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The anelastic origin of mechanical cycling induced rejuvenation in the metallic glass

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Science China(Physics,Mechanics & Astronomy) 2023年第8期66卷 93-100页

作者： Langting Zhang yunjiang wang Yong Yang Jichao Qiao School of Mechanics CivilEngineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 70072China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Department of Mechanical Engineering College of EngineeringCity University of Hong KongHong Kong 999077China Department of Materials Science and Engineering College of EngineeringCity University of Hong KongHong Kong 999077China Innovation Center NPU-ChongqingChongqing 401135China

Mechanical cycling is one of the effective methods to rejuvenate metallic glasses(MGs)and improve their mechanical *** anelastic origin of the rejuvenation by mechanical cycling in a La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10) MG was investigated via differential scanning calorimetry(DSC)and dynamic mechanical analysis(DMA).We demonstrate that mechanical cycling promotes the activation of flow defects with short relaxation times,leading to anelastic strains and therefore considerable energy storage,which manifests itself as larger relaxation enthalpy on the DSC curves of ***,the MGs release the excess relaxation enthalpy caused by anelastic strain with time,thus suppressing atomic mobility and elevating β relaxation activation *** strategy of mechanical cycling at small strains,as demonstrated in the current work,can expand the energy states of MGs over a wide range of relaxation enthalpies.

关键词： metallic glass mechanical cycling rejuvenation anelastic strain structural heterogeneity

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Influence of oscillation strain on the dynamic mechanical relaxation of a La-based metallic glass

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Science China(Technological Sciences) 2023年第11期66卷 3309-3316页

作者： LIANG ShuYi ZHANG LangTing wang yunjiang PINEDA E QIAO JiChao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Department of Physics Institute of Energy TechnologiesUniversitat Politècnica de Catalunya–BarcelonaTechBarcelona 08019Spain Innovation Center NPU-ChongqingChongqing 401135China

Dynamic mechanical relaxation processes,particularly secondary relaxation processes,are closely related to the mechanical and physical properties of metallic *** the effect of oscillation strain amplitude on the secondary relaxation of a typical Labased metallic glass was studied using the dynamic mechanical analysis *** apparent activation energy of theβrelaxation is shown to increase with the oscillation strain *** it changes from 0.02%to 0.16%,the activation energy increases from 0.73 to 0.96 ***,the intensity of theβrelaxation shifts toward high ***,the apparentβrelaxation is found to be sensitive to the physical aging below the glass transition *** findings suggest a correlation between the inelastic deformation and the relaxation behavior of amorphous metals.

关键词： metallic glass dynamic mechanical analysis internal friction βrelaxation oscillation amplitude

Factoring larger integers with fewer qubits via quantum annealing with optimized parameters

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Science China(Physics,Mechanics & Astronomy) 2019年第6期62卷 5-12页

作者： wangChun Peng BaoNan wang Feng Hu yunjiang wang XianJin Fang XingYuan Chen Chao wang Key Laboratory of Specialty Fiber Optics and Optical Access Networks Joint International Research Laboratory of Specialty Fiber Optics and Advanced Communication Shanghai Institute for Advanced Communication and Data ScienceShanghai University State Key Laboratory of Integrated Services Networks (ISN) Xidian University School of Computer Science and Technology Engineering Anhui University of Science and Technology State Key Laboratory of Cryptology

RSA cryptography is based on the difficulty of factoring large integers, which is an NP-hard(and hence intractable) problem for a classical computer. However, Shor's algorithm shows that its complexity is polynomial for a quantum computer, although technical difficulties mean that practical quantum computers that can tackle integer factorizations of meaningful size are still a long way away. Recently, Jiang et al. proposed a transformation that maps the integer factorization problem onto the quadratic unconstrained binary optimization(QUBO) model. They tested their algorithm on a D-Wave 2000 Q quantum annealing machine, raising the record for a quantum factorized integer to 376289 with only 94 qubits. In this study, we optimize the problem Hamiltonian to reduce the number of qubits involved in the final Hamiltonian while maintaining the QUBO coefficients in a reasonable range, enabling the improved algorithm to factorize larger integers with fewer qubits. Tests of our improved algorithm using D-Wave's hybrid quantum/classical simulator qbsolv confirmed that performance was improved, and we were able to factorize 1005973, a new record for quantum factorized integers, with only 89 qubits. In addition, our improved algorithm can tolerate more errors than the original one. Factoring 1005973 using Shor's algorithm would require about 41 universal qubits,which current universal quantum computers cannot reach with acceptable accuracy. In theory, the latest IBM Q System OneTM(Jan. 2019) can only factor up to 10-bit integers, while the D-Wave have a thousand-fold advantage on the factoring scale. This shows that quantum annealing machines, such as those by D-Wave, may be close to cracking practical RSA codes, while universal quantum-circuit-based computers may be many years away from attacking RSA.

关键词： integer factorization quantum annealing QUBO D-Wave

Tailoring the mechanical properties of bulk metallic glasses via cooling from the supercooled liquid region

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Science China(Technological Sciences) 2023年第1期66卷 173-180页

作者： ZHANG LangTing DUAN YaJuan wang yunjiang YANG Yong QIAO JiChao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China Department of Physics Barcelona Research Center in Multiscale Science and TechnologyInstitute of Energy TechnologiesUniversitat PolitecnicadeCatalunyaBarcelona08019Spain State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Department of Mechanical Engineering College of EngineeringCity University of Hong KongHong Kong 999077China Department of Materials Science and Engineering College of EngineeringCity University of Hong KongHong Kong 99077China Innovation Center NPU-ChongqingChongqing 401135China

Structural rejuvenation is vital and attractive for modulating the energetic state and structural heterogeneity of bulk metallic glasses(BMGs). In this paper, we show that cooling a BMG from a supercooled liquid region at laboratory rates can reverse the relaxation enthalpy lost during the preceding structural relaxation. Increasing the cooling rate is beneficial for enhancing atomic mobility and dynamic mechanical relaxation intensity. Therefore, this rejuvenation methodology promotes tailoring the mechanical properties of BMGs and provides a comprehensive understanding of the rejuvenation mechanism.

关键词： bulk metallic glass thermal rejuvenation supercooled liquid region mechanical relaxation structural heterogeneity

On the parity-check matrix of generalized concatenated code

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Science China(Information Sciences) 2020年第4期63卷 233-235页

作者： Sha SHI Yang LIU Junzhi YAN Jingliang GAO yunjiang wang Engineering Research Center of Molecular and Neuro Imaging Ministry of Education School of Life Science and Technology Xidian University National Computer Network Emergency Response Technical Team/Coordination Center of China China Mobile Research Institute State Key Laboratory of Integrated Services Networks Xidian University

Dear editor,Single-level concatenation using a nonbinary code as outer code and a binary code as inner code is widely used in communication and digital data storage systems to achieve high reliability with reduced decoding complexity [1]. Moreover, concatenation can be multilevel, where multiple outer codes are concatenated with multiple inner codes

关键词： On the parity-check matrix of generalized concatenated code

Surface defect and lattice engineering of Bi_(5)O_(7)Br ultrathin nanosheets for efficient photocatalysis

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Nano Research 2023年第1期16卷 248-255页

作者： Yunjing wang Hongchen He yunjiang wang Meili Xie Feng Jing Xianhong Yin Feilong Hu Yan Mi Key Laboratory of Chemistry and Engineering of Forest Products State Ethnic Affairs CommissionGuangxi Key Laboratory of Chemistry and Engineering of Forest ProductsGuangxi Collaborative Innovation Center for Chemistry and Engineering of Forest ProductsGuangxi Minzu UniversityNanning 530006China

The effective separation and migration of photogenerated charge carriers in bulk and on the surface of photocatalysts will significantly promote photocatalytic ***,the synchronous regulation of photocharges on both counts is ***,the simultaneous separation of bulk and surface photocharges is conducted to enhance photocatalytic activity by coupling the surface defects and lattice engineering of bismuth *** depth-modulated Bi_(5)O_(7)Br ultrathin nanosheets with an abundance of bismuth in the crystal structure increased the internal electric field,which propelled the separation and migration of photocharges from bulk to the *** of oxygen vacancies(OVs)on the nanosheet surface forms local electric fields,which can stimulate the migration of charges to active sites on the catalyst ***,the OV-assembled Bi_(5)O_(7)Br nanosheets demonstrated enhanced photocatalytic degradation efficiency under simulated solar-light *** study proved the possibility of charge governing via electric field modulation based on an integrated strategy.

关键词： lattice engineering internal electric field oxygen vacancies photocharge separation bismuth oxybromide

Dynamic mechanical relaxation and thermal creep of high-entropy La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10)bulk metallic glass

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Science China(Physics,Mechanics & Astronomy) 2021年第9期64卷 93-103页

作者： LangTing Zhang YaJuan Duan Daniel Crespo Eloi Pineda yunjiang wang Jean-Marc Pelletier JiChao Qiao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi’an 710072China Department of Physics Barcelona Research Center in Multiscale Science and TechnologyInstitute of Energy TechnologiesUniversitat Politècnica de CatalunyaBarcelona 08019Spain State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 101408China MATEIS UMR CNRS5510Universitéde LyonINSA-LyonVilleurbanne Cedex F-69621

Dynamic mechanical relaxation is a fundamental tool to understand the mechanical and physical properties of viscoelastic materials like *** spectroscopy shows that the high-entropy bulk metallic glass(La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10))exhibits a distinctβ-relaxation *** the present research,dynamic mechanical analysis and thermal creep were performed using this bulk metallic glass material at a temperature domain around theβ*** components of total strain,including ideal elastic strain,anelastic strain,and viscous-plastic strain,were analyzed based on the model of shear transformation zones(STZs).The stochastic activation of STZ contributes to the anelastic *** the temperature or external stress is high enough or the timescale is long enough,the interaction between STZs induces viscous-plastic *** all the spectrum of STZs is activated,the quasi-steady-state creep is achieved.

关键词： high-entropy bulk metallic glass mechanical relaxation creep recovery process shear transformation zone structural heterogeneity

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Ultra‑Efficient and Cost‑Effective Platinum Nanomembrane Electrocatalyst for Sustainable Hydrogen Production

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Nano-Micro Letters 2024年第6期16卷 95-110页

作者： Xiang Gao Shicheng Dai Yun Teng Qing wang Zhibo Zhang Ziyin Yang Minhyuk Park Hang wang Zhe Jia yunjiang wang Yong Yang Department of Mechanical Engineering College of EngineeringCity University of Hong KongTat Chee AvenueKowloon TongKowloonHong KongPeople’s Republic of China State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijingPeople’s Republic of China School of Engineering Science University of Chinese Academy of SciencesBeijingPeople’s Republic of China Laboratory for Microstructures Institute of MaterialsShanghai UniversityShanghaiPeople’s Republic of China School of Materials Science and Engineering Jiangsu Key Laboratory for Advanced Metallic MaterialsSoutheast UniversityNanjingPeople’s Republic of China Department of Materials Science and Engineering College of EngineeringCity University of Hong KongTat Chee AvenueKowloon TongKowloonHong KongPeople’s Republic of China

Hydrogen production through hydrogen evolution reaction(HER)offers a promising solution to combat climate change by replacing fossil fuels with clean energy ***,the widespread adoption of efficient electrocatalysts,such as platinum(Pt),has been hindered by their high *** this study,we developed an easy-to-implement method to create ultrathin Pt nanomembranes,which catalyze HER at a cost significantly lower than commercial Pt/C and comparable to non-noble metal *** Pt nanomembranes consist of highly distorted Pt nanocrystals and exhibit a heterogeneous elastic strain field,a characteristic rarely seen in conventional *** unique feature results in significantly higher electrocatalytic efficiency than various forms of Pt electrocatalysts,including Pt/C,Pt foils,and numerous Pt singleatom or single-cluster *** research offers a promising approach to develop highly efficient and cost-effective low-dimensional electrocatalysts for sustainable hydrogen production,potentially addressing the challenges posed by the climate crisis.

关键词： Platinum Hydrogen evolution reaction Lattice distortion Heterogeneous strain

Deciphering the α relaxation and the anelastic-to-plastic transition in the deep glassy state

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Science China(Physics,Mechanics & Astronomy) 2024年

作者： Qi Hao Guanghui Xing Eloi Pineda Claudio Fusco Laurent Chazeau Jean-Marc Pelletier yunjiang wang Yong Yang Jichao Qiao School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical University Department of Physics Institute of Energy TechnologiesUniversitat Politècnica de Catalunya Univ Lyon INSA LyonUniversitéClaude Bernard Lyon 1CNRSMATEISUMR5510 State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of Sciences School of Engineering Science University of Chinese Academy of Sciences Department of Mechanical Engineering College of EngineeringCity University of Hong Kong Department of Materials Science and Engineering College of EngineeringCity University of Hong Kong State Key Laboratory of Clean and Efficient Turbomachinery Power Equipment Northwestern Polytechnical University Key Laboratory of Aircraft Structural Integrity Ministry of Industry and Information Technology

In contrast to their conventional crystalline counterparts,amorphous solids exhibit diverse dynamic relaxation mechanisms under external *** challenge to understanding their behavior lies in unifying microscopic dynamics,relaxation,and macroscopic *** study establishes a potential link by quantifying the characteristic time of the anelastic-to-plastic transition through dynamic mechanical relaxation and stress relaxation tests across a wide temperature range in both the supercooled liquid and the glassy *** is found that the stress relaxation time in the glassy solids follows an Arrhenius relationship,aligning with the main α relaxation time,and unveils a finding:α relaxation continues to govern deformation even below the glass transition,challenging previous assumptions of the role of secondary β relaxation.A hierarchically constrained atomic dynamics model rationalizes the temperature dependence of α relaxation and the transition from β to α relaxation,also providing evidence that the stretched exponent in the Kohlrausch-Williams-Watts equation can serve as an order *** work highlights the role of α relaxation in the glassy state and contributes to elucidating the potential correlation between relaxation and deformation in amorphous materials.

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