Chalmers Research
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District heating as a flexibility service: Challenges in sector coupling for increased solar and wind power production in Sweden
Get PDFWith expanding solar and wind power production, the topic of flexibility services attracts increased attention in the Swedish energy system. In this context, the potentials in using thermal storage capacities in district heating (DH) systems have been brought forward, primarily by academic scholars. Using a ‘grounded’ approach, this study investigates if professionals assigned to Swedish DH companies and electricity distribution system operators utilise, or plan to utilise, DH systems as flexibility services for the electricity grid. Original data was collected through semi-structured interviews, held with fourteen individuals affiliated to different actors in the Swedish energy system. These individuals were identified as being experts, or practically engaged, in using DH utilities as flexibility services for the electricity grid. The findings show that although technologies for coupling between DH systems and the electricity grid are already in place, initiatives for using DH systems as flexibility services for the electricity system are rare in Sweden. Coupling challenges stem from ownership and operation legislation frameworks, marginal incentives and a widespread focus on firm benefits rather than energy systems benefits. Identified initiatives for using DH systems for flexibility services are primarily run on a local scale, designed and propelled by small groups of engaged individuals
Hydrogen Adsorption on Pd–In Intermetallic Surfaces
Get PDFIt has recently been shown that CO 2 hydrogenation to methanol over PdIn and In 2O 3 depends critically on the adsorption energy of hydrogen. Here we use density functional theory calculations to investigate hydrogen adsorption over Pd–In intermetallic compound surfaces with different Pd:In ratios. The electronic structure and properties of hydrogen adsorption are investigated for a range of surface facets and compared to the corresponding results for the pure parent metals and Cu. Increased In content is found to shift the Pd(d) density of states away from the Fermi level, making the intermetallic Pd–In compounds to appear “Cu-like”. We find a linear correlation between the hydrogen binding energy and the d-band center of surface Pd atoms. Understanding of how the hydrogen adsorption energy depends on composition and structure provides a possibility to enhance the performance of CO 2 hydrogenation catalysts to methanol
Power-Efficient Voronoi Constellations for Fiber-Optic Communication Systems
Get PDFVoronoi constellations (VCs) are considered as an effective geometric shaping method due to their high power efficiencies and low complexity. In this paper, the performance of 16- and 32-dimensional VCs with a variety of spectral efficiencies transmitted in the nonlinear fiber channel are investigated. Both single-channel and wavelength-division multiplexing systems are considered for the transmission of the VCs, as well as different signal processing schemes, including chromatic dispersion compensation and digital backpropagation. Multiple performance metrics including the uncoded bit error rate, mutual information (MI), and generalized mutual information (GMI) of VCs are evaluated. Compared with quadrature amplitude modulation (QAM) formats, the VCs provide 1.0--2.4 dB launch power gains, up to 0.50 bits/symbol/dimension-pair MI gains, up to around 30% potential reach increase at the same MI, and up to 0.30 bits/symbol/dimension-pair GMI gains in a limited launch power range. The observed performance gains over QAM are found higher than in the back-to-back case. Moreover, a general GMI estimation method for very large constellations using importance sampling is proposed for the first time
Fourier expansions of vector-valued automorphic functions with non-unitary twists
No full textWe provide Fourier expansions of vector-valued eigenfunctions of the hyperbolic Laplacian that are twist-periodic in a horocycle direction. The twist may be given by any endomorphism of a finite-dimensional vector space; no assumptions on invertibility or unitarity are made. Examples of such eigenfunctions include vector-valued twisted automorphic forms of Fuchsian groups. We further provide a detailed description of the Fourier coefficients and explicitly identify each of their constituents, which intimately depend on the eigenvalues of the twisting endomorphism and the size of its Jordan blocks. In addition, we determine the growth properties of the Fourier coefficients
HybridMingler: Towards Mixed-Reality Support for Mingling at Hybrid Conferences
Get PDFMingling, the activity of ad-hoc, private, opportunistic conversations ahead of, during, or after breaks, is an important socializing activity for attendees at scheduled events, such as in-person conferences. The Covid-19 pandemic had a dramatic impact on the way conferences are organized, so that most of them now take place in a hybrid mode where people can either attend on-site or remotely. While on-site attendees can resume in-person mingling, hybrid modes make it challenging for remote attendees to mingle with on-site peers. In addressing this problem, we propose a collaborative mixed-reality (MR) concept, including a prototype, called HybridMingler. This is a distributed MR system supporting ambient awareness and allowing both on-site and remote conference attendees to virtually mingle. HybridMingler aims to provide both on-site and remote attendees with a spatial sense of co-location in the very same venue location, thus ultimately improving perceived presence
Scattering of elastic waves by a sphere with cubic anisotropy with application to attenuation in polycrystalline materials
Get PDFScattering of elastic waves by an anisotropic sphere with cubic symmetry inside an isotropic medium is studied. The waves in the isotropic surrounding are expanded in the spherical vector wave functions. Inside the sphere, the elastodynamic equations are first transformed to spherical coordinates and the displacement field is expanded in terms of the vector spherical harmonics in the angular directions and a power series in the radial direction. The governing equations inside the sphere give recursion relations among the expansion coefficients in the power series. The boundary conditions on the sphere then determine the expansion coefficients of the scattered wave. This determines the transition (T) matrix elements which are calculated explicitly to the leading order for low frequencies. Using the theory of Foldy, the T matrix elements of a single sphere are used to study attenuation and phase velocity of polycrystalline materials with cubic symmetry, explicitly for low frequencies and numerically for intermediate frequencies. Numerical comparisons of the present method with previously published results and recent finite element method (FEM) results show a good correspondence for low and intermediate frequencies. The present approach shows a better agreement with FEM for strongly anisotropic materials in comparison with other published methods
Role of bran particles in the formation of dark spots on fresh wet noodle sheets: what are the dark spots?
No full textBackground: Dark spots may affect the appearance of fresh noodles during storage, even when made from flour with low ash content. The effect of flour bran content on the degree of dark spot formation in fresh wet noodle sheets (FWNS) is investigated to explain this phenomenon. Results: Confocal laser scanning microscopy (CLSM) observation revealed that the wheat bran particles were responsible for the formation of dark spots on FWNS, with each bran particle core generating a single dark spot. In wheat flours with low ash content, the number of wheat bran particles causing dark spot formation on FWNS was limited, and these particles were not visible to the naked eye until their size exceeded approximately 50 μm. Tropolone, a polyphenol oxidase inhibitor (PubChem CID: 24900578) and dry heating treatment, which inactivates polyphenol oxidase, was found to inhibit or reduce the formation of dark spots. Conclusion: Based on these findings, it can be concluded that bran particles, rich in polyphenol oxidase, play a key role in dark spot formation. \ua9 2023 Society of Chemical Industry
TTRPG UX: Requirements & Beyond
Get PDFTabletop Role Playing Games (TTRPG) allow the player to immerse themselves in a world where anything can happen - within the rules. You can become someone new, fight demons, play out exciting and speculative storylines, all with the help of your party. This ability to place yourself in the life of another person (or ethereal being) resonates with principles of User Experience Design (UX) where usability experts strive to understand the impact their application or interface might have on a hypothetical audience. This paper explores the parallels and potentials of TTRPG within the context of UX and Requirements, its characters, contexts and interactions. We propose creating playable UX worlds with the potential to provide deeper, more insightful output, and make recommendations for the addition of a TTRPG approach to User Experience processes
Polydopamine/graphene oxide coatings loaded with tetracycline and green Ag nanoparticles for effective prevention of biofilms
Get PDFBacterial adhesion and biofilm formation are significant challenges for medical devices and implants. Surface modification to alter the surface properties of biomedical device surfaces to prevent the biofilm formation is an important driving force for the development of anti-biofilm coatings. Here, a simple and feasible method to fabricate antibacterial coatings that combines the adhesion properties of polydopamine (PDA) and the high drug loading capacity of graphene oxide (GO). Tetracycline and green-synthesized silver nanoparticles were successfully assembled onto the coating surface, endowing the coating an anti-biofilm effect and exhibit strong inhibitory effect on S. aureus and E. coli biofilms by a factor of more than 1000 (3 log10 units). Kirby-Bauer diffusion test, colony forming unit (CFU) counts, biofilm topography studies and live/dead staining were used to evaluate the antibacterial activity of the coatings. This study is proposed that PDA/GO coatings loaded with antibiotics or silver nanoparticles can be used as a potential approach to prevent infection associated with implantable biomedical devices