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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.
181

Long-range Communication Framework for Autonomous UAVs

Elchin, Mammadov January 2013 (has links)
The communication range between a civilian Unmanned Aerial Vehicle (UAV) and a Ground Control Station (GCS) is affected by the government regulations that determine the use of frequency bands and constrain the amount of power in those frequencies. The application of multiple UAVs in search and rescue operations for example demands a reliable, long-range inter-UAV communication. The inter-UAV communication is the ability of UAVs to exchange data among themselves, thus forming a network in the air. This ability could be used to extend the range of communication by using a decentralized routing technique in the network. To provide this ability to a fleet of autonomous dirigible UAVs being developed at the University of Ottawa, a new communication framework was introduced and implemented. Providing a true mesh networking based on a novel routing protocol, the framework combines long-range radios at 900 MHz Industrial, Scientific and Medical (ISM) band with the software integrated into the electronics platform of each dirigible. With one radio module per dirigible the implemented software provides core functionalities to each UAV, such as exchanging flight control commands, telemetry data, and photos with any other UAV in a decentralized network or with the GCS. We made use of the advanced networking tools of the radio modules to build capabilities into the software for route tracing, traffic prioritization, and minimizing self-interference. Initial test results showed that without acknowledgements, packets can be received in the wrong order and cause errors in the transmission of photos. In addition, a transmission in a presence of a third broadcasting node slows down by 4-6 times. Based on these results our software was improved to control to flow of transmit data making the fragmentation, packetization, and reassembly of photos more reliable. Currently, using radios with half-wavelength dipole antennas we can achieve a one-hop communication range of up to 5 km with the radio frequency line-of-sight (RF LOS). This can be extended further by adding as many radio nodes as needed to act as intermediate hops.
182

Physical layer security in emerging wireless transmission systems

Bao, Tingnan 06 July 2020 (has links)
Traditional cryptographic encryption techniques at higher layers require a certain form of information sharing between the transmitter and the legitimate user to achieve security. Besides, it also assumes that the eavesdropper has an insufficient computational capability to decrypt the ciphertext without the shared information. However, traditional cryptographic encryption techniques may be insufficient or even not suit- able in wireless communication systems. Physical layer security (PLS) can enhance the security of wireless communications by leveraging the physical nature of wireless transmission. Thus, in this thesis, we study the PLS performance in emerging wireless transmission systems. The thesis consists of two main parts. We first consider the PLS design and analysis for ground-based networks em- ploying random unitary beamforming (RUB) scheme at the transmitter. With RUB technique, the transmitter serves multiple users with pre-designed beamforming vectors, selected using limited channel state information (CSI). We study multiple-input single-output single-eavesdropper (MISOSE) transmission system, multi-user multiple-input multiple-output single-eavesdropper (MU-MIMOSE) transmission system, and massive multiple-input multiple-output multiple-eavesdropper (massive MI- MOME) transmission system. The closed-form expressions of ergodic secrecy rate and the secrecy outage probability (SOP) for these transmission scenarios are derived. Besides, the effect of artificial noise (AN) on secrecy performance of RUB-based transmission is also investigated. Numerical results are presented to illustrate the trade-off between performance and complexity of the resulting PLS design. We then investigate the PLS design and analysis for unmanned aerial vehicle (UAV)-based networks. We first study the secrecy performance of UAV-assisted relaying transmission systems in the presence of a single ground eavesdropper. We derive the closed-form expressions of ergodic secrecy rate and intercept probability. When multiple aerial and ground eavesdroppers are located in the UAV-assisted relaying transmission system, directional beamforming technique is applied to enhance the secrecy performance. Assuming the most general κ-μ shadowed fading channel, the SOP performance is obtained in the closed-form expression. Exploiting the derived expressions, we investigate the impact of different parameters on secrecy performance. Besides, we utilize a deep learning approach in UAV-based network analysis. Numerical results show that our proposed deep learning approach can predict secrecy performance with high accuracy and short running time. / Graduate
183

Analys av sprickutveckling på markytan i Kiirunavaara gruvområde samt utvärdering av fotogrammetri

Schölund, Oskar January 2020 (has links)
LKAB (Luossavaara-Kiirunavara Aktiebolag) bryter och förädlar järnmalm i Norrbotten. Under 2018 omsatte LKAB cirka 26 miljarder kronor. Koncernen äger två underjordsgruvor, en i Malmberget och en i Kiruna, samt tre dagbrottsgruvor i Svappavaara, varav en för tillfället är i drift. Brytningsmetoden som används i Kiirunavaara-gruvan är storskalig skivrasbrytning. Metoden bygger på principen att sidoberget, i första hand hängväggen, successivt bryts sönder, och fyller upp det utlastade utrymmen. Sönderbrytningen är nödvändig för att brytningsmetoden skall fungera optimalt. En effekt av detta är att omgivande berg så småningom deformeras. Detta omöjliggör, på sikt, att ha bebyggelse och infrastruktur i det område som berörs av större deformationer, vilket har lett till behovet av en pågående samhällsomvandling. Detta innebär att det är av stor vikt att, om möjligt, förbättra förståelsen för deformations- och uppblockningsmekanismer i bergmassan, till följd av skivrasbrytning. Examensarbetet är indelat i två delar: Första delen syftar till att ta fram en rekommendation för en programvara och analysmetodik som kan användas för utvärdering av strukturriktningar från UAV-data, detta då det på många ställen kring gruvområdet är det en säkerhetsrisk att beträda områden för att utföra strukturkartering.   Andra delen omfattar analys och utvärdering av strukturers eventuella påverkan på uppblockning- och deformationsprocessen vid LKAB:s Kiirunavaaragruva för liggvägg, hängvägg samt Sjömalmen-området. Detta innefattar dels tillämpning av ovannämnd programvara och metodik, dels analys och tolkning av alla tillgängliga sprickkarteringar på markytan, samt visualisering, t.ex. med rosdiagram, i CAD-format, etc. I examensarbetet utfördes en mindre fältstudie, detta för att verifiera vad tidigare studier visat på, samt för att testa olika programvaror. Resultaten verifierade de tidigare studierna, att kartering med CloudCompare ger bra resultat jämfört med traditionell kartering med kompass. Från de erhållna resultaten från fältstudien utfördes sedan ett större, storskaligt test över rasgropen. Resultaten visade att den kommersiella programvaran Pix4D tillsammans med den öppna och fria programvaran CloudCompare och plugin-programmet qFacet fungerar bra för att skapa 3D-modeller och analysera bergmekaniska parametrar från UAV-data. Dock var det endast storskaliga strukturer (ytor) som gick att extrahera ur modellerna. Flertalet av dessa visade korrelation med de sprickorienteringarna gjorda från underjordskarteringar för häng- och liggväggen i KUJ och Sjömalmen. För den utförda sammanställningen av sprickinventeringen på häng- och liggväggen samt tolkade strukturer på hängväggen, visade resultaten på att förekomsten av sprickor, sjunkhål samt kanter finns i områden med hög koncentration av deformationszoner/strukturer. Detta är tydligast i norra delen av hängväggen. Sprickgrupperna på markytan uppstår oftast parallellt med deformationszonerna och i flera fall uppstår och utvecklas en kant i de områden där dessa är lokaliserade. Bedömd ”raskant” uppstår ungefär två år efter att de första sprickorna upptäckts. Orienteringen för sprickor och kanter stämmer relativt bra överens med tidigare utförda underjordskarteringar. För sjunkhålen är majoriteten koncentrerade till ett mindre område på hängväggen. I området förekommer två deformationszoner, en som korsar området och en som stupar ner under området. Karaktären på dessa deformationszoner kan vara orsaken till uppkomsten av sjunkhålen i området.
184

Persistent Aerial Tracking

Mueller, Matthias 13 April 2016 (has links)
In this thesis, we propose a new aerial video dataset and benchmark for low altitude UAV target tracking, as well as, a photo-realistic UAV simulator that can be coupled with tracking methods. Our benchmark provides the first evaluation of many state of-the-art and popular trackers on 123 new and fully annotated HD video sequences captured from a low-altitude aerial perspective. Among the compared trackers, we determine which ones are the most suitable for UAV tracking both in terms of tracking accuracy and run-time. We also present a simulator that can be used to evaluate tracking algorithms in real-time scenarios before they are deployed on a UAV ”in the field”, as well as, generate synthetic but photo-realistic tracking datasets with free ground truth annotations to easily extend existing real-world datasets. Both the benchmark and simulator will be made publicly available to the vision community to further research in the area of object tracking from UAVs. Additionally, we propose a persistent, robust and autonomous object tracking system for unmanned aerial vehicles (UAVs) called Persistent Aerial Tracking (PAT). A computer vision and control strategy is applied to a diverse set of moving objects (e.g. humans, animals, cars, boats, etc.) integrating multiple UAVs with a stabilized RGB camera. A novel strategy is employed to successfully track objects over a long period, by ’handing over the camera’ from one UAV to another. We integrate the complete system into an off- 4 the-shelf UAV, and obtain promising results showing the robustness of our solution in real-world aerial scenarios.
185

Advancing the Utility of Thermal Remote Sensing in Irrigated Arid-Lands Agriculture

Rosas, Jorge 10 1900 (has links)
Increasing populations, shifting demographics and changes in diet are driving increases in crop production. However, any increases in food demand are ultimately limited by water availability, which is under pressure globally, but especially so in arid and semi-arid regions. To address this challenge, spatially distributed information on crop water use, vegetation health, soil moisture status and a range of other water, energy and carbon variables are all required. However, critical to the determination of many of these processes is an accurate characterization of the land surface temperature (LST). The only feasible manner by which to estimate this variable across a range of spatial and temporal scales is using thermal infrared (TIR) satellite data. Here we investigate the estimation of LST, focusing on its accurate retrieval across a range of different spatial scales. First, we examine the influence of atmospheric correction on retrieval accuracy by employing a radiative transfer model and Landsat data using a variety of available atmospheric profile data, with the aim of identifying an optimal product combination for retrieval. Using these results, we then investigate the potential to downscale coarse resolution (O~103 m) MODIS satellite data to scales appropriate for agricultural application (less than O~102 m), using a machine-learning approach. To further advance the downscaling technique, we explore the utility of novel Cubesat data to produce within-field scale (O~101 m) distributions of land surface temperature. Finally, to expand upon the multi-resolution/multi-satellite LST strategy explored here, we examine the capacity of ultra-high resolution (O~10-1 m) thermal imagery from an unmanned aerial vehicle to characterize surface temperature response and behavior, focusing on the retrieval accuracy and diurnal variability of these spatially and temporally varying land surface temperature estimates. The ultimate goal of this research is to advance the utility of LST for agricultural application by providing description and insights into product development, accuracy issues, and identifying some limitations and opportunities of both current and future remote observation platforms.
186

Flight Testing Small UAVs for Aerodynamic Parameter Estimation

Chase, Adam Thomas 01 June 2014 (has links)
A flight data acquisition system was developed to aid unmanned vehicle designers in verifying the vehicle's design performance. The system is reconfigurable and allows the designer to choose the correct combination of complexity, risk, and cost for a given flight test. The designer can also reconfigure the system to meet packaging and integration requirements. System functionality, repeatbility, and accuracy was validated by collecting data during multiple flights of a radio-controlled aircraft. Future work includes sensor fusion, thrust prediction methods, stability and control derivative estimation, and growing Cal Poly's small-scale component aerodynamic database.
187

Unmanned Aerial Vehicles for Post Disaster Surveys

Larsen, Thor Liland 01 December 2010 (has links)
In the current built environment, structures require regular observation and maintenance. Many of these structures can be quite challenging to evaluate. The required scaffolding, lifts, or similar access facilities can become quite costly to rent and construct, and can be a long term disturbance to those who use and manage the particular structure. Furthermore, there are situations where examination for the purpose of detailed analysis can be quite hazardous, if not entirely unsafe for humans. In a post-disaster environment traditional methods may not be safe or adequate for gaining access to parts of a structure that require observation or analysis. The use of a remotely controlled unmanned vehicle is a reliable, safe and cost effective substitute for assessing structures before and after seismic, terrorist, or other destructive events.
188

Univerzální řídicí systém pro quadrocopter / Universal Control System for Quadrocopter

Gábrlík, Petr January 2012 (has links)
The Thesis objective is the design and implementation of the universal control system for a flying robot, quadrotor concept. The first part deals with ways of solving program for microcontrollers. The special attention is given to the FreeRTOS real-time operating system, which is designed for microcontrollers. The second part of the Thesis is focused on the description of the chosen microcontroller LM3S8962 and the hardware solution. One chapter is devoted to the integration of the robot to the Cassandra-WPF robotic control system. The third part deals with the identification of the new robot construction and the mathematical model creation. Using the model controllers for stabilization pitch and roll are designed and their functionality is verified on a physical model. The last part of the Thesis is focused on the FreeRTOS implementation and the control application creation.
189

Návrh stabilizačního mechanismu pro FPV kamery s využitím CAD/CAM systémů / Design of stabilization mechanism for FPV camera using CAD/CAM systems

Holuša, David January 2014 (has links)
This diploma thesis provides a comprehensive proposal of stabilization mechanism for sensing and FPV camera for remote controlled propeller plane. Summarizes the current human knowledge milestones in the field and describes the current state of knowledge and the market situation. Taking into account all acquired knowledge the author then describes two different design proposals outlining its related processes, such as manufacturing, electronics installation and commissioning.
190

Možnosti využití vodíku v letectví / Possibilities of Using Hydrogen in Aviation

Jurečka, Radek January 2013 (has links)
The thesis is focused to hydrogen usage in the aviation. There are shown existing types of fuel cells and hydrogen storage possibilities. Main part of the thesis is conceptual design of small UAV with hydrogen fuel cell, which will show potential of hydrogen power system.

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