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
In this paper,effective Eulerian algorithms are introduced for the computation of the forwardfinite time Lyapunov exponent(FTLE)of smoothflowfields.The advantages of the proposed algorithms mainly manifest in two aspe...In this paper,effective Eulerian algorithms are introduced for the computation of the forwardfinite time Lyapunov exponent(FTLE)of smoothflowfields.The advantages of the proposed algorithms mainly manifest in two aspects.First,previous Eulerian approaches for computing the FTLEfield are improved so that the Jacobian of theflow map can be obtained by directly solving a corresponding system of partial differential equations,rather than by implementing certainfinite difference upon theflow map,which can significantly improve the accuracy of the numerical solution especially near the FTLE ridges.Second,in the proposed algorithms,all computations are done on thefly,that is,all required partial differential equations are solved forward in time,which is practically more natural.The new algorithms still maintain the optimal computational complexity as well as the second order accuracy.Numerical examples demonstrate the effectiveness of the proposed algorithms.展开更多
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
In order to study the mechanism of angiographic coronary slow flow phenomenon (SF), intracoronary ultrasound (ICUS) and Doppler (ICD) were performed in 14 patients with angiographic SF phenomenon but with normal angio...In order to study the mechanism of angiographic coronary slow flow phenomenon (SF), intracoronary ultrasound (ICUS) and Doppler (ICD) were performed in 14 patients with angiographic SF phenomenon but with normal angiograms and in 16 patients with normal angiographic coronary flow (NF). A 3.5 F, 20 MHz ultrasound catheter (Boston Scientific) was used for ICUS and a 0.014 inch FloWire (Cardiometrics) was used for ICD. Coronary flow velocity including average peak velocity (APV), maximal peak velocity (MPV) at rest and at hyperemia as well as coronary flow reserve (CFR) were compared in both groups in comparison to the presence or absence of plaque formation based on ICUS. CFR in the SF group (4.2±1.1) was even higher than that of the NF group (3.1±0.6, P<0.001). Department of Cardiology, University GHS Essen, Germany (Ge JB, Simon H, Jeremias A, Liu FQ, Grge G, Haude M, Baumgart D and Erbel R) Significant differences were also found concerning the APV and MPV among both groups (both P <0.001). Plaque formation was found in 7/13 patients with a lumen reduction of 21%±24% in SF group and in 7/16 of the NF group with a lumen reduction of 19%±17%. Comparison of APV, MPV and CFR in SF and NF grups. Comparison of APV, MPV and CFR in SF and NF groups[BHDFG1*2,WK8ZQ1,WK11DW,WK11DWW] SF group NF groupAPV (cm/s) Rest 7.7±2.0 21.1±5.0 * Peak31.7±14.961.3±14.2 *MPV (cm/s) Rest17.4±4.637.0±11.4 * Peak56.8±14.981.8±17.7 *CFR4.2±1.13.1±0.6 # * P<0.001, #P=0.002. Coronary slow flow phenomenon in angiography indicates reduced resting flow velocity without reduction of coronary flow reserve.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
In light of previous work [Phys. Rev. E 60 4000 （1999）], a modified coupled-map car-following model is proposed by considering the headways of two successive vehicles in front of a considered vehicle described by th...In light of previous work [Phys. Rev. E 60 4000 （1999）], a modified coupled-map car-following model is proposed by considering the headways of two successive vehicles in front of a considered vehicle described by the optimal velocity function. The non-jam conditions are given on the basis of control theory. Through simulation, we find that our model can exhibit a better effect as p = 0.65, which is a parameter in the optimal velocity function. The control scheme, which was proposed by Zhao and Gao, is introduced into the modified model and the feedback gain range is determined. In addition, a modified control method is applied to a mixed traffic system that consists of two types of vehicle. The range of gains is also obtained by theoretical analysis. Comparisons between our method and that of Zhao and Gao are carried out, and the corresponding numerical simulation results demonstrate that the temporal behavior of traffic flow obtained using our method is better than that proposed by Zhao and Gao in mixed traffic systems.展开更多
Flow behavior and processing map play important roles in the hot deformation process of titanium alloys. In this research, compression Gleeble tests have been carried out to investigate the stress-strain relationship ...Flow behavior and processing map play important roles in the hot deformation process of titanium alloys. In this research, compression Gleeble tests have been carried out to investigate the stress-strain relationship at temperatures ranging from 700 to 1000 ℃ and strain rates ranging from 0.001 to 1 s-1 for ATI 425 titanium alloy. Arrhenius type constitutive equation was obtained to describe the compressive flow behavior with modification of additional deformation dead zone, friction model, temperature model and strain rate. The introduction of novel calculation method for α value in Arrhenius equation gives more accurate fitting than traditional one. Processing maps were drawn based on the distribution of dissipator co-content, and optimized deformation temperature and strain rate range obtained. It is proven to be accurate and effective through the experimental results. The microstructure analysis shows that more dynamic recrystallization can be achieved in the area with larger ηvalue on the processing map.展开更多
Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformation behavior and microstructural evolution of superalloy GH4742, different types of instability criteria of Prasa...Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformation behavior and microstructural evolution of superalloy GH4742, different types of instability criteria of Prasad, Gegel, Malas, Murty and Semiatin were compared, and the physical significance of parameters was analyzed. Meanwhile, the processing maps with different instability criteria were obtained. It was shown that instability did not occur when average power dissipation rate was larger than 50% in the temperature range of 1020- 1130℃, corresponding to the strain rate range of 5 × 10-4-3.2 × 10-3 s-1. The domain is appropriate for the processing deformation of superalloy GH4742.展开更多
The global existence of the heat flow for harmonic maps from noncompact manifolds is considered. When L^m norm of the gradient of initial data is small, the existence of a global solution is proved.
A weak solution to the heat flow problems is constructed.Nonuniqueness results of such solutions are also shown when the first data is a weak solution to the Euler Lagrange equation but not a weakly stationary soluti...A weak solution to the heat flow problems is constructed.Nonuniqueness results of such solutions are also shown when the first data is a weak solution to the Euler Lagrange equation but not a weakly stationary solution to it.展开更多
The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s^-1 on a Gleeble 1500 D thermal mechanical simulator....The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s^-1 on a Gleeble 1500 D thermal mechanical simulator. The results show the flow stress of Al-Cu-Mg-Ag alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate and temperature, the flow stress equation is estimated to illustrate the relation of strain rate and stress and temperature during high temperature deformation process. The processing maps exhibit two domains as optimum fields for hot deformation at different strains, including the high strain rate domain in 623-773 K and the low strain rate domain in 573-673 K.展开更多
Different researchers select different factors and use different methods to assess the regional hazard degrees of debris now. consequenily, even for the same region, tb.. are often different hazard zonation maps, and ...Different researchers select different factors and use different methods to assess the regional hazard degrees of debris now. consequenily, even for the same region, tb.. are often different hazard zonation maps, and there must be some uncertainty in the zonations. Thus the ceriainty analysis of zonation maps becomes obviously important.For debris now hazard, those zonation maps with a certainty analysis could provide most valuable information for land users, hazard managers and policy makers. By comparison of three researchers’ findings in Yunnan Province, this paPer shows that seven to nine iafluential factors are chosen for the zonation maps. spatial density of debris flow ravines,regional average rock-weathering coefficient, yearly precipitation, days of≥50 mm daily rainfall, and proportion of sloping land with slope≥25℃to the total land are the most acceptable factors. Mathemahcal methods of maximum-minimumvalues, upperlower limit values and Fuzzy values are used to quantify the factors. Step-by-step methodoogy is commonly used for the zonation maps. Research results show that mchmum uncedrinty is 66. 6% and minimum uncertainty is 35.7% in debris now hazard maps of zhaotong Prefecture and Yunnan Province. Therefore there is still much work for us to improve the zonation methedology.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
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
针对动态场景导致视觉定位与建图(simultaneous localization and mapping,SLAM)算法位姿估计精度低和地图质量差等问题,提出一种结合深度学习的动态视觉SLAM算法。该算法在ORB-SLAM3前端引入轻量化且目标识别率高的YOLO11n目标检测网络...针对动态场景导致视觉定位与建图(simultaneous localization and mapping,SLAM)算法位姿估计精度低和地图质量差等问题,提出一种结合深度学习的动态视觉SLAM算法。该算法在ORB-SLAM3前端引入轻量化且目标识别率高的YOLO11n目标检测网络,检测潜在动态区域,并结合Lucas-Kanade(LK)光流法识别其中的动态特征点,从而在剔除动态特征点的同时保留静态特征点,提高特征点利用率和位姿估计精度。此外,新增语义地图构建线程,通过去除YOLO11n识别到的动态物体点云,并融合前端提取的语义信息,实现静态语义地图的构建。在TUM数据集上的实验结果表明,相较于ORB-SLAM3,该算法在高动态序列数据集中的定位精度提升了95.02%,验证了该算法在动态环境下的有效性,能显著提升视觉SLAM系统的定位精度和地图构建质量。展开更多
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supported by the National Natural Science Foundation of China(12071409)the Natural Science Foundation of Jiangsu Province(BK20211293).
文摘In this paper,effective Eulerian algorithms are introduced for the computation of the forwardfinite time Lyapunov exponent(FTLE)of smoothflowfields.The advantages of the proposed algorithms mainly manifest in two aspects.First,previous Eulerian approaches for computing the FTLEfield are improved so that the Jacobian of theflow map can be obtained by directly solving a corresponding system of partial differential equations,rather than by implementing certainfinite difference upon theflow map,which can significantly improve the accuracy of the numerical solution especially near the FTLE ridges.Second,in the proposed algorithms,all computations are done on thefly,that is,all required partial differential equations are solved forward in time,which is practically more natural.The new algorithms still maintain the optimal computational complexity as well as the second order accuracy.Numerical examples demonstrate the effectiveness of the proposed algorithms.
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.
文摘In order to study the mechanism of angiographic coronary slow flow phenomenon (SF), intracoronary ultrasound (ICUS) and Doppler (ICD) were performed in 14 patients with angiographic SF phenomenon but with normal angiograms and in 16 patients with normal angiographic coronary flow (NF). A 3.5 F, 20 MHz ultrasound catheter (Boston Scientific) was used for ICUS and a 0.014 inch FloWire (Cardiometrics) was used for ICD. Coronary flow velocity including average peak velocity (APV), maximal peak velocity (MPV) at rest and at hyperemia as well as coronary flow reserve (CFR) were compared in both groups in comparison to the presence or absence of plaque formation based on ICUS. CFR in the SF group (4.2±1.1) was even higher than that of the NF group (3.1±0.6, P<0.001). Department of Cardiology, University GHS Essen, Germany (Ge JB, Simon H, Jeremias A, Liu FQ, Grge G, Haude M, Baumgart D and Erbel R) Significant differences were also found concerning the APV and MPV among both groups (both P <0.001). Plaque formation was found in 7/13 patients with a lumen reduction of 21%±24% in SF group and in 7/16 of the NF group with a lumen reduction of 19%±17%. Comparison of APV, MPV and CFR in SF and NF grups. Comparison of APV, MPV and CFR in SF and NF groups[BHDFG1*2,WK8ZQ1,WK11DW,WK11DWW] SF group NF groupAPV (cm/s) Rest 7.7±2.0 21.1±5.0 * Peak31.7±14.961.3±14.2 *MPV (cm/s) Rest17.4±4.637.0±11.4 * Peak56.8±14.981.8±17.7 *CFR4.2±1.13.1±0.6 # * P<0.001, #P=0.002. Coronary slow flow phenomenon in angiography indicates reduced resting flow velocity without reduction of coronary flow reserve.
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 supported by the National Natural Science Foundation of China(Grant Nos.11372166,11372147,61074142,and 11072117)the Scientific Research Fund of Zhejiang Province,China(Grant No.LY13A010005)+1 种基金the Disciplinary Project of Ningbo City,China(Grant No.SZXL1067)the K.C.Wong Magna Fund in Ningbo University,China,and the Government of the Hong Kong Administrative Region,China(Grant No.119011)
文摘In light of previous work [Phys. Rev. E 60 4000 （1999）], a modified coupled-map car-following model is proposed by considering the headways of two successive vehicles in front of a considered vehicle described by the optimal velocity function. The non-jam conditions are given on the basis of control theory. Through simulation, we find that our model can exhibit a better effect as p = 0.65, which is a parameter in the optimal velocity function. The control scheme, which was proposed by Zhao and Gao, is introduced into the modified model and the feedback gain range is determined. In addition, a modified control method is applied to a mixed traffic system that consists of two types of vehicle. The range of gains is also obtained by theoretical analysis. Comparisons between our method and that of Zhao and Gao are carried out, and the corresponding numerical simulation results demonstrate that the temporal behavior of traffic flow obtained using our method is better than that proposed by Zhao and Gao in mixed traffic systems.
文摘Flow behavior and processing map play important roles in the hot deformation process of titanium alloys. In this research, compression Gleeble tests have been carried out to investigate the stress-strain relationship at temperatures ranging from 700 to 1000 ℃ and strain rates ranging from 0.001 to 1 s-1 for ATI 425 titanium alloy. Arrhenius type constitutive equation was obtained to describe the compressive flow behavior with modification of additional deformation dead zone, friction model, temperature model and strain rate. The introduction of novel calculation method for α value in Arrhenius equation gives more accurate fitting than traditional one. Processing maps were drawn based on the distribution of dissipator co-content, and optimized deformation temperature and strain rate range obtained. It is proven to be accurate and effective through the experimental results. The microstructure analysis shows that more dynamic recrystallization can be achieved in the area with larger ηvalue on the processing map.
基金supported by the National Key Basic Research Program of China (No. 2010CB631203)
文摘Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformation behavior and microstructural evolution of superalloy GH4742, different types of instability criteria of Prasad, Gegel, Malas, Murty and Semiatin were compared, and the physical significance of parameters was analyzed. Meanwhile, the processing maps with different instability criteria were obtained. It was shown that instability did not occur when average power dissipation rate was larger than 50% in the temperature range of 1020- 1130℃, corresponding to the strain rate range of 5 × 10-4-3.2 × 10-3 s-1. The domain is appropriate for the processing deformation of superalloy GH4742.
基金Supported by the National Natural Science Foundation of China (1057115610671079+1 种基金10701064)the Zijin Project of Zhejiang University
文摘The global existence of the heat flow for harmonic maps from noncompact manifolds is considered. When L^m norm of the gradient of initial data is small, the existence of a global solution is proved.
文摘A weak solution to the heat flow problems is constructed.Nonuniqueness results of such solutions are also shown when the first data is a weak solution to the Euler Lagrange equation but not a weakly stationary solution to it.
基金the National Basic Research Program of China(No.2005CB623705)
文摘The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s^-1 on a Gleeble 1500 D thermal mechanical simulator. The results show the flow stress of Al-Cu-Mg-Ag alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate and temperature, the flow stress equation is estimated to illustrate the relation of strain rate and stress and temperature during high temperature deformation process. The processing maps exhibit two domains as optimum fields for hot deformation at different strains, including the high strain rate domain in 623-773 K and the low strain rate domain in 573-673 K.
文摘Different researchers select different factors and use different methods to assess the regional hazard degrees of debris now. consequenily, even for the same region, tb.. are often different hazard zonation maps, and there must be some uncertainty in the zonations. Thus the ceriainty analysis of zonation maps becomes obviously important.For debris now hazard, those zonation maps with a certainty analysis could provide most valuable information for land users, hazard managers and policy makers. By comparison of three researchers’ findings in Yunnan Province, this paPer shows that seven to nine iafluential factors are chosen for the zonation maps. spatial density of debris flow ravines,regional average rock-weathering coefficient, yearly precipitation, days of≥50 mm daily rainfall, and proportion of sloping land with slope≥25℃to the total land are the most acceptable factors. Mathemahcal methods of maximum-minimumvalues, upperlower limit values and Fuzzy values are used to quantify the factors. Step-by-step methodoogy is commonly used for the zonation maps. Research results show that mchmum uncedrinty is 66. 6% and minimum uncertainty is 35.7% in debris now hazard maps of zhaotong Prefecture and Yunnan Province. Therefore there is still much work for us to improve the zonation methedology.
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.
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.
文摘针对动态场景导致视觉定位与建图(simultaneous localization and mapping,SLAM)算法位姿估计精度低和地图质量差等问题,提出一种结合深度学习的动态视觉SLAM算法。该算法在ORB-SLAM3前端引入轻量化且目标识别率高的YOLO11n目标检测网络,检测潜在动态区域,并结合Lucas-Kanade(LK)光流法识别其中的动态特征点,从而在剔除动态特征点的同时保留静态特征点,提高特征点利用率和位姿估计精度。此外,新增语义地图构建线程,通过去除YOLO11n识别到的动态物体点云,并融合前端提取的语义信息,实现静态语义地图的构建。在TUM数据集上的实验结果表明,相较于ORB-SLAM3,该算法在高动态序列数据集中的定位精度提升了95.02%,验证了该算法在动态环境下的有效性,能显著提升视觉SLAM系统的定位精度和地图构建质量。
