114333 research outputs found
Sort by
Weak wall boundary conditions for compressible flows
No full textWeak imposition of essential boundary conditions (i.e., weak BCs) for the Navier–Stokes equations of incompressible flows allows a certain amount of controlled numerical flow slip on the solid surface. Numerical flow slip mimics the presence of a thin boundary layer that would otherwise need to be captured using a fine mesh resolution. As a result, weak BCs enable the use of coarser meshes near solid walls without sacrificing numerical solution accuracy, which significantly reduces the computational costs, especially for 3D, wall-bounded turbulent flows. However, weak BCs for compressible flows are not as well understood as those for the incompressible-flow case. In particular, numerical instabilities were observed in some cases where the weak BCs were simultaneously imposed for the velocity and temperature fields. In the present effort, to address these stability issues, we develop a methodology for the design of compressible-flow weak BC operators and demonstrate the improved performance of the resulting weak BC formulations using challenging 2D and 3D test cases.This article is published as Jaiswal, Monu, Manoj R. Rajanna, Md Rhyhanul Islam, Ming-Chen Hsu, and Yuri Bazilevs. "Weak wall boundary conditions for compressible flows." Engineering with Computers 42, no. 1 (2026): 16. doi: https://doi.org/10.1007/s00366-025-02232-x.Y. Bazilevs was partially supported through the ONR Grant No. N00014-21-1-2670 and the US Army STTR Contract No. W911NF25P0013. M. Jaiswal and M.-C. Hsu were partially supported through the NSF Grant No. DMS-2436623 and NIH Grant No. R01HL184128
Advancing sustainable pavement management systems through integration of non-traditional factors
No full textThis dissertation develops a comprehensive framework for integrating social equity and environmental sustainability into pavement management systems. Traditional pavement management prioritizes maximizing aggregate network performance within budget constraints, often overlooking the distributional consequences of infrastructure investments across communities with different levels of social vulnerability. This research addresses this gap by establishing quantitative methods for measuring equity, developing optimization frameworks that balance multiple objectives, and demonstrating through empirical analysis that substantial equity improvements are achievable with modest performance trade-offs.
The research begins by establishing a conceptual framework through analysis of California's Bay Area, revealing systematic disparities in pavement conditions correlated with poverty rates and air quality indicators. Building on this foundation, a comprehensive vulnerability assessment methodology is developed using Iowa's statewide transportation network. Feature importance analysis identifies six critical vulnerability dimensions: poverty status, disability status, mobile home prevalence, crowded housing, youth population, and minority status. These factors are weighted based on their influence and spatial patterns to develop vulnerability scores and a five-level priority classification system. The vulnerability metrics are translated into four distinct policy frameworks representing different approaches to balancing performance and equity. Policy A maximizes efficiency without equity considerations and worsens disparities by 33 percent. Policy B incorporates equity as a performance constraint. Policy C minimizes maximum group disparities, reducing the pavement condition index gap from 8 to 3.1 points while maintaining network conditions at 65.0 PCI. Policy D equalizes conditions across all vulnerability groups. Sensitivity analysis demonstrates that equity-focused policies, Policy C and Policy D, exhibit exceptional robustness to parameter uncertainty compared to efficiency-maximizing approaches, maintaining stable distributional outcomes despite variations in budget levels, treatment costs, and technical assumptions.
The framework is expanded to incorporate environmental sustainability through greenhouse gas emissions quantification using life cycle assessment methodologies. Multi-objective optimization examines six scenarios ranging from pure performance maximization to balanced approaches. The analysis reveals that moderate strategies allocating 15 to 45 percent weight to equity and emissions considerations retain 89 to 96 percent of maximum performance improvement while reducing equity gaps by 39 to 54 percent and lowering emissions by 3 to 10 percent. Extreme single-objective optimization produces inferior overall outcomes, while balanced approaches achieve superior results across all three sustainability dimensions.
The findings challenge the conventional view that sustainability objectives inevitably conflict with one another. They show that efficiency and equity often operate in tension but can also align to produce mutually beneficial outcomes. This research offers transportation agencies practical insights that fit within existing data infrastructures and pavement management systems, allowing implementation without major system changes. By highlighting that infrastructure management inherently involves community-based decisions about how resources are distributed and whose needs are prioritized, this work advances pavement management toward a comprehensive form of sustainability that balances social equity, environmental responsibility, and economic efficiency to create infrastructure systems that serve all communities equitably
Innovative applications of recycled plastic-based geosynthetics for enhancing sustainability and resiliency in cold-region transportation infrastructure
No full textGeosynthetics are engineered polymeric materials used in transportation geotechnics, and environmental applications to stabilize soil, enhance drainage, control erosion, and improve overall infrastructure performance. In unpaved roads, geosynthetics can increase bearing capacity, reduce rutting and deformation, improve moisture management, and extend service life while lowering maintenance costs. Traditionally manufactured from virgin polymers, these materials can also be produced from recycled plastics, offering a sustainable alternative that reduces plastic waste, conserves natural resources, and promotes circularity in construction materials. By integrating recycled plastic-based geosynthetics into unpaved road systems, it is possible to simultaneously enhance performance and resilience while advancing environmental sustainability.
This dissertation investigates the use of recycled plastic-based geosynthetics to stabilize transportation infrastructure in cold regions, with emphasis on enhancing structural performance, sustainability, and resilience of unpaved roads. Field implementation and performance monitoring were conducted using advanced field instrumentation, and in-situ and field testing to evaluate both mechanical and moisture-related behaviors. Four types of innovative recycled plastic-based geosynthetics were studied: (i) a recycled plastic composite geosynthetic, consisting of a 100% recycled plastic geogrid bonded to a nonwoven geotextile (developed for the first time and specifically for Iowa), compared with its virgin composite counterpart; (ii) two non-wicking woven geotextiles containing 10–15% recycled plastic; and (iii) a wicking woven geotextile containing 10–15% recycled plastic, referred to as a Moisture Management Geosynthetic (MMG), the first geosynthetic capable of draining water independent of gravity.
Results demonstrated significant improvements in bearing capacity, deformation resistance, and moisture control under freeze–thaw cycles. One year of monitoring indicates that the use of recycled plastic composite geosynthetics and virgin composite geosynthetics results in up to a 35% improvement in the California Bearing Ratio (CBR) compared to the control section, while two non-wicking woven geotextiles show up to a 40% improvement, and MMG shows up to a 40% improvement. Similarly, the results indicate that recycled plastic and virgin composite geosynthetics lead to up to a 15% improvement in elastic modulus based on the Light Weight Deflectometer (LWD) test compared to the control section, while two non-wicking woven geotextiles show up to a 10% improvement, and MMG shows up to a 20% improvement. One year of monitoring and analysis of moisture and temperature data indicates that the use of recycled plastic composite geosynthetics and virgin composite geosynthetics results in a 10–20% average reduction in moisture content in the subgrade and base layers of stabilized sections compared to the control section, while two non-wicking woven geotextiles show up to a 10% reduction, and MMG shows up to a 25% reduction. In addition, field observations and in-situ testing show promise for soil stabilization by reducing pavement distresses, mainly frost boils and heaves caused by freeze–thaw cycles. No rutting or potholes were observed in the stabilized test sections, while no blading operations were required since the installation of the geosynthetics. Recycled plastic-based geosynthetics showed strong potential for soil stabilization by increasing bearing capacity, strength, and stiffness while reducing rutting, deformation, and required granular base thickness. They also effectively lowered soil moisture content, thereby enhancing the performance and durability of unpaved roads against traffic loads and weathering.
By repurposing plastic waste into valuable construction materials such as geosynthetics, both environmental challenges and resource demands of modern infrastructure can be addressed. The findings highlight the potential of recycled plastic-based geosynthetics to reduce greenhouse gas emissions, promote material circularity, and enhance the resilience of transportation infrastructure under extreme climatic conditions. Furthermore, these materials offer performance benefits comparable to those of virgin plastic-based geosynthetics, pending further validation through continuous monitoring and long-term evaluation
Physical nature enhances creativity, while virtual nature strengthens creative self-concept
No full textEnhancing creativity is essential in educational and professional settings. While previous research has demonstrated that physical nature can boost creativity by supporting cognitive restoration, this study explores the effects of both physical nature and virtual nature exposure on creativity. It specifically examines how these environments influence participants’ creative abilities and self-perceived creative identity and compares the relative impact of physical nature vs. virtual nature exposure on creativity. A total of 64 university students in the United States from diverse academic backgrounds were assigned to one of two conditions: exposed to physical nature or virtual nature. Creativity, self-perceived creativity, and restorative perceptions were assessed using the Alternative Uses Task (AUT), Short Scale of Creative Self (SSCS), and Restoration Outcome Scale (ROS). A linear mixed model (LMM) and paired t-tests analyzed changes over time and between groups. Results showed a significant increase in creativity over time in the physical nature group. Both groups reported higher SSCS, with virtual nature participants showing a slightly larger increase. Creativity improvements were positively correlated with restorative outcomes, regardless of nature type. These findings highlight the unique role of physical nature in enhancing divergent thinking while also pointing to the potential of virtual nature to strengthen creative self-concept.This article is published as Jafari Ranjbar, Maral, Yongyeon Cho, Sarah Zenti, and Stephen B. Gilbert. "Physical nature enhances creativity, while virtual nature strengthens creative self-concept." Frontiers in Psychology 16: 1706001. doi: https://doi.org/10.3389/fpsyg.2025.1706001
A word list for Levantine Arabic
No full textGrowing unrest in Palestine, Lebanon, and Syria is contributing to a rising demand for instruction in the Levantine Arabic spoken in those locations. However, few pedagogical materials exist in these dialects, which differ enough from the Modern Standard Arabic (MSA) traditionally taught in U.S. classrooms that specialized instruction is required. The analysis of larger and more representative dialect-specific corpora - or large, principled collections of machine-readable texts - could ameliorate this problem by guiding the creation of pedagogical materials. However, the number of Levantine Arabic dialect corpora available remains small, limitations in breadth and size are the norm, and resources based on Arabic corpora tend to focus on MSA (Althobaiti, 2020; Buckwalter & Parkinson, 2014). The first goal of this dissertation is to describe the target domain of Levantine Arabic, in order to build a larger, more diverse Levantine dialect corpus. The second is to identify high-frequency words that distinguish the Levantine dialects from MSA, and the Levantine dialects from one another. To describe Levantine Arabic, a survey (Hashimoto, 2020) of 16 native speakers' daily use of Levantine Arabic was conducted, and interviews with 10 content producers including a novelist, a Youtuber, and a film director were completed, after existing literature on the dialects was reviewed. Informed by this domain description, the corpus was designed following Egbert et al.(2022). The approach for generating the pedagogical word list was selected by comparing the goals and typical topics of keyword analysis (Baker, 2004) and another statistical analysis (Gardner & Davies, 2014), as well as by conducting both analyses using a pilot corpus, and comparing the results.
After selecting and applying Gardner and Davies’ analysis (2014), over 500 high-frequency words that distinguish the Levantine dialects from MSA were identified, and over 50 words were identified for each Levantine dialect. Findings were evaluated through quantitative and qualitative analyses. In quantitative analyses, the 500+ word list’s average coverage of the target corpus (12.04–23.67%) and outside Levantine corpora (9.91-28.62%) suggested that to some extent this list represents Levantine Arabic, rather than the target corpus alone. However, coverage of the Levantine dialect did not always exceed coverage of non-Levantine corpora, revealing the impact that register - particularly conversation - had on results, despite the safeguards provided by Gardner and Davies (2014). Register had a similar impact on the four country-specific word lists, which had more limited average coverage of their target corpora (7.68-22.88%), and displayed notable orthographic overlap (4-24%). Qualitative analyses showed that dialect words usually differed from their MSA equivalents morphologically or lexicosemantically. More phonological differences would likely have been identified if phonological transcriptions were used in the corpus, offering a direction for future research. Potential uses of the pedagogical word lists were explored, including construction of a frequency dictionary and identification of eleven foci for vocabulary instruction to supplement top Arabic textbooks.
In sum, this dissertation has modeled the application of step-by-step guidelines for designing and evaluating a more representative corpus to a lesser-studied language and has demonstrated its utility in creating materials for some of its less-resourced dialects. Specifically, this dissertation has contributed to Arabic language education by producing a corpus of texts in the Levantine dialects larger and broader than almost any other existing, and has produced some of the first pedagogical word lists for Levantine Arabic. This study has many limitations, including the lack of insight it provides into the phonological differences between Levantine and Modern Standard Arabic. However, bearing these limitations in mind, these word lists could be used to inform vocabulary instruction supplemental to existing textbooks. In this way, the findings of this dissertation have the potential to make Levantine Arabic language learning more efficient by facilitating the prioritization of high-frequency words in the classroom
Assessment of invasive carp reproductive suitability and electrical barrier effectiveness in Iowa rivers
No full textBighead Carp (Hypophthalmichthys nobilis) and Silver Carp (Hypophthalmichthys molitrix) continue to expand their range throughout the Missouri and Mississippi River basins, threatening the ecological integrity and economic value of both invaded and vulnerable aquatic systems. While general spawning requirements have been identified, predicting where reproduction is most likely to occur and how to effectively prevent upstream movement into suitable habitats remains a challenge. Electrical deterrence barriers are increasingly used to control fish movements and have shown potential in laboratory settings. However, their effectiveness under dynamic environmental conditions is less understood. My objectives were to (1) predict invasive carp reproductive suitability in interior Iowa tributaries using multi-criteria habitat models and (2) evaluate the deterrent effectiveness of an electric barrier under variable field conditions to prevent upstream movements of invasive carp.
In Chapter 2, I developed habitat suitability models for 20 interior Iowa tributaries using hydrogeomorphic variables associated with invasive carp spawning. Through automated Geographic Information System (GIS) and multi-criteria decision making (MCDM) weighting methods, I identified river segments with varying levels of reproductive suitability based on habitat preferences of river length, sinuosity, turbulent hardpoints, and flow. I observed strong agreement across model predictions that identified a limited number of segments (21%) with higher reproductive potential while classifying the remaining segments as having comparatively low habitat suitability. However, larval back-calculations indicated spawning primarily occurred in segments classified as having “poor” reproductive habitat. My results highlight the reproductive plasticity of invasive carp and indicate that even the worst habitats identified within a system provide conditions suitable for spawning.
In Chapter 3, I conducted 120 experimental trials in a manipulative field setting to evaluate invasive carp behavioral responses to seven pulsed DC electric barrier waveforms across environmental gradients. While no invasive carp passed upstream during any trial, deterrence effectiveness declined with increasing water depth, especially under gated burst waveforms with shorter pulse widths and higher frequencies. Interactions with the barrier increased with water depth and decreased with rising water temperatures, demonstrating barrier effectiveness varies with hydrological conditions and requires adaptive management of electrical settings to maintain performance.
My results highlight the reproductive plasticity of invasive carp and the importance of evaluating deterrence effectiveness under variable field conditions when developing management strategies. This research improves our understanding of how to identify where invasive carp are most likely to reproduce and how their upstream movements can be limited through adaptive deterrent strategies. Collectively, my results support integrated approaches that combine spatial modeling and environmentally responsive deterrence methods to reduce invasive carp reproduction and expansion in at risk river systems
Development of low-cost photoacoustic imaging systems and their applications
No full textPhotoacoustic / optoacoustic imaging (PAI) is a hybrid imaging technique which combines the optical contrast and the ultrasound resolution in a single imaging modality. In PAI, an object is irradiated with a short-pulsed light source. The light energy is absorbed by the object and is partially converted into heat energy, leading to local temperature rise and subsequently pressure rise due to thermoelastic expansion. The pressure waves propagate as ultrasound waves [also is known as photoacoustic (PA) waves]
Based on the optical illumination pattern and the orientation of the ultrasound transducer and signal detection geometry, PAI is mainly classified as photoacoustic computed tomography (PACT) and photoacoustic microscopy (PAM). In circular scan PACT, the region of interest is illuminated, and the ultrasound transducer is positioned perpendicular to the direction of illumination. The ultrasound transducer is either a single element transducer that rotates around the sample in full circle (360 degree) or a curved array covering the full circle (or a full 3D spherical transducer array). In linear PACT (lPACT) the optical illumination and the UST (usually linear array transducer) is on the surface of the region of interest, and the transducer usually has partial coverage. lPACT system with linear array ultrasound transducers are easier to translate to clinical applications as most clinical ultrasound imaging system used in clinic are based on linear array systems. Therefore, incorporating PA imaging on top of a linear array-based ultrasound system is logical for future clinical applications. Another key component of any PAI system is the expensive pulsed laser sources, making the imaging systems very expensive. Therefore, developing cost effective photoacoustic imaging system is an important task for future translation.
Among the available PAI system on the market, only one system uses an alternate light source such as light emitting diode (LED). Therefore, we first test a LED-based photoacoustic + ultrasound (PAUS) system. The advantages of this system are, (1) the illumination source (LED array) is safe to use (does not need safety precautions) (2) has a desktop form factor, and (3) uses linear array ultrasound transducer. We tested and compared it against other types of PAI developed in the lab for a dental imaging application. The limitations of this imaging system were the low image quality due the less per pulse energy from the LEDs.
To enhance the performance of the LED-based PAUS system we incorporated an additional light source such as pulsed laser diode (PLD), whose per-pulse energy is much higher than the LEDs. We demonstrated temporally delayed, dual-pulse, dual-wavelength photoacoustic imaging (TD-DP-DW-PAI) with the addition of PLD light source together with LED-based PAUS. The image quality improved by a factor of two. The delay between the illumination sources increased the functionality of the system. The added functions were (1) non-linear doubling of the frame rate, and (2) multi-wavelength imaging without compromising the LEDs low energy illumination and frame rate. This imaging system having a desktop form-factor still lacks the portability for point-of-care application.
Next, we demonstrate the feasibility of a low-cost, ultra-compact, portable dual-mode ultrasound and photoacoustic imaging system (wUS-PA) using a wireless ultrasound platform. We adapted a linear array-based ultrasound scanner L15 HD3 (Clarius), an FDA (food and drug administration) approved wireless clinical ultrasound imaging system, to operate as dual-mode ultrasound and photoacoustic imaging system. PLD was used as an illumination source to study the feasibility of wUS-PA imaging. For a 4 cm imaging depth the system can image up to 17 frames/second. The axial and lateral resolution were 150 µm and 300 µm, respectively
Fast and private distributed learning for low rank models
No full textThis dissertation focuses on fast and private distributed learning for low rank models. For this problem, we have proposed fast algorithms and, using techniques from non-convex analysis, linear algebra, and high-dimensional probability, analyzed their convergence. The results of this research have been published in 3 peer-reviewed publications
The Importance of Accounting for Stakeholder Values, Power Relationships and Language in Constructing Relevant and Trustworthy Climate Information
No full textFacing increasing risks from climate change, governments at all levels have started to mainstream the use of climate information. It has been widely acknowledged that the inclusion of stakeholder knowledge and needs, for example, in a co-design and co-production process, is important for producing user-relevant information. Here we start from a hypothetical example and two real-world case studies from South America and West Africa to discuss the role of user values, power relationships and language in the construction of climate information. While these aspects have been discussed individually in several papers, we focus on the mutual influences of these aspects in the information construction and argue that, therefore, they cannot be considered separately. We identify five dimensions—the level of risk, the complexity of the scientific problem, user values, power relationships and language—to characterize the complexity of a given user context. Analyzing these dimensions can guide the choice and design of user engagement in a given situation. In particular, even basic research may benefit from such an engagement. Regularly accounting for these aspects in research projects may require substantial changes in the way research funding is organized and how the work of researchers is rewarded.This article is published as Maraun, Douglas, Dragana Bojovic, Wendy Parker, Theodore G. Shepherd, Stefan Sobolowski, Cyril Caminade, Alessandro Dosio et al. "The importance of accounting for stakeholder values, power relationships and language in constructing relevant and trustworthy climate information." Earth's Future 14, no. 1 (2026): e2024EF005618. https://doi.org/10.1029/2024EF00561
Dietary amelioration of systemic inflammation and immunometabolism in lactating dairy cows
No full textInflammation is an important component of the immune response. It is caused by a
multitude of factors which, if not managed properly, can lead to localized or systemic adverse
effects downstream of an initial stimulus. Livestock can become more vulnerable to immune
activation and subsequent inflammation during specific periods of production and during chronic
exposure to extreme environmental conditions. Many nutritional additives claim to mitigate or
prevent the physiological effects of inflammation through various pathogenic or pathway
interventions. In this thesis, we aimed to elucidate whether systemic inflammation can be
reduced by orally delivered β(1,4) mannobiose.
Mannan oligosaccharides (MOS) are a class of carbohydrates that are commonly used in
livestock diets because of their ability to act as a prebiotic to beneficial bacteria, such as
Lactobacillus and Bifidobacterium in the hindgut. The immunotherapeutic qualities of MOS
have been researched since the late 1970s (Day et al., 1980), and as a result, MOS have become
more refined for use as an anti-inflammatory feed additive. With increased hydrolysis of mannan
oligosaccharides, the concentration of β(1,4) mannobiose increases per mole of mannan. β(1,4)
mannobiose has been shown in cell culture and animal models to interact directly with toll-like
receptor (TLR) 4 and act as a competitive inhibitor of lipopolysaccharide (LPS) in vivo. To
evaluate immune-regulating qualities of this disaccharide in ruminants, mid-lactation dairy cows
were fed an additive rich in β(1,4) mannobiose, and following a baseline period, were challenged
with an i.v. LPS bolus to induce a systemic inflammatory response. To assess the effectiveness
of β(1,4) mannobiose, inflammatory biomarkers, metabolites, and production metrics were
evaluated. Results of this experiment suggest that β(1,4) mannobiose ameliorates systemic
inflammation, based on altered cytokine and acute phase protein responses. While there was
convincing evidence that oral β(1,4) mannobiose appears to attenuate inflammation caused by
LPS, further research is needed to elucidate the relationship between this specific disaccharide
and production parameters in immune-activated, lactating dairy cattle