| 1. |
- Alipour, Nazanin, et al.
(författare)
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Qualitative characterization of nanoclay particle emissions from PP nanocomposites after thermal degradation
- 2015
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Ingår i: 20th International Conference on Composite Materials, ICCM 2015. - : International Committee on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- The use of nanomaterials in polymeric materials is a rapidly expanding field, and the polymer nanocomposites are being introduced into various markets. But there is still little known about the fate of nanocomposites and nanoparticles during service life and end-of-life of the materials. To avoid possible environmental, health and safety problems, simulating different scenarios for nanoparticles release from the polymer matrix plays a key role in commercialization of these advanced materials. The polymer/nanoclay nanocomposites show superior material properties in comparison with the pure polymers, such as improved mechanical properties, heat resistance, flame retardancy and decreased gas permeability. Polypropylene (PP) nanocomposites have attracted a considerable interest due to the material's low cost, low density and extensive production volumes. In this study, in order to obtain reliable results regarding the release of nanoclays from PP nanocomposites, homogenous composite with predetermined content of nanoclay was produced and characterized to obtain information regarding content, dispersion and size of the nanoclays in the matrix. The PP nanocomposite was degraded under controlled conditions and the surface morphology as well as oxidation of the material was characterized with scanning electron microscopy (SEM) and infrared spectroscopy during degradation. A prototype environmental chamber was designed in order to collect nano-sized particles in a controlled manner and subsequent characterization of the released or formed particles was performed with transmission electron microscopy (TEM) and the exposed nanocomposite was analysed with thermogravimetric analysis (TGA).
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| 2. |
- Atari Jabarzadeh, Sevil, et al.
(författare)
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Image Analysis Determination of the Influence of Surface Structure of Silicone Rubbers on Biofouling
- 2015
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Ingår i: International Journal of Polymer Science. - : Hindawi Limited. - 1687-9422 .- 1687-9430.
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on how the texture of the silicone rubber material affects the distribution of microbial growth on the surface of materials used for high voltage insulation. The analysis of surface wetting properties showed that the textured surfaces provide higher receding contact angles and therefore lower contact angle hysteresis. The textured surfaces decrease the risk for dry band formation and thus preserve the electrical properties of the material due to a more homogeneous distribution of water on the surface, which, however, promotes the formation of more extensive biofilms. The samples were inoculated with fungal suspension and incubated in a microenvironment chamber simulating authentic conditions in the field. The extent and distribution of microbial growth on the textured and plane surface samples representing the different parts of the insulator housing that is shank and shed were determined by visual inspection and image analysis methods. The results showed that the microbial growth was evenly distributed on the surface of the textured samples but restricted to limited areas on the plane samples. More intensive microbial growth was determined on the textured samples representing sheds. It would therefore be preferable to use the textured surface silicone rubber for the shank of the insulator.
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| 3. |
- Atari Jabarzadeh, Sevil, et al.
(författare)
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Use of essential oils for the prevention of biofilm formation on silicone rubber high voltage insulators
- 2015
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Ingår i: Polymers from Renewable Resources. - : Rapra Technology Ltd.. - 2041-2479 .- 2045-1377. ; 6:4, s. 119-136
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Tidskriftsartikel (refereegranskat)abstract
- The prevention of biofilm formation on high voltage insulators is important to avoid changes in the surface properties of the material and the subsequent failure of the application. Antimicrobial silicone rubber samples were prepared by the addition of thymol and eugenol to Sylgard 184 to determine the possibility of using natural antimicrobial agents present in essential oils in materials used for high voltage insulators. The antimicrobial effects of thymol and eugenol were studied for different fungal strains and for green algae identified in the biofilms formed on insulators in Tanzania, Sri Lanka and Sweden. It was successfully demonstrated that samples containing high amount of eugenol and different concentrations of thymol could inhibit the fungal growth of strains from Sri Lanka and Tanzania and the growth of green algae. The growth of strains from Sweden was also suppressed. The addition of eugenol to the material resulted in a noncrosslinked system and therefore, the antimicrobial effect of the additive in the material could not be assessed. The addition of thymol did not significantly influence the thermal and mechanical properties of Sylgard184. Although thermal analysis revealed that a large amount of the antimicrobial agent was lost during sample preparation, the materials were effective against microbial growth, even at low thymol concentrations.
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| 4. |
- Badia, J. D., et al.
(författare)
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Effect of sisal and hydrothermal ageing on the dielectric behaviour of polylactide/sisal biocomposites
- 2017
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Ingår i: Composites Science And Technology. - : Elsevier. - 0266-3538 .- 1879-1050. ; 149, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- The dielectric properties of virgin polylactide (PLA) and its reinforced composites with different weight amounts of sisal fibres were assessed at broad temperature (from −130 °C to 130 °C) and frequency ranges (from 10−2–107 Hz), before and after being subjected to accelerated hydrothermal ageing. The synergetic effects of both the loading of sisal and hydrothermal ageing were analysed by means of dielectric relaxation spectra. The relaxation time functions were evaluated by the Havriliak-Negami model, substracting the ohmic contribution of conductivity. The intramolecular and intermolecular relaxations were respectively analysed by means of Arrhenius and Vogel-Fulcher-Tammann-Hesse thermal activation models. The addition of fibre increased the number of hydrogen bonds, which incremented the dielectric permittivity and mainly hindered the non-cooperative relaxations of the biocomposites by increasing the activation energy. Hydrothermal ageing enhanced the formation of the crystalline phase at the so-called transcrystalline region along sisal. This fact hindered the movement of the amorphous PLA fraction, and consequently decreased the dielectric permittivity and increased the dynamic fragility.
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| 5. |
- Badia, J. D., et al.
(författare)
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Relevant factors for the eco-design of polylactide/sisal biocomposites to control biodegradation in soil in an end-of-life scenario
- 2017
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Ingår i: Polymer degradation and stability. - : Elsevier. - 0141-3910 .- 1873-2321. ; 143, s. 9-19
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Tidskriftsartikel (refereegranskat)abstract
- The eco-design considers the factors to prepare biocomposites under an end-of-life scenario. PLA/sisal biocomposites were obtained from amorphous polylactide and sisal loadings of 10, 20 and 30 wt% with and without coupling agent, and subjected to biodegradation in soil according to standard ISO846. Mass-loss, differential scanning calorimetry and size-exclusion chromatography were used for monitoring biodegradation. A statistical factorial analysis based on the molar mass Mn and crystallinity degree XC pointed out the relevance and interaction of amount of fibre and use of coupling agent with the time of burial in soil. During the preparation of biocomposites, chain scission provoked a similar reduction of Mn for coupled and non-coupled biocomposites. The amount of fibre was relevant for the increase of XC due to the increase of nucleation sites. The coupling agent accelerated the evolution of both factors: reduction of Mn and the consequent increase of XC, mainly during biodegradation in soil. Both factors should be balanced to facilitate microbial assimilation of polymer segments, since bacterial digestion is enhanced by chain scission but blocked by the promotion of crystalline fractions.
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| 6. |
- Beheshti, Reza, 1981-
(författare)
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Sustainable Aluminum and Iron Production
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aluminium recycling requires 95% less energy than primary production with no loss of quality. The Black Dross (BD) produced during secondary aluminium production contains high amounts of water-soluble compounds, therefore it is considered as a toxic waste. In the present work, salt removal from BD by thermal treatment has been investigated in laboratory scale. The optimum conditions for treatment were established, i.e., temperature, gas flow rate, holding time, rotation rate, and sample size. The overall degree of chloride removal was established to increase as a function of time and temperature. Even Pretreated Black Dross (PBD) was evaluated as a possible raw material for the production of a calcium aluminate-based ladle-fluxing agent to be used in the steel industry. The effects of different process parameters on the properties of the produced flux were experimentally investigated, i.e. CaO/Al2O3 ratio, temperature, holding time, and cooling media. The utilization of PBD as the alumina source during the production of a calcium aluminate fluxing agent shows promising results. The iron/steel industry is responsible for 9% of anthropogenic energy and process CO2 emissions. It is believed that the only way to a long-term reduction of the CO2 emissions from the iron/steel industry is commercialization of alternative processes such as Direct Reduction (DR) of iron oxide. Detailed knowledge of the kinetics of the reduction reactions is, however, a prerequisite for the design and optimization of the DR process. To obtain a better understanding of the reduction kinetics, a model was developed step-by-step, from a single pellet to a fixed bed with many pellets. The equations were solved using the commercial software COMSOL Multiphysics®. The final model considers the reaction rate and mass transfer inside the pellet, as well as the mass transfers and heat transfer in the fixed bed. All the models were verified against experimental results, and where found to describe the results in a satisfying way.
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| 7. |
- Edvardsson Björnberg, Karin, et al.
(författare)
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Integrating social sustainability in engineering education at the KTH Royal Institute of Technology
- 2015
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Ingår i: International Journal of Sustainability in Higher Education. - 1467-6370 .- 1758-6739. ; 16:5, s. 639-649
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Tidskriftsartikel (refereegranskat)abstract
- Purpose - The purpose of this paper is to investigate what are perceived to be the main challenges associated with the integration of social sustainability into engineering education at the KTH Royal Institute of Technology, Stockholm. Design/methodology/approach - Semi-structured interviews were conducted with programme leaders and teachers from four engineering programmes. The paper focuses on how the concept of social sustainability is defined and operationalised in the selected engineering programmes, how social sustainability is integrated and taught, and what resources are required to support teachers and programme leaders as social sustainability educators. Findings - The findings show that programme leaders and teachers at KTH struggle to understand the concept of social sustainability. The vague and value-laden nature of the concept is considered a challenge when operationalising educational policy goals on social sustainability into effective learning outcomes and activities. A consequence is that the responsibility for lesson content ultimately falls on the individual teacher. Study visits and role-play are seen as the most effective tools when integrating social sustainability into the engineering curriculum. Allocation of specific resources including supplementary sustainability training for teachers and economic incentives are considered crucial to successful integration of social sustainability. The findings indicate that social sustainability education needs to be built on a theoretical foundation. It is therefore suggested that a literature canon be established that clarifies the contours of social sustainability. Practical implications - The findings of the paper can be used as a basis for discussion regarding measures for improving social sustainability training in engineering education, a subject which has attracted relatively little attention, to date. Originality/value - There is a noticeable lack of empirical research on how technical universities integrate social sustainability into engineering education. The paper provides an account of how actors directly involved in this work - programme leaders and teachers - define and operationalise the social dimension of sustainable development in their engineering curricula, the pedagogical tools they consider effective when teaching social sustainability issues to engineering students, and the resources they believe are needed to strengthen those efforts.
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| 8. |
- Engdahl, Johan, 1968, et al.
(författare)
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Geographic and socio-demographic differences in uptake of population-based screening for atrial fibrillation: The STROKESTOP I study
- 2016
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Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 222, s. 430-435
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The rationale behind screening for atrial fibrillation (AF) is to prevent ischemic stroke. Socio-demographic differences are expected to affect screening uptake. Geographic differences may provide further insights leading to targeted interventions for improved uptake. The objective of this study was to evaluate geographic and socio-demographic differences in uptake of AF screening in the population-based study STROKESTOP I. METHODS: STROKESTOP was carried out in two Swedish counties with a total population of 2.3 million inhabitants. Half of the residents aged 75-76years were randomized to the screening arm: invitation to clinical examination followed by ambulant ECG recording. Information on each invited person's residential parish (n=157) was used. On parish-level, aggregated data for the participants and non-participants, respectively, were obtained with respect to socioeconomic variables: educational level, disposable income, immigrant and marital status. Geo-maps displaying participation ratios were estimated by hierarchical Bayes methods. RESULTS: The overall participation rate was similar in men and women but lower in Stockholm, 47.6% (5665/11,903) than in Halland, 61.2% (1495/2443). Participation was clearly associated with the socioeconomic variables. Participation not taking into account socioeconomy varied more markedly across the parishes in the Stockholm county (range: 0.65-1.26) than in the Halland county (0.94-1.27). After adjustment for socioeconomic variables, a geographic variation remained in Stockholm, but not in Halland. CONCLUSION: Participation in AF screening varied according to socioeconomic conditions. Geographic variation in participation was marked in the Stockholm county, with only one screening clinic. Geo-mapping of participation yielded useful information needed to intervene for improved screening uptake.
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| 9. |
- Finnveden, Göran, 1961-, et al.
(författare)
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A Holistic Approach for Integration of Sustainable Development in Education, Research, Collaboration and Operations
- 2017
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Ingår i: Handbook of Theory and Practice of Sustainable Development in Higher Education. - Cham : Springer. - 9783319478883 ; , s. 287-303
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Bokkapitel (refereegranskat)abstract
- In 2011 KTH Royal Institute of Technology started several new sustainable development initiatives. This paper will report on the journey. An Environmental Management System for the entire university has been established and KTH became ISO 14001 certified during 2015. The system includes operations but also education, research and collaboration. In this way we ensure that sustainability goals are integrated in the management system and that improvements are required continuously. For education an aim is that all educational programs should be able to report how they have integrated sustainability. The activities are focused on two complementary approaches: evaluation of the program’s work and providing tools and support for teaching staff and program directors. Preliminary results from the on-going evaluation indicate that progress has been made in several programs, but there is still room for improvements. For research, several bibliometric and external funding indicators show progress. During the winter of 2015 an evaluation was conducted and based on this it was decided that the activities should continue. A new policy for sustainable development as well as new sustainable development goals were decided during 2015.
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| 10. |
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