Computing elliptic membrane high frequencies by Mathieu and Galerkin methods

Resonant modes of an elliptic membrane are computed for a wide range of frequencies using a Galerkin formulation. Results are confirmed using Mathieu functions and finite-element methods. Algorithms and their implementations are described to handle Dirichlet or Neumann boundary conditions and draw animations or contour plots of the modal surfaces. The methods agree to four or more digit accuracy for the first one hundred modes. The effects of high function order and high frequency parameter upon the convergence of the modified Mathieu function series are discussed and quantified. The Galerkin method is conceptually simple and requires only an eigenvalue solver without the need of special functions.     

Model predictive control with learning‐type set‐point: Application to artificial pancreatic β‐cell

A novel combination of model predictive control (MPC) and iterative learning control (ILC), referred to learning‐type MPC (L‐MPC), is proposed for closed‐loop control in an artificial pancreatic β‐cell. The main motivation for L‐MPC is the repetitive nature of glucose‐meal‐insulin dynamics over a 24‐h period. L‐MPC learns from an individual's lifestyle, inducing the control performance to improve from day to day. The proposed method is first tested on the Adult Average subject presented in the UVa/Padova diabetes simulator. After 20 days, the blood glucose concentrations can be kept within 68–145 mg/dl when the meals are repetitive. L‐MPC can produce superior control performance compared with that achieved under MPC. In addition, L‐MPC is robust to random variations in meal sizes within ±75% of the nominal value or meal timings within ±60 min. Furthermore, the robustness of L‐MPC to subject variability is validated on Adults 1–10 in the UVa/Padova simulator. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Stewart H. Hulse (1931–2008).

This obituary describes the life achievements of Steward H. Hulse who lived from 1931-2008. He was an experimental psychologist trained in the field of animal learning. Over the course of his career, he underwent a major transformation and became one of the pioneers of the modern field of animal cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interfirm collaboration through interfirm networks

Abstract. Abstract. Since the late 1980s, interfirm (computer) networks have been diffusing very rapidly. They have not only been adopted by firms across the whole spectrum of sectors; the applications based on such networks have also been extended from routine transactions to strategically more important processes. Using recent evidence gathered from six in-depth cases studies in the UK and a telephone-based survey, this paper will illustrate how the development of interfirm networks has facilitated the emergence of new interfirm collaboration in strategic areas. The empirical evidence has been drawn from the retailing, motor manufacturing and electronics industries. To conclude, the paper will highlight several key issues that have emerged from the study, identify three layers of barriers to the development of interfirm networks, and outline a future research agenda.     

Introducing pocket PCs in schools: Attitudes and beliefs in the first year

As more schools adopt the use of handheld computers in their classrooms, research that systematically tracks their introduction is essential in order to develop a model for successful implementation leading to improved classroom teaching. This research report seeks to explore the realities of introducing and integrating handheld computers into five Victorian schools in Australia where the initiative is owned and funded by the schools themselves. The research focused on how teachers’ attitudes and beliefs evolved over about 6–7 months of implementing the pocket PCs in their teaching. The findings indicated that the effect of pocket PCs on the attitudes of primary teachers were mixed while that on the secondary teachers was uncertainty. However, both primary and secondary teachers shared similar beliefs in the motivational aspect of the technology on student engagement and its capacity to cater for weaker students, particularly in English, but not for the more academic students. Issues such as leadership roles, the time-consuming nature of lesson preparation, the need to integrate higher-order thinking tasks with pocket PC usage and personal ownership for successful integration of the technology are discussed.     

ℓ 2 2 Spreading Metrics for Vertex Ordering Problems

We design approximation algorithms for the vertex ordering problems Minimum Linear Arrangement, Minimum Containing Interval Graph, and Minimum Storage-Time Product, achieving approximation factors of $O(\sqrt{\log n}\log\log n)We design approximation algorithms for the vertex ordering problems Minimum Linear Arrangement, Minimum Containing Interval Graph, and Minimum Storage-Time Product, achieving approximation factors of O(?{logn}loglogn)O(\sqrt{\log n}\log\log n) , O(?{logn}loglogn)O(\sqrt{\log n}\log\log n) , and O(?{logT}loglogT)O(\sqrt{\log T}\log\log T) , respectively, the last running in time polynomial in T (T being the sum of execution times). The technical contribution of our paper is to introduce “ℓ ₂² spreading metrics” (that can be computed by semidefinite programming) as relaxations for both undirected and directed “permutation metrics,” which are induced by permutations of {1,2,…,n}. The techniques introduced in the recent work of Arora, Rao and Vazirani (Proc. of 36th STOC, pp. 222–231, 2004) can be adapted to exploit the geometry of such ℓ ₂² spreading metrics, giving a powerful tool for the design of divide-and-conquer algorithms. In addition to their applications to approximation algorithms, the study of such ℓ ₂² spreading metrics as relaxations of permutation metrics is interesting in its own right. We show how our results imply that, in a certain sense we make precise, ℓ ₂² spreading metrics approximate permutation metrics on n points to a factor of O(?{logn}loglogn)O(\sqrt{\log n}\log\log n) .     

A TUTORIAL ON LINEAR AND DIFFERENTIAL CRYPTANALYSIS

In this paper, we present a detailed tutorial on linear cryptanalysis and differential cryptanalysis, the two most significant attacks applicable to symmetric-key block ciphers. The intent of the paper is to present a lucid explanation of the attacks, detailing the practical application of the attacks to a cipher in a simple, conceptually revealing manner for the novice cryptanalyst. The tutorial is based on the analysis of a simple, yet realistically structured, basic Substitution-Permutation Network cipher. Understanding the attacks as they apply to this structure is useful, as the Rijndael cipher, recently selected for the Advanced Encryption Standard (AES), has been derived from the basic SPN architecture. As well, experimental data from the attacks is presented as confirmation of the applicability of the concepts as outlined.     

Quantifying repetitive hand activity for epidemiological research on musculoskeletal disorders--part I: individual exposure assessment

An exposure measurement approach is described for quantifying repetitive hand activity of individual workers in a prospective epidemiological study on work-related upper extremity musculoskeletal disorders. A total of 733 subjects were involved in this study at the baseline. Hand activities were quantified by force and repetition. Force levels were measured by workers' self-reports, ergonomists' estimates based on observation and measurements with instrumentation. Repetition levels were measured by detailed time-motion analyses using two repetitive hand activity definitions and ergonomists' estimates using scales for the American Conference of Governmental Industrial Hygienists hand activity level and the Strain Index. Results showed that the present exposure assessment approach seems to be able to quantify force level and repetitiveness of hand activities. Repetitive hand activity is quantified differently depending on whether forceful hand exertion or repetitive muscle activity is used as the definition. These hand activity definitions may quantify different physical exposure phenomena. Individual exposure assessment is important in epidemiological research of musculoskeletal disorders as there are interactions between the individual subjects and the measured parameters. These interactions may vary between exposure parameters.     

Designing time at the user interface

This paper describes research that seeks to facilitate the capture, representation, and reasoning about, temporal information by usability engineers. The product, a method we call KAT-LITTER, is an extension of Johnson and Johnson's (1991) Knowledge Analysis of Tasks (KAT). An evaluation of KAT-LITTER showed that it influenced the design process in two significant ways: firstly, designers using KAT-LITTER spent more time reasoning about temporal issues than designers using KAT alone, and secondly these same designers considered a broader spectrum of temporal issues. Further developments of KAT-LITTER are briefly discussed.