Game-theoretic view on intermediated exchange

Intermediaries permeate modern economic exchange. Most classical models on intermediated exchange are driven by information asymmetry and inventory management. These two factors are of reduced significance in modern economies. This makes it necessary to develop models that correspond more closely to modern financial marketplaces. The goal of this dissertation is to propose and examine such models in a game theoretical context. The proposed models are driven by asymmetries in the goals of different market participants. Hedging pressure as one of the most critical aspects in the behavior of commercial entities plays a crucial role. The first market model shows that no equilibrium solution can exist in a market consisting of a commercial buyer, a commercial seller and a non-commercial intermediary. This indicates a clear economic need for non-commercial trading intermediaries: a direct trade from seller to buyer does not result in an equilibrium solution. The second market model has two distinct intermediaries between buyer and seller: a spread trader/market maker and a risk-neutral intermediary. In this model a unique, natural equilibrium solution is identified in which the supply-demand surplus is traded by the risk-neutral intermediary, whilst the market maker trades the remainder from seller to buyer. Since the market maker’s payoff for trading at the identified equilibrium price is zero, this second model does not provide any motivation for the market maker to enter the market. The third market model introduces an explicit transaction fee that enables the market maker to secure a positive payoff. Under certain assumptions on this transaction fee the equilibrium solution of the previous model applies and now also provides a financial motivation for the market maker to enter the market. If the transaction fee violates an upper bound that depends on supply, demand and riskaversity of buyer and seller, the market will be in disequilibrium.

Two-Phase Flow In Microchannels: Morphology And Interface Phenomena

The existence and morphology, as well as the dynamics of micro-scale gas-liquid interfaces is investigated numerically and experimentally. These studies can be used to assess liquid management issues in microsystems such as PEMFC gas flow channels, and are meant to open new research perspectives in two-phase flow, particularly in film deposition on non-wetting surfaces. For example the critical plug volume data can be used to deliver desired length plugs, or to determine the plug formation frequency. The dynamics of gas-liquid interfaces, of interest for applications involving small passages (e.g. heat exchangers, phase separators and filtration systems), was investigated using high-speed microscopy - a method that also proved useful for the study of film deposition processes. The existence limit for a liquid plug forming in a mixed wetting channel is determined by numerical simulations using Surface Evolver. The plug model simulate actual conditions in the gas flow channels of PEM fuel cells, the wetting of the gas diffusion layer (GDL) side of the channel being different from the wetting of the bipolar plate walls. The minimum plug volume, denoted as critical volume is computed for a series of GDL and bipolar plate wetting properties. Critical volume data is meant to assist in the water management of PEMFC, when corroborated with experimental data. The effect of cross section geometry is assessed by computing the critical volume in square and trapezoidal channels. Droplet simulations show that water can be passively removed from the GDL surface towards the bipolar plate if we take advantage on differing wetting properties between the two surfaces, to possibly avoid the gas transport blockage through the GDL. High speed microscopy was employed in two-phase and film deposition experiments with water in round and square capillary tubes. Periodic interface destabilization was observed and the existence of compression waves in the gas phase is discussed by taking into consideration a naturally occurring convergent-divergent nozzle formed by the flowing liquid phase. The effect of channel geometry and wetting properties was investigated through two-phase water-air flow in square and round microchannels, having three static contact angles of 20, 80 and 105 degrees. Four different flow regimes are observed for a fixed flow rate, this being thought to be caused by the wetting behavior of liquid flowing in the corners as well as the liquid film stability. Film deposition experiments in wetting and non-wetting round microchannels show that a thicker film is deposited for wetting conditions departing from the ideal 0 degrees contact angle. A film thickness dependence with the contact angle theta as well as the Capillary number, in the form h_R ~ Ca^(2/3)/ cos(theta) is inferred from scaling arguments, for contact angles smaller than 36 degrees. Non-wetting film deposition experiments reveal that a film significantly thicker than the wetting Bretherton film is deposited. A hydraulic jump occurs if critical conditions are met, as given by a proposed nondimensional parameter similar to the Froude number. Film thickness correlations are also found by matching the measured and the proposed velocity derived in the shock theory. The surface wetting as well as the presence of the shock cause morphological changes in the Taylor bubble flow.