bluuebunny/crossref_metadata_2025 huggingface dataset:
Three Dimensional Vibration Analysis of a Class of Traction-Free Solid Elastic Bodies with an Eccentric Cavity
Authors: Hasheminejad Seyyed M. , Mirzaei Yaser
Published: January 2014

A three-dimensional elasticity-based continuum model is developed for describing the free vibrational characteristics of an important class of isotropic, homogeneous, and completely free structural bodies (i.e., finite cylinders, solid spheres, and rectangular parallelepipeds) containing an arbitrarily located simple inhomogeneity in form of a spherical or cylindrical defect. The solution method uses Ritz minimization procedure with triplicate series of orthogonal Chebyshev polynomials as the trial functions to approximate the displacement components in the associated elastic domains, and eventually arrive at the governing eigenvalue equations. An extensive review of the literature spanning over the past three decades is also given herein regarding the free vibration analysis of elastic structures using Ritz approach. Accuracy of the implemented approach is established through proper convergence studies, while the validity of results is demonstrated with the aid of a commercial FEM software, and whenever possible, by comparison with other published data. Numerical results are provided and discussed for the first few clusters of eigen-frequencies corresponding to various mode categories in a wide range of cavity eccentricities. Also, the corresponding 3D mode shapes are graphically illustrated for selected eccentricities. The numerical results disclose the vital influence of inner cavity eccentricity on the vibrational characteristics of the voided elastic structures. In particular, the activation of degenerate frequency splitting and incidence of internal/external mode crossings are confirmed and discussed. Most of the results reported herein are believed to be new to the existing literature and may serve as benchmark data for future developments in computational techniques.
Semantic and Phonemic Verbal Fluency in Parkinson’s Disease: Influence of Clinical and Demographic Variables
Authors: Obeso Ignacio , Casabona Enrique , Bringas Maria Luisa , Álvarez Lázaro , Jahanshahi Marjan
Published: January 2014

Changes of cognitive function in PD have been extensively documented and defined as a ‘frontal’ type executive dysfunction. One of the main components of this executive dysfunction is the impairment of verbal fluency. The aim of the present study was to assess semantic and phonemic fluency in a large sample of PD patients and to investigate the effect of clinical and sociodemographic variables on verbal fluency in this patient group.

Three hundred patients with idiopathic Parkinson's disease who were consecutive referrals to our clinic and 50 age and education matched healthy controls completed the phonemic and semantic verbal fluency tasks. Both phonemic and semantic verbal fluency were significantly impaired in PD patients relative to matched controls. Stage of illness, presence of depression, education and age influenced verbal fluency measures. Regression analyses established that global measures of cognitive ability (MMSE) and executive function (FAB) and side of onset of motor symptoms predicted 36–37% of variance of phonemic or semantic verbal fluency measures. Thus, future studies aimed at assessing cognitive functioning in PD patients treated by deep brain stimulation (DBS) should adequately take into account several factors (stage of illness, depression, executive functioning) which may potentially influence performance on verbal fluency tasks.
Implementation of the Scanning Laser Doppler Vibrometer Combined with a Light-Weight Pneumatic Artificial Muscle Actuator for the Modal Analysis of a Civil Structure
Authors: Deckers K. , Guillaume P. , Vuye C. , Lefeber D.
Published: January 2014

The identification of the modal parameters of bridges and other large civil constructions has become an important research issue. Different approaches have been proposed depending on the excitation used: ambient excitations (due to wind, traffic, …) or artificial excitations (e.g. impact test with heavy drop weights). In practice it turns out that not all modes are well excited by the ambient forces. Hence the application of an artificial actuator is advisable. The problem is that larger constructions often require large and heavy excitation devices, which are hard to manipulate. Another difficulty encountered in performing a modal analysis on large civil constructions is the necessity for a large number of high sensitivity sensors. Consequently a large number of cables has to be installed resulting in a large setup time.

This paper is a proof-of-concept which demonstrates the possibility of using lightweight Pneumatic Artificial Muscles combined with the scanning laser Doppler vibrometer to perform a modal analysis on a civil structure. This combination allows for an important reduction in setup time and allows for sine testing as well as the application of broadband signals such as periodic chirps, true noise or multisines.
One Size Does Not Fit All: Face Emotion Processing Impairments in Semantic Dementia, Behavioural-Variant Frontotemporal Dementia and Alzheimer’s Disease Are Mediated by Distinct Cognitive Deficits
Authors: Miller Laurie A. , Hsieh Sharpley , Lah Suncica , Savage Sharon , Hodges John R. , Piguet Olivier
Published: January 2014

Patients with frontotemporal dementia (both behavioural variant [bvFTD] and semantic dementia [SD]) as well as those with Alzheimer's disease (AD) show deficits on tests of face emotion processing, yet the mechanisms underlying these deficits have rarely been explored. We compared groups of patients with bvFTD (n= 17), SD (n= 12) or AD (n= 20) to an age- and education-matched group of healthy control subjects (n= 36) on three face emotion processing tasks (Ekman 60, Emotion Matching and Emotion Selection) and found that all three patient groups were similarly impaired. Analyses of covariance employed to partial out the influences of language and perceptual impairments, which frequently co-occur in these patients, provided evidence of different underlying cognitive mechanisms. These analyses revealed that language impairments explained the original poor scores obtained by the SD patients on the Ekman 60 and Emotion Selection tasks, which involve verbal labels. Perceptual deficits contributed to Emotion Matching performance in the bvFTD and AD patients. Importantly, all groups remained impaired on one task or more following these analyses, denoting a primary emotion processing disturbance in these dementia syndromes. These findings highlight the multifactorial nature of emotion processing deficits in patients with dementia.
Boundary Characteristic Orthogonal Polynomials in the Study of Transverse Vibrations of Nonhomogeneous Rectangular Plates with Bilinear Thickness Variation
Authors: Lal R. , Kumar Yajuvindra
Published: January 2014

The free transverse vibrations of thin nonhomogeneous rectangular plates of variable thickness have been studied using boundary characteristic orthogonal polynomials in the Rayleigh-Ritz method. Gram-Schmidt process has been used to generate these orthogonal polynomials in two variables. The thickness variation is bidirectional and is the cartesian product of linear variations along two concurrent edges of the plate. The nonhomogeneity of the plate is assumed to arise due to linear variations in Young's modulus and density of the plate material with the in-plane coordinates. Numerical results have been computed for four different combinations of clamped, simply supported and free edges. Effect of the nonhomogeneity and thickness variation with varying values of aspect ratio on the natural frequencies of vibration is illustrated for the first three modes of vibration. Three dimensional mode shapes for all the four boundary conditions have been presented. A comparison of results with those available in the literature has been made.
Analysis of Nonlinear Structural Dynamics and Resonance in Trees
Authors: Ganji H. Doumiri , Ganji S.S. , Ganji D.D. , Vaseghi F.
Published: January 2014

Wind and gravity both impact trees in storms, but wind loads greatly exceed gravity loads in most situations. Complex behavior of trees in windstorms is gradually turning into a controversial concern among ecological engineers. To better understand the effects of nonlinear behavior of trees, the dynamic forces on tree structures during periods of high winds have been examined as a mass-spring system. In fact, the simulated dynamic forces created by strong winds are studied in order to determine the responses of the trees to such dynamic loads. Many of such nonlinear differential equations are complicated to solve. Therefore, this paper focuses on an accurate and simple solution, Differential Transformation Method (DTM), to solve the derived equation. In this regard, the concept of differential transformation is briefly introduced. The approximate solution to this equation is calculated in the form of a series with easily computable terms. Then, the method has been employed to achieve an acceptable solution to the presented nonlinear differential equation. To verify the accuracy of the proposed method, the obtained results from DTM are compared with those from the numerical solution. The results reveal that this method gives successive approximations of high accuracy solution.
Progressive Dyslexia: Evidence from Hungarian and English
Authors: Druks Judit , Aydelott Jennifer , Genethliou Marios , Jacobs Helen , Weekes Brendan
Published: January 2014

We report a patient with non-fluent Primary Progressive Aphasia who was premorbidly literate in two alphabetic scripts, Hungarian (L1) and English (L2). Testing was performed over a two-year period to assess the impact of progressive illness on oral reading and repetition of single words. Results showed significant decline in oral reading in both languages, and an effect of language status in favour of oral reading in L1. Phonological complexity was a significant predictor of oral reading decline in both languages. Of interest, we observed an effect of language status on task performance whereby repetition was better in L2 than L1 but oral reading was better in L1 than L2. We conclude that language status has an effect on repetition and oral reading abilities for bilingual speakers with non-fluent Primary Progressive Aphasia.
Improved Riccati Transfer Matrix Method for Free Vibration of Non-Cylindrical Helical Springs Including Warping
Authors: Yu A.M. , Hao Y.
Published: January 2014

Free vibration equations for non-cylindrical (conical, barrel, and hyperboloidal types) helical springs with noncircular cross-sections, which consist of 14 first-order ordinary differential equations with variable coefficients, are theoretically derived using spatially curved beam theory. In the formulation, the warping effect upon natural frequencies and vibrating mode shapes is first studied in addition to including the rotary inertia, the shear and axial deformation influences. The natural frequencies of the springs are determined by the use of improved Riccati transfer matrix method. The element transfer matrix used in the solution is calculated using the Scaling and Squaring method and Pad'e approximations. Three examples are presented for three types of springs with different cross-sectional shapes under clamped-clamped boundary condition. The accuracy of the proposed method has been compared with the FEM results using three-dimensional solid elements (Solid 45) in ANSYS code. Numerical results reveal that the warping effect is more pronounced in the case of non-cylindrical helical springs than that of cylindrical helical springs, which should be taken into consideration in the free vibration analysis of such springs.
Design of a Random Decrement Method Based Structural Health Monitoring System
Authors: Buff H. , Friedmann A. , Koch M. , Bartel T. , Kauba M.
Published: January 2014

Structural Health Monitoring (SHM) has reached a high importance in numerous fields of civil and mechanical engineering. Promising damage detection approaches like the Damage Index Method, Gapped Smoothing Technique and Modal Strain Energy Method require the structure's mode shapes [1].

Long term modal data acquisition on real life structures requires a computational efficient system based on a measuring method that can easily be installed. Systems using the Random Decrement Method (RDM) are composed of a decentralized network of smart acceleration sensors applied for both, triggering and pure measuring. They allow the reduction of cabling effort and computational costs to a minimum.

In order to design a RDM measuring network efficiently, an approved procedure for defining hardware as well as measuring settings is required. In addition, optimal sensor positions have to be defined. However, today those decisions are mostly based on expert's knowledge. In this paper a systematic and analytical procedure for defining the hardware requirements and measuring settings as well as optimal sensor positions is presented. The proposed routine uses the outcome of an Experimental Modal Analysis (EMA).

Due to different requirements for triggering and non-triggering sensors in the RDM network a combination of two approaches for sensor placement has to be used in order to find the best distribution of measurement points over the structure. A controllability based technique is used for placing triggering sensors, whereas the Effective Independence (EI) is utilized for the placement of non-triggering sensors.

The combination of these two techniques selects the best set of measuring points for a given number of sensors out of all possible sensor positions.

Damage detection itself is not considered within the scope of this paper.
Effect of Location of Delamination on Free Vibration of Cross-Ply Conical Shells
Authors: Dey Sudip , Karmakar Amit
Published: January 2014

Location of delamination is a triggering parameter for structural instability of laminated composites. In this paper, a finite element method is employed to determine the effects of location of delamination on free vibration characteristics of graphite-epoxy cross-ply composite pre-twisted shallow conical shells. The generalized dynamic equilibrium equation is derived from Lagrange's equation of motion neglecting Coriolis effect for moderate rotational speeds. The formulation is exercised by using an eight noded isoparametric plate bending element based on Mindlin's theory. Multi-point constraint algorithm is utilized to ensure the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. The standard eigen value problem is solved by applying the QR iteration algorithm. Finite element codes are developed to obtain the numerical results concerning the effects of location of delamination, twist angle and rotational speed on the natural frequencies of cross-ply composite shallow conical shells. The mode shapes are also depicted for a typical laminate configuration. Numerical results obtained from parametric studies of both symmetric and anti-symmetric cross-ply laminates are the first known non-dimensional natural frequencies for the type of analyses carried out here.
Estimation of the Impact Duration for Several Types of Structures
Authors: Jacquelin E. , Pashah S. , Lainé J.P. , Massenzio M.
Published: January 2014

The impact duration between two structures is not easy to forecast. Indeed it depends on many parameters including local parameters as well as structural parameters which characterize the dynamics of the structures.

In this paper we will show that it is possible to have a prior estimation of the impact duration. In fact the simulations show that this parameter is connected to some characteristics of a specific model, the so-called antioscillator model, even for the complex case of the impact between two flexible structures. All the simulations carried out on different cases show the close relationship between the first impact duration and the antioscillator characteristics. However some limitations exist and have been highlighted.
Graph Theory of Tower Tasks
Authors: Hinz Andreas M.
Published: January 2014

The appropriate mathematical model for the problem space of tower transformation tasks is the state graph representing positions of discs or balls and their moves. Graph theoretical quantities like distance, eccentricities or degrees of vertices and symmetries of graphs support the choice of problems, the selection of tasks and the analysis of performance of subjects whose solution paths can be projected onto the graph. The mathematical model is also at the base of a computerized test tool to administer various types of tower tasks.
Action and Object Word Writing in a Case of Bilingual Aphasia
Authors: Kambanaros Maria , Messinis Lambros , Anyfantis Emmanouil
Published: January 2014

We report the spoken and written naming of a bilingual speaker with aphasia in two languages that differ in morphological complexity, orthographic transparency and script Greek and English. AA presented with difficulties in spoken picture naming together with preserved written picture naming for action words in Greek. In English, AA showed similar performance across both tasks for action and object words, i.e. difficulties retrieving action and object names for both spoken and written naming. Our findings support the hypothesis that cognitive processes used for spoken and written naming are independent components of the language system and can be selectively impaired after brain injury. In the case of bilingual speakers, such processes impact on both languages. We conclude grammatical category is an organizing principle in bilingual dysgraphia.
Celtic Stone Dynamics Revisited Using Dry Friction and Rolling Resistance
Authors: Awrejcewicz J. , Kudra G.
Published: January 2014

The integral model of dry friction components is built with assumption of classical Coulomb friction law and with specially developed model of normal stress distribution coupled with rolling resistance for elliptic contact shape. In order to avoid a necessity of numerical integration over the contact area at each the numerical simulation step, few versions of approximate model are developed and then tested numerically. In the numerical experiments the simulation results of the Celtic stone with the friction forces modelled by the use of approximants of different complexity (from no coupling between friction force and torque to the second order Padé approximation) are compared to results obtained from model with friction approximated in the form of piecewise polynomial functions (based on the Taylor series with hertzian stress distribution). The coefficients of the corresponding approximate models are found by the use of optimization methods, like as in identification process using the real experiment data.
Potential Consequences of Abandonment in Preschool-Age: Neuropsychological Findings in Institutionalized Children
Authors: Cardona Juan F. , Manes Facundo , Escobar Josefina , López Jéssica , Ibáñez Agustín
Published: January 2014

Objective:Several longitudinal studies had shown that early deprivation and institutionalization during the first six months of life affects the emotional, cognitive, social and neurophysiologic development. Nevertheless, our understanding of possible similar effects of delayed institutionalization, in preschool-age remains unclear to this day. The goal of this study is to evaluate the cognitive performance of institutionalized children with history of preschool-age physical abandonment.

Method:18 male institutionalized children with history of abandonment during the preschool-age (2–5 years old) and comparison group matched by age, handedness, gender, educational and socioeconomic level were tested on multiple tasks of attention, memory and executive functions.

Results:We found a cognitive impairment in the institutionalized children in several measures of attention, memory and executive functions. This is the first report of cognitive impairment related to late abandonment and institutionalization effects (after 2 years old), extending the already known effects on early institutionalization.

Conclusions:This preliminary study suggests that environmental factors including abandonment and institutional care, can affect not only the infancy period, but also the preschool period providing new insights into our understanding of neurocognitive development.
Derivation of an Efficient Non-Prismatic Thin Curved Beam Element Using Basic Displacement Functions
Authors: Shahba Ahmad , Attarnejad Reza , Eslaminia Mehran
Published: January 2014

The efficiency and accuracy of the elements proposed by the Finite Element Method (FEM) considerably depend on the interpolating functions, namely shape functions, used to formulate the displacement field within an element. In this paper, a new insight is proposed for derivation of elements from a mechanical point of view. Special functions namely Basic Displacement Functions (BDFs) are introduced which hold pure structural foundations. Following basic principles of structural mechanics, it is shown that exact shape functions for non-prismatic thin curved beams could be derived in terms of BDFs. Performing a limiting study, it is observed that the new curved beam element successfully becomes the straight Euler-Bernoulli beam element. Carrying out numerical examples, it is shown that the element provides exact static deformations. Finally efficiency of the method in free vibration analysis is verified through several examples. The results are in good agreement with those in the literature.
Stochastic Behaviour of Mistuned Stator Vane Sectors: An Industrial Application
Authors: Sall A.C. , Thouverez F. , Blanc L. , Jean P.
Published: January 2014

Stator vanes which are found in axial compressors are subject to vibratory fatigue. Their division into monoblock sectors makes the prediction of their vibratory behaviour difficult by deterministic methods due to the loss of the cyclic symmetry properties and also to a high sensitivity to mistuning. The purpose is to present a robust calculation strategy based on a stochastic modelisation of the structure. The methodology has been developed first on a simplified model and then applied to an industrial case. Polynomial chaos based results are in good agreement with reference Monte Carlo simulations.
Closed-Loop Input Shaping Control of Vibration in Flexible Structures via Adaptive Sliding Mode Control
Authors: Pai Ming-Chang
Published: January 2014

Input shaping technique is widely used in reducing or eliminating residual vibration of flexible structures. The exact elimination of the residual vibration via input shaping technique depends on the amplitudes and instants of impulse application. However, systems always have parameter uncertainties which can lead to performance degradation. In this paper, a closed-loop input shaping control scheme is developed for uncertain flexible structures. The algorithm is based on input shaping control and adaptive sliding mode control. The proposed scheme does not need a priori knowledge of upper bounds on the norm of the uncertainties, but estimates them by using the adaptation technique. This scheme guarantees closed-loop system stability, and yields good performance and robustness in the presence of parameter uncertainties and external disturbances as well. Furthermore, it is shown that increasing the robustness to parameter uncertainties does not lengthen the duration of the impulse sequence. Simulation results demonstrate the efficacy of the proposed closed-loop input shaping control scheme.
Empirical Mode Decomposition of the Acceleration Response of a Prismatic Beam Subject to a Moving Load to Identify Multiple Damage Locations
Authors: Meredith J. , González A. , Hester D.
Published: January 2014

Empirical Mode Decomposition (EMD) is a technique that converts the measured signal into a number of basic functions known as intrinsic mode functions. The EMD-based damage detection algorithm relies on the principle that a sudden loss of stiffness in a structural member will cause a discontinuity in the measured response that can be detected through a distinctive spike in the filtered intrinsic mode function. Recent studies have shown that applying EMD to the acceleration response, due to the crossing of a constant load over a beam finite element model, can be used to detect a single damaged location. In this paper, the technique is further tested using the response of a discretized finite element beam with multiple damaged sections modeled as localized losses of stiffness. The ability of the algorithm to detect more than one damaged section is analysed for a variety of scenarios including a range of bridge lengths, speeds of the moving load and noise levels. The use of a moving average filter on the acceleration response, prior to applying EMD, is shown to improve the sensitivity to damage. The influence of the number of measurement points and their distance to the damaged sections on the accuracy of the predicted damage is also discussed.
Free Vibration Analysis for Layered Shells Accounting of Variable Kinematic and Thermo-Mechanical Coupling
Authors: Brischetto S. , Carrera E.
Published: January 2014

The free vibration analysis of one-layered and two-layered metallic cylindrical shell panels is evaluated in this work. The free frequency values are investigated for both thermo-mechanical and pure mechanical problems. Thermo-mechanical frequencies are calculated by means of a fully coupled thermo-mechanical model where both the displacement and temperature are primary variables in the considered governing equations. Pure mechanical frequencies are obtained from a mechanical model where the effect of the temperature field is not included in the stiffness matrix and the displacement is the only primary variable of the problem. The inclusion of the thermal part in the stiffness matrix gives larger frequencies. Both thermo-mechanical and pure mechanical models are developed in the framework of Carrera's Unified Formulation (CUF) in order to obtain several variable kinematic models. Both equivalent single layer and layer wise approaches are considered for multilayered shells. The use of refined two-dimensional theories for shells permits the evaluation of the effects of the thermo-mechanical coupling for lower and higher order modes, higher frequency values, multilayered configurations, thick and thin shells and several values of the radius of curvature of the shell geometry. It has mainly been concluded that the thermo-mechanical coupling is not influenced by the curvature of the shells, therefore, the main conclusions already given for the plate geometry are here confirmed: – the thermo-mechanical coupling is correctly determined if both the thermal and mechanical parts are correctly approximated; – it is small for each investigated case; – it influences the various vibration modes in different ways; – it has a limited dependence on the considered case, but this dependence vanishes if a global coupling is considered.
Experimental Dynamic Analysis of Nonlinear Beams under Moving Loads
Authors: Bellino A. , Marchesiello S. , Garibaldi L.
Published: January 2014

It is well known that nonlinear systems, as well as linear time-varying systems, are characterized by non-stationary response signals. In this sense, they both show natural frequencies that are not constant over time; this variation has however different origins: for a time-varying system the mass, and possibly the stiffness distributions, are changing over time, while for a nonlinear system the natural frequencies are amplitude-dependent. An interesting case of time-varying system occurs when analyzing the transit of a train over a railway bridge, easily simulated by the crossing of a moving load over a beam. In this case, the presence of a nonlinearity in the beam behaviour can cause a significant alteration of the modal parameters extracted from the linearized model, such that the contributions of the two effects are no more distinguishable.

For this study, some reinforced concrete beams have been tested in the framework of a vast project: these beams show a clear softening nonlinear behaviour, well detectable when the excitation is produced by a hammer (free response). If the passage of a carriage is considered, moreover, the variation of natural frequencies is always larger than expected because of this softening nonlinearity.

The article first analyzes theoretically the two effects on the natural frequencies of a simply supported beam, then a numerical and an experimental tests are presented. The identification procedure is conducted with a linear algorithm called ST-SSI, which has been demonstrated to be appropriate for the analysis of non-stationary signals, in particular in presence of moving masses. The article shows that the nonlinear contribution can be well estimated by using this linear tool but, on the contrary, when also moving masses are present, it is difficult to separate the nonlinear effects from the time varying ones.
Sylvian Fissure and Parietal Anatomy in Children with Autism Spectrum Disorder
Authors: Knaus Tracey A. , Tager-Flusberg Helen , Foundas Anne L.
Published: January 2014

Autism spectrum disorder (ASD) is characterized by deficits in social functioning and language and communication, with restricted interests or stereotyped behaviors. Anatomical differences have been found in the parietal cortex in children with ASD, but parietal subregions and associations between Sylvian fissure (SF) and parietal anatomy have not been explored. In this study, SF length and anterior and posterior parietal volumes were measured on MRI in 30 right-handed boys with ASD and 30 right-handed typically developing boys (7–14 years), matched on age and non-verbal IQ. There was leftward SF and anterior parietal asymmetry, and rightward posterior parietal asymmetry, across groups. There were associations between SF and parietal asymmetries, with slight group differences. Typical SF asymmetry was associated with typical anterior and posterior parietal asymmetry, in both groups. In the atypical SF asymmetry group, controls had atypical parietal asymmetry, whereas in ASD there were more equal numbers of individuals with typical as atypical anterior parietal asymmetry. We did not find significant anatomical-behavioral associations. Our findings of more individuals in the ASD group having a dissociation between cortical asymmetries warrants further investigation of these subgroups and emphasizes the importance of investigating anatomical relationships in addition to group differences in individual regions.
Age-Related Frontal Hyperactivation Observed across Different Working Memory Tasks: An fMRI Study
Authors: Fakhri Mohammad , Sikaroodi Hajir , Maleki Farid , Ali Oghabian Mohammad , Ghanaati Hosein
Published: January 2014

Purpose:To evaluate patterns of activation, convergence and divergence of three functional magnetic resonance imaging (fMRI) Working Memory (WM) tasks in two different age groups. We want to understand potential impact of task and subjects’ age on WM activations as well as most important areas with regard to WM functions.

Materials and methods:Thirty-five healthy volunteers completed visual, verbal, and novel auditory WM tasks. The subjects were selected from age extremes to depict possible impact of normal aging. The General Linear Model was used to report significant activations and the effect of age group. Contrasts revealed differences in activation between tasks, and Combined Task Analysis was performed to determine common regions of activation across tasks.

Results:Most of the observed differences between the tasks were seen in areas that were responsible for feature processing. Frontal regions were mainstay activation areas, regardless of the utilized stimulus. We found an age-related reduction in activity of visual (in visually-presented tasks) and auditory (in auditory task) cortices but an age-related increase in prefrontal cortex for all tasks.

Conclusion:Regardless of the type of the task stimuli, frontal regions are the most important activation areas in WM processing. These areas are also main targets of age-related changes with regard to activation patterns. Our results also indicate that prefrontal overactivity in working memory might be a compensatory effort to mask age-related decline in sensory processing.
Semi-Active Control Using Magnetorhelogical Dampers with Output Feedback and Distributed Sensing
Authors: Chandiramani N.K. , Purohit S.P.
Published: January 2014

Control of seismic response of a building fitted with magnetorheological dampers is considered using Optimal Static Output Feedback (OSOF) for desired damper forces. The Modified Bouc-Wen damper model is used and two control voltage laws based on the MR constraint filter, i.e., Semi-inverse Quadratic Voltage Law and Semi-inverse On-Off Voltage Law, are proposed. These appear to perform at least as well as an existing Clipped Voltage Law. Comparisons with available results from a robust reliability-based controller show OSOF control to be quite effective. Controlled response using OSOF is compared with Linear Quadratic Guassian (LQG) and passive-on controllers. Moderate to substantial reduction in maximum peak/RMS responses is mostly obtained with base configuration of sensors when using OSOF control, and controller CPU time reduces by two orders of magnitude. Parametric studies regarding sensor configuration and state/control weighting matrices are performed in order to obtain effective control. Effective OSOF control requires drift feedback with drift sensor preferably collocated with damper.
Gearbox Vibration Signal Amplitude and Frequency Modulation
Authors: Chaari Fakher , Bartelmus Walter , Zimroz Radoslaw , Fakhfakh Tahar , Haddar Mohamed
Published: January 2014

Gearboxes usually run under fluctuating load conditions during service, however most of papers available in the literature describe models of gearboxes under stationary load conditions. Main task of published papers is fault modeling for their detection. Considering real situation from industry, the assumption of stationarity of load conditions cannot be longer kept. Vibration signals issued from monitoring in maintenance operations differ from mentioned models (due to load non-stationarity) and may be difficult to analyze which lead to erroneous diagnosis of the system. The objective of this paper is to study the influence of time varying load conditions on a gearbox dynamic behavior. To investigate this, a simple spur gear system without defects is modeled. It is subjected to a time varying load. The speed-torque characteristic of the driving motor is considered. The load variation induces speed variation, which causes a variation in the gearmesh stiffness period. Computer simulation shows deep amplitude modulations with sidebands that don't differ from those obtained when there is a defective tooth. In order to put in evidence the time varying load effects, Short Time Fourier Transform and then Smoothed Wigner-Ville distribution are used. Results show that the last one is well suited for the studied case.

The experimental validation presented at the end of the paper confirms the obtained results. Such results offer useful information when diagnosing gear transmissions by avoiding confusing conclusions from vibration signals.
Dynamic Responses of Supported Beams with Intermediate Supports Under Moving Loads
Authors: Zhang Biaobiao , Shepard Steve
Published: January 2014

In this paper, a new beam shape function configuration method for determining transient responses of a finite Euler-Bernoulli beam with two intermediate supports excited by moving pressure wave loads is developed. To clarify this method, this beam structure is excited by the moving sinusoidal loads as an example. Transient responses of this beam structure are investigated and verified by the traditional finite element method. This method can be used to solve transient response problems of moving pressure loads exciting the beam structure with intermediate support. Actually it can be extended to solve other complicated beam structure problems.
Dynamic Effects of Embedded Macro-Fiber Composite Actuators on Ultra-Light Flexible Structures of Repeated Pattern- a Homogenization Approach
Authors: Salehian A. , Seigler T.M.
Published: January 2014

Motivated by deployable satellite technology, this article presents a homogenization model of an inflatable, rigidized lattice structure with distributed macro-fiber composite (MFC) actuation. The model is based upon a general expression for the strain and kinetic energy of a fundamental repeated element of the structure. These expressions are reduced in order and expressed in terms of the strain and displacement components of an equivalent one-dimensional vibration model. The resulting model is used to analyze changes in the structural natural frequencies introduced by the local effects of the added macro-fiber composite actuators for several configurations. A finite element solution is used as a comparison for the homogenization model, and the two are shown to be in good agreement, although the latter requires significantly less computational effort.
Optimization Design of Structures Subjected to Transient Loads Using First and Second Derivatives of Dynamic Displacement and Stress
Authors: Liu Qimao , Zhang Jing , Yan Liubin
Published: January 2014

This paper developed an effective optimization method, i.e., gradient-Hessian matrix-based method or second order method, of frame structures subjected to the transient loads. An algorithm of first and second derivatives of dynamic displacement and stress with respect to design variables is formulated based on the Newmark method. The inequality time-dependent constraint problem is converted into a sequence of appropriately formed time-independent unconstrained problems using the integral interior point penalty function method. The gradient and Hessian matrixes of the integral interior point penalty functions are also computed. Then the Marquardt's method is employed to solve unconstrained problems. The numerical results show that the optimal design method proposed in this paper can obtain the local optimum design of frame structures and sometimes is more efficient than the augmented Lagrange multiplier method.
Effect of Corrosion Damage on the Performance Level of a 25-Year-Old Reinforced Concrete Building
Authors: Yalciner Hakan , Sensoy Serhan , Eren Ozgur
Published: January 2014

Corrosion is a long-term process resulting in the deterioration of the reinforced concrete (RC) structures. Most of the structural problems observed under the impact of either earthquakes or service loads might occur due to corrosion. Therefore, prediction of the remaining service life of a corroding RC structure plays an important role to prevent serious premature damage. In this study, a corroded, 25-year-old high school building which has been demolished at an earlier time was analyzed as a function of corrosion rate. Bond-slip relationships were taken into account in nonlinear analyses as a function of corrosion rate for different time periods (i.e., non-corroded (t: 0), existing (t: 25) and 50 years after construction); and they were used to ensure the effect of time-dependent slip rotation on the global structural behaviour by modifying the target post-yield stiffness of each structural member. Nonlinear push-over analyses were performed by defining the time-dependent plastic hinge properties as a consequence of corrosion effects. In order to define the performance levels of three different time periods, nonlinear incremental dynamic analyses (IDA) were performed for 20 earthquake ground motion records as a function of corrosion rate. Results showed that bond-slip relationship between concrete and steel is very important in evaluating the non-linear behaviour of corroded RC structures.
An Alarm Method for a Loose Parts Monitoring System
Authors: Cao Yanlong , He Yuanfeng , Zheng Huawen , Yang Jiangxin
Published: January 2014

In order to reduce the false alarm rate and missed detection rate of a Loose Parts Monitoring System (LPMS) for Nuclear Power Plants, a new hybrid method combining Linear Predictive Coding (LPC) and Support Vector Machine (SVM) together to discriminate the loose part signal is proposed. The alarm process is divided into two stages. The first stage is to detect the weak burst signal for reducing the missed detection rate. Signal is whitened to improve the SNR, and then the weak burst signal can be detected by checking the short-term Root Mean Square (RMS) of the whitened signal. The second stage is to identify the detected burst signal for reducing the false alarm rate. Taking the signal's LPC coefficients as its characteristics, SVM is then utilized to determine whether the signal is generated by the impact of a loose part. The experiment shows that whitening the signal in the first stage can detect a loose part burst signal even at very low SNR and thusly can significantly reduce the rate of missed detection. In the second alarm stage, the loose parts' burst signal can be distinguished from pulse disturbance by using SVM. Even when the SNR is −15 dB, the system can still achieve a 100% recognition rate
Familial Comorbidity of Bipolar Disorder and Multiple Sclerosis: Genetic Susceptibility, Coexistence or Causal Relationship?
Authors: Kosmidis Mary H. , Bozikas Vasilis P. , Giannouli Vaitsa , Karavatos Athanasios , Fokas Konstantinos
Published: January 2014

Our purpose in undertaking the present study was to examine the hypotheses proposed for explaining the frequent comorbidity of bipolar disorder and multiple sclerosis. One hypothesis posits that, when there is comorbidity, MS plays a causal role in psychiatric manifestations. Another suggests that both disorders have a common underlying physiological process that increases the likelihood of their co-occurrence. We examined two adult siblings with comorbidity and their relatives, including three generations of family members with psychiatric morbidity. We found an extensive multigenerational history of bipolar disorder in this family. This history would seem to support the hypothesis of a common underlying brain process (potentially genetically-based) to explain the comorbidity of BD and MS, but cannot clarify whether this comorbidity implies a relationship between the two disorders or merely reflects parallel processes of brain deterioration. We cannot, however, rule out the possibility of a subclinical MS-related process leading to the early manifestation of BD, with MS appearing much later in time, or even a third, undetermined factor, leading to familial comorbidity. Although we have insufficient information to support either hypothesis definitively, we present the familial cases as a springboard for a discussion of dilemmas related to teasing apart MS and BD comorbidity. Further observation of the clinical course of the younger family members, who have not yet shown any neurological signs, over the next few years may elucidate the current picture further.
Aerosolization of Water Ejected from a Full Container Impacted by Bomb Fragments
Authors: Stockham Leo W. , Fry Jr. Richard N. , Graham Paul W. , Pierce Todd H.
Published: January 2014

In assessing the potential collateral effects of bomb attacks on tanks of stored liquids, it is useful to separate the liquid that is aerosolized as an escaping cloud from that which remains inside the tank or rapidly falls to the nearby ground. One relationship currently in use partitions the two categories using a linear model of aerosolized fraction versus fragment energy deposited per unit mass of liquid which is based on calculations and a few test data points. Since this model is incorporated in popular programs used by an expanding number of first responders to assess potential hazards, there is a need for high-confidence test data across the parameter space of interest to improve and/or validate the model. Such a series of tests was conducted during November of 2008 in which 7.57-liter (ℓ) sized cans of water were impacted with fragments of known mass using scored cased explosive charges. Impact velocities were measured, and the remaining water in the can and on the nearby ground platform was collected and weighed. The missing water was assumed to be aerosolized. This new data establishes an S-curve as a more accurate relationship between aerosolized fraction (AF) and the fragment energy deposited per unit mass of liquid in the container.
Unpicking the Semantic Impairment in Alzheimer’s Disease: Qualitative Changes with Disease Severity
Authors: Corbett Faye , Jefferies Elizabeth , Burns Alistair , Ralph Matthew A. Lambon
Published: January 2014

Despite a vast literature examining semantic impairment in Alzheimer's disease (AD), consensus regarding the nature of the deficit remains elusive. We re-considered this issue in the context of a framework that assumes semantic cognition can break down in two ways: (1) core semantic representations can degrade or (2) cognitive control mechanisms can become impaired [1]. We hypothesised and confirmed that the nature of semantic impairment in AD changes with disease severity. Patients at mild or severe stages of the disorder exhibited impairment across various semantic tasks but the nature of those deficits differed qualitatively for the two groups. Commensurate with early dysfunction of the cognitive control, temporoparietal-frontal-cingulate network, characteristics of deregulated semantic cognition were exhibited by the mild AD cases. In contrast, the severe AD group reproduced features of additional degradation of core semantic representations. These results suggest that spread of pathology into lateral anterior temporal lobes in later stage AD produces degradation of semantic representations, exacerbating the already deregulated system. Moreover, the dual nature of severe patients’ impairment was highlighted by disproportionately poor performance on tasks placing high demand on both conceptual knowledge and control processes–e.g., category fluency.
Constitutive Theories for Woven Composite Structures Subjected to Shock Loading; Experimental Validation Using a Conical Shock Tube
Authors: Hufner David R.
Published: January 2014

Woven polymer-based composites are currently used in a wide range of marine applications. These materials often exhibit highly nonlinear, rate dependent, anisotropic behavior under shock loadings. Correlation to transient response data, beyond an initial peak, is often difficult. The state of damage evolves throughout the time history and the unloading response varies based on the amount, and nature of, the accumulated damage. Constitutive theories that address the loading and unloading responses have been developed and integrated with each other. A complete theory, applicable to transient dynamic analysis, is presented. The model is implemented within the commercial finite element code, Abaqus, in the form of a user material subroutine. In this study, the conical shock tube is used to experimentally reproduce the high strain rates and fluid structure interactions typical of underwater shock loadings. The conical shock tube data is used to validate analytical model predictions. Simulation results are in good agreement with test data.