The velocity structure of the residual current across an entire section of the Qiongzhou Strait(QS) in summer is presented for the fi rst time. Shipboard Acoustic Doppler Current Profi le measurements, from the mid-re...The velocity structure of the residual current across an entire section of the Qiongzhou Strait(QS) in summer is presented for the fi rst time. Shipboard Acoustic Doppler Current Profi le measurements, from the mid-region of the QS(110.18°E), were collected on 1–4 August 2010. The diurnal tidal currents had their maximum amplitudes between 4.24 and 20.24 m. Their amplitude along the major axis ranged from approximately 0.55 m/s in the middle part of the strait(20.15°N) to 0.84 m/s in the north part of the strait(20.20°N). Both anticlockwise and clockwise tidal current rotations exist in the QS. During the observation period(neap tide), a signifi cant westward residual current occupied almost the entire study section. Two velocity cores of westward current were observed at the northern part and near the deepest trough, although an eastward current appeared in the middle part of the transect. The deepest core was located near 62 m at 20.13°N, with a maximum velocity of-0.34 m/s. The shallower core was located at approximately 16 m at 20.20°N, with a maximum velocity of-0.33 m/s. The estimated total volume of water transported through the QS was-0.16 Sv. This value is an important boundary condition, applicable to numerical models studying coastal ocean circulation in the northwestern South China Sea.展开更多
Artificial graphene structures embedded in semiconductors could open novel routes for studies of electron interactions in 1ow-dimensional systems. We propose a way to manipulate the transport properties of massless Di...Artificial graphene structures embedded in semiconductors could open novel routes for studies of electron interactions in 1ow-dimensional systems. We propose a way to manipulate the transport properties of massless Dirac fermions in an artificial graphene-based tunnel junction. Velocity-modulation control of electron wave propagation in the different regions can be regarded as velocity barriers. Transmission probability of electron is affected profoundly by this velocity barrier. We find that there is no confinement for Dirac electron as the velocity ratio ζ is less than 1, but when the velocity ratio is larger than 1 the confined state appears in the continuum band. These localized Dirac electrons may lead to the decreasing of transmission probability.展开更多
A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control the...A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control theory with neural network using back propagation algorithm. The system is implemented using a real-time TMS320F240 digital signal processor. The simulation study and experiment results indicate that the suggested system has good performance.展开更多
Straight-line motion, albeit simple, manifests itself in numerous applications, from running steam engines and oil wells to manufacturing parts with straight edges and sides. The drive to maximize production creates a...Straight-line motion, albeit simple, manifests itself in numerous applications, from running steam engines and oil wells to manufacturing parts with straight edges and sides. The drive to maximize production creates a need for continuously running assembly-line manufacturing comprised of precise, individually optimized components. While there are many so-called straight-line generating mechanisms, few actually produces a true straight-line, most generate only approximate straight-line. Featured an eight-link rhomboidal system with length constraints,, the Peaucellier mechanism is one that actually produces a true straight line intrinsically. This paper presents a study on the dimension synthesis of the Peaucellier mechanism, namely by identifying the correct ratio of linkage lengths to produce the longest straight line stroke. In addition to designing for stroke, another objective of interest is to attain a desired velocity profile along the path. Kinematic analysis of the velocity profile on the mechanism will render the creation of input angular velocity standards based on desired stroke speed. Given the stroke and velocity specifications, specific steps to size the dimensions of the mechanism developed as result of this study will be presented.展开更多
This study gives a comparison between what occurs when braking on a MOT （Ministry of Transport） brake tester. The results from this research and the exhaustive comparative study carried out by the mechanical enginee...This study gives a comparison between what occurs when braking on a MOT （Ministry of Transport） brake tester. The results from this research and the exhaustive comparative study carried out by the mechanical engineering staffs at the mechanical laboratory at MOT stations in cities such as： Elche, Pilar de la Horadada and Orihuela from Alicante region [2] have led to the following main conclusions： this paper demonstrates that MOT brake testing results can vary depending on parameters variation such as： distance between rollers, roller diameter, roughness of rollers and velocity of the brake test.展开更多
Multimotor transport is studied by Monte-Carlo simulation with consideration of motor detachment fromthe filament.Our work shows, in the case of low load, the velocity of multi-motor system can decrease or increase wi...Multimotor transport is studied by Monte-Carlo simulation with consideration of motor detachment fromthe filament.Our work shows, in the case of low load, the velocity of multi-motor system can decrease or increase withincreasing motor numbers depending on the single motor force-velocity curve.The stall force and run-length reducedgreatly compared to other models.Especially in the case of low ATP concentrations, the stall force of multi motortransport even smaller than the single motor's stall force.展开更多
Effects of wall properties and slip condition on the peristaltic flow of an incompressible pseudoplastic fluid in a curved channel are studied. Series solution of the governing problem is obtained after applying long ...Effects of wall properties and slip condition on the peristaltic flow of an incompressible pseudoplastic fluid in a curved channel are studied. Series solution of the governing problem is obtained after applying long wavelength and low Reynolds number approximations. The results are validated with the numerical solutions through the built-in routine for solving nonlinear boundary value problems via software Mathematica. The variations of different parameters on axial velocity are carefully analyzed. Behaviors of embedding parameters on the dimensionless stream function are also discussed. It is noted that the axial velocity and size of trapped bolus increases with an increase in slip parameter. It is also observed that the profiles of axial velocity are not symmetric about the central line of the curved channel which is different from the case of planar channel.展开更多
The photon transport properties in one-dimensional coupled-resonator waveguide embedded with a quantum dot molecule are investigated. The calculations reveal that one can control the photon transport by using a gate e...The photon transport properties in one-dimensional coupled-resonator waveguide embedded with a quantum dot molecule are investigated. The calculations reveal that one can control the photon transport by using a gate electric field. The phase shift and group velocity delay of the transmitted single photon are discussed. This research may be found applications in integrated optoelectronic devices and solid quantum devices.展开更多
Direct numerical simulation was carried out to investigate the correlation between the momentum and passive scalar transfer in a turbulent channel flow with Re_(τ)=u_(τ)δ/ν=180 and Pr=0.71,where u_(τ)is the frict...Direct numerical simulation was carried out to investigate the correlation between the momentum and passive scalar transfer in a turbulent channel flow with Re_(τ)=u_(τ)δ/ν=180 and Pr=0.71,where u_(τ)is the friction velocity,δis the channel half width,andνis the kinematic viscosity.The one-point and two-point energy transfer and the corresponding scalar transfer are of particular interest.There is a significant positive correlation between the one-point energy and scalar transfer,particularly near the wall,and the correlation between the two production terms is always larger than that between the other terms.By resorting to the Karman-Howarth-Monin-Hill equation and the scale-by-scale scalar transfer budget equation,we explored the two-point energy and scalar transfer at two different vertical locations(i.e.,one location close to the wall y^(+)=10 and the other location slightly away from the wall y^(+)=60).An inverse interscale transfer phenomenon of the energy and scalar is observed in the spanwise direction at y^(+)=10,which is caused by the corresponding streak stretching,whereas along the streamwise and the vertical directions a forward interscale energy and scalar transfer phenomenon is observed.The physical mechanisms(e.g.,production,dissipation,and viscous diffusion terms)contributing to the two-point energy transfer closely resemble those in the two-point scalar transfer.The intrinsic correlation between both the two-point energy and scalar transfer can find its roots in the similarity between the momentum and scalar streaks.展开更多
基金Supported by the National Natural Science Foundation for Young Scientists of China(No.40806012)
文摘The velocity structure of the residual current across an entire section of the Qiongzhou Strait(QS) in summer is presented for the fi rst time. Shipboard Acoustic Doppler Current Profi le measurements, from the mid-region of the QS(110.18°E), were collected on 1–4 August 2010. The diurnal tidal currents had their maximum amplitudes between 4.24 and 20.24 m. Their amplitude along the major axis ranged from approximately 0.55 m/s in the middle part of the strait(20.15°N) to 0.84 m/s in the north part of the strait(20.20°N). Both anticlockwise and clockwise tidal current rotations exist in the QS. During the observation period(neap tide), a signifi cant westward residual current occupied almost the entire study section. Two velocity cores of westward current were observed at the northern part and near the deepest trough, although an eastward current appeared in the middle part of the transect. The deepest core was located near 62 m at 20.13°N, with a maximum velocity of-0.34 m/s. The shallower core was located at approximately 16 m at 20.20°N, with a maximum velocity of-0.33 m/s. The estimated total volume of water transported through the QS was-0.16 Sv. This value is an important boundary condition, applicable to numerical models studying coastal ocean circulation in the northwestern South China Sea.
基金Supported by the National Natural Science Foundation of China under Grants Nos.10174024 and 10474025
文摘Artificial graphene structures embedded in semiconductors could open novel routes for studies of electron interactions in 1ow-dimensional systems. We propose a way to manipulate the transport properties of massless Dirac fermions in an artificial graphene-based tunnel junction. Velocity-modulation control of electron wave propagation in the different regions can be regarded as velocity barriers. Transmission probability of electron is affected profoundly by this velocity barrier. We find that there is no confinement for Dirac electron as the velocity ratio ζ is less than 1, but when the velocity ratio is larger than 1 the confined state appears in the continuum band. These localized Dirac electrons may lead to the decreasing of transmission probability.
文摘A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control theory with neural network using back propagation algorithm. The system is implemented using a real-time TMS320F240 digital signal processor. The simulation study and experiment results indicate that the suggested system has good performance.
文摘Straight-line motion, albeit simple, manifests itself in numerous applications, from running steam engines and oil wells to manufacturing parts with straight edges and sides. The drive to maximize production creates a need for continuously running assembly-line manufacturing comprised of precise, individually optimized components. While there are many so-called straight-line generating mechanisms, few actually produces a true straight-line, most generate only approximate straight-line. Featured an eight-link rhomboidal system with length constraints,, the Peaucellier mechanism is one that actually produces a true straight line intrinsically. This paper presents a study on the dimension synthesis of the Peaucellier mechanism, namely by identifying the correct ratio of linkage lengths to produce the longest straight line stroke. In addition to designing for stroke, another objective of interest is to attain a desired velocity profile along the path. Kinematic analysis of the velocity profile on the mechanism will render the creation of input angular velocity standards based on desired stroke speed. Given the stroke and velocity specifications, specific steps to size the dimensions of the mechanism developed as result of this study will be presented.
文摘This study gives a comparison between what occurs when braking on a MOT （Ministry of Transport） brake tester. The results from this research and the exhaustive comparative study carried out by the mechanical engineering staffs at the mechanical laboratory at MOT stations in cities such as： Elche, Pilar de la Horadada and Orihuela from Alicante region [2] have led to the following main conclusions： this paper demonstrates that MOT brake testing results can vary depending on parameters variation such as： distance between rollers, roller diameter, roughness of rollers and velocity of the brake test.
基金Supported by Chinese Universities Scientific Fund under Grant No.QN2009046 the Research Foundation for Talents of Northwest A&F University
文摘Multimotor transport is studied by Monte-Carlo simulation with consideration of motor detachment fromthe filament.Our work shows, in the case of low load, the velocity of multi-motor system can decrease or increase withincreasing motor numbers depending on the single motor force-velocity curve.The stall force and run-length reducedgreatly compared to other models.Especially in the case of low ATP concentrations, the stall force of multi motortransport even smaller than the single motor's stall force.
文摘Effects of wall properties and slip condition on the peristaltic flow of an incompressible pseudoplastic fluid in a curved channel are studied. Series solution of the governing problem is obtained after applying long wavelength and low Reynolds number approximations. The results are validated with the numerical solutions through the built-in routine for solving nonlinear boundary value problems via software Mathematica. The variations of different parameters on axial velocity are carefully analyzed. Behaviors of embedding parameters on the dimensionless stream function are also discussed. It is noted that the axial velocity and size of trapped bolus increases with an increase in slip parameter. It is also observed that the profiles of axial velocity are not symmetric about the central line of the curved channel which is different from the case of planar channel.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 11004001 and 11105001the Key Project of Chinese Ministry of Education under Grant No. 212076the Anhui Provincial Natural Science Foundation under Grant No. 1208085QA09
文摘The photon transport properties in one-dimensional coupled-resonator waveguide embedded with a quantum dot molecule are investigated. The calculations reveal that one can control the photon transport by using a gate electric field. The phase shift and group velocity delay of the transmitted single photon are discussed. This research may be found applications in integrated optoelectronic devices and solid quantum devices.
基金the National Natural Science Foundation of China(Grant Nos.91952105,11802133 and 12002318)the Six Talent Peaks Project in Jiangsu Province(Grant No.2019-SZCY-005)the Fundamental Research Funds for Central University(Grant No.30918011325).
文摘Direct numerical simulation was carried out to investigate the correlation between the momentum and passive scalar transfer in a turbulent channel flow with Re_(τ)=u_(τ)δ/ν=180 and Pr=0.71,where u_(τ)is the friction velocity,δis the channel half width,andνis the kinematic viscosity.The one-point and two-point energy transfer and the corresponding scalar transfer are of particular interest.There is a significant positive correlation between the one-point energy and scalar transfer,particularly near the wall,and the correlation between the two production terms is always larger than that between the other terms.By resorting to the Karman-Howarth-Monin-Hill equation and the scale-by-scale scalar transfer budget equation,we explored the two-point energy and scalar transfer at two different vertical locations(i.e.,one location close to the wall y^(+)=10 and the other location slightly away from the wall y^(+)=60).An inverse interscale transfer phenomenon of the energy and scalar is observed in the spanwise direction at y^(+)=10,which is caused by the corresponding streak stretching,whereas along the streamwise and the vertical directions a forward interscale energy and scalar transfer phenomenon is observed.The physical mechanisms(e.g.,production,dissipation,and viscous diffusion terms)contributing to the two-point energy transfer closely resemble those in the two-point scalar transfer.The intrinsic correlation between both the two-point energy and scalar transfer can find its roots in the similarity between the momentum and scalar streaks.
