22 research outputs found
Harmonische Oberschwingungen in Windkraftanlagen : Analyse und Lösungsansätze mittels PowerFactory
No full textDiese Arbeit analysiert den Einfluss von Oberschwingungen auf die Spannungsqualität am Netzanschlusspunkt. Neben den mathematischen Grundlagen und den relevanten Normen wird ein Windenergieprojekt in PowerFactory simuliert. Die Simulationsergebnisse werden mit dem Auswertungsbericht und dem Anlagenzertifikats des Zertifizierers verglichen. Abschließend werden Filterkonzepte zur Reduktion harmonischer Belastungen bewertet.This thesis analyzes the impact of harmonic distortions on voltage quality at the grid connection point. In addition to the mathematical fundamentals and relevant standards, a wind energy project is simulated in PowerFactory. The simulation re-sults are compared with the certifier’s evaluation report and the plant certificate. Finally, filter concepts to reduce harmonic distortions are evaluated
THREE ESSAYS ON INTERNATIONAL ASSET PRICING
No full textThe common thread running through my research is to explore the asset price dynamics across countries and across asset classes. In the first chapter of this thesis, I apply Newton's law of universal gravitation to investigate the determinants of the bilateral relationships in returns. Examining the gravity effect in a large set of countries, I find that the size of economies and geographical distance are significant determinants of the contemporaneous as well as the lead-lag correlation patterns observed in stock returns across countries. In addition, decomposing stock market returns into cash-flow and discount-rate news shows that the international transmission of country specific news is more pronounced through discount-rate news, and that the size of economies and geographical distance are significant determinants for both components of returns.
In the second chapter, based on a joint work with Redouane Elkamhi and Mikhail Simutin, we propose a diversification approach that exploits the global connectedness of developed countries to gain exposure to emerging countries' overall economies rather than their shallow equity markets. In doing so, we demonstrate that developed markets still offer substantial diversification benefits beyond those available through equity indices, contrary to a large body of literature claiming that the benefits of international diversification via developed markets have dramatically declined. Our results also suggest that relying on equity indices to assess diversification benefits understates diversification gains.
The third chapter explores the potential risk of investing in global markets. Specifically, my co-author Redouane Elkamhi and I study the two widely-known speculation strategies in the FX market, carry and momentum trades, and provide a risk-based explanation for the excess returns. We construct a common factor that drives correlation across international equity markets and show that the cross-sectional variations in the average excess returns across carry and momentum portfolios can be explained by different sensitivities to our correlation factor. By using a factor constructed from the equity market to explain abnormal return in the FX market, these findings shed light on the important linkage across the two markets through equity correlations as a main instrument of the aggregate risk.Ph.D
THREE ESSAYS ON INTERNATIONAL ASSET PRICING
No full textThe common thread running through my research is to explore the asset price dynamics across countries and across asset classes. In the first chapter of this thesis, I apply Newton's law of universal gravitation to investigate the determinants of the bilateral relationships in returns. Examining the gravity effect in a large set of countries, I find that the size of economies and geographical distance are significant determinants of the contemporaneous as well as the lead-lag correlation patterns observed in stock returns across countries. In addition, decomposing stock market returns into cash-flow and discount-rate news shows that the international transmission of country specific news is more pronounced through discount-rate news, and that the size of economies and geographical distance are significant determinants for both components of returns.
In the second chapter, based on a joint work with Redouane Elkamhi and Mikhail Simutin, we propose a diversification approach that exploits the global connectedness of developed countries to gain exposure to emerging countries' overall economies rather than their shallow equity markets. In doing so, we demonstrate that developed markets still offer substantial diversification benefits beyond those available through equity indices, contrary to a large body of literature claiming that the benefits of international diversification via developed markets have dramatically declined. Our results also suggest that relying on equity indices to assess diversification benefits understates diversification gains.
The third chapter explores the potential risk of investing in global markets. Specifically, my co-author Redouane Elkamhi and I study the two widely-known speculation strategies in the FX market, carry and momentum trades, and provide a risk-based explanation for the excess returns. We construct a common factor that drives correlation across international equity markets and show that the cross-sectional variations in the average excess returns across carry and momentum portfolios can be explained by different sensitivities to our correlation factor. By using a factor constructed from the equity market to explain abnormal return in the FX market, these findings shed light on the important linkage across the two markets through equity correlations as a main instrument of the aggregate risk.Ph.D
Corrigendum to: Enhanced Long-term Stability and Carbon Resistance of Ni/MnxOy-Al2O3 Catalyst in Near-equilibrium CO2 Reforming of Methane for Syngas Production [15(2), 2020, 331-347]
No full textAccording to Authors request (10th December 2020), Corrigendum to: Djebarri, B., Touahra, F., Aider, N., Bali, F., Sehailia, M., Chebout, R., Bachari, K., Halliche, D. (2020). Bulletin of Chemical Reaction Engineering & Catalysis, 15(2), 2020, 331-347 (doi:10.9767/bcrec.15.2.6983.331-347). First Author (Baya Djebarri) is added as member of Corresponding Author because of his largest contribution in the article and his expertise.
Correction:
The Authors Names were corrected to:
Baya Djebarri1,*, Fouzia Touahra2,*, Nadia Aider4, Ferroudja Bali3, Moussa Sehailia2, Redouane Chebout2, Khaldoun Bachari2, Djamila Halliche3
The information detail of Corresponding Authors was corrected to:
* Corresponding Authors.
Email: [email protected] (F. Touahra); [email protected] (B. Djebarri)
Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)
Temps et fonctionnement textuel chez Rachid Mimouni
No full textTime and Textual Functioning at Rachid Mimouni
The temporal dimension is a variable as important as space, and it is far from lacking in interest in the work of Rachid Mimouni. In fact, the issue of time considered as a structuring factor of the event representations which punctuate the story (1) is at the very heart of his romantic enterprise. To show how temporality exercises a locating and regulating function in the Mimounian text, we distinguish four temporal aspects to which the author focuses in his writing universe: romantic time, lived time, historical time and social time
Efficiency of InN/InGaN/GaN Intermediate-Band Solar Cell under the Effects of Hydrostatic Pressure, In-Compositions, Built-in-Electric Field, Confinement, and Thickness
No full textThis paper presents a thorough numerical investigation focused on optimizing the efficiency of quantum-well intermediate-band solar cells (QW-IBSCs) based on III-nitride materials. The optimization strategy encompasses manipulating confinement potential energy, controlling hydrostatic pressure, adjusting compositions, and varying thickness. The built-in electric fields in (In, Ga)N alloys and heavy-hole levels are considered to enhance the results’ accuracy. The finite element method (FEM) and Python 3.8 are employed to numerically solve the Schrödinger equation within the effective mass theory framework. This study reveals that meticulous design can achieve a theoretical photovoltaic efficiency of quantum-well intermediate-band solar cells (QW-IBSCs) that surpasses the Shockley–Queisser limit. Moreover, reducing the thickness of the layers enhances the light-absorbing capacity and, therefore, contributes to efficiency improvement. Additionally, the shape of the confinement potential significantly influences the device’s performance. This work is critical for society, as it represents a significant advancement in sustainable energy solutions, holding the promise of enhancing both the efficiency and accessibility of solar power generation. Consequently, this research stands at the forefront of innovation, offering a tangible and impactful contribution toward a greener and more sustainable energy future.Dynamics of Micro and Nano System
Comparatisme Du Conte Francophone : Poétique De La Réécriture Et Enjeux Transtextuels Chez Tahar Ben Jelloun Et Amélie Nothomb.
No full textElectronic Thesis or DissertationDissertation Abstract Central to this dissertation is a reflection on the properties of deformability and variability that occur in the retelling of an oral tale. The tale is defined as a text with multiple origins whose articulations vary from one storyteller to another, such that variability becomes a defining feature of the story itself. Consequently, inasmuch as a literary tale has no stable form, it is crucial to take into account the intertextual relations that exist between an original text and all the others that extend it through various rewritings. To that end, an investigation is undertaken of the rewriting, by two outstanding figures of Francophone literature, of seven French traditional fairy tales taken from Les Contes by Charles Perrault. The work of the rewriters, the Moroccan Tahar Ben Jelloun and the Belgian Amélie Nothomb, refocuses the question of the transtextual and dialogical relationships that exist in such cases. Reflection and analysis concern the following questions: How to characterize the textual specificities that make every tale recast by Ben Jelloun and Nothmb a different story from Perrault’s. How to account for the manner in which the tales comprising the corpus fit into a discursive and narratological enterprise owing to the authors’ desire to suggest new ways of reading and understanding them. What is at stake, in terms of discourse and meaning-building, in a situation where the voice of the author seems to be absorbed by reading and listening to the tales
Universal differential equations for glacier ice flow modelling
No full textGeoscientific models are facing increasing challenges to exploit growing datasets coming from remote sensing. Universal differential equations (UDEs), aided by differentiable programming, provide a new scientific modelling paradigm enabling both complex functional inversions to potentially discover new physical laws and data assimilation from heterogeneous and sparse observations. We demonstrate an application of UDEs as a proof of concept to learn the creep component of ice flow, i.e. a nonlinear diffusivity differential equation, of a glacier evolution model. By combining a mechanistic model based on a two-dimensional shallow-ice approximation partial differential equation with an embedded neural network, i.e. a UDE, we can learn parts of an equation as nonlinear functions that then can be translated into mathematical expressions. We implemented this modelling framework as ODINN.jl, a package in the Julia programming language, providing high performance, source-to-source automatic differentiation (AD) and seamless integration with tools and global datasets from the Open Global Glacier Model in Python. We demonstrate this concept for 17 different glaciers around the world, for which we successfully recover a prescribed artificial law describing ice creep variability by solving ∼ 500 000 ordinary differential equations in parallel. Furthermore, we investigate which are the best tools in the scientific machine learning ecosystem in Julia to differentiate and optimize large nonlinear diffusivity UDEs. This study represents a proof of concept for a new modelling framework aiming at discovering empirical laws for large-scale glacier processes, such as the variability in ice creep and basal sliding for ice flow, and new hybrid surface mass balance models.Physical and Space Geodes
High-Energy Radiation Effects on Silicon NPN Bipolar Transistor Electrical Performance: A Study with 1 MeV Proton Irradiation
No full textThis study investigates the degradation of the silicon NPN transistor’s emitter-base junction, specifically the 2N2219A model, under both forward and reverse polarization. We examine the current–voltage characteristics under the influence of 1 MeV proton irradiation at various fluencies, which are 5.3×108,5.3×1010,5×1011,5×1012, and 5×1013 protons/cm², all conducted at 307 K. The experimental findings elucidate a pronounced dependency of diode parameters, including the reverse saturation current, series resistance, and the non-idealist factor, on the incident proton flow. This observation underscores that proton-induced degradation is primarily driven by displacement damage, while recorded degradation is predominantly attributed to the generation of defects and interfacial traps within the transistor resulting from exposure to high-energy radiation. Our findings indicate that the effects of irradiation align more closely with the compensation phenomenon in doping rather than its reinforcement.Dynamics of Micro and Nano System
Linear and nonlinear optical absorption coefficients in InGaN/GaN quantum wells: Interplay between intense laser field and higher-order anharmonic potentials
No full textThis computational investigation delves into the electronic and optical attributes of InGaN/GaN nanostructures subjected to both harmonic and anharmonic confinement potentials, coupled with the influence of a nonresonant intense laser field (ILF). The theoretical framework incorporates higher-order anharmonic terms, specifically quartic and sextic terms. The solutions to the Schrödinger equation have been computed employing the finite element method and the effective mass theory. Moreover, linear and third-order nonlinear optical absorption coefficients are derived via a density matrix expansion. Our analysis reveals the feasibility of manipulating electronic and optical properties by adjusting confinement potential parameters, system attributes, and laser field intensity. In addition, the ILF induces remarkable modifications, characterized by reduced resonance peak amplitudes and a blue shift in absorption coefficients. Intriguingly, regardless of potential harmonicity, the impact of incident electromagnetic intensity is notably more pronounced in the absence of the ILF. These findings hold significant promise for advancing theoretical predictions, providing valuable insights into the intricate interplay between confinement potentials, laser fields, and their effects on electronic and optical behaviors within nanostructures
