Simulated various characteristic waves in acoustic full waveform relating to cement bond on the secondary interface     

Hongbing Zhang  Danyan Xie  Zuoping Shang  Xuebing Yang  Hongjian Wang  Honggen Tao 《Journal of Applied Geophysics》2011,73(2):139-154

Bad cement bond with water channeling or low strength cement is usually generated on the first and/or secondary interfaces which lie between the cement and casing, and the cement and formation, respectively. It is an inherently complicated problem to evaluate cement bond on the secondary interface (SICB) in a cased borehole. So we need to find a useful wave for evaluating SICB and provide its propagation features. To achieve this, we simulated the acoustic full waveform, 2-D spectrum and dispersion curves in cased boreholes based on the real axis integration method, and a propagator matrix. Simulation results indicated that “casing-cement mode” wave can be utilized to evaluate SICB, as it is most sensitive to water channeling on the secondary interface. Velocity of this mode wave is in between that of the casing wave and the formation wave, so that it is easy to extract it in time. The dispersion curves showed that the casing-cement wave is a dispersion wave, but not a pseudo-Rayleigh wave. Its velocity is obviously larger than v_s of cement. Simulation results further indicated that the amplitude of casing-cement wave is decreasing with increasing cement sheath thickness, but not water channeling thickness, and its travel time is influenced by casing and cement together. Moreover, we investigated factors influencing the casing–cement wave and found that casing diameter and peak frequency are major factors influencing the amplitude and the travel time, while other factors, such as P-wave velocities of cement and wall thickness of casing, are minor factors. But none of these factors greatly influence bond index which is computed from the amplitude. So the bond index has an advantage over the amplitude during evaluating SICB. Formation wave is a helpful signal to evaluate low strength cement without water channeling, and its amplitude is mainly related to the velocities (or impedances) of both cement and formation except for formation attenuation and disturbance wave. Experimental data in calibration pits and field data detecting channeling demonstrated the simulation results.  相似文献   

Ray-based modeling of reverberation in subsurface circular cylindrical void     

Ping Chen  Dan Xia  Boyuan Chen  Lin Li  Xiuzhong Li  Tian-lin Dong 《Journal of Applied Geophysics》2011,73(3):261-266

Ray representation of electromagnetic resonance (reverberation) mode in subsurface circular cylindrical dielectric resonator (including void) is proposed. The modal ray path must be regular polygon or polystar. Travel time formulas for fundamental resonance multiples and the detecting conditions for non-exact-backscattering rays are derived. Simulation of time–distance curves of a modal hollow concrete block is generally concurred to the measured ground penetrating radar signal pattern. The proposed modeling method can be generalized to other resonant cavities with different profiles and provide a sound base for further applications of other more complicated geophysics science and engineering fields, particularly in ray-based tomography.  相似文献   

Analyzing qualitative and quantitative changes in coastal wetland associated to the effects of natural and anthropogenic factors in a part of Tianjin,China     

Zhenglei Xie  Xuegong Xu  Lei Yan 《Estuarine, Coastal and Shelf Science》2010,86(3):379-386

Natural and anthropogenic factors in coastal wetland changes are widely discussed in wetland studies. Previous literatures have demonstrated that many factors may cause wetland change and argued that the global climate change and nutrient enrichment may become the most important ones in the next 50 years. Through field investigation, with the help of remote sensing technology and geographic information system, this research discusses the wetland change in Tianjin under the great pressure of rapid economic development, population growth, and sea-level rising. These findings include: (1) the wetland area expanded from 466.50 km² to 658.38 km² between 1987 and 1998, but it shrank to 550.5 km² by the year of 2006. (2) The results show that the groundwater has not been contaminated while the surface water has been polluted. (3) The questionnaire survey shows that the social environment in some specific ways impedes the protection of natural reserve. In order to achieve the harmony between human and nature, feasible countermeasures on how to keep ecological balance should be immediately taken. Consequently, natural conservation and sustainable economic development will be realized.  相似文献   

Scientific prospects for spectroscopy of the gamma-ray burst prompt emission with SVOM     

M. G. Bernardini  F. Xie  P. Sizun  F. Piron  Y. Dong  J.-L. Atteia  S. Antier  F. Daigne  O. Godet  B. Cordier  J. Wei 《Experimental Astronomy》2017,44(1):113-127

SVOM (Space-based multi-band astronomical Variable Objects Monitor) is a Sino-French space mission dedicated to the study of Gamma-Ray Bursts (GRBs) in the next decade, capable to detect and localise the GRB emission, and to follow its evolution in the high-energy and X-ray domains, and in the visible and NIR bands. The satellite carries two wide-field high-energy instruments: a coded-mask gamma-ray imager (ECLAIRs; 4–150 keV), and a gamma-ray spectrometer (GRM; 15–5500 keV) that, together, will characterise the GRB prompt emission spectrum over a wide energy range. In this paper we describe the performances of the ECLAIRs and GRM system with different populations of GRBs from existing catalogues, from the classical ones to those with a possible thermal component superimposed to their non-thermal emission. The combination of ECLAIRs and the GRM will provide new insights also on other GRB properties, as for example the spectral characterisation of the subclass of short GRBs showing an extended emission after the initial spike.  相似文献   

Coherent spectroscopy of a strongly driven triple quantum dot molecule     

解研  段素青  楚卫东  杨宁 《海洋学报(英文版)》2010,29(11)

Based on a calculation model, we study the interference phenomena of serially coupled V-type and Λ-type triple quantum dots (CTQDs) driven simultaneously by a strong driving field and a weak probe field. Strongly depending on the configuration of the three-level CTQD, the probe absorption spectra, which are shown in the tunneling current, exhibit various quantum coherence properties. In the case where the two pairs of transitions of the CTQD have a small eigenfrequency difference Δω, the double-coupling effect of the driving field results in two Autler-Townes doublets and one weak Mollow triplet in one spectrum. With the value of Δω increasing, only one Autler-Townes splitting remains due to the single-coupling of the field. We also find that the effect of spontaneous emission of phonons may lead to an obvious background current, which can be used to distinguish which transition is driven by the driving field in experiment. The interesting quantum property of a CTQD revealed in our results suggests its potential applications in quantum modulators and quantum logic devices.  相似文献   

从处理平顶山市矿业纠纷中引出的几点思考     

谢怀阳 《河南国土资源》1999,(2)

作者通过对本部门、本系统所处理的大量的矿业纠纷进行调查、了解和分析，提出了矿业纠纷问题是矛盾激化了的矿业秩序问题，是明显而复杂的社会问题，进而揭示了造成矿业秩序混乱，矿业纠纷难于解决的社会深层次的问题，同时对如何贯彻实施《矿产资源开采登记管理办法》提出了建议，最后提出了实现矿业秩序根本好转的四个前提条件。  相似文献   

福宁湾海域溢油扩散影响的数值模拟研究   总被引：1，自引：0，他引：1       下载免费PDF全文

张海文  赵懿珺  纪平 《应用海洋学学报》2019,38(1):84-92

应用非结构化网格形式的MIKE 21水动力模型及溢油模块建立福宁湾海域海工工程施工期溢油扩散的数学模型,对在静风、全年主导风及不利风等3种不同风况条件下,一个潮周期内包括涨憩、落急、落憩、涨急等4个典型潮时分别发生100 t燃料油持续泄露30 min的事故溢油工况进行溢油扩散数值模拟.分析显示,事故溢油在福宁湾海域的扩散过程主要受潮流和风的影响.计算结果给出了事故溢油发生后24 h内的影响范围及0. 05 mg/dm3油浓度(一类或二类水质标准)溢油最快到达福宁湾内主要敏感目标的时间,为海洋环境影响评价和溢油事故应急措施的制定提供了科学依据.  相似文献   

11颗行星际尘粒中的锂,硼同位素丰度分析     

谢萍 《紫金山天文台台刊》1997,16(2):77-81

我们首次测量了4颗行星际尘粒(IDPs)中的~6Li/~7Li,~(10)B/~(11)B。它们的平均值分别是(8.40±0.37)×10~(-2)和(2.40±0.18)×10~(-2),随后又精确测量了7颗IDPs~6Li/Li的同位素丰度。  相似文献   

SCATTERING PHASE MATRICES OF ICE CRYSTALS WITH HEXAGONAL PRISM AND TRIANGULAR PYRAMID FORM—A VECTOR RAY TRACING METHOD          下载免费PDF全文

Cai Qiming  Yang Ping 《Acta Meteorologica Sinica》1991,5(4):515-526

The work presented previously by the authors(Cai and Liou,1982)has been extended in this paper.By making use of our improved model the calculations on scattering phase matrices of hexagonal prismice crystals(HPIC)have been conducted for monodisperse and polydisperse systems.Compared with themodel of Cai and Liou,the required computational quantity is decreased by about two orders of magni-tude and the errors of results are less for the new model.Meanwhile,the scattering phase matrices of triangularpyramid ice crystals(TPIC)are also computed in the paper,and the comparison between the scatterings of thetwo forms of ice crystals is performed.  相似文献   

测绘工程专业人力资源现状与毕业生需求研究     

谢宏全  徐运  池承洋  周燕峰  琚芳芳 《现代测绘》2009,32(1)

随着国民经济的快速发展,测绘行业得到了迅速发展壮大.江苏省是测绘人力资源大省,同时是测绘教育大省.通过抽样调查方法对江苏省测绘工程专业人力资源现状与毕业生需求情况进行了详细研究.研究得出江苏省测绘行业人才队伍不断壮大,未来需求量不断增加,有利于毕业生就业.  相似文献