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Hydrodynamics of biological propulsion leveraging parametric stiffness modulation
No full textVan Buren, TylerAnimals are exceptional swimmers, often exceeding our technological capabilities for moving quickly, efficiently, maneuverably, and stealthily through water. Natural swimmers have many tools to help them swim, including optimized fin shapes, unique surface textures, and active muscle action. However, it is unknown to what extent animals dynamically use their muscles throughout their swimming gait, specifically whether they change the propulsor stiffness on the time scale of their oscillations. We seek to hydrodynamically show that there is enhanced swimming performance in oscillating propulsors if the stiffness were modulated throughout the gait cycle, particularly enhancing thrust and maneuverability. We use small-amplitude inviscid theory and Floquet theory to study the swimming performance and maneuverability of flexible flapping plates with time-periodic flexibility. Our investigation compares plates with constant and time-periodic stiffness across a range of mean plate stiffness values, oscillating stiffness amplitudes, and phase relationships for isolated heaving, isolated pitching, and combined leading edge kinematics. We examine both the natural response of the system and its behavior under various input actuations, with particular attention to stiffness oscillations at twice the kinematic frequency (to maintain symmetric motion) and at the same frequency (to generate net side forces). The Floquet exponents are calculated for a range of time-periodic systems, and their initial coalescence locations are determined using geometric arguments. Our analysis reveals that time-periodic stiffness enhances thrust for specific frequency values related to both the driving frequency and the structural natural frequency, with the phases of the independent frequencies significantly affecting the long-term system dynamics. For maneuvering applications, we explore two primary control strategies: pitch bias and asymmetric oscillating stiffness. Pitch bias inherently provides a nonzero lift coefficient through an average nonzero angle of attack, with behavior following thin airfoil theory superimposed on the oscillating system for rigid plates, though flexibility attenuates the added lift. Asymmetric stiffness oscillations create a "power stroke" effect, generating high positive (negative) lift during one portion of the motion and low negative (positive) lift during the other. We demonstrate that oscillating flexibility can generate equal or higher average lift compared to pitch bias alone, with stiffness oscillations up to 50\%. Ultimately, combining pitch bias with asymmetric stiffness achieves a lift coefficient of C_L = 3.6, exceeding the performance of either isolated approach.University of Delaware, Department of Mechanical EngineeringPh.D
Groundwater Monitoring Procedures Part 2: Equipment and Procedures for Collection of Water-Quality Samples from Monitoring Wells
No full textGroundwater-quality data provide essential information for assessing groundwater chemistry and identifying and evaluating trends related to regional hydrogeology, water use, and land use. The Delaware Geological Survey (DGS) has been collecting groundwater samples for various projects over the past several decades. This document serves as a reference for collecting groundwater samples from monitoring wells. The methods described in this report were adopted from published federal agency and industry standard operating procedures and modified to fit DGS-specific practices (USEPA, 2007; USGS, variously dated; SOGW, 2013).
This document describes the sampling procedures used by DGS staff to collect routine groundwater samples from monitoring wells using the traditional purge and grab method. This methodology is only appropriate when sampling for certain analytes (major ions, select metals, physical parameters) and it will not be applicable to sampling for volatile compounds or other constituents for which results may be affected by pumping the well before sampling (purging). Groundwater-sample collection includes two parts – purging the well and collecting the sample. Included in this report are equipment recommendations and step-by-step instructions on site preparation, well purging and sampling, post-sampling protocols, and other considerations.
Along with DGS Groundwater Monitoring Procedures, Part 1 (Andres et al., 2018), this report is part of a series documenting groundwater data-collection protocols used by DGS staff
Impact of lateral circulation on transport and fate of buoyant particles in an estuary
No full textKukulka, TobiasEstuaries are a crucial interface between land and the open ocean and are the site of many physical, chemical, biological, and geological processes. For example, they distribute buoyant particles that can be natural (e.g., seafoam, plankton, organic matter) or pollutants (e.g., plastics, oil). While plastics and other buoyant particles are receiving substantial attention in the literature, there are few systematic studies that examine their distribution in an estuary. The Delaware Bay is an ideal system to develop an understanding of particle distributions in an estuary. The Delaware Bay exhibits gravitational circulation and has a deep central channel with shallow flanks, allowing for understandings from theoretical and idealized models to be applied to the bay. Additionally, the Delaware Bay has been the subject of many observational and numerical modeling studies. Here we will use a combination of a realistic hydrodynamic model, an idealized model, and observational data to study the movement of particles in an estuary. ☐ The goal of this dissertation is to systematically study the distribution of particles in the Delaware Bay. We perform this study in three parts. In the first part, we use a hydrodynamic model and particle tracking to study organismal exposure to plastics in the Delaware Bay. We find that exposure to plastics is not constant, but can vary throughout the bay based on initial location and plastics buoyancy effects. Additionally, organismal behavior, such as diel vertical migration, can alter exposure due to slower currents at depth not transporting the organism as far as the faster moving currents transporting plastics at the surface. In part two, we use an idealized estuarine model, a realistic hydrodynamic model, and observational data, to understand the patchy, inhomogeneous distribution of particles in the Delaware Bay as well as the along-channel transport. We find that when vertical mixing is high, a tidally-averaged up-estuary current region forms in the center of the bay and traps particles. Conversely, when vertical mixing is low, the entire surface of water column has down-estuary currents and particles are flushed. In the third and final part, we explore the combined effects and competition of tidally-averaged and time-dependent convergence in a tidally-resolved idealized estuary model. We find that Lagrangian motion can greatly impact the rate and location of aggregation and must be considered to fully understand particle trajectory. We also find the direction of Lagrangian convergence or Lagrangian divergence to be related to the level of stratification in the estuary. We conclude that particle motion in an estuary is controlled by a combination of tidally-averaged and time-dependent motion that aggregates particles, debris, and organisms, and that the underlying tidally-averaged flow is critical in determining if particles are trapped or released from the estuary.University of Delaware, School of Marine Science and PolicyPh.D
INTERSECTIONS OF HOUSING AND TRANSPORTATION INSECURITY IN DELAWARE
No full textenterTo improve conditions for low-income residents, research with an integrated focus on the
combined impacts of housing and transportation on people's experiences is critical. Delaware's
population has been increasing faster than the national average, adding pressure on the housing
market. This has caused securing affordable and safe housing to be increasingly more difficult
for low-income residents. This research aims to connect information on housing and
transportation insecurity in Delaware to investigate the accumulation of the two disadvantages.
The findings are based on interviews with residents who use housing vouchers, state
representatives, and staff members of state agencies. The experiences of residents who use
housing vouchers reveal gaps in the current resources and systems in place that contribute to
housing and transportation instability for low-income families. Residential instability or the risk
of it and limited housing choices were consistently experienced by all the residents interviewed
both before and after receiving housing vouchers. Additionally, some participants emphasized
the significance of having a personal vehicle contributing to their overall well-being, despite the
related financial burdens. The conversations with DSHA, HAD, DART staff members, and state
representatives consistently reflected the concerns found within previous literature regarding the
lack of affordable housing, landlords choosing not to accept housing vouchers, concentrated
poverty in Wilmington, and the redevelopment of manufactured housing communities.
Additionally, these conversations also revealed novel information about increasing action within
these organizations. The findings, overall, emphasize the need for policy changes that address the
underlying issues of residential instability and limited housing choices for low-income
households. It is essential that future research continues to include the perspectives of low income residents in the development of policies and programs relating to housing and
transportation across the state.ente
2025 KIDS COUNT in Delaware Legislative Calendar
No full textPage-a-day style calendar containing data on Delaware children and their families. Calendar counts down to the end of legislative session.Delaware Division of Libraries, the Annie E. Casey Foundation, the University of Delaware and the State of Delawar
Blending the two communities: concurrent evidence use in state-level policy processes
No full textThis is an Accepted Manuscript of an article published by Taylor & Francis in Public Management Review on 01/07/2025, available at: https://doi.org/10.1080/14719037.2024.2448515.
© 2025 Informa UK Limited, trading as Taylor & Francis Group.
This article will be embargoed until 07/01/2026.The evidence-based paradigm is one way to ensure public resources are put to effective use. But the uptake of scientific evidence has been limited. We analyse US state reports on autonomous vehicles and the opioid crisis response to explore how evidence is used in state-level processes. We find evidence of three knowledge types -scientific, practice, and political - visible in the reports and extend existing work on knowledge types in use to illustrate not just that they are used, but that they are used in conjunction with each other. These findings require a re-examination of the way ‘evidence’ is discussed in the literature.The work was supported by the National Science Foundation [2001455]
Handling ‘Poison Books’: Dry Versus Wet Scenarios
No full textThis is an original manuscript of an article published by Taylor & Francis in Studies in Conservation on 01/11/2025, available at: https://doi.org/10.1080/00393630.2024.2448394.
© The International Institute for Conservation of Historic and Artistic Works 2025.
This article will be embargoed until 07/11/2026.Toxic heavy metal pigments are known to be found in nineteenth-century, mass-produced, Euro-American bookbindings. A lack of data, standards, and regulations for exposure to heavy metal pigments in the cultural heritage sector limits understanding of when such bookbindings might present the greatest health and safety risk and how best to assess such risk. This case study measures the friability of arsenic, chromium, and lead based pigments in a sampling of nineteenth-century bookbindings through three scenarios: first, in their naturally aged, intact state; second, during a water event simulation; and third, after salvage and air-drying from the water disaster simulation. The data demonstrate that the risk of exposure to these heavy metals increases during and after a water event, with exposure to arsenic presenting the highest degree of risk.We thank Dr. Johnathan Tedesco and the Lake Erie College STEM Scholars program for supporting intern Janet Wittine’s 2024 summer internship at Winterthur. Alexandra Alvis generously donated a bookbinding for destructive testing from their personal set of emerald green, French cartonnage bookbindings. Todd Pattison provided an emerald green paper binding from his personal collection for non-destructive testing. Brittany Murray (WUDPAC ‘25), Karissa Muratore, and Dr. Joelle Wickens shared helpful suggestions about research questions and parameters, and we appreciate their time and expertise. Winterthur Museum, Garden & Library provided funds for testing library collection materials. The University of Delaware Department of Art Conservation provided research startup funds that supported the additional testing of study collection materials. We are grateful to the Winterthur/University of Delaware Program in Art Conservation (WUDPAC) for investing in an historical bookbinding study collection that can be used for destructive analysis when necessary; we do not make use of this privilege lightly
Weather and glufosinate efficacy; a retrospective analysis looking forward to the changing climate
No full textThis article was originally published in Weed Science. The version of record is available at: https://doi.org/10.1017/wsc.2024.101.
© The Author(s), 2025. Published by Cambridge University Press on behalf of Weed Science Society of America.
This article will be embargoed until 07/08/2025.Foliar-applied postemergence applications of glufosinate are often applied to glufosinate-resistant crops to provide nonselective weed control without significant crop injury. Rainfall, air temperature, solar radiation, and relative humidity near the time of application have been reported to affect glufosinate efficacy. However, previous research may have not captured the full range of weather variability to which glufosinate may be exposed to prior to or following application. Additionally, climate models suggest more extreme weather will become the norm, further expanding this weather range glufosinate can be exposed to. The objective of this research was to quantify the probability of successful weed control (efficacy ≥85%) with glufosinate applied to some key weed species across a broad range of weather conditions. A database of >10,000 North American herbicide evaluation trials was used in this study. The database was filtered to include treatments with a single POST application of glufosinate applied to waterhemp (Amaranthus tuburculatus (Moq.) J. D. Sauer), morningglory species (Ipomoea spp.), and/or giant foxtail (Setaria faberi Herm.) <15cm in height. These species were chosen because they are well represented in the database and listed as common and troublesome weed species in both corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] (Van Wychen 2020, 2022). Individual random forest models were created. Low rainfall (≤20 mm) over the five days prior to glufosinate application was detrimental to the probability of successful control of A. tuburculatus and S. faberi. Lower relative humidity (≤70%) and solar radiation (≤23 MJ m-1 day-1) the day of application reduced the probability of successful weed control in most cases. Additionally, the probability of successful control decreased for all species when average air temperature over the first five days after application was ≤25C. As climate continues to change and become more variable, the risk of unacceptable control of several common species with glufosinate is likely to increase.This research was supported by U.S. Department of Agriculture – Agricultural Research Service Research Project No. 5012-12220- 010-000D. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that also may be suitable
DelaWEAR: An interdisciplinary team’s discovery learning approach to reducing post-consumer textile waste through experiential retail
No full textThis article was originally published in International Textile and Apparel Association Annual Conference Proceedings. The version of record is available at: https://doi.org/10.31274/itaa.18906.
© 2024 The author(s). Published under a Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.DelaWEAR explores a comprehensive, interdisciplinary approach to sustainable fashion by leveraging community partnerships and educational initiatives. In collaboration with Goodwill, discarded textiles are repurposed and sold in an on-campus fabric store at the University of Delaware, marking the first phase, “Collection and Re-Distribution.” The second phase, “Educational Initiatives,” focuses on consumer education through events like Sip and Sew workshops and children’s summer camps, teaching practical skills for clothing repair and upcycling. The final phase, “Merchandise Collection,” involves repurposing textiles into University of Delaware merchandise designed by students, fostering cross-disciplinary collaboration and experiential learning. As a self-sustaining model, the initiative integrates learning into its framework, providing students with hands-on opportunities while addressing critical gaps in consumer education about sustainable fashion. With support from a $50,000 university grant, future efforts will focus on scaling the business model, including real estate acquisition, product development, and curriculum integration, to create long-term impact in sustainability education