Dynamic Crossover in Polymers , Role of Molecular Weight
One of the most characteristic features of glass-forming liquids is the sharp slowing down of relaxation times, τ, upon cooling. In these materials relaxation dynamics exhibit a non-Arrhenius temperature dependence usually described by Vogel-Fulcher-Tamman (VFT) relation [1]. However, for majority of glassforming liquids it is impossible to fit data in the entire temperature range with a single set of VFT parameters. Above some characteristic temperature it is necessary to use another set of VFT parameters. Existence of this dynamic crossover was predicted by the mode-coupling theory (MCT) [2]. The theory predicts a transition from a liquidlike to a solidlike dynamics on a molecular time and length scale at some specific temperature, TC, above the glass transition temperature Tg. The dynamic crossover becomes even more evident with the use of derivative analysis proposed by Stickel et al [3] 2 , where x is the relaxation time or frequency. If
Relaxation in complex systems
The phenomenon of slow relaxation is discussed with emphasis on finding a general explanation of its ubiquity. After a review of the phenomenon, possible causes are considered both at the microscopic level and from a configuration space viewpoint. Quenched randomness and strongly constrained dynamics appear most important microscopically. In configuration space the central requirement seems to be the existence of many valleys connected sparsely in a hierarchical way. Recent toy models are shown to fit into this overall picture.
Numerical Simulation for Natural State of Two-Phase Liquid Dominated Geothermal Reservoir with Steam Cap Underlying Brine Reservoir
Hydrothermal reservoir which liquid-dominated hydrothermal reservoir is a type of geothermal reservoir that most widely used for power plant. The exploitation of mass and heat from the geothermal fluid will decrease the pressure in the reservoir over time. Therefore the pressure drop in the reservoir will have an impact on the formation of boiling zones or boiling will increase. The impacts are an increase in the fraction of steam, dryness, in the reservoir and with good vertical permeability will form a steam cap underlying the brine reservoir. The two- phase liquid dominated reservoir is sensitive to the porosity and difficult to assign average properties of the entire reservoir when there is boiling zone in some area of the reservoir. These paper showed successful development of two-phase liquid dominated geothermal reservoir and discussed the formation of steam cap above brine reservoir through numerical simulation for state natural conditions. The natural state modeling in steam cap shows a match with the conceptual model of the vapor-dominated developed. These paper also proofed the presence of transition zone, boiling zone, between steam cap and brine reservoir.