Zanco Journal of Pure and Applied Sciences

The present study aims to evaluate the activity concentration of effective radium content (Raeff), and radon exhalation rates (222Rn) of 21 imported granite samples that are used as building materials in Erbil Governorate. The measurements were carried out using a Rad7 and LR-119 type II plastic track detectors as an active and passive measuring, respectively. The radon activity concentrations for both detection methods were varied from 25.9 ± 6.85 to 427 ± 38.3 Bq.m-3, and from 31.23 ± 5.8 to 433.63 ± 35.2 Bq.m-3with an average value of 99.35 ± 13.84 Bq.m-3 and 103.16 ± 9.46 Bq.m-3, respectively. The effective radium content, radon exhalation rate in terms of surface and mass were calculated using LR-115 technique, and it was found to vary from (0.2 ± 0.04 to 2.94 ± 1.5) Bq.kg-1, (59.07±7.67 to 819.95±28.5) mBq.m-2 h-1, and (1.5±1.1 to 22.23±4.5) mBq.kg-1.h-1 respectively. The results show that some of the granite samples exceeded the radioactively acceptable limit, which means that they may be harmful to the human health.

In the setting of 5th generation, where the amount of information transferred has drastically expanded along with the skills of communication system attackers, the necessity for a strong security system has garnered crucial relevance. This work proposes and experimentally validates a physical-layer based poly technique for securing orthogonal frequency division multiplexing for machine-to-machine communication (OFDM-M2M). The proposed model is based on a 4-D hyper digital chaotic sequences keys generator that is used to provide the necessary keys to encrypt input image data in the spatial domain using two sub-stages of permutation and one-time pad (XOR) before sending the encrypted data to the second layer of security that involves independently scrambling Quadrature Amplitude Modulation (QAM) symbols into a complex plane. The proposed system proved to enhance the capability to withstand exhaustive attacks and making it more difficult for unauthorized attackers to obtain user data. with 4-D hyper digital chaos, high-security levels are achieved in the simulation result with a sizable key space. The simulation results revealed that the proposed secure OFDM system successfully achieved zero BER at SNR=15, whereas a SNR deterioration of 1.5 dB at 10-4 BER has been recorded with respect to unsecure OFDM system which can be tolerated by the robustness of proposed system with massive key space of ~10220, which is adequate to fend off any exhaustive attacks.

A modified model is proposed to account for the effects of roughness on lattice thermal conductivity (LTC) in Si nanowires (SiNWs). Depending on the modification of the Debye-Callaway models effects of surface roughness is carried out to predict LTC in SiNWs. Through the process of fitting the calculated curve to that of the reported experimental data, phonon scattering strength from the boundary, Umklapp-normal phonon–phonon processes, electron-phonon and defects were estimated. The phonons scattering through roughness boundaries due to rough nanowires indicates a smaller phonon mean free path compared to that of their diameters. However, the Casimir limit for phonons mean free path particularly in 22nm nanowire diameter found to be due to phonons involved in completely diffused boundary scattering processes, while for other diameters (37, 56, 115) nm, the effects were smaller with values ranging from 0.35 to 0.685. In general, for a given temperature, LTC decreases with the decrease of NWs diameter.

An approach is made to calculate and analyze some thermodynamical properties including the combination of Lindemann’s role for melting, dimensionless mass, and structure factor in the role of lattice structure as the mean bond length to examine their dependency in group IV elements and SiC tetrahedral semiconductors. The results were a direct relation for Lindemann’s ratio (f) ad dimensionless mass μ with these materials mean bond length 〖(d〗_mean) in the form of f=0.214d_mean^(-1) and μ=435〖d_mean〗^2 respectively. From the modification of these relations, the nanosize dependence for both Lindemann’s ratio and dimensionless mass with that of the materials structure factor was calculated. The results are a decrease in Lindemann’s ratio and an increase in the dimensionless mass with the size decrease of Si nanoparticles