This thesis investigates the load control of a marine current energy converter using a vertical axis turbine mounted on a permanent magnet synchronous generator. The purpose of this thesis is to show the work done in the so far relatively uncharted territory of control systems for hydro kinetic energy conversion. The work is in its early stage and is meant to serve as a guide forfuture development of the control system. An experimental power station has been deployed and the first results are presented. A comparison between three load control methods has been made; a fixedAC load, a fixed pulse width modulated DC load and a DC bus voltage control of a DC load. Experimental results show that the DC bus voltage control reduces the variation of rotational speed with a factor of 3.5. For all three cases, the tip speed ratio of the turbine can be kept close to the expected optimal tip speed ratio. However, for all three cases the average extracted power was significantly lower than the average power available in the turbine times the estimated maximum power coefficient. A maximum power point tracking system, with or without water velocity measurement, should increase the average extracted power. A simulation model has been validated using experimental data. The simulated system consists of the electrical system and a hydrodynamic vortex model for the turbine. Experiments of no load operation were conducted to calibrate the drag losses of the turbine. Simulations were able to predict the behaviour in a step response for a change in tip speed ratio when the turbine was operated close to optimal tip speed ratio. The start position of the turbine was varied in the simulation to view the influence on the step response from a changed turbine position relative to the direction of the water flow. / <p>Funders: J Gust Richert, Bixia Miljöfond</p>

Performance in visual tasks improves with attention, and this improvement has been shown to stem, in part, from changes in sensory processing. However, the mechanism by which attention affects perception remains unclear. Considering that neurons within the visual areas are selective for basic image statistics, such as orientation or spatial frequency (SF), it is plausible that attention modulates these sensory preferences by altering their so-called ‘tuning curves’. The goal of this project is to investigate this possibility by measuring and comparing the SF tuning curves across a range of attentional states in humans. In Experiment 1, a model-driven approach to fMRI analysis was introduced that allows for fast and efficient estimation of population spatial frequency tuning (pSFT) for individual voxels within human visual cortices. Using this method, I estimated pSFTs within early visual cortices of 8 healthy, young adults. Consistent with previous studies, the estimated SF optima showed a decline with retinotopic eccentricity. Moreover, my results suggested that the bandwidth of pSFT depends on eccentricity, and that populations with lower SF peaks possess broader bandwidths. In Experiment 2, I proposed a new visual task, coined the Numerosity Judgement Paradigm (NJP), for fine-grained parametric manipulation of attentional load. Eight healthy, young adults performed this task in an MRI scanner, and the analysis of the BOLD signal indicated that the activity within the putative dorsal attention network was precisely modulated as a function of the attentional load of the task. In Experiment 3, I used the NJP to modulate attentional load, and exploited the model-based approach to estimate pSFTs under different attentional states. fMRI results of 9 healthy, young adults did not reveal any changes in either peak or the bandwidth of the pSFTs with attentional load. This study yields a full visuocortical map of spatial frequency sensitivity and introduces a new paradigm for modulating attentional load. Although under this paradigm I did not find any changes in SF preferences within human visual areas with attentional load, I cannot preclude the possibility that changes emerge under different attentional manipulations.

<p>Pilot training and certification have largely remained the same since the Practical Test Standards (PTS) were issued more than twenty years ago by the Federal Aviation Administration (FAA). Within the last several years, the general aviation training sector has acquired the capability to collect and analyze digital data from certain training aircraft. With the implementation of digital information analysis, a more accurate picture of the capabilities of student pilots is possible. These advancements could be used by flight instructors in the assessment process of flight students. With the inclusion of digital data from the aircraft, the cognitive load necessary to make an accurate assessment of a student’s performance could be affected, ideally in a positive manner. Cognitive load researchers typically focus on three aspects to enhance the likelihood of success in learning or task completion. There are three techniques to reduce cognitive load: (a) reduce extraneous load, (b) manage intrinsic load, and (c) optimize germane load (Young, Cate, O’Sullivan, & Irby, 2016). The current research project focused on the impact to the cognitive load of flight instructors who were presented with digital information retrieved from an airplane during their assessment of a student pilot’s aircraft landing competence, endorsement readiness for initial solo, the willingness of the instructor to mentor the student, and how well they liked the student pilot. The study found that a digital condition, when presented alone, created extraneous cognitive load and did not enable flight instructors to accurately rate student landing performance. Additionally, flight instructors were not able to use a combined digital + traditional condition to accurately assess student landing performance. When student performance was on the extreme (i.e. ‘poor’ and ‘good’), flight instructors were better able to determine whether or not a student was ready for a solo endorsement, but instructors did have difficulty distinguishing an ‘average’ student from a ‘good’ performing student. Lastly, all of the conditions presented failed to provide the proper visualizations to allow participants to make assessments of their willingness to mentor the students, and participants indicated that they did not like the students presented with the digital condition. Digital visualizations from aircraft data will require careful development in order to limit the extraneous load and reduce the intrinsic load for student flight assessment, and should be developed in collaboration with flight instructors to provide information to assist the analysis of student flight performance. </p>

Today's world is an interconnected global village. Communication and business transactions are increasingly conducted in non-native languages. Literature suggests that biases are present when communicating in non-native languages; that a truth bias is present in first language communication, and a lie bias in second language communication. Less than 10% of South Africa's population identifies with English, the lingua franca of the country, as a first language. Not much research in the presence of bias in second language communication has been published in the South African multi-lingual context. This study evaluated the presences of bias within deception frameworks such as the Truth Default State and the veracity effect. This study investigated whether deception detection can be improved by modifying the conditions under which statements are given by placing statement providers under cognitive load. The accuracy of veracity judgment language profiling software, LIWC2015, using published deception language profiles was compared against the results of the participating veracity judges. Results of the study were mixed. It was consistent with extant literature in a presence of a truth bias overall, but mixed in terms of a lie bias. The results supported the Truth Default Theory and veracity effect frameworks. LIWC2015 performed marginally better than human judges in evaluating veracity.

Post installed anchors come in either mechanical anchors that develop their strength purely through mechanical interlock with the base concrete, or bonded anchors that develop their strength by bonding anchor rod to the base concrete. Bonded anchors are either grouted, typically cementitious material, or adhesive, typically a chemical material. This thesis presents a current literature review of post-installed bonded anchors, preliminary testing of adhesive bonded anchors, and details of short term and long term test setups for future testing. The purpose of this thesis was to develop the test setups that will be used for future testing on anchors.

No description available.

The purpose of this study was to compare changes in static and countermovement jump variables across a competitive season of collegiate soccer to estimated training load and subjective measures of fatigue. Monitoring data from 21 male collegiate soccer players were retrospectively examined. Nine vertical jump sessions occurred across the season in addition to daily training load assessment and daily mood-state assessment. Group average changes from the first testing session were calculated and compared to the group average training load for the 7 days preceding each vertical jump testing session for static and countermovement jump height and allometrically scaled peak power. Statistical analysis demonstrated strong relationships between changes in vertical jump height for both conditions, allometrically scaled peak power for static jumps, and estimated training load. The results indicate changes in static jump height and allometrically scaled peak power may be more useful athlete fatigue monitoring tools than countermovement jump variables.

>Magister Scientiae - MSc / For a long time, fire dynamics has been misunderstood and viewed as either a destructive force or an ecological necessity. The Western Cape Province in South Africa experiences the frequent occurrence of fires, due to the prevailing Mediterranean climatic conditions. This climate is known for its hot and dry summers and its cold and wet winters, which, along with the highly flammable indigenous flora of the Western Cape, provide suitable conditions for the occurrence of fires. However, the local environmental and ecological variables that influence the occurrence of fires and that could assist with fire management practices remain poorly understood. The development of an integrated operational monitoring framework is therefore imperative for detecting and mapping the occurrence of fires in the Western Cape, South Africa.

The Mbesese Initiative for Sustainable Development (MISD) is a group aiming to help eliminate extreme poverty in Africa by creating educational opportunity. One project that the group is currently doing is to build Same Polytechnic College (SPC) in Tanzania. As part of the project, this thesis aims to study and analyze the electrical power system and distribution for the college. Based on the projected load profile of the college and high potential for solar generation in Tanzania, several different power systems utilizing local utility AC electricity and/or photovoltaic (PV) DC electricity are explored and simulated for their feasibility and performance. Analysis of each design is presented and compared to determine the most viable system based on reliability, costs, and space. Results of the study indicate that over designing the DC system may generate wasteful energy while under designing the DC system may cause the overall system to rely heavily on the AC power grid. Ultimately, this thesis demonstrates that integrating a 58.9% DC system mixed with AC system offers the highest payback while efficiently utilizing the PV system, the battery system, and provided land.

There are approximately 4000 railway bridges in Sweden and a common construction type is the short span concrete trough bridge. With the current standards the load distribution through ballast is assumed to be uniformly distributed with a distribution slope of 2:1 according to the Swedish Administration of Transport or 4:1 according to Eurocode 1. Previous research shows that there are a lot of factors that affects the load distribution through the ballast and that the distribution rarely is uniform. Different load patterns on bridges can result in different responses in the structure and it is possible that a more optimized evaluation of the loads could reduce the internal stresses in the bridge. There are gaps in the current literature regarding the structural response to different load patterns on reinforced concretetrough bridges and this master thesis aims to further the research in this area. This report will consist of a literature study where load distribution in ballast is researched in order to find what different load distributions are common and how different parameters affects the load distribution through the ballast. Further, a non-linear FE-model of a typical trough bridge in Sweden that was located in Lautajokki will be developed using ATENA Science. The model will be complete with ballast, sleepers and rails and will be calibrated using the results from a previous full-scale test on the Lautajokki bridge. Four more models will be developed without ballast, sleepers and ballast where the load distribution instead is modelled directly on top of the slab of the bridge. These models will be compared to the model with ballast, sleepers and rail (called the Full model) to see what load distribution that is the closest to reality and how the behavior of the bridge changes depending on the assumed load distribution. The parameters that will be tested and compared during this master thesis is the maximum load capacity, the stiffness, the crack patterns, the stresses in the reinforcement, the moments and shear forces. The load distributions that are tested in this thesis is the Swedish standard, TDOK 2013:0267 (Trafikverket, 2019), the European standard Eurocode 1 (CEN-1991, 2003), a load distribution that is theoretical according to research done by Andersson (2020) (called Realistic load case), and one where the load is assumed to be partially uniformly distributed under the rail seats under a sleeper according to AREMA (2010) (called Partially distributed). The results showed that the realistic load case was the one that was the closest to the Full model since it was the closest load distribution to the Full model for the stiffness of the bridge, the maximum load capacity, the max stress in the reinforcement and the average shear force in the bridge. The only parameters where it was not the closest was for the maximum strain in the concrete and for the average moment in the bridge. This load distribution is however not realistic to use for designing bridges since the pressure distribution is so unnecessarily complex. When it comes to the Swedish standard it also followed the behavior of the Full model closely, it had capacities that were generally larger compared to the Full model, the only exception was the max axle load where it had 1.5% lower capacity. The Swedish standard was also the second closest to the Full model in all tested parameters except for the stiffness. Furthest from the Full model was the load distribution after Eurocode 1 which had the furthest values from the Full model in every tested parameter except for the average moment distribution in the bridge. Eurocode 1 also had lower capacities compared to the Full model for every tested parameterwhich means that this model probably underestimates the capacity of the bridge. The stiffness of this model was however one of the closest to the Full model. The Partially distributed load case had higher capacities compared to the Full model in every measurement. It also had a stiffness that was the stiffest for every measuring point compared to any other load case. This model can probably overestimate the capacity of the bridge. Since non-linear analyses takes a long time to perform linear analyses are more often used to design structures. To test how big the differences are between non-linear and linear analyses all load distribution models will also be run with linear elastic materials to compare the two FEM methods. The comparison between the non-linear analysis and the linear analysis showed that the linear elastic analyses give larger extreme values for both the moments and shear forces which is reassuring since this means that these values are on the safe side. The one exception is the transversal moments for the slab were the moments at the connection to the beam was greater for the non-linear analyses compared to the linear one