849 research outputs found

    Robust Positioning in the Presence of Multipath and NLOS GNSS Signals

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    GNSS signals can be blocked and reflected by nearby objects, such as buildings, walls, and vehicles. They can also be reflected by the ground and by water. These effects are the dominant source of GNSS positioning errors in dense urban environments, though they can have an impact almost anywhere. Non- line-of-sight (NLOS) reception occurs when the direct path from the transmitter to the receiver is blocked and signals are received only via a reflected path. Multipath interference occurs, as the name suggests, when a signal is received via multiple paths. This can be via the direct path and one or more reflected paths, or it can be via multiple reflected paths. As their error characteristics are different, NLOS and multipath interference typically require different mitigation techniques, though some techniques are applicable to both. Antenna design and advanced receiver signal processing techniques can substantially reduce multipath errors. Unless an antenna array is used, NLOS reception has to be detected using the receiver's ranging and carrier-power-to-noise-density ratio (C/N0) measurements and mitigated within the positioning algorithm. Some NLOS mitigation techniques can also be used to combat severe multipath interference. Multipath interference, but not NLOS reception, can also be mitigated by comparing or combining code and carrier measurements, comparing ranging and C/N0 measurements from signals on different frequencies, and analyzing the time evolution of the ranging and C/N0 measurements

    Multi-Epoch 3D-Mapping-Aided Positioning using Bayesian Filtering Techniques

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    The performance of different filtering algorithms combined with 3D mapping-aided (3DMA) techniques is investigated in this paper. Several single- and multi-epoch filtering algorithms were implemented and then tested on static pedestrian navigation data collected in the City of London using a u-blox EVK M8T GNSS receiver and vehicle navigation data collected in Canary Wharf, London, by a trial van with a Racelogic Labsat 3 GNSS front-end. The results show that filtering has a greater impact on mobile positioning than static positioning, while 3DMA GNSS brings more significant improvements to positioning accuracy in denser environments than in more open areas. Thus, multi-epoch 3DMA GNSS filtering should bring the maximum benefit to mobile positioning in dense environments. In vehicle tests at Canary Wharf, 3DMA GNSS filtering reduced the RMS horizontal position error by approximately 68% and 57% compared to the single-epoch 3DMA GNSS and filtered conventional GNSS, respectively

    Height Aiding, C

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    Measuring Retail Visual Cues Using Mobile Bio-metric Responses

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    [EN] This research provides the results of a comprehensive in-store study that utilized eye tracking to determine the initial eye attractiveness of signage and displays used in a Toyota retail dealership. Potential car buyers (n = 24) walked randomly through the showroom for the first time, and were asked to view the various signs, displays, video monitors, decorations, and vehicles on display. Research was conducted while the dealership was open in order to include distractions from human interaction. Subjects’ eye movements and the objects viewed were captured using Tobii II eye tracking glasses at 60Mhz. A typical showroom self-tour lasted approximately 4:31 minutes. Subjects were then shown their results and Retrospective Think Aloud interviews were conducted with the subjects to determine positive and negative reactions to the observed objects. Signage measured included those required by Toyota, as well as those created by the dealership. Types of signage measured included digital, video, posters, stand-up cards, and ads placed on the vehicle. Each potential eye attractive object was identified and classified by type (signage, décor, digital signage, vehicle information, etc.). Every subject’s results were analyzed by the number of fixations and the time spent viewing each object. The study revealed that video or digital messaging was not any more effective than static signage, but that placement of the signage was a determining factor in the effectiveness of message receptivity. Many of the non-signage objects received more attention than did certain types of advertising signage. The various attributes of the objects and signs that received positive attention were analyzed as to their eye attactiveness characteristics. Although signage in a retail showroom is believed to be critical in providing advertising and product messages, this study (in its particular environment) demonstrated that signage is not viewed by customers as often as previouly thought.Dishman, P.; Groves, J.; Jolley, D. (2018). Measuring Retail Visual Cues Using Mobile Bio-metric Responses. En 2nd International Conference on Advanced Reserach Methods and Analytics (CARMA 2018). Editorial Universitat Politècnica de València. 249-249. https://doi.org/10.4995/CARMA2018.2018.8287OCS24924

    Applications of Nondestructive Testing in Civil Engineering

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    Presented in this thesis are two studies that apply nondestructive testing methods to civil engineering problems. The first study examines the relationship between the small-strain and large-strain properties of exhumed cast iron water pipes. Nondestructive and destructive testing programs were performed on eight pipes varying in age from 40 to 130 years. New applications of frequency domain analysis techniques including Fourier and wavelet transforms of ultrasonic pulse velocity measurements are presented. The effects of Lamb wave propagation on the ultrasonic testing results are investigated. Microstructure evaluation revealed two different types of cast iron within the pipes sampled: grey cast iron and ductile iron. A low correlation between wave propagation and large-strain measurements was observed. However, the wave velocities were consistently different between ductile and grey cast iron pipes (14% to 18% difference). Lamb waves were found to contribute significantly to the frequency content of the ultrasonic signals possibly resulting in the poor correlations observed. Therefore, correlations between wave velocities and large strain properties obtained using samples from exhumed water pipes must be used with caution in the condition assessment of aged water pipes especially for grey cast iron pipes. The second study presented in this thesis was performed to evaluate the effectiveness of three geophysical methods for geotechnical site characterization in swamps and environmentally sensitive wetland areas. The geophysical methods evaluated were electrical resistivity imaging (ERI), seismic refraction (SR), and multiple-channel analysis of surface waves (MASW). The geophysical test results were verified against the results from borehole and CPT logs. The ERI results were best for determining the depth to the glacial till. The SR results overestimated the depth to the till because of the presence of a stiffness reversal. The MASW results predicted the depth to the refusal till layer less accurately than the ERI method. However, this method was able to detect the three distinct layers above the till. These methods can be used as a basis for further development to optimize a procedure to reduce the number of boreholes required for conventional site investigations in areas that are environmentally sensitive or where access is restricted

    The Institute of Archaeology & Siegfried H. Horn Museum Newsletter Volume 27.3

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    Tent Dinner and Art Auction, Jennifer L. Green Younker Lecture, Carrie Rhodes Global Moments, Paul J. Ray, Jr. Al-Maktába: The Bookstore Random Surveyhttps://digitalcommons.andrews.edu/iaham-news/1027/thumbnail.jp

    Investigation into the Kinetics of the Rotating Biological Contactor

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    Bioenvironmental Engineerin

    Estimating the health benefits of progeny extraction units as a means of reducing exposure to radon

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    Radon exposure to the general public can be reduced by preventing entry of radon gas into buildings using a passive radon-proof membrane or an active sump and pump system. However, a significant majority of the radiation dose delivered is from the decay products of radon rather than from the gas itself. These decay products (also referred to as progeny) are present in indoor air, with an equilibrium factor – a measure of the ratio of progeny to radon gas – of between 0.4 to 0.5. As a result, systems which extract radon progeny from the air by filtering have been promoted as means of reducing exposure to the general population. The European Community Radon Software (ECRS) offers a means of estimating lung-cancer risk associated with an individual’s exposure to radon, and includes the possibility of estimating the health risk from different proportions of radon gas and its progeny by varying the value of the Equilibrium Factor. This software was used to estimate the health benefits associated with reduced decay products in differing concentrations of radon gas. The results were compared to health benefits expected if the risk was reduced by the standard method of reducing the radon gas concentration below the Action Level, which in the UK is 200 Bq·m-3 for domestic properties. These calculations showed that there is the potential for efficient extraction units to provide the necessary dose and risk reduction where initial average radon gas concentrations are up to 800 Bq·m-3. However, above 1000 Bq·m-3, such systems cannot reduce the health risk sufficiently to reach levels comparable to those resulting from radon gas reduction to below the Action Leve

    Interpolation Method Needed for Numerical Uncertainty

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    Using Computational Fluid Dynamics (CFD) to predict a flow field is an approximation to the exact problem and uncertainties exist. There is a method to approximate the errors in CFD via Richardson's Extrapolation. This method is based off of progressive grid refinement. To estimate the errors, the analyst must interpolate between at least three grids. This paper describes a study to find an appropriate interpolation scheme that can be used in Richardson's extrapolation or other uncertainty method to approximate errors
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