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  • Peltonen, Ella (2013)
    Cloud computing offers important resources, performance, and services nowadays when it has became popular to collect, store and analyze large data sets. This thesis builds on Berkeley Data Analysis Stack (BDAS) as a cloud computing environment designed for Big Data handling and analysis. Especially two parts of the BDAS, the cluster resource manager Mesos and the distribution manager Spark will be introduced. They offer important features, such as efficiency, multi-tenancy, and fault tolerance, for cloud computing. The Spark system expands MapReduce, the well-known cloud computing paradigm. Machine learning algorithms can predict trends and anomalies of large data sets. This thesis will present one of them, a distributed decision tree algorithm, implemented on the Spark system. As an example case, the decision tree will be used on the versatile energy consumption data from mobile devices, such as smart phones and tablets, of the Carat project. The data consists of information about the usage of the device, such as which applications have been running, network connections, battery temperatures, and screen brightness, for example. The decision tree aims to find chains of data features that might lead to energy consumption anomalies. Results of the analysis can be used to advise users on how to improve their battery life. This thesis will present selected analysis results together with advantages and disadvantages of the decision tree analysis.
  • Harjula, Pauliina (2015)
    The attempts of the Canadian government to abolish Indigenous ways of being through forced assimilation has resulted into a collective trauma and marginalization of Indigenous peoples. The legacy of this colonial genocide has been particularly devastating to Indigenous women who experience oppression by Euro-Western patriarchy through both their race and their gender. Colonial mind-sets and structures of the society in the past have denigrated and dehumanized Indigenous womanhood, and persist to victimize the women in particular and hurtful ways today. Despite being one of the most disadvantaged groups in Canada, Indigenous women are not victims – they are survivors, resisting the forces that oppress them by reconstructing the identity of Indigenous womanhood and taking action for social change. Regarding this topic and urban Indigenous realities in general, the city of Winnipeg in Manitoba is a place of special interest. It has lately become the toponym of violence and racism against Indigenous people in Canada, and especially Indigenous women. However, the city also has, for quite a while now, fostered a determinant and organized Indigenous community whose women are strongly expressing themselves and working for social change. This thesis describes the relationships I have built with the urban Indigenous community in Winnipeg to deepen the understanding of some the ways Indigenous women engage in colonial resistance through collective identity constructions and direct action in the city. By participating in the everyday life of the community, having one-on-one conversations and exploring personal narratives in social media I have learned how colonial resistance takes place in the women’s lives and in the city. I have transcribed my learning into three individual stories of three women who were my main participants. These stories speak of resistance through self-expression and action to reclaim spaces of autonomy. They reveal the significance of healing from colonial and personal trauma through the reconnection with spirituality and tradition, education and sense of belonging to a community. This thesis, centering the inspirational stories of resistance, is situated in anti-colonial framework, incorporating philosophical and methodological premises of Indigenous research paradigm. As such, the purpose of this study has been not only to uncover the power of Indigenous resistance but to support the ongoing global effort of Indigenous peoples to decolonize and restore their cultural-political sovereignty, identity and ways of knowing.
  • Niemistö, Juho (2014)
    Googlen kehittämä Android on noussut viime vuosina markkinaosuudeltaan suurimmaksi mobiililaitteiden käyttöjärjestelmäksi. Kuka tahansa voi kehittää Androidille sovelluksia, joiden kehittämiseen tarvittavat välineet ovat ilmaiseksi saatavilla. Erilaisia sovelluksia onkin kehitetty jo yli miljoona. Sovellusten laatu on erityisen tärkeää Android-alustalla, jossa kilpailua on runsaasti ja sovellusten hinta niin alhainen, ettei se muodosta estettä sovelluksen vaihtamiselle toiseen. Sovelluskauppa on myös aina saatavilla suoraan laitteesta. Tämä asettaa sovellusten testaamisellekin haasteita. Toisaalta sovellukset tulisi saada nopeasti sovelluskauppaan, mutta myös sovellusten laadun pitäisi olla hyvä. Testityökalujen pitäisi siis olla helppokäyttöisiä, ja tehokkaita. Androidille onkin kehitetty lukuisia testaustyökaluja Googlen omien työkalujen lisäksi. Tässä tutkielmassa tutustutaan Android-sovellusten rakenteeseen, niiden testaamiseen ja Android-alustalla toimiviin automaattisen testauksen työkaluihin. Erityisesti keskitytään yksikkö- ja toiminnallisen testauksen työkaluihin. Yksikkötestityökaluista vertaillaan Androidin omaa yksikkötestikehystä Robolectriciin. Toiminnallisen testauksen työkaluista vertaillaan Uiautomatoria, Robotiumia ja Troydia.
  • Boström, Fredrik (Helsingin yliopisto, 2008)
    Portable music players have made it possible to listen to a personal collection of music in almost every situation, and they are often used during some activity to provide a stimulating audio environment. Studies have demonstrated the effects of music on the human body and mind, indicating that selecting music according to situation can, besides making the situation more enjoyable, also make humans perform better. For example, music can boost performance during physical exercises, alleviate stress and positively affect learning. We believe that people intuitively select different types of music for different situations. Based on this hypothesis, we propose a portable music player, AndroMedia, designed to provide personalised music recommendations using the user’s current context and listening habits together with other user’s situational listening patterns. We have developed a prototype that consists of a central server and a PDA client. The client uses Bluetooth sensors to acquire context information and logs user interaction to infer implicit user feedback. The user interface also allows the user to give explicit feedback. Large user interface elements facilitate touch-based usage in busy environments. The prototype provides the necessary framework for using the collected information together with other user’s listening history in a context- enhanced collaborative filtering algorithm to generate context-sensitive recommendations. The current implementation is limited to using traditional collaborative filtering algorithms. We outline the techniques required to create context-aware recommendations and present a survey on mobile context-aware music recommenders found in literature. As opposed to the explored systems, AndroMedia utilises other users’ listening habits when suggesting tunes, and does not require any laborious set up processes.
  • Isokoski, Karoliina (Helsingin yliopisto, 2008)
    Rare-gas chemistry is of growing interest, and the recent advances include the "insertion" of a Xe atom into OH and water in the rare-gas hydrides HXeO and HXeOH. The insertion of Xe atoms into the H-C bonds of hydrocarbons was also demonstrated for HXeCC, HXeCCH and HXeCCXeH, the last of which was the first rare-gas hydride containing two rare-gas atoms. We describe the preparation and characterization of a new rare-gas compound, HXeOXeH. HXeOXeH was prepared in solid xenon by photolysis of a suitable precursor, for example water, and subsequent mobilization of the photoproducts. The experimental identification was carried out by FTIR spectroscopy, isotopic substitution and by use of various precursors. The photolytical and thermal stability of the new rare-gas hydride was also studied. The experimental work was supported by extensive quantum chemical calculations provided by our co-workers. HXeOXeH forms in a cryogenic xenon matrix from neutral O and H atoms in a two-step diffusion-controlled process involving HXeO as an intermediate [reactions (1) and (2)]. This formation mechanism is unique in that a rare-gas hydride is formed from another rare-gas hydride. H + Xe + O → HXeO (1) HXeO + Xe + H → HXeOXeH (2) Similarly to other rare-gas hydrides, HXeOXeH has a strongly IR-active H-Xe stretching vibration, allowing its spectral detection at 1379.3 cm-1. HXeOXeH is a very high-energy metastable species, yet thermally more stable than many other rare-gas hydrides. The calculated bending barrier of 0.57 eV, is not enough to explain the observed stability, and HXeOXeH might be affected by additional stabilization from the solid xenon environment. Chemical bonding between xenon and environmentally abundant species like water is of particular importance due to the “missing-xenon” problem. The relatively high thermal stability of HXeOXeH compared to other oxygen containing rare-gas compounds is relevant in this respect. Our work also raises the possibility of polymeric (–Xe–O)n networks, similarly to the computationally studied (XeCC)n polymers.
  • Holopainen, Inka (Helsingin yliopisto, 2012)
    The study is on the human dimension of animal-based tourism. There is a growing interest in nature and wildlife tourism but also a dire need for more research, especially of tourist experiences and expectations. Animal-based tourism is a little studied subject and a rarely used term. Animal-based tourism, unlike wildlife tourism, includes the use of domesticated animals and also other types of encounters than watching. Wildlife, nature and adventure tourism literature is used for defining animal-based tourism. Experiencing is another substantial sector of tourism business nowadays, alongside nature and wildlife tourism. Instead of services and products, the tourists are seeking experiences. Experience is a complex and diverse concept that is comprised of many different elements. The main object of the study is to understand the phenomenon of animal-based tourism, to interpret the experiences animal-based tourism creates and the elements in the animal encounters that contribute to creating them. The study draws from humanistic geography and uses the hermeneutic understanding of the world in the interpretation of tourists' experiences. Travel magazine Matkalehti's destination descriptions and travel stories are used as data. The research includes altogether 419 different articles in 111 magazines over 16 years of time. The articles are studied with content analysis, by looking for the typical characteristics of animal-based tourism (presented in the background chapter) and finding the various experiences and the elements that cause them (defined in the theoretical framework). The study is deductive, leaning strongly on the experience theories and frameworks presented in animal-based tourism literature. It was found that the animal-based tourism presented in the magazines was quite substantial and it reflected the definitions presented in the tourism literature. However, some variations were found: riding as an encounter had a far greater role than was expected. In Finland, alongside fishing, it was almost as important as watching animals. Abroad, watching was clearly the most popular encounter type. The destinations of animal-based tourism in the magazines varied greatly and they reflected the destinations typically of importance for Finns. However, clear focus points were seen. For example safaris (on land) typically took place in Sub-Saharan Africa, and whales and dolphins were watched in Iceland, Norway, Canary islands and the Azores, etc. Animals were encountered in many different settings but between captive- and wild-settings there was not a big difference, both occurred equally often. Captive-settings were usually located near cities or available areas for attracting bigger user groups, when wild-settings demanded more effort from the tourists. Species of animals reflected the findings in similar studies, and it was noticed that specific types of animals were preferred over others. Watching animals in captive-settings and in shows did not seem to evoke as many or as strong experiences as meeting them in the wild. Rare and endangered species as well as exotic and strange ones were preferred over others almost in every case. Some species were found to be icons for certain areas and were always mentioned with the same destinations. With certain species like dolphins, close interaction was sought after, and domesticated animals were found interesting only if there was a chance for touching and feeding them. Especially in fishing, riding and diving the settings and the beauty of the surroundings were important, but also the intensity of the activity. Education and conservation, which are a part of animal-based tourism according to literature, were not mentioned as often as was expected. The naturalness of the settings, the well-being of animals and the engaging nature of the encounters were the most crucial elements for creating experiences in animal-based tourism. Experiences of animal-based tourism were multiple as were the elements creating them.
  • Pannila, Tomi (2016)
    In this master's thesis we develop homological algebra using category theory. We develop basic properties of abelian categories, triangulated categories, derived categories, derived functors, and t-structures. At the end of most of the chapters there is a short section for notes which guide the reader to further results in the literature. Chapter 1 consists of a brief introduction to category theory. We define categories, functors, natural transformations, limits, colimits, pullbacks, pushouts, products, coproducts, equalizers, coequalizers, and adjoints, and prove a few basic results about categories like Yoneda's lemma, criterion for a functor to be an equivalence, and criterion for adjunction. In chapter 2 we develop basics about additive and abelian categories. Examples of abelian categories are the category of abelian groups and the category of R-modules over any commutative ring R. Every abelian category is additive, but an additive category does not need to be abelian. In this chapter we also introduce complexes over an additive category, some basic diagram chasing results, and the homotopy category. Some well known results that are proven in this chapter are the five lemma, the snake lemma and functoriality of the long exact sequence associated to a short exact sequence of complexes over an abelian category. In chapter 3 we introduce a method, called localization of categories, to invert a class of morphisms in a category. We give a universal property which characterizes the localization up to unique isomorphism. If the class of morphisms one wants to localize is a localizing class, then we can use the formalism of roofs and coroofs to represent the morphisms in the localization. Using this formalism we prove that the localization of an additive category with respect to a localizing class is an additive category. In chapter 4 we develop basic properties of triangulated categories, which are also additive categories. We prove basic properties of triangulated categories in this chapter and show that the homotopy category of an abelian category is a triangulated category. Chapter 5 consists of an introduction to derived categories. Derived categories are special kind of triangulated categories which can be constructed from abelian categories. If $\mathcal{A}$ is an abelian category and $C(\mathcal{A})$ is the category of complexes over $\mathcal{A}$, then the derived category of $\mathcal{A}$ is the category $C(\mathcal{A})[S^{-1}]$, where $S$ is the class consisting of quasi-isomorphisms in $C(\mathcal{A})$. In this chapter we prove that this category is a triangulated category. In chapter 6 we introduce right and left derived functors, which are functors between derived categories obtained from functors between abelian categories. We show existence of right derived functors and state the results needed to show existence of left derived functors. At the end of the chapter we give examples of right and left derived functors. In chapter 7 we introduce t-structures. T-structures allow one to do cohomology on triangulated categories with values in the core of a t-structure. At the end of the chapter we give an example of a t-structure on the bounded derived category of an abelian category.
  • Liu, Yanhe (2015)
    Cellular networks are facing a data explosion posed by the increasing bandwidth demand of current mobile applications, and cellular operators are trying to leverage auxiliary networks and offload mobile data for relieving this challenge. However, traffic offloading without comprehensive controlling may result poor network utilization and undesirable user experience. In this thesis, we design and implement an integrated architecture for intelligent traffic offloading over collaborative WiFi-cellular networks. Motivated by our measurement, we formulate a mathematical model to estimate and evaluate potential offloading throughput based on various wireless context information, like AP signal strength and bandwidth. To efficiently manage traffic and collect information, we use a centralized SDN architecture in our design. The proposed system enables mobile devices to choose the most beneficial AP for offloading. The experimental evaluation of our prototype implementation demonstrates that this architecture can achieve optimal traffic offloading by considering different real factors instead of making naive decisions. This effort not only explores the feasibility of context-based traffic offloading, but also provides guidelines for designing and implementing a centralized SDN platform for wireless networks.
  • Liu, Yanhe (2015)
    Cellular networks are facing a data explosion posed by the increasing bandwidth demand of current mobile applications, and cellular operators are trying to leverage auxiliary networks and offload mobile data for relieving this challenge. However, traffic offloading without comprehensive controlling may result poor network utilization and undesirable user experience. In this thesis, we design and implement an integrated architecture for intelligent traffic offloading over collaborative WiFi-cellular networks. Motivated by our measurement, we formulate a mathematical model to estimate and evaluate potential offloading throughput based on various wireless context information, like AP signal strength and bandwidth. To efficiently manage traffic and collect information, we use a centralized SDN architecture in our design. The proposed system enables mobile devices to choose the most beneficial AP for offloading. The experimental evaluation of our prototype implementation demonstrates that this architecture can achieve optimal traffic offloading by considering different real factors instead of making naive decisions. This effort not only explores the feasibility of context-based traffic offloading, but also provides guidelines for designing and implementing a centralized SDN platform for wireless networks.
  • Holmberg, Robert (Helsingin yliopisto, 2006)
    Ett sätt att förbättra resultat i informationssökning är frågeutvidgning. Vid frågeutvidgning utökas användarens ursprungliga fråga med termer som berör samma ämne. Frågor som har stort likhetsvärde med ett dokument kan tänkas beskriva dokumentet väl och kan därför fungera som en källa för goda utvidgningstermer. Om tidigare frågor finns lagrade kan termer som hittas med hjälp av dessa användas som kandidater för frågeutvidgningstermer. I avhandlingen presenteras och jämförs tre metoder för användning av tidigare frågor vid frågeutvidgning. För att evaluera metodernas effektivitet, jämförs de med hjälp av sökmaskinen Lucene och en liten samling dokument som berör cancerforskning. Som jämförelseresultat används de omodifierade frågorna och en enkel pseudorelevansåterkopplingsmetod som inte använder sig av tidigare frågor. Ingen av frågeutvidgningsmetoderna klarade sig speciellt bra, vilket beror på att dokumentsamlingen och testfrågorna utgör en svår omgivning för denna typ av metoder.
  • Bandyopadhyay, Payel (2015)
    The way the users interact with Information Retrieval (IR) systems is an interesting topic of interest in the field of Human Computer Interaction (HCI) and IR. With the ever increasing information in the web, users are often lost in the vast information space. Navigating in the complex information space to find the required information, is often an abstruse task by users. One of the reasons is the difficulty in designing systems that would present the user with an optimal set of navigation options to support varying information needs. As a solution to the navigation problem, in this thesis we propose a method referred as interaction portfolio theory, based on Markowitz’s "Modern Portfolio theory", a theory of finance. It provides the users with N optimal interaction options in each iteration, by taking into account user’s goal expressed via interaction during the task, but also the risk related to a potentially suboptimal choice made by the user. In each iteration, the proposed method learns the relevant interaction options from user behaviour interactively and optimizes relevance and diversity to allow the user to accomplish the task in a shorter interaction sequence. This theory can be applied to any IR system to help users to retrieve the required information efficiently.
  • Nikkilä, Mikko (2015)
    Often it would be useful to be able to calculate the "shape" of a set of points even though it is not clear what is formally meant by the word "shape." The definitions of shapes presented in this thesis are generalizations of the convex hull of a set of points P which is the smallest convex set that contains all points of P. The k-hull of a point set P is a generalization of the convex hull. It is the complement of the union of all such halfplanes that contain at most k points of P. One application of the k-hull is measuring the data depth of an arbitrary point of the plane with respect to P. Another generalization of the convex hull is the α-hull of a point set P. It is the complement of the union of all α-disks (disks of radius α) that contain no points of the set P in their interior. The value of α controls the detail of the α-hull: 0-hull is P and ∞-hull is the convex hull of P. The α-shape is the "straight-line" version of the α-hull. The α-hull and the α-shape reconstruct the shape in a more intuitive manner than the convex hull, recognizing that the set might have multiple distinct data clusters. However, α-hull and α-shape are very prone to outlier data that is often present in real-life datasets. A single outlier can drastically change the output shape. The k-order α-hull is a generalization of both the k-hull and the α-hull and as such it is a link between statistical data depth and shape reconstruction. The k-order α-hull of a point set P is the complement of the union of all such α-disks that contain at most k points of P. The k-order α-shape is the α-shape of those points of P that are not included in any of the α-disks. The k-order α-hull and the k-order α-shape can ignore a certain amount of the outlier data which the α-hull and the α-shape cannot. The detail of the shape can be controlled with the parameter α and the amount of outliers ignored with the parameter k. For example, the 0-order α-hull is the α-hull and the k-order ∞-hull is the k-hull. One possible application of the k-order α-shape is a visual representation of spatial data. Multiple k-order α-shapes can be drawn on a map so that shapes that are deeper in the dataset (larger values of k) are drawn with more intensive colors. Example datasets for geospatial visualization in this thesis include motor vehicle collisions in New York and unplanned stops of public transportation vehicles in Helsinki. Another application presented in this thesis is noise reduction from seismic time series using k-order α-disks. For each time tick, two disks of radius α are put above and below the data points. The upper disk is pulled downwards and the lower disk upwards until they contain exactly k data points inside. The algorithm's output for each time tick is the average of the centres of these two α-disks. With a good choice of parameters α and k, the algorithm successfully restores a good estimate of the original noiseless time series.
  • Darryn, Quirk (2015)
    This thesis looks at an example of how cities can be affected by large scale destruction and subsequent reconstruction, through the case study of post WW2 London bombing and rocket damage and rebuild. This is viewed with the idea that there was a promised effort by planners of the period to move to a more Utopian city layout for London as set forth in the ideals of Ebenezer Howard's Garden Cities of To-Morrow. This thesis seeks to answer three questions: (1) What impact did the Blitz Bombings/V Strikes of WW2 have on London? (2) Which green space or public areas around today were created as a result of the bombings? (3) Did the urban planners apply E. Howard's Garden City Theory to the restructuring of land use as promised? This has been done by the use of a comparative GIS exercise utilising pre and post War maps of six London boroughs forming the study area, and an aggregate of bomb and rocket incidents recorded from various sources, to determine which areas which has been previously urban in nature and then damaged were rebuilt as a Green or Open Space. Emphasis was placed on transformation of the old and new maps as well as categorisation of the various Green and Open Space types. The findings of this thesis were that although the damage to urban areas was extensive during this period, the overall layout of London did not change significantly in terms of Green and Open spaces, and any changes that were made were opportunistic rather than a noted trend towards Howard's ideals. It also offers commentary on the process of utilising pre-GIS maps in a modern context and its shortcomings in terms of data accuracy.
  • Satovuori, Anna (2016)
    The potential of tourism in the development of rural or otherwise marginal areas is nowadays widely acknowledged. From the perspective of community development, community-based tourism (CBT) is often considered as a sustainable form of tourism as opposed to traditional mass tourism. This is due to the emphasis that in CBT is put on the local participation in decision-making and management of tourism as well as the resulting benefits. However, the concept of CBT has often been criticized of failing in practice and resulting e.g. in the benefits being accrued to the elites of the community. It has been proposed that the so called asset-based community development approach (ABCD), an approach to community development that emphasizes the existing assets of the community, could be used to improve the community-based tourism efforts, as the ABCD promotes participation and highlights the potential of also the marginalized groups in the community. The purpose of this thesis was to examine the potential of the asset approach in improving community-based tourism. This was done through analysis of an existing community based hiking tourism project in the West Bank, Palestine. The issue was approached from two angles. Firstly, it was evaluated how the current project meets the ideals of CBT and whether the ABCD in this sense could contribute to improve the project. Secondly, an asset-mapping, which is an essential element of the ABCD approach, was conducted in order to apply the asset approach on a more practical level. In the asset-mapping the local perceptions of the tourism assets of the community were identified and then compared to what is promoted in the existing tourism project. The data was gathered on two separate fieldtrips, in May and August 2015. In total 21 qualitative, semi-structured interviews were conducted with different stakeholders, including the locals involved with the initiative, municipality representatives as well as the organization that is developing tourism in the area. In addition a survey with 74 retrieved responses was conducted in order to map the local perceptions of the assets. The results of the study indicate, that in many ways the CBT initiative already meets the ideals identified in the literature in terms of e.g. promoting cultural exchange as well as socio-economic development goals. On the other hand, as caveats were identified the relatively low level of overall participation and the effects of the local power structures on it, as well as small economic benefits. All these issues have been identified in the literature as typical problems of CBT. It was identified that adopting the principle inherent in the ABCD, that also the marginal segments in the community can contribute, could be useful in making the initiative more fair within the community. On the other hand, even if on a community level it is not the most marginalized that have currently been included, on a regional scale the initiative is doing just that. The initiative is spreading tourism to marginalized, rural areas that struggle with Israeli occupation, beyond the traditional pilgrimage destinations such as Betlehem The asset-mapping revealed that for the most part the assets promoted in current tourism match well with the local perceptions of the community’s tourism assets, which is positive from the ABCD perspective. The survey method proved to function as an effective tool for integrating the locals’ views on the assets. It could be claimed based on my study, that the locals mapping their own tourism assets could indeed provide a practical application of participation that has been called for in tourism research. At the same time agency and sense of control, which are emphasized in the ABCD, would be promoted. In conclusion it can be argued, that the study identified potential of the ABCD in improving CBT both as an approach towards the community and its marginal groups, but also on a methodological level in the form of the locals mapping the community assets. Despite the focus of my study was on natural and cultural assets, in the end the importance of social, human and physical capital became evident. This is also where the ABCD could be seen as useful, in broadening the scope of interest from only touristic (natural and cultural) assets to view the assets in a more comprehensive way, including also more intangible capital. More research on the applicability of the approach in CBT is needed, especially such that would adopt a more comprehensive view on the assets.
  • Jääsaari, Jesse Sebastian (2013)
    Vuonna $1837$ Peter Dirichlet todisti suuren alkulukuja koskevan tuloksen, jonka mukaan jokainen aritmeettinen jono $\{an+d\}_{n=1}^{\infty}$, miss\"a $(a,d)=1$, sis\"alt\"a\"a \"a\"arett\"om\"an monta alkulukua. Todistuksessa h\"an m\"a\"aritteli ns. Dirichlet'n karakterit joille l\"oydettiin my\"ohemmin paljon k\"aytt\"o\"a lukuteoriassa. Dirichlet'n karakteri $\chi$ (mod $q$) on jaksollinen (jakson pituutena $q$), t\"aysin multiplikatiivinen aritmeettinen funktio, jolla on seuraava ominaisuus: $\chi(n)=0$ kun $(n,q)>1$ ja $\chi(n)\neq 0$ kun $(n,q)=1$. T\"ass\"a Pro Gradu-tutkielmassa tutkitaan karakterisumman \begin{equation*} \mathcal{S}_\chi(t)=\sum_{n\leq t}\chi(n) \end{equation*} kokoa, miss\"a $t$ on positiivinen reaaliluku ja $\chi$ (mod $q$) on ei-prinsipaali Dirichlet'n karakteri. Triviaalisti jaksollisuudesta seuraa, ett\"a $|\mathcal{S}_\chi(t)|\leq\min(t,q)$. Ensimm\"ainen ep\"atriviaali arvio on vuodelta $1918$, jolloin George P\'olya ja Ivan Vinogradov todistivat, toisistaan riippumatta, ett\"a $|\mathcal{S}_\chi(t)|\ll\sqrt q\log q$ uniformisti $t$:n suhteen. T\"am\"a tunnetaan P\'olya--Vinogradovin ep\"ayht\"al\"on\"a. Olettamalla yleistetyn Riemannin hypoteesin, Hugh Montgomery ja Robert Vaughan todistivat, ett\"a $|\mathcal{S}_\chi(t)|\ll\sqrt q\log\log q$ vuonna $1977$. Vuonna $2005$ Andrew Granville ja Kannan Soundararajan osoittivat, ett\"a jos $\chi$ (mod $q$) on paritonta rajoitettua kertalukua $g$ oleva primitiivinen karakteri, niin \begin{equation}\label{ensimmainenarvio} |\mathcal{S}_\chi(t)|\ll_g\sqrt q(\log Q)^{1-\frac{\delta_g}{2}+o(1)}, \end{equation} miss\"a $\delta_g$ on $g$:st\"a riippuva vakio ja $Q$ on $q$ tai ($\log q)^{12}$ riippuen siit\"a oletetaanko yleistetty Riemannin hypoteesi. Todistus perustui teknisiin aputuloksiin, jotka saatiin muotoiltua teeskentelevyys-k\"asitteen avulla. Granville ja Soundararajan m\"a\"aritteliv\"at kahden multiplikatiivisen funktion, joiden arvot ovat yksikk\"okiekossa, v\"alisen et\"aisyyden kaavalla \begin{equation*} \mathbb{D}(f,g;x)=\sqrt{\sum_{p\leq x}\frac{1-\Re(f(p)\overline g(p))}{p}}, \end{equation*} ja sanoivat, ett\"a $f$ on $g$-teeskentelev\"a jos $\mathbb{D}(f,g;\infty)$ on \"a\"arellinen. T\"all\"a et\"aisyydell\"a on paljon hy\"odyllisi\"a ominaisuuksia, ja niihin perustuvia menetelmi\"a kutsutaan teeskentelevyys-menetelmiksi. Johdannon j\"alkeen luvussa $2$ esitet\"a\"an m\"a\"aritelmi\"a ja perustuloksia. Luvun $3$ tarkoitus on johtaa luvussa $6$ tarvittavia aputuloksia. Luvussa $4$ m\"a\"aritell\"a\"an teeskentelevyys, todistetaan et\"aisyysfunktion $\mathbb{D}(f,g;x)$ ominaisuuksia ja esitet\"a\"an joitakin sovelluksia. Luvussa $5$ johdetaan j\"alleen teknisi\"a aputuloksia, jotka seuraavat Montgomery--Vaughanin arviosta. Luvussa $6$ tarkastellaan karakterisummia. Aloitamme todistamalla P\'olya--Vinogradovin ep\"ayht\"al\"on ja Montgomery--Vaughanin vahvennoksen t\"alle. P\"a\"atuloksena johdamme arvion ($\ref{ensimmainenarvio}$), jossa $\frac{1}{2}\delta_g$ on korvattu vakiolla $\delta_g$. T\"am\"an todisti alunperin Leo Goldmakher. Lopuksi k\"ayt\"amme teeskentelevyys-menetelmi\"a osoittamaan, ett\"a P\'olya--Vinogradovin ep\"ayht\"al\"o\"a voi vahventaa jos karaktereista tehd\"a\"an erilaisia oletuksia.
  • Michael, Martin Peter (Helsingin yliopisto, 2008)
    Mobile RFID services for the Internet of Things can be created by using RFID as an enabling technology in mobile devices. Humans, devices, and things are the content providers and users of these services. Mobile RFID services can be either provided on mobile devices as stand-alone services or combined with end-to-end systems. When different service solution scenarios are considered, there are more than one possible architectural solution in the network, mobile, and back-end server areas. Combining the solutions wisely by applying the software architecture and engineering principles, a combined solution can be formulated for certain application specific use cases. This thesis illustrates these ideas. It also shows how generally the solutions can be used in real world use case scenarios. A case study is used to add further evidence.
  • Töyrylä, Linnea (Helsingin yliopisto, 2012)
    Happamuus-käsite tulee vastaan niin kemian opetuksessa kuin arkielämässä. Käsite on laaja ja sen ymmärtämiseksi oppilaan on osattava myös muita kemian termejä ja teorioita. Usein happamuuden opetuksen esimerkeissä perehdytään kemian teollisuuden näkökulmiin ja pH:n mittaamiseen erilaisilla välineillä, vaikka useiden tutkimusten mukaan kemia olisi tuotava lähemmäs oppilaiden arkipäivää. Argumentaatio on olennainen osa luonnontieteitä, sillä ilman sitä uutta tietoa ei voi syntyä. Oppilaiden argumentointitaitoja ja argumentaation opetusta luonnontieteissä on tutkittu melko paljon ulkomailla ja on havaittu, että sekä opetuksessa että oppilailla on puutetta argumentaation käytössä. Tässä tutkielmassa kehitettiin kehittämistutkimuksen kautta argumentaatiota tukeva happamuuteen ja erityisesti pHindikaattoreihin perehtyvä oppimateriaali, jossa sovelletaan molekyyligastronomiaa. Molekyyligastronomia ja ruoan kemia valittiin työn konteksteiksi, koska aikaisemman tutkimuskirjallisuuden mukaan oppilaiden arkipäivää lähellä olevat aiheet kannustavat heitä argumentoimaan paremmin. Kehittämistutkimus itsessään koostuu neljästä vaiheesta, jotka ovat tarveanalyysi, oppimateriaalin kehittäminen, tutkimuksen suoritus sekä tulosten tulkinta, arviointi ja jatkokehittely. Tutkielma pyrkii vastaamaan kysymyksiin siitä, kuinka paljon ruoan kemiaan liittyviä esimerkkejä happamuuden opetuksessa käytetään, millainen on hyvä argumentaatiota tukeva happamuuteen liittyvä oppimateriaali ja mitä kyseisen materiaalin avulla opitaan. Oppimateriaalista laadittiin kolme erilaista versiota, joista ensimmäistä testattiin opettajilla, toista oppilailla ja joista kolmas on liitetty tähän tutkielmaan. Tarveanalyysissa tutkittiin peruskoulun yläasteen kemian oppikirjojen happamuutta käsittelevissä kappaleissa olevien ruoan kemiaan liittyviä esimerkkejä. Kokeellisessa osassa oppilaiden argumentaatiotaitoja tutkittiin teoriapohjaisella sisällönanalyysin kautta. Argumentaatiotaitojen tutkimiseen liitettiin tiedon dimensioiden analyysi. Lisäksi oppilaiden oppimista testattiin kyselylomakkeella ennen ja jälkeen materiaalin opettamisen. Oppilaiden argumentaatiotaitojen oppimista tutkittiin tapaustutkimuksen avulla eli tutkimukseen osallistui vain yksi peruskoulun yhdeksäs luokka. Tutkimuksessa havaittiin, että happamuus-aiheen opettamiseen liittyy monia haasteita. Esimerkiksi juuri indikaattori-käsite on oppilaille haastava ja emästen kemia on oppilaille vaikeampaa kuin happojen. Oppilaiden argumentaatiotaitojen analyysissa puolestaan kävi ilmi, että oppilaat osaavat argumentoida melko hyvin, mutta eivät välttämättä pääse alkuun itsenäisesti. Oppilaat osasivat käyttää argumentoinnissaan käsitetietoa, eli esimerkiksi käyttivät happamuuteen liittyviä käsitteitä oikein, ja menetelmätietoa mitatessaan eri aineiden happamuuksia. Opettajan toiminnalla on suuri vaikutus oppilaiden argumentaation käyttämiseen. Koska on tutkimus on tapaustutkimus, ei tuloksista voida tehdä yleistäviä, koko ikäluokkaa koskevia johtopäätöksiä. Sen sijaan tulosten pohjalta voidaan tehdä erilaisia olettamuksia. Kehitetty oppimateriaali vastaa omalta osaltaan haasteeseen, jossa pyritään luomaan kemian luokkaan keskusteleva ja jopa tiedeyhteisön argumentointia muistuttavan ilmapiiri. Lisäksi se tuo yhden esimerkin siitä, miten molekyyligastronomiaa ja ruoan kemiaa voisi tuoda enemmän esiin kemian opetuksessa. Kun oppimateriaalia tämän tutkimuksen puitteissa testattiin, onnistuttiin luokassa saamaan aikaan keskustelua ja oppilaat muodostivat itsenäisesti tai opettajan pienellä avustuksella hyviä argumentteja.
  • Rosama, Veera (2013)
    Tutkielman tarkoituksena on tutkia aritmeettista derivaattaa. Aritmeettinen derivaatta on määritelty vasta muutamia kymmeniä vuosia sitten, vaikka sen alkuperä saattaa hyvinkin olla kaukana historiassa. Luvun aritmeettinen derivaatta perustuu luvun alkutekijöihin jakoon. Alun perin aritmeettisessa derivaatassa on ollut kyse juuri luonnollisten lukujen ominaisuuksista ja jaosta alkutekijöihin. Tekijöihin jaon avulla voidaan selvittää yksiselitteinen muoto derivaatan lausekkeelle ja laajentaa tätä koskemaan myös negatiivisia kokonaislukuja. Myöhemmin käsitettä on laajennettu koskemaan sekä rationaalilukuja, että joitain irrationaalilukuja. Tutkielman alussa esitellään yleisiä määritelmiä, joita käytetään myöhemmin hyväksi. Tämän jälkeen määritellään aritmeettinen derivaatta luonnollisilla luvuilla käyttäen hyväksi Leibnizin sääntöä tulon derivaatalle. Määrittelyn jälkeen tutkitaan aritmeettisen derivaatan ominaisuuksia. Luvussa tutkitaan myös osamäärän derivaattaa sekä laajennetaan määritelmä negatiivisille kokonaisluvuille. Seuraavassa luvussa on tarkoitus laajentaa aritmeettisen derivaatan määritelmää koskemaa myös rationaalilukuja. Luvussa löydetään yleinen laskukaava aritmeettisen derivaatan laskemiselle sekä pohditaan myös muutamien raja-arvojen olemassaoloa. Määritelmän laajennusta jatketaan logaritmin derivaattaan, potenssien derivaattaan sekä myös joidenkin irrationaalilukujen derivaattaan. Viimeisissä luvuissa keskitytään aritmeettisen derivaatan soveltamiseen. Ensin tutkitaan eräitä differentiaaliyhtälöitä ja keskitytään lähinnä ratkaisuiden lukumäärien selvittämiseen. Lopuksi esitellään kaksi käsitettä: Sophie Germainin alkuluku ja Cunninghamin ketju. Näiden kahden ominaisuuksia valotetaan hieman aritmeettisen derivaatan avulla. Viimeisenä tutkielmassa esitellään vielä muutama avoin tutkimusongelma.