University of Waterloo

About: University of Waterloo is a education organization based out in Waterloo, Ontario, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 36093 authors who have published 93906 publications receiving 2948139 citations. The organization is also known as: UW & uwaterloo.

An information-based sequence distance and its application to whole mitochondrial genome phylogeny

Abstract: Motivation: Traditional sequence distances require an alignment and therefore are not directly applicable to the problem of whole genome phylogeny where events such as rearrangements make full length alignments impossible. We present a sequence distance that works on unaligned sequences using the information theoretical concept of Kolmogorov complexity and a program to estimate this distance. Results: We establish the mathematical foundations of our distance and illustrate its use by constructing a phylogeny of the Eutherian orders using complete unaligned mitochondrial genomes. This phylogeny is consistent with the commonly accepted one for the Eutherians. A second, larger mammalian dataset is also analyzed, yielding a phylogeny generally consistent with the commonly accepted one for the mammals. Availability: The program to estimate our sequence distance, is available at http://www.cs.cityu.edu.hk/ ∼cssamk/gencomp/GenCompress1.htm. The distance matrices used to generate our phylogenies are available at http://www.math.uwaterloo.ca/∼mli/distance.html

Recursive Evaluation of a Family of Compound Distributions

Abstract: Compound dlstributmns such as the compound Pmsson and the compound negative binomial are used extensively m the theory of risk to model the distributmn off the total claims incurred m a fixed period of time The usual method of evaluating the dlqtributmn functmn requires the computatmn of many convolutions of the conditional d~atnbutmn of the amount of a claim given that a clmm has occurred When the expected number of claims is large, the computatmn can become unwmldy even with modern large scale electronic computers In tlus paper, a recurs|xe definitmn of the distribution of total clmms is developed for a family of claml numbel distnbutmns and arbitrary claim amount distributions When the clam1 amount is discrete, the recursive dehnitmn can be used to compute the distribution of total claims without the use of convolutions. This can reduce the number of required computations by several orders of magnitude for sufhcmntlv large portfolios Results for some spemfic dlatnbutmna have been prevmusly obtained using generating functions and Laplace transforms (see PANJER (1980) including dlscussmn). The simple algebraic proof of this paper yields all the previous results as special case~

Feedback, minimax sensitivity, and optimal robustness

Abstract: In this paper, we look for feedbacks that minimize the sensitivity function of a linear single-variable feedback system represented by its frequency responses. Sensitivity to disturbances and robustness under plant perturbations are measured in a weighted H^{\infty} norm. In an earlier paper, Zames proposed an approach to feedback design involving the measurement of sensitivity by "multiplicative seminorms," which have certain advantages over the widely used quadratic norm in problems where there is plant uncertainty, or where signal power-spectra are not fixed, but belong to sets. The problem was studied in a general setting, and some H^{\infty} examples were solved. Here, a detailed study of the single-variable case is undertaken. The results are extended to unstable plants, and explicit formulas for the general situation of a finite number of right half-plane (RHP) plant zeros or poles are provided. The Q or "approximate-inverse" parametrization of feedbacks that maintain closed-loop stability is extended to the ease of unstable plants. The H^{\infty} and Wiener-Hopf approaches are compared.

An Efficient Protocol for Authenticated Key Agreement

Abstract: This paper proposes an efficient two-pass protocol for authenticated key agreement in the asymmetric (public-key) setting. The protocol is based on Diffie-Hellman key agreement and can be modified to work in an arbitrary finite group and, in particular, elliptic curve groups. Two modifications of this protocol are also presented: a one-pass authenticated key agreement protocol suitable for environments where only one entity is on-line, and a three-pass protocol in which key confirmation is additionally provided. Variants of these protocols have been standardized in IEEE P1363 [17], ANSI X9.42 [2], ANSI X9.63 [4] and ISO 15496-3 [18], and are currently under consideration for standardization and by the U.S. government's National Institute for Standards and Technology [30].

Children's Peer Relationships: Longitudinal Prediction of Internalizing and Externalizing Problems from Middle to Late Childhood.

Abstract: In this longitudinal study, the predictive relations between social difficulties in early childhood (grade 2) and subsequent internalizing as well as externalizing problems in middle childhood (grade 5) were examined. Of particular interest was whether early indices of social isolation would predict internalizing problems 3 years later. A longitudinal sample of 87 children were assessed in both grades 2 and 5 on a variety of measures, including sociometric ratings, peer assessments of aggression and isolation, and self-appraisals of social competence. In the second grade, observations of isolated and aggressive behavior were made, as well, and teacher ratings of internalizing and externalizing difficulties were obtained. In the fifth grade, teacher ratings of shy-anxious and acting-out behavior and self-reports of loneliness and self-esteem were collected. Consistent with previous research, results demonstrated predictive links between early peer rejection (unpopularity) and aggression and subsequent externalizing difficulties. Internalizing problems in middle childhood were significantly related to early social difficulties, particularly those of an internalizing sort, including poor peer acceptance, social isolation, and perceptions of social incompetence. Social isolation, then, may indeed be a risk factor in early development.