Propagators and Violation Functions for Geometric and Workload Constraints Arising in Airspace Sectorisation

Airspace sectorisation provides a partition of a given airspace into sectors, subject to geometric constraints and workload constraints, so that some cost metric is minimised. We make a study of the constraints that arise in airspace sectorisation. For each constraint, we give an analysis of what algorithms and properties are required under systematic search and stochastic local search

An Empirical Model of Pricing in the Catfish Industry

The adoption of aquacultural products has created an imbalance of market power between catfish producers and a processing sector that exerts a monopsonistic power in certain regions of the U.S. such as west Alabama. However, because of the recent changes caused by vertical integration of the catfish industry, the existence of an oligopolistic power has been identified in the catfish industry. An empirical model of pricing in the catfish industry was developed using a theoretical model proposed by Appelbaum. An analysis of the market structure was conducted to provide estimates of conjectural elasticities over time. Conjectural elasticities were used to construct the oligopoly power index. Results show some evidence of the existence of oligopolistic power in the catfish industry that further suggests some degree of price enhancement.catfish industry, pricing, conjectural elasticity, oligopoly power index, Demand and Price Analysis, Environmental Economics and Policy, Resource /Energy Economics and Policy,

Toward an automaton Constraint for Local Search

We explore the idea of using finite automata to implement new constraints for local search (this is already a successful technique in constraint-based global search). We show how it is possible to maintain incrementally the violations of a constraint and its decision variables from an automaton that describes a ground checker for that constraint. We establish the practicality of our approach idea on real-life personnel rostering problems, and show that it is competitive with the approach of [Pralong, 2007]

Potential Consumer Acceptance of Canned Bighead Carp: A Structural Model Analysis

The effects of socio-demographic factors on consumer ratings of product attributes of an experimental canned bighead product were analyzed. OLS techniques were used to evaluate the effects of experience consuming other canned fish products, race, gender, age, and income on the taste, texture, appearance, and aroma of canned bighead. A logit analysis was then used to measure the effects of these variables on binary choice variables related to preference comparisons and willingness-to-pay as much for canned bighead as for canned salmon and canned tuna. Responses between the comparisons of canned bighead and canned salmon or canned tuna varied. Income, region, and gender significantly affected ratings on product attributes while taste variables significantly affected consumers' willingness-to-pay as much for canned bighead as for canned tuna. Conditional probabilities showed more clearly the effects of age, income, and gender on taste ratings, the subsequent effects of taste on preferences, and ultimately on willingness-to-pay. Probabilities estimated showed that canned bighead competes more favorably with canned tuna than with canned salmon.consumer preferences, structural model analysis, logit, marketing, aquaculture, Demand and Price Analysis, Environmental Economics and Policy, Food Consumption/Nutrition/Food Safety,

Propagating Regular Counting Constraints

Constraints over finite sequences of variables are ubiquitous in sequencing and timetabling. Moreover, the wide variety of such constraints in practical applications led to general modelling techniques and generic propagation algorithms, often based on deterministic finite automata (DFA) and their extensions. We consider counter-DFAs (cDFA), which provide concise models for regular counting constraints, that is constraints over the number of times a regular-language pattern occurs in a sequence. We show how to enforce domain consistency in polynomial time for atmost and atleast regular counting constraints based on the frequent case of a cDFA with only accepting states and a single counter that can be incremented by transitions. We also prove that the satisfaction of exact regular counting constraints is NP-hard and indicate that an incomplete algorithm for exact regular counting constraints is faster and provides more pruning than the existing propagator from [3]. Regular counting constraints are closely related to the CostRegular constraint but contribute both a natural abstraction and some computational advantages.Comment: Includes a SICStus Prolog source file with the propagato

Efficient structural symmetry breaking for constraint satisfaction problems

Symmetry breaking for constraint satisfaction problems (CSPs) has attracted considerable attention in recent years. Various general schemes have been proposed to eliminate symmetries. In general, these schemes may take exponential space or time to eliminate all the symmetries. We identify several classes of CSPs that encompass many practical problems and for which symmetry breaking for various forms of value and variable interchangeability is tractable using dedicated search procedures or symmetry-breaking constraints that allow nogoods and their symmetrically equivalent solutions to be stored and checked efficiently

Dynamic Demand-Capacity Balancing for Air Traffic Management Using Constraint-Based Local Search: First Results

Using constraint-based local search, we effectively model and efficiently solve the problem of balancing the traffic demands on portions of the European airspace while ensuring that their capacity constraints are satisfied. The traffic demand of a portion of airspace is the hourly number of flights planned to enter it, and its capacity is the upper bound on this number under which air-traffic controllers can work. Currently, the only form of demand-capacity balancing we allow is ground holding, that is the changing of the take-off times of not yet airborne flights. Experiments with projected European flight plans of the year 2030 show that already this first form of demand-capacity balancing is feasible without incurring too much total delay and that it can lead to a significantly better demand-capacity balance