Reaction kinetics of methanol and MTBE oxidation and pyrolysis

This study presents experimental data on the decomposition of methanol in several different reaction environments - fuel lean to stoichiometric at a temperature range of 873 and 1073 K and a pressure range of I and 5 atm. Methane fuel is also added in several of the systems studied in order to provide experimental data to understand the methanol addition effect on the methane oxidation. Computer codes: ThermCal, ThermSrt and ThermCvt have been developed for the thermal property calculations of stable molecules by the Benson group additivity method and of radicals by the NJIT hydrogen bond increment method. Pressure dependent rate coefficients have been expressed using Chebyshev polynomials adopted for complex chemical activated reaction systems in this study, as well as unimolecular decomposition reactions. This method has also been tested and shows significant improvement over two convention methods, Troe\u27s and SRI. The Levenberg-Marquardt algorithm has been incorporated with the QRRK code, CHEMACT, for the fitting of Chebyshev polynomials. A pressure dependent mechanism which consists 147 species and 448 elementary reactions, based on thermochemical kinetic principals has been developed and calibrated by the experimental data. The reaction mechanisms (models) include pathways for formation of higher molecular weight products, such as the formation of methyl ethers. This accurate model based on principles of thermochemical kinetics and statistical mechanics will not only provide fundamental understanding, but can be used to suggest directions toward process optimization for experimental testing. A pressure dependent mechanism which consists 147 species and 448 elementary reactions, based on thermochemical kinetic principals has been developed and calibrated by the experimental data. The reaction mechanisms (models) include pathways for formation of higher molecular weight products, such as the formation of methyl ethers. This accurate model based on principles of thermochemical kinetics and statistical mechanics will not only provide fundamental understanding, but can be used to suggest directions toward process optimization for experimental testing. The mechanism is validated with methanol oxidation and pyrolysis experimental data and serves as a basis to build upon during the subsequent efforts on higher molecular weight oxygenated hydrocarbon (MTBE in this study). The methanol addition shows dramatic acceleration effect on the methane oxidation experimentally and predicted by the model

Research and Education in Computational Science and Engineering

Over the past two decades the field of computational science and engineering (CSE) has penetrated both basic and applied research in academia, industry, and laboratories to advance discovery, optimize systems, support decision-makers, and educate the scientific and engineering workforce. Informed by centuries of theory and experiment, CSE performs computational experiments to answer questions that neither theory nor experiment alone is equipped to answer. CSE provides scientists and engineers of all persuasions with algorithmic inventions and software systems that transcend disciplines and scales. Carried on a wave of digital technology, CSE brings the power of parallelism to bear on troves of data. Mathematics-based advanced computing has become a prevalent means of discovery and innovation in essentially all areas of science, engineering, technology, and society; and the CSE community is at the core of this transformation. However, a combination of disruptive developments---including the architectural complexity of extreme-scale computing, the data revolution that engulfs the planet, and the specialization required to follow the applications to new frontiers---is redefining the scope and reach of the CSE endeavor. This report describes the rapid expansion of CSE and the challenges to sustaining its bold advances. The report also presents strategies and directions for CSE research and education for the next decade.Comment: Major revision, to appear in SIAM Revie

Toward improved calibration of hydrologic models: Combining the strengths of manual and automatic methods

Automatic methods for model calibration seek to take advantage of the speed and power of digital computers, while being objective and relatively easy to implement. However, they do not provide parameter estimates and hydrograph simulations that are considered acceptable by the hydrologists responsible for operational forecasting and have therefore not entered into widespread use. In contrast, the manual approach which has been developed and refined over the years to result in excellent model calibrations is complicated and highly labor-intensive, and the expertise acquired by one individual with a specific model is not easily transferred to another person (or model). In this paper, we propose a hybrid approach that combines the strengths of each. A multicriteria formulation is used to "model" the evaluation techniques and strategies used in manual calibration, and the resulting optimization problem is solved by means of a computerized algorithm. The new approach provides a stronger test of model performance than methods that use a single overall statistic to aggregate model errors over a large range of hydrologic behaviors. The power of the new approach is illustrated by means of a case study using the Sacramento Soil Moisture Accounting model

Building the new international science of the agriculture–food–water–environment nexus in China and the world

The multiple, complex and systemic problems of the agriculture–food–water–environment nexus (“Nexus”) are among the most significant challenges of the 21st century. China is a key site for Nexus research amidst profound socio-environmental problems. The policy implications of these problems have been authoritatively summarized elsewhere. This study presents discussions at an international workshop in Guangzhou that asked instead “What science is needed to deliver the growing policy commitments regarding these challenges? And, What changes are needed to the science itself?” Understanding and effective intervention regarding the Nexus calls for a paradigm shift: to a new kind of science of (capacity for) international, interdisciplinary, and impactful research working with and within complex socio-natural systems. We here argue that science must become proactive in approach, striving only for “minimal harm” not “silver bullet” solutions, and adopting an explicitly long-term strategic perspective. Together, these arguments lead to calls for reorienting science and science policy in three ways: from short-term remediation to longer-term optimization; from a focus on environmental threats to one on the opportunities for international collaborative learning; and toward supporting new forms of scientific career. We bring these points together by recommending a new form of scientific institution: a global network of collaborative Nexus Centres, under the umbrella of a global Food Nexus Organization akin to those of the human genome and proteome