bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonlinear Current-Voltage Characteristics of Homojunctions Made by Zinc Oxide Single Crystals
Authors: Harada Takeshi , Nakamura Yoshinobu , Kishimoto Akira , Motohira Naobumi , Yanagida Hiroaki 
Published: April 2011

ABSTRACTZinc oxide (ZnO) single crystals are grown by the traditional chemical vapor reaction method and ZnO crystal pairs with a single boundary are successfully obtained. The obtained specimens with one ZnO–ZnO boundary (ZnO homojunction) show nonlinear current-voltage (I–V) characteristics without the addition of Bi2O3, CoO, MnO2, and/or rare earth metal oxides. A specimen with higher breakdown voltage shows superior nonlinearity with negative resistivity in its I–V characteristics. Electrical characterization of the ZnO homojunction is conducted and extremely slow response with the current (or voltage) stress is confirmed. The phenomenon had never been observed in commercial ZnO varistors. The surface temperature of the ZnO homojunction is enhanced by larger applied current. The effect of the Joule heat on the nonlinearity in the I–V curves of the ZnO homojunction is discussed.
Power-Law Phenomena in Adhesive De-Bonding
Authors: Kendall G. , Cote P. J. , Crayon D. , Bonetto F. J. 
Published: April 2011

ABSTRACTAcoustic emission (AE) events were recorded during the peeling of pressure-sensitive adhesive (PSA) tape from a silicate glass surface. The distributions of AE event durations and energies are found to have the form of power laws. Power-law dependencies (hyperbolic distributions) are recognized as a consequence of self-organized criticality (SOC), resulting from the absence of any characteristic length or time scales. In these studies, standard optical microscopy was used to characterize the fractal nature of the PSA-glass interface. The present results suggest that it is the inherent static structural features found at the fractal PSA-glass interface which produce the observed hyperbolic distributions in AE events, rather than a true SOC process.
Evidence of a Passive Layer Formation from a Conductive Polymer Coating on Aluminum Alloys
Authors: Racicot R. J. , Yang S. C. , Brown R. 
Published: April 2011

ABSTRACTEvidence for the formation of a passive layer between a conductive polymer coating and aluminum alloy surfaces is reported Experimental results from electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) on aluminum alloys coated with a novel double strand conductive polymer coating based on polyaniline reveal the evidence for the formation of passive layer. The key results are: (1) Modeling of EIS data is best fit with a three RC circuit, indicating a third interface between the polymer coating and the alloy's surface; (2) EIS testing in acidic salt solutions shows the conductive polymer coating performs differently and better than a typical anodized or chromáte conversion coating indicating a possibly different interface layer than a typical aluminum oxide and (3) SEM studies of the aluminum surface, after the polymer film is removed, indicates that this interfacial layer has a dense and smooth “oxide type” surface morphology. The experimental results are consistent with a mechanism in which the conducting polymer serves as a surface conversion agent that oxidizes the aluminum metal surface to form a passive layer.
The Grain Boundary Diffusion Kinetics in Nanocrystalline Zirconia
Authors: Zhilyaev A. P. , Gertsman V. Y. , Szpunar J. A. 
Published: April 2011

ABSTRACTIt is expected that the grain boundary diffusion is the principal contributor to the transport properties of nanocrystalline zirconia, and that it controls the oxidation kinetics and hydrogen permeation. This process depends on the grain boundary character distribution (i.e. the fractions of different grain boundary types) and on the topological characteristics of the grain boundary network. Modeling of the random walk problem on a planar honeycomb network for different types of the grain boundary misorientation distributions (GBMD) in nanocrystalline zirconia film is presented in the current paper. The GBMD was calculated using the model texture. Changes of the oxidation rate for different types of the grain boundary character distribution and different ratios of the bulk and grain boundary diffusion coefficients are analyzed. In this study it was found that an increase of the frequency of low energy boundaries lowers the oxidation rate.
Investigations of the Bonding Changes Associated with Grain Boundary Embrittlement
Authors: Keast V. J. , Bruley J. , Williams D. B. 
Published: April 2011

ABSTRACTThe embrittlement of materials through the segregation of impurities to the grain boundaries is a common and industrially important problem. Despite considerable investigation, the mechanism by which the impurity elements cause embrittlement is not well understood. A change in the electron energy loss near edge structure (ELNES) has been observed at Cu grain boundaries containing Bi. This result provides experimental evidence that a change in the electronic structure at the grain boundary is responsible for embritdement.
Domain Wall Contributions to the Piezoelectric Properties of Ferroelectric Ceramics and Thin Films, and Their Significance in Sensor and Actuator Applications
Authors: Damjanovic D. , Taylor D. V. , Kholkin A. L. , Demartin M. , Brooks K. G. , Setter N. 
Published: April 2011

ABSTRACTThe piezoelectric and dielectric properties of ferroelectric thin films and ceramics were investigated in detail as a function of the frequency and amplitude of the driving field. A description, which is based on the theories of domain wall pinning by randomly distributed imperfections in magnetic materials, is used to interpret the electromechanical behaviour of several ferroelectric bulk ceramic and thin film compositions. With this approach, it is possible to make quantitative estimates of the domain wall contributions to the electromechanical properties of ferroelectric sensors and actuators.
Finite Element Modelling of Adaptive Composite
Authors: Wen Y. , Denis S. , Gautier E. , Roytburd A. 
Published: April 2011

ABSTRACTThe deformation of adaptive composite with active polydomain components has been calculated by finite element modelling (FEM). The average deformation, the distribution of stresses and the elastic energy of the composite as a function of different extent of twinning of the composite active component are calculated. Comparing the results of the FEM with the results of the analytical theory demonstrates the effect of the microstresses on the mechanics of the adaptive composite.
Application of Porous Silicon to Bulk Silicon Micromachining
Authors: Kaltsas G. , Nassiopoulos A. G. 
Published: April 2011

ABSTRACTA fully C-MOS compatible process for bulk silicon micromachining using porous silicon technology and front-side lithography is developed. The process is based on the use of porous silicon as a sacrificial layer for the fabrication of deep cavities into monocrystalline silicon, so as to avoid back side lithography. Cavities as deep as several hundreds of micrometers are produced with very smooth surface and sidewalls. The process is used to produce : a) suspended monocrystalline silicon membranes, b) free standing polysilicon membranes in the form of bridges or cantilevers with lateral dimensions from a few μms to several hundreds of μms. Important applications to silicon integrated devices as sensors, actuators, detectors etc., are foreseen.
Flexible Graphite as A Strain/stress Sensor
Authors: Luo Xiangcheng , Chung D.D.L. 
Published: April 2011

ABSTRACTFlexible graphite sandwiched by copper, after stabilization by two cycles of compressive stress, is an effective piezoresistive compressive strain/stress sensor for stresses up to 4 MPa and strains up to 25%. The stress sensitivity (fractional change in resistance per unit stress) is up to 5.4 MPa−1 and strain sensitivity (fractional change in resistance per unit strain) is up to 6.2 in the direction perpendicular to the sheet. The electrical resistance decreases reversibly upon compression, due mainly to reversible decrease in the contact resistivity between graphite and copper. Stabilization removes most of the irreversible effects. The strain/stress sensitivities decrease with increasing strain/stress.
A Study of the Rubber-Like Behavior of Mono-Domain Au-Cd Martensite
Authors: Ren Xiaobing , Otsuka Kazuhiro 
Published: April 2011

ABSTRACTThe origin of the rubber-like behavior in mono-domain Au-Cd martensite was explained in terms of a new model that focused attention on the change of long-range elastic interaction energy among vacancies during a domain reversion. Vacancies in martensite, the lower-symmetry phase, produce stress fields with lower symmetry. During martensite aging, vacancies tend to rearrange themselves to lower elastic interaction energy. The low-symmetry elastic field results in a low-symmetry vacancy configuration. When a stabilized martensite domain reverts to a new domain (twin) under external stress, the original vacancy configuration is inherited to the new domain, but such a configuration becomes a high energy configuration because of the lower symmetry of elastic field, and thus it tends to restore the original configuration by reverse twinning. The above vacancy reconfiguration model is consistent with the fact that the rubber-like behavior is closely related to vacancies.
Improvement of the Corrosion Resistance of NiTi Stents by Surface Treatments
Authors: Trépanier C. , Tabrizian M. , Yahia LH. , Bilodeau L. , Piron D. L. 
Published: April 2011

ABSTRACTBecause of its optimal radiopacity, superelasticity and shape memory properties Nickel-Titanium (NiTi) is an ideal material for the fabrication of stents. Indeed, these properties can facilitate the implantation and precise positioning of those devices. However, in vitro studies on NiTi report the dependency of the alloy biocompatibility and corrosion behavior to surface treatments. Oxidation of the surface seems to be very promising to improve both the corrosion resistance and the biocompatibility of NiTi. The present study investigate the effect of electropolishing, heat treatment (in air and in a salt bath) and nitric acid passivation to modify the oxide layer on NiTi stents. Techniques such as potentiodynamic polarization tests, Scanning Electron Microscopy (SEM) and Auger Electron Spectroscopy (AES) have been used to develop relationships between corrosion behavior, surface characteristics and surface treatment. Results show that all surface treatments improve the corrosion behavior of the alloy. SEM results indicate that treated stents which exhibit a smooth and uniform surface show a higher corrosion resistance than non treated stents which possess a very porous oxide layer. AES results, indicate that the best corrosion behavior was observed for the stents which exhibit the thinnest oxide layer (electropolished and passivated samples).
In-Situ Control of the Direction of Spontaneous Polarization in Ferroelectric thin Films by RF-Magnetron Sputtering
Authors: Iijima K. , Niihara K. 
Published: April 2011

ABSTRACTLa-modified PbTiO3thin films were grown on (100)MgO by rf-magnetron sputtering. Thin films were prepared by “two step method” in which the different Pb/Ti ratios during the growth were used for the first step (0–4nm of thickness) and the subsequent second step (>4nm). The Pb/Ti ratios of the first step were selected from 1.2 to 1.5. The Pb/Ti ratio of the second step, on the other hand, was fixed at 1.4. Strong dependency of the direction of the spontaneous polarization (Ps) to the Pb/Ti ratio of the first step was observed. It is concluded that the direction of the Ps in the films is determined by the atomic species of the first layer of the films.
Structural Defects in the 18R Martensite of CuZnAi Shape Memory Alloys
Authors: Condo A. M. , Lovey F. C. 
Published: April 2011

ABSTRACTThe lattice relaxation at the type I faults in the 18R martensite was studied by high resolution TEM. Local atomic plane rotations and small changes of the interplanar distances were observed over a distance of 1.5 nm. It is shown that this distorted region can be rationalized as an intermediate structure between the martensite and the second variant of the parent phase.
Corrosion Kinetics of Laser Treated NiTi Shape Memory Alloy Biomaterials
Authors: Villermaux F. , Nakatsugawa I. , Tabrizian M. , Piron D. L. , Meunier M. , Yahia U'H. 
Published: April 2011

ABSTRACTNiTi shape memory alloy presents interesting mechanical properties as surgical implants. However, due to its high amount of Ni which may dissolve and release toxic ions in human fluids, the medical use of this material is a great concern. We have developed a laser treatment which modifies the oxide layer and enhances uniform and localised corrosion resistance of NiTi alloy.In this paper we further analysed the effect of this treatment with potentiostatic and AC impedance measurements in physiological Hank's solution. We conclude that the laser treatment creates a stable passive film which results in improved corrosion resistance of this alloy.
A Quantitative Micro-Deformation Field Study of Shape Memory Alloys by High Sensitivity Moiré
Authors: Sun Q. P. , Xu Terry T. , Zhang X. Y. , Tong P. 
Published: April 2011

ABSTRACTQuantitative micro-macro combined experimental research on the deformation field of single crystal CuAINi shape memory alloy (SMA) is performed by using high sensitivity Moiré technique. The study is focused on the micro-macro correspondence of the deformation behavior of single crystal uniaxial tensile specimen during stress induced forward and reverse transformations. The aim of the experiment is to quantitatively relate the macroscopic applied stress with the deformation field in the mesoscale. The large deformation due to the lattice distortion during transformation was first successfully recorded by Moiré interferometry. Some important microstructure-related deformation features of single crystal SMA under uniaxial tension are first reported.
Dielectric Properties of Piezoelectric Polyimides
Authors: Ounaies Z. , Young J. A. , Simpson J. O. , Farmer B. L. 
Published: April 2011

ABSTRACTMolecular modeling and dielectric measurements are being used to identify mechanisms governing piezoelectric behavior in polyimides such as dipole orientation during poling, as well as degree of piezoelectricity achievable. Molecular modeling on polyimides containing pendant, polar nitrile (CN) groups has been completed to determine their remanent polarization. Experimental investigation of their dielectric properties evaluated as a function of temperature and frequency has substantiated numerical predictions. With this information in hand, we are then able to suggest changes in the molecular structures, which will then improve upon the piezoelectric response.
Maintaining Chaos
Authors: Spano Mark L. , In Visarath , Ditto William L. 
Published: April 2011

ABSTRACTThe recognition of chaos as a new type of behavior for complex systems initially spurred efforts to avoid it and, later, to control it. Yet in many cases chaos may be beneficial. We present a method for maintaining chaos in physical systems and implement the method on a simple magnetomechanical system. Application to other systems is discussed briefly.
Giant Magnetostrictive, Spring Magnet Type Multilayers and Torsion Based Microactuators
Authors: Betz J. , Mackay K. , Peuzin J.-C. , Givord D. , Halstrup B. 
Published: April 2011

ABSTRACTThere is a need for powerful active materials in microsystem actuators. Research on thin film magnetostrictive materials has concentrated on optimising the magnetostrictive response notably by reducing the required driving magnetic field. Here we present a novel type of multilayer, where 2 alloys having different properties are coupled together. The resulting composite system represents a new material with novel characteristics, which can not be fulfilled by simple alloys. In particular here we have investigated magnetostrictive multilayers, with remarkable low field performances (i.e. very large ∂λ / ∂H).Most magnetostrictive microactuators are based on a bimorph structure. However, these simple structures are prone to thermal drift. We present here also some results on a torsion based magnetostrictive microactuator prototype being insensitive to thermal drift.
Innovative Process Development of Sx2(Nb0.5Ta0.5)O7/PVDF Hybrid Materials for Sensors and Actuators
Authors: Kowfael W. , Chellappa V. , Wither J. C. , Crocker M. J. , Wada B. 
Published: April 2011

ABSTRACTOver the past several years interest in adaptive ‘smart'materials development has gained momentum. Smart structures utilize both polymeric sensors and lead-based piezo-ceramic actuators. This paper addresses the development of an alternative smart material which consists of a novel lead-free piezo-ceramic/PVDF hybrid composite, to be used as a single component system capable of performing multiple tasks. A lead-free controlled porosity perovskite ceramic of the type A2B2O7 (Sr2 (Nb.5Ta.5)2O7 was developed utilizing hot forging. Long, oriented grains along the x-y plane, perpendicular to the forging direction were obtained in the ceramics. PVDF was subsequently infiltrated into the porous piezo-ceramic resulting in a three dimensional architecture in which the piezo-ceramic is oriented perpendicular to the PVDF. It is anticipated that manufacturability combined with the ease of functional tailorability of such a class of lead-free hybrid materials can be useful in a variety of smart structures applications.
Variation of the Rate of Extension of Actin Networks
Authors: Olbris Donald J. , Herzfeld Judith 
Published: April 2011

ABSTRACTSelf-assembling protein filaments are important components of a cell's superstructure. Among these, actin filaments form the backbone of protrusions and extensions such as pseudopodia. The rates at which these structures extend cover a startlingly wide range: the acrosomal process of the sea cucumber may extend 90 μm in 10 seconds, which is more than 20 times the speed at which an epithelial goldfish keratocyte crawls. We seek to explain this range by examining the delivery of actin monomers to the growing filament ends. We show that the diffusive flux of actin monomers is adequate for fueling the slower movement of crawling cells, but is insufficient to propel the quicker acrosomal process of the sea cucumber. By introducing bulk fluid flow in response to the diffusive movement of water through the cell membrane, actin delivery can be enhanced. We compare the calculated speeds to experimental observations and discuss future refinements to the model.
Dynamically-Stabilized Pores in Bilayer Membranes
Authors: Moroz J. D. , Nelson P. 
Published: April 2011

ABSTRACTZhelev and Needham have recently created large, quasi-stable pores in artificial lipid bilayer vesicles. Initially created by electroporation, the pores remain open for up to several seconds before quickly snapping shut. This result is surprising in light of the large line tension for holes in bilayer membranes and the rapid time scale for closure of large pores. We show how pores can be dynamically stabilized via a new feedback mechanism. We also explain quantitatively the observed sudden pore closure as a tangent bifurcation. Finally we show how Zhelev and Need-ham's experiment can be used to measure accurately the pore line tension, an important material parameter. For their SOPC/CHOL mixture we obtain a line tension of 3.0 × 10−6dyn.
Collision of a Field-Driven Polymer with a Post: Implications for Electrophoresis in Microlithographic Arrays
Authors: Sevick E. M. , Williams D.R.M. 
Published: April 2011

ABSTRACTWe study the simplest model of a polyelectrolyte impinging upon a point, frictionless obstacle in the presence of a field. Using numerical simulation, we show that the wide range of impacts, ranging from direct impact forming a long-lived hairpin conformation, to glancing impacts where the chain slides off of the obstacle in short time, can be described universally. In strong field, the average collision time, 〈tc〉, and average distance traveled during collision, 〈zc〉, depend upon the impact and follow universal curves over a large range of molecular weights and field strengths. This result provides analytic formulas for the chain's mobility in an array of posts and yields insight into the effect of post spacing.
Colloidal Aggregation with a Drift: A computer simulation
Authors: González Agustín E. , Leyvraz François 
Published: April 2011

ABSTRACTPreliminary results of an aggregation model that takes into account both the Brownian motion as well as the gravitational drift experienced by the colloidal particles and clusters is presented. It is shown that for high strengths of the drift the system crosses over to a regime different from diffusion-limited colloid aggregation, for which there is an increase of the fractal dimension, a speeding up of the aggregation rate and a widening of the cluster size distribution, becoming algebraically decaying with an exponent τ.
Phase Transitions, Patterns and Statistical Mechanics of Front Propagation in a Dynamic Random Impurity Model for Strip, Unusual Trees and Other Geometries
Authors: Vandewalle N. , Ausloos M. 
Published: April 2011

ABSTRACTA dynamic random impurity model is studied lor describing the evolution of an advancing interface through a multiphase random medium containing mobile impurities. A short range repulsion between the Iront and the impurities leads to an aggregation process along the front, and to the trapping of aggregates behind the front. The patterns of trapped impurities are found to be self-organized. Some theoretical treatment is performed through a transfer matrix technique in various geometries: trees with loops instead of branches, chains of squares and triangles joined by vertices. Arguments are given for applications of such concepts, techniques and models in various cases: chemistry, biology, trafic, sociology, economy,…
Fluctuations, Lindemann Criterion and Liquid-Solid Transition in Thin Films
Authors: Tkachenko Alexei V. , Rabin Yitzhak 
Published: April 2011

AbstractA simple model of confinement-induced freezing in thin liquid layers is presented. Under boundary conditions of vanishing displacement field at the walls, confinement suppresses the amplitude of fluctuations in a solid film below a critical value determined by the Lindemann criterion of melting. The resulting increase of the melting temperature compared to that of a bulk solid, is estimated and the connection with experiments is discussed.
Foam Drainage: Extended Large-Q Potts Model Simulation
Authors: Jiang Yi , Glazier James A. 
Published: April 2011

ABSTRACTWe study foam drainage using the large-Q Potts model extended to include gravity on a three dimensional lattice. Without adding liquid, homogeneously distributed liquid drains to the bottom of the foam until equilibrium between capillary effects and gravity is reached, while in an ordered dry foam, if a fixed amount of liquid is added from the top, a sharp fiat interface between the wet and dry foam develops. The wetting front profile forms a downward moving pulse, with a constant velocity. The pulse decays over time while its leading edge for a brief time behaves like a solitary wave. With continuous liquid addition from the top, the pulse does not decay and we observe a soliton front moving with a constant velocity. Continuously adding liquid to an initially wet foam keeps the liquid profile constant. Our simulations agree with both experimental data and simplified mean field analytical results for ordered foams but predict an unstable interface for disordered foams.