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Long-Time Asymptotics for the Focusing Hirota Equation with Non-Zero Boundary Conditions at Infinity Via the Deift-Zhou Approach 期刊论文 OAI收割
MATHEMATICAL PHYSICS ANALYSIS AND GEOMETRY, 2021, 卷号: 24, 期号: 2, 页码: 37
作者: Chen, Shuyan; Yan, Zhenya; Guo, Boling

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收藏 | 浏览/下载：54/0 | 提交时间：2021/06/01

Focusing Hirota equation Non-zero boundary conditions Inverse scattering Oscillatory Riemann-Hilbert problem Nonlinear steepest-descent method Long-time asymptotics

Improved TOPS about direction of arrival estimation for wideband signals (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Vibration, Structural Engineering and Measurement, ICVSEM2011, October 21, 2011 - October 23, 2011, Shanghai, China
作者: He B.

收藏 | 浏览/下载：21/0 | 提交时间：2013/03/25

The study about the direction-of-arrival (DOA) estimation for wideband signals is a basic topic of Signal Processing. The method called test of orthogonality of projected subspaces (TOPS) does not require initial values to form focusing matrix compared with the coherent signal subspace method (CSSM) but it has poor performance for coherent wideband signals at low signal-to-noise ratio (SNR). Based on the lack of the conventional TOPS this paper reconstructs a set of new matrices with the narrowband correlated matrices coming from the DFT decomposition of the array output and modifies the method frame of the conventional TOPS. So we get a set of reconstructed matrices with full rank corresponding to each frequency bin and which have no array aperture loss. The improved TOPS can estimate the DOA for coherent wideband sources at low SNR and enhances the performance of the conventional TOPS. Simulation results show that the improved TOPS is effective and the total performance of which is similar to the rotational signal-subspace (RSS) method. (2012) Trans Tech Publications.

An auto-focus algorithm of fast search based on combining rough and fine adjustment (EI CONFERENCE) 会议论文 OAI收割
3rd international Conference on Manufacturing Science and Engineering, ICMSE 2012, March 27, 2012 - March 29, 2012, Xiamen, China
作者: Zhang S.; Zhang Y.

收藏 | 浏览/下载：32/0 | 提交时间：2013/03/25

A coarse and fine combined fast search and auto-focusing algorithm was suggested in this paper. This method can automatically search and find the focal plane by evaluating the image definition. The Krisch operator based edge energy function was used as the big-step coarse focusing and then the wavelet transform based image definition evaluation function which is sensitivity to the variation in image definition was used to realize the small-step fine focusing in a narrow range. The un-uniform sampling function of the focusing area selection used in this method greatly reduces the workload and the required time for the data processing. The experimental results indicate that this algorithm can satisfy the requirement of the optical measure equipment for the image focusing. (2012) Trans Tech Publications.

The analyze and design of focusing system for space camera (EI CONFERENCE) 会议论文 OAI收割
2012 International Conference on Electrical Insulating Materials and Electrical Engineering, EIMEE 2012, May 25, 2012 - May 27, 2012, Shenyang, Liaoning, China
作者: Yu T.

收藏 | 浏览/下载：32/0 | 提交时间：2013/03/25

In order to control the focal plane and guarantee the imaging quality of space camera the focusing system was proposed. Firstly the reasons of defocusing were analyzed and a solution method was given. Secondly the system structure and operating principle were introduced. Thirdly the system design was presented in detail. Finally the system was experimented. Experimental results indicate that the defocusing amount of camera can be controlled below 10 um and the focusing system satisfies the requirement of system design. (2012) Trans Tech Publications Switzerland.

Femtosecond electron pulse compression by using the time focusing technique in ultrafast electron diffraction 期刊论文 OAI收割
chinese physics b, 2011, 卷号: 20, 期号: 11, 页码: 114102
作者: Wen Wen-Long; Lei Xiao-Hong; Hu Xin; Xu Xiang-Yan; Wang Jun-Feng

收藏 | 浏览/下载：41/0 | 提交时间：2012/06/29

time focusing technique temporal pulse compressing time-dependent electric field Monte-Carlo method

Design and analysis of auto-focus assembly for spaceborne remote sensing camera (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
作者: Chen W.; Gao X.

收藏 | 浏览/下载：33/0 | 提交时间：2013/03/25

Spaceborne remote sensing camera may be out of focus when the environment and photographic distance changes. In order to get higher ground sampled distance for the camera based on the experience gained from the development of a remote sensing camera working principle of auto-focus assembly control system was discussed. Time of waveform extraction was reduced. It sets force an auto-focus assembly that uses cam and line guide rail in order to move the lens group. The motion error of the auto-focus assembly was difficult to be eliminated and would affect on the focusing accuracy of the spaceborne remote sensing camera directly. So it was analyzed at both ends of the focusing structure. The CCD detector can keep stable when the remote sensing camera is imaging. The motion error was tested to verify the validity of the simulation result and it is less than 0.01mm. Its accuracy meets using demand. The focusing method of moving focal plane is suitable for spaceborne remote sensing camera. 2011 IEEE.

Accuracy analysis and optimization design of constant-diameter cam (EI CONFERENCE) 会议论文 OAI收割
2011 International Conference on Electric Information and Control Engineering, ICEICE 2011, April 15, 2011 - April 17, 2011, Wuhan, China
Yuan G.-Q.; Ding Y.-L.; Hui S.-W.; Liu Z.-H.; Li Y.-W.

收藏 | 浏览/下载：37/0 | 提交时间：2013/03/25

A constant-diameter cam gets its name because the centers of the rollers are a constant distance apart. This paper presents an Accuracy analysis and optimization design method for constant-diameter cam mechanism. Factors affecting the accuracy of cam are studied in the paper. The influences of the roller radial runout cam machining error and the base circle radius on accuracy are analyzed. Then a method to guarantee the cam diameter constant and remove return stroke error is studied using least-squares method. The analysis results indicate that the focusing accuracy can reach 4.4m and the return stroke error can reach 4.8m the functioning of institutions is stable and reliable. 2011 IEEE.

Analysis of a diffractive microlens using the finite-difference time-domain method (EI CONFERENCE) 会议论文 OAI收割
作者: Liu Y.; Liu H.; Liu H.; Liu H.; Liu Y.

收藏 | 浏览/下载：31/0 | 提交时间：2013/03/25

The finite-difference time-domain (FDTD) method is used as rigorous electromagnetic analysis model to calculate the field for a diffractive microlens (DML). The FDTD is used for the entire solution rather than using a near- to far-field propagation method to obtain the far-field energy distribution thus all the results are vector based. We derived a formula to calculate the magnitude of electric field which is time dependent and can be used to graphically show the light wave propagation and focusing process through a DML. Both the comparison and the integral methods are presented to obtain wave amplitude in full solution space and the distribution of light energy behind a DML is illustrated based on the wave amplitude. The formula of diffractive efficiency of the DML is derived from a time-averaged Ponyting vector which can indicate the propagation direction of light energy. Application of these formulations in the analysis of a DML example demonstrates the high accuracy and efficiency of our method. 2010 Society of Photo-Optical Instrumentation Engineers.

Far-field focusing of laser beam based on digital image processing techniques (EI CONFERENCE) 会议论文 OAI收割
Optoelectronic Imaging and Multimedia Technology, October 18, 2010 - October 20, 2010, Beijing, China
作者: Zhao S.; Tian Y.-Z.; Liu L.-S.; Guo J.; Zhang H.-Y.

收藏 | 浏览/下载：28/0 | 提交时间：2013/03/25

In order to lead the laser beam transmit in the atmosphere convergently an experiment of laser focus at the distance of 450m and 300m has been operated in the outdoor place. The actual manipulations are as follows: Firstly the laser was collimated by a beam expander then the near-parallel laser beam was transmitted with a Galileo telescope system and the distance between the concave lens and the convex lens can be tuned through a precise displacement platform so the focus of the system changed due to the tiny displacement of the concave lens. Secondly the average power of the laser spot can be measured using power meter the power is 47.67mW and the standard deviation is 0.67mW while the focal length is 450m. Thirdly the energy distribution was found through the laser beam analyzer. The spot images were saved using the beam analyzer then the saved image can be processed with Matlab software afterwards. The function named EDGE and Sobel operator was used in the pre-processing of the saved image then method of median filter was used in the course of image de-noising and 53H filter was adopted in the signal analysis. The diameter of laser spot was obtained by the method above the diameter is 5.56mm and the standard deviation is 0.24mm. The spot center excursion is 0.56mm it is 10.43% of the total diameter of the laser spot. At last the key factors of the energy dissipation in the focusing system can be summarized as follows: restriction of the diffraction limit attenuation in the atmosphere geometrical aberration of optical system and the diffraction limit and the geometrical aberration are significant in the three factors above so we can reduce the impact of the both factors during the design of optical system. The reliable referenced data of the system design can be acquired through the primary experiment research. 2010 SPIE.

Application of precision harmonic gear drive in focusing mechanism of space camera (EI CONFERENCE) 会议论文 OAI收割
5th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Smart Structures and Materials in Manufacturing and Testing, April 26, 2010 - April 29, 2010, Dalian, China
作者: Zhang X.; Zhang X.; Zhang X.

收藏 | 浏览/下载：31/0 | 提交时间：2013/03/25

A kind of precision harmonic gear drive in the focusing mechanism of space camera is studied which adopt external meshing complex wave transmission mode. Wave generator is combined with an elliptic cam and a flexible bearing around it. Flexspline is a structure of single wave with the same teeth. The output shaft is supported by a single cross-roller bearing. Ball screws connected the output shaft translate the rotational motion to the linear motion and drive the focusing mirror repeated moving along the linear guide. The output rigid wheel is connected with absolute encoder to detect displacement of focusing movement. It has the characteristics of big transmission ratio high precision compact structure high efficiency and smooth running etc. According to the practical application of this harmonic gear drive in the space camera the location relationship between the displacement of focusing structure and the focal plane movement is derived and the system error is analyzed its accuracy is tested with the open-loop control method. Experimental results show that transmission ratio of the instrument is 1:70 repeated positional accuracy is 2m which meet the requirements for use. 2010 SPIE.