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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.
321

Fully Compliant Mechanisms for Bearing Subtraction in Robotics and Space Applications

Merriam, Ezekiel G. 23 April 2013 (has links) (PDF)
Robotics and space applications represent areas where compliant mechanisms can continue to make a significant impact by reducing costs and weight while improving performance. Because of the nature of these applications, a common need is for bearing replacement mechanisms, or mechanisms that perform the function of a bearing without the complexity and failure modes associated with bearings. Static balancing is a design strategy that attempts to reduce the actuation effort of a mechanism, and has been applied to compliant mechanisms in some applications. Monolithic construction, especially by means of 3D printing technology, is a strategy whereby the mechanism links and joints are built as a single "chunk" of material. This eliminates assembly and failure modes associated with wear and friction in traditional joints. In this work we examine these design strategies in the context of robotics and space applications. Matlab and Ansys batch files can be found in Appendix A. A fully compliant zero-torque, statically balanced mechanism is described that can undergo greater than 100 of motion. Because compliant mechanisms achieve their motion from the deflection of their constituent members, there is some strain energy associated with actuated positions. By introducing an appropriate pre-load, strain energy can be held constant. This can reduce or nearly eliminate the input force required from the actuating device. This paper describes the statically balanced rotary joint concept, and demonstrates its optimization, testing, and implementation for a haptic pantograph mechanism. The statically balanced properties of the constituent joints result in a mechanism with two balanced degrees of freedom. Matlab and Ansys batch files can be found in Appendix B. The conception, modeling, and development of a fully compliant two-degree-of-freedom pointing mechanism for application in spacecraft thruster, antenna, or solar array systems is described. The design objectives and the advantages of a compliant solution are briefly discussed. A single design concept is selected for final development from a field of generated concepts. Analytical and numerical models are accompanied by prototype testing and measurements in several iterations. A final design is described in detail, a fully compliant prototype is fabricated in titanium, and its performance is measured.
322

Effective Data Redistribution and Load Balancing for Sort-Last Volume Rendering Using a Group Hierarchy / Effektiv datadistribution och belastningsutjämning för sort-last volumetrisk rendering med hjälp av en grupphierarki

Walldén, Marcus January 2018 (has links)
Volumetric rendering is used to visualize volume data from e.g. scientific simulations. Many advanced applications use large gigabyte- or terabyte-sized data sets, which typically means that multiple compute nodes need to partake in the rendering process to achieve interactive frame rates. Load balancing is generally used to optimize the rendering performance. In existing load balancing techniques, nodes generally only render directly-connected data and handle load balancing based on data locality in kd-trees. This approach can result in redundant data transfers and unbalanced data distribution, which affect the frame rate and increase the hardware requirements of all nodes. In this thesis we present a novel load balancing technique for sort-last volume rendering which utilizes a group hierarchy. The technique allows nodes to render data from arbitrary positions in the volume, without inducing a costly image compositing stage. The technique is compared to a static load balancing technique as well as a dynamic kd-tree based load balancing technique. Our testing demonstrated that the presented technique performed better than or equal to the kd-tree based technique while also lowering the worst-case memory usage complexity of all nodes. Utilizing a group hierarchy effectively helped to lower the compositing time of the presented technique. / Volumetrisk rendering används för att visualisera bland annat vetenskapligasimuleringar. Inom avancerade användingsområden används ofta dataset med en storlek på flera gigabyte eller terabyte. Detta medför att flera noder ofta måste användas för att uppnå en interaktiv bildfrekvens. Belastningsutjämning används generellt för att optimera renderingsprestandan. I befintliga tekniker renderar noder vanligtvis endast direkt sammankopplad data och utför belastningsutjämning baserat på datalokalitet i kd-träd. Detta kan resultera i redundanta dataöverföringar och en obalanserad datadistribution, vilket påverkar bildfrekvensen och ökar hårdvarukraven för alla noder. I denna avhandling presenterar vi en ny teknik för belastningsutjämning för sort-last volumetrisk rendering som använder en grupphierarki. Tekniken tillåter noder att rendera data från godtyckliga positioner i volymen utan att förorsaka ett kostsamt steg för bildsammansättning. Tekniken jämförs med en statisk belastningsutjämningsteknik såväl som en dynamisk belastningsutjämningsteknik baserad på kd-träd. Våra tester visar att den presenterade tekniken presterar bättre eller likvärdigt med den kd-trädbaserade tekniken medan den samtidigt sänker minneskomplexiteten för alla noder. Användandet av en grupphierarki sänkte effektivt bildsammansättningstiden för den presenterade tekniken.
323

Dynamic Drivers, Risk Management Practices, And Competitive Outcomes: Applying Multiple Research Methods

Deng, Xiyue January 2021 (has links)
No description available.
324

Enhancing the performance of mobile networks using Kubernetes : Load balancing traffic by utilizing workload estimation / Lastbalansering av trafik i ett Kuberneteskluster med hjälp av arbetsbelastningestimering

Laukka, Lucas, Fransson, Carl January 2023 (has links)
As global mobile network usage increases rapidly and users demand lower latency, the importance of stable 5G networks is more critical than ever. One way to orchestrate mobile network backends is by using Kubernetes. Kubernetes allows for automatic restarts and scaling of containers and provides an easy way to route incoming connections to applications running in containers. By routing the incoming connections using different load-balancing algorithms, it is possible to reduce latency through more efficient usage of worker nodes.  This thesis aims to identify ways to use load balancing inside a Kubernetes cluster to increase throughput and reduce latency in a mobile network system. We perform a literature study on possible ways to implement load balancing in Kubernetes and possible algorithms to use in the load balancing. Using the study results, we model a simplified mobile network system in a Kubernetes cluster and implement a load balancer at the Service level. By running simulations on this model, we compare three algorithms existing in Kubernetes as well as a dynamic algorithm using estimated workloads in terms of latency and throughput. The existing algorithms that are compared include Round Robin, Least Connections, and Random. The results show a potential to reduce latency by up to 31% compared to the native Random algorithm when utilizing a dynamic load balancer at the Service level.
325

Uniting the Nation's Power Grids: Opening Markets to Integrate Large Scale Renewable Power

Wilkinson, Jeffrey Kenneth 01 June 2012 (has links) (PDF)
As renewable energy becomes increasingly cost competitive and Renewable Portfolio Standards (RPS) push states to produce more and more of their steadily growing power demands from renewable sources, the need to solve the problems associated with renewable penetration becomes a priority. The intermittent nature of solar and wind power generation require additional cost that inhibit their implementation as penetration levels grow. Reliability remains power utilities' top priority while they struggle to upgrade their systems. Old generation facilities will be decommissioned, renewable energy projects will come on line and transmission upgrades become inevitable. Variability on the grid is currently mitigated through the use of Operational Reserves. These units are costly and utilities are currently looking for ways to reduce the amount of reserves required. Balancing Area cooperation is currently being considered by many as the most economical and environmentally conscience method to mitigate variability. Many aspects of Balancing Area cooperation will be discussed along with the motivations for their implementation. A 22.5 square mile area of land in Clovis, NM will be the home of the Tres Amigas project designed to unite the three asynchronous grids of our Nation with the purpose of improving reliability and reducing cost through the exchange of power and ancillary services such as VAR support and Operating Reserves. This paper will investigate the implications of this project on the Operational Reserves required to mitigate variability due to increasing renewable energy penetration by enabling Balancing Areas to cooperate across regions that are currently not assessable.
326

Dynamics Simulation and Optimal Control of a Multiple-Input and Multiple-Output Balancing Cube

Haimerl, Felix K 01 June 2018 (has links) (PDF)
This thesis document outlines the development of a multibody dynamics simulation of an actively stabilized multiple-input, multiple-output, coupled, balancing cube and the process of verifying the results by implementing the control algorithm in hardware. A non-linear simulation of the system was created in Simscape and used to develop a Linear Quadratic Gaussian control algorithm. To implement this algorithm in actual hardware, the system was first designed, manufactured, and assembled. The structure of the cube and the reaction wheels were milled from aluminum. DC brushless motors were installed into the mechanical system. In terms of electronics, a processor, orientation sensor, motor drivers, analog to digital converters, and a pulse width modulation board were assembled into the cube. Upon completion, the software to control the cube was developed using Simulink and run on a Raspberry Pi computer within the mechanism.
327

Factors Influencing the Uptake and Use of Continuous Positive Airway Pressure Therapy for Women With Sleep Disordered Breathing

Létourneau, Marie 15 November 2021 (has links)
The consequences of sleep disordered breathing (SDB) in women are fatigue, morning headaches, insomnia, depression, low functional status, daytime sleepiness, mood disturbances, and poor neuro-behavioural performance. Women appear to be more symptomatic at lower disease severity than men. When CPAP is prescribed, women use it less than men, they reduce their usage within the first week of treatment, and they discontinue it more than men. There is a need to understand the factors influencing CPAP therapy uptake and usage in women to meaningfully address their needs. The purpose of this qualitative evidence synthesis was to identify and synthesize the factors influencing the uptake and use of CPAP in women by conducting a qualitative evidence synthesis guided by the Bargaining and Balancing Life with CPAP theory for content, and the Theoretical Domains Framework for data analysis. Twenty-one studies were included. Barrier domains were Skills, Emotions, Social/Professional Role and Identity, and Beliefs about Capabilities, while facilitator domains were Reinforcement, Social Influences, Goals, and Optimism. Seven themes emerged : 1) Expectations about CPAP, 2) Learning to use my CPAP machine, 3) The burden of the technology, 4) Improvement of SDB symptoms, 5) Not feeling (or looking) like myself, 6) Receiving support, and 7) Choosing my attitude. To ensure appropriate and meaningful SDB care for women, practices must be based on knowledge relevant to women with SDB. Findings from this thesis can inform the design and development of interventions to support women with CPAP therapy uptake and usage. Research on this topic is urgently needed because there was no study eligible with a sample comprised of women only.
328

Comparative Analysis of Load Balancing in Cloud Platforms for an Online Bookstore Web Application using Apache Benchmark

Pothuganti, Srilekha, Samanth, Malepiti January 2023 (has links)
Background :Cloud computing has transformed the landscape of application deploy-ment, offering on-demand access to compute resources, databases, and services viathe internet. This thesis explores the development of an innovative online book-storeweb application, harnessing the power of cloud infrastructure across AWS,Azure, andGCP. The front end utilises HTML, CSS, and JavaScript to create responsive webpages with an intuitive user interface. The back-end is constructed using Node.jsand Express for high-performance server-side logic and routing, while MongoDB, adistributed NoSQL database, stores the data. This cloud-native architecture facili-tates easy scaling and ensures high availability. Objectives: The main objectives of this thesis are to develop an intuitive onlinebookstore enabling users to add, exchange, and purchase books, deploy it acrossAWS, Azure, and GCP for scalability, implement load balancers for enhanced per-formance, and conduct load testing and benchmarking to compare the efficiency ofthese load balancers. The study aims to determine the best-performing cloud plat-form and load-balancing strategy to ensure an exceptional user experience for ouronline bookstore. Comparing load balancer data across these platforms to determinetheir performance ensures the best user experience for our online bookstore by takingthe metrics. Methods: The website deployment is done on three cloud platforms by creatinginstances separately on each platform, and then the load balance is created for eachof the services. By using the monitoring tools of every platform, we get the resultinggraphs for the metrics. From this, we increase and decrease the load in the ApacheBenchmark tool by taking the specific tasks from the website and comparing thevisualisation of the results done in an aggregate graph and summary reports. It isthen used to test the website’s overall performance by using metrics like throughput,CPU utilisation, error percentage, and cost efficiency. Results: The results are based on the Apache Benchmark Load Testing Tool of aselected website between the cloud platforms. The results of AWS, Azure, and GCPcan be shown in the aggregate graph. The graph results are based on the testingtool to determine which service is best for users because it shows less load on theserver and requests data in the shortest amount of time. We have considered 10 and50 requests, and based on the results, we have compared the metrics of throughput,CPU utilisation, error percentage, and cost efficiency. The 10 and 50 requests’ resultsare compared to determine which cloud platform performs better. Conclusions: According to the results from the 10 and 50 requests, it can be con-cluded that GCP has a higher throughput and CPU utilisation than AWS and Azure.They are less flexible and efficient for users. Thus, it can be said that GCP outper-forms in terms of load balancing.
329

Integrated Design of Electrical Distribution Systems: Phase Balancing and Phase Prediction Case Studies

Dilek, Murat 16 November 2001 (has links)
Distribution system analysis and design has experienced a gradual development over the past three decades. The once loosely assembled and largely ad hoc procedures have been progressing toward being well-organized. The increasing power of computers now allows for managing the large volumes of data and other obstacles inherent to distribution system studies. A variety of sophisticated optimization methods, which were impossible to conduct in the past, have been developed and successfully applied to distribution systems. Among the many procedures that deal with making decisions about the state and better operation of a distribution system, two decision support procedures will be addressed in this study: phase balancing and phase prediction. The former recommends re-phasing of single- and double-phase laterals in a radial distribution system in order to improve circuit loss while also maintaining/improving imbalances at various balance point locations. Phase balancing calculations are based on circuit loss information and current magnitudes that are calculated from a power flow solution. The phase balancing algorithm is designed to handle time-varying loads when evaluating phase moves that will result in improved circuit losses over all load points. Applied to radial distribution systems, the phase prediction algorithm attempts to predict the phases of single- and/or double phase laterals that have no phasing information previously recorded by the electric utility. In such an attempt, it uses available customer data and kW/kVar measurements taken at various locations in the system. It is shown that phase balancing is a special case of phase prediction. Building on the phase balancing and phase prediction design studies, this work introduces the concept of integrated design, an approach for coordinating the effects of various design calculations. Integrated design considers using results of multiple design applications rather than employing a single application for a distribution system in need of improvement relative to some system aspect. Also presented is a software architecture supporting integrated design. / Ph. D.
330

Control of Power Flow in Transmission Lines using Distributed Series Reactors

Nazir, Mohammad Nawaf 19 June 2015 (has links)
Distributed Series Reactors (DSRs) can be used to control power flow to more fully utilize the capacity of a transmission network, delaying investment in new transmission lines. In this study the IEEE 39 bus standard test system is modified to a 3-phase, unbalanced model consisting of 230 kV, 345 kV and 500 kV lines, where lines of different voltage run in parallel. This model is used to study load growth and the effect of adding DSRs to alleviate resulting overloads, and in particular to alleviate overloads on lines of different voltage running in parallel. The economic benefit of adding DSRs to the network is compared to the addition of new transmission lines in the network. In the second part of the work, the effect of unsymmetrical operation of DSRs on a single transmission line is studied and compared to the symmetrical operation of DSRs. It is found that the unsymmetrical operation of DSRs is more economical. Finally the unsymmetrical operation of DSRs to reduce voltage imbalance in the network is considered. / Master of Science

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