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Stability and Receptivity of Three-Dimensional Boundary LayersTempelmann, David January 2009 (has links)
The stability and the receptivity of three-dimensional flat plate boundary layers is studied employing parabolised stability equations. These allow for computationally efficient parametric studies. Two different sets of equations are used. The stability of modal disturbances in the form of crossflow vortices is studied by means of the well-known classical parabolised stability equations (PSE). A new method is developed which is applicable to more general vortical-type disturbances. It is based on a modified version of the classical PSE and describes both modal and non-modal growth in three-dimensional boundary layers. This modified PSE approach is used in conjunction with a Lagrange multiplier technique to compute spatial optimal disturbances in three-dimensional boundary layers. These take the form of streamwise oriented tilted vortices initially and develop into streaks further downstream. When entering the domain where modal disturbances become unstable optimal disturbances smoothly evolve into crossflow modes. It is found that non-modal growth is of significant magnitude in three-dimensional boundary layers. Both the lift-up and the Orr mechanism are identified as the physical mechanisms behind non-modal growth. Furthermore, the modified PSE are used to determine the response of three-dimensional boundary layers to vortical free-stream disturbances. By comparing to results from direct numerical simulations it is shown that the response, including initial transient behaviour, is described very accurately. Extensive parametric studies are performed where effects of free-stream turbulence are modelled by filtering with an energy spectrum characteristic for homogeneous isotropic turbulence. It is found that a quantitative prediction of the boundary layer response to free-stream turbulence requires detailed information about the incoming turbulent flow field. Finally, the adjoint of the classical PSE is used to determine the receptivity of modal disturbances with respect to localised surface roughness. It is shown that the adjoint approach yields perfect agreement with results from Finite-Reynold-Number Theory (FRNT) if the boundary layer is assumed to be locally parallel. Receptivity is attenuated if nonlocal and non-parallel effects are accounted for. Comparisons to direct numerical simulations and extended parametric studies are presented.
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Numerical studies of transtion in wall-bounded flowsLevin, Ori January 2005 (has links)
Disturbances introduced in wall-bounded flows can grow and lead to transition from laminar to turbulent flow. In order to reduce losses or enhance mixing in energy systems, a fundamental understanding of the flow stability and transition mechanism is important. In the present thesis, the stability, transition mechanism and early turbulent evolution of wall-bounded flows are studied. The stability is investigated by means of linear stability equations and the transition mechanism and turbulence are studied using direct numerical simulations. Three base flows are considered, the Falkner-Skan boundary layer, boundary layers subjected to wall suction and the Blasius wall jet. The stability with respect to the exponential growth of waves and the algebraic growth of optimal streaks is studied for the Falkner-Skan boundary layer. For the algebraic growth, the optimal initial location, where the optimal disturbance is introduced in the boundary layer, is found to move downstream with decreased pressure gradient. A unified transition prediction method incorporating the influences of pressure gradient and free-stream turbulence is suggested. The algebraic growth of streaks in boundary layers subjected to wall suction is calculated. It is found that the spatial analysis gives larger optimal growth than temporal theory. Furthermore, it is found that the optimal growth is larger if the suction begins a distance downstream of the leading edge. Thresholds for transition of periodic and localized disturbances as well as the spreading of turbulent spots in the asymptotic suction boundary layer are investigated for Reynolds number Re=500, 800 and 1200 based on the displacement thickness and the free-stream velocity. It is found that the threshold amplitude scales like Re^-1.05 for transition initiated by streamwise vortices and random noise, like Re^-1.3 for oblique transition and like Re^-1.5 for the localized disturbance. The turbulent spot is found to take a bullet-shaped form that becomes more distinct and increases its spreading rate for higher Reynolds number. The Blasius wall jet is matched to the measured flow in an experimental wall-jet facility. Both the linear and nonlinear regime of introduced waves and streaks are investigated and compared to measurements. It is demonstrated that the streaks play an important role in the breakdown process where they suppress pairing and enhance breakdown to turbulence. Furthermore, statistics from the early turbulent regime are analyzed and reveal a reasonable self-similar behavior, which is most pronounced with inner scaling in the near-wall region. / QC 20101025
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Internationalization of a Health Care Organization : An Empirical Study on GambroJech, Martin, Magnani, Federico, Freitas, Rute January 2007 (has links)
The international marketer is challenging new factors in the present globalized world. Such marketer has often to solve conflicts resulting from different laws, cultures and societies, and overcome a variety of constraints when entering or establishing foreign markets. Entering and establishing new markets is a complicated process affected by both, external and internal factors. To be successful in new markets, said marketers must formulate market entry strategy with regard to those factors. This paper was written with the purpose to investigate the relationship between relatedness of core business and business regarding the market in question, government policies and regulations, and entry strategy of companies entering the U.S. renal services market. We have carried out the exploratory research based mainly on secondary data obtained from annual reports from 1995 to 2005. The one case study on the Swedish health care company Gambro was conducted in order to formulate hypotheses, which can be proven in prospective research. The whole paper is written in the context of PSE market entry model developed by Anders Pehrsson. Based on the analysis we suggest that if the perception of barriers is low and the relatedness between core business and business regarding market in question is high, companies prefer a non-organic growth when entering the market.
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Numerical studies of transtion in wall-bounded flowsLevin, Ori January 2005 (has links)
<p>Disturbances introduced in wall-bounded flows can grow and lead to transition from laminar to turbulent flow. In order to reduce losses or enhance mixing in energy systems, a fundamental understanding of the flow stability and transition mechanism is important. In the present thesis, the stability, transition mechanism and early turbulent evolution of wall-bounded flows are studied. The stability is investigated by means of linear stability equations and the transition mechanism and turbulence are studied using direct numerical simulations. Three base flows are considered, the Falkner-Skan boundary layer, boundary layers subjected to wall suction and the Blasius wall jet. The stability with respect to the exponential growth of waves and the algebraic growth of optimal streaks is studied for the Falkner-Skan boundary layer. For the algebraic growth, the optimal initial location, where the optimal disturbance is introduced in the boundary layer, is found to move downstream with decreased pressure gradient. A unified transition prediction method incorporating the influences of pressure gradient and free-stream turbulence is suggested. The algebraic growth of streaks in boundary layers subjected to wall suction is calculated. It is found that the spatial analysis gives larger optimal growth than temporal theory. Furthermore, it is found that the optimal growth is larger if the suction begins a distance downstream of the leading edge. Thresholds for transition of periodic and localized disturbances as well as the spreading of turbulent spots in the asymptotic suction boundary layer are investigated for Reynolds number Re=500, 800 and 1200 based on the displacement thickness and the free-stream velocity. It is found that the threshold amplitude scales like Re^-1.05 for transition initiated by streamwise vortices and random noise, like Re^-1.3 for oblique transition and like Re^-1.5 for the localized disturbance. The turbulent spot is found to take a bullet-shaped form that becomes more distinct and increases its spreading rate for higher Reynolds number. The Blasius wall jet is matched to the measured flow in an experimental wall-jet facility. Both the linear and nonlinear regime of introduced waves and streaks are investigated and compared to measurements. It is demonstrated that the streaks play an important role in the breakdown process where they suppress pairing and enhance breakdown to turbulence. Furthermore, statistics from the early turbulent regime are analyzed and reveal a reasonable self-similar behavior, which is most pronounced with inner scaling in the near-wall region.</p>
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Internationalization of a Health Care Organization : An Empirical Study on GambroJech, Martin, Magnani, Federico, Freitas, Rute January 2007 (has links)
<p>The international marketer is challenging new factors in the present globalized world. Such marketer has often to solve conflicts resulting from different laws, cultures and societies, and overcome a variety of constraints when entering or establishing foreign markets. Entering and establishing new markets is a complicated process affected by both, external and internal factors. To be successful in new markets, said marketers must formulate market entry strategy with regard to those factors. This paper was written with the purpose to investigate the relationship between relatedness of core business and business regarding the market in question, government policies and regulations, and entry strategy of companies entering the U.S. renal services market. We have carried out the exploratory research based mainly on secondary data obtained from annual reports from 1995 to 2005. The one case study on the Swedish health care company Gambro was conducted in order to formulate hypotheses, which can be proven in prospective research. The whole paper is written in the context of PSE market entry model developed by Anders Pehrsson. Based on the analysis we suggest that if the perception of barriers is low and the relatedness between core business and business regarding market in question is high, companies prefer a non-organic growth when entering the market.</p>
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Der Einfluß der Wärmeübertragung auf die Stabilität von StrömungenSeverin, Jan 04 May 1999 (has links) (PDF)
Am Beispiel verschiedener Strömungstypen wird die
Stabilität von Strömungen unter Einfluß eines
Temperaturfeldes untersucht. Eine reguläre Störungs-
rechnung wird durchgeführt, um die Effekte temperatur-
abhängiger Stoffwerte systematisch und allgemein-
gültig erfassen zu können. Die Ergebnisse werden in
Form asymptotischer Reihen für die kritischen Kenn-
zahlen der jeweiligen Probleme angegeben.
Sowohl die Orr-Sommerfeld-Gleichungen als auch die
PSE-Gleichungen, jeweils mit variablen Stoffwerten,
kommen bei der Untersuchung von Grenzschicht-
strömungen zum Einsatz. Von besonderem Interesse
sind hier die Unterschiede in den Lösungen beider
mathematischer Modelle bezüglich der Effekte
variabler Stoffwerte. Es zeigt sich, dass die
Differenzen in den Lösungen beider Theorien für
den Fall konstanter und für den Fall variabler
Stoffwerte gleich groß sind.
Für die Grenzschichtströmung bei natürlicher Kon-
vektion an einer beheizten vertikalen Wand werden
die vollständigen PSE-Gleichungen gelöst. Hier
zeigen sich starke Abweichungen zur lokalen paral-
lelen Theorie (Orr--Sommerfeld--Gleichungen).
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O Programa Saúde na Escola : análise da implementação de uma política pública de educaçãoCosta, Roosevelt Rodrigues da 14 June 2013 (has links)
This research was focused social policies in Brazil with educational interface, in particular the Health Program at school - PSE, which is presented as an intersectoral policy coordination between health and education guided through a process of ongoing formation activities education in schools proposing interventions in the organization of the pedagogical work of schools and teachers. Developed a research on the concepts of education, training and organization of pedagogical work of this policy, explaining that the historical project is concatenated. Thus, we analyze the contradictions between such concepts advocated in the documents that served as the empirical sources (presidential decree establishing the PSE and instructional manuals) and the possibilities of its development in the reality of school education. This analysis was developed with dialectical historical approach by reference to the class struggle, as a category that helps us understand reality by contradiction, given that historically the capitalist mode of production forge a fragmented human existence into classes that are expressed the contradictions between capital and labor, bourgeoisie and proletariat, which are, in turn, expression of exploitation of man by man. In this context, we stand for an analysis from the perspective of the working class, used the method of dialectical historical materialism. For its realization we developed the following scientific problem: what are the links between the design and determinations of permanent training and the design of the school´s pedagogical work organization and teacher contained in the School Health Program? We conducted a theoretical research (literature) having bounded to analyze the Presidential Decree 6,286 / 2007 and the 2011 PES instructional manuals and 2013, which contain concepts of training and organization of pedagogical work. We use as technical content analysis guided by the analytical categories: Reality and Possibilities. With the research argue that the theoretical concepts (educational and pedagogical) present in that educational materials and in-person training and distance proposals do not consider the socio-historical determinations and contradictions concerning the theory and practice of concrete reality in which will be operationalized intervention revealing thus not critical theoretical trends, that is, they are not linked to the needs of working. These determinations and contradictions are explained, (1) the proposal of continuing education and distance as the main route of capillarity; (2) the dichotomy between theory and practice in performing their activities; (3) the impracticability of the principle of intersectionality with planning and implementation of joint activities between education and health professionals within schools; and (4th) in funding, which has the health network as a resource management route. In addition, (5) consider that the PSE has come up with a proposal to meet the needs of adolescents and youth who are in school, however, the questions (problems) by the program are not connected to the real needs of the school, but needs to reach demands of public health, with the school as privileged locus. Thus, falls on the school and on teachers, responsibilities that are not genuinely yours. / Esta pesquisa tem como objeto as políticas sociais no Brasil com interface educacional, em especial, o Programa Saúde na escola PSE, que se apresenta como uma política intersetorial de articulação entre saúde e educação orientando, por meio de um processo de formação permanente, atividades educativas nas escolas propondo intervenções na organização do trabalho pedagógico das escolas e dos professores. Desenvolvemos uma investigação sobre as concepções de educação, formação e organização do trabalho pedagógico dessa política, explicitando a que projeto histórico está concatenada. Assim, analisamos as contradições existentes entre tais concepções preconizadas nos documentos que nos serviram como fontes empíricas (decreto presidencial que instituiu o PSE e os manuais instrutivos) e as possibilidades do seu desenvolvimento na realidade da educação escolar. Essa análise desenvolveu-se com enfoque histórico dialético tomando como referência a luta de classes, enquanto categoria que nos ajuda a compreender a realidade por contradição, tendo em vista que historicamente o modo de produção capitalista forja uma existência humana fragmentada em classes sociais que se expressam pelas contradições entre capital e trabalho, burguesia e proletariado, que são, por sua vez, expressão da exploração do homem pelo homem. Nesse contexto, nos posicionamos para uma análise a partir da perspectiva da classe trabalhadora, utilizado o método do materialismo histórico dialético. Para sua realização elaboramos o seguinte problema científico: quais os nexos e determinações entre a concepção de formação permanente e a concepção de organização do trabalho pedagógico da escola e do professor contidas no Programa Saúde na Escola? Realizamos uma pesquisa teórica (bibliográfica) tendo delimitado para análise o decreto presidencial 6.286/2007 e os Manuais instrutivos do PSE de 2011 e 2013, os quais encerram concepções de formação e organização do trabalho pedagógico. Utilizamos como técnica a análise de conteúdo orientado pelas categorias de análise: Realidade e Possibilidades. Com a pesquisa defendemos que as concepções teóricas (educacionais e pedagógicas) presentes no referido material didático e nas propostas de formação presenciais e à distância não consideram as determinações sócio-históricas e contradições concernentes à teoria e prática da realidade concreta na qual será operacionalizada a intervenção revelando, assim, tendências teóricas não críticas, ou seja, que não estão atreladas às necessidades da classe trabalhadora. Essas determinações e contradições explicitam-se (1º) na proposta de formação permanente e à distância como principal via de capilarização; (2º) na dicotomia teoria-prática para realização das atividades; (3º) na inviabilidade do princípio da intersetorialidade com planejamento e execução de atividades conjuntas entre profissionais de educação e saúde no âmbito das escolas; e (4ª) no financiamento, que tem a rede de saúde como via de gestão do recurso. Além disso, (5º) consideramos que o PSE surgiu com uma proposta de atender as necessidades de uma população adolescente e jovem que está na escola, porém, as perguntas (os problemas) formuladas pelo programa não estão conectadas às necessidades reais da escola, mas sim às necessidades de atingir demandas da saúde pública, tendo a escola como lócus privilegiado. Deste modo, recai sobre a escola e sobre os professores, responsabilidades que não são genuinamente suas.
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Stanovení organických sloučenin ve vzorcích biouhlu získaných mikrovlnou torefakcí biomasy / Determination of organic compounds in biochar produced by microwave torrefaction of biomassMeindl, Jiří January 2019 (has links)
The thesis is focused on a determination of polycyclic aromatic hydrocarbons (PAHs) contained in dried pelletized sewage sludge and pelletized biochar. Biochars were made in mild conditions by microwave torrefaction of prepared sewage sludge. There were analyzed and quantified the 34 of standardized PAHs compounds in two series. The first serie, also called “Sada 1”, has been aimed at comparison of extraction methods for the chosen sample of sewage sludge and the sample of biochar. In serie “Sada 1”, there were compared efficiencies of chosen type of solvent or solvent mixture by comparison of yields for 34 standardized analytes in a sample of biochar and a sample of sewage sludge. There were compared also to total yields of PAHs and to number of quantified compounds in analyzed samples. The most reliable extraction method has been used for the next analyses of samples in the second serie called “Sada 2”. In Sada 2, there were compared different samples of the same type (e.g. biochar, sludge). The origin of sewage sludge (small or big sewage treatment plant expressed as PE) and used additives (cellulose, chaff, hay) as modificators for torrefaction process were variables for different type of sample. The results of analysis were identification of the most suitable sewage sludge and additive to be used as modificator for microwave torrefaction process. The main goal of correctly chosen sludge and additive was to minimize production of PAH’s during torrefaction and in samples of biochar.
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PSE extrakce rostlinného materiálu pro potravinářské účely / Pressurized solvent extraction of plant material for food industry useHolasová, Petra January 2009 (has links)
Flavonoids were identified and quantified in samples of dry leaves of plant Stevia rebaudiana Bertoni. Content of flavonols (kaempherol, quercetin, myricetin, rutin) and flavons (apigenin, luteolin) were compared in three samples (standard leaves of Stevia rebaudiana Bertoni, Stevia rebaudiana Bertoni origin from Ukraine and from Czech republic), that were extracted by three extraction methods (PSE, ultrasonic extraction, Soxhlet extraction) with two polar solvents, methanol and ethanol, in combination with non-polar hexane. Extracts were analyzed by HPLC with detection UV-VIS. Antioxidant activity and total content of flavonoids in extracts were measured by spectrometry. Stable free radical DPPH. was used for determination of scavenging effect in extracts. PSE was the most effective extraction method with this conditions – 120 °C, dynamic mode and with methanol like solvent.
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Computational and accuracy benchmarking of simulation and system-theoretic models for production systems engineeringRamos Calderón, Antonio José January 2021 (has links)
The modern industry has an increasing demand for simulation software able to help workers and decision-makers visualize the outputs of a specific process in a fast, accurate way. In this report, a comparative study between FACTS (Factory Analyses in ConcepTual phase using Simulation), Plant Simulation, and PSE (Production System Engineering) Toolbox is done regarding their capacity to simulate models with increasing complexity, how accurate they are in their outputs with different optimized buffer allocations, and how well they perform on the task of detecting the bottlenecks of a process. Benchmarking simulation software requires an experimental approach, and for gathering and organizing all the data generated using external programs like MATLAB, C, Excel, and R are used. A high level of automatization is required as otherwise the manual input of data would take too long to be effective.The results conclude on major concordances among FACTS and Plant Simulation as the most used commercial DES (Discrete Event Simulation) software and a more mathematical-theoretical approach coming from PSE Toolbox. The optimization done in the report links to sustainability, with an enhanced TH improving the ecological, social and economic aspects, and to Lean philosophy using lean buffers that smooth and improve the production flow.
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