Showing papers by "University of Texas at Arlington published in 2022"

Extra plasticity governed by shear band deflection in gradient metallic glasses

Abstract: Inspired by gradient materials in nature, advanced engineering components with controlled structural gradients have attracted substantial research interests due to their exceptional combinations of properties. However, it remains challenging to generate structural gradients that penetrate through bulk materials, which is essential for achieving enhanced mechanical properties in metallic materials. Here, we report practical strategies to design controllable structural gradients in bulk metallic glasses (BMGs). By adjusting processing conditions, including holding time and/or controlling temperatures, of cryogenic thermal cycling and fast cooling, two different types of gradient metallic glasses (GMGs) with spatially gradient-distributed free volume contents can be synthesized. Both mechanical testing and atomistic simulations demonstrate that the spatial gradient can endow GMGs with extra plasticity. Such an enhanced mechanical property is governed by the gradient-induced deflection of shear deformation that fundamentally suppresses the unlimited shear localization on a straight plane that would be expected in BMGs without such a gradient.

A modified adaptive genetic algorithm for multi-product multi-period inventory routing problem

Abstract: Recent developments in urbanization and e-commerce have pushed businesses to deploy efficient systems to decrease their supply chain cost. Vendor Managed Inventory (VMI) is one of the most widely used strategies to effectively manage supply chains with multiple parties. VMI implementation asks for solving the Inventory Routing Problem (IRP). This study considers a multi-product multi-period inventory routing problem, including a supplier, set of customers, and a fleet of heterogeneous vehicles. Due to the complex nature of the IRP, we developed a Modified Adaptive Genetic Algorithm (MAGA) to solve a variety of instances efficiently. As a benchmark, we considered the results obtained by Cplex software and an efficient heuristic from the literature. Through extensive computational experiments on a set of randomly generated instances, and using different metrics, we show that our approach distinctly outperforms the other two methods. In this way, we created a decision support and computer-based approach to assist policy and decision-makers in the pathway of constructing a sustainable society.

A comparative investigation on the effects of nanocellulose from Bacteria and plant-based sources for cementitious composites

Abstract: Interest in cellulosic nanomaterials has recently gained momentum due to their high tensile strength and hygroscopic properties. This study compared the effects of two different types of cellulose nanomaterials, including cellulose nanofibrils (CNF) produced from wood and bacterial cellulose (BC), on the macro, micro, and nano scale performances of Ordinary Portland Cement (OPC) paste. Effects of CNF and BC on cement paste hydration, microstructure, compressive strength, and flexural strength were monitored. Four dosages of nanocellulose (0%, 0.05%, 0.1% and 0.3%, by weight) were used to prepare cement paste samples. Both CNF and BC were found to increase compressive strengths and flexural strengths by 10% and 55%, respectively, after 90 days of curing. However, only CNF was able to suppress the expansion of mortar samples due to the alkali-silica reaction by 33%. At the microscale, CNF was found to accelerate the early age cement hydration, whereas BC delayed cement hydration. Both nanocellulose types resulted in lower calcium hydroxide (CH) and higher CSH contents compared to the control batch after long-term curing. Statistical nanoindentations showed that the additions of nanocellulose increase the relative amounts of high-density CSH in the hydrated cement paste. The mercury intrusion porosimeter (MIP) and dynamic vapor sorption (DVS) analyses indicated that both types of nanocellulose increase the nano porosity and reduced the microporosity. However, such advantages were more prominent in the case of CNF compared to the BC.

Polydopamine nanoparticles and hyaluronic acid hydrogels for mussel-inspired tissue adhesive nanocomposites

Abstract: Bioadhesives are intended to facilitate the fast and efficient reconnection of tissues to restore their functionality after surgery or injury. The use of mussel-inspired hydrogel systems containing pendant catechol moieties is promising for tissue attachment under wet conditions. However, the adhesion strength is not yet ideal. One way to overcome these limitations is to add polymeric nanoparticles to create nanocomposites with improved adhesion characteristics. To further enhance adhesiveness, polydopamine nanoparticles with controlled size prepared using an optimized process, were combined with a mussel-inspired hyaluronic acid (HA) hydrogel to form a nanocomposite. The effects of sizes and concentrations of polydopamine nanoparticles on the adhesive profiles of mussel-inspired HA hydrogels were investigated. Results show that the inclusion of polydopamine nanoparticles in nanocomposites increased adhesion strength, as compared to the addition of poly (lactic-co-glycolic acid) (PLGA), and PLGA-(N-hydroxysuccinimide) (PLGA-NHS) nanoparticles. A nanocomposite with demonstrated cytocompatibility and an optimal lap shear strength (47 ± 3 kPa) was achieved by combining polydopamine nanoparticles of 200 nm (12.5% w/v) with a HA hydrogel (40% w/v). This nanocomposite adhesive shows its potential as a tissue glue for biomedical applications.

State-of-Charge Balancing for Battery Energy Storage Systems in DC Microgrids by Distributed Adaptive Power Distribution

Abstract: We consider the control problem of fulfilling the desired total charging/discharging power while balancing the state-of-charge (SoC) of the networked battery units with unknown parameters in a battery energy storage system. We develop power allocating algorithms for the battery units. These algorithms make use of distributed estimators for the average desired power and the average unit state and the adaptive parameter estimators, and are showed to fulfill the desired total power while achieving battery unit SoC balancing as long as the undirected graph that represents the communication network among the battery units is connected and there is at least one battery unit with the knowledge of the desired total power. Numerical simulation verifies the effectiveness of the proposed power allocating algorithms.

Service quality assessment and enhancement using Kano model

Abstract: Success in the retail sector is highly dependent on customer satisfaction. Maintaining a competitive edge depends upon the service providers knowing and enacting what is important to their customers. Multiple studies have employed various research approaches to identifying characteristics of customer satisfaction in different sectors as well as retail sector. However, very few have determined such characteristics using multiple approaches simultaneously in the retail store. This study aims to identify, categorize, and rank the retail store attributes, based on their effects on customer satisfaction. A survey focusing on retail store characteristics that impact customer satisfaction was developed and distributed. Over 400 responses were collected and evaluated, using the Kano model. Results showed that visually appealing facilities and error-free transactions are of prime importance to customers. They are taken for granted, but their absence plays a significant role in customer dissatisfaction. An easy-to-navigate store layout and readily available service increase customer satisfaction, but their absence doesn't decrease customer satisfaction. Clean public areas and modern-looking equipment are important, and improvements to them increase customer satisfaction at a proportional rate. The findings of this study will assist service providers in realizing the relative importance of the attributes of retail stores and in evaluating the impacts of their current practices on customer satisfaction levels. Such importance will also help retail sector policy makers in mandating policies focusing on must-have attributes to preserve customer satisfaction.

The effects of COVID‐19 on the mental health and job stress of frontline homelessness services workers in Texas (U.S.)

Abstract: As the COVID-19 pandemic persists in the U.S. and elsewhere, there is a growing need to understand the impacts of the pandemic on essential and frontline workers. Given the dearth of research on the experiences of homelessness services workers during the COVID-19 pandemic, this study aimed to understand the impact of COVID-related stressors in the workplace on the wellbeing of the homelessness services workers in the state of Texas (U.S.). Using a cross-sectional survey design, the analysis focusses on examining the relationship between COVID stressors with mental health symptoms and job stress indictors. Data were collected from a sample of 132 frontline homelessness services workers across the state during April, May and June of 2021. Primary outcomes of interest were measured with the Depression, Anxiety and Stress Scale (DASS-42) and the Professional Quality of Life Scale (ProQOL). Multiple linear regression models were specified to explore associations between the outcomes of interest and predictor variables (i.e. demographics, work experiences and COVID-19 stressors). Results showed that perceiving a decline in job satisfaction because of the COVID-19 pandemic was associated with higher stress (β = ++0.18), 95% CI [.13, 6.68], higher burnout (β = 0.32), 95% CI [2.54, 7.30] and lower compassion satisfaction (β = 0.42), 95% CI [−8.14, −3.69]. Additionally, being worried about contracting COVID-19 at work was associated with an increase in burnout (β = 0.19), 95% CI [.40, 4.79]. Also notable is that older age and Black/African American race were associated with lower stress, lower burnout and higher compassion satisfaction. Implications for supporting the homelessness sector through high-quality supervision, useful training, adequate benefits and routine check-ins are discussed.

Compassion Fatigue Among the Intimate Partner Violence and Sexual Assault Workforce: Enhancing Organizational Practice:

Abstract: Gaps in knowledge related to occupational stress among the intimate partner violence (IPV) and sexual assault (SA) workforce remain. This study examined associations between key risk factors for oc...

Copper Nanoplates for Printing Flexible High-Temperature Conductors

Abstract: Copper has attracted immense interest in advanced electronics attributed to its abundance and high electrical and thermal characteristics. However, the ease of oxidation when subjected to heat and humidity drastically limits its material reliability under extreme environments. Here, we utilize copper nanoplates as a building block to achieve a thermally stable (upwards of 1300 °C), antioxidation, and anticorrosion-printed conductor, with the capability of additively manufacturing on Corning flexible Alumina Ribbon Ceramic. We elucidate the printed copper nanoplates with a low sheet resistance of 4 mΩ/sq/mil by means of a surface-coordinated formate that inculcates high oxidation and corrosion resistance on a molecular level. In addition, an in situ copper–graphene conversion leads to a hybridized conductor displaying stability at elevated temperatures up to 1300 °C with high ampacity. Further mechanistic studies reveal high-temperature stability from in situ graphene conversion for copper and graphene interfaces, and preferential stacking of copper nanoplates, distinctly suited for emerging high-temperature flexible electronics.

Tetranuclear and trinuclear copper(<scp>i</scp>) pyrazolates as catalysts in copper mediated azide–alkyne cycloadditions (CuAAC)

Abstract: Homoleptic, tetranuclear copper(I) pyrazolates {[3,5-(t-Bu)2Pz]Cu}4, {[3-(CF3)-5-(t-Bu)Pz]Cu}4, and {[4-Br-3,5-(i-Pr)2Pz]Cu}4 are excellent stand-alone catalysts for azide-alkyne cycloaddition reactions (CuAAC). This work demonstrates that a range of pyrazolates, including those with electron donating and electron-withdrawing groups to sterically demanding substituents on the pyrazolyl backbones, can serve as effective ligand supports on tetranuclear copper catalysts. However, in contrast to the tetramers and also highly fluorinated {[3,5-(CF3)2Pz]Cu}3, trinuclear copper(I) complexes such as {[3,5-(i-Pr)2Pz]Cu}3 and {[3-(CF3)-5-(CH3)Pz]Cu}3 supported by relatively electron rich pyrazolates display poor catalytic activity in CuAAC. The behavior and degree of aggregation of several of these copper(I) pyrazolates in solution were examined using vapor pressure osmometry. Copper(I) complexes such as {[3,5-(CF3)2Pz]Cu}3 and {[3-(CF3)-5-(t-Bu)Pz]Cu}4 with electron withdrawing pyrazolates were found to break up in solution to different degrees producing smaller aggregates while those such as {[3,5-(i-Pr)2Pz]Cu}3 and {[3,5-(t-Bu)2Pz]Cu}4 with electron rich pyrazolates remain intact. In addition, kinetic experiments were performed to understand the unusual activity of tetranuclear copper(I) pyrazolate systems.

Accurate profiling of forensic autosomal STRs using the Oxford Nanopore Technologies MinION device.

Abstract: The high variability characteristic of short tandem repeat (STR) markers is harnessed for human identification in forensic genetic analyses. Despite the power and reliability of current typing techniques, sequence-level information both within and around STRs are masked in the length-based profiles generated. Forensic STR typing using next generation sequencing (NGS) has therefore gained attention as an alternative to traditional capillary electrophoresis (CE) approaches. In this proof-of-principle study, we evaluate the forensic applicability of the newest and smallest NGS platform available – the Oxford Nanopore Technologies (ONT) MinION device. Although nanopore sequencing on the handheld MinION offers numerous advantages, including low startup cost and on-site sample processing, the relatively high error rate and lack of forensic-specific analysis software has prevented accurate profiling across STR panels in previous studies. Here we present STRspy, a streamlined method capable of producing length- and sequence-based STR allele designations from noisy, error-prone third generation sequencing reads. To assess the capabilities of STRspy, seven reference samples (female: n = 2; male: n = 5) were amplified at 15 and 30 PCR cycles using the Promega PowerSeq 46GY System and sequenced on the ONT MinION device in triplicate. Basecalled reads were then processed with STRspy using a custom database containing alleles reported in the STRSeq BioProject NIST 1036 dataset. Resultant STR allele designations and flanking region single nucleotide polymorphism (SNP) calls were compared to the manufacturer-validated genotypes for each sample. STRspy generated robust and reliable genotypes across all autosomal STR loci amplified with 30 PCR cycles, achieving 100% concordance based on both length and sequence. Furthermore, we were able to identify flanking region SNPs in the 15-cycle dataset with > 90% accuracy. These results demonstrate that when analyzed with STRspy ONT reads can reveal additional variation in and around STR loci depending on read coverage. As the first and only third generation sequencing platform-specific method to successfully profile the entire panel of autosomal STRs amplified by a commercially available multiplex, STRspy significantly increases the feasibility of nanopore sequencing in forensic applications.

Induction Machine Parameterization From Limited Transient Data Using Convex Optimization

Abstract: This article identifies the parameters of an induction machine using limited and nonintrusive observations of available input voltages, stator currents, and the rotor speed. Parameter extraction is formulated as a nonconvex estimation problem, which is then relaxed to a convex conic optimization problem. While the resulting relaxation could exhibit a satisfactory performance, there might be cases where the solution of convex relaxation fails to satisfy the dynamic equations of the machine. This is remedied through a local search approach initiated using the solution obtained from the relaxed problem. The proposed method is experimentally verified on a squirrel-cage induction machine with missing measured data. Using the measured signals as the benchmark, time-domain transients produced by the parameters estimated using the proposed method show almost 20% better match compared to time-domain transients produced by the parameters obtained via conventional testing.

Acceptance- and mindfulness-based techniques for physical activity promotion in breast cancer survivors: a qualitative study

Abstract: The purpose of this study was to develop and characterize the relevance and potential utility of an electronically delivered acceptance- and mindfulness-based approaches to physical activity promotion for insufficiently active breast cancer survivors. The acceptance- and mindfulness-based physical activity intervention was delivered to participants electronically over the course of 4–8 weeks. It consisted of didactic videos, experiential exercises, and workbook-type activities that targeted principles from acceptance and commitment therapy (ACT). We conducted semi-structured, in-depth interviews with participants after they completed the intervention. Three coders conducted qualitative data analysis on interview transcripts to identify overarching themes and subthemes. We recruited 30 participants. Of those, 16 engaged in an individual interview. The mean age of the sample was 58.4 years (SD = 13.8). The sample was relatively well educated (50.0% college graduates) and mostly overweight or obese (58.8%). We identified two overarching themes from interviews. They were centered on (1) internal and external barriers to physical activity adherence and (2) the utility of targeting core ACT processes (acceptance and defusion, mindfulness, and values clarification) for physical activity promotion. Intervention content was perceived to be acceptable, relevant, and to fulfill important needs related to healthy living. Findings suggest that this approach to physical activity promotion can be delivered effectively online. Electronically delivered acceptance- and mindfulness-based approaches hold promise for helping insufficiently active breast cancer survivors increase physical activity.