Investigation of non-metallic inclusions in steel using hot stage Scanning electron microscope

Abstract. Non metallic inclusions in steel are very small non metallic particles trapped inside steel matrix that can have either positive or negative effects on properties of steel. Thus identifying and tracking the behaviour of these inclusions is vital for development of new manufacturing methods and refinement of old ones. Steel is the most used metal in the world and often used as a structural element in buildings, vehicles and tools etc. Therefore improving its properties, such as decreasing weight and improving strength, can have notable positive impact on performance and environmental effects in aforementioned use cases. In this thesis well known non-metallic inclusions were studied by using a hot stage scanning electron microscope and the respective results are discussed. The objective of this experiment was to see if there are any noticeable changes in either size or shape of multicomponent inclusions and if there is any diffusion between NMIs and the steel matrix. At the same time it was evaluated if the hot stage SEM even is suitable for analysing inlcusions in steel. Hot stage scanning electron microscope was found to be a suitable method for carrying out relatively quick and generalized analysis of non metallic inclusions in steel. Poor resolution and accuracy of EDS, lack of proper depth information and the fact that inclusions have to be exposed limit it's capabilities in more thorough local analysis of inclusions or parts of them. In terms of inclusions analysed in this thesis, it was found that CaS has a tendency to dissolve in to the surrounding steel matrix in multicomponent inclusions at temperatures around 900 °C. Some dissolving was also visible in couple of single component CaS and MnS inclusions. Phase changes in surrounding steel matrix were noted to partially prevent any interaction between inclusions and surrounding steel

The History of Fort Kearney

Thesis Presented to the Faculty of The Graduate College of the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Arts Department of History History of Fort Kearny, Nebraska. Traces the history of the fort, both the original at Table Creek and the later one on the Platte River. Also discusses some of the initial 1920s conversion of the fort into a historic site.https://openspaces.unk.edu/spec-coll/1000/thumbnail.jp

The effect of surface temperature and Reynolds number on the leeward heat-transfer for a shuttle orbiter

The effect of windward surface temperature on the heat transfer to the leeward surface of the shuttle orbiter was investigated. Heat-transfer distributions, surface-pressure distributions, and schlieren photographs were obtained for an 0.01-scale model of the 37-0 shuttle orbiter at angles-of-attack of 30 deg and of 40 deg. Similar data were obtained for a fuselage-only configuration at angles-of-attack of 30 deg and of 90 deg. Data were obtained for various Mach numbers, Reynolds numbers, and surface temperatures

Dynamical evidence for a strong tidal interaction between the Milky Way and its satellite, Leo V

We present a chemodynamical analysis of the Leo~V dwarf galaxy, based on Keck II DEIMOS spectra of 8 member stars. We find a systemic velocity for the system of $\langle v_r\rangle = 170.9^{+ 2.1}_{-1.9}$kms$^{-1}$, and barely resolve a velocity dispersion for the system, with $\sigma_{vr} = 2.3^{+3.2}_{-1.6}$kms$^{-1}$, consistent with previous studies of Leo~V. The poorly resolved dispersion means we are unable to adequately constrain the dark matter content of Leo~V. We find an average metallicity for the dwarf of [Fe/H]$= -2.48\pm0.21$, and measure a significant spread in the iron abundance of its member stars, with $-3.1\le$[Fe/H]$\le-1.9$ dex, which cleanly identifies Leo~V as a dwarf galaxy that has been able to self-enrich its stellar population through extended star formation. Owing to the tentative photometric evidence for tidal substructure around Leo~V, we also investigate whether there is any evidence for tidal stripping or shocking of the system within its dynamics. We measure a significant velocity gradient across the system, of $\frac{{\rm d}v}{{\rm d}\chi} = -4.1^{+2.8}_{-2.6}$kms$^{-1}$ per arcmin (or $\frac{{\rm d}v}{{\rm d}\chi} = -71.9^{+50.8}_{-45.6}$kms$^{-1}$~kpc$^{-1}$), which points almost directly toward the Galactic centre. We argue that Leo~V is likely a dwarf on the brink of dissolution, having just barely survived a past encounter with the centre of the Milky Way.Comment: 14 pages, 12 figures, accepted for publication in MNRAS. Updated to include minor revisions from referee proces

Temporal changes in temperature may suggest microhabitat shifts in larval spongillafly Climacia areolaris Hagen (Neuroptera: Sisyridae) abundance and density in a temperate freshwater lake

Abiotic factors such as temperature and depth are known to affect aquatic insect populations and are thought to be major variables that directly impact how communities are assembled and populations distributed. The purpose of this study was to examine the role of temperature and depth in structuring C. areolaris populations within a temperate freshwater quarry. Larval densities among individual sponges at different depths were determined over six months in a Pennsylvania quarry. Sponges from four depths (7.0 - 8.0 m; 8.1 - 9.0 m; 9.1 - 10.0 m and 10.1 - 12.0) were collected once per month (n = 3) using SCUBA. Temperature data were collected at four depths (n = 3 samples/depth). Larval densities significantly varied over the study period, but were not significantly different between depths on any date. Mean total larval density was significantly higher in March, April and May compared to dates later in the season. This result followed an inverse pattern where there was a significant effect of date on temperature, but no difference between depths. There was a detectable change in relative abundance of the sisyrid populations among the depths; the two shallowest depth ranges collectively represented \u3e50% of the population during March and April, but were \u3c 50% throughout the rest of the summer. There was also a significant negative relationship of larval density with temperature. Few studies have documented the role of abiotic factors such as depth and temperature on the spatial and temporal structuring of spongillafly microdistribution within a quarry environment

A Keck/DEIMOS spectroscopic survey of faint Galactic satellites: searching for the least massive dwarf galaxies

[abridged] We present the results of a spectroscopic survey of the recently discovered faint Milky Way satellites Boo, UMaI, UMaII and Wil1. Using the DEIMOS spectrograph on Keck, we have obtained samples that contain from 15 to 85 probable members of these satellites for which we derive radial velocities precise to a few km/s down to i~21-22. About half of these stars are observed with a high enough S/N to estimate their metallicity to within \pm0.2 dex. From this dataset, we show that UMaII is the only object that does not show a clear radial velocity peak. However, the measured systemic radial velocity (v_r=115\pm5 km/s) is in good agreement with recent simulations in which this object is the progenitor of the recently discovered Orphan Stream. The three other satellites show velocity dispersions that make them highly dark-matter dominated systems. In particular the Willman 1 object is not a globular cluster given its metallicity scatter over -2.0<[Fe/H]<-1.0 and is therefore almost certainly a dwarf galaxy or dwarf galaxy remnant. We measure a radial velocity dispersion of only 4.3_{-1.3}^{+2.3} km/s around a systemic velocity of -12.3\pm2.3 km/s which implies a mass-to-light ratio of ~700 and a total mass of ~5x10^5 Msun for this satellite, making it the least massive satellite galaxy known to date. Such a low mass could mean that the 10^7 Msun limit that had until now never been crossed for Milky Way and Andromeda satellite galaxies may only be an observational limit and that fainter, less massive systems exist within the Local Group. However, more modeling and an extended search for potential extra-tidal stars are required to rule out the possibility that these systems have not been significantly heated by tidal interaction.Comment: 24 pages, 11 figures, MNRAS accepte

The Dual Origin of Stellar Halos. II. Chemical Abundances as Tracers of Formation History

This paper is a computational study of the formation of the stellar halos of Milky Way-massed galaxies, and the fingerprint of the formation history imprinted on the chemical abundances of those stars. --author-supplied descriptio