bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Application of High Energy Density Transducer Materials to Smart Systems
Authors: Lindberg J. F. 
Published: April 2011

ABSTRACTRecent NUWC research efforts in the field of high power sonar transducers designed to produce high acoustic outputs over significant bandwidths while being of minimal size and weight have been aided by advances in the continuing development of several new high energy density transducer drive materials. Both Terfenol-D, a rare earth magnetostrictive material, and lead magnesium niobate, a relaxor ferroelectric, have demonstrated a tenfold increase in field-limited energy density over a typical very hard lead zirconate titanate (i.e., Clevite PZT-8) piezoelectric ceramic. The Center's focus is to double the demonstrated performance of each material and to address such issues as hysteresis reduction in the magnetostrictive material and coupling coefficient improvements in the electrostrictive materials. Poly (vinylidene fluoride-trifluoroethylene) can also be considered a high energy density material because of its excellent energy density and its broad bandwidth possibilities. The application of these material technologies, either separately or as hybrid composites, to smart material design will be detailed.
Theory and Applications of Large Stroke Terfenol-D® Actuators
Authors: Gerver M. J. , Berry J. R. , Dozor D. M. , Goldie J. H. , Ilmonen R. T. , Leary K. , Nimblett F. E. , Roderick R. , Swenbeck J. R. 
Published: April 2011

ABSTRACTTraditionally, control algorithms for Terfenol-D® magnetostrictive actuators have modelled the strain as a linear function of magnetic field and stress, but nonlinearity becomes important for strains of more than a few hundred parts per million (ppm), and for many applications even the maximum strain, about 1500 ppm, is inadequate. Larger strokes can be obtained by various types of stroke amplifiers, by resonant operation, or by inchworming. Previously, SatCon successfully used a 10:1 lever arm stroke amplifier in a helicopter flap actuator [1]. Current projects include a water pump using a hydraulic stroke amplifier, which potentially could be more compact and efficient than a lever arm amplifier, and linear and rotary inchworm motors for robotics. In all these designs, satisfactory performance requires careful attention to machining tolerances and to making the mechanisms and housing stiff enough or compliant enough. A model for inchworm motors has been developed, including finite load and resonant effects. Nonlinear control algorithms will be discussed, applicable to arbitrarily large Terfenol-D® strains, stresses, and magnetic fields.
Application of Smart Materials to Wireless ID Tags and Remote Sensors
Authors: Fletcher Richard , Levitan Jeremy A. , Rosenberg Joel , Gershenfeld Neil 
Published: April 2011

ABSTRACTMaterial structures having an electromagnetic or magnetomechanical resonance can be excited or detected remotely using an antenna. Incorporating smart materials into such structures provides new opportunities to encode ID and sensor information in the electromagnetic signature of the “tag.” In this way, it is possible to create tags which not only have a unique ID but which can also respond to local changes in their environment (e. g. force, temperature, light, etc.). This principle forms the basis for a low-cost wireless ID and wireless sensor technology which has many potential applications in manufacturing, inventory control, security, surveillance, and new human-computer interfaces. As a means of illustrating this concept, two simple examples are given: a force sensor incorporating a piezoelectric polymer and a relative position sensor which incorporates a magnetoelastic amorphous metal ribbon.
Giant Magnetostrictive Multilayer Thin Film Transducers
Authors: Quandt E. , Ludwig A. 
Published: April 2011

ABSTRACTMagnetostrictive multilayer films which combine exchange coupled giant magnetostrictive materials (amorphous Tb0.4Fe0.6) and materials with large polarizations (Fe or Fe0.5Co0.5) were prepared by dc or rf magnetron sputtering using a rotary turn-table technique in a stop-and-go mode. The magnetic properties of TbFe/Fe and TbFe/FeCo multilayers were investigated in relation to the layer thicknesses and the annealing temperatures. Giant magnetoelastic coupling coefficients (or magnetostrictions) are achieved at low fields, due to the magnetic polarization enhancement in such multilayers. Saturation magnetoelastic coupling coefficients of 20 MPa at 20 mT in the case of TbFe/Fe and of 28 MPa at 20 mT in the case of TbFe/FeCo were achieved. These high low-field magnetoelastic coupling coeffients and the possibility to engineer the material's properties by layer thickness variation are considered to be important features for applications of these films as thin film transducers in microsystems.
Effect of Noble Metals on Selective Detection of LPG Based on SnO2
Authors: Phani A. Ratna , Pelino M. 
Published: April 2011

ABSTRACTThe present investigation deals with the electrical response of noble metal doped SnO2 to improve the selectivity for Liquid Petroleum Gas (LPG) in the presence of CO and CH4. Addition of small amounts of nobel metals (Pd, Pt and Rh) to the base material SnO2 is carried out by co-precipitation method. X-ray diffraction and X-ray photoelectron spectroscopy studies are carried out to find out the crystalline phase and chemical composition of the SnO2. The sensor element has been tested for cross selectivity to reducing gases by measuring sensitivity versus sintering temperatures and sensitivity versus operating temperatures. The sensor elements with the composition of Pd (1.5 wt%) andPt (1.5 wt%) in the base material SnO2 sintered at 800°C showed high sensitivity towards LPG at an operating temperature of 350°C suggestingthe possibility to utilize the sensor for the detection of LPG.
Size Distributions of Fluid Membrane Vesicles Far From Equilibrium
Authors: Golubović Leonardo , Golubović Mirjana 
Published: April 2011

ABSTRACTWe investigate nonequilibrium behavior of a polydisperse ensemble of fluid membrane vesicles by means of a diffusive Boltzmann transport equation which, incorporates vesicle diffusion and the reactions between vesicles. This approach is used to study the time evolution of the size distribution of an initially monodisperse vesicle ensemble and its interesting properties such as the internal aqueous, encapsulated volume. We investigate various nonequilibrium paths such ensembles may follow during the equilibration process.
Vector Lattice Model of Amphiphilic Mixtures: Interfacial Behavior
Authors: Buzano C. , Evangelista L. R. , Pelizzola A. 
Published: April 2011

ABSTRACTThe interfaces between the water-rich, oil-rich and disordered phases of a balanced ternary mixture of oil, water and amphiphile are studied, on the basis of a vector lattice model, by means of an exact partial integration and a local mean field approximation. The phase diagram exhibits a water/oil-rich phase, structured (ordered bicontinuous and lamellar) phases and a disordered phase with a microemulsion region. The interfacial tension and profiles at oil/water/disordered phase coexistence are calculated and the possibility of a wetting transition is discussed.
An Avoidance Model for Short-Range Order Induced by Soft Repulsions in Systems of Rigid Rods
Authors: Han Jining , Herzfeld Judith 
Published: April 2011

ABSTRACTThe effects of soft repulsions on hard particle systems are calculated using an avoidance model which improves upon the simple mean field approximation. The method not only yields a better free energy, but also gives an estimate for the short-range positional order induced by soft repulsions. The results indicate little short-range order for isotropically oriented rods. However, for parallel rods short-range order increases to significant levels as the particle axial ratio increases.
Comparison of Experimental and Theoretical Melting Behavior of DNA
Authors: Marx Kenneth A. , Bizzaro J. W. , Assil Iman , Blake R. D. 
Published: April 2011

ABSTRACTHigh resolution melting curves of total nuclearDictyostelium discoideumDNA (A×3 strain) are compared to theoretical melting calculated from GENBANK sequences(1.74 % of total) by the statistical thermodynamics program MELTSIM, parameterized for long DNA sequences(1,2). The lower and upper limits of simulated melting agree quantitatively with the experimental melting of total DNA. Calculated melting of coding, intron and flanking regions indicate that intron and flanking DNAs are extremely (A+T)-rich and account for the earliest melting DNA. There is no temperature overlap of these regions with coding DNA. A theoretical denaturation map of DNA containing the ribosomal DNA genes showed excellent agreement with subtransition positions of these genes in experimental curves. Agreement between these calculated and experimental melting data demonstrates our ability to accurately simulate DNA melting in complex eukaryotic genomes. This has important consequences for the understanding of sequence dependent energetic properties of nucleic acids and their potential use as biomaterials.
Pattern Evolution of Granular Media Rotated in a Drum Mixer
Authors: Hill K. M. , Kakalios J. , Caprihan A. 
Published: April 2011

ABSTRACTA homogeneous mixturea of different types of granular material will often segregate when rotated in a drum mixer. In the traditional axial segregation effect, the mixture of two different sizes of granular media will appear from the surface to separate into bands of relatively pure single concentrations along the axis of rotation. The initial pattern is not stable, but evolves in time with continued rotation through metastable states of fewer and fewer bands. We describe two experimental methods for measuring this evolution which provide a more complete picture of the dynamics involved in the pattern progression. The use of a CCD camera in conjunction with digital analysis techniques provides a consistent and precise measure of the state of the surface as a function of time. Nuclear Magnetic Resonance Imaging (MRI) techniques are used to noninvasively measure the segregation beneath the surface. These methods indicate that the underlying mechanisms of the pattern evolution originate in the bulk of the material beneath the avalanching surface.
Random Walks for Magnetic Decay in Porous Media
Authors: Cai Weicheng , Halsey Thomas C. , Hardenbergs John H. , Leibig Michael 
Published: April 2011

ABSTRACTWe propose a Monte Carlo method to simulate the magnetization decay for NMR in porous media. In this method, the diffusive spins in the fluid phase are modeled by 3-d random walkers, whose absorption at the solid surface simulates surface-mediated decay. Our method is 20 times faster than direct relaxation of the diffusion equation when a variable-step size implementation is used. We demonstrate our method by computing the surface relaxivity ρ for a Fontainebleau sandstone, whose structure was determined by X-ray tomography.
Monte Carlo Simulations of Phase Transitions in a Two-Dimensional Random-Bond Potts Model
Authors: Paredes R. , Valbuena J. 
Published: April 2011

ABSTRACTMotivated by recent experiments on phase behavior of systems confined in porous media, we have studied the effect of quenched bond randomness on the nature of the phase transition in the two dimensional Potts model. To model the effects of the porous matrix we chose the couplings of the q state Potts Hamiltonian from the distribution P(Jij) = pδ(Jij – J) + (1 – p)δ(Jij). For a range of p values, away from the percolation threshold, the transition temperature follows the mean field prediction Tc(p) = Tc(1)p. Furthermore, we observed that the strong first order transition, that appears in the pure case for q = 10, changes two a second order transition. It is also clear from our simulations that the second order transition of the q = 3 pure case changes to a second order transition of a different universality class. A finite size scaling analysis suggests that in both cases the critical exponents, in the presence of disorder, fall into the universality class of the two dimensional pure Ising model. This result agrees with theoretical calculations recently published [1].
Pattern Formation and Unusual A + B → 0 Reaction Kinetics between Charged Reactants in Low Dimensions
Authors: Kotomin E. A. , Kuzovkov V. N. , von Niessen W. 
Published: April 2011

AbstractThe effect of non-equilibrium charge screening in the kinetics of the one-dimensional, diffusion-controlled A + B → 0 reaction between charged reactants in solids and liquids is studied. Incorrectness of static, Debye-Hückel theory is shown. Our microscopic formalism is based on the Kirkwood superposition approximation for three-particle densities and the self-consistent treatment of the electrostatic interactions defined by the nonuniform spatial distribution of similar and dissimilar reactants treated in terms of the relevant joint correlation functions. Special attention is paid to the pattern formation due to a reaction-induced non-Poissonian fluctuation spectrum of reactant densities. This reflects a formation of loose domains containing similar reactants only. The effect of asymmetry in reactant mobilities (DA - 0, DB > 0) contrasting the traditional symmetric case, i.e. equal diffusion coefficients, (DA = DB) is studied. In the asymmetric case concentration decay is predicted to be accelerated, n(t) ∞ t−α, α = 1/3 as compared to the well-established critical exponent for fluctuation-controlled kinetics in the symmetric case, α - 1/4 and/or the prediction of the standard chemical kinetics, α = 1/2. Results for the present microscopic theory are compared with the mesoscopic theory.
Stretched, Twisted, Supercoiled and Braided DNA
Authors: Marko John F. 
Published: April 2011

ABSTRACTThe DNA double helix is a semi-flexible polymer with twist rigidity. Its bending elasticity gives rise to entropie polymer elasticity, which can be precisely studied in single-molecule experiments. DNA's twist rigidity causes it to wrap around itself, or ‘supercoil’, when it is sufficiently twisted; thermal fluctuations destabilize supercoiling for DNAs twisted fewer than once per twist persistence length. Twisted DNAs under tension, braided DNAs, and the internal dynamics of supercoiled DNAs are discussed. The interplay between braiding and supercoiling free energy is argued to be important for the decatenation of duplicated DNAs in prokaryote cells.
Avalanche Segregation of Binary Mixtures of Granular Media
Authors: Koeppe J. , Enz M. , Kakalios J. 
Published: April 2011

ABSTRACTWhen an initially homogeneous binary mixture of granular media such as fine and coarse sand is poured near the closed edge of a “quasi-two-dimensional” Hele-Shaw cell consisting of two vertical transparent plates held a narrow distance apart, the mixture spontaneously forms alternating segregated layers. Using digital images taken with a CCD camera and Fourier transformed to obtain the structure function of the banding pattern, the wavelength selection mechanism and degree of segregation are studied as the plate separation of the Hele-Shaw cell is systematically increased. For a given flow rate, the degree of segregation, as reflected in the amplitude of the peak in the structure function, decreases as the plate separation increases. For wider plate spacings the peak in the structure function shifts to lower wavelengths. These results are compared to numerical simulations of the avalanche segregation using a stochastic sandpile model.
Twist-Stretch Elasticity of DNA
Authors: Kamien Randall D. , Lubensky T. C. , Nelson Philip , O'Hern Corey S. 
Published: April 2011

ABSTRACTThe symmetries of the DNA double helix require a new term in its linear response to stress: the coupling between twist and stretch. Recent experiments with torsionally-constrained single molecules give the first direct measurement of this important material parameter. We extract its value from a recent experiment of Stricket al.and find rough agreement with an independent experimental estimate recently given by Marko. We also present a very simple microscopic theory predicting a value comparable to the one observed.
Sponge Phase Under Shear
Authors: Mahjoub H. F. , Bourgaux C. , McGrath K. M. , Tassin J.F. , Kleman M. 
Published: April 2011

ABSTRACTThe L3 phase under shear transforms to a lamellar phase L*α above some critical shear rate. We study the sequence of successive states (rheothinning, flow birefringence, transition region, lamellar) with simultaneous rheooptical methods, in situ X-ray scattering, and light microscopy observations. The transition region is biphasic, and the two phases display epitaxial relationship immediately after shearing is ceased.
Initial Distribution Effects on Diffusion-Limited Reactions in Constrained Geometries
Authors: Lindenberg Katja , Romero A. H. , Sancho J. M. 
Published: April 2011

ABSTRACTWe present a study of the effects of the initial distribution on the kinetic evolution of irreversible binary reactions in low dimensions. We focus on the role of initial density fluctuations and, in particular, on the role of the long wavelength components of the initial fluctuations, in the creation of the macroscopic patterns that lead to the well-known kinetic anomalies in this system. The frequently studied random initial distribution is but one of a variety of possible distributions leading to interesting anomalous behavior. Our discussion includes initial distributions that suppress and ones that enhance the initial long wavelength components.
Dynamics of Spontaneous Spreading with Evaporation for thin Solvent Films
Authors: Dussaud Anne D. , Troian Sandra M. 
Published: April 2011

ABSTRACTWe have investigated the spreading behavior of solvent droplets on a bulk water support using solvents with different vapor pressures and spreading coefficients. Instead of seeding the surface with tracer particles, as is usually done to track moving fronts, we employ laser shadowgraphy to visualize the entire surface of the spreading film including the leading edge. For non-volatile systems it has previously been shown that the leading edge advances in time as t3/4. We find that volatile systems with positive initial spreading coefficients exhibit two spreading fronts, both of which demonstrate power law growth but with exponents closer to 1/2. Surprisingly, differences in the liquid vapor pressure or the spreading coefficient seem only to effect the speed of advance but not the value of the exponent. We are presently investigating the behavior of the subsurface flow to determine the mechanism leading to the smaller spreading exponent.
Molecular dynamics simulations of sliding friction of Langmuir-Blodgett monolayers
Authors: Koike Asako , Yoneya Makoto , Ito Yutaka 
Published: April 2011

AbstractMolecular dynamics simulations have been performed to study friction in Langmuir-Blodgett monolayers of perfluorocarboxylic acid, semifluoro acid and hydrocarboxylic acid on SiO2. The frictional coefficient of perfluorocarboxylic acid is about three times as large as that of hydrocarboxylic acid, while the frictional coefficient of semifluorocarboxylic acid is about two times as large as that of hydrocarboxylic acid. The qualitative aspects of these simulation results are consistent with known experimental results. In order to interpret the difference in the frictional coefficient, a series of simulations have been carried out by changing molecular potential parameters. The simulation results suggest that the 1,4-van der Waals interaction is the main cause of the larger frictional force for perfluorocarboxylic acid than that for hydrocarboxylic acid. Further frictional coefficients of semifluorocarboxylic acid are found to change by the fluorination ratio. The results also show that frictional force is roughly proportional to the excess r.m.s. fluctuation of the potential energy under shear from the equilibrium. The relation between the frictional force and the energy needed for molecular deformation under shear conditions is also discussed.
STM Investigations of Confined Transition Metal Chalcogenide Colloidal Particles
Authors: Kivuitu F. , Kelty S. P. 
Published: April 2011

ABSTRACTThe chemical reactivity of catalytic surfaces often arises from a unique crystal or electronic structure confined to the first few atomic layers. Scanning Tunneling Microscopy (STM) is particularly well suited to studying the spatially confined structural properties of such systems. In this paper, I report recent advances in the characterization of colloidal layered transition metal chalcogenides using STM. These particles mimic the surface (layer edge) properties of bulk catalytic materials. It is found that the materials adopt distinct equilibrium chemical and electronic structures as compared to the bulk. The possible significance of these novel structures in regard to the bulk catalytic functionality of the parent material will be briefly discussed.
Irreversible Adsorption of Polymer Melts
Authors: Sawhney U. , Durning C.J. , O'Shaughnessy B. , Smith G.S. , Majewski J. 
Published: April 2011

ABSTRACTWe studied the equilibrium architecture of polymer layers strongly adsorbed from the melt. Immobilized layers of poly-(methyl methacrylate) (PMMA) were produced by the following method: 1) The polymer was spin-coated onto silanol bearing surfaces of single crystal and fused quartz, and annealed at melt conditions, 2) The annealed layer was quenched to room temperature (below the glass transition temperature) in order to “freeze in” the melt structure near the substrate, 3) Unbound material was leached away in good solvent (benzene) to leave a residual, strongly-adsorbed layer. The architecture of this layer was studied by neutron reflection. Data on dried adsorbed layers indicates a dense PMMA film whose thickness gradually increases with annealing time in the melt from a minimal value. Evidently, annealing gradually relaxes a rather flat non-equilibrium structure produced by spin-coating. The thicknesses, h, in a series of dry layers annealed long enough to achieve equilibrium conditions in the melt scale as h ∼ N1/2. Data on swollen layers suggest a dilute, extended layer, but the preliminary results cannot give a definitive confirmation of the brush structure predicted by Guiselin.11
Experimental Investigations of the Kinetics of a Catalytic Trapping Reaction in Confined Spaces
Authors: Feldman Mark S. , Lin Anna L. , Kopelman Raoul 
Published: April 2011

AbstractWe investigate the anomalous kinetics in one dimension of a diffusion limited catalytic trapping reaction, A + T → T, by measuring the oxidation of glucose. The reaction is carried out in a thin capillary tube, and the depletion of oxygen in the vicinity of the reaction front is monitored by the fluorescence of a Ru(II) dye. Theoretical results and simulations have predicted an asymptotic t1/2 dependence for the rate coefficient. We observe a depedence on t0.56, with what appears to be an asymptotic behavior approaching t1/2.
Massively Parallel Molecular Dynamics Simulation of Gas Permeation across Molecular Sieving Porous Membranes
Authors: Pohl Phillip I. , Heffelfinger Grant S. 
Published: April 2011

AbstractIn this work we simulate the diffusion of gases in a microporous solid models using a newly developed dual control volume grand canonical molecular dynamics technique. This allows spatial variation of chemical potential and hence an accurate simulation of steady-state pressure driven diffusion. The molecular sieving nature of microporous zeolites are discussed and compared with that for amorphous silica from sol-gel methods. Massively parallel supercomputers allow a quick and insightful study of these microporous structures.
Notes on the Interpretation of Nanorheology Experiments
Authors: Dhinojwala Ali , Cai Lenore , Granick Steve 
Published: April 2011

ABSTRACTWe discuss the resolution of shear force measurement in determining the effective shear viscosity of molecularly-thin films. Recent findings for the shear of confined OMCTS (octamethylcyclotetrasiloxane) are presented.