"Hälsa - ja hälsa är väl.." : En kvalitativ undersökning om vad hälsa är för högstadieelever.

Syftet med denna studie är att undersöka vad elever på en utvald skola tycker om hälsoundervisningen i ämnet idrott och hälsa. Vad är hälsa för någonting enligt eleverna, anser eleverna att de har tillräckligt med hälsa i undervisningen och hur tycker eleverna man ska arbeta med hälsa i idrottsundervisningen? För att uppfylla syftet har sju stycken elever i nionde klass intervjuats. Metoden som har använts är individuella kvalitativa intervjuer i en blandning av semistrukturerad och ostrukturerad form. Slutsatsen är att hälsa för eleverna är att röra på sig, äta rätt, sova bra och hålla sin hygien fräsch. Alla dessa faktorer hör till det som kallas för fysisk hälsa. Det är bara två av sju elever som någon gång under intervjuerna nämner psykisk eller social hälsa. Man kan se en viss skillnad på hur nöjda tjejerna respektive pojkarna är med hälsoundervisningen. Tjejerna säger i intervjuerna att de skulle vilja ha mer hälsoundervisning medan två pojkar är helt nöjda med hur de har det nu och två skulle vilja ha lite mer hälsoundervisning. Tjejerna ger även förslag på hur de skulle vilja jobba med hälsa på lektionerna i idrott och hälsa. Pojkarna är antingen nöjda med hur de gör nu eller så har de inga förslag

Återkoppling av sjöpraktik : Hur sjökaptensstudenter upplever återkoppling av sjöpraktik

Feedback is a tool that can be used to give students the confirmation of their accomplishments , helping them to increase understanding of the results of a performance and to alert students if change is required for future performance. Other studies and reports regarding clinical practice in education has shown that students feel that feedback has good impact on learning and positive effects such as enhanced self-confidence. Onboard training forms a major part of the education at the four-year nautical science education in Kalmar, in four years, one year is spent on board ships. Therefore, the purpose of this study was to find out how students at the four-year nautical science program in Kalmar felt that they receive feedback after completing on board training and how they wish that such feedback would be given. Six students were interviewed, three from grade one and three from grade three. The interviews were directed to an open form with a low degree of standardization. The results showed that all respondents felt they would prefer feedback from the school, even though all of them felt they had received good feedback on board the ships. The students would like to be given feedback by mentoring from other students during training, group discussions after on board training or short individual meetings between representative from the school and the student after completing on board training. All of the respondents felt that feedback is important to be able to learn from on board training and to know how to prepare for the next on board training. The study also revealed that students at the four-year nautical science program would like to gain more confirmation of what they are supposed to perform and if good results are obtained after completing on board training.

Autonomous Landing of an Unmanned Aerial Vehicle

This paper is concerned with the problem of autonomously landing an unmanned aerial vehicle (UAV) on a stationary platform. Our solution consists of two parts, a sensor fusion framework producing estimates of the UAV state and a control system that computes appropriate actuator commands. There are three sensors used, a camera, a GPS and a compass. Besides the description of the solution, we also present experimental results illustrating the results obtained in using our system to autonomously land an UAV

Fate of Phosphorus in Fixed Bed Combustion of Biomass and Sewage Sludge

The recovery of phosphorus (P) from societal waste streams, such as sewage sludge, could make a significant contribution to alleviating the global dependency upon non-renewable phosphate sources, such as phosphate rock. This study aims to determine the effect of fuel ash composition, chemical association, and combustion technology on the fate of P in ashes from the combustion of sewage sludge and biomass blends to enable more efficient P recovery from combustion ashes. Experiments were performed in a fixed bed pellet burner (20 kW), combusting two sewage sludge blends and three biomass blends of similar fuel ash composition but with different P source (sewage sludge, dried distiller's grain with solubles, or phosphoric acid). Slag, bottom ash, and particulate matter samples were collected and analyzed by scanning electron microscopy-energy-dispersive X-ray spectroscopy and X-ray diffraction for morphology and elemental and crystalline phase composition and compared to results from experiments in fluidized bed combustion using the same fuel blends reported separately. The distribution and elemental composition of ash fractions indicated that sub-micrometer particles contained a minor share of fuel P, with the significant share of fuel P found in the slag and bottom ash fractions. No apparent difference in phosphate speciation could be observed between the slag and bottom ash from sewage sludge blends and biomass blends, with a range of crystalline Ca, Mg, and K phosphates detected in the ash. By comparison, only Ca-rich phosphates were detected in the ashes from the combustion of the sewage sludge blends in the bench-scale fluidized bed. The difference in P speciation between the technologies was attributed to a difference in the process temperature between the two technologies. In comparison to fluidized bed combustion, fixed bed combustion favored the formation of (Ca, Mg)-K phosphates rather than Ca phosphates for similar fuel blends.Bio4Energ

Systematic Evaluation of the Fate of Phosphorus in Fluidized Bed Combustion of Biomass and Sewage Sludge

Comprehensive knowledge concerning the behavior of phosphorus (P) during combustion is necessary to enable more efficient recovery of P from combustion ashes for agricultural purposes. To this end, parameters that influence the distribution and speciation of P in combustion ashes are important because they may influence which ash fractions are suitable for P recovery. This study aims to determine the fate of P as a result of fuel ash composition and chemical association in the fuel during fluidized bed combustion by a systemic review of previous work. The synthesis was performed by comparing scanning electron microscopy–energy-dispersive X-ray spectroscopy and X-ray diffraction chemical analyses of bed ash, fly ash particles, and deposits from fluidized bed combustion of different blends of P-poor (logging residues or wheat straw) and P-rich (sewage sludge, dried distiller’s grain with solubles, or phosphoric acid) fuels and additives. The blends were produced to have a similar ash composition but with a different P source. The distribution of P among ash fractions indicated that P is mainly found in the coarse ash fractions (bed and cyclone ash), irrespective of fuel ash composition or chemical association in the fuel. The chemical speciation of P in coarse ash fractions differed between biomass blends containing sewage sludge compared to blends with phosphoric acid or dried distiller’s grain with solubles. Phosphates in the ash from the two sewage sludge blends included predominantly Ca with minor inclusion of other cations. In contrast, ashes from the blends with phosphoric acid or dried distiller’s grain with solubles contained phosphates with a significant amount of K, Ca, and Mg. The difference in phosphate speciation could not solely be explained by the combustion conditions and the elemental composition of the ash fractions. These results show that it is necessary to consider the chemical association of P in the fuel to predict the type of phosphates that will form in fluidized bed combustion ashes

Morphology and phosphate distribution in bottom ash particles from fixed-bed co-combustion of sewage sludge and two agricultural residues

The purpose of this study was to provide detailed knowledge of the morphological properties of ash particles, including the volumetric fractions and 3D distributions of phosphates that lay within them. The ash particles came from digested sewage sludge co-combusted with K- and Si-rich wheat straw or K-rich sunflower husks. X-ray micro-tomography were combined with elemental composition and crystalline phase information to analyse the ash particles in 3D. Analyses of differences in the X-ray attenuation enabled calculation of 3D phosphate distributions that showed high heterogeneity in the slag particles. This is underscored by a distinct absence of phosphates in iron-rich and silicon-rich parts. The slag from silicate-based wheat straw mixtures had lower average attenuation than that from sunflower husks mixtures, which contained more calcium. Calculated shares of phosphates between 7 and 17 vol% were obtained, where the highest value for a single assigned phosphate was observed in hard slag from wheat straw with 10 % sewage sludge. The porosity was notably higher for particles from pure wheat straw combustion (62 vol%), compared to the other samples (15–35 vol%). A high open pore volume fraction (60–97 vol%) indicates that a large part of the pores can be accessed by the surroundings. For all samples, more than 60 % of the discrete (closed) pores had an equivalent diameter &lt; 30 μm, while the largest volume fraction consisted of pores with an equivalent diameter &gt; 75 μm. Slag from sunflower husk mixtures had larger pore volumes and a greater relative number of discrete pores &gt;75 µm compared to wheat straw mixtures.Validerad;2024;Nivå 2;2024-02-20 (joosat);Funder: Carl-Fredrik von Horns fond and Stiftelsen för markvård till minne av Sanders Alburg, through the Royal Swedish Academy of Agriculture and Forestry (Grant No. GFS2018-0099)Full text license: CC BY</p

Thermodynamic Equilibrium Study on the Melting Tendency of the K-Ca-Mg-P-Si-O System with Relevance to Woody and Agricultural Biomass Ash Compositions

A major challenge in the combustion of biomass fuels is the heterogeneity of ash-forming elements, which may cause a wide range of ash-related problems. Understanding the melting tendency of the coarse ash fractions is necessary to mitigate agglomeration and slagging. This work aims to evaluate the melting tendency of the K-Ca-Mg-Si-P-O system by use of thermodynamic equilibrium calculations. The formation of condensed phases were systematically assessed in a combustion atmosphere, varying temperatures, and composition. Compositional ranges were based on fuel ash data extracted from the Phyllis 2 database. The speciation and degree of polymerization of phosphates, silicates, and melts were evaluated and indicated a systematic variation in composition. The melt fraction was predicted as a function of temperature and composition. The melting tendency was modeled for three systems, i.e., a P-dominated, a Si-dominated, and a mixed Si-P system. Four ratios between K2O, CaO, MgO, SiO2, and P2O5 were found to have a large effect on the melting tendency of the ash mixtures: the ratio between network formers (SiO2, P2O5), K2O to total network modifiers, CaO to CaO + MgO, and the ratio of network formers to total ash oxides. This modeling approach showed qualitative agreement with ash-related issues seen in previous lab-scale experiments in bubbling fluidized bed and fixed bed combustion. Practical implications of the results are discussed from the perspective of fuel design with the aim of preventing ash-related problems. This study presents a novel method of applying thermodynamic equilibrium calculations for a broad range of compositions and shows potential for predicting ash-related issues related to the melting of coarse ash fractions

Ash Transformation during Fixed-Bed Co-combustion of Sewage Sludge and Agricultural Residues with a Focus on Phosphorus

This work investigates the ash transformation during fixed-bed co-combustion of sewage sludge mixtures with the agricultural residues wheat straw and sunflower husks, focusing on the fate of phosphorus (P) in the resulting ash fractions. The study aims to determine suitable process parameters for fixed-bed combustion of fuels previously investigated in single-pellet experiments. The pure fuels and fuel mixtures were combusted in a 20 kWth residential pellet burner while monitoring the flue gas composition, temperature, and particulate matter formation. Subsequently, the different ash fractions were collected and characterized by CHN, SEM/EDS, and XRD analysis. The results showed that co-combustion of sewage sludge and agricultural residues reduced the formation of particulate matter as well as the formation of slag. Co-combustion of sewage sludge with either agricultural residue resulted in a change in phosphate speciation, displaying higher shares of Ca and lower shares of Fe and Al in the formed orthophosphates as well as amorphous phases containing higher shares of K. The formation of K-bearing phosphates was hindered by the spatial association of P with Ca and Fe in the sewage sludge, the incorporation of available K in K-Al silicates, and the depletion of K in the P-rich melt phase. Compared to mono-combustion, co-combustion experiments showed the potential for improving the combustion performance and reducing the risk of slag formation. The outcome suggests that co-combustion is a feasible path to integrate waste streams in fixed-bed energy conversion with simultaneous formation of phosphates enabling P recovery.Validerad;2023;Nivå 2;2023-04-19 (hanlid);This article has previously appeared as a manuscript in a thesis.</p