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Carbon-Coated Three-Dimensional MXene/Iron Selenide Ball with Core–Shell Structure for High-Performance Potassium-Ion Batteries

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Nano-Micro Letters 2022年第1期14卷 278-294页

作者： Su Hyun Yang Yun jae Lee Heemin Kang Seung-Keun park Yun Chan Kang Department of Materials Science and Engineering Korea UniversityAnam-DongSeongbuk-GuSeoul 136-713Republic of Korea Department of Advanced Materials Engineering Chung-Ang University4726 Seodong-daeroDaedeok-myeonAnseong-siGyeonggi-do 17546Republic of Korea

Two-dimensional(2D)MXenes are promising as electrode materials for energy storage,owing to their high electronic conductivity and low diffusion barrier.Unfortunately,similar to most 2D materials,MXene nanosheets easily restack during the electrode preparation,which degrades the electrochemical performance of MXene-based materials.A novel synthetic strategy is proposed for converting MXene into restacking-inhibited three-dimensional(3D)balls coated with iron selenides and carbon.This strategy involves the preparation of Fe_(2)O_(3)@carbon/MXene microspheres via a facile ultrasonic spray pyrolysis and subsequent selenization process.Such 3D structuring effectively prevents interlayer restacking,increases the surface area,and accelerates ion transport,while maintaining the attractive properties of MXene.Furthermore,combining iron selenides and carbon with 3D MXene balls offers many more sites for ion storage and enhances the structural robustness of the composite balls.The resultant 3D structured microspheres exhibit a high reversible capacity of 410 mAh g^(−1) after 200 cycles at 0.1 A g^(−1) in potassium-ion batteries,corresponding to the capacity retention of 97% as calculated based on 100 cycles.Even at a high current density of 5.0 A g^(−1),the composite exhibits a discharge capacity of 169 mAh g^(−1).

关键词： MXene Spray pyrolysis Iron selenide Potassium-ion batteries 3D structures

Redox Charge Transfer Kinetics and Reversibility of VO_(2) in Aqueous and Non-Aqueous Electrolytes of Na-Ion Storage

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Energy & Environmental Materials 2022年第4期5卷 1222-1228页

作者： Sul Ki park Kang Ho shin Puritut Nakhanivej Harpalsinh H.Rana Ho Seok park School of Chemical Engineering College of EngineeringSungkyunkwan University2066Seobu-roJangan-guSuwon-si Gyeonggi-do 440-746Republic of Korea Department of Engineering University of CambridgeCambridge CB30FSUK Department of Health Sciences and Technology Samsung Advanced Institute for Health Sciences and Technology(SAIHST)Sungkyunkwan University2066SeoburoJangan-guSuwon 440-746South Korea SKKU Advanced Institute of Nano Technology(SAINT) Sungkyunkwan University2066SeoburoJangan-guSuwon 440-746South Korea

The deep understanding about the electrochemical behavior of the nanostructured electrode in electrolytes provides crucial insights for the rational design of electrode for sodium(Na)-ion storage system(NIS).Here,we report redox charge transfer kinetics and reversibility of VO_(2)(B) nanorod electrodes in both aqueous and organic electrolytes for NIS.The assynthesized VO_(2)(B) nanorods show the reversible redox reaction with the higher specific and rate capacitances at high current density in aqueous electrolytes than in organic electrolytes.Temperature-dependent impedance measurements demonstrate the more facile interfacial charge transfer of Na ions into VO_(2)(B) nanorods in aqueous electrolytes.The reversible evolution in oxidation state and chemical composition of VO_(2)(B) nanorods is observed in aqueous electrolytes,as confirmed by ex situ XRD and ex situ X-ray photoelectron spectroscopy analyses.Given by the facile and reversible pseudocapacitive feature,the electrochemical performances of VO_(2)(B) nanorods are further improved by constructing the hierarchical structure of the reduced graphene oxide-VO_(2) composite for aqueous Na+ion storage.

关键词： aqueous electrolyte energy storage mechanism hierarchical structure nanorod sodium ion storage

High efficiency and stable solid-state fiber dye-sensitized solar cells obtained using TiO_(2) photoanodes enhanced with metal organic frameworks

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Journal of Energy Chemistry 2022年第4期31卷 458-466页

作者： jae Ho Kim Hyun Woo park Sung-Jun Koo Daseul Lee Eunyeong Cho Yong-Ki Kim Myunghun shin Jin Woo Choi Hee Jung Lee Myungkwan Song Department of Energy and Electronic Material Korea Institute of Materials Science(KIMS)797 Changwon-daeroSungsan-guChangwonGyeongsangnam-do 51508Republic of Korea Composites Research Division Korea Institute of Materials Science(KIMS)797 Changwon-daeroSungsan-GuChangwonGyeongsangnam-do 51508Republic of Korea School of Electronics and Information Engineering Korea Aerospace UniversityGoyang-cityGyeonggi-do 10540Republic of Korea

Solid-state fiber dye-sensitized solar cells(SS-FDSSCs) have been the subject of intensive attention and development in recent years. Although this field is only in its infancy, metal–organic frameworks(MOFs) are one such material that has been utilized to further improve the power conversion efficiency of solar cells. In this study, MOF-integrated DSSCs were shown to have potential in the development of solar cell devices with efficiency comparable to or better than that of conventional solar cells. The power conversion efficiency(PCE) of SS-FDSSCs was improved by embedding MOF-801 into a mesoporous-TiO_(2)(mp-TiO_(2)) layer, which was used as a photoanode in SS-FDSSCs, which are inherently flexible. The PCE of the MOF-integrated SS-FDSSCs was 6.50%, which is comparable to that of the reference devices(4.19%).The MOF-801 enhanced SS-FDSSCs decreased the series resistance(R_(s)) value, resulting in effective electron extraction with improved short-circuit current density(J_(SC)), while also increasing the shunt resistance(R_(sh)) value to prevent the recombination of photo-induced electrons. The result is an improved fill factor and, consequently, a higher value for the PCE.

关键词： Photoanode Metal organic frameworks Solid-state electrolyte Dye-sensitized solar cells Fiber-shaped solar cells

A feasible route to produce 1.1 GPa ferritic-based low-Mn lightweight steels with ductility of 47%

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Journal of Materials Science & Technology 2022年第22期117卷 225-237页

作者： Kwang Kyu Ko Hyo Ju Bae Eun Hye park Hyeon-Uk Jeong Hyoung Seok park jae Seok Jeong Jung Gi Kim Hyokyung Sung Nokeun park jae Bok Seol Department of Materials Engineering and Convergence Technology Center for K-metalGyeongsang National University(GNU)Jinju 52828South Korea School of Materials Science and Engineering Yeungnam UniversityGyeongbuk 38541South Korea Materials Research Team R&D Hyundai MobisYongin 16891South Korea Materials Technology Development Team Doosan Heavy Industries&ConstructionChangwon 51711South Korea

High- and medium-Mn (H/M-Mn) base lightweight steels are a class of ultrastrong structural materials with high ductility compared to their low-Mn counterparts with low strength and poor ductility.However, producing these H/M-Mn materials requires the advanced or high-tech manufacturing techniques, which can unavoidably provoke labor and cost concerns. Herein, we have developed a facilestrategy that circumvents the strength–ductility trade-off in low-Mn ferritic lightweight steels, by employing low-temperature tempering-induced partitioning (LTP). This LTP treatment affords a typical Fe-2.8Mn-5.7Al-0.3C (wt.%) steel with a heterogeneous size-distribution of metastable austenite embeddedin a ferrite matrix for partitioning more carbon into smaller austenite grains than into the larger austenite ones. This size-dependent partitioning results in slip plane spacing modification and lattice strain,which act through dislocation engineering. We ascribe the simultaneous improvement in strength andtotal elongation to both the size-dependent dislocation movement in austenite grains and the controlleddeformation-induced martensitic transformation. The low-carbon-partitioned large austenite grains increase the strength and ductility as a consequence of the combined martensitic transformation andhigh dislocation density-induced hardening and by interface strengthening. Additionally, high-carbonpartitioned small austenite grains enhance the strength and ductility by planar dislocation glide (inthe low strain regime) and by cross-slipping and delayed martensitic transformation (in the high strainregime). The concept of size-dependent dislocation engineering may provide different pathways for developing a wide range of heterogeneous-structured low-Mn lightweight steels, suggesting that LTP maybe desirable for broad industrial applications at an economic cost.

关键词： Low-Mn lightweight steel Carbon partitioning Metastable austenite Dislocation movement

Blockchain-Based Secure and Fair IoT Data Trading System with Bilateral Authorization

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Computers, Materials & Continua 2023年第8期76卷 1871-1890页

作者： Youngho park Mi Hyeon Jeon Sang Uk shin Electronics and Information Communications Research Center Pukyong National UniversityBusanKorea Department of Information Security Graduate SchoolPukyong National UniversityBusanKorea Division of Computer Engineering Pukyong National UniversityBusanKorea

These days,data is regarded as a valuable asset in the era of the data economy,which demands a trading platform for buying and selling data.However,online data trading poses challenges in terms of security and fairness because the seller and the buyer may not fully trust each other.Therefore,in this paper,a blockchain-based secure and fair data trading system is proposed by taking advantage of the smart contract and matchmaking encryption.The proposed system enables bilateral authorization,where data trading between a seller and a buyer is accomplished only if their policies,required by each other,are satisfied simultaneously.This can be achieved by exploiting the security features of the matchmaking encryption.To guarantee non-repudiation and fairness between trading parties,the proposed system leverages a smart contract to ensure that the parties honestly carry out the data trading protocol.However,the smart contract in the proposed system does not include complex cryptographic operations for the efficiency of onchain processes.Instead,these operations are carried out by off-chain parties and their results are used as input for the on-chain procedure.The system also uses an arbitration protocol to resolve disputes based on the trading proof recorded on the blockchain.The performance of the protocol is evaluated in terms of off-chain computation overhead and on-chain gas consumption.The results of the experiments demonstrate that the proposed protocols can enable the implementation of a cost-effective data trading system.

关键词： Bilateral authorization blockchain data marketplace fair exchange policy matching secure data trading

Differences in Pandemic-Related Factors Associated with Alcohol and Substance Use among Korean Adolescents:Nationwide Representative Study

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Biomedical and Environmental Sciences 2023年第6期36卷 542-548页

作者： Hyunju Yon Sangil park Jung U shin Ai Koyanagi Louis Jacob Lee Smith Chanyang Min Jinseok Lee Rosie Kwon Guillaume Fond Laurent Boyer Sunyoung Kim Namwoo Kim Sang Youl Rhee jae Il shin Dong Keon Yon Ho Geol Woo Department of Medicine Kyung Hee University College of MedicineSeoulRepublic of Korea Department of Neurology Kyung Hee University Medical CenterSeoulRepublic of Korea Department of Dermatology CHA Bundang Medical CenterCHA University School of MedicineSeongnamRepublic of Korea Research and Development Unit Parc Sanitari Sant Joan de DeuCIBERSAMISCIIIBarcelonaSpain Catalan Institution for Research and Advanced Studies(ICREA) Pg.Lluis CompanysBarcelonaSpain Department of Physical Medicine and Rehabilitation Lariboisière-Fernand Widal HospitalAP-HPUniversity Paris CitéParisFrance Centre for Health Performance and WellbeingAnglia Ruskin UniversityCambridgeUK Center for Digital Health Medical Science Research InstituteKyung Hee University Medical CenterKyung Hee University College of MedicineSeoulRepublic of Korea Department of Biomedical Engineering Kyung Hee UniversityYonginRepublic of Korea Assistance Publique-Hôpitaux de Marseille(AP-HM) Aix-Marseille UniversityCEReSSHealth Service Research and Quality of Life CenterMarseilleFrance FondaMental Foundation CreteilFrance Department of Family Medicine Kyung Hee University College of MedicineSeoulRepublic of Korea Department of Psychiatry Seoul St.Mary's HospitalThe Catholic University of KoreaCollege of MedicineSeoulRepublic of Korea Department of Endocrinology and Metabolism Kyung Hee University School of MedicineSeoulRepublic of Korea Department of Pediatrics Yonsei University College of MedicineSeoulRepublic of Korea Department of Pediatrics Kyung Hee University College of MedicineSeoulRepublic of Korea

The coronavirus disease 2019(COVID-19)pandemic has raised concerns about the mental health and social well-being of youth,including its potential to increase or exacerbate substance use behaviors[1].Among adolescents,the COVID-19pandemic has resulted in limited face-to-face school contact and thus missed milestones in preventing alcohol and substance use.

关键词： Alcohol raised alcohol

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国际盆景协会佳作选登(五)

花木盆景（下半月） 2024年第6期 64-67页

作者： [菲律宾]Charlie Lee [波兰]Piotr Tomasz Czernichowski [韩国]park jae Heon [墨西哥]Enrique Castano [印度尼西亚]Oka Sunarya [捷克]Vaclav Novak 罗民轩不详中国台湾

国际盆景协会(Bonsai Clubs International,BCI)于1963年在美国成立,会员分布在50多个国家和地区,每年在不同的国家或地区举行大会和年展,对世界盆景文化的发展起到了重要的推动作用。2023年9月,陈昌先生成功当选BCI主席,成为BCI历史上... 详细信息

国际盆景协会(Bonsai Clubs International,BCI)于1963年在美国成立,会员分布在50多个国家和地区,每年在不同的国家或地区举行大会和年展,对世界盆景文化的发展起到了重要的推动作用。2023年9月,陈昌先生成功当选BCI主席,成为BCI历史上首位中国籍主席。本栏目由花木盆景杂志社与BCI合办,让您通过BCI之窗,领略世界各地盆景魅力。

关键词：花木盆景盆景协会中国籍 BCI

Comprehensive analysis of two-dimensional charge transport mechanism in thin-film transistors based on random networks of single-wall carbon nanotubes using transient measurements

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Nano Research 2022年第2期15卷 1524-1531页

作者： Hyeonwoo shin Sang-Joon park Byeong-Cheol Kang Tae-Jun Ha Department of Electrical Engineering and Computer Science Inter-university Semiconductor Research CenterSeoul National UniversitySeoul 08826Korea Department of Electronic Materials Engineering Kwangwoon UniversitySeoul 01897Korea

Understanding charge transport mechanisms in thin-film transistors based on random networks of single-wall carbon nanotubes(SWCNT-TFTs)is essential for further advances to improve the potential for various nanoelectronic applications.Herein,a comprehensive investigation of the two-dimensional(2D)charge transport mechanism in SWCNT-TFTs is reported by analyzing the temperature-dependent electrical characteristics determined from the direct-current and non-quasi-static transient measurements at 80-300 K.To elucidate the time-domain charge transport characteristics of the random networks in the SWCNTs,an empirical equation was derived from a theoretical trapping model,and a carrier velocity distribution was determined from the differentiation of the transient response.Furthermore,charge trapping and de-trapping in shallow-and deep-traps in SWCNT-TFTs were analyzed by investigating charge transport based on their trapping/de-trapping rate.The comprehensive analysis of this study provides fundamental insights into the 2D charge transport mechanism in TFTs based on random networks of nanomaterial channels.

关键词： single-wall carbon nanotube random networks two-dimensional(2D)charge transport time-domain transient measurements charge trapping/de-trapping shallow-/deep-traps

Pseudo NLP Joint Spam Classification Technique for Big Data Cluster

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Computers, Materials & Continua 2022年第4期71卷 517-535页

作者： WooHyun park Nawab Muhammad Faseeh Qureshi Dong Ryeol shin Department of Electrical and Computer Engineering Sungkyunkwan UniversitySuwon16419Korea Department of Computer Education Sungkyunkwan UniversitySeoul03063Korea

Spam mail classification considered complex and error-prone task in the distributed computing environment.There are various available spam mail classification approaches such as the naive Bayesian classifier,logistic regression and support vector machine and decision tree,recursive neural network,and long short-term memory algorithms.However,they do not consider the document when analyzing spam mail content.These approaches use the bagof-words method,which analyzes a large amount of text data and classifies features with the help of term frequency-inverse document frequency.Because there are many words in a document,these approaches consume a massive amount of resources and become infeasible when performing classification on multiple associated mail documents together.Thus,spam mail is not classified fully,and these approaches remain with loopholes.Thus,we propose a term frequency topic inverse document frequency model that considers the meaning of text data in a larger semantic unit by applying weights based on the document’s topic.Moreover,the proposed approach reduces the scarcity problem through a frequency topic-inverse document frequency in singular value decomposition model.Our proposed approach also reduces the dimensionality,which ultimately increases the strength of document classification.Experimental evaluations show that the proposed approach classifies spam mail documents with higher accuracy using individual document-independent processing computation.Comparative evaluations show that the proposed approach performs better than the logistic regression model in the distributed computing environment,with higher document word frequencies of 97.05%,99.17%and 96.59%.

关键词： NLP big data machine learning TFT-IDF spam mail