Charakterizace tenkovrstvých elektroluminiscenčních součástek

Jádrem této disertační práce bylo studovat optické a elektrické charakteristiky tenkovrstvých elektroluminiscenčních součástek řízených střídavým proudem (ACTFEL) a zejména vliv procesu stárnutí luminiforů na jejich optické a elektrické vlastnosti. Cílem této studie měl být příspěvek ke zvýšení celkové účinnosti luminoforů, vyjádřené pomocí jasu, účinnosti a stability. Vzhledem k tomu, že současnou dominantní technologií plochých obrazovek je LCD, musí se další alternativní technologie plošných displejů porovnávat s LCD. Výhodou ACTFEL displejů proti LCD je lepší rozlišení, větší teplotní rozsah činnosti, větší čtecí úhel, či možnost čtení při mnohem vyšší intenzitě pozadí. Na druhou stranu je jejich nevýhodou vyšší energetická náročnost, problém s odpovídající barevností tří základních barev a podstatně vyšší napětí nutné pro činnost displeje. K dosažení tohoto cíle jsme provedli optická, elektrická a optoelektrická měření ACTFEL struktur a ZnS:Mn luminoforů. Navíc jsme studovali vliv dotování vrstvy pomocí KCl na chování mikrostruktury a na elektroluminiscenční vlastnosti (zejména na jas a světelnou účinnost) ZnS:Mn luminoforů. Provedli jsme i některá, ne zcela obvyklá, měření ACTFEL součástek. Vypočítali jsme i rozptylový poměr nabitých barevných center a simulovali transportní charakteristiky v ACTFEL součástkách. Studovali jsme vliv stárnutí dvou typů ZnS:Mn luminoforů (s vrstvou napařenou či získanou pomocí epitaxe atomových vrstev) monitorováním závislostí svítivost-napětí (L-V), velikost vnitřního náboje - elektrické pole luminoforu (Q-Fp) a kapacitance-napětí (C-V) ve zvolených časových intervalech v průběhu stárnutí. Provedli jsme krátkodobá i dlouhodobá měření a pokusili jsme se i o vizualizaci struktury luminoforu se subvlnovým rozlišením pomocí optického rastrovacího mikroskopu pracujícího v blízkém poli (SNOM). Na praktickém případu zeleného Zn2GeO4:Mn (2% Mn) ACTFEL displeje, pracujícího při 50 Hz, jsme také studovali stabilitu svítivosti pomocí měření závislosti svítivosti na napětí (L-V) a světelné účinnosti na napětí (eta-V). Přitom byl zhodnocen význam těchto charakteristik. Nezanedbatelnou a neoddělitelnou součástí této práce je i její pedagogický aspekt. Předložený text by mohl být využit i jako učebnice pro studenty na mé univerzitě v Lybii.The objective of this thesis is to study the optical and electrical characterization of Alternating-Current Thin-Film ElectroLuminescent (ACTFEL) devices, and specifically the aging process of phosphor materials that comprise the ACTFEL display in an effort to improve the overall performance of the primary phosphor colors in terms of brightness, efficiency and stability. Since the dominant flat-panel display technology is the LCD, an alternative flat-panel display technology must gauge itself in terms of the LCD. The advantages of ACTFEL displays in comparison with LCDs are the ability to pattern much smaller pixel, performance over a wider temperature range, full-viewing angle, and readability with much greater intensity background light. The disadvantages of ACTFEL displays against LCD ones are larger power consumption, lack of adequate chromaticity of the three primary colors, and much larger driving voltages. To achieve these objectives, the optical, electrical, and opto-electric measurements of the ACTFEL structures and ZnS:Mn phosphor hosts were carried out. Moreover, the effect of KCl co-doping on the microstructure and the electroluminescent properties (mainly brightness and luminous efficiency) of ZnS:Mn phosphors has been investigated, too. A non-common electrical characterization of ACTFEL devices has also been provided. We also calculated charged center scattering rates, and simulated the electron transport process in an ACTFEL device The study of the aging characteristics of evaporated and atomic layer epitaxy ZnS:Mn phosphors has been undertaken by monitoring the luminance-voltage (L-V) internal charge-phosphor field (Q-Fp) and capacitance-voltage (C-V) electrical characteristics at in selected time intervals during aging. Short-term and long-term ACTFEL aging studies has been provided and an attempt to visualize locally the structure of phosphor with a subwavelenght resolution using Scanning near-field optical microscope (SNOM) has also been presented. The practical case of a green Zn2GeO4:Mn (2% Mn) ACTFEL device operated at 50 Hz was studied and a luminance stability by a measurement of luminance-voltage (L-V) and luminous efficiency-voltage (eta-V) characteristics has been evaluated. A non-negligible and indiscreptible task of this thesis was also its pedagogical aspect. Therefore, the presented text can be considered as a textbook suitable for our students in Libya.

HAPS Gateway Link in the 5850-7075 MHz and Coexistence with Fixed Satellite Service

Gateway link is essential to connect HAPS platform to terrestrial based networks. This crucial link is incorporated in HAPS fixed service spectrum allocation in considerably high frequencies, renders the link for more attenuations by atmospheric gases, and rain effects, especially when the regional climate is not favorable. However, under the agenda item 1.20 of World Radio Conference-2012 (WRC-12) new HAPS allocation in the 5850-7075 MHz band is proposed. Although, spectrum features are incomparably reliable, on the contrary, Fixed Satellite Service (FSS) uplink transmissions will have signal levels much higher than those in HAPS systems and have the potential for causing interference at the HAPS gateway receiver. In this article a key aspect of co-channel interference phenomena is investigated to facilitate optimum frequency sharing in the band in question. By proposing mitigation techniques and statistical method this generic prediction model enhances the capability of the HAPS spectrum sharing and provides flexibility in spectrum planning for different fixed services

INVESTIGATING UNIVERSITY STUDENTS’ MOTIVATION TOWARDS ENGLISH LANGUAGE LEARNING

This research aims at investigating the motivational factors of university students towards English Language learning. A quantitative method using a descriptive design was recommended for this study. A questionnaire was used as the data collection tool. The population comprises all males and females third year English language learner at colleges of education and languages at Sudan University of Science and Technology. Thus, the researcher used a sample size of 100 English language learners at colleges of Education and languages in Sudan University of Science and Technology being selected as participants in the current study, 99 valid responses were collected. Collected data is entered and treated by using the Statistical Package for Social Sciences (SPSS) version 20. The following are some of important findings based on data analysis and discussion of the collected data: 1. There are many factors that have positive effect on students' attitudes and motivation to learn English language. The most important ones include, having a good English language teacher positively affects their attitudes to learn English, and Learning English is important, as it is one of the requirements for high- education.2. Students were highly motivated to learn English language. There are many factors, motivates the students, on the top of the motivates factors is that, the need for travelling around the world, and the second motivator is that, almost students confirm that, learning English makes them more knowledgeable as they can be able to communicate. Finally, the results of the study, do not detect any statistically significant variations between students of the current study perceptions regarding learning English language related to students’ gender and age.  Article visualizations

Designing optimum water flooding scheme in a heterogeneous depleted reservoir: A simulation case study

Waterflooding is one of the cheapest oil recovery methods and the most popular secondary method to increase oil recovery by injecting water into the reservoir. This research aims to build a model using Eclipse 100 software in order to increase the oil recovery factor in a heterogeneous depleted reservoir. This project discusses the main parameters that affecting waterflooding performance in a heterogeneous depleted reservoir and quantify their importance towards an optimum design. So the main objective of this project is addressing the different interrelated parameters and their impact in order to increase the oil recovery factor. Moreover, this project is determining different scaling up schemes and their impact on the final model besides doing a sensitivity study for the parameters that affecting the waterflooding in a heterogeneous reservoir

The Impact Of Diet On Goat Rumen Microbes And Innate Immune Gene Expression

Gastrointestinal nematodes in goats have developed resistance to chemical anthelmintics, resulting in the need for alternative control strategies. One approach is incorporation of Sericea Lespedeza (SL) as high quality forage that suppresses these parasites in goats due to its high condensed tannin (CT) content. However, little is known about its effect on rumen microorganisms and innate immunity in goats. A diverse collection of microorganisms is found in the goat rumen and Bifidobacteria is one of the important organisms in the immunity, yet its presence in the goat rumen is not fully studied. The objective of this study was to evaluate the impact of a diet containing SL on goat rumen microorganisms, Bifidobacteria and on the goat’s innate immune gene expression. Microbial DNA was isolated from rumen samples using the QIAamp DNA kit (Qiagen, USA) to compare rumen microbes and Bifidobacteria in control group and group that received SL in diet

The Impact Of Diet On Goat Rumen Microbes And Innate Immune Gene Expression

Gastrointestinal nematodes in goats have developed resistance to chemical anthelmintics, resulting in the need for alternative control strategies. One approach is incorporation of Sericea Lespedeza (SL) as high quality forage that suppresses these parasites in goats due to its high condensed tannin (CT) content. However, little is known about its effect on rumen microorganisms and innate immunity in goats. A diverse collection of microorganisms is found in the goat rumen and Bifidobacteria is one of the important organisms in the immunity, yet its presence in the goat rumen is not fully studied. The objective of this study was to evaluate the impact of a diet containing SL on goat rumen microorganisms, Bifidobacteria and on the goat’s innate immune gene expression. Microbial DNA was isolated from rumen samples using the QIAamp DNA kit (Qiagen, USA) to compare rumen microbes and Bifidobacteria in control group and group that received SL in diet

Rapidity Distribution of Charged Pions From Pb+Pb and Au+Au Central Collisions

Rapidity distributions for charged pions produced from central collisions Pb+Pb and Au+Au at (b ≤ 3.4 fm.) in range of energy 2 GeV up to = 200 GeV are investigated. The experimental results are studied  in terms of the Ultra-relativistic Quantum Molecular Dynamic Model Ur-QMD. In general, the model can give suitable predictions of rapidity distributions for production of charged pions from interactions with energies below 160 A GeV. This model is supported the assumption that the onset of de-confinement is located at low energies. It treats the initial nucleon-nucleon interactions within a string-hadronic framework. In addition, it includes effects such as string-string interactions and hadronic re-scattering that expected to be relevant in A+A collisions. There is a kind of similarity for mechanism responsible for production of the two charge states of pions and it can extended to other hadrons. Ultra-relativistic quantum molecular dynamic model give good description on energy dependence for charged pion productions and points of maximum rapidity

Coronavirus Disease Knowledge and Attitudes of Nursing Students: A Cross-Sectional Study in Saudi Arabia

Background: The prevalence of coronavirus disease is increasing rapidly all over the world therefore, this study aimed to understand the knowledge and attitudes among the nursing students about the coronavirus disease. Methods: The design of our study was cross-sectional in the period from January to March, 2020. A survey was conducted by Survey Monkey, the questionnaire link had been shared with the students, according to the inclusion criteria (nursing students in the third and fourth year), the questionnaire included two parts: (i) demographic characteristics of the students and (ii) knowledge and attitudes regarding the coronavirus disease. The number of participants in the study, who completed the questionnaire, was 350. Results: The findings revealed that the average score for their knowledge is good, (13/17 points) reaching 79%. Total 77% students showed a negative attitude about the coronavirus disease and 79.7% students used the website of Ministry of Health for medical information. Conclusion: This study showed that nursing students had a good knowledge about the coronavirus disease and a negative attitude. The Ministry of Health website was instrumental in imparting knowledge to the students about coronavirus

PROPOSED METHODOLOGY FOR OPTIMIZING THE TRAINING PARAMETERS OF A MULTILAYER FEED-FORWARD ARTIFICIAL NEURAL NETWORKS USING A GENETIC ALGORITHM

An artificial neural network (ANN), or shortly "neural network" (NN), is a powerful mathematical or computational model that is inspired by the structure and/or functional characteristics of biological neural networks. Despite the fact that ANN has been developing rapidly for many years, there are still some challenges concerning the development of an ANN model that performs effectively for the problem at hand. ANN can be categorized into three main types: single layer, recurrent network and multilayer feed-forward network. In multilayer feed-forward ANN, the actual performance is highly dependent on the selection of architecture and training parameters. However, a systematic method for optimizing these parameters is still an active research area. This work focuses on multilayer feed-forward ANNs due to their generalization capability, simplicity from the viewpoint of structure, and ease of mathematical analysis. Even though, several rules for the optimization of multilayer feed-forward ANN parameters are available in the literature, most networks are still calibrated via a trial-and-error procedure, which depends mainly on the type of problem, and past experience and intuition of the expert. To overcome these limitations, there have been attempts to use genetic algorithm (GA) to optimize some of these parameters. However most, if not all, of the existing approaches are focused partially on the part of architecture and training parameters. On the contrary, the GAANN approach presented here has covered most aspects of multilayer feed-forward ANN in a more comprehensive way. This research focuses on the use of binaryencoded genetic algorithm (GA) to implement efficient search strategies for the optimal architecture and training parameters of a multilayer feed-forward ANN. Particularly, GA is utilized to determine the optimal number of hidden layers, number of neurons in each hidden layer, type of training algorithm, type of activation function of hidden and output neurons, initial weight, learning rate, momentum term, and epoch size of a multilayer feed-forward ANN. In this thesis, the approach has been analyzed and algorithms that simulate the new approach have been mapped out