1,722,537 research outputs found
Micro-Raman investigation of the nanostructure evolution of Boron-doped SiOC powders after pyrolysis at high temperature
No full textPolymer-derived ceramics, constitute a class of ceramic materials obtained through pyrolysis of pre-ceramic polymers. Initial examples of PDCs were the silicon carbide fibers for high temperature structural applications. Recently, boron doped silicon-based ceramics with enhanced high-temperature stability have attracted great attention [1]. SiOC:B samples, with different B content, were synthesized using the sol gel method at different B concentration and the synthesized samples underwent pyrolysis at 1200°C and 1400°C. Herein, we present the spectroscopic study of thermally treated SiOC:B samples doped with increasing amounts of boron. The study of has been done using micro Raman spectroscopy. In pure SiOC powders, treated at 1400°C , the two D and G bands which are barely visible in SiOC sample treated at 1200°C , turn out in the form of well resolved peaks at about 1332 cm-1 and 1609 cm-1. The temperature evaluation of these two fingerprints indicates that the graphitic component of SiOC powders undergoes an important structural rearrangement. In samples with higher concentration of B, treated at 1400°C, there is a clear evidence of the D’ at 1605 cm-1, G’(2D) at 2658 cm-1 and D+G at 2913 cm-1.The 2D band is sensitive to the stacking of graphene sheets, which becomes well defined at 1400°C
Materials Photonic Bandgap in Heterostructure
No full textIn the present communication We found the large band gap in photonic heterostructure (PC1/PC2) composed of metamaterials and magnetic materials by using simple transfer matrix method. The meta-materials have the unusual electromagnetic properties having negative refractive index. The negative index material is also affected with their optical parameters like refractive index, electrical permittivity, magnetic permeability and thickness of the materials. The PC1 and PC2 are the two photonic crystal containing NIM with different thickness ratio. When these two PCs are combined and make a heterostruture of PC1/PC2 of different thicknesses ratio then the band gap of such heterostruture become large due to the band gap of PC1 and PC2. Such structure may be used as a broad band filter for TE and TM mode
Natural Materials—Interesting Candidates for Carbon Nanomaterials
No full textThis review sums up the techniques used for the synthesis of carbon nanotubes (CNTs), carbon nanofibers (CNFs), and carbon nanospheres (CNSs) by employing catalysts of natural origin. Establishing large-scale production and commercial applications of CNTs for a sustainable society is still of high apprehension. In this regard, one of the major factors is the starting materials such as precursors and catalyst sources. However, natural materials contain a minor quantity of metals or metal oxides and could be employed as a catalyst source for the synthesis of CNTs, providing the possibility to replace expensive catalyst sources. A large number of successful studies have been completed so far and confirm that these developed methods for carbon nanomaterials synthesis exhibiting high quality from common natural materials are not only possible but, most importantly, promising and scalable. This review also highlights purification methods and recent promising applications of as-synthesized CNTs
Investment decision-making under risk (reliability) and uncertainty for infrastructure asset management
Full text linkRisks and uncertainties are inevitable in engineering projects and infrastructure investments. Decisions about investment in infrastructure such as for maintenance, rehabilitation and construction works can pose risks, and may generate significant impacts on social, cultural, environmental and other related issues. This report presents the results of a literature review of current practice in identifying, quantifying and managing risks and predicting impacts as part of the planning and assessment process for infrastructure investment proposals. In assessing proposals for investment in infrastructure, it is necessary to consider social, cultural and environmental risks and impacts to the overall community, as well as financial risks to the investor. The report defines and explains the concept of risk and uncertainty, and describes the three main methodology approaches to the analysis of risk and uncertainty in investment planning for infrastructure, viz examining a range of scenarios or options, sensitivity analysis, and a statistical probability approach, listed here in order of increasing merit and complexity. Forecasts of costs, benefits and community impacts of infrastructure are recognised as central aspects of developing and assessing investment proposals. Increasingly complex modelling techniques are being used for investment evaluation. The literature review identified forecasting errors as the major cause of risk. The report contains a summary of the broad nature of decision-making tools used by governments and other organisations in Australia, New Zealand, Europe and North America, and shows their overall approach to risk assessment in assessing public infrastructure proposals. While there are established techniques to quantify financial and economic risks, quantification is far less developed for political, social and environmental risks and impacts.\ud
The report contains a summary of the broad nature of decision-making tools used by governments and other organisations in Australia, New Zealand, Europe and North America, and shows their overall approach to risk assessment in assessing public infrastructure proposals. While there are established techniques to quantify financial and economic risks, quantification is far less developed for political, social and environmental risks and impacts. For risks that cannot be readily quantified, assessment techniques commonly include classification or rating systems for likelihood and consequence. The report outlines the system used by the Australian Defence Organisation and in the Australian Standard on risk management. After each risk is identified and quantified or rated, consideration can be given to reducing the risk, and managing any remaining risk as part of the scope of the project. The literature review identified use of risk mapping techniques by a North American chemical company and by the Australian Defence Organisation. This literature review has enabled a risk assessment strategy to be developed, and will underpin an examination of the feasibility of developing a risk assessment capability using a probability approach
Raman Spectroscopy and In Situ XRD Probing of the Thermal Decomposition of Sb2Se3 Thin Films
No full textChallenges in residual service life assessment for refurbishment
Full text linkA need for an efficient life care management of building portfolio is becoming increasingly due to increase in\ud
aging building infrastructure globally. Appropriate structural engineering practices along with facility\ud
management can assist in optimising the remaining life cycle costs for existing public building portfolio. A\ud
more precise decision to either demolish, refurbish, do nothing or rebuilt option for any typical building under\ud
investigation is needed. In order to achieve this, the status of health of the building needs to be assessed\ud
considering several aspects including economic and supply-demand considerations.\ud
An investment decision for a refurbishment project competing with other capital works and/or refurbishment\ud
projects can be supported by emerging methodology residual service life assessment. This paper discusses\ud
challenges in refurbishment projects of public buildings and with a view towards development of residual\ud
service life assessment methodolog
Review on Australian and international practices for asset management in building infrastructure
Full text linkBoth in developed and developing economies, major public funding is invested in civil infrastructure assets. Efficiency and comfort level of expected and demanded living standards are largely dependant on the management strategies of these assets. Buildings are one of the major & vital assets, which need to be maintained primarily to ensure its functionality by effective & efficient delivery of services and to optimize economic benefits. Not withstanding, public building infrastructure is not considered in Infrastructure report card published by Australian Infrastructure Report Card Alliance Partners (2001). The reason appears to be not having enough data to rate public building infrastructure. American Infrastructure Report Card (2001) gave “School Buildings” ‘d-’ rating, which is below ‘poor’. For effective asset management of building infrastructure, a need emerged to optimise the budget for managing assets, to cope up with increased user expectations, to response effectively to possible asset failures, to deal with ageing of assets and aging populations and to treat other scenarios including technology advancement and non-asset solutions. John (Asset Management, 2001) suggests that in the area of asset management worldwide, UK, Australia and New Zealand are leading
International practices in investment decision making in road sector
Full text linkThis document provides the findings of an international review of investment decision-making practices in road asset management. Efforts were concentrated on identifying the strategic objectives of agencies in road asset management, establishing and understanding criteria different organisations adopted and ascertaining the exact methodologies used by different countries and international organisations. Road assets are powerful drivers of economic development and social equity. They also have significant impacts on the natural and man-made environment. The traditional definition of asset management is “A systematic process of maintaining, upgrading and operating physical assets cost effectively. It combines engineering principles with sound business practices and economic theory and it provides tools to facilitate a more organised, logical approach to decision-making” (US Dept. of Transportation, 1999). In recent years, the concept has been broadened to cover the complexity of decision making, based on a wider variety of policy considerations as well as social and environmental issues rather than is covered by Benefit-Cost analysis and pure technical considerations. Current international practices are summarised in table 2. It was evident that Engineering-economic analysis methods are well advanced to support decision-making. A range of tools available supports performance predicting of road assets and associated cost/benefit in technical context. The need for considering triple plus one bottom line of social, environmental and economic as well as political factors in decision-making is well understood by road agencies around the world. The techniques used to incorporate these however, are limited. Most countries adopt a scoring method, a goal achievement matrix or information collected from surveys. The greater uncertainty associated with these non-quantitative factors has generally not been taken into consideration. There is a gap between the capacities of the decision-making support systems and the requirements from decision-makers to make more rational and transparent decisions. The challenges faced in developing an integrated decision making framework are both procedural and conceptual. In operational terms, the framework should be easy to be understood and employed. In philosophical terms, the framework should be able to deal with challenging issues, such as uncertainty, time frame, network effects, model changes, while integrating cost and non-cost values into the evaluation. The choice of evaluation techniques depends on the feature of the problem at hand, on the aims of the analysis, and on the underlying information base At different management levels, the complexity in considering social, environmental, economic and political factor in decision-making is different. At higher the strategic planning level, more non-cost factors are involved. The complexity also varies based on the scope of the investment proposals. Road agencies traditionally place less emphasis on evaluation of maintenance works. In some cases, social equity, safety, environmental issues have been used in maintenance project selection. However, there is not a common base for the applications
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