An Analysis of the Spatio-Temporal Factors Affecting Aircraft Conflicts Based on Simulation Modelling

The demand for air travel worldwide continues to grow at a rapid rate, especially in Europe and the United States. In Europe, the demand exceeded predictions with a real annual growth of 7.1% in the period 1985-1990, against a prediction of 2.4%. By the year 2010, the demand is expected to double from the 1990 level. Within the UK international scheduled passenger traffic is predicted to increase, on average, by 5.8 per cent per year between 1999 and 2003. The demand has not been matched by availability of capacity. In Western Europe many of the largest airports suffer from runway capacity constraints. Europe also suffers from an en-route airspace capacity constraint, which is determined by the workload of the air traffic controllers, i.e. the physical and mental work that controllers must undertake to safely conduct air traffic under their jurisdiction through en-route airspace. The annual cost to Europe due to air traffic inefficiency and congestion in en-route airspace is estimated to be 5 billion US Dollars, primarily due to delays caused by non-optimal route structures and reduced productivity of controllers due to equipment inefficiencies. Therefore, to in order to decrease the total delay, an increase in en-route capacity is of paramount importance. At a global scale and in the early 1980s, the International Civil Aviation Organisation (ICAO) recognised that the traditional air traffic control (ATC) systems would not cope with the growth in demand for capacity. Consequently new technologies and procedures have been proposed to enable ATC to cope with this demand, e.g. satellite-based system concept to meet the future civil aviation requirements for communication, navigation and surveillance/ air traffic management (CNS/ATM). In Europe, the organisation EUROCONTROL (established in 1960 to co-ordinate European ATM) proposed a variety of measures to increase the capacity of en-route airspace. A key change envisaged is the increasing delegation of responsibilities for control to flight crew, by the use of airborne separation assurance between aircraft, leading eventually to ?free flight? airspace. However, there are major concerns regarding the safety of operations in ?free flight? airspace. The safety of such airspace can be investigated by analysing the factors that affect conflict occurrence, i.e. a loss of the prescribed separation between two aircraft in airspace. This paper analyses the factors affecting conflict occurrence in current airspace and future free flight airspace by using a simulation model of air traffic controller workload, the RAMS model. The paper begins with a literature review of the factors that affect conflict occurrence. This is followed by a description of the RAMS model and of its use in this analysis. The airspace simulated is the Mediterranean Free Flight region, and the major attributes of this region and of the traffic demand patterns are outlined next. In particular a day?s air traffic is simulated in the two airspace scenarios, and rules for conflict detection and resolution are carefully defined. The following section outlines the framework for analysing the output from the simulations, using negative binomial (NB) and generalised negative binomial (GNB) regression, and discusses the estimation methods required. The next section presents the results of the regression analysis, taking into account the spatio-temporal nature of the data. The following section presents an analysis of the spatial and temporal pattern of conflicts in the two airspace scenarios across a day, highlighting possible metrics to indicate this. The paper concludes with future research directions based upon this analysis.

Hydraulic Jump in One-dimensional Flow

In the presence of viscosity the hydraulic jump in one dimension is seen to be a first-order transition. A scaling relation for the position of the jump has been determined by applying an averaging technique on the stationary hydrodynamic equations. This gives a linear height profile before the jump, as well as a clear dependence of the magnitude of the jump on the outer boundary condition. The importance of viscosity in the jump formation has been convincingly established, and its physical basis has been understood by a time-dependent analysis of the flow equations. In doing so, a very close correspondence has been revealed between a perturbation equation for the flow rate and the metric of an acoustic white hole. We finally provide experimental support for our heuristically developed theory.Comment: 17 Pages, 8 Figures, 1 Table. To appear in European Physical Journal

Quantum Annealing in a Kinetically Constrained System

Classical and quantum annealing is discussed for a kinetically constrained chain of $N$ non-interacting asymmetric double wells, represented by Ising spins in a longitudinal field $h$. It is shown that in certain cases, where the kinetic constraints may arise from infinitely high but vanishingly narrow barriers appearing in the relaxation path of the system, quantum annealing exploiting the quantum-mechanical penetration of sufficiently narrow barriers may be far more efficient than its thermal counterpart. We have used a semiclassical picture of scattering dynamics to do our simulation for the quantum system.Comment: 5 pages, 3 figure

The problem of court congestion : evidence from Indian lower courts

This paper explores the problem of court congestion in Indian lower courts. We use several measures to capture court congestion. These include: caseloads per capita and per judge, the number of cases older than a year per capita and per judge, and congestion rates calculated as the ratio of cases older than a year to cases disposed. We conclude that the Indian state judiciaries differ with respect to the nature and the level of congestion. We can also identify the reasons why some judiciaries are more congested than others. The results show that the large number of judges per capita is negatively related to congestion rates, while judgeship vacancies have a positive effect on caseloads per judge. Court productivity captured by the clearance rates has a significant and negative effect on both caseloads and congestion rates and seems to be crucial for the effectiveness of congestion-reduction programs. Finally, judiciaries with lower litigation rates display a relatively better performance with respect to current caseloads, but are not efficient in addressing the ?real? backlogs of cases pending for more than a year.Diese Arbeit untersucht das Problem der Überlastung an indischen Gerichten. Dabei verwenden wir verschiedene Indikatoren gerichtlicher Überlastung, z.B. die Gerichtsfälle pro Kopf und pro Richter, die Anzahl mehr als ein Jahr alter Gerichtsfälle pro Kopf und pro Richter, und Überlastungsraten aus dem Verhältnis von Fällen die älter als ein Jahr sind und abgeschlossenen Fällen. Wir folgern, dass die staatlichen Gerichte in Indien unterschiedliche Überlastungsarten und ?niveaus aufweisen. Ebenso legen wir die Gründe dar, warum manche Gerichte überlasteter sind als andere. Die Ergebnisse zeigen, dass eine große Richterzahl negativ mit den Überlastungsraten korreliert ist, während offene Stellen für das Richteramt einen positiven Effekt auf die Gerichtsfälle pro Richter ausüben. Die gerichtliche Produktivität, welche anhand von Bearbeitungsraten dargestellt wird, hat eine bedeutende negative Auswirkung sowohl auf die Anzahl an Gerichtsfällen, als auch auf die Überlastungsraten. Darüber hinaus scheint sie ausschlaggebend für die Wirksamkeit von Programmen zur Überlastungsverringerung zu sein. Schließlich weisen Richter mit niedrigen Prozessraten eine vergleichsweise bessere Leistung bezüglich aktueller Gerichtsfälle auf, sind jedoch weniger effizient, wenn es darum geht, die tatsächlichen Rückstände von Fällen die älter als ein Jahr alt sind aufzuarbeiten

Analysis of the long-range random field quantum antiferromagnetic Ising model

We introduce a solvable quantum antiferromagnetic model. The model, with Ising spins in a transverse field, has infinite range antiferromagnetic interactions with random fields on each site, following an arbitrary distribution. As is well-known, frustration in the random field Ising model gives rise to a many-valley structure in the spin-configuration space. In addition, the antiferromagnetism also induces a regular frustration even for the ground state. In this paper, we investigate analytically the critical phenomena in the model, having both randomness and frustration and we report some analytical results for it.Comment: 18 pages, 5 figures, Euro. Phys. J B (to be published