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Volume 13, No. 1, April 2020, Ramadan 1441 H

 English Articles

 

 

Structural and Magnetic Properties of (Mg, Co)2W Hexaferrites
 

Precursor powders of BaMg2-xCoxFe16O27 with (x = 0.0, 1.0, and 2.0) were prepared using high-energy ball milling and the effects of chemical composition and sintering temperature on the structural and magnetic properties were investigated using x-ray diffractometer (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). XRD patterns of the prepared samples indicated that crystallization of pure BaW hexaferrite phase was achieved at a sintering temperature of 1300° C, while BaM and cubic spinel intermediate phases were obtained at lower sintering temperatures of 1100° C and 1200° C. SEM images revealed an improvement of crystallization of the structural phases and a growth of the particle size with increasing the sintering temperature. The magnetic data of the samples sintered at 1300° C revealed an increase of the saturation magnetization from 59.4 emu/g to 72.6 emu/g with increasing Co concentration (x) from 0.0 to 2.0. The coercive field Hc decreased from 0.07 kOe at x = 0.0 to 0.03 kOe at x = 1.0 and then increased to 0.09 kOe at x = 2.0. The thermomagnetic curves of the samples sintered at 1300° C confirmed the existence of the W-type phase and revealed spin reorientation transitions in Co-containing samples.

 

S. H. Mahmood,

Q. Al Sheyab,

I. Bsoul, Y. Maswadeh, Q.I. Mohaidat and

A. Awadallah

JJP, 2020, 13(1) ,  1-16

Chemical Characterization of Harmattan Dust across Oyo and Minna, Nigeria

Harmattan dust haze in Nigeria is due to annual deposition of very fine dust particles as a result of both natural and human activities. There are scanty reports on the mineralogical, elemental and heavy metal composition in the Harmattan dust blowing across the country to support the presence of minerals and elements in the Harmattan dust. The aim of this study is to assess minerals and elemental compositions of Harmattan dust variations across Oyo (7032'N, 3025'E) and Minna (9035'N, 6032'E), Nigeria. Harmattan dust samples were collected using clean plastic bowls of 10 cm diameter and analysis was conducted on the samples collected at the two stations using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Fluoresence (XRF), Particle Induced X-ray Emission (PIXE) and Atomic Absorption Spectroscopy (AAS). It was observed that elements, such as K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Mo, As, Zr, Pb, V, Sr, Cr and Ce, were present in different concentrations in the samples collected. Minerals, such as Quartz [SiO2], Rutile [TiO2], Periclase [MgO], Corundum [Al2O3], Hematite [Fe2O3], Cuprite [Cu2O], Baddeleyite [ZrO2], Litharge [PbO], Monazite [P2O5], Zincite [ZnO], Montroydite [HgO] and Lime [CaO], were present in the samples collected at each station in different proportions. The soil mass concentration of the elements was calculated and observed to be 3.5179μg m3 at Oyo and 3.4745μg m3 at Minna. It was observed that the Harmattan dusts moving across Nigeria have almost all the elements present in Harmattan dust varying from station to station as the dust is moving towards the south of the country. The study concluded that the elemental composition of the dust samples analyzed revealed that the percentage compositions of some elements are higher than the acceptable WHO standard values, which may affect human health. It is therefore recommended that adequate precautionary measures and policies should be made to help mitigate the effects of high elemental concentrations observed.

 

O. A. Falaiye and

F. O. Aweda


 

JJP, 2020, 13(1) ,  17-28

Physical Properties of RhCrZ (Z= Si, Ge, P, As) Half-Heusler Compounds: A First-Principles StudyWe use the first-principles-based density functional theory with full potential linearized augmented plane wave method in order to investigate the structural, elastic, electronic, magnetic and thermoelectric properties of RhCrZ (Z= Si, Ge, P, As) Half-Heusler compounds. The preferred configurations of the RhCrZ alloys are all type a. The structural parameters are in good agreement with the available theoretical results. The Young’s and shear modulus, Poisson’s ratio, sound velocities, Debye temperature and melting temperature have been calculated. Furthermore, the elastic constants Cij and the related elastic moduli confirm their stability in the cubic phase and demonstrate their ductile nature. The compounds RhCrSi, RhCrGe, RhCrP and RhCrAs are found to be half-metallic ferrimagnets (HMFs) with a half-metallic gap EHM of 0.37, 0.35, 0.25 and 0.02 eV, respectively. The half-metallicity of RhCrZ (Z= Si, Ge, P, As) compounds can be kept in a quite large hydrostatic strain and tetragonal distortion. The Curie temperatures of RhCrSi, RhCrGe, RhCrP and RhCrAs compounds are estimated to be 952, 1261, 82 and 297 K, respectively, in the mean field approximation (MFA). Thermoelectric properties of the RhCrZ (Z= Si, Ge, P, As) materials are additionally computed over an extensive variety of temperatures and it is discovered that RhCrAs demonstrates higher figure of merit than RhCrSi, RhCrGe and RhCrP. The properties of half-metallicity and higher Seebeck coefficient make this material a promising candidate for thermoelectric and spintronic device applications

 

B. Amrani,

A. Chahed,

M. Rahmoune,

K. Benkaddour and A. Sayede

 

JJP, 2020, 13(1) ,  29-46

Dark Matter: Could It Be Vacuum Viscosity?

We test a hypothesis that stars located away from the center of the galaxy, moving under the effect of an emergent viscous drag force perpendicular to their velocities, might exhibit the behavior observed in the rotation curves of the spiral galaxies. We construct a simple model for such an assumption, then by using simple fitting technique, we are able to produce the rotation curves for a sample of 18 spiral galaxies. Results show good agreement with the observed rotation curves. The applicability of our hypothesis suggests that an emergent drag force perpendicular to the velocity of the stars might be the cause of the apparent dark matter effect.

 

M. B. Altaie,

N. R. Suleiman and

N. M. Ershaidat

 

JJP, 2020, 13(1) ,  47-57

Solution of the Hamilton – Jacobi Equations in an Electromagnetic Field Using Separation of Variables Method – Staeckel Boundary Conditions

This manuscript aims to resolve the Hamilton-Jacobi equations in an electromagnetic field by two methods. The first uses the separation of variables technique with Staeckel boundary conditions, whereas the second uses the Newtonian formalism to solve the same example. Our results demonstrate that the Hamilton-Jacobi variables can be completely detached by using separation of variables technique with Staeckel boundary conditions that correspond to other results using Newtonian formalism.

 

B. M. Al-Khamiseh,

R. S. Hijjawi and

J. M. Khalifeh

JJP, 2020, 13(1) ,  59-65

Reformulation of Degasperis-Procesi Field by Functional Derivatives

We reformulated the Degasperis-Procesi equation using functional derivatives. More specifically, we used a semi-inverse method to derive the Lagrangian of the Degasperis-Procesi equation. After introducing the Hamiltonian formulation using functional derivatives, we applied this new formulation to the Degasperis-Procesi Equation. In addition, we found that both Euler-Lagrange equation and Hamiltonian equation yield the same result. Finally, we studied an example to elucidate the results.

 

Y. M. Alawaideh,

R. S. Hijjawi and

J. M. Khalifeh
 

JJP, 2020, 13(1) ,  67-72

Assessment of Natural Radionuclides in Local and Imported Cements in Erbil Governorate, Kurdistan Region- Iraq

A total of 10 cement samples were collected from the manufactures and markets. Spectrometry analysis of Sodium Iodide NaI (Tl) detector was used for measuring the samples' specific activity. The obtained specific activities of (226Ra, 232Th and40 K) were (35, 30 and 400) Bq/kg, respectively, which are below the critical values suggested by UNSCEAR2000. The radiological hazard indices of radium equivalent activities (Raeq), the indoor absorbed dose , the internal annual effective dose equivalent (Ein) and the internal index (Hin) were calculated. All of the obtained values were below the world wide recommendation values. Fortunately, from the analyzed results, it was concluded that the local and imported cements in Erbil governorate will make no risk when used in building constructions.

 

Ali H. Ahmed,

Adeeb O. Jafir and Hallo M. Abdullah

 

 

JJP, 2020, 13(1) ,  73-77

Thermoelectric Properties of ALiF3 (A= Ca, Sr and Ba): First-Principles Calculation

The energy band structure obtained from WIEN2k calculations is used to calculate the transport coefficients via the semi-classical Boltzmann transport theory with constant relaxation time (t) as employed in the BoltzTraP package for ALiF3(A= Ca, Sr and Ba) using mBJ-GGA potential. The thermoelectric properties of the above compounds are investigated through the calculation of the main transport properties: Seebeck coefficient (S), electrical (s) and electronic thermal (ke) conductivity, figure of merit (ZT) and power factor. All compounds show insulating behavior.

 

Nada T. Mahmoud,

Ahmad A. Mousa and

J. M. Khalifeh

 

 

JJP, 2020, 13(1) ,  79-86

     

 Technical Note

 

 

High Efficiency of Solar Cell Model Based on Two Types of Nanoparticles

Climatology of aerosols, their trends and classification based on the long-term Moderate Resolution Imaging Spectroradiometer (MODIS) measurements (from February 2000 to July 2015) of aerosol optical depths at 550 nm (τ550) and Angstrom exponent   (α470-660) using the wavelengths of 470 and 660nm in Nairobi, Skukuza and Ilorin AERONET stations were analyzed in this work. The level-2 collection-6 Deep Blue (L2 C006 DB) of the parameters listed above from the aqua- (MYD04) and terra- (MOD04) MODIS of the study area were statistically analyzed using SPSS. To be able to understand the temporal variation in the characteristics of aerosols in the three stations and during each season separately, MODIS measurements of τ, retrieved for the study area, were compared with AERONET τ. Overall, aqua-MODIS τ corroborate the AERONET measurements well in Nairobi and Ilorin stations with underestimation of 29.80 % and overestimation of     2.90 % respectively, whereas Skukuza station has terra-MODIS τ as the best representation of the AERONET measurements with underestimation of 1.90 %. ....

 

Kholoud Kh. Abushaar,

Mohammed M. Shabat,

Dena M. El-Amassi and

Daniel M. Schaadt

 

 

JJP, 2020, 13(1) ,  87-92