An integer programming formulation to allocate series of slots on an airport network

Several authors have introduced mathematical formulations for the airport slot allocation process, and the initial allocation in particular. They mostly replicate the current IATA process, performed on an airport-by- airport basis. However, airports are part of a network. The initial slot allocation should therefore be performed simultaneously at all airports, accounting for flight times to link departures and arrivals. [1] proposes an integer programming formulation to allocate a set of single-day slots on a network of airports. Extending that formulation, this paper additionally models the IATA rule stating that series rather than individual slots are to be allocated. A series of slots includes at least 5 slots at the same time and day-of-the-week, distributed regularly in a season. The objective of the allocation is to minimise airline costs due to the non-allocation of series of slots, their temporal displacement, and the deviation from the requested block or turnaround time for slots of coupled series. Preliminary experiments are based on a network of 152 European airports and consider about 300000 slot requests for seven Fridays of the 2017 summer season. Results quantify the increase of airline costs as a function of congestion. [1] Pellegrini P, Bolic T, Castelli L, Pesenti R, 2017. SOSTA: An effective model for the simultaneous optimisation of airport slot allocation. Transportation Research Part E: Logistics and Transportation Review 99:34-53

Capacity Sharing within Virtual Centre

Airspace Architecture Study proposed the future Single European Airspace System, based on modern technologies that could divide the air traffic service provision from local infrastructure for data provision, enabling the decoupling of geographical location from the service provision. This decoupling would enable virtualisation where service providers could use data from the common data services, opening doors to different organisation of air traffic service provision, namely more advanced capacity sharing. Virtualisation concept is still under development and several recent studies evaluated some aspects of virtualisation in ATM, but did not yet address in detail the impacts of different Virtual Centre implementation scenarios. In this paper, we propose a linear optimisation model to evaluate the impact of virtualisation and capacity sharing in terms of delay reduction. We show that taking into account the current airspace design and air traffic management resources, even the air navigation service providers that accumulate the highest capacity-caused delays could decrease those in the range of 25-50% up to about 80% through internal collaboration. Furthermore, the decrease of over 50% of the total capacity- caused delays could be obtained if FABEC1 were to form a Virtual Centre, and the decrease of about 90% of the total European delay if the Single European Sky (SES) area would form a Virtual Centre. The analysed capacity sharing collaborations indicate the possibility of significant delay reductions, but would not be sufficient, on their own, to eliminate capacity-caused issues in Europe

Phage resistance of acid lactic bacteria isolated from Coalho cheese industries

Este trabalho teve como objetivos isolar bacteriófagos de amostras de leite, soro e queijo de Coalho e avaliar a resistência de cepas de Lactobacillus paracasei, pertencentes à Coleção de Micro-organismos de Interesse para a Agroindústria Tropical da Embrapa Agroindústria Tropical, aos fagos isolados. Posteriormente, a resistência destas cepas a fagos específicos para L. paracasei, da Coleção do Instituto de Lactología Industrial - INLAIN (Santa Fe, Argentina), também foi avaliada. As amostras para isolamento dos fagos foram obtidas em quatro unidades de processamento de queijo de Coalho, sendo duas artesanais e duas industriais, localizadas no Estado do Ceará. Para o isolamento dos bacteriófagos, foi empregado o teste de lise celular (spot), enquanto que a resistência das culturas aos fagos foi avaliada pelos testes de capacidade de produção de ácido e avaliação da turbidez. As cepas avaliadas foram resistentes aos bacteriófagos provenientes das unidades de processamento de queijo de Coalho e aos bacteriófagos da Coleção do INLAIN. Os resultados obtidos indicaram que as culturas láticas testadas, resistentes aos bacteriófagos, podem ser utilizadas na composição de fermento lático destinado à elaboração de queijo de Coalho, a partir de leite pasteurizado.The objectives of this research were to isolate bacteriophages from milk samples, whey and Coalho cheese and to evaluate the resistance of strains of Lactobacillus paracasei from the Collection of Microorganisms of Interest for the Tropical Agroindustry, belonging to Embrapa Tropical Agroindustry, to isolate phages. The strains resistance to specific L. paracasei phages from the collection of the Instituto de Lactolog a Industrial - INLAIN (Santa Fe, Argentina) was also evaluated. Samples for phage isolation were from four Coalho cheese processing units, two artisanal and two industrial, localized in the state of Ceara. Spot test was employed for bacteriophages isolation, while the culture phage resistance was evaluated by the acid production and turbidity tests. The strains were resistant both to phages isolated from Coalho cheese processing units and phages from collection of INLAIN. The results showed that lactic cultures evaluated here were resistant to bacteriophages and they can be used in the composition of lactic cultures specifically for Coalho cheese manufacture from pasteurized milk

The Copernicus Marine Environment Monitoring Service Ocean State Report

The Copernicus Marine Environment Monitoring Service (CMEMS) Ocean State Report (OSR) provides an annual report of the state of the global ocean and European regional seas for policy and decision-makers with the additional aim of increasing general public awareness about the status of, and changes in, the marine environment. The CMEMS OSR draws on expert analysis and provides a 3-D view (through reanalysis systems), a view from above (through remote-sensing data) and a direct view of the interior (through in situ measurements) of the global ocean and the European regional seas. The report is based on the unique CMEMS monitoring capabilities of the blue (hydrography, currents), white (sea ice) and green (e.g. Chlorophyll) marine environment. This first issue of the CMEMS OSR provides guidance on Essential Variables, large-scale changes and specific events related to the physical ocean state over the period 1993–2015. Principal findings of this first CMEMS OSR show a significant increase in global and regional sea levels, thermosteric expansion, ocean heat content, sea surface temperature and Antarctic sea ice extent and conversely a decrease in Arctic sea ice extent during the 1993–2015 period. During the year 2015 exceptionally strong large-scale changes were monitored such as, for example, a strong El Niño Southern Oscillation, a high frequency of extreme storms and sea level events in specific regions in addition to areas of high sea level and harmful algae blooms. At the same time, some areas in the Arctic Ocean experienced exceptionally low sea ice extent and temperatures below average were observed in the North Atlantic Ocean

PHYLOES Un approccio mediante Strategie Evolutive per l'inferenza filogenetica basata sul Balanced Minimum Evolution Criterion

Il Balanced Minimum Evolution (BME) è un potente modello di stima filogenetica basato sulle distanze biologiche fra i genomi, introdotto da Desper e Gascuel e attualmente implementato in efficienti software per le analisi filogenetiche. Il BME è computazionalmente meno impegnativo rispetto a metodi di stima più sofisticati, ad esempio Maximum Likelyhood o inferenza bayesiana, pur conservando la coerenza statistica e la capacità di funzionare con quasi qualsiasi tipo di dati che rappresentano una misura di dissimilarità fra genomi. Il BME può essere formulato in termini di un problema di ottimizzazione combinatoria non lineare e non convessa, denominato Balanced Minimum Evolution Problem (BMEP). Attualmente, lo stato dell’arte tra i metodi approssimati per il BMEP è rappresentato da FastME (versione 2.0), un software che implementa diverse euristiche deterministiche di costruzione filogenetica, combinate con algoritmi di ricerca locale basati sulla manipolazione di alberi filogenetici. Tuttavia, questo approccio, sebbene molto efficiente, non garantisce la convergenza a soluzioni prossime all’ottimo, a causa della mancanza di esplorazione dello spazio delle soluzioni, un fenomeno che si aggrava quando si affrontano insiemi di dati molecolari caratterizzati da un grande numero di taxa. Per ovviare a tali problemi di convergenza, in questo lavoro, proponiamo una nuova metaeuristica, denominata PhyloES, che sfrutta la combinazione di una fase esplorativa, basata su una particolare tipologia di algoritmo evolutivo, denominata Evolution Strategies, con una fase di raffinamento incentrata su due algoritmi di ricerca locale. I nostri esperimenti computazionali mostrano che PhyloES è in grado di superare le prestazioni di FastME, specialmente al crescere delle dimensioni delle istanze, fornendo soluzioni migliori nel senso della funzione obiettivo e significativamente diverse dal punto di vista topologico, fattore di particolare rilevanza dal punto di vista biologico. ​The Balanced Minimum Evolution (BME) is a powerful distance based phylogenetic estimation model introduced by Desper and Gascuel and nowadays implemented in popular tools for phylogenetic analyses. It was proven to be computationally less demanding than more sophisticated estimation methods, e.g. maximum likelihood or Bayesian inference while preserving the statistical consistency and the ability to run with almost any kind of data for which a dissimilarity measure is available. BME can be stated in terms of a nonlinear non-convex combinatorial optimisation problem, usually referred to as the Balanced Minimum Evolution Problem (BMEP). Currently, the state-of-the-art among approximate methods for the BMEP is represented by FastME (version 2.0), a software which implements several deterministic phylogenetic construction heuristics combined with a local search on specific neighbourhoods derived by classical topological tree rearrangements. These combinations, however, may not guarantee convergence to close-to-optimal solutions to the problem due to the lack of solution space exploration, a phenomenon which is exacerbated when tackling molecular datasets characterised by a large number of taxa. To overcome such convergence issues, in this work we propose a novel metaheuristic, named PhyloES, which exploits the combination of an exploration phase based on Evolution Strategies, a special type of evolutionary algorithm, with a refinement phase based on two local search algorithms. Extensive computational experiments show that PhyloES consistently outperforms FastME, especially when tackling larger datasets, providing solutions characterised by a shorter tree length but also significantly different from the topological perspective.

An evolution strategy approach for the Balanced Minimum Evolution Problem

Motivation: The Balanced Minimum Evolution (BME) is a powerful distance based phylogenetic estimation model introduced by Desper and Gascuel and nowadays implemented in popular tools for phylogenetic analyses. It was proven to be computationally less demanding than more sophisticated estimation methods, e.g. maximum likelihood or Bayesian inference, while preserving the statistical consistency and the ability of running with almost any kind of data for which a dissimilarity measure is available. BME can be stated in terms of a nonlinear non-convex combinatorial optimisation problem, usually referred to as the Balanced Minimum Evolution Problem (BMEP). Currently, the state-of-the-art among approximate methods for the BMEP is represented by FastME (version 2.0), a software which implements several deterministic phylogenetic construction heuristics combined with a local search on specific neighbourhoods derived by classical topological tree rearrangements. These combinations, however, may not guarantee convergence to close-to-optimal solutions to the problem due to the lack of solution space exploration, a phenomenon which is exacerbated when tackling molecular datasets characterised by a large number of taxa. Results: To overcome such convergence issues, in this article we propose a novel metaheuristic, named PhyloES, which exploits the combination of an exploration phase based on Evolution Strategies, a special type of evolutionary algorithm, with a refinement phase based on two local search algorithms. Extensive computational experiments show that PhyloES consistently outperforms FastME, especially when tackling larger datasets, providing solutions characterised by a shorter tree length but also significantly different from the topological perspective

An evolution strategy approach for the balanced minimum evolution problem

Motivation: The Balanced Minimum Evolution (BME) is a powerful distance based phylogenetic estimation model introduced by Desper and Gascuel and nowadays implemented in popular tools for phylogenetic analyses. It was proven to be computationally less demanding than more sophisticated estimation methods, e.g. maximum likelihood or Bayesian inference while preserving the statistical consistency and the ability to run with almost any kind of data for which a dissimilarity measure is available. BME can be stated in terms of a nonlinear non-convex combinatorial optimization problem, usually referred to as the Balanced Minimum Evolution Problem (BMEP). Currently, the state-of-the-art among approximate methods for the BMEP is represented by FastME (version 2.0), a software which implements several deterministic phylogenetic construction heuristics combined with a local search on specific neighbourhoods derived by classical topological tree rearrangements. These combinations, however, may not guarantee conver- gence to close-to-optimal solutions to the problem due to the lack of solution space exploration, a phenomenon which is exacerbated when tackling molecular datasets characterized by a large number of taxa. Results: To overcome such convergence issues, in this article, we propose a novel metaheuristic, named PhyloES, which exploits the combination of an exploration phase based on Evolution Strategies, a special type of evolutionary algorithm, with a refinement phase based on two local search algorithms. Extensive computational experiments show that PhyloES consistently outperforms FastME, especially when tackling larger datasets, providing solutions characterized by a shorter tree length but also significantly different from the topological perspective

Influence of dry friction on the irreversibility of cycloidal speed reducer

Gears with involute profile have been used broadly as power transmission mechanisms. High speed reduction ratios can be obtained with trains of gears, resulting in high power losses due to friction. Compound planetary gears allow obtaining high speed reduction ratios with a lower number of gears involved in the power transmission, hence transmitting it with higher efficiency. Although high efficiency is a main requisite for speed reducers, for some applications it may be desirable to have an irreversible mechanism. A modern trend in power transmission systems is to use cycloidal profile gears. These systems present low backlash, high load capability and higher efficiency due to the rolling motion. Furthermore, their large transmission ratio in single stage allows more compact designs. The present paper deals with the development of a simplified model for the calculation of efficiency of cycloidal speed reducers. The followed approach takes into account the main parameters influencing the efficiency, in particular, the friction and the geometrical properties of the components. The resulting model is used to investigate the relation among efficiency and reduction ratio in order to define the conditions for the irreversibility. A test bench is developed for the validation of the results