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Microstructure Evolution and Strain-Dependent Constitutive Modeling to Predict the Flow Behavior of 20Cr–24Ni–6Mo Super-Austenitic Stainless Steel During Hot Deformation

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Acta Metallurgica Sinica(English Letters) 2018年第4期31卷 401-414页

作者： Yan-sen Hao Wan-Chun liu Zhen-Yu liu State Key Laboratory of Rolling and Automation Northeastern University

Hot compression tests were carried out with specimens of 20Cr-24Ni-6Mo super-austenitic stainless steel at strain rate from 0.01 to 10 s^-1 in the temperature range from 950 to 1150 ℃,and flow behavior was *** analysis indicated that dynamic recrystallization（DRX）behavior was more sensitive to the temperature than strain rate,and full DRX was obtained when the specimen deformed at 1150℃.When the temperature reduced to 1050 ℃,full DRX was completed at the highest strain rate 10 s-l rather than at the lowest strain rate 0.01 s-1 because the adiabatic heating was pronounced at higher strain *** addition,flow behavior reflected in flow curves was inconsistent with the actual microstructural evolution during hot deformation,especially at higher strain rates and lower ***,flow curves were revised in consideration of the effects of adiabatic heating and friction during hot *** results showed that adiabatic heating became greater with the increase of strain level,strain rate and the decrease of temperature,while the frictional effect cannot be neglected at high strain ***,based on the revised flow curves,strain-dependent constitutive modeling was developed and verified by comparing the predicted data with the experimental data and the modified *** result suggested that the developed constitutive modeling can more adequately predict the flow behavior reflected by corrected flow curves than that reflected by experimental flow curves,even though some difference existed at 950℃ and 0.01 s^-*** main reason was that plenty of precipitates generated at this deformation condition and affected the DRX behavior and deformation behavior,eventually resulted in dramatic increase of deformation resistance.

关键词： Super-austenitic stainless steel Hot compression Adiabatic heating Constitutive modeling Microstructure evolution

Multicomponent Self-assembly: Spontaneous Formation of a Metallomacrocycle from Two Quinoline Based Linear Ligands and Four Silver(Ⅰ) Nitrates

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Chemical Research in Chinese Universities 2000年第3期16卷 273-275页

作者： LIAO sen XU An wu SU Cheng yong ZHANG ze fu YANG Xiao ping KANG Bei sheng liu Han qin School of Chemistry and Chemical Engineering Zhongshan UniversityGuangzhou 510275China Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Aademy of SciencesLanzhou730000China

A tetrametallotricyclic molecule is constructed by the spontaneous self-assembly of six components altogether consisting of two types of ligands and one type of metal ion. The unprecedented dimension and topology of the complex is derived from the flexible behavior of the ligands. The π-π interactions facilitate the formation of box-like cavity by rigid quinoline rings, while the soft oligoethylene glycol skeleton makes it easy to wrap around to form a macrocycle.

关键词： Silver(Ⅰ) complex Metallosupramolecular complex Self-assembly

A Low-Profile Cylindrical Dielectric Resonator Antenna with Bandwidth-Enhancement Under Triple-Mode Resonance

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Journal of Communications and Information Networks 2020年第4期5卷 447-456页

作者： sen Gao Nengwu liu Guang Fu 不详 State Key Laboratory of Millimeter Waves Nanjing 210096China

A low-profile cylindrical dielectric resonator antenna(CDRA)with enhanced impedance bandwidth is proposed via sharing a single triple-mode dielectric ***,the resonant frequencies of TM01d and TM02d modes of a conventional CDRA are maintained far away from each other under central probe ***,a circular disk with an annular ring is loaded around the conventional CDRA,aiming to excite an additional mode between these dual *** electric fields demon-strate that the previous TM_(02δ) mode is transformed into the TM03d mode for the modified CDRA,and an additional TM_(02δ) mode is successfully excited between the TM_(01δ) and TM_(03δ) *** a result,the resonant frequencies of these three radiative modes are reallocated in proximity to each other,thus achieving the desired bandwidth *** addition,considering the small input impedance of the CDRA,a microstrip feeding line is introduced underneath the central probe for good impedance *** these arrangements,the resultant antenna can generate an extended bandwidth under simultaneous radiation of TM_(01δ),TM_(02δ),and TM_(03δ) ***,the proposed CDRA is designed,fabricated,and measured to validate the predicted *** simulated and measured results show that the impedance bandwidth(|S11|<-10 dB of the antenna is dramatically extended from 8%to about 62%(2.835.36 GHz),while keeping a stable conical radiation *** particular,a low profile property of about 0.15 free space wavelength is achieved as well.

关键词： dielectric resonator antenna triple-mode resonance wide impedance bandwidth low profile

Multi-objective optimization for 10-kW rated power dynamic wireless charging systems of electric vehicles

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Science China(Information Sciences) 2022年第10期65卷 178-195页

作者： ze ZHOU Zhitao liu Hongye SU Liyan ZHANG State Key Laboratory of Industrial Control Technology Institute of Cyber-Systems and Control Zhejiang University School of Automation Wuhan University of Technology

In this paper, we propose a method to optimize the output power, efficiency, and cost of the dynamic wireless charging(DWC) system of electric vehicles by using the transmitting coil spacing as the decision variable. In a set of transmitting equipment, we adopt a structure with two transmitting networks in parallel and derive loss models. The expressions of the output power and efficiency of the DWC system are obtained by data fitting. In addition, combined with the proposed cost function, we construct a multiobjective optimization problem on output power, efficiency, and cost. Due to the complexity of the objective function, it is difficult to solve the problem by the analytic method, and thus we propose a constrained adaptive particle swarm optimization(CAPSO) algorithm with high accuracy to solve the problem. Finally,the simulation results verify the feasibility of the proposed model. The advantages of the proposed CAPSO algorithm and the optimization results under different weight combinations are presented.

关键词： dynamic wireless charging electric vehicles multi-objective optimization constrained adaptive particle swarm optimization

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Cooperative Covert Communication in Multi-Antenna Broadcast Channels

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China Communications 2024年第6期21卷 246-260页

作者： Qiao sen liu Guangjie Ji Xiaopeng liu Weiwei School of Electrical and Information Engineering Nanjing University of Information Science and TechnologyNanjing 210044China School of Automation Nanjing University of Science and TechnologyNanjing 210094China

With the gradual popularization of 5G communications,the application of multi-antenna broadcasting technology has become ***,this study aims to investigate the wireless covert communication in the two-user cooperative multi-antenna broadcast *** focus on the issue that the deteriorated reliability and undetectability are mainly affected by the transmission *** tackle this issue,we design a scheme based on beamforming to increase the reliability and undetectability of wireless covert communication in the multi-antenna broadcast *** first modeled and analyzed the cooperative multi-antenna broadcasting system,and put forward the target *** we use the SCA(successive convex approximation)algorithm to transform the target problem into a series of convex *** the convex problems are solved and the covert channel capacity is *** order to verify the effectiveness of the scheme,we conducted simulation *** simulation results show that the proposed beamforming scheme can effectively improve the reliability and undetectability of covert communication in multi-antenna broadcast channels.

关键词： beamforming covert communication multi-antenna broadcast channels OFDM

A novel approach to with a preparing ultra-lightweight ceramsite large amount of fly ash

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Frontiers of Environmental Science & Engineering 2020年第4期14卷 77-87页

作者： sen liu Congren Yang Wei liu Longsheng Yi Wenqing Qin School of Minerals Processing and Bioengineering Central South UniversityChangsha 410083China Key Laboratory of Hunan Province for Clean and Efficient Utilization of Strategic Calcium-containing Mineral Resources Central South UniversityChangsha 410083China

The disposal of fly ash has become a serious problem in China due to its rapid increase in volume in recent *** most common method of fly ash disposal is solidification-stabilization-landfill,and the most common reuse is low-value-added building materials.A novel processing method for preparing ultra-lightweight ceramsite with fly ash was *** results show that the optimal parameters for preparation of ultra-lightweight ceramsite are as follows:mass ratio of fly ash:kaolin:diatomite=80:15:5,preheating temperature of 800℃,preheating time of 5 min,sintering temperatiire of 1220℃,and sintering time of 10 *** expansion agent is perlite,at 10 wt.% ***,a ceramsite with bulk density of 340 kg/m3,particle density of 0.68 g/cm3,and cylinder compressive strength of 1.02 MPa was *** of its low density and high porosity,ultra-lightweight ceramsite has excellent thermal insulation performance,and its strength is generally low,so it is usually used in the production of thermal insulation concrete and its *** formation of a liquid-phase component on the surface,and generation of a gas phase inside ceramsite during the sintering process,make it possible to control the production of the suitable liquid phase and gas in this system,resulting in an optimization of the expansion behavior and microstructure of *** characteristics show the feasibility of industrial applications of fly ash for the production of ultralightweight ceramsite,which could not only produce economic benefits,but also conserve land resources and protect the environment.

关键词： Fly ash Ultra-lightweight ceramsite Expansion mechanism Sintering process

Asymptotic false discovery control of the Benjamini-Hochberg procedure for pairwise comparisons

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Science China Mathematics 2025年第1期 223-252页

作者： Weidong liu Dennis Leung Qi-Man Shao School of Mathematical Sciences Shanghai Jiao Tong University School of Mathematics and Statistics University of Melbourne Department of Statistics and Data Science SICMSouthern University of Science and Technology

In a one-way analysis-of-variance(ANOVA) model,the number of pairwise comparisons can become large even with a moderate number of *** by this,we consider a regime with a growing number of groups and prove that,when testing pairwise comparisons,the Benjamini-Hochberg(BH) procedure can asymptotically control false discoveries,despite the fact that the involved t-statistics do not exhibit the wellknown positive dependence structure required for exact false discovery rate(FDR) *** Tukey's perspective that the difference between the means of any two groups cannot be exactly zero,our main result provides control over the directional false discovery rate and directional false discovery proportion.A key technical contribution of our work is demonstrating that the dependence among the t-statistics is sufficiently weak to establish the convergence result typically required for asymptotic FDR *** analysis does not rely on conventional assumptions such as normality,variance homogeneity,or a balanced design,thereby offering a theoretical foundation for applications in more general settings.

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Paleoglacial and paleoclimate reconstructions during the global Last Glacial Maximum in the Longriba area, eastern Tibetan Plateau

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Journal of Mountain Science 2021年第2期18卷 307-322页

作者： YANG Wei-lin HAN Ye-song PENG Xu RAN ze-ze liu Qing liu Geng-nian College of Urban and Environmental Sciences Peking UniversityBeijing 100871China

Owing to the remoteness of the Longriba area and the lack of dating records,it is extremely challenging to reconstruct the chronology and extent of the paleoglaciers in this *** this paper,we combined limited observational data with automated modelling for paleoglacial *** first identified a broadly distributed paleoglacier from satellite imagery and field investigation based on the sediment-landform assemblage principle and dated it to 23.1±1.4~19.5±1.2 ka by ^(10)Be exposure dating,corresponding to the global Last Glacial Maximum(gLGM).Then,we reconstructed the extent and ice surface of 171 paleoglaciers formed during the similar period based on geomorphological evidence and‘ice surface profile’*** results showed that the paleoglacial coverage was 426.5 km2,with an ice volume of 38.1 km^(3),in the Longriba *** reconstructed equilibrium line altitudes(ELAs)based on modelled ice surfaces yielded an average of 4245±66 m above sea level(asl),~725±73 m lower than the present ELA(4970±29 m asl).The temperature was~5.51-6.68℃lower,and the precipitation was~30-34%less in Longriba,during the gLGM compared to the present *** glacial advance was mainly driven by colder climate that was synchronous with Northern Hemisphere cooling events.

关键词： Ice surface profile ^(10)Be surface exposure dating Paleoglacial reconstruction Paleoclimate reconstruction Global Last Glacial Maximum Eastern Tibetan Plateau

The Effect of Retardation on the Spontaneous Breaking of Chiral Symmetry in GCM

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Communications in Theoretical Physics 2001年第11期36卷 589-592页

作者： YANG Sheng-Dong ZHAI Chen-Yang ZHOU Zhi-Ning YANG ze-sen Department of Physics Peking UniversityBeijing 100871China Department of Technical PhysicsPeking UniversityBeijing 100871China Department of PhysicsPeking UniversityBeijing 100871China Department of PhysicsPeking UniversityBeijing 100871China

An effective Hamiltonian including current-current coupling from the global color symmetry model is -R2 *** effects are introduced by the factor ( R/ ) e ,instead of δ (r) in the correlation kernel,from which the retardation gap equation with α-α coupling in the 3po vacuum is obtained,qq condensations of different retardation parameters R with or without the α-α term are *** results show the effects of retardation,and indicate that the typical value of R is about 2 fm-1 at reasonable value of qq *** while taking typical value 1 fm-1 of R,the condensation 1/3 is about 13% larger than that with no retardation *** the α-αterms,the condensation (qq) 1/3 is about 17%o larger than that without it for all values of the parameter *** shows that the retardation effects and the α-α terms are important for further studying in the Iow-energy region.

关键词： effect of retardation,condensation,spontaneous breaking of chiral symmetry