565 research outputs found

    Forest Management, Resilience and Climate Change: An Analysis of Legal and Policy Frameworks in Tasmania and New South Wales

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    Climate change poses serious challenges for forests and thus for sustainable forest management (SFM). The concept of resilience has been identified as a useful tool in minimising the impacts of climate change on forests. However, while the utility of the concept has been recognised generally in the literature, and seven principles of ‘Resilience Thinking’ have been designed, application of the concept in the context of SFM has yet to be examined. Under international commitments, Australia is obliged both to account for climate change impacts in SFM and to work to increase forest resilience in order to minimise those impacts and ensure the sustainability of forests into the future. Using the ‘Resilience Thinking’ principles as a framework, this thesis examines SFM legislation and policies in Tasmania and New South Wales (NSW) to ascertain the extent to which they support forest resilience to climate change. In particular, it assesses whether and how each principle is considered in the development and implementation of SFM systems. Four major challenges to the development and implementation of SFM legislation and policies capable of supporting forest resilience are identified: fragmentation of SFM systems; inadequate participation in forest decision-making; the absence of active adaptive management in forest reserves; and SFM legislation and policy mechanisms that fall short in dealing with both the short and long-term uncertainties of climate change impacts on forests. Reflecting on those challenges, the thesis proposes and examines possible solutions including: the application of an integrated landscape approach to SFM; options for improved participation by a more diverse range of actors in periodic goal setting and management actions; the application of active adaptive management aimed specifically at building resilience in reserve areas; and the incorporation of short and long-term goals into decision-making through adequate monitoring, reporting and evaluation systems utilising specific resilience criteria and indicators. In applying the ‘Resilience Thinking’ principles in the SFM context for the first time, the thesis lays the groundwork for further consideration of the challenges and solutions to implementing resilience beyond the case studies

    DEFINITION OF AN ADVANCED PROCESS FOR THE PRODUCTION OF LOW ENVIRONMENTAL IMPACT CONTAINERS AS POTENTIAL ALTERNATIVE TO PLASTICS

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    For decades, petroleum-based synthetic polymers, commonly known as plastics, have become one of the most appealing materials used for a wide variety of applications. Nevertheless, currently, conventional petroleum-based plastics represent a serious problem for global pollution because remain for hundreds of years in the environment when discarded. In order to reduce dependence on fossil resources, bioplastic materials are being proposed as safer and more sustainable alternatives. Bioplastics are bio-based and/or biodegradable materials, typically derived from renewable sources. Among different resources, food waste is attracting more and more attention in the research field of bioplastics’ production. The sources of food waste include household, commercial, industrial and agricultural residues. In fact, every year, around one-third of all food resources produced for human consumption are lost or wasted. Although European Union guidelines stated that food waste should preferentially be used as animal feed, in some cases, it became illegal because of disease control concerns and other times its nutritional value is very poor. On the other hand, the production of bioplastics from food waste is a renewable, sustainable process, in which materials are fabricated from carbon neutral resources, thus aligning itself with the principles of the circular bioeconomy. However, the conversion of fruit and vegetable by-products into eco-friendly materials with mechanical and hydrodynamic performances comparable to those of fuel-based plastics still remains a challenge. In this thesis, different approaches have been investigated for the valorization of fruit and vegetable wastes to produce low environmental impact materials, as a potential alternative to plastics with application in the field of food packaging. In the first section, apple waste and tomato peel by-products have been used as fillers to fabricate starch-based biocomposites. The mechanical characterization of the samples showed their suitability for covering purposes, since a ductile and soft behaviour was exhibited. In the second section, an avocado by-product extract has been incorporated to an ethyl cellulose matrix for the production of impregnated paper with enhanced durability. Since fruit wastes can contain potential pathogens and physical and chemical contaminants which can be released when used as additive for active packaging, a preliminary untargeted metabolomic characterization of the extract was conducted by LC-ESI(-)-Q Exactive-Orbitrap- MS/MS. The lipid components detected in the extract proved to be useful additives to improve paper hydrophobicity, preventing food browning and moisture loss. In general, the addition of all tested wastes (apple waste, tomato peel and avocado by-products) has proved to be useful to increase the biodegradability of the fabricated biomaterials. Hence, the environmental benefits associated with their recovery are proposed as a driving force to expand their further use for these purposes. The upcycling of food waste through the production of value-added products is an ideal and practical end use, allowing to save huge economic and energy losses

    Simulation of Quantum Infrared Photodetectors

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    The topic of research is concerned with modelling and simulation of high temperature long wavelength infrared quantum photodetectors using advanced finite element methods. The aim is to devise novel designs based on quantum well structures to improve quantum efficiency, and operating temperature. These new designs rely on quantum confinement of electrons and holes inside a mixture of materials within which the energies of the carriers become discrete and differ from those observed in bulk materials. Type II InAs / GaSb superlattices is one of these meta–materials which offer a large flexibility in the design of infrared photodetectors, including the possibility to adjust the detected wavelength over a very wide range and to realize a suitable absobers’ unipolar barriers to suppress dark current while maintaining a significant portion of photocurrent at high temperatures. In order to validate this interest, A set of rigorous modelling tools based on multi-band k· p band structure theory and Boltzmann transport theory has been developed, which provide a better understanding of the electronic structure and transport in these heterostructures. The framework takes into account in particular the effect of the intrinsic strained property of the unintentional interfaces on the electronic structure and the optical properties. First, the finite element method is used to solve 8 × 8 k · pHamiltonians for InAs/GaSb superlattices with type II alignment to compute the optical and materials’ characteristics. For InAs and AlAsSb and alloys based detectors, An optical material library has been developed to generate all the needed bulk material properties. Secondly, the transfer matrix method or the Beer-Lambert law is used to compute the optical generation profiles in the device. Finally, the the finite volume method has been employed to solve the transport equations to compute the dark- and photo- currents, quantum efficiency among other device properties. Using this tools, new structures based on nBn and nBp architectures have been designed, with optimized design, which contribute to the realization of mid- and long- wave infrared photodetector based on Type-II superlattices InAs / GaSb material system as well as InAs/AlAsSb alloy mterial system. The developed model allows to study the underlying physics of these devices and to explain the factors limiting the device performances. Based on the simulation results, detectors involving absorbers with period composed of 14 Mono-Layer (ML) of InAs and 7 ML of GaSb was found to have a band gap wavelength close v to 11 μm and exhibit a lower dark current than those with period mainly composed of GaSb. The designed LWIR barrier device consists of a 4 μm thick p-type InAs-rich 14 ML InAs / 7ML GaSb LWIR T2SL absorber, a 200 nm thick p-type InAs/AlSb SL barrier and an n-type InAs-rich 14 ML InAs / 7ML GaSb LWIR T2SL contact layer. The 16.5ML InAs / 4ML AlSb superlattice of the BL is designed to give a smooth conduction band alignment and a large VBO of nearly 400 meV with the AL. The optimum doping level of absorber, barrier and contact layer are found to be 1 × 1016cm3, 5 × 1015cm3 and 1 × 1016cm3 respectively. This nBp detector design exhibits at 77 K a diffusion limited dark-current down to -300 mV with a dark-current level plateau as low as 8.5 × 10−5A/cm2 which is more than one order of magnitude lower compared to a similar PIN photodiode. Furthermore, this value is near the level of the MCT ‘rule 07’ demonstrating that InAs/GaSb SL detectors may provide new opportunities to replace the MCT technology in the LWIR spectral window given the MCT material instability problem at longer wavelengths. Moreover, we have demonstrated that the presence of the majority carriers’ barrier improves the current performances and the operating temperature over the standard PIN device. A temperature improvement of 20 K was found for a given current density of 2x10−4 A/cm−2 compared to a similar LWIR PIN device working at 60 K

    Sustainable EDM of Inconel 600 in Cu-mixed biodegradable dielectrics: Modelling and optimizing the process by artificial neural network for supporting net-zero from industry

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    The properties of Nickel-based superalloy(s) like stability at extreme conditions, greater strength, etc., complicate its cutting through conventional operations. Therefore, electric discharge machining (EDM) is preferred for its accurate cutting. However, the conventional dielectric i.e., kerosene used in EDM is hydrocarbon based which generates toxic fumes and contribute to the CO2 emissions during the discharging process in EDM. This affects the operator’s health and the environment. Therefore, the potentiality of five biodegradable dielectrics has been deeply examined herein to address the said issues. Nano copper powder is also employed for uplifting the cutting proficiency of these dielectrics. A set of 15 experiments was performed via full factorial design. An artificial neural network (ANN) is constructed to model and optimize the material removal rate (MRR), surface roughness (SR), and specific energy consumption (SEC). The highest MRR (5.527 mm3 /min) was achieved in coconut oil whereas for obtaining the lowest SR, the sunflower oil at powder concentration (Cp) of 1.0 g/100 ml is the best choice. Sunflower oil also gave a 17.05% better surface finish compared to other dielectrics. Amongst the biodegradable dielectrics, olive oil consumes lowest specific energy (SEC) i.e., 264.16 J/mm3 which is 28.8% less than the SEC of other oils. Furthermore, the maximum CO2 reduction of 72.8 ± 1.4% is achieved with Olive oil in comparison to that found with kerosene in EDM. The multi-objective optimization is conducted and sunflower oil with Cp of 0.667 g/100 ml is termed out to be optimal solution. The biodegradable dielectrics have demonstrated excellent performance for EDM to support net-zero goals from the industrial sector

    Future Trends in Advanced Materials and Processes

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    The Special Issue “Future Trends in Advanced Materials and Processes” contains original high-quality research papers and comprehensive reviews addressing the relevant state-of-the-art topics in the area of materials focusing on relevant or innovative applications such as radiological hazard evaluations of non-metallic materials, composite materials' characterization, geopolymers, metallic biomaterials, etc

    Physical modeling and numerical simulations of degradation mechanisms in devices and insulators for power applications

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    In this thesis, a TCAD approach for the investigation of charge transport in amorphous silicon dioxide is presented for the first time. The proposed approach is used to investigate high-voltage silicon oxide thick TEOS capacitors embedded in the back-end inter-level dielectric layers for galvanic insulation applications. In the first part of this thesis, a detailed review of the main physical and chemical properties of silicon dioxide and the main physical models for the description of charge transport in insulators are presented. In the second part, the characterization of high-voltage MIM structures at different high-field stress conditions up to the breakdown is presented. The main physical mechanisms responsible of the observed results are then discussed in details. The third part is dedicated to the implementation of a TCAD approach capable of describing charge transport in silicon dioxide layers in order to gain insight into the microscopic physical mechanisms responsible of the leakage current in MIM structures. In particular, I investigated and modeled the role of charge injection at contacts and charge build-up due to trapping and de-trapping mechanisms in the oxide layer to the purpose of understanding its behavior under DC and AC stress conditions. In addition, oxide breakdown due to impact-ionization of carriers has been taken into account in order to have a complete representation of the oxide behavior at very high fields. Numerical simulations have been compared against experiments to quantitatively validate the proposed approach. In the last part of the thesis, the proposed approach has been applied to simulate the breakdown in realistic structures under different stress conditions. The TCAD tool has been used to carry out a detailed analysis of the most relevant physical quantities, in order to gain a detailed understanding on the main mechanisms responsible for breakdown and guide design optimization
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