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Delayed Hopf bifurcation in time-delayed slow-fast systems

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Science china(Technological Sciences) 2010年第3期53卷 656-663页

作者： ZHENG YuanGuang1 & WANG ZaiHua1,2 1 institute of Vibration Engineering Research,nanjing university of Aeronautics and Astronautics,nanjing 210016,china 2 institute of Science,PLA university of Science and Technology,nanjing 211101,china institute of Vibration Engineering Research Nanjing University of Aeronautics and Astronautics Nanjing China institute of Science PLA University of Science and Technology Nanjing China

This paper presents an investigation on the phenomenon of delayed bifurcation in time-delayed slow-fast differential *** the two delayed's have different *** delayed bifurcation means that the bifurcation does not happen immediately at the bifurcation point as the bifurcation parameter passes through some bifurcation point,but at some other point which is above the bifurcation point by an obvious *** a time-delayed system,the evolution of the system depends not only on the present state but also on past *** this paper,the time-delayed slow-fast system is firstly simplified to a slow-fast system without time delay by means of the center manifold reduction,and then the so-called entry-exit function is defined to characterize the delayed bifurcation on the basis of Neishtadt's *** shows that delayed Hopf bifurcation exists in time-delayed slow-fast systems,and the theoretical prediction on the exit-point is in good agreement with the numerical calculation,as illustrated in the two illustrative examples.

关键词： time delay delayed bifurcation Hopf bifurcation slow-fast systems exit-point entry-exit function

NEW EFFICIENT ALGORITHM FOR NONLINEAR CIRCUIT SYSTEM

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Science china Mathematics 1989年第6期32卷 746-757页

作者：孔俊宝 nanjing institute of posts and telecommunications

A new efficient algorithm is given for calculation of the steady-state response of non-linear circuit driven by multifrequency signals, which are possibly made up of incommen-surable frequencies. The algorithm is particularly useful when the steady state responseis not periodic. The algorithm is much more efficient than numerical integration methods for circuitscontaining only a few nonlinear elements, compared with the number of inductors andcapacitors. It is based on a combined application of the "harmonic balancen" and "leastsquare approach", and does not require any transient analysis. The algorithm can be usedin a microcomputer.

关键词： nonlinear circuit computer-aided analysis harmonic balance methed.

A new frequency scale of Chinese whispered speech in the application of speaker identification

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Progress in Natural Science:materials International 2006年第10期16卷 1072-1078页

作者： LIN Wei, YANG Lili and XU Boling (institute of Acoustics & Key Laboratory of Modern Acoustics, nanjing university, nanjing 210093, china) institute of Acoustics and Key Laboratory of Modern Acoustics Nanjing University Nanjing 210093 China

In this paper, the frequency characteristics of Chinese whispered speech were investigated by a filter bank analysis. It was shown that the first and the third formants were more important than the other formants in the speaker identification of Chinese whispered speech. The experiment showed that the 800-1200 Hz and 2800-3200 Hz ranges were the most significant frequency ranges in discriminating the speaker. Based on this result, a new feature scale named whisper sensitive scale (WSS) was proposed to replace the common scale, Mel scale, and to extract the cepstral coefficient from whispered speech signal. Furthermore, a speaker identification system in whispered speech was presented based on the modified Hidden Markov Models integrating advantages of WSCC (the whisper sensitive cepstral coefficient) and LPCC. And the new system performed better in solving the problem of speaker identification of Chinese whispered speech than the traditional method.

关键词： speaker identification Chinese whispered speech whisper sensitive scale.

Analysis of Staggered OFDM Data Transmission With Reduced Complexity

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The Journal of china Universities of posts and telecommunications 1995年第1期2卷 7-17页

作者： Zhang Lijun (Department of Telecommunication Engineering, nanjing university of posts and telecommunications nanjing 210003. P. R. china)

The complexity and performance of staggered orthogonal frequency division multiplexed (OFDM)data transmission systems are discussed in this paper. As improved digital implemention with a computationalcomplexity reduction of 30% compared to previous systems￣[7] is Presented. Staggered OFDM data transmission canprovide high bandwidth efficiency vecy close to 2log_2M for M-ary signalling. For voiceband channels, improve-ment of 3dB and 12dB in Gaussian noise and impulse noise immunities respectively, are abtained over serial QAMtransmission. An analysis of the phase jitter immunsity for the staggered OFDM system with raised cosine shapingfilters is presented. The analysis and simulation results show that a staggered delay of half a baud period betweensubchannels with a 100% rolloff factor optimize the system performance phase jitter and provide an improve-ment of 2dB in phase jitter immunity over nonstaggered systems.

关键词： orthogonal frequency division multiplexing (OFDM) staggered OFDM system,bandwidth efficien-cy Gaussian noise immunity,impulse noise immunity,phase jitter immunity

Study on International Contracting for Construction's Risk Identif ication and Strategy

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china Communications 2009年第2期6卷 106-111页

作者： Zhao Yumei, Lv Tingjie Beijing university of posts and telecommunications, china Beijing university of posts and telecommunications China

Risk management is a key part in project management. International contracting for construction is a market with high risk. Therefore, the most important task in international contracting for construction is the analysis and controlling of risks. In this paper, the risks of international contracting for construction are divided into macroenvironment risks and micro-risks. Risk management is to identify risk factors in the project life cycle, analyze and evaluate them, and take effective measures to maintain the highest standard of safety.

关键词： risk identifi cation international contracting for construcation risk management risk strategy

Superprocesses on Two Space Forms

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The Journal of china Universities of posts and telecommunications 2001年第3期8卷 69-76页

作者： TANG Jia-shan (Department of Applied Mathematics and Physics, nanjing university of posts and telecommunications, nanjing 210003, P.R. china) Department of Applied Mathematics and Physics Nanjing University of Posts and Telecommunications

Superprocess is one class of measure-valued branching Markov processes. Many results of the process on abstract spaces and Euclidean spaces are obtained in the literature. In this paper, we discuss super-Brownian motions on two space forms and reveal partially the relationship between the properties of superprocesses and the geometric structure of the underlying state spaces. Finally, we also presents some open problems.

关键词： superprocess branching mechanism underlying process underlying space space form

An effective absorbing boundary algorithm for acoustical wave propagator

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Progress in Natural Science:materials International 2007年第9期17卷 1012-1017页

作者： Lin Zhibin ,Lu Jing and Xu Boling(Key Laboratory of Modern Acoustics,institute of Acoustics,nanjing university,nanjing 210093,china) Key Laboratory of Modern Acoustics Institute of Acoustics Nanjing University Nanjing 210093 China

In this paper,Berenger’s perfectly matched layer(PML)absorbing boundary condition for electromagnetic waves is introduced as the truncation area of the computational domain to absorb one-dimensional acoustic wave for the scheme of acoustical wave propagator(AWP).To guarantee the efficiency of the AWP algorithm,a regulated propagator matrix is derived in the PML *** simulations of a Gaussian wave packet propagating in one-dimensional duct are carried out to illustrate the efficiency of the combination of PML and *** with the traditional smoothing truncation windows technique of AWP,this scheme shows high computational accuracy in absorbing acoustic wave when the acoustical wave arrives at the computational *** coefficients of the PML configurations are also discussed.

关键词： acoustical wave propagator perfectly matched layer absorbing boundary conditions(ABC).

EXPLICIT SIMULATION ON THE TRACK AND INTENSITY OF TROPICAL CYCLONE WINNIE (1997)

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Journal of Hydrodynamics 2006年第6期18卷 736-741页

作者： ZHONG Zhong ZHANG Jirl-shan institute of Meteorology PLA University of Science and Technology Nanjing 211101 China nanjing Hydraulic Research institute Nanjing 210029 China

An explicit simulation of the tropical cyclone Winnie （1997） was conducted by use of a triply-nested 3-D nonhydrostatic mesoscale model MM5, before and after its landfall. The simulated results show that the model can well reproduce the track of Winnie （1997） with a BOGUS storm-like vortex inserted in the large-scale first-guess field at the initial model time. The mean track error in a 6 h interval is 54.5 km, which is much less than that obtained with the operational prediction. Comparisons between simulation and observation near the landfall place show that the main temporal variation features of sea level pressure and surface wind speed can also be successfully captured. The characteristics of the eyewall, the spiral cloud band and the corresponding precipitation were disclosed, and the applications of the model outputs were also discussed.

关键词： tropical cyclone simulation track intensity,eyewall spiral cloud band storm surge

Alkaline phosphatase activity and the phosphorus mineralization rate of Lake Taihu

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Science china Earth Sciences 2006年第Z1期49卷 176-185页

作者： GAO Guang, ZHU Guangwei, QIN Boqiang, CHEN Jun & WANG Ke nanjing institute of Geography & Limnology, Chinese Academy of Sciences, nanjing 210008, china Hohai university, nanjing 210098, china nanjing institute of Geography & Limnology Chinese Academy of Sciences Nanjing China Hohai university Nanjing China

The phosphorus fractions, the alkaline phosphatase activity (APA) and other water chemical parameters were concomitantly monitored from April 2003 to October 2004 in different ecotype sites of Lake Taihu. During the stages of algae growth, the phosphorus fractions and their relationships with APA in different ecotype sites were discussed and the phosphorus mineralization rate was calculated. In the water of Lake Taihu, most of the phosphorus (70.2%) could be attributed to the suspended particulate phosphorus, while the dissolved reactive phosphorus (DRP) seems to contribute less than 7%. About 58% of the total phosphorus, however, can be hydrolyzed as inorganic phosphate to compensate for phosphorus deficiency of algae and bacteria growth. During the different algae growth stages, the APA and its Kinetic parameters were varied significantly between different ecotype sites of Lake Taihu. This trend is also visible by comparing the phosphorus mineralization rate,and the most rapidly phosphorus turnover time is only several minutes. The fast recycle of phosphorus can, to some extent, be explained that the phosphorus source of algal blooms. The phytoplankton seems to compensate for phosphorus deficiency by using the alkaline phosphatase to hydrolyze phosphomonoesters.

关键词： Lake Taihu, alkaline phosphatase, kinetic parameters, phosphorus, mineralization rate.