536 resultados para DYNAMIC PORTFOLIO SELECTION


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The following paper considers the question, where to office property? In doing so, it focuses, in the first instance, on identifying and describing a selection of key forces for change present within the contemporary operating environment in which office property functions. Given the increasingly complex, dynamic and multi-faceted character of this environment, the paper seeks to identify only the primary forces for change, within the context of the future of office property. These core drivers of change have, for the purposes of this discussion, been characterised as including a range of economic, demographic and socio-cultural factors, together with developments in information and communication technology. Having established this foundation, the paper proceeds to consider the manner in which these forces may, in the future, be manifested within the office property market. Comment is offered regarding the potential future implications of these forces for change together with their likely influence on the nature and management of the physical asset itself. Whilst no explicit time horizon has been envisioned in the preparation of this paper particular attention has been accorded short to medium term trends, that is, those likely to emerge in the office property marketplace over the coming two decades. Further, the paper considers the question posed, in respect of the future of office property, in the context of developed western nations. The degree of commonality seen in these mature markets is such that generalisations may more appropriately and robustly be applied. Whilst some of the comments offered with respect to the target market may find application in other arenas, it is beyond the scope of this paper to explicitly consider highly heterogeneous markets. Given also the wide scope of this paper key drivers for change and their likely implications for the commercial office property market are identified at a global level (within the above established parameters). Accordingly, the focus is necessarily such that it serves to reflect overarching directions at a universal level (with the effect being that direct applicability to individual markets - when viewed in isolation on a geographic or property type specific basis – may not be fitting in all instances)

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John Frazer's architectural work is inspired by living and generative processes. Both evolutionary and revolutionary, it explores informatin ecologies and the dynamics of the spaces between objects. Fuelled by an interest in the cybernetic work of Gordon Pask and Norbert Wiener, and the possibilities of the computer and the "new science" it has facilitated, Frazer and his team of collaborators have conducted a series of experiments that utilize genetic algorithms, cellular automata, emergent behaviour, complexity and feedback loops to create a truly dynamic architecture. Frazer studied at the Architectural Association (AA) in London from 1963 to 1969, and later became unit master of Diploma Unit 11 there. He was subsequently Director of Computer-Aided Design at the University of Ulter - a post he held while writing An Evolutionary Architecture in 1995 - and a lecturer at the University of Cambridge. In 1983 he co-founded Autographics Software Ltd, which pioneered microprocessor graphics. Frazer was awarded a person chair at the University of Ulster in 1984. In Frazer's hands, architecture becomes machine-readable, formally open-ended and responsive. His work as computer consultant to Cedric Price's Generator Project of 1976 (see P84)led to the development of a series of tools and processes; these have resulted in projects such as the Calbuild Kit (1985) and the Universal Constructor (1990). These subsequent computer-orientated architectural machines are makers of architectural form beyond the full control of the architect-programmer. Frazer makes much reference to the multi-celled relationships found in nature, and their ongoing morphosis in response to continually changing contextual criteria. He defines the elements that describe his evolutionary architectural model thus: "A genetic code script, rules for the development of the code, mapping of the code to a virtual model, the nature of the environment for the development of the model and, most importantly, the criteria for selection. In setting out these parameters for designing evolutionary architectures, Frazer goes beyond the usual notions of architectural beauty and aesthetics. Nevertheless his work is not without an aesthetic: some pieces are a frenzy of mad wire, while others have a modularity that is reminiscent of biological form. Algorithms form the basis of Frazer's designs. These algorithms determine a variety of formal results dependent on the nature of the information they are given. His work, therefore, is always dynamic, always evolving and always different. Designing with algorithms is also critical to other architects featured in this book, such as Marcos Novak (see p150). Frazer has made an unparalleled contribution to defining architectural possibilities for the twenty-first century, and remains an inspiration to architects seeking to create responsive environments. Architects were initially slow to pick up on the opportunities that the computer provides. These opportunities are both representational and spatial: computers can help architects draw buildings and, more importantly, they can help architects create varied spaces, both virtual and actual. Frazer's work was groundbreaking in this respect, and well before its time.

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We investigate the potential for the third-order aberrations coma and trefoil to provide a signed cue to accommodation. It is first demonstrated theoretically (with some assumptions) that the point spread function is insensitive to the sign of spherical defocus in the presence of odd-order aberrations. In an experimental investigation, the accommodation response to a sinusoidal change in vergence (1–3 D, 0.2 Hz) of a monochromatic stimulus was obtained with a dynamic infrared optometer. Measurements were obtained in 10 young visually normal individuals with and without custom contact lenses that induced low and high values of r.m.s. trefoil (0.25, 1.03 μm) and coma (0.34, 0.94 μm). Despite variation between subjects, we did not find any statistically significant increase or decrease in the accommodative gain for low levels of trefoil and coma, although effects approached or reached significance for the high levels of trefoil and coma. Theoretical and experimental results indicate that the presence of Zernike third-order aberrations on the eye does not seem to play a crucial role in the dynamics of the accommodation response.