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  • Ojalammi, Sanna (Helsingin yliopisto, 2006)
    This study Contested Lands: Land disputes in semi-arid parts of northern Tanzania. Case Studies of the Loliondo and Sale Division in the Ngorongoro District concentrates on describing the specific land disputes which took place in the 1990s in the Loliondo and Sale Divisions of the Ngorongoro District in northern Tanzania. The study shows the territorial and historical transformation of territories and property and their relation to the land disputes of the 1990s'. It was assumed that land disputes have been firstly linked to changing spatiality due to the zoning policies of the State territoriality and, secondly, they can be related to the State control of property where the ownership of land property has been redefined through statutory laws. In the analysis of the land disputes issues such as use of territoriality, boundary construction and property claims, in geographical space, are highlighted. Generally, from the 1980s onwards, increases in human population within both Divisions have put pressure on land/resources. This has led to the increased control of land/resource, to the construction of boundaries and finally to formalized land rights on village lands of the Loliondo Division. The land disputes have thus been linked to the use of legal power and to the re-creation of the boundary (informal or formal) either by the Maasai or the Sonjo on the Loliondo and Sale village lands. In Loliondo Division land disputes have been resource-based and related to multiple allocations of land or game resource concessions. Land disputes became clearly political and legal struggles with an ecological reference.Land disputes were stimulated when the common land/resource rights on village lands of the Maasai pastoralists became regulated and insecure. The analysis of past land disputes showed that space-place tensions on village lands can be presented as a platform on which spatial and property issues with complex power relations have been debated. The reduction of future land disputes will succeed only when/if local property rights to land and resources are acknowledged, especially in rural lands of the Tanzanian State.
  • Bhattacharya, Sourav (Helsingin yliopisto, 2014)
    In this thesis we develop novel methods for continuous and sustained context inference on mobile platforms. We address challenges present in real-world deployment of two popular context recognition tasks within ubiquitous computing and mobile sensing, namely localization and activity recognition. In the first part of the thesis, we provide a new localization algorithm for mobile devices using the existing GSM communication infrastructures, and then propose a solution for energy-efficient and robust tracking on mobile devices that are equipped with sensors such as GPS, compass, and accelerometer. In the second part of the thesis we propose a novel sparse-coding-based activity recognition framework that mitigates the time-consuming and costly bootstrapping process of activity recognizers employing supervised learning. The framework uses a vast amount of unlabeled data to automatically learn a sensor data representation through a set of extracted characteristic patterns and generalizes well across activity domains and sensor modalities.
  • Liao, Li (Helsingin yliopisto, 2014)
    Atmospheric aerosol particles influence the Earth's climate system, affect air visibility, and harm human health. Aerosol particles originate from both anthropogenic and biogenic sources, either from direct emissions or secondary particle formation. Secondary particle formation from gas phase precursors constitutes the largest fraction of global aerosol budget, yet large uncertainties remain in its mechanisms. This thesis attempted to study the source, the formation mechanisms, and the sink of secondary particles based on data analysis of field measurements and chamber experiments. In addition, numerical simulations were performed to model the processes of secondary particle formation observed in the chamber experiments. We summarized our findings into five main conclusions: 1) Monoterpenes originated from anthropogenic sources (e.g. forest industry) can significantly elevate the local average concentrations and result in a corresponding increase in local aerosol loading; 2) Monoterpenes from biogenic emissions show direct link to secondary particle production: the secondary aerosol masses correlate well with the accumulated monoterpene emissions; 3) Temperature influences biogenic monoterpene emissions, resulting in an indirect effect on the biogenic secondary particle production and corresponding cloud condensation nuclei (CCN) formation; 4) Both data analysis and numerical simulation suggested that nucleation involving the oxidation products of biogenic volatile organic compounds (VOCs) and H2SO4 better explains the nucleation mechanism, yet the specific VOCs participating in the nucleation process remains uncertain; 5) The numerical simulation showed evidence of vapor wall loss effect on the yield of secondary particles from the chamber experiments; a reversible gas-wall partitioning had to be considered to properly capture the observed temporal evolution of particle number size distribution during the chamber experiments. The results of this thesis contribute to the understanding on the role of monoterpenes to secondary particle formation. This thesis raises caution on the parameterization of the temperature dependence of biogenic secondary particle formation in predicting the aerosol production potential due to rising temperatures in the future. This work also points out a way for improving the comprehensive numerical models to better understand the secondary particle formation processes and related climatic effects.
  • Kuusisto-Hjort, Paula (Helsingin yliopisto, 2009)
    Contamination of urban streams is a rising topic worldwide, but the assessment and investigation of stormwater induced contamination is limited by the high amount of water quality data needed to obtain reliable results. In this study, stream bed sediments were studied to determine their contamination degree and their applicability in monitoring aquatic metal contamination in urban areas. The interpretation of sedimentary metal concentrations is, however, not straightforward, since the concentrations commonly show spatial and temporal variations as a response to natural processes. The variations of and controls on metal concentrations were examined at different scales to increase the understanding of the usefulness of sediment metal concentrations in detecting anthropogenic metal contamination patterns. The acid extractable concentrations of Zn, Cu, Pb and Cd were determined from the surface sediments and water of small streams in the Helsinki Metropolitan region, southern Finland. The data consists of two datasets: sediment samples from 53 sites located in the catchment of the Stream Gräsanoja and sediment and water samples from 67 independent catchments scattered around the metropolitan region. Moreover, the sediment samples were analyzed for their physical and chemical composition (e.g. total organic carbon, clay-%, Al, Li, Fe, Mn) and the speciation of metals (in the dataset of the Stream Gräsanoja). The metal concentrations revealed that the stream sediments were moderately contaminated and caused no immediate threat to the biota. However, at some sites the sediments appeared to be polluted with Cu or Zn. The metal concentrations increased with increasing intensity of urbanization, but site specific factors, such as point sources, were responsible for the occurrence of the highest metal concentrations. The sediment analyses revealed, thus a need for more detailed studies on the processes and factors that cause the hot spot metal concentrations. The sediment composition and metal speciation analyses indicated that organic matter is a very strong indirect control on metal concentrations, and it should be accounted for when studying anthropogenic metal contamination patterns. The fine-scale spatial and temporal variations of metal concentrations were low enough to allow meaningful interpretation of substantial metal concentration differences between sites. Furthermore, the metal concentrations in the stream bed sediments were correlated with the urbanization of the catchment better than the total metal concentrations in the water phase. These results suggest that stream sediments show true potential for wider use in detecting the spatial differences in metal contamination of urban streams. Consequently, using the sediment approach regional estimates of the stormwater related metal contamination could be obtained fairly cost-effectively, and the stability and reliability of results would be higher compared to analyses of single water samples. Nevertheless, water samples are essential in analysing the dissolved concentrations of metals, momentary discharges from point sources in particular.
  • Talponen, Jarno (Helsingin yliopisto, 2008)
    The topic of this dissertation is the geometric and isometric theory of Banach spaces. This work is motivated by the known Banach-Mazur rotation problem, which asks whether each transitive separable Banach space is isometrically a Hilbert space. A Banach space X is said to be transitive if the isometry group of X acts transitively on the unit sphere of X. In fact, some weaker symmetry conditions than transitivity are studied in the dissertation. One such condition is an almost isometric version of transitivity. Another investigated condition is convex-transitivity, which requires that the closed convex hull of the orbit of any point of the unit sphere under the rotation group is the whole unit ball. Following the tradition developed around the rotation problem, some contemporary problems are studied. Namely, we attempt to characterize Hilbert spaces by using convex-transitivity together with the existence of a 1-dimensional bicontractive projection on the space, and some mild geometric assumptions. The convex-transitivity of some vector-valued function spaces is studied as well. The thesis also touches convex-transitivity of Banach lattices and resembling geometric cases.
  • Ahmad, Jahir Uddin (Helsingin yliopisto, 2012)
    The oxidation of alcohols to the corresponding carbonyl compounds is a key reaction in the synthesis of organic chemicals. Consequently, a vast number of diverse methods based on copper that accomplish this functional group transformation are reviewed in this work. A successful development from pressurized oxygen to open air and from organic to environmentally friendly water solvent in oxidation of alcohols to the corresponding carbonyl compounds catalyzed by copper is presented. The first direct organocatalytic oxidation of alcohols to aldehydes with O2 in alkaline water was developed. One of the effects metal ions on the reaction was that the Cu ion is the most beneficial recipient of quantitative oxidation. Thus aerobic oxidation of alcohols to the corresponding carbonyl compounds catalyzed by TEMPO/Cu 2 N arylpyrrolecarbaldimine in alkaline water was discovered. The solid and solution structures of sterically hindered salicylaldimine and cis trans isomers of the corresponding Cu(II) complexes are discussed. High yield synthetic routes for mixed ligand Cu(II) complexes derived from salicylaldehyde and the corresponding salicylaldimine were developed. New crystal structures of the above compounds were determined by X ray crystallography. The catalytic property of homo and heteroligated bis(phenoxidoyimino)Cu(II)complexes toward oxidation reactions were investigated. Accordingly, facile base free aerobic oxidations of alcohols to aldehydes and ketones in toluene using low loading of both TEMPO and catalysts under mild conditions were introduced. In addition to the aerobic catalytic methods, oxidation of alcohols to the corresponding carbonyl compounds with H2O2 as an end oxidant in pure water using simple CuSO4 as a catalyst is presented. The effect of various additives, such as acids or bases, radical scavengers and N containing ligands, on the efficiency/selectivity of the catalyst system was studied as well. Finally, highly efficient open air oxidation of alcohols in water catalyzed by in situ made Cu(II) phenoxyimine complexes without additional auxiliarities such as base or co solvent are described.
  • Elers, Kai-Erik (Helsingin yliopisto, 2008)
    Transfer from aluminum to copper metallization and decreasing feature size of integrated circuit devices generated a need for new diffusion barrier process. Copper metallization comprised entirely new process flow with new materials such as low-k insulators and etch stoppers, which made the diffusion barrier integration demanding. Atomic Layer Deposition technique was seen as one of the most promising techniques to deposit copper diffusion barrier for future devices. Atomic Layer Deposition technique was utilized to deposit titanium nitride, tungsten nitride, and tungsten nitride carbide diffusion barriers. Titanium nitride was deposited with a conventional process, and also with new in situ reduction process where titanium metal was used as a reducing agent. Tungsten nitride was deposited with a well-known process from tungsten hexafluoride and ammonia, but tungsten nitride carbide as a new material required a new process chemistry. In addition to material properties, the process integration for the copper metallization was studied making compatibility experiments on different surface materials. Based on these studies, titanium nitride and tungsten nitride processes were found to be incompatible with copper metal. However, tungsten nitride carbide film was compatible with copper and exhibited the most promising properties to be integrated for the copper metallization scheme. The process scale-up on 300 mm wafer comprised extensive film uniformity studies, which improved understanding of non-uniformity sources of the ALD growth and the process-specific requirements for the ALD reactor design. Based on these studies, it was discovered that the TiN process from titanium tetrachloride and ammonia required the reactor design of perpendicular flow for successful scale-up. The copper metallization scheme also includes process steps of the copper oxide reduction prior to the barrier deposition and the copper seed deposition prior to the copper metal deposition. Easy and simple copper oxide reduction process was developed, where the substrate was exposed gaseous reducing agent under vacuum and at elevated temperature. Because the reduction was observed efficient enough to reduce thick copper oxide film, the process was considered also as an alternative method to make the copper seed film via copper oxide reduction.
  • Harun-or-Rashid, S M (Helsingin yliopisto, 2001)
  • Sloth, Martin Snoager (Helsingin yliopisto, 2003)
  • Apiola, Mikko (Helsingin yliopisto, 2013)
    It is known that students' learning approaches, types of motivation, and types of self-regulation are connected with learning outcomes. It is also known, that deep learning approaches, self-regulated learning, and intrinsic types of motivation are connected with creativity. However, in computing pedagogy there is a lack in empirically grounded analyses in integration of the varying educational theories to build learning environments that support creativity. The literature of programming education proposes a variety of theoretical, as well as practical viewpoints in relation to the teaching and learning situation. However, little effort has been put on understanding cultural and contextual differences in pedagogy of programming. Literature shows that education is highly context dependent, and that educational design should account for contextual differences. In programming education, the nature and implications of those differences are hitherto unclear. In this study, the paucity in research about creativity-supporting learning environments in computing education, and about contextual differences in the pedagogy of programming are addressed through two case studies. In the first context (CUH) of this study (Department of Computer Science, University of Helsinki, Finland), a method of learning-by-inventing was designed and integrated into a robotics-based programming class, and its effects on students' learning were investigated through qualitative analysis of 144 interviews. In the second context (CTU) of this study (IT Department, Tumaini University, Iringa University College, Iringa, Tanzania) a number of interventions for supporting intrinsic motivation and deep approaches to learning were designed, and their effects on students' learning were studied through qualitative and quantitative methods, and a controlled research setup. In addition, a mixed methods study about contextual factors, which affect the learning environment design was conducted. In context CUH, the results show that the provided environment supported the learning of creative processes through a number of mechanisms. In general, the provided environment was shown to facilitate changes in students' problem management approaches, and extended students' deep and surface learning approaches to computer science related problem solving and problem management. In context CTU the results reveal that students face many similar challenges than students in other educational contexts, and that the standard learning environment does not offer enough support for gaining the requisite development. Learning is also hindered by many contextually unique factors. Testing a model where students work on their homework under guidance, facilitated by active student-teacher collaboration did not result in significant advantage over the control group. However, the qualitative results about guided environments were exclusively positive. In context CUH, the analysis suggests that learning of creativity may be facilitated by supporting deep learning strategies, intrinsic motivation, and self-regulated learning through utilizing a combination of open learning environment configuration, learning-by-inventing, and robotics as the vehicle for learning. Secondly, the analysis suggests challenges in context CTU to be addressed through increasing the number of practical exercises, by selecting the proper amount of guidance required in the learning environment, and by implementing educational action research as a standard component into the learning and teaching environment.
  • Daniel, Laila (Helsingin yliopisto, 2010)
    The ever expanding growth of the wireless access to the Internet in recent years has led to the proliferation of wireless and mobile devices to connect to the Internet. This has created the possibility of mobile devices equipped with multiple radio interfaces to connect to the Internet using any of several wireless access network technologies such as GPRS, WLAN and WiMAX in order to get the connectivity best suited for the application. These access networks are highly heterogeneous and they vary widely in their characteristics such as bandwidth, propagation delay and geographical coverage. The mechanism by which a mobile device switches between these access networks during an ongoing connection is referred to as vertical handoff and it often results in an abrupt and significant change in the access link characteristics. The most common Internet applications such as Web browsing and e-mail make use of the Transmission Control Protocol (TCP) as their transport protocol and the behaviour of TCP depends on the end-to-end path characteristics such as bandwidth and round-trip time (RTT). As the wireless access link is most likely the bottleneck of a TCP end-to-end path, the abrupt changes in the link characteristics due to a vertical handoff may affect TCP behaviour adversely degrading the performance of the application. The focus of this thesis is to study the effect of a vertical handoff on TCP behaviour and to propose algorithms that improve the handoff behaviour of TCP using cross-layer information about the changes in the access link characteristics. We begin this study by identifying the various problems of TCP due to a vertical handoff based on extensive simulation experiments. We use this study as a basis to develop cross-layer assisted TCP algorithms in handoff scenarios involving GPRS and WLAN access networks. We then extend the scope of the study by developing cross-layer assisted TCP algorithms in a broader context applicable to a wide range of bandwidth and delay changes during a handoff. And finally, the algorithms developed here are shown to be easily extendable to the multiple-TCP flow scenario. We evaluate the proposed algorithms by comparison with standard TCP (TCP SACK) and show that the proposed algorithms are effective in improving TCP behavior in vertical handoff involving a wide range of bandwidth and delay of the access networks. Our algorithms are easy to implement in real systems and they involve modifications to the TCP sender algorithm only. The proposed algorithms are conservative in nature and they do not adversely affect the performance of TCP in the absence of cross-layer information.
  • Veikkolainen, Toni (Helsingin yliopisto, 2014)
    A branch of science concentrated on studying the evolution of the Earth's magnetic field has emerged in the last half century. This is called paleomagnetism, and its applications include calculations of field directions and intensity in the past, plate tectonic reconstructions, variations in the conditions in the Earth s deep interior and the climatic history. With the increasing quantity and quality of observations, it has been even possible to construct models of conterminous continent blocks, or supercontinents, of the Pre-Pangaea time. These are crucial for the understanding of the evolution of our planet from the Archean to today. Paleomagnetists have traditionally heavily relied on the theory that when averaged over a period long enough, the Earth s magnetic field can be approximated as being equivalent to that generated by a magnetic dipole located at the center of the Earth and aligned with the axis of rotation. The credibility of this GAD (Geocentric Axial Dipole) hypothesis is strongest in the geologically most recent eras, such as most of the Phanerozoic and notably in the last 400 million years. Attempts to get an adequate view of the magnetic field in the Earth's earlier history have for a long time been challenged by the reliability limitations of Precambrian paleomagnetic data. With the absence of marine magnetic anomalies, observational data need to be gathered from terrestrial rocks, notably those formed within cratonic nuclei, the oldest and most stable parts of continents. To answer the call for a concise and comprehensive compilation of paleomagnetic data from the early history of the Earth, this dissertation introduces a unique database of over 3300 Precambrian paleomagnetic observations worldwide. The data are freely available at the server of the University of Helsinki (http://h175.it.helsinki.fi/database) and can be accessed via an online query form. All database entries have been coded according to their terranes, rock formation names, ages, rock types and paleomagnetic reliabilities. A new modified version of the commonly applied Van der Voo (MV) classification criteria for filtering the paleomagnetic data is also presented, along with a novel method for binning the entries cratonically to revise the previously employed way of applying binning via a simple evenly spaced geographic grid. Besides compiling data, tests of the validity of the GAD hypothesis in the Precambrian have been conducted using inclination frequency analysis and asymmetries of magnetic field reversals. Results from two self-contained tests of the GAD hypothesis suggest that the time-averaged Precambrian geomagnetic field may include the geocentric axial quadrupole and the geocentric axial octupole, but both with strengths less than 10% of the geocentric axial dipole, with the quadrupole perhaps being smaller than the octupole. In no other study a model so close to GAD has been reasonably fitted to the Precambrian paleomagnetic data. The weakness of the non-dipolar coefficients required also implies that no substantial adjustments need to be made to the novel models of Precambrian continental assemblies (supercontinents), such as the Paleo-Mesoproterozoic Columbia (Nuna) or the Neoproterozoic Rodinia. Although the supercontinent science still has plenty of uncertainty, it is more plausibly caused by the geological incoherence of the data and the lack of precise age information rather than by long-lived non-dipolar geomagnetic fields.
  • Pervilä, Mikko (Helsingin yliopisto, 2013)
    Within the field of computer science, data centers (DCs) are a major consumer of energy. A large part of that energy is used for cooling down the exhaust heat of the servers contained in the DCs. This thesis describes both the aggregate numbers of DCs and key flagship installations in detail. We then introduce the concept of Data Center Energy Retrofits, a set of low cost, easy to install techniques that may be used by the majority of DCs for reducing their energy consumption. The main contributions are a feasibility study of direct free air cooling, two techniques that explore air stream containment, a wired sensor network for temperature measurements, and a prototype greenhouse that harvests and reuses the exhaust heat of the servers for growing edible plants, including chili peppers. We also project the energy savings attainable by implementing the proposed techniques, and show that global savings are possible even when very conservative installation numbers and payback times are modelled. Using the results obtained, we make a lower bound estimate that direct free air cooling could reduce global greenhouse gas (GHG) emissions by 9.4 MtCO2e already by the year 2005 footprint of the DCs. Air stream containment could reduce the GHG emissions by a further 0.7 MtCO2e, and finally heat harvesting can turn the waste heat into additional profits. Much larger savings are already possible, since the DC footprint has increased considerably since 2005.
  • Junninen, Heikki (Helsingin yliopisto, 2014)
    In this thesis the concept of data cycle is introduced. The concept itself is general and only gets the real content when the field of application is defined. If applied in the field of atmospheric physics the data cycle includes measurements, data acquisition, processing, analysis and interpretation. The atmosphere is a complex system in which everything is in a constantly moving equilibrium. The scientific community agrees unanimously that it is human activity, which is accelerating the climate change. Nevertheless a complete understanding of the process is still lacking. The biggest uncertainty in our understanding is connected to the role of nano- to micro-scale atmospheric aerosol particles, which are emitted to the atmosphere directly or formed from precursor gases. The latter process has only been discovered recently in the long history of science and links nature s own processes to human activities. The incomplete understanding of atmospheric aerosol formation and the intricacy of the process has motivated scientists to develop novel ways to acquire data, new methods to explore already acquired data, and unprecedented ways to extract information from the examined complex systems - in other words to compete a full data cycle. Until recently it has been impossible to directly measure the chemical composition of precursor gases and clusters that participate in atmospheric particle formation. However, with the arrival of the so-called atmospheric pressure interface time-of-flight mass spectrometer we are now able to detect atmospheric ions that are taking part in particle formation. The amount of data generated from on-line analysis of atmospheric particle formation with this instrument is vast and requires efficient processing. For this purpose dedicated software was developed and tested in this thesis. When combining processed data from multiple instruments, the information content is increasing which requires special tools to extract useful information. Source apportionment and data mining techniques were explored as well as utilized to investigate the origin of atmospheric aerosol in urban environments (two case studies: Krakow and Helsinki) and to uncover indirect variables influencing the atmospheric formation of new particles.
  • Tripathi, Abhishek (Helsingin yliopisto, 2011)
    The core aim of machine learning is to make a computer program learn from the experience. Learning from data is usually defined as a task of learning regularities or patterns in data in order to extract useful information, or to learn the underlying concept. An important sub-field of machine learning is called multi-view learning where the task is to learn from multiple data sets or views describing the same underlying concept. A typical example of such scenario would be to study a biological concept using several biological measurements like gene expression, protein expression and metabolic profiles, or to classify web pages based on their content and the contents of their hyperlinks. In this thesis, novel problem formulations and methods for multi-view learning are presented. The contributions include a linear data fusion approach during exploratory data analysis, a new measure to evaluate different kinds of representations for textual data, and an extension of multi-view learning for novel scenarios where the correspondence of samples in the different views or data sets is not known in advance. In order to infer the one-to-one correspondence of samples between two views, a novel concept of multi-view matching is proposed. The matching algorithm is completely data-driven and is demonstrated in several applications such as matching of metabolites between humans and mice, and matching of sentences between documents in two languages.
  • Hätönen, Kimmo (Helsingin yliopisto, 2009)
    Telecommunications network management is based on huge amounts of data that are continuously collected from elements and devices from all around the network. The data is monitored and analysed to provide information for decision making in all operation functions. Knowledge discovery and data mining methods can support fast-pace decision making in network operations. In this thesis, I analyse decision making on different levels of network operations. I identify the requirements decision-making sets for knowledge discovery and data mining tools and methods, and I study resources that are available to them. I then propose two methods for augmenting and applying frequent sets to support everyday decision making. The proposed methods are Comprehensive Log Compression for log data summarisation and Queryable Log Compression for semantic compression of log data. Finally I suggest a model for a continuous knowledge discovery process and outline how it can be implemented and integrated to the existing network operations infrastructure.
  • Kontinen, Juha (Helsingin yliopisto, 2004)