Characteristics of planar velocity distribution of viscous debris flow were analyzed using the measured data at Jiangjia Ravine, Yunnan, China. The velocity data were measured through using two radar velocimeters. The...Characteristics of planar velocity distribution of viscous debris flow were analyzed using the measured data at Jiangjia Ravine, Yunnan, China. The velocity data were measured through using two radar velocimeters. The cross-sectional mean velocities were calculated and used to examine Kang et al＇s （2004） relationship, which was established for converting the flow velocity at river centerline measured by a radar velocimeter into the mean velocity based on the stop-watch method. The velocity coefficient, K, defined by the ratio of the mean velocity to the maximum velocity, ranges from 0.2 to 0.6. Kang et al＇s （2004） relationship was found being inapplicable to flows with K smaller than 0.43. This paper contributes to show the complexity of the planar velocity distribution of viscous debris flows and the applicability of Kang et al＇s relationship.展开更多
The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-...The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-maining approximately constant. The experimental results were provided such as the mean velocity field, fluctuat-ing velocities, turbulent kinetic energy, Reynolds shear stress and time series of the velocity in the stirred tank. These results probably provided the valuable basis to further optimize and enlarge the stirred tank in the industrial process.展开更多
The magneto-electric effect in magnetic materials has been widely investigated, but obtaining an enhanced magnetoelectric effect is challenging. In this study, tricolor superlattices composed of manganese oxides-Pr（...The magneto-electric effect in magnetic materials has been widely investigated, but obtaining an enhanced magnetoelectric effect is challenging. In this study, tricolor superlattices composed of manganese oxides-Pr（0.9）Ca（0.1）MnO3,La（0.9）Sr（0.1）MnO3, and La（0.9）Sb（0.1）MnO3-on（001）-oriented Nb：SrTiO3 substrates with broken space-inversion and timereversal symmetries are designed. Regarding the electric polarization in the hysteresis loops of the superlattices at different external magnetic fields, both coercive electric field Ec and remnant polarization intensity Pr clearly show strong magneticfield dependences. At low temperatures（〈 120 K）, a considerable magneto-electric effect in the well-defined tricolor superlattice is observed that is absent in the single compounds. Both maxima of the magneto-electric coupling coefficients ？Ec and ？Pr appear at 30 K. The magnetic dependence of the dielectric constant further supports the magneto-electric effect. Moreover, a dependence of the magneto-electric effect on the periodicity of the superlattices with various structures is observed, which indicates the importance of interfaces. Our experimental results verify previous theoretical results regarding magneto-electric interactions, thereby paving the way for the design and development of novel magneto-electric devices based on manganite ferromagnets.展开更多
Oceanic turbulence measurements made by an acoustic Doppler velocimeter(ADV)suffer from noise that potentially affects the estimates of turbulence statistics.This study examines the abilities of Kalman filtering and a...Oceanic turbulence measurements made by an acoustic Doppler velocimeter(ADV)suffer from noise that potentially affects the estimates of turbulence statistics.This study examines the abilities of Kalman filtering and autoregressive moving average models to eliminate noise in ADV velocity datasets of laboratory experiments and offshore observations.Results show that the two methods have similar performance in ADV de-noising,and both effectively reduce noise in ADV velocities,even in cases of high noise.They eliminate the noise floor at high frequencies of the velocity spectra,leading to a longer range that effectively fits the Kolmogorov-5/3 slope at midrange frequencies.After de-noising adopting the two methods,the values of the mean velocity are almost unchanged,while the root-mean-square horizontal velocities and thus turbulent kinetic energy decrease appreciably in these experiments.The Reynolds stress is also affected by high noise levels,and de-noising thus reduces uncertainties in estimating the Reynolds stress.展开更多
The article presents an experimental study on the flow of an eutectic gallium alloy in a cylindrical cell,which is placed in an alternating magnetic field.The magnetic field is generated by a coil connected to an alte...The article presents an experimental study on the flow of an eutectic gallium alloy in a cylindrical cell,which is placed in an alternating magnetic field.The magnetic field is generated by a coil connected to an alternating current source.The coil is located at a fixed height in such a way that its plane is perpendicular to the gravity vector,which in turn is parallel to the axis of the cylinder.The position of the cylinder can vary in height with respect to the coil.The forced flow of the considered electrically conductive liquid is generated due to the action of the localized electromagnetic force.It is assumed that under the action of the alternating magnetic field,the liquid is heated uniformly,and the resulting heat is quickly absorbed by the forced flow,so that liquid free convection can be neglected.The experiment is carried out using an ultrasonic Doppler anemometer.One transducer is installed in the axially located cylinder sluice and the other transducer is placed in the near-wall region.According to the results,a velocity profile,corresponding to a two-tori flow pattern can be hardly obtained in the low frequency range of the power supply.However,this is possible in the high frequency range.The average velocity profiles depend essentially on the location of the coil relative to the cell.The spectral analysis of velocity signals shows that the amplitude of the velocity pulsations is comparable to the average value of the flow velocity.Such experimental results and their verification through comparison with numerical calculations are intended to support the development of new methods for reducing the intensity of vortex flows during the electromagnetic separation of impurities through an electromagnetic induction mechanism(able to produce an electromotive force that displaces particles).展开更多
基金the National Natural Science Foundation of China (50221903, 50309007)
文摘Characteristics of planar velocity distribution of viscous debris flow were analyzed using the measured data at Jiangjia Ravine, Yunnan, China. The velocity data were measured through using two radar velocimeters. The cross-sectional mean velocities were calculated and used to examine Kang et al＇s （2004） relationship, which was established for converting the flow velocity at river centerline measured by a radar velocimeter into the mean velocity based on the stop-watch method. The velocity coefficient, K, defined by the ratio of the mean velocity to the maximum velocity, ranges from 0.2 to 0.6. Kang et al＇s （2004） relationship was found being inapplicable to flows with K smaller than 0.43. This paper contributes to show the complexity of the planar velocity distribution of viscous debris flows and the applicability of Kang et al＇s relationship.
基金Supported by the Natural Science Foundation of Inner Mongolia (No.200408020715).
文摘The spatial structure of the velocity field in a stirred vessel with water has been measured and analyzed using the laser Doppler velocimeter technique, with the immersing depth and agitation speed of the impeller re-maining approximately constant. The experimental results were provided such as the mean velocity field, fluctuat-ing velocities, turbulent kinetic energy, Reynolds shear stress and time series of the velocity in the stirred tank. These results probably provided the valuable basis to further optimize and enlarge the stirred tank in the industrial process.
基金Project supported by the National Natural Science Foundation of China(Grant No.61471301)
文摘The magneto-electric effect in magnetic materials has been widely investigated, but obtaining an enhanced magnetoelectric effect is challenging. In this study, tricolor superlattices composed of manganese oxides-Pr（0.9）Ca（0.1）MnO3,La（0.9）Sr（0.1）MnO3, and La（0.9）Sb（0.1）MnO3-on（001）-oriented Nb：SrTiO3 substrates with broken space-inversion and timereversal symmetries are designed. Regarding the electric polarization in the hysteresis loops of the superlattices at different external magnetic fields, both coercive electric field Ec and remnant polarization intensity Pr clearly show strong magneticfield dependences. At low temperatures（〈 120 K）, a considerable magneto-electric effect in the well-defined tricolor superlattice is observed that is absent in the single compounds. Both maxima of the magneto-electric coupling coefficients ？Ec and ？Pr appear at 30 K. The magnetic dependence of the dielectric constant further supports the magneto-electric effect. Moreover, a dependence of the magneto-electric effect on the periodicity of the superlattices with various structures is observed, which indicates the importance of interfaces. Our experimental results verify previous theoretical results regarding magneto-electric interactions, thereby paving the way for the design and development of novel magneto-electric devices based on manganite ferromagnets.
基金The National Key Research and Development Program of China under contract No.2017YFC1404000the Basic Scientific Fund for National Public Research Institutes of China under contract No.2018S03the National Natural Science Foundation of China under contract Nos 41776038 and 41821004
文摘Oceanic turbulence measurements made by an acoustic Doppler velocimeter(ADV)suffer from noise that potentially affects the estimates of turbulence statistics.This study examines the abilities of Kalman filtering and autoregressive moving average models to eliminate noise in ADV velocity datasets of laboratory experiments and offshore observations.Results show that the two methods have similar performance in ADV de-noising,and both effectively reduce noise in ADV velocities,even in cases of high noise.They eliminate the noise floor at high frequencies of the velocity spectra,leading to a longer range that effectively fits the Kolmogorov-5/3 slope at midrange frequencies.After de-noising adopting the two methods,the values of the mean velocity are almost unchanged,while the root-mean-square horizontal velocities and thus turbulent kinetic energy decrease appreciably in these experiments.The Reynolds stress is also affected by high noise levels,and de-noising thus reduces uncertainties in estimating the Reynolds stress.
基金supported by Russian Science Foundation Grant RSF-22-19-20106。
文摘The article presents an experimental study on the flow of an eutectic gallium alloy in a cylindrical cell,which is placed in an alternating magnetic field.The magnetic field is generated by a coil connected to an alternating current source.The coil is located at a fixed height in such a way that its plane is perpendicular to the gravity vector,which in turn is parallel to the axis of the cylinder.The position of the cylinder can vary in height with respect to the coil.The forced flow of the considered electrically conductive liquid is generated due to the action of the localized electromagnetic force.It is assumed that under the action of the alternating magnetic field,the liquid is heated uniformly,and the resulting heat is quickly absorbed by the forced flow,so that liquid free convection can be neglected.The experiment is carried out using an ultrasonic Doppler anemometer.One transducer is installed in the axially located cylinder sluice and the other transducer is placed in the near-wall region.According to the results,a velocity profile,corresponding to a two-tori flow pattern can be hardly obtained in the low frequency range of the power supply.However,this is possible in the high frequency range.The average velocity profiles depend essentially on the location of the coil relative to the cell.The spectral analysis of velocity signals shows that the amplitude of the velocity pulsations is comparable to the average value of the flow velocity.Such experimental results and their verification through comparison with numerical calculations are intended to support the development of new methods for reducing the intensity of vortex flows during the electromagnetic separation of impurities through an electromagnetic induction mechanism(able to produce an electromotive force that displaces particles).
