FASTER OPTIMAL AND SUBOPTIMAL HIERARCHICAL SEARCH by Michael Leighton University of New Hampshire, May, 2012 In problem domains for which an informed admissible heuristic function is not available, one attractive approach is hierarchical search. Hierarchical search uses search in an abstracted version of the problem to dynamically generate heuristic values. This thesis makes three contributions...

For a general multirate SD (sampled-data) system, we characterize explicitly the set of all causal, stabilizing controllers that achieve a certain H 1 norm bound; moreover, we give explicitly a particular controller that further minimizes an entropy function for the SD system. The characterization lays the groundwork for synthesizing multirate control systems with multiple/mixed control speciic...

Finding optimal solutions to search problems is often not practical due to run-time constraints. This has led to the development of algorithms that sacrifice solution quality in favour of a faster search. The solution quality of a suboptimal solution is often measured by the ratio C C , where C is the cost of the solution found and C is the cost of the optimal solution. Some search algorithms a...

The ǫ-suboptimal set Xǫ for an optimization problem is the set of feasible points with objective value within ǫ of optimal. In this paper we describe some basic techniques for quantitatively characterizing Xǫ, for a given value of ǫ, when the original problem is convex, by solving a modest number of related convex optimization problems. We give methods for computing the bounding box of Xǫ, esti...

Though the VCG auction assumes a central place in the mechanism design literature, there are a number of reasons for favoring iterative combinatorial auction designs. Several promising ascending auction formats have been developed throughout the past few years based on primal-dual and subgradient algorithms and linear programming theory. Prices are interpreted as a feasible dual solution and th...

This paper is concerned with a problem of control in the queuing systems. Rather than deal with mean waiting time or average queue length, which is the most often used approach to this problem, it concentrates on transient states and minimizing probability of long queue. First a model of a queuing system with controlled service intensity is analyzed. Subsequently, a system with multiple service...

It is widely accepted that the optimal alignment between a pair of proteins or nucleic acid sequences that minimizes the edit distance may not necessarily re ect the correct biological alignment. Alignments of proteins based on their structures or of DNA sequences based on evolutionary changes are often di erent from alignments that minimize edit distance. However, in many cases (e.g. when the ...

OBJECTIVES The study aimed to develop and validate a model to measure psychosocial factors at work among medical staff in China based on confirmatory factor analysis (CFA). The second aim of the current study was to clarify the association between stress-related psychosocial work factors and suboptimal health status. DESIGN The cross-sectional study was conducted using clustered sampling meth...

For discrete-time systems, an H 2 suboptimal control problem is deened and analyzed. Then an algorithm called`H 2 suboptimal state feedback gain sequence' (H 2 SOSFGS) algorithm is developed. Rather than utilizing a `perturbation method' which is numerically stii and computationally prohibitive, the H 2 SOSFGS algorithm utilizes a direct eigenvalue assignment method to come up with a sequence o...