40 resultados para split-step Fourier method

em Deakin Research Online - Australia


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Aluminium nitride (AlN) branched nanostructures with tree shapes and sea urchin shapes are synthesized via a one-step improved DC arc discharge plasma method without any catalyst and template. The branched nanostructures with tree shapes and sea urchin shapes can be easily controlled by the location of collection. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies show that the branches of tree shaped nanostructures grow in a sequence of nanowires, nanomultipeds and nanocombs. The growth mechanisms of these branched nanostructures are discussed in detail. The optical properties of AlN branched nanostructures with tree shapes and sea urchin shapes are investigated.

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The most important prevention in minimizing energy transfer in commercial buildings is the treatment of glazing in the building facade. In a commercial building, while the impacts of roof, walls and floors on the overall heating and cooling loads of the building have low effects, glazing is likely to be the most important factor. This paper investigates the BCA Section-J glazing calculator and the ETTV (Envelope Thermal Transfer Value) methods and tries to look for differences as well as similarities in calculation of building envelopes energy performance. For this investigation, a hypothetical high-rise commercial building in Melbourne, Australia is considered when evaluating the energy performance of the envelope through these two methods. Both methods consider the U-Value of glass and wall materials as well as Solar Heat Gain Coefficient (SHGC) and Shading Coefficient (SC) of the glass. Findings in this research project indicate differences and significant discrepancies between the BCA Section-J and ETTV methods in evaluating the energy performance of commercial building façades. Issues of calculation weaknesses are identified with the lack of air leakage and infiltration of a particular façade design or window to wall ratio (WWR). Suggestions have been made where improvement to the overall energy calculation through facades of a commercial building is needed.

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An improved method for mass production of good-quality graphene nanosheets (GNs) via ball milling pristine graphite with dry ice is presented. We also report the enhanced performance of these GNs as working electrode in lithium-ion batteries (LIBs). In this improved method, the decrease of necessary ball milling time from 48 to 24 h and the increase of Brunauer–Emmett–Teller surface area from 389.4 to 490 m2/g might be resulted from the proper mixing of stainless steel balls with different diameters and the optimization of agitation speed. The as-prepared GNs are investigated in detail using a number of techniques, such as scanning electron microscope, atomic force microscope, high-resolution transmission electron microscopy, selected area electron diffraction, X-ray diffractometer, and Fourier transform infrared spectroscopic. To demonstrate the potential applications of these GNs, the performances of the LIBs with pure Fe3O4 electrode and Fe3O4/graphene (Fe3O4/G) composite electrode were carefully evaluated. Compared to Fe3O4-LIBs, Fe3O4/G-LIBs exhibited prominently enhanced performance and a reversible specific capacity of 900 mAh g−1 after 5 cycles at 100 and 490 mAh g−1 after 5 cycles at 800 mA g−1. The improved cyclic stability and enhanced rate capability were also obtained.

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In 1931, Canada was the first of the copyright countries to adopt a moral rights provision, closely modeled on Article 6bis of the Berne Convention, into its legislation. But this was not the first step that Canada had taken towards the legislative protection of moral rights. Not only had certain provisions protective of the non-economic interests of authors been included in the federal Criminal Code and in the legislation of Quebec prior to 1920, but during the 1920s a sustained effort had been made to give these interests more explicit and systematic protection under the Copyright Act. The present article focuses on a series of bills put to the Canadian Parliament from 1924 onwards. Not only would they have provided increased protection for the non-economic interests of authors but they would have given a legislative definition to the term "moral right". These bills, framed in the absence of any influence from Article 6bis, provide a glimpse of what "moral rights" might have been. They support the view that Canada was moving towards the express legislative protection of these rights significantly earlier that is commonly thought.

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International taxation is concerned mainly with the equitable allocation of cross-border income between countries in which income-earning activities take place. Such allocation has traditionally been governed by the arm’s-length principle, which has been interpreted as requiring a comparable transactional pricing approach. This approach assumes that each member of a multinational enterprise (MNE) group is a separate entity and that the transactions between related parties can be separated and compared with arm’s-length transactions. It has, however, proved difficult to apply comparable transactional pricing to internationally integrated businesses, especially those involving intangibles and services, and formulary apportionment has been suggested as an alternative. Essentially, formulary apportionment treats the MNE group as a single economic entity. The group’s profit is allocated to members according to a formula that reflects the particular member’s contribution to the production of that profit. A rich academic literature exists which either defends or attacks this alternative approach. The OECD and national governments have rejected formulary apportionment mainly on the ground that it violates the arm’s-length principle. This article proposes a global profit split (GPS) method for allocating international income. The GPS would allocate the global profit of an integrated business to each country in accordance with the economic contributions made by components of the business located in that country. The allocation would be based on a formula that would reflect the economic factors that contribute to profit making. While the GPS draws on elements of the traditional formulary apportionment and profit split methods, it also differs from them. The author discusses in detail the key issues involved in designing the GPS. She also presents and evaluates the main policy and pragmatic justifications for the adoption of this innovative approach. The author argues that the GPS is not only theoretically and practically superior to traditional income allocation methods, but also consistent with the arm’s-length principle. On the basis of historical developments, interpretation of article 9 of the OECD model tax convention, and international tax policy considerations, the author establishes that the GPS is not a radical departure from the arm’s-length principle, but rather a natural development in its evolution. She concludes that the law of evolution ison the side of reform because the GPS would provide for a fair and effective allocation of income derived from globally integrated business activities.

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The tree index structure is a traditional method for searching similar data in large datasets. It is based on the presupposition that most sub-trees are pruned in the searching process. As a result, the number of page accesses is reduced. However, time-series datasets generally have a very high dimensionality. Because of the so-called dimensionality curse, the pruning effectiveness is reduced in high dimensionality. Consequently, the tree index structure is not a suitable method for time-series datasets. In this paper, we propose a two-phase (filtering and refinement) method for searching time-series datasets. In the filtering step, a quantizing time-series is used to construct a compact file which is scanned for filtering out irrelevant. A small set of candidates is translated to the second step for refinement. In this step, we introduce an effective index compression method named grid-based datawise dimensionality reduction (DRR) which attempts to preserve the characteristics of the time-series. An experimental comparison with existing techniques demonstrates the utility of our approach.

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Sustainability is becoming increasingly important in the mining and mineral processing industries and must incorporate the associated waste products. Acid mine drainage (AMD) is one such by-product and is one of the most serious environmental problems facing the minerals industry today. The oxidation of sulphidic mine wastes often continues for a substantial period of time after mine closure, resulting in difficult and costly remediation and rehabilitation works. Mining companies are often reluctant to spend increasing amounts of money on waste treatment when the mine life is limited or even finished. Hence a simple, low maintenance and low-cost method of treating AMD is required. Whilst this paper does not address the issue of AMD, it does propose methods for removal of individual species from AMD with potential benefits, including raising AMD pH.

A novel concept of using biosolids as a biological adsorbent, or ‘biosorbent’, of metals from AMD is being investigated at a laboratory/pilot scale level. Biosolids are a by-product resulting from the biological treatment of wastewater, and have been previously shown to adsorb metals from aqueous solutions. This could lead to an environmentally sustainable or ‘green’ method for treating both AMD discharges and disposing/reusing the biosolids.

The result of a laboratory-scale study of the biosorption of Zn(II) is presented in this paper. Physical parameters including reaction kinetics, mixing speed and solution pH were investigated. Solution pH also rose an average of 2 pH units over the 24 hour equilibrium time – a valuable side effect when treating acid mine drainage. The outcome of the study highlights the usefulness of biosolids as a biosorbent for the removal/recovery of metal ions from acid mine drainage. A simple, low-cost treatment technology requiring low maintenance would be beneficial to the mining industry to address some issues relating to AMD and would help integrate environmental and economic considerations into sustainable environmental management.

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One of the content-based image retrieval techniques is the shape-based technique, which allows users to ask for objects similar in shape to a query object. Sajjanhar and Lu proposed a method for shape representation and similarity measure called the grid-based method [1]. They have shown that the method is effective for the retrieval of segmented objects based on shape. In this paper, we describe a system which uses the grid-based method for retrieval of images with multiple objects. We perform experiments on the prototype system to compare the performance of the grid-based method with the Fourier descriptors method [2]. Preliminary results have been presented.

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Generic Fourier Descriptors have been used for image retrieval [12]. In this paper, we have proposed a modification to the Generic Fourier Descriptors. We have performed experiments to compare the performance of the proposed method with the standard method. Tests were performed on Set B of the MPEG-7 Still Images Content Set [13]. The experimental results show the effectiveness of the proposed method.

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This paper describes a potentially faster and cheaper method of determining fibre scale frequencies. The method uses the single fibre analyser (SIFAN) to  determine the along the fibre diameter profile. This information is then analysed by the Fast Fourier Transform technique using computer software. The paper shows the close association between the mean scale frequencies determined by this method and the traditional approach using SEM.

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A major challenge facing freshwater ecologists and managers is the development of models that link stream ecological condition to catchment scale effects, such as land use. Previous attempts to make such models have followed two general approaches. The bottom-up approach employs mechanistic models, which can quickly become too complex to be useful. The top-down approach employs empirical models derived from large data sets, and has often suffered from large amounts of unexplained variation in stream condition.

We believe that the lack of success of both modelling approaches may be at least partly explained by scientists considering too wide a breadth of catchment type. Thus, we believe that by stratifying large sets of catchments into groups of similar types prior to modelling, both types of models may be improved. This paper describes preliminary work using a Bayesian classification software package, ‘Autoclass’ (Cheeseman and Stutz 1996) to create classes of catchments within the Murray Darling Basin based on physiographic data.

Autoclass uses a model-based classification method that employs finite mixture modelling and trades off model fit versus complexity, leading to a parsimonious solution. The software provides information on the posterior probability that the classification is ‘correct’ and also probabilities for alternative classifications. The importance of each attribute in defining the individual classes is calculated and presented, assisting description of the classes. Each case is ‘assigned’ to a class based on membership probability, but the probability of membership of other classes is also provided. This feature deals very well with cases that do not fit neatly into a larger class. Lastly, Autoclass requires the user to specify the measurement error of continuous variables.

Catchments were derived from the Australian digital elevation model. Physiographic data werederived from national spatial data sets. There was very little information on measurement errors for the spatial data, and so a conservative error of 5% of data range was adopted for all continuous attributes. The incorporation of uncertainty into spatial data sets remains a research challenge.

The results of the classification were very encouraging. The software found nine classes of catchments in the Murray Darling Basin. The classes grouped together geographically, and followed altitude and latitude gradients, despite the fact that these variables were not included in the classification. Descriptions of the classes reveal very different physiographic environments, ranging from dry and flat catchments (i.e. lowlands), through to wet and hilly catchments (i.e. mountainous areas). Rainfall and slope were two important discriminators between classes. These two attributes, in particular, will affect the ways in which the stream interacts with the catchment, and can thus be expected to modify the effects of land use change on ecological condition. Thus, realistic models of the effects of land use change on streams would differ between the different types of catchments, and sound management practices will differ.

A small number of catchments were assigned to their primary class with relatively low probability. These catchments lie on the boundaries of groups of catchments, with the second most likely class being an adjacent group. The locations of these ‘uncertain’ catchments show that the Bayesian classification dealt well with cases that do not fit neatly into larger classes.

Although the results are intuitive, we cannot yet assess whether the classifications described in this paper would assist the modelling of catchment scale effects on stream ecological condition. It is most likely that catchment classification and modelling will be an iterative process, where the needs of the model are used to guide classification, and the results of classifications used to suggest further refinements to models.

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The Royal Institution of Chartered Surveyors (RICS) 5th European Conference in November 2004 focussed on enhancing collaboration at master's level in real estate education across Europe. In a context of increased global economic activity and increasing ties within the EU, there are benefits to business and to students in offering this type of educational provision. But is this paradigm true for construction economics (CE) and construction management (CM)? This paper examined the potential for collaboration and joint European awards in CM and CE. There is a political will for collaboration in HE based on economic drivers for the growth of the EU and changes are being implemented to enhance transparency and mobility for students. Professional bodies are expanding their European presence. Globalisation has resulted in greater opportunities for international real estate, and construction and there is growth in these sectors for practitioners. The difficulties with joint European collaboration are short course duration and the need to cover extensive subject matter. Other barriers are university structures, quality assurance procedures, costs and finances issues as well as IT, student services and support issues. The survey revealed that there are no RICS accredited CM / CE courses outside of the UK which inhibits collaboration. The sample was split in perceived demand for collaboration and the European focus within the courses is limited, as are field trips outside the UK. Student exchange on courses is rare. Generally there is a lag between the political will to greater student mobility and collaboration and the market, which is showing growth in multinational organisations and demand for pan European construction services and a professional body keen to deliver and support this growth. Within academia the barriers and current economic climate in HE preclude the widespread adoption of greater collaboration and development of joint awards, however this position may change.

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Enhancing access to education and knowledge is a long-held principle enshrined in education policy. Access to education offers leverage for educational attainment and achievement, at the individual and social levels. In policy, the term equates with concepts of inclusion, social justice and equity. Over the last decades, as education policy has responded to global social, cultural and economic reforms, concepts such as access have also undergone revision. This article revisits the relationship between access, education and knowledgemaking, in order to clarify the meaning of access in current education policies by reevaluating how access is constructed in policy and how the concept associates with other aspects of education. The research examines the concept of access in order to improve the efficacy of policy, opening the way for more systematic and transparent policy analysis and policy making centred on defining and delineating conceptual meanings such as access, as a basis for more targeted policy. Using evidence-based policy research, the article proposes a research process model based on the hierarchy of abstraction, to show that education policy requires systematic examination of key concepts as a fundamental step towards more clearly defined policy postulates that recognise and deal with contextual complexity of education policy. Defining and delineating the meaning of concepts such as access can help in the way that education policy contributes to guiding innovative knowledge construction.

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This work proposes a novel dual-channel time-spread echo method for audio watermarking, aiming to improve robustness and perceptual quality. At the embedding stage, the host audio signal is divided into two subsignals, which are considered to be signals obtained from two virtual audio channels. The watermarks are implanted into the two subsignals simultaneously. Then the subsignals embedded with watermarks are combined to form the watermarked signal. At the decoding stage, the watermarked signal is split up into two watermarked subsignals. The similarity of the cepstra corresponding to the watermarked subsignals is exploited to extract the embedded watermarks. Moreover, if a properly designed colored pseudonoise sequence is used, the large peaks of its auto-correlation function can be utilized to further enhance the performance of watermark extraction. Compared with the existing time-spread echo-based schemes, the proposed method is more robust to attacks and has higher imperceptibility. The effectiveness of our method is demonstrated by simulation results.