Hopping in Disordered Media: A Model Glass Former and A Hopping Model

Two models involving particles moving by ``hopping'' in disordered media are investigated: I) A model glass-forming liquid is investigated by molecular dynamics under (pseudo-) equilibrium conditions. ``Standard'' results such as mean square displacements, intermediate scattering functions, etc. are reported. At low temperatures hopping is present in the system as indicated by a secondary peak in the distribution of particle displacements during a time interval 't'. The dynamics of the model is analyzed in terms of its potential energy landscape (potential energy as function of the 3N particle coordinates), and we present direct numerical evidence for a 30 years old picture of the dynamics at sufficiently low temperatures. Transitions between local potential energy minima in configuration space are found to involve particles moving in a cooperative string-like manner. II) In the symmetric hopping model particles are moving on a lattice by doing thermally activated hopping over energy barriers connecting nearest neighbor sites. This model is analyzed in the extreme disorder limit (i.e. low temperatures) using the Velocity Auto Correlation (VAC) method. The VAC method is developed in this thesis and has the advantage over previous methods, that it can calculate a diffusive regime in finite samples using periodic boundary conditions. Numerical results using the VAC method are compared to three analytical approximations, including the Diffusion Cluster Approximation (DCA), which is found to give excellent agrement with the numerical results.Comment: Ph.D. thesis, 101 pages, 52 figure

Solution of nonlinear algebraic equations characteristic of filter circuits Summary technical report

Digital computer program developed for solving nonlinear algebraic equations characteristic of filter circuit

Crossover to Potential Energy Landscape Dominated Dynamics in a Model Glass-forming Liquid

An equilibrated model glass-forming liquid is studied by mapping successive configurations produced by molecular dynamics simulation onto a time series of inherent structures (local minima in the potential energy). Using this ``inherent dynamics'' approach we find direct numerical evidence for the long held view that below a crossover temperature, $T_x$, the liquid's dynamics can be separated into (i) vibrations around inherent structures and (ii) transitions between inherent structures (M. Goldstein, J. Chem. Phys. {\bf 51}, 3728 (1969)), i.e., the dynamics become ``dominated'' by the potential energy landscape. In agreement with previous proposals, we find that $T_x$ is within the vicinity of the mode-coupling critical temperature $T_c$. We further find that at the lowest temperature simulated (close to $T_x$), transitions between inherent structures involve cooperative, string like rearrangements of groups of particles moving distances substantially smaller than the average interparticle distance.Comment: Expanded from 4 to 7 page

B640: An Evaluation of the Distribution of Trucked Pulpwood in East-Central Maine

The movement of pulpwood from forest to market can be a critical and costly activity. Many factors influence this movement and contribute to its complexity. In 1963, a study was undertaken to quantitatively describe the distribution patterns of trucked pulpwood for a representative area of the state of Maine.https://digitalcommons.library.umaine.edu/aes_bulletin/1074/thumbnail.jp

Students\u27 Perceptions of STEM Learning After Participating in a Summer Informal Learning Experience

Background: Informal learning environments increase students’ interest in STEM (e.g., Mohr‐Schroeder et al. School Sci Math 114: 291–301, 2014) and increase the chances a student will pursue a STEM career (Kitchen et al. Sci Educ 102: 529–547, 2018). The purpose of this study was to examine the impact of an informal STEM summer learning experience on student participants, to gain in-depth perspectives about how they felt this experience prepared them for their in-school mathematics and science classes as well as how it influenced their perception of STEM learning. Students’ attitudes and perceptions toward STEM are affected by their motivation, experience, and self-efficacy (Brown et al. J STEM Educ Innov Res 17: 27, 2016). The academic and social experiences students’ have are also important. Traditionally, formal learning is taught in a solitary form (Martin Science Education 88: S71–S82, 2004), while, informal learning is brimming with chances to connect and intermingle with peers (Denson et al. J STEM Educ: Innovations and Research 16: 11, 2015). Results: Informal learning environments increase students’ interest in STEM (e.g., Mohr‐Schroeder et al. School Sci Math 114: 291–301, 2014) and increase the chances a student will pursue a STEM career (Kitchen et al. Sci Educ 102: 529–547, 2018). The purpose of this study was to examine the impact of an informal STEM summer learning experience on student participants, to gain in-depth perspectives about how they felt this experience prepared them for their in-school mathematics and science classes as well as how it influenced their perception of STEM learning. Students’ attitudes and perceptions toward STEM are affected by their motivation, experience, and self-efficacy (Brown et al. J STEM Educ Innov Res 17: 27, 2016). The academic and social experiences students’ have are also important. Traditionally, formal learning is taught in a solitary form (Martin Science Education 88: S71–S82, 2004), while, informal learning is brimming with chances to connect and intermingle with peers (Denson et al. J STEM Educ: Innovations and Research 16: 11, 2015). Conclusions: By using authentic STEM workplaces, the STEM summer learning experience fostered a learning environment that extended and deepened STEM content learning while providing opportunity and access to content, settings, and materials that most middle level students otherwise would not have access to. Students also acknowledged the access they received to hands-on activities in authentic STEM settings and the opportunities they received to interact with STEM professionals were important components of the summer informal learning experience

Equity-Oriented Conceptual Framework for K-12 STEM Literacy

We introduce a conceptual framework of K-12 STEM literacy that rightfully and intentionally positions each and every student, particularly minoritized groups, as belonging in STEM. In order to conceptualize the equity-based framework of STEM literacy, we conducted a systematic review of literature related to STEM literacy, which includes empirical studies that contribute to STEM literacy. The literature on the siloed literacies within STEM (i.e., science, technology, engineering, and mathematics literacy) also contributed to formulate the necessity of and what it means to develop STEM literacy. The Equity-Oriented STEM Literacy Framework illuminates the complexities of disrupting the status quo and rightfully transforming integrated STEM education in ways that provide equitable opportunities and access to all learners. The Equity-Oriented STEM Literacy Framework is a research-based, equity and access-focused framework that will guide research, inform practice, and provide a lens for the field that will ensure each and every student, especially minoritized students, develop, and are developing STEM literacy