Browsing by Title
Now showing items 2177-2196 of 4203
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(2015)Topological superconductors, combining the principles of topology and condensed-matter physics, are a new field which has seen much progress in the past two decades. In particular, they are theorized to support Majorana bound states, a type of quasiparticle with several interesting properties – most notably, they exhibit nonabelian exchange statistics, which has applications in fault tolerant quantum computing. During the past few years, several groups have observed effects in topological superconductors indicating that an experimental confirmation of their existence may be imminent. Recently experimental focus has been on ferromagnetic systems with spin-orbit coupling, serving as the motivation for our research. In this thesis, we study the topological properties of a system consisting of magnetic adatoms implanted on a two-dimensional superconducting substrate with Rashba spin-orbit coupling. Starting from the mean-field Bogoliubov-de Gennes Hamiltonian, we derive a nonlinear eigenvalue problem describing the system, generalizing previous results which considered a linearized version. In the reciprocal space, we obtain a transcendental equation for the energy of the system. Through numerical solution of these equations in the limit of long coherence length we obtain the topological phase diagram of the system. We further analyse the spatial decay of the Majorana wavefunctions as well as the dependence of their energy splitting on the length of the adatom chain. As an application, we study a prototype topological qubit constructed by intersecting two one-dimensional adatom chains to obtain a cross-shaped geometry that supports two pairs of Majorana bound states. The design allows for braiding of the individual quasiparticles, providing a possible platform for experimental verification of their nonabelian exchange statistics. Using numerical methods, we simulate moving the topological phase boundaries to enact a braid of two Majorana bound states and calculate the system energy for each step. We find that throughout the process the zero-energy modes are separated from the bulk states by a finite energy gap, as required for adiabatic braiding.
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(2018)The Archean Hattu schist belt in eastern Finland is host to several orogenic gold occurrences. One of these deposits is the Pampalo gold deposit located in Hattu, Ilomantsi. Major and trace element characteristics of biotite and chlorite were analyzed from a representative collection of rock types of different degrees of alteration from the Pampalo deposit. The main aim of this study was identifying possible correlation of changes in the elemental composition of biotite and chlorite with distance to gold ore mineralization and testing the two minerals’ use as proxies for mineralization in Pampalo. Biotite and chlorite were chosen for being represented in altered and unaltered ore and adjacent country rock units. Samples were prepared from half and quarter drill core rocks and analyzed with hyperspectral imaging, electron micro probe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS). Hyperspectral imaging and thin section microscopy were used for mineral identification and mineral grain sampling. EMPA and LA-ICP-MS data found weak correlation with distance to mineralization for Mg, Al, Ti, Fe, Zn, Sr and Cs in biotites and Li, B, Mg, Al, Si, P, Sc, Ti, Mn, Fe, Ni, Zn, Ga, As and Sr for chlorite. Moderate correlation was found for Pb and Tl in biotites and Co in chlorites. Strongest correlation was found for Mn, W and Ba in biotites. These three elements all deplete in biotites with decreasing distance to mineralization. Changes in concentrations of manganese are likely variation in host rock chemistry. Tungsten concentrations seem to be linked to fluid flows, but only indirectly related to gold ore mineralization. Barium was found to be the most promising element within biotites due to its high mobility, and its depletion could indicate approaching gold ore mineralization. Changes in As concentrations of chlorites also point to two different types of chlorite grains, one of which indicate an ore mineralization event having taken place.
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(2013)Kompleksianalyysissä Dirichlet'n ongelma voidaan määritellä seuraavasti: Olkoon Ω ⊂ C rajoitettu alue ja olkoon f alueen Ω reunalla määritelty jatkuva reaaliarvoinen funktio. Tällöin Dirichlet'n ongelma on löytää alueessa Ω harmoninen funktio, joka yhtyy jatkuvaan funktioon f alueen Ω reunalla. Ratkaisemme tämän Dirichlet'n ongelman O. Perronin menetelmällä, joka perustuu subharmonisten ja superharmonisten funktioiden käyttöön. Aloitamme esittämällä subharmonisten ja superharmonisten funktioiden määritelmät sekä niiden tärkeimpiä ominaisuuksia. Näiden avulla saamme osoitettua, että jatkuvat reunafunktiot ovat resolutiivisia eli niiden kohdalla yleistetty Dirichlet'n ongelma voidaan ratkaista. Lisäksi konstruktiosta seuraa, että tämä ratkaisu määrittelee positiivisen ja lineaarisen funktionaalin jatkuvien reunafunktioiden joukossa, jolloin Rieszin esityslause antaa tätä funktionaalia vastaavan mitan. Tämä mitta on harmoninen mitta. Alueen Ω reunan osajoukon E harmoninen mitta onkin siis karkeasti sanottuna ratkaisu Dirichlet'n ongelmaan, missä etsitään alueessa Ω harmonista funktiota, joka alueen reunalla vastaa joukon E karakteristista funktiota. Jatkamme osoittamalla harmonisen mitan ominaisuuksia, tärkeimpänä sen, että harmoninen mitta säilyy tason konformisissa muunnoksissa. Näistä päädymme tarkastelemaan tasoalueessa Ω analyyttisten funktioiden käytöstä alueen reunalla. Plessnerin lauseen avulla saamme osoitettua, että analyyttinen injektio ei voi laajentaa liikaa niitä reunan osajoukkoja, missä se on konforminen. Tästä saamme johdettua Makarovin tuloksen, jonka mukaan harmoninen mitta on singulaarinen kaikkien 1-ulotteista karkeampien Hausdorff-mittojen kanssa. Tämä tarkoittaa, että harmonisen mitan kantajan Hausdorff-dimensio on korkeintaan 1. Tarkastelemme myös hieman Bloch-funktioita ja osoitamme niille niin kutsutun Makarovin lain iteroidulle logaritmille. Tämän avulla saamme lopulta osoitettua Makarovin toisen suuren tuloksen koskien harmonista mittaa. Seuraa nimittäin, että harmoninen mitta on absoluuttisesti jatkuva tietynlaisen Hausdorff-mitan kanssa ja näin ollen harmonisen mitan kantajan Hausdorff-dimension täytyy olla vähintään 1. Yhdessä aiemman tuloksen kanssa näistä seuraa, että kompleksitasossa C harmonisen mitan kantajan Hausdorff-dimensio on tasan 1.
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(2021)Dendrite prevention can be achieved by manipulating the local chemical concentration gradient by ultrasound. An ultrasonic field, which generates acoustic streaming, can manipulate the ionic flux at the electrode surface by altering the local ion concentration gradient at said surface according to the streaming pattern. The pattern is determined by the ultrasonic field and the geometry of the sonication volume. The preventive action can be directed to an arbitrary point on the surface, or be swept across it to achieve a smoother electroplating. Dendritic growth is concentrated to areas of higher concentration gradient. This is because at the electrode surface both the electric and convective fluxes tend to zero. If the reduction of ions into their metallic form is fast enough, the metal layer growth rate is determined by the diffusive flux, which is determined by the ion concentration gradient and the diffusion constant of the ion in the electrolyte. In this study, tin was used as the transported ion instead of lithium for safety reasons. A custom-made battery mockup cell was constructed for the experiments. The anode was imaged with a usb microscope camera to determine the growth of the dendrites during the process. The electroplating current and piezo driving power were varied between 100 mA to 275 mA and 0 to 6.6 W, respectively. With piezo driving electrical power less than 10 W, it was possible to lower the maximum lengths of dendrites. Finite element method simulations were conducted to validate the hypothesis and experimental results. This ultrasonic method could be used to allow rechargeable, lightweight, high capacity lithium metal batteries. The piezos could be integrated into battery chargers.
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(2020)DevOps is an ever growing trend in software development and it conveys a mindset that all things should be continuous. Interestingly, one of the common challenges with DevOps adoption is related to software architecture and this is in large due to the fact that architecture is not part of DevOps. This thesis looks at making software architecture a continuous practice and thus bring it into the DevOps space. A prototype solution, Architector, was implemented to solve this and the results indicate that it shows a viable approach to making software architecture a continuous practice. However, further work is necessary to expand the scope of continuous architecture and to fully validate this claim by applying Architector to a real world software development workflow.
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(2012)This thesis is motivated by the need for more knowledge about the factors which influence the plant species richness and biomass in subarctic and alpine environments. It is known that the effects of climate warming will be most severe in arctic, subarctic and alpine regions. A warmer climate will change the vegetation composition and biomass production in these environments. In this thesis I investigate the effects of six nutrients (Ca, Na, Mg, Fe, K and P), hydrological conditions early in the growing season and geomorphology on plant species richness and biomass in the northernmost part of Finland, Kilpisjärvi. The conditions in the study site are subarctic-alpine. In subarctic and alpine regions the varying topography in macro and micro scales leads to a wide variety of habitats even within small spatial dimensions. Materials in this study include field observations about the plant species richness and biomass, geomorphological processes and hydrological conditions; chemical analysis of soil samples; and topography variables derived from a digital elevation model. Methods used are generalized linear models and variation partitioning, which are both more and more used in ecological and geomorphological studies. The results suggest that the most influential of the environmental variables on the plant species richness and biomass is geomorphology. It is the most influential explanatory variable on total, vascular plant, bryophyte and lichen species richness as well as on total, bryophyte and lichen biomass. The amount geomorphology explains varies between 9 - 41 %. The variation in vascular plant species richness is best explained by hydrological conditions (14 %). The variables chosen for this study are able to explain over 50% of the species richness response variables. For total, bryophyte and lichen biomass the amount explained is about 20 - 47 %, and even 77 % of total biomass is explained by the variables. Geomorphology, hydrology and nutrients are able to explain better the variation in biomass than in species richness. These findings support earlier studies in the same field.
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(2015)Organisaatioiden tavoitteena on mahdollisimman tehokas, eniten arvoa sekä hyötyä tuottava toiminta. Se edellyttää jatkuvaa toiminnan parantamista, toimintaympäristön muutoksiin reagoimista ja erilaisten muutosten läpiviemistä organisaatiossa. Koska organisaatio on monista eri toiminnallisista ja rakenteellisista osatekijöistä muodostuva kokonaisuus, sen kaikissa kehittämistoimenpiteissä on syytä huomioida kaikki osa-alueet kokonaisvaltaisesti. Kokonaisarkkitehtuurin kehittäminen on keino läpiviedä muutoksia organisaatiossa, sillä se käsittää organisaation koko toiminnan ja rakenteen. Mallintaminen on systemaattinen tapa visualisoida kokonaisarkkitehtuuriin liittyviä osatekijöitä ja muutoksia kokonaisvaltaisesti. Tässä tutkielmassa esitellään käytännönläheinen malliperustainen lähestymistapa kokonaisvaltaiseen suunnitteluun, jota voidaan hyödyntää kehittämisen apuvälineenä eri laajuisten muutosten läpiviemiseen organisaatiossa. Lähestymistavan avulla mahdollista mallintaa toiminnalliset ja rakenteelliset osatekijät, sekä niiden väliset riipuvuussuhteet. Kokonaisvaltaisudella tarkoitetaan kaikkia kehittämiseen liittyviä asioita strategisista tavoitteista ja vaatimuksista yksittäisten kehitysprojektien tunnistamiseen. Keskeistä kokonaisvaltaisuudessa on huomioida liiketoimintaan, tietojärjestelmiin ja infrastruktuuriin liittyvät osatekijät, sekä niiden väliset riippuvuussuhteet. Malliperustaista lähestymistapaa voidaan soveltaa eri laajudessa ja eri tarkkuustasoilla. Mallintamisen kohteena voi olla koko organisaatio, jokin sen rajattu alue tai yksittäinen ratkaisu. Tarkkuustaso voi vaihdella yleiseltä tasolta hyvinkin yksityiskohtaiseen. Tutkielmassa esitellään kokonaisvaltaisen kehittämisen ja mallintamisen standardit TOGAF-kokonaisarkkitehtuuriviitekehys ja ArchiMate-mallinnuskieli, sekä kuinka niitä voidaan soveltaa yhdessä. Tutkielmassa arvioidaan myös kuinka Sparx Systems Enterprise Architect-mallinnusväline soveltuu kokonaisvaltaiseen kehittämiseen.
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(2016)Mammografia on röntgentutkimus, jonka tarkoituksena on etsiä ihmisten rinnoista mahdollisia syöpäkasvaimia tai muita poikkeamia. Mammografiassa kuvanlaadun pitää olla erityisen korkea, jonka takia mammografiaa tehtäessä käytetään erityisesti mammografiatutkimuksia varten suunniteltuja mammografialaitteita. Mammografialaitteiden laadunvalvonta on tärkeässä asemassa laitteiden toimintakunnossa, kuvanlaadussa sekä potilaiden säteilyaltistuksessa tapahtuvien muutosten seuraamisessa. Mammografialaitteiden kuvanlaatua tutkitaan usein ottamalla kuva testikappaleesta eli fantomista, jossa on erilaisia kohteita, jotka pyrkivät vastaamaan oikeassa rintakudoksessa mahdollisesti olevia kuituja, kalkkeja sekä massoja. Tutkimalla kuvassa näkyvien kohteiden määriä saadaan tietoa kuvanlaadusta. Tämän työn tarkoituksena oli kehittää ohjelma, joka automaattisesti analysoi sille annetun fantomikuvan. Ohjelman toiminta perustuu diskreettiin aallokemuunnokseen, jonka avulla kuvasta tehdään multiresoluutioanalyysi. Multiresoluutioanalyysin avulla kuvasta saadaan lukuisia eri resoluutiotasoilla olevia kuvia. Valitsemalla sopivia resoluutiotasoja vastaavat kuvat saadaan fantomikuvassa olevat kohteet paremmin näkyville, jolloin kuvat on helpompi analysoida. Tässä tutkimuksessa käytettiin Yhdysvaltain radiologiyhdistyksen (American College of Radiology, ACR) mammografiafantomia (ACR-fantomi), jossa on kuusi halkaisijaltaan erikokoista kuitua, viisi erikokoisia kalkkeja sisältävää kalkkiryhmää, joissa jokaisessa on kuusi samankokoista kalkkia, sekä viisi erikokoista massaa. Ohjelman antamat tulokset vastaavat kohtalaisesti ihmissilmällä tehtyjä arvioita ACR-fantomikuvassa näkyvien kuitujen ja massojen määristä. Kalkkiryhmien tapauksessa ohjelman ja ihmissilmällä tehtyjen arvioiden vastaavuus on puolestaan erittäin hyvä. Aikasarjoista havaitaan, että jokaisella laitteella on sille ominainen vaihteluväli sekä kohteiden määrällä mitattuna että kohteiden kontrasti-kohinasuhteella mitattuna. Keskimäärin suurin vaihteluväli on kuitujen määrissä, toiseksi suurin vaihteluväli on puolestaan massojen määrissä ja pienin vaihteluväli on kalkkiryhmien määrissä. Tämä tutkimus osoittaa, että kehitetty ohjelma ja siinä käytetyt menetelmät ovat sopivia ACR-fantomikuvassa olevien kohteiden analysointiin. Ohjelmassa on kuitenkin vielä parannettavaa, jotta tulokset vastaisivat paremmin ihmissilmällä tehtyjä havaintoja.
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(2020)Latency is one of the key performance elements affecting the quality of experience (QoE) in computer games. Latency in the context of games can be defined as the time between the user input and the result on the screen. In order for the QoE to be satisfactory the game needs to be able to react fast enough to player input. In networked multiplayer games, latency is composed of network delay and local delays. Some major sources of network delay are queuing delay and head-of-line (HOL) blocking delay. Network delay in the Internet can be even in the order of seconds. In this thesis we discuss what feasible networking solutions exist for browser multiplayer games. We conduct a literature study to analyze the Differentiated Services architecture, some salient Active Queue Management (AQM) algorithms (RED, PIE, CoDel and FQ-CoDel), the Explicit Congestion Notification (ECN) concept and network protocols for web browser (WebSocket, QUIC and WebRTC). RED, PIE and CoDel as single-queue implementations would be sub-optimal for providing low latency to game traffic. FQ-CoDel is a multi-queue AQM and provides flow separation that is able to prevent queue-building bulk transfers from notably hampering latency-sensitive flows. WebRTC Data-Channel seems promising for games since it can be used for sending arbitrary application data and it can avoid HOL blocking. None of the network protocols, however, provide completely satisfactory support for the transport needs of multiplayer games: WebRTC is not designed for client-server connections, QUIC is not designed for traffic patterns typical for multiplayer games and WebSocket would require parallel connections to mitigate the effects of HOL blocking.
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(2024)Introduction: The need for sustainable development across sectors, including ICT, is essential today to conserve natural resources, maintain biodiversity, and ensure basic living conditions for everyone. Despite growing awareness and regulatory initiatives, software engineering practices lag in integrating sustainability. This gap highlights the call to develop software engineering to embrace sustainability principles, challenge is increasingly recognized but not yet resolved. Objective: To bridge the knowledge gap in software engineering, by identifying key concepts, methodologies, and challenges related to the integration of sustainability into software engineering. Methods: A systematic literature of academic literature with an automated search was conducted. The review included studies published between the year 2011 and 2023. The review covers 31 papers. Results: Integrating sustainability into software engineering is complex and varies widely across different contexts, as sustainability dimensions are dynamic and context-dependent. This complexity hinders the establishment of universal characteristics and underscores the need for common standards. Despite the numerous models for integrating sustainability, there is no direct solution for how to efficiently integrate sustainability into software engineering. The focus of these models tends to be more on the development of sustainable software rather than on the sustainability of the processes themselves, which limits their ability to support comprehensive integration. Additionally, various risks and challenges in integrating sustainability have been identified, with the lack of standardization as one of the biggest challenges at the moment. Conclusions: To effectively achieve sustainability in software engineering, it is crucial to integrate sustainability aspects comprehensively across the entire organizational structure, including development teams, management, and supporting departments.
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(2021)This thesis introduces Robot Configurator, a software for performing variability configuration for a robot cooperation software named Cooperative Brain Service. The variability configuration problem concerns selecting appropriate combinations of components to form a valid complete product. It is applicable to the realm of software as well, as there are approaches where an instance of software is formed from different pre-made components. Cooperative Brain Service is the main product of Creative and Adaptive Cooperation between Diverse Autonomous Robots (CACDAR), a University of Helsinki research project. One of the main principles of the project is enabling cooperation between various types of robots. In Cooperative Brain Service, this is taken into account by having support for any new robots and actions be added as new modules. In the current implementation, the modules to be loaded are determined during startup, through a manually written JSON configuration file. The problem is, managing such JSON files requires beforehand knowledge of what modules there are implemented in Cooperative Brain Service. As it is crucial to be able to flexibly experiment with different cooperation scenarios in CACDAR, I design Robot Configurator as a tool to assist in the creation and management of these JSON configuration files. The main contribution of this thesis is Robot Configurator, for which I provide an architecture description that describes and documents it from multiple stakeholder perspectives. Additionally, a novel approach to modeling variability involved in the initialization of Cooperative Brain Service is also introduced.
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(2013)Fotokatalyysi on osoittautunut hyväksi menetelmäksi erilaisten orgaanisten kemikaalien hajottamisessa aina hiilidioksidiksi ja vedeksi asti. Eniten tutkittu fotokatalyytti on TiO2. Sen käytön haasteena on energia-aukon suuruus vaikka se muuten täyttääkin ideaalisen fotokatalyytin tunnusmerkit. Fotokatalyysiä on tutkittu mm. veden ja ilman puhdistamiseksi sekä erilaisten mikro-organismien tuhoamiseksi. Fotokatalyysistä on myös useita eri kaupallisia sovelluksia mm. itsepuhdistuvat pinnat, joilla voidaan parantaa kaupunkien ilman laatua. Ydinvoimateknologiassa fotokatalyysiä käytetään CORD-UV- menetelmässä hajottamaan dekontaminoinnin lopuksi käytetyt kemikaalit hiilidioksidiksi ja vedeksi vetyperoksidin ja UV-valon avulla. Kirjallisuusosassa tarkastellaan kahta eri fotokatalyysin mekanismia sekä titaanidioksidia ja huokoisia mangaanioksideja fotokatalyytteinä. Lisäksi tarkastellaan katalyyttiseen aktiivisuuteen vaikuttavia tekijöitä mm. pH:n merkitystä. Myös erilaisia fotokatalyysin sovellusalueita käydään läpi. Ydinvoimaloiden dekontaminointiin liittyen tarkastellaan erilaisia dekontaminointitekniikoita ja tarkemmin kemiallisen dekontaminoinnin menetelmiä. Lisäksi käsitellään erilaisia dekontaminointiliuosten puhdistus ja loppukäsittelymenetelmiä. Kokeellisessa osassa tutkittiin hollandiittirakenteisten mangaanioksidien; OMS-2-20, OMS-2-5 ja CryMO; kykyä hajottaa Co-EDTA-kompleksi ja sitoa tästä irronnut Co-ioni. Tämä oli myös työn päätavoite. Tutkitut mangaanioksidit oli valmistettu DeGuzmanin reseptillä tai sitä muuntelemalla. Myös hajottamis- ja sitomiskykyyn vaikuttavien spesiesten vaikutusta tutkittiin, varioimalla liuoksessa olevan EDTA:n ja natriumnitraatin määrää. Tutkimuksessa käytettiin Photocemical reactors LTD:n fotoreaktoria 6W elohopealampulla. Lisäksi määritettiin tutkituille mangaanioksideille niiden energia-aukon koko (Eg). Energia-aukkojen koko määritettiin käyttämällä Perkin Elmerin UV-VIS-NIR-spektrometriä, jossa oli integroiva pallo, käyttäen Tauc:n kuvaajaa hyödyksi. Eri mangaanioksidien kykyä hajottaa ja sitoa Co- EDTA-kompleksia verrattiin toisiinsa jakautumisvakion (Kd) avulla. Tuloksia verrattiin lisäksi TiO2:iin sekä kerrosrakenteiseen birnessiittiin. Tutkittujen mangaanioksidien energia-aukkojen kooksi saatiin OMS-2-20 Eg=1.627±0,003 eV, OMS-2- 5 Eg=1.724±0,008 eV ja CryMO Eg=1.697±0,008 eV. Tutkimuksissa parhaiten Co-ionia sitovaksi mangaanioksidiksi valikoitui OMS-2-20 pH:ssa 6, sen Kd:n ollessa 130000 ± 10000 ml/g, muiden jäädessä selvästi alhaisemmaksi. Referenssinä käytetyn TiO2:n Kd oli 11600 ± 800 ml/g samoissa olosuhteissa. Tutkimuksissa havaittiin, että kaikki tutkitut mangaanioksidit voidaan virittää näkyvää valoa käyttämällä. Tämä on katalyytille eduksi sen tulevaisuuden käyttöä ajatellen. Hajottamis- ja sorptiokykyä tutkittaessa havaittiin, että EDTA:n ylimäärä häiritsee aineen sorptiokykyä. Sen sijaan nitraatti-ionilla ei näyttänyt olevan vaikutusta aineen kykyyn hajottaa Co-EDTA-kompleksi tai sitoa vapautunut Co-ioni. Sitä miksi OMS-2-20 toimi selvästi muita paremmin ei saatu tutkimuksessa selville. Erityisen suuri oli ero lähes samalla tavalla valmistettuun OMS-2-5:een. Tulevaisuudessa onkin syytä selvittää tapahtuneiden reaktioiden mekanismi (sekä hajoamisreaktion että sorptio-reaktion mekanismi) ja se hajottaako OMS-2- 5 ylipäätään Co-EDTA-kompleksia. Myös muiden huokoisten mangaanioksidien (esim. todorokiitti) kyky toimia kaksoisroolissa on hyvä selvittää. Lisäksi reaktio-olosuhteiden vaikutus on syytä selvittää tarkemmin. Erityisesti näkyvän valon rooli mangaanioksidien virittäjänä on hyvä selvittää.
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(2023)The Differential Mobility Particle Sizer (DMPS) is a widely used instrument in the size distribution measurements of sub-micron aerosol particles. The particles are size classified based on their electrical equivalent diameter by a Differential Mobility Analyser (DMA) in the DMPS. Only charged particles can be measured with a DMPS. An aerosol charger is hence required since most ambient particles are neutral. An estimation of the size dependent charge distribution of the aerosol particles is required to reach a representative size distribution of the whole aerosol population from the raw measurement data. The charged fractions of the population are conventionally calculated by applying bipolar charging (i.e., an ion atmosphere including ions of both polarities charges aerosols by diffusion and ion attachment onto the particles) theories. Fixed charger ion properties have been used to derive approximation to these theories. The charger ion properties in ambient “real-world” measurements are, however, not fixed but proven to vary substantially. These variations may lead to significant differences when comparing to the approximations. A new method for aerosol charging that reduces the uncertainties that originate from unknown properties of the charger ions was tested in this thesis. The method consists of the introduction of a known trace compound (hereafter called doping) into the aerosol sample flow upstream of a bipolar charger. The effect of doping on charger ion mobility distribution was successfully tested in laboratory experiments. A possible enhancement of charging efficiencies of nanoparticles was studied. The charger ion doping was also tested in atmospheric measurements, where it showed an effect on charger ion properties.
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(2018)This thesis reports the design and study of new series of thermoresponsive polycations with upper critical solution temperature (UCST) and lower critical solution temperature (LCST) type phase separation properties in water. The polymers were synthesized using reversible addition-fragmentation transfer polymerization process in presence of azobisisobutyronitrile (AIBN) as an initiator and 2-cyano-2-propylbenzoditionate (2-c-2-PBDT) as a chain transfer agent. Various solution properties of obtained polymers were studied. Transmittance measurements were utilized to determine the cloud point temperatures of poly[(4-vinylbenzyl)triethyl]ammonium chloride (P-VB-NEt3-Cl), poly[(4-vinylbenzyl)tripropyl]ammonium chloride (P-VB-NPr3-Cl), poly[(4-vinylbenzyl)tributyl]ammonium chloride (P-VB-NBu3-Cl) and poly[(4-vinylbenzyl)tripentyl]ammonium chloride (P-VB-NPen3-Cl) with several counterions (bis(trifluoromethane) sulfonimide, trifluoromethanesulfonate, CH3(CH2)4SO3 and CH3(CH2)11SO3) and anions belonging to Hofmeister series (Cl, NO3, SCN, H2PO4, SO4). P-VB-NEt3-Cl and P-VB-NPr3-Cl demonstrate both UCST and LCST type phase separation behavior depending on the chosen additive, whereas P-VB-NBu3-Cl and P-VB-NPen3-Cl only show LCST type phase transitions independent of the chosen anions. The phase transition temperature could be manipulated by varying the salt concentration of the polymer solutions; increasing the ionic strength causes the appearance of distinguishable transition in systems with no transition at low ionic strength. Combination of different anions in the system causes either increase or decrease of the cloud point temperature. The reversibility of the aforementioned transitions was studied and irreversibility of the transitions of polymer solutions with some anions was determined. Differential scanning calorimetry measurements were conducted to determine the enthalpy of heating of P-VB-NBu3-Cl and P-VB-NPen3-Cl with specific concentrations of counterions. Cononsolvency behaviour of P-VB-NBu3-Cl in water/DMF mixtures was studied, indicating that the turbidity occurs due to addition of either of solvents and remains regardless of temperature variation. Particle size measurements were conducted to explain the formation and behavior of particles depending on the temperature variation for P-VB-NBu3-Cl solutions with counterions.
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(2014)MAOL-taulukot -kirja on ollut lukiolaisten tukena opinnoissa jo vuodesta 1978 lähtien. Tämän jälkeen kirjaa on uudistettu kolmesti vuosina 1991, 1999 ja 2005. MAOL-taulukot -kirjaa saa käyttää ylioppilastutkintolautakunnan päätöksellä kemian, matematiikan, fysiikan ja maantiedon ylioppilastutkinnossa. MAOL-taulukot -kirja koostuu kolmesta osiosta, jotka ovat matematiikka, fysiikka ja kemia. Tutkimus tarkastelee MAOL-taulukot -kirjan käytettävyyttä ja opetusta lukion kemian opetuksessa. Aineistona on ollut sekä MAOL-taulukot -kirja että opettajilta lomakekyselyllä hankittu aineisto. MAOL-taulukot -kirjan aineisto on analysoitu laadullisen sisällönanalyysin avulla. Analyysissa selvitettiin MAOL-taulukot -kirjan kemian osuuden taulukoiden suhdetta lukion kemian opetussuunnitelman keskeisiin sisältöihin. Sisällönanalyysiä hyödynnettiin myös lomakeaineiston avointen kysymysten luokittelussa ja analysoinnissa. Lomaketutkimus tehtiin verkkokyselynä ja siihen vastasi 107 opettajaa. Tutkimuksen perusteella voidaan todeta, että MAOL-taulukot -kirjan kemian osuuden taulukot tukevat kattavasti lukion kemian opetussuunnitelmassa määriteltyjä keskeisiä sisältöjä. Opettajat näkevät taulukkokirjan monipuolisena materiaalina. Toisaalta sitä pidetään lähdemateriaalina, toisaalta oppikirjana. Tämä jako on merkityksellinen pohdittaessa taulukkokirjan kehittämistä tulevaisuudessa. Opettajien käsitykset taulukkokirjan hyvistä puolista ja kehittämiskohteista olivat ristiriitaisia. Kirjan käytön opetus ei tämän tutkimuksen pohjalta näytä olevan yhtenevää ja monipuolista. Opettajat eivät sanoita omaa hiljaista tietoaan taulukkokirjan käytössä, vaan olettavat oppilailla olevan samat tiedot. Opettajien tausta ei kuitenkaan vaikuta tapaan, jolla he suhtautuvat taulukkokirjaan opetusmateriaalina. MAOL-taulukot -kirjan käyttöä opetuksessa tulisi tutkia lisää sekä opettajien että oppilaiden näkökulmasta. Huolestuttavana tuloksena voidaan pitää, että taulukkokirjan käytön opettaminen ei vaikuta olevan yhtenevää ja monipuolista, koska taulukkokirjaa saa käyttää ylioppilastutkinnossa ja ylioppilastutkinnon merkitystä jatko-opiskelupaikkoja haettaessa pyritään kasvattamaan. Tämä vaarantaa opiskelijoiden tasavertaiset mahdollisuudet.
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(2015)Mapping trees with remote sensing data has been under focus in many studies and many methods have been developed and tested using different kinds of data. Airborne laser scanning (ALS) gives the possibility to investigate vegetation heights and has thus been recently used in many vegetation mapping studies. The objective of this study was to test feasibility of mapping aboveground biomass (AGB) of trees using ALS data and individual tree detection methods. By recognizing individual trees from the ALS data, it is possible to map the tree AGB on a detailed level. The study focused on trees outside forests in the study area, which is situated in the Taita Hills, Kenya. The agriculture and agroforestry in the study area mostly consist of small-holder farming. The purpose was to determine a method that would enable examination of tree biomass on a farm scale. The individual tree detection enables mapping at this scale. The data acquired for this study was high pulse density (9.6 pulses/m²), small footprint, discrete return ALS data. It enables the detection of individual trees based on a high-resolution canopy height model. The processing of the ALS data was done with free software which does not require expensive licensing. For estimating AGB of the individually recognized trees, a prediction model was developed. For developing the prediction model, ground measurements and biomass estimates were needed. The biomass of the ground measured trees was estimated using non-destructive method employing allometric equations. The ground measurements from 77 sample plots of 0.1 ha size were used. A total number of 554 trees were used in the analysis. The tree measurements included diameter at breast height, tree height, crown diameter and species. Mean wood densities were defined on the basis of the species from the online databases and literature. The ground measurements were gathered at the same time as the remote sensing data was acquired. The mean tree AGB for the agricultural and agroforestry areas within the study area were estimated as 23.8 ± 4.2 Mg/ha. The individual tree detection method resulted in a detection rate (correctly identified trees) of 50.1 % and produced 49.9 % omission errors and 36.8 % commission errors. A regression model was developed to estimate AGB for the ALS detected trees. The derived model produces RMSE of 163 kg and bias of 5.75 kg per tree. The correlation between the predicted biomass values and field estimates was 0.659 on the individual tree level and 0.847 when assessed on the plot-level. The individual tree detection method and the derived biomass prediction model was used to map the biomass of individual trees for an area of 9 km² within the study area. The estimated mean biomass for the area was 11.4 Mg/ha. The results show that the use of ALS data and ITD methods can provide good opportunities to map AGB within the Taita Hills agricultural and agroforestry environment on farm scale. With the method presented in this study the individual tree AGB values would be somewhat biased, but on plot-level the estimation accuracy is better. This means that for individual farms that are at least 1 ha in size, the ALS estimated AGB values would be quite good even though somewhat underestimated, and could be used as basis of payment in possible future ecosystem services payment schemes. The AGB estimates accuracies can still be improved by refining the ITD method, for example by analysis of different ALS metrics or by combining ALS data with other remote sensing data.
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(2018)Gathering information on forest structure is vital in estimating forest biodiversity, carbon stocks and temporal changes in standing forests. Currently the only viable method of collecting such information in vast areas is remote sensing (RS). Two commonly used RS methods for acquiring high resolution three dimensional information on forest structure are airborne laser scanning (ALS) and digital aerial photogrammetry (DAP). In quantifying forest structure, the distributions of tree basal areas have been used because the variation in tree sizes is closely linked to the whole concept of forest structure. Retrieving information on these distributions can be done by modelling the relationship of in situ measured distribution indices and the remotely sensed elevation information. One of these distribution indices is the Gini coefficient which has been shown to be a prominent index in describing the forest structure from ALS data. In this study, DAP data was gathered with an unmanned aerial system (UAS) from the vicinity of the Lammi research station with the intention of investigating its suitability on modelling forest structure by using Gini coefficient (GC). Airborne laser scanning data retrieved from the National land survey was used as a comparison dataset. The in situ measured field data consisted of tree circumference measurements from 50 circular plots (r = 5m). From these measurements, the tree basal areas were calculated and the plot level Gini coefficients determined. A comprehensive set of plot level point cloud variables were also calculated from both ALS and DAP point clouds. The most important predictor variables were chosen from the point cloud variables with an automatic exhaustive variable selection function. Then, beta regression modelling was applied to both sets of predictor variables and the best GC models determined. Finally, the models were generalized to the whole study area and GC maps were produced. The resulting GC models for both datasets performed in a mediocre way. The best DAP model had a cross-validated RRMSE of 29.8% and the best ALS model had RRMSE of 27.2%. The coefficient of determination (R2) was also better in the ALS model (0.49) than in the DAP model (0.39). The performance of the ALS model was slightly worse than in previous studies using ALS to predict GC. Part of this might be a repercussion of the non-optimal acquisition time of the ALS dataset. For DAP, there were no previous studies. The results of this study suggest that ALS is a more prominent method in mapping forest structure with GC. The DAP proved to be an inexpensive and flexible method of gathering three dimensional information on forests but it had poor canopy penetration abilities which affected the modelling performance negatively.
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(2016)Information related to forest areas and individual trees, such as number of trees and diversity of different species are essential for sustainable land use planning and land management. Mapping this information using remote sensing (RS) methods has improved a lot over the past decades due to the new high resolution sensors and advanced image processing techniques. Especially in large and remote areas with low accessibility, RS is one cost-effective source for accurate information. Imaging spectroscopy (IS) with high spatial and spectral resolution together with the airborne laser scanning (ALS) data were used to map individual tree species in tropical agroforestry area in Taita Hills, Kenya. Field data from 77 different plots including 534 tree measurements were used as a reference data. Trees were segmented using spectral information from the minimum noise fraction (MNF) transformed bands together with a simple height threshold to extract trees from other vegetation. This was derived from the canopy height model (CHM). Trees were classified using the MNF transformed bands together with vegetation indices (VI's) sensitive to canopy chlorophyll content. Classification was conducted using random forest (RF) classification algorithm. Finally, occurrences of the different tree species were predicted in the study area. Segmentation worked well for estimating the total amount of trees inside the study plots resulting detection rate of 99.8 %, but for correctly identified species the accuracy was quite low of 47 %. Classification could separate three exotic species of Grevillea robusta, Eucalyptys sp. and Acacia mearnsii from the other species with producer's accuracy (PA) varying from 71% –79 % and user's accuracy from 58 %–79%. Overall accuracy (OA) was quite low of 54.2 % as other species were not classified correctly. Classification was repeated using four classes of Grevillea robusta, Eucalyptys sp., Acacia mearnsii and combined tree class with all other species that increased the overall accuracy by 22.3 %.
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(2022)Internet has altered the wildlife trade as it is now easy to trade animals on different online platforms. In the reptile pet trade, distinct appearance and rarity of the species are sought after attributes. Reptiles with small ranges are especially threatened by the pet trade. The Lesser Antilles are home to nearly hundred endemic lizard and snake species which are facing many threats from climate change to habitat loss. In addition, some of them are subject to international pet trade the scale of which is still not assessed properly. In this thesis I have mapped the online pet trade in endemic reptile species of the Lesser Antilles. To do this, I built an automated data collection and processing tool consisting of Python scripts. I used the tool to scrape 366 951 reptile trade advertisements from 90 distinct websites and to filter and extract information on Lesser Antillean reptiles from the collected data. The results show that most of the Lesser Antillean reptile species traded online have not yet been fully assessed for their conservation status by the International Union of the Conservation of Nature (IUCN). Overall, 9,2% off the reptiles on online sales advertisements and 21,4% of the species sold online are assessed as Threatened (i.e., at highest risk of extinction). Only 24,8% of advertisements selling Lesser Antillean reptiles online concern species that are evaluated as not Threatened by the IUCN Red List of Species. Germany was found to be the centre of trade of Lesser Antillean reptile species as the number of trade advertisements and distinct species sold was the highest there. United States was the second biggest trader of all species and the biggest trader of Convention on International Trade in Endangered Species (CITES) listed species. These results show that it is of foremost importance to evaluate the conservation status of all species that are currently traded to fully assess the threat that the pet trade possesses to reptile species. It will also be important to assess the sustainability of the reptile trade, especially in Germany and the United States. The tool used to collect and process the data in this thesis can be modified to assess the pet trade of any species on publicly accessible online platforms
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(Helsingin yliopistoHelsingfors universitetUniversity of Helsinki, 2007)Road transport and infrastructure has a fundamental meaning for the developing world. Poor quality and inadequate coverage of roads, lack of maintenance operations and outdated road maps continue to hinder economic and social development in the developing countries. This thesis focuses on studying the present state of road infrastructure and its mapping in the Taita Hills, south-east Kenya. The study is included as a part of the TAITA-project by the Department of Geography, University of Helsinki. The road infrastructure of the study area is studied by remote sensing and GIS based methodology. As the principal dataset, true colour airborne digital camera data from 2004, was used to generate an aerial image mosaic of the study area. Auxiliary data includes SPOT satellite imagery from 2003, field spectrometry data of road surfaces and relevant literature. Road infrastructure characteristics are interpreted from three test sites using pixel-based supervised classification, object-oriented supervised classifications and visual interpretation. Road infrastructure of the test sites is interpreted visually from a SPOT image. Road centrelines are then extracted from the object-oriented classification results with an automatic vectorisation process. The road infrastructure of the entire image mosaic is mapped by applying the most appropriate assessed data and techniques. The spectral characteristics and reflectance of various road surfaces are considered with the acquired field spectra and relevant literature. The results are compared with the experimented road mapping methods. This study concludes that classification and extraction of roads remains a difficult task, and that the accuracy of the results is inadequate regardless of the high spatial resolution of the image mosaic used in this thesis. Visual interpretation, out of all the experimented methods in this thesis is the most straightforward, accurate and valid technique for road mapping. Certain road surfaces have similar spectral characteristics and reflectance values with other land cover and land use. This has a great influence for digital analysis techniques in particular. Road mapping is made even more complicated by rich vegetation and tree canopy, clouds, shadows, low contrast between roads and surroundings and the width of narrow roads in relation to the spatial resolution of the imagery used. The results of this thesis may be applied to road infrastructure mapping in developing countries on a more general context, although with certain limits. In particular, unclassified rural roads require updated road mapping schemas to intensify road transport possibilities and to assist in the development of the developing world.
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