958 resultados para Construction and Sustainable Development
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The use of MPT in the construction real estate portfolios has two serious limitations when used in an ex-ante framework: (1) the intertemporal instability of the portfolio weights and (2) the sharp deterioration in performance of the optimal portfolios outside the sample period used to estimate asset mean returns. Both problems can be traced to wide fluctuations in sample means Jorion (1985). Thus the use of a procedure that ignores the estimation risk due to the uncertain in mean returns is likely to produce sub-optimal results in subsequent periods. This suggests that the consideration of the issue of estimation risk is crucial in the use of MPT in developing a successful real estate portfolio strategy. Therefore, following Eun & Resnick (1988), this study extends previous ex-ante based studies by evaluating optimal portfolio allocations in subsequent test periods by using methods that have been proposed to reduce the effect of measurement error on optimal portfolio allocations.
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Local, tacit and normally unspoken OHS (occupational health and safety) knowledge and practices can too easily be excluded from or remain below the industry horizon of notice, meaning that they remain unaccounted for in formal OHS policy and practice. In this article we stress the need to more systematically and routinely tap into these otherwise ‘hidden’ communication channels, which are central to how everyday safe working practices are achieved. To demonstrate this approach this paper will draw on our ethnographic research with a gang of migrant curtain wall installers on a large office development project in the north of England. In doing so we reflect on the practice-based nature of learning and sharing OHS knowledge through examples of how workers’ own patterns of successful communication help avoid health and safety problems. These understandings, we argue, can be advanced as a basis for the development of improved OHS measures, and of organizational knowing and learning.
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Cities are responsible for up to 70% of global carbon emissions and 75% of global energy consumption. By 2050 it is estimated that 70% of the world's population will live in cities. The critical challenge for contemporary urbanism, therefore, is to understand how to develop the knowledge, capacity and capability for public agencies, the private sector and multiple users in city-regions (i.e. the city and its wider hinterland) to re-engineer systemically their built environment and urban infrastructure in response to climate change and resource constraints. To inform transitions to urban sustainability, key stakeholders' perceptions were sought though a participatory backcasting and scenario foresight process in order to illuminate challenging but realistic socio-technical scenarios for the systemic retrofit of core UK city-regions. The challenge of conceptualizing complex urban transitions is explored across multiple socio-technical ‘regimes’ (housing, non-domestic buildings, urban infrastructure), scales (building, neighbourhood, city-region), and domains (energy, water, use of resources) within a participatory process. The development of three archetypal ‘guiding visions’ of retrofit city-regional futures developed through this process are discussed, along with the contribution that such foresight processes might play in ‘opening up’ the governance and strategic navigation of urban sustainability.
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In Kazakhstan, a transitional nation in Central Asia, the development of public–private partnerships (PPPs) is at its early stage and increasingly of strategic importance. This case study investigates risk allocation in an ongoing project: the construction and operation of 11 kindergartens in the city of Karaganda in the concession form for 14 years. Drawing on a conceptual framework of effective risk allocation, the study identifies principal PPP risks, provides a critical assessment of how and in what way each partner bears a certain risk, highlights the reasons underpinning risk allocation decisions and delineates the lessons learned. The findings show that the government has effectively transferred most risks to the private sector partner, whilst both partners share the demand risk of childcare services and the project default risk. The strong elements of risk allocation include clear assignment of parties’ responsibilities, streamlined financing schemes and incentives to complete the main project phases on time. However, risk allocation has missed an opportunity to create incentives for service quality improvements and take advantage of economies of scale. The most controversial element of risk allocation, as the study finds, is a revenue stream that an operator is supposed to receive from the provision of services unrelated to childcare, as neither partner is able to mitigate this revenue risk. The article concludes that in the kindergartens’ PPP, the government has achieved almost complete transfer of risks to the private sector partner. However, the costs of transfer are extensive government financial outlays that seriously compromise the PPP value for money.
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A dynamic system for stablishing a known standard gas mixture is necessary for many studies such as development and testing of analytical methods. A permeation tube can be used for this purpose. The work described here shows the construction, operation and calibration of a simple permeation tube which can be used to obtain large amounts of a standard gas.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Includes bibliography
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X-ray computed tomography (CT) refers to the cross-sectional imaging of an object measuring the transmitted radiation at different directions. In this work, we describe the development of a low cost micro-CT X-ray scanner that is being developed for nondestructive testing. This tomograph operates using a microfocus X-ray source and contains a silicon photodiode as detectors. The performance of the system, by its spatial resolution, has been estimated through its Modulation Transfer Function - MTF and the obtained value at 10% of MTF is 661 μm. It was built as a general purpose nondestructive testing device. © 2009 American Institute of Physics.
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Includes bibliography
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Includes bibliography
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Includes bibliography
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Includes bibliography
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Includes a statement of condolences presented to the Government and People of the Bolivarian Republic of Venezuela on the occasion of the passing of President Hugo Chavez
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Includes bibliography