1,721,064 research outputs found
Synthese und Eigenschaften polyurethanbasierter Aerogele auf Basis rohstofflich recycelter Reststoffe
No full textA framework for the environmental assessment of circular interventions to steel products
No full textHuman-induced climate change is progressing and threatens the basis of existence for human beings. The steel industry accounts for a significant proportion of the greenhouse gases emitted each year. One solution for its reduction is the Circular Economy in a broader sense. The strategies of narrowing, slowing, and closing resource flows are intended to increase material efficiency and reduce the environmental impact. Because the steel industry is a leading industry for closing resource flows by implementing recycling and recovery, the potential for improvement is low. In contrast, the so-called 10 Rs, which start at product level, have a large untapped environmental saving potential. To date, little is known about how these circular interventions can be applied to steel products so that they are more material-efficient and environmentally sustainable and thus improved in terms of the Circular Economy. To close this gap, an assessment approach is required that quantifies the extent to which the implementation of circular interventions in steel products is in line with the Circular Economy. At the same time, it is essential to understand how the Circular Economy can be successfully applied to steel products. The aim of this dissertation is to develop an assessment approach for environmental sustainability and to generate knowledge about circular interventions for steel products. The inductive proceeding starts with investigating the mutual relationships between material, process, and product level by using the example of a U-bolt. The application of circular strategies to a machining knife is then analysed. An approach for assessing environmental sustainability is developed on the basis of the findings related to the methodology and steel specific characteristics of process chains. The proceeding is applied and validated to several steel products as part of a circular intervention. In addition to findings on the methodological proceeding, this dissertation also generates insights into how circular interventions can be successfully implemented on steel products. The first case study comprises the Life Cycle Assessment of an alloy development for a U-bolt. While the element-specific balancing of the changed composition at material level led to an increased environmental impact of the new alloy, the changed process chain and the now possible product design achieved an overall reduction in missions as well as energy and resource demand. The different conclusions emphasise the need for a lifecycle-wide assessment. Furthermore, relevant hotspots in the process chains of steel products (e.g. material production and heat treatment) become visible and the importance of material characteristics (cyclic strength) for product functionality and design. The second case study involves a Life Cycle Assessment and the application of mass-based indicators to analyse three circular interventions on a machining knife. These include axial ring rolling (narrowing), reworking a large machining knife into a smaller one (slowing) and recovering steel from the waste stream of grinding sludge (closing). All interventions showed an increase in material efficiency as well as a reduction in emissions and energy demand. In addition, the environmentally relevant influences of steel production, the energy mix and the auxiliary processes became clear. The study also shows that material efficiency as a mass-based indicator does not correlate with the results of the Life Cycle Assessment. Based on the findings, an approach for the environmental assessment of circular interventions on steel products was developed in this thesis. The integration of the Material Flow Analysis and mass-based indicators with the LCA eliminates its previously identified limitations of including product functionality, material quality, time, and dissipative losses. The system definition is fundamental for the definition of the conventional product system and the circular intervention. Then, the data collected on quantitative and qualitative aspects are incorporated into a material flow model of steel. This is followed on the one hand by the application of mass based indicators to quantify the parameters of the Circular Economy and on the other hand by the extension of the model to carry out a Life Cycle Assessment to analyse environmental sustainability. The application of the assessment approach to a further case study validates the procedure and the previous findings. The case study involves the production of hand tools from a machining knife. The results show that the circular intervention achieves only significant improvements regarding the resource and energy demand, provided that the increased functionality leads to a reduction in production volume. In summary, the dissertation shows how the integration of Life Cycle Assessment, Material Flow Analysis and mass-based indicators enables a holistic environmental assessment of circular interventions on steel products. The synergy of the methods, as the strengths of the individual approaches, overcome the individual limits. The integration of key characteristics of steel (e.g. steel production, heat treatment, grinding) and related parameters (e.g. material characteristics) enables the lifecycle-wide assessment of circular interventions, taking into account material quality, product functionality and lifetime. The case studies show that circular interventions in the steel sector can lead to improvements in material efficiency, emissions, and energy demand. To prevent the savings from being offset, the boundary conditions for the subsequent process design must be determined
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Environmental assessment of urban sharing
No full textThis dissertation addresses the environmental assessment of urban sharing within the framework of the circular economy. In response to severe environmental degradation and the growing urgency for sustainable consumption and production patterns, this work pro-poses an innovative approach for environmental assessments, combining life cycle assess-ment (LCA) with theories of social practice. Urban sharing is utilized as a case for reducing resource demand while fostering societal well-being.Urban sharing is conceptualized here as a social innovation embedded in urban environments, with the potential to reshape material flows and societal relationships. Unlike the more commercially driven sharing economy, urban sharing prioritizes community engagement, sustainability, and sufficiency by encouraging social practices that reduce the need for new goods and services. The dissertation argues that, when properly approached, ur-ban sharing could contribute to the transition from a linear to a circular economy. The methodological foundation of this work is built on the integration of social practice theory into LCA, allowing for a more nuanced and comprehensive assessment of how consumption patterns drive environmental impacts. Social practices - routine actions like mobility, food consumption, or community activities - are treated as bundles of meanings, competences, and materials that organize everyday life. By assessing these practices, the research introduces a new LCA framework capable of capturing the environmental potential of transformative social phenomena like urban sharing. The dissertation is structured around three key publications that develop and test this new framework. The first provides a theoretical discussion of LCA’s limitations in addressing transformative change and proposes the social practice-based LCA as an alternative. The second explores how urban sharing is embedded in daily life, using empirical research to reveal the social and material contexts in which these practices operate. The third quanti-fies the environmental impacts of urban sharing activities, applying the newly developed framework to assess their potential for environmental sustainability.The findings suggest that urban sharing holds significant environmental potential, particularly in reducing material consumption and fostering sustainable lifestyles. However, the research also highlights the importance of embedding environmental assessments in their social contexts to accurately reflect the complexities of human action and societal change. This approach can better inform decision-makers about the pathways toward more sus-tainable consumption systems.The dissertation concludes that integrating social practice theory with LCA provides a ro-bust methodological framework for assessing sustainability interventions. By focusing on the practices that drive consumption and environmental impacts, this research offers new insights into how transformative change can be supported and accelerated in the pursuit of a circular economy
Sensor-based characterization of anthropogenic material systems: developing characterization methods and novel applications for optimizing the mechanical recycling of lightweight packaging waste
No full textMechanical recycling of post-consumer plastic packaging is characterized by a high lack of transparency due to the high effort of manual material flow characterization. As a consequence, optimizing collection processes in a targeted manner as well as adaptively designing and operating sorting and processing plants are often not possible, and confidence in secondary raw materials is often missing. This dissertation demonstrates how sensor technology in mechanical recycling can evolve from a sorting technology towards a key technology for enabling value-chain-wide transparency, and what optimization potentials can be derived from this enabled transparency. In the first part of the dissertation, a systematic literature review was conducted, which introduces a unified terminology, provides a comprehensive overview of the current state of research and identifies ten essential future research potentials. In the second part, novel characterization methods for extracting mass-based material flow compositions from area/volume-based sensor data were developed. Machine learning models were successfully trained to determine binary compositions of plastic flakes and post-consumer plastic packaging with a measurement uncertainty of 1.2 vol% and 2.4 wt%, respectively, across different material flow presentations and compositions using near-infrared (NIR) sensors. Based on the developed characterization methods, two novel sensor technology applications were demonstrated at industrial scale in the third part. First, a sensor-based quality monitoring of plastic pre-concentrates from sorting plants was developed using inline NIR sensors. The results showed that for a PET tray fraction as an example, sensor-based quality control of mass-based product purities is possible with a measurement uncertainity of 0.31 wt%. In comparison with state-of-the-art sampling-based quality analyses, it was shown that more than 350 kg of a 600 kg PET tray pre-concentrate bale would need to be analyzed manually to achieve a comparable measurement accuracy. Second, inline NIR sensors were used for sensor-based process monitoring of an industrial sensor-based sorting (SBS) unit. Using artificial neural networks, the process data was used to develop a process model that can predict the sorting behavior of the SBS unit across different sorting scenarios with a mean absolute error of 3.0%. In summary, the dissertation demonstrates the promising potentials of sensor technology in optimizing the circular economy. Based on the generated transparency, future process improvements can be implemented in individual process stages and across value chains, thus increasing the quantity and quality of recycled materials and the resulting ecological and economic benefits
Nachhaltige Rückgewinnung von Rohstoffen aus buntmetallhaltigen Aufbereitungsrückständen : Ein Bewertungs- und Klassifizierungsansatz konform mit der Vorratsrahmenklassifikation für Rohstoffe der Vereinten Nationen (UNFC) zur Identifizierung von Potenzialen und Barrieren zur Projektentwicklung
No full textIn general, mineral raw materials (RMs) are assessed and classified to demonstrate the viability of their exploitation to potential investors. The assessment and classification of anthropogenic RMs such as base metal tailings is currently lacking a systematic and transparent approach which considers all dimensions of sustainability. Hence, the potentials of RMs recovery from base metal tailings are widely unknown and cannot be compared to the ones of other RM sources. The conventional RMs classification with the Committee for Mineral Reserves International Reporting Standards (CRIRSCO) principles from the primary mining industry is focussed on techno- economic aspects. To enable the assessment of a RMs recovery project’s sustainability, environmental and social aspects need to be included. This can be done by applying the United Nations Framework Classification for Resources (UNFC) principles. To the knowledge of the author of this thesis, this is the first systematic application of the UNFC to base metal tailings which considers all dimensions of sustainability. The main research question is: which aspects should be considered in the assessment and classification of base metal tailings to enable a sustainable raw materials recovery? The main research question is answered with the help of 3 published peer-reviewed scientific articles summarised further below. The main research goal is to develop a systematic, transparent and UNFC-compliant assessment and classification approach for (Stage 1) a desk-based screening of tailings storage facilities (TSFs) to quickly identify potentially viable RMs recovery projects, and (Stage 2) for a consecutive assessment of project sustainability based on on-site exploration data. The developed assessment and classification approach is applicable to base metal tailings from industrial processes. A project’s development status is differentiated in terms of geological, technological, economic, environmental, social and legal aspects. Established methods from the conventional mineral RMs classification under the CRIRSCO are combined with methods to account for environmental and social potentials and barriers. In addition, it is demonstrated why tailings in general should be assessed and classified as anthropogenic RMs, what the drawbacks of the sole application of CRIRSCO principle from the primary mining industry to base metal tailings are, how a classification under the UNFC remedies these aspects, and where the current UNFC concept should be developed with respect to guidelines for an anthropogenic RMs assessment. Lastly, recommendations are made for the further development of the developed assessment and classification approach, as well as for the further development of the UNFC as a base for an integrated and sustainable RMs management system. First article: the current UNFC concept is tested for its applicability to base metal tailings with the case study TSF Cabeço do Pião (Portugal) from a private mining company’s perspective with economic focus within a very preliminary study. One rehabilitation scenario, and two RMs recovery scenarios with low and high degree of tailings valorisation are assessed. The necessity for actions to protect human health and the environment is shown with a risk assessment. With a discounted cash flow analysis, under consideration of mineral price uncertainty, the project’s economic viability is indicated. The application of the UNFC principles exemplifies the advantages over an application of the CRIRSCO principles: TSF rehabilitation is identified as a necessary base case and positive socio-environmental acting are prioritised. However, the RMs recovery scenarios cannot be differentiated with the current UNFC Classes. The assessment reveals the necessity for a stronger user guidance in the assessment and classification process. Moreover, a more detailed Subcategorisation is required to identify project potentials and barriers, particularly in social and environmental domains. Second article: a desk-based approach for a first quick, systematic and UNFC-compliant TSF screening is presented. The assessment of specified criteria can support the user of the approach in deciding if a particular TSF should be assessed in a more advanced study including costly on-site exploration. The user is guided in compiling information on a TSF at local scale in a structured manner. The approach is tested with the case study TSF Bollrich (Germany). It is situated in a complex environment close to various stakeholders and ecologically sensitive areas. The case study demonstrates that a preliminary quick assessment based on publicly accessible information is possible. The developed desk-based screening approach can help to create a TSF inventory in the future which captures project potentials and barriers under consideration of all dimensions of sustainability. Since the assessment of base metal tailings with the CRIRSCO principles neglects relevant aspects, it is concluded that tailings should be considered as anthropogenic RMs. Third article: an approach for a practical UNFC-compliant assessment of project sustainability based on on-site exploration data is presented and tested with the case study TSF Bollrich. It is shown how to develop a project from first on-site exploration to a decision whether to intensify costly on-site exploration. The development status of the overall project and the recovery of individual RMs is differentiated. For an easy comparison of the assessment results across different studies, they are summarised in a heat map-like categorisation matrix. It is concluded that with a UNFC-compliant assessment and classification approach, aspects which contribute to a local sustainable development can be identified and communicated transparently. This can serve for stakeholders as a basis for a discussion on how to derive a commonly acceptable solution. The approach presented in this thesis supports the integration of the United Nations Sustainable Development Goals (UN SDGs) into RMs classification. Overall, the following conclusions are drawn: (1) Economic, environmental, social, and legal aspects on a RMs deposit’s classification should be differentiated to so that they become equally important, and their individual development status and individual influence on the classification result becomes transparent; (2) currently uneconomically recoverable RMs deposits with a future potential should be considered for a transparent communication, as well as all contained RMs including potentially contained contaminants and their impacts; (3) local stakeholders should be identified from the beginning of project development to anticipate possible social tensions; (4) site-specific benefits and risks of RMs recovery should be considered and communicated transparently from the beginning of project development; and (5) barriers to RMs recovery from base metal tailings should always be investigated beside the potentials so that market actors can better evaluate the sustainability of an investment
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
