I present a spectroscopic study of the molecular gas in the Whirlpool Galaxy (M51) and the Antennae Galaxies (NGC 4038/39) using data from the Herschel Space Observatory (Herschel) and the Atacama Large Millime- ter/submillimeter Array (ALMA). Using data from the Herschel Spectral and Photometric Imaging REceiver (SPIRE) Fourier Transform Spectrometer (FTS), I perform an excitation analysis to determine the physical characteris- tics (temperature, density, column density) of the cold and warm molecular gas across both systems. I do not find significant variation in the cold molecular gas across an individual system or between the systems. The warm molecular gas temperature is greater in NGC 4038/39 than in M51, while the density in both M51 and the nucleus of NGC 4038 is greater than the rest of the Anten- nae system. Both galaxies exhibit a similar fraction of warm to cold molecular gas. I compare Herschel SPIRE-FTS data to models of photon dominated regions (PDRs) to determine the strength of the background far ultraviolet field (G0) within both systems and find little variation across each system. I find that PDRs alone can explain the observed Herschel SPIRE-FTS data in both systems. Using ALMA observations of dense molecular gas tracers in NGC 4038/39, I investigate the physical processes affecting the dense molecular gas. Ratios of various molecular gas tracers suggest that the contributions of mechanical heating relative to PDR heating are similar across the entire system. The dense gas fraction in the nucleus of NGC 4038 and the nucleus of NGC 4039 is higher than in the overlap region, which I attribute to an increase in the stellar potential within the two nuclei. Furthermore, I find evidence for an increased cosmic ray rate in the overlap region of NGC 4038/39 relative to the two nuclei, which I attribute to an increased supernova rate in the overlap region. Most of the molecular gas in M51 and NGC 4038/39 is in the form of PDRs, while the increased temperature of the warm molecular gas in NGC iii 4038/39 compared to M51 is likely due to an increase in the mechanical heating from both supernova and stellar winds and the ongoing merger. Furthermore, a comparison of these results to previous studies of the interacting galaxy M82 and the late-stage merger Arp 220 suggests that mergers and interactions have a greater effect on the warm molecular gas compared to the cold molecular gas. The results from this thesis help to further our understanding of the effects of merging and interacting galaxies on molecular gas, while helping understand differences between interacting galaxies and merging galaxies. / Thesis / Doctor of Philosophy (PhD)

This project deals with the CFD modelling of a free surface flow. The aim is to develop and validate a fast and accurate numerical model for stratified two-phase flows. Volume of Fluid (VOF) multiphase model is employed. The purpose is to use the developed numerical model for the design of an element within a compact nuclear reactor.Unsteady Reynolds Averaged Navier-Stokes (RANS) simulations are conducted. Two free surface test cases are simulated to verify and ensure robustness of the model: a dam break and a vertical cylindrical obstacle set in a channel. From there, an optimization is performed in order to find the best compromise between accuracy and rapidity with the solver. The proper set of parameter models is found by carrying out extensive sensitivity studies and compare the solutions with available measurements.The obtained numerical results show a reasonable good agreement with the experimental data for the dam-break. Significant time savings are achieved thanks to the implemented optimization process while maintaining accuracy. The optimized model is then applied to the second test case and comparisons with experimental measurements are carried out. The same physical behavior of the flow as in experiments is captured with the simulations. The differences found between the simulation data and experiments are partly due to the difficulty to monitor experimentally with a high accuracy the highly non uniform regions within the flow.

With growing space market and entry of more private companies into the industry, there arecompanies and stakeholders who would like to have a high order of accuracy mission outputrequirements. These requirements vary from mission to mission. This simply means that if acompany wants an Earth observation mission, the main requirement to be fulfilled would be tohave the highest resolution of image possible. In order to achieve this, the satellite carrying the camera payload would be required to bepointed in the right direction with utmost accuracy. For a satellite to be pointed in the rightdirection, the noise generated by the sensors and actuators on-board, which determines theattitude of the satellite and helps in changing it, should be minimized. The aim of this thesisis to design a method which could help in determining the right components to be procuredso that the pointing requirements of the satellite are fulfilled. This objective is achieved bydesigning algorithms in python and MATLAB. The values generated by these algorithms, ultimately describe the type of sensor or actuator to be procured. Finally, the noise generated bysuch individual components act as pointing error source and then PEET is used to translatethese error sources to platform error, to generate a pointing budget and ensure that all pointingrequirements are satisfied.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.