Browsing by Title
Now showing items 901-920 of 4026
-
(Helsingin yliopistoUniversity of HelsinkiHelsingfors universitet, 2005)The urban development of Helsinki Region is characterized by both centralization and decentralization. Concern has recently been expressed in political debate regarding the effects of urban decentralization. Current housing policy has lead to a situation where single-family houses – which are also preferred by wealthy taxpayers – are mainly built in the surrounding municipalities. The growth on the periphery of the region is shaping the city toward a more decentralized, multi-nuclei form. Community structure is organized in region composed of functionally differentiated spaces that are no longer extensions of the traditional city. A functionally differentiated city is suggested to be a new form of urban morphology. These polynucleated areas are not dominated by any central city. Traditional core-periphery relations are replaced by periphery-periphery connections. It has been stated that this emergence of new postsuburban areas has also created a new postsuburban way of life. This research studies urban transformation processes at the periphery of the Helsinki Region. Transformation of urban space is studied through the locations where local residents work, go shopping, make social contacts and concentrate on their hobbies. The study areas are newly built single-family house neighbourhoods Sundsberg in Kirkkonummi and Landbo in Sipoo. The chosen areas are similar for their locational factors but different in their characteristics and thus ideal for a comparative study. The main information presented in this study was obtained from interviews completed in study areas. The data is analysed using quantifying qualitative analysis and presented as maps. Residents’ travel paths seem to follow postsuburban lifestyle patterns closely in both areas, which can be related to urban decentralization. According to this study, if postsuburban neighbourhoods described above become more common, citizens’ moving patterns will change accordingly. Policy on controlling urban decentralization will greatly affect the future of Helsinki Region.
-
(2023)Industrial ultrasonic cleaning plays a crucial role in optimizing processes and production in various industrial equipment by eliminating the need for harmful chemicals and minimizing production downtime. While previous research has focused on optimizing ultrasonic cleaning for larger and complex geometries, by controlling acoustic pressure fields and cavitation, the potential contribution of online cleaning using elastic vibrations of the equipment wall remains insufficiently explored. To bridge this gap, this study employs a combination of simulation techniques and laboratory experiments to investigate the significance of elastic guided waves and evaluate the influence of different pulsed driving waveform properties on cleaning efficacy. Specifically, the study focuses on the delivery of ultrasonic energy along the pipe wall. While confirming the effective delivery of ultrasonic energy across the length of pipes, the mechanisms underlying scale removal are still open to interpretation. Notably, specific flexural wave modes of a fluid-filled pipe, e.g. F_FFP (n,1) mode family, are identified as potential carriers of the cleaning effect. The research highlights the significance of high momentary power and total effective power in achieving efficient cleaning. The presence of liquid introduces complexities such as mode conversions and the possibility of cavitation. Further investigations are recommended to explore the individual roles of normal and tangential vibration components at the wall-scale interface. The study emphasizes the need for comprehensive analysis to optimize ultrasonic cleaning processes for larger and complex geometries, determine effective parameters for particle detachment, and enhance overall cleaning efficiency.
-
(2021)Bonus-malus systems are used globally to determine insurance premiums of motor liability policy-holders by observing past accident behavior. In these systems, policy-holders move between classes that represent different premiums. The number of accidents is used as an indicator of driving skills or risk. The aim of bonus-malus systems is to assign premiums that correspond to risks by increasing premiums of policy-holders that have reported accidents and awarding discounts to those who have not. Many types of bonus-malus systems are used and there is no consensus about what the optimal system looks like. Different tools can be utilized to measure the optimality, which is defined differently according to each tool. The purpose of this thesis is to examine one of these tools, elasticity. Elasticity aims to evaluate how well a given bonus-malus system achieves its goal of assigning premiums fairly according to the policy-holders’ risks by measuring the response of the premiums to changes in the number of accidents. Bonus-malus systems can be mathematically modeled using stochastic processes called Markov chains, and accident behavior can be modeled using Poisson distributions. These two concepts of probability theory and their properties are introduced and applied to bonus-malus systems in the beginning of this thesis. Two types of elasticities are then discussed. Asymptotic elasticity is defined using Markov chain properties, while transient elasticity is based on a concept called the discounted expectation of payments. It is shown how elasticity can be interpreted as a measure of optimality. We will observe that it is typically impossible to have an optimal bonus-malus system for all policy-holders when optimality is measured using elasticity. Some policy-holders will inevitably subsidize other policy-holders by paying premiums that are unfairly large. More specifically, it will be shown that, for bonus-malus systems with certain elasticity values, lower-risk policy-holders will subsidize the higher-risk ones. Lastly, a method is devised to calculate the elasticity of a given bonus-malus system using programming language R. This method is then used to find the elasticities of five Finnish bonus-malus systems in order to evaluate and compare them.
-
(2013)Microfinance has been introduced to poor people as a means for economic and social development. The movement has received significant support worldwide and as a result microfinance is considered an essential part of the current development discourse. Microfinance as a self help strategy depicts the microborrower as an active actor who helps oneself. Yet it is still unclear how and when microfinancing promotes development. Although microborrowers are considered responsible for 'climbing out of poverty' themselves, only little theoretical understanding of the perspective of the customer exists. Against this backgroud the purpose of this study is to research the attributions that microborrowers give to explain the success or failure of microlending. Additionally, this research examines the influence microborrowers have on the success of the microlending process, as seen through the given attributions. The research is based on fieldwork which was conducted in three rural villages in Cambodia. Thirty members of a local non-governmental organisation's Village Bank programme who had been granted a microloan were used as informants in this study. The aim of this research is to give voice to the borrowers themselves, thus the data was gathered by using the method of empathy based stories. The borrowers were asked to tell stories on the success or failure of microlending based on two short frame stories. The data was then analysed using qualitative content analysis that was guided by the attribution theory, which describes how individuals develop causal explanations for behaviours and outcomes. Attributions given to the success or failure of microlending were planning and effort, motivation, devotion, ability and features of personality, influence of other people or the lack of it, as well as chance, conditions and the model used in lending. Attributions found in the stories were distributed in dimensions of control, stability and controllability according to the attribution theory. Attributions given to success as well as failure of microlending were distributed evenly in the locus of control, but in the locus of stability, stable attributions were somewhat emphasised. Also, in the locus of controllability, uncontrollable attributions were told more often, especially in stories on the failure of microlending. The results of the research implicate that borrowers have limited possibilities to change the course of the microlending process. On the other hand, other actors than borrowers themselves can have an influence on many of the given attributions. The depiction of a borrower that helps oneself seems idealised and romanticized according to these results. In reality, the possibilities and limitations of ones' action always form in relation to the local institutional, social, cultural and historical context of microfinance. Also the various attributions given to the success and failure of microlending were seen through local context. Since local aspects define the possibilities of the microlending process, the question of wether microfinancing can perform to further development should always be examined and resolved locally.
-
(2018)In this thesis the transport properties of the superconducting quantum wires are discussed. At first the general introduction to quasi-one-dimensional mesoscopic systems is given. Due to the spatial confinement of transported particles in directions vertical to their motion, there are possibly many discrete transverse modes along the wire. The number of these modes depends on the width of the wire. According to the familiar Ohm's law, the conductance along the wire has linear dependence on the width of the wire. However, when the size of the system is sufficiently small, there exist quantum corrections to this behaviour. The leading order quantum corrections to the Ohm's law are the weak localization and universal conductance fluctuations. These quantum corrections can be determined by calculating the first two conductance cumulants along the wire. In addition, there emerges terms in these cumulants, which depend nonanalytically on the wire length. In this thesis we calculate all these terms by using the diffusion type equation, Dorokhov-Mello-Pereyra-Kumar (DMPK) equation. We calculate also the analytical components of the first 15 current cumulants through the system.
-
(2022)I discuss recent work regarding electronic structure calculations on quantum computers. I introduce quantum computing and electronic structure theory, and then discuss different mappings from electrons and excitation operators, to qubits and unitary operators, mainly Jordan–Wigner and Bravyi–Kitaev. I discuss adiabatic quantum computing in connection to state preparation on quantum computers. I introduce the most important algorithms in the field, namely, quantum phase estimation (QPE) and variational quantum eigensolver (VQE). I also mention recent modifications and improvements to these algorithms. Then I take a detour to discuss noise and quantum operations, a model for understanding how quantum computations fail because of noise from the environment. Because of this noise, quantum simulators have risen as a tool for understanding quantum computers and I have used such simulators to do electronic structure calculations on small atoms. The algorithm I have used, QPE, yields the exact result within the employed basis. As a basis I use numerical orbitals, which are very robust due to their flexibility.
-
(2017)Denna avhandling behandlar elektrokinetisk kapillärkromatografi (EKC) och omfattar en litteraturöversikt och en experimentell studie. Litteraturöversikten består av en inledande teoretisk genomgång av principerna för EKC. Den följs av en presentation av litteraturen rörande tillämpning av EKC vid analys av lokalbedövningsmedel. Micellär elektrokinetisk kapillärkromatografi (MEKC) är den äldsta versionen av EKC och hittills den mest använda för separation av lokalbedövningsmedel. Under de senaste åren har dock speciellt användningen av vesiklar och lipiddispersioner samt mikroemulsioner som pseudostationär fas ökat. I den experimentella delen av arbetet användes liposom elektrokinetisk kapillärkromatografi (LEKC) för att studera växelverkningar mellan bioimiterande membraner och sex lokalbedövningsmedel och ett typiskt konserveringsmedel. De bioimiterande membranerna bestod av liposomer uppbyggda av 1-palmitoyl-2-oleyl-sn-glycero-3-fosfatidylkolin (POPC) och 1-palmitoyl-2-oleyl-sn-glycero-3-[fosfo-rac-(1-glycerol)] (POPG), med eller utan kolesterol. Retentionsfaktorer och fördelningskonstanter bestämdes för samtliga analyter. Liposomernas mobilitet, vilken behövs för beräkning av analyternas retentionsfaktorer, bestämdes genom en iterativ procedur som innebar bestämning av retentionsfaktorer för en homologisk serie alkylbenzoater. Analyternas fördelning i liposomer jämfördes med litteraturvärden för fördelningen i oktanol/vatten-system. Temperaturens inverkan på växelverkningarna undersöktes genom att utföra separationer vid 25°C, 37°C och 42°C. Studierna visade att analyternas fördelning i liposomerna minskar då kolesterol tillsätts till liposomerna. Temperaturförändringen hade en smärre, osystematisk inverkan på växelverkningarna. Korrelationen mellan de experimentellt bestämda fördelningskonstanterna i liposom/vatten-system och litteraturvärden för fördelningen i oktanol/vatten-system är relativt svag.
-
(2018)Purpose of the work is to give an elementary introduction to the Finite Element Method. We give an abstract mathematical formalization to the Finite Element Problem and work out how the method is a suitable method in approximating solutions of Partial Differential Equations. In Chapter 1 we give a concrete example code of Finite Element Method implementation with Matlab of a relatively simple problem. In Chapter 2 we give an abstract formulation to the problem. We introduce the necessary concepts in Functional Analysis. When Finite Element Method is interpreted in a suitable fashion, we can apply results of Functional Analysis in order to examine the properties of the solutions. We introduce the two equivalent formulations of weak formulation to differential equations: Galerkin’s formulation and minimizing problem. In addition we define necessary concepts regarding to certain function spaces. For example we define one crucial complete inner product space, namely Sobolev space. In Chapter 3 we define the building blocks of the element space: meshing and the elements. Elements consists of their geometric shape and of basis functions and functionals on the basis functions. We also introduce the concepts of interpolation and construct basis functions in one, two and three dimensions. In Chapter 4 we introduce implementation techniques in a rather broad sense. We introduce the crucial concepts of stiffness matrix and load vector. We introduce a procedure for implementing Poisson’s equation and Helmholt’z equation. We introduce one way of doing numerical integration by Gaussian quadrature points- and weights. We define the reference element and mathematical concepts relating to it. Reference element and Gaussian quadrature points are widely used techniques when implementing Finite Element Method with computer. In Chapter 5 we give a rigid analysis of convergence properties of Finite Element Method solution. We show that an arbitrary function in Sobolev space can be approximated arbitarily close by a certain polynomial, namely Sobolev polynomial. The accuracy of the approximation depends on the size of the mesh and degree of the polynomial. Polynomial approximation theory in Sobolev spaces have a connection to Finite Element Methods approximation properties through Cèa’s lemma. In Chapter 6 we give some examples of posteriori convergence properties. We compare Finite Element Method solution acquired with computer to the exact solution. Interesting convergence properties are found using linear- and cubic basis functions. Results seem to verify the properties acquired in Chapter 5.
-
(2019)Tiivistelmä/Referat – Abstract African Savanna elephant (Loxodonta africana) is the largest terrestrial mammal. Due to its size, elephants consume large amount of food and water each day and thus modify the environment around them greatly. At the same time, they create living areas for other species. On the other hand, too large number of elephants in confined areas will eventually lead into the destruction of the environment. Humans and elephants have also a twofold relationship: elephants attract tourist but at the same time they can destroy crops, property or even kill humans. The African elephant is thought to be a vulnerable specie that is in risk on becoming endangered in the near future due to the changing environment and the pressure from growing human populations. The population size has been long decreasing and for conservational work to be effective, knowledge about the suitable environments and the needs of the specie is needed. Species distribution modelling (SDM) uses computer algorithms to combine the environmental variables and species occurrence data. SDM can be used for example to predict suitable habitats for species and the method is regularly used in conservational work and is an important part of it. The aim of this study is to increase the knowledge of elephant distribution patterns in Taita Taveta County in Kenya. In contrary to the overall trend of the elephant numbers, the population in Taita Taveta County has been growing. The changes in the population have been monitored from the 60’s and data from three different years, 2005, 2008 and 2011, have been used in this study. The study was divided in to three questions: (1) How elephants are distributed in the area in different years, (2) What environmental variables correlate with elephants in different years, and (3) Can the distribution of the elephants in the area be predicted? Different spatial analyzes and visual comparison was used to study the distribution of elephants in the county. Spearman Rho Rank correlation analyses was used to study the correlation of environmental variables and elephants and predicting of the elephant distribution was done using species distribution modelling method MaxEnt. The results show that the elephant distribution changes each year, but certain key areas can be found in each year that elephants favor. The meaningful environmental variables change each year and between the protected areas in the county and the areas that are not protected. In protected areas the meaning of water sources is highlighted and in the other areas the meaning of human activities grows in importance. The variables used for this study did not create well performing predictions, and thus it would not be advisable to use them for predictions. Presumably, the environmental variables used are not enough to explain the distribution of elephants. Elephants can live in many different habitats and they move around a lot, which also further decrease the performance of the predictions
-
(2022)Ohjelmistotuotannon ammattilaiset tarvitsevat monenlaisia kompetensseja. Yksi näistä kompetensseista on kyky elinikäiseen oppimiseen, joka on tarpeellinen laajalla ja jatkuvasti muutoksessa olevalla alalla. ICT-aloille muodostuneen osaajatarpeen myötä elinikäisen oppimisen rooli onkin alkanut korostumaan entisestään. Tutkielman tarkoituksena on ollut lisätä ymmärrystä elinikäisen oppimisen roolista ohjelmistotuotannon ammattilaisen näkökulmasta. Tutkielmassa on pyritty tunnistamaan, mitä oppimisen muotoja hyödynnetään sekä millaisiin tarkoituksiin niitä käytetään, mitkä elinikäisen oppimisen kompetenssin osatekijät ovat tärkeitä sekä mitä haasteita elinikäiseen oppimiseen liittyy. Tutkimuksen aineisto on kerätty puolistrukturoiduilla haastatteluilla ohjelmistotuotannon ammattilaisten kanssa. Näiden haastattelujen tuloksia on verrattu tutkielmaa varten suoritetun kirjallisuuskatsauksen tuloksiin. Oppimisen muodoista informaalia oppimista hyödynnetään eniten ja erityisesti pienempiin oppimistarpeisiin. Nonformaalia ja formaalia oppimista taas hyödynnetään isompiin tarpeisiin, mutta harvemmin. Motivaatio, tiedonhaku ja metaoppiminen korostuvat keskeisinä elinikäisen oppimisen kompetenssin osatekijöinä. Ajanpuute ja itsensä motivoiminen mielletään yleisimmiksi haasteiksi elinikäistä oppimista koskien. Myös tiedonlähteisiin liittyvät puutteet sekä puutteellinen ymmärrys metaoppimisesta mielletään vaikeuttavan elinikäistä oppimista. Tutkielman havainnot tukevat elinikäisen oppimisen kompetenssin keskeistä roolia ohjelmistotuotannon ammattilaisilla. Kehitettävää löytyy kuitenkin vielä ohjelmistotuotannon ammattilaisten valmiuksista elinikäiseen oppimiseen, esimerkiksi metaoppimista koskien. Havainnot perustuvat kuitenkin lyhyemmän aikaa ohjelmistotuotannon ammattilaisina työskennelleiden kokemuksiin, joten lisää tutkimusta tarvitaan etenkin pitempään työskennelleiltä ohjelmistotuotannon ammattilaisilta.
-
(2014)New transportation links tend to have a major impact on the location decisions of businesses. Although the decision-making process of the location of businesses is too complex to fully open up with a theoretical framework, accessibility in all of its different forms seems to be one of the key factors for all industries. Globalization and the development of ICT were believed to diminish the importance physical location for businesses. However, the impact has been the opposite. In the new urban form, it is possible to find relational economic spaces, which do not depend on borders or predefined areas. Still the predefined area remains a key factor in the coordination and identification of the business. With Kehärata, a commuter railway link set to open in 2015, a new horizontal transportation rail-link and several highly accessible locations will emerge in Vantaa and in the Helsinki region. The purpose of this thesis was to research how Kehärata will affect the locations of workplaces and businesses in Vantaa. The research methods were thematic interviews and GIS analyses. 10 thematic interviews were conducted with real estate investors, businesspeople, construction company representatives and local politicians. The GIS analysis showed that already in the current state, the workplaces in Vantaa form various regional patters in different industries. During the last decades, the workplaces in the Helsinki Metropolitan Region have moved strongly towards a polycentric form and so-called Metapolis structure. This kind of urban form has also been in the core of the new paradigm of urban geography research. The thematic interviews showed that Kehärata is a welcomed improvement to the horizontal transportation network in Vantaa and in the whole region. The urban form in Vantaa is already now polycentric, but Kehärata will increase the number of sub-centers even further with areas like Vehkala, Leinelä and Kivistö, which are highly dependent on the railway. From the point of view of firms, all stations cannot be equally appealing. In this situation the new polycentric urban form should be seen as a resource, where the locations with highest accessibility are developed within the city. However these locations should not be homogenous, but rather be differentiated through branding and urban planning. Differentiated areas within the city enable high level of specialization and make it possible for firms to gain agglomeration benefits. For instance the development and future prospects of Aviapolis area was highlighted in the interviews as very positive. According to the GIS analysis, the amount of workplaces accessible by train in Vantaa, will increase approximately by half after the railway is operational (From one third, to almost half of all workplaces in Vantaa). Additionally new railway connections have the tendency to concentrate workplaces near the stations, so the workplace accessibility by rail is probably even higher in the future. However car transport has had a major impact on the current urban form of Vantaa. The accessibility by car and by train are very different in nature and with Kehärata, two overlapping transportation networks are formed to the city. Despite of the negative environmental impacts of private cars, the city has to be still strongly planned also form the point of view of car owners. Interviewees were hoping that the new station areas would be built as compact urban environments, but contradictory they also saw that good logistical accessibility (with trucks) was one of the key benefits of the current economic environment in Vantaa and it should be supported also in the future. The somewhat poor imago of Vantaa was not seen as an obstacle when firms located to Vantaa, but it was seen as a problem when attracting new residents to the city. In the post-industrial society, the importance of employees to firm location is higher than ever and through tax income it is also a key factor in the public finance of cities.
-
(2014)Tämä pro gradu -työ käsittelee toisen asteen elliptisiä osittaisdifferentiaaliyhtälöitä sekä näiden ominaisarvo-ongelmia. Työssä määrittelemme aluksi Sobolev-avaruudet, joissa osittaisdifferentiaaliyhtälöiden ratkaisuja on luonnollista tutkia. Käymme läpi Sobolev-avaruuksien perusominaisuuksia ja todistamme muun muassa, että Sobolev-avaruus W^{k,p} on Banach-avaruus. Luvun 2 lopuksi esitellään kompaktit upotukset ja kompaktit operaattorit sekä näihin liittyviä tunnettuja lauseita ja tuloksia, joista tärkeimmät ovat Rellich-Kondrachovin upotuslause sekä Fredholmin alternatiivi. Luvussa 3 tarkastellaan elliptisiä osittaisdifferentiaaliyhtälöitä yleisesti. Määrittelemme yhtälön heikot ratkaisut ja todistamme heikon ja vahvan maksimiperiaatteen elliptiselle osittaisdifferentiaaliyhtälölle. Tämän jälkeen tutkimme, millaisilla ehdoilla yhtälöllä on olemassa ratkaisuja ja milloin ratkaisu on yksikäsitteinen. Yksikäsitteisyystodistuksissa hyödynnetään Lax-Milgramin teoriaa. Todistettuamme ratkaisujen olemassaoloa käsittelevän Lauseen 3.50 saamme syyn tutkia differentiaalioperaattorin spektriä, ominaisarvoja sekä ominaisfunktioita. Työn tärkeimmät tulokset ovat Luvussa 4, jossa todistetaan sekä symmetrisen että ei-symmetrisen operaattorin ominaisarvoja sekä ominaisfunktioita koskevia tuloksia.
-
(2014)Elliptisillä osittaisdifferentiaaliyhtälöillä on tärkeä rooli eri ilmiöiden mallinnuksessa. Klassisesti ajatellen ilmiötä mallintavan differentiaaliyhtälön ratkaisun on vaadittu olevan klassisesti derivoituva. Tästä vaatimuksesta voidaan kuitenkin luopua. Ratkaisun kasite yleistetään Lp-avaruuksien, tarkemmin Sobolev-avaruuksien, teorioiden avulla. Yleistetylle ratkaisulle käytetään nimitystä heikko ratkaisu. Luvussa 1 käsitellään Sobolev-avaruudet, jotka tarjoavat pohjan heikkojen ratkaisujen käsitteelle. Painopiste Sobolev-avaruuksien teoriassa on upotuslauseissa, joilla osoitetaan elliptisen osittaisdifferentiaaliyhtälön määrittävän operaattorin spektri diskreetiksi. Lisäksi upotuslauseita voi käyttää osoittamaan heikon ratkaisun klassinen derivoituvuus tietyissä tapauksissa. Luvussa 2 esitellään miten elliptiset osittaisdifferentiaaliyhtälöiden ratkaisun käsite saadaan yleistettyä. Sen jälkeen osoitetaan Hilbert-avaruuksien teorian avulla, että heikkoja ratkaisuja on olemassa. Lopuksi tutkitaan heikkojen ratkaisujen säännöllisyyttä ja klassista derivoituvuutta riippuen annetun osttaisdifferentiaaliyhtälöprobleeman alkuasetelmista.
-
(2016)Kryptografia, eli tiedon salaus, on nopeasti kehittyvä ala, joka on läsnä ihmisten päivittäisessä toiminnassa. Perinteisen tiedon salauksen lisäksi kryptografian avulla voidaan toteuttaa monipuolisia toiminnallisuuksia, kuten digitaaliset allekirjoitukset ja avaimenvaihto. Nämä toiminnallisuudet on mahdollista toteuttaa julkisen avaimen kryptografian avulla. Elliptiset käyrät ovat kuutiollisia tasokäyriä, joiden pisteiden välille voidaan määritellä yhteenlaskuoperaatio. Näin ollen elliptisen käyrän pisteet muodostavat Abelin ryhmän, joten niitä on mahdollista käyttää diskreetin logaritmin ongelmaan perustuvissa kryptosysteemeissä, eli julkisen avaimen kryptosysteemeissä. Elliptisten käyrien kryptografisten algoritmien suojaustaso perustuu elliptisen käyrän diskreetin logaritmin ongelmaan, jonka yleiselle muodolle ei olla löydetty subeksponentiaalista ratkaisua. Näin ollen elliptisten käyrien kryptografialla on mahdollista saavuttaa vastaava suojaustaso lyhyemmillä avaimilla, verrattuna muihin julkisen avaimen kryptografian metodeihin. Tutkielman ensimmäisessä osassa perehdytään elliptisten käyrien teoriaan keskittyen tärkeimpiin teemoihin kryptografian kannalta. Luvussa esitetään yhteenlasku elliptisen käyrän pisteille ja johdetaan ryhmälait. Erityisesti käsitellään kryptografiassa käytettäviä äärellisissä kunnissa määriteltyjä elliptisiä käyriä, joita on kaksi yleisintä luokkaa: alkulukukunnissa ja binäärikunnissa määritellyt käyrät. Tutkielman toisen osan keskiössä on kryptografia; julkisen avaimen kryptografia ja erityisesti elliptisen käyrän kryptografia ovat keskiössä. Luvussa tarkastellaan elliptisen käyrän diskreetin logaritmin ongelmaa ja elliptisen käyrän rakenteeseen liittyviä tuloksia. Tutkielman lopussa esitetään algoritmit kullekin julkisen avaimen kryptografian avulla toteutettavalle toiminnallisuudelle käyttäen elliptisten käyrien kryptografian algoritmeja. Avaimenvaihdosta käytetään esimerkkinä elliptisen käyrän Diffie-Hellman avaimenvaihtoa ja digitaalisesta allekirjoituksesta elliptisen käyrän digitaalista allekirjoitusalgoritmia. Salaus ja purku menetelmänä esitellään elliptisen käyrän integroitu salaus -skeema.
-
(2013)Tutkielmassa tarkastellaan kompakteilla ja reunattomilla monistoilla määriteltyjä elliptisiä osittaisdifferentiaalioperaattoreita käyttäen hyväksi pseudodifferentiaalioperaattoreiden teoriaa. Tutkielman ensimmäisissä luvuissa määritellään tarvittavat pseudodifferentiaalioperaattoriluokat sekä esitetään joitakin osia näiden operaattoriluokkien teoriasta. Kahdessa viimeisessä luvussa määritellään elliptisten osittaisdifferentiaalioperaattoreiden kompleksiarvoiset potenssit ja tutkitaan näiden ominaisuuksia ensimmaisissä luvuissa esitetyn teorian valossa. Tärkeimpiä tavoitteita ovat operaattoriluokkien ja itseadjungoidussa tapauksessa myös spektraaliasymptotiikan selvittäminen.
-
(2019)The Tana fishing agreement was revised for the fishing season of 2017 amidst strong local opposition. The agreement deteriorates the survival prospects of the indigenous Sami culture. The aim of this study was to find out in what ways the legitimacy of the agreement was constructed and contested in the consultation process prior to the passing of the agreement. The results are examined in a broader temporal and geographical context of postcolonial power relations based on earlier research on the social construction of environmental conflicts, political participation of indigenous peoples, and environmental justice. Through a critical discourse analysis of written documents produced during the consultation process in May to October 2016, I identified five different discourses used by representatives of the state, the Sami, and other stakeholders. The passing of the agreement despite negative effects on the Sami was constructed as legitimate by making it appear as the only way to protect the salmon population, taking a short temporal perspective, depicting Tana as an abstract space devoid of culture, accepting existing power relations as given and presenting the Sami cultural rights as secondary to other concerns. The legitimacy was contested by emphasizing the historical legacy of colonial practices against the Sami culture, questioning the motives behind the agreement, proposing alternative ways to protect the salmon population, challenging the state to act according to its own rules and commitments and depicting Tana as a personal place full of cultural meaning. The discourses differ in what is considered as adequate or sufficient for the survival of the Sami culture and the realization of their indigenous rights in terms of cultural practice, participation, the knowledge base on which decisions are made, and owning up to the injustices committed in the past. The discourses used by representatives of the state bear a resemblance to the discriminatory politics of the last century and the othering of indigenous peoples elsewhere. The discursive context of the consultation process makes certain discourses appear more valid than others, which influences the choices of the Sami on how to phrase their opposition and concerns. In discourses used by many other stakeholders the cultural existence of the Sami is bypassed or ignored.
-
(2021)Cloud vendors have many data centers around the world and offer in each data center possibilities to rent computational capacities with different prices depending on the needed power and time. Most vendors offer flexible pricing, where prices can change hourly, for instance, Amazon Web Services. According to those vendors, price changes depend highly on the current workload. The more workload, the pricier it is. In detail, this paper is about the offered spot services. To get the most potential out of this flexible pricing, we build a framework with the name ELMIT, which stands for Elastic Migration Tool. ELMIT’s job is to perform price forecasting and eventually perform migrations to cheaper data centers. In the end, we monitored seven spot instances with ELMIT’s help. For three instances no migration was needed, because no other data center was ever cheaper. However, for the other four instances ELMIT performed 38 automatic migrations within around 42 days. Around 160$ were saved. In detail, three out of four instances reduced costs by 14.35%, 4.73% and 39.6%. The fourth performed unnecessary migrations and cost at the end more money due to slight inaccuracies in the predictions. In total, around 50 cents more. Overall, the outcome of ELMIT’s monitoring job is promising. It gives reason to keep developing and improving ELMIT, to increase the outcome even more.
-
(2014)Originally email was designed for messaging channel between individuals. However, it is now being used as personal file archiving. The growth of email quantity over time makes searching email hard and time-consuming. It even becomes extremely frustrating for people who have huge amount of emails. Firstly, when searching an email, people often look for a piece of information which is temporarily forgotten. If we can remind of them some related information, searching activity will become faster and easier. Secondly, since memory of information is temporarily lost, it is hard for people to define keyword to type in search box. If people misspell the word, search result will return no hits at all. In order to solve those issues, we provide an interface that support people seeking email more interactively. The interface is the combination of studies from email visualization and keyword extraction technique. Email visualization is the process of visually display email attributes such as sender, recipient, date, and content on the interface. Keyword extraction is a technique of extracting words directly from email body. Extracted keyword can describe related topical word which is meaningful and can be easily understood by users. Main objective of the interface is helping people to reinstate their memory of email information while visually interacting with different email attributes.
-
(Helsingin yliopistoUniversity of HelsinkiHelsingfors universitet, 2004)
-
(2019)Emergence of language grounded in perception has been studied in computational agent societies with language games. In this thesis language games are used to investigate methods for grounding language in practicality. This means that the emergence of the language is based on the needs of the agents. The needs of an agent arise from its goals and environment, which together dictate what the agents should communicate to each other. The methods for practicality grounding are implemented in a simulation, where agents fetch items from shelves in a 2D grid warehouse. The agents learn a simple language consisting of words for spatial categories of xy-coordinates and different types of places in the warehouse environment. The language is learned and used through two novel language games called the Place Game and the Query Game. In these games the agents use the spatial categories and place types to refer to different locations in the warehouse, exchanging important information that can be used to make better decisions. The empirical simulation results show that the agents can utilise their language to be more efficient in fetching items. In other words the emerged language is practical.
Now showing items 901-920 of 4026