This paper presents a method to determine the safety threshold of bridge pier settlement in high-speed railways.An analytical expression of the mapping relationship between the pier settlement and the rail deformation...This paper presents a method to determine the safety threshold of bridge pier settlement in high-speed railways.An analytical expression of the mapping relationship between the pier settlement and the rail deformation is derived theoretically for the double block ballastless track-bridge system.By adopting the superposition of the track random irregularity and the rail deformation caused by the pier settlement as the excitation inputs,the variations of vehicle dynamics indices with pier settlement are comparatively analyzed.Then,the safety threshold of the bridge pier settlement is obtained according to the limit of vehicle running safety and ride comfort indices of the high-speed trains.Results show that the dynamics indices of different trains have different sensitivities to the pier settlement,and the train CRH2C is the most sensitive one among all the types of Chinese high-speed trains.When passing through the bridges in common span with pier settlement at the speed of 250–350 km/h,the trains suffer the low-frequency excitations,and the vertical acceleration of car body is most sensitive to the pier settlement of all the dynamics indices.When the car body vertical acceleration just exceeds the allowable limit,the critical settlement value is 23.4 mm,which is much bigger than the pier differential settlement limit in the current code for Chinese high-speed railways.展开更多
Fuel moisture content is one of the important factors that determine ignition probability and fire behaviour in forest ecosystems.In this study,ignition and fire spread moisture content thresholds of 40 dead fuel were...Fuel moisture content is one of the important factors that determine ignition probability and fire behaviour in forest ecosystems.In this study,ignition and fire spread moisture content thresholds of 40 dead fuel were performed in laboratory experiments,with a focus on the source of ignition and wind speed.Variability in fuel moisture content at time of ignition and during fire spread was observed for different fuels.Matches were more efficient to result in ignition and spread fire with high values of fuel moisture content compared to the use of cigarette butts.Some fuels did not ignite at 15%moisture content,whereas others ignited at 40%moisture content and fire spread at 38%moisture content in the case of matches,or ignited at 27%moisture content and spread fire at 25%moisture content using cigarette butts.A two-way ANOVA showed that both the source of ignition and the wind speed affected ignition and fire spread threshold significantly,but there was no interaction between these factors.The relationship between ignition and fire spread was strong,with R2=98%for cigarette butts,and 92%for matches.Further information is needed,especially on the density of fuels,fuel proportion(case of mixed fuels),fuel age,and fuel combustibility.展开更多
To position personnel in mines, the study discussed in this paper built on the tunnel personnel positioning method on the basis of both TOA and location-finger print(LFP) positioning. Given non-line of sight(NLOS) tim...To position personnel in mines, the study discussed in this paper built on the tunnel personnel positioning method on the basis of both TOA and location-finger print(LFP) positioning. Given non-line of sight(NLOS) time delay in signal transmission caused by facilities and equipment shielding in tunnels and TOA measurement errors in both LFP database data and real-time data, this paper puts forth a database data de-noising algorithm based on distance threshold limitation and modified mean filtering(MMF), as well as a real-time data suppression algorithm based on speed threshold limitation and MMF.On this basis, a nearest neighboring data matching algorithm based on historical location and the speed threshold limitation is used to estimate personnel location and realize accurate personnel positioning.The results from both simulation and the experiment suggest that: compared with the basic LFP positioning method and the method that only suppresses real-time data error, the tunnel personnel positioning methods based on TOA and modified LFP positioning permits effectively eliminating error in TOA measurement, making the measured data close to the true positional data, and dropping the positioning error:the maximal positioning error in measurements from experiment drops by 9 and 3 m, respectively, and the positioning accuracy of 3 m is achievable in the condition used in the experiment.展开更多
This paper proposes a new optimization method to improve the performance of a null convention logic asynchronous pipeline.Parallel combinational logic modules in the pipelines can work alternately in null and data cyc...This paper proposes a new optimization method to improve the performance of a null convention logic asynchronous pipeline.Parallel combinational logic modules in the pipelines can work alternately in null and data cycles by using a parallel processing mode.The complete waiting time for both null and data signals of combinational logic output in previous asynchronous register stage is reduced by decoupling the output from combinational logic modules.Performance penalty brought by null cycle is reduced while the data processing capacity is increased.The novel asynchronous pipeline based on asynchronous full adders with different bit widths as asynchronous combination logic modules is simulated using 0.18-μm CMOS technology.Based on 6 bits asynchronous adder as asynchronous combination logic modules, the simulation result of this new pipeline proposal demonstrates a high throughput up to 72.4% improvement with appropriate power consumption.This indicates the new design proposal is preferable for high-speed as ynchronous designs due to its high throughput and delay-insensitivity.展开更多
基金supported by the National Basic Research Program of China("973"Program)(Grant Nos.2013CB036206 and 2013CB036205)the National Natural Science Foundation of China(Grant No.50838006)+1 种基金the Research Project of State Key Laboratory of Traction Power(Grant No.2014TPL_T01)the 2015 Doctors’Innovation Fund of Southwest Jiaotong University
文摘This paper presents a method to determine the safety threshold of bridge pier settlement in high-speed railways.An analytical expression of the mapping relationship between the pier settlement and the rail deformation is derived theoretically for the double block ballastless track-bridge system.By adopting the superposition of the track random irregularity and the rail deformation caused by the pier settlement as the excitation inputs,the variations of vehicle dynamics indices with pier settlement are comparatively analyzed.Then,the safety threshold of the bridge pier settlement is obtained according to the limit of vehicle running safety and ride comfort indices of the high-speed trains.Results show that the dynamics indices of different trains have different sensitivities to the pier settlement,and the train CRH2C is the most sensitive one among all the types of Chinese high-speed trains.When passing through the bridges in common span with pier settlement at the speed of 250–350 km/h,the trains suffer the low-frequency excitations,and the vertical acceleration of car body is most sensitive to the pier settlement of all the dynamics indices.When the car body vertical acceleration just exceeds the allowable limit,the critical settlement value is 23.4 mm,which is much bigger than the pier differential settlement limit in the current code for Chinese high-speed railways.
基金funded by the National Key Research and Development Program of China(2018YFE0207800)the Fundamental Research Funds for the Central Universities(2572019CP10)+1 种基金the National Innovation Alliance of Wildland Fire Prevention and Control Technology of Chinathe Northern Forest Fire Management Key Laboratory of the State Forestry and Grassland Bureau。
文摘Fuel moisture content is one of the important factors that determine ignition probability and fire behaviour in forest ecosystems.In this study,ignition and fire spread moisture content thresholds of 40 dead fuel were performed in laboratory experiments,with a focus on the source of ignition and wind speed.Variability in fuel moisture content at time of ignition and during fire spread was observed for different fuels.Matches were more efficient to result in ignition and spread fire with high values of fuel moisture content compared to the use of cigarette butts.Some fuels did not ignite at 15%moisture content,whereas others ignited at 40%moisture content and fire spread at 38%moisture content in the case of matches,or ignited at 27%moisture content and spread fire at 25%moisture content using cigarette butts.A two-way ANOVA showed that both the source of ignition and the wind speed affected ignition and fire spread threshold significantly,but there was no interaction between these factors.The relationship between ignition and fire spread was strong,with R2=98%for cigarette butts,and 92%for matches.Further information is needed,especially on the density of fuels,fuel proportion(case of mixed fuels),fuel age,and fuel combustibility.
基金Project supports from the National Science Foundation of China(No.51134024)the National High Technology Research and development Program of China(No.2012AA062203)are acknowledged
文摘To position personnel in mines, the study discussed in this paper built on the tunnel personnel positioning method on the basis of both TOA and location-finger print(LFP) positioning. Given non-line of sight(NLOS) time delay in signal transmission caused by facilities and equipment shielding in tunnels and TOA measurement errors in both LFP database data and real-time data, this paper puts forth a database data de-noising algorithm based on distance threshold limitation and modified mean filtering(MMF), as well as a real-time data suppression algorithm based on speed threshold limitation and MMF.On this basis, a nearest neighboring data matching algorithm based on historical location and the speed threshold limitation is used to estimate personnel location and realize accurate personnel positioning.The results from both simulation and the experiment suggest that: compared with the basic LFP positioning method and the method that only suppresses real-time data error, the tunnel personnel positioning methods based on TOA and modified LFP positioning permits effectively eliminating error in TOA measurement, making the measured data close to the true positional data, and dropping the positioning error:the maximal positioning error in measurements from experiment drops by 9 and 3 m, respectively, and the positioning accuracy of 3 m is achievable in the condition used in the experiment.
基金supported by the National Science Fund for Distinguished Young Scholars (No. 60725415)the National Natural Science Foundation of China (Nos. 60676009, 90407016)
文摘This paper proposes a new optimization method to improve the performance of a null convention logic asynchronous pipeline.Parallel combinational logic modules in the pipelines can work alternately in null and data cycles by using a parallel processing mode.The complete waiting time for both null and data signals of combinational logic output in previous asynchronous register stage is reduced by decoupling the output from combinational logic modules.Performance penalty brought by null cycle is reduced while the data processing capacity is increased.The novel asynchronous pipeline based on asynchronous full adders with different bit widths as asynchronous combination logic modules is simulated using 0.18-μm CMOS technology.Based on 6 bits asynchronous adder as asynchronous combination logic modules, the simulation result of this new pipeline proposal demonstrates a high throughput up to 72.4% improvement with appropriate power consumption.This indicates the new design proposal is preferable for high-speed as ynchronous designs due to its high throughput and delay-insensitivity.
