Thermodynamic study of capillary pressure curves based on free energy minimization

This paper presents a new method for pore level network simulation of the distribution of two immiscible phases in a permeable medium. The method requires that the Helmholtz free energy of the system — the medium and the two phases contained within the pore space — be a minimum at all saturation states. We describe the method here and show some typical results from a computer algorithm that implements it. The results include (i) an explanation of the ‘scanning’ behaviour of capillary pressure curves based wholly on the free energy minimization, (ii) predictions of capillary pressure at arbitrary wetting states, including negative capillary pressures, and (iii) illustrations of how the minimized free energy changes along the scanning curves. The method also predicts the known dependency of the capillary pressure on the pore size distribution and interfacial tension. The current work is restricted to two‐dimensional networks, but the free energy minimization appears to be generalizable to three dimensions and to more than two fluid phases. Moreover, functions generated through the minimization, specifically contact areas between the medium surface and the phases, appear to have applications predicting other multiphase petrophysical properties.     

An argument for Classic era Maya market exchange

This paper argues for the importance of complex market exchange in the Maya area prior to the so-called Postclassic “mercantile” period. We suggest that market exchange was foundational to the stability of Classic era polities, and by extension, that it was of key strategic interest to dynasts and their retinues. We reject some of the prevailing dualistic views that the economic activities of royal courts or noble houses were disconnected from the vast majority of production and exchange activities deemed essential for the daily life of supporting populations with the sole exception of tribute payments. Alternatively, we postulate the accessibility and interchangeability of most products through market place commerce, as is well-documented for the Postclassic Period. Correlates of well developed market exchange that are tracked in our analysis include occupational specialization, surplus production, household and community interdependency, and ease of access to valuable goods. We compare these patterns across elite and commoner contexts at Classic Period Tikal to those of Postclassic Period Mayapán. The assemblages at Mayapán provide comparative indices from a city known historically to have had an important regional market exchange system. Similar patterns at Tikal strongly suggest time depth for market exchange, as well as a more complex market system than the solar central place (administered) model that has been most often invoked to characterize Classic Maya market organization.     

A probabilistic framework for assessing spatio-temporal point patterns in the archaeological record

The assessment of spatial patterns in archaeology is hampered by a number of constraints, one of the most serious of which is the intrinsic temporal uncertainty associated with most of the archaeological record. Different types of chronological definition or different degrees of temporal knowledge will suggest different kinds of spatial pattern, ultimately obscuring and restricting our interpretation of the background process, especially in cases where we are seeking a diachronic perspective. This paper addresses these problems by adopting both a probabilistic approach and a more standardised framework for diachronic analysis. First, we define the notion of temporal uncertainty and explore its analytical consequences. Second, we consider two methods by which it might be formally quantified, emphasising (a) the advantages of probability-weighted spatial analysis and (b) the comparison of alternative spatio-temporal patterns via Monte-Carlo simulation. Finally, we apply these methods to a case study that considers the distribution of Middle to Late Jomon (ca.5000–3000 BP) pithouses recorded in the Chiba New Town area of Japan.