Dentro do escopo de estudo de aspectos fundamentais e tecnológicos, este trabalho foi direcionado à avaliação do comportamento da estabilidade e da eficiência de um reator anaeróbio contendo biomassa imobilizada em espuma de poliuretano para o tratamento de água residuária sintética com concentração de aproximadamente 500 mgDQO/L. O reator, de 6 litros de volume nominal, mantido à temperatura de 30 +/- 1ºC e sob a agitação mecânica de 500 rpm, foi operado em bateladas seqüenciais com a renovação de apenas parte do volume de água residuária tratada por ciclo, ou seja, a descarga do reator não foi completa, mas apenas parcial. Neste contexto, a principal característica operacional investigada foi a relação entre o volume de água residuária afluente, o qual era alimentado a cada novo ciclo de operação, e o volume de meio contido no reator, o qual não era descarregado no ciclo anterior, mantendo-se a mesma carga orgânica volumétrica. Desta forma, foi possível verificar a flexibilidade operacional do sistema com relação ao volume de água residuária tratada a cada ciclo e o tempo de duração do ciclo para uma mesma carga orgânica. Os resultados indicaram que o reator pôde operar com diferentes relações entre o volume alimentado e o volume de meio reacional sem diminuição significativa do seu desempenho, permitindo-se, assim, maior flexibilidade operacional. Para as condições em que o volume renovado foi maior ou igual a 50% do volume de meio do reator (ciclos de 4 a 8 horas), as eficiências de remoção de matéria orgânica filtrada e não filtrada mantiveram-se no patamar de 84 e 79%, respectivamente, enquanto que nas demais condições de maior diluição inicial do afluente (ciclos de 1 e 2 horas), essas eficiências foram ligeiramente menores, em torno de 80 e 74%, respectivamente. A alta velocidade de formação de material viscoso de aparência polimérica, nas condições de maior diluição inicial do afluente, dificultou a manutenção do volume de meio reacional do reator constante. / An assessment was performed on the stability and efficiency of an anaerobic reactor containing biomass immobilized on polyurethane foam for the treatment of synthetic wastewater with organic loading of approximately 500 mgCOD/L. The reactor had a total volume of 6 L. Batch operation took place at a temperature of 30 +/- 1ºC and an agitation rate of 500 rpm. During operation only part of the treated wastewater was renewed per cycle, i.e., reactor discharge was not complete, but partial. The main operation characteristic investigated was the ratio between influent wastewater volume, which was fed at each cycle, and the volume of medium contained in the reactor, which had not been discharged in the previous cycle, maintaining the same volumetric organic load. This way, it was possible to verify operation flexibility of the system regarding treated wastewater volume in each cycle as well as cycle time duration for the same volumetric organic loading. Results indicated that the reactor was able to operate at different ratios between feed and reaction medium volume without significant loss in performance, allowing, hence, greater operation flexibility. For conditions at which renewed volume was greater than or equal to 50% of the reactor medium (cycles from 4 to 8 hours), filtered and non-filtered organic matter removal efficiencies were about 84 and 79%, respectively, whereas at conditions of higher initial influent dilution (cycles from 1 to 2 hours) these efficiencies were slightly lower, about 80 and 74%, respectively. The high formation rate of viscous polymer-like material probably of microbiological origin, at the conditions of higher initial influent dilution hindered maintenance of constant reactor medium volume.

No description available.

Estudou-se a influência do fosfato na multiplicação de Saccharomyces cerevisiae em uma fermentação contínua em mini-fermentador. Determinou-se a massa seca, a concentração dos substratos, a velocidade específica de consumo dos substratos, a velocidade específica de formação de gás carbônico, velocidade específica de consumo de oxigênio e o quociente respiratório bem como, o fósforo intracelular em diversas vazões específicas de alimentação, em cultivo contínuo de levedura de panificação, em condições de substratos limitantes. Controlando-se a quantidade de fosfato no meio de alimentação de tal modo que o fosfato residual no meio de fermentação mal pudesse ser detectado, o valor da vazão específica de alimentação crítica era aparentemente aumentado de 0,23 h-1 para 0,32 h-1. Isto sugere uma possível influência do fosfato nas funções anaeróbicas e aeróbicas da levedura de panificação. / The influence of phosphate in a continuous culture was studied using mini-fermentor on the Saccharomyces cerevisiae multiplication. Dry matter, substrate concentration, specific substrate comsumption, specific carbon dioxide release, specific oxygen uptake rates and respiration quotient , as well as phosphorous content of the cells were measured in dependence on the dilutionrate. In continuous culture glicose-limited, of baker\'s yeast if the supply of phosphorous were restricted to a extent that residual phosphate in the medium could hardly be observed, the value of critical dilution rate was apparently enhanced from 0,23 h-1 to 0,32 h-1. This observation suggests a possible mediation by phosphate between anaerobic and aerobic functions of the baker\'s yeast.

This thesis deals mainly with perfusion modeling in optical coherence tomography (OCT). The introductory part deals with basic theory of the OCT, including a description of its basic applications. Part of the work was the testing of selected contrasting materials suitable for the OCT and the design and implementation of phantoms, which were subsequently used in the main part of the thesis. In the practical part, attention is paid to the perfusion analysis in the OCT, first the application of the dilution theory in the OCT for flow estimation, then a study testing the basic theory of perfusion on OCT by means of tissue phantom. Another part of the thesis is devoted to the method of speckle variance analysis for flow visualization.

Es wurde ein Modell zur realistischen Beschreibung der Kühlmittelvermischung innerhalb des Reaktordruckbehälters von Druckwasserreaktoren in den gekoppelten Programmkomplex DYN3D/ATHLET implementiert. Diese Modell basiert auf dem Prinzip der linearen Superposition Dirac-Impuls-ähnlicher Störungen und kann für die Modellierung der Vermischung von Kühlmittel unterschiedlicher Temperatur und/oder unterschiedlicher Borsäurekonzentration eingesetzt werden. Der um das Vermischungsmodell erweiterte Programmkomplex DYN3D/ATHLET wurde für Analyse von Borverdünnungsstörfällen und Frischdampflecks angewandt. Für den Fall "Start der ersten Hauptkühlmittelpumpe bei Vorhandensein eines minderborierten Pfropfens im kalten Strang" zeigten die Ergebnisse der durchgeführten Parameterstudie, dass es selbst bei Annahme des maximal möglichen Pfropfenvolumens nicht zu einer Schädigung des Brennstoffes kommt. Mit den Analysen zu einem generischen Frischdampfleckszenario wurde die Anwendbarkeit des Programmkomplexes DYN3D/ATHLET auf die zweite Störfallklasse, in der die Kühlmittelvermischung eine wichtige Rollen spielt, demonstriert. Im Rahmen der Arbeiten zum Projekt wurde außerdem gezeigt, dass der Einfluss der turbulenten Schwankungen des Geschwindigkeitsfeldes innerhalb des Reaktordruckbehälters auf neutronenkinetische Parameter im Nominalbetrieb und unter Störfallbedingungen nicht zu vernachlässigen ist. A model for the realistic description of the coolant mixing inside the pressure vessel of pressurized water reactors was implemented into the coupled code complex DYN3D/ATHLET. This model is based on the linear superposition Dirac-pulse-like perturbations. The model can be applied to the mixing of coolant of different temperature and/or boron concentration. The coupled code complex DYN3D/ATHLET with the newly implemented model was applied to the analysis of boron dilution and steam line break accidents. The results of a parameter study for the case "Start-up of the first main coolant pump with a slug of lower borated water in the cold leg" have shown, that even under the conditions of the maximum slug volume there is no fuel damage. The applicability to the second class of accidents, where the coolant mixing has to be considered, was demonstrated by the analysis of a generic main steam line break scenario. Further it was shown, that the influence of turbulent fluctuations of the velocity inside the reactor pressure vessel during nominal and accident conditions on neutron-kinetic parameters cannot be neglected.

The goal of the work described in this report was the experimental investigation of the mixing of coolant with different quality (temperature, boron concentration) in nuclear reactors on the way from the cold leg through the downcomer and lower plenum to the core inlet in a systematic way. The obtained data were used for the clarification of the mixing mechanisms and form a data basis for the validation of computational fluid dynamics (CFD) codes. For these purposes, experiments on slug mixing have been performed at two test facilities, modelling different reactor types in scale 1:5, the Rossendorf and Vattenfall test facilities. The corresponding accident scenario is the start-up of first main coolant pump (MCP) after formation of a slug of lower borated water during the reflux-condenser mode phase of a small break loss of coolant accident (LOCA). The matrices for the experiments were elaborated on the basis of the key phenomena, being responsible for the coolant mixing during pump start-up. Slug mixing tests have also been performed at the VVER-1000 facility of EDO Gidropress to meet the specifics of this reactor type. The mixing of slugs of water of different quality is also very important for pre-stressed thermal shock (PTS) situations. In emergency core cooling (ECC) situations after a LOCA, cold ECC water is injected into the hot water in the cold leg and downcomer. Due to the large temperature differences, thermal shocks are induced at the reactor pressure vessel (RPV) wall. Temperature distributions near the wall and temperature gradients in time are important to be known for the assessment of thermal stresses. One of the important phenomena in connection with PTS is thermal stratification, a flow condition with a vertical temperature profile in a horizontal pipe. Due to the fluctuating character of the flow, this may cause thermal fatigue in the pipe. Besides of thermal fatigue, a single thermal shock can also be relevant for structural integrity, if it is large enough, especially in the case, that the brittle fracture temperature of the RPV material is reduced due to radiation embrittlement. Therefore, additional to the investigations of slug mixing during re-start of coolant circulation, the mixing of slugs or streams of water with higher density with the ambient fluid in the RPV was investigated. The aim of these investigations was to study the process of turbulent mixing under the influence of buoyancy forces caused by the temperature differences. Heat transfer to the wall and thermal conductivity in the wall material have not been considered. Experiments on density driven mixing were carried out at the Rossendorf and the Fortum PTS facilities.

Gas turbine engines are one of the primary sources of electricity currently in the world. The assembly consists of multiple subsystems all of which are placed within an acoustic enclosure. Dilution ventilation is a widely used and recommended means of protection against the risk of explosion within gas turbine acoustic enclosures. Leakage and accumulation of flammable gas and its ignition from the turbine are one of the reasons for this explosion. The ISO regulations provide a safety criterion for the allowable size of flammable gas cloud as a proportion of enclosure volume. The effectiveness of the ventilation system in maintaining the clouds and the optimum placement of gas detectors to detect these clouds is determined through CFD simulations. This thesis deals with the primary step in the process of detecting the problematic regions which might allow the growth of the gas clouds to pass safety levels if the engine is not shut down. Using the same methodology, other possible configurations of the ventilation system and the effect on the flow due to the addition of a platform and movement of junction boxes are also studied. It is found out that the configuration where the inlet and outlets of the standard configuration are interchanged is arguably the best followed by the configuration with a split inlet, standard configuration, and lastly, the one with reduced volumetric flow rate. The platform and the movement of junction boxes across the walkway/platform do not affect the flow in any significant manner. The vertical movement of junction boxes affect the size of the low-speed region behind the inlet plenum. The thesis satisfied its objectives and provides a guideline for the same.

No description available.

雖然許多研究已針對認股權證評價進行調整，但是其價格低估的問題仍無法解決。因此，本文將探討認股權證發行對股價報酬動態過程的影響。本文將證實是否認股權證發行將影響其標的股價之動態過程，倘若股價報酬的動態過程已反應了認股權證發行的潛在稀釋效果，則進行充分調整的股權稀釋模型將低估認股權證的價格。為了確認在評價認購權證時充分調整稀釋效果的必要性，本文將檢測權證發行對股票報酬過程的影響。本文利用延伸Garch-M模型，導出四個檢驗稀釋效果的模型。實證結果顯示，在發行認股權證之後，股價報酬的變異數顯著降低，該結果在釐清股權稀釋效果與不對稱效果之後，該稀釋效果依然顯著。 / As the underestimation of warrants remains unsolved after many adjustments presented by previous researchers, we further investigate the impact of the warrant introduction on the underlying stock return processes. This research attempts to determine whether the introduction of warrants influences the return processes of underlying stocks. If the introduction creates a potential dilution effect in stock return processes, full dilution adjustment pricing models would lead to underestimation. To exam whether full dilution adjustments are required for warrant pricing, the GARCH-M model has been extended to derive four models for testing the dilution effect on stock return processes. Empirical results show that the volatilities of underlying stock return processes are significantly reduced following warrant introduction even after clarification and distinguishing dilution from asymmetric effect.

The primary objective of the study as contained in this thesis is the discussion of the approaches to dilution taken by the legal systems of the European Union and South Africa. Although a comparative methodology is employed the discussion grounds the separate development of the anti-dilution provisions in both systems first before discussing comparisons and diverging approaches (should they exist). As a result of the South African anti-dilution provisions being relatively new, there exists a lot of overlap between the approaches in the United Kingdom, European Union and South Africa. Dilution both as a concept and a reality remains controversial as both the courts and commentators grapple with how it fits within greater Trade Mark law. The relationship between traditional infringement and dilution is equally contentious as questions continue to be asked about the relevance of the anti-dilution provisions when traditional infringement already exists and is effective. A question that is constantly asked is: can there be infringement without confusion? Equally contentious is the issue of whether a parody exception should be introduced in Trade Mark law even though there is minimal litigation around the issue of parody and dilution.