This paper describes a linear interference cancellation multi user detector for synchronous DS CDMA systems under the condition that all spread spectrum code waveforms have the constant cross correlating coefficien...This paper describes a linear interference cancellation multi user detector for synchronous DS CDMA systems under the condition that all spread spectrum code waveforms have the constant cross correlating coefficients. The basic idea is to get the estimation for total multiple access interference (MAI) of all users using a reference code waveform, then subtract the total MAI from the received signal. The structure of such a detector is nearly similar to the conventional detector. The BER expression obtained in the paper shows significant performance improvement compared to the other detectors.展开更多
Winds on the earth are commonly strong enough to erode transport and deposit sediment. The modes of sand transport by the wind are greatly different from those by water flow. On the other hand wind-blown sands are of...Winds on the earth are commonly strong enough to erode transport and deposit sediment. The modes of sand transport by the wind are greatly different from those by water flow. On the other hand wind-blown sands are of a material circulation process of the earth surface. They affect wind-sand transport flux and sand ejection of a flux, the damage of grains formed cannot be neglected in engineering. Because of the complexity of windblown sand flux system, the understanding of its basic mechanics is not yet clear. The key forces in sand salutation mainly includes： the valid gravity, air drag force ＇Magnus force＇ Saffman force ＇Basset force＇ additional quality force and scatter force among grains. The most important force in sand salutation is the air drag force. Computation of the single sphere drag coefficient and double spheres drag coefficient is presented for the distance between two spheres being smaller than twelve times of the sphere diameter and the spheres being at different angular positions. The flow interference of two spheres was investigated for the distance s = 0.08 d to 12d, angular position 0 = 0 to 360 and Reynolds number 15≤Re≤1000.展开更多
Partial discharge measurement is one of the most effective methods to find insulation defects and early failure of high voltage power equipments. The accuracy is significantly reduced by the interference in the partia...Partial discharge measurement is one of the most effective methods to find insulation defects and early failure of high voltage power equipments. The accuracy is significantly reduced by the interference in the partial discharge on-site detection or on-line monitoring, especially by the pulse interference. This paper studies the phase correlation of some types of typical partial discharge pulses and their characteristics in time domain and frequency domain. By collecting enough partial discharge pulse data, the correlation coefficient can be calculated based on both phase correlation and waveform similarity. The type of pulse will be determined by the scope of the calculated correlation coefficient. The pulses with very strong correlation will be identified as periodic pulse interference. The pulses with very weak correlation will be identified as random pulse interference. Only the pulses whose correlation coefficients fall into a specific range will be identified as partial discharge signals. In laboratory, simulated pulse interference is injected into measurement circuit, and typical partial discharge pulses are sampled by a high-speed acquisition system. The pulse interference can be effectively separated from partial discharge signals by correlation coefficient.展开更多
The aerodynamic interference effects on aero-static coefficients of twin deck bridges with large span were investigated in detail by means of wind tunnel test.The distances between the twin decks and wind attack angle...The aerodynamic interference effects on aero-static coefficients of twin deck bridges with large span were investigated in detail by means of wind tunnel test.The distances between the twin decks and wind attack angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of twin decks.The research results have shown that the drag coefficients of the leeward deck are much smaller than that of a single leeward deck.The drag coefficients of a windward deck decrease slightly com-pared with that of a single deck.The lift and torque coefficients of windward and leeward decks are also affected slightly by the aerodynamic interference of twin decks.And the aerodynamic interference effects on lift and torque coefficients of twin decks can be neglected.展开更多
文摘This paper describes a linear interference cancellation multi user detector for synchronous DS CDMA systems under the condition that all spread spectrum code waveforms have the constant cross correlating coefficients. The basic idea is to get the estimation for total multiple access interference (MAI) of all users using a reference code waveform, then subtract the total MAI from the received signal. The structure of such a detector is nearly similar to the conventional detector. The BER expression obtained in the paper shows significant performance improvement compared to the other detectors.
基金supported by National Natural Science Foundation (10532030)
文摘Winds on the earth are commonly strong enough to erode transport and deposit sediment. The modes of sand transport by the wind are greatly different from those by water flow. On the other hand wind-blown sands are of a material circulation process of the earth surface. They affect wind-sand transport flux and sand ejection of a flux, the damage of grains formed cannot be neglected in engineering. Because of the complexity of windblown sand flux system, the understanding of its basic mechanics is not yet clear. The key forces in sand salutation mainly includes： the valid gravity, air drag force ＇Magnus force＇ Saffman force ＇Basset force＇ additional quality force and scatter force among grains. The most important force in sand salutation is the air drag force. Computation of the single sphere drag coefficient and double spheres drag coefficient is presented for the distance between two spheres being smaller than twelve times of the sphere diameter and the spheres being at different angular positions. The flow interference of two spheres was investigated for the distance s = 0.08 d to 12d, angular position 0 = 0 to 360 and Reynolds number 15≤Re≤1000.
文摘Partial discharge measurement is one of the most effective methods to find insulation defects and early failure of high voltage power equipments. The accuracy is significantly reduced by the interference in the partial discharge on-site detection or on-line monitoring, especially by the pulse interference. This paper studies the phase correlation of some types of typical partial discharge pulses and their characteristics in time domain and frequency domain. By collecting enough partial discharge pulse data, the correlation coefficient can be calculated based on both phase correlation and waveform similarity. The type of pulse will be determined by the scope of the calculated correlation coefficient. The pulses with very strong correlation will be identified as periodic pulse interference. The pulses with very weak correlation will be identified as random pulse interference. Only the pulses whose correlation coefficients fall into a specific range will be identified as partial discharge signals. In laboratory, simulated pulse interference is injected into measurement circuit, and typical partial discharge pulses are sampled by a high-speed acquisition system. The pulse interference can be effectively separated from partial discharge signals by correlation coefficient.
基金The work was supported by the National Natural Science Foundation of China(Grant No.50608030).
文摘The aerodynamic interference effects on aero-static coefficients of twin deck bridges with large span were investigated in detail by means of wind tunnel test.The distances between the twin decks and wind attack angles were changed during the wind tunnel test to study the effects on aerodynamic interferences of aerostatic coefficients of twin decks.The research results have shown that the drag coefficients of the leeward deck are much smaller than that of a single leeward deck.The drag coefficients of a windward deck decrease slightly com-pared with that of a single deck.The lift and torque coefficients of windward and leeward decks are also affected slightly by the aerodynamic interference of twin decks.And the aerodynamic interference effects on lift and torque coefficients of twin decks can be neglected.
