Asynchronous Variational Integrators

We describe a new class of asynchronous variational integrators (AVI) for nonlinear elastodynamics. The AVIs are distinguished by the following attributes: (i) The algorithms permit the selection of independent time steps in each element, and the local time steps need not bear an integral relation to each other; (ii) the algorithms derive from a spacetime form of a discrete version of Hamilton’s variational principle. As a consequence of this variational structure, the algorithms conserve local momenta and a local discrete multisymplectic structure exactly. To guide the development of the discretizations, a spacetime multisymplectic formulation of elastodynamics is presented. The variational principle used incorporates both configuration and spacetime reference variations. This allows a unified treatment of all the conservation properties of the system.A discrete version of reference configuration is also considered, providing a natural definition of a discrete energy. The possibilities for discrete energy conservation are evaluated. Numerical tests reveal that, even when local energy balance is not enforced exactly, the global and local energy behavior of the AVIs is quite remarkable, a property which can probably be traced to the symplectic nature of the algorith

Holistic engineering design : a combined synchronous and asynchronous approach

To aid the creation and through-life support of large, complex engineering products, organizations are placing a greater emphasis on constructing complete and accurate records of design activities. Current documentary approaches are not sufficient to capture activities and decisions in their entirety and can lead to organizations revisiting and in some cases reworking design decisions in order to understand previous design episodes. Design activities are undertaken in a variety of modes; many of which are dichotomous, and thus each require separate documentary mechanisms to capture information in an efficient manner. It is possible to identify the modes of learning and transaction to describe whether an activity is aimed at increasing a level of understanding or whether it involves manipulating information to achieve a tangible task. The dichotomy of interest in this paper is that of synchronous and asynchronous working, where engineers may work alternately as part of a group or as individuals and where different forms of record are necessary to adequately capture the processes and rationale employed in each mode. This paper introduces complimentary approaches to achieving richer representations of design activities performed synchronously and asynchronously, and through the undertaking of a design based case study, highlights the benefit of each approach. The resulting records serve to provide a more complete depiction of activities undertaken, and provide positive direction for future co-development of the approaches

Asynchronous Variational Contact Mechanics

An asynchronous, variational method for simulating elastica in complex contact and impact scenarios is developed. Asynchronous Variational Integrators (AVIs) are extended to handle contact forces by associating different time steps to forces instead of to spatial elements. By discretizing a barrier potential by an infinite sum of nested quadratic potentials, these extended AVIs are used to resolve contact while obeying momentum- and energy-conservation laws. A series of two- and three-dimensional examples illustrate the robustness and good energy behavior of the method

Online vs. face-to-face discussions in a web-based research methods course for postgraduate nursing students : A quasi-experimental study

Background: Web-based technologies are increasingly being used to create modes of online learning for nurses but their effect has not been assessed in nurse education. Objectives: Assess whether participation in face-to-face discussion seminars or online asynchronous discussion groups had different effects on educational attainment in a webbased course. Design: Non-randomised or quasi-experimental design with two groups – students choosing to have face-to-face discussion seminars and students choosing to have online discussions. Setting: The Core Methods module of a postgraduate research methods course. Participants: All 114 students participating in the first 2 years during which the course teaching material was delivered online. Outcome: Assignment mark for Core Methods course module. Methods: Background details of the students, their choices of modules and assignment marks were collected as part of the routine course administration. Students’ online activities were identified using the student tracking facility within WebCT. Regression models were fitted to explore the association between available explanatory variables and assignment mark. Results: Students choosing online discussions had a higher Core Methods assignment mark (mean 60.8/100) than students choosing face-to-face discussions (54.4); the difference was statistically significant (t = 3.13, df = 102, p = 0.002), although this ignores confounding variables. Among online discussion students, assignment mark was significantly correlated with the numbers of discussion messages read (Kendall’s taub = 0.22, p = 0.050) and posted (Kendall’s taub = 0.27, p = 0.017); among face-to-face discussion students, it was significantly associated with the number of non-discussion hits in WebCT (Kendall’s taub = 0.19, p = 0.036). In regression analysis, choice of discussion method, whether an MPhil/PhD student, number of non-discussion hits in WebCT, number of online discussion messages read and number posted were associated with assignment mark at the 5% level of significance when taken singly; in combination, only whether an MPhil/PhD student (p = 0.024) and number of non-discussion hits (p = 0.045) retained significance. Conclusions: This study demonstrates that a research methods course can be delivered to postgraduate healthcare students at least as successfully by an entirely online method in which students participate in online discussion as by a blended method in which students accessing web-based teaching material attend face-to-face seminar discussions. Increased online activity was associated with higher assignment marks. The study highlights new opportunities for educational research that arise from the use of virtual learning environments that routinely record the activities of learners and tutors

Adaptation of the Electric Machines Learning Process to the European Higher, Education Area

In this paper the basic lines of a complete teaching methodology that has been developed to adaptthe electric machines learning process to the European Higher Education Area (EHEA) arepresented. New teaching materials that are specific to Electric Machines have been created(textbooks, self-learning e-books, guidelines for achieving teamwork research, etc.). Working ingroups has been promoted, as well as problem solving and self-learning exercises, all of which areevaluated in a way that encourages students' participation. Finally, the students' learning process inthe lab has been improved by the development both of a new methodology to follow in the lab andnew workbenches with industrial machines that are easier to use and also enable the labexperiments to be automated. Finally, the first results obtained as a result of applying the proposedmethodology are presented

Gossip Dual Averaging for Decentralized Optimization of Pairwise Functions

In decentralized networks (of sensors, connected objects, etc.), there is an important need for efficient algorithms to optimize a global cost function, for instance to learn a global model from the local data collected by each computing unit. In this paper, we address the problem of decentralized minimization of pairwise functions of the data points, where these points are distributed over the nodes of a graph defining the communication topology of the network. This general problem finds applications in ranking, distance metric learning and graph inference, among others. We propose new gossip algorithms based on dual averaging which aims at solving such problems both in synchronous and asynchronous settings. The proposed framework is flexible enough to deal with constrained and regularized variants of the optimization problem. Our theoretical analysis reveals that the proposed algorithms preserve the convergence rate of centralized dual averaging up to an additive bias term. We present numerical simulations on Area Under the ROC Curve (AUC) maximization and metric learning problems which illustrate the practical interest of our approach