Matemaattis-luonnontieteellinen tiedekunta

 

Recent Submissions

  • Hiltunen, Otto-Matti; Hiltunen, Otto-Matti (Helsingin yliopisto, 2020)
    Copper complexes are versatile catalysts for different fixations of carbon dioxide. Copper-catalyzed carboxylations of unsaturated hydrocarbons with CO2 provide access to valuable carboxylic acids. Generally, the formation of Cu-C species from the substrate and the catalyst is followed by carbon dioxide insertion across the Cu-C bond which produces copper carboxylate RCOO-Cu via C-C bond formation. Moreover, copper complexes can undergo transmetallation with less-nucleophilic organoboron reagents to afford Cu-C species. Copper-catalyzed reductive carboxylations of C-C unsaturated bonds with CO2 entail hydrogenative, alkylative and heterocarboxylation methodologies. This thesis elaborates a protocol for the N-heterocyclic carbene copper (I)-catalyzed synthesis of carboxylic acids from alkynes with carbon dioxide. The main interest lies in a regioselective hydrocarboxylation of alkynes catalyzed by NHC-copper hydrides and copper-catalyzed carboxylation of alkylboranes with CO2. The literature review focuses on the catalytic activity of N-heterocyclic copper (I) complexes in organometallic chemistry, especially within a range of reductive carboxylation reactions. Alkynes insert readily into the copper hydride bond constituting C-Cu species prior to the CO2 insertion. The regioselectivity of this carboxylation reaction derives from the syn addition of Cu-H species to the alkyne. Correspondingly, the alkylboranes can be carboxylized in a regiospecific fashion due to the regioselective manner of the initial hydroboration. In the experimental part, two different catalytic hydrocarboxylation pathways were carried out with in situ- copper (I) catalysts. The use of mild base additive CsF was necessary for the catalyst formation. The first pathway was catalyzed by a NHC-copper(I)-hydride complex in the presence of hydrosilane as the reducing agent. In the second pathway, a tandem hydroboration carboxylation sequence was utilized, catalyzed by copper(I) fluoride species. Both pathways furnished carboxylic acids from terminal and internal alkynes.
  • Olander, Tom (Helsingin yliopisto, 2020)
    Denna avhandling ställer frågor kring vad det innebär för den långa matematiken i gymnasiet när programmering tillkommer enligt läroplanen. Först granskas den tidigare forskningen kring programmering och matematik i gymnasiet och till vilka slutsatser man kommit i dessa. Att programmering kan vara till nytta för studeranden i yrkeslivet är givet, men huruvida programmering skall höra till matematiken är en av huvudfrågorna i avhandlingen. Eftersom det inte finns mycket forskning kring programmering i matematik i Finland har här även används forskning gjort i andra länder. Samma sak gäller för den aktuella åldersgruppen, därför har även forskning med studeranden i ungefär samma ålder använts. Inget undervisningsmaterial ännu finns för programmeringen i gymnasiet. Därför finns här också förslag till uppgiftstyper som kunde användas i undervisningen. Dessa exempel får fritt modifieras och användas som hjälp vid planering av undervisningen. En annan användning av denna avhandling kunde vara att låta den vara som grund för kommande planering av programmering i gymnasiet angående så väl i vilka ämnen programmering hanteras och hur denna undervisning
  • Laakso, Jannica (Helsingin yliopisto, 2020)
    Tutkimuksessa tutkittiin Suomen kemian opettajien käsityksiä kemian teknologiasta sekä tietokonemittauksen näkyvyyttä opetuksessa. Tavoitteena oli selvittää, tietävätkö kemian opettajat, mitä tarkoitetaan kemian teknologialla ja millaiset opettajat käyttävät tietokonemittausta opetuksessa. Tämän tutkimuksen tutkimuskysymykset ovat seuraavat: 1. Miten Suomen kemian opettajat määrittelevät kemian teknologian? 2. Miten opettajat perustelevat tietokonemittausten käyttämistä? 3. Millaiset kemian opettajat käyttävät tietokonemittausta paljon ja millaiset vähän? Tutkimuksen aineisto hankittiin kyselylomakkeella ja vastausten (n = 193) analysoimisessa yhdistettiin kvalitatiivisia ja kvantitatiivisia menetelmiä. Avoimia vastauksia analysoitiin laadullisesti ohjelman Microsoft Excel avulla. Ensimmäisen tutkimuskysymyksen analysoitaessa vastauksista etsittiin yhteisiä piirteitä ja niistä muodostettiin luokkia temaattisella analyysillä. Toisen tutkimuskysymyksen analysoimisessa vastauksia luokiteltiin TPACK-malliin pohjautuen. Kolmanteen tutkimuskysymyksen kohdalla dataa analysoitiin kvantitatiivisesti ohjelmalla SPSS. Tutkimuksen tuloksista havaittiin, ettei kemian teknologian määrittely ole opettajille yksiselitteistä ja että noin kolmasosa vastaajista ei hyödynnä tietokonemittauksia lainkaan kemian opetuksessa. Syy vähäiseen käyttöön saattaa selittyä sillä, että tietokonemittauslaitteet nähdään vain sähköisinä työkaluina, eikä niissä nähdä selkeää pedagogista tai ainesisällöllistä hyötyä. Tutkimuksessa havaittiin tietokonemittauslaitteiden olevan eniten käytössä lukion opettajilla, korkeammin koulutuetuilla opettajilla sekä aktiivisesti täydennyskoulutukseen osallistuvilla opettajilla. Perusteluina tietokonemittauksen käyttämättä jättämiselle olivat lähinnä laitteiden ja oman osaamisen puute sekä laitteiden kokeminen tarpeettomiksi alemmilla luokilla.
  • Kivioja, Timo (Helsingin yliopisto, 2020)
    Kieli on keskeinen osa oppimista ja niitä ei voida erottaa. Tieteellä on oma kieli, joka eroaa merkittävästi opiskelijoiden tuntemasta arkikielestä monella tapaa. Tieteellinen kieli sisältää suuren määrän informaatiota lyhyessä tekstissä, sisältää opiskelijoille tuntemattomia termejä ja myös lauserakenne on erilainen. Opiskelijoiden tieteen oppimisessa tieteellisen kielen oppiminen onkin yksi suurimmista ongelmista. Tämän vuoksi tulevien fysiikan aineenopettajien kielellisten ilmaisujen tutkiminen on tärkeää. Opinnäytetyössä analysoidaan fysiikan aineenopettajaopiskelijoiden tuottamia tekstejä fysiikan aineenopettajakoulutuksen kurssilta. Aineisto koostuu 12 tekstistä kuudelta eri fysiikan aineenopettajaopiskelijalta. Tarkoituksena on vastata tutkimuskysymyksiin: 1. Miten voimme analysoida aineenopettajaopiskelijoiden sanaston käyttöä? ja 2. Miten fysiikan aineenopettajaopiskelijat käyttävät kaksoisrakokokeen sanastoa? ja kehittää luotettava ja toistettavissa oleva analyysiprotokolla, jolla voidaan analysoida suomenkielisiä tekstejä. Analyysinlopputulos on yksinkertaistettu muoto aineistosta, jota voidaan analysoida tulevaisuudessa mahdollisesti tietokoneella. Teoriaosassa käsitellään lisäksi käsitteitä, käsitteellistä muutosta sekä semanttisia ja sanastollisia verkkoja. Tuloksena itse analyysin tuloksien lisäksi on analyysiprotokolla, jolla pystytään analysoimaan suomenkielisiä tekstejä. Fysiikan aineenopettajaopiskelijoiden tekstien analyysistä saatiin selville, että aineenopettajaopiskelijoiden sanaston käyttö on varsin laajaa ja monipuolista. Analyysin perusteella saatiin myös selville teksteissä esiintyviä mm. tekstissä esiintyviä lauseenrakenteita ja että teksteissä fysiikan aineenopettajaopiskelijat vaihtoivat aihetta melkein joka toisessa virkkeessä. Analyysiprotokollaa pystytään kuitenkin vielä jatkossa tarkentamalla ja selventämällä sitä. Analyysiprotokollan luotettavuutta pitäisi myös tutkia siten, että toinen analyysin tekijä suorittaisi analyysin.
  • Haapakangas, Eeva (Helsingin yliopisto, 2020)
    Vuoden 2016 opetussuunnitelmassa ohjelmointi tuotiin uutena alueena yläkouluihin osaksi matematiikan opetusta. Tämän tutkielman tarkoituksena on selvittää, millaisia erilaisia oppimateriaaleja tässä opetuksessa käytetään ja miten yläkoulun ohjelmoinnin opetusta voitaisiin kehittää oppimateriaalien avulla. Oppimateriaaliksi tässä tutkielmassa määritellään oppikirja (digitaalinen tai paperinen), oppi-/tehtäväkirja (digitaalinen tai paperinen), tehtäväkirja (digitaalinen tai paperinen), opettajan materiaali, verkkopohjaiset oppimisympäristöt (voidaan toteuttaa eri teknologioilla, kuten pilvipalveluna tai verkkoympäristössä), muut teknologiaympäristöt, kuten esimerkiksi opetuskäyttöön suunnitellut ohjelmoitavat robotit, elektroniikka-alustat, älypuhelinten ohjelmointi ja pelit. Erityisesti etäopiskelun yhteydessä käytetyt ja kehitetyt teknologiat vaikuttavat myös ohjelmoinnin opetuksessa käytettäviin oppimateriaaleihin. Elektroninen oppiminen, mobiilioppiminen ja ubiikki oppiminen muovaavat tulevaisuudessa myös ohjelmoinnin opetuksessa käytettäviä materiaaleja ja ympäristöjä. Tutkielman osana tehtiin tutkimustehtävä, jossa kysyttiin yläkoulun opettajilta heidän kokemuksiaan ohjelmoinnin opetuksesta sekä parannusehdotuksia erityisesti oppimateriaaleihin. Tutkimus sisälsi sekä monivalinta- että avoimia kysymyksiä ohjelmointikielistä ja -ympäristöistä, koulujen teknologiaympäristöistä ja oppimateriaaleista. Myös opettajien omia kokemuksia ohjelmoinnin opetuksesta kysyttiin. Tutkimuksen aineisto koostui 34 matematiikan opettajan vastauksista. Tämän tutkimuksen tuloksia voi hyödyntää ennen kaikkea suunniteltaessa oppimateriaalia ohjelmoinnin opetukseen yläkouluihin. Yhteenvetona ohjelmoinnin oppimateriaalin kehittämiselle ehdotetaan seuraavat asiat: 1. Käytössä tekstipohjainen ohjelmointikieli, mieluimmin Python. 2. Ohjelmointiympäristö, joka sisältää tuen tehtävien automaattiselle palautukselle ja tarkistamiselle. 3. Harjoitustehtäviä, jotka sisältävät muutakin kuin koodausta, esimerkiksi koodin lukemista, korjaamista, selittämistä ja parantamista. 4. Opetettavaan aiheeseen integroituja harjoitustehtäviä. 5. Eriyttämisen mahdollistavia harjoitustehtäviä. 6. Opettajan materiaalia, joka sisältää tunneilla läpikäytävän aineiston sekä tuntisuunnitelmat. 7. Mahdollisesti erillinen ohjelmoinnin oppimateriaali (oppikirja).
  • Mällinen, Topias (Helsingin yliopisto, 2020)
    Ylioppilaskirjoitusten sähköistämishanke toteutettiin vuosina 2016–2019. Kemian ylioppilaskokeen sähköinen suorittaminen herätti keskustelua hankkeen alusta asti, sillä vaikeuksia tuotti sopivan molekyylimallinnusohjelmiston saaminen osaksi Abittia ja koejärjestelmää. Keväällä 2017 Ylioppilastutkintolautakunta ilmoitti lisäävänsä MarvinSketch- mallinnusohjelmiston osaksi Abittia ja ylioppilaskoejärjestelmää. MarvinSketch-ohjelmistoa ei ollut juuri käytetty ennen tätä, joten suurin osa opettajista on joutunut ja joutuu edelleen omaksumaan ohjelmiston käytön alusta alkaen. Tämän tutkimuksen tavoitteena oli selvittää, millaisia huolenaiheita kemian opettajat kokevat MarvinSketch-ohjelmiston omaksumisen aikana. Tutkimusta ohjasi kolme tutkimuskysymystä: 1) Millaisia huolenaiheita eritasoiset MarvinSketch-ohjelmistoa käyttävät kemian opettajat kokevat ohjelmiston käytössä? 2) Millaisia huolenaiheita kemian opettajat kokevat MarvinSketch-ohjelmiston käytössä opetuskokemuksen mukaan eriteltynä? 3) Millaisia huolenaiheita kemian opettajat kokevat MarvinSketch-ohjelmiston käytössä tarkasteltaessa käyttötason ja opetuskokemuksen yhdistelmiä? Tulosten perusteella on tarkoitus kehittää opettajille suunnattuja MarvinSketch-koulutuksia. Tutkimus toteutettiin kyselylomaketutkimuksena, huolenaiheisiin perustuvan omaksumismallin pohjalta kehitetyn huolenaihekyselyn avulla. Kysely toteutettiin vuosien 2017–2018 aikana ja siihen vastasi 111 kemian opettajaa. Tulokset analysoitiin kvantitatiivisesti huolenaihekyselylle kehitetyn analysointimatriisin avulla. Tutkimuksen tulokset osoittavat, että kemian opettajat kokevat suurta huolta MarvinSketch- ohjelmiston käytöstä ja ohjelmistoon liittyvistä henkilökohtaisista asioista. Ohjelmiston vaikutukset opiskelijoihin tuottavat pienintä huolta. Johtopäätöksenä voidaan todeta, että opettajat haluavat tietoa ohjelmiston perusominaisuuksista ja käyttövaatimuksista sekä siitä, miten ohjelmistoa käytetään pedagogisesti mielekkäällä tavalla.
  • Seppälä, Outi (Helsingin yliopisto, 2020)
    Arctic soils store significant amounts of carbon deposited by plants and litter. Carbon is released from the soil in respiration due to plant roots and decomposition by microbes. In the northern hemisphere, carbon inputs from photosynthesis have exceeded releases of carbon to atmosphere via respiration. Arctic soils have been a globally remarkable carbon sink due to cold and waterlogged conditions. However, rising global temperatures and changes in hydrology have caused the carbon fluxes in soil-atmosphere interface to alter. Arctic areas are considered especially vulnerable to climate change and alterations in the arctic soil carbon pools could create powerful feedbacks to warming. Furthermore, drivers controlling soil respiration flux remain poorly known, especially their contributions in different environments and their dynamics in time. Thus, understanding soil respiration as a process is vital in understanding future changes in the global carbon cycle.The aim of this study was to identify environmental drivers of soil respiration in tundra at landscape-scale and their relative importance in different stages of growing season. The study area was a valley between two fells at Kilpisjärvi, Finland. Soil respiration was measured using the chamber method in 100 study sites on the 3 x 2 km landscape three times during the summer of 2018. Environmental data on soil microclimate and vegetation properties was gathered fromthe area as well. The impact of environmental conditions to respiration flux was studied using multiple generalized linear models with different explanatory variable combinations.Results suggest that abundant vegetation causes high respiration by providing resources for belowground microbes and creating extensive root network. Highest respiration was measured in peak growing season, when elevated temperatures stimulated respiration exclusively in tundra meadows. It seems that vegetation and soil parameters also define the temperature response of respiration. The flux increased with elevated temperatures only on soils that are assumed to have adequate nutrient and carbon composition to support higher respiration. This study suggests that onlandscape-scale, the resources provided by vegetation are of bigger importance to respiration than climatic changes both spatially and temporally.Moving forward, more empiricaldata is needed in order to accurately model future changes in respiration. Intense sampling efforts from the Arctic tundra areasthatcover the large spatial and temporal variabilityof respiration are necessary.
  • Salmela, Niko (Helsingin yliopisto, 2020)
    This thesis examines a conflict situation, which has initiated in consequence of a war of the past. The framework of the study consists of different approaches of both political and functional geography. The research question is how a long conflict situation appears through different geographical scales and how it relates to processes counterproductive to it, like cross border regionalization, globalization and integration projects of states. As a case study I have the territorial dispute in Atacama between three South American states, Bolivia, Chile and Peru, concerning the territorial division resulting from the War of the Pacific (1879-1883). The dispute touches the most Bolivia, who lost all its coastal territory to Chile and thus remained landlocked. Bolivia demands Chile to return to it a sovereign access to the Pacific coast. Chile finds this demand unfounded because the countries made a peace treaty in 1904, that obliged Chile to construct a railway from the coast to Bolivia and guarantee access to its ports. Bolivia argues its demand by claiming that the treaty was dictated by the winning part and that it’s unfavorable to Bolivia. The conflict involves Peru in the case that Chile would intend to cede formerly Peruvian territories to Bolivia. The treaty of Lima in 1929 obliges Chile to consult Peru before ceding any territory. Chile and Bolivia have negotiated several times in order to solve the dispute, but without results. Bolivia took the affair to the International Court of Justice in The Hague in 2013 expecting the court to force Chile to negotiate a sovereign access to the sea for Bolivia. The court ruling in 2018 was favorable to Chile, so there’s no obligation to negotiate. This was a turning point in the history of the conflict situation. The aim of the study is to show the big picture of the conflict situation, to illustrate the political and functional dimensions of the case and to present possible ways to reach a solution. The source material I have used to this paper consist of media content available online, literature written about this case and theory books. My methods have been observations at the area of the study, content analysis of both literature and online sources and discussion. The presented alternatives for solution are based on either cessation of sovereign territory or on integration without sovereignty. As a conclusion it can be noted that nationalistic identity policy and overemphasized significance of legal sovereignty are factors that tend to maintain and reinforce the conflict. Instead globalization, regionalization and integration are such counteracting processes to the conflict that make it less alluring for the parts to continue it.
  • 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.
  • Jahnsson, Niklas (Helsingfors universitet, 2015)
    Bayesian networks are graphical models used to represent the joint probability distribution for all variables in a data set. A Bayesian network can be constructed by an expert, but learning the network from the data is another option. This thesis is centered around exact score-based Bayesian network structure learning. The idea is to optimize a scoring function measuring the fit of the network to the data, and the solution represents an optimal network structure. The thesis adds to the earlier literature by extending an external memory frontier breadth-first branch and bound algorithm by Malone et al. [MYHB11], which searches the space of candidate networks using dynamic programming in a layered fashion. To detect duplicates during the candidate solution generation, the algorithm uses efficiently both semiconductor and magnetic disk memory. In-memory duplicate detection is performed using a hash table, while a delayed duplicate detection strategy is employed when resorting to the disk. Delayed duplicate detection is designed to work well against long disk latencies, because hash tables are currently still infeasible on disk. Delayed duplicate detection allows the algorithm to scale beyond search spaces of candidate solutions fitting only in the comparatively expensive and limited semiconductor memory at disposal. The sorting-based delayed duplicate detection strategy employed by the original algorithm has been found to be inferior to a hashing-based delayed duplicate strategy in other application domains [Kor08]. This thesis presents an approach to use hashing-based delayed duplicate detection in Bayesian network structure learning and compares it to the sorting-based method. The problem faced in the hashing of candidate solutions to disk is dividing the candidate solutions in a certain stage of the search in an efficient and scalable manner to files on the disk. The division presented in this thesis distributes the candidate solutions into files unevenly, but takes into account the maximum number of candidate solutions that can be held in the semiconductor memory. The method works in theory as long as operating system has free space and inodes to allocate for new files. Although the hashing-based method should in principle be faster than the sorting-based, the benchmarks presented in this thesis for the two methods show mixed results. However, the analysis presented also highlights the fact that by improving the efficiency of, for example, the distribution of hashed candidate solutions to different files, the hashing-based method could be further improved.
  • Toivonen, Juhani (Helsingfors universitet, 2015)
    Computation offloading can be used to leverage the resources of nearby computers to ease the computational burden of mobile devices. Cloudlets are an approach, where the client's tasks are executed inside a virtual machine (VM) on a nearby computing element, while the client orchestrates the deployment of the VM and the remote execution in it. Mobile devices tend to move, and while moving between networks, their address is prone to change. Should a user bring their device close to a better performing Cloudlet host, migration of the original Cloudlet VM might also be desired, but their address is then prone to change as well. Communication with Cloudlets relies on the TCP/IP networking stack, which resolves address changes by terminating connections, and this seriously impairs the usefulness of Cloudlets in presence of mobility events. We surveyed a number of mobility management protocols, and decided to focus on Host Identity Protocol (HIP). We ported an implementation, HIP for Linux (HIPL), to the Android operating system, and assessed its performance by benchmarking throughput and delay for connection recovery during network migration scenarios. We found that as long as the HIPL hipfw-module, and especially the Local Scope Identifier (LSI) support was not used, the implementation performed adequately in terms of throughput. On the average, the connection recovery delays were tolerable, with an average recovery time of about 8 seconds when roaming between networks. We also found that with highly optimized VM synthesis methods, the recovery time of 8 seconds alone does not make live migration favourable over synthesizing a new VM. We found HIP to be an adequate protocol to support both client mobility and server migration with Cloudlets. Our survey suggests that HIP avoids some of the limitations found in competing protocols. We also found that the HIPL implementation could benefit from architectural changes, for improving the performance of the LSI support.
  • Eklund, Krister (Helsingfors universitet, 2015)
    Ilmaisia tyypin I virtualisointijärjestelmiä on tarjolla useita. Tässä työssä vertaillaan Hyper-V Server-, Proxmox VE-, vSphere Hypervisor- ja XenServer-järjestelmiä keskenään laitteistovaatimusten, asennuksen, hallittavuuden, ominaisuuksien, resurssien seurannan, suorituskyvyn, varmuuskopioinnin ja päivittämisen suhteen. Järjestelmät asennettiin vuorotellen testikokoonpanolle, jolla arviointi tehtiin. Eroja löytyi kaikilta osa-alueilta. Tulokset koottiin taulukkoon, josta keskinäinen vertailu on yksinkertaista.
  • Sotala, Kaj (Helsingfors universitet, 2015)
    This thesis describes the development of 'Bayes Academy', an educational game which aims to teach an understanding of Bayesian networks. A Bayesian network is a directed acyclic graph describing a joint probability distribution function over n random variables, where each node in the graph represents a random variable. To find a way to turn this subject into an interesting game, this work draws on the theoretical background of meaningful play. Among other requirements, actions in the game need to affect the game experience not only on the immediate moment, but also during later points in the game. This is accomplished by structuring the game as a series of minigames where observing the value of a variable consumes 'energy points', a resource whose use the player needs to optimize as the pool of points is shared across individual minigames. The goal of the game is to maximize the amount of 'experience points' earned by minimizing the uncertainty in the networks that are presented to the player, which in turn requires a basic understanding of Bayesian networks. The game was empirically tested on online volunteers who were asked to fill a survey measuring their understanding of Bayesian networks both before and after playing the game. Players demonstrated an increased understanding of Bayesian networks after playing the game, in a manner that suggested a successful transfer of learning from the game to a more general context. The learning benefits were gained despite the players generally not finding the game particularly fun. ACM Computing Classification System (CCS): - Applied computing - Computer games - Applied computing - Interactive learning environments - Mathematics of computing - Bayesian networks
  • Sudulaganti, Raviteja (Helsingfors universitet, 2015)
    RFID technology emerged as the promising technology for its ease of use and implementation in the ubiquitous computing world. RFID is deployed widely in various applications that use automatic identification and processing for information retrieval. The primary components of an RFID system are the RFID tag (active and passive), the reader and the back-end server (database). Cost is the main factor that drove RFID tags to its immense utilization in which passive tags dominate in today's widely deployed RFID practice. Passive tags are low cost RFID tags conjoined to several consumer products (like clothes, smart cards and devices, courier, container, etc) for the purpose of unique identification. Readers on the other hand act as a source to track and record the passive RFID tag's activities (like modifications, updates and authentication). Due to the rapid growth of RFID practice in the past few years, measures for consumer privacy and security has been researched. The uncertainties that arise with the passive RFID tags are handling of user's private information (like name, ID, house address, credit card number, health statement, etc) which are posed to considerable threat from the adversary. Passive tags are inexpensive and contain less overhead and are considered good performers and consequently lack in providing security and privacy. Lightweight cryptography is an area of cryptography developed for low cost resourced environment. Mutual authentication is defined as the process of verifying an authorized tag and a reader (reader and server respectively) by an agreed algorithm to mutually prove their legitimacy with each other. Adversary is a third party who tries to hear the ongoing communication between the tag and the reader (reader and server respectively) anonymously. In this thesis, symmetric lightweight ciphers like Present and Grain are introduced as mutual authentication protocols to rescue the privacy aspects and properties of the RFID tags. These ciphers are simple, faster and suitable to implement within the passive RFID network and reasonably lay a foundation for the preservation of privacy and security of the RFID system. Lightweight ciphers use hash functions, pseudo random generators, SP networks and linear feedback shift registers to randomize data while mutual authentication scheme uses lightweight ciphers to manage authorize the legitimacy of every device in the RFID network.
  • Ye, Yina (Helsingfors universitet, 2015)
    Gesture recognition is a fundamental technology for understanding human behavior and providing natural human-computer interaction, of which the need has been boosted by the popularity of ubiquitous systems and applications. Currently, there are mainly two classes of gesture recognition approaches: parametric methods and the template matching methods. Although both approaches provide accurate recognition performance, the former is usually highly constrained in time and resources, while the latter is limited within a small range of gesture types that are simple and distinct from each other. The objective of the thesis is to present a novel stroke-based gesture recognition solution, Gestimator, that recognizes dynamic hand gestures with high accuracy, run-time efficiency, and ease for customization, considering a wide range of complexity, ambiguity, and difficulty for user to perform the gesture. A stroke-wise elastic gesture matching framework alongside an adaptive sequence segmentation technique were developed for improving recognition accuracy. We conducted extensive evaluations using three datasets that included pen-based command gestures, character gestures, and mid-air gestures collected from a user authentication experiment. Results from extensive benchmark evaluations prove that Gestimator achieves higher overall accuracy, compared with three state-of-the-art gesture recognizers, dealing with both touch-screen based gestures (98:9%) and spatial gestures (96:61%). Results also show that Gestimator outperforms baseline methods on recognizing ambiguous gestures.
  • Tuominen, Pasi (Helsingfors universitet, 2015)
    Tietovarannoissa esiintyy monesti useita tietueita, jotka kuvaavat samaa objektia. Tässä tutkielmassa on vertailtu näiden tietueiden löytämiseen käytettäviä menetelmiä. Kokeet on suoritettu aineistolla, jossa on 6,4 miljoonaa bibliografista tietuetta. Menetelmien vertailussa käytettiin aineistossa olevien teosten nimekkeitä. Eri menetelmien kahta keskeistä piirrettä on mitattu: löydettyjen duplikaattien lukumäärää ja niiden suhdetta muodostettujen kandidaattien lukumäärään. Kahden menetelmän yhdistelmä osoittautui parhaaksi aineiston deduplikointiin. Järjestetyllä naapurustolla löytyi eniten varsinaisia duplikaatteja, mutta myös eniten irrelevantteja kandidaatteja. Suffiksitauluryhmittelyn avulla löytyi lisäksi joukko duplikaatteja joita muilla menetelmillä ei löytynyt. Yhdessä nämä kaksi menetelmää löysivät lähes kaikki duplikaatit mitä kaikki tutkielmassa verratut menetelmät löysivät. Levenshtein-etäisyyteen perustuvat virhesietoiset menetelmät osoittautuivat tehottomiksi nimekkeiden deduplikoinnissa.
  • Rasku, Lari Olavi (Helsingfors universitet, 2015)
    This thesis considers the problem of preprocessing polygons with holes for efficient two-point Euclidean shortest path queries. Special attention is given to the 1999 paper 'Two-Point Euclidean Shortest Path Queries in the Plane', which sketched a number of solutions to the problem and whose results remain the best in the field. This thesis reviews four of the algorithms presented in the paper and fleshes them out when possible.
  • Lei, Jinmin (Helsingfors universitet, 2016)
    Despite of the efficiency brought by the high-throughput technology in detecting protein-protein interactions, different wet-lab methods still pose different pitfalls. As a complementary strategy, dry-lab methods are less expensive and have an advantage of data fusion that overcomes the biases of individual data sources. This thesis explores the indicative features and the effect of a graph model in the protein-protein interaction prediction task as well as the capability of the multiple kernel learning algorithms in improving the prediction performance.Different kernels are applied in accordance with different features. We integrate 14 global and 10 graph features respectively in the SVM framework via different kernel methods, and then compare the prediction performances of different features. When applying the graph features, we represent individual proteins as labeled graphs and then apply three different graph kernels to explore which one can best capture the relationships between proteins. For merging heterogeneous data, we apply different multiple kernel learning algorithms and explore their capabilities in improving the prediction accuracy. We formulate the prediction of protein-protein interactions as a binary classification problem and in the SVM framework, we need to reconstruct the kernel which measures the similarity between protein pairs from the kernel which measures the similarity between proteins. For this goal, we employ three different pairwise kernels in the SVM framework and explore their effects in capturing the relationships between protein pairs. We perform experiments on 896 Saccharomyces Cerevisiae (baker's yeast) proteins and report the prediction performances of the three pairwise kernels on 10 graph and 14 global features, as well as the prediction results of different multiple kernel learning algorithms. Our experimental results reveal that the overall prediction performance achieved by the 10 graph features applied to the proposed graph model is better than that achieved by the 14 protein global features, and that among all multiple kernel learning methods, the align wins over the others in the protein-protein interaction prediction task. Our methods detect the interacting proteins at a high level. Based on this work, low-level models can be devised to detect the exact interacting spots between proteins.
  • Lu, Yao (Helsingfors universitet, 2016)
    This thesis is an investigation of unsupervised learning for image classification. The state-of-the-art image classification method is Convolutional Neural Network (CNN), which is a purely supervised learning method. We argue that despite of the triumph of supervised learning, unsupervised learning is still important and compatible with supervised learning. For example, in the situation where some classes have no training data at all, so called zero-shot learning task, unsupervised learning can leverage supervised learning to classify the images of unseen classes. We proposed a new zero-shot learning method based on CNN and several unsupervised learning algorithms. Our method achieves the state-of-the-art results on the largest public available labelled image dataset, ImageNet fall2011.
  • Althermeler, Nicole (Helsingfors universitet, 2016)
    Metagenomics promises to shed light on the functioning of microbial communities and their surrounding ecosystem. In metagenomic studies the genomic sequences of a collection of microorganisms are directly extracted from a specific environment. Up to 99% of microbes cannot be cultivated in the lab; thus, traditional analysis techniques have very limited applicability in this challenging setting. By directly extracting the sequences from the environment, metagenomic studies circumvents this dilemma. Thus, metagenomics has become a powerful tool in the analysis of the diversity and metabolic capability of environmental microbes. However, metagenomic studies have challenges of their own. In this thesis we investigate several aspects of metagenomic data set analysis, focusing on means of (1) verifying adequacy of taxonomic unit and enzyme representation and annotation in the sample, (2) highlighting similarities between samples by principal component analysis, (3) visualizing metabolic pathways with manually drawn metabolic maps from the Kyoto Encyclopedia of Genes and Genomes, and (4) estimating taxonomic distributions of pathways with a novel strategy. A case study of deep bedrock groundwater metagenomic samples will illustrate these methods. Water samples from boreholes, up to 2500 meter deep, of two different sites of Finland display the applicability and limitations of aforementioned methods. In addition publicly available metagenomic and genomic samples serve as baseline references. Our analysis resulted in a taxonomic and metabolic characterization of the samples. We were able to adequately retrieve and annotate the metabolic content based on the deep bedrock samples. The visualization provided a tool for further investigation. The microbial community distribution could be characterized on higher levels of abstraction. Previously suspected similarities to fungi or archaea were not verified. First promising results were observed with the novel strategy in estimating taxonomic distributions of pathways. Further results can be found at: http://www.cs.helsinki.fi/group/urenzyme/deepfun/

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