Dissertations / Theses on the topic 'Bottlenecks'

Mining has a long history of production and operation management. Economies of scales have changed drastically and technology has transformed the mining industry significantly. One of the most important technological improvements is increased equipment, human, and plant tracking capabilities. This provided a continuous data stream to the decision makers, considering dynamic operational conditions. However, managerial approaches did not change in parallel. Even though many process improvement tools using equipment/human/plant tracking capabilities were developed (Fleet Management Systems, Plant Monitoring Systems, Workforce Management Systems etc.), to date there is no holistic approach or system to manage the entire value chain in mining. Mining operations are designed and managed around the already known system designated bottlenecks. However, contrary to common belief in mining, bottlenecks are not static. They can shift from one process or location to another. It is important for management to be aware of the new bottlenecks, since their decisions will be effected. Therefore, identification of true bottlenecks in real-time will help tactical level decisions (use of buffers, resource transfer), and identification of historical bottlenecks will help strategic-level decisions (investments, increasing capacity etc.). This thesis aims to address the managerial focus on the true bottlenecks. This is done by first identifying and ranking true bottlenecks in the system. The study proposes a methodology for creating Bottleneck Identification Model (BIM) that can identify true bottlenecks in a value chain in real-time or historically, depending on the available data. This approach consists of three phases to detect and rank the bottlenecks. In the first phase, the system is defined and variables are identified. In the second phase, the capacity, rates, and buffers are computed. In the third phase, considering particularities of the mine exceptions are added by taking mine characteristics into account, and bottlenecks are identified and ranked.

Traffic shockwaves are a regularly occurring phe-nomenon in traffic that are a source of irritation and delaysfor the road users. One type of shockwave is the stop-and-gowave which forces entering drivers to stop and advance slowlyuntil the wave is passed. This project aims to design a controlalgorithm through the use of models and simulations to increasethe rate at which a stop-and-go wave dissipates. To design themodel and algorithm the Simulation of Urban MObility (SUMO)simulator and the Traffic Control Interface (TraCI) were usedin conjunction with Python. The setup used for simulation wasthat of a one way, two lane highway with an artificially inducedstop-and-go wave.The designed algorithm manages to dissipate a stop-and-go wavecompletely without introducing new ones.<br>Trafikvågorär ett vanligt förekommandefenomen i trafiken vilketär en orsak till frustration ochförseningar. En typ av vågär startochstop vågen som tvingarförare att stanna och långsamt fortsätta genom vågen tills denpasserat. Målet med detta projektär att utveckla en kontrol-lalgoritm med hjälp av modeller och simuleringar för attökaavtagandet av en sådan våg. För att utveckla modellen ochalgoritmen används simulatorn Simulation of Urban MObility(SUMO) och Traffic Control Interface (TraCI) i kombinationmed programmeringsspråket Python. Simulering gjordes på ettnätverk bestående av en enkelriktad, tvåfilig motorväg med enkonstgjord startochstop våg.En algoritm utvecklades som kan skingra en startochstop vågutan att skapa nya.<br>Kandidatexjobb i elektroteknik 2020, KTH, Stockholm

This thesis describes an ethnographic field study that examined the design coordination process in two building projects. The goal of the study was to better understand the challenges faced by project teams as they coordinate designs in multi-disciplinary meeting environments. I focus on the bottlenecks encountered during in-person and distributed project coordination meetings. I observed meeting bottlenecks when meeting activities were performed inefficiently, when the meeting process was slowed down, when meeting workflow was interrupted, or when decision-making was hindered. I identified and characterized meeting bottlenecks in a framework that illustrates the nature of the bottleneck, and the frequency of its occurrence. According to my observations, there were two main categories of causes for bottlenecks in coordination meetings: context-based bottlenecks and content-based bottlenecks. Context-based bottlenecks are caused by the people in the design team, the meeting environment and the meeting technology. Content-based bottlenecks are related to the nature of the information artifacts (e.g., drawings and other design information) and the interactions with these artifacts (e.g., navigation and annotation). This study also provides an analysis of the frequency and patterns of various bottlenecks encountered in different meeting settings. For example, in paper-based meetings, there were more “interaction/ access” bottlenecks observed since the meeting activities involved the use of information artifacts and the participants’ interaction with these artifacts. In distributed meetings, the larger number of meeting bottlenecks was observed under the “technology” bottlenecks group. Therefore, this analysis illustrates the specific requirements for different meeting settings. This study enhances our understanding of the work practice of project teams in design coordination meetings. It highlights the many ways that meeting efficiency could be improved for design teams in coordination meetings. By using the vignettes in this study, people from different domains can understand the nature of the meeting processes, the techniques used by project teams when coordinating designs, and the different methods used by meeting participants to interact with information artifacts. My hope is that these findings will inform the design of new interaction, visualization, and integration technologies that better support the meeting processes of design teams.

Snap-through is a striking instability in which an elastic object rapidly jumps from one state to another. It is seen in the leaves of the Venus flytrap plant and umbrellas flipping on a windy day among many other examples. Similar structures that snap-through are used to generate fast motions in soft robotics, switches in micro-scale electronics and artificial heart valves. Despite the ubiquity of snap-through in nature and engineering, its dynamics is usually only understood qualitatively. In this thesis we develop analytical understanding of this dynamics, focussing on how the mathematical structure underlying the snap-through transition controls the timescale of instability. We begin by considering the dynamics of 'pull-in' instabilities in microelectromechanical systems (MEMS) - a type of snap-through caused by electrostatic forces in which the motions are dominated by fluid damping. Using a lumped-parameter model, we show that the observed time delay near the pull-in transition is a type of critical slowing down - a so-called 'bottleneck' due to the 'ghost' of a saddle-node bifurcation. We obtain a scaling law describing this slowing down, and, in the process, unify a large range of experiments and simulations that exhibit delay phenomena during pull-in. We also investigate the pull-in dynamics of MEMS microbeams, extending the lumped-parameter approach to incorporate the details of the beam geometry. This provides a model system in which to understand snap-through of a continuous elastic structure due to external loading. We develop a perturbation method that systematically exploits the proximity to pull-in to reduce the governing equations to a simpler evolution equation, with a structure that highlights the saddle-node bifurcation. This allows us to analyse the bottleneck dynamics in detail, which we compare with previous experimental and numerical data. The remainder of the thesis is concerned with the dynamics of snap-through in macroscopic systems. In particular, we explore the extent to which dissipation is required to explain anomalously slow snap-through. Considering an elastic arch as an archetype of a snapping system, we use the perturbation method developed earlier to show that two bottleneck regimes are possible, depending delicately on the relative importance of external damping. In particular, we show that critical slowing down occurs even in the absence of damping, leading to a new scaling law for the snap-through time that is confirmed by elastica simulations and experiments. In many real systems material viscoelasticity is present to some degree. Finally, we examine how this influences the snap-through dynamics of a simple truss-like structure. We present a regime diagram that characterises when the timescale of snap-through is controlled by viscous, elastic or viscoelastic effects.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 47-48).<br>Effective use of CPU data caches is critical to good performance, but poor cache use patterns are often hard to spot using existing execution profiling tools. Typical profilers attribute costs to specific code locations. The costs due to frequent cache misses on a given piece of data, however, may be spread over instructions throughout the application. The resulting individually small costs at a large number of instructions can easily appear insignificant in a code profiler's output. DProf helps programmers understand cache miss costs by attributing misses to data types instead of code. Associating cache misses with data helps programmers locate data structures that experience misses in many places in the application's code. DProf introduces a number of new views of cache miss data, including a data profile, which reports the data types with the most cache misses, and a data flow graph, which summarizes how objects of a given type are accessed throughout their lifetime, and which accesses incur expensive cross-CPU cache loads. We present two case studies of using DProf to find and fix cache performance bottlenecks in Linux. The improvements provide a 16-57% throughput improvement on a range of memcached and Apache workloads.<br>by Aleksey Pesterev.<br>S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 63-64).<br>One difficulty of programming multicore processors is achieving performance that scales with the number of cores in the system. A common performance optimization is to increase inter-core parallelism. If the application is sufficiently parallelized, developers might hope that performance would scale as core count increases. Unfortunately for some applications, such as operating system kernels, parallelization reveals inter-core communication as a performance bottleneck. When data is updated on one core and read or written on other cores, the cache coherence protocol serializes accesses to the data. The result is that each access to the shared data can take hundreds to thousands of cycles, depending on how many cores are contending for the data. This dissertation focuses on optimizing communication bottlenecks caused by update-heavy workloads, where a data structure is frequently updated but rarely read. Such data structures are commonly used for operating system kernel bookkeeping, such as LRU lists, reverse maps in virtual memory, and file system notification queues. This dissertation identifies bottlenecks in the Linux kernel caused by update-heavy data structures, presents a general approach for optimizing communication in update-heavy data structures, and presents a library called OpLog that embodies this approach and helps developers achieve good scalability for update-heavy data structures. OpLog achieves scalability by logging update operations in per-core logs, and combining the logs only when required by a read to the data structure. Measurements on a 48-core AMD server show that applying OpLog to update-heavy data structures in the Linux kernel significantly improves application performance under certain workloads.<br>by Silas Boyd-Wickizer.<br>Ph. D.

This article describes and analyses the present conditions of the application of the Public Work Tax Deduction (PWTD) mechanism, identifying six main obstacles that difficult on a appreciable way his concrete implementation or the rate of it.For this purpose, this study has identify and analyze the 30 main highlights that conform the critical path of PWTD process, determining the actual times for his performance and comparing them with the legal times established on the PWTD actual law, and so with the optimal times reasonably according with the experience on the public management of similar work projects.<br>El presente artículo describe y analiza las condiciones actuales de la aplicación delmecanismo de Obras por Impuestos (OXI), identificando seis obstáculos principales que dificultan de manera apreciable su implementación concreta o la velocidad de la misma. Para efectos del presente estudio se han identificado y analizado los principales 30 hitos que conforman la ruta crítica del proceso OXI, determinando los tiempos reales para su cumplimiento y comparándolos con los tiempos legales establecidos en la normativa OXI actual, y con los tiempos óptimos estimados razonablemente de acuerdo a la experiencia en la gestión pública de proyectos similares.

Aquaponik-Systeme stellen an sich einen sehr nachhaltigen, innovativen Ansatz für die zukünftige Lebensmittelproduktion dar. Allerdings hat sich bis heute noch kein flächendeckender, ökonomischer Erfolg eingestellt und wesentliche systemische Engpässe wurden wissenschaftlich nicht untersucht. Daher waren die Hauptziele dieser Dissertation, (I) sichere Nitratkonzentrationen in geschlossenen Kreislaufanlagen (RAS) zu ermitteln, unter denen optimales Wachstum und Tierwohl produzierter Tilapien gewährleistet ist, (II) die Evaluierung des besten Designkonzeptes für die optimale, kombinierte Produktion von Fisch und Pflanzen und (III) die allgemeine Effizienz bei der Wiederverwertung des Abwassers und der Nährstoffe aus dem Schlamm der mechanischen Filtrationseinheiten in aquaponischen Systemen zu erhöhen. Das Wachstum und die Gesundheit von Niltilapien (Oreochromis niloticus) wird durch hohe Nitratkonzentrationen (> 500 mgL-1 NO3--N) negativ beeinflusst. Nitratkonzentrationen, die für die Produktion von Pflanzen in aquaponischen Systemen (~ 200 mgL-1 NO3--N) optimal sind, haben keinen negativen Einfluss auf das Tierwohl. Entkoppelte Kreislaufsysteme sind bei einer professionellen aquaponischen Produktion von Fisch und Pflanzen zu bevorzugen. Bei der Produktion von Fisch ergab sich keinerlei Unterschied, jedoch wurde eine deutlich gesteigerte Tomatenproduktion von 36 % in entkoppelten Kreislaufsystemen erreicht. Die aerobe Mineralisation zeigte das beste Rückgewinnungpotential von Phosphat und nur geringe Nitratverluste und kann in der Gesamtheit eine deutliche Effizienzsteigerung aquaponischer Systeme zur Folge haben. Die Ergebnisse dieser Dissertation zeigen die Engpässe in der Aquaponik klar auf und liefern gleichzeitig Lösungsansätze, wie diese Hindernisse in Bezug auf das Nährstoff- und Ressourcenmanagement überwunden werden können. Dadurch kann die Nachhaltigkeit dieser Anlagen gesteigert und die Wahrscheinlichkeit des wirtschaftlichen Erfolges erhöht werden.<br>Aquaponics is the combination of fish production in aquaculture and hydroponic (soilless) production of crop plants. Despite of representing already a sustainable, innovative approach for future food production systems, aquaponics are still missing economic success and up to date major bottlenecks were not scientifically addressed. Therefore the main aims of this thesis were (I) to identify safe nitrate concentrations under which best growth and health status of tilapia can be guaranteed in aquaponics, (II) to evaluate the best design concept for an optimal combined production of fish and plants and (III) to increase the overall system efficiency by recycling waste water and nutrients deposited in the sludge of the mechanical filtration unit. The growth and health status of Nile tilapia (Oreochromis niloticus) is negatively affected by high nitrate concentrations (> 500 mgL-1 NO3--N) commonly reported for RAS. Nevertheless, optimal nitrate concentrations for plant production in aquaponic systems (~ 200 mgL-1 NO3--N) are not affecting fish welfare and allow for an efficient production of Nile tilapia. Decoupled aquaponics proved to be favorable for professional aquaponic production, whereas coupled systems were suboptimal for a combined production of fish and plants. There were no differences in fish production, whereas tomato production within the decoupled system was considerably increased by 36 %. Aerobic mineralization of phosphate revealed best phosphate recovery with only minor losses of nitrate. Recycling of water sludge mixture from clarifiers resulted in a substantial phosphor recovery, an increase in potassium and additional water savings. Conclusively, the results of this holistic thesis clearly revealed the bottlenecks in aquaponic technology and provided guidance in overcoming mayor obstacles in terms of optimized nutrient and resource management to increase the overall sustainability of these systems and improve production efficiency and profitability.

It is generally accepted that populations which experience severe bottlenecks have a reduction in fitness. One of the most frequently reported fitness costs is increased hatching failure in bottlenecked populations of birds. The mechanism responsible for increased hatching failure is unknown. Research on other animals suggest that reduced population numbers cause unavoidable inbreeding that in turn leads to abnormalities in the gametes. In this thesis I examine some of the possible causes for increased hatching failure in severely bottlenecked populations of introduced birds in New Zealand. I look at three traits identified as a cause for infertility or hatching failure previously and determine whether there is a link with the size of a population s bottleneck. It is possible that reduced numbers of sperm reaching the site of fertilisation is a primary cause of hatching failure. I examined the perivitelline membrane of various species of introduced birds and counted the total number of sperm present to compare to how many would be expected in non-bottlenecked species. Although there was no relationship between the size of the bottleneck and the number of sperm present, all species had lower than expected sperm counts. In many species of mammals, a reduction in the quality of sperm is attributed to inbreeding depression bought about by genetic bottlenecks. I next compared the level of sperm abnormalities, variation in midpiece size sperm, and sperm motility with the size of the bottleneck each species passed through when introduced to New Zealand. There was no significant correlation between either the variation in midpiece size or sperm motility with bottleneck size. However, there was a trend for species that passed through more severe bottlenecks to have a slightly higher level of midpiece size and lower motility. Finally, I examined whether there was a link between abnormalities in the eggshell and the size of the respective bottleneck. There was no significant change in eggshell thickness or any change in the number of pores associated bottleneck size. However, there was a decreased number of round pores in severely bottlenecked species, although the consequences of this are unknown. My findings do not directly link a single cause for increased hatching failure in bottlenecked species of birds, but they do highlight the need for monitoring of reproductive traits in endangered species that have experienced a population bottleneck.

This thesis describes a throughput-based technique for identifying the bottleneck of a production system using discrete-event simulation. Most literature defines a bottleneck as being a workstation that has the largest impact on reducing the throughput of a system. However, when identifying a bottleneck using discrete-event simulation, throughput is rarely considered as the parameter of interest. Instead, parameters like percentage utilization and waiting time in an upstream buffer are considered. The technique suggested in this thesis identifies the bottleneck as being the workstation that causes the largest drop in throughput if added to a system. The technique is explained and tested on four different shop-floor arrangements of workstations (serial, job split, conditional branching, and a feedback/rework production line). This demonstrates that the throughput-based technique can be used in most any shop-floor arrangement of workstations and eliminates some of the drawbacks of the other more commonly used bottleneck identification methods, such as percentage utilization and waiting time in queue. A major failure of the percentage utilization technique in identifying system bottlenecks is seen in systems that have static and dynamic resources. However, the throughput-based technique correctly identifies the bottleneck of such systems.

A production system is a system where the raw materials are converted to finished products. A production system is classified in to two types based on the products processed namely single product production system and multi-product production system. The products in any production system would be in either value added or non-value added state. This research focuses on reducing the non-value added state in multi-product or complex production system by analyzing the bottlenecks. A bottleneck machine causes blocking or starving of parts in the system thereby increasing the non-value added time and reducing the system performance. Bottlenecks can be mitigated by control strategies such as buffer allocation and capacity addition. In order to mitigate the bottlenecks, the location, source and type of bottleneck in any system has to be identified. This research uses multiple metrics in order to identify the bottleneck and its type. Based on the metric values, the control strategies are implemented by the developed heuristics such as buffer allocation based on qualitative characteristics, capacity addition based on highest utilization and economic analysis based on sensitivity analysis. Multiple options are given with respect to their performance improvement for the management or the customer to select in order to give flexibility in terms of investment, demand and layout space.<br>Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering.

Analogous to the progeny of other adversely environmental affected cultures like the post-war Dutch and the reservation Pima, today’s African American children are the most at risk for obesity and early onset of type II diabetes. The relationship between the onset of chronic diseases like obesity and diabetes to environmental social stressors has been positively correlated. The relationship between environmental impacts on quantitative trait expression is rooted in genetic fundamentals. This study considers the quasi-breeding and phenotypic selection caused by slavery, and the ensuing generations of African American commoditization, as a bottleneck factor impacting the descendants of slaves thusly affected and examines the cultural inadequacy of body mass indexing (BMI) standards towards validation of the “epidemic” of obesity related diabetes among African Americans. DNA samples, body measurements and survey data were taken from randomly selected populations of Africans and African Americans. Data were examined for correlations among; BMI components; genetic bases for thinness in metabolism; and food choices. Major findings included significant correlations between lean muscle, body fat and BMI. The four populations composed of US resident males and females of African or African American origin differed significantly for these measures. Further, food choices were better among Africans than African Americans, however, socio economic standings differed too. In conclusion, BMI was not a useful measure of fat, therefore not a useful tool to predict obesity; African American food choices were poor compared to Africans; and African American women were the group most negatively affected. African American BMI did not relate exclusively to body fat, but to an array of correlates and determinants, not found to be so in European Americans. There are different correlates and determinates of BMI and diabetes in African Americans that European Americans. Also, some aspects differ between American-born and African-born African Americans.

Des de fa temps s’han estudiat els processos d’eliminació biològica de fòsfor (EBPR) en aigües residuals, però la seva implementació a escala real ve associada moltes vegades a fallades no esperades. S’han detectat interaccions negatives amb el procés d’eliminació de nitrogen i matèria orgànica que no s’havien previst en l’estudi dels mateixos de manera individual. Aquesta tesi aprofundeix en la caracterització, l’estudi i la solució de problemes existents a l’hora d’implementar l’eliminació biològica de fòsfor en aigües residuals conjuntament amb l’eliminació biològica de matèria orgànica i nitrogen. La investigació duta a terme en aquesta tesi té dos enfocaments diferents dins d’aquest marc. D’una banda s’estudien les causes de la interacció negativa entre els processos d’eliminació biològica de nitrogen i de fòsfor. D’altra banda s’estudia la possibilitat d’utilitzar, per part dels organismes acumuladors de fòsfor (PAO), fonts de carboni alternatives, que també s’utilitzen en el procés d’eliminació de nitrogen. En el primer lloc, s’estudia una nova estratègia per l’eliminació de nutrients (nitrogen i fòsfor) que consisteix en la bioaugmentació de microorganismes PAO dins d’un sistema de nitrificació i desnitrificació. En aquest estudi es va comprovar que una configuració de SBR amb una fase anòxica amb dues alimentacions i una fase aeròbica permet aconseguir nitrificació, desnitrificació i EBPR. Un punt clau per l’èxit d’aquesta estratègia és proporcionar condicions operacionals adequades per evitar els problemes de “rising”. Es proporcionar una fase aeròbia amb la suficient durada per assegurar el consum del PHA acumulat pels PAO, i evitar la disponibilitat de font de carboni requerida per la desnitrificació. En aquest mateix context també s’estudia la interacció de diferents espècies intermèdies del procés d’eliminació de nitrogen, com són el nitrit i el nitrat, en el procés EBPR. D’altra banda, s’ha estudiat un dels principals problemes per a implementar a nivell real l’EBPR, la manca d’àcids grassos volàtils a l’aigua residual d’entrada al procés. És per això que, en segon lloc, s’han estudiat diverses estratègies per a la utilització de fonts de carboni diferents a les convencionals en el procés EBPR. S’han provat fonts de carboni que actualment s’utilitzen en el procés d’eliminació de nitrogen, com són el metanol i el glicerol, i que, per tant, abaratirien els costos quan ens trobem aigües residuals amb poca DQO disponible per dur a terme l’eliminació simultània de nitrogen i fòsfor. Les estratègies que es proven també són dues: la primera és la substitució directa de la font de carboni convencional (àcid propiònic) per la font de carboni en qüestió dins d’un sistema enriquit en microorganismes PAO. La segona estratègia, més innovadora, és la formació d’un consorci microbià amb llots de digestió anaeròbia, prèviament seleccionat, amb microorganismes PAO on els primers seran capaços de fermentar la font de carboni més complexa cap a àcids grassos volàtils de cadena curta (àcid acètic i propiònic) que seran utilitzats pels PAO per dur a terme el procés EBPR. En el darrer capítol de la tesi, s’estudia una nova estratègia per a aconseguir uns llots enriquits majoritàriament amb microorganismes PAO. Aquest procediment permet eliminar del sistema aquells microorganismes competidors (GAO) que capten la font de carboni que hi ha disponible pels PAO i perjudiquen al procés EBPR. L’aplicació d’aquesta estratègia va resultar en un llot amb un 85% de PAO i en el rentat dels GAO del sistema.<br>Enhanced biological phosphorus removal (EBPR) has been extensively studied, but its implementation at full-scale is still associated to unpredictable failures. Furthermore, when EBPR is implemented simultaneously to nitrogen and organic matter removal, some negative interactions have been found, while individually does not occur. This thesis aims to improve the understanding of EBPR and solve some of the issues reported when EBPR is implemented in wastewater treatments together with biological removal of nitrogen and organic matter. The research conducted in this thesis has two different approaches within this framework. On the one hand, the negative interaction between the nitrogen and phosphorus removal processes has been studied. On the other hand, the possibility to use alternative carbon sources, also used in nitrogen removal, has been assessed by developing novel strategies focused on obtaining new syntrophic consortia for application in EBPR. In chapter 4, new insights for simultaneous nitrogen and phosphorus removal are presented. These strategies are based on the bioaugmentation of PAO microorganisms in nitrification/denitrification systems. A cycle configuration with an anoxic phase with two feedings and an aerobic phase was used to achieve nitrification, denitrification and EBPR. A key point for the success of this strategy was to provide proper operational conditions to avoid rising problems. Enough aerobic phase length was required to ensure complete PHA depletion for PAO microorganisms, which avoided the carbon source availability required for denitrification. In this context, the interaction of different intermediates of the nitrogen removal process, such as nitrite and nitrate, on the EBPR processes was studied. The conclusion of such experiments was that intermediate products of the nitrogen removal process, such as nitrate, can affect EBPR process when PAO microorganisms have not been previously acclimated to these conditions. Low concentration of volatile fatty acid in wastewaters has been also reported to be one of the main hurdles problems to implement EBPR process in full-scale WWTPs. For this reason, Chapter 5 presents the studies done in order to use different carbon sources for EBPR. Two carbon sources commonly used in nitrogen removal processes, namely methanol and glycerol, were tested, resulting in a cost reduction when nitrogen and phosphorus were removed simultaneously in wastewaters with low COD content. Two different strategies were assessed: first, the direct replacement of conventional carbon source (propionic acid) to the desired carbon source in a PAO-enriched sludge system. The second strategy, a novel one, was to develop a consortium of anaerobic sludge, comprising previously selected microorganisms, and PAO where the first ferment the complex carbon source to short-chain volatile fatty acids (i.e. acetic and propionic acid) which are subsequently used by the PAO in the EBPR process. Finally, Chapter 6 presents the study of a new strategy to achieve a predominantly PAO-enriched sludge, removing GAO, which uptake significant proportions of the carbon source available for EBPR. The application of this strategy resulted in the 85% of PAO in the enriched sludge, washing out GAO of the system.

<p>Problem – The expansion of global trade and supply chain integration has put great emphasison logistics, particularly in the intermediary sector, freight forwarders. Whilst in developedcountries freight forwarders benefit from competitive markets and trade facilitatingpolicies, this sector in West coast Africa exhibits low logistics performance levels. Inorder to address such issues, one needs to analyse the problem and identify the causes; thisthesis focuses on identifying the bottlenecks in the freight-forwarding sector in west coastAfrica.Purpose – The main purpose of this study is to identify the bottleneck/s within thefreight-forwarding industry in west coast Africa, namely: Angola, Cameroon, DR of Congo,Gabon, and Nigeria.Method – This thesis employs a pre-study and case study method, to ensure sufficient collectionof relevant material, taking into account the lack of research in this subject. We usedthe material obtained from the interviews and the secondary source, to structure our purpose,research questions, and to define the case of our study.Results – The study concludes with a series of interesting findings; First, the activity of aFreight Forwarder depends on a series of factors that do not depend on the Freight Forwarderper se. And second, Freight Forwarders in order to accomplish their tasks, have accessto services that are shared by all providers, and that are beyond their control. To conclude,the study identifies infrastructure as a major bottleneck in the Freight Forwarding sector.</p>

Maldives is an island nation that consists of around 1190 islands located in the Indian Ocean, southwest of Sri Lanka. The country virtually imports everything it consumes. Male’ Commercial Harbour handles all international sea cargo for the country. The land area assigned for the port is small; and there are frequent bottlenecks and congestion in the port. By using computer simulation techniques, this research investigates the situation of Male’ Commercial Harbour and identifies logistic bottlenecks that exist at the port. Accordingly, a field research was conducted at Male’ Commercial Harbour to collect required data. Both, qualitative and quantitative data were collected using focus group, interviews, on-site observations, and time and motion measures. The simulation models presented in this thesis were carried out with Arena software (Academic Version of Arena 10.0). The models were used to analyse the vessel turnaround time, berth capacity, yard capacity, container dwell time, queue values, utilisation of ship cranes and other container handling equipment. The results show that berth capacity seems to be the major bottleneck that creates longer queues and ship delays at Male’ Commercial Harbour. Several scenarios were tested to identify the best scenario regarding ship waiting time at berth. Based on the best scenario, a project was proposed focusing on the development of an extended alongside berth at Male’ Commercial Harbour. A cost benefit analysis was performed to see whether the project is financially feasible.

Recurrent congestion is a continually growing problem on urban freeways. Facility expansions cannot keep pace with the growing vehicle demand. Low-cost mitigation measures are one way to alleviate the congestion at recurring bottleneck locations. Low-cost measures typically have a life of approximately 10 years and costs ranging from $8,000 to $2.45 million. While benefits have been realized in field applications, there hasn?t been a lot of study regarding the performance of these measures in terms of added capacity. While modeling has long been a tool for planning and analyzing freeway networks, there has been little reported regarding its use for estimating the benefits of low-cost freeway improvements. In this study, the author tested proposed treatments at two sites using both a macroscopic and microscopic model. Because empirical performance information of these measures is not available, a quantitative analysis would not be reasonable since confidence in the values reported would be low. Current bottleneck identification methods typically either predict breakdown in real-time, or analyze detector data off-line. In order to identify bottlenecks from recorded aggregated data in an off-line model, criteria were generated to identify active bottlenecks and analyze the models? performance in an empirical and qualitative manner. Application of the criteria has been shown to provide reliable bottleneck identification to the calibrated pre-treatment case and expected results in the post-treatment cases.

Size-dependent differences between individuals in size-structured organisms have fundamental effect on population and community dynamics. Intraguild predation (IGP) is one specifically interesting constellation that often arises when two size-structured populations interact. Ontogenetic bottlenecks that determine population size-structure are affected by both population intrinsic as well as population extrinsic factors, and are therefore context-dependent. Surprisingly, size-structured IGP systems have mainly been investigated theoretically and especially long-term empirical studies are widely lacking. In this thesis I investigate empirically how habitat complexity, interaction strength, and stage-specific resource availabilities affect population processes and their effects on the dynamics of a size-structured IGP system. I conducted multi-generation experiments in a size-structured IGP system, with the Least Killifish (Heterandria formosa) as IG prey and the Common Guppy (Poecilia reticulata) as IG predator. With no alternative resource next to the shared resource, IG predator and IG prey could not coexist. Weak interactions only increased IG prey and IG predator persistence times and observed exclusion patterns depended on habitat complexity. An alternative resource for either the juvenile IG predator or the juvenile IG prey on the other hand promoted coexistence. However, this coexistence was context-dependent. Ontogenetic bottlenecks played a central role in the dynamics of the size-structured IGP system in general. In the final study I show that an ontogenetic bottleneck can, through changes in stage-specific resource availabilities, be affected in a way that leads to increased trophic transfer efficiency with potential effects on higher trophic levels. Overall, the results emphasize importance of the broader context in which size-structured communities are embedded. Especially, when managing natural communities it is important to account for the combined effects of size-structure, stage-specific resource availabilities, and habitat structure. Specifically, when managing species that connect habitats or ecosystems all life-stages’ environmental conditions must be consider in order to ensure strong predictive power of tools used for ecosystem management planning.

A maior parte dos mecanismos em processadores superescalares atuais usam granularidade de instrução para criar ou caracterizar especulações, tais como predição de desvios ou prefetchers. No entanto, muitas das características das instruções podem ser obtidas ao analisar uma granularidade mais grossa, o bloco básico de código, aumentando a quantidade de código coberta em um espaço similar de armazenamento. Adicionalmente, códigos podem ser analisados mais precisamente e prover uma variedade maior de informação ao observar diferentes tipos de instruções e suas relações. Devido a estas vantagens, a análise no nível de blocos pode fornecer mais oportunidades para mecanismos que necessitam desta informação. Por exemplo, é possível integrar informações de desvios mal previstos e acessos a memória para gerar informações mais precisas de quais acessos a memória oferecem melhor desempenho ao serem priorizados. Nesta tese propomos o Block-Level Architecture Profiler (BLAP) (Block Level Architecture Profiler), um mecanismo em hardware que caracteriza gargalos no nível microarquitetural, tal como loads delinquentes, desvios de difícil previsão e contenção nas unidades funcionais. O BLAP trabalha no nível de bloco básico, apenas detectando e fornecendo informações que podem ser usada para otimizar tais gargalos. Um mecanismo para a remoção de prefetches e uma política de controlador de memória DRAM foram criados para usar a informação criada pelo BLAP e demonstrar seu potencial. Juntos, estes mecanismos são capazes de melhorar o desempenho do sistema em até 17.39% (3.9% em média). Nosso método mostrou também ganhos médios de 13.14% quando avaliado com uma pressão na memória mais alta devido a prefetchers mais agressivos.<br>Most mechanisms in current superscalar processors use instruction granularity information for speculation, such as branch predictors or prefetchers. However, many of these characteristics can be obtained at the basic block level, increasing the amount of code that can be covered while requiring less space to store the data. Moreover, the code can be profiled more accurately and provide a higher variety of information by analyzing different instruction types inside a block. Because of these advantages, block-level analysis can offer more opportunities for mechanisms that use this information. For example, it is possible to integrate information about branch prediction and memory accesses to provide precise information for speculative mechanisms, increasing accuracy and performance. We propose a BLAP, an online mechanism that profiles bottlenecks at the microarchitectural level, such as delinquent memory loads, hard-to-predict branches and contention for functional units. BLAP works at the basic block level, providing information that can be used to reduce the impact of these bottlenecks. A prefetch dropping mechanism and a memory controller policy were developed to use the profiled information provided by BLAP. Together, these mechanisms are able to improve performance by up to 17.39% (3.90% on average). Our technique showed average gains of 13.14% when evaluated under high memory pressure due to highly aggressive prefetch.

The fact that traffic congestion upstream of a bottleneck causes a reduction in the discharge flow rate through the bottleneck has been well documented in several empirical studies. However, what has been missing is an understanding of the causes of these empirically observed flow reductions. An identification of these causes is important in order to develop various mitigation schemes through the use of emerging technology. The concept of capacity drop can be introduced at time-independent bottlenecks (e.g. freeways) as well as time-dependent bottlenecks (e.g. signalized intersections). While to the author's knowledge no one has attempted to link these phenomena, the research presented in this thesis serves as a first step in doing so. The research uses the INTEGRATION simulation software, after demonstrating its validity against empirical data, to simulate time-independent and time-dependent bottlenecks in an attempt to characterize and understand the contributing factors to these flow reductions. Initially, the INTEGRATION simulation software is validated by comparing its results to empirically observed traffic stream behavior. This thesis demonstrates that the discharge flow rate is reduced at stationary bottlenecks at the onset of congestion. These reductions at stationary bottlenecks are not recovered as the traffic stream propagates downstream. Furthermore, these reductions are not impacted by the level of vehicle acceleration. Alternatively, the drop in the discharge flow rate caused by time-dependent bottleneck is recoverable and is dependent on the level of acceleration. The difference in behavior is attributed to the fact that in the case of a stationary bottleneck the delay in vehicle headways exceeds the losses caused by vehicle accelerations and thus is not recoverable. In the case of vehicles discharging from a backward recovery wave the dominant factor is the delay caused by vehicle acceleration and this can be recuperated as the traffic stream travels downstream.<br>Master of Science

A considerable amount of research has concentrated on the modes of transportation. Research has tended to focus on the growth and trends of the different modes of transportation on the national scale. Very little research has been undertaken into each region, and even less on those factors that prevent or act as barriers for transportation of goods in each region. Furthermore, very little research has been undertaken that examines the bottlenecks of the transportation flows in Jönköping. By interviewing the main actors in the region, this thesis identifies the main product flow in the Jönköping County. The study also examines the perceived bottlenecks to transportation of goods that logistics companies face. In conducting the study, the main impediments to transportation flows were identified, analysed and ranked. The findings indicate that there are many common bottlenecks between firms in Jönköping. The study also, to an extent, supports findings that have been made in studies carried out previously by other researchers.

Cell biology is a branch of science with a seemingly infinite abundance of interesting phenomena which are essential to our understanding of life and which may potentially drive the development of technology that improves our lives. Among the open ended questions within the field, an understanding of how gene networks are affected by limited cellular components is both broad and rich with interest. Common to all cellular systems are enzymes which perform many tasks within cells without which organisms could not remain healthy. Here are presented several explorations of enzymatic processing as well as a tool constructed for this purpose. More specifically, these works consider the effect of coupling of gene networks via competition for enzymes found within the cell. It is shown that a limitation on the number of available enzymes permits the formation of bottlenecks which drastically affect molecular dynamics within cells. These effects potentially afford cell behaviors that in part explain the impressive robustness of life to constantly fluctuating environments.<br>Ph. D.

De nos jours, les systèmes distribués sont constitués de nombreuxcomposants logiciels ayant des interactions complexes et de nombreusespossibilités de configurations. Dès lors, localiser les problèmes deperformance est une tâche difficile, nécessitant une expertisehumaine et de nombreux essais. En effet, la même pile logicielle peutse comporter différemment en fonction dumatériel utilisé, de la logique applicative, des paramètres deconfiguration et des conditions de fonctionnement. Ce travail a pourobjectif (i) d’identifier un ensemble demétriques de référence, générales etfiables, pour localiser les problèmes de performance, (ii) d’identifierles caractéristiques de ces indicateurs, et (iii) deconstruire un outil qui puisse déterminer de manière automatiquesi le système a atteint sa capacité maximale en terme dedébit.Dans cette thèse, nous présentons trois contributionsprincipales. Premièrement, nous présentons une étude analytique d’ungrand nombre de configurations réalistes d’applications distribuéesmulti-tiers, se concentrant sur les chaînes de traitements desdonnées. En analysant un grand nombre de métriques au niveau logicielet matériel, nous identifions celles dont le comportement change aumoment où le système atteint sa capacité maximale. Deuxièmement, nousexploitons les techniques d’apprentissage machine pour développer unoutil capable d’identifier automatiquement les problèmes deperformance dans la chaîne de traitement de données. Pour ce faire,nous évaluons plusieurs techniques d’apprentissage machine, plusieurssélections de métriques, et différentscas de généralisation pour de nouvelles configurations. Troisièmement,pour valider les résultats obtenues sur la chaîne de traitement dedonnées, nous appliquons notre approche analytique et notre approchefondée sur l'apprentissage machine au cas d’une architecture Web.Nous tirons plusieurs conclusions de nos travaux. Premièrement, il estpossible d’identifier des métriques clés qui sont des indicateursfiables de problèmes de performance dans les systèmes distribuésmulti-tiers. Plus précisément, identifier le moment où le serveur aatteint sa capacité maximale peut être identifier grâce à cesmétriques fiables. Contrairement à l’approche adoptée par de nombreuxtravaux existants, nos travaux démontrent qu'une combinaison demétriques de différents types est nécessaire pour assurer uneidentification fiable des problèmes de performance dans un grandnombre de configurations. Nos travaux montrent aussi que les approchesfondées sur des méthodes d’apprentissage machine pour analyser lesmétriques permettent d’identifier les problèmes de performance dansles systèmes distribués multi-tiers. La comparaison de différentsmodèles met en évidence que ceux utilisant les métriques fiablesidentifiées par notre étude analytique sont ceux qui obtiennent lameilleure précision. De plus, notre analyse approfondie montre larobustesse des modèles obtenues. En effet, ils permettent unegénéralisation à de nouvelles configurations, à de nouveaux nombres declients, et à de nouvelles configurations exécutées avec de nouveauxnombres de clients. L'extension de notre étude au cas d'unearchitecture Web confirme les résultats principaux obtenus à traversl’étude sur la chaîne de traitement de données. Ces résultats ouvrentla voie à la construction d'un outil générique pour identifier demanière fiable les problèmes de performance dans les systèmesdistribués<br>Today's distributed systems are made of various software componentswith complex interactions and a large number of configurationsettings. Pinpointing the performance bottlenecks is generally a non-trivial task, which requires human expertise as well as trial anderror. Moreover, the same software stack may exhibit very differentbottlenecks depending on factors such as the underlying hardware, theapplication logic, the configuration settings, and the operatingconditions. This work aims to (i) investigate whether it is possibleto identify a set of key metrics that can be used as reliable andgeneral indicators of performance bottlenecks, (ii) identify thecharacteristics of these indicators, and (iii) build a tool that canautomatically and accurately determine if the system reaches itsmaximum capacity in terms of throughput.In this thesis, we present three contributions. First, we present ananalytical study of a large number of realistic configuration setupsof multi-tier distributed applications, more specifically focusing ondata processing pipelines. By analyzing a large number of metrics atthe hardware and at the software level, we identify the ones thatexhibit changes in their behavior at the point where the systemreaches its maximum capacity. We consider these metrics as reliableindicators of performance bottlenecks. Second, we leverage machinelearning techniques to build a tool that can automatically identifyperformance bottlenecks in the data processing pipeline. We considerdifferent machine learning methods, different selections of metrics,and different cases of generalization to new setups. Third, to assessthe validity of the results obtained considering the data processingpipeline for both the analytical and the learning-based approaches,the two approaches are applied to the case of a Web stack.From our research, we draw several conclusions. First, it is possibleto identify key metrics that act as reliable indicators of performancebottlenecks for a multi-tier distributed system. More precisely,identifying when the server has reached its maximum capacity can beidentified based on these reliable metrics. Contrary to the approachadopted by many existing works, our results show that a combination ofmetrics of different types is required to ensure reliableidentification of performance bottlenecks in a large number ofsetups. We also show that approaches based on machine learningtechniques to analyze metrics can identify performance bottlenecks ina multi-tier distributed system. The comparison of different modelsshows that the ones based on the reliable metrics identified by ouranalytical study are the ones that achieve the bestaccuracy. Furthermore, our extensive analysis shows the robustness ofthe obtained models that can generalize to new setups, to new numbersof clients, and to both new setups and new numbers ofclients. Extending the analysis to a Web stack confirmsthe main findings obtained through the study of the data processingpipeline. These results pave the way towards a general and accuratetool to identify performance bottlenecks in distributed systems

Over the last decade, General Purpose Graphics Processing Units (GPGPUs) have garnered a substantial attention in the research community due to their extensive thread-level parallelism. GPGPUs provide a remarkable performance improvement over Central Processing Units (CPUs), for highly parallel applications. However, GPGPUs typically achieve this extensive thread-level parallelism at the cost of a large power consumption. Consequently, Near-Threshold Computing (NTC) provides a promising opportunity for designing energy-efficient GPGPUs (NTC-GPUs). However, NTC-GPUs suffer from a crucial Process Variation (PV)-inflicted performance bottleneck, which is called Choke Point. Choke Point is defined as one or small group of gates which is affected by PV. Choke Point is capable of varying the path-delay of circuit and causing different forms of timing violation. In this work, a cross-layer design technique is proposed to tackle the performance impediments caused by choke points in NTC-GPUs.

<p>This thesis relates modern speciation theory to the effects of sudden changes in the range and size of populations. Special reference is made to the climatic oscillations during the Quaternary ice ages. A meta-analysis of laboratory experiments showed that support for allopatric speciation is weak, especially for the peripatric type of allopatric speciation. Furthermore, factors traditionally believed to increase the likelihood of speciation have had little effect on the generation of reproductive isolation in speciation experiments. However, the method of testing reproductive isolation appeared important, in the sense that experimentally derived sister populations were likely to demonstrate reproductive isolation from each other but not from the unaffected mother population. Raw data from mating tests showed that the poor isolation between mother and daughter populations was an effect of asymmetric mate preferences towards males from the mother population. This suggests that peripatric speciation can be effective in generating reproductive isolation between sister populations. The proposed mechanism is that males become less attractive to females by losing certain secondary sexual traits during population bottlenecks, and that females shift their preferences towards other male traits. Support for this mode of speciation is found in the widespread bird genus <i>Motacilla</i> (wagtails). This genus is characterised by extensive plumage variation and contains a large number of widely distributed taxa in the northern parts of its distribution. This thesis shows that taxonomic diversity of wagtails is inversely related to complexity in song and to diversity in molecular and mitochondrial markers. The northern taxa seem to be descendants of southern populations, which were subjected to bottlenecks during expansions into re-opened habitats after the last ice age. The bottlenecks would not only reduce genetic diversity but also inhibit cultural transmission of song to the leading edge of colonisers, allowing sexual selection on other traits, such as plumage. Rapid plumage differentiation among wagtail taxa appears to be a recurrent process and has lead to convergent evolution, making the currently recognised species <i>Motacilla flava</i> (Yellow Wagtail) polyphyletic.</p>

In the European Union, there is a driver for a change in the electricity system. The trend is to make the system more environmental friendly and improve the markets functionality. This driver often refers to the development towards a smart grid. In order to accelerate innovation in smart grid and technology application, pilot projects need to be deployed. This master thesis has been done as a part of the Stockholm Royal Seaport urban development project that is a pilot project for smart grid on distribution grid level. The aim of this report is to apply market concept and identify regulatory bottlenecks for smart grid. This report has applied market concept and identified several bottlenecks for two aspects of smart grid. The aspects are integration of distributed energy resources in medium and low voltage level and a changing customer behavior. A changing customer behavior contains both demand response and the implementation of electric vehicles. A state-of-art review on feasible solutions that improve the competition and demand side management of electricity market in smart grid and provide incentives to implement smart grid functions has been performed. The emphasis in the market aspect is on how that new actors like aggregators will enter the market and how the dynamic price can reach consumers. The emphasis in the regulatory aspect is on how regulations promote the application of smart grid supporting technologies for both the DSO and the network users. A case study has been performed for EU countries with a deeper look at Sweden. The case study investigates how far that the current regulations have reached on the way to smart grids. A state-of-art review on conclusion papers of pilot projects has been carried out. However, many pilot projects are still ongoing and not included in the review. The result shows there is still a lack of regulatory incentive to promote smart grid development and supporting market structures. Bottlenecks identified for smart grid services in the Swedish electricity market and regulation are related to four areas. These are the metering system, dynamic consumer price, active distributed units with the possibility to provide services to the system and incentives to the DSO to use new smart grid solutions in the work to enable fast and efficient connection of distributed generation.<br>Stockholm royal seaport project

the European Union, there is a driver for a change in the electricity system. The trend is to make the system more environmental friendly and improve the markets functionality. This driver often refers to the development towards a smart grid. In order to accelerate innovation in smart grid and technology application, pilot projects need to be deployed. This master thesis has been done as a part of the Stockholm Royal Seaport urban development project that is a pilot project for smart grid on distribution grid level. The aim of this report is to apply market concept and identify regulatory bottlenecks for smart grid. This report has applied market concept and identified several bottlenecks for two aspects of smart grid. The aspects are integration of distributed energy resources in medium and low voltage level and a changing customer behavior. A changing customer behavior contains both demand response and the implementation of electric vehicles. A state ‐of‐ art review on feasible solutions that improve the competition and demand side management of electricity market in smart grid and provide incentives to implement smart grid functions has been performed. The emphasis in the market aspect is on how that new actors like aggregators will enter the market and how the dynamic price can reach consumers. The emphasis in the regulatory aspect is on how regulations promote the application of smart grid supporting technologies for both the DSO and the network users. A case study has been performed for EU countries with a deeper look at Sweden. The case study investigates how far that the current regulations have reached on the way to smart grids. A state ‐of art review on conclusion papers of pilot projects has been carried out. However, many pilot projects are still ongoing and not included in the review. The result shows there is still a lack of regulatory incentive to promote smart grid development and supporting market structures. Bottlenecks identified for smart grid services in the Swedish electricity market and regulation are related to four areas. These are the metering system, dynamic consumer price, active distributed units with the possibility to provide services to the system and incentives to the DSO to use new smart grid solutions in the work to enable fast and efficient connection of distributed generation.

Context. Big data visualization is a vital part of today's technological advancement. It is about visualizing different variables on a graph, map, or other means often in real-time. Objectives. This study aims to determine what challenges there are for big data visualization, whether significant amounts of data impact the visualization, and finding existing solutions for the problems. Methods. Databases used in this systematic literature review include Inspec, IEEE Xplore, and BTH Summon. Papers are included in the review if certain criteria are upheld. Results. 6 solutions are found to reduce large data sets and reduce latency when viewing 2D and 3D graphs. Conclusions. In conclusion, many solutions exist in various forms to improve visualizing graphs of different dimensions. Future grows of data might change this though and might require new solutions of the growing data.

In a manufacturing environment, productivity and quality of the system can be improved by focusing on production constraints (bottlenecks). As a result, the bottleneck detection methods have gained more importance in enhancing the performance of the system. There are several short-term and long-term bottleneck detection methods. This research focuses on inactive state duration bottleneck detection for multiple product flow as high complexity arises in material flow due to several products and different processing sequences. The efficiency of the proposed methodology is validated by case studies using discrete event simulation models. The integration of simulation tool to detect bottlenecks in the manufacturing system has been useful in real-time case studies. An automatic bottleneck detection method was proposed to identify the bottleneck time and bottleneck machines in an easier manner. Previous research focuses on additional capacity and buffers to machines to mitigate the bottleneck. This approach spotlights the selection of alternative process plan in the presence of bottlenecks with a objective of minimized bottleneck time and minimized machining cost of the products in the given process plan. A mathematical model was presented with these objectives. Case studies were conducted for initially selected process plan and alternative process plan to show the improvements in system performance.<br>Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering.

In New Zealand, birds and other endangered animals are routinely transferred to offshore islands for conservation purposes. Such transfers typically involve only a small number of individuals and thus the effects of a population bottleneck on the 'fitness' of these organisms is of great interest to conservation biologists. In 1973, two populations of the South Island robin, Petroica australis australis, were established on Motuara and Allports Islands from outbred populations on Nukuwaiata Island and Kaikoura, respectively. The effect of these population bottlenecks on fitness related traits in the South Island robin is the subject of this thesis. Reproductive success is an important measure of individual fitness. I measured hatch rate, number of fledged young, and in some instances, number of young that reach independence. The inbred robin population on Motuara Island was found to have lower clutch size, fewer clutches per season, and lower hatching success compared to mainland outbred populations. The study of fluctuating asymmetry has generated increased enthusiasm over the last few decades as a potential tool for examining the overall stability of a population. Numerous studies have found that individuals exhibiting a higher level of heterozygosity usually have lower fluctuating asymmetry. The results of my study provide no evidence to support this association. Thus, the application of fluctuating asymmetry measurements as an easily interpretable conservation tool may not be useful in all situations. There are two main theories on how bird song might evolve in island populations. First, founder effects may constrain song structure and lead to a reduction in song variation. Second, weaker selective pressures for species-specific signals may lead to an increase in song variation. Song variation in the inbred robin population on Motuara Island seems to support the predictions of the second hypothesis. Since the initial transfer, robins on Motuara Island have increased their song variability. Overall, the low hatching success obtained from the South Island robin population on Motuara Island shows that population bottlenecks have a detrimental effect on individual fitness in the robin. However, fluctuating asymmetry measures, which might provide a quick estimate of the 'health' of a population, offered no evidence of detrimental effects. Consequently, there is a need to examine more than one population parameter when drawing conclusions about the effects of population bottlenecks and inbreeding.

Though comparisons of simulation models have been conducted, few investigations have examined in detail the logical differences between models. If the output measures of effectiveness are to be interpreted correctly, it is important that the analyst understand some of the underlying logic and assumptions upon which the results are based. An understanding of model logic and its inherent effect on the results will aid the transportation analyst in the application and calibration of a simulation model. In this thesis, the car-following behavior of the CORSIM and INTEGRATION simulation models are examined in significant detail, and its impact on output results explained. In addition, the thesis presents a calibration procedure for the CORSIM sub-model, FRESIM. Currently, FRESIM is calibrated by ad hoc trial-and-error, or by utilizing empirically developed cross-referencing tables. The literature reveals that the relationship between the microscopic input parameters of the CORSIM model, and the macroscopic parameters of capacity is not understood. The thesis addresses this concern. Finally, the thesis compares the INTEGRATION and CORSIM models in freeway and urban environments. The comparison is unique in that the simulated networks were configured such that differences in results could be identified, isolated, and explained. Additionally, the simplified nature of the test networks allowed for the formulation of analytical solutions. The thesis begins by relating steady-state car-following behavior to macroscopic traffic stream models. This is done so that a calibration procedure for the FRESIM (Pipes) car-following model could be developed. The proposed calibration procedure offers an avenue to calibrate microscopic car-following behavior using macroscopic field measurements that can be easily obtained from loop detectors. The calibration procedure, while it does not overcome the inherent shortcomings of the Pipes model, does provide an opportunity to better calibrate the network FRESIM car-following sensitivity factor to existing roadway conditions. The thesis then reports an observed inconsistency in the link-specific car-following sensitivity factor of the FRESIM model. Because calibration of a network on a link-specific basis is key to an accurate network representation, a correction factor was developed that should be applied to the analytically calculated link-specific car-following sensitivity factor. The application of the correction factor resulted in observed saturation flow rates that were within 5% of the desired saturation flow rates. The thesis concludes with a comparison of the CORSIM and INTEGRATION models for transient conditions. As a result of the various intricacies and subtleties that are involved in transient behavior, the comparisons were conducted by running the models on simple networks where analytical solutions to the problem could be formulated. In urban environments, it was observed that the models are consistent in estimates of delay and travel time, and inconsistent in estimates of vehicle stops, stopped delay, fuel consumption, and emissions. Specifically, it was observed that the NETSIM model underestimates the number of vehicle stops in comparison with INTEGRATION and the analytical formulation. It was also observed that the NETSIM vehicles speed and acceleration profiles are characterized by abrupt accelerations and decelerations. These abrupt movements significantly impact stopped time delay and vehicle emissions estimates. Inconsistencies in emissions estimates can also be attributed to differences in the embedded rate tables of each model. In freeway environments for under-saturated conditions, INTEGRATION returned higher values of travel time and delay, and lower values of average speed than the FRESIM model. These results are consistent with the analytical solution, and can be attributed to the speed-flow relationship of each model. In saturated conditions, when the capacity of the bottleneck is equal to the demand volume, the emergent vehicle behavior of the FRESIM model was observed to be inconsistent with the analytical solution. The FRESIM vehicles were observed to dramatically decelerate upon entering a lower-capacity link. This deceleration behavior led to higher travel time and delay time estimates in FRESIM than in INTEGRATION. In over-saturated conditions, longer queue lengths were observed in FRESIM than in INTEGRATION, resulting in slightly higher travel and delay estimates in the FRESIM model. The reason for the discrepancy in queue lengths is unclear, as the network jam density in each model was equivalent.<br>Master of Science

Atualmente, existe uma variedade de arquiteturas disponíveis não apenas para a indústria, mas também para consumidores finais. Processadores multi-core tradicionais, GPUs, aceleradores, como o Xeon Phi, ou até mesmo processadores orientados para eficiência energética, como a família ARM, apresentam características arquiteturais muito diferentes. Essa ampla gama de características representa um desafio para os desenvolvedores de aplicações. Os desenvolvedores devem lidar com diferentes conjuntos de instruções, hierarquias de memória, ou até mesmo diferentes paradigmas de programação ao programar para essas arquiteturas. Para otimizar uma aplicação, é importante ter uma compreensão profunda de como ela se comporta em diferentes arquiteturas. Os trabalhos relacionados provaram ter uma ampla variedade de soluções. A maioria deles se concentrou em melhorar apenas o desempenho da memória. Outros se concentram no balanceamento de carga, na vetorização e no mapeamento de threads e dados, mas os realizam separadamente, perdendo oportunidades de otimização. Nesta dissertação de mestrado, foram propostas várias técnicas de otimização para melhorar o desempenho de uma aplicação de exploração sísmica real fornecida pela Petrobras, uma empresa multinacional do setor de petróleo. Os experimentos mostram que loop interchange é uma técnica útil para melhorar o desempenho de diferentes níveis de memória cache, melhorando o desempenho em até 5,3 e 3,9 nas arquiteturas Intel Broadwell e Intel Knights Landing, respectivamente. Ao alterar o código para ativar a vetorização, o desempenho foi aumentado em até 1,4 e 6,5 . O balanceamento de carga melhorou o desempenho em até 1,1 no Knights Landing. Técnicas de mapeamento de threads e dados também foram avaliadas, com uma melhora de desempenho de até 1,6 e 4,4 . O ganho de desempenho do Broadwell foi de 22,7 e do Knights Landing de 56,7 em comparação com uma versão sem otimizações, mas, no final, o Broadwell foi 1,2 mais rápido que o Knights Landing.<br>Nowadays, there are several different architectures available not only for the industry but also for final consumers. Traditional multi-core processors, GPUs, accelerators such as the Xeon Phi, or even energy efficiency-driven processors such as the ARM family, present very different architectural characteristics. This wide range of characteristics presents a challenge for the developers of applications. Developers must deal with different instruction sets, memory hierarchies, or even different programming paradigms when programming for these architectures. To optimize an application, it is important to have a deep understanding of how it behaves on different architectures. Related work proved to have a wide variety of solutions. Most of then focused on improving only memory performance. Others focus on load balancing, vectorization, and thread and data mapping, but perform them separately, losing optimization opportunities. In this master thesis, we propose several optimization techniques to improve the performance of a real-world seismic exploration application provided by Petrobras, a multinational corporation in the petroleum industry. In our experiments, we show that loop interchange is a useful technique to improve the performance of different cache memory levels, improving the performance by up to 5.3 and 3.9 on the Intel Broadwell and Intel Knights Landing architectures, respectively. By changing the code to enable vectorization, performance was increased by up to 1.4 and 6.5 . Load Balancing improved the performance by up to 1.1 on Knights Landing. Thread and data mapping techniques were also evaluated, with a performance improvement of up to 1.6 and 4.4 . We also compared the best version of each architecture and showed that we were able to improve the performance of Broadwell by 22.7 and Knights Landing by 56.7 compared to a naive version, but, in the end, Broadwell was 1.2 faster than Knights Landing.

Today's modern agriculture is totally dependent on phosphorus to sustain their large yields. Several studies have recently expressed a concern for a future phosphorus deficiency. These studies are based on data for estimated reserves which have been increased with more than a fourfold since 2010. Some argue that these concerns are unfounded, despite the fact that only Morocco account for the bulk of these new reserves. This report provides new forecast for the world phosphorus production based on the new available reserve data. These forecasts are using bell shaped curve models to examine how individual countries' future production of phosphate rock affects a global production peak. Estimates of the size of several reserves are highly uncertain and it is therefore difficult to make an accurate forecast of future phosphorus extraction. Despite this uncertainty, a global production peak is likely to occur within this century. The global production will depend largely on China and Morocco's production as they hold a large share of the reserves and the current production. China's production will probably peak in 10-20 years at current production trend. It is uncertain if Morocco can increase production enough to replace China's production in the future. It is not likely that Morocco will be able to produce as much as would be required to meet the highest scenarios. This is mainly due to a number of bottlenecks in production such as water scarcity, increasing proportion of impurities and a decreasing concentration of phosphorus in the phosphate rock.

Thesis (M.S.)--University of Florida, 1999.<br>Title from first page of PDF file. Document formatted into pages; contains xi, 96 p.; also contains graphics. Vita. Includes bibliographical references (p. 94-95).

Biogas produced via the anaerobic digestion (AD) of organic waste materials is considered as an important technology in improving the environment because it solves waste management problems and simultaneously produces biogas as a main product and digestate as a by-product, which can also be used as a fertilizer. Within the rising expectations for the substitution of fossil energy with renewable energy as one of the solutions to cope with climate change, the environmental aspects of small-scale biogas plants, as widely used method for energy creation, should be evaluated in a holistic and systematic way. The use of small-scale biogas plants is mostly common for energy creation from waste in Southeast Asia. This source of energy is mainly lauded for its low costs, clean production and high fertilization effects of digested matter for crops. There are number of advantages of small-scale biogas production on farms, including also savings on firewood or fossil fuels and reduction in odour and greenhouse gas emissions from using other fuels. However, biogas plants are often poorly managed and there is lack of proper distribution systems for biogas. That results in methane being release inadvertently through leaks in digesters and tubing, and intentionally when production exceeds demand. As methane has a global warming potential 25 times higher than that of carbon dioxide, environmental advantages of small-scale biogas plants might be compromised. This dissertation intends to provide in-depth understanding about the issue with taking into accounts possible risks. Investigating of such a topic is within continuing concern about small-scale biogas technology in rural areas of developing countries. For this reason technical, social, economic and environmental assessment of small-scale biogas technology will be done. Methods of data collection will consist of questionnaire survey and focus group discussions among randomly selected owners of biogas plants, semi-structured personal interviews with local authorities and facilitators and observation. Furthermore, prediction of future development of this technology will be created.

The continuing under-representation of female academics in senior classifications at Australian universities is widely acknowledged and documented. It has been proposed that universities fail to take advantage of the leadership skills of female academics, thereby inhibiting their organisation’s competitiveness (Airini et al., 2011). Statistics from the Australian Department of Education and Training (2018) indicate over half of full-time and fractional full-time academics are women, yet female academics constitute only a third of positions above that of Senior Lecturer across Australian universities. Substantial research has been conducted to explore the reasons behind the enduring gender inequity in academia, with a focus on the lack of women at senior classifications and in STEMM (science, technology, engineering, mathematics and medicine) faculties. Statistics indicate significant reductions in the number of female academics between midlevel classifications; this area of research is less well developed. Specifically, the decrease in the number of female academics commences between the mid-levels of academic careers (from Levels B to C, as well as C to D) and accelerates from that point forward. Mid-level promotions have been identified as key promotion levels and indicators of future career progression (Yap & Konrad, 2009). There is a crucial need to understand the reasons for the inability of women to traverse this key point in their academic careers. This study proposes that for the gender distribution across senior classifications in academia to improve, these bottlenecks identified at the levels of Lecturer (Level B) and Senior Lecturer (Level C) should be analysed and addressed. The pipeline theory proposes that the increasing number of women entering the workforce will gradually result in an equal representation of women in leadership. However, the current gender distribution in Australian academia challenges this theory because there are presently more than enough women in academia qualified to be appointed to leadership roles, yet gender inequity remains. Persistent and continuing inequity requires a similarly determined response and it has been proposed that different and novel approaches are needed to return gender to the agenda (Kamberidou, 2010). Much of the gender equity research in academia has focused on the under-representation of female academics in senior classifications, but it has been argued that there is a lack of research exploring drivers of the careers of female academics (Nguyen, 2013). While the identification of career inhibitors remains vital, it can be argued that simultaneously identifying those factors that have assisted female academics in their career progression can provide policymakers and universities with valuable data to guide and assist gender equity efforts further. Researchers suggest that when exploring the career outcomes of female academics, it is also imperative to simultaneously explore family outcomes (Mason et al., 2013). International research suggests that female academics make more career sacrifices for their families as well as more family sacrifices for their careers, highlighting the challenges with which female academics continue to be faced. Data regarding this important measure of gender equity are absent for the Australian academic environment. This study’s aim was therefore to explore the inhibitors, with a focus on the identified bottlenecks, as well as the drivers and family outcomes of a career for female academics at an Australian university. To gain multiple perspectives, data for this research was drawn from chancellery members, Athena SWAN (Scientific Women’s Academic Network) Charter Committee members, human resource professionals, and male and female academics at a public university in Australia. Owing to the exploratory nature of this research and the need for thick and rich data, a two-phased, multi-method qualitative approach was adopted, consisting of nine semi-structured interviews with senior stakeholders at the case study institution (CSI) in Study 1, and 47 “draw, write, reflect” (DWR) sessions with male and female academics in Study 2. DWR is a method specifically designed for this study, adapted from arts-based methods intended for research involving children. The aim of this study was to obtain data that may not lend itself to verbal expression, and the arts offer researchers an opportunity to retrieve experiences that may otherwise be challenging to obtain (Eisner, 2006). For this study, DWR involved asking respondents to draw their careers and associated experiences on an A4 sheet of paper, specifically including any inhibitors and drivers. Because of the novelty of the method adopted, this study includes a review of DWR with the academics who participated in the study, as well as the researcher, to assess the method’s validity, reliability and effectiveness in obtaining data. The study explored the careers of female academics through the lenses of role congruity theory (RCT), self-efficacy theory and attribution theory. For the purposes of this thesis, the roles referred to will be gender roles, which propose that female academics are likely to act in accordance, rather than deviate from, their prescribed female gender role. Gender incongruity is likely to be perceived negatively by others and may be punished through performance devaluation or harassment (Eagly & Karau, 2002). Confidence has been identified as a high-status characteristic for men (Moss-Racusin et al., 2010), while women are expected to be shy and humble (Prentice & Carranza, 2002). Framed by selfefficacy theory, women’s lack of expressed or perceived confidence may contribute to their lack of progression to senior academic classifications. Lastly, attribution theory, in combination with RCT, proposes that female academics are likely to attribute their lack of career progression to themselves while attributing positive career outcomes to external factors, such as luck. Thematic analysis of the data highlighted that female academics have significantly different career experiences from their male colleagues. While some of this study’s findings substantiate contemporary knowledge, others, owing to the inclusion of multiple perspectives, offer unique insights into the career experiences of female academics in Australia. Perspectives and narratives obtained from senior stakeholders were utilised to provide an organisational perspective of gender inequity, while the narratives of male academics served to compare their career experiences with those provided by female academics. The data identified several inhibitors of the career progression of female academics. Gender roles continue to influence career and family decisions and can result in female academics having to choose between a career or a family. Some women in the sample had reconsidered their career aspirations as a result of caring responsibilities, while others had postponed or decided not to have children in order to pursue their careers. The female gender role and the ideal academic role create incongruity in the lives of female academics, who often must shift between these two competing roles. Female academics did not report structural inhibitors of their career progression, and several female academics, who did not have caring responsibilities, had progressed their careers on a par with male academics. RCT posits that men and women are more likely to act in accordance with the male breadwinner model, which prioritises the male career. The female academics in the sample appeared to have accepted this situation and, rather than viewing the structure as inhibiting, viewed their inability to meet this standard, as a result of outside responsibilities, as the problem. A significant finding of this study related to the identification of a distinct “holding pattern” amongst female academics at academic Level B. Seven of the eight female academics at this level indicated that they would not be pursuing a promotion in the near future, suggesting that they will be employed at this level for an extended period. Inhibitors specific to the career progression of female academics, particularly at Levels B and C, were, amongst others, identified as a lack of confidence, academic housework, careful crafting of a work/life balance, fear of work/life conflict, career interruptions and caring responsibilities. As a result of the multi-level approach of this study, several drivers of the career progression of female academics at CSI were unearthed. While no societal drivers were identified, the organisational drivers included leadership, the Athena SWAN Charter, the organisational culture, and promotion and recruitment practices. Female academics reported that individual factors such as individual characteristics, family support, informal mentoring and a love of the job had driven their career progression. In terms of family outcomes, this study found that female academics in the sample were more likely to be divorced, less likely to have children, more likely to struggle with maintaining a work/life balance and more likely to experience tension with their partner regarding working hours than were their male colleagues. This finding indicates that career outcomes are only one aspect of gender equity. A focus on the number of female academics at senior classifications does not convey the full picture of female academics’ career narratives. Academic careers can come at a personal cost to female academics, and, despite the flexibility of academic work, it remains difficult to combine a successful career with caring responsibilities. This research makes several contributions. Firstly, the introduction, employment and review of a novel data collection method—draw, write, reflect—extends contemporary methodology knowledge and provides a clear procedure for researchers interested in employing this method in their research. Secondly, the identification and exploration of the previously unexplored bottlenecks in the academic pipeline revealed that a significant number of female academics remain in stasis at Level B, a situation identified in this research as forming a holding pattern. A possible explanation for this finding, when viewed through the lens of RCT, may be that Level B is congruent with the female gender, but to advance would create incongruity and is therefore less likely to occur. The identification of specific inhibitors contributing to this bottleneck were identified and presented. A third contribution of this study lies in the presentation of drivers of the career progression of female academics that have resulted in an improved gender distribution at CSI. The findings regarding positive strategies for career progression were related to mentoring and changes to recruitment and selection practices and can be utilised as a template for other universities working towards gender equity. Lastly, knowledge about the family outcomes of an academic career for female academics in Australia has thus far been absent in the literature. This study argues that this aspect is an important measure of gender inequity, and it has therefore been included in this research. The findings indicate that female academics have significantly different family outcomes from their male colleagues, with more female academics reporting being divorced and childless. The data obtained in this study can contribute to current knowledge about the careers of female academics and pragmatically to improving career opportunities for female academics in Australia, as well as internationally.

Accessible and affordable access to the Internet is crucial for socio-economic progress in developing countries and reducing Digital Divide. The disparity in mobile broadband penetration between urban and rural areas in the Indian state of Tamil Nadu can be explained by per capita income disparities. However, despite the vast body of multidisciplinary research, there are still large gaps in understanding Tamil Nadu’s upstream Internet market structure and its impact on mobile broadband affordability. Moreover, there is a lack of research analysing the Internet market structure in developing countries using Network Analysis. This dissertation explores the presence of structural connectivity bottlenecks in the upstream Internet market for three mobile operator networks in Tamil Nadu. The exploration employs Complex and Statistical Network Analysis on primary data collected via active Internet periphery measurements through the Portolan application. The results obtained indicate the existence of hierarchical upstream Internet market structures for all operator networks. Moreover, the collected evidence indicates the reliance of mobile operator’s connectivity on Tier-1 Internet Service Providers, while also revealing new Autonomous System relationships. This collected evidence highlights the crucial role that the level of hierarchical structuring of upstream Internet market structures plays in determining affordability. We show that endusers’ prices per Megabyte increase with the level of hierarchical structuring, indicating the policy relevance of assessing Complex Network metrics to understand and address the hierarchical structuring of the relevant markets. In conclusions, this work indicates the importance of studying structural bottlenecks and connectivity hubs, as our evidence shows that the upstream Internet market structure also defines the bargaining powers exerted by Internet Service Providers, resulting in reduced competition and less affordable price plans. These results should also nudge policymakers’ efforts to consider the different roles of ‘bottlenecks’ and ‘hub-like’ Internet Service Providers when aiming to reduce the Digital Divide.

Accessible and affordable access to the Internet is crucial for socio-economic progress in developing countries and reducing Digital Divide. The disparity in mobile broadband penetration between urban and rural areas in the Indian state of Tamil Nadu can be explained by per capita income disparities. However, despite the vast body of multidisciplinary research, there are still large gaps in understanding Tamil Nadu’s upstream Internet market structure and its impact on mobile broadband affordability. Moreover, there is a lack of research analysing the Internet market structure in developing countries using Network Analysis. This dissertation explores the presence of structural connectivity bottlenecks in the upstream Internet market for three mobile operator networks in Tamil Nadu. The exploration employs Complex and Statistical Network Analysis on primary data collected via active Internet periphery measurements through the Portolan application. The results obtained indicate the existence of hierarchical upstream Internet market structures for all operator networks. Moreover, the collected evidence indicates the reliance of mobile operator’s connectivity on Tier-1 Internet Service Providers, while also revealing new Autonomous System relationships. This collected evidence highlights the crucial role that the level of hierarchical structuring of upstream Internet market structures plays in determining affordability. We show that endusers’ prices per Megabyte increase with the level of hierarchical structuring, indicating the policy relevance of assessing Complex Network metrics to understand and address the hierarchical structuring of the relevant markets. In conclusions, this work indicates the importance of studying structural bottlenecks and connectivity hubs, as our evidence shows that the upstream Internet market structure also defines the bargaining powers exerted by Internet Service Providers, resulting in reduced competition and less affordable price plans. These results should also nudge policymakers’ efforts to consider the different roles of ‘bottlenecks’ and ‘hub-like’ Internet Service Providers when aiming to reduce the Digital Divide.

Includes bibliographical references.<br>This research investigates absorptive capacity in South Africa's public health sector in relation to scaling up financing for HIV/AIDS treatment. The thesis constructs a conceptual framework, which follows the flow of public funding for HIV/AIDS treatment. The study combines a quantitative budget analysis, which looks at expenditure and spending patterns, with qualitative in-depth interviews with key stakeholders exploring causes and consequences, which are the main pillar of the primary research. The study applies the conceptual framework nationally, as well as in the Free State and Western Cape provinces. The contributions of the thesis are two-fold: At the conceptual level, the study defines and constructs an analytical framework of absorptive capacity and related bottlenecks in the context of funding for HIV/AIDS treatment in the public health sector. It identifies five major areas where bottlenecks may arise: financial, human, infrastructural, institutional (within the health system) and structural (outside the health system). At the empirical level, the study assesses and compares absorptive capacity and major bottlenecks encountered nationally and in the Free State and Western Cape provinces in respect of the public sector funding for the HIV/AIDS treatment programme. The results confirm that absorptive capacity is not merely about spending funding. Spending should not compromise other programs or elements of the public health system, and it should be efficient, equitable and sustainable. The findings show that South Africa's absorptive capacity was constrained by several obstacles, such as poor practices and a shortage of human resources, insufficient financial capacity and demanding requirements of conditional funding, inadequate infrastructure, and inadequate national leadership. To overcome these obstacles, the mere injection of even more funding would be an insufficient response. Consequently, the study indicates which other reforms are required, including: further integrating antiretroviral treatment services within the public health structures; further decentralising antiretroviral treatment towards primary health care; task shifting; iii balancing the conditional grant and equitable share; and enhancing coordination between the National and Provincial Departments of Health and with Treasury.