Cruise Speed Reduction for Ground Delay Programs: A Case Study for San Francisco International Airport Arrivals

Ground Delay Programs (GDP) are sometimes cancelled before their initial planned duration and for this reason aircraft are delayed when it is no longer needed. Recovering this delay usually leads to extra fuel consumption, since the aircraft will typically depart after having absorbed on ground their assigned delay and, therefore, they will need to cruise at more fuel consuming speeds. Past research has proposed speed reduction strategy aiming at splitting the GDP-assigned delay between ground and airborne delay, while using the same fuel as in nominal conditions. Being airborne earlier, an aircraft can speed up to nominal cruise speed and recover part of the GDP delay without incurring extra fuel consumption if the GDP is cancelled earlier than planned. In this paper, all GDP initiatives that occurred in San Francisco International Airport during 2006 are studied and characterised by a K-means algorithm into three different clusters. The centroids for these three clusters have been used to simulate three different GDPs at the airport by using a realistic set of inbound traffic and the Future Air Traffic Management Concepts Evaluation Tool (FACET). The amount of delay that can be recovered using this cruise speed reduction technique, as a function of the GDP cancellation time, has been computed and compared with the delay recovered with the current concept of operations. Simulations have been conducted in calm wind situation and without considering a radius of exemption. Results indicate that when aircraft depart early and fly at the slower speed they can recover additional delays, compared to current operations where all delays are absorbed prior to take-off, in the event the GDP cancels early. There is a variability of extra delay recovered, being more significant, in relative terms, for those GDPs with a relatively low amount of demand exceeding the airport capacity.

Re-employment hazard of displaced German workers: evidence from the GSOEP

This study investigates the re-employment hazard of displaced German workers using the first fourteen sweeps of the German Socio-Economic Panel (GSOEP) data. As well as parametric and non-parametric discrete-time specifications for the baseline hazard, the study employs alternative mixing distributions to account for unobserved heterogeneity. Findings of the study suggest negative duration dependence, even after accounting for unobserved heterogeneity. In terms of covariate effects, those at the lower end of the skills ladder, those who had been working in manufacturing and those with previous experience of non-employment are found to have lower hazard of exit via reemployment.

e-poltergeist

E-poltergeist takes over the user’s internet browser, automatically initiating Web searches without their permission. Web-based artwork which explores issues of user control when confronted with complex technological systems, questioning the limits of digital interactive arts as consensual reciprocal systems. e-poltergeist was a major web commission that marked an early stage of research in a larger enquiry by Craighead and Thomson into the relationship between live virtual data, global communications networks and instruction-based art, exploring how such systems can be re-contextualised within gallery environments. e-poltergeist presented the 'viewer' with a singular narrative by using live internet search-engine data that aimed to create a perpetual and virtually unstoppable cycle of search engine results, banner ads and moving windows as an interruption into the normal use of an internet browser. The work also addressed the ‘de-personalisation’ of internet use by sending a series of messages from the live search engine data that seemed to address the user directly: 'Is anyone there?'; 'Can anyone hear me?', 'Please help me!'; 'Nobody cares!' e-poltergeist makes a significant contribution to the taxonomy of new media art by dealing with the way that new media art can re-address notions of existing traditions in art such as appropriation and manipulation, instruction-based art and conceptual art. e-poltergeist was commissioned ($12,000) for 010101: Art in Technological Times, a landmark international exhibition presented by the San Francisco Museum of Modern Art, which bought together leading international practitioners working with emergent technologies, including Tatsuo Miyajima, Janet Cardiff, Brian Eno. Peer recognition of the project in the form of reviews include: Curating New Media. Gateshead: Baltic Centre for Contemporary Art. Cook, Sarah, Beryl Graham and Sarah Martin ISBN: 1093655064; The Wire; http://www.wired.com/culture/lifestyle/news/2000/12/40464 (review by Reena Jana); Leonardo (review Barbara Lee Williams and Sonya Rapoport) http://www.leonardo.info/reviews/feb2001/ex_010101_willrapop.html All the work is developed jointly and equally between Craighead and her collaborator, Jon Thomson, Slade School of Fine Art.

Old conflicts, new rivals? Airline competition in the European market

Christoph Franz of Lufthansa recently identified Ryanair, easyJet, Air Berlin and Emirates as the company’s main competitors – gone are the days when it could benchmark itself against BA or Air France-KLM! This paper probes behind the headlines to assess the extent to which different airlines are in competition, using evidence from the UK and mainland European markets. The issue of route versus network competition is addressed. Many regulators have put an emphasis on the former whereas the latter, although less obvious, can be more relevant. For example, BA and American will cease to compete between London and Dallas Fort Worth if their alliance obtains anti-trust immunity but 80% of the passengers on this route are connecting at one or both ends and hence arguably belong to different markets (e.g. London-San Francisco, Zurich-Dallas, Edinburgh-New Orleans) which may be highly contested. The remaining 20% of local traffic is actually insufficient to support a single point to point service in its own right. Estimates are made of the seat capacity major airlines are offering to the local market as distinct from feeding other routes. On a sector such as Manchester–Amsterdam, 60% of KLM’s passengers are transferring at Schiphol as against only 1% of bmibaby’s. Thus although KLM operates 5 flights and 630 seats per day against bmibaby’s 2 flights and 298 seats, in the point to point market bmibaby offers more seats than KLM. The growth of the Low Cost Carriers (LCCs) means that competition increasingly needs to be viewed on city pair markets (e.g. London-Rome) rather than airport pair markets (e.g. Heathrow-Fiumicino). As the stronger LCCs drive out weaker rivals and mainline carriers retrench to their major hubs, some markets now have fewer direct options than existed prior to the low cost boom. Timings and frequencies are considered, in particular the extent to which services are a true alternative especially for business travellers. LCCs typically offer lower frequencies and more unsociable timings (e.g. late evening arrivals at remote airports) as they are more focused on providing the cheapest service rather than the most convenient schedule. Interesting findings on ‘monopoly’ services are presented (including alliances) - certain airlines have many more of these than others. Lufthansa has a significant number of sectors to itself whereas at the other extreme British Airways has direct competition on almost every route in its network. Ryanair and flybe have a higher proportion of monopoly routes than easyJet or Air Berlin. In the domestic US market it has become apparent since deregulation that better financial returns can come from dominating a large number of smaller markets rather than being heavily exposed in the major markets - which are hotly fought over. Regional niches that appear too thin for Ryanair to serve (with its all 189 seat 737-800 fleet) are identified. Fare comparisons in contrasting markets provide some insights to marketing and pricing strategies. Data sources used include OAG (schedules and capacity), AEA (traditional European airlines traffic by region), the UK CAA (airport, airline and route traffic plus survey information of passenger types) and ICAO (international route traffic and capacity by carrier). It is concluded that airlines often have different competitors depending on the context but in surprisingly many cases there are actually few or no direct substitutes. The competitive process set in train by deregulation of European air services in the 1990s is leading back to one of natural monopolies and oblique alternatives. It is the names of the main participants that have changed however!

Just noticeable differences in perceived image contrast with changes in displayed image size

An evaluation of the change in perceived image contrast with changes in displayed image size was carried out. This was achieved using data from four psychophysical investigations, which employed techniques to match the perceived contrast of displayed images of five different sizes. A total of twenty-four S-shape polynomial functions were created and applied to every original test image to produce images with different contrast levels. The objective contrast related to each function was evaluated from the gradient of the mid-section of the curve (gamma). The manipulation technique took into account published gamma differences that produced a just-noticeable-difference (JND) in perceived contrast. The filters were designed to achieve approximately half a JND, whilst keeping the mean image luminance unaltered. The processed images were then used as test series in a contrast matching experiment. Sixty-four natural scenes, with varying scene content acquired under various illumination conditions, were selected from a larger set captured for the purpose. Results showed that the degree of change in contrast between images of different sizes varied with scene content but was not as important as equivalent perceived changes in sharpness.