Modelling network travel time reliability under stochastic demand

A technique is proposed for estimating the probability distribution of total network travel time, in the light of normal day-to-day variations in the travel demand matrix over a road traffic network. A solution method is proposed, based on a single run of a standard traffic assignment model, which operates in two stages. In stage one, moments of the total travel time distribution are computed by an analytic method, based on the multivariate moments of the link flow vector. In stage two, a flexible family of density functions is fitted to these moments. It is discussed how the resulting distribution may in practice be used to characterise unreliability. Illustrative numerical tests are reported on a simple network, where the method is seen to provide a means for identifying sensitive or vulnerable links, and for examining the impact on network reliability of changes to link capacities. Computational considerations for large networks, and directions for further research, are discussed

Estimating anisotropy parameters and traveltimes in the tau-p domain

The presence of anisotropy influences many aspects of seismic wave propagation and has therefore implications for conventional processing schemes. To estimate the anisotropy, we need both forward modelling and inversion tools. Exact forward modelling in anisotropic media is generally done by raytracing. However, we present a new and fast method, using the tau-p transform, to calculate exact P and SV reflection moveout curves in stratified, laterally homogeneous, anisotropic media which requires no ray tracing. Results are exact even if the SV-waves display cusps. In addition, we show how the same method can be used for parameter estimation. Since inversion for anisotropic parameters is very nonunique, we develop expressions requiring only a reduced number of parameters. Nevertheless, predictions using these expressions are more accurate than Taylor series expansions and are also able to handle cusps in the SV traveltime curves. In addition, layer stripping is a linear process. Therefore, both effective (average) and local (interval) estimates can be obtained

The Optimality of the US and Euro Area Taylor Rule

The purpose of this paper is to examine the optimality of the monetary authorities reaction function in the two-area medium size model MARCOS (US and euro areas). The parameters and the horizons of output gap and inflation expectations of the Taylor rule are computed in order to minimise a loss function of the monetary authorities. However, investigating the optimality of the Taylor rule in the context of a large scale macroeconomic model raises several difficulties: the model is non-linear and all the state variables potentially enter the optimal monetary policy rule. Furthermore, the optimality of the Taylor rule is assessed by the minimisation of the loss function under the constraint of a large forward-looking model. To overcome these problems, Black, Macklem and Rose [1998] propose a stochastic simulation based method which has been applied to single-country macroeconomic models. To study the optimality of the Taylor rule in the case of a two-area model, we suppose that the economy is stochastically hit by numerous shocks (supply, demand, monetary, exchange rate and world demand) in each area and simulate MARCOS stochastically.Monetary Policy, Computational Techniques, International Policy Transmission

An inverse Gaussian plume approach for estimating atmospheric pollutant emissions from multiple point sources

A method is developed for estimating the emission rates of contaminants into the atmosphere from multiple point sources using measurements of particulate material deposited at ground level. The approach is based on a Gaussian plume type solution for the advection-diffusion equation with ground-level deposition and given emission sources. This solution to the forward problem is incorporated into an inverse algorithm for estimating the emission rates by means of a linear least squares approach. The results are validated using measured deposition and meteorological data from a large lead-zinc smelting operation in Trail, British Columbia. The algorithm is demonstrated to be robust and capable of generating reasonably accurate estimates of total contaminant emissions over the relatively short distances of interest in this study

A stable and accurate control-volume technique based on integrated radial basis function networks for fluid-flow problems

Radial basis function networks (RBFNs) have been widely used in solving partial differential equations as they are able to provide fast convergence. Integrated RBFNs have the ability to avoid the problem of reduced convergence-rate caused by differentiation. This paper is concerned with the use of integrated RBFNs in the context of control-volume discretisations for the simulation of fluid-flow problems. Special attention is given to (i) the development of a stable high-order upwind scheme for the convection term and (ii) the development of a local high-order approximation scheme for the diffusion term. Benchmark problems including the lid-driven triangular-cavity flow are employed to validate the present technique. Accurate results at high values of the Reynolds number are obtained using relatively-coarse grids

Implications of monetary union for catching-up member states

We examine the implications of monetary union for macroeconomic stabilisation in catching up participating countries. We allow member states’supply conditions to differ inside the union, especially with regard to sectoral characteristics. Sectoral productivity shocks on balance hamper the stabilisation properties of a currency union. In the face of aggregate supply disturbances, the stabilisation costs of renouncing monetary autonomy diminish with a flatter output-inflation tradeoff and - barring idiosyncratic shocks - with a larger reference country size, more homogeneous supply slopes and a higher preference for price stability. JEL Classification: E52, E58, F33, F40Balassa-Samuelson Effect, Exchange Rates, monetary union, price stability

Does immigration affect the Phillips curve? Some evidence for Spain

The Phillips curve has flattened in Spain over 1995?2006: Unemployment has fallen by 15 percentage points, with roughly constant inflation. This change has been much more pronounced than elsewhere. We argue that this stems from the immigration boom in Spain over this period. We show that the New Keynesian Phillips curve is shifted by immigration if natives? and immigrants? labor supply elasticities and bargaining power differ. Estimation of this curve for Spain indicates that the fall in unemployment since 1995 would have led to an annual increase in inflation of 2.5 percentage points if it had not been largely offset by immigration.Publicad

Are monetary-policy reaction functions asymmetric?: The role of nonlinearity in the Phillips curve

This paper investigates the implications of a nonlinear Phillips curve for the derivation of optimal monetary policy rules. Combined with a quadratic loss function, the optimal policy is also nonlinear, with the policy-maker increasing interest rates by a larger amount when inflation or output are above target than the amount it will reduce them when they are below target. Specifically, the main prediction of our model is that such a source of nonlinearity leads to the inclusion of the interaction between expected inflation and the output gap in an otherwise linear Taylor rule. We find empirical support for this type of asymmetries in the interest rate-setting behaviour of four European central banks but none for the US Fed.Publicad

Inflation zone targeting

We study optimal monetary policy design in a simple model that deviates from the linear-quadratic paradigm and provides a rationale for the practice of inflation zone targeting. We show that the presence of either zone-quadratic preferences or a zone-linear relationship between inflation and economic activity provides strong incentives to deviate from conventional linear policies. We calibrate the model based on parameters for the U.S. and the euro area and employ a numerical dynamic programming algorithm to derive the optimal policies. With this algorithm, we examine the role of uncertainty, model structure and relative preference towards economic stability in determining the width of the implied targeted inflation zone. JEL Classification: E31, E52, E58, E61inflation