arXiv subjects

Melissa Morris

Publications and source records attributed to Melissa Morris.

3 recordsLinked to original sources

arXiv2026

The Landscape of Undergraduate Astronomy and Astrophysics Degree Requirements

In this document we summarize the results of a survey of undergraduate degree-granting programs conducted by the 2024-2025 American Astronomical Society Education Committee's Subcommittee on UndeRgraduate and Graduate Education (SURGE). Individuals from 78 institutions completed the survey, representing approximately 1000 majors annually and a majority of undergraduate Astronomy and Astrophysics degree-granting institutions. Information collected from participants include: degree names, degree types, course requirements, elective course options, and learning goals. Our report presents 9 key findings and 10 recommendations, and these are summarized in the preamble to the report. The recommendations are directed primarily to degree-granting departments and the American Astronomical Society, as the principal relevant professional organization, though we earnestly invite all members of the Astronomy and Astrophysics community to contribute to a broader discussion about these findings and recommendations. Appendix A of the report contains detailed descriptions of survey data analyses. Appendices B and C contain recommended undergraduate course requirements and learning goals, respectively. Our survey results show clearly that there is not currently community consensus about what knowledge and competencies an undergraduate Astronomy or Astrophysics degree should instill. This lack of cohesion is a problem for our community, as it dilutes the significance and interpretability of the credential for employers and graduate schools. We view this report as just the beginning of an important dialog, and we look forward to engaging with the Astronomy and Astrophysics community about our findings and recommendations through our feedback form at bit.ly/49c4FYb.

physics.ed-ph↗

arXiv2017

A New Continuum Formulation for Materials--Part I. The Equations of Motion for a Single-Component Fluid

The continuum equations of fluid mechanics are rederived with the intention of keeping certain mechanical and thermodynamic concepts separate. A new "mechanical" mass density is created to be used in computing inertial quantities, whereas the actual mass density is treated as a thermodynamic variable. A new set of balance laws is proposed, including a mass balance equation with a non-convective flux. The basic principles of irreversible thermodynamics are used to obtain linear constitutive equations that are expansions of--not only the usual affinities involving gradients of temperature and velocity--but also the gradient of the chemical potential. Transport coefficients are then chosen based on an elementary diffusion model, which yields simple constitutive laws featuring just two transport parameters: one for the longitudinal part of the motion and one for the rotational part. The resulting formulation differs from the Navier-Stokes-Fourier equations of fluid motion. In order to highlight key similarities and differences between the two approaches, several examples in fluid mechanics are treated in part II, including sound propagation, light scattering, steady-state shock waves, thermophoresis, and Poiseuille flow.

physics.flu-dyn↗

arXiv2017

A New Continuum Formulation for Materials--Part II. Some Applications in Fluid Mechanics

In part I of this paper, I proposed a new set of equations, which I refer to as the M(D,η)-formulation and which differs from the Navier-Stokes-Fourier description of fluid motion. Here, I use these equations to model several classic examples in fluid mechanics, with the intention of providing a general sense of comparison between the two approaches. A few broad facts emerge: (1) it is as simple--or in most cases, much simpler--to find solutions with the M(D,η)-formulation, (2) for some examples, there is not much of a difference in predictions--in fact, for sound propagation and for examples in which there is only a rotational part of the velocity, my transport coefficients D and η are chosen to match Navier-Stokes-Fourier solutions in the appropriate regimes, (3) there are, however, examples in which pronounced differences in predictions appear, such as light scattering, and (4) there arise, moreover, important conceptual differences, as seen in examples like sound at a non-infinite impedance boundary, thermophoresis, and gravity's effect on the atmosphere.

physics.flu-dyn↗