310 research outputs found
Design and testing of a DC Power Electronics Assembly for Experiments involving SMES and Hybrid Storage
No full textSuperconducting Magnetic Energy Storage (SMES) systems offer efficient storage of electrical energy through the use of superconducting coils. However, practical experimentation with SMES systems is limited due to the complexity and cost associated with their development and operation. This paper presents the design and construction of a laboratory power electronics assembly aimed at performing small-scale SMES system tests. The assembly integrates components for linking SMES systems, batteries, loads, and sources like photovoltaic (PV) simulators to a common DC bus. Key components include half-bridge and full-bridge DC choppers, a battery energy storage system (BESS) controller and a DC load controller. The design methodology, construction procedures and cooling simulations are discussed in detail. Experimental testing of the assembly demonstrates its effectiveness in charging, idling, and discharging of the SMES system. Overall, this study contributes to advancing practical experimentation with SMES systems, offering insights into construction methodologies and experimental outcomes
Impact of the economic crisis on household health expenditure in Greece: An interrupted time series analysis
No full textObjectives and setting The 2008 financial crisis had a particularly severe impact on Greece. To contain spending, the government capped public health expenditure and introduced increased cost-sharing. The Greek case is important for studying the impact of recessions on health systems. This study analysed changes in household health expenditure in Greece over the economic crisis and explored whether the impact differed across socioeconomic groups. Participants We used data from the Greek Household Budget Survey for the years 2004 and 2008-2017. The dataset comprised 51 654 households, with a total of 128 111 members. Design We compared pre-crisis and post-crisis trends in Greek household out-of-pocket payments for healthcare from 2004 to 2017 using an interrupted time series analysis. This study explored spending in euros and as a share of total household purchases. Results Our results indicated that the population level trend in household health spending was reversed after the crisis began (pre-crisis trend: €0.040 decrease per quarter (95% CI: -0.785 to -0.022), post-crisis trend: €0.315 increase per quarter (95% CI: -0.004 to 0.635)). We also found that spending on inpatient services and pharmaceuticals has been increasing since the start of the crisis, whereas outpatient services expenditure has been decreasing. Across all households, out-of-pocket payments incurred a greater financial burden after the crisis relative to pre-existing trends, but the poorest households incurred a disproportionately higher burden. Conclusions This was the first study to use an interrupted time series analysis to assess the impact of the economic crisis on household health expenditure in Greece. Our findings suggest that there was an erosion of financial protection for Greek households as a consequence of the economic crisis. This effect was particularly pronounced among poorer households, which is indicative of a regressive financing system
Energy Yield Comparison of Spar & Monopile Offshore Wind Turbines using BEM & OLAF Models
No full textEnergy transition is imperative to effectively address the pressing issue of climate change resulting from global warming. In this transition, offshore wind power assumes a pivotal role as a crucial and indispensable source of clean and renewable energy. Offshore benefits become more pronounced as the offshore locations progress far offshore. In deep-water areas, where 80% of the worldwide offshore wind energy can be potentially harnessed, the utilization of floating foundations becomes essential instead of traditional bottom fixed ones. The present study seeks to investigate the disparities in power generation and energy production that arise from the replacement of bottom fixed wind turbines with floating counterparts. The former is represented by the monopile foundation, while the latter by the spar buoy. The power performance difference lies in the ability of floating structures to move, which can lead to suboptimal positioning of the rotor relative to the incoming wind inflow, mainly due to spar’s pitch and surge motions. The investigation is conducted using two distinct aerodynamic model of lower and higher fidelities, BEM and OLAF, respectively, to assess their effects on the outcomes.In the field of offshore wind turbine design, engineers rely on aero-hydro-servo-elastic software codes to simulate the dynamic behavior of floating offshore wind turbine systems in offshore environments. OpenFAST, an open-source software, has been extensively developed and validated for conducting such investigations. In this study, OpenFAST is employed to develop both floating and bottom fixed wind turbine models. Specifically, a coupled aero-hydro-servo-elastic model of a floating spar wind turbine is created, and the simulated motion of the spar is compared with measurements obtained from an actual floating turbine deployed in the Hywind Scotland floating offshore wind farm. Metocean data, spar measurement data, and spar system descriptions are provided by Equinor to facilitate this benchmarking process. Additionally, an equivalent monopile wind turbine model is developed for energy yield comparison purposes. The simulated spar motion results of the developed OpenFAST model exhibit reasonable realism when benchmarked with the measured data for all load cases and modal analysis, despite assumptions and uncertainties influencing the model's accuracy. Model discrepancies primarily stem from undisclosed wind turbine parameters and controller strategy as well as some modeling simplifications inherent in OpenFAST. Nevertheless, through statistical, time series and power spectral density comparisons against full-scale Hywind measurements encompassing various wind speeds (below-rated, rated, and above cut-out), the developed floating model is validated, thereby ensuring the reliability of its energy production outcomes.It is observed that the spar’s pitch and surge mean offset is mostly affected by the current speeds while varying wave conditions (height and period) influence their oscillation amplitudes. Power is slightly affected by the ocean conditions, primarily the wave effects, while it is more strongly influenced by the spar nacelle’s velocity and direction relative to the incoming wind, especially when subjected to lower wind speed fields. Finally, for both BEM and OLAF simulations, monopile bottom fixed structures produce higher amounts of energy annually compared to the floating spar counterparts. The implementation of alternative controllers specifically designed for FOWT, with optimization objectives focused on either maximizing power performance or ensuring structural integrity and longevity, results in estimated AEP reductions when utilizing a spar floater instead of a monopile foundation. For the BEM model, the estimated AEP decrease ranges from 3.46% to 8.62%, depending on the specific controller optimization objective. On the other hand, when employing the VPM-OLAF model, the estimated AEP reduction for a spar floater compared to a monopile substructure ranges from 4.50% to 9.58%, under similar conditions as previously mentioned. By employing OLAF instead of BEM, the computed annual energy yield for both Bottom Fixed and Floating offshore wind turbines increases by approximately 25%. In conclusion, it is recommended that future research prioritizes resolving identified discrepancies in the model setup, addressing phenomena not adequately captured by the current OpenFAST model, and conducting additional validation of the spar model using a wider range of measured parameters. Electrical Engineering | Sustainable Energy Technolog
Mineral chemistry of sulphide minerals in concentrates of the Kassandra mines (Chalkidiki, Greece)
No full textThe Kassandra mining district contains porphyry Au-Cu and Au-Ag-Pb-Zn-Cu carbonate replacement deposits that are associated with Oligocene-Miocene intrusions emplaced into polydeformed metamorphic basement rocks belonging to the Permo-Carboniferous to Late Jurassic Kerdilion unit and the Ordovician-Silurian Vertiskos unit. Regional extensional tectonics active since the middle Eocene resulted in the development of widespread normal and transtensional faults, including the Stratoni fault zone that hosts carbonate replacement sulfide ore bodies (Siron et al., 2018).
More particularly, Stratoni (Madem Lakkos, Mavres Petres) and Olympias are the two main carbonate-replacement massive sulphide Pb-Zn (Ag-Au) deposits of the district; they are located on the footwall of the Tertiary Stratoni-Varvara fault. Both deposits are interpreted to form the proximal and distal part of a fault-controlled exoskarn-type ore system triggered by nearby small-scale intrusions close to the fault system (Hahn et al., 2012).
The mineral chemistry of basic sulfide minerals (major phases) into concentrates from the flotation plants of Stratoni and Olympias mines was investigated by EPMA using a JEOL 8200 SEM equipped with WDS.
The chemical formulae of the minerals in their relevant concentrates were calculated as following:
Galena (Stratoni Mine): Pb0.975-0.990Zn0.000-0.004Mn0.000-0.002As0.000-0.001S
Sphalerite (Stratoni Mine): Zn0.788-0.845Fe0.118-0.167Mn0.006-0.010Pb0.000-0.001S
Pyrite (Olympias Mine): Fe1.019-1.051As0.000-0.033Pb0.000-0.001Zn0.000-0.001S2
Arsenopyrite (Olympias Mine): FeAs0.848-0.878S1.065-1.131
In addition, the presence of boulangerite was detected in the pyrite/arsenopyrite concentrate, with microprobe analyses revealing the following chemical formula:
Pb5.182-5.253Sb4.214-4.449As0.058-0.154Fe0.040-0.154Zn0.000-0.063Mn0.010-0.020S11
All sulphide minerals studied were found having typical/expected chemical compositions in major elements. Ongoing research on these samples is also targeting the determination of their trace element concentrations, focusing on noble metals (Godelitsas et al., 2015; Kasama et al., 2018) and elements considered as Critical Raw Materials (CRM) for the EU.
Aknowledgments. This research is implemented through IKY scholarships programme and co-financed by the European Union (European Social Fund - ESF) and Greek national funds through the action entitled ”Reinforcement of Postdoctoral Researchers”, in the framework of the Operational Programme ”Human Resources Development Program, Education and Lifelong Learning” of the National Strategic Reference Framework (NSRF) 2014 – 2020
Cognitive work analysis of a sensor to effecter system: implications for network structures
No full textThis paper presents a Cognitive Work Analysis of a command and control experimental environment. The network facilitates the exchange of information between agents in the field and a series of centrally located commanders. The environment developed allows the manipulation of dependent variables to establish the most efficient network structure for a variety of different scenarios. Cognitive Work Analysis has been used to analyse and model the experimental system and hypothesise the implications of changes to the network structure and the resulting influence this will have on the system and the agents contained within. The analysis uses a Work Domain Analysis to capture the purpose of the system. A Control Task Analysis outlines the task required to fulfil the purpose of the system. This task is broken down in a Strategies Analysis, which explains the possible ways that the system can be configured to enable the same end state. A Social Organisation and Cooperation Analysis elucidates which of the actors within the system can perform the tasks required. Finally a Worker Competencies Analysis describes the resulting behavioural characteristics the actors will exert depending on the level of tasks they are assigned
The Geology, Geochemistry, and Origin of the Porphyry Cu-Au-(Mo) System at Vathi, Serbo-Macedonian Massif, Greece
No full textThe Vathi porphyry Cu-Au ± Mo mineralization is located in the Serbo-Macedonian metallogenic province of the Western Tethyan Metallogenic Belt. It is mainly hosted by a latite and is genetically associated with a quartz monzonite intrusion, which intruded the basement rocks of the Vertiskos Unit and the latite, 18 to 17 Ma ago. A phreatic breccia crosscuts the latite. The quartz monzonite was affected by potassic alteration, whereas the latite was subjected to local propylitic alteration. Both styles of alteration were subsequently overprinted by intense sericitic alteration. M-type and A-type veins are spatially associated with potassic alteration, whereas D-type veins are related to the sericitic alteration. Three ore assemblages are associated with the porphyry stage: (1) pyrite + chalcopyrite + bornite + molybdenite + magnetite associated with potassic alteration; (2) pyrite + chalcopyrite related to propylitic alteration; and (3) pyrite + chalcopyrite + native gold ± tetradymite associated with sericitic alteration. A fourth assemblage consisting of sphalerite + galena + arsenopyrite + pyrrhotite + pyrite ± stibnite ± tennantite is related to an epithermal overprint. Fluid inclusion data indicate that the A-type veins and related porphyry-style mineralization formed at 390–540 °C and pressures of up to 646 bars (This article is published as Stergiou, C.L.; Melfos, V.; Voudouris, P.; Spry, P.G.; Papadopoulou, L.; Chatzipetros, A.; Giouri, K.; Mavrogonatos, C.; Filippidis, A. The Geology, Geochemistry, and Origin of the Porphyry Cu-Au-(Mo) System at Vathi, Serbo-Macedonian Massif, Greece. Appl. Sci. 2021, 11, 479. doi:10.3390/app11020479.</p
pH-Αποκρινόμενα Τυχαία Συμπολυμερή P(OEGMA-co-DIPAEMA): Σύνθεση, Αυτο-οργάνωση σε Υδατικά Διαλύματα και Εγκλωβισμός Φαρμάκου
No full textΤα τυχαία συμπολυμερή έχουν ιδιαίτερο επιστημονικό ενδιαφέρον λόγω της γρήγορης και εύκολης παρασκευής τους συγκριτικά με τα κατά συστάδες, καθώς και της ικανότητάς τους να αυτo-οργανώνονται σε υδατικά διαλύματα. Τα αποκρινόμενα σε ερεθίσματα αμφίφιλα τυχαία συμπολυμερή παρουσιάζουν μεγάλο ενδιαφέρον όσο αφορά τη σύνθεση, την αυτο-οργάνωση σε υδατικά διαλύματα και τις εφαρμογές μεταφοράς φαρμάκων. Ο πολυ(μεθακρυλικός 2-(διισοπροπυλάμινο) αιθυλεστέρας) (PDIPAEMA) είναι ένα βιοσυμβατό πολυμερές με pH-αποκρισημότητα στην περιοχή pH 6.2-6.4, παρόμοιο με αυτό στην επιφάνεια των εξωκυτταρικών ιστών των καρκινικών κυττάρων, κάτι που το καθιστά ελκυστικό για εφαρμογές μεταφοράς φαρμάκων στους ιστούς αυτούς του ανθρώπινου σώματος. Η παρούσα εργασία αφορά τη σύνθεση pH-αποκρινόμενων αμφίφιλων τυχαίων συμπολυμερών πολυ(μεθακρυλικός εστέρας της ολιγο αιθυλενογλυκόλης)–co-μεθακρυλικός 2-(δι-ισοπροπυλάμινο αιθυλεστέρας) (poly[(οligo ethylene glycol) methyl ether methacrylate-co-(2-(diisopropylamino) ethyl methacrylate]) (P(ΟEGMA-co-DIPAEMA)) μέσω της τεχνικής πολυμερισμού αντιστρεπτής προσθήκης-μεταφοράς αλυσίδας με απόσπαση (Reversible Addition-Fragmentation Chain Transfer Polymerization, RAFT). Ο μοριακός χαρακτηρισμός των πολυμερών έγινε με χρωματογραφία αποκλεισμού μεγεθών (SEC) και φασματοσκοπικές μεθόδους (1H-NMR και FT-IR). Στη συνέχεια, εξετάστηκε η ικανότητα αυτo-οργάνωσης των τυχαίων συμπολυμερών σε νανοδομές σε υδατικά μέσα. Οι ιδιότητες της αυτο-οργάνωσής τους μελετήθηκαν σαν συνάρτηση μεταβολών στο pH με τη χρήση των μεθόδων σκέδασης φωτός (DLS, SLS, ELS) και την μέθοδο φασματοσκοπίας φθορισμού (FS). Τέλος, εγκλωβίστηκε κουρκουμίνη στον υδρόφοβο πυρήνα των νανοδομών τυχαίων συμπολυμερών και οι προκύπτουσες νέες νανοδομές μελετήθηκαν με ένα σύνολο τεχνικών, συμπεριλαμβάνοντας τη στατική, δυναμική σκέδαση φωτός (SLS, DLS) καθώς και τη φασματοσκοπία UV-Vis και FTIR, οι οποίες έδωσαν πληροφορίες για το μέγεθος και τη δομή των νανοφορέων και τις αλληλεπιδράσεις μεταξύ του φαρμάκου και των συστατικών των τυχαίων συμπολυμερών.Random copolymers are of particular scientific interest because of their fast and easy preparation compared to block copolymers and their ability to self-organize in aqueous solutions. Amphiphilic random stimulus-responsive copolymers are of great interest for synthesis, self-organization in aqueous solutions and drug delivery applications. Poly (2- (diisopropylamino) ethyl methacrylate) (PDIPAEMA) is a biocompatible polymer with a pH response in the range of 6.2-6.4, pH similar to that on the surface of extracellular tissue of cancer cells, which makes it attractive to drug applications in the human body. The present work concerns the synthesis of amorphous random copolymers of poly[(oligo ethylene glycol) methyl ether methacrylate-co-(2-(di isopropylamino) ethyl methacrylate)] (P(OEGMA-co-DIPAEMA)) by reversible addition chain transfer polymerization technique (RAFT). Molecular characterization of the copolymers was achieved by size exclusion chromatography (SEC) and spectroscopic methods (1H-NMR and FTIR). The ability of the random copolymers for self-organization in aqueous solutions was investigated by as a function of pH changes using light scattering methods (DLS, SLS, ELS) and fluorescence spectroscopy (FS). Finally, curcumin was encapsulated in the hydrophobic core of random copolymer aggregates and the resulting novel nanostructures were studied by a variety of techniques, including static and dynamic light scattering (SLS, DLS), FTIR and UV-Vis spectroscopy, which provided information on the structure of the nanoparticles and the existing interactions between the drug and the random copolymer component
MUSDB18Mixtures timestamps used in thesis
No full text<p>Annotations and time stamps used for thesis project "Singing Voice Separation Using Interpretable Deep Learning.</p>
Using IKAROS as a data transfer and management utility within the KM3NeT computing model
No full textKM3NeT is a future European deep-sea research infrastructure hosting a new generation neutrino detectors that - located at the bottom of the Mediterranean Sea - will open a new window on the universe and answer fundamental questions both in particle physics and astrophysics. IKAROS is a framework that enables creating scalable storage formations on-demand and helps addressing several limitations that the current file systems face when dealing with very large scale infrastructures. It enables creating ad-hoc nearby storage formations and can use a huge number of I/O nodes in order to increase the available bandwidth (I/O and network). IKAROS unifies remote and local access in the overall data flow, by permitting direct access to each I/O node. In this way we can handle the overall data flow at the network layer, limiting the interaction with the operating system. This approach allows virtually connecting, at the users level, the several different computing facilities used (Grids, Clouds, HPCs, Data Centers, Local computing Clusters and personal storage devices), on-demand, based on the needs, by using well known standards and protocols, like HTTP
Global trends of flavoured cigarette use and implementation and impact of policies banning menthol cigarettes: a mixed methods study across multiple countries
No full textBackground: Flavours, particularly menthol, increase the appeal and palatability of tobacco use. This mixed methods study examined global trends of flavoured cigarette use and implementation and impact of national menthol cigarette bans.
Methods: Systematic reviews were conducted on use and perceptions and marketing of flavour capsule cigarettes (FCCs). The International Tobacco Control (ITC) Surveys were used to assess use of FCCs and behavioural impact of menthol bans. Key informant interviews were conducted to examine factors influencing implementation of menthol bans in low- and middle-income countries (LMICs).
Results: FCC use was prevalent among adults who smoked in most countries examined (50.3% in Mexico, 31.8% in Republic of Korea, 26.5% in Malaysia, and 21.6% in Japan in 2020/2021), and most popular among young people. Marketing strategies of FCCs included use of packaging and advertising at the point-of-sale. Factors perceived to influence implementation of menthol bans in LMICs included social climate, institutional capacity, and tobacco industry interference. A menthol ban in the Netherlands was associated with reduced prevalence of menthol use (7.8% pre-ban to 4.4% post-ban, p<0.001) and increased post-ban quit attempts among adults who smoked menthol vs non-menthol at pre-ban (66.9% vs 49.6%, aOR=1.89, 95%CI: 1.13-3.16). Post-ban quitting was also higher among adults who smoked menthol vs non-menthol (26.1% vs 14.1%, p=0.002), but after adjusting for other factors was only significant among females (aOR=2.23, 95%CI: 1.10-4.51). There was no evidence that menthol bans led to increased illicit purchasing. Use of menthol accessories, which circumvent the bans, were popular among youth who smoked in England (24.2%) and Canada (15.6%).
Conclusions: FCC use is high in many countries globally. Findings indicate that menthol cigarette bans resulted in reduced menthol use, increased quit outcomes, while not increasing illicit purchasing. The experiences of countries in implementing flavour bans may support other countries in their efforts.Open Acces
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