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Recursive adaptive filter using current innovation for celestial navigation during the Mars approach phase

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science China(Information sciences) 2017年第3期60卷 168-182页

作者： Xiaolin NING Zhuo LI Weiren WU Yuqing YANG Jiancheng FANG Gang LIU school of instrumentation science & opto-electronics engineering Beihang University

Celestial navigation is a commonly used autonomous navigation technique for deep space navigation.A nonlinear filter such as the unscented Kalman filter(UKF) is typically applied in a celestial navigation system(CNS). However, on account of being subject to a number of factors, such as ephemeris errors and centroid determination, the measurement model error of a CNS cannot be accurately determined. The analysis conducted in this study also shows that the measurement model error is time-variant during the Mars approach *** implies that covariance matrix of the measurement error R is usually inaccurate, which may induce large estimation errors that even result in filter divergence. Some adaptive methods are able to address this ***, traditional adaptive filters, for scaling R, usually require a sequence of innovation and are affected by the statistic window size. A new recursive adaptive UKF(RAUKF) is proposed in this paper, which only uses current innovation to scale R. The navigation performance of the proposed RAUKF method is compared with some traditional adaptive filters through simulations. The results show that this method is better than traditional adaptive filters in a CNS during the Mars approach phase.

关键词： deep space adaptive UKF navigation Mars approach variant noise

Sliding mode control of reaction flywheel-based brushless DC motor with buck converter

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Chinese Journal of Aeronautics 2013年第4期26卷 967-975页

作者： Liu Gang Zhang Cong school of instrumentation science and opto-electronics engineering Beihang University

Reaction flywheel is a significant actuator for satellites＇ attitude control. To improve output torque and rotational speed accuracy for reaction flywheel, this paper reviews the modeling and control approaches of DC-DC converters and presents an application of the variable structure system theory with associated sliding regimes. Firstly, the topology of reaction flywheel is constructed. The small signal linearization process for a buck converter is illustrated. Then, based on the state averaging models and reaching qualification expressed by the Lee derivative, the general results of the sliding mode control （SMC） are analyzed. The analytical equivalent control laws for reaction flywheel are deduced detailedly by selecting various sliding surfaces at electromotion, energy consumption braking, reverse connection braking stages. Finally, numerical and experimental examples are presented for illustrative purposes. The results demonstrate that favorable agreement is established between the simulations and experiments. The proposed control strategy achieves preferable rotational speed regulation, strong rejection of modest disturbances, and high-precision output torque and rotational speed tracking abilities.

关键词： DC-DC converter Flywheels State averaging model Sliding mode control Sliding surface Topology

Improvement of speckle noise suppression in digital holography by rotating linear polarization state

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Chinese Optics Letters 2011年第6期9卷 36-38页

作者：肖文张菁戎路潘锋刘烁王璠璟何阿呷 school of instrumentation science and opto-electronics engineering Beihang University

An improved polarization recording approach to reduce speckle noise in digital holography is proposed. Multiple off-axis holograms are obtained by rotating the linear polarization state of both illumination and reference wave simultaneously. By averaging the intensity fields, the speckle noise in the reconstructed images is well suppressed. Statistical evaluation of the experimental results shows the effectiveness and improvement of the proposed method.

关键词： Computer generated holography Holograms Polarization Rotation

Advancements in Liver Tumor Detection:A Comprehensive Review of Various Deep Learning Models

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Computer Modeling in engineering & sciences 2025年第1期142卷 91-122页

作者： Shanmugasundaram Hariharan D.Anandan Murugaperumal Krishnamoorthy Vinay Kukreja Nitin Goyal Shih-Yu Chen Deptartment of Artificial Intelligence and Data science Vardhaman College of EngineeringHyderabad501218India Deptartment of CSE V.S.B College of EngineeringKarur639111India Deptartment of Electrical and electronics engineering Vardhaman College of EngineeringHyderabad501218India Centre for Research Impact&Outcome Chitkara UniversityRajpura140401PunjabIndia Department of Computer science and engineering School of Engineering and TechnologyCentral University of HaryanaMahendergarh123031HaryanaIndia Department of Computer science and Information engineering National Yunlin University of Science and TechnologyYunlin64002Taiwan Intelligence Recognition Industry Service Research Center National Yunlin University of Science and TechnologyYunlin64002Taiwan

Liver cancer remains a leading cause of mortality worldwide,and precise diagnostic tools are essential for effective treatment *** Tumors(LTs)vary significantly in size,shape,and location,and can present with tissues of similar intensities,making automatically segmenting and classifying LTs from abdominal tomography images crucial and *** review examines recent advancements in Liver Segmentation(LS)and Tumor Segmentation(TS)algorithms,highlighting their strengths and limitations regarding precision,automation,and *** metrics are utilized to assess key detection algorithms and analytical methods,emphasizing their effectiveness and relevance in clinical *** review also addresses ongoing challenges in liver tumor segmentation and identification,such as managing high variability in patient data and ensuring robustness across different imaging *** suggests directions for future research,with insights into technological advancements that can enhance surgical planning and diagnostic accuracy by comparing popular *** paper contributes to a comprehensive understanding of current liver tumor detection techniques,provides a roadmap for future innovations,and improves diagnostic and therapeutic outcomes for liver cancer by integrating recent progress with remaining challenges.

关键词： Liver tumor detection liver tumor segmentation image processing liver tumor diagnosis feature extraction tumor classification deep learning machine learning

Performance of third-order ghost imaging with second-order intensity correlation

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Chinese Optics Letters 2011年第8期9卷 27-30页

作者：曹彬张春熹欧攀 school of instrumentation science and opto-electronics engineering Beihang University

The third-order ghost imaging with the second-order intensity correlation is theoretically and experi- mentMly demonstrated. The resolution and visibility of the reconstructed image are discussed, and the relationship between resolution and visibility is analyzed. The theoretical results show that a tradeoff exists between the visibility and resolution of the reconstructed image; the better the image resolution, the worse the image visibility. Numerical simulations are carried out to verify this theory, and a ghost imaging experiment is conducted to validate our calculations. The experimental results agree with the theoretical predictions.

关键词： Image resolution

Robust Consensus of Multi-Agent Systems with Uncertain Exogenous Disturbances

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Communications in Theoretical Physics 2011年第12期56卷 1161-1166页

作者：杨洪勇郭雷韩潮 school of instrumentation science and opto-electronics engineering school of Aircraft Control Technology Beihang University school of Information science and engineering Ludong University school of instrumentation science and opto-electronics engineering Beihang University

The objective of this paper is to investigate the consensus of the multi-agent systems w/th nonlinear coupling function and external disturbances. The disturbance includes two parts, one part is supposed to be generated by an exogenous system, which is not required to be neutrally stable as in the output regulation theory, the other part is the modeling uncertainty in the exogenous disturbance system. A novel composite disturbance observer based control （DOBC） and H∞ control scheme is presented so that the disturbance with the exogenous system can be estimated and compensated and the consensus of the multi-agent systems with fixed and switching graph can be reached by using Hoo control law. Simulations demonstrate the advantages of the proposed DOBC and H∞ control scheme.

关键词： robust controller multi-agent systems consensus uncertain disturbance

Comparison of two absorption imaging methods to detect cold atoms in magnetic trap

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Chinese Physics B 2015年第2期24卷 146-151页

作者：王妍胡朝晖亓鲁 science and Technology on Inertial Laboratory School of Instrumentation Science and Opto-electronics EngineeringBeihang University

Two methods of absorption imaging to detect cold atoms in a magnetic trap are implemented for a high-precision cold atom *** the first method,a probe laser which is in resonance with a cycle transition frequency is used to evaluate the quantity and distribution of the atom *** the second method,the probe laser is tuned to an open transition frequency,which stimulates a few and constant number of photons per *** method has a shorter interaction time and results in absorption images which are not affected by the magnetic field and the light *** make a comparison of performance between these two imaging methods in the sense of parameters such as pulse duration,light intensity,and magnetic field *** experimental results show that the second method is more reliable when detecting the quantity and density profiles of the *** results fit well to the theoretical analysis.

关键词： absorption imaging open-channel transition cold atoms magnetic trap

Research of Optical Fiber Coil Winding Model Based on Large-deformation Theory of Elasticity and Its Application

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Chinese Journal of Aeronautics 2011年第5期24卷 640-647页

作者： JIA Ming YANG Gongliu school of instrumentation science and opto-electronics engineering Beihang University Beijing 100191 China

Optical fiber coil winding model is used to guide proper and high precision coil winding for fiber optic gyroscope （FOG） application. Based on the large-deformation theory of elasticity, stress analysis of optical fiber free end has been made and balance equation of infinitesimal fiber is deduced, then deformation equation is derived by substituting terminal conditions. On condition that only axial tensile force exists, approximate curve equation has been built in small angle deformation scope. The comparison of tangent point longitudinal coordinate result between theory and approximation gives constant of integration, and expression with tangent point as origin of coordinate is readjusted. Analyzing the winding parameters of an example, it is clear that the horizontal distance from the highest point of wheel to fiber tangent point has millimeter order of magnitude and significant difference with fiber tension variation, and maintains invariant when wheel radius changes. The height of tension and accurate position of tangent point are defined for proper fiber guide. For application to fiber optic gyroscope, spiral-disc winding method and nonideal deformation of straddle section are analyzed, and then spiral-disc quadrupole pattern winding method has been introduced and realized by winding system. The winding results approve that the winding model is applicable.

关键词： fibers fiber optics large-deformation fiber optic gyroscope spiral-disc winding quadrupole pattern

Two-Detector Arbitrary NtH^(-)Order HBT-Type Ghost Diffraction

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Chinese Physics Letters 2012年第1期29卷 126-129页

作者： CAO Bin ZHANG Chun-Xi OU Pan LIN Zhi-Li SUN Ming-Jie school of instrumentation science and opto-electronics engineering Beihang UniversityBeijing 100191

The imaging quality using two-detector arbitrary N th-order intensity correlation in optics is *** is theoretically demonstrated that with the order of intensity correlation N increases,the visibility of the retrieved image enhances promptly;and different n-fold intensity on one arm of the intensity correlation leads to different visibility,whereas the resolution is independent of N and *** numerical simulation results are shown to be consistent with our theoretical analysis ***,a particular imaging system of the two-detector N thorder Hanbury-Brown-Twiss(HBT)type ghost diffraction is conceived by using a slit as the object,the image quality by this type of ghost diffraction is *** experimental results coincide with our theoretical analysis.

关键词： ghost Ghost prompt