Simple Load Balancing for Distributed Hash Tables

Distributed hash tables have recently become a useful building block for a variety of distributed applications. However, current schemes based upon consistent hashing require both considerable implementation complexity and substantial storage overhead to achieve desired load balancing goals. We argue in this paper that these goals can b e achieved more simply and more cost-effectively. First, we suggest the direct application of the "power of two choices" paradigm, whereby an item is stored at the less loaded of two (or more) random alternatives. We then consider how associating a small constant number of hash values with a key can naturally b e extended to support other load balancing methods, including load-stealing or load-shedding schemes, as well as providing natural fault-tolerance mechanisms

Fast Approximate Reconciliation of Set Differences

We present new, simple, efficient data structures for approximate reconciliation of set differences, a useful standalone primitive for peer-to-peer networks and a natural subroutine in methods for exact reconciliation. In the approximate reconciliation problem, peers A and B respectively have subsets of elements SA and SB of a large universe U. Peer A wishes to send a short message M to peer B with the goal that B should use M to determine as many elements in the set SB–SA as possible. To avoid the expense of round trip communication times, we focus on the situation where a single message M is sent. We motivate the performance tradeoffs between message size, accuracy and computation time for this problem with a straightforward approach using Bloom filters. We then introduce approximation reconciliation trees, a more computationally efficient solution that combines techniques from Patricia tries, Merkle trees, and Bloom filters. We present an analysis of approximation reconciliation trees and provide experimental results comparing the various methods proposed for approximate reconciliation.National Science Foundation (ANI-0093296, ANI-9986397, CCR-0118701, CCR-0121154); Alfred P. Sloan Research Fellowshi

Design of a dynamic balance assessment system

The aim of this work was to design, build and test a system that could perturb a test subject standing upon it in order to assess their ability to react to these changes. This would be achieved by rapidly t~ltingt he surface on which the person was standing and then returning it to the horizontal position. From this it could be determined whether the test subject was able to maintain a state of balance or how long it took them to return to that state of balance. This state of balance would be determined by measuring the subject's postural sway by using a foot pressure profile plate to determine how much deviation there was during testing. This system was also designed to be more versatile and affordable than what is currently available commercially, as while these machnes are important for studies they are not in common use at present due to their cost. The newly developed system presented in ths thesis, has been used to move test subjects up to 100kg in weight

A Comparison of Instructional Delivery Methods Based on Student Evaluation Data

Distance Education is an increasingly common educational delivery method. At Old Dominion University, all junior and senior level engineering technology courses are offered via distance education at least once every two years. A majority of courses in the distance education system at this university have three simultaneous delivery methods: on-campus, televised (receiving the course at an off-campus site via satellite video/audio), and internet-based video-streamed. This paper explores the results of student course evaluation surveys for trends, in particular those trends which can be a result of the mode of delivery. Results of these surveys for 23 courses over a 4-year period are tabulated, and probable reasons for the trends are given

English guides to etymology from Skeat to Durkin

This paper examines six guides to the etymology of English, written for nonspecialist readers between 1887 and 2009. Four are by etymological lexicographers (two by W. W. Skeat and one each by Anatoly Liberman and Philip Durkin) and two by philologists with strong etymological interests (A. S. C. Ross and W. B. Lockwood). The paper seeks to present their contents, to compare them with each other, and to contextualize them both in the internal history and in the social history of scholarship

English dictionaries as sources for work in English historical linguistics: An overview

An overview of dictionaries of English as primary and secondary sources for the history of the English language, with notes on what can be learned from the study of early dictionaries, and on the development, present state, and possible future of scholarly historical lexicography in English

STEPHEN SKINNER’S ETYMOLOGICON AND OTHER ENGLISH ETYMOLOGICAL DICTIONARIES 1650-1700

STEPHEN SKINNER’S ETYMOLOGICONAND OTHER ENGLISH ETYMOLOGICAL DICTIONARIES1650-170