| 1. |
- Granlund, Daniel
(författare)
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On Mobility Solutions in Heterogeneous Networking Environments
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mobility support for users and devices, such as sensors, connecting to the Internet is a continuously growing trend. Different types of wireless networking technologies like WiFi, LTE, and ZigBee are available, creating a heterogeneous wireless networking environment. In general, the technology, ranging from network equipment to communications protocols, available today, tends to be designed with limited exibility when it comes to supporting heterogeneity. Proprietary technology and highly optimized mechanisms limit the potential use of networking infrastructure for multiple purposes. Supporting mobility for wireless devices between different networking technologies and administrative domains requires secure and scalable mobility management solutions. Current research in the field of mobility management and security in heterogeneous networking environment tends to handle mobility management performance, such as communications characteristics, and security related aspects as separate, and more or less mutually exclusive. The work presented in this thesis serves to challenge this trade-off and proposes solutions that seeks to brigde the gap between the two areas. This thesis proposes using an Authentication, Authorization and Accounting (AAA) system based on the RADIUS AAA protocol that enables a common AAA infrastructure to operate in a heterogeneous networking environment, and that enables a hierarchical interconnection structure between service providers. The proposed AAA architecture offers a highly scalable AAA infrastructure with access technology independent support for user and device authentication as well as mobility on a global scale. Further, to support handoffs between networks, a set of methods for facilitating improved handoff decisions for intra- and inter-operator mobility in heterogeneous networks are presented. These methods rely on metrics that include indicators on network load conditions to improve service stability and decrease application down time during handoff.Results show that the proposed AAA infrastructure can be built to scale in order to support a very large number of entities, more than 1000 user or device authentications per second, using industry standard hardware. Further, an AAA architecture compatible sensor authentication protocol is proposed, implemented, and validated that supports sensor mobility and reduces power consumption, on wireless sensor nodes, with 33% compared to state-of-the-art protocols by reducing CPU and communications overhead. Using the proposed mechanism for facilitating handos in wireless sensor networks, a reduction of 44% in packet loss is achived during a mobility session compared to a traditional solution.
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| 2. |
- Johansson, Maria
(författare)
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Perceptions of mathematics in preschool: "-Now we have a way of talking about the mathematics that we can work with"
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overarching question for this thesis is what is preschool mathematics? This question is examined using different points of views or different perspectives such as the children’s, the preschool teachers and the researchers. The foundation for this thesis is seven articles, two single author articles and five co-authored articles. The project described in this thesis developed out of my research interest and discussions in the research group of which I have been part.In the first article we use video recording to capture the typical situations that children are engaged in when they are at preschool. The videos were analysed in order to classify the mathematics in evidence according to Bishop’s six mathematical activities. This research activity raised the issue of whose perspective- the researcher, the preschool teacher or the children - was important when discussing what is preschool mathematics? The second article discusses the issue of whose perspective in more detail and introduces a methodological tool, the didaktic space to differentiate between the perspectives of the preschool teacher and children as identified by the researcher. The didaktic space makes it possible to simultaneously see the different perspectives separately but also together so the impact of the teacher and the children on the dynamic nature of the situation can be described. In the third article I investigate preschool teachers’ and child care staff’s (barnskötare) perception of mathematics in preschool using data from related professional development courses. The stories that the preschool teachers and childcare staff related as part of a final assignment in the courses were categorised using Bishop’s six mathematical activities. The result from this study shows that the perceptions of preschool teachers are not just on Counting, as is reported in earlier research, but on almost all of the six mathematical activities except for Playing. These results from the preschool teachers are then compared with the results from childcare staff. The childcare staff had more stories involving Counting but they also had more stories connected to Playing. This result led to the investigation discussed in the next article (article four) which was a theoretical discussion on Playing as a mathematical activity, with an empirical example used to highlight some of the issues. In this article, we compare different perspectives to identify the common features of mathematical play. The empirical example came from a video of children in a preschool class engaging in free play and allowed an identification of the mathematics which could be used by children when there is no adult present. In article five, I combine the discussions from the previous articles and focuses on why preschool teachers struggle to identify Playing as a mathematical activity in children’s interactions in preschools. The data come from a large professional development programme in which the preschool teachers read and discussed Playing as a mathematical activity. The results of the analysis suggest that the way that play is discussed as a basis for learning in the Swedish preschool curriculum could contribute to teachers having a professional blind spot in regard to Playing as a mathematical activity. Article six and seven provide insights into children’s perspectives about mathematics in preschools. The data used in these articles comes from the same project as the video used in article four recorded in a preschool class. The data from preschool class, described as the bridge between preschool and school in Swedish educational circles, allows the pedagogy used in preschools to be contrasted with that used in school. In article six we focus on the mathematical inclusion or exclusion that mathematical play provides when there is an adult present.In article seven we also focus on the mathematical inclusion or exclusion but now with comparing the independent play situation from article four with the teacher led situation in article six. The theoretical framework for article six and seven is Bernstein’s vertical and horizontal discourse. This change of theories was a response to the questions about how some children can become mathematically excluded which are issues of a socio-political nature.These different perceptions, children, teacher, researcher, and perspectives, descriptive, theoretical and socio-political, provide a deeper understanding of what preschool mathematics is, how it could be conceptualised and how it includes or excludes children from opportunities to learn. As a consequence of this extended investigation, it can be said in the words of one of the preschool teachers, “now we have a way of talking about the mathematics that we can work with”.
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| 3. |
- Mäkitalo, Maria
(författare)
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Green Liquor Dregs in Sealing Layers to Prevent the Formation of Acid Mine drainage : From characterization to implementation
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One of the mining industry’s main concerns is the management of waste rock and tailings generated by sulfide ore extraction. Upon exposure to atmospheric oxygen, iron sulfides oxidize producing acidity. In the absence of alkaline minerals to neutralize this acidity, elements including harmful heavy metals may be transported with percolated water, forming acid mine drainage (AMD). A common solution to prevent oxygen and water entering sulfide-bearing mine waste, thereby minimizing the formation of AMD, is to construct a dry cover comprised of soil. In Sweden, clayey till is often used. Due to a shortage of fine-grained till close to mines, other sealant materials must be considered. This thesis presents an alternative to the traditional materials used as sealing layers in dry covers. Green liquor dregs (GLD) are a residual waste originating from the recycling of chemicals in sulfate pulp mills. The objective was to evaluate the suitability of GLD for use in sealing layers for sulfidic mine waste. This was carried out by analyzing samples both in the laboratory and in the field in a pilot-scale study. GLD was characterized physically, mineralogically and chemically to determine variations in the properties of the material. Based on the characterization results, the difference between batches was small both mineralogically and physically. In addition, it had favorable qualities with respect to reducing water percolation and oxygen diffusion, as it exhibited low hydraulic conductivity and high water retention potential. However, the shear strength was insufficient for cover applications. In an attempt to improve shear strength, but also to reduce the amount of GLD to save transportation costs, fly ash, tailings and till were blended with GLD. All of these additives increased the shear strength. Humidity cell tests were used to study the effect of GLD on the mobility of elements found in the tailings that are considered to cause major environmental issues. They showed that the alkaline capacity of the GLD raised the pH, thereby stabilizing the tailings and reducing the leaching of Zn, Cd, Cu, Ni, Co and Cr. The amount of leached elements could be directly related to pH. Mo and As leaching increased as a result of the application of GLD. This is explained by the chemical behavior of these elements and their tendency to become mobile at high pH. Because covers on mine waste should be efficient over the long-term, the aging of GLD was studied with material ranging from 0-13 years old. Aged GLD showed a hydraulic conductivity of 10-8 m/s. This is not expected to affect the function of the sealing layer to minimize oxidation because older GLD exhibited a high water retention capacity and a degree of water saturation of >91%, which would effectively limit oxygen diffusion. Leaching, mainly of S and K, was observed but had no major effect on the hydraulic properties of the material. The effects of aging are largely related to the quantity of water passing through the GLD, thereby changing its chemical composition and, in the long term, its pH. An implementation study using GLD as an additive to improve the hydraulic properties of till in the construction of sealing layers in a cover system design was carried out. The results showed that the quality of till, i.e., hydraulic conductivity and water retention capacity, could be improved by the addition of GLD. Addition of 10% GLD was found to be sufficient to take full advantage of its hydraulic properties and sufficient compaction could be achieved. Based on the results, GLD is expected to be a viable alternative to traditional cover materials. The pilot-scale study, as well as a full-scale trial that is currently in progress, will be used to evaluate further the function of a GLD-based sealing layer.
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| 4. |
- Taher, Mamoun
(författare)
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Orthoborate Ionic Liquids for Lubricated Interfaces
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The lifespan and efficiency of various types of machinery is often limited by the performance of its lubricated interfaces, which are formed by two interacting surfaces and a lubricant that separates the surfaces to decrease friction and wear. There is a constant quest for more efficient lubricants capable of lubricating non-ferrous surfaces. Ionic liquids (ILs) possess many unusual physicochemical properties compared to molecular liquids including, but not limited to, high polarity, high conductivity, high thermal stability, and a wide liquid range. Such properties are essential for formulating lubricants for interfaces in challenging applications such as in aerospace and wind turbines. Some ILs have recently shown promising performance in lubricating lightweight non-ferrous alloys and hard coatings, among other materials. However, most of the widely studied ILs contain anions with fluorine, such as [BF4]- and [PF6]-, and are prone to hydrolysis, releasing toxic HF, among other corrosive products. In this work, we designed, synthesized, and thoroughly characterized a number of hydrophobic ILs based on halogen-free and hydrolytically-stable orthoborate anions and different classes of cations such as pyrrolidinium and imidazolium. The potential of these ILs to efficiently lubricate ferrous and non-ferrous interfaces was investigated.The work was planned and carried out through the following steps: Design, synthesis and purification of novel, halogen-free, boron-based ionic liquids (hf-BILs). Physicochemical characterization of the synthesized compounds by liquid-state (1H, 13C, and 11B) and solid-state (13C and 11B) nuclear magnetic resonance (NMR) spectroscopy, Karl Fischer titration, mass spectroscopy, elemental analysis, inductively coupled plasma mass spectrometry (ICP-MS), thermal analysis (TGA, DSC), powder X-ray diffraction, density and rheological measurements. Evaluation of their lubrication performance using ball-on-disc tribometers. Analysis of the lubricated surfaces using Scanning Electron Microscopy coupled with X-ray Energy Dispersive Spectroscopy (SEM/EDS) and a stylus profilometer.A detailed description of the results obtained for selected classes of ILs is given below: I. Nine novel ILs of N-alkyl-N-methylpyrrolidinium bis(salicylato)borate ([CnC1Pyrr][BScB]) were synthesized and physicochemically characterized. They are solids at room temperature and some of them behave as plastic crystals. Some of these compounds were tested as neat lubricants in steel-steel interfaces at 423 K, i.e., above their melting points. The tested compounds showed significantly better anti-wear and friction-reducing performance compared with 5W40 engine oil.II. Eight novel, room-temperature N-alkyl-N-methylpyrrolidinium bis(mandelato)borate ([CnC1Pyrr][BMB]) ILs were synthesized and physicochemically characterized. Their lubrication potential as 3 wt% additives in polyethylene glycol (PEG) was evaluated in steel-steel interfaces at room temperature. Considerably better anti-wear and friction-reducing properties were achieved when compared with neat PEG and 5W40 engine oil.III. Three novel, room-temperature 1-alkyl-3-methyl-imidazolium bis(mandelato)borate ([CnC1Im][BMB]) ILs were synthesized and physicochemically characterized.IV. A room-temperature trihexyltetradecylphosphonium bis(oxalato)borate [P6,6,6,14][BOB] IL, was evaluated as a neat lubricant for alumina-steel and sapphire-steel interfaces at room temperature. [P6,6,6,14][BOB] provided lower friction and wear compared with 5W40 engine oil.
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| 5. |
- Temirkhanova, Ainur
(författare)
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Estimates for Discrete Hardy-type Operators in Weighted Sequence Spaces
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This PhD thesis consists of an introduction and eight papers, which deal with questions of the validity of some new discrete Hardy type inequalities in weighted spaces of sequences and on the cone of non-negative monotone sequences, and their applications. In the introduction we give an overview of the area that serves as a frame for the rest of the thesis. In particular, a short description of the development of Hardy type inequalities is given. In Paper 1 we find necessary and sufficient conditions on weighted sequences $\omega_i$, $i=1, 2,...,n-1$, $u$ and $v$, for which the operator $$ (S_{n}f)_i=\sum\limits_{k_1=1}^i\omega_{1,k_1}\cdots\sum\limits_{k_{n-1}=1}^{k_{n-2}} \omega_{n-1,k_{n-1}}\sum\limits_{j=1}^{k_{n-1}}f_j,~~ i\geq 1,~~~~~(1) $$ is bounded from $l_{p,v}$ to $l_{q,u}$ for $1
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| 6. |
- Tephnadze, George
(författare)
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Martingale Hardy spaces and summability of the one dimensional Vilenkin-Fourier series
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The classical theory of Fourier series deals with decomposition of afunction into sinusoidal waves. Unlike these continuous waves the Vilenkin(Walsh) functions are rectangular waves. Such waves have already been usedfrequently in the theory of signal transmission, multiplexing, filtering,image enhancement, codic theory, digital signal processing and patternrecognition. The development of the theory of Vilenkin-Fourier series hasbeen strongly influenced by the classical theory of trigonometric series.Because of this it is inevitable to compare results of Vilenkin series tothose on trigonometric series. There are many similarities between thesetheories, but there exist differences also. Much of these can be explainedby modern abstract harmonic analysis, which studies orthonormal systems from thepoint of view of the structure of a topological group.In this PhD thesis we discuss, develop and apply this fascinating theoryconnected to modern harmonic analysis. In particular we make new estimationsof Vilenkin-Fourier coefficients and prove some new results concerningboundedness of maximal operators of partial sums. Moreover, we derivenecessary and sufficient conditions for the modulus of continuity so thatnorm convergence of the partial sums is valid and develop new methods toprove Hardy type inequalities for the partial sums with respect to theVilenkin systems. We also do the similar investigation for the Fej\'er means.Furthermore, we investigate some N\"orlund means but only in the case when their coefficients are monotone. Some well-know examples of N\"orlund means areFej\'er means, Ces\`aro means and N\"orlund logarithmic means. In addition, weconsider Riesz logarithmic means, which are not example of N\"orlundmeans. It is also proved that these results are the best possible in aspecial sense. As applications both some well-known and new results arepointed out.This PhD is written as a monograph consisting of four Chapters:Preliminaries, Fourier coefficients and partial sums of Vilenkin-Fourierseries on martingale Hardy spaces, Vilenkin-Fej\'er means onmartingale Hardy spaces, Vilenkin-N\"orlund means on martingale Hardyspaces. It is based on 15 papers with the candidate as author or coauthor,but also some new results are presented for the first time.In Chapter 1 we first present some definitions and notations, which arecrucial for our further investigations. After that we also define somesummabilitity methods and remind about some classical facts and results. We investigate some well-known results and prove new estimates for the kernels of these summabilitity methods, which are very important to prove our main results. Moreover, we define martingale Hardy spaces and construct martingales, which help us to prove sharpness of our main results in the later chapters.Chapter 2 is devoted to present and prove some new and known results about Vilenkin-Fourier coefficients and partial sums of martingales in Hardy spaces.First, we show that Fourier coefficients of martingales are not uniformly bounded when $0
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