Calculation of Optical Constants of As40S60-xSex Thick Films with High Accuracy using Wedge Shape Optical Model

This work has been focused primarily on the extraction of thicknesses, optical, and AC electrical parameters for as-prepared As40S60-xSex thin films, with (x=0, 20, 40, and 60 at. %). The thickness of such films has been calculated by the wedge method depending on the transmission spectra of their shrinkage in the range of 400 to 2500 nm. Swanepoels wedge relationships have been solved using the Mathcad 2000 program by minerr function to extract the film’s thickness. Depending on the obtained thickness of studied the thin films, the main optical parameters have been determined. The structural aspects of the studied thin films have also been studied using XRD and SEM techniques

Estimation of daily flow rate of photovoltaic water pumping systems using solar radiation data

This paper presents a simple model which allows us to contribute in the studies of photovoltaic (PV) water pumping systems sizing. The nonlinear relation between water flow rate and solar power has been obtained experimentally in a first step and then used for performance prediction. The model proposed enables us to simulate the water flow rate using solar radiation data for different heads (50 m, 60 m, 70 m and 80 m) and for 8S × 3P PV array configuration. The experimental data are obtained with our pumping test facility located at Madinah site (Saudi Arabia). The performances are calculated using the measured solar radiation data of different locations in Saudi Arabia. Knowing the solar radiation data, we have estimated with a good precision the water flow rate Q in five locations (Al-Jouf, Solar Village, AL-Ahsa, Madinah and Gizan) in Saudi Arabia. The flow rate Q increases with the increase of pump power for different heads following the nonlinear model proposed. Keywords: Photovoltaic water pumping system, Solar radiation data, Simulation, Flow rat

Structural, Morphological and Optical Parameters of Zn(1-x) CuxS Thin Films for Optoelectronic Devices

In the present work, ZnS and Cu incorporated at (2%, 4%,6%, 8%, and 10%) thin films were growth onto hot glass substrates at substrates temperature 270 oC with thickness about 100 nm by chemical spray pyrolysis technique. The solutions of the spray consists of Zn(CH3COO)2.2H2O, SC(NH2)2 and CuCl2.2H2O with molar concentration 0.1M/L. The structure of the film was studied by XRD pattern, the results shows that the films were polycrystalline with cubic phase for pure ZnS and hexagonal phase for Zn1-xCuxS at x=10%. The optical constants, refractive index, n and extinction coefficient, k were determined The optical energy gap of the direct transition is also estimated, pure ZnS is 3.42 eV, and it increases as the Cu concentration increases from 3.49 to 3.67 eV. The room temperature photoluminescence (PL) of copper-doped zinc sulfide (ZnS:Cu) nanoparticles was studied. Through Gaussian fitting, the PL spectrum of undoped ZnS nanoparticles is deconvoluted into two blue luminescence peaks (centered at 411 nm and 455 nm, respectively), both of which can be attributed to the recombination of ZnS defect states. But for doped samples, a third peak at about 500 nm was also identified. Discussed the changes of all optical constants and PL spectra from the changes of optoelectronics microstructure parameter

Evaluating the Impact of Transmission Range on the Performance of VANET

Recently, interest in the field of Vehicular Ad-hoc Networks (VANETs) has grown among research community to improve traffic safety and efficiency on the roads. Despite the many advantages, the transmission range in vehicular network remains one of the major challenges due to the unique characteristics of VANETs such as various communication environments, highly dynamic topology, high node mobility and traffic density. The network would suffer from a broadcast-storm in high vehicular density when a fixed transmission range in VANET is used, while in sparse vehicular density the network could be disconnected frequently. In this paper, we evaluated the impact of different transmission ranges and number of flows formed between vehicles in a highway scenario using AODV as routing protocol. In order to validate the simulation of VANET, traffic and network simulators (SUMO & NS-2) have been used. The performance was evaluated in terms of packet delivery ratio and end-to-end delay. The simulation results have shown that better performance was achieved in term of higher PDR and lower end-to-end delay for less than 500 meters transmission range. On the contrary, the PDR started to decrease and end-to-end delay increased when the transmission range exceeded 500 meters. The performance degraded as the number of flows increased

Impact of Bat Guano Otonycteris hemprichii Camd and Seaweed Extract on Some Growth and Yield Traits of Barakaseed Nigella Sativa L

Barakaseed was improved as medicinal plant using some agricultural processes. For example, organic farmyard manure was efficiently applied to enhance growth and yield. Therefore, a field experiment was conducted out during 2012/2013 season to investigate the impact of bat guano (0, 75, 125 and 175 kg.ha-1), seaweed extract as kelpak (0, 1, 2, 3ml.l-1) on some growth and yield traits. Two factors were arranged in a factorial experiment system in completely randomized block design with three replicates. Results revealed that application of bat guano at 175 kg. ha-1 was superior in enhancing plant height, fruit branch per plant, dry weight, capsules per plant, seeds per capsule, 1000 seed weight and seed yield of 66.93cm, 13.32 fruit branch. plant-1, 44.75g. plant-1, 14.12caps. plant-1, 93.35seed. caps-1, 5.64g and 943.0 kg. ha-1 than other levels, respectively. Seaweed (kelpak) at 3 ml.l-1 also significantly increased these traits of 61.64cm, 12.11fruit branch.plant-1, 43.93g.plant-1, 12.27caps.plant-1, 82.90seed.caps-1, 5.34g and 805.0kg.ha-1, respectively. Moreover, the interactive combination of the highest level of bat guano with the highest level of kelpak (175Kg. ha-1X3ml. l-1) gave the highest seed yield of 1154.2 kg. ha-1. It could be concluded that bat guano and kelpak efficiently improved some growth traits. Therefore, consequently increased seed yield. The improvement and increase were gradually occurred. Thus, it could be recommended to use bat guano as shifting source over to chemical fertilizer supported with foliar spraying of seaweed extract as kelpak

Protocol for Deciphering the Electrical Parameters of Perovskite Solar Cells Using Immittance Spectroscopy

Here, we present a protocol for the fabrication of inverted (p-i-n)-type perovskite solar cells, unraveling its electrical merits via immittance spectroscopy. The immittance spectroscopy is a prevailing technique for both qualitative and quantitative analyses of charge carrier dynamics in working devices. This technique integrates the temperature-dependent capacitance–frequency (C-f) spectra, impedance spectra, and Mott-Schottky analyses. This protocol is also applicable for typical (n-i-p) perovskite solar cells and other multilayer semiconductor devices.This work has received funding from the European Union H2020 Programme under the European Research Council Consolidator grant (MOLEMAT, 726360). Support from PARASOL (RTI2018-102292-B-I00), Spanish Ministry of Science and Innovation, is also acknowledged. P.H. acknowledges funding from the European Commission via a Marie-Skłodowska-Curie individual fellowship (SMILIES, No. 896211). Authors are also thankful to the deanship of scientific research at Islamic University of Madinah, Saudi Arabia, for the financial support to this work through the Tamayyuz programme of the academic year 1441/1442 H (project No: 497)

A Comprehensive Performance Analysis of IEEE 802.11p based MAC for Vehicular Communications Under Non-saturated Conditions

Reliable and efficient data broadcasting is essential in vehicular networks to provide safety-critical and commercial service messages on the road. There is still no comprehensive analysis of IEEE 802.11p based MAC that portrays the presence of buffer memory in vehicular networks. Besides, most of the analytical works do not fulfill some of the IEEE 802.11p specifications, such as short retry limit and back-off timer freezing. This paper proposes a 1-D and 2-D Markov model to analyze mathematically IEEE 802.11p based MAC for safety and non-safety messages respectively. The work presented in this paper takes into account the traffic arrival along with the first-order buffer memory and freezing of the back-off timer as well, to utilize the channel efficiently and provide higher accuracy in estimation of channel access, yielding more precise results of the system throughput for non-safety messages and lower delay for safety messages. Furthermore, back-off stages with a short retry limit were applied for non-safety messages in order to meet the IEEE 802.11p specifications, guaranteeing that no packet is served indefinitely, avoiding the overestimation of system throughput. A simulation was carried out to validate the analytical results of our model

An Accurate Performance Analysis of Hybrid Efficient and Reliable MAC Protocol in VANET under Non-saturated Conditions

Vehicular Ad Hoc Networks (VANETs) is a technology supporting two types of applications, safety and service applications with higher and lower priorities respectively. Thereby, Medium Access Control (MAC) protocol is designed to provide reliable and efficient data broadcasting based on prioritization. Different from the IEEE 1609.4 (legacy), HER-MAC protocol is a new multi-channel MAC proposed for VANETs, offering remarkable performance with regards to safety applications transmission. This paper focuses on the analysis of packet delivery ratio of the HER-MAC protocol under non-saturated conditions. 1-D and 2-D Markov chains have been developed for safety and non-safety applications respectively, to evaluate mathematically the performance of HER-MAC protocol. The presented work has taken into account the freezing of the backoff timer for both applications and the backoff stages along with short retry limit for non-safety applications in order to meet the IEEE 802.11p specifications. It highlights that taking these elements into consideration are important in modeling the system, to provide an accurate estimation of the channel access, and guarantees that no packet is served indefinitely. More precise results of the system packet delivery ratio have been yield. The probability of successful transmission and collisions were derived and used to compute the packet delivery ratio. The simulation results validate the analytical results of our models and indicate that the performance of our models outperformed the existing models in terms of the packet delivery ratio under different number of vehicles and contention window

High-performance visible light photodetectors based on inorganic CZT and InCZT single crystals

Herein, the optoelectrical investigation of cadmium zinc telluride (CZT) and indium (In) doped CZT (InCZT) single crystals-based photodetectors have been demonstrated. The grown crystals were configured into photodetector devices and recorded the current-voltage (I-V) and current-time (I-t) characteristics under different illumination intensities. It has been observed that the photocurrent generation mechanism in both photodetector devices is dominantly driven by a photogating effect. The CZT photodetector exhibits stable and reversible device performances to 632 nm light, including a promotable responsivity of 0.38 AW−1, a high photoswitch ratio of 152, specific detectivity of 6.30 × 1011 Jones, and fast switching time (rise time of 210 ms and decay time of 150 ms). When doped with In, the responsivity of device increases to 0.50 AW−1, photoswitch ratio decrease to 10, specific detectivity decrease to 1.80 × 1011 Jones, rise time decrease to 140 ms and decay time increase to 200 ms. Moreover, these devices show a very high external quantum efficiency of 200% for CZT and 250% for InCZT. These results demonstrate that the CZT based crystals have great potential for visible light photodetector applicationsAuthors from KKU express their appreciation to the Deanship of Scientifc Research at King Khalid University for funding this work through research groups program under grant number R.G.P. 2/42/4

Modeling and analysis of IEEE 1609.4 MAC in the presence of error-prone channels

Vehicular Ad Hoc Networks (VANETs) have been developed to improve the safety, comfort and efficiency of driving on the road. The IEEE 1609.4 is a standard intended to support multi-channel in VANETs. These channels include one control channel for safety applications and six service channels for service applications. However, there is still no comprehensive analysis for the average delay and system throughput of IEEE 1609.4 MAC in VANETs considering error-prone channel under non-saturated conditions. In this paper, we propose an analytical models based on 1-D and 2-D Markov chain to evaluate the performance analysis of IEEE 1609.4 MAC in the presence of error-prone channels. Besides, freezing of the back-off timer is taken into consideration to provide an accurate estimation of access to the channel. The simulation results have been carried out to validate the analytical results of our model. The results show that the performance of our model outperforms the existing model in terms of packet delivery ratio and average delay of safety packets over CCH, and system throughput of service packets over SCHs