Volume 16, Issue 4, Winter 2005, Page 1-118

Theoretical Model for Vanadium Doped Gallium Arsenide

Adnan M. Al-Sheikh

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 7-14
DOI: 10.33899/rjs.2005.41413

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 in N-Hexane and Cyclo-Hexane Under the Influence of Uniform Electric Field

Haitham A. H. Al- Rawachy

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 15-21
DOI: 10.33899/rjs.2005.41415

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 Effective Atomic Number of Tissue Equivalent Materials

Sleeman Y. Sleeman; Khalid A. Jassim; Hayfa A. AL-Sawaf

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 22-27
DOI: 10.33899/rjs.2005.41420

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.

Pressure Dependence of the Recoilless Fraction For 14.4keV Transition of Fe57 in Copper

Yahya N. Al-Jamal; Mumtaz M. Saleh; Adnan M. Al-Sheikh

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 28-35
DOI: 10.33899/rjs.2005.41423

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 .

Computation of Magnetic Field Dependence of the Dipolar Interaction Frequency of Oxygen Ion Center in CaF2 Crystal

Mekhaiel A. Mossa; Farouk A. Kasir

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 36-48
DOI: 10.33899/rjs.2005.41428

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.

Irreversibility of Current-Voltage Characteristics in Hydrocarbon Liquids.

Haitham A. H. Al- Rawachy

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 49-54
DOI: 10.33899/rjs.2005.41435

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.

Study of Electrical Properties of Some Amphibole Asbestose

Marwan Z. AL-Tai; Yasir A. AL-Jawady; Farouk A. Kasir

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 55-64
DOI: 10.33899/rjs.2005.41442

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

Determination of the Relative Directions of YBCO HTS thin Films with Respect to ZrO2 Single Crystal Substrate

Bassam M. Mustafa

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 65-74
DOI: 10.33899/rjs.2005.41443

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.

Experimental Measurements of Molecular Force Parameter for Ar-CO2 Gas Mixture

Anwar M. AL-Faydhi; Asem A. Azooz

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 75-80
DOI: 10.33899/rjs.2005.41447

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.

Stopping Power of (1.895-7.4 MeV) 4He Ions in Composite Foils and Pure Elements

Nadwa I. Mahmood

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 81-88
DOI: 10.33899/rjs.2005.41457

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.

Theoretical Study of Longitudinal Vibrations of Two Coupled Crystal Slabs Using Difference Equations Method

Mekhaiel A. Mossa

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 89-94
DOI: 10.33899/rjs.2005.41461

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 Effect of Coil Geometry and Magnetic Circuit on the Flux Lines Trajectory of the Magnetic Lenses

Alaa A. H. Ahmed

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 95-108
DOI: 10.33899/rjs.2005.41490

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.

A Guide to Thermal Comfort Environment

Ahmad N. Al-Sabha

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 105-111
DOI: 10.33899/rjs.2005.41497

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.

Separation of Chlorine Isotopes in Sodium Chloride Solution Using Thermal Diffusion Column

Hazim S. Hilal; Asem A. Azooz

Rafidain Journal of Science, 2005, Volume 16, Issue 4, Pages 112-118
DOI: 10.33899/rjs.2005.41502

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.