4,906 research outputs found

    Exploring the issues in knowledge management

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    This paper introduces a general, formal treatment of dynamic constraints, i.e., constraints on the state changes that are allowed in a given state space. Such dynamic constraints can be seen as representations of "real world" constraints in a managerial context. The notions of transition, reversible and irreversible transition, and transition relation will be introduced. The link with Kripke models (for modal logics) is also made explicit. Several (subtle) examples of dynamic constraints will be given. Some important classes of dynamic constraints in a database context will be identified, e.g. various forms of cumulativity, non-decreasing values, constraints on initial and final values, life cycles, changing life cycles, and transition and constant dependencies. Several properties of these dependencies will be treated. For instance, it turns out that functional dependencies can be considered as "degenerated" transition dependencies. Also, the distinction between primary keys and alternate keys is reexamined, from a dynamic point of view.

    Parametric Manifolds I: Extrinsic Approach

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    A parametric manifold can be viewed as the manifold of orbits of a (regular) foliation of a manifold by means of a family of curves. If the foliation is hypersurface orthogonal, the parametric manifold is equivalent to the 1-parameter family of hypersurfaces orthogonal to the curves, each of which inherits a metric and connection from the original manifold via orthogonal projections; this is the well-known Gauss-Codazzi formalism. We generalize this formalism to the case where the foliation is not hypersurface orthogonal. Crucial to this generalization is the notion of deficiency, which measures the failure of the orthogonal tangent spaces to be surface-forming, and which behaves very much like torsion. Some applications to initial value problems in general relativity will be briefly discussed.Comment: Plain TeX, 21 pages, no figure

    The neurobiology of circadian rhythms

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    Purpose of review There is growing awareness of the importance of circadian rhythmicity in various research fields. Exciting developments are ongoing in the field of circadian neurobiology linked to sleep, food intake, and memory. With the current knowledge of critical ‘clock genes’ (genes found to be involved in the generation of circadian rhythms) and novel techniques for imaging cyclic events in brain and peripheral tissue, this field of research is rapidly expanding. We reviewed only some of the highlights of the past year, and placed these findings into a mutual circadian perspective. Recent findings Recent findings on the organization of the circadian clock systems are addressed, ranging from the retina to the suprachiasmatic nucleus and peripheral organs. Novel developments in sleep, food intake, and memory research linked to circadian aspects are discussed. Summary The neurobiology of circadian rhythms is pivotal to the orchestration of the temporal organization of an individual’s physiology and behavior. Endogenous circadian timing systems underlie coupling and uncoupling mechanisms of many neuronal and physiological processes, the latter possibly inducing health risks to the organism. The integration of sleep, food intake and memory in a circadian setting has clear potential as a systems neurobiology line of research.

    Statistical analysis of the velocity and scalar fields in reacting turbulent wall-jets

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    The concept of local isotropy in a chemically reacting turbulent wall-jet flow is addressed using direct numerical simulation (DNS) data. Different DNS databases with isothermal and exothermic reactions are examined. The chemical reaction and heat release effects on the turbulent velocity, passive scalar and reactive species fields are studied using their probability density functions (PDF) and higher order moments for velocities and scalar fields, as well as their gradients. With the aid of the anisotropy invariant maps for the Reynolds stress tensor the heat release effects on the anisotropy level at different wall-normal locations are evaluated and found to be most accentuated in the near-wall region. It is observed that the small-scale anisotropies are persistent both in the near-wall region and inside the jet flame. Two exothermic cases with different Damkohler number are examined and the comparison revealed that the Damkohler number effects are most dominant in the near-wall region, where the wall cooling effects are influential. In addition, with the aid of PDFs conditioned on the mixture fraction, the significance of the reactive scalar characteristics in the reaction zone is illustrated. We argue that the combined effects of strong intermittency and strong persistency of anisotropy at the small scales in the entire domain can affect mixing and ultimately the combustion characteristics of the reacting flow

    Governance Challenges for Not-For-Profit Organisations: Empirical Evidence in Support of a Contingency Approach

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    This article presents empirical evidence of the governance challenges faced by Australian not-for-profit (NFP) organisations. There is a dearth of academic research in the not-for-profit sector on issues of governance. Using survey and interview data, we explore what NFP leaders believe are key governance challenges, and what this means for theory and practice of NFP governance. We demonstrate that the effectiveness of governance systems is influenced by internal and external contingencies that NFP organisations face, such as variations in board roles, stakeholder and membership demands, funding arrangements, board member recruitment processes, skills of board members, and resources for training and development. We argue for a shift of focus away from prescriptive and normative NFP governance models, and contend that generic best practice governance standards for NFPs ought not to be further pursued, and that a contingency approach is more promising

    The Governance of Corporate Sustainability: Empirical Insights into the Development, Leadership and Implementation of Responsible Business Strategy

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    This article explores how corporate governance processes and structures are being used in large Australian companies to develop, lead and implement corporate responsibility strategies. It presents an empirical analysis of the governance of sustainability in fifty large listed companies based on each company's disclosures in annual and sustainability reports. We find that significant progress is being made by large listed Australian companies towards integrating sustainability into core business operations. There is evidence of leadership structures being put in place to ensure that board and senior management are involved in sustainability strategy development and are then incentivised to monitor and ensure implementation of that strategy through financial rewards. There is evidence of a willingness to engage and communicate clearly the results of these strategies to interested stakeholders. Overall, there appears to be a developing acceptance amongst large corporations that efforts towards improved corporate sustainability are not only expected but are of value to the business. We suggest that this is evidence of a managerial shift away from an orthodox shareholder primacy understanding of the corporation towards a more enlightened shareholder value approach, often encompassing a stakeholder-orientated view of business strategy. However, strong underlying tensions remain due to the insistent market emphasis on shareholder value. © 2013 Springer Science+Business Media Dordrecht

    Miscanthus Establishment and Survival

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    Rising costs of petroleum fuels and increased awareness of the adverse effects of greenhouse gases have spurred interest in renewable fuels and other ‘green’ products. Recent legislation has set goals of approximately 20 billion gallons of renewable fuel produced from non-corn starch sources by the year 2022. These driving forces have increased interest in dedicated bioenergy crops. Among perennial grasses, which have received an exceptional amount of attention as dedicated energy crops, one stands out: Miscanthus (Miscanthus × giganteus)
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