892 resultados para Construction and demolition waste
Resumo:
The oceans and coastal seas provide mankind with many benefits including food for around a third of the global population, the air that we breathe and our climate system which enables habitation of much of the planet. However, the converse is that generation of natural events (such as hurricanes, severe storms and tsunamis) can have devastating impacts on coastal populations, while pollution of the seas by pathogens and toxic waste can cause illness and death in humans and animals. Harmful effects from biogenic toxins produced by algal blooms (HABs) and from the pathogens associated with microbial pollution are also a health hazard in seafood and from direct contact with water. The overall global burden of human disease caused by sewage pollution of coastal waters has been estimated at 4 million lost person-years annually. Finally, the impacts of all of these issues will be exacerbated by climate change. A holistic systems approach is needed. It must consider whole ecosystems, and their sustainability, such as integrated coastal zone management, is necessary to address the highly interconnected scientific challenges of increased human population pressure, pollution and over-exploitation of food (and other) resources as drivers of adverse ecological, social and economic impacts. There is also an urgent and critical requirement for effective and integrated public health solutions to be developed through the formulation of politically and environmentally meaningful policies. The research community required to address "Oceans & Human Health" in Europe is currently very fragmented, and recognition by policy makers of some of the problems, outlined in the list of challenges above, is limited. Nevertheless, relevant key policy issues for governments worldwide include the reduction of the burden of disease (including the early detection of emerging pathogens and other threats) and improving the quality of the global environment. Failure to effectively address these issues will impact adversely on efforts to alleviate poverty, sustain the availability of environmental goods and services and improve health and social and economic stability; and thus, will impinge on many policy decisions, both nationally and internationally. Knowledge exchange (KE) will be a key element of any ensuing research. KE will facilitate the integration of biological, medical, epidemiological, social and economic disciplines, as well as the emergence of synergies between seemingly unconnected areas of science and socio-economic issues, and will help to leverage knowledge transfer across the European Union (EU) and beyond. An integrated interdisciplinary systems approach is an effective way to bring together the appropriate groups of scientists, social scientists, economists, industry and other stakeholders with the policy formulators in order to address the complexities of interfacial problems in the area of environment and human health. The Marine Board of the European Science Foundation Working Group on "Oceans and Human Health" has been charged with developing a position paper on this topic with a view to identifying the scientific, social and economic challenges and making recommendations to the EU on policy-relevant research and development activities in this arena. This paper includes the background to health-related issues linked to the coastal environment and highlights the main arguments for an ecosystem-based whole systems approach.
Resumo:
Abstract: Purpose – The aim of this paper is to examine and compare the performance of architects with respect to clients' rating of importance over a set of performance criteria in Nigerian public and private sector building projects. Design/methodology/approach – A survey involving clients from both public and private sectors of recently completed building projects in Nigeria was undertaken. Data analysis includes comparing similarities and differences using standardised ratio, Mann Whitney U and Wilcoxon tests. Findings – The results show that private sector clients are likely to be more concerned with cost, while public sector clients are more concerned with buildability of design. A total of 79 per cent of the criteria were similarly selected by both sectors with respect to importance of the criteria. Architects need to improve their performance significantly in about 82 per cent of the whole set of 28 criteria. The architects performed better in the public sector than the private sector and 14 per cent of the criteria were indicated as being statistically different in terms of architects' performance. Originality/value – The results provide feedback which can be incorporated in architects' future projects so as to ensure successful project implementation in the building delivery process.
Resumo:
Selection power is taken as the fundamental value for information retrieval systems. Selection power is regarded as produced by selection labor, which itself separates historically into description and search labor. As forms of mental labor, description and search labor participate in the conditions for labor and for mental labor. Concepts and distinctions applicable to physical and mental labor are indicated, introducing the necessity of labor for survival, the idea of technology as a human construction, and the possibility of the transfer of human labor to technology. Distinctions specific to mental labor, particular between semantic and syntactic labor, are introduced. Description labor is exemplified by cataloging, classification, and database description, can be more formally understood as the labor involved in the transformation of objects for description into searchable descriptions, and is also understood to include interpretation. The costs of description labor are discussed. Search labor is conceived as the labor expended in searching systems. For both description and search labor, there has been a progressive reduction in direct human labor, with its syntactic aspects transferred to technology, effectively compelled by the high relative costs of direct human labor compared to machine processes.
Strength and drying shrinkage properties of concrete containing furnace bottom ash as fine aggregate
Resumo:
Feminist theorists have long critiqued the hierarchical gender division inherent in Western societies, with the inequalities resulting from this divide being widely decried and some progress made in reducing these. Despite increased efforts to theorise trans identification in recent times, gender is still largely understood, both culturally and theoretically, as adhering to the dualism of male/female. I argue within this paper that consideration of the narratives of transpeople and their partners could expand our conceptualisation of gender and offers possible points of resistance from which to challenge the gender binary, thereby destabilising hegemonic discourses of gender. As such I explore the narratives of transpeople and their partners in relation to the construction and reconstruction of gendered subjectivities. Transpeople’s intimate partnerships, considered here due to the critique of gender norms often evident within them, are examined through the theoretical lens of Foucault’s notion of governmentality. This paper offers an example of how governmentality can be a useful tool in the effort to understand gender regulation, not least for those apparently on the margins of ‘normality’.
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In this paper, we present an investigation into using fuzzy methodologies to guide the construction of high quality feasible examination timetabling solutions. The provision of automated solutions to the examination timetabling problem is achieved through a combination of construction and improvement. The enhancement of solutions through the use of techniques such as metaheuristics is, in some cases, dependent on the quality of the solution obtained during the construction process. With a few notable exceptions, recent research has concentrated on the improvement of solutions as opposed to focusing on investigating the ‘best’ approaches to the construction phase. Addressing this issue, our approach is based on combining multiple criteria in deciding on how the construction phase should proceed. Fuzzy methods were used to combine three single construction heuristics into three different pair wise combinations of heuristics in order to guide the order in which exams were selected to be inserted into the timetable solution. In order to investigate the approach, we compared the performance of the various heuristic approaches with respect to a number of important criteria (overall cost penalty, number of skipped exams, number of iterations of a rescheduling procedure required and computational time) on twelve well-known benchmark problems. We demonstrate that the fuzzy combination of heuristics allows high quality solutions to be constructed. On one of the twelve problems we obtained lower penalty than any previously published constructive method and for all twelve we obtained lower penalty than when any of the single heuristics were used alone. Furthermore, we demonstrate that the fuzzy approach used less backtracking when constructing solutions than any of the single heuristics. We conclude that this novel fuzzy approach is a highly effective method for heuristically constructing solutions and, as such, has particular relevance to real-world situations in which the construction of feasible solutions is often a difficult task in its own right.
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Self-compacting concrete (SCC) flows into place and around obstructions under its own weight to fill the formwork completely and self-compact without any segregation and blocking. Elimination of the need for compaction leads to better quality concrete and substantial improvement of working conditions. This investigation aimed to show possible applicability of genetic programming (GP) to model and formulate the fresh and hardened properties of self-compacting concrete (SCC) containing pulverised fuel ash (PFA) based on experimental data. Twenty-six mixes were made with 0.38 to 0.72 water-to-binder ratio (W/B), 183–317 kg/m3 of cement content, 29–261 kg/m3 of PFA, and 0 to 1% of superplasticizer, by mass of powder. Parameters of SCC mixes modelled by genetic programming were the slump flow, JRing combined to the Orimet, JRing combined to cone, and the compressive strength at 7, 28 and 90 days. GP is constructed of training and testing data using the experimental results obtained in this study. The results of genetic programming models are compared with experimental results and are found to be quite accurate. GP has showed a strong potential as a feasible tool for modelling the fresh properties and the compressive strength of SCC containing PFA and produced analytical prediction of these properties as a function as the mix ingredients. Results showed that the GP model thus developed is not only capable of accurately predicting the slump flow, JRing combined to the Orimet, JRing combined to cone, and the compressive strength used in the training process, but it can also effectively predict the above properties for new mixes designed within the practical range with the variation of mix ingredients.
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There is an increasing need to identify the effect of mix composition on the rheological properties of composite cement pastes using simple tests to determine the fluidity, the cohesion and other mechanical properties of grouting applications such as compressive strength. This paper reviews statistical models developed using a fractional factorial design which was carried out to model the influence of key parameters on properties affecting the performance of composite cement paste. Such responses of fluidity included mini-slump, flow time using Marsh cone and cohesion measured by Lombardi plate meter and unit weight, and compressive strength at 3 d, 7 d and 28 d. The models are valid for mixes with 0.35 to 0.42 water-to-binder ratio (W/B), 10% to 40% of pulverised fuel ash (PFA) as replacement of cement by mass, 0.02 to 0.06% of viscosity enhancer admixture (VEA), by mass of binder, and 0.3 to 1.2% of superplasticizer (SP), by mass of binder. The derived models that enable the identification of underlying primary factors and their interactions that influence the modelled responses of composite cement paste are presented. Such parameters can be useful to reduce the test protocol needed for proportioning of composite cement paste. This paper attempts also to demonstrate the usefulness of the models to better understand trade-offs between parameters and compare the responses obtained from the various test methods which are highlighted. The multi parametric optimization is used in order to establish isoresponses for a desirability function of cement composite paste. Results indicate that the replacement of cement by PFA is compromising the early compressive strength and up 26%, the desirability function decreased.
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A dynamic mathematical model for simulating the coupled heat and moisture migration through multilayer porous building materials was proposed. Vapor content and temperature were chosen as the principal driving potentials. The discretization of the governing equations was done by the finite difference approach. A new experimental set-up was also developed in this study. The evolution of transient temperature and moisture distributions inside specimens were measured. The method for determining the temperature gradient coefficient was also presented. The moisture diffusion coefficient, temperature gradient coefficient, sorption–desorption isotherms were experimentally evaluated for some building materials (sandstone and lime-cement mortar). The model was validated by comparing with the experimental data with good agreement. Another advantage of the method lies in the fact that the required transport properties for predicting the non-isothermal moisture flow only contain the vapor diffusion coefficient and temperature gradient coefficient. They are relatively simple, and can be easily determined.
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In this paper, we postulate the direct relationship that exists between waste production and artistic objects; its manufacturing system, consumption, and subsequent waste. What arises in this relationship then, is another character of interest –and that will serve as a reference to compare its modus operandi with the place of artists and the arts–, in this sick world, the Diogenes. The obsessed that lives among the garbage. The absurdity of the conquest of the infinite of the illogical within the logical. The amount clouded and blinded, nothing is enjoyed, nothing is appreciated; the countless abandons its place in the memory –memorable– and there only exists a pathological accumulation, mountains of garbage, desires to hold on to vital faith of the belief of doing Something for themselves. Working just to work and building something that will not last, like a sand castle, accumulation of detritus and dust. A new logic is born, the enjoyment of diseases and emptiness, the destruction of a world without a history. «Artists of the world, abandon! You have nothing to lose but your own professions!» (Kaprow, 2007, p. 37).
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Sustainability is now recognised as a key issue that must be addressed in the design, construction and lifelong maintenance of civil engineering structures. This paper briefly discusses the generic aspects of sustainability, but the main focus is its application to bridges. Motorway bridges built in the 1960s and 1970s had design lives of 120 years; many, however, were showing signs of deterioration after only 20–40 years. This led to much (ongoing) debate on the issue of initial versus full life-cycle costing. In order to address the highly complex issue of the sustainability of bridges, this paper considers the following specific areas that impinge on this important subject: the impact on sustainability of different forms of bridge construction and maintenance/repair/replacement strategies; the utilisation of innovative in situ testing equipment for assessing the long-term durability of concrete; the development of innovative structural designs for bridges that inherently have greatly extended lives at minimal, if any, additional cost.