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Now showing items 3109-3128 of 4203
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(2017)Oppimisen eräs suurin haaste on opiskelijoiden ennakkokäsitykset tieteellisistä ilmiöistä. Käsitykset ovat yleensä vain osittain lähellä tieteellistä käsitystä tai toisinaan jopa täysin ristiriitaisia sen kanssa. Uudempi tutkimus on keskittynyt selvittämään kognitiivisia tekijöitä ennakkokäsitysten muodostumisen taustalla ja on korostanut relaationaalisen tiedon merkitystä käsitteiden oppimisessa. Relaatioita ja relaationaalista tietoa voidaan siis pitää keskeisessä roolissa myös fysiikan käsitteiden oppimisessa, sillä käsitteiden merkitys rakentuu niiden sisäisen relaatiorakenteen perusteella. Tässä tutkimuksessa selvitettiin yliopisto-opiskelijoiden käsityksiä sähkötehosta siihen liittyvien käsitteiden avulla. Aihe on kiinnostava ja ajankohtainen, sillä aiempaa tutkimusta sähkötehosta ei juurikaan ole. Tutkimuksessa tutkittiin käsitteiden lisäksi niiden yhteydessä käytettyjä kuvailevia sanoja sekä niiden välisiä relaatioita ja kausaalisia suhteita. Tutkimuksen aineisto kerättiin haastattelujen avulla, jotka toteutettiin fysiikan pää- ja sivuaine opettajaopiskelijoille. Haastattelut videoitiin. Haastattelussa oli tutoriaalitehtävistä koostuva perusta, mutta haastattelijat eivät käyttäneet ennalta sovittuja kysymyksiä, vaan haastattelu eteni opiskelijoiden selitysten pohjalta. Tutoriaalitehtävissä opiskelijoiden tuli asettaa kytkentäkaavioiksi piirrettyjen virtapiirien lamput kirkkausjärjestykseen. He pohtivat ensin vastauksia itsenäisesti ja sen jälkeen keskustelivat niistä kolmen-neljän hengen pienryhmissä. Pohdinnan jälkeen he rakensivat kytkentäkaavioista virtapiirit ja vertailivat ennusteitaan tekemiinsä havaintoihin. Videoidut haastattelut litteroitiin ja aineistolle tehtiin aineistolähtöinen laadullinen analyysi. Aineistosta etsittiin opiskelijoiden sähkötehon yhteydessä käyttämiä käsitteitä, käsitteisiin liitettyjä attribuutteja sekä käsitteiden välisiä relaationaalisia suhteita. Aineistosta muodostettiin seitsemän eritasoista selitysmallia sähköteholle. Tutkimuksessa saatujen tulosten perusteella havaittiin, että relaationaalisen tiedon hallinnalla on merkitystä kattavien selitysmallien muodostumisessa. Kehittyneimmät selitysmallit olivat lähimpänä tieteellistä käsitystä sekä sisälsivät eniten relaatioita ja toisistaan eriytyneitä käsitteitä. Kuitenkin suurin osa opiskelijoista käytti selityksissään vain yksinkertaisia relaatioita tai perusteli virtapiirien toimintaa opittujen laskukaavojen avulla tarkemmin erittelemättä mitä ne tarkoittavat. Heidän selitysmalleistaan voidaan päätellä, että puutteellinen relaationaalinen ymmärrys saattaa olla eräs syy tieteellisten käsitysten oppimisvaikeuksien taustalla.
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(2023)Particle jets are formed in high energy proton-proton collisions and then measured by particle physics experiments. These jets, initiated by the splitting and hadronization of color charged quarks and gluons, serve as important signatures of the strong force and provide a view to size scales smaller than the size of an atom. So, understanding jets, their behaviour and structure, is a path to understanding one of the four fundamental forces in the known universe. But, it is not only the strong force that is of interest. Studies of Standard Model physics and beyond Standard Model physics require a precise measurement of the energies of final state particles, represented often as jets, to understand our existing theories, to search for new physics hidden among our current experiments and to directly probe for the new physics. As experimentally reconstructed objects the measured jets require calibration. At the CMS experiment the jets are calibrated to the particle level jet energy scale and their resolution is determined to achieve the experimental goals of precision and understanding. During the many-step process of calibration, the position, energy and structure of the jets' are taken into account to provide the most accurate calibration possible. It is also of great importance, whether the jet is initiated by a gluon or a quark, as this affects the jets structure, distribution of energy among its constituents and the number of constituents. These differences cause disparities when calibrating the jets. Understanding of jets at the theory level is also important for simulation, which is utilized heavily during calibration and represents our current theoretical understanding of particle physics. This thesis presents a measurement of the relative response between light quark (up, down and strange) and gluon jets from the data of CMS experiment measured during 2018. The relative response is a measure of calibration between the objects and helps to show where the difference of quark and gluon jets is the largest. The discrimination between light quarks and gluons is performed with machine learning tools, and the relative response is compared at multiple stages of reconstruction to see how different effects affect the response. The dijet sample that is used in this study provides a full view of the phase space in pT and |eta|, with analysis covering both quark and gluon dominated regions of the space. These studies can then be continued with similar investigations of other samples, with the possibility of using the combined results as part of the calibration chain.
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(Helsingin yliopistoUniversity of HelsinkiHelsingfors universitet, 2000)
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(Helsingin yliopistoUniversity of HelsinkiHelsingfors universitet, 2005)
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(2020)In news agencies, there is a growing interest towards automated journalism. Majority of the systems applied are template- or rule-based, as they are expected to produce accurate and fluent output transparently. However, this approach often leads to output that lacks variety. To overcome this issue, I propose two approaches. In the lexicalization approach new words are included in the sentences, and in relexicalization approach some existing words are replaced with synonyms. Both of the approaches utilize contextual word embeddings for finding suitable words. Furthermore, the above approaches require linguistic resources, which are only available for high- resource languages. Thus, I present variants of the (re)lexicalization approaches that allow their utilization for low-resource languages. These variants utilize cross-lingual word embeddings to access linguistic resources of a high-resource language. The high-resource variants achieved promising results. However, the sampling of words should be further enhanced to improve reliability. The low-resource variants did show some promising results, but the quality suffered from complex morphology of the example language. This is a clear next issue to address and resolving it is expected to significantly improve the results.
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(2015)The ghost town of Varosha is a district of the city of Famagusta, located in the southeast coast of Cyprus. The thesis explores how Varosha is remembered on a specific, now removed, Facebook page called 'Varosha, Cyprus - What they don't want you to see'. It concentrates on the following questions: Why is it important to remember Varosha? How is Varosha pictured before and after the Turkish intervention/invasion of 1974, and how is the district's future seen? What memories are involved in 'specific places' and what are these places? The research material consists of postings and comments on the page, made during a two and a half year long data collection period. The research was conducted by using a thematic analysis. The research approach is deductive, in other words, theory-driven. The study pays more attention to those themes that were repeated by several commentators. A lot of citations is used to back up the notions. Varosha is nowadays a remembered place and a community which cannot be visited by public. It represents a powerful memory to many people, whether they have experienced it first-hand or not. The meanings associated with a place vary according to one's relation to the place. Outsiders want to know how Varosha was and is like inside the fences. The stories that the residents and visitors tell and the feelings and memories they share keep the place alive. The page was aimed at keeping the memory of Varosha alive, getting the word of the district's situation out to the world and exposing what the Turks have done to Varosha by providing photographic evidence. There were some topics that the administrators of the page had ruled out of the discussion. For example, disrespecting the feelings of the Varoshotes led to the removal of several postings, comments and commentators. Words that were used in describing Varosha's current state reflect the bitterness, sorrow and anger that many of the commentators and the administrators were feeling, whereas the words and descriptions connected to pre-1974 Varosha were all very positive. The depictions were divided according to the commentators' relation to the place. The idea of returning to Varosha is fuelled by nostalgia and the feeling of belonging to the fenced off area. For the old residents and their offspring - second generation 'Varoshotes' it is not (just) about returning Varosha habitable again but also in some ways recreating the old community which was forcefully displaced over four decades ago. The research could be duplicated into another Facebook page focused on remembering a place. However, Varosha's special history combined with the on-going conflict in Cyprus have created somewhat special conditions for remembering. The page would also have provided material for studying otherness and hate speech.
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(2023)Coronal mass ejections (CMEs) are large eruptions of magnetized plasma from the solar corona. Fast CMEs can drive shock waves which are capable of accelerating charged particles to high energies. These accelerated particles emit electromagnetic radiation, including radio emission. Studying radio emission associated with CME-driven shocks offers a way to remotely investigate shock-accelerated electrons as well the shock itself. Solar radio bursts are transient events where the radio emission of the Sun rises above the background level. A classical division based on their appearance in a dynamic spectrum divides solar radio bursts into five categories: types I-V. Of these five different types, type II and type IV radio bursts are most commonly associated with CMEs. Occasionally, type II radio bursts exhibit a bursty fine structure known as herringbones. These are regarded as signatures of individual electron beams accelerated by CME-driven shocks. This thesis studies the radio emission associated with a CME that erupted on 1 September 2014. White-light imaging of the CME revealed a prominent shock wave. Simultaneously, the dynamic spectrum exhibited spike-like radio emission resembling herringbones. The aim of the study presented in this thesis is to find the source location of this radio emission relative to a three dimensional reconstruction of the shock. The source location of the radio emission can be used to conclude the likely origin of the electrons responsible for it. Additionally, in situ electron flux measurements are investigated in an attempt to connect the remote and in situ detections of energetic electrons. Using interferometric radio observations of the Sun and reconstructing the CME shock in three dimension revealed the location of the radio emission to be at the flank of the CME-driven shock. Such location suggests that the spike-like radio emission observed in the dynamic spectrum originates from shock-accelerated electrons. The location of the radio emission at the flanks of the CME shock was also used to get an estimation of the lateral expansion of the CME. Although the in situ electron flux measurements detected high-energy electrons, their inferred release time at the Sun did not coincide with observed radio emission.
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(2021)Acidic sulfate soils (a.s. soils) decrease the soil pH and generate an acidic environment that is toxic for vegetation and aquatic life. Therefore, knowledge of potentially dangerous soils is necessary during, e.g. construction planning to reduce ecosystem service loss. Identifying a.s. soils accurately is a difficult task and require expensive and laborious field and lab tests. In order to identify larger areas cost-effectively, remote sensing methods could bring benefits to the construction planning field. This work shows that point clouds acquired with aerial LiDAR scanning can be used to remote sense acid sulfate soils with PointNet and PointNet++ deep learning models. However, additional research with larger data sets is required to improve the accuracy of the models for real-world applications. Therefore, work also suggests further research and improvement ideas for collecting data for such models.
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(2019)Real-world locations can be reconstructed as digital 3D models using 3D scanning. The scans often suffer from missing surface regions caused by occlusions and poor scanning geometry, limiting their usefulness for many tasks. We present an automated system that repairs small missing regions using generative adversarial networks (GANs). The system operates on heightmaps of small round surface patches distributed around the missing region. A neural network model predicts a complete plausible surface for each corrupted patch, which is then integrated to the scan. In addition to geometry, surface colors are also generated. Encouraging results are found in the color reconstruction task, but the output geometry is not clearly superior to the results of a simpler baseline spline model.
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(2022)Determining the optimal rental price of an apartment is typically something that requires a real estate agent to gauge the external and internal features of the apartment, and similar apartments in the vicinity of the one being examined. Hedonic pricing models that rely on regression are commonplace, but those that employ state of the art machine learning methods are still not widespread. The purpose of this thesis is to investigate an optimal machine learning method for predicting property rent prices for apartments in the Greater Helsinki area. The project was carried out at the behest of a client in the real estate investing business. We review what external and inherent apartment features are the most suitable for making predictions, and engineer additional features that result in predictions with the least error within the Greater Helsinki area. Combining public demographic data from Tilastokeskus (Statistics Finland) and data from the online broker Oikotie Oy gives rise to a model that is comparable to contemporary commercial solutions offered in Finland. Using inverse distance weighting to interpolate and generate a price for the coordinates of the new apartment was also found to be crucial in developing an performant model. After reviewing models, the gradient boosting algorithm XGBoost was noted to fare the best for this regression task.
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(2012)In recent years, content-based Publish/Subscribe (pub/sub) has become a popular paradigm to decouple content producers and consumers for Internet-scale content services. Many real applications show that the content workloads frequently follow very skewed distribution, and incur unbalanced workloads. To balance the workloads, the current content-based Publish/Subscribe systems normally adopt a migration scheme (Mis) to move (a subset of) subscription filters from overloaded brokers to underloaded brokers. In this way, the publications that successfully match the moved filters are then o oaded, leading to balanced workloads. Unfortunately, the Mis scheme cannot reduce the overall matching workloads. In the worse case, suppose that all brokers su er from heavy workloads. Mis cannot find available brokers to o oad the heavy workloads of those overloaded brokers, and fail to balance the workloads of the overloaded brokers. To overcome the issue, we develop a set of novel load balancing algorithms, namely a similarity-based replication scheme (Sir). The novelty of Sir is that it not only balances the workloads of brokers but also reduces the overall workloads. Based on both simulation and emulation results, the extensive experiments verify that Sir can achieve much better performance than Mis, in terms of 43.10% higher entropy value (i.e., more balanced workloads) and 46.39% lower workloads.
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(2014)The aim of the research is to solve backpackers IT usage, how they use it and what are their attitudes towards it in a personal and society level. The targets of the study are backpackers who live in a western society and the aim is to investigate what is the role of IT during their travel compared to everyday life. In support for this will be to find out what is the role of time, natural environment and social relations towards IT usage. The study is implemented by data based qualitative methods which means that data is at the center not the theory. Grounded Theory approach could be used when the phenomenon is unknown. Grounded Theory is more like a method than a theory as the english term suggests. Through the approach theory will be constructed during the research process by the observations which have found. The research approach is inductive because the basis is not tested with theory or hypotheses. The researcher will define what is important and what is not. The triangulation of qualitative methods will be fullfilled through theme interviews, participant observation and Grounded Theory. The fieldwork was conducted in the state of Kerala, India and in some destinations of Sri Lanka. Eight theme interviews were gathered all together of which two were couple interviews. Interviews were implemented in a tourist bubble. Based on interviews the most important IT devices were smartphones and cameras. Nowadays the usage of internet cafes to contact friends and relatives could be considered replaced by the features and applications of smartphones. The results show that the smartphone usage is tried to kept in minimum but intensive usage in home environment is hard to change. During the travel remarkably important issue which affects to IT usage is the availability of WiFi network. Inside the tourist bubble it is widely available. The most important properties of smartphones are social media and free message sending through wireless network. In everyday life backpackers use more IT than when traveling even if there is more time to use it. That is cause of natural environment, new social relationships and willingness to cut off everyday life. Interviewees also describe that the development of IT is in the first place a good thing but the usage of it is nowadays too intensive both in individual and society scale. It could be argued that backpackers IT usage and attitudes towards it are complex and paradoxical. The main reason for that is that suddenly users have the device in their hand whereby they can do almost everything. People are not prepared for that and not be able to use in a suitable way and amount. The overuse may cause depression, anxiety, decreasing sociality and fullfilling the spare moments of time with something unnatural. The virtual identities modify life complicated and tricky even though communication has become more easy. In turn wisdom, knowledge and awareness could be spread via internet which is considered almost as an human right by interviewees. It is clear that the availability of WiFi connections increases the usage of IT, mainly smartphones during the travel.
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(2021)Cultural Heritage (CH) collections, data, and artefacts used to be available mainly in galleries, libraries, archives, and museums (GLAM). Due to digitisation, huge collections of CH data are now available online. Since the appearance of these data online, CH data have been searched, analysed and presented using various methods and visualisations. However, many of these methods do not take adequate advantage of the nature of CH data. Even when the CH data dimensions are utilised, the choices of visualisation sometimes fall short. This thesis is a part of the Finnish Archaeological Finds Recording Linked Open Database (SuALT) project. The project aims to develop digital Web services to cater for archaeological finds made by members of the public, especially metal detectorists through ‘citizen science’. Therein, a portion of an innovative prototype that tries to enable serendipitous knowledge discovery by making searching and visualising CH data seamless is presented. The artefact would serve as part of the basis of the FindSampo portal. The prototype is not implemented from scratch, but it is based on the Sampo model, the Sampo-UI framework and several third-party libraries and visualisations. The prototype includes mainly a user-centric faceted search engine, keyword searches to filter the facet options. It also includes data-analytic tools for visualising the filtered data on a table, a timeline chart, pie chart, line chart, maps and an option to export the results in CSV form for further analysis in external tools. However, this thesis focuses on the faceted search engine and the timeline visualisation that presents the spatio-temporal nature of the SuALT data. The portion of the prototype was evaluated based on three principles: serendipity, generosity, and criticality. And the result of the user experience survey suggests that the prototype could provide a good starting point to explore the find collection, make access to individual find information easier, improves the serendipitous discovery of archaeological find data and also make the find data analysis and interpretation easier.
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(2017)In the past few decades there has been increasing interest towards open innovation both among academia and in businesses. Especially software intensive companies face rapid technological change, which forces them to seek new sources of innovation. Companies can do this by using various open innovation approaches where they can share their knowledge and resources or utilize the knowledge and resources of outsiders ranging from other companies to individual developers. Open source software (OSS) is a blooming open innovation strategy used by a growing number of companies. OSS communities can have a large number of members, making the requirements management process challenging. This thesis aims to build an understanding of the requirements management process in a company that is leading an actively developed open source project. The studied OSS community doesn’t only have individual developers, but many companies participate in it as well. The thesis explores first open innovation, open source software development, and requirements engineering with means of a literature review. The goal of the literature review is to investigate open innovation and requirements management in OSS context. The literature review also provides a theoretical background for studying the open innovation and the requirements management process in the case company called Qt Company. The Qt Company leads an OSS project, which is the subject of this study. The project’s requirements management process was studied with the help of several information sources. These included interviews of Qt’s employees. The interviews were conducted in a research project called OpenReq. Additional information was gathered from the company’s websites and the project’s requirements management system. To verify the results, we first studied a few issues from the requirements management system to see whether they followed our conceptual model built based on the interviews, and illustrated as a swimlane diagram. Finally, we had a follow up interview with an employee from Qt Company (Qt’s community manager) to verify the results, and to correct any inaccuracies or misunderstandings. We found Qt Company using both inbound and outbound open innovation approaches in the studied OSS project. The project, and the community around it has many similarities to the OSS community descriptions found in the literature. For example, as often in OSS, the requirements in the studied project are unstructured. The requirements management process in the studied OSS project was found to include 12 different stakeholders. Also a diagram summarizing the whole requirements management process is constructed based on the interviews and presented at the results section of the thesis.
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(2013)The construction of large dams is causing human displacement and resettlement. In many cases indigenous groups of people are forced to move due to these development projects and are at a risk of losing their livelihoods, social networks and rights to customary land. This can cause impoverishment and marginalization. Constructing dams is usually initiated by the state and multinational organizations and have a top-down approach. The indigenous groups of people are not well considered during the planning process and their wishes about the development and resettlement are not properly acknowledged. This may eventually result in lack of integration and rootlessness in their new settlements. In Sudan the construction of large dams is often combined with the development of irrigation schemes, where the displaced people can be resettled as tenant farmers. The construction of the Aswan High Dam at the border between Sudan and Egypt in 1960s caused the inundation of the Nubian town of Wadi Halfa. Most of the residents were resettled in the New Halfa irrigation scheme in east Sudan. New Halfa proved a failure for the state and the farmers as it failed to meet the goals set out for it. The Khasm el Girba dam that feeds the irrigation scheme with water lost some of its capacity and consequently made irrigation more difficult. The agricultural land also lost fertility and the farmers are forced to work harder to make farming profitable. The local nomadic inhabitants of the original area have also lost pastoral land due to the project. Large differences between the livelihoods and economic situations of the residents have emerged which has led to social segregation. This study discusses the social consequences of resettlement and the profitability of irrigation schemes as a development initiative. The study was conducted in Sudan during the summer of 2011 in Khartoum and New Halfa agricultural scheme. The study states that the conditions for agriculture have deteriorated in New Halfa and the farmers are forced to depend on additional sources of income to secure their livelihoods. The different groups of people within the scheme are socially segregated and live in areas with a varying degree of infrastructure and services. The original planning of the scheme failed to acknowledge the needs of the different ethnic groups which led to detachment and social inequality.
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(2017)This thesis offers views on the resident interests and participation in energy refurbishment processes by qualitatively analysing nine thematic resident interviews. Urban areas and buildings largely contribute to energy consumption and carbon emissions. The ageing building stock across Europe offers a window of opportunity for large scale energy refurbishments. Urban sustainability and participatory planning, the framework theories of this thesis, are both threaded by the lack of social focus, reflected in the lack of residential focus in housing refurbishments. Residents' main interests include economic reasoning, quality of life, and energy and environment. Economic reasoning includes concern of costs, interest in energy bill savings and stable living costs, and property value increase, indicating a rising market demand. Quality of life includes building condition, comfort, visual aspects, ease of maintenance, interest in technology, and preference on either shared or private systems. Environmental motivations vary and seem to correlate with one's faith in the effect of individuals and communities in solving climate issues. Good process practices facilitating trust include: activation of different information channels when refurbishments are approaching, personal and technical planning support, and a strong house strategy communicating residents the justifications and their areas of interest. Neighbourhood examples motivate residents and help them plan their own projects. As refurbishments make residents more proudly develop their houses and neighbourhoods, resident ambassadors can be used to replicate the experiences. Sharing and networking are already in place, but lack of promoting the sense of community may hinder such development. Existing co-planning reflects residents' strong position as stakeholders. Differences in participation power are found between housing cooperative boards and other residents. The boards dominate planning, justifying it with technical expertise and the difficulty of including everyone. This is accepted if an open communication culture is on place, as house meetings offer other residents a place to get informed and participate in decision making. The idea of including residents into planning is emerging. Participation benefits include residents offering good ideas, gaining knowledge, and achieving a stronger sense of community. Information and inclusion make residents more engaged to the development, speeding up decision making. A process model for participatory refurbishments is presented. Apart from the resident drivers active in house and neighbourhood levels, four challenging resident groups are identified: the unsocial, the objectors, the uninformed, and the unheard. Resident segmentation offers a good tool for identifying motivators to engage residents, as well as identify their needs as project participants.
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(2021)Understanding local people’s perceptions towards tourism is important to minimize the negative impacts of tourism and to promote sustainable tourism. This thesis researches residents’ perceptions towards tourism, tourism development and tourism impacts in the city of Pokhara in Nepal. The thesis utilises Doxey’s irritation index and social exchange theory as the theoretical framework of the research. Based on Doxey’s irritation index, local people’s attitudes towards tourism shift from positive to negative as the time goes by and tourism develops. Based on the social exchange theory used in tourism studies, local people’s perceptions towards tourism are more positive the more the locals benefit from tourism and interact with tourists and tourism. This thesis aims to also understand what kind of place image local people have of Pokhara and how residents’ place image is connected to the perceptions they have towards tourism in Pokhara. As earlier tourism research has suggested, local people’s place image and perceptions towards tourism are connected and the more positive place image locals have, the more positive their perceptions towards tourism are. This thesis research is based on qualitative methods. The research data was collected with a qualitative questionnaire distributed online for the residents of Pokhara. Open-ended questions were used in the questionnaire, so that the participants could express their place image and perceptions towards tourism with their own words. The data was analysed by using qualitative content analysis. The results of this research indicate that the majority of the participants is satisfied with the tourism situation in Pokhara. The participants are especially content that tourism creates employment and earning opportunities for local people in Pokhara. However, a few participants expressed some irritation towards tourism situation in Pokhara due to different reasons. Despite some of the more negative perceptions towards tourism, almost all of the participants supported future tourism development in the area. Similarly, almost all of the participants thought that positive tourism impacts in the area are greater than the negative impacts, even though the participants also identified several negative tourism impacts, mainly regarding the environmental degradation and westernisation of local culture, habits, and values. On the contrary to the suggestions of the Doxey’s index, locals’ attitudes towards tourism have remained mostly positive even though tourism has developed in Pokhara in the past decades. Also, the results regarding local people’s involvement with tourism and tourists compared to their perceptions towards tourism are not completely in line with the earlier tourism research using the social exchange theory. The results of this research indicate that participants’ perceptions towards tourism are not always more positive the more residents benefit from tourism and interact with tourism or tourists. On the contrary, the perceptions towards tourism might be even more often negative among the participants who have contact with tourism and tourists than those who have not. The results also indicate that the participants have mostly a positive place image of Pokhara. Even though approximately half of the participants had both positive place image and positive perceptions towards tourism, positive place image will not always automatically result in positive perceptions towards tourism among the local people.
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(2019)Työssä käsitellään residyitä ja residylaskentaa. Näiden avulla lasketaan erilaisten reaalisten integraalien ja sarjojen summien arvoja. Ensimmäisen luvun johdannon jälkeen toisessa luvussa kerrataan aluksi kompleksilukujen perusominaisuudet, kuten liittoluku, moduli ja argumentti. Kolmannessa luvussa esitellään Laurentin sarja ja eristetyt erikoispisteet, jotka voidaan jakaa kolmeen luokkaan: poistuviin erikoispisteisiin, napoihin ja oleellisiin erikoispisteisiin. Neljännessä luvussa esitellään residyn määritelmä sekä erilaisia tapoja määrittää niiden arvoja. Tämän jälkeen johdetaan residylause, joka on jatkon kannalta erittäin keskeinen. Luvun lopussa esitetään vielä integraalien arvioimiseen tarvittavia lauseita. Viidennessä ja kuudennessa luvussa tarkastellaan erilaisia tapoja määrittää reaalisten integraalien arvoja. Seitsemännessä luvussa esitellään, miten sarjojen summien arvoja voidaan tietyissä tilanteissa määrittää residylaskennen avulla. Jokaista tapausta havainnollistetaan konkreettisilla esimerkeillä. Kahdeksannessa ja samalla viimeisessä luvussa tarkastellaan todennäköisyysteorian sovellusta. Aluksi esitellään niin sanotun karakteristisen funktion määritelmä, minkä jälkeen tämä johdetaan tietylle jakaumalle residylaskentaa käyttäen.
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(2023)Low-frequency $1/$ noise is ubiquitous, found in all electronic devices and other diverse areas such as as music, economics and biological systems. Despite valiant efforts, the source of $1/f$ noise remains one of the oldest unsolved mysteries in modern physics after nearly 100 years since its initial discovery in 1925. In metallic conductors resistance $1/f$ noise is commonly attributed to diffusion of mobile defects that alter the scattering cross section experienced by the charge carriers. Models based on two-level tunneling systems (TLTS) are typically employed. However, a model based on the dynamics of mobile defects forming temporary clusters would naturally offer long-term correlations required by $1/f$ noise via the nearly limitless number of configurations among a group of defects. Resistance $1/f$ noise due to such motion of mobile defects was studied via Monte Carlo simulations of a simple resistor network resembling an atomic lattice. The defects migrate through the lattice via thermally activated hopping motion, causing fluctuations in the resistance due to varying scattering cross section. The power spectral density (PSD) $S(f)$ of the simulated resistance noise was then calculated and first compared to $S(f)=C/f^\alpha$ noise, where $C$ is a constant and $\alpha$ is ideally close to unity. The value of $\alpha$ was estimated via a linear fit of the noise PSD on a log-log scale. The resistor network was simulated with varying values of temperature, system size and the concentration of defects. The noise produced by the simulations did not yield pure $1/f^\alpha$ noise, instead the lowest frequencies displayed a white noise tail, changing to $1/f^\alpha$ noise between $10^{-4}$ to $10^{-2}$~Hz. In this way the spectrum of the simulated noise resembles a Lorentzian. The value of $\alpha$ was found to be the most sensitive to temperature $T$, which directly affects the motion of the defects. At high $T$ the value of $\alpha$ was closer to 1, whereas at low $T$ it was closer to $1,5$. Varying the size of the system was found to have little impact on $\alpha$ when the temperature and concentration of defects were kept fixed. Increasing the number of defects was found to have slightly more effect on $\alpha$ when the temperature and system size were kept fixed. The value of $\alpha$ was closer to unity when the concentration of defects was higher, but the effect was not nearly as pronounced compared to varying the temperature. In addition, the simulated noise was compared to a PSD of the form $S(f)\propto e^{-\sqrt{N}/T}1/f$, where $N$ is the size of the system, according to recent theoretical proceedings. The $1/f^\alpha$ part of the simulated noise was found to roughly follow the above equation, but the results remain inconclusive. Although the simple toy model did not produce pure $1/f^\alpha$ noise, the dynamics of the mobile defects do seem to have an effect on the noise PSD, yielding noise closer to $1/f$ when there are more interactions between the defects due to either higher mobility or higher concentration of defects. However, this is disregarding the white noise tail. Recent experimental research on high quality graphene employing more rigorous kinetic Monte Carlo simulations have displayed more promising results. This indicates that the dynamics of temporary cluster formation of mobile defects is relevant to understand $1/f$ noise in metallic conductors, offering an objective for future work.
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(2023)Maatalouden ravinnekuormituksella on suuri vaikutus viljelysmaiden alapuolisten vesistöjen rehevöitymiseen ja veden laatuun. Kaksitasouomat on suunniteltu viljelysmaiden tulvavesien hallintaan, mutta ne myös vähentävät ravinteiden huuhtoutumista yläjuoksun valuma-alueilta, kun virran kuljettamat sedimentit kertyvät tulvatasanteille. Tulvatasanteet tarjoavat myös suotuisat olosuhteet liukoisen fosforin sorptiolle sekä saostumiselle. Sedimentin ja siihen liittyvää ravinteiden kertymistä tulvatasanteille seurattiin kolmelta toisistaan erottuvalta eteläsuomalaiselta kaksitasouomalta niiden keskinäisen dynamiikan tutkimiseen. Suomen ympäristökeskuksen Valumavesi projekti asensi 32 keräintä kaksitasouoman tulvatasanteille 2021 kesän ja syksyn aikana, jotka kerättiin vuoden 2022 kesällä ja niistä analysoitiin sedimenttikertymä, geokemiallinen koostumus, ravinnepitoisuudet sekä fosforin eri fraktiot. Sedimenttikertymä oli suurempaa viljellyillä kivennäismailla (2.5–6.4 kg m-2 a-1), kuin orgaanisilla viljelysmailla (0.2 kg m-2 a-1), mikä vaikutti merkittävästi tulvatasanteiden ravinnekertymään. Yhdellä tutkimusalueella tämä tarkoitti 3–4 % uoman kiintoaineksen määrästä (2.3–3.2 tonnin sedimenttikertymää) 250 m tulvatasanteelle 223 päivän aikana. Jos tulvatasanteen kasvillisuuden niitto olisi laajennettu koskemaan koko tulvatasannetta, olisi sedimentin pidätyskyky kasvanut 3.3–4.7 % uoman kiintoaineskuormasta. Sedimenttikertymän paikkakohtaiseen vaihteluun vaikuttivat pinnan topografia, tulvinnan laajuus, tulvimistiheys, uoman vakaus ja kasvillisuuden hoitomenetelmät. Tutkimusalueiden geokemiallisen koostumuksen vaihtelu selittyi enimmäkseen sedimenttien kivennäis- ja orgaanisen aineksen määrällä, joka juontui valuma-alueen maaperästä. Maaperästä riippumattomat mangaanipitoisuudet selittivät tutkimusalueiden paikallista horisontaalista vaihtelua sedimenttikeräin näytteissä ja vertikaalista vaihtelua aikaisempien tutkimuksien sedimenttiprofiileissa. Redox-herkän mangaanin ja fosforifraktioiden vaihtelu tapahtui usein samanaikaisesti, jota käytettiin fosforidynamiikan tutkimiseen. Rautasidonnainen fosfori oli merkittävin fosforifraktio viljellyillä mineraali ja orgaanisilla mailla. Kivennäismailla oli enemmän detritaalista apatiittia vähän rapautuneista Litorinanmeren aikaisista savikoista, kun taas orgaanisilla mailla oli enemmän fosforia kiinnittyneenä ei-redusoituviin metalleihin, jotka muodostuvat hapettomammissa olosuhteissa. Tulvatasanteille kertyneet sedimentit eivät olleet kyllästyneet fosforista, mutta se on mahdollista ravinnerikkaiden sedimenttien edelleen kertyessä, jolla voi olla vaikutusta kaksitasouoman kunnostusmenetelmiin tulevaisuudessa. Kaikki tutkitut kaksitasouomat pidättivät ravinnerikkaita sedimenttejä, jonka tulisi näkyä pienempänä ravinnekuormituksena alajuoksun vesistöissä.
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