Abstract When avibratingstructureisrotatedwithrespecttoinertialspace,thevibratingpatternrotatesatarateproportionalto the inertialrateofrotation.Bryanfirstobservedthiseffectin1890.Theeffect,calledBryan’seffectinthesequel,has numerous navigationalapplicationsandcouldbeusefulinunderstandingthedynamicsofpulsatingstarsandearthquake series inastrophysicsandseismology.Bryan’sfactor(thecoefficientofproportionalitybetweentheinertialandvibrating pattern rotationrates)dependsonthegeometryofthestructureandthevibrationmodenumber.The‘‘gyroscopiceffects’’ of ahollowisotropicsolidspherefilledwithaninviscidacousticmediumareconsideredhere,butthetheoryisreadily adapted toahollowisotropicsolidcylinderfilledwithaninviscidacousticmedium.Alineartheoryisdevelopedassuming, among othermildconditions,thattherotationrateisconstantandmuchsmallerthanthelowesteigenfrequencyofthe vibrating system.Thuscentrifugalforcesareconsideredtobenegligible.Beforecalculatingsolutionsforthedisplacement of aparticleintheisotropic,spherical,distributedbody,Bryan’sfactorisinterpretedusingacomplexfunction.Hereitis demonstrated thatneitherBryan’seffectnorBryan’sfactorisinfluencedbyincludinglight,isotropic,viscousdampingin the mathematicalmodel.Hencedampingisneglectedinthesequel.Twoscenariosarethenidentified.Firstly,wemay assume thattheacousticmediumiscompletelyinvolvedintherotation(thespheroidalmode).Secondly,wemayassume that theacousticmediumremainsstaticwithrespecttotheinertialreferenceframe(thetorsionalmode).Weinvestigatethe spheroidal modeusinganumericalexperimentthatcomparestherotationalangularrateofasphere(filledwithaninviscid acoustic medium)withthoseofitsvibratingpatternsatbothhighandlowvibrationfrequency.

Thesis (M.S.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from openning screen viewed Apr. 22, 2001. Includes bibliographical references.

This thesis proposes a test method for evaluating the perceived vibration which occurs at the driver's hand in automotive steering wheel interface. The objective of the research was to develop frequency weightings for quantifying the human perception of steering wheel hand-arm vibration. Family of frequency weightings were developed from equal sensation curves obtained from the psychophysical laboratory experimental tests. The previous literature suggests that the only internationally standardised frequency weighting Wh is not accurate to predict human perception of steering wheel hand-arm vibration (Amman et. al, 2005) because Wh was developed originally for health effects, not for the human perception. In addition, most of the data in hand-arm vibration are based upon responses from male subjects (Neely and Burström, 2006) and previous studies based only on sinusoidal stimuli. Further, it has been continuously suggested by researchers (Gnanasekarna et al., 2006; Morioka and Griffin, 2006; Ajovalasit and Giacomin, 2009) that only one weighting is not optimal to estimate the human perception at all vibrational magnitudes. In order to address these problems, the investigation of the effect of gender, body mass and the signal type on the equal sensation curves has been performed by means of psychophysical laboratory experimental tests. The test participants were seated on a steering wheel simulator which consists of a rigid frame, a rigid steering wheel, an automobile seat, an electrodynamic shaker unit, a power amplifier and a signal generator. The category-ratio Borg CR10 scale procedure was used to quantify the perceived vibration intensity. A same test protocol was used for each test and for each test subject. The first experiment was conducted to investigate the effect of gender using sinusoidal vibration with 40 test participants (20 males and 20 females). The results suggested that the male participants provided generally lower subjective ratings than the female participants. The second experiment was conducted using band-limited random vibration to investigate the effect of signal type between sinusoidal and band-limited random vibration with 30 test participants (15 males and 15 females). The results suggested that the equal sensation curves obtained using random vibration were generally steeper and deeper in the shape of the curves than those obtained using sinusoidal vibration. These differences may be due to the characteristics of random vibration which produce generally higher crest factors than sinusoidal vibration. The third experiment was conducted to investigate the effect of physical body mass with 40 test participants (20 light and 20 heavy participants) using sinusoidal vibration. The results suggested that the light participants produced generally higher subjective ratings than the heavy participants. From the results it can be suggested that the equal sensation curves for steering wheel rotational vibration differ mainly due to differences of body size rather than differences of gender. The final experiments was conducted using real road signals to quantify the human subjective response to representative driving condition and to use the results to define the selection method for choosing the adequate frequency weightings for the road signals by means of correlation analysis. The final experiment was performed with 40 test participants (20 light and 20 heavy participants) using 21 real road signals obtained from the road tests. From the results the hypothesis was established that different amplitude groups may require different frequency weightings. Three amplitude groups were defined and the frequency weightings were selected for each amplitude group. The following findings can be drawn from the research: • the equal sensation curves suggest a nonlinear dependency on both the frequency and the amplitude. • the subjective responses obtained from band-limited random stimuli were steeper and the deeper in the shape of the equal sensation curves than those obtained using sinusoidal vibration stimuli. • females provided higher perceived intensity values than the males for the same physical stimulus at most frequencies. • light test participants provided higher perceived intensity than the heavy test participants for the same physical stimulus at most frequencies. • the equal sensation curves for steering wheel rotational vibration differ mainly due to differences in body size, rather than differences of gender. • at least three frequency weightings may be necessary to estimate the subjective intensity for road surface stimuli.

Vibration measurement and analysis has been an accepted method since decades to meet a number of objectives - machinery condition monitoring, dynamic qualification of any designed structural components, prediction of faults and structural aging-related problems, and several other structural dynamics studies and diagnosis. However, the requirement of the vibration measurement at number of locations in structures, machines and/or equipments makes the vibration measurement exorbitant if conventional piezoelectric accelerometers are used. Hence, there is a need for cheaper and reliable alternative for the conventional accelerometers. The Micro-Electro-Mechanical Systems (MEMS) accelerometers are one such cheap alternative. However, a significant deviation in the performance of the MEMS accelerometers has been observed in earlier research studies and also confirmed by this presented study when compared with well known conventional accelerometer. Therefore, two methods have been suggested to improve the performance of the existing MEMS accelerometers; one for correction in time domain and other in frequency domain. Both methods are based on the generation of a characteristic function (CF) for the MEMS accelerometer using well known reference accelerometer in laboratory tests. The procedures of both methods have been discussed and validations of these methods have been presented through experimental examples. In addition, a Finite Element (FE) model of a typical MEMS accelerometer has been developed and modal analysis has been carried out to understand the dynamics of capacitive type MEMS accelerometer and to identify the source of errors. It has been observed that the moving fingers behave like a cantilever beam while the fixed fingers showed rigid body motion. This cantilever type of motion seems to be causing non-parallel plates effect in the formed capacitors between moving and fixed fingers which results in errors in the vibration measurement. Hence, design modifications on finger shape have been suggested to remove the cantilever motion and results showed remarkable improvement. Moreover, the effect of using synchronous amplitude modulation and demodulation in the readout circuit has been studied. The experimental study showed that this circuit also introduces errors in amplitude and phase of the output signal compared with the input signal. Thus, in the new design of MEMS accelerometers, improvements in both mechanical design and electronic circuit are required.

A bluff structure placed in a flowing fluid, may be subjected to vortex-induced vibrations (VIV). For a flat plate with only rotational degree of freedom, the VIV is rotational oscillation. Based on the experimental investigation, vortex-induced oscillation of the plate is studied. The Strouhal number is measured from the stationary plate in a low speed steady wind tunnel. A set of vibration tests are conducted to investigate the relationships between shedding frequency and vibration frequency. “lock-in” phenomena is observed with and without large amplitude. An empiricalanalytical model via introducing a nonlinear van der Pol oscillator is developed. This thesis investigates the “lock-in” phenomena of a flat plate in pitch oscillation. Results from wind tunnel experiments on a flat plate indicate the “lock-in” is frequency “lock-in”, resonance which appears large response amplitude occurs in the “lock-in” regime and may be influenced by “lock-in” phenomena.

In this thesis, ground vibrations induced by bench blasting from the Tun&ccedil / bilek Coal Mine, Panel BYH, were measured to find out the site-specific attenuation and to assess the structural damage risk. A statistical approach is applied to the collected data, and from the data analysis an attenuation relationship is established to be used in predicting the peak particle velocity as well as to calculate the maximum allowable charge per delay. The values of frequencies are also analyzed to investigate the damage potential to the structures of Tun&ccedil / bilek Township. A new approach to predict the peak particle velocity is also proposed in this research study. A neural network technique from the branch of the artificial intelligence is put forward as an alternative approach to the statistical technique. Findings of this study indicate, according to USBM (1980) criteria, that there is no damage risk to the structures in Tun&ccedil / bilek Township induced by bench blasting performed at Tun&ccedil / bilek coal mine, Panel BYH. Therefore, it is concluded that the damage claims put forward by the inhabitants of Tun&ccedil / bilek township had no scientific bases. It is also concluded that the empirical statistical technique is not the only acceptable approach that can be taken into account in predicting the peak particle velocity. An alternative and interesting neural network approach can also give a satisfactory accuracy in predicting peak particle velocity when compared to a set of additional recorded data of PPV.

Um experimentell zu klären, ob bestimmte Vibrationsfrequenzen zur osteoanabolen Stimulation des Knochens und speziell zur Verbesserung der Frakturheilung bei Osteoporose geeigneter sind als andere, wurde in dieser Arbeit die Frakturheilung an der proximalen Tibiametaphyse der ovarektomierten Ratte unter einer vertikalen Vibrationsbehandlung mit Frequenzen von 35, 50, 70 und 90 Hz vergleichend untersucht. Die Tiere wurden dafür nach Tibiaosteotomie und Plattenosteosynthese über 30 Tage für jeweils 15 Minuten der für ihre Gruppe spezifischen Vibrationsfrequenz ausgesetzt. Die Amplitude der Vibration betrug dabei stets 0,5 mm. Die quantitative Analyse des Frakturkallus mittels Mikroradiographie und Micro-CT ergab deutliche Anhaltspunkte für eine überlegene osteoanabole Potenz der 70Hz-Vibration in Gestalt einer gegenüber allen anderen Vibrationsgruppen signifikant erhöhten endostalen Kallusdichte sowie einer gegenüber der nichtvibrierten OVX-Gruppe signifikant erhöhten periostalen Kallusdichte und -dicke. Auch kortikaler und trabekulärer Knochen profitierten von der 70Hz-Vibration, was sich in der unter dieser Frequenz - zumindest hinsichtlich der Belastbarkeit - besten Kallusqualität widerspiegelte.  Die 35Hz-Vibration kann die Kallusbildung ebenfalls anregen und damit auch die biomechanischen Eigenschaften des Kallus (Steifheit) verbessern. Kallus und kortikaler Knochen werden durch 35 Hz aber schlechter stimuliert als durch alle anderen untersuchten Frequenzen. Die 50Hz-Vibration verbessert die biomechanischen Eigenschaften in ähnlicher Weise, sie stimuliert Kallus und Kortikalis dabei etwas besser als 35 Hz, aber deutlich schlechter als 70 Hz. Auch die 90Hz-Vibration hat einen stimulierenden Effekt auf Kallus, Kortikalis und trabekulären Knochen, insbesondere die Kallusstimulation ist aber wieder deutlich schlechter als unter der Frequenz von 70 Hz. Die 90Hz-Vibration hat zudem eine übermäßige Reizung des Kallus zur Folge, die sich in den schlechtesten biomechanischen Eigenschaften aller untersuchten Frequenzen manifestiert.  Als Synthese der mit den verschiedenen Untersuchungsverfahren dieser Arbeit gewonnenen Ergebnisse kann eine Überlegenheit der Vibrationsfrequenz von 70 Hz für die Stimulation der Frakturheilung bei Osteoporose festgestellt werden. Diese Ergebnisse am Rattentiermodell sollten - vor Beginn einer klinischen Studie - am Großtiermodell verifiziert werden.

This master thesis is focused on the diagnostics of vibrations and noise of an internal combustion engine. The work also includes a summary of the current state of knowledge in which the quantities used, transmission paths, measuring devices and the possibilities of performing frequency analysis are analysed. As part of the technical experiment on which this work is based, vibrations and noise on the tractor engine are measured. The obtained data are then further processed using the BK Connect program. Subsequently, a frequency analysis is performed, specifically an order analysis. The conclusion of the analysis consists of an evaluation of individual orders that cause excitation that occur in the investigated motor.

L’ostéoporose ménopausique est généralement traitée par une stratégie médicamenteuse à visée anti-résorptive, couplée à des exercices de musculation/proprioception relativement efficaces pour maintenir la masse musculaire et prévenir le risque de chute. Ces dernières années, bien que de nombreuses études animales et cliniques aient suggéré un effet ostéogénique des vibrations corps entier (VCE), les résultats pas toujours concluants et les protocoles très hétérogènes rendent l’interprétation difficile. Dans ce travail, nous avons étudié l’importance de la fréquence de la vibration dans les effets osseux induits par les VCE, sur des rats adultes. Nous avons montré que la stimulation osseuse était dose dépendante de la fréquence, avec un effet ostéogénique d’autant plus important que la fréquence est élevée, et un effet délétère des basses fréquences. Le régime à haute fréquence (90Hz) améliore la micro-macroarchitecture de l’os cortical (épaississement cortical, diminution de la porosité) et de l’os trabéculaire (augmentation du volume osseux, nombre de travées), et stimule la formation osseuse (taux de formation osseuse augmenté), alors que le régime basse fréquence (8Hz) découple les activités de formation et minéralisation, responsable d’une diminution des DMO corticales et trabéculaires, caractéristiques d’une ostéomalacie. Dans cette étude, la réponse ostéogénique plus marquée aux vertèbres vs les os longs (Tibia et fémur) suggère un rôle de la moelle grasse dans la réponse osseuse aux VCE. L’étude clinique réalisée par la suite chez des femmes ménopausées, confirme la capacité des VCE à stimuler la formation osseuse corticale et trabéculaire (épaississement cortical, augmentation de l’aire corticale, maintien de la porosité, augmentation du volume osseux trabéculaire) avec un effet systémique des VCE (os porteurs et non porteurs). L’étude de la propagation du signal vibratoire chez l’animal et l’humain montre une amplification du signal dans les basses fréquences, caractéristique d’un effet de résonance, et une transmission plus importante des vibrations au-delà de 40Hz, expliquant en partie les effets des VCE en fonction de la fréquence. Nos résultats suggèrent l’utilisation des VCE comme moyen non pharmacologique de prévention voir traitement de la fragilité osseuse / The postmenopausal osteoporosis is generally handled by a medicinal strategy with anti-résorptive aim, coupled with relatively effective exercises of body-building / proprioception to maintain the muscular mass and prevent the risk of fall. These last years, although numerous animal and clinical studies suggested an osteogenic effect of the whole-body vibrations (WBV), the not always decisive results and the very heterogeneous protocols make difficult the interpretation. In this work, we studied the importance of the frequency of vibration in the bone effects induced by WBV on adult rats. We have shown that bone stimulation was dependent on the dose frequency, with a particularly important that the frequency is high osteogenic effect and a detrimental effect of low frequency. The high frequency system (90Hz) improves the control of the microarchitecture cortical bone (cortical thickening, reduced porosity) and trabecular bone (bone augmentation, number of spans), and stimulate bone formation (bone formation rate increased), while the low frequency regime (8Hz) decouples training and mineralization, causing a decrease in cortical and trabecular BMD, characteristic of osteomalacia. In this study, the more pronounced the vertebrae vs long bones (femur and tibia) osteogenic response suggests a role of the fat in the bone marrow response to WBV. The clinical study later postmenopausal women, confirms the ability of WBV to stimulate cortical and trabecular bone formation (cortical thickening, increased cortical area, maintaining porosity, trabecular bone volume increase) with a systemic effect of WBV (bearing and non-bearing bones). The study of the propagation of the vibration signal in animals and humans shows an amplification of the signal in the low frequency characteristic of a resonance effect, and a greater transmission of vibrations beyond 40Hz, explaining part of the effects according to the WBV frequency. Our results suggest the use of WBV as non-pharmacological means of prevention, or even treatment, of bone fragility

This diploma thesis is focused on experimental measurement and acoustic and dynamic behavior analysis of railway construction with the Y – steel sleepers and their comparison with concrete sleepers. The measurements were taken in situ, in suitable sections of a railway line. These sections meet the requirements of regional railway tracks in the Czech Republic. Monitored parameters were obtained by measuring a response of testing trains and were analyzed using frequency and time analysis. Based on these evaluations, comparisons of particular constructions and their recommendations for practice were made.