Approved for public release; distribution is unlimited / HY-130 is a high-strength, low-carbon steel used in the quenched and tempered condition . It is designed for high performance and marine applications where good weldability is a requirement. Optimum welding parameters are currently under investigation. In this study, 1/2 inch (12.7 mm) HY-130 steel weldments produced by submerged arc welding (SAW) and gas metal arc welding (GMAW) processes are compared by means of a systematic microstructural characterization of the base metal, weld metal, and heat affected zone (HAZ). The microstructures are characterized by optical and electron micro­scopy and microhardness measurements are performed in the weld metal and across the HAZ to relate the microstructure with the microhardness profiles. The weld metal microstructure of both weldments showed a predominantly martensitic structure. The GMAW weld metal had a finer lath martensite structure and contained more retained austenite and twinned martensite. The SAW weld metal had a less defined lath structure which was more bainitic. The microhardness values were higher in the GMAW weld metal. No significant differences in microstructure and hardness were observed in the HAZ of the two weldments. / http://archive.org/details/effectofweldingp00mcnu / Captain, Canadian Forces

Current proposals for the design of quantum computer architectures include combining different quantum systems with designated tasks to build a device that can efficiently store, process, and transfer quantum information. Electron spins in solid-state quantum systems are a viable platform for storing information in these multi-quantum frameworks. While extensive research has been performed to couple solid-state systems to photons and microwaves, an alternative line of research focuses on coupling these systems to phonons, or mechanical motion. The use of phonons in solid-state devices opens up a new approach to interface different quantum systems. This dissertation presents experimental progress in developing and controlling a spin-mechanical system, specifically the interaction between the electron spin of a nitrogen vacancy (NV) center in diamond and mechanical vibrations on the surface of the diamond, and discusses theoretical methods for limiting decoherence in the system. To investigate the strain properties of the NV center, we couple acoustic waves to the NV spin via an optical excitation. We transfer population between the spin ground states by driving phonon-assisted optical transitions and demonstrate the formation of a non-radiative state, which can be used to adiabatically transfer population between two states, through the same mechanism. To mitigate the effects of the nuclear spin bath on the NV center, we study and show preliminary results on the semiclassical dressed states, or quantum states of the NV interacting with optical fields. The dressed states can be insensitive to magnetic fluctuations, thus preserving the quantum state of the system. Finally, we consider a transitionless quantum driving technique that decouples the NV center from a radiative state, preventing decoherence through spontaneous emission. These developments are essential in advancing our understanding of phonon-based interfaces between quantum systems. This dissertation includes previously published and unpublished co-authored material.

The acoustoelectric effect in graphene and graphene nanoribbons (GNRs) on lithium niobate surface acoustic wave (SAW) devices was studied experimentally. Monolayer graphene produced by chemical vapour deposition was transferred to the SAW devices. The photoresponse of the acoustoelectric current (Iae) was characterised as a function of SAW frequency and intensity, and illumination wavelength (using 450 nm and 735 nm LEDs) and intensity. Under illumination, the measured Iae increased by more than the measured decrease in conductivity, while retaining a linear dependence on SAW intensity. The latter is consistent with the piezoelectric interaction between the graphene charge carriers and the SAWs being described by a relatively simple classical relaxation model. A larger increase in Iae under an illumination wavelength of 450 nm, compared to 735 nm at the same intensity, is consistent with the generation of a hot carrier distribution. The same classical relaxation model was found to describe Iae generated in arrays of 500 nm-wide GNRs. The measured acoustoelectric current decreases as the nanoribbon width increases, as studied for GNRs with widths in the range 200 – 600 nm. This reflects an increase in charge carrier mobility due to increased doping, arising from damage induced at the nanoribbon edges during fabrication. 2 Lastly, the acoustoelectric photoresponse was studied as a function of graphene nanoribbon width (350 – 600 nm) under an illumination wavelength of 450 nm. Under illumination, the nanoribbon conductivity decreased, with the largest percentage decrease seen in the widest GNRs. Iae also decreased under illumination, in contrast to the acoustoelectric photoresponse of continuous graphene. A possible explanation is that hot carrier effects under illumination lead to a greater decrease in charge carrier mobility than the increase in acoustoelectric attenuation coefficient. This causes the measured decrease in Iae.

Little is known about the distribution, abundance, or life histories of the Northern Saw-whet Owl (Aegolius acadicus) in the Southern Appalachian Mountains of Northeast Tennessee. This study relied upon the Pennsylvania Protocol of audio playback of a Northern Saw-whet Owl call to monitor for owl presence at various areas above 3,500 feet in elevation. Owls were found at multiple areas in Northeast Tennessee, including Roan Mountain, Unaka Mountain, Rocky Fork, and the Pond Mountain Area. Statistical analysis revealed that these owls were not limited by habitat, showing equal presence in Hardwood habitats along with Spruce and/or Fir habitats. Data also revealed that the owls showed a statistical preference for higher elevations at the surveyed sites. The habitat and elevation preferences, coupled with the locations where owls were detected, allow for a greater understanding of the life histories and population distribution of the Northern Saw-whet Owl in the Southern Appalachian Mountains.

In this thesis, the author proposes and develops novel multilayered Surface Acoustic Wave (SAW) devices with unique attributes for gas sensing applications. The design, simulation, fabrication and gas sensing performance of three multilayered SAW structures has been undertaken. The investigated structures are based on two substrates having high electromechanical coupling coefficient: lithium niobate (LiNbO3) and lithium tantalate (LiTaO3), with a piezoelectric zinc oxide (ZnO) intermediate layer. Sensitivity towards target gas analytes is provided by thin film indium oxide (InOx) or tungsten trioxide (WO3). The high performance of the gas sensors is achieved by adjusting the intermediate ZnO layer thickness. Sensitivity calculations, undertaken with perturbation theory illustrate how the intermediate ZnO layer can be employed to modify the velocity-permittivity product of the supported SAW modes, resulting in highly sensitive conductometric SAW gas sensors. The work contained within this thesis addresses a broad spectrum of issues relating to multilayered SAW gas sensors. Topics include finite-element modelling, perturbation theory, micro-fabrication, metal oxide deposition, material characterisation and experiential evaluation of the layered SAW sensors towards nitrogen dioxide (NO2), hydrogen (H2) and ethanol gas phase analytes. The development of two-dimensional (2D) and three dimensional (3D) finite-element models provides a deep insight and understanding of acoustic wave propagation in layered anisotropic media, whilst also illustrating that the entire surface of the device can and should be used as the active sensing area. Additionally, the unique and distinctive surface morphology of the layered structures are examined by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The crystalline structure and orientation of the ZnO and WO3 layers are also examined by X-ray Diffraction Spectroscopy (XRD). The novel multilayered SAW structures a re shown to be highly sensitive, capable of sensing NO2 and ethanol concentration levels in the parts-per-billion and parts-per-million range, respectively, and H2 concentrations below 1.00% in air. The addition of platinum or gold catalyst activator layers on the WO3 sensitive layer is shown to improve sensitivity and dynamic performance, with response magnitudes up to 50 times larger than bare WO3. The gas sensing performance of the investigated structures provide strong evidence that high sensitivity can be achieved utilising multilayered SAW structures for conductometric gas sensing applications.

For centuries scientific ingenuity and innovation have been influenced by Mother Natures perfect design. One of her more elusive designs is that of the sensory olfactory system, an array of highly sensitive receptors responsible for chemical vapor recognition. In the animal kingdom this ability is magnified among canines where ppt (parts per trillion) sensitivity values have been reported. Today, detection dogs are considered an essential part of the US drug and explosives detection schemes. However, growing concerns about their susceptibility to extraneous odors have inspired the development of highly sensitive analytical detection tools or biosensors known as electronic noses. In general, biosensors are distinguished from chemical sensors in that they use an entity of biological origin (e.g. antibody, cell, enzyme) immobilized onto a surface as the chemically-sensitive film on the device. The colloquial view is that the term biosensors refers to devices which detect the presence of entities of biological origin, such as proteins or single-stranded DNA and that this detection must take place in a liquid. Our biosensor utilizes biomolecules, specifically IgG monoclonal antibodies, to achieve molecular recognition of relatively small molecules in the vapor phase.

The object of this thesis research is to facilitate the appraisal and analysis of the signatures of the modern acoustic wave biosensors, as well as to improve the experimental methodology to enhance sensor performance. For this purpose, both theoretical characterization of acoustic wave sensor signatures and experimental studies for the most frequently used acoustic wave biosensors, the liquid phase QCM (quartz crystal microbalance) and the vapor phase SAW (surface acoustic wave) sensors, are presented. For the study of SAW vapor phase detection, the author fabricated different types of two-port SAW resonator sensors on quartz substrates and designed and performed a significant number of detection experiments. These were conducted both with calibrated or known target samples under laboratory conditions at Georgia Tech Hunt Lab and with samples of unknown concentrations such as seized crack cocaine (courtesy of Georgia Bureau of Investigation, GBI) to see the sensors capability to work in the field conditions. In addition, the dependence of the SAW sensor signatures on specific locations of the surface perturbation was investigated to account for some observed abnormal responses. Finally, a novel approach to classify and visualize chemically analogous substances is introduced. The author expects that the thesis work herein may contribute to the study of the modern acoustic wave biosensors which includes but is not limited to: the establishment of underpinning theory that will aid in the evaluation of the signatures; the practical aspects of design and fabrication of SAW devices specific to the vapor phase immunoassay; the development of efficient experimental methodologies; the strategic immobilization of a biolayer on SAW resonator based biosensors; and, the acquisition of reference data for the development of commercial acoustic wave sensors.

In this study, Sezawa-mode surface acoustic wave (SAW) devices were employed to construct the allergy biosensor. To fabricate Sezawa-mode SAW devices, the RF magnetron sputtering method for the growth of piezoelectric ZnO thin films onto Si3N4/Si is adopted and influences of the sputtering parameters are investigated. The properties of the ZnO thin films are investigated by X-ray diffraction and scanning electron microscopy which reveal a high c-axis-preferred orientation. A back-etched resonator is used in this study. The wet etching of (100)-oriented silicon wafers is used to form a back-side cavity which is used as the sensing area. Low-stress silicon nitride was deposited by low-pressure chemical vapor deposition (LPCVD) as the etching mask for the integrated SAW device. To investigate the sensing characteristics of SAW, gold (Au) layer was initially deposited onto the sensing area of SAW devices as the binding layer in biochemical sensor and the surface of the Au layer was treated with oxygen plasma to enhance the hydrophilic properties of the Au layer. The self assembly monolayers (SAMs) is used to decorate surface of Au layer and the sandwiched enzyme-linked immunosorbent assay is used for detecting the concentration variation of immunoglobulin E (IgE) in human serum. The frequency response is measured using an E5071C network analyzer. The resonance frequency of the Sezawa-mode SAW device is 1.49 GHz. The sensitivities of the Sezawa-mode biosensor is calculated to be 6.64 MHz cm2/ng for human IgE detection.

No description available.

Aluminum nitride (AlN) thin films were deposited on Z-cut LiNbO3 substrates using the reactive RF magnetron sputtering in this thesis. By means of the analyses of XRD, SEM and AFM, the optimal deposition conditions of highly C-axis oriented AlN films were sputtering pressure of 3.5 mTorr, nitrogen concentration (N2/N2+Ar) of 60%, RF power of 165W and substrate temperature of 400¢J. The piezoelectric bi-layers structure of SAW devices was then fabricated. The interdigital transducers (IDTs) were fabricated on bi-layers structure. The AlN thin film thickness of piezoelectric bi-layers structure was varied in order to discuss its effects on SAW devices. From the experimental results, it reveals that the center frequency of SAW filters increases with the increased AlN thin films thickness. It means that the SAW velocity increases as the AlN thin films thickness increases. The effects of bi-layers structure on SAW devices can be discussed in detail by measuring the parameters of SAW devices like insertion loss (IL), electromechanical coupling coefficient (K2) and the temperature coefficient of delay (TCD).