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Cavitation Diagnostics Based on Self-Tuning VMD for Fluid Machinery with Low-SNR Conditions

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Chinese Journal of Mechanical Engineering 2023年第4期36卷 212-226页

作者： Hao liu Zheming tong Bingyang Shang Shuiguang tong State Key Laboratory of Fluid Power and Mechatronic Systems School of Mechanical EngineeringZhejiang UniversityHangzhou 310027China

Variational mode decomposition(VMD)is a suitable tool for processing cavitation-induced vibration signals and is greatly affected by two parameters:the decomposed number K and penalty factorαunder strong noise interference.To solve this issue,this study proposed self-tuning VMD(SVMD)for cavitation diagnostics in fluid machinery,with a special focus on low signal-to-noise ratio conditions.A two-stage progressive refinement of the coarsely located target penalty factor for SVMD was conducted to narrow down the search space for accelerated decomposition.A hybrid optimized sparrow search algorithm(HOSSA)was developed for optimalαfine-tuning in a refined space based on fault-type-guided objective functions.Based on the submodes obtained using exclusive penalty factors in each iteration,the cavitation-related characteristic frequencies(CCFs)were extracted for diagnostics.The power spectrum correlation coefficient between the SVMD reconstruction and original signals was employed as a stop criterion to determine whether to stop further decomposition.The proposed SVMD overcomes the blindness of setting the mode number K in advance and the drawback of sharing penalty factors for all submodes in fixed-parameter and parameter-optimized VMDs.Comparisons with other existing methods in simulation signal decomposition and in-lab experimental data demonstrated the advantages of the proposed method in accurately extracting CCFs with lower computational cost.SVMD especially enhances the denoising capability of the VMD-based method.

关键词： Fluid machinery Self-tuning VMD Cavitation diagnostics Hybrid optimized sparrow search algorithm

A highly active and stable Sr_(2)Fe_(1.5)Mo(0.5)O_(6)‑δ‑Ce_(0.8)Sm_(0.2)O_(1.95)ceramic fuel electrode for efficient hydrogen production via a steam electrolyzer without safe gas

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International Journal of Coal Science & Technology 2022年第1期9卷 217-224页

作者： Yao Wang tong liu Key Laboratory of Hydraulic Machinery Transients Ministry of EducationSchool of Power and Mechanical EngineeringWuhan UniversityHubei 430072 WuhanChina

High temperature steam(H_(2)O)electrolysis via a solid oxide electrolysis cell is an efficient way to produce hydrogen(H_(2))because of its high energy conversion efficiency as well as simple and green process,especially when the electrolysis process is combined with integrated gasification fuel cell technology or derived by renewable energy.However,about 60%-70%of the electricity input is consumed to overcome the large oxygen potential gradient but not for electrolysis to split H_(2)O to produce H_(2)due to the addition of safe gas such as H_(2)in the fuel electrode.In this work,Sr_(2)Fe_(1.5)Mo_(0.5)O_(6)-δ-Ce_(0.8)Sm_(0.2)O_(1.95)(SFM-SDC)ceramic composite material has been developed as fuel electrode to avoid the use of safe gas,and the open circuit voltage(OCV)has been effectively lowered from 1030 to 78 mV when the feeding gas in the fuel electrode is shifted from 3%H_(2)O-97%H_(2)to 3%H_(2)O-97%N_(2),reasonably resulting in a significantly increased electrolysis efficiency.In addition,it is also demonstrated that the electrolysis current density is greatly enhanced by increasing the humidity in the fuel electrode and the working temperature.A considerable electrolysis current density of−0.54 A/cm^(2)is obtained at 800°C and 0.4 V for the symmetrical electrolyzer by exposing SFM-SDC fuel electrode to 23%H_(2)O-77%N_(2),and durability test at 800°C for 35 h demonstrates a relatively stable electrochemical performance for steam electrolysis under the same operation condition without safe gas and a constant electrolysis current density of−0.060 A/cm2.Our findings achieved in this work indicate that SFM-SDC is a highly promising fuel electrode for steam electrolysis.

关键词： Solid oxide electrolysis cell Steam electrolysis Fuel electrode Molybdenum doped strontium ferrite Safe gas

Advancements in Humanoid Robots: A Comprehensive Review and Future Prospects

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IEEE/CAA Journal of Automatica Sinica 2024年第2期11卷 301-328页

作者： Yuchuang tong Haotian liu Zhengtao Zhang IEEE CAS Engineering Laboratory for Intelligent Industrial Vision Institute of AutomationChinese Academy of SciencesBeijing 100190China School of Artificial Intelligence University of Chinese Academy of SciencesBeijing 100049China

This paper provides a comprehensive review of the current status, advancements, and future prospects of humanoid robots, highlighting their significance in driving the evolution of next-generation industries. By analyzing various research endeavors and key technologies, encompassing ontology structure,control and decision-making, and perception and interaction, a holistic overview of the current state of humanoid robot research is presented. Furthermore, emerging challenges in the field are identified, emphasizing the necessity for a deeper understanding of biological motion mechanisms, improved structural design,enhanced material applications, advanced drive and control methods, and efficient energy utilization. The integration of bionics, brain-inspired intelligence, mechanics, and control is underscored as a promising direction for the development of advanced humanoid robotic systems. This paper serves as an invaluable resource, offering insightful guidance to researchers in the field,while contributing to the ongoing evolution and potential of humanoid robots across diverse domains.

关键词： Future trends and challenges humanoid robots human-robot interaction key technologies potential applications

Review of Research and Development of Supernumerary Robotic Limbs

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IEEE/CAA Journal of Automatica Sinica 2021年第5期8卷 929-952页

作者： Yuchuang tong Jinguo liu the State Key Laboratory of Robotics Shenyang Institute of AutomationChinese Academy of SciencesShenyang 110016 the Institutes for Robotics and Intelligent Manufacturing Chinese Academy of SciencesShenyang 110016 the University of Chinese Academy of Sciences Beijing 100049China

Supernumerary robotic limbs(SRLs) are a new type of wearable human auxiliary equipment, which is currently a hot research topic in the world. SRLs have broad applications in many fields, and will provide a reference and technical support for the realization of human-robot collaboration and integration,while playing an important role in improving social security and public services. In this paper, representative SRLs are summarized from the aspects of related literature analysis,research status, ontology structure design, control and driving,sensing and perception, and application fields. This paper also analyzes and summarizes the current technical challenges faced by SRLs, and reviews development progress and key technologies,thus giving a prospect of future technical development trends.

关键词： Human-robot cooperation human-robot interaction supernumerary robotic finger supernumerary robotic limb wearable robots

MPC‑Based Coordinated Control of Gear Shifting Process for a Power‑split Hybrid Electric Bus with a Clutchless AMT

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Chinese Journal of Mechanical Engineering 2022年第6期35卷 377-389页

作者： tong liu Xiaohua Zeng Dafeng Song State Key Laboratory of Automotive Simulation and Control Jilin UniversityChangchun 130025China

Two-speed clutchless automated manual transmission(AMT)has been widely implemented in electric vehicles for its simple structure and low cost.In contrast,due to the complex response characteristics of powertrain,utilizing clutchless AMT in a hybrid power system comes with complex coordination control problems.In order to address these issues,a power-split hybrid electric bus with two-speed clutchless AMT is studied in this paper,and a coordinated control method based on model predictive control(MPC)is used in gear shifting control strategy(GSCS)to improve gear shifting quality and reduce system jerk.First,the dynamic model of power sources and other main powertrain components including a single planetary gear set and AMT are established on the basis of data-driven and mechanism modeling methods.Second,the GSCS is put forward using the segmented control idea,and the shifting process is divided into five phases,including(I)unloading of drive motor,(II)shifting to neutral gear,(III)active speed synchronization by drive motor,(IV)engaging to new gear,and(V)resuming the drive motor’s power,among which the phases I and V have evident impact on the system jerk.Then,the MPC-based control method is adopted for these phases,and the fast compensation of driving torque is realized by combining the prediction model and quadratic programming method.The simulation results show that the proposed GSCS can effectively reduce shift jerk and improve driving comfort.This research proposes a coordinated control strategy of two-speed clutchless AMT,which can effectively improve the smoothness of gear shifting and provides a reference for the application of two speed clutchless AMT in power-split hybrid powertrains.

关键词： Power-split hybrid electric bus Shift jerk Model predictive control

Housing Boom,Dutch Disease,and the Decline in China's Manufacturing Exports

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China & World Economy 2023年第3期31卷 205-229页

作者： Zhuqing liu Jiadong tong School of Economics Fujian Normal UniversityChina School of Economics Nankai UniversityChina

Drawing on Dutch disease theory,we assess how the recent housing boom has contributed to a decline in China's manufacturing exports.Using Chinese city and enterprise panel data from 2004 to 2013,our analysis reveals that Dutch disease indeed exists and that the housing price increase has played a very important role in affecting China's manufacturing exports through two key channels:resource movement effect and spending effect.Specifically,this paper found that:(i)the housing price increase hindered labor flowing into China's manufacturing industry(resource movement efect)and caused higher inflation(spending effect);(ii)the housing boom clearly impeded China's manufacturing exports,especially after the outbreak of the global economic crisis in 2008;(ii)the impacts of the housing price increase on China's manufacturing exports were heterogenous,and were more significant for labor-intensive manufacturing businesses,businesses that were foreign owned,less R&D intensive,or located in the central and western regions.

关键词： Dutch disease housing boom manufacturing export resource movement effect spendingeffect

Subjective or objective:How the style of text in computational advertising influences consumer behaviors?

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Fundamental Research 2022年第1期2卷 144-153页

作者： Minxue Huang tong liu Economy and Management School Wuhan UniversityWuhan 430072China

In the era of computational advertising,advertising effectiveness can be measured by different metrics at different stages of the sales funnel.In the upper funnel,the click-through rate(CTR,the rate of click per impression)represents the attractiveness of the advertising;the conversion rate(CVR,the rate of conversion per click)in the lower funnel indicates the persuasiveness of the advertising.Achieving higher CTR and CVR may need distinct advertising strategies:improving CTR requires raising more consumers'interest in the ad,which is more beneficial to publishers;boosting CVR needs the ad to inspire more consumers’desire in the product(service),which is more profitable to advertisers.In order to study the performance of advertising texts in terms of the two dimensions and reconcile the two different goals,this paper draws on Speech act theory(SAT)in linguistics to classify advertising texts into three types(i.e.,assertive,expressive,and directive),and analyzes how advertising texts can impact consumer behaviors.We further categorize the above three styles of advertising texts into subjective type(i.e.,expressive and directive)and objective type(i.e.,assertive).Based on a field study,we find that subjective advertising with more personalization leads to a higher CTR,while objective advertising with higher consistency with the brand information results in a higher CVR.The results suggest that firms with different marketing goals should utilize different styles of advertising texts to elicit desirable consumer behaviors during different stages of the sales funnel.

关键词： Advertising text Click-through rate Conversion rate Computational advertising Speech act theory

Semantic segmentation-assisted instance feature fusion for multi-level 3D part instance segmentation

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Computational Visual Media 2023年第4期9卷 699-715页

作者： Chun-Yu Sun Xin tong Yang liu Institute for Advanced Study Tsinghua UniversityBeijing 100084China Microsoft Research Asia Beijing 100080China

Recognizing 3D part instances from a 3D point cloud is crucial for 3D structure and scene understanding.Several learning-based approaches use semantic segmentation and instance center prediction as training tasks and fail to further exploit the inherent relationship between shape semantics and part instances.In this paper,we present a new method for 3D part instance segmentation.Our method exploits semantic segmentation to fuse nonlocal instance features,such as center prediction,and further enhances the fusion scheme in a multi-and cross-level way.We also propose a semantic region center prediction task to train and leverage the prediction results to improve the clustering of instance points.Our method outperforms existing methods with a large-margin improvement in the PartNet benchmark.We also demonstrate that our feature fusion scheme can be applied to other existing methods to improve their performance in indoor scene instance segmentation tasks.

关键词： 3D part instance segmentation feature fusion 3D deep learning

Modeling of Cyclic Bending of Thin Foils Using Higher-Order Strain Gradient Plasticity

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Acta Mechanica Solida Sinica 2022年第4期35卷 616-631页

作者： tong Luo Fenfei Hua Dabiao liu School of Aerospace Engineering Huazhong University of Science and TechnologyWuhan430074China Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment Wuhan430074China

The plastic behaviors of thin metallic foils,including size effect,Bauschinger effect,and passivation effect,are studied under cyclic bending condition using the strain gradient visco-plasticity theory.The finite element simulations are performed on the cyclic bending of the elasto-viscoplastic thin foils with passivated and unpassivated surfaces.The study is also conducted on the transition from a passivated surface to an unpassivated one.The roles of the dissipative and energetic gradient terms are emphasized.From the results,it is found that the dissipative gradient terms increase the yield strength,while the energetic gradient terms increase the strain hardening,resulting in an anomalous Bauschinger effect.Further,it is observed that the surface passivation effect increases both the normalized bending moment at initial yielding and strain hardening.The comparison between the numerical results of cases with and without passivation demonstrates that the switching of boundary conditions significantly affects the plastic behavior of the foils under cyclic bending.

关键词： Strain gradient plasticity Size effect Bauschinger effect Geometrically necessary dislocations Bending