Object-Based Unawareness

The goal of this paper is to construct a user-friendly model of unawareness. We start from an axiom system (in first-order modal logic) that enables us to express the following kinds of sentences: “the agent is not sure whether or not there is anything that he is unaware of”, and “I am not sure whether or not you are aware of something that I am not”. We then prove a characterization theorem which describes a class of structures, called object-based unawareness structures, that correspond to this axiom system. As an application, we explain how an object-based unawareness structure can be use to model those American founding fathers who were opposed to the inclusion of the Bill of Rights in the constitution.unawareness, object-based, modal logic, bill of rights

A tool for compiler testing

A tool for compiler testing is implemented. The tool is driven by a BNF grammar extended by a device called control flags to incorporate those parts of a language that are not controlled by context-free rules (for instance, use of declared names). The tool produced two sets of program strings such that each production in the grammar is used at least once. One set is produced by Purdom\u27s algorithm. The other is produced by a new algorithm designed by the author which builds a tree and then produces a set of strings from it for compiler testing. The program strings produced from the new algorithm differ less in length than those from Purdom\u27s algorithm

Video games as meaningful entertainment experiences

We conducted an experiment to examine individuals’ perceptions of enjoyable and meaningful video games and the game characteristics and dimensions of need satisfaction associated with enjoyment and appreciation. Participants (N = 512) were randomly assigned to 1 of 2 groups that asked them to recall a game that they found either particularly fun or particularly meaningful, and to then rate their perceptions of the game that they recalled. Enjoyment was high for both groups, though appreciation was higher in the meaningful- than fun-game condition. Further, enjoyment was most strongly associated with gameplay characteristics and satisfaction of needs related to competency and autonomy, whereas appreciation was most strongly associated with story characteristics and satisfaction of needs related to insight and relatedness

Physiological and pharmacological implications of AT1 versus AT2 receptors

Physiological and pharmacological implications of AT1versus AT2receptors. Angiotensin II (Ang II) has diverse physiological actions that lead, for instance, to increases in extracellular volume and peripheral vascular resistance and blood pressure, and it has also been implicated in the regulation of cell growth and differentiation. Molecular cloning and pharmacological studies have defined two major classes of Ang II receptors, designated AT1 and AT2. Most effects of Ang II are mediated by AT1 receptors. Much less is known about the physiological role of AT2 receptors. Recent evidence suggests involvement of AT2 receptors in development, cell differentiation, apoptosis, and regeneration in various tissues. AT1 and AT2 receptors have been shown to exert counteracting effects on cellular growth and differentiation, vascular tone, and the release of arginine vasopressin. In each condition, the AT2 receptor appears to down-modulate actions mediated by the AT1 receptor, resulting in decreased cellular proliferation, decreased levels of serum arginine vasopressin levels, or decreased vasoconstrictor responses. In addition, in neuronal cell lines, the AT2 receptor exerts antiproliferative actions and promotes neurite outgrowth, an effect accompanied by significant changes in the expression pattern of growth/differentiation-related genes

Elastocapillary Levelling of Thin Viscous Films on Soft Substrates

A thin liquid film with non-zero curvature at its free surface spontaneously flows to reach a flat configuration, a process driven by Laplace pressure gradients and resisted by the liquid's viscosity. Inspired by recent progresses on the dynamics of liquid droplets on soft substrates, we here study the relaxation of a viscous film supported by an elastic foundation. Experiments involve thin polymer films on elastomeric substrates, where the dynamics of the liquid-air interface is monitored using atomic force microscopy. A theoretical model that describes the coupled evolution of the solid-liquid and the liquid-air interfaces is also provided. In this soft-levelling configuration, Laplace pressure gradients not only drive the flow, but they also induce elastic deformations on the substrate that affect the flow and the shape of the liquid-air interface itself. This process represents an original example of elastocapillarity that is not mediated by the presence of a contact line. We discuss the impact of the elastic contribution on the levelling dynamics and show the departure from the classical self-similarities and power laws observed for capillary levelling on rigid substrates

Optimal Routing for Autonomous Taxis using Distributed Reinforcement Learning

In this paper, a learning-based optimal transportation algorithm for autonomous taxis and ridesharing vehicles is introduced. The goal is to design a mechanism to solve the routing problem for a fleet of autonomous vehicles in real-time in order to maximize the transportation company’s profit. To solve this problem, the system is modeled as a Markov Decision Process (MDP) using past customers data. By solving the defined MDP, a centralized high-level planning recommendation is obtained, where this offline solution is used as an initial value for the real-time learning. Then, a distributed SARSA reinforcement learning algorithm is proposed to capture the model errors and the environment changes, such as variations in customer distributions in each area, traffic, and fares, thereby providing an accurate model and optimal policies in real-time. Agents are using only their local information and interaction, such as current passenger requests and estimates of neighbors’ tasks and their optimal actions, to obtain the optimal policies in a distributed fashion. The agents use the estimated values of each action, provided by distributed SARSA reinforcement learning, in a distributed game-theory based task assignment to select their conflict-free customers. Finally, the customers data provided by the city of Chicago is used to validate the proposed algorithms

Towards Robotic Tree Manipulation: Leveraging Graph Representations

There is growing interest in automating agricultural tasks that require intricate and precise interaction with specialty crops, such as trees and vines. However, developing robotic solutions for crop manipulation remains a difficult challenge due to complexities involved in modeling their deformable behavior. In this study, we present a framework for learning the deformation behavior of tree-like crops under contact interaction. Our proposed method involves encoding the state of a spring-damper modeled tree crop as a graph. This representation allows us to employ graph networks to learn both a forward model for predicting resulting deformations, and a contact policy for inferring actions to manipulate tree crops. We conduct a comprehensive set of experiments in a simulated environment and demonstrate generalizability of our method on previously unseen trees. Videos can be found on the project website: https://kantor-lab.github.io/tree_gnnComment: 7 pages, 10 figure

Senior Recital: Sarah Lynn Oliver, Mezzo Soprano; Jiyoun Chung, Piano; Brian Feldcamp, Piano; October 10, 2009

Kemp Recital HallOctober 10, 2009Saturday Afternoon5:00 p.m

Active Management of Flap-Edge Trailing Vortices

The vortex hazard produced by large airliners and increasingly larger airliners entering service, combined with projected rapid increases in the demand for air transportation, is expected to act as a major impediment to increased air traffic capacity. Significant reduction in the vortex hazard is possible, however, by employing active vortex alleviation techniques that reduce the wake severity by dynamically modifying its vortex characteristics, providing that the techniques do not degrade performance or compromise safety and ride quality. With this as background, a series of experiments were performed, initially at NASA Langley Research Center and subsequently at the Berlin University of Technology in collaboration with the German Aerospace Center. The investigations demonstrated the basic mechanism for managing trailing vortices using retrofitted devices that are decoupled from conventional control surfaces. The basic premise for managing vortices advanced here is rooted in the erstwhile forgotten hypothesis of Albert Betz, as extended and verified ingeniously by Coleman duPont Donaldson and his collaborators. Using these devices, vortices may be perturbed at arbitrarily long wavelengths down to wavelengths less than a typical airliner wingspan and the oscillatory loads on the wings, and hence the vehicle, are small. Significant flexibility in the specific device has been demonstrated using local passive and active separation control as well as local circulation control via Gurney flaps. The method is now in a position to be tested in a wind tunnel with a longer test section on a scaled airliner configuration. Alternatively, the method can be tested directly in a towing tank, on a model aircraft, a light aircraft or a full-scale airliner. The authors believed that this method will have significant appeal from an industry perspective due to its retrofit potential with little to no impact on cruise (devices tucked away in the cove or retracted); low operating power requirements; small lift oscillations when deployed in a time-dependent manner; and significant flexibility with respect to the specific devices selected

Distributed Control Of An Evolving Satellite Assembly During In-Orbit Construction

This paper presents a method for controlling sets of docked satellites during in-orbit construction of a large-scale satellite assembly from a swarm of heterogeneous satellites. Such a system can be used to enable missions from sparse aperture telescopes to elaborate space stations. Once two or more agents from the swarm are docked, the resulting assembly is an over-actuated system so position and attitude controllers must determine which of the available actuators to use. Typically, control allocation for over-actuated systems is done using a simple linear program, but for this scheme the mass properties and number of control points changes. As a result, the linear program solved changes with each new agent that docks with the assembly so the agents must know how to alter the linear program for additional agents and remove control points whose plumes would interact with those agents. In most systems, this linear program is solved by a central computer, but for this system the actuators belong to distinct agents so to increase reliability, each agent solves the same linear program and executes its portion of the resulting control command. This paper sets up the general linear program that each agent in the assembly must solve and then establishes the rules for altering that program when new agents dock. Initial simulations allow the agents to dock as they come into proximity along their respective trajectories to their target locations. This can lead to instability and uncontrollability if the agents dock in certain configurations, so the control allocation rules are extended to prevent uncontrollable or unstable docking scenarios. The logic used for this is based on the moment of inertia and the available actuation ability. Simulations in 6DOF perturbed satellite dynamics show the efficacy of this approach in preventing uncontrollable assemblies and bringing the assemblies together into the desired final configuration