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Progress in helicopter infrared signature suppression

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Chinese Journal of Aeronautics 2014年第2期27卷 189-199页

作者： zhang Jingzhou pan Chengxiong Shan yong Jiangsu Province Key Laboratory of Aerospace Power System College of Energy & Power Engineering Nanjing University of Aeronautics and Astronautics

Due to their low-attitude and relatively low-speed fight profiles, helicopters are subjected to serious threats from radio, infrared （IR）, visual, and aural detection and tracking. Among these threats, infrared detection and tracking are regarded as more crucial for the survivability of helicop- ters. In order to meet the requirements of infrared stealth, several different types of infrared sup- pressor （IRS） for helicopters have been developed. This paper reviews contemporary developments in this discipline, with particular emphasis on infrared signature suppression, advances in mixer-ejectors and prediction for helicopters. In addition, several remaining challenges, such as advanced IRS, emissivity optimization technique, helicopter infrared characterization, etc., are proposed, as an initial guide and stimulation for future research. In the future, the comprehen- sive infrared suppression in the 3-5 μm and 8-14 μm bands will doubtfully become the emphasis of helicopter stealth. Multidisciplinary optimization of a complete infrared suppression system deserves further investigation.

关键词： Helicopter Infrared radiation Infrared suppression Internal aerodynamics Mixer-ejector

Convexity-preserving interpolation of trigonometric polynomial curves with a shape parameter

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第8期8卷 1199-1209页

作者： pan yong-juan WANG Guo-jin Department of Mathematics Zhejiang University Hangzhou 310027 China Department of Applied Mathematics Zhejiang University of Technology Hangzhou 310032 China

In computer aided geometric design(CAGD) ,it is often needed to produce a convexity-preserving interpolating curve according to the given planar data points. However,most existing pertinent methods cannot generate convexity-preserving in-terpolating transcendental curves;even constructing convexity-preserving interpolating polynomial curves,it is required to solve a system of equations or recur to a complicated iterative process. The method developed in this paper overcomes the above draw-backs. The basic idea is:first to construct a kind of trigonometric polynomial curves with a shape parameter,and interpolating trigonometric polynomial parametric curves with C2(or G1) continuity can be automatically generated without having to solve any system of equations or do any iterative computation. Then,the convexity of the constructed curves can be guaranteed by the appropriate value of the shape parameter. Performing the method is easy and fast,and the curvature distribution of the resulting interpolating curves is always well-proportioned. Several numerical examples are shown to substantiate that our algorithm is not only correct but also usable.

关键词： Computer aided geometric design (CAGD) α-trigonometric polynomial curves Interpolation Convexity-preserving Shape parameter

Oxidation Kinetics,Structural Changes and Element Migration during Oxidation Process of Vanadium-titanium Magnetite Ore

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Journal of Iron and Steel Research International 2016年第11期23卷 1160-1167页

作者： Feng pan Qing-shan ZHU zhan DU Hao-yan SUN State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of Sciences(CAS)Beijing 100190China University of Chinese Academy of Sciences Beijing 100039China

The oxidation kinetics, structural changes, and elements migration during the oxidation process of the va- nadium-titanium magnetite （VTM） ore were analyzed. Kinetics analysis indicated that the oxidation process was con- trolled by diffusion control and could be divided into interface diffusion and lattice diffusion with apparent activation energy of 99.69 kJ/mol and 144.08 kJ/mol in the range of 800--1000℃, respectively. The surface structure changed with the oxidization temperature as follows： dense surface→nano sized sheets→submicron particles→molten particles. The compact structure changed into porous one because of the elements migration and enrichment. Both Fe and Ti elements migrated in the opposite direction during the oxidation process. The V etement in the raw ore stably existed in the form of V^5＋ state, some vanadium migrated and occupied the tetrahedral sites of the hematite during the oxidation process.

关键词： vanadium-titanium magnetite ore oxidation kinetics structural change element migration

sl(1|2)Super-Toda Fields

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Communications in Theoretical Physics 2008年第11期50卷 1061-1064页

作者： YANG zhan-Ying XUE pan-pan ZHAO Liu SHI Kang-Jie Department of Physics Northwest University Xi＇an 710069 China Department of Physics Nankai University Tianjin 300071 China Institute of Modern Physics Northwest University Xi＇an 710069 China

Explicit exact solution of supersymmetric Toda fields associated with the Lie superalgebra s/（2｜ 1） is constructed. The approach used is a super extension of Leznov-Saveliev algebraic analysis, which is based on a pair of chiral and antichiral Drienfeld-Sokolov systems. Though such approach is well understood for Toda field theories associated with ordinary Lie algebras, its super analogue was only successful in the super Liouville case with the underlying Lie superalgebra osp（1｜2）. The problem lies in that a key step in the construction makes use of the tensor product decom- position of the highest weight representations of the underlying Lie superalgebra, which is not clear until recently. So our construction made in this paper presents a first explicit example of Leznov-Saveliev analysis for super Toda systems associated with underlying Lie superalgebras of the rank higher than 1.

关键词： Toda field supersymmetry exact solution

Systematic Synthesis of Compressive VDTA-Based T-T Filter with Orthogonal Control of f_o and Q

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Journal of Electronic Science and Technology 2020年第3期18卷 276-286页

作者： yong-An Li Yan-Hua Xi zhan-Ting Fan School of Physics and Electronic Engineering Xianyang Normal UniversityXianyang 712000 School of Information Engineering Shaanxi Institute of International Trade&CommerceXi’an 712046

Based on sixteen nullor-mirror models of the voltage differencing transconductance amplifier (VDTA) and port admittance matrices of the tow-Thomas (T-T) filter with orthogonal control between the characteristic frequency(f_0) and figure of merit (Q),two different categories of the voltage-mode and transconductance-mode T-T filters are synthesized by the means of the nodal admittance matrix (NAM) expansion *** category A filter that employs two compressive VDTAs and two grounded capacitors includes four structures,and the category B filter that uses two compressive VDTAs,two grounded capacitors,and one grounded resistor,also includes four *** circuits are suitable for integrated circuit manufacture,and their parameters f_0 and Q can be orthogonally adjusted with varying the bias currents of *** the paper and pencil test is completed,the computer analyses,including alternating current (AC),parameter sweep,Monte Carlo (MC),and noise analyses,are performed to support the synthesis approach.

关键词： Compressive voltage differencing transconductance amplifier(compressive VDTA) nodal admittance matrix(NAM)expansion method systematic synthesis tow-Thomas(T-T)filter

Double-Shelled L1_(2) Nano-structures in Quaternary Al–Er–Sc–Zr Alloys: Origin and Critical Significance

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Acta Metallurgica Sinica(English Letters) 2021年第9期34卷 1277-1284页

作者： Chao-Min zhang pan Xie yong Jiang Sheng zhan Wen-Quan Ming Jiang-Hua Chen Ke-Xing Song Hao zhang School of Materials Science and Engineering Henan Key Laboratory of Non-Ferrous Materials Science&Processing TechnologyHenan University of Science and TechnologyLuoyang 471023China School of Materials Science and Engineering Central South UniversityChangsha 410083China College of Materials Science and Engineering Hunan UniversityChangsha 410082China Jiangsu Haoran Spray Forming Alloy Co. LtdZhenjiang 212132China

The formation of highly coherent double-shelled L1_(2) nano-precipitates in dilute Al–Er–Sc–Zr alloys was investigated with the combined use of Cs-corrected transmission electron microscopy characterization and first-principles energetics calculations. The double-shelled nano-precipitates are primarily featured with an Er-rich core surrounded by a Sc-rich inner shell and a Zr-rich outer shell. First-principles energetics analyses based on the classic homogenous nucleation theory suggested that once forms, this double-shell structure can be thermally stable. The predominant formation of this double-shell structure has thus both profound kinetic and thermodynamic origins. Its formation and stability preference to all other possible L1_(2) nano-structures would become more pronounced as its size increases, no matter what the solute ratio and aging temperature of interest.

关键词： Al alloys Core–shell L12 nano-phase First-principles

Controllable macrocyclic supramolecular assemblies in aqueous solution

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Science China Chemistry 2018年第8期61卷 979-992页

作者： yong Chen Feihe Huang zhan-Ting Li Yu Liu State Key Laboratory of Elemento-Organic Chemistry College of Chemistry Nankai University Tianjin 300071 China Co-Innovation Center of Chemistry and Chemical Engineering (Tianjin) Tianjin 300072 China State Key Laboratory of Chemical Engineering Center for Chemistry of High-Performance & Novel Materials Department of Chemistry Zhejiang University Hangzhou 310027 China Department of Chemistry Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials and Collaborative Innovation Centre of Chemistry for Energy Materials (iChEM) Fudan University Shanghai 200438 China

A series of macrocycles, including crown ethers, cyclodextrins, calixarenes, pillararenes and cucurbiturils, are well known to be able to associate various organic/inorganic/biological guest molecules and ions in their well-defined cyclic cavities to form stable host-guest complexes and supramolecular systems through the cooperative contributions of various non-covalent *** one or more functional groups are attached to the cavity of macrocycles or guest molecules, enhanced and/or controlled host-guest associations may take place, leading to not only improved host-guest binding abilities but also fascinating *** this review, some representative contributions in the construction of controllable macrocyclic supramolecular assemblies in aqueous solution are presented with an emphasis on the stimuli-responsive control manner and wide applications of this property.

关键词： macrocycle supramolecular assembly stimuli-responsive aqueous solution

Modal parameter identification of flexible spacecraft using the covariance-driven stochastic subspace identification(SSI-COV) method

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Acta Mechanica Sinica 2016年第4期32卷 710-719页

作者： yong Xie pan Liu Guo-Ping Cai Department of Engineering Mechanics State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University

In this paper, the on-orbit identification of modal parameters for a spacecraft is investigated. Firstly, the coupled dynamic equation of the system is established with the Lagrange method and the stochastic state-space model of the system is obtained. Then, the covariance-driven stochastic subspace identification（SSI-COV） algorithm is adopted to identify the modal parameters of the system. In this algorithm, it just needs the covariance of output data of the system under ambient excitation to construct a Toeplitz matrix, thus the system matrices are obtained by the singular value decomposition on the Toeplitz matrix and the modal parameters of the system can be found from the system matrices. Finally,numerical simulations are carried out to demonstrate the validity of the SSI-COV algorithm. Simulation results indicate that the SSI-COV algorithm is effective in identifying the modal parameters of the spacecraft only using the output data of the system under ambient excitation.

关键词： covariance stochastic subspace spacecraft modal validity matrices identifying excitation Toeplitz

A multi-component nanocrystalline FeCrV alloy with improved mechanical properties and excellent irradiation resistance

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Progress in Natural Science:Materials International 2022年第4期32卷 433-442页

作者： Tingting Li Sizhe Diao Pingping Liu yong zhang Qian zhan School of Materials Science and Engineering University of Science and Technology Beijing Beijing Advanced Innovation Center for Materials Genome Engineering State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

An equiatomic low-activated Fe Cr V ternary alloy was prepared by mechanical alloying and spark plasma sintering. The BCC solid solution alloy exhibited an excellent strength-ductility synergy properties, which was 1.85GPa compressive yield strength, 3.04 GPa fracture strength and more than 28% plasticity at room *** at an elevated temperature of 600°C, its yield strength was still more than 1 GPa, revealing a pronounced high temperature resistance. The Fe Cr V alloy had a homogeneous microstructure with high-density dislocations.A nanocrystalline characteristic was demonstrated and the average grain size was about 322 nm, leading to the improved mechanical properties. The strengthening mechanism was discussed in detail and the contributions of strengthening factors were calculated. The Fe Cr V alloy was irradiated up to 160 dpa with 2 Me V Au2+ions at 573K. The nanoindentation test was carried out to simply evaluate the hardening degree under such a high dose irradiation with heavy ions. The semi-quantitative analysis results show that Fe Cr V alloy has an excellent irradiation tolerance compared with pure Fe.

关键词： Mechanical properties Nanocrystalline Strengthening mechanism Au 2+ irradiation Multi-component alloy Mechanical alloying