Hand held mobile devices are widely used today primarily due to their rich functionality and the ease of portability. However, the battery life of these devices is very limited and deploying resource hungry applications such as streaming on these mobile devices is a challenging task. It is extremely important to maximize the efficient use of the contained resources on these devices especially when they participate in a mobile ad hoc network. The optimization can occur in any layer of the OSI stack, however, this thesis work focuses only on the routing protocols used in the network layer. In this thesis work we have been able to evaluate the Energy Efficiency of the four most widely used MANET routing protocols (AODV, OLSR, DSDV and DSR) in terms of their energy consumption and performance. The initial phase of the work was carried out using the Network Simulator 2(NS2) tool and later the observations were done on a real world MANET testbed. The influence of several external factors on the performance and energy consumption are also taken into consideration while performing the simulations and experiments. The results obtained from our observations provide both qualitative and quantitative analysis of the routing protocols. Furthermore, it also highlights how the behaviour of the protocols are sometimes highly unpredictable, yielding results that we may not expect.

Like conventional networks, security is also a big concern in wireless sensor networks. However, security in this type of networks faces not only typical but also new challenges. Constrained devices, changing topology or susceptibility to unprecedented security threats such as node capture and node compromise has refrained developers from applying conventional security solutions into wireless sensor networks. Hence, developing security solutions for wireless sensor networks not only requires well security analysis but also offers a low power and processing consuming.In this thesis, we implemented security solution targeting IRIS sensor motes. In our implementation, a public key-based key exchange is used to establish shared secret keys between sensor nodes. These secret keys are used to provide authenticity, integrity and freshness for transmission data. Our implementation ensures the flexibility in integrating our solution with available TinyOS operating system. Additionally, the thesis work also focuses on evaluating the performance in wireless sensor networks both in memory and energy consuming.

Hybrid optical packet/circuit switched networking architectures are increasingly becoming an interesting research field. They integrate and combine the high resource utilization of statistically multiplexed packet switched networks with the low processing requirements and guaranteed quality of service provided by circuit switched networks. The aim of this thesis is to integrate the OpMiGua hybrid optical network with Ethernet. Specifically, the work is focused on the compatibility of the Ethernet’s loop-free topology protocols with the redundant multiple traffic service paths of OpMiGua. We analyse the problems and limitations imposed on the network architecture and propose our topology solution called the SM chain-connectivity. The analysis and the proposed schemes are verified based on results obtained from simulations. Furthermore, we design an integrated logical OpMiGua node that relies on an Ethernet switch instead of the Optical Packet Switch for the Statistically Multiplexed traffic. To date, to our knowledge there are no studies analysing the compatibility of Ethernet and its protection mechanisms in a hybrid optical network. This is the first work addressing the use of Ethernet in OpMiGua.

Cloud computing has gained remarkable popularity in the recent years by a wide spectrum of consumers, ranging from small start-ups to governments. However, its benefits in terms of flexibility, scalability, and low upfront investments, are shadowed by security challenges which inhibit its adoption. In particular, these highly flexible but complex cloud computing environments are prone to misconfigurations leading to security incidents, eg, erroneous exposure of services due to faulty network security configurations. In this thesis we present a novel approach in the security assessment of multi-tier architectures deployed on infrastructure clouds such as Amazon EC2. In order to perform this assessment for the currently deployed configuration, we automated the process of extracting the configuration using the Amazon API and translating it into a generic data model for later analysis. In the assessment we focused on the reachability and vulnerability of services in the virtual infrastructure, and presented a way for the visualization andautomated analysis based on reachability and attack graphs. We proposed a query and policy language for the analysis which can be used to obtain insights into the configuration and to specify desired and undesired configurations. We have implemented the security assessment in a prototype and evaluated it for practical andtheoretical scenarios. Furthermore, a framework is presented which allows the evaluation of configuration changes in the agile and dynamic cloud environments with regard to properties like vulnerabilities or expected availability. In case of a vulnerability perspective, this evaluation can be used to monitor the securitylevels of the configuration over its lifetime and to indicate degradations.

Nowadays, verification of programs is gaining increased importance. The software industry appears more and more interested in methods and tools to ensure security in their applications. Java Modeling Language has been successfully used in the past by programmers to express their intentions in the Design by Contract fashion in sequential programming. One of the design goals of JML was to improve the functional software correctness of Java applications. Regarding the verification of security properties, JML was mostly successful in Java Smart Card applets due to the specifics of these applications. In this thesis work we investigate the feasibility of JML to express high-level security properties in Java applications that have more realistic requirements and are implemented in the object oriented technology. We do a threat analysis of a case study regarding a medical clinic and derive the required security properties to secure the application. We develop a prototype application where we specify high-level security properties with JML and use a runtime assertion checking tool to verify the code. We model the functional behavior of the prototype that establishes the security proper-ties as a finite state automaton. Our prototype is developed based on this automaton. States and state transitions modeled in the automaton are expressed in the prototype with JML annotations and verified during runtime. We observe that currently available features in JML are not very feasible to capture the security related behavior of Java programs on the level of the entire application.

I denne rapporten er synkrongeneratorens dynamiske oppførsel studert ved direkte faseavbrudd på tre-fase overføringslinjer i regionalnettet, via datamaskinbasert modellering og simulering. Ved feil studeres virkningen av spenningsregulator basert på statisk magnetisering, ulike typer turbinregulatorer, forskjellige koplingsgrupper for transformatorer og tiltak som dempetilsats (PSS). Bakgrunnen for denne oppgaven baserer seg på et reelt tilfelle med faseavbrudd som oppstod i regionalnettet til NTE den 7. mars 2008. Dette førte til at synkrongeneratorene tilknyttet 66 kV nettet fikk ukontrollerte effektpendlinger. Utfordringer ved faseavbrudd i kraftsystemer, uavhengig av om det er på overføringslinjene eller i elektriske komponenter, er kjent innenfor drift av kraftsystemet. Statistikk fra *FASIT for hele Norge i perioden 2001-2004 viser at av 37163 driftsforstyrrelser var 2073 faseavbrudd. Til tross for dette har det ikke vært mulig å finne relevant litteratur som detaljert beskriver den elektromekaniske oppførselen til synkrongenerator ved direkte faseavbrudd på en av fasene ved tre-fase kraftoverføring. Som en del av arbeidet er det etablert en simuleringsmodell av R-nettet til NTE i tillegg til et antall forenklete modeller. Det er foretatt simuleringer som viser endringene som funksjon av tiden i aktiv effekt, polhjulsvinkel, spenning og strøm på synkrongeneratorer ved faseavbrudd. Resultater fra simuleringene i de forenklete modellene viser at et faseavbrudd ikke nødvendigvis medfører ukontrollerte effektpendlinger. Det viser seg at synkrongeneratoren kan svinge seg inn mot et nytt arbeidspunkt i en driftssituasjon med varig faseavbrudd. Ulike regulatorer sammen med total systemimpedans, koplingsgruppe for transformatorer og lastforbruk avgjør hvor stabilt systemet blir. Resultater for simuleringene av R-nettet viser at faseavbrudd, tilsvarende det som oppstod i 2008, gir ukontrollerte effektpendlinger. Dempetilsats (PSS) er innført som tiltak, og det er vist at denne kan være i stand til å dempe pendlingene i startfasen slik at de ikke utarter seg til udempete svingninger. *FASIT – Feil og AvbruddsStatistikk I Totalnettet – Referansegruppe for feil og avbrudd ble opprettet 13.03.1996 og består av representanter fra NVE, Statnett og EnergiAkademiet (EBL). I tillegg er Lier Everk, Troms Kraft Nett AS, Istad Nett AS og Sintef Energiforskning for tiden representert. www.fasit.no

The increased demand of offshore power conversion systems is driven by newly initiated offshore projects for wind farms and oil production. Because of long distances to shore and inaccessibility of the equipment long repair times must be expected. At the same time the offshore environment is extremely harsh. Thus, high reliability is required for the converters and it is important to have good knowledge of the switching devices. This thesis investigates switching characteristics and losses of commercially available IGBT modules to be used for this application. It focuses on switching time and switching energy losses depending on gate resistance, current and voltage levels, operation temperatures, and show differences between several devices of the same type. Some test show how device characteristics and losses when the device has been exposed to stress over a certain period.

This Master’s Thesis work deals with the development of improved hydro turbine models for the evaluation of a hydraulic power generating system performance in response to small disturbances in power system analysis tool. These improved models must be able to reflect the possible interaction between the hydraulic system and power system in the computer simulations of a power plant equipped with Francis turbines.The accuracy of a Hydraulic Power Generating System is studied by means of analysis of the dynamic behaviour of different models of the hydraulic machine and conduit system. The stability study of different models for Synchronous Machines and Turbine Governing System are beyond the scope of this work.Appropriate representations of the hydraulic turbine and conduit system are developed in various models of varying degrees of detail. Firstly, nonlinear models for a simple turbine without surge tank considering the inelastic and elastic travelling wave effects have been developed. After that, nonlinear models considering the inelastic and elastic travelling wave effects for a turbine with surge tank for Hydropower Systems with long length penstocks are implemented. Finally, the nonlinear models for a turbine with long length penstocks are linearized at an operating point considering both the nonlinear turbine characteristics and the travelling wave effects.The Master’s Thesis work is divided into three parts. The first part, comprising Chapters 2 to 8, reviews the physical characteristics and mathematical models of the components of a hydraulic power generating system. The influence of each component of the power system by means of appropriate mathematical models is essential for the understanding of system stability. The second part, comprising Chapters 9 to 11, deals with the dynamic study of the system stability characteristics of the different hydraulic power generating system models implemented in SIMPOW and LVTrans. Finally, the third part, Chapter 12 and Chapter 13, presents the discussion of the simulation results of the hydroelectric power system models, and draws general conclusions on this work and suggests possibilities for the approach further work, respectively.It was concluded that approaches based on nonlinear and linear models including the elasticity of the conduit system and the nonlinear turbine characteristics extracted from the Hill Charts, are the most accurate models for any acceptable study of the interaction between hydraulic system and power system.The study of dynamic performance and interaction between the hydraulic system and power system of these extended linear and nonlinear models including the elastic water hammer effect and varying the nonlinear characteristics of the hydraulic turbine must be studied in detail.

Clustering is currently more and more applied on hyperlinked documents, especially for web search results. Although most commercial web search engines will provide their ranking algorithms sorting the matched results to raise the most relevant pages to the top, the size of results is still so huge that most ones including some pages that suffers are really interested in will be discarded. Clustering for web search results separates unrelated pages and clusters the similar pages with the same topic into the same group, thus helps suffers to locate the pages much faster. Many features of web pages have been studied to be used in clustering, such as content information including title, snippet, anchor text and etc. Hyperlink is another primary feature of web pages, some content-link coupled clustering methods have been studied. We propose an authoritative K-Means clustering method that combines content, in-link, out-link and page rank. In this project, we adjust the construction of in-link and out-link vectors and introduce a new page rank vector with two patterns, one is a single value representation of page rank and the other is a 11-dimensional vector. We study the difference of these two types of page rank in clustering, and compare the different clustering based on different web page representations, such as content-based, content-link coupled and etc. The effect of different elements of web page is also studied in our project. We apply the authoritative clustering for the web search results retrieved from Google search engine. Three experiments are conducted and different evaluation metrics are adopted to analyze the results.

This project work is about mobile learning system that will enable people to learn and collaborate anywhere and at anytime. It is the continuation of the work carried out in autumn 2009, by Noble and Izaz.In this project work, a Mobile Collaborative Learning System (MCLS) prototype was designed and implemented. The project work has been carried out according to the design science research methodology. An evaluation of the usability of the prototype was conducted. Mobile Services Acceptance Model (MSAM) was used to analyze factors that are influential for user adoption of the prototype.The results from the evaluation indicated that the majority of the test users perceived the prototype to be useful and they intend to use the prototype if they have access to it. These results confirm how useful and beneficial the prototype would be to students.