bluuebunny/crossref_metadata_2025 huggingface dataset:
Treatment of Tourette Syndrome with Cannabinoids
Authors: Müller-Vahl Kirsten R.
Published: January 2014

Cannabinoids have been used for hundred of years for medical purposes. To day, the cannabinoid delta-9-tetrahydrocannabinol (THC) and the cannabis extract nabiximols are approved for the treatment of nausea, anorexia and spasticity, respectively. In Tourette syndrome (TS) several anecdotal reports provided evidence that marijuana might be effective not only in the suppression of tics, but also in the treatment of associated behavioural problems. At the present time there are only two controlled trials available investigating the effect of THC in the treatment of TS. Using both self and examiner rating scales, in both studies a significant tic reduction could be observed after treatment with THC compared to placebo, without causing significant adverse effects. Available data about the effect of THC on obsessive-compulsive symptoms are inconsistent. According to a recent Cochrane review on the efficacy of cannabinoids in TS, definite conclusions cannot be drawn, because longer trials including a larger number of patients are missing. Notwithstanding this appraisal, by many experts THC is recommended for the treatment of TS in adult patients, when first line treatments failed to improve the tics. In treatment resistant adult patients, therefore, treatment with THC should be taken into consideration.
Building Spectral Element Dynamic Matrices Using Finite Element Models of Waveguide Slices and Elastodynamic Equations
Authors: Silva P.B. , Goldstein A.L. , Arruda J.R.F.
Published: January 2014

Structural spectral elements are formulated using the analytical solution of the applicable elastodynamic equations and, therefore, mesh refinement is not needed to analyze high frequency behavior provided the elastodynamic equations used remain valid. However, for modeling complex structures, standard spectral elements require long and cumbersome analytical formulation. In this work, a method to build spectral finite elements from a finite element model of a slice of a structural waveguide (a structure with one dimension much larger than the other two) is proposed. First, the transfer matrix of the structural waveguide is obtained from the finite element model of a thin slice. Then, the wavenumbers and wave propagation modes are obtained from the transfer matrix and used to build the spectral element matrix. These spectral elements can be used to model homogeneous waveguides with constant cross section over long spans without the need of refining the finite element mesh along the waveguide. As an illustrating example, spectral elements are derived for straight uniform rods and beams and used to calculate the forced response in the longitudinal and transverse directions. Results obtained with the spectral element formulation are shown to agree well with results obtained with a finite element model of the whole beam. The proposed approach can be used to generate spectral elements of waveguides of arbitrary cross section and, potentially, of arbitrary order.
Development of Time-Reversal Method for Impact Source Identification on Plate Structures
Authors: Chen Chunlin , Li Yulong , Yuan Fuh-Gwo
Published: January 2014

This paper presents a detailed study on the impact source identification of a plate structure using time-reversal (T-R) method. Prior to impact monitoring, the plate is calibrated (or characterized) by transfer functions at discrete locations on the plate surface. Both impact location and impact loading time-history are identified using T-R technique and associated signal processing algorithms. Numerical verification for finite-size isotropic plates under low velocity impacts is performed to demonstrate the versatility of T-R method for impact source identification. The tradeoff between accuracy of the impact location detection and calibration spacing is studied in detail. In particular, the effect of plate thickness on calibration spacing has been examined. A number of parameters selected for determining the impact location, approximated transfer functions and steps taken for reconstructing the impact loading time-history are also examined. Two types of noise with various intensities contaminated in strain response and/or transfer functions are investigated for demonstrating the stability and reliability of the T-R method. The results show that T-R method is robust against noise in impact location detection and force reconstruction in circumventing the inherent ill-conditioned inverse problem. Only transfer functions are needed to be calibrated and four sensors are requested in T-R method for impact identification.
Experimental and Numerical Studies on Vertical Properties of a New Multi-Dimensional Earthquake Isolation and Mitigation Device
Authors: Xu Zhaodong , Lu Liheng , Shi Benqiang , Yuan Fuhgwo
Published: January 2014

When designing critical structures such as long-span structures and high-rise buildings, earthquake excitation in the vertical direction, in addition to the horizontal direction, should also be taken into consideration. Study on new devices that can mitigate and isolate multi-dimensional (including both horizontal and vertical) earthquake actions has a remarkable significance. A new kind of multi-dimensional earthquake isolation and mitigation device was recently developed, and experimental study on vertical performances of the device under different excitation frequencies and amplitudes has been carried out in this paper. The characteristics of the vertical properties including the initial stiffness, the energy dissipation stiffness, the energy dissipation per cycle and the vertical damping ratio changing with excitation frequency and amplitude were studied, and the formulas describing the characteristics were proposed. It can be concluded that the initial stiffness and the energy dissipation stiffness increase slightly with increasing frequency, while the energy dissipation per cycle and the damping ratio decrease slightly with increasing frequency, the initial stiffness, the energy dissipation stiffness and the damping ratio will decrease slightly with increasing excitation amplitudes, and the proposed formulas can describe the vertical properties of the multi-dimensional earthquake isolation and mitigation device changing with excitation frequency and amplitude.
Immune Dysfunction in Tourette Syndrome
Authors: Elamin Ishraga , Edwards Mark J. , Martino Davide
Published: January 2014

The association between immunity and neurodevelopmental disorders has been extensively investigated in autism, suggesting a potential involvement of both cellular and humoral immunity in the establishment of synaptic connectivity modulation during development. A similar link has been proposed also for Tourette syndrome (TS), a complex, multifactorial disorder, in which the interplay between genetic, environmental, hormonal and immunological factors might be relevant. Lymphocyte subpopulation analysis in TS suggests a possible systemic activation of several T- and B-cell subtypes, whereas the observed decreased numbers of T regulatory lymphocytes might predispose to autoimmunity. Genes related to both cell- and antibody-mediated immune responses may be over-expressed at specific ages in youngsters with TS. Data from cytokine measurements and transcriptomics profiles in TS patients are coherent with the systemic immune activation detected by studies on lymphocyte subpopulations. Moreover, TS patients have exhibited IgG3 and IgA dysgammaglobulinemia, which might predispose to recurrent infections and autoimmunity. To date, the association between TS and autoantibodies has not been demonstrated. Interestingly, however, there is a higher degree of maternal family history of autoimmune diseases among TS patients. Finally, TS patients could be prone to allergic illnesses (asthma, atopic dermatitis, rhinitis, conjunctivitis), but more work is needed in this area.
Nonlinear Dynamical Analysis on Four Semi-Active Dynamic Vibration Absorbers with Time Delay
Authors: Shen Yongjun , Ahmadian Mehdi
Published: January 2014

In this paper four semi-active dynamic vibration absorbers (DVAs) are analytically studied, where the time delay induced by measurement and execution in control procedure is included in the system. The first-order approximate analytical solutions of the four semi-active DVAs are established by the averaging method, based on the illustrated phase difference of the motion parameters. The comparisons between the analytical and the numerical solutions are carried out, which verify the correctness and satisfactory precision of the approximate analytical solutions. Then the effects of the time delay on the dynamical responses are analyzed, and it is found that the stability conditions for the steady-state responses of the primary systems are all periodic functions of time delay, with the same period as the excitation one. At last the effects of time delay on control performance are discussed.
Dynamics of Periodic Impulsive Collision in Escapement Mechanism
Authors: Mao Jian , Fu Yu , Li Peichao
Published: January 2014

Among various non-smooth dynamic systems, the periodically forced oscillation system with impact is perhaps the most common in engineering applications. The dynamical study becomes complicated due to the impact. This paper presents a systematic study on the periodically forced oscillation system with impact. A simplified model of the escapement mechanism is introduced. Impulsive differential equation and Poincare map are applied to describe the model and study the stability of the system. Numerical examples are given and the results show that the model is highly accurate in describing/predicting their dynamics.
A Brief History of the European Society for the Study of Tourette Syndrome
Authors: Rickards Hugh , Paschou Peristera , Rizzo Renata , Stern Jeremy S.
Published: January 2014

The European Society for the Study of Tourette syndrome (ESSTS) was established in Denmark in 2000 by Mary Robertson and Anne Korsgaard. The aims of the organisation are to foster research activity and raise awareness of Tourette syndrome throughout Europe. The organisation went into abeyance in 2002 but was resurrected in 2007 in Bari, Italy. Since that time ESSTS has grown and prospered. We have established elected officers and a constitution. We have successfully applied for three large scale European research grants and have members throughout the European Union. We have held yearly meetings across Europe including two training schools and we have developed successful alliances with patient support groups. ESSTS has developed and published the first European guidelines on assessment, diagnosis and treatment of Tourette syndrome.
Comparison of Two Classifiers; K-Nearest Neighbor and Artificial Neural Network, for Fault Diagnosis on a Main Engine Journal-Bearing
Authors: Moosavian A. , Ahmadi H. , Tabatabaeefar A. , Khazaee M.
Published: January 2014

Vibration analysis is an accepted method in condition monitoring of machines, since it can provide useful and reliable information about machine working condition. This paper surveys a new scheme for fault diagnosis of main journal-bearings of internal combustion (IC) engine based on power spectral density (PSD) technique and two classifiers, namely, K-nearest neighbor (KNN) and artificial neural network (ANN). Vibration signals for three different conditions of journal-bearing; normal, with oil starvation condition and extreme wear fault were acquired from an IC engine. PSD was applied to process the vibration signals. Thirty features were extracted from the PSD values of signals as a feature source for fault diagnosis. KNN and ANN were trained by training data set and then used as diagnostic classifiers. Variable K value and hidden neuron count (N) were used in the range of 1 to 20, with a step size of 1 for KNN and ANN to gain the best classification results. The roles of PSD, KNN and ANN techniques were studied. From the results, it is shown that the performance of ANN is better than KNN. The experimental results dèmonstrate that the proposed diagnostic method can reliably separate different fault conditions in main journal-bearings of IC engine.
Topology Optimization of Passive Constrained Layer Damping with Partial Coverage on Plate
Authors: Zheng Weiguang , Lei Yingfeng , Li Shande , Huang Qibai
Published: January 2014

The potential of using topology optimization as a tool to optimize the passive constrained layer damping (PCLD) layouts with partial coverage on flat plates is investigated. The objective function is defined as a combination of several modal loss factors solved by finite element-modal strain energy (FE-MSE) method. An interface finite element is introduced to modeling the viscoelastic core of PCLD patch to save the computational space and time in the optimization procedure. Solid isotropic material with penalization (SIMP) method is used as the material interpolation scheme and the parameters are well selected to avoid local pseudo modes. Then, the method of moving asymptote (MMA) is employed as an optimizer to search the optimal topologies of PCLD patch on plates. Applications of two flat plates with different shapes have been applied to demonstrate the validation of the proposed approach. The results show that the objective function is in a steady convergence process and the damping effect of the plates can be enhanced by the optimized PCLD layouts.
Feature Extraction of Gear Fault Signal Based on Sobel Operator and WHT
Authors: Cai Jian-Hua , Hu Wei-Wen
Published: January 2014

Taking Wigner-Ville distribution of gear fault signal as a picture,Sobeloperator was applied for edge detection of picture and then Hough transform was used to extract signal feature. Some simulated and measured signals have been processed to demonstrate the effectiveness of new method, which was compared with traditional Wigner-Hough transform and SPWD-Hough transform. The results show that the proposed method can suppress cross term which is produced from using Wigner-Ville distribution to analyze multi-component signal, especially under the condition of low signal to noise ratio. The improved Wigner-Hough transform can effectively suppress the influence of noise and has a good real-time performance because its algorithm is fast. The proposed method provides an effective method to determine the state of gear accurately.
Neural Plasticity in Functional and Anatomical MRI Studies of Children with Tourette Syndrome
Authors: Eichele Heike , Plessen Kerstin J.
Published: January 2014

Background:Tourette syndrome (TS) is a neuropsychiatric disorder with childhood onset characterized by chronic motor and vocal tics. The typical clinical course of an attenuation of symptoms during adolescence in parallel with the emerging self-regulatory control during development suggests that plastic processes may play an important role in the development of tic symptoms.

Methods:We conducted a systematic search to identify existing imaging studies (both anatomical and functional magnetic resonance imaging [fMRI]) in young persons under the age of 19 years with TS.

Results:The final search resulted in 13 original studies, which were reviewed with a focus on findings suggesting adaptive processes (using fMRI) and plasticity (using anatomical MRI). Differences in brain activation compared to healthy controls during tasks that require overriding of prepotent responses help to understand compensatory pathways in children with TS. Along with alterations in regions putatively representing the origin of tics, deviations in several other regions most likely represent an activity-dependent neural plasticity that help to modulate tic severity, such as the prefrontal cortex, but also in the corpus callosum and the limbic system.

Discussion:Factors that potentially influence the development of adaptive changes in the brain of children with TS are age, comorbidity with other developmental disorders, medication use, IQ along with study-design or MRI techniques for acquisition, and analysis of data. The most prominent limitation of all studies is their cross-sectional design. Longitudinal studies extending to younger age groups and to children at risk for developing TS hopefully will confirm findings of neural plasticity in future investigations.
Wave Based Method for Free Vibration Analysis of Ring Stiffened Cylindrical Shell with Intermediate Large Frame Ribs
Authors: Chen Meixia , Wei Jianhui , Xie Kun , Deng Naiqi , Hou Guoxiang
Published: January 2014

Wave based method which can be recognized as a semi-analytical and semi-numerical method is presented to analyze the free vibration characteristics of ring stiffened cylindrical shell with intermediate large frame ribs for arbitrary boundary conditions. According to the structure type and the positions of discontinuities, the model is divided into different substructures whose vibration field is expanded by wave functions which are exactly analytical solutions to the governing equations of the motions of corresponding structure type. Boundary conditions and continuity equations between different substructures are used to form the final matrix to be solved. Natural frequencies and vibration mode shapes are calculated by wave based method and the results show good agreement with finite element method for clamped-clamped, shear diaphragm – shear diaphragm and free-free boundary conditions. Free vibration characteristics of ring stiffened cylindrical shells with intermediate large frame ribs are compared with those with bulkheads and those with all ordinary ribs. Effects of the size, the number and the distribution of intermediate large frame rib are investigated. The frame rib which is large enough is playing a role as bulkhead, which can be considered imposing simply supported and clamped constraints at one end of the cabin and dividing the cylindrical shell into several cabins vibrating separately at their own natural frequencies.
Displacement Transmissibility Characteristics of Harmonically Base Excited Damper Isolators with Mixed Viscous Damping
Authors: Sun Xiaojuan , Zhang Jianrun
Published: January 2014

The viscous damping force in the mixed form asfd(x˙)=c1x˙+c2|x˙|x˙can well describe damping characteristics of isolators and dampers in many cases. In this paper, performance characteristics of single-degree-of-freedom (SDOF) linear-stiffness isolators with mixed and piecewise mixed viscous damping are analytically examined under harmonic base excitation. Based on the first-order harmonic balance method (HBM), both relative and absolute displacement transmissibility expressions with the equivalent linear damping coefficient (ELDC) are given. And the analytical calculations show good agreement with the numerical results. Also, the influence of nonlinear damping on the response characteristics is investigated by comparing the transmissibility of linear and nonlinear systems. The resonant frequency always shifts to a lower value as the nonlinear damping component of the forcefd(x˙)=c1x˙+c2|x˙|x˙becomes stronger, and when the damping ratio in the corresponding linear model is relatively high, the relative transmissibility decreases at frequencies higher than the resonance frequency of the corresponding linear damping system and the absolute one increases for the frequency ratios above2. Finally, the displacement transmissibility of a nonlinear isolator with piecewise mixed viscous damping is discussed and the process shows research similarity with the non-piecewise case.
Transfer Matrix Method to Vibration Analysis of Rotors with Coupler Offsets
Authors: Tsai Chao-Yang , Huang Shyh-Chin
Published: January 2014

In this paper a general transfer matrix method (TMM) for rotors containing global and local coupler offset was derived. Rotor response due to imbalances and offsets are then studied via the developed method. The studies showed both global and local offsets played as an external excitation that is a combined effect of all the elements behind the offset. Differences between global offset and local offset were compared and the results showed both types basically retain the same mode patterns but different jumps at the offset. The global offset, yet, imposed more significant dynamic effects since all the offsets accumulate thereafter. The whirling orbits in front and behind the offset were illustrated as well. The results, as expected, showed global offset appeared much larger radii especially after offset. The rotor's whirling orientation reversed, as rotation fell within a certain range and this feature was not changed by offsets. The TMM proposed by this study can be well applied to multiple global and local offsets.
Wavelet Correlation Feature Scale Entropy and Fuzzy Support Vector Machine Approach for Aeroengine Whole-Body Vibration Fault Diagnosis
Authors: Fei Cheng-Wei , Bai Guang-Chen
Published: January 2014

In order to correctly analyze aeroengine whole-body vibration signals, Wavelet Correlation Feature Scale Entropy (WCFSE) and Fuzzy Support Vector Machine (FSVM) (WCFSE-FSVM) method was proposed by fusing the advantages of the WCFSE method and the FSVM method. The wavelet coefficients were known to be located in high Signal-to-Noise Ratio (S/N or SNR) scales and were obtained by the Wavelet Transform Correlation Filter Method (WTCFM). This method was applied to address the whole-body vibration signals. The WCFSE method was derived from the integration of the information entropy theory and WTCFM, and was applied to extract the WCFSE values of the vibration signals. Among the WCFSE values, theWFSE1andWCFSE2values on the scale 1 and 2 from the high band of vibration signal were believed to acceptably reflect the vibration feature and were selected to construct the eigenvectors of vibration signals as fault samples to establish the WCFSE-FSVM model. This model was applied to aeroengine whole-body vibration fault diagnosis. Through the diagnoses of four vibration fault modes and the comparison of the analysis results by four methods (SVM, FSVM, WESE-SVM, WCFSE-FSVM), it is shown that the WCFSE-FSVM method is characterized by higher learning ability, higher generalization ability and higher anti-noise ability than other methods in aeroengine whole-vibration fault analysis. Meanwhile, this present study provides a useful insight for the vibration fault diagnosis of complex machinery besides an aeroengine.
Dynamic Model for Hydro-Turbine Generator Units Based on a Database Method for Guide Bearings
Authors: Xu Yong , Li Zhaohui , Lai Xide
Published: January 2014

A suitable dynamic model of rotor system is of great significance not only for supplying knowledge of the fault mechanism, but also for assisting in machine health monitoring research. Many techniques have been developed for properly modeling the radial vibration of large hydro-turbine generator units. However, an applicable dynamic model has not yet been reported in literature due to the complexity of the boundary conditions and exciting forces. In this paper, a finite element (FE) rotor dynamic model of radial vibration taking account of operating conditions is proposed. A brief and practical database method is employed to model the guide bearing. Taking advantage of the method, rotating speed and bearing clearance can be considered in the model. A novel algorithm, which can take account of both transient and steady-state analysis, is proposed to solve the model. Dynamic response for rotor model of 125 MW hydro-turbine generator units in Gezhouba Power Station is simulated. Field data from Optimal Maintenance Information System for Hydro power plants (HOMIS) are analyzed compared with the simulation. Results illustrate the application value of the model in providing knowledge of the fault mechanism and in failure diagnosis.
Experimental Study ofH∞Control of Flexible Plate with Time Delay
Authors: Zhao Tong , Chen Long-Xiang , Cai Guo-Ping
Published: January 2014

This paper presents theoretical and experimental studies ofH∞control of a flexible plate with time delay. A matrix inequality used for stability analysis is proposed and proved by using the Lyapunov-Krasovskii functional and free-weighting matrix. AnH∞controller is designed based on the matrix inequality and by using the parameter-adjusting method. Three control scenarios are discussed in detail by transforming the problem into parameters optimization: (i) controller design when maximum time delay of the system is known; (ii) allowable time delay when controller is known; (iii) the biggest allowable time delay to guarantee system stability when controller is unknown. Numerical simulations and experiments are also given to demonstrate the validity and feasibility of the proposed methods in this paper.
Forced Vibration of Delaminated Timoshenko Beams under the Action of Moving Oscillatory Mass
Authors: Kargarnovin M.H. , Ahmadian M.T. , Jafari-Talookolaei R.A.
Published: January 2014

This paper presents the dynamic response of a delaminated composite beam under the action of a moving oscillating mass. In this analysis the Poisson's effect is considered for the first time. Moreover, the effects of rotary inertia and shear deformation are incorporated. In our modeling linear springs are used between delaminated surfaces to simulate the dynamic interaction between sub-beams. To solve the governing differential equations of motion using modal expansion series, eigen-solution technique is used to obtain the natural frequencies and their corresponding mode shapes necessary for forced vibration analysis. The obtained results for the free and forced vibrations of beams are verified against reported similar results in the literatures. Moreover, the maximum dynamic response of such beam is compared with an intact beam. The effects of different parameters such as the velocity of oscillating mass, different ply configuration and the delamination length, its depth and spanwise location on the dynamic response of the beam are studied. In addition, the effects of delamination parameters on the oscillator critical speed are investigated. Furthermore, different conditions under which the detachment of moving oscillator from the beam will initiate are investigated.
Stability of Auditory Discrimination and Novelty Processing in Physiological Aging
Authors: Raggi Alberto , Tasca Domenica , Rundo Francesco , Ferri Raffaele
Published: January 2014

Complex higher-order cognitive functions and their possible changes with aging are mandatory objectives of cognitive neuroscience. Event-related potentials (ERPs) allow investigators to probe the earliest stages of information processing. N100, Mismatch negativity (MMN) and P3a are auditory ERP components that reflect automatic sensory discrimination. The aim of the present study was to determine if N100, MMN and P3a parameters are stable in healthy aged subjects, compared to those of normal young adults. Normal young adults and older participants were assessed using standardized cognitive functional instruments and their ERPs were obtained with an auditory stimulation at two different interstimulus intervals, during a passive paradigm. All individuals were within the normal range on cognitive tests. No significant differences were found for any ERP parameters obtained from the two age groups. This study shows that aging is characterized by a stability of the auditory discrimination and novelty processing. This is important for the arrangement of normative for the detection of subtle preclinical changes due to abnormal brain aging.
Damage Identification in Bars with a Wave Propagation Approach: Performance Comparison of Five Hybrid Optimization Methods
Authors: Tenenbaum R.A. , Stutz L.T. , Fernandes K.M.
Published: January 2014

The formulation and solution of the inverse problem of damage identification based on an one-dimensional wave propagation approach are presented in this paper. Time history responses, obtained from pulse-echo synthetic experiments, are used to damage identification. The identification process is built on the minimization of the squared residue between the synthetic experimental echo, obtained by using a sequential algebraic algorithm, and the corresponding analytical one. Five different hybrid optimization methods are investigated. The hybridization is performed combining the deterministic Levenberg-Marquardt method and each one of the following stochastic techniques: The Particle Swarm Optimization; the Luus-Jaakola optimization method; the Simulated Annealing method; the Particle Collision method; and a Genetic Algorithm. A performance comparison of the five hybrid techniques is presented. Different damage scenarios are considered and, in order to account for noise corrupted data, signals with 10 dB of signal to noise ratio are also considered. It is shown that the damage identification procedure built on the Sequential Algebraic Algorithm yielded to very fast and successful solutions. In the performance comparison, it is also shown that the hybrid technique combining the Luus-Jaakola and the Levenberg-Marquardt optimization methods provides the faster damage recovery.
5-DOF Dynamic Model of Vehicle Shimmy System with Clearance at Universal Joint in Steering Handling Mechanism
Authors: Lu Jianwei , Xu Yi , Hu Chen , Vakakis Alexander F. , Bergman Lawrence A.
Published: January 2014

5-DOF dynamic model of vehicle shimmy system with clearance in universal joint of steering handling mechanism is presented. The sub model of cross shaft universal joint with clearance is built based on Hertz' theory, and two-state model is applied to describe the contact force. The sub model of the universal joint is combined with the simplified dynamic model of steering system, and a 5-DOF dynamic model of vehicle shimmy system with consideration of assembling clearance in universal joint of steering handling mechanism is presented. Based on this model, numerical analysis is carried out to evaluate the influence of clearance in universal joint on the dynamic behavior of the vehicle shimmy system. The results show that the clearance and some other parameters, such as vehicle speed, have coupled contribution to the dynamic behavior of the vehicle shimmy system. The conclusions provide theoretical basis for effective attenuation of vehicle shimmy, especially for those in-service vehicles.
Theoretical and Experimental Study on Synchronization of the Two Homodromy Exciters in a Non-Resonant Vibrating System
Authors: Zhang Xue-Liang , Zhao Chun-Yu , Wen Bang-Chun
Published: January 2014

In this paper we give some theoretical analyses and experimental results on synchronization of the two non-identical exciters. Using the average method of modified small parameters, the dimensionless coupling equation of the two exciters is deduced. The synchronization criterion for the two exciters is derived as the torque of frequency capture being equal to or greater than the absolute value of difference between the residual electromagnetic torques of the two motors. The stability criterion of synchronous state is verified to satisfy the Routh-Hurwitz criterion. The regions of implementing synchronization and that of stability of phase difference for the two exciters are manifested by numeric method. Synchronization of the two exciters stems from the coupling dynamic characteristic of the vibrating system having selecting motion, especially, under the condition that the parameters of system are complete symmetry, the torque of frequency capture stemming from the circular motion of the rigid frame drives the phase difference to approach PI and carry out the swing of the rigid frame; that from the swing of the rigid frame forces the phase difference to near zero and achieve the circular motion of the rigid frame. In the steady state, the motion of rigid frame will be one of three types: pure swing, pure circular motion, swing and circular motion coexistence. The numeric and experiment results derived thereof show that the two exciters can operate synchronously as long as the structural parameters of system satisfy the criterion of stability in the regions of frequency capture. In engineering, the distance between the centroid of the rigid frame and the rotational centre of exciter should be as far as possible. Only in this way, can the elliptical motion of system required in engineering be realized.
Modeling and Identification of Electromagnetic Actuator for the Control of Rotating Machinery
Authors: Morais T.S. , Der Hagopian J. , Steffen Jr. V. , Mahfoud J.
Published: January 2014

This work deals with the design and the assessment of electromagnetic actuators (EMAs) for the control of rotating machines. The system studied has a hybrid bearing that exhibits nonlinear behavior. The system is composed of a horizontal flexible shaft supported by two ball bearings at one end and a roller bearing that is located in a squirrel cage at the other end. Four identical EMAs supplied with constant current are utilized. The EMAs associated to the squirrel cage constitutes the hybrid bearing. The aim is to develop a strategy in order to define and to identify a reliable model necessary for the control of rotating machinery in the presence of localized non-linearity. The identification strategy consists in modeling the system with as many sub-models as needed that are identified separately. This enables obtaining a straightforward modeling of rotating machinery even in the case in which system components are frequency or time dependent. For the system studied, two sub-models were necessary. First the EMAs were modeled by using classical equations of electromagnetism and then identified experimentally. Then, a linear model of the shaft mounted on its bearings was defined by using the finite element method and was identified successfully. The model of the system was adjusted after assembling the different identified sub-models. The identification is carried out by using a pseudo-random search algorithm. The model of the system is then assessed for different configurations. The results obtained demonstrate the effectiveness of the developed strategy.
Actuator Saturation and Control Design for Buildings Structural Systems with Improved Uncertainty Description
Authors: Ding Y.C. , Weng F.L. , Yu Z.A.
Published: January 2014

The problem of robustly active vibration control for a class of earthquake-excited structural systems with time-delay and saturation in the control input channel and parameter uncertainties appearing in all the mass, damping and stiffness matrices is concerned in this paper. The objective of the designing controllers is to guarantee the robust stability of the closed-loop system and attenuate the disturbance from earthquake excitation. Firstly, by using the linear combination of some matrices to deal with the system's uncertainties, a new system uncertainties description, namely rank-1 uncertainty description, is presented. Then, by introducing a linear varying parameter, the input saturation model is described as a linear parameter varying model. Furthermore, based on parameter-dependent Lyapunov theory and linear matrix inequality (LMI) technique, the LMIs-based conditions for the closed-loop system to be stable are deduced. By solving those conditions, the controller, considering the actuator saturation, input delay and parameters uncertainties, is obtained. Finally, a three-storey linear building structure under earthquake excitation is considered and simulation results are given to show the effectiveness of the proposed controllers.
He’s Variational Iteration Method for Nonlinear Jerk Equations: Simple but Effective
Authors: Raftari Behrouz
Published: January 2014

The variational iteration method (VIM) for determining periodic solutions of non-linear jerk equations involving third-order time-derivative is presented. This method is based on the use of Lagrange multipliers for identification of optimal value of a parameter in a functional. We propose first-order approximate VIM solution for this equation and we compare this solution with the solution obtained by harmonic balance method.
Impact Vibration Attenuation for a Flexible Robotic Manipulator through Transfer and Dissipation of Energy
Authors: Bian Yushu , Gao Zhihui
Published: January 2014

Due to the presence of system flexibility, impact can excite severe large amplitude vibration responses of the flexible robotic manipulator. This impact vibration exhibits characteristics of remarkable nonlinearity and strong energy. The main goal of this study is to put forward an energy-based control method to absorb and attenuate large amplitude impact vibration of the flexible robotic manipulator. The method takes advantage of internal resonance and is implemented through a vibration absorber based on the transfer and dissipation of energy. The addition of the vibration absorber to the flexible arm generates a coupling effect between vibration modes of the system. By means of analysis on 2:1 internal resonance, the exchange of energy is proven to be existent. The impact vibrational energy can be transferred from the arm to the absorber and dissipated through the damping of the absorber. The results of numerical simulations are promising and preliminarily verify that the method is feasible and can be used to combat large amplitude impact vibration of the flexible manipulator undergoing rigid motion.
Fault Tolerant Vibration-Attenuation Controller Design for Uncertain Linear Structural Systems with Input Time-Delay and Saturation
Authors: Weng Falu , Ding Yuanchun , Liang Liming , Yang Guoliang
Published: January 2014

The problem of fault tolerant vibration-attenuation controller design for uncertain linear structural systems with control input time-delay and saturation is investigated in this paper. The objective of designing controllers is to guarantee the asymptotic stability of closed-loop systems while attenuate disturbance from earthquake excitation. Firstly, based on matrix transformation, the structural system is described as state-space model, which contains actuator fault, input signal time-delay and saturation at the same time. Based on the obtained model, an LMIs-based condition for the system to be stabilizable is deduced. By solving these LMIs, the controller is established for the closed-loop system to be stable with a prescribed level of disturbance attenuation. The condition is also extended to the uncertain case. Finally, an example is included to demonstrate the effectiveness of the proposed theorems.
Forced Vibration Analysis for a FGPM Cylindrical Shell
Authors: Dai Hong-Liang , Jiang Hao-Jie
Published: January 2014

This article presents an analytical study for forced vibration of a cylindrical shell which is composed of a functionally graded piezoelectric material (FGPM). The cylindrical shell is assumed to have two-constituent material distributions through the thickness of the structure, and material properties of the cylindrical shell are assumed to vary according to a power-law distribution in terms of the volume fractions for constituent materials, the exact solution for the forced vibration problem is presented. Numerical results are presented to show the effect of electric excitation, thermal load, mechanical load and volume exponent on the static and force vibration of the FGPM cylindrical shell. The goal of this investigation is to optimize the FGPM cylindrical shell in engineering, also the present solution can be used in the forced vibration analysis of cylindrical smart elements.
Single-Item and Associative Working Memory in Stroke Patients
Authors: van Geldorp Bonnie , Kessels Roy P. C. , Hendriks Marc P. H.
Published: January 2014

In this study, we examined working memory performance of stroke patients. A previous study assessing amnesia patients found deficits on an associative working memory task, although standard neuropsychological working memory tests did not detect any deficits. We now examine whether this may be the case for stoke patients as well. The current task contained three conditions: one spatial condition, one object condition and one binding condition in which both object and location had to be remembered. In addition, subsequent long-term memory was assessed. The results indicate that our sample of stroke patients shows a working memory deficit, but only on the single-feature conditions. The binding condition was more difficult than both single-feature conditions, but patients performed equally well as compared to matched healthy controls. No deficits were found on the subsequent long-term memory task. These results suggest that associative working memory may be mediated by structures of the medial temporal lobe.
Lateralization of Spatial Relation Processing in Natural Scenes
Authors: van der Ham Ineke J. M. , van Zandvoort Martine J. E. , Postma Albert
Published: January 2014

Spatial relations between objects can be represented in a categorical and in a coordinate manner. Categorical representations reflect abstract relations, like ‘left of’ or ‘under’, whereas coordinate representations concern exact metric distances between objects. These two types of spatial relations are thought to be linked to a left hemisphere and a right hemisphere advantage, respectively. This lateralization pattern was examined in a visual search task, making use of natural scenes, in patients with unilateral brain damage and healthy controls. In addition, all participants performed a low-level spatial relation processing task. The results suggest that the lateralization pattern commonly found for spatial relation processing in low-level perceptual tasks is also applicable to the processing of complex visual scenes.
Remedy to Overestimation of Classical Interval Analysis: Analysis of Beams with Uncertain Boundary Conditions
Authors: Elishakoff Isaac , Soret Clément
Published: January 2014

This study investigates both the static and dynamic behaviors for the uniform beam supported at its ends by rotational supports. The stiffness coefficients of these supports are treated as interval variables. It is first demonstrated on the static problem that the classical interval analysis may lead to overestimation of the response. The paper introduces a remedy for this "ill" of the classical interval analysis. The artificial interval parameter is introduced and the extrema of the static displacements and natural frequencies are determined. Finally, the hybrid case of uncertain boundary conditions and uncertain mass density is treated with attendant interesting results.
Evaluating the Capability of the Flux-Limiter Schemes in Capturing Strong Shocks and Discontinuities
Authors: Harimi Iman , Pishevar Ahmad Reza
Published: January 2014

A numerical study is conducted to investigate the capability of the flux-limiter TVD schemes in capturing sharp discontinuities like shock waves. For this purpose, four classical test problems are considered such as slowly moving shock, gas Riemann problem with high density and pressure ratios, shock wave interaction with a density disturbance and shock-acoustic interaction. The governing equations consist of one-dimensional and quasi-one-dimensional Euler equations solved using an in-house numerical code. In order to validate the solution, the obtained results are compared with other results found in the literature.
Vibration Analysis of Thin Plates Resting on Pasternak Foundations by Element free Galerkin Method
Authors: Bahmyari Ehsan , Banatehrani Mohammad Mahdi , Ahmadi Mohammad , Bahmyari Marzieh
Published: January 2014

The element free Galerkin method is used to analyze free vibration of thin plates resting on Pasternak elastic foundations with all possible types of classical boundary conditions. Convergence of solution is studied by increasing number of nodes for different boundary conditions and foundation parameters. Upon comparison with available results in literature, it was found that the method converges very fast and has very good accuracy even with small number of nodes. Applicability of the method was shown by solving numerical examples with all possible combinations of boundary conditions and different values of foundation parameters.
Modelling and Dynamic Response of Steel Reticulated Shell under Blast Loading
Authors: Zhai Ximei , Wang Yonghui
Published: January 2014

Explicit finite element programme LS-DYNA was used to simulate a long-span steel reticulated shell under blast loading to investigate the structural dynamic responses in this paper. The elaborate finite element model of the Kiewitt-8 single-layer reticulated shell with span of 40 m subjected to central blast loading was established and all the process from the detonation of the explosive charge to the demolition, including the propagation of the blast wave and its interaction with structure was reproduced. The peak overpressure from the numerical analysis was compared with empirical formulas to verify the credibility and applicability of numerical simulation for blast loading. The dynamic responses of the structure under blast loading with different TNT equivalent weights of explosive and rise-span ratios were obtained. In addition, the response types of Kiewitt-8 single-layer reticulated shell subjected to central explosive blast loading were defined.
Functional Brain Activity within the Medial and Lateral Portion of BA10 during a Prospective Memory Task
Authors: Barban Francesco , Carlesimo Giovanni Augusto , Macaluso Emiliano , Caltagirone Carlo , Costa Alberto
Published: January 2014

In this study we tested the gateway hypothesis of Broadmann area 10 (BA10). With a functional magnetic resonance imaging (fMRI) protocol we manipulated the saliency–stimulus-oriented (SO) attending– and the memory load – stimulus-independent (SI) attending–during a prospective memory (PM) task. We found a significant main effect of the SO manipulation within the medial BA10 and a significant interaction between SI attending and PM task within the left lateral BA10. Our results give experimental support to the gateway hypothesis.
On the Approximate Analytical Solution to Non-Linear Oscillation Systems
Authors: Bayat Mahmoud , Pakar Iman
Published: January 2014

This study describes an analytical method to study two well-known systems of nonlinear oscillators. One of these systems deals with the strongly nonlinear vibrations of an elastically restrained beam with a lumped mass. The other is a Duffing equation with constant coefficients. A new implementation of the Variational Approach (VA) is presented to obtain highly accurate analytical solutions to free vibration of conservative oscillators with inertia and static type cubic nonlinearities. In the end, numerical comparisons are conducted between the results obtained by the Variational Approach and numerical solution using Runge-Kutta's [RK] algorithm to illustrate the effectiveness and convenience of the proposed methods.
Patterns of Dysgraphia in Primary Progressive Aphasia Compared to Post-Stroke Aphasia
Authors: Faria Andreia V. , Crinion Jenny , Tsapkini Kyrana , Newhart Melissa , Davis Cameron , Cooley Shannon , Mori Susumu , Hillis Argye E.
Published: January 2014

We report patterns of dysgraphia in participants with primary progressive aphasia that can be explained by assuming disruption of one or more cognitive processes or representations in the complex process of spelling. These patterns are compared to those described in participants with focal lesions (stroke). Using structural imaging techniques, we found that damage to the left extrasylvian regions, including the uncinate, inferior fronto-occipital fasciculus, and sagittal stratum (including geniculostriate pathway and inferior longitudinal fasciculus), as well as other deep white and grey matter structures, was significantly associated with impairments in access to orthographic word forms and semantics (with reliance on phonology-to-orthography to produce a plausible spelling in the spelling to dictation task). These results contribute not only to our understanding of the patterns of dysgraphia following acquired brain damage but also the neural substrates underlying spelling.