Open Access Minireview Article

A Short Review of Crystallographic Point Group T: Orbits and Stabilizers for a Regular Tetrahedron

Harun Akkus

Physical Science International Journal, Page 1-7
DOI: 10.9734/PSIJ/2015/20331

The clear definitions of symmetry operations (or elements) of the crystallographic point group T (tetrahedral group) were clearly pictured. For each element of the group, the permutation (P4) counterparts and the matrix representations were obtained. The orbits and stabilizers for vertices, edges, and faces of a regular tetrahedron under the action of T and, by this way, some subgroups of T were found.

 

Open Access Original Research Article

Luminescence Characteristics of Polymer Passivized Strontium Aluminate Phosphor

Abutu A. Nathan, Jubu P. Rex, Atser A. Roy

Physical Science International Journal, Page 1-6
DOI: 10.9734/PSIJ/2015/20601

Trivalent Europium ions doped strontium aluminate as the host and passivized by Polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and carboxyl methyl cellulose (CMC) shows luminescence arising from various 5D2 and 5D07F4 transition of Eu3+ ion upon excitation at 285 nm. The influence of the varied polymers concentration on crystal structures and optical properties was studied by means of X-ray diffraction (XRD) and photoluminescence (PL) spectrometer. XRD pattern revealed a dominant phase characteristics of orthorhombic strontium aluminate compound at 1000°C with an average crystal sizes of the phosphors calculated to be 39 nm – 42 nm. Photoluminescence emission spectral showed a broad peak at 648 nm with PVP sample having the highest luminescence intensity. These materials are likely to have high efficiency of conversion in the LED and display industries without a significance changes in the crystal sizes within the various phosphor samples.

 

Open Access Original Research Article

Regional Magnetic Field Trend and Depth to Magnetic Source Determination from Aeromagnetic Data of Maijuju Area, North Central, Nigeria

Akanbi Eti-Mbuk Stella, Fakoya Ayomikun David

Physical Science International Journal, Page 1-13
DOI: 10.9734/PSIJ/2015/21652

The aim of this study is to estimate regional magnetic field trend and depth to magnetic rocks within Maijuju area, North-Central, Nigeria. The Total Magnetic Intensity (TMI) map was gridded, contoured and interpreted for trends, closures and dislocations. The TMI map was reduced to the equator; Upward continuation to depth 1, 2, 3, km was carried out; the magnetic residual field map was divided into 4 blocks of area each 27 m ´ 27 m for 2-D spectral analysis of the magnetic anomalies over the area. All resultant maps were interpreted.

The TMI map revealed anomalies observed in the study area to trend largely in the NE-SW and E-W directions. Low magnetic intensities values were observed at Jos-Bukuru, Jarawa, Shere, and Kofai and Rop Complexes. Intermediate negative magnetic values (-54.5 to -5.3 nT/m) were observed at the Sara-Fier Complex. Positive magnetic intensity range of 72.9 to 270.7nT/m was seen to dominate the Older Granite region, the Basement Complex and part of Sara-Fier Complex, Magnetic Discontinuities which could represent geologic fractures were also observed. The TMI reduced to equator map was used to centre the peaks of magnetic anomalies over their sources. The upward continuation maps revealed that TMI continued upward to elevations of 1 km, 2 km and 3 km permits a clearer view of the deeper anomaly sources and showed the regional magnetic field trend to be in the NE-SW direction. The spectral depth analysis result showed that the deeper magnetic sources have an average depth of 1.47 km while the shallow magnetic sources have an average depth of 360 m (0.36 km).

The regional magnetic field trend as observed from the upward continuation process is NE-SW trend while the spectral depth analysis result revealed that the deeper sources have an average depth of 1.47 km while the shallow sources have an average depth of 360 m (0.36 km).

 

Open Access Original Research Article

Magneto-Thermal Instability of Rotating Partially Ionized Hall Plasma Flowing Through Porous Medium

R. K. Pensia, V. Shrivastava, A. K. Patidar

Physical Science International Journal, Page 1-21
DOI: 10.9734/PSIJ/2015/10134

The magneto-thermal instability of infinite homogeneous self-gravitating rotating partially ionized Hall plasma in the presence of viscosity, electrical resistivity, permeability, porosity, rotation and finite electron inertia is studied by means of linear perturbation analysis. A general dispersion relation is obtained using the normal mode analysis. Furthermore, the wave propagation parallel and perpendicular to the direction on magnetic field has been discussed. The stability of the system is discussed by applying Routh-Hurwitz criterion. For longitudinal propagation, it is found that the condition of radiative instability is independent of the magnetic field, collision frequency of neutrals with ions, Hall currents, finite electron inertia, porosity and viscosity; but for the transverse mode of propagation it depends on the strength of the magnetic field, rotation, porosity and electron inertia but independent of viscosity, permeability, electrical resistivity and collision frequency. From figures, we found that the effect of collision with neutrals, rotation, magnetic field and temperature dependent heat-loss function have a stabilizing influence while thermal conductivity and density dependent heat-loss functions have destabilizing influence on the self-gravitational instability of partially-ionized gaseous plasma. In addition, the classical Jeans condition regarding the rise of initial break up has been considerably modified due to the radiative heat-loss function.

 

Open Access Original Research Article

Temperature-Frequency Characteristics of the Composition HDPE + x vol.% InP

M. I. Aliev, E. M. Gojaev, S. M. Rzaeva, Sh. Sh. Rashidova

Physical Science International Journal, Page 1-5
DOI: 10.9734/PSIJ/2015/18839

In the work obtained new matrix composite materials of high density polyethylene (HDPE) with a semiconductor additive. With a measuring instrument bridge E8-7 and E7-20 studied temperature and frequency dependence of the permittivity (ε) and the dielectric loss tangent (tgδ) composites HDPE + x vol.% InP at 290-440K temperature and frequency 25-106Hz intervals. Revealed that with increasing the volume content of the filler InP semiconductor is increased and ε tgδ. This occurs so that with increasing the volume content of the filler component the structure becomes unstable and the number of formed clusters is increased, and this leads to an increase the dielectric characteristics.

 

Open Access Review Article

Robustness Analysis of a Closed-loop Controller for a Robot Manipulator in Real Environments

Emmanuel Chukwudi Agbaraji

Physical Science International Journal, Page 1-11
DOI: 10.9734/PSIJ/2015/18253

The need to design a robot manipulator that can complete tasks satisfactorily in the presence of significant uncertainties brought about the continued advance research in robust system design. This paper focuses on the robustness analysis of a closed-loop controller for robot manipulator in real environment. The neglect of wide range of uncertainties and failure to study the fundamental behavioral responses during design stage of a control system result to the system failure in real environments. The robustness analysis studies these essential behavioral responses of a controlled system considering the significant uncertainties that exist in real environment in order to design a robust controlled system. It was concluded that the robot manipulator controlled system can only achieve robustness when it can maintain low sensitivities and zero steady state error, stable over the range of parameter variations and its performance continues to meet the specifications of the designer in the presence of wide set of uncertainties. Robustness and optimization of the robot manipulator can be achieved using closed-loop control technique. Bode plot can be used to ascertain the performance and robustness behavior of the controlled system in frequency domain. The disturbance rejection and disturbance rejection settling time describe how well and fast the controlled system can overcome disturbances.