An assessment of the cost effectiveness of vegetation harvesting as a means of removing nutrient and metals from ponds

This paper reports on an investigation to quantify the mass of pollutants removed from a stormwater retention pond by routine vegetation harvesting. The amount of plants can increase the costs of ponds, and the increased costs of plant maintenance may not be justified by enhanced pollutant removal. This study provides some of the basic information, previously lacking, which is needed to come to such decisions. The study facility was La Costa pond, a retention pond in California used to treat highway runoff. Water quality monitoring data indicate that the pond removed 43 percent of the total nitrogen entering the facility, with 5 to 7 percent directly attributable to harvesting the vegetation – in this case cattails (Typha). The data also indicate that 48 percent of the total annual phosphorus was removed from the runoff, with the harvested vegetation responsible for between 3 and 8 percent. Metal uptake by the vegetation was substantially less than nutrients. Total removal of copper, lead and zinc by the pond varied between 57 and 93 percent, with the harvested vegetation accounting for less than 2 percent of removal. Issues addressed in the paper include the cost implications of harvesting and ways of improving vegetative pollutant removal

Deterministic Dynamics in the Minority Game

The Minority Game (MG) behaves as a stochastically perturbed deterministic system due to the coin-toss invoked to resolve tied strategies. Averaging over this stochasticity yields a description of the MG's deterministic dynamics via mapping equations for the strategy score and global information. The strategy-score map contains both restoring-force and bias terms, whose magnitudes depend on the game's quenched disorder. Approximate analytical expressions are obtained and the effect of `market impact' discussed. The global-information map represents a trajectory on a De Bruijn graph. For small quenched disorder, an Eulerian trail represents a stable attractor. It is shown analytically how anti-persistence arises. The response to perturbations and different initial conditions are also discussed.Comment: 16 pages, 5 figure

Crowd-Anticrowd Theory of Multi-Agent Market Games

We present a dynamical theory of a multi-agent market game, the so-called Minority Game (MG), based on crowds and anticrowds. The time-averaged version of the dynamical equations provides a quantitatively accurate, yet intuitively simple, explanation for the variation of the standard deviation (`volatility') in MG-like games. We demonstrate this for the basic MG, and the MG with stochastic strategies. The time-dependent equations themselves reproduce the essential dynamics of the MG.Comment: Presented at APFA2 (Liege) July 2000. Proceedings: Eur.Phys.J. B [email protected]

From market games to real-world markets

This paper uses the development of multi-agent market models to present a unified approach to the joint questions of how financial market movements may be simulated, predicted, and hedged against. We examine the effect of different market clearing mechanisms and show that an out-of-equilibrium clearing process leads to dynamics that closely resemble real financial movements. We then show that replacing the `synthetic' price history used by these simulations with data taken from real financial time-series leads to the remarkable result that the agents can collectively learn to identify moments in the market where profit is attainable. We then employ the formalism of Bouchaud and Sornette in conjunction with agent based models to show that in general risk cannot be eliminated from trading with these models. We also show that, in the presence of transaction costs, the risk of option writing is greatly increased. This risk, and the costs, can however be reduced through the use of a delta-hedging strategy with modified, time-dependent volatility structure.Comment: Presented at APFA2 (Liege) July 2000. Proceedings: Eur. Phys. J. B Latex file + 10 .ps figs. [email protected]

Discussion: Non-uniqueness of flow liquefaction line for loose sand

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