M. Amin

Pyroelectricity in rubber composite films

Abstract A series of composities of butadiene acrylonitrile rubber (NBR) blended with BaTiCL3 ceramic material were prepared to study their pyroelectric behaviour. Pyroelectricity may arise from the permanent C=N dipoles of the rubber and those of BaTiO3 ferroelectric material. The pyroelectric coefficient (γ3) was found to be dependent on different factors such as; temperature, poling field, poling temperature, thickness and BaTiO3 concentrations. Different dipoles are thought to be more effective at low temperature (: g) while space charge is responsible for pyro-electricity at relatively higher temperatures.

Electrical properties of acrylonitrile-butadiene rubber-barium titanate composites

Abstract Electrical conductivity (σ) and dielectric permittivity (ϵ) together with the pyroelectric coefficient (γ) have been measured for a series of composites containing acrylonitrile butadiene rubber (NBR) and barium titanate ceramic in the form of powder. The possibility of obtaining thermal electrets is discussed.

Ferroelectricity in polycrystalline triglycine sulphate (TGS)

Polycrystalline TGS samples have been prepared under different compressions and with different particle sizes (from 80 μm-630 μm. The dielectric properties were found to depend largely on the particle size and preparation conditions. The dielectric constant was found to decrease with decreasing of the particle size while the phase transition temperature shifted toward higher values. The addition of a small amount of water during preparation has pronounced effect on both the shape and the values of the e vs. T curve. As the hydrostatic pressure increase e increases and the Curie temperature increases.

Investigation on the dependence of the electrical conductivity of FEF/SBR vulcanizates on the cyclic strain

SummaryThe constant deformation fatigue test was found to affect the electrical properties of 70 FEF/SBR vulcanizates. The conductivity of 70 FEF/SBR sample is so sensitive to the value of strain amplitude and the number of cycles. When the specimens were subjected to a large number of rapidly repeating strain cycles, the transverse conductivity, σT, shows an initial rapid fall with increasing number of cycles, probably due to carbon structure breakdown. This is followed by dynamic equilibrium, where the conductivity remains almost constant over the temperature range 30–85 °C.The equilibrium state between destruction and reconstruction of carbon black aggregates has been detected for all strains of certain values of strain cycles (1.2 × l05, 4.7 × 104, 4.7 × 104, and 1.7 × 104 cycles for 50%, 75%, 100%, and 130% strains, respectively).

Efficient decimal leading zero anticipator designs

The leading zero anticipator (LZA) is a vital block in fast floating point addition and fused multiply-add (FMA) operations. So far, there is only one decimal LZA proposed in research literature. This paper introduces two decimal LZA designs, then a comparison between the three designs, the two proposed here and the previous proposed one, is performed.

Pyroelectricity and electrical conductivity in polycrystalline triglycine sulfate (TGS)

Polycrystalline TGS specimens have been prepared under different compressions and with different particle sizes (from 80 to 630 μm). The pyroelectric current, and the electrical conductivity were found to decrease with decreasing particle size. The pyroelectric current at the transition temperature (Tc) was found to be exponentially increasing with the poling field. The effect of adding a small amount of water during preparation was studied. The pyroelectric current has appreciably increased and the samples show higher electrical conductivities only in the region of Tc. As the hydrostatic pressure ncreases the pyroelectric current and the electrical conductivity increase.

Fabrication and stabilization of silicon-based photonic crystals with tuned morphology for multi-band optical filtering

One-dimensional silicon-based photonic crystals are formed by the electrochemical anodization of silicon substrates in hydrofluoric acid-based solution using an appropriate current density profile. In order to create a multi-band optical filter, two fabrication approaches are compared and discussed. The first approach utilizes a current profile composed of a linear combination of sinusoidal current waveforms having different frequencies. The individual frequency of the waveform maps to a characteristic stop band in the reflectance spectrum. The stopbands of the optical filter created by the second approach, on the other hand, are controlled by stacking multiple porous silicon rugate multilayers having different fabrication conditions. The morphology of the resulting optical filters is tuned by controlling the electrolyte composition and the type of the silicon substrate. The reduction of sidelobes arising from the interference in the multilayers is observed by applying an index matching current profile to...

Facile design and stabilization of a novel one-dimensional silicon-based photonic crystal microcavity

A novel silicon-based optical microcavity composed of a defect layer sandwiched between two parallel rugate mirrors is created by the electrochemical anodization of silicon in a hydrofluoric acid-based electrolyte using a precisely controlled current density profile. The profile consists of two sinusoidally modulated current waveforms separated by a fixed current that is applied to produce a defect layer between the mirrors. The spectral response of the rugate-based microcavity is simulated using the transfer matrix method and compared to the conventional Bragg-based microcavity. It is found that the resonance position of both microcavities is unchanged. However, the rugate-based microcavity exhibits a distinct reduction of the sidebands intensity. Further attenuation of the sidebands intensity is obtained by creating refractive index matching layers with optimized thickness at the bottom and top of the rugate-based microcavity. In order to stabilize the produced microcavity against natural oxidation, a...

The effect of electric field on the creep characteristics of low-density polyethylene (LDPE)

SummaryThe effect of electric field on the creep characteristics and the corresponding parameters such as instantaneous strain, strain rate, activation energy, activation volume, stress-sensitivity parameter and viscosity was investigated.