[dipl] Perustieteiden korkeakoulu / SCI

Permanent URI for this collectionhttps://aaltodoc.aalto.fi/handle/123456789/21

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Unveiling Persistent Brain Fingerprints: Exploring Stable Power Spectral Features with Variational Autoencoder-Based Models
Rueda Molano, Mateo
Perustieteiden korkeakoulu | Master's thesis
This thesis investigates utilizing power spectral density (PSD) extracted from magnetoencephalography (MEG) signals and variational autoencoders (VAE) based models to generate distinct brain fingerprints at different time points for subjects not included in the training phase. The promising accuracy results (over 0.83) in both linear and non-linear models reveal the potential of PSD for subject identification tasks. We took advantage of the VAE models’ flexibility by slightly adjusting the VAE loss function, penalizing the distance between latent representations (brain fingerprints) of the same subject at two different time points. This adjustment led to superior subject identification performance compared to standard VAE [31] and beta-VAE [34] models. Furthermore, this modified VAE model demonstrates notable superiority over the ln-BRRR [73] model in this task. While the latter has demonstrated favorable results [7], our model surpasses it by a considerable margin while demanding considerably less training time. Employing a model interpretability technique based on Shapley values, the study identifies sets of frequency bands and brain areas relevant by the model in generating differentiable fingerprints. These findings highlight the complex interplay between diverse brain regions and frequency bands in subject differentiation.
C-RWD: A Computational Responsive Web Design Service
Zhang, Yu
Perustieteiden korkeakoulu | Master's thesis
With the increasing diversity of device screen sizes used by web users, responsive web design (RWD) has become an essential part of website production. However, due to its complexity, RWD often requires the cooperation of a team of interface designers, developers and data analysts and requires the team to invest much time. Besides, it is unrealistic to create personalized, responsive designs for users using manual RWD methods. This thesis proposes C-RWD, which is a computational responsive web design service based on the LaaS platform. The design and implementation of C-RWD are introduced in detail, and the functions of C-RWD are evaluated based on example websites. When an initial interface is provided, C-RWD can (1) automatically collect the interaction data of different users in the interface and generate personalized breakpoints and (2) automatically use combinatorial optimization to generate optimized interfaces at these breakpoints based on user's interaction data to improve usability and then (3) automatically integrate the optimized interfaces under different breakpoint widths into one fully responsive website and present it to users. The contribution of C-RWD is that it proposes a novel framework which can automate the generation of responsive interfaces while optimizing the interface for user's personalization. In practical applications, it can greatly reduce the time and cost of RWD production and generate a personalized and optimized interface for users.
An Interactive C Code Execution and Visualization Tool for Online Learning
Rantanen, Veli-Matti
Perustieteiden korkeakoulu | Master's thesis
Introductory programming courses are notorious for their high drop-out rates and the C programming course at Aalto University is no exception. Studies have suggested that this phenomenon is caused by a combination of factors that result in students experiencing significant amounts of stress. Previous works have sought to address the problem by introducing new pedagogic methods and software. In addition, studies have found that intelligent tutoring can be as effective as traditional tutoring methods. This thesis presents a web-based software that seeks to reduce the stress factors associated with learning the C programming language. The goal of the work is to develop practical methods of generating and visualizing intelligent feedback. The presented tool is capable of analyzing, visualizing and evaluating simple user programs. Initial impressions suggest that the tool could reduce the stress factors significantly, but the implementation has significant limitations. Based on observations made in the implementation of this work, the development of an open-source framework for implementing similar tools is recommended.
Dye-sensitized nanostructured and organic photovoltaic cells: technical review and preliminary tests
(2002) Halme, Janne
School of Science | Master's thesis
The solar electricity is presently a rapidly growing but often relatively expensive renewable energyform. Recently however, new molecular photovoltaic (PV) materials have been developed, whichcould enable a production of low-cost solar cells in the future. The thesis begins with a discussion of the current status of the PV technology and a shortintroduction to the different PV technologies and to the basics of photovoltaics. The dye-sensitized solar cell (DSSC) is an electrochemical solar cell where light absorption occursby dye molecules attached to a nanostructured TiO2 electrode. An introduction to the DSSC is givenincluding a short description of the operating principle of the cell and a discussion of the physicaland chemical processes behind it. A systematic literature review is done on the materials and mostessential preparation methods of the standard DSSC. The performance of the DSSC is reviewed in terms of the energy conversion efficiency and the longtermstability. The important directions of development are the transition from glass substrates toplastic foils and from batch processing to continuous processing as well as the use of solid stateelectrolytes. The glass-based DSSC technology is on the verge of commercialization and themanufacturing cost estimates for the technology are close to the projected costs of other PVtechnologies. The purely organic solar cells are discussed individually beginning with the discussion of thefundamentals of organic photovoltaics and an introduction of different types of organic photovoltaicmaterials including semiconducting polymers, dyes, pigments and liquid crystalline materials. Areview is done on the performance results of organic solar cells categorizing the cells by their devicearchitecture. The development of the organic PV materials is still at an early stage and no clearlyoutperforming materials or cell structures have yet emerged. Experimental results are reported including a demonstration of the dye-sensitization with a naturaldye as well as a preparation and testing of a series of ruthenium-dye based DSSCs. An efficiency of0.6% at about 600 W/m2 solar illumination was obtained for the DSSCs in outdoor measurements.
DC SQUID Microwave Amplifier
(2004) Lehtinen, Teijo
Perustieteiden korkeakoulu | Master's thesis
Alle Kelvinin Iämpötilaan jäähdytetyn DC SQUID vahvistimen kohina on parhaimmillaan kvanttirajoitteista: gigahertsin taajuuksilla sisääntulokohinalämpötila voi olla vain muutamia kymmeniä millikelvenejä. Vastaaviin kohinalämpötiloihin on mahdotonta päästä millään muulla tunnetulla vahvistin tyypillä. Tässä diplomityössä karakterisoitiin uusinta tekniikkaa edustava DC SQUID mikroaaltovahvistin, LTL 800. Laite on valmistettu Valtion teknillisessä tutkimuslaitoksessa (VTT). Toimintaperiaatteiden ymmärtämiseksi kehitimme analyyttisen mallin laitteesta, ja mittaustulokset onnistuttiin selittämään yksityiskohtaisella piirisimulaatiomallilla. Molempia malleja tullaan soveltamaan uusien SQUID vahvistimien suunnitteluun. LTL 800 SQUID vahvistimen vahvistukseksi mitattiin 22 dB taajuudella 630 MHz ja 150 MHz:n taajuuskaistalla. Vahvistus-kaista tulo, 24 GHz, on erinomainen muiden valmistajien tuloksiin verrattuna. Sisääntuloon ekvivalentiksi kohinalämpötilaksi saatiin 5,5 Kelviniä 4,2 Kelvinin mittauslämpötilassa. Mittaustulosten ja simulaatioiden perusteella vahvistimen kohinalämpötilaksi 50 mK:n mittauslämpötilassa voidaan arvioida 150 mK, joka on vain kertoimella kolme suurempi kuin kvanttiraja.
Analysis of human voice production using inverse filtering, high-speed imaging, and electroglottography
(2005) Pulakka, Hannu
Master's thesis
Human voice production was studied using three methods: inverse filtering, digital high-speed imaging of the vocal folds, and electroglottography. The primary goal was to evaluate an inverse filtering method by comparing inverse filtered glottal flow estimates with information obtained by the other methods. More detailed examination of the human voice source behavior was also included in the work. Material from two experiments was analyzed in this study. The data of the first experiment consisted of simultaneous recordings of acoustic speech signal, electroglottogram, and high-speed imaging acquired during sustained vowel phonations. Inverse filtered glottal flow estimates were compared with glottal area waveforms derived from the image material by calculating pulse shape parameters from the signals. The material of the second experiment included recordings of acoustic speech signal and electroglottogram during phonations of sustained vowels. This material was utilized for the analysis of the opening phase and the closing phase of vocal fold vibration. The evaluated inverse filtering method was found to produce mostly reasonable estimates of glottal flow. However, the parameters of the system have to be set appropriately, which requires experience on inverse filtering and speech production. The flow estimates often showed a two-stage opening phase with two instants of rapid increase in the flow derivative. The instant of glottal opening detected in the electroglottogram was often found to coincide with an increase in the flow derivative. The instant of minimum flow derivative was found to occur mostly during the last quarter of the closing phase and it was shown to precede the closing peak of the differentiated electroglottogram.
Image-based detection of defective logs
(2006) Enarvi, Seppo
Perustieteiden korkeakoulu | Master's thesis
This thesis describes the development of a computer vision system that was installed at the Stora Enso wood handling terminal in Uimaharju. A measurement station is responsible for scaling the logs that the terminal receives, but until now grading has been entirely manual. The computer vision system substantially reduces the work load of the human grader by automatically detecting defects from log end images. The human grader will only grade the logs that the software suspects as being defective. A comprehensive survey of basic image segmentation techniques is given. In particular their application for the segmentation of color images is discussed. An explanation of is-sues related to selecting a color space for a particular purpose and a review of the most common color spaces is included. The development of the computer vision system that comprises image acquisition, segmentation, object recognition, and feature classification is described. The major merit of the thesis is the development of algorithms that localize the end of a log from a camera image, and detect if there are visible defects on the surface of the log end. Localization of the log end is based on three-dimensional tables that represent typical wood colors, and the circular shape of the log end. Defects are detected using statistical features of the log end pixel colors.
Mobile Internet usage measurements : case Finland
(2006) Kivi, Antero
Master's thesis
Mobile Internet is the outcome of two intense and global trends of the recent years: mobile/wireless and the Internet. Despite the potential the hundreds of millions of new mobile devices sold globally each year present, little information on mobile data service usage apart from mobile operator portals is currently available. In this research, mobile Internet usage was measured in fall 2005 using three fundamentally different methods to answer the question What are the characteristics of consumer mobile Internet usage in Finland? First, data on 80-90% of all Finnish mobile subscribers and terminals was collected with mobile operators' charging-oriented reporting systems. The observed Finnish mobile terminal installed base was old and did not widely support key features for data usage as e.g. packet data capability was in 48% and WCDMA capability in less than 1% of terminals. Nokia's market share was a remarkable 87%. Smartphones constituted 6% of all terminals, over 99% of which were Nokia's Symbian handsets and one third of these Nokia communicators. The terminal base was fairly concentrated as the 50 most common models made up 88% of all terminals. Some 92-94% of all mobile subscribers were postpaid subscribers, 75% of them consumers. While 99% of consumers had operators' default usage-based packet data tariff plan, the remaining 1% created 82% of all consumer subscriber packet data traffic. Second, 50% of all Finnish mobile network packet data traffic was captured in TCP/IP header collection -based measurements. Strikingly, the Windows operating system originated 65% of all packet data traffic in mobile networks. Moreover, VPN usage created 46% of traffic volume leading to a very high 85% share of UDP traffic. The Internet APN accounted for 90% of all packet data traffic. Third, a panel of 500 Finnish Symbian S60 handsets was monitored with software installed in the handsets. Panelists with higher radio capability handsets used packet data more frequently and in higher volumes. Data usage volumes were also higher for users with relatively cheaper fixed fee packet data plans. Operator sites and infotainment dominated web/wap site visits with 32% and 33% shares of all visits. Using handset as a modem formed a 21-25% part of all smartphone data traffic. The most active 20% of data users created 80% of traffic, even when modem traffic was excluded. Browsing was the most important data application area with a 72% share of non-modem traffic, and its relative share increased with data usage volume. In conclusion, Finnish mobile data usage is currently business driven. Traffic to non-operator controlled sites appears to be important. The usage of 3G terminals and effectively flat-rate packet data tariffs seems to increase data usage considerably, and browser is a central application also in mobiles. Mobile operators are recommended to include items on off portal traffic to their regular reporting. Similar measurements enabling evaluation of the development of Finnish mobile data usage should be repeated. The measurement methods could also be productized or sold to operators as a service by a 3rd party. Potential ways to utilize the handset-based data are numerous.
An Interoperable Equipment Server for Building Automation Systems
(2007) Järvinen, Hannu
School of Science | Master's thesis
Purpose of this Master's Thesis is to explore the possibilities to integrate the management of the building automation systems and equipment. We would like to have a centralized management server, which integrates the monitoring and operating with different automation systems into one. Furthermore, these servers could be connected together to make the system more scalable and flexible. Nowadays, there are a considerable number of different protocols and industry standards at the building automation sector. Manufacturers have made their own customized tools to control the equipment. First step to make building automation systems centrally manageable is to use some standard way for communication between the different parts of the system. Of course, we also want to store all the equipment data in the same format, which makes the system more logical. All the equipment data available in standard format makes the development of the user interface easier. It also opens new possibilities for developing different kind of user interfaces. We should not limit the user interface to only one but to make it possible to make general as well as customized, mobile or automated user interfaces.
Large patent portfolio optimization
(2007) Orelma, Heli
Master's thesis
This master's thesis studies the systematic management and optimization of large patent portfolio. The objective is to explore the main characteristics of large patent portfolio management and to create systematical logic for the selection and management processes. The created logic will also be tested in a practical case. The study is constructive and it is conducted as an action research. It combines both qualitative and quantitative data. The main emphasis of the research is the computational management of patents as a portfolio. The questions concerned are business decision making choices and the study doesn't cover questions like the exact valuation of a single patent or patent portfolio. The studied industry assumed to be the electronic and telecommunication industry. First, the study explores the management of patents as a whole. Subsequently, different mathematical and computational methods are explored to understand, what kind of model and algorithm is needed. A model for managing patents computationally is presented as well as an algorithm for defining which patents should be studied for the decision of discarding them. The procedures also help to evaluate, which parts of the portfolio need additional investments. Finally, the study and assumptions beneath are discussed. The study contributed to the existing knowledge by studying the factors affecting decisions about large patent portfolios and presented a model for the discarding process. It helps the managerial practices by listing the possible patents that could be further studied for discarding decisions. Additionally, it can help to justify the decisions of adding, keeping and discarding patents.
Designing practices for making use of tacit knowledge in a knowledge work environment
(2007) Ylihärsilä, Kari
Master's thesis
This thesis deals with making use of tacit knowledge in a knowledge work environment. Purpose of this research is to design practices, tools and ways of working for making use of tacit knowledge in a knowledge intensive corporation. Making use of tacit knowledge was researched in the areas of new employee introduction, using electronic workspaces and working with virtual teams. The practices were designed using a constructive research approach. 30 persons were interviewed within the study. The research questions are the following: 1) What is tacit knowledge? 2) What are best practices for making use of tacit knowledge in a knowledge work environment? 3) What are key issues to be taken into account when introducing these practices in a knowledge work corporation? In the literature study part tacit knowledge is defined and ways of sharing tacit knowledge are identified. Introducing practices for making use of tacit knowledge inside organizations are also examined. In the empirical part best practices were gathered from the organization, which were refined through theoretical understandings. Different maturity levels were reached in each area of research. Some of these are presented as tools to use and some as conceptual understandings. Concrete tools for transferring tacit knowledge in new employee introduction were designed. These were tested unofficially and have reached a level of maturity ready for pilot-testing. These tools deal mainly with making use of implicit knowledge, which the part of tacit knowledge that can be put into words. In the areas of electronic workspaces and virtual teams the results are presented as conceptual understandings. In addition to understanding and methods, making use of tacit knowledge was found to be mostly about enabling the employees' intrinsic motivation for sharing their knowledge. This can occur for example through stories, comments and concept creation. A model was empirically verified consisting of cultural, intentional, systemic and behavioural perspectives on motivation for knowledge sharing.
Terveydenhuollon vuosittaisten kustannusten ennustettavuus kuntanäkökulmasta
(2008) Malmström, Tomi
Faculty of Information and Natural Sciences | Master's thesis
Small municipalities have difficulties to prepare to fluctuation of healthcare expenses in Finland. Especially fluctuation of hospital care expenses may be very remarkably. The main objective of this study is to clarify the predictability of annual healthcare expenses. Predictability of annual healthcare expenses is examined through the effect of expensive patients. Time series are used to analyze fluctuation of annual healthcare expenses. Research data have been gathered from municipalities of Vantaa, Kalajoki and Kuusamo. Findings of data gathered from Vantaa are compared to Kalajoki and Kuusamo. Simulated municipalities are used to analyze the effect of municipality's size to fluctuation of annual healthcare expenses. There are specific illnesses which are rare, hard to predict and expensive. These illnesses have a great effect on the fluctuation of hospital care expenses. Excluding these illnesses it is possible to predict annual healthcare expenses also in small municipalities. Larger population makes predictability better. Already a population of 10 000 considerably diminishes the significance of very expensive illnesses. Insurance can be used to prepare to the very expensive patients. Insurance pool used in Finland is not certainly equal to all small municipalities. By developing new insurance systems the position of small municipalities can be improved. New insurance systems could help municipalities to cope with surprising expenses of hospital care patients.
Pricing of exotic foreign exchange rate options
(2008) Eloranta, Antti
Faculty of Information and Natural Sciences | Master's thesis
The popularity of exotic foreign exchange rate options has grown rapidly during the past decade. High profit margins and rapid market growth have made the market particularly lucrative for the banks. On the other hand, the correct pricing of exotic options requires more sophisticated models than the traditional Black-Scholes. The objective of this thesis is to build, implement, and validate a pricing model for the exotic foreign exchange rate options. Based on previous research, this thesis models the stochastic behavior of the foreign exchange rates as a stochastic volatility – jump-diffusion process with piecewise constant model parameters. The process is defined in both continuous and discrete times. The continuous time process is used for pricing European options in a semi-closed form, which enables an efficient model calibration. The discrete time model is used for pricing exotic options with Monte Carlo. The model is calibrated using a method customized specifically for the purposes of this thesis. The model is validated by analyzing its performance with real market data from the beginning of July to the end of August 2007. The convergence of the closed-form and Monte Carlo solution option prices shows that the model is internally consistent. The comparison of the model implied and market implied option prices indicate that the model is market consistent. The analysis of the robustness suggests that the model and its calibration are mathematically meaningful.
Reengineering a physical distribution network in the sport instruments industry
(2008) Kauppinen, Petteri
Faculty of Information and Natural Sciences | Master's thesis
Today's fierce competitive environment drives companies to seek competitive advantage from their supply chains. Earlier companies focused on cost reduction, but now the ever changing environment forces companies to increase the responsiveness of their supply chains. Agility and flexibility are today's paradigms towards to more responsive supply chain. This research studies the design of physical distribution network. This research contains two parts. First part, theoretical is based on supply chain management, physical distribution and performance management. Empirical part applies the knowledge build during the theoretical part in Finnish based sport instrument company. The main research question is "What is the optimal physical distribution network for Case Company?". Literature part presents a general framework for companies how to analyze their supply chains and products to devise optimal physical distribution networks. To devise the optimal distribution network company has to go through four steps. First is to define the nature of product, second is to decide priorities in the supply chain, third to define a proposal for the optimal distribution network and fourth to use performance measures to define optimal distribution network. Empirical part analyzed Case Company using the framework that literature review presented. Author conducted the four step analysis presented above in the empirical part. The research approach of thesis was constructive and also principles of the case study approach were applied. The findings of empirical part show that companies whose products' demand patterns are unpredictable and the supply chain requires agile and flexible performance, deliveries directly to retailers can be lucrative choice when considering physical distribution structure. Depending on the As-Is state of physical distribution there is possibility to shorten total order cycle time and cut inventory levels. Distance to customer is not measured anymore in kilometers, but in time. This research shows that Case Company can be nearer to customer in time when the location of distribution centre is further. Direct delivery is possible to implement without increasing logistics cost. Direct retail deliveries will increase the costs of pollution, because companies need use more airfreight to meet the customer requirements. Direct retail deliveries are more attracting choice when delivering goods from east to west. This is due to time difference between consignor and consignee.
Pintojen hyperbolisointi Riccin virtauksen avulla
(2008) Liimatainen, Tony
Master's thesis
Moniston Riemannin metriikan kehittäminen Riccin virtauksella on osoittautunut tehokkaaksi työkaluksi direntiaaligeometrian tutkimuksessa. Riccin virtaus on metriikan evoluutioyhtälö, jolla on epälineaarisuudesta huolimatta lämpöyhtälömäisiä ominaisuuksia. Vuonna 2003 Riccin virtauksen avulla todistettiin Poincarén konjektuuri. Työssä tutkimme Riccin virtausta pinnoilla ja samalla tutustumme Poincarén konjektuurinkin todistuksessa käytettyihin menetelmiin. Tutkimme miten metriikka kehittyy pinnalla Riccin virtauksessa. Selvitämme millä oletuksilla ja miten kauan Riccin virtauksen ratkaisu on olemassa. Tutkimme miten pinnan kaarevuus käyttäytyy virtauksen aikana ja millaiseen metriikkaan virtauksen ratkaisu pinnalla suppenee asymptoottisesti. Työssä johdamme tunnettuihin Riccin virtauksen tuloksiin nojaten virtauksen ratkaisun olemassaoloteorian, joka on voimassa riippumatta moniston ulottuvuudesta. Sen jälkeen sovellamme sitä saadaksemme tarvitsemamme olemassaoloteorian pinnoille. Pinnoilla kaarevuus yksinkertaistuu ja Gauss-Bonnetin teoreema kytkee pinnan kaarevuuden sen topologiaan. Näitä huomioita käyttäen johdamme pinnan Riccin virtaukselle yksinkertaisemman muodon. Pinnan Riccin virtauksen analysointiin käytämme osittaisdirentiaaliyhtälöiden teorian menetelmiä, joita ensin yleistämme monistoille. Osoitamme, että pinnalla Riccin virtauksella on aina yksikäsitteinen ratkaisu koko aikavälillä [0,Inf) mille tahansa alkuhetken CInf-metriikalle. Asymptoottisesti virtauksen ratkaisu pinnalla suppenee vakiokaarevuuden metriikkaan, minkä osoitamme erikoistapauksessa, jossa pinnan Eulerin karakteristika on negatiivinen. Erityisesti negatiivisen Eulerin karakteristikan pinta hyperbolisoituu. Pinnalla ratkaisu on konforminen alkuhetken metriikan kanssa, ja siten jokainen Riemannin metriikka pinnalla on konforminen vakiokaarevuuden metriikan kanssa. Riccin virtaus vaikuttaa hyödylliseltä työkalulta, kun tutkitaan lokaalien suureiden kuten kaarevuuden kytkeytymistä topologiaan. Riccin virtauksen vahvuus on sen kaarevuutta tasoittavassa luonteessa ja siinä, että sen ratkaisu on olemassa minimaalisilla ehdoilla. Riccin virtauksen työkaluja käyttäen voi lähestyä direntiaaligeometrian ongelmia myös korkeammissa ulottuvuuksissa osittaisdirentiaaliyhtälöiden teorian avulla.
Post-acquisition performance of active acquirers of divested assets in the software industry
(2008) Junna, Olli
Faculty of Information and Natural Sciences | Master's thesis
Corporate mergers and acquisitions (M&As) are a popular means by which companies pursue various strategic objectives. However, studies show that M&As on average do not produce positive returns to the acquirer. Furthermore, the existing research on factors contributing to acquisition performance is inconclusive at best. This study complements the existing research on M&A performance by focusing on acquisitions of divestments as a distinct subset of all acquisitions. Besides individual acquisitions, the study considers multiple acquisition programs, continuing the research stream initiated at Helsinki University of Technology. The aim is to find out if acquisitions of divestitures perform on average better than acquisitions of stand-alone firms both in the short and long run. The objective is also to determine what factors affect the performance of acquirers of divested assets. The sample used in this study consists of a total of 1,143 acquisitions undertaken by the 60 most active acquirers during the time period 1988-2005, where the acquirer operated in the US software industry. The data was analyzed by multivariate regression, using the event study methodology for individual acquisitions, and panel regression for acquisition programs. Performance was measured by the acquirer's market value change. The results show that both the short and long term average performance of acquirers buying divested assets was above average. The returns are significantly higher when the divested target enjoys a better fit with the acquirer than with the divesting parent. Also the long term performance of acquirers classified as "strategic" based on their systematic acquisition behavior was found significantly positive. On the other hand, divestiture acquisitions bought from a financially distressed parent contributed negatively to long-term market value. The deal price of divestiture acquisitions did not have a significant effect according to this study. This study makes a valuable contribution to existing research by showing a positive relationship between divestiture acquisitions and buyer performance. The result has implications to corporate managers who plan to use M&As as a strategic move. Furthermore, the study opens up various questions for further research in terms of divestiture acquisitions and acquisition programs. Through triangulation by multiple methods using different time frames it also raises some methodological concerns regarding the prevalence of short-term measures in existing acquisition research.
Privacy aware key establishment for publish/subscribe infrastructures in Ubiquitous environments
(2008) Ergawy, Amr Ibrahim Ahmed
Perustieteiden korkeakoulu | Master's thesis
Ubiquitous Computing, UbiComp, is a vision of embedding computing to every aspect of our day to day life. In ubiquitous computing, interaction among communicating entities exists in highly dynamic, large scale and failure prone environments. Publish/Subscribe interaction paradigm, Pub/Sub, can be used to decouple interacting entities in ubiquitous environments by delivering events based on users interests. In this scenario, securing events dissemination and protecting users' privacy are essential requirements for ubiquitous applications. In this thesis, we propose an encryption key establishment scheme for encrypting disseminated events in ubiquitous Pub/Sub infrastructures. The proposed key establishment scheme considers the dynamism, scalability and failure tolerance issues of ubiquitous environments. More importantly, the generated encryption keys reflect multi level access control polices, which is important to enforce users' privacy polices.
Growth and internationalization of venture capital backed technology-based new companies
(2008) Rönkkö, Perttu S.
Faculty of Information and Natural Sciences | Master's thesis
Previous research on growth models of companies has been focusing on modeling the growth of a company through a sequence of developmental stages. The stages models offer a simple, easy to understand framework to deal with the rather complex phenomenon of corporate growth. However, there are clear deficiencies which compromise the idea of stages models. A large number of different versions of stages models have been published, but yet there is not a widely accepted model. The purpose of this study is to establish a new conceptual framework for modeling the growth and internationalization of venture capital backed technology-based new companies. Based on the literature review and expert interviews, a new model is developed by applying a process view of the corporate growth. The model conceptualizes the growth and value creation of a technology-based new company, while using milestone achievement as the primarily input. The model is based on the idea of four parallel processes: 1) Value creation process, 2) Technology and product development process, 3) Business development process, and 4) Network and market development process. The Value creation process is seen as the backbone of the model, as the value creation is the ultimate target of a venture capital backed company. To map the development of a company on each one of the four processes, a set of key milestones has been composed. The new model developed in this study is further validated and tested through eight exploratory case studies. The case companies were selected from the Finnish ICT cluster. The case studies include detailed case descriptions, but the core of the case studies is the mapping of the acquired milestone information to the new model. The initial model is then further supplemented and finalized based on the case studies. As a result, the final evolution model for a technology-based new company is obtained. Key findings of the study include the discovery of different patterns of evolution revealed by the milestone mapping and the role of venture capital investors in accelerating the milestone achievement. Implications for entrepreneurs and recommendations for further research are also presented.
OBSAI interoperability in multi-vendor WiMAX base station architecture
(2009) Saha, Sumanta
Perustieteiden korkeakoulu | Master's thesis
Wireless networks have become a necessity with the increased mobility in human life. From cellular telephony to the Internet, all types of communication are now provided over wireless networks. However, to offer wireless network coverage over an area requires a potentially expensive infrastructure deployment. Such deployment requires base stations which until now have been completely proprietary to the equipment vendors. Moreover, proprietary equipment is almost always costly and offer less flexibility than standardized modular solutions. This situation results in a high cost for network upgradation and hinders network development. A remedy is available via modularization, hence the Open Base Station Architecture Initiative (OBSAI) is trying to modularize and standardize one of the most expensive elements of the wireless infrastructure, the base station. OBSAI standards aim to modularize the base station architecture and enable true interoperability among the various modules. However, the goal has not yet been achieved due to some features of the standard. This thesis project has studied the standards and pointed out some areas that must be concentrated upon when performing interoperability tests. It also proposes several standards amendments to foster greater interoperability among the modules of a base station. This study focuses on the RP3 interface of the OBSAI specification with the goal of making truly inter-operable baseband and RF modules, thus commoditizing the modules. The result is expected to be lower cost, greater interoperability, faster time-to-market, and more cooperative research.
A network perspective on the genetic population struture of seagrass Posidonia oceanica
(2009) Kivelä, Mikko
Informaatio- ja luonnontieteiden tiedekunta | Master's thesis
Populaatiobiologiassa käytettyjen perinteisten mallipohjaisten menetelmien tiedetään suoriutuvan huonosti, jos käytettävä data ei toteuta niissä tehtyjä oletuksia. Tässä työssä tutkitaan mahdollisuutta käyttää verkostotieteen uusimpia yhteisönhakumenetelmiä populaatiorakenteen löytämiseen geneettisestä samankaltaisuusverkosta, joka on muodostettu 1468 meriheinä Posidonia oceanican yksilön geenisekvenssien perusteella. Käytetyistä mikrosatelliittisekvensseistä voidaan rakentaa geneettinen samankaltaisuusverkko usealla eri tavalla. Työssä kokeiltiin useita tällaisia tapoja, joista sopivin valittiin käyttöön. Useimpia verkostotieteen menetelmiä ei ole suunniteltu sovellettaviksi täysiin painotettuihin verkkoihin, joita tässä työssä käytetyt samankaltaisuusverkot ovat. Tästä johtuen osa verkostomenetelmistä jouduttiin muokkaamaan samankaltaisuusverkoille sopiviksi sekä laskennalliselta toteutukseltaan että yleiseltä toiminnaltaan. Työssä tutkitaan yhteisönhakumenetelmien löytämien geneettisten ryhmien rakennetta sekä vertaillaan näiden suhdetta maantieteeseen ja samoille yksilöille rakennettuun fylogeniapuuhun. Käytetyistä verkostomenetelmistä löydetään useita puutteita ja rajoituksia, mutta näihin ongelmiin ehdotetaan ratkaisuja ja viitoitetaan samalla tietä mahdolliselle lisätutkimukselle.

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