Engineering Commons^™

Behavior Of Piezoelectric Wafer Active Sensor In Various Media, Tuncay Kamas

Theses and Dissertations

The dissertation addresses structural health monitoring (SHM) techniques using ultrasonic waves generated by piezoelectric wafer active sensors (PWAS) with an emphasis on the development of theoretical models of standing harmonic waves and guided waves. The focal objective of the research is to extend the theoretical study of electro-mechanical coupled PWAS as a resonator/transducer that interacts with standing and traveling waves in various media through electro-mechanical impedance spectroscopy (EMIS) method and guided wave propagation. The analytical models are developed and the coupled field finite element analysis (CF-FEA) models are simulated and verified with experiments. The dissertation is divided into two parts …

Context-Sensitive Seismic Strengthening And Repair Of Substandard Confined Masonry, Rahim Ghorbani

Theses and Dissertations

Confined masonry (CM) is a construction system consisting of load-bearing masonry panels that are confined with cast-in-place reinforced concrete tie columns and beams. Due to satisfactory seismic performance, CM has become the predominant low-rise residential construction system in several areas around the world. However, in developing regions, the use of substandard materials, details and construction practices may result in inadequate performance as highlighted in the 2010 earthquakes in Haiti and Chile. In the aftermath of an earthquake, households are often reluctant to reoccupy their dwellings due to concerns about safety of structures. If feasible, preventive (pre-hazard) strengthening or structural repair …

Direct Synthesis Of Methane From Co2-H2O Co-Electrolysis In Tubular Solid Oxide Electrolysis Cells, Long Chen, Fanglin Chen, Changrong Xia

Faculty Publications

Directly converting CO₂ to hydrocarbons offers a potential route for carbon-neutral energy technologies. Here we report a novel design, integrating the high-temperature CO₂–H₂O co-electrolysis and low-temperature Fischer–Tropsch synthesis in a single tubular unit, for the direct synthesis of methane from CO₂ with a substantial yield of 11.84%.

Synthesis And Formation Mechanism Of Cuins2 Nanocrystals With A Tunable Phase, Chao Yu, Linlin Zhang, Long Tian, Dan Liu, Fanglin Chen, Cheng Wang

Faculty Publications

Chalcopyrite CuInS₂ (CIS) hierarchical structures composed of nanoflakes with a thickness of about 5 nm were synthesized by a facial solvothermal method. The thermodynamically metastable wurtzite phase CIS would be obtained by using InCl₃ instead of In(NO₃)₃ as In precursor. The effects of the In precursor and the volume of concentrated HCl aqueous solution on the phases and morphologies of CIS nanocrystals have been systematically investigated. Experimental results indicated that the obtained phases of CIS nanocrystals were predominantly determined by precursor-induced intermediate products. The photocatalytic properties of chalcopyrite and wurtzite CIS in visible-light-driven degradation of …

Biphilic Nanoporous Surfaces Enabled Exceptional Drag Reduction And Capillary Evaporation Enhancement, Xianming Dai, Fanghao Yang, Ronggui Yang, Xinyu Huang, William A. Rigdon, Xiaodong Li, Chen Li

Faculty Publications

Simultaneously achieving drag reduction and capillary evaporation enhancement is highly desired but challenging because of the trade-off between two distinct hydrophobic and hydrophilic wettabilities. Here, we report a strategy to synthesize nanoscale biphilic surfaces to endow exceptional drag reduction through creating a unique slip boundary condition and fast capillary wetting by inducing nanoscopic hydrophilic areas. The biphilic nanoporous surfaces are synthesized by decorating hydrophilic functional groups on hydrophobic pristine multiwalled carbon nanotubes. We demonstrate that the carbon nanotube-enabled biphilic nanoporous surfaces lead to a 63.1% reduction of the friction coefficient, a 61.7% wetting speed improvement, and up to 158.6% enhancement …

Host-Guest Interaction Dictated Selective Adsorption And Fluorescence Quenching Of A Luminescent Lightweight Metal-Organic Framework Toward Liquid Explosives, Dan Liu, Xiaojuan Liu, Yongxin Liu, Yang Yu, Fanglin Chen, Cheng Wang

Faculty Publications

In this article, we report the successful preparation of a Mg-based luminescent MIL-53 metal–organic framework (MOF), namely [Mg2(BDC)2(BPNO)]·2DMF (1) (BDC = 1,4-benzene dicarboxylate, BPNO = 4,4’- dipyridyl-N,N’-dioxide, DMF = N,N-dimethylformamide) in a mixed solvent containing a 2 : 3 volume ratio of DMF and ethanol (EtOH) under solvothermal conditions. Desolvated compound 1a can be used as an absorbent for selective adsorption and separation of liquid explosives, including nitroaromatic (nitrobenzene (NB)) and nitroaliphatic (nitromethane (NM) and nitroethane (NE)) compounds, through single crystal-to-single crystal (SC–SC) transformations. As one of the weakly luminescent MOFs, the luminescence of compound 1a could be quenched by …

Influence Of Crystal Structure On The Electrochemical Performance Of A-Site-Deficient Sr 1-Xnb 0.1 Co 0.9 O 3-Δ Perovskite Cathodes, Yinlong Zhu, Ye Lin, Xuan Shen, Jaka Sunarso, Wei Zhou, Shanshan Jiang, Dong Su, Fanglin Chen, Zongping Shao

Faculty Publications

The creation of A-site cation defects within a perovskite oxide can substantially alter the structure and properties of its stoichiometric analogue. In this work, we demonstrate that by vacating 2 and 5% of A-site cations from SrNb_0.1Co_0.9O_3−δ (SNC1.00) perovskites (Sr_1−sNb_0.1Co_0.9O_3−δ, s = 0.02 and 0.05; denoted as SNC0.98 and SNC0.95, respectively), a Jahn–Teller (JT) distortion with varying extents takes place, leading to the formation of a modified crystal lattice within a the perovskite framework. Electrical conductivity, electrochemical performance, chemical compatibility and microstructure of Sr …

Theoretical Investigation Of Heterogeneous Catalysis At The Solid–Liquid Interface For The Conversion Of Lignocellulosic Biomass Model Molecules, Muhammad Faheem

Theses and Dissertations

Catalytic conversion of biomass-derived oxygenates to fuels and value-added chemicals is a promising strategy in the search for renewable and sustainable energy sources. Most relevant catalytic processes are carried out in an aqueous environment using supported transition metal catalysts. The reaction network consists of multiple series and parallel pathways leading to formation of hydrogen, alkanes, and lighter oxygenates. The final product distribution ultimately depends on the sequence and competition of C−C, C−O, C−H, and O−H bonds scissions. Ethylene glycol (EG) is the simplest model molecule of various biomass-derived polyols that has a C:O stoichiometry of 1:1 and contains all relevant …

Ultrathin Graphene Oxide Membranes/Coatings For Separations, Hang Li

Theses and Dissertations

Graphene oxide (GO) was utilized as a novel material for making ultrathin membranes for gas separation and for making functional coatings for nano-/ultra-filtration in oil/water separation. Fundamental separation mechanisms by ultrathin GO membranes/coatings and potential applications were explored. This work can be divided into three parts. In the first part, ultrathin GO membranes supported on flat and smooth anodic aluminum oxide (AAO) substrates, with thickness down to 1.8 nm, were prepared by a facile vacuum filtration method. The as-prepared GO membranes were then studied for single-gas permeation and hydrogen mixture separation. It was revealed that the separation mechanism for the …

Lost In The Middle Kingdom: Teaching New Languages Using Serious Games And Language Learning Methodologies, Renaldo Justin Doe

Theses and Dissertations

This thesis focuses on the design and development of a serious video game for language learning entitled Lost in the Middle Kingdom. Our game utilizes several language learning methodologies including second language acquisition theory, content-based instruction, and task-based language teaching. This thesis examines previous language learning games and their drawbacks in order to create a more effective experience. Lost in the Middle Kingdom seeks to balance language learning with fun and intuitive gameplay in order to deliver a form of interactive media that is accepted by both the gaming and research communities. Our test data illustrates the strengths and weaknesses …

Thermal Analysis Of High Pressure Micro Plasma Discharge, Mostafa Mobli

Theses and Dissertations

High pressure micro plasma discharge has been at the center of interest in recent years, because of their vast applications, ease of access and cost efficiency. This attributes to atmospheric discharges that are generated in ambient conditions and therefore can be readily applicable to everyday use. The absence of vacuum makes these high pressure discharges to be inexpensive to operate. Despite the ease of operation, the high pressure is a source of enhanced gas heating as the gas temperature cannot be controlled by diffusion alone. Gas heating is therefore an important factor when it comes to the simulation of high …

Applications Of Electromagnetic Principles In The Design And Development Of Proximity Wireless Sensors, Md Nazmul Alam

Theses and Dissertations

Sensors and sensing system are playing dominant roles in monitoring the health of infrastructure, such as bridges, power lines, gas pipelines, rail roads etc. Sensing modalities employing Surface Acoustic Waves (SAW), Electromagnetic (EM) and optical have been investigated and reported. Sensors that utilize the perturbation of EM fields as function of the change in the physical structural or material phenomenon are of particular interest because of their inherent synergy with electronic system and diagnostic techniques, e.g. Time Domain Reflectometry (TDR), Joint-Time-Frequency-Domain-Reflectometry (JTFDR). The focus of this work is to study and develop new sensing and monitoring concepts that are based …

Synthesis Of Graphitic Carbon Nanostructures And Use As Electrocatalyst For Oxygen Reduction Reaction, Daniel A. Moniot

Theses and Dissertations

Graphitic carbon nanostructure (GCN) was synthesized by a simple procedure using cobalt(II) gluconate as a precursor and used as a catalyst support for polymer electrolyte membrane (PEM) fuel cell cathode. A novel stabilization procedure was developed to enhance the thermal stability of the GCN support. Support stabilization resulted in well-defined crystalline graphitic hollow structures as confirmed by highresolution transmission electron microscope (HRTEM). The prepared GCNs are used as support for depositing platinum nanoparticles (size) by modified polyol process. Rotating ring disk electrode (RRDE) and fuel cell studies were carried out to evaluate the catalyst performance. Cycling studies (0.6-1.0 V vs. …

Oxygen Flux And Dielectric Response Study Of Mixed Ionic-Electronic Conducting (Miec) Heterogeneous Functional Materials, Fazle Rabbi

Theses and Dissertations

Dense mixed ionic-electronic conducting (MIEC) membranes consisting of ionic conductive perovskite-type and/or fluorite-type oxides and high electronic conductive spinel type oxides, at elevated temperature can play a useful role in a number of energy conversion related systems including the solid oxide fuel cell (SOFC), oxygen separation and permeation membranes, partial oxidization membrane reactors for natural gas processing, high temperature electrolysis cells, and others. This study will investigate the impact of different heterogeneous characteristics of dual phase ionic and electronic conductive oxygen separation membranes on their transport mechanisms, in an attempt to develop a foundation for the rational design of such …

Investigation Of Thermal Performance Of Nanoparticle Enhanced Ionic Liquids (Neils) For Solar Collector Applications, Titan Chandra Paul

Theses and Dissertations

Concentrated Solar Power (CSP) is a prominent alternative energy technology, where mirrors or lenses are used to concentrate sunlight from a large area and stored in a collector filled with heat transfer fluid (HTF). The energy from this HTF is used to produce steam for power generation. CSP system requires high heat storage capacity and thermally stable HTF to reduce its operating cost. Having suitable thermophysical properties, ionic liquids (ILs) is considered as a potential HTF for the CSP applications; however thermophysical properties of ILs can be further enhanced by dispersing small volume percentages of nanoparticles. This liquid is called …

Vocab4me: A Tool That Provides Vocabulary Recommendations For Publishing Linked Data, Srikar Nadipally

Theses and Dissertations

The web before linked data was a database of html documents. These documents were meant for human consumption and it was hard for machines to make sense of data in html documents. The linked data was introduced with the aim of making the web a global database of data that is machine processable. Linked Data describes a method of publishing structured data so that it can be interlinked and become more useful. Realizing the promise of linked data a lot of people started publishing linked data. But the process of publishing the huge amount of existing data is cumbersome and …

Document Image Analysis Techniques For Handwritten Text Segmentation, Document Image Rectification And Digital Collation, Dhaval Salvi

Theses and Dissertations

Document image analysis comprises all the algorithms and techniques that are utilized to convert an image of a document to a computer readable description. In this work we focus on three such techniques, namely (1) Handwritten text segmentation (2) Document image rectification and (3) Digital Collation.

Offline handwritten text recognition is a very challenging problem. Aside from the large variation of different handwriting styles, neighboring characters within a word are usually connected, and we may need to segment a word into individual characters for accurate character recognition. Many existing methods achieve text segmentation by evaluating the local stroke geometry and …

Dielectric Properties Of Composite Materials During Damage Accumulation And Fracture, Md. Rassel Raihan

Theses and Dissertations

Fiber reinforced polymer matrix composite materials have many unique properties and their high performance makes them available to use in many advanced technologies i.e. aerospace, microelectronics, and energy storage. There is a correlation that exists between the long term behavior of those materials under combined mechanical, thermal, and electrical fields, and the functional properties and characteristics of the composite materials that requires a fundamental understanding of the material state changes caused by deformation and damage accumulation. This will ultimately lead, for example, to the design and synthesis of optimal multifunctional material systems. Composite materials are heterogeneous and the complex morphology …

Ghosts Of The Horseshoe: A Mobilization Of A Critical Interactive, Richard Lee Walker

Theses and Dissertations

Critical Interactives (CIs) are designed to harness the voluntary, reality-bending excitement of discovery as afforded by play, but to do so in the context of rules that mobilize procedural rhetoric to instantiate critical awareness. Critical interactives are not just about improving lives through code or education; rather, they establish a methodology for generating more aesthetic and reflective interactive experiences. To grasp more fully the logic underpinning CIs, we need to understand the powerful nature of interactivity and outline how such interactivity involves a notion of ethics, i.e., a way of living, in and through media practice.

Ghosts of the Horseshoe …

Ultrasonics Transduction In Metallic And Composite Structures For Structural Health Monitoring Using Extensional And Shear Horizontal Piezoelectric Wafer Active Sensors, Ayman Kamal Abdelrahman

Theses and Dissertations

Structural health monitoring (SHM) is crucial for monitoring structures performance, detecting the initiation of flaws and damages, and predicting structural life span. The dissertation emphasizes on developing analytical and numerical models for ultrasonics transduction between piezoelectric wafer active sensors (PWAS), and metallic and composite structures.

The first objective of this research is studying the power and energy transduction between PWAS and structure for the aim of optimizing guided waves mode tuning and PWAS electromechanical (E/M) impedance for power-efficient SHM systems. Analytical models for power and energy were developed based on exact Lamb wave solution with application on multimodal Lamb wave …

A Three-Dimensional In Vitromodel Of Atherogenesis, Pin Hsuan Chang

Theses and Dissertations

Atherosclerosis is the narrowing of arteries caused by accumulation of cholesterol, calcium and other cellular debris in the inner arterial wall. While extensive studies have been focusing on the inflammatory mechanisms of the disease, pathological and experimental evidence has shown that regions of disturbed flow are susceptible to the atherogenesis. To further understand the relationship between hemodynamics and atherogenesis, this research aims to generate a dynamic, 3D in vitro model of atherogenesis. This will allow for the investigation of specific cellular and molecular mechanisms of plaque formation that will pave the way for new therapies for the disease. A novel …

Growth, Fabrication And Characterization Of Cu2Znsn(SXSe1-X)4 Photovoltaic Absorber And Thin-Film Heterojunction Solar Cells, Sandip Das

Theses and Dissertations

Current thin-film solar cell technologies based on CuIn_xGa1_-xSe₂ (CIGS) and CdTe photo-absorber materials use rare and expensive elements, such as In, Te, Ga, and toxic Cd which severely limit the mass production and deployment of these solar cells. Thus, a major research effort is focused toward the development of new photovoltaic (PV) absorber materials comprising of earth-abundant, low-cost, and environmentally benign constituent elements that can support terawatt (TW)-scale PV generation in the near future and be economically sustainable. Cu-based I₂-II-IV-VI₄ quaternary kesterite compound Cu₂ZnSn(S_xSe_1-x)4 (CZTSS_{e …}

Using Genetic Algorithm To Solve Median Problem And Phylogenetic Inference, Nan Gao

Theses and Dissertations

Genome rearrangement analysis has attracted a lot of attentions in phylogenetic com- putation and comparative genomics. Solving the median problems based on various distance definitions has been a focus as it provides the building blocks for maximum parsimony analysis of phylogeny and ancestral genomes. The Median Problem (MP) has been proved to be NP-hard and although there are several exact or heuristic al- gorithms available, these methods all are difficulty to compute distant three genomes containing high evolution events. Such as current approaches, MGR[1] and GRAPPA [2], are restricted on small collections of genomes and low-resolution gene order data of …

Developing A Bioreactor For Biaxial Mechanical Testing And Conditioning Of Vascular Tissue, Steve Marcous

Theses and Dissertations

Cardiovascular diseases are known to be one of the major causes of death around the world. One of the major causes of cardiovascular disease is arterial malfunction. Arteries malfunction when they experience chronic perturbations in their local environment above normal levels. Hence, we developed a bioreactor system in order to study the effect of chronic changes in the arterial global parameters (axial force, luminal pressure, and flow rate) on the behavior of local parameters (circumferential stress, axial stress, and flow induced shear stress). The bioreactor system was designed to (i) perform biaxial mechanical testing, (ii) incorporate, for the first time, …

Gas-Phase, Catalytic Hydrodeoxygenation Of Propanoic Acid Over Supported Group Viii Noble Metals, Yuliana K. Lugo José

Theses and Dissertations

Recent advances for the deoxygenation of biomass, have demonstrated that hydrodeoxygenation (HDO) is one of the most promising route for the upgrading pyrolysis bio-oils. Catalytic hydrodeoxygenation of pyrolysis bio-oil have shown to be an efficient and economical process, since the raw materials consist mainly of waste. Propanoic Acid (PAc) is considered as one of the main constituents of pyrolysis bio-oils. However, these carboxylic acids are extremely corrosive and difficult to deoxygenate. Therefore, much effort have been given to the development of novel catalytic techniques, to improve the activity, stability and selectivity for the HDO of carboxylic acids.

This dissertation explores …

Memory Interface Synthesis For Fpga-Based Computing, Zheming Jin

Theses and Dissertations

This dissertation describes a methodology for the generation of a custom memory interface and associated direct memory access (DMA) controller for FPGA-based kernels that have a regular access pattern. The interface provides explicit support for the following features: (1) memory latency hiding, (2) static access scheduling, and (3) data reuse. The target platform is a multi-FPGA platform, the Convey HC-1, which has an advanced memory system that presents the user logic with three critical design challenges: the memory system itself does not perform caching or prefetching, memory operations are arbitrarily reordered, and the memory performance depends on the access order …

Research On Approximate Bayesian Computation, Jiting Xu

Theses and Dissertations

This thesis presents the development of a new numerical algorithm for statistical inference problems that require sampling from distributions which are intractable. We propose to develop our sampling algorithm based on a class of Monte Carlo methods, Approximate Bayesian Computation (ABC), which are specifically designed to deal with this type of likelihood-free inference. ABC has become a fundamental tool for the analysis of complex models when the likelihood function is computationally intractable or challenging to mathematically specify. The central theme of our approach is to enhance the current ABC algorithms by exploiting the structure of the mathematical models via derivative …

Tunable Graphene Chem-Fet And Graphene/Si Heterojunction Chemi-Diode Sensors, Amol Kumar Singh

Theses and Dissertations

Graphene, a two-dimensional material with very high charge carrier concentration, has drawn large research interest for sensing chemical species based upon charge exchange. Atomically thin 2-dimensional arrangement of carbon in hexagonal fashion in graphene, where each carbon atom is attached to 3 neighboring carbon atoms, and presence of π* and π bands imparts it many amazing properties. Some of these properties such as very high mobility, low 1/f and thermal noise, modulation of carrier concentration and Fermi level by electrical, optical, and chemical means, and very high surface to volume ratio make graphene very promising sensing material. In order to …

Structural Health Monitoring Using Linear And Nonlinear Ultrasonic Guided Waves, Yanfeng Shen

Theses and Dissertations

The dissertation addresses Structural Health Monitoring (SHM) using linear and nonlinear ultrasonic guided waves, with an emphasis on the development of analytical and numerical models of guided wave propagation and interaction with linear and nonlinear structural damage.

An analytical model was developed based on the exact Lamb wave solution for the simulation of Lamb wave propagation and interaction with damage. The damage effects were inserted into the model using complex valued wave damage interaction coefficients (WDICs). The analytical procedure was coded as a framework into a MATLAB Graphical User Interface (GUI), and the software WaveFormRevealer (WFR) was developed as a …

Plant-Biomimetic Hydrogel Actuators: Creating Movement In Hydrogels Through The Study Of Plants, Christen Rhodes

Theses and Dissertations

Plants are sessile organisms that have developed methods of movement to respond to environmental stimuli. Some of the approaches feature the unequal expansion of cells and controlling deformation direction through fibers under swelling and drying. Hydrogels are three dimensional polymer networks that have the capacity for large volume changes due their affinity for water and can be tough and/or stimuli-responsive. In this paper, three preliminary plant-biomimetic hydrogel actuator designs are discussed and tested from wet to dry. The first actuator design, termed a 1%-0.1% bilayer, features two layers of different swelling and drying rates due to differences in cross-linking density. …