Faculty of Science

 

Recent Submissions

  • Vesalainen, Ari (Helsingin yliopisto, 2022)
    Digitization has changed history research. The materials are available, and online archives make it easier to find the correct information and speed up the search for information. The remaining challenge is how to use modern digital methods to analyze the text of historical documents in more detail. This is an active research topic in digital humanities and computer science areas. Document layout analysis is where computer vision object detection methods can be applied to historical documents to identify the document pages’ present objects (i.e., page elements). The recent development in deep learning based computer vision provides excellent tools for this purpose. However, most reviewed systems focus on coarse-grained methods, where only the high-level page elements are detected (e.g., text, figures, tables). Fine-grained detection methods are required to be able to analyze texts on a more detailed level; for example, footnotes and marginalia are distinguished from the body text to enable proper analysis. The thesis studies how image segmentation techniques can be used for fine-grained OCR document layout analysis. How to implement fine-grained page segmentation and region classification systems in practice, and what are the accuracy and the main challenges of such a system? The thesis includes implementing a layout analysis model that uses the instance segmentation method (Mask R-CNN). This implementation is compared against another existing layout analysis using the semantic segmentation method (U-net based P2PaLA implementation).
  • Piela, Emma (Helsingin yliopisto, 2022)
    Organized sports for children provide important health benefits continuing also later in life and are highly segregated based on gender. Having opportunities of organized physical activities within reasonable travel times has been shown to have an effect in participation of sports. In this thesis few of the most popular sports for each gender; dance, horse riding, floorball and football were chosen and the service level of the facilities providing organized sport activities in the age group of 7- to 12-year-olds were analysed in the Helsinki Metropolitan Area. Special interest lied in how equally these services can be reached with different travel modes in reasonable travel times also in relation to spatial socioeconomic differences. As the research on the topic has been inconsistent and sparse, this thesis contributes to the research field with comprehensive outlook on equality considerations and a seldomly used perspective of children’s sports facility accessibility focused on provided services. The methods used included identifying locations used by children in the chosen sports, analysing travel times to these locations with the Helsinki Region Travel Time Matrix and comparing the resulting spatial accessibility conditions to a sum index of disadvantage calculated from a population grid database. This comparison was done through a Student’s t-test and testing of local bivariate relationships. Generally, the results indicated quite similar spatial patterns and good spatial accessibility conditions in floorball, football and dance when it comes to travel times to closest facilities. The horse riding facilities were located in more remote areas and were significantly fewer which resulted in longer travel times. Overall, most children reached their closest floorball, football or dance facilities within 15 minutes of biking, public transport or car travel times. Biking travel times were found to be shorter than public transportation travel times while private car provided the shortest travel times. The t-test revealed many statistically significant relationships indicating difference in travel times in the most and least disadvantaged quintile areas of the sum index of disadvantage. In these results, travel times especially in football were found to be shorter in more disadvantaged areas. This was the direction of the findings also in floorball and dance. Horse riding travel times were longer in most disadvantaged areas. The bivariate relationship tools revealed variation in the local relationships between the travel times and the sum index. In conclusion, due to travel times being of reasonable length considerable inequalities in the spatial accessibility conditions were not found, although horse riding facilities indicated some inequalities.
  • Wallin, Tiia (Helsingin yliopisto, 2021)
    Tämän tutkielman tarkoituksena on tutustuttaa lukija arvopaperimarkkinoihin, niiden yleiseen tasapainoon ja tasapainon olemassaoloon yhden periodin markkinamallissa, jossa toimijat käyvät kauppaa arvopapereista vaihtokauppamarkkinoilla. Yleinen tasapainoteoria on lähestymistapa talouden käyttäytymisen kuvaamiseen kokonaisuutena, jossa selvitetään talouden muodostavien toimijoiden kunkin jäsenen optimaalinen käyttäytyminen ja etsitään keskinäisen yhteensopivuuden pistettä. Tasapainoperiaatteen mukaan hinnat sopeutuvat, kunnes toimijoiden valinnat ovat yhteensopivat toistensa kanssa. Tasapaino voidaan määritellä systeemin tilaksi, jossa sillä ei ole syytä muuttua. Tutkielman toisessa kappaleessa esitetään tarpeellisia esitietoja ja apulauseita. Tutkielman lukijan oletetaan tuntevan tavallisimmat matemaattiset merkintätavat. Hänen tulee hallita peruskäsitteet matemaattisesta analyysistä, todennäköisyyslaskennasta, joukko-opista, lineaarialgebrasta ja topologiasta. Näiden lisäksi taloustieteen peruskäsitteiden tuntemus sekä opit auttavat ymmärtämään kokonaisuutta laajemmin. Tutkielman kolmannessa kappaleessa perehdytään lyhyesti arvopaperimarkkinoiden matemaattiseen esitystapaan, kuluttajan utiliteettiteoriaan sekä arbitraasikäsitteeseen. Kappaleessa esitetään myöhemmin tutkielmassa käytettävät talouden tärkeät standardiolettamukset ja todistetaan yhtenä tärkeimpänä tuloksena, milloin yhden periodin arvopaperimarkkinat ovat arbitraasivapaat. Neljännessä kappaleessa paneudutaan tasapainoon ja sen määrittelemiseen. Kappale lähtee liikkeelle tarkasta taloustieteellisestä näkökulmasta. Se perehtyy ehdollisten markkinoiden talouteen, eli toiselta nimeltä Arrow-Debreu-talouteen, sen merkitsemistapaan ja tasapainoon. Tämän jälkeen johdetaan seuraukset arvopaperimarkkinoille. Normalisoidun arbitraasivapaan tasapainon avulla pystytään näyttämään, että täydelliset arvopaperimarkkinat ovat Arrow-Debreu-markkinat. Kappaleen lopussa käydään läpi Pareto-tehokkuutta ja todistetaan, että täydellisillä arvopaperimarkkinoilla, joissa toimijoiden utiliteettifunktiot ovat kasvavia, jokainen kulutustasapaino on Pareto-tehokas. Tämä tarkoittaa sitä, että ei ole olemassa toista allokaatiota, joka parantaisi toisen toimijan utiliteettia huonontamatta jonkin toisen. Viidennessä kappaleessa esitellään tasapainon olemassaoloa ensiksi Arrow-Debreun taloudessa ja käydään esimerkkien avulla läpi, miksi tietyt oletukset ovat välttämättömiä tasapainon olemassaololle täydellisillä markkinoilla. Tämän jälkeen esitetään lause arvopaperimarkkinoiden tasapainolle, jossa markkinat saattavat olla epätäydelliset.
  • Hannukkala, Karoliina (Helsingin yliopisto, 2021)
    Tavoitteet. Tutkimuksen tavoitteena on kartoittaa ja analysoida vuosina 2007–2021 järjestettyjen pitkän sekä lyhyen matematiikan ylioppilaskokeissa esiintyneiden tilasto- ja todennäköisyyslaskennan tehtävien muutosta. Tutkimuksen erityiset kiinnepisteet ovat tilasto- ja todennäköisyyslaskennan tehtävissä hyödynnetyt ratkaisumenetelmät, tehtävien osaamistasoluokitukset sekä tehtäväkohtaiset pistejakaumat. Osaamistasoluokituksessa tukeudutaan Bloomin taksonomiaan. Tarkastelu jaetaan kolmeen aikajänteeseen matematiikan ylioppilaskokeessa ja sen järjestämistavassa tapahtuneisiin muutoksiin perustuen. Aikajänteet ovat 2007–2011 (perinteinen paperikoe), 2012–2018 (symbolisten laskimet sallittuja) ja 2019–2021 (kokeen toteutus kokonaan digitaalinen). Menetelmät. Tutkimuksessa on käytetty kvantitatiivisia menetelmiä. Ratkaisumenetelmien, osaamistasojen ja pistejakaumien analysoinnissa on kaikissa hyödynnetty määrällisiä menetelmiä. Tulokset ja johtopäätökset. Tilastojen ja todennäköisyyslaskennan ylioppilaskoetehtävät peräänkuuluttavat sekä pitkässä että lyhyessä oppimäärässä laajasti erilaisten ratkaisumenetelmien hallintaa. Erityisen huomion kiinnittää lyhyen oppimäärän ylioppilaskokeiden taulukkolaskentaa vaativien tilasto- ja todennäköisyysaiheisten tehtävien suuri suhteellinen osuus viimeisellä tarkastelujänteellä 2019–2021. Pitkän matematiikan ylioppilaskokeen tilasto- ja todennäköisyysaiheisten tehtävien osaamistasovaade on vuosien saatossa kasvanut huomattavasti. Samaan aikaan suhteellinen tehtäväkohtainen pistemäärä on laskenut. Lyhyen oppimäärän tilasto- ja todennäköisyysaiheisten tehtävien osaamistasovaade on kasvanut hiukan, ja samanaikaisesti tehtäväkohtaiset pistemäärät ovat pysyneet suhteellisen tasaisina
  • Dursun, Sahin (Helsingin yliopisto, 2021)
    This thesis focuses on the initial measurements and development of a 1.5K target temperature cryostat to contain all quantum standards in the quantum metrological triangle. Currently, the cryostat can reach 4.2K end temperature with a cryocooler to liquefy helium for cooling experiments related to the quantum standards of SI-units which require 1.5K end temperature and the 1.5K cooling circuit is one of the research questions of the thesis for future development of the cryostat. Measurements included cooling cycles in a helium environment for liquefaction, as well as no load conditions. Results of the experimentation conclude that liquefaction was unsuccessful at this stage, but could be achieved with improved temperature control. The thesis is based on experimental work carried out in VTT technical research center of Finland, during the course of which the cryostat was progressively developed towards the future utility of combining experiments that realize the quantum standards of Ampere, voltage and resistance under a single low temperature experimental platform, the unified quantum standard cryostat.
  • Mäntysaari, Matti (Helsingin yliopisto, 2021)
    This thesis describes the data and data analysis concerning Compton scattering experiments to obtain the Compton profiles of metallic sodium (Na) as a function of temperature. The temperatures used in the experiment were 6 K and 300 K. The purpose of the work was to visualize the effect of temperature in the electron momentum density in a free electron gas. The effects of temperature were expected to be manifested through changes to the Fermi momentum according to the free-electron theory, but also more subtle changes could have been possible owing to possible deviations from the free electron theory. The measurements were done at the European Synchrotron Radiation Facility (Grenoble, France) beamline ID20. The data was analyzed with a help of a program written with Matlab, and it converted the measured Compton spectra from photon energy space to electron momentum space, while applying self-absorption corrections to the data, subtracting background, and normalizing the data using trapezoidal numerical integral to yield final Compton profiles. Results were obtained as valence Compton profiles and their differences between 300 K and 6 K, and compared with the prediction from free-electron gas theory. The Compton profiles followed the predictions of the free-electron gas theory well, although the theoretical profiles had a higher amplitude than the measured profiles. This is a commonly found phenomenon in Compton spectroscopy and assigned to originate from electron-electron correlations. The effect of the temperature in the Compton profiles is in good agreement with the free-electron theory.
  • Lassila, Petri (Helsingin yliopisto, 2021)
    Lipid-based solid-fat substitutes (such as oleogels) structurally modified using ultrasonic standing waves (USW), have recently been shown to potentially increase oleogel storage-stability. To enable their potential application in food products, pharmaceuticals, and cosmetics, practical and economical production methods are needed compared to previous work, where USW treated oleogel production was limited to 50-500 µL. The purpose of this work is to improve upon the previous procedure of producing structurally modified oleogels via the use of USW by developing a scaled up and convenient approach. To this aim, three different USW chamber prototypes were designed and developed, with common features in mind to: (i) increase process volumes to 10-100 mL, (ii) make the sample extractable from the treatment chamber, (iii) avoid contact between the sample and the ultrasonic transducer. Imaging of the internal structure of USW treated oleogels was used as the determining factor of successful chamber design. The best design was subsequently used to produce USW treated oleogels, of which the bulk mechanical properties were studied using uniaxial compression tests, along with local mechanical properties, investigated using scanning acoustic microscopy. Results elucidated the mechanical behaviour of oleogels as foam-like. Finally, the stability of treated oleogels was compared to control samples using an automated image analysis oil release test. This work enables the effective mechanical-structural manipulation of oleogels in volumes of 10-100 mL, paving the way to possible large-scale lipid-based materials USW treatments.
  • Suuronen, Markus (Helsingin yliopisto, 2021)
    People spend more than 90% of time indoors. That has made the analysis of indoor air quality an subject of interest. There is a growing popularity of miniaturized sample extraction techniques utilizing solid adsorbent materials and thermal desorption allowing direct sample introduction for analysis. This approach is solvent free and there is possibility for reusing adsorbent materials depending of adsorbent properties. This thesis covers the basics of adsorption-desorption process and takes detailed look on different adsorbent materials such as activated carbon (AC), metal-organic framework (MOF) and carbon nanotubes (CNT) and evaluates the effect of surface functionality and pore size distribution for adsorption process. In experimental part, a self-made autosampler functionality and its injection parameters were optimized. The autosampler is able to independently inject up to six in-tube extraction (ITEX) needles with complete desorption. The ITEX was constructed during this experiment with TENAX-GR adsorbent and the repeatability of autosampler and ITEXs were tested and compared to commercial system with extraction of different amines. The effectiveness of this system was also demonstrated for indoor volatile organic compound (VOC) analysis.
  • Kinnula, Ville (Helsingin yliopisto, 2021)
    In inductive inference phenomena from the past are modeled in order to make predictions of the future. The mathematical concept of exchangeability for random sequences provides a mathematical justification for the assumption that observations are independently and identically distributed given some underlying parameters estimable from the empirical distribution of the observations. The theory of exchangeability contains basic elements for inductive inference, such as the de Finetti representation theorem for the probability of a general exchangeable sequence, prior probability distributions for the parameters in the representation theorem, as well as the predictive probabilities, or rule of succession, for new observations from the random sequence under consideration. However, entirely unanticipated observations pose a problem for inductive inference. How can one assign a probability for an event that has never been seen before? This is called the sampling of species problem. Under exchangeability, the number of possible different events t has to be known before-hand to be able to assign an equal prior probability 1/t for each event. In the sampling of species problem an assumption of infinite possible events has to be made, leading to the prior probability 1/∞ for each event, which is impossible. Exchangeability is thus inadequate to handle probability distributions for infinite possible events. It turns out that a solution to the sampling of species problem arises from partition exchangeability. Exchangeable random sequences have the same probability of occurring, if the observations in the sequence have identical frequencies. Under partition exchangeability, the sequences have the same probability of occurring when they share identical frequencies of frequencies. In this thesis, partition exchangeability is introduced as a framework of inductive inference by juxtaposing it with the more familiar type of exchangeability for random sequences. Partition exchangeability has parallel elements to exchangeability, in the Kingman representation theorem, the Poisson-Dirichlet distribution for the prior probability distribution, and a corresponding rule of succession. The rules of succession are required in the problem of supervised classification to provide product predictive probabilities to be maximized by assigning the test data into pre-defined classes based on training data. A Bayesian construction of supervised classification is discussed in this thesis. In theory, the best classification performance is gained when assigning the class labels to the test data simultaneously, but because of computational complexity, an assumption is often made where the test data points are i.i.d. with regards to each other. In the case of a known set of possible events these simultaneous and marginal classifiers converge in their test data predictive probabilities as the amount of training data tends to infinity, justifying the use of the simpler marginal classifier with enough training data. These two classifiers are implemented in this thesis under partition exchangeability, and it is shown in theory and in practice with a simulation study that the same asymptotic convergence between the simultaneous and marginal classifiers applies with partition exchangeable data as well. Finally, a small application in single cell RNA expression is explored.
  • Dovydaitis, Emily (Helsingin yliopisto, 2021)
    Finland and Estonia form a cross-border region in Europe. Unlike other cross-border regions, which share a land border with their neighbor, Finland and Estonia are separated by the Gulf of Finland. The distance is close enough to facilitate regular travel by ferry on a weekly or monthly basis, but for Estonian immigrants living in Finland, daily commutes are unlikely. Given that Finland is the top migration destination for Estonians, the cross-border region of Estonia-Finland poses an interesting case study. In this thesis, the integration and transnationalism of Estonians living in Finland are studied through a spatial mobility lens. First, a theoretical framework is proposed to facilitate empirical research. The framework jointly examines integration and transnationalism by partitioning them into separate domains: social, structural, cultural, civic & political, identity, and spatial. The aim of the framework is to narrow the socio-spatial gap in migration literature, by focusing on the interwoven nature of the social and spatial perspectives. Using data from a comprehensive survey about Estonian immigrants living in Finland, the proposed theoretical framework is operationalized for multiple correspondence analysis (MCA). Three MCA analyses are performed: 1) social integration with host society (Finland), 2) social transnationalism with the sending society (Estonia), and 3) spatial transnationalism between the host society (Finland) and the sending society (Estonia). MCA results show that transnationalism and integration vary both across and within domains. MCA results are connected to one another using correlation analysis and general linear model (GLM) analyses. Correlation analysis and GLM demonstrate that for the study population, integration in the host society and transnationalism with the sending society are inversely associated. This inverse relationship carries over into the spatial domain and can be seen based on which country an immigrant does certain activities (e.g., visiting family, working, accessing healthcare, enjoying leisure time). Immigrants with strong social connections to the host society are more likely to do activities in Finland whereas immigrants with strong social connections to the sending society are more likely to do activities in Estonia. Some immigrants exhibit a multilocal mobility pattern, in which they do activities equally in both Estonia and Finland.
  • Johanson, Jorunn (Helsingin yliopisto, 2021)
    Geodiversity, the natural abiotic variety of the Earth’s surface, is an essential part of natural diversity and plays an important role in providing the abiotic ecosystem services that all life depends on. Geodiversity is increasingly threatened by human activities and climate change, and consequently there is a growing importance of including geodiversity in decision-making. However, there is still a lack of studies assessing the spatial variation and key drivers of geodiversity, especially in high latitude and altitude areas, and this study, therefore, aims to contribute to an improved understanding. In this study, the geodiversity of a subarctic mountainous area in Northern Norway was mapped using remotely sensed data and applying a grid-based approach. The spatial variation of geodiversity was assessed using five different measures, and the relationships between geodiversity and several topographical parameters were analysed using correlation analysis (Spearman’s rank correlation, RS) as well as both univariate and multivariate linear regression. The vertical variation of geodiversity was also examined to analyse the variation of geodiversity along altitudinal gradients. A total of 54 geodiversity elements were observed in the study area and the number of elements per grid cell varied from 7 to 36. Four of the geodiversity measures correlated strongly, resulting in relatively similar spatial patterns of diversity. Higher values tended to follow the valley systems and cluster in the vicinity of rivers and larger streams. Topographically diverse grid cells, containing both steeper slopes and smoother areas, also contained a higher diversity. Low diversity occurred mainly on the highest elevations as well as on the steepest slopes. The majority of the univariate relationships between the measures of geodiversity and the topographical parameters were statistically significant, although the correlations generally were relatively weak. The regression models further confirmed the relationship between topography and geodiversity, and revealed various statistically significant relationships, as well as the presence of both linear and unimodal relationships. Higher geodiversity generally occurred in topographically heterogeneous landscapes, as well as in the vicinity of rivers and larger streams, where both erosion and accumulation processes are prominent, leading to a great variety of geomorphological elements and soil deposits. The summits and slopes of the mountain massifs, on the other hand, displayed a lower geodiversity. In these areas, erosion is significant, but accumulation processes are lacking. Furthermore, the hydrological diversity is generally low there. The vertical patterns of geodiversity were related to the spatial patterns since total geodiversity decreased steadily as mean elevation rose above 600 m a.s.l. The influence of topography on geodiversity patterns could also be seen in the statistically significant relationships between several topographical parameters and the geodiversity measures. There was, however, some variation in the strength of the correlations, and the weaker relationships can partly be explained by the contradictory effect of slope angle and elevation on geodiversity. These patterns were further confirmed by the fact that the regression models revealed not only linear, but also unimodal relationships between the topographical parameters and geodiversity. Although topography seems to have an important effect on all geodiversity measures, there is some variation in which topographic parameters are the most important for the different measures. To conclude, this study of a northern high latitude mountainous area shows that high geodiversity occurs in the vicinity of rivers and larger streams, as well as in landscapes with a varied relief. Topography has a statistically significant influence on geodiversity, although the magnitude and direction of the effect varies between the elements of geodiversity. To facilitate the incorporation of geodiversity in education, land use planning, resource management and nature conservation, more research is still required about the patterns and drivers of geodiversity.
  • Koskikallio, Hanna (Helsingin yliopisto, 2021)
    Ylioppilaslautakunnan (2020) pistejakaumien perusteella lukiolaisten osaaminen todennäköisyys- ja tilastolas- kennan tehtävissä on ollut keskimäärin muita tehtäviä huonompaa vuosina 2011-2020. Tämän maisterintutkiel- man tavoitteena on edistää lukiolaisten todennäköisyys- ja tilastolaskennan osaamista luomalla lukioon sopivaa opiskelumateriaalia kombinatoriikasta. Työn matemaattinen osuus käsittelee lukiossa tarvittavaa kombinatoriikkaa. Osiossa käydään läpi kombinato- riikan peruskäsitteet: tuloperiaate, summaperiaate, kombinaatio ja permutaatio sekä todistetaan niihin liittyviä lauseita. Lisäksi esitellään lyhyesti binomikerroin sekä Pascalin kolmio. Kombinatoriikan itseopiskelu -osio sisältää kasvatustieteellisen teorian, jonka varaan materiaalin valinnat ja linjaukset pohjautuvat. Osiossa keskitytään kombinatoriikan ja ongelmanratkaisun oppimiseen sekä käsitellään teorioita itsenäisen opiskelun näkökulmasta. Matemaattisia representaatioita käydään läpi opiskelumateriaalin sisällön kannalta ja itsearviointia pohditaan lyhyesti. Itseopiskelumateriaali esitellään työn neljännessä osiossa. Osio etenee materiaalin lukujen järjestyksessä viita- ten työn teoriaosion keskeisiin sisältöihin ja niiden näkymiseen materiaalin sisällöissä. Valmis materiaali antaa raamit kombinatoriikan itseopiskeluun soveltuvan materiaalin luomiseen. Se toimii esimerkkinä ja luo mahdol- lisuuksia tutkimusperustaisen opiskelumateriaalin tekemiseen. Materiaalissa olevia ohjeita, esimerkkejä ja teh- tävänantojen tulkintoja voi käyttää sellaisenaan erillisinä osina opetuksen tai itsenäisen opiskelun materiaalina.
  • Metsalo, Vilhelm (Helsingin yliopisto, 2021)
    The cooperation between Finland and Estonia is most visible in the collaboration between the capitals of the countries. The twin city development of Helsinki and Tallinn and the planned tunnel infrastructure between the cities have caused societal debates in both countries. The societal debate on the themes gained new importance when Estonia became part of the EU and NATO in 2004. The tunnel infrastructure connecting the cities became a major news topic from the mid-2010s onwards, and it was also an important part of news coverage regarding the cooperation between the countries. The progress of the public and private tunnel projects sparked interest in the major daily newspapers in both countries. The theoretical background of the thesis is based on the theories of cross-border cooperation, twin cities and spatial planning. The theoretical framework of the thesis revolves also around the strategic framing and anchor infrastructures used in the media as part of territorial cohesion. Discursive framing and regional branding in the media are both important parts of regional formation. The aim of the study was to find out the discourses used in framing the twin city and tunnel connection in the largest daily newspapers of Finland and Estonia. The conclusion of the dissertation is that geographical reality can be interpreted by studying discourses and societal significance. Media discourses convey a broader societal debate on the topics. The material of the study was articles in the online publications of Helsingin Sanomat and Postimees from 2004-2020. The study examined the articles according to the framework of content analysis and critical media discourse analysis. The study examined the forms of discursive framing through media discourses. Based on the data analysis, the tunnel infrastructure is a more newsworthy topic than the twin city. The tunnel plays an important role in shaping the discourses in the research material. The tunnel is framed as a foundational part of the twin city and wider regional context. The tunnel connection gains relevance by forming the area and enabling growth. Improving accessibility and connection to Central Europe are major parts of the Finnish tunnel discourse. Economic perspectives are part of the discourse in both journals. Major political actors in both countries, such as ministers and mayors, are most prominently present in the research material. Political agency is embodied in the framing of anchor infrastructure. The entry of the privately funded tunnel project in 2016 changes the themes of the articles. The private tunnel project is causing occasional opposition from countries’ politicians and officials, manifested in confrontation represented in the media. In Finland the criticism of the private project is focused on the alignment of the tunnel, whereas in Estonia on security policy concerns caused by foreign funding. The largest daily newspapers in Finland and Estonia serve as a platform for the societal debate. Their articles delimit and frame the topics of societal debate. The means of strategic framing and raising the news value of the topic become the focus of the research material as the media focuses more on the tunnel connection after the mid-2010s. The discursive framing of the twin city takes place through a tunnel infrastructure. The discursive framing that emerges in the media reflects the geographical significance of different actors.
  • Heiskanen, Tuomas (Helsingin yliopisto, 2021)
    Työn tarkoitus on kartoittaa verkkopedagogiikan kasvatustieteellisen tutkimuksen keskeisiä alueita ja teoreettista taustaa ja mitä piirteitä laadukkaalla verkkopedagogiikalla ja hyvällä verkkokurssilla on. Työn soveltavana osuutena on lukuteorian teoriaa ja lukuteoriaan liittyviä tehtäviä, jotka on tarkoitettu Lukuteoriaa lukiolaisille -verkkokurssille, jonka sisältö on vuoden 2019 lukion opetussuunnitelman moduulin MAA11 Algoritmit ja lukuteoria mukainen. Opiskelijat toteuttavat tehtävät Python -ohjelmointikielellä. Verkkokursseja voi luokitella muun muassa verkko-opetuksen suhteellisen osuuden, ajoittumisen, avoimuuden ja sen mukaan kuinka paljon kursseilla on yhteistyötä ja yhteisöllisyyttä. Lähes kaikki oppilaitoksien kurssit ovat sekamuotoisia eli sisältävät sekä verkko että lähiopetusta. Verkko-opetus joustavoittaa ja yksilöllistää koulutusta ihmisten ja myös yhteiskunnan tarpeisiin mukautuen. Viimeaikaisen meta-analyysin mukaan lähiopetusta voi vähentää huomattavasti ja silti saada samat tai paremmat oppimistulokset kuin pelkällä lähiopetuksella. Erityisesti tämä tulos pätee luonnontieteiden opetukseen. Vertailtaessa verkkokursseja suhteessa toisiinsa on eroteltu kolme laadukkaan verkko-opetuksen keskeistä piirrettä: suunnittelu, arviointi ja fasilitointi. Suunnittelussa tärkeää oli selkeän oppimispolun ja tarkoituksen tunteen luonti opiskelijoille. Kurssin suunnitelleen ryhmän työn laatua voi arvioida ulkopuoliset asiantuntijat. Fasilitoinnissa tärkeää oli mm. opettajan läsnäolo ja nopea reagointi opiskelijoiden yhteydenottoihin. MOOC-kurssien opiskelijapalautetta arvioitaessa on havaittu, että matemaattisilla ja tietoa käsittelevillä aloilla opettajan ja luennointitaidon merkitys on suurempi kuin muilla aloilla. Verkkopedagogiikan teoreettisesta taustasta löytyy kolme konstruktivistista tutkimustraditiota: tutkiva yhteisö -kehys, käänteinen oppiminen ja tietokoneavusteinen yhteisöllinen oppiminen (CSCL). Konstruktivismissa oppimisen ajatellaan olevan tiedon ja merkitysten rakentumista oppilaan mielessä ja oppimisyhteisön olevan tälle prosessille tärkeä. Keskeinen ongelma ja samalla mahdollisuus on oppimisyhteisön luominen verkkoympäristössä. Tutkiva yhteisö -kehyksen mukaan oppimiselle tärkeitä elementtejä ovat sosiaalinen läsnäolo yhteisössä, opettamisen läsnäolo ja kognitiivinen läsnäolo. Laajojen tähän malliin perustuvien kyselytutkimusten tulokset viittaavat siihen, että sosiaalisen läsnäolon elementin merkitys tiedon rakentumiselle on välillinen, ei suora. Sitävastoin intensiivisemmällä kahden välisellä kommunikaatiolla oli selkeä suora merkitys oppimisen kannalta oli kyse vertaisesta tai opettajasta. Sosiaalista läsnäolon elementtiä voisi siis pitää motivoivana tekijänä ei suoraan tiedon rakentumiseen eli oppimiseen vaikuttavana. Käänteisen oppimisen perusajatus on yhteisen “luokkahuoneajan”, joka voi tapahtua joko verkossa tai kasvokkain, käyttäminen ongelmien ratkaisuun ja käsitteiden selventämiseen, ei tiedon välittämiseen. Käänteisessä oppimisessa painopiste on siirtynyt oppijan oikea-aikaiseen tukemiseen lähikehityksen vyöhykkeellä. Tavoitteena on oppija joka on oppinut oppimaan yksilöllisesti ja itsenäisesti. Suomessa tavoitteena on kaikkien kouluttaminen ja käänteisen oppimisen lähestymistapa sopii tähän hyvin. Meta-analyysissä käänteisellä oppimisella on ollut myönteinen vaikutus oppimistuloksiin. Verkkopedagogiikan tutkimustraditiot muistuttavat puunhaaroja, joista jotkut kuihtuvat ja toiset kasvavat nopeammin. Tyypillistä on, että samoja 20-30 vuotta sitten esitettyjä ajatuksia esitetään uudestaan kaikesta tutkimuksesta ja kritiikistä ja kehitysehdotuksista huolimatta. Traditiot ovat kuitenkin tiukan empiirisiä ja oletetettavasti opetuksessa käyttökelpoisimmat haarat tulevat kasvamaan parhaiten. Mielenkiintoisia tutkimusalueita mielestäni ovat arvioinnin ja kilpailun vaikutus yhteistyöhön ja luova, tuloksia tuottava ja osanottajista miellyttävä yhteistyö. Lukuteorian materiaalien suunnittelussa olen pyrkinyt lähtemään opiskelijoille tutuista laskusäännöistä, joiden avulla laajemmat kokonaisuudet kuten Eukleideen algoritmi tulisivat ymmärrettäviksi. Päämääränä on, että he itse pystyisivät toistamaan lukuteorian rakenteita ymmärtäen ne aikaisempaan tietoon ja intuitioon perustuen
  • Kujala, Sanna (Helsingin yliopisto, 2021)
    This master’s thesis examines the location privacy perceptions, privacy behaviours, and uses of location online. Young adults have grown up in the era of the internet, which means that they have big data collected of them since their first day online as teenagers or younger children. The topic of perceived location privacy is yet to be researched in Finland. The aim of this thesis was to understand; what are the location privacy perceptions and location privacy knowledge of young Finnish adults, and to see if the privacy paradox is in effect within the young Finnish adults. The research is based on a qualitative method and three focus groups were held to collect the data. During focus groups sessions the participants were free to discuss location privacy-related topics and their own experiences. From there on the data was analysed by using inductive content analysis methods on Atlas.ti program. The results of this research indicate that young adults are not confident in their knowledge of location privacy. The participants voiced clear worry over their privacy while using social media and mobile phones, but actions towards protecting personal privacy were not taken. This disparity between privacy concerns and taken privacy protection action was identified as privacy paradox. Most commonly, the individual’s privacy concerns were towards unknown individuals rather than the platforms or companies behind them. Aside from discussing their privacy concerns, the young adults voiced several instances of beneficial usage of personal location sharing, such instances were: location sharing to friends when trying to find each other in public places, personal navigation, quantified self, and others. It was found that young Finnish adults found it concerning that they have a lack of interest in their privacy, but still stated that they might not work to improve their knowledge or measures taken to protect their privacy online. The aspect of geographical location did matter to the young adults, and Finland and Europe were seen as most privacy protective countries of origins for applications and services.
  • Kauppala, Tuuli (Helsingin yliopisto, 2021)
    Children’s height and weight development remains a subject of interest especially due to increasing prevalence of overweight and obesity in the children. With statistical modeling, height and weight development can be examined as separate or connected outcomes, aiding with understanding of the phenomenon of growth. As biological connection between height and weight development can be assumed, their joint modeling is expected to be beneficial. One more advantage of joint modeling is its convenience of the Body Mass Index (BMI) prediction. In the thesis, we modeled longitudinal data of children’s heights and weights of the dataset obtained from Finlapset register of the Institute of Health and Welfare (THL). The research aims were to predict the modeled quantities together with the BMI, interpret the obtained parameters with relation to the phenomenon of growth, as well as to investigate the impact of municipalities on to the growth of children. The dataset’s irregular, register-based nature together with positively skewed, heteroschedastic weight distributions and within- and between-subject variability suggested Hierarchical Linear Models (HLMs) as the modeling method of choice. We used HLMs in Bayesian setting with the benefits of incorporating existing knowledge, and obtaining full posterior predictive distribution for the outcome variables. HLMs were compared with the less suitable classical linear regression model, and bivariate and univariate HLMs with or without area as a covariate were compared in terms of their posterior predictive precision and accuracy. One of the main research questions was the model’s ability to predict the BMI of the child, which we assessed with various posterior predictive checks (PPC). The most suitable model was used to estimate growth parameters of 2-6 year old males and females in Vihti, Kirkkonummi and Tuusula. With the parameter estimates, we could compare growth of males and females, assess the differences of within-subject and between-subject variability on growth and examine correlation between height and weight development. Based on the work, we could conclude that the bivariate HLM constructed provided the most accurate and precise predictions especially for the BMI. The area covariates did not provide additional advantage to the models. Overall, Bayesian HLMs are a suitable tool for the register-based dataset of the work, and together with log-transformation of height and weight they can be used to model skewed and heteroschedastic longitudinal data. However, the modeling would ideally require more observations per individual than we had, and proper out-of-sample predictive evaluation would ensure that current models are not over-fitted with regards to the data. Nevertheless, the built models can already provide insight into contemporary Finnish childhood growth and to simulate and create predictions for the future BMI population distributions.
  • Harju, Tuomas (Helsingin yliopisto, 2021)
    Julkinen tila on kaupungissa keskeinen tekijä ja tori on julkisista tiloista leimallisin. Historiallisesti torien merkitys kaupungissa on suuri ja vaihdellut historian aikana. Tori on mielenkiintoinen keskus kaupungissa: dynaaminen ja eläväinen torikaupan aikoina, hiljainen ja autio niiden ulkopuolella. Julkisten tilojen monipuolistuminen on asettanut torit asemaan, jossa ne eivät enää ole ensisijainen kokoontumispaikka. Tori elää kaupungin mukana ja saa kehityksen tuloksena uusia funktioita. Tutkimus selvittää näitä käyttötarkoitusten muutoksia käyttäen tapausesimerkkinä Porvoon toria 1832–2021. Tutkimus on saanut alkunsa Porvoon kaupungin keskustakehittämishankkeesta, johon liittyen tutkimuksen tekijä laati toriympäristön historiaselvityksen vuonna 2020. Tutkimuksen metodina on temaattinen tarkastelu, joka torin historiallisia vaiheita vertaamalla ja yhteiskunnalliseen kontekstiin asettamalla vastaa kysymykseen, kuinka torin muuttuvat funktiot ovat vaikuttaneet sen rooliin kaupungissa. Lähdeaineisto koostuu arkistolähteistä, valokuvista, sanomalehtijulkaisuista täydennettynä toriyrittäjien haastatteluilla. Kirjallisuus hyödyntää erityisesti julkisen tilan piirteitä sekä Porvoon historiaa selvittäneitä teoksia. Tutkimuksen teoreettinen viitekehys soveltaa Lefebvren tilan tuotannon teoriaa korostamalla ihmisen oikeutta kaupunkiin ja toria kaupunkilaisten arjen tilana. Teoria tarjoaa perustan kaupunkisuunnittelun historiassa tehtyjen arvovalintojen tutkimiseen. Tutkimus teoretisoi myös tilaa suhteellisena käsitteenä ja tarkastelee paikan merkitystä kaupungissa siihen liitettyjen mielikuvien avulla. Tutkimus jakaa torin neljään toiminnalliseen funktioon, jotka ovat tulleet torille eri aikoina, mutta ovat kaikki läsnä nykyisin. Ensimmäinen funktio, torikauppa, on pitkään hiipuneenakin yhä elävä torin käyttötarkoitus. Toinen funktio on torin symbolisesti merkittävä edustusrooli. Se näkyy paitsi torin varrelle sijoittuneissa instituutioissa myös torin ajoittain korostuvassa roolissa kansalaisaktivismin näyttämönä. Kolmas funktio on kaupungin keskeisenä liikennealueena toimiminen. Keskeinen sijainti on tuonut torille linja-auto- ja taksiasemat, jotka ovat merkittävästi muokanneet torikuvaa 1930-luvulta tähän päivään. Neljäs funktio on tapahtumapaikka, joka liittyy kaupunkikeskustojen kehittämisen trendiin. Tori tarjoaa puitteet niin perinteisten kuin uusien kaupunkitapahtumien paikkana. Lisäksi tutkimus vertaa Porvoon toria kolmeen muuhun suomalaiskaupungin samanikäiseen toriin ja niiden historiaan. Torien taustojen analysointi selvittää, miksi ne ovat kehittyneet eri tavoin ja asettaa Porvoon torin historian laajempaan yhteiskunnalliseen kontekstiin.
  • Heikkinen, Johannes (Helsingin yliopisto, 2021)
    Tämän tutkielman kirjallisuuskatsaus käsittelee karbamaattien synteesimenetelmiä. Työssä käydään kevyesti läpi klassisia menetelmiä, joita ovat fosgeeniin pohjautuvat menetelmät, metallikatalysoidut reaktiot ja toisiintumisreaktiot. Moderneihin hiilidioksidiin pohjautuviin menetelmiin syvennytään tarkemmin. Läpi käydäänkin hiilidioksidin ja amiinin reaktio vedessä, orgaanisessa liuottimessa sekä superemästen avustamana. Erilaisia metodeja syklisten ja asyklisten karbamaattien valmistukseen esitellään alkyylihalideilla, epoksideilla, allyyli- ja propargyyliamiineilla sekä aminoalkoholeilla. Lopuksi tarkastellaan hieman karbamaattien atsa-Michael-reaktiota. Kokeellisessa osassa esitellään uusi stereoselektiivinen metodi 5-, 6-, ja 7-renkaisten karbamaattien valmistukseen hiilidioksidista ja aminoalkoholeista propyylifosfonianhydridin (T3P) avustamana. Karbamaattien saannot olivat hyviä.
  • Koutsompinas, Ioannis Jr (Helsingin yliopisto, 2021)
    In this thesis we study extension results related to compact bilinear operators in the setting of interpolation theory and more specifically the complex interpolation method, as introduced by Calderón. We say that: 1. the bilinear operator T is compact if it maps bounded sets to sets of compact closure. 2.\bar{ A} = (A_0,A_1) is a Banach couple if A_0,A_1 are Banach spaces that are continuously embedded in the same Hausdorff topological vector space. Moreover, if (Ω,\mathcal{A}, μ) is a σ-finite measure space, we say that: 3. E is a Banach function space if E is a Banach space of scalar-valued functions defined on Ω that are finite μ-a.e. and so that the norm of E is related to the measure μ in an appropriate way. 4. the Banach function space E has absolutely continuous norm if for any function f ∈ E and for any sequence (Γ_n)_{n=1}^{+∞}⊂ \mathcal{A} satisfying χ_{Γn} → 0 μ-a.e. we have that ∥f · χ_{Γ_n}∥_E → 0. Assume that \bar{A} and \bar{B} are Banach couples, \bar{E} is a couple of Banach function spaces on Ω, θ ∈ (0, 1) and E_0 has absolutely continuous norm. If the bilinear operator T : (A_0 ∩ A_1) × (B_0 ∩ B_1) → E_0 ∩ E_1 satisfies a certain boundedness assumption and T : \tilde{A_0} × \tilde{B_0} → E_0 compactly, we show that T may be uniquely extended to a compact bilinear operator T : [A_0,A_1]_θ × [B_0,B_1]_θ → [E_0,E_1]_θ where \tilde{A_j} denotes the closure of A_0 ∩ A_1 in A_j and [A_0,A_1]_θ denotes the complex interpolation space generated by \bar{A}. The proof of this result comes after we study the case where the couple of Banach function spaces is replaced by a single Banach space.
  • Toukola, Peppi (Helsingin yliopisto, 2021)
    In this thesis the suitability of Nuclear Magnetic Resonance (NMR) spectroscopy in the identification of rubbers in museum collections is discussed through a literature review and experimental work where samples from the rubber collection of Tampere Museums were analysed with different NMR techniques. The literature part of this thesis focuses on recent (2011-2020) scientific publications on analytical instrumental techniques used in the identification of cultural heritage plastics. Vibrational spectroscopy methods utilizing hand-held or portable devices have been the most prominent methods used in characterization of historical plastics materials. Bench-top devices and analytical techniques requiring sampling were used to acquire more detailed analysis results. However, NMR spectroscopy was not used as the main analysis technique in the reviewed publications. In the experimental part altogether 21 rubber object samples and 8 reference samples were identified using 1D and 2D NMR techniques in solution state. Three samples were additionally analysed with solid-state High Resolution Magic Angle Spinning (HRMAS) NMR spectroscopy. The chemical structures of the samples were confirmed with these methods. To further explore fast and more automated identification of the rubber samples a statistical classification model utilizing acquired solution-state 1H NMR data was developed. Three rubber types were chosen for the analysis. The model was created using analysis data from the museum object samples and validated using the reference sample data. Identification rate of 100 % was achieved.

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