Correlation of electrical and swelling properties with nano free‐volume structure of conductive silicone rubber composites

The present study focuses on finding a correlation between the positron annihilation parameters of silicone rubber polydimethylsiloxane (PDMS) composites loaded with different conductive fillers and their swelling and electrical properties. Four types of conductive fillers have been used in this study, i.e., carbon black (CB), graphite (G), copper, and nickel powders. The investigated swelling parameters for PDMS composites such as the maximum degree of swelling Q_m%, the penetration rate, P, and consequently the diffusion coefficient, D, decreased with increasing the filler content due to the reduction of the size of free‐volume, which could be observed through a decrease of the probability of ortho‐positronium (o‐Ps) formation I₃, that has been measured by the positron annihilation spectroscopy (PALS). Accordingly, a positive correlation has been found of 76.78% and 61.1% between Q_m% and the o‐Ps lifetime τ₃, representing the size of free‐volume for the CB and G filled composites, respectively. It is worthwhile, mentioning that the CB filled composites exhibit relatively low values of P, D, and Q_m% as compared to the G filled composites due to the difference in the physical properties of the filler, particle size, surface area as well as the tendency of the filler particles to make aggregates. On the other hand, the variation of the diffusion coefficient with the relative fractional free‐volume F_r is found in good agreement with the Fujita's free‐volume theory. On the other hand, the electrical conductivity increases with increasing the conductive filler content. Positive temperature coefficient of conductivity (PTCC) behavior is detected, except for the composite containing 20 or 25 phr CB, which showed a metallic behavior. Besides, CB filled PDMS composites exhibit higher electrical conductivity as compared to the composites filled with the other three fillers. The electrical conductivity ln (σ) is positively correlated with the probability of free annihilation of positrons at interfaces I₂, thus suggesting an increase in the electron density with the filler content. The activation energy of conduction, E_a, decreases with the increase in the loading of conductive filler. Moreover, it was noticed that E_a varies with the filler type, the values of E_a increase as the particle size of the filler increases. Finally, a correlation between the free‐volume V_f, determined by PALS with the DC electrical conductivity ln(σ) is found to be in accordance with Miyamoto and Shibayma model. POLYM. COMPOS., 34:2105–2115, 2013. © 2013 Society of Plastics Engineers     

Performance of Layered Steered Space–Time Codes in Wireless Systems

Layered Steered Space–Time Codes (LSSTC) is a recently proposed multiple-input multiple-output (MIMO) system that combines the benefits of vertical Bell Labs space–time (VBLAST) scheme, space–time block codes (STBC) and beamforming. In this paper, we derive the error performance and capacity of a single-user LSSTC system. The analysis is general enough to any layer ordering and modulation schemes used. In addition, the derived analysis is general for any LSSTC structure in which layers may have different number of antenna arrays and may be assigned power according to any power allocation. Furthermore, we analytically investigate the tradeoff between the main parameters of the LSSTC system, i.e., diversity, multiplexing and beamforming. Our results give recursive expressions for the probability of error for LSSTC which showed nearly perfect match to the simulation results. Results have also revealed the possibility of designing an adaptive system in which it was shown that combining beamforming, STBC, and VBLAST has better performance than VBLAST at high SNR range.     

Synthesis of uranium nitride by a mechanically induced gas-solid reaction

A high energy, low-temperature, ball-milling route was used to directly produce uranium nitride. Pure uranium metal particles (∼100 μm) were ball milled under a 420 kPa nitrogen atmosphere for 24 h at ambient temperature to yield phase pure U₂N₃ powder as confirmed by X-ray diffraction and energy dispersive spectroscopy. The median particle size was measured to be approximately 6 μm.     

Integration of PV system with SMES based on model predictive control for utility grid reliability improvement.

This paper describes the integration of a photovoltaic (PV) renewable energy source with a superconducting magnetic energy storage (SMES) system. The integrated system can improve the voltage stability of the utility grid and achieve power leveling. The control schemes employ model predictive control (MPC), which has gained significant attention in recent years because of its advantages such as fast response and simple implementation. The PV system provides maximum power at various irradiation levels using the incremental conductance technique (INC). The interfaced grid side converter of the SMES can control the grid voltage by regulating its injected reactive power to the grid, while the charge and discharge operation of the SMES coil can be managed by the system operator to inject/absorb active power to/from the grid to achieve the power leveling strategy. Simulation results based on MATLAB/Simulink® software prove the fast response of the system control objectives in tracking the setpoints at different loading scenarios and PV irradiance levels, while the SMES injects/absorbs active and reactive power to/from the grid during various events to improve the voltage response and achieve power leveling strategy.     

Asymptotic stability and estimating the region of attraction for the swing equations

We state and prove a theorem that asserts the asymptotic stability and provides an estimate of the region of attraction of an equilibrium point of the swing equations. A version of this theorem was originally introduced by Willems; however, his justifications are sketchy and, in our opinion, require additional analysis. All the Liapunov method analyses utilized in the transient stability problem of power systems have been based on the assumed validity of this theorem. The shortcomings of the other proposed proofs in the literature is that they rely on available Liapunov theorems for which an assumption can not be verified. In contrast, the techniques used in the proof here avoid the restriction of the available Liapunov theorems; moreover, they can be extended to apply to a broader class of systems.     

Innovative Fungal Disease Diagnosis System Using Convolutional NeuralNetwork

Fungal disease affects more than a billion people worldwide, resulting in different types of fungus diseases facing life-threatening infections. The outer layer of your body is called the integumentary system. Your skin, hair, nails, and glands are all part of it. These organs and tissues serve as your first line of defence against bacteria while protecting you from harm and the sun. The It serves as a barrier between the outside world and the regulated environment inside our bodies and a regulating effect. Heat, light, damage, and illness are all protected by it. Fungi-caused infections are found in almost every part of the natural world. When an invasive fungus takes over a body region and overwhelms the immune system, it causes fungal infections in people. Another primary goal of this study was to create a Convolutional Neural Network (CNN)-based technique for detecting and classifying various types of fungal diseases. There are numerous fungal illnesses, but only two have been identified and classified using the proposed Innovative Fungal Disease Diagnosis (IFDD) system of Candidiasis and Tinea Infections. This paper aims to detect infected skin issues and provide treatment recommendations based on proposed system findings. To identify and categorize fungal infections, deep machine learning techniques are utilized. A CNN architecture was created, and it produced a promising outcome to improve the proposed system accuracy. The collected findings demonstrated that CNN might be used to identify and classify numerous species of fungal spores early and estimate all conceivable fungus hazards. Our CNN-Based can detect fungal diseases through medical images; earmarked IFDD system has a predictive performance of 99.6% accuracy.     

An air crash due to fatigue failure of a ball bearing

The failure analysis of an air crash conclusively shows that the cage of the central main bearing of the compressor region failed due to fatigue. The broken piece of the cage got struck between the bearing balls and the races and impaired the function of the bearing resulting in the crash.     

Stability analysis of a toroidal pipe-reducer under uniform external pressure

The stability of a toroidal pipe-reducer system is determined here from the solution of non-linear governing equations of axisymmetric deformations of shells of revolution. Numerical solutions are obtained by a modified version of the computer program developed by Uddin for solving the governing equations of axisymmetric shells by the multisegment method of integration. The interpretation of instability of the toroidal reducers is based on Thompson's theorems I and II. Critical pressures for the toroidal reduers are calculated over useful ranges of the curvature ratio, the thickness ratio, and the diameter ratio. It has been found that the critical pressure of these reducers varies almost linearly with the diameter ratio and that the long toroidal reducers are prone to local instability near the larger end. But this critical zone occurs near either one of the two ends as the reducer becomes shorter. The results of stability and stress analysis of toroidal pipe-reducers are compared here with those of conical reducers obtained by Ali and parabolic reducers obtained by Rahman. Comparison shows that toroidal reducers develop uniform stresses of lower magnitude compared to the other two. Further, toroidal reducers are found to sustain higher critical pressure than parabolic reducers except at higher diameter ratio.     

The unattended speech effect: Perception or memory?

D. E. Broadbent (1983) has suggested that the influence of unattended speech on immediate serial recall is a perceptual phenomenon rather than a memory phenomenon. In order to test this, 40 undergraduates were required to classify visually presented pairs of consonants on the basis of either case or rhyme. They were tested both in silence and against a background of continuous spoken Arabic presented at 75 db(A). No effect of unattended speech was observed on either the speed or accuracy of processing. A further study required 20 undergraduates to decide whether visually presented nonwords were homophonous with real words. Again, performance was not impaired by unattended speech, although a clear effect was observed on an immediate serial memory task. It is concluded that the results give no support to the perceptual interpretation of the unattended speech effect. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimization of material formulation and processing parameters in relation to mechanical properties of bioepoxy/clay nanocomposites using Taguchi design of experiments

This article aims to study the effects of material formulation and processing parameters on mechanical properties of bioepoxy/clay nanocomposites based on epoxidized soybean oil (ESO) via Taguchi design of experiments (DoEs). A mixed‐level DoE with an L₁₆ orthogonal array was constructed to achieve maximum levels of tensile strength, tensile modulus, and impact strength for corresponding bionanocomposites. Pareto analysis of variance (ANOVA) was used to identify significant factors and preferred formulations in the manufacture of bioepoxy/clay nanocomposites. The ESO content was found to have the most significant effect with regards to bionanocomposite mechanical properties with contribution percentages of 66.63, 72.96, and 40.14% for their tensile strength, tensile modulus, and impact strength, respectively. With regards to material processing parameters, mechanical mixing speed was identified as a critical factor to achieve optimal tensile and impact properties. Nonetheless, the results also indicated clay content to be a significant factor for tensile strength, whereas curing agent type was vital for the improvement of tensile modulus and impact strength. Clay type and sonication time were also found to be significant factors for impact strength. In contrast to this, manufacturing parameters such as mechanical mixing temperature, mixing time, and sonication frequency were considered to be non‐significant factors due to their low cumulative contribution percentages of <10%. Finally, experimental confirmation tests based on the preferred combination of factors demonstrated good agreement with statistically predicted results. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45769.