College of Science and Engineering
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Browsing College of Science and Engineering by Department "Engineering"
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Item 3D Nanomolding and Fluid Mixing in Micromixers with Micro-patterned Microchannel Walls(Springer, 2017-01) Farshchian, Bahador; Amirsadeghi, Alborz; Choi, Junseo; Park, Daniel S.; Kim, Namwon; Park, SunggookMicrofluidic devices where the microchannel walls were decorated with micro and nanostructures were fabricated using 3D nanomolding. Using 3D molded microfluidic devices with microchannel walls decorated with microscale gratings, the fluid mixing behavior was investigated through experiments and numerical simulation. The use of microscale gratings in the micromixer was predicated by the fact that large obstacles in a microchannel enhances the mixing performance. Slanted ratchet gratings on the channel walls resulted in a helical flow along the microchannel, thus increasing the interfacial area between fluids and cutting down the diffusion length. Increasing the number of walls decorated with continuous ratchet gratings intensified the strength of the helical flow, enhancing mixing further. When ratchet gratings on the surface of the top cover plate were aligned in a direction to break the continuity of gratings from the other three walls, a stack of two helical flows was formed one above each other. This work concludes that the 3D nanomolding process can be a cost-effective tool for scaling-up the fabrication of microfluidic mixers with improved mixing efficiencies.Graphical abstractIn this paper we show that a micromixer with patterned walls can be fabricated using 3D nanomolding and solvent-assisted bonding to manipulate the flow patterns to improve mixing.Item A Collective Impact Model Towards Increasing STEM Major Student Retention(Texas State University, The Education Institute, 2020-02) Martinez Ortiz, Araceli; Novoa, Clara; Sriraman, VedaramanThis article presents the research findings of a multidisciplinary team's collective research effort at one university over a five-year period as funded by the National Science Foundation's Improving Undergraduate STEM Education (IUSE) program. A collaborative learning and retention action research effort at a large Hispanic Serving Institution is analyzed using mixed methods to document the power of collective impact as the foundation for a learning support model for students historically underrepresented majoring in science, technology, engineering and mathematics (STEM) academic programs. The actions of the team of researchers are presented to describe the Rising Stars Collective Impact model and the impacts achieved. This is a model that aligns objectives, intervention efforts, and reports collective results. The long-term goals of the Rising Stars Collective Impact multiple programs managed by the funded program team included the following: (a) to improve the campus sense of community for students historically under-represented in STEM, (b) to establish innovative and robust STEM education research-based practices to support critical skill attainment for students, and (c) to support faculty understanding of the funds of knowledge of diverse students. The positive student retention and success impacts of this research effort are measured through quantitative statistical analysis of the changes in second-year STEM undergraduate student retention rates and representation rates of women, Hispanics, and African American STEM majors.Item A Crystalline Oxide Passivation on In0.53Ga0.47As (100)(American Institute of Physics Publishing, 2017-03-29) Qin, Xiaoye; Wang, Wei-E; Droopad, Ravi; Rodder, Mark S.; Wallace, Robert M.The passivation of In0.53Ga0.47As surfaces is highly desired for transistor performance. In this study, the feasibility of a crystalline oxide passivation on In0.53Ga0.47As (100) is demonstrated experimentally. The (3 x 1) and (3 x 2) crystalline oxide reconstructions are formed on the de-capped In0.53Ga0.47As (100) surfaces through the control of the surface oxidation states. By monitoring the evolution of chemical states and associated structures of the In0.53Ga0.47As (100) surfaces upon O2 and subsequent atomic hydrogen exposure, we find that the control of the Ga oxide states is critical to the formation of the crystalline oxide reconstructions. The stability of the crystalline oxide layers upon the atomic layer deposition of HfO2 is investigated as well. Furthermore, the capacitance voltage behavior of metal oxide semiconductor capacitors with an HfO2 dielectric layer reveals that the crystalline oxide reconstructions result in a decrease in the density of interface traps (D it) from ~1 x 10 13 cm-2 eV-1 to ~1 x 10 12 cm-2 eV-1 compared with the de-capped surface. The crystalline oxide passivation offers a platform to develop In0.53Ga0.47As devices with a low density of interface states.Item A Dataset for the Flood Vulnerability Assessment of the Upper Cross River Basin Using Morphometric Analysis(Elsevier, 2020-02) Ogarekpe, Nkpa; Obio, Ekpe; Tenebe, Imokhai; Emenike, PraiseGod; Nnaji, ChidozieThe on-site collection of data is not only time consuming, but expensive and perhaps near impossible in restive communities within the upper Cross River basin (UCRB). Therefore, the importance of this data cannot be overemphasized. This article presents a Digital Elevation Model (DEM), land use and land cover (LULC) map, soil map, geology map and climatic datasets which enhance the understanding of the physical characteristics of the upper Cross River basin using morphometric analysis. The use of the LULC map, soil map and the DEM in conjunction with the climatic data enhance the creation of the Hydrologic Response Units (HRUs) and the water balance modelling. The simulation of the water balance at the HRU level enables the routing of the runoff to the reaches of the sub-basins and then to the channels. The geology map provides confirmatory information to the morphometric analysis. The compound factor computed from all the derived morphometric parameters enhance the determination of the overall flood potential of the congruent sub-basins.Item A Heuristic Storage Location Assignment Based on Frequent Itemset Classes to Improve Order Picking Operations(Multidisciplinary Digital Publishing Institute, 2021-02-19) Li, Yue; Mendez-Mediavilla, Francis A.; Temponi, Cecilia; Kim, Junwoo; Jimenez, JesusMost large distribution centers’ order picking processes are highly labor-intensive. Increasing the efficiency of order picking allows these facilities to move higher volumes of products. The application of data mining in distribution centers has the capability of generating efficiency improvements, mainly if these techniques are used to analyze the large amount of data generated by orders received by distribution centers and determine correlations in ordering patterns. This paper proposes a heuristic method to optimize the order picking distance based on frequent itemset grouping and nonuniform product weights. The proposed heuristic uses association rule mining (ARM) to create families of products based on the similarities between the stock keeping units (SKUs). SKUs with higher similarities are located near the rest of the members of the family. This heuristic is applied to a numerical case using data obtained from a real distribution center in the food retail industry. The experiment results show that data mining-driven developed layouts can reduce the traveling distance required to pick orders.Item A Meta-Model to Predict the Drag Coefficient of a Particle Translating in Viscoelastic Fluids: A Machine Learning Approach(Multidisciplinary Digital Publishing Institute, 2022-01-21) Faroughi, Salah; Roriz, Ana; Fernandes, CelioThis study presents a framework based on Machine Learning (ML) models to predict the drag coefficient of a spherical particle translating in viscoelastic fluids. For the purpose of training and testing the ML models, two datasets were generated using direct numerical simulations (DNSs) for the viscoelastic unbounded flow of Oldroyd-B (OB-set containing 12,120 data points) and Giesekus (GI-set containing 4950 data points) fluids past a spherical particle. The kinematic input features were selected to be Reynolds number, 0Item Acoustic Properties of Innovative Concretes: A Review(Multidisciplinary Digital Publishing Institute, 2021-01-14) Fediuk, Roman; Amran, Mugahed; Vatin, Nikolai; Vasilev, Yuriy; Lesovik, Valery; Ozbakkaloglu, TogayConcrete is the most common building material; therefore, when designing structures, it is obligatory to consider all structural parameters and design characteristics such as acoustic properties. In particular, this is to ensure comfortable living conditions for people in residential premises, including acoustic comfort. Different types of concrete behave differently as a sound conductor; especially dense mixtures are superior sound reflectors, and light ones are sound absorbers. It is found that the level of sound reflection in modified concrete is highly dependent on the type of aggregates, size and distribution of pores, and changes in concrete mix design constituents. The sound absorption of acoustic insulation concrete (AIC) can be improved by forming open pores in concrete matrices by either using a porous aggregate or foam agent. To this end, this article reviews the noise and sound transmission in buildings, types of acoustic insulating materials, and the AIC properties. This literature study also provides a critical review on the type of concretes, the acoustic insulation of buildings and their components, the assessment of sound insulation of structures, as well as synopsizes the research development trends to generate comprehensive insights into the potential applications of AIC as applicable material to mitigate noise pollution for increase productivity, health, and well-being.Item An Initial Machine Learning-Based Victim’s Scream Detection Analysis for Burning Sites(Multidisciplinary Digital Publishing Institute, 2021-09-10) Saeed, Fairuz Samiha; Bashit, Abdullah Al; Viswanathan, Vishu; Valles, DamianFire incidents are responsible for severe damage and thousands of deaths every year all over the world. Extreme temperatures, low visibility, toxic gases, and unknown locations of victims create difficulties and delays in rescue operations, escalating the risk of injury or death. It is time-critical to detect the victims trapped inside the burning sites for facilitating the rescue operations. This research work presents an audio-based automated system for victim detection in fire emergencies, investigating two machine learning (ML) methods: support vector machines (SVM) and long short-term memory (LSTM). The performance of these two ML techniques has been evaluated based on a variety of performance metrics. Our analyses show that both ML methods provide superior scream detection performance, with SVM slightly overperforming LSTM. Because of its lower complexity, SVM is a better candidate for real-time implementation in our autonomous embedded system vehicle (AESV).Item Atomic-scale Structural and Electronic Properties of SrTiO3/GaAs Interfaces: A Combined STEM-EELS and First-principles Study(American Physical Society, 2017-07-26) Hong, Liang; Bhatnagar, Kunal; Droopad, Ravi; Klie, Robert; Ogut, SerdarThe electronic properties of epitaxial oxide thin films grown on compound semiconductors are largely determined by the interfacial atomic structure, as well as the thermodynamic conditions during synthesis. Ferroelectric polarization and Fermi-level pinning in SrTiO3 films have been attributed to the presence of oxygen vacancies at the oxide/semiconductor interface. Here, we present scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy analyses of GaAs films grown on SrTiO3 combined with first-principles calculations to determine the atomic and electronic structures of the SrTiO3/ GaAs interfaces. An atomically abrupt SrO/As interface is observed and the interfacial SrO layer is found to be O-deficient. First-principles density functional theory (DFT) calculations show SrO/Ga and Sr/As interfaces are favorable under O-rich and O-poor conditions, respectively. The SrO/Ga interface is reconstructed via the formation of Ga-Ga dimers while the Sr/As interface is abrupt and consistent with the experiment. DFT calculations further reveal that intrinsic two-dimensional electron gas (2DEG) forms in both SrO/Ga and Sr/As interfaces, and the Fermi level is pinned to the localized 2DEG states. Interfacial O vacancies can enhance the 2DEG density while it is possible for Ga/As vacancies to unpin the Fermi level from the 2DEG states.Item Bias Temperature Stress Induced Hydrogen Depassivation from Al2O3/InGaAs Interface Defects(American Institute of Physics Publishing, 2018-01) Tang, Kechao; Droopad, Ravi; McIntyre, Paul C.We study the reliability of Al2O3/InGaAs metal-oxide-semiconductor gate stacks by investigating the effect of bias temperature stress on the charge trap density at the Al2O3/InGaAs interface and in the bulk oxide. Under extended negative biasing at 100 °C, the gate stacks display a notable increase in the interface trap density (D it), but little change in the border trap density. This phenomenon is more prominent for samples exposed to a H2/N2 forming gas anneal (FGA) than for the as-deposited samples. Negative gate bias applied during 100 °C thermal stress negates the FGA-induced passivation of interface states and causes convergence of the D it of the post-FGA and as-deposited gate stacks with increasing biasing time. This appears to be caused by hydrogen depassivation of interface traps under bias temperature stress, which is further supported by an observed hydrogen isotope effect when comparing the rate of D it increase after annealing in hydrogenated versus deuterated forming gas. A N2 anneal control experiment also indicates that the stability of the interface trap density of post-FGA Al2O3/InGaAs gate stacks is more strongly influenced by the behavior of hydrogen at the interface than by the thermal treatment effect of the anneal.Item Characteristics and Mechanisms of Asphalt–Filler Interactions from a Multi-Scale Perspective(Multidisciplinary Digital Publishing Institute, 2020-06-17) Xu, Wenyi; Qiu, Xin; Xiao, Shanglin; Hong, Haojue; Wang, Feng; Yuan, JieAsphalt mastic plays an important role in asphalt mixtures for pavement engineering. Understanding the asphalt–filler interaction behavior is essential to improve the pavement performance of asphalt mastics. The objective of this paper was to evaluate the asphalt–filler interaction ability based on macro-rheological measurements and to investigate the asphalt–filler interaction mechanism associated with microstructural characteristics of asphalt mastics. First, the asphalt–filler interaction was characterized using macro-rheological features of asphalt mastics based on dynamic shear rheometer (DSR) tests. Second, the physico-chemical interaction between the asphalt and filler was qualitatively evaluated using a Fourier transform infrared (FTIR) spectrometer. Third, the asphalt–filler interaction behavior was investigated in terms of the micro-morphological properties of mineral fillers and asphalt mastics by conducting scanning electron microscopy (SEM) and atomic force microscope (AFM) tests. Finally, the grey relational analysis (GRA) was employed to identify the correlation between the properties of mineral fillers and the macro–micro performances of asphalt mastics. The results show that a higher content of alkaline mineral filler within the critical volume fraction range produced a greater interaction ability between the asphalt and filler. The asphalt–filler interaction is mainly a physical action since no obvious new adsorption peaks appeared in the FTIR spectrum. The micro-morphological characteristics of asphalt mastic mainly depended on the adsorption effect of mineral fillers on polar fractions and the dispersion effect of mineral fillers on wax crystals in the asphalt binder. Based on the results of the GRA, the acidity and content of mineral fillers exhibited a great influence on the micro-morphological and macro-rheological characteristics of asphalt mastics, and the specific surface area of the mineral filler exerted a significant influence on the asphalt–filler interaction ability. Furthermore, the K-B- δ index was more appropriate for evaluating the asphalt–filler interaction ability.Item Characterization and Mechanism of a New Superhydrophobic Deicing Coating Used for Road Pavement(Multidisciplinary Digital Publishing Institute, 2021-10-27) Huang, Kaijian; Liu, Jiajia; Wang, Jiaqing; Shi, XijunOwing to its high efficiency and low environmental impact, superhydrophobic deicing coating material has a bright future for application on road pavements. In this paper, a heterogeneous nucleation ice crystal growth model is proposed, with particular focus on the effect of surface roughness and the contact angle. The ice suppression mechanism of superhydrophobic materials is determined by this model and experimentally verified. The experimental results of the water contact angle and anti-skid tests illustrated that the prepared TiO2–octadecanoic acid coating material has a contact angle greater than 150° and good skid resistance. The freezing test confirms that the applied coating on the surface can effectively delay the crystallization of water droplets and maintain the waterdrop’s semi-spherical shape after freezing. The microstructure observation demonstrates the TiO2–octadecanoic acid material has a good micro-nano mastoid structure. Consequently, the proposed coating materials could possibly be utilized for effectively enhancing the deicing performance of pavements.Item Comparison of Stress Fields near Longitudinal Construction Joints of Tied and Doweled Sections in Portland Cement Concrete Pavements(Multidisciplinary Digital Publishing Institute, 2021-10-12) Hong, Geuntae; Kim, Jiyoung; Yeon, Jung Heum; Won, Moon; Choi, SeongcheolIn Portland cement concrete (PCC) pavements, tie bars are commonly used at longitudinal construction joints (LCJs) to prevent the lanes from separating. Meanwhile, the increase in multiple lanes due to greater traffic volumes has raised concerns about potential longitudinal cracking; this has led to the use of dowel bars instead of tie bars at LCJs. However, there is a paucity of studies focused on the comparison between the behaviors of concrete pavement based on the restrained conditions provided by tie and dowel bars at LCJs. In this study, we investigated the effects of the placement of tie and dowel bars at LCJs on the potential for longitudinal cracking in response to the increase in concrete stress that may occur when the lanes are tied together in PCC pavements. Field testing verified that the variation in concrete strain was more restrained in the case of a tie bar than a dowel bar, whereas it resulted in higher stress in the concrete element in the tie bar section. However, the use of dowel bars caused more movement in the transverse direction at LCJs as compared with tie bars. Thus, our results indicate that using dowel bars reduces the potential for longitudinal cracking; however, it may increase the potential for lane separation.Item Controller parameter optimization for complex industrial system with uncertainties(Sage, 2019-01) Chen, Heping; Bowels, Seth; Zhang, Biao; Fuhlbrigge, ThomasProportional–integral–derivative control system has been widely used in industrial applications. For complex systems, tuning controller parameters to satisfy the process requirements is very challenging. Different methods have been proposed to solve the problem. However these methods suffer several problems, such as dealing with system complexity, minimizing tuning effort and balancing different performance indices including rise time, settling time, steady-state error and overshoot. In this paper, we develop an automatic controller parameter optimization method based on Gaussian process regression Bayesian optimization algorithm. A non-parametric model is constructed using Gaussian process regression. By combining Gaussian process regression with Bayesian optimization algorithm, potential candidate can be predicted and applied to guide the optimization process. Both experiments and simulation were performed to demonstrate the effectiveness of the proposed method.Item Cooling Performance Characteristics of 20 Ah Lithium-Ion Pouch Cell with Cold Plates along Both Surfaces(Multidisciplinary Digital Publishing Institute, 2018-09) Patil, Mahesh; Panchal, Satyam; Kim, Namwon; Lee, Moo-YeonTemperature control of the lithium-ion pouch cells is crucial for smooth operation, longevity and enhanced safety in the battery-operated electric vehicles. Investigating the thermal behavior of lithium-ion pouch cells and optimizing the cooling performance are required to accomplish better performance, long life, and enhanced safety. In the present study, the cooling performance characteristics of 20 Ah lithium-ion pouch cell with cold plates along both surfaces are investigated by varying the inlet coolant mass flow rates and the inlet coolant temperatures. The inlet coolant mass flow rate is varied from 0.000833 kg/s to 0.003333 kg/s, and the inlet coolant temperature is varied from 5 °C to 35 °C. In addition, the effects of the cold plate geometry parameter on cooling performance of 20 Ah lithium-ion pouch cell are studied by varying the number of the channels from 4 to 10. The maximum temperature and difference between the maximum and the minimum temperatures are considered as important criteria for cooling performance evaluation of the 20 Ah lithium-ion pouch cell with cold plates along both surfaces. The cooling energy efficiency parameter (β) and the pressure drop for 20 Ah lithium-ion pouch cell with cold plates along both surfaces are also reported. The study shows that enhanced cooling energy efficiency is accompanied with low inlet coolant temperature, low inlet coolant mass flow rate, and a high number of the cooling channels. As a result, the temperature distribution, the pressure drop, and the cooling energy efficiency parameter (β) of the 20 Ah lithium-ion pouch cell with cold plates along both surfaces are provided, and could be applied for optimizing the cooling performances of the thermal management system for lithium-ion batteries in electric vehicles.Item Correlated Electrical Conductivities to Chemical Configurations of Nitrogenated Nanocrystalline Diamond Films(Multidisciplinary Digital Publishing Institute, 2022-03-03) Zkria, Abdelrahman; Gima, Hiroki; Abubakr, Eslam; Mahmoud, Ashraf; Haque, Ariful; Yoshitake, TsuyoshiDiamond is one of the fascinating films appropriate for optoelectronic applications due to its wide bandgap (5.45 eV), high thermal conductivity (3320 W m−1·K−1), and strong chemical stability. In this report, we synthesized a type of diamond film called nanocrystalline diamond (NCD) by employing a physical vapor deposition method. The synthesis process was performed in different ratios of nitrogen and hydrogen mixed gas atmospheres to form nitrogen-doped (n-type) NCD films. A high-resolution scanning electron microscope confirmed the nature of the deposited films to contain diamond nanograins embedded into the amorphous carbon matrix. Sensitive spectroscopic investigations, including X-ray photoemission (XPS) and near-edge X-ray absorption fine structure (NEXAFS), were performed using a synchrotron beam. XPS spectra indicated that the nitrogen content in the film increased with the inflow ratio of nitrogen and hydrogen gas (IN/H). NEXAFS spectra revealed that the σ*C–C peak weakened, accompanied by a π*C=N peak strengthened with nitrogen doping. This structural modification after nitrogen doping was found to generate unpaired electrons with the formation of C–N and C=N bonding in grain boundaries (GBs). The measured electrical conductivity increased with nitrogen content, which confirms the suggestion of structural investigations that nitrogen-doping generated free electrons at the GBs of the NCD films.Item Data reference (DR): A Multi-Facility Two-Stage Stochastic Aggregate Production Planning Model with Renewable and Prosumer Microgrids(2021-12) Islam, Sayed Rezwanul; Novoa, Clara; Jin, TongdanNo abstract prepared.Item Design Strategy for Recycled Aggregate Concrete: A Review of Status and Future Perspectives(Multidisciplinary Digital Publishing Institute, 2021-06-17) Makul, Natt; Fediuk, Roman; Amran, Mugahed; Zeyad, Abdullah; Klyuev, Sergey; Chulkova, Irina; Ozbakkaloglu, Togay; Vatin, Nikolai; Karelina, Maria; Azevedo, AfonsoCurrently, a number of disadvantages hampers the use of recycled concrete aggregates (RCA). The current review proves that concretes made with complete replacement of natural aggregate with RCA allow the production of high-quality concrete. One of the possibilities for improving concrete properties with RCA is the use of extended curing and pozzolanic materials with varying cement ratios. The potential use of RCA concretes is in the production of high-value materials that increase environmental and financial benefits. RCA have strong potential in the development of a new generation of concrete and stimulate economic activity in many countries in addition to optimizing natural resources. Economic benefits include minimal travel costs; cheaper sources of concrete than newly mined aggregates; reduction of the landfill area required for the placement of concrete waste; the use of RCA minimizes the need for gravel extraction, etc. The proposed strategy could be to sequentially separate demolition waste such as roof finishes, waterproof materials, interior and exterior materials, etc. Closing life cycles is the main approach used for efficient structures for the recycling and reuse of construction and demolition waste in the production and recovery of materials, especially when recycling and reusing materials. In the life cycle, the recycling of recovered materials allows them to be used for new construction purposes, avoiding the use of natural concrete aggregates. Government, design institutes, construction departments and project managers should be involved in the creation and use of RCA. In demolition and construction, the main players are the project owners. Their obligations, expectations and responsibilities must be properly aligned. For the past 20 years, recycled concrete aggregate from demolition and construction waste has been considered as an alternative to pure concrete in structural concrete to minimize the environmental impact of construction waste and demolition waste and the conversion of natural aggregate resources. It is now recognized that the use of RCA for the generations of concrete is a promising and very attractive technology for reducing the environmental impact of the construction sector and conserving natural resources. In the market, the selling price is not an obstacle for market applications of RCA, as there are scenarios in which their cost is lower than the cost of products made from conventional building materials. This is more of an acceptance factor in the market for recycled concrete aggregates. In this sector, the lack of identification, accreditation and uniform quality certification systems and their narrow application cause some marketing problems. With proper RCA preparation, concrete with standard physical and mechanical properties and performance characteristics can be obtained.Item Designing an Incentive Contract Menu for Sustaining the Electricity Market(Multidisciplinary Digital Publishing Institute, 2015-12) Yu, Ying; Jin, Tongdan; Zhong, ChunjieThis paper designs an incentive contract menu to achieve long-term stability for electricity prices in a day-ahead electricity market. A bi-level Stackelberg game model is proposed to search for the optimal incentive mechanism under a one-leader and multi-followers gaming framework. A multi-agent simulation platform was developed to investigate the effectiveness of the incentive mechanism using an independent system operator (ISO) and multiple power generating companies (GenCos). Further, a Q-learning approach was implemented to analyze and assess the response of GenCos to the incentive menu. Numerical examples are provided to demonstrate the effectiveness of the incentive contract.Item Detailed Numerical Results for Paper: A Set-Partitioning-Based Model for the Stochastic Vehicle Routing Problem(2009-05) Novoa, Clara; Berger, Rosemary T.; Linderoth, Jeff; Storer, RobertFollowing are some tables with detailed results that complement the paper titled "A Set-Partitioning-Based Model for the Stochastic Vehicle Routing Problem."