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Modelling and control of a spatial dynamic cable

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Acta Mechanica Sinica 2019年第4期35卷 866-878页

作者： bo tian Subhrajit Bhattacharya Department of Mechanical Engineering and Mechanics Lehigh University Bethlehem PA 18015 USA

We study the problem of dynamically controlling the shape of a cable that is fixed at one end and attached to an actuated robot at another end. This problem is relevant to unmanned aerial vehicles (UAVs) tethered to a base. While rotorcrafts, such as quadcopters, are agile and versatile in their applications and have been widely used in scientific, industrial and military applications, one of the biggest challenges with such UAVs is their limited battery life that make the flight time for a typical UAVs limited to twenty to thirty minutes for most practical purposes. A solution to this problem lies in the use of cables that tether the UAV to a power outlet for constant power supply. However, the cable needs to be controlled effectively in order to avoid obstacles or other UAVs. In this paper, we develop methods for controlling the shape of a cable using actuation at one end. We propose a discrete model for the spatial cable and derive the equations governing the cable dynamics for both force controlled system and position controlled system. We design a controller to control the shape of the cable to attain the desired shape and perform simulations under different conditions. Finally, we propose a quasi-static model for the spatial cable and discuss the stability of this system and the proposed controller.

关键词： Lagrangian mechanics Discrete model of cable Control of under-actuated systems

Entropy optimization based filtering for non-Gaussian stochastic systems

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Science China(Information Sciences) 2017年第12期60卷 33-43页

作者： bo tian Yan WANG Lei GUO School of Automation Science and Electrical Engineering Beihang University National Key Laboratory on Aircraft Control Technology Beihang University

This paper is concerned with the entropy optimization based filter design for a class of multivariate dynamic stochastic systems with simultaneous presence of non-Gaussian process noise and measurement *** filter consists of time update and measurement update two steps, where the selection of the filter gain in the measurement update equation is a key issue to be addressed. Different from the classic Kalman filter theory, entropy rather than variance is employed as the filtering performance criterion due to the non-Gaussian characteristic of the estimation error. Following the establishment of the relationship between the probability density functions of random noises and estimation error, two kinds of entropy based performance indices are provided. On this basis, the corresponding optimal filter gains are obtained respectively by using the gradient optimization technique. Finally, some numerical simulations are provided to demonstrate the effectiveness of the proposed filtering algorithms.

关键词： non-Gaussian systems joint probability density function(JPDF) quadratic information potential relative entropy optimal filtering

Recursion Formulae for Obtaining Surfaces with Constant MeanCurvature inR^2,1

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Communications in Theoretical Physics 2007年第2期47卷 203-208页

作者： tian Yong-bo NAN Zhi-Jie tian Chou Department of Mathematics University of Science and Technology. of China Hefei 230026China

Though the Bǎcklund transformation on time-like surfaces with constant mean curvature surfaces in R^2,1 has been obtained, it is not easy to obtain corresponding surfaces because the procedure of solving the related integrable system cannot be avoided when the Bǎcklund transformation is used, For sake of this, in this article, some special work is done to reform the Bǎcklund transformation to a recursion formula, by which we can construct time-like surfaces with constant mean curvature form known ones just by quadrature procedure.

关键词： Bǎcklund transformation time-like surfaces with mean curvature Lax pairs recursion formula

Recent advances, perspectives, and challenges inferroelectric synapses

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Chinese Physics B 2020年第9期29卷 15-30页

作者： bo-bo tian Ni Zhong Chun-Gang Duan Key Laboratory of Polar Materials and Devices(MOE) Department of ElectronicsEast China Normal UniversityShanghai 200241China Collaborative Innovation Center of Extreme Optics Shanxi UniversityShanxi 030006China

The multiple ferroelectric polarization tuned by external electric field could be used to simulate the biological synaptic weight. Ferroelectric synaptic devices have two advantages compared with other reported ones: One is that the intrinsic switching of ferroelectric domains without invoking of defect migration as in resistive oxides, contributes reliable performance in these ferroelectric synapses. Another tremendous advantage is the extremely low energy consumption because the ferroelectric polarization is manipulated by electric field which eliminates the Joule heating by current as in magnetic and phase change memories. Ferroelectric synapses have potential for the construction of low-energy and effective brain-like intelligent networks. Here we summarize recent pioneering work of ferroelectric synapses involving the structure of ferroelectric tunnel junctions (FTJs), ferroelectric diodes (FDs), and ferroelectric field effect transistors (FeFETs), respectively, and shed light on future work needed to accelerate their application for efficient neural network.

关键词： ferroelectric synapse ferroelectric tunnel junctions ferroelectric field effect transistors

Diversity in seed oil content and fatty acid composition in Acer species with potential as sources of nervonic acid

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Plant Diversity 2021年第1期43卷 86-92页

作者： Xing He De-Zhu Li bo tian Key Laboratory of Sustainable Utilization of Tropical Plant Resources Xishuangbanna Tropical Botanical GardenChinese Academy of Sciences88 Xuefu RoadKunmingYunnan650223China Germplasm Bank of Wild Species Kunming Institute of BotanyChinese Academy of Sciences132 Lanhei RoadKunmingYunnan650201China Center of Economic botany Core Botanical GardensChinese Academy of SciencesMenglunMenglaYunnan666303China University of Chinese Academy of Sciences Beijing100049China

Nervonic acid(NA,cis-15-tetracosenoic acid)is a very long-chain monounsaturated fatty acid that has been shown to be a core component of nerve fibers and nerve *** can be used to treat and prevent many neurological *** present,commercially available NA is mainly derived from Acer truncatum seeds,which contain about 5%e6%NA in their seed *** aim of this study were to identify and analyze NA-containing Acer species that could be used as NA resource *** this purpose,46 Acer species seeds were collected in China and in some or all of the seed oils from these species 15 fatty acids were detected,including linoleic acid,oleic acid(C18:1D9,C18:1D11),erucic acid,palmitic acid,NA,linolenic acid(C18:3D6,9,12,C18:3D9,12,15),eicosenoic acid(C20:1D11,C20:1D13),stearic acid,behenic acid,tetracosanoic acid,arachidic acid,and docosadienoic *** acid was detected in all samples,but the content was highly variable among *** content over 9%was detected in eleven species,of which Acer elegantulum had the highest levels(13.90%).The seed oil content,seed weight,and fatty acid profiles varied among species,but the comprehensive evaluation value(W)showed that *** could be a new potential NA resources *** results also showed that NA was significantly negatively correlated with palmitic acid,oleic acid,and eicosenoic acid,but positively correlated with eicosadienoic acid,behenic acid,erucic acid,and tetracosanoic acid,which indicate the probable pathway for NA biosynthesis in Acer *** study has identified Acer species that may serve as NA resources and will help guide subsequent species breeding programs.

关键词： Acer Nervonic acid Fatty acid Seed oil Seed weight

Sand particle dislodgement in windblown sand

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Acta Mechanica Sinica 2014年第6期30卷 910-916页

作者： tian-Li bo Zheng Li Xiao-Jing Zheng Key Laboratory of Mechanics on Western Disaster and Environment Lanzhou University Department of Mechanics Lanzhou University School of Electronical and Machanical Engineering Xidian University

The incipient motion of sand particle from sand bed plays a very important role in the prediction of windblown *** this paper,we proposed a new method for predicting the incipient motion of sand particle based on wind speed fluctuation as follows,when the wind speed is larger than the critical wind speed,if the total impulse on sand particle is larger than the critical impulse,incipient motion of sand particle would take place,otherwise if ***,from the analysis of entrainment in the rolling and lifting modes,we come to the following *** the average wind speed is smaller than the critical wind speed,if the average wind speed is used to judge the incipient motion of sand particle,one will underestimate the number of sand particles jumping from the bed,if the instantaneous wind speed is used to judge incipient motion of sand particle,one will overestimate the number of sand particles jumping from the bed;When the average wind speed is larger than the critical wind speed,either the average or the instantaneous wind speeds is used to judge the incipientmotion of sand particles,one will overestimate the number of sand particles jumping from the bed.

关键词： Incipient motion Rolling mode Average wind speed Total impulse Windblown sand

Cross-layer resource allocation for QoS guarantee with finite queue constraint in multirate OFDMA wireless networks

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The Journal of China Universities of Posts and Telecommunications 2008年第3期15卷 87-94页

作者： XU Hai-bo tian Hui FENG Yuan Key Laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

Efficient radio resource allocation is essential to provide quality of service （QoS） for wireless networks. In this article, a cross-layer resource allocation scheme is presented with the objective of maximizing system throughput, while providing guaranteed QoS for users. With the assumption of a finite queue for arrival packets, the proposed scheme dynamically a/locates radio resources based on user＇s channel characteristic and QoS metrics derived from a queuing model, which considers a packet arrival process modeled by discrete Markov modulated Poisson process （dMMPP）, and a multirate transmission scheme achieved through adaptive modulation. The cross-layer resource allocation scheme operates over two steps. Specifically, the amount of bandwidth allocated to each user is first derived from a queuing analytical model, and then the algorithm finds the best subcarrier assignment for users. Simulation results show that the proposed scheme maximizes the system throughput while guaranteeing QoS for users.

关键词： cross-layer resource allocation finite queue dMMPP QoS orthogonal frequency division multiple access (OFDMA)

Effect of Methylene Blue (MB)-value of Manufactured Sand on the Durability of Concretes

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Journal of Wuhan University of Technology(Materials Science) 2012年第6期27卷 1160-1164页

作者：王稷良 NIU Kaimin tian bo SUN liqun Key Laboratory of Road Structure and Material Ministry of Communications(Beijing) Research Institute of Highway Ministry of CommunicationBeijing 100088China Guizhou Province Building Materials Product Quality Supervision and Inspection Center Guiyang 550002China

The relation between the methylene blue （MB） value of MS and its limestone powder content and clay content was investigated. The effects of MB values ranging from 0.35 to 2.5 on the workability of fresh concrete, the mechanical properties, the resistance to freezing as well as the resistance to chlorine ion permeation of the hardened concrete were all investigated. The experimental results showed that the MB value had no correlation with the limestone powder content of MS, while it was directly related to the clay content. With an increase of MB value, concrete workability decreased, as did the flexural and 7-day compressive strengths, however, the 28-day compressive strength was not affected. Furthermore, influence of MB value on concretes of different strength levels was different. For low-strength concretes, an increase of MB value could improve its impermeability, but this was not the case for high-strength concretes. Instead, their resistance to chloride ion permeability decreased slightly. However, even a slight increase in MB value remarkably accelerated freeze-thaw damage of MS concrete. It was thus concluded that the critical MB value of 1.4 would not cause significant deterioration in the performance of MS concretes.

关键词： manufactured sand methylene blue value clay content resistance to freezing chlorine ionpermeability coefficient

A new strategy for synthesis of branched cyclic peptide by Asn side-chain hydrazide ligation

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Chinese Chemical Letters 2015年第8期26卷 946-950页

作者： Jian Lu Xiao-bo tian Wei Huang CAS Key Laboratory of Receptor Research Shanghai Institute of Materia Medica Chinese Academy of Sciences Medical College of Nanchang University

Here, we report a new strategy for rapid synthesis of branched peptide by side-chain hydrazide ligation at Asn. The hydrazide was converted to thioester at Asn side chain by Na NO2 and thiol reagent, and sequential ligation with an N-terminus Cys-peptide efficiently afforded the branched peptide. A branched cyclic peptide was successfully synthesized by side-chain ligation with a two-Cys-peptide and formation of a disulfide bond. This approach provides a new way for expeditious synthesis of branched peptides and facilitates the design of neopeptides as functional bio-mimics.

关键词： ligation branched sequential reagent disulfide thiol Fmoc retention azide simultaneous