The airport Network and Catchment area Competition Model - A comprehensive airport demand forecasting system using a partially observed database

For airport capacity planning long term forecasts of aircraft movements are required. The classical approach to generate such forecasts has been the use of time series data together with econometric models, to extrapolate observed patterns of growth into the future. More recently, the dramatically increased competition between airports, airlines and alliances on the one hand, and serious capacity problems on the other, have made this approach no longer adequate. Airport demand forecasts now need to focus heavily on the many competitive elements in addition to the growth element. In our paper we describe a comprehensive, pragmatic air demand model system that has been implemented for Amsterdam’s Schiphol Airport. This model, called the Airport Network and Catchment area Competition Model (ACCM), provides forecasts of future air passenger volumes and aircraft movements explicitly taking account of choices of air passengers among competing airports in Europe. The model uses a straightforward nested logit structure to represent choices of air passengers among alternative departure airports, transport modes to the airport, airlines/alliances/low cost carriers, types of flight (direct versus transfer), air routes, and main modes of transport (for those distances where car and high-speed train may be an alternative option). Target year passenger forecasts are obtained by taking observed base year passenger numbers, and applying two factors to these: (1)Firstly a growth factor, to express the global impact of key drivers of passenger demand growth such as population size, income, trade volume; (2)Secondly a market share ratio factor, to express the increase (or decline) in attractiveness of the airport due to anticipated changes in its air network and landside-accessibility, relative to other (competing) airports. The target year passenger forecasts are then converted into aircraft movements to assess whether or not the available runway capacity is adequate. Key inputs to the model are data bases describing for base year and target year the level of service (travel times, costs, service frequencies) of the land-side accessibility of all departure airports considered, and the air-side networks of all departure and hub airports considered. The air-side networks (supply) are derived from a detailed OAG based flight simulation model developed elsewhere. A particular characteristic of the ACCM implementation for Schiphol Airport is that it had to be developed using only a partial data set describing existing demand: although detailed OD- information was available for air passengers using Schiphol Airport in 2003, no such data was available for other airports or other transport modes. As a consequence a synthetic modelling approach was adopted, where the unobserved passenger segments for the base year were synthesised using market shares ratios between unobserved and observed segments forecasts for the base year together with the observed base year passenger volumes. This process is elegant and appealing in principle, but is not without a number of problems when applied in a real case. In the paper we will first set out the objectives of the ACCM as it was developed, and the operational and practical constraints that were imposed. Then we will describe how the ACCM fits with model developments in the literature, and sketch the overall structure that was adopted. The following sections will describe the modelled alternatives and the utility structures, the level-of-service data bases used for land-side and air-side networks, for base year and target year. Then we will describe in some detail how we dealt with the partial data issue: the procedure to generate non-observed base year data, the validation, the problems encountered, the solutions chosen. Finally we shall show a number of the results obtained (subject to permission by the Dutch Ministry of Transport), and provide some conclusions and recommendations for further application of the methodology.

Observational Constraints on Kicks in Supernovae

The absence or presence of extremely wide binaries with a radio pulsar and an optical counterpart imposes a strong constraint on the existence and magnitude of kicks in supernova explosions. We search for such systems by comparing the positions of radio pulsars which are not known to be in binaries with the positions of visible stars, and find that the number of associations is negligible. According to the performed population synthesis, this implies that kicks must occur, with a lower limit of at least 10 to 20 km/s.Comment: 4 pages including 2 figs., LaTeX. To appear in A&A letter

Large Language Models: The Need for Nuance in Current Debates and a Pragmatic Perspective on Understanding

Current Large Language Models (LLMs) are unparalleled in their ability to generate grammatically correct, fluent text. LLMs are appearing rapidly, and debates on LLM capacities have taken off, but reflection is lagging behind. Thus, in this position paper, we first zoom in on the debate and critically assess three points recurring in critiques of LLM capacities: i) that LLMs only parrot statistical patterns in the training data; ii) that LLMs master formal but not functional language competence; and iii) that language learning in LLMs cannot inform human language learning. Drawing on empirical and theoretical arguments, we show that these points need more nuance. Second, we outline a pragmatic perspective on the issue of `real' understanding and intentionality in LLMs. Understanding and intentionality pertain to unobservable mental states we attribute to other humans because they have pragmatic value: they allow us to abstract away from complex underlying mechanics and predict behaviour effectively. We reflect on the circumstances under which it would make sense for humans to similarly attribute mental states to LLMs, thereby outlining a pragmatic philosophical context for LLMs as an increasingly prominent technology in society.Comment: 15 pages, 0 figures, Forthcoming in Proceedings of the 2023 Conference on Empirical Methods in Natural Language Processin

Theory of Mind in Large Language Models: Examining Performance of 11 State-of-the-Art models vs. Children Aged 7-10 on Advanced Tests

To what degree should we ascribe cognitive capacities to Large Language Models (LLMs), such as the ability to reason about intentions and beliefs known as Theory of Mind (ToM)? Here we add to this emerging debate by (i) testing 11 base- and instruction-tuned LLMs on capabilities relevant to ToM beyond the dominant false-belief paradigm, including non-literal language usage and recursive intentionality; (ii) using newly rewritten versions of standardized tests to gauge LLMs' robustness; (iii) prompting and scoring for open besides closed questions; and (iv) benchmarking LLM performance against that of children aged 7-10 on the same tasks. We find that instruction-tuned LLMs from the GPT family outperform other models, and often also children. Base-LLMs are mostly unable to solve ToM tasks, even with specialized prompting. We suggest that the interlinked evolution and development of language and ToM may help explain what instruction-tuning adds: rewarding cooperative communication that takes into account interlocutor and context. We conclude by arguing for a nuanced perspective on ToM in LLMs.Comment: 14 pages, 4 figures, Forthcoming in Proceedings of the 27th Conference on Computational Natural Language Learning (CoNLL

A minute of your time: The impact of survey recruitment method and interview location on the value of travel time

Web-based stated preference (SP) surveys are widely used to estimate values of travel time (VTT) for cost–benefit analysis, often with internet panels as the source of recruitment. The recruitment method could potentially bias the results because (1) those who frequently participate in surveys may have a lower opportunity cost of time and (2) people who answer the survey at home or in the office may answer differently because the choice situation is less salient to them. In this paper, we investigate both mechanisms using data from a VTT choice experiment study where respondents were recruited from an internet panel, an alternative email register or on-board/on the station. Within all three groups, some complete the survey while making an actual trip. We find that respondents who were recruited from the internet panel or report being members of a panel have a significantly lower VTT, suggesting that internet panels are less representative in this respect compared to other recruitment methods. We also find that those who answer while traveling have a higher VTT, possibly because the benefits of saving travel time are more salient to them than to those who answer while not traveling.A minute of your time: The impact of survey recruitment method and interview location on the value of travel timepublishedVersio

The Westerbork Flexible Filterbank Backend

The Westerbork Synthesis Radio Telescope (WSRT) has recently been fitted with a new backend designed for pulsar detection. This backend is a filterbank with 32 channels, for both the X and Y polarised signals. A novel feature is that the channel bandwidths are digitally tunable between 6.25 kHz and 2.8 MHz (Vasisht et al. in preparation). The time constant of the integration which follows detection can be digitally set at values between circa 50 ms and 10 μS. For each observing frequency and each pulsar (with a known dispersion measure) we can choose an optimal bandwidth and signal smoothing

New values of time and reliability in passenger transport in The Netherlands

We have established new values of time (VOTs) and values of travel time reliability (VORs) for use in cost-benefit analysis (CBA) of transport projects in The Netherlands. This was the first national study in The Netherlands (and one of the first world-wide) to investigate these topics empirically in a joint framework. Stated preference (SP) questionnaires were designed for interviewing travellers, where the hypothetical alternatives were described in terms of travel time, travel costs and travel time reliability, the latter being presented to the respondents in the form of five possible travel times having equal probability. For passenger transport, we first collected interviews using an existing internet panel. Additional data collection recruitment was done by asking travellers at petrol stations/service areas, parking garages, stations, bus stops, airports and ports to participate in the survey. One important conclusion is that the SP survey using members of this internet panel leads to substantially lower VOTs than the SP survey with en-route recruitment, probably because of self-selection bias in the internet panel. We estimated discrete choice models in which the values of time differ between trips with different time and costs levels, different time and costs changes offered in the SP, and different observed characteristics of the respondents (e.g. education, income, age, household composition). By using a panel latent class model, we also account for unobserved differences between respondents in the value of time and for repeated measurements/panel effects. The reference values of time and the reference reliability ratios were estimated on the 2011 sample only, but the effect of time and cost level, time and cost changes offered and socio-economic attributes was estimated on both the 2009 and 2011 samples

The Evolution of Compact Binary Star Systems

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure

Robotic surgery in emergency setting : 2021 WSES position paper

Background Robotics represents the most technologically advanced approach in minimally invasive surgery (MIS). Its application in general surgery has increased progressively, with some early experience reported in emergency settings. The present position paper, supported by the World Society of Emergency Surgery (WSES), aims to provide a systematic review of the literature to develop consensus statements about the potential use of robotics in emergency general surgery. Methods This position paper was conducted according to the WSES methodology. A steering committee was constituted to draft the position paper according to the literature review. An international expert panel then critically revised the manuscript. Each statement was voted through a web survey to reach a consensus. Results Ten studies (3 case reports, 3 case series, and 4 retrospective comparative cohort studies) have been published regarding the applications of robotics for emergency general surgery procedures. Due to the paucity and overall low quality of evidence, 6 statements are proposed as expert opinions. In general, the experts claim for a strict patient selection while approaching emergent general surgery procedures with robotics, eventually considering it for hemodynamically stable patients only. An emergency setting should not be seen as an absolute contraindication for robotic surgery if an adequate training of the operating surgical team is available. In such conditions, robotic surgery can be considered safe, feasible, and associated with surgical outcomes related to an MIS approach. However, there are some concerns regarding the adoption of robotic surgery for emergency surgeries associated with the following: (i) the availability and accessibility of the robotic platform for emergency units and during night shifts, (ii) expected longer operative times, and (iii) increased costs. Further research is necessary to investigate the role of robotic surgery in emergency settings and to explore the possibility of performing telementoring and telesurgery, which are particularly valuable in emergency situations. Conclusions Many hospitals are currently equipped with a robotic surgical platform which needs to be implemented efficiently. The role of robotic surgery for emergency procedures remains under investigation. However, its use is expanding with a careful assessment of costs and timeliness of operations. The proposed statements should be seen as a preliminary guide for the surgical community stressing the need for reevaluation and update processes as evidence expands in the relevant literature.Peer reviewe

Training curriculum in minimally invasive emergency digestive surgery : 2022 WSES position paper

Background Minimally invasive surgery (MIS), including laparoscopic and robotic approaches, is widely adopted in elective digestive surgery, but selectively used for surgical emergencies. The present position paper summarizes the available evidence concerning the learning curve to achieve proficiency in emergency MIS and provides five expert opinion statements, which may form the basis for developing standardized curricula and training programs in emergency MIS. Methods This position paper was conducted according to the World Society of Emergency Surgery methodology. A steering committee and an international expert panel were involved in the critical appraisal of the literature and the development of the consensus statements. Results Thirteen studies regarding the learning curve in emergency MIS were selected. All but one study considered laparoscopic appendectomy. Only one study reported on emergency robotic surgery. In most of the studies, proficiency was achieved after an average of 30 procedures (range: 20-107) depending on the initial surgeon's experience. High heterogeneity was noted in the way the learning curve was assessed. The experts claim that further studies investigating learning curve processes in emergency MIS are needed. The emergency surgeon curriculum should include a progressive and adequate training based on simulation, supervised clinical practice (proctoring), and surgical fellowships. The results should be evaluated by adopting a credentialing system to ensure quality standards. Surgical proficiency should be maintained with a minimum caseload and constantly evaluated. Moreover, the training process should involve the entire surgical team to facilitate the surgeon's proficiency. Conclusions Limited evidence exists concerning the learning process in laparoscopic and robotic emergency surgery. The proposed statements should be seen as a preliminary guide for the surgical community while stressing the need for further research.Peer reviewe