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Probability distributions and typical sparsity measures of Hilbert transform-based generalized envelopes and their application to machine condition monitoring
No full textThe establishment of probability distributions of machine vibration signals is crucial for calculating theoretical baselines of machine health indicators. Health indicators based on the envelope and squared envelope are an important family for condition monitoring. Under the assumption that the vibration signals of a good machine are Gaussian distributed, the envelope of a normal machine signal with zero mean is proven to follow a Rayleigh distribution with one parameter that depends on the noise variance, and its squared envelope follows an exponential distribution with one parameter, while the exact distribution parameter is undefined. The recently introduced log-envelope (i.e. the logarithm of the envelope) and generalized envelope (GE) exhibit attractive properties against interfering noise, however, their probability distributions have not yet been established. In this paper, the probability distributions of the squared envelope, log-squared envelope (i.e. the logarithm of the squared envelope), log-envelope and GE with parameter greater than 0 of Gaussian noise and corresponding distribution parameters are derived and established theoretically, and the important characteristic that their distribution parameters vary with the noise variance is clarified. On this basis, typical sparsity measures of GE of Gaussian noise are theoretically calculated, including kurtosis, skewness, Li/Lj norm, Hoyer measure, modified smoothness index, negentropy, Gini index, Gini index Ⅱ and Gini index Ⅲ. These typical sparsity measures of GE with parameter greater than 0 of Gaussian noise and the skewness and kurtosis of the log-envelope of Gaussian noise are proven to be independent of the noise variance, which enables them to serve as baselines for machine condition monitoring. Numerical simulations verify the correctness of the probability distributions and theoretical values of typical sparsity measures of GE with different parameters of Gaussian noise. The analysis results of four bearing run-to-failure experiments verify the feasibility and effectiveness of the sparsity measure of Gaussian noise as a condition monitoring baseline and demonstrate the efficacy and performance of GE-based sparsity measures for machine condition monitoring
Full-field extraction of subtle displacement components via phase-projection wavelet denoising for vision-based vibration measurement
No full textWhile vision-based methods are renowned for their ability in full-field vibration measurements, accurately and robustly extracting subtle displacements remains a significant challenge. To address this, this paper presents a novel Optimal Phase-projection Wavelet Denoising (OPWD) method for vision-based vibration measurement that is adept at extracting characteristics of subtle displacement components. The OPWD method enhances signal quality through a structured three-step process: constructing a signal model from pixel array data, transforming this model into the frequency-space domain, and applying wavelet denoising in the spatial dimension. The method was validated through experimental comparisons on a structural beam, confirming consistency with the resonance frequencies obtained from accelerometers and mode shapes from finite element analysis. This study also contributes a comprehensive framework that lays the groundwork for future developments and implementations of additional methods in vision-based vibration measurement.</p
Token-Bucket-Protocol-Based Recursive Remote State Estimation for Complex Networks under Amplify-and-Forward Relays
Get PDFThis article is concerned with a recursive remote estimation problem for a class of nonlinear complex networks subject to the token bucket protocol (TBP) and amplify-and-forward (AF) relays. The influence of the TBP is considered, for the first time, in the context of networked state estimation, where the token consumptions are modeled in a stochastic manner, so as to describe the potential size variability of transmitted measurement signals. Once processed by the TBP, the signals, with stochastic channel coefficients, are transmitted to the remote estimator via AF relays, where a failure in transmission under the TBP may occur due to insufficient tokens in the bucket. An extended-Kalman-filter-based novel recursive estimator is proposed, and by solving Riccati-like difference equations, an upper bound of prediction/estimation error covariance is determined and further minimized through the design of an appropriate estimator gain. The impact of the TBP on estimation performance is also investigated. Some numerical simulations are presented to demonstrate the effectiveness of the proposed estimator and the effects of the TBP.</p
Modeling and analysis of internal excitation and vibration characteristics of gears with early-stage crack and 3D tooth surface error
No full textAffected by the tooth surface errors, the vibration characteristics of early crack failures are usually various under different tooth surface precision level. Therefore, to reveal the influence of three-dimensional (3D) tooth surface error (TSE) on the internal excitation and vibration characteristics of gears with early-stage crack (ESC), a coupling internal excitation model of gears with ESC and 3D errors is proposed based on a double-layer iterative method. In this model, the influence of meshing phase between tooth pair and along tooth width direction (TWD) on the time-varying mesh stiffness (TVMS) are simultaneously considered, which overcomes the limitations of traditional models that are only suitable for characterizing the coupled excitation of the two-dimensional tooth profile errors and TVMS. Based on verifying the proposed model, the effects of TSE type, parameters, and load on the TVMS, loaded static transmission error (LSTE), load distributions, and torsional deformation of the cracked gear teeth are investigated, and the vibration characteristics of ESC failures under the effects of 3D TSE are also explored. The research results show that the distribution parameters of 3D TSE have a significant effect on the internal excitation and vibration characteristics of gears with ESC, and thus measuring and evaluating the distribution parameters of TSE can help improve the accuracy of gear fault identification and diagnosis methods.</p
Thermal performance investigation of latent heat-packed bed thermal energy storage system with axial gas injection
No full textThe latent heat-packed bed thermal energy storage system has a broad application prospect in industrial waste heat recovery and solar thermal energy collection. In this work, a novel design with axial gas injections is proposed with the examination for waste heat recovery from the spodumene calcination process. Part of the heat transfer fluid is diverted from the main inlet to the axial inlets, which leads to heat transfer enhancement due to flow rate drop and elevated temperature difference. Compared to the conventional design, axial gas injection leads to an immediate enhancement in temperature uniformity, with a maximum of 64 K decrease in temperature difference, which could reduce thermally induced damage and improve device safety. The axial design also leads to increased charging efficiency by up to 21 %, with the charging efficiency increasing with the number of axial inlets. Further investigation shows charging efficiency is inversely proportional to porosity, with porosity decreasing from 0.5 to 0.3, charging efficiency increases by 15 % at the end of charging, while the round-trip efficiency is on the contrary. Moreover, studies on heat transfer fluid show that elevated mass flow rate leads to decreased charging efficiency and improved round-trip efficiency, which is due to higher entropy generation and enhanced heat transfer rate. For a dedicated application, the packed bed needs to be optimized depending on the thermal performance, safety, and given requirements.</p
New Directions in Musical Collaborative Creativity:The Glasgow Improvisers Orchestra and the Theater of Home
No full textThe COVID pandemic brought numerous challenges for people working in creative contexts. One such example was the Glasgow Improvisers Orchestra (a critically acclaimed and prolific international ensemble), which began twice weekly online workshops at the start of the UK lockdown in March 2020. The group quickly grew, collecting over 100 musicians from around the world who were interested in maintaining contact via improvising on a virtual platform, Zoom. This book explores the nature of the online sessions, investigating psychological and social benefits and the creative breakthroughs achieved during these sessions. With a particular focus on technology and identities, the book sheds new light on the nature of creative activities and their pivotal role in sustaining and enhancing communities in musical and other contexts. Ten chapters explore topics that include an overview of digital music approaches, an investigation of how improvisations begin and end, the unique context of the online sessions, the integration of audio and visual stimuli to produce audiovisual compositions, and new types of creative activities. The book discusses ways in which improvisation (and in particular, online improvising) can be used to foster a new sense of community while offering new possibilities for experimentation, communication, community engagement, education, new virtuosities, health, and well-being. The book also investigates implications for education and health, emphasizing the importance of new technologies and their potential to produce significant creative breakthroughs. It points to a way forward for new types of technologically mediated community creative engagement.<br/
Demystifying and Preparing for Advanced Practice:A Guide for Healthcare Professionals
No full textWith advanced practice set to transform health service delivery, Demystifying and Preparing for Advanced Practice is the first comprehensive resource that covers all the requirements of the advanced practice qualification, across all health professions and in all settings.Written by expert authors from across the UK, the book explores the four central pillars under which Advanced Practitioners are required to operate: clinical practice, leadership and management, education, and research. It will help the reader understand their role, prepare for and pass their assessments, and go on to practise autonomously.This book is an indispensable guide for all those undertaking their Master’s qualification, and is ideal for both aspiring and student Advanced Practitioners
ARHGAP12 and ARHGAP29 exert distinct regulatory effects on switching between two cell morphological states through GSK-3 activity
No full textCancer cells undergo morphological changes and phenotype switching to promote invasion into healthy tissues. Manipulating the transitional morphological states in cancer cells to prevent tumor dissemination may enhance survival and improve treatment response. We describe two members of the RhoGTPase activating protein (ARHGAP) family, ARHGAP12 and ARHGAP29, as regulators of transitional morphological states in glioma via Src kinase signaling events, leading to morphological changes that correspond to phenotype switching. Moreover, we establish a link between glycogen synthase kinase 3 (GSK-3) inhibition and β-catenin translocation in altering transcription of ARHGAP12 and ARHGAP29. Silencing ARHGAP12 causes loss of N-cadherin and adoption of mesenchymal morphology, a characteristic feature of aggressive cellular behavior. In patients with glioblastoma (GBM), we identify a link between ARHGAP12 and ARHGAP29 co-expression and recurrence after treatment. Consequently, we propose that further investigation of how ARHGAPs regulate transitional morphological events to drive cancer dissemination is warranted
Dynamic Modeling of a Double-Row Cylindrical Roller Bearing with Three-Dimensional Defect
No full textPurpose: The bearing defect in operating machines will expand in circumferential, axial and radial direction, but the defect change in axial direction is rarely considered in existing researches. Methods: A complete dynamic model of double-row cylindrical roller bearing with three-dimensional inner race defect is presented in this paper. Both the inner race and the outer race can move vertically and horizontally, and the inner race can also rotate around its axis. Each roller rotates around its axis and revolves around the bearing shaft. The radial load is applied on the outer race, and the interaction between the roller and the raceway is analysed in detail by formulating different coordinate systems to obtain the contact force and traction force, and then the corresponding moments are calculated. The lubrication state is considered as isothermal elastohydrodynamic lubrication, and the contact between the roller and the defect is simulated based on their spatial relationship. Results: Influences of the defect’s length, width and position on acceleration, contact force, roller slip characteristic and envelope spectrum are presented. In order to understand the coupling mechanism between local defect and distributed defect, dynamic behaviour of bearing with inner race defect and inner race misalignment is investigated. Results show that the fault characteristics of both defects can be observed concurrently. Experiments are performed and the results are in good accordance with the simulation ones Conclusion: The superiority of the three-dimensional fault modelling proposed in this paper is shown.</p
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