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multi-physics multi-scale simulation of unique equiaxed-to-columnar-to-equiaxed transition during the whole solidification process of Al-Li alloy laser welding

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Journal of materials Science & Technology 2024年第4期171卷 235-251页

作者： Chu Han Ping Jiang Shaoning Geng Liangyuan ren School of mechanical Science and Engineering Huazhong University of Science&Technology(HUST)Wuhan430074China

In this study,a novel multi-physics multi-scale model with the dilute multicomponent phase-field method in three-dimensional(3D)space was developed to investigate the complex microstructure evolu-tion in the molten pool during laser welding of Al-Li *** accurately compute mass data within both two and three-dimensional computational domains,three efficient computing methods,including central processing unit parallel computing,adaptive mesh refinement,and moving-frame algorithm,were *** was placed on the distinctive equiaxed-to-columnar-to-equiaxed transition phenomenon that occurs during the entire solidification process of Al-Li alloy laser *** results indi-cated that the growth distance of columnar grains that epitaxially grew from the base metal(Bm)de-creased as the nucleation rate *** the nucleation rate increased,the morphology of the newly formed grains near the fusion boundary(FB)changed from columnar to equiaxed,and newly formed equiaxed grains changed from having high-order dendrites to no obvious dendrite *** the nucleation rate was sufficiently high,non-dendritic equiaxed grains could directly form near the FB,and there was nearly no epitaxial growth from the ***,simulation results illustrated the com-petition among multiple grains with varying orientations that grow in 3D space near the ***,how equiaxed grain bands develop was *** equiaxed band not only hindered the growth of early columnar grains but also some of its grains could grow epitaxially to form new columnar *** predicted results were in good agreement with experimental measurements and observations.

关键词： Laser welding Al-Li alloy Equiaxed-to-columnar-to-equiaxed transition multi-physics multi-scale model multicomponent alloys 3D phase-field model

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Fault diagnosis of HVAC system with imbalanced data using multi-scale convolution composite neural network

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Building Simulation 2024年第3期17卷 371-386页

作者： Rouhui Wu Yizhu ren mengying Tan Lei Nie School of mechanical Engineering Hubei University of TechnologyWuhan430068China Industrial Research Institute of Xiangyang Hubei University of Technology Xiangyang441100China

Accurate fault diagnosis of heating,ventilation,and air conditioning(HVAC)systems is of significant importance for maintaining normal operation,reducing energy consumption,and minimizing maintenance ***,in practical applications,it is challenging to obtain sufficient fault data for HVAC systems,leading to imbalanced data,where the number of fault samples is much smaller than that of normal ***,most existing HVAC system fault diagnosis methods heavily rely on balanced training sets to achieve high fault diagnosis ***,to address this issue,a composite neural network fault diagnosis model is proposed,which combines SmOTETomek,multi-scale one-dimensional convolutional neural networks(m1DCNN),and support vector machine(SVm).This method first utilizes SmOTETomek to augment the minority class samples in the imbalanced dataset,achieving a balanced number of faulty and normal ***,it employs the m1DCNN model to extract feature information from the augmented ***,it replaces the original Softmax classifier with an SVm classifier for classification,thus enhancing the fault diagnosis *** the SmOTETomek-m1DCNN-SVm method,we conducted fault diagnosis validation on both the ASHRAE RP-1043 dataset and experimental dataset with an imbalance ratio of 1:*** results demonstrate the superiority of this approach,providing a novel and promising solution for intelligent building management,with accuracy and F1 scores of 98.45%and 100%for the RP-1043 dataset and experimental dataset,respectively.

关键词： fault diagnosis chiller imbalanced data SmOTETomek multi-scale neural networks

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Conceptual design and control method for a noncontact annular electromagnetic stabilized satellite platform

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Chinese Journal of Aeronautics 2024年第1期37卷 256-270页

作者： He LIAO Daixin WANG Yuan ren Weijie WANG Institute of Astronautics Nanjing University of Aeronautics and AstronauticsNanjing 211106China Department of Basic Course Space Engineering UniversityHuairou DistrictBeijing 101416China

Disturbance-Free Payload(DFP)spacecraft can meet the requirements of ultra-high attitude pointing accuracy and stability for future space ***,as the main control actuators of DFP spacecraft,Linear Non-Contact Lorentz Actuators(LNCLAs)have control output problems with six-degree-of-freedom coupling and nonlinear effects,which will affect the attitude control performance of DFP *** solve this problem,a novel concept for Non-Contact Annular Electromagnetic Stabilized Satellite Platform(NCAESSP)is proposed in this *** concept is centered on replacing the LNCLAs with a non-contact annular electromagnetic actuator to solve the two problems mentioned ***,for the different control requirements of the payload module and the support module of the NCAESSP,a high-precision attitude controller based on the robust model matching method and a dual quaternion-based adaptive sliding mode controller are ***,the simulation results verify the feasibility and effectiveness of the proposed approach.

关键词： Disturbance-free payload Robust model matching Dual quaternion Sliding mode control Collision avoidance

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maximizing conditional independence for unsupervised domain adaptation

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Science China(Information Sciences) 2024年第5期67卷 136-149页

作者： Yiming ZHAI Chuanxian ren Youwei LUO Daoqing DAI School of mathematics Sun Yat-Sen University

Unsupervised domain adaptation(UDA) studies how to transfer a learner from a labeled source domain to an unlabeled target domain with different distributions. Existing methods mainly focus on matching marginal distributions of the source and target domains, which probably leads to a misalignment of samples from the same class but different domains. In this paper, we tackle this misalignment issue by achieving the class-conditioned transferring from a new perspective. Specifically, we propose a method named maximizing conditional independence(mCI) for UDA, which maximizes the conditional independence of feature and domain given class in the reproducing kernel Hilbert spaces. The optimization of conditional independence can be viewed as a surrogate for minimizing class-wise mutual information between feature and domain. An interpretable empirical estimation of the conditional dependence measure is deduced and connected with the unconditional case. Besides, we provide an upper bound on the target error by taking the class-conditional distribution into account, which provides a new theoretical insight for class-conditioned transferring. Extensive experiments on six benchmark datasets and various ablation studies validate the effectiveness of the proposed model in dealing with UDA.

关键词： conditional independence kernel method domain adaptation class-conditioned transferring

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Exogeneous metal ions as therapeutic agents in cardiovascular disease and their delivery strategies

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Regenerative Biomaterials 2024年第2期3卷 1-16页

作者： Xiaoqian Hong Geer Tian Yang Zhu Tanchen ren Department of Cardiology of the Second Affliated Hospital and State Key Laboratory of Transvascular Implantation Devices Cardiovascular Key Laboratory of Zhejiang ProvinceZhejiang University School of MedicineHangzhou 310o09China Binjiang Institute of Zhejiang University Hangzhou 310053China mOE Key Laboratory of macromolecular Synthesis and Functionalization Department of Polymer Science and EngineeringZhejiang UniversityHangzhou 310027China

metal ions participate in many metabolic processes in the human body,and their homeostasis is crucial for *** cardiovascular diseases(CVDs),the equilibriums of metal ions are frequently interrupted,which are related to a variety of disturbances of physiological processes leading to abnormal cardiac *** supplement of metal ions has the potential to work as therapeutic strategies for the treatment of *** with other therapeutic drugs,metal ions possess broad availability,good stability and safety and diverse drug delivery *** delivery strategies of metal ions are important to exert their ther-apeutic effects and reduce the potential toxic side effects for cardiovascular applications,which are also receiving increasing *** local delivery strategies for metal ions based on various biomaterials are constantly being *** this review,we comprehensively summarized the positive roles of metal ions in the treatment of cVDs from three aspects:protecting cells from oxidative stress,inducing angiogenesis,and adjusting the functions of ion *** addition,we introduced the transferability of metal ions in vascular reconstruction and cardiac tissue repair,as well as the currently available engineered strategies for the precise delivery of metal ions,such as integrated with nanoparticles,hydrogels and scaffolds.

关键词： metal ions cardiovascular disease tissue engineering oxidative stress angiogenesis ion channel

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mEmS Huygens Clock Based on Synchronized micromechanical Resonators

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Engineering 2024年第5期36卷 124-131页

作者： Xueyong Wei mingke Xu Qiqi Yang Liu Xu a Yonghong Qi Ziming ren Juan ren Ronghua Huan Zhuangde Jiang State Key Laboratory for manufacturing System Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Construction machinery Chang’an UniversityXi’an 710064China Department of mechanics Zhejiang UniversityHangzhou 310027China

With the continuous miniaturization of electronic devices,microelectromechanical system(mEmS)oscillators that can be combined with integrated circuits have attracted increasing *** study reports a mEmS Huygens clock based on the synchronization principle,comprising two synchronized mEmS oscillators and a frequency compensation *** mEmS Huygens clock improved shorttime stability,improving the Allan deviation by a factor of 3.73 from 19.3 to 5.17 ppb at 1 s.A frequency compensation system based on the mEmS oscillator’s temperature-frequency characteristics was developed to compensate for the frequency shift of the mEmS Huygens clock by controlling the resonator *** effectively improved the long-term stability of the oscillator,with the Allan deviation improving by 1.6343105 times to 30.9 ppt at 6000 *** power consumption for compensating both oscillators simultaneously is only 2.85 mW·℃^(-1).Our comprehensive solution scheme provides a novel and precise engineering solution for achieving high-precision mEmS oscillators and extends synchronization applications in mEmS.

关键词： Frequency stability Huygens clock mEmS Oscillator Synchronization

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CFD investigation of structural effects of internal gas intake on powder conveying performance in fuel supply systems for aerospace engines

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Particuology 2024年第9期92卷 140-154页

作者： Guanlong ren Haijun Sun Fangjun Chen Wen Shen Yunzhen Cai Yihua Xu Henrik Ström Bilainu Oboirien Qingang Xiong School of Aircraft Engineering Nanchang Hangkong UniversityNanchang330063China Engineering Research Center of Aero-engine Technology for General Aviation Ministry of EducationNanchang330063China State Key Laboratory of Pulp and Paper Engineering South China University of TechnologyGuangzhou510640China Department of mechanics and maritime Sciences Chalmers University of TechnologyGöteborg41296Sweden Department of Chemical Engineering University of JohannesburgJohannesburg17011South Africa

Optimal design of gas intake in powder fuel supply systems is crucial for performance of aerospace *** is little research on the impact of intake structure on powder conveying *** novel internal intakes were proposed,which are spherical,cube-shaped,and *** validation,CFD simulations demonstrate that fluctuation of mass flow rate of powders in the dome-shaped intake is reduced by about 73.3%compared with the annular external *** trends of phase velocities are similar for the spherical and cube-shaped intakes,while those are similar for the annular external and dome-shaped internal *** of area of gas zone for the annular external and spherical internal intakes is larger than that for the cube-shaped and dome-shaped internal *** and relative pressure drop in the fluidization chamber have a stable stage,and fluctuation of relative pressure drop is small when dome-shaped internal intake is used.

关键词： Powder supply system Intake structure Dense gas-solid flow Two-fluid model Powder fluidization Pressure drop

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Effects of projectile parameters on the momentum transfer and projectile melting during hypervelocity impact

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Defence Technology（防务技术） 2024年第2期32卷 89-103页

作者： Wenjin Liu Qingming Zhang renrong Long Zizheng Gong ren Jiankang Xin Hu Siyuan ren Qiang Wu Guangming Song State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China Beijing Institute of Spacecraft Environment Engineering China Academy of Space TechnologyBeijing100094China

The effects of projectile/target impedance matching and projectile shape on energy,momentum transfer and projectile melting during collisions are investigated by numerical *** comparing the computation results with the experimental results,the correctness of the calculation and the statistical method of momentum transfer coefficient is *** shapes of aluminum,copper and heavy tungsten alloy projectiles striking aluminum,basalt,and pumice target for impacts up to 10 km/s are *** influence mechanism of the shape of the projectile and projectile/target density on the momentum transfer was *** an increase in projectile density and length-diameter ratio,the energy transfer time between the projectile and targets is *** projectile decelerates slowly,resulting in a larger cratering *** energy consumed by the projectile in the excavation stage increased,resulting in lower mass-velocity of ejecta and momentum transfer *** numerical simulation results demonstrated that for different projectile/target combinations,the higher the wave impedance of the projectile,the higher the initial phase transition velocity and the smaller the mass of phase *** results can provide theoretical guidance for kinetic impactor design and material selection.

关键词： Hypervelocity impact Energy partitioning Impact melting momentum transfer

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Design,Testing and Control of a magnetorheological Damper for Knee Prostheses

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Journal of Bionic Engineering 2024年第4期21卷 1788-1800页

作者： Hounan Song Yu Cao Wei Chen Lei ren Yongxin ma Kunyang Wang Xu Wang Yao Zhang Luquan ren Key Laboratory of Bionic Engineering Ministry of EducationJilin UniversityChangchun130022People’s Republic of China Department of mechanical Aerospace and Civil EngineeringThe University of ManchesterManchesterM139PLUK

This study aims to develop a magnetorheological(mR)damper for semi-active knee prostheses to restore the walking ability of transfemoral *** core dimensions of the mR damper were determined via theoretical magnetic field calculations,and the theoretical relationship between current and joint torque was derived through electromagnetic ***,a physical prototype of the semi-active prosthetic knee equipped with the mR damper was *** on the data obtained from angle sensor,pressure sensor(loadcell),and inertial measurement unit(ImU)on the prosthesis,a matching control algorithm is *** joint torque of the mR damper can be adaptively adjusted according to the walking speed of the amputee,allowing the amputee to realize a natural *** effectiveness of the control program was verified by the ADAmS and mATLAB *** results of the test and simulation show that the mR damper can provide sufficient torque needed for normal human activities.

关键词： Semi-active knee prosthesis magnetorheological damper Theoretical analysis ADAmS and mATLAB co-simulation

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Performance Prediction Based Workload Scheduling in Co-Located Cluster

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Computer modeling in Engineering & Sciences 2024年第5期139卷 2043-2067页

作者： Dongyang Ou Yongjian ren Congfeng Jiang School of Computer Science and Technology Hangzhou Dianzi UniversityHangzhou310018China

Cloud service providers generally co-locate online services and batch jobs onto the same computer cluster,where the resources can be pooled in order to maximize data center resource *** to resource competition between batch jobs and online services,co-location frequently impairs the performance of online *** study presents a quality of service(QoS)prediction-based schedulingmodel(QPSm)for *** performance prediction of QPSm consists of two parts:the prediction of an online service’s QoS anomaly based on XGBoost and the prediction of the completion time of an offline batch job based on ***-line service QoS anomaly prediction is used to evaluate the influence of batch jobmix on on-line service performance,and batch job completion time prediction is utilized to reduce the total waiting time of batch *** the same number of batch jobs are scheduled in experiments using typical test sets such as CloudSuite,the scheduling time required by QPSm is reduced by about 6 h on average compared with the first-come,first-served strategy and by about 11 h compared with the random scheduling *** with the non-co-located situation,QPSm can improve CPU resource utilization by 12.15% and memory resource utilization by 5.7% on *** show that the QPSm scheduling strategy proposed in this study can effectively guarantee the quality of online services and further improve cluster resource utilization.

关键词： Co-located cluster workload scheduling online service batch jobs data center

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