Asymmetric Equilibria and Non-Cooperative Access Pricing in Telecommunications

This paper looks at competition in the Telecommunications industry with non-linear tariffs and network based price discrimination. Allowing for asymmetric networks and non-cooperatively chosen access prices simultaneously allows to explicitly derive non-reciprocal equilibrium access price choices that are above the efficient level.Asymmetric Networks, Access Pricing, Interconnection, Competition Policy, Telecommunications

The Provision of a Public Good with a direct Provision Technology and a Large Number of Agents

This paper provides a limit result for the provision of a public good in a mechanism design framework as the number of agents gets large. What distinguishes the public good investigated in this analysis is its direct provision technology which is commonplace in modern information technologies.Public Goods, Direct Provision, Asymmetric Information, Mechanism Design, Open Source Software

Spacial Predation in the UK Newspaper Industry

This paper investigates the alleged predatory behaviour in the UK quality newspaper industry in the 1990s using a horizontal differentiation model and industry data.Two-Sided Markets; Predation; Newspapers

Equilibrium Market and Pricing Structures in Virtual Platform Duopoly

We investigate the equilibrium market sturcture in virtual platform duopoly (auctions or other market forms) that are prevalent in internet settings. We take full account of the complexity of network effects in such markets and determine optimal pricing strategies. We invstigate the welfare implications of such strategies, look at the impact of non-exclusive services and at what happens in large markets.Two-sided Markets; Duopoly Pricing;

A Concept for Exploring Western Music Tonality in Physical Space

Musical theory about the structure and morphology of Western tonality is quite difficult to teach to young children, due to the relatively complex mathematical concepts behind tonality. Children usually grasp the concepts of musical harmony intuitively through listening to music examples. Placing the 12 notes of the well-tempered scale into a spatial arrangement, in which the proximity of these notes represents their mutual harmonic relationship, would allow to link physical motion through a spatial area with the exploration of music tonality. Music theorists have postulated the Circle of Fifth, the “Spiral Array”, and the “Tonnetz” as paradigms for spatial arrangements of music notes which allow mapping the distance between notes onto their “mutual consonance”. These approaches mostly have been of qualitative nature, leaving the actual numeric parameters of the spatial description undetermined. In this paper, these parameters have been determined, leading to a concrete numerical description of the planar Tonnetz. This allows the design of a physical space in which the music notes are distributed in space according to their musical consonance. Set up in an outdoor area, handheld devices (e.g. PDA) with integrated Global Positioning System can be used to play these notes at their actual physical location. This makes it possible for children to explore this musical space by moving through the real spatial area and experience the relationships of the notes through their proximity. Defining a range for each note as a circular area around each note location, consonant chords can be produced in those areas where those circles overlap. Using this concept, games can be developed in which the listeners have to perform certain tasks related to this musical space. This appears to be a promising approach for the music education of young children who can intuitively learn about music morphology without being explicitly taught about the complex theoretical mathematical background

Microcanonical analysis of small systems

The basic quantity for the description of the statistical properties of physical systems is the density of states or equivalently the microcanonical entropy. Macroscopic quantities of a system in equilibrium can be computed directly from the entropy. Response functions such as the susceptibility are for example related to the curvature of the entropy surface. Interestingly, physical quantities in the microcanonical ensemble show characteristic properties of phase transitions already in finite systems. In this paper we investigate these characteristics for finite Ising systems. The singularities in microcanonical quantities which announce a continuous phase transition in the infinite system are characterised by classical critical exponents. Estimates of the non-classical exponents which emerge only in the thermodynamic limit can nevertheless be obtained by analyzing effective exponents or by applying a microcanonical finite-size scaling theory. This is explicitly demonstrated for two- and three-dimensional Ising systems.Comment: 14 pages, 6 figures, invited talk (M.P.) given at the International Symposion on Structure and Dynamics of Heterogeneous Systems SDHS 2004 in Duisburg November 25-26 2004, to appear in a special issue of Phase Transition

Flame front analysis of ethanol, butanol, iso-octane and gasoline in a spark-ignition engine using laser tomography and integral length scale measurements

Direct-injection spark-ignition engines have become popular due to their flexibility in injection strategies and higher efficiency; however, the high-pressure in-cylinder injection process can alter the airflow field by momentum exchange, with different effects for fuels of diverse properties. The current paper presents results from optical studies of stoichiometric combustion of ethanol, butanol, iso-octane and gasoline in a direct-injection spark-ignition engine run at 1500 RPM with 0.5 bar intake plenum pressure and early intake stroke fuel injection for homogeneous mixture preparation. The analysis initially involved particle image velocimetry measurements of the flow field at ignition timing with and without fuelling for comparison. Flame chemiluminescence imaging was used to characterise the global flame behaviour and double-pulsed Laser-sheet flame tomography by Mie scattering to quantify the local topology of the flame front. The flow measurements with fuel injection showed integral length scales of the same order to those of air only on the tumble plane, but larger regions with scales up to 9 mm on the horizontal plane. Averaged length scales over both measurement planes were between 4 and 6 mm, with ethanol exhibiting the largest and butanol the smallest. In non-dimensional form, the integral length scales were up to 20% of the clearance height and 5–12% of the cylinder bore. Flame tomography showed that at radii between 8 and 12 mm, ethanol was burning the fastest, followed by butanol, iso-octane and gasoline. The associated turbulent burning velocities were 4.6–6.5 times greater than the laminar burning velocities and about 13–20% lower than those obtained by flame chemiluminescence imaging. Flame roundness was 10–15% on the tomography plane, with largest values for ethanol, followed by butanol, gasoline and iso-octane; chemiluminescence imaging showed larger roundness (18–25%), albeit with the same order amongst fuels. The standard deviation of the displacement of the instantaneous flame contour from one filtered by its equivalent radius was obtained as a measure of flame brush thickness and correlated strongly with the equivalent flame radius; when normalised by the radius, it was 4–6% for all fuels. The number of crossing points between instantaneous and filtered flame contour showed a strong negative correlation with flame radius, independent of fuel type. The crossing point frequency was 0.5–1.6 mm−1. The flame brush thickness was about 1/10th of the integral length scale. A positive correlation was found between integral length scale and flame brush thickness and a negative correlation with crossing frequency