A bluff-body has been employed as the flame stabilization scheme for many combustion devices such as gas turbines and aviation engines. Although the bluff-body flame holder has a key advantage of generating a hot gas recirculation zone behind it and assist in stable combustion, it also induces flow field and combustion instabilities such as unstable vortex shedding, which can adversely affect the flame stability and lead to blow-off. The understanding of the physical mechanism of flame stabilization and blow-off processes has been one of the critical subjects in premixed combustion systems under highly turbulent conditions. As considering this, the present dissertation presents insight of flame stabilization and blow-off mechanisms using several series of computational studies and detailed analysis using diagnostic approaches. Two-dimensional direct numerical simulations are conducted to examine flame/flow and blow-off dynamics in lean premixed hydrogen-air and syngas-air flames stabilized on a meso-scale bluff-body in a square channel. Several distinct effects on flame stabilization and blow-off dynamics are investigated, such as reduced confinement, hydrodynamic instability, flame time scale, and differential diffusion effects. For the analysis, a proper time scale analysis is attempted to characterize the flame blow-off mechanism, which turns out to be consistent with the classic blow-off theory of Zukoski and Marble. The combined approach of computational singular perturbation and tangential stretch rate is applied to examine chemical characteristics in blow-off dynamics. As an extension from Eulerian to Lagrangian viewpoint, Lagrangian particle tracking analysis of post-processing the pre-computed results is performed to examine the local characteristics during the critical transient event of local extinction and recovery.

We study the polarization produced by scattering from dust in a bow shock-shaped region of enhanced density surrounding a stellar source, using the Monte Carlo radiative transfer code SLIP. Bow shocks are structures formed by the interaction of the winds of fast-moving stars with the interstellar medium. Our previous study focused on the polarization produced in these structures by electron scattering; we showed that polarization is highly dependent on inclination angle and that multiple scattering changes the shape and degree of polarization. In contrast to electron scattering, dust scattering is wavelength-dependent, which changes the polarization behaviour. Here, we explore different dust particle sizes and compositions and generate polarized spectral energy distributions for each case. We find that the polarization spectral energy distribution behaviour depends on the dust composition and grain size. Including dust emission leads to polarization changes with temperature at higher optical depth in ways that are sensitive to the orientation of the bow shock. In various scenarios and under certain assumptions, our simulations can constrain the optical depth and dust properties of resolved and unresolved bow shock-shaped scattering regions. Constraints on optical depth can provide estimates of local interstellar medium density for observed bow shocks. We also study the impact of dust grains filling the region between the star and bow shock. We see that as the density of dust between the star and bow shock increases, the resulting polarization is suppressed for all the optical depth regimes.

Denna kandidatuppsats gör en ansats till att belysa biodiversitetsproblematiken i Sydostasien, som är ett område med mycket hög artrikedom som samtidigt hotas av en intensifierad förlust av arter. Fyra ’biodiversitet hotspots’ omger Sydostasien, vilka indikerar platser med hög artrikedom vilka sammanfaller med hög förlust av habitat. Det största orsaken till förlust av biologisk mångfald i Sydostasien är omvandlingen utav artrika naturtyper till monokulturodlingar, och expansionen av jordbruk och urbana områden. För att undersöka den pågående biodiversitetsforskningen genomfördes en systematisk litteraturanalys av publicerade artiklar från 2010-2019. Vad litteraturanalysen kom fram till var att flera problem, socioekonomiska samt miljöproblem intensifierar varandra, liksom fattigdom och förlust av biologisk mångfald. Internationellt samarbete krävs för att stoppa exploateringen av de värdefulla arter och naturtyper som går förlorade till fördel för den globala handeln med produkter som kommer från området. Medel för att stoppa denna biodiversitetskatastrof måste riktas till forskning och organisationer som arbetar i området. Vi bör genast agera på ett globalt plan för att förhindra förlusten av biodiversitet samt dess tillhörande ekosystemtjänster, detta skulle kunna tacklas genom att vi rör oss ifrån den antropocentriska och emot den ekocentriska natursynen. / This bachelor thesis focuses on the biodiversity loss problematics in Southeast Asia, since it is one of the most species rich places on Earth, coupled with the highest rate of loss of species. Four biodiversity hotspots encompasses Southeast Asia which implies areas of high endemism coupled with high rates habitat loss. This thesis aim to understand what current research in the field focuses on and what ways of protecting biodiversity in the area that exists. The main driver of biodiversity loss in Southeast Asia as well as in the rest of the world, are land-use alterations; forests and natural habitat being converted to monoculture plantations, as well as agricultural- and urban expansions. Through a systematic literature review of scientific material from 2010-2019, the biodiversity research in Southeast Asia is reviewed. What the literature review concluded was that an array of environmental- as well as socioeconomic problems intensifies each other in the area, such as poverty and biodiversity loss. International cooperation to halt biodiversity loss and the global demand for products produced in the area which greatly damages ecosystems needs to be addressed urgently. Actions to halt the mass-extinction of species and their connected ecosystem services needs to be taken by providing means to organizations and to scientists that work in the area and could possibly be addressed by moving from anthropocentrism towards a biocentric nature view.

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A primary deficit seen in many children with autism, particularly those with limited verbal repertoires, is repetitive and rote verbal behavior. This type of repetitive or rote verbal behavior can be stigmatizing and may severely limit access to primary reinforcers. Therefore, it may be beneficial to attempt to increase response variability in verbal behavior demonstrated by children with autism. Previous researchers have focused their efforts on examining response variability in motor behavior or existing verbal behavior, rather than new or recently taught verbal behavior. A potentially complementary intervention for teaching new verbal interactions is the use of scripts and script fading procedures. However, the effect of scripts and script fading procedures on the response variability of verbal behavior remains unknown. Thus, the present study attempted to answer several research questions. First, we examined the effects on extinction on response variability of mand frames used by young children with autism that exhibit limited manding repertoires. Second, we examined the effects of script training on the variability of mand frames, and finally, the effects of extinction after teaching a variety of mand frames with children with autism. Results demonstrated that (a) extinction prior to any teaching was not successful in increasing response variability, (b) teaching multiple mand frames in a successive pattern did not increase response variability of mand frames for any of the participants, (c) extinction after teaching additional mand frames increased response variability for two of the three participants, and (d) a multiple script presentation intervention increased response variability of mand frames for one participant.

This thesis explores the folk resurrection of the thylacine through artwork and symbolic interaction. The thylacine, better known as the Tasmanian tiger, is a marsupial that suffered a government-sanctioned massacre leading to its extinction in 1936. The thylacine’s status as a hidden animal has inspired what folklorists call “ostensive practice”; people not only actively seek out the thylacine in the wilderness of Tasmania today and share their sightings online, but they have also incorporated the thylacine as a symbol of hope and perseverance into various forms of folk art. There have been upwards of five thousand documented sightings of the thylacine since its extinction. This documentation can take the form of amateur or phone-recorded films, or sightings described in interviews for local news agencies. Some people have even found alleged biological remains of the thylacine and have described hearing its unique call. In addition to these types of legend-tripping activities, the thylacine is also represented in a variety of folk-art forms, including digital, painted, and hand-drawn artwork, written fiction, fiber arts, and costuming. This content is shared widely across the internet. Keeping the thylacine alive through the creation of folk art and legend-tripping search parties helps thylacine enthusiasts cope with the guilt for having lost an ecologically important animal due directly to ignorance and financial gain. If the thylacine is resurrected, whether literally or figuratively, people can symbolically undo some of the damage they have caused the natural world. Thus, the vernacular resurrection of the thylacine, understood through a folklorist lens, offers a model for comparing some of the vernacular ways that people are presently dealing with the general loss of wildlife due to climate change.

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The thesis focus on simulating one-dimensional flame subjected to a microwave and nanosecond pulse. We modified open-source codes Cantera and Ember to perform one-dimensional flame simulations for steady and unsteady state, respectively. Our model is computationally efficient to perform simulations in a range of parameters such as electric field strength, flow strain rate, and pulse repetitive frequency. Our model for the one-dimensional flame subjected to a microwave predicted flame speed enhancement more accurately than the previous studies. <br>

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