Free space optic (FSO) is one of the most effective solution technique to transmit the information due to its advantage such as cost and speed, but it suffers from various disadvantage that affects on the signal performance like weather condition that results loss in optical signal power over the communication path. So, in this paper we study the effect of the rain weather in Iraqi cities [ Baghdad, Basra, Mosul ] during 2017 on the FSO signal with system of hybrid Sub-carrier multiplexing _Spectral amplitude coding _ optical code division multiple access (SCM-SAC-OCDMA) with multi diagonal (MD) code and intermediate stage called ‘optical amplifier’. OCDMA allows multiple users to access the medium without any contention; it provides privacy and security with reducing the interference that may occur due to multiple users. MD code has been use to provide simplicity in design and high data rate. The optical amplifier with controlled gain leads to amplify the power of the signal. Results from simulation analysis for the proposed system can transmit data rate with (1Gbps) for (1 Km) distance and transmit power of (5dB) with bit error rate (BER) 10−12 in Mosul, 3× 10−56 in Baghdad, 1 × 10−62 in Basra.

<span>Several studies have been carried out to investigate the effect of Lanthanum (La³⁺) ion substitution on the structural and magnetic properties of manganese-chromium (Mn-Cr) ferrite of chemical formula Mn La_xCr Fe₂O₄(x=0.0, 0.25 and 0.5). Such studies have made efforts to improve the magnetic and structural properties of manganese-chromium (Mn-Cr) ferrite by using lanthanum substituted nano ferrites and then synthesized using the sol-gel method and annealed at a temperature of 700^oC. The changes that occurred in the structure of the nano ferrites as a result of lanthanum substitution were identified using X-ray diffraction (XRD). Based on Debye-Scherrer equation, the XRD data were used in measuring the particle sizes of different diffraction and average crystallite size by means of Fourier Transform infrared spectroscopy (FTIR). In analyzing the morphology of the nano ferrites, scanning electron microscopy (SEM) was used, elemental compassion was studied using energy dispersive X-ray spectroscopy (EDAX), and the average particle diameter was determined using Transmission electron microscopy (TEM) studies. FTIR spectral analysis of the prepared samples under investigations revealed the formation of a single phase spherical particles. Two important absorption bands were observed; one (<em>ν₁</em>) around 556 cm^-1, which is attributed to the intrinsic vibrations of tetrahedral complexes, while the other low frequency band (<em>ν₂</em>) was around 430 cm^-1, and attributed to octahedral complexes.</span>

<span class="s19">In this paper, An important definitions are to be used to prove the existence of a common fixed point theorem for four mappings incomplete,  partial – b – metric spaces, as well as prove a unique common fixed point by assuming another point and getting that, these points are finally equal. We presented an example thus enhancing us the outcome.</span>

A Lanthanum (La3+) doped Samarium-Cobalt nanoferrites (La_x,Co_0.2,Sm_0.2,Fe_(2-x) O_4, where x=0.0,0.5,1.0) have been synthesized by sol-gel method in citrate media. Obtained spinal ferrites micro structure properties have been investigated by XRD, FTIR, SEM-EDX, and TEM-SAED techniques. All the samples are nano in size with significant hysteresis. Micro structural analysis by XRD confirms the obtained samples showing the single phase cubic spinal structures with an average crystal size found from 12 nm to 25 nm, while the average particles sizes identified from TEM analysis are ranging from 21.5nm-26.8 nm (~23.4nm) and from 20.5 nm to 28(~26.4nm) nm for x=0.5,1.0. The lattice parameter found to be a= 8.402, 8.423, 8.467Å for the respective values of x= 0.0, 0.05, and 1.0. Electrical properties show increase in dc resistivity with increase in La3+ ion concentration. Finally, it was concluded that the doping of Lanthanum ion (La3+) in the ferrites structure is found to influencing the structural and electrical properties without scarifying the ferromagnetic character.