Modal characteristics of a flexible beam with multiple distributed actuators

A flexible structure with surface-bonded piezoceramic patches is modelled using Timoshenko beam theory. Exact mode shapes and natural frequencies associated with the flexural motion are computed for various piezoceramic distributed actuator arrangements. The effects of patch placement and of shear on the modal characteristics are demonstrated using a cantilevered beam as an example. Perfect bonding of the piezoceramic to the beam substructure is assumed, and for the purposes of this paper only passive piezoceramic properties are considered. The modelling technique and results obtained in a closed form are intended to assist investigations into the modelling and control of active structures with surface-bonded piezoceramic actuators. (C) 2003 Elsevier Science Ltd. All rights reserved.

On the relative complexity of labelled modal tableaux

We investigate the relative complexity of two free-variable labelled modal tableaux(KEM and Single Step Tableaux, SST). We discuss the reasons why p-simulation is not a proper measure of the relative complexity of tableaux-like proof systems, and we propose an improved comparison scale (p-search-simulation). Finally we show that KEM p-search-simulates SST while SST cannot p-search-simulate KEM.

Minimum description length, regularisation and multi-modal data

Relationships between clustering, description length, and regularisation are pointed out, motivating the introduction of a cost function with a description length interpretation and the unusual and useful property of having its minimum approximated by the densest mode of a distribution. A simple inverse kinematics example is used to demonstrate that this property can be used to select and learn one branch of a multi-valued mapping. This property is also used to develop a method for setting regularisation parameters according to the scale on which structure is exhibited in the training data. The regularisation technique is demonstrated on two real data sets, a classification problem and a regression problem.

Minimum description length, regularisation and multi-modal data

Conventional feed forward Neural Networks have used the sum-of-squares cost function for training. A new cost function is presented here with a description length interpretation based on Rissanen's Minimum Description Length principle. It is a heuristic that has a rough interpretation as the number of data points fit by the model. Not concerned with finding optimal descriptions, the cost function prefers to form minimum descriptions in a naive way for computational convenience. The cost function is called the Naive Description Length cost function. Finding minimum description models will be shown to be closely related to the identification of clusters in the data. As a consequence the minimum of this cost function approximates the most probable mode of the data rather than the sum-of-squares cost function that approximates the mean. The new cost function is shown to provide information about the structure of the data. This is done by inspecting the dependence of the error to the amount of regularisation. This structure provides a method of selecting regularisation parameters as an alternative or supplement to Bayesian methods. The new cost function is tested on a number of multi-valued problems such as a simple inverse kinematics problem. It is also tested on a number of classification and regression problems. The mode-seeking property of this cost function is shown to improve prediction in time series problems. Description length principles are used in a similar fashion to derive a regulariser to control network complexity.

Logics, thresholds, strategic power, and the promotion of liberalisation by governments: a case study from British Higher Education

Liberalisation has become an increasingly important policy trend, both in the private and public sectors of advanced industrial economies. This article eschews deterministic accounts of liberalisation by considering why government attempts to institute competition may be successful in some cases and not others. It considers the relative strength of explanations focusing on the institutional context, and on the volume and power of sectoral actors supporting liberalisation. These approaches are applied to two attempts to liberalise, one successful and one unsuccessful, within one sector in one nation – higher education in Britain. Each explanation is seen to have some explanatory power, but none is sufficient to explain why competition was generalised in the one case and not the other. The article counsels the need for scholars of liberalisation to be open to multiple explanations which may require the marshalling of multiple sources and types of evidence.

Articulating discursive and materialist conceptions of practice in the logics approach to critical policy analysis

In this article it is argued that while Glynos and Howarth’s logics of critical explanation (LCE) offers an important and promising contribution to critical policy analysis, it, along with other approaches that focus on the meaning of social action, faces a growing challenge in the form of a so-called new materialist turn in social and political theory. The article argues that there is much to be gained for the logics approach in paying closer attention to the materiality of practices in terms not only of lending greater clarity to the conception and role of social practices in the logics approach but also in enabling it fully to deliver on its critical ambition. The article explores an alternative materialist approach to the study of social practices, which hails from the post-actor–networktheory tradition and which has ontological affinities with post-structuralism. The article begins with a brief analysis of the new materialist turn in its various guises. It then critically examines the logics approach, and, in particular its conception of practice. It then explores an alternative materialist and ethnographic reading of practice, focusing on medical and care practices. It concludes with an examination of the implications for a more materialist conception of practices for the LCE’s broad deconstructive, psychoanalytic and onto-political ambitions.

Experimental investigation of inter-modal cross-gain modulation and transient effects in a two mode group erbium doped fiber amplifier

We report what we believe to be the first experimental study of inter-modal cross-gain modulation and associated transient effects as different spatial modes and wavelength channels are added and dropped within a two-mode amplifier for SDM transmission.

Reinsurance trading in Lloyd’s of London:balancing conflicting-yet-complementary logics in practice

Drawing on a year-long ethnographic study of reinsurance trading in Lloyd’s of London, this paper makes three contributions to current discussions of institutional complexity. First, we shift focus from purposeful organizational responses to institutional complexity to the everyday practices by which individuals collectively address competing demands on their work. Based on our findings, we develop a model of how individuals can balance conflicting institutional demands through a set of four interrelated practices, labeled segmenting, switching, bridging, and demarcating. Second, moving beyond the dominant focus on contradiction between logics, we show how these practices comprise a system of conflicting-yet-complementary logics, through which actors are able to both work within contradictions, whilst also exploiting the benefits of interdependent logics. Third, in contrast to most studies of newly formed hybrids and/or novel complexity, our focus on a long-standing context of institutional complexity, shows how balancing logics can become a matter of settled complexity, enacted routinely within everyday practice.

Institutional work taken literally: How logics shift as banking lawyers 'get the deal done'

The role of interest and agency in the creation and transformation of institutions, in particular the “paradox of embedded agency” (Seo & Creed, 2002) have long puzzled institutional scholars. Most recently, Lawrence and Suddaby (2006) coined the term “institutional work” to describe various strategies for creating, maintaining and disrupting institutions. This label, while useful to integrate existing research, highlights institutionalists’ lack of attention to work as actors’ everyday occupational tasks and activities. Thus, the objective of this study is to take institutional work literally and ask: How does practical work come to constitute institutional work? Drawing on concepts of “situated change” (Orlikowski, 1996) I supplement existing macro-level perspectives of change with a microscopic, practice-based alternative. I examine the everyday work of English and German banking lawyers in a global law firm. Located at the intersection of local laws, international financial markets, commercial logics and professional norms, banking lawyers’ work regularly bridges different normative settings. Hence, they must constructively negotiate contradictory meanings, practices and logics to develop shared routines that resonate with different normative frameworks and facilitate task accomplishment. Based on observation and interview data, the paper distils a process model of banking transac-tions that highlights the critical interfaces forcing English and German banking lawyers into cross-border sensemaking. It distinguishes two accounts of cross-border sensemaking: the “old story” in which contradictory practices and norms collide and the “new story” of a synthetic set of practices for collaboratively “editing” (Sahlin-Andersson, 1996) legal documentation. Data show how new practices gain shape and legitimacy over a series of dialectic contests unfolding at work and how, in turn, these contests shift institutional logics as lawyers ‘get the deal done’. These micro-mechanisms suggest that as practical and institutional work blend, everyday work-ing practices come to constitute a form of institutional agency that is situated, emergent, dialectic and, therefore, embedded.

Experimental investigation of inter-modal cross-gain modulation and transient effects in a two mode group erbium doped fiber amplifier

We report what we believe to be the first experimental study of inter-modal cross-gain modulation and associated transient effects as different spatial modes and wavelength channels are added and dropped within a two-mode amplifier for SDM transmission.

Reinsurance trading in Lloyd's of London:balancing conflicting-yet-complementary logics in practice

Drawing on a year-long ethnographic study of reinsurance trading in Lloyd’s of London, this paper makes three contributions to current discussions of institutional complexity. First, we shift focus away from structural and relatively static organizational responses to institutional complexity and identify three balancing mechanisms - segmenting, bridging, and demarcating - which allow individuals to manage competing logics and their shifting salience within their everyday work. Second, we integrate these mechanisms in a theoretical model that explains how individuals can continually keep coexisting logics, and their tendencies to either blend or disconnect, in a state of dynamic tension which makes them conflicting-yet-complementary logics. Our model shows how actors are able to dynamically balance coexisting logics, maintaining the distinction between them, whilst also exploiting the benefits of their interdependence. Third, in contrast to most studies of newly formed hybrids and/or novel complexity our focus on a long-standing context of institutional complexity shows how institutional complexity can itself become institutionalized and routinely enacted within everyday practice.

Imagery in multi-modal object learning

Spatial objects may not only be perceived visually but also by touch. We report recent experiments investigating to what extent prior object knowledge acquired in either the haptic or visual sensory modality transfers to a subsequent visual learning task. Results indicate that even mental object representations learnt in one sensory modality may attain a multi-modal quality. These findings seem incompatible with picture-based reasoning schemas but leave open the possibility of modality-specific reasoning mechanisms.