bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Characterization of Electro-Bonded Laminates
Authors: Di Lillo Luigi , Raither Wolfram , Di Fratta Claudio , Bergamini Andrea , Ermanni Paolo
Published: July 2013

This work reports on the coupled electro-mechanical simulation and mechanical characterization of electro-bonded laminates (EBL). In light of their conceivable implementation in morphing wings as leading/trailing edge reinforcement plates or as active elements for shear center position adaptation, values of shear strength comparable to those achievable by an epoxy resin, i.e. 10–15 [MPa], are needed. Finite element analysis routines have been implemented to gain insights into the shear behavior of EBL under high electric fields. Further, they allowed for the optimization of EBL in terms of electrode shaping in order to obtain a smooth introduction of axial stresses, avoiding thereby the appearance of shear stress singularities at the edges of the structures. Experimental verification was carried out through single lap shear tests. These experiments quantified the mechanical properties of electro bonded interfaces, assessed the importance of the thickness and alignment of electrodes and the degradation of their constitutive layers due to friction.
Observation of the Poling Process in Ferroelectric Ceramics Using Piezoresponse Force Microscopy
Authors: Kim K. L. , Huber J. E.
Published: July 2013

Evolution of the domain structure in bulk polycrystalline PZT during poling was studied using Piezoresponse Force Microscopy (PFM). For the study, two different experimental methods were employed. First, a trapezoidal PZT specimen was subjected to electric field so as to produce a wide variation of electric field intensity in the specimen. PFM images were then acquired from several different areas that have experienced different field strengths. Histograms of pixel intensity show a distinct difference in the pattern of piezoresponse signal between poled and unpoled areas. The presence of non-180° domain structure in the scanned area significantly affects the histogram pattern. At high levels of electric field the presence of mainly 180° domain structures leads to a bi-modal M-shaped histogram. To illustrate the evolution of the non-180° domain structure, in-plane poling was conducted with the electric field level increased in steps, and the domain evolution process was observed by PFM after each step. The resulting images demonstrate that non-180° domain structures gradually disappear from the specimen surface during the poling process. The PFM data can be exploited to study domain evolution in bulk ferroelectric materials via both qualitative observation and statistical analysis.
On the Properties of Ni-Rich NiTi Shape Memory Parts Produced by Selective Laser Melting
Authors: Haberland Christoph , Meier Horst , Frenzel Jan
Published: July 2013

Processing of Nickel-Titanium (NiTi) shape memory alloys (SMAs) is challenging because smallest compositional variances and all types of microstructural features strongly affect the elementary processes of the martensitic transformation and thus the functional properties of the material. Against this background, powder metallurgical near net shape methods are attractive for the production of NiTi components. Especially additive manufacturing technologies (AM) seem to provide high potential, although they have received only little attention for processing NiTi so far. This work is the first to report on pseudoelastic properties of additive manufactured Ni-rich NiTi. We show how to establish pseudoelasticity in NiTi samples prepared by the additive manufacturing technique Selective Laser Melting (SLM). Therefore, we analyze phase transformation behavior, mechanical characteristics and functional properties of our materials subjected to different heat treatments. The obtained results are compared to the behavior of conventional NiTi. The presented results clearly indicate that SLM provides a promising processing route for the fabrication of high quality NiTi parts.
Magnetic Coupled Cantilever Piezoelectric Energy Harvester
Authors: Tang Lihua , Yang Yaowen , Zhao Liya
Published: July 2013

A conventional vibration energy harvester is usually designed as a linear single-degree-of-freedom (1DOF) resonator. The efforts to improve its efficiency involve two aspects, i.e., enlarging the magnitude of output and widening the operating bandwidth. In this paper, we propose a magnetic coupled cantilever piezoelectric energy harvester (PEH) to achieve the above two goals. Different from other reported magnetic coupled PEHs, the magnetic interaction in the proposed design is introduced by a magnetic oscillator. Firstly, the lumped parameter models are established for the conventional linear PEH, the nonlinear PEH with a fixed magnet and the proposed PEH with a magnetic oscillator. The governing equations of the three systems are then provided in the state space form and their dynamics can be simulated by numerical integration. Subsequently, experimental tests are performed to validate the models. Both experiment and simulation show that the dynamics of the magnetic oscillator is able to not only broaden the operating bandwidth but also enhance the maximum power output of the PEH. Based on the validated model, parametric study is conducted to optimize the system performance.
Pre-Yield Shearing Regimes of Magnetorheological Fluids
Authors: Nassar Waad , Boutillon Xavier , Lozada José
Published: July 2013

We analyzed experimentally the pre-yield regime of some MRFs. The hearing response is ruled by two successive regimes and limited by an interfacial phenomenon. The initial response is pseudo-elastic and independent from the magnetic field and of the particle volume fraction. The shear-stress limit of this regime is proportional to the square of the magnetic field and to the particle volume fraction. In the next regime, the shear strain is not uniform in the fluid. The increase in average shear stress varies linearly with the increase in average shear strain. The variation coefficient is proportional to the square of the magnetic field and decreases with the particle volume fraction. Finally, a loss of adhesion of the magnetic aggregates with the shearing plate or the magnetic pole occurs. The corresponding shear stress is proportional to the square of the magnetic field and to the particle volume fraction.
An Efficient Computational Inverse Approach for Optimal Design of Localized Activation and Actuation for Morphing SMP Structures
Authors: Wang Shuang , Brigham John C.
Published: July 2013

A strategy is presented to identify the optimal localized activation and actuation for a morphing thermally-activated SMP structure or structural component to obtain a targeted shape change subject to design objectives such as minimal total required energy and time. This strategy combines numerical representations of the SMP structure’s thermo-mechanical behavior subject to activation and actuation with nonlinear optimization methods to efficiently solve the morphing inverse problem that includes minimizing cost functions which address thermal and mechanical energy, morphing time, and damage. The details of this strategy are presented along with simulated examples to display the capabilities and limitations, as well as potential future directions for improving these techniques.
Preliminary Investigation of a Fishbone Active Camber Concept
Authors: Woods Benjamin King Sutton , Friswell Michael I.
Published: July 2013

This paper introduces a novel airfoil morphing structure known as the Fishbone Active Camber (FishBAC). This design employs a biologically inspired compliant structure to create large, continuous changes in airfoil camber and section aerodynamic properties. The structure consists of a thin chordwise bending beam spine with stringers branching off to connect it to a pre-tensioned Elastomeric Matrix Composite (EMC) skin surface. Actuators mounted in the D-spar induce bending moments on the spine through an antagonistic pair of tendons in a manner similar to natural musculature systems. Several potential morphing configurations using this concept are introduced. The paper then focuses on a trailing edge morph wherein the compliant spine connects a rigid leading edge D-spar to a solid trailing edge strip. The motivation for exploring this novel morphing architecture is established through analytical aerodynamic comparison to the NACA 0012 airfoil with and without a discrete trailing edge flap. A prototype device is built to explore various aspects of manufacturing this concept, and to prove the large deflection capability of the FishBAC.
Fabrication and Characterization of a Membrane Based Hair Cell Sensor That Features Soft Hydrogel Materials
Authors: Tamaddoni Nima , Sarles Andy
Published: July 2013

One of the most common sensory structures in nature is the hair cell. Examples of hair cells include the inner and outer hair cells in the inner ears of vertebrates, external sensory hairs on the legs of spiders, and neuromasts found along the lateral lines of fish. Recent work by Sarles and Leo demonstrated that self-assembly methods could be used to construct a membrane-based hair cell that responds to a physical disturbance of the hair. An artificial cell membrane (or lipid bilayer) formed at the interface of two lipid-encased hydrogel volumes, serves as the transduction element in the device. In this study, a revised sensor embodiment is presented in which the hair is fixed at its base by the encapsulating polymeric substrate. In addition, a highly elastic, photo-polymerizable aqueous gel (PEGDA, 6000g/mole) is used to further increase the resiliency of the hair and to provide a compliant cushion for the bilayer. These changes yield a considerably more durable hair cell sensor. We perform a series of experimental tests to characterize the transduction element (i.e. the bilayer) and the sensing current produced by free vibration of the hair, and we study the directional sensitivity of this hair cell embodiment by perturbing the hair in three directions. These tests demonstrate that the magnitude of the sensing current (30–300pA) is significantly affected by direction of perturbation, where the largest signals result from motion of the hair in a direction perpendicular to the plane of the bilayer.
A Variational Asymptotic Approach for the Effective Magnetostriction of Magnetostrictive Composites
Authors: Tang Tian , Myers Oliver , Horstemeyer M. F.
Published: July 2013

The effective magnetostriction is one of the most important properties of magnetostrictive composites. The focus of this paper was to extend VAMUCH, a recently developed general purpose micromechanics model, for the effective magnetostriction of the multiphase composites containing magnetostrictive phases. Due to the mathematical similarity, the strains induced by magnetostriction were treated as thermal expansion strains. Thus, the effective magnetostriction can be calculated using VA-MUCH thermoelastic model. Numerical examples were used to validate the theory and the code.
SUEX Flapping Wing Mechanisms for Pico Air Vehicles
Authors: Mateti Kiron , Byrne-Dugan Rory A. , Tadigadapa Srinivas A. , Rahn Christopher D.
Published: July 2013

This paper introduces a simple and low cost flapping wing mechanism fabricated monolithically from SUEX dry film, an epoxy based negative photoresist similar to SU-8. The developed process has fewer steps compared to other methods, does not use precious metals, and greatly reduces processing time and cost. It simultaneously defines the PAV airframe, compliant flapping mechanism, and artificial insect wing using photolithography. Rapid prototypes were fabricated with precisely defined features and material properties and geometry that are similar to insects. A linear model with simplified aerodynamics is developed with amplitude dependent damping and validated using experimental results in air and in vacuum. Angles up to 45° at a resonant frequency of 47 Hz are observed that demonstrate applicability of the developed fabrication process for flapping wing air vehicle applications.
Dual Mode Sensing of Crack Growth in Steel Bridge Structures
Authors: Yu Lingyu , Zhao Liuxian , Tian Zhenhua , Giurgiutiu Victor , Ziehl Paul
Published: July 2013

Monitoring of fatigue cracking in steel bridge structures using a combined passive and active scheme has been approached by the authors. Passive acoustic emission (AE) monitoring is able to detect crack growth behavior by picking up the stress waves resulting from the breathing of cracks while active ultrasonic pulsing can quantitatively assess structural defect by sensing out an interrogating pulse and receiving the structural reflections. The dual-mode sensing functionality is pursued by using the R15I ultrasonic transducers.

In the paper, we presented the subject dual-mode sensing on steel compact tension (CT) specimens in a laboratory setup. Passive AE sensing was performed during fatigue loading and showed its capability to detect crack growth and location. At selected intervals of loading cycles, the test was paused to allow for active sensing by pulsing the transducers in a round-robin pattern. Plate waves were excited, propagated and interacted within the structure. Several approaches were proposed to analyze the interrogation data and to correlate the data features with crack growth. Root means square deviation (RMSD) damage index (DI) was found as a good indicator for indicating the overall crack development. Short time Fourier transform (STFT) provided both time and frequency information at the same time. Moreover, wave velocity analysis showed interesting results when crack developed across the transmitter-receiver path.
Detection of Botulinum Neurotoxin/A Insertion Using an Encapsulated Interface Bilayer
Authors: Taylor Graham , Leo Donald , Sarles Andy
Published: July 2013

Many signaling mechanisms in living cells occur at biological boundaries via cell surface receptors and membrane proteins embedded in lipid bilayers. The coordination of actions of sensory and motor neurons in the nervous system represents one example of many that heavily depends on lipid membrane bound receptor mediated signaling. As a result, chemical and biological toxins that disrupt these neural signals can have severe physiological effects, including paralysis and death. Botulinum neurotoxin Type A (BoNT/A) is a proteolytic toxin that inserts through vesicle membranes and cleaves membrane receptors involved with synaptic acetylcholine uptake and nervous system signal conduction.

In this work, we investigate the use of a Bioinspired liquid-supported interface bilayer for studying the insertion of BoNT/A toxin molecules into synthetic lipid bilayers. DPhPC lipid bilayers are formed using the regulated attachment method (RAM), as developed by Sarles and Leo, and we perform current measurements on membranes exposed to BoNT/A toxin to characterize activity of toxin interacting with the synthetic bilayer. Control tests without toxin present are also presented. The results of these tests show an increase in the magnitude of current through the bilayer when the toxin is included. We interpret these initial results to mean that incorporation of BoNT/A toxin at a high concentration in an interface bilayer increases the permeability of the membrane as a result of toxin molecules spanning the thickness of the bilayer.
Full Electromechanical Optimization of Shunted Piezoelectric Patch for Controlling Elastodynamic Waves’ Power Flow
Authors: Tateo Flaviano , Huang Tianli
Published: July 2013

Wave propagation and energy diffusion in smart structures with shunted piezoelectric patches are examined in this study. The dynamic behavior of a structure can be modified through piezoelectric shunts with negative capacitance. This technique is extremely interesting, as it controls the dynamic behavior of the structure in a large frequency range. The effects of this piezoelectric shunt are studied via a wave propagation approach, and energy diffusion properties of specific wave modes in the structure can be obtained. However, for a proper design of the overall structure, a finer analysis of the real-life circuit is required. The aim of the present work is indeed to establish some essential rules that will guide one to choose more suitable design parameters for the actual system.
Non-Linear Modeling and Analysis of Composite Helicopter Blade for Piezoelectric Energy Harvesting
Authors: Vieira Wander G. R. , Nitzsche Fred , De Marqui Carlos
Published: July 2013

Converting aeroelastic vibrations into electricity for low-power generation has received growing attention over the past few years. Helicopter blades with embedded piezoelectric elements can provide electrical energy to power small electronic components. In this paper, the non-linear modeling and analysis of an electromechanically coupled cantilevered helicopter blade is presented for piezoelectric energy harvesting. A resistive load is considered in the electrical domain of the problem in order to quantify the electrical power output. The non-linear electromechanical model is derived based on the Variational-Asymptotic Method (VAM). The coupled non-linear rotary system is solved in the time-domain. A generalized-α integration method is used to guarantee numerical stability, adding numerical damping at high frequencies. The electromechanical behavior of the coupled rotating blade is investigated for increasing rotating speeds (stiffening effect).
Mechanism and Bias Considerations for Design of a Bi-Directional Artificial Muscle Actuator
Authors: Vocke Robert D. , Kothera Curt S. , Wereley Norman M.
Published: July 2013

Pneumatic artificial muscles (PAMs), or McKibben actuators, have received considerable attention for robotic manipulators and in aerospace applications due to their similarity to natural muscles. Like natural muscles, PAMs are a purely contractile actuator, so that, in order to produce bidirectional or rotational motion, they must be arranged in an agonist/antagonist pair, which inherently limits the deflection of the system due to the high parasitic stiffness of the antagonistic PAM. This study presents two methods for increasing the performance of an antagonistic PAM system by decreasing the passive parasitic moment, rather than increasing the active moment. The first involves selection of the kinematic mechanism geometry, and the second involves the introduction of bias into the system, both in terms of PAM contraction, and passive (antagonistic) PAM pressure. It was found with the proper selection of design parameters, including mechanism geometry, PAM geometry, and bias conditions, that an ideal actuator configuration can be found that maximizes deflection for a given arbitrary loading. When comparing a baseline design to an improved design for a simplified case, a nearly 50% increase in maximum deflection was predicted simply by optimizing mechanism geometry and bias contraction.
Characterization of Ferroelectric Single Crystals With Field Induced Phase Transformations
Authors: Gallagher John A. , Lynch Christopher S.
Published: July 2013

As new compositions of single crystal relaxor ferroelectrics are developed, the full thermo-electro-mechanical characterization of each composition and the limitations on linear behavior imposed by field driven phase transformations requires a highly specialized set of experiments. This characterization currently requires two crystal cuts which must each be subjected to five electric field-electric displacement cycles at different stress levels, five stress-strain cycles at different electric field levels, and this process must be repeated at five temperatures. In this document, a new approach to characterizing the linear behavior and phase transformation behavior is proposed based on a combination of a work-energy based model of the driving forces for the phase transformation together with data measured through electrical loading while measuring strain and electric displacement, and a measurement of mechanical compliance.
A Miniature MR Actuator With Impedance Sensing Mechanism for Haptic Applications
Authors: Yang Tae-Heon , Koo Jeong-Hoi , Kim Sang-Youn , Kwon Dong-Soo
Published: July 2013

This paper presents a miniature haptic actuator based on MR fluids, which is designed to convey realistic haptic sensations to users in small electronic devices. The proposed MR actuator can create various kinaesthetic sensations. The haptic sensation, which is generated in the form of resistive force, should vary according to the stroke of the actuator (or the pressed depth of the plunger). Thus, a sensing method for gauging the pressed depth should be integrated into the proposed actuator for demonstrating its real-world haptic application. To determine the pressed depth of the MR actuator, this study proposes an impedance sensing mechanism. The proposed sensing method measures the impedance change of the solenoid coil embedded in the actuator in the form of voltages to estimate the pressed depth. Using a prototype actuator, the sensing performance of the proposed sensing method, was evaluated. The results show that the sensitivity of the proposed impedance sensing method is sufficient to regulate the output resistive force over a small stroke range of the actuator.
Distinguishing the Degradation of the Interdigital Piezoelectric Fibre Transducers From Structural Damage in Multifunctional Composites
Authors: Mehdizadeh Mohammad , John Sabu , Wang Chun H. , Ghorbani Kamran , Rowe Wayne S. T.
Published: July 2013

The next-generation design of structural components involves combining multiple functions. The goal of such Multi-functional structures (MFS) is to incorporate various tasks and functions such as structural, electrical and thermal features within a structural housing. The performance and behaviour characteristics of the multi-functional structures can be affected by degradation of any of the sub-components. This can have consequences on the safety, cost, and operational capability. Therefore, the timely and accurate detection, characterization and monitoring of the degradation in these sub-components are major concerns in the operational environment. This calls for Structural Health Monitoring (SHM) as a possible method to improve the safety and reliability of structures and thereby reduce their operational cost. As the application of SHM systems to monitor the status of the MFS increase, it will be increasingly important to determine the durability, reliability, and reparability of the components of SHM system such as sensors. The sensors themselves must be reliable enough so that they do not require replacement at intervals less than the economic lifetime of the structures and components they are monitoring. This is especially important when the deleterious structural changes in the sensor occurs without any discernible change in the structure being monitored In the present work, an assessment is carried out to quantify the degradation in the electric and electromechanical characteristics of polymer composite PZT sensors, under fatigue loading. Changes in the electrical properties of these sensors such as capacitance and inductance have been measured. The strain measurements of the sensor have also been compared to the theoretically calculated strain. The results show that the delineation of structural damage from sensor degradation is possible by monitoring the changes in the key electrical properties of the sensor components such as electrodes and PZT fibers as well as the comparison of experimentally measured and theoretically calculated strain values.
Characterization of a Porous Multifunctional Nanocomposite for Pressure Sensing
Authors: Rizvi Reza , Naguib Hani , Biddiss Elaine
Published: July 2013

This study focuses on the characterization of a porous multifunctional elastomer-CNT nanocomposites for potential use as pressure sensors. A thermoplastic polyurethane (TPU) was chosen as an elastomeric matrix, which was reinforced with multiwall carbon nanotubes (0–10 wt%) by high shear twin screw extrusion mixing. Porosity was introduced to the composites through the phase separation of a single TPU-CO2 solution. Interactions between MWNT and TPU were elucidated through calorimetry, gravimetric decomposition, conductivity measurements and microstructure imaging. The piezoresistance (pressure-resistance) behavior of the nanocomposites was investigated and found to be dependent on MWNT concentration and nanocomposite microstructure.
In-Plane Field Propagation in EAP Transducers Based on the Equivalent Network Method
Authors: Graf Christian , Maas Jürgen
Published: July 2013

Dielectric Electroactive Polymers belong to a new class of smart materials, whose functional principle is based on electrostatic forces. They can either be used as actuators to provide considerable stretch ratios or as generators to convert mechanical strain energy into electrical energy by use of an initial amount of energy. Since the polymer material and also the covering compliant electrodes show non-ideal electrical properties, like finite resistivity and conductivity respectively, design rules have to be derived, in order to optimize the devices. The electrode conductivity in connection with the polymer resistivity causes a voltage drop along the electrode surface, resulting in a reduced actuation strain or energy conversion. To minimize its parasitic effects, the influence of this effect is studied by the in-plane field propagation based on a model obtained with the equivalent network method. It is shown that the proposed model provides accurate results, which can be used to study the effect of contacting electrodes, especially in case of point contacts.
Tension-Torsion Experiments on Superelastic Shape Memory Alloy Tubes
Authors: Reedlunn Benjamin , Daly Samantha , Shaw John
Published: July 2013

Shape memory alloys have been studied extensively in pure tension, but careful studies of multi-axial behavior are far less common in the published literature. Here, we present room temperature tension-torsion experiments on superelastic NiTi tubes, using stereo digital image correlation (DIC) for the first time to measure the strain on the tube surface. DIC can accurately measure large strains, which permitted us to capture the mechanical response at the beginning and end of the phase transformation. These responses were then used to generate the first measurements of the saturation stress and strain surfaces in the published literature. The full field nature of DIC was also important in this work. The strain fields revealed propagating transformation fronts in pure tension, no propagating fronts in pure torsion, and a progression of behaviors in between, similar to the optical microscopy observations of Sun and Li [1]. By quantitatively measuring the strain fields with DIC, however, we found new features. In tension-dominated tests, the transformation front appeared as a near discontinuity in not only the axial strain field, but also the shear strain field. Also, the shear strain fields in pure torsion were not uniform. Although there were no propagating fronts, torsion caused vertical columns of shear strain to gradually appear and disappear during phase transformation.
Analytical Solution for Pseudoelastic Response of a Shape Memory Alloy Thick-Walled Cylinder Under Internal Pressure
Authors: Tabesh Majid , Liu Bingfei , Boyd James , Lagoudas Dimitris
Published: July 2013

Analytical solutions are derived for the pseudoelastic response of a shape memory alloy (SMA) thick-walled cylinders subjected to internal pressure. A Tresca transformation criterion and linear hardening are used. Equations are given for the stress, total strain, transformation strain, and radial displacement.
Optimal Control of Gun Recoil Using Magnetorheological Dampers
Authors: Singh Harinder J. , Wereley Norman M.
Published: July 2013

Optimal control of a gun recoil absorber is investigated for minimizing recoil loads and maximizing rate of fire. A multi-objective optimization problem was formulated by considering the mechanical model of the recoil absorber employing a spring and a magnetorheological (MR) damper. The damper forces are predicted by evaluating pressure drops using Bingham-plastic model. The optimization methodology provides multiple optimal design configurations with a trade-off between recoil load minimization and increased rate of fire. The configurations with minimum recoil load transmissions have lower rate of fire and vice versa. The gun recoil absorber performance is also analyzed for fluctuations in the firing forces. The adaptive control of the MR damper for varying gun firing forces provides a smooth operation by returning the recoil mass to its battery (ready to reload and fire) position without incurring an end-stop impact. Furthermore, constant load transmissions are observed with respect to the recoil stroke by implementing optimal control during the simulated firing events.
Design, Fabrication, and Testing of a Thermal/Mechanical/Magnetic Hybrid Energy Micro-Harvester
Authors: Chung Tien-Kan , Tseng Chia-Yuan , Chen Chin-Chung , Wang Chieh-Min
Published: July 2013

In this paper, we report a novel hybrid energy micro-harvester. The harvester utilizes ferromagnetic materials combined with piezoelectric cantilever beams to harvest the energy from a thermal, mechanical, and magnetic energy sources and subsequently convert the energy to an electrical output. In addition to energy-harvesting, the harvester utilizes a non-contact approach in its structure to avoid the wear problem which frequently occurs in conventional structural-contact approaches.
Solid-State Dye Sensitized Optoelectronic Carbon Nanotube-Wires: An Energy Harvesting Damage Sensor With Nanotechnology Approach
Authors: Uddin Mohammed Jasim , Dickens Tarik J. , Yan Jin , Olawale David O. , Okoli Okenwa I. , Cesano Federico
Published: July 2013

A novel preparation method of solid state photovoltaic carbon nanotubes (CNT) yarns has been successfully developed by depositing and grafting TiO2 thin films on CNT yarn substrates using a simple sol–gel method and designed for use in structural health monitoring (SHM) applications. The interaligned, ultrastrong and flexible CNYs display excellent electrical conductivity, mechanical integrity and their catalytic properties have been successfully used as working and counter electrodes. The TiO2 nanoparticles have been found to form a homogeneous thin film on the yarn surface, which shows efficient photovoltaic properties with remarkable stability when exposed to simulated solar light (AM 1.5). The yarns’ structure is not altered upon sol-gel treatment and light exposure. The TiO2 film is firmly anchored and the photovoltaic performance is retained even after multiple irradiation cycles. This preparation technique can also be applied to CNT yarn reinforced composite for an innovative in-situ and real-time self damage-sensing properties with infused triboluminescent (TL) materials.
Experimental Investigation of a Loaded Circular Dielectric Electro-Active Polymer Actuator Coupled to Negative-Rate Bias Spring Mechanism
Authors: Hodgins Micah , York Alex , Seelecke Stefan
Published: July 2013

A constant force input, a linear spring, and a bi-stable mechanism are separately tested as the biasing element of a circular/diaphragm DEAP. Each of the bias elements are systematically coupled to an unloaded 2 layer DEAP and are tested under various DEAP pre-deflections, bias element stiffness and electrical loading rates. The out-of-plane displacement output is measured as the voltage is cycled. The tests showed that the bi-stable element, with aid of a mechanical stop, gave the largest displacement output. This bi-stable element actuator is then tested against a hanging mass to examine the work capabilities against a constant force. However, the actuator failed to work even against a hanging mass of 20 grams. This change in behavior of the actuator is analyzed by considering the force equilibrium curves. Finally, suggestions are made for the design of future biasing methods in order to achieve higher actuator performance.
Wireless Excitation and Electrical Impedance Matching of Piezoelectric Wafer Active Sensors
Authors: Bhuiyan Rashed Hossain , Islam MD Mazharul , Huang Haiying
Published: July 2013

Wireless ultrasound inspections using Piezoelectric Wafer Active Sensors (PWAS) are attractive for Structural Health Monitoring (SHM). However, the impedance mismatch between the PWAS and the wireless transponder reduces the wirelessly transmitted signal strength. Electrical Impedance Matching (EIM) circuit can be introduced to maximize the power transmission between the PWAS and the wireless transponder. This paper discusses the wireless excitation of ultrasound as well as the design, simulation, and characterization of the EIM networks for PWAS. To maximize power transmission, a two port EIM network was developed using a computerized smith chart. The equivalent circuit of the PWAS and the EIM network were then combined to establish the equivalent circuit of the matched transducer. Computer simulations were carried out to evaluate the gain, the bandwidth, and the sensitivity of the EIM networks. Two-port EIM networks were implemented for both the actuator and the sensor in an ultrasound pitch-catch inspection system. The performance of the pitch-catch systems with and without the EIM networks was compared. Detailed analysis, simulation, hardware implementation, and measurement results are presented.
High Speed Shape Memory Alloy Activation
Authors: Czechowicz Alexander , Böttcher Jonas , Mojrzisch Sebastian , Langbein Sven
Published: July 2013

Due to their ability to change into a previously imprinted actual shape through the means of thermal and electrical activation, shape memory alloys (SMA) are suitable as actuators. To apply these smart materials to a wide range of high-speed applications like valves or safety systems, an analysis of the application potential is required. The detection of inner electrical resistance of SMA actuators allows gauging the actuator’s stroke. By usage of a microcontroller a smart system without any hardware sensors can be realized which protects the system from overheating during high-current activation. The publication concentrates on different experimental data on high-speed actuation under 20ms and the potentials in the field of industrial applications. The paper gives an overview about different controlling methods for SMA-actuators, experiments concerning the resistance behavior of SMA and the development of systems using a resistance control feedback signal during high-speed activation.
Determining Electromechanical Network Model Parameters of a Piezomagnetic Unimorph Structure With Finite-Element Simulations
Authors: Marschner Uwe , Starke Eric
Published: July 2013

Two-layer piezomagnetic elements within a homogeneous magnetic field have been well studied. In this paper the effect of an inhomogeneous magnetic field distribution in the magnetic layer on the electromechanical properties of a two-layer element with planar conductor arrangement on top is investigated. Based on static Finite Element (FE) simulations the parameters of its network model are determined. The inductance of the arrangement with and without magnetic layer allows the calculation of the reluctances of the magnetic system. Magnetic field strength and moment of the fixed-fixed beam give the magnetomechanical transduction coefficient, moment and deflection the bending compliance. The dynamic behavior of the electromechanical transducer can be calculated efficiently by the completed network model in sensing as well as actuation direction.
Design, Development, and Assembly of Space Flight Structural Health Monitoring Experiment
Authors: Siler David , Cooper Ben , White Chris , Marinsek Stephen , Zagrai Andrei , MacGillivray Joe , Gutierrez Jaclene , Tena Karen , Magnuson Levi , Puckett Lloyd , Klepper Jordan , Jorgensen Anders , Kessler Seth
Published: July 2013

The paper presents the design, development, and assembly of Structural Health Monitoring (SHM) experiments intended to be launch in space on a sub-orbital rocket flight as well as a high altitude balloon flight. The experiments designed investigate the use of both piezoelectric sensing hardware in a wave propagation experiment and piezoelectric wafer active sensors (PWAS) in an electromechanical impedance experiment as active elements of spacecraft SHM systems. The list of PWAS experiments includes a bolted-joint test and an experiment to monitor PWAS condition during spaceflight. Electromechanical impedances of piezoelectric sensors will be recorded in-flight at varying input frequencies using an onboard data acquisition system. The wave propagation experiment will utilize the sensing hardware of the Metis Design MD7 Digital SHM system. The payload will employ a triggering system that will begin experiment data acquisition upon sufficient saturation of g-loading. The experiment designs must be able to withstand the harsh environment of space, intense vibrations from the rocket launch, and large shock loading upon re-entry. The paper discusses issues encountered during design, development, and assembly of the payload and aspects central to successful demonstration of the SHM system during both the sub-orbital space flight and balloon launch.
Performance Modeling of a Smart Material Hydraulic Actuator
Authors: Larson John P. , Dapino Marcelo J.
Published: July 2013

Smart Material Hydraulic Actuators (SMEHAs) allow high-energy-density materials, such as piezoelectrics and magnetostrictives, to be used to develop compact, high-power actuators. Hydraulic rectification using check valves converts the high-frequency, small-displacement motion of a smart material to large displacements of a hydraulic actuator. In this paper, the performance of a magnetostrictive actuator is evaluated over a range of input frequencies and loading conditions and compared to model results of the overall system. The system’s dynamic performance is found to depend highly on the response of both the check valves used to rectify the motion of the smart material driver and the fluid system, including the passages connecting the smart material pump to the output hydraulic cylinder. Using AMESim, a model is developed for the response of the system and compared to experimental results.
A Compound Analogical Design for Low Cost Solar Panel Systems
Authors: Goodman Joseph N. , Yen Jeannette , Gentry Russell , Nagel Kathryn M. , Amador Guillermo J.
Published: July 2013

In support of the Department of Energy Sunshot initiative target of $1.25 per watt photovoltaics systems for commercial applications, whole system designs were pursued using the analogical design methodology, an essential step in the bio inspired design approach. A functional decomposition of solar panel systems was conducted, and then key functions critical to system integrity and cost reduction were identified. Three sources of bio-inspiration were mainly used: hierarchical structures as a common design dimension exploited in natural systems, and leaves’ ability to maintain position through changes in shape and angle of attack when triggered by wind flow, and limpet shells’ reduction of hydrodynamic forces by way of natural geometrical features. The design team developed concepts with varying degrees of abstraction then attempted to reconcile them with other functional requirements. Variants that descended from the leaf concept were generally found to be biophilic and offer aesthetic value; however, presented shortcomings in electrical design and installation procedure (Kellert 2008). Alternatively, concepts inspired by hierarchical structures and limpet shells were found to have greater variability, enabling reconciliation with other functional requirements, resulting in a complete system solution capable of meeting the cost reduction objective. From the analysis of these design variants, we may conclude that transferring solution principles directly from nature is best done when there is small set of functional requirements that must be fulfilled and value in a biophilic design. However, in cases of significant system complexity, abstracted lessons from nature may be found to be more flexible and easily reconciled with multiple requirements.
A Versatile Toolkit to Produce Sensitive FRET Biosensors to Visualize Signaling in Time and Space
Authors: Fritz Rafael D. , Letzelter Michel , Reimann Andreas , Martin Katrin , Fusco Ludovico , Ritsma Laila , Ponsioen Bas , Fluri Erika , Schulte-Merker Stefan , van Rheenen Jacco , Pertz Olivier
Published: July 2013

Next-generation biosensors enable in vivo monitoring of ERK activity and detection of RhoA activity in small cellular extensions.
Accessory to Obesity?
Authors: Kiberstis Paula A.
Published: July 2013

Disruption of a protein required for effective signaling by a melanocortin receptor causes severe obesity in mice.
Centered on SAM
Authors: Gough Nancy R.
Published: July 2013

Cellular availability of methionine and cysteine controls autophagy and translation.
NCR3/NKp30 Contributes to Pathogenesis in Primary Sjögren’s Syndrome
Authors: Rusakiewicz Sylvie , Nocturne Gaetane , Lazure Thierry , Semeraro Michaela , Flament Caroline , Caillat-Zucman Sophie , Sène Damien , Delahaye Nicolas , Vivier Eric , Chaba Kariman , Poirier-Colame Vichnou , Nordmark Gunnel , Eloranta Maija-Leena , Eriksson Per , Theander Elke , Forsblad-d’Elia Helena , Omdal Roald , Wahren-Herlenius Marie , Jonsson Roland , Rönnblom Lars , Nititham Joanne , Taylor Kimberly E. , Lessard Christopher J. , Sivils Kathy L. Moser , Gottenberg Jacques-Eric , Criswell Lindsey A. , Miceli-Richard Corinne , Zitvogel Laurence , Mariette Xavier
Published: July 2013

Genetic and functional analyses implicate NCR3/NKp30 in the pathogenesis of primary Sjögren’s syndrome.
CaMKII Is Essential for the Proasthmatic Effects of Oxidation
Authors: Sanders Philip N. , Koval Olha M. , Jaffer Omar A. , Prasad Anand M. , Businga Thomas R. , Scott Jason A. , Hayden Patrick J. , Luczak Elizabeth D. , Dickey David D. , Allamargot Chantal , Olivier Alicia K. , Meyerholz David K. , Robison Alfred J. , Winder Danny G. , Blackwell Timothy S. , Dworski Ryszard , Sammut David , Wagner Brett A. , Buettner Garry R. , Pope Robert M. , Miller Francis J. , Dibbern Megan E. , Haitchi Hans Michael , Mohler Peter J. , Howarth Peter H. , Zabner Joseph , Kline Joel N. , Grumbach Isabella M. , Anderson Mark E.
Published: July 2013

Ca
2+
/calmodulin-dependent protein kinase (CaMKII) transduces oxidative stress into asthma-related diseases.
TGFβ Receptor Mutations Impose a Strong Predisposition for Human Allergic Disease
Authors: Frischmeyer-Guerrerio Pamela A. , Guerrerio Anthony L. , Oswald Gretchen , Chichester Kristin , Myers Loretha , Halushka Marc K. , Oliva-Hemker Maria , Wood Robert A. , Dietz Harry C.
Published: July 2013

Patients with mutations in the receptors for TGFβ (Loeys-Dietz syndrome) exhibit an increased prevalence of allergic diseases.
Transplanting Interneuron Precursors for Epilepsy Control
Authors: Sohal Vikaas S.
Published: July 2013

Transplantation of precursor cells for GABAergic interneurons suppresses seizures and behavioral deficits associated with epilepsy in mice.
EsiB, a Novel Pathogenic Escherichia coli Secretory Immunoglobulin A-Binding Protein Impairing Neutrophil Activation
Authors: Pastorello Ilaria , Rossi Paccani Silvia , Rosini Roberto , Mattera Rossella , Ferrer Navarro Mario , Urosev Dunja , Nesta Barbara , Lo Surdo Paola , Del Vecchio Mariangela , Rippa Valentina , Bertoldi Isabella , Gomes Moriel Danilo , Laarman Alexander J. , van Strijp Jos A. G. , Daura Xavier , Pizza Mariagrazia , Serino Laura , Soriani Marco
Published: July 2013

In this study, we have characterized the functional properties of a novel
Escherichia coli
antigen named EsiB (

E
. coli

s
ecretory
i
mmunoglobulin A-
b
inding protein), recently reported to protect mice from sepsis. Gene distribution analysis of a panel of 267 strains representative of different
E. coli
pathotypes revealed that
esiB
is preferentially associated with extraintestinal strains, while the gene is rarely found in either intestinal or nonpathogenic strains. These findings were supported by the presence of anti-EsiB antibodies in the sera of patients affected by urinary tract infections (UTIs). By solving its crystal structure, we observed that EsiB adopts a superhelical fold composed of Sel1-like repeats (SLRs), a feature often associated with bacterial proteins possessing immunomodulatory functions. Indeed, we found that EsiB interacts with secretory immunoglobulin A (SIgA) through a specific motif identified by an immunocapturing approach. Functional assays showed that EsiB binding to SIgA is likely to interfere with productive FcαRI signaling, by inhibiting both SIgA-induced neutrophil chemotaxis and respiratory burst. Indeed, EsiB hampers SIgA-mediated signaling events by reducing the phosphorylation status of key signal-transducer cytosolic proteins, including mitogen-activated kinases. We propose that the interference with such immune events could contribute to the capacity of the bacterium to avoid clearance by neutrophils, as well as reducing the recruitment of immune cells to the infection site.

IMPORTANCE
Pathogenic
Escherichia coli
infections have recently been exacerbated by increasing antibiotic resistance and the number of recurrent contagions. Attempts to develop preventive strategies against
E. coli
have not been successful, mainly due to the large antigenic and genetic variability of virulence factors, but also due to the complexity of the mechanisms used by the pathogen to evade the immune system. In this work, we elucidated the function of a recently discovered protective antigen, named EsiB, and described its capacity to interact with secretory immunoglobulin A (SIgA) and impair effector functions. This work unravels a novel strategy used by
E. coli
to subvert the host immune response and avoid neutrophil-dependent clearance.
Clinically Relevant Mutant DNA Gyrase Alters Supercoiling, Changes the Transcriptome, and Confers Multidrug Resistance
Authors: Webber Mark A. , Ricci Vito , Whitehead Rebekah , Patel Meha , Fookes Maria , Ivens Alasdair , Piddock Laura J. V.
Published: July 2013

Bacterial DNA is maintained in a supercoiled state controlled by the action of topoisomerases. Alterations in supercoiling affect fundamental cellular processes, including transcription. Here, we show that substitution at position 87 of GyrA of
Salmonella
influences sensitivity to antibiotics, including nonquinolone drugs, alters global supercoiling, and results in an altered transcriptome with increased expression of stress response pathways. Decreased susceptibility to multiple antibiotics seen with a GyrA Asp87Gly mutant was not a result of increased efflux activity or reduced reactive-oxygen production. These data show that a frequently observed and clinically relevant substitution within GyrA results in altered expression of numerous genes, including those important in bacterial survival of stress, suggesting that GyrA mutants may have a selective advantage under specific conditions. Our findings help contextualize the high rate of quinolone resistance in pathogenic strains of bacteria and may partly explain why such mutant strains are evolutionarily successful.

IMPORTANCE
Fluoroquinolones are a powerful group of antibiotics that target bacterial enzymes involved in helping bacteria maintain the conformation of their chromosome. Mutations in the target enzymes allow bacteria to become resistant to these antibiotics, and fluoroquinolone resistance is common. We show here that these mutations also provide protection against a broad range of other antimicrobials by triggering a defensive stress response in the cell. This work suggests that fluoroquinolone resistance mutations may be beneficial under a range of conditions.