In spite of decades of related research, stream channel initiation is still not well understood. Current theories of channel initiation are grounded in research conducted by Montgomery and Dietrich, largely in the transport limited, temperate, humid climate of the Pacific Northwest, USA. This field data driven work concluded that the drainage area required for channel initiation is directly correlated to the slope of the contributing area. However, there are a host of related variables that have yet to be examined in the field. This study revisits the slope-area relationship focusing on ephemeral overland flow in headwaters of both the Pacific Northwest and an environmentally contrasting island in Greece. By seeking greater understanding of the variables, such as soil properties, vegetation type, and lithology that may influence channel initiation, the study sought to find an equation for remote determination of where ephemeral flow concentrates. However, results indicated that a universal equation does not exist. Rather, the location of ephemeral flow concentration is linked to landscape type, transport versus weathering limited slopes, and corresponding overland flow type. As a result, there is potential for regional models to be developed. Two such models were found as part of this study. One indicates that in a weathering limited environment, Hortonian overland flow is the dominant ephemeral flow type and the driving force behind where it concentrates on the landscape. The other demonstrates that in a transport limited environment, ephemeral flow concentration is due saturated overland flow, with the key to location of concentration being the point of return flow.

Com a consolidação do saneamento em algumas bacias urbanas, um novo desafio surge: o da recuperação dos corpos dágua. O que a principio parece ser uma consequência do processo, na realidade se mostra uma tarefa muito mais complexa e que envolve diversos fatores, tornando o processo de recuperação lento e dispendioso. Muito se diz a respeito da despoluição dos corpos dágua através da eliminação da carga pontual, mas o que se observa na prática é que, mesmo diante do controle das cargas pontuais, os corpos dágua continuam poluídos devido às cargas difusas. A preocupação com a poluição por carga difusa já é um assunto muito estudado em locais onde a poluição por cargas pontuais já possui um controle efetivo, mas este assunto ainda é um grande desafio em países como o Brasil, onde o controle da carga pontual ainda não constitui uma realidade palpável. Atualmente, na região metropolitana de São Paulo, há diversos programas atuando na despoluição de corpos dágua através do controle de cargas pontuais, dentre eles o programa Córrego Limpo se destaca por agir na otimização de sistemas de esgotamento sanitário, e apesar dos bons resultados obtidos, como o programa se baseia no controle de cargas pontuais, estas bacias não se encontram completamente despoluídas. Considerando o caso brasileiro, o programa é pioneiro no que se refere à adoção de medidas que integram a população no processo de recuperação, pois implanta em algumas de suas bacias um programa de governança colaborativa, que, através da mobilização da população, promove a integração desta com o corpo dágua. Diante deste panorama, o presente estudo, tem como intuito, através da análise de córregos de interesse do programa Córrego Limpo, contribuir para a melhor compreensão dos desafios envolvidos no processo de recuperação de corpos dágua urbanos através do controle de cargas pontuais e difusas. No estudo empregou-se o método da Unidade de carga para quantificação da geração de cargas difusas nas bacias e identificação do seu potencial poluidor, resultando na criação de um índice de qualidade da superfície da bacia; Avaliou-se também a qualidade ambiental destes corpos dágua através de indicadores físicos, químicos e biológicos, o que revelou a importância do uso conjunto destes indicadores, já que obteve-se resultados distintos para cada um destes indicadores; com base nos resultados obtidos nestes estudos foi possível avaliar o quão complexo é o processo de recuperação de corpos dágua em áreas urbanas. / With the consolidation of sanitation in some urban watersheds, a new challenge arises: the recovery of bodies of water. What at first appears to be a consequence of the process, in fact it shows to be a much more complex task and involves several facts, making the recovery process slow and costly. Much is said about the remediation of water bodies by removing point charge, but what we notice in practice is that even after controlling of point charge, they remain polluted because nonpoint pollution. The concern with nonpoint pollution is much studied in places where pollution by point charge already has an effective control, but this issue is still a challenge in countries like Brazil, where the control point charge does not constitutes a tangible reality. Currently, the São Paulo metropolitan area there are several programs working on recovering of water bodies through the control of point charge, including the Córrego Limpo that acts optimizing sewage systems, and is notorious the improvement in the quality of water bodies covered its actions. However, as the program based on controlling of point charge, the streams are not completely unpolluted. Considering the Brazilian case, the program is a pioneer when it comes to the adoption of measures that integrate the population in the recovering process. It deploys in some watersheds a program of collaborative governance that, through the people mobilization, promotes the body of water, resulting in reduction of the potential pollution in the watersheds and rendering more effective the process. The present study has the intention, through the analysis of streams of interest to the program Córrego Limpo, contribute to a better understanding of the challenges involved in the recovery process of urban water bodies through the control of the point and nonpoint pollution. In the study was used the method of unit load to quantify the generation of diffuse loads in basins and identification of their pollution potential, resulting in the creation of an index of quality of the surface of the basin, also evaluated the environmental quality of these bodies of water through physical, chemical and biological indicators, which revealed the importance of the combined use of these indicators, since we obtained different results for each of these indicators, the results of this study showed how complex is the recovery process of water bodies in urban areas.

Com a consolidação do saneamento em algumas bacias urbanas, um novo desafio surge: o da recuperação dos corpos dágua. O que a principio parece ser uma consequência do processo, na realidade se mostra uma tarefa muito mais complexa e que envolve diversos fatores, tornando o processo de recuperação lento e dispendioso. Muito se diz a respeito da despoluição dos corpos dágua através da eliminação da carga pontual, mas o que se observa na prática é que, mesmo diante do controle das cargas pontuais, os corpos dágua continuam poluídos devido às cargas difusas. A preocupação com a poluição por carga difusa já é um assunto muito estudado em locais onde a poluição por cargas pontuais já possui um controle efetivo, mas este assunto ainda é um grande desafio em países como o Brasil, onde o controle da carga pontual ainda não constitui uma realidade palpável. Atualmente, na região metropolitana de São Paulo, há diversos programas atuando na despoluição de corpos dágua através do controle de cargas pontuais, dentre eles o programa Córrego Limpo se destaca por agir na otimização de sistemas de esgotamento sanitário, e apesar dos bons resultados obtidos, como o programa se baseia no controle de cargas pontuais, estas bacias não se encontram completamente despoluídas. Considerando o caso brasileiro, o programa é pioneiro no que se refere à adoção de medidas que integram a população no processo de recuperação, pois implanta em algumas de suas bacias um programa de governança colaborativa, que, através da mobilização da população, promove a integração desta com o corpo dágua. Diante deste panorama, o presente estudo, tem como intuito, através da análise de córregos de interesse do programa Córrego Limpo, contribuir para a melhor compreensão dos desafios envolvidos no processo de recuperação de corpos dágua urbanos através do controle de cargas pontuais e difusas. No estudo empregou-se o método da Unidade de carga para quantificação da geração de cargas difusas nas bacias e identificação do seu potencial poluidor, resultando na criação de um índice de qualidade da superfície da bacia; Avaliou-se também a qualidade ambiental destes corpos dágua através de indicadores físicos, químicos e biológicos, o que revelou a importância do uso conjunto destes indicadores, já que obteve-se resultados distintos para cada um destes indicadores; com base nos resultados obtidos nestes estudos foi possível avaliar o quão complexo é o processo de recuperação de corpos dágua em áreas urbanas. / With the consolidation of sanitation in some urban watersheds, a new challenge arises: the recovery of bodies of water. What at first appears to be a consequence of the process, in fact it shows to be a much more complex task and involves several facts, making the recovery process slow and costly. Much is said about the remediation of water bodies by removing point charge, but what we notice in practice is that even after controlling of point charge, they remain polluted because nonpoint pollution. The concern with nonpoint pollution is much studied in places where pollution by point charge already has an effective control, but this issue is still a challenge in countries like Brazil, where the control point charge does not constitutes a tangible reality. Currently, the São Paulo metropolitan area there are several programs working on recovering of water bodies through the control of point charge, including the Córrego Limpo that acts optimizing sewage systems, and is notorious the improvement in the quality of water bodies covered its actions. However, as the program based on controlling of point charge, the streams are not completely unpolluted. Considering the Brazilian case, the program is a pioneer when it comes to the adoption of measures that integrate the population in the recovering process. It deploys in some watersheds a program of collaborative governance that, through the people mobilization, promotes the body of water, resulting in reduction of the potential pollution in the watersheds and rendering more effective the process. The present study has the intention, through the analysis of streams of interest to the program Córrego Limpo, contribute to a better understanding of the challenges involved in the recovery process of urban water bodies through the control of the point and nonpoint pollution. In the study was used the method of unit load to quantify the generation of diffuse loads in basins and identification of their pollution potential, resulting in the creation of an index of quality of the surface of the basin, also evaluated the environmental quality of these bodies of water through physical, chemical and biological indicators, which revealed the importance of the combined use of these indicators, since we obtained different results for each of these indicators, the results of this study showed how complex is the recovery process of water bodies in urban areas.

This Master Thesis report was written by Umeå University Engineering Physics student Richard Tano during his thesis work at Ericsson Luleå. Monitoring network quality is of utmost importance to network providers. This can be done with models evaluating QoS (Quality of Service) and conforming to ITU-T Recommendations. When determining video stream quality there is of more importance to evaluatethe QoE (Quality of Experience) to understand how the user perceives the quality. This isranked in MOS (Mean opinion scores) values. An important aspect of determining the QoEis the video content type, which is correlated to the coding complexity and MOS values ofthe video. In this work the possibilities to improve quality estimation models complying to ITU-T study group 12 (q.14) was investigated. Methods were evaluated and an algorithm was developed that applies time series analysis of packet statistics for determination of videostreams MOS scores. Methods used in the algorithm includes a novel assembling of frequentpattern analysis and regression analysis. A model which incorporates the algorithm for usage from low to high bitrates was dened. The new model resulted in around 20% improvedprecision in MOS score estimation compared to the existing reference model. Furthermore an algorithm using only regression statistics and modeling of related statistical parameters was developed. Improvements in coding estimation was comparable with earlier algorithm but efficiency increased considerably. / Detta examensarbete skrevs av Richard Tano student på Umeå universitet åt Ericsson Luleå. Övervakning av nätets prestanda är av yttersta vikt för nätverksleverantörer. Detta görs med modeller för att utvärdera QoS (Quality of Service) som överensstämmer med ITU-T rekommendationer. Vid bestämning av kvaliten på videoströmmar är det mer meningsfullt att utvärdera QoE (Quality of Experience) för att få insikt i hur användaren uppfattar kvaliten. Detta graderas i värden av MOS (Mean opinion score). En viktig aspekt för att bestämma QoE är typen av videoinnehåll, vilket är korrelerat till videons kodningskomplexitet och MOS värden. I detta arbete undersöktes möjligheterna att förbättra kvalitetsuppskattningsmodellerna under uppfyllande av ITU-T studygroup 12 (q.14). Metoder undersöktes och en algoritm utvecklades som använder tidsserieanalys av paketstatistik för uppskattning av videoströmmars MOS-värden. Metoder som ingår i algoritmen är en nyutvecklad frekventa mönster metod tillsammans med regressions analys. En modell som använder algoritmen från låg till hög bithastighet definierades. Den nya modellen gav omkring 20% förbättrad precision i uppskattning av MOS-värden jämfört med existerande referensmodell. Även en algoritm som enbart använder regressionsstatistik och modellerande av statistiska parametrar utvecklades. Denna algoritm levererade jämförbara resultat med föregående algoritm men gav även kraftigt förbättrad effektivitet.

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A variety of research exists for the processing of continuous queries in large, mobile environments. Each method tries, in its own way, to address the computational bottleneck of constantly processing so many queries. For this research, we present a two-pronged approach at addressing this problem. Firstly, we introduce an efficient and scalable system for monitoring traditional, continuous queries by leveraging the parallel processing capability of the Graphics Processing Unit. We examine a naive CPU-based solution for continuous range-monitoring queries, and we then extend this system using the GPU. Additionally, with mobile communication devices becoming commodity, location-based services will become ubiquitous. To cope with the very high intensity of location-based queries, we propose a view oriented approach of the location database, thereby reducing computation costs by exploiting computation sharing amongst queries requiring the same view. Our studies show that by exploiting the parallel processing power of the GPU, we are able to significantly scale the number of mobile objects, while maintaining an acceptable level of performance. Our second approach was to view this research problem as one belonging to the domain of data streams. Several works have convincingly argued that the two research fields of spatiotemporal data streams and the management of moving objects can naturally come together. [IlMI10, ChFr03, MoXA04] For example, the output of a GPS receiver, monitoring the position of a mobile object, is viewed as a data stream of location updates. This data stream of location updates, along with those from the plausibly many other mobile objects, is received at a centralized server, which processes the streams upon arrival, effectively updating the answers to the currently active queries in real time. iv For this second approach, we present GEDS, a scalable, Graphics Processing Unit (GPU)-based framework for the evaluation of continuous spatio-temporal queries over spatiotemporal data streams. Specifically, GEDS employs the computation sharing and parallel processing paradigms to deliver scalability in the evaluation of continuous, spatio-temporal range queries and continuous, spatio-temporal kNN queries. The GEDS framework utilizes the parallel processing capability of the GPU, a stream processor by trade, to handle the computation required in this application. Experimental evaluation shows promising performance and shows the scalability and efficacy of GEDS in spatio-temporal data streaming environments. Additional performance studies demonstrate that, even in light of the costs associated with memory transfers, the parallel processing power provided by GEDS clearly counters and outweighs any associated costs. Finally, in an effort to move beyond the analysis of specific algorithms over the GEDS framework, we take a broader approach in our analysis of GPU computing. What algorithms are appropriate for the GPU? What types of applications can benefit from the parallel and stream processing power of the GPU? And can we identify a class of algorithms that are best suited for GPU computing? To answer these questions, we develop an abstract performance model, detailing the relationship between the CPU and the GPU. From this model, we are able to extrapolate a list of attributes common to successful GPU-based applications, thereby providing insight into which algorithms and applications are best suited for the GPU and also providing an estimated theoretical speedup for said GPU-based applications

According to the paradigm of lambda-CDM cosmology, the stellar halo ofour Galaxy has been built-up over time through the accretion of other galaxiesand star clusters. The remnants of some of these are still observable today asstellar streams, but are typically very faint and difficult to resolve amidst the farmore numerous foreground Milky Way stars. The VelHel-4 stream, discoveredby Helmi et al. [2017], consists of seven members selected based on their energiesand angular momenta. Further studies of these stars has shown evidence ofglobular cluster (GC) abundance patterns, suggesting that the stream originatedfrom a GC progenitor, but a larger sample is needed to verify this signature. Theobjective of this thesis is to find new candidate members of the VelHel-4 stellarstream in order to better characterize its properties and to confirm a possibleGC origin.The preliminary selection of stars was done kinematically, by computing theorbital actions and energies using astrometric data and radial velocities for abright subset of the Gaia DR3 database, and then analyzing the clustering ofstream members in different combinations of action space. The selected samplewas then cleaned by analyzing the positions of these stars in a colour-magnitudediagram. In total, 34 stars were included in the final selection. Follow-up high-resolution spectroscopy of these candidates is needed to study their stellar abun-dances and confirm the possible GC origin of this stream.

The Stream API was added in Java 8. With the help of lambda expressions (anonymous functions), streams enable functional-style operations on sequences of elements. In this project, we evaluate how streams perform in comparison to imperative loops in terms of execution time, from the perspective of how streams are commonly used in public GitHub repositories. Additionally, two algorithms are implemented with and without streams, to assess the impact of stream usage on algorithmic performance. Parallel streams are only examined briefly due to their infrequent usage. We find that sequential streams in general are slower than imperative loops. However, stream performance heavily relies on how many elements are being processed, which is referred to as input size. For input sizes smaller than 100, most stream pipelines are several times slower than imperative loops. Meanwhile, for input sizes between 10 000 and 1 000 000, streams are on average only 39% to 74% slower than loops, and in some cases, they even slightly outperform them. Additionally, we observe that using streams when implementing algorithms in some cases leads to much slower execution times, while in other cases, it barely affects the execution time at all. We conclude that stream performance primarily depends on input size, presumably because of the high overhead abstraction cost of creating streams, but their performance also depends on other factors, such as operation type and pipeline length. / Med Java 8 introducerades streams. Med hjälp av lambda-uttryck (anonyma funktioner) möjliggör streams användandet av funktionella operationer på sekvenser av element. I detta projekt mäter vi hur streams presterar i jämförelse med imperativa loopar med hänsyn till exekveringstid, från perspektivet av hur streams vanligen används i publika GitHub-projekt. Parallella streams undersöks endast i begränsad utsträckning, på grund av hur sällan de används. Resultaten visar att streams överlag är långsammare än imperativa loopar. Skillnaden i prestanda beror dock starkt på indatastorleken, det vill säga hur många element som streamen bearbetar. För indatastorlekar mindre än 100 element är streams ofta flera gånger långsammare än deras imperativa motsvarigheter. Samtidigt är streams i genomsnitt endast 39% till 74% långsammare än imperativa motsvarigheter för indatastorlekar mellan 10 000 och 1 000 000 element, och i några fall är de till och med något snabbare än imperativ kod. Vidare observerar vi att användning av streams vid implementation av algoritmer i vissa fall leder till mycket längre exekveringstider, medan det i andra fall knappt påverkar exekveringstiden alls. Vi drar slutsatsen att prestandan av streams främst beror på indatastorlek, men också på andra faktorer, såsom operationstyp och hur många operationer som används i en pipeline.

Doctor of Philosophy / Department of Geography / Melinda Daniels / Geomorphic properties of streams are linked to ecosystem function through processes related to storage, transport, and other drivers regulating biogeochemical conditions. Disturbances altering the physical template of a stream are associated with cascading impacts on ecosystem function. However, few disturbances are studied at long time scales and so the legacy of such events and the implications for ecosystem structure and function are not well understood. This research investigates the role of historic tie-driving, a channel disturbance legacy, in shaping present-day stream channel conditions in the Rocky Mountain region and the associated implications for organic matter dynamics. Using a combination of geomorphic and riparian surveys, organic matter and vegetation sampling, and modeling, I show that components of mountain stream ecosystems have recovered from tie-driving at varying rates. First, I addressed how tie-driving has altered channel morphology and wood loading. Tie-driven streams are narrower, shallower, less rough, and have less wood than non-driven reference reaches. In a second study, I focused on differences in carbon storage within the stream and riparian area between tie-driven and non-driven streams. Carbon stored on the landscape represents a long-term component of the terrestrial carbon cycle and some, but not all, components have been impacted by tie-driving. Large instream wood, coarse downed wood, and fine downed wood were identified as carbon storage components that were significantly smaller in tie-driven stream-riparian corridors. Finally, I modeled whole stream ecosystem metabolism and tested whether abiotic drivers influenced variations in rates of gross primary productivity (GPP), ecosystem respiration (ER), and net ecosystem productivity (NEP). Results from this work suggest that rates of GPP were significantly different between tie-driven and non-driven streams and were partially explained by variations in light related to canopy structure. However, variations in ER and NEP were not significantly different between tie-driven and non-driven sites. Taken as a whole, this work shows that ecosystems bear the imprint of historic disturbances but individual ecosystem components recover at differing rates. Additionally, integrating stream hydro-geomorphic and ecological dynamics is an effective approach to understanding the impact of channel disturbances in shaping ecosystem function at a variety of spatial and temporal scales.

Doctor of Philosophy / Department of Biological & Agricultural Engineering / James K. Koelliker / Over the past decades, it has been observed that the streamflow characteristics in the Great Plains rivers have substantially changed. These changes have affected and will continue to affect the management decisions within the watershed. This study was undertaken to document the changes for some unregulated streams in Kansas, characterize the streams in terms of some hydrologic indices, and identify the probable factors influencing the changes. Fourteen unregulated streams with 60 or more years of daily discharge data geographically distributed across the state were used. The analysis focused on hydrologic indices judged to be relevant to the lotic ecosystem. The state was divided into four regions, representing roughly the northwest, southwest, northeast and southeast sections of the state. Log Pearson III method was used for computing flow probabilities, Mann-Kendall test in conjunction with Sen’s slope estimator was used for trend analysis, whereas the indicators of hydrologic alterations software was used to generate most hydrologic indices. Several factors believed to affect the streamflow were identified, and their influence was modeled over time. A multi-variate statistical model was run. Results show that there is substantial difference in the streamflow characteristics between the western and eastern regions. Many streamflow aspects have changed over time, and a number of them show significant and important change. Most streams in western Kansas have longer and more frequent dry periods. Potential recharge rate, land use, water use, soil and water conservation practices, and soil type were significant factors influencing the median to very low flow, but the effect varied among the regions. Results of this study could be useful to decision makers, water users, watershed stakeholders, and environmental conservation advocates in addressing problems and concerns related to stream and river management.