bluuebunny/crossref_metadata_2025 huggingface dataset:
Toward a network model of dystonia
Authors: Hendrix Claudia M. , Vitek Jerrold L.
Published: July 2012

Dystonia has generally been considered a basal ganglia (BG) disorder. Early models hypothesized that dystonia occurred as the result of reduced mean discharge rates in the internal segment of the globus pallidus (GPi). Increasing evidence suggests a more systemwide disruption of the basal ganglia thalamic circuit (BGTC) resulting in altered firing patterns, synchronized oscillations, and widened receptive fields. A model of dystonia incorporating these changes within the BGTC is presented in which we postulate that this pathophysiology arises from disruptions within the striatum. Alterations in the cerebellothalamocortical (CBTC) pathway to the development of dystonia may also play a role. However, the contribution of CBTC abnormalities to dystonia remains unclear and may vary with different etiologies of dystonia. Finally, the relevance of established and emerging theories related to the pathophysiology of dystonia is addressed within the context of improving conventional approaches for deep brain stimulation (DBS) treatment strategies.
Early Pharmacotherapy with Fluoxetine Rescues Dendritic Pathology in the Ts65Dn Mouse Model of Down Syndrome
Authors: Guidi Sandra , Stagni Fiorenza , Bianchi Patrizia , Ciani Elisabetta , Ragazzi Elena , Trazzi Stefania , Grossi Gabriele , Mangano Chiara , Calzà Laura , Bartesaghi Renata
Published: July 2012

Down syndrome DS is a genetic pathology characterized by brain hypotrophy and severe cognitive impairment. Although defective neurogenesis is an important determinant of mental disability, a severe dendritic pathology appears to be an equally important factor. A previous study showed that fluoxetine, a selective serotonin reuptake inhibitor, fully restores neurogenesis in the Ts65Dn mouse model of DS. The goal of the current study was to establish whether fluoxetine also restores dendritic development. In mice aged 45 days, treated with fluoxetine in the postnatal period P3–P15, we examined the dendritic arbor of the granule cells of the dentate gyrus (DG). The granule cells of trisomic mice had a severely hypotrophic dendritic arbor, fewer spines and a reduced innervation than euploid mice. Treatment with fluoxetine fully restored all these defects. In Ts65Dn mice, we found reduced levels of serotonin that were restored by treatment. Results show that a pharmacotherapy with fluoxetine is able to rescue not only the number of granule neurons but also their “quality” in terms of correct maturation and connectivity. These findings strongly suggest that fluoxetine may be a drug of choice for the improvement of the major defects in the DS brain and, possibly, of mental retardation.
Effectiveness of aripiprazole in adolescents and young adults with schizophrenia spectrum disorders: comparison of first‐episode to recurrent psychosis
Authors: Huang Yu‐Shu , Yeh Chin‐Bin , Tang Ching‐Shu , Chen Chih‐Ken , Chou Wen‐Jiun , Chou Miao‐Chun , Wu Yu‐Yu , Liang Hsin‐Yi , Wang Liang‐Jen
Published: July 2012

Aims

The study aims to determine the clinical outcomes of aripiprazole treatment in adolescents and young adults with schizophrenia spectrum disorders.

Methods

This was a 24‐week, observational, prospective study. Patients with schizophrenia spectrum disorders were prescribed a daily dose of 5 mg to 30 mg of aripiprazole. Effectiveness was assessed by the change from baseline in psychotic symptoms and quality of life.

Results

Forty‐two patients with a mean age of 18.1 ± 3.7 years were recruited. Eighteen were experiencing the first episode of psychosis (FEP), whereas the remaining 24 were non‐FEP. Psychotic symptoms, but not quality of life, improved globally from baseline scores by the endpoint of the study (effect size = 0.44). Compared with non‐FEP patients, FEP patients had greater improvements (effect size = 0.45) in some clinical outcome dimensions during the 24‐week aripiprazole treatment.

Conclusion

We observed significant improvements of medium effect sizes in psychotic symptoms of patients with schizophrenia spectrum disorders within a naturalistic clinical setting, especially for FEP patients.
Reading Sociology into Scholarship on School‐Based Sex Education: Structure and Culture
Authors: Smith Sarah H.
Published: July 2012

School‐based sex education (SBSE) represents an attempt on the part of institutions to interrupt and correct the sexual socialization of young people. In this examination of scholarship on SBSE, I provide an overview of the field of academic approaches to SBSE and argue for the application of a variety of sociological frameworks to future studies. Much of the extant sociological literature on SBSE tends to focus on the implications that political rhetoric has for policy and funding, curricula, and stakeholder perspectives. In this paper, I will discuss this literature vis‐a‐vis the structural level (e.g. policy, law, funding). Further, because both structure and interaction are embedded in cultural contexts, I will discuss the role of culture as treated in the literature. I will then discuss the scholarly criticisms of SBSE contained in the literature as opportunities for sociological article of SBSE.
Rethinking Public Opinion in Penal Policymaking: Recommendations for Research
Authors: Brown Elizabeth K.
Published: July 2012

Public opinion is often described as a powerful force in penal policymaking in the USA. Unfortunately, research on public opinion in penal policymaking has been limited by inattention to a number of important variables: definitions of public opinion, individual and interpersonal constructions of public opinion by political leaders themselves, state differences in historical contexts and political cultures regarding public engagement and political influence, and diversity in the roles of public opinion at different levels of government. This paper considers current dilemmas in this area of inquiry and reviews recent research in order to highlight potentially fruitful new directions for research.
Six‐minute walk distance and dyspnoea scores to assess the course of COPD exacerbation in elderly patients
Authors: Blankenburg Thomas , Guettel Anne , Busch Christian , Schuette Wolfgang
Published: July 2012

Introduction

While the severity of stable chronic obstructive pulmonary disease (COPD) has been defined in a valid and relevant prognostic manner, parameters that describe the course of COPD exacerbations are not yet established. Physical performance and dyspnoea are of prognostic relevance in stable COPD. The issue investigated was to assess the course of COPD exacerbations to find parameters that describe this situation better.

Methods

In 82 hospitalised patients with acute exacerbation of COPD who responded to intensified medical treatment (age 67.3 ± 9.5 years; forced expiratory volume in 1 s 1.0l, 40% predicted), we measured the 6‐min walk distance and the visual analogue scale dyspnoea scores before the start of treatment, prior to discharge and after a 4‐week stable period. Additionally, the conventional clinical parameters of COPD and quality of life were documented.

Results

The 6‐min walk distance was significantly increased from 97 ± 114 m to 290 ± 106 m. After 4 weeks of outpatient treatment in clinically stable patients, the 6‐min walk distance fell non‐significantly to 270 ± 120 m. The increment in walk distance fell significantly with advancing severity of COPD: from 112 ± 68 m for grade I and II to 56 ± 88 m for grade IV. Resting as well as exertional dyspnoea scores were significantly reduced (resting dyspnoea from 4 to 2 and exertional dyspnoea from 8 to 6).

Conclusion

We were able to demonstrate that 6‐min walk test and dyspnoea scores, but not pulmonary function test, are suitable parameters to assess the course of COPD exacerbations.
Insight into osteo‐articular digital tomosynthesis: A pictorial essay
Authors: Lacout Alexis , Thariat Juliette , Hajjam Mostafa El , Marcy Pierre‐Yves
Published: July 2012

The objectives of this pictorial essay are to describe osteo‐articular imaging using digital tomosynthesis. We provide characteristic examples in eight patients. Digital tomosynthesis allows easy, fast and low‐dose imaging, with excellent spatial resolution.
Legalizing Indigenous Identities: The Tapeba Struggle for Land and Schools in Caucaia, Brazil
Authors: Aires Max Maranhão Piorsky
Published: July 2012

Em cerca de duas décadas os Tapeba passaram de um grupo sem atenção estatal, pobres, sem escolas e aculturados para a de indígenas sujeitos de direitos e protegidos pelo estado brasileiro. Esta possibilidade não chegou de uma só vez: em meados da decada de 1980 a Teologia da Libertação, na decada de 1990 a escola diferenciada e, em seguida, a implementação da política educacional. Num primeiro momento a transformação da identificação e do lugar político ocupado tornou‐se possível com o apoio de missionários adeptos da Teologia da Libertação, que incentivaram a identificação da população como indígena como uma possibilidade para alcançar direitos, em especial terra, saúde e educação. No entanto, as desconfianças em relação a identidade persistiram e marcaram todo o processo de luta pela terra. Os índios, mais uma vez, entraram na batalha para produção de evidências para o reconhecimento. Um grupo pequeno de lideranças formulou a linguagem de reivindicação das escolas diferenciadas que insistiu na necessidade de exibição pública da cultura e no ensino da identificação para crianças. Esta estratégia articulou as identidades a campos de poder mais amplos que o da luta fundiária na medida em que as lideranças formularam um discurso conectando o problema da auto‐identificação com a disposição do estado em atender demandas estabelecidas com base na diferença cultural num momento em que cresceu a importância mundial da escolarização de crianças como agentes centrais para o crescimento econômico e a internacionalização dos direitos indígenas.
Ancient Calendars and Bolivian Modernity: Tiwanaku's Gateway of the Sun, Arthur Posnansky, and the World Calendar Movement of the 1930s
Authors: Sammells Clare A.
Published: July 2012

Resumén

Los turistas que asisten al sitio arqueológico de Tiwanaku son presentados con calendarios precolombinos, de los cuales la Puerta del Sol es el más importante, famosa y hermosa. A principios de del siglo 20 Arturo Posnansky y otros arqueólogos creyeron que las inscripciones de la Puerta correspondían a un calendario escrito. Estas teorías se sustentan en las narrativas que consideran Tiwanaku como un fuente de sabiduría tanto en la época precolombinos como en el mundo contemporáneo. Posnansky presentó sus interpretaciones de calendarios Tiwanakotas como respuesta a los debates del Movimiento del Calendario Global, el trataba de racionalizar el calendario gregoriano en la década de 1930. En la Puerta, Posnansky encontró una respuesta boliviana alternativa a la que dominaba en la comunidad internacional científica, la cual buscaba una forma racional de medir el tiempo para la economía mundial. Estos intelectuales bolivianos combinaron su interes por el pasado indígena con sus preocupaciones con el rol del estado boliviano moderno en el sistema global.
Scars of Nation: Surgical Penetration and the Ecuadorian State
Authors: Roberts Elizabeth F. S.
Published: July 2012

Resumen

En Ecuador, las mujeres de clase media, y cada vez más las de clase obrera, pagan gustosamente por tener una cicatriz. Las cesáreas que se hacen en las clínicas privadas les deja una cicatriz que es la marca de aquellas mujeres que no están sujetas al uso indigno de los devaluados servicios de salud pública. No es afirmar la ciudadanía per se lo que estas mujeres buscan con estas cicatrices, ya que en Ecuador la ciudadanía es particularmente denigrada en el ámbito médico. Esta cicatriz es más bien el signo de la posibilidad de diferenciarse de las masas de mujeres gobernadas, quienes necesitan hacer demandas ciudadanas de servicios sociales de las instituciones del Estado. Las cicatrices, y los cuerpos que las portan, ejercen una relación racializada con la nación. Los cuerpos morenos pueden aguantar el parto vaginal dentro de la disciplina de las maternidades públicas. Cuando las mujeres pagan por cesáreas, las cicatrices privadas las hacen más blancas y valiosas para la nación. Después de todo, no le han quitado nada al Estado.
Perpetrator programmes for partner violence: A rejoinder to Respect
Authors: Archer John , Dixon Louise , Graham‐Kevan Nicola
Published: July 2012

Purpose. To reply to the comments made by Debbonaire and Todd (2012) in relation to our critique of Respect's Position Statement.

Method. We examined their reply in relation to our original article and to the wider research literature.

Results. We show that Debbonaire and Todd's reply is largely a series of assertions, for which little or no supporting evidence is offered. Their argument is first that we are misplaced in criticizing their Position Statement, and second that the main points of the statement are defendable. We indicate why our criticisms of the statement still stand.

Conclusions. We argue that Respect have not countered our overall criticism of their position that intimate partner violence (IPV) can only be addressed as a gendered issue, that is as a consequence of patriarchal values enacted at the individual level. Instead we advocate a gender‐inclusive approach applying a knowledge base derived from robust empirical research on IPV and more widely from research on human aggression.
Improving the Patch Transfer Function Approach for Fluid-Structure Modelling in Heavy Fluid
Authors: Maxit L. , Aucejo M. , Guyader J.-L.
Published: July 2012

The vibro-acoustic behavior of elastic structures coupled with cavities filled with a heavy fluid can be modeled by using the Finite Element Method. In order to reduce computing time, the Patch Transfer Function (PTF) approach is used to partition the global problem into different sub-problems. Different types of problem partitioning are studied in this paper. Partitioning outside the near field of structures to reduce the number of patches of the coupling surface for frequencies below the critical frequency is of particular interest. This implies introducing a non- standard modal expansion to compute the PTF accurately enough to guarantee the convergence of the PTF method and reduce computation time in comparison to a direct Finite Element resolution. An application on a submarine structure illustrates the interest of this approach.
Stochastic Analysis of the Eigenvalue Problem for Mechanical Systems Using Polynomial Chaos Expansion— Application to a Finite Element Rotor
Authors: Sarrouy E. , Dessombz O. , Sinou J.-J.
Published: July 2012

This paper proposes to use a polynomial chaos expansion approach to compute stochastic complex eigenvalues and eigenvectors of structures including damping or gyroscopic effects. Its application to a finite element rotor model is compared to Monte Carlo simulations. This lets us validate the method and emphasize its advantages. Three different uncertain configurations are studied. For each, a stochastic Campbell diagram is proposed and interpreted and critical speeds dispersion is evaluated. Furthermore, an adaptation of the Modal Accordance Criterion (MAC) is proposed in order to monitor the eigenvectors dispersion.
Probabilistic Solutions of the Stochastic Oscillators With Even Nonlinearity in Displacement
Authors: Er Guo-Kang , Guo Siu-Siu , Pan Iu Vai
Published: July 2012

The probabilistic solutions of the nonlinear stochastic oscillators with even nonlinearity in displacement are investigated with the exponential-polynomial closure method. Numerical results show that the results obtained from the exponential-polynomial closure method agree well with the simulated solution in the presented case, even if the mean of displacement is nonzero and the probability density function of the displacement is nonsymmetric about its mean.
SPICE Modeling Nonlinearity Effects on Ultrasonic Waves
Authors: Aouzale Noureddine , Chitnalah Ahmed , Jakjoud Hicham
Published: July 2012

Nonlinearity is one of the phenomena that affect the ultrasonic wave during its propagation in a given medium. In the time domain the nonlinearity is seen as a variation of the phase velocity which leads to a distortion of the waveform. This corresponds in the frequency domain to energy transfer from the fundamental frequency to the harmonic and among the harmonic themselves. Our purpose in this paper is to introduce a SPICE implementation of the computational model of the nonlinear ultrasound propagation. We first study the plane wave distortion based on the Burgers’ equation. Our SPICE model allowed studying the temporal profile of the ultrasonic wave during its propagation. The simulation results are compared to the analytical solution of the Burgers’ equation showing the validity of the model. An experimental device based on ultrasonic transmission mode is used to carry out measurements and the comparison with the simulation results shows a good agreement.
Sound Radiation From Shear Deformable Stiffened Laminated Plates With Multiple Compliant Layers
Authors: Cao Xiongtao , Hua Hongxing
Published: July 2012

Sound radiation from shear deformable stiffened laminated plates with multiple compliant layers is theoretically studied. Equations of motion for the composite laminated plates are on the basis of the first-order shear deformation plate theory, and the transfer matrix method is used to describe sound transmission through compliant layers. The first and second sets of stiffeners interact with the plate through normal line forces. By using the Fourier transform and stationary phase method, the far-field sound pressure is obtained in terms of analytical expressions. Comparisons are made between the first-order shear deformation plate theory and the classical thin plate theory. Three principal conclusions are drawn in the study. (1) The transverse point force acting on the stiffeners yields lower far-field sound pressure in the middle and high frequency range. Specifically, the transverse point force exerting on the large stiffeners produces the lowest far-field sound pressure among three different reactive points at the plate, small stiffener and large stiffener. (2) The far-field sound pressure spectra are confined by an acoustic circle and remain unchanged. Lots of flexural waves in the structure cannot radiate sound into the far field. (3) The sound attenuation of stiffened plates with compliant layers is mainly caused by the sound isolation of compliant layers rather than vibrational reduction. Compliant layers can effectively reduce the radiated sound pressure in the medium and high frequency range.
Structural Intensity Modeling and Simulations for Damage Detection
Authors: Shepherd Micah R. , Conlon Stephen C. , Semperlotti Fabio , Hambric Stephen A.
Published: July 2012

Structural health monitoring (SHM) techniques have previously been proposed based on structural intensity (SI) due to its sensitivity to changes in boundary and loading conditions, and impedance, as well as to various damage mechanisms. In this paper, computational techniques for SI-based SHM are presented. Finite element solvers combined with SI equations can yield intensity maps over structures to determine characteristic changes in power flow due to damage. Numerical techniques for structural surface intensity (SSI) are also introduced using two alternative methods: A time domain approach that directly uses SSI equations that are valid at the surface of any elastic solid, and a frequency domain technique, which computes SI for very thin plate elements located at the surface of the structure. Advanced contact features such as nonlinearity can also be included in the model to increase the damage detection sensitivity. A plate model is used to illustrate these capabilities using SSI maps at nonlinear harmonics (NSSI). The results show both improved damage sensitivity and more global detection capabilities in a NSSI-based SHM system. A complex structure is also included to show global and local changes in SSI due simulated damage scenario. The techniques developed can be applied to general SI/SSI assessments and the design of SI-based SHM systems.
Comparison of Simulation and Experimental Results of a Tractor Seat With Nonlinear Stiffness and Dead-Band Damping
Authors: Duke Mike , Fow Alista
Published: July 2012

A low friction tractor seat with nonlinear stiffness and dead-band damping was investigated both by simulation and experimentation. The objective was to determine if a practical, “soft” suspension system could be developed that offered improved vibration performance compared to a typical mechanical commercial tractor seat suspension. A “hard” damper was used to prevent end stop impacts that were more likely with the soft suspension. In addition the damper had a dead-band centered at the seat’s static equilibrium position. The dead-band damping was achieved with a switchable damper using relative seat displacement as the control signal. The objective of the dead-band was to allow a soft undamped operating region that gave good vibration attenuation. If the relative seat displacement passed the dead-band limits due to sudden harsh inputs, the hard damping would take over and prevent end stop impacts. An experimental rig with nonlinear seat and switchable damping was built and tested with the same parameters and inputs as those used in the simulations. The simulation and experimental results compared well. Both the simulation and experimental results showed that a combination of nonlinear stiffness and dead-band damping used on a tractor seat gives reduced rms acceleration compared to a linear, conventionally damped seat.
Vibration Induced Directed Transport of Particles
Authors: Viswarupachari Ch. , DasGupta Anirvan , Pratik Khastgir S.
Published: July 2012

This paper reports a study on directed transport of a particle over a flat horizontal rigid plate vibrating asymmetrically in its plane. A friction model with both dry and viscous friction terms has been considered. Nonlinear frictional interaction between the particle and the plate, and asymmetry in the vibrations of the plate are essential for the transport process. Two kinds of asymmetry, namely spatial asymmetry, and temporal asymmetry in the plate vibrations have been considered. The mechanism of transport and the transport properties for both kinds of input motion have been clearly brought out. Three nondimensional parameters are found to characterize the transport properties. Two energy metrics have been defined to study and understand the efficiency of the transport process.
Acoustic Source Data for Medium Speed IC-Engines
Authors: Hynninen Antti , Turunen Raimo , Åbom Mats , Bodén Hans
Published: July 2012

Knowledge of the acoustic source characteristics of internal combustion engines (IC-engines) is of great importance when designing the exhaust duct system and its components to withstand the resulting dynamic loads and to reduce the exhaust noise emission. The goal of the present study is to numerically and experimentally investigate the medium speed IC-engine acoustic source characteristics, not only in the plane wave range but also in the high frequency range. The low frequency acoustic source characteristics were predicted by simulating the acoustic multiload measurements by using a one-dimensional process simulation code. The low frequency in-duct exhaust noise of a medium speed IC-engine can be quite accurately predicted. The high frequency source data is estimated by averaging the measured acoustic pressures with different methods; using the simple cross-spectra averaging method seems promising in this instance.
Design of Laser Treatment Protocols for Bacterial Disinfection in Root Canals Using Theoretical Modeling and MicroCT Imaging
Authors: Gill Jennifer , Arola Dwayne , Fouad Ashraf F. , Zhu Liang
Published: July 2012

Theoretical simulations of temperature elevations in root dentin are performed to evaluate, how heating protocols affect the efficacy of using erbium, chromium; yttrium, scandium, gallium, garnet (Er,Cr;YSGG) pulsed lasers for bacterial disinfection during root canal treatments. The theoretical models are generated based on microcomputer tomography (microCT) scans of extracted human teeth. Heat transfer simulations are performed using the Pennes bioheat equation to determine temperature distributions in tooth roots and surrounding tissue during 500 mW pulsed Er,Cr;YSGG laser irradiation on the root canal for eradicating bacteria. The study not only determines the heat penetration within the deep dentin but also assesses potential thermal damage to the surrounding tissues. Thermal damage is assumed to occur when the tissue is subject to a temperature above at least 47 °C for a minimum duration of 10 s. Treatment protocols are identified for three representative tooth root sizes that are capable of maintaining elevated temperatures in deep dentin necessary to eradicate bacteria, while minimizing potential for collateral thermal tissue damage at the outer root surfaces. We believe that the study not only provides realistic laser heating protocols for various tooth root geometries but also demonstrates utility of theoretical simulations for designing individualized treatments in the future.
Oxidative Stability of Algae Derived Methyl Esters
Authors: Bucy Harrison , Marchese Anthony J.
Published: July 2012

Microalgae are currently receiving strong consideration as a potential biofuel feedstock to help meet the advanced biofuels mandate of the 2007 Energy Independence and Security Act because of its theoretically high yield (gal/acre/year) in comparison to current terrestrial feedstocks. For algal methyl ester biodiesel, fuel properties will be directly related to the fatty acid composition of the lipids produced by the given microalgae strain. Several microalgae species under consideration for wide scale cultivation, such as Nannochloropsis, produce lipids with fatty acid compositions containing substantially higher quantities of long chain-polyunsaturated fatty acids (LC-PUFA) in comparison to terrestrial feedstocks. It is expected that increased levels of LC-PUFA will be problematic in terms of meeting all of the current ASTM specifications for biodiesel. Moreover, these same LC-PUFA fatty acids, such as eicosapentaenoic acid (EPA: C20:5) and docosahexaenoic acid (DHA: C22:6) are known to have high nutritional value, thereby making separation of these compounds economically attractive. Given the uncertainty in the future value of these LC-PUFA compounds and the economic viability of the separation process, the goal of this study was to examine the oxidative stability of algal methyl esters with varying levels of EPA and DHA. Tests were conducted using a Metrohm 743 Rancimat with automatic induction period determination following ASTM D6751 and EN 14214 standards, which call for induction periods of at least 3 and 6 h, respectively. Tests were conducted at a temperature of 110 °C and airflow of 10 l/h with model algal methyl ester compounds synthesized from various sources to match the fatty acid compositions of several algae strains subjected to varying removal amounts of roughly 0% to 100% LC-PUFA. In addition, tests were also conducted with real algal methyl esters produced from multiple sources. The bis-allylic position equivalent (BAPE) was calculated for each fuel sample to quantify the level of unsaturation. The induction period was then plotted as a function of BAPE, which showed that the oxidative stability varied exponentially with the amount of LC-PUFA. The results suggest that removal of 45% to 65% of the LC-PUFA from Nannochloropsis-based algal methyl esters would be sufficient for meeting existing ASTM specifications for oxidative stability.
Fall on Backpack: Damage Minimization of Humanoid Robots by Falling on Targeted Body Segments
Authors: Lee Sung-Hee , Goswami Ambarish
Published: July 2012

Safety and robustness will become critical issues when humanoid robots start sharing human environments in the future. In physically interactive human environments, a catastrophic fall is a major threat to the safety and smooth operation of humanoid robots. It is, therefore, imperative that humanoid robots be equipped with a comprehensive fall management strategy. This paper deals with the problem of reducing the impact damage to a robot associated with a fall. A common approach is to employ damage-resistant design and apply impact-absorbing material to robot limbs, such as the backpack and knee, that are particularly prone to fall related impacts. In this paper, we select the backpack to be the most preferred body segment to experience an impact. We proceed to propose a control strategy that attempts to reorient the robot during the fall such that it impacts the ground with its backpack. We show that the robot can fall on the backpack even when it starts falling sideways. This is achieved by generating and redistributing angular momentum among the robot limbs through dynamic coupling. The planning and control algorithms for a fall are demonstrated in simulation.
A Nonlinear Vehicle-Road Coupled Model for Dynamics Research
Authors: Li Shaohua , Yang Shaopu , Chen Liqun
Published: July 2012

This paper presents a nonlinear vehicle-road coupled model which is composed of a seven-degree of freedom (DOF) vehicle and a simply supported double-layer rectangular thin plate on a nonlinear viscoelastic foundation. The nonlinearity of suspension stiffness, suspension damping and tire stiffness is considered and the Leaderman constitutive relation and Burgers model are applied to describe the nonlinear and viscoelastic properties of the asphalt topping material. The equations of motion for the vehicle-road system are derived and the partial differential equation of road pavement is discretized into an infinite number of second-order ordinary differential equations and first-order ordinary differential equations by Galerkin’s method and a mathematic transform. A numerical integration method for solving this coupled system is developed and the nonlinear dynamic behaviors of the system are analyzed. In addition, the simulation results of the coupled model are compared to those of the uncoupled traditional model. It is found that with the increase of harmonic road surface roughness amplitude, the vehicle body’s vertical response is always periodic, whereas the pavement’s response varies from quasi-periodic motion to chaotic motion. In the case of a heavy-duty vehicle, a soft subgrade or a higher running speed, the application of the proposed nonlinear vehicle-road coupled model would bring higher computational accuracy and make it possible to design the vehicle and pavement simultaneously.
General Noise-Perturbed Superior Julia Sets
Authors: Rani Mamta , Agarwal Rashi
Published: July 2012

The aim of this paper is to offer an integrated approach to study the additive and multiplicative noises with respect to perturbations in superior Julia sets. External and internal perturbations in superior Julia sets are analyzed under the mixed effect of additive and multiplicative noises.
Structural and Continuum Mechanics Approaches for a 3D Shear Deformable ANCF Beam Finite Element: Application to Static and Linearized Dynamic Examples
Authors: Nachbagauer Karin , Gruber Peter , Gerstmayr Johannes
Published: July 2012

In the present paper, a three-dimensional shear deformable beam finite element is presented, which is based on the absolute nodal coordinate formulation (ANCF). The orientation of the beam’s cross section is parameterized by means of slope vectors. Both a structural mechanics based formulation of the elastic forces based on Reissner’s nonlinear rod theory, as well as a continuum mechanics based formulation for a St. Venant Kirchhoff material are presented in this paper. The performance of the proposed finite beam element is investigated by the analysis of several static and linearized dynamic problems. A comparison to results provided in the literature, to analytical solutions, and to the solution found by commercial finite element software shows high accuracy and high order of convergence, and therefore the present element has high potential for geometrically nonlinear problems.
An Efficient Reduced-Order Model to Investigate the Behavior of an Imperfect Microbeam Under Axial Load and Electric Excitation
Authors: Ruzziconi Laura , Younis Mohammad I. , Lenci Stefano
Published: July 2012

In this study an efficient reduced-order model for a MEMS device is developed and investigations of the nonlinear static and the dynamic behavior are performed. The device is constituted of an imperfect microbeam under an axial load and an electric excitation. The imperfections, typically due to microfabrication processes, are simulated assuming a shallow arched initial shape. The axial load is deliberately added with an elevated value. The structure has a bistable static configuration of double potential well with possibility of escape. We derive a single-mode reduced-order model via the Ritz technique and the Padé approximation. This model, while simple, is able to combine both a sufficient accuracy, which enables to detect the main qualitative features of the device response up to elevated values of electrodynamic excitation, and a remarkable computational efficiency, which is essential for systematic global nonlinear dynamic simulations. We illustrate the nonlinear phenomena arising in the device, such as the coexistence of various competing in-well and cross-well attractors, which leads to a considerable versatility of behavior. We discuss their physical meaning and their practical relevance for the engineering design of the microstructure, since this is an uncommon and very attractive aspect in applications.
An Integrated Particle-Tracking Impact/Adhesion Model for the Prediction of Fouling in a Subsonic Compressor
Authors: Borello D. , Rispoli F. , Venturini P.
Published: July 2012

The present paper reports on the analysis of the motion of adhesive particles and deposit formation in a 3D linear compressor cascade in order to investigate the fouling in turbomachinery flows. The unsteady flow field is provided by a prior hybrid large-eddy simulation (LES)/Reynolds-averaged Navier-Stokes (RANS) computation. The particles are individually tracked and the deposit formation is evaluated on the basis of the well-established Thornton and Ning model. Although the study is limited to three regions of the blade, where the most relevant turbulent phenomena occurs, the prediction of fouling shows good agreement with real situations. Deposits form near the casing and the hub, in the zones where there are strong vortical structures originated by the tip leakage and hub vortices. On the blade, the deposit analysis is focused on three main regions: (a) along the stagnation region on the leading edge; (b) on the suction side, where the particles are conveyed by the hub vortex towards blade surfaces; and (c) on the pressure side, where a clean zone forms between leading edge and the blade surface, as can be seen in real compressors.
Prediction of Axial and Circumferential Flow Conditions in a High Temperature Foil Bearing With Axial Cooling Flow
Authors: Ryu Keun
Published: July 2012

A successful implementation of gas foil bearings (GFBs) into high temperature turbomachinery requires adequate thermal management to maintain system reliability and stability. The most common approach for thermal management in a GFB-rotor system is to supply pressurized air at one end of the bearing to remove hot spots in the bearings and control thermal growth of components. This technical brief presents test data for a laboratory rotor-GFB system operating hot to identify the flow characteristics of axial cooling streams flowing through the thin film region and underneath the top foil. A bulk flow model is used for description of the fluid motion and includes the Hirs’ friction factor formulation for smooth surfaces. Laminar flow prevails through the thin film gas region; while for the cooling flow between the top foil and bearing housing, a transition from laminar flow to turbulent flow occurs as the cooling flow rate increases. Large cooling flow rate and the ensuing turbulent flow conditions render limited effectiveness in controlling temperatures in a test rotor-GFB system.
Parametric Design Optimization of Uncertain Ordinary Differential Equation Systems
Authors: Hays Joe , Sandu Adrian , Sandu Corina , Hong Dennis
Published: July 2012

This work presents a novel optimal design framework that treats uncertain dynamical systems described by ordinary differential equations. Uncertainty in multibody dynamical systems comes from various sources, such as system parameters, initial conditions, sensor and actuator noise, and external forcing. The inclusion of uncertainty in design is of paramount practical importance because all real-life systems are affected by it. Designs that ignore uncertainty often lead to poor robustness and suboptimal performance. In this work, uncertainties are modeled using generalized polynomial chaos and are solved quantitatively using a least-square collocation method. The uncertainty statistics are explicitly included in the optimization process. Systems that are nonlinear have active constraints, or opposing design objectives are shown to benefit from the new framework. Specifically, using a constraint-based multi-objective formulation, the direct treatment of uncertainties during the optimization process is shown to shift, or off-set, the resulting Pareto optimal trade-off curve. A nonlinear vehicle suspension design problem, subject to parametric uncertainty, illustrates the capability of the new framework to produce an optimal design that accounts for the entire family of systems within the associated probability space.
Comparison of Selected Methods of Handling Redundant Constraints in Multibody Systems Simulations
Authors: Wojtyra Marek , Frączek Janusz
Published: July 2012

When redundant constraints are present in a rigid body mechanism, only selected (if any at all) joint reactions can be determined uniquely, whereas others cannot. Analytic criteria and numerical methods of finding joints with uniquely solvable reactions are available. In this paper, the problem of joint reactions solvability is examined from the point of view of selected numerical methods frequently used for handling redundant constraints in practical simulations. Three different approaches are investigated in the paper: elimination of redundant constraints; pseudoinverse-based calculations; and the augmented Lagrangian formulation. Each method is briefly summarized; the discussion is focused on techniques of handling redundant constraints and on joint reactions calculation. In the case of multibody systems with redundant constraints, the rigid body equations of motion are insufficient to calculate some or all joint reactions. Thus, purely mathematical operations are performed in order to find the reaction solution. In each investigated method, the redundant constraints are treated differently, which—in the case of joints with nonunique reactions—leads to different reaction solutions. As a consequence, reactions reflecting the redundancy handling method rather than physics of the system are calculated. A simple example of each method usage is presented, and calculated joint reactions are examined. The paper points out the origins of nonuniqueness of constraint reactions in each examined approach. Moreover, it is shown that one and the same method may lead to different reaction solutions, provided that input data are prepared differently. Finally, it is demonstrated that—in case of joints with solvable reactions—the obtained solutions are unique, regardless of the method used for redundant constraints handling.
Controlled Deflection Approach for Rotor Crack Detection
Authors: Kulesza Zbigniew , Sawicki Jerzy T.
Published: July 2012

A transverse shaft crack is a serious malfunction that can occur due to cyclic loading, creep, stress corrosion, and other mechanisms to which rotating machines are subjected. Though studied for many years, the problems of early crack detection and warning are still in the limelight of many researchers. This is due to the fact that the crack has subtle influence on the dynamic response of the machine and still there are no widely accepted, reliable methods of its early detection. This paper presents a new approach to these problems. The method utilizes the coupling mechanism between the bending and torsional vibrations of the cracked, nonrotating shaft. By applying an external lateral force of constant amplitude, a small shaft deflection is induced. Simultaneously, a harmonic torque is applied to the shaft inducing its torsional vibrations. By changing the angular position of the lateral force application, the position of the deflection also changes opening or closing of the crack. This changes the way the bending and torsional vibrations are being coupled. By studying the coupled lateral vibration response for each angular position of the lateral force one can assess the possible presence of the crack. The approach is demonstrated with a numerical model of a rotor. The model is based on the rigid finite element method (RFE), which has previously been successfully applied for the dynamic analysis of many complicated, mechanical structures. The RFE method is extended and adopted for the modeling of the cracked shafts. An original concept of crack modeling utilizing the RFE method is presented. The crack is modeled as a set of spring-damping elements (SDEs) of variable stiffness connecting two sections of the shaft. By calculating the axial deformations of the SDEs, the opening/closing mechanism of the crack is introduced. The results of numerical analysis demonstrate the potential of the suggested approach for effective shaft crack detection.
An Extended Pattern Search Approach to Wind Farm Layout Optimization
Authors: Du Pont Bryony L. , Cagan Jonathan
Published: July 2012

An extended pattern search approach is presented for the optimization of the placement of wind turbines on a wind farm. Problem-specific extensions infuse stochastic characteristics into the deterministic pattern search, inhibiting convergence on local optima and yielding better results than pattern search alone. The optimal layout for a wind farm is considered here to be one that maximizes the power generation of the farm while minimizing the farm cost. To estimate the power output, an established wake model is used to account for the aerodynamic effects of turbine blades on downstream wind speed, as the oncoming wind speed for any turbine is proportional to the amount of power the turbine can produce. As turbines on a wind farm are in close proximity, the interaction of turbulent wakes developed by the turbines can have a significant effect on the power development capability of the farm. The farm cost is estimated using an accepted simplified model that is a function of the number of turbines. The algorithm develops a two-dimensional layout for a given number of turbines, performing local turbine movement while applying global evaluation. Three test cases are presented: (a) constant, unidirectional wind, (b) constant, multidirectional wind, and (c) varying, multidirectional wind. The purpose of this work is to explore the ability of an extended pattern search (EPS) algorithm to solve the wind farm layout problem, as EPS has been shown to be particularly effective in solving multimodal layout problems. It is also intended to show that the inclusion of extensions into the algorithm can better inform the search than algorithms that have been previously presented in the literature. Resulting layouts created by this extended pattern search algorithm develop more power than previously explored algorithms using the same evaluation models and objective functions. In addition, the algorithm’s resulting layouts motivate a heuristic that aids in the manual development of the best layout found to date. The results of this work validate the application of an extended pattern search algorithm to the wind farm layout problem, and that its performance is enhanced by the use of problem-specific extensions that aid in developing results that are superior to those developed by previous algorithms.
Tooth Surface Generation and Geometric Properties of Straight Noncircular Bevel Gears
Authors: Jing Lin
Published: July 2012

A general mathematical model is established to describe the geometries and geometric characteristics of tooth surfaces of straight noncircular bevel gears. One of the direction angles of the normal vector of the tooth surfaces is taken as a function of the angular position of its origin, called the direction angle function (DAF). The normal vector and DAF are introduced to characterize this model. The normal vector including its direction angles and modulus is solved first and then the corresponding tooth surfaces and their geometric properties, such as major curvatures and slide coefficients, could be generated and calculated directly, logically and systematically by using this model and defining various DAFs. This method is applicable to many types of straight noncircular bevel gears with different tooth surfaces including tooth surfaces cut by the crown rack cutter or others. In addition, by using this method, it is relatively easy to realize the desired geometrical and mechanical properties into the design.
A Versatile Acceleration-Based Cam Profile for Single-Dwell Applications Requiring Cam-Follower Clearance During Dwell
Authors: Flocker Forrest W.
Published: July 2012

Presented in this paper is an asymmetric acceleration-derived cam motion program suitable for single-dwell cam-follower systems with clearance between the cam and follower during dwell. Asymmetric rise and fall is included as this is desirable in certain manufacturing operations and machines that require a quick rise or fall. The motion program for the cam-follower actuation is derived from the follower acceleration so that designers can control the ratio of the magnitudes of positive and negative accelerations. This provides cam designers more control over the cam-follower interface force and therefore more control over factors such as cam wear and the potentially destructive phenomenon known as “follower jump.” The motion program used to close and open the clearance gap is derived from a velocity function, allowing more control of follower inertia during the important clearance closing event. The motion program is presented in closed-form, suitable for implementation in standard engineering equation-solving software.
Nonlinear Control of Aircraft Engines Using a Generalized Gronwall-Bellman Lemma Approach
Authors: Wang Jiqiang , Ye Zhifeng , Hu Zhongzhi
Published: July 2012

Model-based design has attracted much attention in the field of aircraft engine control in recent years. As an aircraft engine is a complicated thermomechanical system, it can only be represented by a nonlinear process model. This necessitates the study of the nonlinear control techniques. Based on our recent results, this paper proposes a novel design approach based on a generalized Gronwall-Bellman lemma. Important results are obtained on bounding behavior of the nonlinear states of the engine. The proposed method is easy to design and tune with the appealing feature of enlarging the feasible control envelope. Finally, a simulation study is provided to validate the effectiveness of the control design approach.