102,339 research outputs found
Photoelectrochromic devices with cobalt redox electrolytes
No full textIn this work, the use of cobalt redox electrolytes in partly covered photoelectrochromic devices is investigated experimentally for the first time. The fabricated devices consist of a conductive glass photoanode coated with an electrochromic WO3 film of optical quality, including a mesoporous TiO2 layer (sensitized by the MK2 organic dye) that covers 20% of the device area. The liquid electrolyte is composed of 0.22 M Co(II)(bpy)3(PF6)2, 0.5 M LiClO4 and 0.5 M 4-tert-butylpyridine. A platinized conductive glass cathode completes the cell set-up. The fabricated devices are almost transparent in the bleached state with a Tlum value above 50%. They exhibit coloration speeds in the order of minutes, with a maximum contrast ratio of 2.9:1 after 21 min of illumination at 1000 W m−2 under open circuit conditions (OC), and high reversibility to fully bleached state in short circuit conditions. They provide a maximum measured power conversion efficiency of 0.28% due to limitations imposed by conflicting requirements of the photovoltaic and electrochromic elements, which is nonetheless sufficient to drive the coloration process. Since only the reduced specie Co2+ is present, initial illumination under OC for 3 min at 1000 W m−2 is necessary, prior to measurements, to oxidize Co2+ to Co3+ through the dye regeneration process in the electrolyte. The higher recombination losses of the Co2+/3+ redox shuttle compared to I−/I3−, which lead to a considerable reduction in coloration depth 20 days post fabrication due to loss of photoelectrons at the WO3/electrolyte interface, are suppressed by the use of a 35 nm thick ZnS barrier deposited on top of WO3. Remarkably, it results in a stabilized contrast ratio of 1.5:1, 23 days post fabrication. In addition, the color coordinates of the present devices resemble those of typical electrochromics: they exhibit blue coloration, as a result of the lack of the absorbing iodine in the electrolyte that produces a green tint
3D-Printable Cathode Electrode for Monolithically Printed Microbial Fuel Cells (MFCs)
No full textIntroduction
Biological fuel cells (BFCs) are an increasingly growing area of research as it beholds long-term sustainable advantages over conventional fuel cells. Microbial Fuel Cells (MFCs) are just one type of BFCs, which as the name implies, employ microbial electroactive species to facilitate the conversion of chemical energy stored in organic matter, into electricity. The properties of MFCs have successfully made the technology a primary source of energy for low-power autonomous robots 1 and off-grid urinal units 2. However, a hindrance to the mass production of MFC units is the time-consuming assembly process, which could perhaps be overcome using additive manufacturing (AM) processes. AM or 3D-printing has played an increasing role in advancing the MFC technology, by substituting essential structural components i.e. chassis and separators, with 3D-printed parts 3,4. This is precisely the line of work in the EVOBLISS project, which is investigating materials that can be extruded from the EVOBOT platform 5 for a potentially monolithically printed MFC. The development of such inexpensive, conductive, printable electrode material is described below as well as the advances of this material as a cathode electrode on air-breathing cathodes.
Material and Methods
Three triplicates of analytical size MFCs were assembled for this experiment using laser-cut acrylic sheets. The MFCs had a 25mL anode chamber, a CMI-700 cation exchange membrane (Membrane International, USA) as separator and three different electrodes forming the air-breathing cathodes. A gas diffusion electrode with polytetrafluoroethylene (PTFE) (60% wt. Sigma Aldrich, UK) painted carbon veil sheet that acted as the hydrophilic supporting material for a microporous layer (MPL) was used as the control. This was prepared with a mixture of activated carbon (80 g/120 mL solution. G Baldwin & Co, UK), PTFE and distilled water. The materials tested were a) a solid commercially available sintered Carbon Block CTO (Water Filter Man LTD, UK) and b) a custom made activated carbon-alginate paste which was made using ground activated carbon (80g) and alginate (Minerals Water Ltd, 20 g) that was then mixed with distilled water until a thick paste was made. The paste was then extruded from a syringe directly onto the membrane (10 ml) and dried/solidified on the bench for 24 hrs. The final weight of all the dried electrodes was 3.8 ± 0.2 g. The cells were inoculated with activated sludge (Wessex Water, UK) supplemented with full strength Tryptone Yeast Extract (1.5% w/v) and fed with human urine.
Results
The results showed that the MFCs using alginate electrode as cathode electron and oxygen receiver performed better compared to the MPL or sintered carbon having a maximum power transfer point at 286 μW, 98 μW and 85 μW respectively. An important factor to consider in the effort to improve the MFC performance is not only the power output but also the cost effectiveness of the materials, especially when using alginate. MPL cathode electrode requires a PTFE coated carbon veil sheet as well as a mixture of PTFE and carbon. PTFE is a highly toxic and expensive material (£138/500ml, Sigma Aldrich, 2017) compared to food grade alginate which only costs £8.76 per 500g. Moreover, the alginate electrode does not require a supporting material thus the cost was reduced further by removing the carbon veil from the assembly.
Conclusion
In conclusion, this experiment demonstrated that the development of an air-dried, extrude-able electrode material (similar to 3D printing) could successfully be incorporated in an MFC system and act as a cathode electrode. Such a development brings the field a step closer to monolithically printable MFCs, which can be made using the EVOBOT platform.
References
I. Ieropoulos, J. Greenman, C. Melhuish, and I. Horsfield, in Artificial Life Models in Hardware, p. 185–211 (2009).
I. A. Ieropoulos et al., Environ. Sci. Water Res. Technol., 2, 336–343 (2016).
J. You, R. J. Preen, L. Bull, J. Greenman, and I. Ieropoulos, Sustain. Energy Technol. Assessments, 19, 94–101 (2017).
H. Philamore, J. Rossiter, P. Walters, J. Winfield, and I. Ieropoulos, J. Power Sources, 289, 91–99 (2015).
A. Faíña, F. Nejatimoharrami, and K. Stoy, in IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), (2015)
Bibliographie Hilarion G. Petzold 1958 – 2009 mit Anhang als Einführung
No full textDieses Archiv enthält die Gesamtbibliographie der Werke des Autors nebst einiger Texte „Über H. G. Petzold“ im Schlussteil der Bibliographie sowie einen Anhang mit einer Einführung in die Architektur des Werkes in seinem wissenslogischen Aufbau als Ausarbeitung seines „Tree of Science Modells“ (2007).This archive contains the complete bibliography of the author and some texts about H. G. Petzold, moreover an epilogue with an introduction to the architecture of the works in its epistemological structure and composition and as an elaborations of Petzold’s „Tree of Science Modell (2007).https://www.fpi-publikation.de/polyloge/01-2009-petzold-h-g-gesamtbibliographie-h-g-petzold-1958-2009-updating-november2009/peerReviewedpublishedVersio
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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3346: Samuel G. Freedman, author, 2013
No full textPhotograph of author Samuel G. Freedman, at NT Daily Slash meeting in the Mayborn School of Journalism at UNT
Advancing task involvement, intrinsic motivation and metacognitive regulation in physical education classes: the self-check style of teaching makes a difference
No full textIt was hypothesized that “self-check” style of teaching would be more preferable in terms of creating a mastery-oriented climate, and promoting adaptive achievement goals, intrinsic motivation and metacognitive activity in physical education classes. Two hundred seventy-nine (N = 269) 6-grade students were randomly divided into two groups that were taught four consecutive physical education lessons of the same content following either “practice” or “self-check” styles of teaching respectively. Students responded on questionnaires prior and after the intervention. Results revealed significant interactions between groups and measurements. Students in the “self-check” style group scored higher in scales measuring mastery-oriented climate, mastery goal, intrinsic motivation and metacognitive processes and lower in scales measuring performance-goals and performance-oriented motivational climate. These results underscore the importance of using styles of teaching that enhance opportunities for deep cognitive processing and promote mastery-goals and mastery-oriented climates
Femtosecond Laser Written Plane-by-Plane Bragg Grating Sensors in Bioresorbable Phosphate Optical Fibres
No full textWe report on the realization of different types of optical sensors in a bioresorbable phosphate glass optical fiber using a femtosecond laser operating at 517 nm. We inscribed fiber Bragg grating-based optical filters such as uniform Bragg gratings, chirped gratings, and Fabry–Perot cavities, using the plane-by-plane direct write inscription. The gratings were characterized in reflection and tested as sensors for temperature and relative humidity. We studied the stability and resilience of the gratings when inserted in high humidity environments (>95%) for 52 h and observed the evolution of the grating characteristics during this period
The Right to Strike under the United States Constitution: Theory, Practice, and Possible Implications for Canada
No full textAnswering critics of the Canadian Supreme Court's judgment in B.C. Health, the author argues that the Court laid the foundation for a principled and durable doctrine protecting constitutional labour rights, one that goes directly to the heart of the matter — the inequality of workers’ power in the employment relation. In the author’s view, two paths could lead from B.C. Health to the recognition of Charter protec- tion for a right to strike: one that treats the right as an accessory to col- lective bargaining, and one that upholds the right directly on the basis of the Charter values of equality and participation. The author supports the latter approach, contending that constitutional rights should be defined in relation to fundamental values, in a way that is not contingent on time-bound or fact-sensitive assessments about the role of strikes within a particular collective bargaining regime. Although a Charter right to strike may involve the courts in difficult choices about when to defer to legislative policy decisions, and courts may lack the institutional capac- ity to deal effectively with labour law issues, the author points out that judges can look to ILO standards for expert guidance. Noting that the U.S. experience in this area might be of considerable use to Canadians, the author concludes by providing an overview of American case law concerning a constitutional right to strike.Peer reviewe
G-Rank: Unsupervised Continuous Learn-to-Rank for Edge Devices in a P2P Network
No full textRanking algorithms in traditional search engines are powered by enormous training data sets that are meticulously engineered and curated by a centralized entity. Decentralized peer-to-peer (p2p) networks such as torrenting applications and Web3 protocols deliberately eschew centralized databases and computational architectures when designing services and features. As such, robust search-and-rank algorithms designed for such domains must be engineered specifically for decentralized networks, and must be lightweight enough to operate on consumer-grade personal devices such as a smartphone or laptop computer. We introduce G-Rank, an unsupervised ranking algorithm designed exclusively for decentralized networks. We demonstrate that accurate, relevant ranking results can be achieved in fully decentralized networks without any centralized data aggregation, feature engineering, or model training. Furthermore, we show that such results are obtainable with minimal data preprocessing and computational overhead, and can still return highly relevant results even when a user’s device is disconnected from the network. G-Rank is highly modular in design, is not limited to categorical data, and can be implemented in a variety of domains with minimal modification. The results herein show that unsupervised ranking models designed for decentralized p2p networks are not only viable, but worthy of further research.https://github.com/awrgold/G-RankComputer Scienc
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