中国科学院机构知识库网格系统: 检索

Analysis of Observation Performance of a Mobile Coherent Doppler Wind Lidar Using DBS Scanning Mode 期刊论文 OAI收割
Journal of Physics: Conference Series, 2021, 卷号: 1739
作者: Dong,Debao; Yang,Shizhi; Weng,Ningquan; Zhang,Guangyuan; Huang,Jing

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Coherent Doppler Wind Lidar (CDWL) Observation performance Doppler beam-swinging (DBS) scanning Wind direction and Wind speed Comparison experiment

Comparison of simulated backgrounds with in-orbit observations for HE, ME, and LE onboard Insight-HXMT 期刊论文 OAI收割
Astrophysics and Space Science, 2020, 卷号: 365, 页码: 158
作者: HXMT

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Insight-HXMT Geant4 simulation Background observation Astrophysics - Instrumentation and Methods for Astrophysics Abstract: Insight-HXMT, the first X-ray astronomical satellite in China, aims to reveal new sources in the Galaxy and to study fundamental physics of X-ray binaries from 1 to 250 keV. It has three collimated telescopes, the High Energy X-ray telescope (HE), the Medium Energy X-ray telescope (ME), and the Low Energy X-ray telescope (LE). Before the launch, in-orbit backgrounds of these three telescopes had been estimated through Geant4 simulation, in order to investigate the instrument performance and the achievement of scientific goals. In this work, these simulated backgrounds are compared with in-orbit observations. Good agreements are shown for all three telescopes. For HE, (1) the deviation of the simulated background rate after two years of operation in space is 5 % from the observation (2) the total background spectrum and the relative abundance of the 67 keV line show long-term increases both in simulations and observations. For ME, (1) the deviation of simulated background rate is within 15 % from the observation, and (2) there are no obvious long-term increase features in the background spectra of simulations and observations. For LE, the background level given by simulations is also consistent with observations. The consistencies of these comparisons validate that the Insight-HXMT mass model, i.e., space environment components and models adopted, physics processes selected, and detector constructions built, is reasonable. However, the line features at 7.5 and 8.0 keV, which are obvious in the observed spectra of LE, are not evident in simulations. This might result from uncertainties in the LE constructions.

Gas-liquid two-phase flow behaviors and performance characteristics of proton exchange membrane fuel cells in a short-term microgravity environment 期刊论文 OAI收割
JOURNAL OF POWER SOURCES, 2017, 卷号: 353, 页码: 1-10
作者: Guo H; Liu X; Zhao JF(赵建福); Ye F; Ma CF

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Proton exchange membrane fuel cell Microgravity Performance Two-phase flow Visual observation

A hybrid median filter for enhancing dim small point targets and its fast implementation (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Multimedia and Signal Processing, CMSP 2011, May 14, 2011 - May 15, 2011, Guilin, Guangxi, China
Yang Q.

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Weak stars and middle altitude orbit satellites or high altitude orbit satellites are presented as dim point targets in images of astronomical observation. They have low intensity and occupy few pixels in image. In most situations the background of sky is always ununiform and there exists pulse noises. Thus results in targets submerging in background noises and low signal noise ratio (SNR). Median filter is an effective method for removing pulse noise. But it can blur image after modifying gray of non-noise pixels when image has low SNR. A hybrid median filter algorithm is proposed to process low SNR dim point targets image. The newly proposed method can suppress the pulse noises also can increase target $SNR$ and does not add extra fake targets. The time complexity of median filter is O(N2)(N is the widow size) and is difficult to implement in hardware. For quasi real time application a fast implementation of our hybrid median filter is proposed to reduce the time complexity to O(N). Experimental results show that the newly proposed algorithm is superior to ordinary median filter and fast median filter by comparing visual effect and performance. 2011 IEEE.

Application of improved UKF algorithm in initial alignment of SINS (EI CONFERENCE) 会议论文 OAI收割
2011 2nd International Conference on Artificial Intelligence, Management Science and Electronic Commerce, AIMSEC 2011, August 8, 2011 - August 10, 2011, Zhengzhou, China
Su W. X.

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In order to improve the initial alignment accuracy and convergence rate of the SINS system proposed the improved UKF algorithm (AUKF) based on the Unscented Kalman Filter (UKF). Noise statistical characteristics are mostly unknown in real systems when it was effected by the initial value errors and dynamic model errors AUKF algorithm can real-time adjust the covariance of the state vector and observation vector and balance the right ratio of the state information and observation information in the filter results thereby improving the system performance. The experimental results show: The Improved UKF Algorithm enhances the convergence speed and alignment accuracy effectively. 2011 IEEE.

The stability design and realization of airborne platform based on TMS320F2812 (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Mechatronic Science, Electric Engineering and Computer, MEC 2011, August 19, 2011 - August 22, 2011, Jilin, China
作者: Zhang X.; Zhang X.; Zhang X.

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Airborne electro-optical stable platform can isolate movement and vibration of the airframe stabilizes the optic axis of the photoelectic detector realize the observation and tracking for the object. It has comprehensive application value in army and cicil field. Most of present airborne platforms are analogic control system digital control system can improve the system general performance digital control is the development direction of platform systems. In view of the requirements of isolating disturbances and stabilizing optical axis of high-precision photoelectric guidance system a three-axis stabilized platform system centering on the rate gyro was designed. The disturbance-isolation theory of the stabilized platform was analyzed and the control structure including multiple closed-loops was designed. At last a controller of the servo system based on TMS320F2812 DSP has been designed. Experiment results meet the technical index and precision requirement and illustrate the practicability and effectiveness of the scheme. 2011 IEEE.

Validation of the dust layer structure over the Taklimakan Desert, China by the CALIOP space-borne lidar using ground-based lidar - Part II 会议论文 OAI收割
Proceedings of SPIE - The International Society for Optical Engineering, Remote Sensing and Modeling of the Atmosphere, Oceans, and Interactions III, Incheon, Korea, Republic of, 2010
Jin; Yoshitaka1; Kai; Kenji1; Shibata; Takashi1; Zhang; Kecun2; Zhou; Hongfei3

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Aerosol optical depths - Aerosols and clouds - Backscatter profiles - Backscattering coefficients - Backscattering ratio - CALIPSO - Cirrus clouds - Color ratios - Correlation coefficient - Dust layer - Ground based - Level 2 - lidar - Lidar observation - Lidar ratio - Performance functions - Space-borne lidar - Taklimakan desert - Tropospheric aerosolsC

The synthesis and field emission property of carbon nanotubes on carbon fibers substrate (EI CONFERENCE) 会议论文 OAI收割
Technical Digest of the 20th International Vacuum Nanoelectronics Conference, IVNC 07, July 8, 2008 - July 12, 2008, Chicago, IL, United states
Leyong Z.; Weibiao W.; Jingqiu L.; Yuxue X.; Da L.; Song C.; Haifeng Z.

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Using ferrocene as catalyst precursor C2H2 as carbon source carbon nanotubes (CNTs) with uniform density were synthesized on carbon fibers substrate by floating catalyst method. The morphology and microstructure were characterized by field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (HRTEM). The observation showed that the length of CNTs is about 2 m the average space between adjacent CNTs is about 300 nm and the diameter of CNT is about 45 nm. The less dense "short and stubby" aligned CNTs films should have good electron field emission characteristics. The results of field emission showed that the emission current of CNTs/carbon fibers was 5 A at the field of 2.5 V/m and the emission current can be 280 A with a field of 7 V/m (the specimen area is 0.25 cm2 and the distance between cathode and anode is 200 m). The calculation based on the F-N plot indicated that the field enhancement factor of CNTs tip is 499122. Using the conductivity and chemical stability of carbon fibers and the uniform and sparse density distribution of CNTs on carbon fibers substrate the tip predominance of carbon nanotubes can be exerted and simultaneously the effect of screening effects between adjacent carbon nanotubes on the field emission performance can also be effectively decreased. The CNTs synthesized on carbon fibers substrate has many predominances for the fabrication of cold cathode devices. For example using the removability of carbon fibers the cathode of CNTs/carbon fibers can be arbitrarily moved enlaced or combined to form different patterns and the cathode of CNTs/carbon fibers can be also fabricated in large size. Therefore CNTs/carbon fibers may have potential application in field emission displays.

Design of GPS/INS integrated navigation system based on multisensor information fusion (EI CONFERENCE) 会议论文 OAI收割
6th World Congress on Intelligent Control and Automation, WCICA 2006, June 21, 2006 - June 23, 2006, Dalian, China
Chunmei H.; Yantao T.; Wanxin S.; Mao L.

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Two kinds of design methods of GPS/INS integrated navigation system are presented that is GPS/INS integrative system and integrated navigation system based on information fusion. By analyzing mathematics model of the first system error we found that inertia velocity error would cause code loop track error. Consequently the pseudo range meterage error is interrelated with inertia velocity error which is complex to calculate. If this relativity is ignored in the state equation and observation equation of this system it must affect the estimated precision of the kalman filter and maybe the system is unstable. Therefore the second integrated navigation method is introduced. It adopts information fusion federal kalman filter and covariance. And consider the above pertinence to analyze the navigation performance of the integration system. Then it gives the flow of federal kalman filter algorithm. By analyzing the conclusion is that velocity error of integrated navigation system drops from 0.5m/s to below 0.05m/s and improves the precision and reliability of the navigation system effectively well continuity and real-time capability. It provides an effective way for data analysis and process of fusion navigation system. 2006 IEEE.

Integrated mach-zehnder micro-interferometer for gas trace remote sensing (EI CONFERENCE) 会议论文 OAI收割
ICO20: Remote Sensing and Infrared Devices and Systems, August 21, 2005 - August 26, 2005, Changchun, China
作者: Wang P.

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The realisation process and the preliminary tests on the performances of an integrated Mach-Zehnder Interferometer on LiNbO3 (Lithium Niobate) substrate is presented. The microsystem has been obtained by using medium mass Ion Implantation on X-cut Lithium Niobate crystals. The interferometer is formed by integrated optical channel waveguides: the phase shift between the two optical paths has been obtained 1mm 2 cross section and weights a few grams. The power consumption is in the milliwatt range. In the present work results obtained in the spectral window (0.4m-1.1m) will be presented. The performance of the device without moving parts evaluated on standard radiation sources by applying a suitable electric field. The whole device is 60mm long demonstrates that a spectral resolution better than 0.3nm can be obtained on 400nm spectral windows. The Micro-interferometer has been tested in laboratory with a calibrated cell containing NO2 gas and has demonstrated sensitivity in the ppb range if suitable optical paths are used. Its reduced dimensions and weights make these micro-systems ideal for a wide range of applications has a 0.57times spanning from Space Technology Earth observation for Environment monitoring to Safety and Security applications.