Multipass FSP on AA6063-T6 Al: Strategy to fabricate surface composites

Surface composites were fabricated on AA6063-T6 base metal using silicon carbide (SiC) reinforcement particles by friction stir processing (FSP). Influence of multiple FSP passes was investigated on the SiC particle distribution, processed zone dimensions, and microhardness of fabricated composites. The rotational speed, traverse speed, and tool tilt were kept constant and the numbers of passes were varied at 2, 4, 6, and 8. The particle distribution in processed zone was analyzed using OM and SEM, while microhardness were evaluated by Vickers indentation test. The results reveal that with increase in FSP passes there is increase in processed zone dimensions and elimination of defects such as agglomeration of particles and void. The microhardness of reinforced region was increased uniformly with increasing passes which is attributed to homogeneous distribution of reinforcement particles. The peak microhardness value of 81.9 Hv was obtained in sample which is processed with eight numbers of FSP passes. Processed zone indicates good bonding with the substrate and grain refinement.     

Performance analysis of a generalised radiative heat engine based on new maximum efficient power density approach

Efficient power density (EPD), defined as the ratio of efficient power to the maximum volume of working fluid, is taken as the objective for performance analysis and optimisation of an internally and externally irreversible radiative Carnot heat engine model from the viewpoint of finite-time thermodynamics or entropy generation minimisation. Maximising the value of EPD gives maximum efficient power density (MEPD). Results obtained are compared with those obtained using maximum efficient power (MEP) criteria, maximum power density (MPD) criteria and maximum power (MP) criteria. The results showed that the engine design at MEPD conditions has an advantage of smaller size and is more efficient than those designed at MP, MPD and MEP conditions.     

Erratum to: Development of a Reconfigurable and Miniaturized CPW Antenna for Selective and Wideband Communication

Wireless Personal Communications -     

Some New Properties of Negation of a Probability Distribution

The properties of negation of a probability distribution recently defined by Yager 1 are studied. Furthermore, the negation of joint and marginal probability distributions in the bivariate case has been defined and their properties are studied. Finally, we have defined a new entropy function for determination of uncertainty associated with the negation of a probability distribution and the events associated with it.     

Sodium alginate incorporated with magnesium nitrate as a novel solid biopolymer electrolyte for magnesium-ion batteries

Solid biopolymer electrolytes have gained much attention in recent years. Due to their various advantages, it can be used in advanced electrochemical devices. The present study focuses on synthesizing and characterizing natural solid biopolymer electrolytes that consist of sodium alginate as the host polymer and magnesium nitrate (Mg(NO₃)₂.6H₂O) as the ionic dopant via solution casting technique. X-ray diffraction analysis of prepared solid biopolymer electrolytes validates the increase in the amorphous nature as salt concentration increases. The interaction and the complexation between the host biopolymer and the magnesium salt are confirmed by Fourier transforms infrared spectroscopy. The solid biopolymer electrolyte composition of 40 M wt.% NaAlg:60 M wt.% Mg(NO₃)₂·6H₂O possesses optimum ionic conductivity value of the order of 4.58?×?10^?3 S cm^?1 as observed by the AC impedance spectroscopy analysis at room temperature. The glass transition temperature (T_g) of the prepared solid biopolymer electrolytes has been studied using differential scanning calorimetry. Linear sweep voltammetry study reveals that the highest magnesium ion-conducting membrane has electrochemical stability of 3.5 V. Further, an optimum ionic conducting solid biopolymer membrane (40 M wt.% NaAlg:60 M wt.% Mg(NO₃)₂·6H₂O) has been utilized to fabricate a primary magnesium ion conducting battery. The open circuit voltage of the proposed solid biopolymer membrane is 1.93 V, and the performance of the battery has been studied.

     

The influence of the pore size and its distribution in a carbon paper electrode on the performance of a PEM Fuel cell

Porous conducting carbon paper with its unique combination of properties acts as the backing material of electrode in a fuel cell. It not only assists in the flow of electrons and reactant gases but also acts as an effective support for the electrolyte and the catalyst layer. The electrically conducting porous carbon paper was prepared by adopting a modified process of preparation which involves molding together several carbon fiber preforms in the form of laminates rather than a single preform. The method was found to influence the characteristics of the paper significantly and resulted in improved performance of the unit fuel cell employing the laminated paper as electrode. The I-V performance of the fuel cell using carbon paper formed by molding single ply showed a peak power density of 573 mW/cm² as compared to that of 722 mW/cm² for three ply laminates, a value very close to that of achieved by using Toray (Japan) carbon paper (782 mW/cm²) under identical operating conditions.     

Effect of base dissipation on the granular flow down an inclined plane

The effect of base dissipation on the granular flow down an inclined plane is examined by altering the coefficient of restitution between the moving and base particles in discrete element (DE) simulations. The interaction laws between two moving particles are kept fixed, and the coefficient of restitution (damping constant in the DE simulations) between the base and moving particles are altered to reduce dissipation, and inject energy from the base. The energy injection does result in an increase in the strain rate by up to an order of magnitude, and the temperature by up to two orders of magnitude at the base. However, the volume fraction, strain rate and temperature profiles in the bulk (above about 15 particle diameters from the base) are altered very little by the energy injection at the base. We also examine the variation of h _stop , the minimum height at the cessation of flow, with energy injection from the base. It is found that at a fixed angle of inclination, h _stop decreases as the energy dissipation at the base decreases.     

An automated algorithm for online detection of fragmented QRS and identification of its various morphologies

Fragmented QRS (f-QRS) has been proven to be an efficient biomarker for several diseases, including remote and acute myocardial infarction, cardiac sarcoidosis, non-ischaemic cardiomyopathy, etc. It has also been shown to have higher sensitivity and/or specificity values than the conventional markers (e.g. Q-wave, ST-elevation, etc.) which may even regress or disappear with time. Patients with such diseases have to undergo expensive and sometimes invasive tests for diagnosis. Automated detection of f-QRS followed by identification of its various morphologies in addition to the conventional ECG feature (e.g. P, QRS, T amplitude and duration, etc.) extraction will lead to a more reliable diagnosis, therapy and disease prognosis than the state-of-the-art approaches and thereby will be of significant clinical importance for both hospital-based and emerging remote health monitoring environments as well as for implanted ICD devices. An automated algorithm for detection of f-QRS from the ECG and identification of its various morphologies is proposed in this work which, to the best of our knowledge, is the first work of its kind. Using our recently proposed time–domain morphology and gradient-based ECG feature extraction algorithm, the QRS complex is extracted and discrete wavelet transform (DWT) with one level of decomposition, using the ‘Haar’ wavelet, is applied on it to detect the presence of fragmentation. Detailed DWT coefficients were observed to hypothesize the postulates of detection of all types of morphologies as reported in the literature. To model and verify the algorithm, PhysioNet''s PTB database was used. Forty patients were randomly selected from the database and their ECG were examined by two experienced cardiologists and the results were compared with those obtained from the algorithm. Out of 40 patients, 31 were considered appropriate for comparison by two cardiologists, and it is shown that 334 out of 372 (89.8%) leads from the chosen 31 patients complied favourably with our proposed algorithm. The sensitivity and specificity values obtained for the detection of f-QRS were 0.897 and 0.899, respectively. Automation will speed up the detection of fragmentation, reducing the human error involved and will allow it to be implemented for hospital-based remote monitoring and ICD devices.