2,769 research outputs found
Local-Search Based Heuristics for Advertisement Scheduling
In the MAXSPACE problem, given a set of ads A, one wants to place a subset A'
of A into K slots B_1, ..., B_K of size L. Each ad A_i in A has size s_i and
frequency w_i. A schedule is feasible if the total size of ads in any slot is
at most L, and each ad A_i in A' appears in exactly w_i slots. The goal is to
find a feasible schedule that maximizes the space occupied in all slots. We
introduce MAXSPACE-RDWV, a MAXSPACE generalization with release dates,
deadlines, variable frequency, and generalized profit. In MAXSPACE-RDWV each ad
A_i has a release date r_i >= 1, a deadline d_i >= r_i, a profit v_i that may
not be related with s_i and lower and upper bounds w^min_i and w^max_i for
frequency. In this problem, an ad may only appear in a slot B_j with r_i <= j
<= d_i, and the goal is to find a feasible schedule that maximizes the sum of
values of scheduled ads. This paper presents some algorithms based on
meta-heuristics GRASP, VNS, Local Search, and Tabu Search for MAXSPACE and
MAXSPACE-RDWV. We compare our proposed algorithms with Hybrid-GA proposed by
Kumar et al. (2006). We also create a version of Hybrid-GA for MAXSPACE-RDWV
and compare it with our meta-heuristics. Some meta-heuristics, such as VNS and
GRASP+VNS, have better results than Hybrid-GA for both problems. In our
heuristics, we apply a technique that alternates between maximizing and
minimizing the fullness of slots to obtain better solutions. We also applied a
data structure called BIT to the neighborhood computation in MAXSPACE-RDWV and
showed that this enabled ours algorithms to run more iterations
Approximation algorithms for the MAXSPACE advertisement problem
In the MAXSPACE problem, given a set of ads A, one wants to schedule a subset
A' of A into K slots B_1, ..., B_K of size L. Each ad A_i in A has a size s_i
and a frequency w_i. A schedule is feasible if the total size of ads in any
slot is at most L, and each ad A_i in A' appears in exactly w_i slots. The goal
is to find a feasible schedule that maximizes the sum of the space occupied by
all slots. We introduce a generalization called MAXSPACE-R in which each ad A_i
also has a release date r_i >= 1, and may only appear in a slot B_j with j >=
r_i. We also introduce a generalization of MAXSPACE-R called MAXSPACE-RD in
which each ad A_i also has a deadline d_i <= K, and may only appear in a slot
B_j with r_i <= j <= d_i. These parameters model situations where a subset of
ads corresponds to a commercial campaign with an announcement date that may
expire after some defined period. We present a 1/9-approximation algorithm for
MAXSPACE-R and a polynomial-time approximation scheme for MAXSPACE-RD when K is
bounded by a constant. This is the best factor one can expect, since MAXSPACE
is NP-hard, even if K = 2
Composição florística e parâmetros fitossociólogicos de floresta densa de terra firme da Amazônia em área de manejo e exploração madeireira em Silves, AM.
Euclid: Superluminous supernovae in the Deep Survey
Context. In the last decade, astronomers have found a new type of supernova called superluminous supernovae (SLSNe) due to their high peak luminosity and long light-curves. These hydrogen-free explosions (SLSNe-I) can be seen to z ~ 4 and therefore, offer the possibility of probing the distant Universe.
Aims. We aim to investigate the possibility of detecting SLSNe-I using ESA’s Euclid satellite, scheduled for launch in 2020. In particular, we study the Euclid Deep Survey (EDS) which will provide a unique combination of area, depth and cadence over the mission.
Methods. We estimated the redshift distribution of Euclid SLSNe-I using the latest information on their rates and spectral energy distribution, as well as known Euclid instrument and survey parameters, including the cadence and depth of the EDS. To estimate the uncertainties, we calculated their distribution with two different set-ups, namely optimistic and pessimistic, adopting different star formation densities and rates. We also applied a standardization method to the peak magnitudes to create a simulated Hubble diagram to explore possible cosmological constraints.
Results. We show that Euclid should detect approximately 140 high-quality SLSNe-I to z ~ 3.5 over the first five years of the mission (with an additional 70 if we lower our photometric classification criteria). This sample could revolutionize the study of SLSNe-I at z > 1 and open up their use as probes of star-formation rates, galaxy populations, the interstellar and intergalactic medium. In addition, a sample of such SLSNe-I could improve constraints on a time-dependent dark energy equation-of-state, namely w(a), when combined with local SLSNe-I and the expected SN Ia sample from the Dark Energy Survey.
Conclusions. We show that Euclid will observe hundreds of SLSNe-I for free. These luminous transients will be in the Euclid data-stream and we should prepare now to identify them as they offer a new probe of the high-redshift Universe for both astrophysics and cosmology.Acknowledgements. We thank the internal EC referees (P. Nugent and J.
Brichmann) as well as the many comments from our EC colleagues and friends.
C.I. thanks Chris Frohmaier and Szymon Prajs for useful discussions about
supernova rates. C.I. and R.C.N. thank Mark Cropper for helpful information
about the V IS instrument. C.I. thanks the organisers and participants of the
Munich Institute for Astro- and Particle Physics (MIAPP) workshop “Superluminous supernovae in the next decade” for stimulating discussions and the
provided online material. The Euclid Consortium acknowledges the European
Space Agency and the support of a number of agencies and institutes that
have supported the development of Euclid. A detailed complete list is available on the Euclid web site (http://www.euclid-ec.org). In particular the
Agenzia Spaziale Italiana, the Centre National dEtudes Spatiales, the Deutsches
Zentrum für Luft- and Raumfahrt, the Danish Space Research Institute, the Fundação para a Ciênca e a Tecnologia, the Ministerio de Economia y Competitividad, the National Aeronautics and Space Administration, The Netherlandse
Onderzoekschool Voor Astronomie, the Norvegian Space Center, the Romanian
Space Agency, the State Secretariat for Education, Research and Innovation
(SERI) at the Swiss Space Office (SSO), the United Kingdom Space Agency,
and the University of Helsinki. R.C.N. acknowledges partial support from the
UK Space Agency. D.S. acknowledges the Faculty of Technology of the University of Portsmouth for support during his PhD studies. C.I. and S.J.S. acknowledge funding from the European Research Council under the European
Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant agreement No. [291222]. C.I. and M.S. acknowledge support from EU/FP7-ERC
grant No. [615929]. E.C. acknowledge financial contribution from the agreement ASI/INAF/I/023/12/0. The work by KJ and others at MPIA on NISP was
supported by the Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR) under
grant 50QE1202. M.B. and S.C. acknowledge financial contribution from the
agreement ASI/INAF I/023/12/1. R.T. acknowledges funding from the Spanish
Ministerio de Economía y Competitividad under the grant ESP2015-69020-C2-
2-R. I.T. acknowledges support from Fundação para a Ciência e a Tecnologia
(FCT) through the research grant UID/FIS/04434/2013 and IF/01518/2014. J.R.
was supported by JPL, which is run under a contract for NASA by Caltech and
by NASA ROSES grant 12-EUCLID12-0004
O laboratório científico escolar e a questão do sistema educacional
ESTE TRABALHO INVESTIGA A SITUAÇÃO MATERIAL DOS LABORATÓRIOS DIDÁTICOS, PARA O ENSINO DE CIÊNCIAS, NAS ESCOLAS DO MUNICÍPIO DE SÃO CARLOS (SP), ADOTANDO COMO REFERENCIAL TEÓRICO A PEDAGOGIA HISTÓRICO-CRÍTICA. DAS 17 ESCOLAS DESTA LOCALIDADE COM O OFERECIMENTO DO ENSINO MÉDIO REGULAR DA REDE ESTADUAL, APENAS 8 DELAS DISPÕEM DE LABORATÓRIOS CIENTÍFICOS. NESTAS OITO, REALIZAMOS UMA COLETA DE DADOS VIABILIZADA PELA VISITA A CADA ESTABELECIMENTO, RECORRENDO A OBSERVAÇÕES ESTRUTURADAS, NOTAS DE CAMPO E REGISTROS FOTOGRÁFICOS. DOIS PESQUISADORES QUE COORDENARAM PROJETOS RELACIONADOS AOS LABORATÓRIOS CIENTÍFICOS DIDÁTICOS DA CIDADE CEDERAMDEPOIMENTOS EM ENTREVISTAS SEMI-ESTRUTURADAS. UMA ANÁLISE DOCUMENTAL COMPLETOU ESTES PROCEDIMENTOS. ESTES PRIMEIROS RESULTADOS MOSTRAM A SITUAÇÃO DE DIFICULDADES, ATRAVESSADA PELAS ESCOLAS, QUANTO À MANUTENÇÃO DE SEUS LABORATÓRIOS, E EXPLORA ALGUNS PROBLEMAS, QUE INCIDEM SOBRE ESTA QUESTÃO, DECORRENTES DA INEXISTÊNCIA DE UM SISTEMA EDUCACIONAL NO NÍVEL ESTADUA
Key Aspects for Implementing ISO/IEC 17025 Quality Management Systems at Materials Science Laboratories
Implementing a quality management system based on the requirements specified in ISO/IEC 17025 standard at materials science laboratories is challenging, mainly due to two main factors: (i) the high technical complexity degree of some tests used for materials characterization and (ii) the fact that most materials science laboratories provide materials characterization tests and also carry out research and development activities. In this context, this chapter presents key subjects while implementing a quality management system at materials science laboratories and some considerations on strategies for effectively implementing such systems
Effect of 4-nerolidilcatecol of Pothomorphe umbellata in the chromosomes of Aedes aegypti from Manaus, Amazonas State.
Aedes aegypti is a mosquito with significant importance for public health, due to its vector competence for arbovirus transmission. Among these, the most important in Brazil are the viruses that cause Dengue, Yellow Fever and Chikungunya Fever. Natural plant-based compounds have been shown to be new alternatives for controlling medically important insect vectors with known resistance to synthetic insecticides. Objective: To determine the toxic and genotoxic effects of 4-nerolidilcatechol (4-NC) from Pothomorphe umbellata on larvae and adult females of A. aegypti
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