Open Access Original Research Article

Modeling and Simulation of High Blocking Voltage in 4H Silicon Carbide Bipolar Junction Transistors

Hamid Fardi

Physical Science International Journal, Page 127-136
DOI: 10.9734/PSIJ/2015/17567

For a given breakdown voltage, the drift region thickness and doping concentration of punch-through structure can be optimized to give the lowest specific on-resistance. An optimization scheme performed for a breakdown voltage of 14 kV in 4H-SiC bipolar junction transistor (BJT) at 300 K. The optimum drift region thickness and doping concentration for a 4H-SiC punch-through structure at different breakdown voltages are presented. The optimum drift region thickness and doping concentration are 114 μm and , respectively, which results in the lowest specific on-resistance of 117 mΩcm2. The specific on-resistance is compared with the theoretical specific on-resistance of non punch-through structure. It is shown that the optimized punch-through structure not only has a thinner drift region, but also has a slightly lower specific on-resistance than non punch-through structure. The model is applied and compared to a measured 4H-SiC bipolar transistors with high blocking voltage and results are discussed. The experimental 4H-SiC BJT is able to block 1631 V at 300 K and 2033 V at 523 K, respectively and when the base is open. The simulated blocking voltage when base is open is slightly lower (1600 V at 300 K) than the experimental value due to the current-amplifying properties of the common-emitter BJT.

 

Open Access Original Research Article

Spectroscopic Investigation and Magnetic Study of Iron, Manganese, Copper and Cobalt-doped Hydroxyapatite Nanopowders

H. Kamal, A. M. Hezma

Physical Science International Journal, Page 137-151
DOI: 10.9734/PSIJ/2015/18676

Pure, Mn+2, and Fe+3- doped hydroxyapatite (HAp) nanoparticles were synthesized by the wet chemical method. Another two samples were prepared by mixing Mn+2 with Cu+2 into HAp (Mn-Cu HAp) and Fe+3 with Co+2 into HAp (Fe-Co HAp). All samples were prepared without change in the stoichiometric ratio of Ca/P inside the structure of HAp. Samples were characterized by different types of techniques such as XRD, FTIR, ESR, SEM, and EDX. The measurements revealed that a typical HAp powder patterns were obtained.  Comparing with pure HAp, Mn+2 substituted HAp (Mn-HAp) and Fe+3 substituted HAp (Fe-HAp) did not demonstrate significant structure deviation. Since the ion exchange mechanism was achieved for the preparation process, the morphology and particle size were not significantly affected but the calculated crystallinity index (CI) values were affected.

The absorption spectra of the doped samples are presented as absorption bands a typical Mn+2, and Fe+3 occupying to different crystalline sites. The obtained data agrees well with that obtained from XRD. The crystal field parameters and crystallinity index for sites of these ions in the HAp matrix were calculated. SEM analysis indicated that nanoparticles aggregates were formed. EPR properties make the studied sample to be used in the field of hyperthermia application.

 

Open Access Original Research Article

Electro-Gravity via Geometric Chronon Field

Eytan H. Suchard

Physical Science International Journal, Page 152-185
DOI: 10.9734/PSIJ/2015/18291

Aim: To develop a model of matter that will account for electro-gravity.

Interacting particles with non-gravitational fields can be seen as clocks whose trajectory is not Minkowsky geodesic. A field, in which each such small enough clock is not geodesic, can be described by a scalar field of time, whose gradient has non-zero curvature. This way the scalar field adds information to space-time, which is not anticipated by the metric tensor alone. The scalar field can’t be realized as a coordinate because it can be measured from a reference sub-manifold along different curves. In a “Big Bang” manifold, the field is simply an upper limit on measurable time by interacting clocks, backwards from each event to the big bang singularity as a limit only. In De Sitter / Anti De Sitter space-time, reference sub-manifolds from which such time is measured along integral curves, are described as all events in which the scalar field is zero. The solution need not be unique but the representation of the acceleration field by an anti-symmetric matrix, is unique up to SU(2) x U(1) degrees of freedom. Matter in Einstein Grossmann equation is replaced by the action of the acceleration field, i.e. by a geometric action which is not anticipated by the metric alone. This idea leads to a new formalism of matter that replaces the conventional stress-energy-momentum-tensor. The formalism will be mainly developed for classical but also for quantum physics. The result is that a positive charge manifests small attracting gravity and a stronger but small repelling acceleration field that repels even uncharged particles that measure proper time, i.e. have rest mass. Negative charge, manifests a repelling anti-gravity but also a stronger acceleration field that attracts even uncharged particles that measure proper time, i.e. have rest mass.

 

Open Access Original Research Article

Studies of Pharmaceutical Active Ingredients in Drugs through Radiological Parameters

A. Manjunath, B. R. Kerur

Physical Science International Journal, Page 186-191
DOI: 10.9734/PSIJ/2015/18029

Mass attenuation coefficient and effective atomic number of the active pharmaceutical ingredients viz, Alprazolam, Amiodar, Amiodarone, Ciprofloxacin, Diclofenac Sodium, Femotidine and Nimesulide have been calculated over a wide energy range from 1 keV to 100 GeV for total and partial photon interactions by using WinXCom. The obtained data shows that the change in mass attenuation coefficient and electron density varies with energy and chemical composition of the active pharmaceutical ingredients (API’s) in drugs. The results in the variation of photon interaction with energy and effective atomic number of the API’s in drug are shown in the logarithmic graphs.

 

Open Access Original Research Article

Dynamic Buckling Load of an Imperfect Viscously Damped Spherical Cap Stressed by a Step Load

G. E. Ozoigbo, E. Nwaeze, M. Okpala

Physical Science International Journal, Page 192-213
DOI: 10.9734/PSIJ/2015/18109

This paper determines the dynamic buckling load of a lightly and viscously damped imperfect spherical cap with a step load. The spherical cap is discretized into a pre-buckling symmetric mode and a buckling mode that consists of axisymmetric and non-axisymmetric buckling modes. The imperfection is taken at the shape of the buckling mode. The inherent problem contains a small parameter which necessitated the adoption of regular perturbation procedures, using asymptotic technique. The general result is designed to display the contributions of each of the terms in the governing differential equations. We deduce the results for the respective special cases where the axisymmetric imperfection parameter, namely  and the non-axisymmetric imperfection parameter , are zeros. We also determine the effects of each of the non-linear terms as well as the effects of the coupling term.

Open Access Original Research Article

Bianchi Type-IX Cosmological Model with a Perfect Fluid in f(R) Theory of Gravity

H. R. Ghate, Atish S. Sontakke

Physical Science International Journal, Page 214-222
DOI: 10.9734/PSIJ/2015/18515

Bianchi type-IX space-time is considered in the framework of the ƒ(R) theory of gravity when the source of the energy momentum tensor is a perfect fluid. The cosmological model is obtained by using the condition that the expansion scalar (θ) is proportional to the shear scalar (σ). The physical and geometrical properties of the model are also discussed.