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A lot has changed since that day on December 17, 1903 when the Wright brothers made the first powered manned flight. Even though the concepts behind flying are unaltered, appearance of stat-of-the-art modern aircrafts has undergone a massive evolution. This is mainly owed to our deeper understanding of how to harness and optimize the interaction between fluid flows and aircraft bodies. Flow passing over wings and different junctions on an aircraft faces numerous local features, for instance, acceleration or deceleration, laminar or turbulent state, and interacting boundary layers. In our study we aim to characterize some of these flow features and their physical roles. Primarily, stability characteristics of flow over a wing subject to a negative pressure gradient are studied. This is a common condition for flows over swept wings. Part of the current numerical study conforms to existing experimental studies where a passive control mechanism has been tested to delay laminarturbulent transition. The same flow type has also been considered to study the receptivity of three-dimensional boundary layers to freestream turbulence. The work entails investigation of effects of low-level freestream turbulence on crossflow instability, as well as interaction with micron-sized surface roughness elements. Another common three-dimensional flow feature arises as a resultof stream-lines passing through a junction, the so-calledcorner-flow. For instance, thisflow can be formed in the junction between the wing and fuselage on aplane.A series of direct numerical simulations using linear Navier-Stokes equationshave been performed to determine the optimal initial perturbation. Optimalrefers to perturbations which can gain the maximum energy from the flow overa period of time. In other words this method seeks to determine theworst-casescenario in terms of perturbation growth. Here, power-iterationtechnique hasbeen applied to the Navier-Stokes equations and their adjoint to determine theoptimal initial perturbation. Recent advances in super-computers have enabled advance computational methods to increasingly contribute to design of aircrafts, in particular for turbulent flows with regions of separation. In this work we investigate theturbulentflow on an infinite wing at a moderate chord Reynolds number of Re= 400,000 using a well resolved direct numerical simulation. A conventional NACA4412 has been chosen for this work. The turbulent flow is characterizedusing statistical analysis and following time history data in regions with interesting flow features. In the later part of this work, direct numerical simulation has been chosen as a tool to mainly investigate the effect of freestream turbulence on the transition mechanism of flow from laminar to turbulent around a turbine blade. QC 20151125

The unit of Cognitive Developmental Neuroscience at Karolinska Institutet have developed a method for measuring cognitive performance with handheld devices, which resulted in a mobile application for the iPod Touch. The application was previously used in a clinical trial with individuals suffering from chronic stress disorder, but had to be further developed. The application, which consisted of cognitive tests and questionnaires, required improvements that could be divided into three parts: (1) a long-term memory test, (2) presentation of results and progress, and (3) an interface comprehensible to individuals with cognitive impairments. The work of this thesis was to process a requirement specification and research the areas of long-term memory testing, data presentation, and usability. The findings were used to come up with design suggestions for the application, and eventually implement them. The application was developed using C# and the MonoTouch SDK, to make it run on the iPod Touch. Distributed to physical devices, the application was finally evaluated to make sure the requirements were satisfied. Presentation and evaluation of the application were done with people from Karolinska Institutet. The results from the long-term memory test suggested it was sometimes too easy remembering items, and in a few cases even a ceiling effect appeared. However, the future target group, which was individuals with cognitive impairments, would likely perform less well on the test, and the test was therefore kept after discussion with the unit of Cognitive Developmental Neuroscience. The presentation of results as well as the navigation system were received with positive feedback.

In this thesis, new variants of nonnegative matrix factorization (NMF) based ona convolutional data model, -divergence and sparsication are developed andanalyzed. These NMF variants are collectively referred to as -CNMF. Commonsparsication techniques such as L1-norm minimization and elastic net arediscussed and a new regularizer is proposed. It is shown that the new regularizer,unlike the above-mentioned sparsication techniques, has control overthe number of active bases in the NMF dictionary. Moreover, the -CNMF isextended to multichannel signals: it learns a common dictionary by exploitingthe correlation between channels through a multichannel coecient matrix. Asa result, an algorithm for source separation based on multichannel -CNMF isdeveloped. The algorithm is further tested in a multilayer setting, in which thefrequency-shifted coecient matrices serve as input to the next higher layer.Finally, three variants of the algorithm are evaluated in the context of speechenhancement, focusing on the problem of speech extraction from complex auditoryscenes. Figures obtained from the SiSEC 2016 data show that the proposedalgorithms perform comparably or better than the state of the art. Den här rapporten behandlar utveckling och analys av nya varianter av icke-negativ matrisfaktorisering (eng: nonnegative matrix factorization, NMF), som baseras på en datormodell med faltning, β-divergens och glesa matriser. Dessa varianter av NMF:er kallas allmänt för β-CNMF:er, där C:et står för “convolutional”. Vidare diskuteras vanliga tekniker för regularisering, såsom L1-normminimering och elastiska nät, och en ny formulering för regularisering föreslås. Det visar sig att denna nya formulering, till skillnad från ovan nämnda regulariseringstekniker, möjliggör kontroll av antalet aktiva basfunktioner i NMF:ens bibliotek. Utöver detta så utökas även β-CNMF:en till att behandla multikanalsignaler genom att tränas på en gemensam bibliotek som utnyttjar korskorrelationen mellan kanalerna. Detta möjliggör utveckling av en algoritm för källseparation av multikanalsignaler. Vidare så testas algoritmen i multipla led, där frekvensskiftade koefficientmatriser i ett led utgör indata till nästa led. Slutligen så bedöms tre olika varianter av algoritmen för talförbättring, med fokus på extrahering av tal ur komplexa ljudmiljöer. Mätningar från SiSEC 2016 visar att den föreslagna algoritmen presterar lika bra eller överträffar nu-varande befintliga algoritmer.

“There is no need to reinvent the wheel” – a cliché, often told when you want to come up with something new that in someway can be connected to something that already exist. This study shows the opposite – that inventions emanate from what is given. It can be a detail, a problem in a thing - a wheel - or a situation that catches the inventor’s attention. It is something that seeks a solution or something that generates an idea, a hint or a clue of something new and useful. The art of invention emerges from the ability and skill to broaden the seeing and put thinking, substance and tradition into motion. An old radio dial generates a new ergonomic steering wheel. The connection of memories between a chestnut, a cello and an early morning at a water pump creates three works of art. The epistemology of this study is based on a dialogue between voices from different times and traditions. Some voices are normative examples, drawn from a dialogue between Swedish inventors. The others are those of philosophers from the Age of Enlightenment, fetched from their original writings. Through that dialogue, perspectives and ideas of inventors and classical philosophers meet and are compared. A deeper understanding thus emerges that shows the essence of invention and in fact the essence of all creative work: i) Freedom – in thought and in action ii) Dialogue - to test and try new ideas and things in the ever changing circumstances. iii) Doubt - not taking established fact and assumptions for granted iv) Action – testing and breaking established praxis and rules. The study also illustrates the need for an alternative scientific form and expression concerning studies in the fields of invention, innovation and other practical work. Invention can not be captured or shaped by exact measurements, concepts, definitions or abstract models. It takes place in the borderland between fact and fiction, where technique, aesthetics and philosophy are one working entity. The strive for knowledge is endless and without limits and it is nurtured by wondering, searching and ambiguity. With inspiration from the dialogue seminar method used within KTH Advanced Programme in Reflective Practice – this study point out the actuality and vitality in using the classical philosophical writings, dialogue and analogical thinking as a scientific method within higher education. QC 20100826

The largest modern Pure Car and Truck Carriers (PCTC’s) are typically 230 meters long and have 13 cargo decks. In order to facilitate rapid loading and unloading these ships have been subject to a development of reducing any obstructing structures in the cargo hold, meaning that the transversal shear preventing structures, i.e. the racking bulkheads, has been taken to a minimum. Previous studies have concluded that some points on the racking bulkheads, as a result of the stripped down design, are subject to high stresses resulting from wave induced accelerations of the ship. In this M.Sc. Thesis the fatigue life of a corner of a transverse bulkhead opening in a 230 meter long PCTC with a capacity of 7200 cars is calculated with different methods. •Fatigue life is calculated from recorded ship motion data with the notch stress method in conjunction with rain flow counting and the cumulative damage principal. • Fatigue life is calculated according to (DNV CN. 30.7, 2010), based on a Lloyd’s Register FE model load case. • Actual findings on the ship are compared to the calculated results. Due to the lack of inspection data this comparison is not very extensive and only more briefly discussed. It is concluded that the fatigue life of the examined point, calculated from recorded motion data is 9.6 years and the fatigue life according to DNV is 8.0 years. It is also found that the fatigue damage is cumulated in almost discrete portions and thus the calculated fatigue life can be inaccurate when a short period of time is evaluated as is done in this thesis. A modification to the racking bulkhead with respect to fatigue life is also analyzed and it is concluded that the fatigue life in the examined point could be extended significantly by some simple modifications to the geometry.

Machine-to-machine (M2M) communications have appeared as an advanced technology for next-generation communications and are undergoing rapid development. In this project, we investigate M2M communications in a wireless cellular network. In M2M communications, clustering is a technology for more efficient data gathering and higher network energy efficiency. We will analyze existing clustering designs in literature and propose two new clustering designs for M2M communications in cellular networks. Performance of the proposed designs will be evaluated thoroughly using both analytical and simulation tools across many aspects, including energy consumption, dead device ratio, residual energy, and network life. The results show that with simple static energy-efficient clustering operations, the network life can be extended by about 50%.

An IGBT/diode model with more accurate characteristics than simple switchis required to serve for EMC issues from converter valve. The purpose of thismaster thesis is to develop an IGBT and diode model to achieve both accuratetransient behavior and fast simulation time during single pulse switchingtest circuit for the 4:5 kV and 2:0 kA StakPakTM IGBT module. A gate unitwhich resembles the ABB gate unit is implemented to obtain a good agreementbetween simulation and measurement. For demonstration and verication, theIGBT/diode model is applied in a simplied arm simulation of full scale ABBGeneration 4 HVDC-VSC converter station and capable of a half cell consistingof 8 series-connected IGBTs and their anti-paralleled diodes. The arm simulationresults are analyzed further for converter station EMC studies.Convergence issue is the most important problem in the whole process of modelimplementation and application. To guarantee the convergence in simulationsome characteristics such as the tail voltage at the end of turn-o is disregarded.But overall, the model is validated and adopted successfully. En IGBT-/diodmodell med mer exakta egenskaper an en enkel switch kravs foratt hantera EMC-problem fran omvandlarventilen. Syftet med denna magisteruppsatsar att utveckla en IGBT- och diodmodell for att uppna bade noggrantovergaende beteende och snabb simuleringstid under enkelpulsomkopplingstestkretsfor 4,5 kV och 2,0 kA-StakPak IGBT-modulen. En grindenhetsom liknar ABB-grindenheten implementeras for att fa god overensstammelsemellan simulering och matning. For demonstration och veriering, tillampasIGBT-/diodmodellen i en forenklad armsimulering av en fullskalig ABB Generation4 HVDC-VSC-omvandlarstation och med kapacitet for en halvcell bestaendeav 8 seriekopplade IGBT och deras anti-parallellkopplade dioder. Resultatenfran armsimuleringen analyseras vidare for EMC-studier av omvandlarstationen.Konvergensfragan ar det viktigaste problemet i hela processen for modellimplementeringoch -tillampning. For att garantera konvergensen i simulering ignorerasvissa egenskaper sasom svansspanningen vid slutet av avstangning. Mentotalt sett, valideras och antas modellen framgangsrikt.

Agroekologi är ett jordbrukskoncept baserat på kunskap från ursprungsbefolkning och bönder som syftar till att uppnå hållbara, motståndskraftiga och stabila jordbrukssystem utan externa insatser. Konceptet syftar även till att stärka landsbygdssamhällen och skapa produktiva jordbrukssystem för att säkra livsmedelstillgången världen över. Agroekologi utmanar konventionell odling och exportorienterad livsmedelsproduktion där ekonomisk lönsamhet ofta prioriteras på bekostnad av sociala och ekologiska aspekter. Syftet med denna studie är att undersöka hinder och förutsättningar för en agroekologisk expansion i sydamerikanska länder då dessa länder besitter värdefulla ekosystem som i dagsläget hotas av konventionellt jordbruk. För att uppfylla målen med studien utfördes expertintervjuer samt litterära studier av expertgranskade artiklar. Resultatet av studien visar bland annat att samhälleliga aktörer såsom stat, forskningsinstitutioner, sociala rörelser, bönder och konsumenter har viktiga roller när det gäller agroekologisk expansion, samt att en tydlig kommunikation mellan dessa aktörer är nödvändig. En generell slutsats är att en hållbar omställning inom jordbruket är komplex och svår att genomföra, delvis på grund av de starka nyliberala diskurser som existerar inom stat och näringsliv och försvårar ett främjande av sociala och ekologiska frågor. Agroecology is an agricultural concept based on indigenous and peasant knowledge, which strives to achieve sustainable, resilient and reliable agricultural systems without external inputs. The concept also aims to strengthen rural communities and create productive agricultural systems in order to achieve food sovereignty across the world. Agroecology challenges conventional farming and export-oriented food production which often prioritizes profitability with little regard to ecological and social aspects. The purpose of this study is to investigate the obstacles and possibilities for an agroecological expansion in South American countries, since these countries possess valuable ecosystems that are currently threatened by conventional agriculture. In order to fulfill the goals of this study, literary studies of peer-reviewed articles as well as expert interviews were conducted. The results show that societal actors such as governments, research institutions, social movements, farmers and consumers have important roles in the expansion of agroecology, and that a clear articulation between these actors is necessary. A general conclusion of the study is that a sustainable transition within the agricultural sector is complex and would be difficult to achieve, partly because of the strong neoliberalist discourses that exist within governments and businesses and prevent the promotion of social and ecological issues. 

This thesis presents the application of different protein engineering methods on enzymes and non-catalytic proteins that act upon xyloglucans. Xyloglucans are polysaccharides found as storage polymers in seeds and tubers, and as cross-linking glucans in the cell wall of plants. Their structure is complex with intricate branching patterns, which contribute to the physical properties of the polysaccharide including its binding to and interaction with other glucans such as cellulose. One important group of xyloglucan-active enzymes is encoded by the GH16 XTH gene family in plants, including xyloglucan endo-transglycosylases (XET) and xyloglucan endo-hydrolases (XEH). The molecular determinants behind the different catalytic routes of these homologous enzymes are still not fully understood. By combining structural data and molecular dynamics (MD) simulations, interesting facts were revealed about enzyme-substrate interaction. Furthermore, a pilot study was performed using structure-guided recombination to generate a restricted library of XET/XEH chimeras. Glycosynthases are hydrolytically inactive mutant glycoside hydrolases (GH) that catalyse the formation of glycosidic linkages between glycosyl fluoride donors and glycoside acceptors. Different enzymes with xyloglucan hydrolase activity were engineered into glycosynthases, and characterised as tools for the synthesis of well-defined homogenous xyloglucan oligo- and polysaccharides with regular substitution patterns. Carbohydrate-binding modules (CBM) are non-catalytic protein domains that bind to polysaccharidic substrates. An important technical application involves their use as molecular probes to detect and localise specific carbohydrates in vivo. The three-dimensional structure of an evolved xyloglucan binding module (XGBM) was solved by X-ray diffraction. Affinity-guided directed evolution of this first generation XGBM resulted in highly specific probes that were used to localise non-fucosylated xyloglucans in plant tissue sections. QC 20100902

QC 0130422