Multi-core computation of transfer matrices for strip lattices in the Potts model

The transfer-matrix technique is a convenient way for studying strip lattices in the Potts model since the compu- tational costs depend just on the periodic part of the lattice and not on the whole. However, even when the cost is reduced, the transfer-matrix technique is still an NP-hard problem since the time T(|V|, |E|) needed to compute the matrix grows ex- ponentially as a function of the graph width. In this work, we present a parallel transfer-matrix implementation that scales performance under multi-core architectures. The construction of the matrix is based on several repetitions of the deletion- contraction technique, allowing parallelism suitable to multi-core machines. Our experimental results show that the multi-core implementation achieves speedups of 3.7X with p = 4 processors and 5.7X with p = 8. The efficiency of the implementation lies between 60% and 95%, achieving the best balance of speedup and efficiency at p = 4 processors for actual multi-core architectures. The algorithm also takes advantage of the lattice symmetry, making the transfer matrix computation to run up to 2X faster than its non-symmetric counterpart and use up to a quarter of the original space

Temporal disorder in up-down symmetric systems

The effect of temporal disorder on systems with up-down Z2 symmetry is studied. In particular, we analyze two well-known families of phase transitions: the Ising and the generalized voter universality classes, and scrutinize the consequences of placing them under fluctuating global conditions. We observe that variability of the control parameter induces in both classes "Temporal Griffiths Phases" (TGP). These recently-uncovered phases are analogous to standard Griffiths Phases appearing in systems with quenched spatial disorder, but where the roles of space and time are exchanged. TGPs are characterized by broad regions in parameter space in which (i) mean first-passage times scale algebraically with system size, and (ii) the system response (e.g. susceptibility) diverges. Our results confirm that TGPs are quite robust and ubiquitous in the presence of temporal disorder. Possible applications of our results to examples in ecology are discussed

Discriminacion a un martir: The ballad of Felix Longoria

This thesis looks at how the Felix Longoria Affair propelled Hector P. Garcia, Lyndon B. Johnson and the American G.I. Forum into the national limelight, while also leaving the Longorias, Three Rivers and Texas in a state of disrepair. The affair in general helped expose injustices that were occurring to Mexicans American in Texas at the time, but left the family, Three Rivers and Texas in a battle over the legacy of how each would be seen in the annals of history

Controller time and delay costs - a trade-off analysis

Air traffic controller shortages remain a significant challenge in European ATM. Comparing different rules, we quantify the cost effectiveness of adding controller hours to Area Control Centre regulations to avert the delay cost impact on airlines. Typically, adding controller hours results in a net benefit. Distributions of delay duration and aircraft weight play an important role in determining the total cost of a regulation. Errors are likely to be incurred when analysing performance based on average delay values, particularly at the disaggregate level

Yeast as a production platform in biorefineries: conversion of agricultural residues into value-added products

ArticleIn contrast to a petroleum - based economy, which relies on the unlimited presence of fossi l fuels, a biobased economy utilizes a broad spectrum of natural crops and biomass as raw substrates for the production of valuable materials. Biorefineries represent a promising approach for the co - production of bioenergy (biofuels, biogas) and value - adde d products (biochemicals, biomaterials, food). Within Europe, wheat straw represents the major crop residue and has been extensively considered as a promising feedstock in the biorefining process. Firstly, wheat straw is hydrolysed to obtain a sugar soluti on that is further converted into the desired product in a biocatalytic manner. Microbial fermentation is the core component of biorefineries and yeast, as for instance Candida guilliermondii , is an effective production platform for both, biofuels and bioc hemicals. One limiting aspect in using yeast in the biorefinery approach is the presence of inhibitors in lignocellulosic hydrolysates, such as acetic acid or furfural, influencing cellular growth and diverse metabolic processes. In order to overcome this problem, several genetic engineering approaches are used to increase yeast resistance towards these inhibitors and to enhance the overall production. In this paper, we summarized: 1) the pretreatment technologies for wheat straw bioconversion; 2) the Candi da guilliermondii genetic engineering technologies and their biotechnological potential. In conclusion, biorefineries are a crucial factor in the transition towards a biobased and circular economy, and the implementation of yeast into this system offers a great opportunity to develop innovative strategies for a sustainable production in an environmentally friendly and economically feasible manner

Study on the Modelling of Airport Economic Value

The primary objective of the Airport Economic Value project is to assess the value of additional passengers or additional capacity at an airport. It aims to qualify and quantify the main relationships and trade-offs between capacity, quality of service and profitability. This study provides a better understanding of the interdependencies of various KPIs and assesses the existence and behaviour of an airport economic optimum, in a similar way to the early 2000s, when estimating the economic en-route capacity optimum

Factors influencing European passenger demand for air transport

Passenger air travel demand is influenced by various factors and is crucial to manufacturers, airlines, airports and wider industry. In order to gain detailed insights into drivers of European air transport demand, five factors are analysed, both quantitatively and qualitatively. Focusing on the European air transport market, a detailed description of factors influencing air transport demand serves as input for a statistical analysis. Data from European countries on the gross domestic product per capita (GDP), urbanisation levels, the geographical location of a country, and the degree of education is used for the model. These explanatory variables are tested using a regression analysis in regard to their influence on the passengers’ demand for air transport. Results from the regression analysis reveal that the factors GDP, the geographical location of a country and the level of education are statistically significant, confirming GDP as a demand driver already examined within various studies that also include other factors as explanatory variables. Results also indicate the dynamics between the different factors, such as the positive relationship between income and level of education. Present studies are a good basis to show what drives demand, often focused at a global or country level. This analysis also confirms the essential determinants at a European level

Hub operations delay recovery based on cost optimisation - Dynamic cost indexing and waiting for passengers strategies

In this paper, two strategies for airlines’ operations at a hub are combined and analysed: dynamic cost indexing, to recover delay, and waiting for connecting passengers at the hub. Agent Based Modelling techniques have been used to model the airlines’ operations considering detailed passenger’s itineraries, an extended arrival manager operation with slot negotiation, and delay and uncertainty at different phases of the flights. Results show that, when optimising the total cost, there is a trade-off between connecting and non-connecting passengers with respect to the gate to gate trip time. Waiting for passengers arises as an interesting technique when minimising airline operating costs