Integration of sensors with engineering thermoplastics allows to track their health and surrounding stimuli.As one of vital backbones to construct sensor systems,copper(Cu)is highly conductive and cost-effective,yet t...Integration of sensors with engineering thermoplastics allows to track their health and surrounding stimuli.As one of vital backbones to construct sensor systems,copper(Cu)is highly conductive and cost-effective,yet tends to easily oxidize during and after processing.Herein,an in-situ integrated sensor system on engineering thermoplastics via hybrid laser direct writing is proposed,which primarily consists of laser-passivated functional Cu interconnects and laser-induced carbon-based sensors.Through a one-step photothermal treatment,the resulting functional Cu interconnects after reductive sintering and passivation are capable of resisting long-term oxidation failure at high temperatures(up to 170℃)without additional encapsulations.Interfacing with signal processing units,such an all-in-one system is applied for long-term and real-time temperature monitoring.This integrated sensor system with facile laser manufacturing strategies holds potentials for health monitoring and fault diagnosis of advanced equipment such as aircrafts,automobiles,high-speed trains,and medical devices.展开更多
With the limited production and use of R245fa,environmentally friendly refrigerant has attracted the attention of researchers.Due to the similar thermal characteristics,R1233zd(E)is considered to be an ideal substitut...With the limited production and use of R245fa,environmentally friendly refrigerant has attracted the attention of researchers.Due to the similar thermal characteristics,R1233zd(E)is considered to be an ideal substitute for R245fa in heat pump systems.In this study,the performance and economic analysis of heat pump systems with R245fa and R1233zd(E)as refrigerants are carried out.The results show that the total cost of R1233zd(E)system is more than 10%higher than that of R245fa system under the same heating load.With the increase of condensation temperature,the heating capacity of both systems decreases,and with the increase of evaporation temperature,the heating capacity increases.The variation trend of coefficient of performance(COP)of the two systems is similar to that of heating capacity.Under the same operating conditions,the COP of R1233zd(E)system is 19.2%higher than that of R245fa system,and the volumetric heat capacity of R1233zd(E)is 9.0%–13.9%lower than that of R245fa.The economic analysis results show that the investment cost of R1233zd(E)system is low under the same heat load.展开更多
The reliability of the eddy current testing (ECT) in flaw detection is quantitatively evaluated by theprobability of detection (POD). Precise and efficient modeling of POD gives direction for the implement of ECTon si...The reliability of the eddy current testing (ECT) in flaw detection is quantitatively evaluated by theprobability of detection (POD). Precise and efficient modeling of POD gives direction for the implement of ECTon sites to avoid false or missing flaw detection. Traditional POD analysis focuses on single uncertain factor orsingle response signal with limited credibility in engineering. This paper considers multiple response signals andmultiple flaw parameters to perform POD. The flaw length, the flaw depth, the coil impedance, and the magneticflux density are comprehensively studied under various lift-off distances. A finite element model (FEM) of ECT isestablished and verified with experiments to obtain sufficient simulation data for discrete POD modeling. Thecontinuous POD function is then fitted based on the discrete values to show the superiority of integrating multiplefactors. A comparison with conventional POD analysis further demonstrates the higher reliability of ECT flawdetection considering multiple flaw parameters and multiple response signals, especially for small flaws.展开更多
The hydraulic exoskeleton is one research hotspot in the field of robotics,which can take heavy load due to the high power density of the hydraulic system.However,the traditional hydraulic system is normally centraliz...The hydraulic exoskeleton is one research hotspot in the field of robotics,which can take heavy load due to the high power density of the hydraulic system.However,the traditional hydraulic system is normally centralized,inefficient,and bulky during application,which limits its development in the exoskeleton.For improving the robot's performance,its hydraulic actuating system should be optimized further.In this paper a novel hydraulic actuating system(HAS)based on electric-hydrostatic actuator is proposed,which is applied to hip and knee joints.Each HAS integrates an electric servo motor,a high-speed micro pump,a specific tank,and other components into a module.The specific parameters are obtained through relevant simulation according to human motion data and load requirements.The dynamic models of the HAS are built,and validated by the system identification.Experiments of trajectory tracking and human-exoskeleton interaction are carried out,which demonstrate the proposed HAS has the ability to be applied to the exoskeleton.Compared with the previous prototype,the total weight of the HAS in the robot is reduced by about 40%,and the power density is increased by almost 1.6 times.展开更多
The spherical valve plate/cylinder block pair has the advantages of strong overturning resistance and large bearing area.However,the configurations of the unloading and pre-boosting triangular grooves on the spherical...The spherical valve plate/cylinder block pair has the advantages of strong overturning resistance and large bearing area.However,the configurations of the unloading and pre-boosting triangular grooves on the spherical valve plate are different from those in the planar valve plate,resulting in special cavitation phenomenon on the spherical port plate pair.In order to study cavitation characteristics of spherical port plate pair,a dynamic CFD model of the piston pump including turbulence model,cavitation model and fluid compressibility is established.A detailed UDF compilation scheme is provided for modelling of the micron-sized spherical oil film mesh,which makes up for the lack of research on the meshing of the spherical oil film.In this paper,using CFD simulation tools,from the perspectives of pressure field,velocity field and gas volume fraction change,a detailed analysis of the transient evolution of the submerged cavitation jet in a axial piston pump with spherical valve plate is carried out.The study indicates the movement direction of the cavitation cloud cluster through the cloud image and the velocity vector direction of the observation point.The sharp decrease of velocity and gas volume fraction indicates the collapse phenomenon of bubbles on the part wall surface.These discoveries verify the special erosion effect in case of the spherical valve plate/cylinder block pair.The submerged cavitation jet generated by the unloading triangular grooves distributed on the spherical valve plate not only cause denudation of the inner wall surface of the valve plate,but also cause strong impact and denudation on the lower surface of the cylinder body.Finally,the direction of the unloading triangular groove was modified to extend the distance between it and the wall surface which can effectively alleviate the erosion effect.展开更多
The research on the hydrodynamics of blades is mainly focused on sea areas with high-speed current.However,the average velocity in most territorial waters of China is smaller than 1 m/s,and the lift type of airfoil bl...The research on the hydrodynamics of blades is mainly focused on sea areas with high-speed current.However,the average velocity in most territorial waters of China is smaller than 1 m/s,and the lift type of airfoil blades has limited application in most of these conditions.Therefore,it is of great significance to study the tidal current energy capture of blades in sub-low speed sea areas.The effect of flow impact resistance on the blade at sub-low current speed is considered and a new type of thin-walled blade based on the lift type of blade is proposed,and then the lift-impact combined hydrodynamic model of horizontal axis blade is established.Based on this model,and considering the characteristics of tidal current and velocity in the sea area of Yushan Islands,simulation and optimization of blade design are carried out.Additionally,the horizontal axis thin-walled blade and the NACA airfoil contrast blade under the same conditions are developed.By using a synthetical experimental test system,the power,torque,rotational speed and load characteristics of these two blades are tested.The performance of the thin-walled blade and the design theory are verified.It shows that this type of blade has much better energy capture efficiency in the sub-low speed sea area.This research will promote the study and development of turbines that can be used in low-speed current sea areas in the future.展开更多
For the purpose of improving the mechanical performance indices of uncertain structures with interval parameters and ensure their robustness when fluctuating under interval parameters, a constrained interval robust op...For the purpose of improving the mechanical performance indices of uncertain structures with interval parameters and ensure their robustness when fluctuating under interval parameters, a constrained interval robust optimization model is constructed with both the center and halfwidth of the most important mechanical performance index described as objective functions and the other requirements on the mechanical performance indices described as constraint functions. To locate the optimal solution of objective and feasibility robustness, a new concept of interval violation vector and its calculation formulae corresponding to different constraint functions are proposed. The math?ematical formulae for calculating the feasibility and objective robustness indices and the robustness?based preferential guidelines are proposed for directly ranking various design vectors, which is realized by an algorithm integrating Kriging and nested genetic algorithm. The validity of the proposed method and its superiority to present interval optimization approaches are demonstrated by a numerical example. The robust optimization of the upper beam in a high?speed press with interval material properties demonstrated the applicability and effectiveness of the proposed method in engineering.展开更多
High repeatability of needle insertion experiments is essential to the needle-phantom interaction model validation.However,the influential factors governing the accuracy of the phantom and needle deformations have not...High repeatability of needle insertion experiments is essential to the needle-phantom interaction model validation.However,the influential factors governing the accuracy of the phantom and needle deformations have not been systematically studied.In this paper,the impact of influential factors,including phantom characteristic represented by the ratio of DMSO and thawing time(TT),needle properties represented by needle external diameter(NED)and operating factors such as needle insertion velocity(IV),insertion positions(IP)and repeated insertion times(RITs)are analyzed by orthogonal experiment design.The range calculation shows the most sensitive parameters to phantom deformations are RITs,IV and DMSO while the most sensitive parameters to needle deflection are DMSO,TT and NED.By variance analysis,the significant factors on maximum tissue deformation(MTD)are IV,followed by RITs,DMSO and IP.And NED and TT have nearly no significant impact on MTD.The significant sequence on maximum needle deflection(MND)is as follows:DMSO,TT and NED.Results show that,among all impacting factors,phantom deformation is susceptible to both material properties and operative factors while the needle deflection is more susceptible to material properties of the phantom,which can help researchers in related fields to conduct experiments in a more precise manner and better understand the needle-phantom interaction mechanism.展开更多
To address the limitation of single acceleration sensor signals in effectively reflecting the health status of rolling bearings,a rolling bearing fault diagnosis method based on the fusion of data-level and feature-le...To address the limitation of single acceleration sensor signals in effectively reflecting the health status of rolling bearings,a rolling bearing fault diagnosis method based on the fusion of data-level and feature-level information was proposed.First,according to the impact characteristics of rolling bearing faults,correlation kurtosis rules were designed to guide the weight distribution of multi-sensor signals.These rules were then combined with a weighted fusion method to obtain high-quality data-level fusion signals.Subsequently,a feature-fusion convolutional neural network(FFCNN)that merges the one-dimensional(1D)features extracted from the fused signal with the two-dimensional(2D)features extracted from the wavelet time-frequency spectrum was designed to obtain a comprehensive representation of the health status of rolling bearings.Finally,the fused features were fed into a Softmax classifier to complete the fault diagnosis.The results show that the proposed method exhibits an average test accuracy of over 99.00%on the two rolling bearing fault datasets,outperforming other comparison methods.Thus,the method can be effectively utilized for diagnosing rolling bearing faults.展开更多
This paper presents a velocity controller for the cutting system of a trench cutter(TC). The cutting velocity of a cutting system is affected by the unknown load characteristics of rock and soil. In addition, geologic...This paper presents a velocity controller for the cutting system of a trench cutter(TC). The cutting velocity of a cutting system is affected by the unknown load characteristics of rock and soil. In addition, geological conditions vary with time. Due to the complex load characteristics of rock and soil, the cutting load torque of a cutter is related to the geological conditions and the feeding velocity of the cutter. Moreover, a cutter's dynamic model is subjected to uncertainties with unknown effects on its function. In this study, to deal with the particular characteristics of a cutting system, a novel adaptive fuzzy integral sliding mode control(AFISMC) is designed for controlling cutting velocity. The model combines the robust characteristics of an integral sliding mode controller with the adaptive adjusting characteristics of an adaptive fuzzy controller. The AFISMC cutting velocity controller is synthesized using the backstepping technique. The stability of the whole system including the fuzzy inference system, integral sliding mode controller, and the cutting system is proven using the Lyapunov theory. Experiments have been conducted on a TC test bench with the AFISMC under different operating conditions. The experimental results demonstrate that the proposed AFISMC cutting velocity controller gives a superior and robust velocity tracking performance.展开更多
Three-dimensional(3D)bioprinting is a rapidly growing technology that has been widely used in tissue engineering,disease studies,and drug screening.It provides the unprecedented capacity of depositing various types of...Three-dimensional(3D)bioprinting is a rapidly growing technology that has been widely used in tissue engineering,disease studies,and drug screening.It provides the unprecedented capacity of depositing various types of biomaterials,cells,and biomolecules in a layer-by-layer fashion,with precisely controlled spatial distribution.This technology is expected to address the organ-shortage issue in the future.In this review,we first introduce three categories of 3D bioprinting strategies:inkjet-based printing(IBP),extrusion-based printing(EBP),and light-based printing(LBP).Biomaterials and cells,which are normally referred to as“bioinks,”are then discussed.We also systematically describe the recent advancements of 3D bioprinting in fabricating cell-laden artificial tissues and organs with solid or hollow structures,including cartilage,bone,skin,muscle,vascular network,and so on.The development of organs-onchips utilizing 3D bioprinting technology for drug discovery and toxicity testing is reviewed as well.Finally,the main challenges in current studies and an outlook of the future research of 3D bioprinting are discussed.展开更多
Most current studies about shield tunneling machine focus on the construction safety and tunnel structure stability during the excavation. Behaviors of the machine itself are also studied, like some tracking control o...Most current studies about shield tunneling machine focus on the construction safety and tunnel structure stability during the excavation. Behaviors of the machine itself are also studied, like some tracking control of the machine. Yet, few works concern about the hydraulic components, especially the pressure and flow rate regulation components. This research focuses on pressure control strategies by using proportional pressure relief valve, which is widely applied on typical shield tunneling machines. Modeling of a commercial pressure relief valve is done. The modeling centers on the main valve, because the dynamic performance is determined by the main valve. To validate such modeling, a frequency-experiment result of the pressure relief valve, whose bandwidth is about 3 Hz, is presented as comparison. The modeling and the frequency experimental result show that it is reasonable to regard the pressure relief valve as a second-order system with two low corner frequencies. PID control, dead band compensation control and adaptive robust control（ARC） are proposed and simulation results are presented. For the ARC, implements by using first order approximation and second order approximation are presented. The simulation results show that the second order approximation implement with ARC can track 4 Hz sine signal very well, and the two ARC simulation errors are within 0.2 MPa. Finally, experiment results of dead band compensation control and adaptive robust control are given. The results show that dead band compensation had about 30° phase lag and about 20% off of the amplitude attenuation. ARC is tracking with little phase lag and almost no amplitude attenuation. In this research, ARC has been tested on a pressure relief valve. It is able to improve the valve＇s dynamic performances greatly, and it is capable of the pressure control of shield machine excavation.展开更多
The constitutive behavior of microcrystals remains mysterious since very little,or no information regarding plastic deformation in the measured stress-strain curve is available due to plastic instability.Furthermore,t...The constitutive behavior of microcrystals remains mysterious since very little,or no information regarding plastic deformation in the measured stress-strain curve is available due to plastic instability.Furthermore,the measured stress-strain curves vary greatly under different control modes,while constitutive behavior should remain unaffected by test methods.Beyond these reasons,probing the real constitutive behavior of microcrystals has long been a challenge because the nonlinear dynamical behaviors of micromechanical testing systems are unclear.Here,we perform and carefully analyze the experiments on singlecrystal aluminum micropillars under displacement control and load control.To interpret these experimental results,a lumpedparameter physical model based on the principle of micromechanical testing is developed,which can directly relate nonlinear dynamics of the micromechanical testing system to the constitutive behavior of microcrystals.This reveals that some stages of the measured stress-strain curve attributed to the control algorithm are not related to constitutive behavior.By solving the nonlinear dynamics of the micromechanical testing system,intense plastic instability(large strain burst)starting from the equilibrium state is attributed to the strain-softening stage of microcrystals.Parametric studies are also performed to reduce the influence of plastic instability on the measured responses.This study provides critical insights for developing various constitutive models and designing a reliable micromechanical testing system.展开更多
With the increasing of the installed capacity of wind power,the condition monitoring and maintains technique is becoming more important.Wind Turbines(WT)gearbox is one of the key wind power components as it plays the ...With the increasing of the installed capacity of wind power,the condition monitoring and maintains technique is becoming more important.Wind Turbines(WT)gearbox is one of the key wind power components as it plays the role of power transmission and speed regulation.Towards this,a number of scholars have pay attention to the fault diagnosis of WT gearbox.The efficiency of Machine Learning(ML)algorithms is highly correlated with signal type,data quality,and extracted features employed.The implementation of ML techniques has proven to be advantageous in simplifying the comprehension prerequisites for fault diagnosis technology concerning fault mechanisms.More and more current studies predominantly concentrate on the utilization and fine-tuning of ML algorithms,while providing limited insights into the features of the acquired data.Therefore,it is necessary to review the research in recent years from the perspective of the combination of feature extraction and ML algorithms,and provide a detailed direction for future WT gearbox fault diagnosis technology research.In this paper,data processing algorithms and typical fault diagnosis methods based on ML methods for WT gearbox are reviewed.For the using of ML method in WT gearbox fault diagnosis,the data prepared for training is very important.The paper firstly reviewed the data analysing method which will support the ML method.The data analysing methods include data acquisition,data preprocessing and feature extraction method.Feature extraction plays a pivotal role in the realm of gearbox fault diagnosis,as it serves as the essence of effective detection.This review will primarily focus on exploring methods that enable the utilization of efficient features in combination with ML techniques to achieve accurate gearbox fault diagnosis.Then typical ML method for WT gearbox fault diagnosis are carefully reviewed.Moreover,some prospects for future research directions are discussed in the end.展开更多
The demand for ocean exploration down to the deep seafloor,for instance,ocean resource exploration and ocean observations,has promoted innovations in underwater technology.Underwater unmanned vehicles are urgently req...The demand for ocean exploration down to the deep seafloor,for instance,ocean resource exploration and ocean observations,has promoted innovations in underwater technology.Underwater unmanned vehicles are urgently required to be deployed and operate on the seafloor.Because most underwater vehicles are unable to operate on the seafloor and even have difficulty reaching there,we developed a seafloor-resident autonomous underwater helicopter(AUH).This paper introduces the new idea and design of AUHs and discusses the pros and cons of AUHs in comparison with other underwater vehicles.Afterwards,we verify the importance of developing new facilities to enable mankind to easily operate close to the seafloor.展开更多
In tunnel construction with tunnel boring machines(TBMs),accurate prediction of the remaining useful life(RUL)of disc cutters is critical for timely maintenance and replacement to avoid delays and cost overruns.This p...In tunnel construction with tunnel boring machines(TBMs),accurate prediction of the remaining useful life(RUL)of disc cutters is critical for timely maintenance and replacement to avoid delays and cost overruns.This paper introduces a novel hybrid model,integrating fundamental and data-driven approaches,to enhance wear prediction of TBM disc cutters and enable accurate RUL estimation.The fundamental model is improved by incorporating composite wear mechanisms and load estimation techniques,showcasing superior prediction accuracy compared to single-mechanism models.Additionally,the hybrid model innovatively incorporates a data-driven supplementary residual term into the improved fundamental model,leading to a high-performance wear prediction model.Using actual field data from a highway tunnel project in Shenzhen,the performance of the hybrid model is rigorously tested and compared with pure fundamental and data-driven models.The hybrid model outperforms the other models,achieving the highest accuracy in predicting TBM disc cutter wear(mean absolute error(MAE)=0.53,root mean square error(RMSE)=0.64).Furthermore,this study thoroughly analyzes the hybrid model’s generalization capability,revealing significant impacts of geological conditions on prediction accuracy.The model’s generalization capability is also improved by expanding and updating the data sets.The RUL estimation results provided by the hybrid model are straightforward and effective,making it a valuable tool by which construction staff can monitor TBM disc cutters.展开更多
The field of cancer research is increasingly recognizing the complex interplay between biomechanics and tumor epigenetics.Biomechanics plays a significant role in the occurrence,development,and metastasis of cancer an...The field of cancer research is increasingly recognizing the complex interplay between biomechanics and tumor epigenetics.Biomechanics plays a significant role in the occurrence,development,and metastasis of cancer and may exert influence by impacting the epigenetic modifications of tumors.In this review,we investigate a spectrum of biomechanical tools,including computational models,measurement instruments,and in vitro simulations.These tools not only assist in deciphering the mechanisms behind these epigenetic changes but also provide novel methods for characterizing tumors,which are significant for diagnosis and treatment.Finally,we discuss the potential of new therapies that target the biomechanical properties of the tumor microenvironment.There is hope that by altering factors such as the stiffness of the extracellular matrix or interfering with mechano-sensing pathways,we can halt tumor progression through epigenetic mechanisms.We emphasize the necessity for multidisciplinary efforts to integrate biomechanics with tumor epigenetics more comprehensively.Such collaboration is anticipated to advance therapeutic strategies and enhance our understanding of cancer biology,signaling the dawn of a new era in cancer treatment and research.展开更多
Shape-morphing hydrogels can be widely used to develop artificial muscles,reconfigurable biodevices,and soft robotics.However,conventional approaches for developing shape-morphing hydrogels highly rely on composite ma...Shape-morphing hydrogels can be widely used to develop artificial muscles,reconfigurable biodevices,and soft robotics.However,conventional approaches for developing shape-morphing hydrogels highly rely on composite materials or complex manufacturing techniques,which limit their practical applications.Herein,we develop an unprecedented strategy to edit the shape morphing of monocomponent natural polysaccharide hydrogel films via integrating gradient cross-linking density and geometry effect.Owing to the synergistic effect,the shape morphing of chitosan(CS)hydrogel films with gradient cross-linking density can be facilely edited by changing their geometries(length-to-width ratios or thicknesses).Therefore,helix,short-side rolling,and longside rolling can be easily customized.Furthermore,various complex artificial 3D deformations such as artificial claw,horn,and flower can also be obtained by combining various flat CS hydrogel films with different geometries into one system,which can further demonstrate various shape transformations as triggered by pH.This work offers a simple strategy to construct a monocomponent hydrogel with geometry-directing programmable deformations,which provides universal insights into the design of shape-morphing polymers and will promote their applications in biodevices and soft robotics.展开更多
The high pressures in gasoline direct injection technology lead to structural damage in some hydraulic components,especially annular damage on the contact area of the valve ball and on the valve seat of the spherical ...The high pressures in gasoline direct injection technology lead to structural damage in some hydraulic components,especially annular damage on the contact area of the valve ball and on the valve seat of the spherical unloading valve in the high-pressure pump.In previous study,the authors have analyzed the damage on the unloading valve and demonstrated that it is caused neither by static damage nor fatigue damage and have put forward the hypothesis of fretting wear.This paper is based on the establishment of the statically indeterminate structure of the unloading valve.The micro friction parameters(stress,friction coefficient,etc.)required for the numerical iterative calculation of fretting wear are calculated.In addition,based on the grid adaptive technology and a modified Archard wear model,the fretting wear is calculated quantitatively and is in good agreement with experimental results.Based on that verification,the wear laws of the valve ball and valve seat under the same hardness,different contact angles,and different assembly stresses,are analyzed in detail,and reasoned suggestions for the structural design and assembly design of the ball valve are given.展开更多
Flapping-wing flying insects possess various advantages,such as high agility and efficiency.The design and manufacture of insect-scale flapping-wing micro aerial vehicle(FWMAV)have attracted increasing attention in re...Flapping-wing flying insects possess various advantages,such as high agility and efficiency.The design and manufacture of insect-scale flapping-wing micro aerial vehicle(FWMAV)have attracted increasing attention in recent decades.Due to the limitations of size and weight,the FWMAV with an onboard battery which can fully mimic insect flight has not been achieved.In this work,we design and fabricate a highly integrated flapping-wing microrobot named Robomoth.The Robomoth consists of a carbon chassis,customized power and control devices,and two piezoelectric ceramic actuators symmetrically distributed in the thorax and controlled individually.It weighs 2.487 g,spans 5.9 cm in length,possesses 9 cm of wingspan,and carries a 0.355 g rechargeable lithium battery.We demonstrate the mobility of the Robomoth through untethered gliding and making turns on the water surface.A simplified dynamic model of the flapping system is proposed to explain the relationship between the driving frequency and the flapping amplitude.The Robomoth is one new untethered bioinspired flapping-wing robot that can perform stable water surface motion,which holds potential applications such as search and rescue on the water.The robot can also provide insight for designing insect-scale flying vehicles.展开更多
基金STI 2030-Major Projects(2022ZD0208601)National Natural Science Foundation of China(52105593)+2 种基金Zhejiang Provincial Natural Science Foundation of China(LDQ24E050001)‘Pioneer’and‘Leading Goose’R&D Program of Zhejiang(2023C01051)Fundamental Research Funds for the Central Universities(226-2024-00085)。
文摘Integration of sensors with engineering thermoplastics allows to track their health and surrounding stimuli.As one of vital backbones to construct sensor systems,copper(Cu)is highly conductive and cost-effective,yet tends to easily oxidize during and after processing.Herein,an in-situ integrated sensor system on engineering thermoplastics via hybrid laser direct writing is proposed,which primarily consists of laser-passivated functional Cu interconnects and laser-induced carbon-based sensors.Through a one-step photothermal treatment,the resulting functional Cu interconnects after reductive sintering and passivation are capable of resisting long-term oxidation failure at high temperatures(up to 170℃)without additional encapsulations.Interfacing with signal processing units,such an all-in-one system is applied for long-term and real-time temperature monitoring.This integrated sensor system with facile laser manufacturing strategies holds potentials for health monitoring and fault diagnosis of advanced equipment such as aircrafts,automobiles,high-speed trains,and medical devices.
基金supported by theKorea Institute of Energy Technology Evaluationand Planning (KETEP) grant funded by the Korean Government (MOTIE) (No. 20202020900060,The development and application of operational technology in smart farm utilizing waste heat fromparticulates reduced smokestack).
文摘With the limited production and use of R245fa,environmentally friendly refrigerant has attracted the attention of researchers.Due to the similar thermal characteristics,R1233zd(E)is considered to be an ideal substitute for R245fa in heat pump systems.In this study,the performance and economic analysis of heat pump systems with R245fa and R1233zd(E)as refrigerants are carried out.The results show that the total cost of R1233zd(E)system is more than 10%higher than that of R245fa system under the same heating load.With the increase of condensation temperature,the heating capacity of both systems decreases,and with the increase of evaporation temperature,the heating capacity increases.The variation trend of coefficient of performance(COP)of the two systems is similar to that of heating capacity.Under the same operating conditions,the COP of R1233zd(E)system is 19.2%higher than that of R245fa system,and the volumetric heat capacity of R1233zd(E)is 9.0%–13.9%lower than that of R245fa.The economic analysis results show that the investment cost of R1233zd(E)system is low under the same heat load.
基金supported by the Key Research and Development Project of Zhejiang Province(Grant No.2023C01248,2023C01069)and the National Natural Science Foundation of China(Grant No.52375135,52305137).
文摘The reliability of the eddy current testing (ECT) in flaw detection is quantitatively evaluated by theprobability of detection (POD). Precise and efficient modeling of POD gives direction for the implement of ECTon sites to avoid false or missing flaw detection. Traditional POD analysis focuses on single uncertain factor orsingle response signal with limited credibility in engineering. This paper considers multiple response signals andmultiple flaw parameters to perform POD. The flaw length, the flaw depth, the coil impedance, and the magneticflux density are comprehensively studied under various lift-off distances. A finite element model (FEM) of ECT isestablished and verified with experiments to obtain sufficient simulation data for discrete POD modeling. Thecontinuous POD function is then fitted based on the discrete values to show the superiority of integrating multiplefactors. A comparison with conventional POD analysis further demonstrates the higher reliability of ECT flawdetection considering multiple flaw parameters and multiple response signals, especially for small flaws.
基金Supported by Nati onal Key R&D Program of China(Grant No.2018YFB1305400,2018YFB1305402)National Natural Science Foundation of China(Grant No.518902883)Fun dame ntal Resea rch Funds for the Central Universities(Grant No.2018XZZX001-04).
文摘The hydraulic exoskeleton is one research hotspot in the field of robotics,which can take heavy load due to the high power density of the hydraulic system.However,the traditional hydraulic system is normally centralized,inefficient,and bulky during application,which limits its development in the exoskeleton.For improving the robot's performance,its hydraulic actuating system should be optimized further.In this paper a novel hydraulic actuating system(HAS)based on electric-hydrostatic actuator is proposed,which is applied to hip and knee joints.Each HAS integrates an electric servo motor,a high-speed micro pump,a specific tank,and other components into a module.The specific parameters are obtained through relevant simulation according to human motion data and load requirements.The dynamic models of the HAS are built,and validated by the system identification.Experiments of trajectory tracking and human-exoskeleton interaction are carried out,which demonstrate the proposed HAS has the ability to be applied to the exoskeleton.Compared with the previous prototype,the total weight of the HAS in the robot is reduced by about 40%,and the power density is increased by almost 1.6 times.
基金Supported by National Natural Science Foundation of China(Grant No.51605322)Shanxi Provincial Natural Science Foundation of China(Grant No.201901D111054)+1 种基金International Cooperation Project of Shanxi Province(Grant No.2016-002)Key Laboratory of Fluid and Power Machinery,Ministry of Education(Grant No.GZKF-201815).
文摘The spherical valve plate/cylinder block pair has the advantages of strong overturning resistance and large bearing area.However,the configurations of the unloading and pre-boosting triangular grooves on the spherical valve plate are different from those in the planar valve plate,resulting in special cavitation phenomenon on the spherical port plate pair.In order to study cavitation characteristics of spherical port plate pair,a dynamic CFD model of the piston pump including turbulence model,cavitation model and fluid compressibility is established.A detailed UDF compilation scheme is provided for modelling of the micron-sized spherical oil film mesh,which makes up for the lack of research on the meshing of the spherical oil film.In this paper,using CFD simulation tools,from the perspectives of pressure field,velocity field and gas volume fraction change,a detailed analysis of the transient evolution of the submerged cavitation jet in a axial piston pump with spherical valve plate is carried out.The study indicates the movement direction of the cavitation cloud cluster through the cloud image and the velocity vector direction of the observation point.The sharp decrease of velocity and gas volume fraction indicates the collapse phenomenon of bubbles on the part wall surface.These discoveries verify the special erosion effect in case of the spherical valve plate/cylinder block pair.The submerged cavitation jet generated by the unloading triangular grooves distributed on the spherical valve plate not only cause denudation of the inner wall surface of the valve plate,but also cause strong impact and denudation on the lower surface of the cylinder body.Finally,the direction of the unloading triangular groove was modified to extend the distance between it and the wall surface which can effectively alleviate the erosion effect.
基金This work was financially supported by the Special Funds of the State Oceanic Administration(Grant No.NBME2011CL02)Ningbo Major Science and Technology Public Relations Project(Grant No.2015C110015)Ningbo Natural Science Foundation Project(Grant No.2014A610091).
文摘The research on the hydrodynamics of blades is mainly focused on sea areas with high-speed current.However,the average velocity in most territorial waters of China is smaller than 1 m/s,and the lift type of airfoil blades has limited application in most of these conditions.Therefore,it is of great significance to study the tidal current energy capture of blades in sub-low speed sea areas.The effect of flow impact resistance on the blade at sub-low current speed is considered and a new type of thin-walled blade based on the lift type of blade is proposed,and then the lift-impact combined hydrodynamic model of horizontal axis blade is established.Based on this model,and considering the characteristics of tidal current and velocity in the sea area of Yushan Islands,simulation and optimization of blade design are carried out.Additionally,the horizontal axis thin-walled blade and the NACA airfoil contrast blade under the same conditions are developed.By using a synthetical experimental test system,the power,torque,rotational speed and load characteristics of these two blades are tested.The performance of the thin-walled blade and the design theory are verified.It shows that this type of blade has much better energy capture efficiency in the sub-low speed sea area.This research will promote the study and development of turbines that can be used in low-speed current sea areas in the future.
基金Supported by National Natural Science Foundation of China(Grant Nos.51775491,51475417,U1608256,51405433)
文摘For the purpose of improving the mechanical performance indices of uncertain structures with interval parameters and ensure their robustness when fluctuating under interval parameters, a constrained interval robust optimization model is constructed with both the center and halfwidth of the most important mechanical performance index described as objective functions and the other requirements on the mechanical performance indices described as constraint functions. To locate the optimal solution of objective and feasibility robustness, a new concept of interval violation vector and its calculation formulae corresponding to different constraint functions are proposed. The math?ematical formulae for calculating the feasibility and objective robustness indices and the robustness?based preferential guidelines are proposed for directly ranking various design vectors, which is realized by an algorithm integrating Kriging and nested genetic algorithm. The validity of the proposed method and its superiority to present interval optimization approaches are demonstrated by a numerical example. The robust optimization of the upper beam in a high?speed press with interval material properties demonstrated the applicability and effectiveness of the proposed method in engineering.
基金Supported by Zhejiang Provincial Natural Science Foundation of China(Grant No.LSD19H180004)National Major Scientific Research Instrument Development Project of China(Grant No.81827804)and Science Fund for Creative Group of NSFC(Grant No.51821903).
文摘High repeatability of needle insertion experiments is essential to the needle-phantom interaction model validation.However,the influential factors governing the accuracy of the phantom and needle deformations have not been systematically studied.In this paper,the impact of influential factors,including phantom characteristic represented by the ratio of DMSO and thawing time(TT),needle properties represented by needle external diameter(NED)and operating factors such as needle insertion velocity(IV),insertion positions(IP)and repeated insertion times(RITs)are analyzed by orthogonal experiment design.The range calculation shows the most sensitive parameters to phantom deformations are RITs,IV and DMSO while the most sensitive parameters to needle deflection are DMSO,TT and NED.By variance analysis,the significant factors on maximum tissue deformation(MTD)are IV,followed by RITs,DMSO and IP.And NED and TT have nearly no significant impact on MTD.The significant sequence on maximum needle deflection(MND)is as follows:DMSO,TT and NED.Results show that,among all impacting factors,phantom deformation is susceptible to both material properties and operative factors while the needle deflection is more susceptible to material properties of the phantom,which can help researchers in related fields to conduct experiments in a more precise manner and better understand the needle-phantom interaction mechanism.
基金The National Natural Science Foundation of China(No.U22A20178)National Key Research and Development Program of China(No.2022YFB3404800)Jiangsu Province Science and Technology Achievement Transformation Special Fund Program(No.BA2023019).
文摘To address the limitation of single acceleration sensor signals in effectively reflecting the health status of rolling bearings,a rolling bearing fault diagnosis method based on the fusion of data-level and feature-level information was proposed.First,according to the impact characteristics of rolling bearing faults,correlation kurtosis rules were designed to guide the weight distribution of multi-sensor signals.These rules were then combined with a weighted fusion method to obtain high-quality data-level fusion signals.Subsequently,a feature-fusion convolutional neural network(FFCNN)that merges the one-dimensional(1D)features extracted from the fused signal with the two-dimensional(2D)features extracted from the wavelet time-frequency spectrum was designed to obtain a comprehensive representation of the health status of rolling bearings.Finally,the fused features were fed into a Softmax classifier to complete the fault diagnosis.The results show that the proposed method exhibits an average test accuracy of over 99.00%on the two rolling bearing fault datasets,outperforming other comparison methods.Thus,the method can be effectively utilized for diagnosing rolling bearing faults.
基金supported by the National High-Tech R&D Program(863)of China(No.2012AA041801)
文摘This paper presents a velocity controller for the cutting system of a trench cutter(TC). The cutting velocity of a cutting system is affected by the unknown load characteristics of rock and soil. In addition, geological conditions vary with time. Due to the complex load characteristics of rock and soil, the cutting load torque of a cutter is related to the geological conditions and the feeding velocity of the cutter. Moreover, a cutter's dynamic model is subjected to uncertainties with unknown effects on its function. In this study, to deal with the particular characteristics of a cutting system, a novel adaptive fuzzy integral sliding mode control(AFISMC) is designed for controlling cutting velocity. The model combines the robust characteristics of an integral sliding mode controller with the adaptive adjusting characteristics of an adaptive fuzzy controller. The AFISMC cutting velocity controller is synthesized using the backstepping technique. The stability of the whole system including the fuzzy inference system, integral sliding mode controller, and the cutting system is proven using the Lyapunov theory. Experiments have been conducted on a TC test bench with the AFISMC under different operating conditions. The experimental results demonstrate that the proposed AFISMC cutting velocity controller gives a superior and robust velocity tracking performance.
基金The authors would like to acknowledge support from the National Natural Science Foundation of China(51875518,51475419,and 81501607)the Natural Science Foundation of Zhejiang Province of China(LY15H160019)the Key Research and Development Projects of Zhejiang Province(2017C01054).
文摘Three-dimensional(3D)bioprinting is a rapidly growing technology that has been widely used in tissue engineering,disease studies,and drug screening.It provides the unprecedented capacity of depositing various types of biomaterials,cells,and biomolecules in a layer-by-layer fashion,with precisely controlled spatial distribution.This technology is expected to address the organ-shortage issue in the future.In this review,we first introduce three categories of 3D bioprinting strategies:inkjet-based printing(IBP),extrusion-based printing(EBP),and light-based printing(LBP).Biomaterials and cells,which are normally referred to as“bioinks,”are then discussed.We also systematically describe the recent advancements of 3D bioprinting in fabricating cell-laden artificial tissues and organs with solid or hollow structures,including cartilage,bone,skin,muscle,vascular network,and so on.The development of organs-onchips utilizing 3D bioprinting technology for drug discovery and toxicity testing is reviewed as well.Finally,the main challenges in current studies and an outlook of the future research of 3D bioprinting are discussed.
基金Supported by National Natural Science Funds of China(Grant No.51275451)National Basic Research Program of China(973 Program,Grant No.2013CB035404)+1 种基金Science Fund for Creative Research Groups of National Natural Science Foundation of China(Grant No.51221004)National Hi-tech Research and Development Program of China(863 Program,Grant No.2013AA040203)
文摘Most current studies about shield tunneling machine focus on the construction safety and tunnel structure stability during the excavation. Behaviors of the machine itself are also studied, like some tracking control of the machine. Yet, few works concern about the hydraulic components, especially the pressure and flow rate regulation components. This research focuses on pressure control strategies by using proportional pressure relief valve, which is widely applied on typical shield tunneling machines. Modeling of a commercial pressure relief valve is done. The modeling centers on the main valve, because the dynamic performance is determined by the main valve. To validate such modeling, a frequency-experiment result of the pressure relief valve, whose bandwidth is about 3 Hz, is presented as comparison. The modeling and the frequency experimental result show that it is reasonable to regard the pressure relief valve as a second-order system with two low corner frequencies. PID control, dead band compensation control and adaptive robust control（ARC） are proposed and simulation results are presented. For the ARC, implements by using first order approximation and second order approximation are presented. The simulation results show that the second order approximation implement with ARC can track 4 Hz sine signal very well, and the two ARC simulation errors are within 0.2 MPa. Finally, experiment results of dead band compensation control and adaptive robust control are given. The results show that dead band compensation had about 30° phase lag and about 20% off of the amplitude attenuation. ARC is tracking with little phase lag and almost no amplitude attenuation. In this research, ARC has been tested on a pressure relief valve. It is able to improve the valve＇s dynamic performances greatly, and it is capable of the pressure control of shield machine excavation.
基金supported by the National Natural Science Foundation of China(Grant Nos.51731009,12102216,and 11972205)the Fundamental Research Funds for the Central Universities(Grant No.2020XZZX005-02)the China Postdoctoral Science Foundation(Grant Nos.2021M691796,and 2021T140379).
文摘The constitutive behavior of microcrystals remains mysterious since very little,or no information regarding plastic deformation in the measured stress-strain curve is available due to plastic instability.Furthermore,the measured stress-strain curves vary greatly under different control modes,while constitutive behavior should remain unaffected by test methods.Beyond these reasons,probing the real constitutive behavior of microcrystals has long been a challenge because the nonlinear dynamical behaviors of micromechanical testing systems are unclear.Here,we perform and carefully analyze the experiments on singlecrystal aluminum micropillars under displacement control and load control.To interpret these experimental results,a lumpedparameter physical model based on the principle of micromechanical testing is developed,which can directly relate nonlinear dynamics of the micromechanical testing system to the constitutive behavior of microcrystals.This reveals that some stages of the measured stress-strain curve attributed to the control algorithm are not related to constitutive behavior.By solving the nonlinear dynamics of the micromechanical testing system,intense plastic instability(large strain burst)starting from the equilibrium state is attributed to the strain-softening stage of microcrystals.Parametric studies are also performed to reduce the influence of plastic instability on the measured responses.This study provides critical insights for developing various constitutive models and designing a reliable micromechanical testing system.
基金supported by the National Key R&D Program of China(Grant No.2020YFB1709800)Open Fund of the Intelligent Green Manufacturing Technology and Equipment Collaborative Innovation center of Shandong Province(IGSD-2020-017)+1 种基金ten thousand people plan project of Zhejiang ProvinceThe“Qizhen Program”of Zhejiang University.
文摘With the increasing of the installed capacity of wind power,the condition monitoring and maintains technique is becoming more important.Wind Turbines(WT)gearbox is one of the key wind power components as it plays the role of power transmission and speed regulation.Towards this,a number of scholars have pay attention to the fault diagnosis of WT gearbox.The efficiency of Machine Learning(ML)algorithms is highly correlated with signal type,data quality,and extracted features employed.The implementation of ML techniques has proven to be advantageous in simplifying the comprehension prerequisites for fault diagnosis technology concerning fault mechanisms.More and more current studies predominantly concentrate on the utilization and fine-tuning of ML algorithms,while providing limited insights into the features of the acquired data.Therefore,it is necessary to review the research in recent years from the perspective of the combination of feature extraction and ML algorithms,and provide a detailed direction for future WT gearbox fault diagnosis technology research.In this paper,data processing algorithms and typical fault diagnosis methods based on ML methods for WT gearbox are reviewed.For the using of ML method in WT gearbox fault diagnosis,the data prepared for training is very important.The paper firstly reviewed the data analysing method which will support the ML method.The data analysing methods include data acquisition,data preprocessing and feature extraction method.Feature extraction plays a pivotal role in the realm of gearbox fault diagnosis,as it serves as the essence of effective detection.This review will primarily focus on exploring methods that enable the utilization of efficient features in combination with ML techniques to achieve accurate gearbox fault diagnosis.Then typical ML method for WT gearbox fault diagnosis are carefully reviewed.Moreover,some prospects for future research directions are discussed in the end.
基金the financial support from the State Key Research and Development Project(2017YFC0306100)Hainan Key Research and Development Project(ZDYF2020197)Fundamental Research Funds for the Zhejiang Provincial Universities(2021XZZX014)。
文摘The demand for ocean exploration down to the deep seafloor,for instance,ocean resource exploration and ocean observations,has promoted innovations in underwater technology.Underwater unmanned vehicles are urgently required to be deployed and operate on the seafloor.Because most underwater vehicles are unable to operate on the seafloor and even have difficulty reaching there,we developed a seafloor-resident autonomous underwater helicopter(AUH).This paper introduces the new idea and design of AUHs and discusses the pros and cons of AUHs in comparison with other underwater vehicles.Afterwards,we verify the importance of developing new facilities to enable mankind to easily operate close to the seafloor.
基金This work received partial support from the National Key R&D Program of China(Nos.2018YFB1702503 and 2020YFF0218004)the National Natural Science Foundation of China(Grant No.52105074)the Open Project of State Key Laboratory of Shield Machine and Boring Technology(No.SKLST-2021-K02).
文摘In tunnel construction with tunnel boring machines(TBMs),accurate prediction of the remaining useful life(RUL)of disc cutters is critical for timely maintenance and replacement to avoid delays and cost overruns.This paper introduces a novel hybrid model,integrating fundamental and data-driven approaches,to enhance wear prediction of TBM disc cutters and enable accurate RUL estimation.The fundamental model is improved by incorporating composite wear mechanisms and load estimation techniques,showcasing superior prediction accuracy compared to single-mechanism models.Additionally,the hybrid model innovatively incorporates a data-driven supplementary residual term into the improved fundamental model,leading to a high-performance wear prediction model.Using actual field data from a highway tunnel project in Shenzhen,the performance of the hybrid model is rigorously tested and compared with pure fundamental and data-driven models.The hybrid model outperforms the other models,achieving the highest accuracy in predicting TBM disc cutter wear(mean absolute error(MAE)=0.53,root mean square error(RMSE)=0.64).Furthermore,this study thoroughly analyzes the hybrid model’s generalization capability,revealing significant impacts of geological conditions on prediction accuracy.The model’s generalization capability is also improved by expanding and updating the data sets.The RUL estimation results provided by the hybrid model are straightforward and effective,making it a valuable tool by which construction staff can monitor TBM disc cutters.
基金supported by Science and Technology Program of Zhejiang Province(Grant No.2023C03071).
文摘The field of cancer research is increasingly recognizing the complex interplay between biomechanics and tumor epigenetics.Biomechanics plays a significant role in the occurrence,development,and metastasis of cancer and may exert influence by impacting the epigenetic modifications of tumors.In this review,we investigate a spectrum of biomechanical tools,including computational models,measurement instruments,and in vitro simulations.These tools not only assist in deciphering the mechanisms behind these epigenetic changes but also provide novel methods for characterizing tumors,which are significant for diagnosis and treatment.Finally,we discuss the potential of new therapies that target the biomechanical properties of the tumor microenvironment.There is hope that by altering factors such as the stiffness of the extracellular matrix or interfering with mechano-sensing pathways,we can halt tumor progression through epigenetic mechanisms.We emphasize the necessity for multidisciplinary efforts to integrate biomechanics with tumor epigenetics more comprehensively.Such collaboration is anticipated to advance therapeutic strategies and enhance our understanding of cancer biology,signaling the dawn of a new era in cancer treatment and research.
基金supported by the National Key R&D Program of China(2017YFA0701303,2017YFC0111202)the National Natural Science Foundation of China(52022102,52003287)+3 种基金the Youth Innovation Promotion Association of CAS(2019353)the CAS Key Laboratory of Health Informatics,Shenzhen Institutes of Advanced Technology,Chinese Academy of Sciences(2011DP173015)the Foundation of Hunan Educational Committee(18K030)the Shenzhen Science and Technology Innovation Committee(JCYJ20180507182051636,KQJSCX20180330170232019).
文摘Shape-morphing hydrogels can be widely used to develop artificial muscles,reconfigurable biodevices,and soft robotics.However,conventional approaches for developing shape-morphing hydrogels highly rely on composite materials or complex manufacturing techniques,which limit their practical applications.Herein,we develop an unprecedented strategy to edit the shape morphing of monocomponent natural polysaccharide hydrogel films via integrating gradient cross-linking density and geometry effect.Owing to the synergistic effect,the shape morphing of chitosan(CS)hydrogel films with gradient cross-linking density can be facilely edited by changing their geometries(length-to-width ratios or thicknesses).Therefore,helix,short-side rolling,and longside rolling can be easily customized.Furthermore,various complex artificial 3D deformations such as artificial claw,horn,and flower can also be obtained by combining various flat CS hydrogel films with different geometries into one system,which can further demonstrate various shape transformations as triggered by pH.This work offers a simple strategy to construct a monocomponent hydrogel with geometry-directing programmable deformations,which provides universal insights into the design of shape-morphing polymers and will promote their applications in biodevices and soft robotics.
基金supported by the National Key R&D Program of China(No.2019YFB2001502)the National Natural Science Foundation of China(No.52075387)+2 种基金the Open Foundation of the State Key Laboratory of Fluid Power&Mechatronic Systems(No.GZKF-201907)the Shanghai Municipal Science and Technology Major Project(No.2021SHZDZX0100)the Shanghai Municipal Commission of Science and Technology Project(No.19511132101),China。
文摘The high pressures in gasoline direct injection technology lead to structural damage in some hydraulic components,especially annular damage on the contact area of the valve ball and on the valve seat of the spherical unloading valve in the high-pressure pump.In previous study,the authors have analyzed the damage on the unloading valve and demonstrated that it is caused neither by static damage nor fatigue damage and have put forward the hypothesis of fretting wear.This paper is based on the establishment of the statically indeterminate structure of the unloading valve.The micro friction parameters(stress,friction coefficient,etc.)required for the numerical iterative calculation of fretting wear are calculated.In addition,based on the grid adaptive technology and a modified Archard wear model,the fretting wear is calculated quantitatively and is in good agreement with experimental results.Based on that verification,the wear laws of the valve ball and valve seat under the same hardness,different contact angles,and different assembly stresses,are analyzed in detail,and reasoned suggestions for the structural design and assembly design of the ball valve are given.
基金supported by the National Natural Science Foundation of China(Grant No.91748209)the 111 Project(Grant No.B21034)the Key Research and Development Program of Zhejiang Province(Grant No.2020C05010)。
文摘Flapping-wing flying insects possess various advantages,such as high agility and efficiency.The design and manufacture of insect-scale flapping-wing micro aerial vehicle(FWMAV)have attracted increasing attention in recent decades.Due to the limitations of size and weight,the FWMAV with an onboard battery which can fully mimic insect flight has not been achieved.In this work,we design and fabricate a highly integrated flapping-wing microrobot named Robomoth.The Robomoth consists of a carbon chassis,customized power and control devices,and two piezoelectric ceramic actuators symmetrically distributed in the thorax and controlled individually.It weighs 2.487 g,spans 5.9 cm in length,possesses 9 cm of wingspan,and carries a 0.355 g rechargeable lithium battery.We demonstrate the mobility of the Robomoth through untethered gliding and making turns on the water surface.A simplified dynamic model of the flapping system is proposed to explain the relationship between the driving frequency and the flapping amplitude.The Robomoth is one new untethered bioinspired flapping-wing robot that can perform stable water surface motion,which holds potential applications such as search and rescue on the water.The robot can also provide insight for designing insect-scale flying vehicles.
