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Showing 601 - 735 of 735 Journals sorted alphabetically
Scientific Reports     Open Access   (Followers: 85)
Sensors and Actuators B: Chemical     Hybrid Journal   (Followers: 18)
Sensors and Actuators Reports     Open Access   (Followers: 5)
Separation & Purification Reviews     Hybrid Journal   (Followers: 7)
Separation Science and Technology     Hybrid Journal   (Followers: 12)
Separations     Open Access   (Followers: 5)
Silicon Chemistry     Hybrid Journal   (Followers: 1)
Small Methods     Hybrid Journal   (Followers: 1)
Small Science     Open Access  
Small Structures     Hybrid Journal   (Followers: 1)
Smart Materials Research     Open Access   (Followers: 7)
SmartMat     Open Access  
Soft     Open Access  
Soft Nanoscience Letters     Open Access   (Followers: 1)
Solar RRL     Hybrid Journal  
Solid State Communications     Hybrid Journal   (Followers: 7)
Solid State Nuclear Magnetic Resonance     Hybrid Journal   (Followers: 3)
Solid State Sciences     Hybrid Journal   (Followers: 9)
Solvent Extraction and Ion Exchange     Hybrid Journal   (Followers: 7)
SPE Polymers     Open Access  
Spectral Analysis Review     Open Access  
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy     Hybrid Journal   (Followers: 15)
Spectrochimica Acta Part B: Atomic Spectroscopy     Hybrid Journal   (Followers: 17)
Spectroscopy and Spectral Analysis     Full-text available via subscription   (Followers: 1)
Starch / Staerke     Hybrid Journal   (Followers: 3)
Steel Research International     Hybrid Journal   (Followers: 22)
Structural Chemistry     Hybrid Journal   (Followers: 1)
Substantia     Open Access  
Supramolecular Chemistry     Hybrid Journal   (Followers: 5)
Supramolecular Materials     Full-text available via subscription   (Followers: 2)
Surface and Coatings Technology     Hybrid Journal   (Followers: 32)
Surface Science     Hybrid Journal   (Followers: 21)
Surface Science Reports     Full-text available via subscription   (Followers: 13)
Surfaces     Open Access   (Followers: 2)
Surfaces and Interfaces     Hybrid Journal   (Followers: 1)
Sustainable Chemical Processes     Open Access   (Followers: 3)
Sustainable Chemistry and Pharmacy     Full-text available via subscription   (Followers: 1)
Synfacts     Hybrid Journal   (Followers: 5)
Synlett     Hybrid Journal   (Followers: 47)
Synthesis     Hybrid Journal   (Followers: 56)
Talanta     Hybrid Journal   (Followers: 10)
Talanta Open     Full-text available via subscription   (Followers: 2)
TecnologĂ­a QuĂ­mica     Open Access  
Telematics and Informatics Reports     Full-text available via subscription   (Followers: 2)
Tenside Surfactants Detergents     Full-text available via subscription   (Followers: 2)
Tetrahedron     Hybrid Journal   (Followers: 80)
Tetrahedron Chem     Full-text available via subscription   (Followers: 2)
Tetrahedron Letters     Hybrid Journal   (Followers: 88)
The Alkaloids: Chemistry and Biology     Full-text available via subscription   (Followers: 1)
The All Results Journals : Chem     Open Access  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 5)
The Enzymes     Full-text available via subscription   (Followers: 2)
The Protein Journal     Hybrid Journal   (Followers: 5)
Theoretical and Experimental Chemistry     Hybrid Journal  
Theoretical Chemistry Accounts     Hybrid Journal   (Followers: 6)
Thermochimica Acta     Hybrid Journal   (Followers: 18)
Tip Revista Especializada en Ciencias Quimico-Biologicas     Open Access  
Topics in Current Chemistry     Hybrid Journal  
Toxicology International     Full-text available via subscription   (Followers: 5)
Toxicology Research     Partially Free   (Followers: 8)
Transition Metal Chemistry     Hybrid Journal   (Followers: 6)
Trends in Chemistry     Hybrid Journal  
Turkish Computational and Theoretical Chemistry     Open Access  
Ultrasonics Sonochemistry     Hybrid Journal   (Followers: 2)
Universal Journal of Chemistry     Open Access   (Followers: 1)
Vietnam Journal of Chemistry     Hybrid Journal  
Western Undergraduate Research Journal : Health and Natural Sciences     Open Access  
Wiley Interdisciplinary Reviews : Computational Molecular Science     Hybrid Journal   (Followers: 4)
World Journal of Chemical Education     Open Access   (Followers: 2)
X-Ray Spectrometry     Hybrid Journal   (Followers: 4)

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Smart Materials Research
Number of Followers: 7  

  This is an Open Access Journal Open Access journal
ISSN (Print) 2090-3561 - ISSN (Online) 2090-357X
Published by Hindawi Homepage  [339 journals]
  • Multiresonant Frequency Piezoelectric Energy Harvesters Integrated with
           High Sensitivity Piezoelectric Accelerometer for Bridge Health Monitoring
           Applications

    • Abstract: Wireless Structural Health Monitoring (WSHM) is a less expensive but efficient mode of health monitoring. However, it needs frequent change of batteries since remote WSHM consumes large power. The best scientific solution to this problem is to employ energy harvesters integrated along with the vibration sensors in the same substrate so that the battery is recharged by the energy harvested during vibrations caused by the passing vehicles in bridges. In this work, an attempt has been made to design an energy harvester and a micro accelerometer integrated chip. Civil structures have low natural frequencies and therefore low bandwidth design is adopted to maximize the harvested energy and accelerometer sensitivity. The other special feature of the proposed design is its ability to provide further increase in energy harvesting by the parallel operation of an array of energy harvesters with closely spaced natural frequencies. The studies show that the natural frequencies of the harvesters should be less than that of the structure in healthy condition. Simulation studies conducted on these devices show that it is possible to harvest a maximum power of 2.283 mW/g. The integrated micro accelerometer is also capable of giving a sensitivity of 27.67 V/g with appreciable improvement in other performance indices.
      PubDate: Sun, 29 Jan 2017 11:20:00 +000
       
  • Atomistic Study on Size Effects in Thermally Induced Martensitic Phase
           Transformation of NiTi

    • Abstract: The atomistic study shows strong size effects in thermally induced martensitic phase transformation evolution kinetics of equiatomic NiTi shape memory alloys (SMAs). It is shown that size effects are closely related to the presence of free surfaces; thus, NiTi thin films and nanopillars are studied. Quasi-static molecular dynamics simulations for several cell sizes at various (constant) temperatures are performed by employing well-established interatomic potentials for NiTi. The study shows that size plays a crucial role in the evolution of martensite phase fraction and, importantly, can significantly change the phase transformation temperatures, which can be used for the design of NiTi based sensors, actuators, or devices at nano- to microscales. Interestingly, it is found that, at the nanometer scale, Richard’s equation describes very well the martensite phase fraction evolution in NiTi thin films and nanopillars as a function of temperature.
      PubDate: Tue, 11 Oct 2016 13:14:41 +000
       
  • Thermal Effects on Vibration and Control of Piezocomposite Kirchhoff Plate
           Modeled by Finite Elements Method

    • Abstract: Theoretical and numerical results of the modeling of a smart plate are presented for optimal active vibration control. The smart plate consists of a rectangular aluminum piezocomposite plate modeled in cantilever configuration with surface bonded thermopiezoelectric patches. The patches are symmetrically bonded on top and bottom surfaces. A generic thermopiezoelastic theory for piezocomposite plate is derived, using linear thermopiezoelastic theory and Kirchhoff assumptions. Finite element equations for the thermopiezoelastic medium are obtained by using the linear constitutive equations in Hamilton’s principle together with the finite element approximations. The structure is modelled analytically and then numerically and the results of simulations are presented in order to visualize the states of their dynamics and the state of control. The optimal control LQG-Kalman filter is applied. By using this model, the study first gives the influences of the actuator/sensor pair placement and size on the response of the smart plate. Second, the effects of thermoelastic and pyroelectric couplings on the dynamics of the structure and on the control procedure are studied and discussed. It is shown that the effectiveness of the control is not affected by the applied thermal gradient and can be applied with or without this gradient at any time of plate vibrations.
      PubDate: Wed, 03 Jun 2015 06:56:50 +000
       
  • Microwave Assisted Healing of Thermally Mendable Composites

    • Abstract: Polymer matrix composites offer high specific strength; however, their potential weight savings have been limited by the concern of damage tolerance. If microcracking and similar incurred damage could be autonomously sealed, composite structures could be built thinner and lighter while still addressing damage tolerance, thus achieving the weight savings they promise. Various self-healing mechanisms have been proposed to this end. Herein, a method of thermally reversible polymerization is investigated. To date, thermally activated repair of composites have been accomplished typically through resistive heating, which has certain inherent complexities. An alternate heating method, via microwave exposure of carbon nanotubes incorporated throughout a thermal reversible polymer matrix, is demonstrated. Carbon nanotube-doped composites exhibit enhanced microwave absorption over an undoped control sample. Furthermore, it is shown that these composites can be heated locally by a focused microwave source. The particular composite formulation and layup studied could be uniformly heated to the targeted healing temperature of 100°C in as little as 20 seconds, followed by a healing time on the scale of minutes with total time depending upon the extent of damage.
      PubDate: Wed, 04 Feb 2015 08:30:02 +000
       
  • Porous and Nonporous Film-Shaped Magnetorheological Nanocomposites:
           Dielectric and Electrical Properties

    • Abstract: This paper presents a brief experimental comparative study on electrical and dielectric properties of two sets of porous and nonporous MRNCs, each including five samples of film-shaped magnetorheological nanocomposites (MRNCs) based on room temperature vulcanized (RTV) silicone rubber and nanosized carbonyl iron particles (CIPs). The electrical and dielectric properties of porous and nonporous MRNCs were measured at five different filler concentrations. Several experiments were performed to measure the volume resistivity, dielectric constant, and dielectric loss. The MRNCs dielectric properties were analysed with respect to the parameters like frequency and CIPs loadings. The electrical conductivity was studied in terms of volume resistivity. The comparative investigation suggests the porous MRNCs for smart and light-weighted structures those benefits from a lower electrical property, dielectric losses, and dielectric constants.
      PubDate: Mon, 01 Dec 2014 06:46:02 +000
       
  • Thermoelastic and Pyroelectric Couplings Effects on Dynamics and Active
           Control of Smart Piezolaminated Beam Modeled by Finite Element Method

    • Abstract: Smart structures with integrated sensors, actuators, and control electronics are of importance to the next generation high-performance structural systems. In this study, thermopiezoelastic characteristics of piezoelectric beam continua are studied and applications of the theory to active structures in sensing and optimal control are discussed. Using linear thermopiezoelastic theory and Timoshenko assumptions, a generic thermopiezoelastic theory for piezolaminated composite beam is derived. Finite element equations for the thermopiezoelastic media are obtained by using the linear constitutive equations in Hamilton's principle together with the finite element approximations. The structure consists of a modeling of cantilevered piezolaminated Timoshenko beam with integrated thermopiezoelectric elements between two aluminium layers. The structure is modelled analytically and then numerically and the results of simulations are presented in order to visualize the states of their dynamics and the state of control. The optimal control LQG accompanied by the Kalman filter is applied. The effects of thermoelastic and pyroelectric couplings on the dynamics of the structure and on the control procedure are studied and discussed. We show that the control procedure cannot be perturbed by applying a thermal gradient and the control can be applied at any time during the period of vibration of the beam.
      PubDate: Mon, 24 Nov 2014 07:27:10 +000
       
  • Unit Cell Analysis of the Superelastic Behavior of Open-Cell
           Tetrakaidecahedral Shape Memory Alloy Foam under Quasi-Static Loading

    • Abstract: Cellular solid materials and, more specifically, foams are increasingly common in many industrial applications due to their attractive characteristics. The tetrakaidecahedral foam microstructure, which can be observed in many types of foams, is studied in the present work in association with shape memory alloys (SMA) material. SMA foams are of particular interest as they associate both the shape memory effect and the superelasticity with the characteristics of foam. A Unit Cell Finite Element Method approach is used, an approach that allows accurate predicting of the macroscale response of the foam with a highly reduced numerical effort. The tetrakaidecahedral foam’s responses, both in the elastic and in the superelastic stages, are then extracted and compared with results from the literature. The tetrakaidecahedral geometry is found to be of particular interest when associated with SMA as it takes more advantage of the superelastic property of the material than foams with randomly distributed porosity.
      PubDate: Tue, 08 Jul 2014 08:39:41 +000
       
  • Enhanced Colouration Efficiency of Pulsed DC Magnetron Sputtered WO3 Films
           Cycled in H2SO4 Electrolyte Solution

    • Abstract: In the present investigation, we report on DC power and pulsing frequency induced changes in electrochromic properties of pulsed DC magnetron sputtered WO3 films by intercalating/deintercalating H+ ions from 0.1 M H2SO4 electrolyte solution. The observed efficient colouration bleaching mechanism of WO3 films confirms the effective electrochromic nature of the films associated with the electrochemical intercalation/deintercalation of H+ ions and electrons into WO3 lattice. The higher optical modulation was observed in the visible region of the optical transmittance spectra of colored and bleached WO3 films. The maximum coloration efficiency of 79 cm2/C was observed the first time for the film deposited at a DC power of 150 W and a pulsing frequency of 25 kHz.
      PubDate: Tue, 01 Jul 2014 07:48:35 +000
       
  • An SMA Passive Ankle Foot Orthosis: Design, Modeling, and Experimental
           Evaluation

    • Abstract: Shape memory alloys (SMAs) provide compact and effective actuation for avariety of mechanical systems. In this work, the distinguished superelastic behavior of these materials is utilized to develop a passive ankle foot orthosis to address the drop foot disability. Design, modeling, and experimental evaluation of an SMA orthosis employed in an ankle foot orthosis (AFO) are presented in this paper. To evaluate the improvements achieved with this new device, a prototype is fabricated and motion analysis is performed on a drop foot patient. Results are presented to demonstrate the performance of the proposed orthosis.
      PubDate: Mon, 02 Jun 2014 08:02:31 +000
       
  • The Effects of Piezoelectricity on the Interaction of Waves in
           Fluid-Loaded Poroelastic Half-Space

    • Abstract: The effects of piezoelectricity on the interaction of waves at fluid-poroelastic interface are studied. The constitutive equations and governing equations are formulated and their solution is obtained. The boundary conditions are described at fluid-solid interface. The effects of various parameters on the angle of refraction, amplitude ratios, displacements, electric potentials, and vertical component of slowness are studied numerically for a particular model. The results obtained are in agreement with the general laws of physics.
      PubDate: Thu, 17 Apr 2014 15:01:52 +000
       
  • Recent Advances in Energy Harvesting Technologies for Structural Health
           Monitoring Applications

    • Abstract: This paper reviews recent developments in energy harvesting technologies for structural health monitoring applications. Many industries have a great deal of interest in obtaining technology that can be used to monitor the health of machinery and structures. In particular, the need for autonomous monitoring of structures has been ever-increasing in recent years. Autonomous SHM systems typically include embedded sensors, data acquisition, wireless communication, and energy harvesting systems. Among all of these components, this paper focuses on the energy harvesting technologies. Since low-power sensors and wireless communications are used in newer SHM systems, a number of researchers have recently investigated techniques to extract energy from the local environment to power these stand-alone systems. Ambient energy sources include vibration, thermal gradients, solar, wind, pressure, etc. If the structure has a rich enough loading, then it may be possible to extract the needed power directly from the structure itself. Harvesting energy using piezoelectric materials by converting applied stress to electricity is most common. Other methods to harvest energy such as electromagnetic, magnetostrictive, or thermoelectric generator are also reviewed. Lastly, an energy harvester with frequency tuning capability is demonstrated.
      PubDate: Sun, 13 Apr 2014 13:40:30 +000
       
  • Analytical, FEA, and Experimental Comparisons of Piezoelectric Energy
           Harvesting Using Engine Vibrations

    • Abstract: Piezoelectric elements can be used as sensors and actuators in flexible structures. In this paper, using the most basic concepts of piezoelectric micropower generators, all useful mathematical equations for getting analytical output are discussed and derived for different piezo positions on cantilever beam and then 3D finite element modeling and simulation of generalized piezoelectric laminated beam problem with proper specifications and properties are done in ANSYS12.0. Experimental analysis is also done on the very practical problem to harvest energy (to get electric energy) by applying some deflection (mechanical energy) on piezo-bonded aluminum beam, that is, to harvest energy (at microlevel at least) by using vibrations of 4-stroke car diesel engine with mounting of piezo cantilever beam. Here piezoelectric beam is used to measure the charge generated from the engine vibrations. The vibration amplitudes are measured with a Laser Vibrometer with considerations of maximum number of power cycles is to be covered for analysis. The vibration response data of displacement of the cantilever at free end measured from Vibrometer are considered for harmonic and analytical analyses as mean displacement amplitude of 3.98 mm at free end. The study further carried out for effect of different piezo positions and various engine speeds also. Then comparison is also done among obtained results from these three analyses to get validation of all derived mathematical equations.
      PubDate: Sun, 06 Apr 2014 11:49:35 +000
       
  • Feasibility of Crosslinked Acrylic Shape Memory Polymer for a Thrombectomy
           Device

    • Abstract: Purpose. To evaluate the feasibility of utilizing a system of SMP acrylates for a thrombectomy device by determining an optimal crosslink density that provides both adequate recovery stress for blood clot removal and sufficient strain capacity to enable catheter delivery. Methods. Four thermoset acrylic copolymers containing benzyl methacrylate (BzMA) and bisphenol A ethoxylate diacrylate (Mn∼512, BPA) were designed with differing thermomechanical properties. Finite element analysis (FEA) was performed to ensure that the materials were able to undergo the strains imposed by crimping, and fabricated devices were subjected to force-monitored crimping, constrained recovery, and bench-top thrombectomy. Results. Devices with 25 and 35 mole% BPA exhibited the highest recovery stress and the highest brittle response as they broke upon constrained recovery. On the contrary, the 15 mole% BPA devices endured all testing and their recovery stress (5 kPa) enabled successful bench-top thrombectomy in 2/3 times, compared to 0/3 for the devices with the lowest BPA content. Conclusion. While the 15 mole% BPA devices provided the best trade-off between device integrity and performance, other SMP systems that offer recovery stresses above 5 kPa without increasing brittleness to the point of causing device failure would be more suitable for this application.
      PubDate: Tue, 25 Feb 2014 07:39:54 +000
       
  • Characterization of Shape Memory Polymer Estane by Means of Dynamic
           Mechanical Thermal Analysis Technique

    • Abstract: Commercially available shape memory polymer (SMP) Estane (designation: ETE75DT3 NAT022) is investigated by means of dynamic mechanical thermal analysis (DMTA) technique in torsion mode using the Modular Compact Rheometer MCR-301 (Anton Paar GmbH). Amplitude sweep tests have been run below and above the glass transition temperature to establish the linear viscoelastic range (LVR) in glassy and rubbery phase of this SMP for the correct physical interpretation of DMTA data. Temperature sweep tests were performed at various frequencies to study the influence of this parameter on values of the storage and loss moduli and the storage and loss compliances as well as the viscosities. These tests have been carried out in heating mode with different rates and at different strain amplitudes. The short- and long-term behavior of SMP Estane have been studied by frequency sweep tests performed at different temperatures and data have been transformed into time-domain properties by applying time-temperature superposition principles. All these DMTA data provide the experimental basis for the study of relaxation processes, property-structure relationships, and the shape memory effect in this little-known SMP.
      PubDate: Thu, 09 Jan 2014 11:55:13 +000
       
  • UHF-Band Wireless Power Transfer System for Structural Health Monitoring
           Sensor Network

    • Abstract: For detecting and measuring health conditions of bridges, wireless sensor networks are used in these days. However, battery life is critically restricting the application and maintenance cost of sensor network systems. To extend life time, a wireless power transfer system at UHF band is introduced to supply the current wireless sensor network. This power transfer system is based on electric wave at 950 MHz. This power transfer system is redesigned for tiny power transmission, including a combination of a rectenna and a Cockcroft-Walton boost converter, battery board, and a control board. Also, current wireless sensor network is redesigned for power transfer system. The working flow of sensor network is modified to bottom-to-top to save power of sensor modules which are the power bottleneck of this sensor system. As a result, the system is able to support a sensor module continuously with received power of −14 dBmW, when the transmitting antenna is 30 dBmW at 10 meters distance.
      PubDate: Mon, 11 Nov 2013 14:25:59 +000
       
  • Procedure to Use PZT Sensors in Vibration and Load Measurements

    • Abstract: In situ correlation procedure is developed for electromechanically coupled PZT sensors to output the structural responses in standard engineering format, namely, displacement, strain, acceleration, and so forth. In order to implement this idea, we have used the standard sensing devices such as laser displacement sensor, strain gauge, and accelerometer. Aluminum beams and composite plate are employed in the experiments as specimens. The experimental results have shown that the structural reactions at critical locations can be monitored by a dynamically correlated PZT patch sensor, besides measuring the intensity of load in terms of acceleration. Furthermore, the influence of damage on sensor correlation has been evaluated. It is seen that the presence of damage has significantly modified the interpreted engineering parameters from the PZT patch and if they are appropriately correlated with respect to healthy structure, then the occurrence of damage related information will be ascertained. The developed sensor correlation concept therefore may be useful in load monitoring, health monitoring, and structural control applications.
      PubDate: Wed, 30 Oct 2013 14:52:14 +000
       
  • Development and Application of One-Sided Piezoelectric Actuating Micropump

    • Abstract: Three types of one-sided actuating piezoelectric micropumps are studied in this paper. In the first type, one-sided actuating micropump with two check valves can enhance the flow rate and prevent the back flow in suction mode to keep the flow in one direction. Furthermore, the frequency modulator is applied in the micropump to adjust and promote the maximum flow rate higher than 5.0 mL/s. In the second type, valveless micropump with secondary chamber shows that the secondary chamber plays a key role in the application of the valveless micropump. It not only keeps the flow in one direction but also makes the flow rate of the pump reach 0.989 mL/s. In addition, when a nozzle/diffuser element is used in valveless micropump, the flow rate can be further improved to 1.183 mL/s at a frequency of 150 Hz. In the third type, piezoelectric actuating pump is regarded as an air pump in the application of a microfuel cell system, which can increase more air inlet to improve the fuel/air reaction and further increase the performance of fuel cell.
      PubDate: Thu, 24 Oct 2013 10:09:56 +000
       
  • Density Dependence of the Macroscale Superelastic Behavior of Porous Shape
           Memory Alloys: A Two-Dimensional Approach

    • Abstract: Porous Shape Memory Alloys (SMAs) are of particular interest for many industrial applications, as they combine intrinsic SMA (shape memory effect and superelasticity) and foam characteristics. The computational cost of direct porous material modeling is however extremely high, and so designing porous SMA structure poses a considerable challenge. In this study, an attempt is made to simulate the superelastic behavior of porous materials via the modeling of fully dense structures with material properties modified using a porous/bulk density ratio scaling relation. Using this approach, direct modeling of the porous microstructure is avoided, and only the macroscale response of the model is considered which contributes to a drastic reduction of the computational cost. Foam structures with a gradient of porosity are also studied, and the prediction made using the fully dense material model is shown to be in agreement with the mesoscale porous material model.
      PubDate: Thu, 19 Sep 2013 17:01:43 +000
       
  • Power Consideration in a Piezoelectric Generator

    • Abstract: A piezoelectric generator converts mechanical energy into electricity and is used in energy harvesting devices. In this paper, synchronisation conditions in regard to the excitation vibration are studied. We show that a phase shift of ninety degrees between the vibration excitation and the bender’s displacement provides the maximum power from the mechanical excitation. However, the piezoelectric material is prone to power losses; hence the bender’s displacement amplitude is optimised in order to increase the amount of power which is converted into electricity. In the paper, we use active energy harvesting to control the power flow, and all the results are achieved at a frequency of 200 Hz which is well below the generator’s resonant frequency.
      PubDate: Sun, 15 Sep 2013 11:32:30 +000
       
  • Reflection and Transmission Phenomena in Poroelastic Plate Sandwiched
           between Fluid Half Space and Porous Piezoelectric Half Space

    • Abstract: The reflection and transmission of elastic waves in porous piezoelectric plate, overlying a porous piezoelectric half space and underlying a fluid half space, is studied. The constitutive and governing equations are formulated for porous piezoelectric materials. The expressions for the mechanical displacements, electric displacements, stresses, and electric potentials are derived for porous piezoelectric plate, porous piezoelectric half space, and fluid half space. The boundary conditions are described for the studied model. The behaviour of reflected and transmitted amplitude ratios relative to frequency, incident angle, thickness, and porosity is observed numerically. The impedance mismatching problem between the dense piezoelectric materials and the surrounding medium can be solved by the inclusion of porosity in dense piezoceramics.
      PubDate: Sun, 25 Aug 2013 13:27:27 +000
       
  • Inertia Effects in the Flow of a Herschel-Bulkley ERF between Fixed
           Surfaces of Revolution

    • Abstract: Many electrorheological fluids (ERFs) as fluids with microstructure demonstrate viscoplastic behaviours. Rheometric measurements indicate that some flows of these fluids may be modelled as the flows of a Herschel-Bulkley fluid. In this paper, the flow of a Herschel-Bulkley ER fluid—with a fractional power-law exponent—in a narrow clearance between two fixed surfaces of revolution with common axis of symmetry is considered. The flow is externally pressurized, and it is considered with inertia effect. In order to solve this problem, the boundary layer equations are used. The influence of inertia forces on the pressure distribution is examined by using the method of averaged inertia terms of the momentum equation. Numerical examples of externally pressurized ERFs flows in the clearance between parallel disks and concentric spherical surfaces are presented.
      PubDate: Wed, 24 Jul 2013 08:28:56 +000
       
  • Self-Healing of Ionomeric Polymers with Carbon Fibers from Medium-Velocity
           Impact and Resistive Heating

    • Abstract: Self-healing materials science has seen significant advances in the last decade. Recent efforts have demonstrated healing in polymeric materials through chemical reaction, thermal treatment, and ultraviolet irradiation. The existing technology for healing polymeric materials through the aforementioned mechanisms produces an irreversible change in the material and makes it unsuitable for subsequent healing cycles. To overcome these disadvantages, we demonstrate a new composite self-healing material made from an ionomer (Surlyn) and carbon fiber that can sustain damage from medium-velocity impact and heal from the energy of the impact. Furthermore, the carbon fiber embedded in the polymer matrix results in resistive heating of the polymer matrix locally, melts the ionomer matrix around the damage, and heals the material at the damaged location. This paper presents methods to melt-process Surlyn with carbon fiber and demonstrates healing in the material through medium-velocity impact tests, resistive heating, and imaging through electron and optical microscopy. A new metric for quantifying self-healing in the sample, called width-heal ratio, is developed, and we report that the Surlyn-carbon fiber-based material under an optimal rate of heating and at the correct temperature has a width-heal ratio of >0.9, thereby demonstrating complete recovery from the damage.
      PubDate: Thu, 20 Jun 2013 15:42:46 +000
       
  • Functionality Evaluation of a Novel Smart Expandable Pedicle Screw to
           Mitigate Osteoporosis Effect in Bone Fixation: Modeling and
           Experimentation

    • Abstract: This paper proposes a novel expandable-retractable pedicle screw and analyzes its functionality. A specially designed pedicle screw is described which has the ability to expand and retract using nitinol elements. The screw is designed to expand in body temperature and retract by cooling the screw. This expansion-retraction function is verified in an experiment designed in larger scale using a nitinol antagonistic assembly. The results of this experiment are compared to the results of a finite element model developed in Abaqus in combination with a user material subroutine (UMAT). This code has been developed to analyze the nonlinear thermomechanical behavior of shape memory alloy materials. The functionality of the proposed screw is evaluated with simulation and experimentation in a pullout test as well. The pullout force of a normal screw inserted in a normal bone was simulated, and the result is compared with the results of the expandable screw in osteoporotic bone. Lastly, strength of the designed pedicle screw in a foam block is also verified with experiment. The reported finite element simulations and experiments are the proof for the concept of nitinol expandable-retractable elements on a pedicle screw which validate the functionality in a pullout test.
      PubDate: Thu, 06 Jun 2013 11:34:55 +000
       
  • Semi-Active Pulse-Switching Vibration Suppression Using Sliding Time
           Window

    • Abstract: The performance of pulse-switching vibration control technique is investigated using a new method for switching sequence, in order to enhance the vibration damping. The control law in this method which was developed in the field of piezoelectric damping is based on triggering the inverting switch on each extremum of the produced voltage (or displacement); however, its efficiency in the case of random excitation is arguable because of the local extremum detection process. The new proposed method for switching sequence is only based on the fact that the triggering voltage level was determined using windowed statistical examination of the deflection signal. Results for a cantilever beam excited by different excitation forces, such as stationary and nonstationary random samples, and pulse forces are presented. A significant decrease in vibration energy and also the robustness of this method are demonstrated.
      PubDate: Thu, 23 May 2013 18:50:59 +000
       
  • Synthesis, Structural, and Electrical Properties of Pure PbTiO3
           Ferroelectric Ceramics

    • Abstract: Single-phase polycrystalline samples of lead titanate with perovskite structure have been synthesized using solid-state reaction technique. The processing parameters have been optimized to obtain phase pure, dense, crack-free, and homogeneous samples. The sintering behavior of PT-powders has been investigated using X-ray diffraction patterns. The X-ray powder diffraction data have been analyzed to confirm the phase formation and phase purity, to obtain unit cell parameters and unit cell volume. The porosity of the samples has been obtained through X-ray density and bulk density. The average particle sizes of the phase pure samples were obtained from the X-ray peak width using Scherrer’s formula. The influence of sintering temperature and time on the microstructure of samples has also been studied by carrying out SEM investigations. The notable feature of this microstructure study shows that the samples sintered at 900°C for 12 hours possess a fairly uniform grain distribution. The electrical behavior (complex impedance Z*, complex permittivity ε*, etc.) of the samples sintered at 900°C for 12 hours has been studied by complex impedance spectroscopy. The temperature variation of real permittivity gives evidence of the ferroelectric phase transition as well as of the relaxation behavior.
      PubDate: Thu, 09 May 2013 15:38:47 +000
       
  • Nondestructive Wireless Monitoring of Early-Age Concrete Strength Gain
           Using an Innovative Electromechanical Impedance Sensing System

    • Abstract: Monitoring the concrete early-age strength gain at any arbitrary time from a few minutes to a few hours after mixing is crucial for operations such as removal of frameworks, prestress, or cracking control. This paper presents the development and evaluation of a potential active wireless USB sensing tool that consists of a miniaturized electromechanical impedance measuring chip and a reusable piezoelectric transducer appropriately installed in a Teflon-based enclosure to monitor the concrete strength development at early ages and initial hydration states. In this study, the changes of the measured electromechanical impedance signatures as obtained by using the proposed sensing system during the whole early-age concrete hydration process are experimentally investigated. It is found that the proposed electromechanical impedance (EMI) sensing system associated with a properly defined statistical index which evaluates the rate of concrete strength development is very sensitive to the strength gain of concrete structures from their earliest stages.
      PubDate: Tue, 16 Apr 2013 10:04:16 +000
       
  • Improved Performance of the Piezoelectric Monomorph with Perpendicular
           Electrode Connections for Sensing and Energy Harvesting

    • Abstract: Piezoelectric monomorph, which has only one element, is a potential structure for piezoelectric applications in some extreme conditions. But as the restriction of the strain neutral layer, the traditional parallel electrode connection is not effective for sensing and energy harvesting. In this paper, perpendicular electrode connections were designed to utilize the nonuniform shear piezoelectric effect in the cross section of the monomorph, which made the monomorph avoid the restriction of the strain neutral layer. The PZT5 ceramic monomorph was preliminarily studied in this experiment. By comparing seven forms of perpendicular electrode connections with the traditional parallel electrode connection, the whole superposed perpendicular electrode connection is considered as the optimal output way for the monomorph. It can produce 13 V peak-to-peak (pk-pk) voltage in open circuit and 14.56 μW maximum power with the matching resistance, which are much more than the parallel electrode connection 0.78 V and 0.14 μW.
      PubDate: Tue, 09 Apr 2013 11:57:51 +000
       
  • Process Chain Modelling and Analysis for the High-Volume Production of
           Thermoplastic Composites with Embedded Piezoceramic Modules

    • Abstract: Active composite structures based on thermoplastic matrix systems are highly suited to applications in lightweight structures ready for series production. The integration of additional functional components such as material-embedded piezoceramic actuators and sensors and an electronic network facilitates the targeted control and manipulation of structural behaviour. The current delay in the widespread application of such adaptive structures is primarily attributable to a lack of appropriate manufacturing technologies. It is against this backdrop that this paper contributes to the development of a novel manufacturing process chain characterized by robustness and efficiency and based on hot-pressing techniques tailored to specific materials and actuators. Special consideration is given to detailed process chain modelling and analysis focusing on interactions between technical and technological aspects. The development of a continuous process chain by means of the analysis of parameter influences is described. In conclusion, the use of parameter manipulation to successfully realize a unique manufacturing line designed for the high-volume production of adaptive thermoplastic composite structures is demonstrated.
      PubDate: Wed, 03 Apr 2013 17:13:48 +000
       
  • MR- and ER-Based Semiactive Engine Mounts: A Review

    • Abstract: Hybrid propulsion technologies, including hybrid electric and hydraulic hybrid, equip vehicles with nonconventional power sources (in addition to the internal combustion engine) to provide higher fuel efficiency. However, these technologies tend to lead to higher levels of noise, vibration, and harshness in the vehicles, mainly due to the switching between the multiple power sources involved. In addition, the shocks and vibrations associated with the power sources switching may occur over a wide range of frequencies. It has been proven that passive vibration isolators (e.g., elastomeric and hydraulic mounts) are unable to mitigate or totally isolate such shocks and vibrations. Active mounts, while effective, are more complex, require significant power to operate, and can lead to system instabilities. Semiactive vibration isolators have been shown to be as effective as active mounts while being less complex and requiring less power to operate. This paper presents a review of novel semiactive shock and vibration isolators developed using magnetorheological and electrorheological fluids. These fluids change their yield stress in response to an externally applied magnetic and electric field, respectively. As a result, these fluids allow one to transform a passive hydraulic vibration isolator into a semiactive device.
      PubDate: Wed, 20 Feb 2013 10:20:05 +000
       
  • Energy Harvesting Using an Analog Circuit under Multimodal Vibration

    • Abstract: The efficiency of harvesting energy from a vibrating structure using a piezoelectric transducer and a simple analog circuit is investigated experimentally. This analog circuit was originally invented for a synchronized switch damping on inductor (SSDI) technique, which enhances the damping of mechanical vibration. In this study, the circuit is used to implement a synchronized switch harvesting on inductor (SSHI) technique. A multiple degree of freedom (MDOF) structure is excited by single sinusoidal forces at its resonant frequencies and by random forces. The piezoelectric transducer converts this mechanical energy into electrical energy which is harvested using a standard rectifier bridge circuit with and without our analog circuit. Experimental results show that our analog circuit makes it possible to harvest twice as much energy under both single sinusoidal and random vibration excitations.
      PubDate: Sun, 20 Jan 2013 09:29:15 +000
       
 
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