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Fracture Toughness Of Fly Ash-Based Geopolymer Gels: Evaluations Using Nanoindentation Experiment And Molecular Dynamics Simulation, Gideon A. Lyngdoh, Sumeru Nayak, N.M. Anoop Krishnan, Sumanta Das

Civil & Environmental Engineering Faculty Publications

This paper presents the fracture toughness of sodium aluminosilicate hydrate (N-A-S-H) gel formed through alkaline activation of fly ash. While the fracture toughness of N-A-S-H is obtained experimentally from nanoindentation experiment implementing the principle of conservation of energy, the numerical investigation is performed via reactive force field molecular dynamics. A statistically significant number of indentations are performed on geopolymer paste yielding frequency distribution of Young’s modulus. Four distinct peaks are observed in the frequency distribution plot from which the peak corresponding to N-A-S-H was separated using statistical deconvolution technique. The young’s modulus of N-A-S-H, thus obtained from statistical deconvolution shows …

Strain Sensing Efficiency Of Hierarchical Nano-Engineered Smart Twill-Weave Composites: Evaluations Using Multiscale Numerical Simulations, Sumeru Nayak, Sumanta Das

Civil & Environmental Engineering Faculty Publications

This paper evaluates the strain-sensing ability of a nanoengineered hierarchical twill weave composite using multiscale numerical simulations. Piezoresistivity is incorporated in such composite by introducing carbon nanotubes (CNT) in the polystyrene (PSS) matrix so as to form a percolating microstructure. The glass fiber twill weave, which itself contains CNT-modified PSS matrix inside the yarns, is coated with thin film of such piezoresistive matrix to obtain the smart composite configuration. The methodology, presented in this paper, captures the hierarchical intricacies at multiple length scales and implements various mechanical damage mechanisms at subsequent interactive length scales as well as consequent electrical responses …

Mapping Geographical Inequalities In Access To Drinking Water And Sanitation Facilities In Low-Income And Middle-Income Countries, 2000-17, Ali S. Akanda, Et Al

Civil & Environmental Engineering Faculty Publications

Background: Universal access to safe drinking water and sanitation facilities is an essential human right, recognised in the Sustainable Development Goals as crucial for preventing disease and improving human wellbeing. Comprehensive, high-resolution estimates are important to inform progress towards achieving this goal. We aimed to produce high-resolution geospatial estimates of access to drinking water and sanitation facilities.

Methods: We used a Bayesian geostatistical model and data from 600 sources across more than 88 low-income and middle-income countries (LMICs) to estimate access to drinking water and sanitation facilities on continuous continent-wide surfaces from 2000 to 2017, and aggregated results to policy-relevant …

Mapping Geographical Inequalities In Childhood Diarrhoeal Morbidity And Mortality In Low-Income And Middle-Income Countries, 2000-17: Analysis For The Global Burden Of Disease Study 2017, Ali S. Akanda, Et Al

Civil & Environmental Engineering Faculty Publications

Background: Across low-income and middle-income countries (LMICs), one in ten deaths in children younger than 5 years is attributable to diarrhoea. The substantial between-country variation in both diarrhoea incidence and mortality is attributable to interventions that protect children, prevent infection, and treat disease. Identifying subnational regions with the highest burden and mapping associated risk factors can aid in reducing preventable childhood diarrhoea.

Methods: We used Bayesian model-based geostatistics and a geolocated dataset comprising 15 072 746 children younger than 5 years from 466 surveys in 94 LMICs, in combination with findings of the Global Burden of Diseases, Injuries, and Risk …

Fracture Toughness Of Sodium Aluminosilicate Hydrate (Nash) Gels: Insights From Molecular Dynamics Simulations, Gideon A. Lyngdoh, Sumeru Nayak, Rajesh Kumar, N. M. Anoop Krishnan, Sumanta Das

Civil & Environmental Engineering Faculty Publications

This paper evaluates the fracture toughness of sodium aluminosilicate hydrate (N-A-S-H) gel formed through alkaline activation of fly ash via molecular dynamics (MD) simulations. The short- and medium-range order of the constructed N-A-S-H structures shows good correlation with the experimental observations, signifying the viability of the N-A-S-H structures. The simulated fracture toughness values of N-A-S-H (0.4–0.45 MPa m0.5) appear to be of the same order as the available experimental values for fly ash-based geopolymer mortars and concretes. These results suggest the efficacy of the MD simulation toward obtaining a realistic fracture toughness of N-A-S-H, which is otherwise very challenging to …

Prioritizing Water Security In The Management Of Vector Borne Diseases: Lessons From Oaxaca Mexico, Ali S. Akanda, Kristin Johnson, Howard S. Ginsberg, Janelle Couret

Civil & Environmental Engineering Faculty Publications

Changes in human water use, along with temperature and rainfall patterns, are facilitating habitat spread and distribution of Aedes aegypti and Aedes albopictusmosquitoes, the primary vectors for the transmission of Dengue, Chikungunya, and Zika viruses in the Americas. Artificial containers and wet spots provide major sources of mosquito larval habitat in residential areas. Mosquito abatement and control strategies remain the most effective public health interventions for minimizing the impact of these vector borne diseases. Understanding how water insecurity is conducive to the establishment and elimination of endemic mosquito populations, particularly in arid or semi‐arid regions, is a vital component …

Developing A Forecasting Model For Cholera Incidence In Dhaka Megacity Through Time Series Climate Data, Salima Sultana Daisy, Akm Saiful Islam, Ali S. Akanda, Abu Syed Golam Faruque, Nuhu Amin, Peter Kjaer Mackie Jensen

Civil & Environmental Engineering Faculty Publications

Cholera, an acute diarrheal disease spread by lack of hygiene and contaminated water, is a major public health risk in many countries. As cholera is triggered by environmental conditions influenced by climatic variables, establishing a correlation between cholera incidence and climatic variables would provide an opportunity to develop a cholera forecasting model. Considering the auto-regressive nature and the seasonal behavioral patterns of cholera, a seasonal-auto-regressive-integrated-moving-average (SARIMA) model was used for time-series analysis during 2000–2013. As both rainfall (r = 0.43) and maximum temperature (r = 0.56) have the strongest influence on the occurrence of cholera incidence, single-variable (SVMs) …

Cooling Rate Effects On The Structure Of 45s5 Bioglass: Insights From Experiments And Simulations, Pratik Bhaskar, Rajesh Kumar, Yashasvi Maurya, R. Ravinder, Amarnath R. Allu, Sumanta Das, Nitya Nand Gosvami, Randall E. Youngman, Mikkel S. Bodker, Nerea Mascaraque, Morten M. Smedskjaer, Mathieu Bauchy, N.M. Anoop Krishnan

Civil & Environmental Engineering Faculty Publications

Due to its ability to bond with living tissues upon dissolution, 45S5 bioglass and related compositions materials are extensively used for the replacement, regeneration, and repair of hard tissues in the human body. However, the details of its atomic structure remain debated. This is partially due to the non-equilibrium nature of glasses, as their non-crystalline structure is highly dependent on their thermal history, namely, the cooling rate used during quenching. Herein, combining molecular dynamics (MD) simulations with cooling rates ranging over several orders of magnitude and experimental studies using nuclear magnetic resonance (NMR), we investigate the structure of the nominal …

Sulfite Activation Changes Character Of Ferrate Resultant Particles, Bradley M. Bzdyra, Charles D. Spellman Jr., Irene Andreu, Joseph E. Goodwill

Civil & Environmental Engineering Faculty Publications

The activation of ferrate with sulfite increases oxidative transformation of recalcitrant organic compounds; however, it also changes the characteristics of the iron particulates that result from the ferrate reduction. In this study, particles resulting from ferrate reduction both with and without sulfite were compared in a laboratory matrix simulating water treatment conditions at the bench-scale. Characteristics examined included magnetization, morphology, size, and surface charge. The activation of ferrate with sulfite changed the characteristics of resultant particles in several important ways. Activated ferrate resultant particles were less magnetic, more polydisperse including a higher fraction of nanoparticles, and exhibited a less-crystalline morphology …

Elucidating The Constitutive Relationship Of Calcium–Silicate–Hydrate Gel Using High Throughput Reactive Molecular Simulations And Machine Learning, Gideon A. Lyngdoh, Hewenxuan Li, Mohd Zaki, N. M. Anoop Krishnan, Sumanta Das

Civil & Environmental Engineering Faculty Publications

Prediction of material behavior using machine learning (ML) requires consistent, accurate, and, representative large data for training. However, such consistent and reliable experimental datasets are not always available for materials. To address this challenge, we synergistically integrate ML with high-throughput reactive molecular dynamics (MD) simulations to elucidate the constitutive relationship of calcium–silicate–hydrate (C–S–H) gel—the primary binding phase in concrete formed via the hydration of ordinary portland cement. Specifically, a highly consistent dataset on the nine elastic constants of more than 300 compositions of C–S–H gel is developed using high-throughput reactive simulations. From a comparative analysis of various ML algorithms including …

A Peridynamics-Based Micromechanical Modeling Approach For Random Heterogeneous Structural Materials, Sumeru Nayak, R. Ravinder, N. M. Anoop Krishnan, Sumanta Das

Civil & Environmental Engineering Faculty Publications

This paper presents a peridynamics-based micromechanical analysis framework that can efficiently handle material failure for random heterogeneous structural materials. In contrast to conventional continuum-based approaches, this method can handle discontinuities such as fracture without requiring supplemental mathematical relations. The framework presented here generates representative unit cells based on microstructural information on the material and assigns distinct material behavior to the constituent phases in the random heterogenous microstructures. The framework incorporates spontaneous failure initiation/propagation based on the critical stretch criterion in peridynamics and predicts effective constitutive response of the material. The current framework is applied to a metallic particulate-reinforced cementitious composite. …

Abatement Of Circumneutral Mine Drainage By Co-Treatment With Secondary Municipal Wastewater, Charles D. Spellman Jr., Travis L. Tasker, William H.J. Strosnider, Joseph E. Goodwill

Civil & Environmental Engineering Faculty Publications

Acid mine drainage is a persistent and problematic source of water pollution. Co-treatment with municipal wastewater at existing wastewater treatment plants has several advantages; however, potential impacts on plant physicochemical and biological processes have not been well explored. The primary purpose of this bench-scale study was to examine the impact of co-treatment by combining a mild acid mine drainage at various ratios with municipal wastewater, followed by sludge settling and supernatant comparative analysis using a variety of effluent water quality parameters. These measurements were combined with carbonate system and adsorption isotherm modeling to elucidate the mechanisms underlying the experimental results. …

Potential Implications Of Acid Mine Drainage And Wastewater Cotreatment On Solids Handling: A Review, Charles D. Spellman Jr., Travis L. Tasker, Joseph E. Goodwill, William H.J. Strosnider

Civil & Environmental Engineering Faculty Publications

Acid mine drainage (AMD) is a persistent and extensive source of water pollution and ecological degradation. Cotreating munici- pal wastewater (MWW) with AMD using existing infrastructure at conventional wastewater treatment plants (WWTPs) may serve as a potential option for AMD abatement. However, commonly elevated iron and aluminum concentrations and low pH of AMD could negatively impact various processes at a WWTP. The focus of this mini review was on determining how cotreating MWW with AMD could impact the solids handling processes at a WWTP. While no studies have explored the solids that could be generated during cotreatment in a WWTP, …

Prediction Of The Limiting Flux And Its Correlation With The Reynolds Number During The Microfiltration Of Skim Milk Using An Improved Model, Carolina Astudillo-Castro, Andrés Cordova, Vinka Oyanedel-Craver, Carmen Soto-Maldonado, Pedro Valencia, Paola Henriquez, Rafael Jimenez-Flores

Civil & Environmental Engineering Faculty Publications

Limiting flux (J_L) determination is a critical issue for membrane processing. This work presents a modified exponential model for J_L calculation, based on a previously published version. Our research focused on skim milk microfiltrations. The processing variables studied were the crossflow velocity (CFV), membrane hydraulic diameter (d_h), temperature, and concentration factor, totaling 62 experimental runs. Results showed that, by adding a new parameter called minimum transmembrane pressure, the modified model not only improved the fit of the experimental data compared to the former version (R² > 97.00%), but also revealed the existence of a minimum …

Dynamics Of Confined Water And Its Interplay With Alkali Cations In Sodium Aluminosilicate Hydrate Gel: Insights From Reactive Force Field Molecular Dynamics, Gideon A. Lyngdoh, Rajesh Kumar, N. M. Anoop Krishnan, Sumanta Das

Civil & Environmental Engineering Faculty Publications

This paper presents the dynamics of confined water and its interplay with alkali cations in disordered sodium aluminosilicate hydrate (N-A-S-H) gel using reactive force field molecular dynamics. N-A-S-H gel is the primary binding phase in geopolymers formed via alkaline activation of fly ash. Despite attractive mechanical properties, geopolymers suffer from durability issues, particularly the alkali leaching problem which has motivated this study. Here, the dynamics of confined water and the mobility of alkali cations in N-A-S-H is evaluated by obtaining the evolution of mean squared displacements and Van Hove correlation function. To evaluate the influence of the composition of N-A-S-H …

Seismic Response Mitigation Of Base-Isolated Buildings, Mohammad Hamayoun Stanikzai, Said Elias, Rajesh Rupakhety

Civil & Environmental Engineering Faculty Publications

Earthquake response mitigation of a base-isolated (BI) building equipped with (i) a single tuned mass damper at the top of the building, (ii) multiple tuned mass dampers (MTMDs) at the top of the building, and (iii) MTMDs distributed on different floors of the building (d-MTMDs) is studied. The shear-type buildings are modeled by considering only one lateral degree of freedom (DOF) at the floor level. Numerical approach of Newmark's integration is adopted for solving the coupled, governing differential equations of motion of 5- and 10-story BI buildings with and without TMD schemes. A set of 40 earthquake ground motions, scaled …

Historical Trends In Air Temperature, Precipitation, And Runoff Of A Plateau Inland River Watershed In North China, Along Zhang, Ruizhong Gao, Xixi Wang, Tingxi Liu, Lijing Fang

Civil & Environmental Engineering Faculty Publications

Understanding historical trends in temperature, precipitation, and runoff is important but incomplete for developing adaptive measures to climate change to sustain fragile ecosystems in cold and arid regions, including the Balagaer River watershed on the Mongolian Plateau of northeast China. The objective of this study was to detect such trends in this watershed from 1959 to 2017. The detection was accomplished using a Mann-Kendall sudden change approach at annual and seasonal time scales. The results indicated that the abrupt changes in temperature preceded that in either runoff or precipitation; these abrupt changes occurred between 1970 and 2004. Significant (α = …

Evaluation Of Lead (Pb(Ii)) Removal Potential Of Biochar In A Fixed-Bed Continuous Flow Adsorption System, Pushpita Kumkum, Sandeep Kumar

Civil & Environmental Engineering Faculty Publications

Background. Lead (Pb(II)) exposure from drinking water consumption is a serious concern due to its negative health effect on human physiology. A commercially available filter uses the adsorption potential of activated carbon for removing heavy metals like Pb(II). However, it has some constraints since it uses only surface area for the adsorption of these contaminants. Biochar produced via slow pyrolysis of biomass shows the presence of oxygen-containing functional groups on its surface that take part in the adsorption process, with higher removal potential compared to activated carbon.

Objectives. The current study examined the adsorption kinetics and mechanisms of Pb(II) removing …

Tire-Chip Reinforced Foundation As Liquefaction Countermeasure For Residential Buildings, Hemanta Hazarika, Siavash Manafi Khajeh Pasha, Isao Ishibashi, Norimasa Yoshimoto, Tota Kinoshita, Shigeki Endo, Ashoke Kumar Karmokar, Takuto Hitosugi

Civil & Environmental Engineering Faculty Publications

To prevent vibration-induced and liquefaction-induced damage to residential buildings during earthquakes, a low-cost technique has been developed and described here. It utilizes a mixture of tire chips and gravel as the horizontal reinforcing inclusion under the foundation of residential houses. The horizontal reinforcing inclusion refers to a layer of tire chips and gravel which is placed horizontally beneath the foundation. This mixture of tire chips and gravel provides sufficient bearing capacity to the foundation. In this research, a series of small-scale 1 g model shaking table tests was performed to evaluate the effectiveness of the technique. In addition, cyclic undrained …

Broadening Participation Research Project: Charting A Path To Transdisciplinary Collaborative Design, Mason Andrews, Mujde Erten-Unal, Carol L. Considine

Civil & Environmental Engineering Faculty Publications

The National Climate Assessment has identified foundational cross-cutting research capabilities that need to be developed for climate and global change assessment that include the integration of disciplines across approaches and building capacity for climate assessment that includes training, education and workforce development. The NSF HBCU Research Project, Broadening Participation Research Project: Charting a Path to Transdisciplinary Collaborative Design builds on the work of the Coastal Community Design Collaborative, a partnership between Hampton University, and Old Dominion University, which is a cross-university, cross-disciplinary program, in which architecture and civil engineering and technology students develop real world interventions for communities impacted by …

Multi-Modal Natural Frequency Response Of Utility Transmission Tapered Wood Poles Under Various Soil Foundation Conditions: Natural Frequency Response Under Various Soil Conditions, Ramani Ayakannu, Zia Razzaq

Civil & Environmental Engineering Faculty Publications

Studied herein is the multi-modal natural frequency response of utility transmission tapered wood poles under various soil foundation conditions. Strong winds and hurricanes in various parts of the world have resulted in collapse of such utility poles and have resulted in the disruption of electrical distribution systems in addition to creating hazardous conditions for the public. To avoid the development of resonance under such dynamic loading, the multi-modal natural vibration of the utility poles first needs to be understood in the presence of practical soil foundation conditions. To capture the soil-structure interaction effects on the multi-modal frequencies, a SAP2000 dynamic …

Nonhydrostatic Modeling Of Flow Interactions With Highly Flexible Vegetation, Navid Tahvildari, Ramin Familkhalili, Gangfeng Ma

Civil & Environmental Engineering Faculty Publications

Improving our understanding of the interactions between gravity waves, currents, and coastal vegetation, which are nonlinear in nature, enables coastal engineers and managers to better estimate hydrodynamic forces on coastal infrastructure and utilize natural elements to mitigate their impacts. Aquatic vegetation is ubiquitous in coastal waters and it is well-known that flow loses energy over vegetation. Computational modeling of wave-vegetation interaction has been the subject of numerous recent studies and many improvements have been achieved in reducing limitations applied on wave and vegetation behavior in these models. Mechanisms for highly flexible vegetation have been incorporated in a Boussinesq-type model and …

Lateral-Torsional Buckling Strength Of Two-Span Glass Fiber Reinforced Polymer Beams, Mojtaba B. Sirjani, Zia Razzaq

Civil & Environmental Engineering Faculty Publications

This paper presents the outcome of a study of two-span glass fiber reinforced polymer (GFRP) I-section beams susceptible to lateral-torsional buckling when subjected to gradually increasing concentrated vertical load(s) in the presence of two different types of lateral bracing schemes. It is found that loading one span results in a smaller buckling load as compared with the cases with loading in both spans regardless of the type of bracing scheme used. Also, the study shows that the addition of midspan braces for the GFRP beams results in up to 5.5 times increase in the buckling load capacity.

Influence Of Bracing On Buckling Strength Of Pultruded Glass Fiber Reinforced Polymer Frames, Mojtaba B. Sirjani, Zia Razzaq

Civil & Environmental Engineering Faculty Publications

A numerical study of the influence of structural bracing on the buckling strength of pultruded Glass Fiber Reinforced Polymer (GFRP) frames is presented. Although the influence of bracing on frames made from other materials such as steel have been studied in the past, this paper investigates the performance of pultruded GFRP portal frames with pinned or fixed column bases. Each frame is constructed with pultruded GFRP I-section members. The influence of I-section column major and minor axis orientation is also investigated. The results demonstrate the practical significance of bracing pultruded GFRP frames. The results show that the buckling loads for …