In an orthogonal frequency division multiplexing(OFDM) system,a time and frequency domain least mean square algorithm(TF-LMS) was proposed to cancel the frequency offset(FO).TF-LMS algorithm is composed of two stages....In an orthogonal frequency division multiplexing(OFDM) system,a time and frequency domain least mean square algorithm(TF-LMS) was proposed to cancel the frequency offset(FO).TF-LMS algorithm is composed of two stages.Firstly,time domain least mean square(TD-LMS) scheme was selected to pre-cancel the frequency offset in the time domain,and then the interference induced by residual frequency offset was eliminated by the frequency domain mean square(FD-LMS) scheme in frequency domain.The results of bit error rate(BER) and quadrature phase shift keying(QPSK) constellation figures show that the performance of the proposed suppression algorithm is excellent.展开更多
This paper proposes a new approach to further improving the bandwidth of a typical aperture-coupled stacked microstrip antenna by cutting triangular notches in the radiating sides of both radiating patches together wi...This paper proposes a new approach to further improving the bandwidth of a typical aperture-coupled stacked microstrip antenna by cutting triangular notches in the radiating sides of both radiating patches together with offsetting both patches. An antenna applying this new approach is designed,fabricated,and tested. The experimental antenna could achieve a measured impedance bandwidth of about 37.5% for the Voltage Standing Wave Ratio(VSWR) ≤ 2in X-band.展开更多
There is an increasing demand on wireless communications in subway tunnels to provide video surveillance and sensory data for security,maintenance and train control,and to offer various communication or entertainment ...There is an increasing demand on wireless communications in subway tunnels to provide video surveillance and sensory data for security,maintenance and train control,and to offer various communication or entertainment services(e.g.,Internet,etc.) to passengers as well.The wireless channel in tunnels is quite unique due to the confined space and the waveguide effects.Therefore,modeling the radio channel characteristics in tunnels is critically important for communication systems design or optimization.This paper investigates the key radio channel characteristics of a subway tunnel at 2.4 GHz and 5 GHz,such as the path loss,root mean square(RMS) delay spread,channel stationarity,Doppler shift,and channel capacity.The field measurements show that channel characteristics in tunnels are highly location-dependent and there exist abundant components in Doppler shift domain.In the straight section of the subway tunnel,the measured path loss exponents are close to1.6,lower than that in free space.展开更多
This paper presents an improved algorithm for classification of M-Differential Phase-Shift Keying(MDPSK) signals based on eumulant. The feature proposed in the algorithm is invariant with respect to constellation scal...This paper presents an improved algorithm for classification of M-Differential Phase-Shift Keying(MDPSK) signals based on eumulant. The feature proposed in the algorithm is invariant with respect to constellation scale, rotation, the shift and the carrier frequency offset between transmitter and receiver.The invariant property is proved theoretically.Through computer simulation the performance is evaluated and the results show that the improved classification algorithm is better and valuable in practice.展开更多
A real-time pedestrian detection and tracking system using a single video camera was developed to monitor pedestrians. This system contained six modules: video flow capture, pre-processing, movement detection, shadow ...A real-time pedestrian detection and tracking system using a single video camera was developed to monitor pedestrians. This system contained six modules: video flow capture, pre-processing, movement detection, shadow removal, tracking, and object classification. The Gaussian mixture model was utilized to extract the moving object from an image sequence segmented by the mean-shift technique in the pre-processing module. Shadow removal was used to alleviate the negative impact of the shadow to the detected objects. A model-free method was adopted to identify pedestrians. The maximum and minimum integration methods were developed to integrate multiple cues into the mean-shift algorithm and the initial tracking iteration with the competent integrated probability distribution map for object tracking. A simple but effective algorithm was proposed to handle full occlusion cases. The system was tested using real traffic videos from different sites. The results of the test confirm that the system is reliable and has an overall accuracy of over 85%.展开更多
There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood...There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood speed. It is proved that the speedometer has high space resolving power,high time resolving power, and outstanding capability of approaching target, etc.展开更多
Based on the analysis of the impact of Doppler shift to the railway dedicated mobile communication quality under the condition of high-speed mobility,this paper presents a Doppler shift measurement approach based on t...Based on the analysis of the impact of Doppler shift to the railway dedicated mobile communication quality under the condition of high-speed mobility,this paper presents a Doppler shift measurement approach based on the phase estimation of frequency correction channel(FCCH) which correctly reflects the time-varying characteristic of the channel with a testing system developed.The Doppler shift data under the high-speed condition is collected,processed,analyzed,and compared with the simulation results.The scientific laws of the Doppler shift distribution of radio channel under high-speed condition are obtained.These data and analysis are essential for the establishment of high-speed railway Doppler power spectrum model and the development of the key technology of antiDoppler shift.展开更多
The intensity and phase formulas that are valid for the saturation and intermediate regime (before saturation) are derived, and the analytical expressions with the ratio of saturation intensity to total incident inten...The intensity and phase formulas that are valid for the saturation and intermediate regime (before saturation) are derived, and the analytical expressions with the ratio of saturation intensity to total incident intensity as their explicit variable are obtained. The intensity dependence of stationary energy transfer in photorefractive codirectional two-wave mixing is examined. It is necessary to using these formulas in some problems, such as the temperature or intensity dependence of two-wave mixing. A method of measuring exponential gain coefficient is presented, which is suitable for two-wave mixing in intermediate regime.展开更多
Fast resources discovery and high Quality of Service(QoS) guarantee are the key determinants for efficient Mobile P2P(MP2P) video sharing.In this paper,we propose a CrossLayer and One-Hop Neighbour-Assisted Video Shar...Fast resources discovery and high Quality of Service(QoS) guarantee are the key determinants for efficient Mobile P2P(MP2P) video sharing.In this paper,we propose a CrossLayer and One-Hop Neighbour-Assisted Video Sharing(CNVS) solution in Mobile Ad Hoc Networks(MANETs).By making use of crosslayer approaches to bridge the overlay and the MAC layer and with the help of dissemination assisted by one-hop neighbours,CNVS intelligently builds the resource-centric self-organization node cluster group.In order to meet the QoS requirement,by making use of video resources access cost model,each peer can disconnect a less efficient connection with the original supplier and choose a peer that provides a low access cost as the new supplier.Simulation results also show how CNVS achieves lower average end-to-end delay,less average number of hops for video data delivery,lower routing overhead and packet loss rate,and higher network throughput than another state-of-the-art solution.展开更多
The laser trapping of untransmissive particles are discussed in this paper. Photon can generate the momentum tothe untransmissive particle by diffraction and reflection on the surface of the particles. We tried laser ...The laser trapping of untransmissive particles are discussed in this paper. Photon can generate the momentum tothe untransmissive particle by diffraction and reflection on the surface of the particles. We tried laser trapping ofuntransmissive particles using an attractive force caused by the diffraction and radiation force caused by reflection.The laser trapping system includes CW YAG laser, which has 1.064 μm in wave length and an optical microscope.The motions of particles were monitored by a CCD camera on the top of the microscope and recordedby PC connected to the CCD camera.展开更多
基金Project(60532030) supported by the National Natural Science Foundation of China
文摘In an orthogonal frequency division multiplexing(OFDM) system,a time and frequency domain least mean square algorithm(TF-LMS) was proposed to cancel the frequency offset(FO).TF-LMS algorithm is composed of two stages.Firstly,time domain least mean square(TD-LMS) scheme was selected to pre-cancel the frequency offset in the time domain,and then the interference induced by residual frequency offset was eliminated by the frequency domain mean square(FD-LMS) scheme in frequency domain.The results of bit error rate(BER) and quadrature phase shift keying(QPSK) constellation figures show that the performance of the proposed suppression algorithm is excellent.
文摘This paper proposes a new approach to further improving the bandwidth of a typical aperture-coupled stacked microstrip antenna by cutting triangular notches in the radiating sides of both radiating patches together with offsetting both patches. An antenna applying this new approach is designed,fabricated,and tested. The experimental antenna could achieve a measured impedance bandwidth of about 37.5% for the Voltage Standing Wave Ratio(VSWR) ≤ 2in X-band.
基金supported in part by the NSFC project under grant No.61132003the Fundamental Research Funds for the Central Universities(2013JBZ002)the Ph.D.Program Foundation of Ministry of Education of China under grant No.20120009130002
文摘There is an increasing demand on wireless communications in subway tunnels to provide video surveillance and sensory data for security,maintenance and train control,and to offer various communication or entertainment services(e.g.,Internet,etc.) to passengers as well.The wireless channel in tunnels is quite unique due to the confined space and the waveguide effects.Therefore,modeling the radio channel characteristics in tunnels is critically important for communication systems design or optimization.This paper investigates the key radio channel characteristics of a subway tunnel at 2.4 GHz and 5 GHz,such as the path loss,root mean square(RMS) delay spread,channel stationarity,Doppler shift,and channel capacity.The field measurements show that channel characteristics in tunnels are highly location-dependent and there exist abundant components in Doppler shift domain.In the straight section of the subway tunnel,the measured path loss exponents are close to1.6,lower than that in free space.
基金Supported by China TRAPOYT,863 Project(2001AA123031)National Natural Science Foundation of China(No.69872028)
文摘This paper presents an improved algorithm for classification of M-Differential Phase-Shift Keying(MDPSK) signals based on eumulant. The feature proposed in the algorithm is invariant with respect to constellation scale, rotation, the shift and the carrier frequency offset between transmitter and receiver.The invariant property is proved theoretically.Through computer simulation the performance is evaluated and the results show that the improved classification algorithm is better and valuable in practice.
基金Project(50778015)supported by the National Natural Science Foundation of ChinaProject(2012CB725403)supported by the Major State Basic Research Development Program of China
文摘A real-time pedestrian detection and tracking system using a single video camera was developed to monitor pedestrians. This system contained six modules: video flow capture, pre-processing, movement detection, shadow removal, tracking, and object classification. The Gaussian mixture model was utilized to extract the moving object from an image sequence segmented by the mean-shift technique in the pre-processing module. Shadow removal was used to alleviate the negative impact of the shadow to the detected objects. A model-free method was adopted to identify pedestrians. The maximum and minimum integration methods were developed to integrate multiple cues into the mean-shift algorithm and the initial tracking iteration with the competent integrated probability distribution map for object tracking. A simple but effective algorithm was proposed to handle full occlusion cases. The system was tested using real traffic videos from different sites. The results of the test confirm that the system is reliable and has an overall accuracy of over 85%.
文摘There exist many methods to measure blood speed, all of which have some serious shortcomings. As fiber is characterized by tiny diameter, and low lost ratio of power and flexibility, it is suitable for measuring blood speed. It is proved that the speedometer has high space resolving power,high time resolving power, and outstanding capability of approaching target, etc.
基金Supported by the National Natural Science Foundation of China(No.U133420261222105)+1 种基金the Key Grant Project of Chinese Ministry of Education(No.313006)the Project of State Key Lab of Rail Traffic Control and Safety(No.RCS 2014ZT11)
文摘Based on the analysis of the impact of Doppler shift to the railway dedicated mobile communication quality under the condition of high-speed mobility,this paper presents a Doppler shift measurement approach based on the phase estimation of frequency correction channel(FCCH) which correctly reflects the time-varying characteristic of the channel with a testing system developed.The Doppler shift data under the high-speed condition is collected,processed,analyzed,and compared with the simulation results.The scientific laws of the Doppler shift distribution of radio channel under high-speed condition are obtained.These data and analysis are essential for the establishment of high-speed railway Doppler power spectrum model and the development of the key technology of antiDoppler shift.
文摘The intensity and phase formulas that are valid for the saturation and intermediate regime (before saturation) are derived, and the analytical expressions with the ratio of saturation intensity to total incident intensity as their explicit variable are obtained. The intensity dependence of stationary energy transfer in photorefractive codirectional two-wave mixing is examined. It is necessary to using these formulas in some problems, such as the temperature or intensity dependence of two-wave mixing. A method of measuring exponential gain coefficient is presented, which is suitable for two-wave mixing in intermediate regime.
基金supported in part by the National High Technical Research and Development Program of China (863 Program) under Grant No. 2011AA010701the National KeyBasic Research Program of China (973 Program)under Grant No. 2013CB329102+4 种基金the National Natural Science Foundation of China under Grants No. 61001122,No. 61003283,No. 61232017the Natural Science Foundation of Jiangsu Province under Grant No. BK2011171the Natural Science Foundation of Jiangxi,China under Grant No. 20122BAB201042the Fundamental Research Funds for the Central Universities under Grant No. 2012RC0603the Science Foundation Ireland under Grant No. 10/CE/I1855 to Lero-the Irish Software Engineering Research Centre
文摘Fast resources discovery and high Quality of Service(QoS) guarantee are the key determinants for efficient Mobile P2P(MP2P) video sharing.In this paper,we propose a CrossLayer and One-Hop Neighbour-Assisted Video Sharing(CNVS) solution in Mobile Ad Hoc Networks(MANETs).By making use of crosslayer approaches to bridge the overlay and the MAC layer and with the help of dissemination assisted by one-hop neighbours,CNVS intelligently builds the resource-centric self-organization node cluster group.In order to meet the QoS requirement,by making use of video resources access cost model,each peer can disconnect a less efficient connection with the original supplier and choose a peer that provides a low access cost as the new supplier.Simulation results also show how CNVS achieves lower average end-to-end delay,less average number of hops for video data delivery,lower routing overhead and packet loss rate,and higher network throughput than another state-of-the-art solution.
文摘The laser trapping of untransmissive particles are discussed in this paper. Photon can generate the momentum tothe untransmissive particle by diffraction and reflection on the surface of the particles. We tried laser trapping ofuntransmissive particles using an attractive force caused by the diffraction and radiation force caused by reflection.The laser trapping system includes CW YAG laser, which has 1.064 μm in wave length and an optical microscope.The motions of particles were monitored by a CCD camera on the top of the microscope and recordedby PC connected to the CCD camera.
