Matching Items (189)
Description
Alcohol use disorder (AUD) causes immense global burden and has a significant impact on economic and societal functioning. Efficacious treatments for AUDs have been well-established within the literature, however the most commonly accessed treatments for AUD are alcohol-related services, such as self-help groups, outpatient clinics, and detoxification centers. Though studies suggest these services are effective at treating AUDs, there are numerous differences between individuals who receive alcohol-related services and individuals who do not, causing selection bias. Furthermore, current studies of alcohol-related services frequently define recovery outcomes as abstinence, which reduces variability in viable recovery outcomes, such as reduction of drinking behaviors. In addition, reduction in drinking and alcohol-related problems should theoretically have an impact on broader aspects of functioning, such as familial functioning. Improved familial context may reduce risk to family members, who are otherwise at heightened risk for emotional and behavioral problems when living with a family member with AUD. The current study investigated the effect of alcohol-related services on binary and continuous drinking outcomes after eliminating selection bias using multiple propensity score approaches, to identify the best methodology for a high-risk community sample of individuals with AUD. Propensity scores were created using logistic regression approaches and boosted regression trees. Matching, weighting, and subclassification were used, and matching was performed both using greedy and global approaches. Results suggested subclassification was the most successful method for real world alcohol-related services samples with moderate sample size. Moreover, findings demonstrated that boosted regression approaches were less successful than logistic regression approaches at minimizing the effects of selection bias on known confounding variables that are highly related to group selection. In addition, after removing the effects of selection bias, there were no significant difference between participants who received alcohol-related services and the comparison control group on drinking or family functioning, though both groups reduced drinking from pre- to post-alcohol-related services receipt. Findings suggest careful selection of quasi-experimental methods is warranted in real-world samples, to ensure optimal removal of selection bias. Moreover, future studies should continue to clarify the profile of individual that benefits from alcohol-related services to inform intervention efforts.
ContributorsSternberg, Ariel (Author) / Chassin, Laurie (Thesis advisor) / Corbin, William (Committee member) / Meier, Madeline (Committee member) / Grimm, Kevin (Committee member) / Arizona State University (Publisher)
Created2021
Description
Layer-wise extrusion of soft-solid like cement pastes and mortars is commonly used in 3D printing of concrete. Rheological and mechanical characterization of the printable binder for on-demand flow and subsequent structuration is a critical challenge. This research is an effort to understand the mechanics of cementitious binders as soft solids in the fresh state, towards establishing material-process relationships to enhance print quality. This study introduces 3D printable binders developed based on rotational and capillary rheology test parameters, and establish the direct influence of packing coefficients, geometric ratio, slip velocities, and critical print velocities on the extrudate quality. The ratio of packing fraction to the square of average particle diameter (0.01-0.02), and equivalent microstructural index (5-20) were suitable for printing, and were directly related to the cohesion and extrusional yield stress of the material. In fact, steady state pressure for printing (30-40 kPa) is proportional to the extrusional yield stress, and increases with the geometric ratio (0-60) and print velocity (5-50 mm/s). Higher print velocities results in higher wall shear stresses and was exponentially related to the slip layer thickness (estimated between 1-5μ), while the addition of superplasticizers improve the slip layer thickness and the extrudate flow. However, the steady state pressure and printer capacity limits the maximum print velocity while the deadzone length limits the minimum velocity allowable (critical velocity regime) for printing. The evolution of buildability with time for the fresh state mortars was characterized with digital image correlation using compressive strain and strain rate in printed layers. The fresh state characteristics (interlayer and interfilamentous) and process parameters (layer height and fiber dimensions) influence the hardened mechanical properties. A lower layer height generally improves the mechanical properties and slight addition of fiber (up to 0.3% by volume) results in a 15-30% increase in the mechanical properties. 3D scanning and point-cloud analysis was also used to assess the geometric tolerance of a print based on mean error distances, print accuracy index, and layer-wise percent overlap. The research output will contribute to a synergistic material-process design and development of test methods for printability in the context of 3D printing of concrete.
ContributorsAmbadi Omanakuttan Nair, Sooraj Kumar (Author) / Neithalath, Narayanan (Thesis advisor) / Rajan, Subramaniam (Committee member) / Mobasher, Barzin (Committee member) / Hoover, Christian (Committee member) / Chawla, Nikhilesh (Committee member) / Arizona State University (Publisher)
Created2021
Description
There is a high demand for customized designs of various types of cement-based materials in order to address specific purposes in the construction field. These demands stem from the need to optimize the cementitious matrix properties and reinforcement choices, especially in high reliability, durability, and performance applications that include infrastructure, energy production, commercial buildings, and may ultimately be extended to low risk/high volume applications such as residential applications. The typical tools required to guide practicing engineers should be based on optimization algorithms that require highly efficient capacity and design alternatives and optimal computational tools. The general case of flexural design of members is an important aspect of design of structural members which can be extended to a variety of applications that include various cross-sections such as rectangular, W-sections, channels, angles, and T sections. The model utilized the simplified linear constitutive response of cement-based composite in compression and tension and extends into a two-segment elastic-plastic, strain softening, hardening, tension-stiffening, and a multi-segment system. The generalized parametric model proposed uses a dimensionless system in the stress-strain materials diagram to formulate piecewise equations for an equilibrium of internal stresses and obtains strain distributions for the closed-form solution of neutral axis location. This would allow for the computation of piecewise moment-curvature response. The number of linear residual stress implemented is flexible to a user to maintain a robust response. In the present approach bilinear, trilinear, and quad-linear models are addressed and a procedure for incorporating additional segments is presented. Moreover, a closed-form solution of moment-curvature can be solved and employed in calculating load-deflection response. The model is adaptable for various types of fiber-reinforced and textile reinforced concrete (FRC, TRC, UHPC, AAC, and Reinforced Concrete). The extensions to cover continuous fiber reinforcement such as textile reinforced concrete (TRC, FRCM) strengthening and repair are addressed. The theoretical model is extended to incorporate the hybrid design (HRC) with continuous rebar with FRC to increase the ductility and ultimate moment capacity. HRC extends the performance of the fiber system to incorporate residual capacity into a serviceability-based design that reduced the reliance on the design based on the limit state. The design chart for HRC and as well as conventional RC has been generated for practicing engineering applications. Results are compared to a large array of data from experimental results conducted at the ASU structural lab facilities and other published literature.
Contributorspleesudjai, chidchanok (Author) / Mobasher, Barzin (Thesis advisor) / Neithalath, Narayanan (Committee member) / Rajan, Subramaniam (Committee member) / Arizona State University (Publisher)
Created2021
Description
The tensile stress–strain response of a fiber reinforced concrete dominates the performance under many loading conditions and applications. To represent this property as an average equivalent response, a back-calculation process from flexural testing is employed. The procedure is performed by model fitting of the three-point and four-point bending load deflection data on two types of macro synthetic polymeric fibers, one type of steel fiber and one type of Alkali Resistant (AR) glass fiber. A strain softening tensile model is used to simulate the behavior of different FRC types and obtain the experimental flexural response. The stress–strain model for each age, fiber type and dosage rate is simulated by means of the inverse analysis procedure, using closed-form moment–curvature relationship and load–deflection response of the piecewise-linear material. The method of approach is further applied to one external data set for High Performance Fiber Reinforced Concrete (HPFRC) with two different types of steel fibers and validated by tensile test results reported. Results of back-calculation of stress–strain responses by tri-linear tensile model for all mixtures are compared and correlated with the corresponding standard method parameters used for post crack behavior characterization and a regression analysis for comparative evaluation of test data is presented.
ContributorsMobasher, Barzin (Author) / Bakhshi, Mehdi (Author) / Barsby, Christopher (Author) / Ira A. Fulton Schools of Engineering (Contributor)
Created2014-11-15
Description
This study examined an adverse effect of an adolescent group intervention. Group interventions represent one of the most economical, convenient, and common solution to adolescent behavior problems, although prior findings from program evaluation studies have suggested that these groups can unexpectedly increase the externalizing behaviors that they were designed to reduce or prevent. The current study used data from a longitudinal, randomized controlled trial of the Bridges to High School / Puentes a La Secundaria Program, a multicomponent prevention program designed to reduce risk during the middle school transition, which has demonstrated positive effects across an array of outcomes. Data were collected at the beginning of 7th grade, with follow-up data collected at the end of the 7th, 8th, 9th, and 12th grade from a sample of Mexican American adolescents and their mothers. Analyses evaluated long-term effects on externalizing outcomes, trajectories of externalizing behaviors across adolescence, and potential mediators of observed effects. Results showed that the adverse effect that was originally observed based on adolescent self-report of externalizing symptoms at 1-year posttest among youth with high pretest externalizing symptoms was not maintained over time and was not reflected in changes in adolescents' trajectories of externalizing behaviors. Moreover, neither of the peer mediators that theory suggests would explain adverse effects were found to mediate the relationship between intervention status and externalizing symptoms at 1-year posttest. Finally, only beneficial effects were found on externalizing symptoms based on mother report. Together, these findings suggest that the Bridges intervention did not adversely affect adolescent problem behaviors and that future studies should use caution when interpreting unexpected adverse effects.
ContributorsWong, Jessie Jong-Chee (Author) / Gonzales, Nancy A. (Thesis advisor) / West, Stephen G. (Thesis advisor) / Chassin, Laurie (Committee member) / Dishion, Thomas (Committee member) / Arizona State University (Publisher)
Created2015
Description
Composite materials are finally providing uses hitherto reserved for metals in structural systems applications – airframes and engine containment systems, wraps for repair and rehabilitation, and ballistic/blast mitigation systems. They have high strength-to-weight ratios, are durable and resistant to environmental effects, have high impact strength, and can be manufactured in a variety of shapes. Generalized constitutive models are being developed to accurately model composite systems so they can be used in implicit and explicit finite element analysis. These models require extensive characterization of the composite material as input. The particular constitutive model of interest for this research is a three-dimensional orthotropic elasto-plastic composite material model that requires a total of 12 experimental stress-strain curves, yield stresses, and Young’s Modulus and Poisson’s ratio in the material directions as input. Sometimes it is not possible to carry out reliable experimental tests needed to characterize the composite material. One solution is using virtual testing to fill the gaps in available experimental data. A Virtual Testing Software System (VTSS) has been developed to address the need for a less restrictive method to characterize a three-dimensional orthotropic composite material. The system takes in the material properties of the constituents and completes all 12 of the necessary characterization tests using finite element (FE) models. Verification and validation test cases demonstrate the capabilities of the VTSS.
ContributorsHarrington, Joseph (Author) / Rajan, Subramaniam D. (Thesis advisor) / Neithalath, Narayanan (Committee member) / Mobasher, Barzin (Committee member) / Arizona State University (Publisher)
Created2015
Description
A simplified bilinear moment-curvature model are derived based on the moment-curvature response generated from a parameterized stress-strain response of strain softening and or strain-hardening material by Dr. Barzin Mobasher and Dr. Chote Soranakom. Closed form solutions are developed for deflection calculations of determinate beams subjected to usual loading patterns at any load stage. The solutions are based on a bilinear moment curvature response characterized by the flexural crack initiation and ultimate capacity based on a deflection hardening behavior. Closed form equations for deflection calculation are presented for simply supported beams under three point bending, four point bending, uniform load, concentrated moment at the middle, pure bending, and for cantilever beam under a point load at the end, a point load with an arbitrary distance from the fixed end, and uniform load. These expressions are derived for pre-cracked and post cracked regions. A parametric study is conducted to examine the effects of moment and curvature at the ultimate stage to moment and curvature at the first crack ratios on the deflection. The effectiveness of the simplified closed form solution is demonstrated by comparing the analytical load deflection response and the experimental results for three point and four point bending. The simplified bilinear moment-curvature model is modified by imposing the deflection softening behavior so that it can be widely implemented in the analysis of 2-D panels. The derivations of elastic solutions and yield line approach of 2-D panels are presented. Effectiveness of the proposed moment-curvature model with various types of panels is verified by comparing the simulated data with the experimental data of panel test.
ContributorsWang, Xinmeng (Author) / Mobasher, Barzin (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Neithalath, Narayanan (Committee member) / Arizona State University (Publisher)
Created2015
Description
Despite incremental improvements over decades, academic planning solutions see relatively little use in many industrial domains despite the relevance of planning paradigms to those problems. This work observes four shortfalls of existing academic solutions which contribute to this lack of adoption.
To address these shortfalls this work defines model-independent semantics for planning and introduces an extensible planning library. This library is shown to produce feasible results on an existing benchmark domain, overcome the usual modeling limitations of traditional planners, and accommodate domain-dependent knowledge about the problem structure within the planning process.
To address these shortfalls this work defines model-independent semantics for planning and introduces an extensible planning library. This library is shown to produce feasible results on an existing benchmark domain, overcome the usual modeling limitations of traditional planners, and accommodate domain-dependent knowledge about the problem structure within the planning process.
ContributorsJonas, Michael (Author) / Gaffar, Ashraf (Thesis advisor) / Fainekos, Georgios (Committee member) / Doupe, Adam (Committee member) / Herley, Cormac (Committee member) / Arizona State University (Publisher)
Created2016
Description
Unidirectional glass fiber reinforced polymer (GFRP) is tested at four initial strain rates (25, 50, 100 and 200 s-1) and six temperatures (−25, 0, 25, 50, 75 and 100 °C) on a servo-hydraulic high-rate testing system to investigate any possible effects on their mechanical properties and failure patterns. Meanwhile, for the sake of illuminating strain rate and temperature effect mechanisms, glass yarn samples were complementally tested at four different strain rates (40, 80, 120 and 160 s-1) and varying temperatures (25, 50, 75 and 100 °C) utilizing an Instron drop-weight impact system. In addition, quasi-static properties of GFRP and glass yarn are supplemented as references. The stress–strain responses at varying strain rates and elevated temperatures are discussed. A Weibull statistics model is used to quantify the degree of variability in tensile strength and to obtain Weibull parameters for engineering applications.
ContributorsOu, Yunfu (Author) / Zhu, Deju (Author) / Zhang, Huaian (Author) / Huang, Liang (Author) / Yao, Yiming (Author) / Li, Gaosheng (Author) / Mobasher, Barzin (Author) / Ira A. Fulton Schools of Engineering (Contributor)
Created2016-05-19