Simulating Sequential Search Models with Genetic Algorithms: Analysis of Price Ceilings, Taxes, Advertising and Welfare

This paper studies advertising, price ceilings and taxes in a sequential search model with bilateral heterogeneities in production and search costs. We estimate equilibria using a genetic algorithm (GA) applied to over 100 market scenarios, each differing based on the number of firms, number of consumers, existence of price ceilings or taxes, costs of production, costs of advertising, consumers' susceptibility to advertising and consumers' search costs. We compare our equilibrium results to those of the standard theoretical consumer search literature and analyze the welfare effects of advertising, price ceilings and sales taxes. We find that price ceilings and uninformative advertising can improve welfare, especially if search costs are sufficiently high.Sequential Search Models, Genetic Algorithms, Price Ceilings, Taxes, Advertising, Welfare

Advertising Intensity and Welfare in an Equilibrium Search Model

We analyze an equilibrium search model in a duopoly setting with bilateral heterogeneities in production and search costs in which firms can advertise by announcing price and location. We study existence, stability, and comparative statics in such a setting, compare the market advertising level to the socially optimal level, and find conditions in which firms advertise more or less than the social optimum.Search, Advertising, Welfare

Search Costs and Medicare Plan Choice

There is increasing evidence suggesting that Medicare beneficiaries do not make fully informed decisions when choosing among alternative Medicare health plans. To the extent that deciphering the intricacies of alternative plans consumes time and money, the Medicare health plan market is one in which search costs may play an important role. To account for this, we split beneficiaries into two groups--those who are informed and those who are uninformed. If uninformed, beneficiaries only use a subset of covariates to compute their maximum utilities, and if informed, they use the full set of variables considered. In a Bayesian framework with Markov Chain Monte Carlo (MCMC) methods, we estimate search cost coefficients based on the minimum and maximum statistics of the search cost distribution, incorporating both horizontal differentiation and information heterogeneities across eligibles. Our results suggest that, conditional on being uninformed, older, higher income beneficiaries with lower self-reported health status are more likely to utilize easier access to information.Search, Medicare Health Plan Choice, Discrete Choice Models, Bayesian Methods

Demonstration of sustained and useful converter responses during balanced and unbalanced faults in microgrids

In large power grids where converter penetration is presently low and the network impedance is predominantly reactive, the required response from converters during faults is presently specified by phrases such as “maximum reactive output”. However, in marine and aero power systems most faults are unbalanced, the network impedance is resistive, and converter penetration may be high. Therefore a balanced reactive fault current response to an unbalanced fault may lead to over-voltages or over/under frequency events. Instead, this paper presents a method of controlling the converter as a balanced voltage source behind a reactance, thereby emulating the fault response of a synchronous generator (SG) as closely as possible. In this mode there is a risk of converter destruction due to overcurrent. A new way of preventing destruction but still providing fault performance as close to a SG as possible is presented. Demonstrations are presented of simulations and laboratory testing at the 10kVA 400V scale, with balanced and unbalanced faults. Currents can be limited to about 1.5pu while still providing appropriate unbalanced fault response within a resistive network

Testing Sunyaev-Zel'dovich measurements of the hot gas content of dark matter haloes using synthetic skies

The thermal Sunyaev-Zel'dovich (tSZ) effect offers a means of probing the hot gas in and around massive galaxies and galaxy groups and clusters, which is thought to constitute a large fraction of the baryon content of the Universe. The Planck collaboration recently performed a stacking analysis of a large sample of `locally brightest galaxies' (LBGs) and, surprisingly, inferred an approximately self-similar relation between the tSZ flux and halo mass. At face value, this implies that the hot gas mass fraction is independent of halo mass, a result which is in apparent conflict with resolved X-ray observations. We test the robustness of the inferred trend using synthetic tSZ maps generated from cosmological hydrodynamical simulations and using the same tools and assumptions applied in the Planck study. We show that, while the detection and the estimate of the `total' flux (within $5 r_{500}$) is reasonably robust, the inferred flux originating from within $r_{500}$ (i.e. the limiting radius to which X-ray observations typically probe) is highly sensitive to the assumed pressure distribution of the gas. Using our most realistic simulations with AGN feedback, that reproduce a wide variety of X-ray and optical properties of groups and clusters, we estimate that the derived tSZ flux within $r_{500}$ is biased high by up to to an order of magnitude for haloes with masses $M_{500} \sim 10^{13}$ M$_{\odot}$. Moreover, we show that the AGN simulations are consistent with the total tSZ flux-mass relation observed with Planck, whereas a self-similar model is ruled out.Comment: 16 pages, 10 figures, MNRAS, accepted after minor revisio

Non-thermal X-ray Emission: An Alternative to Cluster Cooling Flows?

We report the results of experiments aimed at reducing the major problem with cooling flow models of rich cluster X-ray sources: the fact that most of the cooled gas or its products have not been found. Here we show that much of the X-ray emission usually attributed to cooling flows can, in fact, be modeled by a power-law component which is indicative of a source(s) other than thermal bremsstrahlung from the intracluster medium. We find that adequate simultaneous fits to ROSAT PSPCB and ASCA GIS/SIS spectra of the central regions of ten clusters are obtained for two-component models that include a thermal plasma component that is attributable to hot intracluster gas and a power-law component that is likely generated by compact sources and/or extended non-thermal emission. For five of the clusters that purportedly have massive cooling flows, the best-fit models have power-law components that contribute $\sim$ 30 % of the total flux (0.14 - 10.0 keV) within the central 3 arcminutes. Because cooling flow mass deposition rates are inferred from X-ray fluxes, our finding opens the possibility of significantly reducing cooling rates.Comment: 11 pages, 3 figures, emulateapj style. Accepted for publication in Ap