An Assessment of Air Service Accessibility in U.S. Metropolitan Regions, 2007-2012

Regional accessibility to air transportation is often of interest to airport executives, politicians, and the general public due to the positive economic impacts of frequent commercial airline service. However, measuring access to air service can be challenging, particularly for regions with multiple airports. While many models exist to measure airline network connectivity at individual airports, there is limited literature on the geographic aggregation of these metrics to assess regional accessibility. In this paper, we propose a new methodology to construct U.S. regional airport catchment areas using U.S. Census Bureau Primary Statistical Areas (PSAs). Using a connectivity index that evaluates airports on the quantity and quality of available service, air service accessibility scores are computed on a regional level for 323 PSAs from 2007-2012. We find that most U.S. regions lost access to air service during the study period in the midst of domestic schedule rationalization and airline “capacity discipline.” Accessibility scores for each PSA from 2007 to 2012 are available in an appendix. On average, metropolitan regions in the United States lost about 11.6% of their accessibility to commercial air transportation between 2007 and 2012. Mid-sized regions of 500,000 - 5 million people lost the most access to air service—about 14.4% on average—aligning with past work that suggests that medium-sized communities have been harmed most by airline capacity discipline. In multi-airport regions, losses in service at primary airports outweighed some consolidation in service at larger hubs, leading to net losses in accessibility in most cases. The results of the accessibility model can be used by regional planners, policy-makers, and airport officials to understand how various regions in the U.S. lost or gained access to air transportation as a result of the Great Recession and airline capacity strategies. Additionally, the proposed catchment area definition provides a useful framework for further discussion of the demographic and geographic determinants of successful commercial air service.MIT Airline Industry Research Consortiu

2013 Data Update: Trends and Market Forces Shaping Small Community Air Service in the United States

This document is an update to MIT Small Community Air Service White Paper No. 1—Trends and Market Forces Shaping Small Community Air Service in the United States1. This report provides updated analysis and data appendices including 2013 schedule data. This will allow readers to investigate the continuing effects of U.S. airline capacity discipline and the changes in available domestic service at the 462 U.S. airports examined in the earlier report. As with the 2013 report, the data contained in this report has been sourced from Diio Mi.MIT Airline Industry Consortiu

Mission Analysis and Aircraft Sizing of a Hybrid-Electric Regional Aircraft

The purpose of this study was to explore advanced airframe and propulsion technologies for a small regional transport aircraft concept (approximately 50 passengers), with the goal of creating a conceptual design that delivers significant cost and performance advantages over current aircraft in that class. In turn, this could encourage airlines to open up new markets, reestablish service at smaller airports, and increase mobility and connectivity for all passengers. To meet these study goals, hybrid-electric propulsion was analyzed as the primary enabling technology. The advanced regional aircraft is analyzed with four levels of electrification, 0 percent electric with 100 percent conventional, 25 percent electric with 75 percent conventional, 50 percent electric with 50 percent conventional, and 75 percent electric with 25 percent conventional for comparison purposes. Engine models were developed to represent projected future turboprop engine performance with advanced technology and estimates of the engine weights and flowpath dimensions were developed. A low-order multi-disciplinary optimization (MDO) environment was created that could capture the unique features of parallel hybrid-electric aircraft. It is determined that at the size and range of the advanced turboprop: The battery specific energy must be 750 watt-hours per kilogram or greater for the total energy to be less than for a conventional aircraft. A hybrid vehicle would likely not be economically feasible with a battery specific energy of 500 or 750 watt-hours per kilogram based on the higher gross weight, operating empty weight, and energy costs compared to a conventional turboprop. The battery specific energy would need to reach 1000 watt-hours per kilogram by 2030 to make the electrification of its propulsion an economically feasible option. A shorter range and/or an altered propulsion-airframe integration could provide more favorable results

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Psychology and aggression

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68264/2/10.1177_002200275900300301.pd

Characterization of cryogenic direct-drive ICF targets during layering studies and just prior to shot time

The characterization of OMEGA cryogenic targets is based on shadowgraphs obtained from multiple angular views taken with the target in the layering sphere. The D$_{2}$ ice has been observed to re-layer during slow rotations, leading to procedural changes that avoid re-layering thus ensuring high-quality, spherical-harmonic, 3-D ice layer reconstructions. Shadowgrams taken inside the target chamber within 20 ms of shot time have verified that the ice layers remain preserved during the transport

Letting the good times roll: A theory of voter inference and experimental evidence

This paper examines inference and attribution in a simple and ubiquitous strategic situation: a voter is faced with discerning whether a leader worked on his or her behalf after observing an informative, but noisy signal about the leader's performance. We characterize perfect Bayesian equilibria, quantal response equilibria (QRE), and provide a simple model of a heuristic-based approach, referred to as strategic naivete, within a wide class of such environments. We also discuss experiments conducted to examine human behavior within such an environment. While it is clear that the observed behavior is inconsistent with perfect Bayesian equilibrium, distinguishing between QRE and strategic naivete will require further work. We conclude with a discussion of the broader implications of probabilistic and/or heuristic-based attribution processes for electoral politics and political economy. Copyright Springer Science + Business Media B.V. 2007