382 research outputs found
Multi-Scale Seismic Hazard Assessment for Egypt
No full textEgypt is a country with mainly moderate seismicity; it has witnessed strong earthquake impacts along its long history from far-field sources and earthquake impacts from the local. The occurrence of these destructive earthquakes ensures the importance of carrying out a reliable and comprehensive characterization of expected seismic ground shaking, which is essential in order to develop effective seismic mitigation strategies and increase earthquake preparedness for Egypt. So, reliable seismic hazard maps that computed based on correct data and methodology should be prepared for building codes applications; also these maps should be updated when needed.
In the first chapter of this thesis, a review of the existing seismic hazard for Egypt is performed. For the understanding and studying the development of seismic hazard studies for Egypt, we had collected and tested the existing SHA maps, computed at different scales, against the available observations and physical assumptions, data quality, and methodology. Then, we propose some suggestions that could be considered before new seismic hazard maps can be produced and then adopted, for the real benefit of society.
In Chapter 2, an update of seismogenic zones and nodes has been performed, which is needed to perform an updated seismic hazard study for Egyptian territory. We think that the incorporation of seismogenic nodes information side by side with the updated seismogenic zones in the seismic hazard computation may improve performance and usefulness of the resulting maps for the studied region, especially for the sites that have been silent in during the earthquake catalog window show no seismic activity in the catalog so far.
Chapter 3 provides an update for the seismic hazard maps available for Egypt that incorporates recent studies, such as reviewed historical earthquake catalogs, morphostructural zonation data (MZ), revised fault plane solutions and laterally non-varying crustal structure using the neo-deterministic seismic hazard assessment (NDSHA) procedure. Also, a sensitivity analysis of different ground motion maps computed adopting different (a) models for the earthquake source process, (b) crustal structure models of the crust and (c) mapmaker’s preconceptions (e.g., different seismotectonic models), is provided.
In Chapter 4, detailed ground motion modeling for the proper characterization of the amplification patterns (site-effects) along three 2D profiles have been accomplished. The expected amplification patterns range between 2 and 5 and occur at a frequency range 1-7Hz based on the location of the site along the profiles, subsurface geometry and the thickness of the sedimentary layer.
In Chapter 5, we provided the seismic input (response spectra and time histories) that can be applied for the proper evaluation of the dynamic performance of the minaret of the Madrasa the Princess Tatar al-Higaziya, which by role will help in proposing a seismic conservation strategy for this valuable structure. A detailed numerical model for the minaret was established, accompanied with installing ambient sensors for calibrating the numerical model.
The careful assessment of the seismic excitation on the historic minaret through conducting the proposed C-MCSI response spectrum and time history analyses predicts severe damage to the minaret: significant lateral displacements at the minaret top and excessive tensile stress concentration, particularly at the geometric transition zone between the squared base and the hexagon shaft, have been developed. Since the minaret is expected to suffer severe damage against the anticipated scenario of earthquake shaking, a vital protection plan is recommended for the minaret to avoid any future damage or collapse
Site-specific ground motion modeling for a historical Cairo site as a step towards computation of seismic input at cultural heritage sites
No full textThroughout time, the area of historical Cairo has been affected by several earthquakes from near and distant seismogenic zones. The maximum earthquake intensity reported in Cairo is VII, on the Modified Mercalli Intensity scale, due to the 1992 Cairo earthquake (Mw=5.9). About 212 Coptic and Islamic monuments were damaged. The spatial distribution of damage, suggests the occurrence of strong local site effects in combination with high vulnerability of the cultural heritage buildings. This study presents the application of a novel seismic hazard analysis approach at a local scale based on physics-based ground motion simulations. A site-specific multi-scenario seismic input (ground motion time histories and response spectra) is computed at a heritage building in Cairo, considering the local site effect. The seismic input is calculated in three steps: a regional scale analysis followed by a site-specific analysis and the combinations of the computed scenarios ground motion. In the regional scale analysis synthetic accelerograms are computed at the site bedrock. Then, the site-specific analysis is performed to calculate the site surface ground motions or response spectra considering the local site effect. Three earthquake scenarios have been considered, characterized by different locations, magnitudes, and fault configurations. The last step consists in the combination of the computed scenario ground motion into one single multi-scenario seismic input specific for the site of interest. This input is represented by spectral ordinates and their variability. For the engineering purpose of time history analysis, the method allows also to extract the computed site specific physics-based accelerograms, requiring no amplitude scaling nor filtering by magnitudes, distances, or site classifications, as usually done with real ground motion records
Electrochemical patterning of tantalum and tantalum oxide thin films
No full text Nanoscale patterning research is motivated by two objectives: (i) tool development and (ii) scientific opportunities at small length scales. The first objective focuses on designing techniques that can be used to fabricate features as small as possible. Synthetic strategies of nanomaterials can be classified into two categories; bottom-up and top-down. The top-down approach involves reducing the size of a bulk material into nanoscale patterns, while the bottom-up approach refers to the build up of a material from the bottom, i.e. particle-by-particle. This particle maybe an atom, a molecule or even a cluster. In this work, two different top-down approaches were applied to create patterns in the nanoscale. Direct selective metal deposition on semiconductors is of interest to electronic device technology, in particular for interconnects and Schottky devices. In this study, we investigated selective Cu electrodeposition on patterned tantalum oxide thin films. Cyclic voltammetry studies showed that tantalum oxide thin films of thicknesses higher than a certain critical value have insulating properties while oxide films of thicknesses less than this value are semiconductors. For the purpose of this study, tantalum oxide patterns of different thicknesses were created by electrochemical oxidation. Based on the aforementioned behavior of insulating and semiconducting tantalum oxide films, Cu lines were selectively electrodeposited on the tantalum oxide thin films patterns forming Schottky junctions. The process demonstrated in this work is compatible to standard processes for semiconductor device fabrication while permitting flexible prototyping for research at the nanoscale. The second method used to pattern nanoscale features on tantalum lead to the discovery of the first highly ordered nanoporous metal (template) prepared by electrochemical oxidation. The nanoporous tantalum has pores not only of high regularity and high diameter monodispersity, but also of tunable diameters in the range 27-55 nm. The template that has the highest hardness among other porous templates can be used for nanoparticles fabrication. The compatibility of the new porous tantalum template with semiconductor industry makes it a candidate for many potential technological applications. ThesisMaster of Science (MSc
Lösungs-Epitaktisch gewachsene Metallhalogenid-Perowskit Mikrokristall-Laser
No full textEpitaxy is a process to grow high-quality crystalline materials in a highly ordered manner, which is a key requirement for the development of modern electronic and optoelectronic devices. In the last few years, metal halide perovskites have revolutionized the field of optoelectronics due to their astonishing properties. Thus, they are promising to compete against conventional semiconductors for certain applications in electronics or optoelectronics. Moreover, their easy solution processing promises low-cost and facile device fabrication as well as high throughput via printing or coating techniques. Recently, perovskites have been demonstrated as efficient laser gain media with high optical gain coefficients comparable to those of commercial lasers. Furthermore, their self-assembled microcrystals can act as optical resonators, offering the fabrication of compact lasers with the potential for integration and use in a wide range of applications. Therefore, the solution epitaxy of perovskites represents a significant step forward toward economical practical applications. Specifically, the epitaxial perovskite microcrystal lasers will advance the development of on-chip integrated miniaturized coherent light sources.
In this doctoral thesis, the epitaxial growth of oriented high-quality microcrystals from formamidinium lead bromide and methylammonium lead bromide perovskites is demonstrated by facile solution methods. The drop casting method and antisolvent vapor-assisted crystallization are introduced to expand the current solution-epitaxial methods of perovskites. Various crystal geometries are grown from both materials, and the growth methods offer the possibility to control the crystals’ sizes and shapes under certain conditions. The microcrystals serve as optical resonators, producing the first solution-epitaxial perovskite microcavity laser. The lasing is achieved under optical pumping with a record low threshold for the epitaxially grown perovskite microcavities. The different geometry microcavities are demonstrated to support various resonant optical modes. Remarkably, the microcavities exhibit high lasing emission stability, which is a record value for the perovskite lasers tested in the air. Furthermore, single-mode lasing –a desirable operation for optical communications– is successfully realized via increasing the lasing mode spacing by decreasing the size of the pumped microcavities. These promising results emphasize that solution-epitaxial perovskite microlasers are competitive to vapor-epitaxial ones, paving the way toward low-cost and energy-efficient fabrication of high-quality optoelectronics.Bei der Epitaxie handelt es sich um ein Verfahren, mit dem hochwertige kristalline Materialien in einer hochgradig geordneten Weise gezüchtet werden können, was eine wichtige Voraussetzung für die Entwicklung moderner elektronischer und optoelektronischer Geräte ist. In den letzten Jahren haben Metallhalogenid-Perowskite aufgrund ihrer erstaunlichen Eigenschaften den Bereich der Optoelektronik revolutioniert. Damit sind sie vielversprechend, um bei bestimmten Anwendungen in der Elektronik oder Optoelektronik mit herkömmlichen Halbleitern zu konkurrieren. Darüber hinaus verspricht ihre einfache Verarbeitung in Lösung eine kostengünstige und einfache Herstellung von Bauelementen sowie einen hohen Durchsatz durch Druck- oder Beschichtungsverfahren. Kürzlich wurden Perowskite als effiziente Lasergewinnungsmedien mit hohen optischen Gewinnkoeffizienten nachgewiesen, die mit denen kommerzieller Laser vergleichbar sind. Darüber hinaus können ihre selbstorganisierten Mikrokristalle als optische Resonatoren fungieren, was die Herstellung kompakter Laser mit dem Potenzial für die Integration und den Einsatz in einer Vielzahl von Anwendungen ermöglicht. Daher stellt die Lösungsepitaxie von Perowskiten einen bedeutenden Schritt in Richtung wirtschaftlicher praktischer Anwendungen dar. Insbesondere werden die epitaktischen Perowskit-Mikrokristall-Laser die Entwicklung von auf dem Chip integrierten, miniaturisierten kohärenten Lichtquellen vorantreiben.
In dieser Dissertation wird das epitaktische Wachstum von orientierten, hochwertigen Mikrokristallen aus Formamidinium-Bleibromid und Methylammonium-Bleibromid-Perowskiten durch einfache Lösungsmethoden demonstriert. Auftropfen und die dampfunterstützte Kristallisation mit Anti-Lösungsmitteln werden eingeführt, um die derzeitigen lösungs-epitaktischen Methoden für Perowskite zu erweitern. Aus beiden Materialien werden verschiedene Kristallgeometrien gezüchtet, und die Wachstumsmethoden bieten die Möglichkeit, die Größe und Form der Kristalle unter bestimmten Bedingungen zu kontrollieren. Die Mikrokristalle dienen als optische Resonatoren, wodurch der erste lösungs-epitaktische Perowskit-Mikroresonatorlaser entstanden war. Das Lasern wird unter optischem Pumpen mit einer rekordverdächtig niedrigen Schwelle für die epitaktisch gewachsenen Perowskit-Mikrokavitäten erreicht. Die Mikrokavitäten mit unterschiedlicher Geometrie unterstützen nachweislich verschiedene optische Resonanzmoden. Bemerkenswerterweise weisen die Mikrokavitäten eine hohe Laseremissionsstabilität auf, was einen Rekordwert für die an der Luft getesteten Perowskitlaser darstellt. Darüber hinaus wird Single-Mode-Lasertätigkeit - ein wünschenswerter Vorgang für die optische Kommunikation - erfolgreich durch Vergrößerung des Laser-Modenabstands durch Verkleinerung der gepumpten Mikrokavitäten realisiert. Diese vielversprechenden Ergebnisse unterstreichen die Konkurrenzfähigkeit der lösungs-epitaktischen Perowskit-Mikrolaser mit epitaktisch aufgedampften Lasern und ebnen den Weg für eine kostengünstige und energieeffiziente Herstellung hochwertiger Optoelektronik
Correction: Guidelines for the prevention, detection and management of the renal complications of COVID-19 in Africa
No full textThe authors of the article ‘Guidelines for the prevention, detection and management of the renal complications of COVID-19 in Africa’ [1] wish to acknowledge the contribution of Professor Hussein El Fishawy. Our guidelines drew on various sources, including the Egyptian Ministry of Health guidelines, portions of which were adapted and reproduced with permission from the Egyptian Ministry of Health. Two of the authors of those guidelines, Professors Elsayed and Zaki, are also coauthors of our paper. Professor El Fishawy was the third author of the Egyptian guidelines and we would like to acknowledge his contribution to our review through this source, especially with respect to the treatment algorithms for patients with kidney transplants and those with acute kidney injury. Reference1. Elsayed HM, Wadee S, Zaki MS, Were AJO, Ashuntantang GE, Bamgboye EL, et al. Guidelines for the prevention, detection and management of the renal complications of COVID-19 in Africa. Afr J Nephrol. 2020; 23(1):109-126
Représentations littéraires du sacré dans le roman maghrébin de langue française
No full textThis interdisciplinary study explores how Driss Chraïbi’s L’Homme du Livre (1995), Assia Djebar’s Loin de Médine (1991), and Anissa Boumediène’s La fin d’un monde (1991) present accounts of particular historical moments in early Islam. This study explores the role of the imagination as well as freedom of invention when reconstructing historical events. It engages the novels through a study of the interplay between the literary text and the sources and traditions that impact and shape the text narrative. Gaining direct access to the original sources in Arabic serves to analyze how religious and early historical materials are considered in and reflected by the fictional texts. Because the sources tend to differ in both content and approach, this study examines their preoccupations in order to determine the criteria of selection applied by each novelist.Ph.D.Includes bibliographical referencesIncludes vitaby Hanan Elsaye
Investigating the associations between executive compensation and firm performance: Agency theory or tournament theory
No full textAbstract Purpose – While there have been extensive empirical investigations of pay-performance sensitivity, the perspective of performance-pay has received less attention to date. While executive compensation is sensitive to firm performance, firm performance is also likely to be affected by executive compensation. Adopting multiple theoretical perspectives, the purpose of this paper is to examine whether executive compensation has a greater influence on firm performance or whether the latter has a greater influence on compensation. Design/methodology/approach – Using data from a five-year period (2010-2014) for Financial Times and Stock Exchange 350 companies, the authors employ a set of simultaneous equation modelling to jointly investigate, after accounting for endogeneity problem, the mutual association of executive compensation and firm performance by employing four control variables (board size, non-executive directors, leverage and boardroom ownership). Findings – The authors find strong evidence for the greater influence of executive compensation on firm performance than the pay-performance framework. This finding supports the tournament theory compared with the agency perspective. Research limitations/implications – Inevitably, there are limitations in a wide-ranging study of this nature that could be addressed in future research. As any empirical study utilising company data, there may be concerns to the effect of survivorship bias and the manner in which companies have reorganised, if there is any, themselves during the period under examination. There are also issues as to missing data, some measures relating to both executive compensation and corporate governance are not provided by the BoardEx database. Practical implications – The study results provide evidence that using the tournament perspective by remuneration committees as a guide for determining executive compensation helps in achieving better performance. This helps in developing appropriate mechanisms for setting executive remuneration. Originality/value – This paper combines an empirical investigation of the frameworks of pay-performance and performance-pay and develops a system of six simultaneous equations to examine the associations between executive compensation and firm performance. Keywords Firm performance, Executive compensation, FTSE 350, Simultaneous equations modelling Paper type Research pape
Intrathecal Drug Delivery Systems Survey: Trends in Utilization in Pain Practice [Corrigendum]
No full textAbd-Sayed A, Fiala K, Weisbein J, et al. J Pain Res. 2022;15:1305–1314.
The authors have advised there is an error in the author list on page 1305. The author name “Alaa Abd-Sayed” should read “Alaa Abd-Elsayed”.
The authors apologize for this error
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