Faculty of Science

 

Recent Submissions

  • Ilonen, Annukka (Helsingin yliopisto, )
    In the 21st century, there is an intensified social-political mindset, where people are no longer separated from nature. As a result concepts and theories of ecological research become part of regional policy and spatial planning. At the same time, ecological knowledge, technology orientation and the economic potential created by them form an equilibrium between them. It may, depending on the context, turn to the barrier or benefit of the economy. Talking about the ecologicalization of politics which affecting all spatial planning levels in Finland. It has caused to conflicts in land use planning, when you try to take into account the importance of the nature of knowledge and to protect the directive species, such as flying squirrels. The aim of the study is to find out about the written material and the interviews with the peasants: what the flying squirrel conservation is all about and how it related to the ecologicalization of politics and what are the reasons for the species's conservation zoning conflicts and how can they be solved? As a case study, I will look at the Tramway project in Tampere, from the point of view of the flying squirrel’s conflict and ecologicalization of politics. At the same time, the aim is to develop the concept of ecologicalization of politics and to produce new information about the prevailing greenish social change. Flying squirrel (Pteromys volans) is protect by a politically determined decision in the European Union area and it’s the small-scale night-life mammal which occurs grown up in mixed forests. In the EU, species occur in Finland and small quantities in Estonia and possibly in Latvia. Given that the EU is responding to the problem of state protection, the common species in Finland is the directive specie which requires special protection. The Habitats Directive has been implemented in Finland's National Nature Conservation Act at the end of the 1990s and the directive prohibits the eradication and deterioration of breeding and resting places of the species. In addition, the guiding regulation of the protection of the flying squirrel is included in the Land Use and Building Act, Land Act and Forest Law. Despite the protection of the flying squirrel population is estimated declined from the period after the Second World War in Finland, but the species is classified as held for an eye only. The calculation of population classification has been criticized. The entry into force of the Land Use and Building Act in 2000 was an important legal reform for the protection of the flying squirrel. A key change in the law had made land use planning objectives addition of "conservation of biodiversity and other natural values". In addition, the sections on increasing interaction and impact assessment of zoning have made the planning process more transparent and added the importance of nature enthusiasts. Influencing people often involves complaining about patterns, which is unfortunate. It offers residents the opportunity to influence the surrounding environment and protect nature, such as flying squirrels. Grown up in mixed forests of the flying squirrel favored often set in the cities, because the mixed forests have reduced and fragmented due to forestry in outside the cities. Urban forests directed to a plurality of user requirements, because it can be flying squirrel homeforests, residents recreational use, commercial forest and zoning residences area. Flying squirrel in the comfort of urban forests is challenging because growing cities expand and condense. The protection of the flying squirrel has caused conflict’s situations in many cities. An example of this is Pirkanmaa long flying squirrel conflict history and its recent case in Tampere’s tram project. The tramway is a matter of valuing of the political decision-making, where the construction the tram means ignoring another environmental value, nature conservation. The flexible nature of ecologicalization of politics is manifested in a tramway project, when ecological knowledge of the flying squirrel turns against economic goals and co-operation between actors. For people who benefit from economic growth and for the city's growth, the flying squirrel is a financial slowdown which complicates regional cooperation in Tampere urban area. Although the protection of flying squirrel is not just a matter of protecting the city's local level, but also regional co-operation, as the dynamic species moves away from the municipal boundaries.
  • Kämäri, Hannu (Helsingfors universitet, 2017)
    Tässä pro gradu -tutkielmassa tavoitteena oli luoda referenssiarkkitehtuuri Big Data -teknologioita hyödyntäen sensoridatan vastaanottamiseksi ja käsittelemiseksi. Luotavan referenssiarkkitehtuurin oli tarkoitus laajentaa olemassa olevaa tietoarkkitehtuuria sensoriaineiston käsittelyn vaatimilla komponenteilla. Nykyinen tietoarkkitehtuuri koostuu operatiivisesta tietokannasta ja tietovarastosta, johon tiedot historioidaan raportoinin tarpeisiin. Toiminnallisena taustana muutokselle on ympäristöterveydenhuollon järjestelmäuudistus. Uuden järjestelmän yhdeksi tavoitteeksi on asetettu sensoridatan käytön lisääminen. Elintarviketurvallisuuden osalta ilmeisin vaihtoehto on Eviran asiantuntijoiden mukaan ravintoloiden kylmätilojen lämpötilan ja kosteuden mittaaminen. Sensoriaineistoa arvioitiin tulevan niin paljon, että sen käsittely ei tietoarkkitehtuurin nykyisillä ratkaisulla olisi mahdollista. Tapauksen pohjalta luotiin vaatimusluettelo ja sen tueksi kerätiin olennaiset kohdat nykyisen järjestelmätoimittajan arkkitehtuuriperiaatteista. Ratkaisua haluttiin etsiä Big Data -teknologioista ja erityisesti reaaliaikaiseen tiedonkäsittelyn mahdollistavista tietovirtojen käsittelyyn suunnatuista teknologioista. Työ on luonteeltaan konstruktiivinen. Siinä luotiin referenssiarkkitehtuuri, joka arvioitiin DCAR-mentelmällä. Arkkitehtuurin rakentamista taustoitettiin teknologiakartoituksella tietovirtojen käsittelyyn tarkoitetuista Big Data -teknologioista. Referenssiarkkitehtuuri kuvatiin JHS-179 -standardilla. Toteutettu kokonaisuus sisältää kuvaukset toiminta, tieto-, tietojärjestelmä ja teknologia-arkkitehtuureista.
  • Kapoor, Shubham (Helsingfors universitet, 2017)
    Challenges in managing cellular networks have grown in magnitude over the years. Upcoming 5G networks will further complicate the problem by introducing a larger number of scattered Network Elements (NEs) and functions than the prior cellular generations. Due to investment costs and user retention reasons, older technologies are not completely scraped out while new technologies are being introduced in the network. This results in a large, heterogeneous and complex network, which makes the data used to manage the network i.e. Management Plane (M-Plane) data, a big data candidate for the telcos. The conventional centralised Network Management Systems (NMS) will face fundamental scaling challenges in processing this big data, be it its collection, storage or quick analysis. In this thesis, we propose a novel concept of Quality of Monitoring (QoM) classes, which could be used for mobile edge compression of M-plane data. QoM classes specify the quality by which M- Plane data can be collected from the NEs. Quality here specifies the amount of relative information loss acceptable by network management applications consuming M-Plane data. The best QoM class with zero information loss could be assigned to monitor most critical NEs, while inferior QoM classes with some degree of information loss could be assigned to monitor auxiliary NEs. The proposed solution is based on the Publish/Subscribe paradigm for data delivery. The Publish/Subscribe paradigm makes the solution scalable and efficient by collecting data only once and providing flexibility to update QoM class subscription on the fly. The solution aggregates raw M-Plane data into a smaller set of the operator-defined performance metrics. This data is further compressed by removing portions of data with redundant or small information content. This helps the proposed solution to achieve reduction in the complexities of 3Vs (Volume, Variety and Velocity) of M-Plane data. The solution achieves quick processing of M-Plane data while saving the computational, bandwidth, storage and energy resources of the cellular operator.
  • Louhiranta, Juha (Helsingin yliopisto, 2020)
    Tämä pro gradu -tutkielma tarkastelee vaatimusmäärittelyä ketteriä menetelmiä hyödyntävissä ohjelmistoprojekteissa. Tavoitteena on selvittää, miten ohjelmiston vaatimukset muodostuvat ketterien menetelmien avulla ja millaisia vaikutuksia niillä on vaatimusmäärittelyprosessiin. Lisäksi tutkielmassa tarkastellaan, millaisia hyötyjä ketterillä menetelmillä voidaan saavuttaa vaatimusmäärittelyssä ja minkälaisia ongelmia ne saattavat aiheuttaa ohjelmistoprojektin eri vaiheissa. Tutkielmassa myös etsitään eroja ketterien menetelmien ja ketterän vaatimusmäärittelyprosessin sekä perinteisten menetelmien välillä. Tutkielman tapaustutkimuksen kohteena on Helsingin yliopiston Software Factory -kurssi, jonka aikana toteutettiin asiakasprojekti sulautettua internet-videopuhelujärjestelmää kehittävälle startup-yritykselle. Tapaustutkimuksessa selvitettiin, voidaanko ketterälle vaatimusmäärittelylle tutkimuskirjallisuudessa raportoituja hyötyjä sekä siihen liittyviä haasteita havaita ketterällä menetelmällä toteutettavassa ohjelmistoprojektissa. Tapaustutkimuksen avulla voitiin empiirisesti havaita kaikki vaatimusmäärittelyn hyödyt sekä yksi epätarkkoihin työmääräarvioihin liittyvä haaste. Tästä voidaan päätellä, että hyötyjen saavuttaminen on mahdollista pienellä tiimillä toteutettavassa asiakasprojektissa, jossa ei ole etukäteen tarkasti määriteltyjä ohjelmiston vaatimuksia. Toisaalta haasteitakin voidaan kohdata jo hyvin lyhyessä ajassa, vaikka rakennettaisiin pientä ja yksinkertaista sovellusta.
  • Galvin, Keith (Helsingin yliopisto, 2020)
    A seismic reflection survey was carried out at the Hannukainen-Rautuvaara Iron (Fe), Copper (Cu), and Gold (Au) deposits as part of the HIRE (High Resolution Reflection Seismics for Ore Exploration, 2007-2010) project. The main discovery from this survey was a regional structure showing three reflective layers dipping to the southwest. The top of this package of reflectors is currently planned to be mined at Hannukainen. The deeper parts of this package may have potential continuation of the economically viable deposits seen at shallow depths. In this work, a target-specific, amplitude-preserving workflow for profiles E1 and V5 of the Hannukainen-Rautuvaara HIRE seismic data will be formulated and applied. Then seismic amplitude vs. offset (AVO) and attribute analyses will be used to analyse the reflective layers and identify potential areas of interest for further study. This is a burgeoning area of seismic research, AVO analysis is typically used in hydrocarbon exploration and has only been sparsely used in hard rock settings for mineral exploration. Attribute analysis is more common in hard rock environments, but still underutilised. The seismic reflection data were re-processed focusing on retaining the high-frequency content of the seismic signal, this is key for further analysis. The results of the AVO analysis consist of determining the AVO class of the responses seen across the CMPs of two selected AVO horizons. AVO product and Poisson’s ratio change across the horizons were calculated, and an area of interest was identified from the correlation of these parameters. Attribute analysis was done using the seismic attributes envelope, first derivative envelope, Hilbert Transform, relative impedance, phase, weighted instantaneous frequency and dip. The amplitude attributes (envelope, first derivative envelope, Hilbert Transform, relative impedance) were useful in determining the areas of the reflector package that showed the strongest amplitudes and selecting horizons on the uppermost reflector for AVO analysis. Phase and weighted instantaneous frequency helped determine the continuity of the reflector package which revealed a clear four-layer signature, differing form the earlier three-layer interpretation. The dip attribute showed vertical anomalies, some of which correlated with mapped faulting in the area. Detailed interpretation of the geophysical results requires better borehole coverage, and petrophysical work, to tie in the seismic data results to the alteration and mineralisation. With open pit mine planning ongoing in the study area, the identification of deep-seated mineral deposits will have direct impact on the planning of the mine and the future of exploration in Hannukainen-Rautuvaara.
  • Rannisto, Meeri (Helsingin yliopisto, 2020)
    Bat monitoring is commonly based on audio analysis. By collecting audio recordings from large areas and analysing their content, it is possible estimate distributions of bat species and changes in them. It is easy to collect a large amount of audio recordings by leaving automatic recording units in nature and collecting them later. However, it takes a lot of time and effort to analyse these recordings. Because of that, there is a great need for automatic tools. We developed a program for detecting bat calls automatically from audio recordings. The program is designed for recordings that are collected from Finland with the AudioMoth recording device. Our method is based on a median clipping method that has previously shown promising results in the field of bird song detection. We add several modifications to the basic method in order to make it work well for our purpose. We use real-world field recordings that we have annotated to evaluate the performance of the detector and compare it to two other freely available programs (Kaleidoscope and Bat Detective). Our method showed good results and got the best F2-score in the comparison.
  • Vuorivirta, Leena (Helsingin yliopisto, 2020)
    Riskin mittaaminen on sijoittajille, vakuutusyhtiöille ja viranomaisille tärkeää. Riskin mittaaminen, vaikka tuottojakauma tai tulevien korvaustapahtumien jakakauma olisikin tiedossa, on haastavaa, mutta samalla tärkeää. Sijoitusmaailmassa yleisesti käytetään varianssia riskin mittamisessa. Vakuutusyhtiöiden viranomaisvaatimuksissa käytetään rinnakkain kahta eri riskimittaa eli sekä niin sanottua VaR(Value at Risk)-mittaa että ES(Expected Shortfall)-mittaa, jotka molemmat voidaan nähdä saman RVaR(Range Value at Risk)-mitan erikoistapauksina. Riskimitalla olisi toivottavaa olla tiettyjä ominaisuuksia, jotta sen soveltaminen tunnettujen talousteorioiden näkökulmasta olisi mielekästä. Jotta riskimittaa voidaan kutsua rahoitusriskimitaksi, sen tulisi olla monotoninen ja toteuttaa kassainvarianssiominaisuus. Jotta taas riskimitta olisi koherentti sen tulisi näiden lisäksi olla positiivisesti homogeninen ja subadditiivinen. Varianssi ei täytä edes rahoitusriskimitalta vaadittuja ominaisuuksia ja edellämainituista vain ES-mitta on koherentti. Rahoitusriskimitan on siis mitattava suuremmasta riskistä suuremman tappion ja riskittömällä sijoituksella ei saisi olla vaikutusta riskiin. Koherentti mitta takaa näiden lisäksi, että sijoitetulla summalla ei ole vaikutusta riskiin ja toisaalta hajautuksesta voi olla hyötyä, muttei haittaa. Näitä kaikkia ominaisuuksia pidetään yleisesti toivottavina. Työn keskiössä on RVaR-mitta, joka ei toteuta koherentilta mitalta haluttua subadditiivisuusominaisuutta. Osoitetaan kuitenkin, että toimijoiden RVaR-mitoista yhdistetyllä RVaR-mitalla on erityinen subadiitiivinen yhteys. Lisäksi tarkastellaan RVaR-mittaa sekä kilpailullisen riskinjaon että toimijoiden yhteistyössä toteuttaman riskinjaon näkökulmista. Ensimmäinen mainituista on tasapainoteoreettinen näkökulma, jossa jokainen toimija pyrkii minimoimaan omia tappioitaan ja jälkimmäinen Pareto-optimaalinen näkökulma, jossa esimerkiksi konserni jakaa tytäryhtiöidensä riskiä optimaalisella tavalla. Lopulta näytetään, että tietyin edellytyksin tasapainoallokaatio on olemassa ja se on tällöin myös Pareto-optimaalinen. Riskimittojen tarkastelua jatketaan salkunvalintaongelman sovelluksella. Esimerkissä tarkastellaan kolmen riskillisen arvopaperin yhden periodin markkinoita, joilta valitaan kaksi salkkua - toinen yleisesti tunnetun arvopapreiden hinnoittelumallin eli niin sanotun CAP-mallin mukainen varianssin minimoiva salkku sekä kilpaileva salkku. Esimerkki osoittaa varianssin heikon kohdan symmetrisenä riskimittana, joka rankaisee myös suuremmista tuottoarvoista.
  • Blom, Patrick (Helsingin yliopisto, 2020)
    In times of epidemics, few people continue living as usual and instead often change their behaviour in light of the new situation. Usually the change in behaviour is taken to be preventive measures aimed the reduce the probability of infectious contact between susceptibles and infected. This thesis considers a different scenario, where susceptibles, once gaining awareness of the disease, begin to consider vaccination against the disease. The basic SIR-model is modified to include awareness of the epidemic or the possibility thereof, that inspires individuals to vaccinate themselves. The awareness is spread either from a constant source outside the population or through contacts between unaware individuals and either the infected or individuals already aware of the disease. The equilibria of these models and the conditions for their stability are established. All three models significantly reductions to the final size of the epidemic. In case of awareness spread being dependent on the size of the infected population, under some conditions the introducing vaccinations can destabilize the endemic equilibrium and lead to oscillations. Constant and aware-dependent awareness models also have disease-free equilibria, which can be stable and prevent a major epidemic from happening if the spread of awareness is strong enough. Lattice-model analogues of the constant and aware-dependent awareness models, where individuals are connected to a limited number of other individuals, are also established along with their equilibria. Also in this case, the disease-free equilibria of the two models can be stabilised with an effective spread of awareness.
  • Lehtonen, Toni (Helsingin yliopisto, 2020)
    Streptococcus pneumoniae is considered to be one of the most common causes of pneumonia and is known to cause a significant disease burden worldwide. During the past two decades much effort has been made globally to prevent pneumococcal illnesses through the use of vaccines. In Finland, all children under the age of five have been eligible to receive pneumococcal conjugate vaccine as part of the national vaccination programme since 2010. The impact of the pneumococcal vaccination has been studied extensively in Finland, and a significant decrease in the incidence of pneumonia has been observed among all vaccine-age children. One research question not yet examined in the previous studies is the exact point of time after which the impact of vaccination can be discerned in the incidence rates. This thesis considers a novel approach to multiple change point detection for time series data, where the change point problem is expressed in the form of a regression model. The model is specified so that potential change point positions are represented as separate explanatory variables. Relevant change points are then chosen by applying several established variable selection methods to the model. Out of these methods, the lasso estimate, its Bayesian analogue and two other Gaussian scale mixture priors are considered in this work. The change point model was implemented with the selected variable selection methods for age-group specific time series of pneumonia incidence rates in Finland between 2001 and 2016 to detect any changes that could be attributed to the introduction of the vaccine. These datasets were produced from routinely generated hospital discharge records, the operationalization of which is also discussed in the thesis. Aside from the vaccinated age group of under five year olds, data for both 25-44 year olds and over 65 year olds were also considered to inspect possible indirect effects of the vaccination. The implementations with different variable selection methods all provided very similar results for each age group. For under five year olds a change point during spring 2011 was selected, while for the over 65 year olds none were chosen during or after the introduction of the vaccine. For 25-44 year olds multiple change points between 2009 and 2014 were selected, but whether any of these could be attributed to the vaccination remains an open question.
  • Pyrylä, Atte (Helsingin yliopisto, 2020)
    In this thesis we will look at the asymptotic approach to modeling randomly weighted heavy-tailed random variables and their sums. The heavy-tailed distributions, named after the defining property of having more probability mass in the tail than any exponential distribution and thereby being heavy, are essentially a way to have a large tail risk present in a model in a realistic manner. The weighted sums of random variables are a versatile basic structure that can be adapted to model anything from claims over time to the returns of a portfolio, while giving the primary random variables heavy-tails is a great way to integrate extremal events into the models. The methodology introduced in this thesis offers an alternative to some of the prevailing and traditional approaches in risk modeling. Our main result that we will cover in detail, originates from "Randomly weighted sums of subexponential random variables" by Tang and Yuan (2014), it draws an asymptotic connection between the tails of randomly weighted heavy-tailed random variables and the tails of their sums, explicitly stating how the various tail probabilities relate to each other, in effect extending the idea that for the sums of heavy-tailed random variables large total claims originate from a single source instead of being accumulated from a bunch of smaller claims. A great merit of these results is how the random weights are allowed for the most part lack an upper bound, as well as, be arbitrarily dependent on each other. As for the applications we will first look at an explicit estimation method for computing extreme quantiles of a loss distributions yielding values for a common risk measure known as Value-at-Risk. The methodology used is something that can easily be adapted to a setting with similar preexisting knowledge, thereby demonstrating a straightforward way of applying the results. We then move on to examine the ruin problem of an insurance company, developing a setting and some conditions that can be imposed on the structures to permit an application of our main results to yield an asymptotic estimate for the ruin probability. Additionally, to be more realistic, we introduce the approach of crude asymptotics that requires little less to be known of the primary random variables, we formulate a result similar in fashion to our main result, and proceed to prove it.
  • Laurén, Toni (Helsingin yliopisto, 2020)
    The Hawk-Dove game has been used as a model of situations of conflict in diverse fields as sociology, politics, economics as well as animal behavior. The iterated Hawk-Dove game has several rounds with payoff in each round. The thesis is about a version of the iterated Hawk-Dove game with the additional new feature that each player can unilaterally decide when to quit playing. After quitting, both players return to the pool of temporally inactive players. New games can be initiated by random pairing of individuals from within the pool. The decision of quitting is based on a rule that takes into account the actions of oneself or one's opponent, or on the payoffs received during the last or previous rounds of the present game. In this thesis, the quitting rule is that a player quits if its opponent acts as a Hawk. The additional feature of quitting dramatically changes the game dynamics of the traditional iterated Hawk-Dove game. The aim of the thesis is to study these changes. To that end we use elements of dynamical systems theory as well as game theory and adaptive dynamics. Game theory and adaptive dynamics are briefly introduced as background information for the model I present, providing all the essential tools to analyze it. Game theory provides an understanding of the role of payoffs and the notion of the evolutionarily stable strategies, as well as the mechanics of iterated games. Adaptive dynamics provides the tools to analyze the behavior of the mutant strategy, and under what conditions it can invade the resident population. It focuses on the evolutionary success of the mutant in the environment set by the current resident. In the standard iterated Hawk-Dove game, always play Dove (all-Dove) is a losing strategy. The main result of my model is that strategies such as all-Dove and mixed strategy profiles that are also not considered as worthwhile strategies in the standard iterated Hawk-Dove game can be worthwhile when quitting and the pool are part of the dynamics. Depending on the relations between the payoffs, these strategies can be victorious.
  • Lindström, Mats Johan Wilhelm (Helsingin yliopisto, 2020)
    Within the last century humanity has grown significantly more numerous and more globally connected than ever before in its history. Together with the increased risks of climate change, we are more susceptible than ever to major epidemics and pandemics caused by novel zoonotic diseases. For these reasons it is not only important understand under which conditions novel pathogens are able to invade and spread in a host population but also to understand how these pathogens can be eradicated following an invasion event. In this thesis we present and study the demographic and evolutionary dynamics of a compartmental epidemiological model that includes a compartment for asymptomatic individuals, who require a second infection to become symptomatic and infectious. We show that the model exhibits a wide variety of demographic dynamical behaviour, all of which can be evolutionarily attracting configurations under simple evolutionary considerations. The model is an extreme simplification of the real world and excludes relevant information such as age and spatial structures of the population at hand. The aim of this thesis is to obtain a general understanding of how varying certain parameters on one hand allows a pathogen to invade a host population and, on the other hand, allows the host to eradicate an established pathogen, in particular, through the process of evolution.
  • Kovanen, Veikko (Helsingin yliopisto, 2020)
    Real estate appraisal, or property valuation, requires strong expertise in order to be performed successfully, thus being a costly process to produce. However, with structured data on historical transactions, the use of machine learning (ML) enables automated, data-driven valuation which is instant, virtually costless and potentially more objective compared to traditional methods. Yet, fully ML-based appraisal is not widely used in real business applications, as the existing solutions are not sufficiently accurate and reliable. In this study, we introduce an interpretable ML model for real estate appraisal using hierarchical linear modelling (HLM). The model is learned and tested with an empirical dataset of apartment transactions in the Helsinki area, collected during the past decade. As a result, we introduce a model which has competitive predictive performance, while being simultaneously explainable and reliable. The main outcome of this study is the observation that hierarchical linear modelling is a very potential approach for automated real estate appraisal. The key advantage of HLM over alternative learning algorithms is its balance of performance and simplicity: this algorithm is complex enough to avoid underfitting but simple enough to be interpretable and easy to productize. Particularly, the ability of these models to output complete probability distributions quantifying the uncertainty of the estimates make them suitable for actual business use cases where high reliability is required.
  • Lahti, Juho (Helsingin yliopisto, 2020)
    Volatiliteetin käsite on keskeisessä roolissa optioiden hinnoittelun teoriassa, ja reaalimaailman op- tiopositioilla realisoituva volatiliteetti on merkittävä tuloksen ajuri. Yksinkertaisilla optiopositioilla on kuitenkin vaikeaa saada aikaiseksi sellainen sijoitussalkku, joka ainoastaan riippuisi toteutuvasta volatiliteetista. Toteutuvaan volatiliteettiin liittyen voidaan kuitenkin sopia varianssin vaihtosopi- muksesta, jossa osapuolet vaihtavat keskenään kiinteän varianssin hinnan ja toteutuvan varianssin erotuksesta johdettua kassavirtaa. Tässä tutkielmassa varianssin vaihtosopimuksille johdetaan markkinaehtoinen hintakaava staat- tisen toistamisen ja synteettisen logaritmisopimuksen avulla. Tämä varianssin vaihtosopimuksen markkinahinta osoittautuu riippuvan kaikista markkinoilla kaupankäynnin kohteena olevista optioista ja erityisesti näiden volatiliteettihymystä. Erilaisten osakepolun neliövariaatiosta riippuvien kaupankäyntistrategioiden analysointia varten sovelletaan erästä stokastisen volatiliteetin mallia toteutuvan tuloksen simuloimiseen. Osoittautuu, että varianssin vaihtosopimus tarjoaa merkittävästi erilaisen sijoitusinstrumentin, jonka varallisuus kehittyy usein hyvin eri tavalla kuin osake, jonka toteutuvalla varianssilla on käyty kauppaa.
  • Thomas, Steven Job (Helsingin yliopisto, 2020)
    Biogenic Volatile Organic Compounds play a major role in the atmosphere by acting as precursors in the formation of secondary organic aerosols and by also affecting the concentration of ozone. The chemical diversity of BVOCs is vast but global emissions are dominated by isoprene and monoterpenes. The emissions of BVOCs from plants are affected by environmental parameters with temperature and light having significant impacts on the emissions. The Downy birch and Norway spruce trees consist of heavy and low volatile compounds but published results are limited up to observing sesquiterpenoid emissions from these two trees. In this study, the Vocus proton-transfer-reaction time-of-flight mass spectrometer is deployed in the field to examine BVOC emissions from Downy birch and Norway spruce trees. With higher mass resolution, shorter time response and lower limits of detection than conventional PTR instruments, the Vocus can effectively measure a broader range of VOCs. For the first time, real-time emissions of diterpenes and 12 different oxygenated compounds were observed from birch and spruce trees. The emission spectrum of birch was dominated by C10H17+, while for spruce C5H9+ contributed the most. The sum emissions of oxygenated compounds contributed significantly to the observed total emissions from both the trees. The emission rates of all compounds varied dramatically throughout the period due to fluctuations in temperature and light. Due to lack of data from spruce, conclusive results for temperature and light response on terpene emissions could not be drawn. For birch, the emission rates were well explained by the temperature and temperature-light algorithms. The terpene emissions modelled using both algorithms correlated similarly with experimental data making it difficult to decisively conclude if the emissions originated from synthesis or pools.
  • McKevitt, Bláthnaid (Helsingin yliopisto, 2020)
    Phosphate is reported to be subject to “high supply risk” by the EU Commission (European Commission 2017). At present, the Siilinjärvi mine in Finland is the only mine in the EU producing phosphate. Optimising the productivity of the Siilinjärvi mine is crucial to address the demand for phosphate within the EU. The current production prognosis of the mine is to the end of 2035. To improve the prognosis of the mine, an exploration program is being undertaken to investigate the extent of the deposit and possible locations for new pits. The main area of interest is the area south of the current Särkijärvi pit. Exploration drilling is limited in this area due to obstacles created by infrastructure of the mine, including the factory area and gypsum pile. To address this, 3D passive source seismic, 2D active-source reflection seismic, Ground Penetrating Radar (GPR) and magnetic surveys were conducted at the Siilinjärvi mine site as part of the H2020 Smart Exploration project. This study focuses on two of the acquired active-source seismic reflection profiles, SM2 and SM3. The aim of the study is to determine the depth and lateral extent southern continuation of the deposit in the area south of the Särkijärvi pit, next to the gypsum pile, and create a 3D model of the Siilinjärvi deposit based on the obtained results. In addition, obtaining information on waste rocks and zones of weakness, such as shear and fracture zones, is also of interest as this information is critical for mine planning. The main focus for seismic data processing was to improve the signal-to-noise ratio. Strong amplitude S-waves and unclear first-breaks were limitations found in the data. As a consequence, in addition to bandpass filtering, seismic line SM2 required a combination of attenuation and muting to supress the impact of S- waves. Seismic line SM3 had a lower data quality in comparison to that of SM2. The suppression of S- waves had a negative impact on the near-surface reflections along SM3 and therefore was not carried out. The GPR and magnetic data were processed using standard workflows. The active-source seismic survey was successful in determining the depth and the lateral extent of the southern continuation of the Siilinjärvi deposit. A 3D model of the deposit was created based on the obtained seismic images. This model expands on the previous model and indicates that the carbonatite- glimmerite deposit expands towards the W, beneath the gypsum pile. This information can be used as a guide for future drilling in the area. In addition, information was obtained on zones of weakness and the waste-rock dike network. Sub-horizontal to gently dipping reflections observed in the seismic data were interpreted as diabase dikes. On a smaller scale, GPR measurements detected shallower near-surface features which are also interpreted to possibly be dikes. For some features, a correlation could be made between the various geophysical measurements. The carbonatite-glimmerite deposit was found to be associated with elevated magnetic total field (nT) values.
  • Louhio, Jaana (Helsingin yliopisto, 2020)
    In the late 2010’s classical games of Go, Chess and Shogi have been considered ’solved’ by deep reinforcement learning AI agents. Competitive online video games may offer a new, more challenging environment for deep reinforcement learning and serve as a stepping stone in a path to real world applications. This thesis aims to give a short introduction to the concepts of reinforcement learning, deep networks and deep reinforcement learning. Then the thesis proceeds to look into few popular competitive online video games and to the general problems of AI development in these types of games. Deep reinforcement learning algorithms, techniques and architectures used in the development of highly competitive AI agents in Starcraft 2, Dota 2 and Quake 3 are overviewed. Finally, the results are looked into and discussed.
  • Vainio, Antero (Helsingin yliopisto, 2020)
    Nowadays the Internet is being used as a platform for providing a wide variety of different services. That has created challenges related to scaling IT infrastructure management. Cloud computing is a popular solution for scaling infrastructure, either by building a self-hosted cloud or by using cloud platform provided by external organizations. This way some the challenges related to large scale can be transferred to the cloud administrators. OpenStack is a group of open-source software projects for running cloud platforms. It is currently the most commonly used software for building private clouds. Since initially published by NASA and Rackspace, it has been used by various organizations such as Walmart, China Mobile and Cern nuclear research institute. The largest production deployments of OpenStack clouds consist of thousands of physical server computers located in multiple datacenters. The OpenStack community has created many deployment methods that take advantage of automated software configuration management. The deployment methods are built with state of the art software for automating different administrative tasks. They take different approaches to automating infrastructure management for OpenStack. This thesis compares some of the automated deployment methods for OpenStack and examines the benefits of using automation for configuration management. We present comparisons based on technical documentations as well as reference literature. Additionally, we conducted a questionnaire for OpenStack administrators about the use of automation. Lastly, we tested one of the deployment methods in a virtualized environment.
  • Sarapalo, Joonas (Helsingin yliopisto, 2020)
    The page hit counter system processes, counts and stores page hit counts gathered from page hit events from a news media company’s websites and mobile applications. The system serves a public application interface which can be queried over the internet for page hit count information. In this thesis I will describe the process of replacing a legacy page hit counter system with a modern implementation in the Amazon Web Services ecosystem utilizing serverless technologies. The process includes the background information, the project requirements, the design and comparison of different options, the implementation details and the results. Finally, I will show how the new system implemented with Amazon Kinesis, AWS Lambda and Amazon DynamoDB has running costs that are less than half of that of the old one’s.
  • Viiri, Kalle (Helsingin yliopisto, 2020)
    Locally checkable labeling problems in the LOCAL model of distributed computation are known to have only three distinct complexity classes when the attention is restricted to problems on toroidic grids only: trivial with time complexity Θ(1), local with time complexity Θ(log∗ n) and global with time complexity Θ(n). Prior work shows that problems belonging to the trivial class are easy to recognize, but that local and global labeling problems are undecidable to separate. However, a method called algorithm synthesis exists for creating an asymptotically optimal normal-form algorithm for any locally checkable labeling problem with a time complexity of Θ(log∗ n). This process, when automated, can be used to process vast amounts of suitably encoded labeling problems in bulk, creating a more defined boundary for the undecidable class of local problems. As a proof-of-concept of this method, this work presents a new asymptotically optimal algorithm for a relaxed form of 3-coloring as well as methods for more general search of local problems.

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