Engineering Commons^™

Superharmonic Resonance Of Second Order For Electrostatically Actuated Mems Cantilevers, Martin Amador Botello

Theses and Dissertations

The nonlinear dynamics of electrostatically actuated micro-electro-mechanical system (MEMS) cantilever resonators are investigated. The applied Alternating Current (AC) voltage is in the realm of superharmonic resonance of the second order (near one-fourth of the natural frequency of the resonator) and hard excitations. Method of Multiple Scales (MMS) and Reduced Order Models (ROMs) are used to solve the dimensionless partial differential equation (PDE) of motion along with boundary and initial conditions. MMS transforms the PDE of motion into zero-order and first-order problems. ROMs uses mode shapes of vibration for undamped cantilever resonator as a basis of functions. ROM is …

Multifunctional Carbon Systems (Interlaminated Carbon Nanofiber Mats/ Carbon Nanotubes Polymer Composites), Homero Gonzalez Guardiola

Theses and Dissertations

Carbon nanomaterials have been an attractive topic within diverse industrial sectors given their outstanding properties for decades. One of the properties that has been calling attention is it’s shielding effectiveness (SE) for electromagnetic interference (EMI), because of the constant race of improving portable electronic and wireless communication devices among other applications. The present study, analyzes the properties of interlaminated Carbon Nanofiber (CNF) mats/Carbon Nanotubes (CNT) polymer composites, emphasizing in its capability to shield EMI. The CNF mats were developed with Polyvinyl alcohol (PVA) as a precursor and by means of the Forcespinning® technology which uses centrifugal force to create fibers …

Lead Doped Carbon Nanofibers In Li-Ion Batteries, Omar Torres

Theses and Dissertations

Lead acid batteries have been a very reliable rechargeable battery since its inception in the mid-1800s. Lithium-Ion batteries have been sought out for their light-weight and capacity of holding large amounts of energy in a small amount of space. Few studies have been conducted in the use of lead in lithium-ion batteries.

In this thesis, lead-doped carbon nanofibers were produced by using the Forcespinning® method and used as an anode on a lithium-ion battery. The morphology, material characterization and thermal properties of the anode material were analyzed using the Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Thermogravimetric Analysis …

Fibers For Skin Regeneration, Astrid Michelle Rodriguez Negron

Theses and Dissertations

This thesis presents the successful development of biocompatible Polyvinyl Butyral (PVB), PVB/Polylysine and PVB/Tannic Acid (TA)/Polylysine fibers from an ethanol solution, Polyhydroxybutyrate (PHB), PHB/Polylysine, PHB/TA/Polylysine fibers from a chloroform solution and Chitosan (CH)/Pullulan (PL)/TA and CH/PL/TA/Polylysine fibers from an aqueous solution. The fibers were mass produced utilizing the Forcespinning® (FS) technology. The morphology of the fibers was characterized using a scanning electron microscope (SEM) and the fibers average diameter was calculated. The thermal properties of the fibers were characterized using a thermogravimetric analyzer (TGA) and a differential scanning calorimeter (DSC). The antibacterial activity of the fibers was assessed using against …

The Effect Of Heat Generation In The Railroad Bearing Thermoplastic Elastomer Suspension Element On The Thermal Behavior Of Railroad Bearing Assembly, Oscar Osvaldo Rodriguez

Theses and Dissertations

Understanding the internal heat generation of the railroad bearing elastomer suspension element during operation is essential to predict its dynamic response and structural integrity, as well as to predict the thermal behavior of the complete railroad bearing assembly including the bearing adapter. The latter is essential for sensor selection and placement within the adapter (e.g., typical temperature sensors have operating ranges of up to 125°C or 257°F). The internal heat generation is a function of the loss modulus, strain, and frequency. Based on experimental studies, estimations of internally generated heat within the thermoplastic elastomer pad were obtained. The calculations show …

The Use Of Mixed Organic/Ionic Liquid Electrolytes With Forcespun Metal Oxides/Carbon Microfiber Electrodes In Lithium Ion Batteries, Jahaziel Villarreal

Theses and Dissertations

Conventional Lithium-Ion Battery (LIB) electrolytes have serious safety concerns because of highly flammability. In order to mitigate this drawback, alternative electrolytes with low volatility and non-flammable need to be synthesis. Ionic liquids (ILs) and mixed organic ionic liquid electrolytes (MOILEs) are the most suitable replacement for the highly flammable commercial organic electrolytes. In this academic investigation, a new perspective on the electrochemical performance of the ionic liquid EMI-TFSI as an alternate non-flammable electrolyte. In parallel, the use of Forcespun nanofibers as binder-free anodes will be analyzed to further improve overall electrochemical performance.

Feasibility Of Harbor-Wide Barrier Systems: Preliminary Analysis For Boston Harbor, Paul Kirshen

Sustainable Solutions Lab

This report presents a preliminary feasibility assessment of harbor-wide barrier systems designed to protect Boston Harbor from coastal flooding caused by sea level rise (SLR) and storm surges. Conducted by the Sustainable Solutions Lab at the University of Massachusetts Boston and supported by the Boston Green Ribbon Commission, the study evaluates two primary configurations: an Outer Harbor Barrier (OHB) and an Inner Harbor Barrier (IHB). Using hydrodynamic modeling, economic cost-benefit analysis, and social vulnerability assessments, the study finds that while both barrier systems may reduce risk from extreme storm events, they do not mitigate regular tidal flooding without frequent gate …

Ph-Responsive Mercaptoundecanoic Acid Functionalized Gold Nanoparticles And Applications In Catalysis, Siyam M. Ansar, Saptarshi Chakraborty, Christopher L. Kitchens

Publications

Mercaptoundecanoic acid (MUA) functionalized gold nanoparticles (AuNP-MUA) were synthesized and demonstrated to possess pH-triggered aggregation and re-dispersion, as well as the capability of phase transfer between aqueous and organic phases in response to changes in pH. The pH of aggregation for AuNP-MUA is consistent with the pK_a of MUA (pH ~4) in solution, while AuNP-MUA phase transition between aqueous and organic phases occurs at pH ~9. The ion pair formation between the amine group in octadecylamine (ODA), the carboxylate group in MUA, and the hydrophobic alkyl chain of ODA facilitates the phase transfer of AuNP-MUA into an organic medium. …

Critical-Point Model Dielectric Function Analysis Of Wo3 Thin Films Deposited By Atomic Layer Deposition Techniques, Ufuk Kılıç, Derek Sekora, Alyssa Mock, Rafał Korlacki, Elena M. Echeverría, Natale J. Ianno, Eva Schubert, Mathias Schubert

Department of Electrical and Computer Engineering: Faculty Publications

WO₃ thin films were grown by atomic layer deposition and spectroscopic ellipsometry data gathered in the photon energy range of 0.72-8.5 eV and from multiple samples was utilized to determine the frequency dependent complex-valued isotropic dielectric function for WO₃. We employ a critical-point model dielectric function analysis and determine a parameterized set of oscillators and compare the observed critical-point contributions with the vertical transition energy distribution found within the band structure of WO₃ calculated by density functional theory. We investigate surface roughness with atomic force microscopy and compare to ellipsometric determined effective roughness layer thickness.

From Digital Traces To Marketing Insights: Recovering Consumer Preferences For Digital Entertainment Services And Online Shopping, Ai Phuong Hoang

Dissertations and Theses Collection (Open Access)

IT innovations disrupt traditional business models and challenge conventional thinking. Thus, industry incumbents face fierce competition from start-ups with new business models and new ways of engaging customers. Digital entertainment goods and personalized services have become a lucrative market, which has undergone a transformation enabled by seamless Internet connections. Meanwhile, social networks and other online platforms have brought people and business even closer.

Entity Summarization Of Reviews And Micro-Reviews, Thanh Son Nguyen

Dissertations and Theses Collection (Open Access)

Along with the regular review content, there is a new type of user-generated content arising from the prevalence of mobile devices and social media, that is micro-review. Micro-reviews are bite-size reviews (usually under 200 char- acters), commonly posted on social media or check-in services, using a mobile device. They capture the immediate reaction of users, and they are rich in information, concise, and to the point. Both reviews and micro-reviews are useful for users to get to know the entity of interest, thus facilitating users in making their decision of purchasing or dining. However, the abundant number of both reviews …

Concomitant Crystallization In Propylene/Ethylene Random Copolymer With Strong Flow At Elevated Temperatures, Lirong Zheng, Lucia Fernandez-Ballester, Gerrit W. M. Peters, Zhe Ma

Department of Mechanical and Materials Engineering: Faculty Publications

Flow-induced crystallization of α- and γ-phases was studied for a propylene/ethylene random copolymer with 3.4 mol % ethylene at two high temperatures of 132 and 142 °C by combining a pressure-driven slit flow device with real-time synchrotron wide-angle X-ray diffraction. At 132 °C, it was found that both α- and γ-phases were generated at shear stresses ranging from 0.091 to 0.110 MPa and that the γ-phase always appeared later than the α-phase. However, for 142 °C and the same stresses, only the α-phase formed. Only upon cooling the partially crystallized copolymer did the γ-phase emerge. The lack of γ-crystals obtained …

Feasibility Study Of A Multi-Purpose Aircraft Concept With A Leading-Edge Cross-Flow Fan, Stanislav Karpuk

Doctoral Dissertations and Master's Theses

A wing-embedded Cross-Flow Fan (CFF) was first proposed as an active flow control (AFC) device nearly 40 years ago. The CFF can be employed as a propulsion device as well as a high-lift system. This thesis research focuses on investigating the use of CFF as a high-lift device for an Extremely Short Take-off and Landing (ESTOL) aircraft. The wing-embedded CFF performance analysis is mostly addressed from an aerodynamic perspective and focuses on using such AFC technology in the conceptual aircraft design process. In particular, the design trade study of an aircraft featuring CFF as a high-lift device applied to a …

2018 Spring Graduate Recognition Program, Propulsion Research Center, Robert Frederick

PRC Graduate Recognition

This program includes the graduate recognition program for spring 2018. Includes photographs, upcoming events, recent publications, and student profiles.

Self-Assembly Of (111)-Oriented Tensile-Strained Quantum Dots By Molecular Beam Epitaxy, Christopher F. Schuck, Robin A. Mccown, Ashlie Hush, Austin Mello, Simon Roy, Joseph W. Spinuzzi, Paul J. Simmonds

Materials Science and Engineering Faculty Publications and Presentations

The authors report on a comprehensive study of the growth of coherently strained GaAs quantum dots (QDs) on (111) surfaces via the Stranski–Krastanov (SK) self-assembly mechanism. Recent reports indicate that the long-standing challenges, whereby the SK growth mechanism could not be used to synthesize QDs on (111) surfaces, or QDs under tensile strain, have been overcome. However, a systematic study of the SK growth of (111)-oriented, tensile-strained QDs (TSQDs) as a function of molecular beam epitaxy growth parameters is still needed. Here, the authors explore the effects of deposition amount, substrate temperature, growth rate, and V/III flux ratio on the …

Routine Million-Particle Simulations Of Epoxy Curing With Dissipative Particle Dynamics, Stephen Thomas, Monet Alberts, Michael M. Henry, Carla E. Estridge, Eric Jankowski

Materials Science and Engineering Faculty Publications and Presentations

Mesoscale simulation techniques have helped to bridge the length scales and time scales needed to predict the microstructures of cured epoxies, but gaps in computational cost and experimental relevance have limited their impact. In this work, we develop an open-source plugin epoxpy for HOOMD-Blue that enables epoxy crosslinking simulations of millions of particles to be routinely performed on a single modern graphics card. We demonstrate the first implementation of custom temperature-time curing profiles with dissipative particle dynamics and show that reaction kinetics depend sensitively on the stochastic bonding rates. We provide guidelines for modeling first-order reaction dynamics in a classic …

Seasonality Of Tides In Southeast Asian Waters, Adam T. Devlin, Edward Zaron, David A. Jay, Stefan Talke

Civil and Environmental Engineering Faculty Publications and Presentations

An analysis of water level time series from 20 tide gauges in Southeast Asia finds that diurnal and semidiurnal astronomical tides exhibit strong seasonal variability of both amplitude and phase, which is not caused by known modulations of the astronomical tide-generating forces. Instead, it is found that the tidal properties are coherent with the western North Pacific monsoon index (WNPMI), indicating that monsoonal mechanisms are the likely cause. The study domain includes the Malacca Strait, Gulf of Thailand, the southern South China Sea, and Java Sea. The character of the geography and the tidal variability is different in each of …

Analyzing Requirements And Traceability Information To Improve Bug Localization, Michael Rath, David Lo, Patrick Mader

Research Collection School Of Computing and Information Systems

Locating bugs in industry-size software systems is time consuming and challenging. An automated approach for assisting the process of tracing from bug descriptions to relevant source code benefits developers. A large body of previous work aims to address this problem and demonstrates considerable achievements. Most existing approaches focus on the key challenge of improving techniques based on textual similarity to identify relevant files. However, there exists a lexical gap between the natural language used to formulate bug reports and the formal source code and its comments. To bridge this gap, state-of-the-art approaches contain a component for analyzing bug history information …

Assessment Of The Evolving Low-Cost Business Model For The Future Importance Of U.S. Secondary Airports, Nurettin Dinler

Theses and Dissertations

Airline deregulation caused a profound reshape in the aviation industry. The liberalization of the aviation sector resulted in a favorable environment for the emergence of low-cost carriers (LCCs). Following deregulation, airlines saw many attempts at their business strategies to gain more passengers in air transportation market. To capture additional market shares of passenger traffic, the business models of LCCs have evolved to mirror the more common business models employed by the traditional legacy airlines. The purpose of this study was to examine what effect, if any, exists between LCCs’ market share of passenger enplanements at secondary airports and their business …

Positive Experiences As Countermeasures To Stress In Spaceflight: An Investigation Of The Experiences Of Astronauts, Morgan M. Eudy

Theses and Dissertations

Long-duration space mission targets such as asteroids, the Moon and Mars in coming years will increase the need to stress management techniques to support crews on increasingly risky, autonomous missions. New stress management approaches may be found by better understanding the reported positive effects resulting from factors in these environments. This study utilized an exploratory case study approach to leverage quantitative and qualitative data to yield research questions for future correlational analysis. This study found that positive experiences and changes in environmental perspectives occurred from viewing Earth from orbit. Furthermore, this study found that personality factors such as extraversion may …

Modeling And Control Of A 6-Dof Multi-Rotorcraft: Air-Ball, Jerry Ja Wang

Theses and Dissertations

The Air-Ball project seeks to develop an omnidirectional, unmanned aerial vehicle with six degrees of freedom. The Air-Ball vehicle uses six propellers powered by six independent electric motors for propulsion and control. Each motor is attached to a hollow shaft that can rotate ±360° actuated by electric servos. Four of these propulsion shafts are configured in an orientation resembling a quad-copter, where the shafts are 90° apart. The other two propulsion shafts extrude perpendicular from each side of the plane of the quadcopter configuration. Under this unique configuration, Air-Ball is capable of decoupling the motion in the translational and rotational …

Using Dispersive Raman Spectroscopy To Assess Remodeling In Vascular Constructs Used In Tissue Engineering, Andrea S. Theus

Theses and Dissertations

Tissue engineered vascular grafts (TEVGs) are a promising alternative to surgery for the treatment of thrombotic occlusion of small diameter (< 6 mm) arteries. It is important that TEVG composition prevent compliance mismatch. Both initial protein incorporation and cellular remodeling are important for blended TEVG compliance. Understanding the distribution of extracellular matrix (ECM) components is also important and may dictate the remodeling response. Raman spectroscopy has been used to assess components of engineered scaffolds non-destructively. However, Raman has not been applied to semi-quantitatively assess 3D engineered-tissues and cellular remodeling of blended materials with low-scattering natural and high-scattering synthetic components. This is important due to the increased use of synthetic biomaterials for TEVG applications. The overall goal of this study was to develop a technique to assess the cellular and matrix remodeling response. Electrospun meshes were prepared with 100% poly(ε-caprolactone) (PCL), 90% PCL/collagen, and 90% PCL/fibrinogen. XPS and Raman results showed differences of protein distribution when incorporated into a PCL scaffold and differences in the resulting effects with cell culturing and incubation. Raman spectra was acquired for all pure materials individually (e.g. PCL, collagen, and fibrinogen) to determine the unique spectral fingerprint of each material. Protein peaks of interest were identified (e.g. 740 and 1040 cm-¹ ) and were analyzed when protein was incorporated into the electrospun meshes. Raman spectra was acquired for the pure PCL control and blended scaffold conditions. The protein peaks remained relevant for proteins even when incorporated into the high scattering PCL polymer and showed remodeling due to incubation and cell culturing over 21 days. Spectra were also analyzed with multi-factor processing techniques (e.g. MFA) and showed that separation between appropriate sample groups can be achieved even with large amounts of spectral data sets. Biochemical analysis (e.g. Hyp, µ-BCA assay) was done to determine if specific remodeling responses, degradation and/or release occur with incubation and culturing of smooth muscle cells. These results showed a negligible loss of protein within electrospun meshes with incubation and culture. Overall, we have shown that Raman spectroscopy can be used to semi-quantitatively detect the incorporation of low levels of specific proteins (e.g. collagen and fibrinogen) within electrospun meshes as well as changes that occur with mesh remodeling.

Automatic Speech Recognition Adaptation For Various Noise Levels, Azhar Sabah Abdulaziz

Theses and Dissertations

The automatic speech recognition (ASR) is a set of complicated algorithms that convert the intended spoken utterance into a textual form. Acoustic features, which are extracted from the speech signal, are matched against a trained network of linguistic and acoustic models. The ASR performance is degraded significantly when the ambient noise is different than that of the training data. Many approaches have been introduced to address this problem with various degrees of complexity and improvement rates. The general pattern of solving this issue lies in three categories: empowering features, train a general acoustic model and transform models to match noisy …

Speech Emotion Recognition Using Connectionist Models In A Tandem System, Mary Najafi

Theses and Dissertations

This article presents a tandem Speech Emotion Recognition (SER) system by which 8 archetypal emotions can be differentiated based upon two different types of acoustic features as inputs to Artificial Neural Network (ANN) models. The two types of features that are fed into the classifiers reveal the degree of excitement and pleasentness of speech. The author has implied the time-based characteristics of speech in the feature extraction method by monitoring the trend of local features through time. Thus, two global features are proposed that are derived from Teager Energy Operator (TEO)-based (T EOg) and spectral features, Mel-Frequency Cepstral Coeffcients (MF …

Infrared Resonant-Coupled Metamaterial Sensing And Phonon-Polariton-Enhanced Infrared Interconnects, Michael Francis Finch

Theses and Dissertations

Coupled-mode theory has been applied to various fields of endeavor from waveguide splitters/combiners and molecular sensing to light-matter interactions. Metamaterials, engineered periodic or aperiodic structures, are employed to sense molecular vibrational fingerprints in the mid to long infrared wavelengths. A metasurface, a 2D metamaterial, can be designed such that it has a resonance at a molecular vibrational frequency. Mode splitting results from the coupling of two electromagnetic field distributions, or modes, spatially and/or temporally. Metamaterial and molecular resonance coupling is a result of near field interaction. Fano resonances have an asymmetric line-shape that results from the coupling of a continuum …

Effect Of Cavitation Regimes On Stepped Diesel Injectors, David Michael Sykes

Theses and Dissertations

The objective of this work was to determine the effects of different cavitating flow regimes on a stepped orifice geometry relevant to diesel injectors. Conventional diesel orifice geometries consist of a single tapered or straight circular passage. The geometry used in this work had two circular passages in series: a first orifice that was similar to conventional geometries and a second larger orifice immediately downstream that induced cavitation. The large orifice served to stabilize the flow, allowing for different flow regimes to exist at the exit plane of the large orifice (single-phase, intermittent bubbly, bubbly, annular, etc.). A series of …

Cfd Analysis Of Resistance For Stepless And Stepped Planing Hulls, Bhanu Prakash Valtheru

Theses and Dissertations

It is the endeavour of naval architects to design hull forms with the least amount of power consumption. In this respect, Naval Architects have been obsessed with the design of various hull forms optimized for a particular service requiring the lowest amount of fuel consumption keeping in mind effects on the climate change and sustainability. Regardless of the way that a considerable measure of research has been done around this area, there remains a level of uncertainty in the reasonably accurate resistance prediction of stepped hull forms in the early design stage. Model tests and full-scale tests are still the …

Development And Validation Of A Numerical Model Of The Co2 Dry-Ice Blasting Process For Aircraft Engine Cleaning Applications, Arthur Rudek

Doctoral

On-wing cleaning of engine compressors for commercial aircraft is a required maintenance task which results in greater operating efficiency and lower emission rates. It is typically carried out by injection of water and detergents into the intake of an engine while the engine is being cranked by the starter. Two drawbacks of this process are the risk of icing in cold weather and the collection and treatment of the water effluent. The dry-ice blasting process, a cleaning system which uses pressurized air and CO2 dry-ice particles as cleaning agent, has been proposed as an alternative method which does not suffer …

An Advanced Context Aware Operator Support System (Caoss) For Chemical Plant Operation, Sujin Babu Alfred Retna Dhason

Theses and Dissertations

Analyzing potential causes for recent industrial accidents and production losses highlights that the majority of these incidents are due to human factor failure: operator error, poor decision-making and violations (Dźwiarek, 2004). In the meantime, the process equipment design, fabrication, metallurgy and control system has improved significantly to combat these unpredictable failures. This research focus on the errors due to human-machine interaction (HMI) in chemical plant. This paper presents an advanced support system for operators in chemical plants, to perform safe and reliable plant operation and maintenance (O&M). In chemical industry, almost every tasks involving human interaction with the machines are …

Helping College Students To Manage Stress: A Human Centered Smartphone Application For Stress Relief, Saad R. Almesalm

Theses and Dissertations

This dissertation represents a Human Centered Design research to evaluate the perception and handling of stress. To successfully evaluate this research, an iOS smartphone application was developed. This research includes five HCD stages: identify needs, research/analysis, design, evaluation and delivery. The importance of this topic was revealed when we realized that stress can affect students internally and externally. We started with understanding the topic and gathering information about stressed students specifically in college. We created an ontology representing the causes of stress based on previous studies. The ontology includes three main factors: Academic, Social, and Personal/Family stress. In addition, the …