Structurally stable output regulation problem with sampled-output measurements using fuzzy immersions

In this paper, a fuzzy nonlinear ripple-free regulator is proposed to solve the sample-data structurally stable regulation problem for the case of nonlinear or generalized immersion. This regulator guarantees asymptotic tracking of time-varying references and rejection of disturbances while maintaining the closed-loop stability. Such a regulator is based on a continuous fuzzy error feedback controller, which updates its states at each sampling period and relies on the existence of an internal model. The internal model is obtained by determining, if possible, an observable generalized immersion of the exosystem dynamics. A key feature is that this immersion allows the generation of all the possible steady-state inputs for all admissible values of the system parameters. The robustness of the proposed fuzzy controller, under parameter uncertainties and changes on disturbance signals, is tested in an illustrative example. © 2006 IEEE

Discrete Time Systems

Discrete-Time Systems comprehend an important and broad research field. The consolidation of digital-based computational means in the present, pushes a technological tool into the field with a tremendous impact in areas like Control, Signal Processing, Communications, System Modelling and related Applications. This book attempts to give a scope in the wide area of Discrete-Time Systems. Their contents are grouped conveniently in sections according to significant areas, namely Filtering, Fixed and Adaptive Control Systems, Stability Problems and Miscellaneous Applications. We think that the contribution of the book enlarges the field of the Discrete-Time Systems with signification in the present state-of-the-art. Despite the vertiginous advance in the field, we also believe that the topics described here allow us also to look through some main tendencies in the next years in the research area

Second Generation General System Theory: Perspectives in Philosophy and Approaches in Complex Systems

Following the classical work of Norbert Wiener, Ross Ashby, Ludwig von Bertalanffy and many others, the concept of System has been elaborated in different disciplinary fields, allowing interdisciplinary approaches in areas such as Physics, Biology, Chemistry, Cognitive Science, Economics, Engineering, Social Sciences, Mathematics, Medicine, Artificial Intelligence, and Philosophy. The new challenge of Complexity and Emergence has made the concept of System even more relevant to the study of problems with high contextuality. This Special Issue focuses on the nature of new problems arising from the study and modelling of complexity, their eventual common aspects, properties and approaches—already partially considered by different disciplines—as well as focusing on new, possibly unitary, theoretical frameworks. This Special Issue aims to introduce fresh impetus into systems research when the possible detection and correction of mistakes require the development of new knowledge. This book contains contributions presenting new approaches and results, problems and proposals. The context is an interdisciplinary framework dealing, in order, with electronic engineering problems; the problem of the observer; transdisciplinarity; problems of organised complexity; theoretical incompleteness; design of digital systems in a user-centred way; reaction networks as a framework for systems modelling; emergence of a stable system in reaction networks; emergence at the fundamental systems level; behavioural realization of memoryless functions

System for detecting fluorescent tracers in streamflow, A

December 1970.Includes bibliographical references (pages 180-186).Covers not scanned.Print version deaccessioned 2021.A system is developed capable of continuously monitoring the relative concentration of a fluorescent tracer in streamflow. Streamside instrumentation automatically registers stream-borne tracer concentrations as a function of time on a gelatin-coated film. The film is routed through a device which passes a continuous sample-aliquot diverted from the tracer-dosed stream over a small segment of the film. The "exposed" film is periodically gathered from stream sites and analyzed in a laboratory-based fluorometer. Utility of the system is studied for the gaging of streamflow to produce a hydrograph, to measure stream discharge instantaneously, and to determine time-of-stream-travel. Hydrographs resulting from 640 hours of gaging two Colorado mountain streams with the system are compared to those obtained from closely located sharp-crested weirs. The maximum instantaneous deviation between hydrographs reaches 10% and average absolute departure equals 1.8%, while algebraic departure averages +0.3%. The practicality of using this system to obtain time-of-stream travels is demonstrated for five Colorado mountain streams. A total of 62 traveling tracer-clouds are registered on gelatin-coated film, from which time-of-stream-travels are determined. Processes involved in the system and factors affecting its precision are investigated. Theoretical and experimental evidence strongly indicates that the bulk of tracer uptake by gelatin follows processes that are physical rather than chemical in nature. Stream temperature changes and duration of film-tracer contact are the two most important factors affecting precision of the system. Neither major factor caused any unsolvable problem when field operations were standardized. The system will have utility in operations where an expensive, temperature-sensitive fluorometer can not be stationed stream-side, and where the particular objectives of stream measurements do not justify the cost of conventional techniques, but where fair accuracy and continuous records of short to moderate duration are desired

Structures and functions of the post-mortem brain: an experimental evaluation of the residual properties of fixed neural tissues

Does brain function irreversibly cease after death? Billions of years of evolution and hundreds of thousands of years of human development have inculcated within us an intuition that death is a deep pit from which thoughts and behaviour cannot emerge. This dissertation serves to challenge the assumption of neurofunctional loss after death by employing modern technology to observe alternative mechanisms by which information can be processed by fixed, post-mortem neural tissues. The central aim of the thesis was to measure periodic, electric potential differences (μV) characteristic of the psychological definition of “response” within neuroanatomical loci while the fixed tissues were exposed to patterned current, complex electromagnetic fields, chemical probes, and other experimental conditions. The findings presented here show that fixed post-mortem tissues express regional, electrical anisotropies which can be modulated by various applications of electrochemical energy and that the areas surrounding the hippocampus are most responsive. We show that neuropathology secondary to repeated and protracted seizure activity can be detected in post-mortem rat brains with coupled depressions of low-frequency signal periodicities. Our findings demonstrate that injections of current into coronal sections of fixed human brain tissue are most potent when patterned to simulate neuronal spike-trains and the dominant frequency of the equivalent living tissue subsection. We also show that fixed, post-mortem brain tissues act as electromagnetic filters, expressing signals non-randomly and preferentially within the right cerebral hemisphere. Further findings indicate that receptor agonist-antagonist probes (e.g., glutamate and ketamine) as well as other chemical applications can induce regional electrical responses as well as habituation-type phenomena over repeated exposure. iv These responses are paired and can be inversely related to photon emission from the tissue proper as inferred by photomultiplier tube measurements. The bases of the electrochemical responses are thought to be due to phenomena associated with pH and ionic gradients in general as inferred by our experiments with post-mortem rat brains. The aforementioned experimental results are then synthesized to produce a working hypothesis upon which further research can be based. We conclude that the brain’s structure-function relationship is sufficient to elicit post-mortem responses characteristic of a composite material of otherwise unknown potential.Doctor of Philosophy (PhD) in Biomolecular Science

Handbook of Mathematical Geosciences

This Open Access handbook published at the IAMG's 50th anniversary, presents a compilation of invited path-breaking research contributions by award-winning geoscientists who have been instrumental in shaping the IAMG. It contains 45 chapters that are categorized broadly into five parts (i) theory, (ii) general applications, (iii) exploration and resource estimation, (iv) reviews, and (v) reminiscences covering related topics like mathematical geosciences, mathematical morphology, geostatistics, fractals and multifractals, spatial statistics, multipoint geostatistics, compositional data analysis, informatics, geocomputation, numerical methods, and chaos theory in the geosciences

Aeronautical Engineering: A continuing bibliography with indexes, supplement 107

Reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1979 are listed in this bibliography