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Development of Agricultural Recycle Economy in Arid Areas of hexi Corridor——A Case Study of Zhangye City, China

Asian Agricultural Research 2010年第12期2卷 23-27页

作者： CHEN Yu Economic and Management Department of hexi University, Zhangye 734000, China

Taking Zhangye City as an example, the thesis analyzes the restricted factors of resources and environment confronted by the agriculture in arid area of hexi Corridor: the first is the agricultural natural resources. The area of cultivated land decreases year by year, and there are sharp decrease of biological diversity as well as the shortage and waste of water resources; the second is the ecological environment. There are critical soil erosion, frequent natural disaster and outstanding agricultural area source pollution; the third is the rural economy. The agricultural structure still can not meet the need of agricultural development in recent years, and the proportion of agricultural product processing is low. It points out that implementation of agricultural recycle economy is the necessary choice of the agricultural development in Zhangye City. Developing recycle economy is conducive to improving ecological environment and realizing agricultural sustainable development; developing recycle economy can solve the agricultural area source pollution to much extent and protect rural environment; developing recycle economy is conducive to adjusting rural industrial structure, increasing job opportunities and increasing farmers' income; developing recycle economy is conducive to elevating the international competitiveness of agricultural products. The thesis also has put forward the countermeasures of developing agricultural recycle economy in Zhangye City as follows: firstly, fostering the ambience of the development of agricultural recycle economy; secondly, forming the incentive mechanism of development of agricultural recycle economy; thirdly, broadening the investment channel of development of agricultural recycle economy; fourthly, perfecting socialized service system of agricultural recycle economy.

关键词： Zhangye City Restriction of resources and environm

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Sequence optimization for multiple asteroids rendezvous via cluster analysis and probability-based beam search

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Science China(Technological Sciences) 2021年第1期64卷 122-130页

作者： LI HaiYang BAOYIN hexi School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

It is of great significance to visit multiple asteroids in a space *** this paper,the multiple asteroids mission optimization is implemented using cluster analysis and probability-based beam *** is performed to select the first asteroid to *** cluster algorithms are investigated and affinity propagation is *** four beam search algorithms that are deterministic beam search and three probability-based beam search variants,probabilistic beam search,ant-colony beam search,and evolving beam search,are applied to search for the rendezvous *** beam search as a heuristic tree search algorithm is widely applied in multitarget sequence optimization,but it has an obvious drawback of the conflict between the number of pruned nodes and the possibility of finding optimal solutions,which can be improved by probability-based beam *** three probability-based beam search,the ant-colony beam search has a learning mechanism,and evolving beam search is constructed based on ant-colony beam search and has an evolutionary *** show that the introduction of randomness can improve beam search,and beam search variants with the learning and evolutionary mechanism have an excellent performance.

关键词： interplanetary trajectory optimization multi-target mission cluster analysis probability-based beam search

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Robust extended Kalman filter with input estimation for maneuver tracking

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Chinese Journal of Aeronautics 2018年第9期31卷 1910-1919页

作者： Yuzi JIANG hexi BAOYIN School of Aerospace Engineering Tsinghua University

This study investigates the problem of tracking a satellite performing unknown continuous maneuvers. A new method is proposed for estimating both the state and maneuver acceleration of the satellite. The estimation of the maneuver acceleration is obtained by the combination of an unbiased minimum-variance input and state estimation method and a low-pass filter. Then a threshold-based maneuver detection approach is developed to determinate the start and end time of the unknown maneuvers. During the maneuvering period, the estimation error of the maneuver acceleration is modeled as the sum of a fluctuation error and a sudden change error. A robust extended Kalman filter is developed for dealing with the acceleration estimate error and providing state estimation. Simulation results show that, compared with the Unbiased Minimum-variance Input and State Estimation(UMISE) method, the proposed method has the same position estimation accuracy, and the velocity estimation error is reduced by about 5 times during the maneuver period. Besides, the acceleration detection and estimation accuracy of the proposed method is much higher than that of the UMISE method.

关键词： Extended Kalman filters Input estimation Maneuver detection Maneuver tracking Orbit determination

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Effect of silver nanoparticles on an integrated fixed-film activated sludge–sequencing batch reactor: Performance and community structure

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Journal of Environmental Sciences 2019年第6期31卷 229-239页

作者： hexi Zhou Guoren Xu State Key Laboratory of Urban Water Resource and Environment Harbin Institute of Technology National Engineering Laboratory for Sustainable Sludge Management & Resourcelization Technology Harbin Institute of Technology

The effects of silver nanoparticles(AgNPs) on reactor performance, extracellular polymeric substances composition and microbial community structure and function in integrated fixed-film activated sludge–sequencing batch reactors(IFAS–SBRs) were *** showed that the addition of AgNPs from 0.1 to 10 mg/L exhibited no significant effects on nutrient removal. The average overall removal of COD, NH4+–N and PO43-–P was96.6%, 99.9% and 98.8%, respectively. The introduction of AgNPs caused an increase in extracellular polymeric substances content for the sludge and biofilm of IFAS–SBRs. The release of Ag+from Ag NPs and lactate dehydrogenase test implied the low toxicity of AgNPs to IFAS–SBRs. High-throughput sequencing revealed that microbial community structure showed significant shifts at phylum and genus levels after long-term exposure to AgNPs,but core functional groups responsible for nutrient removal remained at high *** function prediction indicated that the metabolic categories showed no significant shifts under AgNPs stress, therefore good process performance could still be achieved.

关键词： AgNPs Performance Toxicity Community structure IFAS-SBR

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A new physical model on the capillary phenomenon of granular particles

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Applied Mathematics and Mechanics(English Edition) 2019年第1期40卷 127-138页

作者： Nan ZHANG Bin CHENG hexi BAOYIN Department of Aerospace Engineering Tsinghua University

Similar to the capillary phenomenon of liquid, granular particles can move up to a certain height along a vertically vibrating tube. The certain height, which is called the equilibrium height, is related to some parameters, e.g., the inner diameter of the tube, the amplitude, and the vibration frequency. In this paper, a theoretical model is proposed to explain the physical origin of the capillary phenomenon and the effects of the inner diameter of the tube, the amplitude, and the vibration frequency on the equilibrium height. In this model, the volumes of the inflowing and outflowing particles in a vibration period are calculated, which can significantly broaden our understanding in the flow of particles in the bottom of the tube. In order to prove the assumption of this physical model that the particles in the bottom of the tube move in the form of sine, several experiments are conducted. The granular climbing heights at different granular positions and different time stages are measured. The results show that granules move in the form of sine, which almost coincides with the motion of the tube. Moreover, motivated by the sampling on the asteroid regolith based on this mechanism, the sampling efficiencies for various vibration amplitudes and frequencies are discussed based on the new proposed model. It is found that there is an optimum frequency at which sampling is the most effective.

关键词： granular matter vertical vibration nonlinear dynamics theoretical analysis

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Formation reconfiguration in restricted three body problem

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Acta Mechanica Sinica 2007年第3期23卷 321-328页

作者： Shengping Gong Junfeng Li hexi Baoyin Yunfeng Gao School of Aerospace Tsinghua UniversityBeijing 100084 China

Reconfiguration of formation flying around a halo orbit of the Sun-Earth restricted three body system is investigated with impulse maneuvers. For a short time reconfiguration, the two-impulse maneuver is investigated with both analytical and numerical methods and the Beginning-Ending （BE） method is proven to be an energy-optimal one of all two-impulse （TI） reconfigurations, and the energy consumption of BE is independent of the position of the chief spacecraft, and decreases with the reconfiguration time. Then, genetic algorithm is adopted to optimize the energy consumption. The results show that the optimal energy increases with radius difference between the initial and final orbits, and decreases with the reconfiguration time.

关键词： Three body problem Halo orbit Formation reconfiguration Formation flying

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Entropy method of measuring and evaluating periodicity of quasi-periodic trajectories

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Science China(Physics,Mechanics & Astronomy) 2018年第6期61卷 30-49页

作者： Yanshuo Ni Konstantin Turitsyn hexi Baoyin Junfeng Li School of Aerospace Engineering Tsinghua University Department of Mechanical Engineering Massachusetts Institute of Technology

This paper presents a method for measuring the periodicity of quasi-periodic trajectories by applying discrete Fourier transform （DFT） to the trajectories and analyzing the frequency domain within the concept of entropy. Having introduced the concept of entropy, analytical derivation and numerical results indicate that entropies increase as a logarithmic function of time. Periodic trajectories typically have higher entropies, and trajectories with higher entropies mean the periodicities of the motions are stronger. Theoretical differences between two trajectories expressed as summations of trigonometric functions are also derived analytically. Trajectories in the Henon-Heiles system and the circular restricted three-body problem （CRTBP） are analyzed with the indicator entropy and compared with orthogonal fast Lyapunov indicator （OFLI）. The results show that entropy is a better tool for discriminating periodicity in quasiperiodie trajectories than OFLI and can detect periodicity while excluding the spirals that are judged as periodic cases by OFLI. Finally, trajectories in the vicinity of 243 Ida and 6489 Golevka are considered as examples, and the numerical results verify these conclusions. Some trajectories near asteroids look irregular, but their higher entropy values as analyzed by this method serve as evidence of frequency regularity in three directions. Moreover, these results indicate that applying DFT to the trajectories in the vicinity of irregular small bodies and calculating their entropy in the frequency domain provides a useful quantitative analysis method for evaluating orderliness in the periodicity of quasi-periodic trajectories within a given time interval.

关键词： quasi-periodic trajectories entropy quality evaluating

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Design and optimization of a trajectory for Moon departure Near Earth Asteroid exploration

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Science China(Physics,Mechanics & Astronomy) 2011年第4期54卷 748-755页

作者： CHEN Yang BAOYIN hexi LI JunFeng School of Aerospace Tsinghua University Beijing 100084 China

The lunar probe often has some remaining fuel on completing the predefined Moon exploration mission and may carry out some additional tasks from the Moon orbit using the *** possibility for the lunar probe to escape from the Moon and the Earth is *** and optimization of the trajectory from the Moon orbit to the Near Earth Asteroids (NEAs) using the spacecraft's residual fuel is *** first,the semi-major axis,inclinations and the phase relations with the Earth of all the numbered NEAs are investigated to preliminarily select the possible *** on the Sun-centered two-body problem,the launch window and the asteroid candidates are determined by calculating the minimum delta-v for two-impulse rendezvous mission and one-impulse flyby mission,*** a precise designed trajectory,a full ephemeris dynamical model,which includes gravities of the Sun,the planets and the Moon,is adopted by reading the JPL *** departure time,arrival time,burning time duration and thrust angles are set as variables to be designed and *** optimization problem is solved via the Particle Swarm Optimization (PSO) ***,two feasible NEA flyby missions are presented.

关键词： trajectory design full ephemeris model Near Earth Asteroid exploration Particle Swarm Optimization

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Solar sail attitude control using shape variation of booms

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Chinese Journal of Aeronautics 2022年第10期35卷 326-336页

作者： Feng ZHANG Shengping GONG Haoran GONG hexi BAOYIN School of Aerospace Engineering Tsinghua UniversityBeijing 100084China School of Astronautics Beihang UniversityBeijing 100083China

Active attitude control of solar sails is required to control the direction of the force generated by Solar Radiation Pressure(SRP). It is desirable to control the attitude through propellantfree means. This paper proposes a new method for attitude control of solar sails: A boom consisting of "smart" structural material can be deformed by the piezoelectric actuator, and Solar Radiation Pressure torque will be generated due to shape variation of sail membrane caused by boom deformation. The method has the advantages of simple structure, small disturbance and small additional load, and is not limited by the size of the solar sail. The case of rendezvous with the Asteroid 2000SG344 is used to verify the attitude control around the pitch and yaw axes.

关键词： Attitude control Boom deformation Dynamics Solar radiation pressure Solar sail

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Dynamic modelling and analysis of space webs

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Science China(Physics,Mechanics & Astronomy) 2011年第4期54卷 783-791页

作者： YU Yang BAOYIN hexi LI JunFeng School of Aerospace Tsinghua University Beijing 100084 China

Future space missions demand operations on large flexible structures,for example,space webs,the lightweight cable nets deployable in space,which can serve as platforms for very large structures or be used to capture orbital *** interest in research on space webs is likely to increase in the future with the development of promising applications such as Furoshiki sat-ellite of JAXA,Robotic Geostationary Orbit Restorer (ROGER) of ESA and Grapple,Retrieve And Secure Payload (GRASP) of *** high-tensioned nets in civil engineering,space webs may be low-tensioned or tensionless,and extremely flexible,owing to the microgravity in the orbit and the lack of support components,which may cause computational *** models are necessary in the analysis of space webs,especially in the conceptual design and evaluation for prototypes.A full three-dimensional finite element (FE) model was developed in this *** truss elements were adopted to reduce the computational *** cable is a compression-free material and its tensile stiffness is also variable,we introduced the cable material constitutive relationship to work out an accurate and feasible model for prototype analysis and *** the static analysis,the stress distribution and global deformation of the webs were discussed to get access to the knowledge of strength of webs with different types of *** the dynamic analysis,special attention was paid to the impact *** max stress and global deformation were *** simulation results indicate the interesting phenomenon which may be worth further research.

关键词： space webs finite element method cable material nonlinear constitutive relationship

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