Detecting Industrial Fouling by Monotonicity during Ultrasonic Cleaning

High power ultrasound permits non-invasive cleaning of industrial equipment, but to make such cleaning systems energy efficient, one needs to recognize when the structure has been sufficiently cleaned without using invasive diagnostic tools. This can be done using ultrasound reflections generated inside the structure. This inverse modeling problem cannot be solved by forward modeling for irregular and complex structures, and it is difficult to tackle also with machine learning since human-annotated labels are hard get. We provide a deep learning solution that relies on the physical properties of the cleaning process. We rely on the fact that the amount of fouling is reduced as we clean more. Using this monotonicity property as indirect supervision we develop a semi-supervised model for detecting when the equipment has been cleaned.Peer reviewe

Semi-supervised detection of industrial fouling using ultrasound

Fouling is a large scale problem in industrial equipment such as heat exchangers or pipes, used in factories, ships, airplanes, etc. Traditionally, such equipment is cleaned using sandblasting, chemicals or mechanical methods, all of which require halting the process, which is costly. Recently, high-power ultrasound has become a viable option to these methods. In ultrasonic cleaning ultrasound is projected into the equipment from the outside, which means that the equipment does not need to be halted to perform cleaning. While the cleaning itself is not invasive in nature, in most cases vision cannot be used to determine whether cleaning is actually necessary or not. What remains is to have such a method that is also non-invasive. It is possible to use ultrasound as a kind of a radar to detect whether or not fouling is present, and this has been attempted in previous literature. However, until now, such methods have required extensive manual calculation and knowledge of the physical properties of the setup. We present the first ever system to concurrently clean and detect industrial fouling using ultrasound and deep learning. Our method does not rely on specific properties of the equipment, allowing it to generalize to large industrial processes where it is not practical to calculate or simulate the cleaning scenario. To this end, we extend existing literature on semi-supervised learning by presenting algorithms used to learn from a monotonic process, and model the high-dimensional signal data using a convolutional neural network that is highly robust to temporal variance. This thesis presents the machine learning solution behind the system, and the cleaning components are provided by Altum Technologies. Further, we explore methods to detect and counter the so-called domain shift that occurs when experimenting in the physical world, and provide experimental evidence that our methods work in practice

Roughest hour – approaches to ship hull fouling management

Submerged surfaces at sea are colonized by a high diversity of sessile (i.e. attached) life forms. As the merchant fleet capacity increases, responding to growth in demand for seaborne transport, so does the hull wetted surface area that is prone to colonization by these sessile organisms, i.e. marine biofouling. Such colonization leads to increased ship hull surface roughness, which results in both environmental and economic issues, namely fuel penalties and increased emissions to air. Improved maintenance of the hull would not only reduce these penalties, but also reduce emission of antifoulants and other paint components to the marine environment, as well as risks related to the transport of non-indigenous species on fouled hulls.The work presented in this thesis aimed at improving current approaches to the management of ship hull fouling, which typically rely on a combination of fouling-control coatings and an in-water cleaning scheme. Knowledge on the adhesive strength of fouling to minimize cleaning forces, on the one hand, and evaluation of the hull condition and hull roughness penalties, on the other hand, are therefore central to the aim of this thesis.The outcome of performed work supports a preventive approach to hull maintenance, e.g. gentle and frequent cleanings (hull grooming), or an alternative predictive approach, based on vessel performance and condition monitoring for detecting early forms of fouling. Tools are provided with potential to improve hull maintenance practices. These include minimizing cleaning forces applied during in-water hull cleaning through knowledge on adhesion strength of fouling (Papers I, III and IV), and more-accurate determination of the impact of fouling on vessel performance, namely by accounting for hull form effects (Papers II) or using a novel performance indicator that would be applicable in wider comparisons between vessels (Paper V). Seen as a whole, results indicate that the goal of minimizing the environmental and economic risks involved in hull fouling management can only be achieved through continued collaboration between different industry stakeholders, researchers, technology developers, authorities and policymakers, leading to an optimal path in development

Prognostic-based Life Extension Methodology with Application to Power Generation Systems

Practicable life extension of engineering systems would be a remarkable application of prognostics. This research proposes a framework for prognostic-base life extension. This research investigates the use of prognostic data to mobilize the potential residual life. The obstacles in performing life extension include: lack of knowledge, lack of tools, lack of data, and lack of time. This research primarily considers using the acoustic emission (AE) technology for quick-response diagnostic. To be specific, an important feature of AE data was statistically modeled to provide quick, robust and intuitive diagnostic capability. The proposed model was successful to detect the out of control situation when the data of faulty bearing was applied. This research also highlights the importance of self-healing materials. One main component of the proposed life extension framework is the trend analysis module. This module analyzes the pattern of the time-ordered degradation measures. The trend analysis is helpful not only for early fault detection but also to track the improvement in the degradation rate. This research considered trend analysis methods for the prognostic parameters, degradation waveform and multivariate data. In this respect, graphical methods was found appropriate for trend detection of signal features. Hilbert Huang Transform was applied to analyze the trends in waveforms. For multivariate data, it was realized that PCA is able to indicate the trends in the data if accompanied by proper data processing. In addition, two algorithms are introduced to address non-monotonic trends. It seems, both algorithms have the potential to treat the non-monotonicity in degradation data. Although considerable research has been devoted to developing prognostics algorithms, rather less attention has been paid to post-prognostic issues such as maintenance decision making. A multi-objective optimization model is presented for a power generation unit. This model proves the ability of prognostic models to balance between power generation and life extension. In this research, the confronting objective functions were defined as maximizing profit and maximizing service life. The decision variables include the shaft speed and duration of maintenance actions. The results of the optimization models showed clearly that maximizing the service life requires lower shaft speed and longer maintenance time

Modern Ultrasonics: From Super-Resolution Lens Design to Intraocular Pressure Tester

The aim of this thesis is to lay the foundation for the development of a contactless laser-based tonometer. Tonometers are devices capable of measuring intraocular pressure (IOP). Monitoring intraocular pressure is important for diagnosing glaucoma, which is a condition that may result in blindness and affects 70 million people worldwide. The foundation behind the development of the proposed tonometer, rests on the foundation of four published papers. In the first paper we focused acoustic waves using cylindrical metamaterial lenses. These lenses allow focusing acoustic energy into a beam narrower than half the central wavelength of the wave package. By selecting the speed of sound ratio between the material inside the lens and the surrounding medium, as well as the lens diameter, it is possible to efficiently focus acoustic energy into a jet narrower than half the central wavelength. The generation of said jet involves the focusing of the narrow-bandwidth acoustic waves as they impinge on the lens. The lens’ cylindrical geometry allows the propagation of guided surface waves that tailor the shape of the jet. An alternative approach towards generating a narrow acoustic wave front is the use of a pinhole. A pinhole in an aluminum plate allowed us to direct a shock wave front to a phantom/eye and calculate the intraocular pressure (IOP) from the time-of-flight of the membrane waves. To detect these membrane waves, we used a laser Doppler vibrometer (LDV). To understand the challenges of interferometric measurement with an LDV we conducted a study where we mapped the acoustic field on a rotating propeller. The motivation of this study was the importance of quickly monitoring the structural integrity of propellers in situ for the safe operation of aircraft. Aircraft inspection by ultrasonic means typically involves contacting transducers featuring low spatial resolution and slow measurement times. Alternatively, laser ultrasonics allows fast characterization of materials with high resolution and in a contactless manner. The demonstration of the contactless approach detected a flaw on an aluminum propeller that rotated under stroboscopic illumination of a high-power Q-switched laser. The high-power laser generated acoustic waves that travelled through the material and their measurement by an LDV resulted in acoustic maps. The maps allowed the identification as well as reconstruction of the defect on a 3D model of the sample. We further increased the complexity of the sample from a planar propeller to a geometry closer to a human eye, a metal hemisphere. The complexity introduced by the curvature of the sample ranged from the difficulty of focusing an LDV on a curved target to acoustic resonances in the sample. The motivation for choosing these samples was to develop a method to inspect acetabular implants in a contactless manner. In a similar fashion to the propeller study, a metal hemisphere featuring a defect rotated whilst a high-power laser generated acoustic waves. The detection of these acoustic waves and mapping of the acoustic fields allowed a reconstruction of the defect on a 3D model of the hemisphere. Further increasing the complexity of the sample, we studied an ocular phantom (human eye model) as a first step before measuring porcine eyes. In the phantom, the cornea was simulated by a polymer membrane stretched over a water-filled cavity. Adding water to the cavity increases the tension of the membrane and that is equivalent to increasing the intraocular pressure (IOP). To determine the internal pressure of the phantom, an electrical spark generated a shock wave that impinged on the surface of the eye generating membrane waves. These waves propagated in the cornea and an LDV measured their amplitude and propagation time. By relating the time-of-arrival of the acoustic waves to the internal pressure of the phantom we extracted a calibration curve. We further expanded our database by measuring porcine eyes allowing us to compare the IOP readings of our method to those of the leading rebound tonometer, the iCare TA01. The development of a contactless alternative to rebound tonometers will benefit from localized actuation on the cornea by a focusing structure, such as a metamaterial lens. Such a lens would allow actuation on a predetermined spot of the cornea, thus decreasing the uncertainty of the time-of-flight estimation. Such an uncertainty would be further reduced by eye tracking such that the excitation and detection locations remain fixed. The measurement series on the propeller introduces a method for synchronizing the excitation and generation of guided waves which is further improved in the study of the metal hemisphere. An important difference between eyes and metal hemispheres is the anisotropy of the tissue. Such anisotropy introduces variations in the acoustic impedance thus modifying the propagation velocity of membrane waves propagating in the cornea. Localized guided excitation of membrane waves would aid by launching guided waves along the same path, thus decreasing the error in the estimation of the IOP. Contactless measurement of IOP is possible with the technique suggested in this study. The combination of the lessons learned together with eye-safe interferometric detection of guided waves might pave the way to safe and comfortable alternatives to the current tonometric methods.The aim of this thesis is to lay the foundation for the development of a contactless laser-based tonometer. Tonometers are devices capable of measuring intraocular pressure (IOP). Monitoring intraocular pressure is important for diagnosing glaucoma, which is a condition that may result in blindness and affects 70 million people worldwide. The foundation behind the development of the proposed tonometer, rests on the foundation of four published papers. In the first paper we focused acoustic waves using cylindrical metamaterial lenses. These lenses allow focusing acoustic energy into a beam narrower than half the central wavelength of the wave package. By selecting the speed of sound ratio between the material inside the lens and the surrounding medium, as well as the lens diameter, it is possible to efficiently focus acoustic energy into a jet narrower than half the central wavelength. The generation of said jet involves the focusing of the narrow-bandwidth acoustic waves as they impinge on the lens. The lens’ cylindrical geometry allows the propagation of guided surface waves that tailor the shape of the jet. An alternative approach towards generating a narrow acoustic wave front is the use of a pinhole. A pinhole in an aluminum plate allowed us to direct a shock wave front to a phantom/eye and calculate the intraocular pressure (IOP) from the time-of-flight of the membrane waves. To detect these membrane waves, we used a laser Doppler vibrometer (LDV). To understand the challenges of interferometric measurement with an LDV we conducted a study where we mapped the acoustic field on a rotating propeller. The motivation of this study was the importance of quickly monitoring the structural integrity of propellers in situ for the safe operation of aircraft. Aircraft inspection by ultrasonic means typically involves contacting transducers featuring low spatial resolution and slow measurement times. Alternatively, laser ultrasonics allows fast characterization of materials with high resolution and in a contactless manner. The demonstration of the contactless approach detected a flaw on an aluminum propeller that rotated under stroboscopic illumination of a high-power Q-switched laser. The high-power laser generated acoustic waves that travelled through the material and their measurement by an LDV resulted in acoustic maps. The maps allowed the identification as well as reconstruction of the defect on a 3D model of the sample. We further increased the complexity of the sample from a planar propeller to a geometry closer to a human eye, a metal hemisphere. The complexity introduced by the curvature of the sample ranged from the difficulty of focusing an LDV on a curved target to acoustic resonances in the sample. The motivation for choosing these samples was to develop a method to inspect acetabular implants in a contactless manner. In a similar fashion to the propeller study, a metal hemisphere featuring a defect rotated whilst a high-power laser generated acoustic waves. The detection of these acoustic waves and mapping of the acoustic fields allowed a reconstruction of the defect on a 3D model of the hemisphere. Further increasing the complexity of the sample, we studied an ocular phantom (human eye model) as a first step before measuring porcine eyes. In the phantom, the cornea was simulated by a polymer membrane stretched over a water-filled cavity. Adding water to the cavity increases the tension of the membrane and that is equivalent to increasing the intraocular pressure (IOP). To determine the internal pressure of the phantom, an electrical spark generated a shock wave that impinged on the surface of the eye generating membrane waves. These waves propagated in the cornea and an LDV measured their amplitude and propagation time. By relating the time-of-arrival of the acoustic waves to the internal pressure of the phantom we extracted a calibration curve. We further expanded our database by measuring porcine eyes allowing us to compare the IOP readings of our method to those of the leading rebound tonometer, the iCare TA01. The development of a contactless alternative to rebound tonometers will benefit from localized actuation on the cornea by a focusing structure, such as a metamaterial lens. Such a lens would allow actuation on a predetermined spot of the cornea, thus decreasing the uncertainty of the time-of-flight estimation. Such an uncertainty would be further reduced by eye tracking such that the excitation and detection locations remain fixed. The measurement series on the propeller introduces a method for synchronizing the excitation and generation of guided waves which is further improved in the study of the metal hemisphere. An important difference between eyes and metal hemispheres is the anisotropy of the tissue. Such anisotropy introduces variations in the acoustic impedance thus modifying the propagation velocity of membrane waves propagating in the cornea. Localized guided excitation of membrane waves would aid by launching guided waves along the same path, thus decreasing the error in the estimation of the IOP. Contactless measurement of IOP is possible with the technique suggested in this study. The combination of the lessons learned together with eye-safe interferometric detection of guided waves might pave the way to safe and comfortable alternatives to the current tonometric methods

Particle resuspension: challenges and perspectives for future models

International audienceUsing what has become a celebrated catchphrase, Philip W. Anderson once wrote that "more is different" (Science, Vol. 177, Issue 4047, pp. 393-396, 1972). First formulated in the context of condensed matter, this statement carries far beyond the sole limits of solid-state physics. It emphasizes that collective behavior can be more than the mere sum of what happens for elementary constituents or the mere collation of the evolution of each degree of freedom. Said otherwise, complex phenomena can arise out of the interplay between multiple sub-phenomena each of which can be relatively simple. The process of particle resuspension, in which discrete particles adhering on a surface are pulled off and carried away by a fluid flow, is another example involving a web of phenomena pertaining to fluid mechanics, particle dynamics and interface chemistry whose crosseffects create an intricate topic. The purpose of this review is to analyze the physics at play in particle resuspension in order to bring insights into the rich complexity of this common but challenging concern. Following the more-is-different vision, this is performed by starting from a range of practical observations and experimental data. We then work our way through the investigation of the key mechanisms which play a role in the overall process. In turn, these mechanisms reveal an array of fundamental interactions, such as particle-fluid, particle-particle and particle-surface, whose combined effects create the tapestry of current applications. At the core of this analysis are descriptions of these physical phenomena and the different ways through which they are intertwined to build up various models used to provide quantitative assessment of particle resuspension. The physics of particle resuspension implies to hold together processes occurring at extremely different space and time scales and models are key in providing a single vehicle to lead us through such multiscale journeys. This raises questions on what makes up a model and one objective of the present work is to clarify the essence of a modeling approach. In spite of its ubiquitous nature, particle resuspension is still at the early stages of developments. Many extensions need to be worked out and revisiting the art of modeling is not a moot point. The need to consider more complex objects than small and spherical particles and, moreover, to come up with unified descriptions of mono-and multilayer resuspension put the emphasis on solid model foundations if we are to go beyond current limits. This is very much modeling in the making and new ideas are proposed to stimulate interest into this everyday but challenging issue in physics

Друга міжнародна конференція зі сталого майбутнього: екологічні, технологічні, соціальні та економічні питання (ICSF 2021). Кривий Ріг, Україна, 19-21 травня 2021 року

Second International Conference on Sustainable Futures: Environmental, Technological, Social and Economic Matters (ICSF 2021). Kryvyi Rih, Ukraine, May 19-21, 2021.Друга міжнародна конференція зі сталого майбутнього: екологічні, технологічні, соціальні та економічні питання (ICSF 2021). Кривий Ріг, Україна, 19-21 травня 2021 року

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