Large goods transported in railway are kinds of special goods and they are very important in national construction. In order to transport safely, loading and reinforcing schemes must be made first. How to design a rea...Large goods transported in railway are kinds of special goods and they are very important in national construction. In order to transport safely, loading and reinforcing schemes must be made first. How to design a reasonable scheme will be affected by many factors. This paper presents the characteristic of the large goods, summarizes the process of designing a loading and reinforcing scheme of large good, then probes the factors of affecting the loading and reinforcing scheme and gives a detail analysis. It’s considered that those out-of-gauge and overweight degree of goods, center-of- gravity height of a loaded wagon, position of center-of-gravity of goods, type of wagon for using, reinforcement material and reinforcement method, transport expense and transport organization could affect a scheme in the aspects of safety, economy, rapidity and convenience. This conclusion will instruct and help to make a good scheme.展开更多
The ability of power system to survive the transition from preloading state to the gradual increase in load and thereafter reach an acceptable operational condition is an indication of transient stability of the syste...The ability of power system to survive the transition from preloading state to the gradual increase in load and thereafter reach an acceptable operational condition is an indication of transient stability of the system. The study analyzed load shedding scheme through the use of empirical measurement tools and load-flow simulation techniques. It was geared towards determining effective load shedding strategies to reduce unnecessary overload in order to achieve dynamic stability of the electric power network in the Export Free Trade Zone, Calabar, Nigeria. From the tests and the measurements taken, it was observed that the real and reactive powers from the generator and the mechanical power from the turbine engine were stable when the load shedding controller was switched on, as compared to when it was off. The engine speed, the bus-bar frequency and the output voltage of the generator stabilized within a shorter time (about 8 seconds) when the controller was switched on than when it was on the off condition. Also, there were noticeable fluctuations in the speed of the remaining two generators. It became stable at about 12 seconds after the loss. The variations were 0.3 per cent of the nominal speed value. The excitation voltage fluctuated from 1.2 (pu) to 4.5 (pu) when the bus voltage dipped as a result of additional load. It then came down and stabilized at 1.8 (pu) after few swings. This confirmed that the stability of power system is much enhanced when load shedding controllers are effectively configured on the network.展开更多
It is pointed out that to numerically estimate the effective properties and local fields of matrix-inclusion composites,a commonly adopted method is accompanied with some serious draw- backs.We call this method the no...It is pointed out that to numerically estimate the effective properties and local fields of matrix-inclusion composites,a commonly adopted method is accompanied with some serious draw- backs.We call this method the nominal loading scheme(NLS),which considers the actual inclusion distribution inside a finite domain,Ω say,treats the external domain of Ω to be of the pure matrix ma- terial,and imposes the actural traction,σ~∞ say on the remote boundary.It thus gives rise to the fol- lowing basic problems:(i)Can NLS be improved remarkably just by adjusting σ~∞?(it)What is the relationship between the size of Ω and the,scale of inclusions?(iii)Which choice is better in calculating the effective properties,the whole domain Ω or an appropriately selected sub-domain of Ω? Targeting these problems,the equivalent loading,scheme (ELS)and equivalent matrix scheme(EMS)are proposed.It is theoretically analyzed that both ELS and EMS can be used to precisely simulating the effective properties and local fields of matrix-inclusion composites,and both ELS and EMS are self-approved. As an application,ELS combined with a m-called pseudo-dislocations method is used to evaluate the effective properties and local fields of two-dimensional two-phase compos- ites with close-packed circular inclusions,or randomly distributed circular inclusions, or randomly distributed mierocracks.The results show that substituting the remote trac- tion σ~∞ with the effective stress field σ~E suggested by IDD scheme is a simple and effec- tive method,and the estimation of the effective properties and local fields is very close to the accurate,solution.展开更多
This paper investigates motion coupling disturbance（the so called surplus torque）in the hardware-in-the-loop（HIL）experiments.The＇＇velocity synchronization scheme＇＇was proposed by Jiao for an electro-hydraulic ...This paper investigates motion coupling disturbance（the so called surplus torque）in the hardware-in-the-loop（HIL）experiments.The＇＇velocity synchronization scheme＇＇was proposed by Jiao for an electro-hydraulic load simulator（EHLS）in 2004.In some situations,however,the scheme is limited in the implementation for certain reasons,as is the case when the actuator＇s valve signal is not available or it is seriously polluted by noise.To solve these problems,a＇＇dual-loop scheme＇＇is developed for EHLS.The dual-loop scheme is a combination of a torque loop and a position synchronization loop.The role of the position synchronization loop is to decouple the motion disturbance caused by the actuator system.To verify the feasibility and effectiveness of the proposed scheme,extensive simulations are performed using AMESim.Then,the performance of the developed method is validated by experiments.展开更多
文摘Large goods transported in railway are kinds of special goods and they are very important in national construction. In order to transport safely, loading and reinforcing schemes must be made first. How to design a reasonable scheme will be affected by many factors. This paper presents the characteristic of the large goods, summarizes the process of designing a loading and reinforcing scheme of large good, then probes the factors of affecting the loading and reinforcing scheme and gives a detail analysis. It’s considered that those out-of-gauge and overweight degree of goods, center-of- gravity height of a loaded wagon, position of center-of-gravity of goods, type of wagon for using, reinforcement material and reinforcement method, transport expense and transport organization could affect a scheme in the aspects of safety, economy, rapidity and convenience. This conclusion will instruct and help to make a good scheme.
文摘The ability of power system to survive the transition from preloading state to the gradual increase in load and thereafter reach an acceptable operational condition is an indication of transient stability of the system. The study analyzed load shedding scheme through the use of empirical measurement tools and load-flow simulation techniques. It was geared towards determining effective load shedding strategies to reduce unnecessary overload in order to achieve dynamic stability of the electric power network in the Export Free Trade Zone, Calabar, Nigeria. From the tests and the measurements taken, it was observed that the real and reactive powers from the generator and the mechanical power from the turbine engine were stable when the load shedding controller was switched on, as compared to when it was off. The engine speed, the bus-bar frequency and the output voltage of the generator stabilized within a shorter time (about 8 seconds) when the controller was switched on than when it was on the off condition. Also, there were noticeable fluctuations in the speed of the remaining two generators. It became stable at about 12 seconds after the loss. The variations were 0.3 per cent of the nominal speed value. The excitation voltage fluctuated from 1.2 (pu) to 4.5 (pu) when the bus voltage dipped as a result of additional load. It then came down and stabilized at 1.8 (pu) after few swings. This confirmed that the stability of power system is much enhanced when load shedding controllers are effectively configured on the network.
基金the National Natural Science Foundation of China(No.19525207)
文摘It is pointed out that to numerically estimate the effective properties and local fields of matrix-inclusion composites,a commonly adopted method is accompanied with some serious draw- backs.We call this method the nominal loading scheme(NLS),which considers the actual inclusion distribution inside a finite domain,Ω say,treats the external domain of Ω to be of the pure matrix ma- terial,and imposes the actural traction,σ~∞ say on the remote boundary.It thus gives rise to the fol- lowing basic problems:(i)Can NLS be improved remarkably just by adjusting σ~∞?(it)What is the relationship between the size of Ω and the,scale of inclusions?(iii)Which choice is better in calculating the effective properties,the whole domain Ω or an appropriately selected sub-domain of Ω? Targeting these problems,the equivalent loading,scheme (ELS)and equivalent matrix scheme(EMS)are proposed.It is theoretically analyzed that both ELS and EMS can be used to precisely simulating the effective properties and local fields of matrix-inclusion composites,and both ELS and EMS are self-approved. As an application,ELS combined with a m-called pseudo-dislocations method is used to evaluate the effective properties and local fields of two-dimensional two-phase compos- ites with close-packed circular inclusions,or randomly distributed circular inclusions, or randomly distributed mierocracks.The results show that substituting the remote trac- tion σ~∞ with the effective stress field σ~E suggested by IDD scheme is a simple and effec- tive method,and the estimation of the effective properties and local fields is very close to the accurate,solution.
基金sponsored by the National Basic Research Program of China (No.2014CB046406)the Key Projects of the National Natural Science Foundation (No.51235002)
文摘This paper investigates motion coupling disturbance（the so called surplus torque）in the hardware-in-the-loop（HIL）experiments.The＇＇velocity synchronization scheme＇＇was proposed by Jiao for an electro-hydraulic load simulator（EHLS）in 2004.In some situations,however,the scheme is limited in the implementation for certain reasons,as is the case when the actuator＇s valve signal is not available or it is seriously polluted by noise.To solve these problems,a＇＇dual-loop scheme＇＇is developed for EHLS.The dual-loop scheme is a combination of a torque loop and a position synchronization loop.The role of the position synchronization loop is to decouple the motion disturbance caused by the actuator system.To verify the feasibility and effectiveness of the proposed scheme,extensive simulations are performed using AMESim.Then,the performance of the developed method is validated by experiments.
