Effect of T6 heat treatment on damping characteristics of Al/RHA composites

In the present work, effect of T6 heat treatment on the damping behaviour of aluminum/rice husk ash (RHA) composites fabricated by vortex method was studied using dynamic mechanical analyser (DMA) at frequencies ranging from 1 Hz to 25 Hz at room temperature under three-point bending test mode. The matrix material for the present work was A356·2 and reinforced with different weight % of 4, 6 and 8 rice husk ash particles. It was observed that composite exhibits high damping capacities than unreinforced alloy and increases with increase in weight % and the storage modulus increases with the addition of RHA particles but decreases with the increase in weight %. The heat treated composites exhibit higher damping capacity than the composites without heat treatment and increases with the increase in weight % of the reinforcement and loss in the storage modulus was observed and further decreases with the increase in the weight % of reinforcement. The related mechanisms were also discussed.     

Apparatus and method for heat-run test on high-power PWM converters with low energy expenditure

Before installation, a voltage source converter is usually subjected to heat-run test to verify its thermal design and performance under load. For heat-run test, the converter needs to be operated at rated voltage and rated current for a substantial length of time. Hence, such tests consume huge amount of energy in case of high-power converters. Also, the capacities of the source and loads available in the research and development (R&D) centre or the production facility could be inadequate to conduct such tests. This paper proposes a method to conduct heat-run tests on high-power, pulse width modulated (PWM) converters with low energy consumption. The experimental set-up consists of the converter under test and another converter (of similar or higher rating), both connected in parallel on the ac side and open on the dc side. Vector-control or synchronous reference frame control is employed to control the converters such that one draws certain amount of reactive power and the other supplies the same; only the system losses are drawn from the mains. The performance of the controller is validated through simulation and experiments. Experimental results, pertaining to heat-run tests on a high-power PWM converter, are presented at power levels of 25 kVA to 150 kVA.     

Identification of β-SiC surrounded by relatable surrounding diamond medium using weak Raman surface phonons

It is difficult to detect β-SiC using micro-Raman scattering, if it is surrounded by carbon medium. Here, β-SiC is identified in the presence of a relatable surrounding diamond medium using subtle, but discernible Raman surface phonons. In this study, diamond/β-SiC nanocomposite thin film system is considered in which nanosized β-SiC crystallites are surrounded by a relatable nanodiamond medium that leads to the appearance of a weak Raman surface phonon band at about 855 cm^???1. Change in the nature of the surrounding material structure and its volume content when relatable, will affect the resultant Raman response of β-SiC phase as seen in the present case of diamond/β-SiC nanocomposite thin films.     

Fighter aircraft lateral directional axes full envelope control law design

A decoupled wide envelope lateral/directional axes control design is presented for a supermanoeuvrable version of an F-18 aircraft. A control structure is developed that separates gain scheduling issues from aircraft performance issues. Flight condition dependent state and control effectiveness variations are accounted for by an inner loop controller designed using eigenstructure assignment. Structured singular value synthesis is used to design an implicit model following outer loop controller that addresses flying qualities performance specifications. A control selector is designed that generates lateral/directional aerodynamic and thrust vectoring commands from generalized control inputs of roll and yaw acceleration. Flying qualities and robustness analyses show that the control system performs well despite neglected dynamics and system uncertainties. Nonlinear simulations are presented showing excellent decoupling of roll and yaw responses.     

Investigations on structural,optical and magnetic properties of solution-combustion-synthesized nanocrystalline iron molybdate

Iron molybdate β-Fe₂ (MoO₄)₃ nanoparticles were synthesized by exploiting the self-propagating high-temperature combustion strategy using hexamine as a fuel. The obtained β-Fe₂(MoO₄)₃ nanoparticles exhibited the orthorhombic crystalline structure, which is evidenced from the XRD pattern. FT-IR spectrum revealed the existence of stretching and bending vibrations of Mo–O–Mo and O–Mo–O bonding in the nanocrystals. The binding energy peaks in the X-ray photoelectron spectroscopy (XPS) spectrum positioned at 710 and 725, 231 and 235 and 530 eV, respectively, correspond to the Fe(2p), Mo(3d) and O(1s) orbitals. Absorption spectrum of nanoparticles showed adequate absorbance of visible region photons of the nanoparticles and also optical bandgap value of β-Fe₂ (MoO₄)₃ nanoparticles as 2.26 eV, which is calculated using the Kubelka–Munk function. The existence of Fe³⁺ and Mo⁶⁺ in β-Fe₂ (MoO₄)₃ is authenticated with the aid of electron paramagnetic resonance spectrum measurements. The obtained nanoparticles have showed methylene blue dye degradation of 98.4% under sunlight irradiation.     

ROLE OF COFACTORS IN BREAKDOWN OF TMAO IN FROZEN RED HAKE MUSCLE

Previously indicated results that cofactor concentrations were the rate-limiting factor in the production of DMA in frozen red hake muscle were confirmed. Both the Fe-reducing agent (ascorbate, cysteine) and the flavin-NADH systems which had been previously shown to be effective in vitro, were demonstrated to also function in minced muscle and in reconstituted muscle, i.e., muscle from which the low molecular weight fraction had been removed. The evidence implies that an oxidation-reduction cycle of Fe is involved in the breakdown of TMAO to DMA. Activity with the flavin system is greatly increased in the presence of glucose oxidase and glucose which would remove O₂ from the system. Fe was effective in increasing DMA production under all conditions, whereas Fe⁺³ was effective only in the presence of reducing agents and/or anaerobic conditions. Enzymes capable of destroying cofactors when added to minced muscle tissue before frozen storage inhibited the rate of formation of DMA. The percentage of formaldehyde produced which was bound (unreactive to the Nash reagent) was much higher in minced muscle than in reconstituted muscle, indicating that a large fraction of the formaldehyde produced reacts with the low molecular weight fraction.     

Optimization of burnishing parameters and determination of select surface characteristics in engineering materials

The present study is aimed at filling the gaps in scientific understanding of the burnishing process, and also to aid and arrive at technological solutions for the surface modifications based on Burnishing of some of the commonly employed engineering materials. The effects of various burnishing parameters on the surface characteristics, surface microstructure, micro hardness are evaluated, reported and discussed in the case of EN Series steels (EN 8, EN 24 and EN 31), Aluminum alloy (AA6061) and Alpha-beta brass. The burnishing parameters considered for studies principally are burnishing speed, burnishing force, burnishing feed and number of passes. Taguchi technique is employed in the present investigation to identify the most influencing parameters on surface roughness. Effort is also made to identify the optimal burnishing parameters and the factors for scientific basis of such optimization. Finally, a brief attempt is made to construct the Burnishing maps with respect to strength level (in this case, average micro hardness of unburnished material).     

Triple pulse doppler radar†

A new type of pulse doppler radar has been described, which depends on three pulses transmitted in sequence at three different mutually coherent frequencies. The cancellation of stationary targets and signal processing for extraction of moving targets is by mutual comparison of the echo pulses. The system has no blind speeds for all practical situations and is thus suitable for very high speed targets without resorting to.PRF stagger or wobbulation.     

Framework for morphometric classification of cells in imaging flow cytometry

Imaging flow cytometry is an emerging technology that combines the statistical power of flow cytometry with spatial and quantitative morphology of digital microscopy. It allows high‐throughput imaging of cells with good spatial resolution, while they are in flow. This paper proposes a general framework for the processing/classification of cells imaged using imaging flow cytometer. Each cell is localized by finding an accurate cell contour. Then, features reflecting cell size, circularity and complexity are extracted for the classification using SVM. Unlike the conventional iterative, semi‐automatic segmentation algorithms such as active contour, we propose a noniterative, fully automatic graph‐based cell localization. In order to evaluate the performance of the proposed framework, we have successfully classified unstained label‐free leukaemia cell‐lines MOLT, K562 and HL60 from video streams captured using custom fabricated cost‐effective microfluidics‐based imaging flow cytometer. The proposed system is a significant development in the direction of building a cost‐effective cell analysis platform that would facilitate affordable mass screening camps looking cellular morphology for disease diagnosis.     

Robust control for linear systems with structured state space uncertainty

A recent sufficient condition for the stability robustness of linear systems with time-varying norm bounded state space uncertainty is extended to include the structure of the uncertainty. Our new result requires that the nominal eigenvalues lie to the left of a vertical line in the complex plane which is determined by a norm involving the structure of the uncertainty and the nominal closed-loop eigenvector matrix. Therefore, this robustness result is especially well suited to the design of control systems using eigenstructure assignment. When the uncertainty is time-invariant, our norm is also an upper bound on the incremental eigenvalue perturbations. We also consider the use of Perron weightings to reduce conservatism and the extension of the results to discrete time systems.