Global navigation satellite system could provide accurate positioning results in signal complete condition. However, the performance is severe when signal denied, especially for the single-mode Bei Dou receiver. This ...Global navigation satellite system could provide accurate positioning results in signal complete condition. However, the performance is severe when signal denied, especially for the single-mode Bei Dou receiver. This paper proposes a dual-satellite positioning algorithm to promote the positioning performance in the satellite signal gap. The new algorithm utilizes the previous positioning data stored in complete condition to simplify the positioning equations. As the clock bias persists for a short period, this proposed method could work out accurate positioning results by only two visible satellites, without the need of computing the clock bias. Also, the Kalman filtering algorithm is used to smooth the trajectories, and improve the positioning results. During the incomplete period, only two satellites for 30 seconds and three satellites for 60 seconds, the preliminary experiment result shows that, the presented method could provide almost the same positioning results as in complete condition.展开更多
Because of the complexities of tire-road interaction,the wheels of a multi-wheel distributed electricdrive vehicle can easily slip under certain working conditions.As wheel slip affects the dynamic per-formance and st...Because of the complexities of tire-road interaction,the wheels of a multi-wheel distributed electricdrive vehicle can easily slip under certain working conditions.As wheel slip affects the dynamic per-formance and stability of the vehicle,it is crucial to control it and coordinate the driving force.With this aim,this paper presents a driving force coordination control strategy with road identification for eight-wheeled electric vehicles equipped with an in-wheel motor for each wheel.In the proposed control strategy,the road identification module estimates tire-road forces using an unscented Kalman filter al-gorithm and recognizes the road adhesion coefficient by employing the recursive least-square method According to road identification,the optimal sip ratio under the current driving condition is obtainedand a controller based on sliding mode control with a conditional integrator uses this value for accel-eration slip regulation.The anti-slip controller obtains the adjusting torque,which is integrated with the driver-command-based feedforward control torque to implement driving force coordination control.The results of hardware-in-loop simulation show that this control strategy can accurately estimate tire-roadrces as well as the friction coefficient,and thus,can effectively fulfill the purpose of driving force coordinated control under different driving conditions.展开更多
The influence of light and temperature conditions inside solar greenhouse of winter-spring and autumn-winter crop in northern China on uptake and distribution of nitrogen. phosphorus and potassium of cucumber was stud...The influence of light and temperature conditions inside solar greenhouse of winter-spring and autumn-winter crop in northern China on uptake and distribution of nitrogen. phosphorus and potassium of cucumber was studied. The results showed that plant root development and uptake and distribution of N, P and K benefited more from inside light and temperature changes in winter-spring crop. Root volume and root activity increased more rapidly in winter-spring than in autumn-winter. Uptake of total N, P2O5 and K2O increased with plant development in winter-spring, and declined in autumn-winter crop. Distribution of total N, P2O5 and K2O at different part of cucumber at fruit bearing stage was significantly influenced by inside light and temperature of solar greenhouse. Total N, P2O5 and K2O were mainly distributed to leaves and stems at early stage, and increasingly to fruits after fruit bearing.展开更多
In this short note we discuss the GM property of some special linear transformation pairs over infinite-dimensional vector spaces. In particular, it is proved that if R =- End（VD） is the endomorphism ring of an infi...In this short note we discuss the GM property of some special linear transformation pairs over infinite-dimensional vector spaces. In particular, it is proved that if R =- End（VD） is the endomorphism ring of an infinite-dimensional right vector space V over a division ring D with IC（D）I 〉 3 and g e R, then （a0q-alg, 9） is a GM pair for any ao, ale C（D）. Furthermore, two existing results are obtained as immediate consequences.展开更多
In this paper, the problems of combustion instability and high-temperature corrosion of pulverized coal fired boiler are investigated by numerical simulation and analysis of the momentum moment. Elbow and twisting pla...In this paper, the problems of combustion instability and high-temperature corrosion of pulverized coal fired boiler are investigated by numerical simulation and analysis of the momentum moment. Elbow and twisting plate type of burners are used in the boiler, and the reverse moment of momentum is formed at the outlet of the fuel-rich side of the burner. The momentum moment in the boiler is opposite to the designed tangential circle, and the tangential circle in the boiler is reversed rotation. The reverse moment of momentum at the burner outlet can be eliminated by using louver horizontal bias pulverized coal burner, while the problems of combustion instability and high-temperature corrosion of the boiler are solved, and the combustion efficiency is improved. Accordingly,economic benefit is obviously got.展开更多
This study attempts to make a contribution to the understanding of dihedral application conditions and their aerodynamic mechanisms.The present efforts have finished contrastive investigations on several dihedral blad...This study attempts to make a contribution to the understanding of dihedral application conditions and their aerodynamic mechanisms.The present efforts have finished contrastive investigations on several dihedral blades to their corresponding straight ones with different geometric or aerodynamic conditions including aspect ratio,solidity,aerofoil turning angle,inlet boundary layer configuration and inlet Mach number.A dihedral with the angle between the suction side and the endwall to be obtuse,i.e.,positive dihedral,is chosen.The result reveals the dihedral application conditions consist of aerofoil turning angle,inlet boundary layer,inlet Mach number and so on.The further analysis indicates:in a transonic cascade,two considerations are needed on the contrastive relationship between intensities of the two shocks,namely detached shock and passage shock,and the interaction of the shocks with the corner separation.展开更多
In this paper, nonreflecting artificial boundary conditions are considered for an acoustic problem in three dimensions. With the technique of Fourier decomposition under the orthogonal basis of spherical harmonics, th...In this paper, nonreflecting artificial boundary conditions are considered for an acoustic problem in three dimensions. With the technique of Fourier decomposition under the orthogonal basis of spherical harmonics, three kinds of equivalent exact artificial boundary conditions are obtained on a spherical artificial boundary. A numerical test is presented to show the performance of the method.展开更多
基金partially supported by the National Natural Science Foundation of China under Grant No.61601296, 61601295, and 61671304
文摘Global navigation satellite system could provide accurate positioning results in signal complete condition. However, the performance is severe when signal denied, especially for the single-mode Bei Dou receiver. This paper proposes a dual-satellite positioning algorithm to promote the positioning performance in the satellite signal gap. The new algorithm utilizes the previous positioning data stored in complete condition to simplify the positioning equations. As the clock bias persists for a short period, this proposed method could work out accurate positioning results by only two visible satellites, without the need of computing the clock bias. Also, the Kalman filtering algorithm is used to smooth the trajectories, and improve the positioning results. During the incomplete period, only two satellites for 30 seconds and three satellites for 60 seconds, the preliminary experiment result shows that, the presented method could provide almost the same positioning results as in complete condition.
基金This work was supported by the Weapons and Equipment Pre-Research Project of China(No.301051102).
文摘Because of the complexities of tire-road interaction,the wheels of a multi-wheel distributed electricdrive vehicle can easily slip under certain working conditions.As wheel slip affects the dynamic per-formance and stability of the vehicle,it is crucial to control it and coordinate the driving force.With this aim,this paper presents a driving force coordination control strategy with road identification for eight-wheeled electric vehicles equipped with an in-wheel motor for each wheel.In the proposed control strategy,the road identification module estimates tire-road forces using an unscented Kalman filter al-gorithm and recognizes the road adhesion coefficient by employing the recursive least-square method According to road identification,the optimal sip ratio under the current driving condition is obtainedand a controller based on sliding mode control with a conditional integrator uses this value for accel-eration slip regulation.The anti-slip controller obtains the adjusting torque,which is integrated with the driver-command-based feedforward control torque to implement driving force coordination control.The results of hardware-in-loop simulation show that this control strategy can accurately estimate tire-roadrces as well as the friction coefficient,and thus,can effectively fulfill the purpose of driving force coordinated control under different driving conditions.
基金the National Natural Science Foundation of China (39830230) Beijing Natural Science Foundation (6011002).
文摘The influence of light and temperature conditions inside solar greenhouse of winter-spring and autumn-winter crop in northern China on uptake and distribution of nitrogen. phosphorus and potassium of cucumber was studied. The results showed that plant root development and uptake and distribution of N, P and K benefited more from inside light and temperature changes in winter-spring crop. Root volume and root activity increased more rapidly in winter-spring than in autumn-winter. Uptake of total N, P2O5 and K2O increased with plant development in winter-spring, and declined in autumn-winter crop. Distribution of total N, P2O5 and K2O at different part of cucumber at fruit bearing stage was significantly influenced by inside light and temperature of solar greenhouse. Total N, P2O5 and K2O were mainly distributed to leaves and stems at early stage, and increasingly to fruits after fruit bearing.
文摘In this short note we discuss the GM property of some special linear transformation pairs over infinite-dimensional vector spaces. In particular, it is proved that if R =- End（VD） is the endomorphism ring of an infinite-dimensional right vector space V over a division ring D with IC（D）I 〉 3 and g e R, then （a0q-alg, 9） is a GM pair for any ao, ale C（D）. Furthermore, two existing results are obtained as immediate consequences.
基金the Training Program Fund for Young Teachers in Shanghai Higher Education Institutions(No.405ZK12YQ06)
文摘In this paper, the problems of combustion instability and high-temperature corrosion of pulverized coal fired boiler are investigated by numerical simulation and analysis of the momentum moment. Elbow and twisting plate type of burners are used in the boiler, and the reverse moment of momentum is formed at the outlet of the fuel-rich side of the burner. The momentum moment in the boiler is opposite to the designed tangential circle, and the tangential circle in the boiler is reversed rotation. The reverse moment of momentum at the burner outlet can be eliminated by using louver horizontal bias pulverized coal burner, while the problems of combustion instability and high-temperature corrosion of the boiler are solved, and the combustion efficiency is improved. Accordingly,economic benefit is obviously got.
文摘This study attempts to make a contribution to the understanding of dihedral application conditions and their aerodynamic mechanisms.The present efforts have finished contrastive investigations on several dihedral blades to their corresponding straight ones with different geometric or aerodynamic conditions including aspect ratio,solidity,aerofoil turning angle,inlet boundary layer configuration and inlet Mach number.A dihedral with the angle between the suction side and the endwall to be obtuse,i.e.,positive dihedral,is chosen.The result reveals the dihedral application conditions consist of aerofoil turning angle,inlet boundary layer,inlet Mach number and so on.The further analysis indicates:in a transonic cascade,two considerations are needed on the contrastive relationship between intensities of the two shocks,namely detached shock and passage shock,and the interaction of the shocks with the corner separation.
基金This work is supported partly by the Special Funds for Major State Basic Research Projects of China and the National Science Foundation of China.
文摘In this paper, nonreflecting artificial boundary conditions are considered for an acoustic problem in three dimensions. With the technique of Fourier decomposition under the orthogonal basis of spherical harmonics, three kinds of equivalent exact artificial boundary conditions are obtained on a spherical artificial boundary. A numerical test is presented to show the performance of the method.
