| 1. |
- Abdelaziz, Omar, et al.
(author)
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A Rapid and Tunable Approach for the Fractionation of Technical Kraft Lignin
- 2023
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In: Chemical Engineering Transactions. - : Italian Association of Chemical Engineering - AIDIC. - 1974-9791 .- 2283-9216. ; 99, s. 67-72
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Journal article (peer-reviewed)abstract
- Reducing the heterogeneity of technical lignin is essential to obtain predictable and high-performance polymeric materials that are suitable for high-value applications. Organic solvents with different polarities and solubilities can be used to fractionate lignin and reduce the complexity and diversity of its chemical structure. Among the various solvents and solvent mixtures, acetone-water mixtures offer an energy-efficient, cost-effective, and environmentally friendly means of lignin fractionation. In the present study, temperature-induced acetone-water fractionation was investigated to refine the properties of a technical softwood Kraft lignin, i.e., LignoBoost™ lignin. Relatively mild operating conditions were tested, namely, temperatures of 70-110°C and autogenous pressure. A factorial experimental design was developed using the Design-Expert® software, and three factors (temperature, time, and acetone concentration) were investigated. It was found that temperature-induced fractionation could increase lignin homogeneity and maintain high lignin solubilization with a short processing time (<1 h). It was also possible to tune the properties of the soluble lignin fraction (yield and weight-average molecular weight) based on the factorial models developed. The techno-economic evaluation confirmed the commercial viability of this fractionation process.
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| 2. |
- Abdelraheem, Mohamed Ahmed, et al.
(author)
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Searchable Encrypted Relational Databases: Risks and Countermeasures
- 2017
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In: Cryptology ePrint Archive. - Gewerbestrasse 11, 6330 Cham, Switzerland : Springer Nature. ; 2017:24, s. 1-20, s. 70-85
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Journal article (other academic/artistic)abstract
- We point out the risks of protecting relational databases via Searchable Symmetric Encryption (SSE) schemes by proposing an inference attack exploiting the structural properties of relational databases. We show that record-injection attacks mounted on relational databases have worse consequences than their file-injection counterparts on un- structured databases. Moreover, we discuss some techniques to reduce the effectiveness of inference attacks exploiting the access pattern leakage existing in SSE schemes. To the best of our knowledge, this is the first work that investigates the security of relational databases protected by SSE schemes.
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| 3. |
- Abdelraheem, Mohamed, et al.
(author)
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Practical Attacks on Relational Databases Protected via Searchable Encryption
- 2018
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In: Lecture Notes in Computer Science. - Cham : Springer International Publishing. - 1611-3349 .- 0302-9743. - 9783319991351 ; , s. 171-191
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Conference paper (peer-reviewed)abstract
- Searchable symmetric encryption (SSE) schemes are commonly proposed to enable search in a protected unstructured documents such as email archives or any set of sensitive text files. However, some SSE schemes have been recently proposed in order to protect relational databases. Most of the previous attacks on SSE schemes have only targeted its common use case, protecting unstructured data. In this work, we propose a new inference attack on relational databases protected via SSE schemes. Our inference attack enables a passive adversary with only basic knowledge about the meta-data information of the target relational database to recover the attribute names of some observed queries. This violates query privacy since the attribute name of a query is secret.
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| 4. |
- Abdul Hamid, Akram, et al.
(author)
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Determining the Impact of High Residential Density on Indoor Environment, Energy Use, and Moisture Loads in Swedish Apartments-and Measures for Mitigation
- 2021
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In: Sustainability. - : MDPI AG. - 2071-1050. ; 13:10
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Journal article (peer-reviewed)abstract
- Recently, there has been an increase in apartments with a large number of inhabitants, i.e., high residential density. This is partly due to a housing shortage in general but also increased migration, particularly in suburbs of major cities. This paper specifies issues that might be caused by high residential density by investigating the technical parameters influenced in Swedish apartments that are likely to have high residential density. Interviews with 11 employees at housing companies were conducted to identify issues that might be caused by high residential density. Furthermore, simulations were conducted based on extreme conditions described in the interviews to determine the impact on the energy use, indoor environmental quality, and moisture loads. In addition, the impact of measures to mitigate the identified issues was determined. Measures such as demand-controlled ventilation, increase of a constant ventilation rate, and moisture buffering are shown to reduce the risk for thermal discomfort, mold growth, and diminished indoor air quality; while still achieving a lower energy use than in a normally occupied apartment. The results of this study can be used by authorities to formulate incentives and/or recommendations for housing owners to implement measures to ensure good indoor environmental quality for all, irrespective of residential density conditions.
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| 5. |
- Abdul Hamid, Akram, et al.
(author)
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Impact of high residential density on the building technology, HVAC systems, and indoor environment in Swedish apartments
- 2020
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In: E3S Web of Conferences. Volyme 172, 2020.. - : EDP Sciences. ; 172
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Conference paper (peer-reviewed)abstract
- During the last few years, there has been an increased number of overcrowded apartments, due to increased migration but also housing shortage in general, particularly in the suburbs to major cities. The question is how the indoor environment in these apartments is affected by the high number of persons and how the problems related to high residential density can be overcome. This paper aims to specify the problem by investigating and analysing the technical parameters influenced by residential density in Swedish apartments built between 1965-1974. To map the situation, 11 interviews with employees at housing companies were conducted. Based on extreme conditions described in the interviews, simulations of the indoor climate and moisture risks at some vulnerable parts of constructions were made. Simulations were focused on moisture loads and CO2 concentrations as functions of residential density and ventilation rate. Finally, measures to combat problems associated to overcrowding are suggested. The aim is that the results should be used by authorities to formulate incentives and/or recommendations for housing companies to take actions to ensure a good indoor environment for all, irrespective of residential density conditions. © The Authors.
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| 6. |
- Abrahamsson, Camilla, et al.
(author)
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Aerosolized particulate matter from fragmentation of carbon nanotube-enhanced concrete
- 2023
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In: Abstracts from the 2022 Airmon-10 conference and the 2023 Inhaled Particles and NanOEH conference. - 2398-7316 .- 2398-7308. ; 67:Supplement_1, s. i94-i95
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Conference paper (peer-reviewed)abstract
- Construction and demolition workers are exposed to high levels of particulate matter (PM) from building materials throughout their working life. Although nano-enabled building materials (NEBMs) may improve the performance and functionality of buildings, concerns are being raised regarding health risks from occupational exposure to PM from NEBMs. In this work, an experimental set-up for integrated resuspension and characterization of PM from NEBMs was developed and tested using three types of concrete (low density, normal, high strength), each enhanced with Carbon Nanotubes (CNTs) at different concentrations (0, low, high). The performance of portable devices used in occupational exposure assessments (DustTrak and NanoTracer) was compared with stationary instruments and gravimetric filter techniques. 40-70% of the mass and 90-98% of the number of particles were within the respirable fraction, with primary modes at 150 nm and 2-3 µm. Addition of CNTs significantly decreased mean particle number concentrations (PNCs) across the entire characterized size range (7 nm - 20 µm) for low density concrete, whereas the opposite was the case for normal strength and high strength concrete. It was hypothesised that the concrete matrix primarily governs the PM formation, which is in turn modulated by CNT-matrix interactions either suppressing or supporting fragmentation during crushing. SEM imaging could display partially submerged CNTs protruding from concrete fragments. Fundamental interactions at the interface of the nanomaterial and the surrounding matrix needs to be investigated to determine how the PM generated from NEBMs differ from their non-nano counterparts and how to prevent future exposure during demolition.
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| 7. |
- Abrahamsson, Camilla, et al.
(author)
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Characterization of airborne dust emissions from three types of crushed multi-walled carbon nanotube-enhanced concretes
- 2024
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In: NanoImpact. - : Elsevier B.V.. - 2452-0748. ; 34
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Journal article (peer-reviewed)abstract
- Dispersing Multi-Walled Carbon Nanotubes (MWCNTs) into concrete at low (<1 wt% in cement) concentrations may improve concrete performance and properties and provide enhanced functionalities. When MWCNT-enhanced concrete is fragmented during remodelling or demolition, the stiff, fibrous and carcinogenic MWCNTs will, however, also be part of the respirable particulate matter released in the process. Consequently, systematic aerosolizing of crushed MWCNT-enhanced concretes in a controlled environment and measuring the properties of this aerosol can give valuable insights into the characteristics of the emissions such as concentrations, size range and morphology. These properties impact to which extent the emissions can be inhaled as well as where they are expected to deposit in the lung, which is critical to assess whether these materials might constitute a future health risk for construction and demolition workers. In this work, the impact from MWCNTs on aerosol characteristics was assessed for samples of three concrete types with various amounts of MWCNT, using a novel methodology based on the continuous drop method. MWCNT-enhanced concretes were crushed, aerosolized and the emitted particles were characterized with online and offline techniques. For light-weight porous concrete, the addition of MWCNT significantly reduced the respirable mass fraction (RESP) and particle number concentrations (PNC) across all size ranges (7 nm – 20 μm), indicating that MWCNTs dampened the fragmentation process by possibly reinforcing the microstructure of brittle concrete. For normal concrete, the opposite could be seen, where MWCNTs resulted in drastic increases in RESP and PNC, suggesting that the MWCNTs may be acting as defects in the concrete matrix, thus enhancing the fragmentation process. For the high strength concrete, the fragmentation decreased at the lowest MWCNT concentration, but increased again for the highest MWCNT concentration. All tested concrete types emitted <100 nm particles, regardless of CNT content. SEM imaging displayed CNTs protruding from concrete fragments, but no free fibres were detected.
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| 8. |
- Abualhoul, Mohammad Y., et al.
(author)
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Free space optical link for biomedical applications
- 2012
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In: Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS. - 1557-170X. - 9781424441198 ; , s. 1667-1670
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Conference paper (peer-reviewed)abstract
- Free space optics is an interesting alternative for telemetry with medical implants, due to the high data bandwidths available at optical frequencies. Especially implanted brain-computer interfaces gives rise to large data sets that needs to be transmitted transcutaneous. In this paper we show that it is possible to establish such a link at near-IR wavelengths using a modulated reflector in the implant, thus keeping the laser and the detector on the outside. In addition, we show that it will not only work on short, i.e. touch, distances but also at larger distances, in the range of a meter. We have used an electro absorption modulator to modulate the reflection of an external laser source back towards an external detector. The only part of this system that needs to be implanted is the modulator and drive electronics. The study has been done both by Monte-Carlo simulations of a multi-layer model of a rat skull, and with an experiment demonstrating the feasibility of the link when transmitted through biological tissue. The results show that it is possible to establish a transcutaneous link with an external laser source and light detector, and an internal modulated reflector.
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| 9. |
- Abugabbara, Marwan, et al.
(author)
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How to develop fifth-generation district heating and cooling in Sweden? : Application review and best practices proposed by middle agents
- 2023
-
In: Energy Reports. - : Elsevier Ltd. - 2352-4847. ; 9, s. 4971-4983
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Journal article (peer-reviewed)abstract
- Sweden has an ambitious plan to fully decarbonise district heating by 2030 and to contribute with negative emissions of greenhouse gases in 2050. The vagaries of the energy market associated with climate, political, and social changes entail cross-sectoral integration that can fulfill these national targets. Fifth-generation district heating and cooling (5GDHC) is a relatively new concept of district energy systems that features a simultaneous supply of heating and cooling using power-to-heat technologies. This paper presents best practices for developing 5GDHC systems in Sweden to reach a consensus view on these systems among all stakeholders. A mixed-method combining best practice and roadmapping workshops has been used to disseminate mixed knowledge and experience from middle agents representing industry professionals and practitioners. Four successful implementations of 5GDHC systems are demonstrated and the important learned lessons are shared. The best practices are outlined for system planning, system modeling and simulation, prevailing business models for energy communities, and system monitoring. A roadmap from the middle agents’ point of view is composed and can be utilised to establish industry standards and common regulatory frameworks. © 2023 The Author(s)
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| 10. |
- Ahlgren, Serina, et al.
(author)
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Review of methodological choices in LCA of biorefinery systems - key issues and recommendations
- 2015
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In: Biofuels, Bioproducts and Biorefining. - : Wiley. - 1932-1031 .- 1932-104X. ; 9:5, s. 606-619
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Research review (peer-reviewed)abstract
- The current trend in biomass conversion technologies is toward more efficient utilization of biomass feedstock in multiproduct biorefineries. Many life-cycle assessment (LCA) studies of biorefinery systems have been performed but differ in how they use the LCA methodology. Based on a review of existing LCA standards and guidelines, this paper provides recommendations on how to handle key methodological issues when performing LCA studies of biorefinery systems. Six key issues were identified: (i) goal definition, (ii) functional unit, (iii) allocation of biorefinery outputs, (iv) allocation of biomass feedstock, (v) land use, and (vi) biogenic carbon and timing of emissions. Many of the standards and guidelines reviewed here provide only general methodological recommendations. Some make more specific methodological recommendations, but these often differ between standards. In this paper we present some clarifications (e.g. examples of research questions and suitable functional units) and methodological recommendations (e.g. on allocation).
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