Mechanical Engineering Commons^™

Synthesis And Characterization Of New Ionic And Mixed Ionic/Electronic Conductors, Kevin Gregory Romito

Theses and Dissertations

In a constantly growing and developing world, there is a great need to develop new forms of clean energy generation. Many solutions have been proposed to ameliorate these global concerns, which include fuel cell technology and new processes for reducing polluting chemicals in the atmosphere. These technologies are still in their infancy and require further development before becoming viable options.

In the case of fuel cells, particularly solid oxide fuel cells, and CO2 separation membranes, there is a need to develop ion conducting materials that are highly efficient, less costly to synthesize, and can perform strongly under many real-world conditions. …

Mechanical Characterization Of Composite Repairs For Fiber-Glass Wind Turbine Blades, Tanveer Singh Chawla

Theses and Dissertations

While in service, wind turbine blades experience various modes of loading. An example is impact loading in the form of hail or bird strikes, which might lead to localized damage or formation of cracks a few plies deep on the blade surface. One of the methods to conduct repairs on wind turbine blades that are damaged while in service is hand lay-up of the repair part after grinding out the damaged portion and some of its surrounding area. The resin used for such repairs usually differs from the parent plate resin in composition and properties such as gel time, viscosity, …

Cavitation In Pharmaceutical Manufacturing And Shipping, Donn Sederstrom

Electronic Theses and Dissertations

Therapeutic proteins are used to successfully treat hemophilia, Crohn's Disease, diabetes, and cancer. Recent product recalls have occurred because of sub-visible particle formation resulting from the inherent instability of proteins. It has been suggested that particle formation is associated with late stage processing steps of filling, shipping, and delivery. Previous work at the University of Denver demonstrated that fluid cavitation can generate a large number of sub-visible protein particles in ultra clean formulations, but that mitigation can be achieved with fluid property manipulation. The goal of this research was to (1) assess the risk of cavitation under common pharmaceutical manufacturing …

Representing Intersubject Variability With A Statistical Shape And Alignment Model Of The Knee, Chandreshwar Rao

Electronic Theses and Dissertations

Prior statistical shape models have not considered multiple structures in the knee joint to characterize anatomic variation which are required to investigate joint mechanics further for the successful knee replacement. Accordingly, the study's objective was to develop statistical shape and alignment model (SSAM) to capture intersubject variability and demonstrate the ability to generate realistic instances for use in finite element analysis (FEA). SSAM described the variability in the training set of 20 subjects with a series of modes of variation obtained by performing principal component analysis (PCA). PCA produced modes of variation with the first 3 modes representing 70% and …

Review Of Electrochemical And Electrodischarge Machining, Kamlakar P. Rajurkar, M. M. Sundaram, A. P. Malshe

Department of Mechanical and Materials Engineering: Faculty Publications

Electrochemical and electro-discharge machining processes are the two major electro-machining processes with unique capabilities. Electrical Discharge Machining (EDM) and Electrochemical Machining (ECM) offer a better alternative or sometimes the only alternative in generating accurate 3-D complex shaped macro, micro and nano features and components of difficult–to-machine materials. Technological advances reported in electrochemical and electro discharge machining processes, which reflect the state of the art in academic and industrial research and applications, are briefly reviewed in this paper.

Wire Electro-Discharge Machining Of Titanium Alloy, Farnaz Nourbakhsh, Kamlakar P. Rajurkar, Ajay P. Malshe, Jian Cao

Department of Mechanical and Materials Engineering: Faculty Publications

This paper presents an experimental investigation of wire electro-discharge machining (WEDM) of titanium alloy. The objective is to investigate the effect of seven process parameters including pulse width, servo reference voltage, pulse current, and wire tension on process performance parameters (such as cutting speed, wire rupture and surface integrity). A Taguchi L18 design of experiment (DOE) has been applied. All experiments have been conducted using Charmilles WEDM. It was also found that the cutting speed increases with peak current and pulse interval. Surface roughness was found to increase with pulse width and decrease with pulse interval. The Analysis of Variance …

Selective Detection And Automated Counting Of Fluorescently-Labeled Chrysotile Asbestos Using A Dual-Mode High-Throughput Microscopy (Dm-Htm) Method, Myoung-Ock Cho, Hyo Mi Chang, Donghee Lee, Yeon Gyu Yu, Hwataik Han, Jung Kyung Kim

Department of Mechanical and Materials Engineering: Faculty Publications

Phase contrast microscopy (PCM) is a widely used analytical method for airborne asbestos, but it is unable to distinguish asbestos from non-asbestos fibers and requires time-consuming and laborious manual counting of fibers. Previously, we developed a high-throughput microscopy (HTM) method that could greatly reduce human intervention and analysis time through automated image acquisition and counting of fibers. In this study, we designed a dual-mode HTM (DM-HTM) device for the combined reflection and fluorescence imaging of asbestos, and automated a series of built-in image processing commands of ImageJ software to test its capabilities. We used DksA, a chrysotile-adhesive protein, for selective …

Photovoltaic Device, Jinsong Huang, Bin Yang, Yongbo Yuan

Department of Mechanical and Materials Engineering: Faculty Publications

An apparatus includes a substrate; and a photoactive layer disposed on the substrate. The photoactive layer includes an electron acceptor material; an electron donor material; and a material having dipoles.

Solution-Processed Nanoparticle Super-Float-Gated Organic Field-Effect Transistor As Un-Cooled Ultraviolet And Infrared Photon Counter, Yongbo Yuan, Qingfeng Dong, Bin Yang, Fawen Guo, Qi Zhang, Ming Han, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

High sensitivity photodetectors in ultraviolet (UV) and infrared (IR) range have broad civilian and military applications. Here we report on an un-cooled solution-processed UV-IR photon counter based on modified organic field-effect transistors. This type of UV detectors have light absorbing zinc oxide nanoparticles (NPs) sandwiched between two gate dielectric layers as a floating gate. The photon-generated charges on the floating gate cause high resistance regions in the transistor channel and tune the source-drain output current. This ‘‘super-float-gating’’ mechanism enables very high sensitivity photodetectors with a minimum detectable ultraviolet light intensity of 2.6 photons/µm²s at room temperature as well …

Analysis Of Electrically-Forced Vibrations Of Piezoelectric Mesa Resonators, Huijing He, Guo-Quan Nie, Jin-Xi Liu, Jiashi Yang

Department of Mechanical and Materials Engineering: Faculty Publications

We study the electrically forced thickness-shear and thickness-twist vibrations of stepped thickness piezoelectric plate mesa resonators made of polarized ceramics or 6-mm class crystals. A theoretical analysis based on the theory of piezoelectricity is performed, and an analytical solution is obtained using the trigonometric series. The electrical admittance, resonant frequencies, and mode shapes are calculated, and strong energy trapping of the modes is observed. Their dependence on the geometric parameters of the resonator is also examined.

Constraint Enforcement Methods For Command Governor Based Adaptive Control Of Uncertain Dynamical Systems, Simon P. Schatz, Tansel Yucelen, Eric N. Johnsony, Florian Holzapfelz

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Recently, research has been conducted in order to improve the transient behavior of adaptively controlled uncertain nonlinear dynamical systems. In this paper, an adaptive control architecture is extended in order to achieve predictable transient performance in the presence of state constraints. The methodology at hand is based on a robust command governor framework, which is a dynamical system adjusting the trajectory of a given command in order to track a certain desired closed-loop reference model both in transient time and steady-state. Specifically, the command, which is applied on the reference model and the actual system, is changed by the command …

Consensus Protocols In Networked Multiagent Systems For Cluttered And Hostile Environments, Gerardo De La Torre, Eric N. Johnson, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Consensus refers to the agreement of networked agents upon certain quantities of interest and has widespread applications in diverse areas in science and engineering. This paper focuses on a new consensus protocol for networked multiagent systems operating in cluttered and hostile environments. Specifically, a consensus optimization algorithm is introduced that renders the Laplacian potential to be a nonincreasing function while minimizing a cost function and satisfying state and cost constraints. In addition, we show how to choose this cost function and the aforementioned constraints in order to decay the Laplacian potential to zero strictly. The proposed framework depends on a …

Model Based Adaptive Control Of Underwater Vehicles For Improved Ocean Science, Christopher J. Mcfarland

Link Foundation Ocean Engineering and Instrumentation Fellowship Reports

Recent advances in unmanned underwater vehicle (UUV) capabilities have enabled oceanographic scientists to consider addressing research topics previously thought impractical or impossible. One such topic is the validation of high resolution computer models; long term deployments of coordinated UUV survey teams have been proposed to collect the density of measurements required. Another topic is the study of biological diversity in volatile areas; UUV intervention/sampling deployments have been proposed because of the inherent risks. In general, providing a high density of high accuracy measurements requires passing many targets as quickly and closely as possible. Similarly, efficacy for intervention/sampling deployments requires agile …

Predicting Underwater Radiated Noise From Offshore Impact Pile Driving, Huikwan Kim

Link Foundation Ocean Engineering and Instrumentation Fellowship Reports

Offshore wind turbines have been installed throughout Europe and are expected to be built in the United States water shortly. Offshore wind is an attractive option because 53% of the nation’s population lives in coastal area where energy cost and demands are high. Offshore winds tend to blow harder and more uniformly than on land [1]. However, structure borne noise and vibration generated by offshore impact pile driving radiate into and propagate through the air, water, and sediment media. The objective of this project is quantitatively predicting noise level around the piling location at sea to estimate the effects of …

Approximate Dynamic Programming Based Solutions For Fixed-Final-Time Optimal Control And Optimal Switching, Ali Heydari

Doctoral Dissertations

"Optimal solutions with neural networks (NN) based on an approximate dynamic programming (ADP) framework for new classes of engineering and non-engineering problems and associated difficulties and challenges are investigated in this dissertation. In the enclosed eight papers, the ADP framework is utilized for solving fixed-final-time problems (also called terminal control problems) and problems with switching nature. An ADP based algorithm is proposed in Paper 1 for solving fixed-final-time problems with soft terminal constraint, in which, a single neural network with a single set of weights is utilized. Paper 2 investigates fixed-final-time problems with hard terminal constraints. The optimality analysis of …

Automated Extraction And Classification Of Time-Frequency Contours In Humpback Vocalizations, Hui Ou, Whitlow W.L. Au, Lisa M. Zurk, Marc O. Lammers

Electrical and Computer Engineering Faculty Publications and Presentations

A time-frequency contour extraction and classification algorithm was created to analyze humpback whale vocalizations. The algorithm automatically extracted contours of whale vocalization units by searching for gray-level discontinuities in the spectrogram images. The unit-to-unit similarity was quantified by cross-correlating the contour lines. A library of distinctive humpback units was then generated by applying an unsupervised, cluster-based learning algorithm. The purpose of this study was to provide a fast and automated feature selection tool to describe the vocal signatures of animal groups. This approach could benefit a variety of applications such as species description, identification, and evolution of song structures. The …

Part Height Control Of Laser Metal Additive Manufacturing Process, Yu-Herng Pan

Masters Theses

"Laser Metal Deposition (LMD) has been used to not only make but also repair damaged parts in a layer-by-layer fashion. Parts made in this manner may produce less waste than those made through conventional machining processes. However, a common issue of LMD involves controlling the deposition's layer thickness. Accuracy is important, and as it increases, both the time required to produce the part and the material wasted during the material removal process (e.g., milling, lathe) decrease. The deposition rate is affected by multiple parameters, such as the powder feed rate, laser input power, axis feed rate, material type, and part …

Numerical Modeling Of Heat Transfer And Fluid Flow In Laser Metal Deposition By Powder Injection, Zhiqiang Fan

Doctoral Dissertations

"Laser metal deposition is an additive manufacturing technique which allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. A self-consistent three-dimensional model was developed for the laser metal deposition process by powder injection, which simulates heat transfer, phase changes, and fluid flow in the melt pool, The governing equations for solid, liquid and gas phases in the calculation domain have been formulated using the continuum model. The free surface in the melt pool has been tracked by the Volume of Fluid (VOF) method, while the VOF transport equation was solved using the Piecewise Linear …

Kinematic And Dynamic Collision Statistics Of Cloud Droplets From High-Resolution Simulations, Bogdan Rosa, Hossein Parishani, Orlando Ayala, Wojciech W. Grabowski, Lian-Ping Wang

Engineering Technology Faculty Publications

We study the dynamic and kinematic collision statistics of cloud droplets for a range of flow Taylor microscale Reynolds numbers (up to 500), using a highly scalable hybrid direct numerical simulation approach. Accurate results of radial relative velocity (RRV) and radial distribution function (RDF) at contact have been obtained by taking advantage of their power-law scaling at short separation distances. Three specific but inter-related questions have been addressed in a systematic manner for geometric collisions of same-size droplets (of radius from 10 to 60 μm) in a typical cloud turbulence (dissipation rate at 400 cm² s^-3. Firstly, …

Web-Based Virtual Learning For Digital Manufacturing Fundamentals For Automotive Workforce Training, Vukica Jovanovic, Nathan W. Hartman

Engineering Technology Faculty Publications

Automotive manufacturers are experiencing difficulties in hiring highly qualified workers with ability to adopt new technologies fast. This kind of ongoing need for training is slowing innovation. This problem is related to the difficulty in obtaining consistent training resources and services especially with lack of training for advanced manufacturing practices for specialised industry sectors. More and more occupations require degrees higher than secondary education because of the global need for so called ‘knowledge workers’. An example of an interactive learning programme, developed with the support of narrated presentation technology, podcasts and online access has been shown in this paper. Sixty …