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Dynamic recrystallization behavior and strengthening mechanism of a novel Mo-Ti_(3)AlC_(2) alloy at ultrahigh temperature

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Rare Metals 2024年第8期43卷 3946-3960页

作者： Lu yang xin-Yuan Zheng yang Zhao Xi-Ran Wang Fang-Nao Xiao Shi-Zhong Wei School of Materials Science and Engineering Henan University of Science and TechnologyLuoyang 471023China National Joint Engineering Research Center for Abrasion Control and Molding of Metal Materials Henan University of Science and TechnologyLuoyang 471003China Department of Applied Mechanics Univ.Bourgogne FrancheComteFEMTO-ST InstituteCNRS/UF/ENSMM/UTBM25000BesangonFrance

Increasing the recrystallization temperature to achieve better high-temperature performance is critical in the development of molybdenum alloys for ultrahightemperature applications,such as the newest generation of multitype high-temperature nuclear *** this study,an innovative strategy was proposed to improve the performance of molybdenum alloys at high temperature by using the two-dimensional MAX(where M is an early transition metal,A is an A-group element and X is C or N)ceramic material Ti_(3)AlC_(2).The relationships between flow stress,strain rate and temperature were *** microstructure,distribution of misorientation and evolution of dislocations in the Mo-Ti_(3)AlC_(2) alloy were *** microscopic mechanism of the Ti_(3)AlC_(2) phase in the molybdenum alloy at high temperatures was *** experimental results showed that the peak flow stress of Mo-Ti_(3)AlC_(2) at 1600℃ reached 155 MPa,which was161.8% greater than that of pure *** activation energy of thermal deformation of Mo-Ti_(3)AlC_(2) was as large as537 kJ·mol~(-1),which was 17.6% more than that of pure *** recrystallization temperature reached 1600℃ or even *** topological reaction of the Ti_(3)AlC_(2) phase consumed a large amount of energy at high temperatures,resulting in increases in the deformation activation *** structures of AlTi_3 and Ti-O Magneli-phase oxides(Ti_nO_(2n-1)) were formed in-situ,which relied on kink bands and interlayer slip,resulting in many dislocations during ***,the special two-dimensional of the structure Ti_(3)AlC_(2) ceramic inhibited the recrystallization behavior of the Mo *** results of this study can provide theoretical guidance for the development of a new generation of molybdenum alloys for use in ultrahigh-temperature environments.

关键词： Mo alloy Two-dimensional reinforcement Dynamic recrystallization behavior Hot deformation Mechanical properties

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Adaptive Bistable Stochastic Resonance Based Weak Signal Reception in Additive Laplacian Noise

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China Communications 2024年第1期21卷 228-241页

作者： jin Liu Zan Li Qiguang Miao Li yang School of Computer Science and Technology Xidian UniversityXi’an 710071China State Key Laboratory of Integrated Services Networks Xidian UniversityXi’an 710071China

Weak signal reception is a very important and challenging problem for communication systems especially in the presence of non-Gaussian noise,and in which case the performance of optimal linear correlated receiver degrades *** at this,a novel uncorrelated reception scheme based on adaptive bistable stochastic resonance(ABSR)for a weak signal in additive Laplacian noise is *** analyzing the key issue that the quantitative cooperative resonance matching relationship between the characteristics of the noisy signal and the nonlinear bistable system,an analytical expression of the bistable system parameters is *** this basis,by means of bistable system parameters self-adaptive adjustment,the counterintuitive stochastic resonance(SR)phenomenon can be easily generated at which the random noise is changed into a benefit to assist signal ***,it is demonstrated that approximately 8dB bit error ratio(BER)performance improvement for the ABSR-based uncorrelated receiver when compared with the traditional uncorrelated receiver at low signal to noise ratio(SNR)conditions varying from-30dB to-5dB.

关键词： adaptive bistable stochastic resonance additive Laplacian noise low signal to noise ratio uncorrelated reception scheme weak signal reception

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Superior piezoelectric performance with high operating temperature in bismuth ferrite-based ternary ceramics

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Journal of Materials Science & Technology 2024年第2期169卷 172-181页

作者： Yunyao Huang Leiyang Zhang Ruiyi jing yang yang Vladimir Shur Xiaoyong Wei Li jin Electronic Materials Research Laboratory Key Laboratory of the Ministry of EducationSchool of Electronic Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China Faculty of Materials and Manufacturing Key Laboratory of Advanced Functional MaterialsEducation Ministry of ChinaBeijing University of TechnologyBeijing 100124China School of Natural Sciences and Mathematics Ural Federal UniversityEkaterinburg620000Russia

Due to the thermal depolarization effect,adequate piezoelectric performance with high operating temperature is regarded to be challenging to accomplish concurrently in piezoceramics for applications in specific piezoelectric *** this work,we synthesized(0.8−x)BiFeO_(3)-x PbTi_(3)-0.2Ba(Zr_(0.25)Ti_(0.75))O_(3)(abbreviated as BFO-x PT-BZT)ternary solid solutions with 0.15≤x≤0.30 by conventional solid-state reaction *** MPB composition with a coexisting state of rhombohedral-tetragonal phases exhibits enhanced electromechanical properties,including Curie temperature of 380℃,large-signal equivalent piezoelectric coefficient d^(∗)_(33)of 395 pm V^(-1),small-signal piezoelectric coefficient d_(33)of 302 pC N^(-1),and electromechanical coupling factor k_(p)of 50.2%,which is comparable to commercial PZT-5A ceramics,indicating potential in high-temperature ***,in-situ X-ray diffraction(XRD)and piezoelectric force microscopic(PFM)techniques demonstrate that multiphase coexistence and complex nanodomains promote piezoelectric response via *** x=0.24 composition exhibits the highest in-situ d_(33)of 577 pC N^(-1)and good temperature stability in 30−280℃,indicating that BZT-modified BFO-PT ceramics are promising candidates for high-temperature piezoelectric devices.

关键词： High-temperature piezoelectrics Morphotropic phase boundary In-situ technique Domain structure BFO

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Nickel-catalyzed carbonylative four-component 1,4-dicarbofunctionalization of 1,3-enynes

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Science China Chemistry 2024年第6期67卷 2029-2038页

作者： Yan Zhao Qi-Chao Shan Hong xin Pin Gao Xu yang xin-Hua Duan Li-Na Guo Department of Chemistry School of ChemistryXi’an Key Laboratory of Sustainable Energy Material Chemistry and Engineering Research Center of Energy StorageMaterials and DevicesMinistry of EducationXi’an Jiaotong UniversityXi’an710049China School of Electrical Engineering Xi’an Jiaotong UniversityXi’an710049China

An efficient Ni-catalyzed four-component 1,4-carbocarbonylation of 1,3-enynes with activated alkyl halides and arylboronic acids under atmospheric pressure of CO is *** tuning the electronic and steric effects of alkyl radicals,both electronrich and electron-deficient 1,3-enynes were compatible with this *** protocol features mild conditions,broad substrate scope,excellent functional group compatibility and facile gram-scale synthesis,providing a practical approach to the quaternary carbon center-containing allenyl *** study revealed that the acyl-NiIIspecies plays an important role in both the coupling and the alkyl radical generation processes.

关键词： Ni catalysis four-component 1 4-carbocarbonylation 1 3-enynes

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Video caching and scheduling with edge cooperation

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Digital Communications and Networks 2024年第2期10卷 450-460页

作者： Zhidu Li Fuxiang Li Tong Tang Hong Zhang jin yang School of Communication and Information Engineering Chongqing University of Posts and TelecommunicationsChongqing400065China Advanced Network and Intelligent Connection Technology Key Laboratory of Chongqing Education Commission of China Chongqing400065China Key Laboratory of Ubiquitous Sensing and Networking in Chongqing Chongqing400065China

In this paper,we explore a distributed collaborative caching and computing model to support the distribution of adaptive bit rate video *** aim is to reduce the average initial buffer delay and improve the quality of user *** the difference between global and local video popularities and the time-varying characteristics of video popularity,a two-stage caching scheme is proposed to push popular videos closer to users and minimize the average initial buffer *** on both long-term content popularity and short-term content popularity,the proposed caching solution is decouple into the proactive cache stage and the cache update *** the proactive cache stage,we develop a proactive cache placement algorithm that can be executed in an off-peak *** the cache update stage,we propose a reactive cache update algorithm to update the existing cache policy to minimize the buffer *** results verify that the proposed caching algorithms can reduce the initial buffer delay efficiently.

关键词： Video service Distributed and collaborative caching Long-term popularity Short-term popularity

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A learning-based control pipeline for generic motor skills for quadruped robots

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第6期25卷 443-454页

作者： Yecheng SHAO Yongbin jin Zhilong HUANG Hongtao WANG Wei yang Center for X-Mechanics Zhejiang UniversityHangzhou310027China ZJU-Hangzhou Global Scientific and Technological Innovation Center Hangzhou311200China State Key Laboratory of Fluid Power&Mechatronic Systems Zhejiang UniversityHangzhou310058China Institute of Applied Mechanics Zhejiang UniversityHangzhou310027China

Performing diverse motor skills with a universal controller has been a longstanding challenge for legged *** motion imitation-based reinforcement learning(RL)has shown remarkable performance in reproducing designed motor skills,the trained controller is only suitable for one specific type of *** synthesis has been well developed to generate a variety of different motions for character animation,but those motions only contain kinematic information and cannot be used for *** this study,we introduce a control pipeline combining motion synthesis and motion imitation-based RL for generic motor *** design an animation state machine to synthesize motion from various sources and feed the generated kinematic reference trajectory to the RL controller as part of the *** the proposed method,we show that a single policy is able to learn various motor skills ***,we notice the ability of the policy to uncover the correlations lurking behind the reference motions to improve control *** analyze this ability based on the predictability of the reference trajectory and use the quantified measurements to optimize the design of the *** demonstrate the effectiveness of our method,we deploy the trained policy on hardware and,with a single control policy,the quadruped robot can perform various learned skills,including automatic gait transitions,high kick,and forward jump.

关键词： Quadruped robot Reinforcement learning(RL) Motion synthesis Control

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Efficient cache replacement framework based on access hotness for spacecraft processors

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中国空间科学技术（中英文） 2024年第2期44卷 74-88页

作者： GAO xin NIAN Jiawei LIU Hongjin yang Mengfei Beijing Institute of Control Engineering Beijing 100190China Beijing SunWise Space Technology Co. Ltd.Beijing 100190China School of Computer Science and Technology Xidian UniversityXi'an 710071China China Academy of Space Technology Beijing 100094China

A notable portion of cachelines in real-world workloads exhibits inner non-uniform access ***,modern cache management rarely considers this fine-grained feature,which impacts the effective cache capacity of contemporary high-performance spacecraft *** harness these non-uniform access behaviors,an efficient cache replacement framework featuring an auxiliary cache specifically designed to retain evicted hot data was *** framework reconstructs the cache replacement policy,facilitating data migration between the main cache and the auxiliary *** traditional cacheline-granularity policies,the approach excels at identifying and evicting infrequently used data,thereby optimizing cache *** evaluation shows impressive performance improvement,especially on workloads with irregular access *** from fine granularity,the proposal achieves superior storage efficiency compared with commonly used cache management schemes,providing a potential optimization opportunity for modern resource-constrained processors,such as spacecraft ***,the framework complements existing modern cache replacement policies and can be seamlessly integrated with minimal modifications,enhancing their overall efficacy.

关键词： spacecraft processors cache management replacement policy storage efficiency memory hierarchy microarchitecture

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Quantitative method for calculating spatial release region for laser-guided bomb

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Journal of Systems Engineering and Electronics 2024年第4期35卷 1053-1062页

作者： yang Ping XIAO Bing CHEN xin HAO Yuntao Air Force Early Warning Academy Wuhan 430019China Unit 93175 of the PLA Changchun 136000China

The laser-guided bomb(LGB)is an air-to-ground pre-cision-guided weapon that offers high hit rates,great power,and ease of *** are guided by semi-active laser ground-seek-ing technology,which means that atmospheric conditions can affect their *** spatial release region(SRR)of LGBs is difficult to calculate precisely,especially when there is a poor field of *** can result in a lower real hit *** increase the hit probability of LGBs in tough atmospheric situa-tions,a novel method for calculating the SRR has been *** method is based on the transmittance model of the 1.06μm laser in atmospheric species and the laser diffuse reflection model of the target surface to determine the capture target time of the laser ***,it calculates the boundary ballistic space starting position by ballistic model and gets the spatial scope of the spatial release *** method can determine the release region of LGBs based on flight test data such as instantaneous velocity,altitude,off-axis angle,and atmospheric *** more effectively employing aircraft release conditions,atmospheric visibility and other factors,the SRR calculation method can improve LGB hit probabi-lity by 9.2%.

关键词： laser-guided bombs(LGBs) hit probability atmo-spheric transmittance spatial release region(SRR)boundary ballistic

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An Investigation into the Performances of Cement Mortar Incorporating Superabsorbent Polymer Synthesized with Kaolin

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Fluid Dynamics & Materials Processing 2024年第6期20卷 1393-1406页

作者： Xiao Huang jin yang State Key Laboratory of Featured Metal Materials and Life-Cycle Safety for Composite Structures and School of ResourcesEnvironment and MaterialsGuangxi UniversityNanning530004China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China School of Civil Engineering Architecture and EnvironmentHubei University of TechnologyWuhan430068China

Cement-based materials are fundamental in the construction industry,and enhancing their properties is an ongoing *** use of superabsorbent polymers(SAP)has gained significant attention as a possible way to improve the performance of cement-based materials due to their unique water-absorption and retention *** study investigates the multifaceted impact of kaolin intercalation-modified superabsorbent polymers(K-SAP)on the properties of cement *** results show that K-SAP significantly affects the cement mortar’s rheological behavior,with distinct phases of water absorption and release,leading to changes in workability over ***,K-SAP alters the hydration kinetics,delaying the exothermic peak of hydration and subsequently modifying the heat release ***,K-SAP effectively maintains a higher internal relative humidity within the mortar,reducing the autogenous shrinkage ***,K-SAP can have a beneficial effect on pore structure and this can be ascribed to the internal curing effect of released water from K-SAP.

关键词： Superabsorbent polymer kaolin cement mortar rheological behavior autogenous shrinkage

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Coordination-driven self-assembly of a molecular 818knot and molecular borromean rings

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Science China Chemistry 2024年第11期67卷 3652-3656页

作者： Xiang Gao Dong Liu Hai-Ning Zhang Guo-xin jin Department of Chemistry Fudan University

We report the facile construction of a molecular 818knot and a molecular Borromean rings assembly through self-assembly directed by Cp*Rh corner units. Two curved ligands of similar size and shape were used in this study. The slight steric differences between the two ligands induce the formation of distinctly different topologies of the assembled products. The structures were confirmed by single-crystal X-ray analysis and nuclear magnetic resonance spectroscopy.

关键词： coordination-driven Cp*Rh 818 knot Borromean rings

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