This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design meth...This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design methodology at the very early development stage. The approach is found to be suitable for a periodic loading but requires very large time records to accurately describe random loading processes. This paper is aimed at investigating the effects of surface treatments on the fatigue life of the free piston linear engine’s components. Finite element modelling and frequency response analysis were conducted using computer aided design and finite element analysis commercial codes, respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis commercial code. Narrow band approach was specially applied to predict the fatigue life of the free piston linear engine cylinder block. Significant variation was observed between the surface treatments and untreated cylinder block of free piston engine. The obtained results indicated that nitrided treatment yielded the longest life. This approach can determine premature products failure phenomena, and therefore can reduce time to market, improve product reliability and customer confidence.展开更多
Comparative analysis is carried out by using finite-domain power spectrum and lagged regression methods for the propagating characteristics and air-sea interaction processes of intraseasonal oscillations (ISOs) in the...Comparative analysis is carried out by using finite-domain power spectrum and lagged regression methods for the propagating characteristics and air-sea interaction processes of intraseasonal oscillations (ISOs) in the Asia to western Pacific (AWP) region during the boreal summer between the active and inactive tropical cyclone (TC) years from 1979 to 2004.The results show as follows.(1) There exist more significant eastward propagating characteristics of the ISO in the active TC years over the whole AWP region.The ISOs of convection propagate zonally with more eastward extension in the years with active tropical cyclone activities,during which the 20-60-day period is strengthened,western Pacific becomes an area with evident characteristics of the propagation that is closely related to TC activities.(2) The air-sea interaction processes are the same in both active and inactive TC years,and the energy exchanges between the air and the sea play a role in maintaining the northwestward propagation of ISOs.(3) The air-sea interaction is more intensive in the active TC years than in the inactive ones.It is particularly true for the latent heat release by condensation as the result of convection,which may be one of the reasons resulting in significant differences in characteristics of ISOs between the active and inactive TC years.展开更多
In this paper, a novel detection criterion is proposed to decide whether primary user(PU) exists based on joint analysis of the variance and correlation for observation signal,considering a correlation within the obse...In this paper, a novel detection criterion is proposed to decide whether primary user(PU) exists based on joint analysis of the variance and correlation for observation signal,considering a correlation within the observed signal. Simultaneously, the corresponding detection thresholds are also designed. Simulation experiments verify the proposed method suits for the observation signal in Additive White Gaussian Noise(AWGN), Rayleigh,Rician channel and the detection performance is improved greatly.展开更多
In order to realize the coexistence between the LTE system and the spectrum authorized systems over 700MHz frequency band,the geographical position and operation band location between long term evolution(LTE)base stat...In order to realize the coexistence between the LTE system and the spectrum authorized systems over 700MHz frequency band,the geographical position and operation band location between long term evolution(LTE)base stations and digital tevevision transmission tower should satisfy certain constraints,which are analyzed and deduced in this paper.Under the concluded constraints,the interference to each other is lower than their interference tolerances,so that the coexistance between the two types of systems is performed.Based on the constraints for both LTE and spectrum authorized systems,numerical results of the geographical position interval and operation band location interval are obtained,which have significant practical value for the LTE base station placement,network planning and operation band selection.展开更多
基金Project (No. 03-02-02-0056 PR0025/04-03) supported by the Inten-sification of Research in Priority Areas (IRPA), Ministry of Science,Technology and Innovation, Malaysia
文摘This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design methodology at the very early development stage. The approach is found to be suitable for a periodic loading but requires very large time records to accurately describe random loading processes. This paper is aimed at investigating the effects of surface treatments on the fatigue life of the free piston linear engine’s components. Finite element modelling and frequency response analysis were conducted using computer aided design and finite element analysis commercial codes, respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis commercial code. Narrow band approach was specially applied to predict the fatigue life of the free piston linear engine cylinder block. Significant variation was observed between the surface treatments and untreated cylinder block of free piston engine. The obtained results indicated that nitrided treatment yielded the longest life. This approach can determine premature products failure phenomena, and therefore can reduce time to market, improve product reliability and customer confidence.
基金Natural Development and Plan for Key Fundamental Research (2009CB421505)National Natural Science Foundation (40775058+2 种基金41075073)Tropical Marine & Meteorological Science Foundation (201103)Natural Science Foundation of Guangxi (2010GXNSFA013010)
文摘Comparative analysis is carried out by using finite-domain power spectrum and lagged regression methods for the propagating characteristics and air-sea interaction processes of intraseasonal oscillations (ISOs) in the Asia to western Pacific (AWP) region during the boreal summer between the active and inactive tropical cyclone (TC) years from 1979 to 2004.The results show as follows.(1) There exist more significant eastward propagating characteristics of the ISO in the active TC years over the whole AWP region.The ISOs of convection propagate zonally with more eastward extension in the years with active tropical cyclone activities,during which the 20-60-day period is strengthened,western Pacific becomes an area with evident characteristics of the propagation that is closely related to TC activities.(2) The air-sea interaction processes are the same in both active and inactive TC years,and the energy exchanges between the air and the sea play a role in maintaining the northwestward propagation of ISOs.(3) The air-sea interaction is more intensive in the active TC years than in the inactive ones.It is particularly true for the latent heat release by condensation as the result of convection,which may be one of the reasons resulting in significant differences in characteristics of ISOs between the active and inactive TC years.
文摘In this paper, a novel detection criterion is proposed to decide whether primary user(PU) exists based on joint analysis of the variance and correlation for observation signal,considering a correlation within the observed signal. Simultaneously, the corresponding detection thresholds are also designed. Simulation experiments verify the proposed method suits for the observation signal in Additive White Gaussian Noise(AWGN), Rayleigh,Rician channel and the detection performance is improved greatly.
基金Supported by the National High Technology Research and Development Program of China(No.2011AA01A105)the Key Deplogment Project of China Academic of Sciences(KGZD-EW-103)Shanghai Committee of Science and Technology(11DZ1500500)
文摘In order to realize the coexistence between the LTE system and the spectrum authorized systems over 700MHz frequency band,the geographical position and operation band location between long term evolution(LTE)base stations and digital tevevision transmission tower should satisfy certain constraints,which are analyzed and deduced in this paper.Under the concluded constraints,the interference to each other is lower than their interference tolerances,so that the coexistance between the two types of systems is performed.Based on the constraints for both LTE and spectrum authorized systems,numerical results of the geographical position interval and operation band location interval are obtained,which have significant practical value for the LTE base station placement,network planning and operation band selection.
