Teacher's Mathematical Task Selection

The purpose of this thesis is to study teachers’ task selection to answer the research question “What considerations does mathematics teachers have for a “good” mathematical task?” The framework of this thesis has included Documentational Approach to Didactics, Constructivism and Personal Constructs Psychology, in addition to some theory on what a good task is. For this the theory on cognitive demands in tasks, and the zone of proximal development have been used. To gather and analyse data, I have used Repertory Grid Technique. To follow this technique, I started with making sets of tasks. Three voluntary teachers then compared the tasks and offered constructs. These constructs were used as a base for a Likert-scale the teachers were to fill out. Then I used a qualitative content analysis on the ratings the teachers gave to look for perceptions the teachers had for “good” tasks. In the discussion I compare the teachers' perceptions. What I found was that different teachers have various considerations for what a “good” task is. Some of their considerations are similar, but some of them are not. Evaluating tasks appears to be a complex process for teachers where many features need to be considered

Heavy oil production with energy effective steam-assisted gravity drainage

In reservoirs with extra heavy oil and bitumen, thermal methods are used to reduce the viscosity, in order to extract the oil. Steam-assisted gravity drainage (SAGD) is a thermal method where continuous steam injection is used. In this method, two horizontal wells are placed in parallel. The upper well injects steam and the lower well produces oil and condensed water. The continuous steam injection creates a chamber with uniform temperature. Heavy oil and bitumen reserves in Western Canada, which exceed 175 billion barrels, are becoming increasingly important petroleum sources due to the technical success of the SAGD processes. This study includes Computational fluid dynamics (CFD) modelling and simulations of a horizontal oil well with SAGD. The simulations are performed with inflow control devices (ICD) and autonomous inflow control valves (AICV) completion. In the SAGD processes, it is important that the residence time for steam in the reservoir is high enough to ensure that all the injected steam condenses in the reservoir to reduce the amount of steam injection and thereby making the SAGD process more energy effective. The simulations are carried out with ICD completion to delay the steam breakthrough and with AICV completion to prevent breakthrough of steam and water to the well. The numerical results showed that a most of the steam was produced together with the oil when ICD completion was used. AICV was able to close for steam and water, and the steam was thereby forced to condense in the reservoir, resulting in better utilization of the condensation energy

Distribution Of Co2 In Fractured Carbonate Reservoirs

Deep geologic injection of supercritical carbon dioxide (CO2) for enhanced oil recovery (EOR) has been widely used for improved oil recovery from depleted oilfields since early 1970s. The CO2 injection maintains the pressure, mobilize the oil and release the petroleum resources that would otherwise be inaccessible. In addition to improving the oil recovery, the CO2-EOR contributes to minimize the impact of CO2-emissions to the atmosphere. The injected CO2 will be remained trapped in the underground geological formations, as the CO2 replace the oil and water in the pores. Carbonate reservoirs are characterized by low permeability and high heterogeneity, resulting in early breakthrough of gas and water and hence low oil recovery. The presence of naturally fractures in carbonate reservoirs is a major problem for the oil industry using CO2-EOR, because significant amount of CO2 are recycled to the well, and thereby not distributes in the reservoir. This study focuses on CO2 injection into a naturally fractured carbonate reservoir, including near-well simulations of CO2-distribution in the rock matrix. The simulations are carried out using the reservoir simulation software Rocx in combination with OLGA. The simulations show that CO2-injection into a naturally fractured carbonate reservoir in combination with closing of the fractured zones result in good distribution of CO2 in the reservoir

Å leve med foreldre i brudd og konflikt. Hvilke historier og erfaringer om sårbarhet og resiliens forteller unge voksne?

Formålet med studien har vært å utvide forståelsen av fenomenene resiliens og sårbarhet hos barn og unge knyttet til familier i konflikt etter samlivsbrudd. Problemstillingen er: Hvilke erfaringer om sårbarhet og resiliens forteller unge voksne om å leve med foreldre i konflikt etter samlivsbrudd?  For å besvare problemstillingen har jeg intervjuet seks unge voksne som hadde erfaring med å vokse opp i brutte familier med konfliktdynamikk. Studien belyser resiliens og sårbarhet i et systemisk perspektiv, hvor fokus er resiliens i familie og nettverk, samt informantenes historier om mestring og sårbarhet. Hva har vært positive bidrag til god tilpasning og hva har bidratt til utfordringer? Studiens vitenskapelige ståsted er kritisk realisme og intervjuene er analysert ved hjelp av tematisk analyse. Tre hovedtema er fremkommet i studien: 1. Tilhørighet til hjemmet påvirkes av relasjonen med foreldrene og konflikten 2. Tilhørighet utenfor familien både støtter og kompliserer 3. Mestringsstrategiene både gir kraft og tapper krefter Studien viser at å bli forstått og møtt i følelser var erfaringer som styrket informantenes tilhørighet til hjemmene. Sårbare erfaringer handlet om å føle seg nedprioritert når foreldre etablerte seg med ny familie. Manglende kommunikasjon, subtile konflikter og nedsettende omtale mellom foreldrene utgjorde belastende erfaringer i informantenes oppvekst. Funnene viser til at støttende relasjoner i utvidet nettverk bidro til resiliens og gode erfaringer. Informantene fortalte frem både styrker og utfordringer ved ulike mestringsstrategier. Følgende mestringsstrategier omtales: Å forbli stille, stå opp for seg selv og andre, være budbringer, vokse opp tidlig og kjenne selvstendighet. Studien viser til viktigheten ved å rette fokus på ressurser i utvidet familie og nettverk når barnet vokser opp med konflikter etter brudd. Videre retter studien oppmerksomhet på at barns forsøk på å håndtere utfordringer både kan ha emosjonelle og relasjonelle omkostninger og bidra til vekst

Strength of side-to-side and step-cut repairs in tendon transfers: biomechanical testing of porcine flexor tendons

The aim of the study was to compare side-to-side with step-cut repairs to determine how much of the width it is possible to remove and still keep the repair strong enough to start active mobilization. Porcine flexor tendons were used to create side-to-side, one-third step-cut and half step-cut repairs. There were 15 repairs in each group. The tensile properties of the constructs were measured in a biomechanical testing machine. All repairs failed by the sutures splitting the tendon longitudinally. The maximum load and stiffness were highest in the side-to-side group. Our findings suggest that the half step-cut repair can withstand the forces exerted during active unrestricted movement of the digits in tendons of this size. The advantage of the step-cut repair is reduced bulkiness and less friction, which might compensate for the difference in strength.acceptedVersio

Image Processing and Measurement of the Bubble Properties in a Bubbling Fluidized Bed Reactor

The efficiency of a fluidized bed reactor depends on the bed fluid dynamic behavior, which is significantly influenced by the bubble properties. This work investigates the bubble properties of a bubbling fluidized bed reactor using computational particle fluid dynamic (CPFD) simulations and electrical capacitance tomography (ECT) measurements. The two-dimensional images (along the reactor horizontal and vertical planes) of the fluidized bed are obtained from the CPFD simulations at different operating conditions. The CPFD model was developed in a commercial CPFD software Barracuda Virtual Reactor 20.0.1. The bubble behavior and bed fluidization behavior are characterized form the bubble properties: average bubble diameter, bubble rise velocity, and bubble frequency. The bubble properties were determined by processing the extracted images with script developed in MATLAB. The CPFD simulation results are compared with experimental data (obtained from the ECT sensors) and correlations in the literature. The results from the CPFD model and experimental measurement depicted that the average bubble diameter increased with an increase in superficial gas velocities up to 4.2 Umf and decreased with a further increase in gas velocities due to the onset of large bubbles (potential slugging regime). The bubble rise velocity increased as it moved from the lower region to the bed surface. The Fourier transform of the transient solid volume fraction illustrated that multiple bubbles pass the plane with varying amplitude and frequency in the range of 1–6 Hz. Further, the bubble frequency increased with an increase in superficial gas velocity up to 2.5Umf and decreased with a further increase in gas velocity. The CPFD model and method employed in this work can be useful for studying the influence of bubble properties on conversion efficiency of a gasification reactor operating at high temperatures.publishedVersio

Here I’ve lived, here I want to die

Bacheloroppgave sykepleie, 2017Uansett individ har alle mennesker rett på en verdig død, selv om du er statsminister eller uteligger. Døden for mange er en skremmende opplevelse og mange vegrer seg mot dette temaet, uansett om du jobber i helsevesenet eller er butikkmedarbeider er dette et vanskelig tema. Vi vil påstå at de som jobber i helsevesenet har mer kunnskap og forståelse for døden, men selv den dag i dag er det mange som vegrer seg mot å snakke om det, kanskje fordi de selv ikke vet hvor dem står. I de yrkesetiske retningslinjene for sykepleiere står det at vi har ansvar for å lindre lidelse og bidra til en verdig død. Som sykepleier skal vi ivareta pasientens verdighet, rett til medbestemmelse og gi helhetlig sykepleie (Norsk sykepleierforbund [NSF], 2011). Som et av de rikeste landene i verden ligger Norge svært dårlig an når det kommer til hjemmedød. I år 1981 var det 25% som døde hjemme, i år 2000 var det 15%, og i den siste tiden har det vært stabilt med 14 – 15 % (Grov, 2012). Det kan være flere årsaker til at tallet på dødsfall i hjemmet er gått ned. Grov (2012) skriver om det hun tenker kan være årsakene til nedgang av dødsfall i hjemmet, der hun blant annet stiller seg spørsmål om det kan være fordi tilbudet om oppfølging og tilstedeværelse fra hjemmesykepleien ikke er god nok for den gamle, døende. En annen grunn kan være at kommunehelsetjenesten har lagt mye arbeid i å innføre lindrende enheter/ sengeplasser som er ment for pasienter i palliativ fase (Grov, 2012. s.29). Hun påpeker også at vi må ha mer kunnskap om årsaken til at vi har så lav hjemmedød, og hva som er det beste for pasienten (Grov, 2012. s.28). Etter at den nye samhandlingsreformen er kommet er det blitt mer fokus på at pasientene skal få rett behandling på rett sted til rett tid. Samhandlingsreformen legger til rette for at alvorlige syke og døende skal kunne behandles hjemme. Norge er et av de landene som bruker flest offentlige helsekroner per person men likevel får ikke pasienten det de trenger (Helse- og omsorgsdepartement, 2008-2009 s. 24). Etter det vi har lest er det mange der ute som ønsker å dø hjemme i kjente og trygge omgivelser, men til syvende og sist når døden nærmer seg ønsker dem seg til sykehus eller sykehjem

Sintering Behaviors of Synthetic Biomass Ash

Entrained flow gasification of biomass provides the opportunity to convert low-grade biogenic feedstocks to high-grade synthetic fuels. For a top-fired entrained flow slagging biomass gasifier, the thermophysical properties of the ash and slag limit process operation and affect process energy efficiency. The biomass ash has to be molten and slag viscosity has to be in a certain range for it to flow out of the gasifier. However, direct sampling, analysis, and evaluation of slag formation and behaviors are often challenging as entrained flow biomass gasification operates at high temperatures (i.e., 1200-1500°C) continuously. One alternative is to study synthetic ash's melting and sintering behaviors at elevated temperatures, which represent the major inorganic constituents in biomass ash. For thermochemical conversion of biomass, K, Ca and Si are typically the most common ash-forming elements. In this work, the synthetic ashes were prepared by mixing model compounds K2O, CaO and SiO2 in different mole ratios, which were pressed to form pellets. The selection of mole ratios was based on thermodynamic calculations that indicate that the tested model compound mixtures melt and flow with desired viscosity at certain temperature ranges. The pressed synthetic ashes were preheated at 900 °C for 8 hours to thermally homogenize them. Then the premelted synthetic ashes were heated at 1000 and 1400 °C in a muffle furnace with a residence time of 1 and 8 hours in air to study fusion behaviors and slag formation tendency, and were cooled down to room temperature gradually after the sintering test. The sintered residues were collected and analyzed by SEM/EDX to study the interactions of the model compounds and identify chemical compositions. The results showed that the mole ratios of model compounds have recognizable impacts on the composition, formation and transformation of mineral phases in residues from sintering tests. A strong correlation was also found between the sintering intensity of the synthetic ash and the mole ratios of model compounds.publishedVersio

Analyzing the effects of particle density, size, size distribution and shape for minimum fluidization velocity with Eulerian-Lagrangian CFD simulation

Fluidized bed reactor systems are widely used due to excellent heat and mass transfer characteristics followed by uniform temperature distribution throughout the reactor volume. The importance of fluidized beds is further demonstrated in high exothermic reactions such as combustion and gasification where fluidization avoids the hot spot and cold spot generation. A bed material, such as sand or catalyst, is normally involved in fluidized bed combustion and gasification of biomass. Therefore, it is vital to analyze the hydrodynamics of bed material, especially the minimum fluidization velocity, as it governs the fluid flowrate into the reactor system. There are limitations in experimental investigations of fluidized beds such as observing the bed interior hydrodynamics, where CFD simulations has become a meaningful way with the high computer power. However, due to the large differences in scales from the particle to the reactor geometry, complex interface momentum transfer and particle collisions, CFD modeling and simulation of particle systems are rather difficult. Multiphase particle-in-cell method is an efficient version of Eulerian-Lagrangian modeling and Barracuda VR commercial package was used in this work to analyze the minimum fluidization velocity of particles depending on size, density and size distribution. Wen-YU-Ergun drag model was used to model the interface momentum transfer where default equations and constants were used for other models. The effect of the particle size was analyzed using monodispersed Silica particles with diameters from 400 to 800 microns. Minimum fluidization velocity was increased with particle diameter, where it was 0.225 m/s for the 600 microns particles. The density effect was analyzed for 600 microns particles with seven different density values and the minimum fluidization velocity again showed proportionality to the density. The effect of the particle size distribution was analyzed using Silica. Particles with different diameters were mixed together according to pre-determined proportions as the final mixture gives a mean diameter of 600 microns. The 600 microns monodispersed particle bed showed the highest minimum fluidization velocity. However, some particle mixtures were composed with larger particles up to 1000 micron, but with a fraction of smaller particles down to 200 microns at the same time. This shows the effect of strong drag from early fluidizing smaller particles. The only variability for pressure drop during packed bed is the particle size and it was clearly observed in all three cases

Analysis of the effect of steam-to-biomass ratio in fluidized bed gasification with multiphase particle-in-cell CFD Simulation

Biomass has been identified as a key renewable energy source to cope with upcoming environmental challenges. Gasification of biomass is becoming interested in large scale operation, especially in synthesis of liquid fuels. Bubbling and circulating fluidized bed gasification technology has overrun the interest over fixed bed systems. CFD studies of such reactor systems have become realistic and reliable with the modern computer power. Gasifying agent, temperature and steam or air to biomass ratio are the key parameters, which are responsible for the synthesis gas composition. Therefore, multiphase particle-in-cell CFD modeling was used in this study to analyze the steam to biomass, S/B, ratio in fluidized bed gasification. Due to the complexity of the full loop simulation of dual circulating fluidized bed reactor system, only the gasification reactor was considered in this study. Predicted boundary conditions were implemented for the particle flow from the combustion reactor. The fluidization model was validated against experimental data in beforehand where Wen-Yu-Ergun drag model was found to be the best. The effect of the S/B ratio was analyzed at a constant steam temperature of 1073K and a steam velocity of 0.47 m/s. Four different S/B of 0.45, 0.38, 0.28 and 0.20 were analyzed. The biomass was considered to be in complete dry condition where single step pyrolysis reaction kinetics was used. Each gasification simulation was carried out for 100 seconds. 8% reduction of hydrogen content from 57% to 49% and 17% increment of carbon monoxide from 13% to 30% were observed when the S/B was reduced from 0.45 to 0.20. Countable amounts of methane were observed at S/B of 0.28 and 0.20. The lower heating value of the product gas increased from 10.1 MJ/kg to 12.37 MJ/kg and the cold gas efficiency decreased from 73.2% to 64.6% when the S/B was changed from 0.45 to 0.20. The specific gas production rate varied between 1.64 and 1.04 Nm3/kg of biomass