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(Helsingin yliopistoUniversity of HelsinkiHelsingfors universitet, 2000)
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(2018)Those who snore may suffer from sleep apnea, which causes a person to stop breathing during their sleep. This happens due to a collapse of the upper airway, which seals off the airflow partially or completely. A collapse like this is not necessarily dangerous in itself, as a person who experiences this usually wakes up briefly in order to breathe. These collapses do, however, result in bad sleep and may that way lead to other illnesses. That is why it is of interest to study this phenomenon, in order to improve the treatment of people who suffer from severe sleep apnea. Two mathematical models are analysed in the thesis. The focus of the models is on the breathing of humans and how the respiratory system functions when a patient may stop breathing. The first model in the thesis is used to study the airflow in the upper airway and the second model covers the carbon dioxide transport between alveoli, tissues and blood. The thesis also includes a biological background of the models, as well as explanations and definitions of the methods used when running computational simulations on them. A short analysis is made on the first model and a numerical analysis with some computational simulations is made on the second model. A basic understanding of derivation, partial derivation and the approximation of derivatives is needed for the mathematics used in the thesis.
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(2022)Tässä tutkimuksessa esitellään matematiikan sähköisten ylioppilaskirjoitusten käyttöönottoa ja niiden vaikutusta matematiikan opetukseen lukiossa. Tutkimuksen aineisto muodostuu tekijän omakohtaisista kokemuksista sähköisten ylioppilaskirjoitusten käyttöönotosta vastanneena lukio-opettajana vuosina 2015 - 2020, oppilaiden koevastauksista sähköisiin kurssikokeisiin sekä havainnoinnista todellisilla matematiikan lukiotunneilla. Havainnoidut oppitunnit jaoteltiin kolmeen kategoriaan: Perinteiset tunnit ilman sähköisten menetelmien käyttöä, hybridimenetelmän tunnit joissa vastaukset koostettiin osin perinteisin ja osin sähköisin menetelmin sekä kokonaan sähköisiä menetelmiä käyttävät tunnit. Oppilaiden koevastauksista havaittiin, että opettajan käyttämä opetustekniikka vaikuttaa oppilaiden tapaan tuottaa matemaattista tekstiä. Opetettaviksi valitut ohjelmistot vaikuttavat suuresti oppilaiden koevastausten ulkoasuun ja osin myös vastauksen matemaattiseen sisältöön. Myös oppilaiden tekniset taidot asettavat rajoitteita vastausten tuottamiselle. Lukion matematiikan opetus on kokenut suuren murroksen sähköisten ylioppilaskokeiden käyttöönoton myötä. Sähköinen matematiikan tuottaminen on heterogenisoinut opetusta ja aiheuttanut eroja eri opettajien opetustapojen välille. Tämä tutkimus tarjoaa kvalitatiivisia, pedagogis-sosiologiseen havainnointiin perustuvia näkökulmia aiheeseen.
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(Helsingin yliopistoHelsingfors universitetUniversity of Helsinki, 2010)This master s thesis examines tourism related housing and related discourses in the village of Kilpisjärvi, Finland. I study the tourism development in Kilpisjärvi and the debate related to this process. My methodology is based on discourse and content analysis. The purpose of this study is to examine and classify the discourses of tourism related housing and what are the lessons learned from the recent development of Kilpisjärvi. Kilpisjärvi is the northernmost village in western Finnish Lapland, located in the middle of the highest mountain area of Finland. The area has been reindeer herding area of Saami people for centuries, but it has lacked permanent settlement until the beginning of 20th century. The first tourist accommodation was built in 1930s, followed by the road in 1940s and the hotel in 1950s. Traditionally the area has attracted skiers and hikers. The area is also known for its extraordinary nature and rare plant life. Tourism development was slow in Kilpisjärvi until the turn of millennium when rapid growth in tourism related housing was triggered by extensive land use planning. Small wilderness village of Kilpisjärvi has grown to a tourism centre with over 800 beds in commercial enterprises, more than hundred second-homes, and two large caravan areas. This development has raised conflicts among villagers. The empirical part of this study is based on the interviews of 17 permanent dwellers of Kilpisjärvi and three Norwegian cottage owners. Six discourses can be distinguished: 1) Nature and landscape, 2) Economy, 3) Place, 4)Reindeer herding, 5) Governance and 6) Possibilities to influence decision-making. The first discourse stressed that tourism development and building should adapt to nature and landscape, while economic discourse stressed the economical importance of tourism to Kilpisjärvi and the municipality of Enontekiö. The third discourse noted the change of Kilpisjärvi as a place due to the boom of tourism development. The discourse of reindeer herding was clearly distinguished from others, seeing tourism development merely negative. Governance was seen as an important tool in regulating development, but many saw that the municipal administration has failed to take into account other aspects of tourism development than economical factors. Many villagers saw their influence in decision-making weak, while landowners and municipal decision-makers were seen as oligarchy in land-use planning regardless of formal participatory planning process enforced by law. I conclude that it is important to take into account the diversity of local discourses in tourism development and land use issues. Transparent and genuine participatory planning process would promote sustainable development, prevent conflicts and allow decisions and development which would satisfy larger number of local dwellers than presently.
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(2020)Globalization, climate change and the principles of sustainable development have made responsibility an important part of the societal debate. Responsibility is, above all, responsibility for the effects of activities. As festivals also have complex effects on the surrounding society, corporate responsibility thinking has also become part of festival production. Responsibility can be implemented by considering the stakeholders and their needs, and by ensuring not only economic viability but also the vitality of environmental resources. Sustainable development can be achieved by responsible actions. The purpose of the study was to show how responsibility has been considered in festivals organized in Finland. The aim of the study was to find out what measures and choices the festival organizers have used to promote the festival's economic, socio-cultural and ecological responsibility. The study also explored how the festival organisers see the responsible choices affecting stakeholders and the image of the festival. One of the aims of the study was also to find out what are the reasons behind more responsible activities and what challenges festivals have experienced in implementing responsibility into festival production. In addition, it was studied how festivals have measured and communicated the realization of their responsibility. The research problem is approached by reviewing the literature on tourism impacts, the principles of sustainable tourism and theories of corporate social responsibility. The growth and importance of cultural tourism was used as a basis for defining events and their role in tourism. Through events and event tourism, the definition of festivals and the connection of festivals to tourism was deepened. The context of the responsible festival was approached through the framework of responsible tourism. The empirical part consisted of a survey and interviews for festival organisations. A total of 40 responses were received to the survey and there were three festival representatives interviewed. The study utilized both qualitative and quantitative methods in the processing of the results and material. This wider perspective supported the broad dimensions of both responsibility and festivals. The study found that festivals have already incorporated responsibility into their activities. About every other festival already had responsibility-related action plan and all festivals considered it likely that they would increase their acts of responsibility in the future. Financial responsibility had been promoted, among other things, by supporting the local economy and following good governance. Socio-cultural responsibility had been considered, for example, by positively influencing the image and attractiveness of the festival’s region. In terms of environmental responsibility, the festivals had focused above all on waste management and accessibility. The most significant reason for promoting responsibility was the organisation's own ideology and values behind its activities. In addition, the festival visitors' demands for responsibility were also one of the essential reasons. Surveys aimed for festivalgoers were considered as a primary measure of responsibility. Responsibility had been communicated mainly in the instructions of the employees, but also on the social media sites of the festival. The biggest challenge in responsibility was the lack of common guidance in the event industry. Indeed, festival representatives felt that responsibility could best be promoted in the industry by creating such a guide. Festival representatives felt that responsibility has the most impact on promoting positive image of the event. It was also seen that responsibility influences the satisfaction of festival visitors as well as encourages their own responsibility. Thus, it seems that in festivals, responsibility has already been implemented in many ways, even if the festivals do not have an actual conscious responsibility plan. This also signals that responsibility is becoming part of all festival production activities, which provides good foundation for striving for the sustainability of festivals
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(2015)This work considers learning meaningful sets of chemical reactions called pathways and groups of species called Operational Taxonomical Units (OTUs) from metagenomic data. The methods are based on Nonnegative Matrix Factorization (NMF). The rows of our data matrix correspond to metagenomic samples and columns correspond to chemical reactions present in the samples. In order to learn both pathways and OTUs as well as relationships between them, we consider ways to factorize the data matrix into three factors instead of two. Denoting the samples times reactions data matrix by V, our factorization problem setting is to find nonnegative matrices W, H and P so that V is approximately WHP. The matrix W tells what OTUs are present in each of the samples, P defines pathways as combinations of reactions while H describes what pathways are implemented by which OTUs. We first discuss two standard NMF algorithms based on different objective functions and four sparsity constrained variants. Sparsity constrained variants are designed to produce output matrices with few values significantly above zero. We are interested in sparser variants because metagenomic pathways are short, thus the method should find a representation where only a small set of reactions is present in each pathway. We describe how using a standard two-factor NMF method twice yields a three-factor representation. We briefly mention an existing method, Nonnegative Matrix Tri-factorization (NMTF), that learns all three matrices W, H and P simultaneously. However, this method applies hard orthogonality constraints, i.e. it only finds solutions where the matrices W and P are orthogonal. Because of this constraint, NMTF is not suitable in our biological problem setting. We introduce an unconstrained method called NMF3 as well as a sparsity constrained variant SNMF3 based on Sparse Nonnegative Matrix Factorization (SNMF) and show how both of these algorithms can be derived. In order to compare the different algorithms' performance, we have built two synthetic data sets. Both sets are based on human intestinal species and pathway information available in an existing biological database. One of the data matrices can be exactly factorized into the underlying matrices used to generate the data. The other data set is built through simulating a sampling process that introduces noise and strictly limits the number of observed reactions per sample. We tested factorization methods discussed in the thesis on both data sets, using 100 to 1500 samples. We compare the methods and show and discuss the results. We found differences between NMF variants that use different objective functions. Many methods perform well on our task, surprisingly even in the case where the number of pathways is greater than the number of samples. Varying the number of samples affected the results less than we expected. Instead, we found that all algorithms performed significantly better on the factorizable data than on the simulated set.We conclude that the number of available metagenomic samples does not dramatically affect the performance of the factorization methods. More important is the quality of the samples.
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(2018)This thesis is about Loewner's theory of matrix monotone functions. Matrix monotone functions of order n are real functions which, when lifted via functional calculus, preserve Loewner order on n x n Hermitian matrices. In his seminal 1934 paper Loewner proved two famous results on matrix monotone functions. The first characterizes matrix monotone functions of order n by positivity of certain matrices. The second characterizes functions that are matrix monotone of all orders as certain functions extending analytically to upper half-plane. The goal of this thesis is to reinterpret and give new proofs for these results. Odd numbered chapters 1, 3, 5 and 7 follow the route towards the aforementioned goals. Chapters 1 and 3 discuss various basic facts and heuristics on matrix monotone functions. Chapters 5 and 7 contain the proofs of the main results of this thesis. Even numbered chapters 2, 4 and 6 offer supplementary information. Chapter 2 discusses fundamentals of Loewner order and functional calculus. Chapter 4 introduces divided differences and their key properties. Chapter 6 explores the basic properties of Pick–Nevanlinna functions.
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(2024)In this thesis, we prove the existence of a generalization of the matrix product state (MPS) decomposition in infinite-dimensional separable Hilbert spaces. Matrix product states, as a specific type of tensor network, are typically applied in the context of finite-dimensional spaces. However, as quantum mechanics regularly makes use of infinite-dimensional Hilbert spaces, it is an interesting mathematical question whether certain tensor network methods can be extended to infinite dimensions. It is a well-known result that an arbitrary vector in a tensor product of finite-dimensional Hilbert spaces can be written in MPS form by applying repeated singular value or Schmidt decompositions. In this thesis, we use an analogous method in the infinitedimensional context based on the singular value decomposition of compact operators. In order to acquire sufficient theoretical background for proving the main result, we first discuss compact operators and their spectral theory, and introduce Hilbert-Schmidt operators. We also provide a brief overview of the mathematical formulation of quantum mechanics. Additionally, we introduce the reader to tensor products of Hilbert spaces, in both finite- and infinite-dimensional contexts, and discuss their connection to Hilbert-Schmidt operators and quantum mechanics. We also prove a generalization of the Schmidt decomposition in infinite-dimensional Hilbert spaces. After establishing the required mathematical background, we provide an overview of matrix product states in finite-dimensional spaces. The thesis culminates in the proof of the existence of an MPS decomposition in infinite-dimensional Hilbert spaces.
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(2022)I min Magisteravhandling gör jag en undersökning över möjligheterna med att använda matematikprogrammet Matteva i undervisningen.Jag går igenom hur Matteva påverkar ungas motivation och om elever tycker Matteva är ett användbart program i undervisningen. Jag går först igenom Matteva grundligt genom en intervju jag gjort med Alva Grönqvist som har gjort programmet Matteva, efter det ser jag på olika medel hur Matteva hjälper i undervisningen och tar en närmare titt på geometrin och Matteva. Jag har också utfört en undersökning med 84 elever från Lovisavikens skola i klasserna 7-9. Jag har ett frågeformulär som tar hänsyn till olika aspekt inom pedagogiken och användbarheten av programmet. i mitt frågeformulär går jag igenom om det är möjligt att motivera unga att göra mera och lära sig bättre med hjälp av Matteva. Jag tar också hänsyn till hur Matteva påverkar elever från olika årskurser och med olika vitsord. På grund av att läs- och skrivsvårigheter är så vanligt i Finland har jag också kollat skilt på hur Matteva påverkar deras motivation och vad de tycker om att använda Matteva. Frågorna jag ville få svar på i min undersökning var: - Tycker eleverna att Matteva motiverar i undervisningen. - Tycker eleverna att Matteva är ett användbart program. - Hjälper Matteva elever med läs- och skrisvårigheter. - Påverkar elevens vitsord attityden mot Matteva. - Påverkar elevens årskurs attityden mot Matteva.
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(2020)Ultrasonic transducers convert electric energy into mechanical energy at ultrasonic frequencies. High-power ultrasound is widely used in the industry and in laboratories e.g. in cleaning, sonochemistry and welding solutions. To be effective in these cases, a piezoelectric transducer must deliver maximal power to the medium. Most of these systems rely on having the power delivery maximized during long driving sequences where stable performance is critical. Power ultrasonic transducers are typically narrowband, featuring high Q-value, that are finely tuned to a specific resonance frequency. The resonance frequency can vary during driving due to temperature, mechanical loading and nonlinear effects. When the transducers resonance frequency changes, drastic changes in its impedance (resonance to anti-resonance) can lead quickly to damage or failure of the driving electronics or the transducers themselves. In this work we developed a multi-channel high-power ultrasonic system with a software-based resonance frequency tracking and driving frequency control. The implementation features a feedback loop to maximize power delivery during long driving sequences in an ultrasonic cleaning vessel. The achieved total real power increased from 6.5 kW to almost 10 kW in peak with our feedback loop. The feedback loop also protected the electronics and transducers from breaking due to heating and varying impedance.
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(2017)Tässä tutkielmassa perehdytään niin sanottuun ylimartingaalin hajotelmaan max–plus-algebrassa ja sovelletaan sitä amerikkalaisiin optioihin. Tulokset esitellään pääosin jatkuvassa aika-avaruudessa, mutta myös diskreetin ajan tuloksia käsitellään. Markkinoilla myytävissä optioissa kiinnostavaa ovat se, milloin optio kannattaa käyttää ja se, milloin option myyjä voi saada voittoa. Amerikkalaisen option haltija voi käyttää option milloin tahansa sen voimassaoloaikana. Ylimartingaalin hajotelma max–plus-algebrassa takaa tietynlaisille stokastisille prosesseille sen, että amerikkalaisen option optimointiongelma voidaan ratkaista laskematta option hintaa, toisin sanoen optimaalisen pysäytyshetken etsiminen helpottuu. Jatkuvan ajan tulokset on esitelty Nicole El Karouin ja Asma Mezioun artikkelissa Max-plus Decomposition of Supermartingales and Convex Order. Application to American Options and Portfolio Insurance vuonna 2007. D. A. Darling, T. Liggett ja H. M. Taylor käsittelivät artikkelissaan Optimal Stopping Time for Partial Sums samaa asiaa diskreetissä ajassa jo vuonna 1972. Max–plus-algebra on eksoottinen algebra, jossa on kaksi operaatiota ⊕ = max ja ⊗ = +. Monet normaalissa algebrassa hankalat laskelmat onnistuvat max–plus-algebrassa helposti. Ylimartingaalin hajotelma max–plus-algebrassa mahdollistaa monenlaisia sovelluksia amerikkalaisen option lisäksi muun muassa matemaattisessa fysiikassa ja tietoliikenneverkoissa. Tutkielma etenee siten, että aluksi määritellään todennäköisyysavaruus ja tuodaan avaruuteen mukaan tarpeellisia ominaisuuksia kuten historia, ja esitellään muun muassa martingaalit. Amerikkalaisiin optioihin perehdytään siinä laajuudessa kuin päätulosten kannalta on tarpeellista. Tämän jälkeen tutustutaan max–plus-algebraan ja sen algebrallisiin ominaisuuksiin sekä ylimartingaalin hajotelmaan max–plus-algebrassa jatkuvassa aika-avaruudessa. Tulosta sovelletaan amerikkalaisiin osto-optioihin sekä jatkuvassa että diskreetissä avaruudessa. Tutkielmassa karakterisoidaan optimaalinen pysäytyshetki ylimartingaalin max–plus-hajotelman indeksiprosessin suhteen, missä oletukseksi tarvitaan multiplikatiivinen eli geometrinen Lévy-prosessi. Ensin osoitetaan se, että arvofunktiota ei tarvitse laskea optimaalisen pysäytyshetken ratkaisemiseksi. Sitten huomataan, että äärellisen maturiteetin tapaus on monimutkaisempi kuin äärettömän tapaus. Esimerkkejä käsitellään sekä geometrisesta Brownin liikkeestä että multiplikatiivisesta Lévy-prosessista. Myyntioptiota käsitellään lyhyesti ja pelkästään jatkuvassa aika-avaruudessa, sillä se saadaan osto-optiosta helpolla todennäköisyysmitan vaihdolla. Viimeiseksi kootaan tutkielman tulokset tiiviisti yhteen.
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Measured and modelled nitrous oxide and dinitrogen emissions from drained peatland soil in Finland (2019)Nitrous oxide (N2O), a major greenhouse gas and long-lived trace gas has been increasing in concentration in the atmosphere since the 1900s. Natural sources including soils account for approximately 62% of the total N2O emitted annually into the atmosphere. Biological processes lead to the production and consumption of nitrous gases in soils. Denitrification, the anaerobic reduction of nitrate to dinitrogen (N2), produces N2O as one of the intermediate volatiles. This process is driven by soil environmental factors such as temperature, moisture and nutrient availability as well as various underlying factors. Anthropogenic activities greatly affect these processes. Boreal peat soils are an important source of nitrous gases due to high content of soil nutrients (carbon and nitrogen) and drained peat soils can become potential ‘hotspots’ for N2O emissions. The environmental factors regulating the emissions are complex and remain unclear. The aim of this study is to investigate the importance of these factors on the emissions of N2O and N2, from drained peatland soil under changing temperature and moisture using measured data and process modelling. Soil samples from drained peatland sites in Southern Finland were collected, the N2 and N2O direct fluxes were measured using the helium-gas-flow soil-core method. To further examine the importance of different factors on the nitrous gas emissions in drained organic soil, a dynamic process-based model, CoupModel was used to simulate similar conditions as those in the laboratory experiment setup for measurement of the fluxes. The model includes a number of parameters which aim to quantify the detailed nitrification-denitrification process. A simple parameterization method was used to define parameter values and estimate the emissions based on the experimental conditions and known soil properties. Parameters were carefully selected and tested for their impact on the N-emissions. Key parameters and factors determining the soil N2O and N2 emissions were thus identified. The results show that nutrient-rich Lettosuo peat produced relatively high N2O (6 x 10-4 g N m-2 day-1) and N2 emission (2.6 x 10-3 g N m-2 day-1) on average as compared to nutrient poor Kalevansuo peat, which showed uptake of N2O (-1.5 x 10-5 g N m-2 day-1) and low N2 emission (0.7 x 10-3 g N m-2 day-1) on average. A significant response to changes in soil environmental conditions, temperature and moisture, was observed in both sites. The model output was consistent with the measurements of abiotic (soil temperature and soil moisture) and biotic responses (soil respiration). The model explained 53% of the variability in measured N2O emissions of the nutrient-rich soil. The dynamics of N2O and N2 emissions were simulated successfully by the model but included overestimation (up to 88%) in the case of N2O. The optimum soil water content for N2O production was between 80-85% vol. Most of the N2O and N2 emissions occurred under anaerobic conditions and hence originated from denitrification. In conclusion, denitrification is the main source of N2O in drained peat soils and soil temperature and water content regulating soil oxygen along with nutrient availability are the major factors influencing this process. Management practices as well as climate change can potentially influence these factors thus leading to changes in the greenhouse gas emissions origination from soils.
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(2013)Social networking services (SNSs) bring a new dimension to social life that helps people to easily communicate with each other. As one of the representative products of SNSs, YouTube has gained in popularity since 2005. Today, YouTube is the most well-known video delivery service on the Internet. As a result, YouTube data analysis has become increasingly important for understanding the characteristics of online video sites, which is vital in developing efficient content distribution systems. In this thesis, we examine the characteristics of YouTube data. Our analysis is based on an empirical data gathered from the live YouTube service. In addition to the basic statistics, correlational statistics have been also conducted. The results of basic statistics show an overview of YouTube data and the correlational statistics display the relationship among users and videos. Furthermore, Friend-Commenter Ratio (FCR) and Shortest Responses Time (SRT) have been measured. To the best of our knowledge, this is the first time that these two new metrics are proposed and analyzed.
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(2023)In high energy physics the microscopic nature of our universe is studied. A common experimental way is to collide particles such as protons with almost the speed of light and study the fragments that fly away from the interaction point. The results are compared to existing theories and help to modify or create knowledge of our universe. However, our senses are not capable of directly measuring those tiny and fast fragments from the collisions. Therefore, we need dedicated devices called particle detectors. Several types of radiation detectors are known to us. Most of those utilize the fact that particles in such experiments are ionizing when traversing matter. The detectors we are interested in contain gas as the main interacting material for the ionizing radiation, called gaseous detectors. One of these is the Gas Electron Multiplier (GEM), which uses electric fields to make electrons drift through the holes of one or several foils producing a signal that can be detected. Gain and ion backflow are two properties that can be used to evaluate the effectiveness of the detector. The effect of the hole diameters of the foil on the gain and on the ion backflow is insufficiently known, however. In this thesis such measurements have been performed. For this purpose a GEM detector operating in proportional region was constructed. The detector contained a special foil with four quadrants in such a way that the diameters of the holes were different in each quadrant. The functionality of the detector was verified by measuring the leakage current, by using a multichannel analyzer, and by calculating the sum of all currents. The detector constructed passed all the tests. The diameters of the holes in the foil quadrants were estimated by calculating the amount of pixels from the foil image taken. The outer hole diameters were around 50 µm and inner hole diameters 40 µm in the quadrant with smallest holes. The corresponding diameters in the quadrant with largest holes were around 70 µm and 66 µm. The measurements were started by searching the proper values for the drift and the induction fields and for the GEM voltage range. A drift field of 2 kV/cm, an induction field of 7 kV/cm, and a voltage range from 400 V to 500 V were chosen. The results from the actual measurements were similar on both sides of the foil. The effective gain increased steadily along with the voltage being around 10-fold at 500 V compared to that at 400 V . The ion backflow, on the other hand, stayed constant or even slightly decreased. The results measured from the four quadrants differed clearly from each other. In the quadrant with the smallest holes the effective gain was about twice as high as in the quadrant with the largest holes. Respectively the ion backflow was about 30 % higher in the quadrant with small holes than in the quadrant with large holes.
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(2017)This thesis aims to introduce and describe the importance of small molecule volatiles as biomarkers, and both their present and future roles in disease diagnostics and basic research. A few examples of these molecules are introduced in more detail, including the medical conditions they are related to, as well as the advantages and challenges concerning their analysis. The biomarkers discussed in this thesis are hydrogen cyanide (HCN), ammonia (NH3), nitric oxide (NO), hydrogen sulfide (H2S), acetone (C3H6O) and methane (CH4). The volatility of these molecules makes them suitable for breath analysis, which is described thoroughly in this thesis. The diagnostic potential of breath analysis, as well as its comparability to traditional analysis techniques, such as blood and urine analysis, are also discussed. Measurement of small-molecule volatiles from the headspace of bacterial cultures is also introduced and described in detail, and its importance considering the understanding of bacterial activity and metabolism discussed further. Volatile biomarkers in human breath and produced by bacteria are thus the main themes of this work. This thesis also describes a laser based, cavity-enhanced absorption technique that can be used to measure volatile, small-molecule biomarkers, such as those mentioned above. The measurement technique in question is cavity ring-down spectroscopy (CRDS), and its main features, as well as its advantages and limitations are discussed in detail, with special emphasis on features advantageous in breath analysis and bacterial headspace measurements. Sampling of the bacterial headspace and breath gas are introduced thoroughly. Special emphasis is given to the custom-built sampling line constructed in our laboratory, and it is used as a descriptive example when discussing the handling of gaseous samples. The measurement setups developed in our laboratory for the headspace measurements of both aerobic and anaerobic bacteria are also introduced in more detail. The experimental part of this thesis describes the bacterial headspace measurements done with the custom built CRDS instrument and sampling setup constructed in our laboratory. The aim of this experimental demonstration was to investigate, whether some oral bacteria are able to produce detectable amounts of HCN in vitro, identify these bacteria, and monitor their HCN production as thoroughly as possible. Oral bacteria capable of producing HCN could possibly affect the concentrations measured from human exhaled breath, and this should be taken into account in the HCN breath analysis. In the future, HCN could also be considered a possible biomarker for oral pathogenic bacteria responsible for periodontal diseases, if these bacteria are able to produce HCN in detectable amounts. Another aim of this experimental demonstration was to prove that our suggested measurement setup is suitable for both anaerobic and aerobic bacterial headspace measurement, and that it offers reliable, consistent and reproducible results. We were able to prove that certain oral anaerobes from Porphyromonas, Prevotella and Fusobacterium genera can produce detectable levels of HCN in vitro, which is a novel finding. We also observed a strong correlation between the HCN and carbon dioxide (CO2) productions of Porphyromonas gingivalis, which indicates a connection between bacterial metabolic activity and HCN production. Measurements done for the positive control produced similar results to those observed in previous studies, which demonstrates that our proposed system can be applied in the screening and evaluation of HCN production by both aerobic and anaerobic bacteria. In addition, results from duplicate and triplicate measurements were consistent with each other, further indicating that our proposed measurement and sampling setup are valid.
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(2016)Mobile apps are intended to be created with mobile platforms development tools and programming languages. This native development requires specialized skills and can therefore be prohibitively expensive. HTML5 hybrid app development is a popular alternative for native mobile app development. This development model allows developers to use standard web technologies and the end result can be indistinguishable from a native app by its visual representation. This model enables faster iteration speed, allows any web developer to build apps and supports simultaneous cross-platform development. However, since the web technology is not as performant as native, these hybrid apps have often been criticized for being noticeably 'laggy' by the app developer community and end users. One of the key components that affects HTML5 hybrid apps performance is the native bridge used in the app. This component bridges the embedded HTML5 application to the device features that wouldn't otherwise be available (such as writing to a file on the device's file system). The native bridge is one of the few components that a developer can freely change. Selecting the best native bridge for the app's needs is important as an inefficient native bridge can cause human noticeable delay in the app. The performance of native bridges has been acknowledged in academia and industry, but very little researched systematically. This thesis introduces a systematic method to evaluate native bridges performance. Along with this method, this thesis also describes a new open source tool implementing this method for benchmarking different native bridges. This tool hosts reference implementation for 32 native bridges. Example results from a test suite that tested all implemented native bridges with two embeddable web view engines (UIWebView and WKWebView) on four distinct iOS devices (two iPads, iPhone and iPod Touch) are evaluated. The results show that the majority of the known native bridge methods can cause human noticeable visual and auditory latency. It is also indicated that the performance is largely affected by app usage patterns. The slowest measured native bridge was over two times slower (from no delay to significant user interface delay) than the fastest one.
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(Helsingin yliopistoHelsingfors universitetUniversity of Helsinki, 2007)Free and Open Source Software (FOSS) has gained increased interest in the computer software industry, but assessing its quality remains a challenge. FOSS development is frequently carried out by globally distributed development teams, and all stages of development are publicly visible. Several product and process-level quality factors can be measured using the public data. This thesis presents a theoretical background for software quality and metrics and their application in a FOSS environment. Information available from FOSS projects in three information spaces are presented, and a quality model suitable for use in a FOSS context is constructed. The model includes both process and product quality metrics, and takes into account the tools and working methods commonly used in FOSS projects. A subset of the constructed quality model is applied to three FOSS projects, highlighting both theoretical and practical concerns in implementing automatic metric collection and analysis. The experiment shows that useful quality information can be extracted from the vast amount of data available. In particular, projects vary in their growth rate, complexity, modularity and team structure.
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(2024)The question of how much one logic can express compared to another can be measured with formula size, and important results have been reached with formula size games. These games can separate two classes of structures from each other within a given number of moves. Since formula size can also be expressed through extended syntax trees, we are interested in seeing what attributes or benefits games or trees have in different situations. First-order logic and its fragments are particularly interesting. This thesis discusses formula size games and analyses their use in known succinctness results between fragments of first-order logic and also between first-order logic and modal logic. While extended syntax trees may be preferred for results between fragments of first-order logic, the formula size game can be easily constructed for different languages. We find that both methods have advantages depending on the two logics that are compared to each other.
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(2018)In lattice field theories the partition function is often a very high dimensional integral which can’t be written in a closed form. In order to study the behaviour of the system one needs an efficient algorithm to approximate the high dimensional integral. In this thesis two Markov chain Monte Carlo algorithms the Metropolis algorithm and the Worm algorithm are used to simulate the three dimensional xy-model near its critical point. As the critical point is approached from below in terms of the inverse coupling the correlation length of the system diverges which may lead to the critical slowing down. An efficient algorithm is such that it suffers from the critical slowing down as little as possible which corresponds to a small dynamical critical exponent value. The efficiency of the algorithms is compared by measuring the integrated autocorrelation time of energy for different lattice sizes. The dynamical critical exponent, which controls the computational cost of the simulation, is calculated as a linear least squares fit to the integrated autocorrelation time data. From the simulated data the measured value of the dynamical critical exponent for the Metropolis algorithm is 1.85 and for the Worm algorithm the value is 0.37.
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(2024)In the field of cryogenics and superconducting technology, the effect of eddy currents presents a significant challenge, as large inductive currents can affect the performance and stability of cryogenic components. In our work, we examine how the magnitude of eddy current effects varies with different samples when placed within a changing magnetic field. In high magnetic field applications, any deviation in the magnetic field induces currents within low-resistivity components, leading to eddy current heating and Lorentz forces. This thesis focuses on how to simulate the eddy current phenomena in an accurate way through methods of finite element analysis, utilizing the commercial software of COMSOL Multiphysics. To provide a comprehensive simulation of the effects of eddy currents, our work involves the coupling of three distinct physical fields: solid mechanics, heat transfer, and electromagnetic fields. To solve multiphysical problem in an efficient way, we explain different strategies on how the coupled fields can be solved in a simplified, but effective way. The simulation was examined for two different time scale scenarios: 1. Turning on the magnet, where the time scale of the phenomena is in the order of several hours, and 2. The more demanding scenario of the quench of a superconducting magnet, where the time scale is in the order of several seconds. We found that during the ramping of the magnet the electromagnetic heating of the sample can reach the scales of milliwatts, which is significant head load in a cryogenic setting. During magnet quench, we found that the Lorentz forces can reach up to scales of kilonewtons. The results indicate that the volume of the sample has significant impact to effects of eddy currents, but when considering the magnitude of the Lorentz force the length and spatial location of the sample has significant effect. Hence, it is crucial to pay attention to the appropriate design of the sample that is placed into the magnetic field.
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