Removal of DC power-line magnetic-field effects from airborne total magnetic-field measurements

Power lines carrying DC current can strongly affect total magnetic-field measurements. A simple algorithm using Biot–Savart's law was made to remove magnetic-field components due to a DC power line from airborne total magnetic-field measurements in the Gävle area, Sweden. The power-line location was estimated from observed data and then split into short line segments. The magnetic-field components due to each segment were calculated and summed together to give the total magnetic effect due to the power line at each observation point. The corrected total magnetic field was calculated by subtracting the power-line magnetic-field vector, projected on to the direction of the main field, from the measured total field. The results show a successful removal of the power-line magnetic effect from the total magnetic-field measurements. However, an error in the estimation of the power-line location can result in a magnetic-field residual after correction. A non-linear median filtering was used to remove this residual when needed.     

Solving non-linear Lane–Emden type equations using Bessel orthogonal functions collocation method

The Lane–Emden type equations are employed in the modeling of several phenomena in the areas of mathematical physics and astrophysics. These equations are categorized as non-linear singular ordinary differential equations on the semi-infinite domain $[0,\infty )$ . In this research we introduce the Bessel orthogonal functions as new basis for spectral methods and also, present an efficient numerical algorithm based on them and collocation method for solving these well-known equations. We compare the obtained results with other results to verify the accuracy and efficiency of the presented scheme. To obtain the orthogonal Bessel functions we need their roots. We use the algorithm presented by Glaser et al. (SIAM J Sci Comput 29:1420–1438, 2007) to obtain the $N$ roots of Bessel functions.     

Use of formation pressure test results over a hydrate interval for long-term production forecasting at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Implications of uncertainties

In the first part of this paper, the pressure and temperature measurements obtained using Schlumberger's Modular Formation Dynamics Tester (MDT) conducted on the C2 interval in the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well (Mount Elbert Well) are history matched, with the following three objectives: (i) to obtain a better understanding of hydrate decomposition and its reformation as conditions cross the p/T stability, (ii) to obtain formation properties (e.g., permeability) that are consistent with the measurements, and (iii) to explore the non-uniqueness in the history match; i.e., to explore the ranges of parameters that allow a reasonable match of the measured quantities. In the second part of this paper, long-term production performance is predicted, and the effect of the uncertain parameters on the predictions is demonstrated. The results are used to demonstrate the range of long-term production that may be expected, when a model is calibrated using the MDT data. Usefulness of short-term tests for long-term forecast prediction is then discussed.     

Effect of Pile Driving on Ground Vibration in Clay Soil: Numerical and Experimental Study

Geotechnical and Geological Engineering - In this study, peak particle velocity (PPV) values for driving three piles with diameters of 40 cm, 50 cm, and 70 cm in a clayey...     

Optimization of Gravity Concrete Dams Using the Grasshopper Algorithm (Case Study: Koyna Dam)

Geotechnical and Geological Engineering - The aim of this study is to optimize the geometric dimensions of the Koyna concrete weight dam with and without seismic forces using the grasshopper...     

A numerical technique for simulation of the effect of soil nitrogen transport and transformations on groundwater contamination

Two numerical models, one for the vadose zone and the other for the aquifer system, are utilized to predict nitrate pollution potential in groundwater. Transport by dispersion and convection of mobile species of nitrogen, ammonium ion exchange, first order nitrogen transformations, and nitrogen plant uptake are included in the formulation for the vadose zone. Transport of nitrate in the aquifer is assumed to be affected only by dispersion-convection phenomena. Justifications for one-dimensional conceptualization of flow in the vadose zone and two-dimensional representation for the aquifer, under various field conditions, are presented. To illustrate the concept, a simple hypothetical problem is solved. The approach presented here provides an efficient means of long-term simulation of large-scale field problems.     

Shape factor in the drawdown solution for well testing of dual-porosity systems

One of the important parameters in existing commercial dual-porosity reservoir simulators is matrix–fracture shape factor, which is customarily obtained by assuming a constant pressure at the matrix–fracture boundary. In his work, Chang [1] and [2] addressed the impact of boundary conditions at the matrix–fracture interface and presented analytical solutions for the transient shape factor and showed that for a slab-shaped matrix block a constant pressure boundary condition leads to an asymptotic (long-time) shape factor of π²/L², and that a constant volumetric flux leads to an asymptotic shape factor of 12/L². In a recent paper [3], we reconfirmed Chang’s [1] and [2] results using a Laplace transform approach. In this study, we extend our previous analysis and use infinite-acting radial and linear dual-porosity models, where the boundary condition is chosen at the wellbore, as opposed to at the matrix boundary. The coupled equations for fracture and matrix are solved analytically, taking into account the transient exchange between matrix and fracture. The analytical solution that invokes the time dependency of fracture boundary condition under constant rate is then used to calculate the transient shape factors. It is shown that, for a well producing at constant rate from a naturally fractured reservoir, the appropriate value of stabilized shape factor is 12/L². This contrasts with the commonly used shape factor for a slab-shaped matrix block that is subject to a constant pressure boundary condition, which is π²/L². The errors in the matrix–fracture exchange term in a dual-porosity model associated with the use of a shape factor derived based on constant pressure boundary condition at the matrix boundary are then evaluated.     

Numerical study on static and seismic stability of breakwaters on soft granular marine deposits against deep failure

Marine structures which cover a wide range of offshore and onshore structures are often subjected to different external and internal forces against which a proper design should be performed. Among many, breakwaters constructed over a relatively loose agglomerate of granular soils are much prone to deep seated failure extended beneath the foundation. This type of failure has been given less attention in conventional design approaches. Stability analysis of such failures is the main subject of this research which includes both the static and the seismic stability of breakwaters over granular marine soils. As the subsoil strata in sea beds often comprise loose sand deposits, it is more convenient to assume a rather small angle of dilation, at least at failure, which certainly reduces the potential to resist geotechnical instabilities. The method of stress characteristics along with slight modifications to handle this issue has been used to assess the overall stability of breakwaters against deep seated failures. Investigations revealed that while even under static condition, there is certain potential of failure, under seismic condition, the risk is quite very high. A series of design charts are also developed presenting the factor of stability as a measure of safety against such failure.     

The role of land use patterns in earthquake resilience: a case study of the Ahvaz Manba Ab neighborhood

Natural Hazards - Urban resilience to natural disasters has constantly been a challenge to sustainable development in human societies. Since Iran is always exposed to natural disasters such as...