Browsing by Department "Lund University"

Now showing 1 - 7 of 7
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    Challenge-based, interdisciplinary learning for sustainability in doctoral education
    (Emerald, 2022-11-24) Piccardo, Chiara; Goto, Yutaka; Koca, Deniz; Aalto, Pasi; Hughes, Mark; Department of Bioproducts and Biosystems; Chalmers University of Technology; Lund University; Norwegian University of Science and Technology
    Purpose : Doctoral candidates possess specialized knowledge that could support sustainability transitions. Doctoral education, however, often focusses on discipline-specific topics and working methods, making it difficult to “see the bigger picture”. This summer school on wood construction gathered doctoral candidates from different fields to explore how solutions to complex sustainability issues could be found by working together across disciplines and by engaging multiple stakeholders. The purpose of this study is to report the pedagogical approaches taken and to understand whether these fostered the candidates’ ability to develop systemic solutions and professional competency.  Design/methodology/approach: Twenty doctoral candidates from various backgrounds participated in a two-week summer school organized by a consortium of four universities. Interdisciplinary groups worked on real-life challenges using a systemic approach to co-create tangible solutions. To support the creation of socio-technical innovations, stakeholders and experts from different fields were involved. The participants completed two questionnaires during the summer school to help elucidate their learning experiences.  Findings : The doctoral candidates showed strong willingness to cooperate across disciplines, though they found it important to connect this learning experience to their research. The candidates reported that the experience enhanced their ability to work in a multidisciplinary capacity. The experience identified a solid basis for interdisciplinary learning principles that could be replicated.  Originality/value: The summer school focussed on an innovative learning experience based on a systems thinking approach and the development of interdisciplinary capacity in the research-business ecosystem.
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    The colloidal structure of a cellulose fiber
    (SPRINGER, 2021-03) Gubitosi, Marta; Asaadi, Shirin; Sixta, Herbert; Olsson, Ulf; Lund University; Biorefineries; Department of Bioproducts and Biosystems
    Abstract: We present a small angle X-ray scattering (SAXS) study of the colloidal structure of regenerated cellulose fibers, air-gap spun from an ionic liquid solution. Based on the data, and a different interpretation of the anisotropic SAXS pattern, we propose a slightly different colloidal structure of the fibers, than what is commonly assumed for regenerated cellulose fibers. Fibers with two different degrees of orientation, as produced by different draw ratios, DR = 2 and 15, respectively, are analyzed. The 2D SAXS pattern is highly anisotropic with striking cross-like pattern, having scattering predominantly perpendicular and parallel to the fiber axis. This cross-like pattern suggest a colloidal structure with oriented crystalline lamellae of ca. 10 nm thickness, embedded within a continuous matrix of amorphous cellulose. The lamellae are oriented with their normal parallel with the fiber axis. Complementary wide angle X-ray diffraction data confirm that the lamellae normal direction corresponds to thecellulose chain direction (c-direction) in the monoclinic cellulose crystal (Cellulose II). Graphic abstract: [Figure not available: see fulltext.].
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    Generalized Kakeya sets for polynomial evaluation and faster computation of fermionants
    (2018-01-01) Björklund, Andreas; Kaski, Petteri; Williams, Ryan; Lund University; Professorship Kaski P.; Massachusetts Institute of Technology; Department of Computer Science
    We present two new data structures for computing values of an n-variate polynomial P of degree at most d over a finite field of q elements. Assuming that d divides q- 1 , our first data structure relies on (d+ 1) n + 2 tabulated values of P to produce the value of P at any of the qn points using O(nqd2) arithmetic operations in the finite field. Assuming that s divides d and d / s divides q- 1 , our second data structure assumes that P satisfies a degree-separability condition and relies on (d/ s+ 1) n + s tabulated values to produce the value of P at any point using O(nqssq) arithmetic operations. Our data structures are based on generalizing upper-bound constructions due to Mockenhaupt and Tao (Duke Math J 121(1):35–74, 2004), Saraf and Sudan (Anal PDE 1(3):375–379, 2008) and Dvir (Incidence theorems and their applications, 2012. arXiv:1208.5073) for Kakeya sets in finite vector spaces from linearto higher-degree polynomial curves. As an application we show that the new data structures enable a faster algorithm for computing integer-valued fermionants, a family of self-reducible polynomial functions introduced by Chandrasekharan and Wiese (Partition functions of strongly correlated electron systems as fermionants, 2011. arXiv:1108.2461v1) that captures numerous fundamental algebraic and combinatorial functions such as the determinant, the permanent, the number of Hamiltonian cycles in a directed multigraph, as well as certain partition functions of strongly correlated electron systems in statistical physics. In particular, a corollary of our main theorem for fermionants is that the permanent of an m× m integer matrix with entries bounded in absolute value by a constant can be computed in time 2m-Ω(m/loglogm), improving an earlier algorithm of Björklund (in: Proceedings of the 15th SWAT, vol 17, pp 1–11, 2016) that runs in time 2m-Ω(m/logm).
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    How can airborne transmission of COVID-19 indoors be minimised?
    (Elsevier Limited, 2020-09) Morawska, Lidia; Tang, Julian W.; Bahnfleth, William; Bluyssen, Philomena M.; Boerstra, Atze; Buonanno, Giorgio; Cao, Junji; Dancer, Stephanie; Floto, Andres; Franchimon, Francesco; Haworth, Charles; Hogeling, Jaap; Isaxon, Christina; Jimenez, Jose L.; Kurnitski, Jarek; Li, Yuguo; Loomans, Marcel; Marks, Guy; Marr, Linsey C.; Mazzarella, Livio; Melikov, Arsen Krikor; Miller, Shelly; Milton, Donald K.; Nazaroff, William; Nielsen, Peter V.; Noakes, Catherine; Peccia, Jordan; Querol, Xavier; Sekhar, Chandra; Seppänen, Olli; Tanabe, Shin ichi; Tellier, Raymond; Tham, Kwok Wai; Wargocki, Pawel; Wierzbicka, Aneta; Yao, Maosheng; Queensland University of Technology; University of Leicester; Pennsylvania State University; Delft University of Technology; Federation of European Heating, Ventilation and Air Conditioning Associations (REHVA); University of Cassino and Southern Lazio; Chinese Academy of Sciences; Edinburgh Napier University; University of Cambridge; Franchimon ICM; ISSO, Kennisinstituut voor de installatiesector; Lund University; University of Colorado Boulder; Tallinn University of Technology; University of Hong Kong; Eindhoven University of Technology; University of New South Wales; Virginia Tech; Polytechnic University of Milan; Danmarks Tekniske Universitet; University of Maryland, College Park; University of California at Berkeley; Aalborg University; University of Leeds; Yale University; CSIC; National University of Singapore; Aalto University; Architectural Institute of Japan; McGill University; Peking University
    During the rapid rise in COVID-19 illnesses and deaths globally, and notwithstanding recommended precautions, questions are voiced about routes of transmission for this pandemic disease. Inhaling small airborne droplets is probable as a third route of infection, in addition to more widely recognized transmission via larger respiratory droplets and direct contact with infected people or contaminated surfaces. While uncertainties remain regarding the relative contributions of the different transmission pathways, we argue that existing evidence is sufficiently strong to warrant engineering controls targeting airborne transmission as part of an overall strategy to limit infection risk indoors. Appropriate building engineering controls include sufficient and effective ventilation, possibly enhanced by particle filtration and air disinfection, avoiding air recirculation and avoiding overcrowding. Often, such measures can be easily implemented and without much cost, but if only they are recognised as significant in contributing to infection control goals. We believe that the use of engineering controls in public buildings, including hospitals, shops, offices, schools, kindergartens, libraries, restaurants, cruise ships, elevators, conference rooms or public transport, in parallel with effective application of other controls (including isolation and quarantine, social distancing and hand hygiene), would be an additional important measure globally to reduce the likelihood of transmission and thereby protect healthcare workers, patients and the general public.
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    Intermediation dilemmas in facilitated industrial symbiosis
    (ELSEVIER SCI LTD, 2020-07-10) Patala, Samuli; Salmi, Asta; Bocken, Nancy; Sustainability in Business; University of Vaasa; Lund University; Department of Management Studies
    Industrial symbiosis (IS) is a key paradigm for achieving circular economy among industrial firms. Achieving new IS projects often requires outside facilitation, and intermediaries can help solidify and expand existing IS networks. While various intermediary roles have been identified in the literature, less attention has been paid to the potential challenges that intermediaries might encounter in their activities. Based on the case of the national symbiosis network FISS, the Finnish Industrial Symbiosis system, this study investigates the dilemmas faced when organizing IS networks. It identifies openness and value demonstration dilemmas, which hinder intermediary-firm relations. It also identifies collaborative intermediation processes among intermediaries in seeking to uncover value, ensuring community embedding of new networks and selective integration of intermediation activities. These processes can help overcome the intermediation dilemmas. The results on the collaborative intermediation and its development over time contribute to research on facilitated IS and on intermediaries in sustainability transitions. For policy-makers, the study pinpoints the need for collaborative intermediation where both national and regional intermediaries are involved to ensure both economies of scale and flexibility.
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    Photon emission statistics of a driven microwave cavity
    (American Physical Society, 2023-07) Portugal, Pedro; Brange, Fredrik; Kansanen, Kalle S.U.; Samuelsson, Peter; Flindt, Christian; Quantum Transport; Centre of Excellence in Quantum Technology, QTF; Lund University; Department of Applied Physics
    Recent experimental advances have made it possible to detect individual quantum jumps in open quantum systems, such as the tunneling of single electrons in nanoscale conductors or the emission of photons from nonclassical light sources. Here, we investigate theoretically the statistics of photons emitted from a microwave cavity that is driven resonantly by an external field. We focus on the differences between a parametric and a coherent drive, which either squeezes or displaces the cavity field. We employ a Lindblad master equation dressed with counting fields to obtain the generating function of the photon emission statistics using a theoretical framework based on Gaussian states. We then compare the distribution of photon waiting times for the two drives as well as the g(2) functions of the outgoing light, and we identify important differences between these observables. In the long-time limit, we analyze the factorial cumulants of the photon emission statistics and the large-deviation statistics of the emission currents, which are markedly different for the two drives. Our theoretical framework can readily be extended to more complicated systems, for instance, with several coupled microwave cavities, and our predictions may be tested in future experiments.
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    Trade-offs with longer lifetimes? The case of LED lamps considering product development and energy contexts
    (Elsevier, 2019-07-20) Richter, Jessika Luth; Tähkämö, Leena; Dalhammar, Carl; Lund University; Department of Electrical Engineering and Automation
    Longer product lifetimes are promoted by the EU's Circular Economy Action Plan, but incentivising longer lifetimes could also result in trade-offs between different environmental impacts for some product categories. LED lamps are still experiencing improvements in efficacy and material design, which raises questions about whether longer lifetimes are desirable from an overall environmental perspective. Applying a comprehensive life cycle assessment using actual product cases from 2012 to 2017, the research builds on previous product lifetime studies and lighting product research to determine the scenarios in which longer lifetimes are desirable from an overall environmental perspective. The factors explored in the scenarios included improving products in terms of efficiency and dematerialisation as well as decarbonised electricity contexts. The results indicate that product replacement with improved products resulted in environmental benefits compared to keeping longer life products in use, but there are sometrade-offs between environmental impacts. However, these trade-offs are minimised in the context of decarbonised electricity mixes and will further decrease as LED lamp technology matures and product development slows. The policy implications of the findings are also discussed.