An experimental system was established to explore the plasma flow control effect for helicopter rotors in hover mode.With the plasma actuator applied at the leading edge of the rotor blades,alternating current dielect...An experimental system was established to explore the plasma flow control effect for helicopter rotors in hover mode.With the plasma actuator applied at the leading edge of the rotor blades,alternating current dielectric barrier discharge(AC-DBD) plasma actuation was generated by a sinusoidal AC high-voltage generator.By direct force measurement,the influence of actuation parameters on the aerodynamic performance of the rotor was investigated at a tip Reynolds number of 1.7 × 105.AC-DBD actuation can delay the blade stall to more than 3° with a 20%increase of about in the thrust coefficient at the post-stall pitch.At a constant motor power driving the rotor,AC-DBD actuation could reduce the rotor’s torque at the stalled pitch and increase the rotational speed of the rotor.Also,AC-DBD actuation could maintain a relatively high hover efficiency of the rotor at large collective pitches.In a wide range of actuation parameters,AC-DBD plasma actuation could improve the rotor’s aerodynamic performance at large blade pitches.High-speed photography of the tuft motion on the blade’s upper surface showed that AC-DBD plasma actuation could promote the reattachment of the blade’s separation flow.展开更多
Since flight accidents due to aircraft icing occur from time to time,this paper proposes an array of impact rod-type plasma synthetic jet de-icing methods for aircraft icing problems.The impact rod-type plasma synthet...Since flight accidents due to aircraft icing occur from time to time,this paper proposes an array of impact rod-type plasma synthetic jet de-icing methods for aircraft icing problems.The impact rod-type plasma synthetic jet actuator(PSJA)is based on the traditional PSJA with an additional impact rod structure for better de-icing in the flight environment.In this work,we first optimize the ice-breaking performance of a single-impact rod-type PSJA,and then conduct an array of impact rod-type plasma synthetic jet ice-breaking experiments to investigate the relationship between crack expansion and discharge energy,ice thickness and group spacing.The results show that the impact force and impulse of a single-impact rod-type PSJA are proportional to the discharge energy,and there exists a threshold energy Qmin for a single actuator to break the ice,which is proportional to the ice thickness.Only when the discharge energy reaches above Qmin can the ice layer produce cracks,and at the same time,the maximum radial crack length produced during the ice-breaking process is proportional to the discharge energy.When the ice is broken by an array of impact rod PSJAs,the discharge energy and group spacing together determine whether the crack can be extended to the middle region of the actuator.When the group spacing is certain,increasing the energy can increase the intersection of cracks in the middle region,and the ice-fragmentation degree is increased and the ice-breaking effect is better.At the same time,the energy estimation method of ice breaking by an array of impact rod-type PSJAs is proposed according to the law when a single actuator is breaking ice.展开更多
Purpose–This study aims to introduce the achievements and benefits of applying wheel/rail-force–based maintenance interval extension of the C80 series wagon in China.Design/methodology/approach–Chinese wagons’exis...Purpose–This study aims to introduce the achievements and benefits of applying wheel/rail-force–based maintenance interval extension of the C80 series wagon in China.Design/methodology/approach–Chinese wagons’existing maintenance strategy had left a certain safety margin for the characteristics of widely running range,unstable service environment and submission to transportation organization requirements.To reduce maintenance costs,China railway(CR)has attempted to extend the maintenance interval since 2020.The maintenance cycle of C80 series heavy haul wagons is extended by three months(no stable routing)or 50,000 km(regular routing).However,in the meantime,the alarming rate of the running state,a key index to reflect the severe degree of hunting stability,by the train performance detection system(TPDS)for the C80 series heavy haul wagons has increased significantly.Findings–The present paper addresses a big data statistical way to evaluate the risk of allowing the C80 series heavy haul wagons to remain in operation longer than stipulated by the maintenance interval initial set.Through the maintenance and wayside-detectordata,whichis divided intothreestages,the extension period(three months),the current maintenance period and the previous maintenance period,this method reveals the alarming rate of hunting was correlated with maintenance interval.The maintainability of wagons will be achieved by utilizing wagon performance degradation modeling with the state of the wheelset and the often-contact side bearing.This paper also proposes a statistical model to return to the average safety level of the previous maintenance period’s baseline through correct alarming thresholds for unplanned corrective maintenance.Originality/value–The paper proposes an approach to reduce safety risk due to maintenance interval extension by effective maintenance program.The results are expected to help the railway company make the optimal solution to balance safety and the economy.展开更多
Force measurements of oscillatory flow acting on a single circular cylinder have been carried out. The experiments were done by oscillating a circular cylinder in still water. Instantaneous forces and velocity fields ...Force measurements of oscillatory flow acting on a single circular cylinder have been carried out. The experiments were done by oscillating a circular cylinder in still water. Instantaneous forces and velocity fields around the cylinder were measured by Particle Image Velocimetry (PIV). The Keulegan-Carpenter number (KC) varied in the range from 5 to 20 and the viscous parameter beta = Re / KC was set at 500 (Re is Reynolds number). It was found that the strength and frequency of the lift force increased with KC number, the main frequency of the lift force being three times the frequency of the oscillatory flow at KC = 20. The movement and strength of the vortices around the cylinder are discussed for different KC numbers.展开更多
Recent progresses on quantum control of cold atoms and trapped ions in both the scientific and technological aspects greatly advance the applications in precision measurement. Thanks to the exceptional controllability...Recent progresses on quantum control of cold atoms and trapped ions in both the scientific and technological aspects greatly advance the applications in precision measurement. Thanks to the exceptional controllability and versatility of these massive quantum systems, unprecedented sensitivity has been achieved in clocks, magnetometers, and interferometers based on cold atoms and ions. Besides, these systems also feature many characteristics that can be employed to facilitate the applications in different scenarios. In this review, we briefly introduce the principles of optical clocks, cold atom magnetometers, and atom interferometers used for precision measurement of time, magnetic field, and inertial forces. The main content is then devoted to summarize some recent experimental and theoretical progresses in these three applications, with special attention being paid to the new designs and possibilities towards better performance. The purpose of this review is by no means to give a complete overview of all important works in this fast developing field, but to draw a rough sketch about the frontiers and show the fascinating future lying ahead.展开更多
Friction stir welding( FSW) is a solid-state welding process that utilizes a rotating tool to induce gross material plastic deformation and join two parts together. A large number of studies have indicated that axial ...Friction stir welding( FSW) is a solid-state welding process that utilizes a rotating tool to induce gross material plastic deformation and join two parts together. A large number of studies have indicated that axial force control can be used to achieve good welding quality. However,in the welding process,due to workpiece's geometry error,improper clamping and other process variations,the axial force can vary significantly and produce welding defects.The control of force in the process of FSW is investigated. At first,the development and evaluation of a closed-loop control system is described,which is equipped with a custom real-time wireless force dynamometer for FSW. Then,an axial force controller is designed based on nonlinear force controllers for FSW. Experimental validations are carried out on an FSW platform. The experimental results demonstrate that the controller maintains the constant axial force and shows desirable dynamic behavior, even when the disturbance is encountered during the welding process.展开更多
The Metal Matrix Composites application has increased in many areas of science and technology, because of its additional physical, wear and mechanical properties. In comparison with all MMC’s, aluminum-based MMC’s a...The Metal Matrix Composites application has increased in many areas of science and technology, because of its additional physical, wear and mechanical properties. In comparison with all MMC’s, aluminum-based MMC’s are finding wide applications due to their better strength to weight ratio, better stiffness, and high thermal conductivity as well as very good wear and corrosion properties. The properties of a composite mainly depend on better distribution of reinforcement in the matrix, which is very difficult to achieve. Basically Redmud is a byproduct of alumina, and it is waste product obtained during Bayer’s process. This waste product must be recycled else it may be dangerous to the environment. Redmud can be used as reinforcement for aluminium composites in order to achieve better properties. The proposed research work includes preparation of Aluminum 6061-Red mud metal matrix composites using liquid metallurgy route following stir casting technique. An alloy Al6061 containing 0.60 percent silicon and Magnesium of 0.82 percent was used as the matrix material. Two different compositions of the Aluminum 6061-Red mud composites are prepared in addition to the base matrix and evaluated for mechanical properties also the force acting on the cutting tool at different spindle speeds during machining of the composite materials were analyzed.展开更多
Accurate wheel-rail force data serves as the cornerstone for analyzing the wheel-rail relationship.However,achieving continuous and precise measurement of this force remains a significant challenge in the field.This a...Accurate wheel-rail force data serves as the cornerstone for analyzing the wheel-rail relationship.However,achieving continuous and precise measurement of this force remains a significant challenge in the field.This article introduces a calibration algorithm for the wheel-rail force that leverages graph neural networks and long short-term memory networks.Initially,a comprehensive wheel-rail force detection system for trains was constructed,encompassing two key components:an instrumented wheelset and a ground wheel-rail force measuring system.Subsequently,utilizing this system,two distinct datasets were acquired from the track inspection vehicle:instrumented wheelset data and ground wheel-rail force data,a feedforward neural network was employed to calibrate the instrumented wheelset data,referencing the ground wheel-rail force data.Furthermore,ground wheel-rail force data for the locomotive was obtained for the corresponding road section.This data was then integrated with the calibrated instrumented wheelset data from the track inspection vehicle.Leveraging the GNN-LSTM network,the article establishes a mapping relationship model between the wheel-rail force of the track inspection vehicle and the locomotive wheel-rail force.This model facilitates continuous measurement of locomotive wheel-rail forces across three typical scenarios:straight sections,long and steep downhill sections,and small curve radius sections.展开更多
Understanding solid‐and fluid‐inertia forces and their coupling with the gravity potential in complex motion scenarios is necessary for evaluating system stability and identifying root causes of system failure and a...Understanding solid‐and fluid‐inertia forces and their coupling with the gravity potential in complex motion scenarios is necessary for evaluating system stability and identifying root causes of system failure and accidents.Because solids and fluids have an infinite number of degrees of freedom and distributed inertia and elasticity,having meaningful qualitative and quantitative nominal measures of the kinematics and forces will contribute to a better understanding of the system dynamics.This paper proposes developing new continuum‐based nominal measures for the characterization of the oscillations and forces.By using a material‐point approach,these new nominal measures,which have their roots in the continuum‐mechanics partial‐differential equations of equilibrium and Frenet geometry,are independent of the formulation or generalized coordinates used to develop the dynamic equations of motion.The paper proposes a data‐driven‐science approach to define a nominal continuum space‐curve geometry with nominal curvature and torsion;a nominal instantaneous motion plane(IMP),which contains the resultant of all forces including the inertia forces;and a nominal instantaneous zero‐force axis(IZFA)along which the resultant of all forces vanishes.While using the material‐point approach eliminates the need for introducing moment equations associated with orientation coordinates,the IMP and IZFA concepts can be used to define the instantaneous axis of significant moment components,which can lead to accidents such as in the case of vehicle rollovers.展开更多
The real-time monitoring of the load in farming by the sensor installed on the tractor's three-point hitch can effectively improve the farming efficiency and force-position combined control,reduce the compaction r...The real-time monitoring of the load in farming by the sensor installed on the tractor's three-point hitch can effectively improve the farming efficiency and force-position combined control,reduce the compaction risk of the wheel on the soil and reduce the fuel consumption in farming process.However,the measurement and quantification of the loads on the three-point hitch have some problems remaining unresolved:testing the accuracy and reliability of a load measuring system is hard when the tractor works in a field,the mathematical model of spatial forces usually lacks a practical and effective validation,and the calibration process of the measurement system is inconvenient and incomplete while easily causing a low accuracy.Specifically,this paper builds a new spatial-force mathematical model based on the geometry of a three-point hitch.To eliminate the discrepancy of the geometric model with the actual structure and to refine the mathematical model,a calibration process is conducted by developing a calibration bench,which is equipped with a data acquisition system and a multi-parameter monitoring interface.The three-point hitch installed on this calibration bench is subject to steady-state loading.The loading force,angle of the lower drawbar,and three-component forces(three shaft pin sensors’forces)of the three-point hitch are well measured.With applying for the measured data to calibrate the theoretical mathematic model eventually derives the resultant force from all the three-component forces,a dynamical loading bench was developed to test the calculated resultant force for the three-point hitch during the sinusoidal and randomly variant dynamical loadings tests.A hitch force measurement system is also developed to collect real-time data and calculate the resultant force of measured three-component forces through the calibrated mathematical model.The results of the dynamical loading tests show that the average relative error MRE=1.09%with an average force measurement time delay beingΔt=0.5 s,the root mean square error RMSE=59.3 N,and the coefficient of determination R2=0.9903.As observed,the shape and the trend of the generated resultant force curve are basically the dynamical loading force.The dynamical loading test proves the high efficacy and reliability of the proposed indoor calibration method for calculating the load based on the three-component forces as measured on the three-point hitch.Besides,the preliminary study of the proposed method on the hitch load provides great potential to improve the indoor six-component measurement and quantification of both the force and momentum acting on the three-point hitch.展开更多
The aerodynamic test in the pulse combustion wind tunnel is very important for the design, evaluation and optimization of aerodynamic characteristics of the hypersonic aircraft.The test accuracy even affects the succe...The aerodynamic test in the pulse combustion wind tunnel is very important for the design, evaluation and optimization of aerodynamic characteristics of the hypersonic aircraft.The test accuracy even affects the success or failure of hypersonic aircraft development. In the aerodynamic test of pulse combustion wind tunnel, the aerodynamic signal is disturbed by the inertial force signal, which seriously affects the test accuracy of aerodynamic force. Aiming at the above problems, this paper innovatively proposes an aerodynamic intelligent identification method, that is the transfer learning network based on adaptive Empirical Modal Decomposition(EMD) and Soft Thresholding(TLN-AE&ST). Compared with the existing aerodynamic intelligent identification model based on deep learning technology, this study introduces the transfer learning idea into the aerodynamic intelligent identification model for the first time. The TLN-AE&ST effectively alleviates the problem of scarcity of training samples for intelligent models due to the high cost of wind tunnel tests, and provides a new idea for further implementation of deep learning technology in the field of wind tunnel aerodynamic testing. And this study designed residual attention block with soft threshold and dense block with adaptive EMD in TLN-AE&ST model. Residual attention block with soft threshold module can more effectively suppress the influence of instrument noise signal on model training effect. Dense block with adaptive EMD makes the deep learning model no longer a black box to a certain extent, and has certain physical significance. Finally, a series of wind tunnel tests were carried out in the Φ = 2.4 m pulse combustion wind tunnel of China Aerodynamic Research and Development Center to verify the effectiveness of TLN-AE&ST.展开更多
Capacitive sensors are efficient tools for biophysical force measurement,which is essential for the exploration of cellular behavior.However,attention has been rarely given on the influences of external mechanical and...Capacitive sensors are efficient tools for biophysical force measurement,which is essential for the exploration of cellular behavior.However,attention has been rarely given on the influences of external mechanical and internal electrical interferences on capacitive sensors.In this work,a bionic swallow structure design norm was developed for mechanical decoupling,and the influences of structural parameters on mechanical behavior were fully analyzed and optimized.A bionic feather comb distribution strategy and a portable readout circuit were proposed for eliminating electrostatic interferences.Electrostatic instability was evaluated,and electrostatic decoupling performance was verified on the basis of a novel measurement method utilizing four complementary comb arrays and applicationspecific integrated circuit readouts.An electrostatic pulling experiment showed that the bionic swallow structure hardly moved by 0.770 nm,and the measurement error was less than 0.009% for the area-variant sensor and 1.118% for the gap-variant sensor,which can be easily compensated in readouts.The proposed sensor also exhibited high resistance against electrostatic rotation,and the resulting measurement error dropped below 0.751%.The rotation interferences were less than 0.330 nm and(1.829×10^(-7))°,which were 35 times smaller than those of the traditional differential one.Based on the proposed bionic decoupling method,the fabricated sensor exhibited overwhelming capacitive sensitivity values of 7.078 and 1.473 pF/μm for gap-variant and area-variant devices,respectively,which were the highest among the current devices.High immunity to mechanical disturbances was maintained simultaneously,i.e.,less than 0.369% and 0.058% of the sensor outputs for the gap-variant and area-variant devices,respectively,indicating its great performance improvements over existing devices and feasibility in ultralow biomedical force measurement.展开更多
Cells,wrapped among their neighbors and surrounding extracellular matrix(ECM),form cell-cell adhesions and cell-ECM adhesions.Extracellular biophysical cues exert a far-reaching influence on a sweeping of cell behavio...Cells,wrapped among their neighbors and surrounding extracellular matrix(ECM),form cell-cell adhesions and cell-ECM adhesions.Extracellular biophysical cues exert a far-reaching influence on a sweeping of cell behaviors,including signal transduction,gene expression,and fate determination.Cell-cell adhesions mediated by inter-cellular adhesion molecules bridge the membranes of adjacent cells through either heterophilic or homophilic adhesive interactions,playing a critical part in multicellular structural maintenance and,therefore,a foundation for multicellular organisms.Cell-ECM adhesions are derived from the interaction between cell adhesion receptors and multi-adhesive matrix proteins to ensure cell and tissue cohesion.Whereas cells not only unilaterally respond to certain cues from extracellular environment but can also alter the physicochemical profiles of the externalities and hence hold important implications for clinical applications.The essential function of cell adhesions has cre-ated tremendous interests in developing methods for measuring and studying cell adhesion properties,namely,cellular force.Here,we describe the collection of cell adhesive inputs on cellular signaling cascades and the“crosstalk”between cell-cell adhesions and cell-ECM adhesions.Furthermore,we provide the summary of the current methods to measure such cell adhesive forces.展开更多
The luminescence of semiconductor quantum dots (QDs) can be adjusted using the piezotronic effect. An external mechanical force applied on the QD generates a piezoelectric potential, which alters the luminescence of...The luminescence of semiconductor quantum dots (QDs) can be adjusted using the piezotronic effect. An external mechanical force applied on the QD generates a piezoelectric potential, which alters the luminescence of the QD. A small mechanical force may induce a significant change on the emission spectrum. In the case of InN QDs, it is demonstrated that the unforced emission wavelength is more than doubled by a force of 1 μN. The strategy of using the piezotronic effect to tune the color of the emission leads to promising noncontact force- measurement applications in biological and medical sensors and force-sensitive displays. Several piezoelectric semiconductor materials have been investigated in terms of the tunability of the emission wavelength in the presence of an external applied force. It is found that CdS and CdSe demonstrate much higher tunability δλ/δF, which makes them suitable for micro/nano-newton force measurement applications.展开更多
The use of optical tweezers to measure forces acting upon microscopic particles has revolutionised fields from material science to cell biology.However,despite optical control capabilities,this technology is highly co...The use of optical tweezers to measure forces acting upon microscopic particles has revolutionised fields from material science to cell biology.However,despite optical control capabilities,this technology is highly constrained by the material properties of the probe,and its use may be limited due to concerns about the effect on biological processes.Here we present a novel,optically controlled trapping method based on light-induced hydrodynamic flows.Specifically,we leverage optical control capabilities to convert a translationally invariant topological defect of a flow field into an attractor for colloids in an effectively one-dimensional harmonic,yet freely rotatable system.Circumventing the need to stabilise particle dynamics along an unstable axis,this novel trap closely resembles the isotropic dynamics of optical tweezers.Using magnetic beads,we explicitly show the existence of a linear force-extension relationship that can be used to detect femtoNewton-range forces with sensitivity close to the thermal limit.Our force measurements remove the need for laser-particle contact,while also lifting material constraints,which renders them a particu-larly interesting tool for the life sciences and engineering.展开更多
The mean activity coefficients of KCI in a KCI-K2B407-H20 ternary system were experimentally determined at 308.15 K by the electromotive force measurement(EMF) via a battery cell without a liquid junction: K-ISEIKC...The mean activity coefficients of KCI in a KCI-K2B407-H20 ternary system were experimentally determined at 308.15 K by the electromotive force measurement(EMF) via a battery cell without a liquid junction: K-ISEIKCI(m1), K2B4O7(m2)ICI-ISE(ISE=ion selective electrode) in a total ionic strength of from 0.01 mol/kg to 1.00 mol/kg at different ionic strength fractions of KzB407 with yB=0, 0.200, 0.400, 0.600 and 0.800. K-ISE and CI-ISE presented a good Nernst effect, which implies that this method could be used to measure the activity coefficients of an electrolyte in the above system. The Harned rule was fitted to the experimental data, the Harned coefficients and the Pitzer single-salt ion parameters of KC1 were evaluated, and the relationship diagrams between the mean activity coefficient of KC1 and the ionic strength fraction(yB) were drawn. The mean activity coefficients of KCI(γ±KCI) decreased monotonically with the increase of I. The experimental results obeyed the Harned rule well.展开更多
The morphing wing concept aims to constantly adapt the aerodynamics to different flight stages.The wing is able to adapt to different flight conditions by an adjustable Aspect Ratio(AR)and sweep.A high AR configuratio...The morphing wing concept aims to constantly adapt the aerodynamics to different flight stages.The wing is able to adapt to different flight conditions by an adjustable Aspect Ratio(AR)and sweep.A high AR configuration provides high aerodynamic efficiency,while a low AR configuration,with highly swept wings offers a good maneuverability.Additionally,the flexible membrane allows the wing surface to stretch and contract in-plane as well as the airfoil to adapt to different aerodynamic loads.In the context of this work,the aerodynamic characteristics of a full model with form-adaptive elasto-flexible membrane wings are investigated experimentally.The focus is on the high-lift regime and on the analysis of the aerodynamic coefficients as well as their sensitivities.Especially,the lateral aerodynamic derivatives at asymmetric wing positions are of interest.展开更多
The aerodynamic performance of a simplified aircraft model with a pair of actively deformed membrane wings is investigated experimentally in this work. The active deformation is achieved with Macro fiber composite(MFC...The aerodynamic performance of a simplified aircraft model with a pair of actively deformed membrane wings is investigated experimentally in this work. The active deformation is achieved with Macro fiber composite(MFC) actuators, which are attached to the upper surface of the wings and occupied 13.7% of the wing surface area. Wind tunnel experiments are conducted to evaluate the influence of membrane active deformation on the aerodynamic performance of the aircraft. The results show that the membrane deforms and vibrates under the actuation which can effectively suppress the leading-edge separation and facilitate the reattachment. Therefore, compared with the rigid wing model, the lift coefficient of the actively deformed membrane wing model is enhanced remarkably from the angle of attack of 7° to 22°. The stall angle is delayed by 2°, and a maximum lift coefficient enhancement of 32.5% is reached, which shows a wide potential application in improving the aerodynamic performance of modern aircraft.展开更多
A combined method is proposed to determine the water entry acceleration at a low impact velocity through image processing. The procedure includes: (1) a sequence of images for water impact are recorded by a high sp...A combined method is proposed to determine the water entry acceleration at a low impact velocity through image processing. The procedure includes: (1) a sequence of images for water impact are recorded by a high speed camera, (2) the sub-pixel image processing method is employed to calculate the displacement with an accuracy on the "sub-pixel" level, (3) the acceleration of the object is acquired by differentiating the displacement twice and with results being further filtered by a carefully designed low-pass Butterworth filter. A theoretically based analysis is conducted for designing the parameters of the low-pass filters. It is shown that the water entry can be regarded as a procedure with a slowly changing velocity. The method is validated with the standard sinusoidal motion and the water entry of a sphere. This approach could be considered as an auxiliary method during the early-stage study of the water entry, and it could be further applied to some complicated circumstances, like the water entry of spinning spheres.展开更多
Electrostatic chucks are one of the core components of semiconductor devices. As a key index of electrostatic chucks, the clamping force must be controlled within a reasonable range. Therefore, it is essential to accu...Electrostatic chucks are one of the core components of semiconductor devices. As a key index of electrostatic chucks, the clamping force must be controlled within a reasonable range. Therefore, it is essential to accurately measure the clamping force. To reduce the negative factors influencing measurement precision and repeatability, this article presents a novel method to measure the clamping force and we elaborate both the principle and the key procedure. A micro-force probe component is introduced to monitor, adjust, and eliminate the gap between the wafer and the electrostatic chuck. The contact force between the ruby probe and the wafer is selected as an important parameter to characterize de-chucking, and we have found that the moment of de-chucking can be exactly judged. Moreover, this article derives the formula calibrating equivalent action area of backside gas pressure under real working conditions, which can effectively connect the backside gas pressure at the moment of de-chucking and the clamping force. The experiments were then performed on a self-designed measuring platform.The de-chucking mechanism is discussed in light of our analysis of the experimental data. Determination criteria for de-chucking point are summed up. It is found that the relationship between de-chucking pressure and applied voltage conforms well to quadratic equation. Meanwhile, the result reveals that actual de-chucking behavior is much more complicated than the description given in the classical empirical formula.展开更多
文摘An experimental system was established to explore the plasma flow control effect for helicopter rotors in hover mode.With the plasma actuator applied at the leading edge of the rotor blades,alternating current dielectric barrier discharge(AC-DBD) plasma actuation was generated by a sinusoidal AC high-voltage generator.By direct force measurement,the influence of actuation parameters on the aerodynamic performance of the rotor was investigated at a tip Reynolds number of 1.7 × 105.AC-DBD actuation can delay the blade stall to more than 3° with a 20%increase of about in the thrust coefficient at the post-stall pitch.At a constant motor power driving the rotor,AC-DBD actuation could reduce the rotor’s torque at the stalled pitch and increase the rotational speed of the rotor.Also,AC-DBD actuation could maintain a relatively high hover efficiency of the rotor at large collective pitches.In a wide range of actuation parameters,AC-DBD plasma actuation could improve the rotor’s aerodynamic performance at large blade pitches.High-speed photography of the tuft motion on the blade’s upper surface showed that AC-DBD plasma actuation could promote the reattachment of the blade’s separation flow.
基金financially supported by National Natural Science Foundation of China(No.12002384)National Key Laboratory Foundation of China(No.614220220200107)+1 种基金National Science and Technology Major Project of China(No.J2019-II-0014-0035)Academician Workstation F0undation of the Green Aerotechnics Research Institute of Chongqing Jiaotong University(No.GATRI2020C06003)。
文摘Since flight accidents due to aircraft icing occur from time to time,this paper proposes an array of impact rod-type plasma synthetic jet de-icing methods for aircraft icing problems.The impact rod-type plasma synthetic jet actuator(PSJA)is based on the traditional PSJA with an additional impact rod structure for better de-icing in the flight environment.In this work,we first optimize the ice-breaking performance of a single-impact rod-type PSJA,and then conduct an array of impact rod-type plasma synthetic jet ice-breaking experiments to investigate the relationship between crack expansion and discharge energy,ice thickness and group spacing.The results show that the impact force and impulse of a single-impact rod-type PSJA are proportional to the discharge energy,and there exists a threshold energy Qmin for a single actuator to break the ice,which is proportional to the ice thickness.Only when the discharge energy reaches above Qmin can the ice layer produce cracks,and at the same time,the maximum radial crack length produced during the ice-breaking process is proportional to the discharge energy.When the ice is broken by an array of impact rod PSJAs,the discharge energy and group spacing together determine whether the crack can be extended to the middle region of the actuator.When the group spacing is certain,increasing the energy can increase the intersection of cracks in the middle region,and the ice-fragmentation degree is increased and the ice-breaking effect is better.At the same time,the energy estimation method of ice breaking by an array of impact rod-type PSJAs is proposed according to the law when a single actuator is breaking ice.
文摘Purpose–This study aims to introduce the achievements and benefits of applying wheel/rail-force–based maintenance interval extension of the C80 series wagon in China.Design/methodology/approach–Chinese wagons’existing maintenance strategy had left a certain safety margin for the characteristics of widely running range,unstable service environment and submission to transportation organization requirements.To reduce maintenance costs,China railway(CR)has attempted to extend the maintenance interval since 2020.The maintenance cycle of C80 series heavy haul wagons is extended by three months(no stable routing)or 50,000 km(regular routing).However,in the meantime,the alarming rate of the running state,a key index to reflect the severe degree of hunting stability,by the train performance detection system(TPDS)for the C80 series heavy haul wagons has increased significantly.Findings–The present paper addresses a big data statistical way to evaluate the risk of allowing the C80 series heavy haul wagons to remain in operation longer than stipulated by the maintenance interval initial set.Through the maintenance and wayside-detectordata,whichis divided intothreestages,the extension period(three months),the current maintenance period and the previous maintenance period,this method reveals the alarming rate of hunting was correlated with maintenance interval.The maintainability of wagons will be achieved by utilizing wagon performance degradation modeling with the state of the wheelset and the often-contact side bearing.This paper also proposes a statistical model to return to the average safety level of the previous maintenance period’s baseline through correct alarming thresholds for unplanned corrective maintenance.Originality/value–The paper proposes an approach to reduce safety risk due to maintenance interval extension by effective maintenance program.The results are expected to help the railway company make the optimal solution to balance safety and the economy.
基金National Science Foundation of China and British Council
文摘Force measurements of oscillatory flow acting on a single circular cylinder have been carried out. The experiments were done by oscillating a circular cylinder in still water. Instantaneous forces and velocity fields around the cylinder were measured by Particle Image Velocimetry (PIV). The Keulegan-Carpenter number (KC) varied in the range from 5 to 20 and the viscous parameter beta = Re / KC was set at 500 (Re is Reynolds number). It was found that the strength and frequency of the lift force increased with KC number, the main frequency of the lift force being three times the frequency of the oscillatory flow at KC = 20. The movement and strength of the vortices around the cylinder are discussed for different KC numbers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11522436,11774425,11704408,and 91836106)the Beijing Natural Science Foundation,China(Grant No.Z180013)+1 种基金the Joint Fund of the Ministry of Education of China(Grant No.6141A020333xx)the Research Funds of Renmin University of China(Grant Nos.16XNLQ03 and 18XNLQ15).
文摘Recent progresses on quantum control of cold atoms and trapped ions in both the scientific and technological aspects greatly advance the applications in precision measurement. Thanks to the exceptional controllability and versatility of these massive quantum systems, unprecedented sensitivity has been achieved in clocks, magnetometers, and interferometers based on cold atoms and ions. Besides, these systems also feature many characteristics that can be employed to facilitate the applications in different scenarios. In this review, we briefly introduce the principles of optical clocks, cold atom magnetometers, and atom interferometers used for precision measurement of time, magnetic field, and inertial forces. The main content is then devoted to summarize some recent experimental and theoretical progresses in these three applications, with special attention being paid to the new designs and possibilities towards better performance. The purpose of this review is by no means to give a complete overview of all important works in this fast developing field, but to draw a rough sketch about the frontiers and show the fascinating future lying ahead.
基金Action Plan for Scientific and Technological Innovation of Shanghai,China(No.16DZ0502202)National Natural Science Foundation of China(No.51305272)
文摘Friction stir welding( FSW) is a solid-state welding process that utilizes a rotating tool to induce gross material plastic deformation and join two parts together. A large number of studies have indicated that axial force control can be used to achieve good welding quality. However,in the welding process,due to workpiece's geometry error,improper clamping and other process variations,the axial force can vary significantly and produce welding defects.The control of force in the process of FSW is investigated. At first,the development and evaluation of a closed-loop control system is described,which is equipped with a custom real-time wireless force dynamometer for FSW. Then,an axial force controller is designed based on nonlinear force controllers for FSW. Experimental validations are carried out on an FSW platform. The experimental results demonstrate that the controller maintains the constant axial force and shows desirable dynamic behavior, even when the disturbance is encountered during the welding process.
文摘The Metal Matrix Composites application has increased in many areas of science and technology, because of its additional physical, wear and mechanical properties. In comparison with all MMC’s, aluminum-based MMC’s are finding wide applications due to their better strength to weight ratio, better stiffness, and high thermal conductivity as well as very good wear and corrosion properties. The properties of a composite mainly depend on better distribution of reinforcement in the matrix, which is very difficult to achieve. Basically Redmud is a byproduct of alumina, and it is waste product obtained during Bayer’s process. This waste product must be recycled else it may be dangerous to the environment. Redmud can be used as reinforcement for aluminium composites in order to achieve better properties. The proposed research work includes preparation of Aluminum 6061-Red mud metal matrix composites using liquid metallurgy route following stir casting technique. An alloy Al6061 containing 0.60 percent silicon and Magnesium of 0.82 percent was used as the matrix material. Two different compositions of the Aluminum 6061-Red mud composites are prepared in addition to the base matrix and evaluated for mechanical properties also the force acting on the cutting tool at different spindle speeds during machining of the composite materials were analyzed.
基金supported by the National Key R&D Program of China(Grant No.2021YFF0501101)the National Natural Science Foundation of China(Grant Nos.62173137,62303178)the Project of Hunan Provincial Department of Education of China(Grant Nos.23A0426,22B0577).
文摘Accurate wheel-rail force data serves as the cornerstone for analyzing the wheel-rail relationship.However,achieving continuous and precise measurement of this force remains a significant challenge in the field.This article introduces a calibration algorithm for the wheel-rail force that leverages graph neural networks and long short-term memory networks.Initially,a comprehensive wheel-rail force detection system for trains was constructed,encompassing two key components:an instrumented wheelset and a ground wheel-rail force measuring system.Subsequently,utilizing this system,two distinct datasets were acquired from the track inspection vehicle:instrumented wheelset data and ground wheel-rail force data,a feedforward neural network was employed to calibrate the instrumented wheelset data,referencing the ground wheel-rail force data.Furthermore,ground wheel-rail force data for the locomotive was obtained for the corresponding road section.This data was then integrated with the calibrated instrumented wheelset data from the track inspection vehicle.Leveraging the GNN-LSTM network,the article establishes a mapping relationship model between the wheel-rail force of the track inspection vehicle and the locomotive wheel-rail force.This model facilitates continuous measurement of locomotive wheel-rail forces across three typical scenarios:straight sections,long and steep downhill sections,and small curve radius sections.
文摘Understanding solid‐and fluid‐inertia forces and their coupling with the gravity potential in complex motion scenarios is necessary for evaluating system stability and identifying root causes of system failure and accidents.Because solids and fluids have an infinite number of degrees of freedom and distributed inertia and elasticity,having meaningful qualitative and quantitative nominal measures of the kinematics and forces will contribute to a better understanding of the system dynamics.This paper proposes developing new continuum‐based nominal measures for the characterization of the oscillations and forces.By using a material‐point approach,these new nominal measures,which have their roots in the continuum‐mechanics partial‐differential equations of equilibrium and Frenet geometry,are independent of the formulation or generalized coordinates used to develop the dynamic equations of motion.The paper proposes a data‐driven‐science approach to define a nominal continuum space‐curve geometry with nominal curvature and torsion;a nominal instantaneous motion plane(IMP),which contains the resultant of all forces including the inertia forces;and a nominal instantaneous zero‐force axis(IZFA)along which the resultant of all forces vanishes.While using the material‐point approach eliminates the need for introducing moment equations associated with orientation coordinates,the IMP and IZFA concepts can be used to define the instantaneous axis of significant moment components,which can lead to accidents such as in the case of vehicle rollovers.
基金This work was financially supported by the project of agricultural machinery R&D,manufacturing,promotion,application,and integrationand the 13th Five-Year Plan National Key Research and Development Program of China(Grant No.2016YFD0700102).
文摘The real-time monitoring of the load in farming by the sensor installed on the tractor's three-point hitch can effectively improve the farming efficiency and force-position combined control,reduce the compaction risk of the wheel on the soil and reduce the fuel consumption in farming process.However,the measurement and quantification of the loads on the three-point hitch have some problems remaining unresolved:testing the accuracy and reliability of a load measuring system is hard when the tractor works in a field,the mathematical model of spatial forces usually lacks a practical and effective validation,and the calibration process of the measurement system is inconvenient and incomplete while easily causing a low accuracy.Specifically,this paper builds a new spatial-force mathematical model based on the geometry of a three-point hitch.To eliminate the discrepancy of the geometric model with the actual structure and to refine the mathematical model,a calibration process is conducted by developing a calibration bench,which is equipped with a data acquisition system and a multi-parameter monitoring interface.The three-point hitch installed on this calibration bench is subject to steady-state loading.The loading force,angle of the lower drawbar,and three-component forces(three shaft pin sensors’forces)of the three-point hitch are well measured.With applying for the measured data to calibrate the theoretical mathematic model eventually derives the resultant force from all the three-component forces,a dynamical loading bench was developed to test the calculated resultant force for the three-point hitch during the sinusoidal and randomly variant dynamical loadings tests.A hitch force measurement system is also developed to collect real-time data and calculate the resultant force of measured three-component forces through the calibrated mathematical model.The results of the dynamical loading tests show that the average relative error MRE=1.09%with an average force measurement time delay beingΔt=0.5 s,the root mean square error RMSE=59.3 N,and the coefficient of determination R2=0.9903.As observed,the shape and the trend of the generated resultant force curve are basically the dynamical loading force.The dynamical loading test proves the high efficacy and reliability of the proposed indoor calibration method for calculating the load based on the three-component forces as measured on the three-point hitch.Besides,the preliminary study of the proposed method on the hitch load provides great potential to improve the indoor six-component measurement and quantification of both the force and momentum acting on the three-point hitch.
基金co-supported by the National Natural Science Foundation of China(52105562)the Fundamental Research Funds for the Central Universities,China(XJ2021KJZK037)the Fundamental Research Funds for the Central Universities,China(2682022CX058).
文摘The aerodynamic test in the pulse combustion wind tunnel is very important for the design, evaluation and optimization of aerodynamic characteristics of the hypersonic aircraft.The test accuracy even affects the success or failure of hypersonic aircraft development. In the aerodynamic test of pulse combustion wind tunnel, the aerodynamic signal is disturbed by the inertial force signal, which seriously affects the test accuracy of aerodynamic force. Aiming at the above problems, this paper innovatively proposes an aerodynamic intelligent identification method, that is the transfer learning network based on adaptive Empirical Modal Decomposition(EMD) and Soft Thresholding(TLN-AE&ST). Compared with the existing aerodynamic intelligent identification model based on deep learning technology, this study introduces the transfer learning idea into the aerodynamic intelligent identification model for the first time. The TLN-AE&ST effectively alleviates the problem of scarcity of training samples for intelligent models due to the high cost of wind tunnel tests, and provides a new idea for further implementation of deep learning technology in the field of wind tunnel aerodynamic testing. And this study designed residual attention block with soft threshold and dense block with adaptive EMD in TLN-AE&ST model. Residual attention block with soft threshold module can more effectively suppress the influence of instrument noise signal on model training effect. Dense block with adaptive EMD makes the deep learning model no longer a black box to a certain extent, and has certain physical significance. Finally, a series of wind tunnel tests were carried out in the Φ = 2.4 m pulse combustion wind tunnel of China Aerodynamic Research and Development Center to verify the effectiveness of TLN-AE&ST.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.52105589 and U1909221)in part by the China Postdoctoral Science Foundation(Grant No.2021M692590)+2 种基金in part by the Fundamental Research Funds for the Central Universities,China(Grant No.xzy012021009)in part by the State Key Laboratory of Robotics and Systems(HIT),China(Grant No.SKLRS2021KF17)in part by the Beijing Advanced Innovation Center for Intelligent Robots and Systems,China(Grant No.2019IRS08).
文摘Capacitive sensors are efficient tools for biophysical force measurement,which is essential for the exploration of cellular behavior.However,attention has been rarely given on the influences of external mechanical and internal electrical interferences on capacitive sensors.In this work,a bionic swallow structure design norm was developed for mechanical decoupling,and the influences of structural parameters on mechanical behavior were fully analyzed and optimized.A bionic feather comb distribution strategy and a portable readout circuit were proposed for eliminating electrostatic interferences.Electrostatic instability was evaluated,and electrostatic decoupling performance was verified on the basis of a novel measurement method utilizing four complementary comb arrays and applicationspecific integrated circuit readouts.An electrostatic pulling experiment showed that the bionic swallow structure hardly moved by 0.770 nm,and the measurement error was less than 0.009% for the area-variant sensor and 1.118% for the gap-variant sensor,which can be easily compensated in readouts.The proposed sensor also exhibited high resistance against electrostatic rotation,and the resulting measurement error dropped below 0.751%.The rotation interferences were less than 0.330 nm and(1.829×10^(-7))°,which were 35 times smaller than those of the traditional differential one.Based on the proposed bionic decoupling method,the fabricated sensor exhibited overwhelming capacitive sensitivity values of 7.078 and 1.473 pF/μm for gap-variant and area-variant devices,respectively,which were the highest among the current devices.High immunity to mechanical disturbances was maintained simultaneously,i.e.,less than 0.369% and 0.058% of the sensor outputs for the gap-variant and area-variant devices,respectively,indicating its great performance improvements over existing devices and feasibility in ultralow biomedical force measurement.
基金support from the National Natural Science Foundation of China (Grant T2222020).
文摘Cells,wrapped among their neighbors and surrounding extracellular matrix(ECM),form cell-cell adhesions and cell-ECM adhesions.Extracellular biophysical cues exert a far-reaching influence on a sweeping of cell behaviors,including signal transduction,gene expression,and fate determination.Cell-cell adhesions mediated by inter-cellular adhesion molecules bridge the membranes of adjacent cells through either heterophilic or homophilic adhesive interactions,playing a critical part in multicellular structural maintenance and,therefore,a foundation for multicellular organisms.Cell-ECM adhesions are derived from the interaction between cell adhesion receptors and multi-adhesive matrix proteins to ensure cell and tissue cohesion.Whereas cells not only unilaterally respond to certain cues from extracellular environment but can also alter the physicochemical profiles of the externalities and hence hold important implications for clinical applications.The essential function of cell adhesions has cre-ated tremendous interests in developing methods for measuring and studying cell adhesion properties,namely,cellular force.Here,we describe the collection of cell adhesive inputs on cellular signaling cascades and the“crosstalk”between cell-cell adhesions and cell-ECM adhesions.Furthermore,we provide the summary of the current methods to measure such cell adhesive forces.
文摘The luminescence of semiconductor quantum dots (QDs) can be adjusted using the piezotronic effect. An external mechanical force applied on the QD generates a piezoelectric potential, which alters the luminescence of the QD. A small mechanical force may induce a significant change on the emission spectrum. In the case of InN QDs, it is demonstrated that the unforced emission wavelength is more than doubled by a force of 1 μN. The strategy of using the piezotronic effect to tune the color of the emission leads to promising noncontact force- measurement applications in biological and medical sensors and force-sensitive displays. Several piezoelectric semiconductor materials have been investigated in terms of the tunability of the emission wavelength in the presence of an external applied force. It is found that CdS and CdSe demonstrate much higher tunability δλ/δF, which makes them suitable for micro/nano-newton force measurement applications.
基金We thank Iain Patten for valuable discussions on the structure and layout of the manuscript.IDS kindly acknowledges funding from the Life grant by Volkswagen Foundation(Grant No.92772).
文摘The use of optical tweezers to measure forces acting upon microscopic particles has revolutionised fields from material science to cell biology.However,despite optical control capabilities,this technology is highly constrained by the material properties of the probe,and its use may be limited due to concerns about the effect on biological processes.Here we present a novel,optically controlled trapping method based on light-induced hydrodynamic flows.Specifically,we leverage optical control capabilities to convert a translationally invariant topological defect of a flow field into an attractor for colloids in an effectively one-dimensional harmonic,yet freely rotatable system.Circumventing the need to stabilise particle dynamics along an unstable axis,this novel trap closely resembles the isotropic dynamics of optical tweezers.Using magnetic beads,we explicitly show the existence of a linear force-extension relationship that can be used to detect femtoNewton-range forces with sensitivity close to the thermal limit.Our force measurements remove the need for laser-particle contact,while also lifting material constraints,which renders them a particu-larly interesting tool for the life sciences and engineering.
基金the Open Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,China,the National Natural Science Foundation of China,the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘The mean activity coefficients of KCI in a KCI-K2B407-H20 ternary system were experimentally determined at 308.15 K by the electromotive force measurement(EMF) via a battery cell without a liquid junction: K-ISEIKCI(m1), K2B4O7(m2)ICI-ISE(ISE=ion selective electrode) in a total ionic strength of from 0.01 mol/kg to 1.00 mol/kg at different ionic strength fractions of KzB407 with yB=0, 0.200, 0.400, 0.600 and 0.800. K-ISE and CI-ISE presented a good Nernst effect, which implies that this method could be used to measure the activity coefficients of an electrolyte in the above system. The Harned rule was fitted to the experimental data, the Harned coefficients and the Pitzer single-salt ion parameters of KC1 were evaluated, and the relationship diagrams between the mean activity coefficient of KC1 and the ionic strength fraction(yB) were drawn. The mean activity coefficients of KCI(γ±KCI) decreased monotonically with the increase of I. The experimental results obeyed the Harned rule well.
基金The research project is funded by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)–BR 1511/12-1.Furthermore,the authors thank the team from the Xi’an Jiaotong University for the invitation and the organization of the Smart Aircraft 2019 Conference.
文摘The morphing wing concept aims to constantly adapt the aerodynamics to different flight stages.The wing is able to adapt to different flight conditions by an adjustable Aspect Ratio(AR)and sweep.A high AR configuration provides high aerodynamic efficiency,while a low AR configuration,with highly swept wings offers a good maneuverability.Additionally,the flexible membrane allows the wing surface to stretch and contract in-plane as well as the airfoil to adapt to different aerodynamic loads.In the context of this work,the aerodynamic characteristics of a full model with form-adaptive elasto-flexible membrane wings are investigated experimentally.The focus is on the high-lift regime and on the analysis of the aerodynamic coefficients as well as their sensitivities.Especially,the lateral aerodynamic derivatives at asymmetric wing positions are of interest.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12127802 and 11721202)
文摘The aerodynamic performance of a simplified aircraft model with a pair of actively deformed membrane wings is investigated experimentally in this work. The active deformation is achieved with Macro fiber composite(MFC) actuators, which are attached to the upper surface of the wings and occupied 13.7% of the wing surface area. Wind tunnel experiments are conducted to evaluate the influence of membrane active deformation on the aerodynamic performance of the aircraft. The results show that the membrane deforms and vibrates under the actuation which can effectively suppress the leading-edge separation and facilitate the reattachment. Therefore, compared with the rigid wing model, the lift coefficient of the actively deformed membrane wing model is enhanced remarkably from the angle of attack of 7° to 22°. The stall angle is delayed by 2°, and a maximum lift coefficient enhancement of 32.5% is reached, which shows a wide potential application in improving the aerodynamic performance of modern aircraft.
基金supported by the National Natural Science Foundation of China(Grant No.11172241)the Innovation Foundation of Aerospace Science and Technology of Chinathe National High Technology Research and Development Programs of China(863 Program,Grant No.2012AA011803)
文摘A combined method is proposed to determine the water entry acceleration at a low impact velocity through image processing. The procedure includes: (1) a sequence of images for water impact are recorded by a high speed camera, (2) the sub-pixel image processing method is employed to calculate the displacement with an accuracy on the "sub-pixel" level, (3) the acceleration of the object is acquired by differentiating the displacement twice and with results being further filtered by a carefully designed low-pass Butterworth filter. A theoretically based analysis is conducted for designing the parameters of the low-pass filters. It is shown that the water entry can be regarded as a procedure with a slowly changing velocity. The method is validated with the standard sinusoidal motion and the water entry of a sphere. This approach could be considered as an auxiliary method during the early-stage study of the water entry, and it could be further applied to some complicated circumstances, like the water entry of spinning spheres.
基金Project supported by No.02 National Science and Technology Major Project of China(No.2011ZX02403-004)
文摘Electrostatic chucks are one of the core components of semiconductor devices. As a key index of electrostatic chucks, the clamping force must be controlled within a reasonable range. Therefore, it is essential to accurately measure the clamping force. To reduce the negative factors influencing measurement precision and repeatability, this article presents a novel method to measure the clamping force and we elaborate both the principle and the key procedure. A micro-force probe component is introduced to monitor, adjust, and eliminate the gap between the wafer and the electrostatic chuck. The contact force between the ruby probe and the wafer is selected as an important parameter to characterize de-chucking, and we have found that the moment of de-chucking can be exactly judged. Moreover, this article derives the formula calibrating equivalent action area of backside gas pressure under real working conditions, which can effectively connect the backside gas pressure at the moment of de-chucking and the clamping force. The experiments were then performed on a self-designed measuring platform.The de-chucking mechanism is discussed in light of our analysis of the experimental data. Determination criteria for de-chucking point are summed up. It is found that the relationship between de-chucking pressure and applied voltage conforms well to quadratic equation. Meanwhile, the result reveals that actual de-chucking behavior is much more complicated than the description given in the classical empirical formula.