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

What cost reslience?

Air traffic management research lacks a framework for modelling the cost of resilience during disturbance. There is no universally accepted metric for cost resilience. The design of such a framework is presented and the modelling to date is reported. The framework allows performance assessment as a function of differential stakeholder uptake of strategic mechanisms designed to mitigate disturbance. Advanced metrics, cost- and non-cost-based, disaggregated by stakeholder subtypes, will be deployed. A new cost resilience metric is proposed

CASSIOPEIA II D3.2 - Final technical report

The FlightPath 2050 presents Europe’s Vision for Aviation for the future. In what refers to air traffic management, this vision includes concrete goals for the punctuality of flights and capacity of the air traffic management system. Additionally, the document adds a concrete goal in what refers to passenger mobility, stating that 90% of the passengers should be able to travel door-to-door in Europe within 4 hours. Passenger mobility is obviously the ultimate goal of the air transport system, which mission is to transport passengers and freight, not airplanes. However, punctuality is currently mostly measured as aircraft operations performance. Moreover, most air traffic management technology improvements are targeting aircraft punctuality and not passenger punctuality. Passenger punctuality depends critically on passenger connectivity, as a missed connection impacts very negatively in passenger mobility performance. Increasing the predictability of air transport operations has limits. Not only meteorological conditions can affect the punctuality but also countless operational hazards impact the air traffic management system. Making the system adaptable to changes in the operational conditions, capable of re-configuring itself to accommodate to a new scenario seems a better approach than trying to make the system robust, which ultimately could be too expensive or impossible. Studying how different mechanisms improve the adaptability of the system is a complex problem. On one hand, it is a challenge to design a procedure that provides adaptability without impacting other performance metrics of the system. On the other hand, complex mechanisms usually require dedicated simulation frameworks, capable of modelling realistically a large number of parameters as well as providing a performance framework capable of evaluating in detail (e.g. beyond simple statistical properties) how the system adapts to the new conditions and how those mechanisms target a performance goal. The CASSIOPEIA DCI-4HD2D project extension studied how changing the trajectory of each aircraft to either minimise fuel consumption or to minimise time to destination can be used as a adaptability mechanism, to work together with other ATM improvements, to address passenger connectivity. Understanding how this mechanism, known as Dynamic Cost Indexing (DCI), increases the adaptability of the system, required the analysis, design and implementation of a complex software system as a collection of interacting, autonomous agents. This document reports on the cases of study selected and the analysis of the outcome of the simulations performed, assessing how DCI contributes to passenger connectivity and, ultimately, to passenger mobility improvement

Calculation of Raman optical activity spectra for vibrational analysis

By looking back on the history of Raman Optical Activity (ROA), the present article shows that the success of this analytical technique was for a long time hindered, paradoxically, by the deep level of detail and wealth of structural information it can provide. Basic principles of the underlying theory are discussed, to illustrate the technique's sensitivity due to its physical origins in the delicate response of molecular vibrations to electromagnetic properties. Following a short review of significant advances in the application of ROA by UK researchers, we dedicate two extensive sections to the technical and theoretical difficulties that were overcome to eventually provide predictive power to computational simulations in terms of ROA spectral calculation. In the last sections, we focus on a new modelling strategy that has been successful in coping with the dramatic impact of solvent effects on ROA analyses. This work emphasises the role of complementarity between experiment and theory for analysing the conformations and dynamics of biomolecules, so providing new perspectives for methodological improvements and molecular modelling development. For the latter, an example of a next-generation force-field for more accurate simulations and analysis of molecular behaviour is presented. By improving the accuracy of computational modelling, the analytical capabilities of ROA spectroscopy will be further developed so generating new insights into the complex behaviour of molecules

The Raman optical activity of β-D-xylose: where experiment and theory meet

Besides its applications in bioenergy and biosynthesis, β-D-xylose is a very simple monosaccharide that exhibits relatively high rigidity. As such, it provides the best basis to study the impact of different solvation shell radii on the computation of its Raman optical activity (ROA) spectrum. Indeed, this chiroptical spectroscopic technique provides exquisite sensitivity to stereochemistry, and benefits much from theoretical support for interpretation. Our simulation approach combines density functional theory (DFT) and molecular dynamics (MD) in order to efficiently account for the crucial hydration effects in the simulation of carbohydrates and their spectroscopic response predictions. Excellent agreement between the simulated spectrum and the experiment was obtained with a solvation radius of 10 Å. Vibrational bands have been resolved from the computed ROA data, and compared with previous results on different monosaccharides in order to identify specific structure–spectrum relationships and to investigate the effect of the solvation environment on the conformational dynamics of small sugars. From the comparison with ROA analytical results, a shortcoming of the classical force field used for the MD simulations has been identified and overcome, again highlighting the complementary role of experiment and theory in the structural characterisation of complex biomolecules. Indeed, due to unphysical puckering, a spurious ring conformation initially led to erroneous conformer ratios, which are used as weights for the averaging of the spectral average, and only by removing this contribution was near perfect comparison between theory and experiment achieved

Distinguishing epimers through raman optical activity

The Raman optical activity spectra of the epimers β-d-glucose and β-d-galactose, two monosaccharides of biological importance, have been calculated using molecular dynamics combined with a quantum mechanics/molecular mechanics approach. Good agreement between theoretical and experimental spectra is observed for both monosaccharides. Full band assignments have been carried out, which has not previously been possible for carbohydrate epimers. For the regions where the spectral features are opposite in sign, the differences in the vibrational modes have been noted and ascribed to the band sign changes

Mutagenesis of Trichoderma reesei endoglucanase I: impact of expression host on activity and stability at elevated temperatures.

BackgroundTrichoderma reesei is a key cellulase source for economically saccharifying cellulosic biomass for the production of biofuels. Lignocellulose hydrolysis at temperatures above the optimum temperature of T. reesei cellulases (~50°C) could provide many significant advantages, including reduced viscosity at high-solids loadings, lower risk of microbial contamination during saccharification, greater compatibility with high-temperature biomass pretreatment, and faster rates of hydrolysis. These potential advantages motivate efforts to engineer T. reesei cellulases that can hydrolyze lignocellulose at temperatures ranging from 60-70°C.ResultsA B-factor guided approach for improving thermostability was used to engineer variants of endoglucanase I (Cel7B) from T. reesei (TrEGI) that are able to hydrolyze cellulosic substrates more rapidly than the recombinant wild-type TrEGI at temperatures ranging from 50-70°C. When expressed in T. reesei, TrEGI variant G230A/D113S/D115T (G230A/D113S/D115T Tr_TrEGI) had a higher apparent melting temperature (3°C increase in Tm) and improved half-life at 60°C (t1/2 = 161 hr) than the recombinant (T. reesei host) wild-type TrEGI (t1/2 = 74 hr at 60°C, Tr_TrEGI). Furthermore, G230A/D113S/D115T Tr_TrEGI showed 2-fold improved activity compared to Tr_TrEGI at 65°C on solid cellulosic substrates, and was as efficient in hydrolyzing cellulose at 60°C as Tr_TrEGI was at 50°C. The activities and stabilities of the recombinant TrEGI enzymes followed similar trends but differed significantly in magnitude depending on the expression host (Escherichia coli cell-free, Saccharomyces cerevisiae, Neurospora crassa, or T. reesei). Compared to N.crassa-expressed TrEGI, S. cerevisiae-expressed TrEGI showed inferior activity and stability, which was attributed to the lack of cyclization of the N-terminal glutamine in Sc_TrEGI and not to differences in glycosylation. N-terminal pyroglutamate formation in TrEGI expressed in S. cerevisiae was found to be essential in elevating its activity and stability to levels similar to the T. reesei or N. crassa-expressed enzyme, highlighting the importance of this ubiquitous modification in GH7 enzymes.ConclusionStructure-guided evolution of T. reesei EGI was used to engineer enzymes with increased thermal stability and activity on solid cellulosic substrates. Production of TrEGI enzymes in four hosts highlighted the impact of the expression host and the role of N-terminal pyroglutamate formation on the activity and stability of TrEGI enzymes