Most image interpolation algorithms currently used suffer visually to some extent the effects of blurred edges and jagged artifacts in the image. This letter presents an adaptive feature preserving bidirectional flow ...Most image interpolation algorithms currently used suffer visually to some extent the effects of blurred edges and jagged artifacts in the image. This letter presents an adaptive feature preserving bidirectional flow process, where an inverse diffusion is performed to enhance edges along the normal directions to the iso-phote lines (edges), while a normal diffusion is done to remove artifacts ('jaggies') along the tangent directions. In order to preserve image features such as edges, angles and textures, the nonlinear diffusion coefficients are locally adjusted according to the first order and the second order directional derivatives of the image. Experimental results on the Lena image demonstrate that our interpolation algorithm substantially improves the subjective quality of the interpolated images over conventional interpolations.展开更多
Analysis of dynamic features of pedestrian flows is one of the most exciting topics in pedestrian dynamics. This paper focuses on the effect of homogeneity and heterogeneity in three parameters of the social force mod...Analysis of dynamic features of pedestrian flows is one of the most exciting topics in pedestrian dynamics. This paper focuses on the effect of homogeneity and heterogeneity in three parameters of the social force model, namely desired velocity, reaction time, and body size, on the moving dynamics of bidirectional pedestrian flows in the corridors. The speed and its deviation in free flows are investigated. Simulation results show that the homogeneous higher desired speed which is less than a critical threshold, shorter reaction time or smaller body size results in higher speed of flows. The free dynamics is more sensitive to the heterogeneity in desired speed than that in reaction time or in body size. In particular, an inner lane formation is observed in normal lanes. Furthermore, the breakdown probability and the start time of breakdown are focused on. This study reveals that the sizes of homogeneous desired speed, reaction time or body size play more important roles in affecting the breakdown than the heterogeneities in these three parameters do.展开更多
This paper focuses on a two-dimensional bidirectional pedestrian flow model which involves the next-nearest-neighbor effect. The stability condition and the Korteweg-de Vries （KdV） equation are derived to describe t...This paper focuses on a two-dimensional bidirectional pedestrian flow model which involves the next-nearest-neighbor effect. The stability condition and the Korteweg-de Vries （KdV） equation are derived to describe the density wave of pedestrian congestion by linear stability and nonlinear analysis. Through theoretical analysis, the soliton solution is obtained.展开更多
Non-Newtonian flows have applications in food combination,plasma flow,inherent and organic fluids,antibiotics,and lubrication through oils and greases.This study explores the bidirectional flow of Williamson nanofluid...Non-Newtonian flows have applications in food combination,plasma flow,inherent and organic fluids,antibiotics,and lubrication through oils and greases.This study explores the bidirectional flow of Williamson nanofluid in a porous medium,incorporating thermophoresis,Brownian motion,bioconvection effects,and Arrhenius activation energy over a nonlinear stretching surface.The governing equations are transformed into a dimension-less form using similarity transformations and numerically solved via MATLAB’s bvp4c shooting scheme.Results indicate that increasing the Williamson parameterλand porosity parameterεreduces velocity,with a 10%rise inλleading to an 8%velocity reduction.Tem-perature increases with the thermophoresis parameter(Nt)where a 15%increase in Nt results in a 7%temperature rise.The Nusselt number improves with a higher Prandtl number Pr increasing by 10%when Pr rises from 5 to 7,while the Sherwood number declines with stron-ger Brownian motion.These findings provide key insights into heat and mass transfer Recent advances in modified Arrhenius activation energy and bioconvection mechanisms,contributing to advancements in industrial cooling,biomedical applications,and nanofluid-based thermal systems.展开更多
Flow-based measurement is a popular method for various network monitoring usages.However, many flow exporting softwares have still low performance to collect all flows.In this paper, we propose a IPFIX-based flow expo...Flow-based measurement is a popular method for various network monitoring usages.However, many flow exporting softwares have still low performance to collect all flows.In this paper, we propose a IPFIX-based flow export engine with an enhanced and extensible data structure, called XFix, on the basis of a GPL tool,-nProbe.In the engine, we use an extensible two-dimensional hash table for flow aggregation, which is able to improve the performance of the metering process as well as support bidirectional flow.Experimental results have shown its efficiency in multi-thread processing activity.展开更多
The bottleneck effect on bidirectional crowd dynamics is of great theoretical and practical significance, especially for the designing of corridors in public places, such as subway stations or airports. Based on the f...The bottleneck effect on bidirectional crowd dynamics is of great theoretical and practical significance, especially for the designing of corridors in public places, such as subway stations or airports. Based on the famous social force model, this paper investigates the bottleneck effects on the free flow dynamics and breakdown phenomenon under different scenarios, in which different corridor shapes and inflow ratios are considered simultaneously. Numerical simulation finds an interesting self-organization phenomenon in the bidirectional flow, a typical characteristic of such a phenomenon is called lane formation, and the existence of which is independent of the corridor＇s shape and inflow rate. However, the pattern of the lane formed by pedestrian flow is related to the corridor＇s shape, and the free flow efficiency has close relationship with the inflow rate. Specifically, breakdown phenomenon occurs when inflows from both sides of the corridor are large enough, which mostly originates from the bottleneck and then gradually spreads to the other regions. Simulation results further indicate that the leaving efficiency becomes low as breakdown occurs, and the degree of congestion is proportional to the magnitude of inflow. The findings presented in this paper match well with some of our daily observations, hence it is possible to use them to provide us with theoretical suggestions in design of infrastructures.展开更多
In this paper, analysis, design and implementation of non-isolated soft-switching bidirectional DC-DC converter with an active switch are described. The proposed topology gives the output voltage as twice as the input...In this paper, analysis, design and implementation of non-isolated soft-switching bidirectional DC-DC converter with an active switch are described. The proposed topology gives the output voltage as twice as the input voltage and enhances the efficiency up to 94.5% and 92.9% for boost and buck mode operation by proper selection of the duty cycle. Soft switching can be achieved at both steps up and step down operating modes. Small signal analysis based on state space averaging and transfer functions have been presented in detail for the proposed converter. Finally, the feasibility of the desired converter is confirmed to mat lab simulation and investigational results.展开更多
The counter-rotating type tidal range power unit composed of the axial flow type tandem runners and the peculiar generator with double rotational armatures is proposed to utilize effectively the tidal range. In the un...The counter-rotating type tidal range power unit composed of the axial flow type tandem runners and the peculiar generator with double rotational armatures is proposed to utilize effectively the tidal range. In the unit, the front and the rear runners counter-drive the inner and the outer armatures of the generator, respectively. Besides, the flow runs in the axial direction at the rear runner outlet while the flow has not the swirling component at the front runner inlet, because the angular momentum change through the rear runner must coincides with that through the front runner. Such operations are suitable for bidirectional flows, namely working at the seashore with the rising and the falling tidal ranges, and the unit may be able to take place of the traditional bulb type turbines. To promote more the tidal power generation by this type unit, the runners were modified so as to be suitable for both rising and falling flows. The hydraulic performances are acceptable and take the optimum efficiency at the on-cam operation, while the trailing profiles of the runner blades determine mainly the theoretical output.展开更多
A 59-year-old male with alcoholic cirrhosis presented to our hospital with an acutely painful umbilical hernia,and 4 mo of exertional dyspnea.He was noted to be tachypneic and hypoxic.He had a massive right sided pleu...A 59-year-old male with alcoholic cirrhosis presented to our hospital with an acutely painful umbilical hernia,and 4 mo of exertional dyspnea.He was noted to be tachypneic and hypoxic.He had a massive right sided pleural effusion with leftward mediastinal shift and gross ascites,with a tense,fluid-filled,umbilical hernia.Emergent paracentesis with drain placement and a large volume thoracentesis were performed.Despite improvement in dyspnea and drainage of 15 L of ascitic fluid,the massive transudative pleural effusion remained largely unchanged.He underwent a repeat large volume thoracentesis on hospital day 4.The patient subsequently developed a tension pneumothorax,which resulted in a dramatic reduction in the effusion.A chest tube was placed and serial radiographs demonstrated resolution of the pneumothorax but recurrence of the effusion.The radiographs illustrate the movement of fluid between the peritoneal and pleural cavities.In this case,the mechanism of pleural effusion was confirmed to be a hepatic hydrothorax via an unintended tension pneumothorax.Methods to elucidate a hepatic hydrothorax include Tc99m or indocyanine green injection into the ascitic fluid followed by its demonstration above the diaphragm.The unintended tension pneumothorax in this case additionally demonstrates bi-directional flow across the diaphragm.展开更多
An extended social force model with a dynamic navigation field is proposed to study bidirectional pedestrian movement. The dynamic navigation field is introduced to describe the desired direction of pedestrian motion ...An extended social force model with a dynamic navigation field is proposed to study bidirectional pedestrian movement. The dynamic navigation field is introduced to describe the desired direction of pedestrian motion resulting from the decision-making processes of pedestrians. The macroscopic fundamental diagrams obtained using the extended model are validated against camera-based observations. Numerical results show that this extended model can reproduce collective phenomena in pedestrian traffic, such as dynamic multilane flow and stable separate-lane flow. Pedestrians＇ path choice behavior significantly affects the probability of congestion and the number of self-organized lanes.展开更多
Subway fires often cause significant casualties and property losses.There are some special bidirectional coupling scenarios during subway fires,such as firefighters moving against the evacuation flow to extinguish fir...Subway fires often cause significant casualties and property losses.There are some special bidirectional coupling scenarios during subway fires,such as firefighters moving against the evacuation flow to extinguish fires,emergency managers going to the fire scene to respond to emergencies,or other similar scenarios.How to evacuate passengers quickly and enable responders to enter the fire scene has become a big challenge for subway fire evacuation and response.The core goal is to reduce the degree of mutual interaction between these people moving in opposite directions.In this study,the impact of counterflow individuals and proactive avoidance behavior on evacuation processes was investigated through experiments and simulations.The Fire Dynamic Simulator was used to simulate the development of a fire scenario to determine the available safe egress time.Micro-evacuation experiments were conducted to obtain actual evacuation parameters,such as the speeds of different objects.With these parameters as input,a macro subway fire scenario was built to simulate the bidirectional evacuation process.Consistent conclusions were obtained from the experiments and evacuation simulations.The results indicate that the overall evacuation time increases with the number of retrograders.Proactive avoidance behavior can effectively reduce the travel time of counterflow individuals,but it causes slight delays for forward-moving evacuees.An optimization strategy was implemented through conductor guidance.All passengers can successfully evacuate under the optimization strategy,with a 25.3%improvement in overall evacuation time.This research provides some insights into the coordinated evacuation and emergency response during subway fires or similar scenarios.展开更多
基金Supported by the National Natural Science Foundation of China(No.60472033)the Key Laboratory Project of Information Science & Engineering of Railway of National Ministry of Railways, China (No.tdxx0510)the Technological Innovation Fund of Excellent Doctorial Candidate of Beijing Jiaotong University,China(No.48007)
文摘Most image interpolation algorithms currently used suffer visually to some extent the effects of blurred edges and jagged artifacts in the image. This letter presents an adaptive feature preserving bidirectional flow process, where an inverse diffusion is performed to enhance edges along the normal directions to the iso-phote lines (edges), while a normal diffusion is done to remove artifacts ('jaggies') along the tangent directions. In order to preserve image features such as edges, angles and textures, the nonlinear diffusion coefficients are locally adjusted according to the first order and the second order directional derivatives of the image. Experimental results on the Lena image demonstrate that our interpolation algorithm substantially improves the subjective quality of the interpolated images over conventional interpolations.
基金Project supported jointly by the National Natural Science Foundation of China(Grant No.61233001)the Fundamental Research Funds for Central Universities of China(Grant No.2013JBZ007)
文摘Analysis of dynamic features of pedestrian flows is one of the most exciting topics in pedestrian dynamics. This paper focuses on the effect of homogeneity and heterogeneity in three parameters of the social force model, namely desired velocity, reaction time, and body size, on the moving dynamics of bidirectional pedestrian flows in the corridors. The speed and its deviation in free flows are investigated. Simulation results show that the homogeneous higher desired speed which is less than a critical threshold, shorter reaction time or smaller body size results in higher speed of flows. The free dynamics is more sensitive to the heterogeneity in desired speed than that in reaction time or in body size. In particular, an inner lane formation is observed in normal lanes. Furthermore, the breakdown probability and the start time of breakdown are focused on. This study reveals that the sizes of homogeneous desired speed, reaction time or body size play more important roles in affecting the breakdown than the heterogeneities in these three parameters do.
基金Project supported by the National Natural Science Foundation of China(Grant No.11072117)the Scientific Research Fund of Zhejiang Province,China(Grant No.LY13A010005)+4 种基金the Disciplinary Project of Ningbo City,China(Grant No.SZXL1067)the Scientific Research Fund of Education Department of Zhejiang Province,China(Grant No.Z201119278)the Natural Science Foundation of Ningbo City,China(Grant Nos.2012A610152 and 2012A610038)the K.C.Wong Magna Fund in Ningbo University,Chinathe Research Grant Council,Government of the Hong Kong Administrative Region,China(Grant No.CityU119011)
文摘This paper focuses on a two-dimensional bidirectional pedestrian flow model which involves the next-nearest-neighbor effect. The stability condition and the Korteweg-de Vries （KdV） equation are derived to describe the density wave of pedestrian congestion by linear stability and nonlinear analysis. Through theoretical analysis, the soliton solution is obtained.
基金supported by the Deanship of Scientific Research,Vice Presidency for Graduate Studies and Scientific Research,King Faisal University,Saudi Arabia(Grant No.252032).
文摘Non-Newtonian flows have applications in food combination,plasma flow,inherent and organic fluids,antibiotics,and lubrication through oils and greases.This study explores the bidirectional flow of Williamson nanofluid in a porous medium,incorporating thermophoresis,Brownian motion,bioconvection effects,and Arrhenius activation energy over a nonlinear stretching surface.The governing equations are transformed into a dimension-less form using similarity transformations and numerically solved via MATLAB’s bvp4c shooting scheme.Results indicate that increasing the Williamson parameterλand porosity parameterεreduces velocity,with a 10%rise inλleading to an 8%velocity reduction.Tem-perature increases with the thermophoresis parameter(Nt)where a 15%increase in Nt results in a 7%temperature rise.The Nusselt number improves with a higher Prandtl number Pr increasing by 10%when Pr rises from 5 to 7,while the Sherwood number declines with stron-ger Brownian motion.These findings provide key insights into heat and mass transfer Recent advances in modified Arrhenius activation energy and bioconvection mechanisms,contributing to advancements in industrial cooling,biomedical applications,and nanofluid-based thermal systems.
文摘Flow-based measurement is a popular method for various network monitoring usages.However, many flow exporting softwares have still low performance to collect all flows.In this paper, we propose a IPFIX-based flow export engine with an enhanced and extensible data structure, called XFix, on the basis of a GPL tool,-nProbe.In the engine, we use an extensible two-dimensional hash table for flow aggregation, which is able to improve the performance of the metering process as well as support bidirectional flow.Experimental results have shown its efficiency in multi-thread processing activity.
基金Project supported jointly by the National Natural Science Foundation of China(Grant Nos.61322307 and 2016YJS023)
文摘The bottleneck effect on bidirectional crowd dynamics is of great theoretical and practical significance, especially for the designing of corridors in public places, such as subway stations or airports. Based on the famous social force model, this paper investigates the bottleneck effects on the free flow dynamics and breakdown phenomenon under different scenarios, in which different corridor shapes and inflow ratios are considered simultaneously. Numerical simulation finds an interesting self-organization phenomenon in the bidirectional flow, a typical characteristic of such a phenomenon is called lane formation, and the existence of which is independent of the corridor＇s shape and inflow rate. However, the pattern of the lane formed by pedestrian flow is related to the corridor＇s shape, and the free flow efficiency has close relationship with the inflow rate. Specifically, breakdown phenomenon occurs when inflows from both sides of the corridor are large enough, which mostly originates from the bottleneck and then gradually spreads to the other regions. Simulation results further indicate that the leaving efficiency becomes low as breakdown occurs, and the degree of congestion is proportional to the magnitude of inflow. The findings presented in this paper match well with some of our daily observations, hence it is possible to use them to provide us with theoretical suggestions in design of infrastructures.
文摘In this paper, analysis, design and implementation of non-isolated soft-switching bidirectional DC-DC converter with an active switch are described. The proposed topology gives the output voltage as twice as the input voltage and enhances the efficiency up to 94.5% and 92.9% for boost and buck mode operation by proper selection of the duty cycle. Soft switching can be achieved at both steps up and step down operating modes. Small signal analysis based on state space averaging and transfer functions have been presented in detail for the proposed converter. Finally, the feasibility of the desired converter is confirmed to mat lab simulation and investigational results.
文摘The counter-rotating type tidal range power unit composed of the axial flow type tandem runners and the peculiar generator with double rotational armatures is proposed to utilize effectively the tidal range. In the unit, the front and the rear runners counter-drive the inner and the outer armatures of the generator, respectively. Besides, the flow runs in the axial direction at the rear runner outlet while the flow has not the swirling component at the front runner inlet, because the angular momentum change through the rear runner must coincides with that through the front runner. Such operations are suitable for bidirectional flows, namely working at the seashore with the rising and the falling tidal ranges, and the unit may be able to take place of the traditional bulb type turbines. To promote more the tidal power generation by this type unit, the runners were modified so as to be suitable for both rising and falling flows. The hydraulic performances are acceptable and take the optimum efficiency at the on-cam operation, while the trailing profiles of the runner blades determine mainly the theoretical output.
文摘A 59-year-old male with alcoholic cirrhosis presented to our hospital with an acutely painful umbilical hernia,and 4 mo of exertional dyspnea.He was noted to be tachypneic and hypoxic.He had a massive right sided pleural effusion with leftward mediastinal shift and gross ascites,with a tense,fluid-filled,umbilical hernia.Emergent paracentesis with drain placement and a large volume thoracentesis were performed.Despite improvement in dyspnea and drainage of 15 L of ascitic fluid,the massive transudative pleural effusion remained largely unchanged.He underwent a repeat large volume thoracentesis on hospital day 4.The patient subsequently developed a tension pneumothorax,which resulted in a dramatic reduction in the effusion.A chest tube was placed and serial radiographs demonstrated resolution of the pneumothorax but recurrence of the effusion.The radiographs illustrate the movement of fluid between the peritoneal and pleural cavities.In this case,the mechanism of pleural effusion was confirmed to be a hepatic hydrothorax via an unintended tension pneumothorax.Methods to elucidate a hepatic hydrothorax include Tc99m or indocyanine green injection into the ascitic fluid followed by its demonstration above the diaphragm.The unintended tension pneumothorax in this case additionally demonstrates bi-directional flow across the diaphragm.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant Nos. 11202175, 11275186, 91024026, and FOM2014OF001）, the Research Foundation of Southwest University of Science and Technology （No. 10zx7137）, and a Singapore Ministry of Education Research Grant （Grant No. MOE 2013-T2-2-033）.
文摘An extended social force model with a dynamic navigation field is proposed to study bidirectional pedestrian movement. The dynamic navigation field is introduced to describe the desired direction of pedestrian motion resulting from the decision-making processes of pedestrians. The macroscopic fundamental diagrams obtained using the extended model are validated against camera-based observations. Numerical results show that this extended model can reproduce collective phenomena in pedestrian traffic, such as dynamic multilane flow and stable separate-lane flow. Pedestrians＇ path choice behavior significantly affects the probability of congestion and the number of self-organized lanes.
基金supported by the Beijing Municipal Natural Science Foundation(Grant No.8242014)National Natural Science Foundation of China(Grant Nos.72274123,72004113,72174099,72104123)+2 种基金Henan International Joint Laboratory of Man Machine Environment and Emergency Management,Anyang Institute of Technology(KFKT-001)Key R&D special projects in Henan(221111321000),Interdisciplinary project of University of Science and Technology Beijing(FRF-IDRY-22-017)Science and Technology Commission of Shanghai Municipality(Grant No.24692104600)。
文摘Subway fires often cause significant casualties and property losses.There are some special bidirectional coupling scenarios during subway fires,such as firefighters moving against the evacuation flow to extinguish fires,emergency managers going to the fire scene to respond to emergencies,or other similar scenarios.How to evacuate passengers quickly and enable responders to enter the fire scene has become a big challenge for subway fire evacuation and response.The core goal is to reduce the degree of mutual interaction between these people moving in opposite directions.In this study,the impact of counterflow individuals and proactive avoidance behavior on evacuation processes was investigated through experiments and simulations.The Fire Dynamic Simulator was used to simulate the development of a fire scenario to determine the available safe egress time.Micro-evacuation experiments were conducted to obtain actual evacuation parameters,such as the speeds of different objects.With these parameters as input,a macro subway fire scenario was built to simulate the bidirectional evacuation process.Consistent conclusions were obtained from the experiments and evacuation simulations.The results indicate that the overall evacuation time increases with the number of retrograders.Proactive avoidance behavior can effectively reduce the travel time of counterflow individuals,but it causes slight delays for forward-moving evacuees.An optimization strategy was implemented through conductor guidance.All passengers can successfully evacuate under the optimization strategy,with a 25.3%improvement in overall evacuation time.This research provides some insights into the coordinated evacuation and emergency response during subway fires or similar scenarios.
