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Adaptive path planning for unmanned aerial vehicles based on bi-level programming and variable planning time interval

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Chinese Journal of Aeronautics 2013年第3期26卷 646-660页

作者： liu Wei zheng zheng Cai Kaiyuan School of Automation Science and Electrical Engineering Beihang University Science and Technology on Aircraft Control Laboratory High-Tech Institute of Xi'an

This paper presents an adaptive path planner for unmanned aerial vehicles （UAVs） to adapt a real-time path search procedure to variations and fluctuations of UAVs’ relevant performances, with respect to sensory capability, maneuverability, and flight velocity limit. On the basis of a novel adaptability-involved problem statement, bi-level programming （BLP） and variable planning step techniques are introduced to model the necessary path planning components and then an adaptive path planner is developed for the purpose of adaptation and optimization. Additionally, both probabilistic-risk-based obstacle avoidance and performance limits are described as path search constraints to guarantee path safety and navigability. A discrete-search-based path planning solution, embedded with four optimization strategies, is especially designed for the planner to efficiently generate optimal flight paths in complex operational spaces, within which different surface-to-air missiles （SAMs） are deployed. Simulation results in challenging and stochastic scenarios firstly demonstrate the effectiveness and efficiency of the proposed planner, and then verify its great adaptability and relative stability when planning optimal paths for a UAV with changing or fluctuating performances.

关键词： Adaptive Bi-level programming Motion planning Unmanned aerial vehicles Variable time interval

Experimental investigation of methane explosion fracturing in bedding shales:Load characteristics and three-dimensional fracture propagation

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International Journal of Mining Science and Technology 2024年第10期34卷 1365-1383页

作者： Yu Wang Cheng Zhai Ting liu Jizhao Xu Wei Tang Yangfeng zheng Xinyu Zhu ning Luo School of Safety Engineering China University of Mining and TechnologyXuzhou 221116China National Engineering Research Center for Coal Gas Control China University of Mining and TechnologyXuzhou 221116China State Key Laboratory of Coal Mine Disaster Prevention and Control China University of Mining and TechnologyXuzhou 221116China School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhou 221116China

Methane in-situ explosion fracturing(MISEF)enhances permeability in shale reservoirs by detonating desorbed methane to generate detonation waves in *** propagation in bedding shale under varying explosion loads remains *** this study,prefabricated perforated shale samples with parallel and vertical bedding are fractured under five distinct explosion loads using a MISEF experimental ***-frequency explosion pressure-time curves were monitored within an equivalent perforation,and computed tomography scanning along with three-dimensional reconstruction techniques were used to investigate fracture propagation ***,the formation mechanism and influencing factors of explosion crack-generated fines(CGF)were clarified by analyzing the morphology and statistics of explosion debris *** results indicate that methane explosion generated oscillating-pulse loads within *** characteristic parameters increase with increasing initial *** load and bedding orientation significantly influence fracture propagation *** initial pressure increases,the fracture mode transitions from bi-wing to 4–5 radial *** parallel bedding shale,radial fractures noticeably deflect along the bedding *** bedding facilitates the development of transverse fractures oriented parallel to the ***-merging of explosioninduced fractures generated *** mass and fractal dimension increase,while average particle size decreases with increasing explosion *** study provides valuable insights into MISEF technology.

关键词： Methane in-situ explosion fracturing Bedding shale Fracture propagation Three-dimensional reconstruction Crack-generated fines Fractal dimension

Physics-based Modeling and Simulation for Motional Cable Harness Design

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Chinese Journal of Mechanical Engineering 2014年第5期27卷 1075-1082页

作者： liu Jianhua ZHAO Tao ning Ruxin liu Jiashun School of Mechanical Engineering Beijing Institute of Technology

The design work of motional cable in products is vital due to the difficulty in estimating the potential issues in current *** this paper,a physics-based modeling and simulation method for the motional cable harness design is *** model,based on continuum mechanics,is established by analyzing the force of microelement in *** the analysis procedure,three coordinate systems：inertial,Frenet and main-axis coordinate systems are *** variable substitution and dimensionless processing,the equation set is discretized by differential quadrature method and subsequently becomes an overdetermined nonlinear equation set with boundary conditions solved by Levenberg-Marquardt *** the profile of motional cable harness obtained from the integral of arithmetic solution,a motion simulation system based on＂path＂and＂profile＂as well as the experimental equipments is *** the same parameters as input for the simulation and the real cable harness correspondingly,the issue in designing,such as collision,can be easily found by the simulation *** research obtains a better result which has no potential collisions by redesign,and the proposed method can be used as an accurate and efficient way in motional cable harness design work.

关键词： motional cable harness physics-based modeling motion simulation Kirchhoff rod

Sparse Representation Based Image Super-resolution Using Large Patches

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Chinese Journal of Electronics 2018年第4期27卷 813-820页

作者： liu ning ZHOU Pan liu Wenju KE Dengfeng National Laboratory of Pattern Recognition Institute of Automation Chinese Academy of Sciences Department of Electrical and Computer Engineering National University of Singapore

This paper addresses the problem of generating a high-resolution image from a low-resolution image. Many dictionary based methods have been proposed and have achieved great success in super resolution application. Most of these methods use small patches as dictionary atoms, and utilize a unified dictionary pair to conduct reconstruction for each patch, which may limit the super resolution performance. We use large patches instead of small ones to combine a dictionary and to conduct patch reconstruction. Since a large patch contains more meaningful information than a small one, the reconstruction result may have more high frequency details. To guarantee the completeness of the dictionary with large patch, the scale of the dictionary should be large as well. To handle the storage and calculation problems with large dictionaries,we adopt a binary encoding method. This method can preserve local information of patches. For each patch in the low-resolution image, we search its similar patches in the low-resolution dictionary to obtain a sub-dictionary. We compute its sparse representation to get the corresponding high-resolution version. Global reconstruction constraint is enforced to eliminate the discrepancy between the SR result and the ground truth. Experimental results demonstrate that our method outperforms other super resolution methods, especially when the magnification factor is large or the image is blurred by white Gaussian noise.

关键词： Super resolution Sparse representations Binary encoding

Effects of insurance status on long-term survival among non-small cell lung cancer(NSCLC) patients in Beijing,China: A population-based study

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Chinese Journal of Cancer Research 2020年第5期32卷 596-604页

作者： zheng Wang Lei Yang Shuo liu Huichao Li Xi Zhang ning Wang Jiafu Ji Department of Respiratory and Critical Care Medicine Beijing Institute of Respiratory Medicine and Beijing Chao-Yang HospitalCapital Medical UniversityBeijing 100020China Key Laboratory of Carcinogenesis and Translational Research(Ministry of Education/Beijing) Beijing Office for Cancer Prevention and ControlPeking University Cancer Hospital&InstituteBeijing 100142China Key Laboratory of Carcinogenesis and Translational Research(Ministry of Education/Beijing) Center of Gastrointestinal SurgeryPeking University Cancer Hospital&InstituteBeijing 100142China

Objective: To evaluate the effects of health insurance status on long-term cancer-specific survival of non-small cell lung cancer(NSCLC) in Beijing, China, using a population-based cancer registry ***: Information on NSCLC patients diagnosed in 2008 was derived from the Beijing Cancer *** medical records of 1,134 cases were sampled and re-surveyed to obtain information on potential risk ***-insured status was defined as Uninsured and New Rural Cooperative Medical Insurance Scheme(NRCMS),while well-insured included Urban Employees Basic Medical Insurance(UEBMI) and Free Medical Care(FMC).To estimate survival outcomes, individuals were followed-up until December 31, 2018. Cancer-specific survival probabilities at 5 and 10 years after diagnosis were estimated using the Kaplan-Meier method. Log-rank test was used to compare long-term survival with different characteristics. Multivariable Cox proportional hazard regression model was used to examine the relative effect of insurance status on cancer-specific ***: Well-insured NSCLC patients have longer cancer-specific survival than poorly-insured individuals[hazard ratio(HR)=0.81;95% confidence interval(95% CI): 0.67-0.97), even after adjusting for age, gender, cancer stage, smoking status, family history and residential area. Older age and rural residence were associated with a higher risk of cancer-specific mortality(HR=1.03;95% CI: 1.02-1.03 and HR=1.25;95% CI: 1.07-1.46,respectively). Smoking individuals had a 41% higher long-term cancer-specific mortality risk than non-smoking ones(HR=1.41;95% CI: 1.20-1.66).Conclusions: NSCLC patients with good insurance status had better survival rates than those with poor insurance. An association was significant even after 10 years. Large population-based studies are needed to validate that high reimbursement insurance status can lead to the improvement of long-term cancer prognosis in China.

关键词： Non-small cell lung cancer health insurance status long-term survival

New celestial assisted INS initial alignment method for lunar explorer

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Journal of Systems Engineering and Electronics 2013年第1期24卷 108-117页

作者： Weiren Wu Xiaolin ning Lingling liu Lunar Exploration and Aerospace Engineering Center School of Instrument Science and Opto-electronics Engineering Beihang University Science and Technology on Inertial Laboratory Fundamental Science on Novel Inertial Instrument and Navigation System Technology Laboratory

In the future lunar exploration programs of China, soft landing, sampling and returning will be realized. For lunar explorers such as Rovers, Landers and Ascenders, the inertial navigation system （INS） will be used to obtain high-precision navigation information. INS propagates position, velocity and attitude by integration of sensed accelerations, so initial alignment is needed before INS can work properly. However, traditional ground-based initial alignment methods cannot work well on the lunar surface because of its low rotation rate （0.55°/h）. For solving this problem, a new autonomous INS initial alignment method assisted by celestial observations is proposed, which uses star observations to help INS estimate its attitude, gyroscopes drifts and accelerometer biases. Simulations show that this new method can not only speed up alignment, but also improve the alignment accuracy. Furthermore, the impact factors such as initial conditions, accuracy of INS sensors, and accuracy of star sensor on alignment accuracy are analyzed in details, which provide guidance for the engineering applications of this method. This method could be a promising and attractive solution for lunar explorer＇s initial alignment.

关键词： lunar exploration initial alignment inertial navigation,celestial navigation.

A tightly coupled rotational SINS/CNS integrated navigation method for aircraft

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Journal of Systems Engineering and Electronics 2019年第4期30卷 770-782页

作者： ning Xiaolin YUAN Weiping liu Yanhong School of Instrument and Optoelectronic Engineering Beihang University

Strapdown inertial navigation system(SINS)/celestial navigation system(CNS)integrated navigation is widely used to achieve long-time and high-precision autonomous navigation for *** general,SINS/CNS integrated navigation can be divided into two integrated modes:loosely coupled integrated navigation and tightly coupled integrated *** the loosely coupled SINS/CNS integrated system is only available in the condition of at least three stars,the latter one is becoming a research *** major challenge of SINS/CNS integrated navigation is obtaining a high-precision horizon *** solve this problem,an innovative tightly coupled rotational SINS/CNS integrated navigation method is *** this method,the rotational SINS error equation in the navigation frame is used as the state model,and the starlight vector and star altitude are used as ***-physical simulations are conducted to test the performance of this integrated *** show that this tightly coupled rotational SINS/CNS method has the best navigation accuracy compared with SINS,rotational SINS,and traditional tightly coupled SINS/CNS integrated navigation method.

关键词： celestial navigation system(CNS) rotation modulation technology rotational strapdown inertial navigation system(SINS) rotational SINS/CNS integrated navigation

A Novel Approach of Network Coding in Wireless Networks Overhearing

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Chinese Journal of Electronics 2018年第6期27卷 1297-1304页

作者： ning Zuoting ZHANG Dafang liu Xuchong Department of Information Technology Hunan Police Academy College of Information Science and Engineering Hunan University

Network coding is proved to improve the throughput, decrease network latency and balance the network overhead. Combined with wireless overhearing, some proposed representative schemes on network coding, such as linear network coding and Completely opportunity encoding(COPE). The former scheme is based on complicated linear operation, while the latter is implemented by the way of pairwise XOR-ing which is simple and low efficiency. In order to resolve these problems, we put forward a group-based XOR-ing network coding scheme, which has the characteristics of high efficiency and low *** results and theoretical analysis demonstrate that our scheme has higher throughput gains and lower delay than traditional schemes. In addition, our proposed scheme has the best characteristic of fairness among the state-of-the-art approaches.

关键词： Network coding Wireless network Overhearing Group-based XOR-ing

Kinematics Analysis of Mechanisms Based on Virtual Assembly

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Chinese Journal of Mechanical Engineering 2010年第6期23卷 748-757页

作者： ZHANG Zhixian liu Jianhua ning Ruxin School of Mechanical Engineering Beijing Institute of Technology Beijing 100081 China

Currently, virtual assembly technology has attracted increasing attention due to considerations of solving assembly problems in virtual environment before actual assembly in manufactory. Previous studies on kinematic analysis of mechanism only aim at analyzing motion law of single mechanism, but can not simulate the multi-mechanisms motion process at the same time, let alone simulating the automatic assembly process of products in a whole assembly workshop. In order to simulate the assembly process of products in an assembly workshop and provide effective data for analyzing mechanical performance after finishing assembly simulation in virtual environment, this study investigates the kinematics analysis of mechanisms based on virtual assembly. Firstly, in view of the same function of the kinematic pairs and the assembly constraints on restricting the motion of components （subassembly or part）, the method of identifying kinematic pairs automatically based on assembly constraints is presented. The information of kinematic pairs can be obtained through calculating the constraint degree of the assembly constraints. Secondly, the incidence matrix eliminating element method is proposed in order to search the information and establish the models of mechanisms automatically after finishing assembly simulation in virtual environment. Both methods have important significance for reducing the workload of pretreatment and promoting the level of automation of kinematics analysis. Finally, the method of kinematics analysis of mechanisms is presented. Based on Descartes coordinates, three types of kinematics equations are formed. The parameters, like displacement, velocity, and acceleration, can be obtained by solving these equations. All these data are important to analyze mechanical performance. All the methods are implemented and validated in the prototype system virtual assembly process planning（VAPP）. The mechanism models are established and simulated in the VAPP system, and t

关键词： virtual assembly assembly constraint constraint degree eliminating element method kinematics equations,kinematics analysis