Matching Items (303)
Description
This paper discusses the design of experimental setup and procedures to characterize polymethyl methylate (PMMA) at its glass transition temperature by studying its strain fields, process zone, and crack speed under different loading conditions. These loading conditions are different steady-state temperatures and initial crack lengths. Steady-state temperature testing uses a temperature control loop. Crack speed / resistivity testing is set up using a voltage drop method. From initial steady-state temperature testing, it was confirmed that the behavior of a PMMA sample becomes more ductile at higher temperatures, and that it is plausible for a crack process zone to be measured using DIC as temperature increases. From finite element simulations, it was validated that the crack speed is not constant relative to an initial crack length.
ContributorsKwan, Brandon (Author) / Oswald, Jay (Thesis director) / Hoover, Christian (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Transition metal dichalcogenides (TMDs) are a family of layered crystals with the chemical formula MX2 (M = W, Nb, Mo, Ta and X = S, Se, Te). These TMDs exhibit many fascinating optical and electronic properties making them strong candidates for high-end electronics, optoelectronic application, and spintronics. The layered structure of TMDs allows the crystal to be mechanically exfoliated to a monolayer limit, where bulk-scale properties no longer apply and quantum effects arise, including an indirect-to-direct bandgap transition. Controllably tuning the electronic properties of TMDs like WSe2 is therefore a highly attractive prospect achieved by substitutionally doping the metal atoms to enable n- and p-type doping at various concentrations, which can ultimately lead to more effective electronic devices due to increased charge carriers, faster transmission times and possibly new electronic and optical properties to be probed. WSe2 is expected to exhibit the largest spin splitting size and spin-orbit coupling, which leads to exciting potential applications in spintronics over its similar TMD counterparts, which can be controlled through electrical doping. Unfortunately, the well-established doping technique of ion implantation is unable to preserve the crystal quality leading to a major roadblock for the electronics applications of tungsten diselenide. Synthesizing WSe2 via chemical vapor transport (CVT) and flux method have been previously established, but controllable p-type (niobium) doping WSe2 in low concentrations ranges (<1 at %) by CVT methods requires further experimentation and study. This work studies the chemical vapor transport synthesis of doped-TMD W1-xNbxSe2 through characterization techniques of X-ray Diffraction, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, and X-ray Photoelectron Spectroscopy techniques. In this work, it is observed that excess selenium transport does not enhance the controllability of niobium doping in WSe2, and that tellurium tetrachloride (TeCl4) transport has several barriers in successfully incorporating niobium into WSe2.
ContributorsRuddick, Hayley (Author) / Tongay, Sefaattin (Thesis director) / Jiao, Yang (Committee member) / Barrett, The Honors College (Contributor) / Materials Science and Engineering Program (Contributor)
Created2024-05
Description
This thesis presents an overview of virtual reality (VR)-based teleoperation and describes its benefits and several existing challenges to its implementation, as well as potential solutions to these challenges. VR-based teleoperation of robotic arms enables a user to control and maneuver the robotic system from a remote distance while immersed in a virtual environment that simulates the location site of the robot. By implementing VR-based teleoperation, we can send robotic arms operated by trained professionals into harsh and inaccessible environments, including the deep sea and outer space, to accomplish manipulation tasks that would otherwise be unsafe or impossible. Teleoperated robotic arms can also be used to remotely execute fine manipulation tasks such as surgery, for instance, to reduce contamination or to perform operations in places that lack the required medical services.
In order to be able to reliably and comfortably use VR-based teleoperation, we need to focus on solving the challenges of latency and sensory loss. Since the teleoperator has a limited field of view and cannot rely on certain types of sensory information, they can feel disoriented and disconnected from the environment and robotic arm. Sensory information loss can be mitigated by simulating a wider field of view in the virtual environment, implementing additional sensors such as thermometers and gas detection sensors, and using data sonification techniques. Although it may not be possible to completely eliminate latency, the effects of latency can be reduced through the use of assistive interfaces that predict the trajectory of the robotic arm in real-time based on the teleoperator’s input movement using artificial intelligence (AI)-based predictive models. When visualized in the virtual environment, this predictive real-time feedback enables the user to immediately see the effects of their movements on the robotic arm, even though the arm’s actual motion is delayed due to latency, and thus avoid collisions and improve task performance. VR-based teleoperation can be enhanced with these proposed solutions to enable the user to complete the required manipulation task with high precision and to maneuver the robotic arm with reduced cognitive load.
ContributorsTrejo, Patricia (Author) / Berman, Spring (Thesis director) / Lee, Hyunglae (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2024-05