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TOFD detection of shallow subsurface defects in aluminum alloy thin plates by half-skip mode-converted wave

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Chinese Journal of Aeronautics 2024年第6期37卷 454-463页

作者： Shijie jin Zhicheng WANG Zhongbing LUO NDT&E Laboratory Dalian University of TechnologyDalian 116085China

Aluminum alloy is widely applied to the aerospace ***,the inspection of thin plates using Time-of-Flight Diffraction(TOFD)technique is restricted by the near-surface dead zone because of the coupling between diffracted longitudinal wave and lateral *** halfskip mode-converted wave is introduced to decrease dead zone and detect defects in aluminum alloy thin plates by increasing ray path and propagation *** quantitative correlation for the diffracted shear wave from longitudinal back-wall wave is deduced in combination with the acoustic path,realizing the accurate location of shallow subsurface *** and experimental results indicate that the dead zone is decreased by 38% by the half-skip mode-converted wave,and the location errors are within 5% for the aluminum alloy plate with a thickness of 7.0 *** to other alternative TOFD techniques,half-skip mode-converted wave has better response amplitude and positioning accuracy,demonstrating strong applicability in TOFD inspection of thin plates.

关键词： Ultrasonic testing Time-of-Flight Diffraction(TOFD) Dead zone Half-skip mode-converted wave Quantitative detection

Laboratory evaluation of high-friction thin overlays for pavement preservation

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Frontiers of Structural and Civil Engineering 2024年第6期18卷 936-948页

作者： Ouming XU Rentao XU Lintong jin School of Highway Chang’an UniversityXi’an 710064China School of Materials Science and Engineering Chang’an UniversityXi’an 710061China

Traditional asphalt concrete(AC)and stone matrix asphalt(SMA),which are used as thin asphalt overlays,are common maintenance strategies to enhancing ride quality,skid resistance,and ***,several studies have used a novel asphalt mixture known as a high-friction thin overlay(HFTO)to improve surface ***,it remains uncertain whether the laboratory properties of HFTO differ significantly from those of conventional *** study aims to evaluate the laboratory properties of HFTO mixtures and compare them with those of AC and *** mixtures with nominal maximum size of 9.5 mm were produced in the laboratory,and performance tests were conducted,including wheel tracking test,low temperature flexural creep test,moisture susceptibility test,Cantabro Abrasion Test,Marshall Test,sand patch test,British pendulum test,and indoor tire-rollingdown *** results showed that the HFTO exhibited a lower tire/pavement noise than the AC and ***,HFTO had superior high-temperature stability,larger macro texture,and higher skid resistance in comparison to those of AC,but lower than those of ***,HFTO mixtures may be considered a suitable replacement for traditional AC mixtures in regions where skid resistance and noise reduction are concerns.

关键词： road engineering pavement maintenance high friction thin overlay performance skid resistance tire/pavement noise

Effects of tree size and organ age on variations in carbon,nitrogen,and phosphorus stoichiometry in Pinus koraiensis

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Journal of Forestry Research 2024年第3期35卷 155-165页

作者： Yanjun Wang Guangze jin Zhili Liu Center for Ecological Research Northeast Forestry UniversityHarbin 150040People's Republic of China Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education Northeast Forestry UniversityHarbin 150040People's Republic of China Northeast Asia Biodiversity Research Center Northeast Forestry UniversityHarbin 150040People's Republic of China

Carbon(C),nitrogen(N),and phosphorus(P)are of fundamental importance for growth and nutrient dynamics within plant organs and deserve more attention at regional to global ***,our knowledge of how these nutrients vary with tree size,organ age,or root order at the individual level remains *** determined C,N,and P contents and their stoichiometric ratios(i.e.,nutrient traits)in needles,branches,and fine roots at different organ ages(0-3-year-old needles and branches)and root orders(1st-4th order roots)from 64 Pinus koraiensis of varying size(Diameter at breast height ranged from 0.3 to 100 cm)in northeast *** factors were also *** results show that nutrient traits were regulated by tree size,organ age,or root order rather than soil *** a whole-plant level,nutrient traits decreased in needles and fine roots but increased in branches with tree *** the organ level,age or root order had a negative effect on C,N,and P and a positive effect on stoichiometric *** results demonstrate that nutrient variations are closely related to organ-specific functions and ecophysiological processes at an individual *** is suggested that the nutrient acquisition strategy by younger trees and organ fractions with higher nutrient content is for ***,nutrient storage strategy in older trees and organ fractions are mainly for steady *** results clarified the nutrient utilization strategies during tree and organ ontogeny and suggest that tree size and organ age or root order should be simultaneously considered to understand the complexities of nutrient variations.

关键词： Tree size Organ age(or root order) Carbon(C) Nitrogen(N) Phosphorus(P) Pinus koraiensis

Even Search in a Promising Region for Constrained Multi-Objective Optimization

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IEEE/CAA Journal of Automatica Sinica 2024年第2期11卷 474-486页

作者： Fei Ming Wenyin Gong Yaochu jin School of Computer Science China University of GeosciencesWuhan 430074China IEEE Faculty of Technology Bielefeld UniversityNorth Rhine-Westphalia 33619Germany School of Engineering Westlake UniversityHangzhou 310030China

In recent years, a large number of approaches to constrained multi-objective optimization problems(CMOPs) have been proposed, focusing on developing tweaked strategies and techniques for handling constraints. However, an overly finetuned strategy or technique might overfit some problem types,resulting in a lack of versatility. In this article, we propose a generic search strategy that performs an even search in a promising region. The promising region, determined by obtained feasible non-dominated solutions, possesses two general ***, the constrained Pareto front(CPF) is included in the promising region. Second, as the number of feasible solutions increases or the convergence performance(i.e., approximation to the CPF) of these solutions improves, the promising region shrinks. Then we develop a new strategy named even search,which utilizes the non-dominated solutions to accelerate convergence and escape from local optima, and the feasible solutions under a constraint relaxation condition to exploit and detect feasible regions. Finally, a diversity measure is adopted to make sure that the individuals in the population evenly cover the valuable areas in the promising region. Experimental results on 45 instances from four benchmark test suites and 14 real-world CMOPs have demonstrated that searching evenly in the promising region can achieve competitive performance and excellent versatility compared to 11 most state-of-the-art methods tailored for CMOPs.

关键词： Constrained multi-objective optimization even search evolutionary algorithms promising region real-world problems

Active flutter suppression of nonlinear fin-actuator system via inverse system and immersion and invariance method

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Chinese Journal of Aeronautics 2024年第4期37卷 343-362页

作者： jin LU Zhigang WU Chao YANG Chinese Aeronautical Establishment Beijing 100029China School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China

Structural nonlinearities such as freeplay will affect the stability and even flight safety of the fin-actuator *** is a lack of a practical method for designing Active Flutter Suppression (AFS) control laws for nonlinear fin-actuator systems.A design method for the AFS controller of the nonlinear all-movable fin-electromechanical actuator system is established by combining the inverse system and the Immersion and Invariance (I&I) ***,the composite control law combining the inverse system principle and internal model control is used to offset the nonlinearity and dynamics of the actuator,so that its driving torque can follow the ideal ***,the ideal torque of the actuator is designed employing the I&I *** unfavorable oscillation of the fin is suppressed by making the output torque of the actuator track the ideal *** simulation results reveal that the proposed AFS method can increase the flutter speed of the nonlinear finactuator system with freeplay,and a set of controller parameters is also applicable for wider freeplay within a certain *** power required for the actuator does not exceed the power that can be provided by the commonly used aviation *** method can also resist a certain level of noise and external disturbance.

关键词： Aeroelasticity Active flutter suppression Fin-actuator system Freeplay Inverse system Immersion and invariance

Layered double hydroxides functionalization toward rechargeable batteries Author links open overlay panel

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Particuology 2024年第8期91卷 138-154页

作者： Jianxiong Gao Bowen jin Mingfei Shao State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing100029China Renewable Energy Research Institute Quzhou Institute for Innovation in Resource Chemical EngineeringQuzhou324000China

Layered double hydroxides(LDHs),known as typical two-dimensional materials with unique physicochemical properties,are regarded as promising candidates in energy storage ***,some inherent defects,such as poor conductivity and limited active sites,hinder the further development of ***,various functionalization strategies(e.g.,intercalation of guest molecules;metal ions doping and defect introduction of host layer;exfoliation to monolayer;hybridization with functional materials;construction of hierarchical structure;interface engineering and phase transformation)have been used to modify the characteristics of LDHs,which provides guidance for designing novel *** this review,we discuss how these strategies improve the properties of LDH-based materials,which are expected to possess high electronic and ionic conductivity,high specific surface area and high mechanical and chemical stability ***,the application of LDH-based materials in advanced energy conversion and storage techniques,including metal-ions batteries,lithium-sulfur batteries and metal-air batteries,have been comprehensively summarized.

关键词： Layered double hydroxide Functionalization strategy Rechargeable battery

Effects of thinning on the understory light environment of different stands and the photosynthetic performance and growth of the reforestation species Phoebe bournei

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Journal of Forestry Research 2024年第1期35卷 12-28页

作者： Shicheng Su Nianqing jin Xiaoli Wei College of Forestry Guizhou UniversityGuiyang 550025People’s Republic of China Institute for Forest Resources and Environment of Guizhou Guizhou UniversityGuiyang 550025People’s Republic of China

Light levels determine regeneration in stands and a key concern is how to regulate the light environment of different stand types to the requirements of the *** this study,we selected three stands typical in south China(a Cryptomeria japonica plantation,a Quercus acutissima plantation,and a mixed stand of both)and three thinning intensities to determine the best understory light environ-ment for 3-year-old Phoebe bournei *** canopy structure,understory light environment,and photosynthe-sis and growth indicators were assessed following *** improved canopy structure and understory light availability of each stand;species composition was the reason for differences in the understory light *** the same thinning intensity,the mixed stand had the greatest light radiation and most balanced spectral *** photosynthesis and growth were closely related to the light environment;all three stands required heavy thinning to create an effective and sustained understory light *** a suitable understory light environment,the efficiency of light interception,absorption,and use by seedlings was enhanced,resulting in a higher carbon assimilation the main limiting factor was stomatal *** a shade-avoidance signal,red/far-red radia-tion is a critical factor driving changes in photosynthesis and growth of *** seedlings,and a reduction increased light absorption and use capacity and height:diameter *** growth advantage transformed from diameter to height,enabling seedlings to access more *** findings suggest that the regeneration of shade-tolerant species such as *** could be enhanced if a targeted approach to thinning based on stand type was adopted.

关键词： Thinning Understory light environment Phoebe bournei Photosynthetic performance Growth performance

Simple preparation of C(CS)/g-C_(3)N_(4)/Co carbon aerogel and its catalytic performance for ammonium perchlorate

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Defence Technology（防务技术） 2024年第3期33卷 186-196页

作者： Yujie Yan Bo jin Rufang Peng State Key Laboratory of Environment-friendly Energy Materials School of Materials Science and EngineeringSouthwest University of Science and TechnologyMianyang621010China

Biomass chitosan(CS)was used as a template,graphitic phase carbon nitride(g-C_(3)N_(4))with high nitrogen content and certain catalytic activity was used as a dopant,and nano-transition metal cobalt(Co)was used as a catalytic center *** carbon aerogel(C(CS)/g-C_(3)N_(4)/Co)with a three-dimensional network-like structure was prepared by assembling the three materials through experimental operations such as freeze-drying and high-temperature *** was demonstrated by scanning and transmission characterization that the CS in the carbon aerogel could provide more active sites for the cobalt nanoparticles,and the doping of graphite-phase carbon nitride as a template dispersed the cobalt nanoparticles and changed the conductivity of the *** investigate the catalytic effect of carbon aerogel on ammonium perchlorate(AP),it was investigated by differential thermal analyzer and TG thermal *** carbon aerogel was very effective in catalyzing AP,and the 10 wt% content of the catalyst reduced the AP pyrolysis peak from 703.9 to 595.5 *** to further investigate the synergistic effect of the three materials,further carbon aerogels such as C(CS)/Co,g-C_(3)N_(4)/Co were prepared and applied to catalyze AP,and the same ratio reduced the AP pyrolysis peak by 98.1℃ and 97.7℃.This result indicates a synergistic effect of the assembly of the three materials.

关键词： g-C_(3)N_(4) Chitosan Co Ammonium perchlorate Pyrolysis kinetics

Pb induced dislocation defects of PtCo systems: Strain-triggered oxygen reduction reaction for PEMFC

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Nano Research 2024年第4期17卷 2462-2472页

作者： Chun jin Qiheng Wang jingjun Liu Beijing Key Laboratory of Electrochemical Process and Technology for Materials Beijing 100029China Beijing University of Chemical Technology Beijing 100029China

Design and development of advanced electrocatalysts with high performance and low Pt consumption are crucial for reducing the kinetic energy barrier of the cathode oxygen reduction reaction(ORR)and improving the efficiency of proton exchange membrane fuel cells(PEMFC).In this study,we demonstrate a Pb-modulated PtCo system for efficient ORR,in which the inclusion of Pb in ternary alloys induces dislocation defects due to the significant difference in atomic ***-PtCoPb was confirmed to exhibit significantly higher ORR activity and stability in acidic *** practical PEMFC applications,it outperforms the corresponding commercial Pt/C with a mass activity of 0.58 A·mgPt^(-1),making it a promising alternative to state-of-the-art Pt-based *** combination of experimental results and density functional theory(DFT)calculations offers valuable atomic-level insights into the dislocation *** with a larger atomic radius is located in the lattice stretching region below the dislocation slip plane,forming a structure similar to a Cottrell atmosphere,which reduces the dislocation energy and puts the system in a lower energy *** Cottrell atmosphere pins the dislocation structure and stabilizes the ternary *** adjusting the amount of added Pb,a moderate level of dislocation density induces a tuned strain effect,thereby enhancing the electrocatalytic mechanism by optimizing the electronic structure of the alloy surface and the adsorption and desorption of oxygen *** work provides valuable insights into the design and development of lattice dislocation defect structures to trigger strain effects for improving ORR performance.

关键词： dislocation defect strain effect Pb-modulated oxygen reduction reaction