bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of Fatigue Life of a Continuous Bridge Girder Based on Vehicle Induced Stress History
Authors: Rao V.G. , Talukdar S.
Published: January 2014

The fatigue damage assessment of bridge components by conducting a full scale fatigue testing is often prohibitive. A need, therefore, exists to estimate the fatigue damage in bridge components by a simulation of bridge‐vehicle interaction dynamics due to the action of the actual traffic. In the present paper, a systematic method has been outlined to find the fatigue damage in the continuous bridge girder based on stress range frequency histogram and fatigue strength parameters of the bridge materials. Vehicle induced time history of maximum flexural stresses has been obtained by Monte Carlo simulation process and utilized to develop the stress range frequency histogram taking into consideration of the annual traffic volume. The linear damage accumulation theory is then applied to calculate cumulative damage index and fatigue life of the bridge. Effect of the bridge span, pavement condition, increase of vehicle operating speed, weight and suspension characteristics on fatigue life of the bridge have been examined.
Narcolepsy: Pathophysiology and Neuropsychological Changes
Authors: Naumann Angela , Daum Irene
Published: January 2014

Narcolepsy is now recognized as a distinctive disorder with specific pathophysiology and neurochemical abnormalities. Findings on the role of the neuropeptide hypocretin are opening new avenues of research and new strategies for therapy. Recently, neuropsychological and electrophysiological studies have provided evidence for reduced memory performance on standard memory tests in addition to subjective complaints of forgetfulness which may be related to changes in attentional processing. Further studies are, however, necessary to clarify the neuropsychological profile in narcolepsy. This review focuses on the recent advances in understanding narcolepsy.
Tourette Syndrome and Obsessive‐Compulsive Disorder: Event‐Related Brain Potentials Show Similar Mechansims of Frontal Inhibition but Dissimilar Target Evaluation Processes
Authors: Johannes Sönke , Wieringa Bernardina M. , Nager Wido , Rada Dominik , Müller-Vahl Kirsten R. , Emrich Hinderk M. , Dengler Reinhard , Münte Thomas F. , Dietrich Detlef
Published: January 2014

Objectives: Tourette Syndrome (TS) and Obsessive‐Compulsive Disorders (OCD) share many clinical similarities and show a strong comorbidity. Current theories view a frontal‐striatal dysfunction as the underlying cause of many clinical aspects of both disorders.

This study sought to investigate mechanisms of conceptual integration and attention in both disorders. We hypothesized that the processing of stimuli with interfering aspects would be altered in a similar way while attentional mechanisms could differ.

Methods: Event‐related brain potentials (ERPs) were recorded in a modified STROOP‐paradigm in groups of TS and OCD patients and in a control group. The paradigm involved the presentation of color words in a range of different colors. The subjects had to respond to words of matching word content and color and to ignore mismatching stimuli.

Results: Incongruent stimuli elicited a frontal negative component (“N450”) which was enhanced in amplitude and prolonged in latency in both patient groups. Matching stimuli evoked enhanced N2 and P3b components representing target evaluation mechanisms. The OCD group alone displayed a larger P3b amplitude in comparison to both other groups.

Conclusions: The data are interpreted to indicate that frontal inhibitory mechanisms are altered alike in TS and OCD. In contrast, only the OCD group showed evidence for aberrant target evaluation.
Coupled Bending‐Bending‐Torsion Vibration of a Pre‐Twisted Beam with Aerofoil Cross‐Section by the Finite Element Method
Authors: Yardimoglu Bulent , Inman Daniel J.
Published: January 2014

The present study deals with a finite element model for coupled bending‐bending‐torsion vibration analysis of a pretwisted Timoshenko beam with varying aerofoil cross‐section. The element derived in this paper has two nodes, with seven degrees of freedom at each node. The nodal variables are transverse displacements, cross‐section rotations and the shear angles in two planes and torsional displacement. The advantage of the present element is the exclusion of unnecessary derivatives of fundamental nodal variables, which were included to obtain invertable square matrix by other researchers, by choosing proper displacement functions and using relationship between cross‐sectional rotation and the shear deformation. Element stiffness and mass matrices are developed from strain and kinetic energy expressions by assigning proper order polynomial expressions for cross‐section properties and considering higher order coupling coefficients. The correctness of the present model is confirmed by the experimental results available in the literature. Comparison of the proposed model results with those in the literature indicates that a faster convergence is obtained. The results presented also provide some insights in the formulation by clearly indicating that higher order coupling terms have considerable influence on the natural frequencies.

Erratum to “Coupled Bending-Bending-Torsion Vibration of a Pre-Twisted Beam with Aerofoil Cross-Section by the Finite Element Method”dx.doi.org/10.1155/2003/135305
Influence of Material Properties on the Ballistic Performance of Ceramics for Personal Body Armour
Authors: Kaufmann Christian , Cronin Duane , Worswick Michael , Pageau Gilles , Beth Andre
Published: January 2014

In support of improved personal armour development, depth of penetration tests have been conducted on four different ceramic materials including alumina, modified alumina, silicon carbide and boron carbide. These experiments consisted of impacting ceramic tiles bonded to aluminum cylinders with 0.50 caliber armour piercing projectiles. The results are presented in terms of ballistic efficiency, and the validity of using ballistic efficiency as a measure of ceramic performance was examined. In addition, the correlation between ballistic performance and ceramic material properties, such as elastic modulus, hardness, spall strength and Hugoniot Elastic Limit, has been considered.
Dynamic Analysis of Shell Structures with Application to Blast Resistant Doors
Authors: Koh C.G. , Ang K.K. , Chan P.F.
Published: January 2014

This paper concerns the dynamic analysis of shell structures, with emphasis on application to steel and steel‐concrete composite blast resistant doors. In view of the short duration and impulsive nature of the blast loading, an explicit integration method is adopted. This approach avoids time‐consuming computations of structural stiffness matrix and solving of simultaneous nonlinear equations. Single‐point quadrature shell elements are used, with numerical control to suppress spurious hourglass modes. Composite shells are handled by an appropriate integration rule across the thickness. Both material and geometric nonlinearities are accounted for in the formulation. Contact and gap problems are considered using bilinear spring elements in the finite element analysis. Numerical examples are presented for some benchmark problems and application study to blast resistant doors. Good correlation is generally obtained between the numerical results based on the software developed and the results obtained by other means including field blast tests.
Approximate Potentials with Applications to Strongly Nonlinear Oscillators with Slowly Varying Parameters
Authors: Cai Jianping , Li Y.P.
Published: January 2014

A method of approximate potential is presented for the study of certain kinds of strongly nonlinear oscillators. This method is to express the potential for an oscillatory system by a polynomial of degree four such that the leading approximation may be derived in terms of elliptic functions. The advantage of present method is that it is valid for relatively large oscillations. As an application, the elapsed time of periodic motion of a strongly nonlinear oscillator with slowly varying parameters is studied in detail. Comparisons are made with other methods to assess the accuracy of the present method.
Effects of Superstructure Flexibility on the Response of Base‐Isolated Structures
Authors: Kulkarni Jeevan A. , Jangid R.S.
Published: January 2014

A parametric study of base‐isolated structure with different isolation systems is conducted for investigating the effects of superstructure flexibility. The superstructure is idealized as a one‐storey structure isolated by different systems such as elastomeric bearings (with and without lead core) and sliding systems. The governing equations of motion of the isolated structural system are derived and the response of the system is obtained for stochastic model of earthquake ground motion. The earthquake ground motion is modeled as a uniformly modulated non‐stationary random process. The stochastic response of isolated structure is obtained using the state variable approach. An equivalent linearization technique is used for the approximate response of isolated structure with non‐linear isolation systems. The mean square superstructure acceleration and bearing displacement of the system are plotted under different system parameters and compared with the corresponding response of rigid sup erstructure condition to study the influence of superstructure flexibility. The comparison of response is made under various isolation system parameters (i.e. isolation period, damping, yield strength of elastomeric bearings and friction coefficient of sliding systems). It is observed that the bearing displacement can accurately obtained by modelling the superstructure as a rigid body in a base‐isolated structure. However, such approximation may under‐estimates the superstructure acceleration under certain conditions.
Radical “Visual Capture” Observed in a Patient with Severe Visual Agnosia
Authors: Takaiwa Akiko , Yoshimura Hirokazu , Abe Hirofumi , Terai Satoshi
Published: January 2014

We report the case of a 79‐year‐old female with visual agnosia due to brain infarction in the left posterior cerebral artery. She could recognize objects used in daily life rather well by touch (the number of objects correctly identified was 16 out of 20 presented objects), but she could not recognize them as well by vision (6 out of 20). In this case, it was expected that she would recognize them well when permitted to use touch and vision simultaneously. Our patient, however, performed poorly, producing 5 correct answers out of 20 in the Vision‐and‐Touch condition. It would be natural to think that visual capture functions when vision and touch provide contradictory information on concrete positions and shapes. However, in the present case, it functioned in spite of the visual deficit in recognizing objects. This should be called radical visual capture. By presenting detailed descriptions of her symptoms and neuropsychological and neuroradiological data, we clarify the characteristics of this type of capture.
Component Representation for Shock Qualified Foundation Structure
Authors: Coats Timothy , Cooper Michael , Arden Kevin , Russell Fred
Published: January 2014

Navy ship foundations are typically designed for shock using the Navy′s Dynamic Design Analysis Method. The NAVSEA 0908‐LP‐000‐3010, Rev. 1 manual states that a component modeled as a lumped mass with rigid links should not provide constraint to the support structure. This ensures foundations are designed to withstand all shock loads without accounting for additional stiffness provided by the component. Investigations are provided herein to illustrate the trade‐offs and consequences of several approaches for component representations. The observations reinforce the notion that one must give careful consideration for the system being modeled, the expected modal characteristics, and compliance with NAVSEA 0908‐LP‐000‐3010, Rev. 1.
Vibrational Energy Flow Models of Finite Orthotropic Plates
Authors: Park Do-Hyun , Hong Suk-Yoon , Kil Hyun-Gwon
Published: January 2014

In this paper energy flow models for the transverse vibration of finite orthotropic plates are developed. These models are expressed with time‐ and locally space‐averaged far‐field energy density, and show more general forms than the conventional EFA models for isotropic plates. To verify the accuracy of the developed models, numerical analyses are performed for finite rectangular plates vibrating at a single frequency, and the calculated results expressed with the energy and intensity levels are compared with those of classical models by changing the frequency and the damping.
Dynamic Viscoelastic Effects on Sound Wave Diffraction by Spherical and Cylindrical Shells Submerged in and Filled with Viscous Compressible Fluids
Authors: Hasheminejad Seyyed M. , Safari Naemeh
Published: January 2014

An analysis for sound scattering by fluid‐filled spherical and cylindrical viscoelastic shells immersed in viscous fluids is outlined. The dynamic viscoelastic properties of the scatterer and the viscosity of the surrounding and core fluids are rigorously taken into account in the solution of the acoustic scattering problem. The novel features of Havriliak‐Negami model for viscoelastic material dynamic behaviour description along with the appropriate wave‐harmonic field expansions and the pertinent boundary conditions are employed to develop a closed‐form solution in form of infinite series. Subsequently, the associated acoustic field quantities such as the scattered far‐field pressure directivity pattern, form function amplitude, transmitted intensity ratio, and acoustic force magnitude are evaluated for given sets of medium physical properties. Numerical results clearly indicate that in addition to the traditional fluid viscosity‐related mechanisms, the dynamic viscoelastic properties of the shell material as well as its thickness can be of major significance in sound scattering. Limiting cases are examined and fair agreements with well‐known solutions are established.
Evaluating Noise Sensitivity on the Time Series Determination of Lyapunov Exponents Applied to the Nonlinear Pendulum
Authors: Franca L.F.P. , Savi M.A.
Published: January 2014

This contribution presents an investigation on noise sensitivity of some of the most disseminated techniques employed to estimate Lyapunov exponents from time series. Since noise contamination is unavoidable in cases of data acquisition, it is important to recognize techniques that could be employed for a correct identification of chaos. State space reconstruction and the determination of Lyapunov exponents are carried out to investigate the response of a nonlinear pendulum. Signals are generated by numerical integration of the mathematical model, selecting a single variable of the system as a time series. In order to simulate experimental data sets, a random noise is introduced in the signal. Basically, the analyses of periodic and chaotic motions are carried out. Results obtained from mathematical model are compared with the one obtained from time series analysis, evaluating noise sensitivity. This procedure allows the identification of the best techniques to be employed in the analysis of experimental data.
Upper and Lower Face and Ideomotor Apraxia in Patients with Alzheimer’s Disease
Authors: Capone Jay Guido , Sala Sergio Della , Spinnler Hans , Venneri Annalena
Published: January 2014

Introduction: Apraxia of face movement in Alzheimer′s disease (AD) has been rarely investigated. This study aimed at investigating the frequency of lower (mouth, tongue and throat) and upper (eyes and eyebrows) face apraxia, in AD and its relationship with limb apraxia and severity of dementia.

Methods: Fifty seven patients with AD were tested with a new standardised test of face apraxia including upper and lower face movements, which uses an item‐difficulty weigthed scoring procedure, the IMA test, a test of ideomotor apraxia and the M.O.D.A., a means to assess dementia severity.

Results: Thirteen (23%) and 19 (33%) participants were below cut‐off respectively on the upper and lower face apraxia test. Both sections of the Face Apraxia Test correlated significantly with the Ideomotor Apraxia Test. However, double dissociations between different types of apraxia were observed. Both the upper and lower face apraxia tests correlated significantly with the measure of dementia severity.

Conclusions: The finding show that a proportion of AD patients fails face apraxia tests. Their face apraxia is interlinked with ideomotor limb apraxia, although dissociations are possible. Severity of dementia deterioration accounts for a good proportion of the variability of AD patients’ performance on face apraxia tests.
Developmental Prosopagnosia: A Review
Authors: Kress Thomas , Daum Irene
Published: January 2014

This article reviews the published literature on developmental prosopagnosia, a condition in which the ability to recognize other persons by facial information alone has never been acquired. Due to the very low incidence of this syndrome, case reports are sparse. We review the available data and suggest assessment strategies for patients suffering from developmental prosopagnosia. It is suggested that developmental prosopagnosia is not a unitary condition but rather consists of different subforms that can be dissociated on the grounds of functional impairments. On the basis of the available evidence, hypotheses about the aetiology of developmental prosopagnosia as well as about the selectivity of deficits related to face recognition are discussed.
Experiments on Optimal Vibration Control of a Flexible Beam Containing Piezoelectric Sensors and Actuators
Authors: Abreu Gustavo L.C.M. , Ribeiro José F. , Steffen Jr Valder
Published: January 2014

In this paper, a digital regulator is designed and experimentally implemented for a flexible beam type structure containing piezoelectric sensors and actuators by using optimal control design techniques. The controller consists of a linear quadratic regulator with a state estimator, namely a Kalman observer. The structure is a cantilever beam containing a set of sensor/actuator PVDF/PZT ceramic piezoelectric patches bonded to the beam surface at the optimal location obtained for the first three vibration modes. The equations of motion of the beam are developed by using the assumed modes technique for flexible structures in infinite‐dimensional models. This paper uses a method of minimizing the effect of the removed higher order modes on the low frequency dynamics of the truncated model by adding a zero frequency term to the low order model of the system. A measure of the controllability and observability of the system based on the modal cost function for flexible structures containing piezoelectric elements (intelligent structures) is used. The observability and controllability measures are determined especially to guide the placement of sensors and actuators, respectively. The experimental and numerical transfer functions are adjusted by using an optimization procedure. Experimental results illustrate the optimal control design of a cantilever beam structure.
How Can Spatially Distributed Uncertainties Be Included in FEA and in Parameter Estimation for Model Updating?
Authors: Zehn M.W. , Saitov A.
Published: January 2014

Owing to manufacturing composite materials and others show considerable uncertainties in wall‐thickness, fluctuations in material properties and other parameter, which are spatially distributed over the structure. These uncertainties have a random character and can therefore not being reduced by some kind of mesh refinement within the FE model. What we need is a suitable statistical approach to describe the parameter changing that holds for the statistics of the process and the correlation between the parameter spatially distributed over the structure. The paper presents a solution for a spatial correlated simulation of parameter distribution owing to the manufacturing process or other causes that is suitable to be included in the FEA. The parameter estimation methods used in updating algorithms for FE‐models, depend on the choice of a priori to be determined weighting matrices. The weighting matrices are in most cases assumed by engineering judgement of the analyst carrying out the updating procedure and his assessment of uncertainty of parameters chosen and measured and calculated results. With the statistical description of the spatial distribution at hand, we can calculate a parameter weighting matrix for a Baysian estimator. Furthermore, it can be shown in principle that with model updating it is possible to improve the probabilistic parameter distribution itself.
Laser‐Generated Shocks and Bubbles as Laboratory‐Scale Models of Underwater Explosions
Authors: Jones Theodore G. , Grun Jacob , Bibee L. Dale , Manka Charles , Landsberg Alexandra , Tam Daniel
Published: January 2014

Underwater shocks and bubbles were generated using a high energy pulsed laser system. The advantages of this experimental approach are: (1) precisely controlled and measured experimental conditions; (2) improved diagnostics, including extensive imaging capabilities; (3) unique experiments, including a simultaneously detonated line charge; and (4) the ability to provide validation quality data for hydrodynamic simulation codes. Bubble sensitivity to variation of several experimental parameters was examined. Numerical simulations were performed corresponding to the experimental shots, showing that empirical bubble theory, experimental bubble data, and simulations were all in good agreement.
Experimental and Dynamic Study of the Piston Rod Lateral Friction for the Twin‐Tube Hydraulic Shock Absorber
Authors: Liu Yanqing , Zhang Jianwu , Cheng Xiaoming
Published: January 2014

In this paper, dynamic loads acting on a twin‐tube hydraulic shock absorber are derived out both in wheel and axle planes by modeling mechanically car rear suspensions, and internal and external forces that yield lateral surface damage and wear‐out of the piston rod for the absorber are analyzed according to bench and real road test measures. From viewpoint of vehicle system dynamics and experiment, such key factors as road unevenness, very high car speed and severe shock induced vibrations are investigated, by which stochastic bending moments and dramatically increasing shock loading are introduced directly to the piston rod. From viewpoint of the whole car assembly, on the other hand, due to hardly perfectly placements of the piston rods in their positions between the car suspension and body, unacceptable manufacturing quality of the body may cause additional dynamic forces on the piston rod. Significant results obtained by theoretical and experimental analysis of lateral frictions of the piston rod are presented systematically for improving design of the shock absorber.
Experimental Validation of Elliptical Fin‐Opening Behavior
Authors: Garner James M. , Weinacht Paul , Kaste Robert P.
Published: January 2014

An effort to improve the performance of ordnance has led to the consideration of the use of folding elliptical fins for projectile stabilization. A second order differential equation was used to model elliptical fin deployment history and accounts for: deployment with respect to the geometric properties of the fin, the variation in fin aerodynamics during deployment, the initial yaw effect on fin opening, and the variation in deployment speed based on changes in projectile spin. This model supports tests conducted at the Transonic Experimental Facility, Aberdeen Proving Ground examining the opening behavior of these uniquely shaped fins. The fins use the centrifugal force from the projectile spin to deploy. During the deployment, the fin aerodynamic forces vary with angle‐of‐attack changes to the free stream. Model results indicate that projectile spin dominates the initial opening rates and aerodynamics dominate near the fully open state. The model results are examined to explain the observed behaviors, and suggest improvements for later designs.
Axisymmetric Natural Frequencies of Statically Loaded Annular Plates
Authors: Abdel-Rahman Eihab M. , Faris Waleed F. , Nayfeh Ali H.
Published: January 2014

We present a numerical procedure to solve the axisymmetric vibration problem of statically loaded annular plates. We use the von Kármán nonlinear plate model to account for large deformations and study the effect of static deflections on the natural frequencies and mode shapes for six combinations of boundary conditions. The shooting method is used to solve the resulting eigenvalue problem. Our results show that static deformations have a significant effect on the natural frequencies and small effect on the mode shapes of the plate. Further, the results show that the presence of in‐plane stresses has a significant effect on the natural frequencies.
Control of Rotary Cranes Using Fuzzy Logic
Authors: Al-mousa Amjed A. , Nayfeh Ali H. , Kachroo Pushkin
Published: January 2014

Rotary cranes (tower cranes) are common industrial structures that are used in building construction, factories, and harbors. These cranes are usually operated manually. With the size of these cranes becoming larger and the motion expected to be faster, the process of controlling them has become difficult without using automatic control methods. In general, the movement of cranes has no prescribed path. Cranes have to be run under different operating conditions, which makes closed‐loop control attractive.

In this work a fuzzy logic controller is introduced with the idea of “split‐horizon”; that is, fuzzy inference engines (FIE) are used for tracking the position and others are used for damping the load oscillations. The controller consists of two independent sub‐controllers: radial and rotational. Each of these controllers has two fuzzy inference engines (FIE). Computer simulations are used to verify the performance of the controller. Three simulation cases are presented. In the first case, the crane is operated in the gantry (radial) mode in which the trolley moves along the jib while the jib is fixed. In the second case (rotary mode), the trolley moves along the jib and the jib rotates. In the third case, the trolley and jib are fixed while the load is given an initial disturbance. The results from the simulations show that the fuzzy controller is capable of keeping the load‐oscillation angles small throughout the maneuvers while completing the maneuvers in relatively reasonable times.
A New Simulation Method Providing Shock Mount Selection Assurance
Authors: Talley Michael A. , Sarkani Shahram
Published: January 2014

This paper presents the development and assessment of a practical and efficient process for assessing and/or designing shock isolation systems. This process combines practical methods for determining relative displacements and accelerations (e.g. shock response spectrum analysis) with a new, efficient, easy to use, 6 degree of freedom (6DOF) simulation method known as Shock Isolation Mount Predictions & Loading Estimates (SIMPLE). SIMPLE is also a tool that can easily account for uncertainties in isolated systems and their environments. The implementation of 6DOF rigid body theory in SIMPLE is validated by comparing simulation results with other analytical methods. This paper also summarizes assessments and designs for 60 different mounting systems using SIMPLE. In addition, experimental results from shock tests are compared with pre‐test SIMPLE sensitivity simulations and with results of post‐test model calibrations. These comparisons show the validity of: 1) using 6DOF analysis; 2) using statically derived load‐deflection data for simulations; and 3) assessing and designing isolated systems using uncertainties in model parameters.
Subtyping Obsessive‐Compulsive Disorder: Neuropsychological Correlates
Authors: Harris Catherine L. , Dinn Wayne M.
Published: January 2014

We administered neuropsychological measures considered sensitive to prefrontal dysfunction (both orbitofrontal and dorsolateral prefrontal neocortex) to obsessive‐compulsive disorder (OCD) patients and control subjects. OCD subjects exhibited performance deficits, in comparison to community controls, on three measures sensitive to orbitofrontal neocortex dysfunction. Contrary to expectation, OCD patients also exhibited performance deficits on measures sensitive to dorsolateral prefrontal neocortex dysfunction. However, distinct neurocognitive profiles emerged when we examined the impact of comorbid schizotypal personality features on neuropsychological test performance. Primary OCD patients displayed impaired performance on measures sensitive to orbitofrontal dysfunction; however, they did not differ from control subjects on tests of dorsolateral function. OCD subjects presenting with schizotypal personality features performed poorly not only on tests sensitive to orbitofrontal dysfunction, but also on tests sensitive to dorsolateral dysfunction. Findings suggest that OCD can be subdivided into clinical subtypes, and distinct prefrontal subsystems may be differentially involved in these subtypes.
Measurement of Naval Ship Responses to Underwater Explosion Shock Loadings
Authors: Park Il-Kwon , Kim Jong-Chul , An Chin-Woo , Cho Dae-Seung
Published: January 2014

The shock‐resistance capability of battle ships against a non‐contact underwater explosion (UNDEX) is a very critical factor of survivability. In July 1987 and April 2000, we successfully conducted UNDEX shock tests for a coastal mine hunter (MHC) and a mine sweeper/hunter (MSH) of Republic of Korea Navy (ROKN), at the Chinhae bay, Korea. Test planning for conducting these shock tests included responsibilities, methods, and procedures. Test instruments were developed and tested on a drop shock machine to confirm availability in the actual shock tests with emphasis on shock resistance, remote control and reliability. All vital systems of the ships were confirmed to be capable of normal operational condition without significant damages during the explosion shot. By analyzing the test results, the tactical operational safety zone of the ships in underwater explosion environments was estimated. In this paper, we described the results of measurement of naval ship responses to underwater explosion shock loadings including test planning, sensor locations, data reduction, explosive devices, instrumentation and damage assessments of MSH.
Disturbed Monitoring and Response Inhibition in patients with Gilles De La Tourette Syndrome and Co‐Morbid Obsessive Compulsive Disorder
Authors: Müller Sandra Verena , Johannes Sönke , Wieringa Berdieke , Weber Axel , Müller-Vahl Kirsten , Matzke Mike , Kolbe Hans , Dengler Reinhard , Münte Thomas F.
Published: January 2014

Objective: Fronto‐striatal dysfunction has been discussed as underlying symptoms of Tourette syndrome (TS) with co‐morbid Obsessive Compulsive Disorder (OCD). This suggests possible impairments of executive functions in this disorder, which were therefore targeted in the present study.

Results: A comprehensive series of neuropsychological tests examining attention, memory and executive functions was performed in a group of 14 TS/OCD in co‐occurrence with OCD patients and a matched control group.

Results: While attentional and memory mechanisms were not altered, TS/OCS patients showed deficits in executive functions predominately in the areas of response inhibition and action monitoring.

Conclusions: These findings provide further evidence for a substantial impairment of the frontal‐striatal‐thalamic‐frontal circuit. We propose that the deficits in monitoring, error detection and response inhibition constitute the major impairment of TS/OCD patients in the cognitive domain.
Depression and Cognitive Impairment in Disability‐Free Early Multiple Sclerosis
Authors: Haase Claus G. , Tinnefeld Michael , Lienemann Marc , Ganz Reinhard E. , Faustmann Pedro M.
Published: January 2014

Cognitive and emotional capabilities were evaluated in 73 female patients with stable relapsing‐remitting definite, and/or laboratory‐supported multiple sclerosis (MS) and were compared with 32 matched healthy controls. Patients were categorized according to their score in the expanded disability status scale (EDSS) to either no (EDSS 0, n = 33) or few clinical signs (EDSS 1–2, n = 40) of MS without physical disability. Patients with EDSS > 0 were characterized by significantly (p These results indicate that depression may present as an early sign in MS followed by cognitive impairment, in particular visuo‐spatial short‐term memory, before physical disability appears. Neuropsychological tests as mentioned here could serve as early diagnostic tools to detect subtle disease progression and to initiate and monitor disease modifying therapies.

Patients with EDSS > 0 were characterized by significantly (p < 0.001) higher scores on “von Zerssen’s“ depression scale,
compared to controls. Patients with higher EDSS scores (1–2) showed significantly decreased performance with respect to the total score of Kimura’s Recurring‐Figures‐Test (p < 0.001), in addition. Regarding visuo‐constructive functioning, patients with EDSS = 0 performed to a significantly lower level (p < 0.001), compared to controls.
Perceptual Organization Based Upon Spatial Relationships in Alzheimer’s Disease
Authors: Kurylo Daniel D. , Allan Walter C. , Collins T. Edward , Baron Joshua
Published: January 2014

Alzheimer’s disease (AD) is often accompanied by impaired object recognition, thereby reducing the ability to recognize common objects and familiar faces. Impaired recognition may stem from decreased efficacy in integrating visual information. Studies of perceptual abnormalities in AD indicate an impairment in organizing elements of the visual scene, thereby confusing components of individual forms. This type of impairment is consistent with the characteristics of neural loss, which impact cortical integration. To examine the extent to which perceptual organization is impaired in AD, psychophysical measurements were made of visual perceptual grouping based upon spatial relationships in a group of AD patients and demographically matched elderly control subjects. A comparison was also made between young and elderly control subjects to evaluate the effects of aging on these capacities. Deficits in perceptual organization were found for a subgroup of AD patients, which corresponded to impairment on facial recognition. A less profound functional decline was found for the elderly control group. The degree of impairment for AD subjects did not correlate to level of dementia, but instead appears to be idiosyncratic to individual patients. These results are consistent with impaired integrative function in AD, the degree of which reflects individual differences in the regional distribution of neuropathological changes.
Enhanced Piezoelectric Shunt Design
Authors: Park Chul H. , Inman Daniel J.
Published: January 2014

Piezoceramic material connected to an electronic shunt branch circuit has formed a successful vibration reduction device. One drawback of the conventional electronic shunt circuit is the large inductance required when suppressing low frequency vibration modes. Also, the large internal resistance associated with this large inductance exceeds the optimal design resistance needed for low frequency vibration suppression. To solve this problem, a modified and enhanced piezoelectric shunt circuit is designed and analyzed by using mechanical‐electrical analogies to present the physical interpretation. The enhanced shunt circuit developed in this paper is proved to significantly reduce the targeted vibration mode of a cantilever beam, theoretically and experimentally.
Cognitive and Emotional Dysfunction after Central Pontine Myelinolysis
Authors: Lee Tatia M. C. , Cheung Crystal C. Y. , Lau Esther Y. Y. , Mak Amanda , Li Leonard S. W.
Published: January 2014

The case of a 67‐year‐old right‐handed Chinese man with Central Pontine Myelinolysis [CPM] is described to illustrate the resulting cognitive and emotional disturbances. A comparison of the data in this report with that in published studies suggests that ethnicity does not seem to have much effect on the symptoms of CPM. Possible underlying neural‐pathological mechanisms are discussed. This case further substantiates the speculation that the brainstem plays a role in higher cognitive processes and emotional regulation.
A Hybrid Control Policy for Semi‐Active Vehicle Suspensions
Authors: Goncalves Fernando D. , Ahmadian Mehdi
Published: January 2014

Various control policies, such as skyhook and groundhook control, have often been considered for semi‐active vehicle suspensions. Past studies have shown the performance limitations of these policies, as well as others that have been considered for vehicle applications. This study will provide a look into an alternative control technique called "hybrid control", which attempts to merge the performance benefits of skyhook and groundhook control. The results of this study are based on an experimental evaluation of hybrid control using a quarter‐car rig and a magneto‐rheological damper. The control policy is employed and evaluated under a steady‐state or pure tone input, and a transient or step input. Peak‐to‐peak displacement and peak‐to‐peak acceleration are used to evaluate performance. The results indicate that hybrid control can offer benefits to both the sprung mass and the unsprung mass. The steady‐state results reveal that hybrid control can be used to reduce the peak‐to‐ peak displacements and accelerations of both bodies. The transient evaluation shows that hybrid control can be effective at reducing the peak‐to‐peak displacement of the sprung mass.
A Reduced‐Domain Method of Structural Damage Identification: Application to a Spectral Element Beam Model
Authors: Lee Usik
Published: January 2014

Though there have been many efforts to make the inverse problem of damage identification small by reducing its finite element degrees‐of‐freedom, there have been few efforts to make it small by reducing its spatial domain of problem. Thus, as the extension of the author′s previous work in which the damage identification algorithm was formulated from the dynamic stiffness equation of motion, the present study introduces a spectral element model (SEM)‐based reduced‐domain method (RDM) of damage identification. In the present RDM, a three‐steps process is used to reduce the domain of problem by iteratively searching out and removing damage‐free parts of structure in the course of the damage identification analysis. To validate the present RDM, numerically simulated damage identification tests are conducted. The experimental tests for a damaged cantilevered beam specimen show that the present RDM can fairly well locates and quantifies all local damages (i.e., slots) placed along the beam specimen.
High Strain Rate Characterization of Shock Absorbing Materials for Landmine Protection Concepts
Authors: McArthur Jennifer , Salisbury Christopher , Cronin Duane , Worswick Michael , Williams Kevin
Published: January 2014

Numerical modelling of footwear to protect against anti‐personnel landmines requires dynamic material properties in the appropriate strain rate regime to accurately simulate material response. Several materials (foamed metals, honeycombs and polymers) are used in existing protective boots, however published data at high strain rates is limited.

Dynamic testing of several materials was performed using Split Hopkinson Pressure Bars (SHPB) of various sizes and materials. The data obtained from these tests has been incorporated into material models to predict the initial stress wave propagation through the materials. Recommendations for the numerical modeling of these materials have also been included.
An Improved Wavelet Correction for Zero Shifted Accelerometer Data
Authors: Edwards Timothy S.
Published: January 2014

Accelerometer data from shock measurements often contains a spurious DC drifting phenomenon known as zero shifting. This erroneous signal can be caused by a variety of sources. The most conservative approach when dealing with such data is to discard it and collect a different set with steps taken to prevent the zero shifting. This approach is rarely practical, however. The test article may have been destroyed or it may be impossible or prohibitively costly to recreate the test. A method has been proposed by which wavelets may be used to correct the acceleration data. By comparing the corrected accelerometer data to an independent measurement of the acceleration from a laser vibrometer this paper shows that the corrected data, in the cases presented, accurately represents the shock. A method is presented by which the analyst may accurately choose the wavelet correction parameters. The comparisons are made in the time and frequency domains, as well as with the shock response spectrum.
Involuntary Vocalisations and a Complex Hyperkinetic Movement Disorder Following Left Side Thalamic Haemorrhage
Authors: Dietl T. , Auer D. P. , Modell S. , Lechner C. , Trenkwalder C.
Published: January 2014

A variety of involuntary speech phenomena as for example palilalia have been described as consequences of neurological disorders. Palilalia is the involuntary repetition of syllabels, words and phrases in ongoing speech. We describe a 73 year old woman who suffered from a hypertensive thalamic haemorrhage. MRI revealed that the lesion was predominantly located within the pulvinar, extending to the lateroposterior thalamic nuclei and to the pretectal area with possible involvement of the medial geniculate body. Few months after the event she developed involuntary vocalisations with whole words and meaningless syllables being rapidly reiterated. In contrast to typical palilalia these vocalisations were not meaningfully related to the ongoing speech of the patient. In addition, the patient developed a complex hyperkinetic movement disorder with right‐sided painful hemidystonia and bilateral clonic jerks and a right‐sided postural tremor.
On the Use of Weighted Least Squares for Time Domain Modal Parameter Identification
Authors: Cooper Jonathan E.
Published: January 2014

An approach for the use of the Weighted Least Squares method for time domain modal parameter identification is introduced. The approach enables standard identification methods to be employed in the usual manner, except that sections of the time records with high signal‐noise ratios are given a greater emphasis in the identification process. It is shown how it is possible to apply the method to a wide range of applications, including the analysis of impulse response, input‐output and time varying data. A number of different weighting schemes are explored, based upon exponential weighting and the envelope of the measured data. A series of simulated tests demonstrate how the performance of conventional time domain algorithms can be improved significantly with little extra computational effort though the use of a Weighted Least Squares scheme.
Natural Frequencies of a Cracked Beam Coupled with a Compressible Sloshing Fluid
Authors: Di Sciuva Michele , Surace Cecilia
Published: January 2014

This article describes studies into the flexural vibration of a cracked cantilevered beam in contact with a non‐viscous fluid. The crack has been represented by a mass‐less rotational spring, the flexibility of which has been calculated using linear fracture mechanics. The coupled system is subject to undisturbed boundary condition at infinity in the fluid domain. A range of different boundary conditions have been analysed such as both incompressible and compressible fluid, with and without sloshing. Various crack sizes and positions have been considered in order to assess the effect of damage in the fluid‐structure interaction problem.
A Case of Camptocormia (Bent Spine) Secondary to Early Motor Neuron Disease
Authors: Ozer Feriha , Mutlu Aytul , Meral Hasan
Published: January 2014

Camptocormia is a gait disorder, characterized by hyperflexion of thoracolumbar spine which increases on walking, and disappears in the supine position.

A 48 year‐old man developed progressive gait deterioration for one year and slight weakness and tremor of both hands for five months. It eventually became apparent that the patient had motor neuron disease, as well as symptoms of extrapyramidal disorder.
Capabilities of Helmets for Preventing Head Injuries Induced by Ballistic Impacts
Authors: Balandin D.V. , Bolotnik N.N. , Pilkey W.D.
Published: January 2014

The limiting performance of ballistically loaded helmets designed to reduce head injuries is studied analytically. The projectile does not penetrate the helmet. This analysis evaluates the absolute minimum of the peak displacement of the helmet shell relative to the head, provided that criteria measuring the severity of head injuries lie within prescribed limits. Rather than optimize a specific design configuration, e.g. a viscoelastic foam liner, characteristics of a time‐dependent force representing the helmet liner are calculated. The formulation reduces the limiting performance analysis to an optimal control problem.
Validation of Two Nonlinear System Identification Techniques Using an Experimental Testbed
Authors: Lenaerts V. , Kerschen G. , Golinval J.-C. , Ruzzene M. , Giorcelli E.
Published: January 2014

The identification of a nonlinear system is performed using experimental data and two different techniques, i.e. a method based on the Wavelet transform and the Restoring Force Surface method. Both techniques exploit the system free response and result in the estimation of linear and nonlinear physical parameters.
Theoretical and Numerical Experiences on a Test Rig for Active Vibration Control of Mechanical Systems with Moving Constraints
Authors: Rinchi M. , Gambini E.
Published: January 2014

Active control of vibrations in mechanical systems has recently benefited of the remarkable development of robust control techniques. These control techniques are able to guarantee performances in spite of unavoidable modeling errors. They have been successfully codified and implemented for vibrating structures whose uncertain parameters could be assumed to be time‐invariant. Unfortunately a wide class of mechanical systems, such as machine tools with carriage motion realized by a ball‐screw, are characterized by time varying modal parameters. The focus of this paper is on modeling and controlling the vibrations of such systems. A test rig for active vibration control is presented. An analytical model of the test rig is synthesized starting by design data. Through experimental modal analysis, parametric identification and updating procedures, the model has been refined and a control system has been synthesized.
Vibroacoustic Optimization of Stiffening Ribs and Damping Material Distribution on Sheet Metal Parts
Authors: Carfagni M. , Citti P. , Governi L. , Pierini M.
Published: January 2014

Vehicle noise and vibration levels are basic parameters in passenger comfort. Both static and dynamic stiffness of sheet metal parts is commonly increased by means of stiffening ribs. Vibrations are also reduced by adding a layer of damping material on the floor, the roof, the firewall and other parts of the vehicle. In common practice the panels to be treated are ribbed according to criteria based on the designer’s experience, rather than on well defined design procedures and are uniformly covered by a layer of damping material. However, these are not efficient design solutions, especially with regard to the effectiveness of vibration reduction and to weight containment. In this paper a novel approach to achieve an optimal distribution of stiffening ribs and damping material will be presented. The proposed method is based on a Genetic Algorithm (G.A.) procedure which takes into account both the vibroacoustic performance and the weight and cost reduction. A simple case study will be illustrated to demonstrate the capabilities of the developed procedure.