bluuebunny/crossref_metadata_2025 huggingface dataset:
Phenomenological Interpretation of Energy Loss and Storage Mechanisms in Electrorheological Fluids
Authors: Powell J. A.
Published: August 2009

This work gives insight into the behaviour of an electrorheological (ER) fluid exposed to an oscillatory strain stimulus. Electrorheological fluids can have their behaviour modified by the application of an external electric field. Because an ER fluid consists of a liquid containing small particles, the oscillatory response of the material differs widely from a material subjected to a steady uni-directional shear, due to the effect of the oscillatory motion breaking down the structure formed within the material. The application of a three element model to the oscillatory behaviour of an electrorheological fluid is given. The model consisting of a mechanical three element analogy was proposed in order to provide a parametric description of the behaviour, suitable for use in the design of engineering systems, which will possibly utilise these materials in the future. This model consists of an irreversible yielding type element, a non-linear softening elasticity and viscous energy loss terms. The combination of the elastic, viscous and yielding type elements model the form of the stress-strain rate and stress-strain diagrams very well. These diagrams were obtained experimentally from an oscillatory electrorheometer. Application of the model is shown for a variety of strain amplitudes, oscillatory frequencies and electric field strengths. From these data the variation of energy storage (elasticity) and loss (yielding and Newtonian flow) mechanisms are shown to vary in a complicated manner, dependent for a given field strength on strain amplitude, frequency and hence strain rate.
Elasticity Solution of Polymeric Piezoelectric C-Block Composite Actuator
Authors: Gu Haozhong , Chattopadhyay Aditi
Published: August 2009

An elasticity solution is developed to investigate the mechanical behavior of polymeric piezoelectric C-block composite actuators, which were recently proposed to overcome the limitations of conventional bimorph and stack configurations. The stress functions are used to derive the general equations governing the behavior of induced strain actuation under various load conditions. Closed-form expressions are presented for the displacements and stresses. Comparisons of the present approach are made with classical elasticity solutions for curved beams and existing approximate solutions for curved actuators for a simplified case. The results from the current solution also provide physical insight into the mechanism of C-block actuators.
Micromechanical Prediction of the Effective Coefficients of Thermo-Piezoelectric Multiphase Composites
Authors: Aboudi Jacob
Published: August 2009

The micromechanical generalized method of cells model is employed for the prediction of the effective elastic, piezoelectric, dielectric, pyroelectric and thermal-expansion constants of multiphase composites with embedded piezoelectric materials. The predicted effective constants are compared with other micromechanical methods available in the literature and good agreements are obtained.
Thermally Stable Magnetostrictive Device
Authors: Dozor David M.
Published: August 2009

An extremely small magnetostrictive actuator has been designed for a precision application. This paper outlines the procedure utilized to insure that the device remains thermally stable during operation. A differential constitutive relation, suitable for describing magnetostrictive materials, is used to formulate the design constraints. Using this vector constitutive relation in conjunction with finite element and lumpedparameter (circuit) models, conditions on the design parameters may be derived to insure thermally stable operation. To achieve robustness to parameter uncertainty, it is further shown that thermal stability may be achieved through the use of a properly selected thermal control bias current.
Active Microvibration Control of an Optical Payload Installed on the ARTEMIS Spacecraft
Authors: Gaudenzi Paolo , Giarda Daniele , Morganti Francesco
Published: August 2009

This paper presents a feasibility study for the vibration control of the SILEX optical payload installed on the European ARTEMIS advanced telecommunication satellite. Due to its stringent pointing requirements (being approximately a few microradiants) the payload is particularly sensitive to the transmitted microvibrational disturbances. The vibration suppression problem has been addressed using piezoceramic strain actuators bonded to the payload support structure and designing a high control authority linear quadratic compensator. The plant mathematical model was obtained through a NASTRAN finite element modeling of the payload structure equipped with the surface bonded piezoceramic strain actuators. This high order evaluation model has successively been reduced to a lower order design model using static condensation (Guyan) and modal reduction techniques. Different criteria have been applied in order to check for the controllability of the system. The LQR compensator design was based on the minimization of a quadratic performance index of state and control vectors which included the output behavior. A comparison between the open and closed loop system behavior was carried out for different disturbance inputs and different control weights.
Stacking Technology for a Space Constrained Microsystem
Authors: Heschel M. , Kuhmann J. F. , Bouwstra S. , Amskov M.
Published: August 2009

In this paper we present a stacking technology for an integrated packaging of an intelligent transducer which is formed by a micromachined silicon transducer and an integrated circuit chip. Transducer and circuitry are stacked on top of each other with an intermediate chip in between. This intermediate chip is made of silicon and carries electrical frontside to backside interconnections through anisotropically etched holes. The electrical feedthrough interconnections are realized by means of lift-off technique. The bonding of the transducer and the intermediate chip is done by fluxless flip chip solder bump bonding. The bonding between the above twolayer stack and the circuit chip is done by conductive adhesive bonding combined with gold studs. We demonstrate the stacking technologies on passive test chips rather than real devices and report on technological details.
Vibro-Acoustic Modulation Nondestructive Evaluation Technique
Authors: Donskoy Dimitri M. , Sutin Alexander M.
Published: August 2009

Nonlinear acoustic technique has been recently introduced as a new tool for nondestructive inspection and evaluation of fatigued, defective, and fractured materials. Various defects such as cracks, debonding, fatigue, etc. lead to anomalous high levels of nonlinearity as compared with flawless structures. One of the acoustic manifestations of such nonlinearity is the modulation of ultrasound by low frequency vibration. Two methods employing the nonlinear interaction of ultrasound and vibration were developed, namely vibromodulation (VM) and impactmodulation (IM) methods. VM method employs forced harmonic vibration of a structure tested, while IM method uses impact excitation of structure natural modes of vibration. The feasibility tests were carried out for different objects and demonstrated high sensitivity of the methods for detection of cracks in steel pipes and pins, bonding quality in titanium and thermoplastic plates used for airspace applications, cracks in combustion engine, adhesion flaws in bonded composite structures, and cracks and corrosion in reinforced concrete. The model of the crack allowing to describe the modulation of sound by vibration is discussed. The developed nonlinear technique demonstrated certain advantages as compared with the conventional linear acoustic technique, specifically discrimination capabilities, sensitivity, and applicability to highly inhomogeneous structures.
Embedded Fiber Bragg Grating Sensors for Industrial Composite Cure Monitoring
Authors: Dewynter-Marty V. , Ferdinand P. , Bocherens E. , Carbone R. , Beranger H. , Bourasseau S. , Dupont M. , Balageas D.
Published: August 2009

An embedded Fiber Bragg Grating (FBG) strain sensor and an FBG temperature sensor have been shown to be able to accurately monitor the industrial composite cure process of a glass/ epoxy plate devoted to aeronautical applications. The internal absolute strain level in the plate was determined, free of temperature effect thanks to a differential method. After curing, a residual compression strain of about -0.22% was observed, which represents a short part of the range in compression for a single mode fiber. Later on, the embedded FBG strain sensor could be used as a smart sensor for the health monitoring of composite structures, e.g. for impact or layer delamination detection.
An Embedded Fiber Optic Sensor Method for Determining Residual Stresses in Fiber-Reinforced Composite Materials
Authors: Lawrence Craig M. , Nelson Drew V. , Bennett Thomas E. , Spingarn Jay R.
Published: August 2009

A method to determine process-induced residual stress in fiber-reinforced composite materials using strain measurements from embedded fiber optic sensors is presented. This method allows non-destructive, real-time determination of residual macrostress in these materials and may be useful for both process monitoring and control. Extrinsic Fabry-Perot interferometer strain sensors were embedded in Hercules AS4/3501-6 graphite/epoxy composite specimens prior to cure. The specimens were cured in a press, and the internal strains and temperatures developed during processing were monitored and recorded. Residual macrostresses were computed from these measurements using a viscoelastic model of the material. The results compare favorably with analytical predictions, previous experimental measurements from a destructive technique, and with measurements of warpage of a non-symmetric laminate.
Measurement of Corrosion and Temperature Using a Single-Pitch Bragg Grating Fiber Sensor
Authors: Lo Yu-Lung , Xiao Fu-Yuan
Published: August 2009

A new method to measure metal corrosion using a single-pitch Bragg grating sensor is presented. The prestrained Bragg grating that is only partially coated with a metal can be designed as a corrosion transducer, and the section without a metal coating can be used as a temperature sensor. After releasing the preloading, the two Bragg wavelengths reflecting from the Bragg grating are sufficiently separated and have no cross-talk problems between the corrosion and temperature signals. The principle of corrosion sensors is that environmental corrosion changes the coating thickness; consequently, the residual strain inside the section with a metal coating is released and then causes a Bragg wavelength shift. Since the temperature variation is obtained from the free section, the temperature effect in the Bragg grating corrosion sensor can be measured and compensated. Two analytical methods for the Bragg grating corrosion sensor are developed and they are in good agreement. Also, experimental data shows that Bragg grating corrosion sensors are feasible for a quantitative analysis.
Direct-Drive Electrostatic Micromotors Using Flexible Polysilicon Rotors
Authors: Minotti Patrice , Langlet Philippe , Bourbon Gilles , Masuzawa Takahisa , le Moal Patrice
Published: August 2009

This paper is devoted to the design, the fabrication and the characterization of a new generation of direct-drive silicon based electrostatic micromotors. The following work points out the main torque limitations that occur in the design of conventional electrostatic actuators using electrostatic field interactions. Stator/rotor contact interactions are then considered, in order to provide larger external torque. Distributed motion systems are also investigated, because of significant driving forces that are expected through cooperative arrayed microactuators. According to this analysis, annular-type micromotors having a (500 Atm external diameter are proposed. The motor actuation involves stator/rotor contact interactions by using a flexible polysilicon rotor which combines arrayed elementary bending actuators. Moreover, the rotor integrates a self-adjusted torque sensor that allows the driving torque to be directly measured. Experimental characteristics point out the relevance of the proposed design rules. Unusual driving torque, one thousand times higher than ones obtained using conventional electrostatic wobble motors, have been already measured. Rotation speed ranging from 0.001 up to 750 rpm is also reported, according to the driving voltage frequency which was tuned from 1 Hz up to 500 kHz.
Embedded Self-Sensing Piezoelectric for Damage Detection
Authors: de Vera C. Pardo , Güemes J. A.
Published: August 2009

A method for damage detection based on self-sensing piezoelectrics is presented. When a piezoelectric actuator is electronically excited, it causes stress in the structure to which it is attached. As the structure deformation is influenced by the presence of damage, so will be the response of the sensor. The goal of the method is to use the same piezoelectric element as both actuator and sensor, by analyzing the electromechanical response of the system in the frequency domain. In this way, damaged and undamaged structures can be distinguished and the extent of damage estimated. The distinction between the excitation and the response signals is achieved by an electronic bridge circuit. A comparison between this self-sensing method and the more common cross-talk method is performed, showing the similarity of the two methods and the validity of our technique. A method to differentiate among the spectrum changes due to actual damage and those due to temperature shifts is also presented. As the temperature rises, the PZT characteristics change and the resonance frequencies of the spectrum shift. However, the acquired signal can be processed to compensate for the temperature changes.
Health Monitoring of Civil Structures
Authors: Chong Ken P.
Published: August 2009

Health monitoring of civil infrastructure systems is cost-effective and necessary since these systems are generally the most expensive investments/assets in any country. In the U.S. these assets are estimated at $20 trillion. In addition, these systems have long service life compared with any other kinds of commercial product, and are rarely replaceable once they are erected. Yet the feedback and controls on the "state of health" of constructed systems are practically nonexistent. Nondestructive evaluation (NDE), sensing and smart structures are essential parts of this feedback and monitoring system for infrastructures. The NSF NDE initiative as well as workshops and related awards/projects are described in this paper.
Aircraft Structural Health Monitoring, Prospects for Smart Solutions from a European Viewpoint
Authors: Bartelds G.
Published: August 2009

Structural health is directly related to structural performance and in this respect it is a governing parameter with regard to safety of operation. This aspect of structural health is particularly relevant for transportation systems and in this connection structural health monitoring is a safety issue. In aviation, and particularly in air transportation, structural health monitoring has been developed to a rather satisfactory level albeit using rather unsophisticated methods of inspection involving considerable man-hour requirements as well as very special skills and attitudes on the part of the inspector. Undoubtedly structural reliability of aircraft has increased considerably also as a result of the implementation of damage tolerant design practices and of automated fabrication including joining with a high degree of controllability and repeatability. It is particularly the aspects of sensitivity and reliability of manual inspection that stimulate the study of more sophisticated automated and integrated damage sensing systems as a smart substitute for the current practice relying heavily on human intelligence. The paper identifies the study and development of smart damage detection systems as an interdisciplinary activity involving specialists in different technical areas. The risks involved are of a technical nature but also relate to approval and acceptance of automated systems in air transportation systems. It describes the current situation in Europe that is international in character by definition. Different supranational bodies have recognized the development of smart systems as substitutes for human operations as a key technology and they provide funding that enables the formation of development teams with a good basis for continuity.
Identifying Impacts in Composite Plates with Piezoelectric Strain Sensors, Part I: Theory
Authors: Tracy Michael , Chang Fu-Kuo
Published: August 2009

This paper summarizes the theory used in a system that identifies foreign body impact on a composite plate using built-in strain sensors. The identification system consists of a model of the composite plate and an identification algorithm. The algorithm compares the measured response of the plate to the model response and estimates the impact location and force time history. The solution, which uses a smoother/filter optimization, includes a new computational algorithm that saves considerable computation time for systems with many degrees of freedom.
Optical Sensors and Their Fusion in a Quasi-Smart Structure for Real-Time Vibration Monitoring and Predictive Maintenance of Large Power Electric Power Generators
Authors: López-Higuera J. M. , Cobo A. , Morante M. A. , Madruga F. J. , Santamaria I. , Pantaleon C. , Ibanez J. , Mottier P. , Ollier E. , Chabrol Cl.
Published: August 2009

Optical accelerometers developed in both fiber and integrated optics technologies and several traditional sensors are integrated in a quasi-smart structure for real-time monitoring and predictive maintenance of large Electric Power Generators. The structures were properly tested in field trials.
Optimal Transducer Placement for Active Control of Sound Transmission through Aeroelastic Plates
Authors: Smith G. Clark , Clark Robert L. , Frampton Kenneth D.
Published: August 2009

This paper investigates the effect of convected fluid loading on the optimal locations of colocated transducers for static output feedback control of sound transmission through an aeroelastic plate.The model of a convected fluid loaded plate coupled to a cavity is presented. The physical dimensions and parameters of the model are chosen to replicate a small commercial aircraft. Development of the appropriate cost function and optimization algorithm is discussed in detail. Case studies optimizing a control system with one colocated velocity sensor and point force actuator are presented for external flow speeds varying from Mach 0.1 to Mach 0.8. The initial location of the sensor-actuator pair was selected arbitrarily. Results indicate that optimum transducer placement does not vary considerably over the flow speeds considered. However, in all flow cases the performance of the structural acoustic control system increased with transducer placement optimization. The greatest benefit being 7.9 dB for the Mach 0.8 case. Considerably greater reduction in the low frequency region was also noted after transducer placement optimization. For the Mach 0.8 case, cavity acoustic potential energy in the 1/3 octave band centered at 31.5 Hz decreased 30.1 dB after placement optimization.
Multi-Modal Vibration Control of Laminated Composite Plates Using Piezoceramic Sensors/Actuators
Authors: Kang Young Kyu , Kim Moon Hyun , Park Hyun Chul , Agrawal Brij
Published: August 2009

Multi-modal vibration control of the cantilevered laminated composite plates using collocated piezoceramic sensors/actuators is analyzed theoretically and verified experimentally for various fiber orientations. Impact on the stiffness and the damping properties by varying the stacking sequence of [04/02/902j, for the laminated composite plate is studied. The finite element method is used for the dynamic analysis of the plates with and without the piezoceramics. Natural frequencies and modal damping of the first bending and the first torsional modes are predicted theoretically by taking into account damping and stiffness of the adhesive layer and the piezoceramics in the modeling. Active modal damping of the first bending and the first torsional modes are measured experimentally. It is demonstrated that the active control is more effective for the structure with higher stiffness when the feedback gain is large, whereas it follows trends of the passive control by tailoring when the gain is small.
Dynamic Analysis of Piezoelectric Fiber Composite in an Active Beam Using Homogenization and Finite Element Methods
Authors: Mahut Tony , Agbossou Amen , Pastor Joseph
Published: August 2009

The purpose of this work is to point out the improvement, which could be achieved through use of piezoelectric fiber composite elements in place of piezoelectric patch elements, in structural vibration systems. Therefore, we review the homogenization method for prediction of the overall properties of piezoelectric fiber composite and we propose the Periodic Medium Homogenization model. The results indicated a good correlation between our proposed model and the MoriTanaka approach. Then we considered the cases of incorporated bulk piezoelectric and piezoelectric fiber composite in two epoxy cantilevered beams loaded by static and dynamic forces. The numerical results show that, with the piezoelectric fiber composite, one can adapt the electromechanical coupling coefficient for a specific task by simply changing the fiber content. The results also suggest that increasing fiber content above 35% for the analyzed beam, will effectively result in reduced performance of the active structure.
New Thin Piezoelectric Plate Models
Authors: Rahmoune M. , Benjeddou A. , Ohayon R. , Osmont D.
Published: August 2009

Early investigations on piezoelectric plates were based on a priori mechanical and experimental considerations. They assume plane stress and consider only transverse components of electric displacement and field. Beside, these were supposed constant in the plate thickness. Through an asymptotic analysis, this paper shows that mechanical hypotheses follow Kirchhoff-Love theory of thin plates. However, electric assumptions are found to be strongly dependent on the electric boundary conditions. That is, two regular problems should be distinguished: (1) the short circuited plate, for which only transverse electric displacement and field have to be considered-the electric potential is then found to be the sum of a known part, which depends on prescribed potentials, and an unknown part, which represents an induced potential and cannot be a priori neglected; the mechanical and electrical problems may be uncoupled; (2) the insulated plate, for which only in-plane electric displacement and field components are to be considered; the mechanical and electrical problems may be uncoupled for orthorhombic plates but not in general. Based on the above asymptotic analysis, two variational and local two-dimensional static models are presented for heterogeneous anisotropic plates. They are then applied to homogeneous and orthorhombic piezoelectric plates. For homogeneous orthorhombic piezoelectric plates, the electromechanical problem can be uncoupled. Hence, a mechanical problem is first solved for the mechanical displacement, then electric potentials are explicitly deduced from this displacement. Classical finite element codes having multilayer plate facilities can be used for solving the plate problems obtained.
Energy Analysis of Piezoelectric-Actuated Structures Driven by Linear Amplifiers
Authors: Leo Donald J.
Published: August 2009

Energy expressions for a piezoelectric actuator coupled to a resonant mechanical load are analyzed for the purpose of determining the energy requirements of controlled structures. The analysis illustrates that the energy dissipated within the linear amplifier is a function of four parameters: the driving frequency, the piezoelectric coupling coefficient, the relative stiffness of the actuator and load, and the amplifier supply voltage. The piezoelectric actuator and the mechanical load are assumed to be lossless to highlight the relationship between energy dissipated within the amplifier and the energy stored in the actuator. For a specific frequency, the minimum energy dissipation within the amplifier is equal to twice the stored electrical energy in the piezoelectric when the amplifier voltage is equal to the driving voltage of the actuator. Additional energy is dissipated within the amplifier when the supply voltage is greater than the driving voltage. In the case when the actuator displacement is constant as a function of frequency, the energy dissipation in the amplifier decreases near the resonance of the coupled electromechanical system and reaches a minimum when the piezoelectric charge due to the applied voltage is equal and opposite to the charge induced by the load. The steadystate amplitude of the charge, and hence the actuator current, is equal to zero at this frequency. The results illustrate that energy dissipation is minimized when the actuator is operated at near the resonance or antiresonance of the coupled electromechanical system.
Thickness Vibrations of Sandwich Plates and Beams and Delamination Detection
Authors: Jensen Alf Egil , Irgens Fridtjov
Published: August 2009

In multi-hull marine vehicles assembled by FRP sandwich composite materials, problems with delamination and skin/core debonding are reported. An early damage warning (EDW) system for delamination detection in marine vessels based on measurements of bending vibrations in sandwich structures are under development.

Related to this EDW system development, this paper presents a theory for qualitative determination of thickness vibrations in sandwich plates and beams. The core is modelled as a two-parameter foundation where shearing interaction effects and normal stress effects in the core are included. The skins are modelled as ordinary plates or beams on a foundation. Expressions for both thickness shear and thickness stretch modes are given. In addition to the theoretical development, experiments with a simply supported sandwich beam, using a TV-holography technique, were performed and good agreement between theory and experiments was achieved.

With the expressions for thickness shear and thickness stretch frequencies presented in this paper one is able to qualitatively determine thickness vibration frequencies. It is particularly important to determine whether thickness vibrations are present in the same frequency range as the bending frequencies of interest in the EDW system. The occurrence of a thickness shear frequency and an occasional non-existence of a higher bending frequency may be misinterpreted as a down shift of the bending frequency and thus lead to an incorrect delamination detection.
Passive Vibroacoustic Isolation for Payload Containers
Authors: Griffin Steven F. , Denoyer Keith K. , Das Alok
Published: August 2009

This paper presents analysis and experimental results which examine key issues related to passive vibroacoustic isolation for container type structures. The key noise reduction principle examined is the passive application of a characteristic impedance mismatch in conjunction with a vibration isolation suspension system to limit structural transmission. The characteristic impedance mismatch is created by imposing a near vacuum condition between partitions of a container structure. Unlike active boundary control techniques, this approach is insensitive to the grazing angle of the source acoustics, is simple, and avoids technology challenges such as the need to develop efficient large stroke actuators. The analysis for this problem is performed by extending Fahy's double-leaf partition model. Using the extended model, numerical simulations are conducted to study the effect of various design parameters on acoustic transmission. Guidelines developed from this study are then used to construct an experiment to show the viability of the concept. The experiment demonstrates that at least a 19 dB reduction in sound pressure level (SPL) may be achieved, with a modest level of vacuum.
Polyurethane Actuators Using Bending Piezoelectricity and Bending Electrostriction
Authors: Watanabe Masashi , Hirai Toshihiro , Ueda Tsutomu , Suzuki Makoto , Amaike Yoichi
Published: August 2009

A large bending deformation of monolayer polyurethane films was observed when a high electric field was applied to the film. Using this phenomenon, bending actuators were prepared and their electromechanical properties were investigated. When the electric field of 10 MV/m was applied to the film, the deformation curvature, IhR, reached 36 m-l within about 3 seconds and the generated force was about the same as the film weight.

The degree of the bending deformation was expressed as a combination of the linear term and the square term of the applied electric field. Therefore, it was shown that the bending deformation is caused by bending piezoelectricity (inverse effect) and bending electrostriction.
Modeling, Design, and Zero Gravity Testing of a Doubly Curved Aperture Antenna
Authors: Yoon Hwan-Sik , Washington Gregory
Published: August 2009

A smart aperture antenna whose reflector is deformed by curved piezoelectric actuators is modeled and the results are experimentally verified in a microgravity environment. The reflector is modeled as a shallow spherical shell with a small hole at the apex for mounting. Using Reissner's shallow spherical shell theory, five equations governing the mechanical behavior of the reflector structure are reduced to two equations. These are described in terms of a stress function and the axial deflection. As actuators, four PZT strip actuators are attached along the meridians separated by 90 degrees respectively. The forces developed by the actuators are modeled as distributed pressure loads on the reflector surface. In addition to the analytical model, a finite element model is generated to verify the analytical model on the various surface positions of the reflector. Finally, an actual model of the reflector is built and tested in a zero gravity environment. The experimental data show good agreement with those obtained from the analytical and the finite element models.
A New Wall Motion Actuator Using Magnetic Fluid and Elastic Membrane for Laminar Flow Control
Authors: Han Jae-Hung , Tani Junji , Qiu Jinhao , Kohama Yasuaki , Shindo Yoshihiro
Published: August 2009

A new wall motion actuator for the control of boundary layer flow is presented. The actuator consists of a magnetic fluid layer with an elastic membrane surface and coil system. The vertical motion of the elastic membrane is generated when the magnetic fields are applied to the magnetic fluid. It is possible to control the wall motion by the adjustment of the electric current to the coils. The static and dynamic characteristics of the new actuators have been experimentally investigated. The effectiveness of the actuator for laminar flow control has been shown via wind tunnel testing. Two-dimensional travelling waves, or Tollmien-Schlichting waves (T-S waves), have been effectively attenuated by using the new actuator.
Domain Wall Theory for Ferroelectric Hysteresis
Authors: Smith Ralph C. , Hom Craig L.
Published: August 2009

This paper addresses the modeling of hysteresis in ferroelectric materials through consideration of domain wall bending and translation. The development is considered in two steps. First, dielectric constitutive relations are obtained through consideration of Langevin, Ising spin and preferred orientation theories with domain interactions incorporated through mean field relations. This yields a model for the anhysteretic polarization that occurs in the absence of domain wall pinning. Second, hysteresis is incorporated through the consideration of domain wall dynamics and the quantification of energy losses due to inherent inclusions or pinning sites within the material. This yields a model analogous to that developed by Jiles and Atherton for ferromagnetic materials. The viability of the model is illustrated through comparison with experimental data from a PMN-PT-BT actuator operating at a temperature within the ferroelectric regime.
Detection of the Failure Zone Caused by Cyclic Loading
Authors: Ichinose Kensuke , Kosaka Yoshimi , Fukuda Katsumi , Taniuchi Kiyoshi
Published: August 2009

There is a simplified technique for detecting where the part of a structure undergoes failure due to cyclic loading; this technique appears to be of great practical value in its employment to prevent fracture.

It is well known that when yield stress is applied to a low-carbon steel plate, Luders' lines become visible on its surface to the naked eye. It is a plausible hypothesis that the locations on the surface of the plate where the Luders' lines appear are in a state of failure. The correlation of cyclic loading and Luders' lines should confirm whether or not Luders' lines reliably indicate where failure results from fatigue loading. The Ra value of the surface roughness of the specimen before and after the appearance of Luders' lines is used to ascertain this correlation. The present paper takes up cyclic tensile loading with shoulder fillets as a concrete example of the correlation of failure and stress.
Modified Shape Memory Alloy (SMA) Model for SMA Wire Based Actuator Design
Authors: Huang W.
Published: August 2009

A modified phenomenological model for Shape Memory Alloy (SMA) is presented for design of an SMA wire based rotatory actuator. In this model, the forward and reverse transformation functions are derived from two kinds of tests: standard tension test, carried out at constant temperature, and thermal cyclic test under constant force. This model is verified by the measured behavior of NiTi SMA wire. The analytical result by this model agrees well with the measured performance of an NiTi SMA wire based actuator.
Coupled Electromechanical Behaviour of Piezoelectric Actuators in Smart Structures
Authors: Wang X. D.
Published: August 2009

The static and dynamic electromechanical behaviour of piezoceramic actuators attached to an elastic medium under inplane mechanical and electrical loads is studied. An electroelastic line model is used to characterize the actuators. The load transfer from the piezoelectric actuators to the host structure is determined by using Fourier transform and solving the resulting integral equations. The work is further extended to account for the interaction between different actuators using a pseudo-incident wave method. The influences of different pertinent coefficients are investigated to show the effect of the geometry of actuators, the material combination and the loading frequency upon the load transfer between the actuators and the host structure.
Scattering of Antiplane Shear Waves in a Piezoelectric Fibrous Composite Medium with Slip at Interfaces
Authors: Shindo Y. , Togawa R. , Moribayashi H.
Published: August 2009

This study considers the phase velocity and attenuation of time harmonic axial shear waves in a piezoelectric fibrous composite with slip at interfaces subjected to a steady-state in-plane electrical load. Scattering of plane axial shear waves by a circular piezoelectric fiber with slip is analyzed. We apply the results of the single scattering problem to the propagation of any desired finite frequency waves in a composite containing a dilute concentration of circular piezoelectric fibers. Numerical results for some piezoelectric fibrous composites are obtained and the effects of interfacial slippages and electroelastic interactions on the phase velocity and attenuation of coherent plane waves are discussed in detail.
Fiber Optic Stress Wave Sensor for Detection of Internal Flaws in Concrete Structures
Authors: Chen Xi , Ansari Farhad
Published: August 2009

Internal cracks are frequently initiated in the form of delaminations at the interface between the reinforcement and the concrete in bridges. The most probable cause for the generation of internal cracks and delaminations is the pressure generated by the accumulation of corrosion byproducts at the interface between the reinforcement and the concrete. Failure to detect these defects at the early stages of development results in time consuming and costly repair and replacement operations. This article describes development of a fiber optic ultrasonic sensor for distributed detection of flaws and defects in concrete bridge elements. Distributed sensing provides the opportunity for the optical fiber sensor to detect anomalies throughout the entire structure. An ultrasonic transmitter source or an impact device is used for point-by-point generation of stress waves within the bridge deck. An optical fiber is adhered to the surface of the structure, for sensing of the echoed ultrasonic signals. The optical fiber senses the stress waves, and a one-ended measurement of the optical signal by an interferometer provides information about the integrity of the concrete. This configuration eliminates the need for using a conventional piezoelectric transducer (PZT) that can only make localized measurements. The delamination detection capability of the sensor is demonstrated through experimentation with concrete beams that contain intentionally induced delaminations.
Racial/Ethnic Differences in Patients’ Perceptions of Inpatient Care Using the HCAHPS Survey
Authors: Goldstein Elizabeth , Elliott Marc N. , Lehrman William G. , Hambarsoomian Katrin , Giordano Laura A.
Published: August 2009

Using HCAHPS (Hospital Consumer Assessment of Healthcare Providers and Systems, also known as the CAHPS Hospital Survey) data from 2,684 hospitals, the authors compare the experiences of Hispanic, African American, Asian/Pacific Islander, American Indian/Alaska Native, and multiracial inpatients with those of non-Hispanic White inpatients to understand the roles of between- and within-hospital differences in patients’ perspectives of hospital care. The study finds that, on average, non-Hispanic White inpatients receive care at hospitals that provide better experiences for all patients than the hospitals more often used by minority patients. Within hospitals, patient experiences are more similar by race/ethnicity, though some disparities do exist, especially for Asians. This research suggests that targeting hospitals that serve predominantly minority patients, improving the access of minority patients to better hospitals, and targeting the experiences of Asians within hospitals may be promising means of reducing disparities in patient experience.
The Moderation Theory Revisited
Authors: Tezcür Günes Murat
Published: August 2009

An influential political science literature argues that integration of radical political parties within the political system leads to their moderation. These parties trade off their ideological platforms for electoral viability and political legality. Radicals become moderates through strategic interests. In this article, I revisit this thesis and apply it to the Islamic political actors in Iran and Turkey by employing the comparative method of agreement. Three conclusions are reached. First, moderation helps explain the evolution of Islamists into Muslim reformers. Second, moderation is a double-edged sword, especially in regimes with strong un-democratic characteristics. Moderation of radicals may result in their domestication — a situation that does not contribute to democratic transition or consolidation. Finally, change in the ideologies of political elites is central in our understanding behavioural change. The data sources include ethnography, primary language sources and historical narratives.
Party Direction
Authors: Pelizzo Riccardo
Published: August 2009

The purpose of this article is to further our understanding of the directional nature of left—right scores. I suggest that a party’s ability to modify its perceived position is conditional on whether parties adopt their manifestos to alter their perceived position and on whether voters are persuaded by parties’ attempts to relocate in political space. As voters’ knowledge of political parties is a major determinant of where parties are perceived to be located, new parties or parties with weak identities are more likely than old parties to modify their perceived positions, and for two reasons: they are neither willing nor able to adopt an identity-based platform and their freedom to move in political space is not constrained by what voters know about them. The results of statistical analyses show that while Italian voters modified their perception of party positions in the light of party manifestos, this was not the case in the other countries under study, where parties had longer histories than their Italian counterparts.
Where Are the Disgruntled Voters?
Authors: Birnir Jóhanna Kristín
Published: August 2009

Katz and Mair’s provocative Cartel Party argument continues to create fertile ground for debate. This article contributes to under-explored areas of this debate by enhancing the theoretical and empirical understanding of the change in the relationship between parties and voters resulting from the introduction of the cartelizing condition of public funding. To this end, the article examines vote stability empirically, changes in turnout and individual public opinion data, before and after public funding was instituted. By disconfirming the hypothesized expectations of deteriorating voter—party relationships as a result of funding, the empirical analysis pinpoints a number of contradictions in current understanding of party system change. The article concludes by suggesting that still bound financially to voters at large, parties provide a good that is valued by constituents. If, however, these last ties are severed, rather than being at the cusp of a post-cartel system, the future of party systems is more akin to the elite systems of old.
The construction of Islam as a public issue in western European countries through the prism of the Muhammad cartoons controversy
Authors: Miera Frauke , Sala Pala Valérie
Published: August 2009

This article aims to analyse the way in which the so-called Muhammad cartoons controversy was constructed as a public issue in France and in Germany. We study the reactions of different main actors participating in the definition of this event as a social problem, in particular the media, politicians and intellectuals, as well as Muslim organizations. We ask to what extent national contexts impact on the construction of the debates around religious pluralism and more widely around multiculturalism. The case of the cartoons controversy seems to illustrate a shift towards (re-)codifying migrants and minorities on the lines of culture and religion as the ‘Muslim other’, which coincides with the international debate on the antagonism between Islam and the western world. This may be interpreted as a sign of convergence. Still, national legacies shape these overlapping discourses on national identity, belonging, and valid norms and values.
Efficacy in angiotensin receptor blockade: a comparative review of data with olmesartan
Authors: Redon Josep , Fabia Maria Jose
Published: August 2009

A range of angiotensin II receptor blockers (ARB) is available, and analyses suggest there are differences between agents in terms of antihypertensive efficacy and 24-hour blood pressure control.This review assesses the data comparing olmesartan with other ARBs in terms of blood pressure reductions, goal achievement, 24-hour control and speed of onset. Olmesartan seems to have a more favourable efficacy profile relative to standard doses of the ARBs used in comparative studies; results consistent with the high degree of blockade of the angiotensin II type 1 receptor for olmesartan.Taken together, there might be differences between ARBs regarding their blood pressure lowering efficacy, and these results may provide further support of the benefits of olmesartan therapy since choice of an effective agent is crucial in antihypertensive therapy.
Premodern, Modern, Postmodern? Placing New Urbanism into a Historical Perspective
Authors: Hirt Sonia A.
Published: August 2009

This study explores New Urbanism as part of a contemporary cultural paradigm referred to as postmodernism. By highlighting the complex relationship between New Urbanist design prescriptions and earlier urban development approaches from the premodern and modern periods, I reflect on some seemingly paradoxical aspects of both New Urbanism and postmodernism. Specifically, I argue that whereas New Urbanism rejects the key design tenets of modernist planning and strives to revive premodern urban forms (and in this sense qualifies as “postmodern”), it contradicts one of the foundational premises of postmodern thought—the commitment to pluralism. I further argue that this contradiction relates to a fundamental challenge facing New Urbanists planners: how to achieve premodern urban design ideals within the economic and technological conditions of contemporary society. I illustrate these themes and contradictions with examples of historic and recent planning in the Cleveland region.
Unloader Braces for Medial Compartment Knee Osteoarthritis: Implications on Mediating Progression
Authors: Ramsey Dan K. , Russell Mary E.
Published: August 2009

Background:

For persons with unicompartment knee osteoarthritis (OA), off-unloader braces are a mechanical intervention designed to reduce pain, improve physical function, and possibly slow disease progression. Pain relief is thought to be mediated by distracting the involved compartment via external varus or valgus forces applied to the knee. In so doing, tibiofemoral alignment is improved, and load is shifted off the degenerative compartment, where exposure to potentially damaging and provocative mechanical stresses are reduced.

Objectives:

To provide a synopsis of the evidence documented in the scientific literature concerning the efficacy of offloader knee braces for improving symptomatology associated with painful disabling medial compartment knee OA.

Search Strategy:

Relevant peer-reviewed publications were retrieved from a MEDLINE search using the terms with the reference terms osteoarthritis, knee, and braces (per Medical Subject Headings), plus a manual search of bibliographies from original and review articles and appropriate Internet resources.

Results:

For persons with combined unicompartment knee OA and mild to moderate instability, the strength of recommendation reported by the Osteoarthritis Research Society International in the ability of off-loader knee braces to reduce pain, improve stability, and diminish the risk of falling was 76% (95% confidence interval, 69%–83%). The more evidence the treatment is effective, the higher the percentage.

Conclusions:

Given the encouraging evidence that off-loader braces are effective in mediating pain relief in conjunction with knee OA and malalignment, bracing should be fully used before joint realignment or replacement surgery is considered. With the number of patients with varus deformities and knee pain predicted to increase as the population ages, a reduction of patient morbidity for this widespread chronic condition in combination with this treatment modality could have a positive impact on health care costs and the economic productivity and quality of life of the affected individuals.