We investigate the numerical solution of stable Sylvester equations via iterative schemes proposed for computing the sign function of a matrix. In particular, we discuss how the rational iterations for the matrix sign function can efficiently be adapted to the special structure implied by the Sylvester equation. For Sylvester equations with factored constant term as those arising in model reduction or image restoration, we derive an algorithm that computes the solution in factored form directly. We also suggest convergence criteria for the resulting iterations and compare the accuracy and performance of the resulting methods with existing Sylvester solvers. The algorithms proposed here are easy to parallelize. We report on the parallelization of those algorithms and demonstrate their high efficiency and scalability using experimental results obtained on a cluster of Intel Pentium Xeon processors.

Variants on the choice of nessecary control parameters in the generalized Bramble-Pasciak-CG method are discussed.

A perturbation analysis shows that if a numerically stable procedure is used to compute the matrix sign function, then it is competitive with conventional methods for computing invariant subspaces. Stability analysis of the Newton iteration improves an earlier result of Byers and confirms that ill-conditioned iterates may cause numerical instability. Numerical examples demonstrate the theoretical results.

Agile based development seems to become a favorable model for offshore development. It allows both on and offshore team to work in small iterations minimizing the effect of change in software requirements and at the same time developing regular communication between them. However different factors such as physical distance and lack of communication between on and offshore team becomes a hurdle between them leading to misunderstandings about software requirements. This research work gives an insight about these challenges from the software industry by presenting and discussing the responses of four software companies located in different countries, collected through an online questionnaire. The authors found that lack of communication between on and offshore site is seen as a major challenge for better understanding of software requirements. Shorter iterations at the offshore site require more communication with the onshore site. The language problem seems to exist only when both on and offshore site who are non-English speakers communicate in English. Regular long distance meetings would help in better understanding of software requirements. Previous domain and product knowledge is helpful in better understanding of software requirements. This research work would allow different stakeholders within agile based on/offshore setting to better understand these challenges and deal accordingly with them.

Det här arbetet preciserar ett problem utifrån ett problemområde som faller inom ramen för användarcentrerad design. Den preciserade problemformuleringen är: I vilken utsträckning kan ett gränssnitt göras användbart genom prototyping, aktiv användarmedverkan och iterativ utveckling genom användningen av en modifierad version av ISO 13407 standarden som ett utvecklingsramverk? Den här frågeställningen har tillämpats och avgränsats till ett pekskärmsgränssnitt vid namn Navigator som är utvecklat av Asko. Resultaten visar att de gränssnittsprototyper som har skapats är användbara. Vidare visar resultaten även att det inte är tillräckligt att enbart använda tre nyckelprinciper för användarcentrerad design i syfte att uppnå användbarhet.

Recent developments in deep reinforcement learning applied to abstract strategy games such as Go, chess and Hex have sparked an interest within military planning. This Master thesis explores if it is possible to implement an algorithm similar to Expert Iteration and AlphaZero to wargames. The studied wargame is Risk, which is a turn-based multiplayer game played on a simplified political map of the world. The algorithms consist of an expert, in the form of a Monte Carlo tree search algorithm, and an apprentice, implemented through a neural network. The neural network is trained by imitation learning, trained to mimic expert decisions generated from self-play reinforcement learning. The apprentice is then used as heuristics in forthcoming tree searches. The results demonstrated that a Monte Carlo tree search algorithm could, to some degree, be employed on a strategy game as Risk, dominating a random playing agent. The neural network, fed with a state representation in the form of a vector, had difficulty in learning expert decisions and could not beat a random playing agent. This led to a halt in the expert/apprentice learning process. However, possible solutions are provided as future work.

The preprint delivers an efficient solution technique for the numerical simulation of crack propagation of 2D linear elastic formulations based on finite elements together with the conjugate gradient method in order to solve the corresponding linear equation systems. The developed iterative numerical approach using hierarchical preconditioners comprehends the interesting feature that the hierarchical data structure will not be destroyed during crack propagation. Thus, one gets the possibility to simulate crack advance in a very effective numerical manner including adaptive mesh refinement and mesh coarsening. Test examples are presented to illustrate the efficiency of the given approach. Numerical simulations of crack propagation are compared with experimental data.

Denna systematiska litteraturstudie behandlar barns förmåga att inte bara utföra utan faktiskt förstå vad mätning av längd innebär. Syftet är att redogöra för vilka aspekter som enligt tidigare forskning visat sig väsentliga för att möjliggöra denna typ av förståelse. Detta har gjorts med hjälp av data i form av artiklar och avhandlingar som systematiskt samlats in och analyserats. Det som i den utvalda litteraturen lyfts som mest väsentligt är de kognitiva egenskaperna transitivitet och iteration, att dessa egenskaper utvecklas är en förutsättning för att barn ska förstå mätning av längd. Barn behöver ha förståelse för att samma enhet krävs för att mätning ska kunna utföras och vid jämförelser kan ett tredje objekt användas. Studien belyser dessutom hur undervisning kan utformas så gynnsamt som möjligt i förhållande till barns förståelse av mätning. Detta görs förslagsvis med hjälp av kommunikation och uppgifter kopplade till elevers vardag, men även genom att ta reda på vilken nivå eleverna befinner sig på.

No description available.

No description available.