Publications by authors named "Hyo-Jun Ahn"

Employing copper (Cu) as an anode current collector for metal sulphides is perceived as a general strategy to achieve stable cycle performance in sodium-ion batteries, despite the compatibility of the aluminium current collector with sodium at low voltages. The capacity retention is attributed to the formation of copper sulphide with the slow corrosion of the current collector during cycling which is not ideal. Conventional reports on metal sulphides demonstrate excellent electrochemical performances using excessive carbon coatings/additives, reducing the overall energy density of the cells and making it difficult to understand the underlying side reaction with Cu.

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Article Synopsis
  • Developing bulk Bi anodes for Na-ion batteries presents challenges like slow ion diffusion and material fragmentation, but a new strategy successfully overcomes these issues.
  • The bulk Bi transforms into a porous nanostructure during use, which improves sodium ion storage and allows for ultrafast charging and long-lasting performance.
  • The Na-Bi half-cell shows remarkable capacity retention and performance even at extreme charging rates, highlighting the combination of high energy storage, rapid charging capabilities, and durability in battery design.
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Sulfurized polyacrylonitrile (SPAN) is a promising active material for Li/S batteries owing to its high sulfur utilization and long-term cyclability. However, because SPAN electrodes are synthesized using powder, they require large amounts of electrolyte, conducting agents, and binder, which reduces the practical energy density. Herein, to improve the practical energy density, we fabricated bulk-type SPAN disk cathodes from pressed sulfur and polyacrylonitrile powders using a simple heating process.

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The purpose of this study was to evaluate the structural performance of composite deck slabs containing macro-synthetic fibers. after a fire by proposing a deflection estimation method for non-fireproof structural decks. Therefore, this study evaluated the fire resistance performance and deflection of deck slabs mixed with macro-synthetic fibers.

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Transition-metal sulfides have been extensively studied as anode materials for use in sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) due to their multi-electron reactions, high rate performance, and abundant available resources. However, the practical capacities of metal sulfides remain low due to conductivity issues, volume expansion, and the use of traditional carbonate electrolytes. To overcome these drawbacks, ether electrolytes can be combined with nanoparticle-based metal sulfide anodes.

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Iron sulfide (FeS) anodes are plagued by severe irreversibility and volume changes that limit cycle performances. Here, a synergistically coupled hybrid composite, nanoengineered iron sulfide/S-doped graphene aerogel, was developed as high-capacity anode material for Li/Na-ion half/full batteries. The rational coupling of in situ generated FeS nanocrystals and the S-doped rGO aerogel matrix boosted the electronic conductivity, Li /Na diffusion kinetics, and accommodated the volume changes in FeS.

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Sodium-ion batteries (SIBs) are a viable substitute for lithium-ion batteries due to the low cost and wide availability of sodium. However, practical applications require the development of fast charging sodium-ion-based full-cells with high power densities. NaV(PO) (NVP) is a bipolar material with excellent characteristics as both a cathode and an anode material in SIBs.

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Owing to the speculated price hike and scarcity of lithium resources, sodium-ion batteries are attracting significant research interest these days. However, sodium-ion battery anodes do not deliver good electrochemical performance, particularly rate performance. Herein, we report the facile electrospinning synthesis of a free-standing nickel disulfide (NiS²) embedded on carbon nanofiber.

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A polyacrylonitrile (PAN) nanofiber web was prepared by electrospinning PAN solutions with dimethyl sulfoxide (DMSO) or Dimethylformamide (DMF) as solvent. The PAN web was heated with sulfur to synthesize a sulfurized polyacrylonitrile (SPAN) nanofiber web. The shape of the SPAN web was found to depend on concentration of the PAN solution and properties of the solvent.

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To develop the next-generation energy storage systems, lithium-sulfur batteries represent an attractive option due to its high theoretical capacity, and energy density. In this work, MoS₂/rGO (reduced graphene oxide) was prepared by hydrothermal synthesis and sulfur added by the melt diffusion method. The as-prepared MoS₂/rGO has strong polysulfides entrapping, high conductivity, large surface area, and high catalytic activity, consequently resulting in enhanced rate performance and cycling capability of Li-S batteries.

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In this paper, the relationship between the pore spatial structures, pore sizes, and pore types of highly ordered mesoporous CMK-based carbons (CMK-1, CMK-3, and CMK-5) and their electrochemical performance in Li-S batteries is investigated. CMK-1 has a complex spatial structure and small pores. The structure is good for limiting polysulfide in the pores, but not for rapid transfer of Li ions in the cell.

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An ionic liquid (IL) incorporated in a quasi-solid-state electrolyte (ILQSE) is prepared using 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF) and poly (ethylene glycol dimethacrylayte) (PEGDMA) for high-temperature application of supercapacitors. The prepared ILQSE displays a thermal stability up to 150 °C and the supercapacitors exhibit a specific capacitance of 134 F g.

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In order to satisfy the escalating energy demands, it is inevitable to improve the energy density of current Li-ion batteries. As the development of high-capacity cathode materials is of paramount significance compared to anode materials, here we have designed for the first time a unique synergistic hybrid cathode material with enhanced specific capacity, incorporating cost-effective iron sulfide (FeS) nanoparticles in a sulfurized polyacrylonitrile (SPAN) nanofiber matrix through a rational in situ synthesis strategy. Previous reports on FeS cathodes are scarce and consist of an amorphous carbon matrix to accommodate the volume changes encountered during the cycling process.

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Background/aims: Left ventricular diastolic dysfunction (LVDD) is an early manifestation of cardiac dysfunction in patients with liver cirrhosis (LC). However, the effect of LVDD on survival has not been clarified, especially in decompensated LC.

Methods: We prospectively enrolled 70 patients with decompensated LC, including ascites or variceal bleeding, at Daejeon St.

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Objective: We evaluated the diagnostic performance of CA 125, HE4, and ROMA for ovarian cancer in Koreans and set optimal cutoffs.

Method: Serum levels of HE4 and CA 125 and the ROMA score were determined in 762 patients with benign gynecological disease and 70 with ovarian cancer. Receiver operating characteristic curves were constructed to calculate the areas under the curve (AUC).

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Context.—: Anticyclic citrullinated peptide antibodies are important serologic markers for the diagnosis of rheumatoid arthritis. Several kinds of test reagents for automated immunoassay systems have been developed and used in recent years.

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A 3D sulfur cathode for a large-scale room-temperature (RT) Na/S battery with a high sulfur loading of 14.63 mg cm-2 was fabricated. The first discharge was tested in order to understand the macroscopic changes.

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Tin monoxide (SnO) anodes are promising candidates for use in sodium-ion batteries because of their high theoretical capacities and stable cycle performance. In previous reports, electrodes with excellent performance have been prepared by using nano-sized SnO particles. However, the synthesis of nano-sized SnO particles is complex, time-consuming, and expensive.

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Recently, tin oxide (SnO2) has received significant attention for use as an anode material for next generation lithium-ion batteries (LIBs) owing to its high theoretical capacity (782 mAh g-1), which is more than twice of that of the commercialized graphite (372 mAh g-1). Several additional advantages, such as low cost, environmental friendliness, easy fabrication and natural abundance improve its promise. Although the theoretical capacity of SnO2 is high, volume expansion during cycling causes issue with cycling stability.

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To establish the efficacy and safety of ilaprazole, levofloxacin, and amoxicillin as a first-line eradication treatment for . Patients with gastric ulcer, duodenal ulcer, or gastritis, as detected by esophagogastroduodenoscopy with confirmed infection between September 2014 and November 2015, were enrolled in the study. All participants received ilaprazole (10 mg bid), levofloxacin (500 mg bid), and amoxicillin (1000 mg bid) for 10 days.

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Background: Anti-HCV assays are widely used as a screening tool for HCV infection. However, diagnostic performances and effective signal-to-cut-off ratios (S/COs) for predicting true HCV infections would vary according to the assays used. Thus, we evaluated the diagnostic performances of the new Elecsys Anti-HCV assay.

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Background & Aims: We evaluated the efficacy and safety of Tenofovir disoproxil fumarate (TDF)-based therapy in naïve and treatment-experienced chronic hepatitis B (CHB) patients for 96 weeks in Korean real life practice.

Methods: A total of 209 CHB patients with a prescription for TDF at the Seoul and Daejeon St. Mary's hospitals were enrolled from December 2012 to October 2014.

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Background: In patients with unresectable colorectal cancer (CRC) obstruction, choosing whether to perform self-expandable metal stent (SEMS) or palliative surgery is challenging, especially in those with good performance status. We aimed to compare the long-term outcomes of SEMS with those of palliative surgery in patients with unresectable CRC obstruction.

Methods: This retrospective study comprised 114 patients with unresectable CRC obstruction who underwent SEMS placement (n = 73) or palliative surgery (n = 41).

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Gastric cancer still is a major concern as the third most common cancer worldwide, despite declining rates of incidence in many Western countries. Helicobacter pylori (H. pylori) is the major cause of gastric carcinogenesis, and its infection insults gastric mucosa leading to the occurrence of atrophic gastritis which progress to intestinal metaplasia, dysplasia, early gastric cancer, and advanced gastric cancer consequently.

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