Monitoring system for long-distance pipelines subject to destructive attack

In an era of terrorism, it is important to protect critical pipeline infrastructure, especially in countries where life is strongly dependent on water and the economy on oil and gas. Structural health monitoring (SHM) using acoustic waves is one of the common solutions. However, considerable prior work has shown that pipes are cylindrical acoustic waveguides that support many dispersive, lossy modes; only the torsional T(0, 1) mode has zero dispersion. Although suitable transducers have been developed, these typically excite several modes, and even if they do not, bends and supports induce mode conversion. Moreover, the high-power transducers that could in principle be used to overcome noise and attenuation in long distance pipes present an obvious safety hazard with volatile products, making it difficult to distinguish signals and extract pipeline status information. The problem worsens as the pipe diameter increases or as the frequency rises (due to the increasing number of modes), if the pipe is buried (due to rising attenuation), or if the pipe carries a flowing product (because of additional acoustic noise). Any system is therefore likely to be short-range. This research proposes the use of distributed active sensor network to monitor long-range pipelines, by verifying continuity and sensing small disturbances. A 4-element cuboid Electromagnetic Acoustic Transducer (EMAT) is used to excite the longitudinal L(0,1) mode. Although the EMAT also excites other slower modes, long distance propagation allows their effects to be separated. Correlation detection is exploited to enhance signal-to-noise ratio (SNR), and code division multiplexing access (CDMA) is used to distinguish between nodes in a multi-node system. An extensive numerical search for multiphase quasi-orthogonal codes for different user numbers is conducted. The results suggest that side lobes degrade performance even with the highest possible discrimination factor. Golay complementary pairs (which can eliminate the side lobes completely, albeit at the price of a considerable reduction in speed) are therefore investigated as an alternative. Pipeline systems are first reviewed. Acoustic wave propagation is described using standard theory and a freeware modeling package. EMAT modeling is carried out by numerical calculation of electromagnetic fields. Signal propagation is investigated theoretically using a full system simulator that allows frequency-domain description of transducers, dispersion, multi-mode propagation, mode conversion and multiple reflections. Known codes for multiplexing are constructed using standard algorithms, and novel codes are discovered by an efficient directed search. Propagation of these codes in a dispersive system is simulated. Experiments are carried out using small, unburied air-filled copper pipes in a frequency range where the number of modes is small, and the attenuation and noise are low. Excellent agreement is obtained between theory and experiment. The propagation of pulses and multiplexed codes over distances up to 200 m are successfully demonstrated, and status changes introduced by removable reflectors are detected.Open Acces

Positioning systems using families of binary sequences with low correlation

RESUMEN: El objetivo de este trabajo es el estudio de la aplicación de familias de secuencias binarias de baja correlación para su uso en sistemas de posicionamiento en tiempo real en interiores como por ejemplo en entornos industriales o de almacenamiento. Actualmente es un problemas abierto para el que se han propuesto distintas tecnologías como sistemas basados en visión artificial o en redes de sensores entre otros. En este proyecto se ha implementado un sistema de posicionamiento en interiores de bajos recursos por medio de secuencias binarias de baja correlación. La investigación se ha centrado en la revisión de las tecnologías existentes en el mercado, la búsqueda de las secuencias binarias más apropiadas y el estudio de sus propiedades. Siguiendo el modelo GPS como sistema de localización en exteriores, se ha construido un propotipo basado en placas Arduino. Nuestra propuesta codifica la información mediante secuencias Pseudo Noise, códigos Gold y Kasami. Posteriormente estas secuencias son transmitidas utilizando señales de ultrasonido. En el receptor, las señales recibidas se pueden procesar para obtener medidas como la distancia entre dispositivos y el ángulo de llegada entre otras.ABSTRACT: The aim of this project is the study of families of binary sequences of low correlation and its application to real-time indoor positioning systems in industrial or warehousing environments. Many different approaches based on different technologies such as artificial vision or sensor networks have been proposed for indoor localization but it still remains an open problem. In this work, we have implemented a low resources indoor positioning system over over a embedded system, that uses binary sequences of low correlation. The research has focused on existent technologies in the market, on the search of the most appropriate family of sequences and the study of their properties. Taking GPS as a reference model for outdoor localization, we have built a prototype based on Arduino boards. Our approach encodes messages with Pseudo Noise sequences, Gold and Kasami Codes. Afterwards, the sequences are transmitted as ultrasonic signals. Then, the receiver processes the incoming signal to obtain measures such as the distances between devices and the angle of arrival of the signal.Máster en Matemáticas y Computació

DSP-based CW lidars for clouds and aerosol

This thesis aims at exploring the limits of low peak-power, low-cost, all-semiconductor, compact lidars (laser radars) for range-resolved remote sensing of atmospheric aerosols and clouds. The systems investigated are based on laser diodes for emitter, avalanche photodiodes for the receiver, and digital signal processors for processing the returns from the atmosphere and the system control. The studied systems are built on the use of M-sequences and other derivated ones, which allows retrieving range-dependent information from the returning echoes, while having almost the same number of ones and zeros to maximize the transmitted average power for a limited peak power. The use of digital processors to generate the modulating sequences and to process the lidar returns allows for systems with agile reconfiguration capabilities and the use of very long sequences while keeping the processing time virtually negligible compared with the time employed to transmit the laser pulse-modulated output and receive the echoes from the atmosphere (the measuring time). The theorical developments are tested and demonstrated by the experimental results obtained with two lidar prototypes designed and build according the theoretical framework. The detection of cloud bases up to 8km with transmission peak powers of 125 mW in the near (almost visible) infrared (785 nm wavelength), with spatial resolution of 70 to 100 m and time resolution from 30 seconds to 4 minutes, has been achieved. Aerosols at lower altitudes are also observed in conditions of high aerosol load. In addition to further developments in low-cost lidar systems for detections of particles suspended in the atmosphere, the technical developments of this work pave also the way to the design of low-power systems por open path, range-resolved detection of gases, for example in industrial environments. After an introductory chapter, chapter 2 reviews the basic principles of lidar systems and focuses on continuous-wave systems with pseudorandom sequence modulation of the transmitted power and the constraints set by the requirement of a low peak-power transmitter. Chapter 3 reviews different types of power-modulating digital sequences that can be used, with the constraint of average 50% duty cycle, selects the best ones to be investigated in the experimental study, and unravels some of the issues associated to possible non-linear behavior of the photoreceiver. Chapter 4 presents the theoretical performance of the system, which is compared to a model that takes into account the technical constraints and non-idealities of the system building blocks. Chapter 5 sets out the complete design of the prototypes that have been built and tested, which are presented in chapter 6. Chapter 7 presents the tests and field results obtained with the prototypes built according to the design discussed in chapter 5. Chapter 8 presents the conclusions and outlines possible lines opened by the thesis work. Two appendices (chapter 9) develop further details on the detrimental effect of non-linear behavior in the receiver chain, and practical aspects of the alignment procedure between the lidar transmitter and the receiving optics.Aquesta tesi té com a objectiu explorar els límits dels lidars compactes (radars làser) de baixa potència de pic, baix cost, tot basat en semiconductors per a la detecció remota de núvols i aerosols atmosfèrics amb resolució en distància. Els sistemes investigats es basen en díodes làser per a l 'emissor, fotodíodes d'allau per al receptor i processadors digitals de senyal per a processar els retorns atmosfèrics i el control del sistema. Els sistemes estudiats es basen en l'ús de seqüències M i altres de derivades, el que permet recuperar la informació de la distancia dependent dels ecos del retorn, al mateix temps que té gairebé el mateix nombre d'uns i zeros per maximitzar la potència mitjana transmesa amb una potència de pic limitada. L'ús de processadors digitals per generar seqüències de modulació i retorns del lidar permet sistemes amb capacitat de canviar de configuració àgil i l'ús de seqüències molt llargues, mantenint el temps de processament pràcticament insignificant en comparació amb el temps dedicat a transmetre la sortida modulada del pols làser i rebre ecos de l'atmosfera (temps de mesurament). Els desenvolupaments teòrics són provats i demostrats amb resultats experimentals obtinguts amb dos prototips lidar dissenyats i construïts segons el marc teòric. La detecció de base de núvols fins a 8 km s'ha aconseguit amb potències de transmissió de 125 mW de potència en infraroig proper (quasi visible, 785 nm de longitud d'ona), amb resolució espacial de 70 a 100 m i resolució de temps de 30 segons a 4 minuts. Els aerosols en altituds més baixes també s'observen sota condicions de càrregues d'aerosols elevades. A més de nous desenvolupaments en sistemes lidar de baix cost per a la detecció de partícules en suspensió a l'atmosfera, els desenvolupaments tècnics d'aquest treball també preparen el camí per al disseny de sistemes de detecció de gasos de baix consum, amb resolució en distància, per exemple , en entorns industrials. Després d'un capítol introductori, el capítol 2 revisa els principis bàsics dels sistemes lidar i es centra en els sistemes d'ona contínua amb modulació amb seqüència pseudoaleatòries de la potència transmesa i les restriccions establertes per l'exigència d'un transmissor de potència de baixa potència de pic. El capítol 3 comentaris els diferents tipus de seqüències digitals per a la modulació de potència que es poden utilitzar, amb la restricció del cicle mitjà de treball del 50%, selecciona les millors per ser investigades en l'estudi experimental i desentranya alguns dels problemes associats amb el possible comportament no lineal del fotoreceptor. El capítol 4 presenta el rendiment teòric del sistema, que es compara amb un model que té en compte les limitacions tècniques i les no idealitats dels components bàsics del sistema. El capítol 5 estableix el disseny complet dels prototips que s'han construït i provat, que es presenten en el capítol 6. El capítol 7 presenta les proves i els resultats de camp obtinguts amb prototips construïts d'acord amb el disseny discutit en el capítol 5. El capítol 8 presenta les conclusions i s'esbossen possibles línies obertes pel treball de la tesi. Dos apèndixs (capítol 9) desenvolupen més detalls sobre l'efecte perjudicial del comportament no lineal en la cadena receptora i aspectes pràctics del procediment d'alineació entre el transmissor LIDAR i l'òptica receptora

The History of Lawrence University, 1847-1925

viii, 493 pages. William Francis Raney, David G. Ormsby Professor of European History, was on the faculty at Lawrence University from 1920 to 1955. He researched and wrote this extensive history of Lawrence University between the time of his retirement in 1955 and his death in 1962. Marshall Hulbert \u2726 prepared the work for printing and a limited run was published by Lawrence University in 1984.https://lux.lawrence.edu/archives_selections/1005/thumbnail.jp

STARPROBE: Scientific rationale

The scientific rationale and instrumentation problems in the areas of solar internal dynamics and relativity, solar plasma and particle dynamics, and solar atmosphere structure were studied. Current STARPROBE mission and system design concepts are summarized

A Practical Investigation into Achieving Bio-Plausibility in Evo-Devo Neural Microcircuits Feasible in an FPGA

Many researchers has conjectured, argued, or in some cases demonstrated, that bio-plausibility can bring about emergent properties such as adaptability, scalability, fault-tolerance, self-repair, reliability, and autonomy to bio-inspired intelligent systems. Evolutionary-developmental (evo-devo) spiking neural networks are a very bio-plausible mixture of such bio-inspired intelligent systems that have been proposed and studied by a few researchers. However, the general trend is that the complexity and thus the computational cost grow with the bio-plausibility of the system. FPGAs (Field- Programmable Gate Arrays) have been used and proved to be one of the flexible and cost efficient hardware platforms for research' and development of such evo-devo systems. However, mapping a bio-plausible evo-devo spiking neural network to an FPGA is a daunting task full of different constraints and trade-offs that makes it, if not infeasible, very challenging. This thesis explores the challenges, trade-offs, constraints, practical issues, and some possible approaches in achieving bio-plausibility in creating evolutionary developmental spiking neural microcircuits in an FPGA through a practical investigation along with a series of case studies. In this study, the system performance, cost, reliability, scalability, availability, and design and testing time and complexity are defined as measures for feasibility of a system and structural accuracy and consistency with the current knowledge in biology as measures for bio-plausibility. Investigation of the challenges starts with the hardware platform selection and then neuron, cortex, and evo-devo models and integration of these models into a whole bio-inspired intelligent system are examined one by one. For further practical investigation, a new PLAQIF Digital Neuron model, a novel Cortex model, and a new multicellular LGRN evo-devo model are designed, implemented and tested as case studies. Results and their implications for the researchers, designers of such systems, and FPGA manufacturers are discussed and concluded in form of general trends, trade-offs, suggestions, and recommendations

The 1991 3rd NASA Symposium on VLSI Design

Papers from the symposium are presented from the following sessions: (1) featured presentations 1; (2) very large scale integration (VLSI) circuit design; (3) VLSI architecture 1; (4) featured presentations 2; (5) neural networks; (6) VLSI architectures 2; (7) featured presentations 3; (8) verification 1; (9) analog design; (10) verification 2; (11) design innovations 1; (12) asynchronous design; and (13) design innovations 2

Heuristic Solution Methods for Multi-resource Generalized Assignment Problems

Industrial Engineerin