Investigation on the effect of inclined crest step pool on scouring protection in erodible river beds

Natural Hazards - One of the aquatic structures that are used for protect water channels against bed erosion is serial step-pool. These steps similarity of the vertical drops structure are exposed...     

Comparison between bivariate and trivariate flood frequency analysis using the Archimedean copula functions,a case study of the Karun River in Iran

Natural Hazards - Historically, severe floods have caused great human and financial losses. Therefore, the flood frequency analysis based on the flood multiple variables including flood peak,...     

Assessment of a data-driven evidential belief function model and GIS for groundwater potential mapping in the Koohrang Watershed,Iran

The objective of this study is to produce groundwater potential map (GPM) and its performance assessment using a data-driven evidential belief function (EBF) model. This study was carried out in the Koohrang Watershed, Chaharmahal-e-Bakhtiari Province, Iran. It’s conducted in three main stages such as data preparation, groundwater potential mapping using EBF and validation of constructed model using receiver operating characteristic (ROC) curve. At first, 864 groundwater data were collected from spring locations; out of that, 605 (70%) locations were selected for training/model building and the remaining 259 (30%) cases were used for the model validation. In the next step, 12 effective factors such as altitude, slope aspect, slope degree, slopelength (LS), topographic wetness index (TWI), plan curvature, land use, lithology, distance from rivers, drainage density, distance from faults and fault density were extracted from the spatial database. Subsequently, GPM was prepared using EBF model in ArcGIS environment. Finally, the ROC curve and area under the curves (AUC) were drawn for verification purposes. The validation of results showed that the AUC for EBF model is 81.72%. In general, this result can be helpful for planners and engineers in water resource management and land-use planning.     

Impact of Land use Changes on Landslides Occurrence in Urban Area: The Case of the Constantine City (NE Algeria)

Geotechnical and Geological Engineering - The city of Constantine (NE Algeria), the third largest city of the country (2.374 inhabitants/km2) is facing frequent damaging landslides that constitute...     

U, Th, K and Cs activity concentrations along the southern coast of the Caspian Sea, Iran

The determination of activity concentrations of the radioactive elements ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs was performed on grab samples taken from a polluted environment. The samples were sliced into strata from 5 cm depth, dried and ground to sieved through a 170 mesh size prior to the analysis. Activity concentration was quantified using gamma spectroscopy. The results showed that the concentrations of activity in the sediment samples are 177 ± 12.4, 117 ± 11.5, 1085 ± 101.6 and 131 ± 4.8 Bq kg⁻¹ for ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs, respectively. In general, the distribution of activity concentrations along the southern coast of the Caspian Sea area exceeded international limits. The hazard index of the samples was 0.19-0.88, with an average of 0.49. The mean values of radium equivalent activity and dose rate are 176 Bq kg⁻¹ and 63 nGy h⁻¹, respectively.     

New set of geometrical and physical elements of the two variable stars SW lacertae and OO aquilae

Photoelectric observations of the two eclipsingvariables, were obtained in UBV standard system, for SWLac and, inVB standard system for OOAql.A new set of geometrical and physical elements for thesystems were obtained from both minima, through theirmagnitude variation during the observation time using themethod of: Fourier Analysis Techniques in-Frequency-domain for thelight curve changes. The two eclipsing variables are contact, the firstcontact angle was 48.1^° for SW Lac and 47.7^° for OO Aql.Absolute elements and effective temperatures of the twocomponents for both systems are derived.     

Evaluation of Negative Economic-Environmental Externalities of Overextraction of Groundwater

In recent decades, increased extraction of groundwater for human and agriculture consumption has led to a substantial drop in groundwater level in large areas of across the world. Declining groundwater levels is a serious problem in itself and has multiple economic, social, cultural, political, security-related, and environmental externalities. The negative economic-environmental externalities of overextraction of groundwater in the Orzouiyeh plain in the Kerman Province, Iran, were evaluated using methods such as replacement cost, production function, market prices, shadow price, and the value of the input marginal product. After evaluating externalities, the Positive Mathematical Programming method was used to evaluate different water policies to reduce the consumption of groundwater. The total economic losses due to the externalities were calculated to equal 2.8 U.S. million dollars. The damages caused by environmental externalities were calculated to equal 436.1 U.S. million dollars. The results related to the positive planning model show that the best policy among different options, such as deficit irrigation policy or combined policies, involves implementation of pressurized irrigation systems.     

Head-wave parametric rolling of a surface combatant

Complementary CFD, towing tank EFD, and nonlinear dynamics approach study of parametric roll for the ONR Tumblehome surface combatant both with and without bilge keels is presented. The investigations without bilge keels include a wide range of conditions. CFD closely agrees with EFD for resistance, sinkage, and trim except for Fr>0.5 which may be due to free surface and/or turbulence modeling. CFD shows fairly close agreement with EFD for forward-speed roll decay in calm water, although damping is over/under predicted for largest/smaller GM. Most importantly CFD shows remarkably close agreement with EFD for forward-speed parametric roll in head waves for GM=0.038 and 0.033 m, although CFD predicts larger instability zones at high and low Fr, respectively. The CFD and EFD results are analyzed with consideration ship motion theory and compared with Mathieu equation and nonlinear dynamics approaches. Nonlinear dynamics approaches are in qualitative agreement with CFD and EFD. The CFD and nonlinear dynamics approach results were blind in that the actual EFD radius of gyration k_xx was not known a priori.