bluuebunny/crossref_metadata_2025 huggingface dataset:
ELISA Analysis of Latex Allergens on Wear Particles of Natural Rubber During Rolling-Sliding Contact
Authors: Yamamura Yuki , Iwai Tomoaki , Shokaku Yutaka
Published: February 2010

The wear particles generated from a tire model made of vulcanized natural rubber were analyzed using ELISA (Enzyme-Linked Immunosorbent Assay). Antibodies to 4 different allergens were used to analyze the extracted proteins from the wear particles. Latex allergens were detected when the slip ratio was large. However, no clear relationship between the latex allergen content extracted from the wear debris and either the average size or the number of wear particles was observed.
The Development of Residual Micro-Stresses Surrounding Various Inclusion Types in Wheel Steel
Authors: Dedmon Steven , Pilch James M.
Published: February 2010

Non-metallic inclusions are known to have deleterious affects on fatigue resistance of steels and other metals and alloys. Non-metallic inclusions reduce fatigue life by changing the micro-stresses in the vicinity of a propagating crack. But, some non-metallic types have a greater affect on fatigue life than other, more benign non-metallic types. Residual micro-stresses surrounding a non-metallic inclusion is proposed as one solution as to why these differences exist. Specifically investigated were the non-metallic types of Alumina, Silica and Manganese Sulfide — all of which are found to some extent in AAR M-107/M-208 Class C wheel steel.
Detailed Impact Analyses for Development of the Next Generation Rail Tank Car: Part 1—Model Development and Assessment of Existing Tank Car Designs
Authors: Kirkpatrick Steven W.
Published: February 2010

Significant research has been conducted over the past few years to develop improved railroad tank cars that maintain tank integrity for more severe accident conditions than current equipment. The approach taken in performing this research is to define critical collision conditions, evaluate the behavior of current design equipment in these scenarios, and develop alternative strategies for increasing the puncture resistance. The evaluations are being performed with finite element models of the tank cars incorporating a high level of detail. Both laboratory scale and full-scale impact tests were performed to validate the modeling and ultimately compare the effectiveness of current and alternative equipment designs. This paper describes the development of the detailed finite element model of the tank car and the use of the model for impact and puncture analyses. The validation of the model using the results of the full-scale impact tests is presented. The subsequent application of the model to assess the puncture resistance of existing tank car designs is discussed.
Detailed Impact Analyses for Development of the Next Generation Rail Tank Car: Part 2—Development of Advanced Tank Car Protection Concepts
Authors: Kirkpatrick Steven W.
Published: February 2010

Significant research has been conducted over the past few years to develop improved railroad tank cars that maintain tank integrity for more severe accident conditions than current equipment. The approach taken in performing this research is to define critical collision conditions, evaluate the behavior of current design equipment in these scenarios, and develop alternative strategies for increasing the puncture resistance. The evaluations are being performed with finite element models of the tank cars incorporating a high level of detail. Both laboratory scale and full-scale impact tests were performed to validate the modeling and ultimately compare the effectiveness of current and alternative equipment designs. This paper describes the use of the detailed finite element impact and puncture analyses to assess the performance of advanced puncture protection concepts.
Structural Crashworthiness Standards Comparison: Grade-Crossing Collision Scenarios
Authors: Llana Patricia G.
Published: February 2010

In support of the Federal Railroad Administration’s (FRA) Railroad Equipment Safety Program, American and European grade-crossing collision scenarios were evaluated and compared. Finite element analyses (FEA) were employed to subject an FRA-compliant passenger car to grade-crossing collision scenarios defined in both the proposed FRA Code of Federal Regulations (CFR) and European Standard (EN) 15227. The proposed FRA collision scenario involved a single car impacted by a cart. The cart had a punch mounted to it to hit a specific post of the end frame of the car. The EN 15227 collision scenario involved a complete train consist impacting a large deformable obstacle that approximates a lorry. The analyses show that these collision scenarios, while both grade-crossing scenarios, are very different not only in terms of the impact object and the amount of initial kinetic energy involved, but also in terms of how the car is loaded and deformed during impact. The FRA scenario is shown to be easier to analyze as well as easier to test than the EN 15227 scenario. Additionally, the FRA scenario is safer to test because of the levels of initial energy involved. The FRA scenario also provides clearer metrics of success. The FRA-compliant car utilized in the analyses and test conducted for this paper passed both FRA and EN 15227 grade-crossing collision scenarios according to the requirements for each respective standard. However, the analyses show that despite both scenarios providing for energy absorption in a grade-crossing collision, because the manner in which the car is loaded and deformed (concentrated vs. distributed) is different, the FRA performance standard and EN 15227 grade-crossing collision scenarios are not equivalent and mutual compliance is not guaranteed.
Nonlinear Generalized Predictive Control Approach for Challenging Processes
Authors: Abu-Ayyad Ma’moun , Venkateswararao Lakshamirinyan Chinta , Dubay Rickey
Published: February 2010

This paper presents the implementation of the fundamental concept of the infinite modeling methodology to the generalized predictive control (GPC) algorithm. This method was termed as infinite modeling generalized predictive control (IMGPC) which uses the nonlinear characteristics of the process such as the process gain and time constant to recalculate the dynamic matrix every sampling instant. Computer simulations were performed on nonlinear plants with different degrees of nonlinearity demonstrating that the infinite modeling approach is readily implemented providing improved control performance comparing to the original structure of GPC. Practical work included real-time control application on a steel cylinder temperature control system. Simulation and experimental results demonstrate that the methodology of infinite modeling is applicable to other advanced control strategies making the methodology generic.
Two-Dimensional Thermomechanical Model for Combined Loading of NiTi Wire Structures
Authors: Sedla´k Petr , Frost Miroslav
Published: February 2010

Thin NiTi shape memory wires with unique thermomechanical properties are considered to be promising material for a wide range of new engineering applications. Based on broad experimental research on behavior of NiTi wires, which reveal a significant anisotropy in the transformation behaviors between tension and torsion, a new two-dimensional NiTi SMA material model was developed, particularly for the purpose of simulating NiTi wire structures behavior under combined mechanical and thermal loading. Two mutually perpendicular phase interfaces between autenite and martensite are formed during combined tension/torison loading. The first one, induced by tension, is perpendicular to symmetry axis, whereas the torsion-induced one is parallel to this axis. The model is parameterized by realistic physically-based material parameters and describes motion and evolution of these interfaces. Some numerical simulations — NiTi wire actuator, knitted self-expanding stent, shape memory fastener hook and shape memory helical spring — are presented and discussed to demonstrate the early practical applications of the model.
Thermo-Electro-Mechanical Shakedown Response of Conditioned Shape Memory Alloy Wires
Authors: Churchill Christopher B. , Shaw John A.
Published: February 2010

The shakedown response of conditioned shape memory alloy wires (Flexinol®) is examined experimentally during constant tension thermal cycles, at several load levels. Strain, temperature, and electrical resistivity are measured simultaneously using a specialized experimental setup that enables a relatively rapid temperature rate (1 °C/s) while preserving the temperature uniformity along the gauge length to less than 1.5 °C. Both elongation and electrical resistance are measured from the same local gauge length, allowing strain-corrected electrical resistivity to be inferred. The most repeatable behavior (least shakedown) occurs at the intermediate load of 191 MPa (consistent with the supplier’s maximum stress recommendation), with a small amount of shakedown (and some loss of two-way shape memory) at lower loads and progressively larger shakedown (strain ratcheting and reduction in hysteresis) at higher loads.
Optimally Designed Nonlinear Feedback Excitation for High-Sensitivity Sensing
Authors: Sloboda Andrew R. , Epureanu Bogdan I.
Published: February 2010

Employing sensitivity vector field (SVF) analysis in active micro-sensors can increase both their sensitivity and their ability to differentiate between changes in multiple sensor parameters. However, since SVF analysis is based on quantifying attractor deformations in state space, maximizing its effectiveness depends on selecting a sensor excitation that generates an attractor having suitable deformation with respect to the parameter(s) of interest. This paper addresses issues surrounding such system excitation design for a simple, linear vibration-based sensor having a combination of harmonic and nonlinear feedback excitation. In order to reframe the search for an optimal excitation as a search for a set of optimal control parameters, the excitation is considered to be of a specified form with a set of adjustable control parameters. Determining how to adjust the excitation parameters so as to maximize the magnitude of the resulting sensitivity vectors is then the formal goal. Using a pattern search method that avoids difficulties caused by bifurcations, we show that improved excitation can be designed reliably and efficiently. We also show that for short trajectory evolution times (suitable for “large” sensor perturbations) limit cycle behavior generates the best SVFs while for longer evolution times (suitable for “small” sensor perturbations) chaotic behavior may be more useful. Other issues discussed include the relative importance of various controller terms and the significance of harmonic excitation phase when generating sensitivity vectors.
Vibration Mitigation With a Multi-Axial Magnetorheological Mount
Authors: Anderson Walter , Nguyen The , Elahinia Mohammad
Published: February 2010

This paper presents a multi-axial magnetorheological (MMR) mount. An MMR mount has been developed for use with hydraulic hybrid vehicles (HHV). Like hybrid electric vehicles (HEV), HHV provides better fuel economy. An inherent problem to hydraulic hybrid vehicles is vibration of the hydraulic pump-motor (P/M). This vibration can be classified as shock loading for initial start-up, and periodic vibration over a large frequency range. The latter vibration opportunity can be classified as having large displacement at low frequency and small displacement at high frequency. This requires a stiff mount for the low frequency response and a soft mount for the high frequency response. A single axis magnetorheological (MR) mount has previously been developed and studied by the same group. This was done to develop an understanding of the MR fluid and to discover the limitations of such a mount. Models to predict the experimental results have also been generated. These models show a good correlation to the experimental results. Then, the model has been enhanced from the single axis mount to a multi-axial. This was done by examining the 3-D CAD model to develop the different boundary conditions for the simulation. With a multi-axial magnetorheological mount, damping and stiffness can be altered to yield acceptable transmissibility over the frequency range. This is achieved through the use of an inertia track paired with a pseudo-decoupler. These features are commonly found in a passive hydraulic mount; however through the use of MR fluid, the downfalls of the hydraulic mount can be mitigated, e.g. performance deterioration outside of notch frequency. Additionally, a magnetorheological mount is semi-active so there is an inherent stability to the mount. The MMR mount uses elastomer and MR fluid to achieve the static stiffness to support the P/M and achieve low dynamic stiffness for the high frequency response, which is necessary for a good isolator. The advantages of the use of a multi-axial magnetorheological mount are as follows: fewer mounts are required, stability when compared to an active mount, less power required when compared to an active mount, better isolation when compared to pure elastomeric and passive hydraulic mounts. A model for a multi-axial magnetorheological mount has been developed and simulated. For the purposes of this study, elastomer has been considered to have a linear dynamic response. Additionally, the shock response of the mount has not been considered. Future work includes manufacturing a multi-axial MR mount to verify the simulation results.
Development of a Shape Memory Alloy Composite Actuator for the Whole Skin Locomotion Robot
Authors: Williams Eric , Hong Dennis
Published: February 2010

In this paper the development of a novel actuator is presented that utilizes a flexible shape memory alloy composite (SMAC) to generate motion for the Whole Skin Locomotion (WSL) robot. The WSL mechanism for mobile robots is inspired by how single celled organisms use cytoplasmic streaming to generate pseudopods for locomotion. This mobility mechanism is directly suited for robots traversing tight spaces where flexibility and shape changes are deemed necessary. The body of the WSL robot is comprised of an elongated fluid filled torus which turns itself inside out in a single continuous motion, effectively generating the overall motion of the cytoplasmic streaming ecto-plasmic tube in amoebae. The eversion of the entire outer skin of the WSL is driven by a pair of the SMAC actuators in the shape of a torus. The actuation of the SMAC is accomplished by the individually controlled shape memory alloy wires embedded in an elastic beam that is then deformed into a torus shape. The design of the first prototype, fabrication efforts as well as a qualitative model of the behavior are presented. Experiments validating aspects of the modeling are also discussed.
Pyroelectric Materials: Scaling of Output Power With Dimensions and Substrate Clamping
Authors: Atulasimha Jayasimha , Xie J. , Richeson M. , Mossi K. M.
Published: February 2010

An understanding of the power that can be harvested from pyroelectric materials and its dependence on material properties, geometry and boundary condition is crucial to the design of energy harvesting devices using these materials. In this paper, simple analytical expressions are developed for ideal voltage, power and power densities as a function of pyroelectric constant, permittivity, surface area, thickness, temperature variation and rate of change for unclamped samples. Experiments are performed to specifically study the effect of geometry and are compared with theoretical predictions.
Characterization of Multifunctional Structural Capacitors for Embedded Energy Storage
Authors: Lin Yirong , Sodano Henry A.
Published: February 2010

Multifunctional composites are a new class of materials that combine structural and other functionalities such as sensing, actuation, energy harvesting and vibration control in order to maximize structural performance while minimizing weight and complexity. Among all the multifunctional composites developed so far, piezoelectric composites have been widely studied due to the high coupling of energy between the electrical and mechanical domains and the inherently high dielectric constant. Several piezoelectric fiber composites (PFCs) have been developed for sensing and actuation applications; however, none of the previously studied composites fully embed all components of an energy storage device as load bearing members of the structure. Recently, Lin and Sodano [1] developed a novel multifunctional fiber that can be embedded in a composite material to perform sensing and actuation, in addition to providing load bearing functionality. The design was achieved by coating a common structural fiber, silicon carbide, with a barium titanate piezoelectric shell, and poling the active material radically by employing the structural fiber as one of the electrodes. The silicon carbide core fiber also carries external mechanical loading to protect the brittle barium titanate shell from fracture. The excellent piezoelectric and dielectric properties of the barium titanate material make the novel active structural fiber an outstanding candidate for converting and storing ambient mechanical energy into electrical energy to power other electric devices in the system. This paper focuses on the characterization of energy storage capability of the multifunctional fiber provided by the dielectric properties of the barium titanate shell. The capacitances of the multifunctional fibers with four different aspect ratios are tested and compared with the theoretical expressions for the cylindrical capacitor while the break-down voltages of the multifunctional fibers are tested according to ASTM standard (ASTM D 149-97a). The stored energy is calculated from the testing results and the best aspect ratio for energy storage application can be determined. The resulting capacitive fiber is shown to have an energy density approximately two orders of magnitude higher than structural capacitors in the literature.
Time-Dependent Strain Responses of a Poled PZT Wafer Under Various Constant Magnitudes of Longitudinal Tensile Stress
Authors: Kim Sang-Joo , Lee Chang-Hoan
Published: February 2010

A commercially available soft lead titanate zirconate (PZT) wafer that is poled in thickness direction is subjected to various constant magnitudes of longitudinal tensile stress. The evolutions of longitudinal and transverse in-plane strains over time are measured in short- and open-circuit boundary conditions. The measurements are explained qualitatively in terms of domain switching and predicted quantitatively by a free energy model of normal distribution.
Strain Behaviors of Manganese-Doped (Bi0.5Na0.5)TiO3-BaTiO3-(Bi0.5K0.5)TiO3 Lead-Free Ferroelectric Ceramics
Authors: Shieh Jay , Lin You-Chen , Chen Chuin-Shan
Published: February 2010

The strain hystereses of lead-free a(Bi0.5Na0.5)TiO3-bBaTiO3-c(Bi0.5K0.5)TiO3 (abbrev. as BNBK 100a/100b/100c) ferroelectric compositions inside and outside the morphotropic phase boundary (MPB) are investigated. It is found that BNBK 85.4/2.6/12, a composition well within the MPB, possesses notable actuating properties such as an induced electrostrain of about 0.14% and an apparent d33 of 295 pCN−1. BNBK 85.4/2.6/12 is further doped with various amounts of manganese (Mn) to improve its sinterability and ferroelectric characteristics. Intricate hysteresis behaviors are observed upon Mn doping. The total induced electrostrain of BNBK 85.4/2.6/12 in the 33-directon decreases dramatically from 0.14 to 0.05% when 0.2 mol% of Mn is introduced into the composition. It then recovers sharply as the Mn doping amount is increased progressively to 0.5 and then to 1.0 mol%. However, when the doping amount is further increased above 1.0 mol%, a significant decrease in electrostrain is observed again. The hysteresis data indicate that an electrostrain above 0.1% can be maintained when the Mn doping amount is in between 0.5–1.5 mol%. Once outside this doping range, the induced electrostrain is considerably smaller. By examining the evolution of crystalline phase composition with Mn doping, the mole content of rhombohedral phase is shown to be a critical factor in deciding the straining behaviors of the Mn-doped BNBK 85.4/2.6/12 ceramics. To each increasing step in Mn doping level, there is a marked similarity in the evolutions of the induced electrostrain and rhombohedral phase content.
Damage Detection Using Impedance Measurement With Magnetic Transducer
Authors: Wang X. , Tang J.
Published: February 2010

Impedance method has been explored for damage detection and identification. Typically, when the impedance sensor is integrated onto the mechanical structure to be monitored, its electrical impedance is directly related to the mechanical impedance of the host structure. Thus the change of impedance measurement before and after damage occurrence can be used as the damage indicator. Since the impedance information may be measured at relatively high frequency range, the impedance method could be sensitive to small-sized damage. Generally, piezoelectric transducers are employed in the impedance approach, which can serve as actuator and sensor simultaneously. In this research, a magnetic transducer approach is investigated for impedance based damage detection. To provide design guidelines, the analytical model of the resistive magnetic impedance measurement circuit is formulated. During the formulation, the two-way magneto-mechanical coupling between the transducer and the structure is systematically studied by using the Maxwell’s equations. The preliminary sensor enhancement is achieved by selecting the number of turns of wire in the electrical coil. Moreover, in order to reduce the negative effects of the high inherent inductance and large parasitic resistance of the coil with a large number of turns of wire, a new measurement circuitry is proposed, in which a negative resistive element and a capacitor are introduced to be serially connected with the original resistive circuit. Correlated numerical and experimental studies are carried out to validate the magnetic transducer in impedance based damage detection.
Bioinspired Jellyfish Locomotion Using Macro Fiber Composites for Autonomous Underwater Vehicles
Authors: Hills Zachary , Kim Myung Hyun , Inman Daniel J.
Published: February 2010

This paper presents a bioinspired jellyfish propulsion system with a conceptual design, analysis and experimental tests. Hydrodynamic thrust of jellyfish is generated by fin vibration motion at predetermined resonant frequency. A new type of propulsion system for artificial Jellyfish nodes for the purpose of persistent, autonomous, and energy efficient surveillance is proposed employing smart actuator technology. A MFC (Macro Fiber Composite) actuator is employed for exciting a cantilever beam. The hydrodynamic propulsion is calculated for various excitation frequencies of MFC actuator based on vibration motion of the beam. A prototype of the jellyfish setup has been developed for the experimental validation of the simulation results. Simulation and experimental results demonstrated the feasibility of the proposed system and design. Swimming motion control and power consumption issues will be addressed.
Low Speed Impact of Woven Fiber Composites Including Fiber Bragg Grating Sensors
Authors: Liu K. C. , Hiche Cris , Chattopadhyay Aditi
Published: February 2010

In this paper, the dynamic Fiber Bragg Grating sensor response due to low speed impact on woven fiber composite plates was used to determine the extent of the impact damage. Three types of woven fabrics were considered in this study: plain, twill and 5 harness satin. A brief finite element analysis was used to determine the optimal location for the sensors. The bottom of the plate showed the highest strain response and was chose as the optimal location. The composite plates were fabricated and Fiber Bragg Grating sensors were mounted in the optimal location. The plates were subject to various impact energies using a modified Charpy impactor. The impact damage for each plate due to different impact energies was quantified through flash thermography and correlated with the FBG response. The flash thermography results showed excellent progression of damage in the plates and the sensor strain response was able to distinguish the impacts by considering both peak and plastic strain.
Optimal Sensor Placement for Damage Detection in Complex Structures
Authors: Soni Sunilkumar , Das Santanu , Chattopadhyay Aditi
Published: February 2010

An optimal sensor placement methodology is proposed based on detection theory framework to maximize the detection rate and minimize the false alarm rate. Minimizing the false alarm rate for a given detection rate plays an important role in improving the efficiency of a Structural Health Monitoring (SHM) system as it reduces the number of false alarms. The placement technique is such that the sensor features are as directly correlated and as sensitive to damage as possible. The technique accounts for a number of factors, like actuation frequency and strength, minimum damage size, damage detection scheme, material damping, signal to noise ratio (SNR) and sensing radius. These factors are not independent and affect each other. Optimal sensor placement is done in two steps. First, a sensing radius, which can capture any detectable change caused by a perturbation and above a certain threshold, is calculated. This threshold value is based on Neyman-Pearson detector that maximizes the detection rate for a fixed false alarm rate. To avoid sensor redundancy, a criterion to minimize sensing region overlaps of neighboring sensors is defined. Based on the sensing region and the minimum overlap concept, number of sensors needed on a structural component is calculated. In the second step, a damage distribution pattern, known as probability of failure distribute, is calculated for a structural component using finite element analysis. This failure distribution helps in selecting the most sensitive sensors, thereby removing those making remote contributions to the overall detection scheme.
Joining of Shape Memory NiTi to Structural Materials Using Ultrasonic Soldering
Authors: Hahnlen Ryan , Dapino Marcelo
Published: February 2010

Shape memory nickel-titanium (NiTi) alloys can recover up to 8% of induced strain allowing such alloys to be used in the creation of solid-state actuators. Despite the unique properties of NiTi alloys, their implementation in structural applications is expensive, complex, and in some cases unfeasible due to limitations of traditional joining techniques. This research investigates the joining of NiTi to itself, aluminum 2024, O1 tool steel, and 304 stainless steel by Ultrasonic Soldering (USS), a process that can solder difficult to wet materials without the use of flux. The USS joints were evaluated through strength testing, optical microscopy, and maximum calculated von Mises equivalent stresses developed during testing. Lap shear tests show NiTi/NiTi, NiTi/aluminum 2024, NiTi/O1 tool steel, and NiTi/304 stainless steel USS joints have average ultimate shear strengths of 30.9 MPa, 53.8 MPa, 37.2 MPa, and 40.6 MPa, respectively.
Two-Dimensional Analytical Model and Experimental Validation of Garter Stitch Knitted Shape Memory Alloy Actuator Architecture
Authors: Abel Julianna , Luntz Jonathan , Brei Diann
Published: February 2010

Active knits are a unique architectural approach to meet the industrial need for high strain and simultaneous force generation. This paper presents an analytical state-based model to predict the actuation response of a Shape Memory Alloy (SMA) garter knit textile. Garter knits generate significant contraction against moderate to large loads when heated due to the continuous interlocked network of loops of SMA wire. For this knit architecture, the states of operation are defined based on the thermal and mechanical loading of the textile, the resulting phase change of the SMA, and the load path followed to that state. Transitions between these operational states induce either stick or slip frictional forces depending upon the state and path, which affect the actuation response. A load-extension model of the textile is derived for each operational state using Elastica Theory and Euler-Bernoulli beam bending for the large deformations within a loop of wire based on the stress strain behavior of the SMA material. This provides kinematic and kinetic relations which scale to form analytical transcendental expressions for the net actuation motion against an external load. The model was validated experimentally for an SMA garter knit textile over a range of applied forces with good correlation for both the load-extension behavior in each state as well as the net motion produced during the actuation cycle. Throughout the experiments, large strains (up to 250% recoverable, over 50% actuation strain) against moderate forces (order of tens of Newtons) were achieved which demonstrates promise for a wide range of applications.
Response Time of Magnetorheological (MR) Fluid and MR Valves Under Various Flow Conditions
Authors: Sahin Huseyin , Wang Xiaojie , Miller Mark , Liu Yanming , Gordaninejad Faramarz
Published: February 2010

The response time of magnetorheological (MR) fluids to an external magnetic field is a few milliseconds. However, the overall response time in MR devices under a magnetic field is a function of electromagnetic parameters, the capabilities of the driving electronics, as well as, the operation conditions. Therefore, the overall response time of a MR device depends on the internal device design parameters. In this work, the response times of MR fluid and MR fluid valves have been studied under various flow configurations. Two types of valving geometries; annular flow, and radial flow are considered in the MR fluid valve designs. The transient pressure response of MR fluid valves are evaluated by using a diaphragm pump with a constant volume flow rate. The performance of each MR valve is characterized using a voltage step input, as well as, a current step input while recording the activation electric voltage/current, magnetic flux density, and pressure drop as a function of time. The variation of the response time of the MR valves under constant volume flow rate is experimentally investigated. The system’s time constant is determined under induced pressure changes. In order to obtain the response time of the MR fluid a Maxwell model with a time constant is employed to describe the field induced pressure behavior of MR fluid under a steady flow. The results demonstrate that the pressure response times of the MR fluid and the MR valves depend on the designs of the electric parameters and the valve geometry. MR valves in annular flow geometry have a slow falling response time compared to their rising response time. MR valves in radial flow geometry result in faster pressure response times both in rising and falling states.
A Thermodynamically Based Model of the Superelastic Behavior of Shape Memory Alloys Using a Discrete Preisach Model
Authors: Doraiswamy Srikrishna , Iyer Mrinal , Srinivasa Arun R. , Sivakumar Srinivasan M.
Published: February 2010

Shape Memory Alloys are increasingly being used in aeronautic [1], vibration control and seismic applications [2–6]. These applications require models that faithfully represent the full thermomechanical response of SMA wires but which at the same time are simple and fast to implement. In this paper we present a model for the superelastic behavior of Shape Memory Alloys that combines a thermodynamical framework with a Preisach model. This approach allows us to easily account for both stress and strain controlled responses as well as changes in termperature in a simple and straightforward way.
Broadening the Actuation Temperature Range for Acrylic Dielectric Elastomers
Authors: Jan Antony , Yuan Wei , Brochu Paul , Zhang Han , Pei Qibing , Henry Christopher
Published: February 2010

Dielectric elastomer actuators are an important branch of electroactive polymers with a host of applications proposed. However, the temperature range over which these elastomers are active has been limited by the glass transition temperature and thermal stability. Acrylic elastomers, VHB adhesive films from 3M Company, exhibit high actuation strain and stress at room temperature, but become too rigid to actuate below 0 °C. By lowering their glass transition temperature with the addition of a plasticizer, we show that the soft polymer actuators can be made to function at −40 °C. The plasticized films have been able to achieve >100% areal strain at −40°C. This helps extend the scope of dielectric elastomer actuators to demanding automotive applications.
Preliminary In Vivo Experimental Validation of SMA Based Bowel Extender for Short Bowel Syndrome
Authors: Utter Brent , Brei Diann , Luntz Jonathan , Teitelbaum Daniel , Okawada Manabu , Miyasaka Eiichi
Published: February 2010

Short Bowel Syndrome is a serious medical condition caused by insufficient small bowel length resulting in significantly high rates of morbidity and mortality. The limited success of current therapies has prompted the investigation of a new treatment approach based on mechanotransduction — the process through which mechanical tensile loading on the bowel induces longitudinal growth. To enable clinically relevant mechanotransduction growth studies in large animals, such as pigs, a fully implantable and instrumented bowel extender device based on a Shape Memory Alloy (SMA) ratchet was developed and validated in benchtop and ex vivo tests. These devices, however, must also be validated against the unique in vivo environment which presents challenges such as sealing, battery life, surgical implantation, signal attenuation from tissue, and isolating the measurement of tensile loading on the bowel wall. This paper extends the earlier development work to in vivo validation experiments within live pigs. A brief summary of the bowel extender architecture and operation is provided along with earlier ex vivo results that established device limits for in vivo testing. The wireless communication rate was updated to extend battery life and new surgical implantation procedures and lengthening schemes were developed. Two bowel extenders were tested in in vivo experiments ranging from 2.5 to 4.5 days with data collected to validate the wireless communication, SMA ratcheting and load/displacement measurements, confirming that the bowel extender successfully operates in vivo. More importantly, the bowel extenders successfully induced significant growth, which is promising for future studies comparing different lengthening schemes for optimal growth and the development of a clinical device for treating short bowel syndrome in humans.
Nonlinear Dynamic Modeling of Smart Composite With Peizoelectric Nitinol and MMC
Authors: Amini Abbas , Mehdigholi Hamid , Elahinia Mohammad
Published: February 2010

In this paper, one smart composite involving nitinol, piezoelectric and MMC is modeled. This simulation covers all criteria in these advanced materials and theoretically solves the five-order equation. Furthermore, numerical sample is investigated and results have been explored. The results represent the relationship between natural frequency of the structure, temperature, the lateral deflection and martensite ratio of shape memory alloy. The results show nonlinearity response in dynamic motion in lower natural frequency and linear behavior in higher frequency. In this simulation, numerical approximation has been avoided.
Three-Dimensional Modeling of Rate-Dependent Deformation in Shape Memory Alloys at High Temperatures
Authors: Hartl Darren , Chatzigeorgiou George , Lagoudas Dimitris
Published: February 2010

Active structures composed of Shape Memory Alloys (SMAs) and High Temperature SMAs (HTSMAs) continue to be developed for applications that benefit from solid-state actuation. The need to account for the response of these materials under non-conventional loading paths that include elevated temperature conditions has become important. Conventional SMAs are exposed to such temperatures during processing, including final shape-setting. HTSMAs, by virtue of their title, are exposed to such high temperatures during transformation. This work addresses new developments in the constitutive modeling and numerical analysis pertaining to irrecoverable inelasticity in SMAs at high temperatures, where this behavior becomes rate-dependent. The description of such behavior requires the development of a theoretical framework able to capture the coupling between the rate-independent transformation and the rate-dependent creep. The proposed phase transformation-viscoplastic model is based on continuum thermodynamics; here the elastic relations, the inelastic evolution equations, and the transformation criteria are summarized. The evolution equation for the viscoplastic strain is non-homogeneous in time, and thus rate-dependency results. The viscoplastic parameters are generally assumed to exhibit a strong dependence on temperature. The rate-independent and rate-dependent constitutive equations that comprise the full 3-D model are numerically integrated using a scheme that accounts for both transformation and viscoplastic deformation in a coupled manner. The implementation allows for 3-D analysis of SMA bodies using an FEA framework that includes Abaqus and an associated user material subroutine. Example analyses are discussed, including shape-setting in a conventional SMA and experimentally validated structural analysis of an HTSMA specimen.
Constitutive Modeling of Magnetic Field-Induced Phase Transformation in NiMnCoIn Magnetic Shape Memory Alloys
Authors: Lagoudas Dimitris C. , Haldar Krishnendu , Basaran Burak , Karaman Ibrahim
Published: February 2010

In this work we model the magnetic field induced phase transformation (FIPT) of magnetic shape memory alloys (MSMAs). The working principle of such materials is described by the deformation of continua due to mechanical and magnetic forces. The cross coupling of mechanical and magnetic variables is captured by introducing nonlinear kinematics. The mechanical and magnetic constitutive equations are derived by a thermodynamic consistent way. Finally, the model prediction followed by model calibration is compared with the experimental results.
Electric Field-Manipulation of Cellulose Whisker-Reinforced Polymer Nanocomposites
Authors: Kalidindi Sanjay V. , Ounaies Zoubeida , Kaddami Hamid
Published: February 2010

Aligning cellulose whiskers can significantly enhance electrical and mechanical properties in polymer composites. Here, we report a method of sonication and stirring to disperse and stabilize CWs in solution. Applying an AC electric field led to good alignment and chain formation of CWs in the direction of the applied field. Alignment and chain formation was found to be function of electric field magnitude, frequency and time. Dielectric constant of the solutions as a function of microstructure was studied. Improvement in dielectric constant with increase in frequency was observed. Future work will focus on processing thin films with individually dispersed CWs, and improving their alignment to further increase the electrical and mechanical properties.
Harvesting Wind Energy Using a Galloping Piezoelectric Beam
Authors: Mahadik Rohan R. , Sirohi Jayant
Published: February 2010

Galloping of structures such as transmission line supports and bridges is a classical aeroelastic instability phenomenon that has been looked upon as a harmful and destructive effect. However, there exists potential to harness useful energy from this phenomenon. The study presented in this paper focuses on harvesting wind energy that is being transferred to a galloping beam. The beam has a rigid tip body with a D shaped cross section. Piezoelectric sheets are bonded on the top and bottom surface of beam. During galloping, vibrational motion is input to the system due to aerodynamic forces on the D-section, which is converted into electrical energy by the piezoelectric (PZT) sheets. The significance of various parameters in the system such as wind velocity, material properties of the beam, electrical load and beam natural frequency is discussed. Experimental and analytical investigations of power output are performed on a representative device. A maximum output power of 1.14 mW was measured at a wind velocity of 10.5 mph. A potential application for this device is to power wireless sensor networks on outdoor structures such as bridges and buildings.
Combinatorial characterization of transparent conductive properties of Ga-doped ZnO films cosputtered from electron cyclotron resonance and rf magnetron plasma sources
Authors: Akazawa Housei
Published: February 2010

The simultaneous sputtering of ZnO and Ga2O3 by electron cyclotron resonance and rf magnetron plasma sources produced Ga-doped ZnO (GZO) films with continuously varying Ga concentration over the substrate surface. Combinatorial evaluation of electrical and optical properties of GZO film grown on silica glass substrate without heater annealing enabled identification of minimum resistivity (0.5 mΩ cm) at a Ga2O3 content of 5.5 wt % with an optical transmittance of 90% in the visible wavelength. The monotonically decreasing mobility that was associated with increasing carrier concentration as Ga2O3 content was increased indicated that conduction was governed by ionized impurity scattering. Above the critical Ga2O3 content (6 wt %), carrier concentration decreased since excess Ga atoms that were incorporated beyond the solubility limit at Zn sites hindered large crystalline domains from forming. The ZnO (002) x-ray diffraction peak was suppressed and peaks assigned to Ga2O3 were observed at high Ga2O3 content. The optimum Ga2O3 content shifted to 3.5 wt % at a deposition temperature of 200 °C and 2.5 wt % at 300 °C, and the minimum resistivity was further decreased to 0.28 mΩ cm at 200 °C. However, the resistivities at these elevated temperatures were incredibly high both at the lower and higher side of the optimum Ga2O3 content.
Genetic Risk Scores for Heart Disease: Useful or Useless?
Authors: Damani Samir
Published: February 2010

A measure of risk for heart disease calculated from all 101 associated SNPs in the literature cannot predict disease any better than the traditional clinical risk factors.
SPECTRAL THEORY OF NO-PAIR HAMILTONIANS
Authors: MATTE OLIVER , STOCKMEYER EDGARDO
Published: February 2010

We prove an HVZ theorem for a general class of no-pair Hamiltonians describing an atom or positively charged ion with several electrons in the presence of a classical external magnetic field. Moreover, we show that there exist infinitely many eigenvalues below the essential spectrum and that the corresponding eigenfunctions are exponentially localized. The novelty is that the electrostatic and magnetic vector potentials as well as a non-local exchange potential are included in the projection determining the model. As a main technical tool, we derive various commutator estimates involving spectral projections of Dirac operators with external fields. Our results apply to all coupling constants e2Z < 1.
ELASTIC MODULI AND SOUND VELOCITY IN La1-xSrxMnO3 (x = 0 to 0.3)
Authors: EWE L. S. , ABD-SHUKOR R.
Published: February 2010

The longitudinal and shear sound velocity in colossal magnetoresistive La 1-x Sr x MnO 3 (x = 0.0, 0.05, 0.15 and 0.3) were measured using the pulse-echo-overlap technique in the temperature range of 80 to 300 K. An abrupt increase in the longitudinal velocity was observed immediately below the insulator-metal transition (T im ) in the x = 0.05 and 0.15 samples. This anomaly shifted towards higher temperature with an increase in Sr content. The absolute velocities (measured at 80 K) increased with Sr content. Hystereses in the longitudinal and shear velocity were observed in the x = 0.05 and 0.15 samples. A step-like longitudinal sound velocity anomaly between 150 K and 220 K during warming and cooling was observed in the x = 0.05 sample. A sudden hardening was observed for longitudinal and shear sound velocity coinciding with second broad resistance peak at temperature below T im in x = 0.15 sample. The characteristic Debye temperature increases as Sr content was increased, indicating a hardening trend. These results indicate the importance of phonons in the transport mechanism of these colossal magnetoresistive materials.
DYNAMICS AND DOUBLE HOPF BIFURCATIONS OF THE ROSE–HINDMARSH MODEL WITH TIME DELAY
Authors: MA SUQI , FENG ZHAOSHENG , LU QISHAI
Published: February 2010

In this paper, we are concerned with the Rose–Hindmarsh model with time delay. By applying the generalized Sturm criterion, a number of imaginary roots of the characteristic equation are classified. The absolutely stable regions for any value of time delay are detected. By the continuous software DDE-Biftool, both the Hopf bifurcation curves and double Hopf bifurcation points are illustrated in parametric spaces. The normal form and universal unfolding at double Hopf bifurcation points are considered by the center manifold method. Some examples also indicate that the corresponding unique attractor near each double Hopf point is asymptotically stable.
NEW STUDY ON THE CENTER PROBLEM AND BIFURCATIONS OF LIMIT CYCLES FOR THE LYAPUNOV SYSTEM (I)
Authors: LIU YIRONG , LI JIBIN
Published: February 2010

The center problem and bifurcations of limit cycles for the planar dynamical system with double zero eigenvalues are studied. The concepts of focal values and Lyapunov constants as well as their computational method are given. As an example, for a class of cubic system, the corresponding results are obtained.
THE ∀∃ THEORY OF PEANO Σ1 SENTENCES
Authors: LINDSTRÖM PER , SHAVRUKOV V. YU.
Published: February 2010

We present a decision procedure for the ∀∃ theory of the lattice of Σ1 sentences of Peano Arithmetic.
A CRITERION FOR THE p-SUPERSOLUBILITY OF FINITE GROUPS
Authors: LUKYANENKO VLADIMIR O. , SKIBA ALEXANDER N.
Published: February 2010

Our main result here is the following theorem: Let G = AT, where A is a Hall π-subgroup of G and T is p-nilpotent for some prime p ∉ π, let P denote a Sylow p-subgroup of T and assume that A permutes with every Sylow subgroup of T. Suppose that there is a number pk such that 1 < pk < |P| and A permutes with every subgroup of P of order pk and with every cyclic subgroup of P of order 4 (if pk = 2 and P is non-abelian). Then G is p-supersoluble.
SDpro — THE SOFTWARE PACKAGE FOR STATISTICAL PROCESSING OF EXPERIMENTAL INFORMATION
Authors: KACHIASHVILI K. J. , MELIKDZHANJAN D. I.
Published: February 2010

There is an original software package offered for statistical processing of experimental information. It is designated for users who are not professionals in the field of applied statistics and computer science. The package is universal, simple and convenient for understanding and application. The problems and the algorithms realized in the package, the features and the opportunities of their application are described. Those features which distinguish favorably this package from other similar products are emphasized. The examples showing the efficiency of the algorithms realized in the package are cited. Serviceability of the suggested package was tested in various modes at solving the problems from different fields of knowledge. The obtained results justify the stability and the reliability of algorithms and the high accuracy of the calculated values.