Petroleum, the most important energy source in the world, plays an essential role in securing economic development. If a petroleum shortage happens, it will severely disrupt production and life. Cross-regional emergen...Petroleum, the most important energy source in the world, plays an essential role in securing economic development. If a petroleum shortage happens, it will severely disrupt production and life. Cross-regional emergency scheduling can effectively alleviate a petroleum shortage and further enhance the efficiency of the emergency response. Considering the general lack of focus on cross-regional petroleum dispatching management, we propose a three-layer emergency scheduling network for petroleum based on a supernetwork model that can increase the regional emergency correlation by adding a transfer management process. Then, we compare the total demand for petroleum and the emergency costs considered in the petroleum emergency scheduling supernetwork model（the single-region and the cross-region scenarios）.The result shows that the cross-regional emergency scheduling pattern can effectively enhance the efficiency of the emergency preparations and reduce the emergency costs in most cases. However, when the vulnerabilities in the crossregional link grow or the regional linkage decreases, the effect of single-regional scheduling is better. In addition, the advantages of the cross-regional emergency scheduling network will be strengthened with an increase in its maximum emergency capability. Nonetheless, this advantage will disappear when the petroleum demand in the crisis layer reaches the maximum emergency response capacity. Finally, according to the comparative analysis simulation among scenarios,certain strategic policy recommendations are suggested to improve the petroleum emergency scheduling ability in regions.These recommendations include strengthening the cross-regional coordination mechanism, increasing the modes of petroleum transportation and enhancing the carrying capacity of regional emergency routes.展开更多
The unique ways of information organization and dissemination was examined through the microblog and the real-name social network as the representatives of the new virtual social networks. In order to discuss the inte...The unique ways of information organization and dissemination was examined through the microblog and the real-name social network as the representatives of the new virtual social networks. In order to discuss the interrelation and interaction of the two dimensions-topic and user, a supernetwork model was established based on the supernetwork research method. Through the actual data, a supernetwork topology diagram and the changing rule of user participation were attained. And it was concluded that the key factor of dealing with emergent online public sentiment should start with affecting the opinions of key figures, whose opinions would further affect the public opinions.展开更多
A new car-following model is proposed by considering information from a number of preceding vehicles with intervehicle communication. A supernetwork architecture is first described, which has two layers： a traffic ne...A new car-following model is proposed by considering information from a number of preceding vehicles with intervehicle communication. A supernetwork architecture is first described, which has two layers： a traffic network and a communication network. The two networks interact with and depend on each other. The error dynamic system around the steady state of the model is theoretically analyzed and some nonjam criteria are derived. A simple control signal is added to the model to analyze the criteria of suppressing traffic jams. The corresponding numerical simulations confirm the correctness of the theoretical analysis. Compared with previous studies concerning coupled map models, the controlled model proposed in this paper is more reasonable and also more effective in the sense that it takes into account the formation of traffic congestion.展开更多
Purpose： Compared with traditional course materials used in the classroom, the massive open online course（MOOC） forum that delivers unlimited learning content to students has various advantages. Yet MOOC has also r...Purpose： Compared with traditional course materials used in the classroom, the massive open online course（MOOC） forum that delivers unlimited learning content to students has various advantages. Yet MOOC has also received criticism recently, notably the problem of extremely low participation rates in its discussion forums. This study aims to explore the correlation between forum activity and student course grade in MOOC, and identify more accurately the forum activity levels of participants and the quality of threads in MOOC.Design/Methodology/Approach： We crawled students’ tests, final exams, exercises, discussions performance data and total scores from a course in Chinese College MOOC from May 2014 to August 2014. And we use the data to analyze the correlation between Forum Participation and Course Performance based on nonparametric tests as well as multiple linear regressions with the software of R. The study provides definitions and algorithms of super degrees based on the supernetwork model to help find high-quality threads and active participants.Findings： A positive correlation between forum activity and course grade is found in this study. Students who participate in the forum have better performance than those who do not. Using the definitions and algorithms of super degrees in the supernetwork, forum activity levels of participants as well as the quality of threads they employ are identified. Research limitation： Only limited representative forum participants and threads are used to analyze the activity level and significance of the MOOC forum. Also, the study only investigates one Chinese course on information retrieval. More data and more data sources could be helpful in better understanding the MOOC forum phenomenon.Practical implications： As super degrees can reveal more latent information and recognize high-quality threads as well as active participants, these parameters can be used to assess needs to improve forum settings and alleviate the problem of low forum participation. The proposed super degrees can be applied in social network domains for further research.Originality/Value： Definitions and algorithms of super degrees are provided and used for forum analysis. Super degrees can be applied to find high-quality threads and active participants, which is beneficial to guide students to participate in these high-quality threads and have a better understanding of knowledge MOOC provides.展开更多
Supernetworks have long been adopted to address multi-dimensional choice problems, which are thorny to solve for classic singular networks. Originated from combining transport mode and route choice into a multi-modal ...Supernetworks have long been adopted to address multi-dimensional choice problems, which are thorny to solve for classic singular networks. Originated from combining transport mode and route choice into a multi-modal network, supernetworks have been extended into multi-state networks to include activity-travel scheduling, centered around activity-based models of travel demand. A key feature of the network extensions is that multiple choice facets pertaining to conducting a full activity program can be modeled in a consistent and integrative fashion. Thus, interdependencies and constraints between related choice facets can be readily captured. Given this advantage of integrity, the modeling of supernetwork has become an emerging topic in transportation research. This paper summarizes the recent progress in modeling multi-state supernetworks and discusses future prospects.展开更多
Space-time prism(STP)modeling offers a theoretical base for various person-based space-time accessibility measures.It has been challenging to construct STPs in multimodal transportation networks because of the vast mu...Space-time prism(STP)modeling offers a theoretical base for various person-based space-time accessibility measures.It has been challenging to construct STPs in multimodal transportation networks because of the vast multimodal trip chaining options between private vehicles and public transportation.This study suggests an effective method for narrowing down the trip chaining space.The method involves three incremental strategies to eliminate parking locations that contribute little to enlarging the STP.First,an upper bound potential path area(PPA)is constructed to remove all inferior parking locations.Second,the study area is partitioned and only complementary parking locations attractive to trip chaining are selected.Third,triangular inequalities are applied for pruning.The selected parking locations are used to construct a compact multimodal supernetwork encompassing one episode of activity participation.Consequently,the STP and PPA can be found by an existing twostage bidirectional search method.Experimental tests are conducted to demonstrate the effectiveness of the method.It is found that 1-2 orders of speedups can be achieved with little compromising the accuracy of measuring space-time accessibility.The suggested method is applicable for measuring space-time accessibility in large-scale multimodal transportation networks.展开更多
Space-time prism(STP)is a fundamental concept in time geography and has been predominately constructed in unimodal transportation networks.Due to the vast trip chaining options by private vehicles and public transport...Space-time prism(STP)is a fundamental concept in time geography and has been predominately constructed in unimodal transportation networks.Due to the vast trip chaining options by private vehicles and public transportation,it was challenging to construct STP over multimodal transportation networks.We previously put forward an efficient method to narrow down the action space for trip chaining and construct STPs effectively in a multimodal supernetwork.This study applies multimodal STP modeling to measure space-time accessibility and equality of daily activity opportunities.Two equality measures(Gini coefficient and 20:20 ratio)are derived from two space-time accessibility measures based on delineated STPs.We examine the equality of access to shopping and leisure opportunities in the Rotterdam-The Hague metropolitan area,the Netherlands.The results show the effects of various factors on accessibility and equality.It is found that although the study area has relatively low inequality using single modes,multimodal trip chaining further reduces inequality to access the distributed space-time opportunities.展开更多
This paper is concerned with the algorithm of the supply chain network equilibrium model and its equivalent supernetwork based traffic network equilibrium model with elastic demands. Both models are further written as...This paper is concerned with the algorithm of the supply chain network equilibrium model and its equivalent supernetwork based traffic network equilibrium model with elastic demands. Both models are further written as nonlinear complementarity problems. Semismooth least squares reformulations of the complementarity problems are presented and their convergence properties are investigated. Considering the drawbacks of Quasi-Newton method (using the Fischer-Burmeister function), a semi-smooth Levenberg-Marquardt-type method is proposed to solve the problems. Numerical examples show that the Levenberg-Marquardt-type method can solve the supply chain network equilibrium model and its equivalent supernetwork based traffic network equilibrium model significantly, and is more efficient than the Quasi Newton method and the modified projection method. Furthermore, the Levenberg-Marquardt-type method with the equivalent supernetwork based complementarity formulation can be implemented faster than with the supply chain network equilibrium complementarity formulation.展开更多
This work develops an equilibrium model for finding the optimal distribution strategy to maximize performance of key predistribution protocols in terms of cost, resilience, connectivity, and lifetime. As an essential ...This work develops an equilibrium model for finding the optimal distribution strategy to maximize performance of key predistribution protocols in terms of cost, resilience, connectivity, and lifetime. As an essential attribute of wireless sensor networks, heterogeneity and its impacts on random key predistribution protocols are first discussed. Using supernetworks theory, the optimal node deployment model is proposed and illustrated. In order to find the equilibrium performance of our model, all optimal performance functions are changed into variational inequalities so that this optimization problem can be solved. A small-scale example is presented to illustrate the applicability of our model.展开更多
基金supported by the Fundamental Research Funds for the Central Universities (Grant No. 2014XT06)
文摘Petroleum, the most important energy source in the world, plays an essential role in securing economic development. If a petroleum shortage happens, it will severely disrupt production and life. Cross-regional emergency scheduling can effectively alleviate a petroleum shortage and further enhance the efficiency of the emergency response. Considering the general lack of focus on cross-regional petroleum dispatching management, we propose a three-layer emergency scheduling network for petroleum based on a supernetwork model that can increase the regional emergency correlation by adding a transfer management process. Then, we compare the total demand for petroleum and the emergency costs considered in the petroleum emergency scheduling supernetwork model（the single-region and the cross-region scenarios）.The result shows that the cross-regional emergency scheduling pattern can effectively enhance the efficiency of the emergency preparations and reduce the emergency costs in most cases. However, when the vulnerabilities in the crossregional link grow or the regional linkage decreases, the effect of single-regional scheduling is better. In addition, the advantages of the cross-regional emergency scheduling network will be strengthened with an increase in its maximum emergency capability. Nonetheless, this advantage will disappear when the petroleum demand in the crisis layer reaches the maximum emergency response capacity. Finally, according to the comparative analysis simulation among scenarios,certain strategic policy recommendations are suggested to improve the petroleum emergency scheduling ability in regions.These recommendations include strengthening the cross-regional coordination mechanism, increasing the modes of petroleum transportation and enhancing the carrying capacity of regional emergency routes.
基金National Natural Science Foundation of China (No. 71071098)
文摘The unique ways of information organization and dissemination was examined through the microblog and the real-name social network as the representatives of the new virtual social networks. In order to discuss the interrelation and interaction of the two dimensions-topic and user, a supernetwork model was established based on the supernetwork research method. Through the actual data, a supernetwork topology diagram and the changing rule of user participation were attained. And it was concluded that the key factor of dealing with emergent online public sentiment should start with affecting the opinions of key figures, whose opinions would further affect the public opinions.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61174158,61034004,91024023,and 61272271)the Special Fund from the China Postdoctoral Science Foundation (Grant No. 201104286)+3 种基金the China Postdoctoral Science Foundation (Grant No. 2012M510117)the Natural Science Foundation Program of Shanghai (Grant No. 12ZR1434000)the Fundamental Research Funds for the Central Universitiesthe Hong Kong Research Grants Council (Grant No. GRF Grant CityU1109/12)
文摘A new car-following model is proposed by considering information from a number of preceding vehicles with intervehicle communication. A supernetwork architecture is first described, which has two layers： a traffic network and a communication network. The two networks interact with and depend on each other. The error dynamic system around the steady state of the model is theoretically analyzed and some nonjam criteria are derived. A simple control signal is added to the model to analyze the criteria of suppressing traffic jams. The corresponding numerical simulations confirm the correctness of the theoretical analysis. Compared with previous studies concerning coupled map models, the controlled model proposed in this paper is more reasonable and also more effective in the sense that it takes into account the formation of traffic congestion.
基金supported by grants from the National Natural Science Foundation of China (Grant Numbers: 71373194 and 71573197)the Fundamental Research Funds for the Central Universities
文摘Purpose： Compared with traditional course materials used in the classroom, the massive open online course（MOOC） forum that delivers unlimited learning content to students has various advantages. Yet MOOC has also received criticism recently, notably the problem of extremely low participation rates in its discussion forums. This study aims to explore the correlation between forum activity and student course grade in MOOC, and identify more accurately the forum activity levels of participants and the quality of threads in MOOC.Design/Methodology/Approach： We crawled students’ tests, final exams, exercises, discussions performance data and total scores from a course in Chinese College MOOC from May 2014 to August 2014. And we use the data to analyze the correlation between Forum Participation and Course Performance based on nonparametric tests as well as multiple linear regressions with the software of R. The study provides definitions and algorithms of super degrees based on the supernetwork model to help find high-quality threads and active participants.Findings： A positive correlation between forum activity and course grade is found in this study. Students who participate in the forum have better performance than those who do not. Using the definitions and algorithms of super degrees in the supernetwork, forum activity levels of participants as well as the quality of threads they employ are identified. Research limitation： Only limited representative forum participants and threads are used to analyze the activity level and significance of the MOOC forum. Also, the study only investigates one Chinese course on information retrieval. More data and more data sources could be helpful in better understanding the MOOC forum phenomenon.Practical implications： As super degrees can reveal more latent information and recognize high-quality threads as well as active participants, these parameters can be used to assess needs to improve forum settings and alleviate the problem of low forum participation. The proposed super degrees can be applied in social network domains for further research.Originality/Value： Definitions and algorithms of super degrees are provided and used for forum analysis. Super degrees can be applied to find high-quality threads and active participants, which is beneficial to guide students to participate in these high-quality threads and have a better understanding of knowledge MOOC provides.
文摘Supernetworks have long been adopted to address multi-dimensional choice problems, which are thorny to solve for classic singular networks. Originated from combining transport mode and route choice into a multi-modal network, supernetworks have been extended into multi-state networks to include activity-travel scheduling, centered around activity-based models of travel demand. A key feature of the network extensions is that multiple choice facets pertaining to conducting a full activity program can be modeled in a consistent and integrative fashion. Thus, interdependencies and constraints between related choice facets can be readily captured. Given this advantage of integrity, the modeling of supernetwork has become an emerging topic in transportation research. This paper summarizes the recent progress in modeling multi-state supernetworks and discusses future prospects.
基金supported by the Sino-EU joint research project(NSFC no.71961137001,NWO no.438-18-401).
文摘Space-time prism(STP)modeling offers a theoretical base for various person-based space-time accessibility measures.It has been challenging to construct STPs in multimodal transportation networks because of the vast multimodal trip chaining options between private vehicles and public transportation.This study suggests an effective method for narrowing down the trip chaining space.The method involves three incremental strategies to eliminate parking locations that contribute little to enlarging the STP.First,an upper bound potential path area(PPA)is constructed to remove all inferior parking locations.Second,the study area is partitioned and only complementary parking locations attractive to trip chaining are selected.Third,triangular inequalities are applied for pruning.The selected parking locations are used to construct a compact multimodal supernetwork encompassing one episode of activity participation.Consequently,the STP and PPA can be found by an existing twostage bidirectional search method.Experimental tests are conducted to demonstrate the effectiveness of the method.It is found that 1-2 orders of speedups can be achieved with little compromising the accuracy of measuring space-time accessibility.The suggested method is applicable for measuring space-time accessibility in large-scale multimodal transportation networks.
基金supported by the Dutch Research Council(NWO no.438-18-401).
文摘Space-time prism(STP)is a fundamental concept in time geography and has been predominately constructed in unimodal transportation networks.Due to the vast trip chaining options by private vehicles and public transportation,it was challenging to construct STP over multimodal transportation networks.We previously put forward an efficient method to narrow down the action space for trip chaining and construct STPs effectively in a multimodal supernetwork.This study applies multimodal STP modeling to measure space-time accessibility and equality of daily activity opportunities.Two equality measures(Gini coefficient and 20:20 ratio)are derived from two space-time accessibility measures based on delineated STPs.We examine the equality of access to shopping and leisure opportunities in the Rotterdam-The Hague metropolitan area,the Netherlands.The results show the effects of various factors on accessibility and equality.It is found that although the study area has relatively low inequality using single modes,multimodal trip chaining further reduces inequality to access the distributed space-time opportunities.
基金supported by the National Basic Research Program of China("973" Program) (Grant No. 2006CB705503)the National Natural ScienceFoundation of China (Grant Nos. 70771005, 71071014, 70631001)the Fundamental Research Funds for Central Universities (Grant No.2009JBM044)
文摘This paper is concerned with the algorithm of the supply chain network equilibrium model and its equivalent supernetwork based traffic network equilibrium model with elastic demands. Both models are further written as nonlinear complementarity problems. Semismooth least squares reformulations of the complementarity problems are presented and their convergence properties are investigated. Considering the drawbacks of Quasi-Newton method (using the Fischer-Burmeister function), a semi-smooth Levenberg-Marquardt-type method is proposed to solve the problems. Numerical examples show that the Levenberg-Marquardt-type method can solve the supply chain network equilibrium model and its equivalent supernetwork based traffic network equilibrium model significantly, and is more efficient than the Quasi Newton method and the modified projection method. Furthermore, the Levenberg-Marquardt-type method with the equivalent supernetwork based complementarity formulation can be implemented faster than with the supply chain network equilibrium complementarity formulation.
基金supported by the National Natural Science Foundation of China (Nos.61170241 and 61472097)the Specialized Research Fund for the Doctoral Program of Higher Education (No.20132304110017)the Open Fund of the Key Lab of Network Security and Cryptography of Fujian Province (No.150003)
文摘This work develops an equilibrium model for finding the optimal distribution strategy to maximize performance of key predistribution protocols in terms of cost, resilience, connectivity, and lifetime. As an essential attribute of wireless sensor networks, heterogeneity and its impacts on random key predistribution protocols are first discussed. Using supernetworks theory, the optimal node deployment model is proposed and illustrated. In order to find the equilibrium performance of our model, all optimal performance functions are changed into variational inequalities so that this optimization problem can be solved. A small-scale example is presented to illustrate the applicability of our model.
