The advanced telecom technologies and massive volumes of intelligent mobile phone users have yielded a huge amount of real-time data of people’s all-in-one telecommunication records,which we call telco big data.With ...The advanced telecom technologies and massive volumes of intelligent mobile phone users have yielded a huge amount of real-time data of people’s all-in-one telecommunication records,which we call telco big data.With telco data and the domain knowledge of an urban city,we are now able to analyze the movement and contact patterns of humans in an unprecedented scale.Flow map is widely used to display the movements of humans from one single source to multiple destinations by representing locations as nodes and movements as edges.However,it fails the task of visualizing both movement and contact data.In addition,analysts often need to compare and examine the patterns side by side,and do various quantitative analysis.In this work,we propose a novel spatio-temporal flow map layout to visualize when and where people from different locations move into the same places and make contact.We also propose integrating the spatiotemporal flow maps into existing spatiotemporal visualization techniques to form a suite of techniques for visualizing the movement and contact patterns.We report a potential application the proposed techniques can be applied to.The results show that our design and techniques properly unveil hidden information,while analysis can be achieved efficiently.展开更多
During horizontal well drilling,the interaction between drilling fluid and cuttings entering the annulus generates diverse flow patterns.These solid-liquid two-phase flow patterns must be accurately predicted to optim...During horizontal well drilling,the interaction between drilling fluid and cuttings entering the annulus generates diverse flow patterns.These solid-liquid two-phase flow patterns must be accurately predicted to optimize the determination of hydraulic parameters and improve the efficiency of cuttings transport.Accordingly,this study identified flow patterns and conducted transition experiments under different inclination angles using a visualized wellbore annulus apparatus(120 mm outer diameter/73 mm inner diameter).Through direct visual observations,four primary flow patterns were systematically classified on the basis of the solid-liquid two-phase flow behaviors identified in the experiments:stable bed(SB),sand wave(SW),sand dune(SD),and bed load(BL)flows.The experimental data were then used to construct flow pattern maps with solid/liquid phases as axes,after which the transition boundaries between different flow patterns were established.The morphological characteristics and transition mechanisms of SB,SW,SD,and BL flows were systematically analyzed to develop three predictive models of the fluid dynamics principles governing these flow patterns’transitions:(1)A transition boundary model of SB and SW flows was established using Kelvin-Helmholtz stability,for which a stability analysis of solid-liquid two-phase flow in deviated and horizontal annuli was carried out.(2)A transition boundary model of SW and SD flows was constructed through an analysis of the geometric features of sand waves in the annuli,with the critical ratio of the average height of a cuttings bed to its height after erosion being 0.45.(3)A traditional critical velocity model was refined by adjusting the von Karman constant to account for the effect of solid volume concentration,yielding a boundary model for the transition of SW or SD flow into BL flow.All the models were experimentally validated.Finally,we integrated the models to develop a unified method for identifying and classifying the patterns typifying solid-liquid two-phase flow in deviated and horizontal annuli.展开更多
Summary： Intraventricular hydrodynamics is considered an important component of cardiac function assessment. Vector flow mapping （VFM） is a novel flow visualization method to describe cardiac pathophysiological con...Summary： Intraventricular hydrodynamics is considered an important component of cardiac function assessment. Vector flow mapping （VFM） is a novel flow visualization method to describe cardiac pathophysiological condition. This study examined use of new VFM and flow field for assessment of left ventricular （LV） systolic hemodynamics in patients with simple hyperthyroidism （HT）. Thirty-seven simple HT patients were enrolled as HT group, and 38 gender- and age-matched healthy volunteers as control group. VFM model was used to analyze LV flow field at LV apical long-axis view. The follow- ing flow parameters were measured, including peak systolic velocity （Vs）, peak systolic flow （Fs）, total systolic negative flow （SQ） in LV basal, middle and apical level, velocity gradient from the apex to the aortic valve （AV）, and velocity according to half distance （V1/2）. The velocity vector in the LV cavity, stream line and vortex distribution in the two groups were observed. The results showed that there were no significant differences in the conventional parameters such as left ventricular ejection fraction （LVEF）, left ventricular end-diastolic diameter （LVEDD） and left atrium diameter （LAD） between HT group and control group （P〉0.05）. Compared with the control group, a brighter flow and more vortexes were detected in HT group. Non-uniform distribution occurred in the LV flow field, and the stream lines were discontinuous in HT group. The values of Vs and Fs in three levels, SQ in middle and basal levels, AV and V1/2 were higher in HT group than in control group （P〈0.01）. AV was positively correlated with serum free thyroxin （FT4） （r=0.48, P〈0.01）. Stepwise multiple regression analysis showed that LVEDD, FT4, and body surface area （BSA） were the influence factors of △V. The unstable left ventricular sys- tolic hydrodynamics increased in a compensatory manner in simple PIT patients. The present study in- dicated that VFM may be used for early detection of abnormal ventricle contraction in clinical settings.展开更多
Gas–liquid two-phase flow abounds in industrial processes and facilities. Identification of its flow pattern plays an essential role in the field of multiphase flow measurement. A bluff body was introduced in this s...Gas–liquid two-phase flow abounds in industrial processes and facilities. Identification of its flow pattern plays an essential role in the field of multiphase flow measurement. A bluff body was introduced in this study to recognize gas–liquid flow patterns by inducing fluid oscillation that enlarged differences between each flow pattern. Experiments with air–water mixtures were carried out in horizontal pipelines at ambient temperature and atmospheric pressure. Differential pressure signals from the bluff-body wake were obtained in bubble, bubble/plug transitional, plug, slug, and annular flows. Utilizing the adaptive ensemble empirical mode decomposition method and the Hilbert transform, the time–frequency entropy S of the differential pressure signals was obtained. By combining S and other flow parameters, such as the volumetric void fraction β, the dryness x, the ratio of density φ and the modified fluid coefficient ψ, a new flow pattern map was constructed which adopted S（1–x）φ and （1–β）ψ as the vertical and horizontal coordinates, respectively. The overall rate of classification of the map was verified to be 92.9% by the experimental data. It provides an effective and simple solution to the gas–liquid flow pattern identification problems.展开更多
In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different para...In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.展开更多
The flow patterns and the void fraction related to a gas-liquid two-phase flow in a small channel are experimentally studied.The test channel is a transparent quartz glass circular channel with an inner diameter of 6....The flow patterns and the void fraction related to a gas-liquid two-phase flow in a small channel are experimentally studied.The test channel is a transparent quartz glass circular channel with an inner diameter of 6.68 mm.The working fluids are air and water and their superficial velocities range from 0.014 to 8.127 m/s and from 0.0238 to 0.556 m/s,respectively.The void fraction is determined using the flow pattern images captured by a high-speed camera,while quick closing valves are used for verification.Four flow patterns are analyzed in experiments:slug flow,bubbly flow,annular flow and stratified flow.For intermittent flows(bubbly flow and slug flow),the cross-sectional void fraction is in a borderline condition while its probability distribution function(PDF)image displays a bimodal structure.For continuous flows(annular flow and stratified flow)the cross-sectional void fraction behaves as a fluctuating continuous curve while the(PDF)image displays a single peak structure.The volumetric void fraction data are also compared with available predictive formulas,and the results show that the agreement is very good.An effort is also provided to improve the so-called Gregory and Scott model using the available data.展开更多
In this paper, the stochastic flow of mappings generated by a Feller convolution semigroup on a compact metric space is studied. This kind of flow is the generalization of superprocesses of stochastic flows and stocha...In this paper, the stochastic flow of mappings generated by a Feller convolution semigroup on a compact metric space is studied. This kind of flow is the generalization of superprocesses of stochastic flows and stochastic diffeomorphism induced by the strong solutions of stochastic differential equations.展开更多
The flow stress behavior of high-purity Al-Cu-Mg alloy under hot deformation conditions was studied by Gleeble-1500,with the deformation temperature range from 300 to 500 °C and the strain rate range from 0.01 to...The flow stress behavior of high-purity Al-Cu-Mg alloy under hot deformation conditions was studied by Gleeble-1500,with the deformation temperature range from 300 to 500 °C and the strain rate range from 0.01 to 10 s-1. From the true stress-true strain curve, the flow stress increases with the increasing of strain and tends to be constant after a peak value, showing dynamic recover, and the peak value of flow stress increases with the decreasing of deformation temperature and the increasing of strain rate.When the strain rate is 10 s-1 and the deformation temperature is higher than 400 °C, the flow stress shows dynamic recrystallization characteristic. TEM micrographs were used to reveal the evolution of microstructures. According to the processing map at true strain of 0.7, the feasible deformation conditions are high strain rate(>0.5 s-1) or 440-500 °C and 0.01-0.02 s-1.展开更多
The high temperature deformation behaviors and thermal workability of Cu_（43）Zr_（48）Al_9 and（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glasses in the supercooled liquid region were investigated by the unia...The high temperature deformation behaviors and thermal workability of Cu_（43）Zr_（48）Al_9 and（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glasses in the supercooled liquid region were investigated by the uniaxial compression tests. The results showed that the high temperature deformation behaviors were highly sensitive to strain rate and temperature, and the flow stress decreased with the increase of temperature, as well as with the decrease of strain rate. Additionally, the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass displayed smaller flow stress under the same condition. The flow behavior changed from Newtonian to non-Newtonian with increase of the strain rate, as well as the decrease of temperature, which could be explained by the transition state theory. We found that（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass had better flow behavior than the Cu_（43）Zr_（48）Al_9 bulk metallic glass in the supercooled liquid region. In addition, the processing maps of the two bulk metallic glasses were constructed considering the power dissipation efficiency. The optimum domain for thermal workability of the bulk metallic glass was located using the processing map, where the power dissipation efficiency was larger than 0.8. It was shown that the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass, which had larger area of optimum domain, had excellent thermoplastic forming.展开更多
In Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the fuel debris formed in the Reactor Pressure Vessel (RPV) and Primary Containment Vessel (PCV) at Unit 1</span><span style="font-family:Verdan...In Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the fuel debris formed in the Reactor Pressure Vessel (RPV) and Primary Containment Vessel (PCV) at Unit 1</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">3. To accelerate and decide further decommissioning steps of the FDNPP, it is crucial to obtain realistic information of the debris and localize contaminated water leakage from PCV. Due to high radiation and dark environment inside the PCV, investigating instruments and techniques should necessarily to meet specification of radiation resistance, waterproofness, dust resistance and so on. This study focuses on development of ultrasonic measurement system using a couple of sectorial array sensors to localize contaminated water leakage and visualize shape of object that repre</span><span style="font-family:Verdana;">- </span><span style="font-family:Verdana;">senting fuel debris, simultaneously. In this study, Total Focusing Method</span><span style="font-family:Verdana;"> (TFM) and Ultrasonic Velocity Profiler (UVP) methods are considered to visualize object shape and flow pattern around it, respectively. To demonstrate applicability and reliability of developed measurement system with sectorial array sensors, a mock-up experiment result</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">of simulated water leakage and fuel debris shape were discussed in this paper.展开更多
In situ TiB2 reinforced 6351 Al alloy composites were subjected to compression testing at strain rates and temperatures ranging from 0.001 to 10 s -1 and from 300 to 550？欲espectively,using Gleeble-1500D system.And t...In situ TiB2 reinforced 6351 Al alloy composites were subjected to compression testing at strain rates and temperatures ranging from 0.001 to 10 s -1 and from 300 to 550？欲espectively,using Gleeble-1500D system.And the associated microstructural transformations and instability phenomena were studied by observations of the optical and transmission electron microscope.The power dissipation efficiency and instability parameter were calculated following the dynamic material model and plotted with the temperature and logarithm of strain rate to obtain processing maps for strains of 0.2,0.4,and 0.6.The processing maps present the instability zones at higher strain rates.The result shows that with increasing strain,the instability zones enlarge.The microstructural examination shows that the interface separates even the particle cracks or aligns along the shear direction of the adiabatic shear band in the instability zones.Two domains of higher efficiencies correspond to dynamic recovery and dynamic recrystallization during the hot deformation.Using the processing maps,the optimum processing parameters of stain rates and temperatures can be chosen for effective hot deformation of TiB2/6351 composites.展开更多
In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strai...In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strain rate range of 0.008-5 s^-1. Based on the true stress-true strain curves, a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn. It was found that the flow stress of the Co-Cu alloy increased with the increase of the strain rate and decreased with the increase of the deforming temperature. The hot processing map indicated that there were two unstable regions and one well-processing region. The microstructure, the hardness distribution and the electro- chemical properties of the hot deformed sample were investigated in order to reveal the influence of the hot deformation. Microstructure observation indicated that the grain size increased with the increase of the deformation temperature but decreased with the increase of the strain rate. High temperature and low strain rate promoted the crystallization process but increased the grain size, which results in a reduction in the hardness. The hot deformation at high temperature （1100-1150 ℃） would reduce the corrosion resistance slightly. The final optimized deformation process was： a deformation temperature from 1050to 1100 ℃, and a strain rate from 0.008 to 0.2 s^-1, where a completely recrystallized and homogeneously distributed microstructure would be obtained.展开更多
Background Vector flow mapping is a novel echocardiographic technique that enables the visualization of the intraventricular flow. We aimed to evaluate and compare the index of hemodynamic dissipative energy loss in p...Background Vector flow mapping is a novel echocardiographic technique that enables the visualization of the intraventricular flow. We aimed to evaluate and compare the index of hemodynamic dissipative energy loss in patients with hypertension and the ones with normotensive, unaffected control subjects. Methods & Results Transthoracic echocardiography was performed in eighty-nine hypertensive patients with preserved left ventricular ejection fraction, fifty-one hypertensive patients with left ventricular hypertrophy(LVH group) and thirty-eight hypertensive patients without LVH(non-LVH group). Forty-two healthy volunteers were enrolled as the control group. The stored images were analyzed to calculate the energy loss. The average energy loss of diastole in the LVH group was significantly increased(controls vs. non-LVH vs. LVH: 7.07 ± 0.91 vs. 12.44 ± 3.14 vs. 16.29 ± 3.17 J/s per m^3). Compared with the control group, the energy loss was significantly increased in the LVH group during the different periods in diastole. The energy loss in the non-LVH group was the greatest among the three groups during the atrial contraction period. Conclusions Energy loss provides a promising method for evaluating the energy efficiency in the left ventricle and may be a new indicator of left ventricular cardiac dysfunction.展开更多
Let Mn be an embedded closed submanifold ofR^(k+1) or a smooth bounded domain inR_(n),where n≥3.We show that the local smooth solution to the heat flow of self-induced harmonic map will blow up at a finite time,provi...Let Mn be an embedded closed submanifold ofR^(k+1) or a smooth bounded domain inR_(n),where n≥3.We show that the local smooth solution to the heat flow of self-induced harmonic map will blow up at a finite time,provided that the initial map u0 is in a suitable nontrivial homotopy class with energy small enough.展开更多
For a homotopy class[u]of maps between a closed Riemannian manifold M and a general manifold N,we want to find a Dirac-harmonic map with the map component in the given homotopy class.Most known results require the ind...For a homotopy class[u]of maps between a closed Riemannian manifold M and a general manifold N,we want to find a Dirac-harmonic map with the map component in the given homotopy class.Most known results require the index to be nontrivial.When the index is trivial,the few known results are all constructive and produce uncoupled solutions.In this paper,we define a new quantity.As a byproduct of proving the homotopy invariance of this new quantity,we find a new simple proof for the fact that all the Dirac-harmonic spheres in surfaces are uncoupled.More importantly,by using the homotopy invariance of this new quantity,we prove the existence of Dirac-harmonic maps from manifolds in the trivial index case.In particular,when the domain is a closed Riemann surface,we prove the short-time existence of theα-Dirac-harmonic map flow in the trivial index case.Together with the density of the minimal kernel,we get an existence result for Dirac-harmonic maps from closed Riemann surfaces to K?hler manifolds,which extends the previous result of the first and third authors.This establishes a general existence theory for Dirac-harmonic maps in the context of the trivial index.展开更多
Flow patterns of liquid-gas two-phase flow were experimentally investigated. The experiments were carried out in both vertical and horizontal capillary tubes having inner diameters of 1,60 mm, The working liquid was t...Flow patterns of liquid-gas two-phase flow were experimentally investigated. The experiments were carried out in both vertical and horizontal capillary tubes having inner diameters of 1,60 mm, The working liquid was the mixture of water and Sodium Dodecyl Benzoyl Sulfate （SDBS）. The working gas was Nitrogen. For the water/SDBS mixture-gas flow in the vertical capillary tube, flow-pattern transitions occurred at lower flow velocities than those for the water-gas flow in the same tube. For the water/SDBS mixture-gas flow in the horizontal capillary tube, surface tension had little effect on the bubbly-intermittent transition and had only slight effect on the plug-slug and slug-annular transitions. However, surface tension had significant effect on the wavy stratified flow regime. The wavy stratified flow regime of water/SDBS mixture-gas flow expanded compared with that of water-gas.展开更多
The partial regularity of the weak heat flow of harmonic maps from a Riemannian manifold Al with boundary into general compact Riemannian manifold N without boundary is consid-ered. It is shown that the singular set S...The partial regularity of the weak heat flow of harmonic maps from a Riemannian manifold Al with boundary into general compact Riemannian manifold N without boundary is consid-ered. It is shown that the singular set Sing(u) of the weak heat flow satisfies H(Sing(u)) 0, with is = dimensionM. Here is Hausdorff measure with respect to parabolic metric ρ(x,t),(y,s)=max{|x-y|, }.展开更多
Gas-oil-water three phase flow is of practical significance in oil and gas industries. An insight into the dynamics of such multiphase flows is significantly valuable to obtain optimal design parameters and operationa...Gas-oil-water three phase flow is of practical significance in oil and gas industries. An insight into the dynamics of such multiphase flows is significantly valuable to obtain optimal design parameters and operational conditions. Since flow patterns are sensitive to pipe geometry, flow conditions and thermophysical properties of fluid, it is extremely challenging to provide a universal solution for visualisation of three phase horizontal flows. This study deals with a fully developed, turbulent three phase flow and presents the outcomes of electrical tomographic imaging techniques to visualise gas-oil-water flows in a horizontal pipeline.展开更多
基金This project is partially funded by a grant(Ref:YBCB2009041-44)Huawei Technologies Noah’s Ark Lab and also grant HK RGC GRF 16241916.
文摘The advanced telecom technologies and massive volumes of intelligent mobile phone users have yielded a huge amount of real-time data of people’s all-in-one telecommunication records,which we call telco big data.With telco data and the domain knowledge of an urban city,we are now able to analyze the movement and contact patterns of humans in an unprecedented scale.Flow map is widely used to display the movements of humans from one single source to multiple destinations by representing locations as nodes and movements as edges.However,it fails the task of visualizing both movement and contact data.In addition,analysts often need to compare and examine the patterns side by side,and do various quantitative analysis.In this work,we propose a novel spatio-temporal flow map layout to visualize when and where people from different locations move into the same places and make contact.We also propose integrating the spatiotemporal flow maps into existing spatiotemporal visualization techniques to form a suite of techniques for visualizing the movement and contact patterns.We report a potential application the proposed techniques can be applied to.The results show that our design and techniques properly unveil hidden information,while analysis can be achieved efficiently.
基金sponsored by the National Natural Science Foundation of China(Nos.52174002&52204008)the Heilongjiang Provincial Natural Science Foundation of China(No.LH2022E020).
文摘During horizontal well drilling,the interaction between drilling fluid and cuttings entering the annulus generates diverse flow patterns.These solid-liquid two-phase flow patterns must be accurately predicted to optimize the determination of hydraulic parameters and improve the efficiency of cuttings transport.Accordingly,this study identified flow patterns and conducted transition experiments under different inclination angles using a visualized wellbore annulus apparatus(120 mm outer diameter/73 mm inner diameter).Through direct visual observations,four primary flow patterns were systematically classified on the basis of the solid-liquid two-phase flow behaviors identified in the experiments:stable bed(SB),sand wave(SW),sand dune(SD),and bed load(BL)flows.The experimental data were then used to construct flow pattern maps with solid/liquid phases as axes,after which the transition boundaries between different flow patterns were established.The morphological characteristics and transition mechanisms of SB,SW,SD,and BL flows were systematically analyzed to develop three predictive models of the fluid dynamics principles governing these flow patterns’transitions:(1)A transition boundary model of SB and SW flows was established using Kelvin-Helmholtz stability,for which a stability analysis of solid-liquid two-phase flow in deviated and horizontal annuli was carried out.(2)A transition boundary model of SW and SD flows was constructed through an analysis of the geometric features of sand waves in the annuli,with the critical ratio of the average height of a cuttings bed to its height after erosion being 0.45.(3)A traditional critical velocity model was refined by adjusting the von Karman constant to account for the effect of solid volume concentration,yielding a boundary model for the transition of SW or SD flow into BL flow.All the models were experimentally validated.Finally,we integrated the models to develop a unified method for identifying and classifying the patterns typifying solid-liquid two-phase flow in deviated and horizontal annuli.
基金supported by Independent Innovation Fund of Huazhong University of Science and Technology for Clinical Skills,China(No.2015-01-18-53028)
文摘Summary： Intraventricular hydrodynamics is considered an important component of cardiac function assessment. Vector flow mapping （VFM） is a novel flow visualization method to describe cardiac pathophysiological condition. This study examined use of new VFM and flow field for assessment of left ventricular （LV） systolic hemodynamics in patients with simple hyperthyroidism （HT）. Thirty-seven simple HT patients were enrolled as HT group, and 38 gender- and age-matched healthy volunteers as control group. VFM model was used to analyze LV flow field at LV apical long-axis view. The follow- ing flow parameters were measured, including peak systolic velocity （Vs）, peak systolic flow （Fs）, total systolic negative flow （SQ） in LV basal, middle and apical level, velocity gradient from the apex to the aortic valve （AV）, and velocity according to half distance （V1/2）. The velocity vector in the LV cavity, stream line and vortex distribution in the two groups were observed. The results showed that there were no significant differences in the conventional parameters such as left ventricular ejection fraction （LVEF）, left ventricular end-diastolic diameter （LVEDD） and left atrium diameter （LAD） between HT group and control group （P〉0.05）. Compared with the control group, a brighter flow and more vortexes were detected in HT group. Non-uniform distribution occurred in the LV flow field, and the stream lines were discontinuous in HT group. The values of Vs and Fs in three levels, SQ in middle and basal levels, AV and V1/2 were higher in HT group than in control group （P〈0.01）. AV was positively correlated with serum free thyroxin （FT4） （r=0.48, P〈0.01）. Stepwise multiple regression analysis showed that LVEDD, FT4, and body surface area （BSA） were the influence factors of △V. The unstable left ventricular sys- tolic hydrodynamics increased in a compensatory manner in simple PIT patients. The present study in- dicated that VFM may be used for early detection of abnormal ventricle contraction in clinical settings.
基金Project(51576213)supported by the National Natural Science Foundation of ChinaProject(2015RS4015)supported by the Hunan Scientific Program,ChinaProject(2016zzts323)supported by the Innovation Project of Central South University,China
文摘Gas–liquid two-phase flow abounds in industrial processes and facilities. Identification of its flow pattern plays an essential role in the field of multiphase flow measurement. A bluff body was introduced in this study to recognize gas–liquid flow patterns by inducing fluid oscillation that enlarged differences between each flow pattern. Experiments with air–water mixtures were carried out in horizontal pipelines at ambient temperature and atmospheric pressure. Differential pressure signals from the bluff-body wake were obtained in bubble, bubble/plug transitional, plug, slug, and annular flows. Utilizing the adaptive ensemble empirical mode decomposition method and the Hilbert transform, the time–frequency entropy S of the differential pressure signals was obtained. By combining S and other flow parameters, such as the volumetric void fraction β, the dryness x, the ratio of density φ and the modified fluid coefficient ψ, a new flow pattern map was constructed which adopted S（1–x）φ and （1–β）ψ as the vertical and horizontal coordinates, respectively. The overall rate of classification of the map was verified to be 92.9% by the experimental data. It provides an effective and simple solution to the gas–liquid flow pattern identification problems.
基金supported by the National Natural Science Foundation of China (Grant number 51776015)
文摘In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.
基金This work was supported by the Guangdong Basic and Applied Basic Research Foundation(2019A1515111116)Key R&D Program of Shandong Province(Nos.2019GSF109051,2019GGX101030)+1 种基金Shandong Provincial Postdoctoral Innovation Project(No.201902002)Foundation of Shandong University for Young Scholar’s Future Plans.
文摘The flow patterns and the void fraction related to a gas-liquid two-phase flow in a small channel are experimentally studied.The test channel is a transparent quartz glass circular channel with an inner diameter of 6.68 mm.The working fluids are air and water and their superficial velocities range from 0.014 to 8.127 m/s and from 0.0238 to 0.556 m/s,respectively.The void fraction is determined using the flow pattern images captured by a high-speed camera,while quick closing valves are used for verification.Four flow patterns are analyzed in experiments:slug flow,bubbly flow,annular flow and stratified flow.For intermittent flows(bubbly flow and slug flow),the cross-sectional void fraction is in a borderline condition while its probability distribution function(PDF)image displays a bimodal structure.For continuous flows(annular flow and stratified flow)the cross-sectional void fraction behaves as a fluctuating continuous curve while the(PDF)image displays a single peak structure.The volumetric void fraction data are also compared with available predictive formulas,and the results show that the agreement is very good.An effort is also provided to improve the so-called Gregory and Scott model using the available data.
基金Supported by the Natural Science Foundation of Henan Province(2004601018).
文摘In this paper, the stochastic flow of mappings generated by a Feller convolution semigroup on a compact metric space is studied. This kind of flow is the generalization of superprocesses of stochastic flows and stochastic diffeomorphism induced by the strong solutions of stochastic differential equations.
基金Project(51301209) supported by the National Natural Science Foundation of ChinaProject(201191107) supported by Science and Technology Plan of Xinjiang Province,China
文摘The flow stress behavior of high-purity Al-Cu-Mg alloy under hot deformation conditions was studied by Gleeble-1500,with the deformation temperature range from 300 to 500 °C and the strain rate range from 0.01 to 10 s-1. From the true stress-true strain curve, the flow stress increases with the increasing of strain and tends to be constant after a peak value, showing dynamic recover, and the peak value of flow stress increases with the decreasing of deformation temperature and the increasing of strain rate.When the strain rate is 10 s-1 and the deformation temperature is higher than 400 °C, the flow stress shows dynamic recrystallization characteristic. TEM micrographs were used to reveal the evolution of microstructures. According to the processing map at true strain of 0.7, the feasible deformation conditions are high strain rate(>0.5 s-1) or 440-500 °C and 0.01-0.02 s-1.
基金supported by the Education Department of Shaanxi Province(14JK1351)the Principal Fund of Xi’an Technological University(0852-302021407)
文摘The high temperature deformation behaviors and thermal workability of Cu_（43）Zr_（48）Al_9 and（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glasses in the supercooled liquid region were investigated by the uniaxial compression tests. The results showed that the high temperature deformation behaviors were highly sensitive to strain rate and temperature, and the flow stress decreased with the increase of temperature, as well as with the decrease of strain rate. Additionally, the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass displayed smaller flow stress under the same condition. The flow behavior changed from Newtonian to non-Newtonian with increase of the strain rate, as well as the decrease of temperature, which could be explained by the transition state theory. We found that（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass had better flow behavior than the Cu_（43）Zr_（48）Al_9 bulk metallic glass in the supercooled liquid region. In addition, the processing maps of the two bulk metallic glasses were constructed considering the power dissipation efficiency. The optimum domain for thermal workability of the bulk metallic glass was located using the processing map, where the power dissipation efficiency was larger than 0.8. It was shown that the（Cu_（43）Zr_（48）Al_9）_（98）Y_2 bulk metallic glass, which had larger area of optimum domain, had excellent thermoplastic forming.
文摘In Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, the fuel debris formed in the Reactor Pressure Vessel (RPV) and Primary Containment Vessel (PCV) at Unit 1</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">3. To accelerate and decide further decommissioning steps of the FDNPP, it is crucial to obtain realistic information of the debris and localize contaminated water leakage from PCV. Due to high radiation and dark environment inside the PCV, investigating instruments and techniques should necessarily to meet specification of radiation resistance, waterproofness, dust resistance and so on. This study focuses on development of ultrasonic measurement system using a couple of sectorial array sensors to localize contaminated water leakage and visualize shape of object that repre</span><span style="font-family:Verdana;">- </span><span style="font-family:Verdana;">senting fuel debris, simultaneously. In this study, Total Focusing Method</span><span style="font-family:Verdana;"> (TFM) and Ultrasonic Velocity Profiler (UVP) methods are considered to visualize object shape and flow pattern around it, respectively. To demonstrate applicability and reliability of developed measurement system with sectorial array sensors, a mock-up experiment result</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">of simulated water leakage and fuel debris shape were discussed in this paper.
文摘In situ TiB2 reinforced 6351 Al alloy composites were subjected to compression testing at strain rates and temperatures ranging from 0.001 to 10 s -1 and from 300 to 550？欲espectively,using Gleeble-1500D system.And the associated microstructural transformations and instability phenomena were studied by observations of the optical and transmission electron microscope.The power dissipation efficiency and instability parameter were calculated following the dynamic material model and plotted with the temperature and logarithm of strain rate to obtain processing maps for strains of 0.2,0.4,and 0.6.The processing maps present the instability zones at higher strain rates.The result shows that with increasing strain,the instability zones enlarge.The microstructural examination shows that the interface separates even the particle cracks or aligns along the shear direction of the adiabatic shear band in the instability zones.Two domains of higher efficiencies correspond to dynamic recovery and dynamic recrystallization during the hot deformation.Using the processing maps,the optimum processing parameters of stain rates and temperatures can be chosen for effective hot deformation of TiB2/6351 composites.
基金financially supported by the National Natural Science Foundation of China (Nos. 81071262, 31271024 and 31470930)the Funding from Northeastern University ("985 program", Nos. N141008001 and LZ2014018), China
文摘In order to optimize the deformation processing, the hot deformation behavior of Co-Cr-Mo-Cu （here- after named as Co-Cu） alloy was studied in this paper at a deformation temperature range of 950-1150 ℃ and a strain rate range of 0.008-5 s^-1. Based on the true stress-true strain curves, a constitutive equation in hyperbolic sin function was established and a hot processing map was drawn. It was found that the flow stress of the Co-Cu alloy increased with the increase of the strain rate and decreased with the increase of the deforming temperature. The hot processing map indicated that there were two unstable regions and one well-processing region. The microstructure, the hardness distribution and the electro- chemical properties of the hot deformed sample were investigated in order to reveal the influence of the hot deformation. Microstructure observation indicated that the grain size increased with the increase of the deformation temperature but decreased with the increase of the strain rate. High temperature and low strain rate promoted the crystallization process but increased the grain size, which results in a reduction in the hardness. The hot deformation at high temperature （1100-1150 ℃） would reduce the corrosion resistance slightly. The final optimized deformation process was： a deformation temperature from 1050to 1100 ℃, and a strain rate from 0.008 to 0.2 s^-1, where a completely recrystallized and homogeneously distributed microstructure would be obtained.
基金the Capital Characteristic Clinic Project (No. Z181100001718015)。
文摘Background Vector flow mapping is a novel echocardiographic technique that enables the visualization of the intraventricular flow. We aimed to evaluate and compare the index of hemodynamic dissipative energy loss in patients with hypertension and the ones with normotensive, unaffected control subjects. Methods & Results Transthoracic echocardiography was performed in eighty-nine hypertensive patients with preserved left ventricular ejection fraction, fifty-one hypertensive patients with left ventricular hypertrophy(LVH group) and thirty-eight hypertensive patients without LVH(non-LVH group). Forty-two healthy volunteers were enrolled as the control group. The stored images were analyzed to calculate the energy loss. The average energy loss of diastole in the LVH group was significantly increased(controls vs. non-LVH vs. LVH: 7.07 ± 0.91 vs. 12.44 ± 3.14 vs. 16.29 ± 3.17 J/s per m^3). Compared with the control group, the energy loss was significantly increased in the LVH group during the different periods in diastole. The energy loss in the non-LVH group was the greatest among the three groups during the atrial contraction period. Conclusions Energy loss provides a promising method for evaluating the energy efficiency in the left ventricle and may be a new indicator of left ventricular cardiac dysfunction.
基金supported partially by NSFC(Grant Nos.12141103 and 12301074)Guangzhou Basic and Applied Basic Research Foundation(Grant No.2024A04J3637)+1 种基金supported partially by NSFC(Grant No.11971400)National Key Research and Development Projects of China(Grant No.2020YFA0712500)。
文摘Let Mn be an embedded closed submanifold ofR^(k+1) or a smooth bounded domain inR_(n),where n≥3.We show that the local smooth solution to the heat flow of self-induced harmonic map will blow up at a finite time,provided that the initial map u0 is in a suitable nontrivial homotopy class with energy small enough.
基金supported by National Natural Science Foundation of China(Grant No.12201440)the Fundamental Research Funds for the Central Universities。
文摘For a homotopy class[u]of maps between a closed Riemannian manifold M and a general manifold N,we want to find a Dirac-harmonic map with the map component in the given homotopy class.Most known results require the index to be nontrivial.When the index is trivial,the few known results are all constructive and produce uncoupled solutions.In this paper,we define a new quantity.As a byproduct of proving the homotopy invariance of this new quantity,we find a new simple proof for the fact that all the Dirac-harmonic spheres in surfaces are uncoupled.More importantly,by using the homotopy invariance of this new quantity,we prove the existence of Dirac-harmonic maps from manifolds in the trivial index case.In particular,when the domain is a closed Riemann surface,we prove the short-time existence of theα-Dirac-harmonic map flow in the trivial index case.Together with the density of the minimal kernel,we get an existence result for Dirac-harmonic maps from closed Riemann surfaces to K?hler manifolds,which extends the previous result of the first and third authors.This establishes a general existence theory for Dirac-harmonic maps in the context of the trivial index.
基金supported by Key foundational research project of Science and Technology Bureau of Shanghai (Grant No. 04JC14049).
文摘Flow patterns of liquid-gas two-phase flow were experimentally investigated. The experiments were carried out in both vertical and horizontal capillary tubes having inner diameters of 1,60 mm, The working liquid was the mixture of water and Sodium Dodecyl Benzoyl Sulfate （SDBS）. The working gas was Nitrogen. For the water/SDBS mixture-gas flow in the vertical capillary tube, flow-pattern transitions occurred at lower flow velocities than those for the water-gas flow in the same tube. For the water/SDBS mixture-gas flow in the horizontal capillary tube, surface tension had little effect on the bubbly-intermittent transition and had only slight effect on the plug-slug and slug-annular transitions. However, surface tension had significant effect on the wavy stratified flow regime. The wavy stratified flow regime of water/SDBS mixture-gas flow expanded compared with that of water-gas.
基金supported by National Natural Science Foundation of China(Grant Nos.11025107,10831008 and 10901165)the Fundamental Research Funds for Central Universities(Grant No.201034000-3162643)+2 种基金High Level Talent Project in High Schools in Guangdong Province(Grant No.34000-5221001)the Fundamental Research Funds for the Central Universities(Grant No.101gpy25)China Post-doctoral Science Foundation(Grant No.201003382)
文摘We construct the canonical solitons,in terms of Cabezas-Rivas and Topping,associated with some generalized Ricci flows.
基金the National Natural Science Foundation of China (No.10071013).
文摘The partial regularity of the weak heat flow of harmonic maps from a Riemannian manifold Al with boundary into general compact Riemannian manifold N without boundary is consid-ered. It is shown that the singular set Sing(u) of the weak heat flow satisfies H(Sing(u)) 0, with is = dimensionM. Here is Hausdorff measure with respect to parabolic metric ρ(x,t),(y,s)=max{|x-y|, }.
基金the European Metrology Research Programme (EMRP) project “Multiphase flow metrology in the Oil and Gas production” which is jointly funded by the European Commission and participating countries within Euramet and the European Union
文摘Gas-oil-water three phase flow is of practical significance in oil and gas industries. An insight into the dynamics of such multiphase flows is significantly valuable to obtain optimal design parameters and operational conditions. Since flow patterns are sensitive to pipe geometry, flow conditions and thermophysical properties of fluid, it is extremely challenging to provide a universal solution for visualisation of three phase horizontal flows. This study deals with a fully developed, turbulent three phase flow and presents the outcomes of electrical tomographic imaging techniques to visualise gas-oil-water flows in a horizontal pipeline.
