6 resultados para Longest path

em Helda - Digital Repository of University of Helsinki


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When augmented with the longest common prefix (LCP) array and some other structures, the suffix array can solve many string processing problems in optimal time and space. A compressed representation of the LCP array is also one of the main building blocks in many compressed suffix tree proposals. In this paper, we describe a new compressed LCP representation: the sampled LCP array. We show that when used with a compressed suffix array (CSA), the sampled LCP array often offers better time/space trade-offs than the existing alternatives. We also show how to construct the compressed representations of the LCP array directly from a CSA

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Thin films are the basis of much of recent technological advance, ranging from coatings with mechanical or optical benefits to platforms for nanoscale electronics. In the latter, semiconductors have been the norm ever since silicon became the main construction material for a multitude of electronical components. The array of characteristics of silicon-based systems can be widened by manipulating the structure of the thin films at the nanoscale - for instance, by making them porous. The different characteristics of different films can then to some extent be combined by simple superposition. Thin films can be manufactured using many different methods. One emerging field is cluster beam deposition, where aggregates of hundreds or thousands of atoms are deposited one by one to form a layer, the characteristics of which depend on the parameters of deposition. One critical parameter is deposition energy, which dictates how porous, if at all, the layer becomes. Other parameters, such as sputtering rate and aggregation conditions, have an effect on the size and consistency of the individual clusters. Understanding nanoscale processes, which cannot be observed experimentally, is fundamental to optimizing experimental techniques and inventing new possibilities for advances at this scale. Atomistic computer simulations offer a window to the world of nanometers and nanoseconds in a way unparalleled by the most accurate of microscopes. Transmission electron microscope image simulations can then bridge this gap by providing a tangible link between the simulated and the experimental. In this thesis, the entire process of cluster beam deposition is explored using molecular dynamics and image simulations. The process begins with the formation of the clusters, which is investigated for Si/Ge in an Ar atmosphere. The structure of the clusters is optimized to bring it as close to the experimental ideal as possible. Then, clusters are deposited, one by one, onto a substrate, until a sufficiently thick layer has been produced. Finally, the concept is expanded by further deposition with different parameters, resulting in multiple superimposed layers of different porosities. This work demonstrates how the aggregation of clusters is not entirely understood within the scope of the approximations used in the simulations; yet, it is also shown how the continued deposition of clusters with a varying deposition energy can lead to a novel kind of nanostructured thin film: a multielemental porous multilayer. According to theory, these new structures have characteristics that can be tailored for a variety of applications, with precision heretofore unseen in conventional multilayer manufacture.

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This study explores the role and nature of knowledge management (KM) in small and medium-sized companies (SMEs). Even though the role of knowledge as a competitive advantage is commonly recognized in the SME sector, almost no attention has been paid to the managing and developing of knowledge in SMEs. This thesis consists of three different sub-studies that were reported in four individual essays. The results of the questionnaire study indicate that nearly all companies that responded to the questionnaire (N = 108) found intangible assets, i.e. knowledge resources to be their main source of competitive advantage. However, only less than a third of the companies actively deal with knowledge management. The results also indicate a significant correlation between activity in knowledge management and sustainable organic growth of the company. The interview study (N = 10) explored the context and motives of the SMEs for managing their intangible assets, and the concrete practices of knowledge management. It turned out that KM facilitated change management, clarification of the vision and new strategy formulation. All the interviewed companies were aiming at improved innovation process, new ways of doing business and attaining an increased “knowledge focus” in their business. Nearly all also aspired to grow significantly. Thus, KM provides a strategy for these SMEs to guarantee their survival and sustainability in the turbulent markets. The action research was a process to assess and develop intangible resources in three companies. The experienced benefits were the clarification of future focus and strategy, creation of a common language to discuss strategic issues within the company, as well as improved balance of different categories of intangible assets. After the process all the case companies had developed in the chosen key areas. Thus, by systematic knowledge management the implementation of new strategic orientation (knowledge focusing) was facilitated. The findings can be summarized in two main points. First, knowledge management seems to serve the purpose of change, renewal and new strategic orientation in the SMEs. It also seems to be closely related to organic growth and innovation. All of these factors can be considered dimensions of entrepreneurship. Second, the conscious development of intangible assets can increase the balance of different categories of intangible assets and the overall knowledge focusing of business. In the case companies, this in turn facilitated the path to the improved overall performance.

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The aim of the dissertation is to explore the idea of philosophy as a path to happiness in classical Arabic philosophy. The starting point is in comparison of two distinct currents between the 10th and early 11th centuries, Peripatetic philosophy, represented by al-Fārābī and Ibn Sīnā, and Ismaili philosophy represented by al-Kirmānī and the Brethren of Purity. They initially offer two contrasting views about philosophy in that the attitude of the Peripatetics is rationalistic and secular in spirit, whereas for the Ismailis philosophy represents the esoteric truth behind revelation. Still, they converge in their view that the ultimate purpose of philosophy lies in its ability to lead man towards happiness. Moreover, they share a common concept of happiness as a contemplative ideal of human perfection, which refers primarily to an otherworldly state of the soul s ascent to the spiritual world. For both the way to happiness consists of two parts: theory and practice. The practical part manifests itself in the idea of the purification of the rational soul from its bodily attachments in order for it to direct its attention fully to the contemplative life. Hence, there appears an ideal of philosophical life with the goal of relative detachment from the worldly life. The regulations of the religious law in this context appear as the primary means for the soul s purification, but for all but al-Kirmānī they are complemented by auxiliary philosophical practices. The ascent to happiness, however, takes place primarily through the acquisition of theoretical knowledge. The saving knowledge consists primarily of the conception of the hierarchy of physical and metaphysical reality, but all of philosophy forms a curriculum through which the soul gradually ascends towards a spiritual state of being along an order that is inverse to the Neoplatonic emanationist hierarchy of creation. For Ismaili philosophy the ascent takes place from the exoteric religious sciences towards the esoteric philosophical knowledge. For Peripatetic philosophers logic performs the function of an instrument enabling the ascent, mathematics is treated either as propaedeutic to philosophy or as a mediator between physical and metaphysical knowledge, whereas physics and metaphysics provide the core of knowledge necessary for the attainment of happiness.