Transient and Asymptotic Behavior of a Random-Utility Based Stochastic Search Process in Continuous Space and Time

The paper explores the properties of some simple search and choice behaviors, by exploiting the asymptotic properties of maxima of sequences of random variables. Heterogeneity in the preference is introduced by means of additive random utilities, and the actor is assumed to choose points in a plane region, by sampling them according to a stochastic process. It is shown that asymptotic convergence to a Logit model holds under considerably weaker assumptions than those commonly found in the literature to justify it. This asymptotic property is treated in details for utility-maximizing behavior, and outlined for satisficing behavior. The asymptotic equivalence of the two behaviors suggests that progress in widening the family of asymptotically Logit-equivalence behaviors can be made with further research

Fusaiole 'in forma di vaso' e produzioni femminili nella protostoria: un problema aperto

The author, on the base of the extreme variability in shapes of spindle whorls from Middle Bronze Age in pile-dwelling and 'terramare' area, suggests that many of these spindle whorls can be interpreted as miniature fine vases if we look at the drawings upside down. This evidence, which lasts till Final Bronze Age after the collapse of the âterramareâ system and, in Veneto, till Early Iron Age, suggests to the author that the women, who spin and weave, mirror these everyday tasks in their home-based pottery production, until she is replaced by specialized male craftsmen with potter's wheel. As we find marks made by the handle of 'shovels' (paletta, typical female gravegood) impressed on loom weights before firing, it can be assumed that aristocrat women would shift from actual manufacturing of pottery to controlling its production

The Use of Random-Utility Theory in Building Location-Allocation Models

The most important part of a location-allocation model is the allocation rule, that is, the way clients are assigned to facilities. In the well-known models of the "plant-location" family, the embedded allocation rule is the assignment of the least-travel-cost facility, This allocation rule depends on the assumption that the cost, or more generally utility, associated with each possible facility choice is deterministically known. The simplest way to generalize a plant-location model is to add a random term to travel costs, with a known probability distribution. Such randomness may be shown to arise in many real-life situations, and the resulting choice models constitute the subject of random-utility theory, This paper introduces the use of the random-utility modeling philosophy in location-allocation problems, Some relevant properties of the resulting family of models are derived, Among them, of special importance is the submodularity property, which relates the random-utility-based location models to a recent area of research in combinatorial optimization. Submodularity is exploited to develop simple heuristic algorithms, and the effectiveness of the approach is supported with some numerical results

Fractal Dimension for the Characterization of the Porosity of Asphalt Concretes

Abstract In the design of asphalt mixtures for paving, the choice of components has a remarkable importance, as requirements of quality and durability must be assured in use, guaranteeing adequate standards of safety and comfort. In this paper, an approach of analysis on the aggregate materials using fractal geometry is proposed. Following an analytical and an experimental approach, it was possible to find a correlation between characteristics of the asphalt concrete (specific gravity and porosity) and the fractal dimension of the aggregate mixtures. The studies revealed that this approach allows to draw the optimal fractal dimension and, consequently, it can be used to choose an appropriate aggregate gradation for the specific application; once the appropriate initial physical parameters are finalized. This fractal approach could be employed for predicting the porosity of mixed asphalt concretes, given as input the fractal characteristics of the aggregate mixtures of the concrete material

Extremal polynomials in stratified groups

We introduce a family of extremal polynomials associated with the prolongation of a stratified nilpotent Lie algebra. These polynomials tre related to a new algebraic characterization of abnormal sub-Riemannian extremals in stratified nilpotent Lie groups. They satisfy a set of remarkable structure relations that are used to integrate the adjoint equations, in both normal and abnormal case

Multi-layer model for the web graph

This paper studies stochastic graph models of the WebGraph. We present a new model that describes the WebGraph as an ensemble of different regions generated by independent stochastic processes (in the spirit of a recent paper by Dill et al. [VLDB 2001]). Models such as the Copying Model [17] and Evolving Networks Model [3] are simulated and compared on several relevant measures such as degree and clique distribution

Some Salient Issues in Policy Evaluations of Urban Housing Markets

Housing problems are truly universal. For households the residential choice decision is basic both in view of its influence on their welfare and the substantial portion of their budget it claims. For regions and nations, housing determines centrally the investment sacrifices and has strong influences on the financial markets. These significances of housing problems have entailed a whole range of laws, regulations, and policies to afflict the functioning of the markets both from quantity and distributional aspects. Different nations and regions have developed different arsenals of policy tools. Some attempts have been made to review and compare the national housing policies and the methods used in policy assessment. Such comparative studies are less common at the regional level. The current Working Paper addresses the contemporary issues of policy evaluations of the working of urban housing markets by suggesting a conceptual framework for such analyses, based on systems analytic considerations. The paper contains a claim for the development of a new generation of housing market models for policy evaluations based on modern theories of probabilistic choice and structural change in dynamic systems. It provides an agenda for an international research project on urban housing policies at a time when management and renewal have replaced expansion as traits of urban fabric

Some Proposals for Stochastic Facility Location Models

The static facility location model with a spatial interaction-based allocation rule has been first introduced by Coelho and Wilson (1976). The main interest in introducing a spatial interaction-based allocation rule lies in the more realistic trip patterns that result from its use, which in many cases seem to fit the actual data on customer choice better than the simple nearest-facility allocation rule. A further step towards more realistic models of customer behavior is the introduction of stochastic features, describing both the amount of total demand for facilities and the trip pattern of the customers. In this paper the usefulness of stochastic programming tools to formulate and solve such problems is explored, and some simple, but easily generalizable applied examples are given. Both numerical techniques and exact analytical methods are outlined, and some issues for further research are proposed