Piezoelectrics offer high actuation authority and sensing over a wide range of frequencies. A Macro-Fiber Composite is a type of piezoelectric device that offers structural flexibility and high actuation authority. A challenge with piezoelectric actuators is that they require high voltage input; however the low power consumption allows for relatively lightweight electronic components. Another challenge, for piezoelectric actuated aerodynamic surfaces, is found in operating a relatively compliant, thin structure (desirable for piezoceramic actuators) in situations where there are relatively high external (aerodynamic) forces. Establishing an aeroelastic configuration that is stiff enough to prevent flutter and divergence, but compliant enough to allow the range of available motion is the central challenge in developing a piezocomposite airfoil. The research proposed here is to analyze and implement novel electronic circuits and structural concepts that address these two challenges. Here, a detailed theoretical and experimental analysis of the aerodynamic and electromechanical systems that are necessary for a practical implementation of a piezocomposite airfoil is presented. First, the electromechanical response of Macro-Fiber Composite based unimorph and bimorph structures is analyzed. A distributed parameter electromechanical model is presented for interdigitated piezocomposite unimorph actuators. Necessary structural features that result in large electrically induced deformations are identified theoretically and verified experimentally. A novel, lightweight electrical circuitry is proposed and implemented to enable the peak-to-peak actuation of Macro-Fiber Composite bimorph devices with asymmetric voltage range. Next, two novel concepts of supporting the piezoelectric material are proposed to form two types of variable-camber aerodynamic surfaces. The first concept, a simply-supported thin bimorph airfoil, can take advantage of aerodynamic loads to reduce control input moments and increase control effectiveness. The structural boundary conditions of the design are optimized by solving a coupled fluid-structure interaction problem by using a structural finite element method and a panel method based on the potential flow theory for fluids. The second concept is a variable-camber thick airfoil with two cascading bimorphs and a compliant box mechanism. Using the structural and aerodynamic theoretical analysis, both variable-camber airfoil concepts are fabricated and successfully implemented on an experimental ducted-fan vehicle. A custom, fully automated low-speed wind tunnel and a load balance is designed and fabricated for experimental validation. The airfoils are evaluated in the wind tunnel for their two-dimensional lift and drag coefficients at low Reynolds number flow. The effects of piezoelectric hysteresis are identified. In addition to the shape control application, low Reynolds number flow control is examined using the cascading bimorph variable-camber airfoil. Unimorph type actuators are proposed for flow control in two unique concepts. Several electromechanical excitation modes are identified that result in the delay of laminar separation bubble and improvement of lift. Periodic excitation to the flow near the leading edge of the airfoil is used as the flow control method. The effects of amplitude, frequency and spanwise distribution of excitation are determined experimentally using the wind tunnel setup. Finally, the effects of piezoelectric hysteresis nonlinearity are identified for Macro-Fiber Composite bimorphs. The hysteresis is modeled for open-loop response using a phenomenological classical Preisach model. The classical Preisach model is capable of predicting the hysteresis observed in 1) two cantilevered bimorph beams, 2) the simply-supported thin airfoil, and 3) the cascading bimorph thick airfoil. / Ph. D.

It is important to understand the damage events in composite materials at the micro level, model elastic properties, and understand phenomenological aspects of strength. Development of an accurate representation of these phenomena at the local level is difficult but pioneering work was done by researchers at Virginia Tech. This thesis builds on the previous efforts at Virginia Tech where the experimental and analytical models were improved to include high fiber volume fractions. Experimental techniques were developed to achieve a controlled fiber fracture at a predetermined location and then measure the over-strain experienced by the neighboring rods. A finite element model was used to validate the micromechanical analysis. Quantitative measurements of perturbed strain fields were measured with embedded strain gages which were then compared with the finite element results. / Master of Science

MEMS devices are finding application in diverse fields that include energy harvesting, microelectronics and sensors. In energy harvesting, MEMS scale devices are employed due to its efficiencies of scale. The miniaturization of energy harvesters permit them to be integrated as the power supply for sensors often in the same package and also extends their use to remote and extreme ambient applications. Unlike inductive harvesting, piezoelectric and magnetoelectric devices lend easily to MEMS scaling. The processing of such Piezo-MEMS devices often requires special fabrication, characterization and testing techniques. Our research work has focused on the development of the various technologies for a) the better characterization of the constituent materials that make up these devices, b) the conceptualization and structural design of unique MEMS energy harvesters and finally c) the development of the unit operations (many novel) for fabrication and the mechanical and electrical testing of these devices. In this research work, we have pioneered some new approaches to the characterization of thin films utilized in Piezo-MEMS devices: (1) Temperature-Time Transformation (TTT) diagrams are used to document texture evolution during thermal treatment of ceramics. Multinomial and multivariate regression techniques were utilized to create the predictor models for TTT data of Pb(Zr0.60Ti0.40 O3) sol-gel thin films. (2) We correlated the composition (measured using Energy Dispersive X-ray analysis (EDX) and Electron Probe Micro Analysis (EPMA)) of Pb(Zr0.52Ti0.48 O3) RF sputtered thin films to its optical dispersion properties measured using Variable Angle Spectroscopic Ellipsometry (VASE). Wemple-DiDomenico, Jackson-Amer, Tauc and Urbach optical dispersion factors and Lorentz Lorenz polarizability relationships were combined to realize a model for predicting the elemental content of any thin film system. (3) We developed in house capability for strain analysis of magnetostrictive thin films using laser Doppler Vibrometry (LDV). We determined a methodology to convert the displacements measurements of AC magnetic field induced vibrations of thin film samples into magnetostriction values. (4) Finally, we report the novel use of a thermo-optic technique, Time Domain Thermoreflectance (TDTR) in the study of Pb(Zr,Ti)O3 (PZT) thin film texturing. Time Domain Thermoreflectance (TDTR) has been proved to be capable of measuring thermal properties of atomic layers and interfaces. Therefore, we utilized TDTR to analyze and model the heat transport at the nano scale and correlate with different PZT crystalline orientations. To harvest energy at the low frequency (<100Hz) of ambient vibrations, MEMS energy harvesters require special structures. Extensive research has led us to the development of Circular Zigzag structure that permits inertial mass free attainment of such low frequencies. In addition to Si micromachining, we have fabricated such structures using a new Micro water jet micromachining of thin piezo sheets, unimorphs and bimorphs. For low frequency magnetic energy harvesting, we also fabricated the first magnetoelectric macro fiber composite. This device also employs a novel low temperature metallic bonding technique to fuse the magnetostrictive layer to the piezoelectric layers. A special low viscosity epoxy enabled the joining of the flexible circuit to the magnetoelectric fibers. Lastly, we developed a nondimensional tunable Piezo harvester, called PiezoCap, which decouples the energy harvesting component of the device from the resonant vibration component. We do so by using magnets loaded on piezo harvester strips, thereby making them piezomagnetoelastic and vary the spacing between 2 magnet+piezoelectric pairs to eliminate dimensionality and permit active tunability of the harvester's resonant frequency. / Ph. D.

The purpose of this research is to characterize the response of an airfoil with an oscillatory morphing, Macro-fiber composite (MFC) trailing edge. Correlation of the airfoil lift with the oscillatory input is presented. Modal analysis of the test airfoil and apparatus is used to determine the frequency response function. The effects of static MFC inputs on the FRF are presented and compared to the unactuated airfoil. The transfer function is then used to determine the lift component due to cambering and extract the inertial components from oscillating airfoil. Finally, empirical wind tunnel data is modeled and used to simulate the deflection of airfoil surfaces during dynamic testing conditions. This research serves to combine modal analysis, empirical modeling, and aerodynamic testing of MFC driven, oscillating lift to formulate a model of a dynamic, loaded morphing airfoil. / Master of Science

On February 17, 2008 Kosovo declared its independence from Serbia and the event spurred significant media attention. Countries like Spain, Romania, and Russia feared that the event would engender separatism on their own territories, while the U.S., Germany, France, Italy, and UK regarded it as a democratic step. This thesis uses the framing theory to content analyze newspaper articles in seven languages (N=191) that appeared between November 17, 2007 and May 17, 2008, three months before and three months after Kosovo became an independent state. The thesis uses the five generic frames (responsibility, human interest, consequences, morality, and conflict) developed by Semetko and Valkenburg (2000) as well as the three 'macro-frames' (cynicism, speculation, and metacommunication) established by Constantinescu and Tedesco (2007). Results revealed that media from the countries that supported the Kosovo independence framed the event from the perspective of democracy and were almost twice more likely to discuss the position of the U.S., a key decision- maker in the Kosovo issue, than media from the countries that opposed it. Furthermore, newspaper articles from countries that did not support the event were nearly three times more inclined to present the Kosovo independence from the perspective of a precedent for separatism in Europe and the world. By applying the framing theory in an international study, this thesis sheds light on the discrepancies in media coverage from these different democratic systems. / Master of Arts

The popular cable show South Park has steadily entertained audiences since its debut in 1997. Much of the show's humor and entertainment value comes from its satirical treatment of public figures, institutions, and timely trends. One of the institutions often lampooned on the show is that of television news broadcasting. This thesis project seeks to shed light on entertainment media portrayals of television news journalists and television news journalism as a whole by examining the issues covered, how those issues are framed, and how the journalist is used as a figure on the border of entertainment and information in one show. A content analysis was performed on all news broadcasts contained within all 181 episodes of South Park through its twelfth season. Results indicate that Semetko and Valkenburg's (2000) five generic frames penetrate well into the entertainment realm; a broadcast's "relationship to reality" is framed significantly differently when Conflict and Speculation frames are employed; news broadcasters are not portrayed as exemplars of the media's "liberal bias;" and that South Park has used significantly more reality-based storylines in recent years than in its early years. / Master of Arts

The application of smart materials to control the flight dynamics of a Micro Air Vehicle (MAV) has numerous benefits over traditional servomechanisms. Under study is wing morphing achieved through the use of piezoelectric Macro Fiber Composites (MFCs). These devices exhibit low power draw but excellent bandwidth characteristics. This thesis provides a background in the 2D analytical and computer modeling tools and methods needed to design and characterize an MFC-actuated airfoil. A composite airfoil is designed with embedded MFCs in a bimorph configuration. The deflection capabilities under actuation are predicted with the commercial finite element package NX Nastran. Placement of the piezoelectric actuator is studied for optimal effectiveness. A thermal analogy is used to represent piezoelectric strain. Lift and drag coefficients in low Reynolds number flow are explored with XFOIL. Predictions are made on static aeroelastic effects. The thin, cambered Generic Micro Aerial Vehicle (GenMAV) airfoil is fabricated with a bimorph actuator. Experimental data are taken with and without aerodynamic loading to validate the computer model. This is accomplished with in-house 2D wind tunnel testing. / Master of Science

The research presented in this thesis uses the macro-fiber composite (MFC) actuator that was recently developed at the NASA Langley Research Center for two major themes, sensing and actuation for vibration control, and power harvesting. The MFC is constructed using piezofibers embedded in an epoxy matrix and coated with Kapton skin. The construction process of the MFC affords it vast advantages over the traditionally used piezoceramic material. The MFC is extremely flexible, allowing it to be bonded to structures that have curved surface without fear of accidental breakage or additional surface treatment as is the case with monolithic piezoceramic materials. Additionally the MFC uses interdigitated electrodes that capitalize on the higher d33 piezoelectric coupling coefficient that allow it to produce higher forces and strain than typical monolithic piezoceramic materials. The research presented in this thesis investigates some potential applications for the MFC as well as topics in power harvesting. This first study performed was to determine if the MFC is capable of being used as a sensor for structural vibration. The MFC was incorporated into a self-sensing circuit and used to provide collocated control of an aluminum beam. It was found that the MFC makes a very accurate sensor and was able to provide the beam with over 80% vibration suppression at its second resonant frequency. Following this work, the MFC was used as both a sensor and actuator to apply multiple-input-multiple-output vibration control of an inflated satellite component. The control system used a positive position feedback (PPF) controller and two pairs of sensors and actuators in order to provide global vibration suppression of an inflated torus. The experiments found that the MFC and control system was very effective at attenuating the vibration of the first mode but ineffective at higher modes. It was found the positioning of the sensors and actuators on the structure contributed heavily to the controller's performance at higher modes. A discussion of the reasons for the controller's ineffectiveness is supply and a solution using self-sensing techniques for collocated vibration suppression was investigated. Subsequent to the research in vibration sensing and control, the ability to use piezoelectric materials to convert ambient vibration into usable electrical energy was tested and quantified. First, a model of a power harvesting beam is developed using variational methods and is validated on a composite structure containing four separate piezoelectric wafers. It is shown that the model can accurately predict the power generated from the vibration of a cantilever beam regardless of the load resistance or excitation frequency. The damping effects of power harvesting on a structure are also demonstrated and discussed using the model. Next, the ability of the piezoelectric material to recharge a battery and a quantification of the power generated are investigated. After determining that the rechargeable battery is compatible with the power generated through the piezoelectric effect, the MFC was compared with the traditional monolithic PZT for use as a power harvesting material. It was found that the MFC produces a very low current, making it less efficient than the PZT material and unable to charge batteries because of their need for relatively large current. Due to the MFC being incapable of charging batteries, only the PZT was used to charge batteries and the charge times for several nickel metal hydride batteries ranging from 40 to 1000mAh are supplied. / Master of Science

Yes / Blockchain has enormous capabilities to transform traditional business models in countless ways. Banks in India are building collaborative blockchain ecosystems to create an innovative business model and disrupt the traditional one to create more competitive advantage. This study’s purpose was to examine the relationship between blockchain capabilities (BCC), competitive advantage (CA), and organizational performance (OP), as well as evaluate CA’s mediating role in the relationship between BCC and OP. In this context, a scientific research model, including a hypothesis, has been developed from extant literature. The proposed model was tested using statistical data collected from blockchain specialists, blockchain product marketing managers, experts in future and emergent technology, and banking, finance, and tech managers or executives who are involved in planning and deploying practical blockchain in the financial sector. Data were analyzed and tested using AMOS 22.0 and a process macro using a sample comprising 289 responses. Our empirical results indicated a significant positive relationship between BCC, CA, and OP, as well as a relationship between BCC and OP, partially mediated by CA. This paper took an original approach and contributes to the literature on this subject to understand CA’s mediating role in the relationship between BCC and OP in the Indian banking sector.

No / Core-shell particles have been prepared by surfactant-free emulsion polymerisations of butyl methacrylate in the presence of either linear or highly branched poly(acrylamidomethylpropane sulphonate)s (L-PAMPS or HB-PAMPS) with dithioate end groups: using a "shell-first" approach. In this method the water soluble PAMPS shells were anchored to the cores by polymerisation of BMA from the chain ends. The linear PAMPS produced non-crosslinked poly(AMPS-BMA) particles but the multiple chain ends of the highly branched PAMPS led to crosslinked particles. The particles were loaded with vascular endothelial growth factor or platelet derived growth factor, both of which are cytokines that are known to be important in the production of new blood vessels. The release of the growth factors was shown to be controlled by the architecture of the shell and we propose a mechanism that involves both ionic interaction of the PAMPS with the heparin-binding domains of the growth factors and size exclusion mediated diffusion.