A data acquisition system based on LabVIEW and NI PXI-5105 is presented for multi-channel data acquisition. It can realize the functions of parameter setting, data acquisition and storage, waveform display and data an...A data acquisition system based on LabVIEW and NI PXI-5105 is presented for multi-channel data acquisition. It can realize the functions of parameter setting, data acquisition and storage, waveform display and data analysis using LabVIEW and NI-SCOPE device driver. The advantages of the system are that the setting is convenient, the operation is easy, the interface is friendly and the functions are practical. The experiment results show that the system has good stability and high reliability and is a powerful tool for multi-channel data acquisition.展开更多
The conception of multilevel security (MLS) is commonly used in the study of data model for secure database. But there are some limitations in the basic MLS model, such as inference channels. The availability and data...The conception of multilevel security (MLS) is commonly used in the study of data model for secure database. But there are some limitations in the basic MLS model, such as inference channels. The availability and data integrity of the system are seriously constrained by it′s 'No Read Up, No Write Down' property in the basic MLS model. In order to eliminate the covert channels, the polyinstantiation and the cover story are used in the new data model. The read and write rules have been redefined for improving the agility and usability of the system based on the MLS model. All the methods in the improved data model make the system more secure, agile and usable.展开更多
PARASOL(Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) multi-channel and multi-directional polarized data for different aerosol types were compared.The P...PARASOL(Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) multi-channel and multi-directional polarized data for different aerosol types were compared.The PARASOL polarized radiance data at 490 nm,670 nm,and 865 nm increased with aerosol optical thickness(AOT) for fine-mode aerosols;however,the polarized radiances at 490 nm and 670 nm decreased as AOT increased for coarse dust aerosols.Thus,the variation of the polarized radiance with AOT can be used to identify fine or coarse particle-dominated aerosols.Polarized radiances at three wavelengths for fine-and coarse-mode aerosols were analyzed and fitted by linear regression.The slope of the line for 670 nm and 490 nm wavelength pairs is less than 0.35 for dust aerosols.However,the value for fine-mode aerosols is greater than 0.60.The Support Vector Machine method(SVM) based on 12 vector features was used to discriminate clear sky,coarse dust aerosols,fine-mode aerosols,and cloud.Two cases were given and validated by AErosol RObotic NETwork(AERONET) measurements,MODIS(Moderate Resolution Imaging Spectroradiometer) FMF(Fine Mode Fraction at 550 nm) images,PARASOL RGB(Red Green Blue) images,and CALIOP(Cloud-Aerosol Lidar with Orthogonal Polarization) VFM(Vertical Feature Mask) data.展开更多
In order to resolve the hidden and exposed terminal problems and improve the probability of concurrent packet transmissions for multihop Mobile Ad Hoc Networks （MANETs）, a novel slotted Asyrmaetric Dual-Channel Medi...In order to resolve the hidden and exposed terminal problems and improve the probability of concurrent packet transmissions for multihop Mobile Ad Hoc Networks （MANETs）, a novel slotted Asyrmaetric Dual-Channel Medium Access Control （ADC-MAC） protocol is proposed. It exploits sirmltaneous reservation with less collisions and conision-flee data packet transmissions, and achieves optimal transmission balance on the Control Channel （CCH） and Data Channel （DCH） by adjusting the relationship between Reservation Slot （RS） on the CCH and the data packet Transmission Slot （TS） on the DCH. Transmission interferences can be avoided by only observing CCH for the transmission time of a data packet. The proposed RS and contention micro-slot backoff mechanisms also greatly improve channel access efficiency. Simulation results show that compared to IFEE 802. 11 DCF and -Mc protocols, the proposed protocol can achieve a throughput gain of 88% in singlehop networks and 151% in nltihop networks at the same total data rate.展开更多
Our research aim is to investigate the buffet alleviation effect of static or vibrating bulges attached on the forebody surface of the model.Experiments and numerical simulations on a model consisting of a sharp-edged...Our research aim is to investigate the buffet alleviation effect of static or vibrating bulges attached on the forebody surface of the model.Experiments and numerical simulations on a model consisting of a sharp-edged,70°-leading edge sweep delta wing and twin swept back vertical tails were conducted.Models with different bulges were tested and computed at 10 and 20 m/s of free stream velocity at angles of attack ranging from 20°–50°.Dynamic strain gauge and multichannel data acquisition and analysis system were employed for the measurement of unsteady root strain on the vertical tails.Experimental and computational results show that both static and vibrating bulges behave effectively as a novel tool to alleviate tail buffet,and the alleviation effect depends largely on the vibrating frequency.Besides,one-sided bulge can only alleviate the buffeting response for the tail of the same side,and it has no obvious alleviation effect for the opposite tail.Results of the spectral analysis reveal that there are generally three peaks of spectral density for aircrafts of this configuration,and bulges used in this paper could alleviate tail buffeting,but the total lift and drag of the whole model show no obvious deviation compared to the base model and the dominant frequency of the vibration of the tails has not shifted.展开更多
文摘A data acquisition system based on LabVIEW and NI PXI-5105 is presented for multi-channel data acquisition. It can realize the functions of parameter setting, data acquisition and storage, waveform display and data analysis using LabVIEW and NI-SCOPE device driver. The advantages of the system are that the setting is convenient, the operation is easy, the interface is friendly and the functions are practical. The experiment results show that the system has good stability and high reliability and is a powerful tool for multi-channel data acquisition.
文摘The conception of multilevel security (MLS) is commonly used in the study of data model for secure database. But there are some limitations in the basic MLS model, such as inference channels. The availability and data integrity of the system are seriously constrained by it′s 'No Read Up, No Write Down' property in the basic MLS model. In order to eliminate the covert channels, the polyinstantiation and the cover story are used in the new data model. The read and write rules have been redefined for improving the agility and usability of the system based on the MLS model. All the methods in the improved data model make the system more secure, agile and usable.
基金supported by the National Basic Research Program of China (Grant Nos.2010CB950804 and 2013CB955801)the Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues (Grant No.XDA05040202)
文摘PARASOL(Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) multi-channel and multi-directional polarized data for different aerosol types were compared.The PARASOL polarized radiance data at 490 nm,670 nm,and 865 nm increased with aerosol optical thickness(AOT) for fine-mode aerosols;however,the polarized radiances at 490 nm and 670 nm decreased as AOT increased for coarse dust aerosols.Thus,the variation of the polarized radiance with AOT can be used to identify fine or coarse particle-dominated aerosols.Polarized radiances at three wavelengths for fine-and coarse-mode aerosols were analyzed and fitted by linear regression.The slope of the line for 670 nm and 490 nm wavelength pairs is less than 0.35 for dust aerosols.However,the value for fine-mode aerosols is greater than 0.60.The Support Vector Machine method(SVM) based on 12 vector features was used to discriminate clear sky,coarse dust aerosols,fine-mode aerosols,and cloud.Two cases were given and validated by AErosol RObotic NETwork(AERONET) measurements,MODIS(Moderate Resolution Imaging Spectroradiometer) FMF(Fine Mode Fraction at 550 nm) images,PARASOL RGB(Red Green Blue) images,and CALIOP(Cloud-Aerosol Lidar with Orthogonal Polarization) VFM(Vertical Feature Mask) data.
基金Acknowledgements This work was supported partially by the National Natural Science Foundation of China under Gants No. 60872011, No. 61171074 the National S＆T Major Project of China under Gant No. 2010ZX03003-003-03+1 种基金 the Program for New Century Excellent Talents in University the Fundamental Research Funds for the Central Universities.
文摘In order to resolve the hidden and exposed terminal problems and improve the probability of concurrent packet transmissions for multihop Mobile Ad Hoc Networks （MANETs）, a novel slotted Asyrmaetric Dual-Channel Medium Access Control （ADC-MAC） protocol is proposed. It exploits sirmltaneous reservation with less collisions and conision-flee data packet transmissions, and achieves optimal transmission balance on the Control Channel （CCH） and Data Channel （DCH） by adjusting the relationship between Reservation Slot （RS） on the CCH and the data packet Transmission Slot （TS） on the DCH. Transmission interferences can be avoided by only observing CCH for the transmission time of a data packet. The proposed RS and contention micro-slot backoff mechanisms also greatly improve channel access efficiency. Simulation results show that compared to IFEE 802. 11 DCF and -Mc protocols, the proposed protocol can achieve a throughput gain of 88% in singlehop networks and 151% in nltihop networks at the same total data rate.
基金supported by the National Natural Science Foundation of China(Grant No.11072199)
文摘Our research aim is to investigate the buffet alleviation effect of static or vibrating bulges attached on the forebody surface of the model.Experiments and numerical simulations on a model consisting of a sharp-edged,70°-leading edge sweep delta wing and twin swept back vertical tails were conducted.Models with different bulges were tested and computed at 10 and 20 m/s of free stream velocity at angles of attack ranging from 20°–50°.Dynamic strain gauge and multichannel data acquisition and analysis system were employed for the measurement of unsteady root strain on the vertical tails.Experimental and computational results show that both static and vibrating bulges behave effectively as a novel tool to alleviate tail buffet,and the alleviation effect depends largely on the vibrating frequency.Besides,one-sided bulge can only alleviate the buffeting response for the tail of the same side,and it has no obvious alleviation effect for the opposite tail.Results of the spectral analysis reveal that there are generally three peaks of spectral density for aircrafts of this configuration,and bulges used in this paper could alleviate tail buffeting,but the total lift and drag of the whole model show no obvious deviation compared to the base model and the dominant frequency of the vibration of the tails has not shifted.
