Chris C. Handley

Permutations of a Multiset Avoiding Permutations of Length 3

Abstract We consider permutations of a multiset which do not contain certain ordered patterns of length 3. For each possible set of patterns we provide a structural description of the permutations avoiding those patterns, and in many cases a complete enumeration of such permutations according to the underlying multiset.

Programming contest strategy

Each year the ACM hosts a truly international programming contest - the International Collegiate Programming Contest (ICPC). Dating back to a contest held by Texas AM and, if so, then what that strategy should be. We show that a team can gain an advantage by choosing a good strategy, but that there is no one best strategy. A team must choose between winning by number of solved problems and winning by points. Finding the optimal strategy to win by problems is shown to be NP-complete, while to win by points a team must solve problems in order from easiest to hardest.

High-Resolution Modeling of Energy-Services Supply Systems Using deeco: Overview and Application to Policy Development

Contemporary energy policy problems typically involve issues of (1) technology selection, placement, and scheduling, (2) energy-services demand modification by location and time-of-use, and/or (3) new sourcing options including emerging renewables. The high-resolution energy systems modeling environment deeco (dynamic energy, emissions, and cost optimization) naturally captures interactions between these components. deeco can assist with the search for policy sets which reduce CO2 and/or displace depletable resource use and which take advantage of cost-effective system integration synergies. The network management objective may be treated as an exogenous variable and process performance can depend on the thermodynamic intensive state of the system. Numerical studies indicate that multiple policy interventions cannot be assumed to be independent and that staging can be significant.

The analysis and reconstruction of repetitive textures

Many interesting textures, whether natural, such as reptile skin, or synthetic, such as knitting, are made up of repeating elements. For these textures it can be shown that a suitably painted parallelogram tile can recreate the original image. This tile can be characterised by the vectors that define adjacent sides. Several methods have been proposed to extract these vectors. The paper examines and extends these and introduces new ones. These methods have been applied to a wide variety of images, and interesting and novel ways of modifying the synthesis process to introduce local deformations are explored.

Restricted permutations and queue jumping

A connection between permutations that avoid 4231 and a certain queuing discipline is established. It is proved that a more restrictive queuing discipline corresponds to avoiding both 4231 and 42513, and enumeration results for such permutations are given.

Monotonic sequence games

In a monotonic sequence game, two players alternately choose elements of a sequence from some fixed ordered set. The game ends when the resulting sequence contains either an ascending subsequence of length a or a descending one of length d. We investigate the behaviour of this game when played on finite linear orders or Q and provide some general observations for play on arbitrary ordered sets.

Permuting machines and priority queues

Machines whose sole function is to re-order their input data are considered. Every such machine defines a set of allowable input-output pairs of permutations. These sets are studied in terms of the minimal disallowed pairs (the basis). Some allowable sets with small bases are considered including the one defined by a priority queue machine. For more complex machines defined by two or more priority queues in series or parallel, the basis is proved to be infinite.