Many cities in the world are aspiring to have a world-class, sustainable public transport system. However, the cost of building new mass transport systems, especially metro projects, is so high it can lead to the post...Many cities in the world are aspiring to have a world-class, sustainable public transport system. However, the cost of building new mass transport systems, especially metro projects, is so high it can lead to the postponement of such projects. New mass transit modes such as Bus Rapid Transit (BRT), Trackless Tram (TT) and suspended systems are continuously emerging. Some of the new emerging modes can deliver high capacity that can be equivalent to Light Rail Transit and Metro Systems but with significantly less cost. This research is meant to develop a comprehensive approach for comparing & assessing several aspects of different mass transit modes. Different research tools, including in-depth literature review, content, and case study analysis, multicriteria assessment, benchmarking and efficiency analysis, are used to reach conclusions for optimum mass transit options from different perspectives.展开更多
In order to find a method which can describe the passenger flow dynamical distribution of urban mass transit during interval interrupted operation,an urban railway network topology model was built based on the travel ...In order to find a method which can describe the passenger flow dynamical distribution of urban mass transit during interval interrupted operation,an urban railway network topology model was built based on the travel path dual graph by considering interchange,crowd and congestion.The breadth first valid travel path search algorithm is proposed,and the multipath passenger flow distribution logit model is improved.According to the characteristics of passengers under the interruption condition,the distribution rules of different types of passenger flow are proposed.The method of calculating the aggregation number of station is proposed for the case of insufficient transport capacity.Finally,the passenger flow of Beijing urban mass transit is simulated for the case study.The results show that the relative error of most of transfer passenger flow is below 10%.The proposed model and algorithm can accurately assign the daily passenger flow,which provides a theoretical basis for urban mass transit emergency management and decision.展开更多
The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corr...The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.展开更多
Due to multiple advantages in terms of capacity,safety,dependability and punctuality,rail mass transit plays a vital role in easing urban traffic congestion.In addition,rail mass transit is environmentally friendly.Ev...Due to multiple advantages in terms of capacity,safety,dependability and punctuality,rail mass transit plays a vital role in easing urban traffic congestion.In addition,rail mass transit is environmentally friendly.Even though it is beneficial to passengers in urban areas,security issues have become increasingly serious in recent years.To improve the safety and dependability of the rail mass transit system to some extent and limit the loss to a bare minimum,it is necessary to identify and evaluate the hazards connected with rail mass transit in the early stages of the system’s operation.Against this backdrop,this research employs a riskmatrix approach to examine the dangers connected with Abuja’s rail mass transit system(ARMT).The questionnaire is designed and delivered to 100 participants,including personnel and passengers,to get their perceptions of hazards at the ARMT.The questionnaire is the initial step in the research process.The four safety variables discussed in this study are human error,equipment design failure,environmental conditions and management.Human error is the most significant factor covered in this research.Understanding the source of risk stemming from these four safety variables at the early stages of rail mass transit operation can significantly improve the system’s overall safety and reliability,which can be paramount.According to the findings of the investigations,human-related activity is the most significant possible cause of risk at that ARMT,with a high level of risk portrayed by the data.展开更多
Constituent quark mass model is adopted as a tentative one to study the phase transition between two-flavour quark matter and more stable three-flavour quark matter in the core of supernovae. The result shows that the...Constituent quark mass model is adopted as a tentative one to study the phase transition between two-flavour quark matter and more stable three-flavour quark matter in the core of supernovae. The result shows that the transition has a significant influence on the increasing of the core temperature, the neutrino abundance and the neutrino energies, which contributes to the enhancement of the successful probability of supernova explosion. However, the equilibrium values of these parameters （except the temperature） from the constituent quark mass model in this work are slightly bigger than those obtained from the other model. And we find that the constituent quark mass model is also applicable to describing the transition in the supernova core.展开更多
为研究冷金属过渡(cold metal transition,CMT)电弧增材制造铝合金传热传质与熔池流动特性,基于Fluent软件建立了三维CMT电弧增材制造数值模型.模型中,采用动网格技术模拟焊丝竖直方向上的往复运动,利用流体体积法捕获气/液界面,焓-孔...为研究冷金属过渡(cold metal transition,CMT)电弧增材制造铝合金传热传质与熔池流动特性,基于Fluent软件建立了三维CMT电弧增材制造数值模型.模型中,采用动网格技术模拟焊丝竖直方向上的往复运动,利用流体体积法捕获气/液界面,焓-孔隙率法追踪固/液界面,并施加周期热量输入和阶段电弧力作用来等效电弧放电行为,研究分析了焊道成形传热传质过程与熔池动态行为.结果表明,焊道成形初期,熔池余高和坡度较大,形貌犹如半个球体,成形后期热量积累造成焊道余高后方较前方略小,而后端熔宽较前端略宽;单滴过渡周期内,焊丝机械回抽对熔池表面流动影响最为明显,液桥断裂产生较大反冲作用于熔池;熔池内部则是电磁力作为主导驱动力产生一股顺时针环流,环流随燃弧阶段周期切换而不断加强与减弱,并基本贯穿整个过渡周期,使得熔池内部热对流更加充分.模拟结果与试验结果显示吻合良好.展开更多
A cell model to describe and optimize heat and mass transfer in contact heat exchangers for utilization of exhaust gases heat is proposed. The model is based on the theory of Markov chains and allows calculating heat ...A cell model to describe and optimize heat and mass transfer in contact heat exchangers for utilization of exhaust gases heat is proposed. The model is based on the theory of Markov chains and allows calculating heat and mass transfer at local moving force of the processes in each cell. The total process is presented as two parallel chains of cells (one for water flow and one for gas flow). The corresponding cells of the chains can exchange heat and mass, and water and gas can travel along their chains according to their transition ma-trices. The results of numerical experiments showed that the most part of heat transfer occurs due to moisture condensation from gas and the most intense heat transfer goes near the inlet of gas. Experimental validation of the model showed a good correlation between calculated and experimental data for an industrial contact heat exchanger if appropriate empirical equations were used to calculate heat and mass transfer coefficient. It was also shown that there exists the optimum height of heat exchanger that gave the maximum gain in heat energy utilization.展开更多
The mass dependence of critical parameters for the liquid-gas phase transition and multiplicity of intermediate mass fragment in the heavy ion reaction is qualitatively explored under the framework of lattice gas mode...The mass dependence of critical parameters for the liquid-gas phase transition and multiplicity of intermediate mass fragment in the heavy ion reaction is qualitatively explored under the framework of lattice gas model.Some results are compared with experimental data.展开更多
The solar transition region （TR） is the temperature regime from roughly 0.02 MK to 0.8 MK in the solar atmosphere. It is the transition layer from the collisional and partially ionized chromosphere to the collisionl...The solar transition region （TR） is the temperature regime from roughly 0.02 MK to 0.8 MK in the solar atmosphere. It is the transition layer from the collisional and partially ionized chromosphere to the collisionless and fully ionized corona. The TR plays an important role in the mass and energy transport in both the quiet solar atmosphere and solar eruptions. Most of the TR emission lines fall into the spectral range of far ultraviolet and extreme ultraviolet （~400/^-1600/~）. Imaging and spec- troscopic observations in this spectral range are the most important ways to obtain information about the physics of the TR. Static solar atmosphere models predict a very thin TR. However, recent high- resolution observations indicate that the TR is highly dynamic and inhomogeneous. I will summarize some major findings about the TR made through imaging and spectroscopic observations in the past 20 years. These existing observations have demonstrated that the TR may be the key to understanding coronal heating and origin of the solar wind. Future exploration of the solar TR may need to focus on the upper TR, since the plasma in this temperature regime （0.1 MK-0.8 MK） has not been routinely imaged before. High-resolution imaging and spectroscopic observations of the upper TR will not only allow us to track the mass and energy from the lower atmosphere to the corona, but also help us to understand the initiation and heating mechanisms of coronal mass ejections and solar flares.展开更多
文摘Many cities in the world are aspiring to have a world-class, sustainable public transport system. However, the cost of building new mass transport systems, especially metro projects, is so high it can lead to the postponement of such projects. New mass transit modes such as Bus Rapid Transit (BRT), Trackless Tram (TT) and suspended systems are continuously emerging. Some of the new emerging modes can deliver high capacity that can be equivalent to Light Rail Transit and Metro Systems but with significantly less cost. This research is meant to develop a comprehensive approach for comparing & assessing several aspects of different mass transit modes. Different research tools, including in-depth literature review, content, and case study analysis, multicriteria assessment, benchmarking and efficiency analysis, are used to reach conclusions for optimum mass transit options from different perspectives.
基金The National Natural Science Foundation of China(No.61374157)the Science and Technology Project of the Education Department of Jiangxi Province(No.GJJ151524)
文摘In order to find a method which can describe the passenger flow dynamical distribution of urban mass transit during interval interrupted operation,an urban railway network topology model was built based on the travel path dual graph by considering interchange,crowd and congestion.The breadth first valid travel path search algorithm is proposed,and the multipath passenger flow distribution logit model is improved.According to the characteristics of passengers under the interruption condition,the distribution rules of different types of passenger flow are proposed.The method of calculating the aggregation number of station is proposed for the case of insufficient transport capacity.Finally,the passenger flow of Beijing urban mass transit is simulated for the case study.The results show that the relative error of most of transfer passenger flow is below 10%.The proposed model and algorithm can accurately assign the daily passenger flow,which provides a theoretical basis for urban mass transit emergency management and decision.
基金Project(BE2010043) supported by the Technology Support Program of Jiangsu Province,ChinaProject(CXZZ13_0928) supported by the Graduate Education Innovation Project of Jiangsu Province,China
文摘The novel method to analyze metallic structure corrosion status was proposed in the presence of stray current in DC mass transit systems. Firstly, the characteristic parameter and the influence parameters for the corrosion status were determined. Secondly, an experimental system was established for simulating the corrosion process within the stray current interference. Then, a predictive model for the corrosion status was built, using a support vector machine(SVM) method and experimental data. The data were divided into two sets, including training set and testing set. The training set was used to generate the SVM model and the testing set was used to evaluate the predictive performance of the SVM model. The results show that the relationship between the characteristic parameter and the influence parameters is nonlinear and the SVM model is suitable for predicting the corrosion status.
基金The National Science Foundation of China(Grand No.71971220)the National Science Foundation of Hunan Province,China(Grant No.2019JJ50829).
文摘Due to multiple advantages in terms of capacity,safety,dependability and punctuality,rail mass transit plays a vital role in easing urban traffic congestion.In addition,rail mass transit is environmentally friendly.Even though it is beneficial to passengers in urban areas,security issues have become increasingly serious in recent years.To improve the safety and dependability of the rail mass transit system to some extent and limit the loss to a bare minimum,it is necessary to identify and evaluate the hazards connected with rail mass transit in the early stages of the system’s operation.Against this backdrop,this research employs a riskmatrix approach to examine the dangers connected with Abuja’s rail mass transit system(ARMT).The questionnaire is designed and delivered to 100 participants,including personnel and passengers,to get their perceptions of hazards at the ARMT.The questionnaire is the initial step in the research process.The four safety variables discussed in this study are human error,equipment design failure,environmental conditions and management.Human error is the most significant factor covered in this research.Understanding the source of risk stemming from these four safety variables at the early stages of rail mass transit operation can significantly improve the system’s overall safety and reliability,which can be paramount.According to the findings of the investigations,human-related activity is the most significant possible cause of risk at that ARMT,with a high level of risk portrayed by the data.
基金Project supported by the National Natural Science Foundation of China (Grant No 10347008)the Scientific Research and Fund of Sichuan Provincial Education Department (Grant No.2006A079)the Science and Technological Foundation of China West Normal University
文摘Constituent quark mass model is adopted as a tentative one to study the phase transition between two-flavour quark matter and more stable three-flavour quark matter in the core of supernovae. The result shows that the transition has a significant influence on the increasing of the core temperature, the neutrino abundance and the neutrino energies, which contributes to the enhancement of the successful probability of supernova explosion. However, the equilibrium values of these parameters （except the temperature） from the constituent quark mass model in this work are slightly bigger than those obtained from the other model. And we find that the constituent quark mass model is also applicable to describing the transition in the supernova core.
文摘为研究冷金属过渡(cold metal transition,CMT)电弧增材制造铝合金传热传质与熔池流动特性,基于Fluent软件建立了三维CMT电弧增材制造数值模型.模型中,采用动网格技术模拟焊丝竖直方向上的往复运动,利用流体体积法捕获气/液界面,焓-孔隙率法追踪固/液界面,并施加周期热量输入和阶段电弧力作用来等效电弧放电行为,研究分析了焊道成形传热传质过程与熔池动态行为.结果表明,焊道成形初期,熔池余高和坡度较大,形貌犹如半个球体,成形后期热量积累造成焊道余高后方较前方略小,而后端熔宽较前端略宽;单滴过渡周期内,焊丝机械回抽对熔池表面流动影响最为明显,液桥断裂产生较大反冲作用于熔池;熔池内部则是电磁力作为主导驱动力产生一股顺时针环流,环流随燃弧阶段周期切换而不断加强与减弱,并基本贯穿整个过渡周期,使得熔池内部热对流更加充分.模拟结果与试验结果显示吻合良好.
文摘A cell model to describe and optimize heat and mass transfer in contact heat exchangers for utilization of exhaust gases heat is proposed. The model is based on the theory of Markov chains and allows calculating heat and mass transfer at local moving force of the processes in each cell. The total process is presented as two parallel chains of cells (one for water flow and one for gas flow). The corresponding cells of the chains can exchange heat and mass, and water and gas can travel along their chains according to their transition ma-trices. The results of numerical experiments showed that the most part of heat transfer occurs due to moisture condensation from gas and the most intense heat transfer goes near the inlet of gas. Experimental validation of the model showed a good correlation between calculated and experimental data for an industrial contact heat exchanger if appropriate empirical equations were used to calculate heat and mass transfer coefficient. It was also shown that there exists the optimum height of heat exchanger that gave the maximum gain in heat energy utilization.
基金Supported by the National Natural Science Foundation for Distinguished Young Scholar under Grant No.19725521 National Natural Science Foundation under Grant No.19705021Science and Technology Development Foundation of shanghai under Grant No.97QA
文摘The mass dependence of critical parameters for the liquid-gas phase transition and multiplicity of intermediate mass fragment in the heavy ion reaction is qualitatively explored under the framework of lattice gas model.Some results are compared with experimental data.
基金supported by the Recruitment Program of Global Experts of Chinathe Max Planck Partner Group program+4 种基金the space mission concept study led by the National Space Science Center, Chinese Academy of SciencesThe SUMER project is financially supported by DLRCNESNASAthe ESA PRODEX programme (Swiss contribution)
文摘The solar transition region （TR） is the temperature regime from roughly 0.02 MK to 0.8 MK in the solar atmosphere. It is the transition layer from the collisional and partially ionized chromosphere to the collisionless and fully ionized corona. The TR plays an important role in the mass and energy transport in both the quiet solar atmosphere and solar eruptions. Most of the TR emission lines fall into the spectral range of far ultraviolet and extreme ultraviolet （~400/^-1600/~）. Imaging and spec- troscopic observations in this spectral range are the most important ways to obtain information about the physics of the TR. Static solar atmosphere models predict a very thin TR. However, recent high- resolution observations indicate that the TR is highly dynamic and inhomogeneous. I will summarize some major findings about the TR made through imaging and spectroscopic observations in the past 20 years. These existing observations have demonstrated that the TR may be the key to understanding coronal heating and origin of the solar wind. Future exploration of the solar TR may need to focus on the upper TR, since the plasma in this temperature regime （0.1 MK-0.8 MK） has not been routinely imaged before. High-resolution imaging and spectroscopic observations of the upper TR will not only allow us to track the mass and energy from the lower atmosphere to the corona, but also help us to understand the initiation and heating mechanisms of coronal mass ejections and solar flares.
