Rafidain Journal of Science

By method of difference equations an equation of motion have been calculated for two coupled linear chains with different atoms. Special cases are discussed and shows full agreement with the above results.

An orthorhombic strain model for V2+ in GaAs is presented in this work. Spin and effective Hamiltonians are derived for this model. A brief summary of the Jahn-Teller effects and random strains has been given. The JTEs show them selves by introducing reduction factors in the first and second terms of effective Hamilltonian and the random strains by lowering the local symmetry at V2+ ion sites.

Electrical conduction is observed in n-hexane and cyclo-hexane under the influence of uniform electric field which is produced by using plate-plate electrode geometry, this paper discusses the action of ignites bubbles and streamer initiation on the electrical conductivity, which definitely leads to electrical breakdown in dielectric liquids.

The photoelectric cross-section for the tissue equivalent materials is in the first place dependent on the effective atomic number calculated on the basis of the exponent m, where m varies with photon energy and the elements involved.
In the present work, a graphical method was used to evaluate the effective atomic number Zeff for any material at any photon energy independent on the value of the parameter m. The results are in good agreement with the calculated values using the known empirical formula.

The effect of pressur on the recoilless fraction (1) for the gamma-ray transition 14.4 keV emitted by Fe57 as an impurity in copper, using phonon frequency spectrum (pfs) analysis and Debye model calculations has been studied. The variation in Grüneisen parameter () and Debye temperature (D) with pressure are included as included as improvement over previous studies. The transition results which have been obtained are in good agreement with the experimental values .

The work is concerned with the analyzing and studing the magnetic field dependence of the dipole- dipole interaction frequency for Oxygen ion center and it’s neighbours. Six groups of ions are described by their geometrical part tensors and analyzed for two different combinations of axes in presence of an external magnetic field. Discussion is given for the interpretation of these results.

The I-V characteristics curves in this work have been seen irreversible , in purified saturated hydrocarbon liquids, in other words, the conduction Current curves in increasing direction does not coincide with that of decreasing one . Such behaviour may be attributed to the effect of space charges. It is also believed that the build up of the space charges is quicker during the increasing direction than its distraction direction in recombination processes, or due to creation of gas bubbles and liquid clusters which leads definitely to complex changes in refractive index and dielectric constant of the tested liquid.

The dielectric constant Ke, electrical susceptibility  and the voltage dependence of the electrical conductivity  have been studied at room temperature for five specimens of amphibole asbestos, including anthophyllite, grunerite, tremolite, actinolite and rebeckite. The sudden increase in electrical conductivity at voltage 400 volt for our specified grunerite specimen indicated a surprising phenomenon and correlated with the beginning of the transition of oxidation states of iron in the specimen and creation of new electrical carriers. It is a phenomenon of voltage stabilization

In this research a method is proposed to determine the direction of the axis of YBCO HTS (high temperature superconductor ) thin films epitaxially grown on ZrO2 single crystals, with respect to the directions of axis of crystals of ZrO2 of the substrate, using the data from Laue and osillating crystal methods. .After making calculations on Laue and vibrating crystal difraction pictures by projecting them on computer screen, the lattice parameters was determined by drawing the reciprocal lattice picture.The angle between the YBCO and substrate crystals was found to be 45 degree. This method can be equally applied to determine the direction of any epitaxially grown thin film with respect to the crystals of the substrate.

A binary mixture of Ar-CO2 with equal percentage was used in the thermal diffusion column. A set of different temperature and pressures were applied. Through the operation of separation, the separation factor and the thermal diffusion factor were calculated. The molecular force parameter was calculated through a special computer program using the well known Lennard-Jones (12-6) molecular model. The results are in agreement with those extracted from viscosity measurement.

This paper deals with the calculation of stopping power for solid media. A semi-empirical formula for stopping power used by other author for liquid media, was adjusted via the values of the parameter K in order to suit the solid media. This modification proved to give better agreement of the calculated stopping power with the experimental value.

A Mathematical model describing lattice vibration is built for solid state lattice. The lattice considered consist of two crystal slabs with different atoms. Difference equation method formed the building stone of the model. Results of calculation indicate good agreement with results obtained by other authors

The present research includes studying the effect of position and geometrical shape of the coil on magnetic flux lines trajectory also on the shape of the magnetic flux density distribution of a single polepiece lens where by its objective focal properties were designed and studied previously by researchers.
It has been noticed that the change in coil position in comparison
with the original design causes important improvement in the magnetic flux lines distribution inside the structure of the lens and clearly increasing the value of the magnetic flux density peak.
Besides, the conical and vertical iron shroud was introduced to the original lens giving a clear effect in improving the lens performance and magnetic flux lines path, furthermore, increasing the magnetic flux peak as well as decreasing the half-width as a result the objective focal properties of the lens lead to a large improvement in lens performance comparing with the optical properties of the original lens design.

This paper presents a simple design procedure for dealing with the requirements for a comfortable thermal environment. From the expected activity level and clothing insulation of the people concerned, a subjective temperature is calculated which will provide thermal comfort. This subjective temperature is a combination of physical parameters of the environment, i.e., air and mean radiant temperatures, and air speed.
Consequently a heating system must be designed so that the parameters would combine to give the optimum subjective temperature. This proposed procedure also considers other possible sources of discomfort, and gives an acceptable limits for them.

The separation of chlorine isotopes in an aqueous solution is demonstrated… the separation took place in thermal diffusion, column TDC. Separation action was proved using four types of measurements. These measurements include density, electrical conductivity, melting temperature and PH values. The TDC used is 1.5 m high. The TDC heating process was that which employs skin effect electromagnetic heating.