319 research outputs found
Polybenzimidazole (PBI) Functionalized Nanographene as Highly Stable Catalyst Support for Polymer Electrolyte Membrane Fuel Cells (PEMFCs)
No full textNanoscale graphenes were used as cathode catalyst supports in proton exchange membrane fuel cells (PEMFCs). Surface-initiated polymerization that covalently bonds polybenzimidazole (PBI) polymer on the surface of graphene supports enables the uniform distribution of the Pt nanoparticles, as well as allows the sealing of the unterminated carbon bonds usually present on the edge of graphene from the chemical reduction of graphene oxide. The nanographene effectively shortens the length of channels and pores for O2 diffusion/water dissipation and significantly increases the primary pore volume. Further addition of p-phenyl sulfonic functional graphitic carbon particles as spacers, increases the specific volume of the secondary pores and greatly improves O2 mass transport within the catalyst layers. The developed composite cathode catalyst of Pt/PBI-nanographene (50 wt%) + SO3H-graphitic carbon black demonstrates a higher beginning of life (BOL) PEMFC performance as compared to both Pt/PBI-nanographene (50 wt%) and Pt/PBI-graphene (50 wt%) + SO3H-graphitic carbon black (GCB). Accelerated stress tests show excellent support durability compared to that of traditional Pt/Vulcan XC72 catalysts, when subjected to 10,000 cycles from 1.0 V to 1.5 V. This study suggests the promise of using PBI-nanographene + SO3H-GCB hybrid supports in fuel cells to achieve the 2020 DOE targets for transportation applications.This article is published as Xin, Le, Fan Yang, Yang Qiu, Aytekin Uzunoglu, Tommy Rockward, Rodney L. Borup, Lia A. Stanciu, Wenzhen Li, and Jian Xie. "Polybenzimidazole (PBI) functionalized nanographene as highly stable catalyst support for polymer electrolyte membrane fuel cells (PEMFCs)." Journal of The Electrochemical Society 163, no. 10 (2016): F1228. DOI: 10.1149/2.0921610jes. Posted with permission.</p
Status of anadromous salmonids in Oregon coastal basins
No full textThomas E. Nickelson, Jay W. Nicholas, Alan M. McGie, Robert B. Lindsay, Daniel L. Bottom (Research and Development Section, Oregon Department of Fish and Wildlife), and Rodney J. Kaiser, Steven E. Jacobs (Ocean Salmon Management, Oregon Department of Fish and Wildlife).This archived document is maintained by the State Library of Oregon as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Includes bibliographical references (pages 71-81).Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Single- and Multi-carrier Quadrature Amplitude Modulation: Principles and Applications for Personal Communications, WATM and Broadcasting: 2nd
No full textSingle- and Multi-carrier Quadrature Amplitude Modulation Principles and Applications for Personal Communications, WLANs and Broadcasting L. Hanzo Department of Electronics and Computer Science, University of Southampton, UK W. Webb Motorola, Arlington Heights, USA formerly at Multiple Access Communications Ltd, Southampton, UK T. Keller Ubinetics, Cambridge Technology Centre, Melbourn, UK formerly at Department of Electronics and Computer Science, University of Southampton, UK Motivated by the rapid evolution of wireless communication systems, this expanded second edition provides an overview of most major single- and multi-carrier Quadrature Amplitude Modulation (QAM) techniques commencing with simple QAM schemes for the uninitiated through to complex, rapidly-evolving areas, such as arrangements for wide-band mobile channels. Targeted at the more advanced reader, the multi-carrier modulation based second half of the book presents a research-orientated outlook using a variety of novel QAM-based arrangements. * Features six new chapters dealing with the complexities of multi-carrier modulation which has found applications ranging from Wireless Local Area Networks (WLAN) to Digital Video Broadcasting (DVB) * Provides a rudimentary introduction for readers requiring a background in the field of modulation and radio wave propagation * Discusses classic QAM transmission issues relevant to Gaussian channels * Examines QAM-based transmissions over mobile radio channels * Incorporates QAM-related orthogonal techniques, considers the spectral efficiency of QAM in cellular frequency re-use structures and presents a QAM-based speech communications system design study * Introduces Orthogonal Frequency Division Multiplexing (OFDM) over both Gaussian and wideband fading channels By providing an all-encompassing self-contained treatment of single- and multi- carrier QAM based communications, a wide range of readers including senior undergraduate and postgraduate students, practising engineers and researchers alike will all find the coverage of this book attractive
PEM Fuel Cell Degradation
No full textThe durability of PEM fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. While significant progress has been made in understanding degradation mechanisms and improving materials, further improvements in durability are required to meet commercialization targets. Catalyst and electrode durability remains a primary degradation mode, with much work reported on understanding how the catalyst and electrode structure degrades. Accelerated Stress Tests (ASTs) are used to rapidly evaluate component degradation, however the results are sometimes easy, and other times difficult to correlate. Tests that were developed to accelerate degradation of single components are shown to also affect other component's degradation modes. Non-ideal examples of this include ASTs examining catalyst degradation performances losses due to catalyst degradation do not always well correlate with catalyst surface area and also lead to losses in mass transport.</jats:p
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Durability Study of Membrane Electrode Assembly for Heavy-Duty Fuel Cells
No full textPolymer electrolyte membrane fuel cells (PEMFCs) are a zero emission replacement for heavy duty applications due to their range, energy density and fast refueling times.[1] In 2020, the U.S. Department of Energy (DOE) lunched the Million Mile Fuel Cell Truck (M2FCT) consortium to fund fuel cell R&D to meet heavy duty truck standards.[2] Durability studies focusing on heavy-duty applications for advanced materials testing under the M2FCT consortium have been extensively explored and continue to be analyzed to standardize the evaluation of next generation fuel cell materials.
This study combines in situ electrochemical characterization with ex situ analysis of single cell PEMFCs membrane electrode assemblies (MEAs) to predict long-term durability for heavy-duty applications. Various accelerated stress test (AST) parameters were analyzed to determine the stressors affecting the long-term durability. Local degradation resulting from repeated high voltage to low current cycles was analyzed by testing state-of-the-art materials. High potential holds at various conditions were analyzed to determine membrane chemical degradation. Repeated wet and dry cycles were performed to test the membrane mechanical durability. In situ electrochemical analysis include mass activity, electrochemical surface area, hydrogen crossover, and polarization curves were collected and compared among the MEAs. Ex situ analysis includes quantification of membrane thinning at end of life and fluoride emission rate measurement for water effluent throughout the test was conducted to study the membrane degradation.
Acknowledgement:
This work was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy (EERE), US DOE through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.
References:
David A. Cullen, K. C. Neyerlin, Rajesh K. Ahluwalia, Rangachary Mukundan, Karren L. More, Rodney L. Borup, Adam Z. Weber, Deborah J. Myers, and Ahmet Kusoglu, New roads and challenges for fuel cells in heavy-duty transportation. Nat. Energy, 2021. 6(5): 462-474.
DOE Launches Two Consortia to Advance Fuel Cell Truck and Electrolyzer R&D. 2020; Available from: https://www.energy.gov/eere/articles/doe-launches-two-consortia-advance-fuel-cell-truck-and-electrolyzer-rd
Using phage to detect phospho-tau at position 217
No full textAlzheimer's Disease (AD) remains mostly undiagnosed in the early stages of the disease.
• By the time that AD is clinically observed, it is thought that the damage done to the brain is too severe to be reversible.
• There is significant research suggesting AD-mediated changes to tau exist such as phosphorylation, oxidation, proteolysis and others
• Furthermore, recent data have shown that hyperphosphorylation on the tau protein is a critical post-translational modification (PTM) in AD that appear to manifest up to decades before clinical diagnosis.
• Specifically, tau phosphorylated at the 217-threonine position has shown promising results in other studie
The Alimentary Canal of Philaenus Leucophthalmus L.
No full textAuthor Institution: U. S. Bureau of Entomolog
Author Guidelines for MSS Symposium Proceedings
No full textThe abstract is to be in fully-justified italicized text, at the top of the left-hand column, below the author and affiliation information. Use the word “Abstract ” as the title, in 12-point Times, boldface type, centered relative to the column, initially capitalized. The abstract is to be in 10-point, single-spaced type. The abstract may be up to 3 inches (7.62 cm) long. Leave two blank lines after the Abstract, then begin the main text. 1
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