Cellular Automata (CA) for Simulations of Complex Geothermal Reservoirs

The exploitation of geothermal power is a renewable energy source with great potential in future. But the exploration and development of deep geothermal energy is connected with high cost and risk. These require a reliable functionality of geological heat exchanger. However the geothermal reservoirs are really complicated as phenomena and concrete downhole data are not completely discovered at present. In order to simulate them, complex modelings combined with different time scale are necessary. Recently, the cellular automata (CA) method is being developed and widely used for solving many complex problems in different fields. Here we introduced CA method combined with Navier-Stoke equation and heat transfer; the domains of reservoirs are initially discretized into many lattice cells. The different cell type and their physical properties (e.g. water cell, porous cell, etc.) are introduced. Thermodynamically correct computation and computing fluid flow in different formations are performed. The paper will give some computational results, showing the efficiency and accuracy of this method, in order to complete the phenomena of complex geothermal problem. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multi-Fracture Reservoir Simulations for Long Time Physical Processes

Reservoirs with multi-fracture techniques are developed and frequently used for oil and gas industry. Recently, they are also used for deep geothermal reservoirs especially for Hot Dry Rock (HDR). The analysis of the reservoir is generally interested in long time physical properties (10–100 years), e.g. fluid flow, heat transport etc. Typical CFD simulations are limited in this context. Here we developed a fluid flow and heat transport modeling in a multi-fracture reservoir based on the so-called Mixed Dimensional Model (MDM), which describes the different characteristic flows and the heat transport in different dimensions. In the mathematical point of view, these models are discretized based on the Cellular Automaton (CA) method combined with other necessary numerical techniques. The different cases of fluid flow and heat transport in multi-fracture reservoirs have been simulated and shown physical results very reasonably with less computational time. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Engineering Non‐sintered,Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Transition‐metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide‐scale use as catalysts. A method is presented for the production of metal‐terminated TMC nanoparticles in the 1–4 nm range with tunable size, composition, and crystal phase. Carbon‐supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo_xW_1−xC) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100‐fold higher than commercial WC and within an order of magnitude of platinum‐based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.     

On the Wellbore Contact of Drill Strings in a Finite Element Model

In drill string dynamics the Finite Element Method is usually applied to models of very long drill strings in a wellbore with arbitrary curvature. Taking account of geometrical constraint between the drill string and the wellbore, a high density of nodes is necessary. This density is much higher than the one needed to describe the natural vibrations properly, so this firstly leads to an extension of the computing time. A penalty function is frequently utilized to describe the contact problem between the drill string and the wellbore where the contact normal force acts only on the nodal points of the drill string. It was recognized that only node-to-surface contact models cannot fulfill this geometrical constraint, because the segment between two nodal points deeply penetrates the wellbore wall in some cases. A process with Gaussian points along the segment in time domain will be introduced, so that the drill string will be described according to this geometrical constraint with good accuracy but with a smaller density of nodes and less computing time. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Wearing the Letter Jacket: Legitimate Participation in a Collaborative Science,Mathematics, Engineering,and Technology Education Reform Project

This study examines one NSF‐funded Collaborative for Excellence in Teacher Preparation and describes the complexities of such a science education reform effort. A theoretical model based in community, culture, and identity is used to address key questions: How did institutional ideologies, structures, policies, and practices influence the Collaborative's success? What unique problems were associated with the university and school partnership? How did K‐12 teachers' participation affect their development and the success of the Collaborative? Findings indicate that though K‐12 participants were deemed as “pedagogy experts” and shared the inquiry‐based culture espoused in the Collaborative, they felt both as project insiders and outsiders. This was due to issues of status between university faculty and K‐12 teachers; teachers' less‐than‐active role in the Collaborative; and the constraints and narrow focus that resulted from long‐established institutional, social, and political structures and that marginalized, delegitimized, excluded, and proved unattractive to teachers.     

Mössbauer spectroscopy on57Fe: NaCl crystals

Mössbauer absorbtion spectra of⁵⁷Fe-doped NaCl crystal were measured and correlated with an adequate electric field gradient computation to describe the dipolar complexes occuring at the decay of Suzuki-phase under thermal treatment and X-ray irradiation. An electrostatic potential of the type was taken into account in the evaluation of EFG tensor.     

Mössbauer spectroscopy on57Fe in highT c superconductor Bi2Sr2Ca1Cu2O y

Mössbauer measurements were performed on polycrystalline⁵⁷Fe: Bi₂Sr₂Ca₁Cu₂O _y , super-conductor in the temperature range of 77–296 K. The samples were obtained in a solid phase synthesis using 0.01, 0.03, 0.1 and 0.5 mol fractions of α-Fe₂O₃ (96% enriched in⁵⁷Fe). A prevailing quadrupole doublet practically independent of temperature and iron concentration characterizes the obtained Mössbauer spectra. The corresponding hyperfine parameters suggest the presence of high spin Fe¹¹¹ ions in a strongly distorted octahedral symmetry which indicates a probable copper substitution by iron in the system.     

Engineering Non‐sintered,Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Transition‐metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide‐scale use as catalysts. A method is presented for the production of metal‐terminated TMC nanoparticles in the 1–4 nm range with tunable size, composition, and crystal phase. Carbon‐supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo_xW_1?xC) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100‐fold higher than commercial WC and within an order of magnitude of platinum‐based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.