Natural Hazards - Climate change is evident with the extreme climatic indices changing all over the world. Bangladesh is one of the most vulnerable countries to climate change. The patterns of... 相似文献
Artesian aquifers offer interesting opportunities for water supply by providing a low-vulnerability groundwater resource that is easily abstracted without any installation of pumps or power supply costs. However, hydraulic tests are challenging to perform, notably where the piezometric head is above ground level with free-flowing wells not equipped with valves and open for years. This paper describes a low-cost, easy to reproduce and adaptable device, the free-flowing artesian well device (FFAWD), which is mainly designed with a set of PVC tubes equipped with a pressure probe and a valve. This device is used to perform hydraulic tests on free-flowing artesian wells, to measure the piezometric head of the aquifer and to compute its transmissivity. The practical use of the FFAWD is described and a method is proposed to compute the piezometric head and the transmissivity of the aquifer from this data set (free-flowing well discharge and pressure increase measurements) with any adapted analytical solution, using the Houpeurt-Pouchan method. Artefacts such as post-production effects, surge effects, and the impact of a leaky well are identified to avoid any misinterpretation. The FFAWD was applied to the volcano-sedimentary artesian plain of Pasuruan (Indonesia). The advantages and limitations of using the device, along with the interpretation methodology, are also discussed.
Soil erosion is a major environmental problem that threatens the sustainability and productivity of agricultural areas. Assessment
and mapping of soil erosion are extremely important in the management and conservation of natural resources. The universal
soil loss equation (USLE/RUSLE) is an erosion model that predicts soil loss as a function of soil erodibility (K-factor), as well as topographic, rainfall, cover, and management factors. The traditional approach assumes that one soil
erodibility value represents the entire area of each soil series. Therefore, that approach does not account for spatial variability
of soil series. This study was carried out to evaluate the use of the sequential Gaussian simulation (SGS) for mapping soil
erodibility factor of the USLE/RUSLE methodology. Five hundred and forty-four surface soil samples (0–20 cm) were collected
from the study area to determine the soil erodibility. A simulation procedure was carried out on 300 realizations, and histogram
and semivariogram of the simulation were compared to the observed values. The results showed that the summary statistics,
histogram, and semivariogram of the simulation results were close to the observed values. In contrary to the traditional approach
and kriging, 95% confidence interval of the simulated realizations was formed in order to determine uncertainty standard deviation
map, and the uncertainty was explained numerically. The SGS produced a more reliable soil erodibility map and it can be more
successfully used for monitoring and improving effective strategies to prevent erosion hazards especially to improve site
specific management plans. 相似文献
We use a semi-analytic model of halo formation to study the dynamical history of giant field galaxies like the Milky Way.
We find that in a concordance LCDM cosmology, most isolated disk galaxies have remained undisturbed for 8–10 Gyr, such that
the age of the Milky Way's thin disk is unremarkable. Many systems also have older disk components which have been thickened
by minor mergers, consistent with recent observations of nearby field galaxies. We do have a considerable problem, however,
reproducing the morphological mix of nearby galaxies. In our fiducial model, most systems have disk-to-bulge mass ratios of
order 1, and look like S0s rather than spirals. This result depends mainly on merger statistics, and is unchanged for most
reasonable choices of our model parameters. We discuss two possible solutions to this morphology problem in LCDM.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
Artificial neural networks (ANNs) were used to predict the differential global positioning system (DGPS) pseudorange and carrier
phase correction information. Autoregressive moving average (ARMA) and autoregressive (AR) models were bounded with neural
networks to provide predictions of the correction. The neural network was employed to realize time-varying implementation.
Online training for real-time prediction of the carrier phase enhances the continuity of service of the differential correction
signals and, therefore, improves the positioning accuracy. When the correction signal from the DGPS was lost, the artificial
neural networks predicted the correction data with good accuracy for the navigation system during a limited period. Comparisons
of the prediction results using the two models are given.
Emerald deposits in Swat, northwestern Pakistan, occurring in talc-magnesite and quartz-magnesite assemblages, have been investigated through stable isotope studies. Isotopic analyses were performed on a total of seven emeralds, associated quartz (seven samples), fuchsite (three samples) and tourmaline (two samples) from the Mingora emerald mines. The oxygen isotopic composition (
18O SMOW) of emeralds shows a strong enrichment in18O and is remarkably uniform at + 15.6 ± 0.4 (1,n = 7). Each of the two components of water in emerald (channel and inclusion) has a different range of hydrogen isotopic composition: the channel waters being distinctly isotopically heavier (D = –51 to –32 SMOW) than the other inclusion waters (D = –96 to –70 SMOW). Similarly the oxygen isotopic compositions of tourmaline and fuchsite are relatively constant (
18O = + 13 to + 14 SMOW) and show enrichment in18O. The
18O values of quartz, ranging from + 15.1 to + 19.1 SMOW, are also high (+ 16.9 ± 1.4 1, n = 7). The meanD of channel waters measured from emerald (–42 ± 6.6 SMOW) and that of fluid calculated from hydrous mineralsDcalculated (–47 ± 7.1 SMOW) are consistent with both metamorphic and magmatic origin. However, the close similarity between the measuredD values of the hydroxyl hydrogen in fuchsite (–74 to –6 SMOW) and tourmaline (–84 and –69 SMOW) with pegmatitic muscovite and tourmaline suggests that the mineralization was probably caused by modified (18O-enriched) hydrothermal solutions derived from an S-type granitic magma. The variation in the carbon and oxygen isotopic composition of magnesite, locally associated with emerald mineralization, is also very restricted (
13 –3.2 ± 0.7%, PDB;18O + 17.9 ± 1.27 SMOW). On the basis of the isotopic composition of fluid (
13C –1.8 ± 0.7 PDB;
18O + 13.6 ± 1.2 SMOW calculated for the 250-550 °C temperature), it is proposed that the Swat magnesites formed due to the carbonation of previously serpentinized ultramafic rocks by a CO2-bearing fluid of metamorphic origin. 相似文献
The interoperability of geographic data sets is required between geo-information system applications to use geographic data sets effectively. Thus, international standardisation organisation/technical committee 211 standards supporting model-driven architecture were examined to test the ability of producing interoperable geographic data sets. With Turkey case, unified modelling language application schemas were designed for base geographic data themes and encoded to data interchange model based on geography markup language. To test the applicability of the open data models, extract-transform-load (ETL) tools were developed and applied for case applications such as topographic map and web urban atlas. This study gives a methodology and indicates that ETL tools should be created to enable multiple uses of geo-data sets without spending time and labour. However, data model design should be refined and kept as simple as possible because data transformation is laborious to use the models in the applications. 相似文献