Накладные вихретоковые преобразователи: системы возбуждения оптимального электромагнитного поля (обзор)

Development of technical tools with improved metrological and operational characteristics is the actual problem of the eddy current testing. Ensuring the optimal distribution of the electromagnetic excitation field in the testing zone carries out confident detection of the defects and determination of their geometrical parameters by means of eddy current testing. The purpose of the work was to conduct an analysis of scientific and technical information in the field of eddy current testing to study of the use of electromagnetic excitation fields with a priori specified properties, as well as to generalize and systematize the accumulated experience and approaches to conduct theoretical research in this direction.A review of publications in the field of non-destructive electromagnetic testing devoted to the improvement of the excitation systems of eddy current flaw probes was carried out. The authors considered approaches in which a uniform distribution of the electromagnetic field on the control object surface was achieved by linear and non-linear optimal synthesis of excitation systems, provided the immobility of the probe relative to the testing object. Analysis of eddy current probe designs with a homogeneous excitation field created by circular, rectangular tangential and normal coils, as well as by creating a rotational excitation field was carried out. The authors studied designs of the excitation coils of probes with fields of complex configuration characterized by the original fractal geometry which can increase the probability of identifying defects that were not amenable to detection by classical probes.Studies that suggested the formation of optimal configuration fields in a given area using magnetic cores, field concentrators made of conductive materials and specially shaped screens were analyzed. The authors studied approaches to the implementation of the optimal synthesis of excitation systems of probes with uniform sensitivity in the testing zone using surrogate optimization for cases of moving testing objects taking into account the speed effect.The experience, as well as the results of theoretical studies devoted to the problem of designing eddy current probes with uniform sensitivity in the testing zone due to the uniform density distribution of the induced currents flowing in the object were generalized and systematized. As a result, the classification of probes on a number of features that characterize the excitation systems was proposed.Актуальной задачей вихретокового контроля является разработка технических средств с улучшенными метрологическими и эксплуатационными характеристиками. Уверенное обнаружение дефектов и определение их геометрических параметров средствами вихретокового контроля осуществляется при обеспечении оптимального распределения электромагнитного поля возбуждения в зоне контроля. Цель работы заключалась в проведении анализа научно-технической информации в области вихретокового контроля для изучения сведений об использовании электромагнитных полей возбуждения с априори заданными свойствами, а также обобщения, систематизации накопленного опыта и подходов к проведению теоретических исследований в данном направлении.Проведён обзор публикаций в области неразрушающего электромагнитного контроля, посвящённых совершенствованию систем возбуждения преобразователей вихретоковых дефектоскопов. Рассмотрены подходы, в которых однородное распределение электромагнитного поля на поверхности объекта контроля достигается линейным и нелинейным оптимальным синтезом систем возбуждения при условии неподвижности преобразователя относительно объекта контроля. Проведён анализ конструкций вихретоковых преобразователей с однородным полем возбуждения, созданным круговыми, прямоугольными тангенциальными и нормальными катушками, а также за счёт создания вращательного поля возбуждения. Изучались конструкции катушек возбуждения преобразователей с полями сложной конфигурации, характеризующиеся оригинальной фрактальной геометрией, которые позволяют увеличить вероятность выявления дефектов, не поддающихся обнаружению классическими преобразователями.Также проанализированы исследования, в которых предлагается формирование полей оптимальной конфигурации в заданной зоне с применением магнитопроводов, концентраторов поля из проводящих материалов и экранов специальной формы. Изучались подходы к реализации оптимального синтеза систем возбуждения преобразователей с равномерной чувствительностью в зоне контроля с использованием суррогатной оптимизации для случаев движущихся объектов контроля с учётом эффекта скорости. Обобщён и систематизирован опыт, а также результаты теоретических исследований, посвящён-ных проблеме проектирования вихретоковых преобразователей с равномерной чувствительностью в зоне контроля, обусловленной однородным распределением плотности индуцированных токов, протекающих в объекте. Предложена классификация преобразователей по ряду признаков, характеризующих их системы возбуждения

Magnetic and Newtonian noises in Advanced Virgo: evaluation and mitigation strategies

In the present study, I table the first detailed estimation of the magnetic noise contribution to the Advanced Virgo sensitivity to gravitational waves. I tackle the topic by performing experimental assessments and numerical finite element simulations, all accompanied by careful data analysis. Results suggest that the magnetic noise impact for Advanced Virgo is not dramatic, but it will eventually be a considerable issue once the detector will approach its final design. In anticipation of that, I propose a mitigation strategy based on passive magnetic field shielding. In the second part, I deal with seismic newtonian noise, focusing on two crucial aspects involving the noise cancellation pipeline. These are the choice of the subtraction filter and the optimization of the seismic sensor array placement. The former issue required the definition of a machine learning algorithm based on deep neural networks, and its fine tuning. Results give some indication of good performances compared to the standard Wiener filter approach. The problem of the sensors deployment is instead addressed with the finite element analysis of the actual Virgo infrastructure and underground soil layers surrounding the test masses

Accelerated neuromorphic cybernetics

Accelerated mixed-signal neuromorphic hardware refers to electronic systems that emulate electrophysiological aspects of biological nervous systems in analog voltages and currents in an accelerated manner. While the functional spectrum of these systems already includes many observed neuronal capabilities, such as learning or classification, some areas remain largely unexplored. In particular, this concerns cybernetic scenarios in which nervous systems engage in closed interaction with their bodies and environments. Since the control of behavior and movement in animals is both the purpose and the cause of the development of nervous systems, such processes are, however, of essential importance in nature. Besides the design of neuromorphic circuit- and system components, the main focus of this work is therefore the construction and analysis of accelerated neuromorphic agents that are integrated into cybernetic chains of action. These agents are, on the one hand, an accelerated mechanical robot, on the other hand, an accelerated virtual insect. In both cases, the sensory organs and actuators of their artificial bodies are derived from the neurophysiology of the biological prototypes and are reproduced as faithfully as possible. In addition, each of the two biomimetic organisms is subjected to evolutionary optimization, which illustrates the advantages of accelerated neuromorphic nervous systems through significant time savings

Frustration in Biomolecules

Biomolecules are the prime information processing elements of living matter. Most of these inanimate systems are polymers that compute their structures and dynamics using as input seemingly random character strings of their sequence, following which they coalesce and perform integrated cellular functions. In large computational systems with a finite interaction-codes, the appearance of conflicting goals is inevitable. Simple conflicting forces can lead to quite complex structures and behaviors, leading to the concept of "frustration" in condensed matter. We present here some basic ideas about frustration in biomolecules and how the frustration concept leads to a better appreciation of many aspects of the architecture of biomolecules, and how structure connects to function. These ideas are simultaneously both seductively simple and perilously subtle to grasp completely. The energy landscape theory of protein folding provides a framework for quantifying frustration in large systems and has been implemented at many levels of description. We first review the notion of frustration from the areas of abstract logic and its uses in simple condensed matter systems. We discuss then how the frustration concept applies specifically to heteropolymers, testing folding landscape theory in computer simulations of protein models and in experimentally accessible systems. Studying the aspects of frustration averaged over many proteins provides ways to infer energy functions useful for reliable structure prediction. We discuss how frustration affects folding, how a large part of the biological functions of proteins are related to subtle local frustration effects and how frustration influences the appearance of metastable states, the nature of binding processes, catalysis and allosteric transitions. We hope to illustrate how Frustration is a fundamental concept in relating function to structural biology.Comment: 97 pages, 30 figure

Intermittent Theta Burst Stimulation: Application to Spinal Cord Injury Rehabilitation and Computational Modeling

Loss of motor function from spinal cord injuries (SCI) results in loss of independence. Rehabilitation efforts are targeted to enhance the ability to perform activities of daily living (ADLs), but outcomes from physical therapy alone are often insufficient. Neuromodulation techniques that induce neuroplasticity may push the limits on recovery. Neuromodulation by intermittent theta burst transcranial magnetic stimulation (iTBS) induces neuroplasticity by increasing corticomotor excitability, though this has most frequently been studied with motor targets and on individuals not in need of rehabilitation. Increased corticomotor excitability is associated with motor learning. The response to iTBS, however, is highly variable and unpredictable, while the mechanisms are not well understood. Studies have proposed brain anatomy and individual subject differences as a source of variability but have not quantified the effects. Existing models have not incorporated known neurotransmitter changes at the synaptic level to pair mechanisms to cell output in a neural circuit. To use iTBS in practical rehabilitative efforts, the technique must either be consistent, have a predictable responsiveness, or present with enough mechanistic understanding to improve its efficacy. To that effect, this study has two primary objectives for the improvement of rehabilitation techniques. The first is to establish how iTBS affects both a motor target and population that typically undergoes physical rehabilitation often with unsatisfactory outcomes, in this case the biceps brachii in individuals with SCI and relate the empirical effects of iTBS to individual anatomy. This will establish the consistency of the technique and predictability of its effects, relevant to rehabilitative efforts. The secondary objective is to create the foundation of a model that exhibits circuit organization, which would start the development of a motor neuroplasticity functional unit with simulation of the synaptic long-term potentiation (LTP) like effects of iTBS. Summary of Methods: iTBS was performed targeting the biceps, on multiple cohorts, with changes in motor evoked potential amplitude (MEP) tracked after sham and active intervention. This was compared between nonimpaired individuals and those with SCI. Furthermore, iTBS of both biceps and first dorsal interosseus (FDI) was compared to simulation of TMS on MRI derived head models to establish the impact of individualized neuroanatomy. Finally, a motor canonical neural circuit was programmed to display fundamental physiological spiking behavior of membrane potentials. Summary of Results: iTBS did facilitate corticomotor excitability in the biceps of nonimpaired individuals and in those with SCI. iTBS had no group-wide effect on the FDI, highlighting the variability in response to the protocol. TMS response (motor thresholds) and iTBS response (change in MEPs) both were related to parameters extracted from MRI-derived head models representing variations in individual neuroanatomy. The neural circuit model represents a canonical networked unit. In the future, this can be further tuned to exhibit biological variability and generate population-based values being run in parallel, while matching the understood mechanisms of neuroplasticity: disinhibition and LTP. Conclusion: These studies provide missing information of iTBS responsivity by (1) determining group-wide responsiveness in a clinically relevant target; (2) establishing individual level influences that affect responsivity which can be measured prior to iTBS; and (3) beginning design of a tool to test a single neural circuit and its mechanistic responses

Computerized Analysis of Magnetic Resonance Images to Study Cerebral Anatomy in Developing Neonates

The study of cerebral anatomy in developing neonates is of great importance for the understanding of brain development during the early period of life. This dissertation therefore focuses on three challenges in the modelling of cerebral anatomy in neonates during brain development. The methods that have been developed all use Magnetic Resonance Images (MRI) as source data. To facilitate study of vascular development in the neonatal period, a set of image analysis algorithms are developed to automatically extract and model cerebral vessel trees. The whole process consists of cerebral vessel tracking from automatically placed seed points, vessel tree generation, and vasculature registration and matching. These algorithms have been tested on clinical Time-of- Flight (TOF) MR angiographic datasets. To facilitate study of the neonatal cortex a complete cerebral cortex segmentation and reconstruction pipeline has been developed. Segmentation of the neonatal cortex is not effectively done by existing algorithms designed for the adult brain because the contrast between grey and white matter is reversed. This causes pixels containing tissue mixtures to be incorrectly labelled by conventional methods. The neonatal cortical segmentation method that has been developed is based on a novel expectation-maximization (EM) method with explicit correction for mislabelled partial volume voxels. Based on the resulting cortical segmentation, an implicit surface evolution technique is adopted for the reconstruction of the cortex in neonates. The performance of the method is investigated by performing a detailed landmark study. To facilitate study of cortical development, a cortical surface registration algorithm for aligning the cortical surface is developed. The method first inflates extracted cortical surfaces and then performs a non-rigid surface registration using free-form deformations (FFDs) to remove residual alignment. Validation experiments using data labelled by an expert observer demonstrate that the method can capture local changes and follow the growth of specific sulcus

Theoretical Engineering and Satellite Comlink of a PTVD-SHAM System

This paper focuses on super helical memory system's design, 'Engineering, Architectural and Satellite Communications' as a theoretical approach of an invention-model to 'store time-data'. The current release entails three concepts: 1- an in-depth theoretical physics engineering of the chip including its, 2- architectural concept based on VLSI methods, and 3- the time-data versus data-time algorithm. The 'Parallel Time Varying & Data Super-helical Access Memory' (PTVD-SHAM), possesses a waterfall effect in its architecture dealing with the process of voltage output-switch into diverse logic and quantum states described as 'Boolean logic & image-logic', respectively. Quantum dot computational methods are explained by utilizing coiled carbon nanotubes (CCNTs) and CNT field effect transistors (CNFETs) in the chip's architecture. Quantum confinement, categorized quantum well substrate, and B-field flux involvements are discussed in theory. Multi-access of coherent sequences of 'qubit addressing' in any magnitude, gained as pre-defined, here e.g., the 'big O notation' asymptotically confined into singularity while possessing a magnitude of 'infinity' for the orientation of array displacement. Gaussian curvature of k(k<0) is debated in aim of specifying the 2D electron gas characteristics, data storage system for defining short and long time cycles for different CCNT diameters where space-time continuum is folded by chance for the particle. Precise pre/post data timing for, e.g., seismic waves before earthquake mantle-reach event occurrence, including time varying self-clocking devices in diverse geographic locations for radar systems is illustrated in the Subsections of the paper. The theoretical fabrication process, electromigration between chip's components is discussed as well.Comment: 50 pages, 10 figures (3 multi-figures), 2 tables. v.1: 1 postulate entailing hypothetical ideas, design and model on future technological advances of PTVD-SHAM. The results of the previous paper [arXiv:0707.1151v6], are extended in order to prove some introductory conjectures in theoretical engineering advanced to architectural analysi