3,247 research outputs found

    Organizing sustainable development

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    The role and meaning of sustainable development have been recognized in the scientific literature for decades. However, there has recently been a dynamic increase in interest in the subject, which results in numerous, in-depth scientific research and publications with an interdisciplinary dimension. This edited volume is a compendium of theoretical knowledge on sustainable development. The context analysed in the publication includes a multi-level and multi-aspect analysis starting from the historical and legal conditions, through elements of the macro level and the micro level, inside the organization. Organizing Sustainable Development offers a systematic and comprehensive theoretical analysis of sustainable development supplemented with practical examples, which will allow obtaining comprehensive knowledge about the meaning and its multi-context application in practice. It shows the latest state of knowledge on the topic and will be of interest to students at an advanced level, academics and reflective practitioners in the fields of sustainable development, management studies, organizational studies and corporate social responsibility

    Dynamic analysis and energy management strategies of micro gas turbine systems integrated with mechanical, electrochemical and thermal energy storage devices

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    The growing concern related to the rise of greenhouse gases in the atmosphere has led to an increase of share of renewable energy sources. Due to their unpredictability and intermittency, new flexible and efficient power systems need to be developed to compensate for this fluctuating power production. In this context, micro gas turbines have high potential for small-scale combined heat and power (CHP) applications considering their fuel flexibility, quick load changes, low maintenance, low vibrations, and high overall efficiency. Furthermore, the combination of micro gas turbines with energy storage systems can further increase the overall system flexibility and the response to rapid load changes. This thesis aims to analyse the integration of micro gas turbines with the following energy storage systems: compressed air energy storage (CAES), chemical energy storage (using hydrogen and ammonia), battery storage, and thermal energy storage. In particular, micro gas turbines integrated with CAES systems and alternative fuels operate in different working conditions compared to their standard conditions. Applications requiring increased mass flow rate at the expander, such as CAES and the use of fuels with low LHV, such as ammonia, can potentially reduce the compressor surge margin. Conversely, sudden composition changes of high LHV fuels, such as hydrogen, can cause temperature peaks, detrimental for the turbine and recuperator life. A validated model of a T100 micro gas turbine is used to analyse transitions between different conditions, identify operational limits and test the control system. Starting from the dynamic constraints defined in the related chapters, in the final part, an optimisation tool for energy management is developed to couple the micro gas turbine with energy storage systems, maximizing the plant profitability and satisfying the local electrical and thermal demands. For the modelling of the CAES system and alternative fuels, the operating constraints obtained from the initial analyses are implemented in the optimisation tool. In addition, a battery and thermal energy storage system are also considered. In the first part, a comprehensive analysis of the T100 combined with a second-generation CAES system showed enhanced efficiency, reduced fuel consumption, reduced thermal power output and increased maximum electrical power output due to the reduction of the rotational speed. The study identified optimal air injection constraints, demonstrating a +3.23% efficiency increase at 80 kW net power with a maximum mass flow rate of 50 g/s. The dynamic analysis exposed potential instabilities issues during air step injections, mitigated by using ramps at a rate of +0.5 (g/s)/s for safe and rapid dynamic mode operation. The second part explored the effects of varying H2-NG and NH3-NG blends on the T100 mGT. Steady-state results showed increased power output with hydrogen or ammonia, notably +6.1 kW for 100% H2 and up to +11.3 kW for 100% NH3. Transient power steps simulations showed surge margin reductions, especially at lower power levels with high concentrations of ammonia, highlighting the need for controlled transitions. Controlled ramps were effective in preventing extreme temperature peaks during fuel composition changes. The final chapter focused on developing an energy scheduler for different plant setups, evaluating four configurations. For a typical day of the month of April of the Savona Campus, the integration of the CAES lead to relative savings of +8.1% and power-to-H2 of +5.3% when surplus electricity was not sold to the grid. Conversely, with the ability to sell excess electricity, CAES and battery energy storage (BES) systems exhibit modest savings of +1.2% and +2.4%, respectively, while the power-to-H2 system failed to provide economic advantages

    Agricultural wastes: A practical and potential source for the isolation and preparation of cellulose and application in agriculture and different industries

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    Cellulose is an organic compound belonging to polysaccharides. This biopolymer is made of glucose subunits. This compound plays an essential role in the structure and strength of plants. This polymer has biodegradable, biocompatible, and renewable properties. Agricultural wastes are excellent sources for cellulose extraction. Agricultural wastes are lignocellulosic materials, and cellulose and lignin are the main components of these wastes. Millions of tons of agricultural waste are thrown away and burned yearly. This large amount of waste leads to environmental pollution and waste of renewable energy resources. Upgrading such waste by developing innovative products such as cellulose nanomaterials and nanocomposites can have high environmental and economic benefits. The intelligent use of agricultural waste as a rich source of cellulose can be primarily responsible for the increase in population and industrialization of countries. Optimal cellulose extraction from agricultural waste can be widely used in various fields of agriculture, industry, medicine, and energy. Different chemical, physical, physicochemical, and biological methods have been presented to extract cellulose and its derivatives from agricultural waste. In this review, we will discuss the position and importance of cellulose, the importance of agricultural waste in the extraction of cellulose, and the use of extracted cellulose from agrarian wastes in various sources

    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    Edge-emitting mode-locked quantum dot lasers

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    Edge-emitting mode-locked quantum-dot (QD) lasers are compact, highly efficient sources for the generation of picosecond and femtosecond pulses and/or broad frequency combs. They provide direct electrical control and footprints down to few millimeters. Their broad gain bandwidths (up to 50 nm) for ground to ground state transitions as discussed below, with potential for increase to more than 200 nm by overlapping ground and excited state band transitions) allow for wavelength-tuning and generation of pico- and femtosecond laser pulses over a broad wavelength range. In the last two decades, mode-locked QD laser have become promising tools for low-power applications in ultrafast photonics. In this article, we review the development and the state-of-the-art of edge-emitting mode-locked QD lasers. We start with a brief introduction on QD active media and their uses in lasers, amplifiers, and saturable absorbers. We further discuss the basic principles of mode-locking in QD lasers, including theory of nonlinear phenomena in QD waveguides, ultrafast carrier dynamics, and mode-locking methods. Different types of mode-locked QD laser systems, such as monolithic one- and two-section devices, external-cavity setups, two-wavelength operation, and master-oscillator power-amplifier systems, are discussed and compared. After presenting the recent trends and results in the field of mode-locked QD lasers, we briefly discuss the application areas

    Innovations and trends in the coconut agroindustry supply chain: A technological surveillance and foresight analysis

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    Coconut (Cocos nucifera) is a raw material that has gained particular relevance for agribusiness in recent years. This has come about largely owing to the paradigm shift regarding its genuine nutritional benefits. It is especially due to innovation that has been incorporated into agro-industrial processing and the development of new products, and the fruits of such labor can be seen in the growing demand by consumers around the world. Integrally making full use of coconut, it turns out, is extremely important for agribusiness. Coconut indeed has become a benchmark, not only from the environmental dimension but also from the social and economic perspectives both of the communities that plant it and the agribusinesses that transform it. This study aims to identify technologies, new uses, trends, and innovations related to the coconut agro-industrial chain, as well as their prioritization, by means of a prospective study, using the Delphi method in two rounds. Two methods applied at the methodological level comprised a technological surveillance study by means of a literature review in a SCOPUS database, PatentsInspiration, complemented with commercial surveillance for the four major topics of plastic wood, coconut oil extraction, high salinity and moisture, and small-scale coconut by-products. Moreover, the Delphi method was used, in two rounds, with 178 topics, technologies, and innovations, classified into seven thematic groups. The Delphi was answered by 32 experts in the two rounds. Vantage Point text mining software was also applied for the analysis of the surveillance results. Within the seven thematic groups, the following 10 priority technologies are highlighted: functional phytochemicals, non-caloric sweeteners, coconut milk preservation technologies, water activity and shelf life, coconut sugar extraction methods, batch and continuous drying technologies, lyophilization, coconut fiber and shredded recycled PET, magnetic particle modification of activated carbon derived from coconut shell and biochar to effectively remove phenol from water, and biodegradable packaging for coconut derivatives. In addition, the following topics were prioritized in the sustainability grouper: sustainable agriculture, bioeconomy, family agriculture, and circular economy

    Evaluating the anticipated outcomes of MRI seizure image from open-source tool- Prototype approach

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    Epileptic Seizure is an abnormal neuronal exertion in the brain, affecting nearly 70 million of the world's population (Ngugi et al., 2010). So many open-source neuroimaging tools are used for metabolism checkups and analysis purposes. The scope of open-source tools like MATLAB, Slicer 3D, Brain Suite21a, SPM, and MedCalc are explained in this paper. MATLAB was used by 60% of the researchers for their image processing and 10% of them use their proprietary software. More than 30% of the researchers use other open-source software tools with their processing techniques for the study of magnetic resonance seizure image

    Recommended Implementation of Quantitative Susceptibility Mapping for Clinical Research in The Brain: A Consensus of the ISMRM Electro-Magnetic Tissue Properties Study Group

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    This article provides recommendations for implementing quantitative susceptibility mapping (QSM) for clinical brain research. It is a consensus of the ISMRM Electro-Magnetic Tissue Properties Study Group. While QSM technical development continues to advance rapidly, the current QSM methods have been demonstrated to be repeatable and reproducible for generating quantitative tissue magnetic susceptibility maps in the brain. However, the many QSM approaches available give rise to the need in the neuroimaging community for guidelines on implementation. This article describes relevant considerations and provides specific implementation recommendations for all steps in QSM data acquisition, processing, analysis, and presentation in scientific publications. We recommend that data be acquired using a monopolar 3D multi-echo GRE sequence, that phase images be saved and exported in DICOM format and unwrapped using an exact unwrapping approach. Multi-echo images should be combined before background removal, and a brain mask created using a brain extraction tool with the incorporation of phase-quality-based masking. Background fields should be removed within the brain mask using a technique based on SHARP or PDF, and the optimization approach to dipole inversion should be employed with a sparsity-based regularization. Susceptibility values should be measured relative to a specified reference, including the common reference region of whole brain as a region of interest in the analysis, and QSM results should be reported with - as a minimum - the acquisition and processing specifications listed in the last section of the article. These recommendations should facilitate clinical QSM research and lead to increased harmonization in data acquisition, analysis, and reporting

    Growth of Group IV and III-V Semiconductor Materials for Silicon Photonics: Buffer Layer and Light Source Development

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    High data transmission speeds, high levels of integration, and low manufacturing costs have established Si photonics as a crucial technology for next-generation data interconnects and communications systems. It involves a variety of components including light emitters, photodetectors, amplifiers, waveguides, modulators, and more. Because of its indirect bandgap, silicon is unable to serve as an efficient light source on a chip, hence this has been one of the formidable challenges. Within the framework of the monolithic approach, this thesis presents the study of two essential aspects of this challenge, the optimisation of buffer layers and development of light sources, by incorporating and improving different systems of Group IV thin films and III-V quantum dots (QDs) semiconductor materials. The monolithic approach focuses on the direct epitaxial growth of highly efficient light sources, usually by the epitaxy of III-V semiconductors lasers on a single Si chip. However, because of the material dissimilarities between III-V materials and Si, during the heteroepitaxy, a high density of crystalline defects such as threading dislocations (TDs), thermal cracks and anti-phase domains are introduced, severely impeding the performance and yield of the laser. For instance, TDs act as non-radiative recombination centres, while thermal cracks cause issues with the efficient evanescent coupling of the emitted light with Si waveguide. To address these defects, typically complex buffer growth techniques with micron-scale thickness are employed. The research in this thesis is divided into two parts, namely buffer layer optimisation and light source development. Each part outlines alternative strategies for overcoming the above-mentioned hurdles for monolithic growth. The first part highlights the optimisation of buffer layer growth to reduce threading dislocations for the monolithic integration of high-performance direct-bandgap III-V and group IV light sources on Si. The growth optimisation of low defect-density Ge buffer layers epitaxially grown on Si was first investigated. Defect elimination in Ge buffers with doped and undoped seed layers of increasing total thickness is studied under a variety of growth regimes, doping techniques, and annealing processes. This study demonstrates that a 500 nm thin Ge achieves the same defect level (1.3 × 108 cm -2) as 2.2 μm GaAs grown on Si, which greatly increases the thickness budget for the subsequent dislocation filter layers (DFLs) and laser structure growth before the formation of thermal cracks. Meanwhile, a low threading dislocation density of 3.3 × 107 cm -2 is obtained for 1 μm Ge grown on Si. The second part places emphasis on the development of light sources in the near-infrared wavelength range for Si photonics. 1) The development of GeSn, an emerging direct bandgap light source for Si photonics, is shown, which has wide bandgap tuneability and full compatibility with Si complementary metal-oxide semiconductor (CMOS). Growing the high Sn composition of GeSn required for efficient light generation is challenging and its growth generally severely affected by large surface roughness and Sn segregation. In this work, first, ex-situ rapid thermal annealing for the grown GeSn layer is investigated, showing that by proper annealing the strain can be relaxed by 90% without intriguing Sn segregation. This method shows its potential for both material growth and device fabrication. Besides, strain compensated layer and in-situ annealing techniques have been developed. Significantly improved surface quality has been confirmed by in-situ reflection high-energy electron diffraction (RHEED) observations and atomic force microscopy (AFM) images. Transmission electron microscopy (TEM) results reveal the high crystal quality of the multiple quantum wells (MQWs) grown on such buffer layers. 2) The final section details the development of InAs/InP QDs emitting near the strategic 1.55 μm, the lowest optical fibre loss window. The InAs/InP QDs growth is prone to inhomogeneous quantum dash morphologies which broaden the photoluminescence (PL) spectra and degrade the carrier confinement. Research has been conducted on growth parameters and techniques including deposition thickness, growth temperature and Indium-flush technique is applied to improve the uniformity of the dots, and narrow room temperature PL linewidths of 47.9 meV and 50.9 meV have been achieved for single-layer and five-layer quantum dot samples, respectively. The structures enable the fabrication of small footprint microdisk lasers with lasing thresholds as low as 30 μW

    Ultra High Strength Steels for Roll Formed Automotive Body in White

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    One of the more recent steel developments is the quenching and partitioning process, first proposed by Speer et al. in 2003 on developing 3rd generation advanced high-strength steel (AHSS). The quenching and partitioning (Q&P) process set a new way of producing martensitic steels with enhanced austenite levels, realised through controlled thermal treatments. The main objective of the so-called 3rd generation steels was to realise comparable properties to the 2nd generation but without high alloying additions. Generally, Q&P steels have remained within lab-scale environments, with only a small number of Q&P steels produced industrially. Q&P steels are produced either by a one-step or two-step process, and the re-heating mechanism for the two-step adds additional complexities when heat treating the material industrially. The Q&P steels developed and tested throughout this thesis have been designed to achieve the desired microstructural evolution whilst fitting in with Tata’s continuous annealing processing line (CAPL) capabilities. The CALPHAD approach using a combination of thermodynamics, kinetics, and phase transformation theory with software packages ThermoCalc and JMatPro has been successfully deployed to find novel Q&P steels. The research undertaken throughout this thesis has led to two novel Q&P steels, which can be produced on CAPL without making any infrastructure changes to the line. The two novel Q&P steels show an apparent reduction in hardness mismatch, illustrated visually and numerically after nano-indentation experiments. The properties realised after Q&P heat treatments on the C-Mn-Si alloy with 0.2 Wt.% C and the C-Mn-Si alloy with the small Cr addition is superior to the commercially available QP980/1180 steels by BaoSteel. Both novel alloys had comparable levels of elongation and hole expansion ratio to QP1180 but are substantially stronger with a > 320MPa increase in tensile stress. The heat treatment is also less complex as there is no requirement to heat the steel back up after quenching due to one-step quenching and partitioning being employed on the novel alloys
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