Optimal capital investment under uncertainty: An extension

This paper develops a model for optimal capital investment in continuous time when both existing and new capital stocks are subject to uncertainty. The model is generalized to allow for large and infrequent changes in the dynamics of the capital stock, which may arise as a result of natural and man-made disasters.

Exchange rate regimes and international business cycle transmission revisited

노트 : A paper prepared for the conference on 'Korea and the World Economy', 21-22 July 2002, Seoul, South Korea

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

A simple test of exogeneity for recursively structured VAR models

The restriction of exogeneity of certain variables in structural VAR models is rarely tested for consistency with the actual data. The reason is obvious: such a test requires estimates of the structural parameters. This paper proposes a solution for models that assume long-run or contemporaneous recursive structures in identification. We show that in such cases, the exogeneity restriction can be assessed statistically using the well-known Granger non-causality test which is conveniently performed in the reduced-form VAR model. Two empirical examples are offered to demonstrate the usefulness of this result.

How well does the Mundell-Fleming model fit Australian data since the collapse of Bretton Woods?

Australian time series for the nominal interest rate, real output, the nominal exchange rate, prices and nominal money since 1973 are characterized by a vector autoregressive process driven by five exogenous disturbances. Those disturbances are identified so that they can be interpreted as the five main sources of fluctuations found in the Mundell - Fleming model of a small open economy under flexible exchange rates, namely: world interest rate, aggregate supply, IS, money supply and money demand shocks. The dynamic responses of the estimated model to the structural shocks are analysed and shown to match most of the predictions of the Mundell - Fleming model.