28 research outputs found

    Stabilization and pumping of giant vortices in dilute Bose-Einstein condensates

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    Recently, it was shown that giant vortices with arbitrarily large quantum numbers can possibly be created in dilute Bose-Einstein condensates by cyclically pumping vorticity into the condensate. However, multiply quantized vortices are typically dynamically unstable in harmonically trapped nonrotated condensates, which poses a serious challenge to the vortex pump procedure. In this theoretical study, we investigate how the giant vortices can be stabilized by the application of a Gaussian potential peak along the vortex core. We find that achieving dynamical stability is feasible up to high quantum numbers. To demonstrate the efficiency of the stabilization method, we simulate the adiabatic creation of an unsplit 20-quantum vortex with the vortex pump.Comment: 8 pages, 6 figures; to be published in J. Low Temp. Phys., online publication available at http://dx.doi.org/10.1007/s10909-010-0216-

    Procedural and declarative knowledge: an evolutionary perspective

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    It appears that there are resemblances in the organization of memory and the visual system, although the functions of these faculties differ considerably. In this article, the principles behind this organization are discussed. One important principle regards the distinction between declarative and procedural knowledge, between knowing that and knowing how. Declarative knowledge is considered here not as an alternative kind of knowledge, as is usually the case in theories of memory, but as part of procedural knowledge. In our view this leads to another approach with respect to the distinction. Declarative knowledge has occupied more attention in (cognitive) psychological research than can be justified on the basis of the importance of procedural knowledge for behavior. We also discuss the question whether there are other brain faculties that reflect the same organizational characteristics. We conclude with some speculations about the consequent role of consciousness in such a tentative model

    Managing the tension between performance measurement and strategy : coping strategies

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    Purpose - The aim of this paper is to explore an important but relatively uncharted territory: the actual functioning of performance measurement systems (PMS) in their organisational context. The objective of the paper is to document the ways in which managers go about aligning operational measures with their organisation's strategy in practice. Design/methodology/approach - This research adopts an interpretive multiple-case approach in order to gather rich data on the strategies used in managing operational PMS. Data were collected from detailed interviews with managers and supervisors in four government agencies. Findings - The expectations were that the operations managers would adjust their performance measures to support the changes in strategy. This was not the case. All the interviewees employed one or more tactics to cope with the tensions between strategy and performance measures. The ten tactics identified are collected into three strategies; do-nothing strategy, pseudo-realigning strategy, and distracting strategy. Research limitations/implications - This paper casts some doubt on the practice, rather than the principle, of strategy-aligned performance management. More work needs to be carried out to ascertain how other, both for profit and public sector, organisations deal with these tensions in practice. Practical implications - From a practitioner point of view it raises the question as to whether senior managers are exerting sufficient control over the alignment issue or providing suitable tools, methods or indeed incentives to bring alignment about. Originality/value - The paper highlights a gap between theory and practice and suggests that the way to ensure implementation of "modern management methods," might be to deal firstly with the issues of relevance, timeliness, structure, integration, and symmetry
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