10,481 research outputs found
Skyscrapers and Skylines: New York and Chicago, 1885-2007
This paper compares and contrasts the determinants of the market for skyscrapers in Chicago and New York from 1885 to 2007, using annual time series data. I estimate the factors that determine both the number of skyscraper completions and the height of the tallest building completed each year in the two cities. I find that each city responds differently to the same economic fundamentals. Also, regressions test for and find the presence of strategic interaction across the two cities. I also estimate the effects of zoning regulations on height. Compared to New York, Chicago's zoning policies significantly reduced the height of its skyline.New York, Chicago, skyscrapers, building height
Estimating snow cover from publicly available images
In this paper we study the problem of estimating snow cover in mountainous
regions, that is, the spatial extent of the earth surface covered by snow. We
argue that publicly available visual content, in the form of user generated
photographs and image feeds from outdoor webcams, can both be leveraged as
additional measurement sources, complementing existing ground, satellite and
airborne sensor data. To this end, we describe two content acquisition and
processing pipelines that are tailored to such sources, addressing the specific
challenges posed by each of them, e.g., identifying the mountain peaks,
filtering out images taken in bad weather conditions, handling varying
illumination conditions. The final outcome is summarized in a snow cover index,
which indicates for a specific mountain and day of the year, the fraction of
visible area covered by snow, possibly at different elevations. We created a
manually labelled dataset to assess the accuracy of the image snow covered area
estimation, achieving 90.0% precision at 91.1% recall. In addition, we show
that seasonal trends related to air temperature are captured by the snow cover
index.Comment: submitted to IEEE Transactions on Multimedi
Skyline Identification in Multi-Armed Bandits
We introduce a variant of the classical PAC multi-armed bandit problem. There
is an ordered set of arms , each with some stochastic
reward drawn from some unknown bounded distribution. The goal is to identify
the of the set , consisting of all arms such that
has larger expected reward than all lower-numbered arms . We
define a natural notion of an -approximate skyline and prove
matching upper and lower bounds for identifying an -skyline.
Specifically, we show that in order to identify an -skyline from
among arms with probability , samples are necessary and sufficient. When , our results improve over the naive algorithm, which draws enough samples
to approximate the expected reward of every arm; the algorithm of (Auer et al.,
AISTATS'16) for Pareto-optimal arm identification is likewise superseded. Our
results show that the sample complexity of the skyline problem lies strictly in
between that of best arm identification (Even-Dar et al., COLT'02) and that of
approximating the expected reward of every arm.Comment: 18 pages, 2 Figures; an ALT'18/ISIT'18 submissio
Skyscrapers and the Skyline: Manhattan, 1895-2004
This paper investigates the determinants of skyscraper building cycles in Manhattan from 1895 to 2004. We first provide a simple model of the market for tall buildings. Then we empirically estimate the determinants of the time series of the number of skyscraper completions and their average heights over the 110 year period. We estimate the model under the assumption of rational expectations and myopic expectations, and find that the myopic model provides a better fit of the data. Furthermore, we find that several local and national variables determine both the number of completions and the average height of skyscrapers, including New York City area population; national employment in finance, insurance and real estate; building costs; access to financing; property tax rates and zoning regulations.Skyscrapers, building cycles, building height, Manhattan,New York City, myopic expectations, rational expectations
Improvements in sparse matrix operations of NASTRAN
A "nontransmit" packing routine was added to NASTRAN to allow matrix data to be refered to directly from the input/output buffer. Use of the packing routine permits various routines for matrix handling to perform a direct reference to the input/output buffer if data addresses have once been received. The packing routine offers a buffer by buffer backspace feature for efficient backspacing in sequential access. Unlike a conventional backspacing that needs twice back record for a single read of one record (one column), this feature omits overlapping of READ operation and back record. It eliminates the necessity of writing, in decomposition of a symmetric matrix, of a portion of the matrix to its upper triangular matrix from the last to the first columns of the symmetric matrix, thus saving time for generating the upper triangular matrix. Only a lower triangular matrix must be written onto the secondary storage device, bringing 10 to 30% reduction in use of the disk space of the storage device
Metallicity Gradients at Large Galactocentric Radii Using the Near-infrared Calcium Triplet
We describe a new spectroscopic technique for measuring radial metallicity
gradients out to large galactocentric radii. We use the DEIMOS multi-object
spectrograph on the Keck telescope and the galaxy spectrum extraction technique
of Proctor et al. (2009). We also make use of the metallicity sensitive
near-infrared (NIR) Calcium triplet (CaT) features together with single stellar
population models to obtain metallicities. Our technique is applied as a pilot
study to a sample of three relatively nearby (<30 Mpc) intermediate-mass to
massive early-type galaxies. Results are compared with previous literature
inner region values and generally show good agreement. We also include a
comparison with profiles from dissipational disk-disk major merger simulations.
Based on our new extended metallicity gradients combined with other
observational evidence and theoretical predictions, we discuss possible
formation scenarios for the galaxies in our sample. The limitations of our new
technique are also discussed.Comment: 13 Pages, 9 Figures, 7 Tables, Accepted for publication in MNRA
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