207,382 research outputs found
Image-Processing Techniques for the Creation of Presentation-Quality Astronomical Images
The quality of modern astronomical data, the power of modern computers and
the agility of current image-processing software enable the creation of
high-quality images in a purely digital form. The combination of these
technological advancements has created a new ability to make color astronomical
images. And in many ways it has led to a new philosophy towards how to create
them. A practical guide is presented on how to generate astronomical images
from research data with powerful image-processing programs. These programs use
a layering metaphor that allows for an unlimited number of astronomical
datasets to be combined in any desired color scheme, creating an immense
parameter space to be explored using an iterative approach. Several examples of
image creation are presented.
A philosophy is also presented on how to use color and composition to create
images that simultaneously highlight scientific detail and are aesthetically
appealing. This philosophy is necessary because most datasets do not correspond
to the wavelength range of sensitivity of the human eye. The use of visual
grammar, defined as the elements which affect the interpretation of an image,
can maximize the richness and detail in an image while maintaining scientific
accuracy. By properly using visual grammar, one can imply qualities that a
two-dimensional image intrinsically cannot show, such as depth, motion and
energy. In addition, composition can be used to engage viewers and keep them
interested for a longer period of time. The use of these techniques can result
in a striking image that will effectively convey the science within the image,
to scientists and to the public.Comment: 104 pages, 38 figures, submitted to A
Agnostic notes on regression adjustments to experimental data: Reexamining Freedman's critique
Freedman [Adv. in Appl. Math. 40 (2008) 180-193; Ann. Appl. Stat. 2 (2008)
176-196] critiqued ordinary least squares regression adjustment of estimated
treatment effects in randomized experiments, using Neyman's model for
randomization inference. Contrary to conventional wisdom, he argued that
adjustment can lead to worsened asymptotic precision, invalid measures of
precision, and small-sample bias. This paper shows that in sufficiently large
samples, those problems are either minor or easily fixed. OLS adjustment cannot
hurt asymptotic precision when a full set of treatment-covariate interactions
is included. Asymptotically valid confidence intervals can be constructed with
the Huber-White sandwich standard error estimator. Checks on the asymptotic
approximations are illustrated with data from Angrist, Lang, and Oreopoulos's
[Am. Econ. J.: Appl. Econ. 1:1 (2009) 136--163] evaluation of strategies to
improve college students' achievement. The strongest reasons to support
Freedman's preference for unadjusted estimates are transparency and the dangers
of specification search.Comment: Published in at http://dx.doi.org/10.1214/12-AOAS583 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Passenger ride quality determined from commercial airline flights
The University of Virginia ride-quality research program is reviewed. Data from two flight programs, involving seven types of aircraft, are considered in detail. An apparatus for measuring physical variations in the flight environment and recording the subjective reactions of test subjects is described. Models are presented for predicting the comfort response of test subjects from the physical data, and predicting the overall comfort reaction of test subjects from their moment by moment responses. The correspondence of mean passenger comfort judgments and test subject response is shown. Finally, the models of comfort response based on data from the 5-point and 7-point comfort scales are shown to correspond
The Effect of World Bank Trade Adjustment Assistance on Trade and Growth: 1987-2004, Is the Glass Half Full of Half Empty?
This paper studies the association between trade reform, growth, and trade adjustment assistance, in a sample of developing countries that underwent trade reforms during 1987-2004. Our analysis explicitly differentiates between a group of countries that received trade-adjustment loans from the World Bank, and a non-recipient group. The results suggest that trade adjustment assistance is positively associated with economic growth after trade reform in a medium- to long-run. Comparing to a pre-reform period and to the non-recipient group, the recipient countries registered 0.2 percent higher growth of real GDP/capita, 5.0 percent higher import growth, and 2.5 percent higher export growth during a period of three to five years after trade reform
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