Probabilistic Airline Reserve Crew Scheduling Model

This paper introduces a probabilistic model for airline reserve crew scheduling. The model can be applied to any schedules which consist of a stream of departures from a single airport. We assume that reserve crew demand can be captured by an independent probability of crew absence for each departure. The aim of our model is to assign some fixed number of available reserve crew in such a way that the overall probability of crew unavailability in an uncertain operating environment is minimised. A comparison of different probabilistic objective functions, in terms of the most desirable simulation results, is carried out, complete with an interpretation of the results. A sample of heuristic solution methods are then tested and compared to the optimal solutions on a set of problem instances, based on the best objective function found. The current model can be applied in the early planning phase of reserve crew scheduling, when very little information is known about crew absence related disruptions. The main conclusions include the finding that the probabilistic objective function approach gives solutions whose objective values correlate strongly with the results that these solutions will get on average in repeated simulations. Minimisation of the sum of the probabilities of crew unavailability was observed to be the best surrogate objective function for reserve crew schedules that perform well in simulation. A list of extensions that could be made to the model is then provided, followed by conclusions that summarise the findings and important results obtained

A simulation scenario based mixed integer programming approach to airline reserve crew scheduling under uncertainty

Airlines operate in an uncertain environment for many reasons, for example due to the efects of weather, traffic or crew unavailability (due to delay or sickness). This work focuses on airline reserve crew scheduling under crew absence and journey time uncertainty for an airline operating a single hub and spoke network. Reserve crew can be used to cover absent crew or delayed connecting crew. A fixed number of reserve crew are available for scheduling and each requires a daily standby duty start time. Given an airline's crew schedule and aircraft routings we propose a Mixed Integer Programming approach to scheduling the airline's reserve crew. A simulation of the airline's operations with stochastic journey time and crew absence inputs and without reserve crew is used to generate disruption scenarios for the MIPSSM formulation (Mixed Integer Programming Simulation Scenario Model). Each disruption scenario corresponds to a record of all of the disruptions in a simulation for which reserve crew use would have been beneficial. For each disruption in a disruption scenario there is a record of all reserve crew that could have been used to solve or reduce the disruption. This information forms the input to the MIPSSM formulation, which has the objective of finding the reserve schedule that minimises the overall level of disruption over a set of scenarios. Additionally, modifications of the MIPSSM are explored, and a heuristic solution approach and a reserve use policy derived from the MIPSSM are introduced. A heuristic based on the proposed Mixed Integer Programming Simulation Scenario Model or MIPSSM outperforms a range of alternative approaches. The heuristic solution approach suggests that including the right disruption scenarios is as important as ensuring that enough disruption scenarios are added to the MIPSSM

A simulation scenario based mixed integer programming approach to airline reserve crew scheduling under uncertainty

Airlines operate in an uncertain environment for many reasons, for example due to the efects of weather, traffic or crew unavailability (due to delay or sickness). This work focuses on airline reserve crew scheduling under crew absence and journey time uncertainty for an airline operating a single hub and spoke network. Reserve crew can be used to cover absent crew or delayed connecting crew. A fixed number of reserve crew are available for scheduling and each requires a daily standby duty start time. Given an airline's crew schedule and aircraft routings we propose a Mixed Integer Programming approach to scheduling the airline's reserve crew. A simulation of the airline's operations with stochastic journey time and crew absence inputs and without reserve crew is used to generate disruption scenarios for the MIPSSM formulation (Mixed Integer Programming Simulation Scenario Model). Each disruption scenario corresponds to a record of all of the disruptions in a simulation for which reserve crew use would have been beneficial. For each disruption in a disruption scenario there is a record of all reserve crew that could have been used to solve or reduce the disruption. This information forms the input to the MIPSSM formulation, which has the objective of finding the reserve schedule that minimises the overall level of disruption over a set of scenarios. Additionally, modifications of the MIPSSM are explored, and a heuristic solution approach and a reserve use policy derived from the MIPSSM are introduced. A heuristic based on the proposed Mixed Integer Programming Simulation Scenario Model or MIPSSM outperforms a range of alternative approaches. The heuristic solution approach suggests that including the right disruption scenarios is as important as ensuring that enough disruption scenarios are added to the MIPSSM

Scheduling airline reserve crew using a probabilistic crew absence and recovery model

Airlines require reserve crew to replace delayed or absent crew, with the aim of preventing consequent flight cancellations. A reserve crew schedule specifies the duty periods for which different reserve crew will be on standby to replace any absent crew. For both legal and health-and-safety reasons the reserve crew's duty period is limited, so it is vital that these reserve crew are available at the right times, when they are most likely to be needed and will be most effective. Scheduling a reserve crew unnecessarily, or earlier than needed, wastes reserve crew capacity. Scheduling a reserve crew too late means either an unrecoverable cancellation or a delay waiting for the reserve crew to be available. Determining when to schedule these crew can be a complex problem , since one crew member could potentially cover a vacancy on any one of a number of different flights, and flights interact with each other, so a delay or cancellation for one flight can affect a number of later flights. This work develops an enhanced mathematical model for assessing the impact of any given reserve crew schedule, in terms of reduced total expected cancellations and any resultant reserve induced delays, whilst taking all of the available information into account, including the schedule structure and interactions between flights, the uncertainties involved, and the potential for multiple crew absences on a single flight. The interactions between flights have traditionally made it very hard to predict the effects of cancellations or delays, and hence to predict when best to allocate reserve crew and lengthy simulation runs have traditionally been used to make these predictions. This work is motivated by the airline industry's need for improved mathematical models to replace the time-consuming simulation-based approaches. The improved predictive probabilistic model which is introduced here is shown to produce results that match a simulation model to a high degree of accuracy, in a much shorter time, making it an effective and accurate surrogate for simulation. The modelling of the problem also provides insights into the complexity of the problem that a purely simulation based approach would miss. The increased speed enables potential deployment within a real time decision support context, comparing alternative recovery decisions as disruptions occur. To illustrate this, the model is used in this paper as a fitness function in meta-heuristics algorithms to generate disruption minimising reserve crew schedules for a real airline schedule. These are shown to be of a high quality, demonstrating the effectiveness and reliability of the proposed approach

Verbal Descriptions of Cue Direction Affect Object Desirability.

Approach-avoidance behaviors are observed across a broad range of species. For humans, we tend move toward things we like, and away from things we dislike. Previous research tested whether repeatedly shifting visuo-spatial attention toward an object in response to eye gaze cues can increase liking for that object. Here, we tested whether a gaze-liking effect can occur for verbal descriptions of looking behavior without shifts of attention. Also, we tested the gaze specificity hypothesis - that the liking effect is specific to gaze cues - by comparing the effect of different types of cue (pointing gestures and arrow cues). In Experiment 1, participants (N = 205) were split into 5 groups according to the type of cue that was described as directed either toward or away from an object. The results show that (1) attention is not necessary; the liking effect was recorded for verbal descriptions of looking, (2) the effect also occurs for descriptions of pointing and arrows, and (3) the liking effect is enhanced for gaze cues compared to arrows, consistent with the gaze specificity hypothesis. Results from a further experiment suggest that the effect is not due to demand compliance. We conclude that the gaze-liking effect occurs for verbal descriptions of eye gaze. Indeed, because our method bypasses altogether the use of visual cues, objects, and shifts in visual selective attention, our paradigm appears to be more sensitive at tapping into the fundamental approach-avoidance response that mediate the implicit liking effect. As such, it offers new opportunities for research investigations in the future

Including Limited Partners in the Diversity Jurisdiction Analysis

This paper presents the results of the Dynamic Pricing Challenge, held on the occasion of the 17th INFORMS Revenue Management and Pricing Section Conference on June 29–30, 2017 in Amsterdam, The Netherlands. For this challenge, participants submitted algorithms for pricing and demand learning of which the numerical performance was analyzed in simulated market environments. This allows consideration of market dynamics that are not analytically tractable or can not be empirically analyzed due to practical complications. Our findings implicate that the relative performance of algorithms varies substantially across different market dynamics, which confirms the intrinsic complexity of pricing and learning in the presence of competition

Exo70-Mediated Recruitment of Nucleoporin Nup62 at the Leading Edge of Migrating Cells is Required for Cell Migration

Nucleoporin Nup62 localizes at the central channel of the nuclear pore complex and is essential for nucleocytoplasmic transport. Through its FG-repeat domain, Nup62 regulates nuclear pore permeability and binds nuclear transport receptors. Here, we report that Nup62 interacts directly with Exo70 and colocalizes with Exo70 at the leading edge of migrating cells. Nup62 binds the N-terminal domain of Exo70 through its coiled-coil domain but not through its FG-repeat domain. Selective inhibition of leading edge Nup62 using RNA interference significantly reduces cell migration. Furthermore, Exo70 recruits Nup62 at the plasma membrane and at filopodia. Removal of the Exo70-binding domain of Nup62 prevents leading edge localization of Nup62. Analogous to Exo70, Nup62 cycles between the plasma membrane and the perinuclear recycling compartment. Altogether, we propose that Nup62 not solely regulates access to the cell nucleus, but additionally functions in conjunction with Exo70, a key regulator of exocytosis and actin dynamics, at the leading edge of migrating cells

Are Coping Strategies a Cop Out?

Summary Few would dispute the legitimacy of putting indigenous coping strategies firmly on the food security and famine mitigation agenda. Yet the idea of coping strategies needs to be regarded with caution, especially when used to identify famine early warning indicators. There is a tendency for ‘coping strategies’ to become shorthand for a complex web of processes at work, making for great confusion in identifying what is being talked about. With respect to famine early warning, the complexity of these processes makes for potentially huge difficulties in data collection and interpretation. In the quest to incorporate coping strategies into policy?making and planning, hard choices have to be made between operational feasibility and confronting the intricacies of ? and limitations to ? indigenous response, close to where the action is; and it is essential to be clear as to what they are. A first step is to distinguish at a conceptual level between coping and adapting. If coping strategies are to be monitored as part of early warning systems, it is the motivation for, the timing of and the effectiveness of their use which must be tracked: a formidable task. Resumé Les Stratégies D'Adaptation: Sont?Elles Tout Simplement Échappatoires? Peu de gens ne nieraient la légitimité d'inclure les stratégies autochtones adaptation aux problèmes à l'ordre du jour de tout programme de sécurité alimentaire et d'allégement de la famine. Ceci dit, il y aurait néanmoins lieu de se méfier tant soit peu de ces stratégies, surtout comme première alerte de famine. Une tendance existe par laquelle le terme stratégie d'adaptation (‘coping strategy’) est de plus en plus emprunté comme fourre?tout linguistique qui avale tout un éventail de transactions très complexes; ce qui rend l'identification exacte de ces stratégies d'autant plus compliqée. En ce qui concerne les systèmes d'alerte précoce de famine, la complexité même de ces stratégies présente de très graves difficultés au niveau du rassemblement et de l'analyse des données. Dans toute tentative d'inclure des stratégies d'adaptation dans la formulation et la mise en viguer des politiques, des choix difficiles s'imposent entre la faisabilité opérationnelle et le moyen de tenir compte des détours de la réponse autochtone et dans un même temps, de tenir compte de ses propres limites; ainsi, il est essentiel de connaitre ces détours et ces limites à fond. Un premier pas serait d'établir, au niveau conceptuel, la différence entre les stratégies d'adaptation en tant que réponses conjoncturelles face aux conditions anormales, et le processus d'adaptation permanente qui entraine des changements fondamentaux dans les systèmes de production concernés. Si l'on veut que les stratégies d'adaptation constituent un élément qui puisse être compris dans le système de'alerte précoce, il y aurait lieu de faire le suivi de la motivation, de l'incidence et de l'efficacité de leur exploitation, ce qui représenterait une tache de recherche très onéreuse. Resumen Estrategias De Solución: Una ‘Salida Fácil?’ Dentro de la agenda de soluciones para los problemas de seguridad alimentaria y mitigación del hambre, las estrategias indígenas tienan una legitimidad que muy pocos disputan. Sin embargo, esta idea de estrategias para resolver el problema del hambre debe ser abordada con precaución, especialmente cuando se usa para identificar indicadores precoces de hambre. Hay una tendencia a transformar las estrategias de solución en una versión condensada de una compleja red de procesos en acción, creando gran confusión al tratar de individualizar el asunto específico de que se trata. Con respecto a indicadores precoces, la complejidad de estos procesos ocasiona dificultades potencialmente graves en la compilación e interpretación de datos. Al tratar de incorporar estrategias dentro de la elaboración y planeamiento de programas de acción, se deben llevar a cabo elecciones muy difíciles entre la viabilidad operativa y la confrontación con la intricada ? y limitada ? respuesta local, y es esencial tener en claro qué es cada una. El primer paso es distinguir a nivel conceptual entre solución y adaptación. Para regular estas estrategias como parte del sistema de aviso precoz, se debe seguir la trayectoria de su motivación, su oportinidad y su eficacia; y ésta es una tarea formidable

Draft Genome Sequences of Salinivibrio proteolyticus, Salinivibrio sharmensis, Salinivibrio siamensis, Salinivibrio costicola subsp. alcaliphilus, Salinivibrio costicola subsp. vallismortis, and 29 New Isolates Belonging to the Genus Salinivibrio

The draft genome sequences of 5 type strains of species of the halophilic genus Salinivibrio and 29 new isolates from different hypersaline habitats belonging to the genus Salinivibrio have been determined. The genomes have 3,123,148 to 3,641,359 bp, a G+C content of 49.2 to 50.9%, and 2,898 to 3,404 open reading frames (ORFs).España, Ministerio de Ciencia e Innovación CGL2013-46941-

HATS-17b: A Transiting Compact Warm Jupiter in a 16.3 Days Circular Orbit

We report the discovery of HATS-17b, the first transiting warm Jupiter of the HATSouth network. HATS-17b transits its bright (V=12.4) G-type (M$_{\star}$=1.131 $\pm$ 0.030 M$_{\odot}$, R$_{\star}$=1.091$^{+0.070}_{-0.046}$ R$_{\star}$) metal-rich ([Fe/H]=+0.3 dex) host star in a circular orbit with a period of P=16.2546 days. HATS-17b has a very compact radius of 0.777 $\pm$ 0.056 R$_J$ given its Jupiter-like mass of 1.338 $\pm$ 0.065 M$_J$. Up to 50% of the mass of HATS-17b may be composed of heavy elements in order to explain its high density with current models of planetary structure. HATS-17b is the longest period transiting planet discovered to date by a ground-based photometric survey, and is one of the brightest transiting warm Jupiter systems known. The brightness of HATS-17b will allow detailed follow-up observations to characterize the orbital geometry of the system and the atmosphere of the planet.Comment: 12 page, 8 figures, submitted to A