22,950 research outputs found
Insertion Heuristics for Central Cycle Problems
A central cycle problem requires a cycle that is
reasonably short and keeps a the maximum distance
from any node not on the cycle to its nearest
node on the cycle reasonably low. The objective
may be to minimise maximumdistance or cycle
length and the solution may have further constraints.
Most classes of central cycle problems
are NP-hard. This paper investigates insertion
heuristics for central cycle problems, drawing on
insertion heuristics for p-centres [7] and travelling
salesman tours [21]. It shows that a modified
farthest insertion heuristic has reasonable worstcase
bounds for a particular class of problem.
It then compares the performance of two farthest
insertion heuristics against each other and
against bounds (where available) obtained by integer
programming on a range of problems from
TSPLIB [20]. It shows that a simple farthest insertion
heuristic is fast, performs well in practice
and so is likely to be useful for a general problems
or as the basis for more complex heuristics
for specific problems
NICHE: The Non-Imaging CHErenkov Array
The accurate measurement of the Cosmic Ray (CR) nuclear composition around
and above the Knee (~ 10^15.5 eV) has been difficult due to uncertainties
inherent to the measurement techniques and/or dependence on hadronic Monte
Carlo simulation models required to interpret the data. Measurement of the
Cherenkov air shower signal, calibrated with air fluorescence measurements,
offers a methodology to provide an accurate measurement of the nuclear
composition evolution over a large energy range. NICHE will use an array of
widely-spaced, non-imaging Cherenkov counters to measure the amplitude and
time-spread of the air shower Cherenkov signal to extract CR nuclear
composition measurements and to cross-calibrate the Cherenkov energy and
composition measurements with TA/TALE fluorescence and surface detector
measurements.Comment: 6 pages, 5 figures, to be published in the Proceedings of the
Centenary Symposium 2012:Discovery of Cosmic Rays (University of Denver, June
26-28, 2012), AIP Conference Proceedings, Editor Jonathan F. Ormes, in Pres
The Legal Road To Replicating Silicon Valley
Must policymakers seeking to replicate the success of Silicon Valleyâs venture capital market first replicate other US institutions, such as deep and liquid stock markets? Or can legal reforms alone make a significant difference? In this paper, we compare the economic and legal determinants of venture capital investment, fundraising and exits. We introduce a cross-sectional and time series empirical analysis across 15 countries and 13 years of data spanning an entire business cycle. We show that the legal environment matters as much as the strength of stock markets; that government programmes more often hinder than help the development of private equity, and that temperate bankruptcy laws stimulate entrepreneurial demand for venture capital. Our results provide generalizable lessons for legal reform.venture capital, law and finance, bankruptcy
Bankruptcy Law and Entrepreneurship
Entrepreneurs, catalysts for innovation in the economy, are increasingly the object of policymakersâ attention. Recent initiatives both in the UK and at EU level have sought to promote entrepreneurship by reducing the harshness of the consequences of personal bankruptcy law. Whilst there is an intuitive link between the two, little attention has been paid to the question empirically. We investigate the link between bankruptcy and entrepreneurship using data on self employment over 13 years (1990-2002) and 15 countries in Europe and North America. We compile a new index of the level of how âforgivingâ personal bankruptcy laws are, reflecting the time to discharge. This measure varies over time and across the countries studied. We show that bankruptcy law has a more statistically and economically significant effect on self employment rates relative to GDP growth, MSCI stock returns, and a variety of other legal and economic factors. The results have clear implications for policymakers.Personal Bankruptcy Law, Entrepreneurship
Fishes of the Mountain Province Section of the Ouachita River
A survey of the fishes of the mountain province section of the Ouachita River from the headwaters to Remmel Dam using field collections, literature records, and museum collections showed the ichthyofauna to be made up of 80 species representing 16 families. Fourteen species not previously reported from the mountain province section of the river were collected in this survey. These species include Ichthyomyzon gagei, Nocomis asper, Notropis ortenburgeri, N. rubellus, Pimephales promelas, Moxostoma carinatum, Noturus taylori, Fundulus notatus, Lepomis humilis, Etheostoma histrio, E. proeliare, Percina maculata, P. nasuta, and P. uranidea. The Nocomis specimens were the first collected from the Ouachita River system and the discovery of Noturus taylori represents a major range extension
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