A digital physics method for two phase flow

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1997.Includes bibliographical references (leaves 246-253).by David M. Freed.Ph.D

Development and validation of an astronomy self-efficacy instrument for understanding and doing

This paper presents a new astronomy self-efficacy instrument, composed of two factors; one relating to learning astronomy content, which we call astronomy personal self-efficacy, and the other relating to the use of astronomical instrumentation, specifically the use of remote robotic telescopes for data collection. The latter is referred to as the astronomy instrumental self-efficacy factor. The instrument has been tested for reliability and construct validity. Reliability testing showed that factor 1 had a Cronbach\u27s α of 0.901 and factor 2 had a Cronbach\u27s α of 0.937. Construct validity was established by computing one-way analyses of variances, with the p value suitably protected, using independent variables peripherally related to the constructs. These analyses demonstrate that both scales possess high construct validity. The development of this astronomy specific instrument is an important step in evaluating self-efficacy as a precursor to investigating the construct of science identity in the field of astronomy

Confirmatory factor analysis of two self-efficacy scales for astronomy understanding and robotic telescope use

This paper presents the results of a confirmatory factor analysis on two self-efficacy scales designed to probe the self-efficacy of college-level introductory astronomy (Astro-101) students (n=15181) from 22 institutions across the United States of America and Canada. The students undertook a course based on similar curriculum materials, which involved students using robotic telescopes to support their learning of astronomical concepts covered in the traditional Astro-101 courses. Previous research by the authors using these self-efficacy scales within a pre-/post-test approach showed both high reliabilities and very high construct validities. However, the scale purporting to measure students\u27 self-efficacy in relation to their use of the astronomical instrumentation associated with online robotic telescopes was particularly skewed and required further investigation. This current study builds on the previous work and shows how a slight adjustment of the survey items presents an improved and robust scale for measuring self-efficacy

The Self-Dual String and Anomalies in the M5-brane

We study the anomalies of a charge $Q_2$ self-dual string solution in the Coulomb branch of $Q_5$ M5-branes. Cancellation of these anomalies allows us to determine the anomaly of the zero-modes on the self-dual string and their scaling with $Q_2$ and $Q_5$. The dimensional reduction of the five-brane anomalous couplings then lead to certain anomalous couplings for D-branes.Comment: 13 pages, Harvmac, refs adde

Deformation Associated with Ghost Craters and Basins in Volcanic Smooth Plains on Mercury: Strain Analysis and Implications for Plains Evolution

Since its insertion into orbit about Mercury in March 2011, the MESSENGER spacecraft has imaged most previously unseen regions of the planet in unprecedented detail, revealing extensive regions of contiguous smooth plains at high northern latitudes and surrounding the Caloris basin. These smooth plains, thought to be emplaced by flood volcanism, are populated with several hundred ghost craters and basins, nearly to completely buried impact features having rims for which the surface expressions are now primarily rings of deformational landforms. Associated with some ghost craters are interior groups of graben displaying mostly polygonal patterns. The origin of these graben is not yet fully understood, but comparison with numerical models suggests that the majority of such features are the result of stresses from local thermal contraction. In this paper, we highlight a previously unreported category of ghost craters, quantify extensional strains across graben-bearing ghost craters, and make use of graben geometries to gain insights into the subsurface geology of smooth plains areas. In particular, the style and mechanisms of graben development imply that flooding of impact craters and basins led to substantial pooling of lavas, to thicknesses of ∼1.5 km. In addition, surface strains derived from groups of graben are generally in agreement with theoretically and numerically derived strains for thermal contraction

Understanding and influencing agency and behavior change - Work Package 5 Activity Guidance, CGIAR Initiative on Agroecology

This document provides guidance on two activities conducted under Work Package 5 if the CGIAR Initiative on Agroecology in 2022: 1) a theories of change review and 2) a participatory timeline of agency and behaviour change in agroecological transformation. The guidance includes research methods for Activities 1 and 2 as well as data analysis and writeup for Activity 1

Polymer flooding – Does Microscopic Displacement Efficiency Matter?

Polymer flooding is an enhanced oil recovery (EOR) technique that aims to enhance the stability of the flood front in order to increase sweep efficiency and thereby increase hydrocarbon recovery. Polymer flooding studies often focus on large-scale sweep efficiency and neglect the impact of the pore-scale displacement efficiency of the multi-phase flow. This work explores the pore-scale behavior of water vs polymer flooding, and examines the impact of rock surface wettability on the microscopic displacement efficiency using digital rock physics. In this study, a micro-CT image of a sandstone rock sample was numerically simulated for both water and polymer flooding under oil-wet and water-wet conditions. All simulations were performed at a capillary number of 1E-5, corresponding to a capillary dominated flow regime. Results of the four two-phase flow imbibition simulations are analyzed with respect to displacement character, water phase break-through, viscous/capillary fingering, and trapped oil. In the water-wet scenario, differences between water flood and polymer flood are small, with the flood front giving a piston-like displacement and breakthrough occurring at about 0.4 pore volume (PV) for both types of injected fluid. On the other hand, for the oil-wet scenario, water flood and polymer flood show significant differences. In the water flood, fingering occurs and much of the oil is bypassed early on, whereas the polymer flood displaces more oil and thereby provides better microscopic sweep efficiency throughout the flood and especially around breakthrough. Overall the results for this rock sample indicate that water flood and polymer flood provide similar recovery for a water-wet condition, while the reduced mobility ratio of polymer flood gives significantly improved recovery for an oil-wet condition by avoiding the onset of microscopic (pore-scale) fingering that occurs in the water flood. This study suggests that depending on the rock-fluid conditions, the use of polymer can impact microscopic sweep efficiency, in addition to the well-known effect on macroscopic sweep behavior.La inyección de polímeros es una técnica de recobro mejorado de petróleo (EOR) que tiene como objetivo mejorar la estabilidad del frente de inyección para aumentar la eficiencia del desplazamiento de hidrocarburos y, por lo tanto, incrementar el factor de recobro. Lo estudios de inyección de polímeros a menudo se centran en la eficiencia del desplazamiento a gran escala e ignoran el impacto de los mecanismos de desplazamiento a escala microscópica, y rara vez evalúan la variabilidad de parámetros de flujo multifásico en el medio poroso. Este trabajo explora el comportamiento del agua contra la inyección de polímeros en el medio poroso, y examina el impacto de la humectabilidad de la superficie de la roca en la eficiencia de desplazamiento microscópico, utilizando tomografía computarizada de rayos X en muestras de roca. En este estudio, se simuló numéricamente una imagen de microtomografía computarizada de una muestra de roca arenisca, para un proceso de inyección de agua y polímeros en condiciones de mojabilidad al aceite y al agua. Todas las simulaciones se realizaron a un número capilar de 1E-5, correspondiente a un régimen de flujo dominado por fuerzas capilares y que es típico del flujo en yacimientos de hidrocarburos. Los resultados de las cuatro simulaciones de imbibición de flujo de dos fases se analizan con respecto al carácter desplazante, el avance de la fase acuosa, la digitación viscosa y capilar, y el aceite atrapado. En el escenario de mojabilidad al agua, las diferencias entre la inyección de agua y la inyección de polímeros son pequeñas, dado que el frente de inyección produce un  desplazamiento en forma de pistón y un avance que se produce a aproximadamente 0,4 volúmenes porosos para ambos tipos de fluido inyectado. Por otro lado, para el escenario de mojabilidad al petróleo, la inyección de agua y la inyección de polímeros muestran diferencias significativas. En la inyección de agua, se produce digitación y gran parte del petróleo se pasa por alto al principio; mientras que la inyección de polímeros desplaza más aceite y, por lo tanto, proporciona una mejor eficiencia de desplazamiento microscópico durante la inyección, especialmente alrededor de la ruptura. En general, los resultados para esta muestra de roca indican que la inyección de agua y la inyección de polímeros proporcionan un efecto de recobro similar para una condición de mojabilidad al agua, mientras que la relación de movilidad reducida de la inyección de polímeros proporciona un efecto de recobro significativamente mejorado para una condición de mojabilidad al aceite, al evitar la aparición de digitación microscópica (a escala de poro) que se produce en la inyección de agua. Este estudio sugiere que, dependiendo de las condiciones roca-fluido, el uso del polímero puede impactar la eficiencia de desplazamiento microscópico, además del efecto conocido sobre el comportamiento del desplazamiento macroscópico

Geometric phases in adiabatic Floquet theory, abelian gerbes and Cheon's anholonomy

We study the geometric phase phenomenon in the context of the adiabatic Floquet theory (the so-called the $(t,t')$ Floquet theory). A double integration appears in the geometric phase formula because of the presence of two time variables within the theory. We show that the geometric phases are then identified with horizontal lifts of surfaces in an abelian gerbe with connection, rather than with horizontal lifts of curves in an abelian principal bundle. This higher degree in the geometric phase gauge theory is related to the appearance of changes in the Floquet blocks at the transitions between two local charts of the parameter manifold. We present the physical example of a kicked two-level system where these changes are involved via a Cheon's anholonomy. In this context, the analogy between the usual geometric phase theory and the classical field theory also provides an analogy with the classical string theory.Comment: This new version presents a more complete geometric structure which is topologically non trivia