263 research outputs found

    Utilizing Latent Multi-Redox Activity of p-Type Organic Cathode Materials toward High Energy Density Lithium-Organic Batteries

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    Organic electrode materials hold great potential due to their cost-efficiency, eco-friendliness, and possibly high theoretical capacity. Nevertheless, most organic cathode materials exhibit a trade-off relationship between the specific capacity and the voltage, failing to deliver high energy density. Herein, it is shown that the trade-off can be mitigated by utilizing the multi-redox capability of p-type electrodes, which can significantly increase the specific capacity within a high-voltage region. The molecular structure of 5,10-dihydro-5,10-dimethylphenazine is modified to yield a series of phenoxazine and phenothiazine derivatives with elevated redox potentials by substitutions. Subsequently, the feasibility of the multi-redox capability is scrutinized for these high-voltage p-type organic cathodes, achieving one of the highest energy densities. It is revealed that the seemingly impractical second redox reaction is indeed dependent on the choice of the electrolyte and can be reversibly realized by tailoring the donor number and the salt concentration of the electrolyte, which places the voltage of the multi-redox reaction within the electrochemical stability window. The results demonstrate that high-energy-density organic cathodes can be practically achieved by rational design of multi-redox p-type organic electrode materials and the compatibility consideration of the electrolyte, opening up a new avenue toward advanced organic rechargeable batteries.

    spatio temporal contextualization of queries for microtexts in social media mathematical modeling

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    Abstract In this paper, we present our ongoing project on query contextualization by integrating all possible IoT-based data sources. Most importantly, mobile users are regarded as the IoT sensors which can be the textual data sources with spatio-temporal contexts. Given a large amount of text streams, it has been difficult for the traditional information retrieval systems to conduct the searching tasks. The goal of this work is i ) to understand and process microtexts in social media (e.g., Twitter and Facebook), and ii ) to reformulate the queries for searching for relevant microtexts in these social media

    Clinical Characteristics of Patients Diagnosed With Odontogenic Rhinosinusitis After Dental Implants

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    Background and Objectives With the ongoing development of intraoral surgical treatment and invasive dental treatments such as implants, odontogenic rhinosinusitis (ORS) is on the rise. ORS related to dental implants accounts for 8% to 37% of cases. The purpose of this study is to define the characteristics of patients with ORS related to dental implants. Methods From 2015 to 2019, the medical records of 15 patients who developed maxillary sinus disease after receiving dental implants were retrospectively analyzed among patients who visited the ear nose and throat and dentistry departments. We reviewed the chief complaint, assessment, diagnosis, treatment and prognosis of these patients. Results Of the 15 patients, all were diagnosed with ORS. One patient with a post-operative cheek cyst, 1 with fungal sinusitis, 1 with an inverted papilloma, 1 with chronic rhinosinusitis, and 1 with a radicular cyst were diagnosed after surgery. Endoscopic sinus surgery was performed in 14 patients and 2 patients underwent a combined operation. One patient improved after medical treatment. The follow-up period was about 8.6 months. No recurrence was found in any of the patients. Conclusion If an implant problem is suspected based on history-taking and physical examination, active consultation with dentistry is needed to diagnose ORS

    Bio-inspired Molecular Redesign of a Multi-redox Catholyte for High-Energy Non-aqueous Organic Redox Flow Batteries

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    Redox-active organic materials (ROMs) have recently attracted significant attention for redox flow batteries (RFBs) to achieve green and cost-efficient energy storage. In particular, multi-redox ROMs have shown great promise, and further tailoring of these ROMs would yield RFB technologies with the highest possible energy density. Here, we present a phenazine-based catholyte material, 5,10-bis(2-methoxyethyl)-5,10-dihydrophenazine (BMEPZ), that undergoes two single-electron redox reactions at high redox potentials (-0.29 and 0.50 V versus Fc/Fc(+)) with enhanced solubility (0.5 M in acetonitrile), remarkable chemical stability, and fast kinetics. Moreover, an all-organic flow battery exhibits cell voltages of 1.2 and 2.0 V when coupled with 9-fluorenone (FL) as an anolyte. It shows capacity retention of 99.94% per cycle over 200 cycles and 99.3% per cycle with 0.1 M and 0.4 M BMEPZ catholyte, respectively. Notably, the BMEPZ/FL couple results in the highest energy density (similar to 17 Wh L-1) among the non-aqueous all- organic RFBs reported to date

    Regulating the surface of anion-doped TiO2 nanorods by hydrogen annealing for superior photoelectrochemical water oxidation

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    Dedications to achieve the highly efficient metal oxide semiconductor for the photoelectrochemical water splitting system have been persisted to utilize the TiO2 as the promising photoanode material. Herein, we report notable progress for nanostructured TiO2 photoanodes using facile sequential one-pot hydrothermal synthesis and annealing in hydrogen. A photocurrent density of 3.04 mA·cm−2 at 1.23 V vs. reversible hydrogen electrode was achieved in TiO2 nanorod arrays annealed in hydrogen ambient, which is approximately 4.25 times higher than that of pristine TiO2 annealed in ambient air. 79.2% of incident photon-to-current efficiency at 380 nm wavelength demonstrates the prominence of the material at the near-UV spectral range region and 100 h chronoamperometric test exhibits the stability of the photoanode. Detailed studies regarding crystallinity, bandgap, and elemental analysis provide the importance of the optimized annealing condition for the TiO2-based photoanodes. Water contact angle measurement displays the effect of hydrogen annealing on the hydrophilicity of the material. This study clearly demonstrates the marked improvement using the optimized hydrogen annealing, providing the promising methodologies for eco-friendly mass production of water splitting photoelectrodes.The authors gratefully acknowledge the fnancial support from the Creative, Material Discovery Program (2016M3D1A1027666, 2017M3D1A1040834, 2018M3D1A1058793) through the National Research Foundation of Korea funded by Ministry of Science and ICT, the Basic Research Laboratory Program through an NRF grant funded by the Korean Ministry of Science, ICT and Future Planning (2021R1A4A302787811), the KRISS (Korea Research Institute of Standards and Science) MPI Lab. Program and the National Research Foundation of Korea (NRF) grant funded by the Korea Government MSIT (2021R1C1C2006142), and Nuclear Energy R&D Program(2020M2D8A206983012). The Inter-University Semiconductor Research Center and Institute of Engineering Research at Seoul National University provided research facilities for this work
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