Academic literature on the topic 'Vibration period'
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Journal articles on the topic "Vibration period"
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Ryazancev, V., M. Gerasimov, and Y. Brazhnik. "REDUCTION OF DIFFERENTLY DIRECTIONAL VIBRATIONS TO ASYMMETRICAL BY CHANGING THE RATIO OF VALUES COMPOSING THE DRIVING FORCE." Bulletin of Belgorod State Technological University named after. V. G. Shukhov 6, no. 5 (2021): 87–94. http://dx.doi.org/10.34031/2071-7318-2021-6-5-87-94.
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Vibrating machines play a primary role in the implementation of programs in the construction and road construction kit. The improvement of vibration machines allows to significantly increase the speed of construction and road construction work. The main working unit of a vibrating machine is a vibrating device or vibrator. Currently, in the industry, vibration devices are used with circular or directional, along a certain straight line of vibrations. Further improvement of vibrating machines is carried out in the direction of creating vibration devices with asymmetric vibrations. At present, there are practically no vibrating machines with asymmetric vibrations. These machines allow to distinguish between the "working" process phase and the "idle" phase within each oscillation period. Moreover, the value of the driving force in the phase of performing useful work is several times higher than the value of the driving force in the direction of idling. Therefore, much less work is spent on idling. This allows to get rid of massive elements - overloads that extinguish the magnitude of the driving force in the direction of idling. Therefore, the urgency is to develop a method for converting existing machines with directional vibrations into asymmetric ones, with a given coefficient of asymmetry of the driving force. This makes it possible to reduce the specific indicators of the metal consumption of vibrating machines and the energy consumption of the work performed.
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Dong, Jie, Yue Yang, and Zhi-Hui Wu. "Propagation characteristics of vibrations induced by heavy-haul trains in a loess area of the North China Plains." Journal of Vibration and Control 25, no. 4 (2018): 882–94. http://dx.doi.org/10.1177/1077546318802980.
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To study heavy train-related vibration, this paper examines the world's largest heavy-freight railway – the Daqin Railway – to study the impacts of the seasonally frozen soil layer on vibrational acceleration. With increasing axle weight, the peak and mean values of the acceleration increased. Vibration acceleration attenuated the most from the shoulder to the embankment footing (51%–71%), while the vibrations at 70 m were attenuated by more than 90%. Certain measures must be taken by those living within 70 m of the railway shoulder. In addition, the acceleration peak caused by trains running in parallel after meeting amplified the vibration by 10%–39%. Moreover, the overall vibrations attenuate with increasing distance, whereas the local vibrations fluctuate. During the freezing period, the acceleration is 13%–26% greater than that of the unfrozen period. The vibration acceleration spectrum is comparatively wider, and is dominated by high-frequency components. Finally, using a three-dimensional model verified by field measurements, the vibrational features were analyzed at different embankment and foundation depths.
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Susastro, Susastro, and Novi Indah Riani. "Pendekatan Eksperimen Karakteristik Respon Getaran Sistem Two Degree of Freedom dengan Penambahan Independent Dual Dynamic Vibration Absorber." R.E.M. (Rekayasa Energi Manufaktur) Jurnal 3, no. 2 (2019): 85. http://dx.doi.org/10.21070/r.e.m.v3i2.1729.
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Vibration is one of the problems that must be reduced in a vehicle. There are many ways to reduce vibration in vehicles, one of them is by adding Dynamic vibration absorber (DVA). While Dual Dynamic vibration absorber (dDVA) is a DVA period that is able to move in the translational direction given to the system to reduce translation vibration and when there is resonance. Translation DVA is an additional type of time used to reduce the vibration of the translation direction. So far there is not much research related to the use of translational DVA to reduce rotational vibrations as well as translation. In this study, a study was conducted related to the use of independent double translational DVA (dDVA) to reduce translation vibrations as well as rotation of the beam. The research was conducted by modeling the system obtained into mathematical equations and simulations were carried out to determine the characteristics of vibrations that arise. In the simulation, one of the DVA periods is placed at the center of the main system period, while the other DVA period is given a change between the center period and the end of the system. The results of the study show that the maximum reduction in translational vibration is 95.51% and occurs when the absorber is placed at the center of the system, while the maximum rotation vibration reduction is 56.62% and is obtained when the system is given with an arm ratio of 1 and zero.
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Wang, Rongrong, Bingnan Wang, Yachao Wang, Wei Li, Zhongbin Wang, and Maosheng Xiang. "Time-Varying Vibration Compensation Based on Segmented Interference for Triangular FMCW LiDAR Signals." Remote Sensing 13, no. 19 (2021): 3803. http://dx.doi.org/10.3390/rs13193803.
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Frequency modulation continuous wave (FMCW) light detection and ranging (LiDAR) 3D imaging system may suffer from time-varying vibrations which will affect the accuracy of ranging and imaging of a target. The system uses only a single-period FMCW LiDAR signal to measure the range of each spot; however, traditional methods may not work well to compensate for the time-varying vibrations in a single period because they generally assume the vibration velocity is constant. To solve this problem, we propose a time-varying vibration compensation method based on segmented interference. We first derive the impact of time-varying vibrations on the range measurement of the FMCW LiDAR system, in which we divide the time-varying vibration errors into primary errors caused by the vibrations with a constant velocity and quadratic errors. Second, we estimate the coefficients of quadratic vibration errors by using a segmented interference method and build a quadratic compensation filter to eliminate the quadratic vibration errors from the original signals. Finally, we use the symmetrical relations of signals in a triangular FMCW period to estimate the vibration velocity and establish a primary compensation filter to eliminate the primary vibration errors. Numerical tests verify the applicability of this method in eliminating time-varying vibration errors with only a one-period triangular FMCW signal and its superiority over traditional methods.
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Anzani, Yunita Ayudhia Anzani, Syahri Ramadhanti, and Noval Mulya Dava. "Analysis of Factors Affecting Period on GHS Using PhET Simulation." Sunan Kalijaga Journal of Physics 5, no. 2 (2023): 63–68. https://doi.org/10.14421/physics.v5i2.3994.
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Physics is one of the sciences that is studied based on facts, natural phenomena, ideas and results of experiments/experiments. Physics is a science that is closely related to everyday life, one of which is found in Simple Harmonic Motion which discusses pendulums on clocks and strings on guitars. Simple vibrations (GHS) are an example of periodic motion when the amplitude of vibrations in the system is relatively small and the displacement is less than 15°. GHS is a regular alternating motion through the equilibrium point and the number of vibrations in one second is always constant. If the movement occurs repeatedly within a certain time interval, it is called periodic motion. One of the experiments that can be done with simple vibrations is to make a mathematical pendulum or a simple pendulum. The method used in this research to determine the factors that affect the period of pendulum vibrations is a literature review and experiments using PhET simulations. The results of this study are data generated from experiments and calculations which state that the factors that affect the period of pendulum vibrations in simple harmonic motion are the length of the rope and the acceleration due to gravity. While the mass has no effect on the period of the pendulum vibration. The effect of the length of the string is directly proportional to the period of the pendulum's vibration, and the effect of gravity is inversely proportional to the period of the pendulum's vibration.
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Chang, Seongkyu. "Active Mass Damper for Reducing Wind and Earthquake Vibrations of a Long-Period Bridge." Actuators 9, no. 3 (2020): 66. http://dx.doi.org/10.3390/act9030066.
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An active mass damper (AMD) was developed that uses a linear motor and coil spring to reduce the vertical vibration of a long-period cable-stayed bridge subjected to wind and earthquake loads. A scaled-down bridge model and AMD were fabricated, and the control effect of the AMD was investigated experimentally and analytically. The AMD was controlled via a linear quadratic Gaussian algorithm, which combines a linear quadratic regulator and Kalman filter. The dynamic properties were investigated using a 1/10 scale indoor experimental model, and the results confirmed that the measured and analytical accelerations were consistent. A vibrator was used to simulate the wind-induced vibration, and the experimental and analytical results were consistent. The proposed AMD was confirmed to damp the free vibration and harmonic load and increase the damping ratio of the bridge model from 0.17% to 9.2%. Finally, the control performance of the proposed AMD was numerically investigated with the scaled-down bridge model subjected to the El Centro and Imperial Valley-02 earthquakes. These results were compared with those of a TMD, and they confirmed that the proposed AMD could reduce excessive vertical vibrations of long-period cable-stayed bridges subjected to wind and earthquakes.
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Khomenko, Andrei P., Sergey K. Kargapoltsev, and Andrey V. Eliseev. "Development of Approaches to Creation of Active Vibration Control System in Problems of the Dynamics for Granular Media." MATEC Web of Conferences 148 (2018): 11004. http://dx.doi.org/10.1051/matecconf/201814811004.
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The article deals with the development of mathematical models and evaluation criteria of the vibration field in the dynamic interactions of the elements of the vibrational technological machines for the processes of vibrational strengthening of long-length parts with help of a steel balls working medium. The study forms a theoretical understanding of the modes of motions of material particles in interaction with a vibrating surface of the working body of the vibration machine. The generalized approach to the assessment of the dynamic quality of the work of vibrating machines in multiple modes of tossing, when the period of free flight of particles is a multiple of the period of the surface oscillations of the working body, is developed in the article. For the correction of vibration field of the working body, the characteristics of dynamic interactions of granular elements of the medium are taken into account using original sensors. The sensors that can detect different particularities of interaction of the granular medium elements at different points of the working body are proposed to evaluate the deviation from a homogeneous and one-dimensional mode of vibration field. Specially developed sensors are able to register interactions between a single granule, a system of granules in filamentous structures, and multipoint interactions of the elements in a close-spaced cylindrical structure. The system of regularization of the structure of vibration fields based on the introduction of motion translation devices is proposed using the multi-point sensor locations on the working body. The article refers to analytical approaches of the theory of vibration displacements. For the experimental data assessment, the methods of statistical analysis are applied. It is shown that the peculiar features of the motion of granular medium registered by the sensors can be used to build active control systems of field vibration.
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Cveticanin, L. "Period of vibration of axially vibrating truly nonlinear rod." Journal of Sound and Vibration 374 (July 2016): 199–210. http://dx.doi.org/10.1016/j.jsv.2016.03.027.
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An, Xue Li, Dong Xiang Jiang, Ming Hao Zhao, and Chao Liu. "Numerical Analysis of Coupled Lateral and Torsional Vibrations of a Vertical Unbalanced Rotor." Applied Mechanics and Materials 20-23 (January 2010): 352–57. http://dx.doi.org/10.4028/www.scientific.net/amm.20-23.352.
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A model for the coupled lateral and torsional vibrations of a vertical unbalanced rotor is developed. The equation of motion is obtained using Lagrangian dynamics without considering the external actuating forces and torque. The equation showed coupling and nonlinear interaction between the rotor lateral and torsional vibrations. Most of the earlier work on coupled vibrations has been done for the horizontal rotor model. The coupled vibrations for a vertical rotor have not been reported in the past. An attempt is made to reveal dynamic characteristics of vertical rotor. The results of the simulation showed the coupled between torsional and lateral vibrations is induced by mass eccentricity. Coupled vibrations have appeared in the start period of the vibration. After a transient vibration process, the vibrations are not coupling. The lateral vibration becomes equal amplitude with shafting speed. And the torsional vibration keeps on attenuating until it stops. When the vibration is coupled, the coupling effect on which torsional vibration to lateral vibration is evident. But there’s no coupling effect on the lateral to the torsional. It is also shown that for some operational parameters, the controlling action may excite large lateral vibrations due to coupling with the torsional motion.
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BASTRUKOV, S. I., J. W. YU, R. X. XU, and I. V. MOLODTSOVA. "RADIATIVE ACTIVITY OF MAGNETIC WHITE DWARF UNDERGOING LORENTZ-FORCE-DRIVEN TORSIONAL VIBRATIONS." Modern Physics Letters A 26, no. 05 (2011): 359–66. http://dx.doi.org/10.1142/s0217732311034761.
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We study radiative activity of magnetic white dwarf undergoing torsional vibrations about axis of its own dipole magnetic moment under the action of Lorentz restoring force. It is shown that pulsating white dwarf can convert its vibration energy into the energy of magneto-dipole emission, oscillating with the frequency equal to the frequency of Alfvén torsional vibrations, provided that internal magnetic field is decayed. The most conspicuous feature of the vibration energy powered radiation in question is the lengthening of periods of oscillating emission; the rate of period elongation is determined by the rate magnetic field decay.
Dissertations / Theses on the topic "Vibration period"
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Dominguez, Morales Martha. "Fundamental period of vibration for reinforced concrete buildings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/MQ58450.pdf.
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Young, Kelly Christine. "An Investigation of the Fundamental Period of Vibration of Irregular Steel Structures." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316473829.
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Ticona, A. M., M. A. Rosales, and J. D. Orihuela. "Correction coefficients of distortion and vibration period for buildings due to soil-structure interaction." OP Publishing Ltd, 2020. http://hdl.handle.net/10757/656571.
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The present research analyzed the influence of the soil structure interaction (SSI) in buildings, varying geotechnical parameters and height, considering 3 international codes. The responses obtained from the structures taking into account the SSI, were compared with the responses of fixed-base buildings, being the main control variables: the period and the drift. It was determined that the estimated range in which the period of the structure increases is from 30 to 98%, demonstrating the influence of considering soil flexibility. Due to the variability of the responses obtained, an adjustment factor is proposed to predict said amplification of the control variables, depending on the height of the building and the ground.
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Hafeez, Ghazanfarah. "Dynamic Characteristics of Light-frame Wood Buildings." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36223.
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This research project deals with dynamic field testing of light-frame wood buildings with wood based shear walls. The primary objective of the investigation is to evaluate the code formula for estimating light wood frame building’s fundamental period, through intensive field testing and numerical modelling. The project also aims to propose an alternative simplified rational approach where applicable. The thesis provides insight to the ambient vibration testing procedures of light-frame wood buildings and explains the protocol adopted for the current research program.
Ambient vibration (AV) field tests were conducted on several multi-storey wood and beam-and-post buildings in Canada. Modal parameters of measured buildings, such as natural frequency, mode shapes and equivalent structural damping were obtained from Frequency Domain (FD) analysis of ambient motion records.
Experimental and numerical investigations were performed to evaluate the effect of non-structural components, and the connectivity between firewall-separated buildings, on dynamic properties of light-frame wood buildings. The study provides a reliable expression for building period estimate based on field testing and numerical modeling.
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Navrátilová, Martina. "Nelineární dynamická analýza konstrukce zatížena seismickými účinky." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227701.
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Diploma thesis compares the methods for the calculation of the response of structures with seismic loads. Linear and nonlinear analyses are used for the calculations. In the case of linear analysis response spectrum method is applied. For nonlinear analysis pushover method is used. These two methods are compared in programs AxisVM and RFEM on the examples of high-rise building and space frame.
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Sun, Xiangkun. "Elastic wave propagation in periodic structures through numerical and analytical homogenization techniques." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC041/document.
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Dans ce travail, la méthode homogénéisation de multi-échelle, ainsi que diverses méthodes non homogénéisation, seront présentés pour étudier le comportement dynamique des structures périodiques. La méthode de multi-échelle commence par la séparation d'échelles. Dans ce cas, une échelle microscopique pour décrire le comportement local et une échelle macroscopique pour décrire le comportement global sont introduites. D'après la théorie de l'homogénéisation, la longueur d'onde est supposée grande, et la longueur de la cellule doit être beaucoup plus petite que la longueur caractéristique de la structure. Ainsi, le domaine d'homogénéisation est limité à la première zone de propagation. Le modèle d'homogénéisation traditionnel utilise des valeurs moyennes des éléments, mais le domaine de validité pratique est beaucoup plus petit que la première bande interdite. Alors, le développement de nouveaux modèles homogénéisés est beaucoup motivé par cet inconvénient. Par rapport au modèle d'homogénéisation traditionnel, équations d'ordre supérieur sont proposées pour fournir des modèles homogénéisation plus précises. Deux méthodes multi-échelles sont introduites: la méthode de développement asymptotique, et la méthode de l'homogénéisation des milieux périodiques discrètes (HMPD). Ces méthodes seront appliquées de façon séquentielle dans le cas d'onde longitudinale et le cas d'onde transversale. Les mêmes modèles d'ordre supérieur sont obtenus par les deux méthodes dans les deux cas. Ensuite, les modèles proposés sont validés en examinant la relation de dispersion et de la fonction de réponse fréquentielle. Des solutions analytiques et la méthode des ondes éléments finis(WFEM) sont utilisés pour donner les références. Des études paramétriques sont effectuées dans le cas infini, et deux différentes conditions aux limites sont prises en compte dans le cas fini. Ensuite, le HMPD et CWFEM sont utilisés pour étudier les vibrations longitudinales et transversales des structures réticulées dans le cas 1D et 2D. Le domaine de validité du HPDM est réévalué à l'aide de la fonction de propagation identifiée par le CWFEM. L'erreur relative au nombre d'onde obtenue par HPDM est illustré sur la fonction de la fréquence et le rapport d'échelle. Des études paramétriques sur l'épaisseur de la structure sont réalisées par la relation de dispersion. La dynamique des structures finies sont également étudiés en utilisant la HPDM et CWFEM<br>In this work, the multi-scale homogenization method, as well as various non homogenization methods, will be presented to study the dynamic behaviour of periodic structures. The multi-scale method starts with the scale-separation, which indicates a micro-scale to describe the local behaviour and a macro-scale to describe the global behaviour. According to the homogenization theory, the long-wave assumption is used, and the unit cell length should be much smaller than the characteristic length of the structure. Thus, the valid frequency range of homogenization is limited to the first propagating zone. The traditional homogenization model makes use of material properties mean values, but the practical validity range is far less than the first Bragg band gap. This deficiency motivated the development of new enriched homogenized models. Compared to traditional homogenization model, higher order homogenized wave equations are proposed to provide more accuracy homogenized models. Two multi-scale methods are introduced: the asymptotic expansion method, and the homogenization of periodic discrete media method (HPDM). These methods will be applied sequentially in longitudinal wave cases in bi-periodic rods and flexural wave cases in bi-periodic beams. Same higher order models are obtained by the two methods in both cases. Then, the proposed models are validated by investigating the dispersion relation and the frequency response function. Analytical solutions and wave finite element method (WFEM) are used as references. Parametric studies are carried out in the infinite case while two different boundary conditions are considered in the finite case. Afterwards, the HPDM and the CWFEM are employed to study the longitudinal and transverse vibrations of framed structures in 1D case and 2D case. The valid frequency range of the HPDM is re-evaluated using the wave propagation feature identified by the CWFEM. The relative error of the wavenumber by HPDM compared to CWFEM is illustrated in the function of frequency and scale ratio. Parametric studies on the thickness of the structure is carried out through the dispersion relation. The dynamics of finite structures are also investigated using the HPDM and CWFEM
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石田, 幸男, Yukio ISHIDA, 剛志 井上 та ін. "重力と非線形ばね特性の作用を受ける偏平軸の振動 (内部共振の影響)". 日本機械学会, 2001. http://hdl.handle.net/2237/9052.
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Bao, Bin. "Distributed, broadband vibration control devices using nonlinear approaches." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI086/document.
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L’amélioration du confort des usagers ainsi que l’augmentation du niveau de sécurité des structures requièrent le développement de techniques permettant de limiter efficacement les vibrations. Dans cette optique, les travaux exposés ici proposent le développement et l’analyse de méthodes de contrôle vibratoire pour des structures de faibles dimensions et utilisant peu d’énergie. Afin de satisfaire à ces deux critères, il est ici proposé d’utiliser des éléments piézoélectriques électriquement interfacés de manière non-linéaire et périodiquement distribués sur la structure-cible à contrôler. Ainsi, l’approche proposée permet de bénéficier à la fois des avantages des techniques de contrôle non-linéaires appliquées aux matériaux intelligents de type piézoélectrique, offrant des performances remarquables tout en étant peu consommatrices d’énergie, avec ceux des structures périodiques exhibant des bandes fréquentielles interdites présentant de fortes atténuations de la propagation d’onde. Plus particulièrement, ce mémoire s’intéresse à différentes architectures d’interconnexion des interfaces électriques non-linéaires permettant un bon compromis entre la bande fréquentielle contrôlée et les performances en termes d’atténuation des vibrations. Ainsi, trois architectures principales sont proposées, allant de structures totalement périodiques, tant au niveau mécanique qu’électrique (interconnexions), à des structures présentant un certain degré d’apériodicité sur le plan électrique (entrelacement), impactant ainsi la propagation de l’onde acoustique en élargissant la bande de contrôle, pour enfin proposer une architecture hybride entre interconnexion et entrelacement conduisant à des systèmes large bande performants<br>For ameliorating vibration reduction systems in engineering applications, miscellaneous vibration control methods, including vibration damping systems, have been developed in recent years. As one of intelligent vibration damping systems, nonlinear electronic damping system using smart materials (e.g., piezoelectric materials), is more likely to achieve multimodal vibration control. With the development of meta-structures (a structure based upon metamaterial concepts), electronic vibration damping shunts, such as linear resonant damping or negative capacitance shunts, have been introduced and integrated abundantly in the electromechanical meta-structure design for wave attenuation and vibration reduction control. Herein, semi-passive Synchronized Switch Damping on the Inductor (SSDI) technique (which belongs to nonlinear electronic damping techniques), is combined with smart meta-structure (also called smart periodic structure) concept for broadband wave attenuation and vibration reduction control, especially for low frequency applications. More precisely, smart periodic structure with nonlinear SSDI electrical networks is investigated from the following four aspects, including three new techniques for limiting vibrations: First, in order to dispose of a tool allowing the evaluation of the proposed approaches, previous finite element (FE) modeling methods for piezoelectric beam structures are summarized and a new voltage-based FE modeling method, based on Timoshenko beam theory, is proposed for investigating smart beam structure with complex interconnected electrical networks; then, the first developed technique lies in smart periodic structure with nonlinear SSDI interconnected electrical networks, which involves wave propagation interaction between continuous mechanical and continuous nonlinear electrical media; the second proposed topology lies in smart periodic structures with nonlinear SSDI interleaved / Tri-interleaved electrical networks involving wave propagation interaction between the continuous mechanical medium and the discrete nonlinear electrical medium. Due to unique electrical interleaved configuration and nonlinear SSDI electrical features, electrical irregularities are induced and simultaneously mechanical irregularities are also generated within an investigated periodic cell; the last architecture consists in smart periodic structures with SSDI multilevel interleaved-interconnected electrical networks, involving wave propagation interaction between the continuous mechanical medium and the multilevel continuous nonlinear electrical medium. Compared with the SSDI interconnected case, more resonant-type band gaps in the primitive pass bands of purely mechanical periodic structures can be induced, and the number of such band-gaps are closely related to the interconnection / interleaved level. Finally, the main works and perspectives of the thesis are summarized in the last chapter
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Rodrigues, Cunha Leandro. "Robust bandgaps for vibration control in periodic structures." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD060.
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Dans cette thèse, une méthodologie simple pour trouver des bandes interdites robustes est présentée. Quatre cellules unitaires différentes sont utilisées comme exemples numériques pour des modèles infinis et finis. Les deux premiers sont liés aux zones d'atténuation créées pour les ondes longitudinales en utilisant des cellules unitaires de masse et ressort et de barres. La méthode Matrice de Transfert est utilisée pour modéliser la cellule unitaire. Avec cette méthode, il est possible d'obtenir les réponses en fréquence, en utilisant une méthode spectrale, et des constantes de dispersion, en résolvant un problème a valeur propre. Les paramètres physiques et géométriques les plus influents sont déterminés en effectuant une analyse de sensibilité aux dérivées partielles et aux différences finies à travers un modèle infini. Dans ce cas, pour le deuxième exemple, la section de la demi-cellule est considérée comme une variable stochastique, représentée par une fonction densité de probabilité pour une analyse probabiliste. Le troisième exemple concerne les bandes interdites pour les ondes de flexion utilisant des cellules unitaires de poutres. Dans ce cas, la méthode habituelle de Matrice de Transfert ne peut pas être utilisée pour obtenir une réponse de structures finies en basse fréquence en raison de la présence de matrices mal conditionnées. Par conséquent, une méthode récursive est utilisée pour éviter la multiplication de matrices. Une analyse expérimentale est également réalisée pour ce cas, mais considérant que la longueur de la moitié des cellules unitaire comme incertaine. Le dernier exemple est un treillis périodique considérée avec et sans propriétés intelligentes. La cellule unitaire de cette structure en treillis peut avoir des membres passifs et actifs. À cause de la complexité de ce type de cellule, la méthode des éléments finis est utilisée. Cependant, ce type de structure ne présente pas de ruptures d'impédance suffisamment fortes pour ouvrir des bandes interdites même avec la présence de sous-structures répétitives. En vertu de cela, huit scénarios sont étudiés en considérant l'introduction de masse concentrée dans les articulations et les actionneurs piézoélectriques dans les circuits shunt résonants qui sont considérés comme stochastiques pour des cas spécifiques. À la fin, les résonances internes sont analysées à l'aide d'un modèle plus précis. Pour chaque modèle de structure, une simulation de Monte Carlo avec Latin Hypercube est effectuée, les distinctions entre les zones d'atténuation incertaines correspondantes pour les modèles finis et infinis sont exposées et la relation avec les modes localisés est clarifiée. Ces résultats suggèrent que les modèles finis ont une bande interdite plus large que les modèles infinis en considérant les incertitudes. En d'autres termes, les incertitudes entre les cellules voisines se compensent et les structures finies sont naturellement plus robustes. Enfin, l'effet de l'augmentation du niveau d'incertitude, en faisant varier un coefficient stochastique, est analysé et le concept de bande interdite robuste est présenté<br>In this thesis, a simple methodology to find robust bandgaps is presented. Four different periodic structures are used as numerical examples for infinite and finite models. The first two are related to attenuation zones created for longitudinal waves using spring-mass and stepped rod unit cells. The Transfer Matrix method is used to model the unit cell. With this method, it is possible to obtain the frequency responses, using a spectral method, and dispersion constants, solving an eigenvalue prob-lem. The most influential physical and geometrical parameters are determined by performing partial derivative and finite difference sensitivity analysis through an infinite model. Therein, for the second example, the cross-section area of half-cell is considered as a stochastic variable represented by a probability density function with specific deviation properties for a probabilistic analysis. The third example concerns the bandgaps for flexural waves using stepped beams unit cells. For this case, the classical Transfer Matrix method cannot be used to obtain finite structures response in low frequency because of the presence of ill-conditioned matrices. Therefore, a recursive method termed Translation Matrix, which avoid matrix multiplication, is used and the corresponding probabilistic analysis is per-formed using the half-cell thickness as a random variable. An experimental analysis is also performed for this case, but considering half-cell length as uncertain. The last example is a periodic truss that is considered with and without smart components. The unit cell of this lattice structure can present pas-sive and active members. As long as the type of unit cell is more complex, the finite element method is used. However, this kind of structure does not have impedance mismatches strong enough to open bandgaps although the presence of repetitive substructures. In virtue of this, eight scenarios are inves-tigated considering the introduction of concentrated mass on joints and piezoelectric actuators in reso-nant shunt circuit which are considered as stochastic for specific cases. For each structure model, a Monte Carlo Simulation with Latin Hypercube sampling is carried out, the distinctions between the corresponding uncertain attenuation zones for finite and infinite models are exposed and the relation with localized modes is clarified. These results lead to conclude that the finite models present a larger stop zone considering stochastic parameters than infinite models. In other words, the uncertainties be-tween neighbors’ cells compensate each other and the finite structures is naturally more robust. Final-ly, the effect of increasing the uncertainty level, by varying a stochastic coefficient, is analyzed and the concept of robust band gap is presented
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Ben, Brahim Nadia. "Approche multiéchelle pour le comportement vibratoire des structures avec un défaut de rigidité." Phd thesis, Université Nice Sophia Antipolis, 2014. http://tel.archives-ouvertes.fr/tel-01066795.
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Nous considérons un système mécanique en vibration non linéaire, pour lequel nous fournissons une solution approchée par l'utilisation des développements multiples échelles; nous proposons d'abord une étude avec double échelles puis avec triple échelles où nous comparons les deux approches. Une preuve rigoureuse de ces développements a été faite. L'étude de la stabilité de la solution est nécessaire pour montrer la convergence au voisinage de la résonance. Un lien entre l'amplitude de la réponse vibratoire et la fréquence du système en vibration libre a été mis en évidence.
Books on the topic "Vibration period"
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United States. National Aeronautics and Space Administration, ed. Vibration and structureborne noise in space station: Progress report for NASA grant NAG-1-541 for the period January 1, 1986 - June 30, 1986. National Aeronautics and Space Administration, 1986.
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United States. National Aeronautics and Space Administration., ed. Vibration and structureborne noise in space station: Progress report for NASA grant NAG-1-541 for the period January 1, 1986 - June 30, 1986. National Aeronautics and Space Administration, 1986.
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Mei, C. Component mode synthesis and large deflection vibration of complex structures: Final report for the period ended January 31, 1987. National Aeronautics and Space Administration, 1987.
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Britcher, Colin P. Large angle magnetic suspension test fixture: Final report for the period ended October 31, 1995. Old Dominion University Research Foundation, 1995.
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United States. National Aeronautics and Space Administration., ed. Vibration isolation technology: Sensitivity of selected classes of experiments to residual accelerations : final report ... period of performance 7/1/88 - 6/30/91. Center for Microgravity and Materials Research, University of Alabama in Huntsville, 1991.
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Britcher, Colin P. Large angle magnetic suspension test fixture: Progress report for the period November 1, 1992 to May 31, 1993. Dept. of Mechanical Engineering & Mechanics, College of Engineering & Technology, Old Dominion University, 1993.
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Jen-Kuang, Huang, and Langley Research Center, eds. Large angle magnetic suspension test fixture: Final report for the period 11-1-95 thru 10-31-96. National Aeronautics and Space Administration, 1996.
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Britcher, Colin P. Large angle magnetic suspension test fixture: Final report for the period 11-1-95 thru 10-31-96. National Aeronautics and Space Administration, 1997.
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Britcher, Colin P. Large angle magnetic suspension test fixture: Progress report for the period November 1, 1995 through May 1, 1996. Dept. of Aerospace Engineering, Dept. of Mechanical Engineering, College of Engineering & Technology, Old Dominion University, 1996.
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Barbieri, Enrique. Momentum management in redundant manipulators for vibration suppression: Final report, NASA research grant NAG-1-1270 : report period June 1, 1992 - August 31, 1993. National Aeronautics and Space Administration, 1993.
Find full textBook chapters on the topic "Vibration period"
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Charney, Finley A. "Period of Vibration." In Seismic Loads. American Society of Civil Engineers, 2015. http://dx.doi.org/10.1061/9780784413524.ch17.
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Luo, Albert C. J., and Chuan Guo. "Independent Period-12 Motions." In Nonlinear Vibration Reduction. Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-17499-5_7.
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Luo, Albert C. J., and Chuan Guo. "Independent Period-3 Motions." In Nonlinear Vibration Reduction. Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-17499-5_5.
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Luo, Albert C. J., and Chuan Guo. "Independent Period-9 Motions." In Nonlinear Vibration Reduction. Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-17499-5_6.
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Luo, Albert C. J., and Chuan Guo. "Period-1 Motion to Chaos." In Nonlinear Vibration Reduction. Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-17499-5_4.
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Manyin, Hu, Liu Yujing, Yin Qi, Liu Zhong, and Gao Xianglin. "Research on Vibration Period Optimization of Electrostatic Precipitator." In Electrostatic Precipitation. Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-540-89251-9_19.
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Soni, Prabhat K., Prakash Sangamnerkar, and S. K. Dubey. "Fundamental Time Period of Vibration in Seismic Analysis." In Lecture Notes in Civil Engineering. Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-0890-5_56.
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Roy, Anuja, Atanu Sahu, and Debasish Bandyopadhyay. "A Novel Sloshing Damper for Vibration Control of Short Period Structures." In Lecture Notes in Civil Engineering. Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-8138-0_26.
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Pandey, Dhirendra Kumar, and Sudib Kumar Mishra. "Modified Tuned Liquid Damper for Vibration Control of Short Period Structures." In Lecture Notes in Civil Engineering. Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-15-9976-7_24.
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Kawamura, Shozo, Tetsuhiko Owa, Tomohiko Ise, and Masami Matsubara. "Proposition of Isolation Table Considering the Long-Period Earthquake Ground Motion (Method of Changing Natural Frequency of Isolation System with Additional Spring)." In Vibration Engineering for a Sustainable Future. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-48153-7_32.
Full textConference papers on the topic "Vibration period"
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Romano, Peter, Michael Seifert, and Michael Smith. "The 505 Low Vibration Solution." In Vertical Flight Society 73rd Annual Forum & Technology Display. The Vertical Flight Society, 2017. http://dx.doi.org/10.4050/f-0073-2017-12028.
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The original 505 Jet Ranger X prototype used a simple hard-mounted focal pylon to attach the transmission to the airframe. In developmental flight tests, the design resulted in 2/rev vibration levels that exceeded program objectives for ride quality in high speed forward flight. To address the vibration levels, a LIVE pylon mount was designed over a 4-month period to serve as a drop-in replacement with minimal impact to existing systems. An overview of the rapid design process is presented with supporting analysis and test data that led to its incorporation on the aircraft. The LIVE pylon design cut the vertical 2/rev vibrations in half, without negatively impacting existing structures, drive systems, flight controls, or handling qualities. The LIVE pylon mount is part of the Bell 505 Type Design that was certified in December 2016.
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Takeya, Kouichi, Yuichi Ito, Eiichi Sasaki, and Tang Xu. "Enhancement of B-WIM Using Time-Frequency Analysis of Bridge Acceleration Responses and Neural Networks." In IABSE Symposium, Tokyo 2025: Environmentally Friendly Technologies and Structures: Focusing on Sustainable Approaches. International Association for Bridge and Structural Engineering (IABSE), 2025. https://doi.org/10.2749/tokyo.2025.2149.
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<p>This study aimed to enhance Bridge Weigh-in-Motion (B-WIM) by utilizing bridge vibration responses to obtain detailed traffic information. Time-frequency analysis of acceleration responses was performed to extract key features, followed by deflection calculations through double integration with drift correction. Vehicle entry and exit times were detected using longitudinal acceleration, enabling accurate deflection calculations. Forced vibrations were identified, and features such as RMS value, waveform area, and wave group period were employed to analyze vibrations caused by vehicles, pedestrians, and train traffic. A Neural Network (NN) classified traffic types, while vehicle weights were estimated using a direct search method based on influence lines. Validation with real bridge data demonstrated the effectiveness of these methods in improving B-WIM accuracy and enabling comprehensive traffic monitoring.</p>
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Gerasimenko, Yaroslav A., Carmen Roelcke, Lukas Z. Kastner, et al. "Ultrafast scanning tunneling spectroscopy of a phonon-driven atomic vacancy in a monolayer crystal." In CLEO: Fundamental Science. Optica Publishing Group, 2024. http://dx.doi.org/10.1364/cleo_fs.2024.fw3b.5.
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Understanding the interplay of atomic and electronic motion requires probing at intrinsic space-time-energy scales. We resolve phonon modulations of defect-bound states by sampling electronic spectra with atomic and sub-ps precision, faster than a vibration period.
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Lee, Seung-Yop. "Free Vibration Energy and Period of a String With Time-Varying Length." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2011.
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Abstract We introduce a new technique to analyze free vibration energy and natural frequencies of a string with time-varying length by dealing with traveling waves. One of boundaries is vertically fixed but it moves axially at a constant rate. When the string length is varied, the free vibration energy and period also change with time. String tension and non-zero instantaneous vertical velocity at the moving boundary results in the energy variation. When the string undergoes retraction, the vibration energy increases with time. The new technique using traveling waves gives the exact amount of energy transferred into the vibrating system at the moving boundary. The free vibration energy are compared with previous results using the perturbation method and Kotera’s approach.
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Takeuchi, Makoto, Satoshi Tanaka, Shingo Tekuramori, Atsushi Wada, and Nobuaki Takahashi. "Mechanical vibration sensing using cascaded long period fiber grating." In 2013 Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR). IEEE, 2013. http://dx.doi.org/10.1109/cleopr.2013.6600331.
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Somatomo, Hiroyuki, Satoshi Tanaka, and Nobuaki Takahashi. "Vibration sensing of solid using long-period fiber grating." In 19th International Conference on Optical Fibre Sensors, edited by David D. Sampson. SPIE, 2008. http://dx.doi.org/10.1117/12.785961.
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Pi, Jun, and Xiangji Bu. "Analysis of Full-Period and Non-full-Period Sampling of Vibration Signal for Engine Rotors." In 2015 International Conference on Industrial Technology and Management Science. Atlantis Press, 2015. http://dx.doi.org/10.2991/itms-15.2015.121.
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Zhang, Zhao, Xinwen Yang, Dingwei Qian, and Zhijun Zhao. "Study on Vibration Damping Performance of Period-Structure Rail Pad." In Second International Conference on Rail Transportation. American Society of Civil Engineers, 2022. http://dx.doi.org/10.1061/9780784483886.020.
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Black, Jared L. "Using Vibration Measurements to Assess Structural Integrity." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79144.
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Structural vibration monitoring can aid in assessing offshore platform structural integrity. The method utilizes topside acceleration measurements to detect the platform’s natural periods of vibration; the periods depend only on platform weights (mass) and resistance (stiffness). If the platform’s natural period increases over time, in the absence of a change in mass, it can indicate a loss of structural integrity. The vibration survey utilizes a portable monitoring system, which includes sensitive low frequency accelerometers. The above water monitoring provides information on the below water structural integrity; the method is very low cost when compared to diver or ROV surveys. Examples of structural monitoring surveys are presented, including the following: verification that a platform remained fit for purpose despite having its foundation disturbed by a shallow gas release, two cases of using surveys to confirm jacket stiffness recovery following repairs of structural damage caused by Gulf of Mexico hurricanes and evaluation of a minimal platform after a heavy compressor was installed. The development of a natural period database is reviewed. The database, covering 95 platforms in Asian waters, was developed to reduce inspection costs and aid in life extension reviews, as well as providing quick integrity assessments should a tropical cyclone cross the production area.
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Chen, Yuanhao, Bin Chen, Xinya Wang, Yeyin Xu, and Tieyan Wang. "Nonlinear Vibration and Bifurcations of a Bending-Twisting Rotor System." In ASME 2024 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2024. https://doi.org/10.1115/imece2024-144858.
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Abstract In this paper, a nonlinear dynamic system of a bending-twisting rotor is studied. Analytical prediction of nonlinear vibrations in such a nonlinear dynamic system are presented from the implicit mapping method. Bifurcations on vibration evolution are obtained and the stability of the corresponding vibrations are discussed by eigenvalue analysis. Period-doubling bifurcations occur when the rotating frequency varies where subharmonic vibrations emerge. The discrete Poincare displacements and velocities of periodic vibrations exhibit the motion complexity and give good scenarios of the bifurcations. Illustrations are given for comparison of the analytical and numerical results of nonlinear vibrations. The obtained results can be used to design and control the bending-twisting rotor with environmental noise.
Reports on the topic "Vibration period"
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Paidoussis, Michael. PR-593-16703-R01 Lab and Analytical Model - Flow Induced Vibration of Brine Strings. Pipeline Research Council International, Inc. (PRCI), 2018. http://dx.doi.org/10.55274/r0011505.
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This is the report on the 3rd phase of "Brine String Stability Studies" at McGill University for the period of April 2017 to November 2017. Some recent modifications on experimental setup, results of both theoretical and experimental investigations for a discharging tube with an aspirating annulus (configuration (iii)) and experimental achievements for an aspirating tube with a discharging annulus (configuration (iv)) are given. In addition to the results for the brine string problem with internal and external axial flow, a new idea for developing nonlinear dynamics of cantilevered plates in reverse axial flows is also presented.
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Mazzoni, Silvia, Nicholas Gregor, Linda Al Atik, Yousef Bozorgnia, David Welch, and Gregory Deierlein. Probabilistic Seismic Hazard Analysis and Selecting and Scaling of Ground-Motion Records (PEER-CEA Project). Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, 2020. http://dx.doi.org/10.55461/zjdn7385.
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This report is one of a series of reports documenting the methods and findings of a multi-year, multi-disciplinary project coordinated by the Pacific Earthquake Engineering Research Center (PEER) and funded by the California Earthquake Authority (CEA). The overall project is titled “Quantifying the Performance of Retrofit of Cripple Walls and Sill Anchorage in Single-Family Wood-Frame Buildings,” henceforth referred to as the “PEER–CEA Project.” The overall objective of the PEER–CEA Project is to provide scientifically based information (e.g., testing, analysis, and resulting loss models) that measure and assess the effectiveness of seismic retrofit to reduce the risk of damage and associated losses (repair costs) of wood-frame houses with cripple wall and sill anchorage deficiencies as well as retrofitted conditions that address those deficiencies. Tasks that support and inform the loss-modeling effort are: (1) collecting and summarizing existing information and results of previous research on the performance of wood-frame houses; (2) identifying construction features to characterize alternative variants of wood-frame houses; (3) characterizing earthquake hazard and ground motions at representative sites in California; (4) developing cyclic loading protocols and conducting laboratory tests of cripple wall panels, wood-frame wall subassemblies, and sill anchorages to measure and document their response (strength and stiffness) under cyclic loading; and (5) the computer modeling, simulations, and the development of loss models as informed by a workshop with claims adjustors. This report is a product of Working Group 3 (WG3), Task 3.1: Selecting and Scaling Ground-motion records. The objective of Task 3.1 is to provide suites of ground motions to be used by other working groups (WGs), especially Working Group 5: Analytical Modeling (WG5) for Simulation Studies. The ground motions used in the numerical simulations are intended to represent seismic hazard at the building site. The seismic hazard is dependent on the location of the site relative to seismic sources, the characteristics of the seismic sources in the region and the local soil conditions at the site. To achieve a proper representation of hazard across the State of California, ten sites were selected, and a site-specific probabilistic seismic hazard analysis (PSHA) was performed at each of these sites for both a soft soil (Vs30 = 270 m/sec) and a stiff soil (Vs30=760 m/sec). The PSHA used the UCERF3 seismic source model, which represents the latest seismic source model adopted by the USGS [2013] and NGA-West2 ground-motion models. The PSHA was carried out for structural periods ranging from 0.01 to 10 sec. At each site and soil class, the results from the PSHA—hazard curves, hazard deaggregation, and uniform-hazard spectra (UHS)—were extracted for a series of ten return periods, prescribed by WG5 and WG6, ranging from 15.5–2500 years. For each case (site, soil class, and return period), the UHS was used as the target spectrum for selection and modification of a suite of ground motions. Additionally, another set of target spectra based on “Conditional Spectra” (CS), which are more realistic than UHS, was developed [Baker and Lee 2018]. The Conditional Spectra are defined by the median (Conditional Mean Spectrum) and a period-dependent variance. A suite of at least 40 record pairs (horizontal) were selected and modified for each return period and target-spectrum type. Thus, for each ground-motion suite, 40 or more record pairs were selected using the deaggregation of the hazard, resulting in more than 200 record pairs per target-spectrum type at each site. The suites contained more than 40 records in case some were rejected by the modelers due to secondary characteristics; however, none were rejected, and the complete set was used. For the case of UHS as the target spectrum, the selected motions were modified (scaled) such that the average of the median spectrum (RotD50) [Boore 2010] of the ground-motion pairs follow the target spectrum closely within the period range of interest to the analysts. In communications with WG5 researchers, for ground-motion (time histories, or time series) selection and modification, a period range between 0.01–2.0 sec was selected for this specific application for the project. The duration metrics and pulse characteristics of the records were also used in the final selection of ground motions. The damping ratio for the PSHA and ground-motion target spectra was set to 5%, which is standard practice in engineering applications. For the cases where the CS was used as the target spectrum, the ground-motion suites were selected and scaled using a modified version of the conditional spectrum ground-motion selection tool (CS-GMS tool) developed by Baker and Lee [2018]. This tool selects and scales a suite of ground motions to meet both the median and the user-defined variability. This variability is defined by the relationship developed by Baker and Jayaram [2008]. The computation of CS requires a structural period for the conditional model. In collaboration with WG5 researchers, a conditioning period of 0.25 sec was selected as a representative of the fundamental mode of vibration of the buildings of interest in this study. Working Group 5 carried out a sensitivity analysis of using other conditioning periods, and the results and discussion of selection of conditioning period are reported in Section 4 of the WG5 PEER report entitled Technical Background Report for Structural Analysis and Performance Assessment. The WG3.1 report presents a summary of the selected sites, the seismic-source characterization model, and the ground-motion characterization model used in the PSHA, followed by selection and modification of suites of ground motions. The Record Sequence Number (RSN) and the associated scale factors are tabulated in the Appendices of this report, and the actual time-series files can be downloaded from the PEER Ground-motion database Portal (https://ngawest2.berkeley.edu/)(link is external).
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Wang, Kon-Well. Piezoelectric Tailoring with Enhanced Electromechanical Coupling for Concurrent Vibration Control of Mistuned Periodic Structures. Defense Technical Information Center, 2006. http://dx.doi.org/10.21236/ada471779.
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Taylor. L51755 Development and Testing of an Advanced Technology Vibration Transmission. Pipeline Research Council International, Inc. (PRCI), 1996. http://dx.doi.org/10.55274/r0010124.
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Fiber optic sensors have been under development in industrial and government laboratories around the world for over a decade. The commercial market for fiber sensors for measuring parameters such as temperature, displacement, and liquid level is now estimated to exceed $100 M/year. Aside from the commercial interest, the U. S. Department of Defense has vigorously pursued the development of fiber gyroscopes and hydrophones. In spite of the high level of research and development activity, however, until recently fiber sensors had not been successfully applied in high-temperature engine environments. The goal of this effort is to develop and test high-temperature fiber optic sensors and show that they are suitable for monitoring vibration and other instabilities in gas turbine engines. The underlying technology developed during the course of PRCI projects PR- 219-9120 and PR-219-9225 during 1991-94 serves as the foundation for PR-240-9416. Transducers with the fiber optic Fabry-Perot interferometer (FFPI) configuration have been adapted for use in the turbomachinery environment.To ensure the survival of the FFPI sensors at high temperatures, two techniques for coating the fibers with metal have been developed: electroplating and vacuum deposition. Coated sensors have subsequently been embedded in aluminum and brass alloys. Experiments on a small Sargent Welch turbine engine have shown the high sensitivity of embedded FFPI strain sensors to vibration in rolling bearings. Data have been collected in both the time and frequency domain. A new accelerometer design in which a metal-coated fiber containing the FFPI element is soldered directly to a diaphragm in a stainless steel housing shows response similar to a piezoelectric accelerometer in shaker table tests. The high sensitivity of the FFPI accelerometer has been demonstrated in field tests in a Solar Centaur turbine engine, and the design has survived temperatures greater than 500�C in a test oven. A magnetometer with a physical configuration similar to that of the accelerometer has been used to measure the distance from the sensor head to a rotating shaft made of ferromagnetic material. This device, which functions as a proximity probe, has been used to monitor shaft rotation rate (keyphasor application) and as a shaft thrust position sensor. These results indicate the potential for performing critical measurements in turbine engines with FFPI sensors. They can measure acceleration, distance (proximity), strain (as it relates to bearing defect diagnosis), and gas pressure, and can operate at higher temperatures than conventional transducers.
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Xi, X. Vibrational and Electronic Properties of Fullerene and Carbon-Based Clustors. Final Reports for period July 1, 1997 - June 30, 2001. Office of Scientific and Technical Information (OSTI), 2002. http://dx.doi.org/10.2172/833761.
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Stevens, R. D., B. V. Chapnik, and B. Howe. L51960 Acoustical Pipe Lagging Systems Design and Performance. Pipeline Research Council International, Inc. (PRCI), 1998. http://dx.doi.org/10.55274/r0010392.
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Noise levels radiated from the exterior of a pipe wall can significantly contribute to the overall noise levels on the site of a gas plant and at neighboring properties. The noise inside the piping is generated both by the gas compressor itself, and by the flow of gas through valves, elbows and fittings. Sound inside the pipe couples to the pipe wall by exciting vibration modes, some of which are radiated from the exterior of the pipe into the air. Piping is geometrically circular, which provides it with considerable increased stiffness versus a flat plate, and thereby assists in its ability to contain low frequency sound inside the pipe. At high frequencies, where the wavelength of sound is short compared to the dimensions of the pipe, the response of the pipe approaches that of a flat plate, and considerably more sound is transmitted. Between the low and high frequency ranges lies the ring frequency, at which the wavelength of sound is equal to the circumference of the pipe; at this resonant frequency, a maximum amount of noise is transmitted out the pipe wall. For smaller pipe sizes, the ring frequency occurs above 5 kHz. For larger pipe sizes on the order of 24 inches to 36 inches, the ring frequency occurs in the range 1 kHz to 3 kHz. These frequencies fall in the most audible range of the sound spectrum. Low frequency sound is not usually of concern for pipe radiated noise, unless the source generates considerably low frequency energy. Acoustical lagging systems typically include one or more layers of porous insulation, to absorb sound and decouple vibration, and one or more layers of an impervious, heavy barrier material to contain the sound. The test configurations for this study were based on systems reported as commonly being used by PRCI member companies. Most of the member companies use fixed-in-place lagging configurations in which the various materials are applied in discrete layers to the pipe during installation. Self-contained, removable blanket systems are also in use by some member companies instead of fixed-in-place configurations, or around equipment such as valves where periodic removal of the lagging is necessary. This study provides a review of acoustic lagging systems for above ground gas piping to minimize noise.
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Mizrach, Amos, Michal Mazor, Amots Hetzroni, et al. Male Song as a Tool for Trapping Female Medflies. United States Department of Agriculture, 2002. http://dx.doi.org/10.32747/2002.7586535.bard.
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This interdisciplinaray work combines expertise in engineering and entomology in Israel and the US, to develop an acoustic trap for mate-seeking female medflies. Medflies are among the world's most economically harmful pests, and monitoring and control efforts cost about $800 million each year in Israel and the US. Efficient traps are vitally important tools for medfly quarantine and pest management activities; they are needed for early detection, for predicting dispersal patterns and for estimating medfly abundance within infested regions. Early detection facilitates rapid response to invasions, in order to contain them. Prediction of dispersal patterns facilitates preemptive action, and estimates of the pests' abundance lead to quantification of medfly infestations and control efforts. Although olfactory attractants and traps exist for capturing male and mated female medflies, there are still no satisfactorily efficient means to attract and trap virgin and remating females (a significant and dangerous segment of the population). We proposed to explore the largely ignored mechanism of female attraction to male song that the flies use in courtship. The potential of such an approach is indicated by studies under this project. Our research involved the identification, isolation, and augmentation of the most attractive components of male medfly songs and the use of these components in the design and testing of traps incorporating acoustic lures. The project combined expertise in acoustic engineering and instrumentation, fruit fly behavior, and integrated pest management. The BARD support was provided for 1 year to enable proof-of-concept studies, aimed to determine: 1) whether mate-seeking female medflies are attracted to male songs; and 2) over what distance such attraction works. Male medfly calling song was recorded during courtship. Multiple acoustic components of male song were examined and tested for synergism with substrate vibrations produced by various surfaces, plates and loudspeakers, with natural and artificial sound playbacks. A speaker-funnel system was developed that focused the playback signal to reproduce as closely as possible the near-field spatial characteristics of the sounds produced by individual males. In initial studies, the system was tasted by observing the behavior of females while the speaker system played songs at various intensities. Through morning and early afternoon periods of peak sexual activity, virgin female medflies landed on a sheet of filter paper at the funnel outlet and stayed longer during broadcasting than during the silent part of the cycle. In later studies, females were captured on sticky paper at the funnel outlet. The mean capture rates were 67 and 44%, respectively, during sound emission and silent control periods. The findings confirmed that female trapping was improved if a male calling song was played. The second stage of the research focused on estimating the trapping range. Initial results indicated that the range possibly extended to 70 cm, but additional, verification tests remain to be conducted. Further studies are planned also to consider effects of combining acoustic and pheromonal cues.
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Schofield, Ian S., Paul L. Brown, Mark J. Logsdon, and Matthew P. Wickham. Waste Rock Dump Characterization Studies at the Bingham Canyon Mine. Utah Geological Survey, 2024. http://dx.doi.org/10.34191/mp-179.
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The Bingham Canyon Mine, located near Salt Lake City, Utah, is surrounded by more than 6 billion tons of waste rock developed over the open cut mining history from 1903 to present; the surface area of the waste rock is approximately 5000 acres. Waste rock dumps have a thickness of more than 1 200 feet from crest to toe. From 1930 to 2000, selected portions of the waste rock dumps were commercially leached using a ferric-sulfate-based lixiviant to extract copper, whereas other portions have only received meteoric leaching. From 2011 to present, Rio Tinto Kennecott has studied the evolution and geochemical controls on water chemistry associated with the waste rock dumps at the Bingham Canyon Mine. In this program, the waste rock dumps have been characterized in detail from the field logging of, and data collected from instrumentation installed within, 13 paired borings. At 12 of the 13 locations, the borings penetrated the full depth of the dumps, through the pre-mine soil contact, and into bedrock. Borings were installed to depths approaching 900 feet below ground surface using roto-sonic drilling methods to enable (1) core recovery and (2) measurement of near in situ properties. Field logging of the borings included Unified Soil Classification System descriptions, clast lithology, relative oxidation, paste pH, and geophysical methods (gyroscopic, temperature, neutron, and gamma). Core from the borings was analyzed for geotechnical properties (density, grain size distribution, moisture content, plasticity index and limit, and direct and block shear), quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN), modified acid-base accounting (ABA), modified synthetic precipitation leaching procedure (SPLP), and hyperspectral analysis by CoreScan. If water was encountered during the drilling process at sufficient volumes for collection from the core barrel, samples were collected for chemical analysis. Instrumentation installed within the borings included lysimeters, thermistor nodes, direct temperature sensing (DTS) fiber optic cables, time domain reflectometry (TDR), shear cables, gas (oxygen, carbon dioxide) measurement tubes, and vibrating wire piezometers (VWPs). Additionally, each drill site had multiple measurements of oxygen consumption in the surface layer of the local waste rock. Data acquired from the borings were linked with historical information (covering a period of greater than 50 years) from extensive drilling, mineralogical and litho-geochemical evaluations, hydraulic and tracer testing, and 20 years of seepage f low and water chemistry data to develop a conceptual model that describes the hydraulic, geochemical, and physical behavior of the waste rock dumps. Pyrite and other sulfide minerals in the waste rock dumps are oxidized by both diffusive and convective ingress of air, producing acidic, high-total dissolved solids effluents, and jarosite that has formed within the waste rock as a secondary phase that stores additional acidity. The dominant air ingress mechanism is convection, which accounts for greater than 90% of the sulfide oxidation within the waste rock dumps. Based on temperature profiles and water balance for the dumps, moisture loss to geochemical reactions is a significant part of the water budget.
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Quinn, Meghan. Geotechnical effects on fiber optic distributed acoustic sensing performance. Engineer Research and Development Center (U.S.), 2021. http://dx.doi.org/10.21079/11681/41325.
Full textAbstract:
Distributed Acoustic Sensing (DAS) is a fiber optic sensing system that is used for vibration monitoring. At a minimum, DAS is composed of a fiber optic cable and an optic analyzer called an interrogator. The oil and gas industry has used DAS for over a decade to monitor infrastructure such as pipelines for leaks, and in recent years changes in DAS performance over time have been observed for DAS arrays that are buried in the ground. This dissertation investigates the effect that soil type, soil temperature, soil moisture, time in-situ, and vehicle loading have on DAS performance for fiber optic cables buried in soil. This was accomplished through a field testing program involving two newly installed DAS arrays. For the first installation, a new portion of DAS array was added to an existing DAS array installed a decade prior. The new portion of the DAS array was installed in four different soil types: native fill, sand, gravel, and an excavatable flowable fill. Soil moisture and temperature sensors were buried adjacent to the fiber optic cable to monitor seasonal environmental changes over time. Periodic impact testing was performed at set locations along the DAS array for over one year. A second, temporary DAS array was installed to test the effect of vehicle loading on DAS performance. Signal to Noise Ratio (SNR) of the DAS response was used for all the tests to evaluate the system performance. The results of the impact testing program indicated that the portions of the array in gravel performed more consistently over time. Changes in soil moisture or soil temperature did not appear to affect DAS performance. The results also indicated that time DAS performance does change somewhat over time. Performance variance increased in new portions of array in all material types through time. The SNR in portions of the DAS array in native silty sand material dropped slightly, while the SNR in portions of the array in sand fill and flowable fill material decreased significantly over time. This significant change in performance occurred while testing halted from March 2020 to August 2020 due to the Covid-19 pandemic. These significant changes in performance were observed in the new portion of test bed, while the performance of the prior installation remained consistent. It may be that, after some time in-situ, SNR in a DAS array will reach a steady state. Though it is unfortunate that testing was on pause while changes in DAS performance developed, the observed changes emphasize the potential of DAS to be used for infrastructure change-detection monitoring. In the temporary test bed, increasing vehicle loads were observed to increase DAS performance, although there was considerable variability in the measured SNR. The significant variation in DAS response is likely due to various industrial activities on-site and some disturbance to the array while on-boarding and off-boarding vehicles. The results of this experiment indicated that the presence of load on less than 10% of an array channel length may improve DAS performance. Overall, this dissertation provides guidance that can help inform the civil engineering community with respect to installation design recommendations related to DAS used for infrastructure monitoring.
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Correlation Between Vibration Level, Lubricating Oil Viscosity and Total Number Base of an Internal Combustion Engine Operated with Gasoline and Ethanol. SAE International, 2022. http://dx.doi.org/10.4271/2022-01-0620.
Full textAbstract:
Lubricating oils for automotive engines have been incorporating important improvements in chemical properties to increase engine performance, reduce fuel consumption and vehicular emissions indices, in addition to increasing the time interval for changing the lubricant itself. The objective of this study is to investigate the vibrational behavior of the block and crankshaft an Otto cycle internal combustion engine operated with ethanol and gasoline fuel as a function of the viscosity and total base number (TBN) of the lubricant. The study consisted of instrumenting the block and the 1st and 5th fixed bearings of the crankshaft with accelerometers to measure the engine vibration intensity and operating the engine on a bench dynamometer in a specific test cycle. Each experiment lasted 600 hours and every 50 hours a block and crankshaft engine vibration level were measured and 100ml sample of lubricating oil was collected to check viscosity and TBN chemical lubricant's properties. The results show that the block and crankshaft engine vibration level increases with the time of use of the lubricating oil and that this increase is very significant when the oil viscosity an TBN chemical properties reaches the minimum value stipulated by the manufacturer lubricating oil. Semi-synthetic and synthetic lubricating oils have similar engine protection characteristics, but synthetic oil protects the engine for a longer period of time due to less degradation of viscosity an TBN chemical properties compared to semi-synthetic. Mineral lubricating oil presented protection for a very short test period, due to the rapid degradation of chemical properties and measurements showed an average increase of 20% of vibration engine running with mineral lubricating oil in relation synthetic and semi-synthetic oils. This research is important because it correlates the degradation of the lubricating oil with the engine vibration level and vibration problems in internal combustion engines produce premature wear on the internal components of the engine, which contributes to reduce the lifespan of the engine. This study also shows how is important to observe the correct application of automotive oils.