Workload balancing for flight dispatcher scheduling

Unlike other airline operations planning problems, optimization in flight dispatching is not common in literature. Flight dispatchers are centrally located and monitor multiple flights in different places simultaneously. Their work involves planning fuel requirements, routing, and weather monitoring, both before and during a flight. An area of opportunity exists in the assignment of work amongst dispatchers. A desk contains a series of flights, and is served by a dispatcher or a series of dispatchers working consecutive shifts. In this work, we do not consider shifts and instead focus on assigning flights amongst a set number of desks. Our goal is to balance the workload of each desk, which is measured by the sum of each desk’s maximum workload throughout the day. Two formulations are presented that model the assignment of flights to desks, which we call the Flight Dispatching Problem. The Flight Dispatcher Schedule Formulation (FDSF) assigns flights amongst a set number of desks. The Set Covering Formulation (SCF) selects from known schedules (the assignment of flights to a single desk) to cover all flights with the specified number of desks (i.e., schedules). The base implementation solves the SCF using a column generation approach that creates new schedules with each iteration. Additional variants are also modelled where we limit which flights are assigned to the same desk. Testing is performed on European Airline Data and American Airlines data. The instances range in size from 46 to 297 flights in one day. We find that the FDSF solves to optimality quickly for small instances but not for the larger ones. The base implementation converges within two hours for the small and mid-size instances. Gaps are reduced using an improvement heuristic in some cases. For the larger instances, neither implementation solves within two hours and the gaps after that time are very large. Constraining the flight assignments provides trade-offs between computation time (which is typically faster) and solution quality (which is typically worse). We also tested the case where load varies throughout the flight. For the base implementation, most of the computation time for larger instances is spent in the pricing problem. In some cases, this is improved by generating multiple columns in each iteration instead of just one. The solution of the pricing problem is an area where future work could be focused to improve the computational performance. Other areas for future work include modelling dispatch zones instead of decomposing the problem by zones, changing the balance metric in the objective, incorporating uncertainty, and including the shift component of the dispatching problem

Does masking matter? Shipping noise and fish vocalizations

Shipping creates large near-field background noises at levels similar to or higher than fish vocalizations and in the same critical bandwidths. This noise has the potential to "mask" biologically important signals and prevent fish from hearing them; any interference with the detection and recognition of sounds may impact fish survival. The Lombard effect, whereby vocalizations are altered to reduce or exclude masking effects, is an adaptation that has been observed in mammals and birds. Research is needed to establish whether the Lombard effect occurs in fish to gain a better understanding of the implications of noise pollution on fish populations

Going beyond two degrees? The risks and opportunities of alternative options

Since the mid-1990s, the aim of keeping climate change within 2 °C has become firmly entrenched in policy discourses. In the past few years, the likelihood of achieving it has been increasingly called into question. The debate around what to do with a target that seems less and less achievable is, however, only just beginning. As the UN commences a two-year review of the 2 °C target, this article moves beyond the somewhat binary debates about whether or not it should or will be met, in order to analyse more fully some of the alternative options that have been identified but not fully explored in the existing literature. For the first time, uncertainties, risks, and opportunities associated with four such options are identified and synthesized from the literature. The analysis finds that the significant risks and uncertainties associated with some options may encourage decision makers to recommit to the 2 °C target as the least unattractive course of action

Survival of native seedlings planted by volunteers: The Lower Cotter, ACT case study

Volunteer labour is often used for planting native seedlings for revegetation projects. The survival of such plantings is seldom monitored and reported. The overall survival of seedlings at three years of age was assessed for eight years of plantings established by nearly 15,000 volunteers in the Lower Cotter River catchment in the Australian Capital Territory. Mean survival was 66.8% across all years. We conclude that volunteers can be effectively integrated into large-scale revegetation projects if they are well trained and organisedThis report was commisioned by Ecological Management & Restoratio

Understanding by older patients of dialysis and conservative management for chronic kidney failure

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License CC BY NC-ND 4.0 ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.BACKGROUND: Older adults with chronic kidney disease stage 5 may be offered a choice between dialysis and conservative management. Few studies have explored patients' reasons for choosing conservative management and none have compared the views of those who have chosen different treatments across renal units. STUDY DESIGN: Qualitative study with semistructured interviews. SETTINGS & PARTICIPANTS: Patients 75 years or older recruited from 9 renal units. Units were chosen to reflect variation in the scale of delivery of conservative management. METHODOLOGY: Semistructured interviews audiorecorded and transcribed verbatim. ANALYTICAL APPROACH: Data were analyzed using thematic analysis. RESULTS: 42 interviews were completed, 4 to 6 per renal unit. Patients were sampled from those receiving dialysis, those preparing for dialysis, and those choosing conservative management. 14 patients in each group were interviewed. Patients who had chosen different treatments held varying beliefs about what dialysis could offer. The information that patients reported receiving from clinical staff differed between units. Patients from units with a more established conservative management pathway were more aware of conservative management, less often believed that dialysis would guarantee longevity, and more often had discussed the future with staff. Some patients receiving conservative management reported that they would have dialysis if they became unwell in the future, indicating the conditional nature of their decision. LIMITATIONS: Recruitment of older adults with frailty and comorbid conditions was difficult and therefore transferability of findings to this population is limited. CONCLUSIONS: Older adults with chronic kidney disease stage 5 who have chosen different treatment options have contrasting beliefs about the likely outcomes of dialysis for those who are influenced by information provided by renal units. Supporting renal staff in discussing conservative management as a valid alternative to dialysis for a subset of patients will aid informed decision making. There is a need for better evidence about conservative management to support shared decision making for older people with chronic kidney failure.Peer reviewedFinal Published versio

Machine learning reveals singing rhythms of male Pacific field crickets are clock controlled

Circadian rhythms are ubiquitous in nature and endogenous circadian clocks drive the daily expression of many fitness-related behaviors. However, little is known about whether such traits are targets of selection imposed by natural enemies. In Hawaiian populations of the nocturnally active Pacific field cricket (Teleogryllus oceanicus), males sing to attract mates, yet sexually selected singing rhythms are also subject to natural selection from the acoustically orienting and deadly parasitoid fly, Ormia ochracea. Here, we use T. oceanicus to test whether singing rhythms are endogenous and scheduled by circadian clocks, making them possible targets of se lection imposed by flies. We also develop a novel audio-to-circadian analysis pipeline, capable of extracting useful parameters from which to train machine learning algorithms and process large quantities of audio data. Singing rhythms fulfilled all criteria for endogenous circadian clock control, including being driven by photoschedule, self-sustained periodicity of approximately 24 h, and being robust to variation in temperature. Furthermore, singing rhythms varied across individuals, which might suggest genetic variation on which natural and sexual selection pressures can act. Sexual signals and ornaments are well-known targets of selection by natural enemies, but our findings indicate that the circadian timing of those traits’ expression may also determine fitnes

A silent orchestra: convergent song loss in Hawaiian crickets is repeated, morphologically varied, and widespread

Host-parasite interactions are predicted to drive the evolution of defences and counter-defences, but the ability of either partner to adapt depends on new and advantageous traits arising. The loss of male song in Hawaiian field crickets (Teleogryllus oceanicus) subject to fatal parasitism by eavesdropping flies (Ormia ochracea) is a textbook example of rapid evolution in one such arms race. Male crickets ordinarily sing to attract females by rubbing their forewings together, which produces sound by exciting acoustic resonating structures formed from modified wing veins (‘normal-wing’). The resulting song is the target of strong sexual selection by conspecific females. However, male song also attracts female flies that squirt larvae onto males or nearby female crickets; the larvae then burrow into, consume, and ultimately kill the host. The flies thus impose strong natural selection on male song, producing silent males, which have spread rapidly in populations on two islands – Kauai and Oahu. On both islands, song loss is caused by genetic mutations that drastically reduce or eliminate sound-producing structures on the male forewing by feminising wing venation – these males are called ‘flatwing’. On recent visits to parasitized cricket populations, we discovered two additional wing phenotypes – ‘small-wing’ and ‘curly-wing’. These two phenotypes differ noticeably from flatwing, and from each other, but all have the effect of eliminating or reducing acoustic signals that attract the parasitoid fly. These discoveries illustrate how the evolutionary process can repeatedly, and through a remarkable variety of independent mechanisms, drive adaptation to the same selection pressure

Using E-Z Reader to examine the concurrent development of eye-movement control and reading skill

Compared to skilled adult readers, children typically make more fixations that are longer in duration, shorter saccades, and more regressions, thus reading more slowly (Blythe & Joseph, 2011). Recent attempts to understand the reasons for these differences have discovered some similarities (e.g., children and adults target their saccades similarly; Joseph, Liversedge, Blythe, White, & Rayner, 2009) and some differences (e.g., children?s fixation durations are more affected by lexical variables; Blythe, Liversedge, Joseph, White, & Rayner, 2009) that have yet to be explained. In this article, the E-Z Reader model of eye-movement control in reading (Reichle, 2011; Reichle, Pollatsek, Fisher, & Rayner, 1998) is used to simulate various eye-movement phenomena in adults versus children in order to evaluate hypotheses about the concurrent development of reading skill and eye-movement behavior. These simulations suggest that the primary difference between children and adults is their rate of lexical processing, and that different rates of (post-lexical) language processing may also contribute to some phenomena (e.g., children?s slower detection of semantic anomalies; Joseph et al., 2008). The theoretical implications of this hypothesis are discussed, including possible alternative accounts of these developmental changes, how reading skill and eye movements change across the entire lifespan (e.g., college-aged vs. older readers), and individual differences in reading ability