Dynamic modeling and analysis of proton exchange membrane fuel cells for control design

This dissertation seeks to address a number of issues facing the advancement of Proton Exchange Membrane (PEM) fuel cell technology by improving control-oriented modeling strategies for these systems. Real-time control is a major ongoing challenge for PEM fuel cell technologies, particularly with regards to water and temperature dynamics. This can lead to a number of operational concerns, such as membrane flooding and dehydration, which can seriously diminish the efficiency, reliability, and long term health of the system. To combat these issues, comprehensive models that are capable of capturing the dynamics of the key operating conditions and can be processed in real time are needed. Also, given the inherently distributed nature of the system, such a model would ideally account for the changes in the conditions from cell-to-cell in the stack, which can be very significant. With this goal in mind, the main focus of this dissertation is the development and experimental validation of control-oriented modeling techniques for PEM fuel cell stacks. The first major work in this study was the verification of a relative humidity model in response to varying loads. Through this work, a multiple control volume (CV) approach was developed and experimentally validated to model the distribution of operating conditions more accurately while keeping the computational expense sufficiently low. To optimize the modeling efforts, further analysis of the temperature and vapor distribution was performed starting from first principles. This led to the creation of various techniques to optimally size CVs based on the parameters and operating conditions of the system in question. Finally, it was noted throughout the testing that the performance of the membrane electrolyte assemblies in the test stack declined significantly from their initial state. To compensate for this, a Kalman filter was implemented to quantify the membrane degradation. SEM analysis of membranes from the test stack confirmed the validity of this technique. This work can be used to significantly improve real-time models for PEM fuel cells for model-based control applications.Mechanical Engineerin

Economic strategies for coping with black cutworms in Northwest Missouri

Cover title."April, 1983."Includes bibliographical references (pages 30-31)

Large Area Scene Selection Interface (LASSI). Methodology of Selecting Landsat Imagery for the Global Land Survey 2005

The Global Land Survey (GLS) 2005 is a cloud-free, orthorectified collection of Landsat imagery acquired during the 2004-2007 epoch intended to support global land-cover and ecological monitoring. Due to the numerous complexities in selecting imagery for the GLS2005, NASA and the U.S. Geological Survey (USGS) sponsored the development of an automated scene selection tool, the Large Area Scene Selection Interface (LASSI), to aid in the selection of imagery for this data set. This innovative approach to scene selection applied a user-defined weighting system to various scene parameters: image cloud cover, image vegetation greenness, choice of sensor, and the ability of the Landsat 7 Scan Line Corrector (SLC)-off pair to completely fill image gaps, among others. The parameters considered in scene selection were weighted according to their relative importance to the data set, along with the algorithm's sensitivity to that weight. This paper describes the methodology and analysis that established the parameter weighting strategy, as well as the post-screening processes used in selecting the optimal data set for GLS2005

Post-poliomyelitis syndrome as a possible viral disease

Summary This review summarizes current concepts on post-polio syndrome (PPS), a condition that may arise in polio survivors after partial or complete functional recovery followed by a prolonged interval of stable neurological function. PPS affects 15–20 million people worldwide. Epidemiological data are reported, together with the pathogenic pathways that possibly lead to the progressive degeneration and loss of neuromuscular motor units. As a consequence of PPS, polio survivors experience new weakness, generalized fatigue, atrophy of previously unaffected muscles, and a physical decline that may culminate in the loss of independent life. Emphasis is given to the possible pathogenic role of persistent poliovirus infection and chronic inflammation. These factors could contribute to the neurological and physical decline in polio survivors. A perspective is then given on novel anti-poliovirus compounds and monoclonal antibodies that have been developed to contribute to the final phases of polio eradication. These agents could also be useful for the treatment or prevention of PPS. Some of these compounds/antibodies are in early clinical development. Finally, current clinical trials for PPS are reported. In this area, the intravenous infusion of normal human immunoglobulins appears both feasible and promising

Characterization of oil sands naphthenic acids by negative-ion electrospray ionization mass spectrometry : influence of acidic versus basic transfer solvent

Considerable effort and progress has been made over the past decade with respect to development of analytical tools for the determination of naphthenic acids and related components in environmental samples. However, experimental variables that influence the analytical results have not been fully explored. The relative contributions of Ox classes are of particular interest in data obtained using negative-ion electrospray ionization mass spectrometry. Using two types of ultrahigh resolution mass spectrometers (Orbitrap and FT-ICR), the apparent pH of the transfer solvent was observed to have a significant impact upon compound class distributions. A basic transfer solvent favored the detection of Ox species of lower oxygen content, while acidic pH favored the preferential observation of organic compounds with higher oxygen contents. These observed trends were independent of the instrument type. In addition, when using an acidic transfer solvent, the overall observed response was reduced by a factor of ∼20. Thus, the apparent pH of the transfer solvent has critical influence upon detection and upon the profile of different components observed within a complex mixture. In turn, this significantly impacts oil sands environmental monitoring for toxicity, forensic interpretation, and quantitation; when comparing data sets from different laboratories, these findings should therefore be taken into account