本文分析了并行Costas信号脉压方法,设计了基于"通用图形处理单元(GPGPU)"的处理模型,并基于"铺路爪"雷达参数实现了Costas信号的方案。该方案在8片Nvidia tesla C1060的异构系统上对5418个通道脉压处理耗时514.3ms...本文分析了并行Costas信号脉压方法,设计了基于"通用图形处理单元(GPGPU)"的处理模型,并基于"铺路爪"雷达参数实现了Costas信号的方案。该方案在8片Nvidia tesla C1060的异构系统上对5418个通道脉压处理耗时514.3ms,比通用CPU处理系统速度提升574倍。研究结果对新一代异构高性能雷达信号处理系统的设计具有很好的参考意义。展开更多
To control the electron beam emitted from the carbon nanotube (CNT) cathode, four different electron chunnels are designed. A common basic structure used in the simulation is an insulating chunnel. When primary elec...To control the electron beam emitted from the carbon nanotube (CNT) cathode, four different electron chunnels are designed. A common basic structure used in the simulation is an insulating chunnel. When primary electrons hit the surface of the chunnel, secondary electrons are generated, which make the electron distribution at the exit hole of the chunnel more uniform. By analyzing and comparing the state of electrons emitted from the exit of chunnel among the four structures, an optimal structure is obtained. In the optimized structure, the electron distribution at the exit hole of the chunnel is more uniform and the electron beam is rather slim. Furthermore, by adding a magnetic field along the slow wave line, the electron beam can be constrained. In the optimized structure, a very small magnetic field is needed to make most of electrons pass through the slow wave line.展开更多
The non-stationary behavior, caused by the train rmverrent, is the rmin factor for the variation of high speed railway channel. To measure the tirce-variant effect, the parameter of stationarity interval, in which the...The non-stationary behavior, caused by the train rmverrent, is the rmin factor for the variation of high speed railway channel. To measure the tirce-variant effect, the parameter of stationarity interval, in which the channel keeps constant or has no great change, is adopted based on Zhengzfiou- Xi'an (Zhengxi) passenger dedicated line measurement with different train speeds. The stationarity interval is calculated through the definition of Local Region of Stationarity (LRS) under three train ve- locities. Furthermore, the time non-stationary characteristic of high speed pared with five standard railway channel is corn- Multiple-Input MultipleOutput (MIMO) channel models, i.e. Spatial Channel Model (SCM), extended version of SCM (SCME), Wireless World Initiative New Radio Phase II (WINNERII), International Mobile Teleconmnications-Advanced (IMT-Advanced) and WiMAX models which contain the high speed moving scenario. The stationarity interval of real channel is 9 ms in 80% of the cases, which is shorter than those of the standard models. Hence the real channel of high speed railway changes more rapidly. The stationarity intervals of standard models are different due to different modeling methods and scenario def- initions. And the compared results are instructive for wireless system design in high speed railway.展开更多
The characteristics of a new type of drainage channel with staggered indented sills for controlling debris flows were studied. The intermediate fluid in the non-viscous debris flow exhibited a helical movement, wherea...The characteristics of a new type of drainage channel with staggered indented sills for controlling debris flows were studied. The intermediate fluid in the non-viscous debris flow exhibited a helical movement, whereas the fluid near the sidewall had a stop-start movement pattern; the viscous debris flow exhibited a stable structure between the indented sills. The experimental results indicate that the mean velocity of the debris flow increased with increasing channel gradients, and the debris flow velocity was slightly affected by the angle of the sills. The average velocity of the non-viscous debris flow increased in the range of(0.5–1.5) interval between the indented sills, whereas the average velocity of the viscous debris flow increased initially and then decreased in the range of(0.75–1.25) interval between the indented sills. The depth of the non-viscous debris flow tended to gradually increase as the channel gradients increased, whereas the depth of the viscous debris flow gradually decreased as the channel gradients increased. When the discharge of the debris flow was constant, the angle and the interval between the indented sills had a slight effect on the depth of the viscous debris flow, whereas the depth of the non-viscous debris flow exhibited a different trend, as the sill angles and intervals were varied.展开更多
A SN (structural number) can be calculated for a road pavement from the properties and thicknesses of the surface, basecourse, sub-base and subgrade. Historically, the cost of collecting structural data has been ver...A SN (structural number) can be calculated for a road pavement from the properties and thicknesses of the surface, basecourse, sub-base and subgrade. Historically, the cost of collecting structural data has been very high. Data was initially collected using Benkelman Beams and now by FWD (falling weight deflectometer). The structural strength of pavements weakens over time due to environmental and traffic loading factors but due to a lack of data, no structural deterioration curve for pavements has been implemented in a PMS (pavement management system). IRI (international roughness index) is a measure of the road longitudinal profile and has been used as a proxy for a pavement’s structural integrity. This paper offers two conceptual methods to develop PSDC (pavement structural deterioration curves). Firstly, structural data are grouped in sets by design ESA (equivalent standard axles). An ISN (“initial” SN), SNI (intermediate SN) and a TSN (terminal SN), are used to develop the curves. Using FWD data, the ISN is the SN after the pavement is rehabilitated (Financial Accounting “Modern Equivalent”). Intermediate SNIs, are SNs other than the ISN and TSN. The TSN was defined as the SN of the pavement when it was approved for pavement rehabilitation. The second method is to use TSD (traffic speed deflectometer) data. The road network already divided into road blocks, is grouped by traffic loading. For each traffic loading group, road blocks that have had a recent pavement rehabilitation, are used to calculate the ISN and those planned for pavement rehabilitation to calculate the TSN. The remaining SNs are used to complete the age-based or if available, historical traffic loading-based SNIs.展开更多
As two kinds of management modes of highway tramc control, lane-control, and speed-control produce different effect under different conditions. In this paper, traffic flow cellular automaton models for four-lane highw...As two kinds of management modes of highway tramc control, lane-control, and speed-control produce different effect under different conditions. In this paper, traffic flow cellular automaton models for four-lane highway system with two opposing directions under the above two modes are established considering car and truck mixed running. Through computer numerical simulating, the fundamental diagrams with different parameters are obtained, and after the analysis of density-flux diagrams, the variation discipline of flux with traffic density under different control models is gained. The results indicate that, compared with lane-control, utilization ratio of road can be further improved with speed-control when the truck number increases. The research result is of great significance for reasonable providing theoretical guidance for highway traffic control.展开更多
This paper reports a study concerning occurrence and growth of traffic jam in a harbor tunnel. The single-lane with three sections (downgrade, fiat, and upgrade) is taken into account and they are characterized with...This paper reports a study concerning occurrence and growth of traffic jam in a harbor tunnel. The single-lane with three sections (downgrade, fiat, and upgrade) is taken into account and they are characterized with different velocity limit. At the low density, the traffic current increases linearly with density and saturates at some values of immediately density. As the density increases, the traffic jam appears firstly before the upgrade section and then extends to the downgrade section. Additionally, the relationships of the velocity and headway against position in different densities are obta/ned from simulation. These results clearly clarify where and when the traffic jam appears. Finally, the critical densities are derived via the theoretical analysis before and after the discontinuous fronts and the theoretical results are consistent with the critical values of simulation results.展开更多
The lateral distributions of depth-averaged velocity in open compound channels with emerged and submerged vegetated floodplains were analyzed based on the analytical solution of the depth-integrated Reynolds-Averaged ...The lateral distributions of depth-averaged velocity in open compound channels with emerged and submerged vegetated floodplains were analyzed based on the analytical solution of the depth-integrated Reynolds-Averaged Navier-Stokes equation with a term to account for the effects of vegetation.The three cases considered for open channels were two-stage rectangular channel with emerged vegetated floodplain,rectangular channel with submerged vegetated corner,and two-stage rectangular channel with submerged vegetated floodplain,respectively.To predict the depth-averaged velocity with submerged vegetated floodplains,we proposed a new method based on a two-layer approach where flow above and through the vegetation layer was described separately.Moreover,further experiments in the two-stage rectangular channel with submerged vegetated floodplain were carried out to verify the results.The analytical solutions of the cases indicated that the corresponding analytical depth-averaged velocity distributions agree well with the simulated and experimental prediction.The analytical solutions of the cases with theoretical foundation and without programming calculation were reasonable and applicable,which were more convenient than numerical simulations.The analytical solutions provided a way for future researches to solve the problems of submerged vegetation and discontinuous phenomenon of depth-averaged velocity at the stage point for compound channels.Understanding the hydraulics of flow in compound channels with vegetated floodplains is very important for supporting the management of fluvial processes.展开更多
This study focused on differences in vehicle-to-vehicle radio channel character- istics in the same region but different traffic density and speeds at 5.9 GHz (congestion and non-congestion). The continuous measurem...This study focused on differences in vehicle-to-vehicle radio channel character- istics in the same region but different traffic density and speeds at 5.9 GHz (congestion and non-congestion). The continuous measurement campaign was conducted on a city expressway through the complex dense urban area in Wu- hart, China. Small-scale channel characteris- tics including power delay profile, amplitude fading distribution, K-factor, delay spread and Doppler shift were obtained, respectively. Spe- cifically, the cumulative distribution function of root mean square delay spreads and root mean square Doppler spreads in the non-con- gested scenario and congested scenario were all fitted well with Lognormal distribution. We also found out that different intensity of traffic and speed of vehicles have little effect on root mean square delay spreads, but have a big im- pact on root mean square Doppler spreads and level crossing rate. According to estimation outcomes, the V2V channel characteristics for urban areas in Chinese big city were differ- ent from the previous measured results under similar scenarios in Europe. Delay spread and level crossing rate in this study can provide significant references to design the wireless communication system for vehicle-to-vehicle channel.展开更多
An experimental platform is constructed to photograph fibers' motion within rotor spinning unit, which is mainly composed of a transparent rotor and a transport channel based on the similarity theory. The fibers will...An experimental platform is constructed to photograph fibers' motion within rotor spinning unit, which is mainly composed of a transparent rotor and a transport channel based on the similarity theory. The fibers will stretch and gather into a fiber bundle in the transport channel. The velocity of fibers is increasing along the inlet to the outlet of the transport channel, and the fibers' maximum velocity appears at the outlet of transport channel. The straightness of the fiber bundle is related to the convergence degree of the transport channel, and the greater the convergence degree is, the straighter the fiber bundle stretches. The results will provide a useful insight to the yam-forming mechanism of rotor spinning.展开更多
In this article, a computational model and related methodologies have been tested for simulating the motion of a malaria infected red blood cell (iRBC for short) in Poiseuille flow at low Reynolds numbers. Besides t...In this article, a computational model and related methodologies have been tested for simulating the motion of a malaria infected red blood cell (iRBC for short) in Poiseuille flow at low Reynolds numbers. Besides the deformability of the red blood cell membrane, the migration of a neutrally buoyant particle (used to model the malaria parasite inside the membrane) is another factor to determine the iRBC motion. Typically an iRBC oscillates in a Poiseuille flow due to the competition between these two factors. The interaction of an iRBC and several RBCs in a narrow channel shows that, at lower flow speed, the iRBC can be easily pushed toward the wall and stay there to block the channel. But, at higher flow speed, RBCs and iRBC stay in the central region of the channel since their migrations axe dominated by the motion of the RBC membrane.展开更多
Present study examines the mixed convective peristaltic transport of Cu-H2O nanofluid with velocity slip and convective boundary conditions. Analysis is performed using the two-phase model of the nanofluid. Viscous di...Present study examines the mixed convective peristaltic transport of Cu-H2O nanofluid with velocity slip and convective boundary conditions. Analysis is performed using the two-phase model of the nanofluid. Viscous dissipation and heat generation/absorption effects are also taken into account. Problem is formulated using the long wavelength and low Reynolds number approach. Numerical solutions for the pressure rise per wavelength, pressure gradient, axial velocity, temperature and heat transfer rate at the boundaxy are obtained and studied through graphs. Results show that the area of peristaltic pumping decreases with an increase in the nanoparticles volume fraction. Increase in the velocity slip parameter shows an increase of the pressure gradient in the occluded part of the channel. Further, addition of copper nanoparticles reduces both the axial velocity and temperature of the base fluid. Temperature of the nanofluid also decreases sufficiently for an increase in the value of Blot number.展开更多
文摘本文分析了并行Costas信号脉压方法,设计了基于"通用图形处理单元(GPGPU)"的处理模型,并基于"铺路爪"雷达参数实现了Costas信号的方案。该方案在8片Nvidia tesla C1060的异构系统上对5418个通道脉压处理耗时514.3ms,比通用CPU处理系统速度提升574倍。研究结果对新一代异构高性能雷达信号处理系统的设计具有很好的参考意义。
文摘To control the electron beam emitted from the carbon nanotube (CNT) cathode, four different electron chunnels are designed. A common basic structure used in the simulation is an insulating chunnel. When primary electrons hit the surface of the chunnel, secondary electrons are generated, which make the electron distribution at the exit hole of the chunnel more uniform. By analyzing and comparing the state of electrons emitted from the exit of chunnel among the four structures, an optimal structure is obtained. In the optimized structure, the electron distribution at the exit hole of the chunnel is more uniform and the electron beam is rather slim. Furthermore, by adding a magnetic field along the slow wave line, the electron beam can be constrained. In the optimized structure, a very small magnetic field is needed to make most of electrons pass through the slow wave line.
基金Acknowledgements This work was supported partially by the Beijing Natural Science Foundation under Crant No. 4112048 the Program for New Century Excellent Talents in University under Gant No. NCET-09-0206+4 种基金 the National Natural Science Foundation of China under Crant No. 60830001 the Key Project of State Key Laboratory of Rail Traffic Control and Safety under Crants No. RCS2008ZZ006, No. RCS2011ZZ008 the Program for Changjiang Scholars and Innovative Research Team in University under Crant No. IRT0949 the Project of State Key kab. of Rail Traffic Control and Safety under C~ants No. RCS2008ZT005, No. RCS2010ZT012 the Fundamental Research Funds for the Central Universities under Crants No. 2010JBZ(~8, No. 2011YJS010.
文摘The non-stationary behavior, caused by the train rmverrent, is the rmin factor for the variation of high speed railway channel. To measure the tirce-variant effect, the parameter of stationarity interval, in which the channel keeps constant or has no great change, is adopted based on Zhengzfiou- Xi'an (Zhengxi) passenger dedicated line measurement with different train speeds. The stationarity interval is calculated through the definition of Local Region of Stationarity (LRS) under three train ve- locities. Furthermore, the time non-stationary characteristic of high speed pared with five standard railway channel is corn- Multiple-Input MultipleOutput (MIMO) channel models, i.e. Spatial Channel Model (SCM), extended version of SCM (SCME), Wireless World Initiative New Radio Phase II (WINNERII), International Mobile Teleconmnications-Advanced (IMT-Advanced) and WiMAX models which contain the high speed moving scenario. The stationarity interval of real channel is 9 ms in 80% of the cases, which is shorter than those of the standard models. Hence the real channel of high speed railway changes more rapidly. The stationarity intervals of standard models are different due to different modeling methods and scenario def- initions. And the compared results are instructive for wireless system design in high speed railway.
基金sponsored by the Key Deployment Project of Chinese Academy of Sciences(Grant No.KZZD-EW-05-01)the National Science Foundation of China(Grant No.41072270)
文摘The characteristics of a new type of drainage channel with staggered indented sills for controlling debris flows were studied. The intermediate fluid in the non-viscous debris flow exhibited a helical movement, whereas the fluid near the sidewall had a stop-start movement pattern; the viscous debris flow exhibited a stable structure between the indented sills. The experimental results indicate that the mean velocity of the debris flow increased with increasing channel gradients, and the debris flow velocity was slightly affected by the angle of the sills. The average velocity of the non-viscous debris flow increased in the range of(0.5–1.5) interval between the indented sills, whereas the average velocity of the viscous debris flow increased initially and then decreased in the range of(0.75–1.25) interval between the indented sills. The depth of the non-viscous debris flow tended to gradually increase as the channel gradients increased, whereas the depth of the viscous debris flow gradually decreased as the channel gradients increased. When the discharge of the debris flow was constant, the angle and the interval between the indented sills had a slight effect on the depth of the viscous debris flow, whereas the depth of the non-viscous debris flow exhibited a different trend, as the sill angles and intervals were varied.
文摘A SN (structural number) can be calculated for a road pavement from the properties and thicknesses of the surface, basecourse, sub-base and subgrade. Historically, the cost of collecting structural data has been very high. Data was initially collected using Benkelman Beams and now by FWD (falling weight deflectometer). The structural strength of pavements weakens over time due to environmental and traffic loading factors but due to a lack of data, no structural deterioration curve for pavements has been implemented in a PMS (pavement management system). IRI (international roughness index) is a measure of the road longitudinal profile and has been used as a proxy for a pavement’s structural integrity. This paper offers two conceptual methods to develop PSDC (pavement structural deterioration curves). Firstly, structural data are grouped in sets by design ESA (equivalent standard axles). An ISN (“initial” SN), SNI (intermediate SN) and a TSN (terminal SN), are used to develop the curves. Using FWD data, the ISN is the SN after the pavement is rehabilitated (Financial Accounting “Modern Equivalent”). Intermediate SNIs, are SNs other than the ISN and TSN. The TSN was defined as the SN of the pavement when it was approved for pavement rehabilitation. The second method is to use TSD (traffic speed deflectometer) data. The road network already divided into road blocks, is grouped by traffic loading. For each traffic loading group, road blocks that have had a recent pavement rehabilitation, are used to calculate the ISN and those planned for pavement rehabilitation to calculate the TSN. The remaining SNs are used to complete the age-based or if available, historical traffic loading-based SNIs.
文摘As two kinds of management modes of highway tramc control, lane-control, and speed-control produce different effect under different conditions. In this paper, traffic flow cellular automaton models for four-lane highway system with two opposing directions under the above two modes are established considering car and truck mixed running. Through computer numerical simulating, the fundamental diagrams with different parameters are obtained, and after the analysis of density-flux diagrams, the variation discipline of flux with traffic density under different control models is gained. The results indicate that, compared with lane-control, utilization ratio of road can be further improved with speed-control when the truck number increases. The research result is of great significance for reasonable providing theoretical guidance for highway traffic control.
基金Supported by Research Grants from City University of Hong Kong,HKSAR under Grant No.CityU-SRG 7002684Science&Technology Program of Shanghai Maritime University under Grant No.20110046+1 种基金Shanghai Municipal Natural Science Foundation under Grant No.10190502500National Natural Science Foundation of China under Grant Nos.11172164,71101088 and 71171129
文摘This paper reports a study concerning occurrence and growth of traffic jam in a harbor tunnel. The single-lane with three sections (downgrade, fiat, and upgrade) is taken into account and they are characterized with different velocity limit. At the low density, the traffic current increases linearly with density and saturates at some values of immediately density. As the density increases, the traffic jam appears firstly before the upgrade section and then extends to the downgrade section. Additionally, the relationships of the velocity and headway against position in different densities are obta/ned from simulation. These results clearly clarify where and when the traffic jam appears. Finally, the critical densities are derived via the theoretical analysis before and after the discontinuous fronts and the theoretical results are consistent with the critical values of simulation results.
基金Under the auspices of National Basic Research Program of China(No.2011CB403303)National Key Research and Development Program of China(No.2016YFC0402408-5)National Natural Science Foundation of China(No.51179181,40788001)
文摘The lateral distributions of depth-averaged velocity in open compound channels with emerged and submerged vegetated floodplains were analyzed based on the analytical solution of the depth-integrated Reynolds-Averaged Navier-Stokes equation with a term to account for the effects of vegetation.The three cases considered for open channels were two-stage rectangular channel with emerged vegetated floodplain,rectangular channel with submerged vegetated corner,and two-stage rectangular channel with submerged vegetated floodplain,respectively.To predict the depth-averaged velocity with submerged vegetated floodplains,we proposed a new method based on a two-layer approach where flow above and through the vegetation layer was described separately.Moreover,further experiments in the two-stage rectangular channel with submerged vegetated floodplain were carried out to verify the results.The analytical solutions of the cases indicated that the corresponding analytical depth-averaged velocity distributions agree well with the simulated and experimental prediction.The analytical solutions of the cases with theoretical foundation and without programming calculation were reasonable and applicable,which were more convenient than numerical simulations.The analytical solutions provided a way for future researches to solve the problems of submerged vegetation and discontinuous phenomenon of depth-averaged velocity at the stage point for compound channels.Understanding the hydraulics of flow in compound channels with vegetated floodplains is very important for supporting the management of fluvial processes.
基金supported by Norwegian Research Council(No.256309)supported by an International Cooperation Project:5G-Channel Measurement and Channel Modeling for Ocean Scenario(No.20172h0046)+3 种基金Hubei college excellent young science and technology innovation team project:Fast Varying Channel Modeling and Analysis(No.T201736)Young Scientists Found of National Natural Science Foundation of China(No.61701356)Fundamental Research Funds for the Central Universities(No.2017-JL-004)(China Scholarship Council) CSC agency for funding and the Super Radio AS
文摘This study focused on differences in vehicle-to-vehicle radio channel character- istics in the same region but different traffic density and speeds at 5.9 GHz (congestion and non-congestion). The continuous measurement campaign was conducted on a city expressway through the complex dense urban area in Wu- hart, China. Small-scale channel characteris- tics including power delay profile, amplitude fading distribution, K-factor, delay spread and Doppler shift were obtained, respectively. Spe- cifically, the cumulative distribution function of root mean square delay spreads and root mean square Doppler spreads in the non-con- gested scenario and congested scenario were all fitted well with Lognormal distribution. We also found out that different intensity of traffic and speed of vehicles have little effect on root mean square delay spreads, but have a big im- pact on root mean square Doppler spreads and level crossing rate. According to estimation outcomes, the V2V channel characteristics for urban areas in Chinese big city were differ- ent from the previous measured results under similar scenarios in Europe. Delay spread and level crossing rate in this study can provide significant references to design the wireless communication system for vehicle-to-vehicle channel.
基金supported by National Natural Science Foundation of China under Grant No.51576180Zhejiang Provincial Natural Science Foundation under Grant No.LZ14E050004Project of 521 Talents Cultivation in Zhejiang Sci-Tech University
文摘An experimental platform is constructed to photograph fibers' motion within rotor spinning unit, which is mainly composed of a transparent rotor and a transport channel based on the similarity theory. The fibers will stretch and gather into a fiber bundle in the transport channel. The velocity of fibers is increasing along the inlet to the outlet of the transport channel, and the fibers' maximum velocity appears at the outlet of transport channel. The straightness of the fiber bundle is related to the convergence degree of the transport channel, and the greater the convergence degree is, the straighter the fiber bundle stretches. The results will provide a useful insight to the yam-forming mechanism of rotor spinning.
基金supported by the National Science Foundation of the United States(Nos.DMS-0914788,DMS-1418308)
文摘In this article, a computational model and related methodologies have been tested for simulating the motion of a malaria infected red blood cell (iRBC for short) in Poiseuille flow at low Reynolds numbers. Besides the deformability of the red blood cell membrane, the migration of a neutrally buoyant particle (used to model the malaria parasite inside the membrane) is another factor to determine the iRBC motion. Typically an iRBC oscillates in a Poiseuille flow due to the competition between these two factors. The interaction of an iRBC and several RBCs in a narrow channel shows that, at lower flow speed, the iRBC can be easily pushed toward the wall and stay there to block the channel. But, at higher flow speed, RBCs and iRBC stay in the central region of the channel since their migrations axe dominated by the motion of the RBC membrane.
文摘Present study examines the mixed convective peristaltic transport of Cu-H2O nanofluid with velocity slip and convective boundary conditions. Analysis is performed using the two-phase model of the nanofluid. Viscous dissipation and heat generation/absorption effects are also taken into account. Problem is formulated using the long wavelength and low Reynolds number approach. Numerical solutions for the pressure rise per wavelength, pressure gradient, axial velocity, temperature and heat transfer rate at the boundaxy are obtained and studied through graphs. Results show that the area of peristaltic pumping decreases with an increase in the nanoparticles volume fraction. Increase in the velocity slip parameter shows an increase of the pressure gradient in the occluded part of the channel. Further, addition of copper nanoparticles reduces both the axial velocity and temperature of the base fluid. Temperature of the nanofluid also decreases sufficiently for an increase in the value of Blot number.