• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 84
  • 31
  • 20
  • 19
  • 9
  • 5
  • 5
  • 4
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 212
  • 45
  • 41
  • 35
  • 34
  • 34
  • 27
  • 27
  • 24
  • 22
  • 22
  • 20
  • 19
  • 17
  • 16
  • 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.
91

Fleet management strategies for urban Mobility-on-Demand systems

Chaudhari, Harshal Anil 23 February 2022 (has links)
In recent years, the paradigm of personal urban mobility has radically evolved as an increasing number of Mobility-on-Demand (MoD) systems continue to revolutionize urban transportation. Hailed as the future of sustainable transportation, with significant implications on urban planning, these systems typically utilize a fleet of shared vehicles such as bikes, electric scooters, cars, etc., and provide a centralized matching platform to deliver point-to-point mobility to passengers. In this dissertation, we study MoD systems along three operational directions – (1) modeling: developing analytical models that capture the rich stochasticity of passenger demand and its impact on the fleet distribution, (2) economics: devising strategies to maximize revenue, and (3) control: developing coordination mechanisms aimed at optimizing platform throughput. First, we focus on the metropolitan bike-sharing systems where platforms typically do not have access to real-time location data to ascertain the exact spatial distribution of their fleet. We formulate the problem of accurately predicting the fleet distribution as a Markov Chain monitoring problem on a graph representation of a city. Specifically, each monitor provides information on the exact number of bikes transitioning to a specific node or traversing a specific edge at a particular time. Under budget constraints on the number of such monitors, we design efficient algorithms to determine appropriate monitoring operations and demonstrate their efficacy over synthetic and real datasets. Second, we focus on the revenue maximization strategies for individual strategic driving partners on ride-hailing platforms. Under the key assumption that large-scale platform dynamics are agnostic to the actions of an individual strategic driver, we propose a series of dynamic programming-based algorithms to devise contingency plans that maximize the expected earnings of a driver. Using robust optimization techniques, we rigorously reason about and analyze the sensitivity of such strategies to perturbations in passenger demand distributions. Finally, we address the problem of large-scale fleet management. Recent approaches for the fleet management problem have leveraged model-free deep reinforcement learning (RL) based algorithms to tackle complex decision-making problems. However, such methods suffer from a lack of explainability and often fail to generalize well. We consider an explicit need-based coordination mechanism to propose a non-deep RL-based algorithm that augments tabular Q-learning with a combinatorial optimization problem. Empirically, a case study on the New York City taxi demand enables a rigorous assessment of the value, robustness, and generalizability of the proposed approaches.
92

Exploring the weather impact on bike sharing usage through a clustering analysis

Quach, Jessica January 2020 (has links)
Today bike sharing systems exists in many cities around the globe after a recent growth and popularity in the last decades. It is attractive for cities and users who wants to promote healthier lifestyles; to reduce air pollution and gas emission as well as improve traffic. One major challenge to docked bike sharing system is redistributing bikes and balancing dock stations. There are studies that propose models that can help forecasting bike usage; strategies for rebalancing bike distribution; establish patterns or how to identify patterns. Some of these studies proposes to extend the approach by including weather data. Some had limitations and did not include weather data. This study aims to extend upon these proposals and opportunities to explore on how and in what magnitude weather impacts bike usage. Bike usage data and weather data are gathered for the city of Washington D.C. and are analyzed by using a clustering algorithm called k-means. K-means is suitable for discovering patterns within the data by grouping (clustering) similar instances, which literature review also advocated. In this project, the k-means algorithm managed to identify three clusters that corresponds to bike usage depending on weather. The results show that weather impact on bike usage was noticeable between clusters. It showed that temperature followed by precipitation weighted the most, out of five weather variables. Results also supported that the use of k-means was appropriate for this type of study.
93

Inställning till den smarta elcykeln som tjänst : Finns det samband?

Smedberg, Johanna January 2020 (has links)
Vi befinner oss i en transformation där elcykeln tillför en ny dimension av mobilitet. Samtidigt sker ett teknologiskifte där Internet of Things (IoT) möjliggör uppkoppling av produkter till varandra och från produkt till människa, på ett sätt som tillför nya värden. Elcykeln är inget undantag. Med IoT blir elcykeln intelligent; den smarta elcykeln är här. Smarta elcyklar är nytt på den svenska marknaden. För att förstå hur affärsmodeller och betalningsmodeller kan skapas kring denna nya produkt undersöks inställning till, och drivkrafter för, den smarta elcykeln. Vidare prövas inställningen till olika betalningsmodeller.Resultaten visar att elcykelcyklisten är intresserad av att skaffa sig en smart elcykel och helst vill man betala hela beloppet direkt vid köpet, även om man är öppen för alternativa betalformer som bygger på cykeln som tjänst.I arbetet konstateras att det finns samband mellan teknikintresse och inställningen till smarta elcyklar liksom samband mellan inställning till olika betalningsmodeller och inställning till den smarta elcykeln.Arbetet utgör en grund för vidare forskning kring den smarta elcykeln och affärsmodeller baserade på elcyklar uppkopplade genom IoT.
94

Are Dominant Routes the Least Stressful Routes in a Bike Share System? An Investigation of Hamilton Bike Share using Weighted Level of Traffic Stress

Ubhi, Rajveer January 2021 (has links)
Level of Traffic Stress (LTS) is a four-level system that classifies the stress experienced by cyclists on road segments and at intersections. While LTS has been used in past studies to assess cycling connectivity, accessibility, and safety, very little is known concerning its influence on cycling preferences. This study investigates this topic using a dataset containing 323,163 unique GPS trajectories of Hamilton Bike Share (HBS) users collected over a 12-month period (January 1st to December 31st, 2019). A GIS-based map-matching algorithm is used to generate users’ routes from these trajectories along with attributes such as route length, number of intersections, and number of turns. Unique routes and their use frequencies are then extracted from all routes. The most popular routes between bike share hub (station) pairs are then identified as dominant routes while shortest distance routes are derived by minimizing distance traveled. Weighted level of traffic stress (WLTS), a novel measure of impedance (travel cost) developed for this study, is used to derive the least stressful routes between hub pairs. The three types of routes are compared statistically. The comparison finds that HBS users tend to choose longer routes with bicycle infrastructure in an effort to reduce their traffic stress. However, they do not choose to minimize traffic stress in its entirety by choosing the lowest WLTS routes. In other words, dominant routes are not the least stressful routes in a bike share system. Likewise, minimizing distance is not the sole consideration of HBS users. The findings suggest that other factors also influence route choice. This study not only enhances our understanding of cyclist route preferences with respect to LTS, it also presents a novel measure of impedance – WLTS – that could be used when planning new cycling infrastructure or as an alternative means to route cyclists between origins and destinations. / Thesis / Master of Science (MSc)
95

The importance of safety on the bicycle friendliness of cities

Böhmer, Thomas 28 December 2022 (has links)
In the framework of questions like climate protection, healthy lifestyles and more livable cities it is important to increase cycle use and replace motorized traffic. Safe cycling is one of the preconditions for the growth of cycle use, especially considering the more vulnerable user groups. But how important is safety in relation to other factors influencing bicycle friendliness like comfort of the cycle path and bike parking, accessibility or communication? And how is the relation between 'objective safety' - represented by the number of recorded accidents - and 'subjective safety' as the perceived safety feeling ofthe bike users? [From: Introduction]
96

Influence of Short Term Electric Bike Use on Measures of Vascular Function in Healthy Adults

Hayward, Katelyn Marie 21 April 2023 (has links)
No description available.
97

Cargo E-Bike as a service : A concept study / Elektrisk lådcykel som tjänst : En konceptstudie

Steenberg, Marcus January 2017 (has links)
This Master’s thesis was done with the research group Green Leap at KTH. Green Leap is working for engaging design in sustainable development to act as a catalyst for change. A project that Green Leap has worked with is Ett bilfritt år, where families exchanged their cars for lightweight electric vehicles for a year and the changes in their behaviours were studied. The project resulted in positive experiences of the electric cargo bikes in the everyday life without owning a car. This master thesis became a concept study to investigate different possibilities of providing electric cargo bikes as a service. Research were carried out on how existing cargo bike services were conducted and user studies were conducted to get the understanding of who the users of cargo bikes were and how their needs and behaviours looked like. Through further insights from a variety of actors, five different possibilities were identified for services for the electric cargobikes. By comparing the possibilities of the various services, there was an opportunity of designing the same cargo bike for three of the services. The common hardware had a business opportunity for establishing a common platform for different purposes. Different hardware concepts were also developed during the project to facilitate the sharing of the cargo bikes. This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.Carge e-bike as a service, Marcus Steenberg, KTH Green Leap, www.ettbilfrittar.se/cargo / Detta examensarbete är ett arbete utfört för forskningsgruppen Green Leap på KTH. Forskningsgruppen arbetar med att engagera design i hållbar utveckling för att verka som en katalysator för förändring. Ett projekt som Green Leap har arbetat med är Ett bilfritt år, där familjer bytte ut sina bilar mot lätta elfordon under ett års tid och deras beteendeförändringar studerades. Projektet resulterades i positiva upplevelser av fordonet lådcykel i vardagslivet utan bil. Detta examensarbete blev en konceptstudie för att undersöka olika möjligheter att tillhandahålla lådcykel som en tjänst. Det utfördes undersökningar på hur befintliga lådcykelstjänster var uppbyggda och det utfördes en användarundersökning på vilka användarna av lådcyklar var och hur deras behov och beteende såg ut. Genom ytterligare insikter från en mängd olika aktörer, kartlades fem olika möjligheter på tjänster för lådcykeln. Genom jämförelse av de olika tjänsternas möjligheter sågs en möjlighet att utforma liknande lådcyklar till tre av tjänsterna. Detta hade en affärsmässig möjlighet för att få fram en gemensam plattform för olika ändamål. Det utvecklades även olika förslag på hårdvara för att underlätta delning med en stor variation avbehov. Detta verk är licensierad under en Creative Commons Erkännande 4.0 Internationell license. Föratt ta del av en kopia av licensen besök följande http://creativecommons.org/licenses/by/4.0/.Carge e-bike as a service, Marcus Steenberg, KTH Green Leap, www.ettbilfrittar.se/cargo
98

Implementation of additive manufacturing on bike stems for road bikes / Implementering av additiv tillverkning för styrstammar till högprestationscyklar

Virta, Daniel, Säflund, Carl January 2017 (has links)
This thesis explores the possibilities with additive manufacturing, applied to the engineering of high performance bike parts. The goal was to study the technique and materials that make up the additive manufacturing in order to apply this to bike stems. Also, the goal was to develop both a physical and a virtual model to further evaluate the possibilities with additive manufacturing. Knowledge of the additive manufacturing processes was gained through an extensive information study. After that, a focus on a particular method, EBM, electron beam melting, was made. The process of development of a bike part, the steering stem, was documented to identify the strength and weaknesses of the technique and to finally evaluate it to a traditionally manufactured reference stem. The design process started with a state-of-the-art study and concept stage to later be followed with an iterative process of modelling and simulating. The concepts were created with accordance of the constraints set upon them from our technical specification and the European standards regarding bike parts which limits the maximum allowed deformation and fatigue. One concept was selected to be modelled as a physical component. Finally, the developed component is discussed and compared to a chosen reference stem. The final concept did not outperform the reference in weight, but valuable insight and knowledge were gained along the way. The main conclusion of the thesis is that additive manufacturing is a suitable tool for manufacturing of high performing bike parts. Suggestions for future work are also given, where a further analysis with other materials using the EBM-technique is suggested. / Detta kandidatsexamensarbete utforskar möjligheterna med additiv tillverkning applicerat på högpresterande cykelkomponenter. Målet med arbetet var att utforska möjligheterna att utnyttja additiv tillverkning för styrstammar, samt ta fram en virtuell och en fysisk modell av en styrstam anpassad för detta. Genom en omfattande infosökning hämtades kunskap in om de tekniker och material som utgör den additiva tillverkningsgruppen. Därefter gjordes en fördjupning i en specifik teknik, nämligen EBM, electron beam melting. Produktutvecklingsprocessen för cykelkomponenten, en styrstam, dokumenterades för att identifiera styrkorna och svagheterna hos tekniken och för att i slutet utvärderas mot en traditionellt tillverkad referenskomponent. Designprocessen inleddes med infosökning och konceptgenerering för att sedan, med hjälp av digital mjukvara såsom Solid Edge och ANSYS, övergå till en iterativ process av modellering och simulering. Koncepten modellerades efter önskade egenskaper definierat i en kravspecifikation samt rådande EU-standard för styrstammar i tillåten deformation och utmattningsbrott. Ett slutgiltigt koncept valdes och sedan tillverkades en 3D-utskriven fysisk prototyp. I den avslutande delen diskuteras den utvecklade komponenten och jämförs med en vald referenskomponent. Det slutgiltiga konceptet lyckades inte prestera bättre än referenskomponenten i vikt. Men däremot erhölls värdefull insikt och kunskap angående den additiva processen. Slutsatsen som drogs var att additiv tillverkning är en legitim tillverkningsmetod för konstruktion av högpresterande cykelkomponenter. Förslag ges även för framtida arbete där framförallt en vidare analys med andra material som utnyttjar EBM-tekniken föreslås.
99

Cykelbanors bredd och cyklisters beteende : En metod för att uppskatta cyklisters upplevda risknivåer på olika bredder av cykelbanor / Bike lane width and cyclists’ behaviour : A method for assessing cyclists' perceived risk levels on bidirectional bike lanes

Egeskog, Johan January 2019 (has links)
The aim of this study was to investigate different standards of bidirectional bike lanes and investigate if they provide enough space for the needs of cyclists. A method was developed for evaluating cyclists’ behaviour using the theory of risk homeostasis and two risk-factors; speed and sideways position. An experimental design was also constructed and the results from the subsequent experiment implies that the two chosen risk markers could be useful in future studies relating to the design of bicycle infrastructure. A significant difference in the positioning of cyclists was found on different bike lane widths. The risk markers for sideways position show significant results at bidirectional bike lane widths below 2.4 meters. At such widths, cyclists seem to actively position themselves closer to the curb in the presence of oncoming cyclists. This is interpreted as a risk compensation which indicates that cyclists are not completely comfortable on that standard of bike lane. A conclusion would be to view bidirectional bike lanes at 2.4 meters width on flat surfaces, with adequate safety-zones beside the bike lanes, as a good standard for regular cyclists in many situations. More widening is not believed to provide major additional experienced safety or passability until the width allow for safe overtaking in the presence of oncoming cyclists. / Syftet med denna studie var att undersöka olika standarder av cykelbanor och se om de tillgodoser cyklisternas utrymmesbehov. En metod utvecklades för att utvärdera cyklisters beteende på olika standarder av dubbelriktade cykelbanor med hjälp av riskhomeostasteorin och två riskmarkörer; sidledsposition och hastighet. En experimentdesign utvecklades och experimentet genomfördes. Resultaten tyder på att metoden fungerar och kan vara till nytta i framtida studier gällande cyklisters behov, relaterat till designen av cykelinfrastruktur. Resultaten visar att cyklisterna placerar sig längre från kanten på cykelbanan ju bredare den är. En statistiskt signifikant skillnad i sidledsposition uppmättes också vid möten av andra cyklister när bredden på cykelbanan sjönk till under 2,4 meter. Vid dessa bredder placerade sig cyklisterna aktivt närmare kanten vid möten. Resultatet tolkas som en form av riskkompensation och indikerar att cyklisterna inte är helt trygga på cykelbanor av den bredden. Slutsatsen blir att vi kan betrakta 2,4 meter breda, dubbelriktade cykelbanor på horisontella ytor med tillräckliga säkerhetsavstånd till hinder vid sidan av cykelbanan som en god standard för många förhållanden. Ytterligare breddning tordes inte ge några större upplevda säkerhets- eller framkomlighetsfördelar förrän bredden tillåter säkra omkörningar även vid möten.
100

Assessing the Impact of Bicycle Infrastructure and Modal Shift on Traffic Operations and Safety Using Microsimulation

Lee, Katherine E. 01 March 2022 (has links) (PDF)
A transportation system designed to prioritize the mobility of automobiles cannot accommodate the growing number of road users. The Complete Streets policy plays a crucial part in transforming streets to accommodate multiple modes of transportation, especially active modes like biking and walking. Complete streets are referred to as streets designed for everyone and enable safety and mobility to all users. A strategy of complete streets transformation is to connect isolated complete street segments to form a complete network that improves active mobility and public transit ridership. This research assessed the impact of efficiently and equitably connecting and expanding the biking network using dedicated lanes on the safety and operation of the network in Atlanta, Georgia. These connections are aimed at increasing the multimodal use of the streets in midtown and downtown Atlanta and achieving the mobility and public health goals through the integration of various modes of travel. The evaluation was done by modeling a well-calibrated and validated network of Midtown and Downtown Atlanta in VISSIM using existing travel demand and traffic design conditions (i.e., the baseline or Scenario 0). A total of three different conditions: existing, proposed, and alternative conditions, were modeled to see the effectiveness of bike infrastructure design improvement and expansion. Three scenarios were then modeled as variations of modal demand of the different condition models. Scenarios modeled are based on input from the City and Community stakeholders. Using the trajectory data from microsimulation, the surrogate safety assessment model (SSAM) from FHWA was used to analyze the safety effect on the bike infrastructure improvement and expansion. Results of this study showed a positive impact of complete streets transformation on the streets of Midtown and Downtown Atlanta. These impacts are quantified in this thesis.

Page generated in 0.1185 seconds