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Global production of soybeans continues to increase, reflecting the value of soybeans in food products, soil amendments, and petroleum replacements. While the N2O aspect of the legume greenhouse gas (GHG) budget has been given substantial, and mostly negative, attention, the CO2 side needs to be explored. During nitrogen fixation, hydrogen is produced. As a result of hydrogen-coupled CO2 fixation, legume soils have the ability to increase the amount of atmospheric carbon fixed into the soil. However, the amount and fate of this fixed carbon has yet to be determined. Therefore, two experiments were conducted. The first experiment explored the methods of 13C labeling of four soil treatments over a period of 28 days. Results showed that most of this carbon uptake was through biotic processes, and that the pattern of carbon uptake was similar for all four soil treatments. The ideal labeling time for both ‘root’ and ‘nodule’ soil was determined to be between 7 and 14 days. The second experiment incubated four 13C labeled soil treatments in a continuous soybean field for 11 months. Throughout this time, bags of soil were removed and separated into three soil organic matter (SOM) fractions; the microbial biomass fraction (MBF), the light fraction (LF), and the acid stable fraction (ASF). These fractions were then measured for δ13C, providing a time series showing carbon movement through the soil which enabled an estimation of the MRT of fixed carbon in the soil. Results showed that the MBF was responsible for the initial flux of carbon uptake in all soil treatments, and that the ‘nodule + H2’ MBF continued to fix carbon at the end of the 11 months. While the LF was not ideal at representing the intermediate SOM pool, the ASF did increase in enrichment at the end of the experiment, showing the movement of newly fixed carbon into long-term carbon storage. Therefore, hydrogen-coupled CO2 fixation does contribute to long-term carbon storage in legume soils, however, longer study times with focus on different legume plants and soil types are required to determine the mean residence time (MRT) of fixed carbon in the ASF. / Thesis (Master, Geography) -- Queen's University, 2013-01-30 09:28:01.899

Summary Coupled spring equations for modelling the motion of two springs with weights attached, hung in series from the ceiling are described. For the linear model using Hooke’s Law, the motion of each weight is described by a fourthorder linear differential equation. A nonlinear model is also described and damping and external forcing are considered. The model has many features that permit the meaningful introduction of many concepts including: accuracy of numerical algorithms, dependence on parameters and initial conditions, phase and synchronization, periodicity, beats, linear and nonlinear resonance, limit cycles, harmonic and subharmonic solutions. These solutions produce a wide variety of interesting motions and the model is suitable for study as a computer laboratory project in a beginning course on differential equations or as an individual or a small-groupundergraduate research project.

The engineering problems in Geomechanics and Geotechnical fields are commonly treated through the infinite or semi-infinite media. The best approach to solve these problems numerically is by coupling a finite element or a finite difference with boundary element numerical methods. Coupling the bounded domain modelled by Flac3D, a well-known program that implements an explicit finite difference method, with the boundary element method, which satisfies exactly the governing Partial Differential Equations (PDE) in the surrounding infinite or semi-infinite medium, combines the capabilities and the advantages of both methods. The Domain Decomposition Method (DDM) partitions the task of solving the PDE into separate computations over the coupled sub-domains. This method allows the FDM (Flac3D program) and the Boundary Element Method (BEM) program to work independently and interactively. In contrast, at the level of discretized equations, the coupling method requires building a complicated unified system of equations. Therefore, a Domain Decomposition Sequential Dirichlet-Neumann Iterative Coupling Method is developed in this thesis to couple both programs. The method is applied in four cases, 2D and 3D infinite and semi-infinite domains, using the appropriate fundamental solutions in the Boundary Integral Equation required for each case. After applying this method, the mechanical responses computed by Flac3D is corrected and the same responses far from the bounded domain are computed with less computer runtime (CPU) compared with the uncoupled Flac3D solution. The method is also verified by comparing the obtained numerical results with the corresponding analytical solutions. Two BEM pre and post processing intrinsic plug-ins are created, which provide access to the data of Flac3D, as well as the internal structure of the programming language embedded within Flac3D program. These intrinsics are 10 to 100 times faster to execute than the functions created using the Flac3D embedded language. Furthermore, the complementary part of the Kernels is derived based on Mindlin's fundamental solutions. These Kernels are required to compute the stress inside the 3D semi-infinite domain.

In this work, we studied the optical characteristics of the coupled double DBR structure. We use the conventional transfer matrix simulation to find the intermediate multilayer periods (NC), and control the position of the transmission peak and stop band. Sample is grown by solid source molecular beam epitaxy (MBE) on n+GaAs (001) substrate, and the InGaAs QDs (quantum dots) are grown in the coupled cavity structure. The 23 periods of DBR multilayer, GaAs (91.8 nm) / AlAs (108.1 nm), obtain 99.5% reflectivity in the 1260 nm wavelength by the simulation. After the simulation from the conventional transfer matrix method, we choose NC = 13.5, the position of the transmission peak are at 1177 and 1188 nm, and optical frequency difference = 2.27 THz (£G=11 nm) in this study.From PL spectra, we observed interference between the enhanced light fields of the two cavity modes and the agreement between measurement and simulation. This structure is potential to be a compact terahertz emission device or vertical cavity surface emitting laser in room temperature.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also in a digital version from Dissertation Abstracts.

Zugl.: Karlsruhe, Univ., Diss., 2009 / Hergestellt on demand. - Zusätzliches Online-Angebot unter http://uvka.ubka.uni-karlsruhe.de/shop/isbn/978-3-86644-392-1

abstract / Chemistry / Doctoral / Doctor of Philosophy

Not available / text

One of the main objectives in the Oil & Gas Industry is to constantly improve the reservoir management capabilities by using production optimization strategies that can positively impact the so-called net-present value (NPV) of a given project. In order to achieve this goal the industry is faced with the difficult task of maximizing hydrocarbon production and minimizing unwanted fluids, such as water, while sustaining or even enhancing the reservoir recovery factor by handling properly the fluids at surface facilities. A key element in this process is the understanding of the interactions between subsurface and subsurface dynamics in order to provide insightful production strategies which honor reservoir management surface facility constraints. The implementation of the ideal situation of fully coupling surface/subsurface has been hindered by the required computational efforts involved in the process. Consequently, various types of partially coupling that require less computational efforts are practically implemented. Due to importance of coupling surface and subsurface model on production optimization and taking the advantage of advancing computational performance, this research explores the concept of surface and subsurface model couplings and production optimization. The research aims at demonstrating the role of coupling of surface and subsurface model on production optimization under simple production constraint (i.e. production and injection pressure limit). The normal production prediction runs with various reservoir description (homogeneous-low permeability, homogeneous-high permeability, and heterogeneous permeability) and different fluid properties (dead-oil PVT and lived-oil PVT) were performed in order to understand the effect of coupling level, and coupling scheme with different reservoir descriptions and fluid properties on production and injection rate prediction. The result shows that for dead-oil PVT, the production rate from different coupling schemes in homogeneous and heterogeneous reservoir is less sensitive than lived-oil PVT cases. For lived-oil PVT, the production rate from different coupling schemes in homogeneous high permeability and heterogeneous permeability are more sensitive than homogeneous low permeability. The production optimization on water flooding under production and injection constraint cases is considered here also.