827 resultados para SPIRAL STRUCTURES


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The aim of this thesis was to study network structures and modularity among biofuel heating system manufacturers in the Finnish bioenergy sector by utilizing the perspectives of numerous Finnish bioenergy specialists. The study is qualitative due to the fact that the research material was gathered with semi-structured theme interviews during May and June 2010. The research methodology used in the thesis combines conceptual and action-oriented approach. Networks, value nets, and modularity were studied from different perspectives. Three network and platform strategies were discovered and a general network structure was formed. Moreover, benefits and disadvantages of networks and modularity among biofuel heating system manufacturers were illustrated. The analysis provides a comprehensive perception of the industry. The results of the research were constructed by implementing existing theories into practice. Also future recommendations for the biofuel heating system manufacturers were given. The results can be considered to be beneficial because the number of previous studies about the subject is relatively small. The reliability of the study is eminent because the number of the interviews was inclusive.

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The structures of the principal oligosaccharides in the honeydew exudate of the sorghum ergot pathogen Claviceps africana, which has become epidemic in the Americas, have been characterized through linkage analysis using FAB-MS and GC-MS techniques, as 1,6-di-b-D-fructofuranosyl-D-mannitol and 1,5-di-b-D-fructofuranosyl-D-arabitol trisaccharides, 1-b-D-fructofuranosyl-D-mannitol and 5-b-D-fructofuranosyl-D-arabitol disaccharides and other minor disaccharides and trisaccharides. Their structural diversity is explained according to perceived biosynthetic interrelationships in pathways that appear to be unique amongst ergot fungi, particularly concerning intra-molecular reduction of fructose. The oligosaccharide, 1,6-di-b-D-fructofuranosyl-D-mannitol, which inhibits C. africana macrospore germination at a concentration in water of 1 g/mL or more, forms together with other slightly less bioactive oligosaccharides, the basis of a novel strategy to limit ergot disease losses in hybrid sorghum seed production.

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This study is made in the context of basic research within the field ofcaring science. The aim is to make a theoretical and ontological investigation of what the space is in the world of caring. The basic proposition is that the space, as a fundamental dimension, has an impact on how the appreciation of one's mental health and suffering is shaped, and vice versa. The overall purpose is to develop a theoretical model of space from the caring science point of view andalso to offer an ideal concept of space to caring science. Guided by a theoretical horizon (Eriksson 1993, Eriksson 1995, Eriksson 2001) and methodological approach grounded in Gadamer's philosophic and existential hermeneutics a three-stage analysis and interpretation is conducted. The hermeneutic spiral of this investigation starts through a procedure in accordance with Eriksson's model (1997) of concept definition. The goal is to clarify the etymology of the concept as well as semantic differences between synonymous concepts, i.e. to identify the different extents of the concept of `space` (`rum`) in order to bring these closer for an exploration. The second phase is to analyse and interpret a sample of narratives in order to explicate the ontological nature and meaning of the space. The material used here is literary texts. The goal is to clarify the characteristics of the very inside of the space when it is shaped in relation to the human being in encountering suffering. In the third phase an interview study is taken place. The focus of the study is directed towards the phenomenon of space as it is known by a patient in a landscape of psychiatric care, i.e. what the space is in a contextual meaning. Then, a gradual hermeneutic understanding of the space is attempted by using theories from the field of caring science as well as additional theories from other disciplines. Metaphors are used as they are vivid and expressive tools for generating meaning. Different metaphoric space formations depict here a variety of purports that, although not quite the same, share extensive elements. Six metaphorically summarized entities of meaning emerged. The comprehensive form of space is pointed out as the Mobile-Immobile Room. Furthermore, the Standby, the Asylum, the Wall and the Place. In the further dialogue with the texts the understanding has deepened ontologically. The theoretical model ofthe space sums up the vertical, horizontal and the inward extent of deepness inthe movement of mental health. Three entities of ontological meaning have emerged as three significant rooms: the Common Land emerges as the ideal concept of mutual creation in the freedom of doing, being and becoming health. On the interpersonal level it means freedom, which includes sovereignty, choice and dignity of the human being. The Ice World signifies, ultimately, the space as a kind of frozenness of despair which "wallpapers" the person's entire being in the world in the drama of suffering. The Spiritual Home is shaped when the human being has acquired the very core of his/her inner and outer placeness as a kind of "at-homeness" and rootedness. Time is a central element and the inward extent of deepness of this trialectic space. Each of the metaphors is then the human being's unique, although even paradoxical, way of conceiving reality, and mastering spiritual suffering. They condense characteristic structures and patterns of dynamic scenery, which take place within the movement of health. The space encloses a contradictory spatiality constituted through the dynamic field of meaningfulness and meaninglessness. Anyway, it is not through a purging of these contradictions but through bringing them together in a drama of suffering that the space is shaped as ontologically good and meaningful in the world of caring.

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Rapid depletion of easy-to-access fossil fuel, predominantly, oil and gas resources has now necessitated increase in need to develop new oil and gas sources in ever more remote and hostile environments. This is necessary in order to explore more oil and gas resources to meet rapidly rising long-term energy demand in the world, both at present and in the nearest future. Arctic is one of these harsh environments, where enormous oil and gas resources are available, containing about 20% of the world total oil and gas, but the environmental conditions are very harsh and hostile. However, virtually all the facilities required for the exploration and development of this new energy source are constructed with metals as well as their alloys and are predominantly joined together by welding processes and technologies. Meanwhile, due to entirely different environment from the usual moderate temperate region, conventional welding technologies, common metals and their alloys cannot be applied as this Arctic environment demand metals structures with very high toughness and strength properties under extremely low temperature. This is due to the fact that metals transit from ductility to brittleness as the temperature moves toward extreme negative values. Hence, this research work investigates and presents the advanced welding technologies applicable to Arctic metal structures which can give satisfactory weldments under active Arctic service conditions. .

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With an increasingly growing demand for natural resources, the Arctic region has become an attractive area, holding about 15% of world oil. Ice shrinkage caused by global warming encourages the development of offshore and ship-building sectors. Russia, as one of the leading oil and gas production countries is participating actively in cold resistant materials research, since half of its territory belongs to the Arctic environment, which held considerable stores of oil. Nowadays most Russian offshore platforms are located in the Sakhalin Island area, which geographically does not belong to the Arctic, but has com-parable environmental conditions. Russia recently has manufactured several offshore platforms. It became clear that further development of the Arctic off-shore structures with necessary reliability is highly depending on the materials employed. This work pursues the following objectives:  to provide a comprehensive review on Russian metals used for Arctic offshore structures on the base of standards, books, journal articles and companies reports  to overview various Arctic offshore structures and its structural characteristics  briefly discuss materials testing methods for low temperatures Master`s thesis focuses on specifications and description of Russian metals which are already in use and can be used for Arctic offshore structures. Work overviews several groups of steel, such as low carbon, low alloy, chromium containing steels, stainless steels, aluminium and nanostructured steels. Materials under discussion are grouped based on the standards, for instance the work covers shipbuilding and structural steels at the different sections. This paper provides an overview of important Russian Arctic offshore projects built for use in Russia and ordered by foreign countries. Future trends in development of the Arctic materials are discussed. Based on the information provided in this Master`s thesis it is possible to learn about Russian metals used for ships and offshore platforms operated in the Arctic region. Paper can be used as the comprehensive review of current materials, such as various steels, aluminium and nanomaterials.

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High strength steel (HSS) has been in use in workshops since the 1980s. At that time, the significance of the term HSS differed from the modern conception as the maximum yield strength of HSSs has increased nearly every year. There are three different ways to make HSS. The first and oldest method is QT (quenched and tempered) followed by the TMCP (thermomechanical controlled process) and DQ (direct quenching) methods. This thesis consists of two parts, the first of which part introduces the research topic and discusses welded HSS structures by characterizing the most important variables. In the second part of the thesis, the usability of welded HSS structures is examined through a set of laboratory tests. The results of this study explain the differences in the usability of the welded HSSs made by the three different methods. The results additionally indicate that usage of different HSSs in the welded structures presumes that manufacturers know what kind of HSS they are welding. As manufacturers use greater strength HSSs in welded structures, the demands for welding rise as well. Therefore, during the manufacturing process, factors such as heat input, cooling time, weld quality, and more must be under careful observation.

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This study examined relationships of organizational dependencies, change management and developed intellectual knowledge resources, in different intellectual capital based development programs on ICT-sector. Study was carried out in a research context, where high degree of external organizational contingencies existed and lots of changes in several development programs had taken place in the last years. From a scientific perspective the main contribution was that evidence between relationships of organizational dependencies, change model portfolio and developed knowledge resources could be suggested. From managerial perspective the primary implication was that in situations where sustainable competitive advantage is pursued by means of increasing knowledge based productivity of labor, firms should seek to pursue organizational settings where external dependencies have minimal amount of effect.

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Communication, the flow of ideas and information between individuals in a social context, is the heart of educational experience. Constructivism and constructivist theories form the foundation for the collaborative learning processes of creating and sharing meaning in online educational contexts. The Learning and Collaboration in Technology-enhanced Contexts (LeCoTec) course comprised of 66 participants drawn from four European universities (Oulu, Turku, Ghent and Ramon Llull). These participants were split into 15 groups with the express aim of learning about computer-supported collaborative learning (CSCL). The Community of Inquiry model (social, cognitive and teaching presences) provided the content and tools for learning and researching the collaborative interactions in this environment. The sampled comments from the collaborative phase were collected and analyzed at chain-level and group-level, with the aim of identifying the various message types that sustained high learning outcomes. Furthermore, the Social Network Analysis helped to view the density of whole group interactions, as well as the popular and active members within the highly collaborating groups. It was observed that long chains occur in groups having high quality outcomes. These chains were also characterized by Social, Interactivity, Administrative and Content comment-types. In addition, high outcomes were realized from the high interactive cases and high-density groups. In low interactive groups, commenting patterned around the one or two central group members. In conclusion, future online environments should support high-order learning and develop greater metacognition and self-regulation. Moreover, such an environment, with a wide variety of problem solving tools, would enhance interactivity.

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This work presents an application of the Mobility Approach to the analysis of the power flow through grillage-like structures. Such structures are usually found in offshore platforms, supporting large and heavy machines. Different wave kinds (longitudinal, flexural and torsional) were initially considered in the power flow analysis between two beams joined in L. Beams excited by an in-plane point force showed strong coupling between longitudinal-flexural waves, while that for out-of-plane point force excitation, flexural-torsional waves coupling represents the most important mechanism of energy transmission. The response determination of grillages by the mobility approach requires the structure to be separated into simple beam-like structural components. Equations for rotations and displacements at the joints of all beams are written for as mobility functions, and moments and forces acting at the joints. A system of equations relating all such internal forces and moments is obtained. This approach was applied to simple grillages. Response results showed good agreement when compared to those provided by Finite Elements.

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Crack formation and growth in steel bridge structural elements may be due to loading oscillations. The welded elements are liable to internal discontinuities along welded joints and sensible to stress variations. The evaluation of the remaining life of a bridge is needed to make cost-effective decisions regarding inspection, repair, rehabilitation, and replacement. A steel beam model has been proposed to simulate crack openings due to cyclic loads. Two possible alternatives have been considered to model crack propagation, which the initial phase is based on the linear fracture mechanics. Then, the model is extended to take into account the elastoplastic fracture mechanic concepts. The natural frequency changes are directly related to moment of inertia variation and consequently to a reduction in the flexural stiffness of a steel beam. Thus, it is possible to adopt a nondestructive technique during steel bridge inspection to quantify the structure eigenvalue variation that will be used to localize the grown fracture. A damage detection algorithm is developed for the proposed model and the numerical results are compared with the solutions achieved by using another well know computer code.

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This paper studies the effect of time delay on the active non-linear control of dynamically loaded flexible structures. The behavior of non-linear systems under state feedback control, considering a fixed time delay for the control force, is investigated. A control method based on non-linear optimal control, using a tensorial formulation and state feedback control is used. The state equations and the control forces are expressed in polynomial form and a performance index, quadratic in both state vector and control forces, is used. General polynomial representations of the non-linear control law are obtained and implemented for control algorithms up to the fifth order. This methodology is applied to systems with quadratic and cubic non-linearities. Strongly non-linear systems are tested and the effectiveness of the control system including a delay for the application of control forces is discussed. Numerical results indicate that the adopted control algorithm can be efficient for non-linear systems, chiefly in the presence of strong non-linearities but increasing time delay reduces the efficiency of the control system. Numerical results emphasize the importance of considering time delay in the project of active structural control systems.

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In this paper is Analyzed the local dynamical behavior of a slewing flexible structure considering nonlinear curvature. The dynamics of the original (nonlinear) governing equations of motion are reduced to the center manifold in the neighborhood of an equilibrium solution with the purpose of locally study the stability of the system. In this critical point, a Hopf bifurcation occurs. In this region, one can find values for the control parameter (structural damping coefficient) where the system is unstable and values where the system stability is assured (periodic motion). This local analysis of the system reduced to the center manifold assures the stable / unstable behavior of the original system around a known solution.

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Optimization of high strength and toughness combination on the effect of weldability is very vital to be considered in offshore oil and gas industries. Having a balanced and improved high strength and toughness is very much recommended in offshore structures for an effective production and viable exploration of hydrocarbons. This thesis aims to investigate the possibilities to improve the toughness of high strength steel. High carbon contents induce hardness and needs to be reduced for increasing toughness. The rare combination of high strength with high toughness possibilities was examined by determining the following toughening mechanism of: Heat treatment and optimal microstructure, Thermomechanical processing, Effect of welding parameters on toughness and weldability of steel. The implementation of weldability of steels to attain high toughness for high strength in offshore structures is mostly in shipbuilding, offshore platforms, and pipelines for high operating pressures. As a result, the toughening mechanisms suggested have benefits to the aims of the effect of high strength to high toughness of steel for efficiency, production and cost reduction.

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The meristematic endodermis in adventitious roots of Richterago species originates in one of the fundamental meristem cells, which undergo sucessive anticlinal and periclinal divisions to build the inner cortex. The meristematic endodermis or proendodermis remains as a meristematic layer until its differentiation into endodermis, with Casparian strip. When sieve elements differentiate, endodermic secretory canals of esquizogenous origin are present at the region adjacent to primary phloem. Articulated laticifers, with cells perforated at both terminal and transversal walls, also occur during initial phases of secondary development. Presence of inulin as reserve carbohydrate in the inner cortex and vascular tissue may be related to abiotic factors, as an adaptive strategy of these species.