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Search Results: 1 - 10 of 297674 matches for " Broder J. Merkel "
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Analytical and Numerical Modeling of Flow in a Fractured Gneiss Aquifer  [PDF]
Ramadan Abdelaziz, Broder J. Merkel
Journal of Water Resource and Protection (JWARP) , 2012, DOI: 10.4236/jwarp.2012.48076
Abstract: Investigating and modeling fluid flow in fractured aquifers is a challenge. This study presents the results of a series of packer tests conducted in a fractured aquifer in Freiberg, Germany, where gneiss is the dominant rock type. Two methods were applied to acquire hydraulic properties from the packer tests: analytical and numerical modeling. MLU (Multi-Layer Unsteady state) for Windows is the analytical model that was applied. ANSYS-FLOTRAN was used to build a two-dimensional numerical model of the geometry of the layered aquifer. A reasonable match between experimental data and simulated data was achieved with the 2D numerical model while the solution from the analytical model revealed significant deviations with respect to direction.
Lattice Boltzmann modeling for tracer test analysis in a fractured Gneiss aquifer  [PDF]
Ramadan Abdelaziz, Andrew J. Pearson, Broder J. Merkel
Natural Science (NS) , 2013, DOI: 10.4236/ns.2013.53050
Abstract:

Fractured Gneiss aquifers present a challenge to hydrogeologists because of their geological complexity. Interpretation methods which can be applied to porous media cannot be applied to fractured Gneiss aquifers because flow and transport occur in fractures, joints, and conduits. In contrast, the rock matrix contribution to groundwater flow is not very important in Gneiss aquifers. Sodium chloride was injected into groundwater flow under steady state condition as tracer to determine transport parameters which are needed for transport modeling. QTRACER2 was used to evaluate the tracer test data. Lattice Boltzmann method was applied to simulate flow and tracer transport through a fracture zone in Gneiss. Experimental tracer data and the numerical solution by lattice Boltzmann method are compared. In general, the results indicate that a 2D Lattice Boltzmann model is able to simulate solute transport in fractured gneiss aquifer at field scale level.

Automated Watershed Evaluation of Flat Terrain  [PDF]
Sameh W. Al-Muqdadi, Broder J. Merkel
Journal of Water Resource and Protection (JWARP) , 2011, DOI: 10.4236/jwarp.2011.312099
Abstract: Catchment area and watershed delineation is a common task in hydrology. The determination of the catchment is still as a challenge considered being crucial key issues particular in flat terrains. Three concepts could be briefly identified through: the manual delineation of a catchment based on a topographic map with contour lines which is a difficult task for flat terrains, by combination of field survey or evaluation of satellite images. The present research is focus on evaluating the possibility to delineate catchments from flat and arid areas by means of DTM avoiding hard techniques like river burning or other manual hydrological DTM corrections. Three GIS packages were used (Arc Hydrotools, TNTmips and RiverTools) within two DEM: the 90 m and 30 m SRTM in addition to the ASTER 30 m, the application sample presented by western Iraq desert—Ubaiydh wadi. A brief review is given how the delineation algorithms have been developed since the 1980’s. Where result shows that automated watershed analysis of flat terrains is cannot be done without manual evaluation and correction either by using several seeding points or river burning technique.
Interpretation of Groundwater Flow into Fractured Aquifer  [PDF]
Sameh W. Al-Muqdadi, Broder J. Merkel
International Journal of Geosciences (IJG) , 2012, DOI: 10.4236/ijg.2012.32039
Abstract: The region of investigation is part of the western desert of Iraq covering an area of about 12,400 km2, this region includes several large wadis discharging to the Euphrates River. Since the Tectonic features in particular fault zones play a significant role with respect to groundwater flow in hard rock terrains. The present research is focus on investigate lineaments that have been classified as suspected faults by means of remote sensing techniques and digital terrain evaluation in combination with interpolating groundwater heads and MLU pumping tests model in a fractured rock aquifer, Lineaments extraction approach is illustrated a fare matching with suspected faults, moreover these lineaments conducted an elevated permeability zone.
Generate Reservoir Depths Mapping by Using Digital Elevation Model: A Case Study of Mosul Dam Lake, Northern Iraq  [PDF]
Mohammed F. O. Khattab, Rudy K. Abo, Sameh W. Al-Muqdadi, Broder J. Merkel
Advances in Remote Sensing (ARS) , 2017, DOI: 10.4236/ars.2017.63012
Abstract: Not many bathymetric maps are available for many lakes and reservoirs in developing countries. Usually the bathymetric mapping requires investment in expensive equipment and fieldwork, both of which are not accessible in these countries. This work demonstrates the ability to develop bathymetric map of Mosul Lake by using a digital elevation model (DEM). The depths model of the lake was designed through the use of three main stages; a coastline extraction, dataset interpolation and a triangular irregular network model. The normalized difference water index (NDWI) was used for automatic delineation of the lake coastline from satellite images. The ordinary kriging interpolation with a stable model was used to interpolate the water depths dataset. Finally a triangulated irregular network (TIN) model was used to visualize the resulting interpolation model. Calculated values of area and volume of a TIN model during 2011 were compared with values of supposed initial operation of the reservoir. The differences of water volume storage between these stages at 321 m water level was about 0.81 × 109 m3, where the lake lost around 10% of storage value. Also the results of depths lake model show that the change in water storage between March and July 2011 was about 3.08 × 109 m3.
Numerical Groundwater Flow Modeling of the Coastal Plain Sand Aquifer, Akwa Ibom State, SE Nigeria  [PDF]
Aniekan Edet, Ramadan Abdelaziz, Broder Merkel, Chiedu Okereke, Therese Nganje
Journal of Water Resource and Protection (JWARP) , 2014, DOI: 10.4236/jwarp.2014.64025
Abstract:

Akwa Ibom State is located in the Niger delta region of Nigeria. The coastal plain sand aquifer, which underlies the area, is the major source of potable water for domestic, agricultural, and industrial use. The increase in demand for water has led to an increased exploitation of the aquifer in the last few years. Hence it is essential to quantify the amount of exploitable water in the aquifer. To achieve this goal, a regional numerical groundwater flow model using MODFLOW was calibrated under steady-state conditions to determine the aquifer’s hydraulic conductivity (K) and the recharge characteristics of the area. The hydraulic conductivity and recharge values from the pilot points calibration ranged from 1 to 75 m/d and 5.89 × 10-6 m3/d to1.23 × 10-4 m3/d. The calculations of the model showed that the average recharge rate amounts 0.40l/s/km2 or 12.60 mm/year. The estimated recharge suggests a high groundwater potential for the area. This is the first time that such a study has been carried out in the area, and it will serve as an important basis for future groundwater management and simulation of transient groundwater flow modeling in Akwa Ibom State.

Detecting Microsatellites in Genome Data: Variance in Definitions and Bioinformatic Approaches Cause Systematic Bias
Angelika Merkel,Neil J. Gemmell
Evolutionary Bioinformatics , 2008,
Abstract: Microsatellites are currently one of the most commonly used genetic markers. The application of bioinformatic tools has become common practice in the study of these short tandem repeats (STR). However, in silico studies can suffer from study bias. Using a meta-analysis on microsatellite distribution in yeast we show that estimates of numbers of repeats reported by different studies can differ in the order of several magnitudes, even within a single genome. These differences arise because varying definitions of microsatellites, spanning repeat size, array length and array composition, are used in different search paradigms, with minimum array length being the main influencing factor. Structural differences in the implemented search algorithm additionally contribute to variation in the number of repeats detected. We suggest that for future studies a consistent approach to STR searches is adopted in order to improve the power of intra- and interspecific comparisons
Masses of the physical mesons from an effective QCD--Hamiltonian
H. C. Pauli,J. Merkel
Physics , 1996, DOI: 10.1103/PhysRevD.55.2486
Abstract: The front form Hamiltonian for quantum chromodynamics, reduced to an effective Hamiltonian acting only in the $q\bar q$ space, is solved approximately. After coordinate transformation to usual momentum space and Fourier transformation to configuration space a second order differential equation is derived. This retarded Schr\"odinger equation is solved by variational methods and semi-analytical expressions for the masses of all 30 pseudoscalar and vector mesons are derived. In view of the direct relation to quantum chromdynamics without free parameter, the agreement with experiment is remarkable, but the approximation scheme is not adequate for the mesons with one up or down quark. The crucial point is the use of a running coupling constant $\alpha_s(Q^2)$, in a manner similar but not equal to the one of Richardson in the equal usual-time quantization. Its value is fixed at the Z mass and the 5 flavor quark masses are determined by a fit to the vector meson quarkonia.
On the Masses of the Physical Mesons: Solving the Effective QCD--Hamiltonian by DLCQ
Hans-Christian Pauli,J"org Merkel
Physics , 1995,
Abstract: The effective QCD-interaction as obtained from the front form Hamiltonian by DLCQ is Fourier transformed on the Retarded Schr\"odinger Equation for to describe the constituents of physical mesons. The crucial point is the use of a running coupling constant $\alpha_s(Q^2)$, in a manner similar but not equal to the one of Richardson in the equal usual-time quantization. Fixing the running coupling constant at the Z mass, the only parameters are the flavor masses. Without the top quark one needs thus 5 parameters to calculate the physical masses of 30 pseudoscalar and vector mesons, consistently within the same model. Applying variational methods to a caricature of the model, the biggest technical challenge is the solution of a cubic algebraic equation. -- In view of an oversimplified model and a very simple technology, the agreement with the empirical data is much too good.
Individual-Based Modelling Potentials and Limitations
Broder Breckling
The Scientific World Journal , 2002, DOI: 10.1100/tsw.2002.179
Abstract:
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