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

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

Facility Location with Spatially Interactive Travel Behavior

This paper sets out a spatially interactive facility location model that specifies client travel behavior according to a "gravity" formula. The well-known uncapacitated facility location model is a limiting case of this model. Analytical partial optimization yields a condensed formulation that can be solved by a nonlinear branch-and-bound approach. Computational results are presented for several problems having as many as 69 potential facility locations

ADS-B Crowd-Sensor Network and Two-Step Kalman Filter for GNSS and ADS-B Cyber-Attack Detection

Automatic Dependent Surveillance-Broadcast is an Air Traffic Control system in which aircraft transmit their own information (identity, position, velocity, etc.) to ground sensors for surveillance purposes. This system has many advantages compared to the classical surveillance radars: easy and low-cost implementation, high accuracy of data, and low renewal time, but also limitations: dependency on the Global Navigation Satellite System, a simple unencrypted and unauthenticated protocol. For these reasons, the system is exposed to attacks like jamming/spoofing of the on-board GNSS receiver or false ADS-B messages' injection. After a mathematical model derivation of different types of attacks, we propose the use of a crowd sensor network capable of estimating the Time Difference Of Arrival of the ADS-B messages together with a two-step Kalman filter to detect these attacks (on-board GNSS/ADS-B tampering, false ADS-B message injection, GNSS Spoofing/Jamming). Tests with real data and simulations showed that the algorithm can detect all these attacks with a very high probability of detection and low probability of false alarm