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BROADBAND ROTOR NOISE PREDICTION BASED ON A NEW FREQUENCY-DOMAIN FOUMULATION

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Journal of Hydrodynamics 2010年第3期22卷 387-392页

作者： XIE Jian-bo ZHOU Qi-dou FANG Bin Department of naval Architecture and Ocean Engineering Naval University of Engineering Wuhan 430033China

This article studies the broadband noise of a rotor in upstream turbulence. A numerical approach is proposed, based on frequency domain, for predicting rotor broadband noise which requires the aerodynamic sources to be integrated over the actual blade surface rather than over the mean-chord surface. The prediction of the radiated rotor broadband noise due to turbulence is made This method is validated through a comparison between numerical predictions and measured data, with a reasonable agreement. Noise level directivity shows that the main lobe is located along the rotor axis, while the minimum noise occurs in the direction vertical to the rotor axis.

关键词： acoustics broadband noise rotor frequency-domain formulation

Noise reduction method for nonlinear signal based on maximum variance unfolding and its application to fault diagnosis

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Science China(Technological Sciences) 2010年第8期53卷 2122-2128页

作者： ZHANG Yun &LI BenWei Department of Airborne Vehicle Engineering,naval Aeronautical Engineering Institute,Yantai 264001,China Department of Airborne Vehicle Engineering Naval Aeronautical Engineering Institute Yantai China

A new noise reduction method for nonlinear signal based on maximum variance unfolding(MVU)is *** noisy sig- nal is firstly embedded into a high-dimensional phase space based on phase space reconstruction theory,and then the manifold learning algorithm MVU is used to perform nonlinear dimensionality reduction on the data of phase space in order to separate low-dimensional manifold representing the attractor from noise ***,the noise-reduced signal is obtained through reconstructing the low-dimensional *** simulation results of Lorenz system show that the proposed MVU-based noise reduction method outperforms the KPCA-based method and has the advantages of simple parameter estimation and low parameter *** proposed method is applied to fault detection of a vibration signal from rotor-stator of aero engine with slight rubbing *** denoised results show that the slight rubbing features overwhelmed by noise can be effectively extracted by the proposed noise reduction method.

关键词： nonlinear noise reduction manifold learning maximum variance unfolding fault diagnosis

MOLECULAR DYNAMICS SIMULATION OF INTERFACIAL DEFECTS WITH MODIFIED POTENTIAL BASED ON THE FIRST-PRINCIPLE

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Acta Mechanica Solida Sinica 2010年第5期23卷 400-406页

作者： Dongwei Ren Jinquan Xu 1(School of naval Architecture and Civil Engineering,Shanghai Jiaotong University,Shanghai 200240,China) School of naval Architecture and Civil Engineering Shanghai Jiaotong University Shanghai China

The interfacial molecular structure of materials with different lattice constants is simulated by using the method of molecular dynamics （MD）. Potential of modified analytical embedded atom method （MAEAM） is used for nominterfacial atoms. To simulate the state of interracial atoms, further modifications are applied to the MAEAM potential based on the first- principle simulation results. It is concluded that a small change of potential may greatly influence the interfacial molecular structure. Void and diffusions can be observed in the simulation results. It is also found that the pre-existed dot defects before bonding can decrease the number of interfacial defects greatly, thereby, can increase the strength of the interface.

关键词： molecular dynamics interface defect potential first-principle

APPLICATION OF COMPUTER GRAPHICS IN MARTENSITIC TRANSFORMATION

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Acta Metallurgica Sinica(English Letters) 1994年第2期7卷 103-106页

作者： Zhou JianqiSouthern naval Unit of Institute of naval Technical Equipment in Zhanjiang Manuscript received 18 April, 1994

This paper discuss the stereographic method of martensitic transformation (MT)in the view of computer graphics (CG) and programs are programmed to realize this method. Habit plane resulting from the programs agrees with that of numerical analysis in terms of the lattice parameters of austenite and martensite and shear mechanism supposed in Fe-22%Ni-0.8%C alloy, so does orientation relationships.

关键词： stereograpllic projection martensitic transformation computer graphics

Dynamics of Sea Ice and Spectrum of Ice Force

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China Ocean Engineering 1995年第2期10卷 131-138页

作者： Shi Qingzeng and Chen Xing Professor, Dept. of Ocean Eng. and naval Arch, Tianjin Univ., Tianjin Lecturer, Dept. of Ocean Eng. and naval Arch., Tianjin Univ., Tianjin

Spectrum and self-excite characters are the two significant characters of the dynamics of sea ice. The spectrum character of sea ice is mainly shown by the spectrum of ice force. The spectrum character of the sea ice is its intrinsic attributes. When the spectrum of ice force from the dynamic response of ice and structure interaction are evaluated, the effect of dynamic character of the structure must be eliminated. In this paper, the ice force spectrum at Bohai Bay and Liaodong Bay is evaluated from the displacement and strain responses of a single degree and a multi-degree freedom structure. The evaluated ice force spectrum can be used to define the spectrum character of ice in the analysis of ice induced vibration.

关键词： dynamic ice force ice force spectrum frequency domain single degree of freedom multi-degree of freedom

Research on Flow Loss of Inlet Duct of Marine Waterjets

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Journal of Shanghai Jiaotong university(Science) 2010年第2期15卷 158-162页

作者：丁江明王永生 College of naval Architecture and Power Engineering Naval University of Engineering

In the process of performance prediction of waterjet system,the flow loss of inlet duct is usually reckoned by the rule of thumb. But its value is often overestimated to some extent,resulting in error of prediction accuracy. This paper introduces a new method to determine the flow loss by means of computational fluid dynamic (CFD). Firstly,the fluid field around waterjet system is simulated by solving the Reynolds Averaged Navier-Stokes (RANS) equations using commercial CFD code Fluent. Then an additional User-Defined Scalar (UDS) equation is embedded into Fluent to get the virtual dividing surface between the internal flow ingested into the inlet duct and the external flow beneath the hull,which is named as streamtube. By virtual of the streamtube the flow loss can be calculated according to the difference of total pressure between the duct outlet and the capture area ahead of the intake. The results from CFD calculation show that the flow loss coeflcient of a typical flush-type inlet duct is varying from 0.05 to 0.12 at different operation conditions,being obviously less than the value of 0.2-0.3 from empirical rules. With the results of this paper the prediction accuracy on propulsive performance of the waterjet system can be improved further.

关键词： ships waterjet propulsion inlet duct flow loss computational fluid dynamics

On a Delay Reaction-Diffusion Difference Equation of Neutral Type

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Acta Mathematica Sinica,English Series 2002年第4期18卷 755-764页

作者： Bao SHI Department of Basic Sciences, naval Aeronautical Engineering Academy. Yantai 264001. P. R. China Department of Basic Sciences Naval Aeronautical Engineering Academy Yantai P. R. China

In this paper, we first consider a delay difference equation of neutral type of the form: Δ(y_n+py_(n-k))+q_ny_(n-)=0 for n∈Z^+(0) (1*) and give a different condition from that of Yu and Wang (Funkcial Ekvac, 1994, 37(2): 241 248) to guarantee that every non-oscillatory solution of (1~*) with p=1 tends to zero as n→∞ Moreover, we consider a delay reaction-diffusion difference equation of neutral type of the form: Δ_1(u_(n,m)+pu_(n-k,m)+q_(n,m)u_(n-m)=a^2Δ_2~2u_(n+1,m-1) for (n,m)∈Z^+(0)×Ω. (2*) study various casks of p in the neutral term and obtain that if p≥-1 then every non-oscillatory solution of (2~*) tends uniformly in m∈Ω to zero as n→∞: if p=-1 then every solution of (2~*) oscillates and if p<-1 then every non-oscillatory solution of (2~*) goes uniformly in m∈Ω to infinity or minus infinity as n→∞ under some hypotheses.

关键词： Delay reaction-diffusion difference equations Nentral type Asymptotic behavior Oscillation

Parametric Analysis and Experimental Study on Local Flexibility of TY-Type Tubular Joints

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China Ocean Engineering 1996年第1期11卷 71-84页

作者： XuHantao Chen Bozhen HuYuren Pan Hao Department of naval Architecture and Ocean Engineering, Shanghai Jiao Tong University (SJTU), Shanghai 200030 Professor, Department of naval Architecture and Ocean Engineering, Shanghai Jiao Tong University (SJTU), Shanghai 200030 Department of naval Architecture and Ocean Engineering Shanghai Jiao Tong University (SJTU) Shanghai 200030

Loal flexibility of tubular joints has important effect on the static and dynamic behaviour of offshore platforms, therefore, the determination of it becomes an important research subject in the field of offshore engineering. In this paper, the local flexibility of TY-type tubular joints, which are widely used in offshore platforms, is calculated by using semi- analytical method. Based on the calculated results, parametric formulae for evaluating element in the local joint flexibility matrix of TY- type tubular joints are derived by regression. A test on PVC models of TY-type tubular joints to measure the local joint flexibility is also reported. A comparison of the results calculated from the parametric formulae presented in this paper with those measured from the model test shows that the parametric formulae are reliable. It is recommended that these formulae be used in the global structural analysis of offshore platforms.

关键词： parametric analysis off shore platform turbulent joint local flexibility experimental study

System Reliability Analysis of Offshore Strctures and Component Safety Rank Assessment

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China Ocean Engineering 1998年第2期13卷 173-181页

作者： YANG Zhiyong and XIAO Xi Lecturer, School of naval Architecture and Ocean Engineering, Shanghai Jiaotong University (SJTU), Shanghai 200030, P. R. China. Professor, School of naval Architecture and Ocean Engineering, SJTU, Shanghai 200030, P. R. China. School of naval Architecture and Ocean Engineering Shanghai Jiaotong University (SJTU) Shanghai 200030 China School of naval Architecture and Ocean Engineering SJTU Shanghai 200030 China

Offshore structures will encounter serious environmental load, so it is important to study the structural system reliability and to evaluate the structural component safety rank. In this paper, the bracnch-and-bound method is adopted to search the main failure path, and the Ditlevsen bound method is used to calculate the system failure probability. The structure is then assessed by the fuzzy comprehensive assessment method, which evaluates the structural component safety rank. The ultimate equation of the tubular cross- section is analyzed on the basis of ultimate stregnth analysis. The influence of effect coefficients on the structural system failure probability is investigated, and basic results are obtained. A general program for spatial frame structures by means of the above method is developed, and verified by the numerical examples.

关键词： structural system reliability, branch-and-bound method fuzzy comprehensive assessment safety rank offshore structure platform