For the simplified model of the internal cooling passage in the turbine blade of an aero-engine,the present study applies a newly developed turbulence modeling method,very-large eddy simulation(VLES),for analyzing rot...For the simplified model of the internal cooling passage in the turbine blade of an aero-engine,the present study applies a newly developed turbulence modeling method,very-large eddy simulation(VLES),for analyzing rotational effects on the characteristics of complex turbulent flow.For comparison,not only are the delayed detached eddy simulation(DDES)method(recognized as one of the most popular hybrid Reynolds-averaged Navier-Stokes–large eddy simulation(RANS-LES)methods)and the LES method used with the same numerical setup,but also three RANS turbulence models,including the k-ωshear stress transport(SST),standard k-ε,and Reynolds stress models,are applied to analyze the flow structure in the ribbed channel(whether rotating or stationary).Complex turbulent flows in a square ribbed channel at high Reynolds number of 100000 in the stationary state and different rotational numbers(Ro)between 0.1 and 0.4 are simulated and analyzed in detail.The comparisons show that when compared with the experimental data the VLES method works best in both the stationary and rotating states.It can capture unsteady flow characteristics such as wall shear layer separation and the vortex structure resulting from the rib disturbance.The DDES method can only capture the larger-scale vortex structures,and its predictions of the time-averaged velocity differ considerably from experiments,especially in the stationary state.With a relatively coarse grid,satisfactory prediction cannot be achieved in either rotating or stationary state by the LES method with wall-adapting local eddy-viscosity(WALE)and dynamic Smagorinsky models.The three RANS models perform poorly in both the stationary and rotating states.The results demonstrate the advantages of the VLES method in analyzing the unsteady flow characteristics in the ribbed channel at high Reynolds numbers for both stationary and rotating conditions.On that basis,the study uses the VLES method to analyze the flow evolution under different rotational numbers,and the rotational effects on the fluid mechanisms are analyzed.展开更多
In this review we investigate the rotation effect in the motion of coupled dimer in a two-dimensional asymmetric periodic potential. Free rotation does not generate directed transport in translational direction, while...In this review we investigate the rotation effect in the motion of coupled dimer in a two-dimensional asymmetric periodic potential. Free rotation does not generate directed transport in translational direction, while we find it plays an critical role in the motors motility when the dimer moves under the effect of asymmetry ratchet potential. In the presence of external force, we study the relation between the average current and the force numerically and theoretically. The numerical results show that only appropriate driving force could produce nonzero current and there are current transitions when the force is large enough. An analysis of stability analysis of limit cycles is applied to explain the occurrence of these transitions. Moreover, we numerically simulate the transport of this coupled dimer driven by the random fluctuations in the rotational direction. The existence of noise smooths the current transitions induced by the driving force and the resonance-like peaks which depend on the rod length emerge in small noise strength. Thanks to the noise in the rotational direction, autonomous motion emerges without the external force and large noise could make the current reversal happen. Eventually, the new mechanism to generate directed transport by the rotation is studied.展开更多
Purpose-Under the high-speed operating conditions,the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed condition.In order to meet different an...Purpose-Under the high-speed operating conditions,the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed condition.In order to meet different analysis requirements and selecting appropriate models to analyzing the wheel rail interaction,it is crucial to understand the influence of wheelset flexibility on the wheel-rail dynamics under different speeds and track excitations condition.Design/methodology/approach-The wheel rail contact points solving method and vehicle dynamics equations considering wheelset flexibility in the trajectory body coordinate system were investigated in this paper.As for the wheel-rail contact forces,which is a particular force element in vehicle multibody system,a method for calculating the Jacobian matrix of the wheel-rail contact force is proposed to better couple the wheel-rail contact force calculation with the vehicle dynamics response calculation.Based on the flexible wheelset modeling approach in this paper,two vehicle dynamic models considering the wheelset as both elastic and rigid bodies are established,two kinds of track excitations,namely normal measured track irregularities and short-wave irregularities are used,wheel-rail geometric contact characteristic and wheel-rail contact forces in both time and frequency domains are compared with the two models in order to study the influence of flexible wheelset rotation effect on wheel rail contact force.Findings-Under normal track irregularity excitations,the amplitudes of vertical,longitudinal and lateral forces computed by the flexible wheelset model are smaller than those of the rigid wheelset model,and the virtual penetration and equivalent contact patch are also slightly smaller.For the flexible wheelset model,the wheel rail longitudinal and lateral creepages will also decrease.The higher the vehicle speed,the larger the differences in wheel-rail forces computed by the flexible and rigid wheelset model.Under track short-wave irregularity excitations,the vertical force amplitude computed by the flexible wheelset is also smaller than that of the rigid wheelset.However,unlike the excitation case of measured track irregularity,under short-wave excitations,for the speed within the range of 200 to 350 km/h,the difference in the amplitude of the vertical force between the flexible and rigid wheelset models gradually decreases as the speed increase.This is partly due to the contribution of wheelset's elastic vibration under short-wave excitations.For low-frequency wheel-rail force analysis problems at speeds of 350 km/h and above,as well as high-frequency wheel-rail interaction analysis problems under various speed conditions,the flexible wheelset model will give results agrees better with the reality.Originality/value-This study provides reference for the modeling method of the flexible wheelset and the coupling method of wheel-rail contact force to the vehicle multibody dynamics system.Furthermore,by comparative research,the influence of wheelset flexibility and rotation on wheel-rail dynamic behavior are obtained,which is useful to the application scope of rigid and flexible wheelset models.展开更多
The optical rotational Doppler effect associated with orbital angular momentum provides a new means for rotational velocity detection.In this paper,we investigate the influence of atmospheric turbulence on the rotatio...The optical rotational Doppler effect associated with orbital angular momentum provides a new means for rotational velocity detection.In this paper,we investigate the influence of atmospheric turbulence on the rotational Doppler effect.First,we deduce the generalized formula of the rotational Doppler shift in atmospheric turbulence by mode decomposition.It is found that the rotational Doppler signal frequency spectrum will be broadened,and the bandwidth is related to the turbulence intensity.In addition,as the propagation distance increases,the bandwidth also increases.And when C_(n)^(2)≤5×10^(-15)m^(-2/3)and 2z≤2 km,the rotational Doppler signal frequency spectrum width d and the spiral spectrum width d_(0)satisfy the relationship d=2d_(0-1).Finally,we analyze the influence of mode crosstalk on the rotational Doppler effect,and the results show that it destroys the symmetrical distribution of the rotational Doppler spectrum about 2l·Ω/2π.This theoretical model enables us to better understand the generation of the rotational Doppler frequency and may help us better analyze the influence of the complex atmospheric environment on the rotational Doppler frequency.展开更多
In this work,we have investigated the rotating effect on the thermodynamic properties of a 2D quantum ring.Accordingly,we have considered the radial potential of a 2D quantum ring and solved the Schrödinger equat...In this work,we have investigated the rotating effect on the thermodynamic properties of a 2D quantum ring.Accordingly,we have considered the radial potential of a 2D quantum ring and solved the Schrödinger equation in the presence of the Aharonov-Bohm effect and a uniform magnetic field for the considered potential.According to the solution of the equation,we calculated the eigenvalues and eigenfunctions of the considered system.Using the calculated energy spectrum,we obtained the partition function and thermodynamic properties of the system,such as the mean energy,specific heat,entropy and free energy.Our results show that the rotating effect has a significant influence on the thermophysical properties of a 2D quantum ring.We also study other effects of the rotating term:(1)the effect of different values of rotating parameters,and(2)the effect of negative rotation on the thermodynamic properties of the system.Our results are discussed in detail.展开更多
In this article,we investigate the nonrelativistic quantum motion of a charged particle within a rotating frame,taking into account the Aharonov–Bohm(AB)effect and a uniform magnetic field.Our analysis entails the de...In this article,we investigate the nonrelativistic quantum motion of a charged particle within a rotating frame,taking into account the Aharonov–Bohm(AB)effect and a uniform magnetic field.Our analysis entails the derivation of the equation of motion and the corresponding radial equation to describe the system.Solving the resulting radial equation enables us to determine the eigenvalues and eigenfunctions,providing a clear expression for the energy levels.Furthermore,our numerical analysis highlights the substantial influence of rotation on both energy levels and optical properties.Specifically,we evaluate the photoionization cross-section with and without the effects of rotation.To elucidate the impact of rotation on the photoionization process of the system,we present graphics that offer an appealing visualization of the intrinsic nature of the physics involved.展开更多
The rotational Doppler effect holds significant potential for remote sensing of rotating objects due to its real-time performance and non-contact advantages.A single-ring beam is used to measure rotation speed.To enha...The rotational Doppler effect holds significant potential for remote sensing of rotating objects due to its real-time performance and non-contact advantages.A single-ring beam is used to measure rotation speed.To enhance the signal-to-noise ratio and measure additional parameters,multiple rings are introduced in the context of a rotational Doppler effect.However,the interference between these rings poses a challenge for multitasking detection applications.In this study,cross-polarization superposition was applied to generate an ultra-dense vector perfect vortex beam that exhibited sensitivity to spatial position and object size,and flexibility in designing topological charge combinations for generating frequency combs.A proof-of-principle experiment was conducted to demonstrate its capability in improving the signal-to-noise ratio,and accurately perceiving both the radius of rotation and radial size.An ultra-dense vector perfect vortex beam provides a general strategy for beam construction and the multi-parameter perception of rotating objects,thereby enabling potential applications in the measurement of velocity gradient measurement of fluids.展开更多
Dysprosium compounds with high magnetic anisotropy are widely studied as single molecule magnets(SMMs).Here the anisotropic magnetocaloric effect in a Dy(Ⅲ)SMM,{[Dy(OSiMe_(3))_(2)(4-Mepy)5(BPh_(4))]0.5 Toluene},was s...Dysprosium compounds with high magnetic anisotropy are widely studied as single molecule magnets(SMMs).Here the anisotropic magnetocaloric effect in a Dy(Ⅲ)SMM,{[Dy(OSiMe_(3))_(2)(4-Mepy)5(BPh_(4))]0.5 Toluene},was studied by single crystals.Angular dependent magnetization can be observed at 300 K because of its high magnetic anisotropy.SMM behavior measured along the easy axis direction is identical to that of the polycrystalline sample.Rotating magnetization from the easy axis to the hard plane gives a maximum magnetic entropy change(-ΔSR)of 3.05 J/(kg·K)at 19 K atΔB=5 T,which enables the Dy(Ⅲ)SMM to be used as a low-temperature rotating magnetic refrigerant.展开更多
We report microstructure,magnetocaloric effect and thermal transfer properties of highly orientated Nd0.8Pr0.2Co5 alloy prepared by powder metallurgical processing.Two spin-reorientation transitions of easy magnetizat...We report microstructure,magnetocaloric effect and thermal transfer properties of highly orientated Nd0.8Pr0.2Co5 alloy prepared by powder metallurgical processing.Two spin-reorientation transitions of easy magnetization direction,easy plane to easy cone at TSR1=206 K,easy cone to easy axis at TSR2=242 K,are observed.The present textured alloy exhibits a rotating entropy change of 2.6 J/(kg·K)and refrigerant capacity of 155 J/kg under a magnetic field of 2 T,and high thermal conductivity of 11 W/(m·K).The sintered Nd0.8Pr0.2Co5 alloy with good combination of excellent magnetocaloric and thermal transfer properties are promising for scientific research and practical applications as room-temperature rotating magnetic refrigeration materials.展开更多
A pocket coherent population trapping（CPT） atomic magnetometer scheme that uses a vertical cavity surface emitting laser as a light source is proposed and experimentally investigated.Using the differential detecting...A pocket coherent population trapping（CPT） atomic magnetometer scheme that uses a vertical cavity surface emitting laser as a light source is proposed and experimentally investigated.Using the differential detecting magneto–optic rotation effect,a CPT spectrum with the background canceled and a high signal-to-noise ratio is obtained.The experimental results reveal that the sensitivity of the proposed scheme can be improved by half an order,and the ability to detect weak magnetic fields is extended one-fold.Therefore,the proposed scheme is suited to realize a pocket-size CPT magnetometer.展开更多
The effects of pressure and solvent on the intramolecular spin exchange of biradicals having two nitroxide fragments linked by a long flexible chain were studied by means of highpressure EPR technique.It was found tha...The effects of pressure and solvent on the intramolecular spin exchange of biradicals having two nitroxide fragments linked by a long flexible chain were studied by means of highpressure EPR technique.It was found that the intramolecular exchange interaction between nitroxides of biradical took place through the direct contact between them.By analyzing the observed EPR spectra,we have estimated the ratio(in/out)value of the average lifetime of the radical fragments inside a cage(in)to that outside the cage(out).The in/out values decreased with decreasing temperature and increasing pressure.The results suggest that the nearly cyclic conformation in a cage is favorable in solution.Further,the rotational correlation time of individual nitroxide was estimated from the anisotropic EPR signal,and the information on the segmental motion of the nitroxide group in biradical was obtained.展开更多
Aiming at the approximate measurement of magnetic rotation angle in optical current sensor based on light intensity detection mode,this paper proposes a current measurement method based on triangular constant transfor...Aiming at the approximate measurement of magnetic rotation angle in optical current sensor based on light intensity detection mode,this paper proposes a current measurement method based on triangular constant transformation to reconstruct magnetic rotation angle,so as to avoid the large current measurement error caused by the approximate measurement of the magnetic rotation angle.By extracting the direct current(DC)component and the alternating current(AC)component of the light intensity signal detected by the photoelectric detector(PD),the sine signal containing the magnetic rotation angle is directly obtained by dividing the two components,and then the triangular identity transformation method is used to linearly demodulate the magnetic rotation angle and reconstruct the current waveform.The experimental results show that the relative error of current measurement does not exceed 1.40%in the current range of 0.05—0.50 A,which is less than the approximate linear measurement(ALM)method,and the magnetic rotation angle and the current have a good linear relationship.展开更多
The stereodynamics of the C^NO reaction is investigated at O.06eV by means of the quasi-classical trajectory method on a recent ab initio 4^A＂ potential energy surface （PES）. The influences of rotation excitation ...The stereodynamics of the C^NO reaction is investigated at O.06eV by means of the quasi-classical trajectory method on a recent ab initio 4^A＂ potential energy surface （PES）. The influences of rotation excitation （j = 0 -3） on stereodynamics are discussed. The obtained stereodynamical information is compared with the previously reported results on the 2A′ and 2^A＂ PESs to give a full insight into the chemical stereodynamics of the title reaction.展开更多
A series of experiments were performed in a rotating annulus of fluid to study effects of rotation rate on pianeta ry-scale baroclinic wave flows. The experiments reveal that change in rotation rate of fluid container...A series of experiments were performed in a rotating annulus of fluid to study effects of rotation rate on pianeta ry-scale baroclinic wave flows. The experiments reveal that change in rotation rate of fluid container causes variation in Rossby number and Taylor number in flows and leads to change in flow patterns and in phase and amplitude of quasi-stationary waves. For instance, with increasing rotation rate, amplitude of quasi-stationary waves increases and phase shifts upstream. On the contrary, with decreasing rotation rate, amplitude of quasi-stationary waves de creases and phase shifts downstream. In the case of the earth's atmosphere, although magnitude of variation in earth's rotation rate is very small, yet it causes a very big change in zonal velocity component of wind in the atmosphere and of currents in the ocean, and therefore causes a remarkable change in Rossby number and Taylor number determining regimes in planetary-scale geophysical flows. 1 he observation reveals that intensity and geographic location of subtropic anticyclones in both of the Northern and Southern Hemispheres change consistently with the variation in earth's rotation rate. The results of fluid experiments are consistent, qualitatively, with observed phenomena in the atmospheric circulation.展开更多
Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing ...Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing neutron stars. It is shown that the maximum value of the spin parameter jmax of a neutron star rotating at the Keplerian frequency fK is .jmax - 0.7 when the star mass M 〉 0.SM⊙, which is sustained for various versions of equations of state without and with hyperons. The relationship between j and the scaled rotation frequency f /fK is found to be insensitive to the star mass or the adopted equation of state in the models without hyperons. However, the emergence of byperons in neutron stars will lead to an uncertainty of the spin parameter j, which in turn could generate a complexity in the theoretical study of the quasi-periodic oscillations observed in disk-accreting compact-star systems.展开更多
We analyze in this work anisotropic heat conduction induced by a harmonically oscillating laser source incident on rotating conductors, exploiting an analogy with an effect discovered long ago, called the Zel’dovich ...We analyze in this work anisotropic heat conduction induced by a harmonically oscillating laser source incident on rotating conductors, exploiting an analogy with an effect discovered long ago, called the Zel’dovich effect. We re-covered the main results of a recently published paper that predicts the translational Doppler frequency shift of a thermal wave induced on a sample moving with uniform rectilinear motion. We extend then this framework to take into account the frequency shift of a thermal field propagating on a rotating platform. We show that it coincides with the rotational frequency shift which has been recently observed on surface acoustic waves and hydrodynamic surface waves, called rotational superradiance. Finally, we use an analogy with the Tolman effect to deduce a simple estimate of the average temperature gradient induced by rotation, showing the existence of a new cooling effect associated with heat torque transfer.展开更多
Blade rubbing faults cause detrimental impact on the operation of aeroengines. Most of the existing studies on blade rubbing in the shaft-disk-blade-casing(SDBC) system have overlooked the elastic deformation of the b...Blade rubbing faults cause detrimental impact on the operation of aeroengines. Most of the existing studies on blade rubbing in the shaft-disk-blade-casing(SDBC) system have overlooked the elastic deformation of the blade, while some only consider the whirl of the rotor, neglecting its spin. To address these limitations, this paper proposes a dynamic model with large rotation for the SDBC system. The model incorporates the spin and whirl of the rotor, enabling the realistic reproduction of multiblade rubbing faults. To verify the accuracy of the SDBC model with large rotation and demonstrate its capability to effectively consider the rotational effects such as the centrifugal stiffening and gyroscopic effects, the natural characteristics and dynamic responses of the proposed model are compared with those obtained from reported research and experimental results. Furthermore, the effects of the rotating speed, contact stiffness,and blade number on the dynamic characteristics of the SDBC system with multi-blade rubbing are investigated. The results indicate that the phase angle between the rotor deflection and the unbalance excitation force increases with the increasing rotating speed,which significantly influences the rubbing penetration of each blade. The natural frequency of the SDBC system with rubbing constrain can be observed in the acceleration response of the casing and the torsional response of the shaft, and the frequency is related to the contact stiffness. Moreover, the vibration amplitude increases significantly with the product of the blade number under rubbing, and the rotating frequency approaches the natural frequency of the SDBC system. The proposed model can provide valuable insight for the fault diagnosis of rubbing in bladed rotating machinery.展开更多
Objective To compare the preliminary clinical outcome between fixed platform and rotating high-flexion prosthesis following total knee replacement(TKR).Methods Form January 2007 to December 2009,68 patients with osteo...Objective To compare the preliminary clinical outcome between fixed platform and rotating high-flexion prosthesis following total knee replacement(TKR).Methods Form January 2007 to December 2009,68 patients with osteoarthritis of展开更多
Investigating the interaction between purge flow and main flow in gas turbines is crucial for optimizing thermal management,and enhancing aerodynamic efficiency.Measuring the high-speed rotating rotor poses challenges...Investigating the interaction between purge flow and main flow in gas turbines is crucial for optimizing thermal management,and enhancing aerodynamic efficiency.Measuring the high-speed rotating rotor poses challenges;however,employing the pre-swirl method to model rotational effect can facilitate experimental measurements.This study evaluates the validity of the pre-swirl method for modeling rotational effects.Numerical simulations are conducted under both stationary conditions,with seven swirl ratios,and rotational conditions.The investigation focuses on the underlying mechanisms of pre-swirl and rotation.Pre-swirl and rotation impart circumferential velocity to the purge flow relative to the blade,resulting in a diminishing effect on endwall cooling.On the other hand,pre-swirl reduces the adverse pressure gradient,and the rotation generates Coriolis forces acting on the passage vortex,both contribute to an increasing effect on endwall cooling.Under pre-swirl condition,the diminishing effect is dominant,while in rotational condition,neither the diminishing nor the increasing effect exhibits an overwhelmingly dominant trend.展开更多
In recent years,with the clarification of the mechanism of the rotational Doppler effect(RDE),there has attracted extensive attention to its development of applications,especially in the detection of the angular veloc...In recent years,with the clarification of the mechanism of the rotational Doppler effect(RDE),there has attracted extensive attention to its development of applications,especially in the detection of the angular velocity of rotating objects.On the other hand,optical fiber technology is widely applied in laser velocimetry from beam delivery to scattered light collection,aiding the miniaturization of instruments.Here we report the first all-fiber rotational Doppler velocimetry(AF-RDV)with a single probe based on a fabricated mode-sculpted fiber-optic element.The constructed AF-RDV can be operated in two reciprocal schemes wherein exchanging the illuminating mode and detected mode.Using this,we experimentally demonstrate the mode-changing dependent nature of the RDE.Particularly,the results suggest that the rotational Doppler shift can be observed by mode-filtering the scattered signal even with a nontwisted probe light.We also show the achromatic property of the RDE by scanning the incident wavelength,enabling the AF-RDV within an ultra-broadband operation range.The AF-RDV exhibits favorable performance for detecting spinning rough surfaces.It may provide an exciting new practical sensing instrument with significant prospects for monitoring angular motion in both research and industry.展开更多
基金the National Natural Science Foundation of China(No.91841302)the Jiangsu Provincial Natural Science Foundation of China(No.BK20200069)+1 种基金the Shanghai Academy of Spaceflight Technology(SAST)Innovation Fundthe Fundamental Research Funds for the Central Universities,China。
文摘For the simplified model of the internal cooling passage in the turbine blade of an aero-engine,the present study applies a newly developed turbulence modeling method,very-large eddy simulation(VLES),for analyzing rotational effects on the characteristics of complex turbulent flow.For comparison,not only are the delayed detached eddy simulation(DDES)method(recognized as one of the most popular hybrid Reynolds-averaged Navier-Stokes–large eddy simulation(RANS-LES)methods)and the LES method used with the same numerical setup,but also three RANS turbulence models,including the k-ωshear stress transport(SST),standard k-ε,and Reynolds stress models,are applied to analyze the flow structure in the ribbed channel(whether rotating or stationary).Complex turbulent flows in a square ribbed channel at high Reynolds number of 100000 in the stationary state and different rotational numbers(Ro)between 0.1 and 0.4 are simulated and analyzed in detail.The comparisons show that when compared with the experimental data the VLES method works best in both the stationary and rotating states.It can capture unsteady flow characteristics such as wall shear layer separation and the vortex structure resulting from the rib disturbance.The DDES method can only capture the larger-scale vortex structures,and its predictions of the time-averaged velocity differ considerably from experiments,especially in the stationary state.With a relatively coarse grid,satisfactory prediction cannot be achieved in either rotating or stationary state by the LES method with wall-adapting local eddy-viscosity(WALE)and dynamic Smagorinsky models.The three RANS models perform poorly in both the stationary and rotating states.The results demonstrate the advantages of the VLES method in analyzing the unsteady flow characteristics in the ribbed channel at high Reynolds numbers for both stationary and rotating conditions.On that basis,the study uses the VLES method to analyze the flow evolution under different rotational numbers,and the rotational effects on the fluid mechanisms are analyzed.
基金We thank Peter Hanggi for valuable dis- cussions. This work has been financially supported by grants from the National Natural Science Foundation of China （Grant No. 11075016） and the Foundation for Doctoral Training from Min- istry of Education （Grant No. 20100003110007）.
文摘In this review we investigate the rotation effect in the motion of coupled dimer in a two-dimensional asymmetric periodic potential. Free rotation does not generate directed transport in translational direction, while we find it plays an critical role in the motors motility when the dimer moves under the effect of asymmetry ratchet potential. In the presence of external force, we study the relation between the average current and the force numerically and theoretically. The numerical results show that only appropriate driving force could produce nonzero current and there are current transitions when the force is large enough. An analysis of stability analysis of limit cycles is applied to explain the occurrence of these transitions. Moreover, we numerically simulate the transport of this coupled dimer driven by the random fluctuations in the rotational direction. The existence of noise smooths the current transitions induced by the driving force and the resonance-like peaks which depend on the rod length emerge in small noise strength. Thanks to the noise in the rotational direction, autonomous motion emerges without the external force and large noise could make the current reversal happen. Eventually, the new mechanism to generate directed transport by the rotation is studied.
基金China National Railway Group Science and Technology Program(N2022J009)China Academy of Railway Sciences Group Co.,Ltd.Program(2021YJ036).
文摘Purpose-Under the high-speed operating conditions,the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed condition.In order to meet different analysis requirements and selecting appropriate models to analyzing the wheel rail interaction,it is crucial to understand the influence of wheelset flexibility on the wheel-rail dynamics under different speeds and track excitations condition.Design/methodology/approach-The wheel rail contact points solving method and vehicle dynamics equations considering wheelset flexibility in the trajectory body coordinate system were investigated in this paper.As for the wheel-rail contact forces,which is a particular force element in vehicle multibody system,a method for calculating the Jacobian matrix of the wheel-rail contact force is proposed to better couple the wheel-rail contact force calculation with the vehicle dynamics response calculation.Based on the flexible wheelset modeling approach in this paper,two vehicle dynamic models considering the wheelset as both elastic and rigid bodies are established,two kinds of track excitations,namely normal measured track irregularities and short-wave irregularities are used,wheel-rail geometric contact characteristic and wheel-rail contact forces in both time and frequency domains are compared with the two models in order to study the influence of flexible wheelset rotation effect on wheel rail contact force.Findings-Under normal track irregularity excitations,the amplitudes of vertical,longitudinal and lateral forces computed by the flexible wheelset model are smaller than those of the rigid wheelset model,and the virtual penetration and equivalent contact patch are also slightly smaller.For the flexible wheelset model,the wheel rail longitudinal and lateral creepages will also decrease.The higher the vehicle speed,the larger the differences in wheel-rail forces computed by the flexible and rigid wheelset model.Under track short-wave irregularity excitations,the vertical force amplitude computed by the flexible wheelset is also smaller than that of the rigid wheelset.However,unlike the excitation case of measured track irregularity,under short-wave excitations,for the speed within the range of 200 to 350 km/h,the difference in the amplitude of the vertical force between the flexible and rigid wheelset models gradually decreases as the speed increase.This is partly due to the contribution of wheelset's elastic vibration under short-wave excitations.For low-frequency wheel-rail force analysis problems at speeds of 350 km/h and above,as well as high-frequency wheel-rail interaction analysis problems under various speed conditions,the flexible wheelset model will give results agrees better with the reality.Originality/value-This study provides reference for the modeling method of the flexible wheelset and the coupling method of wheel-rail contact force to the vehicle multibody dynamics system.Furthermore,by comparative research,the influence of wheelset flexibility and rotation on wheel-rail dynamic behavior are obtained,which is useful to the application scope of rigid and flexible wheelset models.
基金Project supported by the Research Plan Project of the National University of Defense Technology(Grant No.ZK18-0102)the National Natural Science Foundation of China(Grant No.61871389)+1 种基金the State Key Laboratory of Pulsed Power Laser Technology(Grant No.KY21C604)the Postgraduate Scientific Research Innovation Project of Hunan Province(Grant Nos.CX20220007 and CX20230024)。
文摘The optical rotational Doppler effect associated with orbital angular momentum provides a new means for rotational velocity detection.In this paper,we investigate the influence of atmospheric turbulence on the rotational Doppler effect.First,we deduce the generalized formula of the rotational Doppler shift in atmospheric turbulence by mode decomposition.It is found that the rotational Doppler signal frequency spectrum will be broadened,and the bandwidth is related to the turbulence intensity.In addition,as the propagation distance increases,the bandwidth also increases.And when C_(n)^(2)≤5×10^(-15)m^(-2/3)and 2z≤2 km,the rotational Doppler signal frequency spectrum width d and the spiral spectrum width d_(0)satisfy the relationship d=2d_(0-1).Finally,we analyze the influence of mode crosstalk on the rotational Doppler effect,and the results show that it destroys the symmetrical distribution of the rotational Doppler spectrum about 2l·Ω/2π.This theoretical model enables us to better understand the generation of the rotational Doppler frequency and may help us better analyze the influence of the complex atmospheric environment on the rotational Doppler frequency.
文摘In this work,we have investigated the rotating effect on the thermodynamic properties of a 2D quantum ring.Accordingly,we have considered the radial potential of a 2D quantum ring and solved the Schrödinger equation in the presence of the Aharonov-Bohm effect and a uniform magnetic field for the considered potential.According to the solution of the equation,we calculated the eigenvalues and eigenfunctions of the considered system.Using the calculated energy spectrum,we obtained the partition function and thermodynamic properties of the system,such as the mean energy,specific heat,entropy and free energy.Our results show that the rotating effect has a significant influence on the thermophysical properties of a 2D quantum ring.We also study other effects of the rotating term:(1)the effect of different values of rotating parameters,and(2)the effect of negative rotation on the thermodynamic properties of the system.Our results are discussed in detail.
基金partially supported by the Brazilian agencies CAPES,CNPqthe support from the grants CNPq/306308/2022-3+3 种基金CNPq Grant No.153635/2024-0FAPEMAFAPEMA/UNIVERSAL-06395/22,FAPEMA/APP-12256/22financed in part by the Coordenacao de Aperfeicoamento de Pessoal de Nível Superior—Brasil(CAPES)—Finance Code 001。
文摘In this article,we investigate the nonrelativistic quantum motion of a charged particle within a rotating frame,taking into account the Aharonov–Bohm(AB)effect and a uniform magnetic field.Our analysis entails the derivation of the equation of motion and the corresponding radial equation to describe the system.Solving the resulting radial equation enables us to determine the eigenvalues and eigenfunctions,providing a clear expression for the energy levels.Furthermore,our numerical analysis highlights the substantial influence of rotation on both energy levels and optical properties.Specifically,we evaluate the photoionization cross-section with and without the effects of rotation.To elucidate the impact of rotation on the photoionization process of the system,we present graphics that offer an appealing visualization of the intrinsic nature of the physics involved.
基金National Key Research and Development Program of China(2022YFA1404800,2019YFA0705000)National Natural Science Foundation of China(12174280,12204340,12192254,92250304,12434012)+3 种基金China Postdoctoral Science Foundation(2022M722325)Priority Academic Program Development of Jiangsu Higher Education InstitutionsJiangsu Funding Program for Excellent Postdoctoral Talent(2022ZB593)Key Lab of Modern Optical Technologies of Jiangsu Province(KJS2138)。
文摘The rotational Doppler effect holds significant potential for remote sensing of rotating objects due to its real-time performance and non-contact advantages.A single-ring beam is used to measure rotation speed.To enhance the signal-to-noise ratio and measure additional parameters,multiple rings are introduced in the context of a rotational Doppler effect.However,the interference between these rings poses a challenge for multitasking detection applications.In this study,cross-polarization superposition was applied to generate an ultra-dense vector perfect vortex beam that exhibited sensitivity to spatial position and object size,and flexibility in designing topological charge combinations for generating frequency combs.A proof-of-principle experiment was conducted to demonstrate its capability in improving the signal-to-noise ratio,and accurately perceiving both the radius of rotation and radial size.An ultra-dense vector perfect vortex beam provides a general strategy for beam construction and the multi-parameter perception of rotating objects,thereby enabling potential applications in the measurement of velocity gradient measurement of fluids.
基金Project supported by Shenzhen Science and Technology Program(JCYJ20180306170859634)National Natural Science Foundation of China(21620102002,21773130,21871219,21801202,21971203)+3 种基金China Postdoctoral Science Foundation(2019T120891,2019T120892,2018M643615,2018M631138)Postdoctoral Foundation of Shaanxi Province(2018BSHEDZZ100)Natural Science Basic Research Plan in Shaanxi Province(2019JQ-292)Key Laboratory Construction Program of Xi’an Municipal Bureau of Science and Technology(201805056ZD7CG40)。
文摘Dysprosium compounds with high magnetic anisotropy are widely studied as single molecule magnets(SMMs).Here the anisotropic magnetocaloric effect in a Dy(Ⅲ)SMM,{[Dy(OSiMe_(3))_(2)(4-Mepy)5(BPh_(4))]0.5 Toluene},was studied by single crystals.Angular dependent magnetization can be observed at 300 K because of its high magnetic anisotropy.SMM behavior measured along the easy axis direction is identical to that of the polycrystalline sample.Rotating magnetization from the easy axis to the hard plane gives a maximum magnetic entropy change(-ΔSR)of 3.05 J/(kg·K)at 19 K atΔB=5 T,which enables the Dy(Ⅲ)SMM to be used as a low-temperature rotating magnetic refrigerant.
基金the National Natural Science Foundation of China(51601208,51531008,51601209)the Fujian Institute of Innovation,Chinese Academy of Sciences(FJCXY18040301)。
文摘We report microstructure,magnetocaloric effect and thermal transfer properties of highly orientated Nd0.8Pr0.2Co5 alloy prepared by powder metallurgical processing.Two spin-reorientation transitions of easy magnetization direction,easy plane to easy cone at TSR1=206 K,easy cone to easy axis at TSR2=242 K,are observed.The present textured alloy exhibits a rotating entropy change of 2.6 J/(kg·K)and refrigerant capacity of 155 J/kg under a magnetic field of 2 T,and high thermal conductivity of 11 W/(m·K).The sintered Nd0.8Pr0.2Co5 alloy with good combination of excellent magnetocaloric and thermal transfer properties are promising for scientific research and practical applications as room-temperature rotating magnetic refrigeration materials.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304362 and 61434005)
文摘A pocket coherent population trapping（CPT） atomic magnetometer scheme that uses a vertical cavity surface emitting laser as a light source is proposed and experimentally investigated.Using the differential detecting magneto–optic rotation effect,a CPT spectrum with the background canceled and a high signal-to-noise ratio is obtained.The experimental results reveal that the sensitivity of the proposed scheme can be improved by half an order,and the ability to detect weak magnetic fields is extended one-fold.Therefore,the proposed scheme is suited to realize a pocket-size CPT magnetometer.
文摘The effects of pressure and solvent on the intramolecular spin exchange of biradicals having two nitroxide fragments linked by a long flexible chain were studied by means of highpressure EPR technique.It was found that the intramolecular exchange interaction between nitroxides of biradical took place through the direct contact between them.By analyzing the observed EPR spectra,we have estimated the ratio(in/out)value of the average lifetime of the radical fragments inside a cage(in)to that outside the cage(out).The in/out values decreased with decreasing temperature and increasing pressure.The results suggest that the nearly cyclic conformation in a cage is favorable in solution.Further,the rotational correlation time of individual nitroxide was estimated from the anisotropic EPR signal,and the information on the segmental motion of the nitroxide group in biradical was obtained.
基金the Joint Guidance Project of Natural Science Foundation of Heilongjiang Province(No.LH2021F008)。
文摘Aiming at the approximate measurement of magnetic rotation angle in optical current sensor based on light intensity detection mode,this paper proposes a current measurement method based on triangular constant transformation to reconstruct magnetic rotation angle,so as to avoid the large current measurement error caused by the approximate measurement of the magnetic rotation angle.By extracting the direct current(DC)component and the alternating current(AC)component of the light intensity signal detected by the photoelectric detector(PD),the sine signal containing the magnetic rotation angle is directly obtained by dividing the two components,and then the triangular identity transformation method is used to linearly demodulate the magnetic rotation angle and reconstruct the current waveform.The experimental results show that the relative error of current measurement does not exceed 1.40%in the current range of 0.05—0.50 A,which is less than the approximate linear measurement(ALM)method,and the magnetic rotation angle and the current have a good linear relationship.
基金Supported by the National Natural Science Foundation of China under Grant No 11204392the Scientific and Technological Research Program of Chongqing Municipal Education Commission under Grant Nos KJ1400920 and KJ130821
文摘The stereodynamics of the C^NO reaction is investigated at O.06eV by means of the quasi-classical trajectory method on a recent ab initio 4^A＂ potential energy surface （PES）. The influences of rotation excitation （j = 0 -3） on stereodynamics are discussed. The obtained stereodynamical information is compared with the previously reported results on the 2A′ and 2^A＂ PESs to give a full insight into the chemical stereodynamics of the title reaction.
文摘A series of experiments were performed in a rotating annulus of fluid to study effects of rotation rate on pianeta ry-scale baroclinic wave flows. The experiments reveal that change in rotation rate of fluid container causes variation in Rossby number and Taylor number in flows and leads to change in flow patterns and in phase and amplitude of quasi-stationary waves. For instance, with increasing rotation rate, amplitude of quasi-stationary waves increases and phase shifts upstream. On the contrary, with decreasing rotation rate, amplitude of quasi-stationary waves de creases and phase shifts downstream. In the case of the earth's atmosphere, although magnitude of variation in earth's rotation rate is very small, yet it causes a very big change in zonal velocity component of wind in the atmosphere and of currents in the ocean, and therefore causes a remarkable change in Rossby number and Taylor number determining regimes in planetary-scale geophysical flows. 1 he observation reveals that intensity and geographic location of subtropic anticyclones in both of the Northern and Southern Hemispheres change consistently with the variation in earth's rotation rate. The results of fluid experiments are consistent, qualitatively, with observed phenomena in the atmospheric circulation.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11175108,U1432119,1146114100,11205075,11375076 and 11475104the Shandong Natural Science Foundation under Grant No ZR2014AQ012the Foundation of Shandong University under Grant No 2015WHWLJH01
文摘Based on the equations of state from the relativistic mean field theory without and with the inclusion of strangeness-bearing hyperons, we study the dimensionless spin parameter j = cJ/（GM2） of uniformly rotat- ing neutron stars. It is shown that the maximum value of the spin parameter jmax of a neutron star rotating at the Keplerian frequency fK is .jmax - 0.7 when the star mass M 〉 0.SM⊙, which is sustained for various versions of equations of state without and with hyperons. The relationship between j and the scaled rotation frequency f /fK is found to be insensitive to the star mass or the adopted equation of state in the models without hyperons. However, the emergence of byperons in neutron stars will lead to an uncertainty of the spin parameter j, which in turn could generate a complexity in the theoretical study of the quasi-periodic oscillations observed in disk-accreting compact-star systems.
文摘We analyze in this work anisotropic heat conduction induced by a harmonically oscillating laser source incident on rotating conductors, exploiting an analogy with an effect discovered long ago, called the Zel’dovich effect. We re-covered the main results of a recently published paper that predicts the translational Doppler frequency shift of a thermal wave induced on a sample moving with uniform rectilinear motion. We extend then this framework to take into account the frequency shift of a thermal field propagating on a rotating platform. We show that it coincides with the rotational frequency shift which has been recently observed on surface acoustic waves and hydrodynamic surface waves, called rotational superradiance. Finally, we use an analogy with the Tolman effect to deduce a simple estimate of the average temperature gradient induced by rotation, showing the existence of a new cooling effect associated with heat torque transfer.
基金Project supported by the National Science and Technology Major Project of China (No. 2017-V-0009)the National Natural Science Foundation of China (Nos. 12032015 and 12121002)the National Funding Program for Postdoctoral Researchers of China (No. GZC20231586)。
文摘Blade rubbing faults cause detrimental impact on the operation of aeroengines. Most of the existing studies on blade rubbing in the shaft-disk-blade-casing(SDBC) system have overlooked the elastic deformation of the blade, while some only consider the whirl of the rotor, neglecting its spin. To address these limitations, this paper proposes a dynamic model with large rotation for the SDBC system. The model incorporates the spin and whirl of the rotor, enabling the realistic reproduction of multiblade rubbing faults. To verify the accuracy of the SDBC model with large rotation and demonstrate its capability to effectively consider the rotational effects such as the centrifugal stiffening and gyroscopic effects, the natural characteristics and dynamic responses of the proposed model are compared with those obtained from reported research and experimental results. Furthermore, the effects of the rotating speed, contact stiffness,and blade number on the dynamic characteristics of the SDBC system with multi-blade rubbing are investigated. The results indicate that the phase angle between the rotor deflection and the unbalance excitation force increases with the increasing rotating speed,which significantly influences the rubbing penetration of each blade. The natural frequency of the SDBC system with rubbing constrain can be observed in the acceleration response of the casing and the torsional response of the shaft, and the frequency is related to the contact stiffness. Moreover, the vibration amplitude increases significantly with the product of the blade number under rubbing, and the rotating frequency approaches the natural frequency of the SDBC system. The proposed model can provide valuable insight for the fault diagnosis of rubbing in bladed rotating machinery.
文摘Objective To compare the preliminary clinical outcome between fixed platform and rotating high-flexion prosthesis following total knee replacement(TKR).Methods Form January 2007 to December 2009,68 patients with osteoarthritis of
基金supported by the National Natural Science Foundation of China(Grant No.52106064)。
文摘Investigating the interaction between purge flow and main flow in gas turbines is crucial for optimizing thermal management,and enhancing aerodynamic efficiency.Measuring the high-speed rotating rotor poses challenges;however,employing the pre-swirl method to model rotational effect can facilitate experimental measurements.This study evaluates the validity of the pre-swirl method for modeling rotational effects.Numerical simulations are conducted under both stationary conditions,with seven swirl ratios,and rotational conditions.The investigation focuses on the underlying mechanisms of pre-swirl and rotation.Pre-swirl and rotation impart circumferential velocity to the purge flow relative to the blade,resulting in a diminishing effect on endwall cooling.On the other hand,pre-swirl reduces the adverse pressure gradient,and the rotation generates Coriolis forces acting on the passage vortex,both contribute to an increasing effect on endwall cooling.Under pre-swirl condition,the diminishing effect is dominant,while in rotational condition,neither the diminishing nor the increasing effect exhibits an overwhelmingly dominant trend.
基金supported by the National Natural Science Foundation of China(NSFC)(62125503,62261160388)the Natural Science Foundation of Hubei Province of China(2023AFA028).
文摘In recent years,with the clarification of the mechanism of the rotational Doppler effect(RDE),there has attracted extensive attention to its development of applications,especially in the detection of the angular velocity of rotating objects.On the other hand,optical fiber technology is widely applied in laser velocimetry from beam delivery to scattered light collection,aiding the miniaturization of instruments.Here we report the first all-fiber rotational Doppler velocimetry(AF-RDV)with a single probe based on a fabricated mode-sculpted fiber-optic element.The constructed AF-RDV can be operated in two reciprocal schemes wherein exchanging the illuminating mode and detected mode.Using this,we experimentally demonstrate the mode-changing dependent nature of the RDE.Particularly,the results suggest that the rotational Doppler shift can be observed by mode-filtering the scattered signal even with a nontwisted probe light.We also show the achromatic property of the RDE by scanning the incident wavelength,enabling the AF-RDV within an ultra-broadband operation range.The AF-RDV exhibits favorable performance for detecting spinning rough surfaces.It may provide an exciting new practical sensing instrument with significant prospects for monitoring angular motion in both research and industry.
