| 1. |
- Algaba-Brazalez, A., et al.
(författare)
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Compact Polarization Transformation in a Geodesic Luneburg Lens Antenna
- 2021
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Ingår i: 2021 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting, APS/URSI 2021 - Proceedings. - : Institute of Electrical and Electronics Engineers Inc.. ; , s. 1992-1993
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Konferensbidrag (refereegranskat)abstract
- This paper describes the design of a compact polarizer that rotates the linear polarization of a fully metallic geodesic Luneburg lens antenna for applications requiring polarization diversity. The polarization rotation is achieved by loading the radiating aperture of the antenna with two metallic screens. The integrated antenna operates in the Ka-band, from 25 to 31 GHz, showing around 20% bandwidth with S11 below -10 dB, and a scanning range of 100°.
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| 2. |
- Algaba-Brazalez, Astrid, et al.
(författare)
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Crossover level improvement between beams in a geodesic lens antenna based on a generalized Luneburg lens
- 2022
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Ingår i: 2022 16th European Conference on Antennas and Propagation (EuCAP). - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a geodesic generalized Luneburg lens operating in the 60-GHz band, from 57 to 67 GHz, designed with the goal to improve the crossover level between beams with respect to previously reported fully metallic Luneburg lenses, while providing highly directive beams and wide scanning coverage. We have combined the use of a generalized Luneburg lens and the design of a compact feeding type based on ridge waveguide in order to achieve an optimum crossover level between beams keeping in mind manufacturing simplicity. The numerical evaluation of the final integrated lens design including 21 ridge waveguide feeding ports shows a vertical bar S-11 vertical bar parameter below -13.6 dB over the frequency band of interest, a scanning range of +/- 52 degrees, a realized gain higher than 19 dBi over the whole operating bandwidth, and a crossover level value between -3.5 dB and -4.2 dB from the lowest to the highest frequency of operation.
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| 3. |
- Ben Henda, N., et al.
(författare)
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OpenSAW : Open security analysis workbench
- 2017
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Ingår i: 20th International Conference on Fundamental Approaches to Software Engineering, FASE 2017 Held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2017. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783662544938 ; , s. 321-337
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Konferensbidrag (refereegranskat)abstract
- Software is today often composed of many sourced componets, which potentially contain security vulnerabilities, and therefore require testing before being integrated. Tools for automated test case generation, for example, based on white-box fuzzing, are beneficial for this testing task. Such tools generally explore limitations of the specific underlying techniques for solving problems related to, for example, constraint solving, symbolic execution, search heuristics and execution trace extraction. In this article we describe the design of OpenSAW, a more flexible general-purpose white-box fuzzing framework intended to encourage research on new techniques identifying security problems. In addition, we have formalized two unaddressed technical aspects and devised new algorithms for these. The first relates to generalizing and combining different program exploration strategies, and the second relates to prioritizing execution traces. We have evaluated OpenSAW using both in-house and external programs and identified several bugs.
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| 4. |
- Castillo Tapia, Pilar, et al.
(författare)
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Azimuth and Elevation Scanning with Stacked Modulated Geodesic Luneburg Lenses
- 2022
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Ingår i: 2022 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 5-6
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Konferensbidrag (refereegranskat)abstract
- Here, we propose a modulated geodesic lens antenna array in E-band (56-62 GHz), which has scanning abilities in both azimuth and elevation. The array consists of four lens antenna elements, and each lens antenna produces 13 independent beams that cover 110 degrees in the H-plane with scan losses below 1 dB. The array is fed with a 1:4 power divider comprising three phase shifters to scan in the E-plane. The distance between lenses in the E-plane is 0.7 wavelengths at 60 GHz. The E-plane coverage is 60 degrees with scan losses around -2.2 dB. The maximum realized gain varies from 20.8 to 24.1 dB across the frequency band.
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| 5. |
- Castillo Tapia, Pilar, et al.
(författare)
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Two-Dimensional Beam Steering Using a Stacked Modulated Geodesic Luneburg Lens Array Antenna for 5G and Beyond
- 2023
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Ingår i: IEEE Transactions on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-926X .- 1558-2221. ; 71:1, s. 487-496
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Tidskriftsartikel (refereegranskat)abstract
- Antennas for future communication systems are required to be highly directive and steerable to compensate for the high path loss in the millimeter-wave band. In this work, we propose a linear array of modulated geodesic Luneburg lens (the so-called water drop lens) antennas operating at 56-62 GHz. The lens array antenna features 2-D beam scanning with low structural complexity. The lenses are fully metallic and implemented in parallel plate waveguides (PPWs), meaning that they are highly efficient. Each lens is fed with 13 rectangular waveguides surrounded by glide-symmetric holes to suppress leakage. The lenses provide 110? beam coverage in the H-plane with scan losses below 1 dB. In order to scan in the E-plane, we use a feeding network based on a 1:4 power divider and three phase shifters. In this configuration, the array can scan 60? in the E-plane, albeit with higher scanning losses than in the H-plane. The lens array is manufactured and a good agreement between simulated and experimental results is obtained.
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| 6. |
- Galván, Ignacio Fdez., et al.
(författare)
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OpenMolcas : From Source Code to Insight
- 2019
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 15:11, s. 5925-5964
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Tidskriftsartikel (refereegranskat)abstract
- In this Article we describe the OpenMolcas environment and invite the computational chemistry community to collaborate. The open-source project already includes a large number of new developments realized during the transition from the commercial MOLCAS product to the open-source platform. The paper initially describes the technical details of the new software development platform. This is followed by brief presentations of many new methods, implementations, and features of the OpenMolcas program suite. These developments include novel wave function methods such as stochastic complete active space self-consistent field, density matrix renormalization group (DMRG) methods, and hybrid multiconfigurational wave function and density functional theory models. Some of these implementations include an array of additional options and functionalities. The paper proceeds and describes developments related to explorations of potential energy surfaces. Here we present methods for the optimization of conical intersections, the simulation of adiabatic and nonadiabatic molecular dynamics, and interfaces to tools for semiclassical and quantum mechanical nuclear dynamics. Furthermore, the Article describes features unique to simulations of spectroscopic and magnetic phenomena such as the exact semiclassical description of the interaction between light and matter, various X-ray processes, magnetic circular dichroism, and properties. Finally, the paper describes a number of built-in and add-on features to support the OpenMolcas platform with postcalculation analysis and visualization, a multiscale simulation option using frozen-density embedding theory, and new electronic and muonic basis sets.
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| 7. |
- Jansson, Emil
(författare)
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Challenges with Driverless and Unattended Train Operations
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Demand for transportation continues to increase, for both freight and passenger services. One of the most energy-efficient modes of transportation is rail. One solution to increase the attractiveness of rail transport is to introduce automatic train operation (ATO) with a high grade of automation (GoA). Driverless and unattended train operation could entail positive effects but would also bring challenges when removing the train driver. Thus, there is a need to understand the role of train drivers, especially in unplanned events. The main research objectiveis to understand the train driver roles during unplanned events and the frequency of such events. This thesis includes three papers to fulfill the research objective.This thesis studied delay logs and trackside sensor logs. A qualitative method, thematic analysis, was used to identify themes of the roles performed by train driver from the delay logs. The chi-square test statistical method was used to analyze these trackside sensor logs.Six main categories of tasks for train drivers were identified for unplanned events. Detect, Report, Inspect, Adjust, Manage passengers, and Respond to train orders. Each category was analyzed for each grade of automation by giving the responsibility for each category. The results highlight in a novel way the varied challenges between grade of automation in mainline systems. Detecting abnormalities was the most common task train drivers performed during unplanned events. Train drivers use four human senses to detect abnormalities: sight, hearing, touch, and smell. This indicates the need for onboard sensors. However, the real challenge is in processing all sensor data to gain anaccurate evaluation of any fault. One specific type of unplanned event in which the train driver is needed involves trackside sensor alarms. Freight trains are ten times more likely to trip an alarm than passenger trains. Alarms are more frequent in colder climate zones during winter months. These differences are statistically significant and indicate that not all lines and train types might be suitable for a high grade of automation.If driverless or unattended train operation will become a reality in future, many challenges must be met. This thesis gives deeper understanding of these challenges using a novel way to identify and quantify train driver tasks during unplanned events.
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| 8. |
- Johansson, Ingrid, 1990-
(författare)
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Simulation Studies for Improved Efficiency in Road and Rail Freight Transports
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The demand for road and rail freight transport continues to grow with the expanding economy, while the climate crisis requires reduction in greenhouse gas emissions. Therefore, tools and solutions for reducing fossil fuel use and enabling more efficient use of infrastructure are needed. This thesis utilises microscopic and macroscopic traffic simulation as tools to improve certain aspects of road and rail transport planning in the operational, tactical, and strategic planning time horizons.For road freight transports conducted with heavy-duty vehicles, fuel consumption can be reduced by smarter driving. Strategic planning concerning introduction of intelligent and connected vehicles is needed, along with planning of actual vehicle operations. Microscopic road traffic simulation is utilised to show that heavy-duty vehicle platooning, which lowers the fuel consumption through reduced aerodynamic drag, can be conducted on two-lane highway stretches without disturbing surrounding traffic. Further, substantial reduction of the fuel consumption can be achieved by applying fuel-optimal deceleration trajectories, assuming available information about the traffic situation ahead.Shifting freight transports from roads to railways is another possible measure to reduce emissions. Previous simulation studies of railway traffic has mainly focused on passenger trains, combined with not including freight train departures before the scheduled timetable, even though it commonly occurs in Sweden. Therefore, both microscopic and macroscopic railway traffic simulation, with and without allowing early freight train departures, is conducted in a case study. The resulting freight train punctuality is closer to empirical punctuality when early departures are included.A modal shift from road to rail transport increases capacity utilisation of railway networks, and is only possible within available capacity. Therefore, reliable methods for capacity analysis are needed. A method for capacity analysis is introduced and evaluated, with particular focus on railway station analysis. An advantage of this method is it can be used in tactical and strategic planning of future timetables and infrastructure.
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| 9. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Nilsson, Anders K., 1982, et al.
(författare)
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Acylated monogalactosyl diacylglycerol : prevalence in the plant kingdom and identification of an enzyme catalyzing galactolipid head group acylation in Arabidopsis thaliana
- 2015
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Ingår i: The Plant Journal. - : Wiley-Blackwell. - 0960-7412 .- 1365-313X. ; 84:6, s. 1152-1166
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Tidskriftsartikel (refereegranskat)abstract
- The lipid phase of the thylakoid membrane is mainly composed of the galactolipids mono-and digalactosyl diacylglycerol (MGDG and DGDG, respectively). It has been known since the late 1960s that MGDG can be acylated with a third fatty acid to the galactose head group (acyl-MGDG) in plant leaf homogenates. In certain brassicaceous plants like Arabidopsis thaliana, the acyl-MGDG frequently incorporates oxidized fatty acids in the form of the jasmonic acid precursor 12-oxo-phytodienoic acid (OPDA). In the present study we further investigated the distribution of acylated and OPDA-containing galactolipids in the plant kingdom. While acyl-MGDG was found to be ubiquitous in green tissue of plants ranging from non-vascular plants to angiosperms, OPDA-containing galactolipids were only present in plants from a few genera. A candidate protein responsible for the acyl transfer was identified in Avena sativa (oat) leaf tissue using biochemical fractionation and proteomics. Knockout of the orthologous gene in A. thaliana resulted in an almost total elimination of the ability to form both non-oxidized and OPDA-containing acyl-MGDG. In addition, heterologous expression of the A. thaliana gene in E. coli demonstrated that the protein catalyzed acylation of MGDG. We thus demonstrate that a phylogenetically conserved enzyme is responsible for the accumulation of acyl-MGDG in A. thaliana. The activity of this enzyme in vivo is strongly enhanced by freezing damage and the hypersensitive response.
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