Thermally Conducting Polymer Composites with EMI Shielding: A review

Journal of Electronic Materials - Polymer composites have been a material of choice for lightweight and durable applications in sectors ranging from automobile, packaging, structural components,...     

Application of minimal radial basis function neural network todistance protection

The paper presents a new approach for the protection of power transmission lines using a minimal radial basis function neural network (MRBFNN). This type of RBF neural network uses a sequential learning procedure to determine the optimum number of neurons in the hidden layer without resorting to trial and error. The input data to this network comprises fundamental peak values of relaying point voltage and current signals, the zero-sequence component of current and system operating frequency. These input variables are obtained by a Kalman filtering approach. Further, the parameters of the network are adjusted using a variant of extended Kalman filter known as locally iterated Kalman filter to produce better accuracy in the output for harmonics, DC offset and noise in the input data. The number of training patterns and the training time are drastically reduced and significant accuracy is achieved in different types of fault classification and location in transmission lines using computer simulated tests     

Growth of silicon carbide nanotubes in arc plasma treated silicon carbide grains and their microstructural characterizations

Silicon carbide nanotubes were found to grow in straight as well as curved configurations by treating silicon carbide grains in an arc plasma reactor/furnace followed by 3 h of cooling (in air). By increasing the plasma treatment time from 16 min to 20 min, multi-wall tubes were found to change to single wall tubes with reduction in diameter from few nm to sub-nm. Typical in situ grown nanotubes were characterized by XRD, TEM, SAED, HRTEM, EDS and micro Raman spectroscopy, and it is established from these evaluations that the nanotubes are made up of silicon carbide and not carbon. A possible mechanism, involving reaction between the plasma dissociated carbon (solid) forming carbon nanotube and the left-out silicon (existing in vapour state) during the cooling period (3000–2680 °C), is suggested to be responsible for silicon carbide nanotube formation in the plasma assisted process.     

Thermo-mechanical vibration of a single-walled carbon nanotube embedded in an elastic medium based on nonlocal elasticity theory

A single-elastic beam model has been developed to analyze the thermal vibration of single-walled carbon nanotubes (SWCNT) based on thermal elasticity mechanics, and nonlocal elasticity theory. The nonlocal elasticity takes into account the effect of small size into the formulation. Further, the SWCNT is assumed to be embedded in an elastic medium. A Winkler-type elastic foundation is employed to model the interaction of the SWCNT and the surrounding elastic medium. Differential quadrature method is being utilized and numerical solutions for thermal-vibration response of SWCNT is obtained. Influence of nonlocal small scale effects, temperature change, Winkler constant and vibration modes of the CNT on the frequency are investigated. The present study shows that for low temperature changes, the difference between local frequency and nonlocal frequency is comparatively high. With embedded CNT, for soft elastic medium and larger scale coefficients (e₀a) the nonlocal frequencies are comparatively lower. The nonlocal model-frequencies are always found smaller than the local model-frequencies at all temperature changes considered.     

Dielectric and impedance spectroscopy of Ni doped BiFeO<Subscript>3</Subscript>-BaTiO<Subscript>3</Subscript> electronic system

A nickel modified BiFeO₃–BaTiO₃ electronic system has been fabricated by using a high-temperature solid-state reaction process. Preliminary X-ray structural analysis has confirmed the formation of a single-phase material in the orthorhombic crystal system. The dielectric and impedance characteristics of the prepared material have been studied in a wide range of frequency (1 kHz-1 MHz) at different temperatures (25–500 °C) for the better understanding of the frequency-temperature dependence of its capacitive and resistive behavior respectively. A significant effect of grains and grain boundaries of the resistive characteristics of the material is observed at high temperatures. The electrical conductivity of the material increases with increase in frequency in the low-temperature region. Preliminary study of a small amount of Ni doping in the above binary system (i.e., BiFeO₃–BaTiO₃) has provided many interesting results which may be useful for the fabrication of an electronic device.     

A new mechanistic model for liquid-liquid phase transfer catalysis: Reaction of benzyl chloride with aqueous ammonium sulfide

A new mechanistic model for reactions involving two liquid phases and a homogeneous phase transfer catalyst (PTC) has been developed based on extraction mechanism considering the equilibrium of catalyst and active catalysts at the interface. The proposed kinetic model considers thermodynamic framework based aqueous phase ionic equilibrium and the separate contributions of non-PTC and PTC-enhanced reactions towards the overall reactions. The developed model was then applied to an industrially important reaction of benzyl chloride with aqueous ammonium sulfide for synthesis of dibenzyl sulfide and benzyl mercaptan. The kinetic parameters of the developed model were estimated at different temperatures using an indigenously developed non-linear regression technique based on modified Levenberg-Marquardt algorithm. Sensitivity analysis was then performed under various experimental conditions using the estimated parameters and the results were compared with experimental observations. A good agreement was observed between experimental and calculated values with proper trends of the results.     

Source Coding With Feed-Forward: Rate-Distortion Theorems and Error Exponents for a General Source

In this work, we consider a source coding model with feed-forward. We analyze a system with a noiseless, feed-forward link where the decoder has knowledge of all previous source samples while reconstructing the present sample. The rate-distortion function for an arbitrary source with feed-forward is derived in terms of directed information, a variant of mutual information. We further investigate the nature of the rate-distortion function with feed-forward for two common types of sources- discrete memory- less sources and Gaussian sources. We then characterize the error exponent for a general source with feed-forward. The results are then extended to feed-forward with an arbitrary delay larger than the block length.     

Corrosion zones of rebar in chloride contaminated concrete through potentiostatic study in concrete powder solution extracts

In this paper an experimental investigation has been carried out to identify semi-immune, active, passive and pitting zones of corrosion of the steel reinforcement in concrete powder solution extracts at different levels of admixed chloride. Potentiostatic linear sweeping test was carried out on three different types of steel reinforcement in the solution extracts made from concrete with three different types of cement at four levels of admixed chloride content with three w/c ratios for two test conditions, i.e., with and without deaeration. From the results obtained it was concluded that chloride content is the major factor in defining the zones of corrosion and the same was further confirmed through ANOVA.