Graduate College

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The doctoral dissertation and master's thesis reflects the scholarly research in a graduate program as required for the completion of the degree at the University of Delaware.

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    100 Hz 512x512 SLEDS system design
    (University of Delaware, 2014) Nabha, Kassem
    Infrared (IR) detectors applications are widely used across fields from scientific and military to medical and industrial. IR can detect information that human eyes cannot perceive allowing the advancement in science and technology. ☐ Due to the importance of the infrared detectors in today's world, it is necessary to accurately test and characterize these detectors with a frame of reference related to the application. IR projection systems are a great way to characterize the detectors because they can be used as high accuracy reference. ☐ Described in this work is a 512x512 super-latticed light emitting diode system (SLEDS) operating at a frame rate of 100Hz. This system has been fully developed, tested, and corrected for non-uniformity (NUC). Further work will be done to achieve higher frame rates and two frequencies of emission (colors) instead of one.
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    210Polonium and 210lead radionucidles in the Delaware and Chesapeake estuarine and coastal regions
    (University of Delaware, 2013) Marsan, David
    One of the primary objectives of this thesis is to present an integrated study of the 210Pb and 210Po radioactive tracers, and assess their use as tracers for particle and trace element export from different estuarine and coastal environments. In order to achieve this main objective, the thesis was split into three sections, each enhancing the understanding of the natural radionuclides 210Pb and 210Po in the estuarine and costal system. Chapter 1 is dedicated to testing the sampling and analytical methods of 210Po and 210Pb extraction from estuarine and coastal waters, specifically comparing the two most widely used scavenging methods, Fe(OH)3 and CoRAPDC. The chapter describes experiments conducted on about 100 samples collected from the Delaware estuary, Chesapeake estuary, Delaware intertidal marsh and an offshore continental slope site. Data in the chapter clarifies the accuracy and reliability of each method and includes suggestions to enhance them. Other details include results of calculations, error propagation, spike calibration, plating efficiency and the MnO2 scavenging method. Chapter 2 presents a synthesis of the estuarine and coastal biogeochemistry of 210Po and 210Pb in the Delaware and Chesapeake estuaries. A single box model is presented using steady state equations to determine residence times of the radionuclides. This chapter presents five highlights: 1) How 210Pb and 210Po dissolved and particulate data can revel key biogeochemical processes and rates in estuaries; 2) Are regional differences in estuaries dominated by a single or compilation of biogeochemical process; 3) Do subRoxic bottom waters affect the distribution of 210Po and 210Pb; 4) Can disequilibria between parent (210Pb) and grandRdaughter (210Po) be used to identify and quantify principle processes; 5) Will a simple mass balance model result in reliable net scavenging residence times for the Delaware and Chesapeake estuaries. Chapter 3 will advance the simple single boxRmodel from chapter 2 to a more complex twoRlayer model. The model will include evaluations of the fate of not only 210Po and 210Pb in the Delaware and Chesapeake estuaries but also the trace elements Fe, Cu, Cd, Ni, Zn, Pb, Cr, Co and Mn. Residences times, presented as halfRlives along with rates and partition coefficients will be identified for the water column including at the sediment water interface. The thesis will revisit the major conclusions obtained from the work presented along with suggestions for future work. Appendix sections include supporting hydrographic data and a compilation of salt marsh trace metal results conducted in Graz, Austria. Trace metal work included a suite of 26 elements measured in a core, two species of mussels, Spartina)alterniflora marsh plant and the sea surface microlayer (SML) from an intertidal Delaware salt marsh.
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    3D permeability characterization of fibrous media
    (University of Delaware, 2010) Okonkwo, Kenneth
    In Liquid Composite Molding (LCM) processes, a liquid resin is forced to flow through dry fibrous preform, usually fabrics, to impregnate it and create the composite part in net or near-net shape. The principal advantage of LCM processes is their capacity to produce high fiber volume fraction and high quality parts under low pressure at low cost. The main conditions for successful manufacturing are complete filling of the mold and perfect impregnation of the reinforcement material. If these conditions are not met the structural properties of the finished part are significantly impaired by defects like voids. The mold filling depends on the permeability of the fibrous media. Permeability is an intrinsic property of fiber reinforcement, which includes all interactions between fibers and fluid and characterizes the ease of flow through the medium. The complete prediction of second-order permeability tensor is critical to understanding and prediction of flow in the resin transfer molding process of thick composites or where the flow process is three dimensional In this thesis a new approach for characterizing the three dimensional permeability tensor of fabrics used as reinforcement in liquid injection molding processes from a single experiment is presented and validated. In this approach, a liquid is injected into a preform placed in a mold containing 192 electrical resistance flow sensors radially embedded in the top and the bottom platens of the mold. The proposed method uses an optimization routine in which the permeabilities in a 3D flow simulation of the identical mold is updated continuously until the error between the simulation arrival times at all the 192 sensor locations and the experimental arrival time is minimum. The optimization routine systematically changes the values of the components of the permeability tensor using golden search method until the best match is obtained. The validation and sensitivity of this method is explored and it has been shown that this technique is promising for permeability characterization. The approach is shown to be valid for reinforcements with anisotropic and isotropic nature The advantage of this approach is that it can be used to obtain permeability values from a single experiment; there is no need to scale the circular injection inlet, and it is not limited to principal permeability values. The sensors utilized are unobtrusive to the flow unlike say optic fibers embedded in the fabric that interfere with the flow of the test fluid. The electrical resistance sensors used in this approach are embedded in mold platens instead and which flush with the surface. The method can be used to help predict and understand resin flow behavior during liquid molding of advanced composite materials.
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    A 3D photonic sensor integrated tissue model for strain sensing
    (University of Delaware, 2019) Geiger, Sarah J.
    The study of wound healing and wound healing therapies is motivated by the need to prevent the formation of thick scar tissue in pathologically healing wounds and tissues that rely on their elasticity and modulus to perform their function, such as cardiac and vocal fold tissues. The development of in vitro platforms that can detect cell-induced strain in mimics of healing wounds has expanded our understanding of the mechanical, chemical, and physical cues that drive wound healing. However, these platforms are limited in their resolution, dimensionality, and ability to gather information about changes in strain throughout thick, opaque tissue models. In this work we describe the development of flexible, deterministically buckled 3D photonic device arrays that are designed and fabricated to meet the specific spatial, temporal, and strain resolution requirements needed for the detection of cell-induced strains in a millimeters-thick tissue model. ☐ A polymer or silicone-clad Ge23Sb7S70 chalcogenide glass resonant cavity array is selected for this application, as high-quality chalcogenide glasses devices can be deposited at low temperatures onto flexible and cytocompatible substrates. However, the reliability of these and other highly sensitive chalcogenide glass devices is affected by their aging-induced structural relaxation. The refractive index shifts resulting from this relaxation are on the same order of magnitude as the index shifts used to small-scale strain with our device arrays. In order to overcome this limitation, we develop and demonstrate a high-precision refractometry technique that tracks small changes in the refractive index of Ge23Sb7S70 chalcogenide glass, down to 10-5 RIU. This technique allows us to both identify the aging mechanism in this glass with high accuracy and compare different index stabilization methods to optimize our device processing. ☐ The expected performance of these arrays was tested both through finite element modeling and a proof-of-concept in vitro experiment. In the modeling experiments, PDMS buckled geometries were deformed in cardiac graft tissue-like environments. From these experiments we showed that devices embedded in these materials could easily detect small, localized changes in stiffness theoretically caused by limited perfusion of growth factor throughout this model. In vitro, an SU-8 clad, symmetrically buckled device was exposed to a contracting collagen gel, and the device response as a result of this deformation was analyzed. ☐ These deterministically buckled arrays of polymer or silicone-clad chalcogenide glass resonant cavities demonstrate sensitivity to relevant strains in 3D cell culture platforms, excellent ease of use, and the potential for a wide range of applications. This technique can be used as a standalone, low cost, plug-and-play local strain gauge for use in soft material systems. Thus, this technique’s flexibility both in terms of its deformability and range of applications easily surpasses other methods of in vitro force or strain detection.
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    3D reconstruction from coded plenoptic sampling
    (University of Delaware, 2019) Zhou, Mingyuan
    The plenoptic function describes a scene in terms of light rays, it is a 7-dimensional function with spectral, directional, spatial, and temporal variation. Traditional plenoptic sampling is acquired either by employing a standard plenoptic camera or a camera array, and the spatial-angular sampling can be potentially used to model 3D surface. ☐ In this dissertation, I present three coded plenoptic sampling schemes, i.e., the rotational cross-slit (R-XSlit) plenoptic sampling, the wavelength coded plenoptic sampling, and the polarimetric plenoptic sampling. The additional coded sampling information, such as non-centric sampling, spectral sampling, and polarization sampling, are conducive to 3D reconstruction. Therefore, I also develop the corresponding 3D reconstruction framework for each of them. ☐ First, I introduce the R-XSlit plenoptic sampling scheme by exploiting a special noncentric camera called the crossed-slit or XSlit camera. An XSlit camera acquires rays that simultaneously pass through two oblique slits. I show that instead of translating the camera as in the pinhole case, we can effectively sample the 4D plenoptic sampling by rotating individual or both slits while keeping the camera fixed, which makes the plenoptic sampling coded in the spatial-angular domain. The theoretical analysis shows that it provides denser spatial-angular sampling, which is beneficial for scene reconstruction and rendering. I develop a volumetric reconstruction scheme for scene reconstruction. ☐ Second, I present two wavelength coded plenoptic sampling schemes in the visible and infrared spectrum respectively. I firstly design a compact system with lights and cameras arranged on concentric circles to acquire a concentric wavelength coded plenoptic sampling in the visible spectrum, the cameras on each ring capture images in a unique spectrum. I employ the Phong dichromatic model onto its plenoptic function for 3D reconstruction and spectral reflectance map estimation. Experiments show that our technique can achieve high accuracy and robustness in geometry recovery. Moreover, I present an infrared wavelength coded plenoptic sampling and develop a hybrid sensing framework to efficiently achieve pose estimation and face reconstruction by exploiting the captured reflected infrared rays from human eyes. ☐ Finally, I present a polarimetric plenoptic sampling framework for recovering 3D surfaces, the polarization of light is included in its plenoptic function. I employ a new analysis analogous to the optical flow to correlate the polarization radiance function with both surface normal and depth. The proposed framework effectively resolves the azimuth-zenith ambiguity by forming an over-determined system. Extensive experiments on both synthetic and real data demonstrate that the technique is capable of recovering extremely challenging glossy and textureless objects.
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    95 GHz silicon germanium low noise amplifier as front-end receiver for sparse aperture millimeter wave imaging
    (University of Delaware, 2015) Wright, Andrew Alexander
    Demand for the ability to navigate in degraded visual environments (DVE) such as dust, smoke, and fog, has lead the development of millimeter wave (mm-wave) real-time imaging systems. Millimeter wavelength radiation has shown that the wavelengths are long enough to penetrate the obscurants while also allowing sufficient resolution. A low attenuation atmospheric window in the 95 GHz region has pushed for these systems to operate at these millimeter wavelength frequencies. Due to low signal levels at these frequencies, the system requires high gain in the front-end to boost the signals of mm-wave frequencies. This involves collecting the electromagnetic waves with a horn antenna and then amplifying the signal with a low noise amplifier (LNA) to maximize the signal to noise ratio (SNR). In photonics-based imaging systems, the mm-wave signal is then up-converted to optical domain, where it then propagates through optical fibers to an infrared camera for further processing. The horn, LNA and up-converter comprise a single module. A large distributed array of modules, around 200, are required for a real-time mm-wave imaging system capable of peering through DVE. As a result, pushing this technology to higher frequencies can be very costly, due to the high prices of individual high frequency components. Therefore, an alternative technology is required to keep the costs to a minimum. One approach to controlling costs of components operating at higher frequencies is to adopt an alternative amplifier technology. Conventionally, commercially available GaAs and InP LNAs are used to obtain high gain at the high frequencies, but at 95 GHz, each amplifier used to be thousands of dollars. Since then, costs for each amplifier decreased to $100. With each module requiring three or more amplifiers, costs become prohibitively high for many applications. Therefore, this thesis focuses on the development of a 95 GHz amplifier using silicon germanium (SiGe) technology to obtain the required high gain while maintaining low costs. To date, extensive efforts have been made in the development of SiGe amplifier technology and high gain was demonstrated at the W-band. However, existing amplifier technology does not meet the requirements of the mm-wave imager. In particular, major limitation is the 3-dB bandwidth of the gain curve. A distributed aperture system with a wide field of view and broadband response will experience a phenomenon known as fringe-washing if an off-axis signal arrives with significant delay between the receivers on the opposite ends of the longest baseline. Severe fringe-washing occurs when this delay of the projected baseline is comparable to the correlation time of the signal, i.e. the inverse bandwidth of the system. To mitigate fringe-washing, each module must limit the bandwidth of operation, which can be accomplished either with a filter or an amplifier. Since filters can be lossy, ideally a narrow-band amplifier is preferred. In this thesis, using the basic principle of amplifier design, an LNA is developed based on advanced SiGe-foundry processes to operate in the 95 GHz regime. The advantage of a custom SiGe amplifier is the ability to design it to meet the imager's specific demands, including gain, noise figure, bandwidth, and power consumption in a single low cost device. This thesis details such design, and includes the discussion of tradeoffs and limitations imposed by the commercial SiGe-foundry processes employed.
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    A balancing act: examining the relationship between school leadership and political tension in education decision making
    (University of Delaware, 2023) Cahill, Amanda
    The United States has a long history of political tension around education at the federal, state, and local level. District and school leaders must balance students’ learning and social needs while working to address political tension barriers on education decisions. Political tension involves the feeling of strain or anxiety around topics aligned with political ideology. The strain and anxiety generally result in difficulty with efficiently moving forward with clear decision making, specifically in education. Education decisions are choices made by district and school leaders that affect students’ growth academically within the school setting. Examples of education decisions could include restructuring the administration team, endorsing a specific curriculum, or implementing an enrichment program. Researchers have written extensively about effective leadership approaches but there is a lack of literature on strategies for how school leaders, particularly at the district level, can address political tensions that create barriers to decision making. School leaders' abilities to address political tension would support efficacious decision making with a focus on positive outcomes for students. ☐ Overtime, as politics has become more contentious, districts’ decision making has come under attack. These attacks significantly disrupt the ways in which school districts make and implement reforms, school improvements, policy changes, and the like. District and school leaders lack strategies and resources to proactively address political tension barriers which results in sporadic and often poorly implemented or communicated decision making. These implementation and communication failures are then poorly received by the community. The constant politicization of school decisions has caused leaders to focus on responding to political tensions, rather than focusing on decision making that can positively impact students’ learning needs. Therefore, it is imperative that educational leaders are equipped and prepared to address political tensions that cause barriers so that they can remain focused on decision-making processes that result in positively supporting students’ learning and social needs. Education leaders need both the resources and the opportunity to apply decision-making strategies that simultaneously address political tensions and remove barriers in order to communicate more effectively and work harmoniously with their school community. ☐ In my educational leadership portfolio (ELP), I focus specifically on how political tensions on the national level are influencing the decision making of local district and school leaders. I evaluated the relationship between district and school leaders’ decision-making process and political tension barriers within a rural school district in the Mid-Atlantic region. I used a rural school district as a case study to explore strategies district and school leaders need to manage political tension barriers without compromising decision making aimed at supporting student growth academically, socially, and emotionally. In this ELP, I gathered data through a case study. The ELP proposes a decision-making framework that district and school leaders can proactively utilize when they predict, or encounter, political tensions that result in barriers that may impede their ability to make decisions.
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    A BALLAST BOX TO STUDY THE EFFECT OF SAND FOULING ON BALLAST, TRACK STIFFNESS, TRACK DEFORMATION, AND PREDICTING MAINTENANCE TIME
    Alzhrani, Mohammed Abdullah J
    Railroad track crossings through sandy areas, like deserts, face the unique challenge of sand infiltrating into the ballast, leading to ballast fouling. Geographical conditions make these areas particularly prone to windblown sand infiltration, causing fine sand to gradually fill the ballast voids, ultimately resulting in fouling issues. Over time, fouled ballasts become a significant concern because of their negative impacts on track performance. This study explores the impact of ballast fouling primarily caused by sand infiltration on track deflection, stiffness (modulus), and overall track degradation. The main goal is to establish a clear relationship between these factors and fouling levels due to sand infiltration. The research was conducted at the University of Delaware's Civil Engineering laboratory, utilizing an 18-cubic-foot (0.67 cubic yards) ballast box. A rail/tie/fastener assembly was placed on the ballast and subjected to cyclic loading at a rate of 12 cycles per minute. The testing began with clean ballast, and dynamic load tests were carried out under simulated vehicle wheel loading conditions for up to five hours, with load-deflection behavior recorded during each cycle. Sand was introduced to the ballast in two series: Series 1, representing unconsolidated tests, and Series 2, simulating progressive fouling. These tests were repeated with varying levels of sand fouling, ranging from moderate to severe. Load deflection curves were analyzed using the Beam on Elastic Foundation (BOEF) theory to determine track modulus (stiffness) values and cumulative deformation, corresponding to cumulative plastic strain under repeated wheel loading. The study's results reveal a consistent pattern in load deflection curves, track modulus values, and cumulative plastic strain for different levels of sand fouling. It was observed that as sand fouling increased, both track stiffness (modulus) and track settlement also increased, aligning with field measurements conducted under similar conditions. As a result of these findings, a predictive application was developed to estimate maintenance time based on the degree of fouling. This application can offer valuable insights into maintenance planning and decision-making for tracks traversing sandy regions.
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    A Bayesian Cue Integration approach to racial bias in pain assessment and treatment
    (University of Delaware, 2023) Goharzad, Azaadeh
    Patients' reports of subjective pain experience are at least nominally a primary diagnostic cue in assessment and treatment of pain. Despite this, there is low concordance between provider assessments and self-reported pain ratings, such that patient pain is regularly underestimated and undertreated. Such discrepancies in care are particularly stark for Black patients, who receive less adequate pain care compared to White patients. While attending to facial expressions of pain marginally improves concordance in patient-provider pain ratings, it is not clear that this would improve concordance for Black patients given previous work demonstrating blunted recognition of pain on Black faces. Moreover, it is unclear how self-reported pain information is integrated with facial expressions of pain, and whether this integration is similarly biased as a function of patient race. In the present paper we construct three models of pain assessment for both Black and White targets to examine how individuals use facial expression and self-reported pain cues in making holistic judgements of pain intensity as well as subsequent treatment decisions. Overall, we find that the Bayesian Cue Integration model (compared to Face Dominant and Self-Report Dominant models) best predict participant assessments of pain as well as treatment outcomes for both Black and White targets, suggesting that both facial expression and self-report are integrated in pain assessment. ☐ Keywords: Social cognition, pain, race, cue integration
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    A bioorthogonal hydrogel platform for the development of an engineered vocal fold tissue model
    (University of Delaware, 2022) Song, Jiyeon
    Vocal fold lamina propria, with a complex multilayered structure, exhibits optimal biomechanical properties for voice production. Vocal fold scarring disrupts the laminated structure, alters the tissue viscoelasticity, and severely compromises the phonatory function. Therapeutic interventions are limited because of the lack of understanding of molecular mechanisms contributing to vocal fold scarring. The situation is exacerbated due to the scarcity of healthy human tissues, inability of animal models to recapitulate the human physiology, and unavailability of in vitro physiologically relevant tissue models. ☐ The goal of this dissertation is to develop a bioorthogonal hydrogel platform for the engineering of a human vocal fold tissue model. To this end, hydrogel precursors tagged with bioorthogonal tetrazine (Tz), trans-cyclooctene (TCO), norbornene (Nb), thiol (SH) or acrylate (AC) groups were synthesized using hyaluronic acid, synthetic polymers, and bioactive peptides. Various dienophiles with different reactivities toward tetrazine were conjugate to matrix metalloprotease (MMP)-degradable peptides, integrin-binding RGD peptide, and basic fibroblast growth factor-mimetic peptide. The composition and purity of these conjugates were characterized by proton nuclear magnetic resonance (1HNMR), high performance liquid chromatography (HPLC), mass spectrometry (MS), and ultraviolet-visible spectroscopy (UV-vis). ☐ Using the modular building blocks, a lamina propria-mimetic construct with a layered structure was developed. Taking advantage of the exceptional rate of the Tz/TCO reaction, a diffusion-controlled interfacial crosslinking method was devised for the fabrication of a hydrogel sphere with a 3D core-shell pattern. By changing the ratio of the monofunctional capper and the bifunctional TCO crosslinker, hydrogels with a Young’s modulus ranging from 4 kPa to 20 kPa, comparable to that for human vocal fold LP, were obtained. Additionally, the diffusion-controlled method permitted precise spatial control of the enzymatic degradability and cell adhesivity in core and shell layers where homogeneously encapsulated human mesenchymal stem cells (hMSCs) exhibited different cell morphologies at each layer. ☐ Finally, a bioorthogonal hydrogel platform that recapitulates dynamic alterations in matrix properties during wound healing was engineered. The slow Tz/Nb was utilized to establish the covalent hydrogel networks for 3D cell encapsulation. The rapid Tz/TCO ligation enabled real time in situ modulation of the density of RGD ligands. The diffusion-controlled reaction also allowed the time-delayed introduction of RGD peptides to cell-laden hydrogel constructs, mimicking the progressive deposition of fibronectin during the early stage of wound healing. Transforming growth factor beta 1 (TGFβ1)-induced myofibroblast differentiation from primary vocal fold fibroblasts was observed only at a high RGD concentration, as evidenced by the development of alpha-smooth muscle actin (αSMA) positive F-actin stress fibers. The RGD-driven phenotype change was accompanied by enhanced cytokine secretions and matrix remodeling. ☐ Overall, I presented a powerful bioorthogonal platform for spatiotemporal presentation of biochemical and biomechanical signals to direct cellular responses and differentiation. This work represents the first step towards the development of a hydrogel-based cellular model of the human vocal fold lamina propria in both healthy and diseased states.
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    A BOUNDING SURFACE PLASTICITY-BASED HYPERELASTIC CONSTITUTIVE MODEL FOR UNSATURATED GRANULAR SOILS
    Kadivar, Mehdi
    One-third or more of the earth’s surface is situated in arid or semi-arid regions where the potential evaporation exceeds the precipitation and soils exist in their unsaturated state. Unsaturated soils are also abundant in most parts of the world where there is seasonal groundwater table fluctuation. The variation in the degree of saturation gives rise to a gamut of variability in soil’s hydromechanical behavior. The co-existence of pore-air and water in the void spaces and their interaction with each other and the solid particles are the main reasons why such variability exists and why unsaturated soils are more complex than saturated or dry ones. A robust understanding of the hydromechanical properties of unsaturated soils is crucial for geotechnical engineers worldwide, as well as for those concerned with the interaction of structures with the ground. Some engineering problems associated with unsaturated soils include precipitation-induced shallow-depth landslides, settlement of soil in the vadose zone, drainage of roadway materials, and borehole stability. Proper understanding of unsaturated behavior requires considerations that go beyond those available for saturated soils. In pursuit of addressing this requirement, a plethora of research has been devoted to measuring, modeling, predicting, and interpreting unsaturated soil behavior. Many theories for characterizing the mechanical response, methodologies for laboratory testing, as well as equipment to determine the constitutive parameters have been developed. Instruments to study in-situ behavior of unsaturated soils have also been promoted and used in a few cases. The outcomes of past research include: the development and critical evaluation of various forms of the effective stress principle and its fundamental role in determining strength and deformation properties of unsaturated soils; identification of independent state variables; development of failure envelopes and yield surfaces; formulation of macromechanical and micromechanical constitutive relationships; and formulation of suction-induced stress as a component of the intergranular stress tensor. Despite the volume of work dedicated to the field of unsaturated soil mechanics, compared to two-phase (i.e., saturated) soils, relatively few advancements have been made in the development of characterization frameworks for unsaturated soils. In this doctoral research, a novel, 14-parameter, state-dependent bounding surface plasticity model that simulates the behavior of unsaturated granular soils is developed. In the development of this model, a critical state compatible hyperelastic formulation for saturated granular soils is selected as a base model and is enhanced and extended to predict unsaturated granular soil behavior. Accounting for deformation phenomena in unsaturated soils, the elastoplastic response has no purely elastic component. The hyperelasticity and assumption of no purely elastic deformation sets this model apart from existing ones. To handle the inherent hydro-mechanical coupling in unsaturated soils, a newer generation stress framework, consisting of the Bishop-type effective stress with a second stress variable, is used in conjunction with a soil-water characteristic curve function. Available unsaturated soil data for sands and silty sands were used to calibrate, validate, and assess the performance of the new model. Additional laboratory data, consisting of a suite of consolidated drained triaxial shear tests, were generated. The shear strength and volumetric behavior of a native mid-Atlantic transitional silty sand were investigated under varying values of matric suction, confining pressure, strain rate, and fines content. The experimental results are used to validate the predictive capabilities of the new bounding surface plasticity constitutive model for unsaturated granular soils. It is shown that with a set of parameter values, the model realistically simulates the main features that characterize the shear and volumetric behavior of unsaturated granular soils over a wide range of matric suction, density, and net confining pressure. In the literature, it was observed that multiple analytical expressions exist for effective stress, critical void ratio, and soil water characteristic curve. To see the effects that variations in these different analytical forms have on the model simulations of unsaturated soil behavior, a parametric investigation is performed using the constitutive model developed and the aforementioned in-house generated laboratory data. It is observed that, depending on the desired prediction accuracy, a variety of functions (with varying numbers of model parameters) could be implemented as part of the constitutive model.