bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid Modulation of Distributed Brain Activity by Transcranial Magnetic Stimulation of Human Motor Cortex
Authors: Lee Lucy , Siebner Hartwig , Bestmann Sven
Published: January 2014

This paper reviews the effects of single and repetitive transcranial magnetic stimuli (rTMS) delivered to one cortical area and measured across distributed brain regions using electrophysiological measures (e.g. motor thresholds, motor evoked potentials, paired‐pulse stimulation), functional neuroimaging (including EEG, PET and fMRI) and behavioural measures. Discussion is restricted to changes in excitability in the primary motor cortex and behaviour during motor tasks following transcranial magnetic stimulation delivered to primary motor and premotor areas. Trains of rTMS have lasting effects on the excitability of intrinsic and corticofugal neurones, altering the responsiveness of local and remote sites. These effects lead to distributed changes in synaptic activity at rest, and during a range of motor tasks. It is possible to impair or improve performance following rTMS, but for most simple motor tasks performance is unaltered. Changes in distributed activity observed with functional imaging during motor behaviour may represent compensatory activity, enabling maintenance of performance; stimulation of additional cortical areas appears to impair performance. A detailed understanding of the distributed changes in excitability following rTMS may facilitate future attempts to modulate motor behaviour in the healthy brain and for therapeutic purposes.
Vibrational Energy Flow Analysis of Corrected Flexural Waves in Timoshenko Beam – Part I: Theory of an Energetic Model
Authors: Park Young-Ho , Hong Suk-Yoon
Published: January 2014

In this paper, an energy flow model is developed to analyze transverse vibration including the effects of rotatory inertia as well as shear distortion, which are very important in the Timoshenko beam transversely vibrating in the medium‐to‐high frequency ranges. The energy governing equations for this energy flow model are newly derived by using classical displacement solutions of the flexural motion for the Timoshenko beam, in detail. The derived energy governing equations are in the general form incorporating not only the Euler‐Bernoulli beam theory used for the conventional energy flow model but also the Rayleigh, shear, and Timoshenko beam theories. Finally, to verify the validity and accuracy of the derived model, numerical analyses for simple finite Timoshenko beams were performed. The results obtained by the derived energy flow model for simple finite Timoshenko beams are compared with those of the classical solutions for the Timoshenko beam, the energy flow solution, and the classical solution for the Euler‐Bernoulli beam with various excitation frequencies and damping loss factors of the beam. In addition, the vibrational energy flow analyses of coupled Timoshenko beams are described in the other companion paper.
Current and Emerging Pharmacological Treatment Options for Dementia
Authors: Ringman John M. , Cummings Jeffrey L.
Published: January 2014

Treatments for the symptomatic relief of Alzheimer’s disease are available but despite advances in our ability to treat persons with various forms of dementia, more effective treatments are needed. The cholinesterase inhibitors donepezil, rivastigmine, and galantamine have demonstrated efficacy in improving cognition and global status and to a lesser extent, behavioral abnormalities relative to placebo in patients with mild‐to‐moderate Alzheimer’s disease. Rivastigmine has been shown to benefit patients with dementia with Lewy Bodies and with dementia associated with Parkinson′s disease. Donepezil and galantamine have also been shown to be mildly effective in dementia due to cerebral ischemia. Memantine has a distinct mechanism of action and is effective in moderate‐to‐severe AD. The benefits from these drugs, however, are limited and their long‐term effectiveness has not been well‐demonstrated. Their clinical utility is controversial. Many novel approaches that promise to provide more effective treatments are currently being pursued.
A Case of Frontotemporal Lobar Degeneration with Progressive Dysarthria
Authors: Ihori Nami , Araki Shigeo , Ishihara Kenji , Kawamura Mitsuru
Published: January 2014

We investigated the evolution of the neurological and neuropsychological characteristics in a right‐handed woman who was 53‐years‐old at the onset and who showed personality changes and behavioral disorders accompanied by progressive dysarthria. She had hypernasality and a slow rate of speech with distorted consonants and vowels, which progressed as motor disturbances affecting her speech apparatus increased; finally, she became mute two years post onset. Her dysarthria due to bilateral voluntary facio‐velo‐linguo‐pharyngeal paralysis accompanied with automatic‐voluntary dissociation fit the description of anterior opercular syndrome. She showed personality changes and behavioral abnormalities from the initial stage of the disease, as is generally observed in frontotemporal degeneration (FTD), and her magnetic resonance image showed progressive atrophy in the frontotemporal lobes; thus, she was clinically diagnosed with FTLD. This patient’s symptoms suggest that FTLD, including bilateral anterior operculum degeneration, causes progressive pseudobulbar paretic dysarthria accompanied by clinical symptoms of FTD, which raises the possibility of a new clinical subtype in the FTLD spectrum.
Nonlinear Dynamics and Chaos in Systems with Discontinuous Support
Authors: Divenyi Sandor , Savi Marcelo Amorim , Franca Luiz Fernando Penna , Weber Hans Ingo
Published: January 2014

Non‐smooth systems are abundant in nature being usually related to physical systems with dry friction, impact and backlash. These systems operate in different modes, and the transition from one mode to another can often be idealized as an instantaneous or discrete transition. Since the time scale of this transition is much smaller than the scale of the individual modes dynamics, its mathematical modeling can be lead as non‐smooth. This contribution uses a smoothened switch model to analyze non‐smooth systems. The procedure seems to be effective to deal with this kind of system, presenting advantages for the numerical implementation. As an application of the general formulation, a single‐degree of freedom oscillator with discontinuous support is analyzed. System dynamical behavior shows a rich response, presenting dynamical jumps, bifurcations and chaos.
An Experimental Study on Steel and Teflon Squeeze Film Dampers
Authors: Khalid Asad A. , Albagul A. , Faris W. , Ismail Godem A.
Published: January 2014

In this paper, the vibration analysis on Teflon and steel squeeze film dampers has been carried out. At different frequency ranges, vibration amplitude and the resonance frequency are measured. The eccentricity ratio at resonance speed has been determined. Results show that the vibration amplitude of the steel damper is 10% less at resonance compared with the Teflon damper. On the other hand, saving weight of 36% has been achieved by using the Teflon damper.

A rotor bearing system for vibration analysis has been designed and fabricated. The test rig consists of mild steel shaft with two supports, oil pressure gauge system and two self‐alignment ball bearings fixed on each end support. Two squeeze film dampers are used at each of the rotor support ends. Teflon and steel squeeze film dampers (SFD) were fabricated and tested using turning machine.
Suppression of Extinction with TMS in Humans: From Healthy Controls to Patients
Authors: Oliveri Massimiliano , Caltagirone Carlo
Published: January 2014

We review a series of studies exemplifying some applications of single‐pulse and paired‐transcranial magnetic stimulation (TMS) in the study of spatial attention and of its deficits. We will focus primarily on sensory extinction, the failure to consciously perceive a contralesional sensory stimulus only during bilateral stimulation of homologous surfaces. TMS studies in healthy controls show that it is possible either to interfere or modulate the excitability of the parietal cortex during sensory (i.e. tactile and visual) attentional tasks, thus reproducing a condition of virtual extinction. TMS studies in patients with unilateral (mainly right) brain damage show that the modulation of the unbalance in cortical excitability between the two cerebral hemispheres transiently improves contralesional sensory extinction. These studies show the possible application of TMS not only as a research method in healthy subjects, but also as a tool for inducing brain excitability changes in patients with sensory extinction, which could be useful for supporting the rehabilitation of this deficit.
Control of Rotor‐Blade Coupled Vibrations Using Shaft‐Based Actuation
Authors: Christensen René Hardam , Santos Ilmar Ferreira
Published: January 2014

When implementing active control into bladed rotating machines aiming at reducing blade vibrations, it can be shown that blade as well as rotor vibrations can in fact be controlled by the use of only shaft‐based actuation. Thus the blades have to be deliberately mistuned. This paper investigates the dynamical characteristics of a mistuned bladed rotor and shows how, why and when a bladed rotor becomes controllable and observable if properly mistuned. As part of such investigation modal controllability and observability of a tuned as well as a mistuned coupled rotor‐blade system are analysed. The dependency of the controllability and observability on varying rotational speed and mode shape interaction phenomena between parametric and basis mode shape components are also analysed. Numerical results reveal a limitation of the achievable controllability and observability, once quantitative measures of modal controllability and observability converge toward steady levels as the degree of mistuning is increased. Finally, experimental control results are presented to prove the theoretical conclusions and to show the feasibility of controlling rotor and blade vibrations by means of shaft‐based actuation in practice.
Application of Evolutionary Computation in Automotive Powertrain Mount Tuning
Authors: Akanda Anab , Adulla Chandu
Published: January 2014

Engine mount tuning is a multi‐disciplinary exercise since it affects Idle‐shake, Road‐shake and power‐train noise response. Engine inertia is often used as a tuned absorber for controlling suspension resonance related road‐shake issues. Last but not least, vehicle ride and handling may also be affected by mount tuning. In this work, Torque‐Roll‐Axis (TRA) decoupling of the rigid powertrain was used as a starting point for mount tuning. Nodal point of flexible powertrain bending was used to define the envelop for transmission mount locations. The frequency corresponding to the decoupled roll mode of the rigid powertrain was then adjusted for idle‐shake and road‐shake response management.

A TRA decoupling procedure, cast as a multi‐objective optimization problem, was applied to a body‐on‐frame sport‐utility vehicle powertrain system. In addition to a standard gradient based optimization algorithm, available in commercial finite element software, an evolutionary computation paradigm known as Evolutionary Strategies (ES) was used to solve the optimization problem. The primary advantages of evolutionary computation over gradient based algorithms are as follows: i) They are less likely to get trapped in local minima and less dependent on initial values of the design parameters and therefore able to handle multi‐modal optimization problems unlike gradient based algorithms, ii) They produce a population of viable solutions, unlike gradient based algorithms which yields a single solution. The second advantage is very attractive in a production environment since packaging and other multi‐disciplinary constraints often require multiple quality solutions for the same problem. The process outlined in this work was verified by exercising a full‐vehicle finite element model. The process produced a set of production feasible powertrain mount parameters for acceptable idle and road shake performance.
Dynamical Modelling, Stochastic Simulation and Optimization in the Context of Damage Tolerant Design
Authors: Butkewitsch Sergio
Published: January 2014

This paper addresses the situation in which some form of damage is induced by cyclic mechanical stresses yielded by the vibratory motion of a system whose dynamical behaviour is, in turn, affected by the evolution of the damage. It is assumed that both phenomena, vibration and damage propagation, can be modeled by means of time depended equations of motion whose coupled solution is sought. A brief discussion about the damage tolerant design philosophy for aircraft structures is presented at the introduction, emphasizing the importance of the accurate definition of inspection intervals and, for this sake, the need of a representative damage propagation model accounting for the actual loading environment in which a structure may operate. For the purpose of illustration, the finite element model of a cantilever beam is formulated, providing that the stiffness matrix can be updated as long as a crack of an assumed initial length spreads in a given location of the beam according to a proper propagation model. This way, it is possible to track how the mechanical vibration, through its varying amplitude stress field, activates and develops the fatigue failure mechanism. Conversely, it is also possible to address how the effect of the fatigue induced stiffness degradation influences the motion of the beam, closing the loop for the analysis of a coupled vibration‐degradation dynamical phenomenon. In the possession of this working model, stochastic simulation of the beam behaviour is developed, aiming at the identification of the most influential parameters and at the characterization of the probability distributions of the relevant responses of interest. The knowledge of the parameters and responses allows for the formulation of optimization problems aiming at the improvement of the beam robustness with respect to the fatigue induced stiffness degradation. The overall results are presented and analyzed, conducting to the conclusions and outline of future investigation.
Pharmacotherapy of Posttraumatic Cognitive Impairments
Authors: Arciniegas David B. , Silver Jonathan M.
Published: January 2014

Pharmacotherapy may contribute to the rehabilitation of persons with posttraumatic cognitive impairments. This article reviews first the neurobiological consequences of traumatic brain injury with a particular emphasis on acute and long‐term posttraumatic neurochemical disturbances. Studies of pharmacotherapies for posttraumatic cognitive impairments are reviewed next, and are organized according to medication class and the neurotransmitter system they affect most. Based on the evidence provided by that review, augmentation of posttraumatic cerebral catecholaminergic and cholinergic function are suggested as potentially useful neurochemical targets for pharmacologic intervention in this population. More specifically, it is suggested that persons with posttraumatic impairments in arousal, speed of processing, and possibly attention may benefit most from treatment with an agent that augments cerebral catecholaminergic function, and that persons whose predominant posttraumatic impairment is in the domain of memory may benefit most from treatment with cholinesterase inhibitors. Practical considerations regarding the use of pharmacotherapies for posttraumatic cognitive impairments are offered, and the need for additional research in this area is highlighted.
Improving Neglect by TMS
Authors: Fierro Brigida , Brighina Filippo , Bisiach Edoardo
Published: January 2014

Hemispatial neglect refers to the defective ability of patients to explore or act upon the side of space contralateral to the lesion and to attend to stimuli presented in that portion of space. Evidence from animal models suggests that many of the behavioural sequelae associated with visual neglect may result not solely from the size of the lesion, but also from a pathological state of increased inhibition exerted on the damaged hemisphere by the contralesional hemisphere. On the basis of these potential mechanisms underlying neglect, in this review we discuss therapeutic approaches, focusing particularly on recent research using transcranial magnetic stimulation (TMS). This technique, besides representing an ideal tool to investigate visuo‐spatial attentive mechanisms in humans, has shown promising beneficial effects that might have an impact on clinical practice.
Enhancement of Phonological Memory Following Transcranial Magnetic Stimulation (TMS)
Authors: Kirschen Matthew P. , Davis-Ratner Mathew S. , Jerde Thomas E. , Schraedley-Desmond Pam , Desmond John E.
Published: January 2014

Phonologically similar items (mell, rell, gell) are more difficult to remember than dissimilar items (shen, floy, stap), likely because of mutual interference of the items in the phonological store. Low‐frequency transcranial magnetic stimulation (TMS), guided by functional magnetic resonance imaging (fMRI) was used to disrupt this phonological confusion by stimulation of the left inferior parietal (LIP) lobule. Subjects received TMS or placebo stimulation while remembering sets of phonologically similar or dissimilar pseudo‐words. Consistent with behavioral performance of patients with neurological damage, memory for phonologically similar, but not dissimilar, items was enhanced following TMS relative to placebo stimulation. Stimulation of a control region of the brain did not produce any changes in memory performance. These results provide new insights into how the brain processes verbal information by establishing the necessity of the inferior parietal region for optimal phonological storage. A mechanism is proposed for how TMS reduces phonological confusion and leads to facilitation of phonological memory.
Nonlinear Dynamic Behavior of a Flexible Structure to Combined External Acoustic and Parametric Excitation
Authors: Varoto Paulo S. , Silva Demian G.
Published: January 2014

Flexible structures are frequently subjected to multiple inputs when in the field environment. The accurate determination of the system dynamic response to multiple inputs depends on how much information is available from the excitation sources that act on the system under study. Detailed information include, but are not restricted to appropriate characterization of the excitation sources in terms of their variation in time and in space for the case of distributed loads. Another important aspect related to the excitation sources is how inputs of different nature contribute to the measured dynamic response. A particular and important driving mechanism that can occur in practical situations is the parametric resonance. Another important input that occurs frequently in practice is related to acoustic pressure distributions that is a distributed type of loading. In this paper, detailed theoretical and experimental investigations on the dynamic response of a flexible cantilever beam carrying a tip mass to simultaneously applied external acoustic and parametric excitation signals have been performed. A mathematical model for transverse nonlinear vibration is obtained by employing Lagrange’s equations where important nonlinear effects such as the beam’s curvature and quadratic viscous damping are accounted for in the equation of motion. The beam is driven by two excitation sources, a sinusoidal motion applied to the beam’s fixed end and parallel to its longitudinal axis and a distributed sinusoidal acoustic load applied orthogonally to the beam’s longitudinal axis. The major goal here is to investigate theoretically as well as experimentally the dynamic behavior of the beam‐lumped mass system under the action of these two excitation sources. Results from an extensive experimental work show how these two excitation sources interacts for various testing conditions. These experimental results are validated through numerically simulated results obtained from the solution of the system’s nonlinear equation of motion.
Modelling and Experimental Investigation of an Active Damper
Authors: Teixeira Rafael Luís , Neto Francisco Paulo Lépore , Ribeiro José Francisco
Published: January 2014

This paper presents a validation methodology of the dynamic behavior of an active viscous damper. The damper has two flexible metallic bellows connected to a rigid reservoir filled with fluid. When one of the bellows is connected to a vibrating structure a periodic flow passes through a variable internal orifice and the damping effect is produced. The size of the orifice is adjusted by a controlled linear piezoelectric actuator that positions the conical core into a conical cavity. The device finite element structural model consists of the valve body and its conical core that are assumed rigid and the flexible bellows are represented by two pistons with elastic suspensions. The flow developed inside the damper is modeled considering the fluid‐structure interation, using the Lagrangean‐Eulerian formulation. To validate the proposed model a prototype was constructed and experimental tests and numerical simulations are accomplished in the time domain, applying harmonic excitations. The results are compared using curves that relate the damping coefficient with the orifice size and with the input velocity applied at the bellows face. However, for the proper control design and system operation, the direct use of the finite element model becomes unviable due to its high computational time. Then, a reduced second order discrete dynamic model for the damper was developed. The model parameters are identified by analysis in the frequency domain, using impulsive excitation force, for constant and variable orifice sizes. At low excitation frequencies, the damper prototype behaves like a single degree of freedom system which damping factor changes with the orifice size A fuzzy controller was designed and it generates the orifice reference size associated to the desired damping factor. The active system presented better performance when compared to the passive one.
Closed Loop Finite Element Modeling of Piezoelectric Smart Structures
Authors: Meng Guang , Ye Lin , Dong Xing-jian , Wei Ke-xiang
Published: January 2014

The objective of this paper is to develop a general design and analysis scheme for actively controlled piezoelectric smart structures. The scheme involves dynamic modeling of a smart structure, designing control laws and closed‐loop simulation in a finite element environment. Based on the structure responses determined by finite element method, a modern system identification technique known as Observer/Kalman filter Identification (OKID) technique is used to determine the system Markov parameters. The Eigensystem Realization Algorithm (ERA) is then employed to develop an explicit state space model of the equivalent linear system for control law design. The Linear Quadratic Gaussian (LQG) control law design technique is employed to design a control law. By using ANSYS parametric design language (APDL), the control law is incorporated into the ANSYS finite element model to perform closed loop simulations. Therefore, the control law performance can be evaluated in the context of a finite element environment. Finally, numerical examples have demonstrated the validity and efficiency of the proposed design scheme. Without any further modifications, the design scheme can be readily applied to other complex smart structures.
Oscillations of a Beam on a Non‐Linear Elastic Foundation under Periodic Loads
Authors: Santee Donald Mark , Gonçalves Paulo Batista
Published: January 2014

The complexity of the response of a beam resting on a nonlinear elastic foundation makes the design of this structural element rather challenging. Particularly because, apparently, there is no algebraic relation for its load bearing capacity as a function of the problem parameters. Such an algebraic relation would be desirable for design purposes. Our aim is to obtain this relation explicitly. Initially, a mathematical model of a flexible beam resting on a non‐linear elastic foundation is presented, and its non‐linear vibrations and instabilities are investigated using several numerical methods. At a second stage, a parametric study is carried out, using analytical and semi‐analytical perturbation methods. So, the influence of the various physical and geometrical parameters of the mathematical model on the non‐linear response of the beam is evaluated, in particular, the relation between the natural frequency and the vibration amplitude and the first period doubling and saddle‐node bifurcations. These two instability phenomena are the two basic mechanisms associated with the loss of stability of the beam. Finally Melnikov′s method is used to determine an algebraic expression for the boundary that separates a safe from an unsafe region in the force parameters space. It is shown that this can be used as a basis for a reliable engineering design criterion.
An FFT‐Based Spectral Analysis Method for Linear Discrete Dynamic Systems with Non‐Proportional Damping
Authors: Cho Jooyong , Lee Usik
Published: January 2014

This paper proposes a fast Fourier transforms (FFT)‐based spectral analysis method for the dynamic analysis of linear discrete dynamic systems which have non‐proportional viscous damping and are subjected to non‐zero initial conditions. To evaluate the proposed FFT‐based spectral analysis method, the forced vibration of a three degree‐of‐freedom (DOF) system is considered as an illustrative problem. The accuracy of the proposed FFT‐based spectral analysis method is evaluated by comparing the forced vibration responses obtained by the present FFT‐based spectral analysis method with those obtained by using the well‐known Runge‐Kutta method and modal analysis method.
Chaos Control in Mechanical Systems
Authors: Savi Marcelo A. , Pereira-Pinto Francisco Heitor I. , Ferreira Armando M.
Published: January 2014

Chaos has an intrinsically richness related to its structure and, because of that, there are benefits for a natural system of adopting chaotic regimes with their wide range of potential behaviors. Under this condition, the system may quickly react to some new situation, changing conditions and their response. Therefore, chaos and many regulatory mechanisms control the dynamics of living systems, conferring a great flexibility to the system. Inspired by nature, the idea that chaotic behavior may be controlled by small perturbations of some physical parameter is making this kind of behavior to be desirable in different applications. Mechanical systems constitute a class of system where it is possible to exploit these ideas. Chaos control usually involves two steps. In the first, unstable periodic orbits (UPOs) that are embedded in the chaotic set are identified. After that, a control technique is employed in order to stabilize a desirable orbit. This contribution employs the close‐return method to identify UPOs and a semi‐continuous control method, which is built up on the OGY method, to stabilize some desirable UPO. As an application to a mechanical system, a nonlinear pendulum is considered and, based on parameters obtained from an experimental setup, analyses are carried out. Signals are generated by numerical integration of the mathematical model and two different situations are treated. Firstly, it is assumed that all state variables are available. After that, the analysis is done from scalar time series and therefore, it is important to evaluate the effect of state space reconstruction. Delay coordinates method and extended state observers are employed with this aim. Results show situations where these techniques may be used to control chaos in mechanical systems.
Treatment of Cognitive Impairment in Multiple Sclerosis
Authors: Pierson Susan H. , Griffith Nathan
Published: January 2014

Cognitive impairment in multiple sclerosis is an increasingly recognized entity. This article reviews the cognitive impairment of multiple sclerosis, its prevalence, its relationship to different types of multiple sclerosis, and its contribution to long‐term functional prognosis. The discussion also focuses on the key elements of cognitive dysfunction in multiple sclerosis which distinguish it from other forms of cognitive impairment. Therapeutic interventions potentially effective for the cognitive impairment of multiple sclerosis are reviewed including the effects of disease modifying therapies and the use of physical and cognitive interventions.
Design and Test of a Blast Shield for Boeing 737 Overhead Compartment
Authors: Dang Xinglai , Chan Philemon C.
Published: January 2014

This work demonstrates the feasibility of using a composite blast shield for hardening an overhead bin compartment of a commercial aircraft. If a small amount of explosive escapes detection and is brought onboard and stowed in an overhead bin compartment of a passenger aircraft, the current bins provide no protection against a blast inside the compartment. A blast from the overhead bin will certainly damage the fuselage and likely lead to catastrophic inflight structural failure. The feasibility of using an inner blast shield to harden the overhead bin compartment of a Boeing 737 aircraft to protect the fuselage skin in such a threat scenario has been demonstrated using field tests. The blast shield was constructed with composite material based on the unibody concept. The design was carried out using LS‐DYNA finite element model simulations. Material panels were first designed to pass the FAA shock holing and fire tests. The finite element model included the full coupling of the overhead bin with the fuselage structure accounting for all the different structural connections. A large number of iterative simulations were carried out to optimize the fiber stacking sequence and shield thickness to minimize weight and achieve the design criterion. Three designs, the basic, thick, and thin shields, were field‐tested using a frontal fuselage section of the Boeing 737–100 aircraft. The basic and thick shields protected the integrity of the fuselage skin with no skin crack. This work provides very encouraging results and useful data for optimization implementation of the blast shield design for hardening overhead compartments against the threat of small explosives.
Vibrational Energy Flow Analysis of Corrected Flexural Waves in Timoshenko Beam – Part II: Application to Coupled Timoshenko Beams
Authors: Park Young-Ho , Hong Suk-Yoon
Published: January 2014

This paper presents the methodology for the energy flow analysis of coupled Timoshenko beam structures and various numerical applications to verify the developed methodology. To extend the application of the energy flow model for corrected flexural waves in the Timoshenko beam, which is developed in the other companion paper, to coupled structures, the wave transmission analyses of general coupled Timoshenko beam systems are performed. First, power transmission and reflection coefficients for all kinds of propagating waves in the general, coupled Timoshenko beam structures are derived by the wave transmission approach. In numerical applications, the energy flow solutions using the derived coefficients agree well with the classical solutions for various exciting frequencies, damping loss factors, and coupled Timoshenko beam structures. Additionally, the numerical results for the Timoshenko beam are compared with those for the Euler‐Bernoulli beam.
Some Recent Developments in Adaptive Tuned Vibration Absorbers/Neutralisers
Authors: Brennan Michael J.
Published: January 2014

The vibration absorber has been used for vibration control purposes in many sectors of engineering from aerospace, to automotive to civil, for the past 100 years or so. A limitation of the device, however, is that it acts like a notch filter, only being effective over a narrow band of frequencies. Recent developments have overcome this limitation by making it possible to tune the device over a range of frequencies. This has been achieved by incorporating a variable stiffness element that can be adjusted in real‐time. In this paper, some ways in which stiffness change can be achieved in practice are reviewed and some examples of prototype adaptive tuned vibration absorbers (ATVAs) are described. A simple control scheme to automatically tune an ATVA is also presented.
On the Investigation of State Space Reconstruction of Nonlinear Aeroelastic Response Time Series
Authors: Marques Flávio D. , Belo Eduardo M. , Oliveira Vilma A. , Rosolen José R. , Simoni Andréia R.
Published: January 2014

Stall‐induced aeroelastic motion may present severe non‐linear behavior. Mathematical models for predicting such phenomena are still not available for practical applications and they are not enough reliable to capture physical effects. Experimental data can provide suitable information to help the understanding of typical non‐linear aeroelastic phenomena. Dynamic systems techniques based on time series analysis can be adequately applied to non‐linear aeroelasticity. When experimental data are available, the methods of state space reconstruction have been widely considered. This paper presents the state space reconstruction approach for the characterization of the stall‐induced aeroelastic non‐linear behavior. A wind tunnel scaled wing model has been tested. The wing model is subjected to different airspeeds and dynamic incidence angle variations. The method of delays is used to identify an embedded attractor in the state space from experimentally acquired aeroelastic response time series. To obtain an estimate of the time delay used in the state space reconstruction from time series, the autocorrelation function analyis is used. For the calculation of the embedding dimension the correlation integral approach is considered. The reconstructed attractors can reveal typical non‐linear structures associated, for instance, to chaos or limit cycles.
Natural Frequencies and Modal Damping Ratios Identification of Civil Structures from Ambient Vibration Data
Authors: Ta Minh-Nghi , Lardiès Joseph , Marc Berthillier
Published: January 2014

Damping is a mechanism that dissipates vibration energy in dynamic systems and plays a key role in dynamic response prediction, vibration control as well as in structural health monitoring during service. In this paper a time domain and a time‐scale domain approaches are used for damping estimation of engineering structures, using ambient response data only. The use of tests under ambient vibration is increasingly popular today because they allow to measure the structural response in service. In this paper we consider two engineering structures excited by ambient forces. The first structure is the 310 m tall TV tower recently constructed in the city of Nanjing in China. The second example concerns the Jinma cable‐stayed bridge that connects Guangzhou and Zhaoqing in China. It is a single tower, double row cable‐stayed bridge supported by 112 stay cables. Ambient vibration of each cable is carried out using accelerometers. From output data only, the modal parameter are extracted using a subspace method and the wavelet transform method.
Paradoxical Facilitation of Attention in Healthy Humans
Authors: Fecteau Shirley , Pascual-Leone Alvaro , Théoret Hugo
Published: January 2014

Transcranial magnetic stimulation (TMS)‐induced virtual lesions in healthy subjects can be used to test neurofunctional models of disease. The interhemispheric rivalry model of heminglect is well suited for such investigations, as simple predictions derived from clinical data can be tested without the caveats normally associated with lesion studies. One of these predictions is that release from contralateral inhibition should lead to increased parietal responsiveness, which, in turn, would enhance spatial attention. Here, we detail studies showing TMS‐induced paradoxical functional facilitation of attention in healthy individuals and highlight their contribution to the understanding and treatment of neglect syndromes.
Transient Dynamic Response of Delaminated Composite Rotating Shallow Shells Subjected to Impact
Authors: Karmakar Amit , Kishimoto Kikuo
Published: January 2014

In this paper a transient dynamic finite element analysis is presented to study the response of delaminated composite pretwisted rotating shallow shells subjected to low velocity normal impact. Lagrange′s equation of motion is used to derive the dynamic equilibrium equation and moderate rotational speeds are considered wherein the Coriolis effect is negligible. An eight noded isoparametric plate bending element is employed in the finite element formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin′s theory. To satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front a multipoint constraint algorithm is incorporated which leads to unsymmetric stiffness matrices. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark′s time integration algorithm. Parametric studies are performed in respect of location of delamination, angle of twist and rotational speed for centrally impacted graphite‐epoxy composite cylindrical shells.
The Effect of Degree of Saturation of Sand on Detonation Phenomena Associated with Shallow‐Buried and Ground‐Laid Mines
Authors: Grujicic M. , Pandurangan B. , Cheeseman B.A.
Published: January 2014

A new materials model for sand has been developed in order to include the effects of the degree of saturation and the deformation rate on the constitutive response of this material. The model is an extension of the original compaction materials model for sand in which these effects were neglected. The new materials model for sand is next used, within a non‐linear‐dynamics transient computational analysis, to study various phenomena associated with the explosion of shallow‐buried and ground‐laid mines. The computational results are compared with the corresponding experimental results obtained through the use of an instrumented horizontal mine‐impulse pendulum, pressure transducers buried in sand and a post‐detonation metrological study of the sand craters. The results obtained suggest that the modified compaction model for sand captures the essential features of the dynamic behavior of sand and accounts reasonably well for a variety of the experimental findings related to the detonation of shallow‐buried or ground‐laid mines.
Cognitive Assessment in Chinese Patients with Aneurysmal Subarachnoid Hemorrhage
Authors: Cheng Huilin , Shi Jixin , Zhou Mengliang
Published: January 2014

A subgroup of patients who survive aneurysmal subarachnoid hemorrhage (SAH) may have significant cognitive deficits. The aim of the current study was to determine the efficiency of cognitive tests and frequency of cognitive impairments associated with aneurysmal SAH in Chinese. A series of 116 patients with aneurysmal SAH were assessed before surgery. Only 37 patients have completed all tests. The other 79 patients had discontinued because of their clinical conditions, recurring severe headaches, refusing or misunderstanding due to low education. We found that one or more cognitive functions were impaired in 70.3% of the 37 patients, SAH patients were especially impaired in functions that are related to visual reproduction, verbal fluency, and executive functions. The results suggest that the patients have impressive cognitive deficits after aneurysmal SAH. A battery of appropriate cognitive tests should be developed for use by doctors and nurses.
Enhancing Picture Naming with Transcranial Magnetic Stimulation
Authors: Mottaghy Felix M. , Sparing Roland , Töpper Rudolf
Published: January 2014

The enhancement of cognitive function in healthy subjects by medication, training or intervention yields increasing political, social and ethical attention. In this paper facilitatory effects of single‐pulse TMS and repetitive TMS on a simple picture naming task are presented. A significant shortening of picture naming latencies was observed after single‐pulse TMS over Wernicke′s area. The accuracy of the response was not affected by this speed effect. After TMS over the dominant motor cortex or over the non‐dominant temporal lobe, however, no facilitation of picture naming was observed. In the rTMS experiments only rTMS of Wernicke’s area had an impact on picture naming latencies resulting in a shortening of naming latencies without affecting the accuracy of the response. rTMS over the visual cortex, Broca′s area or over the corresponding sites in the non‐dominant hemisphere had no effect. Single‐pulse TMS is able to facilitate lexical processes due to a general preactivation of language‐related neuronal networks when delivered over Wernicke′s area. Repetitive transcranial magnetic stimulation over Wernicke’s area also leads to a brief facilitation of picture naming possibly by shortening linguistic processing time. Whether TMS or rTMS can be used to aid linguistic therapy in the rehabilitation phase of aphasic patients should be subject of further investigations.
Influence of Journal Bearing Axial Grooves on the Dynamic Behavior of Horizontal Rotors
Authors: de Carvalho Michalski Miguel Angelo , Zindeluk Moysés , de Oliveira Rocha Renato
Published: January 2014

Journal bearing design and the lubricant characteristics are very influential in a rotating machine behaviour. The bearing geometry can drastically affect the lubricant flow and also the rotor dynamics. Approaching that issue, this paper presents an experimental study of the dynamic behavior of a horizontal rotor suported by journal bearings with semi‐circular axial grooves. The journal bearings were manufactured with a varied number of axial grooves and a versatile test rig is used, making possible the analysis of different configurations. The acquired signals are analyzed with classical and non‐linear tools and the differences among the rotors’ configurations can be shown.
An Ethics Perspective on Transcranial Magnetic Stimulation (TMS) and Human Neuromodulation
Authors: Illes Judy , Gallo Marisa , Kirschen Matthew P.
Published: January 2014

This paper concerns the ethics of human neuromodulation using transcranial magnetic stimulation (TMS). We examine the challenges of modulating the brain with TMS through the research ethics lens and in clinical medicine for treating frank pathology, primarily in psychiatric diseases. We also consider contemporary issues raised in the neuroethics literature about managing unexpected findings, and relate these to TMS and to other frontier neurotechnology that is becoming openly available in the public domain. We argue that safety and informed consent are of paramount importance for TMS, but that personal values and sociocultural factors must also be considered when examining the promise of this technology and applications that ought to be highlighted for extra precautions.
rTMS For PTSD: Induced Merciful Oblivion or Elimination of Abnormal Hypermnesia?
Authors: Rossi Simone , Cappa Stefano F. , Ulivelli Monica , De Capua Alberto , Bartalini Sabina , Rossini Paolo M.
Published: January 2014

Neuroimaging studies and experimental data suggest that symptoms of posttraumatic stress disorder (PTSD) are associated with dysfunctions of neural circuits linking prefrontal cortex and the limbic system that have a role in autobiographic episodic memory. High‐frequency repetitive transcranial magnetic stimulation (rTMS) of the right dorsolateral prefrontal cortex (DLPFC) has been suggested to be beneficial to patients with PTSD, transiently alleviating re‐experiencing as well as avoidance reactions and associated anxiety symptoms. In healthy humans, converging evidence suggests that rTMS of the right DLPFC interferes with episodic memory retrieval. Hence, we hypothesize that daily applications of rTMS in PTSD patients may reduce access to the set of autobiographical stored events, that, if re‐experienced, may cause the overt PTSD symptoms.
A Monolithic High‐G SOI‐MEMS Accelerometer for Measuring Projectile Launch and Flight Accelerations
Authors: Davis Bradford S. , Denison Tim , Kuang Jinbo
Published: January 2014

Analog Devices (ADI) has designed and fabricated a monolithic high‐g acceleration sensor (ADXSTC3‐HG) fabricated with the ADI silicon‐on‐insulator micro‐electro‐mechanical system (SOI‐MEMS) process. The SOI‐MEMS sensor structure has a thickness of 10 um, allowing for the design of inertial sensors with excellent cross‐axis rejection. The high‐g accelerometer discussed in this paper was designed to measure in‐plane acceleration to 10,000 g while subjected to 100,000 g in the orthogonal axes. These requirements were intended to meet Army munition applications. The monolithic sensor was packaged in an 8‐pin leadless chip carrier (LCC‐8) and was successfully demonstrated by the US Army Research Laboratory (ARL) as part of an inertial measurement unit during an instrumented flight experiment of artillery projectiles launched at 15,000 g.
Can Cognitive and Behavioural Disorders Differentiate Frontal Variant‐Frontotemporal Dementia From Alzheimer’s Disease at Early Stages?
Authors: Jenner C. , Reali G. , Puopolo M. , Silveri M. C.
Published: January 2014

Frontal variant‐Frontotemporal dementia (fvFTD) and Alzheimer′s disease (AD) patients matched for severity of dementia at the Clinical Dementia Rating (CDR) received neuropsychological testing in order to explore if the dysexecutive disorder might characterise fvFTD at early stage, when AD is dominated by the episodic memory defect. We also determined if the behavioural syndrome was more severe in fvFTD than AD, and if specific patterns of behavioural symptoms could differentiate the two types of dementia, using the Neuropsychiatry Inventory (NPI). AD patients performed worse than fvFTD not only in memory but also in executive tasks. Apathy and eating disorders proved to be more severe or frequent in fvFTD even if the two groups did not differ in the total NPI score. CDR score significantly correlated with the NPI score in fvFTD and with the MMSE in AD. Our data confirm that the memory disorders may differentiate the two types of dementia; however, the dysexecutive syndrome is as severe, and even more severe in AD. The severity of the behavioural syndrome is comparable in the two groups but the nature of the behavioural disorders may vary to some extent. We conclude that AD dementia at early stage is a behavioural‐cognitive syndrome, while in fvFTD the behavioural disorders appear when the cognitive deficit is still relatively mild.
Vibroacoustic Analysis of Cyclic Structures by Using Dof’s Size Reduction and Holographic Measurements
Authors: Hami Abdelkhalak El , Borza Dan , Souza de Cursi José Eduardo
Published: January 2014

We propose a method for the vibroacoustic analysis of structures having symmetry properties. This method is based on the reduction of the number of the degrees of freedom involved (size reduction) and the use of experimental data (confrontation numerical/experimental). We propose the extension of the method of the linear representations of finite symmetry groups to problems of coupling fluid‐structure. This approach, while keeping the quality of the approximations, leads to a significant reduction of the number of degrees of freedom, with a maximal reduction for the so called repetitive structures. Finally, we present a practical case of modal analysis – in air and water – of a ship propeller formed by 3 stainless steel blades. The experimental results are obtained by using the whole‐field, non‐contact technique of electronic holography.