1,657 research outputs found
Dynamic Demand-Capacity Balancing for Air Traffic Management Using Constraint-Based Local Search: First Results
Using constraint-based local search, we effectively model and efficiently
solve the problem of balancing the traffic demands on portions of the European
airspace while ensuring that their capacity constraints are satisfied. The
traffic demand of a portion of airspace is the hourly number of flights planned
to enter it, and its capacity is the upper bound on this number under which
air-traffic controllers can work. Currently, the only form of demand-capacity
balancing we allow is ground holding, that is the changing of the take-off
times of not yet airborne flights. Experiments with projected European flight
plans of the year 2030 show that already this first form of demand-capacity
balancing is feasible without incurring too much total delay and that it can
lead to a significantly better demand-capacity balance
New insights into the structure of early-type galaxies: the Photometric Plane at z~0.3
We study the Photometric Plane (PHP), namely the relation between the
effective radius re, the mean surface brightness within that radius e, and
the Sersic index n, in optical (R and I) and near-infrared (K) bands for a
large sample of early-type galaxies (ETGs) in the rich cluster MS1008-1224 at
z=0.306. The PHP relation has an intrinsic dispersion of ~32% in re, and turns
out to be independent of waveband. This result is consistent with the fact that
internal colour gradients of ETGs can have only a mild dependence on galaxy
luminosity (mass). There is no evidence for a significant curvature in the PHP.
We show that this can be explained if this relation origins from a systematic
variation of the specific entropy of ETGs along the galaxy sequence, as was
suggested from previous works. The intrinsic scatter of the PHP is
significantly smaller than for other purely photometric relations, such as the
Kormendy relation and the photometric Fundamental Plane, which is constructed
by using colours in place of velocity dispersions. The scatter does not depend
on the waveband and the residuals about the plane do not correlate with
residuals of the colour-magnitude relation. Finally, we compare the
coefficients of the PHP at z~0.3 with those of ETGs at z~0, showing that the
PHP is a valuable tool to constrain the luminosity evolution of ETGs with
redshift. The slopes of the PHP do not change significantly with redshift,
while the zero-point is consistent with cosmological dimming of the surface
brightness in an expanding universe plus the passive fading of galaxy stellar
populations with a high formation redshift (z_f >1-2).Comment: 21 pages, 10 figures, MNRAS in pres
Scaling properties of velocity and temperature spectra above the surface friction layer in a convective atmospheric boundary layer
International audienceWe report velocity and temperature spectra measured at nine levels from 1.42 meters up to 25.7 m over a smooth playa in Western Utah. Data are from highly convective conditions when the magnitude of the Obukhov length (our proxy for the depth of the surface friction layer) was less than 2 m. Our results are somewhat similar to the results reported from the Minnesota experiment of Kaimal et al. (1976), but show significant differences in detail. Our velocity spectra show no evidence of buoyant production of kinetic energy at at the scale of the thermal structures. We interpret our velocity spectra to be the result of outer eddies interacting with the ground, not "local free convection". We observe that velocity spectra represent the spectral distribution of the kinetic energy of the turbulence, so we use energy scales based on total turbulence energy in the convective boundary layer (CBL) to collapse our spectra. For the horizontal velocity spectra this scale is (zi ?o)2/3, where zi is inversion height and ?o is the dissipation rate in the bulk CBL. This scale functionally replaces the Deardorff convective velocity scale. Vertical motions are blocked by the ground, so the outer eddies most effective in creating vertical motions come from the inertial subrange of the outer turbulence. We deduce that the appropriate scale for the peak region of the vertical velocity spectra is (z ?o)2/3 where z is height above ground. Deviations from perfect spectral collapse under these scalings at large and small wavenumbers are explained in terms of the energy transport and the eddy structures of the flow. We find that the peaks of the temperature spectra collapse when wavenumbers are scaled using (z1/2 zi1/2). That is, the lengths of the thermal structures depend on both the lengths of the transporting eddies, ~9z, and the progressive aggregation of the plumes with height into the larger-scale structures of the CBL. This aggregation depends, in top-down fashion, on zi. The whole system is therefore highly organized, with even the smallest structures conforming to the overall requirements of the whole flow
Toward an automaton Constraint for Local Search
We explore the idea of using finite automata to implement new constraints for
local search (this is already a successful technique in constraint-based global
search). We show how it is possible to maintain incrementally the violations of
a constraint and its decision variables from an automaton that describes a
ground checker for that constraint. We establish the practicality of our
approach idea on real-life personnel rostering problems, and show that it is
competitive with the approach of [Pralong, 2007]
Cloud-based learning system for improving students’ programming skills and self-efficacy
Cloud-based Learning Systems (CBLS) refers to the systems that
provide electronic or online content to enable the learning process
by offering tools and functionalities through platform available
in Cloud. This research seeks to examine the effectiveness of
CBLS in improving programming skills among undergraduate
students by measuring students’ performance in solving
programming problems. This is because there is no empirical
evidence on the effectiveness of CBLS when compared with
the traditional method of learning programming among student
beginners. Traditionally, teaching programming courses has been
performed in a classroom setting and it can be very challenging
for an instructor to go beyond covering the language’s syntax
such as program design skills and problem-solving skills due
to the wide variety of students’ background in such bounded
class duration. In this study, three single-subject experiments
were conducted using 40 undergraduate students enrolled in
Web Programming course. The experiments compared the time
students spent to solve programming tasks by using traditional
learning method and CBLS. A survey to measure students’ selfefficacy was administered before and after the experiments. The findings of this study showed that there is a statistically significant
difference in learning programming using CBLS when compared
with traditional method. Our results showed that students solve
programming problems in less time when using CBLS. The study
also found out that CBLS is effective for improving students’
self-efficacy
"$29,000,000,000,000: A Detailed Look at the Fed's Bailout by Funding Facility and Recipient"
There have been a number of estimates of the total amount of funding provided by the Federal Reserve to bail out the financial system. For example, Bloomberg recently claimed that the cumulative commitment by the Fed (this includes asset purchases plus lending) was 29 trillion.Global Financial Crisis; Fed Bailout; Lender of Last Resort; Term Auction Facility; Central Bank Liquidity Swaps; Single Tranche Open Market Operation; Term Securities Lending Facility and Term Options Program; Maiden Lane; Primary Dealer Credit Facility; Asset-backed Commercial Paper Money Market Mutual Fund Liquidity Facility; Commercial Paper Funding Facility; Term Asset-backed Securities Loan Facility; Agency Mortgage-backed Security Purchase Program; AIG Revolving Credit Facility; AIG Securities Borrowing Facility
Novel pathway for corrinoid compounds production in lactobacillus
Vitamin B12 or cobalamin is an essential metabolite for humans, which makes it an interesting compound for many research groups that focus in different producer-strains synthesis pathways. In this work, we report the influence of key intermediaries for cobalamin synthesis added to the culture medium in two Lactobacillus (L.) strains, L. reuteri CRL 1098 and L. coryniformis CRL 1001. Here, we report that addition of Co2+ and 5,6-dimethylbenzimidazole increased the corrinoid compounds production in both strains while addition of L-threonine increased only the corrinoid compounds production by CRL 1001 strain. Then, we purified and characterized by LC-MS the corrinoid compounds obtained. Physiological studies besides in silico analysis revealed that L. reuteri CRL 1098 and L. coryniformis CRL 1001 follow different pathways for the last steps of the corrinoid compounds synthesis.Fil: Torres, Andrea Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Vannini, María Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Font, Graciela Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia; ArgentinaFil: Saavedra, Maria Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Taranto, Maria Pia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentin
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