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Science China(Physics,Mechanics & Astronomy) 2005年第3期48卷 282-299页

作者： BI Chuanxing CHEN Jian CHEN Xinzhao YU Fei LI Weibing Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China

Study on a multi-source hybrid acoustic field is very important for nearfield acoustic holography (NAH) to be applied in the practical engineering field. In this paper, two methods based on the distributed source boundary point method (DSBPM) for holographic reconstruction and prediction of multi-source hybrid acoustic field, namely combination method with single surface measurement and combination method with multi-surface measurement, are proposed. Then, an experiment on two coherent speakers is carried out. By comparison of the reconstructed and predicted results and the actual measured results, the validity of the two methods and the superiority of the combination method with multi-surface measurement are proved. Considering the high sensitivity of the reconstructed results to measurement errors, the Tikhonov regularization method is proposed to stabilize the reconstruction procedure and restrict the influence of errors. And then, the optimal reconstructed results can be obtained and the reliability of holographic reconstruction and prediction is assured.

关键词： acoustic holography, boundary point, distributed source, acoustic radiation, regularization.

Hydrogen isotopic compositions, distributions and source signals of individual n-alkanes for some typical crude oils in Lunnan Oilfield, Tarim Basin, NW China

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Science China Earth Sciences 2005年第8期48卷 1220-1226页

作者： LU Hong1, LI Chao1, SUN Yongge1, PENG Ping’an1 & XIAO Zhongyao2 1. State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou510640, China 2. Tarim Research Institute of Exploration and Development of Petroleum, China Petroleum, Korla 841000, China State Key Laboratory of Organic Geochemistry Guangzhou Institute of Geochemistry Chinese Academy of Sciences Guangzhou China Tarim Research Institute of Exploration and Development of Petroleum China Petroleum Korla China

Isotopic compositions of carbon-bound hydrogen in individual n-alkanes from sev-eral typical crude oil samples from Lunnan Oilfield, Tarim Basin, NW China, were firstly measured using newly developed gas chromatography-thermal conversion-isotope ratio mass spectrometry. The similar range of δ D of individual n-alkanes of crude oils among reservoirs of different geo-logical times reflects that hydrocarbons are all derived from the same marine depositional envi-ronment. Compared to the theoretic value (?150‰) and the reported δ D values (nC13―nC27, ?160‰―?90‰) of individual n-alkanes for Ordovician-sourced crude oils in the Canadian Wil-liston Basin, the hydrogen isotopic composition of individual n-alkanes in crude oils from Lunnan Oilfield is characterized by heavy hydrogen isotopic values (nC12―nC27, ?120‰―?60‰). In terms of the factors that control the fractionation of hydrogen isotopes, relatively saline deposi-tional environment and higher thermal maturation were attributed to the heavy δ D values of in-dividual n-alkanes in crude oils from Lunnan Oilfield.

关键词： hydrogen isotopes, individual n-alkanes, distribution, hydrocarbon source, Lunnan Oilfield.

Reconstruction and prediction of multi-source acoustic field with the distributed source boundary point method based nearfield acoustic holography

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Science China(Technological Sciences) 2004年第2期47卷 216-228页

作者： BI Chuanxing CHEN Jian CHEN Xinzhao Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China

In a multi-source acoustic field, the actual measured pressure is a scalar sum of pressures from all the sources. The pressure belonging to every source cannot be separated out with the existing techniques. Consequently, routine formulas cannot be used to reconstruct the acoustic source and predict the acoustic field directly. In this paper, a novel theoretical model of reconstruction and prediction of multi-source acoustic field in the distributed source boundary point method (DSBPM) based nearfield acoustic holography (NAH) is established. Three different methods, namely combination method with single surface measurement, combination method with multi-surface measurement and elimination method with multi-surface measurement, are proposed to realize the holographic reconstruction of sources. With these methods, the problem of reconstruction and prediction of acoustic field existing multiple coherent sources synchronously is solved effectively. Using the particular solutions constructed by the DSBPM to establish the vibro-acoustic transfer matrix, the calculation time, calculation precision and calculation stability are improved. These methods are valuable in localizing acoustic source and predicting acoustic field in engineering field.

关键词： acoustic holography, boundary point, distributed source, acoustic radiation.

source model for blasting vibration

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Science China(Technological Sciences) 2002年第4期45卷 395-407页

作者：丁桦郑哲敏 Division of Engineering Sciences Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

By analyzing and comparing the experimental data, the point source moment theory and the cavity theory, it is concluded that the vibrating signals away from the blasting explosive come mainly from the natural vibrations of the geological structures near the broken blasting area. The source impulses are not spread mainly by the inelastic properties (such as through media damping, as believed to be the case by many researchers) of the medium in the propagation pass, but by this structure. Then an equivalent source model for the blasting vibrations of a fragmenting blasting is proposed, which shows the important role of the impulse of the source's time function under certain conditions. For the purpose of numerical simulation, the model is realized in FEM, The finite element results are in good agreement with the experimental data.

关键词： blasting vibration, equivalent source, finite element method

Spatial structure and scale feature of the atmospheric pollution source impact of city agglomeration

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Science China Earth Sciences 2005年第Z2期48卷 1-24页

作者： XU Xiangde ZHOU Xiuji SHI Xiaohui State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing 100081 China

The spatial structure and multi-scale feature of the atmospheric pollution influence domain of Beijing and its peripheral areas (a rapidly developed city agglomeration) is dissected and analyzed in this paper on the basis of the atmospheric pollution dynamic-chemical process observation data of the urban building ensemble boundary layer of the Beijing City Air Pollution Observation Experiment (BECAPEX) in winter (February) and summer (August) 2003, and relevant meteorological elements and satellite retrieval aerosol optical depth (AOD), etc. comprehensive data with the dynamic-statistical integrated analysis of "point-surface" spatial structure. Results show that there existed significant difference in the contribution of winter/summer different pollution emission sources to the component character of atmospheric pollution, and the principal component analysis (PCA) results of statistical model also indicate that SO2 and NOX dominated in the component structure of winter aerosol particle; instead, CO and NOX dominated in summer. Surface layer atmospheric dynamic and thermal structures and various pollutant species at the upper boundary of building ensembles at urban different observational sites of Beijing in winter and summer showed an "in-phase" variation and its spatial scale feature of "influence domain". The power spectrum analysis (PSA) shows that the period spectrum of winter/summer particle concentration accorded with those of atmospheric wind field: the longer period was dominative in winter, but the shorter period in summer, revealing the impact of the seasonal scale feature of winter/summer atmospheric general circulation on the period of atmospheric pollution variations. It is found that from analyzing urban area thermal heterogeneity that the multiscale effect of Beijing region urban heat island (UHI) was associated with the heterogeneous expansion of tall buildings area. In urban atmospheric dynamical and thermal characteristic spatial structures, the

关键词： atmospheric pollution source, contribution rate, boundary layer structure, multi-scale, backward trajec- tory, correlation vector, climatic effect, interaction of water, soil and atmosphere.

The structure of molecular cloud W51 and dense cores——CO(J=1-0)and HCO^+(J=1-0)spectral line mapping

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Science China(Physics,Mechanics & Astronomy) 2005年第2期48卷 168-177页

作者： MA Hongjun PEI Chunchuan ZENG Qin Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China

We present a large scale map of about 15′×15′of CO(J=1-0) toward W51 giant molecular cloud (GMC), which covers the most active star-forming region of W51 GMC, and an interferometry HCO+(J=1-0) map of a high spatial resolution (i.e. 8″.7× 6″.1) with a field of view (2′×2′) centered at W51IRS1. A structure model of W51GMC is obtained according to the results of the observations and analyses. The observations demonstrate that some small molecular cores generated by the collision between the W51GMC and the 60—73 km·s-1 foreground cloud are collapsing toward their own centers. In addition, 16 new molecular cores are discovered from the HCO+(J=1-0) map.

关键词： molecular core, continuum source, star formation.

ANALYSIS OF THE LEAKY BUCKET OUTPUT PROCESSES FOR BURSTY sourceS IN ATM NETWORKS

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Journal of Electronics(China) 1997年第3期14卷 228-235页

作者： Liao Jianxin(National Lab. of Switching Tech. and Telecom. Networks BUPT of China, Beijing 100088)Li Lemin Sun Hairong(National Key Lab. of Optical Fiber Commun. UEST of China, Chengdu 610054)

In ATM networks, bursty sources can be described as the Interrupted Bernoulli Process(IBP). With the use of the thin process theory, the Probability Generating Function(PGF) of the IBP is obtained. An iterative algorithm, which can be used to calculate the IBP probability distribution, is presented. The bursty source’s equivalent description is discussed. It is proposed that the leaky bucket output process can be approximately described as the IBP. The accuracy of the analytical results has been largely validated by means of the simulation approach. Moreover, how to improve its accuracy is discussed. The smoothing function of the leaky bucket algorithm is quantitatively analyzed.

关键词： ATM Bursty source, IBP, Leaky bucket algorithm, Output process, Traffic smoothing