Engineering Commons^™

Facet Dependent Oxygen Evolution Activity Of Spinel Cobalt Oxides, Li-Hua Zhang, Hong-Yuan Chuai, Hai Liu, Qun Fan, Si-Yu Kuang, Sheng Zhang, Xin-Bin Ma

Journal of Electrochemistry

Water splitting is a promising technology to produce clean hydrogen if powered by renewable energies, where oxygen evolution is the rate determining step at an anode. Here we adjust the different crystal planes of the cobalt oxides catalyst to expose more effective active sites through a hydrothermal process, so as to improve the reaction activity for oxygen evolution. The samples were well characterized by TEM, SEM and XRD. Among the three synthetic crystal planes (100), (111) and (110) of spinel cobalt oxides, the (100) crystal plane has the highest intrinsic activity. Combining in-situ infrared and DFT calculations, we …

Structural Degradation Of Ni-Rich Layered Oxide Cathode For Li-Ion Batteries, Jia-Yi Wang, Sheng-Nan Guo, Xin Wang, Lin Gu, Dong Su

Journal of Electrochemistry

Nickel(Ni)-rich layered oxide has been regarded as one of the most important cathode materials for the lithium-ion batteries because of its low cost and high energy density. However, the concerns in safety and durability of this compound are still challenging for its further development. On this account, the in-depth understanding in the structural factors determining its capacity attenuation is essential. In this review, we summarize the recent advances on the degradation mechanisms of Ni-rich layered oxide cathode. Progresses in the structure evolution of Ni-rich oxide are carefully combed in terms of inner evolution, surface evolution, and the property under thermal …

Recent Advances In Structural Regulation On Non-Precious Metal Catalysts For Oxygen Reduction Reaction In Alkaline Electrolytes, Xue Wang, Li Zhang, Chang-Peng Liu, Jun-Jie Ge, Jian-Bing Zhu, Wei Xing

Journal of Electrochemistry

Oxygen reduction reaction (ORR) in alkaline electrolytes is an important electrochemical process for metal-air batteries and anion exchange membrane fuel cells (AEMFCs). However, the sluggish kinetics spurs intensive research on searching robust electrocatalysts. Non-precious metal catalysts (NPMCs) that can circumvent the cost and scarcity issues associated with platinum (Pt)-based materials have been pursued and the challenges lie in the performance improvement to rival Pt-based benchmarks. As the composition and structure of the NPMCs have a significant impact on the catalytic performance, precise regulation on the catalyst structure holds great promise to bridge the activity gap between NPMCs and Pt-based benchmarks. …

Selective Co2 Reduction To Formate On Heterostructured Sn/Sno2 Nanoparticles Promoted By Carbon Layer Networks, Xue Teng, Yanli Niu, Shuaiqi Gong, Xuan Liu, Zuofeng Chen

Journal of Electrochemistry

Tin (Sn)-based materials have emerged as promising electrocatalysts for selective reduction of CO₂ to formate, but their overall performances are still limited by electrode structures which govern the accessibility to active sites, the electron transfer kinetics, and the catalytic stability. In this study, the heterostructured Sn/SnO₂ nanoparticles dispersed by N-doped carbon layer networks (Sn/SnO₂@NC) were synthesized by a melt-recrystallization method taking the low melting point of Sn (m.p. 232^oC). The N-doped carbon layer networks derived from polydopamine could attract more electrons on the electrocatalyst, serve as conductive agents and protect the ultrafine nanoparticles from …

Mass Loading Optimization For Ethylene Glycol Oxidation At Different Potential Regions, Sheng-Nan Sun, Zhi-Chuan Xu

Journal of Electrochemistry

Designing and fabricating the electrocatalysts is attracting more and more attention in recent years due to a global interest in developing techniques for electrochemical energy conversion and storage, as well as elelectro-synthesis of valuable chemicals. The activity is one of the key performance parameters for electrocatalysts, while the observed activity can be affected by mass loading of electrocatalysts. Here, we take cobalt oxide (Co₃O₄)/graphite paper electrode (Co₃O₄/GPE) as a model electrode to demon-strate how the mass loading of Co₃O₄ catalyst influences ethylene glycol (EG) oxidation in alkaline (KOH) by …

Recent Advances In Electrochemical Kinetics Simulations And Their Applications In Pt-Based Fuel Cells, Ji-Li Li, Ye-Fei Li, Zhi-Pan Liu

Journal of Electrochemistry

Theoretical simulations of electrocatalysis are vital for understanding the mechanism of the electrochemical process at the atomic level. It can help to reveal the in-situ structures of electrode surfaces and establish the microscopic mechanism of electrocatalysis, thereby solving the problems such as electrode oxidation and corrosion. However, there are still many problems in the theoretical electrochemical simulations, including the solvation effects, the electric double layer, and the structural transformation of electrodes. Here we review recent advances of theoretical methods in electrochemical modeling, in particular, the double reference approach, the periodic continuum solvation model based on the modified Poisson-Boltzmann …

Magnetic Resonance In Metal-Ion Batteries: From Nmr (Nuclear Magnetic Resonance) To Epr (Electron Paramagnetic Resonance), Bing-Wen Hu, Chao Li, Fu-Shan Geng, Ming Shen

Journal of Electrochemistry

Metal-ion batteries have changed our quotidian lives. The research on the electrode materials for metal-ion battery is the key to improve the performance of the battery. Therefore, understanding the structure-performance relationship of the electrode materials can help to improve the energy density and power density of the materials. Magnetic resonance, including nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR), has been continuously improved during the past three decades, and has gradually become one of the important technologies to study the structure-performance relationship of electrode materials. This paper summarizes the progress of magnetic resonance research from our group on several …

Development Of Intensity-Duration-Frequency (Idf) Models For Manually Operated Rain Gauge Catchment: A Case Study Of Port Harcourt Metropolis Using 50 Years Rainfall Data, Francis Ogbozige

Tanzania Journal of Engineering and Technology (TJET)

Hydraulic structures such as surface drainages and culverts are usually constructed in urban areas with the intention of draining runoff into nearby streams and rivers in order to avoid flooding. However, most of these structures frequently fail to serve the intended use due to the occurrence of high intensity rainfall accompanied with long duration, which produce runoff discharge higher than their designed capacities. This is common in many developing countries as drainages and culverts are most times constructed without considering hydrological analysis of the catchment. Hence, this research considered Port Harcourt city as a case study by utilizing 50 years …

Real-Time Complex Hand Gestures Recognition Based On Multi- Dimensional Features, Isack Bulugu

Tanzania Journal of Engineering and Technology (TJET)

Gesture recognition is broadly utilized within the field of sensing. There are basically three gesture recognition methods based on computer vision, depth sensor and motion sensor. Motion sensor-based gesture recognition has few input data, fast speed, and direct access to three- dimensional information of the hand. The advantages of traditional motion sensor-based gesture recognition have gradually become a current research hotspot. The essence of traditional motion sensor-based gesture recognition is a pattern recognition problem, and its accuracy depends heavily on the feature dataset extracted from prior experience. Unlike traditional pattern recognition methods, deep learning can be used to a large …

Resilient Modulus Of Siliciclastic Unbound Granular Materials Under Repeated Wheel Loading, Siya Rimoyi

Tanzania Journal of Engineering and Technology (TJET)

The Resilient Modulus (Mr) is a fundamental material property input in modern Mechanistic-Empirical (M-E) pavements structural design. Empirical pavement design methods have been in use over a long period during which large databases of four- days-soaked California Bearing Ratio (CBR) values at or near the Maximum Dry Density have been generated in the strength assessments for Unbound Granular Materials (UGMs). In the adoption of the M-E design approach researchers have so far attempted with various degrees of success to develop models to derive resilient modulus from the conventional CBR-based databases. This study provides an extensive laboratory experimental study to investigate …

Complete Neighbourhood Search Heuristic Algorithm For Portfolio Optimization, Collether John

Tanzania Journal of Engineering and Technology (TJET)

In portfolio optimization, the fundamental goal of an investor is to optimally allocate investments between different assets. Mean-variance optimization methods make unrealistic assumptions to solve the problem of optimal allocation. On the other hand, when realistic constraints like holding size and cardinality are introduced it leads to optimal asset allocation which differ from the mean variance optimization. The resulting optimization problem become quite complex as it exhibits multiple local extrema and discontinuities. Heuristic algorithms work well for the complex problem. Therefore, a heuristic algorithm is developed which is based on hill climbing complete (HC-C). It is utilized to solve the …

Assessment Of Quality Of Fresh Concrete Delivered At Varying Temperatures, Maroua Saidi, Kazem Jadidi, Moses Karakouzian

Civil and Environmental Engineering and Construction Faculty Research

Concrete is increasingly utilized in the construction field in Southern Nevada. This area has an arid and hot summer and freezing cold winter conditions. These extreme conditions affect the properties of fresh concrete, which can cause cracking. Hot weather conditions may adversely affect both fresh and hardened concrete properties. Even though practices can minimize the detrimental effects, good quality control of fresh concrete, from mixing to finishing, is crucial under hot weather conditions. The objective of the present study is to evaluate the seasonal consistency of concrete quality, considering strength and slump properties. Another objective of this research is to …

Efficacy Of Softener For Enhancing Fatigue And Low-Temperature Performance Of Asphalt Binders With High Rap, Sumon Roy

Student Theses and Dissertations

The use of a higher percentage of reclaimed asphalt pavement (RAP) in asphalt concrete can lead to developing premature failure of asphalt pavements due to fatigue and/or low-temperature cracking. The incorporation of softening agents in asphalt binders can resolve these problems and enhance pavement durability. This study aims to evaluate the effectiveness of waste-based softening agents for enhancing the properties of asphalt mixes with high RAP contents. Waste cooking oil (WCO), and engine bottom oil (EBO) along with a commercial rejuvenator were investigated in this study. Three types of Performance Grade (PG) binders, each collected from two different sources, used …

Influence Of Supplementary Cementitious Material (Scm) On Concrete Durability (Drying Shrinkage And Alkali-Silica Reactivity), Raiyan Chowdhury

Student Theses and Dissertations

This study investigates the long-term durability of concrete by replacing cement (10%, 20%, and 30%) with four potential Supplementary Cementitious Material (SCMs), namely, Reclaimed Fly Ash (RFA), Ground Bottom Ash (GBA), Class F Fly Ash (FA), and Metakaolin® (MK). For long-term durability, drying shrinkage and alkali-silica reactivity (ASR) tests were performed along with workability (slump) and compressive strength tests. The FA and RFA demonstrated better workability compared to GBA, MK, and combined mixes (RFA-MK or GBA-MK). The GBA and RFA modified specimens exhibited better compressive strength than other SCMs. Modifying concrete mix with SCMs lowered the ASR expansion than the …

A Flexible Enzymeless Glucose Sensor Via Electrodepositing 3d Flower-Like Cos Onto Self-Supporting Graphene Tape Electrode, Jiang Li, Zuo-Peng Li, Yun-Feng Bai, Su-Xing Luo, Yong Guo, Ya-Yan Bao, Rong Li, Hai-Yan Liu, Feng Feng

Journal of Electrochemistry

Three-dimensional (3D) nanostructural Flower-like cobalt sulfide (CoS) on flexible self-supporting graphene tape electrode (GTE) with remarkably electrocatalytic activity toward glucose was successfully prepared by electrodeposition. Structural characterizations revealed that the electrodeposited CoS was highly dispersed on GTE as an active material. The fabricated binder-free and self-standing CoS/GTE shows a good linear response in the range of 0.025 ~ 1.0 mmol·L^-1, reaching a high glucose sensitivity value of 323.3 μA·(mmol·L ^-1)^-1·cm^-2 and a low detection limit of 8.5 μmol·L ^-1 (S/N = 3). Moreover, the as-prepared sensor was well applied for glucose …

Acetate Solutions With 3.9 V Electrochemical Stability Window As An Electrolyte For Low-Cost And High-Performance Aqueous Sodium-Ion Batteries, Dao-Yun Lan, Xiao-Feng Qu, Yu-Ting Tang, Li-Ying Liu, Jun Liu

Journal of Electrochemistry

Low-cost and high-safety aqueous sodium-ion batteries have received widespread attention in the field of large-scale energy storage, but the narrow electrochemical stability window (1.23 V) of water limits the energy density of aqueous sodium-ion batteries. The “water-in-salt” strategy which uses the interaction between cations and water molecules in the solution can inhibit water decomposition and broaden the electrochemical stability window of water. In this work, two types of low-cost salts, namely, ammonium acetate (NH₄CH₃COOH) and sodium acetate (NaCH₃COOH), were used to configure a mixed aqueous electrolyte for aqueous sodium-ion batteries. The solution consisted of …

Synthesis Of Lithium-Rich Manganese-Based Layered Cathode Materials And Study On Its Structural Evolution Of First Cycle Overcharge, Chen-Xu Luo, Chen-Guang Shi, Zhi-Yuan Yu, Ling Huang, Shi-Gang Sun

Journal of Electrochemistry

Lithium-rich manganese-based cathode materials have become one of promising cathode materials due to their low cost and large discharge specific capacity exceeding 250 mAh·g^-1. However, their problems such as low coulombic efficiency of first cycle and apparent voltage decay influence commercialization process. The high charging voltage will cause instability of structure and increase the hidden danger of the battery. Therefore, structural evolution of first cycle at higher voltage needs to be further studied. In this work, the precursor was synthesized by the co-precipitation method, and the lithium-rich manganese-based layered cathode materials were prepared by lithium-mixed and high-temperature sintering, …

Progress Of Pt-Based Catalysts In Proton-Exchange Membrane Fuel Cells: A Review, Long Huang, Hai-Chao Xu, Bi Jing, Qiu-Xia Li, Wei Yi, Shi-Gang Sun

Journal of Electrochemistry

Fuel cells are energy conversion devices that convert chemical energy directly into electricity. It has the advantages of high energy density, high utilization efficiency of fuel, clean and noiseless during working. Among all kinds of fuel cells, proton exchange membrane fuel cells (PEMFCs) are most popular since PEMFCs function at near ambient temperature, while their power densities are higher than those of other fuel cells. Currently, Pt-based nanomaterials are still the unreplaceable catalysts in commercialized PEMFCs. The lack of low-cost and high-performance cathode catalysts is still one of key factors that hampers the commercialization of PEMFCs. In this review, the …

Advances Of Phosphide Promoter Assisted Pt Based Catalyst For Electrooxidation Of Methanol, Meng Li, Li-Gang Feng

Journal of Electrochemistry

Transition metal phosphide (TMP), as an ideal catalytic promoter in methanol fuel oxidation, has received increased attention because of its multifunctional active sites, tunable structure and composition, as well as unique physical and chemical properties and efficient multi-composition synergistic effect. Some advances have been made for this catalyst system recently. In the current review, the research progresses of transition metal phosphides (TMPs) in the assisted electrooxidation of methanol including the catalysts fabrication and their performance evaluation for methanol oxidation are reviewed. The promotion effect of TMPs has been firstly presented and the catalyst systems based on the different metal centers …

A High-Performance Continuous-Flow Mea Reactor For Electroreduction Co2 To Formate, Pei-Xuan Liu, Lu-Wei Peng, Rui-Nan He, Lu-Lu Li, Jin-Li Qiao

Journal of Electrochemistry

The electrochemical carbon dioxide reduction reaction (CO₂RR) is a promising approach to produce liquid fuels and industrial chemicals by utilizing intermittent renewable electricity for mitigating environmental problems. However, the traditional H-type reactor seriously limits the electrochemical performance of CO₂RR due to the low CO₂ solubility in electrolyte, and high ohmic resistance caused by the large distance between two electrodes, which is unbeneficial for industrial application. Herein, we demonstrated a high-performance continuous flow membranes electrode assembly (MEA) reactor based on a self-growing Cu/Sn bimetallic electrocatalyst in 0.5 mol·L^-1 KHCO₃ for converting CO₂ to …

Oxidative Efficiency Of Ozonation Coupled With Electrolysis For Treatment Of Acid Wastewater, Ze-You Hu, Feng-Yun Xiang, Ji-Qiang Mao, Ya-Lei Ding, Shao-Ping Tong

Journal of Electrochemistry

Establishment of an ozone-based advanced oxidation process (AOPs-O₃) for effective treatment of acid wastewater is an important and difficult task. The process of ozonation coupled with electrolysis (electrolysis-ozonation, E-O₃) has been reported to effectively degrade pollutants in neutral solution. We studied the efficiency of E-O₃ for degradation of acetic acid (HAc, an ozone inert chemical) in acid solution and found that E-O₃ had high oxidative efficiency at pH less than 3. For example, 52.2% of 100 mg·L^-1 HAc could be removed by E-O₃ in 120 min at pH 1.0, but only 2.2% …

A Simulation Model To Determine The Supply Chain Optimum Order Quality, Ahmed Mohamed Saleh

Archived Theses and Dissertations

No abstract provided.

A Trusted Platform For Unmanned Aerial Vehicle-Based Bridge Inspection Management System, Hwapyeong Song

Theses, Dissertations and Capstones

Bridge inspection has a pivotal role in assuring the safety of critical structures constituting society. However, high cost, worker safety, and low objectivity of quality are classic problems in traditional visual inspection. Recent trends in bridge inspection have led to a proliferation of research utilizing Unmanned Aerial Vehicles (UAVs). This thesis proposes a Trusted Platform for Bridge Inspection Management System (Trusted-BIMS) for safe and efficient bridge inspection by proving the UAV-based inspection process and improving the prototype of the previous study. Designed based on a Zero-Trust (ZT) strategy, Trusted-BIMS consist of (1) a database-driven web framework with security features for …

Influence Of Fill Percentage And Baking Parameters On The Feedability Of Metal-Cored Arc Welding Wires, Angelica Marie Black

Browse all Theses and Dissertations

Adequate feedability is essential for GMAW processes to ensure efficiency. The feedability of a wire refers to the wire’s ability to feed continuously through the contact tip. While there are several known causes of feedability difficulties when using cored welding wires, there are many variables that have yet to be explored thoroughly. Three factors are investigated in this research to determine their effects on feedability of cored wires: fill percentage, baking time, and baking temperature. A set of metal-cored arc welding wires were created with various fill percentages, baking times, and baking temperatures. Tension testing, microhardness testing, microstructural characterization, and …

Effect Of The Extended Rigid Flapping Trailing Edge Fringe On An S833 Airfoil, Hongtao Yu, Zifeng Yang

Mechanical and Materials Engineering Faculty Publications

A 2D numerical simulation was conducted to investigate the effect of an extended rigid trailing edge fringe with a flapping motion on the S833 airfoil and its wake flow field, as an analogy of an owl’s wing. This study aims to characterize the influence of the extended flapping fringe on the aerodynamic performance and the wake flow characteristics downstream of the airfoil. The length (Le) and flapping frequencies (fe) of the fringe are the key parameters that dominate the impact on the airfoil and the flow field, given that the oscillation angular amplitude is fixed at 5◦. The simulation results …

Fabrication Of Soft Gripper Via Direct Inkjet Writing Additive Manufacturing, Evan D. Johnson

College of Graduate Studies: Theses & Dissertations

Additive manufacturing (AM) has bloomed recently in the manufacturing field due to its many applications. Direct inkjet writing (DIW) is one of the main am technologies used in the production of grippers. DIW is the most popular taking advantage of materials like silicone and hydrogels. The technology of 3D printing with silicone is still in early stages ,nevertheless, the ability to print with soft materials is very alluring. The implementation of complex geometries in the silicone world would yield vast opportunities in the medical and robotics fields. Additive manufacturing allows for this to be thoroughly examined. In this research these …

Recent Advances In Biosensors For Detection Of Covid-19 And Other Viruses, Shobhit K. Patel, Jaymit Surve, Juveriya Parmar, Kawsar Ahmed, Francis M. Bui, Fahad Ahmed Al-Zahrani

Department of Mechanical and Materials Engineering: Faculty Publications

This century has introduced very deadly, dangerous, and infectious diseases to humankind such as the influenza virus, Ebola virus, Zika virus, and the most infectious SARS-CoV-2 commonly known as COVID-19 and have caused epidemics and pandemics across the globe. For some of these diseases, proper medications, and vaccinations are missing and the early detection of these viruses will be critical to saving the patients. And even the vaccines are available for COVID-19, the new variants of COVID-19 such as Delta, and Omicron are spreading at large. The available virus detection techniques take a long time, are costly, and complex and …

Rational Design Of Flexible And Stretchable Electronics Based On 3d Printing, Yuanhang Yang

Theses and Dissertations

Flexible and stretchable electronics have been considered as the key component for the next generation of flexible devices. There are many approaches to prepare the devices, such as dip coating, spin coating, Mayer bar coating, filtration and transfer, and printing, etc. The effectiveness of these methods has been proven, but some drawbacks cannot be ignored, such as lacking pattern control, labor consuming, requiring complex pretreatment, wasting conductive materials, etc.

In this investigation, we propose to adopt 3D printing technology to design flexible and stretchable electronics. The objective is to rationally design flexible and stretchable sensors, simplify the preparation process, form …

Visualization And Validation Of Twin Nucleation And Early-Stage Growth In Magnesium, Lin Jiang, Mingyu Gong, Jian Wang, Zhiliang Pan, Xin Wang, Dalong Zhang, Y. Morris Wang, Jim Ciston, Andrew M. Minor, Mingjie Xu, Xiaoqing Pan, Timothy J. Rupert, Subhash Mahajan, Enrique J. Lavernia, Irene J. Beyerlein, Julie M. Schoenung

Department of Mechanical and Materials Engineering: Faculty Publications

The abrupt occurrence of twinning when Mg is deformed leads to a highly anisotropic response, making it too unreliable for structural use and too unpredictable for observation. Here, we describe an in-situ transmission electron microscopy experiment on Mg crystals with strategically designed geometries for visualization of a long-proposed but unverified twinning mechanism. Combining with atomistic simulations and topological analysis, we conclude that twin nucleation occurs through a pure-shuffle mechanism that requires prismatic-basal transformations. Also, we verified a crystal geometry dependent twin growth mechanism, that is the early-stage growth associated with instability of plasticity flow, which can be dominated either by …

Evaluation Of Static Recrystallization And Grain Growth Kinetics Of Hot-Rolled Az31 Alloy, Salaheddine Sadi, Abdelkader Hanna, Thierr Baudin, Anne-Laure Helbert, François Brisset, Djamel Bradai, Hiba Azzeddine

Journal of Metals, Materials and Minerals

The static recrystallization/grain growth kinetics of the AZ31 (Mg-3Al-1Zn, wt%) alloy were investigated employing Vickers microhardness and electron backscatter diffraction (EBSD) measurements. The AZ31 alloy was subject to a hot-rolling for 70% of thickness reduction and then annealed at various temperatures (150°C, 250°C, and 350°C) from 5 min to 24 h. First, the static recrystallization kinetics were analysed by means of the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The results showed that the recrystallization occurred under two regimes both involving their own Avrami exponent/ activation energy. In regime I, the Avrami exponent was found in the range of 1.5-0.35 depending on the annealing …