| 1. |
- Kajko-Mattsson, Mira, et al.
(author)
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Refounding software engineering : The Semat initiative (Invited presentation)
- 2012
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In: Software Engineering (ICSE), 2012 34th International Conference on. - : IEEE Computer Society. - 9781467310673 ; , s. 1649-1650
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Conference paper (peer-reviewed)abstract
- The new software engineering initiative, Semat, is in the process of developing a kernel for software engineering that stands on a solid theoretical basis. So far, it has suggested a set of kernel elements for software engineering and basic language constructs for defining the elements and their usage. This paper describes a session during which Semat results and status will be presented. The presentation will be followed by a discussion panel.
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| 2. |
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| 3. |
- Adolfsson, Gundula
(author)
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Om recensenter och recensioner
- 1984
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In: Fornvännen. - 0015-7813 .- 1404-9430. ; , s. 196-197
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Journal article (other academic/artistic)
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| 4. |
- Bauwens, Luc, et al.
(author)
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On the econometrics of multivariate marked ultra-high-frequency data
- 2006
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Other publication (other academic/artistic)abstract
- In this paper we consider the modelling of multivariate marked ultra-high-frequency data. Such data consists, for example, of the trading times of several stocks together with the associated prices. We give an example how this kind of data may be modelled in the framework of marked point processes. The proposed model is a multivariate model for the trading times and the associated returns. We suggest a simple generalization of existing GARCH–type models for univariate ultra-high-frequency data to the multivariate setting. Preliminary remarks concerning the the stationarity of the proposed model are given, and maximum likelihood estimation is discussed.
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| 5. |
- Bauwens, Maite, et al.
(author)
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A Nonlinear Multi-Proxy Model Based on Manifold Learning to Reconstruct Water Temperature from High Resolution Trace Element Profiles in Biogenic Carbonates
- 2010
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In: Geoscientific Model Development. - : Copernicus Publications. - 1991-959X .- 1991-9603. ; 3:3, s. 653-667
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Journal article (peer-reviewed)abstract
- A long standing problem in paleoceanography concerns the reconstruction of water temperature from δ18O carbonate, which for freshwater influenced environments is hindered because the isotopic composition of the ambient water (related to salinity) affects the reconstructed temperature. In this paper we argue for the use of a nonlinear multi-proxy method called Weight Determination by Manifold Regularization to develop a temperature reconstruction model that is less sensitive to salinity variations. The motivation for using this type of model is twofold: Firstly, observed nonlinear relations between specific proxies and water temperature motivate the use of nonlinear models. Secondly, the use of multi-proxy models enables salinity related variations of a given temperature proxy to be explained by salinity-related information carried by a separate proxy. Our findings confirm that Mg/Ca is a powerful paleothermometer and highlight that reconstruction performance based on this proxy is improved significantly by combining its information with the information of other trace elements in multi-proxy models. Using Mg/Ca, Sr/Ca, Ba/Ca and Pb/Ca the WDMR model enabled a temperature reconstruction with a root mean squared error of ±2.19 °C for a salinity range between 15 and 32.
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| 6. |
- Bauwens, Maite, et al.
(author)
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On Climate Reconstruction using Bivalve Shells : Three Methods to interpret the Chemical Signature of a Shell
- 2010
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Reports (other academic/artistic)abstract
- The chemical composition of a bivalve shell is strongly coupled to the seasonal variations in the environment. The nonlinear nature of this relation however makes it hard to predict, e.g. the temperature, from the chemical composition of a shell. In this paper we compare the ability of three nonlinear system identification methods to reconstruct the temperature from the chemical composition of a shell. The comparison shows that nonlinear multi-proxy approaches are potential tools for climate reconstructions with a preference for manifold based methods that results in smoother and a more precise temperature reconstruction.
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| 7. |
- Bengtsson, Johan, 1971-
(author)
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Clocks, DBMs and States in Timed Systems
- 2002
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Doctoral thesis (other academic/artistic)abstract
- Today, computers are used to control various technical systems in our society. In many cases, time plays a crucial role in the operation of computers embedded in such systems. This thesis is about techniques and tools for the analysis of timing behaviours of computer systems. Its main contributions are in the development and implementation of UPPAAL, a tool designed to automate the analysis process of systems modelled as timed automata. As the first contribution, we present a software package for timing constraints represented as Difference Bound Matrices. We describe in details, all data-structures and operations for DBMs needed in state-space exploration of timed automata, as well as techniques for efficient implementation. In particular, we have developed two normalisation algorithms to guarantee termination of reachability analysis for timed automata containing constraints on clock differences, that transform DBMs according to not only maximal constants of clocks as in algorithms published in the literature, but also difference constraints appearing in the automata. The second contribution of this thesis is a collection of low level optimisations on the internal data-structures and algorithms of UPPAAL to minimise memory and time consumption. We present compression techniques to allow the state-space of a system to be efficiently stored and manipulated in main memory. We also study super-trace and hash-compaction methods for timed automata to deal with system-models for which the size of available memory is too small to store the explored state-space. Our experiments show that these techniques have greatly improved the performance of UPPAAL. The third contribution is in partial-order reduction techniques for timed-systems. A major problem in automatic verification is the large number of redundant states and transitions introduced by modelling concurrent events as interleaved transitions. We propose a notion of committed locations for timed automata. Committed locations are annotations that can be used for not only modelling of intermediate states within atomic transitions, but also guiding the model checker to ignore unnecessary interleavings in state-space exploration. The notion of committed locations has been generalised to give a local-time semantics for networks of timed automata, which allows for the application of existing partial order reduction techniques to timed systems.
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| 8. |
- Daurer, Benedikt J., et al.
(author)
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Experimental strategies for imaging bioparticles with femtosecond hard X-ray pulses
- 2017
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In: IUCrJ. - : INT UNION CRYSTALLOGRAPHY. - 2052-2525. ; 4, s. 251-262
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Journal article (peer-reviewed)abstract
- This study explores the capabilities of the Coherent X-ray Imaging Instrument at the Linac Coherent Light Source to image small biological samples. The weak signal from small samples puts a significant demand on the experiment. Aerosolized Omono River virus particles of similar to 40 nm in diameter were injected into the submicrometre X-ray focus at a reduced pressure. Diffraction patterns were recorded on two area detectors. The statistical nature of the measurements from many individual particles provided information about the intensity profile of the X-ray beam, phase variations in the wavefront and the size distribution of the injected particles. The results point to a wider than expected size distribution (from similar to 35 to similar to 300 nm in diameter). This is likely to be owing to nonvolatile contaminants from larger droplets during aerosolization and droplet evaporation. The results suggest that the concentration of nonvolatile contaminants and the ratio between the volumes of the initial droplet and the sample particles is critical in such studies. The maximum beam intensity in the focus was found to be 1.9 * 10(12) photons per mu m(2) per pulse. The full-width of the focus at half-maximum was estimated to be 500 nm (assuming 20% beamline transmission), and this width is larger than expected. Under these conditions, the diffraction signal from a sample-sized particle remained above the average background to a resolution of 4.25 nm. The results suggest that reducing the size of the initial droplets during aerosolization is necessary to bring small particles into the scope of detailed structural studies with X-ray lasers.
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| 9. |
- Fu, Zhang, 1982, et al.
(author)
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Managing your Trees: Insights from a Metropolitan-Scale Low-Power Wireless Network
- 2013
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Reports (other academic/artistic)abstract
- Low-power wireless, such as IEEE 802.15.4, is envisioned as one key technology for wireless control and communication.In the context of the Advanced Metering Infrastructure (AMI), it serves as an energy-efficient communication technology for both communications at building-scale networks and city-scale networks. Understanding real-world challenges and key properties of 802.15.4 based networks is an essential requirement for both the research community and practitioners:When deploying and operating low-power wireless networks at metropolitan-scale, a deep knowledge is essential to ensure network availability and performance at production-level quality.Similarly, researchers require realistic network models when developing new algorithms and protocols.In this paper, we present new and real-world insights from a deployed metropolitan-scale low-power wireless network:It includes 300,000 individual wireless sensors and cover a city with roughly 600,000 inhabitants.Our findings, for example, help to estimate real-world parameters such as the typical size of routing trees, their balance, and their dynamics over time.Moreover, these insights facilitate the understanding and the realistic calibration of simulation models in key properties such as reliability and throughput.
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| 10. |
- Gidofalvi, Gyözö, 1975-, et al.
(author)
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Frequent route based continuous moving object location- and density prediction on road networks
- 2011
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In: GIS '11 Proceedings of the 19th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems. - New York, NY, USA : ACM Press. - 9781450310314 ; , s. 381-384
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Conference paper (peer-reviewed)abstract
- Emerging trends in urban mobility have accelerated the need for effective traffic prediction and management systems. The present paper proposes a novel approach to using continuously streaming moving object trajectories for traffic prediction and management. The approach continuously performs three functions for streams of moving object positions in road networks: 1) management of current evolving trajectories, 2) incremental mining of closed frequent routes, and 3) prediction of near-future locations and densities based on 1) and 2). The approach is empirically evaluated on a large real-world data set of moving object trajectories, originating from a fleet of taxis, illustrating that detailed closed frequent routes can be efficiently discovered and used for prediction.
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