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Study on modal characteristics and vibration reduction of an aircraft rotor–stator brake-induced squeal system

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Acta Mechanica Sinica 2020年第6期36卷 1350-1359,I0004页

作者： Qiaozhi yin Xiaohui Wei Hong Nie jian Deng State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing210016China Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and AstronauticsNanjing210016China Nanjing Center for Multifunctional Lightweight Materials and Structures Nanjing University of Aeronautics and AstronauticsNanjing210016China

Based on the modal coupling theory,the rotor and stator contact stiffness and axial relative velocity are considered to build an electric aircraft brake dynamic system model in this *** the complex modal analysis and transient dynamic analysis methods are used to study the aircraft brake squeal performance and vibratory *** unstable vibration modes indicate that the out-of-plane vibration plays an important role and the feed-in energy is larger than the output energy in the brake rotor–stator module so that brake squeal takes *** the influences of the contact stiffness,friction damping and frictional coefficient on the brake squeal system are carried out,laying the foundation for the three proposed vibration suppression *** show that the coefficient negative-slope condition will intensify the ***,a linear relationship between the squeal factor and the frictional coefficient is obtained to provide a guidance to predict squeal stability under more *** reduction design shows that adding a damping layer to the brake mechanism and chamfering the edge of braking stators both can reduce brake squeal effectively,while slotting braking stators is invalid in aircraft braking system.

关键词： Aircraft rotor-stator bake-induced vibration Brake squeal-Vibration stability Modal coupling Vibration suppression

Parameter effects on high-speed UAV ground directional stability using bifurcation analysis

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Chinese Journal of Aeronautics 2021年第11期34卷 1-14页

作者： Qiaozhi yin Xiaohui WEI Hong NIE jian DENG State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle Nanjing University of Aeronautics and AstronauticsNanjing 210016China MIIT Key Laboratory of Multifunctional Lightweight Materials and Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China

A loss of ground directional stability can trigger a high-speed Unmanned Aerial Vehicle(UAV)to veer off the *** order to investigate the combined effects of the key structural and operational parameters on the UAV ground directional stability from a global perspective,a fully parameterized mathematical high-speed UAV ground nonlinear dynamic model is developed considering several nonlinear *** bifurcation analysis procedure of a UAV ground steering system is introduced,following which the simulation efficiency is greatly improved comparing with the time-domain simulation *** the numerical continuation method is employed to investigate the influence of the nose wheel steering angle and the global stability region is *** bifurcation parameter plane is divided into several parts with different stability properties by the saddle nodes and the Hopf bifurcation *** find that the UAV motion states will never cross the bifurcation curve in the nonlinear ***,the dual-parameter bifurcation analyses are presented to give a complete description of the possible steering *** is also found that BT bifurcation appears when the UAV initial rectilinear velocity and the tire frictional coefficient *** addition,results indicate that the influence of tire frictional coefficient has an opposite trend to the influence of initial rectilinear ***,using bifurcation analysis method to identify the parameter regions of a UAV nonlinear ground dynamic system helps to improve the development efficiency and quality during UAV designing phase.

关键词： Bifurcation analysis Ground directional stability High-speed UAV Nonlinear system Numerical continuation

Spin-resolved quantum transport in graphene-based nanojunctions

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Frontiers of physics 2017年第4期12卷 29-41页

作者： jian-Wei Li Bin Wang Yun-Jin Yu Ya-dong Wei Zhi-Zhou Yu yin Wang College of Physics and Energy Shenzhen University Shenzhen 518060 China Department of Physics The University of Hong Kong Hong Kong China

First-principles calculations were performed to explore the spin-resolved electronic and thermoelectric transport properties of a series of graphene-nanoribbon-based nanojunctions. By flipping the mag- netic moments in graphene leads from parallel to antiparallei, very large tunneling magnetoresistance can be obtained under different gate voltages for all the structures. Spin-resolved alternating-current conductance increases versus frequency for the short nanojunctions but decreases for the long nano- junctions. With increasing junction length, the behavior of the junctions changes from capacitive-like to inductive-like. Because of the opposite signs of spin-up thermopower and spin-down thermopower near the Fermi level, pure spin currents can be obtained and large figures of merit can be achieved by adjusting the gate voltage and chemical potential for all the nanojunctions.

关键词： TMR AC conductance thermoelectric transport NEGF-DFT

Polarization visualization for low-irradiance regions by perceptually uniform color space

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Defence Technology（防务技术） 2021年第2期17卷 505-511页

作者： Feng Zhao Yue dong jian-lei Zhang Xi’an University of Posts and Telecommunications School of Electronic EngineeringXi’an710121China

Currently,polarization visualization strategies are accomplished by mapping polarization information into a perceptually uniform color appearance model ***,the deviation of the CAM02-UCS space from the lightness prediction results in an inaccurate match between the polarization information and the perceptual *** this paper,we propose a novel polarization visualization strategy based on the perceptual uniform space *** polarization visualization be completed by placing the polarization information into the lightness Jz,colorfulness Cz and hue angle hz channels of the Jzazbz *** experimental results show that the proposed method can significantly improve the lightness of the low irradiance and high polarization region,hence more polarization information can be sensed by human visual system.

关键词： Polarization visualization Perceptually uniform space Lightness prediction Low irradiance

List 2-distance Coloring of Planar Graphs with Girth Five

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Acta Mathematicae Applicatae Sinica 2022年第3期38卷 540-548页

作者： yin-dong JIN Lian-ying MIAO School of Mathematics China University of Mining and TechnologyXuzhou 221116China

A 2-distance coloring of a graph is a coloring of the vertices such that two vertices at distance at most two receive distinct colors.A list assignment of a graph G is a mapping L which assigns to each vertex v a set L(v)of positive *** list 2-distance chromatic number of G denoted byχ_(2)^(l)(G)is the least integer k for which G is list 2-distance *** this paper,we prove that every planar graph with g(G)≥5 and△(G)≥40 is list 2-distance(△(G)+4)-colorable.

关键词： 2-distance coloring list 2-distance coloring girth maximum degree

Redefined generalized fuzzy ideals of near-rings

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Applied Mathematics(A Journal of Chinese Universities) 2010年第3期25卷 341-348页

作者： ZHAN jian-ming yin Yun-qiang Department of Mathematics Hubei Institute for Nationalities Enshi 445000 China College of Mathematics and Information Sciences East China Institute of Technology Fuzhou Jiangxi 344000 China

With a new idea, we redefine generalized fuzzy subnear-rings （ideals） of a near- ring and investigate some of its related properties. Some new characterizations are given. In particular, we introduce the concepts of strong prime （or semiprime）（∈, ∈∨ q）-fuzzy ideals of near-rings, and discuss the relationship between strong prime （or semiprime）（∈, ∈∨ q）-fuzzy ideals and prime （or semiprime）（∈, ∈∨ q）-fuzzy ideals of near-rings.

关键词： Near-ring subnear-ring (ideal) (∈^- ∈^-∨ q^-)-fuzzy subnear-ring (ideal) prime (semiprime) (∈ ∈∨ q)-fuzzy subnear-ring (ideal).

Solution to an Extremal Problem on Bigraphic Pairs with a Z3-connected Realization

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Acta Mathematica Sinica,English Series 2017年第8期33卷 1131-1153页

作者： jian Hua yin Xiang Yu DAI Department of Mathematics College of Information Science and TechnologyHainan UniversityHaikou 570228P.R.China

Let S = （a1,...,am;b1,...,bn）, where a1,...,am and b1,...,bn are two nonincreasing sequences of nonnegative integers. The pair S= （a1,..., am; b1,..., bn） is said to be a bigraphic pair if there is a simple bipartite graph G = （X ∪ Y, E） such that a1,…, am and b1,..., bn are the degrees of the vertices in X and Y, respectively. Let Z3 be the cyclic group of order 3. Define σ（Z3, m, n） to be the minimum integer k such that every bigraphic pair S = （a1,..., am; b1,..., bn） with am, b ≥ 2 and σ（S） = a1 ＋ ... ＋ am ≥ k has a Z3-connected realization. For n = m, yin [Discrete Math., 339, 2018-2026 （2016）] recently determined the values of σ（Z3,m,m） for m ≥ 4. In this paper, we completely determine the values of σ（Z3, m, n） for m ≥ n ≥4.

关键词： Bigraphic pair Z3-connected realization group connectivity

Diverse and variable sex determination mechanisms in vertebrates

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Science China(Life Sciences) 2018年第12期61卷 1503-1514页

作者： Xi-yin Li jian-Fang Gui State Key Laboratory of Freshwater Ecology and Biotechnology Institute of Hydrobiology College of Modern Agriculture Sciences University of Chinese Academy of Sciences The Innovative Academy of Seed Design Chinese Academy of Sciences

Sex is prevalent in nature and sex determination is one of the most fundamental biological processes, while the way of initiating female and male development exhibits remarkable diversity and variability across vertebrates. The knowledge on why and how sex determination mechanisms evolve unusual plasticity remains limited. Here, we summarize sex determination systems,master sex-determining genes and gene-regulatory networks among vertebrates. Recent research advancements on sex determination system transition are also introduced and discussed in some non-model animals with multiple sex determination mechanisms. This review will provide insights into the origin, transition and evolutionary adaption of different sex determination strategies in vertebrates, as well as clues for future perspectives in this field.

关键词： sex determination sex-determining gene sex chromosome sex transition sex differentiation sex control breeding

The 2-pebbling Property for Dense Graphs

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Acta Mathematica Sinica,English Series 2013年第3期29卷 557-570页

作者： Ze Tu GAO jian Hua yin Department of Mathematics College of Information Science and Technology

Given a distribution of pebbles on the vertices of a connected graph G, a pebbling move on G consists of taking two pebbles off one vertex and placing one on an adjacent vertex. The pebbling number f（G） is the smallest number m such that for every distribution of m pebbles and every vertex v, a pebble can be moved to v. A graph G is said to have the 2-pebbling property if for any distribution with more than 2f（G） - q pebbles, where q is the number of vertices with at least one pebble, it is possible, using pebbling moves, to get two pebbles to any vertex. Snevily conjectured that G（s, t） has the 2- pebbling property, where G（s, t） is a bipartite graph with partite sets of size s and t （s 〉 t）. Similarly, the ~,pebbling number fl（G） is the smallest number m such that for every distribution of m pebbles and every vertex v, ~ pebbles can be moved to v. Herscovici et al. conjectured that fl（G） ≤ 1.5n ＋ 8l -- 6 for the graph G with diameter 3, where n = IV（G）I. In this paper, we prove that if s ≥ 15 and G（s,t）

关键词： Pebbling number 2-pebbling property bipartite graph