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Journal of Materials Science & Technology 2008年第3期24卷 296-301页

作者： Sangwon Lee Bonggyu Park Yongho Park Ikmin Park Department of Material Science and Engineering Pusan National University 30Jangjeon-dongGeumjeong-gu

The effect of Sn addition on the microstructures and mechanical properties of Mg-5Al-2Si alloys was investigated with variations of Sn contents （3 and 6 wt pct）. The microstructure of the alloy was characterized by the presence of Mg2Sn particles within matrix and at grain boundaries. As the Sn contents increased, yield and ultimate tensile strength were increased at room temperatures and 150℃. Creep properties were improved with the increasing amount of Sn due to the fine precipitation of Mg2Sn phases within grain during creep.

关键词： Magnesium Tin Microstructure Mechanical properties

K2Ti6O13 Nanoparticle-Loaded Porous rGO Crumples for Supercapacitors

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Nano-Micro Letters 2020年第1期12卷 115-123页

作者： Chongmin Lee Sun Kyung Kim Hankwon Chang Hee Dong Jang Department of Nanomaterials Science and Engineering University of Science and TechnologyYuseong‑guDaejeon 34113Republic of Korea Resources Utilization Research Center Korea Institute of Geoscience and Mineral ResourcesYuseong‑guDaejeon 34132Republic of Korea

One-dimensional alkali metal titanates containing potassium,sodium,and lithium are of great concern owing to their high ion mobility and high specific surface *** those titanates are combined with conductive materials such as graphene,carbon nanotube,and carbon nanofiber,they are able to be employed as efficient electrode materials for *** hexa-titanate(K2Ti6O13,KTO),in particular,has shown superior electrochemical properties compared to other alkali metal titanates because of their large lattice parameters induced by the large radius of potassium ***,we present porous rGO crumples(PGC)decorated with KTO nanoparticles(NPs)for application to *** KTO NP/PGC composites were synthesized by aerosol spray pyrolysis and post-heat *** NPs less than 10 nm in diameter were loaded onto PGCs ranging from 3 to 5μ*** porous structure of the composites was obtained by the activation of rGO by adding an excessive amount of KOH to the *** KTO NP/PGC composite electrodes fabricated at the GO/KOH/TiO2 ratio of 1:3:0.25 showed the highest performance(275 F g−1)in capacitance with different KOH concentrations and cycling stability(83%)after 2000 cycles at a current density of 1 A g−1.

关键词： Potassium hexa-titanate Porous graphene crumples Supercapacitors

Synthesis of Cobalt Containing Block Copolymers Via Ring Opening Metathesis Polymerizastion (ROMP)

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Journal of Rare Earths 2004年第Z2期22卷 145-152页

作者： Bongjin Moon Minhyuk Kang Departmen of Chemistry Sogang UniversityShinsoo-Dong 1-1Mapo-GuSeoul121-742Korea Departmen of ChemistrySogang UniversityShinsoo-Dong 1-1Mapo-GuSeoul121-742Korea

In order to realize a metal containing nano-structure, a block-copolymer containing alkynyl groups in one block was designed and synthesized by living ring opening metathesis polymerization (ROMP) technique. The newly developed bis-3-bromopyridine complex of Grubbs catalyst was employed in the series of polymerization and it yielded the desired polymers with great molecular weight control and narrow polydispersities. The characteristics of the block copolymers were investigated by gel permeation chromatography, H- and 13H- NMR spectroscopy. Complexation of the alkynyl group containing block copolymers by treatment with dicobalt octacarbonyl occurred smoothly in 5 min at room temperature. GPC analysis before and after cobalt complexation indicated a significant increase of the hydrodynamic volume. AFM images of the films before and after the complexation also showed a noticeable change in its morphology where grain sizes become smaller and more regular upon complexation.

关键词： ring opening metathesis polymerization (ROMP) metal containing block copolymer polynorbornene derivative

Fatigue-Induced Micro-damage Characterization of Austenitic Stainless Steel 316 Using Innovative Nonlinear Acoustics

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Chinese Physics Letters 2012年第6期29卷 82-85页

作者： Chung-Seok KIM Kyung-Young JHANG Automotive Engineering Hanyang UniversityHangdang-dongSeongdong-guSeoul133-791South Korea Mechanical Engineering Hanyang UniversityHangdang-dongSeongdong-guSeoul133-791South Korea

We present innovative nonlinear acoustics for characterizing fatigue-induced micro-damage of austenitic stainless steel 316 subjected to high-cycle *** fatigue-driven deformations are accumulated at several positions near the middle of hourglass-shaped specimens.A bell-shaped curve of acoustic nonlinearity as a function of position is observed,and the variation in acoustic nonlinearity is attributed to the evolution of a lattice defect (dislocation) and stress-induced martensite based on transmission electron microscopy (TEM) *** oblique incidence technique using a longitudinal waveform is a potentially viable method for characterizing the high-cycle fatigue deformation of austenitic stainless steel 316 alloys.

关键词： fatigue steel martensite

Suppression of Self-Discharge in Aqueous Supercapacitor Devices Incorporating Highly Polar Nanofiber Separators

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Energy & Environmental Materials 2023年第3期6卷 74-86页

作者： Wesley G.Buxton Simon G.King Vlad Stolojan Advanced Technology Institute University of SurreyGuildford SurreyGU27XHUK

One of the major problems limiting the applications of electric double-layer(EDLC)supercapacitor devices is their inability to maintain their cell voltage over a significant ***-discharge is a spontaneous decay in charged energy,often resulting in fully depleted devices in a matter of ***,a new method for suppressing this self-discharge phenomenon is proposed by using directionally polarized piezoelectric electrospun nanofiber films as separator *** engineering of polyvinylidene fluoride(PVDF)nanofiber films containing a small concentration of sodium dodecyl sulfate(SDS)results in a high proportion of polarβphases,reaching 380.5%of the total *** polarity into the separator material provides a reverse-diode mechanism in the device,such that it drops from an initial voltage of 1.6 down to 1 V after 10 h,as opposed to 0.3 V with a nonpolarized,commercial separator ***,the energy retained for the polarized separator is 37%and 4%for the nonpolarized separator,making supercapacitors a more attractive solution for long-term energy storage.

关键词： piezoelectric polar nanofibers PVDF separators self-discharge supercapacitors

Multi-Generator Discriminator Network Using Texture-Edge Information

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Computers, Materials & Continua 2023年第5期75卷 3537-3551页

作者： Kyeongseok Jang Seongsoo Cho Kwang Chul Son Department of Plasma Bio Display Kwangwoon University20Gwangun-roNowon-guSeoul01897Korea School of Software Soongsil University369Sangdo-roDongjak-guSeoul06978Korea Department of Information Contents Kwangwoon University20Gwangun-roNowon-guSeoul01897Korea

In the proposed paper,a parallel structure type Generative Adversarial Network(GAN)using edge and texture information is *** the existing GAN-based model,many learning iterations had to be given to obtaining an output that was somewhat close to the original data,and noise and distortion occurred in the output image even when learning was *** solve this problem,the proposed model consists of two generators and three discriminators to propose a network in the form of a parallel *** the network,each edge information and texture information were received as inputs,learning was performed,and each character was combined and outputted through the Combine *** this,edge information and distortion of the output image were improved even with fewer iterations than DCGAN,which is the existing GAN-based *** a result of learning on the network of the proposed model,a clear image with improved contour and distortion of objects in the image was output from about 50,000 iterations.

关键词： Deep learning convolution neural network generative adversarial network edge information texture information

New results on stability criteria for neural networks with time-varying delays

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Chinese Physics B 2011年第5期20卷 163-173页

作者： O.M.Kwon J.W.Kwon S.H.Kim School of Electrical Engineering Chungbuk National University410 SungBong-RoHeungduk-guCheongju 361-763Republic of Korea Department of Computer Engineering Kyungwon UniversitySan 65Sujung-guSungnam 461-701Republic of Korea School of Integrated Technology College of EngineeringYonsei University50 Yonsei-RoSeodaemun-guSeoul 120-749Republic of Korea

In this paper, the problem of stability analysis for neural networks with time-varying delays is considered. By constructing a new augmented Lyapunov-Krasovskii＇s functional and some novel analysis techniques, improved delaydependent criteria for checking the stability of the neural networks are established. The proposed criteria are presented in terms of linear matrix inequalities （LMIs） which can be easily solved and checked by various convex optimization algorithms. Two numerical examples are included to show the superiority of our results.

关键词： neural networks time-varying delays stability Lyapunov method

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

Reconfigurable transmissive metasurface with a combination of scissor and rotation actuators for independently controlling beam scanning and polarization conversion

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Microsystems & Nanoengineering 2024年第2期10卷 173-180页

作者： Chhunheng Lor Ratanak Phon Sungjoon Lim Intelligent Semiconductor Engineering Chung-Ang UniversityHeukseok-DongDongjak-GuSeoul06974Republic of Korea School of Electrical and Electronic Engineering Chung-Ang UniversityHeukseok-DongDongjak-GuSeoul06974Republic of Korea

Polarization conversion and beam scanning metasurfaces are commonly used to reduce polarization mismatch and direct electromagnetic waves in a specific direction to improve the strength of a wireless ***,identifying suitable active and mechanically reconfigurable metasurfaces for polarization conversion and beam scanning is a considerable challenge,and the reported metasurfaces have narrow scanning ranges,are expensive,and cannot be independently *** this paper,we propose a reconfigurable transmissive metasurface combined with a scissor and rotation actuator for independently controlling beam scanning and polarization conversion *** metasurface is constructed with rotatable unit cells(UCs)that can switch the polarization state between right-handed(RHCP)and left-handed circular polarization(LHCP)by flipping the UCs to reverse their phase ***,independent beam scanning is achieved using the scissor actuator to linearly change the distance between the *** and experimental results confirm that the proposed metasurface can perform beam scanning in the range of 28°for both the positive and negative regions of a radiation pattern(RHCP and LHCP beams)at an operational frequency of 10.5 GHz.

关键词： beam rotation controlling