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Articles 1 - 17 of 17
Full-Text Articles in Acoustics, Dynamics, and Controls
Bayesian Model Updating Of Structural Parameters Using Temperature Variation Data., Ujjwal Adhikari
Bayesian Model Updating Of Structural Parameters Using Temperature Variation Data., Ujjwal Adhikari
Electronic Theses and Dissertations
Physical digital twins have now emerged as a technology in structural health monitoring and other domains of structural modeling. A Finite Element Model can be a tool for digital twin technology in conjunction with measured physical data. Developing an accurate digital model requires the integration of various parameters to replicate the real structure; however, temperature is dynamically changing, resulting in difficulty in the identification of structural parameters. Typically, temperature is considered noise or filtered out. Limited research has addressed the physics-based model using temperature variation related to structural modal properties. Finite Element Model Updating (FEMU) is a typical inverse problem-solving …
Novel Designs Of Soft Tactile Sensor And Robot Finger Manipulator Based On Optical Fibers., Seokyoung Han
Novel Designs Of Soft Tactile Sensor And Robot Finger Manipulator Based On Optical Fibers., Seokyoung Han
Electronic Theses and Dissertations
Robotic manipulation is one of the main types of automated labor that humans want to achieve in order to free ourselves from mundane and hazardous tasks. The range of realizations could be very broad, from massive industrial robots to highly advanced medical devices for human healthcare. Given the critical nature of these application spaces, they require robust, safe, and most of all versatile designs. In that direction, one of the most interesting topics is the anthropomorphic robotic manipulator. Since it is inspired by human hands’ function and structure, it is able to achieve the aforementioned system requirements. However, the perfect …
Modeling, Simulation And Control Of Microrobots For The Microfactory., Zhong Yang
Modeling, Simulation And Control Of Microrobots For The Microfactory., Zhong Yang
Electronic Theses and Dissertations
Future assembly technologies will involve higher levels of automation in order to satisfy increased microscale or nanoscale precision requirements. Traditionally, assembly using a top-down robotic approach has been well-studied and applied to the microelectronics and MEMS industries, but less so in nanotechnology. With the boom of nanotechnology since the 1990s, newly designed products with new materials, coatings, and nanoparticles are gradually entering everyone’s lives, while the industry has grown into a billion-dollar volume worldwide. Traditionally, nanotechnology products are assembled using bottom-up methods, such as self-assembly, rather than top-down robotic assembly. This is due to considerations of volume handling of large …
Assessing The Effectiveness Of Cfd To Solve An Inverse Problem Of Thermal Profiles For The Protodune-Sp Neutrino Detector, Cecilia Anne Streff
Assessing The Effectiveness Of Cfd To Solve An Inverse Problem Of Thermal Profiles For The Protodune-Sp Neutrino Detector, Cecilia Anne Streff
Electronic Theses and Dissertations
Computational fluid dynamics (CFD) is a branch of fluid mechanics which is employed to numerically solve complex fluid, heat transfer, and multiphysics problems. Traditionally, CFD techniques are used to solve “forward” problems—using some known information of a system as inputs to a representative model to predict experimental measurements or expected system behavior. The work presented here demonstrates how CFD may be used to solve an “inverse” problem—given limited experimental data and some model, predict (previously unidentified) “input” system (or system model) parameters. The case study for this research uses a validated CFD modeling approach of the liquid argon (LAr) region …
Dynamic Analysis And Fabrication Of A Bi-Stable Structure Designed For Mems Energy Harvesting Applications., Masoud Derakhshani
Dynamic Analysis And Fabrication Of A Bi-Stable Structure Designed For Mems Energy Harvesting Applications., Masoud Derakhshani
Electronic Theses and Dissertations
Thanks to the rapid growth in demand for power in remote locations, scientists’ attention has been drawn to vibration energy harvesting as an alternative to batteries. Over the past ten years, the energy harvesting community has focused on bistable structures as a means of broadening the working frequency range and, by extension, the effective efficiency of vibration-based power scavenging systems. In the current study, a new method is implemented to statically and dynamically analyze a bistable buckled, multi-component coupled structure designed specifically for low-frequency vibration energy harvesting systems in both macro and MEMS-scale sizes. Furthermore, several micro-fabrication steps using advanced …
Ultrasonic Nondestructive Evaluation Of Metal Additive Manufacturing., Venkata Karthik Nadimpalli
Ultrasonic Nondestructive Evaluation Of Metal Additive Manufacturing., Venkata Karthik Nadimpalli
Electronic Theses and Dissertations
Metal Additive Manufacturing (AM) is increasingly being used to make functional components. One of the barriers for AM components to become mainstream is the difficulty to certify them. AM components can have widely different properties based on process parameters. Improving an AM processes requires an understanding of process-structure-property correlations, which can be gathered in-situ and post-process through nondestructive and destructive methods. In this study, two metal AM processes were studied, the first is Ultrasonic Additive Manufacturing (UAM) and the second is Laser Powder Bed Fusion (L-PBF). The typical problems with UAM components are inter-layer and inter-track defects. To improve the …
Elastodynamic Model For Wind Induced Ground Motion, Mohammad Mohammadi
Elastodynamic Model For Wind Induced Ground Motion, Mohammad Mohammadi
Electronic Theses and Dissertations
No abstract provided.
Habitat Use Of Blacktip Sharks (Carcharhinus Limbatus) At Fishing Piers, Kelsey L. Spencer
Habitat Use Of Blacktip Sharks (Carcharhinus Limbatus) At Fishing Piers, Kelsey L. Spencer
Electronic Theses and Dissertations
Blacktip sharks (Carcharhinus limbatus) can be observed near fishing piers throughout the summer along the northeast coast of South Carolina. These piers attract and support a wide variety of potential prey and sharks are able to forage on fishers’ discards with minimal energetic cost. I tagged 12 blacktip sharks with acoustic transmitters, monitored piers with acoustic receivers, and conducted pier-creel surveys to determine the habitat use of blacktip sharks at fishing piers, factors that influenced residence time and presence/absence at piers, and any cyclical patterns in visits to piers. Data were analyzed with pier association indices (PAI), mixed models, and …
The Effects Of Ball Interactions On The Dynamic Behavior Of A Ball Balancer Rotating At Speeds Above The Translational Resonant Frequency Of The System., Gregory A. Dedow
The Effects Of Ball Interactions On The Dynamic Behavior Of A Ball Balancer Rotating At Speeds Above The Translational Resonant Frequency Of The System., Gregory A. Dedow
Electronic Theses and Dissertations
Many applications are inherently rotational in nature. These applications range from industrial products to consumer products. As seen in a traditional frequency response plot, the motion of a rotating imbalance does not approach zero as the forcing frequency is increased. Unlike a traditional forced mass spring oscillator, the motion of the rotating imbalance approaches some non-zero value. To account for this residual motion, some systems utilize a balancing device to reduce this motion. These balancing devices can be passive or active, depending on the design considerations. This paper will focus on the traditional, passive ball-type balancer due to its simplicity …
Application Of The Aeroacoustic Analogy To A Shrouded, Subsonic, Radial Fan., Bryan Buccieri
Application Of The Aeroacoustic Analogy To A Shrouded, Subsonic, Radial Fan., Bryan Buccieri
Electronic Theses and Dissertations
A study was conducted to investigate the predictive capability of computational aeroacoustics with respect to a shrouded, subsonic, radial fan. A three dimensional unsteady fluid dynamics simulation was conducted to produce aerodynamic data used as the acoustic source for an aeroacoustics simulation. Two acoustic models were developed: one modeling the forces on the rotating fan blades as a set of rotating dipoles located at the center of mass of each fan blade and one modeling the forces on the stationary fan shroud as a field of distributed stationary dipoles. Predicted acoustic response was compared to experimental data. The blade source …
Temperature Dependence Of Shear Speed In Micellar Fluid, E.G. Sunethra Kumari Dayavansha
Temperature Dependence Of Shear Speed In Micellar Fluid, E.G. Sunethra Kumari Dayavansha
Electronic Theses and Dissertations
Wormlike micellar (WM) fluids are viscoelastic and can support shear waves. Phase transitions of the micellar aggregates are temperature dependent and can manifest as sharp changes in the shear wave speed as a function of temperature. Thus, shear waves provide a good tool for detecting the existence of phase transitions. In this work, the variation of shear speed with temperature of 200mM CTAB/NaSal micellar fluid in a 5:3 ratio was studied. The dependence of shear wave speed on time between fluid synthesis and measurement was also investigated. Shear wave propagation through the fluid was observed as a time varying birefringence …
Using Acoustic Emission Monitoring For Energy-Based Fatigue Life Prediction, Sepehr Nesaei
Using Acoustic Emission Monitoring For Energy-Based Fatigue Life Prediction, Sepehr Nesaei
Electronic Theses and Dissertations
The study of fatigue and fracture mechanics is crucial to the health monitoring and overall safety of aerospace and civil structures. The materials used to manufacture these industry parts have inherent anomalies that eventually grow under cyclic loadings during regular operation. The ASTM and/or military testing guidelines used to analyze and qualify structures and materials for use are costly and time consuming. Therefore, any additional methods or knowledge that can be used to reduce the number of tests will be useful to the industry to avoid unnecessary costs. Acoustic emission (AE) monitoring is currently used in many applications to assess …
Optimization Of Wind Fence Enclosures For Infrasonic Wind Noise Reduction, Johnpaul Russell Abbott
Optimization Of Wind Fence Enclosures For Infrasonic Wind Noise Reduction, Johnpaul Russell Abbott
Electronic Theses and Dissertations
A large porous wind barrier enclosure has been built and tested to optimize wind noise reduction at infrasonic frequencies between 0.01-10 Hz in order to develop a technology that is simple, cost effective, and improves upon the limitations of pipe and porous hose arrays. The effects of varying the fence's porosity, modifying its top condition and bottom gap, doubling the height and diameter, and adding a secondary wind barrier were investigated. A simple mathematical model which estimates the wind noise measured at the center of the enclosure was derived based on the measured turbulence and velocity profiles measure outside the …
Characterizing The Acoustic Properties Of The Jet Lab At The National Center For Physical Acoustics, Joshua Anderson Lieblong
Characterizing The Acoustic Properties Of The Jet Lab At The National Center For Physical Acoustics, Joshua Anderson Lieblong
Electronic Theses and Dissertations
Aerodynamic noise has been a problem since the first use of the jet engine for military aircraft in World War II. For further uses of the jet engine to be possible, problems due to jet noise must be researched and addressed. Anechoic chambers were proposed as a testing facility for research in aerodynamic noise because of their supposed free-field characteristics. The international standard ISO 3745-1977 was introduced to determine whether the facilities could be considered anechoic, semi-anechoic, or neither. An experiment was designed to determine at what frequencies the National Center for Physical Acoustics' Jet Lab Facility is non-anechoic, semi-anechoic, …
Effects Of A Heated Turbulent Boundary Layer On Surface Pressure Fluctuations, David William Rich
Effects Of A Heated Turbulent Boundary Layer On Surface Pressure Fluctuations, David William Rich
Electronic Theses and Dissertations
Recent work has shown that spatial correlation of surface pressure fluctuations in a fully turbulent atmospheric boundary layer (ABL) can give information about the velocity field and turbulence. This is of particular importance to the future of wind energy to predict the incoming velocity flow field of wind turbines so as to actively control them for peak operating efficiency and damage reduction. All of the environmental effects on the surface pressure fluctuations need to be fully understood before a suitable flow prediction algorithm can be constructed. One such environmental effect which has not been previously studied is the effect of …
Quantification Of An Ultrasound Test Apparatus And Its Potential Use To Control Nuisance Species In Commercial Aquaculture Settings, Bradley T. Goodwiller
Quantification Of An Ultrasound Test Apparatus And Its Potential Use To Control Nuisance Species In Commercial Aquaculture Settings, Bradley T. Goodwiller
Electronic Theses and Dissertations
As one step in the investigation of using acoustics to improve aquaculture production, work was pursued on the possible use of ultrasound to control the Bolbophorus trematode in commercial catfish ponds. The trematode population can be controlled by eliminating the host ram's horn snail via exposure to high amplitude ultrasound. Initial laboratory tests indicated that a commercially available sonicator (operating at 20 kHz) is capable of killing individual snails in fish tanks. More thorough testing indicated efficiency rates of approximately 35% on batches of 10 snails. In addition to the snails killed immediately, there was evidence that the sonication technique …
The Effect Of Static Pressure On The Inertial Cavitation Threshold And Collapse Strength, Kenneth Bryan Bader
The Effect Of Static Pressure On The Inertial Cavitation Threshold And Collapse Strength, Kenneth Bryan Bader
Electronic Theses and Dissertations
The amplitude of the acoustic pressure required to nucleate a gas and/or vapor bubble in a fluid, and to have that bubble undergo an inertial collapse, is termed the inertial cavitation threshold. The hydrostatic dependence of the inertial cavitation threshold was measured up to 30 MPa in ultrapure water using a high quality factor spherical resonator. The threshold increased linearly with the hydrostatic pressure and was found to be temperature dependent. The strength of the bubble collapse at the threshold was measured in terms of shock waves and light emissions. The shock amplitudes increased linearly with the hydrostatic pressure, while …