of Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 nanopowders by solution based auto combustion method

Ba(Zr_0.2Ti_0.8)O₃–0.5(Ba_0.7Ca_0.3)TiO₃ (BZT–BCT) nanopowders were synthesized by citrate–nitrate auto combustion method using TiO₂ as a source of titanium. The formation mechanism, phase evolution and particle size were investigated using thermal analysis, Fourier transform infra-red spectroscopy, X-ray diffraction, Raman spectroscopy and transmission electron microscope. The molar ratio of metal, citric acid and ethylene diamine tetraacetic acid was kept at 1:1.5:0.1 and pH ~ 9, to get a uniform and complete combustion. Perovskite BZT–BCT was formed in the as-burnt state (280 °C), though calcination at 700 °C is required to remove a small amount of impurities, which is significantly lower than the solid state reaction method. The particle size of BZT–BCT powder was in the range of 40–70 nm.     

Spectroscopic ellipsometry of multilayer dielectric coatings

Multilayer dielectric coatings deposited by e-beam evaporation have been characterised by the phase modulated spectroscopic ellipsometer (PMSE). Measurements have been done on various multilayer thin films devices e.g., high reflectivity mirror, narrow band filter, beam combiner, beam splitter, etc. consisting of several bilayers of TiO₂/SiO₂. Results have been shown here for the first two samples. The measured Ellipsometry spectra are fitted with theoretical spectra generated assuming appropriate models regarding the sample structures. Optical constants of the substrates and the SiO₂ films have been supplied and trial dispersion relations have been used for the optical constants of the TiO₂ layers. The fittings have been done by minimising the squared difference (χ²) between the measured and calculated values of the ellipsometric parameters (ψ and Δ) and accurate information have been derived regarding the thickness and refractive indices of the different layers.     

Alginate-coated alginate-polyethyleneimine beads for prolonged release of furosemide in simulated intestinal fluid

Furosemide-loaded calcium alginate (ALG), calcium alginate-polyethyleneimine (ALG-PEI) and alginate-coated ALG-PEI (ALG-PEI-ALG) beads were prepared by ionotropic/polyelectrolyte complexation method to achieve controlled release of the drug. Effects of several formulation factors on the characteristics of the beads were investigated. Although variation in formulation factors did not influence the drug-loading efficiency (DLE) of ALG beads, rapid release of the drug in simulated intestinal fluid (SIF) could not be prevented. PEI treatment of ALG beads, however, prolonged the drug release considerably. Ionic interaction, as appeared from FTIR studies, between alginate and PEI led to the formation of polyelectrolyte complex membrane, the thickness of which was dependent on the conditions of PEI treatment as demonstrated by scanning electron microscopy (SEM). The membrane acted as a physical barrier to drug release from ALG-PEI beads. Alginate coating of ALG-PEI beads further prolonged the release of the drug by increasing membrane thickness and reducing swelling of the beads possibly by blocking the surface pores. Differential scanning calorimetry (DSC) study indicated that drug was not degraded by PEI treatment. The release data from ALG-PEI beads showed a good fit in power law expression, whereas the release data from ALG-PEI-ALG beads were found to fit in modified power law expression, and the mechanism of drug release changed from super case II transport to nearly Fickian transport, depending on the degree of gelation and formation of polyelectrolyte complex membrane.     

Effect of Microstructure on the Creep Properties of Ti–6Al–4V Alloys: An Analysis

The effects of microstructure types and microstructural parameters on creep properties were investigated systematically through an analysis of microstructure and creep properties of Ti–6Al–4V alloys based on the available literature data. The results indicated that the creep properties of the Ti–6Al–4V alloy are strongly dependent on microstructure type. Creep resistance of Ti–6Al–4V alloys is better in lamellar microstructure followed by bimodal and equiaxed microstructure respectively. Also, microstructural parameters such as the size of both prior beta grain and alpha colony and thickness of alpha lamellae in the lamellar microstructure, the volume fraction of primary alpha phase in bimodal microstructure and size of alpha phase in equiaxed microstructure can influence the creep properties.     

An approach toward multiscale modeling of direct metal laser sintering process

Direct Metal Laser Sintering (DMLS) is a relatively new technology which produces three dimensional fully dense complex shaped components directly from the powder material in a layer by layer fashion. This is a rapid manufacturing technique, in which the qualities of build parts are dependent completely on the microstructure along with process parameters. Thus, for fabricating of a sound defect-free component in DMLS process, it is required to understand the processing mechanism as well as the process parameter effect. Also to predict the part microstructures during the process may be an important factor for process optimization. The present article gives an idea about the DMLS process with its process feature and provides a comprehensive knowledge for further application of numerical modeling approaches on multiple lengths and time scales to describe different aspects of DMSL process.     

Cooperative Target-centric Formation Control without Relative Velocity Measurements under Heterogeneous Networks

This paper proposes distributed control laws for a group of unmanned aerial vehicles (UAVs) to make and maintain a circular formation around a maneuvering target. The work considers usage of heterogeneous communication networks to achieve the desired formation. Two different scenarios are considered on velocity information. In both scenarios, it is assumed that each UAV has its own position and velocity measurements available to itself. However, the team is unable to exchange velocity information among themselves. In the first scenario, each agent uses its own position and velocity information in the consensus algorithm. In the second scenario, agents need only position information for the consensus algorithm. For both the approaches, each agent calculates a virtual estimate of target’s velocity from the received information and exchanges the estimate with its neighbors. The control algorithms are developed using heterogeneous communication networks to satisfy a communication bandwidth constraint. Three different communication networks are used to circulate position information, virtual estimates, and its time derivatives. The graphs representing communication networks are undirected and connected. Further, it is considered that there is at least one UAV (agent) receiving position, velocity, and acceleration information of the target. The agent receiving target’s position need not be the same agent which receives velocity and/or acceleration information of the maneuvering target. However, the target does not receive any information from any agent. Using Barbalat’s lemma, the stability of the target-centric formation of a group of UAVs is analyzed. The performance of the proposed laws are illustrated through numerical simulations.     

Strain induced melt activation — an effective route to produce high performance alloy plates and sheets

Processing of alloys in the semi solid state, within the liquidus and solidus temperature, has several potential advantages over casting and forging, such as reduction of macrosegregation, porosity and improved properties. A356 alloy produced by means of conventional gravity die casting, rheocasting and strain induced melt activation (SIMA) process has been investigated and their microstructure, mechanical and tribological properties were compared. The microstructure of conventional cast sample is fully dendritic in contrast to spheroidal morphology in rheocast and SIMA samples. The mechanical properties of the SIMA samples are considerably higher than that of conventional cast and rheocast samples. The volumetric wear loss and co-efficient of friction in SIMA samples are always less than those in conventional cast samples at all loads.     

Microstructure and second-phase particles in low- and high-pressure die-cast magnesium alloy AM50

The microstructure and phase composition of low-pressure die-cast (LPDC) and high-pressure diecast (HPDC) magnesium alloy AM50 were examined by transmission electron microscopy (TEM) techniques in combination with optical microscopy, scanning electron microscopy (SEM), and electron-probe microanalysis (EPMA). It has been established that the dimensions and morphology of the constituent phases (α-Mg solid solution, Mg₁₇Al₁₂, and Al₈Mn₅) depend on the processing parameters. The results obtained suggest that there is a ternary eutectic with the aforementioned three phases in the Mg-Al-Mn system. Phase transformations leading to the observed microstructures are discussed.     

TFMD-SDVN: a trust framework for misbehavior detection in the edge of software-defined vehicular network

The Journal of Supercomputing - In this paper, a trust framework is proposed for misbehavior detection in software defined vehicular networks (TFMD-SDVN) to detect the correct events in the network...