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Phase-controlled synthesis of thermally stable nitrogen-doped carbon supported iron catalysts for highly efficient Fischer-Tropsch synthesis

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Nano Research 2019年第10期12卷 2568-2575页

作者： Jin Hee Lee Hack-Keun Lee Dong Hyun Chun Hyunkyung Choi Geun Bae Rhim Min Hye Youn Heondo Jeong Shin Wook Kang jung-ll Yang Heon jung Chui Sung Kim Ji chan Park Clean Fuel Laboratory Korea Institute of Energy ResearchDaejeon 34129Republic of Korea Department of Chemical Engineering University of SeoulSeoul 02504Republic of Korea Advanced Energy and System Technology University of Science and TechnologyDaejeon 34113Republic of Korea Department of Physics Kookmin UniversitySeoul 02707Republic of Korea

Iron-based nan oparticles with un iform and high particle dispersi on,which are supported on carb on structures,have been used for various ***,their preparation still suffers from complicated synthesis involving multiple steps and from the high price of precursors and solve *** the prese nt work,a new carbon en capsulated iron-carbide nano particle supported on n itroge rvdoped porous carbon(Fe5C2@C/NPC)structure was *** was made using a simple solid-state reaction with sequential thermal ***5C2@C/NPC is a highly active and stable catalyst for the high-temperature Fischer-Tropsch synthesis *** showed very high hydrocarbon productivity(4.71 gHc gcat^-1·h^-1)with high CO conversions(up to 96%).

关键词： iron-carbide one-pot synthesis nitrogen-doped graphene Fischer-Tropsch synthesis Mdssbauer spectroscopy

Occipital artery bypass importance in unsuitable superficial temporal artery:Two case reports

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World Journal of Clinical Cases 2023年第9期11卷 2091-2097页

作者： Jong-Hwan Hong Sung-chan jung Han-Seung Ryu Tae-Sun Kim Sung-Pil Joo Department of Neurosurgery Chonnam National University Hospital and Medical SchoolGwangju 61469South Korea

BACKGROUND Superficial temporal artery-middle cerebral artery(STA-MCA)bypass helps treat cerebral ***,the STA is not available for bypass in some ***,with some technical tips,the authors introduced a bypass technique using the occipital artery(OA).CASE SUMMARY Two female patients complained of *** magnetic resonance imaging(MRI)indicated contralateral infarction from the MCA *** Diamox single photon emission computed tomography or perfusion MRI,the contralateral front parietotemporal reserve was *** transfemoral cerebral angiography,the STA was thin with a weak flow;however,the OA was *** OA-MCA end-to-side extracranial-intracranial bypass surgery was implemented instead of STA because the caliber was too *** postoperative course was uneventful in both cases,with well-maintained bypass patency and neurological stability during *** OA might be an acceptable alternative for MCA cerebral ischemic cases with an unsuitable STA.

关键词： Bypass Occipital artery Superficial temporal artery Cerebral ischemia Case report

Efficient synthesis of IrPtPdNi/GO nanocatalysts for superior performance in water electrolysis

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Nano Research 2024年第11期17卷 10208-10215页

作者： Sanha Jang Young Hwa Yun Jin Gyu Lee Kyung Hee Oh Shin Wook Kang jung-Il Yang MinJoong Kim changsoo Lee Ji chan Park Clean Fuel Research Laboratory Korea Institute of Energy Research Daejeon 34129 Korea Hydrogen Research Department Korea Institute of Energy Research Daejeon 34129 Korea Energy Engineering University of Science and Technology Daejeon 34113 Korea

Traditional iridium (Ir) oxide catalysts have faced significant limitations in water electrolysis, particularly under acidic conditions where instability and degradation severely restrict the efficiency of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). To overcome these challenges, this study successfully synthesized highly dispersed IrPtPdNi alloy nanoparticles on a graphene oxide support using a vertically moving reactor, demonstrating exceptional performance in water electrolysis. These nanoparticles, synthesized via a fast-moving bed pyrolysis method, combine iridium, platinum, palladium, and nickel. They exhibit lower overpotentials in OER and comparable performance in HER to commercial catalysts, while also offering enhanced stability. These results surpass the limitations of traditional catalysts, marking significant progress toward more efficient and sustainable hydrogen production technologies. This advancement is expected to contribute significantly to the development of sustainable energy systems by innovatively enhancing the performance of catalysts in the electrochemical water-splitting process.

关键词： multicomponent nanoparticles rapid synthesis water electrolysis alloy iridium cat

Study on durability of Pt supported on graphitized carbon under simulated start-up/shut-down conditions for polymer electrolyte membrane fuel cells

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Journal of Energy Chemistry 2018年第1期27卷 326-334页

作者： Won Suk jung Department of Chemical Engineering University of South CarolinaColumbiaSC 29208USA

The primary issue for the commercialization of proton exchange membrane fuel cell（PEMFC） is the carbon corrosion of support under start-up/shut-down conditions. In this study, we employ the nanostructured graphitized carbon induced by heat-treatment. The degree of graphitization starts to increase between 900 and 1300 ℃ as evidenced by the change of specific surface area, interlayer spacing, and ID/IG value. Pt nanoparticles are deposited on fresh carbon black（Pt/CB） and carbon heat-treated at 1700 ℃（Pt/HCB17） with similar particle size and distribution. Electrochemical characterization demonstrates that the Pt/HCB17 shows higher activity than the Pt/CB due to the inefficient microporous structure of amorphous carbon for the oxygen reduction reaction. An accelerating potential cycle between 1.0 and 1.5 V for the carbon corrosion is applied to examine durability at a single cell under the practical start-up/shutdown conditions. The Pt/HCB17 catalyst shows remarkable durability after 3000 potential cycles. The Pt/HCB17 catalyst exhibits a peak power density gain of 3%, while the Pt/CB catalyst shows 65% loss of the initial peak power density. As well, electrochemical surface area and mass activity of Pt/HCB17 catalyst are even more stable than those of the Pt/CB catalyst. Consequently, the high degree of graphitization is essential for the durability of fuel cells in practical start-up/shut-down conditions due to enhancing the strong interaction of Pt and π-bonds in graphitized carbon.

关键词： Polymer electrolyte membrane fuel ceils Membrane electrolyte assembly Carbon corrosion Start-up/shut-down Durability

Tolerating Permanent State Transition Faults in Asynchronous Sequential Machines

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Journal of Computer Science & Technology 2016年第5期31卷 1028-1037页

作者： jung-Min Yang School of Electronics Engineering Kyungpook National University Daegu 41566 Korea

Corrective control theory lays a novel foundation for the fault-tolerant control of asynchronous sequential machines. In this paper, we present a corrective control scheme for tolerating permanent state transition faults in the dynamics of asynchronous sequential machines. By a fault occurrence, the asynchronous machine may be stuck at a faulty state, not responding to the external input. We analyze the detectability of the considered faults and present the necessary and sufficient condition for the existence of a controller that overcomes any permanent transition faults. Fault tolerance is realized by using potential reachability and asynchronous mechanisms in the machine. A case study on an asynchronous counter is provided to illustrate the proposed fault detection and tolerance scheme.

关键词： asynchronous sequential machine corrective control permanent fault fault tolerance

Next High Performance and Low Power Flash Memory Package Structure

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Journal of Computer Science & Technology 2007年第4期22卷 515-520页

作者： jung-Hoon Lee ERI Control Instrumentation EngineeringGyeongSang National UniversityJinju660-701Korea

In general, NAND flash memory has advantages in low power consumption, storage capacity, and fast erase/write performance in contrast to NOR flash. But, main drawback of the NAND flash memory is the slow access time for random read operations. Therefore, we proposed the new NAND flash memory package for overcoming this major drawback. We present a high performance and low power NAND flash memory system with a dual cache memory. The proposed NAND flash package consists of two parts, i.e., an NAND flash memory module, and a dual cache module. The new NAND flash memory system can achieve dramatically higher performance and lower power consumption compared with any conventionM NAND-type flash memory module. Our results show that the proposed system can reduce about 78% of write operations into the flash memory cell and about 70% of read operations from the flash memory cell by using only additional 3KB cache space. This value represents high potential to achieve low power consumption and high performance gain.

关键词： flash memory NAND-type NOR-type memory localities buffer or cache memory

Plant-pollinator metanetworks in fragmented landscapes:a simulation study

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Ecological Processes 2023年第1期12卷 415-424页

作者： Ehsan Rahimi Chuleui jung Agricultural Science and Technology Institute Andong National UniversityAndong City 36729Republic of Korea Department of Plant Medicals Andong National UniversityAndong CityRepublic of Korea

Background The topology of the plant-pollinator network can be explained by the species’abundance and their random ***-pollinator networks can be studied in the context of a landscape,because each patch can accommodate a certain local *** populations of pollinators in the landscape can be connected through migration and then constitute a metanetwork that is known as a combination of spatial and ecological *** this regard,habitat fragmentation can affect the topology of plant-pollinator metanetworks through changes in the species abundance and limiting their ***,it is not clear what pattern(fragmented or aggregated)of the landscape structure can accommodate networks with a higher degree of *** we created simulated landscapes with different forest proportions scenarios(from 5%to 50%of the total landscape)and degrees of ***,for each landscape,we limited the proportion of pollinators to the forest *** assumed that plants and pollinators are randomly distributed around the landscape and interact *** used landscape metrics to measure different aspects of landscape structure and bipartite metrics for calculating the degree of specialization in plant-pollinator *** The statistical relationship between bipartite and landscape metrics showed that the relationship between the topology of plant-pollinator networks and the landscape structure is affected by the forest amount in the landscape and the degree of forest *** also found that according to the nestedness and H2(a measure of specialization)metrics,fragmented landscapes contain more general plant-pollinator *** Our findings suggest that fragmented landscapes,characterized by scattered forest patches,can promote higher levels of interaction between limited pollinators and diverse flowers,leading to more general plant-pollinator networks.

关键词： Plant–pollinator metanetwork Habitat fragmentation Simulated landscape Landscape metrics Bipartite metrics

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Asymptotic T_u-Toeplitzness of weighted composition operators on H^2

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Science China Mathematics 2018年第5期61卷 881-896页

作者： Sungeun jung Department of Mathematics Hankuk University of Foreign Studies

Given a unilateral forward shift S acting on a complex,separable,infinite dimensional Hilbert space H,an asymptotically S-Toeplitz operator is a bounded linear operator T on H satisfying that{S^(*n)T S^n}is convergent with respect to one of the topologies commonly used in the algebra of bounded linear operators on *** this paper,we study the asymptotic T_u-Toeplitzness of weighted composition operators on the Hardy space H^2,where u is a nonconstant inner function.

关键词： Toeplitz operator asymptotically S-Toeplitz operator weighted composition operator inner function

Calcium-and sulfate-functionalized artificial cathode–electrolyte interphases of Ni-rich cathode materials

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Rare Metals 2021年第10期40卷 2793-2801页

作者： Kwangeun jung Taeeun Yim Department of Chemistry Incheon National UniversityIncheon 22012Republic of Korea

Ni-rich lithium nickel–cobalt-manganese oxides(NCM) are considered the most promising cathode materials for lithium-ion batteries(LIBs);however, relatively poor cycling performance is a bottleneck preventing their widespread use in energy systems. In this work, we propose the use of a dually functionalized surface modifier, calcium sulfate(CaSO_(4), CSO), in an efficient one step method to increase the cycling performance of Ni-rich NCM cathode materials. Thermal treatment of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811) cathode materials with a CSO precursor allows the formation of an artificial Ca-and SO_(x)-functionalized cathode–electrolyte interphase(CEI) layer on the surface of Ni-rich NCM cathode materials. The CEI layer then inhibits electrolyte decomposition at the interface between the Ni-rich NCM cathode and the electrolyte. Successful formation of the CSO-modified CEI layer is confirmed by scanning electron microscopy(SEM) and Fourier transform infrared(FTIR) spectroscopy analyses, and the process does not affect the bulk structure of the Ni-rich NCM cathode material. During cycling, the CSO-modified CEI layer remarkably decreases electrolyte decomposition upon cycling at both room temperature and 45 ℃, leading to a substantial increase in cycling retention of the cells. A cell cycled with a 0.1 CSO-modified(modified with 0.1% CSO)NCM811 cathode exhibits a specific capacity retention of90.0%, while the cell cycled with non-modified NCM811 cathode suffers from continuous fading of cycling retention(74.0%) after 100 cycles. SEM, electrochemical impedance spectroscopy(EIS), X-ray photoelectron spectroscopy(XPS), and inductively coupled plasma mass spectrometry(ICP-MS) results of the recovered electrodes demonstrate that undesired surface reactions such as electrolyte decomposition and metal dissolution are well controlled in the cell because of the artificial CSO-modified CEI layer present on the surface of Ni-rich NCM811 cathodes.

关键词： Lithium-ion battery Cathode Cathode–electrolyte interphase Calcium sulfate Electrochemical performance