Institute of Applied Geosciences

Darmstadt, Germany

Institute of Applied Geosciences

Darmstadt, Germany
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Hergert T.,Karlsruhe Institute of Technology | Hergert T.,Institute of Applied Geosciences | Heidbach O.,German Research Center for Geosciences | Reiter K.,German Research Center for Geosciences | And 4 more authors.
Solid Earth | Year: 2015

The stress field at depth is a relevant parameter the design of subsurface constructions and reservoir management. Yet the distortion of the regional stress field due to features such as sedimentary and tectonic structures or topography is often poorly constrained. We conduct stress sensitivity analysis using 3-D numerical geomechanical modelling with an elasto-plastic material law to explore impact of such site-specific features on the stress field in sedimentary sequence of the Swiss Alpine foreland. The dimensions are 14 × 14 × 3 km3 and it contains 10 with different mechanical properties, intersected by two fault zones. An initial stress state is established involving a semi-empirical relationship between the ratio of to vertical stress and the overconsolidation ratio of sediments. The model results indicate that local can affect the stress field significantly to depths than the relief contrasts at the surface, especially in with horizontal tectonic loading. The complexity frictional properties of faults are also relevant. The greatest variability of the stress field arises across the different units. Stress magnitudes and stress anisotropy much larger in stiffer formations such as massive limestones than in softer argillaceous formations. The stiffer formations essentially carry the load of the far-field forces and therefore more sensitive to changes of the boundary conditions. This general characteristic of stress distribution in stiff and soft formations is broadly maintained also with loading towards the plastic limit. The stress field argillaceous sediments within a stack of formations with contrasting mechanical properties like in the Alpine appears to be relatively insensitive to changes in the boundary conditions and is largely controlled by the stiffness contrast with respect to the load-bearing formation. © Author(s) 2015.

Chen H.-F.,Institute of Applied Geosciences
Geochemistry, Geophysics, Geosystems | Year: 2016

X-ray fluorescence (XRF) core-scanning is a fast and nondestructive technique to assess elemental variations of unprocessed sediments. However, although the exposure time of XRF-scanning directly affects the scanning counts and total measurement time, only a few studies have considered the influence of exposure time during the scan. How to select an optimal exposure time to achieve reliable results and reduce the total measurement time is an important issue. To address this question, six geological reference materials from the Geological Survey of Japan (JLK-1, JMS-1, JMS-2, JSD-1, JSD-2, and JSD-3) were scanned by the Itrax-XRF core scanner using the Mo- and the Cr-tube with different exposure times to allow a comparison of scanning counts with absolute concentrations. The regression lines and correlation coefficients of elements that are generally used in paleoenvironmental studies were examined for the different exposure times and X-ray tubes. The results show that for those elements with relatively high concentrations or high detectability, the correlation coefficients are higher than 0.90 for all exposure times. In contrast, for the low detectability or low concentration elements, the correlation coefficients are relatively low, and improve little with increased exposure time. Therefore, we suggest that the influence of different exposure times is insignificant for the accuracy of the measurements. Thus, caution must be taken when interpreting the results of elements with low detectability, even when the exposure times are long and scanning counts are reasonably high. © 2016. American Geophysical Union.

Augustin-Bauditz S.,Leibniz Institute for Tropospheric Research | Wex H.,Leibniz Institute for Tropospheric Research | Denjean C.,Leibniz Institute for Tropospheric Research | Denjean C.,National Center for Meteorological Research | And 5 more authors.
Atmospheric Chemistry and Physics | Year: 2016

Biological particles such as bacteria, fungal spores or pollen are known to be efficient ice nucleating particles. Their ability to nucleate ice is due to ice nucleation active macromolecules (INMs). It has been suggested that these INMs maintain their nucleating ability even when they are separated from their original carriers. This opens the possibility of an accumulation of such INMs in soils, resulting in an internal mixture of mineral dust and INMs. If particles from such soils which contain biological INMs are then dispersed into the atmosphere due to wind erosion or agricultural processes, they could induce ice nucleation at temperatures typical for biological substances, i.e., above-20 up to almost 0 °C, while they might be characterized as mineral dust particles due to a possibly low content of biological material. We conducted a study within the research unit INUIT (Ice Nucleation research UnIT), where we investigated the ice nucleation behavior of mineral dust particles internally mixed with INM. Specifically, we mixed a pure mineral dust sample (illite-NX) with ice active biological material (birch pollen washing water) and quantified the immersion freezing behavior of the resulting particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). A very important topic concerning the investigations presented here as well as for atmospheric application is the characterization of the mixing state of aerosol particles. In the present study we used different methods like single-particle aerosol mass spectrometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray analysis (EDX), and a Volatility-Hygroscopicity Tandem Differential Mobility Analyser (VHTDMA) to investigate the mixing state of our generated aerosol. Not all applied methods performed similarly well in detecting small amounts of biological material on the mineral dust particles. Measuring the hygroscopicity/volatility of the mixed particles with the VH-TDMA was the most sensitive method.We found that internally mixed particles, containing ice active biological material, follow the ice nucleation behavior observed for the pure biological particles. We verified this by modeling the freezing behavior of the mixed particles with the Soccerball model (SBM). It can be concluded that a single INM located on a mineral dust particle determines the freezing behavior of that particle with the result that freezing occurs at temperatures at which pure mineral dust particles are not yet ice active. © 2016 Author(s).

Chang P.Y.,Institute of Applied Geosciences | Chen Y.W.,National Chiao Tung University | Tsai J.P.,National Chiao Tung University | Chang L.-C.,National Chiao Tung University | And 3 more authors.
Journal of the Chinese Institute of Civil and Hydraulic Engineering | Year: 2013

Hydraulic conductivity (K) is an important aquifer parameter and is usually obtained using conventional pumping test. However, only limited amount of data can be collected, because pumping test is time consuming and expensive. In recent years, some studies estimated K by using pumping test data and surface electrical resistivity survey. These studies cost less because less pumping tests are required. However, majority of these studies don't consider the effects caused by layers of clay. In fact, clay layers are commonly distributed in middle-fan and distal-fan. Therefore, this study divides Zhuoshui River Alluvial Fan into several zones based on the sediment distribution. A linear regression equation is derived from the pumping test data and formation factors for each zone. This study applied these equations to develop the distribution of K in the shallow aquifer of major fan, which is bounded by the Old Zhuoshui River at the north side and by New Hu-Wei River at the south side. The result shows that the shallow aquifer of the major fan of Zhuoshui River can be divided into two zones, which are top-fan and non-top-fan areas. The regression results show good correlation between K and the formation factor in each zone. These regression equations are then used to estimate K in the study area. The results are compared between the field measurement and the results obtained from Khalil's equations. The results indicate that the estimation error, between 11 m/day and 58 m/day, is much smaller than the estimation error obtained using Khalil's equation. The developed methodology for estimating K can contribute to related groundwater research and can be applied to other alluvial fans with similar sediment distribution to this study area.

Hamed Y.,P.A. College | Ahmadi R.,P.A. College | Ahmadi R.,Institute of science and Technology of Water of Gabes | Mokadem N.,P.A. College | And 2 more authors.
Desalination and Water Treatment | Year: 2014

The expansion of irrigated agriculture and the overexploitation of groundwater aquifers are leading to saltwater intrusion, severe deterioration of groundwater quality and soil subsidence at arid areas. The geochemical processes taking place along an 800 km flow line in the non-carbonate Continental Intercalaire aquifer (CI) in North Africa are described using chemical (major and trace element) and isotopic indicators. The aquifer is hydraulically continuous from the Atlas Mountains in Algeria to the Chotts of Tunisia and the geochemical evidence corroborates this. The CI aquifer of North Africa is one of the largest confined aquifers in the world. The aquifer is hydraulically continuous from the Atlas Mountains in Algeria (recharge area) to the Chotts of Tunisia (discharge area) and the geochemical evidence corroborates this. The isotopic study (Delta18O, Delta2H) permits classifying groundwater into three groups. The first group is characterized by low 3H concentrations, low 14C activities and depleted stable isotope contents. It corresponds to an old end-member in relation with palaeoclimatic recharge which occurred during the Late Pleistocene and the Early Holocene humid periods. The second group is distinguished by high to moderate 3H concentrations, high 14C activities and enriched heavy isotope signatures. It corresponds to a modern end-member originating from a mixture of post-nuclear and present-day recharge in relation to return flow of irrigation. The third group is characterized by an average composition of stable and radiogenic isotope signatures. It provides evidence for the mixing between the upward moving palaeoclimatic end-member and the downward moving present-day end-member. Rainfall, originating from a mixture of Atlantic and Mediterranean air masses. Balaban Desalination Publications. All rights reserved.

Ruhaak W.,TU Darmstadt | Bar K.,Institute of Applied Geosciences | Sass I.,Institute of Applied Geosciences
Energy Procedia | Year: 2014

Subsurface temperature is one of the key parameters in geothermal exploration. The estimation of the reservoir temperature is of high importance and usually done either by interpolation of temperature data or numerical modeling. However, temperature measurements of depths larger than a few hundred meters are generally very sparse. A pure interpolation of such sparse data always involves big uncertainties and usually neglects knowledge of the reservoir geometry or reservoir properties. Kriging with trend does allow including secondary data to improve the interpolation of the primary one. Using this approach temperature measurements of depths larger than 1,000 m of the federal state of Hessen/Germany have been interpolated in 3D. A conductive numerical 3D temperature model was used as secondary information. This way the interpolation result reflects also the geological structure. As a result the quality of the estimation improves considerably. © 2014 The Authors.

PubMed | CNR Institute of Science and Technology for Ceramics, Missouri University of Science and Technology and Institute of Applied Geosciences
Type: | Journal: Scientific reports | Year: 2017

Ceramics based on group IV-V transition metal borides and carbides possess melting points above 3000C, are ablation resistant and are, therefore, candidates for the design of components of next generation space vehicles, rocket nozzle inserts, and nose cones or leading edges for hypersonic aerospace vehicles. As such, they will have to bear high thermo-mechanical loads, which makes strength at high temperature of great importance. While testing of these materials above 2000C is necessary to prove their capabilities at anticipated operating temperatures, literature reports are quite limited. Reported strength values for zirconium diboride (ZrB

Augustin-Bauditz S.,Leibniz Institute for Tropospheric Research | Wex H.,Leibniz Institute for Tropospheric Research | Kanter S.,Leibniz Institute for Tropospheric Research | Ebert M.,Institute of Applied Geosciences | And 6 more authors.
Geophysical Research Letters | Year: 2014

In this study we present results from immersion freezing experiments with size-segregated mineral dust particles. Besides two already existing data sets for Arizona Test Dust (ATD), and Fluka kaolinite, we show two new data sets for illite-NX, which consists mainly of illite, a clay mineral, and feldspar, a common crustal material. The experiments were carried out with the Leipzig Aerosol Cloud Interaction Simulator. After comparing the different dust samples, it became obvious that the freezing ability was positively correlated with the K-feldspar content. Furthermore, a comparison of the composition of the ATD, illite-NX, and feldspar samples suggests that within the K-feldspars, microcline is more ice nucleation active than orthoclase. A coating with sulfuric acid leads to a decrease in the ice nucleation ability of all mineral dusts, with the effect being more pronounced for the feldspar sample. Key Points The freezing ability of mineral dusts correlated with the K-feldspar contentAmong feldspars, microcline shows a better ice nucleation ability than orthoclaseAfter coating, all investigated dusts feature a similar ice nucleation ability ©2014. The Authors.

Al-Zyoud S.,Institute of Applied Geosciences | Ruhaak W.,Institute of Applied Geosciences | Sass I.,Institute of Applied Geosciences
Renewable Energy | Year: 2014

Geothermal energy has the potential to significantly contribute to the cooling of buildings. A shallow aquifer system in north east Jordan was proven as a geothermal resource for its efficiency for cooling utilization. A numerical 3D model was developed in order to predict the future performance of the geothermal cooling reservoir. Different possible geothermal installations were studied, using various approaches. The study shows that a geothermal utilization of the respective basaltic reservoir is feasible. It features sufficient hydraulic and thermal properties to be utilized for cooling purposes. The developed model has proven to be robust and flexible. It can be easily extended for analyzing other sites. © 2013 Elsevier Ltd.

Mundhenk N.,Institute of Applied Geosciences | Huttenloch P.,Institute for Energy Research of Germany | Kohl T.,Institute of Applied Geosciences | Steger H.,Institute of Applied Geosciences | Zorn R.,Institute for Energy Research of Germany
Transactions - Geothermal Resources Council | Year: 2012

A major factor in the economic exploitation of geothermal resources will be the cost-effective selection of materials that have sufficient resistance to corrosion to maintain component integrity during plant operation. Various metals have been tested in laboratory and in-situ weight-loss exposure tests (Soultz-sous-Forêts) and instrumented exposure (electrochemical polarization) in geothermal brine from Soultz-sous-Forêts, France. Mild steels (N80, P110, P235GH and P265GH) are subject to corrosion. However, the formation of secondary corrosion products (mainly FeCO3) contributes to materials corrosion resistance and reduces the corrosion rate over time. Potentiodynamic polarization has been used to study the passivation tendency of stainless steels and alloys, showing good agreement with exposure tests. 430F showed pitting after 4 weeks of in in-situ and autoclave exposure, while higher-strength materials (316L, 318L, 904L, alloy 31 and Ti grade 2) showed no obvious sign of surface degradation and/or scaling.

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