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Effect of Ti_(p) Content on the Work Hardening and Softening Behavior of Mg-Zn-Ca Alloy

Acta Metallurgica Sinica(English Letters) 2024年第3期37卷 551-560页

作者： jin-kai zhang Cui-Ju Wang Yi-Dan Fan Chao Xu kai-Bo Nie Kun-Kun Deng Shanxi Key Laboratory of Advanced Magnesium-Based Materials College of Materials Science and EngineeringTaiyuan University of TechnologyTaiyuan 030024China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

The Ti_(p)/ZX60 composites with different Ti_(p) contents were prepared by semi-solid stirring *** extrusion,the microstructure,work hardening and softening behavior of the Ti_(p)/ZX60 composites were analyzed compared with the ZX60(Mg-6Zn-0.2Ca)*** results showed that the addition of Ti_(p) could not only promote the nucleation of dynamic recrystallized(DRXed)grains,but also be propitious to the refinement of DRXed *** increasing Ti_(p) content,the size of DRXed grains decreased accompanied with increasing volume fraction of DRXed *** the Ti_(p) content increased to 15 vol.%,the average size and volume fraction of DRXed grains reached to~0.32μm and 93.2%,***,both the strength and elongation were improved by the addition of Ti_(p).With increasing content of Ti_(p),a substantial increase in the strength was achieved with little change in the ***,the elongation decreased sharply when the Ti_(p) content further increased to 15 vol.%.The addition of Ti_(p) led to an increase in the work hardening rate,which gradually increased with increasing Ti_(p) ***,the softening rate did not demonstrate the same tendency with increasing Ti_(p) *** the conventional ceramic particles,the Ti_(p) can be deformed in coordination with the matrix alloy,which imparted a higher softening rate to the matrix *** though the softening rate improved as the Ti_(p) content increased from 5 to 10 vol.%,it dropped deeply as the Ti_(p) content increased to 15 vol.%owing to the fracture of Ti_(p) during extrusion.

关键词： Titanium particle content Particle reinforced magnesium matrix composites Work hardening Softening behavior Mechanical properties

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Prescribed Performance Tracking Control of Time-Delay Nonlinear Systems With Output Constraints

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IEEE/CAA Journal of Automatica Sinica 2024年第7期11卷 1557-1565页

作者： jin-Xi zhang kai-Di Xu Qing-Guo Wang IEEE the State Key Laboratory of Synthetical Automation for Process Industries Northeastern UniversityShenyang 110819China Institute of Artificial Intelligence and Future Networks Beijing Normal UniversityZhuhai 519087 Guangdong Key Laboratory of Artificial Intelligence and Multi-Modal Data Processing Beijing Normal University-Hong Kong Baptist University United International CollegeZhuhai 519087

The problem of prescribed performance tracking control for unknown time-delay nonlinear systems subject to output constraints is dealt with in this paper. In contrast with related works, only the most fundamental requirements, i.e., boundedness and the local Lipschitz condition, are assumed for the allowable time delays. Moreover, we focus on the case where the reference is unknown beforehand, which renders the standard prescribed performance control designs under output constraints infeasible. To conquer these challenges, a novel robust prescribed performance control approach is put forward in this ***, a reverse tuning function is skillfully constructed and automatically generates a performance envelop for the tracking error. In addition, a unified performance analysis framework based on proof by contradiction and the barrier function is established to reveal the inherent robustness of the control system against the time delays. It turns out that the system output tracks the reference with a preassigned settling time and good accuracy,without constraint violations. A comparative simulation on a two-stage chemical reactor is carried out to illustrate the above theoretical findings.

关键词： Nonlinear systems output constraints prescribed performance reference tracking time delays

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Ignition and Lean Blowout Characteristics of a Reverse-Flow Combustor for an Ultra-Compact Gas Turbine Engine

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Journal of Thermal Science 2024年第5期33卷 1897-1906页

作者： jin Yi HUANG Yakun YAO Kanghong zhang kai WANG Yunbiao WANG Donghao College of Energy and Power Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China National Key Laboratory of Transient Physics Nanjing University of Science and TechnologyNanjing 210094China Low-carbon Aerospace Power Engineering Research Center of Ministry of Education Nanjing 210016China

The flame stability limit and propagation characteristics of a reverse-flow combustor without any flame-stabilized device were experimentally investigated under room temperature and *** results indicate that it is feasible to stabilize the flame in the recirculation zones constructed by the impact jet flow from the primary holes and dilution *** flame projected area is mainly distributed in the recirculation zone upstream of the primary holes,whose presence and absence mark the ignition and *** the ignition process,the growth rate and value of the flame projected area first increase and then decrease with the inlet velocity increasing from 9.4 m/s to 42.1 m/s.A rapid reduction followed by a slow reduction of ignition and lean blowout equivalence ratios is achieved by the increased inlet *** the non-reacting fluid structure in three sections was measured,and detailed velocity profiles were analyzed to improve the understanding of the flame stabilization *** results are conducive to the design of an ultra-compact combustor.

关键词： ultra-compact combustor gas turbine reverse-flow combustor ignition lean blowout

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N,O-Bidentated difluoroboron complexes based on pyridine-ester enolates:Facile synthesis,post-complexation modification,optical properties,and applications

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Chinese Chemical Letters 2024年第9期35卷 169-174页

作者： Chaochao jin kai Li Jiongpei zhang Zhihua Wang Jiajing Tan College of Chemistry Beijing University of Chemical Technology(BUCT)Beijing 100029China College of Materials Science and Engineering Shenzhen UniversityShenzhen 518055China

An array of pyridine-ester enolate based organoboron complexes has been designed and synthesized via a one-pot cascade of Pd-catalyzedα-arylation and *** rapid structure-activity relationship(SAR)studies indicated that unsymmetrical N,O-chelated BF2complexes were highly fluorescent in solid state,and exhibited large Stokes shifts,excellent photostability,along with insensitivity to p ***α-aryl group could not only modulate the electronic effect but also inhibit the intermolecularπ-πstacking to promote the aggregation-induced emission(AIE)*** calculations and experiments identified that the intramolecular charge transfer properties of these N,O-chelates could be switched by the modification of substituents,resulting tunable fluorescence ***,post-complexation modification was accomplished,including Suzuki-Miyaura cross-coupling,Buchwald-Hartwig amination,oxidative cleavage,along with a unique triple substitution reaction involving propargyl Grignard *** exemplificative application of dimethylamine substituted boron complex as a reversible acidic vapor sensor was also demonstrated.

关键词： N,O-Bidentate BF2 complexes Aggregation-induced emission Large Stokes shift Post-complexation modification Reversible acidic vapor sensor

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Two-dimensional particle-in-cell modeling of blow-off impulse by X-ray irradiation

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Nuclear Science and Techniques 2024年第3期35卷 53-69页

作者： Ruibo Li jin-Long Jiao Hui Luo Dezhi zhang Dengwang Wang kai Wang Graduate School of China Academy of Engineering Physics Beijing 100193China Zhejiang Institute of Modern Physics Institute of AstronomySchool of PhysicsZhejiang UniversityHangzhou 310027China National Key Laboratory of Intense Pulsed Radiation Simulation and Effect Northwest Institute of Nuclear TechnologyXi’an 710024China

Space objects such as spacecraft or missiles may be exposed to intense X-rays in outer space,leading to severe *** reinforcement of these objects to reduce the damage caused by X-ray irradiation is a significant *** blow-off impulse(BOI)is a crucial physical quantity for investigating material damage induced by X-ray ***,the accurate calculation of BOI is challenging,particularly for large deformations of materials with complex *** this study,we develop a novel two-dimensional particle-in-cell code,Xablation2D,to calculate BOIs under far-field X-ray *** significantly reduces the dependence of the numerical simulation on the grid *** reliability of this code is verified by simulation results from open-source codes,and the calculated BOIs are consistent with the experimental and analytical results.

关键词： X-ray irradiation Energy deposition Blow-off impulse Particle in cells

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Engineering and finetuning expression of SerC for balanced metabolic flux in vitamin B6 production

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Synthetic and Systems Biotechnology 2024年第2期9卷 388-398页

作者： kai Chen Linxia Liu jinlong Li Zhizhong Tian Hongxing jin Dawei zhang School of Chemical Engineering and Technology Hebei University of TechnologyTianjinChina Tianjin Institute of Industrial Biotechnology Chinese Academy of SciencesTianjinChina National Center of Technology Innovation for Synthetic Biology TianjinChina Key Laboratory of Engineering Biology for Low-Carbon Manufacturing Tianjin Institute of Industrial BiotechnologyChinese Academy of SciencesTianjinChina University of Chinese Academy of Sciences BeijingChina

Vitamin B6 plays a crucial role in cellular metabolism and stress response,making it an essential component for growth in all known ***,achieving efficient biosynthesis of vitamin B6 faces the challenge of maintaining a balanced distribution of metabolic flux between growth and *** this study,our focus is on addressing this challenge through the engineering of phosphoserine aminotransferase(SerC)to resolve its redundancy and *** enzyme SerC was semi-designed and screened based on sequences and predicted kcat values,*** and heterologous proteins showing potential were then fine-tuned to optimize the production of vitamin *** resulting strain enhances the production of vitamin B6,indicating that different fluxes are distributed to the biosynthesis pathway of serine and vitamin *** study presents a promising strategy to address the challenge posed by multifunctional enzymes,with significant implications for enhancing biochemical production through engineering processes.

关键词： Vitamin B6 Phosphoserine aminotransferase SerC Protein engineering Multifunctional enzymes Metabolic flux distribution

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Studies on Fixed-depth Control of Supercavitating Vehicles

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自动化学报 2010年第3期36卷 421-426页

作者： LI Dai-jin LUO kai zhang Yu-Wen DANG Jian-Jun College of Marine Engineering Northwestern Polytechnical University Xi'an 710072 P. R. China

A supercavitating vehicle is a complex high-speed underwater body that is exposed to extreme operating conditions due to its speed. To successfully control the depth and attitude,it is necessary to study the motion characteristics of the vehicles on a vertical plane. This study investigates the motion model on the vertical plane and analyzes the dynamic characteristics of supercavitating vehicles. Then,a fixed-depth control method is developed. For validating the designed control-algorithm, related simulation and experiments have been carried out for the control system. Analytical results show that the proposed control system accomplishes precise depth control of the supercavitating vehicles, providing a necessary theoretical basis for further study of the dynamic control problem for underwater supercavitating vehicles

关键词：运动特性控制算法计算方法动态控制

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Transient AC Overvoltage Suppression Orientated Reactive Power Control of the Wind Turbine in the LCC-HVDC Sending Grid

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CES Transactions on Electrical Machines and Systems 2024年第2期8卷 152-161页

作者： Bo Pang Xiao jin Quanwang zhang Yi Tang kai Liao Jianwei Yang Zhengyou He IEEE College of Electrical Engineering Southwest Jiaotong UniversityChengdu 610031China State Grid Zhejiang Electric Power Company HangzhouChina

High-voltage direct current(HVDC) transmission is a crucial way to solve the reverse distribution of clean energy and loads. The line commutated converter-based HVDC(LCCHVDC) has become a vital structure for HVDC due to its high technological maturity and economic advantages. During the DC fault of LCC-HVDC, such as commutation failure, the reactive power regulation of the AC grid always lags the DC control process, causing overvoltage in the AC sending grid, which brings off-grid risk to the wind power generation based on power electronic devices. Nevertheless, considering that wind turbine generators have fast and flexible reactive power control capability, optimizing the reactive power control of wind turbines to participate in the transient overvoltage suppression of the sending grid not only improves the operational safety at the equipment level but also enhances the voltage stability of the system. This paper firstly analyses the impact of wind turbine's reactive power on AC transient overvoltage. Then, it proposes an improved voltage-reactive power control strategy, which contains a reactive power control delay compensation and a power command optimization based on the voltage time series prediction. The delay compensation is used to reduce the contribution of the untimely reactive power of wind turbines on transient overvoltage, and the power command optimization enables wind turbines to have the ability to regulate transient overvoltage, leading to the variation of AC voltage, thus suppressing the transient overvoltage. Finally, the effectiveness and feasibility of the proposed method are verified in a ±800kV/5000MW LCC-HVDC sending grid model based on MATLAB/Simulink.

关键词： Commutation failure LCC-HVDC Transient overvoltage Wind power

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Lanthanide-based microlasers:Synthesis,structures,and biomedical applications

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Nano Research 2024年第1期17卷 97-111页

作者： Qian zhang Yawei Liu kai Liu Hongjie zhang Engineering Research Center of Advanced Rare Earth Materials(Ministry of Education) Department of ChemistryTsinghua UniversityBeijing 100084China State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Xiangfu Laboratory Jiaxing 314102China

The large size of lasers limits their applications in confined spaces,such as in biosensing and in vivo brain tissue *** this regard,micron-sized lasers have been *** exhibit great potential for biological detecting,remote sensing,and depth tracking due to their small sizes,sensitive properties of their spectral fingerprints,and flexible positional modulation in the ***-based luminescent materials that possess long excited-state lifetime,narrow emission bandwidth,and upconversion behaviors are promising as gain mediums for novel *** addition,lanthanide-based microlasers could be generated under natural ambient conditions with pumped or continuous light sources,which significantly promotes the practical applications of *** progress in the design,synthesis,and biomedical applications of lanthanide-based microlasers has been outlined in this *** ions doped and upconverted lanthanide-based microlasers are highlighted,which exhibit advantageous structures,miniaturized dimensions,and high lasing *** applications of lanthanide-based microlasers are further discussed,the upconverted microlasers show great advantages for biological applications owing to their tunable excitation and emission characteristics and excellent environmental ***,perspectives and challenges in the field of lanthanide-based microlasers are presented.

关键词： microlasers lanthanide-based luminescent materials upconversion nanoparticles biological applications

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MXene supported PtCo bimetallic catalyst for hydrogen evolution in acidic conditions

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Frontiers in Energy 2024年第3期18卷 369-377页

作者： Guangxun CHEN Jian-hua zhang kai-Ling ZHOU Yang YANG Haoxiang MA Yuhong jin jingbin LIU Hao WANG Faculty of Materials and Manufacturing Beijing University of TechnologyBeijing 100124China Institute of Deep-Sea Science and Engineering Chinese Academy of SciencesSanya 572000China

Using the electrochemical technology to split water molecules to produce hydrogen is the key to obtain green hydrogen for solving the energy crisis. The large-scale application of hydrogen evolution reaction (HER) in water dissociation requires a highly active catalyst. In this paper, the highly dispersed PtCo bimetallic nanoparticles loading on MXene (PtCo/MXene) were prepared by using a step-to-step reduction strategy. The mentioned PtCo/MXene catalyst exhibits a high current density of −100 mA/cm2 in an acidic medium with just a 152 mV overpotential. In addition, the PtCo/MXene catalyst also displays a superior stability. Computational analysis and experimental testing demonstrate that the electronic interaction between Pt and Co can effectively modify the electronic structure of the active site, thereby enhancing the inherent catalytic performance of the material. More importantly, MXene two-dimensional nanosheets can expose more active sites because of their large specific surface area. Furthermore, MXene substrate with excellent electrical conductivity and harmonious interfaces between PtCo and MXene enhance charge transfer efficiency and lower the reaction activation energy.

关键词： MXene PtCo bimetallic hydrogen evolution reaction(HER)

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