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Abnormal grain growth behavior and mechanism of 6005A aluminum alloy extrusion profile

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Journal of Materials Science & Technology 2023年第26期157卷 42-59页

作者： Haixiao Zhao Lu Sun Guoqun Zhao Junquan Yu Fei Liu Ximan Sun zhengfeng lv Shanpeng Cao Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan 250061China Shandong Nanshan Aluminum Co. Ltd.Longkou 264000China

Peripheral coarse grain(PCG)structure is a common microstructural defect appearing in the aluminum alloy extrusion process,which seriously affects the mechanical properties of the *** this work,a series of extrusion experiments and numerical simulations were conducted to investigate the influence of billet temperature and ram speed on the microstructure,mechanical properties and thickness of PCG layers of 6005A aluminum alloy *** mechanism of abnormal grain growth(AGG)occurring on the surface and in the core of profiles was *** result showed that lower ram speed could sup-press the formation of coarse *** AGG on the surface of the profiles was activated by the shear deformation and lattice distortion derived from the friction on the interface between the profile and *** the billet was heated to a relatively high temperature,dynamic recrystallization(DRX)was dominant,and the Cube{100}and R-Cube{100}grains underwent abnormal growth to form surface coarse *** the billet was heated to a relatively low temperature,the degree of static recrystallization(SRX)became stronger,and the Goss{110}and R-Cube{100}grains under-went abnormal growth to form surface coarse *** AGG in the core of profiles was activated by the large grain boundary misorientation and a strain gradient formed because the Cube{100}re-crystallized grains were surrounded by the Copper{112}and Brass{110}deformed *** second phases in the 6005A aluminum alloy extrusion profiles were mainlyβ(Mg_(2) Si)and *** the billet temperature increased,moreβphases dissolved into the aluminum matrix,thus enhancing the strength and hardness of the *** the ram speed decreased,the thickness of PCG layers reduced,thus resulting in higher strength and hardness of the *** to the integrated effect of solution strengthening and grain refinement strengthening mechanisms,the combination of extrusion parameters for

关键词： Recrystallization Abnormal grain growth Microstructure Mechanical properties Solution strengthening Grain refinement strengthening

A fast forward computational method for nuclear measurement using volumetric detection constraints

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Nuclear Science and Techniques 2024年第2期35卷 47-63页

作者： Qiong Zhang Lin-lv Lin University of Electronic Science and Technology of China Chengdu 610000China

Owing to the complex lithology of unconventional reservoirs,field interpreters usually need to provide a basis for interpretation using logging simulation *** the various detection tools that use nuclear sources,the detector response can reflect various types of information of the *** Monte Carlo method is one of the primary methods used to obtain nuclear detection responses in complex ***,this requires a computational process with extensive random sampling,consumes considerable resources,and does not provide real-time response ***,a novel fast forward computational method(FFCM)for nuclear measurement that uses volumetric detection constraints to rapidly calculate the detector response in various complex environments is ***,the data library required for the FFCM is built by collecting the detection volume,detector counts,and flux sensitivity functions through a Monte Carlo ***,based on perturbation theory and the Rytov approximation,a model for the detector response is derived using the flux sensitivity function method and a one-group diffusion *** environmental perturbation is constrained to optimize the model according to the tool structure and the impact of the formation and borehole within the effective detection ***,the method is applied to a neutron porosity tool for *** various complex simulation environments,the maximum relative error between the calculated porosity results of Monte Carlo and FFCM was 6.80%,with a rootmean-square error of 0.62 *** field well applications,the formation porosity model obtained using FFCM was in good agreement with the model obtained by interpreters,which demonstrates the validity and accuracy of the proposed method.

关键词： Nuclear measurement Fast forward computation Volumetric constraints

Control of chiral-optical activities by magnetic field based on the transformation of achiral binary crystals into chiral ternary crystals

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Science China Chemistry 2024年第7期67卷 2300-2305页

作者： Zhiyan Chen Yan lv Wei Qin College of Physics Qingdao UniversityQingdao 266071China School of Physics State Key Laboratory of Crystal MaterialsShandong UniversityJinan 250100China Shandong Linuo Photovoltaic Hi-Tech Co. Ltd.Jinan 250100China

Multicomponent self-assembled chiral systems have attracted great attention due to their promising application in the area of spin-photonics and *** this work,through introducing an achiral third component into an achiral binary crystal,a chiral organic ternary crystal is fabricated,where both pronounced chiral-optical coupling and magnetic field dependence of chiral-optical activities are *** transformation of achiral structure into chiral structure generates a significant effect on the polarized state of light and the electron spin resonance ***,the coupling between circularly polarized photon and spin is observed in chiral ternary crystal with pronounced chiral orbit,where obvious magnetic field-transmissivity loop is ***,temperature could increase the magnitude of lattice parameters to lead to a larger helix radius to increase the chiral orbit ***,this work indicates that the further exploration of photon-chiral orbit-spin interactions in organic chiral ternary crystals is promising.

关键词： organic chiral ternary crystals chiral orbit chiral-optical activities magnetic field

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Event-triggered sliding mode control of linear repetitive processes and its application in metal rolling process

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Science China(Information Sciences) 2024年第3期67卷 167-181页

作者： Xinyu lv Yugang NIU James LAM Key Laboratory of Smart Manufacturing in Energy Chemical Process (East China University of Science and Technology) Ministry of Education Department of Mechanical Engineering The University of Hong Kong

This paper investigates the design problem of a sliding mode controller for linear repetitive processes(LRPs) with a finite pass length on each pass. Under limited communication resources, an eventtriggered mechanism is implemented from the sensors to the controller, whose triggered sequence is consistent with the evolution direction of LRPs. To periodically orchestrate communication between the controller and actuator, a round-robin scheduling mechanism is established based on the pass length. A sliding function involving the state and pass profile is constructed, and the sliding mode controller is designed using triggered states and pass profile signals. Feasible controller gains are attained to ensure the stability of the resultant closed-loop system. Finally, the proposed strategy is implemented for a multi-roll metal rolling process.

关键词： event-triggered mechanism linear repetitive processes metal rolling process round-robin scheduling sliding mode control

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Numerical Study on Local Flow and Heat Transfer Characteristics of Supercritical CO_(2) in PCHE with Sinusoidal Channels

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Journal of Thermal Science 2024年第1期33卷 41-55页

作者： WENZhexi lv Yigao LI Qing WU Jinglin School of Energy Science and Engineering Central South UniversityChangsha 410083China

Local heat transfer and flow characteristics,which is crucial to the overall performance of supercritical CO_(2) recuperators,is rarely examined in details in reported *** this paper,the local heat transfer and flow characteristics of supercritical CO_(2) in sinusoidal channel printed circuit heat exchangers are numerically investigated under the working conditions of *** on the simplified physical model constituted by10 pitches,the variations of Re,heat flux,Nu,secondary flow and other relevant parameters along the flow direction are analyzed *** is further made between the high and low temperature recuperators(HTR and LTR).It's observed that the local heat transfer and flow characteristics vary greatly from the inlet to the outlet,especially in the *** of 127.5% and 61.7% can be observed on the cold side of the LTR for Re and heat transfer coefficient h, *** indicate that the temperature difference and heat transfer coefficient h should not be regarded as constant and the distribution of h should be carefully considered in the design of the *** complicated interactions among the varying thermophysical properties,buoyancy and the periodically changed centrifugal force are believed to be the key that shapes the flow ***,the changes of the wavy angle θ are found to have greater influence than the changes of mass flow rate in reshaping the flow field when θ>25°.Though gravity direction strongly affects the local heat transfer and flow characteristics,it's also found that the effects on the overall thermal-hydraulic performance are relatively *** the installation direction that yields a_y=g should better be avoided for the sinusoidal channel printed circuit heat exchanger.

关键词： printed circuit heat exchanger supercritical CO_(2) sinusoidal channel heat transfer recuperator

A Generalized MSST Algorithm for Counting Points of Elliptic Curves over F_(p)^(n)

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Journal of Systems Science & Complexity 2024年第4期37卷 1738-1754页

作者： LI Xiao lv Chang PAN Zhizhong Key Laboratory of Cyberspace Security Defense Institute of Information EngineeringChinese Academy of SciencesBeijing 100085China School of Cyber Security University of Chinese Academy of SciencesBeijing 100085China Huawei Technologies Co. Ltd.Shenzhen 518129China

Elliptic curve cryptography is an important part of nowaday's public key *** points of elliptic curves over finite fields is of great significance to the selection of safety *** present,there are many p-adic algorithms,such as SST algorithm,generalized AGM algorithm,Kedlaya algorithm,etc.,which can deal with the situation of finite fields of small *** this paper,the authors generalize the MSST algorithm of characteristic 2 to general fields of odd characteristic,and propose the generalized MSST *** generalized MSST algorithm is achieved by combining the advantages of the SST algorithm and the generalized AGM *** the time complexity of the multiplication of two n-bit numbers is denoted as O((n)^(μ)),then the time complexity of the generalized MSST algorithm is O(n^(2μ+1/1+μ)),which is the same as the improved SST *** practical experiments,the running time of the generalized MSST algorithm is less than that of the improved SST algorithm.

关键词： Elliptic curve generalized AGM algorithm generalized MSST algorithm SST algorithm

Toward Trustworthy Decision-Making for Autonomous Vehicles:A Robust Reinforcement Learning Approach with Safety Guarantees

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Engineering 2024年第2期33卷 77-89页

作者： Xiangkun He Wenhui Huang Chen lv School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore

While autonomous vehicles are vital components of intelligent transportation systems,ensuring the trustworthiness of decision-making remains a substantial challenge in realizing autonomous ***,we present a novel robust reinforcement learning approach with safety guarantees to attain trustworthy decision-making for autonomous *** proposed technique ensures decision trustworthiness in terms of policy robustness and collision ***,an adversary model is learned online to simulate the worst-case uncertainty by approximating the optimal adversarial perturbations on the observed states and environmental *** addition,an adversarial robust actor-critic algorithm is developed to enable the agent to learn robust policies against perturbations in observations and ***,we devise a safety mask to guarantee the collision safety of the autonomous driving agent during both the training and testing processes using an interpretable knowledge model known as the Responsibility-Sensitive Safety ***,the proposed approach is evaluated through both simulations and *** results indicate that the autonomous driving agent can make trustworthy decisions and drastically reduce the number of collisions through robust safety policies.

关键词： Autonomous vehicle Decision-making Reinforcement learning Adversarial attack Safety guarantee

Characteristics Variation of Atmospheric CO_(2)and CH_(4)in Yongxing Island,South China Sea

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Journal of Ocean University of China 2024年第2期23卷 438-446页

作者： lv Honggang JIANG Yifei WANG Haiyan Key Laboratory of Marine Hazards Forecasting National Marine Environmental Forecasting CenterMinistry of Natural Resources(MNR)Beijing 100081China National Marine Environmental Forecasting Center Beijing 100081China

Using the observation data in Yongxing Island,South China Sea(SCS)from December 2013 to November 2018,the multiple time scales variation of atmospheric CO_(2)and CH_(4)were analyzed to understand their temporal variation characteristics and controlling *** regional-averaged background mole fractions of CO_(2)and CH_(4)both show a single-period sinusoidal variation with a lower value at noon and a higher value in the wee *** the seasonal scale,they exhibited a significant seasonal difference with higher values in winter and lower values in *** the annual scale,CO_(2)and CH_(4)both show an increasing trend,with an annual growth rate of approximately 3.2 ppm and 12 ppb,*** annual growth rate at this site was higher than the global *** change in atmospheric CO_(2)and CH_(4)in Yongxing Island was probably caused by the higher emission of the surrounding areas and the airflows driven by ***,the long-term and high-resolution greenhouse gases(GHGs)dataset will aid relevent researchers and decision-makers in performing more in-depth studies for GHG sources in order to derive effective strategies.

关键词： carbon dioxide methane observation backward trajectory atmospheric transport

Transcriptomic analysis reveals the effects of maternal exposure to bisphenol AF on hypothalamic development in male neonatal mice

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Journal of Environmental Sciences 2024年第7期141卷 304-313页

作者： Lin lv Yuanyuan Li Xuanyue Chen Zhanfen Qin State Key Laboratory of Environmental Chemistry and Ecotoxicology Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China

Fragmented data suggest that bisphenol AF(BPAF),a chemical widely used in a variety of products,might have potential impacts on the ***,we employed male neonatal mice following maternal exposure to explore the effects of low-dose BPAF on hypothalamic development by *** found that maternal exposure to approximately 50μg/(kg·day)BPAF from postanal day(PND)0 to PND 15 altered the hypothalamic transcriptome,primarily involving the pathways and genes associated with extracellular matrix(ECM)and intercellular adhesion,neuroendocrine regulation,and neurological *** RNA analysis confirmed the changes in the expression levels of concerned ***,we further revealed that low-dose BPAF posed a stimulatory impact on pro-opiomelanocortin(POMC)neurons in the arcuate nucleus of the hypothalamus and induced the browning of inguinal white adipose *** findings indicate that developmental exposure to low-dose BPAF could interfere with hypothalamic development and thereby lead to alterations in the ***,5000μg/(kg·day)BPAF caused slighter,non-significant or even inverse alterations than the low dose of 50μg/(kg·day),displaying a dose-independent *** observations suggest that the the dose-independent effects of BPAF might be associated with oxidative stress and inflammatory responses caused by the high ***,our study highlights a risk of low-dose BPAF to human neuroendocrine regulation and metabolism.

关键词： Bisphenol AF Hypothalamus Transcriptomic alteration Pro-opiomelanocortin(POMC)neurons White adipose tissue browning