A Formal Preparation for Object-Oriented Query Optimisation

This paper describes work that is in progress on a formalised preparation to object-oriented query optimisation. Such preparation is conducive to the development of optimisation strategies. As an example of a formal preparation, this paper presents a formalised object algebra, a suggested optimisation method and an implementation of an algebraic converter suitable for DAPLEX

The Interactions of Small Molecules on Astrochemically Relevant Surfaces

The known Universe is composed of 99.9% hydrogen and helium. The remaining 0.1 % constitutes the abundance of the rest of the elements. Despite their low abundance relative to the lighter elements, the reactions of these heavier elements account for the complexity of species found in space. In particular, more than 200 complex organic species have been detected in the interstellar medium. They, along with carbonaceous and silicate dust grains, accumulate together in interstellar clouds. This thesis focusses on the reactions taking place within dense interstellar dust clouds, where the inner core is shielded from radiation emitted by nearby stellar objects by a dense, opaque outer layer of gas and dust. Within the cores of these dense clouds, molecular lifetimes are extended which allows for the formation of complex molecules through further reactions. The species observed within the interstellar medium can be formed via ion-neutral reactions in the gas-phase. However, for many molecules, the observed abundance cannot be accounted for by gas-phase chemistry alone. Therefore, reactions must also be occurring on the cold surfaces of the interstellar dust grains. This thesis will focus on the reactions taking place on these grains, presenting investigations into the interactions with, and reactions of, various species upon astrochemically relevant surfaces. The investigation into the reaction of acrolein with atomic oxygen on a graphitic surface is discussed in Chapter 4. Multilayer doses of both species were co-dosed onto a graphite substrate held at temperatures ranging from 20 K to 140 K. A product with m/z 72 is observed for this reaction, suggesting the addition of oxygen across the double bond of the organic molecule: C3H4O2. The kinetics of this reaction were modelled to gain a deeper understanding of the mechanisms occurring on the cold surface. Specifically, the contribution of the two prototypical surface mechanisms, Langmuir-Hinshelwood and Eley-Rideal mechanisms, was assessed at each surface temperature. Additionally, the desorption characteristics of various astrochemically relevant molecules are outlined in Chapter 5. The behaviour of each species on a graphite surface was investigated and compared to the desorption characteristics previously investigated in the literature. The behaviour of the species observed in our desorption experiments is in good agreement with the behaviour observed in previous studies. The cohesion between our data and interactions observed previously, validates our experimental technique as a method to model the interactions of molecules under conditions similar to those in the ISM. In Chapter 6 the desorption characteristics of molecular oxygen, acrolein and carbon dioxide from an amorphous carbonaceous surface are investigated. The amorphous surface is composed of porous, broken fullerene-like cage structures. Through analysis of the desorption spectra of the gases, it was found that each molecule had significantly larger binding energies to this amorphous surface than previously observed on graphite. This is consistent with previous studies into the desorption characteristics of various gases from the surface of single walled carbon nanotubes (SWCNTs) by Ulbricht et al. where the gas molecules showed enhanced binding to the SWCNTs compared to graphite surfaces. The implications of the discovery of these higher energy binding sites to astrochemistry is discussed. Finally, in Chapter 7, results concerning the reaction of atomic oxygen with propene on a different amorphous carbonaceous surface are presented. The new surface is hydrogenated and consists of a large proportion of sp3 hybridised carbon. Interestingly, the expected product, showing the addition of oxygen across the double bond of the propene was not observed for the reaction on this surface. On the other hand, a product with m/z 90 was detected, suggesting the addition of ozone across the double bond to form a product with the general formula C3H6O3. The ozonolysis of an alkene is a well-known reaction in gas-phase chemistry but has not yet been observed under astrochemically relevant conditions. Additionally, in the gas phase, the C3H6O3 product is known to undergo a rearrangement via the Criegee mechanism before breaking down into various oxygen-containing molecules, such as aldehydes, ketones, carboxylic acids and alcohols. If this mechanism can occur on the surfaces of interstellar dust grains it could help to account for the rich variety of complex organic molecules observed in the ISM

Prevalence and Trends of Depression among Cyberbullied Adolescents - Youth Risk Behavior Survey, United States, 2011 – 2019

The difference in depression between non-cyberbullied and cyberbullied youth is not well understood. To describe the prevalence and trends in depression among cyberbullied adolescents. Using cross-sectional, nationally-representative data from the YRBS 2011 - 2019, we estimated the prevalence and trends of depression across the total years and within cyberbullied groups that include biological sex and race and ethnicity among adolescents. The results indicated the prevalence of depression was higher among those that were cyberbullied. Within the cyberbullied groups the total trend was higher than the non-cyberbullied, females had a higher prevalence of depression than males, and Hispanics had a higher prevalence of depression than blacks. Further, the results showed the trends for cyberbullied, males, females, whites, and blacks had significant linear increases, but Hispanics remained stable. Further, the non-cyberbullied trend was quadratic where there was no change from 2011-2015, but an increase occurred between 2015-2019. Depression is high among adolescents. It appears to be increasing among individuals that are cyberbullied, with the exception of Hispanics. These results are discussed with programming recommendations

Metal Inert Gas (MIG) Welding of ASTM A500 Grade B Steel Pipes: Infrared Thermal Imaging and Analysis

In this investigation, welding of circular pipes is undertaken. An experimental setup was designed and built to observe the welding process and gather temperature isotherms under different welding conditions. Thermal images of welding of ASTM A500 Grade B steel pipes are collected using an infrared camera. An analytical solution is used to calculate the temperature isotherms for comparison with the experimental data. The analytical approach, developed by Komanduri and Hou, uses Jaegers moving heat source method, is extended to calculate spot temperature data in pipe welding to determine the temperature profiles under various welding conditions. The analytical and experimental temperature isotherms were compared. Some differences in the temperature distributions produced by the analytical and experimental results were observed. They include the geometry and magnitude of the temperature distributions. An attempt has been made to explain for these differences.Engineering and Technology Managemen

A Survey of the Prior Programming Experience of Undergraduate Computing and Engineering Students in Ireland

It has become apparent that increasing numbers of students arriving into undergraduate computing and engineering degree programmes in Irish 3rd-level institutions have prior experience of computer programming. As the extent of this prior exposure as well as its nature, origins, and usefulness is not known beyond anecdotal evidence, an annual survey of prior programming experience of freshman undergraduates who study programming as part of their degree has been designed and administered. This paper reports on the first two years of this survey in 2015 and 2016. It found that around one third had some prior experience of programming with nearly half of that group reporting a reasonable level of fluency in one or more languages. The authors expect that the effect of proposed changes to primary and 2nd-level curricula alongside the increasing popularity of informal programming clubs will be increasingly felt in coming years and therefore plan to continue and extend the survey in order to clarify the effect of such developments. The results should be of interest to 3rd-level educators in the planning of curriculum and teaching practice

Working Partnerships, Partnerships Working

Involvement in community partnerships at Virginia Commonwealth University has its roots in the institution\u27s history. The Medical College of Virginia, founded in1838, and the Richmond Professional Institute, founded in 1917, both sought to extend knowledge into the community to change peoples\u27 lives for the better. Today, the VCU campuses are even more entwined with the City of Richmond -- physically, and increasingly so as a partner in the economic and social challenges and opportunities facing the City

A novel method to include the free surface in a CFD model of jet injection into partially-baffled mixing vessels

International audienceA novel methodology that can be used to perform simulations of fluid jet injection into a mixing vessel with a deformed free surface is presented and validated. The idea is to first use a two-fluid model to determine the location and shape of the free surface, and then results from the simulation are used to generate a single-phase model that has the same free surface shape. Example simulations are performed using ANSYS CFX for a pilot-scale partially-baffled vessel. Application of the methodology in the study of reaction quenching is presented but it is believed that this methodology has many other possible applications involving fluid or solid injection