Mapping and initial dilution estimation of an ocean outfall plume using an autonomous underwater vehicle     

P.A. Ramos  M.V. Neves  F.L. Pereira 《Continental Shelf Research》2007

A monitoring mission to study the shape and estimate initial dilution of the S. Jacinto outfall plume using an autonomous underwater vehicle (AUV) was performed on July 30, 2002. In order to reduce the uncertainty about plume location and to concentrate the vehicle mission only in the hydrodynamic mixing zone, outputs of a near-field prediction model, based on effective real-time in situ measurements of current speed and direction and density stratification, were opportunistically used to specify in real time the mission transects. The surface characteristics of the outfall plume were found to be influenced strongly by the relatively weak stratification and low current velocities. Dilution was estimated using a temperature–salinity (TS-) diagram with initial mixing lines between wastewater and ambient waters. Effluent dilutions were at least 30:1 in this study. In order to efficiently map the plume dispersion we applied the least-squares collocation method technique. Our results demonstrate that AUVs can provide high-quality measurements of physical properties of effluent plumes in a quite effective manner and valuable considerations about the initial mixing processes under real oceanic conditions can be further investigated.  相似文献   

Comments on “Steady- and transient-state inversion in hydrogeology by successive flux estimation” by P. Pasquier and D. Marcotte     

Giansilvio Ponzini  Mauro GiudiciChiara Vassena 《Advances in water resources》2007

Pasquier and Marcotte [Pasquier P, Marcotte D. Steady- and transient-state inversion in hydrogeology by successive flux estimation. Adv Wat Res 2006;29:1934–52] propose some modifications to the Comparison Model Method (CMM), in order to apply it to transient 3D ground water flow data for conductivity identification. We present some remarks on that paper to improve the comprehension of the basic features of the CMM and of the real value of the novelties introduced by Pasquier and Marcotte.  相似文献   

Seismic,petrologic, and geodetic analyses of the 1999 dome-forming eruption of Guagua Pichincha volcano,Ecuador     

Alexander Garcia-Aristizabal  Hiroyuki Kumagai  Pablo Samaniego  Patricia Mothes  Hugo Yepes  Michel Monzier 《Journal of Volcanology and Geothermal Research》2007

Guagua Pichincha, located 14 km west of Quito, Ecuador, is a stratovolcano bisected by a horseshoe-shaped caldera. In 1999, after some months of phreatic activity, Guagua Pichincha entered into an eruptive period characterized by the extrusion of several dacitic domes, vulcanian eruptions, and pyroclastic flows. We estimated the three-dimensional (3-D) P-wave velocity structure beneath Guagua Pichincha using a tomographic inversion method based on finite-difference calculations of first-arrival times. Hypocenters of volcano-tectonic (VT) earthquakes and long-period (LP) events were relocated using the 3-D P-wave velocity model. A low-velocity anomaly exists beneath the caldera and may represent an active volcanic conduit. Petrologic analysis of eruptive products indicates a magma storage region beneath the caldera, having a vertical extent of 7–8 km with the upper boundary at about sea level. This zone coincides with the source region of deeper VT earthquakes, indicating that a primary magma body exists in this region. LP swarms occurred in a cyclic pattern synchronous with ground deformation during magma extrusions. The correlation between seismicity and ground deformation suggests that both respond to pressure changes caused by the cyclic eruptive behavior of lava domes.  相似文献   

Shear waves at a corrugated interface between anisotropic elastic and visco-elastic solid half-spaces     

S. K. Tomar  Jatinder Kaur 《Journal of Seismology》2007,11(3):235-258

Rayleigh’s method of approximation is employed to find out the reflection and transmission coefficients due to an incident plane SH wave at a corrugated interface between a laterally and vertically inhomogeneous anisotropic elastic solid half-space and a laterally and vertically inhomogeneous isotropic visco-elastic solid half-space. The lateral and vertical inhomogeneities are described by the exponential variations of elastic parameters. The formulae of reflection and transmission coefficients are derived in closed form for the first-order approximation of the corrugation. The effects of the corrugation of the interface, the inhomogeneity, the anisotropy, the visco-elasticity and the frequency of the incident wave on these coefficients are studied analytically and numerically for a specific model containing a periodic interface. The results of earlier workers have been reduced as particular cases from the present formulation.  相似文献   

A Least-squares Window Curves Method for Interpretation of Magnetic Anomalies Caused by Dipping Dikes   总被引：1，自引：0，他引：1  

E. M. Abdelrahman  E. R. Abo-Ezz  K. S. Soliman  T. M. El-Araby  K. S. Essa 《Pure and Applied Geophysics》2007,164(5):1027-1044

We have developed a least-squares method to determine simultaneously the depth and the width of a buried thick dipping dike from residualized magnetic data using filters of successive window lengths. The method involves using a relationship between the depth and the half-width of the source and a combination of windowed observations. The relationship represents a family of curves (window curves). For a fixed window length, the depth is determined for each half-width value by solving one nonlinear equation of the form f (z) = 0 using the least-squares method. The computed depths are plotted against the width values representing a continuous curve. The solution for the depth and the width of the buried dike is read at the common intersection of the window curves. The method involves using a dike model convolved with the same moving average filter as applied to the observed data. As a result, this method can be applied to residuals as well as to measured magnetic data. Procedures are also formulated to estimate the amplitude coefficient and the index parameter. The method is applied to theoretical data with and without random errors. The validity of the method is tested on airborne magnetic data from Canada and on a vertical component magnetic anomaly from Turkey. In all cases examined, the model parameters obtained are in good agreement with the actual ones and with those given in the published literature.  相似文献   

平坦地区转换GPS高程的混合转换方法   总被引：48，自引：0，他引：48  

胡伍生  华锡生  张志伟 《测绘学报》2002,31(2):128-133

简要介绍了转换GPS高程的二次曲面拟合法和神经网络方法。然而 ,这 2种方法都有缺点 ,介绍的CF&NNM方法充分利用了 2者的优点 ,通过 2个平坦地区的工程实例 ,证实该方法的有效性 ,并得到一些有工程应用价值的结论。  相似文献   

拟合推估新解之一——两步解法   总被引：8，自引：0，他引：8  

周江文 《测绘学报》2002,31(3):189-191

拟合推估的一般模式AmnmZ BrnrY=L Δ（1）通常用双拟合法则（2）求解，它有一定的缺陷^[1] 。本文提出一种解法，分为2步：1、将Y项并入Δ，在单拟合下求X的优估值X。2、把X项纳入L，Y作确定未知量，也在单拟合下求其估值Y。  相似文献   

带权约束参数平差在工程控制网优化中的应用     

鲍峰  程效军 《测绘学报》2002,31(Z1):73-76

介绍用带权约束平差原理编制的工程控制网试验修正法设计和平差程序,并用于设计工程导线和平差变形观测控制网等实际工程的例子,据此提供一些结论和建议.  相似文献   

全站仪近距离测距精度检验方法的探讨   总被引：3，自引：0，他引：3  

李宗春  李广云  范生宏  张森 《测绘信息与工程》2002,27(4):37-39

提出了室内基线法，给出了相应的数据处理方法，并用实测数据进行了计算，结果显示全站仪在室内、短边条件下的测距精度较标称精度有很大的提高。该法所得结果与现存两种方法的结果基本相当，从而证明了该法能够客观地反映出工业测量用全站仪的近距离测距精度。  相似文献   

半参数回归与模型精化   总被引：31，自引：4，他引：31  

孙海燕  吴云 《武汉大学学报(信息科学版)》2002,27(2):172-174,207

就一般情况给出了半参数平差的算法，并结合一种特定的情况，讨论了正规化矩阵半正定时的计算方法，给出了相应的公式，最后构造了一个模拟的平差问题，对半参数法和最小二乘法的计算结果进行了比较，计算表明，半参数法能够发现并识别模型误差或观测值中的系统误差。  相似文献