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浏览/检索结果: 共15条，第1-10条 帮助

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A two-angle model of dynamic wetting in microscale capillaries under low capillary numbers with experiments 期刊论文  OAI收割
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2018, 卷号: 520, 页码: 91-100
作者:  Lei D;  Lin M(林缅);  Li Y;  Jiang WB(江文滨)
  |  收藏  |  浏览/下载：72/0  |  提交时间：2018/10/30
Numerical simulation on solid-liquid two-phase flow in cross fractures 期刊论文  OAI收割
CHEMICAL ENGINEERING SCIENCE, 2018, 卷号: 181, 页码: 1-18
作者:  Li P(李鹏);  Zhang XH(张旭辉);  Lu XB(鲁晓兵)
  |  收藏  |  浏览/下载：47/0  |  提交时间：2018/07/17
Structural analysis of dendrimers based on polyhedral oligomeric silsesquioxane and their assemblies in solution by small-angle neutron scattering: Fits to a modified two correlation lengths model 期刊论文  OAI收割
POLYMER, 2016, 卷号: 100, 页码: 119-125
作者:  Yuan, Guangcui;  Wang, Xing;  Wu, Decheng;  Hammouda, Boualem
收藏  |  浏览/下载：23/0  |  提交时间：2016/12/29
Numerical Prediction of Film Cooling Effectiveness over Flat Plate using Variable Turbulent Prandtl Number Closures 期刊论文  OAI收割
2016
作者:  Ochrymiuk, T.
收藏  |  浏览/下载：32/0  |  提交时间：2017/05/27
Reentry guidance based on feedback linearization (EI CONFERENCE) 会议论文  OAI收割
2011 International Conference on Electronics, Communications and Control, ICECC 2011, September 9, 2011 - September 11, 2011, Ningbo, China
Li D.-W.
收藏  |  浏览/下载：31/0  |  提交时间：2013/03/25
This paper presents a new reentry guidance algorithm for RLV (Reusable Launching Vehicle). The algorithm consists of two integrated components: trajectory planning algorithm and tracking algorithm. The most striking feature of algorithm here lies in that both planning and tracking are executed directly in height-velocity space  which is different from the methodology of configuration of drag in traditional shuttle guidance. In the session of trajectory planning  all trajectory constraints can be expressed with upper bound and lower bound in height-velocity space  then a linear interpolation is carried to search the nominal trajectory satisfying the requirement of downrange and target constraints. Then the tracking algorithm uses feedback linearization method to track this nominal profile and meet all constraints. Another typical feature of this algorithm is the strategy of downrange extension using FPA (flight path angle) controller to fulfill the requirement of large downrange. Proper combination of planning-tracking algorithm and FPA controller can bring great flexibility and adaptability to reentry guidance. The algorithm is proved to be robust enough to accommodate the model error and noises in the dynamics. 2011 IEEE.  
Design of motion compensation mechanism of satellite remote sensing camera (EI CONFERENCE) 会议论文  OAI收割
International Symposium on Photoelectronic Detection and Imaging 2011: Space Exploration Technologies and Applications, May 24, 2011 - May 26, 2011, Beijing, China
Gu S.; Yan Y.; Xu K.; Jin G.
收藏  |  浏览/下载：49/0  |  提交时间：2013/03/25
With the development of aerospace remote sensing technology  the ground resolution of remote sensing camera enhances continuously. Since there is relative motion between camera and ground target when taking pictures  the target image recorded in recording media is moved and blurred. In order to enhance the imaging quality and resolution of the camera  the image motion had to be compensated. In order to abate the effect of image motion to image quality of space camera and improve the resolution of the camera  the compensation method of image motion to space camera is researched. First  the reason of producing drift angle and adjustment principle are analyzed in this paper. This paper introduce the composition and transmission principle of image motion compensation mechanism. Second  the system adopts 80C31 as controller of drift angle  and adopts stepping motor for actuators  and adopts absolute photoelectric encoder as the drift Angle measuring element. Then the control mathematical model of the image motion compensation mechanism are deduced  and it achieve the closed-loop control of the drift angle position. At the last  this paper analyses the transmission precision of the mechanism. Through the experiment  we measured the actual precision of the image motion compensation mechanism  and compared with the theoretical analysis. There are two major contributions in this paper. First  the traditional image motion compensation mechanism is big volume and quality heavy. This has not fit for the development trend of space camera miniaturization and lightweight. But if reduce the volume and quality of mechanism  it will bring adverse effects for the precision and stiffness of mechanism. For this problem  This paper designed a image motion compensation that have some advantages such as small size  light weight at the same time  high precision  stiffness and so on. This image motion compensation can be applicable to the small optics cameras with high resolution. Second  the traditional mechanism control need to corrected  fitting and iterative for the control formula of mechanism. Only in this way  we can get the optimal control mathematical model. This paper has high precision of the control formula derived. It can achieve the high precision control without fitting  It also simplify the difficulty of control mathematical model establishment. This paper designed the range of adjusting of image motion compensation mechanism between -5 +5. Based on choosing-5  -4  -3  -2  -1  0  +1  +2  +3  +4  +4 as the expectation value of the imaginary drift angle  we get ten groups of the fact data in adjusting drift angle measured. The test results show that the precision of the drift angle control system can be achieved in 1. It can meet the system requirements that the precision of the control system is less than 3'  and it can achieve the high-precision image motion compensation. 2011 SPIE.  
Analysis of zenith pass problem in a roll-pitch optics seeker (EI CONFERENCE) 会议论文  OAI收割
2011 International Conference on Electronics and Optoelectronics, ICEOE 2011, July 29, 2011 - July 31, 2011, Dalian, China
作者:  Jiang H.
收藏  |  浏览/下载：36/0  |  提交时间：2013/03/25
There are mainly two kind of structures for a missile two-axes seeker  which is always mentioned as elevate-azimuth and roll-pitch. The elevate-azimuth structured seeker has been studied for a long time  and it is applied in all sort of missiles. Not only structure design but also control algorithm of the elevate-azimuth seeker are deeply developed. But for elevate-azimuth seeker there are several disadvantages such as big size and large abaxial angle blind. So the elevate-azimuth seeker gimbal angle is designed up to 65 according to relative references. In modern air war  it is important for a missile to have the ability of "first recognize" and "first attack". That means the air to air missile seeker is required to be a system with large gimbal angle and large abaxial launch angle. With the mentioned requirement  roll-pitch seeker with its advantages smart size and large gimbal angle is studied widely and deeply. The pitch angle of roll-pitch is up to 90 while its roll angle up to n 360. But there are also some disadvantages for the roll-pitch seeker  the most troublesome one is the zenith pass problem. The zenith pass problem is brought about from the gimbal kinematics  it is said that when target moves in the center of image plane  roll servo command gotten from the kinematics algorithm will go to infinite. Math model of zenith pass problem is proposed in this paper and two ways to solve the problem are brought forward. 2011 IEEE.  
3R intersection target positioning in real time based on distance (EI CONFERENCE) 会议论文  OAI收割
2010 International Conference on Computer, Mechatronics, Control and Electronic Engineering, CMCE 2010, August 24, 2010 - August 26, 2010, Changchun, China
Nengwei W.; Juan C.; Jian C.
收藏  |  浏览/下载：16/0  |  提交时间：2013/03/25
The positioning error based on angle  angle-distance or single station positioning increases with the distance increasing. 3R target positioning based on distance can obtain the high precision measurements in long distance. Here we give the 3R model for the intersection positioning  provide the two necessary conditions for getting the optimum intersection point. The experimental results show that the intersection precision based on angle is over 2m and will degrade greatly with the increasing of distance while the one based on 3R model will improve and the error decrease gradually. That the precision of the distance measurement is about 1m means the 3R model is better than the angle positioning  which can compensate the drawbacks of the angle positioning at short distance. 2010 IEEE.  
Parallel estimation of translation for video stabilization (EI CONFERENCE) 会议论文  OAI收割
2010 6th International Conference on Wireless Communications, Networking and Mobile Computing, WiCOM 2010, September 23, 2010 - September 25, 2010, Chengdu, China
作者:  Wang H.;  Liu G.;  Wang H.;  Wang H.;  Wang H.
收藏  |  浏览/下载：102/0  |  提交时间：2013/03/25
Translation motion estimation is the major aspect of video motion compensation  especially in two-dimensional turntable. This paper presents a robust parallel estimation algorithm of translation in video stabilization system. The equivalent model of translation that derived is accorded with small rotation angle comparatively. A parallel algorithm based on grey mapping is used in local motion estimation to shorten the estimation time and improve the computation efficiency. After local motion vectors are calculated  a fast filter can detect the spurious vectors avoiding possible jerks. The suggested translation estimation algorithm has been implemented on NVIDIA GTX 260  the experimental results show that  the average time of the estimation and compensation finished in 16 ms/frame  and stabilize 1k1k pixels sequence gray video up to 60 frames/s. 2010 IEEE.  
Earth elevation map production and high resolution sensing camera imaging analysis (EI CONFERENCE) 会议论文  OAI收割
Optoelectronic Imaging and Multimedia Technology, October 18, 2010 - October 20, 2010, Beijing, China
作者:  Dai L.
收藏  |  浏览/下载：148/0  |  提交时间：2013/03/25
The Earth's digital elevation which impacts space camera imaging has prepared and imaging has analysed. Based on matching error that TDI CCD integral series request of the speed of image motion  statistical experimental methods-Monte Carlo method is used to calculate the distribution histogram of Earth's elevation in image motion compensated model which includes satellite attitude changes  orbital angular rate changes  latitude  longitude and the orbital inclination changes. And then  elevation information of the earth's surface from SRTM is read. Earth elevation map which produced for aerospace electronic cameras is compressed and spliced. It can get elevation data from flash according to the shooting point of latitude and longitude. If elevation data between two data  the ways of searching data uses linear interpolation. Linear interpolation can better meet the rugged mountains and hills changing requests. At last  the deviant framework and camera controller are used to test the character of deviant angle errors  TDI CCD camera simulation system with the material point corresponding to imaging point model is used to analyze the imaging's MTF and mutual correlation similarity measure  simulation system use adding cumulation which TDI CCD imaging exceeded the corresponding pixel horizontal and vertical offset to simulate camera imaging when stability of satellite attitude changes. This process is practicality. It can effectively control the camera memory space  and meet a very good precision TDI CCD camera in the request matches the speed of image motion and imaging. 2010 SPIE.