The effect of carbon nanotube orientation on erosive wear resistance of CNT-epoxy based composites

Aligned carbon nanotube (CNT) polymer composites are envisioned as the next-generation composite materials for a wide range of applications. In this work, we investigate the erosive wear behavior of epoxy matrix composites reinforced with both randomly dispersed and aligned carbon nanotube (CNT) arrays. The aligned CNT composites are prepared in two different configurations, where the sidewalls and ends of nanotubes are exposed to the composite surface. Results have shown that the composite with vertically aligned CNT-arrays exhibits superior erosive wear resistance compared to any of the other types of composites, and the erosion rate reaches a similar performance level to that of carbon steel at 20° impingement angle. The erosive wear mechanism of this type of composite, at various impingement angles, is studied by Scanning Electron Microscopy (SEM). We report that the erosive wear performance shows strong dependence on the alignment geometries of CNTs within the epoxy matrix under identical nanotube loading fractions. Correlations between the eroded surface roughness and the erosion rates of the CNT composites are studied by surface profilometry. This work demonstrates methods to fabricate CNT based polymer composites with high loading fractions of the filler, alignment control of nanotubes and optimized erosive wear properties.     

Structural, dielectric and conductivity studies of Na2Pb2La2W2Ti4Nb4O30 ferroelectric ceramic

A new single phase orthorhombic ferroelectric ceramic Na₂Pb₂La₂W₂Ti₄Nb₄O₃₀ (NPLWTN) was prepared via high-temperature solid-state reaction method. The grain morphology of the compound was analyzed by scanning electron microscopy (SEM). Studies of dielectric properties (??_r and tan??) of the compound at different frequencies (10²?C10⁶?Hz) in a wide temperature range (300?C700?K) showed multiple phase transitions in it. First phase transition observed at 335?K related to structural type (ferroelectric-ferroelectric) and the second one observed at 536?K is related to the ferroelectric to paraelectric. The ferroelectric property of the compound at room temperature was confirmed by polarization (hysteresis) study. Broadened dielectric peaks at low frequencies were observed above ferroelectric to paraelectric phase transition temperature (Tc). The values of exponent n(T) and pre-factor A(T) at and around Tc were obtained by the fitting ac conductivity data with Jonscher??s universal power law. From the variation of n(T) and A(T) with temperature, the strength of interaction among the charge carriers with the crystal lattice and the strength of polarisability at phase transition are observed. The activation energy of the compound in low and high temperature range suggests the conduction mechanism in the material.     

Sustainability Assessment and Machinability Investigation of Austenitic Stainless Steel in Finish Turning with Advanced Ultra-Hard SiAlON Ceramic Tool under Different Cutting Environments

Silicon - This paper presents the evaluation of the performances of the various cooling-lubrication techniques (dry, compressed-air cooled, flooded and minimum quantity lubrication) applied in...     

A new method for optimal location and sizing of capacitors in distorted distribution networks using PSO algorithm

This paper presents an optimization algorithm for simultaneous improvement of power quality (PQ), optimal placement and sizing of fixed capacitor banks in radial distribution networks in the presence of voltage and current harmonics. The algorithm is based on particle swarm optimization (PSO). The objective function includes the cost of power losses, energy losses and those of the capacitor banks. Constraints include voltage limits, number/size of installed capacitors at each bus, and PQ limits of standard IEEE-519. Using a newly proposed fitness function, a suitable combination of the objective function and relevant constraints is defined as a criterion to select a set of the most suitable buses for capacitor placement. This method is also capable of improving particles in several steps for both converging more readily to the near global solution as well as improving satisfaction of the power quality constraints. Simulation results for the 18-bus and 33-bus IEEE distorted networks using the proposed method are presented and compared with those of previous works. In the 18-bus IEEE distorted network, this indicated an improvement of 3.29% saving compared with other methods. Using the proposed optimization method and simulation performed on the 33-bus IEEE distorted network an annual cost reduction of 31.16% was obtained.     

A generalized stability criterion for a class of second-order non-linear control systems†

A condition for the existence of a limit cycle for a class of second-order non-linear control systems with a type zero linear plant is derived. The limit cycle stability is assured when F(a, b, α, β)/E curve has a positive slope at the point of intersection of F(a, b, α, β) and K loci. A typical second-order non-linear system is analysed for the purpose of illustrating the method of finding the amplitude and frequency of sustained oscillation. The method of studying the effects of variation of K, α and β on the amplitude and frequency of oscillation of the system is indicated. With regard to this, the proposed method has certain advantages over the usual method of analysis.     

Frequency estimation of distorted non-stationary signals using complex H∞ filter

Mechanical vibration signals are always composed of harmonics of different order. A novel estimator is proposed for estimating the frequency of sinusoidal signals from measurements corrupted by White Gaussian noise with zero mean. Also low frequency sinusoidal signal is considered along with third and fifth order harmonics in presence of noise for estimating amplitudes and phases of different harmonics. The proposed estimator known as complex H_∞ filter is applied to a noisy sinusoidal signal model. State space modeling with two and three state variables is used for estimation of frequency in presence of white noise. Various comparisons in terms of simulation results for time varying frequency reveal that the proposed adaptive filter has significant improvement in noise rejection and estimation accuracy. Comparison in performance between two and three states modeling is presented in terms of mean square error (MSE) under different SNR conditions .The computer simulations clearly indicate that two states modeling based on Hilbert transform performs better than three states modeling under high noisy condition. Frequency estimation performance of the proposed filter is also being compared with extended complex Kalman filter (ECKF) under same noisy conditions through simulations.     

Polyvinyl Chloride Reinforced with Areca Sheath Fiber Composites—An Experimental Study

ABSTRACT

This research work deals with fibrous composites obtained by using treated and untreated areca sheath (AS) fibers reinforced in polyvinyl chloride (PVC) by injection molding process. Surface treatments of fibers have been carried out to have a better compatibility with PVC matrix. The tensile and flexural strength have been found to increase at the early stage with the increase in treated areca fiber content till optimum (18 wt% of fiber) fiber loading thereafter declines. At optimum fiber loading, the tensile strength, flexural strength and young’s modulus values are 42.38 MPa, 18.22 MPa and 2.38 GPa, respectively, which give maximum values in comparison to other fiber loadings. Thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), biodegradability tests and scanning electron microscopy (SEM) have been used for analysis. The TGA inferred that the thermal stability of the composites increased as compared to neat PVC matrix. Further, the composites exhibit excellent biodegradability property and their biodegradability increases with the increase of areca fiber content. From the properties obtained at optimum fiber loading (18 wt% of fiber), the composite can be suitable for automotive dashboard and door panel applications.     

Design and evaluation of new majority gate-based RAM cell in quantum-dot cellular automata

Quantum-dot cellular automata is one of the candidate technologies used in Nano scale computer design and a promising replacement for conventional CMOS circuits in the near future. Since memory is one of the significant components of any digital system, designing a high speed and well-optimized QCA random access memory (RAM) is a remarkable subject. In this paper, a new robust five-input majority gate is first presented, which is appropriate for implementation of simple and efficient QCA circuits in single layer. By employing this structure, a novel RAM cell architecture with set and reset ability is proposed. This architecture has a simple and robust structure that helps achieving minimal area, as well as reduction in hardware requirements and clocking zone numbers. Functional correctness of the presented structures is proved by using QCADesigner tool. Simulation results confirm efficiency and usefulness of the proposed architectures vis-à-vis state-of-the-art.     

Products and coke from the conversion of bio-oil acids,esters, aldehydes and ketones over equilibrium FCC catalysts

Reactivity and product distributions in the conversion of five different compounds representing typical species in bio-oils were studied over an equilibrium FCC catalyst at 500 °C during 60 s in a fixed bed reactor. Acetic acid, methyl acetate, furfural, 3-methyl-2-pentanone and 2-hidroxy-3-methylcyclopentenone were dissolved at 5% wt. in water. Thermal conversions were performed under the same conditions with inert SiC in the bed. The test compounds converted very differently, deoxygenation being produced by decarboxylation and dehydration. Furfural and 3-methyl-2-pentanone gave the highest yields of hydrocarbons, with high selectivity to light olefins and, when liquid (case of ketones), to aromatics. Methyl acetate gave the highest yield of oxygenated compounds. Coke yields were important (maximum 12.8% wt., 2-hidroxy-3-methylcyclopentenone). Thermal conversions were similar to the catalytic ones with acetic acid and methyl acetate, and much lower for the other reactants. Compared catalytic experiments, the thermal yields of hydrocarbons were much higher with acetic acid, and the yields of oxygenated higher with methyl acetate ester. Much less hydrocarbons were produced thermally with the other reactants. This information may be useful for predicting contributions if these compounds are to be co-processed in existing FCC units or upgraded over acidic catalysts.