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Intelligent reflecting surface for sum rate enhancement in MIMO systems

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Digital Communications and Networks 2024年第1期10卷 94-100页

作者： Chan-Yeob park Ji-sung Jung Yeong-Rong Lee Beom-Sik Shin Hyoung-Kyu Song Department of Information and Communication Engineering Sejong UniversitySeoulGwangjin-guGunja-dong 98Republic of Korea Department of Convergence Engineering for Intelligent Drone Sejong University SeoulGwangjin-guGunja-dong 98Republic of Korea

The research for the Intelligent Reflecting Surface(IRS)which has the advantages of cost and energy efficiency has been *** capacity can be effectively increased by appropriately setting the phase value of IRS elements according to the channel ***,the problem of obtaining an appropriate phase value of IRs is difficult to solve due to the non-convex *** paper proposes an iterative algorithm for the alternating optimal solution in the Single User Multiple-Input-Multiple-Output(SU-MIMO)*** proposed iterative algorithm finds an alternating optimal solution that is the phase value of IRS one by *** results show that the proposed method has better performance than that of the randomized IRS *** number of iterations for maximizing the performance of the proposed algorithm depends on the channel state between the IRS and the receiver.

关键词： Intelligent reflecting surface MIMO Sum rate

TEAM:Transformer Encoder Attention Module for Video Classification

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Computer Systems Science & Engineering 2024年第2期48卷 451-477页

作者： Hae sung park Yong Suk Choi Department of Artificial Intelligence Hanyang UniversitySeoulKorea Department of Computer Science Hanyang UniversitySeoulKorea

Much like humans focus solely on object movement to understand actions,directing a deep learning model’s attention to the core contexts within videos is crucial for improving video *** the recent study,Video Masked Auto-Encoder(VideoMAE)employs a pre-training approach with a high ratio of tube masking and reconstruction,effectively mitigating spatial bias due to temporal redundancy in full video *** steers the model’s focus toward detailed temporal ***,as the VideoMAE still relies on full video frames during the action recognition stage,it may exhibit a progressive shift in attention towards spatial contexts,deteriorating its ability to capture the main spatio-temporal *** address this issue,we propose an attention-directing module named Transformer Encoder Attention Module(TEAM).This proposed module effectively directs the model’s attention to the core characteristics within each video,inherently mitigating spatial *** TEAM first figures out the core features among the overall extracted features from each *** that,it discerns the specific parts of the video where those features are located,encouraging the model to focus more on these informative ***,during the action recognition stage,the proposed TEAM effectively shifts the VideoMAE’s attention from spatial contexts towards the core spatio-temporal *** attention-shift manner alleviates the spatial bias in the model and simultaneously enhances its ability to capture precise video *** conduct extensive experiments to explore the optimal configuration that enables the TEAM to fulfill its intended design purpose and facilitates its seamless integration with the VideoMAE *** integrated model,i.e.,VideoMAE+TEAM,outperforms the existing VideoMAE by a significant margin on Something-Something-V2(71.3%vs.70.3%).Moreover,the qualitative comparisons demonstrate that the TEAM encourages the model to disregard insignificant featur

关键词： Video classification action recognition vision transformer masked auto-encoder

Effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on tensile and bending properties of high-Al-containing Mg alloys

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Journal of Magnesium and Alloys 2024年第2期12卷 779-793页

作者： Sumi Jo Gyo Myeong Lee Jong Un Lee Young Min Kim sung Hyuk park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Magnesium Korea Institute of Materials ScienceChangwon 51508Republic of Korea

This study investigates the effect of characteristics and distribution of Mg_(17)Al_(12)precipitates on the uniaxial tensile and three-point bending properties of extruded Mg alloys containing high Al *** extruded Mg–9Al–1Zn–0.3Mn(AZ91)alloy contains lamellar-structured Mg_(17)Al_(12)discontinuous precipitates along the grain boundaries,which are formed via static precipitation during natural air *** extruded Mg–11Al–1Zn–0.3Mn(AZ111)alloy contains spherical Mg_(17)Al_(12)precipitates at the grain boundaries and inside the grains,which are formed via dynamic precipitation during *** to inhomogeneous distribution of precipitates,the AZ111 alloy consists of two different precipitate regions:precipitate-rich region with numerous precipitates and finer grains and precipitate-scarce region with a few precipitates and coarser *** AZ111 alloy exhibits a higher tensile strength than the AZ91 alloy because its smaller grain size and more abundant precipitates result in stronger grain-boundary hardening and precipitation hardening effects,***,the tensile elongation of the AZ111 alloy is lower than that of the AZ91 alloy because the weak cohesion between the dynamic precipitates and the matrix facilitates the crack initiation and *** bending,a macrocrack initiates on the outer surface of bending specimen in both *** AZ111 alloy exhibits higher bending yield strength and lower failure bending strain than the AZ91 *** bending specimens of the AZ91 alloy have similar bending formability,whereas those of the AZ111 alloy exhibit considerable differences in bending formability and crack propagation behavior,depending on the distribution and number density of precipitates in the *** bending specimens of the AZ111 alloy,it is found that the failure bending strain(ε_(f,bending))is inversely proportional to the area fraction of precipitates in the outer zone of bending specimen(A_(ppt)),with a relation

关键词： Mg–Al alloy Extrusion Bending Precipitation Microstructure

Enhanced prediction of anisotropic deformation behavior using machine learning with data augmentation

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Journal of Magnesium and Alloys 2024年第1期12卷 186-196页

作者： Sujeong Byun Jinyeong Yu Seho Cheon Seong Ho Lee sung Hyuk park Taekyung Lee School of Mechanical Engineering Pusan National UniversityBusan 46241South Korea School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566South Korea

Mg alloys possess an inherent plastic anisotropy owing to the selective activation of deformation mechanisms depending on the loading *** characteristic results in a diverse range of flow curves that vary with a deformation *** study proposes a novel approach for accurately predicting an anisotropic deformation behavior of wrought Mg alloys using machine learning(ML)with data *** developed model combines four key strategies from data science:learning the entire flow curves,generative adversarial networks(GAN),algorithm-driven hyperparameter tuning,and gated recurrent unit(GRU)*** proposed model,namely GAN-aided GRU,was extensively evaluated for various predictive scenarios,such as interpolation,extrapolation,and a limited dataset *** model exhibited significant predictability and improved generalizability for estimating the anisotropic compressive behavior of ZK60 Mg alloys under 11 annealing conditions and for three loading *** GAN-aided GRU results were superior to those of previous ML models and constitutive *** superior performance was attributed to hyperparameter optimization,GAN-based data augmentation,and the inherent predictivity of the GRU for *** a first attempt to employ ML techniques other than artificial neural networks,this study proposes a novel perspective on predicting the anisotropic deformation behaviors of wrought Mg alloys.

关键词： Plastic anisotropy Compression Annealing Machine learning Data augmentation

Indolocarbazole-Based Small Molecule Cathode-Active Material Exhibiting Double Redox for High-Voltage Li-Organic Batteries

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Energy & Environmental Materials 2024年第5期7卷 90-98页

作者： Hyunji park Hyojin Kye Jong-sung Lee Young-Chang Joo Dong Joo Min Bong-Gi Kim Soo Young park Ji Eon Kwon Laboratory for Supramolecular Optoelectronic Materials (LSOM) Department of Materials Science and Engineering Research Institute of Advanced Materials (RIAM) Seoul National University Functional Composite Materials Research Center Jeonbuk Institute of Advanced Composite Materials Korea Institute of Science and Technology (KIST) Department of Organic and Nano System Engineering Konkuk University Department of Materials Science and Engineering Seoul National University Department of JBNU-KIST Industry Academia Convergence Research Jeonbuk National University

Most organic electrode materials （OEMs） for rechargeable batteries employ n-type redox centers, whose redox potentials are intrinsically limited <3.0 V versus Li+/Li. However, p-type materials possessing high redox potentials experience low specific capacities because they are capable of only a single redox reaction within the stable electrochemical window of typical ***, we report 5,11-diethyl-5,11-dihydroindolo[3,2-b]carbazole （DEICZ） as a novel p-type OEM, exhibiting stable plateaus at high discharge potentials of3.44 and 4.09 V versus Li+/Li. Notably, the second redox potential of DEICZ is within the stable electrochemical window. The mechanism of the double redox reaction is investigated using both theoretical calculations and experimental measurements, including density functional theory calculations, ex situ electron spin resonance, and X-ray photoelectron spectroscopy. Finally,hybridization with single-walled carbon nanotubes （SWCNT） improves the cycle stability and rate performance of DEICZ owing to theπ–πinteractions between the SWCNT and co-planar molecular structure of DEICZ, preventing the dissolution of active materials into the electrolyte. The DEICZ/SWCNT composite electrode maintains 70.4%of its initial specific capacity at 1-C rate and also exhibits high-rate capability, even performing well at 100-C rate.

关键词： composite electrodes flexible batteries indolocarbazoles organic rechargeable batteries p-type

Body-Shaping Membrane to Regenerate Breast Fat by Elastic Structural Holding

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Research 2024年第1期2023卷 165-180页

作者： Hye-Seon Kim Jeongeun park Hyun-Su Ha Sewoom Baek Chan Hee Lee Kyubae Lee Suji park Jueun Kim Se Won Yi Hak-Joon sung Department of Medical Engineering Graduate School of Medical ScienceBrain Korea 21 ProjectYonsei University College of MedicineSeoul 03722Republic of Korea TMD LAB Co.Ltd. 6th Floor31Gwangnaru-ro 8-gilSeongdong-guSeoul 04799Republic of Korea

Tissue regeneration requires structural holding and movement support using tissue-type-specific aids such as bone casts,skin bandages,and joint ***,an unmet need exists in aiding breast fat regeneration as the breast moves following continuous body motion by exposing the breast fat to dynamic ***,the concept of elastic structural holding is applied to develop a shape-fitting moldable membrane for breast fat regeneration(“adipoconductive”)after surgical defects are *** membrane has the following key characteristics:(a)It contains a panel of honeycomb structures,thereby efficiently handling motion stress through the entire membrane;(b)a strut is added into each honeycomb in a direction perpendicular to gravity,thereby suppressing the deformation and stress concentration upon lying and standing;and(c)thermo-responsive moldable elastomers are used to support structural holding by suppressing large deviations of movement that occur *** elastomer became moldable upon a temperature shift above T_(m).The structure can then be fixed as the temperature *** a result,the membrane promotes adipogenesis by activating mechanotransduction in a fat miniature model with pre-adipocyte spheroids under continuous shaking in vitro and in a subcutaneous implant placed on the motion-prone back areas of rodents in vivo.

关键词： thereby shaking Elastic

Practical operating flexibility of a bifunctional freestanding membrane for efficient anion exchange membrane water electrolysis across all current ranges

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Carbon Energy 2024年第9期6卷 306-324页

作者： Hong-Jin Son Jeemin Hwang Min Young Choi Seung Hee park Jae Hyuk Jang Byungchan Han sung Hoon Ahn Department of Bio-Chemical Engineering Chosun UniversityGwangjuRepublic of Korea Fuel Cell Research and Demonstration Center Hydrogen Energy Research DivisionKorea Institute of Energy Research(KIER)Buan-gunJeollabuk-doRepublic of Korea Department of Chemical and Biomolecular Engineering Yonsei UniversitySeoulRepublic of Korea Center for Research Equipment Korea Basic Science InstituteDaejeonRepublic of Korea

This study explores a symmetric configuration approach in anion exchange membrane(AEM)water electrolysis,focusing on overcoming adaptability challenges in dynamic ***,a rapid and mild synthesis technique for fabricating fibrous membrane-type catalyst electrodes is *** method leverages the contrasting oxidation states between the sulfur-doped NiFe(OH)2 shell and the metallic Ni core,as revealed by electron energy loss *** evaluations confirm that the S–NiFe(OH)_(2) active sites optimize free energy for alkaline water electrolysis *** technique bypasses traditional energy-intensive processes,achieving superior bifunctional activity beyond current *** symmetric AEM water electrolyzer demonstrates a current density of 2 A cm^(-2) at 1.78 V at 60℃ in 1 M KOH electrolyte and also sustains ampere-scale water electrolysis below 2.0 V for 140 h even in ambient *** results highlight the system's operational flexibility and structural stability,marking a significant advance-ment in AEM water electrolysis technology.

关键词： AEM water electrolysis fibrous membrane iR correction free operational stability symmetric configuration

Bidirectional rotating direct-current triboelectric nanogenerator with self-adaptive mechanical switching for harvesting reciprocating motion

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International Journal of Extreme Manufacturing 2024年第4期6卷 324-335页

作者： Donghan Lee Joonmin Chae Sumin Cho Jong Woo Kim Awais Ahmad Mohammad Rezaul Karim Moonwoo La sung Jea park Dongwhi Choi Department of Mechanical Engineering(Integrated Engineering Program) Kyung Hee University1732 Deogyeong-daeroYonginGyeonggi 17104Republic of Korea Department of Chemistry University of LahoreLahorePakistan Department of Mechanical Engineering College of EngineeringKing Saud UniversityRiyadh 11421Saudi Arabia School of Mechanical Engineering Korea University of Technology and Education1600 Chungjeol-roCheonanChungnam 31253Republic of Korea

Amid the growing interest in triboelectric nanogenerators(TENGs)as novel energy-harvesting devices,several studies have focused on direct current(DC)TENGs to generate a stable DC output for operating electronic ***,owing to the working mechanisms of conventional DC TENGs,generating a stable DC output from reciprocating motion remains a ***,we propose a bidirectional rotating DC TENG(BiR-TENG),which can generate DC outputs,regardless of the direction of rotation,from reciprocating *** distinct design of the BiR-TENG enables the mechanical rectification of the alternating current output into a rotational-direction-dependent DC ***,it allows the conversion of the rotational-direction-dependent DC output into a unidirectional DC output by adapting the configurations depending on the rotational *** to these tailored design strategies and subsequent optimizations,the BiR-TENG could generate an effective unidirectional DC *** of the BiR-TENG for the reciprocating motions of swinging doors and waves were demonstrated by harnessing this *** study demonstrates the potential of the BiR-TENG design strategy as an effective and versatile solution for energy harvesting from reciprocating motions,highlighting the suitability of DC outputs as an energy source for electronic devices.

关键词： direct-current triboelectric nanogenerator mechanical rectification self-adaptive mechanical design harvesting reciprocation motion

Enhancement of vertical phase separation in sequentially deposited organic photovoltaics through the independent processing of additives

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Journal of Energy Chemistry 2024年第7期94卷 768-777页

作者： Damin Lee Changwoo park Gayoung Ham Young Yong Kim sung-Nam Kwon Junyeong Lee sungjin Jo Seok-In Na Hyojung Cha Department of Hydrogen and Renewable Energy Kyungpook National UniversityDaegu 41566Republic of Korea Department of Energy Convergence and Climate Change Kyungpook National UniversityDaegu 41566Republic of Korea Pohang Accelerator Laboratory(PAL) Pohang University of Science and Technology(POSTECH)PohangGyeongbuk 37673Republic of Korea Department of Flexible and Printable Electronics Jeonbuk National UniversityJeonju-siJeollabuk-do 54896Republic of Korea School of Energy Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

Herein,the impact of the independent control of processing additives on vertical phase separation in sequentially deposited (SD) organic photovoltaics (OPVs) and its subsequent effects on charge carrier kinetics at the electron donor-acceptor interface are *** film morphology exhibits notable variations,significantly depending on the layer to which 1,8-diiodooctane (DIO) was *** incidence wide-angle X-ray scattering analysis reveals distinctly separated donor/acceptor phases and vertical crystallinity details in SD ***-of-flight secondary ion mass spectrometry analysis is employed to obtain component distributions in diverse vertical phase structures of SD films depending on additive *** addition,nanosecond transient absorption spectroscopy shows that DIO control significantly affects the dynamics of separated charges in SD *** SD OPVs,DIO appears to act through distinct mechanisms with minimal restriction,depending on the applied *** study emphasizes the significance of morphological optimization in improving device performance and underscores the importance of independent additive control in the advancement of OPV technology.

关键词： Sequential deposition Vertical phase separation Charge dynamics Organic photovoltaics Nonfullerene acceptors