Ester liquids including both natural ester and synthetic ester are being considered as potential alternatives to mineral oil, due to their better environmental performance and for some liquids their higher fire point. Although these liquids have been widely used in distribution and traction transformers, it is still a significant step to adopt ester liquids in high-voltage power transformers because the high cost and severe consequence of a factory test failure and the high level of safety and reliability required in service for these units, tend to lead to a cautious approach to any step change in technology. Lightning impulse strength as basic insulation level is of importance for insulation design of power transformers and lightning impulse test is commonly required in the factory routine tests for high-voltage power transformers, so this thesis is aimed to investigate the electrical performances including pre-breakdown and breakdown of natural ester and synthetic ester under impulse voltage. Two types of field geometry were considered in the study, one is sphere-sphere configuration which represents the quasi-uniform fields inside a transformer and another is strongly non-uniform point-plane configuration which represents the situation of a defect or a source of discharge. In quasi-uniform field study, standard breakdown tests were carried out under negative lightning and switching impulse voltages. Influence of various testing methods on the measured lightning breakdown voltage was studied and the 1% lightning withstand voltage was obtained based on Weibull distribution fitting on the cumulative probability plot built up using the approximately 1000 impulse shots. As for strongly non-uniform field study, streamer propagation and breakdown event in ester liquids either with or without pressboard interface were investigated at various gap distances under both positive and negative lightning impulse voltages. A relationship between the results under lightning impulse and previously published results under step voltage was built up to predict the lightning breakdown voltage of ester liquids at very large gaps. The results indicated that impulse strengths of ester liquids for both breakdown and withstand in a quasi-uniform field, are comparable to those of mineral oil. In a strongly non-uniform field, streamers in ester liquids propagate faster and further, than in mineral oil at the same voltage level. Thus breakdown voltages of ester liquids are generally lower than those of mineral oil, which could be as low as 40% at a large gap distance of approximately 1000 mm. Introduction of parallel pressboard interface has no influence on the streamer propagation and thus does not weaken the breakdown voltage, but it tends to reduce the acceleration voltage particularly for mineral oil under positive polarity. Last but not least, a unique phenomenon of secondary reverse streamer (SRS) was observed in ester liquids, which occurs subsequently and well after the extinction of the primary streamer (PS) propagation within a single shot of impulse voltage and has the reverse polarity to the PS. The formation mechanism of SRS is explained mainly due to the reverse electric field induced by the residual space charges left by the PS.

Multisource Least-Squares Migration (LSM) of phase-encoded supergathers has shown great promise in reducing the computational cost of conventional migration. But for the marine acquisition geometry this approach faces the challenge of erroneous misfit due to the mismatch between the limited number of live traces/shot recorded in the field and the pervasive number of traces generated by the finite-difference modeling method. To tackle this mismatch problem, I present a frequency selection strategy with LSM of supergathers. The key idea is, at each LSM iteration, to assign a unique frequency band to each shot gather, so that the spectral overlap among those shots—and therefore their crosstallk—is zero. Consequently, each receiver can unambiguously identify and then discount the superfluous sources—those that are not associated with the receiver in marine acquisition. To compare with standard migration, I apply the proposed method to 2D SEG/EAGE salt model and obtain better resolved images computed at about 1/8 the cost; results for 3D SEG/EAGE salt model, with Ocean Bottom Seismometer (OBS) survey, show a speedup of 40×. This strategy is next extended to multisource Full Waveform Inversion (FWI) of supergathers for marine streamer data, with the same advantages of computational efficiency and storage savings. In the Finite-Difference Time-Domain (FDTD) method, to mitigate spectral leakage due to delayed onsets of sine waves detected at receivers, I double the simulation time and retain only the second half of the simulated records. To compare with standard FWI, I apply the proposed method to 2D velocity model of SEG/EAGE salt and to Gulf Of Mexico (GOM) field data, and obtain a speedup of about 4× and 8×. Formulas are then derived for the resolution limits of various constituent wavepaths pertaining to FWI: diving waves, primary reflections, diffractions, and multiple reflections. They suggest that inverting multiples can provide some low and intermediate-wavenumber components of the velocity model not available in the primaries. In addition, diffractions can provide twice or better the resolution as specular reflections for comparable depths of the reflector and diffractor. The width of the diffraction-transmission wavepath is on the order of λ at the diffractor location for the diffraction-transmission wavepath.

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La industria gamer ha llevado a la posibilidad de subsistir económicamente del streaming. Dado que los streamers generan ingresos en relación con su audiencia, mientras mayor sea esta y esté más conectada con ella mayor probabilidad habrá de que genere mayores ingresos. Por ende, surge un nuevo modelo de negocio que requiere de una gestión reputacional para construir esta audiencia. Para ello, se necesita un primer análisis del contexto peruano desde la percepción que mantienen los jugadores de Dota 2 peruanos frente a los streamers peruanos de Dota 2. Por ello, este trabajo utiliza el paradigma naturalista/interpretativo que estudia al público en su contexto natural, es decir los gamers y el Dota 2. El diseño para este sería fenomenológico pues se busca entender la percepción (reputación) del streamer peruano desde el punto de vista de los jugadores de Dota 2 en general. Finalmente, se usa un enfoque cualitativo para obtener las opiniones de los usuarios que juegan Dota 2 sobre los streamers peruanos, con el uso de entrevistas semiestructuradas para alinearlas en los 3 aspectos para medir reputación: sólida dimensión axiológica, comportamiento comprometido y calidad de servicio. / The gaming industry has led to the possibility of economically subsisting on streaming. Since streamers generate income in relation to their audience, the larger their audience and the more connected they are, the greater probability of generating more income will exist. Therefore, a new business model emerges that requires reputational management to build this audience. To do this, a first analysis of the Peruvian context is needed from the perception that Peruvian Dota 2 players maintain compared to Peruvian Dota 2 streamers. That’s why, this work uses the naturalistic paradigm /interpretive that studies the public in its natural context, that is, the gamers in their gameplay and the design for this would be phenomenological because it seeks to understand the perception (reputation) of the Peruvian streamer from the point of view of Dota 2 players in general. Finally, a qualitative approach is used to obtain the opinions of the users who play Dota 2 on the Peruvian streamers, with the use of semi-structured interviews to align them in the 3 aspects to measure reputation: solid axiological dimension, committed behavior and quality of service. / Trabajo de investigación

Les procédés de couplage d'un plasma à pression atmosphérique et d'un catalyseur représentent une solution prometteuse pour la dépollution atmosphérique, ou plus spécifiquement pour le traitement des Composés Organiques Volatils. En particulier, le faible coût énergétique de cette technique la rend très intéressante pour les petites concentrations (traitement d'odeurs), difficiles à traiter avec les techniques habituelles. Parmi les catalyseurs qui peuvent être employés, le TiO2 (photocatalyseur) est avantageux pour son faible coût, sa non toxicité, et surtout son excellente sélectivité en CO2. Le couplage avec un plasma pourrait améliorer la vitesse de traitement qui est très lente en photocatalyse seule. La synergie plasma/TiO2 est étudiée depuis 2000 seulement. Le but de ce travail est d'identifier les mécanismes responsables de cette synergie en séparant les contributions de la décharge, de la porosité et de l'activité photocatalytique du TiO2. Pour y parvenir, une approche originale à été utilisée en étudiant à la fois une décharge à pression atmosphérique (DBD) et une décharge à basse pression (DC pulsée) autorisant l'utilisation de diagnostics lasers infra-rouge pour effectuer des mesures in situ résolues en temps.

Pour des raisons autant écologiques qu'économiques ou techniques, des huiles de base d'esters naturels ont été utilisées pour remplacer de l'huile minérale dans les appareillages basse et moyenne tensions. Ce travail consiste en étude de caractérisation d'un mélange des esters naturels de faible viscosité (RS50) basant sur l'huile de colza pour les applications dans les transformateurs haute tension. L'influence des facteurs humidité, température, teneur en particules ainsi que vieillissement thermique sur ses propriétés diélectriques telles que : permittivité, conductivité, pertes et rigidité électrique sous tension alternative a été mise en évidence. La RS50 présente une solubilité de l'eau élevée, la conductivité, la permittivité et les pertes plus élevées que celles de l'huile minérale mais ces différences sont réduites dans des huiles vieillies. Sa rigidité électrique en tension alternative est similaire à l'huile minérale, même après le vieillissement. Pourtant, une analyse des phénomènes de préclaquage et de claquage dans des configurations particulières ont montré que les esters naturels sont moins favorables pour les applications à haute tension que l'huile minérale. Parallèlement, des études méthodologiques ont été effectuées. L'intérêt d'une application de la méthode de mesure spectroscopique fréquentielle à la caractérisation des isolants liquides est la mise en évidence et la validité des conditions de mesure de la rigidité électrique du liquide isolant, ce qui est traditionnellement imposé suivant les normes, a été discutée.

De så kallade donationer som erhålls via streaming på Twitch är ett område i svensk skatterätt där oklarhet fortfarande råder. Lagstiftning finns gällande hur gåvor skall behandlas skattemässigt, dock är vägledning till just dessa så kallade donationer som erhålls vid streaming begränsad. Den vägledning som finns i rättskällor är ett förhandsavgörande från Skatterättsnämnden, DNR 85-15/D. Där fastslog nämnden att donationer som erhålls vid streaming inte utgör benefika förvärv enligt 8:2 inkomstskattelagen (1999:1229) (IL) och att de utgör en skattepliktig inkomst. Det är just det som undersökts i denna uppsats. Skall så kallade donationer som erhålls från streaming via Twitch ses som en skattepliktig inkomst och, om så är fallet, hur bör de beskattas enligt svensk lag? Uppsatsen beskriver vad Twitch är och dess ekonomiska aspekter. Efter det sker en genomgång av vad som utgör skattepliktiga inkomster. Därefter sker även en genomgång av vad som utgör skattefria inkomster samt gåvor enligt svensk rätt. Slutligen analyseras all den fakta som har samlats för att besvara problemformuleringen i denna uppsats. I uppsatsen konstateras att de så kallade donationerna erhållna via streaming inte utgör skattefria inkomster enligt 8:2 IL, på grund av att överföringarna utgör ersättning för streamingen. Sedan undersöks det om överföringarna kan utgöra skattepliktiga inkomster enligt IL, då det inte utgör skattefria gåvor. Resultatet av analysen visar att överföringarna kan utgöra skattepliktiga inkomster i inkomstslagen näringsverksamhet och tjänst. Vilket inkomstslag de så kallade donationerna skall hänföras till beror på hur streamingen bedrivs.

Longshore sediment transport rate was measured during energetic sea breeze activity, on intermediate-to-reflective sandy beaches in Southwestern Australia. Estimates of suspended load were obtained using backscatter sensors, current meters and streamer traps. Total load was determined using fluorescent tracer sand and an impoundment study. The measurementsw ere cross-compareda nd usedt o evaluates everalw idely-used longshore transport equations. The streamer trap measurement revealed an exponential distribution of the suspended sediment flux with vertical mixing decreasing in the onshore direction. A continuous time series of the longshore suspended sediment flux across the surf zone was obtained by combining the streamer trap measurements with data collected using surf zone instruments. Comparison of the suspended longshore flux with the total longshore flux derived from the dispersal of the sand tracer indicated that the relative contribution of the suspendedlo ad to the total load was at least 59 %. The movement of sandt racer on four different beaches demonstrated that nearshore sediments were transported obliquely across the surf zone, challenging our conventional view of dividing nearshore sediment transport into cross-shore and longshore components. Furthermore, tracer was found to move from the outer surf zone to the swash zone and vice versa, indicating a cross-shore sediment exchange. The contribution of the swash zone to the total longshore flux was estimated around 30-40 %. Despite large differences in the temporal and spatial scales of the measurement techniques, the littoral drift rates are comparable, suggesting a northward transport rate of 138,000-200,000 m3 year-1. Longshore sediment transport during sea breezes is mainly the result of a high longshore energy flux exerted by wind waves. This is accurately predicted by the equations of Inman and Bagnold (1963) and CERC (1984). The bimodal wave field, characteristic of Southwestern Australia, renders the Kamphuis (1991b) formula unsuitable in this instance.

The development of technology has created many platforms for entertainment, participatorycommunities and socialization online. One of the largest current platforms for live streamingis Twitch.tv with a focus on gaming and eSports. This is a male-dominated field wherewomen often face harassment and a non-welcoming community. This paper is a qualitativestudy of the negative communication towards female streamers on Twitch with a focus onthe context in which said communication takes place. The aim of the study is to understandthe circumstances in which negative communication occurs and how it changes dependingon context. The study takes a qualitative approach and analyses the content of six streamsfrom five different channels, as well the negative communication in their chat room. Theresults show that negative communication varies depending on the content as well as thenature of the community built around the channel.

Background：Live streaming shopping is becoming a mainstream method in China since the livestreaming feature has been applied to e-commerce. Live streaming commerce reflects theinterdependence between consumers and live streamers. Past studies have found that the ability,social presence and reputation of live streamers influence consumers' purchase intentions.However, there is a gap in how consumers' purchase intentions are affected by negative incidentsand a lack of qualitative perspective. Purpose：To explore consumers' understanding of their purchase intentions in relation to liveshopping streamers, in the context of negative incidents with streamers. Methodology：This study used qualitative research as the research method and abductivereasoning to conduct the data analysis. This study used semi-structured interviews and developedinterview questions based on the content of the theory chapter. The researchers usednon-probability sampling and general purpose sampling as the sampling strategy. The requireddata were obtained from 12 Chinese interviewees who had experience with live shopping. Theobtained data were then coded using grounded theory as the analysis method for qualitative data,which helped the researchers understand the thoughts of the interviewees. The final attempt is todevelop a theory that can explain the phenomenon. Moreover, the methods chapter explores thequality of the research in this study, as well as possible ethical and social issues. Findings：This paper identified three consumer needs (utilitarian, pleasure-seeking andemotional needs) and factors associated with streamers (attitude, streaming style, impact,characteristics and ability) that influence purchase intentions in the presence of negative streamerincidents. The paper also found how consumers' purchase intentions were influenced by thesefactors in different negative incident situations. Conclusion：This study obtained consumers' understanding of the relationship between theirpurchase intentions and streamers. Consumers exhibit three different levels of purchase3intention: willing to buy, wait-and-see (unsure of purchase intention) and no purchase intention.In the case of negative incidents, consumers' different purchase intentions are influenceddifferently by their own needs and streamer factors.