Nonlinear Time-Domain Structure/Aerodynamics Coupling in Systems with Concentrated Structural Nonlinearities

This paper details a practical approach for predicting the aeroelastic response (structure/aerodynamics coupling) of flexible pod/missile-type configurations with freeplay/hysteresis concentrated structural nonlinearities. The nonlinear aeroelastic response of systems in the presence of these nonlinearities has been previously studied by different authors; this paper compiles methodologies and related airworthiness regulations. The aeroelastic equations of the pod/missile configuration are formulated in state-space form and time-domain integrated with Fortran/Matlab codes developed ad hoc for dealing with freeplay/hysteresis nonlinearities. Results show that structural nonlinearities change the classical aeroelastic behaviour with appearence of non-damped motion (LCOs and chaotic motion)

Limitations of free energy diagrams to predict the catalytic activity: the reverse water gas shift reaction catalyzed by Ni/TiC

The temporal evolution at the catalyst surface is a result of an intricate interplay between all involved microscopic events such as adsorption, desorption, diffusion, and bond breaking/formation steps, and the interaction with the surrounding environment. By properly including these effects, kinetic Monte Carlo (kMC) simulations can accurately describe the complexity of real catalysts, unravel the dominant reaction mechanisms and provide fundamental understanding towards the rational design of novel catalysts. In this work, we combine density functional theory (DFT) calculations, statistical thermodynamics and kMC simulations to study the reverse water–gas shift (RWGS) reaction on Ni/TiC, a bifunctional catalyst. The predictions from DFT energy profiles do not coincide with the outcome of the kMC simulations, evidencing the limitations of the former, especially in including the effect of coverage of surface species, which plays a crucial role. The kMC simulations results are in remarkable agreement with the experimental data, proving that the kMC simulations are able to describe the complex chemistry of the RWGS reaction on a bifunctional catalyst

Reverse logistics process identification in the business to consumer electronic commerce

Thesis (M.Eng.)--Massachusetts Institute of Technology, Engineering Systems Division, 2000.Includes bibliographical references (leaves 60-66).commerce will have to prove its reliability and convenience. Operational excellence and coordination among the supply chain will allow e-vendors to offer services like on-time delivery and simple return processes, vital factors for electronic vendors' success. The purpose of this thesis is to identify the differences across the reverse logistics process. To accomplish this, the return policies and procedures of ninety-three leading companies that sell products on the Internet directly to consumers were carefully studied. Seven different return processes and four main activities included in them were identified and formally described. Each process is designed to satisfy a specific set of needs, thus they differ considerably from each other. Since logistics is a major part of the cost structure of operating a virtual store (e-tailer) every aspect of it has to be carefully studied and efficiently performed. The author has selected this sole aspect of reverse logistics to focus the research of this thesis and identify and describe the different processes that are currently used by e-vendors.by Hector Lozano Pruneda.M.Eng

Binding of Al(III) to synthetic RNA and metal-mediated strand aggregation

Over the last few years, focused interest in aluminum has been heightened by recent studies regarding its health effects. Its possible relation with chronic diseases makes it convenient to address more in depth the reactivity of aluminum with biologically relevant molecules. The present work investigates the interaction of the aluminum ion with two synthetic RNAs, poly(rA) and poly(rU), through a detailed thermodynamic and kinetic study. The trivalent aluminum ion was kept in solution by complexation with the cacodylate anion, even at neutral pH, thus making the study with biological molecules feasible. The results obtained by spectrophotometry, circular dichroism, viscometry and thermal stability measurements indicate that aluminium strongly interacts with single and duplex RNA structures. The kinetic experiments point out that, even though cacodylate is required to keep the metal in solution, it actually inhibits the reaction of aluminum with RNA as it converts the metal into an unreactive dimer species. Notably, further interaction occurred in an excess of the aluminum/cacodylate complex, inducing aggregation of single-stranded RNAs. An analysis of the kinetic data has shown that the modes of aggregation of the two RNAs differ and such a difference can be ascribed to the diverse polynucleotide secondary structures. The observed stabilization of multiple-stranded systems by aluminum can serve as a model for future studies due to the interest aroused by this metal in the study of non-canonical nucleic acid structures

Design and Validation of a Portable Handheld Device to Produce Fine Fibers Using Centrifugal Forces

In the present research project, a novel portable battery-powered handheld device able to produce micron and submicron fibers using centrifugal forces is proposed. The design includes spinnerets with a clamshell configuration with multiple chambers or reservoirs (2, 4, and 8) and different exit orifice diameters (400, 500, 600, and 800 µm). The rotational speed is controlled via an Arduino microcontroller. To validate the design, a series of experiments were conducted and the effect of the orifice diameter, number of chambers, and velocity on the resulting fibers’ diameter and yield was studied. For the experiments, a polymeric solution of Polyvinyl Alcohol (PVA) was prepared. The fiber yield was gravimetrically quantified, and the fiber morphology and diameter were analyzed by means of scanning electron microscopy (SEM). The experimental results showed that spinnerets with an orifice diameter of 500 microns yielded the greatest amount of fibers (0.0777 g). In addition, the number of chambers also affected the amount of fibers produced, and it was determined that the fiber diameter size is dependent on the spinneret speed. Fibers 80 nm in diameter were observed at 6500 rpm

Friedensförderung in Zeiten von COVID-19: Risikoadaptierte Strategien von Kooperations- und Entwicklungsprojekten

National and international cooperation and development projects (CDP) are fundamental for peacebuilding. However, unforeseen global crises, like COVID-19, can endanger such projects, requiring rapid adaption. In Colombia, the coronavirus outbreak threatens to slow the implementation of peace-related projects, while simultaneously violence over control and ownership of land increases. Although the mid- to long-term consequences for peacebuilding are unknown, exploring risk-adapted strategies of national and international CDP can help identify crucial aspects for future processes and implementations. This study explores the key challenges and coping strategies of implementing agencies and stakeholders to COVID-19, thus helping to derive and improve risk-adapted strategies. After reviewing academic and grey literature, and implementing a semi-structured survey, peacebuilding risked-adapted strategies to COVID-19 are explored with respect to conflict-affected and vulnerable areas of Colombia. Findings show that increasing complexity rooted in top down governmental measures, the rise of new local power relations (e.g. armed groups, illicit activities), and social alienation are negatively affecting peacebuilding in Colombia. Future CDP risk adapted strategies should build on local interests and needs through public-private and environmental cooperation.Nationale und internationale Kooperations- und Entwicklungsprojekte (CDP) sind für die Friedensförderung von grundlegender Bedeutung. Unvorhergesehene globale Krisen, wie COVID-19, können solche Projekte jedoch gefährden und erfordern eine rasche Anpassung. In Kolumbien droht der Ausbruch des Coronavirus die Durchführung friedensbezogener Projekte zu verlangsamen, während gleichzeitig die Gewalt über die Kontrolle und den Besitz von Land zunimmt. Obwohl die mittel- bis langfristigen Folgen für die Friedenskonsolidierung unbekannt sind, kann die Untersuchung risikoangepasster Strategien des nationalen und internationalen CDP dazu beitragen, entscheidende Aspekte für künftige Prozesse und Implementierungen zu ermitteln. Diese Studie untersucht die Herausforderungen und Bewältigungsstrategien der Durchführungsorganisationen und Interessengruppen im Kontext von COVID-19, umso risikoangepasste Strategien abzuleiten und zu verbessern. Basierend auf Literaturrecherche und der Durchführung semi-strukturierter Interviews werden risikoangepasste Strategien der Friedensförderung für COVID-19 in unterschiedlichen Teilen Kolumbiens untersucht. Die Ergebnisse zeigen, dass die zunehmende Komplexität, die in den Maßnahmen der Regierung von oben nach unten, dem Entstehen neuer lokaler Machtverhältnisse (z. B. bewaffnete Gruppen, illegale Aktivitäten) und in zunehmend sozialer Entfremdung wurzelt, die Friedensförderung in Kolumbien negativ beeinflusst. Künftige risikoangepasste Strategien des CDP sollten auf lokalen Interessen und Bedürfnissen durch öffentlich-private und umweltpolitische Zusammenarbeit aufbauen.Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) e.V. (3493)Peer Reviewe

Hierarchy of graph matchbox manifolds

We study a class of graph foliated spaces, or graph matchbox manifolds, initially constructed by Kenyon and Ghys. For graph foliated spaces we introduce a quantifier of dynamical complexity which we call its level. We develop the fusion construction, which allows us to associate to every two graph foliated spaces a third one which contains the former two in its closure. Although the underlying idea of the fusion is simple, it gives us a powerful tool to study graph foliated spaces. Using fusion, we prove that there is a hierarchy of graph foliated spaces at infinite levels. We also construct examples of graph foliated spaces with various dynamical and geometric properties.Comment: New examples added at the end of Section 2; Introduction is rewritten. To appear in Topology and its Application

Natural dynamics: understanding natural dynamics of seagrasses of the north west of Western Australia. Report of Theme 5 - Project 5.3 prepared for the Dredging Science Node

Relatively little is known of the spatial and temporal dynamics of seagrass meadows in the north west of Western Australia, but such knowledge is needed when designing and evaluating studies that aim to detect potential dredging-related impacts on seagrass, and when making predictions about the likelihood of, and speed of recovery from, such impacts. This study was undertaken to improve our understanding of the spatial and temporal patterns in seagrass composition, abundance and reproductive phenology in the Pilbara. We also characterised key environmental parameters, especially light, that influence seagrass survival and can be altered by dredging..

Análisis de la aplicación metodológica para el desarrollo de proyectos de la agencia de renovación del territorio – ART

Las metodologías aplicadas a diferentes  proyectos en el mundo, son analizadas en este artículo cuyo propósito es  la identificación de criterios y aspectos que pueden ser aplicados en una metodología propuesta para la Agencia de Renovación del Territorio-ART,  en Colombia. Lecciones aprendidas tanto de casos exitosos como otros que promueven una revisión más amplia de los enfoques y procesos aplicados a proyectos, permiten en este artículo una propuesta metodológica, frente a la gestión de involucrados, las fases de los proyectos, un marco regulatorio, un enfoque de bienestar y colaborativo, cuya eventual aplicación en la ART, puedan generar resultados de desarrollo local sostenible