This work analyzes the solid flow dynamics of gas-solid downer fluidized bed reactor in co-current and, particularly, in counter-current mode. This reactor is potentially interesting for catalytic applications where very short (sub second) and precise contact times are required between the solid catalyst and the gaseous reactants-products. To this aim, a 1.5 m and 36 mm ID downer reactor setup was built to replicate the conditions in a real unit in cold flow and using materials that enable the observation of the solid particle dynamics. Specifically, two state-of-the-art techniques have been used: Particle Image Velocimetry (PIV) and Digital Image Analysis (DIA). Three types of particles have been used: two commercial fluidized catalytic cracking (FCC) particles (ρp = 1300 kg/m3, dp = 75 and 56 μm) and sand (ρp=2600 kg/m3, dp= 370 μm). High-speed cameras were positioned in two axial positions: 70 and 140 cm from the top, to reveal the flow behavior across the reactor. It was found that the solid flow initially was segregated because of the solid feeding design. Thus, 3D printed re-distributer was used to even the solid flow. The solid particles in the counter-current downer was approaching the plug-flow behavior with 23% variation in the velocity gradient across the radial direction, compared with 40% for the co-current counterpart. A method to estimate solid hold-up based on images was developed, yielding values in a good agreement with literature. Keywords: Hydrodynamics, counter-current, downer, PIV, DIA, Solid hold-up

Conventional methods for diagnosis of human disease are, at times, limited in different regards including time requirement, either experimental or data processing, sensitivity, and selectivity. It is then that a Point of Care Criteria, which considers the true utility and usefulness of the device, is employed to propose new diagnostic devices capable of overcoming the aforementioned shortcomings of conventional tools. Nucleic acid, characterized for its predictable base-pairing nature, is considered to be a highly-selective, yet greatly modifiable device. Its behavior is then described through Boolean Logic, where “true” or “false” outputs are mathematically described as “1” and “0”, respectively. This mathematical approach is then referred to as Logic Gates, where outputs can be predicted based on satisfied environmental conditions. The mechanisms, capable of exhibiting Logic Gate behavior, are described.

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No description available.

L’idée que le football professionnel en Europe est en crise fait très largement consensus parmi les économistes. Dans notre thèse, nous montrons que ce diagnostic suppose de négliger un certain nombre d’éléments constitutifs de l’inscription du football dans le monde économique. C’est pourquoi, nous défendons que, loin d’être en crise, le football professionnel européen est, depuis les années 1980, dans une phase de très forte croissance. Pour ce faire, nous adoptons une démarche mésoéconomique régulationniste et procédons à une analyse systémique et multi-niveaux du football professionnel européen. Nous aboutissons ainsi à la caractérisation d’un « régime économique de fonctionnement » que nous qualifions de « financiarisé » compte tenu de l’instrumentalisation du football par des intérêts financiarisés et de leur influence sur les stratégies des acteurs traditionnels du football. Cette financiarisation du football engendre une forte instabilité de son régime puisque l’activité des clubs implique du déficit et du surendettement. En effet, l’incitation à la performance sportive (ligue ouverte), le fort pouvoir de négociation des joueurs (hold-up) et la souplesse de l’environnement réglementaire du football conduisent les clubs à des niveaux de dépenses élevés. Au contraire des « petits » clubs, cette situation n’est pas problématique pour les « grands » clubs, puisqu’ils sont soutenus par des agents à forte capacité de financement et tirent des revenus élevés de leur participation aux compétitions supranationales. Dans ce contexte, le régime est donc durable : sous l’effet de l’instabilité, les acteurs nouent de nouveaux compromis qui modifient les « dispositifs institutionnels » existants et rendent ainsi pérenne la logique de croissance en vigueur. Il y a donc régulation (au sens de la théorie de la régulation) du football. Il reste toutefois que ces modalités de régulation conduisent à accroître les inégalités entre les clubs et que cela pourrait, à terme, amener à une crise économique majeure du football professionnel européen. / Economists argue that the European professional football is in crisis. This thesis discusses this postulate by testing the relationship between the changes in football and the transformations of modern capitalism. Our methodology is based on a meso-level analysis from the French “Régulation theory” which provides a systemic and multilevel analysis. The thesis thus emphasizes how the progressive integration of financialised interests in football has an influence on the strategies of football traditional stakeholders. It actually shows that the financialisation process of the European professional football leads to growth since the 1980s. However, this growth is rather unstable because losses and indebtedness are part of clubs activity. The incentive for sports performance (open league), the players’ strong bargaining power (hold-up) and the flexibility of the regulatory environment are the main determinants of the clubs’ high spendings. Contrary to the “small” clubs, this situation is not a constraint for the “big” clubs thanks to the financial contributions they obtain from their owners, from their funding partners and from their participation to supranational competitions. In this environment and despite instability, the growth regime remains nevertheless sustainable. The stakeholders create new compromises to reduce imbalances: these compromises are the roots for new institutional arrangements that finally support the growth logic which is in place. There is therefore a “régulation” in European professional football, that is to say a process that contributes to the reproduction of the sector. However, this process paradoxically increases inequalities and may encourage the conditions for a major economic crisis.

Signal-integrity degradation from such factors as supply and substrate noise and cross talk between interconnects restricts the performance advances in Very Large Scale Integration (VLSI). To avoid this and to keep the signal-integrity, accurate measurements of the on-chip signal must be performed to get an insight in how the physical phenomenon affects the signals. High-speed digital signals can be taken off chip, through buffers that add delay. Propagating a signal through buffers restores the signal, which can be good if only information is wanted. But if the waveform is of importance, or if an analog signal should be measured the restoration is unwanted. Analog buffers can be used but they are limited to some hundred MHz. Even if the high-speed signal is taken off chip, the bandwidth of on-chip signals is getting very high, making the use of an external oscilloscope impossible for reliable measurement. Therefore other alternatives must be used. In this work, an on-chip measuring circuit is designed, which makes use of the principle of a sampling oscilloscope. Only one sample is taken each period, resulting in an output frequency much lower than the input frequency. A slower signal is easier to take off-chip and it can easily be processed with an ordinary oscilloscope.

<p>Signal-integrity degradation from such factors as supply and substrate noise and cross talk between interconnects restricts the performance advances in Very Large Scale Integration (VLSI). To avoid this and to keep the signal-integrity, accurate measurements of the on-chip signal must be performed to get an insight in how the physical phenomenon affects the signals. </p><p>High-speed digital signals can be taken off chip, through buffers that add delay. Propagating a signal through buffers restores the signal, which can be good if only information is wanted. But if the waveform is of importance, or if an analog signal should be measured the restoration is unwanted. Analog buffers can be used but they are limited to some hundred MHz. Even if the high-speed signal is taken off chip, the bandwidth of on-chip signals is getting very high, making the use of an external oscilloscope impossible for reliable measurement. Therefore other alternatives must be used. </p><p>In this work, an on-chip measuring circuit is designed, which makes use of the principle of a sampling oscilloscope. Only one sample is taken each period, resulting in an output frequency much lower than the input frequency. A slower signal is easier to take off-chip and it can easily be processed with an ordinary oscilloscope.</p>

På 1980-talet handlade en grupp, som kallades för The Turtle Traders, med två trendföljande handelsstrategier helt baserade på teknisk analys på ett stort antal finansmarknader. De två handelsstrategierna byggde på mekaniska regler för köp- respektive säljbeslut och riskhantering, men även regler för vilka marknader som var tillåtna att handla på. Gruppen var mycket framgångsrik under flera år och medlemmarnas avkastningar översteg marknadernas avkastningar med råge. Den svaga varianten av den effektiva marknadshypotesen säger att detta ska vara omöjligt på effektiva marknader. På en effektiv marknad är det enligt hypotesen istället bättre att följa en buy-and-hold strategi. Hur kommer det sig att The Turtle Traders lyckades? Var det bara tur att de två trendföljande strategierna, som genererade köp- och säljbesluten, gav väldigt höga avkastningar under några år på 1980-talet? Eller är inte marknaderna effektiva? Inom forskningen råder det idag en oklar bild kring den effektiva marknadshypotesen och huruvida marknaderna är effektiva. Olika vetenskapliga studier presenterar tester som både stöder och förkastar hypotesen. Syftet med det här examensarbetet är att visa huruvida de två trendföljande strategierna fortfarande är vinstgivande och därmed användbara strategier på dagens finansmarknader. Syftet är också att jämföra de två strategierna med buy-and-hold strategin på olika marknaderna och därmed bidra med ytterligare insikter till den numera alltmer ifrågasättande diskussionen kring den effektiva marknadshypotesen, med speciellt fokus på den svaga varianten. För att få fram vilka avkastningar de två trendföljande strategierna ger på dagens marknader konstrueras inom ramen för detta examensarbete ett datorprogram som simulerar de köp- och säljbeslut som skulle tas med hjälp av de mekaniska regler som de två trendföljande strategierna bygger på. Undersökningen i examensarbetet ger, precis som många andra undersökningar, en oklar bild kring den effektiva marknadshypotesen. Hälften av de finansmarknader som undersöks tycks vara ineffektiva och hälften effektiva, enligt den svaga varianten av hypotesen. Undersökningen visar även att de två trendföljande strategierna inte är så pass vinstgivande att de kan rekommenderas att använda på dagens finansmarknader. / During the 1980s a group called The Turtle Traders used two trend following trading strategies, based on technical analysis, to trade a large number of financial markets. The two trading strategies used mechanical rules to make buy and sell decisions and to manage risk. The rules also specified which markets to trade. The group was very successful during several years in the 1980s and the returns the members of the group generated, using the two trading strategies, widely surpassed the returns of the markets. The weak form of the efficient market hypothesis states that this should be impossible on markets that are efficient. On efficient markets it is instead better to follow a buy-and-hold strategy. How come that The Turtle Traders succeeded? Was is just luck that the two trend following strategies, that generated the buy and sell decisions, resulted in such high returns during a few years in the 1980s? Or are the markets inefficient? Current research gives an unclear picture regarding the efficient market hypothesis and whether or not the markets are efficient. Different studies present results that both support and reject the hypothesis. The purpose of this bachelor thesis is to show whether or not the two trend following strategies still are profitable and therefor useful strategies on the financial markets of today. The purpose is also to compare the two strategies with the buy-and-hold strategy on different markets and in this way contribute with more insights to the ongoing and nowadays often increasingly questioning discussion regarding the efficient market hypothesis, with special focus on the weak form of the hypothesis. To get the returns of the two trend following strategies on the financial markets of today a computer program is constructed as part of this bachelor thesis. This computer program simulates the buy and sell decisions that would have been taken by the mechanical rules the two trend following strategies are built upon. The study done in this bachelor thesis gives, just as many other studies, an unclear picture of the efficient market hypothesis. Half of the markets that are studied in this thesis seem to be inefficient and half seem to be efficient, according to the weak form of the hypothesis. The study also shows that none of the two trend following strategies are profitable enough that they can be recommended to be used on the financial markets of today.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Distillation continues to be the most widely used method of separation in the processing industry, in spite of its inherently low thermodynamic efficiency. Two of the critical distillation research needs that arose from the US-Initiative Vision 2020 were to develop a better understanding of the physical phenomena as well as developing better predictive models. Also, characterisation of modern packing materials is required to assist in the CO2 capture optimisation. This thesis deals with both these aspects by establishing a facility that can accurately measure the hydraulic capacity of packed columns. This setup eliminates mass transfer and specific attention can be given to the hydrodynamic behaviour of packed columns. Two phenomena that have a large impact on the mass transfer efficiency of packing materials are the loading and flooding point. The loading point is signified by the following: a.) where the packed column hold-up increases, b.) higher increase in pressure drop, and c.) a decrease in Height Equivalent to a Theoretical Plate (HETP). The onset of flooding is where the shear forces between the gas and liquid become so large (relative to the gravitational forces) that a net upwards movement of liquid occurs, resulting in liquid droplets being heavily entrained. This is normally accompanied by a sharp increase in HETP, pressure drop and liquid hold-up. The prediction of these operating limits is of great value but, despite the many contributions that were made from 1960 to 2010, there is still room for improvement. The operating region of particular interest is between the loading and flooding point, especially for fluids with physical properties significantly different from that of water. In the past, this operating region was not of great importance, but industries are constantly striving to increase their production with minimal capital expenditure. Thus, packed columns are being pushed to their limits and a good understanding of the phenomena occurring near these operational limits is now required. A 400 mm diameter glass packed bed setup (with a bed height of 3000 mm) was designed and constructed to test the effect of the following parameters on packed bed pressure drop and liquid hold-up: · Gas and liquid physical properties · Gas and liquid rates · Type of packing (either random or structured) The experimental setup has been designed so that in the future the influences of the above mentioned parameters on entrainment can also be measured. Initially, hydrodynamic tests on random packing materials (1.5” Pall® Rings, 1.5” IMTP®, 1.5” Intalox® Ultra™) were conducted over a liquid range of 6 - 122 m3/(m2·h). Through a thorough literature study it was found that the most likely semi-theoretical model, that would be able to predict the pressure drop and the liquid hold-up over most of the random packing test range, was the model developed by Billet [1991; 1993; 1995; 1999]. The other models found throughout the literature had at least one of the following deficiencies: · Limited to only the pre-loading region. · Tested (and thus applicable) only over a very select group of packing materials with no attempt to generalise. · Lacked the proper validation of significantly variable fluid properties over multitudes of liquid and gas rates especially, at higher gas and liquid rates. The experimental setup was successfully commissioned, noting the following maximum experimental errors: Vapour flow factor - 2.6 %; liquid rate - 0.75 %; packed bed pressure drop - 0.75 %; liquid hold-up - 1.25 % and entrainment - 1.05 %. Significant deviations were observed between the experimental hold-up and the hold-up from the predictive model of Billet (using Pall® Rings). Careful inspection revealed that this predictive model potentially uses two definitions for hold-up at flooding, one which has a theoretical basis and the other purely empirical. Upon substituting the theoretical value with the empirical value, a significant improvement was observed between the measured and predicted results. Deviations were still observed near the flooding point and were attributed to the difficulty of obtaining reliable flooding data. The range of liquid hold-up prediction by Billet was only verified up to a liquid rate of 82 m3/(m2·h) and the pressure drop prediction only verified up to a liquid rate of 60 m3/(m2·h). This reinforces the need for high liquid, high gas rate data. Due to the empirical nature of the liquid hold-up at flooding prediction, and since pressure drop prediction is directly linked to liquid hold-up, another model was used to compare the experimental pressure drop data. The KG-TOWER® simulator was used to predict IMTP® data and compare it to the experimentally measured values. It was found that the experimental IMTP® data followed the same trends as those from KG-TOWER® within the operating limits of the program. Thus, since the experimental data follows similar trends as models found in the literature, as well as falling within their reliable limits, the experimental setup can correctly measure the parameters in question. The experimental data from the different random packings were compared to one another by using a statistical method to determine the loading point and onset of flooding. This method uses prediction confidence intervals by fitting empirical curves to each operating region and was found to be useful in determining these critical points from experimental hydraulic data (in the absence of HETP data).The only useful comparison was between IMTP® and Intalox® Ultra™ as they both have roughly the same density, size and void fraction. It was found that, on average, the pressure drop of Intalox® Ultra™ is 20 % lower than that of IMTP® over the entire operating range. The hydraulic operating range of Intalox® Ultra™ was found to be on average 16 % larger than that of IMTP®. It is recommended that further testing should be done to investigate the influence of fluid properties (specifically liquid viscosity and to a lesser extent surface tension) on the hydraulic capacity of packed columns. Also, high gas and high liquid rate data should be generated to assist current modelling techniques. Lastly, a comparative characterisation between Intalox® Ultra™ and Raschig Super-Rings would serve as a benchmark for fourth generation random packings. / AFRIKAANSE OPSOMMING: Distillasie is vandag nog die skeidingsproses wat die meeste gebruik word in the prosesnywerhede ten spyte van ‘n lae termodinamiese effektiwiteit. Twee van die kritieke distillasie navorsing behoeftes wat vanuit die US-Initiative Vision 2020 ontstaan het, was om die fisiese verskynsels beter te verstaan, asook om beter voorspellende modelle te ontwikkel. Die karakterisering van moderne pakking materiale is ook nodig vir die optimering van die verwydering van CO2 uit uitlaatstrome. Hierdie tesis spreek beide van hierdie faktore aan deur ‘n fasiliteit op te rig wat die hidrouliese kapasiteit van gepakte kolomme akkuraat kan meet. Hierdie opstelling elimineer massa-oordrag en dus kan spesifieke aandag gegee word aan die hidrodinamiese gedrag van gepakte kolomme. Twee verskynsels wat ‘n groot impak het op die massaoordrag effektiwiteit van pakkingsmateriale is die ladingspunt en die vloedpunt. Die ladingspunt word deur die volgende gekenmerk: a.) waar die vloeistof inhoud in die gepakte bed toeneem, b.) ‘n toename in drukval en c.) ‘n afname in die hoogte ekwivalent aan ‘n teoretiese plaat (HETP). Die vloed gebied word gekenmerk waar die skuifkragte tussen die vloeistof en gas so groot raak (relatief tot die gravitasionele kragte), dat daar ‘n netto opwaartse beweging van vloeistof druppels in die kolom is. Hierdie gaan normaalweg gepaard met ‘n skerp toename in HETP, drukval en vloeistof inhoud. Die voorspelling van hierdie bedryfslimiete is baie waardevol, maar ten spyte van die bydrae wat tussen 1960 en 2010 gemaak was, is daar nog steeds ruimte vir verbetering. Die spesifieke bedryfsgebied van belang is die gebied tussen die ladingspunt en die vloedpunt en spesifiek vir sisteme waar die fisiese eienskappe van die vloeistowwe drasties verskil van die van water. In die verlede was hierdie gebied van minder belang gewees, maar maatskappye probeer deesdae hul produksie opstoot met minimale kapitale uitleg. Dus is ‘n goeie kennis van massa-oordrag verskynsels naby aan die bedryfslimiete van kardinale belang. ‘n 400 mm Diameter gepakte kolom (met ‘n bed hoogte van 3000 mm en bestaande uit glas) opstelling is ontwerp en gebou om die effek van die volgende parameters te toets op gepakte bed drukval en vloeistof inhoud: · Gas en vloeistof fisiese eienskappe · Gas vloeistof vloeitempos · Tipe pakking (beide ongeordend en gestruktureerd) Die eksperimentele opstelling is ontwerp om die bogenoemde eienskappe op vloeistofmeesleuring te meet vir toekomstige navorsing. Hidrodinamiese toetse op ongeordende pakkingsmateriale (1.5” Pall® Ringe, 1.5” IMTP®, 1.5” Intalox® Ultra™) is uitgevoer vir vloeistof vloeitempos tussen 6 en 122 m3/(m2·h). Vanuit ‘n deeglike literatuurstudie is daar gevind dat die mees toepaslike semi-teoretiese model, wat die drukval sowel as die vloeistof inhoud kan voorspel oor al die bedryfsgebiede, is die model wat deur Billet [1991; 1993; 1995; 1999] ontwikkel is. Die ander modelle in die literatuur het ten minste een van die volgende tekortkominge gehad: · Is slegs van toepassing in die voor-ladings gebied. · Is slegs van toepassing vir ‘n paar pakkingsmateriale en geen poging is aangewend om dit te veralgemeen nie. · Is nie geldig waar die vloeistof eienskappe drasties verskil van ‘n lug/water sisteem nie, sowel as by hoë gas en vloeistof vloeitempos. Die eksperimentele opstelling is suksesvol in werking gestel met die volgende waargenome eksperimentele foute: Gas vloei faktor – 2.6 %; vloeistof vloeitempo – 0.75 %; gepakte bed drukval – 0.75 %; vloeistof inhoud – 1.25 %; vloeistof-meesleuring tempo – 1.05 %. Noemenswaardige verskille is waargeneem tussen die eksperimentele en teoretiese vloeistof inhoud (deur Pall® Ringe te gebruik). Na gelang van noukeurige inspeksie, is daar gevind dat die Billet-model twee moontlike definisies voorstel vir die voorspelling van vloeistofinhoud by die vloedpunt. Een van hierdie is teoreties van aard en die ander een suiwer empiries. ‘n Vervanging van die teoretiese waardes met die empiriese waardes het gelei tot ‘n merkwaardige verbetering tussen die eksperimentele en teoretiese voorspellings. Daar was nog steeds verskille naby aan die vloedpunt, maar dit kon toegeskryf word aan die feit dat min betroubare data naby aan die vloedpunt beskikbaar is. Die voorspelling van vloeistof inhoud deur Billet is slegs gekontroleer tot ‘n vloeistof vloeitempo van 82 m3/(m2·h) en die drukval slegs tot ‘n vloeistof vloeitempo van 60 m3/(m2·h). Die bogenoemde bewys dus die tekort aan hoë gas- en hoë vloeistofvloeitempo data. Die voorspellende model se drukval is gekoppel aan die vloeistof inhoud, en dus is ‘n ander model gebruik om die eksperimentele drukval data teen te vergelyk. Die KG-TOWER® simulasie program is gebruik om die IMTP® drukval te voorspel en dit het goed vergelyk met die eksperimentele data. Dus, aangesien die eksperimentele data dieselfde tendens toon as dié van die modelle in die literatuur en aangesien dit binne die modelle se foutbande val, kan die eksperimentele opstelling die verlangde parameters akkuraat meet. Die eksperimentele data van al drie pakkingsmateriale is teenoor mekaar vergelyk deur gebruik te maak van ‘n statistiese metode wat die ladings- en vloedpunt bepaal. Hierdie metode maak gebruik van voorspellings vertroue intervalle deur empiriese kurwes op die eksperimentele data in elke bedryfsgebied te pas. Hierdie metode is ontwikkel om toepaslike te wees in die afwesigheid van HETP data. Die enigste nuttige vergelyking is tussen IMTP® en Intalox® Ultra™ omdat albei dieselfde pakkingsdigtheid, grootte en pakkings oop ruimte het. Daar is gevind dat die drukval van Intalox® Ultra™ ‘n gemiddeld van 20 % laer is as dié van IMTP® oor die hele bedryfsgebied. Die hidrouliese bedryfsgebied van Intalox® Ultra™ is 16 % groter as dié van IMTP®. Daar word voorgestel dat bykomende toetswerk gedoen moet word om die invloed van vloeistof eienskappe (spesifiek vloeistof viskositeit en vloeistof oppervlak spanning) op die hidrouliese kapasiteit van gepakte kolomme te ondersoek. Bykomende toestwerk by hoë gas- en hoë vloeistofvloeitempo word benodig om die bestaande modelle aan te vul. Laastens, sal ‘n vergelykende studie tussen Intalox® Ultra™ en Raschig Super-Rings die grondslag lewer vir die karakterisering van vierde generasie ongeordende pakkingsmateriale.

In this dissertation I focus on two considerations that influence the product strategy of a firm. The first is consumers’ choice and its influence on a firm’s product offering, and the second is the interaction between durable products and their contingent consumables. First, I study the assortment planning problem for a firm; I illustrate the complexity of solving this product selection problem, present simple solutions for some commonly used choice models, and develop heuristics for other practically motivated models. Second, I study the incentives of a durable goods monopolist when she can lock-in consumers through a contingent consumable. Adopting a lock-in strategy has two interesting effects on the incentives of a durable goods manufacturer. On one hand, by locking-in consumers to its consumable, a durable goods monopolist can curb its temptation to reduce durable prices over time, thereby mitigating the classic time inconsistency problem. On the other hand, lock-in will create a hold-up issue and adversely affect consumers’ expectations of future prices for the consumable. My research demonstrates the trade-off between time inconsistency and hold-up, and derives insights about the conditions under which a lock-in strategy can be effective. I further analyze the trade-off between time inconsistency and hold-up associated with lock-in in the presence of consumable stock-piling. My findings indicate in the presence of consumer stock-piling, lock-in has an effect similar to that of competition in the consumables market: they help to dampen the hold-up problem that arises from lock-in and at the same time increase the manufacturer’s incentive to reduce durable prices over time. / text