No abstract

Let A be a matrix with real entries and let j(i) be the index of the leftmost column containing the maximum value in row i ofA. A is said to be monotone if il > i2 implies thatj(il) >-j(i2). A is totally monotone if all of its submatrices are monotone. We show that finding the maximum entry in each row of an arbitrary n x m monotone matrix requires O(m log n) time, whereas if the matrix is totally monotone the time is O(m) when m-> n and is O(m(l+log(n/m))) when m < n.The problem of finding the maximum value within each row of a totally monotone matrix arises in several geometric algorithms such as the all-farthest-neighbors problem for the vertices of a convex polygon. Previously only the property of monotonicity, not total monotonicity, had been used within these algorithms. We use the | bound on finding the maxima of wide totally monotone matrices to speed up these algorithms by a factor of log n.

In this paper we present algorithms, which given a circular arrangement of n uniquely numbered processes, determine the maximum number in a distributive manner . We begin with a simple unidirectional algorithm, in which the number of messages passed is bounded by 2n log n + 0(n) . By making several improvements to the simple algorithm, we obtain a unidirectional algorithm in which the number of messages passed is bounded by 1 .5n logn + 0(n) . These algorithms disprove Hirschberg and Sinclair's'conjecture that 0(n 2 ) is a lower bound on the number of messages passed in undirectional algorithms for this problem . At the end of the paper we indicate how our methods can be used to improve an algorithm due to Peterson, to obtain a unidirectional algorithm using at most 1 .356n log n + 0(n) messages. This is the best bound so far on the number of messages passed in both the bidirectional and unidirectional cases .

No abstract

Aphasia is a cognitive disorder that impairs speech and language. From interviews with aphasic individuals, their caregivers, and speech-language pathologists, the need was identified for a daily planner that allows aphasic users to independently manage their appointments. We used a participatory design approach to develop ESI Planner (the Enhanced with Sound and Images Planner) for use on a PDA and subsequently evaluated it in a lab study. This methodology was used in order to achieve both usable and adoptable technology. In addition to describing our experience in designing ESI Planner, two main contributions are provided: general guidelines for working with special populations in the development of technology, and design guidelines for accessible handheld technology.