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Formation mechanism of hierarchical twins in the CoCrNi medium entropy alloy

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Journal of Materials Science & Technology 2023年第9期140卷 19-32页

作者： Dongpeng Hua Xiaorong Liu Wan Wang Qing Zhou Qiaosheng Xia Shuo Li junqin shi Haifeng Wang State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi’anShaanxi 710072PR China Queen Mary University of London Engineering School Northwestern Polytechnical UniversityXi’anShaanxi 710072PR China

The three-dimensional hierarchical twin network has been proved to be the source of the excellent strength-ductility combination in the CoCrNi medium entropy alloy.Revealing the formation mechanism of hierarchical twins,however,remains a challenge using either the post-mortem or the in-situ microstructural characterization.In this study,the atomistic formation mechanism of hierarchical twins was investigated using molecular dynamics simulations,with special focus on the effects of strain rate and deformation temperature.Compared to the primary twin boundaries kink-driven hierarchical twinning tendency in pure FCC metals,the chemical inhomogeneity in CoCrNi can reduce the necessary kink height to trigger conjugate twins(CTWs),fascinating the formation of twin networks.At room temperature,the plastic deformation is dominated by primary twins(PTWs)and conjugate slips at a relatively lower strain rate(e.g.,5×10^(7)s^(−1)).The hierarchical twins can be activated in cases of deforming at a higher strain rate(e.g.,2×10^(8)s^(−1)).Further increasing the strain rate(e.g.,1×10^(10) s^(−1))leads to the phase-transformation induced plasticity.At cryogenic temperatures,the hierarchical twins are promoted within a large range of strain rates(e.g.,5×10^(7)–1×10^(10) s^(−1)).A higher temperature leads to the synergy of CTWs and primary slips at a lower strain rate,but hierarchical twins at a higher strain rate.On this basis,a qualitative comparison and scalable trends between experiments and simulations were revealed.The present study would not only provide the basic understanding for the twinning behavior found experimentally,but also contribute to the design of medium/high entropy alloys with excellent mechanical performances by tuning microstructures.

关键词： Hierarchical twin Medium entropy alloy Strain rate Deformation temperature Molecular dynamics simulation

Movement pattern of an ellipsoidal nanoparticle confined between solid surfaces: Theoretical model and molecular dynamics simulation

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Friction 2021年第5期9卷 1098-1109页

作者： junqin shi Xiangzheng ZHU Kun SUN Liang FANG State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi’an 710072China School of Mechanical and Electrical Engineering Xiamen University Tan Kah Kee CollegeZhangzhou 363105China

The movement pattern of ellipsoidal nanoparticles confined between copper surfaces was examined using a theoretical model and molecular dynamics simulation.Initially,we developed a theoretical model of movement patterns for hard ellipsoidal nanoparticles.Subsequently,the simulation indicated that there are critical values for increasing the axial ratio,driving velocity of the contact surface,and lowering normal loads(i.e.,0.83,15 m/s,and 100 nN under the respective conditions),which in turn change the movement pattern of nanoparticles from sliding to rolling.Based on the comparison between the ratio of arm of force(e/h)and coefficient of friction(μ),the theoretical model was in good agreement with the simulations and accurately predicted the movement pattern of ellipsoidal nanoparticles.The sliding of the ellipsoidal nanoparticles led to severe surface damage.However,rolling separated the contact surfaces and thereby reduced friction and wear.

关键词： movement pattern friction and wear reduction ellipsoidal nanoparticle additive molecular dynamics simulation

Quantization and Event-Triggered Policy Design for Encrypted Networked Control

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IEEE/CAA Journal of Automatica Sinica 2024年第4期11卷 946-955页

作者： Yongxia shi Ehsan Nekouei the Department of Electrical Engineering City University of Hong KongHong KongChina

This paper proposes a novel event-driven encrypted control framework for linear networked control systems(NCSs),which relies on two modified uniform quantization policies,the Paillier cryptosystem,and an event-triggered strategy.Due to the fact that only integers can work in the Pailler cryptosystem,both the real-valued control gain and system state need to be first quantized before encryption.This is dramatically different from the existing quantized control methods,where only the quantization of a single value,e.g.,the control input or the system state,is considered.To handle this issue,static and dynamic quantization policies are presented,which achieve the desired integer conversions and guarantee asymptotic convergence of the quantized system state to the equilibrium.Then,the quantized system state is encrypted and sent to the controller when the triggering condition,specified by a state-based event-triggered strategy,is satisfied.By doing so,not only the security and confidentiality of data transmitted over the communication network are protected,but also the ciphertext expansion phenomenon can be relieved.Additionally,by tactfully designing the quantization sensitivities and triggering error,the proposed event-driven encrypted control framework ensures the asymptotic stability of the overall closedloop system.Finally,a simulation example of the secure motion control for an inverted pendulum cart system is presented to evaluate the effectiveness of the theoretical results.

关键词： Cyber-security encrypted control event-triggered control(ETC) networked control systems(NCSs) semi-homomorphic encryption

Adaptive Space Expansion for Fast Motion Planning

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IEEE/CAA Journal of Automatica Sinica 2024年第6期11卷 1499-1514页

作者： Shenglei shi Jiankui Chen State Key Laboratory of Digital Manufacturing Equipment and Technology School of Mechanical Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China

The sampling process is very inefficient for sam-pling-based motion planning algorithms that excess random sam-ples are generated in the planning space.In this paper,we pro-pose an adaptive space expansion(ASE)approach which belongs to the informed sampling category to improve the sampling effi-ciency for quickly finding a feasible path.The ASE method enlarges the search space gradually and restrains the sampling process in a sequence of small hyper-ellipsoid ring subsets to avoid exploring the unnecessary space.Specifically,for a con-structed small hyper-ellipsoid ring subset,if the algorithm cannot find a feasible path in it,then the subset is expanded.Thus,the ASE method successively does space exploring and space expan-sion until the final path has been found.Besides,we present a particular construction method of the hyper-ellipsoid ring that uniform random samples can be directly generated in it.At last,we present a feasible motion planner BiASE and an asymptoti-cally optimal motion planner BiASE*using the bidirectional exploring method and the ASE strategy.Simulations demon-strate that the computation speed is much faster than that of the state-of-the-art algorithms.The source codes are available at https://***/shshlei/ompl.

关键词： Adaptive space expansion(ASE) hyper-ellipsoid ring informed sampling motion planning.

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Impact of frailty on outcomes of elderly patients undergoing percutaneous coronary intervention: A systematic review and metaanalysis

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World Journal of Clinical Cases 2024年第1期12卷 107-118页

作者： shi-shi Wang Wang-Hao Liu Department of Emergency Medicine Huzhou Third Municipal HospitalThe Affiliated Hospital of Huzhou UniversityHuzhou 313000Zhejiang ProvinceChina Department of Geriatrics Huzhou Third Municipal Hospitalthe Affiliated Hospital of Huzhou UniversityHuzhou 313000Zhejiang ProvinceChina

BACKGROUND Frailty is a common condition in elderly patients who receive percutaneous coronary intervention(PCI).However,how frailty affects clinical outcomes in this group is unclear.AIM To assess the link between frailty and the outcomes,such as in-hospital complic-ations,post-procedural complications,and mortality,in elderly patients post-PCI.METHODS The PubMed/MEDLINE,EMBASE,Cochrane Library,and Web of Science databases were screened for publications up to August 2023.The primary outcomes assessed were in-hospital and all-cause mortality,major adverse cardiovascular events(MACEs),and major bleeding.The Newcastle-Ottawa Scale was used for quality assessment.RESULTS Twenty-one studies with 739693 elderly patients undergoing PCI were included.Frailty was consistently associated with adverse outcomes.Frail patients had significantly higher risks of in-hospital mortality[risk ratio:3.45,95%confidence interval(95%CI):1.90-6.25],all-cause mortality[hazard ratio(HR):2.08,95%CI:1.78-2.43],MACEs(HR:2.92,95%CI:1.85-4.60),and major bleeding(HR:4.60,95%CI:2.89-7.32)compared to non-frail patients.CONCLUSION Frailty is a pivotal determinant in the prediction of risk of mortality,development of MACEs,and major bleeding in elderly individuals undergoing percutaneous coronary intervention.

关键词： Frailty Elderly Percutaneous coronary intervention Systematic review Meta-analysis

No Reference Image Sharpness Assessment Based on Global Color Difference Variation

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Chinese Journal of Electronics 2024年第1期33卷 293-302页

作者： Chenyang shi Yandan LIN School of Artificial Intelligence Anhui Polytechnic University School of Mechanical Engineering Anhui Polytechnic University Department of Light Sources and Illuminating Engineering Fudan University Academy for Engineering & Technology Fudan University

Image quality assessment(IQA) model is designed to measure the image quality in consistent with subjective ratings by computational models. In this research, a valid no reference IQA(NR-IQA) model for color image sharpness assessment is proposed based on local color difference map in a color space. In the proposed model, the absolute color difference variation and relative color difference variation are combined to evaluate sharpness in YIQ color space(a color coordinate system for the development of the United States color television system). The difference between sharpest and blurriest spot of an image is represented by the absolute color difference variation, and relative color difference variation expresses the variation in the image content. Extensive experiments are performed on five publicly available benchmark synthetic blur databases and two real blur databases, and the results prove that the proposed model work better than the other state-of-the-art and latest NR-IQA models for the prediction accuracy on blurry images. Besides, the model maintains the lowest computational complexity.

关键词： Image sharpness assessment No reference Color difference variation Image quality

An uncertainty investigation for liner impedance eduction methods

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Chinese Journal of Aeronautics 2024年第3期37卷 49-59页

作者： Weihao shi Xiaodong JING School of Energy and Power Engineering Beihang UniversityBeijing 100191China

Impedance eduction methods have been developed for decades to meet the increasing need for high-quality impedance data in the design and optimization of acoustic liners.To this end,it is important to fully investigate the uncertainty problem,to which only limited attention has been devoted so far.This paper considers the possibility of acoustically-induced structural vibration as a nonnegligible uncertainty or error source in impedance eduction experiments.As the frequency moves away from the resonant frequency,with the increase in the value of cavity reactance,the acoustic particle velocity inside liner orifices possibly decreases to the extent comparable to the vibration velocity of liner facing sheet.Thus,the acoustically-induced vibration,although generally being weak except at the inherent structural frequencies,may considerably affect the impedance eduction results near the anti-resonant frequency where the liner has poor absorption.To demonstrate the effect of structural vibration,the vibration velocity of liner facing sheet is estimated from the experimentally educed admittance of the liner samples whose orifices are sealed with tape.Further,a three-dimensional numerical model is set up,in which normal particle velocity is introduced over the solid portion of liner facing sheet to imitate structural vibration,rather than directly solving the acoustic-structural coupling problem.As shown by the results,the vibration of liner facing sheet,whose velocity is as small as estimated by the experiment,can result in anomalous deviation of the educed impedance from the impedance model near the anti-resonant frequency.The trend that the anomalous deviation varies with frequency is numerically captured.

关键词： Impedance eduction Uncertainty analysis Acoustically-induced structural vibration Anti-resonant frequency Perforated liner

Novel milestones for early esophageal carcinoma:From bench to bed

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World Journal of Gastrointestinal Oncology 2024年第4期16卷 1104-1118页

作者： Ji-Han Qi shi-Ling Huang shi-Zhu Jin Department of Gastroenterology and Hepatology The Second Affiliated Hospital of Harbin Medical UniversityHarbin 150086Heilongjiang ProvinceChina

Esophageal cancer(EC)is the seventh most common cancer worldwide,and esophageal squamous cell carcinoma(ESCC)accounts for the majority of cases of EC.To effectively diagnose and treat ESCC and improve patient prognosis,timely diagnosis in the initial phase of the illness is necessary.This article offers a detailed summary of the latest advancements and emerging technologies in the timely identification of ECs.Molecular biology and epigenetics approaches involve the use of molecular mechanisms combined with fluorescence quanti-tative polymerase chain reaction(qPCR),high-throughput sequencing technology(next-generation sequencing),and digital PCR technology to study endogenous or exogenous biomolecular changes in the human body and provide a decision-making basis for the diagnosis,treatment,and prognosis of diseases.The invest-igation of the microbiome is a swiftly progressing area in human cancer research,and microorganisms with complex functions are potential components of the tumor microenvironment.The intratumoral microbiota was also found to be connected to tumor progression.The application of endoscopy as a crucial technique for the early identification of ESCC has been essential,and with ongoing advancements in technology,endoscopy has continuously improved.With the advancement of artificial intelligence(AI)technology,the utilization of AI in the detection of gastrointestinal tumors has become increasingly prevalent.The implementation of AI can effectively resolve the discrepancies among observers,improve the detection rate,assist in predicting the depth of invasion and differentiation status,guide the pericancerous margins,and aid in a more accurate diagnosis of ESCC.

关键词： Early esophageal squamous cell carcinoma Epidemiology and risk factors Molecular biology Epigenetic Microbiology Endoscopy and artificial intelligence

The Enhanced Period Map and Equivariant Deformation Quantizations of Nilpotent Orbits

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Acta Mathematica Sinica,English Series 2024年第3期40卷 885-934页

作者： shi Lin YU Department of Mathematics School of Mathematical SciencesXiamen UniversityXiamen 361005P.R.China

In a previous paper,the author and his collaborator studied the problem of lifting Hamil-tonian group actions on symplectic varieties and Lagrangian subvarieties to their graded deformation quantizations and apply the general results to coadjoint orbit method for semisimple Lie groups.Only even quantizations were considered there.In this paper,these results are generalized to the case of general quantizations with arbitrary periods.The key step is to introduce an enhanced version of the(truncated)period map defined by Bezrukavnikov and Kaledin for quantizations of any smooth sym-plectic variety X,with values in the space of Picard Lie algebroid over X.As an application,we study quantizations of nilpotent orbits of real semisimple groups satisfying certain codimension condition.

关键词： Coadjoint orbit method deformation quantization Harish-Chandra modules semisimple Liegroups