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Improving estimates of tropical cyclone forecast uncertainty remains an important goal of the Hurricane Forecast Improvement Project (HFIP). Intensity forecast uncertainty near landfall is especially complicated because intensity forecasts depend on track forecasts. Ensembles can be difficult to interpret near land due to differences in both spatial and temporal resolution and differences in landfall timing (if at all) and location. The Monte Carlo Wind Speed Probability (WSP) model is a statistical ensemble based on the error characteristics of forecasts by the National Hurricane Center (NHC) and the spread of several track forecast models. The landfall distribution product (LDP) introduced in this paper was developed to use the statistical ensemble of forecasts from the WSP model to estimate both the track and intensity forecast uncertainty associated with potential landfalls. The LDP includes probabilistic intensity estimates as well as estimates of the most likely and reasonable strongest intensity at landfall. These products could communicate concise intensity uncertainty information to users at risk for tropical cyclone impacts. Demonstration on a retrospective dataset from 2010-2018 and evaluation of the LDP on the 2020-2021 Atlantic hurricane seasons shows that the probability of landfall and the landfall intensity probabilities generated by the WSP model are reliable and potentially useful for preparedness decision making. A case study of Hurricane Ida (2021) highlights how the LDP can be implemented to communicate landfall uncertainty to a broad range of users.

Made available in DSpace on 2021-06-25T10:48:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 National Outstanding Youth Science Fund Project of National Natural Science Foundation of China Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Impulse response functions (IRFs) and frequency response functions (FRFs) are fundamental quantities that describe the dynamic behaviour of a linear vibrating system in the time and frequency domains respectively. The acceleration IRF is of particular concern in this paper, because unlike the displacement and velocity IRFs it contains a Delta function as well as a decaying oscillation. The origin of this Delta function is shown to be due to the causality constraint rather than the system. To illustrate the characteristics of the IRFs and FRFs, simulations are presented for a single-degree-of-freedom system, and are supported by some laboratory experimental work. The acceleration IRF is partitioned into the impulse component (Delta function for the simulations) and the oscillatory component. They are separately transformed to the frequency domain to illustrate their effects in the accelerance FRFs for both simulated and measured data. Department of Mechanical Engineering UNESP-FEIS Institute of Internal Combustion Engine Dalian University of Technology Faculty of Science and Engineering UNESP-FCE Department of Mechanical Engineering UNESP-FEB Department of Mechanical Engineering UNESP-FEIS Faculty of Science and Engineering UNESP-FCE Department of Mechanical Engineering UNESP-FEB National Outstanding Youth Science Fund Project of National Natural Science Foundation of China: 11672058 FAPESP: 2013/50412-3 FAPESP: 2017/14432-0 FAPESP: 2017/16953-8 CNPq: 88887.374001/2019-00

Recently, a lot of attention has been given to a mechanical device known as the inerter. It is a mechanical component that can be compared to a capacitor with two ungrounded terminals in the mechanical-electrical systems analogy. In this paper, it is shown that although the concept of an inerter as a separate mechanical element is relatively new, there are several well-established vibration isolation systems that exhibit similar behavior to a simple lumped parameter system containing an inerter. Through a review of the literature, a link is established between the old and new ideas. Furthermore, a comparison between the systems is carried out using the quantities of mechanical impedance and displacement transmissibility. The advantages and disadvantages of using the inerter in vibration isolation are discussed, and a simple way of improving the high-frequency performance without severely degrading the low-frequency performance is described.

Breast cancer is the most commonly diagnosed female cancer. Diagnosis in younger women (under 35 years) is different to their older counterparts, and mammography is not considered as sensitive in this cohort. Consequentially, younger patients may present later with more advanced disease. This is a retrospective analysis of a prospectively updated database containing consecutive patients who presented to the symptomatic breast unit of Galway University Hospital between 2009 and 2015. Patient clinicopathologic factors, clinical examination features, diagnostic radiological modalities and Bi-RADS score were all assessed. Data was analysed using Statistical Package for the Social Sciences version 25. One thousand eight hundred thirty-six patients were diagnosed with breast cancer, and of these, 51 (2.8%) patients were

Made available in DSpace on 2020-12-10T17:06:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-14 Operational modal analysis is an experimental modal analysis approach, which uses vibration data collected when the structure is under operating conditions. Amongst the methods for operational modal analysis, blind source separation-based methods have been shown to be efficient and powerful. The existing blind source separation modal identification methods, however, require the number of sensors to be at least equal to the number of modes in the frequency range of interest to avoid spatial aliasing. In this article, a frequency domain algorithm that overcomes this problem is proposed, which is based on the joint diagonalization of a set of weighted covariance matrices. In the proposed approach, the frequency range of interest is partitioned into several frequency ranges in which the number of active modes in each band is less than the number of sensors. Numerical simulations and an experimental example demonstrate the efficacy of the method. Harbin Engn Univ, Harbin, Peoples R China Univ Lyon, INSA Lyon, Lyon, France Univ Estadual Paulista, Sao Paulo, Brazil Univ Estadual Paulista, Sao Paulo, Brazil

Made available in DSpace on 2022-04-28T19:50:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 There is an ever-increasing requirement for higher power vibrating platforms to test large-scale structures. Whilst this may be achieved with a single shaker, this is an expensive option. An alternative solution is to drive a platform with two or more smaller shakers. To do this effectively, however, requires the identical amplitude and phase response of the shakers. In practice, due to manufacturing tolerances and uneven loading, this is not possible without a control system. The design and implementation of such a system is the objective of this paper. An adaptive FxLMS algorithm is used in the synchronous control of a dual-shaker system, considering the dynamic coupling between the shakers. A simulation is presented to verify the effectiveness of the control algorithm before the control system is integrated with practical a dual-shaker system driving a vibrating platform. It is shown that there are significant differences between the controlled and the uncontrolled system, demonstrating the efficacy of the control approach. College of Power and Energy Engineering Harbin Engineering University Department of Mechanical Engineering UNESP Department of Mechanical Engineering UNESP

Made available in DSpace on 2022-04-29T08:33:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Acoustic correlators are often used to pinpoint leaks in water distribution systems. Generally, these devices are tested for their efficacy in bespoke test rigs that are also used for training purposes. However, this can be problematic as it is difficult to expose the correlators to identical conditions, and only a limited number of situations is possible. An alternative approach is described in this paper, in which a bench-top device, called a leak noise simulator (LNS), is used to generate pipe vibration representative of measured leak noise. The LNS comprises a computer to generate and supply the signals, a dual channel power amplifier and two electrodynamic shakers and accelerometers to generate and measure the vibrations. There are two modes of operation. One involves the generation of leak noise signals using a theoretical model of the buried water pipe implemented in the computer, and the other replicates measured signals from the field that are stored in the computer. To faithfully replicate the pipe vibration due to leak noise, the dynamic effects of the power amplifier and shakers are compensated for by using a filter implemented in the computer. The design and testing of the LNS in both modes are reported in detail, demonstrating the potential of the device. Department of Mechanical Engineering UNESP-FEIS, Ilha Solteira Faculty of Science and Engineering UNESP-FCE, Tupã Department of Mechanical Engineering UNESP-FEB, Bauru Department of Mechanical Engineering UNESP-FEIS, Ilha Solteira Faculty of Science and Engineering UNESP-FCE, Tupã Department of Mechanical Engineering UNESP-FEB, Bauru CAPES: 1836088 FAPESP: 2013/50412-3 FAPESP: 2017/14432-0 FAPESP: 2017/16953-8 CAPES: 88887.374001/2019-00

Made available in DSpace on 2022-04-29T08:32:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-12-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A common way to pinpoint a leak in a buried plastic water pipe is to use a leak noise correlator. This is performed by using the time delay between two measured signals and the velocity at which such signals travel along the pipe. In this paper, an investigation is carried out into the use of a geophone in reverse, driven by an oscillating voltage. It then acts as a tapping device, exciting the wave responsible for leak noise propagation, when it is attached to an access point to estimate leak noise velocity. Two different ways of exciting the geophone were investigated. Initial tests were conducted in the laboratory to determine the effectiveness of the device in generating a force over a wide frequency range. Field tests were then carried out on a buried pipe test rig and the predominantly fluid-borne wave was generated by the tapping device, that travelled at least 7 m. São Paulo State University (Unesp) Faculty of Science and Engineering (FCE) Department of Biosystem Engineering São Paulo State University (Unesp) School of Engineering (FEB) Department of Mechanical Engineering São Paulo State University (Unesp) Faculty of Engineering (FEIS) Department of Mechanical Engineering São Paulo State University (Unesp) Faculty of Science and Engineering (FCE) Department of Biosystem Engineering São Paulo State University (Unesp) School of Engineering (FEB) Department of Mechanical Engineering São Paulo State University (Unesp) Faculty of Engineering (FEIS) Department of Mechanical Engineering FAPESP: 2013/50412-3 FAPESP: 2016/01733-0 FAPESP: 2017/14432-0 FAPESP: 2017/16953-8 CAPES: 88887.374001/2019-00

Made available in DSpace on 2020-12-12T02:15:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Vibration isolation of a floating raft system typically found in a marine application is of concern in this paper. Housed on the raft are electrical motors each driving two counter rotating shafts with eccentric masses attached. An experimental study is described in which vibration transmitted to a large-scale, laboratory-based hull-like structure is attenuated by using three measures. They are, the use of vibration isolators between the raft and the hull-like structure, adjustment of the phase of the electrical supply between the motors to minimize vibration transmitted through the isolators, and the application of an active vibration control system using hydraulic actuators placed in parallel with the isolators. The results show that this combination of measures is extremely effective at reducing the vibration transmission to the hull-like structure, and consequent reduction the sound radiation. It is more effective than the application of any of the vibration control measures applied by themselves. Power and Energy Engineering College Harbin Engineering University Departamento de Engenharia Mecânica Universidade Estadual Paulista (UNESP) Ilha Solteira (SP) Departamento de Engenharia Mecânica Universidade Estadual Paulista (UNESP) Ilha Solteira (SP)

Made available in DSpace on 2019-10-06T17:14:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-09-01 There are well-known expressions for natural frequencies and mode shapes of a Euler-Bernoulli beam which has classical boundary conditions, such as free, fixed, and pinned. There are also expressions for particular boundary conditions, such as attached springs and masses. Surprisingly, however, there is not a method to calculate the natural frequencies and mode shapes for a Euler–Bernoulli beam which has any combination of linear boundary conditions. This paper describes a new method to achieve this, by writing the boundary conditions in terms of dynamic stiffness of attached elements. The method is valid for any boundaries provided they are linear, including dissipative boundaries. Ways to overcome numerical issues that can occur when computing higher natural frequencies and mode shapes are also discussed. Some examples are given to illustrate the applicability of the proposed method. São Paulo State University (UNESP) School of Engineering Zayed University Dalian University of Technology Institute of Internal Combustion Engine São Paulo State University (UNESP) School of Engineering

A global BCG vaccine shortage began in 2013 which impacted availability for infant vaccinations, as well as preclinical studies and clinical trials of new TB vaccines. Stakeholders met in 2015 at McGill University in Montreal to discuss the shortage and potential mitigation strategies. Manufacturing BCG through a more tractable liquid fermentation process instead of the traditional pellicle growth method was considered a potentially viable strategy. This pilot program compared pellicle-grown and shake flask-grown BCG strains (as a first step towards modeling fermenter-produced BCG vaccine) in selected quality control assays, as well as mouse and guinea pig protection studies. Conventional pellicle-grown, lyophilized BCG WHO Reference Reagents (Danish, Moreau, Russian, Tokyo strains) were obtained from the National Institute for Biological Standards and Control (NIBSC), UK. Strains were grown in shake flasks and glycerol stocks prepared. Shake flask-grown BCG culture preparations generally met the requirements of quality control testing at NIBSC. In mouse and guinea pig protection studies there were no significant differences in lung colony forming units (CFUs) between shake flask-grown and pellicle-grown preparations, with the exception of BCG Russian, where the shake flask-grown preparation protected better in mice (P = 0.0042), but the pellicle-grown preparation protected better in guinea pigs (P = 0.0015). Producing BCG vaccines by a more tractable liquid growth process could be a viable solution to the global BCG shortage.

Made available in DSpace on 2019-10-06T15:18:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 There is an increasing desire to monitor the structural integrity of railway tracks and the supporting ballast and subgrade. Track vibration has been proposed as a potential energy source to power wireless sensors for this purpose. Vibration-based energy harvesting devices generally exploit resonance, and hence need to be tuned to a particular target frequency. Thus, to harvest energy from the vibrations of a passing train, the spectral content of the track vibration needs to be known. This paper describes a fundamental investigation into the factors that govern this spectral content. A simple model of the train and the track, together with data from five trains passing at four different sites are used in this investigation. It is shown that the deflection under an individual wheel effectively acts as a bandpass filter, restricting the acceleration spectrum of sleeper vibration to low frequencies. The train geometry has an important effect on which specific trainload frequency has the largest response amplitude. For the trains studied, it was found that the 7th trainload frequency had the highest amplitude in four out of the five cases. The physical reasons as to why this trainload frequency is the largest are discussed. Departamento de Engenharia Mecânica Universidade Estadual Paulista (UNESP) Department of Mechanical Energy and Management Engineering Univeristy of Calabria Institute of Sound and Vibration Research University of Southampton Departamento de Engenharia Mecânica Universidade Estadual Paulista (UNESP)

In the last two decades, the subject area of smart/intelligent materials and structures has experienced tremendous growth in terms of research and development. One reason for this activity is that it may be possible to create certain types of structures and systems capable of adapting to or correcting for changing operating conditions. The advantage of incorporating these special types of materials into the structure is that the sensing and actuating mechanism becomes part of the structure by sensing and actuating strains directly. Piezoelectric material is often suitable for this purpose. This type of material possesses direct and converse piezoelectric effects; when a mechanical force is applied to the piezoelectric material, an electric voltage or change is generated, and when an electric field is applied to the material, a mechanical force is induced. With the recent advances in piezoelectric technology, it has been shown that the piezoelectric actuators based on the converse piezoelectric effect can offer excellent potential for active vibration control techniques, especially for vibration suppression or isolation. A truss structure is one of the most commonly used structures in aerospace and civil engineering (Yan & Yam, 2002). Because it is desirable to use the minimum amount of material for construction, trusses are becoming lighter and more flexible which means they are more susceptible to vibration. Passive damping is not a preferred vibration control solution because it adds weight to the system, so it is of interest to study the active control of such a structure. A convenient way of controlling a truss structure is to incorporate a piezoelectric stack actuator into one of the truss members (Anthony & Elliot, 2005). An important feature of control system in the truss structure is the collocation between the actuator and the sensor. An actuator/sensor pair is collocated if it is physically located at the same place and energetically conjugated, such as force and displacement or velocity, or torque and angle. The properties of collocated systems are remarkable; in particular, the

Made available in DSpace on 2021-06-25T10:17:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-01 In some applications, such as ground vibration testing in the aerospace industry, it is of interest to observe the modal behaviour of a slender structure while it is statically loaded. One way of statically loading such a structure is to suspend masses using very soft springs. If the springs are linear, then this results in an extremely large static deflection of the springs. This problem could be overcome by dynamically isolating the masses using quasi-zero stiffness (QZS) springs. This paper describes the design, construction and experimental testing of a device that can exhibit QZS. A novel design is proposed that allows the stiffness and the symmetry of the device to be adjusted independently using separate adjustment mechanisms. Quasi-static and dynamic testing of the device show that it can be adjusted to have an extremely low stiffness within the limits of measurement. The main trend of the force-displacement curve shows that it has a cubic stiffness characteristic, and that friction is responsible for its hysteretic behaviour. Dynamic testing shows that the device locks-up due to friction at low frequencies, but at high frequencies the device acts as an efficient linear isolator. An experiment was also performed where a mass was suspended on a multi-modal beam structure via the QZS device. It was shown that a static load could be applied to the beam without the attached mass appreciably affecting the dynamic response of the beam, even though the suspended mass was about 12% of that of the host structure. College of Engineering Swansea University Department of Mechanical Energy and Management Engineering University of Calabria Department of Mechanical Engineering Faculty of Engineering UNESP Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Department of Mechanical Engineering Faculty of Engineering UNESP

Tuberculosis (TB) vaccine candidates must be tested for safety and efficacy using preclinical challenge models prior to advancement to human trials, because of the lack of a validated immune correlate or biomarker of protection. New, unbiased tools are urgently needed to expedite the selection of vaccine candidates at an early stage of development and reduce the number of animals experimentally infected with virulent Mycobacterium tuberculosis (M.tb). In recent years, there has been a concerted effort to develop standardised functional ex vivo mycobacterial growth inhibition assays (MGIAs) as a potential surrogate read-out of vaccine efficacy. We have previously described a direct MGIA for use with mouse splenocytes. In the current study, we set out to systematically compare co-culture conditions for the murine direct splenocyte MGIA with respect to both intra-assay repeatability and inter-site reproducibility. Common sample sets were shared between laboratory sites and reproducibility and sensitivity to detect a BCG-vaccine induced response were assessed. Co-culturing 5×106 splenocytes in 48-well plates resulted in improved reproducibility and superior sensitivity to detect a vaccine response compared with standing or rotating sealed 2ml screw-cap tubes. As the difference between naïve and BCG vaccinated mice was not consistently detected across both sample sets at both sites, we sought to further improve assay sensitivity by altering the multiplicity of infection (MOI). Cell viability at the end of the co-culture period was improved when splenocyte input number was reduced, with the highest viability for the condition of 3×106 splenocytes in 48-well plates. This cell input was also associated with the greatest sensitivity to detect a BCG vaccine-mediated MGIA response using an M.tb inoculum. Based on our findings, we recommend optimal co-culture conditions in a move towards aligning direct MGIA protocols and generating a cross-species consensus for early evaluation of TB vaccine candidates and biomarker studies.

Made available in DSpace on 2020-12-12T01:34:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-01 The free vibration displacement of an undamped hardening Duffing oscillator is described in exact form by a Jacobi elliptic function. Unlike an undamped linear oscillator, whose displacement is described by a trigonometric function, a Jacobi elliptic function is difficult to interpret by a simple inspection of the function arguments. The displacement of a linear oscillator is often visualised as a rotating vector, which has two characteristics — a constant amplitude and a phase (or frequency). These parameters are readily related to the physical response of the system. In this paper, a similar approach is applied to the free vibration displacement of a Duffing oscillator. However, the rotating vector description of the motion is much more complicated than for a linear system. It still has two characteristics though — an amplitude and a phase, but in general both these quantities are dependent on the position of the vector, i.e., they are frequency modulated. It is shown that there is not a unique rotating vector representation of the cn Jacobi elliptic function. Indeed, there are an infinite number of elliptical loci bounded between an elliptical and a circular locus of the vector. There are two specific cases. One is where the amplitude of the vector is constant and the phase angle is frequency modulated (the circle), and the other is when the amplitude of the vector is frequency modulated and the angular velocity is constant. In all other cases, both the amplitude and the angular velocity of the rotating vector are frequency modulated. To aid in the visualisation of the rotating vectors that represent the free vibration solution of a highly nonlinear hardening Duffing oscillator, two animations are provided. Department of Mechanical Engineering UNESP Department of Mechanical Energy and Management Engineering University of Calabria Centre for Vibro-Acoustic Systems and Signal Processing Faculty of Technical Sciences University of Novi Sad Department of Mechanical Engineering UNESP

Made available in DSpace on 2020-12-12T01:38:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Ministero degli Affari Esteri e della Cooperazione Internazionale Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Guided waves at high frequency are used in structural health monitoring systems to detect damage. The successful application of the technique, however, requires a deep understanding of wave mode propagation and scattering, as this allows the correct choice of frequency range and wave types to be used to interrogate the structure. Often, this is not the case and systems are developed in an ad hoc way. There is, thus, a greater need to understand the way in which guided waves interact with, and are scattered by, damage. This paper aims to contribute to knowledge in this area. A wave finite element method is applied in a study of wave scattering from symmetric and asymmetric changes of cross-sectional area over a finite length in a waveguide, which are intended to be crude models of corrosion damage. To facilitate analysis of the results, Lamb wave scattering is first investigated in such a system for a point discontinuity involving a change in cross-sectional area. The wave scattering characteristics are evaluated by using the time-averaged kinetic energy of the reflected and transmitted wave fields considering components in the vertical and horizontal directions. This, together with the traditionally used displacement and energy flow coefficients, allows an investigation into the rich wave scattering behaviour due to multi-mode behaviour and wave mode conversion which can complicate the interpretation of the results. In particular, it is shown that care needs to be taken in the interpretation of a sudden increase in the amplitude of a reflected wave from damage. At certain frequencies, this can be due to evanescent waves starting to propagate, rather than an increase in the severity of the damage. School of Mechanical Engineering UNIFESSPA – Universidade Federal do Sul e Sudeste do Pará, Folha 17, quadra 04 Department of Engineering and Architecture University of Parma, Parco Area delle Scienze 181/A Department of Mechanical Engineering UNESP - São Paulo State University, Avenida Brasil 56 Department of Mechanical Engineering UNESP - São Paulo State University, Avenida Brasil 56 CAPES: 001

Made available in DSpace on 2020-12-12T01:10:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-01 National Natural Science Foundation of China Fundamental Research Funds for the Central Universities Measurement uncertainty can affect the accuracy of estimating parameters of vibrating systems. This article is concerned with the development of a method for estimating parameters from the free vibration response of a nonlinear system in which the response signal is contaminated with Gaussian white noise. The backbone curve and envelope of the response are first estimated from the free vibration signal. An algorithm based on the Bayesian approach is then used to identify the stiffness and damping parameters of a nonlinear system excited at a single resonant frequency. A numerical example is provided to illustrate the proposed method, which is then applied to the experimental data from a nonlinear vibration absorber system that was excited at its first resonant frequency. The proposed approach provides the distribution and confidence intervals of the parameter estimates, which is an improvement on methods that provide a single number for each estimate. As the signal-to-noise ratio decreases, the variances of the posterior distributions increase as do the confidence intervals, reflecting greater uncertainty in the parameter estimates. The approach is effective provided that the signal-to-noise ratio is greater than about 10. Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education Dalian University of Technology Institute of Internal Combustion Engine Dalian University of Technology Faculty of Engineering Department of Mechanical Engineering UNESP Qian Xuesen Laboratory of Space Technology China Academy of Space Technology Faculty of Engineering Department of Mechanical Engineering UNESP National Natural Science Foundation of China: 11672058 Fundamental Research Funds for the Central Universities: DUT18LAB15

Made available in DSpace on 2020-12-12T01:25:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-01 An active vibration isolation system is retrofitted to a diesel generator set in a tugboat to determine the effectiveness of such a system in a realistic practical environment. The system consists of six bespoke inertial actuators chosen to make minimal modifications to the machinery arrangement, and a DSP-based controller. Six accelerometers are collocated with the actuators on the top of six isolators to act as error sensors, and six accelerometers are placed below the isolators to give a measure of the global vibration of the ships structure below the generator set. A hydrophone is also placed in the water to give an indication of the underwater noise due to the generator. The control strategy employed is six-input and six-output decentralized adaptive feedforward control with the reference signal being derived from the signal from an optical tachometer on shaft between the engine and the generator. To suppress the vibration at all the dominant forcing frequencies, an electrical circuit generated the half engine orders required from the measured reference signal. The experimental results show that the combination of the active control system and the passive isolators is effective in reducing the global vibration and the acoustic pressure at the hydrophone position. Institute of Vibration and Noise Control Harbin Engineering University Departamento de Engenharia Mecânica Universidade Estadual Paulista (UNESP) Departamento de Engenharia Mecânica Universidade Estadual Paulista (UNESP)

Made available in DSpace on 2020-12-12T01:13:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-02-01 National Natural Science Foundation of China The detection and location of pipeline leakage can be deduced from the time difference between the arrival leak signals measured by sensors placed at the pipe access points on either side of a suspected leak. Progress has been made in this area to offer a potential improvement over the conventional cross-correlation method for time delay estimation. This paper is concerned with identifying suitable sensors that can be easily deployed to monitor the pipe vibration due to the propagation of leak noise along the pipeline. In response to this, based on the low-frequency propagation characteristics of leak noise in our previous study, polyvinylidene fluoride (PVDF) wire sensors are proposed as a potential solution to detect the pipeline leak signals. Experimental investigations were carried out at a leak detection pipe rig built in the Chinese Academy of Sciences. Their performances for leak detection were shown in comparison with hydrophones. It is suggested that with special considerations given to aspects pertaining to non-intrusive deployment and low cost, the PVDF wire sensors are of particular interest and may lead to a promising replacement for commercial leak noise transducers. Key Laboratory of Noise and Vibration Research Institute of Acoustics Chinese Academy of Sciences University of Chinese Academy of Sciences Department of Mechanical Engineering UNESP Department of Mechanical Engineering UNESP National Natural Science Foundation of China: 11774378

Made available in DSpace on 2022-04-28T19:43:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-02-01 A translational Lanchester damper is a device that adds damping to a structure at a point using a series combination of a viscous damper and a mass. The problem in the practical realisation of such a device is that a stiffness is required to support the mass, which changes the dynamic behaviour of the device, introducing a resonance frequency due to the interaction of the stiffness and inertia forces. This is a dynamic vibration absorber. To achieve a device that behaves broadly as a Lanchester damper rather than a dynamic vibration absorber, a very low stiffness is required, and this is the focus of this paper. The low stiffness is realised using a combination of linear springs and rigid links arranged with specific geometry into a compact device. Although the geometric configuration of the components leads to an inherently nonlinear device, the aim is to limit its working condition and exploit the linear-like behaviour. To this end, how the geometry affects the nonlinear behaviour is studied in detail, providing general guidelines for its design. A prototype Lanchester damper incorporating the low stiffness element was manufactured and tested on a single mode and two multi-modal vibrating structures. Department of Mechanical Energy and Management Engineering University of Calabria College of Engineering Swansea University Department of Mechanical Engineering Faculty of Engineering UNESP Department of Mechanical Engineering Faculty of Engineering UNESP

In this paper we present empirical tests of an extended version of the capital asset pricing model (CAPM) that replaces the single-period horizon with a probability distribution over different horizons. Adopting a simple parameterization of the probability distribution of the length of the horizon, we estimate the parameters of the distribution as well as the parameters of the CAPM. We find that the extended model is not rejected for several different samples of common stocks, and for these samples it outperforms not only the standard CAPM but also the Fama–French (1993) 3-factor model. The probability distribution over horizon dates varies over time with the New York Stock Exchange (NYSE) turnover rate. We also find that returns satisfy the Euler equation of a representative financial institution that holds the market portfolio and has horizon probabilities estimated from 13F filings.

Made available in DSpace on 2018-12-11T16:55:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 High-static-low-dynamic-stiffness (HSLDS) nonlinear isolators have proven to have an advantage over linear isolators, because HSLDS nonlinear isolators allow low-frequency vibration isolation without compromising the static stiffness. Previously, these isolators have generally been assumed to have linear viscous damping, degrading the performance of the isolator at high frequencies. An alternative is to use nonlinear damping, where the nonlinear behavior is achieved by configuring linear dampers so they are orthogonally aligned to the excitation direction. This report compares the performances of single-stage and two-stage isolators with this type of damping with the corresponding isolators containing only linear viscous damping. The results show that both isolators with linear viscous damping and nonlinear damping reduce the transmissibility around the resonance frequencies, but the results show that the isolators with nonlinear damping perform better at high frequencies. Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Departamento de Engenharia Mecânica Universidade Estadual Paulista (UNESP) Department of Mechanics Shanghai University Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai University Departamento de Engenharia Mecânica Universidade Estadual Paulista (UNESP)

Made available in DSpace on 2020-12-10T19:46:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 Natural Science Foundation of China In this paper, the single-sided vibro-impact track nonlinear energy sink (SSVI track NES) is studied. The SSVI track NES, which is attached to a primary structure, has nonlinear behavior caused by the NES mass moving on a fixed track and impacting on the primary structure at an impact surface. Unlike previous studies of the SSVI track NES, both the horizontal and vertical dynamics of the primary structure are considered. A numerical study is carried out to investigate the way in which energy is dissipated in this system. Assuming a track shape with a quartic polynomial, an optimization procedure that considers the total energy dissipated during a time period is carried out, to determine the optimum NES mass and track parameter. It is found that there is dynamic coupling between the horizontal and vertical directions caused by the SSVI track NES motion. The vibrational energy, originally in the structure in the horizontal direction, is transferred to the vertical motion of the structure where it is dissipated. Considering that many civil and mechanical systems are particularly vulnerable to extreme loads in the horizontal direction, this energy transformation can be beneficial to prevent or limit damage to the structure. The effect on energy dissipation of the position of the impact surface in the SSVI track NES and the ratio of the vertical to horizontal stiffness in the primary structure are discussed. Numerical results demonstrate a robust and stable performance of the SSVI track NES over a wide range of stiffness ratios. Harbin Engn Univ, Coll Power & Energy Engn, 145 Nantong St, Harbin 150001, Peoples R China Univ Tennessee, Dept Civil & Environm Engn, John D Tickle Bldg, Knoxville, TN 37996 USA Univ Estadual Paulista UNESP, Dept Mech Engn, Av Brasil Centro, BR-15385000 Ilha Solteira, SP, Brazil Univ Estadual Paulista UNESP, Dept Mech Engn, Av Brasil Centro, BR-15385000 Ilha Solteira, SP, Brazil Natural Science Foundation of China: 51375103 Natural Science Foundation of China: 10.13039/501100001809

The interpretation of experimental data from nonlinear structures is challenging, primarily because of dependency on types and levels of excitation, and coupling issues with test equipment. In this paper, the use of the dynamic stiffness method, which is commonly used in the analysis of linear systems, is used to interpret the data from a vibration test of a controllable compressed beam structure coupled to a test shaker. For a single mode of the system, this method facilitates the separation of mass, stiffness and damping effects, including nonlinear stiffness effects. It also allows the separation of the dynamics of the shaker from the structure under test. The approach needs to be used with care, and is only suitable if the nonlinear system has a response that is predominantly at the excitation frequency. For the structure under test, the raw experimental data revealed little about the underlying causes of the dynamic behaviour. However, the dynamic stiffness approach allowed the effects due to the nonlinear stiffness to be easily determined.

In the use of acoustic correlation methods for water leak detection, sensors are placed at pipe access points either side of a suspected leak, and the peak in the cross-correlation function of the measured signals gives the time difference (delay) between the arrival times of the leak noise at the sensors. Combining this information with the speed at which the leak noise propagates along the pipe, gives an estimate for the location of the leak with respect to one of the measurement positions. It is possible for the structural dynamics of the pipe system to corrupt the time delay estimate, which results in the leak being incorrectly located. In this paper, data from test-rigs in the United Kingdom and Canada are used to demonstrate this phenomenon, and analytical models of resonators are coupled with a pipe model to replicate the experimental results. The model is then used to investigate which of the two commonly used correlation algorithms, the Basic Cross-Correlation (BCC) function or the Phase Transform (PHAT), is more robust to the undesirable structural dynamics of the pipe system. It is found that time delay estimation is highly sensitive to the frequency bandwidth over which the analysis is conducted. Moreover, it is found that the PHAT is particularly sensitive to the presence of resonances and can give an incorrect time delay estimate, whereas the BCC function is found to be much more robust, giving a consistently accurate time delay estimate for a range of dynamic conditions.

We explore the dynamics of informed trading around corporate announcements of merger bids, dividend initiations, SEOs, and quarterly earnings by calculating daily posterior probabilities of informed buying and selling. We find evidence of informed trading before the announcements and a significant part of the news in announcements is impounded in stock prices before the announcements by pre-event informed trading. We also find evidence of informed trading after the announcements. Most strikingly, the probability of informed trading after merger bids predicts the probability of the bid being withdrawn or met with a competing bid. For other announcements, post-announcement informed-trading probabilities predict subsequent returns. Received September 26, 2016; editorial decision December 17, 2017 by Editor Andrew Karolyi.

There is a need to identify safe and effective opioid-sparing multimodal alternative treatment strategies and approaches, including topical analgesics, for opioid-experienced chronic pain patients to mitigate the risk of addiction, misuse, and abuse of opioids.This subset analysis from a prospective, observational study evaluated changes in opioid use, other concurrent medication use, and pain severity and interference in opioid-experienced patients (OEP) treated with topical analgesics for chronic pain with measures obtained at baseline and 3- and 6- month follow-up.The 3-month opioid-experienced patient (3-month OEP) group included 121 patients who completed baseline and 3-month follow-up assessments; 27 opioid-experienced patients completed baseline and 6-month follow-up assessments (6-month OEP). Demographic characteristics, and mean pain severity and interference scores were similar between groups at baseline. After treatment with topical analgesics, 49% of patients in the 3-month and 56% of patients in the 6-month group reported they had completely discontinued use of opioids. In addition, 31% of patients at the 3-month assessment and 30% at the 6-month assessment reported that they were no longer taking any pain medication. Other concurrent medications decreased by 65% after 3 months, and 74% after 6 months. There were statistically significant decreases from baseline in pain severity and interference scores within the 3- (CI:0.7-1.4, 1.4-2.2) and 6-month (CI:0.7-2.4 (severity); CI:1.2-3.5 (interference)) OEP groups.Opioid use and other concurrent medications decreased among opioid-experienced chronic pain patients after 3- and 6- months of treatment with topical analgesics. Pain severity and interference scores also decreased. The topical analgesics were reported to be effective and safe for the treatment of chronic pain, with randomized controlled trials needed to confirm these findings.

Anionic emulsions are widely used in North America for road maintenance applications but are less popular in Europe. Due to their distinctive characteristics, the use of anionic emulsions is advantageous when local aggregate is excessively dusty and the cost to wash them to meet requirements would be too expensive. However, anionic emulsions’ compatibility, in terms of adhesion, with certain types of aggregate is reported to be limited. This paper presents the results of an experimental study that was conducted firstly to investigate the effect of aggregate mineralogy on the degree of adhesion (i.e. the bond) between the aggregate and the bitumen using anionic and cationic bitumen emulsions, and secondly to evaluate the potential development and use of new adhesion agents/anti-strips for anionic rapid-set emulsions used in chip seal applications. For this purpose, the degree of adhesion that was achieved between the emulsions used and a range of selected aggregates was measured by means of a series of internationally recognised laboratory adhesion tests. The experimental laboratory work confirmed that the degree of adhesion between the aggregate and emulsion is governed to a large extent by aggregate mineralogical composition and, in particular, its associated electrostatic interaction with a given emulsion. The results obtained indicated that a higher degree of adhesion was achieved when an aggregate was combined with an emulsion possessing the opposite surface charge. Further laboratory test results suggest that the addition of amine-based adhesion agents to an anionic emulsion can significantly improve its degree of adhesion with aggregates possessing an electro-negative surface charge.

Made available in DSpace on 2022-04-28T19:42:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-10-27 Periodic structures have an important role to play in the reduction of vibration within a targeted frequency range. Much of the literature concerning vibrations in periodic structures involves the description of wave behaviour in infinite structures. This paper concerns the dynamic behaviour of a finite mono-coupled periodic structure, concentrating on the prediction of the vibration transmission through the complete structure in terms of the displacement transmissibility of a single cell. An investigation is conducted into the effects of either using an array of symmetric or asymmetric cells comprised of rods, on the lowest frequency range targeted for vibration attenuation. The importance of the orientation of asymmetric cells with respect to the source is also discussed. Analysis of the systems shows that correctly orientated asymmetric cells offer better performance than an array of symmetric cells for a finite mono-coupled periodic structure. Provided that the periodic structure is not connected to a structure that significantly affects its dynamics, there is improved performance both in terms of a wider frequency range in which there is vibration attenuation, and the maximum vibration attenuation within this frequency range. Analytical expressions are derived that allow the prediction of the maximum attenuation within the attenuation band based on the number of symmetric or asymmetric cells. Some experimental work is also presented to support the theoretical predictions. State University of São Paulo – UNESP- School of Engineering Federal University of Grande Dourados – Faculty of Engineering State University of São Paulo – UNESP- School of Engineering

Made available in DSpace on 2021-06-25T10:19:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-06-01 The study of mono-coupled periodic structures has gained renewed interest by the scientific community due to the new applications of metamaterials and meta-structures. Much research has focused on the wave propagation properties of infinite structures. However, this paper focuses on finite periodic structures, in particular the parameters that govern the behaviour of a low frequency stop-band of such a structure. From an engineering perspective, these are the lower and upper cut-off frequencies, i.e., the bandwidth, and the minimum transmission of vibration within the band. Using the Caley-Hamilton theorem, analytical expressions are derived for the receptance, dynamic stiffness and transmissibility of a finite mono-coupled structure. It is shown that the properties of the whole structure can be determined from the transmissibility of a single element. If the element is symmetric, then the expressions describing the stop-band are particularly simple. An approximate analytical expression has been derived that allows the number of elements needed for a given maximum attenuation in a low frequency stop-band to be determined. To illustrate the approach, lumped parameter systems are considered, in which the stop-band behaviour is governed by the addition of mass, stiffness and a vibration absorber. Expressions are derived for the maximum vibration attenuation within the first stop-band, for each case, enabling clear physical insight into the controlling parameters. Expressions are provided for the lower and upper cut-off frequencies of the stop-band. Some experimental results are also presented to support the theoretical analysis. State University of São Paulo UNESP School of Engineering State University of São Paulo UNESP School of Engineering