Cap-layer and charge sheet effect in InP based pnp δ-doped heterojunction bipolar transistor

Microsystem Technologies - The effect of varying the cap layer and the δ doped charge sheet has been investigated for an InP based heterojunction bipolar transistor (HBT) using the SILVACO...     

A simplified state-of-the-art sample shifting technique for microcontroller based single phase power measurement

A unique state-of-the art sample shifting technique (SST), proposed in recent literature, is utilized particularly for the estimation of reactive power from sample values of voltage and current signals only while the active power is evaluated from their as usual product. Also all other related parameters, as described in the IEEE 1459-2010 standard, are estimated in this measurement. A hardware prototype is developed to study its viability by estimating the measurement errors under pure and different polluted environment conditions.     

Effect of zirconium oxide nanopowder on the thermal,chemical and gas barrier properties of starch

Starch/zirconium oxide (Starch/ZrO₂) bionanocomposites were prepared using various percentages of nano-ZrO₂ by a solution technique. The interaction of ZrO₂ nanocomposites with starch was studied by Fourier transform infrared spectroscopy (FTIR) and their structural behavior was investigated by X-ray diffraction (XRD). The dispersion of ZrO₂ within virgin starch was investigated by a field emission scanning electron microscope (FESEM), a high resolution transmission electron microscope (HRTEM) and selected area electron diffraction (SAED). Thermal properties of starch/ZrO₂ bionanocomposites were studied by thermogravimetric analysis (TGA). An increase in thermal stability was observed with increase in filler loading. The conductivity of starch/ZrO₂ bionanocomposites was measured and an increase in conductivity was observed due to the increase in ZrO₂ concentration. Starch/ZrO₂ bionanocomposites were more resistant towards chemicals like dilute acid and alkali. The oxygen barrier property of composites was studied and a substantial reduction in permeability was observed. Further, the biodegradability of starch/ZrO₂ bionanocomposites was reduced. Thermally stable, chemical resistant, and gas barrier starch bionanocomposites with conducting property may enable the materials for manufacturing packaging materials and semiconducting devices.     

Sensitivity of transverse shift inside a double-grating Talbot interferometer

We study the Talbot interferometry with an additional mask grating located behind the diffraction grating. The self-imaging so-called, Talbot carpet, can be very sensitive to an external perturbation. We here show the measurement and the optimization of sensitivity of transverse shift of one of the two gratings inside Talbot interferometer as a function of grating constant and opening fraction of the grating itself. The results show that the sensitivity of the transverse shift is increased dramatically at smaller grating constants while no effect for different opening fractions. A sensor of our simple scheme can be suggested as an excellent inertial sensing applications such as displacement sensor, spectrometer, and vibration sensor.     

Ferroelectric,dielectric properties and electrical conduction mechanism of epitaxial B1-xDyxFeO3 (x = 0.05, 0.075, 0.1, 0.125) thin films prepared by pulsed laser deposition

We report that Dy doping can be used to enhance ferroelectric properties and reduce leakage current in (001) epitaxial Bi_1-xDy_xFeO₃ (BD_xFO) thin films where x = 0.05, 0.075, 0.1, 0.125. The 120 nm thin BD_xFO films were prepared by pulsed laser deposition (PLD). Saturated ferroelectric hysteresis (P-E) loops were observed at room temperature with an increase in remanent polarization (P_r) with the increase in applied electric field and Dy concentration. The improved P_r in BD_xFO films from x = 0.05 to 0.1 is attributed to reduction in oxygen vacancies with an increase in Dy content that prevents electric domain back-switching. However, BD_xFO (x = 0.125) film exhibit leaky and unsaturated loop which may be due to the appearance of microscopic defects in the film. The leakage current in BD_xFO films decreased by an order of magnitude as Dy content increased from x = 0.05 to 0.1. The detailed leakage current mechanism analysis is also presented. The results of positive up negative down (PUND) method confirmed that intrinsic polarization is due to ferroelectricity and not due to leakage. Relative permittivity (ɛ') of BD_xFO films increased whereas dielectric loss tangent (tan δ) reduced as Dy content increased from x = 0.05 to 0.1.     

Application of fuzzy VIKOR and environmental impact analysis for material selection of an automotive component

Material selection is a complex process, since the process includes many criteria, determination of criteria weight and the most important factor is that the selection of appropriate criterion. The last factor indicates that the criterion must be selected in a manner, such that the selection based upon the known material parameters and the requirements of the application. Therefore the material selection can be done using MCDM (Multi Criterion Decision Making) methods. Since the inputs provided by the decision maker in linguistic manner, there is a possible chance of getting incomplete problems. So in order to overcome the problem, the inputs could be provided as fuzzy numbers. Since fuzzy set represents the uncertainty in human perceptions. In this paper, VIKOR (VlseKriterijumska Optimizacija I Kompromisno Resenje in Serbian, means Multicriteria Optimisation and Compromise Solution) has been used a MCDM tool for the selection of alternate material for instrument panel used in electric car and in order to evaluate this selection process in fuzzy environment, fuzzy based VIKOR is used. In addition to the fuzzy VIKOR method, the environmental impacts are also considered and compared for the four materials. The results achieved in both the assessment, showed that Polypropylene could be an alternate material for the instrument panel. The objective of this study is to develop a rational method to select the best material for an application based upon known material parameters and the requirements of the application.     

Free vibration and stability of angle-ply laminated composite and sandwich plates under thermal loading

A two-dimensional global higher-order deformation theory is presented for the free vibration and stability problems of angle-ply laminated composite and sandwich plates subjected to thermal loading. By using the method of power series expansion of continuous displacement components, a set of fundamental governing equations which can take into account the effects of both transverse shear and normal stresses is derived through Hamilton’s principle. Several sets of truncated Mth order approximate theories are applied to solve the eigenvalue problems of a simply supported angle-ply multilayered plate. Natural frequencies and critical temperatures of angle-ply laminated composite and sandwich plates subjected to thermal loading are obtained. Critical temperatures are obtained by increasing the temperature until the natural frequency vanishes. The effects of prebuckling displacements on the natural frequencies and critical temperatures are taken into account. Modal displacement distributions through the transverse direction of the laminates are plotted for the specific temperature parameter. Numerical results are compared with those of the published existing theories. The present global higher-order approximate theories can predict the natural frequencies and critical temperatures of angle-ply laminated composite and sandwich plates subjected to thermal loading accurately within small number of unknowns.     

Synthesis and characterization of poly(acrylonitrile-co-methylmethacrylate) nanocomposites reinforced by functionalized multiwalled carbon nanotubes

Polyacrylonitrile-co-poly(methylmethacrylate)/multiwalled carbon nanotubes (PAN-co-PMMA/MWCNTs) nanocomposites were synthesized by an in situ emulsifier-free polymerization method with variable percentages of functionalized carbon nanotube (f-MWCNT). MWCNTs were functionalized with concentrated H₂SO₄ and HNO₃ with a continuous sonication process. Chemical interaction of f-MWCNT with the copolymer was studied by UV-visible spectroscopy. Fourier transform infrared spectroscopy proved the interaction of f-MWCNT with the PAN-co-PMMA copolymer matrix. The structural interaction of f-MWCNT with copolymer matrix was investigated by X-ray diffraction study. The dispersion and morphology of the f-MWCNT in the copolymer matrix were studied by scanning electron microscopy and high-resolution transmission electron microscopy. It was noticed that the f-MWCNTs were uniformly dispersed within the copolymer matrix. The thermal property of the PAN-co-PMMA/f-MWCNT nanocomposite was analyzed by thermogravimetric analysis. It was noticed that the thermal stability of the PAN-co-PMMA/f-MWCNT nanocomposite was more than that of the virgin copolymer matrix. When the electrical conductivity property of the synthesized nanocomposite was measured, it was noticed that the better dispersion of f-MWCNT in the non-conductive PAN-co-PMMA copolymer matrix made the PAN-co-PMMA/f-MWCNT nanocomposites conductive. From the measurement of gas barrier properties of synthesized nanocomposites, it was assumed that the well-dispersed f-MWCNT in the copolymer matrix creates the huddles for penetration of oxygen gas. It was noticed that the oxygen permeability of the PAN-co-PMMA/f-MWCNT nanocomposite was reduced by five times as compared to that of the neat PAN-co-PMMA copolymer matrix. The PAN-co-PMMA/f-MWCNT nanocomposites with higher thermal stability and reduced oxygen permeability properties may be suitable for application as conducting packaging materials.     

Dielectric relaxation behavior of conducting carbon black reinforced ethylene acrylic elastomer vulcanizates

The dielectric relaxation characteristics of conductive carbon black (CCB) reinforced ethylene acrylic elastomer (AEM) vulcanizates have been studied as a function of frequency (10¹–10⁶ Hz) at different filler loading over a wide range of temperatures (30–120°C). The effect of filler loadings on the dielectric permittivity (ε′), loss tangent (tan δ), complex impedance (Z*), and electrical conductivity (σ_ac) were studied. The variation of ε′ with filler loading has been explained based on the interfacial polarization of the fillers within a heterogeneous system. The effect of filler loading on the imaginary (Z″) and real (Z′) part of Z* were distinctly visible, which may be due to the relaxation dynamics of polymer chains at the polymer–filler interface. The frequency dependency of σ_ac has been investigated using percolation theory. The phenomenon of percolation in the composites has been discussed in terms of σ_ac. The percolation threshold (?_crit) occurred in the range of 20–30 phr (parts per hundred) of filler loading. The effect of temperature on tan δ, ε′, σ_ac, and Nyquist plots of CCB‐based AEM vulcanizates has been investigated. The CCB was uniformly dispersed within the AEM matrix as studied from the transmission electron microscope (TEM) photomicrographs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012