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Tihomir Engelsfeld Franjo &#x;umanovac Vladimir Krsti&#x; 《Journal of Applied Geophysics》2011,74(1):59-64
Results obtained by SASW and PS-logging (in-hole) seismic techniques are compared with the relatively new ReMi (Refraction microtremor) method at a common site with a well-known soil profile: a recently constructed high-speed railway embankment. PS-logging is the most accurate technique in identifying the soil profile of the embankment followed by Re-Mi and SASW. Mean shear wave velocity estimations are also higher for PS-logging, followed by SASW and ReMi, while mean deviation is similar in each technique. The ReMi technique has provided very accurate results in the study of the embankment profile, which in addition to its high operability and its fast data processing, makes it a very convenient technique for extensive geotechnical surveys. 相似文献
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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
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Li?ka Jesenica is a sinking river situated in the Dinaric karst environment of the Lika region of Croatia. The two main karst springs, Veliko Vrelo and Malo Vrelo, provide the majority of Li?ka Jesenica's water. Because of the quality and abundance of the water they contain, these springs are strategically important to the public water supply. Previous knowledge regarding the springs` karst system has been negligible. Therefore, a bulk hydrogeological research program was conducted with the purposes of establishing protection zones and assessing the springs' water‐supply potential. The research work comprised the following methods: hydrogeological mapping, setting up of monitoring stations for evaluating discharge and water quality, time series analyses (hydrograph–chemograph), hydrochemical analyses, and geophysical surveys. The main results and conclusions of the research include the following: (i) confirmation that both springs drain a common aquifer; (ii) determination of the highly vulnerable nature of the karst systems; (iii) identification of the Veliko Vrelo Spring's more direct connection to the aquifer‐drainage system in comparison to the Malo Vrelo; (iv) estimation of the positions and depths of the springs` main feeding conduits; (v) confirmation of the extent of the geologically presumed catchment area; and (vi) finally, establishment of sanitary protection zones. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Ulf Högström Anna Rutgersson Erik Sahlée Ann-Sofi Smedman Tihomir S. Hristov W. M. Drennan K. K. Kahma 《Boundary-Layer Meteorology》2013,147(1):139-163
A systematic comparison of wind profiles and momentum exchange at a trade wind site outside Oahu, Hawaii and corresponding data from the Baltic Sea is presented. The trade wind data are to a very high degree swell dominated, whereas the Baltic Sea data include a more varied assortment of wave conditions, ranging from a pure growing sea to swell. In the trade wind region swell waves travel predominantly in the wind direction, while in the Baltic, significant cross-wind swells are also present. Showing the drag coefficient as a function of the 10-m wind speed demonstrates striking differences for unstable conditions with swell for the wind-speed range 2 m s?1 < U 10 < 7 m s?1, where the trade-wind site drag values are significantly larger than the corresponding Baltic Sea values. In striking contrast to this disagreement, other features studied are surprisingly similar between the two sites. Thus, exactly as found previously in Baltic Sea studies during unstable conditions and swell, the wind profile in light winds (3 m s?1) shows a wind maximum at around 7–8 m above the water, with close to constant wind speed above. Also, for slightly higher wind speeds (4 m s?1 < U 10 < 7 m s?1), the similarity between wind profiles is striking, with a strong wind-speed increase below a height of about 7–8 m followed by a layer of virtually constant wind speed above. A consequence of these wind-profile features is that Monin–Obukhov similarity is no longer valid. At the trade-wind site this was observed to be the case even for wind speeds as high as 10 m s?1. The turbulence kinetic energy budget was evaluated for four cases of 8–16 30- min periods at the trade-wind site, giving results that agree very well with corresponding figures from the Baltic Sea. 相似文献
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Tihomir S. Hristov 《Boundary-Layer Meteorology》2008,129(3):497-507
Although recognized as important, measurements of turbulent atmospheric pressure are considered difficult and are conducted
infrequently. Here we discuss the essential elements in the design of an instrument for measuring turbulent fluctuations of
atmospheric pressure. Our analysis of the instrument’s dynamics is focused on the signal distortions resulting from a pneumatic
filter, a necessary element in the instrument’s design. Such distortions substantially affect the observed spectral scaling
of the pressure field as well as other quantities of physical interest, such as pressure-velocity 〈p, v〉 and pressure-wave 〈p, η〉 covariances. We propose a computationally efficient discrete-time signal processing method for complete compensation of
pneumatic filter distortions and review the criteria for selecting the instrument parameters (sampling frequency and time
constant), so that digital filter distortions, precision degradation, clipping, and over-damping, are simultaneously avoided.
This correction method must be an inherent part of the instrument’s design. 相似文献
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