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Characterization, preparation, and reuse of metallic powders for laser powder bed fusion: a review

International Journal of Extreme Manufacturing 2024年第1期6卷 52-91页

作者： Xiaoyu Sun Minan Chen Tingting Liu Kai Zhang Huiliang wei Zhiguang Zhu Wenhe liao School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing 210094People’s Republic of China

Laser powder bed fusion(L-PBF) has attracted significant attention in both the industry and academic fields since its inception, providing unprecedented advantages to fabricate complex-shaped metallic components. The printing quality and performance of L-PBF alloys are infuenced by numerous variables consisting of feedstock powders, manufacturing process,and post-treatment. As the starting materials, metallic powders play a critical role in infuencing the fabrication cost, printing consistency, and properties. Given their deterministic roles, the present review aims to retrospect the recent progress on metallic powders for L-PBF including characterization, preparation, and reuse. The powder characterization mainly serves for printing consistency while powder preparation and reuse are introduced to reduce the fabrication *** powder characterization and preparation methods are presented in the beginning by analyzing the measurement principles, advantages, and limitations. Subsequently, the effect of powder reuse on the powder characteristics and mechanical performance of L-PBF parts is analyzed, focusing on steels, nickel-based superalloys, titanium and titanium alloys, and aluminum alloys. The evolution trends of powders and L-PBF parts vary depending on specific alloy systems, which makes the proposal of a unified reuse protocol infeasible. Finally,perspectives are presented to cater to the increased applications of L-PBF technologies for future investigations. The present state-of-the-art work can pave the way for the broad industrial applications of L-PBF by enhancing printing consistency and reducing the total costs from the perspective of powders.

关键词： laser powder bed fusion powder characterization powder preparation powder reuse

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Creep rupture life predictions for Ni-based single crystal superalloys with automated machine learning

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Rare Metals 2024年第6期43卷 2884-2890页

作者： Chang-Lu Zhou Rui-Hao Yuan wei-Jie liao Ting-Huan Yuan Jiang-Kun Fan Bin Tang ping-Xiang Zhang Jin-Shan Li Turab Lookman State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi'an 710072China Chongqing Innovation Center Northwestern Polytechnical UniversityChongqing 401120China AiMaterials Research LLC Santa FeNM 87501USA

The state of the art for data-driven creep rupture life predictions incorporates microstructural and deformation characteristics into machine ***,the microstructures and deformation mechanisms for unknown alloys are inaccessible and uncertain before experiments are carried out,and therefore prevents extrapolations of the learned models.

关键词： deformation life creep

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Equilibrium Reinsurance Strategy and Mean Residual Life Function

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Acta Mathematicae Applicatae Sinica 2024年第3期40卷 758-777页

作者： Dan-ping LI Lv CHEN Lin-yi QIAN wei WANG School of Statistics Key Laboratory of Advanced Theory and Application in Statistics and Data Science-MOEEast China Normal UniversityShanghai 200062China Academy of Statistics and Interdisciplinary Sciences Key Laboratory of Advanced Theory and Application in Statistics and Data Science-MOEEast China Normal UniversityShanghai 200062China School of Mathematics and Statistics Ningbo UniversityNingbo 315211China

In this paper,we analyze the relationship between the equilibrium reinsurance strategy and the tail of the distribution of the *** Mean Residual Life(MRL)has a close relationship with the tail of the distribution,we consider two classes of risk distributions,Decreasing Mean Residual Life(DMRL)and Increasing Mean Residual Life(IMRL)distributions,which can be used to classify light-tailed and heavy-tailed distributions,*** assume that the underlying risk process is modelled by the classical CramérLundberg model *** the mean-variance criterion,by solving the extended Hamilton-Jacobi-Bellman equation,we derive the equilibrium reinsurance strategy for the insurer and the reinsurer under DMRL and IMRL,***,we analyze how to choose the reinsurance premium to make the insurer and the reinsurer agree with the same reinsurance *** find that under the case of DMRL,if the distribution and the risk aversions satisfy certain conditions,the insurer and the reinsurer can adopt a reinsurance premium to agree on a reinsurance strategy,and under the case of IMRL,the insurer and the reinsurer can only agree with each other that the insurer do not purchase the reinsurance.

关键词： mean residual life excess-of-loss reinsurance insurer reinsurer stochastic control

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Coupling effect of cement-stabilization and biopolymer-modification on the mechanical behavior of dredged sediment

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第8期16卷 3284-3298页

作者： Lei Lang Jiangshan Li Xiao Huang ping Wang wei Zhang State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Hubei Provincial Key Laboratory of Contaminated Sludge and Soil Science and Engineering Wuhan430071China University of Chinese Academy of Sciences Beijing100049China

Nowadays,biopolymer stabilization as a promising eco-friendly approach in soft ground improvement has attracted wide ***,the feasibility of using biopolymer as a green additive of cementstabilized dredged sediment(CDS)with high water content is still *** this study,guar gum(GG)and xanthan gum(XG)were adopted as typical biopolymers,and a series of unconfined compressive strength(UCS),splitting tensile strength(STS)and scanning electron microscopy(SEM)tests were performed to evaluate the mechanical and microstructural properties of XG-and GG-modified CDSs considering several factors including biopolymer modification,binderesoil ratio and wateresolid ***,the micro-mechanisms revealing the evolutions of mechanical properties of biopolymermodified CDS were *** results indicate that the addition of XG can effectively improve the strength of CDS,while the GG has a side *** XG content of 9%was recommended,which can improve the 7 d-and 28 d-UCSs by 196%and 51.8%,together with the 7 d-and 28 d-STSs by 118.3%and 42.2%,*** the binderesoil ratio or decreasing the wateresolid ratio significantly improved the strength gaining but aggravated the brittleness characteristics of *** XG to CDS contributed to the formation of microstructure with more compactness and higher cementation degrees of ordinary Portland cement(OPC)-XG-stabilized DS(CXDS).The micro-mechanism models revealing the interactions of multiple media including OPC cementation,biopolymer film bonding and bridging effects inside CXDS were *** key findings confirm the feasibility of XG modification as a green and high-efficiency mean for improving the mechanical properties of CDS.

关键词： Dredged sediment(DS) Stabilization Biopolymer modification Mechanical properties Micro-mechanism

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Towards sustainable adversarial training with successive perturbation generation

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Frontiers of Information Technology & Electronic Engineering 2024年第4期25卷 527-539页

作者： wei LIN Lichuan liao College of Computer Science and Mathematics Fujian University of TechnologyFuzhou 350118China College of Economics and Management Xi’an University of TechnologyXi’an 710048China Fujian Provincial Key Laboratory of Big Data Mining and Applications Fujian University of TechnologyFuzhou 350118China

Adversarial training with online-generated adversarial examples has achieved promising performance in defending adversarial attacks and improving robustness of convolutional neural network ***,most existing adversarial training methods are dedicated to finding strong adversarial examples for forcing the model to learn the adversarial data distribution,which inevitably imposes a large computational overhead and results in a decrease in the generalization performance on clean *** this paper,we show that progressively enhancing the adversarial strength of adversarial examples across training epochs can effectively improve the model robustness,and appropriate model shifting can preserve the generalization performance of models in conjunction with negligible computational *** this end,we propose a successive perturbation generation scheme for adversarial training(SPGAT),which progressively strengthens the adversarial examples by adding the perturbations on adversarial examples transferred from the previous epoch and shifts models across the epochs to improve the efficiency of adversarial *** proposed SPGAT is both efficient and effective;e.g.,the computation time of our method is 900 min as against the 4100 min duration observed in the case of standard adversarial training,and the performance boost is more than 7%and 3%in terms of adversarial accuracy and clean accuracy,*** extensively evaluate the SPGAT on various datasets,including small-scale MNIST,middle-scale CIFAR-10,and large-scale *** experimental results show that our method is more efficient while performing favorably against state-of-the-art methods.

关键词： Adversarial training Adversarial attack Stochastic weight average Machine learning Model generalization

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Single-Ni-atoms on nitrogenated humic acid based porous carbon for CO_(2) electroreduction

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Frontiers of Chemical Science and Engineering 2024年第5期18卷 37-47页

作者： Delei Yu Ying Chen Yao Chen Xiangchun Liu Xianwen wei ping Cui Anhui Key Laboratory of Coal Clean Conversion&Utilization School of Chemistry and Chemical EngineeringAnhui University of TechnologyMa’anshan 243002Chin

tWe proposed a facile synthesis of single-Ni-atom catalysts on low-cost porous carbon using a calcina-tion method at the temperatures of 850-1000°C,which were used for CO_(2) electrochemical reduction to *** porous carbon was prepared by carbonizing cheap and abundant humic *** structural characterizations of the as-synthesized catalysts and their electrocatalytic performances were *** results showed that the single-Ni-atom catalyst activated at 950°C showed an optimum catalytic performance,and it reached a CO Faradaic efficiency of 91.9% with a CO partial current density of 6.9 mAcm^(-2)at-0.9 V *** hydrogen electrode(RHE).Additionally,the CO Faradaic efficiency and current density of the optimum catalyst changed slightly after 8 h of continuous operation,suggesting that it possessed an excellent *** structure-activity relations indicate that the variation in the CO_(2) electroche-mical reduction performance for the as-synthesized catalysts is ascribed to the combined effects of the increase in the content of pyrrolic N,the evaporation of Ni and N,the decrease in pore volume,and the change in graphitization degree.

关键词： CO_(2) electroreduction single-Ni-atom cataly-sts humic acid based porous carbon

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New approach to measuring topological phase transitions utilizing Floquet technology

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Chinese Physics B 2024年第9期33卷 282-288页

作者： Xue-Ying Yang wei Wu ping-Xing Chen College of Sciences National University of Defense TechnologyChangsha 410073China

The Floquet technique provides a novel anomalous topological phase for non-equilibrium phase *** on the high symmetry of the quantum anomalous Hall model,the findings suggest a one-to-one correspondence between the average spin texture and the Floquet quasi-energy spectrum.A new approach is proposed to directly measure the quasienergy spectrum,replacing previous measurements of the average spin ***,we proposed a reliable experimental scheme based on ion trap *** scheme markedly reduces the measurement workload,improves the measurement fidelity,and is applicable to multiple platforms such as cold atoms and nuclear magnetic resonance.

关键词： topological phase transition Floquet technique ion trap

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A New Method to Identify the Maximum Time Interval between Individual Events in Compound Rainstorm and Heatwave Events

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International Journal of Disaster Risk Science 2024年第3期15卷 453-466页

作者： Junlin Zhang wei Xu Yu Qiao Xinli liao Chenna Meng Qinmei Han Key Laboratory of Environmental Change and Natural Disaster of Ministry of Education Faculty of Geographical Science Beijing Normal University Academy of Disaster Reduction and Emergency Management Ministry of Emergency Management and Ministry of Education Beijing Normal University State Key Laboratory of Earth Surface Processes and Resource Ecology Beijing Normal University National Climate Center China Meteorological Administration

Growing evidence indicates that extreme heat and rain may occur in succession within short time periods and cause greater impacts than individual events separated in time and space. Therefore, many studies have examined the impacts of compound hazard events on the social-ecological system at various scales. The definition of compound events is fundamental for such research. However, there are no existing studies that support the determination of time interval between individual events of a compound rainstorm and heatwave(CRH) event, which consists of two or more potentially qualifying component heatwave and rainstorm events. To address the deficiency in defining what individual events can constitute a CRH event, this study proposed a novel method to determine the maximum time interval for CRH events through the change in CRH event frequency with increasing time interval between individual events, using southern China as a case study. The results show that the threshold identified by the proposed method is reasonable. For more than 90% of the meteorological stations, the frequency of CRH events has reached a maximum when the time interval is less than or equal to the threshold. This study can aid in time interval selection, which is an important step for subsequent study of CRH events.

关键词： Compound extreme weather event Rainstorm and heatwave Southern China Threshold Time interval

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Overview of computation strategies on the dispersion analysis for explicit finite difference solution of acoustic wave equation

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Petroleum Science 2024年第4期21卷 2311-2328页

作者： Jian-ping Huang wei-Ting Peng Ji-Dong Yang Lu-Feng Lou School of Geosciences China University of Petroleum (East China) Pilot National Laboratory for Marine Science and Technology (Qingdao)

Finite-difference(FD) method is the most extensively employed numerical modeling technique. Nevertheless, when using the FD method to simulate the seismic wave propagation, the large spatial or temporal sampling interval can lead to dispersion errors and numerical instability. In the FD scheme, the key factor in determining both dispersion errors and stability is the selection of the FD weights. Thus,How to obtain appropriate FD weights to guarantee a stable numerical modeling process with minimum dispersion error is critical. The FD weights computation strategies can be classified into three types based on different computational ideologies, window function strategy, optimization strategy, and Taylor expansion strategy. In this paper, we provide a comprehensive overview of these three strategies by presenting their fundamental theories. We conduct a set of comparative analyses of their strengths and weaknesses through various analysis tests and numerical modelings. According to these comparisons, we provide two potential research directions of this field: Firstly, the development of a computational strategy for FD weights that enhances stability; Secondly, obtaining FD weights that exhibit a wide bandwidth while minimizing dispersion errors.

关键词： Finite-difference scheme FD coefficients Dispersion error Forward modeling Numerical simulation

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MicroRNA let-7 targets BmCDK1 to regulate cell proliferation and endomitosis of silk gland in the silkworm,Bombyx mori

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Insect Science 2024年第4期31卷 1026-1040页

作者： wei Wang Linshengzhe Ji Xinyuan Jing ping Zhao Qingyou Xia Integrative Science Center of Germplasm Creation in Western China(Chongqing)Science City Biological Science Research CenterSouthwest UniversityChina Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River Ministry of Agriculture and Rural AffairsChongqingChina Engineering Laboratory of Sericultural and Functional Genome and Biotechnology Development and Reform CommissionChongqingChina

MicroRNAs play critical roles in multiple developmental processes in *** previous study showed that CRISPR/Cas9-mediated knock down of the microRNA let-7 in silkworms increased the size of larvae and silk glands,thereby improving the silk production *** this study,we elucidate the molecular mechanism underlying of let-7 regulates *** of differentially expressed genes in response to let-7 knock down revealed enrichment of pathways associated with cell proliferation and DNA ***-7 dysregulation affected the cell cycle and proliferation of the Bombyx mori cell line ***-luciferase and target site mutation assays showed that BmCDK1 is a direct target gene of let-7,with only 1 binding site on its 3′-untranslated *** interference of BmCDK1 inhibited cell proliferation,but this effect was counteracted by co-transfection with let-7 ***,let-7 knock down induced BmCDK1 expression and promoted cell proliferation in multiple tissues,and further induced endomitosis in the silk gland in *** down of BmCDK1 resulted in abnormal formation of a new epidermis,and larval development was arrested at the 2nd or 3rd molt *** together,our results demonstrated that BmCDK1 is a novel target of let-7 in cell fate determination,possessing potential for improving silk yield in silkworm.

关键词： BmCDKI CRISPR/Cas9 cell proliferation let-7 silkworm

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