bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Analysis of Wind Turbine Towers on Flexible Foundations
Authors: Adhikari S. , Bhattacharya S.
Published: January 2014

Offshore wind turbines are considered as an essential part to develop sustainable, alternative energy sources. The structures themselves are both slender and highly flexible, with a subsea foundation typically consisting of a single large diameter monopile. They are subject to intense wind and wave loadings, with the result that significant movement of both the exposed structure and the upper part of the monopile can occur. Although the structures are intended for design life of 25 to 30 years, very little is known about the long term behaviour of these structures. This paper characterizes the dynamic behaviour of these structures. A simplified approach has been proposed for the free vibration analysis of wind turbines taking the effect of foundation into account. The method is based on an Euler-Bernoulli beam-column with elastic end supports. The elastic end-supports are considered to model the flexible nature of the interaction of these systems with the foundation. A closed-form expression of the characteristic equation governing all the natural frequencies of the system has been derived. Theoretical developments are explained by practical numerical examples. Analytical as well as a new experimental approach has been proposed to determine the parameters for the foundation. Some design issues of wind turbine towers are discussed from the point of view of the foundation parameters.
Prediction of Full Field Dynamic Strain from Limited Sets of Measured Data
Authors: Avitabile Peter , Pingle Pawan
Published: January 2014

Dynamic response is an important consideration for design of structures due to operating or occasional loadings. The resulting dynamic stress strain is also of concern for fatigue and structural health monitoring. Typically, the actual loading and structural condition (boundary conditions, environmental condition, geometry, mechanical properties, etc.) are not necessarily known. Much effort is expended in attempting to identify the loads and appropriate model for prediction of these types of events. At best, the forces and actual boundary conditions are approximate and have an effect on the overall predicted response and resulting stress-strain that is identified for subsequent evaluation.

Experimental data can only be obtained from limited sets of points, such as those typically collected with accelerometers. These are normally used in the evaluation the state of a structure in service condition. More recently, Digital Image Correlation (DIC) and Dynamic Photogrammetry (DP) have become very important techniques to measure the surface response. These are non-contact and full-field techniques, which allow that much more simultaneous data to be measure. The sets of limited surface data that are collected can be used in conjunction with an expansion algorithm to obtain full field information. The finite element model mass and stiffness matrices are used to obtain the normal constitutive relations as well as the modal characteristics. This information is used to develop the expansion algorithm and for the stress recovery during the back substitution process typically employed.
Modeling and Control of the Vibration of Two Beams Coupled with Fluid and Active Links
Authors: Zhang Zhiyi , Hu Fang , Li Zeng , Hua Hongxing
Published: January 2014

Investigated are modeling and control approaches for vibration analysis of two identical beams which are coupled with fluid and active mechanical links. In the modeling of the coupled beam system, orthogonal functions are used to represent vibration of the beams and the fluid-structure interaction is considered. Frequency Response Functions (FRFs) are derived from the coupled governing equations and the superposition principle for linear vibration systems. In the control of vibration of the beams, impulse response functions corresponding to the FRFs and an adaptive control algorithm are employed to attenuate vibration transmission between the two beams. Natural frequencies, mode shapes as well as the pressure distribution in the fluid are computed. The results obtained by the proposed modeling method are in good consistency with those obtained by the finite element analysis. Moreover, it is demonstrated that the active mechanical link is able to reduce vibration transmission and change the deformation of beams as well as the distribution of fluid pressure.
Sloshing of Liquid in Rigid Cylindrical Container with a Rigid Annular Baffle. Part II: Lateral Excitation
Authors: Wang J.D. , Zhou D. , Liu W.Q.
Published: January 2014

Sloshing response of liquid in a rigid cylindrical container with a rigid annual baffle subjected to lateral excitation has been studied. The complicated liquid domain is separated into several simple sub-domains by introducing the artificial interfaces. The analytical solutions of potential function corresponding to every sub-domain are obtained by using the method of separation of variables and the superposition principle. The total potential function under lateral excitation is taken as the sum of the container potential function and the liquid perturbed function. The expression of the liquid perturbed function is obtained by introducing the generalized coordinates. On the base of the natural frequencies and modes having been obtained by the sub-domain method, the orthogonality among the sloshing modes has been demonstrated. Substituting the potential functions into the free surface wave equation establishes the dynamic response equation of liquid. Then, the generalized coordinates are solved. The sloshing surface displacement, the hydrodynamic pressure distribution, the resultant hydrodynamic force and moment are discussed for the containers subjected to harmonic and seismic lateral excitation, respectively.
Specificity in Rehabilitation of Word Production: A Meta-Analysis and a Case Study
Authors: Jacquemot Charlotte , Dupoux Emmanuel , Robotham Laura , Bachoud-Lévi Anne-Catherine
Published: January 2014

Speech production impairment is a frequent deficit observed in aphasic patients and rehabilitation programs have been extensively developed. Nevertheless, there is still no agreement on the type of rehabilitation that yields the most successful outcomes. Here, we ran a detailed meta-analysis of 39 studies of word production rehabilitation involving 124 patients. We used a model-driven approach for analyzing each rehabilitation task by identifying which levels of our model each task tapped into. We found that (1) all rehabilitation tasks are not equally efficient and the most efficient ones involved the activation of the two levels of the word production system: the phonological output lexicon and the phonological output, and (2) the activation of the speech perception system as it occurs in many tasks used in rehabilitation is not successful in rehabilitating word production. In this meta-analysis, the effect of the activation of the phonological output lexicon and the phonological output cannot be assessed separately. We further conducted a rehabilitation study with DPI, a patient who suffers from a damage of the phonological output lexicon. Our results confirm that rehabilitation is more efficient, in terms of time and performance, when specifically addressing the impaired level of word production.
Use ofIn-SituDynamic Measurements to Calibrate Analytical Models of RC-Elevated Water Tanks
Authors: Lopes H.M. , Oliveira C.S.
Published: January 2014

Before establishing the priority settings for the reduction of seismic risk of water supply infrastructures, it is necessary to understand the dynamic behavior of elevated water tanks, which are components of those infrastructures. Among other information, the main frequencies of vibration of these structures must be estimated and the analytical models used in their analysis and design should reproduce the frequency values obtained by in-situ dynamic tests. This work focuses exclusively on reinforced concrete (RC) elevated water tanks (200–750 m^3 of water at heights of 30–40 m), which are very common structures in the water supply systems in Portugal since the mid XXth century. This type of structures can also be seen in many regions around the world. First, a nationwide survey was conducted to determine the most common typologies in the country in terms of structural layout. Second, an in-situ campaign using ambient vibration as input was performed for a group of selected structures to determine the main frequencies of vibration and to identify modal shapes and damping values. Third, a finite element model of several different typologies was developed using the water simply as a concentrated mass at the top; the elastic properties of the model of the structure including the foundation were calibrated, so that the frequencies of various mode shapes obtained by the analytical model would match the frequencies of the real structure. Finally, an expression was derived to estimate the fundamental frequency of a group of elevated water tank typologies based on the total mass at the top of the supporting structure, which include the water, the global lateral stiffness, and the height of the tank. This study, providing important information on the frequencies of vibration of RC-elevated water tanks, contributes in a definite way to the analysis and design of such water tanks.
Bearing Fault Detection Using Multi-Scale Fractal Dimensions Based on Morphological Covers
Authors: Zhang Pei-Lin , Li Bing , Mi Shuang-Shan , Zhang Ying-Tang , Liu Dong-Sheng
Published: January 2014

Vibration signals acquired from bearing have been found to demonstrate complicated nonlinear characteristics in literature. Fractal geometry theory has provided effective tools such as fractal dimension for characterizing the vibration signals in bearing faults detection. However, most of the natural signals are not critical self-similar fractals; the assumption of a constant fractal dimension at all scales may not be true. Motivated by this fact, this work explores the application of the multi-scale fractal dimensions (MFDs) based on morphological cover (MC) technique for bearing fault diagnosis. Vibration signals from bearing with seven different states under four operations conditions are collected to validate the presented MFDs based on MC technique. Experimental results reveal that the vibration signals acquired from bearing are not critical self-similar fractals. The MFDs can provide more discriminative information about the signals than the single global fractal dimension. Furthermore, three classifiers are employed to evaluate and compare the classification performance of the MFDs with other feature extraction methods. Experimental results demonstrate the MFDs to be a desirable approach to improve the performance of bearing fault diagnosis.
Multi-Component BEM for the Helmholtz Equation: A Normal Derivative Method
Authors: Hamdin H.A.M. Ben , Tanner G.
Published: January 2014

We describe a multi-component boundary element method for predicting wave energy distributions in a complex built-up system with material properties changing discontinuously at boundaries between sub-components. We point out that depending on the boundary conditions and the number of interfaces between sub-components, it may be advantageous to use a normal derivative method to set up the integral kernels. We describe how the resulting hypersingular integral kernels can be regularised. The method can be used to minimise the number of weakly singular integrals thus leading to BEM formulations which are easier to handle.
An Efficient Approach for Determining Forced Vibration Response Amplitudes of a MDOF System with Various Attachments
Authors: Wu J.S. , Chen J.H.
Published: January 2014

The frequency-response curve is an important information for the structural design, but the conventional time-history method for obtaining the frequency-response curve of a multi-degree-of-freedom (MDOF) system is time-consuming. Thus, this paper presents an efficient technique to determine the forced vibration response amplitudes of a multi-span beam carrying arbitrary concentrated elements. To this end, the "steady" response amplitudes|Y(x)|sof the above-mentioned MDOF system due to harmonic excitations (with the specified frequencieswe) are determined by using the numerical assembly method (NAM). Next, the corresponding "total" response amplitudes|Y(x)|tof the same vibrating system are calculated by using a relationship between|Y(x)|tand|Y(x)|sobtained from the single-degree-of-freedom (SDOF) vibrating system. It is noted that, near resonance (i.e.,we/w≈1.0), the entire MDOF system (with natural frequencyw) will vibrate synchronously in a certain mode and can be modeled by a SDOF system. Finally, the conventional finite element method (FEM) incorporated with the Newmark's direct integration method is also used to determine the "total" response amplitudes|Y(x)|tof the same forced vibrating system from the time histories of dynamic responses at each specified exciting frequencywe. It has been found that the numerical results of the presented approach are in good agreement with those of FEM, this confirms the reliability of the presented theory. Because the CPU time required by the presented approach is less than 1% of that required by the conventional FEM, the presented approach should be an efficient technique for the title problem.
Loading on a Rigid Target from Close Proximity Underwater Explosions
Authors: Riley Mark , Smith Malcolm , van Aanhold J.E. , Alin Niklas
Published: January 2014

The study describes recent simulation results for underwater explosions in close-proximity to rigid targets. Simulations are performed using Chinook, an Eulerian computational fluid dynamics (CFD) code. Predicted target loadings are compared with measurements taken from a series of experiments conducted under an international collaboration between Canada, The Netherlands, and Sweden. The simulations of the rigid target tests focused on the modelling of gas bubble collapse and water jetting behaviour. Both two-dimensional and three-dimensional simulations were performed. It was found that the two-dimensional analyses produced good bubble periods and reasonable impulse loading compared to experimental data. The time of arrival of the bubble collapse and water jetting were found to be very mesh dependent and refining the mesh did not always produce better results. The two-dimensional approach provides a good initial understanding of the problem for a reasonable computational effort. The three-dimensional simulations were found to produce improved impulse predictions. The numerical gas bubble radii time histories are also compared to empirical time histories.
Model Tests and FE-Modelling of Dynamic Soil-Structure Interaction
Authors: Kodama N. , Komiya K.
Published: January 2014

The forces applied to a structure from the soil ground during an earthquake and the dynamic response of a structure are problems that are not well understood. In recent years, seismic design technology aided by numerical simulation is under active development. Successful improvement of the accuracy and reliability of numerically simulated results relies on a clear understanding of the seismic force transmission mechanism between the soil and a structure associated with mechanical properties of soil.

In this study, laboratory shaking tests were conducted using the unique apparatus designed to have a structure move only by its inertial force and the lateral earth pressure that comes from surrounding sandy soils. The earth pressure at the structure surface and the relative displacement between the soil and the structure were measured in the experiments under various conditions. A new Finite Element interface model for sandy soil-structure dynamic interaction is proposed from the experimental results. Estimated seismic responses of a bridge pier calculated by the proposed interface model, conventional linear elastic model and tension cut-off model are compared.
Neural Network Based Vibration Analysis with Novelty in Data Detection for a Large Steam Turbine
Authors: Kumar K. P. , Rao K.V.N.S. , Krishna K.R. , Theja B.
Published: January 2014

Health of rotating machines like turbines, generators, pumps and fans etc., is crucial to reliability in power generation. For real time, integrated health monitoring of steam turbine, novel fault detection data is essential to reduce operating and maintenance costs while optimizing the life of the critical engine components. This paper describes about normal and abnormal vibration data detection procedure for a large steam turbine (210 MW) using artificial neural networks (ANN). Self-organization map is trained with the normal data obtained from a thermal power station, and simulated with abnormal condition data from a test rig developed at laboratory. The optimum size of self-organization map is determined using quantization and topographic errors, which has a strong influence on the quality of the clustering. The Mat lab 7 codes are applied to generate program using neural networks toolbox.
Cognitive Structure of Writing Disorders in Russian: What Would Luria Say?
Authors: Kozintseva Elena , Skvortsov Anatoly , Ulicheva Anastasia , Vlasova (Zaykova) Anna
Published: January 2014

Acquired disorders of writing in the Russian language have been reported for more than a century. The study of these disorders reflects the history of Russian neuropsychology and is dominated by the syndrome approach most notably by the writings of Luria. Indeed, our understanding of acquired dysgraphia in Russian speakers is conceptualized according to the classical approach in Modern Russia. In this review, we describe the classical approach and compare it to the cognitive neuropsychological models of writing disorders that are developed to explain dysgraphia in English and in other Western European languages. We argue that the basic theoretical assumptions of the two approaches – cognitive and classical or syndrome approach – share similarities. It is therefore proposed that identification of acquired cases of dysgraphia in Russian could potentially benefit from taking the cognitive neuropsychological perspective. We also conclude that adopting elements of the syndrome approach would substantially enrich the understanding of acquired dysgraphia since these offer an insight into processes not described in the cognitive neuropsychological approach.
Importance of the Wheel Vertical Dynamics in the Squeal Noise Mechanism on a Scaled Test Bench
Authors: Collette C.
Published: January 2014

This paper investigates the influence of the wheel vertical dynamics in the mechanism of squeal noise on a scaled test bench. To this purpose, sustained oscillations are first studied on a single degree of freedom oscillator, considering both a decreasing slope of the friction curve and a vertical excitation. Their relative importance to sustain the oscillations is discussed. Then, a mathematical model of a quarter scale test bench is developed in the frequency domain. Using this model, it is shown that the squeal noise resulting from the excitation of the bending modes of the wheel is sustained because these bending modes are associated with variations of the vertical contact force. Results are further confirmed by experiments conducted on a scaled test bench.
The Principal Parametric Resonance of Coupled van der Pol Oscillators under Feedback Control
Authors: Li Xinye , Zhang Huabiao , He Lijuan
Published: January 2014

The principal parametric resonance of two van der Pol oscillators under coupled position and velocity feedback control with time delay is investigated analytically and numerically on the assumption that only one of the two oscillators is parametrically excited and the feedback control is linear. The slow-flow equations are obtained by the averaging method and simplified by truncating the first term of Taylor expansions for those terms with time delay. It is found that nontrivial solutions corresponding to periodic motions exist only for one oscillator if no feedback control is applied although the two oscillators are nonlinearly coupled. Based on Levenberg-Marquardt method, the effects of excitation and control parameters on the amplitude of periodic solutions of the system are graphically given. It can be seen that both of the two oscillators can be excited in periodic vibration with proper feedback. However, the amplitudes of the periodic vibrations are independent of the sign of feedback gains. In addition, the influence of time delay on the response of the system is periodic. In terms of numerical simulations, it is shown that both of the two oscillators can also have quasi-periodic motions, periodic motions about a new equilibrium position and other complex motions such as relaxation oscillation when feedback control is considered.
Uncertainty in Loading and Control of an Active Column Critical to Buckling
Authors: Enss G.C. , Platz R. , Hanselka H.
Published: January 2014

Buckling of load-carrying column structures is an important design constraint in light-weight structures as it may result in the collapse of an entire structure. When a column is loaded by an axial compressive load equal to its individual critical buckling load, a critically stable equilibrium occurs. When loaded above its critical buckling load, the passive column may buckle. If the actual loading during usage is not fully known, stability becomes highly uncertain.

This paper presents an approach to control uncertainty in a slender flat column structure critical to buckling by actively stabilising the structure. The active stabilisation is based on controlling the first buckling mode by controlled counteracting lateral forces. This results in a bearable axial compressive load which can be theoretically almost three times higher than the actual critical buckling load of the considered system. Finally, the sensitivity of the presented system will be discussed for the design of an appropriate controller for stabilising the active column.
Synthesis of Vibration Waves Based on Wavelet Technology
Authors: Zou L.H. , Liu A.P. , Ma X. , Zhang C. , Huang K.
Published: January 2014

A novel method to generate time series of vibration waves is proposed in the paper. Considering the frequency band energy as the criterion, synthesis formulas for fluctuating wind pressure and earthquake ground motion are developed in terms of Daubechies wavelet and Harr wavelet respectively. The wavelet reconstruction method is applicable to both stationary and non-stationary process simulation. Theoretically, for non-stationary (such as seismic) process synthesis, it has a better non-stationarity in time-frequency domain than the traditional trigonometric series. Influence of wavelet delamination number and wavelet function type is also analyzed. Numerical results show that the synthesis of vibration waves based on wavelet reconstruction method contains main components of vibration, and can reflect the main properties of practical vibrations.
Dynamic Response of a Beam Resting on a Nonlinear Foundation to a Moving Load: Coiflet-Based Solution
Authors: Koziol Piotr , Hryniewicz Zdzislaw
Published: January 2014

This paper presents a new semi-analytical solution for the Timoshenko beam subjected to a moving load in case of a nonlinear medium underneath. The finite series of distributed moving loads harmonically varying in time is considered as a representation of a moving train. The solution for vibrations is obtained by using the Adomian's decomposition combined with the Fourier transform and a wavelet-based procedure for its computation. The adapted approximating method uses wavelet filters of Coiflet type that appeared a very effective tool for vibration analysis in a few earlier papers. The developed approach provides solutions for both transverse displacement and angular rotation of the beam, which allows parametric analysis of the investigated dynamic system to be conducted in an efficient manner. The aim of this article is to present an effective method of approximation for the analysis of complex dynamic nonlinear models related to the moving load problems.
GOOD or BAD Responder? Behavioural and Neuroanatomical Markers of Clinical Response to Donepezil in Dementia
Authors: Bottini Gabriella , Berlingeri Manuela , Basilico Stefania , Passoni Serena , Danelli Laura , Colombo Nadia , Sberna Maurizio , Franceschi Massimo , Sterzi Roberto , Paulesu Eraldo
Published: January 2014

We explored the neuropsychological and neuromorphometrical differences between probable Alzheimer's disease patients showing a good or a bad response to nine months treatment with donepezil. Before treatment, the neuropsychological profile of the two patient groups was perfectly matched. By the ninth month after treatment, theBAD-respondersshowed a decline of the MMSE score together with a progressive impairment of executive functions. A voxel-based morphometry investigation (VBM), at the time of the second neuropsychological assessment, showed that theBAD-respondershad larger grey and white matter atrophies involving the substantia innominata of Meynert bilaterally, the ventral part of caudate nuclei and the left uncinate fasciculus, brain areas belonging to the cholinergic pathways. A more widespread degeneration of the central cholinergic pathways may explain the lack of donepezil efficacy in those patients not responding to a treatment that operates on the grounds that some degree of endogeneous release of acetylcholine is still available.
Bionic Design for Column of Gantry Machining Center to Improve the Static and Dynamic Performance
Authors: Liu Shihao , Ye Wenhua , Lou Peihuang , Chen Weifang , Huang Jungui , Xiao Lili
Published: January 2014

In order to improve the machining accuracy of a gantry machining center, structural bionic design for column was conducted. Firstly, the bionic design method for stiffener plate structure was established based on distribution principles of gingko root system. The bionic design method was used to improve column structure of the gantry machining center, and three kinds of bionic columns were put forward. The finite element analysis on original and bionic columns indicates that the mass of the column with the best bionic stiffener plate structure is reduced by 2.74% and the first five order natural frequencies are increased by 6.62% on average. The correctness of column's bionic design method proposed in this paper was verified by the static and dynamic experiments. Finally, the bionic principles for stiffener plate of column were concluded, which provides a new idea for updating traditional design concepts and achieving lightweight structure of machine tool components.
The Left Superior Longitudinal Fasciculus within the Primary Sensory Area of Inferior Parietal Lobe Plays a Role in Dysgraphia of Kana Omission within Sentences
Authors: Shinoura Nobusada , Midorikawa Akira , Onodera Toshiyuki , Yamada Ryozi , Tabei Yusuke , Onda Yasumitsu , Itoi Chihiro , Saito Seiko , Yagi Kazuo
Published: January 2014

Functional neurological changes after surgery combined with diffusion tensor imaging (DTI) tractography can directly provide evidence of anatomical localization of brain function. Using these techniques, a patient with dysgraphia before surgery was analyzed at our hospital in 2011. The patient showed omission of kana within sentences before surgery, which improved after surgery. The brain tumor was relatively small and was located within the primary sensory area (S1) of the inferior parietal lobe (IPL). DTI tractography before surgery revealed compression of the branch of the superior longitudinal fasciculus (SLF) by the brain tumor. These results suggest that the left SLF within the S1 of IPL plays a role in the development of dysgraphia of kana omission within sentences.
A Theoretical and Experimental Investigation on Free Vibration Vehavior of a Cantilever Beam with a Breathing Crack
Authors: Rezaee M. , Fekrmandi H.
Published: January 2014

In this paper the free nonlinear vibration behavior of a cracked cantilever beam is investigated both theoretically and experimentally. For simplicity, the dynamic behavior of a cracked beam vibrating at its first mode is simulated using a simple single degree of freedom lumped parameter system. The time varying stiffness is modeled using a harmonic function. The governing equation of motion is solved by a perturbation method – the method of Multiple Scales.

Results show that the correction term that is added to the main part of the response reflects the effect of breathing crack on the vibration response. Moreover, this part of response consists of the superharmonic components of the spectrum which is due to the system's intrinsic nonlinearity. Using this method an analytical relation is established between the system characteristics and the crack parameters in one hand and the nonlinear characteristics of system response on the other hand. Results have been validated by the experimental tests and a numerical method.
Receptance-Based Partial Pole Assignment for Asymmetric Systems Using State-Feedback
Authors: Tehrani M. Ghandchi , Ouyang H.
Published: January 2014

Many structures or machines interact with some internal nonconservative forces and present asymmetric systems in which the stiffness and damping matrices are asymmetric. Examples include friction-induced vibration and aeroelastic flutter. Asymmetric systems are prone to flutter instability as a result of the real parts of some poles becoming positive when certain system parameters vary.

This paper presents a receptance-based inverse method for assigning a number of complex poles of second-order damped asymmetric systems while keeping other unassigned poles unchanged. It uses state-feedback (active damping and active stiffness) to shift the poles to desired locations where all poles have negative real parts. Receptances at only a small, limited number of degrees-of-freedom of the underlying symmetric system are required. Simulated numerical examples indicate that this is an effective method and is capable of assigning negative real parts to unstable poles to stabilise an otherwise unstable second-order dynamic system.
Damage Identification in Bars with a Wave Propagation Approach and a Hybrid Optimization Method
Authors: Tenenbaum R.A. , Fernandes K.M. , Stutz L.T. , Neto A.J. Silva
Published: January 2014

The formulation and solution of the inverse problem of damage identification based on wave propagation approach are presented. Different damage scenarios for a bar are considered. Time history responses, obtained from pulse-echo synthetic experiments, are used to identify damage position, severity and shape. In order to account for noise corrupted data, different levels of signal to noise ratio – varying from 30 to 0 dB – are introduced. In the identification process, different optimization methods are investigated: the deterministic Levenberg-Marquardt; the stochastic Particle Swarm Optimization; and a hybrid technique combining the aforementioned methods. It is shown that the damage identification procedure built on the wave propagation approach was successful, even for highly corrupted noisy data. Test case results are presented and a few comments on the advantages of deterministic and stochastic methods and their combination are also reported. Finally, an experimental validation of the sequential algebraic algorithm, used for modeling the direct problem, is presented.
Free and Forced Vibrations of an Axially-Loaded Timoshenko Multi-Span Beam Carrying a Number of Various Concentrated Elements
Authors: Yesilce Yusuf
Published: January 2014

In the existing reports regarding free and forced vibrations of the beams, most of them studied a uniform beam carrying various concentrated elements using Bernoulli-Euler Beam Theory (BET) but without axial force. The purpose of this paper is to utilize the numerical assembly technique to determine the exact frequency-response amplitudes of the axially-loaded Timoshenko multi-span beam carrying a number of various concentrated elements (including point masses, rotary inertias, linear springs and rotational springs) and subjected to a harmonic concentrated force and the exact natural frequencies and mode shapes of the beam for the free vibration analysis. The model allows analyzing the influence of the shear and axial force and harmonic concentrated force effects and intermediate concentrated elements on the dynamic behavior of the beams by using Timoshenko Beam Theory (TBT). At first, the coefficient matrices for the intermediate concentrated elements, an intermediate pinned support, applied harmonic force, left-end support and right-end support of Timoshenko beam are derived. After the derivation of the coefficient matrices, the numerical assembly technique is used to establish the overall coefficient matrix for the whole vibrating system. Finally, solving the equations associated with the last overall coefficient matrix one determines the exact dynamic response amplitudes of the forced vibrating system corresponding to each specified exciting frequency of the harmonic force. Equating the determinant of the overall coefficient matrix to zero one determines the natural frequencies of the free vibrating system (the case of zero harmonic force) and substituting the corresponding values of integration constants into the related eigenfunctions one determines the associated mode shapes. The calculated vibration amplitudes of the forced vibrating systems and the natural frequencies of the free vibrating systems are given in tables for different values of the axial force. The dynamic response amplitudes and the mode shapes are presented in graphs. The effects of axial force and harmonic concentrated force on the vibration analysis of Timoshenko multi-span beam are also investigated.
The Influence of Playing a Non-Reward Game on Motor Ability and Executive Function in Parkinson’s Disease
Authors: Lima Alisson Menezes Araújo , de Campos Cordeiro Hirata Fabiana , de Bruin Gabriela Sales , Mota Rosa Maria Salani , de Bruin Veralice Meireles Sales
Published: January 2014

The aim of this study is to evaluate the acute effect of playing games on executive function and motor ability in Parkinson's disease (PD). Consecutive cases with PD were studied with the Unified Parkinson Disease Rating Scale (UPDRS), Mini-Mental State examination (MMSE), Beck Depression Inventory (BDI), Stroop test, finger tapping and 14-meter walk test. After randomization, patients performed a game of dominoes and were tested before and after experiment being further categorized as control, winners or non-winners. Forty patients, 27 male (67.5%), aged 48 to 84 years (63.2 ± 8.5), Hoehn & Yahr I to III were included. Twenty-eight (70%) presented depressive symptoms (BDI > 10). Groups (Control N = 13; Winners = 14 and Non-winners = 13) were not different regarding age, disease duration, age at onset, BMI, MMSE scores, depressive symptoms, levodopa dose, and previous practice of games. Winners presented significantly better results on executive function (Stroop test,p= 0.002) and on motor activity (Finger tapping,p= 0.01). Non-winners showed a trend of better performance in the 14-meter-walk test. This study shows that the practice of a non-reward game acutely improved memory and motor skills in PD. Our results suggest a role for the reward system in the modulation of the dopaminergic function of the basal ganglia in these patients.
Piezoceramic Cantilever Sensor Design for Weak-Impact Detection on Plates
Authors: Lee Young-Sup , Lee Sang-Kwon , Shin Kihong
Published: January 2014

A piezoelectric cantilever type sensor for locating the precise weak-impact or touch position on a plate is presented in this paper. Since the importance of human-computer interface such as a touch panel system has been rapidly increasing recently, this study could suggest an appropriate sensor for the detection of a weak-impact point effectively and accurately for such a system. This sensor detects the out-of-plane vibration of a panel when a touch with a finger or pen is applied on it. The sensor is made with a steel beam and a single crystal PMN-PT patch is bonded on the beam, which is designed to detect the base vibration of the panel. The sensor was designed, manufactured to verify the detect ability of a weak-impact and attached on two different plates of a glass of 400 × 400 × 4 mm and a wooden MDF of 600 × 600 × 9 mm. The experiment result of the sensor was compared with that of an accelerometer which can also be used for the same purpose and shows clear weak-impact responses with a narrow-band property at its resonant frequency. It is expected that the cantilever type sensor in this study could be applied to make a simple flat plate into a touch panel when the time difference of arrivals method is used to locate the weak-impact point.
Decision Making Cognition in Primary Progressive Aphasia
Authors: Gleichgerrcht Ezequiel , Torralva Teresa , Roca María , Szenkman Daniela , Ibanez Agustin , Richly Pablo , Pose Mariángeles , Manes Facundo
Published: January 2014

We sought to investigate the decision making profile of Primary Progressive Aphasia (PPA) by assessing patients diagnosed with this disease (n= 10), patients diagnosed with behavioral variant frontotemporal dementia (bvFTD,n= 35), and matched controls (n= 14) using the Iowa Gambling Task, a widely used test that mimics real-life decision making. Participants were also evaluated with a complete neuropsychological battery. Patients with PPA were unable to adopt an advantageous strategy on the IGT, which resulted in a flat performance, different to that exhibited by both controls (who showed advantageous decision making) and bvFTD patients (who showed risk-appetitive behavior). The decision making profile of PPA patients was not associated with performance on language tasks and did not differ between sub-variants of the disease (namely, semantic dementia and progressive nonfluent aphasia). Investigating decision making in PPA is crucial both from a theoretical perspective, as it can shed light about the way in which language interacts with other cognitive functions, as well as a clinical standpoint, as it could lead to a more objective detection of impairments of decision making deficits in this condition.
Natural Frequencies and Vibrating Modes for a Magnetic Planetary Gear Drive
Authors: Xu Lizhong , Zhu Xuejun
Published: January 2014

In this paper, a dynamic model for a magnetic planetary gear drive is proposed. Based on the model, the dynamic equations for the magnetic planetary gear drive are given. From the magnetic meshing forces and torques between the elements for the drive system, the tangent and radial magnetic meshing stiffness is obtained. Using these equations, the natural frequencies and the modes of the magnetic planetary gear drive are investigated. The sensitivity of the natural frequencies to the system parameters is discussed. Results show that the pole pair number and the air gap have obvious effects on the natural frequencies. For the planetary gear number larger than two, the vibrations of the drive system include the torsion mode of the center elements, the translation mode of the center elements, and the planet modes. For the planetary gear number equal to two, the planet mode does not occur, the crown mode and the sun gear mode occur.
Effects of Strain Rates on Kinetics of Elements of Repeated Pattern Structures: A Continuous Modeling Approach
Authors: Salehian A.
Published: January 2014

Space inflatable technology is a promising solution to placing large metrology systems in space. Lighter weight, higher packaging efficiency, and easier maintenance are among a few of their advantages over mechanically deployed structures. On the other hand, their large volume after deployment makes them susceptible to disturbances in space. Therefore, vibration control is one major issue for this technology. The present work is an extension of the previous work of the author on continuum modeling of these structures for their vibrations analysis. Kinetic and strain energy expressions of the fundamental lattice elements of a structure are expanded in terms of the nodal displacement components. Certain assumptions are made to reduce the order of strain components in a three-dimensional structure in order to find the equivalent continuum model. Additionally, this work includes the effects of strain rates on the kinetics of these structures. The frequency results for various structures are compared to those of a previous model which neglects such effects. It is shown that the frequency changes are noticeable when the strain rate components are included in the kinetic energy derivations.
On the Benefits of Semi-Active Suspensions with Inerters
Authors: Zhang Xin-Jie , Ahmadian Mehdi , Guo Kong-Hui
Published: January 2014

Inerters have become a hot topic in recent years especially in vehicle, train, building suspension systems, etc. Eight different layouts of suspensions were analyzed with a quarter-car model in this paper. Dimensionless root mean square (RMS) responses of the sprung mass vertical acceleration, the suspension travel, and the tire deflection are derived which were used to evaluate the performance of the quarter-car model. The behaviour of semi-active suspensions with inerters using Groundhook, Skyhook, and Hybrid control has been evaluated and compared to the performance of passive suspensions with inerters. Sensitivity analysis was applied to the development of a high performance semi-active suspension with an inerter. Numerical simulations indicate that a semi-active suspension with an inerter has much better performance than the passive suspension with an inerter, especially with the Hybrid control method, which has the best compromise between comfort and road holding quality.
Impact Force Magnitude Analysis of an Impact Pendulum Suspended in a Vibrating Structure
Authors: Aguiar R.R. , Weber H.I.
Published: January 2014

The purpose of this work is the experimental investigation and the mathematical modeling of the impact force behavior in a vibro-impact system, where an impact pendulum is mounted on a cart that moves with a prescribed displacement. The dynamics of the system will be evaluated considering different excitation frequencies and changing the impact gap. Experimental data are used to validate the mathematical model. The mathematical model allows a detailed nonlinear analysis, showing the rich response of the system, which includes dynamical jumps, bifurcations and chaos. In impact systems, discrepancies between numerical results and experimental measurements are common due to the difficulty in describing all factors that influence the resulting impact force profile. The use of wires to suspend the impacting body has the purpose to limit these uncertainties.
Measurement of Join Patch Properties and Their Integration into Finite-Element Calculations of Assembled Structures
Authors: Schmidt A. , Bograd S. , Gaul L.
Published: January 2014

The vibration and damping characteristics of an assembled structure made of steel are investigated by an experimental modal analysis and compared with the results of a finite element modal analysis. A generic experiment is carried out to evaluate the stiffness and the damping properties of the structure's join patches. Using these results, an appropriate finite element model of the structure is developed where the join patches are represented by thin-layer elements containing material properties which are derived from the generic experiment's results. The joint's stiffness is modeled by orthotropic material behavior whereas the damping properties are represented by the model of constant hysteresis, leading to a complex-valued stiffness matrix. A comparison between the experimental and the numerical modal analysis shows good agreement. A more detailed damping model in conjunction with an optimization procedure for the joint's parameters results in an improved correlation between the experimental and the numerical modal quantities and reveals that the results of the generic experiment are sound.
Two-Mode Operation Engine Mount Design for Automotive Applications
Authors: Tikani Reza , Vahdati Nader , Ziaei-Rad Saeed
Published: January 2014

Hydraulic engine mounts are applied to the automotive applications to isolate the chassis from the high frequency noise and vibration generated by the engine as well as to limit the engine shake motions resulting at low frequencies. In this paper, a new hydraulic engine mount with a controllable inertia track profile is proposed and its dynamic behavior is investigated. The profile of the inertia track is varied by applying a controlled force to a cylindrical rubber disk, placed in the inertia track. This design provides a hydraulic engine mount design with an adjustable notch frequency location and also damping characteristics in shake motions. By using a simple control strategy, the efficiency of the proposed hydraulic engine mount in two-mode operation meaning isolating mode in the highway driving condition and damping mode in the shock motions, is investigated.
Wavelet-Based Analysis of the Regular and Chaotic Dynamics of Rectangular Flexible Plates Subjected to Shear-Harmonic Loading
Authors: Awrejcewicz J. , Papkova I.V. , Krylova E.U. , Krysko V.A.
Published: January 2014

We investigate non-linear dynamics of flexible rectangular plates subjected to external shear harmonic load action. We show that an application of the classical and widely used Fourier analysis does not allow to obtain real picture of the frequency vibration characteristics in each time instant. On the other hand, we show that application of the wavelets approach allows to follow frequency time evolutions. Our numerical results indicate that vibrations in different plate points occur with the same frequencies set although their power is different. Hence, the vibration characteristics can be represented by one arbitrary taken plate point. Furthermore, using wavelets scenarios of transitions from regular to chaotic dynamics are illustrated and discussed including two novel scenarios not reported so far in the existing literature.
Simulation of Payne Effect of Elastomeric Isolators with a Harmonic Balance Method
Authors: Jaumouillé V. , Sinou J.-J. , Petitjean B.
Published: January 2014

In the presented work, a non linear effect of rubber referred as Fletcher-Gent effect or Payne effect is investigated. It leads to a change in the rubber dynamic modulus with vibration amplitudes and, consequently, modifies resonance frequencies of mechanical systems including non linear elastomers. In this study a new methodology is developed to take into account Payne effect in a linear viscoelastic rubber material. Small vibration amplitudes around a no-preloaded state are predicted by considering frequency and amplitude dependencies of the material. This methodology has the advantage of using tabular experimental data from characterization tests which avoids the development of a complex model. In order to compute frequency responses, the non linear harmonic balance method is used and, for each iteration, new rubber properties are affected at each element according to its strain state. An equivalent strain measure is evaluated from the element strain energy density. This equivalent strain allows to associate dynamic properties of a material element subjected to multiaxial strain state with experimental dynamic properties of a material sample subjected to an uniaxial strain state. Practically, DMAP alter procedures are developed in order to evaluate energies in models defined with MSC.Nastran and the non linear solver is developed with Matlab. The method is applied on a satellite instrument isolator including four non linear rubber mounts. A non homogeneous spatial distribution of element equivalent strains is observed. Moreover, the maximum equivalent strain varies with frequency. These two observations validate the use of a specific methodology to deal with amplitude dependency of rubber.