The influence of non-newtonian oil film short journal bearings on the stability of a rigid rotor

The stability behaviour of rotors supported in plain cylindrical cavitated non-Newtonian fluid film journal bearings is investigated. Expressions for the journal force due to the fluid film are developed for the short bearing approximate solution to the modified form of Reynolds' equation. Linearised fluid film coefficients are used for the stability analysis. The results show that the dynamic fluid film coefficients for non-Newtonian lubricants are different from Newtonian coefficients and that they have a strong influence on the stability of rotor-bearing systems.     

Studies on miscibility of polyacrylamide/polyethylene glycol blends

Miscibility studies have been conducted on solutions of blends of polyacrylamide (PAAm) and polyethylene glycol (PEG) over an extended range of concentrations in water. The ultrasonic velocity, viscosity, density, and refractive index of the blends have been measured for different compositions viz., 0/100, 10/90, 20/80, 30/70, 40/60, 50/50, 60/40, 70/30, 80/30, 90/10, and 100/0 of PAAm/PEG blends at 30°C. The interaction parameters such as μ and α have been evaluated using the viscosity data to probe the miscibility. The obtained results have been confirmed by the ultrasonic velocity, density, and refractive index. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2048–2053, 2007     

Load effects on fracture of concrete

Failure of concrete under any type of loading is associated with the development of visible cracks and very large inelastic deformations. These cracks are the precipitation of internal microcracks under high strains. The concrete system consists of microcracks even before the application of load. These microcracks propagate under different types of loading to form failure planes with a resulting loss in structural strength leading to failure. This paper discusses the formation of microcracks in concrete under short-term and sustained loadings. Concrete specimens were subjected to constant and incremental sustained loading and the deformations observed are related to the intensity of microcracking. The results show that at equal strains, the degree of internal microcracking is considerably reduced if the sustained load is applied incrementally over a period of time rather than applied as a step. It is concluded that the development of combined bond and mortar cracks is essential to cause failure under sustained loading. The longer the time to failure the higher the intensity of internal cracking at failure.     

Improved performance of iron-based redox flow batteries using WO3 nanoparticles decorated graphite felt electrode

Iron flow batteries are having tremendous attraction because of their economic feasibility and environmentally favorable electrolytes. Electrode and electrolyte used in iron-based redox flow batteries (IRFBs) have a vital role in the performances of electrochemical energy storage devices. Therefore designing a suitable electrode and optimization of electrolyte composition is highly needed. Graphite is one of the appropriate electrodes used in flow batteries but they have to be modified to improve the electrical performance. Here, for the first time, WO₃ nanoparticles (WONs) were used to modify graphite felt electrode for IRFBs applications. The effect of loading mass per unit cm² of electrochemically active material has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (Tafel) studies. The ligand based iron-electrolyte along with anion exchange membrane has been selected for the studies. The performance of the modified graphite felt electrode (3 mg/cm²) assembled in 132 cm² cell results in a peak power density of 53 mW/cm² at 40 mA/cm². This study provides information about the improvement in the electrochemical performance of IRFBs.     

Conversion of aluminum foil to powders that react and burn with water

In the US, the total amount of aluminum scrap and waste, including foil, is outpacing efforts to recycle it into conventional aluminum materials. It would be attractive to develop technologies for converting aluminum foil scrap and waste to useful products and energy carriers. The present paper focuses on the feasibility of converting foil to activated Al powders that chemically split water, releasing hydrogen. As a method for this conversion, high-energy ball milling of Al foil with sodium chloride is investigated, with removing NaCl from the obtained powder by dissolution in cold water or methanol. The powders are characterized using BET specific surface area analysis, laser diffraction particle size analysis, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The obtained micron-sized Al powders readily react with warm (35–80 °C) water. Hydrogen evolution is studied using water displacement, while solid byproducts are examined by X-ray diffraction and thermal analysis. The powders are also mixed with gelled water at various mass ratios and combustion of these mixtures is studied in argon environment. With increasing Al concentration, the combustion front velocity increases despite the decrease in the combustion temperature. The burning rate of the stoichiometric mixture of the activated Al powder with water is comparable with the values reported previously for the mixtures based on nanoscale aluminum, while the content of active Al in the obtained micron-sized powder is significantly higher.     

Extended-aperture angle-range estimation of multipleFresnel-region sources with a linear tripole array using cumulants

This paper presents a cumulant-based algorithm to achieve aperture extension for estimating the directions-of-arrival (DOAs) and the ranges of multiple Fresnel-region sources using a linear tripole array. The proposed algorithm defines two cumulant-based matrices, from which the DOA and the range of each source are estimated from the source's tripole steering vector using the ESPRIT technique. These are then used as coarse reference estimates to disambiguate the cyclic phase ambiguities induced from the spatial phase factors when the inter-sensor spacing exceeds a half wavelength. The algorithm does not require two-dimensional searching or parameter pairing, and can resolve 3(L−1) sources with L tripoles. The extension of the proposed algorithm by formulating multiple cumulant matrices and using parallel factor (PARAFAC) analysis is also presented. Simulation results are provided demonstrating the significant improvement in the performance over that of several existing algorithms.     

Analytical synthesis and comparison of voltage‐mode Nth‐order OTA‐C universal filter structures

Complementary single‐ended‐input operational transconductance amplifier (OTA)‐based filter structures are introduced in this paper. Through two analytical synthesis methods and two transformations, one of which is to convert a differential‐input OTA to two complementary single‐ended‐input OTAs, and the other to convert a single‐ended‐input OTA and grounded capacitor‐based one to a fully differential OTA‐based one, four distinct kinds of voltage‐mode nth‐order OTA‐C universal filter structures are proposed. TSMC H‐Spice simulations with 0.35µm process validate that the new complementary single‐ended‐input OTA‐based one holds the superiority in output precision, dynamic and linear ranges than other kinds of filter structures. Moreover, the new voltage‐mode band‐pass, band‐reject and all‐pass (except the fully differential one) biquad structures, all enjoy very low sensitivities. Both direct sixth‐order universal filter structures and their equivalent three biquad stage ones are also simulated and validated that the former is not absolutely larger in sensitivity than the latter. Finally, a very sharp increment of the transconductance of an OTA is discovered as the operating frequency is very high and leads to a modified frequency‐dependent transconductance. Copyright © 2010 John Wiley & Sons, Ltd.     

Intramuscular EMG classifier for detecting myopathy and neuropathy

This article presents an automatic diagnostic system to classify intramuscular electromyography (iEMG) signals, thereby detecting neuromuscular disorders. To this end, we tailored the center symmetric local binary pattern (CSLBP) to analyze one-dimensional ($1$-D) signals. In this approach, the $1$-D CSLBP feature extracted from a decimated iEMG signal is fed to a combination of classifiers, which in turn assigns a set of labels to the signal, and ultimately the signal category is determined by the Boyer-Moore majority voting (BMMV) algorithm. The proposed framework was investigated with a benchmark iEMG dataset that contains signals recorded from three different muscles: biceps brachii (BB), deltoideus (DE), and vastus medialis (VM). In a repeated $10$-fold cross-validation, CSLBP-Combined-Classifiers-BMMV (CSLBP-CC-BMMV) achieved an average classification accuracy of $92.80$%, $94.25$%, and $93.71$% for the iEMG signals recorded from BB, DE, and VM muscle, respectively. Interestingly, the performance of CSLBP-CC-BMMV surpassed the other published approaches and ensemble learning methods that are akin to our scheme in terms of classification accuracy and computational time.