Reactive Trajectory Generation in an Unknown Environment

Autonomous trajectory generation for unmanned aerial vehicles (UAVs) in unknown environments continues to be an important research area as UAVs become more prolific. We define a trajectory generation algorithm for a vehicle in an unknown environment with wind disturbances, that relies only on the vehicle's on-board distance sensors and communication with other vehicles within a finite region to generate a smooth, collision-free trajectory up to the fourth derivative. The proposed trajectory generation algorithm can be used in conjunction with high-level planners and low-level motion controllers. The algorithm provides guarantees that the trajectory does not violate the vehicle's thrust limitation, sensor constraints, or a user-defined clearance radius around other vehicles and obstacles. Simulation results of a quadrotor moving through an unknown environment with a moving obstacle demonstrates the trajectory generation performance.Comment: Revised version with minor text updates and more representative simulation results for IROS 2017 conferenc

Jobs and Income Growth of Top Earners and the Causes of Changing Income Inequality: Evidence from U.S. Tax Return Data

This paper presents summary statistics on the occupations of taxpayers in the top percentile of the national income distribution and fractiles thereof, as well as the patterns of real income growth between 1979 and 2005 for top earners in each occupation, based on information reported on U.S. individual income tax returns. The data demonstrate that executives, managers, supervisors, and financial professionals account for about 60 percent of the top 0.1 percent of income earners in recent years, and can account for 70 percent of the increase in the share of national income going to the top 0.1 percent of the income distribution between 1979 and 2005. During 1979-2005 there was substantial heterogeneity in growth rates of income for top earners across occupations, and significant divergence in incomes within occupations among people in the top 1 percent. We consider the implications for various competing explanations for the substantial changes in income inequality that have occurred in the U.S. in recent times. We then use panel data on U.S. tax returns spanning the years 1987 through 2005, to estimate the elasticity of gross income with respect to net-of-tax share (that is, one minus the marginal tax rate). Information on occupation allows us to control for other influences on income in a flexible way using interactions among occupation, position in the income distribution, stock prices, housing prices, and the business cycle. We also allow for income shifting across years in response to anticipated tax changes, for the long-run effect of a tax reform to differ from the short-run effects, for heterogeneous mean-reversion across incomes, and for heterogeneous elasticities across income classes. In a specification that does all this, we estimate a significant elasticity of 0.7 among taxpayers in the top 0.1 percent of the income distribution. Outside of the top 0.1 percent of the income distribution, we find no conclusive evidence of a positive elasticity of income with respect to net-of-tax shares. We find that the estimate for the top 0.1 percent is not robust to controlling for a spline in lagged income that is very flexible at the upper reaches of the income distribution, suggesting that the method used to allow for income dynamics is very important. Allowing for income shifting across years in response to anticipated tax changes has important consequences for the estimates.income distribution, behavioral response to taxation

You Say You Want a Revolution: Argentina\u27s Recovered Factory Movement

The Recovered Factory Movement in Argentina - in which workers assume control and ownership of factories abandoned by their owners - has piqued the interest of social activists worldwide. However, despite a noticeable buzz within leftist circles, the movement has received little more than a cursory examination from its enthusiasts. This note attempts to nudge the discourse in a substantive direction by explaining the pertinent law, discussing the changes sought by the movement, and analyzing the accompanying policy issues. In so doing, this note is meant to serve as a starting point to encourage more exhaustive treatment of the relevant laws and issues

Gray is the new black : great power competition in the Gray Zone

The 2017 National Security Strategy and 2018 National Defense Strategy herald the return of great power competition as the focus of U.S. national security after an almost three-decade hiatus. While the United States was enraptured with the “Unipolar Moment” and consumed with fighting terrorism, the character of great power conflict was changing. Leveraging disruptive information technologies and potent amalgamations of national power in a dynamic hyper-globalized environment, great power competitors are exposing U.S. vulnerabilities in the ambiguity of the Gray Zone between war and peace. U.S. adversaries like China and Russia are increasingly operating outside of traditional conflict models, exploiting our struggle to clearly conceptualize and counter Gray Zone methods. Examining recent literature and utilizing profiles of China and Russia, this work argues that the Gray Zone is an urgently relevant concept for framing the unique character of great power conflict in the present age.Public Affair

On Liking and Perceived Authenticity

Previous studies in our lab have found that liking is a significant predictor of authenticity (Kelley, Schlegel, Hicks, & Kim, manuscript in prep). The current study seeks to examine whether this relationship holds over and above a variety of other possible predictors, such as perceptions of a target’s personality, character, and social power. Specifically, we predict that the more a participant reports liking a target, the higher they will rate the target’s authenticity. The study consisted of an interaction task where a research assistant led a group 2-5 participants in a discussion of their most embarrassing moments and their favorite memories. Afterwards participants rated the other group members on their perceived authenticity, similarity, liking, mood, Big 5 personality traits, and power. We tested our hypothesis by using bivariate correlation and multiple regression models

GSK3 as a Sensor Determining Cell Fate in the Brain

Glycogen synthase kinase 3 (GSK3) is an unusual serine/threonine kinase that controls many neuronal functions, including neurite outgrowth, synapse formation, neurotransmission, and neurogenesis. It mediates these functions by phosphorylating a wide range of substrates involved in gene transcription, metabolism, apoptosis, cytoskeletal dynamics, signal transduction, lipid membrane dynamics, and trafficking, amongst others. This complicated list of diverse substrates generally follow a more simple pattern: substrates negatively regulated by GSK3-mediated phosphorylation favor a proliferative/survival state, while substrates positively regulated by GSK3 favor a more differentiated/functional state. Accordingly, GSK3 activity is higher in differentiated cells than undifferentiated cells and physiological (Wnt, growth factors) and pharmacological inhibitors of GSK3 promote the proliferative capacity of embryonic stem cells. In the brain, the level of GSK3 activity influences neural progenitor cell proliferation/differentiation in neuroplasticity and repair, as well as efficient neurotransmission in differentiated adult neurons. While defects in GSK3 activity are unlikely to be the primary cause of neurodegenerative diseases, therapeutic regulation of its activity to promote a proliferative/survival versus differentiated/mature functional environment in the brain could be a powerful strategy for treatment of neurodegenerative and other mental disorders