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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Automated Shuttles as Traffic Calming: Evidence from a Pilot Study in City Traffic

Huot-Orellana, Amelie, Saunier, Nicolas 03 January 2023 (has links)
Discourse about the real-world effects of automated vehicles has intensified over the last decade, but few observational studies have been made examining their integration in real traffic. This research is based on the dataset prepared by Beauchamp et al. in [1] where video footage from two pilot projects involving automated shuttles in Montreal and Candiac in 2019 was analyzed to compute safety indicators from road user trajectories. The study showed that automated shuttles have safer interactions with other road users compared to human drivers following the same trajectories. Yet, this may not be the only characteristic of automated shuttles. These vehicles are notoriously slow, 10 to 15 km/h slower than human-driven cars in city traffic [1], which on city streets is bound to influence other road users, in particular following cars. lt is therefore hypothesized that automated shuttles may have a traflic calming effect, slowing other motorized vehicles [2]. Slower speed and the predictability of automated shuttles, obeying the rules of the road and yielding more willingly to vulnerable road users (pedestrians and cyclists) may also have an impact on these users' behavior [3]: for example, cyclists may pass the shuttle, pedestrians may cross outside of crosswalks. The present study aims to explore the potential effects of automated shuttles, with their slower spceds and more predictable behavior, on the behavior of other road users. [from Introduction]
12

Bacterial iron and manganese reduction driven by organic sulfur electron shuttles

Cooper, Rebecca Elizabeth 27 May 2016 (has links)
Dissimilatory metal-reducing bacteria (DMRB) play an important role in the biogeochemical cycling of metals. DMRB are unique in that they possess the ability to couple metal reduction with their metabolism. Microbial Fe(III) respiration is a central component of a variety of environmentally important processes, including the biogeochemical cycling of iron and carbon in redox stratified water and sediments, the bioremediation of radionuclide-contaminated water, the degradation of toxic hazardous pollutants, and the generation of electricity in microbial fuel cells. Despite this environmental and evolutionary importance, the molecular mechanism of microbial Fe(III) respiration is poorly understood. Current models of the molecular mechanism of microbial metal respiration are based on direct enzymatic, Fe(III) solubilization, and electron shuttling pathways. Fe(III) oxides are solid at circumneutral pH and therefore unable to come into direct contact with the microbial inner membrane, these bacteria must utilize an alternative strategy for iron reduction. Reduced organic compounds such as thiols are prominent in natural environments where DMRB are found. These thiol compounds are redox reactive and are capable of abiotically reducing Fe(III) oxides at high rates S. oneidensis wild-type and ΔluxS anaerobic biofilm formation phenotypes were examined under a variety of electron donor-electron acceptor pairs, including lactate or formate as the electron donor and fumarate, thiosulfate, or Fe(III) oxide-coated silica surfaces as the terminal electron acceptor. The rates of biofilm formation under the aforementioned growth conditions as well as in the presence of exogenous thiol compounds indicate that ∆luxS formed biofilms at rates only 5-10% of the wild-type strain and ∆luxS biofilm formation rates were restored to wild-type levels by addition of a variety of exogenous compounds including cysteine, glutathione, homocysteine, methionine, serine, and homoserine. Cell adsorption isotherm analyses results indicate that wild-type is can attach to the surface of hematite particles attachment , but ΔluxS is unable to attach the hematite surfaces. These results indicate that biofilm formation is not required for Fe(III) oxide reduction by S. oneidensis ∆luxS anaerobic biofilm formation rates were restored to wild-type levels by addition of exogenous auntoinducer-2 (AI-2), a by-product of homocysteine production in the Activated Methyl Cycle. This discovery led to subsequent experiments performed to detect the production and utilization of AI-2 by wild-type and ∆luxS strains under aerobic and anaerobic conditions. AI-2 production experiments showed wild-type, but not ΔluxS, was capable of producing AI-2. The addition of exogenous S. oneidensis and Vibrio harveyi-produced AI-2 to wild-type and ∆luxS resulted in the swift depletion of AI-2 from the media. These results provide evidence that S. oneidensis can produce AI-2 and subsequently utilize its’ own AI-2 as well as AI-2 produced by other bacteria as a carbon and electron source in the absence of preferred carbon sources. S. oneidensis produces and secretes a suite of extracellular thiols under anaerobic Fe(III)-reducing and Mn(III) and Mn(IV)-reducing conditions including cysteine, homocysteine, glutathione, and cyteamine. Exogenous thiols produced by S. oneidensis are intermediates of the Activated Methyl Cycle (AMC) and Transulfurylation Pathway (TSP). Reduced and oxidized thiols were detected, indicating that the thiols are in a constant state of flux between the reduced and oxidized forms and that the concentration of reduced thiols to its’ oxidized counterpart is indicative of the state of metal reduction by the microorganisms. Respiratory phenotypes Based on Fe(III) and Mn(IV) respiratory phenotypes observed in the AMC and TSP pathway mutants (∆luxS, ∆metB, ∆metC and ∆metY) we can infer that cysteine, glutathione, and cysteamine contribute to metal reduction by serving as efficient electron shuttling molecules, while homocysteine is critical for maintenance of the AMC, propagation of thiol biosynthesis, and maintenance of cellular metabolism via the AMC intermediate SAM. Furthermore, these findings suggest that all metal-reducing bacteria require thiol formation to reduce solid metal oxides. Direct contact mechanism is not the dominant means through electrons are transferred and metals are reduced, instead electron shuttles are the maid reduction mechanism.
13

Biasing positional change in interlocked and non-interlocked molecular machines

Barrell, Michael Jack January 2010 (has links)
This Thesis explores the topic of large amplitude motion within molecular machines and the different mechanisms and molecular architectures that are exploited in order to achieve control over the relative positions of submolecular components with respect to one another. Chapter One provides a thorough survey of a vast range of molecular switches and machines that have been developed during the last two decades. The focus is on interlocked and non-interlocked systems that display highly controlled large amplitude motion and the principles that govern their operation. Initially, simple molecular switches and shuttles are described with the chapter finally arriving at complex molecular machines such as motors, ratchets and walking molecules. The importance of understanding the different mechanisms that dictate the operation of switchable molecular machines and their fundamental differences are highlighted throughout the chapter. Chapters Two to Four are devoted to reporting the author’s contributions to novel switchable molecular systems. Chapter Two describes the serendipitous discovery of an ion-pair template which has been exploited in rotaxane formation and the operation of an orthogonal interaction anion-switchable molecular shuttle. The macrocycle moves back and forth along the thread between a cationic pyridinium station and a metal coordinating triazole motif when chloride anions are bound and removed respectively from a palladium centre which is located inside the cavity of the macrocycle. Excellent positional integrity (>98%) of the ring at both stations is achieved due to the orthogonal binding modes in the two states of the shuttle. Chapter Three presents a non-interlocked molecular switch that operates through the manipulation of dynamic covalent chemistry. The switch is comprised of a “two legged”, small organic molecule (a “walking unit”), anchored to a three foothold track via one disulfide and one hydrazone bond. The acid promoted hydrazone exchange allows a specific ratio of the two positional isomers to be achieved at equilibrium. However, the system is also arranged in such a manner that the ratio can be biased towards one positional isomer when the hydrazone exchange is carried out alongside the photoisomerisation (Z  E) of a stilbene motif which is incorporated in the track. The isomerisation alters the relative free energies of the products by increasing the ring strain of one positional isomer with respect to the other, hence introducing bias into the system. The final chapter reports the logical progression of the work presented in Chapter Three and describes the pursuit of a four-station dynamic covalent energy ratchet, of which the net position of the walker unit can be driven away from a steady state, minimum energy distribution by orthogonal disulfide and hydrazone exchange and concomitant stilbene isomerisation. The endeavour towards the successful synthesis of this rather complex molecule is described alongside the principles for its proposed operation. Chapter Two is presented in the form of an article that has already been published in a peer-reviewed journal. No attempt has been made to rewrite this work other than a slight alteration in the order of figures in the text to allow for easier reading and re-formatting to ensure consistency of presentation throughout this thesis. The original paper is reproduced, in its published format in the Appendix. Chapters Two, Three and Four begin with a synopsis to provide a general overview of the work that is presented in addition to a grateful acknowledgement of the contribution of my fellow researchers.
14

Commercial off The Shelf (COTS) security issues and approaches

Doan, Dung. 09 1900 (has links)
Custom built products do not always meet the new Department of Defense (DoD) requirements. Their high cost and lengthy development cycle does not suit the Information Age where communication information and technology develop rapidly. To adapt to this new environment, Commercial off The Shelf (COTS) software products have become the core for Military systems. This is the only way to approach the readiness requirements for armed forces. Like any other products, COTS software brings a lot of advantages but also carries side effects for military systems. One of the most serious issues for military use of a COTS software product is its security. This thesis provides an analysis of approaches to identify the security vulnerabilities and recommends an acquisition approach to minimize the issue. It is not the intent of this thesis to find a universal approach to solve the security issue of COTS products.
15

Assessment of a space shuttle trajectory evaluation system (DOLILU II)

Chakravarthy, Diwakar. January 2000 (has links)
Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains vii, 105 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 76-79).
16

Effect of Thermal Protection System on Vibration of Aerospace Structural Panels

Derar, Hind D. January 2008 (has links) (PDF)
No description available.
17

ELECTRODE AND ELECTROLYTE ADDITIVES FOR LIFETIME EXTENSION IN LITHIUM-ION BATTERIES

Narayana, Kishore Anand 01 January 2014 (has links)
Lithium-ion batteries (LIBs) are the most commonly used type of rechargeable batteries with a global market estimated at $11 billion, which is predicted to grow to $60 billion by 2020. The global commercialization of Li-ion batteries is impeded by issues such as poor cycle life (5000 cycles achieved in some LIBs) in high energy and power density applications because of the rising internal resistance due to aging and safety concerns such as overcharge which ultimately leads to thermal runaway and explosions. A battery’s performance mainly depends on external factors such as electrode thickness and degree of compacting, and the type of conductive additive and electrolyte mixture used, and internal factors such as its internal temperature and state of charge. The performance suffers due to aging or erroneous mechanisms such as decomposition of the electrode or electrolyte material affecting the lifetime. In this thesis, an attempt is made to improve the lifetimes of the Li-ion batteries by incorporating suitable electrolyte additives, which were incorporated in the battery electrolyte to prevent overcharge. Also, several conductive electrode additives were incorporated as filler materials in an anode to explore the effects on its discharge capacities.
18

A case study of NASA's Columbia tragedy an organizational learning and sensemaking approach to organizational crisis /

James, Eric Preston. Richardson, Brian K., January 2007 (has links)
Thesis (M.A.)--University of North Texas, Dec., 2007. / Title from title page display. Includes bibliographical references.
19

Traffic Simulation of Automated Shuttles in Linköping University Campus

Gugsa Gebrehiwot, Rihanna January 2021 (has links)
Automated shuttles are designed to provide a clean transportation and improve access to areas such as where travelers have to walk long distances to/from bus stops. The introduction of automated shuttles in the road network might affect the safety of pedestrians and cyclists as well as traffic performance of motorized vehicles. Several demonstration trials are being conducted to study how automated shuttles operate in real traffic conditions, but they are limited to few vehicles and evaluations of traffic effects at higher penetration rates are not possible. Traffic simulation is a tool that can be used to study effects on traffic performances at different penetration rates of e.g., automated shuttles. However, automated shuttles have not yet been modeled, calibrated, and validated in microscopic traffic simulation tools. Therefore, the objective of this thesis is to model, calibrate and validate automated shuttle’s behavior using the simulation tool SUMO and data collected from the demonstration trial on the area of campus Valla Linköping University, Sweden. The pilot study consists of two automated shuttles, and they operate on a 2.1 km fixed route. The collected data by one of the automated shuttles is analyzed with a focus on the free driving behavior. The analysis shows that the automated shuttle has different maximum operation speeds at different locations and defining one value for the maximum speed when setting up the simulation is not enough. Therefore, virtual speed limits are derived by mimicking the maximum operation speed of the shuttle from the data and used to define segment specific speed limits in the simulation. Additionally, the data is used to calibrate the acceleration and deceleration parameters. The Krauss and the IDM car-following models have been investigated by calibrating the acceleration and deceleration parameters for the free driving situation. The results indicate that both the Krauss and IDM car-following models follows the general trend of the speed and acceleration profiles. The speed profiles produced with the IDM model have smoother profiles at the start and end of acceleration and deceleration phases while in Krauss model the transition of the speed change is more direct and there are in principle no delays for reaction. Although the IDM model performs slightly better for the free driving situation, it can be of interest to consider both models for the calibration of interactions with other roads users since both models are able to capture the general trend of the speed and acceleration profiles. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>
20

CARLA-based Simulation Environment for Testing and Developing Autonomous Vehicles in the Linden Residential Area

Fernandez Narvaez, Pedro Jezel January 2021 (has links)
No description available.

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