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131.
Sándor Szalai László Szarka 《Journal of Applied Geophysics》2011,75(1):1-8
Recent two-dimensional multielectrode measurements are restricted to only a few geoelectric arrays. Realizing that specific features of nearly 90 other arrays are totally ignored, all original intentions as published about the development of new geoelectric arrays were reviewed. Apart from arrays, either already applied in two-dimensional geoelectric arrays or impossible to be applied in such systems, 61 forgotten once-developed arrays were found. These provide altogether 102 various solutions, which would be able to increase the efficiency of two-dimensional multielectrode measurements in some respect. 46 array solutions are able to enhance the depth of investigation; 9/11 array solutions give better vertical/horizontal resolution; 17 array solutions provide better planview images; 8 array solutions are worth applying in areas with limited access; 11 array solutions may reduce the effect of near-surface inhomogeneities. By reviving these forgotten arrays, it will be possible to develop versatile multielectrode systems, which are more adaptive to the diverse field needs. 相似文献
132.
Determining the location of buried plastic water pipes from measurements of ground surface vibration
J.M. MuggletonY. Gao 《Journal of Applied Geophysics》2011,75(1):54-61
‘Mapping the Underworld’ is a UK-based project, which aims to create a multi-sensor device that combines complementary technologies for remote buried utility service detection and location. One of the technologies to be incorporated in the device is low-frequency vibro-acoustics, and techniques for detecting buried infrastructure, in particular plastic water pipes, are being investigated. One of the proposed techniques involves excitation of the pipe at some known location with concurrent vibrational mapping of the ground surface in order to infer the location of the remainder of the pipe. In this paper, measurements made on a dedicated pipe rig are reported. Frequency response measurements relating vibrational velocity on the ground to the input excitation were acquired. Contour plots of the unwrapped phase revealed the location of the pipe to within 0.1-0.2 m. Magnitude contour plots revealed the excitation point and also the location of the pipe end. By examining the unwrapped phase gradients along a line above the pipe, it was possible to identify the wave-type within the pipe responsible for the ground surface vibration. Furthermore, changes in the ground surface phase speed computed using this method enabled the location of the end of the pipe to be confirmed. 相似文献
133.
A. Vandenbohede L. Lebbe Stefaan Gysens Kevin Delecluyse Peter DeWolf 《Journal of Hydrology》2008,360(1-4):77-86
In the dune area of the Westhoek Nature Reserve, situated in the western Belgian coastal plain, two artificial tidal inlets were made aiming to enhance biodiversity. The infiltration of salt water in these tidal inlets was carefully monitored because a fresh water lens is present in the phreatic dune aquifer. This forms an important source of fresh water which is for instance exploited by a water company. The infiltration was monitored over a period of two years by means of electromagnetic borehole measurements (EM39) and by measurements of fresh water heads and temperature using a large number of observation wells. EM39 observations point to aquifer heterogeneity as a determining factor in the movement of the salt infiltration water. It is shown that part of the infiltration water moves further in the dunes instead of towards the sea. On the long term run, possibility exists that salt water enters the extraction’s capture zone. This issue needs further monitoring and study. Fresh water head and temperature data illustrate that the main period of infiltration is confined to spring tide when large amounts of salt water enter the tidal inlets. 相似文献
134.
J. J. Wijetunge 《Pure and Applied Geophysics》2009,166(4):593-622
This paper employs a numerical model of tsunami propagation together with documented observations and field measurements of
the evidence left behind by the tsunami in December 2004, to identify and interpret the factors that have contributed to the
significant spatial variability of the level of tsunami impact along the coastal belt of the eastern province of Sri Lanka.
The model results considered in the present analysis include the distribution of the amplitude of the tsunami and the pattern
of wave propagation over the continental shelf off the east coast, while the field data examined comprise the maximum water
levels measured at or near the shoreline, the horizontal inundation distances and the number of housing and other buildings
damaged. The computed maximum amplitude of the tsunami at water points nearest the shoreline along the east coast shows considerable
variation ranging from 2.2 m to 11.4 m with a mean value of 5.7 m; moreover, the computed amplitudes agree well with the available
field measurements. We also show that the shelf bathymetry off the east coast, particularly the submarine canyons at several
locations, significantly influences the near-shore transformation of tsunami waves, and consequently, the spatial variation
of the maximum water levels along the coastline. The measured values of inundation also show significant variation along the
east coast and range from 70 m to 4560 m with a median value of 700 m. Our analyses of field data also show the dominant influence
of the coastal topography and geomorphology on the extent of tsunami inundation. Furthermore, the measured inundation distances
indicate no apparent correlation with the computed tsunami heights at the respective locations. We also show that both the
computed tsunami heights and the measured inundation distances for the east coast closely follow the log-normal statistical
distribution. 相似文献
135.
Wave-induced sediment resuspension in nearshore regions has been observed occurring in an event-like manner and associated with the passage of wave groups. This paper describes field measurements of turbulent velocities obtained simultaneously with suspended sediment concentration and water surface elevation from Floreat Beach, Perth, Western Australia. The data were used to study the relationship between turbulent kinetic energy (TKE) on suspension events caused by wave groups and the intermittent nature of bottom turbulence production and sediment suspension. The field measurements showed the high TKE events occurred under wave crests, and sometimes under wave toughs, when the wave heights were increasing during the passage of a wave group; the TKE decreased after the maximum wave in the wave group had passed over the measurement location. High suspended sediment concentrations (ssc) and the intermittent high TKE events were not related rather the higher ssc events were associated with a secondary peak in the surface elevation, close to the maxima in the offshore velocity, and “burst” events in the Reynolds stress. 相似文献
136.
An experimental investigation of the airflow structure in the near surface region over the wind-sheared air–water interface
is reported. The two-dimensional velocity fields in a plane perpendicular to the water surface were measured using particle
image velocimetry (PIV) technique over a wind speed range from 1.5 to 4.4 m s−1. The results show a reduction in the mean velocity magnitudes and the tangential stresses when gravity waves appear on the
surface. An enhanced vorticity layer was observed immediately above the water surface that extended to a height of approximately
2 cm. The vorticity was enhanced by an order of magnitude, and the energy dissipation rate was enhanced by a factor of 7 in
this layer at all wind speeds. The vertical profiles of Reynolds stress, energy production, and dissipation indicate the contribution
of surface waves in the enhanced transfer of momentum and energy between the two fluids. The results in this study show that
the flow dynamics in a layer immediately adjacent to the water surface whose thickness is of the order of the significant
wave height is significantly different from that at greater heights. Thus, it is concluded that the quantitative investigation
of the flow in the immediate vicinity of the interface is vital for an improved understanding of the heat, mass, and momentum
exchange between air and water. The present study demonstrates that PIV is an effective technique to accurately measure the
velocity fields in this region. 相似文献
137.
阳江抽水蓄能电站岩体水压致裂综合测试与应用研究 总被引:2,自引:0,他引:2
阳江抽水蓄能电站的输水隧洞围岩承受最大静内水压力高达7.83MPa, 因此原地应力状态、围岩自身承载能力及高压透水性状等对工程的科学设计不可或缺。测量结果表明, 工程区现今地壳应力场的总体特征为:水平主应力为最大主应力, 最大水平主应力的优势方向为NW-NWW向; 厂房和高压岔管区围岩的最大主应力值一般为14.5±0.5MPa, 最小主应力值一般为9±0.5MPa; 围岩自身的抗载强度一般为10~14MPa; 在8~10MPa高压力作用下围岩基本不透水。洞室围岩物理力学参数的这些测试成果, 为工程的科学设计提供了可靠依据。 相似文献
138.
Towards continuous long-term measurements of suspended particulate matter (SPM) in turbid coastal waters 总被引:1,自引:1,他引:0
Thomas H. Badewien Elke Zimmer Alexander Bartholomä Rainer Reuter 《Ocean Dynamics》2009,59(2):227-238
The dynamics of sediment transport in the East Frisian Wadden Sea are important for the coastal zone and for ecosystem functioning.
The tidal inlets between the East Frisian islands connect the back-barrier intertidal flats to the North Sea. Here, concentrations
of suspended particulate matter (SPM) in the water column are highly variable, depending on weather conditions and tides.
In order to estimate the nature and quantity of sediment transport, in situ measurements were carried out at a Time Series
Station in the tidal inlet between the islands of Spiekeroog and Langeoog. This study shows the suitability of multispectral
transmissometry (MST) for obtaining long-term SPM measurements with high resolution. The comparability of this technique to
the standard filter method and the laser diffraction method [laser in situ scattering and transmissometry (LISST)] is demonstrated.
In addition, the Junge coefficients derived from both MST and LISST measurements are compared. A time series of SPM data covering
nearly 4 months is presented. As a major result, the data reveal that a single storm surge can have less impact on SPM dynamics
than longer-lasting gales. This high-resolution long-term data set is very valuable for modelling suspended matter flux. It
also provides background information for studying the influence of SPM dynamics on coastal sediments. 相似文献
139.
组合码和相位观测值在线解双差模糊度的算法 总被引:4,自引:0,他引:4
如何在线精确地求解整周模糊度,是GPS高精度动态相对定位的关键问题。在线解算取决于很多因素:基线长度、数据处理方法、接收机的性能(如双频还是单频)以及抗AS和SA的能力等。现代双频GPS接收机能获得载波相位和L1、L2频道上的精度伪距观测值,组合这4个观测值可进行单历元整周模糊度解算。文中对组合码和相位观测值在线解整周度的算法进行了试验和分析,得出了很有实用意义的结合。 相似文献
140.
We propose a method to compensate for the phase lag and the amplitudeattenuation in the cup anemometer signal. These two effects, caused by theinstrument's inertia, are the major flaws of the cup anemometer in additionto over-speeding. Since the instrument's response is invariant in wavenumber (not frequency) representation, we transform the signals to becompensated from the time domain to the spatial domain by using Taylor'shypothesis. In the spatial domain we apply a linear time-invariant filterto eliminate the phase lag and the amplitude attenuation. The proposedprocedure improves instrument performance down to spatial scales equal toor smaller than the distance constant of the anemometer. The method for cupanemometer compensation is presented in detail and later adapted for vanes. 相似文献