System Development And Integration Of An Airborne Laser Communications Payload For Unmanned Aircraft Systems

Free space laser communications provides wide bandwidth and high security capabilities to Unmanned Aircraft Systems (UAS) in order to successfully accomplish Intelligence, Surveillance, Target Acquisition, and Reconnaissance (IST AR) missions. A practical implementation of a laser-based video communications payload flown by a small U AS aircraft is described as a proof-of-concept. The two-axis gimbal pointing control algorithm calculates the line-of-sight vector in real-time by using Differential Global Positioning System (DGPS) and Inertial Measurement Unit (IMU) information gathered from the UAS vehicle\u27s autopilot so that the laser transmitter in the airborne payload can accurately track a ground-based photodiode array receiver with a known DGPS location. One of the future goals of this project is to move from DAS-to-ground communications to UAS-to-UAS free space laser communications. A communications system has been developed using Light Amplification by Stimulated Emission of Radiation (LASER) to transmit data to a known location on the ground. Several main subsystems including the laser transmitter, laser receiver, gimbal, subsystem, and tracking software are discussed, along with the integration and testing phase. The laser transmitter is mounted within the Super Hauler small UAS payload bay. The UAS was custom made in compliance with the Super Hauler requirements, specifically regarding the size and shape of the payload bay. A two-axis gimbal system is controlled via the tracking software to point the laser beam to a specified DGPS coordinate throughout the flight. In addition to the GPS system, there is a machine vision-based tracking system in development that works in parallel with the GPS system and takes over gimbal control for precise alignment. At the known DGPS coordinate, the ground-based receiver is stationary and converts the video data carried by the laser to a viewable format. The receiver, like any other subsystem, is a very crucial component of a successful data transmission system; therefore, significant time and effort was designated for its development. To ensure successful operation of the free space laser communications payload, a series of subsystem tests were performed. For each subsystem, a test procedure was developed with specific pass-fail criteria. After each subsystem was tested, a full system test was also carried out. The full system included the integration of all subsystems inside the payload bay of the Super Hauler UAS. Detailed analyses of the testing procedures along with the integration process are presented in this thesis. After the full system was successfully tested in the laboratory, preliminary flight tests took place in July and October of 2009 within military-restricted airspace over Camp Grafton South, a National Guard training facility in North Dakota, followed by another flight tests in June 2010. While these preliminary flights did not result in video transmission, they were very successful in gathering preliminary data and field test information. These results are crucial in the continued development of the system. Recommendations for future payload improvements are discussed in the last section of this thesis

Unia Europejska - dylematy ochrony środowiska

"Najmniejszy kontynent - Europa - geograficznie ciągnący się od Portugalii po Ural, w ubiegłym stuleciu swą wschodnią granicę zmieniał pod wpływem nacisków politycznej natury tak, że wędrowała ona od Łaby, przez Odrę, Bug, Linię Curzona aż do Ufy. Zachodnia część Europy od ponad dwóch tysięcy lat stanowi centrum ziemskiej cywilizacji, ulokowanej na 5 min km2, bowiem pozostałe 5 min znajduje się na wschód od linii Bugu. Część przesunięta poza Łabę i Dunaj uważana jest za „prawdziwą Europę”, liczącą niewiele ponad 2 min km2 i obecnie ok. 375 min mieszkańców."(...

Influence of vegetation on streambank hydraulics

Proper use of vegetation in streambank bioengineering practices requires a comprehensive understanding of the influence of vegetation density on streambank hydraulics. A series of studies were conducted to investigate the relationship between independent variables vegetation density, bank angle, and discharge and dependent variables channel velocity, resistance, turbulence, and shear stress. Flume experiments were conducted varying vegetation stem density (number of plants/horizontal area) and frontal area (number of leaves/vertical area) on 30° and 15° vegetated bank-toes at three discharge rates. Three sets of 3D velocity measures were collected using an ADV at: 1) 0.6 x depth, 2) near-boundary, and 3) velocity profiles. Resistance parameters for drag coefficient (C[subscript d]) and Manning's n were estimated. Turbulent stress measures based on turbulent kinetic energy and Reynolds stress were used to evaluate boundary shear stress. Tensor fields were visualized to explore vorticity and near-boundary hydraulics. Results demonstrated that as vegetation density increased, water was increasingly redirected from the bank-toe to the main channel, decreasing downstream velocity along the bank-toe by 35-95% and increasing downstream velocity in the main channel by 80-240%. As vegetation density increased and water velocity decreased along the bank-toe, depths increased, surface slope flattened, and an eddy formed downstream of the vegetated patch. C[subscript d] increased with increasing vegetation density, and decreasing stem Reynolds number. Estimates of C[subscript d] and n were high relative to commonly published values, especially when vegetation density was high. Increasing vegetation density also increased turbulence and shear stress, creating greater opportunity for erosion at sensitive locations along the bottom of the bank-toe and in the main channel. Reynolds stresses also increased under the canopy, resulting in higher shearing forces along the bank-toe, especially on the 30° bank-toe. Differences in results between bank-toe angles were minimal, dominated by the influence of vegetation. Magnitude of results decreased with decreasing discharge, but patterns were similar. Findings suggest planting at higher densities may protect the bank from erosion, but may increase the potential for erosion along the interface between the bank and main channel if unprotected, though further research with natural plant communities is encouraged to confirm findings

Improved Calibration Functions of Three Capacitance Probes for the Measurement of Soil Moisture in Tropical Soils

Single capacitance sensors are sensitive to soil property variability. The objectives of this study were to: (i) establish site-specific laboratory calibration equations of three single capacitance sensors (EC-20, EC-10, and ML2x) for tropical soils, and (ii) evaluate the accuracy and precision of these sensors. Intact soil cores and bulk samples, collected from the top 20 and 80 cm soil depths at five locations across the Upper Mākaha Valley watershed, were analyzed to determine their soil bulk density (ρb), total porosity (θt), particle size distribution, and electrical conductivity (EC). Laboratory calibration equations were established using soil packed columns at six water content levels (0–0.5 cm3 cm−3). Soil bulk density and θt significantly varied with sampling depths; whereas, soil clay content (CC) and EC varied with sampling locations. Variations of ρb and θt at the two depths significantly affected the EC-20 and ML2x laboratory calibration functions; however, there was no effect of these properties on calibration equation functions of EC-10. There was no significant effect of sampling locations on the laboratory calibration functions suggesting watershed-specific equations for EC-20 and ML2x for the two depths; a single watershed-specific equation was needed for EC-10 for both sampling depths. The laboratory calibration equations for all sensors were more accurate than the corresponding default equations. ML2x exhibited better precision than EC-10, followed by EC-20. We conclude that the laboratory calibration equations can mitigate the effects of varying soil properties and improve the sensors’ accuracy for water content measurements

The Effects of Replacing Native Forest on the Quantity and Impacts of In-Channel Pieces of Large Wood in Chilean Streams

Dead trees in rivers can significantly affect their morphological and ecological properties by increasing flow resistance, affecting sediment transport, and storing organic matter. Logs are usually recruited from banks or along the entire upstream basin. Although it is generally acknowledged that forested headwater streams feature higher volumes of in-channel pieces of large wood, the influence of forest type and forest management of the potential recruitment zone on the volumes and effects of wood have been less explored, especially in relation to the effects of replacing native forests with pine plantations. This paper presents a comparison of volumes of wood, and characteristics and effects on streams draining paired basins with comparable slopes, areas, and hydrologic regimes, but different in terms of land use. The five selected pairs of basins are located in the Coastal and Andean mountain Ranges in central Chile, in order to compare native forest and pine plantation basins. The results show that logs tend to be shorter and with larger diameters in streams draining native forest basins. Because of their smaller dimensions, logs and jams tend to be more mobile and oriented parallel to the flow. Volumes of in-channel wood in native forest basins are only slightly larger than in pine plantation basins, and no differences have been identified in terms of morphological effects on channel geometry. Also, fish type and biomass were comparable among pairs. Evidence highlights the importance of the width of riparian buffers in mitigating the effects of land use change, especially the substitution of native forest with plantations

Recent advances quantifying the large wood dynamics in river basins: New methods and remaining challenges

Citation: Ruiz-Villanueva, V., Piégay, H., Gurnell, A. A., Marston, R. A., & Stoffel, M. (2016). Recent advances quantifying the large wood dynamics in river basins: New methods and remaining challenges. Reviews of Geophysics. doi:10.1002/2015RG000514Large wood is an important physical component of woodland rivers and significantly influences river morphology. It is also a key component of stream ecosystems. However, large wood is also a source of risk for human activities as it may damage infrastructure, block river channels, and induce flooding. Therefore, the analysis and quantification of large wood and its mobility are crucial for understanding and managing wood in rivers. As the amount of large-wood-related studies by researchers, river managers, and stakeholders increases, documentation of commonly used and newly available techniques and their effectiveness has also become increasingly relevant as well. Important data and knowledge have been obtained from the application of very different approaches and have generated a significant body of valuable information representative of different environments. This review brings a comprehensive qualitative and quantitative summary of recent advances regarding the different processes involved in large wood dynamics in fluvial systems including wood budgeting and wood mechanics. First, some key definitions and concepts are introduced. Second, advances in quantifying large wood dynamics are reviewed; in particular, how measurements and modeling can be combined to integrate our understanding of how large wood moves through and is retained within river systems. Throughout, we present a quantitative and integrated meta-analysis compiled from different studies and geographical regions. Finally, we conclude by highlighting areas of particular research importance and their likely future trajectories, and we consider a particularly underresearched area so as to stress the future challenges for large wood research. ©2016. American Geophysical Union

Untangling Geomorphic Processes in the Grand Canyon with Topographic Time Series from Hybrid Surveys

Sandbars along the Colorado River in the Grand Canyon are a fundamental part of the landscape – creating habitat for native plants and animals, providing camping beaches, and supplying sediment needed to protect archaeological resources. The Glen Canyon Dam just upstream of the Grand Canyon reduces the amount of sediment available for sandbars and the flows available to deliver sediment. Decades of intensive monitoring and research have been conducted to better understand the altered sediment budget of the Colorado River, particularly the erosion and restoration of sandbars. To make management decisions that aid in sandbar retention it is important to understand the sediment budget, specifically the fluxes and changes in storage. Recently, the explosion of different methods for collecting high-resolution repeat topographic datasets in rivers has led to the ability to monitor longer reaches and build topographic spatiotemporal time-series of river reaches. Unfortunately, no single data collection method works everywhere and many methods have been combined to build a representation of the Colorado River. For nearly two decades, over 30 miles of river and over 60 discrete sandbar sites along the Colorado River below Glen Canyon Dam have been surveyed repeatedly with a combination of multi-beam SONAR, single-beam SONAR, photogrammetry, LiDaR and total station surveys. Survey data has been analyzed to explore how experimental flood releases, timed with natural sediment inputs, alter landforms downstream of the dam. However, current monitoring efforts do not and cannot produce a complete (spatial) sample of all the change in storage throughout the Canyon. Here we present results of analyses using a new version of the Geomorphic Change Detection software. A budget segregation feature is exploited to decompose the budget by specific geomorphic mechanisms of change. We explore whether changes in storage can be explained by geomorphic, hydrologic, and vegetative metrics collected through topographic surveys and existing discharge data. By utilizing a hybrid of available datasets for estimating changes in storage, we gain insight into how different eddybar - fan complexes are evolving through time in response to a highly regulated flow regime and experimental flood releases

Návrh a optimalizace procesu automatizovaného integračního testování

The bachelor thesis deals with the analysis of the current process of manual integration testing used in daily operation in the company Engel strojírenská spol. s.r.o., and creating own solution in the form of a tool to automate this process