[pt] O fato que a dissolução de pequenas quantidades de polímero de cadeias moleculares longas em fluxo turbulento através dutos reduz drasticamente o atrito, é conhecido há muitos anos. No entanto, muitos aspectos fundamentais deste fenômeno ainda não são bem compreendidos, particularmente os mecanismos de interação entre o polímero e o solvente. O presente trabalho descreve os resultados de um estudo voltado para fornecer informações detalhadas sobre as características da turbulência no escoamento de água com aditivo polimérico através de tubos. Para isto, foram realizados experimentos para medir o campo instantâneo de velocidade em uma seção longitudinal de um tubo, empregando a técnica de Velocimetria de Partículas por Imagem, PIV, em sua versão bidimensional. As grandezas estatísticas turbulentas foram obtidas a partir de uma série de 2.500 campos instantâneos de velocidade medidos para cada configuração de escoamento caracterizada pelo número de Reynolds e pela concentração de polímero em água. Foram medidos campos de velocidade média, de flutuações de velocidade dadas por valores RMS e perfis de tensão turbulenta. Especial atenção foi dedicada ao projeto da seção de testes, de modo a minimizar as distorções de imagem junto à parede do tubo. Na região de visualização, a parede do tubo foi usinada com uma espessura de 500 μm para minimizar a refração óptica da superfície curva. Esta tubulação de paredes finas, em combinação com uma caixa de acrílico preenchida com água posicionada ao redor do tubo, permitiu medições de velocidade com a técnica PIV em posições a cerca de 250 μm da parede do tubo, o que equivale a menos de 10 unidades em coordenadas de parede. A análise dos campos de deslocamento das partículas traçadoras nas imagens capturadas empregou uma combinação da técnica PIV clássica com técnicas de acompanhamento de partículas, resultando em medidas com resolução espacial substancialmente melhorada. Os testes foram conduzidos para uma faixa de números de Reynolds de 23000 a 80000, e para 20 ppm de concentração de polímero Superfloc A110 em água. As medidas da queda de pressão indicaram reduções no coeficiente de atrito da ordem de 50%. Os resultados obtidos demonstraram que a presença do aditivo polimérico produz alterações na estrutura do escoamento turbulento junto à parede, o que se reflete em mudanças na camada de amortecimento do perfil de velocidade. / [en] The fact that dissolving a minuscule amount of long-chain polymer molecules in a turbulent pipe flow reduces drastically the frictional drag, has been known for many years. However, many fundamental aspects of this phenomenon are still not well understood, particularly the mechanisms of interaction between the polymer and the solvent. The present paper describes the results of an ongoing project aimed at providing detailed information on the turbulence characteristics of turbulent pipe flow of water with polymer additive. To this end, an experimental program was conducted for measuring the instantaneous longitudinal velocity field employing a two-dimensional Particle Image Velocimetry technique – PIV. Turbulence statistics were obtained from a series of approximately 2500 instantaneous velocity fields measured for each flow configuration characterized by the pipe Reynolds number and the polymer concentration. Profiles of Time-averaged velocity, RMS velocity fluctuations and turbulent shear stresses were measured. Special attention was dedicated to the test section design so as to minimize image distortions close to the pipe wall. At the visualization region, the pipe wall was machined to a thickness of 500 μm to minimize optical refraction of the curved surface. This thin-walled pipe in combination with a plexiglass box filled the water surrounding the pipe, allowed for PIV velocity measurements at approximately 250 μm from the pipe wall, which is equivalent to less than 10 wall units. A combination of classical PIV with particle tracking techniques was employed in the analysis of the particle displacements, what substantially enhanced the spatial resolution of the measurements. Tests were conducted for a Reynolds number range from 23000 to 80000, and for 20 ppm of Superfloc A110 polymer in water. Wall pressure measurements indicated reductions in the friction factor of the order of 50%. The results obtained demonstrated that the presence of the polymer additive alters the turbulence structure at the wall, what produces a shift in the buffer layer of the velocity profile.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第23059号 / 医博第4686号 / 新制||医||1048(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 長船 健二, 教授 平井 豊博, 教授 羽賀 博典 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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The thesis deals with study of surface tension of liquids and measuring possibilities of this parameter. The paper is then focused on design of measuring apparatus based on pendant drop method. The apparatus is controlled with software written in Matlab. Several measurements are done at the end of this work, which confirm possibility to practical use of this apparatus for surface tension measurements. A part of this work is manual to use the apparatus and complete design documentation.

The first part of the diploma thesis with name „Evaluation of dynamic damage of composite structure“ focuses on designing device for impact experiments and suitable laminate samples made from prepregs. The conditions and problems of impact tests are also demonstrated here. The second part of the thesis deals with non-destructive control of damaged specimens based on thermography. This is mainly the extent of defects in the impaired area and the evaluation of results using the pulse infrared thermography method. Finally, the relative deviation in the crack size comparison between the visual method and thermographic are compared. Consequently, the residual strength of the damaged samples against undamaged specimens are compared using bending tests.

This master’s thesis deals with the design of heat recovery system from melting furnace waste gases. The first part is devoted to a brief description of heat exchangers, with the special importance being placed on the shell-and-tube heat exchanger. The second part contains a calculation of stoichiometric combustion, design of geometrical dimensions, calculation of pressure drops and power. At the end of the thesis there are various possibilities of utilization of the obtained waste heat and their basic economic assessment.

The work's main topic is a recently published slow DoS attack called SlowDrop. The work focuses on the subject of describing the current state of the DoS problem as a whole and the SlowDrop attack as well. It works with this theoretical basis during the implementation of it's own SlowDrop attack model. This model is tested in various scenarios and the outcome results are analyzed and constructively discussed. Furthermore defensive mechanisms against this threat and DoS attacks in general are proposed, specific methods shown and configurations recommended. These methods are followingly tested and evaluated. Last but not least the traffic of a SlowDrop attacker and a legitimate client with bad connection, which the SlowDrop attack is trying to immitate, are compared. From this comparison final conclusions of this work are drawn.

Frost formation is of a major research interest as it can affect many industrial processes. Frost appears as a thin deposit of ice crystals when the temperature of the surface is below the freezing point of the liquid. The objective of this research is to study icing with hope to propose new anti-icing and deicing methods. In the beginning of the research, cracking of the ice layer was observed when a deionized water droplet impacts a ?50 oC cooled sphere surface that is in contact with dry ice. To further investigate the cracks occurrence, multiple experiments were conducted. It was observed that the sphere surface temperature and droplet temperature (ranges from 10-80 oC) have no effect on the crack formation. On the other hand, it was observed that formation of a thin layer of frost on the sphere before the drop impact leads the lateral cracking of the ice. Thus, attempts to reproduce the cracks on clean super cold sphere surfaces were made using scratched and sandblasted spheres as well as superhydrophobized and polymer particle coated spheres. Furthermore, innovative methods were tried to initiate the cracks by placing epoxy glue bumps and ice-islands coatings on the surface of the spheres. All of these attempts to reproduce the crack formation without the presence of frost, failed. Nonetheless, the adding of isolated frost on the sphere surfaces always leads to the crack formation. Generally, frost forms on the small spheres faster than it does on the bigger ones. Additionally, the cold water droplet produces thicker water and ice layer compared to a hot water droplet; and the smaller the sphere the larger its water and ice layer thicknesses.

Philosophiae Doctor - PhD / It has become a world trend that the opportunity for university education should be made available to all. The twentieth century witnessed the partial demolition of the barrier that retained higher education as the privilege of the élite group. Attendance at a university is seen today as the gateway to the membership of a profession, and to all the benefits of improved economic and social status. Rapid economic and industrial development in South Africa and overseas in the second half of this century has caused a general shortage of scientific manpower. Malherbe (1977, 496) stresses that full opportunities for developing the talent of every individual are no longer an idealistic aim but an economic necessity. The Wiehahn Commission (1980, 12), appointed by the South African Government to inquire into labour legislation and labour systems in South Africa, reported that a serious shortage of skilled manpower for professional, managerial and technical positions still exists. The universities, now having a major responsibility in the preparation of such personnel, have assumed greater significance as far as the public and private sectors are concerned. Educated people are a part of the nation's best human resources, and because education is one of the chief assets of the individual, there is a compelling need for research to improve the academic performance of students at all levels, especially at university. Arising from the shortage of skilled manpower and the increasingly growing demand for tertiary -education, more students enter universities. The rapid increase in university enrolment has brought with it new interest and concern relating to those students who fail or drop out. The problems of failure and drop-out at university have been the subject of many investigations in Western countries, especially Great Britain (Miller, 1970; Butcher and Rudd, 1972) and the United States of America (Pervin et aZ, -1965; Astin, 1971). In South Africa, the Government appointed a Commission of Inquiry into White universities (Van Wyk de Vries, 1974). Included in its terms of reference were: transition from school to university, and the high failure rate among undergraduates. As Astin (1975, 1) points out, most studies take the view that decision-makers legitimately want to know more about how to increase the students' chances of graduating. This concern is based, inter aZia, on: loss of talent; waste of limited educational resources; vocational and personal setbacks resulting from the student's impeded career development; futile expenditure of money, time and effort. The incidence of failure and drop-out evokes painful responses not only from the student but also from others, including his parents and his university. To parents, the admission to university of their son or daughter often represents a fulfilled ambition and the fruition of years of struggle and hope. Therefore failure or drop-out by the student is also a shattering experience for most parents - many of whom feel that they have failed as parents

Design of reconstruction the damaged streambed Rusava in the village Rusava The task of this thesis is to evaluate the existing capacity of the streambed and design the reconstruction of Rusava river km 26,000 to 28,230. Rusava watercourse takes place in urban area of village Rusava in Zlín region. Channel revetment was badly damaged by floods in July 2011. The assessment of the current state of the watercourse was based on personal visit of the place and taken photos. Current state was modeled in HEC – RAS 3.1.3 software. The reconstruction is designed according to the assessment of the current river channel condition and also contains proposals for new buildings on the river.