Thesis (PhD (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2003. / The thermal performance prediction of wet-cooling towers is critically analyzed and refined. Natural draft counterflow towers and mechanical draft counterflow and crossflow towers are considered. The Merkel, Poppe and e-NTU heat and mass transfer methods of analysis are derived from first principles, as these methods form the cornerstone of wet-cooling tower performance evaluation. The critical differences between these methods, when applied to fill performance analyses and cooling tower performance evaluations, are highlighted. The reasons for these differences are discussed with the aid of psychrometric charts. A new extended empirical relation for the loss coefficient of fills is proposed where the viscous and form drag effects are accounted for as well as the buoyancy, momentum and fill height effects. The empirical equation for the transfer characteristic of fills is extended to include the effects of fill height and the inlet water temperature. Empirical equations to predict the temperature inversion profile, height of the temperature inversion and the height from which air is drawn into the cooling tower are developed. The influence of temperature and humidity inversions on the performance of wet-cooling towers is subsequently investigated. A comprehensive analytical computer program is developed to predict and optimize the performance of wet-cooling towers. Computer programs are also developed to generate cooling tower performance curves, analyze fill performance test data and plot psychrometric charts.

<p>Syftet med den här undersökningen är att beskriva och analysera vilka fördelar och nackdelar det finns med att utkontraktera en transportplaneringsprocess till en extern part. Undersökningen genomfördes på uppdrag av BT-Europe i Mjölby på avdelningen som ansvarar för distribution av produkter och reservdelar. BT är i grunden ett svenskt företag som startade sin verksamhet 1946 och är idag världsledande tillverkare av eldrivna lagertruckar. År 2000 förvärvades BT av Toyota och detta skapade en världsledande konstellation inom truckbranschen.</p><p>Bakgrunden till undersökningens syfte är att arbetet med att effektivisera och förbättra transportplaneringsprocessen inom BT har blivit eftersatt på grund av den kraftiga produktionsökningen de senaste 5 åren. Detta har lett till stigande kostnader för distribution av färdiga produkter och reservdelar.</p><p>I dagsläget finns inget centralt kontrollorgan över transportplaneringsprocessen på BT utan all transportplanering av produkter och reservdelar till truckar, sker lokalt på varje marknadsbolag i Västeuropa. I en framtid har BT som förhoppning att bedriva transportplaneringsprocessen på central nivå, antingen inom koncernen eller genom att utkontraktera transportplaneringsprocessen till en extern part, det vill säga till ett fjärdepartslogistikföretag.</p><p>Vid beslut om transportplaneringsprocessen ska genomföras centralt internt eller utföras externt med hjälp av en fjärdepartslogistiker finns en rad viktiga faktorer att ta i beaktning. De faktorer som valts att studera i denna undersökning är kärnverksamhet, processens mognad, flexibilitet, kontroll, beroende och transaktionskostnader. Dessa faktorer studeras genom att undersöka inom vilka områden BT anser sig att besitta kärnkompetens idag och i en framtid, samt hur BT ser på faktorer som flexibilitet, beroende och kontroll vid en eventuell outsourcing. Genom att ställa detta mot vad fjärdepartlogistikföretag erbjuder för lösningar till sina kunder och hur de hantera faktorer som flexibilitet, kontroll och beroende, kan för- och nackdelar med en utkontraktering av transportplaneringsprocessen definieras.</p><p>En fördel med att utkontraktera transportplaneringsprocessen uppnås genom att ingå ett samarbete med en fjärdepartslogistiker och därigenom kan BT få tillgång till spetskompetens och tillgång till större distributionsnätverk.</p><p>En annan fördel med ett nära samarbete med en leverantör av fjärdepartslogistiska tjänster är att det kan skapa ökad flexibilitet för BT. Detta genom att BT i ett samarbete kan tillgå skräddarsydda lösningar för företagsunika behov samtidigt som möjligheten att byta transportleverantörer ökar, då fjärdepartsaktörer vanligen arbeter med korttidskontrakt emot transportföretagen</p><p>Nackdelar som kan uppkomma med utkontraktering av transportplaneringsprocessen är att denna process kan komma att ses som betydande för framtida verksamhet. Det kan då vara förenat med risk att tappa kompetens inom området.</p><p>En nackdel är även att outsourcing av transportplaneringsprocessen kan innebär en beroendeställning för BT gentemot en tilltänkt fjärdepartsleverantör. Kontrollen av processen som koordinerar försörjningen av färdiga produkter och reservdelar från BT till företagets kunder eller marknadsbolag överlämnas därmed till en extern part.</p>

Alors que la démolition tend à s'imposer au sein de l'intervention publique sur le parc HLM des années 1950-1970, ce mode d'action commence aussi à être utilisé en réponse aux problèmes rencontrés par des tours et des barres en copropriété. On peut cependant se demander si les difficultés d'un grand ensemble en copropriété sont assimilables à celles d'un grand ensemble HLM et si la démolition ne prend pas un sens différent dans ce contexte particulier. Pour répondre à ces questions, cette thèse étudie l'une des premières copropriétés des trente glorieuses qui a fait l'objet d'une action publique et de démolitions : Les Bosquets à Clichy-sous-Bois/Montfermeil (93). En explorant l'histoire de cet ensemble immobilier, cette recherche montre que les problèmes qu'il a connus sont propres au statut juridique de la copropriété. Ils sont principalement dus à des difficultés de gestion, liées aux financements publics qui sont à l'origine de sa construction, à la conjoncture immobilière dans laquelle il a été livré et à des malfaçons juridiques. Or, cette dimension propre à la gestion n'a pas été prise en compte au sein de l'intervention publique déployée sur ce site depuis 1981. Celle-ci a transposé à la copropriété les schémas cognitifs et normatifs appliqués aux ensembles HLM de même typologie architecturale et urbaine. Privilégiant la démolition, les restructurations du bâti et la diversification du peuplement, l'action publique a aggravé les déséquilibres de gestion de la copropriété. Le relogement a constitué un nouveau facteur de fragilisation des trajectoires des ménages – en particulier des propriétaires occupants – déjà fortement pénalisés par les difficultés de la copropriété / While demolition of public rental housing projects from the 1960s and 1970s is an obvious public intervention nowadays, we are starting to witness a similar handling of condominium tower blocks. However, one may ask whether similar interventions for these two different housing types lead to different outcomes. To answer these questions, this thesis analyses one of the first condominium project from the Trente Glorieuses period (1945-1975) that was the target of such intervention : Les Bosquets located in Clichy sous Bois/Montfermeil (a Parisian suburb). Looking at the history of that housing complex, this research shows that the problems relate to the legal status of the joint ownership. These problems arose from management difficulties linked to the public financing that has permitted its construction, to the real estate circumstances of its delivery, and to juridical defects. It appears that this management dimension wasn't considered by the public intervention implemented at that site since 1981. Cognitive and normative patterns originally applied to moderate rental estates with similar architectural and urban typology were simply transferred to the condominium. Favouring demolition, redevelopments of the building, and diversification of residents, public interventions have aggravated imbalances in the management of the condominium. Rehousing has also participated in the weakening of the residential itineraries of the households (especially owner occupiers) already strongly penalised by the condominium's difficulties

Bear Lodge/Devils Tower National Monument, a spectacular rock formation in northeastern Wyoming, has a multiplicity of meanings, not all of which were fully acknowledged until the 1990s. It is widely known as a geologic wonder, the first national monument, a marker of local and pioneer heritage, and a premier rock climbing area. In the 1980s and ‘90s, however, the National Park Service began to acknowledge that the Tower also holds cultural and historical meaning for the Northern Plains tribes, dating back long before the colonization of the American West. Some of the tribes expressed to the Park Service that they were offended by rock climbers desecrating the Tower, a sacred site, leading the Park Service to seek to compromise between these competing uses of this public land. The controversy over climbing at Bear Lodge/Devils Tower was, and remains, a debate over history, and this thesis examines the historical foundations for the discourses of climbers, local white residents, tribal members, and the Park Service, as these various groups asserted their claims to this public space. This thesis contends that the language used by climbers and local white residents in arguing against the Park Service’s accommodation of tribal cultures and beliefs appropriated the languages of spirituality and tradition used by the tribes, and sought to delegitimize the tribal claims to the Tower. The Park Service is complicit in controlling the discourses surrounding the Tower and erasing the traditions and complex history of the Northern Plains tribal ties to this sacred place.

Vertical-axis wind turbines (VAWTs) have with time been outrivaled by the today more common and economically feasible horizontal-axis wind turbines (HAWTs). However, VAWTs have several advantages which still make them interesting, for example, the VAWTs can have the drive train at ground level and it has been argued that they have lower noise emission. Other proposed advantages are suitability for both up-scaling and floating offshore platforms. The work within this thesis is made in collaboration between Halmstad University and Uppsala University. A 200-kW semi-guy-wired VAWT H-rotor, owned by Uppsala University but situated in Falkenberg close to Halmstad, has been the main subject of the research although most results can be generalized to suit a typical H-rotor. This thesis has three main topics regarding VAWTs: (1) how the wind energy extraction is influenced by turbulence, (2) aerodynamical noise generation and (3) eigenfrequencies of the semi-guy-wired tower. The influence from turbulence on the wind energy extraction is studied by evaluating logged operational data and examining how the power curve and the tip-speed ratio for maximum Cp is impacted by turbulence. The work has showed that the T1-turbine has a good ability to extract wind energy at turbulent conditions, indicating an advantage in energy extraction at turbulent sites for VAWTs compared to HAWTs.The noise characteristics are studied experimentally, and models of the two most likely aerodynamic noise mechanisms are applied. Here, inflow-turbulence noise is deemed as the prevailing noise source rather than turbulent-boundary-layer trailing-edge noise (TBL-TE) which is the most important noise mechanism for HAWTs. The overall noise emission has also been measured and proven low compared to similar sized HAWTs. The eigenfrequencies of a semi-guy-wired tower are also studied. Analytical expressions describing the first-mode eigenfrequency of both tower and guy wire has been derived and verified by experiments and simulations.

The thesis focuses on the reflection of the discovery of America by the Norsemen, and does so in three steps. Firstly, the approach to and the significance of the Norse voyages to America in the medieval materials, and especially in the Vinland sagas, are presented. This part is accompanied by a general introduction into the sagas. Secondly, the situation in the 19th century is introduced. In this period a lot of scientific works as well as works of art aiming at the Norse voyages to the New continent arose. The factors that led to this increased interest are explored, e.g. national movement in Scandinavia. Thirdly, the contemporary reflexion of the Norse discovery of America is analyzed (particularly its influence on works of art, society, politics and scientific research). The methodology used in this thesis is discourse analysis, which points out to the changing reflexion of the given topic.

O lixiviado de aterros sanitários é um efluente líquido poluente devido, principalmente, à sua elevada concentração de amônia. Seu tratamento faz-se necessário para que sejam atendidas as exigências das legislações ambiental e trabalhista, além de minimizados os impactos ambientais de seu lançamento nos corpos d\'água. Esta pesquisa propõe a remoção da amônia presente no lixiviado por meio do processo físico-químico \"air stripping\", que promove a transferência da amônia da fase líquida para gasosa. Para que não se contribua com a poluição atmosférica, o efluente gasoso do \"air stripping\" deve ser tratado em solução de ácido sulfúrico ou água. A neutralização da amônia com solução de ácido sulfúrico gera o sulfato de amônio, e com água, a aquamônia. Tais subprodutos podem ser usados como fertilizantes. Nesta pesquisa, para remoção da amônia do lixiviado foi utilizada uma torre de PVC, com 2,24 m de altura e 15 cm de diâmetro, recheada com anéis do tipo Rashing de polietileno corrugados, com diâmetro de 1,5 cm e 5 cm de comprimento. As vazões de ar utilizadas foram 1200, 1600 e 3600 L/h e as vazões de lixiviado foram 18 e 30 L/h. Para ajuste no pH do lixiviado, utilizou-se hidróxido de cálcio (padrão analítico) e cal comercial. Os fluxos de líquido e ar eram em contracorrente. Para o recolhimento da amônia foram usados dois frascos de 6 L, preenchidos com 4 L de solução de ácido sulfúrico 0,4 mol/L ou água. Os resultados obtidos indicaram remoção praticamente completa de toda a amônia contida no lixiviado. Nas diferentes condições operacionais avaliadas, a concentração de amônia remanescente no lixiviado foi igual ou inferior aos 20 mg/L determinados pela Resolução 397/08 do CONAMA. Quanto ao recolhimento da amônia, a eficiência média obtida nos frascos lavadores próxima a 80%, tanto ) quando utilizada a solução de ácido sulfúrico 0,4 mol/L quanto quando utilizada água. / Sanitary landfill leachate is a pollutant liquid effluent mainly due to its high ammonia concentration. Its treatment is necessary due to environmental and labour legislation requirements, besides prevention of environmental impacts of leachate release in water bodies. This research proposes ammonia removal from leachate by air stripping process, which transfers ammonia from liquid to gaseous phase. In order to prevent atmospheric pollution, air stripping gaseous effluent must be treated with sulphuric acid solution or water. Ammonia neutralization by sulfuric generates ammonium sulfate and by water, aquammonia is generated. Such by-products may be used as fertilizer. In this research, in order to remove leachate ammonia it was used a PVC tower of 2.24 m high and 15 cm diameter, packed with Rashing rings of corrugated polyethylene of 1.5 cm diameter and 5 cm length. Air flows were 1200, 1600 and 3600 L/h and leachete flows were 18 e 30 L/h. Calcium carbonate (standard grade) and commercial hydrated lime were used for pH adjustments. Air and liquid flows were countercurrent. In order to recover ammonia, two flasks of 6 L were used and filled with 4 L of 0.4 mol/L sulfuric acid solution or water. Results showed that ammonia was almost completely removed from leachate. In all operational conditions evaluated, remaining ammonia concentration in leachate was equal or less than 20 mg/L, value established by Resolution 397/08 of Brazilian Council of the Environment. Ammonia recovery with water or a 0.4 mol/L sulfuric acid solution was about 80%.

Neste trabalho, foi estudado o desempenho de um sistema constituído de torres de resfriamento e a sua integração em uma planta industrial de hidrogenação de butadieno. Caracterizou-se o desempenho das torres de resfriamento com base em um modelo fenomenológico, cujos parâmetros foram obtidos a partir da medição de variáveis operacionais reais. O processo de hidrogenação foi configurado em um simulador de processos, sendo o caso base estabelecido nas condições de projeto. Elaborou-se um módulo específico referente às torres de resfriamento, que foi integrado ao processo configurado no simulador. Em seguida, analisaram-se as interações das condições operacionais da torre de resfriamento no desempenho do processo industrial. / In the present work, the performance of a system composed of a cooling tower integrated in butadiene hydrogenation plant was studied. An experimental investigation was made to characterize the cooling towers based on a phenomenological model and in real process conditions. The hydrogenation process was configured on a process simulator and design specifications were considered as base case. A cooling tower module was developed and integrated to the process simulator. The interaction of the cooling tower system and the plant operation was investigated.

This thesis introduces a new tower field representation, optimal tower fields (OTFs), that facilitates efficient finite field operations. The recursive direct inversion method presented for OTFs has significantly lower complexity than the known best method for inversion in optimal extension fields (OEFs), i.e., Itoh-Tsujii's inversion technique. The complexity of OTF inversion algorithm is shown to be O(m^2), significantly better than that of the Itoh-Tsujii algorithm, i.e. O(m^2(log_2 m)). This complexity is further improved to O(m^(log_2 3)) by utilizing the Karatsuba-Ofman algorithm. In addition, it is shown that OTFs are in fact a special class of OEFs and OTF elements may be converted to OEF representation via a simple permutation of the coefficients. Hence, OTF operations may be utilized to achieve the OEF arithmetic operations whenever a corresponding OTF representation exists. While the original OTF multiplication and squaring operations require slightly more additions than their OEF counterparts, due to the free conversion, both OTF operations may be achieved with the complexity of OEF operations. Furthermore, efficient finite field algorithms are introduced which significantly improve OTF multiplication and squaring operations. The OTF inversion algorithm was implemented on the ARM family of processors for a medium and a large sized field whose elements can be represented with 192 and 320 bits, respectively. In the implementation, the new OTF inversion algorithm ran at least six to eight times faster than the known best method for inversion in OEFs, i.e., Itoh-Tsujii inversion technique. According to the implementation results obtained, it is indicated that using the OTF inversion method an elliptic curve scalar point multiplication operation can be performed at least two to three times faster than the known best implementation for the selected fields.

This work is concerned with five problems in combinatorics. In Josephus problem, people are standing in a circle or in a row and every q-th is executed until only one person remains. We show how to find the survivor, and discuss the generalization when each person has more lives. In Tower of Hanoi, we study the numbers and properties of moves necessary to transport the tower from one rod to another, where the total number of rods is either three or four. We mention related problems with restrictions on the legal moves. In ménage problem, we calculate the number of seatings of couples around a table such that men and women alternate and nobody sits next to his or her partner. We also discuss permutations with restricted positions and rook polynomials. In ballot problem, we consider two candidates competing against each other and calculate the probability that, throughout the count, the first candidate always had more votes than k times the number of votes of the second one; we also mention the relation to Catalan numbers. In Kirkman's schoolgirl problem, the task is to find a weekly schedule for fifteen girls walking daily out in triads so that no two go together more than once. We also discuss the social golfer problem and Schurig's tables.