Adding Value to Message Mediation in Multioperator MMS Network Architecture

Mobiiliviestintään käytetystä lyhytsanomapalvelusta (Short Messaging Service, SMS) on tullut ilmiömäinen menestys. SMS-palvelulle on tulossa seuraaja, jota kutsutaan monimediaviestipalveluksi (Multimedia Messaging Service, MMS). MMS-viestit voivat sisältää useita erilaisia kuva-, ääni- ja videoformaatteja. Vaikka yhteensopimattomia SMS-keskuksia yhdistämään tarvitaan Intellitel Messaging Gatewayn kaltaisia sanomanvälitystuotteita, ei tällainen SMS-keskeinen lähestyminen sanomanvälitykseen ole MMS-kykyisen sanomanvälittimen kannalta järkevä ratkaisu. MMS-kykyisen sanomanvälittimen täytyy lisätä arvoa itse sanomanvälitysprosessiin, jotta tuotteesta tulisi menestyksekäs. Tässä työssä käsitellään MMS-sanomanvälityksen ongelmallisuuksia. Erityisesti painotetaan MMS-kykyisen sanomanvälittimen kehittämistä olemassaolevasta SMS-sanomanvälitintuotteesta, sekä selvitetään syitä arvonlisäyksen välttämättömyydelle. Työssä esitetään myös erilaisia arvonlisäystapoja MMS-sanomanvälitykseen. Eräitä esitetyistä arvonlisäystavoista käytetään käytännön osassa toteutetussa Nokian MMS-keskuksen MM7/VAS-rajapintaan kytkeytymään kykenevässä sanomanvälityskomponentissa.

High Performance Electrical Drive System for a Biomechanical Test and Rehabilitation Equipment

Suunniteltiin ja rakennettiin suoraa vääntömomenttisäätöä soveltava taajuudenmuuttajakäyttö oikosulkumoottorin ohjaukseen korvaamaan passiivinen jarrukäyttö. Laite on kuntoutuslaite, jolla tehdään lihasvoiman mittauksia ja voimaharjoituksia. Selvitettiin kaupallisten moottoreiden ja taajuudenmuuttajien suoritusominaisuuksia ja tämän perusteella valittiin käyttöön sopivat laitteet. Työssä esitetään kaksi oikosulkumoottorin ohjaustapaa: vektorisäätö ja suora vääntömomenttisäätö. Merkittävin osa tästä työstä käsittelee - tarkan turvallisuussuunnitelman lisäksi - kuntoutuslaitteen prototyypin komponentteja, kokoamista ja suoritustestien tuloksia.

Kaakkois-Suomen metsäklusterin innovatiiviset kehittämisprosessit

Avoin globaali liiketoimintaympäristö tuo jatkuvasti uusia haasteita metsäteollisuudelle ja sitä kautta koko metsäklusterille, ja kilpailussa menestyminen edellyttää proaktiivista lähestymistapaa. Diplomityön tarkoituksena on kartoittaa metsäklusterin tulevaisuudennäkymiä sekä esittää näkemyksiä ja ajatuksia siitä, miten Kaakkois-Suomen osaamiskeskus (Koske) voisi jatkossa omalta osaltaan edesauttaa Kaakkois-Suomen metsäklusterin edellytyksiä menestyä globaalissa kilpailussa. Työssä on hyödynnetty skenaariomenetelmää, jonka tuloksena syntyi metsäklusterin skenaarionelikenttä. Tutkimus toi esille myös näkemyksiä siitä, mitä skenaarionelikentän skenaarioista Kaakkois-Suomessa tulisi lähteä aktiivisesti tavoittelemaan, ja millaisia toimenpiteitä tämä edellyttää. Kun perinteiset kilpailuedun lähteet murentuvat, ja tuotanto sekä kysyntä siirtyvät yhä enemmän nouseville talousalueille, on toimintatavoissa tapahduttava merkittäviä muutoksia. Tavoiteltava skenaario mahdollistaa pääsyn uusille kasvumarkkinoille innovatiivisuuden ja asiakaslähtöisyyden kautta sekä edellyttää tehokkaamman metsäklusteria tukevan innovaatioketjun rakentamista, eli panostusta alueelliseen innovaatioympäristöön. Mallissa tuetaan pienten, innovatiivisten, yritysten alkutaivalta tarjoamalla niille tukea, osaamista ja rahoitusta. Innovaatioympäristön kehittäminen voisi tapahtua laajan alueellisen ohjelman avulla. Kuitenkin myös pienemmillä kehityshankkeilla on tärkeä merkitys päämäärien saavuttamisessa.

Omistajalähtöinen johtaminen ja ylimmän johdon palkitseminen - näkökohtia hallitustyöskentelyyn

Tutkielman tavoitteena on selvittää miten hallituksen tulisi johtaa ja valvoa yritystä ja palkita sen ylintä johtoa, jotta yritykselle asetetut tavoitteet saavutetaan ja omistajien edut varmistetaan. Tutkimus on käsiteanalyyttinen ja perustuu olemassa olevaan doktriiniin. Omistajien aktivoituminen ilmenee heidän lisääntyneenä kiinnostuksena hallitustyöskentelystä. Hallituksissa on yhä enemmän omistajien edustajia, jotka johtavat yritystä siten, että sen omistaja-arvo nousee ja omistajat vaurastuvat. Corporate governance -suositukset antavat ohjeita yrityksen hallituksen kokoonpanosta, jäsenten ominaisuuksista ja hallituksen tehtävistä. Hallituksen jäsenillä tulee olla taitoa ja kokemusta ajaa omistajien etuja. Hallituksen alaisuuteen suositellaan perustettavaksi palkitsemiskomitea ulkopuolisista hallituksen jäsenistä. Palkitsemiskomitean tehtävänä on määrittää palkitsemisjärjestelmät, joilla yrityksen johto saadaan työskentelemään omistajien etujen mukaisesti.

Strategisten reaalioptioiden mallintaminen Monte Carlo -simulointimenetelmällä, case Voest Alpine Stahl Ag

Tutkielman päätavoitteena oli selvittää, miten Monte Carlo –simulointi soveltuu strategisten reaalioptioiden arvonmääritykseen. Tutkielman teoriaosuudessa käytiin läpi reaalioptioteoriaa ja Monte Carlo –simulointimenetelmää toiminta-analyyttisella tutkimusotteella. Tuloksena todettiin, että simulointimenetelmää on reaalioptioiden yhteydessä yleensä käytetty, kun muu menetelmä ei ole ollut mahdollinen. Tutkielman pääpaino on tapaustutkimukseen pohjautuvassa empiriaosuudessa, jossa rakennettiin päätöksentekometodologista tutkimusotetta seuraten simulointimalli, jolla tutkittiin Voest Alpine Stahl Ag:n vaihtoehtoisten hinnoittelustrategioiden taloudellista vaikutusta. Mallin rakentaminen perustui yrityksen tilinpäätösaineistoon. Havaittiin, ettei yritys ole valitsemansa strategian vuoksi juurikaan menettänyt tuottoja, mutta toisaalta pelkkä tilinpäätösaineisto ei riitä kovin luotettavaan tarkasteluun. Vuosikertomusten antaman tiedon pohjalta analysoitiin lisäksi yrityksen toiminnassa havaittuja reaalioptioita. Monte Carlo –simulointimenetelmä sopii reaalioptioiden arvonmääritykseen, mutta kriittisiä tekijöitä ovat mallin rakentaminen ja lähtötietojen oikeellisuus. Numeerisen mallin rinnalla on siksi aiheellista suorittaa myös laadullista reaalioptioanalyysia.

Operational Reliability Analysis of a Three-Tiered Thin-Client ERP-system in an International Corporate Environment

Internationalization and the following rapid growth have created the need to concentrate the IT systems of many small-to-medium-sized production companies. Enterprise Resource Planning systems are a common solution for such companies. Deployment of these ERP systems consists of many steps, one of which is the implementation of the same shared system at all international subsidiaries. This is also one of the most important steps in the internationalization strategy of the company from the IT point of view. The mechanical process of creating the required connections for the off-shore sites is the easiest and most well-documented step along the way, but the actual value of the system, once operational, is perceived in its operational reliability. The operational reliability of an ERP system is a combination of many factors. These factors vary from hardware- and connectivity-related issues to administrative tasks and communication between decentralized administrative units and sites. To accurately analyze the operational reliability of such system, one must take into consideration the full functionality of the system. This includes not only the mechanical and systematic processes but also the users and their administration. All operational reliability in an international environment relies heavily on hardware and telecommunication adequacy so it is imperative to have resources dimensioned with regard to planned usage. Still with poorly maintained communication/administration schemes no amount of bandwidth or memory will be enough to maintain a productive level of reliability. This thesis work analyzes the implementation of a shared ERP system to an international subsidiary of a Finnish production company. The system is Microsoft Dynamics Ax, currently being introduced to a Slovakian facility, a subsidiary of Peikko Finland Oy. The primary task is to create a feasible base of analysis against which the operational reliability of the system can be evaluated precisely. With a solid analysis the aim is to give recommendations on how future implementations are to be managed.

Performance benchmarking and incentive regulation – considerations of directing signals for electricity distribution companies

After the restructuring process of the power supply industry, which for instance in Finland took place in the mid-1990s, free competition was introduced for the production and sale of electricity. Nevertheless, natural monopolies are found to be the most efficient form of production in the transmission and distribution of electricity, and therefore such companies remained franchised monopolies. To prevent the misuse of the monopoly position and to guarantee the rights of the customers, regulation of these monopoly companies is required. One of the main objectives of the restructuring process has been to increase the cost efficiency of the industry. Simultaneously, demands for the service quality are increasing. Therefore, many regulatory frameworks are being, or have been, reshaped so that companies are provided with stronger incentives for efficiency and quality improvements. Performance benchmarking has in many cases a central role in the practical implementation of such incentive schemes. Economic regulation with performance benchmarking attached to it provides companies with directing signals that tend to affect their investment and maintenance strategies. Since the asset lifetimes in the electricity distribution are typically many decades, investment decisions have far-reaching technical and economic effects. This doctoral thesis addresses the directing signals of incentive regulation and performance benchmarking in the field of electricity distribution. The theory of efficiency measurement and the most common regulation models are presented. The chief contributions of this work are (1) a new kind of analysis of the regulatory framework, so that the actual directing signals of the regulation and benchmarking for the electricity distribution companies are evaluated, (2) developing the methodology and a software tool for analysing the directing signals of the regulation and benchmarking in the electricity distribution sector, and (3) analysing the real-life regulatory frameworks by the developed methodology and further develop regulation model from the viewpoint of the directing signals. The results of this study have played a key role in the development of the Finnish regulatory model.

A Dependency Parsing Approach to Biomedical Text Mining

Biomedical research is currently facing a new type of challenge: an excess of information, both in terms of raw data from experiments and in the number of scientific publications describing their results. Mirroring the focus on data mining techniques to address the issues of structured data, there has recently been great interest in the development and application of text mining techniques to make more effective use of the knowledge contained in biomedical scientific publications, accessible only in the form of natural human language. This thesis describes research done in the broader scope of projects aiming to develop methods, tools and techniques for text mining tasks in general and for the biomedical domain in particular. The work described here involves more specifically the goal of extracting information from statements concerning relations of biomedical entities, such as protein-protein interactions. The approach taken is one using full parsing—syntactic analysis of the entire structure of sentences—and machine learning, aiming to develop reliable methods that can further be generalized to apply also to other domains. The five papers at the core of this thesis describe research on a number of distinct but related topics in text mining. In the first of these studies, we assessed the applicability of two popular general English parsers to biomedical text mining and, finding their performance limited, identified several specific challenges to accurate parsing of domain text. In a follow-up study focusing on parsing issues related to specialized domain terminology, we evaluated three lexical adaptation methods. We found that the accurate resolution of unknown words can considerably improve parsing performance and introduced a domain-adapted parser that reduced the error rate of theoriginal by 10% while also roughly halving parsing time. To establish the relative merits of parsers that differ in the applied formalisms and the representation given to their syntactic analyses, we have also developed evaluation methodology, considering different approaches to establishing comparable dependency-based evaluation results. We introduced a methodology for creating highly accurate conversions between different parse representations, demonstrating the feasibility of unification of idiverse syntactic schemes under a shared, application-oriented representation. In addition to allowing formalism-neutral evaluation, we argue that such unification can also increase the value of parsers for domain text mining. As a further step in this direction, we analysed the characteristics of publicly available biomedical corpora annotated for protein-protein interactions and created tools for converting them into a shared form, thus contributing also to the unification of text mining resources. The introduced unified corpora allowed us to perform a task-oriented comparative evaluation of biomedical text mining corpora. This evaluation established clear limits on the comparability of results for text mining methods evaluated on different resources, prompting further efforts toward standardization. To support this and other research, we have also designed and annotated BioInfer, the first domain corpus of its size combining annotation of syntax and biomedical entities with a detailed annotation of their relationships. The corpus represents a major design and development effort of the research group, with manual annotation that identifies over 6000 entities, 2500 relationships and 28,000 syntactic dependencies in 1100 sentences. In addition to combining these key annotations for a single set of sentences, BioInfer was also the first domain resource to introduce a representation of entity relations that is supported by ontologies and able to capture complex, structured relationships. Part I of this thesis presents a summary of this research in the broader context of a text mining system, and Part II contains reprints of the five included publications.

Assessment of Coastal Bird Populations and Habitats on the Finnish Coast of the Baltic Sea: Implications for Monitoring and Management

Coastal birds are an integral part of coastal ecosystems, which nowadays are subject to severe environmental pressures. Effective measures for the management and conservation of seabirds and their habitats call for insight into their population processes and the factors affecting their distribution and abundance. Central to national and international management and conservation measures is the availability of accurate data and information on bird populations, as well as on environmental trends and on measures taken to solve environmental problems. In this thesis I address different aspects of the occurrence, abundance, population trends and breeding success of waterbirds breeding on the Finnish coast of the Baltic Sea, and discuss the implications of the results for seabird monitoring, management and conservation. In addition, I assess the position and prospects of coastal bird monitoring data, in the processing and dissemination of biodiversity data and information in accordance with the Convention on Biological Diversity (CBD) and other national and international commitments. I show that important factors for seabird habitat selection are island area and elevation, water depth, shore openness, and the composition of island cover habitats. Habitat preferences are species-specific, with certain similarities within species groups. The occurrence of the colonial Arctic Tern (Sterna paradisaea) is partly affected by different habitat characteristics than its abundance. Using long-term bird monitoring data, I show that eutrophication and winter severity have reduced the populations of several Finnish seabird species. A major demographic factor through which environmental changes influence bird populations is breeding success. Breeding success can function as a more rapid indicator of sublethal environmental impacts than population trends, particularly for long-lived and slowbreeding species, and should therefore be included in coastal bird monitoring schemes. Among my target species, local breeding success can be shown to affect the populations of the Mallard (Anas platyrhynchos), the Eider (Somateria mollissima) and the Goosander (Mergus merganser) after a time lag corresponding to their species-specific recruitment age. For some of the target species, the number of individuals in late summer can be used as an easier and more cost-effective indicator of breeding success than brood counts. My results highlight that the interpretation and application of habitat and population studies require solid background knowledge of the ecology of the target species. In addition, the special characteristics of coastal birds, their habitats, and coastal bird monitoring data have to be considered in the assessment of their distribution and population trends. According to the results, the relationships between the occurrence, abundance and population trends of coastal birds and environmental factors can be quantitatively assessed using multivariate modelling and model selection. Spatial data sets widely available in Finland can be utilised in the calculation of several variables that are relevant to the habitat selection of Finnish coastal species. Concerning some habitat characteristics field work is still required, due to a lack of remotely sensed data or the low resolution of readily available data in relation to the fine scale of the habitat patches in the archipelago. While long-term data sets exist for water quality and weather, the lack of data concerning for instance the food resources of birds hampers more detailed studies of environmental effects on bird populations. Intensive studies of coastal bird species in different archipelago areas should be encouraged. The provision and free delivery of high-quality coastal data concerning bird populations and their habitats would greatly increase the capability of ecological modelling, as well as the management and conservation of coastal environments and communities. International initiatives that promote open spatial data infrastructures and sharing are therefore highly regarded. To function effectively, international information networks, such as the biodiversity Clearing House Mechanism (CHM) under the CBD, need to be rooted at regional and local levels. Attention should also be paid to the processing of data for higher levels of the information hierarchy, so that data are synthesized and developed into high-quality knowledge applicable to management and conservation.

Use of the Optical Cantilever Microphone in Photoacoustic Spectroscopy

A novel cantilever pressure sensor was developed in the Department of Physics at the University of Turku in order to solve the sensitivity problems which are encountered when condenser microphones are used in photoacoustic spectroscopy. The cantilever pressure sensor, combined with a laser interferometer for the measurement of the cantilever movements, proved to be highly sensitive. The original aim of this work was to integrate the sensor in a photoacoustic gas detector working in a differential measurement scheme. The integration was made successfully into three prototypes. In addition, the cantilever was also integrated in the photoacoustic FTIR measurement schemes of gas-, liquid-, and solid-phase samples. A theoretical model for the signal generation in each measurement scheme was created and the optimal celldesign discussed. The sensitivity and selectivity of the differential method were evaluated when a blackbody radiator and a mechanical chopper were used with CO₂, CH4, CO, and C2H4 gases. The detection limits were in the sub-ppm level for all four gases with only a 1.3 second integration time and the cross interference was well below one percent for all gas combinations other than those between hydrocarbons. Sensitivity with other infrared sources was compared using ethylene as an example gas. In the comparison of sensitivity with different infrared sources the electrically modulated blackbody radiator gave a 35 times higher and the CO2-laser a 100 times lower detection limit than the blackbody radiator with a mechanical chopper. As a conclusion, the differential system is well suited to rapid single gas measurements. Gas-phase photoacoustic FTIR spectroscopy gives the best performance, when several components have to be analyzed simultaneously from multicomponent samples. Multicomponent measurements were demonstrated with a sample that contained different concentrations of CO₂, H₂O, CO, and four different hydrocarbons. It required an approximately 10 times longer measurement time to achieve the same detection limit for a single gas as with the differential system. The properties of the photoacoustic FTIR spectroscopy were also compared to conventional transmission FTIR spectroscopy by simulations. Solid- and liquid-phase photoacoustic FTIR spectroscopy has several advantages compared to other techniques and therefore it also has a great variety of applications. A comparison of the signal-to-noise ratio between photoacoustic cells with a cantilever microphone and a condenser microphone was done with standard carbon black, polyethene, and sunflower oil samples. The cell with the cantilever microphone proved to have a 5-10 times higher signal-to-noise ratio than the reference detector, depending on the sample. Cantilever enhanced photoacoustics will be an effective tool for gas detection and analysis of solid- and liquid-phase samples. The preliminary prototypes gave good results in all three measurement schemes that were studied. According to simulations, there are possibilities for further enhancement of the sensitivity, as well as other properties, of each system.

Knapsack sets for cryptography

The basic goal of this study is to extend old and propose new ways to generate knapsack sets suitable for use in public key cryptography. The knapsack problem and its cryptographic use are reviewed in the introductory chapter. Terminology is based on common cryptographic vocabulary. For example, solving the knapsack problem (which is here a subset sum problem) is termed decipherment. Chapter 1 also reviews the most famous knapsack cryptosystem, the Merkle Hellman system. It is based on a superincreasing knapsack and uses modular multiplication as a trapdoor transformation. The insecurity caused by these two properties exemplifies the two general categories of attacks against knapsack systems. These categories provide the motivation for Chapters 2 and 4. Chapter 2 discusses the density of a knapsack and the dangers of having a low density. Chapter 3 interrupts for a while the more abstract treatment by showing examples of small injective knapsacks and extrapolating conjectures on some characteristics of knapsacks of larger size, especially their density and number. The most common trapdoor technique, modular multiplication, is likely to cause insecurity, but as argued in Chapter 4, it is difficult to find any other simple trapdoor techniques. This discussion also provides a basis for the introduction of various categories of non injectivity in Chapter 5. Besides general ideas of non injectivity of knapsack systems, Chapter 5 introduces and evaluates several ways to construct such systems, most notably the "exceptional blocks" in superincreasing knapsacks and the usage of "too small" a modulus in the modular multiplication as a trapdoor technique. The author believes that non injectivity is the most promising direction for development of knapsack cryptosystema. Chapter 6 modifies two well known knapsack schemes, the Merkle Hellman multiplicative trapdoor knapsack and the Graham Shamir knapsack. The main interest is in aspects other than non injectivity, although that is also exploited. In the end of the chapter, constructions proposed by Desmedt et. al. are presented to serve as a comparison for the developments of the subsequent three chapters. Chapter 7 provides a general framework for the iterative construction of injective knapsacks from smaller knapsacks, together with a simple example, the "three elements" system. In Chapters 8 and 9 the general framework is put into practice in two different ways. Modularly injective small knapsacks are used in Chapter 9 to construct a large knapsack, which is called the congruential knapsack. The addends of a subset sum can be found by decrementing the sum iteratively by using each of the small knapsacks and their moduli in turn. The construction is also generalized to the non injective case, which can lead to especially good results in the density, without complicating the deciphering process too much. Chapter 9 presents three related ways to realize the general framework of Chapter 7. The main idea is to join iteratively small knapsacks, each element of which would satisfy the superincreasing condition. As a whole, none of these systems need become superincreasing, though the development of density is not better than that. The new knapsack systems are injective but they can be deciphered with the same searching method as the non injective knapsacks with the "exceptional blocks" in Chapter 5. The final Chapter 10 first reviews the Chor Rivest knapsack system, which has withstood all cryptanalytic attacks. A couple of modifications to the use of this system are presented in order to further increase the security or make the construction easier. The latter goal is attempted by reducing the size of the Chor Rivest knapsack embedded in the modified system. '

Technological and business challenges of smart grids

Growing recognition of the electricity grid modernization to enable new electricity generation and consumption schemes has found articulation in the vision of the Smart Grid platform. The essence of this vision is an autonomous network with two-way electricity power flows and extensive real-time information between the generation nodes, various electricity-dependent appliances and all points in-between. Three major components of the Smart Grids are distributed intelligence, communication technologies, and automated control systems. The aim of this thesis is to recognize the challenges that Smart Grids are facing, while extinguishing the main driving factors for their introduction. The scope of the thesis also covers possible place of electricity Aggregator Company in the current and future electricity markets. Basic functions of an aggregator and possible revenue sources along with demand response feasibility calculations are reviewed within this thesis.

Multilevel converter modulation: implementation and analysis

Multilevel converters provide an attractive solution to bring the benefits of speed-controlled rotational movement to high-power applications. Therefore, multilevel inverters have attracted wide interest in both the academic community and in the industry for the past two decades. In this doctoral thesis, modulation methods suitable especially for series connected H-bridge multilevel inverters are discussed. A concept of duty cycle modulation is presented and its modification is proposed. These methods are compared with other well-known modulation schemes, such as space-vector pulse width modulation and carrier-based modulation schemes. The advantage of the modified duty-cycle modulation is its algorithmic simplicity. A similar mathematical formulation for the original duty cycle modulation is proposed. The modified duty cycle modulation is shown to produce well-formed phase-to-neutral voltages that have lower total harmonic distortion than the space-vector pulse width modulation and the duty cycle modulation. The space-vector-based solution and the duty cycle modulation, on the other hand, result in a better-quality line-to-line voltage and current waveform. The voltage of the DC links in the modules of the series-connected H-bridge inverter are shown to fluctuate while they are under load. The fluctuation causes inaccuracies in the voltage production, which may result in a failure of the flux estimator in the controller. An extension for upper-level modulation schemes, which changes the switching instants of the inverter so that the output voltage meets the reference voltage accurately regardless of the DC link voltages, is proposed. The method is shown to reduce the error to a very low level when a sufficient switching frequency is used. An appropriate way to organize the switching instants of the multilevel inverter is to make only one-level steps at a time. This causes restrictions on the dynamical features of the modulation schemes. The produced voltage vector cannot be rotated several tens of degrees in a single switching period without violating the above-mentioned one-level-step rule. The dynamical capabilities of multilevel inverters are analyzed in this doctoral thesis, and it is shown that the multilevel inverters are capable of operating even in dynamically demanding metal industry applications. In addition to the discussion on modulation schemes, an overvoltage in multilevel converter drives caused by cable reflection is addressed. The voltage reflection phenomenon in drives with long feeder cables causes premature insulation deterioration and also affects the commonmode voltage, which is one of the main reasons for bearing currents. Bearing currents, on the other hand, cause fluting in the bearings, which results in premature bearing failure. The reflection phenomenon is traditionally prevented by filtering, but in this thesis, a modulationbased filterless method to mitigate the overvoltage in multilevel drives is proposed. Moreover, the mitigation method can be implemented as an extension for upper-level modulation schemes. The method exploits the oscillations caused by two consecutive voltage edges so that the sum of the oscillations results in a mitigated peak of the overvoltage. The applicability of the method is verified by simulations together with experiments with a full-scale prototype.

A generalized 1D particle transport method for convection diffusion reaction model

This work is devoted to the development of numerical method to deal with convection diffusion dominated problem with reaction term, non - stiff chemical reaction and stiff chemical reaction. The technique is based on the unifying Eulerian - Lagrangian schemes (particle transport method) under the framework of operator splitting method. In the computational domain, the particle set is assigned to solve the convection reaction subproblem along the characteristic curves created by convective velocity. At each time step, convection, diffusion and reaction terms are solved separately by assuming that, each phenomenon occurs separately in a sequential fashion. Moreover, adaptivities and projection techniques are used to add particles in the regions of high gradients (steep fronts) and discontinuities and transfer a solution from particle set onto grid point respectively. The numerical results show that, the particle transport method has improved the solutions of CDR problems. Nevertheless, the method is time consumer when compared with other classical technique e.g., method of lines. Apart from this advantage, the particle transport method can be used to simulate problems that involve movingsteep/smooth fronts such as separation of two or more elements in the system.

Distributed ControlArchitecture of Power Electronics Building-Block-Based Frequency Converters

The increasing power demand and emerging applications drive the design of electrical power converters into modularization. Despite the wide use of modularized power stage structures, the control schemes that are used are often traditional, in other words, centralized. The flexibility and re-usability of these controllers are typically poor. With a dedicated distributed control scheme, the flexibility and re-usability of the system parts, building blocks, can be increased. Only a few distributed control schemes have been introduced for this purpose, but their breakthrough has not yet taken place. A demand for the further development offlexible control schemes for building-block-based applications clearly exists. The control topology, communication, synchronization, and functionality allocationaspects of building-block-based converters are studied in this doctoral thesis. A distributed control scheme that can be easily adapted to building-block-based power converter designs is developed. The example applications are a parallel and series connection of building blocks. The building block that is used in the implementations of both the applications is a commercial off-the-shelf two-level three-phase frequency converter with a custom-designed controller card. The major challenge with the parallel connection of power stages is the synchronization of the building blocks. The effect of synchronization accuracy on the system performance is studied. The functionality allocation and control scheme design are challenging in the seriesconnected multilevel converters, mainly because of the large number of modules. Various multilevel modulation schemes are analyzed with respect to the implementation, and this information is used to develop a flexible control scheme for modular multilevel inverters.