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Method for determining number of coherent signals in the presence of colored noise

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Journal of Systems engineering and Electronics 2010年第1期21卷 27-30页

作者： Jiaqi Zhen, Xicai Si, and Lutao Liu college of Information & Communication engineering, harbin engineering university, harbin 150001, P. R. china college of Information & Communication engineering Harbin Engineering University Harbin 150001 P. R. China

The approach of estimating the number of signals based on information theoretic criteria has good performance in the assumption of white noise, but it always leads to false estimation of the coherent sources in colored noise. An approach combining the combined information theoretic criteria and eigen- value correction, is presented to determine number of signals. The method uses maximum likelihood （ML） and information theoretic criteria to estimate coherent signals alternately, then eliminate the inequality of the eigenvalues caused by colored noise by correcting the noise eigenvalues. The computer simulation results prove the effective performance of the method.

关键词： determining the number of signals coherent signals colored noise information theoretic criteria.

Novel adaptive Hatch filter to mitigate the effects of ionosphere and multipath on LAAS

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Journal of Systems engineering and Electronics 2010年第6期21卷 1046-1053页

作者： Lin Zhao, Liang Li, Ming Sun, and Xiaoxu Wang college of Automation, harbin engineering university, harbin 150001, P. R. china college of Automation Harbin Engineering University Harbin 150001 P. R. China

It has been proven that carrier smoothing and differential global positioning system （DGPS） are effective to improve the accuracy of pseudorange by reducing the noise in it and eliminating almost all the common mode errors between the ground station and user. However, another issue coming with local area augmentation system （LAAS） is how to find an adaptive smoothing window width to minimize the error on account of ionosphere delay and multipath. Based on the errors analysis in carrier smoothing process, a novel algorithm is formulated to design adaptive Hatch filter whose smoothing window width flexibly varies with the characteristic of ionosphere delay and multipath in the differential carrier smoothing process. By conducting the simulation in LAAS and after compared with traditional Hatch filers, it reveals that not only the accuracy of differential correction, but also the accuracy and the robustness of positioning results are significantly improved by using the designed adaptive Hatch filter.

关键词： Hatch filter adaptive ionosphere delay multipath differential correction local area augmentation system.

AN ORDINARY DIFFERENTIAL EQUATION FOR THE 2D TRANSIENT FREE-SURFACE GREEN FUNCTIONS

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Journal of Hydrodynamics 2002年第2期14卷 24-28页

作者： Duan Wen-yang college of Shipbuilding engineering, harbin engineering university, harbin 150001, chinaPrice W.G. School of engineering sciences, Ship science, university of Southampton, UK Coll. of Shipbuilding Eng. Harbin Eng. Univ. Harbin 150001 China Sch. of Eng. Sci. Ship Sci. Univ. of Southampton Southampton United Kingdom

Based on the Laplace transform an ordinary differential equation for the two-dimensional time-domain free-surface Green function in ship hydrodynamics is presented. The results for 2D Green function and its horizontal derivative are fifth-order ODEs and the vertical derivative satisfies a fourth-order ODE. All of these results may be used to accelerate the numerical computations for the time-domain BEM in marine hydrodynamics.

关键词： ship hydrodynamics time-domain Green function Laplace transform

Spinning Deformation Criteria of Thin-walled Tubular Part with Longitudinal Inner Ribs

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Journal of Wuhan university of Technology(Materials science) 2006年第4期21卷 169-172页

作者：江树勇 engineering Training Center Harbin Engineering University Harbin 150001China

As a successive and local plastic deformation process, backward ball spinning was applied for the purpose of prodacing thin-walled tubular parts with longitudinal inner ribs. According to the local plastic deformation theoo,, the application of yield criterion to the spinning process and the influence of the radial spinning force component on the formability of inner ribs were analyzed. Based on yield criterion and plastic mechanics, the stable flow rule of metal material and forming criteria of the inner ribs were obtained aad conformed to the experimental results so as to contribute greatly to improving the ball spinning process and optimizing the process variables, such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank, which have a significant influenee on the formability of the inner ribs. The knowledge of the influence of the process variables such as the diameter of ball, the reduction in a pass and the wall thickness of tubular blank on the spinning process is essential to preventing the quality defects of the spun parts and obtaining the desired spun parts.

关键词： ball spinning power spinning spinning force criterion

Formation,thermal stability and mechanical properties of Ti_(42.5)Zr_(7.5)Cu_(40)Ni_5Sn_5 bulk metallic glass

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science china(Physics,Mechanics & Astronomy) 2008年第4期51卷 372-378页

作者： HUANG YongJiang,SHEN Jun & SUN JianFei School of Materials science and engineering,harbin Institute of Technology,harbin 150001,china School of Materials science and engineering Harbin Institute of Technology Harbin China

Ti42.5Zr7.5Cu40Ni5Sn5 bulk metallic glass with a critical diameter of 4 mm was fabri-cated by the conventional copper mould casting method. The supercooled liquid region ΔTx,reduced glass transition temperature Trg,γ parameter,and δparameter of the alloy were measured to be 63.9 K,0.561,0.393,and 1.400,respectively,im-plying that the alloy has an excellent glass-forming ability. The bulk metallic glass exhibits high compressive fracture strength of 2162 MPa with distinct plastic strain of 0.9%. The fracture surface consists mainly of vein-like patterns,typical of bulk glassy alloys.

关键词： amorphous alloy mechanical properties thermal stability glass-forming ability

Underwater hybrid near-field acoustical holography based on the measurement of vector hydrophone array

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science china(Physics,Mechanics & Astronomy) 2010年第6期53卷 1073-1079页

作者： HU Bo,YANG DeSen & SUN Yu college of Underwater Acoustic engineering,harbin engineering university,harbin 150001,china college of Underwater Acoustic engineering Harbin Engineering University Harbin China

Hybrid near-field acoustical holography(NAH) is developed for reconstructing acoustic radiation from a cylindrical source in a complex underwater environment. In hybrid NAH,we combine statistically optimized near-field acoustical holography(SONAH) and broadband acoustical holography from intensity measurements(BAHIM) to reconstruct the underwater cylindrical source field. First,the BAHIM is utilized to regenerate as much acoustic pressures on the hologram surface as necessary,and then the acoustic pressures are taken as input to the formulation implemented numerically by SONAH. The main advantages of this technology are that the complex pressure on the hologram surface can be reconstructed without reference signal,and the measurement array can be smaller than the source,thus the practicability and efficiency of this technology are greatly enhanced. Numerical examples of a cylindrical source are demonstrated. Test results show that hybrid NAH can yield a more accurate reconstruction than conventional NAH. Then,an experiment has been carried out with a vector hydrophone array. The experimental results show the advantage of hybrid NAH in the reconstruction of an acoustic field and the feasibility of using a vector hydrophone array in an underwater NAH measurement,as well as the identification and localization of noise sources.

关键词： near-field acoustical holography intensity measurement statistically optimized vector hydrophone array

An Expert System in FRP Composite Material Design

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Journal of Materials science & Technology 2001年第5期17卷 556-560页

作者： Qingfen LI, Zhaoxia CUI and Weimin WANG college of Mechanical & Electrical engineering, harbin engineering university, harbin 150001, china Jianhua GAO Department of Mechanical engineering, Shanghai Jiao Tong university, Shanghai 200030, china Coll. of Mech. and Electron. Eng. Harbin Eng. Univ. Harbin 150001 China

An expert system prototype for fibre-reinforced plastic matrix (FRP) composite material design, ESFRP, has been developed. The system consists of seven main functional parts: a general inference engine, a set of knowledge bases, a material properties algorithm base, an explanation engine, various data bases, several function models and the user interface. The ESFRP can simulate human experts to make design scheme for fibre-reinforced plastics design, FRP layered plates design and FRP typical engineering components design. It can also predict the material properties and make strength analysis according to the micro and macro mechanics of composite materials. A satisfied result can be gained through the reiterative design.

关键词： An Expert System in FRP Composite Material Design FRP

GLOBAL EXISTENCE AND BLOW-UP OF SOLUTIONS FOR GENERALIZED POCHHAMMER-CHREE EQUATIONS

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Acta Mathematica Scientia 2010年第5期30卷 1793-1807页

作者：徐润章刘亚成 college of science Harbin Engineering University

In this article, we study the initial boundary value problem of generalized Pochhammer-Chree equation utt-uxx-uxxt-uxxtt=f（u）xx,x∈Ω,t〉0,u（x,0）=u0（x）,ut（x,0）=u1（x）,x∈Ω,u（0,t）=u（1,t）=0,t≥0, where Ω = （0, 1）. First, we obtain the existence of local Wkp solutions. Then, we prove that, if f（s） ∈ Ck＋1（R） is nondecreasing, f（0） = 0 and ｜f（u）｜ ≤ C1｜u｜∫0uf（s）ds ＋ C2, u0（x）,u1（x） ∈ WkP（Ω） ∩ W01,P（Ω）, k≥ 1, 1 〈 p≤ ∞, then for any T 〉 0 the problem admits a unique solution u（x, t） ∈ W2,∞（0, T; WkP（Ω） ∩ W01,P（Ω））. Finally, the finite time blow-up of solutions and global Wkp solution of generalized IMBo equations are discussed.

关键词： Pochhammer-Chree equations initial boundary value problem Wkp solu-tion global existence blow-up

Oxidation-induced strengthening behavior of reaction formed Al_4SiC_4 ceramics

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Rare Metals 2007年第S1期26卷 94-98页

作者： HUANG Xiaoxiao1,2),WEN Guangwu1,3),LIU Ruitang2),and ZHENG Xin1)1) School of Materials science and Technology,harbin Institute of Technology,harbin 150001,china 2) School of Material science and Chemical engineering,harbin engineering university,harbin 150001,china 3) School of Materials science and Technology,harbin Institute of Technology at Weihai,Weihai 264209,china harbin Inst Technol Sch Mat Sci & Technol Harbin 150001 Peoples R China harbin Inst Technol Sch Mat Sci & Chem Engn Harbin 150001 Peoples R China harbin Inst Technol Sch Mat Sci & Technol Weihai 264209 Peoples R China

The bending strengths of Al4SiC4 ceramics were investigated from room temperature to 1300 ℃ in air and in vacuum,*** is a novel property that the bending strength increases with increasing test temperatures up to 1300 ℃ in *** strength value of Al4SiC4 ceramics is 449.7 MPa at 1300 ℃ in air,which is about 1.5 times of that at room temperature(300 MPa).The self-healing behavior of the flaws on the specimen surface due to the oxidation of the surface layer of the Al4SiC4 ceramics is considered as the main enhancement mechanism at high temperatures.

关键词： calcination and hot pressing surface strength Al_4SiC_4