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.


Recent Submissions

Effect of Dynamic and Preferential Decoration of Pt Catalyst Surfaces by WOx on Hydrodeoxygenation Reactions
(Journal of the American Chemical Society, 2024-05-22) Marlowe, Justin; Deshpande, Siddharth; Vlachos, Dionisios G.; Abu-Omar, Mahdi M.; Christopher, Phillip
Catalysts containing Pt nanoparticles and reducible transition-metal oxides (WOx, NbOx, TiOx) exhibit remarkable selectivity to aromatic products in hydrodeoxygenation (HDO) reactions for biomass valorization, contrasting the undesired aromatic hydrogenation typically observed for metal catalysts. However, the active site(s) responsible for the high selectivity remains elusive. Here, theoretical and experimental analyses are combined to explain the observed HDO reactivity by interrogating the organization of reduced WOx domains on Pt surfaces at sub-monolayer coverage. The SurfGraph algorithm is used to develop model structures that capture the configurational space (∼1000 configurations) for density functional theory (DFT) calculations of a W3O7 trimer on stepped Pt surfaces. Machine-learning models trained on the DFT calculations identify the preferential occupation of well-coordinated Pt sites (≥8 Pt coordination number) by WOx and structural features governing WOx–Pt stability. WOx/Pt/SiO2 catalysts are synthesized with varying W loadings to test the theoretical predictions and relate them to HDO reactivity. Spectroscopy- and microscopy-based catalyst characterizations identify the dynamic and preferential decoration of well-coordinated sites on Pt nanoparticles by reduced WOx species, consistent with theoretical predictions. The catalytic consequences of this preferential decoration on the HDO of a lignin model compound, dihydroeugenol, are clarified. The effect of WOx decoration on Pt nanoparticles for HDO involves WOx inhibition of aromatic ring hydrogenation by preferentially blocking well-coordinated Pt sites. The identification of preferential decoration on specific sites of late-transition-metal surfaces by reducible metal oxides provides a new perspective for understanding and controlling metal–support interactions in heterogeneous catalysis.
Biphasic Plasma Microreactor for Oxyfunctionalization of Liquid Hydrocarbons
(Industrial & Engineering Chemistry Research, 2024-05-22) Nguyen, Darien K.; Cameli, Fabio; Dimitrakellis, Panagiotis; Vlachos, Dionisios G.
Oxyfunctionalization of linear alkanes is important but challenging to achieve. Herein, we demonstrate a biphasic gas–liquid modular plasma microreactor utilizing Ar/O2 gas to selectively oxidize liquid n-dodecane (C12) in an electrified, catalyst-free fashion. C12 secondary alcohols and ketones are the major products, with selectivities of 45–60% and a maximum yield of 23%. Fine-tuning gas and liquid flow rates enhance the plasma–liquid interfacial area, leading to a conversion of >50%. Difunctional and oligomerized oxygenates, alongside lighter hydrocarbons stemming from carbon–carbon cleavage, form at higher conversions. The energy efficiency (0.189 μmol/J) of the modular microreactor is the highest reported among plasma systems. Alkane conversion can be further improved by increasing the length of the plasma region while maintaining excellent energy efficiencies. Similarly, sequential processing/recirculation can enhance the extent of the reaction. This system is also amenable to treating mixtures of liquid n-alkanes, where smaller hydrocarbons are oxidized preferentially to a certain extent. The vapor pressure and liquid temperature are the key parameters. The chemistry occurs primarily in the gas phase for the lighter hydrocarbons and switches to interfacial reactions for the larger ones.
The Use of Research in Schools: Principals’ Capacity and Contributions
(Education Sciences, 2024-05-23) Farley-Ripple, Elizabeth N.
Policy expectations for the role of research evidence in educational decision-making have grown exponentially in the U.S. and globally, yet there has been limited attention to school capacity to engage in evidence-informed improvement. In this paper, I address this gap by first conceptualizing principal leadership for evidence use and, second, use this conceptual lens to examine large-scale survey data about school evidence use practices and capacity. Drawing on data from a national survey of more than 4000 educators in 134 schools in the US, I explore school practices and capacity to use research and surface opportunities and needs for principal leadership in evidence-informed improvement. Findings suggest that there is an opportunity to improve the role of research in school improvement decision-making, and that principals may contribute to school capacity in specific ways that relate to developing human capital, influencing culture, leveraging resources, and shaping decision-making. Data reveal moderate evidence of research use in agenda setting and of organizational routines that support research use, but lack of uptake of those routines for research use as well as limited investment in resources (e.g., time). Further, decision-making was distributed across a wide range of improvement initiatives, with evidence of a lack of clarity about goals. Although principals report confidence and experience with using research, overall school staff also reported limited experience with prior research, including coursework or participation in research, and low confidence in critically consuming research. Implications point to the need to strengthen principals’ own evidence use capacity as well as focus on dimensions school capacity as part of evidence use initiatives. Recommendations suggest strategies for developing principals’ knowledge and skills around leadership for evidence-informed improvement.
Unwrapping the Native Plant Black Box: Consumer Perceptions and Segments for Target Marketing Strategies
(HortTechnology, 2024-05-23) Rihn, Alicia L.; Torres, Ariana; Behe, Bridget K.; Barton, Sue
The increasing demand for sustainable products has helped spur demand for native plants. This study used an online survey of 2066 US consumers, a factor analysis, and Ward’s linkage cluster analysis to identify unique customer segments in the native plant marketplace. The following three clusters were identified: native averse (31.6%), native curious (35.7%), and native enthusiast (32.7%). The native enthusiast cluster agreed strongly with positive statements related to native plant perceptions and attributes. The native averse cluster exhibited the lowest level of agreement with these items and the greatest level of agreement with negative or neutral statements about native plants. The native curious cluster was intermediate between the other clusters but generally agreed with positive attributes. Demographic characteristics impacted cluster membership. The marketing implications are discussed.
A Simple Mobile Plausibly Deniable System Using Image Steganography and Secure Hardware
(Proceedings of the 2024 ACM Workshop on Secure and Trustworthy Cyber-Physical Systems, 2024-06-19) Xia, Lichen; Liao, Jinghui; Chen, Niusen; Chen, Bo; Shi, Weisong
Traditional encryption methods cannot defend against coercive attacks in which the adversary captures both the user and the possessed computing device, and forces the user to disclose the decryption keys. Plausibly deniable encryption (PDE) has been designed to defend against this strong coercive attacker. At its core, PDE allows the victim to plausibly deny the very existence of hidden sensitive data and the corresponding decryption keys upon being coerced. Designing an efficient PDE system for a mobile platform, however, is challenging due to various design constraints bound to the mobile systems. Leveraging image steganography and the built-in hardware security feature of mobile devices, namely TrustZone, we have designed a Simple Mobile Plausibly Deniable Encryption (SMPDE) system which can combat coercive adversaries and, meanwhile, is able to overcome unique design constraints. In our design, the encoding/decoding process of image steganography is bounded together with Arm TrustZone. In this manner, the coercive adversary will be given a decoy key, which can only activate a DUMMY trusted application that will instead sanitize the sensitive information stored hidden in the stego-image upon decoding. On the contrary, the actual user can be given the true key, which can activate the PDE trusted application that can really extract the sensitive information from the stego-image upon decoding. Security analysis and experimental evaluation justify both the security and the efficiency of our design.