Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

National Institute of Standards and Technology における超伝導研究及び生活

To investigate the initial chemical events associated with high-temperature gas-phase oxidation of hydrocarbons, we have expanded the ReaxFF reactive force field training set to include additional transition states and chemical reactivity of systems relevant to these reactions and optimized the force field parameters against a quantum mechanics (QM)-based training set. To validate the ReaxFF potential obtained after parameter optimization, we performed a range of NVT−MD simulations on various hydrocarbon/O2 systems. From simulations on methane/O2, o-xylene/O2, propene/O2, and benzene/O2 mixtures, we found that ReaxFF obtains the correct reactivity trend (propene > o-xylene > methane > benzene), following the trend in the C−H bond strength in these hydrocarbons. We also tracked in detail the reactions during a complete oxidation of isolated methane, propene, and o-xylene to a CO/CO2/H2O mixture and found that the pathways predicted by ReaxFF are in agreement with chemical intuition and our QM results. We o...

ReaxFF Reactive Force Field for Molecular Dynamics Simulations of Hydrocarbon Oxidation

https://www3.nd.edu/~powers/ame.60636/maas1992.pdf

Simplifying chemical kinetics: Intrinsic low-dimensional manifolds in composition space

Introduction * Fundamental Definitions and Phenomena * Experimental Investigation of Flames * Mathematical Description of Premixed Laminar Flat Flames * Thermodynamics of Combustion Processes * Transport Phenomena * Chemical Kinetics * Reaction Mechanisms * Laminar Prefixed Flames * Laminar Nonpremixed Flames * Ignition Processes * The Navier-Stokes Equations for Three-Dimensional Reacting Flows * Turbulent Reacting Flows * Turbulent Nonpremixed Flames * Turbulent Premixed Flames * Combustion of Liquid and Solid Fuels * Low-Temperature Oxidation, Engine Knock * Formation of Nitric Oxides * Formation of Hydrocarbons and Soot.

Combustion: Physical and Chemical Fundamentals, Modelling and Simulation, Experiments, Pollutant Formation

https://www3.nd.edu/~powers/ame.60636/maas1988.pdf

Ignition processes in hydrogenoxygen mixtures

A general procedure for simplifying chemical kinetics and its use in reacting flow models is developed, which is based on the dynamical systems approach. In contrast to conventional reduced mechanisms no information is required concerning which reactions are to be assumed to be in partial equilibrium nor which species are assumed to be in steady state. Based on a local eigenvector analysis, the method identifies the fast time scales of the chemical reaction systems, which differ typically by orders of magnitude. Assuming that the fastest relaxation processes in chemical reactions proceed infinitely fast (i.e., are in local equilibrium), it is then possible to reduce the state space globally, such that it can be described by means of only a small number of reaction progress variables. The only “inputs” to the procedure are the detailed kinetics mechanism and the number of degrees of freedom required in the simplified scheme. Then the state properties given by the simplified scheme are automatically determined as functions of the coordinates associated with the degrees of freedom. A tabulation procedure allows an efficient use of the results in CFD codes. Furthermore a general procedure for coupling the reduced mechanism with other than chemical processes like flow and molecular transport is discussed. Results are presented for the CO/H2/air system both for a simple homogeneous closed system and a flow reactor.

Implementation of simplified chemical kinetics based on intrinsic low-dimensional manifolds

In the present work, the method of simplifying chemical kinetics based on Intrinsic Low-Dimensional Manifolds (ILDMs) is modified to deal with the coupling of reaction and diffusion processes. Several problems of the ILDM method are overcome by a relaxation to an invariant system manifold (Reaction–Diffusion Manifold – REDIM). This relaxation process is governed by a multidimensional parabolic partial differential equation system, where, as an initial solution, an extended ILDM is used. Furthermore, a method for the solution and tabulation of the manifold is proposed in terms of generalized coordinates, with a subsequent procedure for the integration of the reduced system on the found manifold. This modification of the ILDM significantly improves the performance of the concept and allows us to extend its area of applicability. Illustrative comparative calculations of detailed and reduced models of flat laminar flames verify the approach.

Ulrich Maas

Papers

Simplifying chemical kinetics: Intrinsic low-dimensional manifolds in composition space

Combustion: Physical and Chemical Fundamentals, Modelling and Simulation, Experiments, Pollutant Formation

Ignition processes in hydrogenoxygen mixtures

Implementation of simplified chemical kinetics based on intrinsic low-dimensional manifolds

The extension of the ILDM concept to reaction–diffusion manifolds