With the purpose of on-line structural health monitoring,a transducer network was embedded into compos- ite structure to minimize the influence of surroundings.The intrinsic dispersion characteristic of Lamb wave make...With the purpose of on-line structural health monitoring,a transducer network was embedded into compos- ite structure to minimize the influence of surroundings.The intrinsic dispersion characteristic of Lamb wave makes the wavelet transform an effective signal processing method for guided waves.To get high precision in feature extrac- tion,an information entropy-based optimal mother wavelet selection approach was proposed,which was used to choose the most appropriate basis function for particular Lamb wave analysis.By using the embedded sensor network and extracting time-of-flight,delamination in the composite laminate was identified and located.The results demon- strate the effectiveness of the proposed methods.展开更多
Modelica-based object-orient method is proved to be rapid, accurate and easy to modify, which is suitable for prototype modeling and simulation of rotor system, whose parameters need to be modified frequently. Classic...Modelica-based object-orient method is proved to be rapid, accurate and easy to modify, which is suitable for prototype modeling and simulation of rotor system, whose parameters need to be modified frequently. Classical non-object-orient method appears to be inefficient because the code is difficult to modify and reuse. An adequate library for object-orient modeling of rotor system with multi-faults is established, a comparison with non-object-orient method on Jeffcott rotor system and a case study on turbo expander with multi-faults are implemented. The relative tolerance between object-orient method and non-object-orient is less than 0.03%, which proves that these two methods are as accurate as each other. Object-orient modeling and simulation is implemented on turbo expander with crack, rub-impact, pedestal looseness and multi-faults simultaneously. It can be conclude from the case study that when acting on compress side of turbo expander separately, expand wheel is not influenced greatly by crack fault, the existence of rub-impact fault forces expand wheel into quasi-periodic motion and the orbit of expand wheel is deformed and enhanced almost 1.5 times due to pedestal looseness. When acting simultaneously, multi-faults cannot be totally decomposed but can be diagnosed from the feature of vibration. Object-orient method can enhance the efficiency of modeling and simulation of rotor system with multi-faults, which provides an efficient method on prototype modeling and simulation.展开更多
随着核电厂数字化的发展,核仪表系统(Ex-core Nuclear Instrumentation System,简称RPN)[1,2]的控制和保护功能已在安全级分布式控制系统(Safety Digital Control System,简称安全级DCS)平台内实现。为了保证核仪表系统能够连续稳定地...随着核电厂数字化的发展,核仪表系统(Ex-core Nuclear Instrumentation System,简称RPN)[1,2]的控制和保护功能已在安全级分布式控制系统(Safety Digital Control System,简称安全级DCS)平台内实现。为了保证核仪表系统能够连续稳定地监视反应堆核功率,某核电厂调试期间,通过对安全级DCS与RPN系统接口的试验信号进行改进优化,避免了安全级DCS试验时误切除RPN系统源量程,消除了源量程探测器误触发非预期停堆保护信号的风险,保证了核电厂商运后的安全稳定运行。同时作为经验反馈,对RPN源量程投运和退出信号逻辑的原理进行了详细分析,为在运核电厂的数字化改造及三代核电技术的设计研究提供借鉴和思考。展开更多
In order to solve the mixed nonlinear multi-objective optimization problem of discrete/continuous variables of the spherical transducer under the multi-constraint conditions, the electrical-mechanical-acoustic model o...In order to solve the mixed nonlinear multi-objective optimization problem of discrete/continuous variables of the spherical transducer under the multi-constraint conditions, the electrical-mechanical-acoustic model of the spherical transducer is built based on the equivalent circuit theory. The multi-objective optimization mathematical model of the spherical transducer is constructed. The transmitting sound level, input electric power and mass are taken as the optimization objective functions, and the material property parameters, structural size parameters, frequency range and input voltage are taken as the design variables. Besides, the physical properties such as piezoelectric ceramic depolarization,structural strength limit, power capacity and the value of design variables are taken as constraints. The multi-objective optimization design of the spherical transducer is carried out by using the non-dominated sorting genetic algorithm-II(NSGA-II), and the Pareto front solution set is obtained. The effectiveness of the optimization results is verified by experiments. The results show that the transducer prototype designed and manufactured by the multi-objective optimization method reduces the input power by 32.8% and the mass by 27.4% under the premise of meeting the requirements of the transmitting sound level. The results are of great value to the optimization design of transmitting transducer under severe conditions.展开更多
Peeling strength can comprehensively reflect slider track safety and is crucial in car seat safety assessments.Current methods for determining slider peeling strength are primarily physical testing and numerical simul...Peeling strength can comprehensively reflect slider track safety and is crucial in car seat safety assessments.Current methods for determining slider peeling strength are primarily physical testing and numerical simulation.However,these methods encounter the potential challenges of high costs and overlong time consumption which have not been adequately addressed.Therefore,the efficient and low-cost surrogate model emerges as a promising solution.Nevertheless,currently used surrogate models suffer from inefficiencies and complexity in data sampling,lack of robustness in local model predictions,and isolation between data sampling and model prediction.To overcome these challenges,this paper aims to set up a systematic framework for slider track peeling strength prediction,including sensitivity analysis,dataset sampling,and model prediction.Specifically,the interpretable linear regression is performed to identify the sensitivity of various geometric variables to peeling strength.Based on the variable sensitivity,a distance metric is constructed to measure the disparity of different variable groups.Then,the sparsity-targeted sampling(STS)is proposed to formulate a representative dataset.Finally,the sequentially selected local weighted linear regression(SLWLR)is designed to achieve accurate track peeling strength prediction.Additionally,a quantitative cost assessment of the supplementary dataset is proposed by utilizing the minimum adjacent sample distance as a mediator.Experimental results validate the efficacy of sequential selection and the weighting mechanism in enhancing localization robustness.Furthermore,the proposed SLWLR method surpasses similar approaches and other common surrogate methods in terms of prediction performance and data quantity requirements,achieving an average absolute error of 3.3 kN in the simulated test dataset.展开更多
As a typical contact-free manipulation technique that removes friction and contamination risk,levitation has gradually become a preferred candidate for various applications.Magnetic levitation using diamagnetism,beyon...As a typical contact-free manipulation technique that removes friction and contamination risk,levitation has gradually become a preferred candidate for various applications.Magnetic levitation using diamagnetism,beyond Earnshaw’s theorem,is a kind of passive stable levitation that can be achieved at normal temperatures with no energy input.Appealingly,most seemingly nonmagnetic materials can be levitated in a magnetic field and can stabilize free levitation of magnetic materials.This review focuses on the fundamental principles of magnetic levitation using diamagnetism,with emphasis on its burgeoning applications.The theoretical basis associated with the magnetic levitation using diamagnetism is discussed by elucidating the characteristics of diamagnetic materials,and the key levitation mechanisms are clarified.Afterwards,state-of-the-art applications in various aspects,including sensing and measurement,actuating and micromanipulation,energy harvesting and magnetic gravity compensation,are summarized and compared.Finally,the review concludes with a brief outlook on future perspectives.展开更多
We report a highly band-selective,bifunctional meta-surface that serves as an ultra-wide perfect absorber for near-infrared(NIR)band and a visible-band sensor,based on a rational design strategy involving stacking and...We report a highly band-selective,bifunctional meta-surface that serves as an ultra-wide perfect absorber for near-infrared(NIR)band and a visible-band sensor,based on a rational design strategy involving stacking and/or grating of metals,inorganic insulators,and stimuli-responsive materials.PNIPAAm-based hydrogel was utilized as a layer of stimuli-responsive insulator,which is allowed to reversibly swell and collapse in one dimension in response to stimuli such as ambient temperature and chemical environment to empower the sensing capability in the visible band,with the perfect absorption in NIR region intact.The average absorption reached an impressive 99.4%from 780 to 2500 nm,which is attributed to the synergy of localized surface plasmon(LSP),propagating surface plasmon(PSP),and cavity mode.The reported bi-functional meta-surface is particularly attractive for band-selective solar energy harvesting,naked-eye sensing,and adaptive imaging.展开更多
基金Supported by Natural Science Foundation of China(NSFC No.10702041)NSFC Joint Research Fund for Overseas Chinese Young Scholars(10528206)+1 种基金Key International S&T Cooperation Project of China Ministry of Science and Technnlogy(2005DFA00110)Australian Research Council(Discovery Project).
文摘With the purpose of on-line structural health monitoring,a transducer network was embedded into compos- ite structure to minimize the influence of surroundings.The intrinsic dispersion characteristic of Lamb wave makes the wavelet transform an effective signal processing method for guided waves.To get high precision in feature extrac- tion,an information entropy-based optimal mother wavelet selection approach was proposed,which was used to choose the most appropriate basis function for particular Lamb wave analysis.By using the embedded sensor network and extracting time-of-flight,delamination in the composite laminate was identified and located.The results demon- strate the effectiveness of the proposed methods.
基金supported by National Basic Research Program of China(973 Program,Grant No.2011CB706502)
文摘Modelica-based object-orient method is proved to be rapid, accurate and easy to modify, which is suitable for prototype modeling and simulation of rotor system, whose parameters need to be modified frequently. Classical non-object-orient method appears to be inefficient because the code is difficult to modify and reuse. An adequate library for object-orient modeling of rotor system with multi-faults is established, a comparison with non-object-orient method on Jeffcott rotor system and a case study on turbo expander with multi-faults are implemented. The relative tolerance between object-orient method and non-object-orient is less than 0.03%, which proves that these two methods are as accurate as each other. Object-orient modeling and simulation is implemented on turbo expander with crack, rub-impact, pedestal looseness and multi-faults simultaneously. It can be conclude from the case study that when acting on compress side of turbo expander separately, expand wheel is not influenced greatly by crack fault, the existence of rub-impact fault forces expand wheel into quasi-periodic motion and the orbit of expand wheel is deformed and enhanced almost 1.5 times due to pedestal looseness. When acting simultaneously, multi-faults cannot be totally decomposed but can be diagnosed from the feature of vibration. Object-orient method can enhance the efficiency of modeling and simulation of rotor system with multi-faults, which provides an efficient method on prototype modeling and simulation.
文摘随着核电厂数字化的发展,核仪表系统(Ex-core Nuclear Instrumentation System,简称RPN)[1,2]的控制和保护功能已在安全级分布式控制系统(Safety Digital Control System,简称安全级DCS)平台内实现。为了保证核仪表系统能够连续稳定地监视反应堆核功率,某核电厂调试期间,通过对安全级DCS与RPN系统接口的试验信号进行改进优化,避免了安全级DCS试验时误切除RPN系统源量程,消除了源量程探测器误触发非预期停堆保护信号的风险,保证了核电厂商运后的安全稳定运行。同时作为经验反馈,对RPN源量程投运和退出信号逻辑的原理进行了详细分析,为在运核电厂的数字化改造及三代核电技术的设计研究提供借鉴和思考。
基金supported by the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (SL2022ZD102)the Yunnan Technological Innovation Talent Training Project (202305AD160068)。
文摘In order to solve the mixed nonlinear multi-objective optimization problem of discrete/continuous variables of the spherical transducer under the multi-constraint conditions, the electrical-mechanical-acoustic model of the spherical transducer is built based on the equivalent circuit theory. The multi-objective optimization mathematical model of the spherical transducer is constructed. The transmitting sound level, input electric power and mass are taken as the optimization objective functions, and the material property parameters, structural size parameters, frequency range and input voltage are taken as the design variables. Besides, the physical properties such as piezoelectric ceramic depolarization,structural strength limit, power capacity and the value of design variables are taken as constraints. The multi-objective optimization design of the spherical transducer is carried out by using the non-dominated sorting genetic algorithm-II(NSGA-II), and the Pareto front solution set is obtained. The effectiveness of the optimization results is verified by experiments. The results show that the transducer prototype designed and manufactured by the multi-objective optimization method reduces the input power by 32.8% and the mass by 27.4% under the premise of meeting the requirements of the transmitting sound level. The results are of great value to the optimization design of transmitting transducer under severe conditions.
基金supported by the National Natural Science Foundation of China(Grant Nos.12272219 and 12121002).
文摘Peeling strength can comprehensively reflect slider track safety and is crucial in car seat safety assessments.Current methods for determining slider peeling strength are primarily physical testing and numerical simulation.However,these methods encounter the potential challenges of high costs and overlong time consumption which have not been adequately addressed.Therefore,the efficient and low-cost surrogate model emerges as a promising solution.Nevertheless,currently used surrogate models suffer from inefficiencies and complexity in data sampling,lack of robustness in local model predictions,and isolation between data sampling and model prediction.To overcome these challenges,this paper aims to set up a systematic framework for slider track peeling strength prediction,including sensitivity analysis,dataset sampling,and model prediction.Specifically,the interpretable linear regression is performed to identify the sensitivity of various geometric variables to peeling strength.Based on the variable sensitivity,a distance metric is constructed to measure the disparity of different variable groups.Then,the sparsity-targeted sampling(STS)is proposed to formulate a representative dataset.Finally,the sequentially selected local weighted linear regression(SLWLR)is designed to achieve accurate track peeling strength prediction.Additionally,a quantitative cost assessment of the supplementary dataset is proposed by utilizing the minimum adjacent sample distance as a mediator.Experimental results validate the efficacy of sequential selection and the weighting mechanism in enhancing localization robustness.Furthermore,the proposed SLWLR method surpasses similar approaches and other common surrogate methods in terms of prediction performance and data quantity requirements,achieving an average absolute error of 3.3 kN in the simulated test dataset.
基金supported by the Innovation Program of Shanghai Municipal Education Commission(Grant No.2019-01-07-00-02-E00030)the National Science Fund for Distinguished Young Scholars(Grant No.11625208)the Program of Shanghai Academic/Technology Research Leader(Grant No.19XD1421600)。
文摘As a typical contact-free manipulation technique that removes friction and contamination risk,levitation has gradually become a preferred candidate for various applications.Magnetic levitation using diamagnetism,beyond Earnshaw’s theorem,is a kind of passive stable levitation that can be achieved at normal temperatures with no energy input.Appealingly,most seemingly nonmagnetic materials can be levitated in a magnetic field and can stabilize free levitation of magnetic materials.This review focuses on the fundamental principles of magnetic levitation using diamagnetism,with emphasis on its burgeoning applications.The theoretical basis associated with the magnetic levitation using diamagnetism is discussed by elucidating the characteristics of diamagnetic materials,and the key levitation mechanisms are clarified.Afterwards,state-of-the-art applications in various aspects,including sensing and measurement,actuating and micromanipulation,energy harvesting and magnetic gravity compensation,are summarized and compared.Finally,the review concludes with a brief outlook on future perspectives.
基金supported by the Natural Science Foundation of Shanghai (Grant No. 20ZR1471700)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (Grant No. SL2020MS009)the Prospective Research Program at Shanghai Jiao Tong University (Grant No. 19X160010008)
文摘We report a highly band-selective,bifunctional meta-surface that serves as an ultra-wide perfect absorber for near-infrared(NIR)band and a visible-band sensor,based on a rational design strategy involving stacking and/or grating of metals,inorganic insulators,and stimuli-responsive materials.PNIPAAm-based hydrogel was utilized as a layer of stimuli-responsive insulator,which is allowed to reversibly swell and collapse in one dimension in response to stimuli such as ambient temperature and chemical environment to empower the sensing capability in the visible band,with the perfect absorption in NIR region intact.The average absorption reached an impressive 99.4%from 780 to 2500 nm,which is attributed to the synergy of localized surface plasmon(LSP),propagating surface plasmon(PSP),and cavity mode.The reported bi-functional meta-surface is particularly attractive for band-selective solar energy harvesting,naked-eye sensing,and adaptive imaging.
