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21.
Underwater ultrasonic acoustic transducers are frequently used in ocean wave measurements as they measure surface level using acoustic waves. However, their effectiveness can be severely affected in rough sea conditions, when bubbles generated by breaking waves interfere with their acoustic signals. When the seas are rough, one therefore often has to rely on a pressure transducer, which is generally used as a back-up for the acoustic wave gauge. A pressure transfer function is then used to obtain the surface wave information. Alternatively, the present study employed an artificial neural network to convert the pressure signal into significant wave height, significant wave period, maximum wave height, and spectral peakedness parameter using data obtained from various water depths. The results showed that, for water depths greater than 20 m, the wave parameters obtained from the artificial neural network were significantly closer to those obtained by the acoustic measurements than those obtained by using a linear pressure transfer function. Moreover, for a given water depth, the wave heights estimated by the network model from pressure data were not as good as those estimated by linear wave theory for large wave heights (above a 4 m significant wave height in this study). This can be improved if the training data set has more records with large wave heights. 相似文献
22.
23.
N. V. Chertkova A. E. Tsai N. L. Mironov V. D. Shcherbakov 《Moscow University Geology Bulletin》2010,65(1):39-48
Theoretical models and experimental data on the thermodynamic and rheological properties of basalts from the Apakhonchich
lava flow (Klyuchevskoi Volcano, Kamchatka) were invoked for plotting projections of water-containing and dry liquidus and
solidus curves on the P
s
-T plane. The P-T-X
H
2O conditions for the formation of basaltic magma and the degree of its differentiation were determined from data on melt inclusions.
The calculated apparent viscosity of the melt containing 10% crystals at 1100°C, 1 GPa, and 3 wt % water is 1.1 × 103 Pa s, and the density is 2.5 g/cm3. 相似文献
24.
The empirical rainfall threshold concept and the physical-based model are two commonly used approaches for the assessment
of shallow landslides triggered by rainfall. To investigate in detail the rainfall-triggered shallow landslides, many physical-based
models coupling the infinite slope stability analysis with the rainfall infiltration modeling in variably saturated soil were
developed. However, in those physical-based shallow landslide models, the unit weight and the unsaturated shear strength were
assumed constant rather than depending on the degree of saturation. In this study, the effects of the unit weight and the
unsaturated shear strength as function of degree of saturation on rainfall-triggered shallow landslides are examined. Several
designed scenarios and a real case scenario are used to conduct the examinations. The results show that not only the occurrence
of shallow landslides but also the failure depth and the time to failure could be misassessed if the influences of degree
of saturation on the unit weight and the unsaturated shear strength are neglected. 相似文献
25.
Hsiao-Chung Tsai Russell L. Elsberry 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(4):507-518
A version of our situation-dependent intensity prediction (SDIP) is proposed for operational application after three modifications: (i) Ten historical track analogs are matched with Joint Typhoon Warning Center (JTWC) official track forecasts rather than besttracks; (ii) Giving two times as much weight to the 72 h — 120 h portion of the track as to the 0–72 h portion to give higher rankings for analog tracks with similar landfall or recurvature positions and timing; and (iii) Weighting both the intensity prediction technique and a new intensity spread guidance product according to new rankings of the track analogs rather than assuming all track analogs are equally likely. These special matchings and weightings of the track analogs in this weighted-analog intensity (WANI) add skill in the 72–120 h forecast intervals in regions where landfalls occur. Viability as an operational technique is demonstrated as the WANI has only 1 kt larger mean absolute errors than the JTWC intensity errors from 12 h through 72 h, and the WANI is 5 kt (20%) better at 120 h. The WANI rank-weighted intensity spreads each 12 h among the 10 best historical track analogs are processed to reduce any intensity bias and calibrated to reduce (increase) the over-determined (under-determined) intensity spreads at early (later) forecast intervals. Thus, the situation-dependent intensity spread guidance is generated that will include about 68% of the verifying intensities at all forecast intervals. Four examples of the WANI intensity predictions and intensity spread guidance are presented to illustrate how the forecaster might use this information in potential landfall and intensity bifurcation situations. 相似文献
26.
Spatial distribution of soil erosion and suspended sediment transport rate for Chou-Shui river basin
Chin-Ping Lin Ching-Nuo Chen Yu-Min Wang Chih-Heng Tsai Chang-Tai Tsai 《Journal of Earth System Science》2014,123(7):1517-1539
In this study, a Physiographic Soil Erosion–Deposition Model (PSED) is applied for better management of a watershed. The PSED model can effectively evaluate the key parameters of watershed management: surface runoff discharge, suspended sediment transport rate, quantity of soil erosion, and spatial distribution of soil erosion and deposition. A basin usually contains multiple watersheds. These watersheds may have complex topography and heterogeneous physiographic properties. The PSED model, containing a physiographic rainfall-runoff model and a basin scale erosion–deposition model, can simulate the physical mechanism of the entire erosion process based on a detailed calculation of bed-load transportation, surface soil entrainment, and the deposition mechanism. With the assistance of Geographic Information Systems (GIS), the PSED model can handle and analyze extremely large hydrologic and physiographic datasets and simulate the physical erosion process without the need for simplification. We verified the PSED model using three typhoon events and 40 rainfall events. The application of PSED to Chou-Shui River basin shows that the PSED model can accurately estimate discharge hydrographs, suspended sediment transport rates, and sediment yield. Additionally, we obtained reasonable quantities of soil erosion as well as the spatial distribution of soil erosion and deposition. The results show that the PSED model is capable of calculating spatially distributed soil erosion and suspended sediment transport rates for a basin with multiple watersheds even if these watersheds have complex topography and heterogeneous physiographic properties. 相似文献
27.
Both laboratory experiments and numerical modelling were conducted to study the biodegradation and transport of benzene–toluene–xylenes (BTX) in a simulated semi‐confined aquifer. The factors incorporated into the numerical model include advection, hydrodynamic dispersion, adsorption, and biodegradation. The various physico‐chemical parameters required by the numerical model were measured experimentally. In the experimental portion of the study, BTX compounds were introduced into the aquifer sand. After the contaminants had been transported through the system, BTX concentrations were measured at 12 equally spaced wells. Subsequently, microorganisms obtained from the activated sludge of a sewage treatment plant and cultured in BTX mixtures were introduced into the aquifer through the 12 sampling wells. The distribution data for BTX adsorption by the aquifer sand form a nonlinear isotherm. The degree of adsorption by the sand varies, depending on the composition of the solute. The degradation time, measured from the time since the bacteria were added to the aquifer until a specific contaminant was no longer detectable, was 35–42 h for BTX. The dissolved oxygen, after degradation by BTX compounds and bacteria, was consumed by about 40–60% in the entire simulated aquifer; thus the aerobic conditions were maintained. This study provides insights for the biodegradation and transport of BTX in aquifers by numerical modelling and laboratory experiments. Experimental and numerical comparisons indicate that the results by Monod degradation kinetics are more accurate than those by the first‐order degradation kinetics. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
28.
Yu-Li Wang Liang-Cheng Chang Fei Liu Yen-Te Ho Tzu Bin Wang Tian-Chyi Jim Yeh Jui-Pin Tsai 《Ground water》2022,60(4):518-529
Groundwater responses measured from multiple wells at different depths are essential for delineating the aquifer heterogeneity using hydraulic tomography (HT). In general, conducting HT requires many wells because traditional well monitoring is usually partially open at a specific depth interval or is fully penetrating. Accordingly, conducting an HT survey is typically costly and time-consuming. To tackle these issues, a new multi-level monitoring system (MLMS) for the HT survey was developed using the fiber Bragg grating (FBG) technique. This FBG MLMS could collect the depth-discrete groundwater observations from a fully penetrated 2-inch well. Three field campaigns were conducted to validate the capability of the FBG MLMS for HT surveys. The results show that the accuracy and stability of this MLMS are reliable and that FBG MLMS is beneficial for conducting an HT survey. Specifically, compared to the traditional monitoring well in an injection event, this FBG MLMS can concurrently cause an increase in the number of cross-hole tests several times and collect many more head observations than the standard methods, resulting in the observed flow fields efficiently reaching ergodic conditions and effectively improving the accuracy of the estimated hydraulic heterogeneity. Therefore, the FBG MLMS could be an alternative MLMS for efficiently and economically conducting an HT survey. 相似文献
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