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- Abola, Benard
(author)
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Perturbed Markov Chains with Damping Component and Information Networks
- 2020
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Doctoral thesis (other academic/artistic)abstract
- This thesis brings together three thematic topics, PageRank of evolving tree graphs, stopping criteria for ranks and perturbed Markov chains with damping component. The commonality in these topics is their focus on ranking problems in information networks. In the fields of science and engineering, information networks are interesting from both practical and theoretical perspectives. The fascinating property of networks is their applicability in analysing broad spectrum of problems and well established mathematical objects. One of the most common algorithms in networks' analysis is PageRank. It was developed for web pages’ ranking and now serves as a tool for identifying important vertices as well as studying characteristics of real-world systems in several areas of applications. Despite numerous successes of the algorithm in real life, the analysis of information networks is still challenging. Specifically, when the system experiences changes in vertices /edges or it is not strongly connected or when a damping stochastic matrix and a damping factor are added to an information matrix. For these reasons, extending existing or developing methods to understand such complex networks is necessary.Chapter 2 of this thesis focuses on information networks with no bidirectional interaction. They are commonly encountered in ecological systems, number theory and security systems. We consider certain specific changes in a network and describe how the corresponding information matrix can be updated as well as PageRank scores. Specifically, we consider the graph partitioned into levels of vertices and describe how PageRank is updated as the network evolves.In Chapter 3, we review different stopping criteria used in solving a linear system of equations and investigate each stopping criterion against some classical iterative methods. Also, we explore whether clustering algorithms may be used as stopping criteria.Chapter 4 focuses on perturbed Markov chains commonly used for the description of information networks. In such models, the transition matrix of an information Markov chain is usually regularised and approximated by a stochastic (Google type) matrix. Stationary distribution of the stochastic matrix is equivalent to PageRank, which is very important for ranking of vertices in information networks. Determining stationary probabilities and related characteristics of singularly perturbed Markov chains is complicated; leave alone the choice of regularisation parameter. We use the procedure of artificial regeneration for the perturbed Markov chain with the matrix of transition probabilities and coupling methods. We obtain ergodic theorems, in the form of asymptotic relations. We also derive explicit upper bounds for the rate of convergence in ergodic relations. Finally, we illustrate these results with numerical examples.
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| 2. |
- Barac, Filip, et al.
(author)
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Channel Coding and Interleaving in Industrial WSN : Abiding to Timing Constraints and Bit Error Nature
- 2013
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In: Proceedings - M and N 2013: 2013 IEEE International Workshop on Measurements and Networking. - 9781467328739 ; , s. 46-51
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Conference paper (peer-reviewed)abstract
- Forward Error Correction is a preemptive manner of improving communication reliability. Albeit not a part of IEEE 802.15.4-2006 standard, its application in Industrial Wireless Sensor Networks has been widely considered. Nevertheless, this study is the first performance analysis on real error traces with sufficiently lightweight channel codes, with respect to IEEE 802.15.4-2006 and industrial wireless communication timing constraints. Based on these constraints and bit error properties from the collected traces, the use of Reed-Solomon (15,7) block code is suggested, which can be implemented in software. Experiments show that bit error nature on links affected by multipath fading and attenuation in industrial environments is such that RS(15,7) can correct ≥95% of erroneously received packets, without the necessity for interleaving. On links under IEEE 802.11 interference, typically up to 50% of corrupted packets can be recovered by combining RS(15,7) with symbol interleaving, which has proven to be more effective than its bit counterpart. The optimal interleaving depth is found empirically and it is shown that simple bit-interleaved 1/3 repetition code achieves at least 90% of correcting performance of RS(15,7) code on uninterfered links that operate ≥10 dB above the sensitivity threshold.
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| 3. |
- Blanksvärd, Thomas
(author)
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Mechanical properties of different geometries of CFRP grid : tensile evaluation of material properties
- 2006
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Reports (other academic/artistic)abstract
- There are a number of components included in strengthening of concrete with mineral based composites; base concrete that is in need of strengthening, primers, polymer modified cement bonding agents and carbon fibre reinforced polymers (CFRP). CFRP are light weight composites of carbon fibres imbedded in a matrix that can be tailor-made into different geometries. This report is a part of an ongoing evaluation of a concrete strengthening technique using mineral based composites. This report was done to evaluate the tensile properties of different CFRP grids included in strengthening of concrete with mineral based composites. The experimental test set-up was performed as pure tensile of smaller parts of the different grids. The main mechanical properties presented in the report are failure stress, modulus of elasticity and failure strain. The result was compared to the values provided by the manufacturer. In the results no clear trends was evident between the experimental values and the manufacturer values. In the results it can be concluded that the mechanical properties provided by the manufacturer can not be used as design values. The experimental values were both higher and lower than the manufacturer values for the failure stress and modulus of elasticity. Different failure types of the grids are illustrated in the report.
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| 5. |
- Van Couvering, Elizabeth, 1969-
(author)
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Faces and charts : platform strategies for visualising the audience, the case of Facebook
- 2022
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In: Information, Communication and Society. - : Taylor & Francis. - 1369-118X .- 1468-4462. ; 25:11, s. 1524-1541
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Journal article (peer-reviewed)abstract
- Although the audience as an industrial media product has been scrutinised by scholars for decades, the visual presentation of the audience has been nearly absent from scholarly analysis. This article examines the interfaces that Facebook uses to present its audience to three different user groups (ordinary Facebook members, publishers, and finally advertisers) using a social semiotic analytical framework to analyse visuals, interactive elements and desired user paths. The interface displayed to ordinary users, the Facebook Friends page, uses a visual language with roots in the college yearbook, showing rows of faces with minimal available interactivity. This interface preserves the humanity of the audience, suggesting egalitarian social structures and timeless space outside Facebook's ordinary flow. The interfaces displayed to institutional users, Page Insights and Audience Insights, for publishers and advertisers respectively, are quite different, characterised by a multiplicity of charts and high interactivity, with a clear path for the user that ends in 'boosting' your page or 'buying' your audience. The Audience Insights pages for advertisers feature advanced interactive tools which use the conventions of experimental science. These two interfaces do significant rhetorical work, dehumanising and abstracting audiences into data quantities which can be packaged as products, and encouraging publishers to focus on the production of data measuring engagement. Both the promotion of the value of data and the elision of audience work and surveillance, graphically represented in the different interfaces, help platform businesses like Facebook strategically, by increasing the value of their data and by suppressing audience concerns about surveillance.
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