6 resultados para Circular shortest path

em Helda - Digital Repository of University of Helsinki


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Although changes in urban forest vegetation have been documented in previous Finnish studies, the reasons for these changes have not been studied explicitly. Especially, the consequences of forest fragmentation, i.e. the fact that forest edges receive more solar radiation, wind and air-borne nutrients than interiors have been ignored. In order to limit the change in urban forest vegetation we need to know why it occurs. Therefore, the effects of edges and recreational use of urban forests on vegetation were investigated together in this thesis to reveal the relative strengths of these effects and to provide recommendations for forest management. Data were collected in the greater Helsinki area (in the cities of Helsinki, Vantaa and Espoo, and in the municipalities of Sipoo and Tuusula) and in the Lahti region (in the city of Lahti and in the municipality of Hollola) by means of systematic and randomized vegetation and soil sampling and tree measurements. Sample plots were placed from the forest edges to the interiors to investigate the effects of forest edges, and on paths of different levels of wear and off these paths to investigate the effects of trampling. The natural vegetation of mesic and sub-xeric forest site types studied was sensitive both to the effects of the edge and to trampling. The abundances of dwarf shrubs and bryophytes decreased, while light- and nitrogen-demanding herbs and grasses - and especially Sorbus aucuparia – were favoured at the edges and next to the paths. Results indicated that typical forest site types at the edges are changing toward more nitrophilic vegetation communities. Covers of the most abundant forest species decreased considerably – even tens of percentages – from interiors to the edges indicating strong edge effects. These effects penetrated at least up to 50 m from the forest edges into the interiors, especially at south to west facing open edges. The effects of trampling were pronounced on paths and even low levels of trampling decreased the abundances of certain species considerably. The effects of trampling extended up to 8 m from path edges. Results showed that the fragmentation of urban forest remnants into small and narrow patches should be avoided in order to maintain natural forest understorey vegetation in the urban setting. Thus, urban forest fragments left within urban development should be at least 3 ha in size, and as circular as possible. Where the preservation of representative original forest interior vegetation is a management aim, closed edges with conifers can act as an effective barrier against solar radiation, wind and urban load, thereby restricting the effects of the edge. Tree volume at the edge should be at least 225-250 m3 ha-1 and the proportion of conifers (especially spruce) 80% or more of the tree species composition. Closed, spruce-dominated edges may also prevent the excessive growth of S. aucuparia saplings at urban forest edges. In addition, closed edges may guide people’s movements to the maintained paths, thus preventing the spontaneous creation of dense path networks. In urban areas the effects of edges and trampling on biodiversity may be considerable, and are important to consider when the aim of management is to prevent the development of homogeneous herb-grass dominated vegetation communities, as was observed at the investigated edges.

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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.

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The European Union has agreed on implementing the Policy Coherence for Development (PCD) principle in all policy sectors that are likely to have a direct impact on developing countries. This is in order to take account of and support the EU development cooperation objectives and the achievement of the internationally agreed Millennium Development Goals. The common EU migration policy and the newly introduced EU Blue Card directive present an example of the implementation of the principle in practice: the directive is not only designed to respond to the occurring EU labour demand by attracting highly skilled third-country professionals, but is also intended to contribute to the development objectives of the migrant-sending developing countries, primarily through the tool of circular migration and the consequent skills transfers. My objective in this study is to assess such twofold role of the EU Blue Card and to explore the idea that migration could be harnessed for the benefit of development in conformity with the notion that the two form a positive nexus. Seeing that the EU Blue Card fails to differentiate the most vulnerable countries and sectors from those that are in a better position to take advantage of the global migration flows, the developmental consequences of the directive must be accounted for even in the most severe settings. Accordingly, my intention is to question whether circular migration, as claimed, could address the problem of brain drain in the Malawian health sector, which has witnessed an excessive outflow of its professionals to the UK during the past decade. In order to assess the applicability, likelihood and relevance of circular migration and consequent skills transfers for development in the Malawian context, a field study of a total of 23 interviews with local health professionals was carried out in autumn 2010. The selected approach not only allows me to introduce a developing country perspective to the on-going discussion at the EU level, but also enables me to assess the development dimension of the EU Blue Card and the intended PCD principle through a local lens. Thus these interviews and local viewpoints are at the very heart of this study. Based on my findings from the field, the propensity of the EU Blue Card to result in circular migration and to address the persisting South-North migratory flows as well as the relevance of skills transfers can be called to question. This is as due to the bias in its twofold role the directive overlooks the importance of the sending country circumstances, which are known to determine any developmental outcomes of migration, and assumes that circular migration alone could bring about immediate benefits. Without initial emphasis on local conditions, however, positive outcomes for vulnerable countries such as Malawi are ever more distant. Indeed it seems as if the EU internal interests in migration policy forbid the fulfilment of the PCD principle and diminish the attempt to harness migration for development to bare rhetoric.