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Tuning heterogeneous microstructures to enhance mechanical properties of nano-TiN particle reinforced Haynes 230 composites by laser powder bed fusion

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Rare Metals 2024年第9期43卷 4548-4565页

作者： Wen-Jie Liu Hui Li Qian-Xing Yin He-Jun Du School of Power and mechanical engineering Wuhan University The institute of Technological Sciences Wuhan University School of mechanical&Aerospace engineering Nanyang Technological University

Laser powder bed fusion(LPBF) is considered to be one of the most promising additive manufacturing technologies for producing components with geometries and high geometrical precision that are unattainable by traditional technologies. The superalloy exhibits exceptional mechanical and high-temperature performances,rendering it a prime candidate for advanced aero-engine applications. Despite the high demand for LPBF-manufactured superalloys, the superalloy is one of the materials manufactured difficultly by LPBF due to their large laser absorptivity fluctuation, poor molten pool stability and sharp temperature gradient. Hence, superalloys are characterized by severe pores, undesirable coarse columnar grains and poor mechanical properties. In this work, the effect of nano-Ti N particles on defects, molten pool characteristics and microstructure and performance of the composites were investigated. The 4.5 wt% Ti N/Haynes230 samples exhibited exceptional nanohardness and elastic modulus with maximum values reaching 5.53 GPa and 240.03 GPa, respectively. These superior mechanical properties were attributed to the combined effects of spatter and gas pore inhibition, grain refinement and duplex nanophases strengthening. Moreover, the stability of molten pool was enhanced, and spatter was effectively suppressed by adding nano-Ti N particles, while grain refinement and columnar to equiaxed transitions were promoted. Furthermore, the matrix exhibited a high dislocation density due to a significant hindrance of dislocation movement caused by massive nano-phases(e.g., Ti N and M23C6), resulting in the formation of extensive dislocation tangles and *** work offers novel insights into the role of nanoparticles reinforced superalloy composites by LPBF.

关键词： Composites Laser powder bed fusion mechanical properties Microstructure Molten pool characteristics

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An Imbalanced Data Classification Method Based on Hybrid Resampling and Fine Cost Sensitive Support Vector Machine

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Computers, Materials & Continua 2024年第6期79卷 3977-3999页

作者： Bo Zhu Xiaona Jing Lan Qiu Runbo Li College of mechanical and electrical engineering Kunming University of Science&TechnologyKunming650500China

When building a classification model,the scenario where the samples of one class are significantly more than those of the other class is called data *** imbalance causes the trained classification model to be in favor of the majority class(usually defined as the negative class),which may do harm to the accuracy of the minority class(usually defined as the positive class),and then lead to poor overall performance of the model.A method called MSHR-FCSSVM for solving imbalanced data classification is proposed in this article,which is based on a new hybrid resampling approach(MSHR)and a new fine cost-sensitive support vector machine(CS-SVM)classifier(FCSSVM).The MSHR measures the separability of each negative sample through its Silhouette value calculated by Mahalanobis distance between samples,based on which,the so-called pseudo-negative samples are screened out to generate new positive samples(over-sampling step)through linear interpolation and are deleted finally(under-sampling step).This approach replaces pseudo-negative samples with generated new positive samples one by one to clear up the inter-class overlap on the borderline,without changing the overall scale of the *** FCSSVM is an improved version of the traditional *** considers influences of both the imbalance of sample number and the class distribution on classification simultaneously,and through finely tuning the class cost weights by using the efficient optimization algorithm based on the physical phenomenon of rime-ice(RIME)algorithm with cross-validation accuracy as the fitness function to accurately adjust the classification *** verify the effectiveness of the proposed method,a series of experiments are carried out based on 20 imbalanced datasets including both mildly and extremely imbalanced *** experimental results show that the MSHR-FCSSVM method performs better than the methods for comparison in most cases,and both the MSHR and the FCSSVM played significan

关键词： Imbalanced data classification Silhouette value Mahalanobis distance RIME algorithm CS-SVM

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Design and experiment of the pneumatic double disc precision seed metering device for Chinese flowering cabbage

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International Journal of Agricultural and Biological engineering 2024年第4期17卷 128-135页

作者： Yan Yu Ruchao Ge Guoying Li Xing Zhang Xiaozhi Tan Dazhi Yi Xiaomin Wang Zhuxin Xu College of mechanical and electrical engineering Qingdao Agricultural UniversityQingdao 266109China

Single seed metering devices for Chinese flowering cabbage planting machines have suffered such deficiencies as low efficiency,poor accuracy,and *** overcome these limitations,a pneumatic double disc precision seed metering device was *** innovative device can simultaneously plant four rows,considering the specific agricultural requirements and the geometric characteristics for Chinese flowering cabbage *** precise parameters of the key component seed disc were derived through theoretical *** addition,a detailed account was given for the working principle and workflow of the seed metering *** discrete element method and EDEM software were employed to optimize the seed disc by exploring the effects of seed disc rotational speed and interleaving seed slots on seed *** rotation experiments were conducted to evaluate the impact of seed disc rotational speed and negative *** rates of qualified seeding,double seeding and missing seeding were adopted as test *** results show that,at a seed disc rotational speed of 41.5 r/min and a negative pressure of 3.80 kPa,the average qualified seeding rate is 90.13%,the average missing seeding rate is 3.30%,and the average double seeding rate is 6.02%.These values satisfy the agricultural requirements for planting Chinese flowering *** findings can also provide valuable insights for the structural optimization and design of precision seed metering devices for Chinese flowering cabbage.

关键词： Chinese flowering cabbage precision seed metering device double seed discs pneumatic experiment

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Hybrid stochastic control strategy by two-layer networks for dissipating urban traffic congestion

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Science China(Information Sciences) 2024年第4期67卷 40-41页

作者： Xiaojing ZHONG Bin PANG Feiqi DENG Xueyan ZHAO School of mechanical and electrical engineering Guangzhou University School of Automation Science and engineering South China University of Technology

With the rapid development of mobile devices and geographic information systems, social network data have become part of the traffic condition dissemination system,thereby influencing traffic conditions. Current research has indicated that the dissemination of traffic congestion information can partially alleviate congestion problems and thus enhance road transportation efficiency [1].

关键词： Traffic congestion

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Experimental Analysis of Radial Centrifugal Pump Shutdown

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Fluid Dynamics & Materials Processing 2024年第4期20卷 725-737页

作者： Xiao Sun Jiangbo Tong Yuliang Zhang Haibing Cai Wen Zhou Xiaoqi Jia Litao Ou School of mechanical engineering Hunan University of TechnologyZhuzhou412007China College of mechanical engineering Quzhou UniversityQuzhou324000China zhejiang Testing&Inspection institute for mechanical and electrical Products Quality Co. Ltd.Hangzhou310014China Quzhou Special Equipment Inspection Center Quzhou324000China The zhejiang Provincial Key Lab of Fluid Transmission Technology Zhejiang Sci-Tech UniversityHangzhou310018China Zhuzhou Nanfang Valve Co. Ltd.Zhuzhou412000China

Centrifugal pumps are widely used in the metallurgy,coal,and building *** order to study the hydraulic characteristics of a closed impeller centrifugal pump during its shutdown in the so-called power frequency and frequency conversion modes,experiments were carried to determine the characteristic evolution of parameters such as speed,inlet and outlet pressure,head,flow rate and shaft power.A quasi-steady-state method was also used to further investigate these transient *** results show that,compared to the power frequency input,the performance parameter curves for the frequency conversion input are less volatile and *** characteristic time is longer and the response to shutdown is *** quasi-steady-state theoretical head-flow curves match the experimental head-flow curves more closely at low flow rates when the frequency conversion input is ***,in this case,the similarity law predicts the hydraulic performance more accurately.

关键词： Centrifugal pump power frequency frequency conversion shutdown external characteristic experimental study

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Design and test of a double compression seeder for pre-sowing and seed furrow of wheat in wide-seedling belts

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International Journal of Agricultural and Biological engineering 2024年第4期17卷 136-145页

作者： Xun He Run Zhang Jingfeng Zhang Yinghao Zhu Wanzhang Wang Hongmei Zhang College of mechanical and electrical engineering Henan Agricultural UniversityZhengzhou 450002China

To solve the problem of poor sowing quality due to loose soil in wheat seedbed after land preparation in the Huang-Huaihai region of China,a double compression seeder for pre-sowing and seed furrow of wheat in wide-seedling belts was *** machine sowing operation was divided into two processes:pre-sowing compression and seed ditch compression,pre-sowing compression was carried out homogenization of the pre-sowing seed bed that the tractor wheel has crushed,and the seed ditch compression compresses the seeds and soil in the seed ditch,so that the seeds were embedded in the seed ditch *** analyzing the kinematics of the pre-planting compression device and the spiral blade in the process of soil levelling and compression,the structure of the equal-difference variable-diameter equal-pitch spiral conveying winch was designed,and the key parameters of the drum spiral blade were determined,and then the height of the spiral blades,the rutting distance and the speed of the compression roller were taken as the test factors,and the soil flatness was used as the index to carry out the discrete element simulation *** simulation results show that when the spiral blade was 4.85 cm,the rut distance was 37.4 cm,and the rotation speed was 327.16 r/min,the optimal land flatness was ***,field experiments were carried out on the seeder,and the results showed that:the soil bulk density after operation was 22.7%greater than that before sowing(p<0.01),and the soil flatness was 1.9 cm,which was consistent with the simulated *** use of pre-sowing compression and seed furrow compression methods improved the soil environment of the seed bed,increased the uniformity of the seeding depth,and promoted the root growth of *** study provides equipment support and technical reference for agricultural production in wheat-corn rotation areas in the Huang-Huaihai region of China.

关键词： wheat seeding quality pre-sowing compression seed furrow compression field experiment

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Nonlinear Flap-Wise Vibration Characteristics ofWind Turbine Blades Based onMulti-Scale AnalysisMethod

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Energy engineering 2024年第2期121卷 483-498页

作者： Qifa Lang Yuqiao Zheng Tiancai Cui Chenglong Shi Heyu Zhang School of mechanical and electrical engineering Lanzhou University of TechnologyLanzhou730050China

This work presents a novel approach to achieve nonlinear vibration response based on the Hamilton *** chose the 5-MW reference wind turbine which was established by the National Renewable Energy Laboratory(NREL),to research the effects of the nonlinear flap-wise vibration *** turbine wheel is simplified by treating the blade of a wind turbine as an Euler-Bernoulli beam,and the nonlinear flap-wise vibration characteristics of the wind turbine blades are discussed based on the simplification ***,the blade’s large-deflection flap-wise vibration governing equation is established by considering the nonlinear term involving the centrifugal ***,it is truncated by the Galerkin method and analyzed semi-analytically using the multi-scale analysis method,and numerical simulations are carried out to compare the simulation results of finite elements with the numerical simulation results using Campbell diagram analysis of blade *** results indicated that the rotational speed of the impeller has a significant impact on blade *** the wheel speed of 12.1 rpm and excitation amplitude of 1.23 the maximum displacement amplitude of the blade has increased from 0.72 to *** the amplitude-frequency curve,it can be seen that the multi-peak characteristic of blade amplitude frequency is under centrifugal *** phase trajectories in blade nonlinear vibration,exhibiting periodic motion characteristics,are found through phase diagrams and Poincare section diagrams.

关键词： Wind turbine blades nonlinear vibration Galerkin method multi-scales method

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Systematic Elastostatic Stiffness Model of Over-Constrained Parallel Manipulators Without Additional Constraint Equations

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Chinese Journal of mechanical engineering 2024年第4期 271-289页

作者： Chao Yang Wenyong Yu Wei Ye Qiaohong Chen Fengli Huang College of mechanical and electrical engineering Jiaxing University zhejiang Siekon Transmission Technology Co. Ltd. National and Local Joint engineering Research Center of Reliability Analysis and Testing for mechanical and electrical Products Zhejiang Sci-Tech University School of Computer Science and Technology Zhejiang Sci-Tech University

The establishment of an elastostatic stiffness model for over constrained parallel manipulators(PMs), particularly those with over constrained subclosed loops, poses a challenge while ensuring numerical stability. This study addresses this issue by proposing a systematic elastostatic stiffness model based on matrix structural analysis(MSA)and independent displacement coordinates(IDCs) extraction techniques. To begin, the closed-loop PM is transformed into an open-loop PM by eliminating constraints. A subassembly element is then introduced, which considers the flexibility of both rods and joints. This approach helps circumvent the numerical instability typically encountered with traditional constraint equations. The IDCs and analytical constraint equations of nodes constrained by various joints are summarized in the appendix, utilizing multipoint constraint theory and singularity analysis, all unified within a single coordinate frame. Subsequently, the open-loop mechanism is efficiently closed by referencing the constraint equations presented in the appendix, alongside its elastostatic model. The proposed method proves to be both modeling and computationally efficient due to the comprehensive summary of the constraint equations in the Appendix, eliminating the need for additional equations. An example utilizing an over constrained subclosed loops demonstrate the application of the proposed method. In conclusion, the model proposed in this study enriches the theory of elastostatic stiffness modeling of PMs and provides an effective solution for stiffness modeling challenges they present.

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Dynamic recrystallization mechanism, texture evolution development and mechanical characteristics of a Mg–8.7Gd–4.18Y–0.42Zr magnesium alloy by ECAP

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Progress in Natural Science:Materials International 2024年第02期34卷 376-388页

作者： Ling Zhang Yinglong Li School of Materials Science and engineering Northeastern University School of mechanical and engineering Ningxia Institute of Science and Technology

Equal channel angle pressing is recognized for its ability to refine alloy grains and alter grain orientation, thereby achieve better mechanical performance of the magnesium alloy. This study investigates the microstructures,dynamic recrystallization mechanism, texture development, and mechanical performance of GW94K(Mg–8.7Gd–4.18Y–0.42Zr wt. %) Mg alloy following ECAP-4 passes at 400°C and 3 mm/min. Results show that when high-temperature deformation is undertaken, twin formation is suppressed while dislocation slip is facilitated, increasing dislocation density during deformation. Following ECAP deformation, the sample displayed higher fracture elongation, TYS, and UTS than the as-solutioned GW94K alloy. In particular, the GW94K alloy performed well mechanically after ECAP-4 passes, with an ultimate TYS of 231 MPa, an UTS of 290 MPa, and an elongation of 14.8 %. DDRX and shear bands induce CDRX, both of which are important in plastic deformation. as well as in modifying microstructure and grain orientation during ECAP deformation.

关键词： Dynamic recrystallization mechanism Equal channel angular pressing Magnesium alloy mechanical performance Mg-Gd-Y-Zr alloy Texture development

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Research of caged dynamics of clusters center atoms in Pd_(82)Si_(18) amorphous alloy

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Chinese Physics B 2024年第4期33卷 623-629页

作者：邓永和陈贝祁清华李兵兵高明文大东王小云彭平 School of Computational Science and Electronics Hunan Institute of EngineeringXiangtan 411104China School of Physics and mechanical&electrical engineering Jishou UniversityJishou 416000China School of Materials Science and engineering Hunan UniversityChangsha 410082China

To date,there is still a lack of a comprehensive explanation for caged dynamics which is regarded as one of the intricate dynamic behaviors in amorphous *** study focuses on Pd_(82)Si_(18)as the research object to further elucidate the underlying mechanism of caged dynamics from multiple perspectives,including the cage's lifetime,atomic local environment,and atomic potential *** results reveal that Si atoms exhibit a pronounced cage effect due to the hindrance of Pd atoms,resulting in an anomalous peak in the non-Gaussian *** in-depth investigation was conducted on the caged dynamics differences between fast and slow Si *** comparison to fast Si atoms,slow Si atoms were surrounded by more Pd atoms and occupied lower potential energy states,resulting in smaller diffusion displacements for the slow Si ***,slow Si atoms tend to be in the centers of smaller clusters with coordination numbers of 9 and *** the isothermal relaxation process,clusters with coordination numbers 9 and 10 have longer lifetimes,suggesting that the escape of slow Si atoms from their cages is more *** findings mentioned above hold significant implications for understanding the caged dynamics.

关键词： caged dynamics Pd_(82)Si_(18) amorphous alloy fast and slow atoms clusters lifetime

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