In order to optimize the atmospheric tower overhead low-temperature system,the physical parameters,multiphase composition,aqueous dew point temperature,and ammonium salt crystallization temperature are simulated with ...In order to optimize the atmospheric tower overhead low-temperature system,the physical parameters,multiphase composition,aqueous dew point temperature,and ammonium salt crystallization temperature are simulated with process simulation software.The temperature distribution in overhead heat exchanger is calculated by heat transfer calculation.The special parts with elbows near the inlet and outlet of heat exchanger are studied by fluid field analysis.Results indicate that under current operating conditions,the aqueous dew point temperature and initial crystallization temperature of NH4Cl are 91°C and 128°C,respectively.Ammonium salt appears in the distillation tower and liquid water occurs in heat exchanger tubes,in which the dew point induced corrosion is the most direct factor for heat exchanger corrosion.In the heat exchanger,condensate water appearing in the area 2.7 meters away from the bundle inlet can give rise to corrosion risk under the moist NH4Cl and high concentration of acidic solution circumstance.For the pipes and elbows located near the inlet and the outlet of heat exchanger,the flow field presents an unsymmetrical distribution.High risk areas are mainly concentrated on the external bend of elbows where the liquid water concentration is higher.The coupling of simulation methods established thereby is approved as an effective way to evaluate the corrosion risk in the atmospheric column overhead system and can provide a scientific basis for corrosion control.展开更多
Today, the growth of aerospace industry has led to the development of modular overhead systems that can be applied to a wide variety of aircraft.?It actually maximizes training effectiveness by working in a similar wa...Today, the growth of aerospace industry has led to the development of modular overhead systems that can be applied to a wide variety of aircraft.?It actually maximizes training effectiveness by working in a similar way as to the real aircraft maneuverability. Overhead system control device for aircraft simulator is developed as a module and integrated to the flight simulator. The developed system can replace the similar products imported from overseas at a much lower price, about one third of the imports, while maintaining the same level of functionality and the performance with the counterparts. This price advantage is the main motivation of this development, which is expected to enlarge the commercial training simulator market in our country. This development has been also funded by the government, and we invited several commercial airline pilots to test the equipment. The post operation interview revealed that the developed system at least matches or exceeds the performance of the imported products. With the development completed, it is ready for the commercial production and will help promote the expansion of flight training education at various aerospace universities in Korea.展开更多
Optimizing Flow Path Design(FPD)is a popular research area in transportation system design,but its application to Overhead Transportation Systems(OTSs)has been limited.This study focuses on optimizing a double-spine f...Optimizing Flow Path Design(FPD)is a popular research area in transportation system design,but its application to Overhead Transportation Systems(OTSs)has been limited.This study focuses on optimizing a double-spine flow path design for OTSs with 10 stations by minimizing the total travel distance for both loaded and empty flows.We employ transportation methods,specifically the North-West Corner and Stepping-Stone methods,to determine empty vehicle travel flows.Additionally,the Tabu Search(TS)algorithm is applied to branch the 10 stations into two main layout branches.The results obtained from our proposed method demonstrate a reduction in the objective function value compared to the initial feasible solution.Furthermore,we explore howchanges in the parameters of the TS algorithm affect the optimal result.We validate the feasibility of our approach by comparing it with relevant literature and conducting additional tests on layouts with 20 and 30 stations.展开更多
Heavy routing overhead in Mobile Ad hoc Network(MANET)is a main bottleneck limiting the network performance.In this paper,we propose a novel Clustering OLSR(C-OLSR)approach,which utilizes two schemes,i.e.,clustering a...Heavy routing overhead in Mobile Ad hoc Network(MANET)is a main bottleneck limiting the network performance.In this paper,we propose a novel Clustering OLSR(C-OLSR)approach,which utilizes two schemes,i.e.,clustering and optimized Topology Control(TC)message transfer to reduce the control overhead of OLSR while guaranteeing its realtime requirement.To reduce the control overhead,in C-LOSR,flooding of TC messages is only limited in the cluster.All TC messages are integrated into a Cluster Topology Control(CTC)message by the cluster header and broadcast over the network.To satisfy the real-time requirement,any topology change will trigger CTC messages over the network.Extensive simulations have been done to evaluate the performance of the proposed C-OLSR.Results show that C-OLSR can achieve lower control overhead than OLSR by 44.32%in static networks and by 23.21%in dynamic networks.展开更多
Purpose–Adding an appropriate pre-sag to the geometry of simple catenary systems for electric railways can improve their performance in dynamic interaction with the pantographs of trains operating under them.The valu...Purpose–Adding an appropriate pre-sag to the geometry of simple catenary systems for electric railways can improve their performance in dynamic interaction with the pantographs of trains operating under them.The value of pre-sag can be obtained by empirical approximation or computationally expensive optimisation.This study aims to define a simple but accurate method to determine a suitable pre-sag without dynamic simulations and to find its limitations.Design/methodology/approach–A quasi-static method to determine the ideal value of pre-sag is described based on elasticity variations.It considers variations of the static contact force.The limits of this method are investigated by comparing it to a parametric dynamic simulation study.In the dynamic simulation,an optimal level of pre-sag is identified for each contact force level.The influence of the speed in the dynamic simulation results is expressed in two parameters:the quasi-static influence in the mean contact force and the dynamic influence in the ratio between the vehicle speed and the wave propagation speed in the contact wire.Findings–The comparison between the suggested method and the dynamic simulations shows a high consistency up to a speed limit of around 40%of the wave propagation speed.The best agreement with the dynamic results is achieved by calculating the optimal pre-sag based on the absolute elasticity variation.Practical implications–The simplified approach for determining the pre-sag is valid for low-speed applications,such as suburban railway lines.For these cases,a highly suitable geometry can be obtained with the suggested method,meaning a significantly reduced computational effort.As a case study for this work,the results are applied to a Swedish suburban rail line upgrade case.Originality/value–The static uplift force is added as a varied parameter in dynamic simulations.The shift in system behaviour from low to high dynamics is described,and how the benefits from pre-sag are visible and then disappear.The limit value of the low-dynamics regime is identified to be 40%.展开更多
A pH predictive model based on acid–base equilibria and ion equilibria was proposed to calculate the pH value of the overhead condensing system of crude distillation unit. The pH model could be used to predict the ap...A pH predictive model based on acid–base equilibria and ion equilibria was proposed to calculate the pH value of the overhead condensing system of crude distillation unit. The pH model could be used to predict the appropriate amounts of neutralizers by measuring the Cl-ion concentration of the overhead knockout drum. The pH values of various neutralized streams were estimated by this model. The results showed that the predicted pH values were in good agreement with the experimental ones. The trend of the corrosion inhibition efficiency decreases in the following order: ethylenediamine > N,Ndimethylethanolamine> triethylamine > 3-methoxypropylamine > morpholine. The difficulty in the accurate control of corrosion was solved, and a good instruction was provided for mitigating corrosion in refinery.展开更多
In this paper, an adaptive proportional-derivative sliding mode control(APD-SMC) law, is proposed for 2D underactuated overhead crane systems. The proposed controller has the advantages of simple structure, easy to im...In this paper, an adaptive proportional-derivative sliding mode control(APD-SMC) law, is proposed for 2D underactuated overhead crane systems. The proposed controller has the advantages of simple structure, easy to implement of PD control, strong robustness of SMC with respect to external disturbances and uncertain system parameters, and adaptation for unknown system dynamics associated with the feedforward parts. In the proposed APD-SMC law, the PD control part is used to stabilize the controlled system, the SMC part is used to compensate the external disturbances and system uncertainties,and the adaptive control part is utilized to estimate the unknown system parameters. The coupling behavior between the trolley movement and the payload swing is enhanced and, therefore, the transient performance of the proposed controller is improved.The Lyapunov techniques and the La Salle's invariance theorem are employed in to support the theoretical derivations. Experimental results are provided to validate the superior performance of the proposed control law.展开更多
Owing to the potential for intercell cochannel interference mitigation and significant spectral efficiency improvement, coordinating transmission techniques by multiple radio access points have recently attracted a lo...Owing to the potential for intercell cochannel interference mitigation and significant spectral efficiency improvement, coordinating transmission techniques by multiple radio access points have recently attracted a lot of attention. In this paper, the system structure and mathematical signal model based on clustered structure are presented for multipoint coordinating downlink transmission, the clustered supercell configurations with static/dynamic approaches are discussed, and then optimal precod- ing design is provided for an accepted level of scheduling complexity and reduced signaling over- head. Some simulation results are given to evaluate the performance of different cell-clustering approaches, and to show that a clustered supercell size of 7 is a reasonable choice for clustered coordination with the given transmit power and the reduced feedback.展开更多
It is important for the safety of transmission system to accurately calculate single-phase earth fault current distribution.Features of double sided elimination method were illustrated.Quantitative calculation of sing...It is important for the safety of transmission system to accurately calculate single-phase earth fault current distribution.Features of double sided elimination method were illustrated.Quantitative calculation of single-phase earth fault current distribution and case verification were accomplished by using the loop method.Influences of some factors,such as single-phase earth fault location and ground resistance of poles,on short-circuit current distribution were discussed.Results show that:1) results of the loop method conform to those of double sided elimination method;2) the fault location hardly influences macro-distribution of short-circuit current.However,current near fault location is evidently influenced;and 3) the short-circuit current distribution is not so sensitive to the ground resistance of poles.展开更多
The seismic damage to ancillary facilities on high-speed railway(HSR)bridges can affect the normal movement of trains.To propose the bridge deck acceleration response spectra of the typical HSR simply-supported girder...The seismic damage to ancillary facilities on high-speed railway(HSR)bridges can affect the normal movement of trains.To propose the bridge deck acceleration response spectra of the typical HSR simply-supported girder bridge for simplifying the seismic responses analysis of the facilities on bridges,the finite element models of the HSR multi-span simply-supported girder bridges with CRTSII track were established,and the numerical model was validated by tests.Besides,the effects of the span number,peak ground acceleration(PGA),pier height on the seismic acceleration and response spectra of the bridge deck were investigated.Afterward,the bridge acceleration amplification factor curves and bridge deck response spectra with different PGAs and pier heights were obtained.The formula for bridge deck acceleration amplification factor,with a 95%guarantee rate,was fitted.Moreover,the finite element models of the overhead contact lines(OCL)mounted on rigid base and bridges were established to validate the fitted formula.The results indicated that the maximum seismic acceleration response is in the midspan of the beam.The proposed formula for the bridge deck acceleration response spectra can be used to analyze the earthquake response of the OCL and other ancillary facilities on HSR simply-supported girder bridges.The bridge deck acceleration response spectra are conservative in terms of structural safety and can significantly improving the analysis efficiency.展开更多
Electrical power transmission is dominated by overhead line systems at present.This is mainly based on more than hundred years of experience of utilities in running overhead lines.Furthermore,overhead lines have prove...Electrical power transmission is dominated by overhead line systems at present.This is mainly based on more than hundred years of experience of utilities in running overhead lines.Furthermore,overhead lines have proven their operational reliability and functional assurance.In the past,cables were used in distribution networks in urban areas for the most part with the exception of direct current submarine cables.New developments of high voltage XLPE cables make it possible to use this technology for EHV level applications in transmission networks.Within this paper,mixed network configurations,consisting of overhead lines and high voltage cables,are investigated.An exemplary EHV transmission line with a total length of about 100 km,which is quite typical for Central Europe,has been studied.Several different line combinations are discussed with varied rates between overhead line sections and cable sections length in practice.The length of the cable sections are ranging from several kilometers up to lengths of 100 km.In this paper the work focuses on the transient behavior of combined 400 kV overhead and cable lines during switching processes and lightning impacts.A number of calculations were carried out to get an overview of the transient stress in numerous network nodes along the transmission system.Numerical programs like ATP/EMTP have been used for these simulations.Peak values and wave shapes of the transient voltage stress have been evaluated,based on different systems and within possible combinations.In respect of the insulation coordination and transient stress at network nodes,the voltage-time trends are also analyzed.The combination of high voltage overhead and cable transmission systems,especially such with lengths of more than about 50 km,are making tightened and extended demands to the network design,to the operational management and of course to the network protection also.As an output of this investigations,the results might influence the strategy in running this new type of combined transmission systems.展开更多
基金This research was financially supported by the scientific research project through the SINOPEC Science and Technology Division(Contract No.318021-8).
文摘In order to optimize the atmospheric tower overhead low-temperature system,the physical parameters,multiphase composition,aqueous dew point temperature,and ammonium salt crystallization temperature are simulated with process simulation software.The temperature distribution in overhead heat exchanger is calculated by heat transfer calculation.The special parts with elbows near the inlet and outlet of heat exchanger are studied by fluid field analysis.Results indicate that under current operating conditions,the aqueous dew point temperature and initial crystallization temperature of NH4Cl are 91°C and 128°C,respectively.Ammonium salt appears in the distillation tower and liquid water occurs in heat exchanger tubes,in which the dew point induced corrosion is the most direct factor for heat exchanger corrosion.In the heat exchanger,condensate water appearing in the area 2.7 meters away from the bundle inlet can give rise to corrosion risk under the moist NH4Cl and high concentration of acidic solution circumstance.For the pipes and elbows located near the inlet and the outlet of heat exchanger,the flow field presents an unsymmetrical distribution.High risk areas are mainly concentrated on the external bend of elbows where the liquid water concentration is higher.The coupling of simulation methods established thereby is approved as an effective way to evaluate the corrosion risk in the atmospheric column overhead system and can provide a scientific basis for corrosion control.
文摘Today, the growth of aerospace industry has led to the development of modular overhead systems that can be applied to a wide variety of aircraft.?It actually maximizes training effectiveness by working in a similar way as to the real aircraft maneuverability. Overhead system control device for aircraft simulator is developed as a module and integrated to the flight simulator. The developed system can replace the similar products imported from overseas at a much lower price, about one third of the imports, while maintaining the same level of functionality and the performance with the counterparts. This price advantage is the main motivation of this development, which is expected to enlarge the commercial training simulator market in our country. This development has been also funded by the government, and we invited several commercial airline pilots to test the equipment. The post operation interview revealed that the developed system at least matches or exceeds the performance of the imported products. With the development completed, it is ready for the commercial production and will help promote the expansion of flight training education at various aerospace universities in Korea.
基金funded by Ho Chi Minh City University of Technology(HCMUT),VNU-HCM under Grant Number B2021-20-04.
文摘Optimizing Flow Path Design(FPD)is a popular research area in transportation system design,but its application to Overhead Transportation Systems(OTSs)has been limited.This study focuses on optimizing a double-spine flow path design for OTSs with 10 stations by minimizing the total travel distance for both loaded and empty flows.We employ transportation methods,specifically the North-West Corner and Stepping-Stone methods,to determine empty vehicle travel flows.Additionally,the Tabu Search(TS)algorithm is applied to branch the 10 stations into two main layout branches.The results obtained from our proposed method demonstrate a reduction in the objective function value compared to the initial feasible solution.Furthermore,we explore howchanges in the parameters of the TS algorithm affect the optimal result.We validate the feasibility of our approach by comparing it with relevant literature and conducting additional tests on layouts with 20 and 30 stations.
文摘Heavy routing overhead in Mobile Ad hoc Network(MANET)is a main bottleneck limiting the network performance.In this paper,we propose a novel Clustering OLSR(C-OLSR)approach,which utilizes two schemes,i.e.,clustering and optimized Topology Control(TC)message transfer to reduce the control overhead of OLSR while guaranteeing its realtime requirement.To reduce the control overhead,in C-LOSR,flooding of TC messages is only limited in the cluster.All TC messages are integrated into a Cluster Topology Control(CTC)message by the cluster header and broadcast over the network.To satisfy the real-time requirement,any topology change will trigger CTC messages over the network.Extensive simulations have been done to evaluate the performance of the proposed C-OLSR.Results show that C-OLSR can achieve lower control overhead than OLSR by 44.32%in static networks and by 23.21%in dynamic networks.
基金Trafikföorvaltningen Region Stockholm and Trafikverket for funding and supporting this study.
文摘Purpose–Adding an appropriate pre-sag to the geometry of simple catenary systems for electric railways can improve their performance in dynamic interaction with the pantographs of trains operating under them.The value of pre-sag can be obtained by empirical approximation or computationally expensive optimisation.This study aims to define a simple but accurate method to determine a suitable pre-sag without dynamic simulations and to find its limitations.Design/methodology/approach–A quasi-static method to determine the ideal value of pre-sag is described based on elasticity variations.It considers variations of the static contact force.The limits of this method are investigated by comparing it to a parametric dynamic simulation study.In the dynamic simulation,an optimal level of pre-sag is identified for each contact force level.The influence of the speed in the dynamic simulation results is expressed in two parameters:the quasi-static influence in the mean contact force and the dynamic influence in the ratio between the vehicle speed and the wave propagation speed in the contact wire.Findings–The comparison between the suggested method and the dynamic simulations shows a high consistency up to a speed limit of around 40%of the wave propagation speed.The best agreement with the dynamic results is achieved by calculating the optimal pre-sag based on the absolute elasticity variation.Practical implications–The simplified approach for determining the pre-sag is valid for low-speed applications,such as suburban railway lines.For these cases,a highly suitable geometry can be obtained with the suggested method,meaning a significantly reduced computational effort.As a case study for this work,the results are applied to a Swedish suburban rail line upgrade case.Originality/value–The static uplift force is added as a varied parameter in dynamic simulations.The shift in system behaviour from low to high dynamics is described,and how the benefits from pre-sag are visible and then disappear.The limit value of the low-dynamics regime is identified to be 40%.
基金supported by the PetroChina Company Limited (20151191)
文摘A pH predictive model based on acid–base equilibria and ion equilibria was proposed to calculate the pH value of the overhead condensing system of crude distillation unit. The pH model could be used to predict the appropriate amounts of neutralizers by measuring the Cl-ion concentration of the overhead knockout drum. The pH values of various neutralized streams were estimated by this model. The results showed that the predicted pH values were in good agreement with the experimental ones. The trend of the corrosion inhibition efficiency decreases in the following order: ethylenediamine > N,Ndimethylethanolamine> triethylamine > 3-methoxypropylamine > morpholine. The difficulty in the accurate control of corrosion was solved, and a good instruction was provided for mitigating corrosion in refinery.
基金supported in part by the National High Technology Research and Development Program of China(863 Program)(2015AA042307)Shandong Provincial Scientific and Technological Development Foundation(2014GGX103038)+3 种基金Shandong Provincial Independent Innovation and Achievement Transformation Special Foundation(2015ZDXX0101E01)National Natural Science Fundation of China(NSFC)Joint Fund of Shandong Province(U1706228)the Fundamental Research Funds of Shandong University(2015JC027)
文摘In this paper, an adaptive proportional-derivative sliding mode control(APD-SMC) law, is proposed for 2D underactuated overhead crane systems. The proposed controller has the advantages of simple structure, easy to implement of PD control, strong robustness of SMC with respect to external disturbances and uncertain system parameters, and adaptation for unknown system dynamics associated with the feedforward parts. In the proposed APD-SMC law, the PD control part is used to stabilize the controlled system, the SMC part is used to compensate the external disturbances and system uncertainties,and the adaptive control part is utilized to estimate the unknown system parameters. The coupling behavior between the trolley movement and the payload swing is enhanced and, therefore, the transient performance of the proposed controller is improved.The Lyapunov techniques and the La Salle's invariance theorem are employed in to support the theoretical derivations. Experimental results are provided to validate the superior performance of the proposed control law.
文摘Owing to the potential for intercell cochannel interference mitigation and significant spectral efficiency improvement, coordinating transmission techniques by multiple radio access points have recently attracted a lot of attention. In this paper, the system structure and mathematical signal model based on clustered structure are presented for multipoint coordinating downlink transmission, the clustered supercell configurations with static/dynamic approaches are discussed, and then optimal precod- ing design is provided for an accepted level of scheduling complexity and reduced signaling over- head. Some simulation results are given to evaluate the performance of different cell-clustering approaches, and to show that a clustered supercell size of 7 is a reasonable choice for clustered coordination with the given transmit power and the reduced feedback.
文摘It is important for the safety of transmission system to accurately calculate single-phase earth fault current distribution.Features of double sided elimination method were illustrated.Quantitative calculation of single-phase earth fault current distribution and case verification were accomplished by using the loop method.Influences of some factors,such as single-phase earth fault location and ground resistance of poles,on short-circuit current distribution were discussed.Results show that:1) results of the loop method conform to those of double sided elimination method;2) the fault location hardly influences macro-distribution of short-circuit current.However,current near fault location is evidently influenced;and 3) the short-circuit current distribution is not so sensitive to the ground resistance of poles.
基金Project(HNTY2022K03)supported by the Hunan Tieyuan Civil Engineering Testing Co.,Ltd.,ChinaProject(52478573)supported by the National Natural Science Foundation of China。
文摘The seismic damage to ancillary facilities on high-speed railway(HSR)bridges can affect the normal movement of trains.To propose the bridge deck acceleration response spectra of the typical HSR simply-supported girder bridge for simplifying the seismic responses analysis of the facilities on bridges,the finite element models of the HSR multi-span simply-supported girder bridges with CRTSII track were established,and the numerical model was validated by tests.Besides,the effects of the span number,peak ground acceleration(PGA),pier height on the seismic acceleration and response spectra of the bridge deck were investigated.Afterward,the bridge acceleration amplification factor curves and bridge deck response spectra with different PGAs and pier heights were obtained.The formula for bridge deck acceleration amplification factor,with a 95%guarantee rate,was fitted.Moreover,the finite element models of the overhead contact lines(OCL)mounted on rigid base and bridges were established to validate the fitted formula.The results indicated that the maximum seismic acceleration response is in the midspan of the beam.The proposed formula for the bridge deck acceleration response spectra can be used to analyze the earthquake response of the OCL and other ancillary facilities on HSR simply-supported girder bridges.The bridge deck acceleration response spectra are conservative in terms of structural safety and can significantly improving the analysis efficiency.
文摘Electrical power transmission is dominated by overhead line systems at present.This is mainly based on more than hundred years of experience of utilities in running overhead lines.Furthermore,overhead lines have proven their operational reliability and functional assurance.In the past,cables were used in distribution networks in urban areas for the most part with the exception of direct current submarine cables.New developments of high voltage XLPE cables make it possible to use this technology for EHV level applications in transmission networks.Within this paper,mixed network configurations,consisting of overhead lines and high voltage cables,are investigated.An exemplary EHV transmission line with a total length of about 100 km,which is quite typical for Central Europe,has been studied.Several different line combinations are discussed with varied rates between overhead line sections and cable sections length in practice.The length of the cable sections are ranging from several kilometers up to lengths of 100 km.In this paper the work focuses on the transient behavior of combined 400 kV overhead and cable lines during switching processes and lightning impacts.A number of calculations were carried out to get an overview of the transient stress in numerous network nodes along the transmission system.Numerical programs like ATP/EMTP have been used for these simulations.Peak values and wave shapes of the transient voltage stress have been evaluated,based on different systems and within possible combinations.In respect of the insulation coordination and transient stress at network nodes,the voltage-time trends are also analyzed.The combination of high voltage overhead and cable transmission systems,especially such with lengths of more than about 50 km,are making tightened and extended demands to the network design,to the operational management and of course to the network protection also.As an output of this investigations,the results might influence the strategy in running this new type of combined transmission systems.
