Modified filter for mean elements estimation with state jumping

To investigate the real-time mean orbital elements(MOEs)estimation problem under the influence of state jumping caused by non-fatal spacecraft collision or protective orbit trans-fer,a modified augmented square-root unscented Kalman filter(MASUKF)is proposed.The MASUKF is composed of sigma points calculation,time update,modified state jumping detec-tion,and measurement update.Compared with the filters used in the existing literature on MOEs estimation,it has three main characteristics.Firstly,the state vector is augmented from six to nine by the added thrust acceleration terms,which makes the fil-ter additionally give the state-jumping-thrust-acceleration esti-mation.Secondly,the normalized innovation is used for state jumping detection to set detection threshold concisely and make the filter detect various state jumping with low latency.Thirdly,when sate jumping is detected,the covariance matrix inflation will be done,and then an extra time update process will be con-ducted at this time instance before measurement update.In this way,the relatively large estimation error at the detection moment can significantly decrease.Finally,typical simulations are per-formed to illustrated the effectiveness of the method.

A simplified two-dimensional boundary element method with arbitrary uniform mean flow

To reduce computational costs, an improved form of the frequency domain boundary element method（BEM） is proposed for two-dimensional radiation and propagation acoustic problems in a subsonic uniform flow with arbitrary orientation. The boundary integral equation（BIE） representation solves the two-dimensional convected Helmholtz equation（CHE） and its fundamental solution, which must satisfy a new Sommerfeld radiation condition（SRC） in the physical space. In order to facilitate conventional formulations, the variables of the advanced form are expressed only in terms of the acoustic pressure as well as its normal and tangential derivatives, and their multiplication operators are based on the convected Green＇s kernel and its modified derivative. The proposed approach significantly reduces the CPU times of classical computational codes for modeling acoustic domains with arbitrary mean flow. It is validated by a comparison with the analytical solutions for the sound radiation problems of monopole,dipole and quadrupole sources in the presence of a subsonic uniform flow with arbitrary orientation.

STUDY ON THE SEPARATION AND EXTRACTION MECHANISM OF RARE EARTH ELEMENTS BY MEANS OF REVERSED-PHASE PAPER CHROMATOGRAPHY

Reversed-phase paper chromatography technique is used for study on the extraction mechanism and sep- aration of rare earth elements.As the stationary phase,chromatographic paper strips are impregnated with a solution of monomyristyl phosphoric acid (MPA) in chloroform.Mineral acids are used as developers. The effect of concentration of acids and/or salts upon R_f has been investigated.According to the re- sults of R_f values for a given rare earth element in various acids,the order of extraction ability is HCl>HNO_3>H_2SO_4.A tetrad effect is clearly observed.for the R_f value of rare earth elements.The effects of other parameters on the R_f value,such as the quantities of extractant retained by the paper and the temperature are also examined.Based on the determination of the molar ratio of MPA to rare earth elements and the number of H^+ ions released in extraction reaction,a reasonable mechanism is proposed.The mutual separation of heavy rare earth elements will be better than that of the light rare earth group because of the larger separation coefficient of the former.A mixture of Ho-Er-Tm-Lu is successfully separated by the present method.

材料·元素·融入:经管类课程思政如何开展?——以新华网课程思政平台经管类课程为例

在大思政课背景下,如何切实开展好课程思政,关乎我国思想政治教育体系的进一步完善与深化。本文以经管类课程为例,结合新华网课程思政优秀案例的文本材料,借助Nvivo20软件进行内容分析,对相关内容进行编码,归纳出经管类课程的思政材料、思政元素以及融入方式体系。研究发现,我国经管类课程思政能够多渠道选取思政材料、全方位挖掘思政元素、引导学生自主学习,呈现出素材上重视实践和制度类材料,元素上偏重道德与品质的培养,方式上理论教育重于实践教育的特点。结合有意义学习理论,本研究认为,课程思政应在吸收已有优点的基础上,重视实践和制度类材料的选取;挖掘思政元素时以理想信念教育为基础,兼顾素质与能力;更加重视师生互动,提高实践教育占比,提高学生学习主动性,从而实现有意义学习,更好地构建理论学习与实践学习共同发展的大思政课格局。

室内内涵设计探析

本文从室内内涵设计的设计元素入手,旨在倡导一种综合性的人本设计思想,使室内设计满足功能的前提下更具人文关怀,从而走出一条健康、和谐,底蕴丰富、内涵优美的设计之路。

简析新批评派的文学本质观

在文论史上,关于“文学的本质是什么”的问题一直众说纷纭,主要有几种观点:文学是对科学真理的抽象传输、是对世界的再现、是作者的表现、是读者的体验。而兴起于19世纪的新批评派在这个问题上有着独到的见解,它摒弃了前人观点的不足,将文学看成是一个以文本为中心的独立自足的世界,为推进文学本质研究起到了重要作用。

Artificial Sun synchronous frozen orbit control scheme design based on J_2 perturbation

Sun synchronous orbit and frozen orbit formed due to J 2 perturbation have very strict constraints on orbital parameters,which have restricted the application a lot.In this paper,several control strategies were illustrated to realize Sun synchronous frozen orbit with arbitrary orbital elements using continuous low-thrust.Firstly,according to mean element method,the averaged rate of change of the orbital elements,originating from disturbing constant accelerations over one orbital period,was derived from Gauss＇ variation of parameters equations.Then,we proposed that binormal acceleration could be used to realize Sun synchronous orbit,and radial or transverse acceleration could be adopted to eliminate the rotation of the argument of the perigee.Finally,amending methods on the control strategies mentioned above were presented to eliminate the residual secular growth.Simulation results showed that the control strategies illustrated in this paper could realize Sun synchronous frozen orbit with arbitrary orbital elements,and can save much more energy than the schemes presented in previous studies,and have no side effect on other orbital parameters＇ secular motion.

Impulsive orbit control for spacecraft around asteroid

An impulse feedback control law to change the mean orbit elements of spacecraft around asteroid is presented. First, the mean orbit elements are transferred to the osculating orbit elements at the burning time. Then, the feedback control law based on Gauss’s perturbation equations of motion is given. And the impulse control for targeting from the higher circulation orbit to the specified periapsis is developed. Finally, the numerical simulation is performed and the simulation results show that the presented impulse control law is effective.

Influence of process parameters on deep drawing of AA6111 aluminum alloy at elevated temperatures

To gain a deep insight into the hot drawing process of aluminum alloy sheet, simulations of cylindrical cup drawing at elevated temperatures were carried out with experimental validation. The influence of four important process parameters, namely,punch velocity, blank holder force(BHF), friction coefficient and initial forming temperature of blank on drawing characteristics(i.e.minimum thickness and thickness deviation) was investigated with the help of design of experiments(DOE), analysis of variance(ANOVA) and analysis of mean(ANOM). Based on the results of ANOVA, it is shown that the blank holder force has the greatest influence on minimum thickness. The importance of punch velocity for thickness deviation is 44.35% followed by BHF of 24.88%,friction coefficient of 15.77% and initial forming temperature of blank of 14.995%. After determining the significance of each factor on forming characteristics, how the individual parameter affects characteristics was further analyzed by ANOM.

Artificial frozen orbit control scheme based on J_2 perturbation

Since the inclination of frozen orbit with non-rotation of the perigee that occurs due to J2 perturbation must be equal to the critical inclination, this regulation has restricted the application of frozen orbit a lot. In this paper, we propose two control strategies to eliminate the secular growth of the argument of the perigee for orbits that are not at the critical inclination. One control strategy is using transverse continuous low-thrust, and the other is using both the transverse and the radial continuous low-thrusts. Fuel optimization in the second control strategy is addressed to make sure that the fuel consumption is the minimum. Both strategies have no effect on other orbital parameters’ secular motion. It is proved that the strategy with transverse control could save more energy than the one with radial control. Simulations show that the second control strategy could save 54.6% and 86% of energy, respectively, compared with the two methods presented in the references.