Sound power measurements of acoustic sources are generally made in reverberation or anechoic chambers using acoustic pressure measurements as outlined in specific ISO or other standards. A reverberation chamber produces an approximate diffuse-field condition, wherein the sound power is determined from the spatially averaged squared pressure. An anechoic chamber produces an approximate free-field condition, wherein the sound power is estimated from squared pressure over an enveloping measurement surface. However, in many cases it is desirable to estimate sound power within nonideal semi-reverberant spaces. In these environments, both direct and reverberant energies may contribute significantly to the total acoustic field. This paper introduces two measurement methods that utilize a weighted combination of potential and kinetic energy densities, known as generalized acoustic energy density, to estimate sound power in nonideal semi-reverberant rooms. The first method employs a generalized sound power formulation, which is an adaptation to an equation developed in 1948 for semi-reverberant spaces. The second, called the two-point in situ method, is a technique based on the generalized sound power formulation for quick and accurate in situ sound power estimates. Since the generalized acoustic energy density is more spatially uniform than the squared acoustic pressure in an enclosed field, these methods have the advantage of achieving the same accuracy in sound power determination with fewer measurement positions. This thesis explores the possibility of using these new methods in place of methods outlined in current ISO standards by describing analytical, numerical, and experimental results.

This thesis considers the development of settlement landscapes in the Iron Age across two adjacent regions, the upland eastern Cotswolds and lowland upper Thames valley. Previous studies have focused on the differences in settlement form, economic practice and social development and therefore the possible dichotomy of heartland and hinterland landscapes. It is clear, however, that this is due to an imbalance of research brought about as a result of the natural landscape, interests of antiquarians and archaeologists and modern settlement focus and development. A new dataset of cropmark and geophysical survey material is presented as a way of redressing the imbalance. The focus within this study on banjo enclosures also provides an opportunity to analyse what remains a relatively enigmatic and understudied site-type that appeared during the Middle and Late Iron Age. The results illustrated and discussed here provide the chance to outline new narratives that take into account both practical and non-functional interpretations. From this, more is elucidated regarding these sites within the context of Middle and Late Iron Age settlement landscape developments. By integrating this new dataset within the wider context of the upper Thames and immediate environs a number of further and more general questions have been raised. These focus on the chronology of settlement development, the appearance and growth of exchange networks and the changing significance of open and enclosed settlements throughout the period. Differences have been used in the past to symbolise alternative social systems apparent across two settlement landscapes. However, as a result of the evidence presented here these perceptions are no longer viable as an interpretive framework. Instead, aspects of chronological development, settlement space and sphere of influence and interaction are discussed in relation to the evidence from Midlands and central southern Britain.

Partial enclosures are commonly used to reduce machinery noise. However, it is well known in industry that enclosures sometimes amplify the sound at low frequencies due to strong acoustic resonances compromising the performance. These noise issues are preventable if predicted prior to prototyping and production. Though boundary and finite element approaches can be used to accurately predict partial enclosure insertion loss, modifications to the model require time for remeshing and solving. In this work, partial enclosure performance at low frequencies is simulated using a plane wave transfer matrix approach. Models can be constructed and the effect of design modifications can be predicted rapidly. Results are compared to finite element analysis and measurement with good agreement. The approach is then used to design and place resonators into a sample enclosure. Improvements in enclosure performance are predicted using plane wave simulation, compared with acoustic finite element analysis, and then validated via measurement.

A simplified computational fluid dynamics and heat transfer (CFD-HT) model of an electronics enclosure was developed. The compact model was based on a server simulator, which dissipates a variable amount of heat at an adjustable air flow rate. Even though a server simulator does not accurately represent the geometry of an actual electronics enclosure, the modeling of such a unit deals with many of the same issues as the modeling of actual enclosures. Even at the server simulator level, a disparity in length scales prevents detailed modeling of intricate components most notably grilles, fins, and fans. Therefore, a compact model for each of these components was developed. Fan performance curves were determined experimentally for varying fan rotational speeds. In addition, component pressure drop characteristics were found experimentally for grilles and fin banks, and these empirical relationships were applied to the model as well. To determine the validity of the simplifications employed in the model, experimental outlet temperature and velocity measurements were taken to compare to those provided by the CFD-HT simulations.

Externe Einträge von Nährstoffen, vor allem von Phosphor, fördern die Phytoplanktonentwicklung und sind damit die primäre Ursache für die Verschlechterung der Gewässergüte in Seen. Die pelagische Nahrungsnetzstruktur kann dabei sowohl positiv als auch negativ auf die Gewässergüte einwirken. Deshalb lässt sich der Gewässerzustand durch eine gezielte Steuerung der Räuber-Beute-Verhältnisse verändern. In der vorliegenden Arbeit wurden Ergebnisse der Groß-Enclosure-Experimente zu den Auswirkungen von Nährstoffen (mit/ohne Zugabe von Nährstoffen) sowie von einer manipulierten Nahrungsnetzstruktur (mit/ohne Zugabe von planktivoren Fischen) auf die pelagische Phyto- und Zooplanktongemeinschaft eines thermisch geschichteten Sees (Dagowsee, Brandenburg) präsentiert. Im Schwerpunkt der Untersuchungen lagen dabei die qualitativen und quantitativen Effekte dieser beiden Faktoren auf die Sedimentationsprozesse sowie den mikrobiellen Umsatz von Kohlenstoff und Phosphor im Hypolimnion und an der Sediment-Wasser-Kontaktzone des Sees. Es wurde gezeigt, dass die Manipulation der Nahrungsnetzstruktur sich auf die Menge und Zusammensetzung des Phyto- und Zooplanktons im Epilimnion des Sees sowie auf den quantitativen vertikalen Transport von Kohlenstoff und Phosphor auswirkte, während die unterschiedliche Nährstoffbelastung im Epilimnion die spezifischen Stoffgehalte des Kohlenstoffs und Phosphors im sedimentierten Material beeinflussten. Anhand der Sauerstoff- und Methanmessungen wurde festgestellt, dass die Intensität des mikrobiellen Abbaus der sedimentierten organischen Substanz vor allem von ihrer Menge abhängig war. Weiterhin konnten die Auswirkungen der manipulierten Nahrungsnetzstruktur auf die Effizienz während des Abbaus vom organischen Kohlenstoff in den Laborversuchen nachgewiesen werden. Diese Effekte waren allerdings in den Freilandexperimenten schwer nachweisbar aufgrund der Beteiligung der Abbauprodukte in anderen oxidativ-reduktiven Prozessen, die gleichzeitig im See verliefen. Anhand des Phosphor-Fraktionierungsverfahrens konnte festgestellt werden, dass dieser Stoff nicht organisch sondern zum größten Teil an Eisen und Mangen gebunden sowie labil adsorbiert die Sedimentoberfläche erreichte. An dieser Stelle zeigten diese beiden Fraktionen einen systematischen Unterschied, der nur auf eine Wirkung der epilimnischen Nährstoffkonzentration und nicht auf die des manipulierten Nahrungsnetzes hinwies. Weitere Analysen der Sedimente zeigten starke Transformationen des sedimentierten Phosphors, aufgrund deren vor allem die dominierenden labilen und redoxsensitiven Phosphorfraktionen betroffen waren. Sie wurden zum einen ins Wasser zurückgelöst und zum anderen in die organische Biomasse gespeichert. Die Veränderungen des Phosphorgehaltes in den Sedimenten waren wieder auf die vorherigen Effekte der Nährstoffe als der manipulierten Nahrungsnetzstruktur zurückzuführen. Die Effekte der Nahrungsnetzmanipulation waren also vor allem an der pelagischen Planktongemeinschaft im Epilimnion und an den Sedimentations- und Kohlenumsatzprozessen in tieferen Schichten des Sees zu sehen. Der vertikale Phosphortransport wurde weniger von der Nahrungsnetzstruktur beeinflusst. Dafür spielte dabei die epilimnische Nährstoffkonzentration sowie die Phosphorbindungspotenzial des Wassers für den internen Kreislauf des Stoffes eine wichtige Rolle. / External load of nutrients, above all from phosphorus, promote the phytoplankton development and are with it the primary cause for the deterioration of the waters quality in lakes. Further, the pelagic food web structure can affect the water quality in a positive as well as in a negative way. Therefore, the water trophic state can be changed by a specific control of the predator-prey relations. In the present study the results of the large enclosure experiments to the impact by nutrients (with/without addition of nutrients) as well as by a manipulated food web structure (with/without addition of planktivorous fish) on the pelagic phyto- and zooplankton community of a thermally stratified lake (Dagowsee, Brandenburg) were presented. Furthermore, the qualitative and quantitative effects of these both factors on the sedimentation processes as well as the microbial turnover of settled carbon and phosphorus in the hypolimnion and at the sediment-water layer of the lake were in the main focus of the investigations. It has been shown that the manipulation of the food web structure affected the amount and composition of the phyto- and zooplankton in the epilimnion as well as the quantitative vertical transport of carbon and phosphorus, while the different nutrient load in the epilimnion influenced the specific material content of the carbon and phosphorus in the sedimented material. With the help of the oxygen and methane measurements it was found out that the intensity of the microbial decomposition of the settled organic matter was dependent above all on her quantity. Furthermore, the effects of the manipulated food web structure on the decomposition efficiency of the organic carbon could be proved in the laboratory tests. However, these effects were in the free land experiments hardly provably due to the participation of the endproducts in other redox processes which ran at the same time in the lake. With the help of the phosphorus fractionation procedure could be found out that settled phosphorus for the most part not organically but in iron and manganese bound as well as loosely adsorbed the sediment surface reached. At this point these both forms showed a systematic difference which pointed only to an effect of the epilimnetic nutrient concentration and not on those of the manipulated food web. Other analyses of the sediments showed strong transformations of the settled phosphorus, which influenced above all the dominating labile and redox sensitive phosphorus fractions. They were released, on the one hand, in the water and stored, on the other hand, in the organic biomass. The changes of the phosphorus content in the sediments were to be led on the previous effects of the nutrients than of the manipulated food web structure. To conclude, the effects of the food net manipulation were to be seen above all in the pelagic plankton community in the epilimnion, and further in sedimentation and carbon turnover processes in deeper layers of the lake. The vertical phosphorus transport was influenced of less by the food web structure. Moreover, for it the epilimnic nutrient concentration as well as the phosphorus binding potential of the water played an important role for the internal circulation of the material.

The project originated as a means to find a solution to the lack of legibility that the National Zoological Gardens’ entrance expresses where it is situated on the Northern gateway into the Pretoria CBD. In order to develop an appropriate responsive architecture, the proposed solution aims to find the requirements for a successful public interface for tourist attractions and the local community. Attention will also be given to the transitional spaces between the natural environments of the Zoo and the city. The aim firstly is to steer away from mono-functional urban spaces and tourist attractions hidden behind built barrier, in order to ensure that the architecture will be an asset to tourism and the general public. / Dissertation (MArch(Prof))--University of Pretoria, 2010. / Architecture / unrestricted

The focus of this thesis was to use active noise control (ANC) to globally minimize the tonal and broadband noise radiating from a diesel generator enclosure. The major goal of this research was to show that minimizing the noise within the enclosure can lead to an overall sound pressure level (SPL) reduction of radiated noise. The target levels for overall SPL reduction were at least 2 dBA. The control algorithms used in this research were based on a filtered-x LMS adaptive algorithm, which minimizes energy density (ED). Both feedforward and feedback control approaches were investigated. The noise spectrum produced by the diesel generator enclosure includes tonal and broadband components. The target range for control was from 0 to 300 Hz. Tonal frequencies at exterior locations were often reduced by 20 to 30 dB using feedforward control. With feedback control, tones were reduced 5 to 10 dB. Broadband control results were obtained at an exterior location using a feedforward control configuration. This control was achieved for frequencies between 100 and 600 Hz and levels were reduced by up to 5 dB. Some broadband control was achieved using feedback control, but this was limited to regions at the error sensor. An overall SPL reduction of 1.9 dBA outside the enclosure was achieved near the power terminal side of the enclosure. This was accomplished using tonal and broadband feedforward control. Experimental results show that control source placement, as well as error and reference sensor location, is key to global noise reduction.

This essay provides a study of five Swedish locales in the Mälar Valley and Öland, namely Arkels tingstad, Aspa löt, Tingstad flisor, Anundshög and Signhilds kulle/Fornsigtuna, and their possible use as sites of Viking Age thing assemblies. Historical texts, place names and archaeological excavations are queried through the aid of a theoretical assemblage drawing on De Landa, Deleuze & Guattari, as well as Icelandic, British and Scandinavian research. Following this, I propose that the locales chosen as thing sites were communicational nexuses localised on commons in borderzones between land domains. Thus, space commonly understood as in the elite's periphery insteadbecomes of central importance.

Studies that show discrepancy between nocturnal and diurnal activity under laboratory and field conditions, respectively, have become increasingly common in rodents and suggest that the definition of temporal niche is far more plastic than originally suspected. Recently, it has been proposed that factors that challenge the animal\'s energy balance play an important role in temporal niche switches. Food availability and environmental temperatures could then be one of the fundamental differences between field and laboratory that could alter the temporal daily pattern of activity. In laboratory, animals are fed ad libitum, while in nature they need to expend energy for foraging. The \"circadian thermo-energetics hypothesis\" suggests that daytime activity could be a response to the high energetic costs of foraging, allowing the animal to save energy during the cooler night hours by resting and taking shelter in burrows where temperatures are higher than on the surface. In this thesis, we explored the interplay of plasticity in nocturnal/diurnal activity definition and energetic metabolism in two rodent species, tuco-tucos (Ctenomys aff. knighti) and laboratory mice (Mus musculus). Tuco-tucos are subterranean rodents which face peculiar energetic challenges in their habitat and were shown to be diurnal in the field and nocturnal in the laboratory. We characterized how their energy expenditure varies across day and night and described the peculiar finding of some factor inside the metabolic chamber being itself a trigger for the nocturnal to diurnal switch. Moreover, we estimated the amount of energy tuco-tucos would save by being diurnal in the field, by combining metabolic rate measurements at various ambient temperatures with records of environmental temperature in the tuco-tuco\'s natural habitat. We also described further investigations of circadian plasticity in both locomotor activity and body temperature of laboratory mice subjected to food restriction in semi-natural conditions. The findings of these three studies provided valuable evidence for the discussion of the role of environmental factors, particularly energetic challenges, in the plasticity of daily rhythms / Estudos que apontam discrepâncias entre atividade noturna e diurna, respectivamente, sob condições de laboratório e de campo, estão cada vez mais comuns em roedores e sugerem que a definição de nicho temporal é muito mais plástica do que se suspeitava inicialmente. Recentemente, foi proposto que fatores que desafiam o balanço energético do animal desempenham um papel importante em mudanças de nicho temporal. A disponibilidade de alimento e as temperaturas ambientais poderiam ser algumas das diferenças fundamentais entre campo e laboratório, os quais poderiam alterar o padrão temporal de atividade diária. No laboratório, os animais são alimentados ad libitum, enquanto na natureza eles precisam gastar energia para forrageamento. A \"hipótese circadiana termoenergética\" sugere que a atividade diurna pode ser uma resposta aos altos custos energéticos do forrageamento, permitindo que o animal economize energia durante as horas mais frias da noite, descansando e se abrigando em tocas onde as temperaturas são mais altas do que na superfície. Nesta tese, exploramos a interação entre a plasticidade da definição noturnalidade/diurnalidade e o metabolismo energético em duas espécies de roedores, o tuco-tucos (Ctenomys aff. knighti) e o camundongo de laboratório (Mus musculus). Tuco-tucos são roedores subterrâneos que enfrentam desafios energéticos peculiares em seu habitat e verificamos que são diurnos em campo e noturnos em laboratório. Nós caracterizamos a variação de seu gasto energético ao longo do dia e da noite e descrevemos o achado peculiar de que algum fator presente no interior da câmara metabólica pode ser um gatilho para a mudança de noturnalidade para diurnalidade. Além disso, estimamos a quantidade de energia que os tuco-tucos economizariam ao serem diurnos em campo, combinando medidas de taxa metabólica em várias temperaturas ambientes com registros dessa temperatura no habitat natural do tuco-tuco. Descrevemos também investigações adicionais sobre a plasticidade circadiana na atividade locomotora e na temperatura corporal de camundongos submetidos à restrição alimentar, em condições seminaturais. Os achados desses três estudos forneceram evidências valiosas para a discussão do papel dos fatores ambientais, particularmente os desafios energéticos, na plasticidade dos ritmos diários

The complex turbulent flow regimes encountered in many thermal-fluid engineering applications have proven resistant to the effective application of systematic design because of the computational expense of model evaluation and the inherent variability of turbulent systems. In this thesis the integration of the Proper Orthogonal Decomposition (POD) for reduced order modeling of turbulent convection with the application of robust design principles is proposed as a practical design approach. The POD has been used successfully to create low dimensional steady state flow models within a prescribed range of parameters. The underlying foundation of robust design is to determine superior solutions to design problems by minimizing the effects of variation on system performance, without eliminating their causes. The integration of these constructs utilizing the compromise Decision Support Problem (DSP) results in an efficient, effective robust design approach for complex turbulent convective systems. The efficacy of the approach is illustrated through application to the configuration of data center server cabinets. Data centers are computing infrastructures that house large quantities of data processing equipment. The data processing equipment is stored in 2 m high enclosures known as cabinets. The demand for increased computational performance has led to very high power density cabinet design, with a single cabinet dissipating up to 20 kW. The computer servers are cooled by turbulent convection and have unsteady heat generation and cooling air flows, yielding substantial inherent variability, yet require some of the most stringent operational requirements of any engineering system. Through variation of the power load distribution and flow parameters, such as the rate of cooling air supplied, thermally efficient configurations that are insensitive to variations in operating conditions are determined. This robust design approach is applied to three common data center server cabinet designs, in increasing levels of modeling detail and complexity. Results of the application of this approach to the example problems studied show that the resulting thermally efficient configurations are capable of dissipating up to a 50% greater heat load and 15% decrease in the temperature variability using the same cooling infrastructure. These results are validated rigorously, including comparison of detailed CFD simulations with experimentally gathered temperature data of a mock server cabinet. Finally, with the approach validated, augmentations to the approach are considered for multi-scale design, extending approaches domain of applicability.