An Embarrassment of Riches: Data Integration in VR Pompeii

It is fair to say that Pompeii is the most studied archaeological site in the world. Beyond the extensive remains of the city itself, the timing of its rediscovery and excavation place it in a unique historiographical position. The city has been continuously studied since the 18th century, with historians and archaeologists constantly reevaluating older sources as our knowledge of the ancient world expands. While several studies have approached the city from a data driven perspective, no studies of the city have taken a quantitative holistic approach on the scale of the VR Pompeii project. Hyper-specificity has been the order of the day, leaving our knowledge of the city structure incomplete. The VR Pompeii project at the University of Arkansas aims to address this by performing, in concert, topographical network analysis of houses and neighborhoods, convolutional neural network identification and categorization of wall images, and analysis of space usage through subject tracking and electroencephalogram (EEG) data. Coordination of this data to maintain search-ability for non-technical scholars is a major challenge. To this end, the purpose of this research has been to design and then implement a database that allows for all of the VR Pompeii project data to be accessed together, with room for expansion, while maintaining a simple user interface to empower non technical users to ask questions that no researcher has been able to ask about the ancient city of Pompeii

External communication displays for connected truck platoons in mixed traffic : a federated simulator study

Truck platooning is anticipated to be the first widespread deployment of connected or automated vehicles (CAV). In addition to familiarizing the public with the function of CAV, a truck platoon has proven benefits to fuel consumption by minimizing drag. These are the primary motivations that have caused companies to develop and deploy these systems, but there are still obstacles opposing their implementation. One obstacle is the issue of communication between CAVs and the surrounding traffic. For example, research has shown that communication between CAV and pedestrians and cyclists is facilitated by using external status displays on the CAVs. In order to investigate the communication between truck platoons and surrounding traffic, a similar model is proposed in this study. The scenario examined in this study involves trucks forming a truck platoon. Two different external displays in addition to a control display were evaluated for how surrounding traffic behaves while the trucks form their platoon. The three displays are the control (no signal), the word "PLATOON," and a graphic of two trucks with a link. Each of the displays were tested using a federated truck simulator and passenger vehicle simulator. The approaching truck was driven by the same human driver up until the completion of platooning while the passenger vehicle was driven by the research participants. The simulation scenario involved a passenger vehicle following a semi-truck while an approaching truck comes up from behind the passenger vehicle to form the platoon. The actions taken by the passenger vehicle to clear the way for the approaching truck were observed and recorded. After the participants were exposed to the signs once, they were provided with an explanation of truck platoons and were able to ask questions before experiencing three displays scenarios again. Overall, the primary performance result was that the text display after being provided with information on truck platoons significantly changed the behavior of the passenger vehicle. Furthermore, as in the AV-Pedestrian studies, participants indicated that the external displays were useful. In conclusion, though the behavior was not drastically affected, the results indicate that the displays provide the passenger vehicle drivers with important information that they want to have and that drivers tend to move out of the way when they learn that a truck platoon is forming around them.by Michael SchoelzIncludes bibliographical reference

Mirror Buckling Transitions in Freestanding Graphene Membranes induced through Scanning Tunneling Microscopy

Graphene has the ability to provide for a technological revolution. First isolated and characterized in 2004, this material shows promise in the field of flexible electronics. The electronic properties of graphene can be tuned by controlling the shape of the membrane. Of particular interest in this endeavor are the thermal ripples in graphene membranes. Years of theoretical work by such luminaries as Lev Landau, Rudolf Peierls, David Mermin and Herbert Wagner have established that 2D crystals should not be thermodynamically stable. Experimental research on thin films has supported this finding. Yet graphene exists, and freestanding graphene films have been grown on large scales. It turns out that coupling between the bending and stretching phonons can stabilize the graphene in a flat, albeit rippled phase. These ripples have attracted much attention, and recent work has shown how to arrange these ripples in a variety of configurations. In this thesis, I will present work done using a scanning tunneling microscope (STM) to interact with freestanding graphene membranes. First I will present STM images of freestanding graphene and show how these images show signs of distortion under the electrostatic influence of the STM tip. This electrostatic attraction between the STM tip and the graphene sample can be used to pull on the graphene sample. At the same time, by employing Joule heating in order to heat graphene using the tunneling current, and exploiting the negative coefficient of thermal expansion, a repulsive thermal load can be generated. By repeatedly pulling on the graphene using the electrostatic potential, while sequentially increasing the setpoint current we can generate a thermal mirror buckling event. Slowly heating the graphene using the tunneling current, prepares a small convex region of graphene under the tip. By increasing thermal stress, as well as pulling using the out of plane electrostatic force, the graphene suddenly and irreversibly switches the sign of its curvature. This event is discovered using STM measurements and supplemented by molecular dynamics simulations. Finally, I will show how to characterize this transition using the famed Ising model. The ripples are modeled as individual Ising spins, which at low temperature exhibit antiferromagnetic coupling. By heating the graphene membrane, the strain increases, changing the antiferromagnetic coupling to ferromagnetic coupling, which characterizes the irreversible transition from a soft, flexible state to a rigid configuration

Graphene Ripples as a Realization of a Two-Dimensional Ising Model: A Scanning Tunneling Microscope Study

Ripples in pristine freestanding graphene naturally orient themselves in an array that is alternately curved-up and curved-down; maintaining an average height of zero. Using scanning tunneling microscopy (STM) to apply a local force, the graphene sheet will reversibly rise and fall in height until the height reaches 60-70 percent of its maximum at which point a sudden, permanent jump occurs. We successfully model the ripples as a spin-half Ising magnetic system, where the height of the graphene is the spin. The permanent jump in height, controlled by the tunneling current, is found to be equivalent to an antiferromagnetic-to-ferromagnetic phase transition. The thermal load underneath the STM tip alters the local tension and is identified as the responsible mechanism for the phase transition. Four universal critical exponents are measured from our STM data, and the model provides insight into the statistical role of graphenes unusual negative thermal expansion coefficient.Comment: 12 pages, 5 figures, 1 tabl