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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.
21

Long-Term Ambient Noise Statistics in the Gulf of Mexico

Snyder, Mark Alan 15 December 2007 (has links)
Long-term omni-directional ambient noise was collected at several sites in the Gulf of Mexico during 2004 and 2005. The Naval Oceanographic Office deployed bottom moored Environmental Acoustic Recording System (EARS) buoys approximately 159 nautical miles south of Panama City, Florida, in water depths of 3200 meters. The hydrophone of each buoy was 265 meters above the bottom. The data duration ranged from 10-14 months. The buoys were located near a major shipping lane, with an estimated 1.5 to 4.5 ships per day passing nearby. The data were sampled at 2500 Hz and have a bandwidth of 10-1000 Hz. Data are processed in eight 1/3-octave frequency bands, centered from 25 to 950 Hz, and monthly values of the following statistical quantities are computed from the resulting eight time series of noise spectral level: mean, median, standard deviation, skewness, kurtosis and coherence time. Four hurricanes were recorded during the summer of 2004 and they have a major impact on all of the noise statistics. Noise levels at higher frequencies (400-950 Hz) peak during extremely windy months (summer hurricanes and winter storms). Standard deviation is least in the region 100-200 Hz but increases at higher frequencies, especially during periods of high wind variability (summer hurricanes). Skewness is positive from 25-400 Hz and negative from 630-950 Hz. Skewness and kurtosis are greatest near 100 Hz. Coherence time is low in shipping bands and high in weather bands, and it peaks during hurricanes. The noise coherence is also analyzed. The 14-month time series in each 1/3- octave band is highly correlated with other 1/3-octave band time series ranging from 2 octaves below to 2 octaves above the band's center frequency. Spatial coherence between hydrophones is also analyzed for hydrophone separations of 2.29, 2.56 and 4.84 km over a 10-month period. The noise field is highly coherent out to the maximum distance studied, 4.84 km. Additionally, fluctuations of each time series are analyzed to determine time scales of greatest variability. The 14-month data show clearly that variability occurs primarily over three time scales: 7-22 hours (shipping-related), 56-282 hours (2-12 days, weather-related) and over an 8-12 month period.
22

OMNI-DIRECTIONAL INFRARED 3D RECONSTRUCTION AND TRACKING OF HUMAN TARGETS

Benli, Emrah 01 January 2017 (has links)
Omni-directional (O-D) infrared (IR) vision is an effective capability for mobile systems in robotics, due to its advantages: illumination invariance, wide field-of-view, ease of identifying heat-emitting objects, and long term tracking without interruption. Unfortunately, O-D IR sensors have low resolution, low frame rates, high cost, sensor noise, and an increase in tracking time. In order to overcome these disadvantages, we propose an autonomous system application in indoor scenarios including 1) Dynamic 3D Reconstruction (D3DR) of the target view in real time images, 2) Human Behavior-based Target Tracking from O-D thermal images, 3) Thermal Multisensor Fusion (TMF), and 4) Visual Perception for Social Cognition from the motion behavior of the human target.
23

Řízení inteligentních pohonů IclA s využitím sběrnice CAN / Control Design of Intelligent Integrated closed loop Actuator by force of CAN

Škranc, Martin January 2009 (has links)
This diploma thesis deals with automatization technology by B&R Automation Company. CANopen protocol is used for communication and control design of actuator part of omni-directional mobile robot. The control algorithms are implemented for compact PLC automata X20 series. The PLC X20 communicates with PC by means of Ethernet TCP/IP protocol. There are four motion control patterns implemented. The robot uses three IclA D065 actuators. This research has been supported by the Czech Ministry of Education in the frame of MSM 0021630529 Research Intention Inteligent Systems in Automation.
24

Návrh řízení všesměrového mobilního robotu O3-X / Design of omni directional mobile robot (O3-X) control

Olša, Petr January 2010 (has links)
This thesis deals with the design of a three-wheeled omni-directional robot control. The model of control is designed for robot´s omni-directional platform driven by maxon motor with the intelligent positioning controller EPOS. The design of control contains: - installation of the coordinated systems and transformation from one of them into another - design of system´s kinematical model - creation of classes for control and communication with EPOS - creation of the simulative program - planning of the mobile robot´s path - verification that the system is working The solution was based on continuous accelerated motion and the maximal acceleration of wheels was concerned, so that the slip would be suppressed. The function of the model was partly verified.
25

Deep Synthesis of Distortion-free 3D Omnidirectional Imagery from 2D Images

Christopher K May (18422640) 22 April 2024 (has links)
<p dir="ltr">Omnidirectional images are a way to visualize an environment in all directions. They have a spherical topology and require careful attention when represented by a computer. Namely, mapping the sphere to a plane introduces stretching of the spherical image content, and requires at least one seam in the image to be able to unwrap the sphere. Generative neural networks have shown impressive ability to synthesize images, but generating spherical images is still challenging. Without specific handling of the spherical topology, the generated images often exhibit distorted contents and discontinuities across the seams. We describe strategies for mitigating such distortions during image generation, as well as ensuring the image remains continuous across all boundaries. Our solutions can be applied to a variety of spherical image representations, including cube-maps and equirectangular projections.</p><p dir="ltr">A closely related problem in generative networks is 3D-aware scene generation, wherein the task involves the creation of an environment in which the viewpoint can be directly controlled. Many NeRF-based solutions have been proposed, but they generally focus on generation of single objects or faces. Full 3D environments are more difficult to synthesize and are less studied. We approach this problem by leveraging omnidirectional image synthesis, using the initial features of the network as a transformable foundation upon which to build the scene. By translating within the initial feature space, we correspondingly translate in the output omnidirectional image, preserving the scene characteristics. We additionally develop a regularizing loss based on epipolar geometry to encourage geometric consistency between viewpoints. We demonstrate the effectiveness of our method with a structure-from-motion-based reconstruction metric, along with comparisons to related works.</p>
26

Planární antény na substrátech s elektromagnetickými zádržnými pásmy / Planar Antennas on Electromagnetic Bandgap Substrates

Horák, Jiří January 2009 (has links)
Planar antennas are used in several technical applications. The family of planar antennas contains microstrip antennas, which are very popular due to the low weight, low profile, simple manufacturing and easy mass production. Lower gain and excitation of surface waves are disadvantages of microstrip antennas. The propagation of surface waves can be efficiently suppressed if the conventional substrate is replaced by an electromagnetic bandgap (EBG) substrate. Microstrip antennas on EBG substrates have been presented in an open literature for several years. Nevertheless, no published work is devoted to the design of EBG substrates, which can suppress surface waves at several frequencies those cannot be covered by a single bandgap. In order to reach optimum parameters of designed antennas, selected global optimization methods are applied (genetic algorithms, particle swarm optimization, ant colony optimization).

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