Failed supernovae are the implosive final fates of massive stars, where ablack hole is formed. During the collapse, the proto-neutron star emits a huge number of neutrinos, and when the black hole is finally formed, it engulfs theneutrino-emitting material and the signal is cut off. Inspired by the recent work of Nagakura & Hotokezaka (2020), this thesis improves on some parts of theirs imulation work and further explores the neutrino signal from failed supernovae, using a supercomputer to perform Monte Carlo simulations. In particular, we realized the neutrino flux’ time evolution around black hole formation hasn’t previously been studied well, and so it is investigated here, as well as the plausibility of measuring the black hole mass through the shape of the decay. A new component of the signal is presented, an echo of neutrinos emitted before black hole formation that, due to scattering in supersonic material around the black hole, arrive with a time delay of up to 15 ms, and with a significantly higher average energy, for heavy lepton neutrinos around 50 MeV.

The project compares the technology of welding of CO2 laser and fiber laser in terms of engineering study, the welds will be made by same welding conditions on two materials (S235JRG2 a X5CrNi 18-10), by using different protective gases (Helium and Argon). In the terms of literal background research both the technologies and questions of laser welding are described. The geometry of welds is carried out in the experimental part. The final results of the experiment are concluded at the end of the diploma thesis.

This project, elaborated within the master degree presents plates welding. Based on the literature study the problems of laser welding were designed optimal welding parameters. The material, on which were in the experimental part test and geometry analysis performed was steel Hardox 400 with thickness 5 mm. These welds were compared with welds made by MAG. Equipment used for werding was fiber laser.

The diploma thesis deals with the design of the hole-making technology for hydraulic components that are specific for its high requirements on size and shape accuracy. The aim of diploma thesis is to compare the productivity, efficiency and accuracy of reaming with two different reamers – the solid carbide reamer and the newly designed reamer that combines two cermets on cutting part of the tool. In the practical part, the data analyses and calculations were made. It was discovered that the newly designed tool brings economic benefits while the qualities of final hole are improving or remaining at the same level.

The increased human impact on the environment and climate after the retreat of the Last Glacial has strengthened its importance in the region of Västernorrland where Mesolithic sites are evident. This study focuses on a multiproxy analysis, where archaeological and natural science methods are combined to test several techniques in a peat sample. The origin of the peat sample is coming from the formation of a postglacial kettle hole situated near to Mesolithic sites. The aim of this thesis is twofold. Firstly, to estimate the value and the weakness of each method as also the combination of multiple results. Secondly, to reconstruct the palaeoenvironment including the detection of possible indications from past cultures. To begin with, the peat sample was collected from a kettle hole near Lillsjön lake, see (fig. 1) in 2010. The total depth of the peat sample was 80 cm and after its sampling, it was placed in a cold storage room until the spring of 2019, when analysis was conducted. Initially, a theoretical background will be presented as well as information for the area of study in the section of Scientific background. Moreover, a short theory is going to be given for the formation of the landscapes in cold environments as also the validity of beetle fossils with examples from previous case studies. After the theory part, all the methods are specified with results and appropriate diagrams and tables. After the analysis, the discussion will follow by combining all the methods and give potential theories for the reconstruction of the palaeoenvironment. The discussion part is divided into smaller chapters and after the conclusion an appendix is given with fossil photographs that were taken during the identification, see (fig.15,16,17).

Orientador: Luiz Antonio Barreiro / Resumo: O objetivo deste trabalho é apresentar um método alternativo, conhecido em matéria condensada como método holográfico, cuja origem remonta à conhecida dualidade AdS (Espaço anti-d’Sitter) e CFT (Teoria de Campo Conforme). Esse método é especialmente adaptado para resolução de problemas nos quais as partículas encontram-se fortemente ligadas, e que não permitem um tratamento perturbativo usual. Problemas desse tipo aparecem constantemente em atuais fenômenos da física da matéria condensada, como o caso da supercondutividade em “altas temperaturas”. Assim nessa dissertação é considerado um modelo baseado no método holográfico, no qual são incluidos termos não lineares na lagrangeana de interação eletromagnética, cuja origem vem de teoria de cordas bosônicas. Os resultados indicam que existe a possibilidade de se explicar esses materiais supercondutores com alta temperatura crítica. / Abstract: The objective of this work is to present an alternative method, known in condensed matter as a holographic method, whose origin dates back to the well-known AdS (Space Anti-Space) and CFT (Conformal Field Theory) duality. This method is especially adapted for solving problems in which the particles are tightly bound, and which do not allow a usual perturbative treatment. Problems of this type appear constantly in the current phenomena of condensed matter physics, as in the case of superconductivity in "high temperatures". Thus in this dissertation is considered a model based on the holographic method, in which are included non-linear terms in the Lagrangian of electromagnetic interaction, whose origin comes from the theory of bosonic strings. The results indicate that it is possible to explain these superconducting materials at high critical temperature. / Mestre

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Thesis: S.M., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2019 / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 129-132). / This thesis evaluates automated open-circuit scuba diver detection using low-cost passive sonar and machine learning. Previous automated passive sonar scuba diver detection systems required matching the frequency of diver breathing transients to that of an assumed diver breathing frequency. Earlier work required prior knowledge of both the number of divers and their breathing rate. Here an image processing approach is used for automated diver detection by implementing a deep convolutional neural network. Image processing was chosen because it is a proven method for sonar classification by trained human operators. The system described here is able to detect a scuba diver from a single acoustic emission from the diver. Twenty dives were conducted in support of this work at the WHOI pier from October 2018 to February 2019. The system, when compared to a trained human operator, correctly classified approximately 93% of the data. When sequential processing techniques were applied, system accuracy rose to 97%. This demonstrated that a combination of low-cost, passive sonar and a properly tuned convolutional neural network can detect divers in a noisy environment to a range of at least 12.49 m (50 feet). / by Andrew M. Cole. / S.M. / S.M. Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Mechanical Engineering; and the Woods Hole Oceanographic Institution)

Title: Dynamics of photoexcited charge carriers in diamond Author: Bc. Tomas Popelar Department: KCHFO MFF UK Supervisor: prof. RNDr. Petr Maly DrSc., KCHFO MFF UK Abstract: In this work we examine the luminescence from diamond in the strong excitation regime by one-photon or two-photon absorption of femtosecond laser beam. Measured sample was very pure type IIa diamond prepared by CVD method which was held in cryostat in order to measure temperature dependant luminescence in range from 12 K to 300 K. The signal was collected and analyzed either by spectrograph or streak camera so we gained time-integrated and time-resolved results. We analyzed only the part of the spectrum containing contributions from electron-hole liquid (for low temperatures), free excitons and probably exciton complexes. For higher temperatures where the condensation is not possible the contribution from e-h plasma was too weak compared to free excitons and was only detectable by time-resolved measurements. Other time-dependant results were obtained by pump and probe experiment with which we examined a change of life- times based on mode of excitation (one-photon or two-photon one) and also an influence of other beams on the condensation into electron-hole drops. Keywords: CVD diamond, dynamics, e-h liquid, excitons

Personality, or behavioural differences among individuals, which are stable both in time and across contexts, is a highly popular topic. Currently there has been an increase of interest in the relationship between personality and repeatability, which is a methodical approach developed to measure the stability of interindividual differences in time. The aim of this thesis is to evaluate the personality of rats according to behavioural patterns exhibited under widely used testing procedures in new environment (open field test, hole board test) and to compare, how behavioural traits in these tests mutually correlate and change over time. Each test trial was repeated eight times with different intervals (24 hours, 6 days, 4 weeks). The results suggest that most of the recorded behavioural variability can be explained with three principal axes. The first one is associated with loco-exploratory activity of the subject. The elements of behaviour associated with this axis are the most repeatable. The second axis is mostly associated with time the animal spent in the central part of the arena and the third axis represents the interest in holes in hole board test. These two axes are less repeatable. A significant effect of the identity of the animal was found in all behavioural traits, associated with these...

The consequences of two key approximations of accretion-disc physics near black holes are studied in this thesis. First, the question of effective ``pseudo-Newtonian" potentials mimicking a black hole is investigated both through numerical simulations and analytical means, and second, the neglect of additional gravitating matter near accreted-upon black holes and its consequences are put to test. After some broader discussion of integrability, resonance and chaos, a general "pseudo-Newtonian" limit for geodesic motion is derived, and applied for the case of null geodesics near a glowing toroid and for time-like geodesics in the Kerr metric. Afterwards, a new Newtonian gravitational potential for non- singular toroids is proposed and its usefulness for the so-called Weyl space-times is discussed. Finally, a new pseudo-Newtonian potential is introduced and applied alongside already known potentials in models of free test particle motion in the field of a black hole with a disc or ring, in complete analogy with previous exact-relativistic studies, and the previous conclusion of chaos in disc/ring-hole models is confirmed. Overall, the pseudo-Newtonian framework is able to reproduce a number of key features of the original systems with notable differences arising only as a consequence of extremely strong or...