Annealing Effect on the Structural and Optical Properties of Sol- Gel Deposited Nanocrystalline CdO Thin Films

In this paper CdO thin films have been prepared by using SOL-GEL method with spin coating technique, by depoited four layers  of mixtuer solution contians Cadmium acetate dehydrate, Triethylamine, glycerol and ethanol.The spin coated solution were dried at 100°C and annealied at (300,350 and 400 oC temperatures ). The x-ray diffraction techniques and UV-VIS spectrophotometer have confirmed the structural and the optical properties the prepared thin films. CdO thin films were found to have polycrystalline nature with cubic rock salt phase. The crystallinity being improved, the FWHM decreases and the grain size of the CdO thin films increased with increasing the annealing temperatures. The average grain size is observed in the range  (23.97 - 30.47) nm which indicate that the prepared film have a nanocrystalline structure. From optical analysis, it can be seen that there are an increases in the absorbance and decreases in the trancemittance  of the prepared films with the increasing of the annealing temperatures.The optical band gap decreases  from 2.556, to 2.081 eV with increasing of annealing temperature fromm 300 to 400° C, this suggested that the optical band gap for CdO nanocrystalline thin films is strongly dependent on the annealing temperature. Keywords: CdO thin films, Sol–gel spin–coating, Structural and Optical properties, annealing temperature

Structure, surface topography and optical characterization of Ag co – doped Cd1-xCuxO nanostructure thin films

Cd1-xCuxO and Ag co-doped Cd1-xCuxO nanostructure thin films with x = 0.2 and different Ag content (0-8%) were deposited by chemical spray pyrolysis technique on glass substrates at a temperature of 350 oC. The XRD results showed that the prepared films have polycrystalline with low crystallinity nature for CdO cubic structure. The preferential orientation of all films was absorbed along (111) plane. CuO monoclinic phase has appeared with low intensity while the Ag cubic phase appeared only in 8% of Ag content. Structural parameters such as average crystallite size, dislocation density and micro-strain were also investigated. SEM images revealed that the surface morphology of the films consists of spherical shaped grains uniformly distributed without detectable micro-cracks and improved by Ag Co-doping. EDXS spectrum analysis confirmed purity and stoichiometry of the prepared compositions. AFM results showed that the surface topography and the surface quality of the deposited thin films can be controlled by the variation of the Ag co-doping concentration. Optical absorbance and transmittance of Ag co-doped Cd1-xCuxO thin films has high values in the visible and near infrared regions respectively and varied with Ag co-doping content. Direct optical energy band gap of Cd1-xCuxO exhibits a blue shift with Ag co-doping, due to the quantum size and Burstein–Moss (BM) effects. The increasing of optical energy gap was confirmed by the decrease in the Urbach tails energy EU after Ag co-doping.

Assessment and improvement of quality of service in wireless networks using fuzzy and hybrid genetic-fuzzy approaches

Fuzzy and hybrid genetic-fuzzy approaches were used to assess and improve quality of service (QoS) in simulated wireless networks. Three real-time audio and video applications were transmitted over the networks. The QoS provided by the networks for each application was quantitatively assessed using a fuzzy inference system (FIS). Two methods to improve the networks' QoS were developed. One method was based on a FIS mechanism and the other used a hybrid genetic-fuzzy system. Both methods determined an optimised value for the minimum contention window (CW (min)) in IEEE 802.11 medium access control (MAC) protocol. CW (min) affects the time period a wireless station waits before it transmits a packet and thus its value influences QoS. The average QoS for the audio and video applications improved by 42.8% and 14.5% respectively by using the FIS method. The hybrid genetic-fuzzy system improved the average QoS for the audio and video applications by 35.7% and 16.5% respectively. The study indicated that the devised methods were effective in assessing and significantly improving QoS in wireless networks

Rheological and optical characterization of Polyvinylpyrrolidone (PVP) - Polyethylene glycol (PEG) polymer blends

Polymer blends of different concentrations for PVP-K30 and different additive weights of PEG8000 have been prepared as polymeric blends solutions. The rheological and optical properties of the blends samples have been investigated using Ostwald viscometer and Refractometer. The results showed that the density, shear, relative and specific viscosities are increases with the increasing of PVP concentration and additive weight of PEG. The optical constant values such as refractive index, reflectance, molar reflectance, coefficient of finesse and Brewster Angle are increase with the increasing of PVP concentration and additive weight of PEG while the critical angle has the revers behavior. DOI: http://dx.doi.org/10.31257/2018/JKP/2019/11020

A comparative study of IEEE 802.11 MAC access mechanisms for different traffic types

The fast growth and development of wireless computer networks and multimedia applications make the Quality of Service (QoS) provided to their transmission an important issue. This paper aims to investigate the impact of varying the number of active stations on the network performance. This was carried out using different data rates. The investigations also considered both MAC protocol access mechanisms, i.e. the basic access and the Request To Send / Clear To Send (RTS/CTS). The effect of traffic type i.e. Constant Bit Rate (CBR) and Variable Bit Rate (VBR) traffics was also examined. The findings revealed that in large networks (larger than 15 stations), the RTS/CTS access mechanism outperformed the basic access mechanism since the performance of the latter was more sensitive to the increase and decrease of the number of active stations. Increasing the data rate improved the network performance in term of delay and jitter but it degraded the network performance in term of channel utilisation and packet loss ratio

Prioritized Shufflenet Routing in TOAD based 2X2 OTDM Router.

packet-switched network topology, which has been widely used in the optical communication. The adaptive routing algorithm used in shufflenet provides multiple shortest paths from source to destination. Here shufflenet is applied for optical time division multiplexing (OTDM) based networks, where nodes are composed of a terahertz optical asymmetric demultiplexer (TOAD) based 2x2 routers. Here we have introduced a simple priority scheme, where packets are routed via the transmission port (having lower crosstalk compared with the reflection port) of the router as much as possible. Simulation results show that transmission-to-reflection ratio (TRR) greater than one is achievable over a wide range of system load

The Effect of Magnetic Field on Helium Plasma Characteristics of Discharge Tube

The effect of discharge voltage of a discharge tube were investigated.The discharge voltage (700,800,900,1000,1100,1200) volt were applied under pressure of helium gas was (7Pa) and the inter electrode distance was (130mm). The measurements were achieved without and with parallel magnetic field of (25 mT). The electron temperature calculated from Id – Vd characteristics curves of double Langmuir probe. Results  of electron temperature indicated that the behavior of electron temperature decreased with increasing the discharge voltage with and without the magnetic field.But their values at (B=0) was smaller than the corresponding values at (B=25 mT)