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Enhancing the Robustness of Rib-Groove Filling and Strain Homogeneity in the Isothermal Forging of Titanium Alloy Multi-Rib Components

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CHINESE JOURNAL OF MEchanICAL ENGINEERING 2024年第1期37卷 1-28页

作者： Ding, Tong Wei, Ke Hou, Yong Dong, Xianjuan Huang, Long lee, Myoung-gyu Nanchang Hangkong Univ Sch Aeronaut Mfg Engn Nanchang 330063 Peoples R China Seoul Natl Univ Dept Mat Sci & Engn Seoul 08826 South Korea Seoul Natl Univ RIAM Seoul 08826 South Korea

Isothermal forging stands as an effective technology for the production of large-scale titanium alloy multi-rib components. However, challenges have persisted, including die underfilling and strain concentration due to the complex material flow and heterogeneous deformation within the forging die cavity. While approaches centered on optimized billet designs have mitigated these challenges, uncertainties in process parameters continue to introduce unacceptable variations in forming accuracy and stability. To tackle this issue, this study introduced a multi-objective robust optimization approach for billet design, accounting for the multi-rib eigenstructure and potential uncertainties. The approach includes finite element (FE) modeling for analyzing the die-filling and strain inhomogeneity within the multi-rib eigenstructure. Furthermore, it integrated image acquisition perception and feed back technologies (IAPF) for real-time monitoring of material flow and filling sequences within die rib-grooves, validating the accuracy of the FE modeling. By incorporating dimensional parameters of the billet and uncertainty factors, including friction, draft angle, forming temperature, speed, and deviations in billet and die, quantitative analyses on the rib-groove filling and strain inhomogeneity with fluctuation were conducted. Subsequently, a dual-response surface model was developed for statistical analysis of the cavity filling and strain homogeneity. Finally, the robust optimization was processed using a non-dominated sorting genetic algorithm II (NSGA-II) and validated using the IAPF technologies. The proposed approach enables robust design enhancements for rib-groove filling and strain homogeneity in titanium alloy multi-rib components.

关键词： Titanium alloy multi-rib components Die rib-groove filling Strain homogeneity Multi-objective robust optimization Real-time monitoring

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In situ infrared, Raman and X-ray spectroscopy for the mechanistic understanding of hydrogen evolution reaction

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Journal of Energy Chemistry 2024年第3期90卷 632-651,I0014页

作者： Andi Haryanto Kyounghoon Jung chan Woo lee Dong-Wan Kim Department of Chemistry Kookmin UniversitySeoul 02707Republic of Korea School of Civil Environmental and Architectural EngineeringKorea UniversitySeoul 02841Republic of Korea

Hydrogen production by water reduction reactions has received considerable attention because hydrogen is considered a clean-energy carrier,key for a sustainable energy *** methods have been widely used to study the reaction mechanism of the hydrogen evolution reaction(HER),but the calculation results need to be supported by experimental results and direct evidence to confirm the mechanistic *** this review,we discuss the fundamental principles of the in situ spectroscopic strategy and a theoretical model for a mechanistic understanding of the *** addition,we investigate recent studies by in situ Fourier transform infrared(FTIR),Raman spectroscopy,and X-ray absorption spectroscopy(XAS) and cover new findings that occur at the catalyst-electrolyte interface during *** spectroscopic strategies provide practical ways to elucidate catalyst phase,reaction intermediate,catalyst-electrolyte interface,intermediate binding energy,metal valency state,and coordination environment during HER.

关键词： Hydrogen evolution reaction Infrared spectroscopy Raman spectroscopy X-ray absorption spectroscopy Reaction mechanism

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Identification and comparison of the local physicochemical structures of transition metal-based layered double hydroxides for high performance electrochemical oxygen evolution reactions

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Journal of Energy Chemistry 2023年第12期87卷 89-97,I0004页

作者： Min Sung Kim Bipin Lamichhane Ju-Hyeon lee Jin-gyu Bae Jeong Yeon Heo Hyeon Jeong lee Shyam Kattel Ji Hoon lee School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea KNU Advanced Material Research Institute Kyungpook National UniversityDaegu 41566Republic of Korea Department of Materials Science and Engineering Ulsan National Institute of Science and TechnologyUlsan 44919Republic of Korea Department of Physics Florida A&M UniversityTallahasseeFlorida 32307United States

Layered double hydroxides(LDHs) have attracted considerable attention as a cost effective alternative to the precious iridium-and ruthenium-based electrocatalysts for an oxygen evolution reaction(OER),a bottleneck of water electrolysis for sustainable hydrogen *** their excellent OER performance,the structural and electronic properties of LDHs,particularly during the OER process,remain to be poorly *** this study,a series of LDH catalysts is investigated through in situ X-ray absorption fine structure analyses and density functional theory(DFT) *** experimental results reveal that the LDH catalyst with equal amounts of Ni and Fe(NF-LDH) exhibits the highest OER activity and catalytic life span when compared with its counterparts having equal amounts of Ni and Co(NC-LDH)and Ni only(Ni-LDH).The NF-LDH shows a markedly enhanced OER kinetics compared to the NC-LDH and the Ni-LDH,as proven by the lower overpotentials of 180,240,and 310 mV,respectively,and the Tafel slopes of 35.1,43.4,and 62.7 mV dec^(-1),*** DFT calculations demonstrate that the lowest overpotential of the NF-LDH is associated with the active sites located at the edge planes of NF-LDH in contrast to those located at the basal planes of Ni-LDH and *** current study pinpoints the active sites on various LDHs and presents strategies for optimizing the OER performance of the LDH catalysts.

关键词： Layered double hydroxides Oxygen evolution reaction In situ X-ray analyses Density functional theory Catalytic active sites

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Regulation of sleep by astrocytes in the hypothalamic ventrolateral preoptic nucleus

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Neural Regeneration Research 2025年第4期20卷 1098-1100页

作者： Jae-Hong Kim Ruqayya Afridi Il-Sung Jang Maan Gee lee Kyoungho Suk Brain Korea 21 four KNU Convergence Educational Program of Biomedical Sciences for Creative Future Talents School of MedicineKyungpook National UniversityDaeguRepublic of Korea Department of Pharmacology School of MedicineKyungpook National UniversityDaeguRepublic of Korea Department of Pharmacology School of DentistryKyungpook National UniversityDaeguRepublic of Korea Brain Science&Engineering Institute Kyungpook National UniversityDaeguRepublic of Korea

Astrocytes are functionally dynamic cells that support neurons in multiple ways throughout an organism’s *** astrocytic regulation of neuronal activity has been increasingly recognized in recent *** are now recognized as playing a more complex role than mere bystanders in the central nervous ***,their role in regulating the sleep neurocircuitry is not well *** this perspective,we highlight the role of astrocytes in sleep modulation,with a particular focus on regulatory mechanisms related to the ventrolateral preoptic nucleus(VLPO)of the *** briefly discuss recent literature reporting the role of VLPO astrocytes in regulating sleep-associated behaviors.

关键词： sleep ventrolateral astrocytes

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Does friction contribute to formability improvement using servo press?

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Friction 2023年第5期11卷 820-835页

作者： Kali PRASAD Aishwary GUPTA Hariharan KRISHNASWAMY Uday CHAKKINGAL Dilip K.BANERJEE Myoung-gyu lee Department of Mechanical Engineering Indian Institute of Technology MadrasChennai 600036India Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Republic of Korea Department of Metallurgical and Materials Engineering Indian Institute of Technology MadrasChennai 600036India Material Measurement Laboratory National Institute of Standards and Technology(NIST)Gaithersburg 20899USA

Servo press forming machines are advanced forming systems that are capable of imparting interrupted punch motion,resulting in enhanced room temperature *** exact mechanism of the formability improvement is not yet *** contribution of interrupted motion in the ductility improvement has been studied through stress relaxation phenomena in uniaxial tensile(UT)***,the reason for improved formability observed when employing servo press is complicated due to the additional contribution from frictional *** the present work,an attempt is made to decouple the friction effect on formability improvement *** improved formability is studied using a hole expansion test(HET).The limit of forming during hole expansion is modeled using the Hosford–Coulomb(HC)damage criteria,which is implemented as a user subroutine in a commercial explicit finite element(FE)*** the contribution of stress relaxation is accounted for in the evolution of the damage variable during interrupted ***,the difference between simulation and experimental hole expansion ratio(HER)can be used to decouple the friction effect from the overall formability improvement during hole *** improvement in HER due to stress relaxation and friction effect is *** study showed that the model effectively captures the hole expansion deformation process in both monotonic and interrupted loading *** to stress relaxation,friction effect played a major role during interrupted HET.

关键词： servo press hole expansion test(HET) dual phase steel finite element(FE)analysis Hosford-Coulomb(HC)ductile fracture model

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Spacing optimization of high power LED arrays for solid state lighting

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Journal of Semiconductors 2011年第1期32卷 45-49页

作者： Y.Sing chan S.W.Ricky lee Electronic Packaging Laboratory Center for Advanced Microsystems Packaging Hong Kong University of Science and Technology

This paper provides an analytical approach to determine the optimum pitch by utilizing a thermal resistance network, under the assumption of constant luminous efficiency. This work allows an LED array design which is mounted on a printed circuit board （PCB） attached with a heat sink subject to the natural convection cooling. Being validated by finite element （FE） models, the current approach can be shown as an effective method for the determination of optimal component spacing in an LED array assembly for SSL.

关键词： high power LED thermal resistance network finite element modeling

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Network coding-aware cache replacement policy in on-demand broadcast environments

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Journal of Harbin Institute of Technology(New Series) 2012年第5期19卷 92-100页

作者：陈君 lee Victor C S chan Edward School of Information Management Wuhan UniversityWuhan 430072China Dept.of Computer Science City University of Hong KongHong KongChina

Network coding has been proved to be an effective technique in improving the performance of data broadcast systems because clients requesting different data items can be served simultaneously in one broadcast. Previous studies showed that its efficiency is highly related to the content of clients' cache. However, existing data broadcast systems do not take network coding information into account when making cache replacement decisions. In this paper, we propose two networks coding-aware cache replacement policies called DLRU and DLRU-CP to supplement network coding assisted data broadcast in on-demand broadcast environments. In DLRU, both data access and decoding contribution are taken into account to make replacement decisions. DLRU-CP is based on DLRU but allows clients to retrieve decodable data items that have not been requested yet. The performance gain of our proposed cache replacement policies over traditional cache replacement policy is shown in the simulation results, which demonstrate conclusively that the proposed policies can effectively reduce the overall response time.

关键词： Network coding cache replacement on-demand broadcast mobile computing

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Effect of esterification reaction of citric acid and ethylene glycol on the formation of multi-shelled cobalt oxide powders with superior electrochemical properties

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Nano Research 2014年第12期7卷 1738-1748页

作者： Gi Dae Park Jong-Heun lee Jung-Kul lee Yun chan Kang Department of Materials Science and Engineering Korea University Anam-Dong Seongbuk-Gu Seou1136-713 Republic of Korea Department of Chemical Engineering Konkuk University 1 Hwayang-dong Gwangjin-gu Seou1143-701 Republic of Korea

In this study, for the first time, polymeric precursors have been used in the preparation of yolk-shell powders using a large-scale spray drying process. An esterification reaction between the carboxyl group of citric acid and the hydroxyl group of ethylene glycol inside the droplet produced organic polymers during the drying process of the droplet. During the spray drying process, the polymeric precursors enabled the formation of multi-shell cobalt oxide yolk- shell powders with superior electrochemical properties. The maximum number of shells of the particles in the yolk-shell powders post-treated at 300, 400, and 500 ℃ were six, five, and four, respectively. The initial discharge capacities of the cobalt oxide yolk-shell powders post-treated at 300, 400, and 500 ℃ were 1,188, 1,331, and 1,110 mAh·g^-1, and their initial charge capacities were 868, 1,005, and 798 mAh·g^-1, respectively. The discharge capacities of the powders post- treated at 300, 400, and 500 ℃ after 100 cycles were 815, 958, and 670 mAh·g^-1, respectively and their corresponding capacity retentions measured after the first cycles were 92%, 93%, and 82%, respectively. The pure phase Co3O4 yolk-shell powders post-treated at 400 ℃ had low charge transfer resistance and high lithium-ion diffusion rate.

关键词： yolk-shell energy storage synthesis design lithium battery spray drying

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CRISPR/Cas9-mediated gene editing to confer turnip mosaic virus (TuMV) resistance in Chinese cabbage (Brassica rapa)

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Horticulture Research 2023年第6期10卷 135-143页

作者： Ye-Rin lee Muhammad Irfan Siddique Do-Sun Kim Eun Su lee Koeun Han Sang-gyu Kim Hye-Eun lee Vegetable Research Division National Institute of Horticultural and Herbal ScienceRural Development AdministrationWanju55365Republic of Korea Department of Horticultural Sciences North Carolina State University Mountain Horticultural Crops ResearchExtension Center 455 Research DriveMills RiverNC 28759USA Department of Biological Sciences Korea Advanced Institute for Science and TechnologyDaejeon34141Republic of Korea

Genome editing approaches,particularly the CRISPR/Cas9 technology,are becoming state-of-the-art for trait development in numerous breeding *** advances in improving plant traits are enabled by this influential tool,especially for disease resistance,compared to traditional *** of the potyviruses,the turnip mosaic virus(TuMV),is the most widespread and damaging virus that infects Brassica *** generated the targeted mutation at the eIF(iso)4E gene in the TuMV-susceptible cultivar“Seoul”using CRISPR/Cas9 to develop TuMV-resistant Chinese *** detected several heritable indel mutations in the edited T0 plants and developed T1 through generational *** was indicated in the sequence analysis of the eIF(iso)4E-edited T1 plants that the mutations were transferred to succeeding *** edited T1 plants conferred resistance to *** was shown with ELISA analysis the lack of accumulation of viral ***,we found a strong negative correlation(r=-0.938)between TuMV resistance and the genome editing frequency of eIF(iso)***,it was revealed in this study that CRISPR/Cas9 technique can expedite the breeding process to improve traits in Chinese cabbage plants.

关键词： CRISPR/Cas9 TuMV breeding

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Statistical Prediction of Heavy Rain in South Korea

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Advances in Atmospheric Sciences 2005年第5期22卷 703-710页

作者： Keon Tae SOHN Jeong Hyeong lee Soon Hwan lee chan Su RYU Pusan National University Busan 609-735 KoreaDong-A University Busan 604-714 Korea Chosun University Gwangju 501-759 KoreaChosun University Gwangju 501-759 Korea

This study is aimed at the development of a statistical model for forecasting heavy rain in South Korea. For the 3-hour weather forecast system, the 10 km×10 km area-mean amount of rainfall at 6 stations （Seoul, Daejeon, Gangreung, （Jwangju, Busan, and Jeju） in South Korea are used. And the corresponding 45 synoptic factors generated by the numerical model are used as potential predictors. Four statistical forecast models （linear regression model, logistic regression model, neural network model and decision tree model） for the occurrence of heavy rain are based on the model output statistics （MOS） method. They are separately estimated by the same training data. The thresholds are considered to forecast the occurrence of heavy rain because the distribution of estimated values that are generated by each model is too skewed. The results of four models are compared via Heidke skill scores. As a result, the logistic regression model is recommended.

关键词： heavy rain model output statistics linear regression logistic regression neural networks,decision tree

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