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1
Harju, J., F. Daniel, O. Sipilae, P. Caselli, J. E. Pineda, R. K. Friesen, A. Punanova, et al. "Deuteration of ammonia in the starless core Ophiuchus/H-MM1." EDP SCIENCES S A, 2017. http://hdl.handle.net/10150/624367.
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Context. Ammonia and its deuterated isotopologues probe physical conditions in dense molecular cloud cores. The time-dependence of deuterium fractionation and the relative abundances of different nuclear spin modifications are supposed to provide a means of determining the evolutionary stages of these objects. Aims. We aim to test the current understanding of spin-state chemistry of deuterated species by determining the abundances and spin ratios of NH2D, NHD2 and ND3 in a quiescent, dense cloud. Methods. Spectral lines of NH3, NH2D, NHD2, ND3 and N2D+ were observed towards a dense, starless core in Ophiuchus with the APEX, GBT and IRAM 30-m telescopes. The observations were interpreted using a gas-grain chemistry model combined with radiative transfer calculations. The chemistry model distinguishes between the different nuclear spin states of light hydrogen molecules, ammonia and their deuterated forms. Different desorption schemes can be considered. Results. High deuterium fractionation ratios with NH2D = NH3 similar to 0 : 4, NHD2 = NH2D similar to 0 : 2 and ND3 = NHD2 similar to 0 : 06 are found in the core. The observed ortho/para ratios of NH2D and NHD2 are close to the corresponding nuclear spin statistical weights. The chemistry model can approximately reproduce the observed abundances, but consistently predicts too low ortho/para-NH2D, and too large ortho/para-NHD2 ratios. The longevity of N2H+ and NH3 in dense gas, which is prerequisite to their strong deuteration, can be attributed to the chemical inertia of N-2 on grain surfaces. Conclusions. The discrepancies between the chemistry model and the observations are likely to be caused by the fact that the model assumes complete scrambling in principal gas-phase deuteration reactions of ammonia, which means that all the nuclei are mixed in reactive collisions. If, instead, these reactions occur through proton hop/hydrogen abstraction processes, statistical spin ratios are to be expected. The present results suggest that while the deuteration of ammonia changes with physical conditions and time, the nuclear spin ratios of ammonia isotopologues do not probe the evolutionary stage of a cloud.
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Thom, Christopher, and na. "High velocity clouds and the Milky Way Halo." Swinburne University of Technology, 2006. http://adt.lib.swin.edu.au./public/adt-VSWT20060920.101419.
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This thesis presents an exploration of stars and gas in the halo of our Galaxy. A sample
of 8321 field horizontal branch (FHB) stars was selected from the Hamburg/ESO Survey.
The stars make excellent tracers of the Milky Way halo, and we studied the kinematics
of a subset of the HES FHB stars, comparing their velocity dispersions to those predicted
by several models. Since these stars are intrinsically luminous, hot and numerous they
make ideal probes of the distances to high-velocity clouds (HVCs) - clouds of neutral
hydrogen gas whose distances are largely unknown and which do not fit simple models
of Galaxy rotation. A catalogue of stars which align with the HVCs was developed. High
resolution spectroscopy of 16 such HVC probes with the Magellan telescope has yielded
a remarkably tight distance constraint to complex WB. This is one of only a handful of
such distance limits so far established. Lower distance limits were set for several other
clouds. Finally, we have suggested that some of the HVCs may be associated with the
accretion onto the MilkyWay of the Sagittarius dwarf galaxy.
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Bieging, John H., Saahil Patel, William L. Peters, L. Viktor Toth, Gábor Marton, and Sarolta Zahorecz. "THE ARIZONA RADIO OBSERVATORY CO MAPPING SURVEY OF GALACTIC MOLECULAR CLOUDS. V. THE SH2-235 CLOUD IN CO J = 2 − 1, 13 CO J = 2 − 1, AND CO J = 3 − 2." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621984.
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We present the results of a program to map the Sh2-235 molecular cloud complex in the CO and (CO)-C-13 J = 2 - 1 transitions using the Heinrich Hertz Submillimeter Telescope. The map resolution is 38 '' (FWHM), with an rms noise of 0.12K brightness temperature, for a velocity resolution of 0.34 km s(-1). With the same telescope, we also mapped the CO J = 3 - 2 line at a frequency of 345 GHz, using a 64 beam focal plane array of heterodyne mixers, achieving a typical rms noise of 0.5 K brightness temperature with a velocity resolution of 0.23 km s(-1). The three spectral line data cubes are available for download. Much of the cloud appears to be slightly sub-thermally excited in the J = 3 level, except for in the vicinity of the warmest and highest column density areas, which are currently forming stars. Using the CO and (CO)-C-13. J = 2 - 1 lines, we employ an LTE model to derive the gas column density over the entire mapped region. Examining a 125 pc(2). region centered on the most active star formation in the vicinity of Sh2-235, we find that the young stellar object surface density scales as approximately the 1.6-power of the gas column density. The area distribution function of the gas is a steeply declining exponential function of gas column density. Comparison of the morphology of ionized and molecular gas suggests that the cloud is being substantially disrupted by expansion of the H II regions, which may be triggering current star formation.
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Svoboda, Brian E., Yancy L. Shirley, Cara Battersby, Erik W. Rosolowsky, Adam G. Ginsburg, Timothy P. Ellsworth-Bowers, Michele R. Pestalozzi, et al. "THE BOLOCAM GALACTIC PLANE SURVEY. XIV. PHYSICAL PROPERTIES OF MASSIVE STARLESS AND STAR-FORMING CLUMPS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621258.
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We sort 4683 molecular clouds between 10 degrees < l < 65 degrees from the Bolocam Galactic Plane Survey based on observational diagnostics of star formation activity: compact 70 mu m sources, mid-IR color-selected YSOs, H2O and CH3OH masers, and UCH II. regions. We also present a combined NH3-derived gas kinetic temperature and H2O maser catalog for 1788 clumps from our own GBT 100 m observations and from the literature. We identify a subsample of 2223 (47.5%) starless clump candidates (SCCs), the largest and most robust sample identified from a blind survey to date. Distributions of flux density, flux concentration, solid angle, kinetic temperature, column density, radius, and mass show strong (>1 dex) progressions when sorted by star formation indicator. The median SCC is marginally subvirial (alpha similar to 0.7) with >75% of clumps with known distance being gravitationally bound (alpha < 2). These samples show a statistically significant increase in the median clump mass of Delta M similar to 170-370 M-circle dot from the starless candidates to clumps associated with protostars. This trend could be due to (i) mass growth of the clumps at (M) over dot similar to 200-440 M-circle dot Myr(-1) for an average freefall 0.8 Myr timescale, (ii) a systematic factor of two increase in dust opacity from starless to protostellar phases, and/or (iii). a variation in the ratio of starless to protostellar clump lifetime that scales as similar to M-0.4. By comparing to the observed number of CH3OH maser containing clumps, we estimate the phase. lifetime of massive (M > 10(3) M-circle dot) starless clumps to be 0.37 +/- 0.08 Myr (M/10(3) M-circle dot)(-1); the majority (M < 450 M-circle dot) have phase. lifetimes longer than their average freefall time.
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Seo, Youngmin, and Youngmin Seo. "The L1495-B218 Filaments in Taurus Seen in NH₃ & CCS and Dynamical Stability of Filaments and Dense Cores." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621572.
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We present deep NH₃ and CCS maps of L1495-B218 filaments and the dense cores embedded within the filaments in Taurus. The L1495-B218 filaments form an interconnected, nearby, large complex extending over 8 pc. We observed the filaments in NH₃ (1,1)&(2,2), CCS Nⱼ = 1₂-0₁, and HC₇N J = 21-20 with spectral resolution of 0.038 km/s and spatial resolution of 31". The CSAR algorithm, which is a hybrid of seeded-watershed and binary dendrogram algorithm, identifies 39 leaves and 16 branches in NH₃ (1,1). Applying a virial analysis for the 39 NH₃ leaves, we find only 9 out of 39 leaves are gravitationally bound, and 12 out of 30 gravitationally unbound leaves are pressure-confined. Our analysis suggests that a dense core may form as a pressure-confined structure, evolve to a gravitationally bound core, and then undergo collapse to form a protostar. We find that the L1495A, B213E, and B216 regions have strong CCS emission and the B211 and B218 regions have weak CCS emission. Analysis of CCS emission with NH₃ (1,1) and dust continuum emission shows that CCS is not a good tracer for starless core evolution. On the other hand, CCS appears to trace recently accreted gas in L1495A and L1521D. We also present more realistic dynamic stability conditions for dense cores and filaments. In a new analysis of stability conditions we account for converging motions which have been modeled toward starless cores and take the effect of radiation fields. We find that the critical size of a dense core having a homologous converging motion with its peak speed being the sound speed is roughly half of the critical size of the Bonnor-Ebert sphere. We also find the critical mass/line density of a dense core/filament irradiated by radiation to be considerably smaller than that of the Bonnor-Ebert sphere/isothermal cylinder when the radiation pressure is stronger than the central gas pressure of dense core/isothermal cylinder. For regions in the inner Galaxy and near OB associations, the critical mass/line density of a dense structure may be less than 20% of the critical mass/line density of Bonnor-Ebert sphere/isothermal cylinder.
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Olofsson, Sven. "Extinction in Molecular Clouds : Case of Barnard 335." Doctoral thesis, Stockholms universitet, Institutionen för astronomi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-72523.
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The Bok globule B335 is a small molecular cloud in the solar neighbourhood near the galactic plane. The aim for this three-paper-study is to construct and analyze the extinction for this globule. The method we apply is to use the light from field stars behind the cloud in broadband filters ranging from UV to the mid-infrared. We have observations performed at the ESO telescopes at La Silla and Paranal as well as at the Nordic 2.5 m telescope at La Palma. Together with images and spectra from 2MASS-, ISO- and Spitzer-archives we are able to cover the wavelength range from 0.35 to 24 μm. An important tool to analyze these observations results in order to get the extinction is the grid of synthetic stellar atmospheric spectra provided by Hauschildt (2005). The extinction so received is a result in itself. From the analysis of the extinction wavelength dependence we derive properties of the dust, especially its composition and grain size distribution. By modeling the grain size distribution we are able to find the extinction from the reddening of the stars. We find that the extinction in the optical wavelength 0.35 to 2 μm range nicely follows the functional form described by Cardelli et al. (1989). Our result from the wavelength range redward of 2 μm show an extinction dependent on the part of the cloud examined. For the rim of the cloud we get an extinction similar to that reported earlier for the diffuse interstellar medium. From the central parts of the cloud, however, a higher extinction was found. Our grain size model contains a carbonaceous particle distribution and a silicate one. The result can be explained by depletion of carbon onto carbonaceous grains and also by carbon onto all grains including the silicates. Our modeling of the extinction and our classification of the background stars allow us to - determine the distance to the globule - estimate the gas column density ratio - estimate the mass of globule - get a handle on the dust conversion processes through the grain size distribution From the water- and CO-ice spectra we are able to estimate the ice column densities. We find similar ice column densities for the two ices. The estimates differ, when calculated from band strengths or from Lorenz-Mie calculations of ice mantles on the grain size distribution, by a factor of two.
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Wu, Ya-Lin, Kazushi Sakamoto, and Hsi-An Pan. "Submillimeter Array 12CO (2-1) Imaging of the NGC 6946 Giant Molecular Clouds." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623951.
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We present a (CO)-C-12 (2-1) mosaic map of the spiral galaxy NGC 6946 by combining data from the Submillimeter Array and the IRAM 30m telescope. We identify 390 giant molecular clouds (GMCs) from the nucleus to 4.5 kpc in the disk. GMCs in the inner 1 kpc are generally more luminous and turbulent, some of which have luminosities > 10(6)K. km. s(-1) pc(2) and velocity dispersions > 10. km s(-1). Large-scale bar-driven dynamics likely regulate GMC properties in the nuclear region. Similar to the MilkyWay and other disk galaxies, GMC mass function of NGC 6946 has a shallower slope (index > -2) in the inner region, and a steeper slope (index < -2) in the outer region. This difference in mass spectra may be indicative of different cloud formation pathways: gravitational instabilities might play a major role in the nuclear region, while cloud coalescence might be dominant in the outer disk. Finally, the NGC 6946 clouds are similar to those inM33 in terms of statistical properties, but they are generally less luminous and turbulent than the M51 clouds.
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Seo, Young Min, and Andrew N. Youdin. "The role of non-ionizing radiation pressure in star formation: the stability of cores and filaments." OXFORD UNIV PRESS, 2016. http://hdl.handle.net/10150/621725.
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Stars form when filaments and dense cores in molecular clouds fragment and collapse due to self-gravity. In the most basic analyses of gravitational stability, the competition between self-gravity and thermal pressure sets the critical (i.e. maximum stable) mass of spheres and the critical line density of cylinders. Previous work has considered additional support from magnetic fields and turbulence. Here, we consider the effects of non-ionizing radiation, specifically the inward radiation pressure force that acts on dense structures embedded in an isotropic radiation field. Using hydrostatic, isothermal models, we find that irradiation lowers the critical mass and line density for gravitational collapse, and can thus act as a trigger for star formation. For structures with moderate central densities, similar to 10(3) cm(-3), the interstellar radiation field in the Solar vicinity has an order unity effect on stability thresholds. For more evolved objects with higher central densities, a significant lowering of stability thresholds requires stronger irradiation, as can be found closer to the Galactic centre or near stellar associations. Even when strong sources of ionizing radiation are absent or extincted, our study shows that interstellar irradiation can significantly influence the star formation process.
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Stanimirović, Snežana. "The complex nature of the ISM in the SMC : an HI and infrared study /." View thesis, 1999. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030826.143835/index.html.
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Thesis (PhD) -- University of Western Sydney, Nepean, 1999."A thesis submitted for the degree of Doctor of Philosophy at the University of Western Sydney Nepean" "July, 1999" Bibliography : p. 177-185.
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Imara, Nia, Charles Lada, John Lewis, John H. Bieging, Shuo Kong, Marco Lombardi, and Joao Alves. "X Marks the Spot: Nexus of Filaments, Cores, and Outflows in a Young Star-forming Region." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624336.
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We present a multiwavelength investigation of a region of a nearby giant molecular cloud that is distinguished by a minimal level of star formation activity. With our new (CO)-C-12(J = 2-1) and (CO)-C-13(J = 2-1) observations of a remote region within the middle of the California molecular cloud, we aim to investigate the relationship between filaments, cores, and a molecular outflow in a relatively pristine environment. An extinction map of the region from Herschel Space Observatory observations reveals the presence of two 2 pc long filaments radiating from a highextinction clump. Using the (CO)-C-13 observations, we show that the filaments have coherent velocity gradients and that their mass-per-unit-lengths may exceed the critical value above which filaments are gravitationally unstable. The region exhibits structure with eight cores, at least one of which is a starless, prestellar core. We identify a low-velocity, low-mass molecular outflow that may be driven by a flat spectrum protostar. The outflow does not appear to be responsible for driving the turbulence in the core with which it is associated, nor does it provide significant support against gravitational collapse.
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Litke, Katrina C., You-Hua Chu, Abigail Holmes, Robert Santucci, Terrence Blindauer, Robert A. Gruendl, Chuan-Jui Li, Kuo-Chuan Pan, Paul M. Ricker, and Daniel R. Weisz. "Nature of the Diffuse Source and Its Central Point-like Source in SNR 0509-67.5." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624374.
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We examine a diffuse emission region near the center of SNR 0509-67.5 to determine its nature. Within this diffuse region we observe a point-like source that is bright in the near-IR, but is not visible in the B and V bands. We consider an emission line observed at 6766 angstrom and the possibilities that it is Ly alpha, H alpha, and [O II] lambda 3727. We examine the spectral energy distribution (SED) of the source, comprised of Hubble Space Telescope B, V, I, J, and H bands in addition to Spitzer/IRAC 3.6, 4.5, 5.8, and 8 mu m bands. The peak of the SED is consistent with a background galaxy at z approximate to 0.8 +/- 0.2 and a possible Balmer jump places the galaxy at z approximate to 0.9 +/- 0.3. These SED considerations support the emission line's identification as [O II] lambda 3727. We conclude that the diffuse source in SNR 0509-67.5 is a background galaxy at z approximate to 0.82. Furthermore, we identify the point-like source superposed near the center of the galaxy as its central bulge. Finally, we find no evidence for a surviving companion star, indicating a double-degenerate origin for SNR 0509-67.5.
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Rey, Raposo Ramon. "The interplay between stellar feedback and galactic environment in molecular clouds." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/21022.
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In this thesis we address the problem of understanding the star formation process in giant molecular clouds in a galactic context. Most simulations of molecular clouds to date use an oversimplified set of initial conditions (turbulent spheres/boxes or colliding flows). Full galactic scale models are able to generate molecular clouds with complex morphologies and velocity fields but they fail to reproduce in detail the effects that occur at sub-pc scales (e.g. stellar feedback). Our goal is to build the bridge between these two scenarios, and to model the star formation process in molecular clouds produced in a galactic context. We extract our molecular clouds from full-scale galactic simulations, hence we need to increase the resolution by two orders of magnitude. We introduce the details of the program used to simulate molecular clouds in Chapter 2, and describe in detail the method we follow to increase the resolution of the galactic clouds. In Chapter 3 we compare our simulated galactic clouds with the more conventional approach of using turbulent spheres. We create turbulent spheres to match the virial state of three galactic clouds. We perform isothermal simulations and find that the velocity field inherited from the full-scale galactic simulations plays an important role in the star formation process. Clouds affected by strong galactic shear produce less stars compared with clouds that are compressed. We define (and test) a set of parameters to characterise the dynamical state of our clouds. To include stellar feedback in our simulations we need to introduce a cooling/heating algorithm. In Chapter 4 we analyse how the different velocity fields of our clouds change the temperature distribution even in the absence of feedback. To study the formation of molecules we need to model the chemistry of H2 in our clouds. We also add CO chemistry, and produce synthetic observations of our clouds. The effect of feedback from winds and supernovae in galactic clouds is studied in Chapter 5. We analyse the effect of winds in clouds with very different velocity fields. We find that the effect of winds is stronger in highly virialised, high star forming clouds, with clouds with weak galactic shear, compared to unbound shear-dominated clouds. The steady and continuous action of the winds appears to have a greater effect than the supernovae. In summary, the inherited properties from the galaxy have an impact on many relevant processes in star formation, influencing gravitational collapse, the formation of filamentary structures, the temperature field of the cloud, and have a considerable effect on the impact of feedback in the clouds.
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Shaw, Gargi, G. J. Ferland, and I. Hubeny. "The Validity of 21 cm Spin Temperature as a Kinetic Temperature Indicator in Atomic and Molecular Gas." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625168.
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The gas kinetic temperature (T-K) of various interstellar environments is often inferred from observations that can deduce level populations of atoms, ions, or molecules using spectral line observations; H I 21 cm is perhaps the most widely used, and has a long history. Usually the H I 21 cm line is assumed to be in thermal equilibrium. and the populations are given by the Boltzmann distribution. A variety of processes, many involving Ly alpha, can affect the 21 cm line. Here we show how this is treated in the spectral simulation code Cloudy, and present numerical simulations of environments where this temperature indicator is used, with a detailed treatment of the physical processes that determine level populations within H-0. We discuss situations where this temperature indicator traces TK, cases where it fails, as well as the effects of Lya pumping on the 21 cm spin temperature. We also show that the Lya excitation temperature rarely traces the gas kinetic temperature.
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Neves, Joao Fernando Ciotta. "Simulations of high mass star formation in the Milky Way." Thesis, University of Hertfordshire, 2013. http://hdl.handle.net/2299/10039.
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Massive star formation takes place in the dense cores of molecular clouds where the stars may be obscured at optical wavelengths. An excellent signpost of a massive young stellar object is the presence of an ultra-compact HII region (UCHii), which is a dense photo-ionised cocoon of gas surrounding the newly formed star. The aim of this project is to develop an assembly of numerical tools, caravela, that can simulate realistic data streams representing high-mass star forming regions in our Galaxy. The synthetic output consists in images and photometric point source catalogues, in the IRAS and Herschel wavebands. In an era when large observational surveys are increasingly important, this tool can produce simulated infrared point-source catalogues of high-mass star forming regions on a Galactic scale. The approach used is to construct a synthetic Galaxy of star-forming regions represented by SED templates. The star-forming regions are distributed randomly along a four spiral arm morphology, although a wide range of geometries can be used including rings and different numbers of spiral arms. The caravela code then observes the synthetic Galaxy to produce simulated images and point source catalogues with appropriate sensitivity and angular resolution. caravela was first used to model the simulated Galaxy by constraining the synthetic output to observations made by IRAS. This numerical tool will allow the user to infer physical properties of the Galactic population of high-mass star forming regions from such observations. Second, the selected model was again observed with caravela in Herschel mode. These are therefore predictive results for the future Herschel observations. A model with 4.0×104 compact proto-stars embedded in larger grey-body envelopes (with T = 40 K and linear size scale lIII = 5.0 × 106 AU) is the best-fit model to the IRAS observational data set studied. We found a level of contamination from low- and intermediate-mass objects of " 90%. The modelled data set resulting from the Herschel simulation resulted in the detection of approximately twice as many Herschel objects than IRAS, which is consistent, in a limited way, with the real observed companion clump fraction (CCF) of 0.90 ± 0.07 (Thompson et al., 2006) means that on average there were observed 2 sources per one IRAS source. Our caravela and the real observed CCF are therefore consistent. caravela was coupled with an independent diffuse emission model (Paladini et al., 2007) and the resulting analysis is presented as an interesting seed for the future.
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Schneider, Evan E., and Brant E. Robertson. "HYDRODYNAMICAL COUPLING OF MASS AND MOMENTUM IN MULTIPHASE GALACTIC WINDS." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623100.
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Using a set of high-resolution hydrodynamical simulations run with the Cholla. code, we investigate how mass and momentum couple to the multiphase components of galactic winds. The simulations model the interaction between a hot wind driven by supernova explosions and a cooler, denser cloud of interstellar or circumgalactic media. By resolving scales of Delta x < 0.1 pc over > 100 pc distances, our calculations capture how the cloud disruption leads to a distribution of densities and temperatures in the resulting multiphase outflow and quantify the mass and momentum associated with each phase. We find that the multiphase wind contains comparable mass and momenta in phases over a wide range of densities and temperatures extending from the hot wind (n approximate to 10(-2.5) cm(-3), T approximate to 10(6.5) K) to the coldest components (n approximate to 10(2) cm(-3), T approximate to 10(2) K). We further find that the momentum distributes roughly in proportion to the mass in each phase, and the mass loading of the hot phase by the destruction of cold, dense material is an efficient process. These results provide new insight into the physical origin of observed multiphase galactic outflows and inform galaxy formation models that include coarser treatments of galactic winds. Our results confirm that cool gas observed in outflows at large distances from the galaxy (greater than or similar to 1 kpc) likely does not originate through the entrainment of cold material near the central starburst.
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Takeuchi, Shun. "The Nature of Super-Eddington Outflow around Black Holes." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188449.
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Cabral, Ana Isabel Duarte. "Kinematics and physical properties of young proto-clusters." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/kinematics-and-physical-properties-of-young-protoclusters(8eb34d15-b343-4aab-b4b0-ede4bba903be).html.
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The formation of stars begins with the fragmentation of molecular clouds and the formation of dense cores. This fragmentation process can either be the result of classical gravitational instabilities or triggered by some external event. The gas and dust of young protoclusters often hold the imprints of the initial conditions and triggers of that specific star forming episode. In this context, my thesis work is a study of the gas properties of young protoclus- ters within the Gould Belt. The first part of my work consists of a detailed study of the young Serpens star forming region with CO isotopologues. This study has revealed a complex temperature, column density and velocity structure. I proposed a scenario where a collision between two filamentary clouds or flows is responsible for the observed complex structure and the most recent burst of star formation in Serpens. This hypothesis was tested with SPH simulations and provides a plausible scenario. I am currently extending this work to other regions with a variety of star formation efficiencies, in search of the particular physical properties and dynamics of a molecular cloud that allow or prevent clouds to be in the verge of forming stars. As such, I have included in this manuscript my study of the gas in the B59 star forming region, the only active clump in the Pipe Nebula. The results from this study have shown it to be very different from Serpens, even though further studies are needed to provide a complete picture of the region. B59 was taken as the starting point for a larger study of the entire Pipe Nebula, driven by the peculiarly low star formation efficiency in the cloud and a test to the physical properties of cores prior to star formation.
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Rice, Johnathan Scott. "The Transition From Diffuse to Dense Molecular Clouds." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1534945134382193.
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Schlingman, Wayne M. "Interstellar Gas Clouds and Gen. Ed. Astronomy Students: Who Are They? How Do They Behave?" Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/242359.
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The first chapter begins with the observations of 1,882 sources from the Bolocam Galactic Plane Survey (BGPS) at 1.1 mm in HCO⁺ J = 3 − 2 and N₂H⁺ J = 3 − 2. We determine kinematic distances for 529 sources and derive the size, mass, and average density for this subset of clumps. The median size of BGPS clumps is 0.75 pc with a median mass of 330 M⊙ (assuming T(Dust) = 20 K). The median HCO⁺ linewidth is 2.9 km s⁻¹ indicating the clumps are not thermally supported and provide no evidence for a size-linewidth relationship. This collection of objects is a less-biased sample of star-forming regions in the Milky Way that likely span a wide range of evolutionary states. We study in detail the G111 Infrared Dark Cloud northwest of NGC 7538 with the K-band Focal Plane Array. We map NH₃ (1,1) and (2,2), H₂O maser, and CCS emission simultaneously with the GBT. We find the NH₃ gas traces the 1.1 mm BGPS structure very well with gas kinetic temperatures consistently close to 15 K. Typical column densities are 2.5 × 10¹⁴ cm⁻² with a median abundance of NH₃ to H₂ of 5.94 × 10⁻⁸. The median linewidth of the NH₃ emission is 0.64 km s⁻¹ indicating the filament is not thermally supported. The NH₃ is subthermally populated along the entire filament. Individual NH3 peaks have a median size of 0.61 pc, mass of 188M⊙, and density of 3.4×10³ cm⁻³. An activity analysis shows the most active star forming regions are found at the junctions of the subfilaments that make up the larger G111 IRDC. The last chapter describes our systematic examination of individual student responses to the Light and Spectroscopy Concept Inventory national dataset. We use classical test theory to form a framework of results that is used to evaluate item difficulties, item discriminations, and the overall reliability of the LSCI. We perform an analysis of individual student’s normalized gains, providing further insight into the prior results from this data set. This investigation allows us to better understand the efficacy of using the LSCI to measure student achievement.
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El, Yajouri Meriem. "Diffuse Interstellar Bands (DIBs) : a new look at an old problem." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEO017/document.
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Les bandes interstellaires diffuses (DIBs) représentent un mystère centenaire : aucune des centaines de bandes n'a pu être identifiée avec certitude avec un porteur spécifique, à l'exception très probable du cation buckminsterfullerène C60+. Il est obligatoire d'identifier et de quantifier la quantité de grosses molécules carbonées interstellaires qui sont très probablement responsables des DIBs : Les porteurs de DIB représentent probablement le plus grand réservoir de matière organique dans le Milieu interstellaire (MIS) et constituent un élément important de la chaîne des processus qui régissent le cycle interstellaire/stellaire. Jusqu'à récemment, la plupart des études liées aux DIBs avaient pour objectif unique l'identification des porteurs et, pour ce faire, se concentraient sur un nombre limité d'étoiles chaudes, distantes et rougies. Mon travail de recherche en thèse marque un tournant dans les méthodes et les objectifs associés aux DIBs, une évolution permise et motivée par le nombre croissant de relevés stellaires avec des instruments de plus en plus puissants à haute résolution spectrale. En effet, il est aujourd'hui possible de recueillir des quantités massives de données, tant du point de vue du nombre d'étoiles cibles que du point de vue du nombre de DIBs observées simultanément. Cela a ouvert la voie à de nouveaux types d'études, à des objectifs plus ambitieux et, surtout, à de nouvelles comparaisons potentielles avec les données de laboratoire. Ma thèse présente un grand nombre d'extractions de DIBs et quatre de ces nouvelles analyses :- Méthodes d'extraction et recherche de nouvelles DIBs.- Lien avec les propriétés physiques des nuages.- Constitution de bases de données pour la cartographie du MIS.- Tomographie des structures individuelles.- Des extractions de profils de DIBs basées sur des lignes de visée soigneusement sélectionnées, des études de leurs sous-structures et de leur variabilité spatiale et des contraintes subséquentes sur leurs porteurs moléculaires potentielsDiffuse interstellar bands (DIBs) represent a century-old mystery: none of the hundreds of bands could be identified with certainty with a specific carrier, at the very likely exception of the buckminsterfullerene cation C60+. Identifying and quantifying the amount of the large interstellar carbonaceous molecules that are very likely responsible for the DIBs is mandatory: DIB carriers likely represent the largest amount of organic matter in the Universe and are an important piece of the chain of processes that govern the interstellar/stellar cycle.Up to recently, most of the DIB studies have had as a unique goal the identification of the carriers, and to do so have been focusing on a limited number of hot, distant and reddened stars, using increasingly powerful instruments. This thesis marks a turning point in the methods and goals associated with the DIBs, an evolution allowed and motivated by the increasing number of stellar surveys with high multiplex instruments. As a matter of fact, it is possible today to gather massive amounts of data, both from the point of view of the number of target stars and from the point of view of the number of DIBs simultaneously observed. This has opened the way to new types of studies, more ambitious goals, and, importantly, new potential comparisons with laboratory data. This thesis presents a large number of DIB extractions and four of these novel analyses :- Methods of extraction and search for new DIBs.- Statistical studies of the link between DIB strengths and the physical properties of their hosting clouds.- Tomographic studies of the carriers on large and small spatial scales.- Line profile extractions based on carefully selected sightlines, studies of their substructures and spatial variability and subsequent constraints on their potential molecular carriers
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Li, Shanghuo, Junzhi Wang, Zhi-Yu Zhang, Min Fang, Juan Li, Jiangshui Zhang, Junhui Fan, Qingfeng Zhu, and Fei Li. "Millimetre spectral line mapping observations towards four massive star-forming H ii regions." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/623847.
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We present spectral line mapping observations towards four massive star-forming regions Cepheus A, DR21S, S76E and G34.26+0.15 - with the IRAM 30-m telescope at the 2 and 3 mm bands. In total, 396 spectral lines from 51 molecules, one helium recombination line, 10 hydrogen recombination lines and 16 unidentified lines were detected in these four sources. An emission line of nitrosyl cyanide (ONCN, 14(0), 14-13(0), (13)) was detected in G34.26+0.15, as the first detection in massive star-forming regions. We found that c-C3H2 and NH2D show enhancement in shocked regions, as suggested by the evidence of SiO and/or SO emission. The column density and rotational temperature of CH3CN were estimated with the rotational diagram method for all four sources. Isotope abundance ratios of C-12/C-13 were derived using HC3N and its C-13 isotopologue, which were around 40 in all four massive star-forming regions and slightly lower than the local interstellar value (similar to 65). The N-14/N-15 and O-16/O-18 abundance ratios in these sources were also derived using the double isotopic method, which were slightly lower than in the local interstellar medium. Except for Cep A, the S-33/S-34 ratios in the other three targets were derived, which were similar to that in the local interstellar medium. The column density ratios of N(DCN)/N(HCN) and N( DCO+)/N(HCO+) in these sources were more than two orders of magnitude higher than the elemental [D]/[H] ratio, which is 1.5 x 10(-5). Our results show that the later stage sources, G34.26+0.15 in particular, present more molecular species than earlier stage sources. Evidence of shock activity is seen in all stages studied.
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Drabek-Maunder, Emily Rae. "A submillimetre study of nearby star formation using molecular line data." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14587.
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This thesis primarily uses submillimetre molecular line data from HARP, a heterodyne array on the James Clerk Maxwell Telescope (JCMT), to further investigate star formation in the Ophiuchus L1688 cloud. HARP was used to observe CO J = 3-2 isotopologues: 12CO, 13CO and C18O; and the dense gas tracer HCO+ J = 4-3. A method for calculating molecular line contamination in the SCUBA-2 450 and 850 μm dust continuum data was developed, which can be used to convert 12CO J =6-5and J =3-2 maps of integrated intensity (K km s−1) to molecular line flux (mJy beam−1) contaminating the continuum emission. Using HARP maps of 12CO J = 3-2, I quantified the amount of molecular line contamination found in the SCUBA-2 850 μm maps of three different regions, including NGC 1333 of Perseus and NGC 2071 and NGC 2024 of Orion B. Regions with ‘significant’ (i.e. > 20%) molecular line contamination correspond to molecular outflows. This method is now being used to remove molecular line contamination from regions with both SCUBA-2 dust continuum and HARP 12CO map coverage in the Gould Belt Legacy Survey (GBS). The Ophiuchus L1688 cloud was observed in all three CO J = 3-2 isotopologues. I carried out a molecular outflow analysis in the region on a list of 30 sources from the Spitzer ‘c2d’ survey [Evans et al., 2009]. Out of the 30 sources, 8 had confirmed bipolar outflows, 20 sources had ‘confused’ outflow detections and 2 sources did not have outflow detections. The Ophiuchus cloud was found to be gravitationally bound with the turbulent kinetic energy a factor of 7 lower than the gravitational binding energy. The high-velocity outflowing gas was found to be only 21% of the turbulence in the cloud, suggesting outflows are significant but not the dominant source of turbulence in the region. Other factors were found to influence the global high-velocity outflowing gas in addition to molecular outflows, including hot dust from nearby B-type stars, outflow remnants from less embedded sources and stellar winds from the Upper Scorpius OB association. To trace high density gas in the Ophiuchus L1688 cloud, HCO+ J = 4-3 was observed to further investigate the relationship between high column density and high density in the molecular cloud. Non-LTE codes RADEX and TORUS were used to develop density models corresponding to the HCO+ emission. The models involved both constant density and peaked density profiles. RADEX [van der Tak et al., 2007] models used a constant density model along the line-of-sight and indicated the HCO+ traced densities that were predominantly subthermally excited with den- sities ranging from 10^3–10^5 cm^−3. Line-of-sight estimates ranged from several parsecs to 90 pc, which was unrealistic for the Ophiuchus cloud. This lead to the implementation of peaked density profiles using the TORUS non-LTE radiative transfer code. Initial models used a ‘triangle’ density profile and a more complicated log-normal density probability density function (PDF) profile was subsequently implemented. Peaked density models were relatively successful at fitting the HCO+ data. Triangle models had density fits ranging from 0.2–2.0×10^6 cm^−3 and 0.1–0.3×10^6 cm^−3 for the 0.2 and 0.3 pc cloud length models re- spectively. Log-normal density models with constant-σ had peak density ranges from 0.2–1.0 ×10^5 cm^−3 and 0.6–2.0×10^5 cm^−3 for 0.2 and 0.3 pc models respectively. Similarly, log-normal models with varying-σ had lower and upper density limits corresponding to the range of FWHM velocities. Densities (lower and upper limits) ranged from 0.1–1.0 ×10^6 and 0.5–3.0 ×10^5 cm^-3 for the 0.2 and 0.3 pc models respectively. The result of the HCO+ density modelling indicated the distributions of starless, prestellar and protostellar cores do not have a preference for higher densities with respect to the rest of the cloud. This is contrary to past research suggesting the probability of finding a submillimetre core steeply rises as a function of column density (i.e. density; Belloche et al. 2011; Hatchell et al. 2005). Since the majority of sources are less embedded (i.e Class II/III), it is possible the evolutionary state of Ophiuchus is the main reason the small sample of Class 0/I protostars do not appear to have a preference for higher densities in the cloud.
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Hindson, Luke Paul. "The G305 star forming complex : a panoramic view of the environment and star formation." Thesis, University of Hertfordshire, 2012. http://hdl.handle.net/2299/9197.
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This thesis presents molecular line and radio continuum observations of the giant molecular cloud (GMC) complex known as G305. The energy input from high-mass stars in the form of powerful winds and ionising radiation is one of the primary feedback mechanisms in GMCs. This feedback is thought to play a dual role both dispersing and destroying the natal environment but also sweeping up and compressing molecular gas and potentially triggering new episodes of star formation. Despite their importance to the evolution of GMCs and galaxies as a whole, the physical processes behind the formation and evolution of high-mass stars remains poorly understood. We therefore set out to obtain wide-field observations of the ionised and molecular environment to study the impact of high-mass stars on the evolution of G305. Observations conducted with the Mopra telescope of the molecular gas traced by NH3 in the (1,1), (2,2) and (3,3) transition and CO (12CO, 13CO and C18O J = 1–0) reveals the reservoir for future star formation in G305 and allows the physical properties and kinematics of the region to be studied. We identify 15 large molecular clouds and 57 smaller molecular clumps towards G305. The physical properties of the molecular gas are consistent with G305 being amongst the most massive a vigorous star forming regions in the Galaxy. We find a total molecular gas mass of 2:5–6:5 105M indicating that there is a large reservoir for future star formation. By considering virial equilibrium within the molecular clumps we discover that only 14% of the molecular clumps in G305 are gravitationally unstable, however these clumps contain > 30% of the molecular mass in G305 suggesting there is scope for considerable future star formation. To study the ionised environment towards G305 we have obtained some of the largest and most detailed wide-area mosaics with the Australia Telescope Compact Array to date. These radio continuum observations were performed simultaneously at 5.5 and 8.8 GHz and by applying two imaging techniques we are able to resolve HII regions from the ultra-compact to classical evolutionary phase. This has allowed high-mass star formation within G305 to be traced over the extent and lifetime of the complex. We discover that more than half of the observable total ionising flux in G305 is associated with embedded high-mass star formation around the periphery of a central cavity that has been driven into the molecular gas by a cluster of optically visible massive stars. By considering the contribution of embedded and visible massive stars to the observed radio continuum we suggest that more than 45 massive stars exist within G305. Combination of these two studies and recent and ongoing star formation provides the most in depth view of G305 to date and allows the star formation history and impact of high-mass stars to be investigated. We find compelling morphological evidence that suggests triggering is responsible for at least some of the observed high-mass star formation and construct a star formation history for the region.
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Quiros, Antonio Armstrong Pereyra. "Poeira e campo magnético em regiões densas do meio interestelar." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/14/14131/tde-20022019-165047/.
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Neste trabalho estudamos a geometria do campo magnético e algumas propriedades da poeira interestelar em duas regiões do Meio Interestelar da Galáxia: a Nuvem Escura de Musca e uma parte da IRAS Vela Shell, na direção de HD62542. Empregamos a técnica da polarimetria de imagem CCD. Na primeira parte desta tese mostramos nosso aporte no aprimoramento do hardware e software do grupo de polarimetria do IAGUSP. Basicamente, um código de controle da gaveta polarimétrica do IAG foi desenvolvido e explicamos em detalhe um pacote (PCCDPACK) de redução semi-automática e análise de imagens polarimétricas para objetos pontuais criado especificamente para este fim. Na segunda parte desta tese aplicamos a técnica de polarimetria de imagem CCD para um estudo observacional em duas regiões selecionadas: a nuvem escura de musca (NEM) e a região IRAS Vela Shell (IVS) / nebulosa de Gum (NG) na direção de HD62542. Nosso interesse foi explorar a técnica polarimétrica desenvolvida para a redução e análise de campos estelares densos. O produto deste estudo foi a construção de dois catálogos polarimétricos, um para cada região, de ao redor de 2500 objetos para a NEM e quase 900 objetos para a região IVS/NG. Mostramos também como tais medidas podem ser utilizadas para mapear o campo magnético em regiões densas do meio interestelar, especificamente em nuvens escuras e frentes de ionização/shocks onde a presença de grãos de poeira é prevista. Informamos sobre a intensidade do campo magnético e das razões de energia cinética turbulenta a magnética é obtida do estudo das dispersões do ângulo de polarização dos vetores de polarização em cada uma das regiões. Paralelamente, um estudo de extinção utilizando a técnica de contagem automática de estrelas foi feito em cada uma das regiões e sua correlações com os dados polarimétricos são exploradas. Combinando as medidas polarimétricas com as de extinção, a eficiência da polarização é ) investigada assim como suas implicâncias na determinação do tipo de grãos presentes ao serem comparados com aqueles próprios do meio interestelar difuso. A análise da polarimetria na NEM mostra um limite inferior de polarização de aprox. 2% ao longo da estrutura filamentar da nuvem, com picos de polarização de 6-7% na região central. A geometria do campo magnético, como é inferida do mapa de polarização, é quase perpendicular ao filamento, sugerindo um colapso ao longo das linhas do campo. No entanto, uma análise em pequena escala angular mostra variações no ângulo de polarização de aprox. 30% ao redor do valor médio de 110º. O campo magnético estimado ao longo da nuvem se encontra dentro de uma faixa de 0.05 mgauss a o.30 mgauss. Um limite inferior para a massa da nuvem de 139 M SOL é encontrado e um grande numero de condensações foram detectadas na estrutura filamentar com uma escala típica de tamanho \'L\' aprox. 0.26pc. As correlações entre polarização e extinção sugerem que a poeira na NEM possui diferentes propriedades que as do meio interestelar difuso e que uma privilegiada visão geométrica do campo magnético pode estar presente ao longo da nuvem. O estudo da região IVS/NG permitiu estabelecer uma geometria do campo magnético que parece acompanhar, em algumas regiões, a borda da parede de emissão Halfa. No entanto, em outras regiões, parece evidente uma tendência perpendicular parede. O campo magnético estimado ao longo da frente de ionização está na faixa de 0.02 mgauss a 0.11 mgauss e a pressão magnética parece dominar a pressão turbulenta do gás em algumas regiões. Uma evidência de estruturas tipo clumpy foi detectada com limites inferiores típicos de (1-4) masas solares e uma escala de tamanho de L\' aprox. 0.47pc. A eficiência da polarização muda ao longo da frente de ionização e parece claro que em algumas regiões as propriedades da poeira diferem daquelas ) observadas no meio interestelar difuso. Um ótimo alinhamento é observado em algumas regiões o que sugere uma ótima visão geométrica do campo magnético com respeito à frente de ionização vista edge on.We have used CCD imaging polarimetry to study the geometry of the magnetic field and some properties of the interstellar dust in two regions of the Interstellar Medium of the Galaxy: the Musca Dark Cloud and a section of the IRAS Vela Shell towards HD62542. We initially describe the instrument employed with the Musca cloud, the IAG polarimeter, for which we developed control software. A very similar instrument was used at CTIO for the Vela Shell. We have also developed an IRAF software package to reduce and analyze polarimetric images in crowded fields (PCCDPACK). We next apply the technique to study two selected regions: the Musca Dark Cloud (MDC) and a section of IRAS Vela Shell (IVS). The end product is the construction of two catalogues, of approximately 2500 objects for MDC and 900 objects for IVS. For MDC, the analyses of the polarimetric data show a polarization lower limit of ~2% along the filamentary structure of the cloud, with peaks of 6-7% in the central regions. The geometry of the magnetic field is approximately perpendicular to filament, suggesting collapse along the field lines. However, when looked in detail, we detect variations in the polarization angle of ~30deg respect to the mean value of 110deg. The estimated strength of the magnetic field is in a range of 0.05-0.30 mgauss. The star count technique yields a lower limit of the total mass of the cloud of 139 solar masses. A large number of condensations are found, with a typical length scale L ~ 0.26 pc. The observed correlation between polarization and extinction suggests that the dust in MDC have different properties with respect to the dust in the diffuse Interstellar Medium. It also appears that the magnetic field along the cloud is viewed favorably so as to produce the observed polarization. The study in the section of the IVS towards HD 62542 allows us to detect a magnetic field parallel to the ionization front in sections of the cloud. However, in others regions, a perpendicular geometry is also evident. The estimated magnetic field is in the range of 0.02-0.11 mgauss and the magnetic pressure may dominate the turbulent pressure of gas in some regions. Evidence of clumpy structure is found with typical masses (1-4) solar masses and a length scale L ~ 0.47 pc. The polarization efficiency changes along the ionization front. It is clear that the properties of the dust are different of the interstellar medium in some regions. An optimum alignment of the polarization vectors is seen in some regions and it may reflect a favorable viewing geometry of the magnetic field with respect of the ionization front seeing edge on.
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Marchal, Antoine. "On the multiphase structure of the turbulent neutral interstellar medium." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS249.
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La formation des étoiles dans les galaxies est intimement liée aux processus physiques qui régissent l'évolution du milieu interstellaire. Les étoiles se forment dans les nuages moléculaires par effondrement gravitationnel de structures denses et froides, mais le processus qui mène à la formation de ces surdensités est encore relativement mal compris. Un des élément clé semble être lié à l'efficacité de la formation de nuages froids d'hydrogène neutre (HI), également appelé "Cold neutral Medium" (CNM).Plusieurs études ont visé à comprendre la production du CNM par condensation du "Warm Neutral Medium" (WNM) dans un écoulement turbulent et thermiquement instable à l'aide de simulations numériques. De façon générale, ces études indiquent la présence d'une fraction significative de la masse dans le régime instable (c'est-à-dire avec une température à mi-chemin entre les états stables CNM et WNM). Cependant, les conditions thermodynamiques du gaz restent largement inexplorées du point de vue de l'observation : pour aller plus loin, et comparer réellement avec les simulations numériques, il est nécessaire de cartographier la structure de densité des colonnes de chaque phase et d'étudier les variations spatiales de leurs champs de vitesse et de dispersion des vitesses. Par nature, cela nécessite le développement de méthodes pouvant extraire ces informations de données entièrement échantillonnées spatialement: l'émission de la raie à 21 cm.Un nouvel algorithme de décomposition en Gaussiènne, appelé ROHSA, est présenté dans cette thèse. Basée sur un processus multi-résolution, et utilisant un critère de moindres carrés non-linéaires régularisés prenant en compte simultanément la cohérence spatiale de l'émission et la nature multiphase du gaz, cette méthode nous permet d'inférer une vision spatialement cohérente des phases milieu interstellaire neutre.Une analyse détaillée est ensuite présentée sur un champ à haute latitude centré sur le pôle nord écliptique. En particulier, nous apportons de nouvelles contraintes sur les propriétés thermodynamiques du WNM, ainsi que sur les propriétés statistiques de la cascade turbulente agissant dans le fluide. Enfin, nous discutons dans quelles conditions l'instabilité thermique peut se développer dans ce milieu et converger vers la phase froide du milieu interstellaire neutre, le CNMStar formation in galaxies is strongly linked to the physical processes that govern the evolution of the interstellar medium. Stars form by gravitational collapse of dense and cold structures in molecular clouds but the process that leads to the formation of these over-densities is still unclear. One key element seems to be related to the efficiency of the formation of cold clouds of neutral hydrogen (HI) also called the Cold Neutral Medium (CNM).Several studies have aimed at understanding the production of the CNM through the condensation of the Warm Neutral Medium (WNM) in a turbulent and thermally unstable flow using numerical simulations. In general, these studies indicate the presence of a significant fraction of the mass being in the thermally unstable regime, (i.e., with a temperature mid-way between the CNM and WNM stable states). However, the thermodynamical conditions of the gas remain largely unexplored from the observational point of view.To go further, and really compare with numerical simulation that are, for now, under-constrained by observation, it is mandatory to map the column density structure of each phase and study the spatial variations of their centroid velocity and velocity dispersion. This calls for methods that can extract the information of each HI phase from fully sampled 21 cm emission data only.An original Gaussian decomposition algorithm, named ROHSA, is presented is this thesis. Based on a multi-resolution process from coarse to fine grid, and using a regularized non-linear least-square criterion to take into account simultaneously the spatial coherence of the emission and the multiphase nature of the gas, this method allows us to infer a spatially coherent vision of the three-phase neutral ISM.A detailed analysis is then presented on a high latitude HI field centred on the North Ecliptic Pole. In particular we provide new constraints on the thermodynamical properties of the WNM, and the statistical properties of the turbulent cascade acting in the fluid. Finally, we discuss under which condition the condensation mode of the thermal instability can grow in this medium and converge toward the cold phase of the neutral ISM, the CNM
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Stanimirovic, Snezana, University of Western Sydney, and Centre for Astronomy. "The complex nature of the ISM in the SMC." THESIS_XXXX_CFA_Stanimirovic_S.xml, 1999. http://handle.uws.edu.au:8081/1959.7/516.
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This thesis presents the results of a combination of new observations with the Parkes telescope of neutral hydrogen (HI) in the Small Magellanic Cloud (SMC) with an Australia Telescope Compact Array aperture synthesis mosaic. The data are used to study the HI distribution and mass, the velocity field and rotation curve of the SMC, as well as to probe the 3-D structure of the SMC. A kinematic study of the HI data reveals the existence of three supergiant shells which were previously undetectable in the ATCA data alone. The HI spatial power spectrum has been investigated over a range of contiguous scale sizes wider than those previously achieved in any other galaxy. This thesis also demonstrates that the infrared data obtained with the Infrared Astronomical Satellite for the SMC can be successfully reconstructed with much higher resolution using the Pyramid Maximum Entropy algorithm. The new infrared (IR) data are used to study the integrated IR spectrum, the dust temperature and dust column density in the SMC. The high resolution HI and IR data enable an investigation of the spatial correlation of dust and gas and the assumption of the dust and gas being well-mixed in the ISM. The spatial power spectrum of the dust column density shows that, as with the HI power spectrum, there is no preferred scale size for dust clouds. The remarkable similarity of the spatial power spectra for the HI and dust column density distributions suggests a unique hierarchical structure organisation for the ISM in the SMC. Such an organisation is likely to be governed by the Kolmogorov type turbulence and could be described by fractal nature with the volume fractal dimension of 2.4.Doctor of Philosophy (PhD)
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Habibi, Farhang. "Searching for missing baryons through scintillation." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00625486.
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Cool molecular hydrogen H2 may be the ultimate possible constituent to the Milky-Way missing baryon. We describe a new way to search for such transparent matter in the Galactic disc and halo, through the diffractive and refractive effects on the light of background stars. By simulating the phase delay induced by a turbulent medium, we computed the corresponding illumination pattern on the earth for an extended source and a given passband. We show that in favorable cases, the light of a background star can be subjected to stochastic fluctuations of the order of a few percent at a characteristic time scale of a few minutes. We have searched for scintillation induced by molecular gas in visible dark nebulae as well as by hypothetical halo clumpuscules of cool molecular hydrogen (H2_He) during two nights, using the NTT telescope and the IR SOFI detector. Amongst a few thousands of monitored stars, we found one light-curve that is compatible with a strong scintillation effect through a turbulent structure in the B68 nebula. Because no candidate were found toward the SMC, we are able to establish upper limits on the contribution of gas clumpuscules to the Galactic halo mass. We show that the short time-scale monitoring of a few 10^6 star _ hour in the visible band with a >4 m telescope and a fast readout camera should allow one to interestingly quantify or constrain the contribution of turbulent molecular gas to the Galactic halo.
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Саенко, В. И. "Технологические решения использования сервисов IBM CLOUD BLUEMIX." Thesis, ДРУКАРНЯ МАДРИД, 2017. http://openarchive.nure.ua/handle/document/9463.
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Gryc, Václav. "Integrace ITSM aplikací prostřednictvím webových služeb a IBM cloudu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442350.
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This thesis is focused on developing software with ITSM integration features. The aim of this work is to design a suitable software architecture for integration applications in a cloud environment. Due to the use of the solution for many customers, emphasis is placed on sustainability and reusability. After wide technology analysis, a web application has been created that is fully configurable to meet a wide range of customer needs. It is decided to use the Node.js environment and the Loopback 4 framework for application development. To ensure lower costs for the operation of cloud resources, compared to competing technologies such as Java. The entire system is deployed in IBM Cloud. The resulting application is put into production by IBM.
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Jouin, Lionel. "Network Service Mesh Solving Cloud Native IMS Networking Needs." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-425220.
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With the growing demand for mobile networks and specially IPMultimedia subsystem (IMS), new cloud native orchestration tools providing more flexibility and efficiency start to be used within telecommunication companies in order to improve the robustness and the reliability of these systems. However, Kubernetes, the most used among cloud native orchestration tools does not fulfill completelyall the needs and use cases in terms of networking the telecommunication industry meets. Network Service Mesh (NSM), a new Cloud Native Computing Foundation (CNCF) project, aiming to address complex networking use cases in Kubernetes might solve the different issues IP multimedia subsystem face. Detailed designs and implementations using Network Service Mesh coupled with diverse networking technologies are shown in this thesis with the objectiveof solving the networking IP multimedia subsystem requirements (e.g. the NAT issue and the secondary network). In addition, an analysis and an evaluation of Network Service Mesh is given together with a presentation of the ability of this new project to bring solutions toIP Multimedia subsystem based on a cloud native technology.
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Rings, Thomas. "Assessing and Improving Interoperability of Distributed Systems." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://hdl.handle.net/11858/00-1735-0000-000D-FB51-1.
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Interoperabilität von verteilten Systemen ist eine Grundlage für die Entwicklung von neuen und innovativen Geschäftslösungen. Sie erlaubt es existierende Dienste, die auf verschiedenen Systemen angeboten werden, so miteinander zu verknüpfen, dass neue oder erweiterte Dienste zur Verfügung gestellt werden können. Außerdem kann durch diese Integration die Zuverlässigkeit von Diensten erhöht werden. Das Erreichen und Bewerten von Interoperabilität stellt jedoch eine finanzielle und zeitliche Herausforderung dar. Zur Sicherstellung und Bewertung von Interoperabilität werden systematische Methoden benötigt.
Um systematisch Interoperabilität von Systemen erreichen und bewerten zu können, wurde im Rahmen der vorliegenden Arbeit ein Prozess zur Verbesserung und Beurteilung von Interoperabilität (IAI) entwickelt. Der IAI-Prozess beinhaltet drei Phasen und kann die Interoperabilität von verteilten, homogenen und auch heterogenen Systemen bewerten und verbessern. Die Bewertung erfolgt dabei durch Interoperabilitätstests, die manuell oder automatisiert ausgeführt werden können. Für die Automatisierung von Interoperabilitätstests wird eine neue Methodik vorgestellt, die einen Entwicklungsprozess für automatisierte Interoperabilitätstestsysteme beinhaltet. Die vorgestellte Methodik erleichtert die formale und systematische Bewertung der Interoperabilität von verteilten Systemen. Im Vergleich zur manuellen Prüfung von Interoperabilität gewährleistet die hier vorgestellte Methodik eine höhere Testabdeckung, eine konsistente Testdurchführung und wiederholbare Interoperabilitätstests.
Die praktische Anwendbarkeit des IAI-Prozesses und der Methodik für automatisierte Interoperabilitätstests wird durch drei Fallstudien belegt. In der ersten Fallstudie werden Prozess und Methodik für Internet Protocol Multimedia Subsystem (IMS) Netzwerke instanziiert. Die Interoperabilität von IMS-Netzwerken wurde bisher nur manuell getestet. In der zweiten und dritten Fallstudie wird der IAI-Prozess zur Beurteilung und Verbesserung der Interoperabilität von Grid- und Cloud-Systemen angewendet. Die Bewertung und Verbesserung dieser Interoperabilität ist eine Herausforderung, da Grid- und Cloud-Systeme im Gegensatz zu IMS-Netzwerken heterogen sind. Im Rahmen der Fallstudien werden Möglichkeiten für Integrations- und Interoperabilitätslösungen von Grid- und Infrastructure as a Service (IaaS) Cloud-Systemen sowie von Grid- und Platform as a Service (PaaS) Cloud-Systemen aufgezeigt. Die vorgestellten Lösungen sind in der Literatur bisher nicht dokumentiert worden. Sie ermöglichen die komplementäre Nutzung von Grid- und Cloud-Systemen, eine vereinfachte Migration von Grid-Anwendungen in ein Cloud-System sowie eine effiziente Ressourcennutzung. Die Interoperabilitätslösungen werden mit Hilfe des IAI-Prozesses bewertet. Die Durchführung der Tests für Grid-IaaS-Cloud-Systeme erfolgte manuell. Die Interoperabilität von Grid-PaaS-Cloud-Systemen wird mit Hilfe der Methodik für automatisierte Interoperabilitätstests bewertet. Interoperabilitätstests und deren Beurteilung wurden bisher in der Grid- und Cloud-Community nicht diskutiert, obwohl sie eine Basis für die Entwicklung von standardisierten Schnittstellen zum Erreichen von Interoperabilität zwischen Grid- und Cloud-Systemen bieten.
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Umair, Muhammad. "Performance Evaluation and Elastic Scaling of an IP Multimedia Subsystem Implemented in a Cloud." Thesis, KTH, Radio Systems Laboratory (RS Lab), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-124578.
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Network (NGN) technology which enables telecommunication operators to provide multimedia services over fixed and mobile networks. All of the IMS infrastructure protocols work over IP which makes IMS easy to deploy on a cloud platform. The purpose of this thesis is to analysis a novel technique of “cloudifying” the OpenIMS core infrastructure. The primary goal of running OpenIMS in the cloud is to enable a highly available and horizontally scalable Home Subscriber Server (HSS). The resulting database should offer high availability, and high scalability. The prototype developed in this thesis project demonstrates a virtualized OpenIMS core with an integrated horizontal scalable HSS. Functional and performance measurements of the system under test (i.e. the virtualized OpenIMS core with horizontally scalable HSS) were conducted. The results of this testing include an analysis of benchmarking scenarios, the CPU utilization, and the available memory of the virtual machines. Based on these results we conclude that it is both feasible and desirable to deploy the OpenIMS core in a cloud.IP Multimedia Subsystem (IMS) ramverk är ett Next Generation Network (NGN) teknik som möjliggör teleoperatörer att erbjuda multimediatjänster via fasta och mobila nät. Alla IMS infrastruktur protokollen fungera över IP som gör IMS lätt att distribuera på ett moln plattform. Syftet med denna uppsats är att analysera en ny teknik för “cloudifying” den OpenIMS kärninfrastrukturen. Det primära målet med att köra OpenIMS i molnet är att möjliggöra en hög tillgänglighet och horisontellt skalbara Server Home Subscriber (HSS). Den resulterande databasen bör erbjuda hög tillgänglighet och hög skalbarhet. Prototypen utvecklas i detta examensarbete visar en virtualiserad OpenIMS kärna med en integrerad horisontell skalbar HSS. Funktionella och prestanda mätningar av systemet under test (dvs. virtualiserade OpenIMS kärnan med horisontellt skalbara HSS) genomfördes. Resultaten av detta test inkluderar en analys av benchmarking scenarier, CPU-användning, och tillgängligt minne för de virtuella maskinerna. Baserat på dessa resultat drar vi slutsatsen att det är både möjligt och önskvärt att distribuera OpenIMS kärnan i ett moln.
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Eriksson, Patrik, and Philip Wester. "Granskning av examensarbetesrapporter med IBM Watson molntjänster." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232057.
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Cloud services are one of the fast expanding fields of today. Companies such as Amazon, Google, Microsoft and IBM offer these cloud services in various forms. As this field progresses, the natural question occurs ”What can you do with the technology today?”. The technology offers scalability for hardware usage and user demands, that is attractive to developers and companies. This thesis tries to examine the applicability of cloud services, by combining it with the question: ”Is it possible to make an automated thesis examiner?” By narrowing down the services to IBM Watson web services, this thesis main question reads ”Is it possible to make an automated thesis examiner using IBM Watson?”. Hence the goal of this thesis was to create an automated thesis examiner. The project used a modified version of Bunge’s technological research method. Where amongst the first steps, a definition of an software thesis examiner for student theses was created. Then an empirical study of the Watson services, that seemed relevant from the literature study, proceeded. These empirical studies allowed a deeper understanding about the services’ practices and boundaries. From these implications and the definition of a software thesis examiner for student theses, an idea of how to build and implement an automated thesis examiner was created. Most of IBM Watson’s services were thoroughly evaluated, except for the service Machine Learning, that should have been studied further if the time resources would not have been depleted. This project found the Watson web services useful in many cases but did not find a service that was well suited for thesis examination. Although the goal was not reached, this thesis researched the Watson web services and can be used to improve understanding of its applicability, and for future implementations that face the provided definition.Molntjänster är ett av de områden som utvecklas snabbast idag. Företag såsom Amazon, Google, Microsoft och IBM tillhandahåller dessa tjänster i flera former. Allteftersom utvecklingen tar fart, uppstår den naturliga frågan ”Vad kan man göra med den här tekniken idag?”. Tekniken erbjuder en skalbarhet mot använd hårdvara och antalet användare, som är attraktiv för utvecklare och företag. Det här examensarbetet försöker svara på hur molntjänster kan användas genom att kombinera det med frågan ”Är det möjligt att skapa en automatiserad examensarbetesrapportsgranskare?”. Genom att avgränsa undersökningen till IBM Watson molntjänster försöker arbetet huvudsakligen svara på huvudfrågan ”Är det möjligt att skapa en automatiserad examensarbetesrapportsgranskare med Watson molntjänster?”. Därmed var målet med arbetet att skapa en automatiserad examensarbetesrapportsgranskare. Projektet följde en modifierad version av Bunge’s teknologiska undersökningsmetod, där det första steget var att skapa en definition för en mjukvaruexamensarbetesrapportsgranskare följt av en utredning av de Watson molntjänster som ansågs relevanta från litteratur studien. Dessa undersöktes sedan vidare i empirisk studie. Genom de empiriska studierna skapades förståelse för tjänsternas tillämpligheter och begränsningar, för att kunna kartlägga hur de kan användas i en automatiserad examensarbetsrapportsgranskare. De flesta tjänster behandlades grundligt, förutom Machine Learning, som skulle behövt vidare undersökning om inte tidsresurserna tog slut. Projektet visar på att Watson molntjänster är användbara men inte perfekt anpassade för att granska examensarbetesrapporter. Även om inte målet uppnåddes, undersöktes Watson molntjänster, vilket kan ge förståelse för deras användbarhet och framtida implementationer för att möta den skapade definitionen.
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Gustafsson, Alex, and Carl Stensson. "The Performance of Post-Quantum Key Encapsulation Mechanisms : A Study on Consumer, Cloud and Mainframe Hardware." Thesis, Blekinge Tekniska Högskola, Institutionen för datavetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-21849.
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Background. People use the Internet for communication, work, online banking and more. Public-key cryptography enables this use to be secure by providing confidentiality and trust online. Though these algorithms may be secure from attacks from classical computers, future quantum computers may break them using Shor’s algorithm. Post-quantum algorithms are therefore being developed to mitigate this issue. The National Institute of Standards and Technology (NIST) has started a standardization process for these algorithms. Objectives. In this work, we analyze what specialized features applicable for post-quantum algorithms are available in the mainframe architecture IBM Z. Furthermore, we study the performance of these algorithms on various hardware in order to understand what techniques may increase their performance. Methods. We apply a literature study to identify the performance characteristics of post-quantum algorithms as well as what features of IBM Z may accommodate and accelerate these. We further apply an experimental study to analyze the practical performance of the two prominent finalists NTRU and Classic McEliece on consumer, cloud and mainframe hardware. Results. IBM Z was found to be able to accelerate several key symmetric primitives such as SHA-3 and AES via the Central Processor Assist for Cryptographic Functions (CPACF). Though the available Hardware Security Modules (HSMs) did not support any of the studied algorithms, they were found to be able to accelerate them via a Field-Programmable Gate Array (FPGA). Based on our experimental study, we found that computers with support for the Advanced Vector Extensions (AVX) were able to significantly accelerate the execution of post-quantum algorithms. Lastly, we identified that vector extensions, Application-Specific Integrated Circuits (ASICs) and FPGAs are key techniques for accelerating these algorithms. Conclusions. When considering the readiness of hardware for the transition to post-quantum algorithms, we find that the proposed algorithms do not perform nearly as well as classical algorithms. Though the algorithms are likely to improve until the post-quantum transition occurs, improved hardware support via faster vector instructions, increased cache sizes and the addition of polynomial instructions may significantly help reduce the impact of the transition.Bakgrund. Människor använder internet för bland annat kommunikation, arbete och bankärenden. Asymmetrisk kryptering möjliggör att detta sker säkert genom att erbjuda sekretess och tillit online. Även om dessa algoritmer förväntas vara säkra från attacker med klassiska datorer, riskerar framtida kvantdatorer att knäcka dem med Shors algoritm. Därför utvecklas kvantsäkra krypton för att mitigera detta problem. National Institute of Standards and Technology (NIST) har påbörjat en standardiseringsprocess för dessa algoritmer. Syfte. I detta arbete analyserar vi vilka specialiserade funktioner för kvantsäkra algoritmer som finns i stordator-arkitekturen IBM Z. Vidare studerar vi prestandan av dessa algoritmer på olika hårdvara för att förstå vilka tekniker som kan öka deras prestanda. Metod. Vi utför en litteraturstudie för att identifiera vad som är karaktäristiskt för kvantsäkra algoritmers prestanda samt vilka funktioner i IBM Z som kan möta och accelerera dessa. Vidare applicerar vi en experimentell studie för att analysera den praktiska prestandan av de två framträdande finalisterna NTRU och Classic McEliece på konsument-, moln- och stordatormiljöer. Resultat. Vi fann att IBM Z kunde accelerera flera centrala symmetriska primitiver så som SHA-3 och AES via en hjälpprocessor för kryptografiska funktioner (CPACF). Även om befintliga hårdvarusäkerhetsmoduler inte stödde några av de undersökta algoritmerna, fann vi att de kan accelerera dem via en på-plats-programmerbar grind-matris (FPGA). Baserat på vår experimentella studie, fann vi att datorer med stöd för avancerade vektorfunktioner (AVX) möjlggjorde en signifikant acceleration av kvantsäkra algoritmer. Slutligen identifierade vi att vektorfunktioner, applikationsspecifika integrerade kretsar (ASICs) och FPGAs är centrala tekniker som kan nyttjas för att accelerera dessa algortmer. Slutsatser. Gällande beredskapen hos hårdvara för en övergång till kvantsäkra krypton, finner vi att de föreslagna algoritmerna inte presterar närmelsevis lika bra som klassiska algoritmer. Trots att det är sannolikt att de kvantsäkra kryptona fortsatt förbättras innan övergången sker, kan förbättrat hårdvarustöd för snabbare vektorfunktioner, ökade cachestorlekar och tillägget av polynomoperationer signifikant bidra till att minska påverkan av övergången till kvantsäkra krypton.
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Kodam, Triveni. "A roadmap for ensuring SAML authentication using Identity server for on- premises and cloud." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-73988.
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Cloud-based applications especially SaaS applications have become essential for startups and various sized businesses. Adapting to these web applications helps to reduce operational costs and further provide flexibility in accessing individual data of the users. On the other hand, usage of these cloud services poses security-related issues such as authentication, authorization, web application security. Additionally, if the on-premises application is moved to the cloud then the traditional Identity solutions will not work, which affects the user authentication. This thesis considers ‘Authentication’ as one of the main security issues to be addressed. Thus, a new federated Identity and Access Management (IAM) system needs to be realized, which can be used for both on-premises and cloud to authenticate users correctly and securely. To meet the described challenges within the cybersecurity domain, this thesis focuses on two aspects of IT Security: 1) SaaS application rely on IAM; 2) IAM for securely authenticating users. This thesis work addresses both these aspects in two parts. First, by developing a SaaS web application that includes an authentication module with the support of the SAML 2.0 standard protocol. Second, the use of open source WSO2 IAM server for authenticating the users securely. To implement a SaaS application, a play framework PAC4j security library is used to support SAML SSO profile for authenticating users. The profile provides functionality for the two scenarios: SAML- Service provider and SAML- Identity Provider. The developed SaaS application acts as a service provider while WSO2 identity server acts as an Identity Provider. The SAML request-response authentication workflow between these providers are verified to prove the correctness and security of user login information. The research presented in this thesis is helpful for startup companies, that are initially looking to minimize application cost that works both on-premises and cloud without compromising on the security of user’s login information.
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Decorte, Andrea. "Analisi e sviluppo di strumenti performance-aware per la migrazione cloud enterprise." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3314/.
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Wagle, Gururaj. "MODELING IONIZED AND MOLECULAR REGIONS OF THE INTERSTELLAR MEDIUM USING THE SPECTRAL SYNTHESIS CODE CLOUDY." UKnowledge, 2014. http://uknowledge.uky.edu/physastron_etds/23.
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The focus of this dissertation is to study the star-forming regions of the interstellar medium (ISM), using two very diverse environments: the Polaris Flare, high-galactic latitude, cirrus cloud complex consisting of several starless molecular cores with no nearby hot stars; and the Orion Nebula, which is the closest massive star forming region. The two environments provide a wide range of physical conditions.
It is commonly assumed that the Herschel far-infrared (FIR) fluxes are a good measure of column density, hence, mass of interstellar clouds. We find that the FIR fluxes are insensitive to the column density if AV ≳ 2. The Polaris Flare has been previously observed with the Herschel Space Telescope. We use Cloudy to model the molecular cores in MCLD 123.5+24.9 of the Polaris Flare. The Polaris Flare, 150 pc distant, is well within the Galactic disc. There are no nearby hot stars. Therefore, the cloud is illuminated by an external far-ultraviolet (FUV) flux (6-13 eV) due to the galactic background interstellar radiation field (ISRF). The dust grains absorb the incident FUV flux and re-emit in the FIR continuum emission. We use detailed grain models that suggest that the grains in dense regions are coated with water and ammonia ices, increasing their sizes and opacities. In our models, dust temperatures decline rapidly into the cloud. Therefore, the cloud interiors contribute very little additional FIR flux, leading to an underestimate of inferred column density. Cloudy also predicts mm-wavelength molecular lines for comparison with published observations. Our models suggest that at low temperatures (≲ 20K), molecules freeze-out on grain surfaces, and desorption by cosmic rays becomes important. Our models of inter-core regions in MCLD 123.5+24.9 significantly under predict molecular line strengths unless the gas is clumped into high-density regions.
We use Cloudy to construct a detailed model of the Orion H ii region. This study is an improvement over the work of Baldwin et al. 1991 with the new atomic data and stellar atmosphere models, and a wealth of archival observational data obtained over last two decades. We use collisionally excited lines to determine the elemental abundance of the region.
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Mortazavi, Maryam. "Network Testing Evolution in Telco Cloud for VoLTE Services." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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Today Network Function Virtualization (NFV) is one of the fields in telecommunications that is developing and growing at the fastest pace as a fundamental element in the Telco equipment marketplace. Network Functions that have traditionally been deployed over proprietary hardware now are remarkably decoupling of that, taking the functions and moving them into the software and putting them into the common hardware. There are a lot of elements which are moving to software such as IMS, Mobile Core, PE Router, etc. IMS is just one of them, and even within IMS architecture there are significant elements include the CSCF, the HSS, the SBC, the MRF, voice application servers which are starting to move to NFV and each of these elements considered to be a virtual network function (VNF). Migration to the virtual IMS bring the operators the benefits of lower cost regarding CAPEX, fast scaling services, introducing fast new network services, reducing complexity, operational efficiency, etc. In the future, testing network elements will be more necessary since the aim is to implement as software as an on-demand service similar in networks for some aspects such as protocol compliance performance. Moreover, load balancing can join with Software Defined Networking (SDN) to bring the possibility to vary routing of the packets in an NFV enabled network, but routing is not mandatory to be by the software. This dissertation presents the testing on the general NFV and, particularly it study the testing on a network element of virtualized IMS that is Call Session Control Function (CSCF).
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Siddiqui, Muhammad Anas. "Cloud Computing : Evaluation, as a platform for Scania Architecture." Thesis, Mittuniversitetet, Institutionen för informationsteknologi och medier, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-18896.
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Cloud computing has been given a great deal of attention during recent years. Almost all the technology market leaders and leading hosting service providers (like IBM, Microsoft and Verizon) have entered into the Cloud market as Cloud Providers. Cloud computing promises to provide highly available, secure, low cost, agile and highly scalable solution to the consumers. Scania is a global company and one of the world’s leading heavy vehicle manufacturers with 35,000+ employees. All the large organizations such as Scania, aim to constantly update themselves with the latest technology in order to meet their business requirements but, these organizations must always be convinced that there is a strong reason(s) to implement new technology. This research provides the method and criteria in relation to initiating Cloud computing. A number of Scania’s specific business requirements that it is possible to map to the Cloud are addressed in this thesis. The methodology of research is split in two parts. Firstly, the identification of business cases at Scania and their requirements with the Cloud and Secondly, the evaluation and comparison of the functionalities and capabilities of different vendors. The accumulated data is then compared and suitable vendors, according to those business requirements are suggested. This thesis also shares the experience of moving on premise applications to the Cloud. These are Scania specific applications which are currently being hosted in-house. The research also addresses the possibilities of portability between the Cloud providers. Although there is no standardization in relation to Cloud computing, some initiatives such as OpenStack are available and its current position and some application and data migration tools are also discussed. The thesis concludes with a general discussion, recommendations in relation to adapting Cloud computing and selecting the Cloud provider. This recommendation applies to every organization including Scania.
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Esposito, Federico. "Interpreting the CO SLED with starburst and AGN feedback." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14102/.
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Il presente lavoro di tesi si basa sullo spettro rotazionale del monossido di carbonio (CO) di 4 galassie locali, e lo interpreta sulla base della densità del mezzo molecolare responsabile dell'emissione e del tipo di sorgente radiativa che eccita tale molecola. Due
tipi di sorgente sono stati considerati: popolazioni stellari giovani (modello PDR) e AGN (modello XDR). La CO SLED è stata ricavata principalmente da osservazioni del satellite infrarosso Herschel. Per le 4 galassie studiate (IRAS F05189-2524, NGC 34, NGC 4418 e NGC 6240) sono state prodotte le mappe spazialmente risolte dell'emissione del CO delle osservazioni ALMA. Questo ci ha permesso di stabilire un'area fisica all'interno delle galassie entro cui il gas molecolare è presente ed emette radiazione. Con il codice di sintesi spettrale Cloudy (Ferland et al. 2013) abbiamo preparato due griglie di simulazioni per i modelli PDR e XDR. I risultati di queste simulazioni sono stati combinati nei modelli finali, composti di due PDRs o di una PDR ed una XDR; la CO SLED simulata è stata quindi comparata a quella osservata tramite una procedura di minimizzazione. I risultati ottenuti sono i seguenti: per due galassie (NGC 34 e NGC 6240) il modello di best-fit è quello a doppia PDR, per le altre due (IRAS F05189-2524 e NGC 4418) è il PDR + XDR. I risultati riguardanti NGC 4418 vanno considerati con cautela in quanto il codice di minimizzazione non è riuscito a trovare un buon fit della CO SLED. I 4 oggetti selezionati non sembrano in generale dominati dalla presenza delle XDRs per quanto riguarda l'eccitazione del gas molecolare, da cui si conclude che il contributo dell'AGN (osservato in tutte tranne che in NGC 4418) nel determinare la fisica del gas interstellare non è dominante. Dai modelli di best-fit sono state ricavate le masse di gas, e da queste sono stati calcolati i fattori di conversione del CO e i depletion times. Tali grandezze sono state confrontate con galassie presenti in letteratura.
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Kolbe, Isa [Verfasser]. "The interplay of central and peripheral circadian clocks in white adipose function and metabolic homeostasis / Isa Kolbe." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2018. http://d-nb.info/1153844974/34.
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Hurych, Tomáš. "Návrh kontrol systému řízení přístupů a správy identit." Master's thesis, Vysoká škola ekonomická v Praze, 2014. http://www.nusl.cz/ntk/nusl-203961.
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Nowadays, the focus of IT security is increasingly concerned with the safety of the identities of employees and users of information systems. This phenomenon is even more compounded by the rapidly growing number of cloud services. This thesis briefly explains the basic concepts of access control and identity management. The thesis also contains identification of requirements and implications of risks on identity and access management system. The main objective is the general design of controls for identity and access management system, which has been designed to match legislative requirements, regulations, standards or frameworks commonly used in enterprise IT practice. For describing of the controls, mainly Cobit framework and IT Assurance Guide were used. The thesis also contains a suggestion how to adjust proposed controls in a cloud environment.
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Surampudi, Roop Sai. "Developing Random Compaction Strategy for Apache Cassandra database and Evaluating performance of the strategy." Thesis, Blekinge Tekniska Högskola, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-21246.
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Introduction: Nowadays, the data generated by global communication systems is enormously increasing. There is a need by Telecommunication Industries to monitor and manage this data generation efficiently. Apache Cassandra is a NoSQL database that manages any formatted data and a massive amount of data flow efficiently. Aim: This project is focused on developing a new random compaction strategy and evaluating this random compaction strategy's performance. In this study, limitations of generic compaction strategies Size Tiered Compaction Strategy and Leveled Compaction Strategy will be investigated. A new random compaction strategy will be developed to address the limitations of the generic Compaction Strategies. Important performance metrics required for the evaluation of the strategy will be studied. Method: In this study, a grey literature review is done to understand the working of Apache Cassandra, different compaction strategies' APIs. A random compaction strategy is developed in two phases of development. A testing environment is created consisting of a 4-node cluster and a simulator. Evaluated the performance by stress-testing the cluster using different workloads. Conclusions: A stable RCS artifact is developed. This artifact also includes the support of generating random threshold from any user-defined distribution. Currently, only Uniform, Geometric, and Poisson distributions are supported. The RCS-Uniform's performance is found to be better than both STCS and LCS. The RCS-Poisson's performance is found to be not better than both STCS and LCS. The RCS-Geometric's performance is found to be better than STCS.
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Bartík, Branislav. "Využití virtualizace v podnikovém prostředí." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2016. http://www.nusl.cz/ntk/nusl-241481.
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Diplomová práca sa zaoberá návrhom riešenia pre fiktívnu spoločnosť XYZ s.r.o., ako ušetriť náklady vybudovaním výukového prostredia pre jej zamestnancov za účelom rozvíjať ich zručnosti a skúsenosti v danom obore. Toto riešenie môže byť taktiež použité zamestnancami a študentami univerzít, aby si mohli otestovať podnikový softvér pre výukové účely. Autor zdôrazňuje výhody používania Cloud Computingu a otvoreného softvéru, ako aj využitie technológie Docker kontajnerov v kombinácii s komerčným softvérom ako je napr. IBM WebSphere Application Server.
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Charalampidis, Vasileios. "Real-Time Monitoring System of Sedentary Behavior with Android Wear and Cloud Computing : An office case study." Thesis, KTH, Skolan för teknik och hälsa (STH), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210017.
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Nowadays, prolonged sitting among office workers is a widespread problem, which is highly related to several health problems. Many proposals have been reported and evaluated to address this issue. However, motivating and engaging workers to change health behavior to a healthier working life is still a challenge. In this project, a specific application has been deployed for real-time monitoring and alerting office workers for prolonged sitting. The proposed system consists of three distinct parts: The first one is an android smartwatch, which was used to collect sensor data e.g., accelerometer and gyro data, with a custom android wear app. The second one is an android application, which was developed to act as a gateway for receiving the smartwatch’s data and sending them to IBM Bluemix cloud with MQTT protocol. The final part is a Node-Red cloud application, which was deployed for storing, analyzing and processing of the sensor data for activity detection i.e., sitting or walking/standing. The main purpose of the last one was to return relevant feedback to the user, while combining elements from gaming contexts (gamification methods), for motivating and engaging office workers to a healthier behavior. The system was firstly tested for defining appropriate accelerometer thresholds to five participants (control group), and then evaluated with five different participants (treatment group), in order to analyze its reliability for prolonged sitting detection. The results showed a good precession for the detection. No confusing between sitting and walking/standing was noticed. Communication, storage and analysis of the data was successfully done, while the push notifications to the participants, for alerting or rewarding them, were always accurate and delivered on time. Every useful information was presented to the user to a web-based dashboard accessed through a smartphone, tablet or a PC. The proposed system can easily be implemented at a real-life scenario with office workers. Certainly, there is a lot space for improvement, considering mostly the type of data registered at the system, the method for sitting detection, and the user interface for presenting relevant information.Numera är förlängt sittande bland kontorsarbetare ett utbrett problem som är väldigt relaterat till flera hälsoproblem. Många förslag har rapporterats och utvärderas för att ta itu med denna fråga. Tydligen är det fortfarande en utmaning att motivera och engagera arbetstagare för att förändra deras hälsobeteende till hälsosammare arbetsliv. I detta projekt har en särskild applikation använts för realtidsövervakning och varnar kontorsarbetare för förlängt sittande. Det föreslagna systemet består av tre olika delar: Den första är en android smartwatch, som användes för att samla sensordata t.ex. accelerometer och gyrodata, med en anpassad android wear app. Den andra är en en androidapplikation som fungerade som en gateway för att ta emot smartwatchens data och skickar datan till IBM Bluemix-Cloud med MQTT-protokollet. Den sista delen är en Node-RED Cloud-Applikation som användes för lagring, analysering och behandling av sensordata för aktivitetsdetektering. Detta innebär sittande eller gå/stående med det huvudsakliga ändamålet att returnera relevant återkoppling till användaren, samtidigt som man kombinerar element från spelkontekster (gamification metoder), för att motivera och engagera arbetarna till ett hälsosammare beteende. Systemet testades först för att definiera lämpliga accelerometertrösklar till fem deltagare (kontroll grupp) och utvärderades sedan med fem olika deltagare (behandingsgrupp) för att analysera dess tillförlitlighet för långvarig sittdetektering. Resultaten visade en bra precession för detektionen. Ingen förvirring mellan att sitta och gå / stående märktes. Kommunikation, lagring och analys av data gjordes framgångsrikt, medan push-meddelandena till deltagarna, för att varna eller belöna dem, var alltid korrekta och levererade i tid. All användbar information presenterades för användaren på en webbaserad dashboard som nås via en smartphone surfplatta eller en dator. Det föreslagna systemet kan enkelt implementeras i ett verkligt scenario med kontorsarbetare. Visst finns det mycket utrymme för förbättring om man tänker på majoriteten av data som registrerats i systemet, metoden för sittande detektion och användargränssnittet för presentering av relevant information.
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Boraie, Alexander. "Efficient parallel installation of software collections on a PaaS." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-83353.
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This master thesis analyses and investigates how to speed up the deployment of a suite of services to a Platform as a Service. The project use IBM’s Cloud Pak for Applications together with Red Hats OpenShift to provide insights on important factors that influences the deployment process. In this thesis, a modification was done on the installer such that the deployment instructions were sent in parallel instead of sequentially. Except for the parallel suggestion, this thesis also investigates different options on how constraints could be applied to the CPU and what the consequences are. At the end of this report, the reader will also see how the deployment times are affected by cluster scaling. An implementation of the parallel deployment showed that the installation time of Cloud Pak for Applications could be decreased. It was also shown that the CPU was not utilized fully and that there exists significant CPU saturation during the deployment. The evaluation of the scaling analysis showed that, in regards of this thesis, it is more beneficial both timewise and cost-wise to scale horizontally rather than vertically.
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Ceccarelli, Viviana. "Data Logger: cognitive analysis." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
This work is developed on the basis of data related to the driving experience of a motorcycle in its aspects. The drivers point of view is supported by the analysis of the data produced by the sensors and collected by a data logger.
The two aspects, human and technical, have been standardized from a technological point of view so that they can be analysed and related to each other. The need for cognitive algorithms has led to the use of Cloud PaaS and SaaS technologies: these have allowed the rapid realization of the project without technical constraints.
All of this is part of the specific requirements set up by Ducati's PQ department whose aim is to evaluate the response on the road of new models or technological improvements before the production in series.
The final solution for the proposed data collection was realized using different services of IBM Cloud: a web app was built using a virtual assistant based on cognitive technology that guides the user in the collection of information and verifies its consistency.
The application required backend services such as an Object Storage and a Database, to store multimedia content and data respectively. Concerning the front-end instead, the automation of the collection mode has led to the introduction of an acquisition process that was easier to use and always available in terms of reachability and flexibility.
The information related to the data collected by the logger did not need to be mediated by further technological components.
The technology used for the analytical part is Microsoft's Power BI. The integration with the two data sources is plug and play: the data are automatically updated.
Several types of analysis have been done and range from reconstruction and correlation of measurements on a route to text analysis of driver sensations.
In addition to this, a PCB has been developed to solve an issue related to the data logger itself.
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Maraczek, Patrik. "Návrh a realizace systému zpracování dat z environmentálních čidel v prostředí IoT." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417775.
Full textAbstract:
The master’s thesis deal with design and realization of measuring station, which process data from environmental sensors in IoT environment. Thesis includes research of sensors, cloud services for IoT, microcontrollers and environmental data available online. Thesis contains detailed procedure for realization of designed system, including code description for microcontrollers STM32W55 and STM32 B-L475E-IOT01A2 Discovery kit, configuration of IBM Watson IoT Platform cloud service and procedure for correct programming of Node-RED application responsible for logic of whole system. Source code, which might be used for simple implementation of designed system, is attached to the master’s thesis.
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David, Östling. "IBMs stordators framtid i en molnbaserad IT värld : Kommer IBMs stordator att överleva ytterligare ettparadigmskifte eller har den spelat ut sin roll?" Thesis, Karlstads universitet, Handelshögskolan, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-43408.
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IT analytiker har många gånger gett IBMs stordator en dödsdom. Redan 1991 skrev denerkände kritikern Stewart Alsop, dåvarande chefredaktör på InfoWorld att den sista stordatornskulle tas ur bruk den 15 mars 1996. Det visade sig att detta uttalande var felaktigt, vilketStewart Alsop även erkände i InfoWorld bara dagar innan hans förutsägelse skulle ha infallit.När vi nu går in i ytterligare ett paradigmskifte i och med att många tjänster går över tillmolnet, ställer jag i denna uppsats frågan om IBMs stordator har en framtid i en molnbaseradIT värld, och hur den i så fall ser ut. Syftet är att genom litteraturstudier och intervjuer undersöka om IBMs stordator kan överlevaytterligare en genomomgripande teknikrevolution eller om den har spelat ut sin roll.Undersökningen mynnar ut i slutsatserna att IBMs stordator har en stark position i dagsläget,framförallt inom bank och finanssektorn d.v.s. inom branscher med speciellt höga kravbeträffande tillgänglighet, skalbarhet, och säkerhet. Sannolikt har stordatorn en viktig roll attspela även för framtidens satsningar i molnet. IBM erbjuder redan idag molnlösningar sominkluderar mainframes, och det framgick även i de intervjuer som gjordes på IBM, att de seren ljus framtid för IBMs stordatorer. De menar att IBM inte bara följer med, utan även är medoch leder utvecklingen inom molntjänster, och att det är främst för de öppna standarderna somLinux och Unix som IBM kommer att ha den ljusaste framtiden. Det faktum att IBM varje årinvesterar miljardbelopp i utvecklingen av sina stordatorer talar också sitt tydliga språk, d.v.s.att IBM fullt ut verkar tro på att stordatorn har en viktig roll att spela i den molnbaserade ITvärldsom just nu växer fram
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Slavětínský, Radek. "Analýza cloudových řešení Business Intelligence pro SME." Master's thesis, Vysoká škola ekonomická v Praze, 2017. http://www.nusl.cz/ntk/nusl-358847.
Full textAbstract:
The thesis is focused on the analysis of presently offered products supporting Business Intelligence (BI) which are affordable for small and medium-sized enterprises (SMEs). Current BI solutions available to SMEs are mostly offered via Cloud computing, specifically in the form of Software as a Service (SaaS) as it requires low initial acquisition costs. The objectives of this thesis are to analyse the work in applications for BI in cloud that can be used by SMEs and to analyse in detail the comparison the worldwide extended reporting tools distributed as SaaS in the lower price category. The theoretical part provides a description of the Cloud computing and the BI system. In the practical part are selected following products: IBM Watson Analytics, Qlik Sense Cloud, Zoho Reports, Tableau Public and Microsoft Power BI. Practical testing of these applications was based on evaluation of the selected metrics with weights calculated by using the Fuller's triangle. Analyses and the information form the basis for comparison of selected applications. The contribution of this thesis is in discovering the strengths and weaknesses of these BI solutions. The output of this thesis can be used as a source for the selection of BI applications for SMEs.