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A trigonometric interval method for dynamic response analysis of uncertain nonlinear systems

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Science China(Physics,Mechanics & Astronomy) 2015年第4期58卷 45-57页

作者： liU ZhuangZhuang WANG TianShu li junfeng School of Aerospace Tsinghua University

This paper proposes a new non-intrusive trigonometric polynomial approximation interval method for the dynamic response analysis of nonlinear systems with uncertain-but-bounded parameters and/or initial *** method provides tighter solution ranges compared to the existing approximation interval *** consider trigonometric approximation polynomials of three types:both cosine and sine functions,the sine function,and the cosine ***,special interval arithmetic for trigonometric function without overestimation can be used to obtain interval *** interval method using trigonometric approximation polynomials with a cosine functional form exhibits better performance than the existing Taylor interval method and Chebyshev interval ***,two typical numerical examples with nonlinearity are applied to demonstrate the effectiveness of the proposed method.

关键词： non-intrusive interval method dynamic response analysis uncertain nonlinear systems trigonometric polynomial ap-proximation interval arithmetic

Multiscale models of compact bone

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International Journal of Biomathematics 2016年第3期9卷 271-292页

作者： junfeng li Shugang li School of Mathematics and Statistics Central China Normal University Wuhan 430079 P. R. China

This work is concerned about multiscale models of compact bone. We focus on the lacuna-canalicular system. The interstitial fluid and the ions in it are regarded as sol- vent and others are treated as solute. The system has the characteristic of solvation process as well as non-equilibrium dynamics. The differential geometry theory of sur- faces is adopted. We use this theory to separate the macroscopic domain of solvent from the microscopic domain of solute. We also use it to couple continuum and discrete descriptions. The energy functionals are constructed and then the variational principle is applied to the energy functionals so as to derive desirable governing equations. We consider both long-range polar interactions and short-range nonpolar interactions. The solution of governing equations leads to the minimization of the total energy.

关键词： Compact bone lacuna-canalicular system multiscale Laplace-Beltramiequation Poisson Boltzmann equation.

Solution set on the natural satellite formation orbits under first-order earth's non-spherical perturbation

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Acta Mechanica Sinica 2005年第5期21卷 503-510页

作者： Humei Wang Wei Yang junfeng li School of Aerospace Tsinghua University Beijing100084 China

Using the reference orbital element approach, the precise governing equations for the relative motion of formation flight are formulated. A number of ideal formations with respect to an elliptic orbit can be designed based on the relative motion analysis from the equations. The features of the oscillating reference orbital elements are studied by using the perturbation theory. The changes in the relative orbit under perturbation are divided into three categories, termed scale enlargement, drift and distortion respectively. By properly choosing the initial mean orbital elements for the leader and follower satellites, the deviations from originally regular formation orbit caused by the perturbation can be suppressed. Thereby the natural formation is set up. It behaves either like non-disturbed or need little control to maintain. The presented reference orbital element approach highlights the kinematics properties of the relative motion and is convenient to incorporate the results of perturbation analysis on orbital elements. This method of formation design has advantages over other methods in seeking natural formation and in initializing formation.

关键词： Orbital mechanics . Satellite formation flight .Orbital elements . Reference orbital elements . Perturbation

Low-thrust trajectory optimization of asteroid sample return mission with multiple revolutions and moon gravity assists

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Science China(Physics,Mechanics & Astronomy) 2015年第11期58卷 107-120页

作者： TANG Gao JIANG FangHua li junfeng School of Aerospace Engineering Tsinghua University

Near-Earth asteroids have gained a lot of interest and the development in low-thrust propulsion technology makes complex deep space exploration missions possible. A mission from low-Earth orbit using low-thrust electric propulsion system to rendezvous with near-Earth asteroid and bring sample back is investigated. By dividing the mission into five segments, the complex mission is solved separately. Then different methods are used to find optimal trajectories for every segment. Multiple revolutions around the Earth and multiple Moon gravity assists are used to decrease the fuel consumption to escape from the Earth. To avoid possible numerical difficulty of indirect methods, a direct method to parameterize the switching moment and direction of thrust vector is proposed. To maximize the mass of sample, optimal control theory and homotopic approach are applied to find the optimal trajectory. Direct methods of finding proper time to brake the spacecraft using Moon gravity assist are also proposed. Practical techniques including both direct and indirect methods are investigated to optimize trajectories for different segments and they can be easily extended to other missions and more precise dynamic model.

关键词： sample return optimization gravity assist

Solar sailing trajectory optimization with planetary gravity assist

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Science China(Physics,Mechanics & Astronomy) 2015年第1期58卷 54-64页

作者： CAI XingShan li junfeng GONG ShengPing School of Aerospace Tsinghua University

Significant propellant mass saving can be obtained with the use of complex multiple intermediate flyby maneuvers for conventional propulsion systems,and trip time also decreases for a portion of the proper solar sail *** paper discusses the performance of gravity assist(GA)in the time-optimal control problem of solar sailing with respect to sail lightness number and the energy difference between the initial and final orbit in the rendezvous problem in a two-body model,in which the GA is modeled as a substantial change in the velocity of the sailcraft at the GA *** addition,this paper presents a method to solve the time-optimal problem of solar sailing with GA in a full ephemeris model,which introduces the third body’s gravity in a dynamic *** study builds a set of inner constraints that can describe the GA process ***,this study presents an example for evaluating the accuracy and rationality of the two-body model’s simplification of GA by comparison with the full ephemeris model.

关键词： solar sailing trajectory optimization gravity assist full ephemeris model

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实现慢性乙型肝炎临床治愈的治疗策略

兰州大学学报（医学版） 2024年第2期50卷 66-72页

作者：高兴雪李俊峰兰州大学第一临床医学院甘肃兰州730000 兰州大学第一医院肝病科甘肃兰州730000 兰州大学第一医院传染病研究室甘肃兰州730000

目前慢性乙型肝炎的理想治疗终点是实现临床治愈,然而乙型肝炎表面抗原自发清除率较低,长期核苷酸类似物联合干扰素治疗有助于提高乙型肝炎表面抗原清除率,核酸类分子及免疫调节药物在临床研究中也显示出提高乙型肝炎表面抗原清除率的价... 详细信息

目前慢性乙型肝炎的理想治疗终点是实现临床治愈,然而乙型肝炎表面抗原自发清除率较低,长期核苷酸类似物联合干扰素治疗有助于提高乙型肝炎表面抗原清除率,核酸类分子及免疫调节药物在临床研究中也显示出提高乙型肝炎表面抗原清除率的价值,可能成为实现乙肝临床治愈较有潜力的治疗策略。

关键词：乙型肝炎乙型肝炎病毒乙型肝炎表面抗原临床治愈治疗策略

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选区激光熔化成形铝合金材料体系研究进展

中国有色金属学报 2024年第1期34卷 1-24页

作者：朱浩文刘文才蒋志达陶新苗吴国华李俊锋上海交通大学材料科学与工程学院轻合金精密成型国家工程研究中心上海200240 上海云铸三维科技有限公司上海201306

铝合金是工业生产中运用最为广泛的金属材料,高比强度、良好的耐蚀性使其适用于生产各种复杂结构件。选区激光熔化技术不仅具有定制化成形能力,高加工精度与短生产周期也可大幅推进铝合金构件的成形与应用。本文介绍了近年来选区激光熔... 详细信息

铝合金是工业生产中运用最为广泛的金属材料,高比强度、良好的耐蚀性使其适用于生产各种复杂结构件。选区激光熔化技术不仅具有定制化成形能力,高加工精度与短生产周期也可大幅推进铝合金构件的成形与应用。本文介绍了近年来选区激光熔化铝合金的研究进展,简述了选区激光熔化技术所生产铝合金的工艺缺陷及形成机理,聚焦于不同合金的组织演变和力学性能,着重分析不同合金体系下元素对微观形貌的影响及强化效应。针对选区激光熔化铝合金的应用现状与存在壁垒,指出实现普及的关键在于通过成分设计实现成形性能与力学性能的平衡。

关键词：选区激光熔化增材制造铝合金材料体系

基于PTFE/ZnO/Ti_(3)C_(2)T_(x)复合薄膜的抗湿性氨气传感器研究

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复合材料学报 2024年第7期41卷 3656-3667页

作者：高风娇常雪婷李俊峰王东胜高炜翔孙士斌上海海事大学物流工程学院上海201306 上海海事大学海洋材料科学与工程研究院上海201306 上海海事大学物流科学与工程研究院上海201306

开发基于半导体功能材料的抗湿性室温气体传感器一直都是气体传感器领域的研究热点和难点。本文从金属氧化物半导体的高灵敏度和稳定性、MXene(Ti_(3)C_(2)T_(x))的室温气敏性以及聚四氟乙烯(PTFE)的疏水性出发,以MXene薄膜为基体,采用... 详细信息

开发基于半导体功能材料的抗湿性室温气体传感器一直都是气体传感器领域的研究热点和难点。本文从金属氧化物半导体的高灵敏度和稳定性、MXene(Ti_(3)C_(2)T_(x))的室温气敏性以及聚四氟乙烯(PTFE)的疏水性出发,以MXene薄膜为基体,采用磁控溅射法分别将ZnO和PTFE沉积到Ti_(3)C_(2)T_(x)表面,制备了PTFE/ZnO/MXene复合薄膜,同时构筑了基于复合薄膜的气体传感器。通过SEM、TEM和XPS对复合薄膜进行了表征,并对气体传感器的气敏性能和抗湿性能进行了研究。研究结果表明:基于PTFE/ZnO/Ti_(3)C_(2)T_(x)复合薄膜的气体传感器在室温下对氨气具有良好的选择性、较高的灵敏度和优异的循环稳定性。随着PTFE薄膜厚度的增加,基于复合薄膜的气体传感器的抗湿性能逐渐增加,但灵敏度有所下降。

关键词： PTFE/ZnO/MXene复合薄膜抗湿性磁控溅射气体传感器氨气

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益生菌在反刍动物中的应用

中国饲料 2024年第17期 197-202页

作者：李俊峰廖凯威李彪戴晋军蔡大亮安琪酵母股份有限公司湖北宜昌443000

近年来,随着我国饲料资源短缺,人畜争粮现象日益严峻,大量农副类产物资源被广泛应用于反刍动物日粮配方体系。为了进一步提升农副类饲料资源利用效率,降低环境污染,益生菌类产品得到了普遍关注。然而在实际应用过程中,益生菌面临着胃肠... 详细信息

近年来,随着我国饲料资源短缺,人畜争粮现象日益严峻,大量农副类产物资源被广泛应用于反刍动物日粮配方体系。为了进一步提升农副类饲料资源利用效率,降低环境污染,益生菌类产品得到了普遍关注。然而在实际应用过程中,益生菌面临着胃肠原生菌群竞争、瘤胃存活率、菌剂配伍、活菌数、添加方式及阶段等诸多实际问题,导致应用效果良莠不齐。本文重点围绕益生菌的应用功效及作用机制、添加方式及使用时期等方面逐一阐述,以期为实际生产中益生菌的使用提供科学的理论依据和实践指导。

关键词：益生菌 DFM 替抗反刍动物