Open Access Short Research Article

Cathode Plasma Radiation in a Repetitive Pulsed Diffuse Discharge in an Inhomogeneous Electric Field

E. Kh. Baksht, A. G. Burachenko, M. V. Erofeev, V. F. Tarasenko

Physical Science International Journal, Page 669-673
DOI: 10.9734/PSIJ/2014/8589

The radiation produced by nanosecond repetitive pulsed discharges in nitrogen, air and argon was studied, including its study with a CCD camera. It is shown that within the first nanosecond, diffuse plasma covers the lateral surface of a conical cathode at relatively low electric field strength (~105 V/cm). The nature of this phenomenon is discussed. Photos of the discharges in nitrogen, air and argon in an inhomogeneous electric field with different cathode materials and at different pressures are presented.

 

Open Access Short Research Article

Effect of Polarity of the Voltage Pulse on the Appearance of the Discharge at the Breakdown in the Non-uniform Electric Field

D. V. Beloplotov, M. I. Lomaev, D. A. Sorokin, V. F. Tarasenko

Physical Science International Journal, Page 686-691
DOI: 10.9734/PSIJ/2014/8590

At the pressures 0.5-3 atm of the air, nitrogen, argon and sulfur hexafluoride (SF6) an appearance of the nanosecond discharge in the nonuniform electric field is investigated. In all gases at the negative polarity of the voltage pulses, supershort avalanches electron beam (SAEB) and (or) x-ray were registered.  It was obtained, that formation of the bright spots on the flat electrode at the negative polarity of the electrode with small radius of curvature was observed during the changing of the discharge current polarity. It was shown, that at the positive polarity of the electrode with a small radius of curvature bright spots on the flat electrode arise due to the participation of the dynamic displacement current in the gap conductance.

 

Open Access Original Research Article

Evidence for Negative Electron Affinity in Laser Irradiated ZnTe Thin Films

Sachin D. Kshirsagar, M. Ghanashyam Krishna

Physical Science International Journal, Page 657-668
DOI: 10.9734/PSIJ/2014/5907

Local transport properties of laser irradiated ZnTe thin films are reported.  By rastering the laser beam (of 532 nm wavelength) appropriately, ZnTe decomposes into n-type ZnTe and Te and a grating like structure with micro-stripes of ZnTe separated by grooves of Te is obtained. Conductive atomic force microscopy studies and local I-V measurements made on the stripes and grooves show that the film properties are mainly determined by chemical composition, rather than by the topography of the film. When the tip is positively biased, the current images closely match the topography images.  In contrast, when the tip is negatively biased the current and topography images are very different and a large negative current was also observed in the grooves. This is attributed to the variation in charge separation (interface capacitance) caused by the rough surface. It is shown that Te forms ohmic contact with Au tip, but the junction exhibits Schottky diode behavior under low biasing voltages.  The large current at both high positive and negative tip biasing may arise due to semi-metallic properties of Te. The I-V characteristics measurement reveals formation of Schottky barrier between ZnTe-Au junctions with a very low value (32.4 – 78.3 meV) of barrier which indicates the presence of negative electron affinity.

 

Open Access Original Research Article

Computer Implementation of the Drbem for Studying the Classical Coupled Thermoelastic Responses of Functionally Graded Anisotropic Plates

M. A. Fahmy, A. M. Salem, M. S. Metwally, M. M. Rashid

Physical Science International Journal, Page 674-685
DOI: 10.9734/PSIJ/2014/7403

A numerical computer model based on the dual reciprocity boundary element method (DRBEM) is extended to study the generalized thermoelastic responses of functionally graded anisotropic rotating plates. In the case of plane deformation, a predictor-corrector implicit-explicit time integration algorithm was developed and implemented for use with the DRBEM to obtain the solution for the displacement and temperature fields in the context of the classical coupled thermo-elasticity theory. Numerical results that demonstrate the validity of the proposed method are also presented in the tables.

 

Open Access Original Research Article

Geometric Structure and Some Exact Solutions of Plateau Equation

Mehdi Nadjafikhah, Naser Asadi

Physical Science International Journal, Page 692-698
DOI: 10.9734/PSIJ/2014/6746

In this paper, we get the set of symmetry of Plateau differential equation. Using Lie symmetry method to obtain the classical symmetry operators. Also, we get one-dimensional optimal system of the Plateau equation and reduction Lie invariants, corresponding to infinitesimal symmetries.

 

Open Access Original Research Article

Optical Functions and Effective Masses of Electrons and Holes in InGaTe2

E. M. Godzhaev, U. S. Abdurahmanova, Z. A. Dzhakhangirli, S. M. Mehdieva

Physical Science International Journal, Page 699-707
DOI: 10.9734/PSIJ/2014/7555

The optical functions and effective masses of electrons and holes of ternary compound InGaTe2 crystallizing in a tetragonal syngony are calculated in the energy interval 0-12eV using pseudo-potential method. Imaginary and real parts of dielectric permeability, optical conductivity, index of refraction and spectral dependences of coefficient of reflection and imaginary part of inverse value of complex dielectric permeability of compound  InGaTe2 for e||c and ec polarization are reported.

 

Open Access Original Research Article

Biodegradation, Bioactivity and In vivo Biocompatibility Analysis of Plasma Electrolytic Oxidized (PEO) Biodegradable Mg Implants

Mehdi Razavi, Mohammad Hossein Fathi, Omid Savabi, Daryoosh Vashaee, Lobat Tayebi

Physical Science International Journal, Page 708-722
DOI: 10.9734/PSIJ/2014/9265

In this paper, a plasma electrolytic oxidation (PEO) coating was prepared on AZ91 magnesium (Mg) implant to improve its degradation resistance, bioactivity and biocompatibility. The phase composition and surface morphology of the samples were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM). The corrosion rate and the bioactivity behavior of the samples were investigated via electrochemical measurements and immersion tests in simulated body fluid (SBF). The biocompatibility of samples was evaluated both in vitro and in vivo. To performed in vitro examinations, L-929 cells were cultured on both coated and uncoated substrates, and for the in vivo study, samples were implanted into the greater trochanter of rabbits as our animal model. The results showed that the PEO coating enhanced the corrosion resistance and in vitro and in vivo biocompatibility of AZ91 Mg implants.  

 

Open Access Original Research Article

Vibration Technique for Processing and Monitoring Electrical and Mechanical Defects in Electrical Drives Using 2-D Mathematical Model

Ali S. Hennache, Lazhar Bougoffa

Physical Science International Journal, Page 723-733
DOI: 10.9734/PSIJ/2014/5713

The radial flux density in the air-gap of rotating machines sets up a force of attraction between the stator and the rotor surfaces. In a symmetrical machine, the radial stresses distributions are balanced resulting in zero net force on the rotor. However, if the rotor of a rotating machine is supported eccentrically with respect to the stator or if rotor short circuits occur, a one-sided magnetic force will be developed which generally tends to increase the eccentricity and increases considerably the critical speed of the machine. The resultant force created by the unbalanced forces of attraction is called unbalanced magnetic pull (ump). Under certain conditions these forces may cause the individual parts of the machine to vibrate and thus develop a noise. The vibrating parts are more stressed and are frequent sources of troubles, they also cause a rapid ageing of the machine. Furthermore, the  machine  vibrations  are  transferred  to  the bases and may, with  large  machines,  cause a  vibration  of  the  entire surroundings of the machine. In the following paper a brief outline of the mathematical analysis associated with a technique for monitoring defects in rotating machine whilst the machine is running in normal service is described. This technique is based upon the use of sensors in the air-gap, so arranged that the symmetrical air-gap is eliminated and only the lack of symmetry due predominantly to the missing flux associated with electrical and mechanical failures (eccentricity, increased vibrations, bending of the rotor shaft etc.), are displayed. A small four-pole machine with a modified field winding and bearings is used to examine experimentally both electrical and mechanical anomalies of various magnitude and position.

 

Open Access Original Research Article

Bianchi Type-III Magnetized Perfect Fluid Cosmological Model with Time-Varying

M. K. Singh and Shri Ram

Physical Science International Journal, Page 742-753
DOI: 10.9734/PSIJ/2014/8403

Bianchi type-III model of universe filled with a magnetized perfect fluid together with a time-varying cosmological constant is investigated in general relativity. We assume that F12 is the only non-vanishing component of the electromagnetic tensor Fij . We obtain exact solutions to Einstein’s field equations by using an ad-hoc mathematical relation. The physical and geometrical behaviors of the cosmological model are discussed.

Open Access Review Article

Investigation on Characteristics of PVDF/ZnO Nanocomposite Films for High-k Capacitors

A. K. Chilvery, A. K. Batra, Mychal Thomas

Physical Science International Journal, Page 734-741
DOI: 10.9734/PSIJ/2014/9026

Aims: To investigate the dielectric and electrical properties of nanocomposite films for their application as high-k capacitors

Study Design: The ferroelectric polymer PVDF is doped with ZnO nanoparticles (ZnO-NP) to study the dielectric properties

Place and Duration of Study: Material Science laboratories at the Department of Physics, Chemistry and Mathematics at Alabama A&M University during the months from February 2013 to December 2013

Methodology: In this work, homogeneous ceramics-polymer nanocomposites consisting of zinc oxide (ZnO) nanoparticles as fillers and poly (vinylidene fluoride) (PVDF) polymer as matrix have been prepared using a solution casting process.  The temperature dependency of the dielectric permittivity of the nanocomposite films suggests that the introduced ZnO phase and interface areas contribute to the improvement of the dielectric response.

Results: In comparison with pure PVDF film, dielectric permittivity of the nanocomposite with a small amount of filler volume fraction (8.6%) significantly improved by two times. Thus, it can be predictedwith higher concentrations of ZnO nanoparticles, composite films will have higher dielectric constants and warrants in applications as high-k capacitors for printed organic electronics.

Conclusion: The nanocomposites thick films by embedding ZnO-NPs in PVDF matrix have been successfully fabricated. The nanocomposite displayed better dielectric properties than the pristine PVDF specimens did. As expected, the effective dielectric constant of PVDF increased when it was mixed with ZnO-NPs over the entire temperature range investigated. However, as the concentration of ZnO-NPs increased, the dielectric constant for the PVDF/ZnO-NPs nanocomposite doubled over that of pure PVDF. It can be concluded nanocomposites fabricated with higher concentration of ZnO-NPs have a potential to meet both present and future technological demands of high-k dielectrics and embedded capacitors/organic substrates.