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Coronal mass ejections (CMEs) are large eruptions of magnetized plasma from the solar corona. Fast CMEs can drive shock waves which are capable of accelerating charged particles to high energies. These accelerated particles emit electromagnetic radiation, including radio emission. Studying radio emission associated with CME-driven shocks offers a way to remotely investigate shock-accelerated electrons as well the shock itself. Solar radio bursts are transient events where the radio emission of the Sun rises above the background level. A classical division based on their appearance in a dynamic spectrum divides solar radio bursts into five categories: types I-V. Of these five different types, type II and type IV radio bursts are most commonly associated with CMEs. Occasionally, type II radio bursts exhibit a bursty fine structure known as herringbones. These are regarded as signatures of individual electron beams accelerated by CME-driven shocks. This thesis studies the radio emission associated with a CME that erupted on 1 September 2014. White-light imaging of the CME revealed a prominent shock wave. Simultaneously, the dynamic spectrum exhibited spike-like radio emission resembling herringbones. The aim of the study presented in this thesis is to find the source location of this radio emission relative to a three dimensional reconstruction of the shock. The source location of the radio emission can be used to conclude the likely origin of the electrons responsible for it. Additionally, in situ electron flux measurements are investigated in an attempt to connect the remote and in situ detections of energetic electrons. Using interferometric radio observations of the Sun and reconstructing the CME shock in three dimension revealed the location of the radio emission to be at the flank of the CME-driven shock. Such location suggests that the spike-like radio emission observed in the dynamic spectrum originates from shock-accelerated electrons. The location of the radio emission at the flanks of the CME shock was also used to get an estimation of the lateral expansion of the CME. Although the in situ electron flux measurements detected high-energy electrons, their inferred release time at the Sun did not coincide with observed radio emission.

Real-world locations can be reconstructed as digital 3D models using 3D scanning. The scans often suffer from missing surface regions caused by occlusions and poor scanning geometry, limiting their usefulness for many tasks. We present an automated system that repairs small missing regions using generative adversarial networks (GANs). The system operates on heightmaps of small round surface patches distributed around the missing region. A neural network model predicts a complete plausible surface for each corrupted patch, which is then integrated to the scan. In addition to geometry, surface colors are also generated. Encouraging results are found in the color reconstruction task, but the output geometry is not clearly superior to the results of a simpler baseline spline model.

In recent years, content-based Publish/Subscribe (pub/sub) has become a popular paradigm to decouple content producers and consumers for Internet-scale content services. Many real applications show that the content workloads frequently follow very skewed distribution, and incur unbalanced workloads. To balance the workloads, the current content-based Publish/Subscribe systems normally adopt a migration scheme (Mis) to move (a subset of) subscription filters from overloaded brokers to underloaded brokers. In this way, the publications that successfully match the moved filters are then o oaded, leading to balanced workloads. Unfortunately, the Mis scheme cannot reduce the overall matching workloads. In the worse case, suppose that all brokers su er from heavy workloads. Mis cannot find available brokers to o oad the heavy workloads of those overloaded brokers, and fail to balance the workloads of the overloaded brokers. To overcome the issue, we develop a set of novel load balancing algorithms, namely a similarity-based replication scheme (Sir). The novelty of Sir is that it not only balances the workloads of brokers but also reduces the overall workloads. Based on both simulation and emulation results, the extensive experiments verify that Sir can achieve much better performance than Mis, in terms of 43.10% higher entropy value (i.e., more balanced workloads) and 46.39% lower workloads.

Cultural Heritage (CH) collections, data, and artefacts used to be available mainly in galleries, libraries, archives, and museums (GLAM). Due to digitisation, huge collections of CH data are now available online. Since the appearance of these data online, CH data have been searched, analysed and presented using various methods and visualisations. However, many of these methods do not take adequate advantage of the nature of CH data. Even when the CH data dimensions are utilised, the choices of visualisation sometimes fall short. This thesis is a part of the Finnish Archaeological Finds Recording Linked Open Database (SuALT) project. The project aims to develop digital Web services to cater for archaeological finds made by members of the public, especially metal detectorists through ‘citizen science’. Therein, a portion of an innovative prototype that tries to enable serendipitous knowledge discovery by making searching and visualising CH data seamless is presented. The artefact would serve as part of the basis of the FindSampo portal. The prototype is not implemented from scratch, but it is based on the Sampo model, the Sampo-UI framework and several third-party libraries and visualisations. The prototype includes mainly a user-centric faceted search engine, keyword searches to filter the facet options. It also includes data-analytic tools for visualising the filtered data on a table, a timeline chart, pie chart, line chart, maps and an option to export the results in CSV form for further analysis in external tools. However, this thesis focuses on the faceted search engine and the timeline visualisation that presents the spatio-temporal nature of the SuALT data. The portion of the prototype was evaluated based on three principles: serendipity, generosity, and criticality. And the result of the user experience survey suggests that the prototype could provide a good starting point to explore the find collection, make access to individual find information easier, improves the serendipitous discovery of archaeological find data and also make the find data analysis and interpretation easier.

The construction of large dams is causing human displacement and resettlement. In many cases indigenous groups of people are forced to move due to these development projects and are at a risk of losing their livelihoods, social networks and rights to customary land. This can cause impoverishment and marginalization. Constructing dams is usually initiated by the state and multinational organizations and have a top-down approach. The indigenous groups of people are not well considered during the planning process and their wishes about the development and resettlement are not properly acknowledged. This may eventually result in lack of integration and rootlessness in their new settlements. In Sudan the construction of large dams is often combined with the development of irrigation schemes, where the displaced people can be resettled as tenant farmers. The construction of the Aswan High Dam at the border between Sudan and Egypt in 1960s caused the inundation of the Nubian town of Wadi Halfa. Most of the residents were resettled in the New Halfa irrigation scheme in east Sudan. New Halfa proved a failure for the state and the farmers as it failed to meet the goals set out for it. The Khasm el Girba dam that feeds the irrigation scheme with water lost some of its capacity and consequently made irrigation more difficult. The agricultural land also lost fertility and the farmers are forced to work harder to make farming profitable. The local nomadic inhabitants of the original area have also lost pastoral land due to the project. Large differences between the livelihoods and economic situations of the residents have emerged which has led to social segregation. This study discusses the social consequences of resettlement and the profitability of irrigation schemes as a development initiative. The study was conducted in Sudan during the summer of 2011 in Khartoum and New Halfa agricultural scheme. The study states that the conditions for agriculture have deteriorated in New Halfa and the farmers are forced to depend on additional sources of income to secure their livelihoods. The different groups of people within the scheme are socially segregated and live in areas with a varying degree of infrastructure and services. The original planning of the scheme failed to acknowledge the needs of the different ethnic groups which led to detachment and social inequality.

Understanding local people’s perceptions towards tourism is important to minimize the negative impacts of tourism and to promote sustainable tourism. This thesis researches residents’ perceptions towards tourism, tourism development and tourism impacts in the city of Pokhara in Nepal. The thesis utilises Doxey’s irritation index and social exchange theory as the theoretical framework of the research. Based on Doxey’s irritation index, local people’s attitudes towards tourism shift from positive to negative as the time goes by and tourism develops. Based on the social exchange theory used in tourism studies, local people’s perceptions towards tourism are more positive the more the locals benefit from tourism and interact with tourists and tourism. This thesis aims to also understand what kind of place image local people have of Pokhara and how residents’ place image is connected to the perceptions they have towards tourism in Pokhara. As earlier tourism research has suggested, local people’s place image and perceptions towards tourism are connected and the more positive place image locals have, the more positive their perceptions towards tourism are. This thesis research is based on qualitative methods. The research data was collected with a qualitative questionnaire distributed online for the residents of Pokhara. Open-ended questions were used in the questionnaire, so that the participants could express their place image and perceptions towards tourism with their own words. The data was analysed by using qualitative content analysis. The results of this research indicate that the majority of the participants is satisfied with the tourism situation in Pokhara. The participants are especially content that tourism creates employment and earning opportunities for local people in Pokhara. However, a few participants expressed some irritation towards tourism situation in Pokhara due to different reasons. Despite some of the more negative perceptions towards tourism, almost all of the participants supported future tourism development in the area. Similarly, almost all of the participants thought that positive tourism impacts in the area are greater than the negative impacts, even though the participants also identified several negative tourism impacts, mainly regarding the environmental degradation and westernisation of local culture, habits, and values. On the contrary to the suggestions of the Doxey’s index, locals’ attitudes towards tourism have remained mostly positive even though tourism has developed in Pokhara in the past decades. Also, the results regarding local people’s involvement with tourism and tourists compared to their perceptions towards tourism are not completely in line with the earlier tourism research using the social exchange theory. The results of this research indicate that participants’ perceptions towards tourism are not always more positive the more residents benefit from tourism and interact with tourism or tourists. On the contrary, the perceptions towards tourism might be even more often negative among the participants who have contact with tourism and tourists than those who have not. The results also indicate that the participants have mostly a positive place image of Pokhara. Even though approximately half of the participants had both positive place image and positive perceptions towards tourism, positive place image will not always automatically result in positive perceptions towards tourism among the local people.

Low-frequency $1/$ noise is ubiquitous, found in all electronic devices and other diverse areas such as as music, economics and biological systems. Despite valiant efforts, the source of $1/f$ noise remains one of the oldest unsolved mysteries in modern physics after nearly 100 years since its initial discovery in 1925. In metallic conductors resistance $1/f$ noise is commonly attributed to diffusion of mobile defects that alter the scattering cross section experienced by the charge carriers. Models based on two-level tunneling systems (TLTS) are typically employed. However, a model based on the dynamics of mobile defects forming temporary clusters would naturally offer long-term correlations required by $1/f$ noise via the nearly limitless number of configurations among a group of defects. Resistance $1/f$ noise due to such motion of mobile defects was studied via Monte Carlo simulations of a simple resistor network resembling an atomic lattice. The defects migrate through the lattice via thermally activated hopping motion, causing fluctuations in the resistance due to varying scattering cross section. The power spectral density (PSD) $S(f)$ of the simulated resistance noise was then calculated and first compared to $S(f)=C/f^\alpha$ noise, where $C$ is a constant and $\alpha$ is ideally close to unity. The value of $\alpha$ was estimated via a linear fit of the noise PSD on a log-log scale. The resistor network was simulated with varying values of temperature, system size and the concentration of defects. The noise produced by the simulations did not yield pure $1/f^\alpha$ noise, instead the lowest frequencies displayed a white noise tail, changing to $1/f^\alpha$ noise between $10^{-4}$ to $10^{-2}$~Hz. In this way the spectrum of the simulated noise resembles a Lorentzian. The value of $\alpha$ was found to be the most sensitive to temperature $T$, which directly affects the motion of the defects. At high $T$ the value of $\alpha$ was closer to 1, whereas at low $T$ it was closer to $1,5$. Varying the size of the system was found to have little impact on $\alpha$ when the temperature and concentration of defects were kept fixed. Increasing the number of defects was found to have slightly more effect on $\alpha$ when the temperature and system size were kept fixed. The value of $\alpha$ was closer to unity when the concentration of defects was higher, but the effect was not nearly as pronounced compared to varying the temperature. In addition, the simulated noise was compared to a PSD of the form $S(f)\propto e^{-\sqrt{N}/T}1/f$, where $N$ is the size of the system, according to recent theoretical proceedings. The $1/f^\alpha$ part of the simulated noise was found to roughly follow the above equation, but the results remain inconclusive. Although the simple toy model did not produce pure $1/f^\alpha$ noise, the dynamics of the mobile defects do seem to have an effect on the noise PSD, yielding noise closer to $1/f$ when there are more interactions between the defects due to either higher mobility or higher concentration of defects. However, this is disregarding the white noise tail. Recent experimental research on high quality graphene employing more rigorous kinetic Monte Carlo simulations have displayed more promising results. This indicates that the dynamics of temporary cluster formation of mobile defects is relevant to understand $1/f$ noise in metallic conductors, offering an objective for future work.

Tässä pro gradu -tutkielmassa tutkimme Dirichlet'n ja Neumannin ongelmia Helmholtzin yhtälölle, ja etsimme näille reuna-arvo-ongelmille ratkaisuja reunaintegraaliyhtälöiden avulla. Tutkittavana alueena on $\Omega \subset \mathbb{R}^3$, joka on rajoitettu, avoin ja yhtenäinen $\mathbb{R}^3$:n osajoukko. Alueen $\Omega$ reunan $\partial\Omega$ oletetaan olevan $C^2$-pinta. Helmholtzin yhtälö on muotoa $\Delta u(x) + k^2 u(x) = 0,~x\in\mathbb{R}^3$, missä lukua $k$ kutsutaan aaltoluvuksi. Helmholtzin yhtälö on aaltoyhtälön aikaharmoninen muoto ja se kuvaa aallon muutosta paikan funktiona. Luvussa 2 määrittelemme käsiteltävän alueen ja sen reunan sekä käymme läpi muutamia perustuloksia, joita tarvitsemme jatkossa. Lisäksi johdamme aaltoyhtälöstä Helmholtzin yhtälön ja määrittelemme tälle yhtälölle Dirichlet'n ja Neumannin ongelmat sisäalueessa $\Omega$. Luvussa 3 käsittelemme Hölder-avaruuksia $C^{k,\alpha}(G)$, missä $k\in\mathbb{N}_0$ ja $0<\alpha\le 1$, heikosti singulaarisia integraalioperaattoreita ja Fredholmin alternatiivia. Lisäksi määrittelemme kerrospotentiaalit sekä tutkimme niiden jatkuvuusominaisuuksia ja reuna-arvoja. Yksi- ja kaksikerros-potentiaalit toteuttavat Helmholtzin yhtälön joukossa $\mathbb{R}^3\setminus\partial\Omega$. Kerrospotentiaalit ovat tässä työssä merkittävässä osassa reuna-arvo-ongelmien ratkaisemisessa, sillä niiden avulla voimme muuntaa reuna-arvo-ongelmat reunaintegraaliyhtälöiksi ja näin ollen löytää ratkaisut alkuperäisille ongelmille. Luvussa 4 muotoilemme sisäalueen Dirichlet'n ja Neumannin ongelmat toisen lajin reunaintegraaliyhtälöinä. Sisäalueen Dirichlet'n ongelmaa vastaava reunaintegraaliyhtälö voidaan esittää muodossa $(\boldsymbol{I}-\boldsymbol{K})\psi = -2f$ ja sisäalueen Neumannin ongelmaa vastaava reunaintegraaliyhtälö muodossa $(\boldsymbol{I}+\boldsymbol{K^*})\phi = 2g$. Integraaliyhtälöissä esiintyvät reunaintegraalioperaattorit $\boldsymbol{K}$ ja $\boldsymbol{K^*}$ ovat kompakteja avaruuksissa $C(\partial\Omega)$ ja $C^{0,\alpha}(\partial\Omega)$, kun $0<\alpha< 1$. Tulemme osoittamaan, että sopivalla tiheysfunktion $\psi \in C(\partial\Omega)$ valinnalla kaksikerros-potentiaali $v$ on sisäalueen Dirichlet'n ongelman ratkaisu. Vastaavasti sopivalla tiheysfuktion $\phi \in C(\partial\Omega)$ valinnalla yksikerros-potentiaali $u$ on sisäalueen Neumannin ongelman ratkaisu. Lopuksi tutkimme näiden reuna-arvo-ongelmien ratkeavuutta. Tyypillisesti sisäalueen reuna-arvo-ongelmille ei löydy yksikäsitteistä ratkaisua. Reuna-arvo-ongelmia vastaavat reunaintegraaliyhtälöt ovat yksikäsitteisesti ratkeavia silloin, kun Helmholtzin yhtälössä esiintyvä aaltoluku $k$ ei ole sisäalueen reuna-arvo-ongelman ominaisarvo. Fredholmin alternatiivin avulla voimme tutkia näiden reunaintegraaliyhtälöiden ratkeavuutta. Jos reunaintegraaliyhtälö on ratkeava, niin myös sitä vastaava sisäalueen reuna-arvo-ongelma on ratkeava.

I den här avhandlingen behandlas cellulära automater och speciellt deras reversibilitet. Avhandlingens fokus ligger vid att bevisa att reversibilitetsproblemet är oavgörbart för tvådimensionella cellulära automater, med andra ord att det inte existerar en algoritm för att bestämma om en tvådimensionel cellulär automat är reversibel. Avhandlingen inleds med introduktionen av grundläggande definitioner och begrepp gällande cellulära automater. I kapitel 2 undersöker vi existensen av Edens trädgård-konfigurationer hos cellulära automater. En Edens trädgård-konfiguration är en konfiguration som endast kan förekomma som startkonfiguration hos den cellulära automaten ifråga. Vi bevisar också Edens trädgård-satsen som ursprungligen presenterades av Edward F. Moore och John Myhill. Tillsammans med Curtis-Hedlund-Lyndon satsen som presenteras i kapitel 3, möjliggör Edens trädgård-satsen beviset av att en cellulär automat är reversibel om och endast om dess globala funktion är injektiv. Detta bevis presenteras i kapitel 3 och utgör en grundläggande ingredient i beviset av att reversibilitetsproblemet är oavgörbart för tvådimensionella cellulära automater. I kapitel 4 bekantar vi oss med begrepp som krävs för att förstå vad oavgörbarhet innebär. Begrepp som behandlas är bl.a. Turingmaskin och algoritm. Kapitel 5 inleds med introduktionen av kaklingsproblemet samt diverse viktiga definitioner i anknytning till detta problem. Här presenteras och bevisas också en sats som utgör det sista grundantagandet i beviset av reversibilitetsproblemets oavgörbarhet för tvådimensionella cellulära automater. Detta bevis behandlas i avhandlingens sista kapitel.

System logs are the diagnostic window to the state of health of the server. Logs are collected to files from which system administrators can monitor the status and events in the server. The logs are usually unstructured textual messages which are difficult to go through manually, because of the ever-growing data. Natural language processing contains different styles and techniques for a computer to interpret textual data. Word2vec and fastText are popular word embedding methods which project words to vectors of real numbers. Doc2vec is the equivalent for paragraphs and it is an extension to Word2vec. With these embedding models I will attempt to create an anomaly detector to assist the log monitoring task. For the actual anomaly detection, I will utilize Independent component analysis (ICA), Hidden Markov Model (HMM) and Long short-term memory to dig deeper in to the vectorized event log messages. The embedding models are then reviewed for their performance in this task. The results of this study show that there is no clear difference between the success of Word2vec and fastText, but it seems that Doc2vec does not work well with the short messages the event logs contain. The anomaly detector would still need some tuning in order to work reliably in production, but it is a decent attempt to achieve useful tool for event log analysing.