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1,303 results on '"Dahl A"'

2. Rapid Technology Maturation using the ESRA CubeSat Mission

Author

Maldonado, Carlos A., primary, Deming, Jonathan, additional, Mosley, Brooke N., additional, McGlown, Justin, additional, Nelson, Anthony, additional, Fernandes, Phil A., additional, Rogers, Anthony J., additional, Patrick, Douglas, additional, Kroupa, Martin, additional, Caffrey, Michael, additional, Mendel, Susan, additional, Boyd, Kerry, additional, Gula, August, additional, Katko, Kim, additional, Hehlen, Markus P., additional, Arnold, Daniel, additional, Barney, Jonathan, additional, Schultz, Ted, additional, Reisenfeld, Dan, additional, Skoug, Ruth, additional, Guider, Angus, additional, Holloway, Michael, additional, Morning, Heidi, additional, Steinberg, John T., additional, Krause, Erik, additional, Kirby, Andrew, additional, Beckman, Darrel, additional, Tripp, Justin, additional, Morgan, Keith S., additional, Miller, Zachary, additional, Merl, Rob, additional, Graham, Paul S., additional, Hoose, Bradley, additional, Ortner, Joshua, additional, Cole, Quinn, additional, Clanton, Chuck, additional, Larsen, Brian A., additional, Fairbanks, Tom, additional, George, Jeff, additional, Scobie, Rory, additional, Subsomboon, Kasidit, additional, McKeown, Kristina, additional, Alano, Katherine, additional, Michel, John, additional, Harvey, Darren, additional, Harvilla, Andrew, additional, Dahl, Daniel, additional, Bhaskar, Gautam, additional, Pino, Evan, additional, and Ford, Kirsten, additional

Published
2024
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3. Vehicle Detection in Aerial Images Based on 3D Depth Maps and Deep Neural Networks

Author

Saleh Javadi, Mattias Dahl, and Mats I. Pettersson

Subjects
Convolutional neural networks, 3D depth maps, object detection, aerial images, Electrical engineering. Electronics. Nuclear engineering, TK1-9971
Abstract

Object detection in aerial images, particularly of vehicles, is highly important in remote sensing applications including traffic management, urban planning, parking space utilization, surveillance, and search and rescue. In this article, we investigate the ability of three-dimensional (3D) feature maps to improve the performance of deep neural network (DNN) for vehicle detection. First, we propose a DNN based on YOLOv3 with various base networks, including DarkNet-53, SqueezeNet, MobileNet-v2, and DenseNet-201. We assessed the base networks and their performance in combination with YOLOv3 on efficiency, processing time, and the memory that each architecture required. In the second part, 3D depth maps were generated using pairs of aerial images and their parallax displacement. Next, a fully connected neural network (fcNN) was trained on 3D feature maps of trucks, semi-trailers and trailers. A cascade of these networks was then proposed to detect vehicles in aerial images. Upon the DNN detecting a region, coordinates and confidence levels were used to extract the corresponding 3D features. The fcNN used 3D features as the input to improve the DNN performance. The data set used in this work was acquired from numerous flights of an unmanned aerial vehicle (UAV) across two industrial harbors over two years. The experimental results show that 3D features improved the precision of DNNs from 88.23 % to 96.43 % and from 97.10 % to 100 % when using DNN confidence thresholds of 0.01 and 0.05, respectively. Accordingly, the proposed system was able to successfully remove 72.22 % to 100 % of false positives from the DNN outputs. These results indicate the importance of 3D features utilization to improve object detection in aerial images for future research.

Published
2021
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4. Investigating the Technological and Political Challenges of V2V Communication in Light of an Experimental Scenario Set Up

Author

Petter Arnesen, Erlend Dahl, Odd Andre Hjelkrem, and Hanne Seter

Subjects
V2V, ITS-G5, package loss, RSSI, radio communication, CAV, Electrical engineering. Electronics. Nuclear engineering, TK1-9971
Abstract

The suggested benefits of automated vehicles are plentiful, but many of the benefits depend on connectivity with other vehicles and infrastructure to be useful to the society at large. This paper identifies two main research gaps: first, to identify whether ITS-G5 can be a reliable communication link for V2V communication. Second, to discuss which implications the results have for practitioners working with the future implementation of CAVs. We answer these research gaps by introducing a conceptualization of V2V communication operationalized through controlled experiments with vehicles on a closed runway. In the experiments, onboard ITS-G5 communication devices are used for measuring signal strength and package loss between the vehicles. The results indicate that ITS-G5 technology has some limitations, especially for long range communication (>1500 m), and in cases with other traffic shadowing the signal. We conclude that although ITS-G5 has high risk of reduced radio link in non-line-of-sight situations and in situations where the radio signal is shadowed by other traffic, the latency and operational range would be sufficient for safety critical services in line-of-sight situations. For policymakers and practitioners working with implementing communication for vehicles, the results imply that large-scale piloting is critical for testing the technology in a realistic environment outside of the laboratories. In such environments different stakeholders and disciplines can meet and collaborate to avoid siloed approaches.

Published
2021
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5. Multiangle, Frequency, and Polarization Radar Measurement of Ice Sheets

Author

Jie-Bang Yan, Linfeng Li, Joshua A. Nunn, Dorthe Dahl-Jensen, Charles O'Neill, Ryan A. Taylor, Christopher D. Simpson, Shashank Wattal, Daniel Steinhage, Prasad Gogineni, Heinrich Miller, and Olaf Eisen

Subjects
Greenland, ice, radar, radio echo sounding, Ocean engineering, TC1501-1800, Geophysics. Cosmic physics, QC801-809
Abstract

Radio echo sounding of polar ice sheets provides important information on the ice bed topography and internal layers. These data have been used by scientists to create 3-D maps of polar ice sheets for climate modeling as well as to reconstruct the climate history that dates back to hundreds of thousands of years. In this article, we present the design and development of three surface-based multichannel radars in the VHF and UHF bands. We provide results from radar data multifrequency and polarization radar data collected over the Greenland ice sheet. All the three radars shared the same digital waveform generator and digitizer, and were installed in and operated on a tracked vehicle. The radars are operated with three different antenna arrays designed for operation over 170-230, 180-340, and 600-900 MHz. The results we obtained sounded more than 2.7 km thick ice with radars operating at frequencies as high as 850 MHz with more than 40 dB signal-to-noise ratio.

Published
2020
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17. Progress in the Design of the Atacama Large Aperture Submillimeter Telescope

Author

Mroczkowski, Tony, primary, Cicone, Claudia, additional, Reichert, Matthias, additional, Gallardo, Patricio, additional, Kaercher, Hans, additional, Hills, Richard, additional, Bok, Daniel, additional, Dahl, Erik, additional, Dubois-Dit-Bonclaude, Pierre, additional, Kiselev, Aleksej, additional, Timpe, Martin, additional, Zimmerer, Thomas, additional, Dicker, Simon, additional, Macintosh, Mike, additional, Klaassen, Pamela, additional, and Niemack, Michael, additional

Published
2023
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20. Experimental Investigation of Reduced Complexity MIMO Equalization in a 55-Mode Fiber SDM Transmission System

Author

Ospina, Ruby S. B., primary, Rademacher, Georg, additional, Luís, Ruben S., additional, Puttnam, Benjamin J., additional, Fontaine, Nicolas K., additional, Mazur, Mikael, additional, Chen, Haoshuo, additional, Ryf, Roland, additional, Neilson, David T., additional, Dahl, Daniel, additional, Carpenter, Joel, additional, Sillard, Pierre, additional, Achten, Frank, additional, Bigot, Marianne, additional, Mello, Darli A. A., additional, and Furukawa, Hideaki, additional

Published
2023
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21. Comparison of 2D SURE and 3D CT imaging of cortical vessels in a rat kidney

Author

Hansen, Lauge Naur, Kjer, Hans Martin, Amin Naji, Mostafa, Panduro, Nathalie Sarup, Sørensen, Charlotte Mehlin, Gundlach, Carsten, Dahl, Anders Bjorholm, Jensen, Jørgen Arendt, Hansen, Lauge Naur, Kjer, Hans Martin, Amin Naji, Mostafa, Panduro, Nathalie Sarup, Sørensen, Charlotte Mehlin, Gundlach, Carsten, Dahl, Anders Bjorholm, and Jensen, Jørgen Arendt

Abstract

SUper-Resolution ultrasound imaging using the Erythrocytes (SURE) can visualize blood vessels at about 25 to 50 µm resolution, but validation is required to assess how accurately the vasculature and its morphology are represented. Previous work compared ultrasound imaging to maximum intensity projections (MIP) of micro-CT volumes at an insufficient voxel size of 22.6 µm. Here, a 5 µm voxel size micro-CT volume of a cortical region in an excised rat kidney was acquired to test the hypothesis that blood vessels down to 50 µm in diameter are detected with SURE imaging. For the micro-CT volume, the blood vessels were segmented by an intensity threshold, and local thickness estimates were computed using expanding spheres within the segmentation mask. An affine registration between the SURE image and the micro-CT volume was manually defined, and a MIP of the microCT volume across 2 mm from the ultrasound imaging plane was computed for vessels with diameter estimates greater than 50 µm. The SURE image depicts 12 cortical radial vessels with high intensities and 9 dimmer cortical radial vessels. Notably, the 12 high intensity vessels are also depicted in the microCT projection, but 5 cortical radial vessels and 2 arcuate blood vessels are only visible in the SURE image. Of the faintly depicted cortical radial vessels, 5 vessels are not readily matched to vessels in the micro-CT projection. On the other hand, the microCT projection contains 6 cortical radial vessel segments and 2 arcuate blood vessels not depicted in the SURE image. These discrepancies in the comparison may arise from the challenging registration of the ultrasound focus beam and the micro-CT volume that is complicated further by the different states of the imaged tissue. Despite these challenges, SURE depicts most vessels at least down to 50 µm and even resolves parallel vessels not visible in the micro-CT projection, thus highlighting its clinical potential.

Published
2023

22. Fully Time-Based PID Controller for a High Frequency Buck Converter

Author

Dahl, Nicolai Jerram, Muntal, Pere L., Andersen, Michael A. E., Dahl, Nicolai Jerram, Muntal, Pere L., and Andersen, Michael A. E.

Abstract

With the shrinkage of process nodes for integrated circuits, analog circuits, like analog feedback control, have become increasingly expensive and more challenging to design. Here timebased control is a compelling alternative to traditional analog feedback control circuits due to its better scaling with the process node. Several publications about time-based PID-type controllers exist. There the PI-part is implemented in the time domain, but the D-part remains in the analog domain thereby limiting the process scaling benefits. This paper proposes a new PID structure that fully integrates the PID in the time domain. The proposed structure has improved ripple attenuation and maps directly to a typical PID. Simulations shows that the performance of the theoretical small signal controller translates well to the large signal time-based response

Published
2023

23. Marine Vessel and Power Plant System Simulator

Author

Torstein I. Bo, Andreas R. Dahl, Tor A. Johansen, Eirik Mathiesen, Michel R. Miyazaki, Eilif Pedersen, Roger Skjetne, Asgeir J. Sorensen, Laxminarayan Thorat, and Kevin K. Yum

Subjects
Marine technology, Marine vehicles, Power system simulation, Dynamic positioning, Electrical engineering. Electronics. Nuclear engineering, TK1-9971
Abstract

Modern marine electric propulsion vessels have many systems. These interactions and integration aspects are essential when studying a system and subsystem behavior. This is especially important when considering fault scenarios,s harsh weather, and complex marine operations. However, many simulators, including a selection presented here, study the positioning system and the power system separately. This paper proposes a simulator combining the two systems, as an extension to the marine systems simulator MATLAB/Simulink library. The intended use cases and the according design choices are presented. New subsystem models include a power-based electrical bus model and a simplified diesel engine model. Both are validated through the simulation against established models. In addition, established models for generators, electrical storage devices, thrusters, and a mean-value diesel engine model are summarized with rich references. Three case studies illustrate the multi-domain use of the simulator: 1) a semi-submersible drilling rig performing station keeping under environmental disturbances; 2) the same vessel subject to an electrical bus reconfiguration; and 3) a supply vessel with a hybrid power plant.

Published
2015
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28. Visual Exploration of Rheological Test Results from Soft Materials

Author

Jonas Madsen, Lasse Sode, Julie Frost Dahl, Milena Corredig, and Hans-Jorg Schulz

Abstract

Rheological testing of soft materials aims to characterize them through a complex combination of elastic and viscous properties. Its fundamental idea is to apply a force and register the resulting deformation of the material. These tests have applications in a wide range of domains from adjusting oil drilling muds for different rock strata to developing fast-drying paints and quality control in food processing. Yet, visual-interactive means for the explorative analysis of the resulting data are scarce if they exist at all. Hence, we present VAOS - an open-source visual analysis software for exploring the complex rheological properties of soft materials subjected to oscillatory tests. VAOS offers a specific focus on the visual analysis across multiple samples and test runs at once, which is currently not well supported by existing software. We showcase the utility of VAOS in a usage scenario and two expert interviews, effectively demonstrating the improved ability of scientists to swiftly obtain a rheological fingerprint of complex materials.

Published
2022

35. In Vivo Super Resolution Ultrasound Imaging using the Erythrocytes - SURE

Author

Jensen, Jorgen Arendt, primary, Schou, Mikkel, additional, Andersen, Sofie Bech, additional, Tomov, Borislav G., additional, Sogaard, Stinne Byrholdt, additional, Sorensen, Charlotte Mehlin, additional, Nielsen, Michael Bachmann, additional, Gundlach, Carsten, additional, Kjer, Hans Martin, additional, Dahl, Anders Bjorholm, additional, and Stuart, Matthias Bo, additional

Published
2022
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45. Faster Multi-Object Segmentation using Parallel Quadratic Pseudo-Boolean Optimization

Author

Niels Jeppesen, Patrick Møller Jensen, Anders Nymark Christensen, Anders Bjorholm Dahl, and Vedrana Andersen Dahl

Abstract

We introduce a parallel version of the Quadratic PseudoBoolean Optimization (QPBO) algorithm for solving binary optimization tasks, such as image segmentation. The original QPBO implementation by Kolmogorov and Rother relies on the Boykov-Kolmogorov (BK) maxflow/mincut algorithm and performs well for many image analysis tasks. However, the serial nature of their QPBO algorithm results in poor utilization of modern hardware. By redesigning the QPBO algorithm to work with parallel maxflow/mincut algorithms, we significantly reduce solve time of large optimization tasks. We compare our parallel QPBO implementation to other state-of-the-art solvers and benchmark them on two large segmentation tasks and a substantial set of small segmentation tasks. The results show that our parallel QPBO algorithm is over 20 times faster than the serial QPBO algorithm on the large tasks and over three times faster for the majority of the small tasks. Although we focus on image segmentation, our algorithm is generic and can be used for any QPBO problem. Our implementation and experimental results are available at DOI: 10.5281/zenodo.5201620

Published
2021

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