254 research outputs found

    The Effect of Pupil Size on Stimulation of the Melanopsin Containing Retinal Ganglion Cells, as Evaluated by Monochromatic Pupillometry

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    Purpose: To evaluate the influence of the size of the light exposed pupil in one eye on the pupillary light reflex of the other eye. Method: Using a monochromatic pupillometer, the left eye in each of 10 healthy subjects was exposed to 20 s of monochromatic light of luminance 300 cd/m2, first red (660 nm) and in a following session, blue (470 nm) light. The consensual pupillary diameter in the right eye was continuously measured before, during, and after light exposure. Subsequently, Tropicamide 1% or Pilocarpine 2% was instilled into the left eye and when the pupil was either maximally dilated or contracted, the entire sequence of red and blue light exposure repeated. After at least 3 days, when the effect of the eye drop had subsided, the entire experiment was repeated, this time employing the other substance. Results: Prior dilatation of the left pupil augmented the post light contraction to blue (p < 0.0001), but not to red light. The contraction during light exposure did not change. Prior contraction of the left pupil decreased the post-stimulus contraction to blue light (p < 0.04). Conclusion: The size of the light exposed pupil influences the magnitude of the response to blue, but not to red light. Prior dilatation may therefore prove useful, when the response to blue light – as a marker of melanopsin containing retinal ganglion cell function – is of interest, especially when this response is weak

    Instrumentation and Control of Unmanned Air Vehicles

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    This thesis treats a number of instrumentation and control problems related to autonomous Unmanned Aerial Vehicles (UAV’s). Autonomous Micro Air Vehicles (MAV’s) are of special interest to the Author. These are characterised by their small size, typically below 10kg takeoff weight. Due to their small size, normal avionics are not suited for MAV’s. Instead it is more appropriate to use standard model airplane components and actuators. This has the added benefit of reducing the vehicle cost. However this also means that the vehicle designer has to characterise and design many of the instruments and actuators used for MAV’s.The first part of this thesis concentrates on obtaining an aerodynamic model for a canard configuration fixed wing UAV. Particular emphasis is placed on treatment of uncertainties in the model and the resulting influence on the UAV dynamics. A model of an electric propulsion system is also proposed, based partly on propeller characteristics obtained by comparing the geometry of the propeller with that of a propeller with known characteristics.Model airplane actuators are a logical choice for MAV’s because of there availability, price and performance. It is however difficult to obtain published data concerning the dynamics of these actuators. For these reasons a part of this thesis treats the procedure used in experimentally identifying a dynamic model of model airplane actuators. It is shown that a particular make of actuators employ a proportional-derivative bang-bang controller scheme. As a result of this observation, a feedback linearization scheme is proposed and simulated for this type of actuator.Different lateral guidance strategies are discussed based on the assumption that the desired flight path of the UAV is defined by a number of “waypoints”. It is shown that a “moving point” guidance strategy has certain advantages with respect to autopilot implementation and smooth transition from one heading to another in the vicinity of a waypoint.The most critical flight phase with respect to guidance and navigation accuracy is the approach and landing. In order to accomplish an autonomous landing it is important to be able to determine the position of the UAV with great accuracy and reliability. The only practical system for accurate navigation at the present, which does not require expensive ground based equipment, is the satellite based Global Positioning System, commonly known as GPS. However this alone does not have sufficient accuracy for the task. By using a differential positioning approach involving a ground based GPS receiver at a known location, it is possible to construct a Differential GPS (DGPS). Such a system has been implemented and studied in detail using a pair of commercially available receivers. It is shown through analysis of experimental data that the most significant error source in DGPS systems is multipath, caused by reflections of the signal from objects in the vicinity of the receiver antennas. Furthermore it is shown that these errors can be correlated with the receiver Signal to Noise Ratio (SNR). Using this information a kinematic Kalman filter is proposed for filtering the raw measurement data. “Simulation” of this filter using actual measurement data shows that a significant improvement in positioning accuracy is obtained.Finally some issues relating to the design of an Inertial Navigation System (INS) and realtime synchronized instruments are discussed

    The Burden of diseases caused by congenital toxoplasmosis

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    MiljÞpÄvirkninger af importerede Þkologiske fÞdevarer:frugt, grÞnt og ost

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    CropSAT

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    Vi utvecklade CropSAT, ett webbaserat system för tillhandahĂ„llande av satellitdata över Ă„kermarken dĂ€r tilldelningsfiler kan laddas ned och anvĂ€ndas för styrning av gödselspridare. Systemet testades under 2014 och vidareutvecklades under 2015 inom ramen för Greppa NĂ€ringen. VĂ„r slutsats Ă€r att satellitdata som omrĂ€knats till vegetationsindexkartor kan anvĂ€ndas i praktiken för anpassning av kvĂ€vegivan inom fĂ€lt. Det Ă€r ett mycket kostnadseffektivt sĂ€tt att skapa underlag för bĂ€ttre kvĂ€vehushĂ„llning. Även under ett molnigt Ă„r som 2015 tĂ€cktes 2/3 av Ă„kermarken in av minst 3 bilder under kompletterings-gödslingssĂ€songen. Den relativa variationen inom fĂ€lt Ă€r ofta stabil över tid sĂ„ Ă€ven 1-2 veckor gamla bilder kan vara möjiga att utnyttja om man anvĂ€nder den relativa variationen som grund för beslut. Satellitdata kan kalibreras med handsensormĂ€tningar sĂ„ att kartor över N-upptag skapas. Flera tusen anvĂ€ndare har utnyttjat CropSAT som har potential att utvecklas med nya funktioner
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