bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Development of Multiaxial Phenomenological Constitutive Laws for Ferroelectric Ceramics
Authors: Lynch Christopher S.
Published: August 2009

Multiaxial constitutive laws for ferroelectric ceramics that include hysteresis, rate dependence, saturation, and are capable of simulating nonproportional loading are needed for stress analysis and reliable design of smart structures. The relationship between constitutive behavior of ferroelectric ceramics and phenomena that occur across multiple length scales is reviewed. A framework for the development of phenomenological constitutive laws at the macroscopic scale is presented, and a multiaxial law with 900 (70.5 and 109.5 when rhombohedral) and 1800 switching effects is described.
Complex Properties and Composition of Electrorheological Fluids
Authors: Filisko F. E. , Henley S. , Quist G.
Published: August 2009

Various base ER fluid compositions are shown to have dramatically enhanced shear stresses when dispersed into poly(hexyl isocyanate)/xylene solutions as compared to being dispersed into polystyrene/xylene solutions. The concentration of the PHIC solutions was 4.5% which is well below that for liquid crystallinity. Further, the additon of small amounts (1-3%) of other particles to the suspensions show significant enhancement of the shear stresses for softer particles.
Particulate/Liquid Electrically Structured Functional Fluids-A Computer Fluid Mechanics Technique for Engineering Design
Authors: Bullough W. A. , Kinsella J. , Peel D. J. , Boysan F. E.
Published: August 2009

A method for the rapid solution of flows of electrically structured fluids of the particle/liquid type is described. The technique is indicated for heavily loaded fluids and for flows in complex controller geometries. Its basis lies in the modification of a commercial computer routine which can deal with Bingham plastics, by the inclusion of a sub-routine which represents the ERF/MRS constitutive equations for a wide range of excitation. The entire system of working is validated against known and well proven analytical and experimental results.
Idealized Hysteresis Modeling of Electrorheological and Magnetorheological Dampers
Authors: Wereley Norman M. , Pang Li , Kamath Gopalakrishna M.
Published: August 2009

The hysteresis behavior of a linear stroke magnetorheological damper is characterized for sinusoidal displacement excitation at 2.0 Hz (nominal). Four different modeling perspectives are discussed for purposes of system identification procedures, including: (1) equivalent viscous damping, (2) nonlinear Bingham plastic model, (3) nonlinear biviscous model, and (4) nonlinear hysteretic biviscous model. By progressively adding model parameters with which to better represent pre-yield damper behavior, the force vs. velocity hysteresis model is substantially improved. The three nonlinear models represent the force vs. displacement hysteresis behavior nearly equally well. Thus, any of the three nonlinear damper models could be used equally successfully if only a prediction of energy dissipation or damping were of interest. The nonlinear hysteretic biviscous model provides the best representation of force vs. velocity hysteresis of the four models examined here.
Homogeneous Magnetorheological Materials
Authors: Lazareva T. G. , Kabisheva I. V. , Prodan S. A.
Published: August 2009

The conditions of formation of homogeneous magnetorheological media are discussed using, as an example, the compositions of polyvinyl alcohol with variable-valance metals (Cu, Ni, Co, Fe), some polyacids, and orthophosphoric acid. A comparative evaluation is made of the magnetorheological properties of the compositions depending on the introduced cations, inorganic and polymeric acids. The influences of the type and the concentration of components, the method of preparing the compositions, pH of the medium, the solution temperature, the shear rate, and the magnetic induction on the magnetorheological effect are discussed.
Characterization of Particle Motion for Polishing and Texturing under AC Field by Using Particle Dispersion Type ER Fluid
Authors: Akagami Yoichi , Asari Koichi , Jeyadevan Balachandaran , Fujita Toyohisa
Published: August 2009

The authors have already proposed a new method of polishing using particle dispersion type ER fluid. And also have applied this method for polishing micro hole in a ceramic disk. In this paper, we characterize the particle dispersion type ER fluid and particle motion suitable for polishing and texturing. We selected the type of abrasive material to be used in ER fluid based on theoretical calculation of the force exerted by an individual particle under alternative electric field. And also, we have experimentally obtained the force generated by ER fluid dispersing diamond particles of different size range, concentrations and dispersing media with different viscosity. Furthermore, we have observed the particle response using a high-speed video camera.
Theoretical and Experimental Studies of an Electro-Rheological Grease Shock Absorber
Authors: Marksmeier Thomas M. , Wang Eric L. , Gordaninejad Faramarz , Stipanovic Arthur
Published: August 2009

One method of achieving fail-safe, semi-active damping is to utilize a controllable fluid with a high zero-field damping capacity. To this end, this paper introduces a prototype electrorheological grease (ERG) as a new concept in electro-rheological fluids (ERF's). The general properties of grease-like fluids imply a non-Newtonian post yield viscosity. The fluid model developed in this paper considers the influence of a non-Newtonian post yield viscosity by using a power law model to account for shear thinning behavior. This model can be applied to all controllable fluids since it reduces to a Newtonian viscosity as a special case. The theoretical study includes a lumped parameter dynamic system model to predict the behavior of an actual damper, which takes into consideration inertial and compressibility effects. To validate the proposed models, a prototype damper was designed and used to collect data for a known ERF and the new ERG. Results from the ERG test data indicate that a good match between experimental and theoretical data was achieved. A sensitivity analysis shows that the model was insensitive to the mass of the fluid, but sensitive to the bulk modulus of the fluid. Comparisons are also made between the performance of the ERG and the existing ERF. The ERG demonstrates higher zero-electric field damping capacities than those of the ERF, yet produces an increase in damping when an electric field is applied.
Neural Network Modeling of a Magnetorheological Damper
Authors: Chang Chih-Chen , Roschke Paul
Published: August 2009

The magnetorheological (MR) damper is a newly developed semiactive control device that possesses unique advantages such as low power requirement and adequately fast response rate. The device has been previously tested in a laboratory to determine its dynamic properties and characterized by a system of nonlinear differential equations. This paper presents an alternative representation of the damper in terms of a multilayer perceptron neural network. A neural network model with 6 input neurons, one output neuron and twelve neurons in the hidden layer is used to simulate the dynamic behavior of the MR damper. Training of the model is done by a Gauss-Newton based Levenberg-Marquardt method using data generated from the numerical simulation of the nonlinear differential equations. An optimal brain surgeon strategy is adopted to prune the weights and optimize the neural networks. An optimal neural network is presented that satisfactorily represents dynamic behavior of the MR damper.
Search Strategies for Identifying a Composite Plate Delamination Using Built-In Transducers
Authors: Keilers, Charles H.
Published: August 2009

Search strategies are compared that can potentially identify single, rectangular, midplane delaminations in composite plates using the signals from surface-mounted piezoceramics. The strategies are demonstrated by repeatedly assuming a single delamination and then running a delaminated plate model, also described, that predicts transducer frequency responses. An objective function compares the responses to those for a hypothetical plate with unknown damage. When the objective function is minimized, the responses agree, and the assumed delamination is the best-estimate. The chosen objective function is well-behaved but has several local minima; therefore, rardom search strategies are used to find the global minimum. The most efficient strategy starts with assumed delaminations selected from a uniform random distribution at discrete points in the parameter space (i.e., a combinatorial search). Some of these points will be close to local minima. The strategy continues by using a random walk with shrinking step size across the parameter space. This latter search is made more robust by using probabilistic hill climbing acceptance tests, also known as simulated annealing. The overall technique systematically investigates several possible local minima and identifies a best-estimate delamination to a preset accuracy.
Structural Damage Detection Using Localized Flexibilities
Authors: Park K. C. , Reich Gregory W. , Alvin K. F.
Published: August 2009

The present paper offers structural damage detection methods based on the relative changes in localized flexibility properties. The localized flexibility matrices are obtained either by applying a decomposition procedure to an experimentally determined global flexibility matrix or by processing the output signals of a vibration test in a substructure-by-substructure manner. Three methods are evaluated in the present paper: a free-free substructural flexibility method, a deformation-based flexibility method, and a strain-basis flexibility method. These methods are applied to a model ten-story building problem, an experimental bridge damage data, and a hybrid experimental-simulated engine structure. The present methods are found to correctly identify damage locations.
Identifying Impacts in Composite Plates with Piezoelectric Strain Sensors, Part II: Experiment
Authors: Tracy Michael , Chang Fu-Kuo
Published: August 2009

This paper summarizes the implementation of an impact identification system on a composite plate. The impact, normal to the surface of the plate, generates a traveling wave that is measured by surface mounted sensors. The identification system compares the measured response of the plate to the model response and estimates the impact location and force time history. The accuracy and reliability of the system was tested using many impacts distributed across the plate and the robustness of the system was tested by adding simulated noise to the data. The system was tested on the composite plate with free boundaries and clamped boundaries. The system proved to be accurate with an average location error ranging from .39 inches for the free boundary case to .49 inches for the clamped plate with noise. The area monitored by the 13 sensor array was 20 inches by 20 inches.
Eddy Current Microsensor for Use in Micromachine Applications
Authors: Zmood R. B. , Yu P. L.
Published: August 2009

In this paper we investigate an eddy current microsensor which uses a low input impedance trans-impedance amplifier to minimise the influence of stray capacitances on the sensor operation when being used for micromachine applications. A technique using a two transistor feedback pair for realising very low input impedance over a wide bandwidth in these amplifiers is studied. An improved circuit configuration, which further reduces the amplifier input impedance at higher frequencies, is investigated by computer simulation. At the same time as minimising the influence of the stray capacitances, the trans-impedance amplifier improves the signal conditioner sensitivity and output drift performance. The operation of the sensor signal conditioner has been investigated experimentally using target materials suitable for micromachine applications. Results of these experiments are presented which show that acceptable sensitivities are achieved.
Hover Testing of Active Rotor Blade-Tips Using a Piezo-Induced Bending-Torsion Coupled Beam
Authors: Bernhard Andreas P. F. , Chopra Inderjit
Published: August 2009

This paper presents the development of an active on-blade vibration-reduction system using smart active blade tips (SABT), that are driven by a piezo-induced, bending-torsion coupled actuator. The actuator beam has a graphite substructure with surface bonded piezoceramic elements. A spanwise variation in both the bending-torsion coupling and the piezo element phasing is used to generate a pure tip twist. A small scale rotor, with 10% span active tips, was tested on the hover stand, at a reduced tip speed of Mach 0.25. At a mean thrust loading (CT/σ) of 0.07, and for an activation of 100 Vrms, SABT deflection amplitudes from 1.8 deg at 2/rev to 2.25 deg at 4/rev were achieved (half peak-to-peak). The rotor normal force measurements show a distinct coupling of the activation with the first and second flap frequencies of the rotor. The corresponding dynamic thrust, generated by a single active tip, relative to the steady thrust, ranges from 4.5% at 2/rev to 8.3% at 5/rev. For a 1/rev excitation, the single active tip generates a dynamic lift amplitude of 15% of the steady rotor thrust. The same actuator beam was used to test a rotor with controllable twist blades. The active twist blades used the same main blade section as the rotor blades with the active tips, and hence were not optimized for active twist configuration. Nonetheless, in hover, at a mean thrust loading (CT/σ) of 0.07, and with an activation of 100 Vrms, dynamic tip-twist amplitudes of 0.4 deg at 4/rev and 0.5 deg (at 5/rev) were achieved (half peak-to-peak).
Method for Multiple Mode Piezoelectric Shunting with Single PZT Transducer for Vibration Control
Authors: Wu Shu-Yau
Published: August 2009

We report a method for passive piezoelectric shunt-damping of multiple vibration modes using a single piezoelectric transducer (PZT). The method, which is different from other multiple-mode shunting (Edberg et al., 1992; Hollkamp, 1994), is to employ a blocking circuit in series with each parallel resistor-inductor shunt circuit designed to control one structural mode. The blocking circuit consists of one parallel capacitor-inductor antiresonant circuit or a series of them. The number of the antiresonant circuits in each shunt circuit depends on the number of the structural modes to be controlled simultaneously. These antiresonant circuits are designed to produce infinite electrical impedance, or antiresonance, at the natural frequencies of all other shunt circuits. Each shunt circuit with the addition of the blocking circuit is functional for its own mode yet blocks or causes open circuit for all other frequency modes. Therefore, when the individual shunt circuits are all connected to the two terminals of the PZT to form a composite shunt circuit for the multiple-mode shunting, they will not interfere with each other. The method is also easier and more reliable for finetuning and damping control.

We analyze first the multiple-mode shunt-damping circuit with both the generalized circuit and the modified circuit. The latter derived from the former is intended to reduce the number of the antiresonant circuits and to make the composite shunt circuit simpler to operate. Experimentally we have designed two modified shunt circuits and successfully demonstrated vibration reduction of two and three structural modes with a single PZT transducer bonded on a two-wing aluminum cantilever beam. For three-mode shunt damping, the resonant amplitudes at 206, 348.5, and 484.5 Hz are reduced for 13.28, 7.30, and 9.45 dB, respectively.
An Optimal Neural Network Design Methodology for Fast Convergence and Vibration Suppression
Authors: Yang S. M. , Lee G. S.
Published: August 2009

An optimal neural network design is to select the network configuration and the learning rule for fast convergence and best system performance. This paper develops a network design methodology so that the optimal design can be determined in a systematic way. The methodology combines the Taguchi method of quality engineering and the back-propagation network with an adaptive learning rate for their advantages in implementation feasibility and performance robustness. Vibration suppression experiments of a composite smart structure with embedded piezoelectric sensor/actuator validate that the methodology provides an efficient neural controller design, including the plant order, the number of hidden layer neurons, the number of training patterns, and the coefficients of adaptive learning rate.
A Parallel Control System for Continuous Architecture Using Finite Element Method
Authors: Isobe Daigoro , Nakagawa Hisashi
Published: August 2009

In this paper, a parallel control system for continuous architecture formed by bimorph piezoelectric actuators has been developed and verified. Finite Element Method (FEM) is adopted as the control scheme for it is capable of expressing the behavior of the whole system by evaluating the stiffness equations. Conventional control system requires a slight change in its state equations, depending on the shape of a system or the quantity of the linked members. Although FEM is mainly a computational tool for analyzing structures, fluids, etc., the capability of expressing the whole continuous system can be applied to parallel control schemes, and may be practical if the computational time is reduced to real-time use.

An inverse theory, which is simplified by using the linearity of the electric potential distribution in a bimorph piezoelectric actuator, is applied for calculating control voltage of the actuators. The algorithm using this theory consumes less computational memory, and runs faster than the numerical schemes using generalized inverse matrices. This paper seeks the reduction of dofs and thus the computational time, by implementing noncompatible four-node element to the FEM control program. The finite element allows in-plane bending mode by considering noncompatible mode in shape functions, and can obtain practical solutions by minimum number of elements.

By examining the experiments on static displacement control of connected piezoelectric actuators, the validity of the FEM parallel control system has been confirmed.
Adaptive Control of Nozzle Melt Packing Pressure
Authors: Yang Yi , Gao Furong
Published: August 2009

An adaptive system for the control of nozzle melt pressure during the packing phase has been successfully designed, implemented, and experimentally tested for injection molding machines. It has shown that this system works well with different set points, different molds, and different barrel temperatures. This paper discusses the technical strategies in implementing the system together with some experimental results.
Micromechamical Analysis for Hysteretic Behavior of Unidirectional TiNi SMA Fiber Composites
Authors: Kawai M. , Ogawa H. , Baburaj V. , Koga T.
Published: August 2009

Mechanical behavior of a unidirectional TiNi shape memory alloy (SMA) fiber composite subjected to a single isothermal loading and unloading cycle is analyzed using a threedimensional micromechanical method of cells. The multiaxial rhombohedral and martensitic phase transformations of TiNi SMA fibers embedded in an elastic matrix are taken into account. Numerical simulations are performed for different fiber volume fractions and for different fiber orientation angles. It is clearly observed that a pseudoelasticity-like hysteretic behavior appears in the stress-strain relationships of the composite system of TiNi SMA fibers and an elastic matrix under the prescribed isothermal loading and unloading conditions. The shape and size of the hysteresis are significantly influenced by the volume fraction of TiNi SMA fibers. For a high volume fraction of fibers, in particular, the rhombohedral transformation of the embedded TiNi SMA fibers characterizes the overall hysteretic behavior of the TiNi SMA composite. The present simulations manifest the significance of the capability to predict the rhombohedral transformation of TiNi SMAs under multiaxial loading conditions, and also demonstrate the efficiency of the micromechanical composite model for evaluating the average characteristics of the TiNi SMA fiber composites.
Terfenol-D Nonlinear Vibration Absorber
Authors: Pratt Jon R. , Oueini Shafic S. , Nayfeh Alu H.
Published: August 2009

An active nonlinear vibration absorber scheme for flexible structures is demonstrated. The absorber exploits the nonlinear transduction of nonbiased Terfenol-D actuators. It uses a quadratic feedback control law and the "quadratic" strain-field characteristic of a nonbiased Terfenol-D actuator to achieve a nonlinear coupling between the absorber and the forced structure. A saturation phenomenon is induced by tuning the frequency of the underdamped second-order absorber to one-half that of the primary structure. As a result, the structural vibrations are greatly reduced. This type of control has been demonstrated previously using linear actuators; the nonlinearities have been introduced via the control algorithm. Here, we show that nonbiased Terfenol-D actuators can perform effectively the "squaring" operation, instead of the algorithm, and achieve similar results.

We develop the theory and present experimental results for the control of the first and second modes of a cantilever beam. We also consider application of the strategy experimentally when the forcing is due to a rotating imbalance. In this case, the excitation source is nonideal. Our results indicate that the saturation-based control technique implemented with a Terfenol-D actuator constitutes an effective nonlinear vibration absorber.
Experiments on the Use of Fiber-Optic Strain Sensors in Active Structural Acoustic Control
Authors: Masson P. , Berry A. , Morin A.
Published: August 2009

Among the sensors available for active control of noise, strain sensors are of great interest as they can eliminate the need for far-field acoustic sensors, such as microphones. Fiber-optic strain sensors are especially of interest because they are easily embeddable into composite materials. This paper aims at a validation of the use of Fabry-Perot fiber-optic strain sensors in active structural control strategies. Two control approaches based on the direct use of discrete strain sensing are herein employed for the minimization of the acoustic radiation from a vibrating beam. The first approach involves the direct minimization of the strain levels at discrete points on the beam. The second cost function is defined as the radiated acoustic power; it involves the beam's displacement reconstruction from the strain field and is expressed in the wavenumber domain. Proper concentration of the control effort is expected with the cost function defined in the wavenumber domain but experimental constraints do not allow to demonstrate this clearly. The use of fiber-optic sensors is first validated for both control approaches with respect to an optimal solution and the impact of both approaches on radiated acoustic power is presented. It is shown that optimal and controller solutions agree well on a wide frequency band with the exception of some discrepancies arising from real-time approximations and fiber-optic reading unit limitations. The control mechanism of both approaches is then highlighted through experimental results combining acoustic and vibration measurements. Finally, the control performance obtained using the fiber-optic sensors is compared with the control performance obtained using PVDF strain sensors and it is shown that fiber-optic sensors offer a comparable performance.
Vibration Control of a Steering Wheel Using Piezoelectric Actuators
Authors: Zhu Ye , Qiu Jinhao , Tani Junji , Suzuki Shunji , Urushiyama Yuta , Hontani Yasuharu
Published: August 2009

In this paper active control is used to reduce the vibration of a steering wheel without changing static stiffness significantly. Multi-layer piezoelectric actuators are bonded to spokes to actively suppress the vibration of the wheel under environmental disturbance. A FEM model of the wheel is derived using structural analysis software NASTRAN and modified according to experimental data. Four natural vibration modes of the wheel are included in the state space model for control design and the others are neglected. The controller is designed using ji synthesis due to its ability of improving robust stability and robust performance. The digital counterpart of the controller is realized on a PC with A/D and D/A converters. Both simulation and experimental investigations are performed to show the effectiveness of the whole approach. Results show that the vibration level is considerably reduced. And, it is also found that the output capacity of the piezoelectric actuators and the performance of the digital controller are the main obstacles to obtain further improvement of the control performance.
Integrated Interfaces for Low-Cost Multiple-Sensor Systems
Authors: Meijer Gerard C. M. , van der Goes Frank M. L. , de Jong Paul C. , Li Xiujun , Toth Ferry N.
Published: August 2009

The paper reviews the architecture and design of low-cost high-performance sensor systems. These systems consist of a number of multiplexed sensor elements, sensor-specific front-ends, modifiers and microcontroller or digital signal processors (DSPs). Important properties that act as focus points for the system design are: adaptability, accuracy, dynamic range, speed, power consumption, reliability and costs. To enable low-cost design and implementation, a universal set-up, using universal components, is used. Universal sensor interfaces with front-ends for resistive, capacitive, resistive-bridge sensing elements, as well as voltage-, current-and charge-generating sensing elements are discussed. The analog sensor signals are converted to analog signals in the time domain using period-modulated oscillators. The A/D conversion of the time-domain signal can be implemented in the microcontroller or DSP. It is shown that, also in this case, the principles of the sigma-delta converters can be applied. The paper shows that in a systematic overall design approach it is even possible to reduce many of the physical nonidealities of the sensor elements. As an example, the paper deals with the design problems of reliable, high-performance low-cost capacitive sensors. The problems and their solutions of both the physical and the electrical-signal processing are discussed. The examples consider the application of capacitive sensors in position detectors, liquid-level detectors and personnel detectors.
Modeling of Nonlinear Hysteresis in Elastomers under Uniaxial Tension
Authors: Banks H. T. , Pintér Gabriella A. , Potter Laura K. , Gaitens M. J. , Yanyo L. C.
Published: August 2009

As a fundamental component of an overall program in modeling smart material damping devices, we consider inactive host material models for moderate to highly filled rubbers undergoing uniaxial tensile deformations. Beginning from a neo-Hookean strain energy function formulation for nonlinear extension, we develop general constitutive models for both quasi-static and dynamic deformations of a viscoelastic rod. The constitutive laws are nonlinear and contain hysteresis through a Boltzmann superposition integral term. The resulting integropartial differential equations models are shown to be equivalent to the usual Lagrangian dynamic distributed parameter models coupled with linear ordinary differential equations for internal variables (internal strains). Comprehensive well-posedness results (existence, uniqueness and continuous dependence) are summarized in a discussion of theoretical aspects of the systems.

The models are validated with experiments designed and carried out explicitly for this study. In particular, quasi-static Instron experimental data are used in a least squares inverse problem formulation to estimate nonlinear elastic and nonlinear viscoelastic contributions to the general stress-strain constitutive laws proposed. It is shown that the models provide an excellent prediction of nested hysteresis loops manifested in the data. These models are then used as initial estimates in determining the nonlinear hysteretic constitutive laws for the dynamic experiments. It is shown that in cases of more highly filled rubbers, multiple internal variable models lead to best fits to the data.
Stiffness of Smart Composites with Shape Memory Alloy Fibers in the Presence of Matrix Cracks
Authors: Birman Victor
Published: August 2009

The paper presents a methodology for evaluating the effective stiffness of unidirectional composite materials with shape memory alloy (SMA) fibers in the presence of matrix cracks. The solution is obtained for the case where SMA fibers in the intact composite are in the austenitic phase. However, elevated stresses in the sections of SMA fibers adjacent to the crack planes cause the martensitic transformation affecting the stiffness of the material. The solution has to account for thermal residual stresses in SMA and "ordinary" fibers and in the matrix. The order of magnitude of these stresses is calculated in the paper for two representative composite systems. As follows from the numerical examples, thermal residual stresses in the SMA fibers increase proportionally to their volume fraction but remain relatively small. However, thermal stresses in the matrix may reach rather high values reducing the strength of the matrix by a significant factor.
A Phenomenological Constitutive Law for Ferroelastic Switching and a Resulting Asymptotic Crack Tip Solution
Authors: Landis Chad M. , McMeeking Robert M.
Published: August 2009

An isothermal, multiaxial, phenomenological constitutive law for ferroelastic switching in polycrystalline ceramics is developed. The law is valid for unpoled ferroelectric ceramics loaded by mechanical stress but no electric fields or other materials in which permanent deformation accumulates by a similar volume conserving twinning mechanism. The initial switching behavior of the material is described using perfectly plastic J2 flow theory. Unlike metal plasticity in which dislocations are generated by sources, deformation as a result of twinning is limited by a finite transformation strain. Hence, special yield surfaces and associated flow rules are introduced to account for plastic deformation in the two possible "lock-up" states of the material. To demonstrate the constitutive law we have analyzed the stress and displacement fields occurring in the lock-up regime asymptotically close to a crack tip under mode I loading.
Location of Embedded Fiber Optic Sensors for Minimized Impact Vulnerability
Authors: Jarlas Rolf , Levin Klas
Published: August 2009

Vulnerability of embedded fiber optic sensors such as Bragg grating sensors to impact has been studied in composite laminated plates. The effects of the distance from the supporting boundary and the sensor thickness position were determined. The main objective was to develop an accurate numerical procedure to calculate the local stresses at the sensor from impact in order to determine the criticality with respect to damage initiation. A semi-analytical and a finite element based method were used to consider the contact at impact. From the analysis, it was found that a lower impact energy was required to cause damage in the sensor region when the sensor was embedded close to the boundary. At locations far from boundaries, sensors should not be embedded close to the plate surfaces. For sensors embedded close to a boundary, a thickness position close to the upper surface was found to be less suitable than other positions.
Performance Analysis of Magneto-Rheological Mounts
Authors: Ahmadian Mehdi , Ahn Young Kong
Published: August 2009

The effect of various parameters for a magneto-rheological (MR) mount on the vibration isolation performance of the mount is studied. The mount that is used for this study incorporates MR fluid in a conventional fluid mount to open and close an inertia track between the fluid chambers of the mount. It has been shown in previous studies that such switching of the inertia track improves the mount's isolation effect by eliminating the large transmissibility peak that commonly exists at frequencies larger than the notch frequency for conventional fluid mounts. A sensitivity analysis is conducted to evaluate the effect of different parameters, such as the rubber stiffness, inertia track, fluid resistance, piston area, and volumetric stiffness on the transmissibility of the mount. The results show that varying the rubber stiffness, piston area, and volumetric stiffness of the mount have the greatest effect on the vibration performance of the mount, as measured by its transmissibility.
Method and Theory for a Multi-Gauge Distributed Fiber Optic Crack Sensor
Authors: Gu Xianglin , Chen Zhongyu , Ansari Farhad
Published: August 2009

A distributed sensor is developed for detection of cracks and measurement of crack widths in composite materials. The sensor consists of a number of individual segments on one line with gauge lengths designed according to the structural and materials requirements. Return loss measurements at the interfaces between adjoining segments provide the basis for crack detection and measurement. An optical time domain reflectometer (OTDR) is employed for interrogation of the sensor signal. The quasi-distributed sensors were embedded in reinforced concrete beams in order to evaluate their crack detection capability. Experiments involved both monotonic as well as fatigue loading. The sensors were embedded in the tension zone of the concrete beams in order to facilitate comparison of sensor response with visual crack observations. Experimental results in terms of crack detection capability and resolution are presented and discussed.
Monitoring of Concrete Bridges with Long-Gage Fiber Optic Sensors
Authors: Inaudi Daniele , Vurpillot Samuel
Published: August 2009

In many bridges, the vertical displacements are the most relevant parameters to be monitored in both the short and long term. Current methods (such as triangulation, water levels or mechanical extensometers...) are often tedious to use and require the intervention of specialized operators. The resulting complexity and costs limit the temporal frequency of these traditional measurements. The spatial resolution obtained is in general low and only the presence of anomalies in the global structural behavior can be detected and warrant a deeper and more precise evaluation.

To measure bridge vertical displacements at low cost and frequently in time, one solution consists of installing a network of fiber optic sensors during concrete pouring or installing them on the surface of the structure. By subdividing the whole structure into structural elements and those elements into cells that are analyzed by the sensors, it is possible to obtain information about the average cell deformation (e.g., mean curvature) that can then be combined to obtain the global structural displacement field.

In 1996, a concrete highway bridge near Geneva (Switzerland) was instrumented with more than 100 low-coherence fiber optic deformation sensors. The Versoix Bridge is a classical concrete bridge consisting in two parallel pre-stressed concrete beams supporting a 30-cm concrete deck and two overhangs. To enlarge the bridge, the beams were widened and the overhang extended. In order to increase the knowledge on the interaction between the old and the new concrete, we choose low-coherence fiber optic sensors to measure the displacements of the fresh concrete during the setting phase and to monitor the long term deformations of the bridge. The aim is to retrieve the spatial displacements of the bridge in an earth-bound coordinate system by monitoring its internal deformations. The vertical and horizontal curvatures of the bridge are measured locally at multiple locations along the bridge span by installing sensors at different positions in the girder cross-section. By taking the double integral of the curvature and respecting the boundary conditions, it is then possible to retrieve the deformations of the bridge.

This measurement methodology was also applied to the Lutrive Highway Bridge in Switzerland in order to measure the variation in vertical bridge displacements due to a static load test. The results obtained using the low coherence interferometric sensors of the SOFO system were then compared with the displacements obtained through an optic leveling system. In the case of this cantilever bridge of 60 meters half-span equipped with 30 fiber optic sensors, a discrepancy of less than 7% was obtained between the two measuring systems.
Fiber Optic Sensing of a Bridge in Waterbury, Vermont
Authors: Fuhr Peter L. , Huston Dryver R. , Nelson Matthew , Nelson Orpheous , Hu Jing , Mowat Euan , Spammer Stephanus , Tamm William
Published: August 2009

The use of fiber optic sensors for the internal state measurements of large civil structures has been increasing in recent years. Sensors are embedded into the reinforced concrete structure in order to obtain information about the internal structural health and overall structural performance. The installation process is of utmost importance for if incorrectly done, the sensors will not withstand the rigorous conditions present during the construction and concrete pouring process. A detailed description of the sensor installation and excavation process undertaken when a suite of fiber optic sensors were embedded into a 67 m long steel truss bridge spanning the Winooski River in Waterbury, Vermont (USA) arise is presented.
Reliability Monitoring of CFRP Structural Elements in Bridges with Fiber Optic Bragg Grating Sensors
Authors: Bronnimann R. , Nellen Ph. M. , Sennhauser U.
Published: August 2009

Fiber optical sensors based on Bragg gratings were used to monitor the strain in suspension or prestressing CFRP (carbon fiber reinforced polymer) cables in bridges. The sensors were either adhered to the surface of the CFRP wires for the suspension cables, or directly embedded during the production process for the prestressing cables, where the load is closer to the limit. Tests for the two applications were performed to validate the suitability of the sensing system. Results accumulated over three years on a stay cable demonstrate the reliability of those sensors.
Embedded Quasi-Distributed Fiber-Optic Sensors for the Long-Term Monitoring of the Grouting Area of Rock Anchors in a Large Gravity Dam
Authors: Habel Wolfgang R. , Feddersen Ingo , Fitschen Carsten
Published: August 2009

Steel anchors were installed in a gravity-dam, in order to increase the stability of the dam. Quasi-distributed fiber-optic strain sensors are centrally positioned in the complete length of these anchors to detect the long-term behavior of the tendon bonded to the rock foundation. Because the sensor rod containing the measuring lengths is directly bonded to the grout in the fixed anchor length area, it is able to measure the longitudinal strain distribution in the anchor bond area. Such sensors help to evaluate the bonding of the fixed anchor bond length in a rock or in difficult ground areas.

Design of the anchors, manufacturing and on-site installations are described. The measuring principle and its characteristics are also described. Measured results given show the ability of sensorequipped anchors to monitor the tendon bond behavior over a period of years. Results four years after sensor system installation are presented.
Brillouin Scattering Based Distributed Sensors for Structural Applications
Authors: Brown Anthony W. , Smith Jeffrey P. , Bao Xiaoyi , Demerchant Michael D. , Bremner Theodore
Published: August 2009

Over the past four years the Fibre Optics Group at the University of New Brunswick has been developing a distributed sensor for use in smart civil structures. By using Brillouin loss, the sensor is capable of measuring strain or temperature at any region on a sensing fibre, even those that are kilometers in length. This paper outlines the development of the sensor system, and discusses some of the experiments that have been performed with it. New results are presented that demonstrate 100 mm spatial resolution under laboratory conditions. This represents a four-fold improvement in the spatial resolution over previously reported results attained with a Brillouin scattering based distributed sensor.
A Review of Humor for Computer Games: Play, Laugh and More
Authors: Dormann Claire , Biddle Robert
Published: August 2009

Computer games are now becoming ways to communicate, teach, and influence attitudes and behavior. In this article, we address the role of humor in computer games, especially in support of serious purposes. We begin with a review of the main theories of humor, including superiority, incongruity, and relief. These theories and their interrelationships do well in helping us understand the humor process, but they have been developed in the context of traditional human activity. To explore how they relate to computer games, we present the findings of a qualitative study of player experience of humor and show how it relates to the theoretical perspectives. We then review the main functions of humor, especially its effects on social, emotional, and cognitive behavior. We show how each of these functions can be used in game design to support the specific experiences and outcomes of game-play. Finally, we address the issue of serious games and make suggestions on how humor can inform and support the design of those games. We suggest that humor can support design by smoothing and sustaining the game mechanics. Moreover, games can draw on the functions of humor in the real world for enhancing communication, learning, and social presence. Using humor makes games richer and more powerful, as well as fun.
Defending the Network Organization: An Analysis of Information Warfare with Reference to Heidegger
Authors: Munro Iain
Published: August 2009

It is now a commonplace notion in management thinking that information and communication networks can be used as a tool for productive purposes and for innovation. However, such networks can also be used as a weapon for destructive and defensive puproses, which has been characterized by the phrase ‘information warfare’. As yet, there has been relatively little theoretical elaboration of the sociological implications of this phenomenon beyond the initial work pioneered by researchers of the RAND Corporation. This article will adapt concepts taken from Heiddeger’s philosophy of Being, and use them for increasing our understanding of information warfare with specific reference to a diversity of real world exemplars of network organizations.
Muslim claims-making in context
Authors: Larsson Göran , Lindekilde Lasse
Published: August 2009

The aim of this article is to investigate through a comparison of the Danish and the Swedish Muhammad cartoons controversies (1) why only the Danish controversy escalated into a conflict of global dimensions; and (2) what accounts for the differences in level and form of local Muslim claims-making in the two cases. The article takes advantage of the initial similarities of the two controversies in making a paired comparison, which provides an opportunity to evaluate the importance of context-specific particularities and of specific events/actions taken in the two cases. Despite several initial similarities, why did the two controversies produce such different outcomes? The article argues that the answer should be found in the interplay between distant contextual characteristics such as dominant elite discourses about Islam/Muslims, different styles of institutionalization of Islam in the two countries, and more situational circumstances of how the publications were initially framed by the relevant newspapers, the contingent choices of action by the political elites and cross-context lesson drawing.
The Muhammad cartoons and multicultural democracies
Authors: Levey Geoffrey Brahm , Modood Tariq
Published: August 2009

The Danish cartoon affair presents a vehicle for rethinking some of our longstanding assumptions about liberal democracy and its capacity to accommodate cultural difference. The public and academic debates have tended to frame the affair as either a clash between liberal-democratic and illiberal religious values or as a question of whose position is most consistent with liberal-democratic values. We begin, instead, from the assumption that liberal-democratic values conflict, not only between liberalism and democracy, but also within liberalism and democracy. We argue that cases such as the Muhammad cartoons controversy present liberal democracies with choices about which liberal-democratic principles and conceptions of these principles they emphasize and when. Guiding these choices should also be the pragmatic question of how best to make multicultural democracies work. We suggest that the Muhammad cartoons encompass not one, but three distinct problem areas: the violation of a religious norm in the representation of Muhammad, attacks on Islam as a religion, and attacks on Muslims as a group. We examine how liberal democratic values and multicultural citizenship relate to each of these cases, and argue that attacks on Muslims as a group are a form of racism.
“Planning with People”: Urban Renewal in Boston’s Washington Park, 1950-1970
Authors: Spiers John H.
Published: August 2009

This article examines urban renewal in Washington Park, a 502-acre area in the Roxbury section of Boston, the heart of the Black community, that the city made the center of its residential urban renewal program in the 1960s. It analyzes the way Washington Park, in contrast to earlier projects, emphasized rehabilitation, offered a “planning with people” approach that solicited community input, and witnessed the growth of social service programming for “people renewal.” The article discusses how instead of planning with the community, leaders of local community organization Freedom House worked with the Boston Redevelopment Authority to develop a project that privileged middle-class values of home ownership and community design over the needs and interests of the predominantly working-class residents.
Soft Tissue Injections in the Athlete
Authors: Nepple Jeffrey J. , Matava Matthew J.
Published: August 2009

Background:

Injections into or adjacent to soft tissue structures, including muscle, tendon, bursa, and fascia, for pain relief and an earlier return to play have become common in the field of sports medicine.

Study Design:

Clinical review.

Results:

Corticosteroids, local anesthetics, and ketorolac tromethamine (Toradol) are the most commonly used injectable agents in athletes. The use of these injectable agents have proven efficacy in some disorders, whereas the clinical benefit for others remain questionable. All soft tissue injections performed for pain control and/or an anti-inflammatory effect have potentially serious side effects, which must be considered, especially in the pregame setting.

Conclusions:

The primary concern regarding corticosteroid and local anesthetic injections is an increased risk of tendon rupture associated with the direct injection into the tendon. Intramuscular Toradol injections provide significant analgesia, as well as an anti-inflammatory effect via its inhibitory effect on the cyclooxygenase pathway. The risk of bleeding associated with Toradol use is recognized but not accurately quantified.