Current-Voltage (I-V) Characteristics of Poly(vinylidene fluoride)/Potassium Nitrate Composite Thick Film

This article describes the experimental results of the polyvinylidene fluoride (PVDF)/Potassium nitrate (KNO₃), composite films. To explain the nature of ferroelectric phase (phase III) of potassium nitrate (KNO₃), we have prepared the composite films of poly (vinylidene fluoride)/potassium nitrate in the relative amount of 50–50 wt.% by using simple melt pressing. The results of the temperature dependence of the capacitance and conductance of the composite films have been carried out. The current vs. voltage (I-V) characteristics exhibit the polarization current, which is the nature of ferroelectricity in the composite films. Capacitance vs. voltage (C-V) measurements have been performed to identify the ferroelectric properties of the composite films.     

Size and Shape of Calcium Alginate Beads Produced by Extrusion Dripping

Alginate hydrogel beads are widely used as an encapsulation medium for biomedical, bioprocessing, and pharmaceutical applications. The size and shape of the beads are often critically controlled since in many usages the beads are monodisperse in size and spherical in shape. Extrusion dripping is a well‐known method to produce alginate beads. Nevertheless, the production of beads of desired size and spherical shape is often achieved based on one's experience or trial and error. An overview is provided on alginate properties, formulation and preparation of alginate and gelling solutions, production conditions, and post‐production treatment that may influence the bead size and shape. Various methods of bead size and shape measurement are also discussed.     

Development of surface functionalized activated carbon fiber for control of NO and particulate matter

This study investigates the development and potential application of activated carbon fibers (ACF) functionalized with ammonia for control of NO and particulate matter (PM) in diesel engine exhaust. A tubular reactor packed with ACF was used to experimentally study the oxidation of NO at room temperature. Tests were conducted at ACF functionalized with three aqueous ammonia concentrations (3, 5, 10 M), three basic reagents (ammonia, pyridine, amine) and three NO concentrations (100, 300, 500 ppm). After offline investigation, the ACF-packed tubular reactor was installed downstream of the engine's exhaust to ascertain the PM capturing efficiency of ACF. The experimental conditions for PM removal included three weights of ACF (2, 3.5, 4.5 g), three engine loads (0, 25, 50 Nm) and three temperatures (150, 300, 450 °C). The maximum 70% conversion for NO was obtained at NO concentration of 300 ppm for ACF functionalized with 5 M ammonia, whereas maximum 90% reduction in PM was observed at engine load of 25 Nm and 450 °C. The study shows significant potential for the ACF based filters in capturing both homogeneous and heterogeneous pollutants emitted from automobiles. Our previously developed transport model incorporating the mechanism for the oxidation of NO was also used to explain the experimental data.     

Structural and Electrical Properties of Lead-Free Perovskite Ba(Al1/2Nb1/2)O3

Lead-free perovskite Ba(Al_1/2Nb_1/2)O₃ was prepared by conventional ceramic fabrication technique at 1350°C/5 h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were determined from the experimental results using FullProf software whereas crystallite size and lattice strain were estimated from Williamson-Hall approach. X-ray diffraction analysis of the compound indicated the formation of a single-phase monoclinic structure with the space group P 2/ m . EDAX and SEM studies were carried out in order to evaluate the quality and purity of the compound. Permittivity data showed low-temperature coefficient of capacitance ( T _CC=14%) up to 100°C. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were presented using the impedance data. Complex impedance analyses suggested the dielectric relaxation to be of non-Debye type. The correlated barrier-hopping model was used to successfully explain the mechanism of charge transport in Ba(Al_1/2Nb_1/2)O₃.     

Moisture sorption isotherms of dietetic Rabri at different storage temperatures

Moisture sorption isotherms of dietetic Rabri were determined at 10, 25 and 37 °C over a water activity range of 0.113–0.868. Sorption isotherms at 37 °C were sigmoidal (type II) curves, while at 10 °C, they were of type V and Type I at 25 °C for both adsorption and desorption processes. Five sorption models were tested to fit the experimental data. Halsey's model for 10 °C, Caurie's model for 25 °C and Modified Mizrahi's model for 37 °C were found to be the best fit. There was a clear hysteresis effect at 10 °C, whereas the effect gradually decreased and diminished at 37 °C.     

Causality in propagation of a pulse in a nonlinear dispersive medium

We investigate the causal propagation of the pulse through dispersive media by very precise numerical solution of the coupled Maxwell–Bloch equations without any approximations about the strength of the input field. We study full nonlinear behaviour of the pulse propagation through solid state media like ruby and alexandrite. We have demonstrated that the information carried by the discontinuity, i.e. front of the pulse, moves inside the media with velocity c even though the peak of the pulse can travel either with sub-luminal or with super-luminal velocity. Our numerical demonstration is subject to the condition that the background refractive index of the medium is unity. We extend the argument of Levi-Civita to prove that the discontinuity would travel with velocity c even in a nonlinear medium.     

On-line quality control procedures for a random walk model with measurement error

An economical on-line quality control procedure is given for cases where measurement error u present.The unobservable quality characteristic procw is assumed to follow a normal random walk.model independent of the measurement error which is white noise. The off-target loss function used is proportional to the squared deviation from the target value.The procw is inspected at regular intervals of m time units and adjusted at the end of a cycle when the process goes out of the control limit d.The limning long-run average cost rate is evaluated.The optimum value of the control parameters,the inspection interval m,and the control limit d are obtained by minimlzlng the long-run average cost rate.When m is small and d is large, explicit expressions for the control parameters are given.     

Effect of Tin on the Wear Properties of Spray Formed Al–17Si Alloy

In the present study, the effect of Sn on the dry sliding wear behavior of spray formed and hot pressed Al–17Si alloy as a function of applied load and sliding speed has been investigated and compared with that of as-cast alloy. The microstructure of spray formed Al–17Si alloy consists of fine and uniformly distributed Si particles and that of Al–17Si–10Sn alloy consists of fine and uniform dispersion of Si particles and ultra-fine Sn particles in α-Al matrix. Coarse and segregated microstructures were observed in as-cast alloys. The wear resistance of spray formed alloys is higher than that of as-cast alloys. The wear resistance of as-cast Al–17Si–10Sn alloy is higher than that of as-cast Al–17Si alloy. The high wear resistance of spray formed Al–17Si–10Sn alloy is discussed in the light of its microstructural features and the nature of worn-out surfaces.