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Electromagnetic and microwave absorbing properties of W-type barium ferrite doped with Gd^(3+)

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Rare Metals 2011年第1期30卷 44-48页

作者： HUAng Xiaogu CHEN Jiao WAng Lixi ZHAng Qitu college of Materials Science and engineer.ng Nanjing University of Technology Nanjing 210009 China Jiangsu Provincial Key Laboratory of Inorganic and Composite New Materials Nanjing University of Technology Nanjing 210009 China

W-type barium ferrites doped with Gd^3＋,Ba1-xGdx（Zn0.3Co0.7）2Fe16O27（x = 0,0.05,0.10,0.15,0.20）,were prepared by a sol-gel *** effects of Gd^3＋ substitution on their microstructure,electromagnetic properties and microwave absorptive behavior were *** XRD patterns showed the single phase of W-type barium ferrite when x ≤ *** electromagnetic properties of samples were studied at the frequency range from 2 GHz to 18 GHz using a network analyzer（Agilent 8722ET）.The complex permittivity ε（ε＇,ε＇＇） increased gradually when x ≤ 0.10,but it decreased as x = *** real permeability（μ＇） decreased with the increase of Gd^3＋ content,while the imaginary permeability（μ＇＇） increased when x ≤ *** these reasons were discussed using the electromagnetic ***,the ferrite-epoxy compound coating materials with 80 wt.% of Ba0.9Gd0.1（Zn0.3Co0.7）2Fe16O27 were prepared to measure the microwave absorbing *** maximum of reflection loss（RL） reached about-27 dB and RL was below-10 dB in the frequency range of 8-18 GHz when the thickness was 1.92 mm.

关键词： nonmetallic material barium compounds ferrite sol-gel process materials properties doping

A new smoothing scheme for mathematical programs with complementarity constraints

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Science china Mathematics 2010年第7期53卷 1881-1890页

作者： YAN TaoDepartment of Information and Computational Sciences, college of Science, nanjing university of Science and technology, nanjing 210094, china 1. Department of Information and Computational Sciences College of Science Nanjing University of Science and Technology Nanjing 210094 China

In this paper, we consider a mathematical program with complementarity constraints (MPCC). We present a new smoothing scheme for this problem, which makes the primal structure of the complementarity part unchanged mostly. For the new smoothing problem, we show that the linear independence constraint qualification (LICQ) holds under some conditions. We also analyze the convergence behavior of the smoothing problem, and get some sufficient conditions such that an accumulation point of stationary points of the smoothing problems is C (M, B)-stationarity respectively. Based on the smoothing problem, we establish an algorithm to solve the primal MPCC problem. Some numerical experiments are given in the paper.

关键词： mathematical program with complementarity constrains MPEC-LICQ B-stationarity C-stationarity M-stationarity

A NOVEL INTERPRETATION OF CONCENTRATION DEPENDENCE OF VISCOSITY OF DILUTE POLYMER SOLUTION

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Chinese Journal of Polymer Science 2000年第1期18卷 57-67页

作者： Yan Pan Rong-shi Cheng college of Material Science and engineer.ng, South china university of technology, Guangzhou 510641, china college of Chemistry and Chemical engineer.ng, nanjing university, nanjing 210093, china S china Univ Technol Coll Mat Sci & Engn Guangzhou 510641 Peoples R China nanjing Univ Coll Chem & Chem Engn Nanjing 210093 Peoples R China

The concentration dependence of the reduced viscosity of dilute polymer solution is interpreted in the light of a new concept of the self-association of polymer chains in dilute solution. The apparent self-association constant is defined as the molar association constant divided by the molar mass of individual polymer chain and is numerically interconvertible with the Huggins coefficient. The molar association constant is directly proportional to the effective hydrodynamic volume of the polymer chain in solution and is irrespective of the chain architecture. The effective hydrodynamic volume accounts for the non-spherical conformation of a short polymer chain in solution and is a product of a shape factor and hydrodynamic volume. The observed enhancement of Huggins coefficient for short chain and branched polymer is satisfactorily interpreted by the concept of self-association. The concept of self-association allows us to predict the existence of a boundary concentration C-s(dynamic contact concentration) which divides the dilute polymer solution into two regions.

关键词： self-association polymer solution viscosity concentration dependence

Research into a theoretical mode of coherent structures in the wall region of a turbulent boundary layer induced by a wall local disturbance

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Progress in Natural Science:Materials International 2009年第9期19卷 1119-1124页

作者： Changgen Lua,*, Qinjuan Qi b a college of Atmospheric Sciences, nanjing university of Information Science & technology, nanjing 210044, china b college of Public Management, nanjing university of Information Science & technology, nanjing 210044, china [a]college of Atmospheric Sciences Nanjing University of Information Science & Technology Nanjing 210044 China [b]College of Public Management Nanjing University of Information Science & Technology Nanjing 210044 China

The idea of applying direct numerical simulation (DNS), a theoretical mode of coherent structures in the wall region of a turbulent boundary layer, has been discussed in the literature. The various aspects of the formation mechanism of the coherent structures agree well with both DNS and experimental results. In addition, a close relationship has been found between the evolutional characteristics and factors such as the magnitude and structural distribution of the wall local impulse disturbance, and the amount of energy a local disturbance introduces into the wall region. Moreover, these parameters play key roles in the formation of coherent structures near the wall region of a turbulent boundary layer. Therefore, the wall local impulse disturbance provides a theoretical model for triggering the formation of coherent structures in the wall region of a turbulent boundary layer.

关键词： Turbulent boundary layer Wall region Coherent structure Local disturbance

Performance analysis of variable-power adaptive modulation in space-time block coded MIMO diversity systems

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Science china(Information Sciences) 2010年第10期53卷 2106-2115页

作者： YU XiangBin 1,2 & SHI HuiBin 1 1 college of Information Science and technology, nanjing university of Aeronautics and Astronautics, nanjing 210016, china 2 National Mobile Communications Research Laboratory, Southeast university, nanjing 210096, china 1. college of Information Science and technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China2. National Mobile Communications Research Laboratory Southeast University Nanjing 210096 China

In this paper, the performance analysis of multi-antenna MIMO systems with variable-power (VP) adaptive modulation and space-time coding is presented. The fading gain value is partitioned into a number of regions by which we decide the transmission power according to the region the fading gain falls in. The optimum fading gain region boundaries (switching thresholds) for maximizing spectrum efficiency (SE) under a target BER and average power constraint are derived. It is shown that the Lagrange multiplier in the constrained SE optimization will be unique if the existence condition for multi-antenna systems is satisfied, and is unique for single antenna systems. A practical iterative calculation method based on Steepest Descent Algorithm for finding the Lagrange multiplier is proposed. With the switching thresholds, the closed-form expressions of the SE and average BER, respectively for VP system and constant-power (CP) system are achieved. Simulation results for SE and average BER are in good agreement with the theory analysis. The results show that VP adaptive modulation with space-time coding provides better SE than the counterpart with CP under a target BER and average power constraint.

关键词： adaptive modulation variable power space-time block code constant power multiple input multiple output (MIMO)

The Synthetic Evaluation of Warhead Overall Efficiency

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Journal of Systems engineer.ng and Electronics 2003年第1期14卷 12-17页

作者： Gu Xiaohui & Cao Bing college of Mechanics, nanjing university of Science & technology, nanjing 210094, P. R. china college of Mechanics Nanjing University of Science & Technology Nanjmg 210094 P. R. China

The evaluation system of smart ammunition warhead overall efficiency has been established in this paper. Allkinds of evaluation methods have been analyzed. Having led the concept of hierarchical structure into technique for orderpreference by similarity to ideal solution (TOPSIS) method, we put forward the step TOPSIS method which is suitable forevaluating the overall efficiency of smart ammunition warheads. In the calculation of index weight, the graded weight cal-culus is put forward which hardly relies on the subjectivity of decision-makers and can reflect the sensitivity and compatibili-ty of the index. In the graded weight calculation, the proportional-arithmetic weight value calculus and sensitivity-compati-bility weight value calculus are given respectively.

关键词： Step analysis TOPSIS method Warhead Efficiency evaluation.

Performance analysis of compact MIMO system based on network theory

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The Journal of china Universities of Posts and Telecommunications 2009年第6期16卷 6-10,37页

作者： XU Dan,ZHAng Jing,ZHAng Ye-rong college of Communication and Information technology,nanjing university of Posts and Telecommunications,nanjing 210003,china [a] college of Communication and Information technology nanjing university of Posts and Telecommunications nanjing 210003 china

The impact of mutual coupling on the performance of multiple-input multiple-output（MIMO） systems with compact antenna arrays is *** article aims to use the S-parameter modeling approach to examine the impact of mutual coupling on three system-related performance measures：antenna correlation,efficiency and *** is shown that implementing a good matching network can drastically improve the system performance in the presence of strong mutual *** results indicate the superiority of cross-shaped antenna to dipole antenna.

关键词： MIMO mutual coupling wireless channel

MMSE relay precoding schemes based on quantization error compensation for multi-relay system

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Science china(Information Sciences) 2010年第12期53卷 2548-2556页

作者： LI Ting 1,2 & YAng LuXi 2 1 college of Communication and Information engineer.ng,nanjing university of Posts and Telecommunications,nanjing 210003,china 2 School of Information Science and engineer.ng,Southeast university,nanjing 210096,china 1. college of Communication and Information engineer.ng Nanjing University of Posts and Telecommunications Nanjing 210003 China2. School of Information Science and Engineering Southeast University Nanjing 210096 China

In order to deal with the performance degradation resulting from the quantization error,this paper introduces the statistics of Grassmannian codebook's quantization error into relay precoding design for multirelay *** on the two-step MMSE optimization algorithm for relay precoding and receiver equalizing with full feedback under QoS requirements,we first propose a limited feedback two-step MMSE optimization scheme for relay precoding and receiver equalizing with quantization error compensation,and then we propose a limited feedback joint MMSE optimization scheme for relay precoding and receiver equalizing with quantization error compensation subject to a global power constraint at the output of *** results show that the proposed joint MMSE optimization scheme with quantization error compensation has a much lower bit-error rate than the two-step MMSE optimization scheme with quantization error compensation and the joint MMSE optimization scheme without quantization error compensation.

关键词： multi-relay precoding limited feedback minimum mean square error

Effects of Silane Coupling Agent on Microstructure and Mechanical Properties of EPDM/Carbonyl Iron Microwave Absorbing Patch

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Journal of Wuhan university of technology(Materials Science) 2006年第4期21卷 78-82页

作者：冯永宝 college of Materials Science and engineer.ng Nanjing University of Technology Nanjing 210009 China

The effects of types and amounts of silane coupling agent on mechanical properties of vuleanized rubber microwave absorbing patch （VRMAP） were studied. The mechanisms of silane coupling agent＇s effects on mechanical properties of rubber microwave absorbing patch （ RMAP ） and microvave absorbing patch＇s （MAP＇s） mierostrueture were also discussed by using SEM and FT-IR. The experimental results show that the tensile strength of RMAP could be increased through adding the filler of carbonyl iron powder （CIP） modified by silane coupling agent. RMAP fiUed with CIP, which was treated by silane coupling agent KH550, possessed a high tensile strength of 11.5 MPa, which was 448% more than that of MAP whose filler wus not modified by any coupling agent. It was found that the optimal amount of KH550 was 1.0 phr to 100.0 phr carbonyl iron powder. The effects of different modifying techniques on RMAP＇s mechanical properties were also inrestigated. It is indieated that MAP whose filler is modified by the wet process has the highest tensile strength, but it is not the optimal modiifying technique due to complieated wet process. On the contrary, the dry process was very simple, and VRMAP possessed fairly high mechanical properties, therefore, it was the perfect modifying process.

关键词： silane coupling ageat carbonyl iron powder microwave absorbing patch mechanical property mierostructure