Browsing by Title
Now showing items 709-728 of 4247
-
(2016)Helium has two stable isotopes: more common 4He with four nucleons, and the very rare 3He with three nucleons. At sufficiently low temperature, helium can become superfluid that has no viscosity. This transition is quantum mechanical in nature, and since bosonic 4He and fermionic 3He follow different quantum statistics, there is a significant difference in the transition temperature between them. It is about 2 K for pure 4He, but for pure 3He it is three orders of magnitude lower, around 1 mK. 3He – 4He mixtures also have several interesting properties at very low temperatures, such as the finite solubility of 3He in 4He even at absolute zero limit. However, at kelvin range, where our experiment took place, the notable feature is the shifting of the supefluid transition temperature of 4He to a lower temperature due to addition of 3He. Bulk superfluid helium can support two different sound modes: first sound is ordinary pressure (or density) wave, whereas second sound is a temperature (or entropy) wave, unique to superfluid systems. In inviscid superfluid systems, temperature fluctuations can propagate as second sound wave, but in normal systems, on the other hand, this is not possible, as all temperature fluctuations are strongly damped. First sound and second sound do not usually exist independent of each other, rather pressure variations are accompanied by variations in temperature, and vice versa. In this thesis, we studied experimentally the coupling between first and second sound in dilute 3He - superfluid 4He mixtures, at saturated vapor pressure, at temperatures between 2.2 K and 1.7 K, and at 3He concentrations ranging from 0 % to 11%, using a quartz tuning fork mechanical oscillator. Second sound that is coupled to first sound can create anomalies in the resonance response of the quartz tuning fork, so-called second sound resonances. We learned that there exists a temperature and concentration region, where these anomalies disappear, which would indicate two sound modes decoupling from each other. We also present a hydrodynamical model that correctly predicts the decoupling behavior.
-
(2023)Power ultrasound increases production efficiency in the industry, and therefore reduces emissions. This advantage arises from the ability of ultrasound to mitigate fouling. Ultrasound solution requires clamping the transducers onto the external wall of the production equipment, typically made of steel. A challenge then arises, since mechanical loading by the wall hampers the natural resonating of the ultrasonic transducer and therefore reduces power transmission. To overcome this limitation, airgap contact coupling (ACC) is proposed. ACC features an airgap to reduce the mechanical loading and two protruding elements for mechanical contacting and sound delivery. Finite-element method (FEM) simulations are employed to evaluate the physical mechanisms behind ACC. For the comparison, direct traditional contact coupling (TCC) is evaluated. To assess the acoustic power delivery by ACC and TCC, calorimetric measurements were used. A water-filled stainless-steel pipe with a 2 mm thick wall and 136 mm outer diameter was sonicated. To prevent heat transmission to ambient air, it was covered by isolating foam. ACC and TCC were sonicated at their coupled resonance frequencies, respectively at 19.2 kHz and 28.1 kHz. A power delivery ratio was determined by the calorimetric power against the sonication power. ACC resulted in a power delivery ratio of 27.4±6.3 % whereas that for TCC was 6.1±0.6 %. ACC was thereby shown to transmit 6 dB more acoustic power than TCC. In conclusion, a novel contact coupling method is proposed for industrial metal-walled equipment. The proposed new approach enhances the utility of power ultrasound for online cleaning and prevention.
-
(2016)In computer science, introductory programming course is one of the very first courses taken. It sets the base for more advanced courses as programming ability is usually assumed there. Finding the students that are likely to fail the course allows early intervention and more focused help for them. This can potentially lower the risk of dropping out in later studies, because of the lack of fundamental skills. One measure for programming ability is the outcome of a course and the prediction of these outcomes is the focus also in this thesis. In educational context, differences between courses set huge challenges for traditional machine learning methods as they assume identical distribution in all data. Data collected from different courses can have very different distributions as there are many factors that can change even between consecutive courses such as grading, contents, and platform. To address this challenge transfer learning methods can be used to as they make no such assumption about the distribution. In this thesis, one specific transfer learning algorithm, TrAdaBoost, is evaluated against selection of traditional machine learning algorithms. Methods are evaluated using real-life data from two different introductory programming courses, where contents, participants and grading differ. Main focus is to see how these methods perform in the first weeks of the course that are educationally the most critical moments.
-
(2014)Coxeterin ryhmät ovat ryhmiä, joille voidaan antaa esitys G=<s_1, ... s_d: s2_i=1, (s_i s_j)^m_{ij}=1> missä m_{ij}ЄZ. Tämän pro gradun tehtävänä on näyttää, että kyseisen rajoitetun esityksen ryhmiä on rajallinen määrä sekä esittää niiden luokittelu. Luokitteluun tarvittavia työkaluja ovat Coxeterin graafit ja matriisit. Pro gradussa muistutetaan tarpeellisista lineaarialgebran määritelmistä sekä annetaan taustatietoa positiividefiniitti ja positiivisemidefiniitti matriiseista. Lisäksi käydään läpi ryhmäteorian taustoja ja erityisesti ryhmien esittämistä generaattoreiden ja relaatioiden avulla. Taustatietojen jälkeen määritellään Coxeterin graafit muutamien esimerkkien kera ja selitetään miten matriisi voidaan johtaa Coxeterin graafin esityksestä. Työssä näytetään, että kaikki listatut Coxeterin graafit ovat joko positiividefiniittejä tai positiivisemidefiniittejä sekä todistetaan, että ne ovat ainoat positiividefiniitti ja -semidefiniitti graafit. Luokittelu loppuu siihen. Lopuksi pro gradussa annetaan yleisempi kuvaus rajallisten heijastusten ryhmistä (finite reflection groups).
-
(2015)Crime in cities and the safety of urban environment has created broad debate and interest. Fear of crime and perceptions of safety can be affected by many socio-demographic, socio-psychological and environmental factors, such as age, sex, media stories or different characteristics of the built environment. Fear of crime and insecurity in urban environments can restrict the use of public spaces and influence the quality of life. Crime and fear of crime are distributed unevenly in the environment and previous research has identified some concentrations of fear and crime. Crime and fear of crime are related to the urban environment in many ways. There has been a growing interest towards different kinds of strategies and security plans, which might improve the safety of cities. Crime Prevention through Environmental design (CPTED) is one example of planning methods aimed at preventing crime and fear of crime. CPTED model seeks to provide safer urban environments. CPTED approach has been influenced especially by the works of Jane Jacobs and Oscar Newman, who drew attention to the relationship between crime and urban planning. The main principles of CPTED are territoriality, surveillance, maintenance/image, access control, activity support and target hardening. CPTED strategies have been a part of urban planning since the 1970s and CPTED principles have been widely used in North America, England and Australia. In recent years there has also been wider interest in Europe towards the relationship between crime prevention and planning. In Finland CPTED model has been used only in a couple of places so far. This research has focused on the role of the built environment from the factors that are related to the safety of neighbourhoods. The aim of this study was to examine how does the 'feared places' in the neighbourhood of Leppävaara in Espoo look like from the CPTED perspective. The 'feared places' were identified by the use of a previous study called 'safety walks in Leppävaara' and supported by data from the police. The research data was collected through observations. A 'CPTED checklist' was used as an evaluation form which was based on previous CPTED safety audit checklists. CPTED observations revealed that there are many CPTED elements present in the 'feared places' of Leppävaara. However, the quantity and quality of these elements varied between the places. CPTED analysis clearly showed how the different elements of CPTED are connected to each other and partly overlap. The biggest problems concerning territoriality where related to poor signage and the separation of certain functions. The possibilities of surveillance seemed to be closely related to the activities and land uses in the areas. The overall level of maintenance and image was good, and the biggest problems were general litter and graffiti. The means of access control and target hardening were mostly natural/informal and moderate. The built environment is by no means the only and most important factor which influences the safety of urban environments and crime. However, the evaluation of the environment by the use of CPTED model could make it possible to identify places which have safety or crime related problems. The use of CPTED or other similar design concepts as a part of urban planning and development may increase the feeling of safety and help prevent crime.
-
(2015)Electrical breakdowns occasionally occur near the first walls of fusion reactor chambers and the accelerating cavities of linear colliders, such as CLIC. These arcing events are localised plasma discharges, which are formed under high voltage electrical fields. Vacuum arcs cause various surface damage on the fusion reactor and linear accelerator structures. The surface damage, most significantly craters, have been studied experimentally, but the mechanism of the formation of this damage is still not clear. In this thesis we use the large-scale molecular dynamics simulations to study crater formation on Cu surface. We used ion irradiation to model the arcing events, where plasma ions are accelerated via the shield potential towards the metal surface. This ion irradiation causes multiple overlapping cascades in Cu surface, what can lead to the crater formation. The main goal was to be able to produce surface damage, which is identical to experimental results. Our results are divided to three categories. First we examined which are initial conditions needed to form experimental like craters. The electric field emission current accompanying the plasma discharge process, most likely, is to heat the sample locally to very high temperatures. Therefore we tested molten and solid structures at different temperatures, as well as different scenarios of cooling of the sample via electronic heat conduction. Second, we examined how different variables, such as the fluence of the ions, the energy flux or the potential model, affect on the crater shape. These results were compared with the experimental crater profiles in order to find out reasonable values. We also analysed how the volume of the produced crater depends on fluence. Our third part of investigation was not actually concentrated on the surface damage, but on dislocations and other damage under the surface. We again studied how different parameters affect on the results. We compared the simulations by calculating the number and ratio of non-FCC atoms in the bulk. The fluence dependency of the defects was studied as well.
-
(2020)Computer programs are common in our daily environment and new robotic devices emerge constantly. One of the key skills for the future is understanding the general purpose as well as intricate details of both concepts. Programs written in conventional programming languages are purely text with syntax cryptic to an unexperienced observer and errors can easily be made in the writing process, which is far from ideal basis to introduce programming or robotics to children on elementary school level. We set to investigate how a visual learning environment could reduce this chasm between the skills of the young and the perceived difficulty of computer technology and with what assortment of technologies and working methods such platforms, both programming and robotic, could be produced in a project with multiple parties. A joint endeavor was started between two research groups in different universities and the education services of a municipality in Finland. In the project, a visual programming environment was created where the users can assemble programs by stacking and manipulating colorful blocks to form a command flow. The set of functions are traditional with calculations, variables and loops, but also include commands to pilot a robotic platform with wheels, arms and a facial expression indicating display. This robot is a product of the project also, based on a commercial design. The venture can be concluded a success. The learning environment and the roving robot were created in the course of the project and architectural design and selected technologies proved sensible. The empirical exploration accumulated knowledge for academic research.
-
(2020)This thesis examines designing and implementing adaptive visual cues for a social virtual reality meditation environment. The system described here adapts into user’s bio- and neurofeedback and uses that data in visual cues to convey information of physiological and affective states during meditation exercises supporting two simultaneous users. The thesis shows the development process of different kinds of visual cues and attempts to pinpoint best practices, design principles and pitfalls regarding the visual cue development in this context. Also examined are the questions regarding criteria for selecting correct visual cues and how to convey information of biophysical synchronization between users. The visual cues examined here are created especially for a virtual reality environment which differs as a platform from traditional two dimensional content such as user interfaces on a computer display. Points of interests are how to embody the visual cues into the virtual reality environment so that the user experience remains immersive and the visual cues convey information correctly and in an intuitive manner.
-
(2023)The study of forest fragmentation, the break-up of forests into smaller patches, has become increasingly important due to increases in human-induced deforestation. Currently, approximately 12 million ha of forest are lost per year and 32% of this loss is tropical. There is substantial evidence showing that edge effects can alter the structure and functioning of remaining tropical forests, even hundreds of meters from the forest edge. However, implementing empirical experiments to understand the effects of fragmentation on forest structural metrics is logistically and scientifically challenging and limited to smaller areas. The use of forest models may help overcome these limitations, as they are able to quickly reproduce long-term ecological processes, as well as simulate a broad range of boundary forcings, such as biogeographical variability. This study evaluates the capability of a state-of-the-art forest dynamic model in reproducing the three-dimensional vertical distribution of plants in Amazonian forests affected by fragmentation. To achieve this, we optimized parameters driving plant demography and mortality, as well as their response to edge effects. FORMIND is an individual and process-based gap model suited for species rich vegetation communities, with the option of a fragmentation module. We modified processes and parameters in FORMIND to mimic the dynamics observed in a long-term (40 years-old) forest fragmentation experiment in the Brazilian Amazon. Forest structural metrics extracted from the FORMIND model output were compared with those obtained from terrestrial laser scans of the Amazonian Forest fragments. The resulting simulations demonstrated that, after 40 years of edge effects, the model in its original state was not capable of reproducing comparable results to those observed using the terrestrial LiDAR system. However, the addition of a new parameter capable of adjusting tree mortality at varying edge distances and inclusion of understory vegetation, drastically improved the model’s ability to replicate the three-dimensional distribution of plant material in the forest fragments. Total Plant Area Index (PAI), and PAI at varying height intervals (PAI 0-10m, PAI 10-20m, PAI 20-30m), amongst other metrics, showed consistent responses from edge effects, thus resulting in an adequate vertical plant distribution. Results demonstrate that, with the implementation of new parameters, forest models such as FORMIND have strong potential to study the mechanisms and the impact of environmental changes on forests. Models can also expand the possibilities of in-situ studies, which are limited in time and space, when calibrated carefully with suitable in-situ data, here delivered by terrestrial LiDAR.
-
(2022)Topological defects and solitons are nontrivial topological structures that can manifest as robust, nontrivial configurations of a physical field, and appear in many branches of physics, including condensed matter physics, quantum computing, and particle physics. A fruitful testbed for experimenting with these fascinating structures is provided by dilute Bose–Einstein condensates. Bose–Einstein condensation was first predicted in 1925, and Bose–Einstein condensation was finally achieved in a dilute atomic gas for the first time in 1995 in a breakthrough experiment. Since then, the study of Bose–Einstein condensates has expanded to the study of a variety of nontrivial topological structures in condensates of various atomic species. Bose–Einstein condensates with internal spin degrees of freedom may accommodate an especially rich variety of topological structures. Spinor condensates realized in optically trapped ultracold alkali atom gases can be conveniently controlled by external fields and afford an accurate mean-field description. In this thesis, we study the creation and evolution of a monopole-antimonopole pair in such a spin-1 Bose–Einstein condensate by numerically solving the Gross–Pitaevskii equation. The creation of Dirac monopole-antimonopole pairs in a spin-1 Bose–Einstein condensate was numerically demonstrated and a method for their creation was proposed in an earlier study. Our numerical results demonstrate that the proposed creation method can be used to create a pair of isolated monopoles with opposite topological charges in a spin-1 Bose–Einstein condensate. We found that the monopole-antimonopole pair created in the polar phase of the spin-1 condensate is unstable against decay into a pair of Alice rings with oscillating radii. As a result of a rapid polar-to-ferromagnetic transition, these Alice rings were observed to decay by expanding on a short timescale.
-
(2016)The major concern of lenders is to answer the next question: 'Who we lend to?' Until 1970s the traditional schema was used to answer this question. Traditional credit assessment relied on 'gut feel', which means that a bank clerk or manager analyses a borrower's character, collateral and ability to repay. Also, some recommendations from the borrower's employer or previous lender are used. The alternative approach is credit scoring, which is a new way to approach a customer. Credit scoring is one of the most successful applications of statistics in finance and banking industry today. It lowers the cost and time of application processing and gives flexibility in making trade off between risk and sales for financial institution. Credit scorecards are essential instruments in credit scoring. They are based on the past performance of customers with characteristics similar to a new customer. So, the purpose of a credit scorecard is to predict risk, not to explain reasons behind it. The purpose of this work is to review credit scoring and its applications both theoretically and empirically, and to end up with the best combination of variables used for default risk forecasting. The first part of the thesis is focused on theoretical aspects of credit scoring - statistical method for scorecard estimation and measuring scorecard's performance. Firstly, I explain the definition of the scorecard and underlying terminology. Then I review the general approaches for scorecard estimation and demonstrate that logistic regression is the most appropriate approach. Next, I describe methods used for measuring the performance of the estimated scorecard and show that scoring systems would be ranked in the same order of discriminatory power regardless the measure used. The goal of the second part is empirical analysis, where I apply the theoretical background discussed in the first part of the master's thesis to a data set from a consumer credit bank, which includes variables obtained from the application forms and from credit bureau data, and extracted from social security numbers. The major finding of the thesis is that that the estimated statistical model is found to perform much better than a non-statistical model based on rational expectations and managers' experience. This means that banks and financial institutions should benefit from the introduction of the statistical approach employed in the thesis.
-
(2013)Creep is time dependent plastic malformation of solids, that happen in static stress and temperature when threshold values are met. Creep occurs at high temperature, meaning temperature more than 30% of material's absolute melting temperature (this limit is a little lower with plastics, and higher in ceramics). The malformations it causes can lead to rupture, which usually happen in a short time compared to the duration of the whole process. The creep effect itself is known from already the 19th century, and for metals it's quite clear that diffusion is always present in creep (Coble and Nabarro-Herring creep), and that dislocations can increase the rate of creep strain. Effects of creep can be seen e.g. in power plants and engines, where turbine blades, turbines, pipes and vessels are all the time at high temperature and stress. Also creep relaxation is often 'loosening' bolts which needs to be retightened. In regular office creep can be seen in paper clips, especially in plastic ones, which relax and lose grip fast because of the low melting point of plastics. Creep, because it usually needs long time to be visible, has been part of accidents, too, e.g. in '9/11'. Creep appears in 3 stages (primary (transient), secondary (steady-state), tertiary), and depending on the application, either secondary or tertiary is the most important one. The secondary creep is important for displacement-, buckling- and relaxation-limited situations, and tertiary for the rupture-limited ones.
-
(2020)We study the use of data collected via electroencephalography (EEG) to classify stimuli presented to subjects using a variety of mathematical approaches. We report an experiment with three objectives: 1) To train individual classifiers that reliably infer the class labels of visual stimuli using EEG data collected from subjects; 2) To demonstrate brainsourcing, a technique to combine brain responses from a group of human contributors each performing a recognition task to determine classes of stimuli; 3) To explore collaborative filtering techniques applied to data produced by individual classifiers to predict subject responses for stimuli in which data is unavailable or otherwise missing. We reveal that all individual classifier models perform better than a random baseline, while a brainsourcing model using data from as few as four participants achieves performance superior to any individual classifier. We also show that matrix factorization applied to classifier outputs as a collaborative filtering approach achieves predictive results that perform better than random. Although the technique is fairly sensitive to the sparsity of the dataset, it nonetheless demonstrates a viable proof-of-concept and warrants further investigation.
-
(2016)The Baltic Sea is a popular cruising area during the summer months (April till September) with international cruise lines. During these months cruising ports of the Baltic Sea handle the cruise ship generated waste. As the cruising business has been rapidly growing the waste streams has become larger. Present laws and regulations prevent most discharges into the Baltic sea. According to these regulations a ship has to discharge all waste at the port of call produced on board since last port of call. Thus, ports have different waste management strengths and weaknesses. Therefore, it is here argued that an updated collaboration among the ports where individual ports would be specialized in specific types of waste handlings ought to benefit the environmental work of the port and the cruise lines and thus also the environment. The thesis will through experts' ideas and opinions from each port study whether an updated waste management can be introduced in the ports of the study. The individual ports are Port of Helsinki, Port of Tallinn, Ports of Stockholm and Copenhagen Malmö Port. Cruise ship generated waste has been study to some extent around the world, but there are only a few studies in the Baltic Sea area. Secondary data and semi structured thematic professional interviews was used to find answers on the research questions. Secondary data in form of waste streams quantities from cruise ships 2010–2014 in the ports of the study was gathered. The gathered data enabled comparisons among the ports and shows in what way the fractions are divided among them. The interviews were held at each port with one to three participants at the time. In total 12 persons were interviewed at nine occasions. The transcribed material was analysed through thematising. The research shows cruise ship generated waste fractions are unevenly distributed among the ports in the Baltic Sea. Hence, this also means the ports are already specialized in receiving special types of waste fractions. The ports are receiving sorted waste and different fractions are being handled. The ports have a close cooperation regarding cruise ships but the study shows the ports are open for new sustainable solutions. This thesis opens up the discussion on cruise ship generated waste in the Baltic Sea. The study shows there is little research done on this matter and further studies are needed. The waste management of all parties involved are important in order to act environmentally friendly and harm the surrounding areas the least. This research provides the Baltic Sea cruising ports with one possible solution on an updated waste handling management in the area.
-
(2019)Jurassic (182 Ma) Karoo flood basalt province shows great variety in geochemistry. The complexity is thought to be inherited from distinct mantle sources. Luenha River exposure in northern parts of Mozambique includes primitive picrites possibly representing the still undefined parental magma type for the North Karoo Lavas. The previously determined whole-rock data revealed chondritic to very radiogenic 87Sr/86Sr ratios and nearly chondritic eNd values. The diverse 87Sr/86Sr ratios can result from processes such as e.g. subsolidus alteration, contamination, magma mixing or source heterogeneities, which complicates assessment of petrogenetic processes. To make a contribution to this, plagioclase phenocrysts from six Luenha samples were used as tracers of magma chamber processes. In situ studies on plagioclase growth zones were performed using the CIS methods (crystal isotope stratigraphy). Cold-cathode cathodolumenescence microscopy (CL) was used to visually reveal zonation, the electron microprobe (EMPA) was utilized for major element content (core-to-rim), and laser ablation-multicollector- inductively coupled plasma- mass spectrometry (LA-MC-ICP-MS) was used for in situ (87Sr/86S)i ratio measurements. The anorthite content of plagioclase cores (n = 65) is An65 ̶ 90 and core to rim variations alternate between normal oscillatory to reverse zoning. Is situ isotope examination revealed isotopic disequilibrium in (87Sr/86Sr)i between phenocrysts (cores 0.70511–0.70671, n = 10; rims 0.70539–0.70709, n = 11) and bulk groundmass (0.70660– 0.71061, n = 12). Plagioclase cores are always less radiogenic compared to whole rock (0.70690–0.71019), but internal variation within and between lava flows exists. Core-to-rim microsampling revealed four different (87Sr/86Sr)i evolution paths reflecting heterogeneous crystallization conditions. An, open complex magma plumbing system with progressing contamination is the likely scenario. The relatively radiogenic plagioclase cores compared with the uncontaminated plume-like sample (87Sr/86Sr 0.70410) indicate that contamination was ongoing prior to plagioclase crystallization and continued until eruption. Phenocryst migration between compositionally and thermally distinct reservoirs at crustal depths could explain the heterogeneous plagioclase (An and (87Sr/86Sr)i) of Luenha picrites.
-
(2021)Africa has recently increased its share of the global market, and the continent’s potential has been recognized globally. The continent has experienced a lot of oppression and forced changes in history, and it is currently developing its new identity with relatively young states and its fast-growing population. African Union (AU) is calling pan-African ideology to bring together the African people in their blueprint and master plan Agenda 2063, where the cultural heritage is at the core. Culture is also at the core of the creative economy, and the creative economy's share of the global economy is growing. Due to globalization and digitalization, the knowledge from other cultures is spreading rapidly, which is the basis of a cultural shift both at local and global levels. This research investigated the culture and the creative economy as builders of society in Kenya. Kenya has been very successful in the field of Information and Communications Technology (ICT), the state takes its cultural heritage seriously in its development programs and their focus is especially on the potential of the youth in the creative economy. Kenya has a vast cultural diversity in the state with its officially recognized 44 tribes. This cultural diversity plays a significant role in the creative economy. According to the United Nations Conference on Trade and Development (UNCTAD, 2020), the creative economy has no single meaning, as the concept is constantly evolving. The basic elements of the concept are from human creativity, ideas, and intellectual property, knowledge and technology. The creative industries include such as music, film, video, arts and crafts and performing arts. These elements are the basis of the creative economy, in addition, they have a significant commercial and cultural value. The research was conducted in Kenya during January and February 2021, and the data was collected from two main geographical research areas, the city of Nairobi and Taita-Taveta County. The geographical research areas were chosen by their cultural diversity, the creative economy and their urban and rural statuses. Nairobi has a classification of a creative city where the digital creative economy is booming, and the city is attracting people around East Africa. Taita-Taveta respectively is a rural county near the Kenyan coast, where the creative economy is mainly in the traditional form, for example, crafting and basket making. The research combined the elements from the ethnographical, hermeneutical and critical approaches by using unstructured, structured interviews and observation, as the methods combined qualitative methods with numerical data. The results show that the culture and the creative economy do build the society in Kenya. It is seen in each level of society, for example, among the families, tribes, counties and even the government. Each level influences and controls the way culture and the creative economy build the society in Kenya. The meaning of the community arose in culture and the creative economy shifts, as they provide help in the mitigation and adaptation into new situations. With the exponential population growth, the share of the youth is rising, culture and the creative economy have the potential to provide jobs for the youth in the future. There are challenges with culture and the creative economy in Kenya. First, to preserve the cultural diversity in Kenya among the youth. Second, to target the governmental policies to the right actions and towards the right groups, which would then support the sector itself. Due to attitude shifts, the role of the youth is a significant point to consider. Furthermore, there is a vast gap between the government and the community, which causes a lot of harm to the creative economy, as the policies do not support the creative sector. If these significant points are solved, there is a vast potential for the culture and the creative economy to continue building the society in Kenya.
-
(2016)The purpose of this thesis is to study the cumulative probability of a false-positive (FP) test result during the Finnish 20-year breast cancer screening program. This study is based on breast cancer screening data provided by the Mass Screening Registry of the Finnish Cancer Registry, which consists of women aged 50–51 years at the time of their first invitation to mammography screening in 1992–1995. Generalized estimating equations (GEE) are used to estimate the cumulative probability of a FP screening result. In the theoretical part we present the corresponding theory together with reviewing the theory of generalized linear models (GLM). The cumulative probabilities are calculated from the modeling of individual examinations by using the theory and formulas of conditional probability. The confidence intervals (Cl) are calculated by using Monte Carlo simulation relying on the asymptotic properties of the GEE estimates. The estimated cumulative risk of at least one FP during the screening program was 15.84% (95% Cl: 15.49–16.18%). Previous FP findings increased the risk of (another) FP results with an odds ratio (OR) of 1.91 (95% Cl: 1.78–2.04), and OR 3.09 (95% Cl: 2.49–3.83) for one or more previous FP results, respectively. Irregular screening attendance increased the risk of FP results with an OR of 1.46 (95% Cl: 1.37–1.56).
-
(2021)Cumulonimbus (Cb) clouds form a serious threat to aviation as they can produce severe weather hazards. Therefore, it is important to detect Cb clouds as well as possible. Finnish Meteorological Institute (FMI) provides aeronautical meteorological services in Finland, including METeorological Aerodrome Report (METAR). METAR describes weather at the aerodrome and its vicinity. Significant weather is reported in METARs, and therefore Cb clouds must be included in it. At Helsinki-Vantaa METARs are done manually by human observer. Sometimes Cb detection can be more difficult, for example, when it is dark, and it is also expensive to have human observers working around the clock all year round. Therefore, automation of Cb detection is a topical matter. FMI is applying an algorithm that uses weather radar observations to detect Cb clouds. This thesis studies how well the algorithm can detect Cb clouds compared to manual observations. The dataset used in this thesis contains summer months (June, July and August) from 2016 to 2020. Various verification scores can be calculated to analyse the results. In addition, daytime and night-time differences are calculated as well as different years and months are compared together. The results show that the algorithm is not adequate to replace human observers at Helsinki-Vantaa. However, the algorithm could be improved, for instance, by adding satellite observations to improve detection accuracy.
-
(2014)Massive improvements of the services in the public cloud provide many opportunities for online users. One of the most valuable services of this virtual place is the infrastructure to store data in distributed storages. The public cloud storages let different organizations and enterprises to use the high availability of data, in a cost efficient way, with lowered maintenance burden. However, utilizing the large scale capacity of (public) cloud storages is not mature trend yet among the individual customers, businesses, and organizations. The cloud storages are still unreliable places for the sensitive and confidential information or back-up copies from trust and privacy perspective. Hence, some public and private organizations, universities, as well as ordinary citizens avoid uploading their critical files to the cloud. The thesis suggests the idea of customer-oriented data storages as a solution to the shortcomings of public cloud storages. This idea would be a new way to customize the cloud storages which bears more involvement of the customer in managing aspects, as a solution to the current distrust issue on the cloudbased storages and would be a great courage to different type of customers. Furthermore, the thesis evaluates feasibility of the proposed customer-oriented cloud storage architecture based on scenarios inspired from the Architecture Tradeoff Analysis Method (ATAM) evaluation approach. Results of the evaluating discussion on the proposed solution in boosting trust in cloud storages and providing more control for cloud storage customers are presented.
-
(2022)In the modern era, using personalization when reaching out to potential or current customers is essential for businesses to compete in their area of business. With large customer bases, this personalization becomes more difficult, thus segmenting entire customer bases into smaller groups helps businesses focus better on personalization and targeted business decisions. These groups can be straightforward, like segmenting solely based on age, or more complex, like taking into account geographic, demographic, behavioral, and psychographic differences among the customers. In the latter case, customer segmentation should be performed with Machine Learning, which can help find more hidden patterns within the data. Often, the number of features in the customer data set is so large that some form of dimensionality reduction is needed. That is also the case with this thesis, which includes 12802 unique article tags that are desired to be included in the segmentation. A form of dimensionality reduction called feature hashing is selected for hashing the tags for its ability to be introduced new tags in the future. Using hashed features in customer segmentation is a balancing act. With more hashed features, the evaluation metrics might give better results and the hashed features resemble more closely the unhashed article tag data, but with less hashed features the clustering process is faster, more memory-efficient and the resulting clusters are more interpretable to the business. Three clustering algorithms, K-means, DBSCAN, and BIRCH, are tested with eight feature hashing bin sizes for each, with promising results for K-means and BIRCH.
Now showing items 709-728 of 4247