Institutional Repository
The UDSpace Institutional Repository collects and disseminates research material from the University of Delaware.
- Faculty, staff, and graduate students can deposit their research material directly into UDSpace. Faculty may use UDSpace to fulfill the University of Delaware Faculty Senate Open Access Resolution, and in many cases may use it to fulfill open access requirements from grant funding agencies.
- Departments can use UDSpace to publish or distribute their working papers, technical reports, or other research material.
- UDSpace also includes all doctoral dissertations from winter 2014 forward, and all master's theses from fall 2009 forward.
To learn more about UDSpace, and how you can make your research openly accessible to the public, visit our UDSpace Policies website.
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Recent Submissions
Advances on the Global Human Settlement Layer by joint assessment of Earth Observation and population survey data
(International Journal of Digital Earth, 2024-08-30) Pesaresi, Martino; Schiavina, Marcello; Politis, Panagiotis; Freire, Sergio; Krasnodębska, Katarzyna; Uhl, Johannes H.; Carioli, Alessandra; Corbane, Christina; Dijkstra, Lewis; Florio, Pietro; Friedrich, Hannah K.; Gao, Jing; Leyk, Stefan; Lu, Linlin; Maffenini, Luca; Mari-Rivero, Ines; Melchiorri, Michele; Syrris, Vasileios; Van Den Hoek, Jamon; Kemper, Thomas
The Global Human Settlement Layer (GHSL) project fosters an enhanced, public understanding of the human presence on Earth. A decade after its inception in the Digital Earth 2020 vision, GHSL is an established project of the European Commission’s Joint Research Centre and an integral part of the Copernicus Emergency Management Service. The 2023 GHSL edition, a result of rigorous research on Earth Observation data and population censuses, contributes significantly to understanding worldwide human settlements. It introduces new elements like 10-m-resolution, sub-pixel estimation of built-up surfaces, global building height and volume estimates, and a classification of residential and non-residential areas, improving population density grids. This paper evaluates the key components of the GHSL, including the Symbolic Machine Learning approach, using novel reference data. These data enable a comparative assessment of GHSL model predictions on the evolution of built-up surface, building heights, and resident population. Empirical evidence suggests that GHSL estimates are the most accurate in the public domain today, e.g. achieving an IoU of 0.98 for the water class, 0.92 for the built-up class, and 0.8 for the non-residential class at 10 m resolution. At 100 m resolution, we find that the MAE of built-up surface estimates corresponds to 6% of the grid cell area, the MAE for the building height estimates is 2.27 m, and we find a total allocation accuracy of 83% for resident population. This paper consolidates the theoretical foundation of the GHSL and highlights its innovative features for transparent Artificial Intelligence, facilitating international decision-making processes.
Terrestrial Organic Matter Contributes to CO2 Production From Siberian Shelf Sediments
(Journal of Geophysical Research: Biogeosciences, 2025-01-01) Sauerland, Lewis; Ray, Nicholas; Martens, Jannik; Tesi, Tommaso; Dudarev, Oleg; Gustafsson, Örjan; Semiletov, Igor; Wild, Birgit
Arctic climate warming is causing permafrost thaw and erosion, which may lead to enhanced inputs of terrestrial organic matter into Arctic Ocean shelf sediments. Degradation of terrestrial organic matter in sediments might contribute to carbon dioxide production and bottom water acidification. Yet, the degradability of organic matter in shallow Arctic Ocean sediments, as well as the contribution of terrestrial input, is poorly quantified. Here, potential organic matter degradation rates were investigated for 16 surface sediments from the Kara Sea, Laptev Sea, and the western East Siberian Sea and compared with physicochemical sediment properties including molecular biomarkers, stable and radioactive carbon isotopes, and grain size. Aerobic oxygen and carbon dioxide fluxes, measured in laboratory incubations of sediment slurry, showed high spatial variability and correlated significantly with organic carbon content as well as with the amount and degradation state of terrestrial organic matter. The dependency on terrestrial organic matter declined with increasing distance from land, indicating that the presence of terrestrial organic matter is likely a constraining factor for organic matter degradation in shallow shelf seas. However, sediment oxygen consumption rates, measured in incubations of intact sediment cores, also exhibited substantial spatial variability but were not related to organic carbon content or terrestrial influence. Oxygen consumption of intact sediments may be more strongly influenced by in situ redox conditions. Together with previous observations, our findings support that terrestrial organic matter is easily degradable in shelf sea sediments and might substantially contribute to aerobic carbon dioxide production and oxygen consumption.
Plain Language Summary
The Arctic climate is warming rapidly, which is leading to thawing of frozen deposits on land. These deposits contain large amounts of terrestrial organic matter that is being eroded and deposited into shallow ocean sediments. The breakdown of terrestrial organic matter in sediments might contribute to carbon dioxide release into the ocean water. There is insufficient knowledge on how fast this breakdown is happening and which parameters influence it. We investigated organic matter breakdown rates for sediment samples taken from shallow Siberian seas and compared them with sediment properties. Oxygen consumption and carbon dioxide release were measured in laboratory experiments and showed high variability between different samples. The release was related to the amount of terrestrial organic matter and its state of decomposition. This relationship decreased strongly for sediments further away from land. During a second incubation experiment, using intact sediment cores, oxygen consumption rates were measured and also showed high variability between samples. Oxygen consumption rates were not related to organic matter content. These findings support previous observations that terrestrial organic matter breaks down rapidly in shallow Arctic Ocean sediments and might also substantially contribute to the release of carbon dioxide and consumption of oxygen from the seawater.
Key Points
- Carbon dioxide fluxes from sediment slurry incubations showed high variability and were dependent on the input of terrestrial organic matter
- Pronounced variability in oxygen consumption of intact sediment cores could not be explained by the input of terrestrial organic matter
Enhancing cathode composites with conductive alignment synergy for solid-state batteries
(Science Advances, 2025-01-03) Cao, Zhang; Yao, Xinxin; Park, Soyeon; Deng, Kaiyue; Zhang, Chunyan; Chen, Lei; Fu, Kelvin
Enhancing transport and chemomechanical properties in cathode composites is crucial for the performance of solid-state batteries. Our study introduces the filler-aligned structured thick (FAST) electrode, which notably improves mechanical strength and ionic/electronic conductivity in solid composite cathodes. The FAST electrode incorporates vertically aligned nanoconducting carbon nanotubes within an ion-conducting polymer electrolyte, creating a low-tortuosity electron/ion transport path while strengthening the electrode’s structure. This design not only mitigates recrystallization of the polymer electrolyte but also establishes a densified local electric field distribution and accelerates the migration of lithium ions. The FAST electrode showcases outstanding electrochemical performance with lithium iron phosphate as the active material, achieving a high capacity of 148.2 milliampere hours per gram at 0.2 C over 100 cycles with substantial material loading (49.3 milligrams per square centimeter). This innovative electrode design marks a remarkable stride in addressing the challenges of solid-state lithium metal batteries.
Transforming CO2 into advanced 3D printed carbon nanocomposites
(Nature Communications, 2024-12-04) Crandall, Bradie S.; Naughton, Matthew; Park, Soyeon; Yu, Jia; Zhang, Chunyan; Mahtabian, Shima; Wang, Kaiying; Liang, Xinhua; Fu, Kelvin; Jiao, Feng
The conversion of CO2 emissions into valuable 3D printed carbon-based materials offers a transformative strategy for climate mitigation and resource utilization. Here, we 3D print carbon nanocomposites from CO2 using an integrated system that electrochemically converts CO2 into CO, followed by a thermocatalytic process that synthesizes carbon nanotubes (CNTs) which are then 3D printed into high-density carbon nanocomposites. A 200 cm2 electrolyzer stack is integrated with a thermochemical reactor for more than 45 h of operation, cumulatively synthesizing 37 grams of CNTs from CO2. A techno-economic analysis indicates a 90% cost reduction in CNT production on an industrial scale compared to current benchmarks, underscoring the commercial viability of the system. A 3D printing process is developed that achieves a high nanocomposite CNT concentration (38 wt%) while enhancing composite structural attributes via CNT alignment. With the rapidly rising demand for carbon nanocomposites, this CO2-to-nanocomposite process can make a substantial impact on global carbon emission reduction efforts.
Visualizing fiber end geometry effects on stress distribution in composites using mechanophores
(Soft Matter, 2024-11-14) Haque, Nazmul; Chang, Hao Chun; Chang, Chia-Chih; Davis, Chelsea S.
Localized stress concentrations at fiber ends in short fiber-reinforced polymer composites (SFRCs) significantly affect their mechanical properties. Our research targets these stress concentrations by embedding nitro-spiropyran (SPN) mechanophores into the polymer matrix. SPN mechanophores change color under mechanical stress, allowing us to visualize and quantify stress distributions at the fiber ends. We utilize glass fibers as the reinforcing material and employ confocal fluorescence microscopy to detect color changes in the SPN mechanophores, providing real-time insights into the stress distribution. By combining this mechanophore-based stress sensing with finite element analysis (FEA), we evaluate localized stresses that develop during a single fiber pull-out test near different fiber end geometries—flat, cone, round, and sharp. This method precisely quantifies stress distributions for each fiber end geometry. The mechanophore activation intensity varies with fiber end geometry and pull-out displacement. Our results indicate that round fiber ends exhibit more gradual stress transfer into the matrix, promoting effective stress distribution. Also, different fiber end geometries lead to distinct failure mechanisms. These findings demonstrate that fiber end geometry plays a crucial role in stress distribution management, critical for optimizing composite design and enhancing the reliability of SFRCs in practical applications. By integrating mechanophores for real-time stress visualization, we can accurately map quantified stress distributions that arise during loading and identify failure mechanisms in polymer composites, offering a comprehensive approach to enhancing their durability and performance.