Forward-Looking Echoic Flow for Guidance of an Unmanned Aerial System

Echoic flow is a formula derived from natural phenomena that has the potential to control vehicles with great efficiency using range information. Initially studied in bats, echoic flow allows animals to use sonar as a navigation tool. Downward-facing echoic flow used in the vertical landing of an Unmanned Aerial System (UAS) has been studied in past research. Forward-looking echoic flow on a UAS could allow for new approaches to braking and following techniques in the horizontal plane of motion towards both fixed and moving targets. The goal of this project was to demonstrate forward-looking echoic flow guidance towards a fixed target using a quadcopter and to gather data showing the accuracy and precision of the process. In initial forward-looking tests, a modified Parrot AR Drone with an added ultrasonic sensor and Raspberry Pi were used as the UAS. Preliminary findings showed erratic and often inaccurate range finding measurements. These measurements were attributed in part to the inability of the UAS to aim directly at the small target. A software filter was designed to minimize the impact of erroneous measurements. Further tests conducted using a flat wall as the approach target still yielded trials that did not follow the ideal echoic flow approach accurately. In an attempt to improve the performance of trials, the equation used to convert velocities to motor thrust values was recalibrated. Though trial results did improve due to this modification, imprecise quadcopter movement control prevented the achievement of a smooth echoic flow approach. Finally, simulations of forward-looking trials were performed to test the impact of measurement and velocity error on the performance of echoic flow approaches. The values of measurement error that resulted in acceptable echoic flow performance were found to be lower than the expected values for the UAS in this study. Further forward-looking echoic flow research is recommended using a more accurate and robust rangefinder. A UAS capable of more precise horizontal plane movement is also recommended.No embargoAcademic Major: Electrical and Computer Engineerin

Low frequency shelf current fluctuations in the Gulf of Alaska

Thesis (M.S.) University of Alaska Fairbanks, 1977A general oceanographic study of a shelf region in the Gulf of Alaska has revealed low-frequency, current fluctuations. A current meter mooring was located approximately 20 km offshore, in a water depth of 100 m. The time dependent flow is found to be baroclinic and semi-periodic. The effects of local bottom topography, nearshore dilution by river discharge, orographic coastal features, and an island barrier are important to the shelf circulation in this region. The movement of a boundary associated with the Copper River appears to be an important process in controlling the water motion at the mooring site

Birdsong dialect patterns explained using magnetic domains

The songs and calls of many bird species, like human speech, form distinct regional dialects. We suggest that the process of dialect formation is analogous to the physical process of magnetic domain formation. We take the coastal breeding grounds of the Puget Sound white crowned sparrow as an example. Previous field studies suggest that birds of this species learn multiple songs early in life, and when establishing a territory for the first time, retain one of these dialects in order to match the majority of their neighbours. We introduce a simple lattice model of the process, showing that this matching behaviour can produce single dialect domains provided the death rate of adult birds is sufficiently low. We relate death rate to thermodynamic temperature in magnetic materials, and calculate the critical death rate by analogy with the Ising model. Using parameters consistent with the known behavior of these birds we show that coastal dialect domain shapes may be explained by viewing them as low temperature "stripe states"

Manager Perceptions of the Impact of Consolidation on the U.K. Independent Television Production Industry

This paper explores the impact that consolidation has had on the UK’s Independent Television Production Industry over the past decade and how this process had affected the running of different sized production companies. In-depth interviews with a number of influential professionals revealed five themes: the management of small companies, post acquisition, had not changed; economies of scale can be attributed to an increase in scale; medium sized companies would find it increasingly difficult to compete; the emergence of the Super Indie had not stifled creativity in the industry; a key driver in the consolidation process is that of individual gain. Key words: Independent Television Production, Industry Consolidation, Key Drivers, Super Indies, United Kingdom

How costly is sustained low inflation for the U.S. economy?

We study the welfare cost of inflation in a general equilibrium life cycle model with growth, costly financial intermediation, and taxes on nominal quantities. We find a stationary equilibrium of the model matches a wide variety of facts about the postwar U.S. economy. We then calculate that the inflation policy of the monetary authority has welfare consequences for agents that are an order of magnitude larger than existing estimates in the literature. These effects are large even at very low inflation rates. The bulk of the welfare cost of inflation can be attributed to the fact that inflation increases the effective tax rate on capital income.Economic conditions - United States ; Inflation (Finance)

The Deletion of the Bre1 Gene in Aspergillus nidulans Impairs Mitotic Growth, Meiosis, and DNA Damage Repair

Bre1 is a homotetrameric E3 ubiquitin-protein ligase that heterodimerizes with Rad6, an E2 ubiquitin-conjugating enzyme, in order to ubiquitinate lysine 123 in Aspergillus nidulans. This post-translational modification promotes methylation of lysines 4 and 79 on histone H3, which are required for certain damage repair pathways and for both optimal mitotic cell growth and meiosis [1-3, 12]. ΔBre1 mutants were generated by exposing protoplasts from strains auxotrophic for pyridoxine to a three-way fusion construct made from the Bre1 5’ and 3’ flanking regions and the Aspergillus fumigatus pyroA gene, which served as a selectable marker. Molecular diagnosis was confirmed via trans-locus PCR. Phenotypic analysis indicates that the loss of Bre1 increases sensitivity to DNA damage agents, decreases mitotic cell growth, and inhibits meiosis. The severe developmental defects of ΔBre1 mutants are consistent with the known roles of Bre1 as an upstream regulator of several important cellular functions. [excerpt

Transcription start site scanning and the requirement for ATP during transcription initiation by RNA polymerase II

Saccharomyces cerevisiae RNA polymerase (Pol) II locates transcription start sites (TSS) at TATA-containing promoters by scanning sequences downstream from the site of preinitiation complex formation, a process that involves the translocation of downstream promoter DNA toward Pol II. To investigate a potential role of yeast Pol II transcription in TSS scanning, HIS4 promoter derivatives were generated that limited transcripts in the 30-bp scanned region to two nucleotides in length. Although we found that TSS scanning does not require RNA synthesis, our results revealed that transcription in the purified yeast basal system is largely ATP-independent despite a requirement for the TFIIH DNA translocase subunit Ssl2. This result is rationalized by our finding that, although they are poorer substrates, UTP and GTP can also be utilized by Ssl2. ATPγS is a strong inhibitor of rNTP-fueled translocation, and high concentrations of ATPγS make transcription completely dependent on added dATP. Limiting Pol II function with low ATP concentrations shifted the TSS position downstream. Combined with prior work, our results show that Pol II transcription plays an important role in TSS selection but is not required for the scanning reaction