In this paper, two cellular automata traffic models are proposed to simulate the operation of an expressway. The results show that the flow rate and the average velocity are generally equal in the same density which i...In this paper, two cellular automata traffic models are proposed to simulate the operation of an expressway. The results show that the flow rate and the average velocity are generally equal in the same density which is different among the lanes. The analysis of lane changing times and the velocity total deviation show some characteristics which are difficult to explain phase transitions under fundamental diagram theory. Therefore,the concept of lane changing probability is introduced, and it is concluded that the speed-limit rule can reduce the motivation of lane changing effectively.展开更多
This paper presents a risk evaluation model of water and mud inrush for tunnel excavation in karst areas.The factors affecting the probabilities of water and mud inrush in karst tunnels are investigated to define the ...This paper presents a risk evaluation model of water and mud inrush for tunnel excavation in karst areas.The factors affecting the probabilities of water and mud inrush in karst tunnels are investigated to define the dangerousness of this geological disaster.The losses that are caused by water and mud inrush are taken into consideration to account for its harmfulness.Then a risk evaluation model based on the dangerousness-harmfulness evaluation indicator system is constructed,which is more convincing in comparison with the traditional methods.The catastrophe theory is used to evaluate the risk level of water and mud inrush and it has great advantage in handling problems involving discontinuous catastrophe processes.To validate the proposed approach,the Qiyueshan tunnel of Yichang-Wanzhou Railway is taken as an example in which four target segments are evaluated using the risk evaluation model.Finally,the evaluation results are compared with the excavation data,which shows that the risk levels predicted by the proposed approach are in good agreements with that observed in engineering.In conclusion,the catastrophe theory-based risk evaluation model is an efficient and effective approach for water and mud inrush in karst tunnels.展开更多
By the generalized Kelvin creep model,rheological characteristics of deep softrock and long-term mechanical behaviors of support structures were simulated.Mechanicaldeformation characteristics of support structures un...By the generalized Kelvin creep model,rheological characteristics of deep softrock and long-term mechanical behaviors of support structures were simulated.Mechanicaldeformation characteristics of support structures under different lining circumstanceswere also analyzed on the basis of deducing the relationship between the generalizedKelvin creep model and implicit creep equations in ANSYS FEM software.The resultsshow that high stress of deep tunnels is the main factor in creep damage;the surroundingrock's deformation binding effect due to lining increases as the thickness increases but theeffect becomes very weak when it increases to a certain value;contact pressure on thelining decreases as its thickness decreases.展开更多
In this paper,we present a new method of intelligent back analysis(IBA)using grey Verhulst model(GVM)to identify geotechnical parameters of rock mass surrounding tunnel,and validate it via a test for a main openings o...In this paper,we present a new method of intelligent back analysis(IBA)using grey Verhulst model(GVM)to identify geotechnical parameters of rock mass surrounding tunnel,and validate it via a test for a main openings of−600 m level in Coal Mine“6.13”,Democratic People's Republic of Korea.The displacement components used for back analysis are the crown settlement and sidewalls convergence monitored at the end of the openings excavation,and the final closures predicted by GVM.The non-linear relation between displacements and back analysis parameters was obtained by artificial neural network(ANN)and Burger-creep viscoplastic(CVISC)model of FLAC3D.Then,the optimal parameters were determined for rock mass surrounding tunnel by genetic algorithm(GA)with both groups of measured displacements at the end of the final excavation and closures predicted by GVM.The maximum absolute error(MAE)and standard deviation(Std)between calculated displacements by numerical simulation with back analysis parameters and in situ ones were less than 6 and 2 mm,respectively.Therefore,it was found that the proposed method could be successfully applied to determining design parameters and stability for tunnels and underground cavities,as well as mine openings and stopes.展开更多
A new method integrating support vector machine (SVM),particle swarm optimization (PSO) and chaotic mapping (CPSO-SVM) was proposed to predict the deformation of tunnel surrounding rock mass.Since chaotic mapping was ...A new method integrating support vector machine (SVM),particle swarm optimization (PSO) and chaotic mapping (CPSO-SVM) was proposed to predict the deformation of tunnel surrounding rock mass.Since chaotic mapping was featured by certainty,ergodicity and stochastic property,it was employed to improve the convergence rate and resulting precision of PSO.The chaotic PSO was adopted in the optimization of the appropriate SVM parameters,such as kernel function and training parameters,improving substantially the generalization ability of SVM.And finally,the integrating method was applied to predict the convergence deformation of the Xiakeng tunnel in China.The results indicate that the proposed method can describe the relationship of deformation time series well and is proved to be more efficient.展开更多
Seventeen coupled general circulation models from the Coupled Model Intercomparison Project Phase 5 （CMIP5） are employed to assess the relationships of interannual variations of sea surface temperature （SST） betwe...Seventeen coupled general circulation models from the Coupled Model Intercomparison Project Phase 5 （CMIP5） are employed to assess the relationships of interannual variations of sea surface temperature （SST） between the tropical Pacific （TP） and tropical Indian Ocean （TIO）. The eastern/central equatorial Pacific features the strongest SST interannual variability in the models except for the model CSIRO-Mk3-6-0, and the simulated maximum and minimum are produced by models GFDL-ESM2M and GISS-E2-H respectively. However, It remains a challenge for these models to simulate the correct climate mean SST with the warm pool-cold tongue structure in the equatorial Pacific. Almost all models reproduce E1 Nifio-Southem Oscillation （ENSO）, Indian Ocean Dipole mode （IOD） and Indian Ocean Basin-wide mode （lOB） together with their seasonal phase lock features being simulated; but the relationship between the ENSO and IOD is different for different models. Consistent with the observation, an Indian Ocean basin-wide warming （cooling） takes place over the tropical Indian Ocean in the spring following an E1 Nifio （La Nifia） in almost all the models. In some models （e.g., GFDL-ESM2G and MIROC5）, positive ENSO and IOB events are stronger than the negative events as shown in the observation. However, this asymmetry is reversed in some other models （e.g., HadGEM2-CC and HadGEM2-ES）.展开更多
The long-term stability of backfill material is the key to retaining roadways successfully. In order to study the rheological deformation of backfill material and its long-term stability, given the visco-elastoplastic...The long-term stability of backfill material is the key to retaining roadways successfully. In order to study the rheological deformation of backfill material and its long-term stability, given the visco-elastoplastic properties of this material, we introduced a softening and a hardening function for a new nonlinear the- ological model with time-varying parameters. Based on this, we presented the instability condition of this model by using the principle of minimum potential energy. Combined with engineering practice, we cal- culated the urlstable time period of backfill material. The results show that the time of instability of the backfill material relate to the initial parameters of the material, ＂the coefficients decided by temperature and the ratio of the plastic zone of the backfill material. Based on the results of our analysis from the point of view of energy, we can quickly obtain the time of instability of this model from our graphical analysis. The time of instability of the backfill material obtained from our investigation coincides with an actual project.展开更多
In this paper, we develop a cellular automaton model to describe the phase transition of traffic flow on urban expressway systems with on-off-ramps and accessory roads. The lane changing rules are given in detailed, t...In this paper, we develop a cellular automaton model to describe the phase transition of traffic flow on urban expressway systems with on-off-ramps and accessory roads. The lane changing rules are given in detailed, the numerical results show that the main road and the accessory road both produce phase transitions. These phase transitions will omen be influenced by the number of lanes, lane changing, the ramp flow, the input flow rate, and the geometry structure.展开更多
Loss of function and gain of function mutations of the sodium channel were investigated using an intact two-dimensional rabbit sinoatrial node (SAN) and atrial cell model. The effects of three external stimuli (acetyl...Loss of function and gain of function mutations of the sodium channel were investigated using an intact two-dimensional rabbit sinoatrial node (SAN) and atrial cell model. The effects of three external stimuli (acetylcholine secretion by the vagal nerve, acid-base concentration, and tissue temperature) on cardiac pacemaker function and conduction were studied. Our results show that these two groups of mutations have different effects on pacemaker function and conduction. Furthermore, we found that the negative effects of these mutations could be altered by external stimuli. The bradycardic effects of mutations were magnified by an increase in acetylcholine level. Changes in acid-base concentration and tissue temperature increased the ability of the SAN to recover its pacemaker function. The results of this study increase our understanding of sodium channel disorders, and help to advance research on the treatment of these conditions.展开更多
A further development of exclusively inverse frequency domain method for leak detection in pipelines is presented and validated.The location and leakage can be determined by analyzing the difference of transient water...A further development of exclusively inverse frequency domain method for leak detection in pipelines is presented and validated.The location and leakage can be determined by analyzing the difference of transient water head response between the simulated and measured data in frequency domain.The transient signals are generated by portion sharp closure of a valve from the small constant opening and it needs only a few meters of water.The discrete boundary conditions and observation data are both transformed in frequency domain by Laplace transform.Example in numerical simulation is studied for demonstration of this approach.The application of the method to an experimental pipeline confirms the analysis and illustrates successful detection of the single pipeline leak.The precalibration approach is presented to minimize the effect of data and model error and it splits the method into two parts.One uses data from a known state to fit the parameters of the model and the other uses data from the current state for the fitting of leak parameters using the now calibrated model.Some important practical parameters such as wave speed,friction in steady and unsteady state and the adaptability of the method are discussed.It was found that the nonlinearity errors associated with valve boundary condition could be prevented by consideration of the induced flow perturbation curve shape.展开更多
The immersed tube tunnel section of the Shenzhen-Zhongshan Link exhibits complex geological conditions and high back sludge strength. The tunnel cushion adopts the gravel and flaky stone combined cushion. The major in...The immersed tube tunnel section of the Shenzhen-Zhongshan Link exhibits complex geological conditions and high back sludge strength. The tunnel cushion adopts the gravel and flaky stone combined cushion. The major influencing factors of the mechanical deformation characteristics of the gravel and flaky stone composite cushion are studied through a physical model experiment. The following results are reported.(1) The load–settlement curves of the flaky stone cushion become more compact with a dense increment under the design load. These curves can be regarded as nonlinear mechanical characteristics. The load–settlement curves of the gravel cushion and the gravel and flaky stone composite cushion exhibit the characteristics of a two-stage linear change.(2) The flatness of the top of flaky stone cushion considerably affects settlement and secant modulus. The flatness of the top of flaky stone should be ensured during construction.(3) Gradation and thickness exert no evident effect on the compressibility of a cushion. The preloading pressure caused by the construction height difference of the cushion materials plays an important role in improving the initial stiffness of a cushion and reducing initial settlement and overall settlement.(4) This study investigates the preloading under 30 kPa of the 0.7-m flaky stone and 1.0-m gravel combination cushion. It recommends the following secant modulus values: 48.89 MPa for the section of 0–30 kPa and 10.47 MPa for the section of 30–110 kPa.展开更多
An integrated nonlinear planning(NLP) model is built for space station long-duration orbital missions considering both the vehicle visiting schedules and the interaction effects between target phasing,vehicle return a...An integrated nonlinear planning(NLP) model is built for space station long-duration orbital missions considering both the vehicle visiting schedules and the interaction effects between target phasing,vehicle return adjusting and Earth observation aiming.A two-level optimization approach is proposed to solve this complicated problem.The up-level problem employs the launch times of visiting vehicles as design variables,considers the constraints of crew rotations,resource resupplies and rendezvous launch windows,and is solved by a genetic algorithm.The low-level problems employ the maneuver impulses and burn times within each orbital mission as design variables,and a high-efficient shooting iteration method is proposed based on an analytical equation for the phase angle correction considering the J 2 perturbation.The results indicate that the integrated NLP model for space station long-duration orbital missions is effective,and the proposed optimization approach can obtain the optimal solutions that satisfy the multiple constraints and reduce the total propellant consumption.展开更多
文摘In this paper, two cellular automata traffic models are proposed to simulate the operation of an expressway. The results show that the flow rate and the average velocity are generally equal in the same density which is different among the lanes. The analysis of lane changing times and the velocity total deviation show some characteristics which are difficult to explain phase transitions under fundamental diagram theory. Therefore,the concept of lane changing probability is introduced, and it is concluded that the speed-limit rule can reduce the motivation of lane changing effectively.
基金Project(51378510)supported by National Natural Science Foundation of China。
文摘This paper presents a risk evaluation model of water and mud inrush for tunnel excavation in karst areas.The factors affecting the probabilities of water and mud inrush in karst tunnels are investigated to define the dangerousness of this geological disaster.The losses that are caused by water and mud inrush are taken into consideration to account for its harmfulness.Then a risk evaluation model based on the dangerousness-harmfulness evaluation indicator system is constructed,which is more convincing in comparison with the traditional methods.The catastrophe theory is used to evaluate the risk level of water and mud inrush and it has great advantage in handling problems involving discontinuous catastrophe processes.To validate the proposed approach,the Qiyueshan tunnel of Yichang-Wanzhou Railway is taken as an example in which four target segments are evaluated using the risk evaluation model.Finally,the evaluation results are compared with the excavation data,which shows that the risk levels predicted by the proposed approach are in good agreements with that observed in engineering.In conclusion,the catastrophe theory-based risk evaluation model is an efficient and effective approach for water and mud inrush in karst tunnels.
基金Supported by Open Foundation Project of Education Ministry Key Laboratory about Mine Disaster Prevention and Control(MDPC0811)Research Project"Spring Bud Plan"of Shandong University of Science and TechnologyShandong University of Science and Technology Innovation Fund Grant(yca2008-04-01)
文摘By the generalized Kelvin creep model,rheological characteristics of deep softrock and long-term mechanical behaviors of support structures were simulated.Mechanicaldeformation characteristics of support structures under different lining circumstanceswere also analyzed on the basis of deducing the relationship between the generalizedKelvin creep model and implicit creep equations in ANSYS FEM software.The resultsshow that high stress of deep tunnels is the main factor in creep damage;the surroundingrock's deformation binding effect due to lining increases as the thickness increases but theeffect becomes very weak when it increases to a certain value;contact pressure on thelining decreases as its thickness decreases.
基金Project(32-41)supported by the National Science and Technical Development Foundation of DPR of Korea。
文摘In this paper,we present a new method of intelligent back analysis(IBA)using grey Verhulst model(GVM)to identify geotechnical parameters of rock mass surrounding tunnel,and validate it via a test for a main openings of−600 m level in Coal Mine“6.13”,Democratic People's Republic of Korea.The displacement components used for back analysis are the crown settlement and sidewalls convergence monitored at the end of the openings excavation,and the final closures predicted by GVM.The non-linear relation between displacements and back analysis parameters was obtained by artificial neural network(ANN)and Burger-creep viscoplastic(CVISC)model of FLAC3D.Then,the optimal parameters were determined for rock mass surrounding tunnel by genetic algorithm(GA)with both groups of measured displacements at the end of the final excavation and closures predicted by GVM.The maximum absolute error(MAE)and standard deviation(Std)between calculated displacements by numerical simulation with back analysis parameters and in situ ones were less than 6 and 2 mm,respectively.Therefore,it was found that the proposed method could be successfully applied to determining design parameters and stability for tunnels and underground cavities,as well as mine openings and stopes.
基金Project(NCET-08-0662)supported by Program for New Century Excellent Talents in University of ChinaProject(2010CB732006)supported by the Special Funds for the National Basic Research Program of ChinaProjects(51178187,41072224)supported by the National Natural Science Foundation of China
文摘A new method integrating support vector machine (SVM),particle swarm optimization (PSO) and chaotic mapping (CPSO-SVM) was proposed to predict the deformation of tunnel surrounding rock mass.Since chaotic mapping was featured by certainty,ergodicity and stochastic property,it was employed to improve the convergence rate and resulting precision of PSO.The chaotic PSO was adopted in the optimization of the appropriate SVM parameters,such as kernel function and training parameters,improving substantially the generalization ability of SVM.And finally,the integrating method was applied to predict the convergence deformation of the Xiakeng tunnel in China.The results indicate that the proposed method can describe the relationship of deformation time series well and is proved to be more efficient.
基金supported by the National Basic Research Program of China 2012CB955602 and 2012CB955603the Natural Science Foundation of China(41176006,40921004 and 41106010)
文摘Seventeen coupled general circulation models from the Coupled Model Intercomparison Project Phase 5 （CMIP5） are employed to assess the relationships of interannual variations of sea surface temperature （SST） between the tropical Pacific （TP） and tropical Indian Ocean （TIO）. The eastern/central equatorial Pacific features the strongest SST interannual variability in the models except for the model CSIRO-Mk3-6-0, and the simulated maximum and minimum are produced by models GFDL-ESM2M and GISS-E2-H respectively. However, It remains a challenge for these models to simulate the correct climate mean SST with the warm pool-cold tongue structure in the equatorial Pacific. Almost all models reproduce E1 Nifio-Southem Oscillation （ENSO）, Indian Ocean Dipole mode （IOD） and Indian Ocean Basin-wide mode （lOB） together with their seasonal phase lock features being simulated; but the relationship between the ENSO and IOD is different for different models. Consistent with the observation, an Indian Ocean basin-wide warming （cooling） takes place over the tropical Indian Ocean in the spring following an E1 Nifio （La Nifia） in almost all the models. In some models （e.g., GFDL-ESM2G and MIROC5）, positive ENSO and IOB events are stronger than the negative events as shown in the observation. However, this asymmetry is reversed in some other models （e.g., HadGEM2-CC and HadGEM2-ES）.
基金Project (No. 50874089) is supported by the National Natural Science Foundation of ChinaProject (No. 20096121110002) by the College of Doctoral Foundation of the Ministry of Education the Scientific Research Program Funded by Shaanxi Provincial Education Commission (No. 2010JK692)
文摘The long-term stability of backfill material is the key to retaining roadways successfully. In order to study the rheological deformation of backfill material and its long-term stability, given the visco-elastoplastic properties of this material, we introduced a softening and a hardening function for a new nonlinear the- ological model with time-varying parameters. Based on this, we presented the instability condition of this model by using the principle of minimum potential energy. Combined with engineering practice, we cal- culated the urlstable time period of backfill material. The results show that the time of instability of the backfill material relate to the initial parameters of the material, ＂the coefficients decided by temperature and the ratio of the plastic zone of the backfill material. Based on the results of our analysis from the point of view of energy, we can quickly obtain the time of instability of this model from our graphical analysis. The time of instability of the backfill material obtained from our investigation coincides with an actual project.
基金Supported by grants from the Humanities and Social Sciences Foundation of Ministry of Education of China under Grant No. 09YJC790193Funding Project for Academic Human Resources Development in Institutions of Higher Learning Under the Jurisdiction of Beijing Municipality the Research Funds of Capital University of Economics and Business under Grant No. 00591056721621the National Natural Science Foundation of China under Grant No. 70971007
文摘In this paper, we develop a cellular automaton model to describe the phase transition of traffic flow on urban expressway systems with on-off-ramps and accessory roads. The lane changing rules are given in detailed, the numerical results show that the main road and the accessory road both produce phase transitions. These phase transitions will omen be influenced by the number of lanes, lane changing, the ramp flow, the input flow rate, and the geometry structure.
基金supported by the National Natural Science Foundation for Theoretical Physics of China (11047017)the Wellcome Trust (081808/Z/06/Z)+1 种基金the Biotechnology and Biological Sciences Research Council (BBS/B1678X), UKthe Special Foundation of Education of Anhui Province for Excellent Young Scientists (2011SQRL023)
文摘Loss of function and gain of function mutations of the sodium channel were investigated using an intact two-dimensional rabbit sinoatrial node (SAN) and atrial cell model. The effects of three external stimuli (acetylcholine secretion by the vagal nerve, acid-base concentration, and tissue temperature) on cardiac pacemaker function and conduction were studied. Our results show that these two groups of mutations have different effects on pacemaker function and conduction. Furthermore, we found that the negative effects of these mutations could be altered by external stimuli. The bradycardic effects of mutations were magnified by an increase in acetylcholine level. Changes in acid-base concentration and tissue temperature increased the ability of the SAN to recover its pacemaker function. The results of this study increase our understanding of sodium channel disorders, and help to advance research on the treatment of these conditions.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51109230, 50679085)the Special Funds of IWHR (Grant No. 0912)
文摘A further development of exclusively inverse frequency domain method for leak detection in pipelines is presented and validated.The location and leakage can be determined by analyzing the difference of transient water head response between the simulated and measured data in frequency domain.The transient signals are generated by portion sharp closure of a valve from the small constant opening and it needs only a few meters of water.The discrete boundary conditions and observation data are both transformed in frequency domain by Laplace transform.Example in numerical simulation is studied for demonstration of this approach.The application of the method to an experimental pipeline confirms the analysis and illustrates successful detection of the single pipeline leak.The precalibration approach is presented to minimize the effect of data and model error and it splits the method into two parts.One uses data from a known state to fit the parameters of the model and the other uses data from the current state for the fitting of leak parameters using the now calibrated model.Some important practical parameters such as wave speed,friction in steady and unsteady state and the adaptability of the method are discussed.It was found that the nonlinearity errors associated with valve boundary condition could be prevented by consideration of the induced flow perturbation curve shape.
基金supported by the National Key Research and Development Program of China(Nos.2018YFC0809600 and 2018YFC0809602)。
文摘The immersed tube tunnel section of the Shenzhen-Zhongshan Link exhibits complex geological conditions and high back sludge strength. The tunnel cushion adopts the gravel and flaky stone combined cushion. The major influencing factors of the mechanical deformation characteristics of the gravel and flaky stone composite cushion are studied through a physical model experiment. The following results are reported.(1) The load–settlement curves of the flaky stone cushion become more compact with a dense increment under the design load. These curves can be regarded as nonlinear mechanical characteristics. The load–settlement curves of the gravel cushion and the gravel and flaky stone composite cushion exhibit the characteristics of a two-stage linear change.(2) The flatness of the top of flaky stone cushion considerably affects settlement and secant modulus. The flatness of the top of flaky stone should be ensured during construction.(3) Gradation and thickness exert no evident effect on the compressibility of a cushion. The preloading pressure caused by the construction height difference of the cushion materials plays an important role in improving the initial stiffness of a cushion and reducing initial settlement and overall settlement.(4) This study investigates the preloading under 30 kPa of the 0.7-m flaky stone and 1.0-m gravel combination cushion. It recommends the following secant modulus values: 48.89 MPa for the section of 0–30 kPa and 10.47 MPa for the section of 30–110 kPa.
基金supported by the National Natural Science Foundation of China(Grant No.11222215)the Foundation for the Author of National Excellent Doctoral Dissertation of China(Grant No.201171)
文摘An integrated nonlinear planning(NLP) model is built for space station long-duration orbital missions considering both the vehicle visiting schedules and the interaction effects between target phasing,vehicle return adjusting and Earth observation aiming.A two-level optimization approach is proposed to solve this complicated problem.The up-level problem employs the launch times of visiting vehicles as design variables,considers the constraints of crew rotations,resource resupplies and rendezvous launch windows,and is solved by a genetic algorithm.The low-level problems employ the maneuver impulses and burn times within each orbital mission as design variables,and a high-efficient shooting iteration method is proposed based on an analytical equation for the phase angle correction considering the J 2 perturbation.The results indicate that the integrated NLP model for space station long-duration orbital missions is effective,and the proposed optimization approach can obtain the optimal solutions that satisfy the multiple constraints and reduce the total propellant consumption.
