| 1. |
- Abadias, Gregory, et al.
(author)
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Preface
- 2020
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In: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 404
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Journal article (other academic/artistic)abstract
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| 2. |
- Abadie, J., et al.
(author)
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All-sky search for gravitational-wave bursts in the second joint LIGO-Virgo run
- 2012
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In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 85:12
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Journal article (peer-reviewed)abstract
- We present results from a search for gravitational-wave bursts in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operation, with a total observation time of 207 days. The analysis searches for transients of duration less than or similar to 1 s over the frequency band 64-5000 Hz, without other assumptions on the signal waveform, polarization, direction or occurrence time. All identified events are consistent with the expected accidental background. We set frequentist upper limits on the rate of gravitational-wave bursts by combining this search with the previous LIGO-Virgo search on the data collected between November 2005 and October 2007. The upper limit on the rate of strong gravitational-wave bursts at the Earth is 1.3 events per year at 90% confidence. We also present upper limits on source rate density per year and Mpc(3) for sample populations of standard-candle sources. As in the previous joint run, typical sensitivities of the search in terms of the root-sum-squared strain amplitude for these waveforms lie in the range similar to 5 x 10(-22) Hz(-1/2) to similar to 1 x 10(-20) Hz(-1/2). The combination of the two joint runs entails the most sensitive all-sky search for generic gravitational-wave bursts and synthesizes the results achieved by the initial generation of interferometric detectors.
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| 3. |
- Abadie, J., et al.
(author)
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Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts
- 2012
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In: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 539
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Journal article (peer-reviewed)abstract
- Aims. A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods. During two observing periods (Dec. 17, 2009 to Jan. 8, 2010 and Sep. 2 to Oct. 20, 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipeline's ability to reconstruct source positions correctly. Results. For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with similar to 50% or better probability with a few pointings of wide-field telescopes.
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| 4. |
- Grumert, Ellen F., 1983-
(author)
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Using Connected Vehicles in Variable Speed Limit Systems: : System Design and Effects
- 2018
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Doctoral thesis (other academic/artistic)abstract
- Motorway traffic management systems are useful for improving the traffic conditions on urban motorways. One of the most common motorway traffic management systems are variable speed limit systems. These systems adapt the speed limits based on the prevailing traffic conditions measured by roadside detectors and recommended or compulsory speed limits are shown on variable message signs installed on gantries over the road.Thesystems consist of three parts; the control algorithm used to determine which speed limit to be displayed, a method for estimating the traffic conditions to be used as input for the control algorithm and the infrastructure for application of the variable speed limits. The goal of the systems is often to increase safety or efficiency.Recent development in the field of connected vehicles have opened up for a new type of data source, as the status of a connected vehicle and its surroundings can be communicated at arbitrary locations. Hence, by the use of connected vehicles in variable speed limit systems there is a potential of reducing the amount of roadside equipment. It is even possible to control the connected vehicles towards the current speed limit without the use of variable message signs. This allows for the application of variable speed limits at arbitrary locations.The aim of this thesis is to examine how connected vehicles can be used to improve the efficiency of variable speed limit systems. The thesis contribute with new and improved methods using connected vehicles in all three parts of a variable speed limit system. The suggested methods are evaluated by microscopic traffic simulation. The overall conclusion is that the use of connected vehicles in variable speed limit systems can contribute to improvements in traffic efficiency compared to existing systems.The six papers included in the thesis can be summarized as follows. First, it is shown that traditional variable speed limit systems can be effective for improving the traffic conditions on the motorway and the results can be comparable to more costly alterations by reconstruction of the infrastructure to increase the capacity. Next, the usefulness of connected vehicles for application and control of the speed limits in an existing variable speed limit system is investigated. It is concluded that the design of the control algorithm and the accuracy of the estimated traffic conditions have a great effect on the final outcome of the system. The design of the control algorithm is then examined by evaluation of a number of control algorithms with respect to safety, efficiency and environmental impacts. The main benefits and drawbacks of the algorithms are highlighted and desirable characteristics to include when designing a control algorithm are identified. In two studies, methods making use of connected vehicles for estimating the traffic conditions are proposed. The results show that connected vehicles are useful for improving the accuracy of the estimated traffic conditions through the inclusion of more detailed information and information at locations where detector measurements are not available. Finally, a variable speed limit system is proposed in which connected vehicles play a central role in the estimation of the traffic conditions, as well as in the control algorithm and for application of the speed limit. The system is shown to be useful for improving traffic efficiency during an incident at an arbitrary location along the controlled road.
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| 5. |
- Bell, David
(author)
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Forest restoration guided by an umbrella species : will measures to protect the white-backed woodpecker benefit saproxylic beetles?
- 2015
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Licentiate thesis (other academic/artistic)abstract
- Management shortcuts in conservation biology, like the umbrella species concept, have been debated worldwide. Umbrella species have been used to identify and delineate protective areas, but habitat requirements of umbrella species can also provide tangible targets in ecological restoration. In Sweden, forest habitats have been restored for the white-backed woodpecker (WBW, Dendrocopos leucotos) under the assumption that it will benefit other habitat-associated (background) species. In this thesis, the umbrella species concept was evaluated based on the response of wood-inhabiting (saproxylic) beetles to forest restoration for the WBW. The WBW is a top-predator in saproxylic food webs associated with broadleaved trees, but it is also critically endangered in Sweden because of commercial forestry practices that disadvantage broadleaved trees and reduce dead wood availability. Spruce trees (Norway spruce, Picea abies) were selectively harvested during forest restoration to make way for broadleaved trees like birch (Betula spp.) and European aspen (Populus tremula). Some broadleaved trees were also killed to create high-stumps (snags) and downed logs. Commercially managed forests were compared with restored forests; either directly in comparative studies, or before and after forest restoration. Two types of flight-intercept traps were used to catch saproxylic beetles: IBL2-traps and trunk-window traps. Results presented in this thesis show that habitat requirements of an umbrella species can be used to guide forest restoration. There were many beneficiary species at the stand-level. Commercially managed and restored forests were inhabited by different communities of saproxylic beetles, and species positively associated with broadleaved trees and sun-exposed substrates were particularly responsive. This was reflected by an increased species richness and abundance. Several near-threatened and vulnerable species were also attracted to substrates created for the WBW. This shows that efforts to bring back the WBW can benefit other resource-limited groups of conservation concern. Saproxylic beetles might even facilitate restoration efforts since many important prey species for the WBW were attracted to restored sites. Umbrella species, like the WBW, will require landscape-level efforts to recover. This is a strength of the umbrella species concept, but also a weakness since landscape-level efforts are time consuming. The WBW is still struggling in Sweden, and failed attempts to re-establish viable populations might undermine conservation incentives. Early signs of progress, however, are sometimes provided by less demanding species, like many saproxylic beetles in this thesis. Background species can also provide much needed examples of restoration success at the stand-level.
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| 6. |
- Grumert, Ellen
(author)
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Cooperative Variable Speed Limit Systems : Modeling and Evaluation using Microscopic Traffic Simulation
- 2014
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Licentiate thesis (other academic/artistic)abstract
- During the last decades the road traffic has increased tremendously leading to congestion, safety issues and increased environmental impacts. As a result, many countries are continuously trying to find improvements and new solutions to solve these issues. One way of improving the traffic conditions is by the use of so called intelligent transport systems, where information and communication technologies are being used for traffic management and control. One such system commonly used for traffic management purposes are variable speed limit systems. These systems are making use of signs to show speed limits adjusted to the prevailing road or traffic conditions. The rapid development in telecommunication technologies has enabled communication between vehicles, and between vehicles and the infrastructure, so called cooperative systems. This opens up for the possibility to further improve the performance of a standard variable speed limit system by adding cooperative system features.The overall aim of this thesis is to investigate the potential benefits of incorporating infrastructure to vehicle communication and autonomous control to an existing variable speed limit system. We show how such a cooperative variable speed limit system can be modeled and evaluated by the use of microscopic traffic simulation. Results from the evaluation indicate increased flow harmonization in terms of narrowing of the acceleration rate distribution and reduced exhaust emissions.Further, we compare four control algorithms for deciding on speed limits in variable speed limit systems. Differences in the resulting traffic performance between the control algorithms are quantified by the use of microscopic traffic simulation. It is concluded that the dened objective for the algorithms have a decisive influence on the effects of the variable speed limit system.The results from this thesis are useful for further development of variable speed limit systems, both with respect to incorporating cooperative features and by improving the speed setting control algorithms.
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| 7. |
- Ni, Peiyuan, et al.
(author)
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A Kinetic Model of Mass Transfer and Chemical Reactions at a Steel/Slag Interface under Effect of Interfacial Tensions
- 2019
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In: ISIJ International. - : IRON STEEL INST JAPAN KEIDANREN KAIKAN. - 0915-1559 .- 1347-5460. ; 59:5, s. 737-748
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Journal article (peer-reviewed)abstract
- A new kinetic model was developed to predict the dynamic change of the interfacial oxygen content and the steel/slag interfacial tension. This model mainly describes the following interfacial physicochemical phenomena: i) Silica decomposition and oxygen adsorption at the interface, ii) Oxygen and aluminum reactions at the interface, iii) Oxygen desorption from the interface, iv) Silica mass transfer from the slag to the interface, v) Dissolution of the formed alumina into the slag and its transfer in slag and vi) Blockage on the silica mass transfer, to come in contact with the steel, by the accumulation of the formed alumina at the interface. With this model, the dynamic changes of the interfacial oxygen contents under different aluminum contents in steel and different slag viscosities were predicted. Overall, the interfacial oxygen content was found to increase with a decreased aluminum content and a decreased slag viscosity. Furthermore, the aluminum reaction rate can significantly influence the interfacial oxygen content as well as the interfacial tension. In addition, the model captured the fast increase of the interfacial tension after passing the minimum value point for the system of a high -Al content steel and a low viscous slag, which is in agreement with the experimental observations. Furthermore, a parameter study was carried out to show the influence of various parameters on the dynamic interfacial phenomena.
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| 8. |
- Drobyshev, Igor, et al.
(author)
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Lifespan and mortality of old oaks - combining empirical and modelling approaches to support their management in Southern Sweden
- 2008
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In: Annals of Forest Science. - : Springer Science and Business Media LLC. - 1286-4560 .- 1297-966X. ; 65:4, s. 401-401
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Journal article (peer-reviewed)abstract
- Old oaks (Quercus robur L.) play an important role in the southern Scandinavian landscape by providing habitat for a wide range of species, a large proportion of them being currently on the National Redlists. To provide support for the management of these trees, we review data on oak mortality and formulate a mortality-driven stochastic model analysing interactions between mortality rate, oak recruitment rate into 100-150 age class, and amount of oaks older than 200 years. Empirical annual mortality rates varied between 0 and 13% with average 1.68%. Trees older 200 years had an average mortality rate of 1.1%. Oaks in the high density forests showed higher mortality (3.2%) as compared to the trees growing in the low density forests (1.2%). A 400-year long modelling exercises indicated that under current mortality rates (regular mortality being centred around 1% annually; and irregular mortality 7% with average return time of 13 years) the long-term maintenance of 20 trees older than 200 years per ha would require an input rate of 1 to 5 trees x year(-1) x ha(-1) into the 100-150 years old class. The modelling highlighted the importance of initial oak abundance affecting amount of old trees at the end of shorter (100 years) simulation period.
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| 9. |
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