Rheological Measurements in Liquid-Solid Flows

The behavior of liquid-solid flows varies greatly depending on fluid viscosity, particle and liquid inertia, and collisions between particles. While particle collisions in inviscid fluids can be understood statistically, liquid-solid flows are complicated by the fluid viscosity and forces acting on the particles (e.g. lift, drag, added mass). These flows were first studied by Bagnold, whose investigation found two different flow regimes: a macro-viscous regime where the shear and pressure forces are proportional to the shear rate, and a grain-inertia regime defined by a dependance on the square of the shear rate [1, 2]. The scaling relations he developed have been used to model and understand natural phenomena since

Self-similar voiding solutions of a single layered model of folding rocks

In this paper we derive an obstacle problem with a free boundary to describe the formation of voids at areas of intense geological folding. An elastic layer is forced by overburden pressure against a V-shaped rigid obstacle. Energy minimization leads to representation as a nonlinear fourth-order ordinary differential equation, for which we prove their exists a unique solution. Drawing parallels with the Kuhn-Tucker theory, virtual work, and ideas of duality, we highlight the physical significance of this differential equation. Finally we show this equation scales to a single parametric group, revealing a scaling law connecting the size of the void with the pressure/stiffness ratio. This paper is seen as the first step towards a full multilayered model with the possibility of voiding

Alkalinity and Buffering in Estuarine, Coastal and Shelf Waters

As anthropogenic climate change continues to elevate the amount of carbon dioxide (CO2) in the Earth’s atmosphere, the absorption of a large portion of this CO2 by Earth’s oceans has resulted in a steady decrease in pH. The consequent phenomenon of ocean acidification (OA) is a result of shifts in the carbonate chemistry system of the ocean- a system which can be analytically described by several factors, including total alkalinity (TA). TA in the oceans has been measured for over a century, but analytical and operational constraints have limited these measurements in time and space. Additionally, recent work has highlighted gaps in our knowledge of the species which collectively comprise TA. This dissertation describes efforts to examine TA through several novel applications: by deploying an automated TA analyzer aboard a survey vessel to map East Coast USA TA distributions, using the same analyzer in a long-term fixed coastal location to build a timeseries and examine seasonal biogeochemical dynamics, and measuring the concentrations and properties of the poorly understood organic component of TA in two Gulf of Maine estuaries. East Coast regional distributions of salinity (S) and TA generally agreed with prior findings, but linear TA:S regressions varied markedly over time and deviated from previously developed models. This variability is likely due to a combination of biological, seasonal, and episodic influences and indicates that substantial errors of ±10-20 μmol kg−1 in TA estimation from S can be expected due to these factors. This finding has likely implications for numerical ecosystem modeling and inorganic carbon system calculations. New results presented in Chapter 1 provide refined surface TA:S relationships, present more data in space and time, and improve TA modeling uncertainty. Coastal timeseries observations were collected hourly over 28 months representing all seasons between May 2016 and December 2019. Results presented in Chapter 2 indicated that endmember mixing explained most of the observed variability in TA and dissolved inorganic carbon (DIC), concentrations of which varied strongly with season. For much of the year, mixing dictated the relative proportions of salinity-normalized TA and DIC as well, but a fall season shift in these proportions indicated that aerobic respiration was observed, which would decrease buffering (β-H) by decreasing TA and increasing DIC. However, fall was also the season of weakest statistical correspondence between salinity and both TA and DIC, as well as the overall highest salinity, TA and β-H. Potential biogeochemically-driven β-H decreases were overshadowed by increased buffering capacity supplied by coastal ocean water. A simple modeling exercise showed that mixing processes controlled most monthly change in TA and DIC, obscuring impacts from air-sea exchange or metabolic processes. Advective mixing contributions, more than biogeochemically-driven changes, are critical to observe when evaluating local estuarine and coastal ocean acidification. Chapter 3 describes the first comparison study of both organic alkalinity (OrgAlk) distributions and acid-base properties in contrasting Gulf of Maine estuary-plume systems: the Pleasant (Maine USA) and St. John (New Brunswick CA). Four surveys of each estuary were conducted between May 2018 and October 2019. Substantial amounts of OrgAlk were measured in each estuary, whose distributions were sometimes not conservative with salinity. Two measures of OrgAlk produced consistently differing results, indicating acid-base characteristics that may be inconsistent with the definition of TA. OrgAlk and dissolved organic carbon (DOC) concentrations varied seasonally in the St. John Estuary, but not in the St. John. The fraction of TA represented by OrgAlk ranged from a maximum of 78% at low salinity in the St. John Estuary to less than 0.4% at the coastal ocean endmember. While the range of St. John OrgAlk concentrations was comparable to other studies, the St. John Estuary demonstrated a broader distribution. The acid dissociation constant (pKa) of the estuary samples was modeled according to a combined speciation and mixing approach, while the organic carbon acid dissociation constant (pKDOC) was estimated using a separate method. Results showed general agreement, but with some notable exceptions in the St. John estuary. OrgAlk modeling results from the Pleasant Estuary were more consistent than the St. John, despite St. John OrgAlk, DOC and pH results exhibiting much less seasonal variability. The mean OrgAlk pKa was higher in the Pleasant than in the St. John, while the mean Pleasant pKDOC was higher or lower than that in the St. John depending on which OrgAlk analysis approach was employed. Application of a bulk pKa or pKDOC to model OrgAlk from more common measurements such as pH, salinity, or DOC may offer promise (as in the Pleasant), but should be undertaken with caution as variability can pose challenges (as in the St. John). Future work should blend the analyses described in the chapters of this dissertation. For example, by collecting discrete samples aboard the survey vessel or at the coastal laboratory organic alkalinity contributions could be used to refine carbonate system calculations. Regional shifts in TA:S could be used to differentiate local and remote coastal endmember TA shifts. While this work utilized novel TA and OrgAlk analyses in three specific applications, the applicability of these analyses is broad and offers the potential to greatly enhance monitoring efforts and ecosystem biogeochemical studies

Effects of vertical vibration on hopper flows of granular material

This paper examines the flow of granular material through a wedge-shaped hopper subject to vertical, sinusoidal oscillations. Experiments and discrete element computer simulations were conducted to investigate particle trajectories within and mass discharge rates from the hopper. With the hopper exit closed, side wall convection cells are observed in both the experiments and simulations. The convection cells are oriented such that particles move up along the inclined walls of the hopper and down along the centerline. Results from the computer simulation indicate that the convection cells are a result of the dilation of the granular bed during free fall and interaction with hopper walls. Measurements of the mean mass discharge rate for various vibration parameters were also made in both the experiments and simulations. The ratio of the mass discharge rate for a vibrating hopper to the mass discharge rate for a non-vibrating hopper scales with the oscillation velocity amplitude and exhibits a maximum value just greater than one for oscillation velocity amplitudes less than 0.5. The ratio is less than one for larger velocity amplitudes. A simple model taking into account the change in the effective gravity acting on the granular material over an oscillation cycle is examined. A significant deficiency in the model is that is assumes no material discharges from the hopper during part of each oscillation cycle for acceleration amplitudes greater than gravitational acceleration. Data from the simulations indicate that although the discharge rate from the hopper varies throughout an oscillation cycle, it never equals zero. The simulation was also used to examine particle horizontal position and velocity profiles at the hopper exit. Lastly, preliminary observations of the effects of localized vibration on a granular material in a closed hopper are presented

Investigation of f/2 and f/4 Waves in Granular Beds Subject to Vertical, Sinusoidal Oscillations

When a deep bed of granular material is subject to vertical, sinusoidal oscillations, a number of phenomena appear including two regimes of standing surface waves that form at one-half and one-quarter of the oscillation forcing frequency. These waves are referred to as f/2 and f/4 waves where f is the oscillation frequency. This paper presents the results from experiments and computer simulations designed to study the wavelength and wave amplitude dependence of the surface waves on the vibration parameters, collision coefficient of restriction, and the particle bed depth

Organochloride Pesticides Present in Animal Fur, Soil, and Streambed in an Agricultural Region of Southeastern Arkansas

Animals in agricultural settings may be subject to bioaccumulation of toxins. For the last several years, we collected hair samples from bats and rodents in an agricultural area near Bayou Bartholomew in Drew County, Arkansas. Samples were submitted to the Center of Environmental Sciences and Engineering at the University of Connecticut for wide-screen toxin analysis. Several of these samples contained measurable amounts of organochloride pesticides or their metabolites, including some that have been banned for decades, such as dichlorodiphenyltrichloroethane (DDT) and chlordane. In addition, we collected several samples of soil from within an agricultural field, from adjacent edge habitat, from alongside the bank of the Bayou, and from the bed of the Bayou itself. Although none of these samples tested positive for DDT or chlordane, all of the samples except one contained measurable amounts of metabolites from these pesticides. This study raises questions about environmental persistence of DDT/DDE and other organochlorides. There may be risk to wildlife populations, warranting further investigation into effects of long-term exposure to these toxins

CORGI: Compute Oriented Recumbent Generation Infrastructure

Creating a bicycle with a rideable geometry is more complicated than it may appear, with today’s mainstay designs having evolved through years of iteration. This slow evolution coupled with the bicycle’s intricate mechanical system has lead most builders to base their new geometries off of previous work rather than expand into new design spaces. This crutch can lead to slow bicycle iteration rates, often causing bicycles to all look about the same. To combat this, several bicycle design models have been created over the years, with each attempting to define a bicycle’s handling characteristics given its physical geometry. However, these models often analyze a single bicycle at a time, and as such, using them in an iterative design process can be cumbersome. This work seeks to improve an existing model used by the Cal Poly Mechanical Engineering department such that it can be used in a proactive, iterative fashion (as opposed to the reactive, single-design paradigm that it currently supports). This is accomplished by expanding the model’s inputs to include more bicycle components as well as differently sized riders. This augmented model is then incorporated into several search platforms ranging from a brute-force implementation to several variants using genetic algorithm concepts. These models allow the designer to specify a bicycle design search space as well as a set of riders upfront, from which the algorithms search out and find strong candidate designs to return to the user. This in turn reduces the overhead on the designer while also potentially discovering new bicycle designs which had not been considered previously viable. Finally, a front-end was created to make it easier for the user to access these algorithms and their results

Preservice Candidates\u27 Rating of Effectiveness in Agricultural Education through Structured Communication with Cooperating Teachers

The relationship between cooperating teacher and student has been found as one of the key elements that affect the overall teaching efficacy of student teachers and their decision to enter the teaching field after graduation (Edgar, 2007; Edgar, Roberts, & Murphy, 2011,2008; Kasperbauer et al., 2007a; Roberts, Greiman, Murphy, Ricketts, Harlin, & Briers 2009; Roberts, Harlin, & Briers, 2007, Roberts, Harlin, & Ricketts, 2006; Roberts Mowen, Edgar, Harlin & Briers, 2007, Stripling, Ricketts, Roberts & Harlin, 2008; Wolf, 2011; Wolf et al., 2010). Therefore, determining impacts towards teaching efficacy during the student teaching experience could play a vital role in future teachers\u27 success. The purpose of this study was to assess teaching efficacy and the relationship between student teacher and cooperating teacher through a structured communication instrument at multiple universities. Data was collected from participants of this study on three variables; teaching efficacy, communication, and relationship. Data to address teaching efficacy was collected during the 2012 and 2013 spring semester at two universities {University of Arkansas (N = 27) and the University of Georgia (N = 32)}. To determine if a difference existed between universities based on teaching efficacy an ANOVA was used. The overall model was not significant (Between Groups, f = .568 and p = .687). The null hypothesis was accepted. To determine if a difference existed in student teachers perceptions bet multiple universities towards teaching an ANOVA was used. The overall model was not significant (Between Groups, f = 1.631 and p = .180). The null hypothesis was accepted. To determine if there was difference in teaching efficacy and student teachers/cooperating teacher relationship a MANOVA was used to test the hypothesis. The overall model was not significant therefore the null hypothesis was retained. Further research should be conducted to see the direct effects of the behaviors, personal factors, and the environment of preservice teaching. It is also suggested that future research be conducted to define the specifics of the behavioral factors, environmental, and personal factors in terms of agriculture education