bluuebunny/crossref_metadata_2025 huggingface dataset:
Association between Hypotension, Low Ejection Fraction and Cognitive Performance in Cardiac Patients
Authors: Gottesman Rebecca F. , Grega Maura A. , Bailey Maryanne M. , Zeger Scott L. , Baumgartner William A. , McKhann Guy M. , Selnes Ola A.
Published: January 2014

Background and Purpose:Impaired cardiac function can adversely affect the brain via decreased perfusion. The purpose of this study was to determine if cardiac ejection fraction (EF) is associated with cognitive performance, and whether this is modified by low blood pressure.

Methods:Neuropsychological testing evaluating multiple cognitive domains, measurement of mean arterial pressure (MAP), and measurement of EF were performed in 234 individuals with coronary artery disease. The association between level of EF and performance within each cognitive domain was explored, as was the interaction between low MAP and EF.

Results:Adjusted global cognitive performance, as well as performance in visuoconstruction and motor speed, was significantly directly associated with cardiac EF. This relationship was not entirely linear, with a steeper association between EF and cognition at lower levels of EF than at higher levels. Patients with low EF and low MAP at the time of testing had worse cognitive performance than either of these alone, particularly for the global and motor speed cognitive scores.

Conclusions:Low EF may be associated with worse cognitive performance, particularly among individuals with low MAP and for cognitive domains typically associated with vascular cognitive impairment. Further care should be paid to hypotension in the setting of heart failure, as this may exacerbate cerebral hypoperfusion.
Identification of Damage in a Beam Structure by Using Mode Shape Curvature Squares
Authors: Rucevskis S. , Wesolowski M.
Published: January 2014

During the last decades a great variety of methods have been proposed for damage detection by using the dynamic structure characteristics, however, most of them require modal data of the structure for the healthy state as a reference. In this paper the applicability of the mode shape curvature squares determined from only the damaged state of the structure for damage detection in a beam structure is studied. To establish the method, two aluminium beams containing different-size mill-cut damage at different locations are tested by using the experimentally measured modal data. The experimental modal frequencies and the corresponding mode shapes are obtained by using a scanning laser vibrometer with a PZT actuator. From the mode shapes, mode shape curvatures are obtained by using a central difference approximation. With the example of the beams with free-free and clamped boundary conditions, it is shown that the mode shape curvature squares can be used to detect damage in the structures. Further, the extent of a mill-cut damage is identified via modal frequencies by using a mixed numerical-experimental technique. The method is based on the minimization of the discrepancy between the numerically calculated and experimentally measured frequencies.
Does Diabetes Mellitus Alter the Onset and Clinical Course of Vascular Dementia?
Authors: Murthy Santosh B. , Jawaid Ali , Qureshi Salah U. , Kalkonde Yogeshwar , Wilson Andrew M. , Johnson Michael L. , Kunik Mark E. , Schulz Paul E.
Published: January 2014

Background:Vascular dementia (VaD) is the second most common dementing illness. Multiple risk factors are associated with VaD, but the individual contribution of each to disease onset and progression is unclear. We examined the relationship between diabetes mellitus type 2 (DM) and the clinical variables of VaD.

Methods:Data from 593 patients evaluated between June, 2003 and June, 2008 for cognitive impairment were prospectively entered into a database. We retrospectively reviewed the charts of 63 patients who fit the NINDSAIREN criteria for VaD. The patients were divided into those with DM (VaDDM, n = 29) and those without DM(VaD,n= 34). The groups were compared with regard to multiple variables.

Results:Patients with DM had a significantly earlier onset of VaD (71.9 ± 6.54 vs. 77.2 ± 6.03,p< 0.001), a faster rate of decline per year on the mini mental state examination (MMSE; 3.60 ± 1.82 vs. 2.54 ± 1.60 points,p= 0.02), and a greater prevalence of neuropsychiatric symptoms at the time of diagnosis (62% vs. 21%,p= 0.02).

Conclusions:A history of premorbid DM was associated with an earlier onset and faster cognitive deterioration in VaD. Moreover, DM was associated with neuropsychiatric symptoms in patients with VaD. A larger study is needed to verify these associations. It will be important to investigate whether better glycemic control will mitigate the potential effects of DM on VaD.
Decision Making under Risk Condition in Patients with Parkinson’s Disease: A Behavioural and fMRI Study
Authors: Labudda Kirsten , Brand Matthias , Mertens Markus , Ollech Isabelle , Markowitsch Hans J. , Woermann Friedrich G.
Published: January 2014

We aimed to study whether previously described impairment in decision making under risky conditions in patients with Parkinson's disease (PD) is affected by deficits in using information about potential incentives or by processing feedback (in terms of fictitious gains and losses following each decision). Additionally, we studied whether the neural correlates of using explicit information in decision making under risk differ between PD patients and healthy subjects. We investigated ten cognitively intact PD patients and twelve healthy subjects with the Game of Dice Task (GDT) to assess risky decision making, and with an fMRI paradigm to analyse the neural correlates of information integration in the deliberative decision phase. Behaviourally, PD patients showed selective impairment in the GDT but not on the fMRI task that did not include a feedback component. Healthy subjects exhibited lateral prefrontal, anterior cingulate and parietal activations when integrating decision-relevant information. Despite similar behavioural patterns on the fMRI task, patients exhibited reduced parietal activation. Behavioural results suggest that PD patients’ deficits in risky decision making are dominated by impaired feedback utilization not compensable by intact cognitive functions. Our fMRI results suggest similarities but also differences in neural correlates when using explicit information for the decision process, potentially indicating different strategy application even if the interfering feedback component is excluded.
The Use of Transmissibility Properties to Estimate FRFs on Modified Structures
Authors: Almeida R.A.B. , Urgueira A.P.V. , Maia N.M.M.
Published: January 2014

When deriving an experimental model from Frequency Response Functions (FRFs), it may happen that the measurement of certain FRFs is impossible. This may be an important issue, mainly in the field of condition monitoring and damage detection, since some points of interest may become inaccessible in operational conditions. In this circumstance, it is useful to have some tools that can provide the prediction of such dynamic information. The transmissibility concept, extended to a general multiple degree-of-freedom system, can play an important role to circumvent these situations. The authors have shown in previous works that the estimation of such FRFs can be made possible by invoking important properties associated with the transmissibility function. The objective of this work is to evaluate different sets of FRFs, estimated by using the transmissibility concept and its associated properties, in an actual continuous structure to which different patterns of structural modification are applied. A supplementary study in this work shows that some of the sets for applied forces/known responses can better estimate the FRF data.
Recovery from Transient Global Amnesia Following Restoration of Hippocampal and Fronto–Cingulate Perfusion
Authors: Caffarra Paolo , Concari Letizia , Gardini Simona , Spaggiari Sabrina , Dieci Francesca , Copelli Sandra , Ghetti Caterina , Venneri Annalena
Published: January 2014

A patient who suffered a transient global amnesia (TGA) attack underwent regional cerebral blood flow (rCBF) SPECT imaging and neuropsychological testing in the acute phase, after one month and after one year. Neuropsychological testing in the acute phase showed a pattern of anterograde and retrograde amnesia, whereas memory was within age normal limits at follow up. SPECT data were analysed with a within subject comparison and also compared with those of a group of healthy controls. Within subject comparison between the one month follow up and the acute phase detected increases in rCBF in the hippocampus bilaterally; further rCBF increases in the right hippocampus were detected after one year. Compared to controls, significant hypoperfusion was found in the right precentral, cingulate and medial frontal gyri in the acute phase; after one month significant hypoperfusion was detected in the right precentral and cingulate gyri and the left postcentral gyrus; after one year no significant hypoperfusion appeared. The restoration of memory was paralleled by rCBF increases in the hippocampus and fronto-limbic-parietal cortex; after one year neither significant rCBF differences nor cognitive deficits were detectable. In conclusion, these data indicate that TGA had no long lasting cognitive and neural alterations in this patient.
Assessment of an Existing RC Building before and after Strengthening Using Nonlinear Static Procedure and Incremental Dynamic Analysis
Authors: Hedayat Amir A. , Yalciner Hakan
Published: January 2014

Inadequate attention during design and construction of some of reinforced concrete (RC) buildings in Cyprus has raised questions about the performance level of these existing buildings under future earthquakes. This study aimed to assess the seismic structural response of a four story existing RC building. For this purpose, first, the weak structural elements (e.g.\ the not safety column-beam joints and weak columns) were detected using linear static procedure (LSP) analyses on the basis of Turkish earthquake code. Then, two different strengthening methods were examined. In the first method which is common in Cyprus, the existing building was strengthened based on LSP, using column jacketing to satisfy seismic code requirements to remove the weak elements. The second strengthening method was carried out using nonlinear static procedures (NSP) to achieve the basic safety objective (BSO) performance level described in FEMA 356. For existing and both strengthened structures, pushover curves were obtained and following FEMA 356, performance points were calculated and compared. The seismic responses of existing and strengthened buildings were also assessed using incremental dynamic analyses (IDA). Nonlinear dynamic time history analyses have been performed by using SDOF models of these buildings under action of different scales of 20 ground motion records. Then IDA curves for each earthquake have been constructed. Limit – states at each performance level have been defined and summarizing the multi – record IDA curves, 16%, 50% and 84% fractile curves were obtained. Since selected structure represents common existing buildings in Cyprus, probabilistic structural damage estimation fragility curves were also obtained in terms of peak ground acceleration (PGA) for each considered performance level. Results showed that the strengthening method based on the NSP to satisfy the BSO requirements is much more effective than the one based on the LSP to improve the building performance and to reduce the probability of exceeding of limit states IO, LS and CP at any seismic zone.
Modal Characteristics of Two Operating Power Transmission Poles
Authors: Chen Shen-En , Dai Kaoshan
Published: January 2014

Unique conductor-pole couplings complicate the dynamic behaviors of electric transmission pole line systems. Finite element modeling is performed on two typical transmission poles used in southeastern USA – a steel pole and a prestressed concrete pole. The two poles are representative of unique structure types: a heavy rod-like structure and a lightweight, shell-type structure. Since coupling issues between the pole and the cable introduce great complexities for modeling the pole line system, simplified numerical models are used. Limited full-scale modal test results are presented to verify the numerical models. The prestressed concrete pole is shown to be easier for mode identification than the steel pole – but both numerical models show complicated coupled vibration modes. This study is part of a larger study to establish an understanding of the dynamic response analyses of power grid under ground vibrations.
Structural Health Monitoring System Using Piezoelectric Networks with Tuned Lamb Waves
Authors: Rocha Bruno , Silva Carlos , Suleman Afzal
Published: January 2014

The paper presents a structural health monitoring system based on propagation of tuned Lamb waves and their interference with discontinuities. The dispersion curves are studied to determine the appropriate type and dimension of transducers and to select the optimum scanning frequencies and relevant propagation modes. A piezoelectric sensor network was implemented in an aluminum plate in order to generate and to sense the wave propagation and associated reflections. The algorithm developed for damage detection relies on the comparison of undamaged and damaged responses of the structure. Combinations of filters and statistical methods were applied to detect differences in the sensor signals acquired for the two different states (damaged and undamaged), corresponding to damage reflections. In order to eliminate the false positives due to noise, a probability analysis is performed to obtain the final damage position. The software designed for the current application allows the automatic calculation of dispersion curves, it executes the scans, performs data processing, executes the detection algorithm and presents the probable damages and their positions in a graphical form. Experiments were performed with the introduction of cumulative damages in the plate such as surface and through-the-thickness holes and cuts, ranging from 7 mm to 1 mm in diameter. Additionally, a stringer was attached to the plate by a single rivet line to simulate an aircraft skin structure. Cuts originating from rivet holes and connecting adjacent rivets, as well as loosened rivets were detected by the system. The introduction of the stringer resulted in a loss of precision in the determination of the radial position of the damages near it. Also, the network revealed significant difficulties in the detection of damages beyond the stringer.
Performance Analysis of a Hybrid One-Sided Magnetic Exciter Mounted on a Piezoelectric Stack
Authors: Nandi A. , Neogy S.
Published: January 2014

The present work proposes a non-contact hybrid exciter especially useful for harmonic excitation of lightly damped structures/rotors. In the proposed exciter an electromagnet is placed on a piezoelectric stack and the extension of the piezoelectric stack is made almost equal to the displacement of the structure using a simple tracking control. This largely eliminates stiffness coupling between the structure/rotor and the exciter and non-linearity in the excitation force due to the vibration of the structure/rotor. The stiffness and inertia of the piezoelectric stack is considered in the analysis. A SIMULINK model of the combined structure and the exciter is developed for a full time-domain simulation of the excitation system.
Comparing Two Strategies to Model Uncertainties in Structural Dynamics
Authors: Sampaio Rubens , Cataldo Edson
Published: January 2014

In the modeling of dynamical systems, uncertainties are present and they must be taken into account to improve the prediction of the models. Some strategies have been used to model uncertainties and the aim of this work is to discuss two of those strategies and to compare them. This will be done using the simplest model possible: a two d.o.f. (degrees of freedom) dynamical system. A simple system is used because it is very helpful to assure a better understanding and, consequently, comparison of the strategies. The first strategy (called parametric strategy) consists in taking each spring stiffness as uncertain and a random variable is associated to each one of them. The second strategy (called nonparametric strategy) is more general and considers the whole stiffness matrix as uncertain, and associates a random matrix to it. In both cases, the probability density functions either of the random parameters or of the random matrix are deduced from the Maximum Entropy Principle using only the available information. With this example, some important results can be discussed, which cannot be assessed when complex structures are used, as it has been done so far in the literature. One important element for the comparison of the two strategies is the analysis of the samples spaces and the how to compare them.
An fMRI Study of Intra-Individual Functional Topography in the Human Cerebellum
Authors: Stoodley Catherine J. , Valera Eve M. , Schmahmann Jeremy D.
Published: January 2014

Neuroimaging studies report cerebellar activation during both motor and non-motor paradigms, and suggest a functional topography within the cerebellum. Sensorimotor tasks activate the anterior lobe, parts of lobule VI, and lobule VIII, whereas higher-level tasks activate lobules VI and VII in the posterior lobe. To determine whether these activation patterns are evident at a single-subject level, we conducted functional magnetic resonance imaging (fMRI) during five tasks investigating sensorimotor (finger tapping), language (verb generation), spatial (mental rotation), working memory (N-back), and emotional processing (viewing images from the International Affective Picture System). Finger tapping activated the ipsilateral anterior lobe (lobules IV-V) as well as lobules VI and VIII. Activation during verb generation was found in right lobules VII and VIIIA. Mental rotation activated left-lateralized clusters in lobules VII-VIIIA, VI-Crus I, and midline VIIAt. The N-back task showed bilateral activation in right lobules VI-Crus I and left lobules VIIB-VIIIA. Cerebellar activation was evident bilaterally in lobule VI while viewing arousing vs. neutral images. This fMRI study provides the first proof of principle demonstration that there is topographic organization of motor execution vs. cognitive/emotional domains within the cerebellum of a single individual, likely reflecting the anatomical specificity of cerebro-cerebellar circuits underlying different task domains. Inter-subject variability of motor and non-motor topography remains to be determined.
Study of the Fatigue Life and Weight Optimization of an Automobile Aluminium Alloy Part under Random Road Excitation
Authors: Saoudi A. , Bouazara M. , Marceau D.
Published: January 2014

Weight optimization of aluminium alloy automobile parts reduces their weight while maintaining their natural frequency away from the frequency range of the power spectral density (PSD) that describes the roadway profile. We present our algorithm developed to optimize the weight of an aluminium alloy sample relative to its fatigue life. This new method reduces calculation time; It takes into account the multipoint excitation signal shifted in time, giving a tangle of the constraint signals of the material mesh elements; It also reduces programming costs. We model an aluminium alloy lower vehicle suspension arm under real conditions. The natural frequencies of the part are inversely proportional to the mass and proportional to flexural stiffness, and assumed to be invariable during the process of optimization. The objective function developed in this study is linked directly to the notion of fatigue. The method identifies elements that have less than 10% of the fatigue life of the part's critical element. We achieved a weight loss of 5 to 11% by removing the identified elements following the first iteration.
Eigenpath Following for Systems with Symmetric Complex-Valued Stiffness Matrices
Authors: Miller U. , Bograd S. , Schmidt A. , Gaul L.
Published: January 2014

A vibration analysis of a structure with joints is performed. The simulation is conducted with finite element software capable of performing a numeric modal analysis with hysteretic damping assumption. The joints are modeled with thin layer elements, representing dissipation and stiffness of the joints. The matrices describing the system consist of the mass, as well as real and complex-valued stiffness matrices. If the eigenvalues of this system are found in one step, due to the mode crossing occurring for the closely spaced modes, it is difficult and time consuming to assign calculated modal damping factors to the corresponding undamped eigenvalues. In order to avoid this problem, an eigenvalue following method is used. The outcome of the solution is the graphical presentation of continuous eigenvalue paths, showing the change in the eigenvalues from the undamped to the fully damped case. For every undamped eigenvalue exists its equivalent eigenfrequency and damping factor that can be used for further numerical analysis.

In scope of this article a Predictor-Corrector and a Rayleigh-Quotient Iteration algorithms are applied to the problem. The algorithms are tested specifically on the type of matrices resulting from the weakly damped hysteretic formulation arising from the simulation of metallic structures with joints.
The Spectrum Dip of Deck Mounted Systems
Authors: Scavuzzo R.J. , Hill G.D. , Saxe P.W.
Published: January 2014

In this paper, a detailed model of a ship deck and attached dynamic systems was developed and subjected to dynamic studies using two different shock inputs: a triangular shaped velocity pulse and the vertical motion of the innerbottom of the standard Floating Shock Platform (FSP). Two studies were conducted, one considering four single degree-of-freedom systems attached at various deck locations and another considering a three-mass system attached at one location. The two shock inputs were used only for the multi-mass system study. The triangular pulse was used for the four single degree-of-freedom systems study. For the single degree-of-freedom systems study, shock spectra were first calculated at the four mounting locations assuming the oscillators were not present. Then the oscillator systems were added to these grid points to determine the change in the shock spectra. First, the oscillators were added one at a time, and then all the oscillators were added to the deck. The multi-mass system was analyzed using both shock inputs. First, the fixed-base modal masses and frequencies were determined. Then, the system as a whole was attached to the deck and the spectrum values at the base point were determined and compared to those for the free deck case. In the last step each mode of the multi-mass system, represented by a single degree-of-freedom system with the modal mass and appropriate spring stiffness, was considered individually to determine the spectrum responses. Results of the free deck, the entire system and individual modal responses are compared.
Prevention of Pressure Oscillations in Modeling a Cavitating Acoustic Fluid
Authors: Klenow B. , Brown A.
Published: January 2014

Cavitation effects play an important role in the UNDEX loading of a structure. For far-field UNDEX, the structural loading is affected by the formation of local and bulk cavitation regions, and the pressure pulses resulting from the closure of the cavitation regions. A common approach to numerically modeling cavitation in far-field underwater explosions is Cavitating Acoustic Finite Elements (CAFE) and more recently Cavitating Acoustic Spectral Elements (CASE). Treatment of cavitation in this manner causes spurious pressure oscillations which must be treated by a numerical damping scheme. The focus of this paper is to investigate the severity of these oscillations on the structural response and a possible improvement to CAFE, based on the original Boris and Book Flux-Corrected Transport algorithm on structured meshes [6], to limit oscillations without the energy loss associated with the current damping schemes.
Remediation Effects on N170 and P300 in Children with Developmental Dyslexia
Authors: Jucla Mélanie , Nenert Rodolphe , Chaix Yves , Demonet Jean-François
Published: January 2014

This study aimed at investigating the ERP correlates (N170 and P300 components) of a multimodal training program focused in dyslexia. ERPs were obtained from 32 electrodes in 24 French children with developmental dyslexia (mean age 10 years 7 months) during a visual lexical decision task. All the children received two intensive two-month evidence-based training programs: one based on phonemic awareness and the other on visual and orthographic processing in a cross-over design. Ten control children matched on chronological age were also tested. We showed dissociation between N170, P300 and behavioral improvement. In the dyslexic group, P300 amplitude decreased for non-words and words as the latter yielded performance improvement. In the control group, the same effect was observed for pseudo-words. At the same time, the opposite pattern occurred for the N170 latency, which was shortened for pseudo-words and pseudo-homophones in the dyslexic group and for words in the typically achieving children. We argue that training might modulate cortical activity in dyslexic children in a visual word recognition task. Considering the well-known implication of P300 in attentional processes, our results reflect the strong link between reading skill improvement after remediation and visual attentional process maturation.
Transient Response of Partially-Bonded Sandwich Plates Subject to Underwater Explosions
Authors: Liu Zhanke , Young Yin L. , Motley Michael R.
Published: January 2014

This paper investigated the influence of interfacial bonding on the transient response of sandwich plates subject to underwater explosions. It was found that un-bonded sandwich plates receive lower impact energy, and are able to dissipate more energy through plastic deformation of the foam core, than perfectly bonded plates. Consequently, interfacial de-bonding leads to lower net energy transfer from the explosion to the target structure although it also increases the structural deformation due to stiffness reduction. Parametric studies showed that theadvantage(diminishing of net energy transfer) is more significant than thedisadvantage(magnification of the interface deflection). Thus, interfacial de-bonding through active/passive mechanisms may be beneficial for blast-resistant designs.
The Contribution of the Dorsolateral Prefrontal Cortex in Full and Divided Encoding: A Paired-Pulse Transcranial Magnetic Stimulation Study
Authors: Blanchet Sophie , Gagnon Geneviève , Schneider Cyril
Published: January 2014

This research investigated the contribution of the dorsolateral prefrontal cortex (DLPFC) in the attentional resources in episodic encoding for both verbal and non-verbal material. Paired-pulse transcranial magnetic stimulations (TMS) were used to interfere transiently with either the left or right DLPFC during encoding under full attention (FA) or under divided attention (DA) in a recognition paradigm using words and random shapes. Participants recognized fewer items after TMS over the left DLPFC than over the right DLPFC during FA encoding. However, TMS over the left DLPFC did not impair performance when compared to sham condition. Conversely, participants produced fewer items after TMS over the right DLPFC in DA encoding compared to sham condition, but not compared to TMS over the left DLPFC. These effects were found for both words and random shapes. These results suggest that the right DLPFC play an important role in successful encoding with a concomitant task regardless of the type of material.
Modelling of Damping Force of Dynamically Loaded Specimen of Polyurethane Foam in Dependence on Its Density
Authors: Cirkl David
Published: January 2014

Article deals with measurement and modelling of damping force of polyurethane foam specimen being compressed. The specimens were taken from car seats and differ by material density. For modelling of damping force during harmonical kinematical excitation the explicit formula is used. Its parameters are found by means of method based on evaluation of energy dissipated during one loading cycle and also on evaluation of position of damping force extreme.
Fuzzy Sliding Mode Control of Plate Vibrations
Authors: Sharma Manu , Singh S.P.
Published: January 2014

In this paper, fuzzy logic is meshed with sliding mode control, in order to control vibrations of a cantilevered plate. Test plate is instrumented with a piezoelectric sensor patch and a piezoelectric actuator patch. Finite element method is used to obtain mathematical model of the test plate. A design approach of a sliding mode controller for linear systems with mismatched time-varying uncertainties is used in this paper. It is found that chattering around the sliding surface in the sliding mode control can be checked by the proposed fuzzy sliding mode control approach. With presented fuzzy sliding mode approach the actuator voltage time response has a smooth decay. This is important because an abrupt decay can excite higher modes in the structure. Fuzzy rule base consisting of nine rules, is generated from the sliding mode inequality. Experimental implementation of the control approach verify the theoretical findings. For experimental implementation, size of the problem is reduced using modal truncation technique. Modal displacements as well as velocities of first two modes are observed using real-time kalman observer. Real time implementation of fuzzy logic based control has always been a challenge because a given set of rules has to be executed in every sampling interval. Results in this paper establish feasibility of experimental implementation of presented fuzzy logic based controller for active vibration control.
Target Loading from a Submerged Explosion
Authors: Wardlaw Andrew , Fourney William , Leiste Ulrich
Published: January 2014

The pressure on a flat plate suspended over a submerged detonation is measured and simulated. Calculation and experiment are in relatively good agreement, although there is variation in experimental results and simulations are sensitive, near the centerline, to the computational details. This sensitivity is linked to the instability of the accelerating plume, typical of a Richtmyer-Meshkov instability. The plate loading features an initial force at plate center, followed by an expanding circular loading pattern. The initial load is due to plume impact, while the circular load arises from the impact of water transported up the edges of the explosion cavity.
Limitations of Smoothening Functions for Automotive Vibro-Impact Problems
Authors: Zhang Zhiwei , Singh Rajendra , Crowther Ashley R.
Published: January 2014

Nonlinear torsional models are used to analyze automotive transmission rattle problems and find solutions to reduce noise, vibration and dynamic loads. The torsional stiffness and inertial distribution of such systems show that the underlying mathematical problem is numerically stiff. In addition, the clearance nonlinearities in the gear meshes introduce discontinuous functions. Both factors affect the efficacy of time domain integration and smoothening functions are widely used to overcome computational difficulties and improve the simulation. In this paper, alternate smoothening functions are studied for their influence on the numerical solutions and their impact on global convergence and computation times. In particular, four smoothening functions (arctan, hyperbolic-cosine, hyperbolic-tan and quintic-spline) are applied to a five-degree-of-freedom generic torsional system with two backlash (clearance) elements. Each function is assessed via a global convergence metric across an excitation map (a design of experiment). Regions of the excitation map, along with multiple solutions, are studied and the implications to assessing convergence are critically examined. It is observed that smoothening functions do not lead to better convergence in many cases. The smoothening parameter needs to be carefully selected, or over-smoothened solutions may be found. The system studied is representative of a typical automotive rattle problem and it was found that benefits were limited from applying such smoothening functions.
The Global Workspace (GW) Theory of Consciousness and Epilepsy
Authors: Bartolomei Fabrice , Naccache Lionel
Published: January 2014

The global workspace (GW) theory proposes that conscious processing results from coherent neuronal activity between widely distributed brain regions, with fronto-parietal associative cortices as key elements. In this model, transition between conscious and non conscious states are predicted to be caused by abrupt non-linear massive changes of the level of coherence within this distributed neural space. Epileptic seizures offer a unique model to explore the validity of this central hypothesis. Seizures are often characterized by the occurrence of brutal alterations of consciousness (AOC) which are largely negatively impacting patients' lives. Recently, we have shown that these sudden AOC are contemporary to non-linear increases of neural synchrony within distant cortico-cortical and cortico-thalamic networks. We interpreted these results in the light of GW theory, and suggested that excessive synchrony could prevent this distributed network to reach the minimal level of differentiation and complexity necessary to the coding of conscious representations. These observations both confirm some predictions of the GW model, and further specify the physiological window of neural coherence (minimum and maximum) associated with conscious processing.
The Presence of Consciousness in Absence Seizures
Authors: Bayne Tim
Published: January 2014

This paper examines three respects in which the study of epileptic absence seizures promises to inform our understanding of consciousness. Firstly, it has the potential to bear on debates concerning the behavioural and cognitive functions associated with consciousness. Secondly, it has the potential to illuminate the relationship between background states (or ‘levels’) of consciousness and the contents of consciousness. Thirdly, it has the potential to bear on our understanding of the unity of consciousness.
Vibro-Impact Response of a Cracked Bar
Authors: Hiwarkar Vikrant R. , Babitsky Vladimir I. , Silberschmidt Vadim V.
Published: January 2014

The presence of a crack in a structure affects its dynamic behaviour under working conditions. Cracks introduce nonlinearities into the system; the use of such nonlinearities for damage detection should be investigated. A model of a one-dimensional cracked cantilever bar subjected to longitudinal harmonic excitation is used to analyse a vibro-impact response as a way to monitor structural health. The effect of contact nonlinearity due to crack's faces interaction is considered. This nonlinear information is obtained based on a combination of the analytical technique and the Matlab-Simulink computation. The procedure uses a numerical approximation for dynamic compliance operators and a nonlinear model of contact faces interaction implemented numerically as a nonlinear feedback. Nonlinear resonant phenomena due to vibro-impact interaction in the cracked bar are obtained and analysed. A distribution of the higher harmonics along the bar length, generated due to the nonlinear response of the crack, is revealed as a function of the distance from the crack. Recommendations on structural health monitoring of cracked bars due to contact nonlinearity are presented
Assessing Executive Abilities Following Acute Stroke with the Trail Making Test and Digit Span
Authors: Tamez Elaine , Myerson Joel , Morris Lucy , White Desirée A. , Baum Carolyn , Connor Lisa Tabor
Published: January 2014

The Trail Making Test and Digit Span are neuropsychological tests widely used to assess executive abilities following stroke. The Trails B and Digits Backward conditions of these tests are thought to be more sensitive to executive impairment related to frontal lobe dysfunction than the Trails A and Digits Forward conditions. Trails B and Digits Backward are also thought to be more sensitive to brain damage in general. Data from the Stroke and Lesion Registry maintained by the Washington University Cognitive Rehabilitation Research Group were analyzed to compare the effects of frontal versus nonfrontal strokes and to assess the effects of stroke severity. Results showed that the performance of patients with frontal and nonfrontal strokes was comparable in each condition of both the Trail Making Test and Digit Span, providing no support for the widely held belief that Trails B and Digits Backward are more sensitive to frontal lobe damage. Further, Trails A was as strongly correlated with stroke severity as Trails B, whereas Digits Backward was more strongly correlated with stroke severity than Digits Forward. Overall, the Trail Making Test and Digit Span are sensitive to brain damage but do not differentiate between patients with frontal versus nonfrontal stroke.
Emotional Dysfunction in Parkinson’s Disease
Authors: Blonder Lee X. , Slevin John T.
Published: January 2014

In addition to motor symptomatology, idiopathic Parkinson’s disease is characterized by emotional dysfunction. Depression affects some 30 to 40 percent of Parkinson patients and other psychiatric co-morbidities include anxiety and apathy. Neuropsychological and neuroimaging studies of emotional dysfunction in Parkinson patients suggest abnormalities involving mesolimbic and mesocortical dopaminergic pathways. There is also evidence suggesting that the interaction between serotonin and dopamine systems is important in the understanding and treatment of mood disorders in Parkinson’s disease. In this review we discuss the neuropsychiatric abnormalities that accompany Parkinson's disease and describe their neuropsychological, neuropharmacologic, and neuroimaging concomitants.
Shapes of Obstacles in the Longitudinal Road Profile
Authors: Kropáč Oldřich , Múčka Peter
Published: January 2014

A voluminous set of longitudinal road profiles gathered from the Long Term Pavement Performance (LTPP) program was processed using median filtering to separate individual large obstacles from the basic quasi-homogeneous random road unevenness. The shapes of 16590 obstacles were analysed partitioned into four sub-groups according to the asphalt-concrete vs. cement-concrete road surfaces, and positive (bumps) vs. negative (potholes) vertical elevations. The empirical obstacle shapes were fitted using seven symmetric and two asymmetric analytical shapes. Based on the root mean square error (RMSE) criterion and accounting for some practical aspects connected with the possible use for the simulation of road profiles with obstacles generalized parabolic shapes (power function) and half-sine shapes seem to be recommendable as adequate approximation functions. Asymmetric obstacle shapes of cosine and parabolic shapes were also briefly discussed and their impact on the vibration transient response of a quarter-car model outlined.
Gear Tooth Failure Detection by the Resonance Demodulation Technique and the Instantaneous Power Spectrum Method – A Comparative Study
Authors: Ghasemloonia Ahmad , Khadem Siamak Esmaeel Zadeh
Published: January 2014

The role of gears in industry for speed and torque variation purposes is obvious. The gearbox diagnostic methods have been improved quickly in recent years. In this paper, two of the newest methods, the resonance demodulation technique (R.D), and the instantaneous power spectrum technique (IPS) are applied to gearbox vibration signals and their capabilities in fault detection are compared. Yet, the important role of time averaging should not be dispensed with, as it is the primary step for both techniques. In the present study, the mathematical method of these techniques, according to the mathematical vibration model of gears, is introduced, these techniques are applied to the test rig data, and finally the results of both methods are compared. The results indicate that in each method, the location of fault can be estimated and it is located in the same angular position in both methods. The IPS method is applicable to severe faults, whereas the resonance demodulation technique is a simple tool to recognize the fault at each severity and at the early stages of fault generation.
In-Plane free Vibration Analysis of an Annular Disk with Point Elastic Support
Authors: Bashmal S. , Bhat R. , Rakheja S.
Published: January 2014

In-plane free vibrations of an elastic and isotropic annular disk with elastic constraints at the inner and outer boundaries, which are applied either along the entire periphery of the disk or at a point are investigated. The boundary characteristic orthogonal polynomials are employed in the Rayleigh-Ritz method to obtain the frequency parameters and the associated mode shapes. Boundary characteristic orthogonal polynomials are generated for the free boundary conditions of the disk while artificial springs are used to account for different boundary conditions. The frequency parameters for different boundary conditions of the outer edge are evaluated and compared with those available in the published studies and computed from a finite element model. The computed mode shapes are presented for a disk clamped at the inner edge and point supported at the outer edge to illustrate the free in-plane vibration behavior of the disk. Results show that addition of point clamped support causes some of the higher modes to split into two different frequencies with different mode shapes.
Stochastic Responses of Multi-Degree-of-Freedom Uncertain Hysteretic Systems
Authors: Zhang Yimin
Published: January 2014

On the basis of the Bouc-Wen hysteretic model, the effective numerical method for the response of nonlinear multi-degree-of-freedom (MDOF) stochastic hysteretic systems is presented using second moment method. Using this method, the mean values, variances and covariances are computed. The Monte Carlo simulation is applied to validate the method. The results obtained by the two methods are contrasted, and the solutions of the method in this paper agreed very well with the Monte Carlo simulation. It has solved the random response of nonlinear stochastic vibration systems which is caused by the stochastic hysteretic loop itself.
Nonlinear Dynamics Analysis of Tilting Pad Journal Bearing-Rotor System
Authors: Ying Jiayang , Jiao Yinghou , Chen Zhaobo
Published: January 2014

The nonlinear dynamics theory is increasingly applied in the dynamics analysis of tilting pad journal bearing-rotor system. However, extensive work on system dynamics done previously neglects the influence caused by the moment of inertia of the pad. In this paper, a comparison is made between the responses of the rotor in the bearings with and without pad inertia effect. Taking the Jeffcott rotor system as an example, the characteristics of bearing-rotor system, such as bifurcation diagram, cycle response, frequency spectrum, phase trajectories, and Poincaré maps, were attained within a certain rotation rate range. The pivotal oil-film force of tilting pad journal bearing was calculated by database method. The results directly demonstrate that considering the influence of the pad moment of inertia, system dynamics characteristics are found more complicated when rotor-bearing system works around natural frequency and system bifurcation is observed forward when rotor-bearing system works on high-speed range.
Deformation and Rupture of Thin Steel Plates due to Cumulative Loading from Underwater Shock and Bubble Collapse
Authors: Lee Julian J. , Smith Malcolm J. , Huang James , Paulgaard Geoffrey T.
Published: January 2014

The damage sustained by rigidly-clamped square steel plates when subjected to close-proximity underwater explosions has been investigated. The test specimens consisted of plates 0.76 mm and 1.21 mm thick made of either ASTM A1008 mild steel or 350 WT structural-grade steel with a low-temperature notch-toughness requirement. The explosively-loaded area of the plates was square, with dimensions of 254 mm X 254 mm. High-explosive charges from 1.1 g to 50 g were used at different standoff distances to obtain different shock strengths and bubble collapse intensities. Although the main impulsive load on the plate was due to the shock impact, because the standoff distances were less than twice the maximum free-field bubble radius, a strong interaction between the detonation product bubble and the target plate caused a rapid water jet to impinge on the plate, resulting in additional loading and damage. As a result, four main regimes of loading and damage were identified: a) holing/petaling due to shock loading, b) edge tearing due to shock loading only, c) edge tearing due to the cumulative loading from shock and bubble collapse, and d) large deformation due to shock and bubble collapse loading. The damage mechanisms and dynamic response of the plates were measured using dynamic displacement sensors, pressure gauges, and high-speed video. A fracture analysis was performed on the damaged plates to analyze the mechanisms of failure. Finally, finite-element analysis using a failure criterion based on normalized shear stress and effective strain has been used to examine the failure limits.
Nonlinear Dynamics of a Vibratory Cone Crusher with Hysteretic Force and Clearances
Authors: Jiang Jing , Han Qing-Kai , Li Chao-Feng , Yao Hong-Liang , Liu Shu-Ying
Published: January 2014

Based on the analysis on crushing process and hysteresis of material layers, a hysteretic model with symmetrical clearances is presented. The mechanical model of two-degree of freedom with bilinear hysteresis and its dynamical equations of system are proposed. In order to further investigate the dynamic characteristics of the novel vibratory cone crusher, the system is also simplified into a dynamical system of single degree of freedom with a bilinear hysteretic component together with clearances. According to some nonlinear dynamic analysis tools such as bifurcation diagram, Lyapunov exponents, Poincare section, etc., different motion patterns of the system are discussed, including periodic, periodic doubling, chaos and other characteristics. These theoretical results will provide readers with deep understanding on the regular and complex dynamical behaviors of the vibratory cone crusher due to the hysteresis with clearances.
Asymptotical Behavior of the Solution of a SDOF Linear Fractionally Damped Vibration System
Authors: Wang Z.H. , Du M. L.
Published: January 2014

Fractional-order derivative has been shown an adequate tool to the study of so-called "anomalous" social and physical behaviors, in reflecting their non-local, frequency- and history-dependent properties, and it has been used to model practical systems in engineering successfully, including the famous Bagley-Torvik equation modeling forced motion of a rigid plate immersed in Newtonian fluid. The solutions of the initial value problems of linear fractional differential equations are usually expressed in terms of Mittag-Leffler functions or some other kind of power series. Such forms of solutions are not good for engineers not only in understanding the solutions but also in investigation. This paper proves that for the linear SDOF oscillator with a damping described by fractional-order derivative whose order is between 1 and 2, the solution of its initial value problem free of external excitation consists of two parts, the first one is the 'eigenfunction expansion' that is similar to the case without fractional-order derivative, and the second one is a definite integral that is independent of the eigenvalues (or characteristic roots). The integral disappears in the classical linear oscillator and it can be neglected from the solution when stationary solution is addressed. Moreover, the response of the fractionally damped oscillator under harmonic excitation is calculated in a similar way, and it is found that the fractional damping with order between 1 and 2 can be used to produce oscillation with large amplitude as well as to suppress oscillation, depending on the ratio of the excitation frequency and the natural frequency.